Aberration compensation method and device

Abstract

The present invention discloses an aberration compensation method and device, the method comprising: step S1, compensating and superimposing a conjugate wavefront aberration phase on an initial input phase to obtain a pre-compensated phase; step S2, superimposing the pre-compensated phase through the wavefront aberration phase distortion of an optical element itself to obtain a compensated phase, and subjecting the compensated phase to Fourier transformation to obtain aberration-compensated Fourier surface intensity; the aberration-compensated Fourier surface intensity information has a low bit error rate and a good reconstruction effect; it is a numerical compensation method without the need to add additional optical components; thereby reducing the number of optical elements used in an optical system and reducing the complexity of the optical system, providing good technical support for aberration compensation in, for example, the field of holographic storage, and having good application prospects in, for example, the field of holographic data storage research; it can be applied to the fields of holographic storage, biomedical image processing, digital holographic microscopy, etc.

Description

Technical Field

[0001] The present invention relates to the field of imaging technology, and to an aberration compensation method and device, and in particular to an aberration compensation method and device suitable for a holographic storage system. Background Art

[0002] For new generation storage technologies such as holographic optical storage, the transition from theoretical and laboratory research to marketization has begun. For example, the three-dimensional storage technology of holographic optical storage technology, whose phase-type storage method has ultra-high storage density and ultra-fast data conversion rate, has gradually become the next generation of mainstream storage technology. Compared with traditional amplitude-type holographic storage technology, phase-type holographic storage technology has greatly improved in coding rate and signal-to-noise ratio, and can significantly improve data storage density and data conversion rate.

[0003] Since phase information cannot be directly obtained through the detector, it is necessary to use interference and non-interference methods to detect phase information through calculation iteration. Among them, the interference method requires high system stability and cumbersome operation, which is not conducive to practical application. The traditional non-interference system needs to obtain the Fourier surface intensity of the reconstructed light, and phase reconstruction can be performed through an iterative method.

[0004] In the prior art, whether it is the interference method or the non-interference method, the lens structure used in the holographic optical storage system for information recording has defects such as complex structure, large volume, and heavy weight, which affect the speed and accuracy of the servo, thereby reducing the data access rate. If the lens structure is simplified, it will bring about larger aberration noise, which will cause the light field wavefront to distort, and then change the Fourier surface intensity distribution, which will affect the subsequent phase recovery. Therefore, it is necessary to compensate for the aberration noise in the experiment.

[0005] Existing aberration compensation generally uses increasing the number of imaging lens groups to compensate for aberrations. Its essence is to optimize the control of phase. However, this method has the following shortcomings: on the one hand, increasing the lens group will lead to an increase in the volume and weight of the optical imaging system, which is not conducive to rapid recording and reading of information and achieving system miniaturization. Summary of the invention

[0006] The present invention proposes an aberration compensation method and device, which breaks through the traditional aberration compensation method technology. In the phase encoding stage, based on the optical phase conjugation principle, the conjugate aberration phase is superimposed on the encoded data, thereby realizing the aberration compensation of the system. Not only can the system aberration be compensated in a targeted manner, but also the number of optical elements used is greatly reduced, and the complexity of the optical system is reduced, which provides good technical support for aberration compensation in the field of holographic storage, and has good application prospects in the field of holographic data storage research.

[0007] In a first aspect, the present invention provides an aberration compensation method, comprising the following steps:

[0008] Step S1, compensating and superimposing the conjugate wavefront aberration phase on the initial input phase to obtain a pre-compensation phase;

[0009] Step S2, superimposing the pre-compensated phase with the wavefront aberration phase distortion of the optical element itself to obtain a compensated phase, and performing Fourier transformation on the compensated phase to obtain the aberration-compensated Fourier surface intensity.

[0010] The above-mentioned aberration compensation method obtains pre-compensated phase information by compensating and superimposing the conjugate wavefront aberration phase information on the initial input phase information; then after distorting and superimposing the wavefront aberration phase information of the optical element itself on the pre-compensated phase information, the compensated and superimposed conjugate wavefront aberration phase information and the distorted and superimposed wavefront aberration phase information are compensated and canceled out to obtain the compensated phase information whose distortion has been compensated; after Fourier transformation, the obtained aberration-compensated Fourier surface intensity information has a low bit error rate and a good reconstruction effect.

[0011] In one embodiment, step S1 comprises the following steps:

[0012] Step S11, generating the conjugate wavefront aberration phase by Zernike polynomials, or generating the conjugate wavefront aberration phase by wavefront detector detection;

[0013] Step S12, compensating and superimposing the conjugate wavefront aberration phase on the initial input phase to obtain the pre-compensation phase.

