KR102041881B1 - 3-Degree Of Freedom Planar Alignment Apparatus - Google Patents

Abstract

The present invention provides a three degree of freedom planar alignment device having a novel absolute X-Y-Θ position sensor for planar motion measurement of a precision multi-axis stage system. An image of a rotated region of interest (ROI) of a 2D phase-encoded binary scale (2D PEBS) is analyzed to obtain an absolute position value at two separate points, respectively. The absolute X-Y-Θ position can be calculated by combining these values.

Description

3-Degree Of Freedom Planar Alignment Apparatus}

The present invention relates to a three degree of freedom plane alignment device, and more particularly, to a three degree of freedom plane alignment device having an X-Y-Θ sensor for measuring rotation angle and position.

In various precision systems and scientific instruments, precise position measurement is a fundamental component of monitoring and controlling actuating systems. Laser interferometers and optical encoders are typical position sensors. The laser interferometer counts and sub-divides the interference fringes to measure position with sub-nanometer resolution. The period of the interference fringe is determined by the wavelength of the laser light source.

Optical encoders use scale. The scale has a uniform and periodic pattern. The pattern has a pitch of several to tens of micrometers. The optical encoder processes the interference fringe or intensity profile to obtain position readouts.

The laser interferometer can achieve high precision. However, the laser interferometer requires well controlled environmental conditions and delicate alignment.

In incremental position measurement, the position value is obtained by accumulating relative displacements from the initial position. The incremental position measurement is applied in many applications such as precision stage and position monitoring.

However, the incremental position measurement only measures relative displacement and requires initialization with an additional sensor to measure the absolute position.

The absolute position measurement increases the efficiency and robustness of the precision system. Because absolute position measurement does not require initialization, it can handle various emergencies. The absolute position measurement also has advantages in applications where power consumption must be tightly controlled.

Since optical encoders can be implemented without increasing cost and complexity, optical encoders are widely used for absolute position measurements.

Absolute encoders require a specially designed scale. Absolute position binary code (APBC) is encoded at this scale. Initially, the APBC was encoded using multi-track code, and incremental tracks were added for high resolution. However, the complex configuration and alignment issues of the encoder head are inevitable due to the multi-track configuration of this scale.

The encoder is divided into a linear encoder measuring linear motion and a rotary encoder measuring rotational motion.

Therefore, there is a need for a new high-precision encoder having a new structure that simultaneously measures the exact position of the absolute position according to the linear motion and the rotation angle by the rotational motion.

One technical problem to be solved of the present invention is to provide a three degree of freedom planar alignment device for providing a linear motion and a rotational motion with high precision. The three degree of freedom planar alignment device requires an absolute position measuring device with high precision and simple structure. The absolute position measuring apparatus uses a two-dimensional absolute position scale arranged in a matrix form orthogonal to two one-dimensional absolute position binary code. One-dimensional absolute position binary code is encoded by changing the phase of one binary state representation.

The two-dimensional absolute position scale can be efficiently decoded using optical and structural properties. The two-dimensional absolute position scale can accurately decode the two-dimensional position and rotation angle.

Sub-division of the two-dimensional absolute position binary code is possible by sensing the relative position of the binary state representation used for absolute position encoding. Thus, the absolute position encoding does not interfere with the sub-division process. Thus, any pseudo-random sequence can be used as the absolute location code.

The method proposed in the present invention does not require an additional sensing unit for the sub-division. The proposed method can be realized with a simple configuration and efficient data processing.

A three degree of freedom planar alignment device according to an embodiment of the present invention comprises: a stage comprising a stationary plate and a moving plate and providing three degree of freedom position alignment; An X-Y-Θ sensor head mounted to the fixed plate of the stage; A two-dimensional absolute position scale mounted to the moving plate of the stage; A signal processor for analyzing a scale image of the two-dimensional absolute position scale captured by the X-Y-Θ sensor head to extract a position of three degree of freedom motion of the moving plate of the stage; And a stage driver for driving the stage with the displacement amount of the movable plate.

In one embodiment of the present invention, the stage may be an XYΘ stage or a UVW stage.

In one embodiment of the present invention, the two-dimensional absolute position scale may be mounted to be exposed to the lower surface of the moving plate.

In one embodiment of the present invention, the displacement amount of the stage is based on the position of the three degree of freedom movement of the stage, the position of the three degree of freedom movement may include two translational movement and one rotational movement.

In one embodiment of the present invention, the two-dimensional absolute position scale is a two-dimensional data consisting of a combination of the first absolute position binary code arranged in the first direction of the reference coordinate system and the second absolute position binary code arranged in the second direction It may include cells. Each of the first absolute position binary code and the second absolute position binary code may be composed of one-dimensional data cells. The one-dimensional data cell may include a data section, a neutral section, and a clock section. A two-dimensional data cell representing a (0,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Can be marked at the intersection of D). A two-dimensional data cell representing a (0,1) state has a data section (D) representing "1" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Can be marked at the intersection of D). A two-dimensional data cell representing a (1,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("1" of absolute position binary code in the first direction). Can be marked at the intersection of D). A two-dimensional data cell representing a (1,1) state has a data section (D) representing "1" of absolute position binary code in the second direction and a data section ("1" of absolute position binary code in the first direction). Can be marked at the intersection of D).

In one embodiment of the present invention, each of the data section, the neutral section, and the clock section comprises one or more regularly spaced segments, wherein the one-dimensional data cell represents a first state (“0”) and is continuous. And a data section, a neutral section, and a clock section, wherein the one-dimensional data cell represents a second state (“1”) and may include a neutral section, a data section, and a clock section arranged in succession. .

In one embodiment of the present invention, the neutral section may be two segments, the data section may be three segments, and the clock section may be three segments.

A degree of freedom planar alignment device according to an embodiment of the present invention comprises: a stage comprising a stationary plate and a moving plate and providing three degree of freedom position alignment; An X-Y-Θ sensor head mounted to the fixed plate of the stage; A two-dimensional absolute position scale mounted to the moving plate of the stage; A signal processor configured to analyze the scale image of the two-dimensional absolute position scale from the X-Y-Θ sensor head to extract the position of three degrees of freedom motion of the stage; And a stage driver for driving the stage with the displacement amount of the stage. The operating method of the three degree of freedom planar alignment device may include: measuring an initial position of a moving plate of the stage; Setting a displacement amount of the stage by a difference between a target position of the moving plate of the stage and the initial position; Calculating a driving amount of the stage based on the displacement amount; And driving the motor of the stage with the driving amount, respectively.

In one embodiment of the present invention, after moving the stage may further comprise the step of confirming the arrival to the target position by measuring the current position of the stage.

A three degree of freedom planar alignment device according to an embodiment of the present invention comprises: a stage comprising a stationary plate and a moving plate and providing three degree of freedom position alignment; An X-Y-Θ sensor head mounted to the fixed plate of the stage; A two-dimensional absolute position scale mounted to the moving plate of the stage; A signal processor extracting a position of three degrees of freedom motion of the stage by analyzing a scale image of the two-dimensional absolute position scale captured by the X-Y-Θ sensor head; At least one vision camera inspecting an alignment mark of a substrate mounted to the moving plate of the stage; And a stage driver for driving the stage with a driving amount of the stage based on a difference between the alignment mark of the substrate and the final alignment position of the alignment mark.

In one embodiment of the present invention, the stage may be an XYΘ stage or a UVW stage.

In one embodiment of the present invention, the two-dimensional absolute position scale may be mounted to be exposed to the lower surface of the moving plate.

In one embodiment of the present invention, the position of the three degrees of freedom movement may include two translational movements and one rotational movement.

In one embodiment of the present invention, the two-dimensional absolute position scale is a two-dimensional data consisting of a combination of the first absolute position binary code arranged in the first direction of the reference coordinate system and the second absolute position binary code arranged in the second direction May contain cells. Each of the first absolute position binary code and the second absolute position binary code may be composed of one-dimensional data cells, and the one-dimensional data cell may include a data section, a neutral section, and a clock section. A two-dimensional data cell representing a (0,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Can be marked at the intersection of D). A two-dimensional data cell representing a (0,1) state has a data section (D) representing "1" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Can be marked at the intersection of D). A two-dimensional data cell representing a (1,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("1" of absolute position binary code in the first direction). Can be marked at the intersection of D). A two-dimensional data cell representing a (1,1) state has a data section (D) representing "1" of absolute position binary code in the second direction and a data section ("1" of absolute position binary code in the first direction). Can be marked at the intersection of D).

In one embodiment of the present invention, each of the data section, the neutral section, and the clock section comprises one or more regularly spaced segments, wherein the one-dimensional data cell represents a first state (“0”) and is continuous. And a data section, a neutral section, and a clock section, wherein the one-dimensional data cell represents a second state (“1”) and may include a neutral section, a data section, and a clock section arranged in succession. ..

In one embodiment of the present invention, the neutral section may be two segments, the data section may be three segments, and the clock section may be three segments.

A three degree of freedom planar alignment device according to an embodiment of the present invention comprises: a stage comprising a stationary plate and a moving plate and providing three degree of freedom position alignment; An X-Y-Θ sensor head mounted to the fixed plate of the stage; A two-dimensional absolute position scale mounted to the moving plate of the stage; A signal processor extracting three degrees of freedom of the stage by analyzing a scale image of the two-dimensional absolute position scale captured by the X-Y-Θ sensor head; At least one vision camera inspecting an alignment mark of a substrate mounted to the moving plate of the stage; And a stage driver for driving the stage with a driving amount of the stage based on a difference between the three degrees of freedom position of the alignment mark of the substrate and the last three degrees of freedom position of the alignment mark. A method of operating the three degree of freedom plane alignment device may include: measuring an initial position of three degrees of freedom of the two-dimensional absolute position scale using the X-Y-Θ sensor head and the signal processor; Measuring an initial position of three degrees of freedom of the alignment marker of the substrate using the vision camera; Setting a displacement amount by a difference between an initial position of three degrees of freedom of the alignment markers of the substrate and a final alignment position of the three degrees of freedom of the alignment markers of the substrate; Converting the initial position of the absolute position binary scale and the displacement amount into a driving amount of the stage; Driving each of the motors of the stage with the driving amount; And measuring a current position of three degrees of freedom of the moving plate of the stage by using the X-Y-Θ sensor head and the signal processor.

