Far-field imaging system, metasurface grating and imaging terminal

Abstract

The present invention discloses a far-field imaging system, a metasurface grating and an imaging terminal, and relates to the field of image generation technology. The system uses multiple modules to collaboratively realize dynamic environmental compensation and imaging quality optimization: the ambient temperature is read in real time, the refractive index of the metasurface grating is corrected according to a pre-stored mapping relationship, and a target wavefront function is constructed and discretized to obtain an initial phase distribution matrix; the focus area is divided in combination with the user's line of sight, and the phase distribution matrix is regulated by voltage gradient compensation; based on this, the buffer and background areas are divided, and a multi-area sampling rate is configured to generate a mask to improve the acquisition efficiency of key areas; far-field information changes are monitored in real time, and an interpolation or total variation strategy is selected to update the image; with the help of image clarity feedback, a quadratic phase correction term is superimposed to optimize the phase distribution matrix. The present invention solves the problems of traditional far-field imaging in environmental adaptation, dynamic focusing, data acquisition and imaging quality, and is suitable for augmented reality glasses, etc.

Description

Technical Field

[0001] The present invention relates to the field of image generation technology, and more particularly to a far-field imaging system, a metasurface grating, and an imaging terminal. Background Art

[0002] As a cutting-edge carrier of human-computer interaction, the innovation of optical display technology for augmented reality glasses has always been a core challenge for the development of the industry. Traditional surface relief grating technology forms a periodic structure on the surface of the material through a nanoimprint process. Although it realizes optical waveguide transmission, the high-order diffraction energy dispersion leads to low light utilization and high back-light leakage rate, and the complex process makes the production cost high. Geometric optical waveguide technology expands the field of view through a reflector array, but it is difficult to popularize due to the problem of light and dark stripes and low mass production yield. Although polarized holographic optical waveguide technology improves light utilization and reduces forward light leakage rate through holographic interference, its phase distribution is fixed and cannot adapt to dynamic changes such as ambient light intensity and wearing posture. The phase drift error is large in high-temperature environments, affecting imaging stability.

[0003] On the other hand, the rapid development of augmented reality glasses has put forward higher requirements on the optical system. Existing products rely on optical modules with fixed parameters, resulting in significant imaging noise in dark environments, long delays in multi-target tracking, and complex optical path designs that result in high system power consumption, affecting user experience. In particular, the optical system in the existing technology lacks dynamic control capabilities and cannot compensate in real time for phase drift caused by factors such as changes in ambient temperature and changes in the user's gaze area; the image sensor and the optical module are designed independently, resulting in a mismatch between the sampling strategy and the optical path characteristics, and the coexistence of information redundancy in key areas and missing information in background areas; at the same time, there is a lack of effective image quality feedback mechanism, making it difficult to dynamically optimize optical parameters during the imaging process, resulting in blurred images and loss of details in complex scenes. Existing technologies make it difficult to dynamically compensate for environmental disturbances, adapt to the user's visual focus, optimize data acquisition efficiency, and improve imaging quality in real time. Therefore, in order to overcome these limitations, the present invention proposes a far-field imaging system, a metasurface grating, and an imaging terminal. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the purpose of the present invention is to provide a far-field imaging system, a metasurface grating and an imaging terminal. Through temperature compensation, eye tracking and dynamic phase optimization technology, the technical problems of traditional far-field imaging systems in complex environments, such as unstable imaging quality, insufficient dynamic focusing capability and low data acquisition efficiency, are solved.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A far-field imaging system comprising:

[0007] Receive user instructions for initialization, read ambient temperature data, call the temperature and refractive index mapping relationship to correct the metasurface grating refractive index and construct the target wavefront function, and discretize the target wavefront function into an initial phase distribution matrix corresponding to the metasurface grating;

[0008] The focus target area of the metasurface grating is divided based on the user's line of sight data, the focus size is set, and local high-density phase control is performed on the focus target area to obtain the adjusted phase distribution matrix;

[0009] After adjusting the metasurface grating based on the phase distribution matrix, the buffer area and background area of the sampling area are divided with the focused target area as the center. The sampling frequency is configured and optimized, and a sampling mask is generated for each sampling area to obtain the number of samples in each sampling area and divide it into sub-areas. Each sub-area is synchronously sampled to obtain the far-field information of the target scene.

[0010] Set a monitoring time window and calculate the change rate of the target scene's far-field information to determine whether the far-field information is stable. If it is stable, reconstruct the initial reconstructed image and determine the image update strategy based on the far-field information update change to update the target scene image.

[0011] Based on the image clarity index of the target scene image, determine whether the imaging quality is qualified. If it is unqualified, obtain the quadratic phase correction term based on the image clarity index, and superimpose the quadratic phase correction term value on the element at the corresponding position in the phase distribution matrix to dynamically adjust the phase distribution matrix until the imaging quality is qualified.

[0012] Specifically, the specific steps of adjusting the phase distribution matrix include:

[0013] Collect the user's gaze direction data, configure a focus time window, calculate the change in each gaze direction data within the focus time window, and determine whether the user's gaze is focused based on the change;

[0014] If the user's line of sight is focused, the line of sight focused area is mapped onto the metasurface grating to determine the subwavelength units of the metasurface grating covered by the line of sight focused area, so as to divide the focus target area of the metasurface grating;

[0015] Setting a focus size, performing voltage gradient compensation on the sub-wavelength units within the focus target area based on the focus size, and calculating a driving voltage of the sub-wavelength units within the focus target area;

[0016] Convert the driving voltage value into an analog signal, output it to the sub-wavelength unit electrode of the focus target area, and synchronously update the phase distribution matrix;

[0017] Boundary effect compensation is performed on the updated phase distribution matrix, and an adjusted phase distribution matrix is output.

[0018] Specifically, the specific steps of dynamically adjusting the phase distribution matrix include:

[0019] Obtaining a clarity index of an image acquired by the current phase distribution matrix imaging, setting a clarity threshold, and determining whether the clarity index is less than the clarity threshold to determine whether the current phase distribution matrix imaging quality is qualified;

[0020] If the imaging quality of the current phase distribution matrix is judged to be unqualified, the dynamic adjustment of the phase distribution matrix is started, that is:

[0021] Obtaining the point spread function of the image acquired by the current phase distribution matrix imaging, and performing Gaussian fitting on the point spread function to obtain its half-height half-width to calculate the target defocus amount;

[0022] The defocus search interval is set with the target defocus as the center. Within the search interval, the maximization of the clarity index is used as the objective function. The image clarity index is calculated according to the current defocus. By comparing the clarity indices under different defocus amounts, the search interval is narrowed to obtain the optimal defocus.

