CN118103757A

CN118103757A - Light projection system using white light illumination

Info

Publication number: CN118103757A
Application number: CN202280069309.9A
Authority: CN
Inventors: J·D·杰克逊; N·S·温赖特; F·J·波拉迪什; D·亨尼根; D·S·德瓦尔德; J·P·佩蒂埃拉; M·J·理查兹; B·利佩伊; J·S·米勒; T·戴维斯; P·F·范凯塞尔; D·R·B·坎贝尔
Original assignee: Dolby Laboratories Licensing Corp
Current assignee: Dolby Laboratories Licensing Corp
Priority date: 2021-10-14
Filing date: 2022-10-14
Publication date: 2024-05-28

Abstract

Light projection systems using white light illumination are disclosed. One embodiment provides a projection system using white light illumination. The projection system includes an illumination assembly configured to receive a white light input. The prism is configured to separate the white light input into color light inputs, redirect the color light inputs to respective modulators, and combine the modulated color light inputs from the respective modulators into a white light output. The filter is configured to spatially fourier transform the white light output to generate a filtered white light output. A projection lens assembly is configured to project the filtered white light output.

Description

Light projection system using white light illumination

Cross Reference to Related Applications

The present application claims priority from the following priority applications: european patent application number 22163730.9 (reference number: D21099 EP) filed on 3/month 23 of 2022, U.S. provisional patent application number 63/322,669 (reference number: D21099USP 2) filed on 3/month 23 of 2022, U.S. provisional patent application number 63/255,694 (reference number: D21099USP 1) filed on 14 of 10/month 2021, each of which is hereby incorporated by reference in its entirety.

Technical Field

The present application relates generally to projection systems, and more particularly to a projection system including a single illumination assembly that incorporates a dichroic reflecting prism and filters to deliver white light to increase the contrast of an image provided by the prism.

Background

The contrast of the projector indicates the brightest output of the projector relative to the darkest output of the projector. The contrast ratio is a quantitative measure of contrast, defined as the ratio of the brightness of the brightest output of the projector to the brightness of the darkest output of the projector. This definition of contrast ratio is also referred to as "static" or "native" contrast ratio.

Due to the visual adaptability of the human visual system, the range of brightness detectable by the viewer corresponds to a contrast ratio of about 1,000,000,000:1, even at any instant in time, the range of brightness detectable corresponds to a contrast ratio of less than this value. For example, in scotopic vision, mediated only by rod cells of the human eye, the detectable contrast ratio may be as high as 1,000,000:1 for some viewers at any time, depending on the scene observed, the adaptation state of the user, and biological factors.

Viewers in a cinema environment may be in different adaptation states at any time and thus may see different contrast ratios for the same scene. The change in adaptation state between viewers may be due to the different seat positions relative to the screen, the position where each viewer is focused on the screen, and when and how often each viewer closes the eye. When multiple viewers use a movie theater, the contrast ratio of an ideal projector is high enough to accurately reproduce images for all viewers.

Some projectors that meet the Digital Cinema Initiative (DCI) specification have a contrast ratio of 2,000:1 or less. For these digital projectors, dark and/or black regions of the image may be projected with a sufficiently high brightness to make the regions appear brighter than intended.

In addition, many Digital Light Processing (DLP) projectors use a three-way prism assembly having a common optical path that passes bi-directionally through the color prism. The color prism receives light for each color channel (red, green, and blue), transmits each color channel to the modulator, and combines the modulator channels into a white light output. Such projectors may include dual modulator and/or multi-modulator projector display systems.

Disclosure of Invention

Projector display systems that receive and individually modulate multiple color channels can achieve high contrast, e.g., 70k:1. However, in some projector display systems, lower contrast ratios, such as 30K:1, may also be acceptable. When a lower contrast is acceptable, no separate illumination angle adjustment is required for each color channel. Accordingly, embodiments described herein provide a single illumination assembly that delivers white light to a white light prism. After splitting the white light with a white light prism, each color channel is provided to a modulator that modulates the color channel. Since each color channel is separate from the same white light input, each color channel has the same illumination angle. The modulated color channels are then recombined into a white light output within a white light prism. The white light output is provided to a filter configured to spatially fourier transform the white light output from the white light prism.

Various aspects of the present disclosure relate to devices, systems, and methods for white light illumination in projector systems. One embodiment provides a projection system using white light illumination. The projection system includes an illumination assembly configured to receive a white light input. The prism is configured to separate the white light input into separate color light inputs, redirect the color light inputs to respective modulators, and combine the modulated color light inputs from the respective modulators into a white light output. The filter is configured to spatially fourier transform the white light output to generate a filtered white light output. A projection lens assembly is configured to project the filtered white light output.

Another embodiment provides a method for modulating white light in a projector system. The method comprises the following steps: receiving a white light input with a prism assembly; and separating the white light with the prism assembly into a plurality of separate color light inputs, each color light input provided to a separate prism path at an illumination angle. The method comprises the following steps: modulating each color light input with a color light modulator in each individual prism path; and combining each modulated color light input into a white light output within the prism assembly. The method comprises the following steps: providing the white light output to a projection lens assembly; filtering the white light output within the projection lens assembly; and projecting the filtered white light output.

Another embodiment provides a projection system using white light illumination. The projection system includes a prism configured to separate white light into a plurality of color channels, redirect the color channels to respective modulators, and combine the modulated color channels from the respective modulators into a white light output. The projection system includes a projection lens assembly configured to project the white light output, the projection lens assembly including a filter configured to spatially fourier transform the white light output.

In this way, various aspects of the present disclosure provide for the display of images with high dynamic range and high resolution, and at least significant improvements in the technical fields of image projection, holography, signal processing, and the like.

Drawings

These and other more detailed and specific features of the various embodiments are more fully disclosed in the following description, with reference to the accompanying drawings, in which:

fig. 1 illustrates a filter configured to improve contrast of an image generated by a spatial light modulator according to an embodiment.

Fig. 2 and 3 are front and side views, respectively, of an example prior art Digital Micromirror Device (DMD) 200 for generating an image as part of a digital projector.

Fig. 4 is a side view of a filter configured to filter modulated light from a DMD, according to an embodiment.

Fig. 5 and 6 are side views of an example digital projector having a DMD and a projector lens.

Fig. 7 and 8 are intensity diagrams of exemplary fraunhofer diffraction patterns of ON and OFF modulated light, respectively.

Fig. 9 to 14 are front views of examples of the filter mask of fig. 4, showing example configurations of transmission regions of the filter mask.

Fig. 15 illustrates a multi-color digital projector that achieves contrast ratio increase by filtering each color channel in a spatially multiplexed manner, according to an embodiment.

Fig. 16 illustrates a multi-color digital projector that achieves contrast ratio increase by time division multiplexing filtering of different color channels according to an embodiment.

Fig. 17 is a graph of optical power versus time of time-division multiplexed light for the input light used as the digital projector of fig. 16 according to an embodiment.

Fig. 18 is a front view of an example filter wheel having three sectors, each containing one filter mask.

Fig. 19 is a front view of an example filter wheel having six sectors, each containing one filter mask.

Fig. 20 illustrates a method for improving contrast of an image generated by a spatial light modulator according to an embodiment.

Fig. 21 illustrates a method for projecting a color image with increased contrast by filtering each color channel in a spatially multiplexed manner, according to an embodiment.

Fig. 22 illustrates a time division multiplexing method for generating and projecting a color image with increased contrast according to an embodiment.

Fig. 23 is a side view of a simulation experiment.

Fig. 24 to 26 are numerical graphs of contrast ratio and light efficiency versus half angle obtained for the simulation experiment of fig. 23.

FIG. 27 is a fraunhofer diffraction pattern of the simulation experiment of FIG. 23 when the wavelength of light is 532nm and all micromirrors of the DMD are in the ON position.

FIG. 28 is a fraunhofer diffraction pattern of the simulation experiment of FIG. 23 when the light wavelength is 617nm and all micromirrors of the DMD are in the ON position.

Fig. 29 is a graph of contrast ratio versus light efficiency obtained for the simulation experiment of fig. 23 operating at 617nm wavelength when the ON and OFF tilt angles of the micromirror are +12.1 degrees and-12.1 degrees, respectively.

Fig. 30 and 31 are numerical graphs of contrast ratio versus micromirror inclination angle obtained for the simulation experiment of fig. 23.

Fig. 32 is a graph of the numerical values of contrast ratio and light efficiency as a function of angular diversity of the input light obtained for the simulation experiment of fig. 23 at a wavelength of 532 nm.

Fig. 33 and 34 are fraunhofer diffraction patterns of the simulation experiment of fig. 23, showing the broadening of diffraction peaks due to the angular diversity of the input light.

Fig. 35 illustrates an exemplary projection lens system in accordance with aspects of the present disclosure.

Fig. 36 illustrates an example lens configuration of a portion of the example projection lens system of fig. 35.

Fig. 37 illustrates an exemplary lens configuration of another portion of the exemplary projection lens system of fig. 35.

Fig. 38 illustrates an exemplary assembled lens configuration of the exemplary projection lens system of fig. 35.

FIG. 39 illustrates an example projection system.

FIG. 40 illustrates an example projection system including a nine-piece prism system and a plurality of illumination assemblies.

FIG. 41 illustrates an example projection system including a white light prism system and a single illumination assembly.

Fig. 42 illustrates an example nine-piece prism for individual color channel input.

Fig. 43 illustrates an example white light prism with a total internal reflection prism for white light input.

Fig. 44 illustrates an example white light prism without a total internal reflection prism.

Fig. 45 illustrates an example wobble frequency oscillator used in conjunction with the example prism of fig. 41.

Fig. 46A-46B illustrate an example wobble frequency oscillator used in conjunction with the example prisms of fig. 41 and 42.

Fig. 47 illustrates a method of using white light illumination within the projection system of fig. 41.

Detailed Description

The present disclosure and aspects thereof may be embodied in various forms including: hardware, devices or circuits controlled by computer implemented methods, computer program products, computer systems and networks, user interfaces and application programming interfaces; and hardware implemented methods, signal processing circuits, memory arrays, application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs), and the like. The foregoing summary is intended merely to give a general idea of various aspects of the disclosure and is not intended to limit the scope of the disclosure in any way.

In the following description, numerous details are set forth, such as optical device configurations, timings, operations, etc., to provide an understanding of one or more aspects of the present disclosure. It will be apparent to one skilled in the art that these specific details are merely examples and are not intended to limit the scope of the application.

Optical filter

Fig. 1 is a functional diagram illustrating one filter 110 configured to improve the contrast of an image generated by a spatial light modulator. Fig. 1 shows the filter 110 in a use scenario in which the filter 110 is implemented in the digital projector 100 to increase the contrast of an image projected by the digital projector 100. The digital projector 100 includes a Spatial Light Modulator (SLM) 102 that modulates input light 106 into modulated light 104 in accordance with input data representing an image to be projected by the digital projector 100.

The filter 110 filters the modulated light 104 by blocking a portion 114 of the modulated light 104. The blocked portion 114 includes light that the digital projector 100 would project onto the screen 116 without the filter 110, even when the SLM 102 is controlled not to output light to the screen 116. The filter 110 outputs the transmitted portion of the modulated light 104 as the filtering light 108. The digital projector 100 includes a projection lens 112 that projects the filter 108 onto a screen 116. In the absence of the filter 110, the blocked portion 114 of the modulated light 104 corresponds to the lower limit of the luminous intensity of the digital projector 100 and thus determines the darkness of the projected image. By blocking the blocked portion 114 of the modulated light 104, the filter 110 reduces the lower bound, thereby increasing the contrast of the digital projector 100.

As described in more detail below, the blocked portion 114 of the modulated light 104 corresponds to one or more diffraction orders of the modulated light 104 that result from the diffraction of the input light 106 from the SLM 102. The SLM 102 may be any type of spatial light modulator as follows: which (1) has a periodic structure that acts as a diffraction grating, and (2) modulates the optical phase of the input light 106 to steer the light between two states, e.g., an ON (ON) and an OFF (OFF) state. In one example, SLM 102 of fig. 1 is a Digital Micromirror Device (DMD) that steers light by tilting a plurality of micromirrors to modulate the optical phase of input light 106. In other examples, SLM 102 is a reflective Liquid Crystal On Silicon (LCOS) phase modulator or a transmissive Liquid Crystal (LC) phase modulator, each of which steers light by modulating the refractive index of the liquid crystal.

Fig. 2 and 3 are front and side views, respectively, of a prior art DMD 200 for generating an image as part of a digital projector (e.g., digital projector 100). DMD 200 is an example of SLM 102. Fig. 2 and 3 are best seen together in the following description.

