Holographic multiplexing method based on off-axis vortex beam

Abstract

The invention relates to a holographic multiplexing method based on an off-axis vortex beam. The holographic multiplexing method comprises an encoding process and a decoding process. Wherein the encoding process comprises the following steps: for each image channel, distributing off-axis vortex beams with different off-axis amounts; sampling the image of each image channel, and generating a phase-type hologram corresponding to each image channel; determining the phase distribution of the off-axis vortex beam; superposing the phase type hologram of each image channel and the phase distribution of the off-axis vortex light beam to obtain a superposed hologram; and summing the superposed holograms of all the image channels to obtain a holographic multiplexing graph. The decoding process comprises the following steps: determining a complex conjugate of an off-axis vortex beam of a to-be-decoded channel; and adding complex conjugation of the off-axis vortex beam of the to-be-decoded channel to the holographic multiplexing graph to obtain a reconstructed image corresponding to the to-be-decoded channel. Due to orthogonality between different off-axis quantities, the information capacity of the hologram is improved, and crosstalk between images of all channels can be effectively restrained.

Description

Technical Field

[0001] The present application relates to the technical field of image data processing, and in particular to a holographic multiplexing method based on off-axis vortex beams. Background Art

[0002] With the development of computer technology and information technology, holographic technology has made significant progress. In order to improve the information capacity of holographic technology, researchers have proposed the concept of holographic multiplexing, which is to reconstruct multiple sets of image information using only one hologram. Among them, orbital angular momentum (OAM), as a basic property of light field, has been widely used in OAM holographic multiplexing. Researchers have used the selection of different OAM modes in OAM holographic multiplexing to greatly improve the information capacity of holograms.

[0003] However, how to further improve information capacity based on holographic multiplexing is still a problem that needs to be solved urgently in related technologies. Summary of the invention

[0004] In order to at least overcome the problem of insufficient holographic information capacity of OAM modes in the related art to a certain extent, the present application provides a holographic multiplexing method based on off-axis vortex beams.

[0005] The scheme of this application is as follows: A holographic multiplexing method based on off-axis vortex beams includes an encoding process and a decoding process, wherein the encoding process includes: For each image channel, an off-axis vortex beam with different off-axis amounts is allocated; Sampling the image of each image channel to generate a phase-type hologram corresponding to each image channel; determining the phase distribution of the off-axis vortex beam; The phase-type hologram of each image channel and the phase distribution of the off-axis vortex beam are superimposed to obtain a superimposed hologram; The superimposed holograms of all image channels are summed to obtain a holographic multiplexed image; The decoding process includes: Determining the complex conjugate of the off-axis vortex beam of the channel to be decoded; The complex conjugate of the off-axis vortex light beam of the channel to be decoded is added to the holographic multiplexed image to obtain a reconstructed image corresponding to the channel to be decoded.

[0006] Preferably, the off-axis amount of the off-axis vortex light beam is one-dimensional or two-dimensional.

[0007] Preferably, the off-axis amount of the off-axis vortex light beam of the current image channel corresponds to the channel number of the current image channel.

[0008] Preferably, the off-axis amount of the off-axis vortex light beam of the current image channel is a multiple of the channel number of the current image channel.

[0009] Preferably, the off-axis amount of the off-axis vortex light beam of the current image channel is the product of the channel number of the current image channel and the off-axis distance.

[0010] Preferably, sampling the image of each image channel to generate a phase-type hologram corresponding to each image channel includes: The image of each image channel is sampled by a two-dimensional Dirac function; The phase-type hologram corresponding to each image channel is generated by the Gerchberg-Saxton algorithm.

[0011] Preferably, determining the phase distribution of the off-axis vortex beam comprises: The phase distribution of the off-axis vortex beam is determined according to the topological charge and the off-axis amount of the off-axis vortex beam.

[0012] Preferably, determining the complex conjugate of the off-axis vortex beam of the channel to be decoded comprises: The complex conjugate of the off-axis vortex beam of the channel to be decoded is determined according to the negative value of the topological charge, the off-axis amount and the beam width of the off-axis vortex beam.

