Polarization holographic multiplexing display system based on acousto-optic modulator and method thereof

Abstract

The application relates to a polarization holographic multiplexing display system and method based on an acousto-optic modulator, wherein a beam splitter is arranged in front of a spatial light modulator; a laser, a first linear polarizer and the beam splitter are sequentially arranged on an optical path of the laser; a first lens, a pinhole, a second lens and a first polarization grating are sequentially arranged on a reflection optical path of the beam splitter; four circularly polarized lights are arranged behind the first polarization grating; a reflecting mirror, an acousto-optic modulator, a third lens and an image sensor are sequentially arranged on an optical path of a first light beam; a second polarization grating, a second linear polarizer and an image sensor are sequentially arranged on optical paths of a second light beam, a third light beam and a fourth light beam. The application can obtain three kinds of reconstructed images with different effects at different reconstruction distances, and has a good application prospect in the fields of holographic display, holographic storage and the like.

Description

Technical Field

[0001] This invention relates to a polarization holographic multiplexing display system and method based on an acousto-optic modulator, belonging to the field of digital holography technology. Background Technology

[0002] Holographic display reuse using traditional spatial light modulators has been a significant challenge and has received considerable attention over the past few decades. However, spatial light modulators typically reconstruct only one holographic image. To improve display performance, polarization gratings (PGs) are introduced into holographic display systems, leveraging their polarization selectivity. Specific applications include Yoo et al.'s use of polarization grating systems to implement extended eye movement frames, and Lin et al.'s use of polarization gratings to achieve two-dimensional pupil replication in Maxwell's near-eye display system.

[0003] However, existing technologies, due to limitations in spatial light modulator technology, face challenges in holographic display using polarization gratings, including small display area and difficulties in reuse. This invention addresses these issues by introducing polarization gratings into the holographic display system, utilizing their polarization selectivity to improve system display performance. Summary of the Invention

[0004] The purpose of this invention is to split two incident beams into four sub-beams using the polarization beam-splitting property of a polarization grating. Then, by utilizing the high-pass filtering effect of an acousto-optic modulator, the principle of interference biphase coding, and the Fourier iterative algorithm to encode and modulate each sub-beam, three different reconstructed images can be obtained at different reconstruction distances, thereby achieving holographic reuse.

[0005] The present invention first provides the following technical solution:

[0006] A polarization holographic multiplexing display system based on an acousto-optic modulator, comprising:

[0007] A beam splitter is placed in front of the spatial light modulator;

[0008] The laser, the first linear polarizer, and the beam splitter are sequentially arranged in the optical path of the laser.

[0009] The beam splitter's reflected light path is sequentially provided with a first lens, a pinhole, a second lens, and a first polarization grating; four circularly polarized beams are emitted after the first polarization grating;

[0010] The optical path of the first beam is sequentially equipped with a reflector, an acousto-optic modulator, a third lens, and an image sensor;

[0011] The second beam, the third beam, and the fourth beam are respectively equipped with a second polarizing grating, a second linear polarizer, and an image sensor in their optical paths.

[0012] Convert the laser emitted from the laser into linearly polarized light;

[0013] The spatial light modulator has two different holographic images loaded in its upper and lower parts;

[0014] The linearly polarized light is reflected by a beam splitter to a spatial light modulator to obtain two incident beams of the system.

[0015] The incident light field is filtered using a 4f system to remove background noise from the spatial light modulator.

[0016] Two filtered linearly polarized incident beams are split into four circularly polarized beams by the first polarization grating.

[0017] The first beam is reflected by a mirror, modulated by an acousto-optic modulator, and then received by an image sensor via a third lens.

[0018] The second beam and the third beam are superimposed at the second polarization grating, and after passing through the second linear polarizer, they interfere and are received by the image sensor.

[0019] The fourth beam passes through the second polarization grating and then through the second linear polarizer before being received by the image sensor;

[0020] In some more specific embodiments, the processing includes:

[0021] The light emitted from the laser is linearly polarized by a first linear polarizer, then reflected by a beam splitter to a pure phase spatial light modulator, where two different holographic images are loaded onto the upper and lower parts of the spatial light modulator. , The two diffracted light fields, after being filtered by a 4f system, are incident on the first polarization grating. The polarization grating decomposes the two linearly polarized diffracted light fields into combinations of two left-handed and right-handed circularly polarized beams, resulting in a total of four beams after passing through the grating. The first beam is reflected by a mirror to an acousto-optic modulator and then received by an image sensor via a third lens. The second and third beams are superimposed at the second polarization grating, interfere after passing through a second linear polarizer, and are then received by the image sensor. The fourth beam passes through the second polarization grating and the second linear polarizer before being received by the image sensor. Thus, the reconstruction of three holographic images by this holographic reconstruction system is completed.