In one embodiment of the present invention, determining whether the current position of the three degrees of freedom of the moving plate of the stage is the target position given by the lowest position of the three degrees of freedom of the two-dimensional absolute position scale and the displacement amount; Measuring the current position of three degrees of freedom of the alignment marker of the substrate using the vision camera; And comparing the difference between the current position of the three degrees of freedom of the alignment marker of the substrate and the final alignment position of the three degrees of freedom; It may further include at least one of.

The three-degree-of-freedom plane alignment device according to an embodiment of the present invention can decode a scale image obtained by photographing a two-dimensional absolute position binary code scale, and precisely measure the rotation angle and position to control the rotation angle and position of the stage. have.

1 is a conceptual diagram illustrating a one-dimensional absolute position binary code scale according to an embodiment of the present invention.
2 is a conceptual diagram illustrating two-dimensional data cells of a two-dimensional absolute position binary code scale according to another embodiment of the present invention.
3 is a conceptual diagram illustrating a two-dimensional absolute position binary code scale according to another embodiment of the present invention.
4 illustrates a two-dimensional binary code scale and scale image according to another embodiment of the present invention.
5 illustrates a two-dimensional binary code scale and scale image according to another embodiment of the present invention.
6 illustrates a scale image, a Fourier transform region of interest, and a region of interest according to another embodiment of the present invention.
FIG. 7 is a result of Fourier transforming the Fourier transform region of interest FFT ROI of FIG. 6 into the spatial frequency domain domain FX-FY.
8 shows a second ROI 2 ′ cut in the preliminary reference coordinate system X ''-Y '' rotated and rotated at a preliminary rotation angle θ of the second preliminary ROI ROI of FIG. 7, and FIG. The first direction intensity profile Isum (x) is obtained by adding the second ROI 2 ′ in the Y ″ axis direction.
9 shows a part of the first directional intensity profile Isum (x) of the second region of interest ROI2 ′, a scale corresponding thereto, and an absolute position code corresponding thereto, respectively.
10 is a conceptual diagram illustrating a scale image, a Fourier transform region of interest, a preliminary region of interest, and a region of interest according to an absolute position measuring method according to another exemplary embodiment of the present invention.
FIG. 11 illustrates a second direction intensity profile summed in the first region of interest ROI1 ′ and the first direction X ″ in FIG. 10.
FIG. 12 illustrates the first direction intensity profile summed in the third ROI 3 ′ and the second direction Y ″ in FIG. 10.
13 is a conceptual view illustrating an absolute position measuring apparatus according to another embodiment of the present invention.
14 is a perspective view illustrating an absolute position measuring apparatus 100a according to still another embodiment of the present invention.
15 are graphs illustrating a measurement result of the absolute position measuring apparatus 100a according to another embodiment of the present invention.
16 shows the results of an absolute position sensor in accordance with another embodiment of the present invention.
17 is a conceptual diagram illustrating a plane alignment apparatus according to another embodiment of the present invention.
FIG. 18 is a flowchart for describing a method of operating the planar alignment device of FIG. 17.
19 is a conceptual diagram illustrating a plane alignment apparatus according to another embodiment of the present invention.
20 is a flowchart for explaining a method of operating the flat alignment device of FIG. 19.
21A and 21B are plan views illustrating the operation of the planar alignment device of FIG. 19.
22 is a perspective view illustrating a UVW stage according to another embodiment of the present invention.
FIG. 23 is a plan view illustrating a motion of the UVW stage of FIG. 22.

The present invention provides a new absolute X-Y-Θ position sensor for planar motion measurement of precision multi-axis stage systems. An image of a rotated region of interest (ROI) of a 2D phase-encoded binary scale (2D PEBS) is analyzed to obtain absolute position values at two separate points, respectively. By combining these values, we can calculate the absolute X-Y-Θ position.

The sensor head 101 of the X-Y-Θ position sensor can be configured using a board level camera, a light emitting diode light source, an imaging lens and a cube beam splitter. In order to obtain a uniform spatial intensity profile in the scale image of all or part of the two-dimensional phase encoded binary scale, the averaging or summation direction is intentionally selected. Also, higher resolution can be obtained in angular measurements by increasing the allowable offset size (or distance) between regions of interest (ROI). The performance of the X-Y-Θ position sensor was evaluated in terms of resolution, nonlinearity and repeatability. The X-Y-Θ position sensor can linearly resolve 25 nm and clearly resolve 0.001 angular displacement, with standard deviations of less than 18 nm when repeatedly measuring 2D grid positions.

In various advanced manufacturing systems and scientific instruments, precision stages are used as key components to generate accurate position and scanning trajectories. In order to control and calibrate the stage with high precision, a precise X-Y-Θ position sensor must be used.

In order to perform complex motions in the plane, the precise stage system has a multi-axis configuration. The generated motion is measured using a plurality of single stage motion sensors. In-plane precision alignment can be used with X-Y-Θ stages and UVW stages with three degrees of freedom. That is, measurement of two linear motions and one rotational motion is required. In-plane precision alignment is a typical example that requires three degrees of freedom planar motion measurement (X-Y-Θ).

The position measuring device according to the embodiment of the present invention is an optical encoder, and precisely measures the X-Y-Θ position, and may be configured as a single sensor head. This can provide a competitive solution for multi-axis measurements.

The absolute position encoder according to an embodiment of the present invention provides absolute position without initialization and ensures higher robustness than incremental encoders. The absolute position measurement method uses a specially designed scale pattern encoded with a multi-bit absolute position code, and uses sub-division algorithms to increase the measurement resolution.

Two-dimensional planar position can be accurately measured using a phase-encoded binary scale (PEBS). However, a large microscope imaging system is used to verify the validity of this proposed method and the rotation angle Θ cannot be measured. Therefore, to get a practical effect, a small sensor head is required that provides all the information about the plane motion (X-Y-Θ).

In the X-Y-Θ position measuring device according to an embodiment of the present invention, the size of the sensor head can be integrated into a small, precision multi-axis stage and position sensor embedded in the operating system so as not to interfere with other components.

The 2D phase encoded binary scale (PEBS), in which the absolute position binary code (APBC) is encoded, is constructed by orthogonally superimposing two single track binary codes. A single track binary code consists of a series of data cells representing the data bits of an absolute position binary code. The single track binary code scale is represented by data cells. The 2D phase encoded binary scale may be determined by an AND logic operation of a single track binary code scale orthogonal to each other. One data cell includes a data section (D), a neutral section (N), and a clock section (C). One data cell is of two types to represent a binary state.

The clock section C of each data cell is repeated in periodic positions to provide an alignment key pattern for data processing. The position of the data section (D) is exchanged with the neutral section (N) to represent the binary state of each cell in the absolute position binary code. The multi-bit binary code is decoded to identify an absolute position by analyzing an image of the binary code scale, and the position of the data section (D) is sub-division process (sub-). division process.).

The camera captures a 2D phase encoded binary scale (PEBS) to produce a scale image. The absolute X-Y-Θ position at the center point of the scale image is calculated using the set of X-Y positions (X1, Y1; X2, Y2), which are the center points of two ROIs of equidistant distance 2L.

When the coordinate axes of the 2D Phase-Encoded Binary Scale (PEBS) and the optical sensor array do not match, data processing is used to align these axes through image rotation to obtain the XY position at each point. . The preliminary rotation angle θ may be calculated by applying a 2D fast Fourier transform (FFT) to the image of the FFT region of interest (FFT ROI). Two images of the first preliminary region of interest ROI1 and the second preliminary region of interest ROI2 are cut out to an appropriate size to form a first region of interest ROI1 ′ and a second region of interest ROI2 ′, respectively. The first region of interest ROI1 ′ and the second region of interest ROI2 ′ are rotated by a preliminary rotational angle θ to be suitable for data processing. The center positions of the first ROI 1 ′ and the second ROI 2 ′ calculated through data processing provide an absolute position value X−Y−Θ through calculation.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed subject matter is thorough and complete, and that the spirit of the invention will be fully conveyed to those skilled in the art. In the drawings, the components are exaggerated for clarity. Portions denoted by like reference numerals denote like elements throughout the specification.

The two-dimensional absolute position binary code scale 110 is arranged two-dimensionally on the plane. The camera captures all or a portion of the two-dimensional absolute position binary code scale 110 to provide a scale image 110 '. The pixel coordinate axis of the scale image 110 ′ may rotate with respect to the coordinate axis of the data cells of the two-dimensional absolute position binary scale 100. In order to describe the two-dimensional absolute position binary scale 110, a one-dimensional absolute position binary code scale is described.

1 is a conceptual diagram illustrating a one-dimensional absolute position binary code scale according to an embodiment of the present invention.

[Single Track Binary Code Scale]

Referring to FIG. 1, a one-dimensional absolute position binary code scale is formed by replacing an absolute position binary code with a predetermined code (or data cell). The absolute position binary code may be formed by a pseudo-random-code. A data cell representing one data bit of absolute position binary code (APBC) consists of three sections. One data cell includes a data section (D), a clock section (C), and a neutral section (N). Each section contains one or more evenly spaced segments. Thus, each data cell consists of three or more segments. The data section D may be three segments, the neutral section N may be two segments, and the clock section C may be three segments. The absolute position binary code is replaced with a predetermined sign (or data cell) and patterned on a one-dimensional scale.

In order for the data cell to exhibit a " 0 " state (first binary state), the data section D and the clock section C have different binary states (different light reflectivity, different light transmittance), and the neutral Section (N) may have the same state as the clock section (C). For example, the data section D may be coded with a conductive material to have a high reflectance, and the clock section C and the neutral section N may be transparent.

The data section D and the clock section C may exchange positions with each other in order for the data cell to exhibit a " 1 " state (second binary state).

A data cell representing a "0" state (first binary state) may have data sections D, neutral sections N, and clock sections C arranged in succession. A data cell exhibiting a " 1 " state (second binary state) can have a neutral section N, a data section D, and a clock section C arranged in succession.

The clock section C is repeated at periodic positions, and the clock section C can provide us with an alignment key pattern for data processing.

The position of the data section D is shifted to represent another second binary state of each data cell in the absolute position binary code. The movement is possible at other sites except for the clock section (C). The shift magnitude is an integer multiple of one segment width. The neutral section (N) is segments that do not belong to the data section (D) and the clock section (C).

Specifically, each data cell consists of eight segments, the data section (D) consists of three segments, the neutral section (N) consists of two segments, and the clock section (C) consists of three segments. It is composed. The data section D is moved by two segments to indicate the " 1 " state (second binary state).