[0013] Preferably, the off-axis amount of the off-axis vortex light beam is not greater than the beam width.

[0014] Preferably, in the encoding process, the phase-type hologram of each image channel, the phase distribution of the off-axis vortex beam and the orbital angular momentum of the off-axis vortex beam are superimposed to obtain a superimposed hologram; In the decoding process, the complex conjugate of the off-axis vortex beam of the channel to be decoded is added to the holographic multiplexed image, and the reconstructed image corresponding to the channel to be decoded is obtained according to the orbital angular momentum of the off-axis vortex beam.

[0015] The technical solution provided by this application may have the following beneficial effects: The holographic multiplexing method based on off-axis vortex beams in the present application includes an encoding process and a decoding process. The encoding process includes: allocating off-axis vortex beams with different off-axis amounts to each image channel; sampling the image of each image channel to generate a phase-type hologram corresponding to each image channel; determining the phase distribution of the off-axis vortex beam; superimposing the phase-type hologram of each image channel and the phase distribution of the off-axis vortex beam to obtain a superimposed hologram; summing the superimposed holograms of all image channels to obtain a holographic multiplexing image.

[0016] The decoding process includes: determining the complex conjugate of the off-axis vortex beam of the channel to be decoded; adding the complex conjugate of the off-axis vortex beam of the channel to be decoded to the holographic multiplexed image to obtain a reconstructed image corresponding to the channel to be decoded.

[0017] The core of this technical solution is to use off-axis vortex beams to give different spatial characteristics to the image of each channel, and multiplex multiple images in an optical carrier through holographic multiplexing. During decoding, the original image is restored with the help of a complex conjugated off-axis vortex beam, thereby achieving distortion-free restoration of multi-channel images. This technical solution introduces a new parameter, the off-axis amount, in the encoding and decoding process of the hologram. Due to the orthogonality between different off-axis amounts, the information capacity of the hologram is improved, and the crosstalk between the images of each channel can also be effectively suppressed. Through efficient optical multiplexing, this technical solution can realize the multiplexing and decoding of multiple images through off-axis vortex beams with different off-axis amounts, and is suitable for large-capacity data transmission, storage and other optical information processing applications.

[0018] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0020] Figure 1 It is a flow chart of a holographic multiplexing method based on off-axis vortex beams provided by an embodiment of the present application; Figure 2 It is a schematic diagram of a hologram encoding process based on an off-axis vortex beam provided by an embodiment of the present application; Figure 3 It is a schematic diagram of a hologram decoding process based on an off-axis vortex beam provided by an embodiment of the present application; Figure 4 It is a schematic diagram of a holographic optical path based on an off-axis vortex beam provided by an embodiment of the present application; Figure 5 It is a schematic diagram of the phase distribution of an off-axis vortex light beam corresponding to a channel m provided by an embodiment of the present application; Figure 6 An embodiment of the present application provides a holographic multiplexed image obtained by summing up the superimposed holograms of all image channels. DETAILED DESCRIPTION

[0021] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0022] Figure 1 is a flow chart of a holographic multiplexing method based on off-axis vortex beams provided by an embodiment of the present application, with reference to Figure 1 , a holographic multiplexing method based on off-axis vortex beams, including an encoding process and a decoding process, the encoding process includes: S11: for each image channel, allocating off-axis vortex beams with different off-axis amounts; It should be noted that the off-axis amount of the off-axis vortex beam is one-dimensional or two-dimensional.

[0023] One-dimensional off-axis: Off-axis beam deviation can occur along only one direction (such as the x-axis or y-axis).

[0024] 2D Off-Axis: Off-axis beam displacement can occur in both the x-axis and y-axis directions.

[0025] The off-axis amount can be selected in one or two dimensions. This means that the technical solution has greater flexibility in practical applications and can adapt to different optical systems and application requirements. If in some cases the beam deviation is limited to one direction (for example, along the x-axis or y-axis), a one-dimensional off-axis amount can be selected; in more complex systems, a two-dimensional off-axis amount may be required to accommodate the full range of beam deviations. For different experimental needs or application scenarios, the one-dimensional or two-dimensional selection of the off-axis amount can provide a higher degree of freedom.

