A holographic multiplexing method based on off-axis vortex beams

Abstract

The present application relates to a holographic multiplexing method based on off-axis vortex beams, including an encoding process and a decoding process. Among them, the encoding process includes: for each image channel, allocating off-axis vortex beams with different off-axis amounts; sampling the images of each image channel to generate a phase-type hologram corresponding to each image channel; determining the phase distribution of the off-axis vortex beams; superimposing the phase-type holograms of each image channel and the phase distribution of the off-axis vortex beams to obtain a superimposed hologram; summing up the superimposed holograms of all image channels to obtain a holographic multiplexing map. The decoding process includes: determining the complex conjugate of the off-axis vortex beam of the channel to be decoded; attaching the complex conjugate of the off-axis vortex beam of the channel to be decoded to the holographic multiplexing map to obtain the reconstructed image corresponding to the channel to be decoded. 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.

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 remarkable progress. To improve the information capacity of holographic technology, researchers have proposed the concept of holographic multiplexing, that is, using only one hologram to reconstruct multiple sets of image information. Among them, orbital angular momentum (OAM), as a fundamental property of the light field, has been widely used in OAM holographic multiplexing. Researchers have greatly improved the information capacity of holograms by using the selection of different OAM modes in OAM holographic multiplexing.

[0003] However, on the basis of holographic multiplexing, how to further improve the information capacity is still an urgent problem to be solved in the related technology. Summary of the Invention

[0004] To at least overcome to some extent the problem of insufficient information capacity of holograms with OAM modes in the related technology, the present application provides a holographic multiplexing method based on off-axis vortex beams.

[0005] The solution of the present application is as follows:

[0006] A holographic multiplexing method based on off-axis vortex beams, including an encoding process and a decoding process, where the encoding process includes:

[0007] For each image channel, off-axis vortex beams with different off-axis amounts are allocated; wherein, the off-axis amount of the off-axis vortex beam is not greater than the beam width; the off-axis spacing of the off-axis vortex beams is the same;

[0008] Sampling the images of each image channel to generate a phase-type hologram corresponding to each image channel;

[0009] Determining the phase distribution of the off-axis vortex beam;

[0010] Superposing the phase-type hologram of each image channel and the phase distribution of the off-axis vortex beam to obtain a superposed hologram;

[0011] Summing the superposed holograms of all image channels to obtain a holographic multiplexing map;

[0012] Determining the phase distribution of the off-axis vortex beam includes:

[0013] Determining the phase distribution of the off-axis vortex beam according to the topological charge number and the off-axis amount of the off-axis vortex beam;

[0014] The decoding process includes:

[0015] Determine the complex conjugate of the off-axis vortex beam of the channel to be decoded;

[0016] Attach the complex conjugate of the off-axis vortex beam of the channel to be decoded to the holographic multiplexing pattern to obtain the reconstructed image corresponding to the channel to be decoded;

[0017] Determining the complex conjugate of the off-axis vortex beam of the channel to be decoded includes:

[0018] Determine the complex conjugate of the off-axis vortex beam of the channel to be decoded according to the negative value of the topological charge number, the off-axis amount, and the beam width of the off-axis vortex beam.

[0019] Preferably, the off-axis amount of the off-axis vortex beam is one-dimensional or two-dimensional.

[0020] Preferably, there is a corresponding relationship between the off-axis amount of the off-axis vortex beam of the current image channel and the channel number of the current image channel.

[0021] Preferably, 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.

[0022] Preferably, 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.

[0023] Preferably, sampling the images of each image channel to generate a phase-type hologram corresponding to each image channel includes:

[0024] Sample the images of each image channel through a two-dimensional Dirac function;

[0025] Generate a phase-type hologram corresponding to each image channel through the Gerchberg-Saxton algorithm.

[0026] Preferably, determining the phase distribution of the off-axis vortex beam includes:

[0027] Determine the phase distribution of the off-axis vortex beam according to the topological charge number and the off-axis amount of the off-axis vortex beam.

