Method for determining design parameters of nanograting device and nanograting device

Abstract

The application provides a method for determining design parameters of a nano-grating device and the nano-grating device. The nano-grating device is configured to perform pixel-by-pixel modulation on light emitted by a ciphertext image to propagate to a plaintext image plane to reconstruct the plaintext image. The method comprises: obtaining a scrambling sequence; performing coordinate normalization on each element in the scrambling sequence to obtain a scrambling coordinate sequence; obtaining first pixel coordinates of each pixel in the plaintext image and mapping dimensions used for encryption; wherein at least one of the mapping dimensions is greater than or equal to 2; determining a mapping relationship between the first pixel coordinates of each pixel in the plaintext image and second pixel coordinates of each pixel in the ciphertext image according to the first pixel coordinates of each pixel in the plaintext image, the mapping dimensions and the scrambling coordinate sequence; and determining the design parameters of the nano-grating device according to the mapping relationship.

Description

Technical Field

[0001] This invention relates to the field of image encryption technology, and in particular to a method for determining the design parameters of a nanograting device, as well as a method for encrypting, decrypting, and processing images using the nanograting device. Background Technology

[0002] With the popularization and widespread application of technologies such as the Internet, mobile communications, and the Internet of Things, a large amount of sensitive information, such as personal privacy data, trade secrets, and national security information, is transmitted through networks. During the transmission of information, we often need to encrypt the data to ensure its security. Among various encryption technologies, optical encryption uses optical transmission media, which can reduce the risk of electromagnetic interference and eavesdropping. Furthermore, optical encryption can achieve parallel processing, encrypting or decrypting large amounts of data simultaneously, thereby improving processing efficiency.

[0003] However, current optical encryption systems have a limited number of encryption channels, which can only encrypt and decrypt a limited number of images. Furthermore, the number of encryption channels is directly related to the complexity and design difficulty of the encryption system, which is not conducive to improving encryption integration. Summary of the Invention

[0004] Based on this, the present invention aims to provide a method for determining the design parameters of a nanograting device and a nanograting device, so as to solve at least one of the above problems.

[0005] In a first aspect, this application provides a method for determining the design parameters of a nanograting device, wherein the nanograting device is configured to modulate light emitted from a ciphertext image pixel by pixel to propagate it to a plaintext image plane for reconstruction of the plaintext image.

[0006] The method includes:

[0007] Obtain a scrambled sequence; wherein the number of elements in the scrambled sequence is greater than the number of first pixels in the plaintext image; convert each element in the scrambled sequence to coordinates to obtain a scrambled coordinate sequence; obtain the first pixel coordinates of each pixel in the plaintext image and the mapping dimension used for encryption; wherein at least one of the mapping dimensions is greater than or equal to 2; determine the mapping relationship between the first pixel coordinates of each pixel in the plaintext image and the second pixel coordinates of each pixel in the ciphertext image based on the first pixel coordinates of each pixel in the plaintext image, the mapping dimension, and the scrambled coordinate sequence; determine the design parameters of the nanograting device based on the mapping relationship.

[0008] The method for determining the design parameters of the aforementioned nanograting device involves using a pixel-by-pixel encryption strategy to determine the pixel coordinates of the ciphertext image, and then determining the design parameters of the nanograting device based on the mapping relationship between the pixel coordinates of the plaintext image and the pixel coordinates of the ciphertext image. This approach not only ensures the number of encryption channels for optical encryption but also facilitates the acquisition of nanograting devices for decryption, thereby resolving the trade-off between the number of optical encryption channels and system complexity.

[0009] In one embodiment, obtaining the scrambled sequence includes: obtaining a shifted chaotic sequence; wherein each element in the shifted chaotic sequence has a random arrangement order; obtaining an integer sequence; wherein the number of elements in the integer sequence is the same as the number of elements in the shifted chaotic sequence; shifting the integer sequence according to the arrangement order of each element in the shifted chaotic sequence to obtain the scrambled sequence.