[0026] It should be noted that the off-axis amount of the off-axis vortex light beam of the current image channel has a corresponding relationship with the channel number of the current image channel.

[0027] The off-axis amount of each channel corresponds to its channel number. The channel number determines the size of the off-axis amount, which ensures that each image channel has a different off-axis amount, thereby distinguishing different channels in the multiplex diagram. By making a one-to-one correspondence between the off-axis amount and the channel number, the system can automatically assign a unique off-axis amount to each channel during encoding, avoiding design complexity. This correspondence ensures that the off-axis amount of each channel is different, thereby avoiding interference between channels and ensuring that multiple image channels in the multiplex diagram can be correctly decoded.

[0028] Preferably, the off-axis amount of the off-axis vortex light beam of the current image channel is a multiple of the channel number of the current image channel.

[0029] In specific practice, the off-axis amount of the off-axis vortex beam of the current image channel is the product of the channel number of the current image channel and the off-axis spacing.

[0030] S12: Sampling the image of each image channel to generate a phase-type hologram corresponding to each image channel.

[0031] In specific practice, the images of each image channel are sampled through the two-dimensional Dirac function; The phase-type hologram corresponding to each image channel is generated by the Gerchberg-Saxton algorithm.

[0032] The Dirac function can accurately sample the image and provide precise data for subsequent holographic reconstruction. The Gerchberg-Saxton algorithm (GS algorithm for short) ensures the high quality of the generated hologram through iterative optimization and can accurately reconstruct the image during the decoding process.

[0033] S13: determining the phase distribution of the off-axis vortex beam; In this embodiment, the phase distribution of the off-axis vortex beam is determined according to the topological charge and the off-axis amount of the off-axis vortex beam. By combining the topological charge and the off-axis amount, the phase distribution of the off-axis vortex beam can be accurately controlled so that the beam of each channel has a unique phase characteristic, thereby ensuring the effective multiplexing of information from different channels.

[0034] S14: superimposing the phase-type hologram of each image channel and the phase distribution of the off-axis vortex beam to obtain a superimposed hologram; S15: summing the superimposed holograms of all image channels to obtain a holographic multiplexed image; The decoding process includes: S21: determining the complex conjugate of the off-axis vortex beam of the channel to be decoded; In this embodiment, the complex conjugate of the off-axis vortex beam of the channel to be decoded is determined according to the negative value of the topological charge, the off-axis amount and the beam width of the off-axis vortex beam. The complex conjugation operation negates the topological charge, which can reverse the phase of the beam. The off-axis amount of the complex conjugate beam should be consistent with the original beam, but the offset should not exceed the width of the beam. Through the complex conjugation operation, the image of each channel can be accurately restored. By controlling the topological charge and the off-axis amount, it is ensured that the phase change in the decoding process is effectively reversed, thereby restoring the image information.

[0035] S22: Adding the complex conjugate of the off-axis vortex beam of the channel to be decoded to the holographic multiplexed image to obtain a reconstructed image corresponding to the channel to be decoded.

[0036] Example description: Firstly, the total number of image channels is determined to be M, and for each image channel, an off-axis vortex beam with different off-axis amounts is allocated; Figure 2 is a schematic diagram of a hologram encoding process based on an off-axis vortex beam provided by an embodiment of the present application, with reference to Figure 2 , the image of the mth (m=1,2,…,M) image channel is sampled using the two-dimensional Dirac function. The sampled image can be expressed as ; Generate the mth channel image using the Gerchberg-Saxton algorithm The corresponding phase hologram is f m ; Hologram for the mth channel f m Phase distribution of off-axis vortex beam corresponding to the channel number m j m Superposition, where j m It can be expressed as: ; In the formula, is the topological charge number, , are the off-axis amounts of the off-axis vortex beam in the x-axis and y-axis, Indicates the symbol, Indicates phase.