Sub-division of the absolute position binary code is required to obtain high resolution. Sub-divided absolute position is calculated by sensing the positions of the data sections.

The sub-division process is performed using data obtained for absolute position decoding without additional sensing or data acquisition. The position measuring method according to the present invention does not remove the information about the sub-division to encode the absolute position binary code.

Thus, we can apply any pseudo-random code that represents absolute position in the sub-division process without sacrificing accuracy.

[2D Binary Code Scale]

2 is a conceptual diagram illustrating two-dimensional data cells of a two-dimensional absolute position binary code scale according to another embodiment of the present invention.

Referring to FIG. 2, a two-dimensional absolute position binary code scale 110 is formed by replacing a two-dimensional absolute position binary code with a predetermined code (or data cell). The two-dimensional absolute position binary code scale includes two-dimensional data cells that two-dimensionally arranged two one-dimensional absolute position binary codes. The two-dimensional data cell may represent a (0,0) state, a (0,1) state, a (1,0) state, and a (1,1) state. That is, the two-dimensional data cells are divided into four types.

The two-dimensional data cells are formed by a combination of an absolute position binary code in a first direction (X-axis direction) and an absolute position binary code in a second direction (Y-axis direction) in the reference coordinate system X-Y.

The two-dimensional absolute position scale is a combination of a first absolute position binary code arranged in a first direction (X-axis direction) of the reference coordinate system XY and a second absolute position binary code arranged in a second direction (Y-axis direction). It includes two-dimensional data cells consisting of. Each of the first absolute position binary code and the second absolute position binary code is composed of one-dimensional data cells. The one-dimensional data cell includes a data section, a neutral section, and a clock section. The one-dimensional data cell represents a first state ("0") or a second state ("0"). The pair of first absolute position binary codes and the second absolute position binary codes orthogonal to each other form two-dimensional data cells at their intersections.

A two-dimensional data cell representing a (0,0) state is a data section D representing a "0" of a second absolute position binary code in a second direction and a "0" of a first absolute position binary code in a first direction. It is marked so as to exhibit different optical properties at the intersection of the data section D that it represents.

A two-dimensional data cell representing a (0,1) state is a data section D representing a "1" of a second absolute position binary code in a second direction and a "0" of a first absolute position binary code in a first direction. Marked to exhibit different optical properties at the intersection of the data section (D) it represents

A two-dimensional data cell representing a (1,0) state is a data section D representing a "0" of a second absolute position binary code in a second direction and a "1" of a first absolute position binary code in a first direction. Marked to exhibit different optical properties at the intersection of the data section (D) it represents

The two-dimensional data cell representing the (1,1) state has a data section D representing the "1" of the second absolute position binary code in the second direction and "1" of the first absolute position binary code in the first direction. It is marked so as to exhibit different optical properties at the intersection of the data section D that it represents.

That is, a two-dimensional data cell representing a (0,0) state provides a one-dimensional data cell representing a "0" state when projected in the first direction (X axis), and is projected in the second direction (Y axis). In this case, a one-dimensional data cell representing a "0" state is provided.

A two-dimensional data cell representing the (0,1) state provides a one-dimensional data cell representing the "0" state when projected in the first direction, and a one-dimensional representing the "1" state when projected in the second direction. Provide a data cell.

A two-dimensional data cell representing the (1,0) state provides a one-dimensional data cell representing the "1" state when projected in the first direction, and a one-dimensional representing the "0" state when projected in the second direction. Provide a data cell.

A two-dimensional data cell representing the (1,1) state provides a one-dimensional data cell representing the "1" state when projected in the first direction, and a one-dimensional representing the "1" state when projected in the second direction. Provide a data cell.

One one-dimensional data cell constituting each of the first absolute position binary code and the second absolute position binary code is a data section (D), a clock section (C), and a neutral section (N). ). Each section contains one or more segments. Each one-dimensional data cell represents a first state ("0") or a second state ("0"). A one-dimensional data cell having a first state (“0”) may have a data section (D), a neutral section (N), and a clock section (C) arranged sequentially. A one-dimensional data cell having a second state (“1”) may have a neutral section (N), a data section (D), and a clock section (C) arranged sequentially. The data section (D) has different optical properties than the neutral section (N) and clock section (C). The data section D may be three segments, the neutral section N may be two segments, and the clock section C may be three segments. Each segment may have a constant spacing. One-dimensional data cells may be a total of eight segments. Accordingly, one two-dimensional data cell may be composed of 8 X 8 segments.

3 is a conceptual diagram illustrating a two-dimensional absolute position binary code scale according to another embodiment of the present invention.

Referring to FIG. 3, an absolute position binary code may be selected as a pseudo random code. The sequence of three bits of the pseudo random code (or absolute position binary code) may be '001110100'. The pseudo random code may include a 3-bit code word. One codeword may be decoded to indicate a particular location. Each bit of the pseudo random code represents a "first state (HIGH)" or a "second state (LOW)".

The sequence of pseudo random codes is arranged in the first direction X and the second direction Y, and corresponding two-dimensional data cells are formed. The two-dimensional data cell may represent a (0,0) state, a (0,1) state, a (1,0) state, or a (1,1) state.

The two-dimensional absolute position binary code scale is formed by replacing a two-dimensional absolute position binary code (or two-dimensional pseudo random code) with a predetermined code (or data cell).

The two-dimensional absolute position binary code scale 110 may be photographed by a camera to include at least one code word in a first direction and a second direction to provide a scale image. The scale image may be decoded to extract a codeword in a first direction X, and a codeword in a second direction Y may be extracted. The extracted codeword may be converted to an absolute position. In addition, the phase may be calculated by subdivision of the data cells. The codeword and phase can provide a precise absolute position.

4 illustrates a two-dimensional binary code scale and scale image according to another embodiment of the present invention.

Referring to FIG. 4, the scale image 110 ′ photographing the 2D binary code scale 110 is captured to extract one or more codewords for each coordinate axis.

On the left side of the two-dimensional binary code scale 110, a three-bit one-dimensional scale and a second direction intensity profile averaged in the first direction (X-axis) are respectively displayed.

Above the two-dimensional binary code scale 110, a three-dimensional one-dimensional scale and a first direction intensity profile averaged in the second direction (Y-axis) are respectively displayed.

The first directional intensity profile is decoded to provide the codeword and relative phase of the first direction. The second directional intensity profile may be decoded to provide the codeword and relative phase of the second direction. Accordingly, the position of the 2D binary code scale 110 may be calculated.

5 illustrates a two-dimensional binary code scale and scale image according to another embodiment of the present invention.

Referring to FIG. 5, the two-dimensional binary code scale 110 of the reference coordinate system X-Y may rotate with respect to the rectangular-shaped scale image 110 ′ obtained by the camera. The two-dimensional binary code scale 110 may be arranged along the axis direction of the reference coordinate system X-Y, and the scale image 110 'may be arranged along the axis direction of the rotation coordinate system X'-Y'. The reference coordinate system X-Y and the rotation coordinate system X'-Y 'may rotate by the rotation angle Θ. Calculation of the center position X and Y and the rotation angle Θ of the scale image 110 ′ is required from the scale image 110 ′.

First, all or part of the scale image 110 ′ may be selected to select a Fourier Transform region of interest (FFT ROI). The Fourier transform region of interest FFT ROI may provide a preliminary rotation angle θ through Fourier transform. The Fourier transform region of interest FFT ROI may have a square shape.

 Subsequently, the scale image 110 ′ rotated at the preliminary rotation angle θ may be cut along the coordinate axis of the preliminary reference coordinate system X ″ −Y ″ to form the ROI. The ROI may have a square shape and may include at least one codeword for each coordinate axis. The preliminary reference coordinate system X ''-Y '' and the reference coordinate system X-Y may be identical within an error range.

The ROI may be summed or averaged in the first direction (X ″ axis) of the preliminary reference coordinate system X ″ -Y ″ to provide a second direction intensity profile. The ROI may be summed or averaged in the second direction (Y ″ axis) of the preliminary reference coordinate system X ″ −Y ″ to provide a first direction intensity profile. The first directional strength profile may be decoded to provide a codeword and phase of the first direction. The second directional intensity profile may be decoded to provide a codeword and a relative phase of the second direction. Accordingly, the location of the ROI may be calculated.

6 illustrates a scale image, a Fourier transform region of interest, and a region of interest according to another embodiment of the present invention.

Referring to FIG. 6, a two-dimensional absolute position binary code scale 110 is used. In the two-dimensional binary code scale 110, gray and white colors represent reflective and non-reflective regions, respectively. An n-bit linear shift feedback register (LSFR) was used for the generation of absolute position binary code. The absolute position binary code (APBC) has a combination of 2n-1 numbers except when all n bits are zero-state. The magnification of the optical system may be adjusted such that the width of one pixel of the photosensor array corresponds to the width of one segment of the two-dimensional absolute position binary code scale 110. The photosensor array acquires an intensity profile or image on a two-dimensional scale. The photosensor array may have a 1286 × 960 pixel array.

 The two-dimensional scale in which the absolute position binary code (APBC) is encoded is constructed by orthogonally overlaping two single track binary code scales and then providing specific optical properties at the intersections. A single track binary code scale consists of a series of data cells representing the data bits of an absolute position binary code (APBC).

The clock section C of each data cell is repeated in periodic positions to provide an alignment key pattern for data processing. The position of the data section (D) is exchanged with the neutral section (N) to represent the binary state of each cell in the absolute position binary code (APBC). The multi-bit binary code is decoded to identify the absolute position by analyzing the scale image of the binary code scale, and the position of the data section is sub-division process. .) Is detected at a higher resolution.

The two-dimensional absolute position binary code scale 110 includes two-dimensional data cells arranged along a coordinate axis in the reference coordinate system X-Y. Meanwhile, the scale image 110 ′ includes pixels arranged along an arrangement axis of the pixels of the optical sensor array in the rotation coordinate system X′-Y ′.

The absolute position (X, Y) and the rotation angle (Θ) at the center point of the scale image 110 'are obtained by using the first position (X1, Y1) and the second position (X2, Y2) separated by an equidistant distance (L). Calculated as

[Equation 1]

When the coordinate axis of the reference coordinate system XY of the 2D phase-encoded binary scale (PEBS) does not coincide with the coordinate axis of the rotational coordinate system X'-Y 'of the optical sensor array, the data processing is performed. Image rotation is performed to obtain the first position X1, Y1 and the second position X2, Y2. The rotation coordinate system X'-Y 'may be a pixel coordinate axis of the optical sensor array.

