A method, apparatus and system for light field shaping

Abstract

The application relates to an optical field shaping method, device and system. The method comprises: acquiring pixel parameters of a liquid crystal device; generating first configuration parameters of a first phase-type metasurface according to the pixel parameters, the first phase-type metasurface being arranged on the incident side of the liquid crystal device to construct a transverse phase gradient towards a pixel opening area in a pixel dead zone, so that light originally falling into the pixel dead zone can be deflected into an adjacent pixel opening area; generating second configuration parameters of a second phase-type metasurface according to the outcoming light field characteristics after modulation of the first phase-type metasurface, the second phase-type metasurface being arranged on the outgoing side of the liquid crystal device to perform angle spectrum and wavefront reshaping on the light field outcoming from the liquid crystal device; and outputting the first configuration parameters and the second configuration parameters for preparing corresponding metasurface devices through the first configuration parameters and the second configuration parameters. Through the technical scheme, the light transmission efficiency can be improved and the output light field quality can be ensured.

Description

Technical Field

[0001] This application relates to the field of optical technology, specifically to a method, apparatus, and system for shaping an optical field. Background Technology

[0002] Transmissive LCDs, as core components such as programmable amplitude masks and phase modulators, are widely used in fields such as structured light projection, machine vision, and interferometry. However, their pixel structure generally contains non-transparent dead zones formed by black matrices, thin-film transistors, and wiring, resulting in an effective fill factor significantly lower than 1. This leads to unavoidable fixed optical losses, directly causing problems such as insufficient available optical power, reduced signal-to-noise ratio, prolonged exposure time, and increased thermal load on the light source.

[0003] The current mainstream approach to reducing losses has obvious drawbacks: First, it relies on miniaturizing the dead zone in panel manufacturing processes, which is costly, has a long development cycle, and is constrained by the physical limits of the manufacturing process. Second, while stacking a microlens array on the outside of the panel can locally improve brightness, it introduces problems such as angular spectral expansion and sidelobe enhancement, resulting in a decrease in the available energy in the optical path with a limited numerical aperture. At the same time, the wavefront distortion caused by light focusing can also cause crosstalk between pixels and distortion of the modulation function, which seriously affects the functional reliability of LCDs in high-precision scenarios such as phase encoding.

[0004] Existing technologies cannot simultaneously improve light transmission efficiency and output light field quality, making it difficult to achieve a real increase in the end-to-end usable energy of the system. Summary of the Invention

[0005] This application provides a light field shaping method, apparatus, and system to at least partially solve the above-mentioned technical problems.

[0006] To achieve the above objectives, according to a first aspect of this application, a light field shaping method is provided, comprising: Obtain the pixel parameters of the liquid crystal device; The first construction parameters of the first phase-type metasurface are generated according to the pixel parameters, wherein the first phase-type metasurface is used to be disposed on the incident side of the liquid crystal device to construct a lateral phase gradient toward the pixel opening region in the pixel dead zone, so that the light energy that originally falls into the pixel dead zone is deflected into the adjacent pixel opening region. The second construction parameters of the second phase-type metasurface are generated based on the characteristics of the emitted light field modulated by the first phase-type metasurface. The second phase-type metasurface is used to be disposed on the emission side of the liquid crystal device to perform angular spectrum and wavefront reshaping on the light field emitted by the liquid crystal device. The first construction parameter and the second construction parameter are output to prepare the corresponding metasurface device using the first construction parameter and the second construction parameter.

[0007] Further, the first construction parameter includes a first phase distribution, the pixel parameter includes a dead half-width, and the first construction parameter for generating the first phase-type metasurface based on the pixel parameter includes determining the first phase distribution based on the dead half-width, wherein the formula for determining the first phase distribution includes: , ; , ; in, For any point within the dead zone The shortest distance from that point to the pixel opening region; For wave number, The operating wavelength; , L1 is the designed spacing between the first phase-type metasurface and the incident surface of the liquid crystal device; s is the phase gradient intensity coefficient; γ is the power exponent parameter; and w is the dead zone half-width.

