CN101957171B - Coaxial digital holography method capable of effectively inhibiting zero-order and conjugate images - Google Patents

Abstract

The invention relates to a coaxial digital holography method capable of effectively inhibiting zero-order and conjugate images. The method is characterized in that: aiming at a diffuse reflection type object or a transmission type object, through special design of a digital hologram recording process, a holographic reproduction image inhibiting the zero-order diffraction and conjugate image is acquired through simple numerical calculation by using only one digital hologram; and in a hologram reproduction process, an aperture or low-pass filtering operation can buffer zero-order + one-order diffraction optical waves and all the high-order diffraction optical waves and only allows the -1-order diffraction optical wave to transmit, so that the -1-order hologram is separated and reproduced. Compared with the traditional coaxial digital hologram, of which the reproduction of the hologram is seriously interfered by the zero-order and conjugate image, the holographic reproduction image by the method has ideal effect and overcomes the defects of non-instantaneity of the methods, such as phase shift, HRO substraction and the like, and complexity, multi-step calculation and the like of numerical iteration algorithm.

Description

A kind of coaxial digital hologram method that can effectively suppress zero level and conjugate image

Technical field

The present invention relates to the holographic technique field, particularly a kind of coaxial digital hologram method that can effectively suppress zero level and conjugate image.

Background technology

When how Britain nationality scholar Jia Bai improves the resolving power of electron microscope in research, the thought of in-oline holography has been proposed first.The characteristics of in-oline holography are that reference light wave is coaxial with the thing light wave, and recording beam path is simple, and are lower to coherence's requirement of environment and light source.But shortcoming is that Zero-order diffractive (being direct transmission light) and conjugate image are also coaxial with the reproduction picture of original field, thereby makes the reproduction of original field look like to receive very strong background interference, and the Reconstructed Image Quality amount descends.Compare with in-oline holography; Thing light and reference light have certain included angle in the off-axis holography; Thereby Zero-order diffractive, reproduction picture and conjugate image thereof in the hologram reconstruction process are separated from each other; But off-axis holography is had relatively high expectations to hologram record light path, environmental vibration and recording medium, and and is not suitable for fields such as Particle Field measurement.

In recent years, digital holography becomes the focus of research gradually.Digital holography is with solid imaging device CCD (Charge Coupled Device; Charge-coupled image sensor) or CMOS (Complementary Metal-OxideSemiconductor; Metal-oxide semiconductor (MOS)) substitutes traditional silver salt dry plate and come recorded hologram; Through the diffraction process of Computer Numerical Simulation hologram, utilize fast fourier transform algorithm and spectral filtering processing etc. to obtain the amplitude and the phase information of thing light wave fields, realize the reconstruct of article light wave fields; Avoid traditional wet-chemical treatment process, had advantages such as quick, real-time.Based on the different recording light channel structure, digital holography also is divided into coaxial and leaves two types on axle.Coaxial digital holography is low than the off-axis digital holography to the spatial resolution requirement of CCD, but similar with traditional coaxial optical holography, the reproduction picture of coaxial digital holography receives the interference of Zero-order diffractive and conjugate image equally, thereby has limited its widespread use.

At present, coaxial digital holography mainly adopts the numerical value iterative algorithm of phase-shifting technique, HRO subtraction technique or process of reconstruction etc., eliminates the influence of Zero-order diffractive and conjugate image in the numerical reconstruction picture.Phase-shifting technique requires to record successively four width of cloth or several digital holograms of certain phase shift difference; And through several holograms that write down are carried out numerical evaluation; To eliminate Zero-order diffractive and conjugate image; But in the recording process of several holograms, often be difficult to accurately control phase shift, and can't utilize this method for fast-changing object.The HRO subtraction technique need utilize CCD write down respectively thing light, reference light with and formed digital hologram, and it is carried out relevant numerical calculates, but similar with phase-shifting technique, be difficult to use in the dynamic changing process of object equally.The numerical value iterative algorithm of process of reconstruction is introduced iteration factor through the numerical reconstruction process at coaxial digital hologram; Obtain not have the holographic reconstructed image that does not have direct transmission light and conjugate image influence fully through the multistep iterative computation; But its computing is complicated, and multi-step operation is consuming time more of a specified duration.

Summary of the invention

The technical matters that solves

Weak point for fear of prior art; The present invention proposes a kind of in-line holographic method that can effectively suppress Zero-order diffractive and conjugate image; Particular design through the digital hologram recording process; Only utilize a width of cloth digital hologram, and, overcome the method for having and to write down shortcomings such as several holograms or computing complicacy through the be inhibited holographic reconstructed image of Zero-order diffractive and conjugate image of simple numerical operation.