DMD 200 is a micro-electro-mechanical system (MOEMS) SLM with a plurality of square micromirrors 202 arranged in a two-dimensional rectangular array on a substrate 204 lying in the xy-plane (see right-hand coordinate system 220). In certain embodiments, DMD 200 is a Digital Light Processor (DLP) from texas instruments (Texas Instruments) in the united states. Each micromirror 202 may correspond to a pixel of an image and may be tilted by electrostatic actuation about an axis of rotation 208 oriented at-45 degrees to the x-axis to steer the input light 206. For clarity, fig. 2 shows only representative micromirrors 202 at the corners and center of DMD 200, and not all micromirrors 202 are labeled in fig. 3.

Fig. 3 shows the micro mirrors 202 tilted to steer the input light 206. The micro mirror 202 (1) is actuated to an ON position to specularly reflect the input light 206 into ON reflected light 306 (see coordinate system 120) parallel to the z-axis. The micro mirror 202 (2) is actuated to the OFF position to specularly reflect the input light 206 as OFF reflected light 320 directed to a beam dump (not shown) that absorbs the OFF reflected light 320. The micromirror 202 (3) is not actuated and is in a flat state parallel to the substrate 204 (e.g., xy plane). The front surface 304 of each micromirror 202 may be coated with a deposited metal (e.g., aluminum) layer that acts as a reflective surface for reflecting the input light 206. The gap 310 may be absorptive, i.e., the input light 206 entering the gap 310 is absorbed by the substrate 204. For clarity, the mechanical structure that physically couples the micro mirrors 202 to the substrate 204 is not shown. DMD 200 may be implemented to direct ON reflected light 306 and OFF reflected light 320 in respective directions other than those shown in fig. 3 without departing from the scope of the present invention. In addition, DMD 200 may be configured such that when not actuated, micromirrors 202 are at an angle to substrate 204.

A digital projector with DMD 200 may be designed by considering only the specular reflection of input light 206 from micro-mirrors 202. However, the micro mirrors 202 and the gaps 310 separating the micro mirrors 202 cooperate to form a two-dimensional grating that diffracts the input light 206. Thus, modulated light propagating away from DMD 200 may form multiple diffraction orders in the far field region of DMD 200 or in the focal plane of the lens that may be observed as fraunhofer diffraction patterns (see diffraction patterns 700 and 800 of fig. 7 and 8, respectively). Each diffraction order corresponds to one light beam propagating away from DMD 200 in a unique corresponding direction. By design, most of the optical power of the modulated light from DMD 200 is in the zero diffraction order, corresponding to specularly reflected ON and OFF reflected light 306 and 320.

Diffraction of input light 206 by DMD 200 may reduce the Projector Contrast Ratio (PCR) of a digital projector using DMD 200 (e.g., digital projector 100 of fig. 1 without filter 110). The PCR of a projector is defined herein as the ratio of ON to OFF luminous intensities (or equivalently, first and second photometric intensities) measured at the projection screen illuminated by the projector. When the projector is controlled to output its brightest output (e.g., white) and darkest output (e.g., black), respectively, ON and OFF light emission intensities are generated. When the DMD 200 is used by a digital projector, ON and OFF luminous intensities will be generated when all micromirrors 202 are in ON and OFF positions, respectively.

How the DMD 200 diffracts the input light 206 may be determined by various parameters such as (1) the wavelength of the input light 206, (2) the direction of the input light 206, (3) the pitch 212 of the DMD 200, (4) the width 210 of the gap 310 of the DMD 200, and (5) the ON and OFF tilt angles of the micromirrors 202. As shown in FIG. 2, pitch 212 is equal to the sum of width 210 and micromirror edge length 208 along the x and y directions of DMD 200. Pitch 212 may be between 5 microns and 15 microns. The width 210 may be less than 1 micron. In one example, pitch 212 is between 7 and 8 microns and width 210 is between 0.7 and 0.9 microns.

Fig. 4 is a side view of an optical filter 400 configured to spatially filter modulated light 402 from DMD 200 to enhance PCR of digital projector 100. Filter 400 is an embodiment of filter 110. DMD 200 is an embodiment of SLM 102. In filter 400, DMD 200 may be replaced by another embodiment of SLM 102 (e.g., a reflective LCOS or a transmissive LC phase modulator) without departing from the scope of the invention. The filter 400 includes a lens 404 that spatially fourier transforms the modulated light 402 by focusing the modulated light 402 onto a fourier plane 408. Modulated light 402 is depicted in fig. 4 as a plurality of arrows, each arrow corresponding to a respective diffraction order and pointing in a unique direction of propagation of the diffraction order. Lens 404 defines an optical axis 422. In one embodiment, as shown in FIG. 4, DMD 200 is centered on optical axis 422. In another embodiment, DMD 200 is off-center with respect to optical axis 422. Lens 404 has a focal length 410 and fourier plane 408 coincides with the focal plane of lens 404. When fourier transformed by lens 404, filter mask 412, located at fourier plane 408, spatially filters modulated light 402. The spatial fourier transform applied by lens 404 converts the propagation angle of each diffraction order of modulated light 402 into a corresponding spatial position on fourier plane 408. The lens 404 is thus able to select the desired diffraction orders and reject the undesired diffraction orders by spatial filtering at the fourier plane 408. The spatial fourier transform of the modulated light 402 on the fourier plane 408 is equivalent to the fraunhofer diffraction pattern of the modulated light 402.

The filter mask 412 has at least one transmissive region 416 configured to transmit all or part of the modulated light 402 of at least one diffraction order through the filter mask 412 as a filtering light 414. In some embodiments, the filter mask 412 is substantially opaque when the modulated light 402 of the undesired diffraction order is incident. In some embodiments, when the filter mask 412 does not have the transmissive region 416, the filter mask 412 is substantially opaque. In other embodiments, the filter mask 412 is configured to reflect the desired diffraction orders as opposed to transmission in order to spatially separate the desired diffraction orders from undesired diffraction orders.

In an embodiment, the filter 400 is configured with a collimating lens 418 that collimates the filter 414 into collimated light 420. The collimating lens 418 may simplify the integration of the filter 400 with other optical elements or optical systems. For example, lens 418 may optically couple filter 414 to additional optics located behind filter 400 (e.g., projector lens 112 or beam combiner 1504 discussed below with reference to fig. 15). The collimating lens 418 has a focal length 424 and is positioned such that the focal plane of the collimating lens 418 coincides with the fourier plane 408. Although focal lengths 410 and 424 are shown as being equal in fig. 4, focal lengths 410 and 424 may be different from each other in some embodiments. In another embodiment, filter 400 is configured with a lens similar to collimating lens 418 that optically couples filter 414 to additional optics (e.g., projector lens 112) located behind filter 400.

For clarity, fig. 4 shows only the diffracted beams diffracted in one dimension (e.g., x-direction). However, DMD 200 diffracts in two dimensions such that modulated light 402 also includes a diffracted beam that has been diffracted by DMD 200 in a second dimension (e.g., y-direction) perpendicular to optical axis 422. Each diffracted beam in the two-dimensional diffraction pattern may be marked with a pair of integers that identify the diffraction orders of the diffracted beam for each dimension in the two dimensions. Herein, "zero order" refers to one diffracted beam having zero order in both dimensions. Also, each arrow depicted in fig. 4 as part of modulated light 402 may indicate a set of adjacent diffraction orders, such as a zero order diffraction order and a plurality of order diffraction orders, without departing from the scope of the invention.

Fig. 5 and 6 are side views of a digital projector 500 that includes DMD 200 and projector lens 112, but does not include filter 110. Fig. 5 and 6 illustrate how the diffraction order of modulated light 402 from DMD 200 reduces the PCR of digital projector 500. DMD 200 is an embodiment of SLM 102. DMD 200 may be replaced by another embodiment of SLM 102 (e.g., a reflective LCOS or transmissive LC phase modulator) in digital projector 500 without departing from the scope of the present invention. In fig. 5, digital projector 500 generates ON luminous intensity by actuating all of the micromirrors 202 of DMD 200 to the ON position (see micromirror 202 (1) in magnified view 516). In fig. 6, digital projector 500 generates OFF luminous intensity by actuating all of the micromirrors 202 of DMD 200 to the OFF position (see micromirrors 202 (2) in enlarged view 616). In fig. 5 and 6, DMD 200 and projector lens 112 are centered on optical axis 422 in the x and y directions (see coordinate system 220). Fig. 5 and 6 are best seen together in the following description.

In fig. 5, DMD 200 diffracts input light 206 into ON modulated light 502 having a plurality of ON diffracted beams 504. In fig. 6, DMD 200 diffracts input light 206 into OFF modulated light 602 having a plurality of OFF diffracted beams 604. In the far field region of DMD 200, each ON diffracted beam 504 corresponds to one diffraction order or one peak of the fraunhofer diffraction pattern formed by ON modulated light 502, and each OFF diffracted beam 604 corresponds to one diffraction order or one peak of the fraunhofer diffraction pattern formed by OFF modulated light 602. In the far field region of DMD 200, each of ON diffracted beam 504 and OFF diffracted beam 604 corresponds to a k vector having one of a plurality of propagation directions 510. In the examples of fig. 5 and 6, the propagation direction 510 is represented as a dashed line; each of the ON and OFF diffracted beams 504, 604 is aligned with one of the propagation directions 510 and is represented by a solid arrow whose length corresponds to the power or intensity of the diffracted beam.

One aspect of the present embodiment recognizes that for a fixed direction of input light 206, the power/intensity of ON diffracted beam 504 and OFF diffracted beam 604 change when micromirror 202 of DMD 200 is switched between the ON and OFF positions, whereas the propagation direction 510 of ON diffracted beam 504 and OFF diffracted beam 604 remains unchanged when micromirror 202 of DMD 200 is switched between the ON and OFF positions.

In the example of fig. 5, input light 206 is a monochromatic plane wave that illuminates DMD 200 and propagates toward DMD 200 such that ON diffracted beam 504 (1) propagates along optical axis 422. The ON diffracted beam 504 (1) contains most of the power of the ON modulated light 502. The ON diffracted beam 504 (1) may represent a zero order diffraction order or a plurality of adjacent diffraction orders (e.g., a zero order diffraction order and several orders of diffraction) of the ON modulated light 502.

Fig. 5 also shows that ON diffracted beam 504 (2) propagates in a different direction than ON diffracted beam 504 (1), but still passes through clear aperture 508 of projector lens 112. The power of ON diffracted beam 504 (2) is less than the power of ON diffracted beam 504 (1). A plurality of ON diffracted beams 518, including ON diffracted beams 504 (1) and 504 (2), pass through clear aperture 508 of projector lens 112, which projects the plurality of ON diffracted beams 518 onto a projection screen as ON projected light 514.

Fig. 5 also shows the ON diffracted beam 504 (3) propagating in a direction without the clear aperture 508. Projector lens 112 does not project ON diffracted beam 504 (3) onto the projection screen. The power of the ON diffracted beam 504 (3) is a fraction of the power of the ON modulated light 502. Thus, excluding ON diffracted beam 504 (3) from ON projected light 514 is very inefficient in the optical power of digital projector 500.

Fig. 6 shows OFF diffracted beams 604 (1), 604 (2), 604 (3) corresponding to the respective ON diffracted beams 504 (1), 504 (2), 504 (3) of fig. 5. The OFF diffracted beam 604 (3) propagates away from the optical axis 422 without passing through the clear aperture 508. Most of the power of OFF modulated light 602 is in OFF diffracted beam 604 (3) and will therefore not be projected onto the projection screen.

In fig. 6, OFF diffracted beams 604 (1) and 604 (2) pass through clear aperture 508 to be projected as part of OFF projected light 614. The power of OFF diffracted beams 604 (1) and 604 (2) is smaller than the power of OFF diffracted beam 604 (3). However, the power of OFF diffracted beams 604 (1) and 604 (2) increases the OFF luminous intensity of digital projector 500, thereby reducing the PCR of digital projector 500.

With a majority of the optical power of ON modulated light 502 in ON diffracted beam 504 (1), the other ON diffracted beams 504 of the plurality of ON diffracted beams 518 pass through clear aperture 508, thereby forming ON projected light 514 comprising relatively little power, and thus having a negligible contribution to the power of ON projected light 514. However, the corresponding OFF diffracted beam 604 passing through clear aperture 508 may significantly increase the power of OFF projected light 614, thereby reducing PCR of digital projector 500.

Another aspect of this embodiment recognizes that the diffraction orders corresponding to the lower optical power ON diffracted beams, like ON diffracted beam 504 (2) described above, may be filtered to increase PCR with minimal degradation in optical power output and efficiency of digital projector 500. To identify the diffraction orders to be filtered, a Diffraction Order Contrast Ratio (DOCR) may be used. For each propagation direction 510 through the clear aperture 508, docr may be defined as the ratio of the optical powers of a corresponding ON and OFF diffracted beam having the same diffraction order and propagation direction. For example, the diffraction orders of the ON diffracted beam 504 (1) and OFF diffracted beam 604 (1) corresponding to fig. 5 and 6 have a height DOCR. Having a diffraction order of high DOCR is advantageous for increasing PCR and can be advantageously selected for projection onto a projection screen. ON the other hand, ON diffracted beam 504 (2) and OFF diffracted beam 604 (2) correspond to diffraction orders having a low DOCR. Having a low DOCR diffraction order reduces PCR and can advantageously be filtered out to increase PCR for digital projector 500.