A quadrature Fourier transform region of interest (FFT ROI) may be selected from the scale image 110 ′ photographed by the photosensor array. The number of pixels of the Fourier transform region of interest FFT ROI is 2 ^{n for} each axis of the rotation coordinate system X'-Y '. Can be a dog. The Fourier transform region of interest (FFT ROI) may be appropriately selected in consideration of data processing time. In detail, the number of pixels on the first axis (X ′ axis) may be 256 and the number of pixels on the second axis (Y ′ axis) may be 256.

[Extraction of Preliminary Rotation Angle (θ)]

FIG. 7 is a result of Fourier transforming the Fourier transform region of interest FFT ROI of FIG. 6 into the spatial frequency domain FX-FY.

Referring to FIG. 7, the Fourier transform region of interest FFT ROI is Fourier transformed into a spatial frequency domain FX-FY. The Fourier transformed Fourier transform spectrum shows four peaks in the Fourier domain. A DC filter for removing a DC component is applied to the Fourier transformed Fourier transform spectrum. Thus, four peaks are extracted. By selecting one of four peak spectra, the preliminary rotation angle [theta] is obtained based on the center point (origin) of the spatial frequency domain.

Specifically, the preliminary rotation angle θ may be calculated by applying the 2D fast Fourier transform (FFT) to the Fourier transform region of interest (FFT ROI). In the spatial frequency domain FX-FY, the Fourier transform region of interest (FFT ROI) may be represented by four points excluding the DC component. For example, the preliminary rotation angle θ of the Fourier transform region of interest FFT ROI may be calculated as follows based on the center point (origin) of the spatial frequency domain with respect to the peak spectrum present in the first quadrant. .

[Equation 2]

Referring back to FIG. 6, a first preliminary ROI ROI and a second preliminary ROI ROI2 may be selected from the entire image (1286 × 960 pixels) of the photosensor array. The first preliminary ROI and the second preliminary ROI include a first direction (X 'direction) of the rotation coordinate system X'-Y' with respect to the center point of the full scale image 110 '. It can be selected to have a symmetrically constant interval (L) or ROI offset (L) symmetrically.

8 shows a second ROI 2 ′ cut in the preliminary reference coordinate system X ''-Y '' rotated and rotated at a preliminary rotation angle θ of the second preliminary ROI ROI of FIG. 7, and FIG. The first direction intensity profile Isum (x) is obtained by adding the second ROI 2 ′ in the Y ″ axis direction.

Referring to FIG. 8, each of the first preliminary ROI ROI and the second preliminary ROI ROI rotates in a clockwise direction with respect to the reference coordinate system X-Y by the preliminary rotation angle θ.

The rotated first preliminary ROI is cut into a square shape to include at least one codeword in the axial direction of the preliminary reference coordinate system X ''-Y '' to provide the first ROI1 '. can do. The number of pixels of the first region of interest ROI1 ′ may be 184 × 184. Scale 110 uses a 10-bit binary code. The 184 pixels may correspond to 23 data cells composed of 8 segments (or pixels). 23 bits is sufficient to analyze a 10-bit codeword.

In addition, the rotated second preliminary ROI ROI2 is cut into a square shape to include at least one codeword in the axial direction of the preliminary reference coordinate system X ''-Y '' to form the second ROI2 '. Can be provided.

The first region of interest ROI1 ′ may provide absolute positions X1 and Y1 of the center through data processing. In addition, the second region of interest ROI2 ′ may provide absolute positions X2 and Y2 of the center through data processing.

The center positions (X1, Y1) and (X2, Y2) of the first ROI ROI and the second ROI ROI calculated through data processing are calculated. Subsequently, the absolute position (X, Y) and the rotation angle Θ are obtained by performing Equation (1).

 [Data processing in the area of interest]

The pixels constituting the first ROI1 'are summed or averaged in a first direction (X' '-axis direction) of the preliminary reference coordinate system X' '-Y' 'to the first ROI1'. Second directional intensity profile Isum (y). The second direction intensity profile Isum (y) of the first region of interest ROI1 ′ is summed or averaged in the first direction X ″ of the preliminary reference coordinate system X ″ -Y '' to improve stability. Improve.

The pixels constituting the first ROI1 'are summed or averaged in a second direction (Y' '-axis direction) of the preliminary reference coordinate system X' '-Y' 'to form the first ROI1'. Is the first directional intensity profile Isum (x).

The pixels constituting the second ROI ROI2 'are summed or averaged in a first direction (X' 'axis direction) of the preliminary reference coordinate system X' '-Y' 'to form the second ROI2'. Provides a second directional intensity profile of Isum (y).

The pixels constituting the second region of interest ROI2 'are summed or averaged in the second direction (Y' 'axis direction) of the preliminary reference coordinate system X' '-Y' 'to form the second region of interest ROI2'. Provides a first directional intensity profile of Isum (x).

For example, a method of extracting an absolute position from the first directional intensity profile Isum (x) of the second region of interest ROI2 ′ is described below.

For two-dimensional data cells with 8 x 8 segments, an intensity profile of 8 x n pixels or more is required for data processing of n-bit absolute position binary code (APBC). The state of the n bits of data cells provides a code word, which is converted into a coarse absolute positio through a look-up table. The phases of the data cells are then calculated to yield a precise absolute position.

The first directional intensity profile Isum (x) of the second region of interest ROI2 ′ may include 80 pixels or more in the case of a 10-bit binary code. In this example, the first directional intensity profile Isum (x) of the second region of interest ROI2 ′ comprises 184 pixels.

From the first directional intensity profile Isum (x), the absolute position with the sub-divided resolution can be obtained through the following process.

_y1)을 추출하고 상기 제1 관심 영역(ROI1')의 제2 방향 중심 위치(Y1)를 산출된다.The absolute position code and phase (using the second direction intensity profile Isum (y) of the first ROI ') may be

_y1 ) is extracted and a second direction center position Y1 of the first ROI 'is calculated.

_x1)을 추출하고 상기 제1 관심 영역(ROI1')의 제1 방향 중심 위치(X1)를 산출된다.The absolute position code and phase (using the first directional intensity profile Isum (x) of the first region of interest ROI1 ′)

_x1 ) is extracted and a first direction center position X1 of the first ROI 'is calculated.

_y2)을 추출하고 상기 제2 관심 영역(ROI2')의 제2 방향 중심 위치(Y2)를 산출한다.Absolute location code and phase (using the second direction intensity profile Isum (y) of the second region of interest ROI2 ')

_y2 ) is extracted to calculate a second direction center position Y2 of the second region of interest ROI2 ′.

_x2)을 추출하고 상기 제2 관심 영역(ROI2')의 제1 방향 중심 위치(X2)를 산출한다.Using the first directional intensity profile Isum (x) of the second region of interest ROI2 ′, an absolute position code and phase (

_x2 ) and calculates a first direction center position X2 of the second ROI 2 ′.

Center coordinates (X, Y) and rotation angle of the scale image using the center positions (X1, Y1) of the first ROI 'and the center positions (X2, Y2) of the second ROI'. (Θ) is calculated through Equation 1.

9 shows a part of the first directional intensity profile Isum (x) of the second region of interest ROI2 ′, a scale corresponding thereto, and an absolute position code corresponding thereto, respectively.

 [Step S110 of finding clock pixels Cp]

 Referring to FIG. 9, we find the clock pixels Cp most closely aligned with the clock section C of the data cell. The clock pixels Cp may be detected by checking an intensity sum Sm of pixels having an 8-pixel interval.

[Equation 3]

Where I _j represents the intensity of the j th pixel. Since the clock sections C are periodic non-reflective areas, the sum of the intensities of the clock pixels Cp has a minimum value. The width of one data cell corresponds to one pixel subset. Alternatively, one segment of the data cell corresponds to one pixel of the first directional intensity profile Isum (x).

The order of the clock pixel Cp is assigned as the clock pixel index (Cpi = 1, ..., 8). The sum of 7, 15, 23, and 31 pixels has a minimum value. Thus, the seventh (Cpi = 7) pixel corresponds to the center segment of the clock section C.

 [Step for finding absolute location code (S120)]

In order to decode the absolute position binary code APBC, an absolute code pixel index Ap is obtained by circularly shifting in the direction of decreasing the clock pixel index by two. In this example, the absolute code pixel index Ap is five.

The intensity of the absolute code pixels Ap corresponding to the absolute code pixel index Ap in each pixel subset is compared with a reference value (about 1600). If the intensity of the absolute code pixels Ap corresponding to the absolute code pixel index Ap is greater than or equal to a reference value, the data cell indicates “1”. If the intensity of the absolute code pixels Ap corresponding to the absolute code pixel index Ap is less than a reference value, the data cell indicates “0”. That is, binary states of the pixel subset are determined (S124). That is, the values of 5, 13, 21, and 29 pixels are compared with the reference value to represent data of "1100". Ten bits are read through the continued operation for one codeword.

If each of the 5, 13, 21, and 29 pixels has an intensity greater than the average intensity of all the absolute code pixels Aps, the subset containing the pixel is determined to be a "1" state (second binary state). do. In the opposite case, the subset represents a " 0 " state (first binary state). The resulting binary code is converted to an absolute location code (P _LUT ) using a lookup table (LUT).

The subdivision of the absolute position binary code (APBC) is processed in two steps. First, we use the absolute code pixel index (Api) to get the relative position between the photosensor array and the scale with the resolution of one pixel. In the next step, using a phase calculation algorithm, the relative position of the data section D is calculated with high resolution.

 [Step S130 of finding the data pixels Dp]

From the absolute code pixel index Ap obtained in the above step, we locate the data pixels Dp which are the position of the data section D and are expected to have the maximum intensity in each pixel subset ( S130).

 If the subset has a "0" state, the pixel two pixels ahead of Ap is assigned to the data pixel Dp. If the subset has a state of " 1 ", a pixel one pixel before Ap is assigned to the data pixel Dp. That is, the data pixels Dp may be 4, 12, 18, and 26 pixels.

Phase calculation phase

The precise relative position of the data section D is calculated using the pixel values around the data pixel Dp. The intensity distribution of the three pixels around the data pixel Dp may be the same for all pixel subsets. Averages of the pixel values of the same order are used to calculate the precise relative position. Thus, we can avoid iterative calculation of the relative position of each Dp.

If the intensity profile around the data pixel Dp is assumed to have a non-ideal sinusoidal waveform, and if harmonic terms above the third order term are reduced using low numerical aperture optics, then each pixel around the data pixel Dp With a phase difference of π / 3, the intensity values of the five pixels around the data pixel Dp are expressed as follows.