[0010] In one embodiment, obtaining the shifted chaotic sequence includes: determining the second number of pixels in the ciphertext image based on the mapping dimension and the first number of pixels in the plaintext image; generating a random chaotic sequence using a chaotic system and an encryption key based on the second number of pixels; and rounding down each element of the random chaotic sequence to obtain the shifted chaotic sequence.

[0011] In one embodiment, the design parameters of the nanograting device include one or more of the following: spatial frequency, orientation, and groove depth of the nanograting.

[0012] Secondly, this application provides a nanograting device comprising a plurality of pixelated nanograting units arranged in an array, wherein each pixelated nanograting unit has design parameters as determined by the method described above.

[0013] The aforementioned nanograting device can reconstruct plaintext images through pixel-by-pixel decryption, which helps to solve the problem of the mutual constraint between the number of optical encryption channels and system complexity.

[0014] In one embodiment, the pixelated nanograting unit includes a plurality of pixelated sub-nanograting units, which are configured to modulate light emitted from the ciphertext image to converge the light onto the plaintext image plane for pixel reconstruction of the plaintext image.

[0015] Thirdly, this application provides an image encryption method, comprising:

[0016] Obtain a scrambled sequence; wherein the number of elements in the scrambled sequence is greater than the number of first pixels in the plaintext image; convert each element in the scrambled sequence to coordinates to obtain a scrambled coordinate sequence; obtain the first pixel coordinates of each pixel in the plaintext image and the mapping dimension used for encryption; wherein at least one of the mapping dimensions is greater than or equal to 2; determine the second pixel coordinates of each pixel in the ciphertext image based on the first pixel coordinates, the mapping dimension, and the scrambled coordinate sequence; obtain the first grayscale of each pixel in the plaintext image; determine the second grayscale of each pixel in the ciphertext image based on the first grayscale of each pixel in the plaintext image and the mapping dimension; generate the ciphertext image based on the second pixel coordinates and the second grayscale of each pixel in the ciphertext image.

[0017] The above-mentioned image encryption method, by encrypting the pixel coordinates and grayscale of the plaintext image pixel by pixel, can make the same plaintext image into a completely different ciphertext image after the same encryption process, thus greatly increasing the difficulty of cracking.

[0018] In one embodiment, obtaining the scrambled sequence includes: determining the second number of pixels in the ciphertext image based on the mapping dimension and the first number of pixels in the plaintext image; generating a random chaotic sequence using a chaotic system and an encryption key based on the second number of pixels; rounding down each element of the random chaotic sequence to obtain a shifted chaotic sequence; obtaining an integer sequence; wherein the number of elements in the integer sequence is the same as the number of elements in the shifted chaotic sequence; and shifting the integer sequence according to the arrangement order of the elements in the shifted chaotic sequence to obtain the scrambled sequence.

[0019] Fourthly, this application provides a method for decrypting an image, comprising:

[0020] The encrypted image is loaded onto the liquid crystal display panel; light is projected onto the liquid crystal display panel; the pixels of the liquid crystal display panel are aligned one by one with the pixels of the nano-grating device as described above, so as to modulate the light emitted from the liquid crystal display panel, so that the light is emitted from the nano-grating device and propagates to the plaintext image plane to reconstruct the plaintext image.

[0021] The above image decryption method can use the nanograting device mentioned above to decrypt the encrypted image pixel by pixel, which helps to reduce the complexity of the system while ensuring the number of encryption channels.

[0022] Fifthly, this application provides an image processing system, comprising:

[0023] light source;

[0024] A liquid crystal display panel is configured to receive a light beam emitted by the light source;

[0025] As described above, each pixel in the nanograting device is aligned with each pixel in the liquid crystal display panel;

[0026] When the encrypted image is loaded onto the liquid crystal display panel, the light emitted from the liquid crystal display panel is incident on the nanograting device for modulation, so as to propagate to the plaintext image plane for reconstruction of the plaintext image.