For clarity, fig. 5 and 6 only show diffracted beams 504, 604 diffracted in one dimension (e.g., the x-direction). However, DMD 200 diffracts input light 206 in two dimensions such that modulated light 502 and 602 also include diffracted beams that have been diffracted by DMD 200 in a second dimension (e.g., y-direction) perpendicular to optical axis 512. Each diffracted beam in the two-dimensional diffraction pattern may be marked with a pair of integers that identify the diffraction orders of the diffracted beam for each dimension in the two dimensions. Herein, "zero order" refers to one diffracted beam having zero order in both dimensions.

Fig. 7 and 8 are the intensities of exemplary fraunhofer diffraction patterns 700 and 800 of ON modulated light 502 and OFF modulated light 602, respectively. Diffraction patterns 700 and 800 correspond to fourier transforms produced by one example of lens 404 at fourier plane 408 in one embodiment of filter 400 implemented in an embodiment of digital projector 100 configured with DMD 200. Diffraction patterns 700 and 800 are digitally generated according to the process described in more detail in the "numerical analysis" section below. Each diffraction pattern comprises a plurality of equidistant diffraction peaks, each corresponding to a respective one of the diffracted beams 504 or 604 of fig. 5 and 6, respectively. The horizontal axis 704 and the vertical axis 706 of fig. 7 and 8, respectively, indicate the directional cosine of the diffraction peaks relative to the x-axis and the y-axis of the coordinate system 220. Fig. 7 and 8 indicate the intensities of the diffraction patterns 700 and 800 according to an intensity scale 708.

Circle 702 of fig. 7 and 8 represents clear aperture 508 of fig. 5 and 6. Diffraction peaks lying within circle 702 represent diffracted beams 518, 618 projected by projector lens 112 as ON projection light 514 and OFF projection light 614, respectively. In fig. 7, the brightest (e.g., highest intensity) diffraction peak 710 at the center of the circle 702 corresponds to the zero order of the ON diffracted beam 504 (1) and/or ON modulated light 502 of fig. 5. Diffraction peaks outside of circle 702 will not project onto the projection screen.

In fig. 8, the brightest diffraction peak 810 corresponding to OFF diffraction beam 604 (3) is at a higher value of the directional cosine outside circle 702 and therefore will not be projected onto the projection screen. However, the plurality of low power diffraction peaks 812 in circle 702 will be projected as OFF projected light 614 onto the projection screen, increasing OFF luminous intensity and decreasing PCR.

To increase PCR, filter 400 may be implemented to reduce OFF luminous intensity by blocking diffraction orders located within circle 702 that contribute more to OFF luminous intensity than ON luminous intensity. Fraunhofer diffraction patterns 700 and 800 represent fourier transforms of modulated light 402 and illustrate how transmission region 416 may be configured such that filter mask 412 transmits desired diffraction orders for projection while blocking all other undesired diffraction orders that would otherwise be projected. Specifically, using the parameters of lens 404, the directional cosine associated with each desired diffraction peak may be converted to a spatial location on filter mask 412 where transmission region 416 may be positioned to transmit the desired diffraction peak through filter mask 412. Similarly, the directional cosine associated with each undesired diffraction peak may be converted to a spatial location on the filter mask 412 where the filter mask 412 is opaque to block (e.g., filter) the undesired diffraction peak.

In one embodiment, the filter mask 412 includes a transmissive region 416 that is selected to optimize PCR and/or optical power efficiency of the digital projector in size, geometry, position, and orientation. In another embodiment, the filter mask 412 has a plurality of transmissive regions 416, and the size, geometry, position, and orientation of each transmissive region 416 is selected to optimize PCR and/or optical power efficiency of the digital projector.

Fig. 9-14 are front views of examples of the filter mask 412 of fig. 4, showing example configurations of the transmissive region 416. In each of fig. 9-14, a plurality of positions 902 of diffraction orders are represented by X forming a two-dimensional grid, such as diffraction orders associated with different pairs of corresponding ON and OFF diffraction beams 504, 604. For example, in fig. 9, position 902 (2) indicates one diffraction order blocked by the filter mask 900, and position 902 (1) indicates one diffraction order transmitted by the filter mask 900.

Fig. 9 and 10 illustrate example filter masks 900 and 1000 with circular transmissive regions 904 and 1004, respectively. Each of the circular transmissive regions 904 and 1004 may be an aperture or a material that is at least partially transmissive to light. Circular transmissive regions 904 and 1004 are examples of transmissive region 416. The circular transmissive region 904 is sized to transmit one diffraction order through the filter mask 900. The circular transmissive region 1004 is sized to transmit multiple diffraction orders through the filter mask, e.g., nine diffraction orders forming a 3 x3 grid, as shown in fig. 9. Although fig. 9 and 10 illustrate the circular transmissive regions 904 and 1004 centered on the filter masks 900 and 1000, respectively, and thus centered on the optical axis 422, the circular transmissive regions 904 and 1004 may be off-centered without departing from the scope of the present invention.

Fig. 11 and 12 illustrate example filter masks 1100 and 1200 having square transmissive regions 1104 and 1204, respectively. Each of the square transmissive regions 1104 and 1204 may be an aperture or a material that is at least partially transmissive to light. Square transmissive regions 1104 and 1204 are examples of transmissive region 416. The square transmissive region 1104 is centered on the filter mask 1100 and is sized to transmit multiple diffraction orders through the filter mask 1100, such as nine diffraction orders forming a 3 x3 grid, as shown in fig. 11. The square transmissive region 1204 is off-centered on the filter mask 1200 and is sized to transmit multiple diffraction orders through the filter mask 1200, such as four diffraction orders forming a 2x 2 grid.

Fig. 13 illustrates an example filter mask 1300 having irregular polygonal transmissive regions 1304 configured to transmit three adjacent diffraction orders through the filter mask 1300. The irregular polygonal transmissive region 1304 is an example of transmissive region 416 and may be an aperture or an at least partially light transmissive material.

Fig. 14 shows an example filter mask 1400 having a plurality of circular transmissive regions 1404, each positioned and sized to transmit one diffraction order through the filter mask 1400, such as four transmissive regions 1404. The circular transmissive region 1404 is an example of a plurality of transmissive regions 416.

The transmissive region 416 may have another shape, size, and position than shown in the examples of fig. 9-14 without departing from its scope. In one class of embodiments, each example of the transmissive region 416 shown in fig. 9-14 is a hole formed in the filter mask 412 (e.g., by drilling, milling, or etching). In another class of embodiments, each example of a transmissive region 416 shown in fig. 9-14 is a light transmissive window, a semi-transmissive window, or a color filter (e.g., a dichroic filter or a thin film filter) physically coupled to the filter mask 412 or embedded within the filter mask 412. In the examples of fig. 9-14, the filter mask (e.g., filter mask 900) is circular; each of these filter masks may alternatively have another shape (e.g., square or rectangular) without departing from the scope of the invention. In some of the examples of fig. 9-14 (e.g., filter masks 900 and 1000), the filter masks are configured to be centered on optical axis 422; each of these filter masks may alternatively be configured off-center from optical axis 422 without departing from the scope of the present invention.

The filter mask 412 may be formed of a metal such as aluminum or stainless steel. The metal may be anodized or blackened to enhance the absorption of light blocked by the filter mask 412. Alternatively, the filter mask 412 may be formed of a semiconductor substrate, such as silicon, into which the transmissive region 416 is etched or polished. In another embodiment, the filter mask 412 is formed from a light transmissive substrate (e.g., glass) coated with a light absorbing material (e.g., black paint) to block light in areas that do not coincide with the transmissive region 416. In another embodiment, the filter mask 412 is an active filter mask having a dynamically configurable transmissive region 416, such as an electronically controlled mirror array.

Fig. 15 shows a multi-color digital projector 1500 that achieves PCR augmentation by filtering each color channel in a spatially multiplexed manner. The digital projector 1500 has a plurality of filters 400 and a matching number of DMDs 200. Each filter 400 is paired with a respective DMD 200 to operate with a different respective primary color. Each DMD 200 is an embodiment of SLM 102. In digital projector 1500, each DMD 200 may be replaced by another embodiment of SLM 102 (e.g., a reflective LCOS or transmissive LC phase modulator) without departing from the scope of the present invention. Fig. 15 depicts a digital projector 1500 having three color channels, and the following discussion relates to the three color channels. However, it should be understood that digital projector 1500 may alternatively be configured to have only two color channels, or to have more than three color channels.

DMDs 200 (1), 200 (2), and 200 (3) modulate respective input light 206 (1), 206 (2), and 206 (3) into respective modulated light 402 (1), 402 (2), and 403 (3), which is filtered by respective filters 400 (1), 400 (2), and 400 (3) into respective filtered light 414 (1), 414 (2), and 414 (3). Digital projector 1500 also includes beam combiner 1504, which combines filter 414 (1), 414 (2), and 414 (3) into polychromatic light 1510. Projector lens 112 is configured to project polychromatic light 1510 onto a projection screen. Digital projector 1500 is an embodiment of digital projector 100 that is extended to process three separate color inputs to output polychromatic light.

In one embodiment, digital projector 1500 includes collimating lenses 418 (1), 418 (2), and 418 (3) that collimate respective filter 414 (1), 414 (2), and 414 (3) into respective collimated light 420 (1), 420 (2), and 420 (3). In this embodiment, beam combiner 1504 combines collimated light 420 (1), 420 (2), and 420 (3), as shown in fig. 15. In an embodiment of digital projector 1500 that does not include collimating lens 418, beam combiner 1504 combines uncollimated filtered light 414 (1), 414 (2), and 414 (3).

In one embodiment, digital projector 1500 includes Total Internal Reflection (TIR) prisms 1502 (1), 1502 (2), and 1503 (3) that reflect input light 206 (1), 206 (2), and 206 (3) to respective DMDs 200 (1), 200 (2), and 200 (3) and transmit respective modulated light 402 (1), 402 (2), and 402 (3) to respective filters 400 (1), 400 (2), and 400 (3). Digital projector 1500 may be configured with mirrors 1506 and 1508 that turn collimated light 420 (1) and 420 (3) toward beam combiner 1504, as shown in fig. 15. While shown in fig. 15 as cross dichroic or x-cube prisms, beam combiner 1504 may be another type of beam combiner known in the art.

In one embodiment of digital projector 1500, the first, second, and third primary colors are red, green, and blue, respectively. When the input light 206 (1), 206 (2), and 206 (3) is monochromatic, the wavelength of each input light 206 (1), 206 (2), and 206 (3) may be selected such that the input light 206 (1), 206 (2), and 206 (3) represent spectrally pure red, green, and blue primary colors, respectively. In one such example, the wavelength of the input light 206 (1) representing the red primary color is one of 615nm, 640nm, and 655nm, the wavelength of the input light 206 (2) representing the green primary color is one of 525nm, 530nm, and 545nm, and the wavelength of the input light 206 (3) representing the blue primary color is one of 445nm, 450nm, and 465 nm. Alternatively, the input light 206 (1), 206 (2), and 206 (3) may be polychromatic, such that the red, green, and blue primary colors are not spectrally pure colors. The three primary colors may be a different set of colors than red, green, and blue without departing from the scope of the invention.

The digital projector 1500 increases PCR by increasing PCR for each primary color (e.g., red, green, and blue). Several optical processes used by digital projector 1500 depend on wavelength, including diffraction of input light 206 by DMD 200, refraction of modulated light 402 by TIR prism 1502, and focusing of modulated light 402 by lens 404. Thus, the fraunhofer diffraction pattern of each modulated light 402 (1), 402 (2), and 402 (3) is wavelength dependent. In one embodiment, the filter masks 412 (1), 412 (2), and 412 (3) are individually configured based on the wavelength of each of the respective input lights 206 (1), 206 (2), and 206 (3) to increase the PCR of the first, second, and third primary colors, respectively.

Fig. 16 shows an example of a multi-color digital projector 1600 that achieves PCR augmentation by time division multiplexing filtering of different color channels. Digital projector 1600 includes a DMD 200 and a filter 1610 having a filter wheel 1612. Fig. 17 is a graph of optical power versus time for time-division multiplexed light 1601 used as input light to digital projector 1600. Fig. 18 and 19 show examples of filter wheel 1612. Fig. 16 to 19 are best seen together in the following description.