[0037] Off-axis , It has a corresponding relationship with the number of channels and can be, but is not limited to, a multiple of m, expressed as: ； In the formula, , are the off-axis distances of the x-axis and y-axis respectively.

[0038] The holograms of M channels are summed to obtain the phase distribution of the hologram , which can be expressed as: ; The complex amplitude of the encoded hologram It can be expressed as: ; Figure 3is a schematic diagram of a hologram decoding process based on an off-axis vortex beam provided by an embodiment of the present application, with reference to Figure 3 , when decoding, determine the complex conjugate of the off-axis vortex beam of the channel m to be decoded ; Complex conjugation of off-axis vortex beams It is expressed as: ; In the formula, is the beam width of the off-axis vortex beam.

[0039] It should be noted that the off-axis amount of the off-axis vortex beam should not be greater than the beam width to avoid excessive off-axis amount. The off-axis phase of the corresponding channel does not satisfy the complex conjugation, resulting in image crosstalk or decoding difficulties.

[0040] Reconstructed image of the channel to be decoded It is expressed as: ; Figure 4 is a schematic diagram of a hologram decoding process based on an off-axis vortex beam provided by an embodiment of the present application, Figure 4 In the process, the light beam emitted by the laser passes through the aperture, wave plate and beam expander to become a collimated light beam. The function of the liquid crystal spatial light modulator is to load the hologram on the collimated light beam, thereby realizing image reconstruction.

[0041] Figure 5 is a schematic diagram of the phase distribution of an off-axis vortex beam corresponding to a channel m provided in an embodiment of the present application, Figure 5 In the figure, the topological charge of the off-axis vortex beam is l =2, the off-axis spacing of the x-axis and y-axis is 0.1 , 0.1 , Figure 6 It is a holographic multiplexed image obtained by summing up the superimposed holograms of all image channels.

[0042] It should be noted that, when the present technical solution is implemented, the complex conjugate of the off-axis vortex beam with the same off-axis spacing is used, which can achieve a better image reconstruction effect. When the complex conjugate of off-axis vortex beams with different off-axis spacing is used, the image reconstruction effect cannot be effectively achieved. Therefore, when the off-axis amount and topological charge of the off-axis vortex beam added to the holographic multiplexed image do not meet the conditions, the image of the corresponding number of channels cannot be reconstructed.

[0043] It should be noted that, in specific practice, the off-axis amount and orbital angular momentum of the off-axis vortex beam can be used independently and jointly as parameters for holographic multiplexing.

[0044] It manifests as: In the encoding process, the phase-type hologram of each image channel, the phase distribution of the off-axis vortex beam and the orbital angular momentum of the off-axis vortex beam are superimposed to obtain a superimposed hologram; During the decoding process, the complex conjugate of the off-axis vortex beam of the channel to be decoded is added to the holographic multiplexed image, and the reconstructed image corresponding to the channel to be decoded is obtained according to the orbital angular momentum of the off-axis vortex beam.

[0045] The off-axis amount and orbital angular momentum can be used independently or together as parameters for holographic multiplexing. This provides flexibility for the implementation of the present technical solution, and the appropriate combination of parameters can be selected according to the needs to optimize the multiplexing effect. For example, in some systems, only the off-axis amount may need to be adjusted to achieve effective multiplexing, while in other cases, orbital angular momentum also needs to be used in conjunction with the off-axis amount, thereby providing more adjustment space and optimization capabilities. This flexibility helps to improve the efficiency of multiplexing, and when designing the system, the off-axis amount and orbital angular momentum can be adjusted according to the actual optical conditions and needs, thereby achieving more precise control and efficient information multiplexing.

[0046] In summary, the core of this technical solution is to use off-axis vortex beams to give different spatial characteristics to the image of each channel, and multiplex multiple images in an optical carrier through holographic multiplexing. During decoding, the original image is restored with the help of a complex conjugated off-axis vortex beam, thereby achieving distortion-free restoration of multi-channel images. This technical solution introduces a new parameter, the off-axis amount, in the encoding and decoding process of the hologram. Due to the orthogonality between different off-axis amounts, the information capacity of the hologram is improved, and the crosstalk between the images of each channel can also be effectively suppressed. Through efficient optical multiplexing, this technical solution can realize the multiplexing and decoding of multiple images through off-axis vortex beams with different off-axis amounts, and is suitable for large-capacity data transmission, storage and other optical information processing applications.