[0014] In one embodiment, step S11 includes the following steps:

[0015] Step S111, reconstructing the Fourier surface intensity before aberration compensation obtained after Fourier transform of the initial input phase by an iterative Fourier transform algorithm, and calculating the bit error rate before compensation;

[0016] Step S112: generating the conjugate wavefront aberration phase by using Zernike polynomials, or generating the conjugate wavefront aberration phase by detecting with a wavefront detector.

[0017] In one embodiment, step S10 is performed before step S11 to generate random phase encoding data as the initial input phase.

[0018] In one embodiment, step S10 includes the following steps:

[0019] Step S101, randomly generating the phase encoding data;

[0020] Step S102, photographing a distribution image of the Fourier surface intensity before aberration compensation obtained after Fourier transform of the initial input phase.

[0021] In one embodiment, step S2 comprises the following steps:

[0022] Step S21, superimposing the pre-compensated phase with the wavefront aberration phase distortion of the optical element itself to obtain a compensated phase, and performing Fourier transformation on the compensated phase to obtain aberration-compensated Fourier surface intensity;

[0023] Step S22, reconstructing the phase of the aberration-compensated Fourier surface intensity obtained after Fourier transform of the compensated phase through an iterative Fourier transform algorithm, and calculating the compensated bit error rate; then adjusting the value of the compensation coefficient, and as the compensation coefficient increases, when the reconstructed compensated bit error rate is the lowest, the aberration compensation is completed.

[0024] In a second aspect, the present invention provides an aberration compensation device, which can be used as an optical system to which the above-mentioned aberration compensation method can be applied, and can be used in combination with a data processing system such as a computer.

[0025] The aberration compensation device includes a laser, and a parallel light adjustment component, a 1 / 2 wave plate, an aperture, a first imaging component, a polarizer and a first non-polarizing stereoscopic beam splitter are arranged in sequence along the direction of the laser output light beam; a phase-type spatial light modulator is arranged in the transmitted light direction of the first non-polarizing stereoscopic beam splitter; a second imaging component and a second non-polarizing stereoscopic beam splitter are arranged in sequence in the reflected light direction of the first non-polarizing stereoscopic beam splitter, a recording lens and a material reflector are arranged in sequence in the transmitted light direction of the second non-polarizing stereoscopic beam splitter, and a Fourier lens and an intensity detector are arranged in sequence in the reflected light direction of the second non-polarizing stereoscopic beam splitter.

[0026] In the above-mentioned aberration compensation device, the laser emits a laser beam, which is converted into a parallel beam with good beam quality by the parallel light adjustment member, and then forms a beam in the shape of an aperture after passing through the 1 / 2 wave plate and the aperture. Then, the beam is transmitted through the first imaging member, the polarizer and the first non-polarizing stereoscopic beam splitter, and is imaged on the phase-type spatial light modulator, and the direction of the reflected light reflected by the first non-polarizing stereoscopic beam splitter is perpendicular to the direction of the original optical path.

[0027] The phase-type spatial light modulator carries a phase image of the conjugate wavefront aberration phase. The light beam incident on the phase-type spatial light modulator carries the phase information of the pre-compensated phase after reflection. The light beam with the pre-compensated phase information continues to pass through the second imaging element, and then after being transmitted through the second non-polarized stereoscopic beam splitter, it is imaged on the front focal plane of the recording lens, and then continues to be focused by the recording lens and incident on the material reflector to record data information. The light beam with the compensated phase information reflected from the material reflector is Fourier transformed by the Fourier lens and then imaged on the back focal plane of the Fourier lens. The intensity detector is located on a plane far away from the back focal plane of the Fourier lens. Finally, the phase information is Fourier transformed into intensity information and received by the intensity detector.

[0028] In one embodiment, the parallel light adjustment component includes a pinhole filter and a collimating lens which are arranged in sequence.

[0029] In one embodiment, the first imaging element includes a first relay lens and a second relay lens arranged in sequence, and the first relay lens and the second relay lens constitute a 4f system.

[0030] In one embodiment, the second imaging element includes a third relay lens and a fourth relay lens which are arranged in sequence, and the third relay lens and the fourth relay lens constitute a 4f system.

[0031] The 4f system means that the focal lengths of the two relay lenses are f respectively. In the entire system, the focal length of the object plane is f, the distance between the two relay lenses is 2f, and the focal length of the image plane is f.

[0032] When implemented, the aberration compensation method of the first aspect of the present invention can be applied to the aberration compensation device of the second aspect of the present invention.