The time division multiplexed light 1601 includes a repeating sequence 1702 of a plurality of time separated input lights 206. Although digital projector 1600 may be configured to accept and output input light having three different colors, fig. 17-19 and the following discussion may relate to a three-color embodiment of digital projector 1600. In this embodiment, the time division multiplexed light 1601 includes time-separated input light 206 (1), 206 (2), and 206 (3). Fig. 17 shows an example of time division multiplexed light 1601, where sequence 1702 includes a first pulse of input light 206 (1), a second pulse of input light 206 (2), and a third pulse of input light 206 (3). Input light 206 (1), 206 (2), and 206 (3) may represent red, green, and blue primary colors, respectively. The pulses of input light 206 (1), 206 (2), and 206 (3) spatially overlap to use the same DMD 200, filter 1610, and projector lens 112. In the example of fig. 17, pulses of input light 206 (1), 206 (2), and 206 (3) are depicted as having similar power (e.g., pulse height), duration (e.g., pulse width), and "off" time between pulses (e.g., pulse interval). Digital projector 1600 may accept input light 206 featuring other configurations of power, duration, and "off time without departing from the scope of the invention. For example, a selected one of the first, second, and third pulses of input light 206 (1), 206 (2), and 206 (3) may have a higher power to compensate for the lower diffraction efficiency of DMD 200 at the wavelength of the input light corresponding to the selected pulse.

DMD 200 is configured to synchronously modulate input light 206 (1), 206 (2), and 206 (3) of time-division multiplexed light 1601 into time-division multiplexed modulated light 1602 according to an image. In other words, the micromirrors 202 of the DMD 200 are manipulated to have a first configuration when the time division multiplexed modulated light 1602 is the first input light 206 (1), a second configuration when the time division multiplexed modulated light 1602 is the second input light 206 (2), and a third configuration when the time division multiplexed modulated light 1602 is the third input light 206 (3). The first, second and third configurations may be different. DMD 200 is an embodiment of SLM 102. DMD 200 may be replaced by another embodiment of SLM 102 (e.g., a reflective LCOS or transmissive LC phase modulator) in digital projector 1600 without departing from the scope of the present invention.

Filter 1610 is similar to filter 400 of fig. 4 except that filter wheel 1612 replaces filter mask 412. The filter wheel 1612 includes a plurality of filter masks 412 configured to synchronously filter the input light 206 (1), 206 (2), and 206 (3) of the time multiplexed modulated light 1602. For example, in embodiments where the filter wheel 1612 includes first, second, and third filter masks corresponding to the first, second, and third input lights 206 (1), 206 (2), and 206 (3), the motor 1614 rotates the filter wheel 1612 such that when the time division multiplexed modulated light 1602 is the first input light 206 (1), the first filter mask 412 intercepts and filters the time division multiplexed modulated light 1602 at the fourier plane 408, when the time division multiplexed modulated light 1602 is the second input light 206 (2), the second filter mask 412 intercepts and filters the time division multiplexed modulated light 1602 at the fourier plane 408, and when the time division multiplexed modulated light 1602 is the third input light 206 (3), the third filter mask 412 intercepts and filters the time division multiplexed modulated light 1602 at the fourier plane 408.

In one embodiment of digital projector 1600, motor 1614 rotates filter wheel 1612 in a stepwise manner to switch between different filter masks 412 in synchronization with the sequence of pulses of input light 206 (1), 206 (2), and 206 (3), while maintaining a fixed position of filter wheel 1612 during propagation of each of these pulses through fourier plane 408. In this embodiment, the motor 1614 operates as follows: before the pulses of input light 206 (1), 206 (2), and 206 (3) reach the fourier plane 408, the motor 1614 rotates the filter wheel 1612 to position the corresponding filter mask 412 in the path of the time division multiplexed modulated light 1602 at the fourier plane 408. After the corresponding filtered light pulse has completed propagating through the filter mask 412, the motor 1614 then rotates the filter wheel 1612, thereby positioning the next filter mask 412 in the path of the time division multiplexed modulated light 1602 at the fourier plane 408.

In some embodiments, the lens 404 implemented in the filter 1610 to focus the time division multiplexed modulated light 1602 may be configured to reduce chromatic aberration that causes the focal length of the lens 404 to change with wavelength. In one such embodiment, lens 404 is an achromatic lens designed to similarly focus on the wavelengths of input light 206 (1), 206 (2), 206 (3) such that the fourier planes corresponding to each of the three wavelengths are similarly positioned. In another such embodiment, lens 404 is an apochromatic lens, an ultra-chromatic lens, an objective lens, a compound lens having multiple lens elements, an assembly of several lenses and/or other optical elements, or another type of lens known in the art. The lens 404 may have one or more anti-reflective coatings that enhance the transmission of the time division multiplexed modulated light 1602 through the lens 404 at the wavelengths of the input light 206 (1), 206 (2), 206 (3).

In one embodiment, digital projector 1600 is configured with a collimating lens 1618 that collimates the filtered time division multiplexed light transmitted by filter wheel 1612 into collimated time division multiplexed light 1606 that is projected onto a screen by projector lens 112. In another embodiment, projector lens 112 is configured to accept uncollimated time-division multiplexed light, wherein digital projector 1600 does not include collimating lens 1618.

Fig. 18 is a front view of a filter wheel 1800 having three sectors 1802, each sector containing a filter mask. Filter wheel 1800 is an example of filter wheel 1612. The motor 1614 rotates the filter wheel 1800 about the axis 1804, and each rotation of the filter wheel 1800 corresponds to one sequence 1702 of time-division multiplexed light 1602. In some embodiments, motor 1614 rotates filter wheel 1800 in a stepwise manner as previously described. In the example of fig. 18, a first filter mask of a first sector 1802 (1) is shown as the example filter mask 900 of fig. 9, a second filter mask of a second sector 1802 (2) is shown as the example filter mask 1300 of fig. 13, and a third filter mask of a third sector 1802 (3) is shown as the example filter mask 1400 of fig. 14. However, the filter mask of sector 1802 may be configured with transmissive regions (e.g., transmissive region 416) having other shapes, sizes, and locations than those shown in fig. 18 without departing from the scope of the present invention.

In one embodiment, digital projector 1600 is configured to display images without some temporal artifacts, and for this purpose, sequence 1702 has a duration shorter than the response time of the human visual system. For example, the multiplexing frequency of the time-division multiplexed light 1601, which is equal to the inverse of the duration of the sequence 1702, may be higher than the flash fusion rate to take advantage of the persistence of vision. The multiplexing frequency may be 1 kilohertz or higher, corresponding to a pulse width of less than 1 millisecond for each of the input lights 206 (1), 206 (2), and 206 (3).

Fig. 19 is a front view of another filter wheel 1900 having six sectors 1902, each containing a filter mask. The motor 1614 rotates the filter wheel 1900 about the axis 1804 such that each complete revolution of the filter wheel 1900 corresponds to two consecutive iterations of the sequence 1702. One advantage of filter wheel 1900 over filter wheel 1800 is that filter wheel 1900 rotates at half the multiplexing frequency of time division multiplexed light 1601, thereby reducing the power consumption and speed requirements of motor 1614. In another embodiment, filter wheel 1612 has 3n sectors, where n is a positive integer. Each set of three sectors contains three filter masks and each complete revolution of the filter wheel 1900 corresponds to n successive iterations of the sequence 1702, thereby allowing the motor 1614 and filter wheel 1612 to rotate at a multiplexing frequency of 1/n times the time division multiplexed light 1601. In one use case, the motor 1614 rotates the filter wheel 1900 in a stepwise manner such that each filter mask of the filter wheel 1900 is stationary while filtering the corresponding pulses of input light 206.

Fig. 20 illustrates a method 2000 for improving the contrast of an image generated by a spatial light modulator. The method 2000 may be performed by the optical filter 400. The method 2000 includes a step 2002 of spatially fourier transforming the modulated light from the spatial light modulator onto a fourier plane. The modulated light includes a plurality of diffraction orders. In one example of step 2002, lens 404 spatially fourier transforms modulated light 402 onto fourier plane 408. The method 2000 further includes a step 2004 of filtering the modulated light after the fourier transform of step 2002. Step 2004 includes two steps 2006 and 2008 that may be performed simultaneously. Step 2006 transmits at least one diffraction order of the modulated light at the fourier plane. Step 2008 blocks the remainder of the modulated light at the fourier plane. In one example of steps 2006 and 2008, the filter mask 412 transmits at least one diffraction order of the modulated light 402 through the transmissive region 416 at the fourier plane 408 and blocks the remainder of the modulated light 402 at the fourier plane 408. In another example of steps 2006 and 2008, filter mask 412 transmits the zero-order diffraction order of modulated light 402 through transmissive region 416 at fourier plane 408 and blocks the remainder of modulated light 402 at fourier plane 408. In another example of method 2000, modulated light 402 is monochromatic light. In another example of method 2000, modulated light 402 is one of red, green, and blue light. In another example of method 2000, modulated light 402 is polychromatic light formed by combining red, green, and blue light. In this example, modulated light 402 may be white light. In one embodiment, the method 2000 further includes step 2010 after step 2006: at least one diffraction order of the transmitted modulated light is collimated. In one example of step 2010, collimating lens 418 collimates filter 414.

Fig. 21 illustrates a method 2100 for projecting a color image with increased contrast by filtering each color channel in a spatially multiplexed manner. Method 2100 may be performed by digital projector 1500. Method 2100 includes step 2102: the first, second and third input lights are spatially modulated according to the image to generate respective first, second and third modulated lights. The first, second and third input light represent light of three different respective color channels of a color image, e.g., as discussed above with reference to fig. 15. Each of the first modulated light, the second modulated light, and the third modulated light includes a plurality of diffraction orders. In one example of step 2102, DMDs 200 (1), 200 (2), and 200 (3) of fig. 15 spatially modulate respective first, second, and third input lights 206 (1), 206 (2), and 206 (3) into respective first, second, and third modulated lights 402 (1), 402 (2), and 402 (3). The method 2100 further includes step 2104: the first, second, and third modulated light (generated in step 2102) is filtered into respective first, second, and third filters. In one embodiment, step 2104 performs method 2002 on each of the first modulated light, the second modulated light, and the third modulated light to produce a first filter, a second filter, and a third filter. In one example of such an embodiment of step 2104, filter masks 412 (1), 412 (2), and 412 (3) of digital projector 1500 filter the fourier transformed respective first, second, and third modulated lights 402 (1), 402 (2), and 402 (3) into respective first, second, and third filtered lights 414 (1), 414 (2), and 414 (3). Step 2104 includes steps 2106 and 2108, which may be performed simultaneously. Step 2106 transmits at least one diffraction order for each of the first modulated light, the second modulated light, and the third modulated light. Step 2108 blocks the remaining portions of the first, second, and third modulated light. In one example of steps 2106 and 2108, filter masks 412 (1), 412 (2), and 412 (3) of digital projector 1500 transmit at least one diffraction order of each of the first, second, and third modulated lights 402 (1), 402 (2), and 402 (3) after fourier transform and block the remaining portions of the first, second, and third modulated lights 402 (1), 402 (2), and 402 (3). The method 2100 further includes step 2110: the first, second, and third filters generated in step 2104 are combined to form output light. In one example of step 2110, beam combiner 1504 combines first, second, and third filters 414 (1), 414 (2), and 414 (3) into output light 1510. In an embodiment, method 2100 further includes a step 2112 of projecting output light onto a screen. In one example of step 2112, projector lens 112 projects output light 1510 onto a screen, such as screen 116.

The method 2100 may be extended to handle only two color channels, or more than three color channels, such as four color channels, without departing from the scope of the present invention.

Fig. 22 illustrates a time division multiplexing method 2200 for generating and projecting color images with increased contrast. Method 2200 may be performed by digital projector 1600. The method 2200 includes the steps 2202: the time-division multiplexed light is modulated by a spatial light modulator according to a color image to be projected to generate time-division multiplexed modulated light having a repeating sequence of first modulated light, second modulated light, and third modulated light. The first modulated light, the second modulated light and the third modulated light represent light of three different respective color channels of a color image, e.g., as discussed above with reference to fig. 16. In one example of step 2202, DMD 200 of digital projector 1600 modulates time-division multiplexed light 1601 into time-division multiplexed modulated light 1602. The method 2200 further comprises step 2204: the time division multiplexed modulated light (generated in step 2202) is spatially fourier transformed with a lens. In one example of step 2204, lens 1604 performs a spatial fourier transform on time multiplexed modulated light 1602. The method 2200 further comprises step 2206: the time division multiplexed modulated light that has been spatially fourier transformed in step 2204 is filtered by rotating the filter wheel in synchronization with the time division multiplexed modulated light. The filter wheel includes a plurality of filter masks, each configured to filter a corresponding one of the first, second, and third modulated lights spatially fourier transformed by the lens in step 2204. When the time division multiplexed modulated light is a corresponding one of the first, second, and third modulated light, step 2206 rotates the filter wheel to position each filter mask in the spatially fourier transformed light. In one example of step 2206, the motor 1614 rotates the filter wheel 1612 in synchronization with the time division multiplexed modulated light 1602, as discussed above with reference to fig. 16. In another example of step 2206, the motor 1614 rotates the filter wheel 1612 in a stepwise manner such that each filter mask is stationary while the corresponding modulated light is filtered. In one embodiment, the method 2200 further comprises step 2208: the filtered time-division multiplexed modulated light is projected onto a screen. As an example of step 2208, projector lens 112 projects the time-division multiplexed light filtered by filter mask 1612 and optionally collimated by collimating lens 1618 onto a projector screen.