[0028] Preferably, determining the complex conjugate of the off-axis vortex beam of the channel to be decoded includes:

[0029] Determine the complex conjugate of the off-axis vortex beam of the channel to be decoded according to the negative value of the topological charge number, the off-axis amount, and the beam width of the off-axis vortex beam.

[0030] Preferably, the off-axis amount of the off-axis vortex beam is not greater than the beam width.

[0031] Preferably, during the encoding process, the phase-type holograms 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;

[0032] During the decoding process, the complex conjugate of the off-axis vortex beam of the channel to be decoded is added to the holographic multiplexing pattern, and according to the orbital angular momentum of the off-axis vortex beam, the reconstructed image corresponding to the channel to be decoded is obtained.

[0033] The technical solution provided by this application may include the following beneficial effects:

[0034] The holographic multiplexing method based on off-axis vortex beams in this application includes an encoding process and a decoding process. Among them, the encoding process includes: for each image channel, an off-axis vortex beam with a different off-axis amount is allocated; the images of each image channel are sampled to generate the phase-type hologram corresponding to each image channel; the phase distribution of the off-axis vortex beam is determined; the phase-type holograms 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 multiplexing pattern.

[0035] 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 multiplexing pattern to obtain the reconstructed image corresponding to the channel to be decoded.

[0036] The core of this technical solution lies in using off-axis vortex beams to endow the images of each channel with different spatial characteristics, and multiplexing multiple images in an optical carrier through holographic multiplexing. When decoding, the original image is restored by means of the complex conjugate off-axis vortex beam, so as to realize the distortion-free restoration of multi-channel images. This technical solution introduces a new parameter, the off-axis amount, in the encoding and decoding processes 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. This technical solution can realize the multiplexing and decoding of multiple images through off-axis vortex beams with different off-axis amounts through efficient optical multiplexing, and is applicable to large-capacity data transmission, storage, and other optical information processing applications.

[0037] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit this application. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings here are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with this application, and are used together with the specification to explain the principles of this application.

[0039] Figure 1It is a schematic flow chart of a holographic multiplexing method based on off-axis vortex beams provided by an embodiment of the present application;

[0040] Figure 2 It is a schematic diagram of the hologram encoding process of a holographic multiplexing method based on off-axis vortex beams provided by an embodiment of the present application;

[0041] Figure 3 It is a schematic diagram of the hologram decoding process of a holographic multiplexing method based on off-axis vortex beams provided by an embodiment of the present application;

[0042] Figure 4 It is a schematic diagram of the holographic optical path of a holographic multiplexing method based on off-axis vortex beams provided by an embodiment of the present application;

[0043] Figure 5 It is a schematic diagram of the phase distribution of the off-axis vortex beam corresponding to channel m provided by an embodiment of the present application;

[0044] Figure 6 It is a holographic multiplexing diagram obtained by summing the superimposed holograms of all image channels provided by an embodiment of the present application. Detailed implementation manners

[0045] Here, the exemplary embodiments will be described in detail, and the examples are shown in the drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present application. On the contrary, they are only examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0046] Figure 1 It is a schematic flow chart of a holographic multiplexing method based on off-axis vortex beams provided by an embodiment of the present application. Refer 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:

[0047] S11: For each image channel, allocate off-axis vortex beams with different off-axis amounts;

[0048] It should be noted that the off-axis amount of the off-axis vortex beam is one-dimensional or two-dimensional.

[0049] One-dimensional off-axis amount: The off-axis beam offset can occur only along one direction (for example, the x-axis or the y-axis).

[0050] Two-dimensional off-axis amount: The offset of the off-axis beam can occur simultaneously in the x-axis and y-axis directions.

[0051] The off-axis amount can be selected in one or two dimensions. This means that this technical solution has stronger flexibility in practical applications and can adapt to different optical systems and application requirements. If the beam offset is limited to one direction in some cases (for example, along the x-axis or y-axis), then a one-dimensional off-axis amount can be selected; while in more complex systems, a two-dimensional off-axis amount may be required to adapt to the omnidirectional offset of the beam. For different experimental requirements or application scenarios, the one-dimensional or two-dimensional selection of the off-axis amount can provide a higher degree of freedom.