[0023] Specifically, the specific steps of dynamically adjusting the phase distribution matrix also include:

[0024] Converting the row and column indices of the phase distribution matrix into two-dimensional coordinates on the metasurface grating;

[0025] Combining the optimal defocus value with the metasurface grating coordinates, the quadratic phase correction term corresponding to the phase distribution matrix element is calculated;

[0026] Traverse each element in the phase distribution matrix, superimpose the calculated quadratic phase correction term value on the element at the corresponding position in the original phase distribution matrix, obtain the updated value of each element of the phase distribution matrix, and automatically adjust the adjustment amplitude of the phase distribution matrix through the controller to obtain an updated phase distribution matrix;

[0027] After the phase distribution matrix is dynamically adjusted, imaging acquisition is performed to obtain the image clarity index, and the clarity index after adjustment is compared with the index before adjustment to determine whether the adjustment effect is significant;

[0028] If the adjustment effect is significant, continue to adjust the phase distribution matrix; if the adjustment effect is not significant, recalculate the secondary phase correction term and perform superimposed adjustment on the phase distribution matrix;

[0029] Configure an iteration threshold to count the number of overlay adjustments. If the number of overlay adjustments exceeds the iteration threshold, a warning of overlay adjustment anomaly is issued.

[0030] Specifically, the steps for obtaining the far-field information of the target scene include:

[0031] Configure an initial sampling rate, and generate a binary matrix with the same shape as the sampling area based on the initial sampling rate as a first sampling mask;

[0032] Determine the user's focus target area, configure a buffer ratio, and expand outward from the focus target area according to the configured buffer ratio to form a buffer area. The remaining part of the sampling area is used as the background area.

[0033] Setting a sampling rate increase threshold, setting the sampling rates of the focus target area and the buffer area respectively based on the initial sampling rate and the sampling rate increase threshold, and generating a second sampling mask and a third sampling mask;

[0034] Performing a logical OR operation on the first sampling mask, the second sampling mask, and the third sampling mask to obtain the number of samples corresponding to each sampling area;

[0035] According to the number of samples in each sampling area, each sampling area is divided into multiple sub-areas, and each sub-area is sampled synchronously to obtain the far-field information of the target scene.

[0036] Specifically, the specific steps of updating the target scene image include:

[0037] Perform real-time monitoring of the received far-field information, configure a monitoring time window, and calculate the real-time change rate of the collected far-field information within the monitoring time window;

[0038] Set a change rate threshold. If the real-time change rate of the far-field information is less than the change rate threshold, the far-field information is considered stable and image reconstruction is started, that is:

[0039] The real-time far-field information is obtained after the far-field information is stabilized, normalized, and input into the built-in reconstruction algorithm to reconstruct the initial reconstructed image and output the initial reconstructed image.

[0040] Specifically, the specific steps of updating the target scene image also include:

[0041] After obtaining the initial reconstructed image, the far-field information is continuously received and compared with the far-field information of the current reconstructed image to calculate the updated change;

[0042] Determine the image update strategy based on the size of the update change, namely:

[0043] Configure update change thresholds, including upper and lower update change thresholds.

[0044] If the update change threshold is less than the update change lower threshold, an interpolation-based update strategy is used to update the pixel value at the corresponding position in the initial reconstructed image, thereby generating an updated target scene image;

[0045] If the update change threshold is greater than the update change upper threshold, the image is reconstructed based on the new far-field information to generate an updated target scene image;

[0046] Otherwise, a total variation-based reconstruction algorithm is used, which takes the initial reconstructed image and the new far-field information as input to generate an updated target scene image;

[0047] After completing the target scene image update, continue to monitor the far-field information and update the target scene image.

[0048] Specifically, the specific calculation steps of the image clarity index include:

[0049] Convert the target scene image into a grayscale image and use a filtering algorithm to remove noise;

[0050] Construct horizontal and vertical gradient operators to calculate the horizontal and vertical gradient values of each pixel of the grayscale image, and calculate the gradient amplitude of each pixel;

[0051] Based on the division of the acquisition area, the gradient amplitude of the pixel points in each sampling area is accumulated and normalized based on the number of pixels in each sampling area to obtain the image clarity index of each sampling area;

[0052] The image clarity index of the focused target area is used as the basic clarity index. The relative deviations of the image clarity indices between the focused target area and other areas are calculated respectively. The basic clarity index is weightedly adjusted based on the relative deviations of the image clarity indices to obtain the image clarity index of the target scene image.

[0053] A metasurface grating is composed of subwavelength units, each of which contains liquid crystal molecules and transparent electrodes. The voltage drives the liquid crystal molecules to rotate, changing the optical path difference and performing continuous phase modulation on light.

[0054] The metasurface grating uses the temperature-refractive index mapping relationship to modify the metasurface grating refractive index based on the ambient temperature sensor data to construct the target wavefront function and generate the initial phase distribution matrix;

[0055] Divide the focus target area of the metasurface grating based on the user's line of sight data to adjust the phase distribution matrix of the focus target area;

[0056] The driving voltage of the sub-wavelength unit of the metasurface grating is regulated based on the phase distribution matrix to perform imaging and obtain the target scene image;

[0057] Based on the image clarity index feedback of the target scene image, the phase distribution matrix is dynamically adjusted by superimposing the quadratic phase correction term.

[0058] An imaging terminal includes a far-field imaging system, a display device, a central processing unit, an optical control system, a data acquisition component, an eye movement interaction device, a power management system, and a communication device;

[0059] The display device is used to display the reconstructed target scene image and its image clarity index in real time;

[0060] The central processing unit dynamically adjusts the phase distribution matrix according to the image clarity index and realizes real-time image refresh based on the change in far-field information;

[0061] The optical control system includes a sub-wavelength liquid crystal unit array, a transparent electrode drive circuit, and a temperature sensor to generate a dynamic phase distribution matrix and perform temperature compensation.

[0062] The data acquisition component is equipped with an optical signal sensor, an analog-to-digital conversion circuit, and a random number generator to perform compressed sensing sampling and far-field information acquisition;

[0063] The eye-movement interaction device includes an infrared camera, an eye feature recognition chip, and a three-dimensional posture sensor to achieve eye tracking and gesture recognition;

[0064] The power management system is used to provide power consumption control and charging functions;

[0065] The communication device is used to realize data transmission and remote control.