[Equation 4]

는 광센서 어레이의 픽셀에 대한 데이터 섹션의 정밀 상태 위치에 의하여 정해지는 위상이다.Here, I _{i, j} (j = -2, ..., 2) is an intensity value around the data pixel Dp of the i-th data cell. A ₁ , A ₂ , and A ₃ are the 0th, 1st and 2nd Fourier components of the intensity profile, respectively.

Is the phase determined by the precise state position of the data section with respect to the pixels of the photosensor array.

If the intensity value of each pixel is shift-averaged to the intensity value of two neighboring pixels, the average intensity value of these three pixels is calculated as follows.

[Equation 5]

)을 계산할 수 있다.In the mean intensity value, the third harmonic term is removed by the sum of the third order terms having a phase difference of π. Therefore, using these intensity values, we can calculate the relative phase without the nonlinear error as

) Can be calculated.

[Equation 6]

Here, n used to calculate the relative phase is the number of data cells.

)은 -π/2 부터 -π 범위의 값을 가진다.The phase (

) Ranges from -π / 2 to -π.

However, if Dp and another adjacent pixel have similar intensity values, the sum of these adjacent pixels may be greater than the sum of Dp, and the phase does not have a value in the range -π / 2 to -π. Because of the discontinuity of the arctangent function, the phase value shows a sharp change near -π. To compensate for the discontinuity, we subtract 2π from the computed phase if the phase has a positive value.

[Step Calculate Absolute Position Value (S150)]

The absolute position value Pabs is given by

[Equation 7]

The first term on the right side is the decoded absolute position with the resolution of one cell. The second term represents a particular pixel. 8 is the number of pixels per cell. The third term is the relative phase of Dp in one pixel. Here, the conversion factor is 3/4. The pitch of the sinusoidal profile of Dp is 6 pixels and the pitch of one cell is 8 pixels. To obtain the absolute position value Pabs in the longitudinal direction, the sum of the three terms is multiplied by the pitch of the data cell (p).

FIG. 10 is a conceptual diagram illustrating a scale image, a Fourier transform region of interest, a preliminary region of interest, and a region of interest according to another embodiment of the present disclosure.

FIG. 11 illustrates a second direction intensity profile summed in the first region of interest ROI1 ′ and the first direction X ″ in FIG. 10.

FIG. 12 illustrates the first direction intensity profile summed in the third ROI 3 ′ and the second direction Y ″ in FIG. 10.

Referring to FIG. 10, the scale image 110 ′ may have a form in which the intensity gradually decreases as it proceeds to the edge at the center position. This scale image 110 ′ may depend on the spatial profile of the light source that illuminates the scale. Therefore, there is a need for a method of calculating a rotation angle Θ and a center position that is not sensitive to the shell-shaped spatial distribution of the light source. That is, the intensity profiles of the ROIs can be summed or averaged radially from the center of the rotated scale image.

The absolute position measuring method according to an embodiment of the present invention uses a two-dimensional absolute position scale 110. The photosensor array captures all or a portion of the two-dimensional absolute position scale to provide a scale image 110 '.

Absolute position measuring method according to an embodiment of the present invention, the scale image 110 of the rotation coordinate system (X'-Y ') by capturing all or part of the two-dimensional absolute position scale 110 of the reference coordinate system (XY) Providing a '). Specifically, the two dimensional absolute position scale 110 uses the two dimensional data cells of FIG. 2. The two-dimensional data cells represent an absolute position binary code and are arranged along the axis of the reference coordinate system X-Y. The coordinate system of the rotation coordinate system X'-Y 'of the scale image 110' is an array coordinate system of the optical sensor array.

Subsequently, a portion of the scale image 110 ′ is selected as a Fourier transform region of interest FFT ROI and a Fourier transform region of interest FFT ROI is Fourier transformed to calculate a preliminary rotation angle θ. The same as that described in FIG. 7 of the preliminary rotation angle θ.

Subsequently, the first preliminary ROI ROI spaced apart by a predetermined distance L in the first direction X 'of the rotational coordinate system X'-Y' based on the center position of the scale image 110 '. The second preliminary ROI is selected, the first preliminary ROI and the second ROI ROI2 are rotated at the preliminary rotation angle θ, and the preliminary reference coordinate system X ''-Y The first region of interest ROI1 ′ and the second region of interest ROI2 ′ may be calculated based on the reference point ″. The first preliminary region of interest ROI1 and the second preliminary region of interest ROI2 are disposed outside the Fourier transform region of interest FFT ROI. The first region of interest ROI1 ′ and the second region of interest ROI2 ′ may include at least one codeword in the axial direction of the preliminary reference coordinate system X ″ −Y ″.

In addition, the ROI3 is spaced apart from the third ROI3 at a predetermined distance L in a second direction Y ′ perpendicular to the first direction X ′ based on the center position of the scale image 110 ′. The fourth ROI is selected. The third preliminary ROI 3 and the fourth ROI ROI 4 are rotated at the preliminary rotational angle θ, and the third preliminary ROI 3 is cut based on the preliminary reference coordinate system X ''-Y '' to cut the third preliminary ROI. The region of interest ROI3 'and the fourth region of interest ROI4' are calculated.

Referring to FIG. 11, the first ROI 1 ′ is decoded to calculate a second direction center position Y1 of the first ROI 1 ′. The second region of interest ROI2 ′ is decoded to calculate a second direction center position Y2 of the second region of interest ROI2 ′.

Specifically, decoding the first ROI 1 ′ and calculating a second direction center position Y1 of the first ROI 1 ′ constitutes the first ROI 1 ′. The second direction intensity profile Isum (y) of the first region of interest ROI1 ′ is summed or averaged in the first direction X ″ of the preliminary reference coordinate system X ″ −Y ″. To provide. The absolute position code and the phase are extracted using the second direction intensity profile Isum (y) of the first ROI, and the second direction center position of the first ROI1 'is extracted. Calculate Y1). The method of calculating the second direction center position Y1 of the first region of interest ROI1 ′ is the same as that described with reference to FIG. 9.

Decoding the second region of interest ROI2 ′ and calculating a second direction center position Y2 of the second region of interest ROI2 ′ may include pixels constituting the second region of interest ROI2 ′. Sum or average in the first direction X ″ of the preliminary reference coordinate system X ″ −Y ″ to provide a second direction intensity profile Isum (y) of the second region of interest ROI2 ′. . The absolute position code and the phase are extracted using the second direction intensity profile Isum (y) of the second region of interest ROI2 ', and the second direction center position of the second region of interest ROI2' is extracted. Calculate Y2). The method of calculating the second direction center position Y2 of the second region of interest ROI2 ′ is the same as that described with reference to FIG. 9.

Referring to FIG. 12, the first ROI 3 ′ is decoded to calculate a first direction center position X1 of the third ROI 3 ′. The fourth ROI ROI4 ′ is decoded to calculate a first direction center position X2 of the fourth ROI ROI4 ′.

The decoding of the third region of interest ROI3 ′ and calculating a first direction center position X1 of the third region of interest ROI3 ′ may include pixels constituting the third region of interest ROI3 ′. Sum or average in the second direction Y ″ of the preliminary reference coordinate system X ″ −Y ″ to provide a first direction intensity profile Isum (x) of the third region of interest ROI3 ′. . The absolute position code and the phase are extracted by using the first directional intensity profile Isum (x) of the third region of interest ROI3 'and the first direction central position of the third region of interest ROI3' Calculate X1).

The decoding of the fourth region of interest ROI4 ′ and calculating a first direction center position X2 of the fourth region of interest ROI4 ′ may include pixels constituting the fourth region of interest ROI4 ′. Sum or average in the second direction Y ″ of the preliminary reference coordinate system X ″ −Y ″ to provide a first direction intensity profile Isum (x) of the fourth ROI 4 ′. . The absolute position code and the phase are extracted using the first directional intensity profile Isum (x) of the fourth ROI, and the first directional center position of the fourth ROI ROI4 'is extracted. Calculate X2).

Subsequently, a second direction center position Y1 of the first ROI, a second direction center position Y2 of the second ROI, a first direction center position X1 of the third ROI, and the first direction The position X, Y and the rotation angle Θ of the two-dimensional absolute position scale are calculated using the first direction center position X2 of the region of interest.

[Equation 8]

Increasing the ROI offset L increases the accuracy of the angle measurement. However, the intensity uniformity decreases as it deviates from the central region. We obtained intensity profiles in four regions of interest by switching the averaging directions to simultaneously increase uniformity and ROI offset.

The intensity profiles were obtained by averaging the images aligned in the first ROI 'and the second ROI' in the horizontal direction (x '' axis direction). Each of these intensity profiles is processed to calculate Y1 and Y2 respectively.

An intensity profile was obtained by averaging the images aligned in the third ROI 'and the fourth ROI' in the vertical direction (y '' axis direction). Each of these intensity profiles is processed to calculate X1 and X2 respectively. Thus, the averaged intensity profile shows a spatially uniform distribution even at a larger ROI offset (L).

Specifically, the ROI offset L was determined to be 250 pixels and converted to the actual length at 1.00503 mm using the magnification and pixel width of the imaging system.

13 is a conceptual view illustrating an absolute position measuring apparatus according to another embodiment of the present invention.

Referring to FIG. 13, an absolute X-Y-Θ position sensor is constructed using an imaging lens, a board level camera, a cube beam splitter, and an LED light source used in a camera module of a cellular phone. The overall package size is approximately 27mm x 22mm x 27mm (W X H X D). The camera delivers 54 fps 12-bit grayscale images (1280 pixels by 960 pixels) with a pixel width of 3.75μm. The cell width of one segment and 2D phase-encoded binary scale (PEBS) is 4 μm and 32 μm, respectively. The spacing between the camera and the imaging lens is adjusted so that one pixel matches one segment of the 2D phase encoded binary scale. The absolute position binary code is coded using a 10-bit linear shift feedback register. The 2D phase encoded binary scale may be 20 mm × 20 mm or more. The 2D data cell of the 2D phase encoded binary scale is the same as described with reference to FIG. 2.

Absolute position measuring device 100 according to an embodiment of the present invention, two-dimensional absolute position scale 110 consisting of an absolute position binary code; A light source 120 irradiating light onto the two-dimensional absolute position scale 110; An optical sensor array (130) for sensing the two-dimensional absolute position scale (110); And a signal processor 150 processing the scale image 110 ′ generated by the photosensor array 130 to calculate the position (X, Y) and the rotation angle Θ of the two-dimensional absolute position scale. .