[0022] The holographic reconstruction process described above is more specifically as follows: a spatial light modulator loads two holographic images. , A specific phase distribution is obtained in advance through holographic algorithms. , It is composed of three superimposed holographic images. Among them: ;

[0023] in, , and These are three computational holograms, and the reconstruction distances of the three holograms are respectively... , , .

[0024] According to some preferred embodiments of the present invention, the computational hologram , The result was obtained through a holographic algorithm, which is a Fourier iterative algorithm.

[0025] More specifically, the Fourier iterative algorithm may include: using the forward and inverse Fourier transforms between the spatial and frequency domains and the respective constraints in the spatial and frequency domains, iterating repeatedly until the pre-designed convergence conditions with the loaded initial field are met.

[0026] According to some preferred embodiments of the present invention, the computational hologram The holographic algorithm is used to obtain the result, and the holographic algorithm is a two-phase encoding method.

[0027] More specifically, the dual-phase encoding method is as follows: after normalizing the amplitude of the expected complex amplitude hologram, the complex amplitude can then be expressed as the sum of two pure phase distributions, i.e. .

[0028] According to some preferred embodiments of the present invention, the two filtered linearly polarized incident beams are split into four circularly polarized beams by a first polarization grating (8), wherein, After being split by the first polarization grating, the first beam is ( ), second beam ( ), After being split by the first polarization grating, the third beam ( ), fourth beam ( The first holographic reconstructed image was created by The second holographic reconstructed image was obtained from... The first holographic reconstructed image was obtained from... The overall reconstruction result of the system is obtained by superimposing three holograms.

[0029] According to some preferred embodiments of the present invention, the optical transfer function of the acousto-optic modulator is... Set to: ;

[0030] in, represents the frequency domain coordinates; j represents the imaginary unit.

[0031] According to some preferred embodiments of the present invention, the first beam ( The reconstructed light field obtained after the aforementioned acousto-optic modulation satisfy: ;

[0032] in, Indicates Fourier transform, Indicates the inverse Fourier transform. The optical transfer function is given by the high-pass filtering effect of the acousto-optic modulator on the optical information. This is usually the result of edge extraction.

[0033] According to some preferred embodiments of the present invention, the second beam ( ) and the third beam ( The optical fields are superimposed at the second polarization grating and then interfered with after passing through the second linear polarizer to obtain the reconstructed optical field. : ;

[0034] According to some preferred embodiments of the present invention, the fourth beam ( The reconstructed optical field is obtained after passing through a second polarization grating and a second linear polarizer. ;

[0035] The total reconstructed light field obtained by the system at this time is: ;

[0036] The three results include the reconstruction results of edge extraction, the reconstruction results of encoded complex amplitude distribution, and the reconstruction results of the Fourier iterative algorithm. Since the reconstruction distances of the three holograms are respectively... , , Therefore, any of the three reconstruction results can be obtained by controlling the reconstruction distance.

[0037] The present invention further provides some reconstruction systems for processing holographic images using the above reconstruction methods.

[0038] The present invention has the following beneficial effects:

[0039] (1): Based on the selectivity of polarization gratings to incident light and combined with computational holography algorithms, this invention can obtain holographic reconstructed images with three properties at different reconstruction positions. While expanding the field of view of the holographic reconstructed image, it also improves the reconstruction quality of the holographic reconstruction system. Unlike traditional reconstruction systems, this system also introduces an acousto-optic modulator, making the system a real-time programmable system.

[0040] (2): In some specific implementations, based on the beam splitting effect of the polarization grating on the incident light, multi-beam imaging with different effects is achieved through algorithm coding.

[0041] (3): In some specific implementations, based on the modulation of light information by the acousto-optic modulator, the present invention achieves significant edge enhancement of the image through the acousto-optic filter transfer function that plays a significant high-pass filtering role on the incident light.

[0042] (4): In some specific embodiments, since multiple reconstruction results are encoded at different reconstruction distances in this invention, different reconstruction results can be selected by changing the reconstruction distance of the system. Attached Figure Description

[0043] Figure 1 The holographic image reconstruction system described in the specific implementation includes: 1. a laser; 2. a first linear polarizer; 3. a beam splitter; 4. a spatial light modulator; 5. a first lens; 6. a pinhole; 7. a second lens; 8. a first polarizing grating; 9. a mirror; 10. an acousto-optic modulator; 11. a third lens; 12. an image sensor; 13. a second polarizing grating; and 14. a second linear polarizer.

[0044] Figure 2a This is one of the reconstruction results of Example 1 at different reconstruction distances.

[0045] Figure 2b This is the second reconstruction result of Example 1 at different reconstruction distances.