[0052] It should be noted that the off-axis amount of the off-axis vortex beam in the current image channel has a corresponding relationship with the channel number of the current image channel.

[0053] The off-axis amount of each channel has a corresponding relationship with its channel number. The channel number determines the size of the off-axis amount, which can ensure that each image channel has a different off-axis amount, so as to distinguish different channels in the multiplexed figure. By corresponding the off-axis amount with the channel number one by one, the system can automatically assign a unique off-axis amount to each channel during encoding, avoiding design complexity. This corresponding relationship ensures that the off-axis amount of each channel is different, thus avoiding interference between channels and ensuring that multiple image channels in the multiplexed figure can be correctly decoded.

[0054] Preferably, the off-axis amount of the off-axis vortex beam in the current image channel is a multiple of the channel number of the current image channel.

[0055] In specific practice, the off-axis amount of the off-axis vortex beam in the current image channel is the product of the channel number of the current image channel and the off-axis spacing.

[0056] S12: Sample the images of each image channel to generate a phase-type hologram corresponding to each image channel.

[0057] In specific practice, sample the images of each image channel through a two-dimensional Dirac function;

[0058] Generate a phase-type hologram corresponding to each image channel through the Gerchberg-Saxton algorithm.

[0059] The Dirac function can accurately sample the image and provide accurate data for subsequent holographic reconstruction. The Gerchberg-Saxton algorithm (abbreviated as the GS algorithm) ensures a high-quality hologram through iterative optimization and can accurately reconstruct the image during the decoding process.

[0060] S13: Determine the phase distribution of the off-axis vortex beam;

[0061] In this embodiment, according to the topological charge number and off-axis amount of the off-axis vortex beam, the phase distribution of the off-axis vortex beam is determined. By combining the topological charge number and the off-axis amount, the phase distribution of the off-axis vortex beam can be precisely controlled, so that the beams of each channel have unique phase characteristics, thereby ensuring the effective multiplexing of information in different channels.

[0062] S14: Superimpose the phase-type holograms of each image channel and the phase distribution of the off-axis vortex beam to obtain the superimposed hologram;

[0063] S15: Sum the superimposed holograms of all image channels to obtain the holographic multiplexing map;

[0064] The decoding process includes:

[0065] S21: Determine the complex conjugate of the off-axis vortex beam of the channel to be decoded;

[0066] In this embodiment, according to the negative value of the topological charge number, the off-axis amount and the beam width of the off-axis vortex beam, the complex conjugate of the off-axis vortex beam of the channel to be decoded is determined. The complex conjugate operation takes the negative of the topological charge number, which can reverse the phase of the beam. The off-axis amount of the complex conjugate beam should be the same as that of the original beam, but the offset amount shall not exceed the beam width. Through the complex conjugate operation, the image of each channel can be accurately restored. By controlling the topological charge number and the off-axis amount, it is ensured that the phase change in the decoding process is effectively reversed, thereby restoring the image information.

[0067] S22: Attach the complex conjugate of the off-axis vortex beam of the channel to be decoded to the holographic multiplexing map to obtain the reconstructed image corresponding to the channel to be decoded.

[0068] Exemplary illustration:

[0069] First, determine that the total number of image channels is M. For each image channel, an off-axis vortex beam with a different off-axis amount is allocated;

[0070] 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. Referring to Figure 2 , the image of the m-th (m = 1, 2,..., M) image channel is sampled by using a two-dimensional Dirac function, and the sampled image can be expressed as ;

[0071] Use the Gerchberg-Saxton algorithm to generate the phase-type hologram corresponding to the m-th channel image as ;

[0072] For the hologram of the m-th channel and the phase distribution of the off-axis vortex beam corresponding to the channel number m Superposition, where can be expressed as:

[0073] ;

[0074] In the formula, is the topological charge number, , are respectively the off-axis amounts of the off-axis vortex beam on the x-axis and y-axis, represents taking the sign, represents taking the phase.

