CN108957999B - Phase shift holographic device based on phase type vortex lens and imaging method - Google Patents
Phase shift holographic device based on phase type vortex lens and imaging method Download PDFInfo
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- CPBQJMYROZQQJC-UHFFFAOYSA-N helium neon Chemical compound [He].[Ne] CPBQJMYROZQQJC-UHFFFAOYSA-N 0.000 description 2
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- G03H—HOLOGRAPHIC PROCESSES OR APPARATUS
- G03H1/00—Holographic processes or apparatus using light, infrared or ultraviolet waves for obtaining holograms or for obtaining an image from them; Details peculiar thereto
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Abstract
A phase shift holographic device and imaging method based on phase type vortex lens, the device includes light source, beam splitter, rotating mirror holder, phase type vortex focusing lens, collimating lens, first reflector, beam combiner, first three-dimensional translation stage, imaging detector, computer, second reflector, second three-dimensional translation stage and measured object, the phase type vortex focusing lens used in the invention can be used in the coherent wave band from visible light to terahertz wave band; the invention can fully utilize the space bandwidth product of the imaging detector, can quickly realize accurate reproduction of the measured object, can effectively inhibit the conjugate image of the reproduction result, and obviously improves the quality of the reproduced image of the measured object.
Description
Technical Field
The invention belongs to holographic imaging, and particularly relates to a phase-shift holographic device and an imaging method based on a phase-shift vortex lens.
Background
Since the concept of holography was proposed by d.gabor in 1948, holography has become an important research topic in the international physical field with its wide application prospect in various fields. In microscopic imaging, the three-dimensional volume imaging of holography can realize the ultra-focal depth microscopy; in optical storage, the Fourier transform hologram is adopted to realize large-capacity high-density information storage of information such as characters, images and the like; in interferometry, holography can be used to perform interferometry by comparing two wavefronts generated before and after object deformation. Holography is increasingly used in various fields, and research on holographic imaging devices and imaging methods is becoming more and more important.
In conventional optical holography, an interference hologram can record sufficient three-dimensional imaging information, but the holographic recording process requires physicochemical processes such as development, fixing, bleaching, and the like, and the reproduction time is long. In 1967, the concept of digital holography was proposed by j.w.goodman et al, the basic principle of which is to record interference holograms with a photosensitive electronic imaging device instead of conventional holographic recording material and to complete the reconstruction process with a computer, which can greatly shorten the reconstruction time. However, the target image reconstructed by this method usually includes conjugate images, zero-order interference images, and the like, and these components blur the reconstructed light field, reducing the accuracy of recovering the object to be measured from a single interference hologram. In 1979, l.m.frantz et al proposed a phase shift holography technique, which can fully utilize the spatial bandwidth product of an imaging detector, can rapidly and real-timely achieve accurate reconstruction of a measured object, can effectively suppress a conjugate image in a detected sample image, improve the quality of an interference hologram, and simultaneously recover the diffraction distribution of an object on a recording surface, thereby obtaining a reconstructed complex amplitude image of a high-fidelity object by diffraction return.
Terahertz waves are electromagnetic waves with the frequency within the range of 0.1 to 10THz, are located between microwaves and infrared in an electromagnetic spectrum, and have great application value in scientific fields such as biological detection, safety detection, communication technology and the like. However, the current coherent terahertz source is often high in cost, expensive and low in output power, and for the coherent terahertz source, the existing amplitude lens is often low in diffraction efficiency, and the use efficiency is only a few percent. However, the vortex focusing lens used by the device is a phase type lens, can be used for coherent wave bands including visible light to terahertz wave bands, and has low cost and high use efficiency.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a phase-shift holographic device and an imaging method based on a phase-type vortex lens, and the method can realize phase-shift digital holographic imaging from a coherent optical field from visible light to a terahertz waveband. The method can fully utilize the space bandwidth product of the imaging detector, can quickly realize accurate reproduction of the measured object, can effectively inhibit conjugate images in the reproduction result, and obviously improves the quality of the reproduced images of the measured object.