[0047] It can be understood that the same or similar parts of the above embodiments can be referenced to each other, and the contents not described in detail in some embodiments can refer to the same or similar contents in other embodiments.

[0048] It should be noted that, in the description of this application, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance. In addition, in the description of this application, unless otherwise specified, the meaning of "plurality" refers to at least two.

[0049] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present application includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by technicians in the technical field to which the embodiments of the present application belong.

[0050] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0051] A person skilled in the art may understand that all or part of the steps in the method for implementing the above-mentioned embodiment may be completed by instructing related hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one or a combination of the steps of the method embodiment.

[0052] In addition, each functional unit in each embodiment of the present application may be integrated into a processing module, or each unit may exist physically separately, or two or more units may be integrated into one module. The above-mentioned integrated module may be implemented in the form of hardware or in the form of a software functional module. If the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it may also be stored in a computer-readable storage medium.

[0053] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0054] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0055] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A holographic multiplexing method based on off-axis vortex beams, comprising an encoding process and a decoding process, characterized in that: The encoding process includes: For each image channel, an off-axis vortex beam with different off-axis amounts is allocated; Sampling the image of each image channel to generate a phase-type hologram corresponding to each image channel; determining the phase distribution of the off-axis vortex beam; The phase-type hologram of each image channel and the phase distribution of the off-axis vortex beam are superimposed to obtain a superimposed hologram; The superimposed holograms of all image channels are summed to obtain a holographic multiplexed image; The decoding process includes: Determining the complex conjugate of the off-axis vortex beam of the channel to be decoded; The complex conjugate of the off-axis vortex light beam of the channel to be decoded is added to the holographic multiplexed image to obtain a reconstructed image corresponding to the channel to be decoded.

2. The method according to claim 1, characterized in that The off-axis amount of the off-axis vortex light beam is one-dimensional or two-dimensional.

3. The method according to claim 2, characterized in that The off-axis amount of the off-axis vortex beam of the current image channel has a corresponding relationship with the channel number of the current image channel.

4. The method according to claim 3, characterized in that The off-axis amount of the off-axis vortex beam of the current image channel is a multiple of the channel number of the current image channel.

5. The method according to claim 4, characterized in that The off-axis amount of the off-axis vortex beam of the current image channel is the product of the channel number of the current image channel and the off-axis spacing.

6. The method according to claim 1, characterized in that The image of each image channel is sampled to generate a phase-type hologram corresponding to each image channel, including: The image of each image channel is sampled by a two-dimensional Dirac function; The phase-type hologram corresponding to each image channel is generated by the Gerchberg-Saxton algorithm.

7. The method according to claim 1, characterized in that Determine the phase distribution of an off-axis vortex beam, including: The phase distribution of the off-axis vortex beam is determined according to the topological charge and the off-axis amount of the off-axis vortex beam.

8. The method according to claim 7, characterized in that Determine the complex conjugate of the off-axis vortex beam of the channel to be decoded, including: The complex conjugate of the off-axis vortex beam of the channel to be decoded is determined according to the negative value of the topological charge, the off-axis amount and the beam width of the off-axis vortex beam.

9. The method according to claim 8, characterized in that The off-axis amount of the off-axis vortex light beam is not greater than the beam width.

10. The method according to claim 1, characterized in that In the encoding process, the phase-type hologram of each image channel, the phase distribution of the off-axis vortex beam and the orbital angular momentum of the off-axis vortex beam are superimposed to obtain a superimposed hologram; In the decoding process, the complex conjugate of the off-axis vortex beam of the channel to be decoded is added to the holographic multiplexed image, and the reconstructed image corresponding to the channel to be decoded is obtained according to the orbital angular momentum of the off-axis vortex beam.

Images