Technical scheme

A kind of diffuse reflection type object can effectively suppress the coaxial digital hologram method of Zero-order diffractive and conjugate image, it is characterized in that step is following:

Step 1 is provided with an aperture between object under test and holographic interference pattern digital recording position, laser radiation also sees through object under test or passes through aperture from the laser beam of object under test surface reflection, arrives record position along same optical axis direction and forms the thing light wave; This thing light wave interferes at record position and reference light wave, forms the holographic interference pattern of reflection object under test; Said reference light wave is relevant and laser light wave optical axis coincidence with the thing light wave;

Step 2, with the light wave of reference light wave conjugation reproduction lighting light wave as the numerical simulation calculation process, utilize Fresnel-Kirchhoff diffraction integral formula of describing the light wave diffraction propagation

$U(\mathrm{\&xi;},\mathrm{\&eta;})=-\frac{i}{\mathrm{\&lambda;}}{\&Integral;}_{-\&infin;}^{\&infin;}{\&Integral;}_{-\&infin;}^{\&infin;}h(x,y)R(x,y)\frac{\exp \left(\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">i</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}\right)}{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}}\&times;(\frac{1}{2}+\frac{1}{2}\cos \mathrm{\&theta;})\mathrm{dxdy}$

Obtain COMPLEX AMPLITUDE U (ξ, η), wherein: (ξ; The plane that η) calculates for integral formula, (x y) is the coordinate of the holographic interference plan of object under test; Wavelength of Laser when λ equals laser radiation for reproducing the lighting light wave wavelength; R equals the conjugation of the complex amplitude of reference light wave for the COMPLEX AMPLITUDE of reproducing lighting light wave, and (x y) is the intensity that the complex amplitude transmission function of hologram equals holographic interference pattern to h; Cos θ is an inclination factor, and d is that the diffraction distance equals the distance of aperture to record position;

(ξ, η) delivery value and ask square obtains diffraction pattern H to COMPLEX AMPLITUDE U then ₁Intensity distributions;

Step 3 is chosen diffraction pattern H ₁Low frequency part to diffraction pattern H ₁Carry out filtering, obtain filtered diffraction pattern H ₂Described low frequency part is diffraction pattern H ₁Inscribed circle radius 1%～70%;

Step 4 is to diffraction pattern H ₂The digital hologram that utilizes Fresnel-Kirchhoff diffraction integral formula to calculate effective inhibition zero level and conjugate image once more reproduces the diffraction pattern H of picture ₃Diffraction is got the distance of object under test to aperture apart from d in the calculating.

A kind of transmission-type object can effectively suppress the coaxial digital hologram method of Zero-order diffractive and conjugate image, it is characterized in that step is following:

Step 1 arrives record position formation thing light wave to converge laser radiation and to see through object under test, and this thing light wave interferes at record position and reference light wave, forms the holographic interference pattern of reflection object under test; Said reference light wave is relevant and laser light wave optical axis coincidence with the thing light wave; Described record position is arranged at and converges laser radiation also through after the convergent point that forms behind the object under test;

Step 2, with the light wave of reference light wave conjugation reproduction lighting light wave as the numerical simulation calculation process, utilize Fresnel-Kirchhoff diffraction integral formula of describing the light wave diffraction propagation

$U(\mathrm{\&xi;},\mathrm{\&eta;})=-\frac{i}{\mathrm{\&lambda;}}{\&Integral;}_{-\&infin;}^{\&infin;}{\&Integral;}_{-\&infin;}^{\&infin;}h(x,y)R(x,y)\frac{\exp \left(\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">i</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}\right)}{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}}\&times;(\frac{1}{2}+\frac{1}{2}\cos \mathrm{\&theta;})\mathrm{dxdy}$

Obtain COMPLEX AMPLITUDE U (ξ, η), wherein: (ξ; The plane that η) calculates for integral formula, (x y) is the coordinate of the holographic interference plan of object under test; Wavelength of Laser when λ equals laser radiation for reproducing the lighting light wave wavelength; R equals the conjugation of the complex amplitude of reference light wave for the COMPLEX AMPLITUDE of reproducing lighting light wave, and (x y) is the intensity that the complex amplitude transmission function of hologram equals holographic interference pattern to h; Cos θ is an inclination factor, and d is that the diffraction distance equals to converge laser radiation also through the distance of the convergent point that forms behind the object under test to record position;

(ξ, η) delivery value and ask square obtains diffraction pattern H to COMPLEX AMPLITUDE U then ₁Intensity distributions;

Step 3 is chosen diffraction pattern H ₁Low frequency part to diffraction pattern H ₁Carry out filtering, obtain filtered diffraction pattern H ₂Described low frequency part is diffraction pattern H ₁Inscribed circle radius 1%～70%;

Step 4 is to diffraction pattern H ₂The digital hologram that utilizes Fresnel-Kirchhoff diffraction integral formula to calculate effective inhibition zero level and conjugate image once more reproduces the diffraction pattern H of picture ₃Diffraction is got the distance of the convergent point that object under test forms after converge laser radiation and see through object under test in the calculating apart from d.