[0027] The aforementioned image processing system decrypts encrypted images pixel by pixel using the nanograting device described above, which helps to reduce system complexity while ensuring the number of encryption channels. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this specification or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the composition of an image processing system according to an embodiment of this application;

[0030] Figure 2 This is a schematic diagram illustrating a one-to-many mapping between plaintext image pixels and ciphertext image pixels according to an embodiment of this application;

[0031] Figure 3 A flowchart illustrating the steps of a method for determining design parameters of a nanograting device according to an embodiment of this application;

[0032] Figure 4 This is a schematic diagram illustrating the formation of a mapping lookup table between plaintext image pixels and ciphertext image pixels according to an embodiment of this application;

[0033] Figure 5 This is a schematic diagram illustrating the formation of a shift-chaotic sequence according to an embodiment of this application;

[0034] Figure 6 This is a flowchart illustrating the steps of an image encryption method according to an embodiment of this application.

[0035] Component designation explanation:

[0036] 1. Light source; 2. Liquid crystal display panel; 3. Nano grating device; 4. Plain text image plane; 5. Encrypted text image pixel; 6. Plain text image pixel.

[0037] 100. Processing system. Detailed Implementation

[0038] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0039] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0041] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0042] This application provides an image (including video image) processing system for multi-channel optical encryption and decryption of images. It offers a high level of encryption and its low complexity helps reduce design and maintenance costs. Specifically, the processing system mainly performs the following steps:

[0043] a. Encrypt the plaintext image to generate a ciphertext image; wherein the number of pixels in the ciphertext image is greater than the number of pixels in the plaintext image;

[0044] b. Determine the design parameters of the nanograting device pixel by pixel based on the mapping relationship between the coordinates of each pixel in the encrypted image and the coordinates of each pixel in the plaintext image.

[0045] c. The fabricated nanograting device is used to perform pixel-by-pixel optical decryption of the encrypted image, thereby reconstructing the plaintext image.

[0046] For example, such as Figure 1 As shown, the processing system 100 includes: a light source 1; a liquid crystal display panel 2 configured to receive a light beam emitted from the light source 1; and a nanograting device 3, with each pixel in the nanograting device 3 aligned with each pixel in the liquid crystal display panel 2. When a ciphertext image is loaded onto the liquid crystal display panel 2, the light emitted from the liquid crystal display panel 2 is modulated by the nanograting device 3 and propagated to the plaintext image plane 4 for plaintext image reconstruction. Optionally, each pixel 6 in the reconstructed plaintext image corresponds to multiple ciphertext image pixels 5, so that the grayscale of each pixel 6 in the reconstructed plaintext image comes from the grayscale mapping and superposition of multiple ciphertext image pixels 5.

[0047] For example, the nanograting device 3 includes multiple pixelated nanograting units arranged in an array, wherein each pixelated nanograting unit has its own design parameters that can control the direction of the emitted light, so that the emitted light propagates to the plaintext image plane 4 for plaintext image reconstruction. Optionally, the nanograting device 3 can be fabricated by nanoimprinting, which is beneficial to improving fabrication efficiency and the integration of the encryption system.

[0048] For example, light source 1 can combine three laser beams (red, green, and blue) and then expand and collimate them to emit parallel white light. This parallel white light serves as backlight and is incident on the liquid crystal display panel 2 at a certain angle. Figure 2 As shown, the pixel size, arrangement, and number of the liquid crystal display panel 2 are consistent with the pixelated nanograting units in the nanograting device 3. The grating period and grating orientation of the pixelated nanograting units are designed by the grating equation to control the exit direction of the incident light. The pixels of the liquid crystal display panel 2 are aligned one by one with the pixels of the nanograting device 3 to ensure that the light passing through each pixel of the liquid crystal display panel 2 can enter the pixel of the nanograting device 3. At the same time, the nanograting device 3 propagates the grayscale information of the encrypted image to the plaintext image plane according to a predetermined vector light field propagation path for plaintext image reconstruction. In this way, the pixel-by-pixel alignment and bonding of the liquid crystal display panel 2 and the nanograting device 3 helps to improve the compactness of the processing system. Moreover, the liquid crystal display panel has the characteristic of high refresh rate. Therefore, the above encryption and decryption process can not only encrypt and decrypt image information, but also encrypt and decrypt video, with extremely high encryption integration.

