Method for recording and displaying photopolymer based on computational holographic bin algorithm

Abstract

The present invention discloses a method for recording and displaying photopolymers based on a computer-generated holographic bin algorithm. S1: After a beam of light emitted by a femtosecond pulse laser is expanded and collimated, the pulse laser is focused on a photopolymer material through an objective lens, causing the refractive index of the photopolymer to change. The position of the photopolymer is controlled by controlling a translation stage to achieve three-dimensional recording of two pieces of material. S2: The complex amplitude distribution of the object is calculated through the computer-generated holographic bin algorithm and the two pieces of material are encoded. The exposure time and other parameters are controlled by a computer, and the femtosecond laser is used to write the calculated and encoded phase information diagram on the photopolymer. S3: After recording, the second beam splitter and the objective lens in front of the recording position are removed, and a plane wave is used to simultaneously irradiate the two pieces of engraved photopolymer and combine the beams to obtain a reproduced image of the three-dimensional object. The recording and display of the three-dimensional object can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of computer-generated holography technology, in particular to a method for recording and displaying photopolymers using a computer-generated holographic facet algorithm. Background Art

[0002] Applying computational holography (CGH) technology to 3D display can fully reproduce the amplitude and phase of a 3D object, encompassing all the information about the original 3D object. Holographic 3D display combines the interdisciplinary research fields of traditional optical holography, fast algorithmic computation, micro-nanomaterial processing, and display-bearing devices. Compared to traditional 3D display technologies such as binocular parallax display and volumetric display, holographic 3D display offers numerous advantages, including providing full depth cues, conforming to the natural observation habits of the human eye, and employing a simpler device structure. It is considered one of the most promising 3D display technologies.

[0003] CGH is similar to traditional holography in that it also includes a wavefront recording process and a 3D reconstruction process. Unlike traditional optical holography, the wavefront recording process of CGH-based holographic 3D display technology can be completed by computer, thus avoiding the complex interference recording optical path. It is also flexible and has a wide range of applications. As long as there is a mathematical description of the light wave, it can recreate non-existent virtual 3D objects. With the development of micro-nanofabrication technology and spatial light modulator (SLM) technology, precise phase modulation of the wavefront can be achieved using diffractive optical elements and phase-type SLMs. By encoding the calculated complex amplitude distribution of the 3D object on the holographic surface in a suitable manner on the selected display medium and illuminating it with coherent light, the optical reconstruction of the 3D object can be completed.

[0004] Currently, 3D display technology based on computational holography is developing rapidly. Advances in computing hardware such as GPUs, CPUs, and field-programmable gate arrays (FPGAs) are providing the necessary computing power for the development of computational holography. Combining disciplines such as computer graphics and micro-nano optics with computational holography offers a broader perspective on computational methods and complex amplitude coding, accelerating the application of 3D display technology in key industries such as medicine, education, architecture, and national defense. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a method for recording and displaying photopolymers based on a computer-generated holographic bin algorithm, which can realize the recording and display of three-dimensional objects.

[0006] The technical solution of the present invention is:

[0007] Method for recording and displaying photopolymer based on computer generated holographic bin algorithm,

[0008] S1: After a beam of light emitted by a femtosecond pulse laser is expanded and collimated, it is focused on a photopolymer material through an objective lens, causing the refractive index of the photopolymer to change. The position of the photopolymer is controlled by controlling the translation stage, achieving three-dimensional recording of the two materials.

[0009] S2: The complex amplitude distribution of the object is calculated using a computational holographic binning algorithm and the two materials are encoded. Parameters such as exposure time are controlled by a computer, and a femtosecond laser is used to write the calculated encoded kinoform pattern into the photopolymer.

[0010] S3: After recording, remove the second beam splitter and the objective lens in front of the recording position, use a plane wave to simultaneously illuminate the two engraved photopolymers and combine the beams to obtain a reconstructed image of the three-dimensional object.