A kind of transmission-type object can effectively suppress the coaxial digital hologram method of Zero-order diffractive and conjugate image, it is characterized in that step is following:

Step 1 is provided with lens between object under test and holographic interference pattern digital recording position, with the parallel laser irradiation and through object under test, converge back arrival record position through lens and form the thing light wave; This thing light wave interferes at record position and reference light wave, forms the holographic interference pattern of reflection object under test; Said reference light wave is relevant and laser light wave optical axis coincidence with the thing light wave; Described record position is arranged at and converges laser radiation also through after the convergent point that forms behind the object under test;

Step 2, with the light wave of reference light wave conjugation reproduction lighting light wave as the numerical simulation calculation process, utilize Fresnel-Kirchhoff diffraction integral formula of describing the light wave diffraction propagation

$U(\mathrm{\&xi;},\mathrm{\&eta;})=-\frac{i}{\mathrm{\&lambda;}}{\&Integral;}_{-\&infin;}^{\&infin;}{\&Integral;}_{-\&infin;}^{\&infin;}h(x,y)R(x,y)\frac{\exp \left(\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">i</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}\right)}{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}}\&times;(\frac{1}{2}+\frac{1}{2}\cos \mathrm{\&theta;})\mathrm{dxdy}$

Obtain COMPLEX AMPLITUDE U (ξ, η), wherein: (ξ; The plane that η) calculates for integral formula, (x y) is the coordinate of the holographic interference plan of object under test; Wavelength of Laser when λ equals laser radiation for reproducing the lighting light wave wavelength; R equals the conjugation of the complex amplitude of reference light wave for the COMPLEX AMPLITUDE of reproducing lighting light wave, and (x y) is the intensity that the complex amplitude transmission function of hologram equals holographic interference pattern to h; Cos θ is an inclination factor, and d is that the diffraction distance equals to converge laser radiation also through the distance of the convergent point that forms behind the object under test to record position;

(ξ, η) delivery value and ask square obtains diffraction pattern H to COMPLEX AMPLITUDE U then ₁Intensity distributions;

Step 3 is chosen diffraction pattern H ₁Low frequency part to diffraction pattern H ₁Carry out filtering, obtain filtered diffraction pattern H ₂Described low frequency part is diffraction pattern H ₁Inscribed circle radius 1%～70%;

Step 4 is to diffraction pattern H ₂Utilize Fresnel-Kirchhoff diffraction integral formula to calculate diffraction pattern H once more ₄Diffraction in the calculating is got the distance of the convergent point that lens form after converge laser radiation and see through object under test apart from d;

Step 5 is to diffraction pattern H ₄Intensity distributions multiply by Wherein P (x y) is the pupil function of lens, Be the phase tranformation that lens are introduced, continue to utilize Fresnel-Kirchhoff diffraction integral formula to calculate the H of the digital hologram reproduction picture of effective inhibition zero level and conjugate image afterwards ₃Diffraction in the calculating is got the distance of lens to object under test apart from d.

The invention has the beneficial effects as follows: utilize that method finally can obtain to reproduce picture clearly among the present invention, and suppressed zero level and conjugate image influence in the in-line holographic.Method is simple among the present invention; Feasible; Only need light path be adjusted slightly, promptly can only utilize a width of cloth digital hologram through the particular design of digital hologram recording process in the record and the reproduction process of hologram; And through simple numerical operation, carry out the inhibition that digital filtering is realized zero level and conjugate image in the in-line holographic.In the recording process of hologram of the present invention, the effect of aperture is a limiter surface diffusion direction of light, only allows the light wave in very little in the sphere wavelet of the last every some generation in the surface solid angle unit to arrive the record plane through aperture.Reference light wave can adopt assembles spherical wave, plane wave, also can adopt divergent spherical wave, so that the interference fringe spacing on the record plane is bigger, reduces the spatial resolution requirement to recording mediums such as CCD.At this moment; Aperture filtering during recorded hologram is actually by the pinhole imaging system principle, because diffusion, each point all has scattered light and passes through aperture on the object; For hologram; Physical record be the equal of the Fresnel hologram of aperture, and this aperture is characterized by its transmission light field, so physical record the holographic images of diffusion thing.And for the transmission-type object, can be directly with assembling spherical wave illumination, this moment, the convergent point place need not to place aperture, and object space can arbitrarily move vertically.Also can throw light on plane wave for the transmission-type object, but behind object, must place an imaging len, same convergent point place need not to place aperture.For the transmission-type object; Assemble illumination itself or add lens and just be equivalent to the frequency spectrum compression; Thereby recorded hologram need not to add aperture filtering again; This moment physical record be the Fresnel hologram of convergent point, and this convergent point characterizes by converging light wave accordingly, so physical record the holographic images of transparency.In the reproduction process of hologram, diaphragm or low-pass filtering operation can be kept off 0 grade+1 grade and all high order diffraction light waves, only let-1 order diffraction light wave see through, and reappear thereby make-1 grade of holographic images obtain separating.Than common coaxial digital hologram; It reproduces the serious interference that picture receives zero level and conjugate image; This method holographic reconstructed image satisfactory for result, its avoided methods such as phase shift and HRO subtract each other can not real-time and the numerical value iterative algorithm complicated and need the shortcoming of multistep calculating etc.

Description of drawings

Fig. 1: diffusion type object holographic recording process synoptic diagram;

Fig. 2: diffusion type object reconstruction of hologram process synoptic diagram;

Fig. 3: the transmission-type object adopts and converges sphere optical illumination holographic recording process synoptic diagram;

Fig. 4: the transmission-type object adopts and converges sphere optical illumination reconstruction of hologram process synoptic diagram;

Fig. 5: the transmission-type object adopts parallel light holographic recording process synoptic diagram;

Fig. 6: the transmission-type object adopts parallel light reconstruction of hologram process synoptic diagram.