[0066] Beneficial effects of the present invention:

[0067] The present invention integrates an ambient temperature sensor to correct the refractive index of the metasurface grating in real time, combines eye tracking technology to dynamically divide the focus area and implement local high-density phase control, thereby achieving precise optimization of the phase distribution matrix in complex environments; adopts a compressed sensing differentiated sampling strategy to improve the efficiency of information acquisition in key areas and reduce redundant data; continuously improves the imaging quality through a closed-loop optimization mechanism of image clarity index feedback and superposition of secondary phase correction terms; a multimodal image update strategy ensures the consistency of the image with the actual environment when the scene changes dynamically; the regional weighted clarity evaluation method comprehensively reflects the overall image quality, effectively solving the technical difficulties of traditional far-field imaging systems in environmental adaptability, dynamic focusing capability, data acquisition efficiency and imaging stability, and providing a high-performance imaging solution for smart terminals such as augmented reality glasses. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 This is a schematic structural diagram of a far-field imaging system according to the present invention;

[0069] Figure 2 A flow chart showing the specific steps of generating and adjusting the phase distribution matrix of the present invention;

[0070] Figure 3 Flowchart of the specific steps of dynamic adjustment of the phase distribution matrix of the present invention;

[0071] Figure 4 This is a flow chart of sampling far-field information of a target scene according to the present invention;

[0072] Figure 5 The present invention is a flowchart of the specific steps of generating an updated target scene image. DETAILED DESCRIPTION

[0073] Example 1

[0074] See also Figure 1 ,This embodiment introduces a far-field imaging system, including a main control module, a metasurface control module, a compressed sensing acquisition module, an image reconstruction module, a quality assessment module and a feedback display module;

[0075] The main control module is used to initialize and set up each module of the far-field imaging system according to the instructions when the imaging terminal is started. In this embodiment, the imaging terminal is a smart glasses with an integrated far-field imaging system. The main control module is set in the main control compartment of the temple of the smart glasses. When the user issues an instruction, it parses the instruction, identifies the user's identity and detects the scene, and assigns the work tasks of each module according to the user's instruction or the preset task plan. For example, when the user issues an imaging task, the main control module will trigger the compressed sensing acquisition module to perform data acquisition and the image reconstruction module to perform image reconstruction in sequence to ensure that the entire imaging process is carried out in an orderly manner. The generated data is managed, including data storage, transmission and call. The collected raw data, reconstructed image and quality assessment results and other data are stored in the designated storage device.

[0076] See also Figure 2 The metasurface control module responds to control commands from the main control module, generates a target wavefront function based on geometric phase theory, and uses ambient temperature sensor data to compensate for changes in the refractive index of the liquid crystal material to generate the initial phase distribution matrix of the metasurface grating. Specifically, a table lookup method is used to establish a mapping between temperature and refractive index. The wavefront function parameters are modified in real time based on the current ambient temperature to ensure the accuracy of the phase distribution matrix.

[0077] When the eye tracking sensor detects the user's gaze area, it divides the corresponding area of the metasurface and activates the local high-density phase control mode. By dynamically adjusting the subwavelength unit size and the gradient distribution of the phase distribution matrix in the area, the phase distribution matrix is adjusted.

[0078] During the imaging process, after the quality assessment module feeds back the image clarity index, a defocused phase plate design strategy is adopted to dynamically adjust the phase distribution matrix by superimposing a quadratic phase correction term. The specific implementation is: a phase modulation term is added to the original phase distribution to improve the imaging quality.

[0079] In this embodiment, the metasurface grating is composed of multiple subwavelength units, each of which contains vertically arranged liquid crystal molecules and transparent electrodes. Under the action of voltage, the liquid crystal molecules rotate, changing the optical path difference to achieve continuous phase modulation; this continuous phase modulation capability enables the metasurface grating to flexibly control the wavefront of light to meet different imaging requirements.

[0080] After receiving control instructions from the main control module, the metasurface control module reads data from the ambient temperature sensor to obtain the current ambient temperature. Changes in ambient temperature can significantly affect the refractive index of the liquid crystal material in the metasurface grating, thereby affecting the phase modulation effect of light. To mitigate this effect, the metasurface control module calls upon a pre-stored mapping between temperature and refractive index. This mapping, derived from a large amount of experimental data, accurately reflects the correspondence between temperature and refractive index. Based on this mapping, the metasurface control module corrects for changes in the metasurface grating's refractive index, ensuring that the metasurface grating maintains stable optical performance under varying ambient temperatures. Next, the target wavefront function is constructed based on the scenario requirements. These scenarios include focused imaging, beam splitting imaging, and aberration correction. For focused imaging, the metasurface control module constructs a focusing wavefront function, which enables the metasurface grating to focus incident light to a specific location, producing a clear image. For beam splitting imaging, the metasurface control module constructs a beam splitting wavefront function, which splits the incident light into multiple beams, enabling multi-channel imaging. When constructing the wavefront function, the metasurface control module combines the corrected refractive index with specific scene parameters such as focal length and beam splitting angle to ensure that the wavefront function accurately describes the desired light field distribution. By constructing a suitable wavefront function, the foundation is laid for the subsequent generation of a precise phase distribution matrix.

[0081] Based on the constructed target wavefront function, it is discretized to fit the subwavelength unit structure of the metasurface grating. After discretization, an initial phase distribution matrix is generated based on the phase values corresponding to each subwavelength unit obtained from the discretization. Each element in this matrix corresponds to the phase value of a subwavelength unit in the metasurface grating, and the matrix dimensions match the subwavelength unit arrangement structure of the metasurface grating.

[0082] After obtaining the initial phase distribution matrix, the user's line of sight is monitored in real time through the eye tracking sensor. When the user focuses their line of sight on a specific area, the corresponding focus target area on the metasurface is divided according to the layout of the metasurface grating and the specific area provided by the eye tracking. The local high-density phase control mode is activated for the focus target area to adjust the initial phase distribution matrix.

[0083] Preferably, the specific steps of adjusting the phase distribution matrix include:

[0084] When the smart glasses are started, the eye tracking sensor is initialized and the user's gaze direction data, including horizontal and vertical eye angle information and pupil position, is collected at a fixed frequency through the eye tracking sensor.

[0085] Configure a focus time window. Within the focus time window, calculate the change in each gaze direction data separately, and judge whether the user's gaze is focused based on the change. For example, set an angle change threshold. If the angle change range of the gaze direction within the focus time window is less than the angle change threshold, then the user's gaze is determined to be in a focused state; otherwise, the user's gaze is considered to be unfocused.

[0086] If the user's line of sight is focused, the metasurface grating layout information is obtained, including the arrangement of subwavelength units, such as rectangular arrangement, hexagonal arrangement, unit size and spacing; and the line of sight focus area is mapped onto the metasurface grating to determine the subwavelength units of the metasurface grating covered by the line of sight focus area, so as to divide the focus target area of the metasurface grating; in the determination process, combined with boundary expansion, the subwavelength units around the target area are also included to ensure the focusing effect.