[0075] Off-axis amount , has a corresponding relationship with the number of channels, and can be but is not limited to being a multiple of m, expressed as:

[0076] ;

[0077] In the formula, , are respectively the off-axis spacings on the x-axis and y-axis.

[0078] Sum the holograms of M channels to obtain the phase distribution of the hologram , which can be expressed as:

[0079] ;

[0080] The complex amplitude of the encoded hologram can be expressed as:

[0081] ;

[0082] Figure 3 is a schematic diagram of a hologram decoding process based on an off-axis vortex beam provided by an embodiment of the present application. Referring to Figure 3 , during decoding, determine the complex conjugate of the off-axis vortex beam of the channel to be decoded;

[0083] The complex conjugate of the off-axis vortex beam is expressed as:

[0084] ;

[0085] In the formula, is the beam width of the off-axis vortex beam.

[0086] It should be noted that the off-axis amount of the off-axis vortex beam is not greater than the beam width to avoid excessive off-axis amount causing not to satisfy the complex conjugate with the off-axis phase of the corresponding channel, resulting in image crosstalk or decoding difficulties.

[0087] Reconstructed image of the channel to be decoded It is expressed as:

[0088] ;

[0089] Figure 4 FIG. 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 beam emitted by the laser passes through the aperture, wave plate and beam expander to become a collimated beam, and the function of the liquid crystal spatial light modulator is to load the hologram on the collimated beam, thereby realizing the reconstruction of the image.

[0090] Figure 5 FIG. is a schematic diagram of the phase distribution of the off-axis vortex beam corresponding to channel m provided by an embodiment of the present application. Figure 5 In, the topological charge number of the off-axis vortex beam is 2, and the off-axis distances on the x-axis and y-axis are 0.1w and 0.1w respectively. Figure 6 is the holographic multiplexing pattern obtained by summing the superimposed holograms of all image channels.

[0091] It should be noted that in the implementation of the present technical solution, when using the complex conjugate of the off-axis vortex beam with the same off-axis distance, the image reconstruction effect can be better achieved.

[0092] When using the complex conjugate of the off-axis vortex beam with different off-axis distances, the image reconstruction effect cannot be effectively achieved. Therefore, when the off-axis amount and topological charge number of the off-axis vortex beam added to the holographic multiplexing pattern do not meet the conditions, the image corresponding to the channel number cannot be reconstructed.

[0093] It should be noted that in specific practice, the off-axis amount of the off-axis vortex beam and the orbital angular momentum can be used independently and jointly as the parameters of holographic multiplexing.

[0094] It is expressed as:

[0095] In the encoding process, the phase-type holograms 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 the superimposed hologram;

[0096] In the decoding process, the complex conjugate of the off-axis vortex beam of the channel to be decoded is added to the holographic multiplexing pattern, and according to the orbital angular momentum of the off-axis vortex beam, the reconstructed image corresponding to the channel to be decoded is obtained.

[0097] The off-axis amount and orbital angular momentum can be used independently or jointly as parameters for holographic multiplexing. This provides flexibility for the implementation of this technical solution, allowing for the selection of an appropriate parameter combination according to requirements to optimize the multiplexing effect. For example, in some systems, it may only be necessary to adjust the off-axis amount to achieve effective multiplexing, while in other cases, the orbital angular momentum also needs to be used in conjunction with the off-axis amount, thus providing more adjustment space and optimization capabilities. This flexibility helps to improve the multiplexing efficiency, and during system design, the action modes of the off-axis amount and orbital angular momentum can be adjusted according to the actual optical conditions and requirements, thereby achieving more precise control and efficient information multiplexing.