[0033] The aberration compensation method and device of the present invention can at least achieve the following beneficial effects:

[0034] 1. The aberration compensation method of the present invention, in the phase encoding stage, based on the principle of optical phase conjugation, superimposes the conjugate aberration phase into the encoded data, thereby realizing targeted compensation for the aberration of the system; compared with the traditional physical compensation method that relies on superimposing the number of optical elements, introducing aspheric parts, and eliminating the aberration of optical devices through microlens arrays, it is a numerical compensation method without the need for additional optical components; thereby reducing the number of optical elements used in the optical system and the complexity of the optical system, providing good technical support for aberration compensation in the field of holographic storage, for example, and having good application prospects in the field of holographic data storage research; it can be applied to the fields of holographic storage, biomedical image processing, digital holographic microscopy, etc.

[0035] 2. The aberration compensation method of the present invention can iteratively reconstruct the intensity of the Fourier surface after aberration compensation, thereby improving the efficiency of phase reconstruction, and the obtained Fourier surface intensity information after aberration compensation has a low bit error rate and a good reconstruction effect.

[0036] 3. The aberration compensation device of the present invention can be applied to the aberration compensation method of the present invention, which reduces the number of optical elements used, simplifies the optical system, reduces costs, improves phase compensation accuracy and reliability, and has good stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0038] Figure 1 Schematic diagram of Fourier surface intensity I0 before aberration compensation;

[0039] Figure 2 is a flow chart of the aberration compensation method according to embodiment 1 of the present invention;

[0040] Figure 3 Schematic diagram of Fourier surface intensity I1 after aberration compensation;

[0041] Figure 4 is a flow chart of an aberration compensation method according to Embodiment 2 of the present invention;

[0042] Figure 5 is a flow chart of an aberration compensation method according to Embodiment 3 of the present invention;

[0043] Figure 6 is a flow chart of an aberration compensation method according to Embodiment 4 of the present invention;

[0044] Figure 7 is a flow chart of an aberration compensation method according to Embodiment 5 of the present invention;

[0045] Figure 8 is a schematic structural diagram of an aberration compensation device according to Embodiment 6 of the present invention;

[0046] Fig. 9 A phase-encoded image of the initial input phase in the aberration compensation method of the present invention;

[0047] Fig.10 It is a schematic diagram of phase reconstruction of the Fourier surface intensity I0 before aberration compensation in the aberration compensation method of the present invention;

[0048] Fig.11 A schematic diagram of compensating for spherical aberration in the aberration compensation method of the present invention;

[0049] Fig.12A schematic diagram of the bit error rate of phase reconstruction before and after aberration compensation in the aberration compensation method of the present invention;

[0050] Fig.13 It is a schematic diagram of phase reconstruction results before and after aberration compensation in the aberration compensation method of the present invention;

[0051] Fig.14 It is a selection form for compensating the aberration phase of the superimposed conjugate wavefront in the aberration compensation method of the present invention.

[0052] In the figure, a is the initial input phase, b is the conjugate wavefront aberration phase, c is the pre-compensation phase, d is the wavefront aberration phase, e is the compensated phase, e1 is the selected iterative compensation phase, f is the distortion phase, f1 is the selected iterative distortion phase, I0 is the Fourier surface intensity before aberration compensation, I1 is the Fourier surface intensity after aberration compensation, P0 is the reconstruction phase before aberration compensation, and P1 is the reconstruction phase after aberration compensation;

[0053] 1 is a laser, 2 is a pinhole filter, 3 is a collimating lens, 4 is a 1 / 2 wave plate, 5 is an aperture, 6 is a first relay lens, 7 is a second relay lens, 8 is a polarizer, 9 is a first non-polarizing stereo beam splitter, 10 is a phase-type spatial light modulator, 11 is a third relay lens, 12 is a fourth relay lens, 13 is a second non-polarizing stereo beam splitter, 14 is a recording lens, 15 is a reflector with material, 16 is a Fourier lens, and 17 is an intensity detector. DETAILED DESCRIPTION

[0054] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0055] Figure 1 It means that the initial input phase a is not compensated for aberration, and is directly distorted and superimposed with the wavefront aberration phase d by the optical element. The resulting distortion phase f is transformed into the Fourier surface intensity I0 before aberration compensation.

[0056] It can be seen that due to the wavefront aberration of the optical element, the encoding phase of the initial input phase a is superimposed with the wavefront aberration phase d during the transmission process. Here, the wavefront aberration phase d can be understood as the aberration phase brought by the optical element, which causes the encoding phase of the initial input phase a to be changed, and the distorted phase f is obtained. The phase encoding of the distorted phase f is Fourier transformed through the Fourier lens 16, and the obtained Fourier surface intensity I0 before aberration compensation will also change, thereby affecting the final phase reconstruction result, resulting in a low bit error rate and poor reconstruction effect after the Fourier surface intensity I0 before aberration compensation is iteratively reconstructed.