The sensor head 101 includes the light source 120, the optical system 120, and the optical sensor array 130. The optical system 120 provides an optical path between the light source 140, the two-dimensional absolute position scale 110, and the optical sensor array 130. The optical system 120 reflects the output light of the light source 140 and provides it to the two-dimensional absolute position scale 110 and transmits the light reflected from the two-dimensional absolute position scale 110. ; An imaging lens (123) for focusing the light transmitted through the beam splitter (122) to the optical sensor array (130); A support part 121 for supporting the light source 140, the beam splitter 122, and the imaging lens 123; And a spacer 124 for maintaining a gap between the photosensor array 130 and the imaging lens 123.

The absolute position measuring apparatus 100 may include a 2D binary code scale 110, an optical system 120, a light source 140, and a photo-sensor array 130. The photosensor array 130 may be a CIS, CCD or photodiode array.

The two-dimensional binary code scale 110 patterns the two-dimensional data cells by patterning a reflective chrome mask on a transparent substrate. The measuring principle is made of a reflective chrome mask, and the absolute position can be calculated by analyzing the reflected intensity profile of the two-dimensional binary code scale. The two-dimensional binary code scale 110 may be transformed into a transmissive type. The two-dimensional binary code scale 110 may be formed by painting a black pattern on a white substrate.

The light source 140 may be an LED light source in a gas ray region or an infrared region. The light provided by the light source 140 may provide spatially uniform diffused light through the diffuser plate 142.

The diffused light is provided to the beam splitter 122. The beam splitter 122 may be a cube beam splitter. The light reflected by the beam splitter 164 is reflected by the two-dimensional binary code scale 110, passes through the beam splitter 164, and is provided to the imaging lens unit 123. Light passing through the imaging lens unit 123 is provided to the optical sensor array 130. The photosensor array 130 may generate a scale image of the 2D binary code scale.

The support 121 may be a cuboid block that fixes the light source 140, the imaging lens 123, and the beam splitter 122, and has an optical path. The support 121 may be made of plastic.

Spacer 124 provides a gap between the image lens and the photosensor array 140. Accordingly, the 2D binary code scale 110 forms an image in the placement plane of the photosensor array 140.

The scale image 110 ′ obtained by the photosensor array 140 is provided to the signal processor 150 to process data. The signal processor 150 may calculate a position (X, Y) and a rotation angle Θ of the 2D binary code scale 110.

The two-dimensional absolute position scale 110 may be fixed to the moving plate of the stage 160. The stage 160 may mount an object to be moved and perform an X-Y-Θ motion. The photosensor array 140 captures a two-dimensional binary code scale 110 that moves as the stage 160 moves. The signal processor 150 calculates a position change and a rotation angle with respect to a reference position of the 2D binary code scale 110.

In addition, the stage driver 170 receives the position (X, Y) and the rotation angle (Θ) from the signal processing unit 150 to provide the X direction movement, Y direction movement, and rotation movement to the stage 160 The stop 160 may be aligned at a predetermined position and rotation angle.

[Data Acquisition]

We need to obtain a scale image 110 'of the two dimensional binary code scale 110 for data processing.

The data processing depends on the structural nature of the absolute position binary code that must be maintained in the scale image 110 '. Thus, to precisely decode the absolute position binary code, the width of the image of one segment is equal to the pixel width of detector array of the optical sensor array 140. It can be processed to reflect the magnification. Also, the image of the ROI obtained by obtaining and rotating the preliminary rotation angle θ may again satisfy an integer multiple magnification condition.

For sub-division of the absolute position binary code, the relative position of the data sections in the intensity profile can be calculated with sub-pixel resolution.

Several algorithms, such as the center of gravity algorithm and zero-crossing algorithm, are widely used for peak detection. However, the algorithms require an intensity profile that represents the peak shape of the data section with many pixels in order to obtain sufficient precision. Thus, these algorithms require a lot of resources and computation time for data acquisition and processing.

In order to efficiently obtain the relative position, we have adopted the phase calculation algorithm used in the phase-shifting interferometery. The phase calculation algorithm can calculate the phase of a sinusoidal intensity profile precisely with a small number of equally spaced pixel data.

However, the fully-resolved image of the binary code is not a sinusoidal shape but a rectangular shape.

The FFT spectrum of the image has odd order high harmonic terms except for a first order term representing a single frequency sinusoidal function. Thus, we can use an imaging lens portion 123 with a low numerical aperture (NA) to reduce the odd order high frequency terms and obtain an intensity profile of the data section that is similar to the sinusoidal function.

14 is a perspective view illustrating an absolute position measuring apparatus 100a according to still another embodiment of the present invention.

 Referring to FIG. 14, the absolute position measuring apparatus 100a may include a two-dimensional absolute position scale 110 configured of an absolute position binary code; A light source 120 irradiating light onto the two-dimensional absolute position scale 110; An optical sensor array (130) for sensing the two-dimensional absolute position scale (110); And a signal processor 150 processing the scale image 110 ′ generated by the photosensor array 130 to calculate the position (X, Y) and the rotation angle Θ of the two-dimensional absolute position scale. . The sensor head 101 includes the light source 120, the optical system 120, and the optical sensor array 130.

The stage 160 includes an X-axis stage 162 disposed on the reference plate 161, a Y-axis stage 163 that depends on the X-axis stage 162, and a rotation stage 164 that depends on the Y-axis stage 163. ). The biaxial translation stage includes an X axis stage 162 and a Y axis stage 163 dependent on the X axis stage. The moving plate 165 is disposed on the rotation stage 164. The two-dimensional absolute position binary code scale 110 is disposed on the upper surface of the moving plate 165. The sensor head 101 is disposed spaced apart on the dimensional absolute position binary code scale 110.

According to a modified embodiment of the present invention, the sensor head 101 is disposed on the reference plate 161 of the stage 160, and is mounted on the lower surface of the moving plate 165, the two-dimensional absolute position scale 110 ) Can be measured.

For evaluation of the sensor, a two-axis laser interferometer (not shown) senses the movement of the two-axis translational stage. Also, an angle encoder (not shown) detects a rotational movement of the rotation stage 164. The uncertainty of the angular encoder is less than ± 2.5 seconds of arc.

15 are graphs illustrating a measurement result of the absolute position measuring apparatus 100a according to another embodiment of the present invention.

Referring to FIG. 15, when a translational and rotational displacement input is applied to the stage 160, the resolution of the position sensor is evaluated (a). The prototype is the measurement result by the sensor head 101 of the present invention, and the solid line is the measurement result of the biaxial laser interferometer or the high precision angle encoder.

 In the experimental results, the absolute position measuring sensor of the present invention can clearly resolve the stepwise displacement of 25 nm and 0.001 degrees. The nonlinearity error of each measurement axis is estimated to be greater than 32 μm, corresponding to the length of one data cell of 2D phase-encoded binary scale (PEBS), within the ± 5 degree range actually required for precision angle alignment applications.

For the X and Y axes, the nonlinearity error was less than ± 15 nm and did not show a periodic component of 4 μm period (b). Nonlinearity error of rotation angle is less than ± 2 X 10 ^-3 degree.

Compensation algorithm for nonlinear error works effectively in the sensor configuration of the present invention.

When the angular displacements measured by the position sensor and angle encoder were analyzed using linear regression analysis, the scale factor and R square were 0.999 922 and 0.999 999 8, respectively.

The linearity of the angular measurement is mainly limited by the positional error of the scale pattern, which is estimated to be hundreds of nanometers. Therefore, to improve the performance of the angle measurement, improve the position accuracy of the phase-encoded binary scale (PEBS) pattern, and the larger ROI offset (L) can be less sensitive to this error source.

The squareness of the 2D phase encoded binary scale was evaluated at 114 μrad using the reversal technique, and was compensated before evaluating the accuracy of the 2D position measurement.

16 shows the results of an absolute position sensor in accordance with another embodiment of the present invention.

Referring to FIG. 16, an absolute position measuring device (or X-Y-Θ sensor) according to an exemplary embodiment measures 2D positions equally spaced at 50 nm intervals in a range of ± 200 nm. Each measurement position is generated by a two-axis lead zirconate titanate (PZT) stage controlled using a laser interferometer. The position values obtained in 10 measurements are displayed as data points. The standard deviation of repeat measurements is less than 18 nm. The average position value of the X-Y-Θ sensor was consistent with the position value of the laser interferometer within 11 nm.

When the accuracy of the absolute positioning device 100a is evaluated in the 16 mm X 16 mm range, the maximum deviation is 0.51 μm. However, it is mainly due to the uncorrected position error of the 2D phase encoded binary scale. This error can be reduced by using a higher quality scale.

The precision of the absolute position measuring apparatus 100a can be improved by increasing the number of data used for data processing. The size of the region of interest is currently set to a minimum with low computational burden.

The refresh rate is mainly limited by the camera frame rate. The measurement range of 2D position is generally limited by the size of the 2D phase encoded binary scale, but due to the ambiguity of the preliminary rotation angle estimation using 2D FFT, absolute angular displacement can be measured within ± 45 degrees.

Absolute position measuring device according to an embodiment of the present invention can accurately measure the accurate 3D plane position (X-Y-Θ) in a simple and miniaturized configuration. Thus, user-defined scale sizes and single or multiple sensor heads can be placed, which can be effectively used for position control and calibration of multi-axis stages of varying precision.

17 is a conceptual diagram illustrating a plane alignment apparatus according to another embodiment of the present invention.

FIG. 18 is a flowchart for describing a method of operating the planar alignment device of FIG. 17.

Referring to FIGS. 17 and 18, a three degree of freedom planar alignment device 200 includes a stage 160 that includes a stationary plate 161 and a moving plate 165 and provides three degree of freedom position alignment; An X-Y-Θ sensor head 101 mounted to the fixed plate 161 of the stage 160; A two-dimensional absolute position scale 101 mounted to the moving plate 165 of the stage 160; Analyze the scale image 110 'of the two-dimensional absolute position scale 110 captured by the XY-Θ sensor head 101 to position the three degrees of freedom motion of the movable plate 165 of the stage 160. Signal processing unit 150 for extracting the; And a stage driver 170 driving the stage 160 by the displacement amount of the movable plate 165.