[0049] Optionally, the parallel light source designed based on the pixel-by-pixel nanograting device 3 can be replaced with any other light source of any waveform, which helps to increase the difficulty of cracking the encrypted image.

[0050] In some embodiments of this application, the design parameters of the nanograting device can be determined by using a pixel-by-pixel encryption strategy to determine the pixel coordinates of the ciphertext image, and then by using the mapping relationship between the pixel coordinates of the plaintext image and the pixel coordinates of the ciphertext image. This approach not only ensures the number of encryption channels for optical encryption but also facilitates the acquisition of nanograting devices for decryption, thereby resolving the trade-off between the number of optical encryption channels and system complexity.

[0051] Optional, such as Figure 3 As shown, the method for determining the design parameters of the nanograting device 3 may include the following steps:

[0052] S100. Obtain the scrambled sequence; wherein the number of elements in the scrambled sequence is greater than the number of the first pixel of the plaintext image;

[0053] S200. Coordinate each element in the scrambled sequence to obtain the scrambled coordinate sequence;

[0054] S300, Obtain the first pixel coordinates of each pixel in the plaintext image and the mapping dimension used for encryption; wherein, at least one of the mapping dimensions is greater than or equal to 2;

[0055] S400. Based on the first pixel coordinates, mapping dimension, and scrambled coordinate sequence of each pixel in the plaintext image, determine the mapping relationship between the first pixel coordinates of each pixel in the plaintext image and the second pixel coordinates of each pixel in the ciphertext image.

[0056] S500. Determine the design parameters of the nanograting device based on the mapping relationship.

[0057] Optional, such as Figure 4 As shown, the scrambled sequence Ti is formed by shuffling the sequence elements from 1 to 160000. Then, the scrambled sequence is coordinated to obtain the scrambled coordinate sequence (Mi, Ni), where M... i =ceil(T i / 400), N i =mod(T) iThe process begins by adding 1 to the first pixel coordinates (400) of the plaintext image. Then, based on the first pixel coordinates, mapping dimension, and scrambled coordinate sequence of each pixel in the plaintext image, a mapping lookup table between the plaintext and ciphertext image pixels is obtained. Finally, based on this lookup table, the directional relationship between the first pixel coordinates and each second pixel coordinate is determined. Combined with the grating equation, the design parameters such as the spatial frequency, orientation, and groove depth of each pixelated nanograting unit in the nanograting device are determined. Here, ceil represents the floor function, i.e., the smallest integer greater than or equal to the input; mod represents the modulo function, i.e., the remainder between two inputs.

[0058] Optionally, the mapping dimension represents the number of ciphertext image pixels corresponding to plaintext image pixels. For example, if the mapping dimension of a plaintext image pixel is 2, it means that the plaintext image pixel corresponds to 2 ciphertext image pixels. Correspondingly, the 2 ciphertext image pixels correspond to 2 pixelated nanograting units (or 2 pixelated sub-nanograting units in 1 pixelated nanograting unit) on the nanograting device 3. The 2 pixelated nanograting units (or 2 pixelated sub-nanograting units in 1 pixelated nanograting unit) can modulate the light emitted from the ciphertext image so that the light converges to the plaintext image plane for pixel reconstruction of the plaintext image. If the mapping dimension of a plaintext image pixel is 4, it means that the plaintext image pixel corresponds to 4 ciphertext image pixels. Correspondingly, the 4 ciphertext image pixels correspond to 4 pixelated nanograting units (or 4 pixelated sub-nanograting units in 1 pixelated nanograting unit) on the nanograting device 3, and so on. Optionally, the mapping dimension of each plaintext image pixel can be consistent, for example, it can all be one of 2, 3, 4, 5, or 6, or it can be partially the same and partially different, or all different. This application does not impose any restrictions on this.