[0057] The aberration compensation method provided in the embodiment of the present invention adopts a non-interference phase reconstruction mode and is based on the phase conjugation principle. The conjugate wavefront aberration phase b is compensated and superimposed on the initial input phase a, thereby compensating the Fourier surface intensity I0 before aberration compensation that is affected by the wavefront aberration phase d.

[0058] The technical solutions provided by various embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0059] Example 1

[0060] Figure 2 The step flow of the aberration compensation method 100 in Example 1 is shown. Figure 3 It shows the Fourier surface intensity I1 after aberration compensation.

[0061] Please refer to Figure 2 The aberration compensation method of this embodiment comprises the following steps:

[0062] Step S1, compensating and superimposing the conjugate wavefront aberration phase b on the initial input phase a to obtain a pre-compensation phase c;

[0063] Step S2, the pre-compensated phase c is distorted and superimposed by the wavefront aberration phase d of the optical element itself to obtain the compensated phase e, and the compensated phase e is subjected to Fourier transformation to obtain the aberration-compensated Fourier surface intensity I1.

[0064] Please refer to Figure 3It can be seen that the aberration compensation method of this embodiment, based on the phase conjugation principle, uses the conjugate wavefront aberration phase b as the pre-compensation aberration phase, and pre-compensates and superimposes it on the input initial input phase a, which is equivalent to compensating the wavefront aberration phase d superimposed on the initial input phase a by the conjugate wavefront aberration phase b pre-compensated on the initial input phase a; that is, the compensation of subsequent distortion is achieved through pre-superposition. Then, during the light beam transmission process, the conjugate wavefront aberration phase b as the pre-compensation aberration phase offsets the wavefront aberration phase d generated by the optical element in the light field, thereby eliminating the influence of the aberration generated by the optical element, and finally obtaining the distortion-free compensated phase e. The distortion-free compensated phase e information is transformed by Fourier transform to obtain the ideal aberration-compensated Fourier surface intensity I1, which has a low bit error rate and good reconstruction effect, thereby achieving compensation for system aberrations.

[0065] Before step S1 , step S10 may be performed to generate random phase encoding data as an initial input phase a.

[0066] Furthermore, step S10 may include the following steps:

[0067] Step S101, randomly generating phase encoding data;

[0068] Step S102, photographing a distribution image of the Fourier surface intensity I0 before aberration compensation obtained after Fourier transform of the initial input phase a.

[0069] Example 2

[0070] Figure 4 The step flow of the aberration compensation method 200 in Example 2 is shown.

[0071] Please refer to Figure 4 The aberration compensation method of this embodiment comprises the following steps:

[0072] Step S11, generating a conjugate wavefront aberration phase b by using a Zernike polynomial, or generating a conjugate wavefront aberration phase b by detecting with a wavefront detector;

[0073] Step S12, compensating and superimposing the conjugate wavefront aberration phase b on the initial input phase a to obtain a pre-compensation phase c.

[0074] Step S2, the pre-compensated phase c is distorted and superimposed by the wavefront aberration phase d of the optical element itself to obtain the compensated phase e, and the compensated phase e is subjected to Fourier transformation to obtain the aberration-compensated Fourier surface intensity I1.

[0075] The Zernike polynomials are shown in the following formula: The wavefront aberration phase d distribution of the corresponding optical element can be generated by the Zernike polynomials, thereby obtaining the conjugate wavefront aberration phase b that needs to be compensated and superimposed.

[0076]

[0077] In the above Zernike polynomials, r, θ are the normalized polar coordinates of the pupil plane, i is the order of the Zernike polynomial, ψ(r, θ) is the wavefront phase distribution function, and Z i (r,θ) is the i-th order Zernike basis function, a i is the coefficient of the i-th order Zernike aberration.

[0078] Alternatively, the wavefront aberration phase d of the optical element may be detected by a wavefront detector, thereby obtaining the conjugate wavefront aberration phase b that needs to be compensated and superimposed.

[0079] The aberration compensation method of this embodiment obtains the wavefront aberration phase d of the optical element distortion superposition by pre-detection or calculation, thereby correspondingly determining the conjugate wavefront aberration phase b that needs to be compensated and superimposed, thereby improving the aberration compensation accuracy and efficiency.

[0080] Example 3

[0081] Figure 5 The step flow of the aberration compensation method 300 in Example 3 is shown.