[0087] The focus size is set based on the actual focusing requirements and the performance of the metasurface grating. This focus size can be adjusted to suit different application scenarios. Based on the electrical characteristics of the subwavelength unit, a voltage-phase model, derived from fitting a large amount of experimental data, is used to apply voltage gradient compensation to the subwavelength units within the target focus area. The driving voltage for the subwavelength units within the target focus area is calculated based on the preset focus size and the electrical characteristics of the subwavelength units, such as capacitance and resistance. Changes in the driving voltage cause changes in the orientation of the liquid crystal molecules within the subwavelength unit, thereby altering its optical properties and adjusting the effective size. By precisely controlling the voltage, the effective size of the subwavelength unit can be gradually reduced to the target value.

[0088] The calculated driving voltage value is converted into an analog signal and output to the sub-wavelength unit electrode in the focus target area, and the phase distribution matrix is updated synchronously. The change in driving voltage will cause the orientation of the liquid crystal molecules in the sub-wavelength unit to change, thereby changing its optical properties and achieving effective size adjustment.

[0089] The updated phase distribution matrix is compensated for boundary effects by applying a Gaussian weight window to the edge units of the focus area to alleviate the diffraction effect caused by phase mutation, and the adjusted new phase distribution matrix is output.

[0090] The adjusted phase distribution matrix is used for imaging and imaging testing. During the imaging testing process, the quality assessment module analyzes the reconstructed image in real time and calculates the image clarity index. Based on the clarity index, a defocused phase plate design strategy is adopted. That is, a quadratic phase correction term is superimposed on the original phase distribution to dynamically adjust the phase distribution matrix.

[0091] Preferably, the specific steps of dynamically adjusting the phase distribution matrix include:

[0092] Obtain the clarity index of the image acquired by the current phase distribution matrix imaging. Set a clarity threshold based on the actual application scenario and requirements to determine whether the imaging quality is qualified. If the clarity index is less than the clarity threshold, the current phase distribution matrix imaging quality is determined to be unqualified, and dynamic adjustment of the phase distribution matrix is initiated.

[0093] See also Figure 3 , the image obtained by the current phase distribution matrix imaging is estimated by blind deconvolution method to estimate the point spread function of the image, and Gaussian fitting is performed on the point spread function to obtain its half-maximum full width to calculate the target defocus amount, that is:

[0094] ;

[0095] in, is the target defocus amount, It is the wavelength of light that determines the basic properties of light. When light of different wavelengths propagates in the metasurface grating, its phase change law is different. It is the focal length of the optical system. In the far-field imaging system integrated in smart glasses, it reflects the ability of the metasurface grating to converge or diverge light. It is the characteristic size of the subwavelength unit, such as the thickness of the liquid crystal molecular layer, which affects the change of the optical path when light propagates in the subwavelength unit, and thus affects the phase modulation effect. It is the full width at half maximum of the point spread function, which reflects the size of the light spot after the imaging system images an ideal point light source. The smaller the full width at half maximum, the clearer the image. When calculating the optimal defocus amount, this value is used to quantify the degree of imaging blur to determine the amount of defocus that needs to be compensated.

[0096] A defocus search interval is set with the target defocus as the center. The golden section algorithm is used to search within the search interval. The maximum clarity index is used as the objective function. The image clarity index is calculated based on the current defocus. By comparing the clarity indexes at different defocus values, the search interval is narrowed to obtain the optimal defocus value.

[0097] For each element in the phase distribution matrix, determine its corresponding position on the metasurface grating, and convert the row and column indexes of the phase distribution matrix into two-dimensional coordinates on the metasurface grating through the coordinate conversion formula;

[0098] Combining the optimal defocus amount and the metasurface grating coordinates, the quadratic phase correction term corresponding to the phase distribution matrix element is calculated, namely:

[0099] ;

[0100] in, is the phase distribution matrix Row, No. The quadratic phase correction term corresponding to the column elements, is the optimal defocus amount, is the phase distribution matrix Row, No. The metasurface grating coordinates corresponding to the column elements;

[0101] Traverse each element in the phase distribution matrix and perform edge phase smoothing. Superimpose the calculated quadratic phase correction term value on the element at the corresponding position in the original phase distribution matrix, obtain the updated value of each element of the phase distribution matrix, and perform modulo operation to make each element value of the phase distribution matrix between 0 and 2. within the scope;

[0102] After completing the superposition adjustment of the quadratic phase correction term of the phase distribution matrix, the updated phase distribution matrix is obtained, and the adjustment amplitude of the phase distribution matrix is automatically adjusted through the adaptive PID controller; the adaptive PID controller first calculates the error value between the current clarity index and the clarity threshold, and dynamically adjusts the proportional coefficient, integral coefficient and differential coefficient according to the size and change trend of the error value to calculate the adjustment amplitude of the phase distribution matrix.

[0103] After the adaptive PID controller determines the adjustment range of the phase distribution matrix, the image acquisition is performed again, and the image clarity is evaluated. The clarity index is calculated and compared with the clarity index before adjustment. The comparison method can be to directly calculate the difference between the two or to calculate the ratio between the two. If the difference or ratio exceeds the pre-set threshold, the adjustment effect is considered significant; otherwise, the adjustment effect is considered insignificant.

[0104] If the adjustment effect is significant, the phase distribution matrix is adjusted through the adaptive PID controller, the PID parameters are adjusted again according to the newly calculated error value, and the new phase distribution matrix adjustment amplitude is determined, so that the phase distribution matrix is continuously optimized to further improve the image clarity until the target clarity is reached or other stop conditions are met.

[0105] If the adjustment effect is not significant, the secondary phase correction term is recalculated, the phase distribution matrix is superimposed and adjusted, and a new round of phase distribution matrix adjustment is performed.

[0106] Configure an iteration threshold and count the number of overlay adjustments. If the number of overlay adjustments exceeds the iteration threshold, a warning of overlay adjustment anomaly is issued. This indicates that an abnormality in the phase distribution matrix overlay adjustment indicates that the current imaging system cannot effectively improve image quality. Further inspection of the system hardware status and parameter settings is necessary, or consideration of alternative imaging optimization methods is needed.

[0107] The compressed sensing acquisition module is used to collect light modulated by the metasurface grating after the metasurface control module completes the phase distribution matrix adjustment, and samples the far-field information of the target scene according to the principle of compressed sensing.