[0008] Furthermore, the pixel parameters also include the pixel period and the planar positions of the pixel opening region and the pixel dead region, and the first construction parameters include the cell period and the current guiding region; the first construction parameters for generating the first phase-type metasurface based on the pixel parameters further include: Generate the cell period that matches the pixel period; Generate the flow guiding region corresponding to the planar positions of the pixel opening region and the pixel dead region.

[0009] Further, the second construction parameters include a second phase distribution; the second construction parameters for generating the second phase-type metasurface based on the emitted light field characteristics modulated by the first phase-type metasurface include: A target region is defined in a preset plane of the second phase-type metasurface, wherein the preset plane includes a focal plane or a Fourier plane; Based on preset constraints, the light field is repeatedly propagated between the device surface of the second phase-type metasurface and the preset plane, and the second phase distribution is iteratively updated until the preset convergence condition is reached.

[0010] Furthermore, the preset constraint conditions include at least one of the following: Within the target region, a target distribution constraint is applied to the output amplitude; Outside the target region, a suppression constraint or a soft penalty constraint is applied to the output amplitude; In each iteration update, the target amplitude is scale-matched to maintain energy consistency between the iterative target and the current light field; Within the target area, the target distribution is weighted and mixed with the original output field amplitude.

[0011] Furthermore, the step of generating the second construction parameters of the second phase-type metasurface based on the emitted light field characteristics modulated by the first phase-type metasurface further includes: Construct target amplitude functions for multiple target optical field modulation tasks respectively; During the iterative update process, the phase distributions of multiple target optical field modulation tasks are weighted and summed to obtain the second phase distribution.

[0012] Furthermore, the target optical field modulation task includes a focusing task and a deflection task; the formula for determining the weighted summation includes: ; in, The second phase distribution constructed on the second phase-type metasurface during the k-th iteration update; To focus on task weights, The weight for each deflection task is M, where M is the number of deflection tasks. This represents the phase distribution of the focusing task in the k-th iteration; Let be the phase distribution of the m-th deflection task in the k-th iteration.

[0013] According to a second aspect of this application, a light field shaping device is provided, comprising: A first phase-type metasurface is provided on the incident side of a liquid crystal device, and its first construction parameters are generated according to the method described above. A second phase-type metasurface is provided on the emission side of the liquid crystal device, and its second construction parameters are generated according to the method described above.

[0014] Furthermore, both the first phase-type metasurface and the second phase-type metasurface are composed of a substrate and a superatomic array arranged on the substrate; the substrate material is selected from at least one of silicon, silicon dioxide, silicon nitride, germanium, and titanium dioxide, and the superatomic structure is selected from at least one of cylinder, ring, and rectangular pillar.

[0015] According to a third aspect of this application, a light field shaping system is proposed, comprising: The light source and collimation assembly are used to output a collimated incident beam; The light field shaping device as described in claim 8 or 9 is disposed on the emission side of the light source and collimation assembly along the light propagation direction; A liquid crystal device is disposed between the first phase-type metasurface and the second phase-type metasurface of the light field shaping device; The detection component is located on the output side of the light field shaping device and is used to receive and record the output light field after it has been processed by the light field shaping device.

[0016] The light field shaping method of this application embodiment achieves precise transfer of dead zone energy to the aperture region by designing a first phase-type metasurface, and performs closed-loop compensation for wavefront distortion generated after the transfer by designing a second phase-type metasurface. Without changing the structure and driving method of the liquid crystal device itself, the first and second phase-type metasurfaces are subsequently arranged on the light-incident and light-out sides of the liquid crystal device to process the light entering and exiting the liquid crystal device. This can improve the aperture utilization rate of the liquid crystal device, reduce the fixed light transmission loss caused by the finite fill factor, increase the light energy passing through the liquid crystal device, and at the same time ensure the quality of the output light field. It avoids the problems of angular spectrum expansion, inter-pixel crosstalk and modulation function distortion introduced by traditional microlens schemes, and can significantly improve the energy efficiency and working stability of various optical systems based on liquid crystal modulators.