Among the figure, 1-irradiation also sees through or reproduction lighting light wave, 8-transmission-type object to be measured, the 9-imaging len of reference light wave, the 3-diffusion type to be measured object, 4-aperture, 5-CCD camera, 6-light-splitting device, 7-and reference light wave 2 conjugation that are concerned with from body surface laser light reflected bundle, 2-and laser beam 1.

Embodiment

Below in conjunction with accompanying drawing and embodiment the present invention is further specified.

Embodiment 1: see also Fig. 1 and Fig. 2.Present embodiment is the coaxial digital hologram method that can effectively suppress Zero-order diffractive and conjugate image to the wooden draughtsman of diffusion type object; Present embodiment comprise diffusion type object to be measured 3, CCD camera 5, aperture 4, light-splitting device 6, from the laser beam 1 of 3 reflections of diffusion type object or transmission, with the relevant reference light wave 2 of laser beam 1, with the reproduction lighting light wave 7 and the holographic interference pattern H of reference light wave 2 conjugation, diffraction pattern H ₁, H ₂And H ₃

The course of work of present embodiment is: between the CCD camera 5 of diffuse reflection type object under test 3 and digital recording holographic interference pattern, aperture 4 is set; Laser radiation also sees through diffusion type object 3 or passes through aperture 4 from the laser beam 1 of diffusion type object 3 surface reflections; Arrive CCD camera 5 along same optical axis direction and form the thing light wave, the wavelength of laser beam 1 is 532nm.This thing light wave interferes in CCD camera 5 positions and reference light wave 2, forms the holographic interference pattern H of reflection object under test information.Said reference light wave 2 is and thing light wave 1 relevant and laser light wave optical axis coincidence.With with the light wave of reference light wave 2 conjugation reproduction lighting light wave as the numerical simulation calculation process, utilize Fresnel-Kirchhoff diffraction integral formula of describing the light wave diffraction propagation

$U(\mathrm{\&xi;},\mathrm{\&eta;})=-\frac{i}{\mathrm{\&lambda;}}{\&Integral;}_{-\&infin;}^{\&infin;}{\&Integral;}_{-\&infin;}^{\&infin;}h(x,y)R(x,y)\frac{\exp \left(\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">i</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}\right)}{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}}\&times;(\frac{1}{2}+\frac{1}{2}\cos \mathrm{\&theta;})\mathrm{dxdy}$

Calculate COMPLEX AMPLITUDE U (ξ, η), wherein: (ξ, the plane that η) calculates for integral formula; (x y) is the coordinate of the holographic interference plan of object under test, Wavelength of Laser when λ equals laser radiation for reproducing the lighting light wave wavelength; Be 532nm, R is the conjugation that the COMPLEX AMPLITUDE of reproduction lighting light wave equals the complex amplitude of reference light wave, h (x; Y) be the intensity that the complex amplitude transmission function of hologram equals holographic interference pattern, cos θ is an inclination factor, in hologram record and numerical reconstruction process because satisfy paraxial approximation; The value of cos θ gets 1, and d is that the diffraction distance equals the distance of aperture to record position, gets 4cm among this embodiment.(ξ, η) delivery value and ask flat ten thousand obtains diffraction pattern H to COMPLEX AMPLITUDE U then ₁Intensity distributions.Choose diffraction pattern H ₁Low frequency part to diffraction pattern H ₁Carry out filtering, obtain filtered diffraction pattern H ₂Described low frequency part is diffraction pattern H ₁Inscribed circle radius 20%; To diffraction pattern H ₂The digital hologram that utilizes Fresnel-Kirchhoff diffraction integral formula to calculate effective inhibition zero level and conjugate image once more reproduces the diffraction pattern H of picture ₃Diffraction is got the distance of object under test to aperture apart from d in the calculating, gets 4cm among this embodiment.

Said diffusion type object 3 is required Measuring Object, and light beam can see through this object or from the body surface reflection and carry and need the information measured, be wooden draughtsman in the present embodiment;

Said laser beam 1 is for irradiation and see through diffusion type object 3 perhaps from the light beam of its surface reflection, includes the information that needs Measuring Object, as the thing light of hologram record process;

Said reference light wave 2 is relevant with laser beam 1, is spherical light wave or plane light wave, as the reference light of hologram record process;

Said CCD camera 5 is the optical imagery numerical recording device of recording holographic interferogram;

Said aperture 4 is a pair of from object under test 3 transmissions or laser light reflected bundle 1 opaque screen; Opened wherein; Aperture radius r adjustable size is whole, and r gets 0.5mm among this embodiment, mainly plays the effect of the spatial frequency that limits the thing light light beam that arrives CCD camera 5;

Said light-splitting device 6 is a spectroscope, mainly be to merge with thing light wave 1 with reference light wave 2 to interfere, and the angle of thing light and reference light is zero the formation in-line hologram at CCD camera 5 places;

Said reproduction lighting light wave 7 be in the numerical procedure with the light wave of the numerical simulation of reference light wave 2 conjugation;

Said holographic interference pattern H is the digital hologram that CCD camera 5 writes down and obtains;

Said diffraction pattern H ₁, H ₂And H ₃Intensity distributions pattern for the diffraction light that obtains in the numerical procedure.