[0082] Please refer to Figure 5 The aberration compensation method of this embodiment comprises the following steps:

[0083] Step S111, reconstructing the Fourier surface intensity I0 before aberration compensation obtained by Fourier transforming the initial input phase a through an iterative Fourier transform algorithm, and calculating the bit error rate before compensation;

[0084] Step S112, generating a conjugate wavefront aberration phase b by using a Zernike polynomial, or generating a conjugate wavefront aberration phase b by detecting with a wavefront detector;

[0085] Step S12, compensating and superimposing the conjugate wavefront aberration phase b on the initial input phase a to obtain a pre-compensation phase c.

[0086] Step S2, the pre-compensated phase c is distorted and superimposed by the wavefront aberration phase d of the optical element itself to obtain the compensated phase e, and the compensated phase e is subjected to Fourier transformation to obtain the aberration-compensated Fourier surface intensity I1.

[0087] It can be seen that the aberration compensation method of this embodiment includes step S111 and step S112 in step S11 of embodiment 2. In step S111, the Fourier surface intensity I0 before aberration compensation obtained after Fourier transformation of the initial input phase a is firstly reconstructed through the iterative Fourier transform algorithm, and the bit error rate before compensation is calculated, so as to compare the bit error rate and phase reconstruction effect after the subsequent compensation iteration.

[0088] Further, step S2 may include the following steps:

[0089] Step S21, the pre-compensation phase c is distorted and superimposed by the wavefront aberration phase d of the optical element itself to obtain the compensated phase e, and the compensated phase e is subjected to Fourier transformation to obtain the aberration-compensated Fourier surface intensity I1;

[0090] Step S22, the aberration compensated Fourier surface intensity I1 obtained after Fourier transform of the compensated phase e is phase reconstructed through an iterative Fourier transform algorithm, and the compensated bit error rate is calculated; then the value of the compensation coefficient is adjusted, and the aberration compensation is completed when the reconstructed compensated bit error rate is the lowest as the compensation coefficient increases or decreases.

[0091] Example 4

[0092] Figure 6 The step flow of the aberration compensation method 400 in Example 4 is shown.

[0093] Please refer to Figure 6 The aberration compensation method of this embodiment comprises the following steps:

[0094] Step S411, constructing a non-interference phase reconstruction aberration compensation device;

[0095] Step S412, corresponding to step S10 and step S101 in embodiment 1, randomly generates phase encoding data of an initial input phase a and loads it to the spatial light modulator;

[0096] Step S413, corresponding to step S102 in embodiment 1 and step S111 in embodiment 3, the Fourier surface intensity I0 before aberration compensation obtained after Fourier transform of the initial input phase a is phase reconstructed by an iterative Fourier transform algorithm, and the bit error rate before compensation is calculated;

[0097] Step S414, corresponding to step S11 in embodiment 2 and step S112 in embodiment 3, generates a conjugate wavefront aberration phase b by using a Zernike polynomial, or generates a conjugate wavefront aberration phase b by detecting with a wavefront detector;

[0098] Step S415, corresponding to step S1 in embodiment 1 and step S12 in embodiment 2, by loading the conjugate wavefront aberration phase b onto the spatial light modulator, the conjugate wavefront aberration phase b is compensated and superimposed on the initial input phase a to obtain a pre-compensation phase c;

[0099] Step S421 corresponds to step S2 in Example 1 and Example 3. The pre-compensated phase c is distorted and superimposed with the wavefront aberration phase d of the optical element itself to obtain the compensated phase e. The compensated phase e is Fourier transformed to obtain the aberration-compensated Fourier surface intensity I1 and iteratively reconstruct the phase.

[0100] Example 5

[0101] Figure 7 The step flow of the aberration compensation method 500 in Example 5 is shown.

[0102] Please refer to Figure 7 The aberration compensation method of this embodiment comprises the following steps:

[0103] Step S511, corresponding to step S412 in embodiment 4, generating an experimental image: randomly generating an n-order grayscale phase matrix code of an initial input phase a, where n≥2, and n is an integer;

[0104] Step S512, corresponding to step S413 in Example 4, experimental image shooting: loading the initial input phase a into the spatial light modulator to phase modulate the light beam, and using the detector to shoot the Fourier surface intensity I0 before aberration compensation under the corresponding phase modulation;

[0105] Step S513, corresponding to step S413 in embodiment 4, phase reconstruction bit error rate calculation: the Fourier surface intensity I0 captured by the detector before aberration compensation is phase reconstructed by an iterative Fourier transform algorithm and the bit error rate before compensation is calculated;

[0106] Step S514, corresponding to step S414 in embodiment 4, aberration compensation preparation: generating a corresponding conjugate wavefront aberration phase b by Zernike polynomials according to the aberration type generated by the optical element in the optical system, or detecting the conjugate wavefront aberration phase b by a wavefront detector;