[0108] See also Figure 4 Preferably, the specific steps of obtaining the far-field information of the target scene include:

[0109] After identifying the focus target area and adjusting the phase distribution matrix of the hyperplane grating, the initial sampling rate is configured. The initial sampling rate can be adjusted according to user needs and scene complexity.

[0110] Using a random number generation algorithm and the configured initial sampling rate, a binary matrix with the exact same shape as the sampling area is generated. This serves as the first sampling mask. During the generation of this sampling mask, effective methods such as Poisson disk sampling are used to verify and adjust the generated mask to prevent excessive concentration of consecutive sampling points, which could adversely affect sampling performance. The verification process involves analyzing the generated mask and counting the number of consecutive sampling points and their concentration. If these metrics exceed pre-set thresholds, the current mask is discarded, and the random number generation algorithm is re-executed to generate a new mask and verify it again. This cycle repeats until the generated mask meets the preset requirements.

[0111] Determine the user's focus target area, configure a buffer ratio, and then expand outward from the focus target area according to the configured buffer ratio to form a buffer area. The remaining area in the sampling area is defined as the background area. During the division process, ensure that there is no overlap between the areas and that they cover the entire sampling area.

[0112] Setting a sampling rate boost threshold, including an upper boost threshold and a lower boost threshold, wherein the upper boost threshold is greater than the lower boost threshold; setting a sampling rate for the focus target area based on the initial sampling rate and the upper boost threshold; and setting a sampling rate for the buffer area based on the initial sampling rate and the lower boost threshold;

[0113] Generating a second sampling mask and a third sampling mask according to the increased sampling rate by using the same random number generation algorithm and Poisson disk sampling check adjustment method as the first sampling mask, respectively;

[0114] Perform a logical OR operation on the first, second, and third sampling masks. For elements in corresponding positions in the three masks, the result is 1 if any one is 1; the result is 0 only if all three elements are 0. This operation yields the number of samples corresponding to each sampling region. This number reflects the number of samples that should be taken for each sampling region, taking into account the characteristics of different regions and the initial sampling rate.

[0115] Divide each sampling area into several sub-areas with similar sampling numbers based on the sampling number, shape, and size of each sampling area, so that the deviation of the sampling number of each sub-area is within a preset deviation range;

[0116] After completing the sub-area division, sampling is carried out synchronously on each sub-area to obtain the far-field information of the target scene, that is, the light-related information after being modulated by the metasurface grating, including the intensity information and the phase information of the light.

[0117] The image reconstruction module reconstructs the target scene image based on the collected far-field information of the target scene, combined with the imaging requirements, and based on the reconstruction algorithm. Through continuous iterative optimization, it gradually approaches the real image of the target object.

[0118] Preferably, the specific steps of updating the target scene image include:

[0119] Monitor the received far-field information in real time, configure a monitoring time window, and calculate the real-time rate of change of the collected far-field information within the monitoring time window. For example, for the received far-field light intensity information, calculate the change in the extreme value within the monitoring time window as its real-time rate of change;

[0120] Set a change rate threshold. If the real-time change rate of the far-field information is less than the change rate threshold, the far-field information is considered stable and image reconstruction is started. Otherwise, monitoring is continued.

[0121] If the image reconstruction algorithm is started, the initial reconstructed image is reconstructed based on a built-in reconstruction algorithm, such as an iterative shrinkage threshold algorithm based on compressed sensing. The algorithm utilizes the sparsity of the signal and approximates the real image through continuous iteration.

[0122] Set the reconstruction algorithm parameters, including the number of iterations, step size, and regularization parameters. These parameters affect the algorithm's convergence speed and reconstruction accuracy and need to be adjusted according to actual conditions.

[0123] Obtain the real-time far-field information after the far-field information is stabilized and perform normalization processing, specifically, normalizing the light intensity information to the [0,1] range and the light phase information to the [0,2 ] interval;

[0124] The normalized far-field information is input into the reconstruction algorithm, and the initial reconstructed image is output through calculation;

[0125] See also Figure 5 ,After obtaining the initial reconstructed image, it continues to receive subsequent ,far-field information to obtain new far-field light intensity and ,phase information.

[0126] Compare the subsequent far-field information with the far-field information used for the current reconstructed image and calculate the updated change. Specifically, for light intensity, calculate the difference in intensity values at each corresponding position to obtain the intensity change; for phase, calculate the difference in phase to obtain the phase change;

[0127] Determine the image update strategy according to the magnitude of the update variation, that is, according to the magnitude of the calculated intensity variation and phase variation;

[0128] Configure the update change threshold, including the update change upper threshold and the update change lower threshold, and the update change upper threshold is greater than the update change lower threshold. If the update change threshold is less than the update change lower threshold, an interpolation-based update strategy is adopted. The specific operation is to substitute the calculated change amount into the interpolation formula and fine-tune the pixel value of the corresponding position in the initial reconstructed image to generate an updated target scene image.

[0129] If the update change threshold is greater than the update change upper threshold, the image is reconstructed based on the new far-field light intensity and phase information. Otherwise, a reconstruction algorithm more suitable for large changes is selected, such as the model-based total variation reconstruction algorithm. The total variation reconstruction algorithm is run using the initial reconstructed image and the new far-field information as input to generate an updated target scene image.

[0130] After completing the target scene image update, continue to monitor the far-field information and repeat the above image update process to maintain the consistency between the image and the actual scene.

[0131] The quality assessment module is used to assess the quality of the reconstructed target scene image when generating the target scene image, and calculate the image clarity index of the target scene image;

[0132] Preferably, the specific steps of calculating the image clarity index of the target scene image include:

[0133] The target scene image is converted into a grayscale image and denoised using a filtering algorithm to simplify the subsequent calculation process. It can also effectively retain the main structure and brightness information of the image, laying the foundation for subsequent clarity calculations.

[0134] Construct horizontal and vertical gradient operators to calculate the horizontal and vertical gradient values of each pixel of the grayscale image. The gradient value reflects the rate of change of the pixel in the corresponding direction, and calculate the gradient amplitude of each pixel. The gradient amplitude represents the intensity of the image edge at the pixel. The larger the gradient amplitude, the more drastic the image change at that point, that is, the more obvious the edge of the image, providing a key data basis for the subsequent clarity index calculation.

[0135] According to the division of the acquisition area, the gradient amplitudes of the pixel points in each sampling area are accumulated, and normalized based on the number of pixels in each sampling area to obtain the image clarity index of each sampling area. This eliminates the influence of the area size on the clarity index and makes the clarity indices of different areas comparable.