Utilize the method among the present invention finally can obtain the picture of in-line holographic reproduction clearly, and suppressed zero level and conjugate image influence.Method among the present invention is simple, feasible, only need in hologram record and holographic images reproduction process, adjust slightly light path, can realize that promptly the zero level of traditional coaxial optical holography and conjugate image suppress.In the hologram record process that the present invention proposes; The effect of aperture is to limit the body surface diffused light of some direction to arrive the hologram record plane, only allows the light wave in very little in the sphere wavelet of the last every some generation in the surface solid angle unit to arrive the record plane through aperture.Reference light wave can adopt assembles spherical wave or plane wave, also can adopt divergent spherical wave, so that the interference fringe on the record plane has bigger spacing, reduces the spatial resolution requirement to recording mediums such as CCD.At this moment; Aperture filtering during recorded hologram is actually by the pinhole imaging system principle, because diffusion, each point all has scattered light and passes through aperture on the object; For hologram; Physical record be the equal of the Fresnel hologram of aperture, and this aperture is characterized by its transmission light field, so physical record the holographic images of diffusion thing.

Embodiment 2: see also Fig. 3 and Fig. 4.Present embodiment is the coaxial digital hologram method that can effectively suppress Zero-order diffractive and conjugate image to transmission-type object transparent organism cell section; Present embodiment comprises transmission-type object to be measured 8, CCD camera 5, light-splitting device 6, see through diffusion type object 8 converge sphere laser beam 1, with the relevant reference light wave 2 of laser beam 1, with the reproduction lighting light wave 7 and the holographic interference pattern H of reference light wave 2 conjugation, diffraction pattern H ₁, H ₂And H ₃

The course of work of present embodiment is: to converge laser beam 1 irradiation and to see through the CCD camera 5 formation thing light waves that transmission-type object 8 to be measured arrives the digital recording holographic interference pattern; This thing light wave interferes at record position and reference light wave 2; Form the holographic interference pattern H of reflection object under test, the wavelength of laser beam 1 is 640nm; Said reference light wave 2 is relevant and laser light wave optical axis coincidence with the thing light wave.Described CCD camera 5 positions are arranged at converges laser radiation also through after the convergent point that forms behind the object under test.With with the light wave of reference light wave conjugation reproduction lighting light wave as the numerical simulation calculation process, utilize Fresnel-Kirchhoff diffraction integral formula of describing the light wave diffraction propagation

$U(\mathrm{\&xi;},\mathrm{\&eta;})=-\frac{i}{\mathrm{\&lambda;}}{\&Integral;}_{-\&infin;}^{\&infin;}{\&Integral;}_{-\&infin;}^{\&infin;}h(x,y)R(x,y)\frac{\exp \left(\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">i</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}\right)}{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}}\&times;(\frac{1}{2}+\frac{1}{2}\cos \mathrm{\&theta;})\mathrm{dxdy}$

Calculate COMPLEX AMPLITUDE U (ξ, η), wherein: (ξ; The plane that η) calculates for integral formula, (x y) is the coordinate of the holographic interference plan of object under test; Wavelength of Laser was 640nm when λ equaled laser radiation for reproducing the lighting light wave wavelength, and R is the conjugation that the COMPLEX AMPLITUDE of reproduction lighting light wave equals the complex amplitude of reference light wave, h (x; Y) be the intensity that the complex amplitude transmission function of hologram equals holographic interference pattern; Cos θ is an inclination factor, because satisfy paraxial approximation, the value of cos θ gets 1 in hologram record and numerical reconstruction process; D is that the diffraction distance equals to converge laser radiation and through the distance of the convergent point that forms behind the object under test to record position, gets 5cm among this embodiment.(ξ, η) delivery value and ask square obtains diffraction pattern H to COMPLEX AMPLITUDE U then ₁Intensity distributions, choose diffraction pattern H ₁Low frequency part to diffraction pattern H ₁Carry out filtering, obtain filtered diffraction pattern H ₂Described low frequency part is diffraction pattern H ₁Inscribed circle radius 5%.To diffraction pattern H ₂The digital hologram that utilizes Fresnel-Kirchhoff diffraction integral formula to calculate effective inhibition zero level and conjugate image once more reproduces the diffraction pattern H of picture ₃Diffraction is got object under test to converging laser radiation also through the distance of the convergent point that forms behind the object under test apart from d in the calculating, gets 6cm among this embodiment.

Said transmission-type object 8 is required Measuring Object, and light beam can directly see through this object and carry the information that needs measurement, is the transparent organism cell section in the present embodiment;

Said laser beam 1 converges the sphere light beam for what see through transmission-type object 8, includes the information that needs Measuring Object, as the thing light of hologram record process;

Said laser beam 2 is relevant with laser beam 1, is plane light wave, as the reference light of hologram record process;

Said CCD camera 5 is the optical imagery numerical recording device of recording holographic interferogram;

Said light-splitting device 6 is a spectroscope, mainly be to merge with thing light wave 1 with reference light wave 2 to interfere, and the angle of thing light and reference light is zero the formation in-line hologram at CCD camera 5 places;

Said reproduction lighting light wave 7 be in the numerical procedure with the light wave of the numerical simulation of reference light wave 2 conjugation;

Said holographic interference pattern H is the digital hologram that CCD camera 5 writes down and obtains;

Said diffraction pattern H ₁, H ₂And H ₃Intensity distributions pattern for the diffraction light that obtains in the numerical procedure.