The technical scheme of the invention is as follows:
a phase shift holographic device based on a phase type vortex lens is characterized by comprising a light source, a beam splitter, a rotating mirror frame, a phase type vortex focusing lens, a collimating lens, a first reflecting mirror, a beam combiner, a first three-dimensional translation table, an imaging detector, a computer, a second reflecting mirror, a second three-dimensional translation table and a measured object; light pulse emitted by the light source is divided into a transmission beam and a reflection beam by the beam splitter, the transmission beam is used as a reference beam, and the reflection beam is used as an object beam;
the reference light beam reaches the collimating lens through a phase type vortex focusing lens fixed on the rotating mirror bracket, the light beam collimated by the collimating lens reaches the beam combiner through a first reflecting mirror, and the reference light beam is reflected into an imaging detector fixed on a first three-dimensional translation table through the beam combiner;
the object beam reaches a measured object fixed on the second three-dimensional translation table through the second reflecting mirror, and the light beam passing through the measured object enters the imaging detector through the beam combiner;
the beam area of the object beam is larger than the size of the object to be measured;
the output end of the imaging detector is connected with the input end of the computer;
the phase type vortex focusing lens is a circular phase type vortex focusing lens or an elliptical phase type vortex focusing lens;
the imaging detector is a CCD camera, a CMOS image sensor or a thermoelectric array camera;
the imaging method for obtaining the measured object by utilizing the phase shift holographic device based on the phase type vortex lens is characterized by comprising the following steps of:
1) starting a light source, placing a measured object on the second three-dimensional translation table and in the object beam, rotating the phase type vortex focusing lens fixed on the rotating mirror frame for N times, and sequentially introducing reference beams R (x, y, phi) with different phase shiftsm) Where m is 1,2, … N, phimIs the m-th phase shift of the reference beam, the diffracted light wave U (x, y) of the measured object and the reference beam R (x, y, phi) with different phase shiftsm) Interference hologram I (x, y, phi) formed by interactionm)＝|U(x,y)+R(x,y,φm)|2The imaging detector records N interference holograms I (x, y, phi)m)；
2) When the number of rotations N and the phase shift phi of the reference beam are knownmThen, based on the recorded N interference holograms I (x, y, phi)m) Calculating the diffraction light wave U (x, y) of the measured object on the recording surface according to the following formula:
wherein, a1、a2…aNIs the intensity coefficient, phi1、φ2…φNIs the phase shift of the reference beam;
3) reversely transmitting the diffracted light waves U (x, y) obtained in the step 2) to an object plane by utilizing an angular spectrum diffraction transmission inverse algorithm to obtain the complex amplitude distribution O (x) of the measured object0,y0)：
Wherein,
is an angular spectrum transfer function, fXAnd fYIs the spatial frequency, z0Is the distance from the object to be measured to the imaging detector.
The object to be measured may be a resolution plate or a biological sample.
The invention has the following technical effects and advantages:
1. the invention can introduce a plurality of reference beams with different phase shifts through the rotating phase type vortex focusing lens, so that the imaging detector can record a plurality of interference holograms and quickly realize accurate reappearance of a measured object.
2. The vortex focusing lens adopted by the invention is a phase type lens, so that focusing and imaging from visible light to terahertz wave band under coherent condition can be realized.
3. The invention can effectively inhibit the conjugate image in the reproduction result and can obviously improve the quality of the reproduction image of the measured object.
Drawings
FIG. 1 is a schematic structural diagram of a phase shift holographic device based on a phase type vortex lens according to the present invention;
FIG. 2 is a diagram of simulation results of the resolution board of the present invention as the object to be measured.
Detailed Description
The present invention will be further described with reference to the following examples and drawings, but the scope of the present invention should not be limited thereto.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a phase shift holographic device based on a phase type vortex lens according to the present invention, and it can be seen from the figure that the phase shift holographic device based on a phase type vortex lens according to the present invention includes a light source 1, a beam splitter 2, a rotating frame 3, a phase type vortex focusing lens 4, a collimating lens 5, a first reflector 6, a beam combiner 7, a first three-dimensional translation stage 8, an imaging detector 9, a computer 10, a second reflector 11, a second three-dimensional translation stage 12, and an object to be measured 13. The light pulse emitted by the light source 1 is split into a transmitted beam as a reference beam and a reflected beam as an object beam by the beam splitter 2. The reference light beam reaches the collimating lens 5 through the phase type vortex focusing lens 4 fixed on the rotating frame 3, the light beam collimated by the collimating lens 5 reaches the beam combiner 7 through the first reflecting mirror 6, and the reference light beam is reflected by the beam combiner 7 to enter the imaging detector 9 fixed on the first three-dimensional translation stage 8; the object beam reaches a measured object 13 fixed on a second three-dimensional translation table 12 through a second reflecting mirror 11, and the light beam passing through the measured object 13 enters the imaging detector 9 through the beam combiner 7; the beam area of the object beam is larger than the size of the object to be measured 13; the output end of the imaging detector 9 is connected with the input end of the computer 10.