[0017] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0020] Figure 1 This is a flowchart illustrating an exemplary embodiment of a light field shaping method provided in this disclosure; Figure 2 This is a schematic diagram of the structure of a light field shaping system provided in an exemplary embodiment of this disclosure; Figure 3 This is a schematic diagram of the phase distribution of the first phase-type metasurface provided in an exemplary embodiment of this disclosure; Figure 4 This is a schematic diagram of the phase distribution of the second phase-type metasurface provided in an exemplary embodiment of this disclosure; Figure 5 This is a schematic diagram of a superatomic structure provided in an exemplary embodiment of this disclosure; Figure 6This is a schematic diagram showing the point spread function (PSF) of the original Gaussian light in an exemplary embodiment of the Gaussian light incident system, the PSF with only LCD, the PSF with only MS1 added, and the PSF with both MS1 and MS2 added. Figure 7 This is a schematic diagram showing the one-dimensional PSF and full width at half maximum (FWHM) size of three systems: the original LCD, only MS1, and MS1+MS2, in an exemplary embodiment of this disclosure. Figure 8 This disclosure illustrates, through exemplary embodiments, the angle deflection of three systems—the original LCD, the system with only MS1 added, and the system with MS1+MS2—under three different cycles. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the protection scope of this application.

[0022] In the description of this application, 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. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0023] In the specific implementation of this application, all English abbreviations are marked with their full names and Chinese translations when they first appear: LCD (Liquid Crystal Display), MS1 (Metasurface1), MS2 (Metasurface2), IFTA (Iterative Fourier Transform Algorithm), ROI (Region of Interest), FF (Fill Factor), PSF (Point Spread Function), and FWHM (Full Width that Half Maximum).

[0024] According to a first aspect of this application, this application provides a light field shaping method, comprising: Step 100: Obtain the pixel parameters of the liquid crystal device.

[0025] Specifically, the pixel parameters of a liquid crystal device (LCD) refer to the inherent structural parameters of the LCD device at the time of manufacture, which can be obtained without any modification to the LCD device itself. The LCD device includes pixel dead zones and pixel aperture regions. A pixel dead zone is a non-transparent area within a liquid crystal pixel occupied by a black matrix, thin-film transistors, metal traces, or support structures. This area blocks or absorbs incident light, resulting in unavoidable light energy loss that is fixed to the pixel structure. A pixel aperture region is a transparent area within a liquid crystal pixel that enables amplitude or phase modulation.

[0026] In one specific embodiment, the pixel parameters specifically include pixel period, fill factor, and dead zone half-width. The pixel period refers to the distance between the centers of two adjacent pixels, the fill factor is the ratio of the pixel aperture area to the total pixel area, and the dead zone half-width is the width of the dead zone on one side of the pixel. These three parameters satisfy the geometric relationship: the equivalent side length of the pixel aperture a = ... The dead zone half-width w = (pa) / 2, FF is the fill factor, and p is the pixel period.

[0027] Step 200: Generate first construction parameters of the first phase-type metasurface according to the pixel parameters, wherein the first phase-type metasurface is used to be disposed on the incident side of the liquid crystal device to construct a lateral phase gradient toward the pixel opening region in the pixel dead zone, so that light energy that originally falls into the pixel dead zone is deflected into the adjacent pixel opening region.

[0028] The first construction parameters refer to all the design data required for the fabrication of the first phase-type metasurface, including but not limited to phase distribution, cell period, flow-guiding region layout, alignment marks, and spacing control parameters.

[0029] The core function of the first phase-type metasurface is to realize "energy transport at the pixel edge". Unlike the light-concentrating imaging principle of traditional microlens arrays, it constructs a continuous lateral phase gradient in the dead zone region that points towards the opening region. This causes the incident light to be laterally deflected towards the pixel opening region during propagation. In this way, the energy that would have been absorbed by the pixel dead zone (when the first phase-type metasurface is not set) is redirected back to the pixel opening region. This effectively improves the effective fill factor of the liquid crystal device and solves the problem of light loss caused by pixel dead zone occlusion.