Method among the present invention is simple, feasible, only through the particular design of digital hologram record recording process, only utilizes a width of cloth digital hologram simultaneously, through simple numerical operation, and carries out a digital filtering and gets final product.In the present invention, can be for the transmission-type object directly with assembling spherical wave illumination, this moment, the convergent point place need not to place aperture; And object space can arbitrarily move vertically; Assembles illumination itself and just be equivalent to the frequency spectrum compression, thereby recorded hologram need not to add aperture filtering again, this moment physical record be the Fresnel hologram of convergent point; And this convergent point characterizes by converging light wave accordingly, so physical record the holographic images of transparency.During reproduction, low-pass filtering operation can keep off 0 grade ,+1 grade and all high order diffraction light waves, only let-1 order diffraction light wave see through, thereby make-1 grade of holographic images obtain separate reappearing.Than common coaxial digital hologram; It reproduces the serious interference that picture receives zero level and conjugate image; By this method obtain holographic reconstructed image satisfactory for result, avoided methods such as phase shift and HRO subtract each other can not real-time and the numerical value iterative algorithm complicated and need the shortcoming of multistep calculating etc.

Embodiment 3: see also Fig. 5 and Fig. 6.Present embodiment is the coaxial digital hologram method that can effectively suppress Zero-order diffractive and conjugate image to the section of transmission-type object red blood cell; Present embodiment comprises transmission-type object to be measured 8, imaging len 9, CCD camera 5, light-splitting device 6, sees through the collimated laser beam 1 of diffusion type object 8, with the relevant reference light wave 2 of laser beam 1, with the reproduction lighting light wave 7 and the holographic interference pattern H of reference light wave 2 conjugation, diffraction pattern H ₁, H ₂, H ₃And H ₄

The course of work of present embodiment is: an imaging len 9 is set between the CCD camera 5 of transmission-type object 8 to be measured and digital recording holographic interference pattern; With collimated laser beam 1 irradiation and through object under test 8; Converge the back through lens and arrive record position CCD camera 5 formation thing light waves, the wavelength of laser beam 1 is 632.8nm.This thing light wave interferes at record position and reference light wave 2, forms the holographic interference pattern H of reflection object under test.Said reference light wave 2 is relevant and laser light wave optical axis coincidence with the thing light wave.Described record position that is CCD camera 5 present positions are passed after the convergent point of lens formation after being arranged at the parallel laser irradiation and seeing through object under test 8.With with the light wave of reference light wave 2 conjugation reproduction lighting light wave as the numerical simulation calculation process, utilize Fresnel-Kirchhoff diffraction integral formula of describing the light wave diffraction propagation

$U(\mathrm{\&xi;},\mathrm{\&eta;})=-\frac{i}{\mathrm{\&lambda;}}{\&Integral;}_{-\&infin;}^{\&infin;}{\&Integral;}_{-\&infin;}^{\&infin;}h(x,y)R(x,y)\frac{\exp \left(\mathrm{<figure-callout\; id="2"\; label="i"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">i</figure-callout>}\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}\right)}{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="d"\; filenames="HSA00000236614600011.png,HSA00000236614600013.png"\; state="\{\{state\}\}">d</figure-callout>}}^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}}\&times;(\frac{1}{2}+\frac{1}{2}\cos \mathrm{\&theta;})\mathrm{dxdy}$

Calculate COMPLEX AMPLITUDE U (ξ, η), wherein: (ξ, the plane that η) calculates for integral formula; (x y) is the coordinate of the holographic interference plan of object under test, Wavelength of Laser when λ equals laser radiation for reproducing the lighting light wave wavelength; Be 632.8nm, R is the conjugation that the COMPLEX AMPLITUDE of reproduction lighting light wave equals the complex amplitude of reference light wave, h (x; Y) be the intensity that the complex amplitude transmission function of hologram equals holographic interference pattern, cos θ is an inclination factor, in hologram record and numerical reconstruction process because satisfy paraxial approximation; The value of cos θ gets 1, and d is that the diffraction distance equals to converge laser radiation and through the distance of the convergent point that forms behind the object under test to record position, gets 10cm among this embodiment; (ξ, η) delivery value and ask square obtains diffraction pattern H to COMPLEX AMPLITUDE U then ₁Intensity distributions, choose diffraction pattern H ₁Low frequency part to diffraction pattern H ₁Carry out filtering, obtain filtered diffraction pattern H ₂Described low frequency part is diffraction pattern H ₁Inscribed circle radius 10%.To diffraction pattern H ₂Utilize Fresnel-Kirchhoff diffraction integral formula to calculate diffraction pattern H once more ₄, the diffraction in the calculating is got the distance of the convergent point that lens form after converge laser radiation and see through object under test apart from d.To diffraction pattern H ₄Intensity distributions multiply by

Wherein P (x y) is the pupil function of lens,

Be the phase tranformation that lens are introduced, continue to utilize Fresnel-Kirchhoff diffraction integral formula to calculate the H of the digital hologram reproduction picture of effective inhibition zero level and conjugate image afterwards ₃Diffraction in the calculating is got the distance of lens to object under test apart from d, gets 10cm among this embodiment.