[0011] Preferably, the device for recording and displaying photopolymer based on the computer generated holographic facet algorithm comprises: a femtosecond laser, a switch for controlling parameters such as exposure time, a first pinhole, a first Fourier lens, a first beam splitter, a second beam splitter, an objective lens, a three-dimensional translation stage, a first photopolymer material, a second Fourier lens, a photomultiplier tube, a computer, a solid-state laser, a second pinhole, a third Fourier lens, a third beam splitter, a reflector, a second photopolymer material, a beam combiner, and a CCD; a control device is set behind the femtosecond laser. A switch for controlling parameters such as exposure time, the switch for controlling parameters such as exposure time is connected to a computer, a first pinhole is arranged behind the switch for controlling parameters such as exposure time, a first Fourier lens is arranged behind the first pinhole, a first beam splitter is arranged behind the first Fourier lens, a second beam splitter is arranged behind the first beam splitter, an objective lens is arranged behind the second beam splitter, a three-dimensional translation stage is arranged at the bottom of the objective lens, a first photopolymer material is arranged behind the objective lens, a beam combiner is arranged behind the first photopolymer material, and a CCD is arranged behind the beam combiner;

[0012] A third beam splitter is arranged at the bottom of the first beam splitter, a second small hole is arranged in front of the third beam splitter, a solid laser is arranged in front of the second small hole, a reflector is arranged behind the third beam splitter, a second photopolymer material is arranged above the reflector, and a beam combining mirror is arranged above the second photopolymer material.

[0013] Preferably, the laser wavelength emitted by the femtosecond pulse laser is 800 nm, the average light intensity is 20 mW, the single point exposure is 5 ms, the magnification of the objective lens is 20 times, and the numerical aperture of the objective lens is 0.75.

[0014] Preferably, the two photopolymers are both polymethyl methacrylate photopolymer materials doped with silicon dioxide nanoparticles.

[0015] Preferably, the CGH facet algorithm is an analytical facet algorithm based on three-dimensional affine transformation; the calculated three-dimensional object surface is discretized into n triangles, and the complex amplitude distribution F of the triangles in the hologram plane is H (x,y) can be expressed as:

[0016]

[0017] Where x, y are the coordinates of the hologram plane, F i (x, y) is the complex amplitude distribution of the discretized i-th triangle in the hologram plane.

[0018] Preferably, the calculation result in claim 5 is subjected to a dual-phase decomposition encoding method, and F H (x,y) is decomposed into:

[0019]

[0020] in Respectively represent the phase distribution on two pieces of photopolymer materials:

[0021]

[0022] Preferably, after recording is completed, the second beam splitter and the objective lens before the recording position are removed, a piece of photopolymer material is placed at the second Fourier lens at the recording position, and another piece of photopolymer is placed at the beam combiner. The two pieces can be arbitrarily replaced to form two holograms.

[0023] The two recorded holograms are illuminated with 532nm parallel light and combined with a beam combiner to obtain a reconstructed three-dimensional object.

[0024] The beneficial effects of the present invention are:

[0025] 1. This invention is based on computer-generated holographic 3D display technology, which includes calculating the complex amplitude of a 3D object on a holographic surface and encoding it on a photopolymer material. By using a precise 3D affine transformation algorithm to rapidly calculate the complex amplitude distribution on the holographic surface, dual-phase encoding is applied to the phase distribution on two pieces of photopolymer material. A femtosecond pulse processing system is then used to record the 3D display on each piece of material at the recording position, achieving holographic storage of 3D information.

[0026] 2. In the reproduction process of the present invention, the light beam emitted by the solid laser is collimated and expanded and then split into two beams by a third beam splitter. The two beams are respectively irradiated on two pieces of recorded photopolymer materials and then combined by a beam combiner to reproduce the recorded three-dimensional object. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural diagram of the holographic recording and reproduction system used in the present invention.

[0028] Figure 2 This is a flow chart of the computational holographic facet algorithm used in the present invention.

[0029] Figure 1: Femtosecond laser, 2. Switch for controlling parameters such as exposure time, 3. First pinhole, 4. First Fourier lens, 5. First beam splitter, 6. Second beam splitter, 7. Objective lens, 8. Three-dimensional translation stage, 9. First photopolymer material, 10. Second Fourier lens, 11. Photomultiplier tube, 12. Computer, 13. Solid-state laser, 14. Second pinhole, 15. Third Fourier lens, 16. Third beam splitter, 17. Reflector, 18. Second photopolymer material, 19. Beam combiner, 20. CCD. DETAILED DESCRIPTION

[0030] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0031] like Figures 1 to 2 As shown, a method for recording and displaying photopolymers based on a CGH binning algorithm involves expanding and collimating a beam of light emitted by a femtosecond pulsed laser. The pulsed laser is then focused on the photopolymer material through an objective lens, causing the refractive index of the polymer to change. The position of the polymer is controlled by a translation stage, enabling three-dimensional recording of two materials. The CGH binning algorithm calculates the complex amplitude distribution of the object and encodes the two materials. A computer controls parameters such as exposure time, and the femtosecond laser writes the calculated encoded kinoform pattern onto the photopolymer.