[0030] Step 300: Generate second construction parameters for the second phase-type metasurface based on the characteristics of the emitted light field modulated by the first phase-type metasurface, wherein the second phase-type metasurface is used to be disposed on the emission side of the liquid crystal device to perform angular spectrum and wavefront reshaping on the light field emitted by the liquid crystal device; Correspondingly, the second construction parameters refer to all the design data required for the fabrication of the second phase-type metasurface, mainly including the phase distribution.

[0031] Since the energy transport process of the first-phase metasurface inevitably introduces angular spectral expansion, sidelobe enhancement and wavefront distortion, if only the first-phase metasurface is used, although the proportion of energy passing through the liquid crystal aperture can be increased, this extra energy may be distributed in the region that the subsequent optical path cannot effectively receive, resulting in the system's end-to-end available energy not being truly improved, or even the situation of local brightening but system performance deterioration.

[0032] Therefore, in this embodiment, a second phase-type metasurface is added. The emitted light field, modulated by the first phase-type metasurface and then truncated by the pixel opening / dead zone of the liquid crystal device, is used as the only input to perform angular spectrum and wavefront reshaping on the light field, thereby reconcentrating the dispersed energy into the target area and suppressing side lobes and stray energy to compensate for wavefront distortion.

[0033] Step 400: Output the first construction parameters and the second construction parameters to prepare the corresponding metasurface device using the first construction parameters and the second construction parameters.

[0034] Finally, the output first and second construction parameters can be directly imported into semiconductor photolithography equipment to fabricate corresponding metasurface devices (first-phase metasurface and second-phase metasurface). After pixel-level alignment and fixation, the fabricated metasurface devices can be combined with liquid crystal devices to form a complete light field shaping system, thereby achieving light energy gain and improving performance.

[0035] In this embodiment, without changing the pixel electrode structure, voltage driving mechanism, wiring layout and display control logic of the liquid crystal device, the first phase-type metasurface and the second phase-type metasurface are simply attached to the two sides of the liquid crystal device as external optical layers, or they can be directly attached as an integrated composite layer, which can achieve a complete compatibility upgrade with the existing liquid crystal device supply chain.

[0036] The light field shaping method of this application embodiment achieves precise transfer of dead zone energy to the aperture region by designing a first phase-type metasurface, and performs closed-loop compensation for wavefront distortion generated after the transfer by designing a second phase-type metasurface. Without changing the structure and driving method of the liquid crystal device itself, the first and second phase-type metasurfaces are subsequently arranged on the light-incident and light-out sides of the liquid crystal device to process the light entering and exiting the liquid crystal device. This can improve the aperture utilization rate of the liquid crystal device, reduce the fixed light transmission loss caused by the finite fill factor, increase the light energy passing through the liquid crystal device, and at the same time ensure the quality of the output light field. It avoids the problems of angular spectrum expansion, inter-pixel crosstalk and modulation function distortion introduced by traditional microlens schemes, and can significantly improve the energy efficiency and working stability of various optical systems based on liquid crystal modulators.

[0037] In an optional embodiment of this application, the first construction parameter includes a first phase distribution, the pixel parameter includes a dead half-width, and the first construction parameter for generating the first phase-type metasurface based on the pixel parameter includes determining the first phase distribution based on the dead half-width, wherein the formula for determining the first phase distribution includes: , ; , ; in, For any point within the dead zone The shortest distance from that point to the pixel opening region; For wave number, The operating wavelength; , L1 is the designed spacing between the first phase-type metasurface and the incident surface of the liquid crystal device; s is the phase gradient intensity coefficient; γ is the power exponent parameter; w is the dead zone half-width.

[0038] Specifically, in the embodiments of this application, the first construction parameter includes the first phase distribution of the first metasurface device, which is calculated based on the dead half-width and the above formula.

[0039] The design principle of this formula is to construct a phase function within the pixel dead zone that monotonically decreases with distance from the pixel opening region, ensuring the phase gradient at any position within the dead zone. / When r < 0, the direction of the lateral phase gradient continuously points towards the nearest pixel opening region, thereby causing the incident light to continuously deflect towards the opening region during propagation.