[0107] Step S515, corresponding to step S415 in embodiment 4, aberration compensation: superimpose the phase encoding data of the randomly generated initial input phase a with the conjugate wavefront aberration phase b, and load it onto the spatial light modulator; obtain the Fourier surface intensity I1 after aberration compensation by photographing with the detector; calculate the bit error rate after phase reconstruction compensation of the Fourier surface intensity I1 after aberration compensation and increase the compensation coefficient; as the compensation coefficient increases, the bit error rate after compensation of the Fourier surface intensity I1 after aberration compensation will first drop to the minimum and then rise. When the phase reconstruction makes the bit error rate after compensation of the Fourier surface intensity I1 after aberration compensation drop to the minimum, the aberration compensation process is completed;

[0108] Step S521 corresponds to step S421 in Example 4, and the aberration compensation method is applied: combining the phase encoding of any new randomly generated initial input phase a with the conjugate wavefront aberration phase b compensation can realize the aberration compensation of the optical system; the phase reconstruction of the Fourier surface intensity I1 after aberration compensation is compared with the phase reconstruction of the Fourier surface intensity I0 before aberration compensation without aberration compensation, which improves the phase reconstruction efficiency and reduces the bit error rate.

[0109] Example 6

[0110] Aberration compensation device, see Figure 8 , which can be used to implement the aberration compensation method of each embodiment of the present invention, includes a laser 1, along the direction of the output light beam of the laser 1, a parallel light adjustment component, a 1 / 2 wave plate 4, an aperture 5, a first imaging component, a polarizer 8 and a first non-polarizing stereoscopic beam splitter 9 are sequentially arranged; a phase-type spatial light modulator 10 is arranged in the transmitted light direction of the first non-polarizing stereoscopic beam splitter 9; a second imaging component and a second non-polarizing stereoscopic beam splitter 13 are sequentially arranged in the reflected light direction of the first non-polarizing stereoscopic beam splitter 9, a recording lens 14 and a material reflector 15 are sequentially arranged in the transmitted light direction of the second non-polarizing stereoscopic beam splitter 13, and a Fourier lens 16 and an intensity detector 17 are sequentially arranged in the reflected light direction of the second non-polarizing stereoscopic beam splitter 13.

[0111] The parallel light adjusting member may include a pinhole filter 2 and a collimating lens 3 which are arranged in sequence.

[0112] The first imaging element may include a first relay lens 6 and a second relay lens 7 which are arranged in sequence, and the first relay lens 6 and the second relay lens 7 constitute a 4f system.

[0113] The second imaging element may include a third relay lens 11 and a fourth relay lens 12 which are arranged in sequence, and the third relay lens 11 and the fourth relay lens 12 constitute a 4f system.

[0114] When in use, the laser 1 emits a laser, for example, a green laser with a wavelength of 532nm, and the laser beam passes through the pinhole filter 2 and the collimating lens 3 to become a parallel light with good beam quality. After the parallel laser beam passes through the 1 / 2 wave plate 4 and the aperture 5, its circular beam is transformed into an aperture-shaped beam in the aperture 5. The first relay lens 6 and the second relay lens 7 form a 4f system, the purpose of which is to image the aperture 5 onto the plane where the phase-type spatial light modulator 10 is located. After the light beam passes through the polarizer 8 and the first non-polarizing stereoscopic beam splitter 9 and is incident on the phase-type spatial light modulator 10, its reflected light passes through the first non-polarizing stereoscopic beam splitter 9 again and is reflected in a direction perpendicular to the original optical path. The function of the phase-type spatial light modulator 10 is to upload a specific phase image. The light beam incident on the phase-type spatial light modulator 10 can carry accurate phase information after reflection. The light beam with phase information continues to pass through the third relay lens 11 and the fourth relay lens 12. The third relay lens 11 and the fourth relay lens 12 also form a 4f system, the purpose of which is to image the phase-type spatial light modulator 10 onto the front focal plane of the recording lens 14. After the light beam passes through the 4f system composed of the third relay lens 11 and the fourth relay lens 12, it continues to be focused by the recording lens 14 and incident on the material reflector 15. The function of the material reflector 15 is to record data information. The light beam with phase information reflected from the material reflector 15 is Fourier transformed by the Fourier lens 16 and then imaged onto the rear focal plane of the Fourier lens 16. The intensity detector 17 is located on a plane away from the rear focal plane of the Fourier lens 16. Finally, the phase information is Fourier transformed into intensity information by the Fourier lens 16 and received by the intensity detector 17.