[0059] Optional, such as Figure 4 As shown, when the mapping dimension of each plaintext image pixel is 4, the pixel coordinates can be matched by taking four adjacent coordinates from the scrambled coordinate sequence according to the arrangement order of the plaintext image pixels, thereby obtaining the mapping lookup table (i.e., mapping relationship) between the plaintext image pixel coordinates and the ciphertext image pixel coordinates.

[0060] In some embodiments of this application, see also [link to previous document]. Figure 4 Step S100 may include:

[0061] S110. Obtain the shifted chaotic sequence Si; wherein, each element in the shifted chaotic sequence Si has a random arrangement order;

[0062] S120. Obtain the integer sequential sequence t i ; where the integer sequence t i The number of elements is the same as the number of elements in the shifted chaotic sequence;

[0063] S130. Based on the arrangement order of elements in the shifted chaotic sequence Si, the integer sequence t is processed. i The scrambled sequence T is obtained by shifting the bits. i .

[0064] It should be noted that, due to the scrambled sequence T i It is a sequence of integers t i The number of elements in the scrambled sequence is obtained by shifting, therefore the number of elements in the scrambled sequence is the same as that in the integer ordered sequence t. i The number of elements is also the same.

[0065] Optional, such as Figure 5 As shown, step S110 may include:

[0066] S111. Determine the number of second pixels in the ciphertext image based on the mapping dimension and the number of first pixels in the plaintext image;

[0067] S112. Generate a random chaotic sequence s based on the number of second pixels using a chaotic system and an encryption key. i ;

[0068] S113, regarding the random chaotic sequence s i The shifted chaotic sequence Si is obtained by rounding down each element.

[0069] By determining the number of the second pixel in the ciphertext image, a random chaotic sequence s with the same number of elements can be generated. i Then, for the random chaotic sequence s i Rounding down yields the result for the integer sequence t. i The shifted chaotic sequence Si is subjected to shifting. It is important to note that... Figure 4 The illustrated embodiment uses a second pixel count of 160,000 for the encrypted image. Figure 5 The embodiment shown takes an example where the number of the second pixel of the encrypted image is 1000.

[0070] This application also provides an image encryption method. By encrypting the pixel coordinates and grayscale of the plaintext image pixel by pixel, the same plaintext image can be encrypted into a completely different ciphertext image through the same encryption process, thereby greatly increasing the difficulty of cracking.

[0071] For example, such as Figure 6 As shown, the encryption method includes:

[0072] S10. Obtain the scrambled sequence; wherein the number of elements in the scrambled sequence is greater than the number of the first pixel of the plaintext image;

[0073] S20. Coordinate each element in the scrambled sequence to obtain the scrambled coordinate sequence;

[0074] S30. Obtain the first pixel coordinates of each pixel in the plaintext image and the mapping dimension used for encryption; wherein, at least one mapping dimension is greater than or equal to 2;

[0075] S40. Determine the second pixel coordinates of each pixel in the ciphertext image based on the first pixel coordinates, mapping dimension, and scrambled coordinate sequence of each pixel in the plaintext image.

[0076] S50. Obtain the first gray level of each pixel in the plaintext image;

[0077] S60. Determine the second gray level of each pixel in the ciphertext image based on the first gray level and mapping dimension of each pixel in the plaintext image;

[0078] S70. Generate the ciphertext image based on the second pixel coordinates and second grayscale of each pixel in the ciphertext image.