The phase type vortex focusing lens 4 is a circular phase type vortex focusing lens or an elliptical phase type vortex focusing lens.
The imaging detector 9 is a CCD camera, a CMOS image sensor or a pyroelectric array camera.
An imaging method for obtaining a measured object 13 by using a phase-shift holographic device based on a phase-type vortex lens comprises the following steps:
1) starting the light source 1, placing the object to be measured 13 on the second three-dimensional translation table 12 and in the object beam, rotating the phase type vortex focusing lens 4 fixed on the rotating mirror frame 3 for N times, and sequentially guidingInto reference beams R (x, y, phi) of different phase shiftsm) Where m is 1,2, … N, phimIs the m-th phase shift of the reference beam, the diffracted light wave U (x, y) of the measured object and the reference beam R (x, y, phi) with different phase shiftsm) Interference hologram I (x, y, phi) formed by interactionm)＝|U(x,y)+R(x,y,φm)|2The imaging detector 9 records N interference holograms I (x, y, phi)m)；
2) When the number of rotations N and the phase shift phi of the reference beam are knownmThen, based on the recorded N interference holograms I (x, y, phi)m) Calculating the diffraction light wave U (x, y) of the measured object on the recording surface according to the following formula:
wherein, a1、a2…aNIs the intensity coefficient, phi1、φ2…φNIs the phase shift of the reference beam;
3) reversely transmitting the diffracted light waves U (x, y) obtained in the step 2) to an object plane by utilizing an angular spectrum diffraction transmission inverse algorithm to obtain the complex amplitude distribution O (x) of the measured object0,y0)：
Wherein,
is an angular spectrum transfer function, fXAnd fYIs the spatial frequency, z0Is the distance of the object to be measured 13 to the imaging detector 9.
The object to be measured 13 is a resolution plate or a biological sample.
Example (b): the object to be measured being a resolution board
The light source 1 is a He-Ne laser with a central wavelength of 632.8nm, the beam splitter 2 is a beam splitter with a ratio of T: R to 1:1, and the phase type vortex focusing lens 4 is a focusA round phase type vortex focusing lens with a distance of 150mm, a collimating lens 5 which is a biconvex lens with a focal length of 150mm, and a distance z between the object to be measured 13 and the imaging detector 90For example 156mm, the imaging detector 9 is a CCD camera with a resolution of 1392 × 1040, the measured object 13 is a resolution plate, and the phase-shift holographic device based on the phase-type vortex lens is embodied: as shown in FIG. 1, the helium-neon laser 1, the beam splitter 2, the rotating frame 3, the phase type vortex focusing lens 4, the collimating lens 5, the first reflecting mirror 6, the beam combiner 7, the first three-dimensional translation stage 8, the CCD camera 9, the computer 10, the second reflecting mirror 11, the second three-dimensional translation stage 12 and the resolution board 13 are used for realizing the functions of the laser, the laser and the optical system. The light pulse emitted by the helium-neon laser 1 is divided into a transmitted beam and a reflected beam by a beam splitter 2, wherein the transmitted beam is used as a reference beam, and the reflected beam is used as an object beam. The reference light beam reaches the collimating lens 5 after passing through the phase type vortex focusing lens 4 fixed on the rotating mirror bracket 3, the light beam collimated by the collimating lens 5 reaches the beam combiner 7 after being reflected by the first reflecting mirror 6, and the reference light beam is reflected by the beam combiner 7 to enter the CCD camera 9 fixed on the first three-dimensional translation stage 8; the object beam is reflected by the second reflecting mirror 11 and reaches a resolution plate 13 fixed on the second three-dimensional translation stage 12, and the light beam passing through the resolution plate 13 enters the CCD camera 9 through the beam combiner 7; the beam area of the object beam is larger than the size of the resolution plate 13; the output end of the CCD camera 9 is connected with the input end of the computer 10.
The phase type vortex focusing lens 4 is a circular phase type vortex focusing lens or an elliptical phase type vortex focusing lens.