The stage 160 may provide three degrees of freedom motion in a plane. The stage can be an XYΘ stage providing two translational movements and one rotational movement or a UVW stage using three linear movements.

The stage 160 includes a fixed plate 161 and a moving plate 165 for performing three degrees of freedom. The X-Y-Θ sensor head 101 may be fixed to the fixed plate 161, and the two-dimensional absolute position scale 110 may be mounted on the moving plate 165 of the stage. The two-dimensional absolute position scale 110 may move together with the moving plate 165 of the stage. Accordingly, the X-Y-Θ sensor head 101 may capture the two-dimensional absolute position scale 110 to provide a scale image 110 ′.

The stage 160 may include a motor for each axis of three degrees of freedom. Each motor may move the moving plate 165 by providing a linear motion or a rotary motion.

The X-Y-Θ sensor head 101 may include the light source 120, the optical system 120, and the optical sensor array 130. The photosensor array 130 provides the signal processor 150 with a scale image 110 ′ of the 2D absolute position scale 110. The signal processor 150 may calculate a center position (X, Y) and a rotation angle Θ of the scale image 110 ′ or a position and rotation angle of the moving plate 165. Accordingly, the substrate mounted on the movable plate can move at a predetermined position and rotation angle.

The two-dimensional absolute position scale 110 may be a two-dimensional phase encoded binary scale with an absolute position binary code encoded.

The controller 172 receives an initial center position X ₀ , Y ₀ and an initial rotation angle Θ ₀ of the two-dimensional absolute position scale from the signal processor 150. The controller 172 may be provided with a displacement amount dX, dY, dΘ that is preset or detected through another sensor. The displacements dX, dY, dΘ may be converted into driving amounts dU, dV, dW of each motor. When the stage 160 is a UVW stage, the driving amounts dU, dV, and dW may include coordinate transformation. When the stage 160 is an XYΘ stage, the driving amounts dU, dV, and dW may be converted into physical quantities for directly driving a motor without coordinate transformation. The target position (X = X ₀ + dX, Y = Y ₀ + dY, Θ = Θ ₀ + dΘ) of the moving plate of the stage 160 is the displacement amount at the initial position (X ₀ , Y ₀ , Θ ₀ ). dX, dY, dΘ) may be the sum of the values. The stage driver 170 may receive the driving amounts dU, dV, and dW from the controller 172 to control each motor.

The stage driver 170 may include a driving circuit for driving the stage. The motor of the stage may include a rotating motor and a scour for converting the rotational motion of the motor into a linear motion. The motor of the stage may comprise a linear motor, a linear actuator.

A method of operating a three degree of freedom planar alignment device may include: measuring an initial position (X ₀ , Y ₀ , Θ ₀ ) of the moving plate 165 of the stage 160 (S111); Setting a displacement amount (dX, dY, dΘ) of the stage by a difference between a target position of the moving plate of the stage 160 and the initial position (X ₀ , Y ₀ , Θ ₀ ) (S112); Calculating a driving amount (dU, dV, dW) of the stage based on the displacement amount (dX, dY, dΘ) (S113); And driving each of the motors of the stage 160 with the driving amounts dU, dV, and dW (S114).

After the stage 160 is moved, the current position (X, Y, Θ) of the stage is measured (S115) to confirm that the target position (X ₀ + dX, Y ₀ + dY, Θ ₀ + dΘ) is reached. It includes the step (S116). If there is a difference between the current position (X, Y, Θ) and the target position (X ₀ + dX, Y ₀ + dY, Θ ₀ + dΘ), the above steps are repeated again or an error message is generated.

The two-dimensional absolute position scale 110 and the XY-Θ sensor head 101 directly measure the center positions X and Y and the rotation angle Θ in real time. Given a target position (X = X ₀ + dX, Y = Y ₀ + dY, Θ = Θ ₀ + dΘ), after the stage completes the movement through the driving amounts dU, dV, dW, It may be confirmed whether the 2D absolute position scale 110 has reached the target position. Accordingly, the three degree of freedom planar alignment device 200 can scan a plurality of elements arranged on a substrate or perform a predetermined process with high speed and precision.

19 is a conceptual diagram illustrating a plane alignment apparatus according to another embodiment of the present invention.

20 is a flowchart for explaining a method of operating the flat alignment device of FIG. 19.

21A and 21B are plan views illustrating the operation of the planar alignment device of FIG. 19.

Referring to FIGS. 19, 20, 21A, and 21B, a three degree of freedom planar alignment device 300 includes a stage (161) and a movable plate (165), and a stage providing three degrees of freedom position alignment ( 160); An X-Y-Θ sensor head 101 mounted to the fixed plate 161 of the stage; A two-dimensional absolute position scale 110 mounted to the moving plate 165 of the stage; A signal processor 150 for analyzing the scale image 110 'of the two-dimensional absolute position scale 110 captured by the X-Y-Θ sensor head to extract the position of three degrees of freedom motion of the stage 160; At least one vision camera (182) for inspecting an alignment mark (12) of the substrate (10) mounted on the movable plate (165) of the stage (160); The stage 160 with the driving amount dU, dV, dW of the stage based on the difference between the initial position P of the alignment mark 12 of the substrate 10 and the final alignment position O of the alignment mark. Stage driving unit 170 for driving).

The coordinate system of the fixed plate may be X-Y, the coordinate system of the moving plate may be X'-Y ', and the coordinate system of the substrate may be X' '-Y' '. The two-dimensional absolute position scale 110 may be aligned to the X'-Y 'coordinate system.

The stage 160 may be an XYΘ stage or a UVW stage. The two-dimensional absolute position scale 110 may be mounted to be exposed to the lower surface of the moving plate 165. The position of the three degrees of freedom movement may include two translational movements and one rotational movement.

The substrate 10 may be disposed on the moving plate 165 of the stage. The substrate 10 may be a printed circuit board, a semiconductor substrate, an LCD, an OLED, a plastic substrate, a metal substrate, a glass substrate, or a ceramic substrate. The substrate 10 may include at least one alignment mark 12. The alignment mark 12 may be cross-shaped.

At least one vision camera 182 may image an alignment mark 12 of a substrate mounted on the moving plate 165. The vision camera 182 may provide an image to the vision controller 184, and the vision controller 184 may provide an initial position P of the alignment mark 12 of the substrate through data processing. The vision control unit 184 calculates displacement amounts dX, dY, dΘ using the final alignment position O of the alignment marker 12 and the initial position P of the alignment mark 12 of the substrate. Can be.

The displacements dX, dY, and dΘ may be calculated by analyzing a difference between the final alignment position O and the initial position P of the alignment marker 12 in the image captured by the vision camera 182.

The stage 160 may be moved based on the displacements dX, dY, and dΘ. In detail, the controller 172 receives the displacements dX, dY, and dΘ and changes the driving amounts dU.dV and dW to drive the motors of the stage 160, and the driving amount dU.dV. , dW) may be provided to the stage driver 170, and the stage driver 170 may control a motor.

When the stage 160 is an XYΘ stage, the controller 172 changes the displacement amount dx, dy, dΘ into the driving amount dU.dV, dW without coordinate transformation. On the other hand, when the stage 160 is a UVW stage, the control unit 172 changes the displacement amount (dx, dy, dΘ) to the driving amount (dU.dV, dW) through coordinate transformation.

The controller 172 receives an initial center position X ₀ , Y ₀ and an initial rotation angle Θ ₀ of the two-dimensional absolute position scale 110 from the signal processor 150. The XY-Θ sensor head 101 and the signal processor 150 may check in real time the current position (X, Y, Θ) of the stage 160 as the stage 160 moves. When the current position (X, Y, Θ) of the stage 160 is a target position (X ₀ + dX, Y ₀ + dY, Θ ₀ + dΘ), the vision camera 182 is an alignment mark 12 of the substrate. Image, the vision camera provides an image to the vision control unit, and the vision control unit 184 performs a data processing so that the current position P ′ of the alignment mark 12 of the substrate is the final alignment position O. Make sure you are located in.

The X-Y-Θ sensor head 101 and the signal processor can track the current position (X, Y, Θ) of the stage, so that no additional algorithm is required.

The operating method of the 3 degree of freedom plane alignment device may include an initial position (X ₀ , Y) of 3 degrees of freedom of the 2D absolute position scale 110 using the XY-Θ sensor head 101 and the signal processor 150. ₀ , Θ ₀ ) (S212); Measuring (S213) an initial position (P) of three degrees of freedom of the alignment marker (12) of the substrate using the vision camera (182); Setting a displacement amount (dX, dY, dΘ) by a difference between an initial position P of three degrees of freedom of alignment markers of the substrate and a final alignment position O of three degrees of freedom of alignment markers of the substrate (S214); Calculating a driving amount (dU.dV, dW) of the stage by using the initial position (X ₀ , Y ₀ , Θ ₀ ) of the scale (110) and the displacement amount (dX, dY, dΘ) (S215); Driving each of the motors of the stage 160 with the driving amounts dU.dV and dW (S216); And measuring the current position (X, Y, Θ) of three degrees of freedom of the movable plate 165 of the stage by using the XY-Θ sensor head 101 and the signal processor 150 (S217). do.

The initial position (X ₀ , Y ₀ , Θ ₀ ) of the absolute position binary scale provides information about a rotation origin when converting the displacement amount dX, dY, dΘ into the drive amount dU.dV, dW. can do.

In the method of operating a three degree of freedom plane alignment device, the current position (X, Y, Θ) of three degrees of freedom of the moving plate 165 of the stage is the initial position (X) of three degrees of freedom of the two-dimensional absolute position scale 110. Determining whether it is a target position (X ₀ + dX, Y ₀ + dY, Θ ₀ + dΘ) given by ₀ , Y ₀ , Θ ₀ and the displacements dX, dY, dΘ (S218); Measuring (S219) the current position of three degrees of freedom of the alignment marker (12) of the substrate using the vision camera (182); And comparing the difference between the current position P ′ of the three degrees of freedom of the alignment marker 12 of the substrate and the final alignment position O of the three degrees of freedom (S220). It may further include at least one of.

22 is a perspective view illustrating a UVW stage according to another embodiment of the present invention.

FIG. 23 is a plan view illustrating a motion of the UVW stage of FIG. 22.