[0046] Figure 2c This is the third reconstruction result of Example 1 at different reconstruction distances. Detailed Implementation

[0047] The present invention will now be described in detail with reference to embodiments and accompanying drawings. However, it should be understood that the embodiments and drawings are for illustrative purposes only and do not constitute any limitation on the scope of protection of the present invention. All reasonable modifications and combinations included within the inventive spirit of the present invention fall within the scope of protection of the present invention.

[0048] According to the technical solution of the present invention, a specific embodiment is as follows: Figure 1 The polarization holographic multiplexing display system based on an acousto-optic modulator shown includes:

[0049] A beam splitter 3 is placed in front of the spatial light modulator 4;

[0050] Laser 1, first linear polarizer 2, and beam splitter 3 are sequentially arranged in the optical path of laser 1;

[0051] The beam splitter 3 has a first lens 5, a pinhole 6, a second lens 7, and a first polarizing grating 8 arranged sequentially on the reflected light path; four circularly polarized beams are generated after the first polarizing grating 8.

[0052] The optical path of the first beam is sequentially provided with a reflector 9, an acousto-optic modulator 10, a third lens 11, and an image sensor 12;

[0053] The second beam, the third beam, and the fourth beam are sequentially provided with a second polarization grating 13, a second linear polarizer 14, and an image sensor 12;

[0054] The first linear polarizer 2, located on the optical path of laser 1, reflects the laser beam to the beam splitter 3 of the spatial light modulator 4. The laser beam, modulated by the spatial light modulator 4 with two holographic images, is filtered by a 4f system consisting of a first lens 5, a pinhole 6, and a second lens 7, and then incident on the first polarization grating 8. The first polarization grating 8 decomposes the two holographic images into four circularly polarized beams. The first beam is reflected by the mirror 9 and modulated by the acousto-optic modulator 10, and then imaged onto the image sensor 12 by the third lens 11. The second and third beams are superimposed at the second polarization grating 13, interfere after passing through the second linear polarizer 14, and are imaged onto the image sensor 12. The fourth beam is imaged onto the image sensor 12 after passing through the second polarization grating 13.

[0055] The image processing procedure based on the above system includes:

[0056] The light emitted from laser 1 is linearly polarized by the first linear polarizer 2, and then reflected by the beam splitter 3 to a pure phase spatial light modulator 4. The spatial light modulator 4 has two different holographic images loaded on its upper and lower parts. , The two diffracted light fields, after being filtered by the 4f system, are incident on the first polarization grating 8. The first polarization grating 8 decomposes the two linearly polarized diffracted light fields into combinations of two left-handed and right-handed circularly polarized beams, resulting in a total of four beams after passing through the first polarization grating 8. The first beam ( The image is reflected by mirror 9 to acousto-optic modulator 10, and then received by image sensor 12 via third lens 11. The result is... ; second beam ( ) and the third beam ( The light is superimposed at the second polarization grating 13, and after passing through the second linear polarizer 14, it interferes and is received by the image sensor 12, resulting in... Fourth beam ( After passing through the second polarization grating 13 and the second linear polarizer 14, the image is received by the image sensor 12, and the result is... Thus, the reconstruction of the three holographic images of this holographic reconstruction system is complete. The total reconstructed light field obtained by the system at this point is... .

[0057] in:

[0058] The optical transfer function of the acousto-optic modulator Set to: ;

[0059] in, represents the frequency domain coordinates; j represents the imaginary unit.

[0060] According to some preferred embodiments of the present invention, the first beam ( The reconstructed light field obtained after the aforementioned acousto-optic modulation satisfy: ;

[0061] in, Indicates Fourier transform, Indicates the inverse Fourier transform. The optical transfer function is given by the high-pass filtering effect of the acousto-optic modulator on the optical information. This is usually the result of edge extraction.

[0062] Second beam ( ) and the third beam ( The light field is superimposed at the second polarization grating 13 and interfered with after passing through the second linear polarizer 14 to obtain the reconstructed light field. : ;

[0063] According to some preferred embodiments of the present invention, the fourth beam ( The reconstructed optical field is obtained after passing through the second polarization grating 13 and the second linear polarizer 14. ;

[0064] The total reconstructed light field obtained by the system at this time is: ;

[0065] The three results include the reconstruction results of edge extraction, the reconstruction results of encoded complex amplitude distribution, and the reconstruction results of the Fourier iterative algorithm. Since the reconstruction distances of the three holograms are respectively... , , Therefore, this invention can control the reconstruction distance to be respectively , or This allows you to obtain any one of the three reconstruction results.