[0079] For example, the encrypted image includes the second pixel coordinates and second grayscale values ​​of each pixel in the encrypted image. When the first grayscale value of a pixel in the plaintext image is 240 and the mapping dimension is 4, the second grayscale values ​​of the four pixels in the corresponding encrypted image can be randomly distributed with a total of 240, for example, the grayscale values ​​of the four encrypted image pixels can be 60, 50, 70, and 60 respectively, or they can be evenly distributed with a total of 240, for example, the grayscale values ​​of the four encrypted image pixels can be 60, 60, 60, and 60 respectively. Thus, when the encrypted image is loaded onto the liquid crystal display panel 2, the liquid crystal display panel 2 emits light of corresponding intensity to illuminate the nanograting device 3, and the plaintext image is reconstructed through the nanograting device 3.

[0080] In some embodiments of this application, step S10 may include:

[0081] S11. Determine the number of second pixels in the ciphertext image based on the mapping dimension and the number of first pixels in the plaintext image;

[0082] S12. Generate a random chaotic sequence based on the number of second pixels using a chaotic system and an encryption key;

[0083] S13. Rounding down each element of the random chaotic sequence yields a shifted chaotic sequence.

[0084] S14. Obtain the integer sequential sequence; wherein the number of elements in the integer sequential sequence is the same as the number of elements in the shifted chaotic sequence;

[0085] S15. Shift the integer sequence according to the arrangement order of each element in the shifted chaotic sequence to obtain the scrambled sequence.

[0086] In some embodiments of this application, the encryption method can be executed in an image encryption device. Optionally, the image encryption device may include an input module for inputting a plaintext image and a processor connected to the input module for encrypting the plaintext image. Optionally, the processor may be connected to a liquid crystal display panel 2 to load the encrypted image onto the liquid crystal display panel 2.

[0087] This application also provides an image decryption method that uses the nanograting device described above to decrypt the encrypted image pixel by pixel, thereby reducing the complexity of the system while ensuring the number of encryption channels.

[0088] For example, the decryption method includes:

[0089] S10' Load the encrypted image onto the LCD panel;

[0090] S20' Projecting light onto the LCD panel;

[0091] S30' Align the pixels of the liquid crystal display panel with the pixels of the nano-grating device as described above one by one to modulate the light emitted from the liquid crystal display panel, so that the light is emitted from the nano-grating device and propagates to the plaintext image plane for plaintext image reconstruction.

[0092] For example, after the encrypted image is loaded onto the liquid crystal display panel, the light carrying amplitude information through each pixel of the encrypted image is incident on the corresponding pixelated nanograting unit of the nanograting device 3. In this way, the emission direction and intensity of the vector beam can be adjusted pixel by pixel, and the plaintext image can be reconstructed on the reconstructed plaintext image plane 4.

[0093] It should be noted that the numbers used to describe and claim certain embodiments of this application, representing quantities or properties, should be understood to be modified in some cases by the terms "approximately," "about," "approximately," or "essentially." For example, unless otherwise stated, "approximately," "about," "approximately," or "essentially" can indicate a variation of ±20% of the value they describe. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed according to the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of range in some embodiments of this application are approximate values, in specific embodiments, such numerical values ​​are set as precisely as feasible.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for determining the design parameters of a nanograting device, characterized in that, The nanograting device is configured to modulate the light emitted from the ciphertext image pixel by pixel to propagate it to the plaintext image plane for reconstruction of the plaintext image. The method includes: Obtain a scrambled sequence; wherein the number of elements in the scrambled sequence is greater than the number of the first pixels of the plaintext image; The elements in the scrambled sequence are converted to coordinates to obtain a scrambled coordinate sequence. Obtain the first pixel coordinates of each pixel in the plaintext image and the mapping dimension used for encryption; wherein at least one of the mapping dimensions is greater than or equal to 2; Based on the first pixel coordinates of each pixel in the plaintext image, the mapping dimension, and the scrambled coordinate sequence, determine the mapping relationship between the first pixel coordinates of each pixel in the plaintext image and the second pixel coordinates of each pixel in the ciphertext image; The design parameters of the nanograting device are determined based on the mapping relationship.