[0136] The image clarity index of the focused target area is used as the basic clarity index. Since the focused target area is often the core area of user attention, its clarity plays an important role in overall image quality assessment. The relative deviation of the image clarity index between the focused target area and other areas is calculated. This relative deviation, expressed as a percentage, intuitively reflects the degree of deviation of the clarity index of other areas compared to the clarity index of the focused target area, helping to assess the difference in clarity between different areas. Based on the relative deviation of the image clarity index, the basic clarity index is weighted and adjusted to obtain an index that more comprehensively and accurately reflects the overall clarity of the target scene image, providing a reliable basis for image quality assessment and subsequent image processing.

[0137] The feedback display module is used to display the target scene image to the user so that the user can detect and mark the target scene image;

[0138] The target scene image is displayed clearly and intuitively on the imaging terminal, supporting multiple display modes, such as color and grayscale, to meet the needs of different users. In addition to the target scene image, other imaging-related information, such as imaging parameters and quality assessment results, is also displayed. This information allows users to better understand the imaging process and results, providing a reference for subsequent analysis and decision-making.

[0139] The feedback display module has a user interaction function, and the user can operate the displayed target scene image, such as zooming in, zooming out, rotating, marking, etc. This makes it convenient for the user to detect and analyze the target scene based on the displayed information and imaging results.

[0140] Example 2

[0141] A metasurface grating, which is composed of subwavelength units, each of which includes liquid crystal molecules and transparent electrodes. The voltage drives the liquid crystal molecules to rotate, changing the optical path difference and performing continuous phase modulation on light.

[0142] The metasurface grating is equipped with an integrated ambient temperature sensor that acquires real-time ambient temperature data. This sensor then uses a pre-stored temperature-refractive index mapping, fitted with extensive experimental data, to accurately reflect the relationship between temperature and refractive index. This mapping is then used to correct the metasurface grating's refractive index. Based on geometric phase theory, the target wavefront function is constructed in conjunction with the corrected refractive index. This target wavefront function is then discretized to generate an initial phase distribution matrix that matches the subwavelength unit arrangement.

[0143] The metasurface grating works in conjunction with an eye-tracking sensor, which monitors the user's gaze direction in real time. When the user's gaze is focused on a specific area, a corresponding focus target area on the metasurface is demarcated based on the layout of the metasurface grating and the specific area provided by the eye tracking. A local high-density phase control mode is activated for this focus target area. Based on a voltage-phase model, voltage gradient compensation is applied to the subwavelength units in this area according to the focusing requirements and the performance of the metasurface grating. By precisely controlling the voltage, the orientation of the liquid crystal molecules within the subwavelength units is altered, thereby adjusting the phase distribution matrix of this area.

[0144] During the imaging process, the metasurface grating drives the subwavelength units through transparent electrodes based on the adjusted phase distribution matrix, controls the wavefront of light, images the light modulated by the metasurface grating, and obtains the target scene image. The quality assessment module analyzes the target scene image, calculates the image clarity index and provides feedback. Based on this feedback, the metasurface grating adopts a defocus phase plate design strategy. By calculating the target defocus amount, it superimposes a quadratic phase correction term on the original phase distribution matrix and dynamically adjusts the phase distribution matrix to improve the imaging quality. At the same time, the updated phase distribution matrix is compensated for boundary effects. By applying a Gaussian weight window to the edge units of the focus area, the diffraction effect caused by phase mutation is alleviated to ensure the stability and accuracy of the imaging effect.

[0145] Example 3

[0146] An imaging terminal includes a far-field imaging system, a display device, a central processing unit, an optical control system, a data acquisition component, an eye movement interaction device, a power management system, and a communication device;

[0147] The display device utilizes a high-resolution display screen with excellent display performance, capable of displaying the reconstructed target scene image in real time and supporting multiple display modes to meet the needs of different users. Furthermore, the display device simultaneously displays imaging-related information, including the target scene image's image clarity index and imaging parameters, allowing users to intuitively understand the imaging process and results.

[0148] The central processing unit integrates a high-performance processor, memory, and storage devices, providing data processing capabilities. During the imaging process, the central processing unit receives feedback from the quality assessment module on the image clarity index. Based on the actual application scenario and requirements, it dynamically adjusts the phase distribution matrix of the metasurface control module to optimize the imaging effect. Simultaneously, based on the changes in far-field information captured by the data acquisition component, the reconstructed target scene image is refreshed in real time to ensure consistency between the image and the actual scene.

[0149] The optical control system includes a subwavelength liquid crystal unit array, a transparent electrode drive circuit, and a temperature sensor. The temperature sensor monitors the ambient temperature in real time and, using a pre-stored mapping between temperature and refractive index, corrects for changes in the refractive index of the liquid crystal material, ensuring that the metasurface grating maintains stable optical performance under varying ambient temperatures. Based on geometric phase theory and the corrected refractive index, a target wavefront function is constructed to generate an initial phase distribution matrix. Based on the user's gaze area as indicated by the eye-movement interaction device, a local high-density phase control mode is activated for the corresponding area of the metasurface grating. The phase distribution matrix is dynamically adjusted to achieve flexible control of the light wavefront to meet diverse imaging requirements.

[0150] The data acquisition component is equipped with an optical signal sensor, an analog-to-digital conversion circuit, and a random number generator. After the metasurface control module completes the phase distribution matrix adjustment, the optical signal sensor collects the light modulated by the metasurface grating. Based on the principles of compressed sensing, a random number generator generates a binary matrix with the same shape as the sampling area as a sampling mask. The sampling mask is then verified and adjusted using effective methods such as Poisson disk sampling to ensure the rationality of the sampling point distribution. Based on the user's focus target area and the set buffer ratio, the buffer area and background area are divided. The sampling rate of each area is set, and a sampling mask is generated for each corresponding area. The number of samples corresponding to each sampling area is obtained through a logical OR operation. Each sampling area is divided into several sub-areas with similar sampling numbers. Sampling is performed simultaneously on each sub-area to obtain far-field information of the target scene, including light intensity and phase information. The optical signal is converted into a digital signal through the analog-to-digital conversion circuit and transmitted to the central processing unit for subsequent processing.

[0151] The eye-movement interaction device includes an infrared camera, an eye feature recognition chip, and a three-dimensional posture sensor. The infrared camera collects the user's gaze direction data at a fixed frequency, including the horizontal and vertical angles of the eyeballs and the position of the pupil. The eye feature recognition chip analyzes and processes the collected data to determine whether the user's gaze is focused. When the user's gaze is focused, the focus area is mapped onto the metasurface grating according to the layout of the metasurface grating, dividing the focus target area. At the same time, the three-dimensional posture sensor monitors the three-dimensional posture of the user's head in real time, compensating for imaging deviations that may be caused by head movement, and improving imaging accuracy. The eye-movement interaction device also supports gesture recognition. Users interact with the imaging terminal through simple gestures such as zooming in, out, rotating, and marking, facilitating the detection and analysis of the target scene image.