[0066] Example 1

[0067] The holographic image reconstruction process described in the specific implementation method is simulated, wherein the wavelength of the laser emitted by the laser is λ = 6.32 × 10⁻⁶. -7The spatial light modulator used is a pure phase type with 1920*1080 pixels and a pixel pitch of 8 micrometers. The acousto-optic modulator is a general acousto-optic modulator with parameters set to grating pitch Ʌ = 7 × 10⁻⁵ m.

[0068] In the simulation experiment, the convergence threshold of the Fourier iterative algorithm was set to 0.95, and the two holographic images pre-loaded on the spatial light modulator were of the same size, 800×1000. The reconstruction distance of the three holographic images was set to... , , .

[0069] Figures 2a-2c The image shown is an image obtained by the reconstruction method of the present invention at different reconstruction distances. It can be seen that the present invention reconstructs three different reconstruction results at different reconstruction distances, namely edge extraction reconstruction image, complex amplitude reconstruction image, and pure phase reconstruction image.

[0070] The above embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A polarization holographic multiplexed display system based on an acousto-optic modulator, characterized in that, include: A beam splitter (3) is placed in front of the spatial light modulator (4); The laser (1), the first linear polarizer (2), and the beam splitter (3) are sequentially arranged in the optical path of the laser (1). The beam splitter (3) has a first lens (5), a small hole (6), a second lens (7), and a first polarization grating (8) arranged sequentially on the reflected light path; there are four circularly polarized beams after the first polarization grating (8); The optical path of the first beam is provided with a reflector (9), an acousto-optic modulator (10), a third lens (11), and an image sensor (12) in sequence. The second beam, the third beam, and the fourth beam are respectively provided with a second polarization grating (13), a second linear polarizer (14), and an image sensor (12) in their optical paths. The first linear polarizer (2) located on the optical path of the laser (1) reflects the laser to the beam splitter (3) of the spatial light modulator (4). The laser modulated by the spatial light modulator (4) with two holographic information is filtered by a 4f system composed of the first lens (5), the pinhole (6) and the second lens (7) and then incident on the first polarization grating (8). The first polarization grating (8) decomposes the two holographic information into four circularly polarized beams. The first beam is reflected by the mirror (9) to the acousto-optic modulator (10) for modulation and is imaged onto the image sensor (12) by the third lens (11). The second beam and the third beam are superimposed at the second polarization grating (13), interfere after passing through the second linear polarizer (14), and are imaged onto the image sensor (12). The fourth beam is imaged onto the image sensor (12) after passing through the second polarization grating (13).

2. A polarization holographic multiplexing display method based on an acousto-optic modulator, characterized in that, The image processing process of the polarization holographic multiplexing display system based on an acousto-optic modulator as described in claim 1 includes: The light emitted from the laser (1) is linearly polarized by the first linear polarizer (2), and then reflected by the beam splitter (3) to the pure phase spatial light modulator (4), wherein the upper and lower parts of the spatial light modulator (4) are loaded with two different holographic information. , The two diffracted light fields, after being filtered by the 4f system, are incident on the first polarization grating (8); the first polarization grating (8) decomposes the two linearly polarized diffracted light fields into a combination of two left-handed and right-handed circularly polarized beams, respectively. After passing through the first polarization grating (8), the system has a total of four beams; the first beam The image is reflected by the mirror (9) to the acousto-optic modulator (10), and then received by the image sensor (12) via the third lens (11), resulting in... Second beam and the third beam The light is superimposed at the second polarization grating (13), and after passing through the second linear polarizer (14), it interferes and is received by the image sensor (12), resulting in... Fourth beam After passing through the second polarization grating (13) and the second linear polarizer (14), the image sensor (12) receives the result. The reconstruction of three holographic images by this holographic reconstruction system has been completed. At this point, the total reconstructed light field obtained by the system is .

3. The polarization holographic multiplexing display method based on an acousto-optic modulator according to claim 2, characterized in that, The optical transfer function of the acousto-optic modulator Set to: ， in, Represents frequency domain coordinates; j represents the imaginary unit; First beam The reconstructed light field obtained after the acousto-optic modulation satisfy: ， in, Indicates Fourier transform, Indicates the inverse Fourier transform. The optical transfer function represents the high-pass filtering effect of the acousto-optic modulator on the optical information. This is the result of edge extraction; Second beam and the third beam The reconstructed optical field is obtained by superimposing the light at the second polarization grating (13) and interfering with it after passing through the second linear polarizer (14). : ， Fourth beam The reconstructed light field is obtained after passing through the second polarization grating (13) and the second linear polarizer (14). ; The total reconstructed light field obtained by the system is: ， The three results include the reconstruction results of edge extraction, the reconstruction results of encoded complex amplitude distribution, and the reconstruction results of Fourier iterative algorithm.

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