[0098] In summary, the core of this technical solution lies in using off-axis vortex beams to endow the images of each channel with different spatial characteristics, and multiplexing multiple images in an optical carrier through holographic multiplexing. During decoding, the original images are restored by means of the complex conjugate off-axis vortex beams, thereby achieving the distortion-free restoration of multi-channel images. This technical solution introduces a new parameter, the off-axis amount, during the encoding and decoding processes of the hologram. Due to the orthogonality between different off-axis amounts, the information capacity of the hologram is increased, and crosstalk between the images of each channel can also be effectively suppressed. Through efficient optical multiplexing, this technical solution can achieve the multiplexing and decoding of multiple images through off-axis vortex beams with different off-axis amounts, and is applicable to large-capacity data transmission, storage, and other optical information processing applications.

[0099] It can be understood that the same or similar parts in the above embodiments can be referred to each other, and the content not detailed in some embodiments can be referred to the same or similar content in other embodiments.

[0100] 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 construed as indicating or implying relative importance. In addition, in the description of this application, unless otherwise specified, the meaning of "a plurality" refers to at least two.

[0101] Any process or method description shown in the flowchart or described in other ways herein can be understood as representing a module, segment, or part of code including one or more executable instructions for implementing a specific logical function or process. The scope of the preferred embodiments of this application includes additional implementations, where the functions can be executed in a manner that is not shown or discussed in sequence, including in a substantially simultaneous manner or in a reverse order according to the functions involved, which should be understood by those skilled in the technical field to which the embodiments of this application belong.

[0102] It should be understood that each part of the present application can be implemented by hardware, software, firmware, or a combination thereof. In the above 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, any one or a combination of the following technologies well known in the art can be used: discrete logic circuits having logic gate circuits for implementing logical functions on data signals, application specific integrated circuits having appropriate combinational logic gate circuits, programmable gate arrays (PGAs), field programmable gate arrays (FPGAs), and the like.

[0103] Those of ordinary skill in the art can understand that all or part of the steps carried by the methods of the above embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiments.

[0104] In addition, in each embodiment of the present application, each functional unit can be integrated in a processing module, or each unit can exist physically alone, or two or more units can be integrated in a module. The above integrated module can be implemented in the form of hardware or in the form of a software functional module. When the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0105] The above-mentioned storage medium can be a read-only memory, a magnetic disk, an optical disc, or the like.

[0106] In the description of this specification, the descriptions with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0107] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A holographic multiplexing method based on off-axis vortex beams, including 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 assigned; wherein, the off-axis amount of the off-axis vortex beam is not greater than the beam width; the off-axis spacing of the off-axis vortex beams is the same; Sample the images of each image channel to generate a phase-type hologram corresponding to each image channel; Determine the phase distribution of the off-axis vortex beam; Superimpose the phase-type hologram of each image channel and the phase distribution of the off-axis vortex beam to obtain a superimposed hologram; Sum the superimposed holograms of all image channels to obtain a holographic multiplexing pattern; Determine the phase distribution of the off-axis vortex beam, including: Determine the phase distribution of the off-axis vortex beam according to the topological charge number and off-axis amount of the off-axis vortex beam; The decoding process includes: Determine the complex conjugate of the off-axis vortex beam of the channel to be decoded; Attach the complex conjugate of the off-axis vortex beam of the channel to be decoded to the holographic multiplexing pattern to obtain a reconstructed image corresponding to the channel to be decoded; Determine the complex conjugate of the off-axis vortex beam of the channel to be decoded, including: Determine the complex conjugate of the off-axis vortex beam of the channel to be decoded according to the negative value of the topological charge number, off-axis amount and beam width of the off-axis vortex beam.

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

3. The method according to claim 2, wherein There is a corresponding relationship between the off-axis amount of the off-axis vortex beam of the current image channel and 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, wherein Sample the images of each image channel to generate a phase-type hologram corresponding to each image channel, including: Sample the images of each image channel through a two-dimensional Dirac function; Generate a phase-type hologram corresponding to each image channel through the Gerchberg-Saxton algorithm.

7. The method according to claim 1, wherein During the encoding process, superimpose 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 to obtain a superimposed hologram; During the decoding process, attach the complex conjugate of the off-axis vortex beam of the channel to be decoded to the holographic multiplexing pattern and obtain a reconstructed image corresponding to the channel to be decoded according to the orbital angular momentum of the off-axis vortex beam.

Images