[0152] The power management system provides a stable power supply to each module of the imaging terminal. It utilizes a rechargeable battery and is equipped with a charge management circuit and dynamic power consumption control. This allows it to rationally allocate power based on the operating status of each module, reducing overall power consumption and extending battery life. It also supports fast charging technology, which allows for quick battery replenishment to meet user needs.

[0153] The communication device integrates wireless communication modules such as Bluetooth and Wi-Fi, supporting multiple wireless communication protocols and enabling data transmission and remote control between the imaging terminal and other devices. Through the wireless communication module, the imaging terminal can transmit data such as collected raw data, reconstructed images, and quality assessment results to other devices for further processing and analysis. It can also receive commands and configuration information from other devices, enabling remote control of various imaging terminal functions and improving ease of use and flexibility.

[0154] Working principle and its effect:

[0155] The working principles and effects of a far-field imaging system, metasurface grating, and imaging terminal are as follows:

[0156] Upon user command, the far-field imaging system immediately initializes. It reads the ambient temperature, corrects the metasurface grating's refractive index according to a pre-stored relationship, constructs and discretizes the target wavefront function, and generates an initial phase distribution matrix, improving the phase modulation accuracy of the optical signal at different temperatures. Using an eye-tracking interactive device, the system collects real-time user gaze direction data. After determining the focal area, it then delineates subwavelength elements based on the metasurface grating layout and divides the focus target area. The system sets the focal size and uses voltage gradient compensation to adjust the subwavelength element drive voltage, changing the optical path difference and optimizing the phase distribution matrix to improve image clarity in the key area. After adjusting the phase distribution matrix, the system divides the buffer and background regions centered on the focus target area. The sampling frequency is optimized based on regional characteristics, and a sampling mask is generated. The number of samples in each region is determined and divided into subregions. Synchronous sampling is performed to acquire far-field information of the target scene, reducing data redundancy and improving the efficiency of information acquisition in key areas. The system monitors the rate of change of far-field information in real time. If the information is stable, the system reconstructs the image from the normalized far-field information using a built-in algorithm. The system then continuously compares the new and old far-field information, flexibly updating the image using interpolation, reconstruction, or total variation reconstruction strategies based on the amount of change to ensure consistency with the actual scene. After imaging, the image is converted to grayscale and denoised. A gradient operator is constructed to calculate pixel gradient values and amplitudes, which are then accumulated and normalized by region. The overall clarity index is then derived using the focus area clarity index as a benchmark. If the image quality does not meet the standard, the system calculates a secondary phase correction term based on the clarity index, adds it to the phase distribution matrix, and dynamically adjusts it using adaptive PID control until the image quality is acceptable.

[0157] The metasurface grating modifies the refractive index and generates a phase distribution matrix based on temperature data and mapping relationships. It dynamically adjusts the phase based on the user's line of sight, controls the subwavelength unit drive voltage for imaging based on the phase, and optimizes the phase distribution matrix based on image clarity feedback to ensure precise phase modulation and high-quality imaging. The components of the imaging terminal work together: the display presents the image and clarity index, the central processing unit adjusts the phase distribution matrix and refreshes the image based on the index and far-field information, the optical control system is responsible for phase distribution matrix generation and temperature compensation, the data acquisition component performs sampling and information collection, the eye-movement interaction device enables gaze tracking and gesture recognition, the power management system provides power consumption control and charging, and the communication device ensures data transmission and remote control. This creates an efficient, intelligent, and stable far-field imaging experience for users and promotes the application of smart terminals in multiple fields.

[0158] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A far-field imaging system, characterized in that: include: Receive user instructions for initialization, read ambient temperature data, call the temperature and refractive index mapping relationship to correct the metasurface grating refractive index and construct a target wavefront function, and discretize the target wavefront function into an initial phase distribution matrix corresponding to the metasurface grating; Dividing the focus target area of the metasurface grating in combination with the user's line of sight direction data, setting the focus size, and performing local high-density phase control on the focus target area to obtain an adjusted phase distribution matrix; After adjusting the metasurface grating based on the phase distribution matrix, the sampling area is divided into a buffer area and a background area with the focus target area as the center; Configure and optimize the sampling frequency, generate a sampling mask for each sampling area, obtain the number of samples in each sampling area and divide it into sub-areas, and synchronously sample each of the sub-areas to obtain far-field information of the target scene; Setting a monitoring time window and calculating the change rate of the far-field information of the target scene to determine whether the far-field information is stable. If it is stable, reconstructing the initial reconstructed image and determining an image update strategy based on the change amount of the far-field information update to update the target scene image; Based on the image clarity index of the target scene image, determine whether the imaging quality is qualified. If it is unqualified, obtain the quadratic phase correction term based on the image clarity index, and superimpose the quadratic phase correction term value on the element at the corresponding position in the phase distribution matrix to dynamically adjust the phase distribution matrix until the imaging quality is qualified.

2. A far-field imaging system according to claim 1, characterized in that: The specific steps of adjusting the phase distribution matrix include: Collect the user's gaze direction data, configure a focus time window, calculate the change in each gaze direction data within the focus time window, and determine whether the user's gaze is focused based on the change; If the user's line of sight is focused, the line of sight focused area is mapped onto the metasurface grating to determine the subwavelength units of the metasurface grating covered by the line of sight focused area, so as to divide the focus target area of the metasurface grating; Setting a focus size, performing voltage gradient compensation on the sub-wavelength units within the focus target area based on the focus size, and calculating a driving voltage of the sub-wavelength units within the focus target area; Convert the driving voltage value into an analog signal, output it to the sub-wavelength unit electrode of the focus target area, and synchronously update the phase distribution matrix; Boundary effect compensation is performed on the updated phase distribution matrix, and an adjusted phase distribution matrix is output.

3. The far-field imaging system according to claim 1, wherein: The specific steps of dynamically adjusting the phase distribution matrix include: Obtaining a clarity index of an image acquired by the current phase distribution matrix imaging, setting a clarity threshold, and determining whether the clarity index is less than the clarity threshold to determine whether the current phase distribution matrix imaging quality is qualified; If the imaging quality of the current phase distribution matrix is judged to be unqualified, the dynamic adjustment of the phase distribution matrix is started, that is: Obtaining the point spread function of the image acquired by the current phase distribution matrix imaging, and performing Gaussian fitting on the point spread function to obtain its half-height half-width to calculate the target defocus amount; A defocus search interval is set with the target defocus as the center. Within the search interval, the image clarity index is calculated according to the current defocus with maximizing the clarity index as the objective function. By comparing the clarity indices under different defocus amounts, the search interval is narrowed to obtain the optimal defocus.