22 and 23, the UVW stage 260 is a fixed plate 161. The moving plate 165 includes four XYΘ stages 262, 263, 264, and 265 disposed between the fixed plate and the moving plate. The four XYΘ stages 262, 263, 264, and 265 may be arranged symmetrically with each other at regular intervals with respect to the X-Y coordinate axis. The four XYΘ stages 262, 263, 264, 265 may include three XYΘ driving stages 262, 263, 264 and one XYΘ driverless stage 265. Three XYΘ driving stages 262, 263, 264 may be provided with driving force through a motor. The three XYΘ driving stages 262, 263, 264 provided with the driving force may include a U driving stage 263, a V driving stage 264, and a W driving stage 262. The U driving stage 263 and the V driving stage 264 may have driving axes in the Y-axis direction and may be spaced apart from each other in the x-axis direction. The W driving stage 262 may have a driving force in the X axis direction. The W driving stage 262 and the dummy stage 265 may be spaced apart from each other in the y-axis direction.

Each of the U driving stage 263 and the V driving stage 264 receives a driving force from a motor and is mounted on the first direction driving linear stage 263a and the second direction driving linear stage 263b mounted on the first direction linear stage. . And a non-driven rotation stage 263c mounted on the second direction non-driven linear stage. The first directional driving linear stage 263a of the U driving stage and the V driving stage may move in the Y-axis direction of the fixed plate.

The W drive stage 262 receives a driving force from a motor and is mounted in a first direction drive linear stage 262a and a second direction driveless linear stage 262b mounted on the first direction linear stage. And a non-driven rotation stage 262c mounted in the second direction non-driven linear stage. The first direction driving linear stage of the W driving stage 262 may move in the X axis direction of the fixed plate.

The dummy stage 262 is a first direction non-linear linear stage, a second direction non-linear linear stage mounted on the first direction linear stage. And a non-driven rotating stage mounted on the second directionless linear stage.

The X-Y-Θ sensor head 101 may be disposed at the center of the fixing plate 161. In order to maintain a constant distance between the XY-Θ sensor head 101 and the two-dimensional absolute position scale 110, the XY-Θ sensor head 101 can be fixed at a constant height from the fixed plate 161. have.

A rectangular through hole 165a may be disposed at the center of the moving plate 165. The two-dimensional absolute position scale 110 may be inserted into and fixed to the through hole 165a to face the X-Y-Θ sensor head 101.

While the invention has been shown and described with respect to certain preferred embodiments thereof, the invention is not limited to these embodiments, and has been claimed by those of ordinary skill in the art to which the invention pertains. It includes all the various forms of embodiments that can be implemented without departing from the spirit.

100: absolute position measuring device
110: 2-D absolute position scale
110 ': scale image

Claims (18)

A stage comprising a stationary plate and a moving plate and providing three degrees of freedom position alignment;
An XY-Θ sensor head mounted to the fixed plate of the stage;
A two-dimensional absolute position scale mounted to the moving plate of the stage;
A signal processor configured to analyze a scale image of the two-dimensional absolute position scale picked up by the XY-Θ sensor head and extract a position of three degrees of freedom motion of the moving plate of the stage; And
It includes a stage driving unit for driving the stage by the displacement amount of the moving plate,
The two-dimensional absolute position scale comprises two-dimensional data cells composed of a combination of a first absolute position binary code arranged in a first direction of a reference coordinate system and a second absolute position binary code arranged in a second direction,
Each of the first absolute position binary code and the second absolute position binary code consists of one-dimensional data cells,
The one-dimensional data cell comprises a data section, a neutral section, and a clock section,
A two-dimensional data cell representing a (0,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (0,1) state has a data section (D) representing "1" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (1,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("1" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (1,1) state has a data section (D) representing "1" of absolute position binary code in the second direction and a data section ("1" of absolute position binary code in the first direction). 3 degrees of freedom planar alignment device, characterized in that marked at the intersection of D). According to claim 1,
And said stage is an XYΘ stage or a UVW stage. According to claim 1,
And the two-dimensional absolute position scale is mounted to be exposed to the lower surface of the moving plate. According to claim 1,
The displacement amount of the movable plate is based on the position of three degrees of freedom motion of the stage,
And wherein the position of the three degrees of freedom motion comprises two translational motions and one rotational motion. delete The method of claim 1,
Each of the data section, the neutral section, and the clock section comprises one or more regularly spaced segments,
The one-dimensional data cell exhibits a first state (“0”) and comprises a data section, a neutral section, and a clock section arranged in succession,
And said one-dimensional data cell comprises a neutral section, a data section, and a clock section in a second state ("1") and arranged in series. The method of claim 6,
The neutral section is 2 segments,
The data section is 3 segments,
And said clock section is three segments. A stage comprising a stationary plate and a moving plate and providing three degrees of freedom position alignment; An XY-Θ sensor head mounted to the fixed plate of the stage; A two-dimensional absolute position scale mounted to the moving plate of the stage; A signal processor configured to analyze the scale image of the two-dimensional absolute position scale from the XY-Θ sensor head to extract the position of three degrees of freedom motion of the stage; And a stage driver for driving the stage with the displacement amount of the stage.
Measuring an initial position of a moving plate of the stage;
Setting a displacement amount of the stage by a difference between a target position of the moving plate of the stage and the initial position;
Calculating a driving amount of the stage based on the displacement amount; And
Driving each of the motors of the stage with the driving amount;
The two-dimensional absolute position scale comprises two-dimensional data cells composed of a combination of a first absolute position binary code arranged in a first direction of a reference coordinate system and a second absolute position binary code arranged in a second direction,
Each of the first absolute position binary code and the second absolute position binary code consists of one-dimensional data cells;
The one-dimensional data cell comprises a data section, a neutral section, and a clock section,
A two-dimensional data cell representing a (0,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (0,1) state has a data section (D) representing "1" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (1,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("1" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (1,1) state has a data section (D) representing "1" of absolute position binary code in a second direction and a data section ("1" of absolute position binary code in a first direction). A method of operating a three degree of freedom planar alignment device, characterized in that marked at the intersection of D). The method of claim 8,
And measuring the current position of the stage after the stage is moved to confirm the arrival at the target position. A stage comprising a stationary plate and a moving plate and providing three degrees of freedom position alignment;
An XY-Θ sensor head mounted to the fixed plate of the stage;
A two-dimensional absolute position scale mounted to the moving plate of the stage;
A signal processor extracting a position of three degrees of freedom motion of the stage by analyzing a scale image of the two-dimensional absolute position scale captured by the XY-Θ sensor head;
At least one vision camera inspecting an alignment mark of a substrate mounted to the moving plate of the stage; And
And a stage driver for driving the stage with a driving amount of the stage based on a difference between the alignment mark of the substrate and the final alignment position of the alignment mark.
The two-dimensional absolute position scale comprises two-dimensional data cells composed of a combination of a first absolute position binary code arranged in a first direction of a reference coordinate system and a second absolute position binary code arranged in a second direction,
Each of the first absolute position binary code and the second absolute position binary code consists of one-dimensional data cells,
The one-dimensional data cell comprises a data section, a neutral section, and a clock section,
A two-dimensional data cell representing a (0,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (0,1) state has a data section (D) representing "1" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (1,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("1" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (1,1) state has a data section (D) representing "1" of absolute position binary code in the second direction and a data section ("1" of absolute position binary code in the first direction). D) 3 degrees of freedom planar alignment device, which is marked at the intersection point. The method of claim 10,
And said stage is an XYΘ stage or a UVW stage. The method of claim 10,
And the two-dimensional absolute position scale is mounted to be exposed to the lower surface of the moving plate. The method of claim 10,
And wherein the position of the three degrees of freedom motion comprises two translational motions and one rotational motion. delete The method of claim 10,
Each of the data section, the neutral section, and the clock section comprises one or more regularly spaced segments,
The one-dimensional data cell exhibits a first state (“0”) and comprises a data section, a neutral section, and a clock section arranged in succession,
And said one-dimensional data cell comprises a neutral section, a data section, and a clock section in a second state ("1") and arranged in series. The method of claim 15,
The neutral section is 2 segments,
The data section is 3 segments,
And said clock section is three segments. A stage comprising a stationary plate and a moving plate and providing three degrees of freedom position alignment; An XY-Θ sensor head mounted to the fixed plate of the stage; A two-dimensional absolute position scale mounted to the moving plate of the stage; A signal processor extracting three degrees of freedom positions of the stage by analyzing a scale image of the two-dimensional absolute position scale picked up by the XY-Θ sensor head; At least one vision camera inspecting an alignment mark of a substrate mounted to the moving plate of the stage; And a stage driver for driving the stage with the driving amount of the stage based on the difference between the three degrees of freedom position of the alignment mark of the substrate and the last three degrees of freedom position of the alignment mark. silver:
Measuring an initial position of three degrees of freedom of the two-dimensional absolute position scale using the XY-Θ sensor head and the signal processor;
Measuring an initial position of three degrees of freedom of the alignment marker of the substrate using the vision camera;
Setting a displacement amount by a difference between an initial position of three degrees of freedom of the alignment markers of the substrate and a final alignment position of the three degrees of freedom of the alignment markers of the substrate;
Converting the initial position of the two-dimensional absolute position scale and the displacement amount into the driving amount of the stage;
Driving each of the motors of the stage with the driving amount; And
Measuring the current position of three degrees of freedom of the moving plate of the stage using the XY-Θ sensor head and the signal processor;
The two-dimensional absolute position scale comprises two-dimensional data cells composed of a combination of a first absolute position binary code arranged in a first direction of a reference coordinate system and a second absolute position binary code arranged in a second direction,
Each of the first absolute position binary code and the second absolute position binary code consists of one-dimensional data cells,
A two-dimensional data cell representing a (0,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (0,1) state has a data section (D) representing "1" of absolute position binary code in the second direction and a data section ("0" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (1,0) state has a data section (D) representing "0" of absolute position binary code in the second direction and a data section ("1" of absolute position binary code in the first direction). Marked at the intersection of D),
A two-dimensional data cell representing a (1,1) state has a data section (D) representing "1" of absolute position binary code in the second direction and a data section ("1" of absolute position binary code in the first direction). A method of operating a three degree of freedom planar alignment device, characterized in that it is marked at the intersection of D). The method of claim 17,
Determining whether the current position of the three degrees of freedom of the moving plate of the stage is a target position given by the lowest position of the three degrees of freedom of the two-dimensional absolute position scale and the displacement amount;
Measuring the current position of three degrees of freedom of the alignment marker of the substrate using the vision camera; And
Comparing the difference between the current position of the three degrees of freedom of the alignment marker of the substrate and the final alignment position; Method of operation of a three degree of freedom planar alignment device further comprising at least one of.

Images