Said transmission-type object 8 is required Measuring Object, and light beam can directly see through this object and carry the information that needs measurement, is the red blood cell section in the present embodiment;

Said laser beam 1 includes the information that needs Measuring Object, as the thing light of hologram record process for seeing through the parallel laser light beam of transmission-type object 8;

Said laser beam 2 is relevant with laser beam 1, is plane light wave, as the reference light of hologram record process;

Said CCD camera 5 is the optical imagery numerical recording device of recording holographic interferogram;

Said light-splitting device 6 is a spectroscope, mainly be to merge with thing light wave 1 with reference light wave 2 to interfere, and the angle of thing light and reference light is zero the formation in-line hologram at CCD camera 5 places;

Said reproduction lighting light wave 7 be in the numerical procedure with the light wave of the numerical simulation of reference light wave 2 conjugation;

Said holographic interference pattern H is the digital hologram that CCD camera 5 writes down and obtains;

Said diffraction pattern H ₁, H ₂, H ₃And H ₄Intensity distributions pattern for the diffraction light that obtains in the numerical procedure.

Method is simple, feasible among the present invention; Only need in the reproduction process of the record of hologram and holographic images, adjust slightly,, only utilize a width of cloth digital hologram through the particular design of digital hologram recording process to light path; And, carry out a digital filtering and get final product through simple numerical operation.In the recording process of hologram of the present invention, can throw light on plane wave for the transmission-type object, but behind object, must place an imaging len, same convergent point place need not to place aperture.For the transmission-type object; Adds lens and just be equivalent to frequency spectrum compression, thereby recorded hologram need not to add aperture filtering again, this moment physical record be the Fresnel hologram of convergent point; And this convergent point characterizes by converging light wave accordingly, so physical record the holographic images of transparency.In the reproduction process of hologram, diaphragm or low-pass filtering operation can be kept off 0 grade+1 grade and all high order diffraction light waves, only let-1 order diffraction light wave see through, and reappear thereby make-1 grade of holographic images obtain separating.Than common coaxial digital hologram; It reproduces the serious interference that picture receives zero level and conjugate image; The holographic reconstructed image that obtains by this method satisfactory for result, its avoided methods such as phase shift and HRO subtract each other can not real-time and the numerical value iterative algorithm complicated and need the shortcoming of multistep calculating etc.

Claims (3)

1. a diffuse reflection type object can effectively suppress the coaxial digital hologram method of Zero-order diffractive and conjugate image, it is characterized in that step is following:

Step 1 is provided with an aperture between object under test and holographic interference pattern digital recording position, laser radiation also sees through object under test or passes through aperture from the laser beam of object under test surface reflection, arrives record position along same optical axis direction and forms the thing light wave; This thing light wave interferes at record position and reference light wave, forms the holographic interference pattern of reflection object under test; Said reference light wave is relevant and laser light wave optical axis coincidence with the thing light wave;

Step 2, with the light wave of reference light wave conjugation reproduction lighting light wave as the numerical simulation calculation process, utilize Fresnel-Kirchhoff diffraction integral formula of describing the light wave diffraction propagation

$U(\mathrm{\&xi;},\mathrm{\&eta;})=-\frac{i}{\mathrm{\&lambda;}}{\&Integral;}_{-\&infin;}^{\&infin;}{\&Integral;}_{-\&infin;}^{\&infin;}h(x,y)R(x,y)\frac{\exp \left(i\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}\sqrt{d^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}\right)}{\sqrt{d^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}}\&times;(\frac{1}{2}+\frac{1}{2}\cos \mathrm{\&theta;})\mathrm{dxdy}$

Obtain COMPLEX AMPLITUDE U (ξ, η), wherein: ((x y) is the coordinate of the holographic interference plan of object under test, and λ is for reproducing lighting light wave wavelength, Wavelength of Laser when equaling laser radiation for ξ, the plane that η) calculates for integral formula; R equals the conjugation of the complex amplitude of reference light wave for reproducing the COMPLEX AMPLITUDE of lighting light wave; (x is the complex amplitude transmission function of hologram y) to h, equals the intensity of holographic interference pattern; Cos θ is an inclination factor, and d is the diffraction distance, equals the distance of aperture to record position;

(ξ, η) delivery value and ask square obtains diffraction pattern H to COMPLEX AMPLITUDE U then ₁Intensity distributions;

Step 3 is chosen diffraction pattern H ₁Low frequency part to diffraction pattern H ₁Carry out filtering, obtain filtered diffraction pattern H ₂Described low frequency part is diffraction pattern H ₁Inscribed circle radius 1%～70%;

Step 4 is to diffraction pattern H ₂The digital hologram that utilizes Fresnel-Kirchhoff diffraction integral formula to calculate effective inhibition zero level and conjugate image once more reproduces the diffraction pattern H of picture ₃Diffraction is got the distance of object under test to aperture apart from d in the calculating.