[0032] The device for recording and displaying photopolymers based on a computer-generated holographic binning algorithm uses a femtosecond pulsed laser 1, controlled by a switch, to sequentially pass through a first aperture 2, a first Fourier lens 3, a first beam splitter 4, a second beam splitter 5, and an objective lens 6. The laser then focuses on the photopolymer material, modulating its refractive index. The material's position is controlled by a three-dimensional translation stage 8, and the recording process for the two materials is completed sequentially according to the holograms calculated and encoded using the computer-generated holographic binning algorithm. Before recording, the recording depth is determined by an optical signal reflected from the surface of the photopolymer material through a second beam splitter 6 and a second Fourier lens 10 to a photomultiplier tube 11. The femtosecond laser 1, photomultiplier tube 11, and three-dimensional translation stage 8 are all automatically controlled by a computer. During the three-dimensional reconstruction process, the femtosecond laser 1 is turned off, the second beam splitter 6 and objective lens 7 are removed, and the light beam emitted by the solid-state laser 13 passes through a second aperture 14, a third Fourier lens 15, and is split into two beams by a third beam splitter 16. One of the beams passes through the first beam splitter 5 and is irradiated onto the first photopolymer material 9, and the other beam is reflected by the reflector onto the second photopolymer material 18. The two beams passing through the first photopolymer material 9 and the second photopolymer material 18 are combined by the beam combiner 19 to reconstruct a three-dimensional object in the CCD20 plane.

[0033] The laser wavelength emitted by the femtosecond pulse laser 1 is 800 nm, the average light intensity is 20 mW, and the single-point exposure is 5 ms. The objective lens has a magnification of 20 times and a numerical aperture of 0.75. When the writing spot is 5 mm, the xy resolution is 3 μm.

[0034] The computational holographic surface element algorithm used is an analytical surface element algorithm based on three-dimensional affine transformation. The calculated three-dimensional object surface is discretized into n triangles, and its complex amplitude distribution F on the hologram plane is H (x,y) can be expressed as:

[0035]

[0036] Where x, y are the coordinates of the hologram plane, and F i (x,u) is the complex amplitude distribution of the discretized i-th triangle in the hologram plane. i (x,y) can be calculated using the following flow chart:

[0037] The femtosecond pulse laser emits a laser wavelength of 800 nm, an average light intensity of 20 mW, and a single-point exposure of 5 ms. The objective lens has a magnification of 20 times and a numerical aperture of 0.75. When the writing spot is 5 mm, the xy resolution is 3 μm.

[0038] The computational holographic surface element algorithm used is an analytical surface element algorithm based on three-dimensional affine transformation. The calculated three-dimensional object surface is discretized into n triangles, and its complex amplitude distribution F on the hologram plane is H (x,y) can be expressed as:

[0039]

[0040] Where x, y are the coordinates of the hologram plane, and F i (x,y) is the complex amplitude distribution of the discretized i-th triangle in the hologram plane. i (x,y) can be calculated using the following flow chart:

[0041] The two photopolymers are both polymethyl methacrylate photopolymer materials doped with silicon dioxide nanoparticles.

[0042] The encoding method is bi-phase encoding, and F H (x,y) is decomposed into:

[0043]

[0044] in Respectively represent the phase distribution on two pieces of photopolymer materials:

[0045]

[0046] The amplitude and phase information of a three-dimensional object can be recorded in a photopolymer material through the above encoding.

[0047] After recording is complete, the objective lens in front of the recording position is removed, and a piece of photopolymer material is placed at the second Fourier lens in the recording position, and another piece of photopolymer material is placed at the beam combiner. The two pieces can be interchanged at will. The two holograms recorded using 532nm parallel light are then combined using the beam combiner to reconstruct the 3D object. This method enables real-time recording and reproduction of 3D objects, is easy to operate, and has strong practicality. It has important applications in holographic storage, 3D display, and other fields.