The method 2200 may be extended to handle only two color channels, or more than three color channels, such as four color channels, without departing from the scope of the invention.

Numerical analysis

The following discussion is related to numerical analysis to investigate how the contrast ratio of a digital projector configured with DMD 200 depends ON various parameters including wavelength, ON and OFF tilt angles of micromirrors 202, tolerances of ON and OFF tilt angles, geometry of transmissive regions 416 of filter mask 412, angular and spectral diversity of input light 206, and the effective size of the illumination source generating input light 206. The digital projectors 100, 500, 1500, and 1600 may be configured according to parameters studied in these numerical analyses.

Fig. 23 is a side view of a simulation experiment 2300 in which the numerical results of the simulation experiment are presented. In the simulation experiment 2300, the DMD 200 modulates the input light 206 into modulated light 402 comprising a plurality of diffraction orders. The fraunhofer diffraction pattern of modulated light 402 is calculated and spatial filter 2302 is modeled by marking each diffraction order of fraunhofer diffraction pattern as transmitted or blocked by spatial filter 2302, depending on the geometry and configuration of spatial filter 2302. Spatial filter 2302 is one example of a filter mask 412. The contrast ratio of the simulation experiment 2300 was obtained by integrating the values of the diffraction orders marked as transmitted by the spatial filter 2302 once the micromirror 202 of the DMD 200 was configured in the ON position, and also when the micromirror 202 of the DMD 200 was configured in the OFF position. These two numerical integrals correspond to the ON and OFF luminous intensities, respectively, the ratio of which defines the contrast ratio.

The fraunhofer diffraction pattern of simulation experiment 2300 may be calculated using the Rayleigh-solfei form system of scalar diffraction theory (Rayleigh-Sommerfeld formalism). This form of system is characterized by rayleigh-solifeine integration, which represents the complex amplitude of the diffracted electric field as an integral (e.g., sum) over a spherical wave.

It should be understood that the numerical analysis presented herein is not limited to a DMD 200, but can be easily extended to other embodiments of the SLM 102, such as a reflective LCOS phase modulator or a transmissive LC phase modulator.

Fig. 24 to 26 are numerical graphs of contrast ratio and light efficiency versus half angle obtained for the simulation experiment 2300. To produce the results of fig. 24-26, spatial filter 2302 is modeled as a circular aperture centered on optical axis 422 and having aperture diameter 2304. Spatial filter 2302 is centered ON the zero order diffraction order of modulated light 402 (e.g., first ON and OFF diffracted beams 504 (1) and 604 (1)). The circular aperture of spatial filter 2302 forms the bottom of a cone with its apex centered on the front face of DMD 200, with the axis of the cone coincident with optical axis 422. Half angle 2308 is defined herein as half the apex angle of the cone.

In fig. 24 to 26, wavelengths of light of 532nm, 465nm, and 617nm, respectively, were used in the simulation experiment 2300. For the micro mirrors 202 of the DMD 200, nominal ON and OFF position tilt angles of +12 degrees and-12 degrees, respectively, are used. The DMD 200 uses 81% and 90% size and area fill factors, respectively.

As half angle 2308 in fig. 24 decreases, green contrast ratio 2402 increases with a series of "steps" because spatial filter 2302 increasingly blocks the diffraction orders of modulated light 402. The highest green contrast ratio of 757,000:1 is obtained when spatial filter 2302 transmits only the zero diffraction order of modulated light 402. As half angle 2308 increases, green light efficiency 2404 increases with a series of "steps" because spatial filter 2302 is increasingly transmitting diffraction orders. Since most of the optical power of the green modulated light is in low diffraction orders (e.g., zero, first order, and second order diffraction orders), the largest step in green efficiency 2404 occurs at a smaller value of half angle 2308. At the highest green contrast ratio, green light efficiency 2404 is about 80%, i.e., 80% of modulated light 402 is transmitted by spatial filter 2302.

In fig. 25, the blue contrast ratio 2502 and blue light efficiency 2504 appear similar to the green contrast ratio 2402 and green light efficiency 2404, respectively. The highest blue contrast ratio of 850,000:1 is obtained when spatial filter 2302 transmits only the zero diffraction order of modulated light 402. At the highest blue contrast ratio, blue light efficiency 2504 drops rapidly from 80% to below 50%.

In fig. 26, the red contrast ratio 2602 and the red light efficiency 2604 appear similar to the green and blue contrast ratios 2402, 2502 and the green and blue light efficiencies 2404, 2504, respectively. However, the highest red contrast ratio is only 450,000:1. One of the reasons for the highest red contrast ratio being lower than the corresponding highest green and blue contrast ratios is that at a red wavelength of 617nm, DMD 200 is illuminated farther from the sparkle condition. At the highest red contrast ratio, the red light efficiency 2604 is about 80%.

FIG. 27 is a Fraunhofer diffraction pattern of simulation experiment 2300 when the wavelength of light is 532nm and all of micromirrors 202 of DMD 200 are in the ON position. In fig. 27, each of the four brightest diffraction orders is enclosed by one of the boxes 2702. Block 2702 (1) contains the maximum optical power and corresponds to the zero diffraction order of modulated light 402. For each block 2702, DOCR is calculated using the block 2702 as a rectangular aperture (e.g., transmission region 416) of the spatial filter 2302. The numerical calculated DOCR is printed in each box. For example, in block 2702 (1), the zero diffraction order of modulated light 402 has DOCR of 758,075:1. In one embodiment, filter mask 412 is configured to transmit the zero diffraction order of modulated light 402 and block all other diffraction orders; filter mask 900 is one example of a filter mask 412 that may be used with this embodiment. In another embodiment, filter masks 412 (1), 412 (2), and 412 (3) of digital projector 1500 may each be configured to transmit the zero-order diffraction orders of modulated light 402 (1), 402 (2), and 402 (3) and block all other diffraction orders.

Fig. 28 is a fraunhofer diffraction pattern of simulation experiment 2300 when the wavelength of light is 617nm and all micromirrors 202 of DMD 200 are in the ON position. In fig. 28, the four diffraction orders contain most of the optical power of modulated light 402. In this figure, compared to fig. 27, a wavelength of 532nm is used, and since the wavelength of 617nm is farther from the blaze condition of the DMD 200, the optical power is more uniformly distributed among the four diffraction orders. By forming spatial filter 2302 that transmits only the diffraction orders in block 2802 (1), contrast ratios as high as 852,000:1 can be obtained. However, by blocking the diffraction orders in blocks 2802 (2), 2802 (3), and 2802 (4), the light efficiency will be greatly reduced.

As a tradeoff between contrast ratio and light efficiency, spatial filter 2302 may be configured to transmit the three diffraction orders with highest DOCR, corresponding to boxes 2802 (1), 2802 (2), and 2802 (4). In this example of spatial filter 2302, the apertures corresponding to boxes 2802 (1), 2802 (2), and 2802 (4) are not symmetrically positioned about optical axis 422. In one embodiment, according to fig. 28, the filter 400 is configured to transmit three diffraction orders of modulated light 402; filter mask 1300 is one example of a filter mask 412 that may be used with this embodiment. In other embodiments, filter 412 is configured to transmit a non-zero integer number of diffraction orders of modulated light 402 up to a maximum number determined by the clear aperture of lens 404.

Fig. 29 is a graph of the numerical values of contrast ratio 2902 versus light efficiency 2904 obtained for a simulation experiment 2300 operating at a wavelength of 617nm when the ON and OFF tilt angles of the micro mirror 202 are +12.1 degrees and-12.1 degrees, respectively. The contrast ratio may be sensitive to small changes in the tilting angle of the micromirror. Changing the tilt angle by 0.1 degrees compared to fig. 26 increases the maximum red contrast ratio by more than 2 times, almost to 1,000,000:1, while the red light efficiency 2904 remains at about 80%. For comparison purposes, commercial DMDs are typically designated as having a tilt angle tolerance of ±0.5 degrees.

Fig. 30 and 31 are numerical graphs of contrast ratio versus micromirror inclination angle obtained for the simulation experiment 2300. In fig. 30, the OFF position inclination angle is fixed at-12 degrees, and the ON position inclination angle varies between 11.5 degrees and 12.5 degrees. In fig. 31, the ON position inclination angle is fixed at +12 degrees, and the OFF position inclination angle varies between-12.5 degrees and-11.5 degrees. In fig. 30, contrast ratios 3002, 3004, and 3006 correspond to wavelengths of 617nm, 465nm, and 532nm, respectively. In fig. 31, contrast ratios 3102, 3104, and 3106 correspond to wavelengths of 617nm, 465nm, and 532nm, respectively. Fig. 30 and 31 are best seen together in the following description.

In general, the value of the contrast ratio is more sensitive to the variation of the OFF luminous intensity than to the ON luminous intensity. Thus, the contrast ratio may be more significantly dependent ON the OFF tilt angle than ON tilt angle. As shown in fig. 30, in the case where the ON inclination angle is within the inclination angle tolerance of ±0.5 degrees, the contrast ratios 3002, 3004, and 3006 show extremely small changes. On the other hand, in the case where the OFF-tilt angle is within a similar angular tolerance, the contrast ratios 3102, 3104, and 3106 of fig. 31 vary significantly more.

Fig. 32 is a graph of the contrast ratio 3202 and optical efficiency 3204 obtained for the simulation experiment 2300 at 532nm wavelength as a function of angular diversity of the input light 206. Fig. 33 and 34 are fraunhofer diffraction patterns of the simulation experiment 2300, showing the broadening of diffraction peaks due to the angular diversity of the input light 206. In fig. 33, the input light 206 is a plane wave without angle diversity. In fig. 34, the input light 206 has an angle diversity half angle of 8 degrees. To obtain the data in fig. 32, spatial filter 2302 is configured to have a rectangular aperture, represented by block 3302 in fig. 33 and 34. Fig. 32 to 34 are best seen together in the following description.

In cinema and other critical viewing environments, digital laser projection of images benefits from angular diversity and reduced laser illumination coherence, as this reduces the visibility of dust and other deleterious diffraction artifacts. It is also beneficial for the laser illumination to have an increased bandwidth to reduce the visibility of spots on the screen.

Angular diversity and bandwidth increase of laser illumination may reduce the contrast ratio of the filtering systems and methods presented herein. Specifically, at the fourier plane, the increased angular diversity and bandwidth may broaden the diffraction peaks, causing their tails to blur from other tails of adjacent peaks. This broadening of the peaks may prevent individual diffraction orders from transmitting through spatial filter 2302, nor transmitting a portion of adjacent diffraction orders that are intended to be blocked. As shown in fig. 32, as the half angle of the input light 206 increases to 8 degrees, the contrast ratio decreases by half from 721,000:1 to 346,000:1.

Thus, when angular diversity and spectral bandwidth are considered, a tradeoff is required between (1) dust visibility and reduced speckle to (2) contrast ratio.

It should be appreciated that the contrast reduction may be due to factors other than diffraction of input light 206 by DMD 200, such as scattering of input light 206 from the surface of micro-mirrors 202, undesirable stray light and reflection, optical aberrations, and/or polarization effects in the projection chamber. However, in most digital projectors, diffraction of DMD 200 is expected to be the primary source of contrast degradation, or at least one primary source. The disclosed systems and methods can be easily extended to scenes where contrast is reduced by other factors in addition to diffraction, such as those listed above. The disclosed systems and methods are capable of enhancing contrast even in the presence of other such factors.

Experimental results of the optical filter

The numerical analysis presented above has been verified using an experimental setup similar to that shown in fig. 4. To demonstrate the highest contrast, the experimental setup was configured to filter the zero diffraction order at 532 nm. The filter mask 412 is configured to have a circular aperture centered on the optical axis 422. The diameter of the circular aperture and the lens (e.g., lens 404) are selected to form a 2 degree half angle at the fourier plane. Input light is provided to DMD 200 by a 532nm polarized laser having M ² < 1.1. The input light is spread to fill the front face of DMD 200 using a galilean beam expander formed of two doublets, which results in diffraction limited performance. For simplicity, no TIR prism is used to couple light to DMD 200.DMD 200 operates at the brightest (e.g., white level) and darkest (e.g., black level) outputs and measures contrast using a spectrometer.

The contrast ratio of two identical 4K DMDs was measured. The contrast ratio predicted by simulation experiment 2300 is approximately 757,000:1 at 532nm and 2 degree half-angles (see highest green contrast ratio in fig. 24). The contrast ratios were measured to be 254,234:1 and 277,966:1. These values are approximately one third of the predicted values; the differences are due to overfilled stray light from the DMD, stray light from gaps between the micromirrors of the DMD, and scattering from the surfaces and edges of the micromirrors.