[0115] Example 7

[0116] The aberration compensation method of this embodiment is combined with practical applications. Fig. 9 , randomly generate the n-order grayscale phase matrix encoding of the initial input phase a, n is 4, that is, randomly generate the phase encoding image of the initial input phase a of 4-order grayscale, and then generate the conjugate aberration grayscale image of the conjugate wavefront aberration phase b through the Zernike polynomial, combined with the reference Figure 8 , and then the phase-encoded image combined with the conjugate aberration grayscale image is loaded onto the phase-type spatial light modulator 10 to achieve aberration compensation for the optical system.

[0117] The aberration compensation method of this embodiment includes the following steps:

[0118] Step S611, experimental image generation: refer to Fig. 9 , generate a randomly encoded 4-level grayscale phase-coded image;

[0119] Combined with reference Figure 8, step S612, experimental image shooting: the generated 4-order grayscale phase-coded image is loaded onto the spatial light modulator to phase modulate the light beam, the recorded information is recorded in the material reflector 15 through the recording lens 14 and read out to form the data information to be tested; then the data information to be tested is Fourier transformed through the Fourier lens 16 and detected by the intensity detector 17.

[0120] The recording lens 14 may be a short focal length, plano-convex single lens with a focal length of 40 mm. The purpose of using a short focal length single lens for the recording lens 14 is as follows:

[0121] Firstly, a large wavefront aberration is introduced, and the feasibility of the aberration compensation method of the present invention is verified by aberration compensation;

[0122] Secondly, aberration compensation for single-lens imaging is performed in order to achieve good imaging effects and replace complex optical elements with simple optical elements, thereby achieving the goal of optimizing the optical system structure and reducing the complexity of the optical system.

[0123] Step S613, refer to Fig.10 , Phase reconstruction calculation: The Fourier surface intensity I0 before aberration compensation recorded by the recording lens 14 detected by the intensity detector 17 is phase reconstructed and restored, and the bit error rate before compensation is calculated.

[0124] The recording lens 14 may be a single lens.

[0125] Step S614, aberration compensation: using the Zernike polynomial as shown in the following formula to generate the conjugate wavefront aberration phase b for aberration compensation,

[0126]

[0127] Where r, θ are the normalized polar coordinates of the pupil plane, i is the order of the Zernike polynomial, ψ(r,θ) is the wavefront phase distribution function, and Z i (r, θ) is the i-th order Zernike basis function, a i is the coefficient of the i-th order Zernike aberration. Different types of aberration patterns can be generated by the Zernike polynomials shown in the above formula. For example, Fig.11 As shown, the main aberration existing in the holographic optical storage system is spherical aberration, so the spherical aberration is compensated.

[0128] The conjugate wavefront aberration phase b is generated by the Zernike polynomial, and the coded data obtained by compensating and superimposing the conjugate wavefront aberration phase b with the generated fourth-order grayscale initial input phase a is used as Figure 3 The pre-compensation phase c in the spatial light modulator is then loaded to phase modulate the light beam, for example, loaded to Figure 8The phase-type spatial light modulator 10 in the embodiment of the present invention records the recorded information in the reflector 15 with the material through the recording single lens 14 and reads out to form the data information to be measured, which is the compensated phase e after the wavefront aberration phase d of the distortion superimposed optical element itself; then the data information to be measured is Fourier transformed through the Fourier lens 16 and detected by the intensity detector 17.

[0129] Step S615, phase reconstruction calculation: performing phase reconstruction and recovery on the Fourier surface intensity I1 after aberration compensation detected by the intensity detector 17, and calculating the bit error rate after compensation;

[0130] Step S616, phase reconstruction result analysis: the phase reconstruction bit error rate before and after aberration compensation is as follows: Fig.12 The phase reconstruction results before and after aberration compensation are shown in Fig.13 As shown, f is the uncompensated distortion phase, f1 is the iterative distortion phase selected from the distortion phase f, e is the compensated phase, e1 is the iterative compensated phase selected from the compensated phase e. P0 is the reconstructed phase before aberration compensation, and P1 is the reconstructed phase after aberration compensation.

[0131] By comparing the Fourier surface intensity I0 before aberration compensation and the Fourier surface intensity I1 after aberration compensation, it can be seen that after aberration compensation, the texture of the Fourier surface intensity I1 after aberration compensation becomes clearer than that of the Fourier surface intensity I0 before aberration compensation, and some details are restored.

[0132] The phase iteratively recovered by directly performing phase reconstruction on the Fourier surface intensity I0 before aberration compensation is the reconstructed phase P0 before aberration compensation, and the phase iteratively recovered by performing phase reconstruction on the Fourier surface intensity I1 after aberration compensation is the reconstructed phase P1 after aberration compensation. By comparing the reconstructed phase P1 after aberration compensation with the reconstructed phase P0 before aberration compensation, it can be seen that after aberration compensation, the reconstructed phase P1 after aberration compensation is closer to the original real initial input phase a than the reconstructed phase P0 before aberration compensation. It can be seen from the phase reconstruction bit error rate that after the same number of numerical iterations, the phase reconstruction bit error rate is reduced by more than 40% through aberration compensation.