[0048] The above describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for recording and displaying photopolymers based on a computer-generated holographic binning algorithm, characterized in that: S1: After a beam of light emitted by a femtosecond pulse laser is expanded and collimated, it is focused on a photopolymer material through an objective lens, causing the refractive index of the photopolymer to change. The position of the photopolymer is controlled by controlling the translation stage, achieving three-dimensional recording of the two materials. S2: The complex amplitude distribution of the object is calculated by the computational holographic binning algorithm and the two materials are encoded. The exposure time parameters are controlled by a computer, and the femtosecond laser is used to write the calculated encoded phase pattern into the photopolymer. S3: After recording, remove the second beam splitter and the objective lens in front of the recording position, use a plane wave to illuminate the two inscribed photopolymers simultaneously and combine the beams to obtain a reconstructed image of the three-dimensional object; The device for recording and displaying photopolymer based on the computer generated holographic facet algorithm comprises: a femtosecond laser (1), a switch for controlling exposure time parameters (2), a first pinhole (3), a first Fourier lens (4), a first beam splitter (5), a second beam splitter (6), an objective lens (7), a three-dimensional translation stage (8), a first photopolymer material (9), a second Fourier lens (10), a photomultiplier tube (11), a computer (12), a solid laser (13), a second pinhole (14), a third Fourier lens (15), a third beam splitter (16), a reflector (17), a second photopolymer material (18), a beam combiner (19), and a CCD (20); a switch for controlling exposure time parameters is provided behind the femtosecond laser (1). The switch (2) for controlling exposure time parameters is connected to a computer (12); a first pinhole (3) is arranged behind the switch (2) for controlling exposure time parameters; a first Fourier lens (4) is arranged behind the first pinhole (3); a first beam splitter (5) is arranged behind the first Fourier lens (4); a second beam splitter (6) is arranged behind the first beam splitter (5); an objective lens (7) is arranged behind the second beam splitter (6); a three-dimensional translation stage (8) is arranged at the bottom of the objective lens (7); a first photopolymer material (9) is arranged behind the objective lens (7); a beam combiner (19) is arranged behind the first photopolymer material (9); and a CCD (20) is arranged behind the beam combiner (19); A third beam splitter (16) is arranged at the bottom of the first beam splitter (5), a second small hole (14) is arranged in front of the third beam splitter (16), a solid laser (13) is arranged in front of the second small hole (14), a reflector (17) is arranged behind the third beam splitter (16), a second photopolymer material (18) is arranged above the reflector (17), and a beam combining mirror (19) is arranged above the second photopolymer material (18).

2. The method for recording and displaying photopolymers based on a computer-generated holographic binning algorithm according to claim 1, wherein: The laser wavelength emitted by the femtosecond pulse laser is 800 nm, the average light intensity is 20 mW, the single point exposure is 5 ms, the magnification of the objective lens is 20 times, and the numerical aperture of the objective lens is 0.

75.

3. The method for recording and displaying photopolymers based on a computer-generated holographic binning algorithm according to claim 1, wherein: The two photopolymers are both polymethyl methacrylate photopolymer materials doped with silicon dioxide nanoparticles.

4. The method for recording and displaying photopolymers based on a computer-generated holographic binning algorithm according to claim 1, wherein: The CGH facet algorithm is an analytical facet algorithm based on three-dimensional affine transformation. The calculated three-dimensional object surface is discretized into n triangles, and the complex amplitude distribution F of the triangles on the hologram plane is H (x,y) can be expressed as: Where x, y are the coordinates of the hologram plane, F i (x, y) is the complex amplitude distribution of the discretized i-th triangle in the hologram plane.

5. The method for recording and displaying photopolymers based on a computer-generated holographic binning algorithm according to claim 4, wherein: The calculation result in claim 4 is subjected to a dual-phase decomposition encoding method, and F H (x,y) is decomposed into: in Respectively represent the phase distribution on two pieces of photopolymer materials:

6. The method for recording and displaying photopolymers based on a computer-generated holographic binning algorithm according to claim 1, wherein: After recording is completed, the second beam splitter and the objective lens before the recording position are removed, and a piece of photopolymer material is placed at the second Fourier lens at the recording position, and another piece of photopolymer is placed at the beam combiner. The two can be arbitrarily replaced to form two holograms. The two recorded holograms are illuminated by 532 nm parallel light, and the beams are combined by a beam combiner to obtain a reconstructed three-dimensional object.

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