It has also been observed that the propagation direction of the input light 206 towards the DMD 200 affects the contrast ratio as expected in view of the dependence of the contrast ratio on the OFF tilt angle. In addition, it has been observed that the polarization of the input light 106 affects the black level of the DMD 200, thereby affecting the contrast ratio. For the experimental results described above, a wave plate was used to rotate the polarization of the input light to maximize contrast.

In view of the sensitivity of the contrast ratio to the micromirror tilt angle and the propagation direction of the input light 206, combining (binning) can be used to group DMDs with similar tilt angles. In one embodiment of three-color digital projector 1500, three combined DMDs with similar tilt angles are used for DMDs 200 (1), 200 (2), and 200 (3). In another embodiment, three combined DMDs (e.g., from three different bins) with different tilt angles are used for DMDs 200 (1), 200 (2), and 200 (3), each DMD having a tilt angle selected to maximize the contrast ratio of a particular wavelength of input light 206 used by the DMD.

Advantages of the optical filter

One advantage of the filter systems and methods presented herein is that the contrast ratio can be increased without the use of an additional DMD. For example, as an alternative to the disclosed systems and methods, the contrast ratio may be increased by using multi-level modulation, i.e., two or more DMDs connected in series such that the OFF diffracted beam from the first DMD is blocked by the second DMD. As a method of increasing the contrast ratio, multi-level modulation disadvantageously increases the cost and complexity of the digital projector due to the second DMD and corresponding electronics. In addition, one type of digital projector uses three DMDs, one for each of red, green, and blue light; in this type of digital projector, the use of two DMDs per color increases the total number of DMDs from three to six, further increasing cost and complexity.

Another advantage of the filtering systems and methods presented herein is that the filtered projection light can reduce the occurrence of moire patterns (moire patterns) due to interference between unfiltered projection light and periodic perforations of a screen onto which the projection light is projected. In particular, the filtering may be configured to reduce the high frequency component of the projected light, thereby "smoothing" the hard edges between pixels appearing on the screen. Smoothing reduces the beat (beating) between the periodic intensity of the projected light and the periodic perforations of the screen.

Yet another advantage of the filtering systems and methods presented herein is that filtering can increase the contrast ratio of digital projectors with tilted and scrolling pixel (TRP) DLP chips from texas instruments, usa. The micromirrors of the TRP DLP chip are not tilted about an axis oriented at 45 degrees (e.g., the micromirror rotation axis 208 of fig. 2). As a result, compared to other types of DMD chips, the modulated light propagates away from the TRP chip, making the diffraction order of OFF-state light (e.g., OFF diffraction beam 604 of fig. 6) brighter, thereby increasing the OFF luminous intensity and decreasing the contrast ratio. By reducing the OFF luminous intensity, the filtering systems and methods presented herein advantageously enable TRP chips to be included in projectors for applications requiring high contrast ratios, which should be projections such as according to the Digital Cinema Initiative (DCI) specification.

Example projection lens System

In some embodiments, the optical filter is provided within the projection lens architecture. Fig. 35 is an exploded view of an exemplary projection lens system in accordance with aspects of the present disclosure. Projection lens system 3500 is one example of projection lens 112 shown in fig. 1. To allow access to the fourier aperture, projection lens system 3500 has a modular design. Projection lens system 3500 includes a fourier portion 3501 (e.g., fourier lens assembly, lens 404), an aperture 3502, and a zoom portion 3503 (also referred to as a zoom lens assembly) configured to form a fourier transform of an object at an exit pupil as previously described. The spatial fourier transform applied by fourier portion 3501 converts the propagation angle of each diffraction order of the modulated light into a corresponding spatial position on the fourier plane. Fourier portion 3501 is thus able to achieve selection of desired diffraction orders and rejection of undesired diffraction orders by spatial filtering at the fourier plane. The spatial fourier transform of the modulated light at the fourier plane is equivalent to the fraunhofer diffraction pattern of the modulated light.

Fourier portion 3501 includes a first attachment section 3504, which may include threads, fasteners, or the like. The zoom portion 3503 includes a second attachment section 3505, which may include complementary threads, fasteners, etc., to allow mating with the first attachment section 3504. In one example, the first attachment segment 3504 includes an externally threaded portion and the second attachment segment 3505 includes an internally threaded portion, or vice versa. In another example, the first and second attachment segments 3504, 3505 are configured as friction fits, in which case one or more fastening elements, such as screws, cams, flanges, etc., may be provided. In yet another example, the first attachment section 3504 may include one or more radial pins and the second attachment section 3505 may include a corresponding number of L-shaped grooves, or vice versa, to connect the fourier portion 3501 and the zoom portion 3503 using a bayonet connection. By way of these examples, fourier portion 3501 may be removably attached to zoom portion 3503 to provide a modular assembly as will be described in more detail below.

Although fig. 35 illustrates the fourier portion 3501 and the zoom portion 3503 as being completely separable, the present disclosure is not limited thereto. In some implementations, fourier portion 3501 and zoom portion 3503 can only be partially separated, for example, by disposing the proximity portion in one of fourier portion 3501 and zoom portion 3503. The access portion may be a slot, door, window, etc. that allows an operator to access and/or replace the aperture 3502 via the access portion. In such embodiments, the fourier portion 3501 and the zoom portion 3503 can be bonded (e.g., via adhesive on the first attachment segment 3504 and/or the second attachment segment 3505) to prevent complete separation. Alternatively, the fourier portion 3501 and the zoom portion 3503 may be provided with an integral housing including an attachment portion.

Aperture 3502 may be one example of filter mask 412 shown in fig. 4. Aperture 3502 is configured to block a portion of light (e.g., modulated light corresponding to one or more diffraction orders) in projection lens system 3500. As illustrated in fig. 35, the aperture 3502 is a square opening having sides of, for example, 6mm in length. Fig. 35 also illustrates an optical axis 3510 of projection lens system 3500. After assembly, the fourier portion 3501 and the zoom portion 3503 are substantially coaxial with each other and with the optical axis 3510. In some implementations (e.g., depending on the illumination angle), the aperture 3502 is further substantially coaxial with the optical axis 3510.

Projection lens system 3500 can include or be associated with one or more non-optical elements including a heat sink device such as a heat sink (or cooling fins), one or more adhesives (or fasteners), and the like. In some embodiments, the aperture 3502 may block, and thus absorb, approximately 15% of the incident light, and thus the heat sink or cooling fins may be positioned and configured to properly dissipate heat from the aperture 3502. In some embodiments, aperture 3502 is thermally isolated from other portions of projection lens system 3500.

Together, fourier portion 3501 and aperture 3502 operate as a fourier lens with a spatial filter, which fourier lens can also be used as a stationary projection lens. In other words, the fourier portion 3501 and the aperture 3502 can be used together as the filter 110 or the filter 400. The zoom portion 3503 illustrated in fig. 35 may be one of a series of zoom lens assemblies configured to be attached to the fourier portion 3501, thereby creating a series of projection zoom lens systems and accommodating different theaters. In other words, the fourier portion 3501 and the aperture 3502 can be adapted for any theatre setting, while the zoom portion 3503 provides a particular projected light pattern tailored for a particular theatre. Thus, by selecting a particular zoom portion 3503 from a series of zoom lens components, and attaching the selected zoom portion 3503 to the fourier portion 3501 and the aperture 3502, a projection lens system 3500 that accommodates a particular theater can be implemented.

Both the fourier portion 3501 and the zoom portion 3503 may include a plurality of individual lens elements. Exemplary configurations of lens elements of the fourier portion 3501 and the zoom portion 3503 are illustrated in fig. 36 and 37, respectively.

Fig. 36 illustrates exemplary optics of an exemplary fourier portion 3600 that includes a prism 3601 (only a portion of which is shown in fig. 36) and a fourier lens system 3602 that includes a plurality of lenses (also referred to as lens elements). Also illustrated is a fourier plane 3603 of fourier lens system 3602, and an exemplary ray 3610 for illustrating the optical behavior of fourier portion 3600. Fourier lens system 3602 may be contained within a housing of fourier portion 3501 illustrated in fig. 35. In some examples, prism 3601 is also contained within the housing of fourier portion 3501; however, in other examples, prism 3601 may be located optically upstream of projection lens system 3500 and optically downstream of a modulator (such as DMD 200). The fourier plane 3603 may correspond to the position of the aperture 3502 approximately (e.g., within 10 mm).

The individual lens elements that make up fourier lens system 3602 may be selected so as to produce a low distortion image at infinity with the exit pupil at fourier plane 3603. Reducing the aberrations of fourier lens system 3602 may make it easier to design one or more associated zoom portions. The distortion of the particular fourier lens system 3602 illustrated in fig. 36 is less than 0.1%.

Fourier lens system 3602 is telecentric; exhibit low wavefront errors, thereby minimizing any impact on fourier plane 3603 imaging; exhibit low lateral chromatic aberration; introducing low distortion; and includes an exit pupil (approximately coincident with fourier plane 3603) at a distance d _f from the nearest optical element, thereby mitigating small area thermal loads on the nearest optical element. As illustrated, the nearest optical element is the downstream surface of the last lens included in fourier lens system 3602. The minimum size of the distance d _f for sufficiently reducing the thermal load depends on the parameters of the fourier lens system 3602, including the type of material of the lenses in the fourier lens system 3602 and/or the type of material of the aperture 3502 that will be located substantially at the fourier plane 3602. The size of d _f >12mm can sufficiently reduce the small-area heat load; however, in some embodiments, the distance d _f is preferably equal to about 40mm (e.g., within 10% thereof).

In addition to prism 3601 and fourier lens system 3602, fourier portion 3600 may include other optical elements. In some examples, fourier portion 3600 may include one or more electronic crystals (e.g., a transmissive liquid crystal component that imparts a deflection to light passing therethrough based on an applied voltage profile) or other deflection elements, thereby shifting a projected image on screen 116.

Furthermore, if refocused, fourier lens system 3602 may be used as a projection lens, allowing adjustment of the fourier aperture and/or contrast of the projected image to facilitate calibration or defect detection, etc., without having to disassemble the entire projection lens system 3500.

In addition to serving as part of projection lens system 3500, fourier portion 3600 may have additional applications due to its separability from other elements in projection lens system 3500. Such additional applications may include facilitating calibration or installation of projector 100. For example, fourier portion 3600 may be used as a stand-alone optical system to test convergence and focus of a DMD (including but not limited to DMD 200); may be used to provide a preliminary view of potential image quality problems with elements of projector 100; may be used to facilitate sizing and positioning of the fourier aperture 3502; or may be used to measure the on/off contrast of projector 100. Alternatively, a simplified fixed lens may be attached to fourier portion 3600 for calibration, testing, defect detection, sizing and positioning, measurement, etc. purposes.

Fig. 37 illustrates an exemplary optic of an exemplary zoom portion 3700 in several zoom configurations. The zoom portion 3700 includes a fixed lens group 3701, a first movable lens group 3702, a second movable lens group 3703, and a fourth movable lens group 3704. Also illustrated is a fourier plane 3705, and an exemplary ray 3710 illustrating the optical behavior of the zoom portion 3700. The lens group illustrated in fig. 37 may be contained in a housing of the zoom portion 3503 illustrated in fig. 35. When the zoom portion 3700 and the fourier portion 3600 are assembled together, the fourier plane 3603 and the fourier plane 3705 may correspond to each other, and may be further positioned approximately at the position of the aperture 3502.

In addition to the fixed lens group 3701, the first movable lens group 3702, the second movable lens group 3703, and the third movable lens group 3704, the zoom portion 3700 may include other optical elements. In some examples, zoom portion 3700 may include an electronic crystal or other deflection element to offset the projected image on screen 116.

Zoom portion 3700 functions in a manner similar to a telescope. That is, suppose that the object of the zoom portion 3700 approaches infinity, and the image side of the zoom portion 3700 is configured to generate a real image at a common screen distance (e.g., 10-30 m). The zoom portion 3700 illustrated in fig. 37 is configured for a series of zoom configurations, depending on the specific positions of the first movable lens group 3702, the second movable lens group 3703, and the third movable lens group 3704. By appropriately moving the first movable lens group 3702, the second movable lens group 3703, and the third movable lens group 3704, the projection ratio of the zoom portion 3700 (i.e., the distance between the zoom portion 3700 and the screen 116 divided by the width of the screen 116) can be changed. In the particular example illustrated in fig. 37, zoom portion 3700 is configured to provide a range of zoom configurations from a 2:1 projection ratio (top configuration) to a 3:1 projection ratio (bottom configuration) with the exemplary DMD. However, in the actual embodiment, the range of the zoom configuration is not limited thereto. In some examples, the projection ratio may be between 1.2:1 and 4:1 (inclusive).