4. A far-field imaging system according to claim 3, characterized in that: The specific steps of dynamically adjusting the phase distribution matrix also include: Converting the row and column indices of the phase distribution matrix into two-dimensional coordinates on the metasurface grating; Combining the optimal defocus value with the metasurface grating coordinates, the quadratic phase correction term corresponding to the phase distribution matrix element is calculated; Traverse each element in the phase distribution matrix, superimpose the calculated quadratic phase correction term value on the element at the corresponding position in the original phase distribution matrix, obtain the updated value of each element of the phase distribution matrix, and automatically adjust the adjustment amplitude of the phase distribution matrix through the controller to obtain an updated phase distribution matrix; After the phase distribution matrix is dynamically adjusted, imaging acquisition is performed to obtain the image clarity index, and the clarity index after adjustment is compared with the index before adjustment to determine whether the adjustment effect is significant; If the adjustment effect is significant, continue to adjust the phase distribution matrix; if the adjustment effect is not significant, recalculate the secondary phase correction term and perform superimposed adjustment on the phase distribution matrix; Configure an iteration threshold to count the number of overlay adjustments. If the number of overlay adjustments exceeds the iteration threshold, a warning of overlay adjustment anomaly is issued.

5. The far-field imaging system according to claim 1, wherein: The specific steps of obtaining the far-field information of the target scene include: Configure an initial sampling rate, and generate a binary matrix with the same shape as the sampling area based on the initial sampling rate as a first sampling mask; Determine the user's focus target area, configure a buffer ratio, and expand outward from the focus target area according to the configured buffer ratio to form a buffer area. The remaining part of the sampling area is used as the background area. Setting a sampling rate increase threshold, setting the sampling rates of the focus target area and the buffer area respectively based on the initial sampling rate and the sampling rate increase threshold, and generating a second sampling mask and a third sampling mask; Performing a logical OR operation on the first sampling mask, the second sampling mask, and the third sampling mask to obtain the number of samples corresponding to each sampling area; According to the number of samples in each sampling area, each sampling area is divided into multiple sub-areas, and each sub-area is sampled synchronously to obtain the far-field information of the target scene.

6. The far-field imaging system according to claim 1, wherein: The specific steps of updating the target scene image include: Perform real-time monitoring of the received far-field information, configure a monitoring time window, and calculate the real-time change rate of the collected far-field information within the monitoring time window; Set a change rate threshold. If the real-time change rate of the far-field information is less than the change rate threshold, the far-field information is considered stable and image reconstruction is started, that is: The real-time far-field information is obtained after the far-field information is stabilized, normalized, and input into the built-in reconstruction algorithm to reconstruct the initial reconstructed image and output the initial reconstructed image.

7. The far-field imaging system according to claim 6, wherein: The specific steps of updating the target scene image also include: After obtaining the initial reconstructed image, the far-field information is continuously received and compared with the far-field information of the current reconstructed image to calculate the updated change; Determine the image update strategy based on the size of the update change, namely: Configure update change thresholds, including upper and lower update change thresholds. If the update change threshold is less than the update change lower threshold, an interpolation-based update strategy is used to update the pixel value at the corresponding position in the initial reconstructed image, thereby generating an updated target scene image; If the update change threshold is greater than the update change upper threshold, the image is reconstructed based on the new far-field information to generate an updated target scene image; Otherwise, a total variation-based reconstruction algorithm is used, which takes the initial reconstructed image and the new far-field information as input to generate an updated target scene image; After completing the target scene image update, continue to monitor the far-field information and update the target scene image.

8. The far-field imaging system according to claim 1, wherein: The specific calculation steps of the image clarity index include: Convert the target scene image into a grayscale image and use a filtering algorithm to remove noise; Construct horizontal and vertical gradient operators to calculate the horizontal and vertical gradient values of each pixel of the grayscale image, and calculate the gradient amplitude of each pixel; Based on the division of the acquisition area, the gradient amplitude of the pixel points in each sampling area is accumulated and normalized based on the number of pixels in each sampling area to obtain the image clarity index of each sampling area; The image clarity index of the focused target area is used as the basic clarity index. The relative deviations of the image clarity indices between the focused target area and other areas are calculated respectively. The basic clarity index is weightedly adjusted based on the relative deviations of the image clarity indices to obtain the image clarity index of the target scene image.

9. A metasurface grating, applied to a far-field imaging system according to any one of claims 1 to 8, wherein the metasurface grating is composed of subwavelength units, each of which includes liquid crystal molecules and transparent electrodes. The liquid crystal molecules are driven by voltage to rotate, changing the optical path difference, thereby continuously phase modulating light. The metasurface grating is characterized in that: The metasurface grating, based on the ambient temperature sensor data, calls the temperature and refractive index mapping relationship to correct the metasurface grating refractive index to construct the target wavefront function and generate the initial phase distribution matrix; Dividing the focus target area of the metasurface grating in combination with the user's line of sight direction data to adjust the phase distribution matrix of the focus target area; Regulating the driving voltage of the sub-wavelength unit of the metasurface grating based on the phase distribution matrix to perform imaging and acquire an image of the target scene; Based on the image clarity index feedback of the target scene image, the phase distribution matrix is dynamically adjusted by superimposing a quadratic phase correction term.

10. An imaging terminal comprising a far-field imaging system according to any one of claims 1 to 8, characterized in that: It also includes a display device, a central processing unit, an optical control system, a data acquisition component, an eye movement interaction device, a power management system, and a communication device; The display device is used to display the reconstructed target scene image and its image clarity index in real time; The central processing unit dynamically adjusts the phase distribution matrix according to the image clarity index and realizes real-time image refresh based on the change amount of far-field information; The optical control system includes a sub-wavelength liquid crystal unit array, a transparent electrode driving circuit and a temperature sensor to generate a dynamic phase distribution matrix and perform temperature compensation; The data acquisition component is configured with an optical signal sensor, an analog-to-digital conversion circuit, and a random number generator to perform compressed sensing sampling and far-field information acquisition; The eye-movement interaction device includes an infrared camera, an eye feature recognition chip, and a three-dimensional posture sensor to achieve eye tracking and gesture recognition; The power management system is used to provide power consumption control and charging functions; The communication device is used to realize data transmission and remote control.

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