2. a transmission-type object can effectively suppress the coaxial digital hologram method of Zero-order diffractive and conjugate image, it is characterized in that step is following:

Step 1 arrives record position formation thing light wave to converge laser radiation and to see through object under test, and this thing light wave interferes at record position and reference light wave, forms the holographic interference pattern of reflection object under test; Said reference light wave is relevant and laser light wave optical axis coincidence with the thing light wave; Described record position is arranged at and converges laser radiation also through after the convergent point that forms behind the object under test;

Step 2, with the light wave of reference light wave conjugation reproduction lighting light wave as the numerical simulation calculation process, utilize Fresnel-Kirchhoff diffraction integral formula of describing the light wave diffraction propagation

$U(\mathrm{\&xi;},\mathrm{\&eta;})=-\frac{i}{\mathrm{\&lambda;}}{\&Integral;}_{-\&infin;}^{\&infin;}{\&Integral;}_{-\&infin;}^{\&infin;}h(x,y)R(x,y)\frac{\exp \left(i\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}\sqrt{d^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}\right)}{\sqrt{d^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}}\&times;(\frac{1}{2}+\frac{1}{2}\cos \mathrm{\&theta;})\mathrm{dxdy}$

Obtain COMPLEX AMPLITUDE U (ξ, η), wherein: ((x y) is the coordinate of the holographic interference plan of object under test, and λ is for reproducing lighting light wave wavelength, Wavelength of Laser when equaling laser radiation for ξ, the plane that η) calculates for integral formula; R equals the conjugation of the complex amplitude of reference light wave for reproducing the COMPLEX AMPLITUDE of lighting light wave; (x is the complex amplitude transmission function of hologram y) to h, equals the intensity of holographic interference pattern; Cos θ is an inclination factor, and d is the diffraction distance, equals to converge laser radiation also through the distance of the convergent point that forms behind the object under test to record position;

(ξ, η) delivery value and ask square obtains diffraction pattern H to COMPLEX AMPLITUDE U then ₁Intensity distributions;

Step 3 is chosen diffraction pattern H ₁Low frequency part to diffraction pattern H ₁Carry out filtering, obtain filtered diffraction pattern H ₂Described low frequency part is diffraction pattern H ₁Inscribed circle radius 1%～70%;

Step 4 is to diffraction pattern H ₂The digital hologram that utilizes Fresnel-Kirchhoff diffraction integral formula to calculate effective inhibition zero level and conjugate image once more reproduces the diffraction pattern H of picture ₃Diffraction is got the distance of the convergent point that object under test forms after converge laser radiation and see through object under test in the calculating apart from d.

3. a transmission-type object can effectively suppress the coaxial digital hologram method of Zero-order diffractive and conjugate image, it is characterized in that step is following:

Step 1 is provided with lens between object under test and holographic interference pattern digital recording position, with the parallel laser irradiation and through object under test, converge back arrival record position through lens and form the thing light wave; This thing light wave interferes at record position and reference light wave, forms the holographic interference pattern of reflection object under test; Said reference light wave is relevant and laser light wave optical axis coincidence with the thing light wave; Described record position is arranged at and converges laser radiation also through after the convergent point that forms behind the object under test;

Step 2, with the light wave of reference light wave conjugation reproduction lighting light wave as the numerical simulation calculation process, utilize Fresnel-Kirchhoff diffraction integral formula of describing the light wave diffraction propagation

$U(\mathrm{\&xi;},\mathrm{\&eta;})=-\frac{i}{\mathrm{\&lambda;}}{\&Integral;}_{-\&infin;}^{\&infin;}{\&Integral;}_{-\&infin;}^{\&infin;}h(x,y)R(x,y)\frac{\exp \left(i\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}\sqrt{d^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}\right)}{\sqrt{d^2+{(x-\mathrm{\&xi;})}^2+{(y-\mathrm{\&eta;})}^2}}\&times;(\frac{1}{2}+\frac{1}{2}\cos \mathrm{\&theta;})\mathrm{dxdy}$

Obtain COMPLEX AMPLITUDE U (ξ, η), wherein: ((x y) is the coordinate of the holographic interference plan of object under test, and λ is for reproducing lighting light wave wavelength, Wavelength of Laser when equaling laser radiation for ξ, the plane that η) calculates for integral formula; R equals the conjugation of the complex amplitude of reference light wave for reproducing the COMPLEX AMPLITUDE of lighting light wave; (x is the complex amplitude transmission function of hologram y) to h, equals the intensity of holographic interference pattern; Cos θ is an inclination factor, and d is the diffraction distance, equals to converge laser radiation also through the distance of the convergent point that forms behind the object under test to record position;

(ξ, η) delivery value and ask square obtains diffraction pattern H to COMPLEX AMPLITUDE U then ₁Intensity distributions;

Step 3 is chosen diffraction pattern H ₁Low frequency part to diffraction pattern H ₁Carry out filtering, obtain filtered diffraction pattern H ₂Described low frequency part is diffraction pattern H ₁Inscribed circle radius 1%～70%;

Step 4 is to diffraction pattern H ₂Utilize Fresnel-Kirchhoff diffraction integral formula to calculate diffraction pattern H once more ₄Diffraction in the calculating is got the distance of the convergent point that lens form after converge laser radiation and see through object under test apart from d; Step 5 is to diffraction pattern H ₄Intensity distributions multiply by

Wherein P (x y) is the pupil function of lens,

Be the phase tranformation that lens are introduced, continue to utilize Fresnel-Kirchhoff diffraction integral formula to calculate the H of the digital hologram reproduction picture of effective inhibition zero level and conjugate image afterwards ₃Diffraction in the calculating is got the distance of lens to object under test apart from d.

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