In some implementations, the zoom portion 3700 is not configured for a range of zoom configurations, but is provided with a fixed projection ratio. In such an embodiment, the first, second, and third movable lens groups 3702, 3703, and 3704 of fig. 37 may be replaced with corresponding fixed lens groups. For example, to provide the zoom portion 3700 with a fixed projection ratio of 2:1, the top configured first, second, and third movable lens groups 3702, 3703, and 3704 in fig. 37 may be replaced with a second, third, and fourth fixed lens groups, respectively. The fixed projection ratio may be between 1.2:1 and 4:1 (inclusive). Zoom portion 3700 can still be referred to as a "zoom" portion, regardless of whether the zoom portion includes a movable lens group to provide a range of projection ratios or only a fixed lens group to provide a fixed projection ratio.

Because fourier lens system 3602 produces an image of the DMD (e.g., DMD 200) at infinity (if so placed), zoom portion 3700 operates as a zoom telescope. Furthermore, the particular design of the lenses and lens groups in zoom portion 3700 may be independent of the particular design of fourier lens system 3602. The complexity of the variable focus lens package is related to the degree of aberration correction achieved. In some aspects of the present disclosure, the performance of the complete projection lens system 3500 meets the Digital Cinema Initiative (DCI) image specification; for example, DCI Digital Cinema System Specification (DCSS) release 1.3 or an updated release.

Fourier portion 3600 and zoom portion 3700 may be combined to achieve a complete lens system. Fig. 38 illustrates an exemplary assembled lens configuration according to such a combination. In fig. 38, elements having the same reference numerals as those previously described are denoted by the same reference numerals, and detailed description of these elements is not repeated here. Fig. 38 illustrates an assembled lens configuration with zoom portion 3700 in a 2:1 projection ratio configuration (top, corresponding to the top of fig. 38) and zoom portion 3700 in a 3:1 projection ratio configuration (bottom, corresponding to the bottom of fig. 38).

Fourier portion 3600 and zoomed portion 3700 are assembled such that fourier plane 3603 of fourier portion 3600 and fourier plane 3705 of zoomed portion 3700 are coplanar. Because the two parts are joined in a collimated or substantially collimated optical space, the tolerance requirements for mating the two parts are relaxed. For example, even in the case where the optical axes of the fourier portion 3600 and the zoom portion 3700 are misaligned (e.g., one of the two portions is shifted in a direction perpendicular to the optical axis) so that the aperture spot is shifted from the optical axis, there may be no significant loss of image quality, although the projected image on the screen 116 may be shifted. In some examples, fourier portion 3600 and zoom portion 3700 are considered substantially coaxial if the optical axis of fourier portion 3600 is parallel to the optical axis of zoom portion 3700 and within 1mm of each other.

Prism projection system

The filter 110 of fig. 1 may be implemented within a variety of light projector systems. Fig. 39 illustrates one possible embodiment of an image projector display system 3900. Projector display system 3900 may be a dual modulator/multi-modulator projector system 3900. Projector display system 3900 employs a light source 3902 that supplies the desired illumination to projector display system 3900 such that the final projected image is sufficiently bright for the intended viewer of the projected image. Light source 3902 may include any possible suitable light source, such as a xenon lamp, a laser, a Light Emitting Device (LED), a coherent light source, a partially coherent light source, and the like.

In some embodiments, light source 3902 projects light 3904 that illuminates first modulator 3906. The first modulator 3906 may then illuminate the second modulator 3910 via a set of optical components 3908. The light from the second modulator 3910 may be projected by a projection lens 3912 (or other suitable optical component) to form a final projected image on a screen 3914. Projection lens 3912 may be, for example, projection lens system 3500. The first modulator 3906 and the second modulator 3910 may be controlled by a controller 3916, which may receive input image and/or video data. The controller 3916 may perform certain image processing algorithms, gamut mapping algorithms, or other suitable processing on the input image/video data and output control/data signals to the first modulator 3906 and the second modulator 3910 in order to achieve a desired final projected image. In addition, in some projector systems, the light source 3902 may be modulated in order to achieve additional control over the image quality of the final projected image.

The light recovery module 3903 is depicted in fig. 39 as a dashed box that may be placed in the optical path from the light source 3902 to the first modulator 3906. It should be appreciated that light recycling may be inserted into projector display system 3900 at various points in projector display system 3900. For example, light recycling may be placed between the first modulator 3906 and the second modulator 3910. In addition, light recycling may be placed at more than one point in the optical path of the display system. While such an embodiment may be more expensive due to an increase in the number of components, such an increase may be balanced against the energy costs saved due to the light recovery at multiple points.

While the embodiment of FIG. 39 is presented in the context of a dual-modulation, multi-modulation projection system, it should be appreciated that the techniques and methods of the present application will apply to single-modulation or other dual-modulation, multi-modulation display systems. For example, a dual modulation display system including a backlight, a first modulator (e.g., LCD, etc.), and a second modulator (e.g., LCD, etc.) may employ suitable blur optics and image processing methods and techniques to affect the performance and efficiency discussed herein in the context of a projection system.

It will also be appreciated that even though fig. 39 depicts a two-level or dual modulator display system, the methods and techniques of the present application may be applied to display systems having only one modulator or display systems having three or more modulators (multi-modulator) display systems.

In at least some embodiments, the present disclosure provides a method of simplifying a multi-chip (e.g., 3-chip) projection system with reduced size and cost. In some embodiments, a multi-chip projection system may use separate illumination assemblies for each color channel, allowing independent control of illumination angles. The disclosed techniques may be used with projection systems such as those disclosed in U.S. patent application 17/043,734, U.S. patent application 17/439,786, U.S. patent application 17/280,009, PCT patent application PCT/US2021/028827, PCT patent application PCT/US 2020/0631169, the entire disclosures of which are hereby incorporated by reference in their entirety for all purposes.

Fig. 40 illustrates an example projection system 4000 that includes a nine-piece prism system and a plurality of illumination assemblies. Projection system 4000 includes a number of individual color illumination assemblies 4004 that receive fiber optic input 4002 for each color prism, respectively. For example, the projection system includes a first fiber optic input 4002A associated with red light provided to a first illumination assembly 4004A. The second fiber optic input 4002B is associated with blue light provided to the second lighting assembly 4004B. The third fiber input 4002C is associated with green light provided to the third illumination assembly 4004C. The color beams output from each illumination assembly 4004 are fed into a modulator 4006. Modulator 4006 comprises a nine-piece prism 4008 and at least one reflector apparatus 4010. The function of the reflector device 4010 can be similar to the SLM 102 as previously described. The nine-piece prism 4008 relays each color beam received from each illumination assembly 4004 into projection optics 4014 (e.g., a projection lens). In some embodiments, each color beam is individually modulated by a respective reflector device 4010 prior to combining. The modulated color beams are then combined into an output that is provided to projection optics 4014. A controller 4012 can be coupled to the reflector arrangement 4010 to control the modulation of each color beam. The nine-piece prism 4008 can be a High-9 prism such as disclosed in U.S. patent application 15/540,946, the entire disclosure of which is hereby incorporated by reference in its entirety for all purposes.

In some embodiments, each illumination assembly 4004 comprises an integrator rod (e.g., integrator tube, integrator box) that receives light from a respective fiber optic input 4002. The integrator rod may include a substantially reflective surface within its interior such that light incident on its surface is reflected until the light exits. Once the light exits the integrator rod, illumination assembly 4004 may include a set of optical elements, such as lenses, filters, and/or polarizers, that optically act on the light before passing the light to modulator 4006.

Additionally, in some embodiments, a white light 3-chip TIR prism (e.g., 5 parts or 6 parts) may be used with a single illumination assembly. This is achieved by modulator conditions and performance requirements that enable the use of a single illumination angle that is common across color channels.

Fig. 41 illustrates an example projection system 4100 that includes a single illumination assembly 4104. The illumination assembly 4104 receives white light from the white light fiber 4102 and feeds the white light into the modulator 4106. The modulator 4106 comprises a white light prism 4108 and at least one reflector device 4110. While the conventional white light prism includes three parts, the white light prism 4108 includes additional prism parts. For example, a spectral filter such as a yellow notch filter may be provided in the white light prism 4108. The additional component may be used as a TIR prism. In some embodiments, modulator 4106 may include three reflector devices (e.g., 3 chips) for modulating the received white light. The white light prism 4108 splits the white light into several color beams (e.g., three color channels), one for each reflector device 4110. A controller may be coupled to each reflector device 4110 to control the modulation of each color beam. The reflector apparatus 4110 then modulates their respective color beams before combining the modulated color beams. In other embodiments, the reflector device 4110 may directly modulate white light. In both embodiments, the modulator 4106 then relays the output beam into projection optics 4114 of the projection system 4100. In some embodiments, projection optics 4114 is included in a projection lens as previously described. In other embodiments, a portion or section of projection optics 4114 is included in the projection lens.

In some embodiments, the illumination assembly 4104 includes an integrator rod (e.g., integrator tube, integrator box) that receives light from the white light fiber 4102. The integrator rod may include a substantially reflective surface within its interior such that light incident on its surface is reflected until the light exits. Once the light exits the integrator rod, illumination assembly 4104 may include a set of optical elements, such as lenses, filters, and/or polarizers, that optically act on the light before passing the light to modulator 4106.

Prism

As previously described, the projection system 4000 of fig. 40 provides the color beam output from each illumination assembly 4004 to modulator 4006. Fig. 42 illustrates a modulator 4006 for single color channel input. Modulator 4006 receives input light 4200 (e.g., incident light, single channel color light) from illumination assembly 4004 for a single color channel. Input light 4200 may be received, for example, by a nine-piece prism 4006. The reflector device 4010 modulates the input light 4200. The reflector device 4010 may comprise a Digital Micromirror Device (DMD) array of reflectors (e.g., mirrors), a microelectromechanical system (MEMS) array, a Liquid Crystal On Silicon (LCOS) modulator, or any other suitable reflector group that can reflect light in at least two or more paths.

The reflector device 4010 may reflect the input light 4200 in an ON state, an OFF state, or a flag state. When the reflector apparatus 4010 is set to the ON state, the reflected ON light beam 4220 may be transmitted through the projection optics 4014 to provide light for further modulation and/or projection. In some embodiments, the mirror of the reflector apparatus 4010 is disposed between about 11 degrees and 13 degrees when in the ON state. When reflector device 4010 is set to an OFF state, reflected OFF light beam 4215 may be directed to a light trap (not shown) to be absorbed and/or processed so as not to affect the dynamic range of the display. When the reflector apparatus 4010 is set to the FLAT state, the reflected FLAT light beam 4210 is directed away from the operative downstream optical path which may include further modulation and/or projection. In general, the reflector apparatus 4010 and/or the projection system 4000 as a whole may not be in use when in the FLAT state.

As previously described, the projection system 4100 of fig. 41 provides white light from a single illumination assembly 4104 to modulator 4106. Fig. 43 illustrates a modulator 4106 according to one embodiment. Modulator 4106 receives input light 4300 (e.g., incident light, white light) from illumination assembly 4104. The input light 4300 may be received, for example, by a white light prism 4108. In the example of fig. 41, modulator 4106 includes a first prism segment 4330 and a second prism segment 4335. The first prism segment 4330 can be a Total Internal Reflection (TIR) prism at the interface of the second prism segment 4335. The first prism segment 4330 and the second prism segment 4335 together form a white light prism 4108 (shown in fig. 41). The reflector apparatus 4110 modulates the input light 4300. The reflector device 4110 may include a Digital Micromirror Device (DMD) array of reflectors (e.g., mirrors), or a microelectromechanical system (MEMS) array, or any other suitable group of reflectors that may reflect light in at least two or more paths.

The reflector apparatus 4110 may reflect the input beam 4300 in an ON state, an OFF state, or a flag state. When the reflector apparatus 4110 is set to the ON state, the reflected ON beam 4320 may be transmitted through the projection optics 4114 to provide light for further modulation and/or projection. In some embodiments, the mirror of the reflector apparatus 4110 is disposed between about 11 degrees and 13 degrees when in the ON state. When reflector device 4110 is set to the OFF state, reflected OFF light beam 4315 may be directed to a light trap (not shown) to be absorbed and/or processed so as not to affect the dynamic range of the display. When the reflector apparatus 4110 is set to the flag state, the reflected flag beam 4310 is directed away from the operative downstream optical path, which may include further modulation and/or projection. In general, the reflector apparatus 4110 and/or the projection system 4100 as a whole may not be in use when in the FLAT state.

In some embodiments, the first prism section 4330 and the second prism section 4335 separate the input light 4300 into color channels (e.g., red channel, green channel, blue channel). The color channels are each provided to a color channel path in the white light prism 4108. In such an embodiment, modulator 4106 includes a reflector device 4110 for each color channel such that each color channel is modulated separately. The first and second prism segments 4330, 4335 may then recombine each color channel into a reflected ON beam 4320. In other embodiments, each color channel is optically recombined downstream of modulator 4106. For example, a beam combiner (not shown) optically downstream of modulator 4106 may recombine each color channel. Each color channel may have an equal illumination angle, such as between about 24 degrees and 28 degrees. In addition, each reflector device 4110 may include its own color light trap for its respective color channel.