[0133] It should be noted that, firstly, the aberration compensation in the embodiment of the present invention can compensate for any type of aberration, and the specific compensation aberration mode performs corresponding compensation according to the type of aberration generated by the system. The aberration compensation device used as an example in the embodiment of the present invention mainly generates spherical aberration.

[0134] Secondly, when compensating the superimposed conjugate wavefront aberration phase b, it is preferred to take the maximum circular domain area of ​​the conjugate wavefront aberration phase b, that is, take the circumscribed circle form of the encoding data of the conjugate wavefront aberration phase b, such as Fig.14 As shown in Process II.

[0135] That is, compared to Fig.14 Among the selection processes I and III of the conjugate wavefront aberration phase b, selection process II is more preferred, which can better meet the needs of compensating for the superposition conjugate aberration.

[0136] Finally, the aberration compensation method of the embodiment of the present invention is not limited to generating the conjugate wavefront aberration phase b through the Zernike polynomials, but can also obtain the wavefront aberration through other means such as wavefront detector detection, and then take the conjugate aberration phase and superimpose it with the encoding information of the initial input phase a, and then load it onto the spatial light modulator to achieve aberration compensation.

[0137] The above are only embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. An aberration compensation method, characterized in that: The following steps are involved: Step S1, compensating and superimposing the conjugate wavefront aberration phase on the initial input phase to obtain a pre-compensation phase; Step S2, superimposing the pre-compensated phase with the wavefront aberration phase distortion of the optical element itself to obtain a compensated phase, and performing Fourier transformation on the compensated phase to obtain aberration-compensated Fourier surface intensity; Reconstruct the phase of the aberration-compensated Fourier surface intensity obtained by Fourier transforming the compensated phase through an iterative Fourier transform algorithm, and calculate the compensated bit error rate; Then, the value of the compensation coefficient is adjusted. As the compensation coefficient increases, when the reconstructed compensated bit error rate is the lowest, the aberration compensation is completed.

2. The aberration compensation method according to claim 1, characterized in that: Step S1 includes the following steps: Step S11, generating the conjugate wavefront aberration phase by Zernike polynomials, or generating the conjugate wavefront aberration phase by wavefront detector detection.

3. The aberration compensation method according to claim 2, characterized in that: Step S11 includes the following steps: The Fourier surface intensity before aberration compensation obtained after Fourier transformation of the initial input phase is phase reconstructed through an iterative Fourier transformation algorithm, and the bit error rate before compensation is calculated.

4. The aberration compensation method according to claim 2, characterized in that: Step S10 is performed before step S11 to generate random phase encoding data as the initial input phase.

5. The aberration compensation method according to claim 4, characterized in that: Step S10 includes the following steps: Step S101, randomly generating the phase encoding data; Step S102, photographing a distribution image of the Fourier surface intensity before aberration compensation obtained after Fourier transform of the initial input phase.

6. An aberration compensation device, characterized in that: A method for implementing the aberration compensation method according to any one of claims 1 to 5, comprising a laser, wherein a parallel light adjustment member, a 1 / 2 wave plate, an aperture, a first imaging member, a polarizer and a first non-polarizing stereoscopic beam splitter are sequentially arranged along the direction of the laser output light beam; a phase-type spatial light modulator is arranged in the transmitted light direction of the first non-polarizing stereoscopic beam splitter; a second imaging member and a second non-polarizing stereoscopic beam splitter are sequentially arranged in the reflected light direction of the first non-polarizing stereoscopic beam splitter, a recording lens and a reflector with a material are sequentially arranged in the transmitted light direction of the second non-polarizing stereoscopic beam splitter, and a Fourier lens and an intensity detector are sequentially arranged in the reflected light direction of the second non-polarizing stereoscopic beam splitter; the recording lens adopts a plano-convex single lens, and the intensity detector is located on a plane away from the rear focal plane of the Fourier lens.

7. The aberration compensation device according to claim 6, characterized in that: The parallel light adjustment component includes a pinhole filter and a collimating lens which are arranged in sequence.

8. The aberration compensation device according to claim 6, characterized in that: The first imaging element includes a first relay lens and a second relay lens which are arranged in sequence, and the first relay lens and the second relay lens constitute a 4f system.

9. The aberration compensation device according to claim 6, characterized in that: The second imaging element includes a third relay lens and a fourth relay lens which are arranged in sequence, and the third relay lens and the fourth relay lens constitute a 4f system.

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