2. The method according to claim 1, characterized in that, The process of obtaining the scrambled sequence includes: Obtain a shifted chaotic sequence; wherein the elements in the shifted chaotic sequence have a random arrangement order; Obtain an integer sequential sequence; wherein the number of elements in the integer sequential sequence is the same as the number of elements in the shifted chaotic sequence; The integer sequence is shifted according to the arrangement order of the elements in the shifted chaotic sequence to obtain the scrambled sequence.

3. The method according to claim 2, characterized in that, The acquisition of the shifted chaotic sequence includes: The number of second pixels in the ciphertext image is determined based on the mapping dimension and the number of first pixels in the plaintext image. Based on the second number of pixels, a random chaotic sequence is generated using a chaotic system and an encryption key; The shifted chaotic sequence is obtained by rounding down each element of the random chaotic sequence.

4. The method according to any one of claims 1 to 3, characterized in that, The design parameters of the nanograting device include one or more of the following: spatial frequency, orientation, and groove depth.

5. A nanograting device, characterized in that, It includes multiple pixelated nanograting units arranged in an array, wherein each pixelated nanograting unit has design parameters determined by the method as described in any one of claims 1 to 4.

6. The nanograting device according to claim 5, characterized in that, The pixelated nanograting unit includes multiple pixelated sub-nanograting units, which are configured to modulate the light emitted from the ciphertext image so that the light converges to the plaintext image plane to perform pixel reconstruction of the plaintext image.

7. An image encryption method, characterized in that, include: Obtain a scrambled sequence; wherein the number of elements in the scrambled sequence is greater than the number of the first pixels of the plaintext image; The elements in the scrambled sequence are converted to coordinates to obtain a scrambled coordinate sequence. Obtain the first pixel coordinates of each pixel in the plaintext image and the mapping dimension used for encryption; wherein at least one of the mapping dimensions is greater than or equal to 2; The second pixel coordinates of each pixel in the ciphertext image are determined based on the first pixel coordinates, the mapping dimension, and the scrambled coordinate sequence of each pixel in the plaintext image. Obtain the first grayscale value of each pixel in the plaintext image; The second gray level of each pixel in the ciphertext image is determined based on the first gray level and mapping dimension of each pixel in the plaintext image; The encrypted image is generated based on the second pixel coordinates and second grayscale of each pixel in the encrypted image.

8. The method according to claim 7, characterized in that, The process of obtaining the scrambled sequence includes: The number of second pixels in the ciphertext image is determined based on the mapping dimension and the number of first pixels in the plaintext image. Based on the second number of pixels, a random chaotic sequence is generated using a chaotic system and an encryption key; The shifted chaotic sequence is obtained by rounding down each element of the random chaotic sequence. Obtain an integer sequential sequence; wherein the number of elements in the integer sequential sequence is the same as the number of elements in the shifted chaotic sequence; The integer sequence is shifted according to the arrangement order of the elements in the shifted chaotic sequence to obtain the scrambled sequence.

9. A method for decrypting an image, characterized in that, include: Load the encrypted image onto the LCD panel; Projecting light onto the liquid crystal display panel; The pixels of the liquid crystal display panel are aligned one by one with the pixels of the nanograting device as described in claim 5 or 6, so as to modulate the light emitted through the liquid crystal display panel, so that the light is emitted through the nanograting device and propagates to the plaintext image plane for reconstruction of the plaintext image.

10. An image processing system, characterized in that, include: light source; A liquid crystal display panel is configured to receive a light beam emitted by the light source; The nanograting device as described in claim 5 or 6, wherein each pixel in the nanograting device is aligned with each pixel in the liquid crystal display panel; in, When the encrypted image is loaded onto the liquid crystal display panel, the light emitted from the liquid crystal display panel is incident on the nanograting device for modulation, so as to propagate to the plaintext image plane for reconstruction of the plaintext image.

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