Fig. 44 illustrates a modulator 4106 according to another embodiment. In particular, the modulator 4106 of fig. 44 does not have a first prism segment 4330 (e.g., a TIR prism) that receives the input beam 4300, but rather includes a fold mirror 4430 that reflects the input light 4300 toward a second prism segment 4335.

Table 1 provides the transmission efficiency of the modulators of fig. 42, 43 and 44 for the green channel illumination path. In table 1, the illumination path transmission of the white light prism 4108 with TIR prism (as shown in fig. 43) and the white light prism 4108 without TIR prism (as shown in fig. 44) are equal because the fold mirror 4430 has about the same efficiency as the first prism segment 4330 (e.g., TIR prism).

	9-Piece prism	White light prism with TIR	White light prism without TIR
				Illumination path	99.1％	94.8％	94.8％
Projection path	93.1％	93.4％	95.7％
				Total transmission of	92.3％	88.5％	90.7％
Relative efficiency	1	0.959	0.983

Table 1: transmission efficiency

In some embodiments, a wobble frequency oscillator may be used in conjunction with the nine-piece prism 4008 or the white light prism 4108. For example, fig. 45 illustrates an example wobble oscillator 4500 optically disposed between modulator 4006 and projection optics 4014. The wobble frequency oscillator 4500 amplifies the output of the modulator 4006 (e.g., from 2K resolution to 4K resolution). Fig. 46A illustrates an example wobble frequency oscillator 4600 optically disposed between a first prism section 4330 (see fig. 43) of a modulator 4106 and projection optics 4114. Fig. 46B illustrates an example wobble frequency oscillator 4650 optically disposed between a second prism section 4335 (see fig. 43) and projection optics 4114. In some embodiments, the wobble frequency oscillator 4650 is coupled to or otherwise in contact with the fold mirror 4430.

In some embodiments, a filter (such as filter 110 or fourier portion 3501) is included in projection optics 4114 (e.g., a projection lens). In other embodiments, a filter is optically disposed between modulator 4106 and projection optics 4114.

In some cases, the filter may be a reflective filter. For example, light that does not pass through the filter may be directed to a light trap (not shown). In other examples, the filter refracts or scatters the light such that the light is directed away from downstream optics, thereby preventing certain diffraction orders from being projected onto screen 3914. In some embodiments, the filter may be a filter that filters light without a fourier plane (such as a lens with a certain F-number), rather than a fourier filter.

Fig. 47 illustrates a method 4700 for projecting an image using a projection system 4100. At block 4705, the method 4700 includes receiving a white light input with a modulator 4106. For example, the white light prism 4108 receives white light from the illumination assembly 4104. At block 4710, the method 4700 includes separating the white light input into a first color channel, a second color channel, and a third color channel. For example, the white light prism 4108 separates the input light 4300 into a first color channel (e.g., red), a second color channel (e.g., green), and a third color channel (e.g., blue).

At block 4715, the method 4700 includes modulating the first color channel, the second color channel, and the third color channel to generate respective first modulated light, second modulated light, and third modulated light. For example, the first color channel, the second color channel, and the third color channel are each modulated by a respective reflective device 4110. At block 4720, the method 4700 includes combining the first color channel, the second color channel, and the third color channel into a white light output. For example, after modulation, the white light prism 4108 combines the first, second, and third modulated color channels into a single white light output.

At block 4725, the method 4700 includes filtering the white light output to generate a filtered white light output. For example, as previously described, the filter 110 included in the projection lens performs a spatial fourier transform on the white light output. At block 4730, method 4700 includes projecting the filtered white light output onto a screen (such as screen 3914).

The illumination angle within projection systems 4000, 4100 may be controlled based on diffraction orders filtered by a filter (e.g., filter 110). For example, in the projection system 4100, the output of the white light fiber 4102 can have an illumination angle selected based on the diffraction configuration of the filter. In addition, the tilt angle of the reflective device 4110 may be selected to ensure that the angled light and/or the selected diffraction orders are filtered by the filter.

Systems, methods, and devices according to the present disclosure may employ any one or more of the following configurations.

(1) A projection system using white light illumination, the projection system comprising: an illumination assembly configured to receive a white light input; a prism configured to separate the white light input into separate color light inputs, redirect the color light inputs to respective modulators, and combine the modulated color light inputs from the respective modulators into a white light output; a filter configured to spatially fourier transform the white light output to generate a filtered white light output; and a projection lens assembly configured to project the filtered white light output.

(2) The projection system of (1), wherein the color light input comprises red light, green light, and blue light, and wherein the respective modulators comprise a first modulator configured to modulate the red light, a second modulator configured to modulate the green light, and a third modulator configured to modulate the blue light.

(3) The projection system of any one of (1) to (2), wherein the filter comprises a lens configured to focus the white light output onto a fourier plane, wherein the fourier plane coincides with a focal plane of the lens.

(4) The projection system according to any one of (1) to (3), further comprising: a wobble oscillator optically disposed between at least one modulator of the plurality of modulators and the projection lens assembly.

(5) The projection system of any one of (1) to (4), wherein the filter is configured to block one or more diffraction orders of the white light output.

(6) The projection system of any one of (1) to (5), wherein the optical filter is integrated within the projection lens assembly.

(7) The projection system of any of (1) to (6), wherein the prism comprises a Total Internal Reflection (TIR) prism section configured to separate the white light into the color light input.

(8) The projection system according to any one of (1) to (7), further comprising: a fold mirror configured to direct the white light input to the prism.

(9) The projection system of any one of (1) to (8), wherein each of the color light inputs has the same illumination angle.

(10) The projection system of any one of (1) to (9), wherein a broadband anti-reflection coating is applied to the prism.

(11) The projection system of any one of (1) to (10), wherein when a first modulator of the respective modulators is in an OFF state, the respective color light input modulated by the first modulator is directed toward a light trap.

(12) The projection system of any one of (1) to (11), wherein each of the respective modulators is a modulator selected from the group consisting of: digital micromirror devices, microelectromechanical systems arrays, and liquid crystal on silicon arrays.

(13) A method for modulating white light in a projector system, the method comprising: receiving a white light input with a prism assembly; splitting the white light into a plurality of separate color light inputs with the prism assembly, each color light input being provided to a separate prism path at an illumination angle; modulating each color light input with a color light modulator in each individual prism path; combining each modulated color light input into a white light output within the prism assembly; providing the white light output to a projection lens assembly; filtering the white light output within the projection lens assembly; and projecting the filtered white light output.

(14) The method of (13), wherein the color light inputs comprise red, green, and blue light, and wherein modulating each color light input with a color light modulator in each separate prism path comprises: modulating the red light with a first color light modulator; modulating the green light with a second color light modulator; and modulating the blue light with a third color light modulator.

(15) The method according to any one of (13) to (14), further comprising: focusing the white light output with a lens included in the projection lens assembly onto a fourier plane, wherein the fourier plane coincides with a focal plane of the lens.

(16) The method of any one of (13) to (15), wherein filtering the white light output within the projection lens assembly includes blocking one or more diffraction orders of the white light output.

(17) A projection system using white light illumination, the projection system comprising: a prism configured to separate white light into a plurality of color channels, redirect the color channels to respective modulators, and combine the modulated color channels from the respective modulators into a white light output; and a projection lens assembly configured to project the white light output, the projection lens assembly comprising a filter configured to spatially fourier transform the white light output.

(18) The projection system of (17), wherein the plurality of color channels includes a red channel, a green channel, and a blue channel, and wherein the respective modulators include a first modulator configured to modulate the red channel, a second modulator configured to modulate the green channel, and a third modulator configured to modulate the blue channel.

(19) The projection system of any of (17) to (18), wherein the prism comprises a Total Internal Reflection (TIR) prism section configured to separate the white light into the plurality of color channels.

(20) The projection system of any one of (17) to (19), wherein each of the color channels has the same illumination angle.

With respect to the processes, systems, methods, heuristics, etc. described herein, it should be understood that, while the steps of such processes, etc. have been described as occurring in a particular ordered sequence, such processes may be practiced with the described steps performed in an order different than that described herein. It is further understood that certain steps may be performed concurrently, other steps may be added, or certain steps described herein may be omitted. In other words, the process descriptions herein are provided for the purpose of illustrating certain embodiments and should in no way be construed as limiting the claims.

Accordingly, it is to be understood that the above description is intended to be illustrative, and not restrictive. Many embodiments and applications other than the examples provided will be apparent from a reading of the above description. The scope should be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. It is anticipated and intended that the technology discussed herein will evolve in the future, and that the disclosed systems and methods will be incorporated into such future embodiments. In summary, it should be understood that the application is capable of modification and variation.

All terms used in the claims are intended to be given their broadest reasonable constructions and their ordinary meanings as understood by those knowledgeable in the art described herein unless an explicit indication to the contrary is made herein. In particular, the use of singular articles such as "a," "the," "said," and the like should be understood to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.

The Abstract of the disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. This Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing detailed description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments incorporate more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the detailed description, with each claim standing on its own as a separately claimed subject matter.

Claims

1. A projection system using white light illumination, the projection system comprising:

an illumination assembly configured to receive a white light input;

A prism configured to separate the white light input into separate color light inputs, redirect the color light inputs to respective modulators, and combine the modulated color light inputs from the respective modulators into a white light output;

A filter configured to spatially fourier transform the white light output to generate a filtered white light output; and

A projection lens assembly configured to project the filtered white light output.

2. The projection system of claim 1, wherein the color light input comprises red light, green light, and blue light, and wherein the respective modulators comprise a first modulator configured to modulate the red light, a second modulator configured to modulate the green light, and a third modulator configured to modulate the blue light.

3. The projection system of any of claims 1-2, wherein the filter comprises a lens configured to focus the white light output onto a fourier plane, wherein the fourier plane coincides with a focal plane of the lens.

4. The projection system of any of claims 1 to 3, further comprising: a wobble oscillator optically disposed between at least one modulator of the plurality of modulators and the projection lens assembly.

5. The projection system of any of claims 1-4, wherein the filter is configured to block one or more diffraction orders of the white light output.

6. The projection system of any of claims 1-5, wherein the optical filter is integrated within the projection lens assembly.

7. The projection system of any of claims 1-6, wherein the prism comprises a Total Internal Reflection (TIR) prism segment configured to separate the white light into the color light input.

8. The projection system of any of claims 1 to 7, wherein each of the color light inputs has the same illumination angle.

9. The projection system of any of claims 1-8, wherein a broadband anti-reflection coating is applied to the prism.

10. The projection system of any of claims 1-9, wherein when a first modulator of the plurality of modulators is in an OFF state, a respective color light input modulated by the first modulator is directed toward a light trap.

11. The projection system of any one of claims 1 to 10, further comprising:

a fold mirror configured to direct the white light input to the prism.

12. The projection system of any of claims 1 to 11, wherein each of the respective modulators is a modulator selected from the group consisting of: digital micromirror devices, microelectromechanical systems arrays, and liquid crystal on silicon arrays.

13. A method for using white light in a projector system, the method comprising:

receiving a white light input with a prism assembly;

Splitting the white light into a plurality of separate color light inputs with the prism assembly, each color light input being provided to a separate prism path at an illumination angle;

modulating each color light input with a color light modulator in each individual prism path;

Combining each modulated color light input into a white light output within the prism assembly;

providing the white light output to a projection lens assembly;

Filtering the white light output within the projection lens assembly; and

The filtered white light output is projected.

14. The method of claim 13, wherein the color light inputs comprise red, green, and blue light, and wherein modulating each color light input with a color light modulator in each separate prism path comprises: modulating the red light with a first color light modulator; modulating the green light with a second color light modulator; and modulating the blue light with a third color light modulator.

15. The method of any one of claims 13 to 14, further comprising:

Focusing the white light output with a lens included in the projection lens assembly onto a fourier plane, wherein the fourier plane coincides with a focal plane of the lens.

16. The method of any of claims 13-15, wherein filtering the white light output within the projection lens assembly includes blocking one or more diffraction orders of the white light output.

17. A projection system using white light illumination, the projection system comprising:

A prism configured to separate white light into a plurality of color channels, redirect the color channels to respective modulators, and combine the modulated color channels from the respective modulators into a white light output; and

A projection lens assembly configured to project the white light output, the projection lens assembly comprising a filter configured to spatially fourier transform the white light output.

18. The projection system of claim 17, wherein the plurality of color channels includes a red channel, a green channel, and a blue channel, and wherein the respective modulators include a first modulator configured to modulate the red channel, a second modulator configured to modulate the green channel, and a third modulator configured to modulate the blue channel.

19. The projection system of any of claims 17-18, wherein the prism comprises a Total Internal Reflection (TIR) prism segment configured to separate the white light into the plurality of color channels.

20. The projection system of any of claims 17 to 19, wherein each of the color channels has the same illumination angle.