The imaging method for obtaining the measured object 13 by utilizing the phase shift holographic device based on the phase type vortex lens comprises the following steps:
1) starting the He-Ne laser 1, placing a resolution plate 13 on the second three-dimensional translation stage 12 and on the object beam, rotating the phase type vortex focusing lens 4 fixed on the rotating frame 3 for N times, and sequentially introducing reference beams R (x, y, phi) with different phase shiftsm) Where m is 1,2, … N, phimIs the mth phase shift of the reference beam,the diffracted light wave U (x, y) of the resolution plate 13 is brought into contact with the differently phase-shifted reference beam R (x, y, phi)m) Interference hologram I (x, y, phi) formed by interactionm)＝|U(x,y)+R(x,y,φm)|2The CCD camera 9 records N interference holograms I (x, y, phi)m)；
2) When the number of rotations N is 3, the phase shift phi of the reference beam1＝0、
φ3When pi, the interference hologram I (x, y,0) is recorded,
And I (x, y, π) deduces that the diffracted light wave U (x, y) at the recording surface of the resolution plate 13 satisfies the formula:
3) reversely transmitting the diffracted light wave U (x, y) obtained in the step two to the object plane by utilizing an angular spectrum diffraction transmission inverse algorithm to obtain the complex amplitude distribution O (x) of the resolution plate 130,y0)：
Wherein,
is an angular spectrum transfer function, fXAnd fYIs the spatial frequency, z0156mm is the distance of the resolution plate 13 to the CCD camera 9.
Experiments show that the phase type vortex focusing lens used by the invention can be used for coherent wave bands from visible light to terahertz wave bands; the invention can fully utilize the space bandwidth product of the imaging detector, can quickly realize accurate reproduction of the measured object, can effectively inhibit the conjugate image of the reproduction result, and obviously improves the quality of the reproduced image of the measured object.
The above-mentioned embodiments further explain the objects, technical solutions and advantages of the present invention in detail. It should be understood that the above description is only exemplary of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (2)
1. An imaging method for obtaining a measured object (13) by using a phase-shift holographic device based on a phase-shift vortex lens comprises a light source (1), a beam splitter (2), a rotary mirror frame (3), the phase-shift vortex focusing lens (4), a collimating lens (5), a first reflector (6), a beam combiner (7), a first three-dimensional translation table (8), an imaging detector (9), a computer (10), a second reflector (11), a second three-dimensional translation table (12) and the measured object (13); light pulse emitted by the light source (1) is divided into a transmission beam and a reflection beam by the beam splitter (2), the transmission beam is used as a reference beam, and the reflection beam is used as an object beam;
the reference light beam reaches the collimating lens (5) through a phase type vortex focusing lens (4) fixed on the rotating mirror frame (3), the light beam collimated by the collimating lens (5) reaches the beam combiner (7) through a first reflecting mirror (6), and the reference light beam is reflected into an imaging detector (9) fixed on a first three-dimensional translation stage (8) through the beam combiner (7); the object beam reaches a measured object (13) fixed on a second three-dimensional translation table (12) through a second reflecting mirror (11), and the light beam passing through the measured object (13) enters the imaging detector (9) through the beam combiner (7); the beam area of the object beam is larger than the size of the object to be measured (13); the output end of the imaging detector (9) is connected with the input end of the computer (10); the method is characterized by comprising the following steps:
1) starting a light source (1), placing a measured object (13) on the second three-dimensional translation table (12) and in the object beam, and rotating a phase type vortex focusing lens (4) fixed on the rotating mirror frame (3)N times, sequentially introducing reference beams R (x, y, phi) with different phase shiftsm) Where m is 1,2, … N, phimIs the m-th phase shift of the reference beam, the diffracted light wave U (x, y) of the measured object and the reference beam R (x, y, phi) with different phase shiftsm) Interference hologram I (x, y, phi) formed by interactionm)＝|U(x,y)+R(x,y,φm)|2The imaging detector (9) records N interference holograms I (x, y, phi)m)；
2) When the number of rotations N and the phase shift phi of the reference beam are knownmThen, based on the recorded N interference holograms I (x, y, phi)m) Calculating the diffraction light wave U (x, y) of the measured object on the recording surface according to the following formula:
wherein, a1、a2…aNIs the intensity coefficient, phi1、φ2…φNIs the phase shift of the reference beam, (x, y) is the spatial coordinate distribution of the imaging detector surface;
3) reversely transmitting the diffracted light waves U (x, y) obtained in the step 2) to an object plane by utilizing an angular spectrum diffraction transmission inverse algorithm to obtain the complex amplitude distribution O (x) of the measured object0,y0)：
Wherein,
is an angular spectrum transfer function, fXAnd fYIs the spatial frequency, z0Is the distance from the object to be measured (13) to the imaging detector (9), and lambda is the wavelength of the light source.
2. The method according to claim 1, characterized in that the object (13) to be measured is a resolution plate or a biological sample.
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