[0040] When r(x,y)=0, that is, the point is located on the boundary of the pixel aperture region, the phase value is set to 0 to ensure that the phase inside the aperture region remains continuous and without additional modulation, so as not to interfere with the modulation function of the liquid crystal device itself.

[0041] The wavenumber k is determined by the operating wavelength λ, which can be selected from the visible, near-infrared, or mid-infrared bands depending on the actual application scenario. The metasurface material can be different depending on the wavelength, such as one or more combinations of silicon, silicon dioxide, silicon nitride, germanium, and titanium dioxide. θ0 is the maximum deflection angle from the first-phase metasurface to the liquid crystal device plane, determined by the dead zone half-width w and the design spacing L1 (the arrangement spacing between the first-phase metasurface and the liquid crystal device). The phase gradient intensity coefficient s is used to control the overall intensity of the phase gradient, and the power exponent parameter γ is used to control the shape of the phase gradient curve as a function of distance. By adjusting these two parameters through parameter scanning, the energy transport efficiency can be optimized, allowing as much dead zone energy as possible to be accurately deflected into the opening region.

[0042] The embodiments of this application achieve directional and efficient transport of pixel dead zone energy by determining the first phase distribution in the above-described specific form. The formula is simple in form, has a small computational load, and can be adapted to liquid crystal pixels of different sizes and fill factors. It has a more significant gain effect on liquid crystal devices with low fill factors and large dead zone ratios, and has strong versatility and practicality.

[0043] In an optional embodiment of this application, the pixel parameters further include a pixel period, and the first construction parameters include a cell period and a current-guiding region; the first construction parameters for generating the first phase-type metasurface based on the pixel parameters further include: Generate the cell period that matches the pixel period.

[0044] Specifically, in this embodiment, the cell period of the first phase-type metasurface is set to be equal to the pixel period of the liquid crystal device.

[0045] The function of the first phase-type metasurface is to direct the energy of the dead zone of each pixel to the aperture region of that pixel itself, thus ensuring that each functional unit of the first phase-type metasurface corresponds one-to-one with a complete pixel of the liquid crystal device. If the unit period does not match, the target aperture region corresponding to the phase gradient will be misaligned with the actual liquid crystal aperture region. The energy that should have entered the aperture region of this pixel will be deflected to adjacent pixels, causing serious inter-pixel crosstalk, which will reduce the light transmission efficiency and system performance.

[0046] Since the function of the first phase-type metasurface is to redirect some of the light energy originally incident on the dead zone of the pixel of the liquid crystal device to the corresponding pixel aperture region, a one-to-one correspondence is established between the functional period of the first phase-type metasurface and the pixel period of the liquid crystal device, and pixel-level alignment is performed to avoid problems such as increased crosstalk, decreased aperture utilization, and deterioration of focal plane spot quality.

[0047] To address this, in one specific embodiment of this application, the first phase-type metasurface and the liquid crystal device employ a pixel-level alignment method combining mechanical coarse positioning, optical marking fine alignment, and optical feedback fine adjustment. Specifically, the alignment process is as follows: 1. Alignment Mark Design. In this embodiment, a first alignment mark group is set around the periphery of the first phase-type metasurface substrate, and a second alignment mark group is set around the periphery of the effective pixel area of ​​the liquid crystal device or the black border area of ​​the encapsulation. Both the first and second alignment mark groups can use cross-shaped marks, concentric square marks, box-in-box marks, or Vernier ruler marks. During layout design, each mark establishes a fixed geometric correspondence with the center of the periodic array of the first phase-type metasurface and the center of the pixel array of the liquid crystal device, thereby enabling the relative offset between the functional area of ​​the first phase-type metasurface and the pixel array of the liquid crystal device to be deduced from the mark positions. In this embodiment, it is preferable to set at least one set of alignment marks near the four corners and center of the device to simultaneously monitor translation and rotation errors and improve the stability and accuracy of large-area alignment.

[0048] 2. Mechanical Coarse Positioning. First, the liquid crystal device is fixed on the translation adjustment platform, and the first phase-type metasurface is fixed on the transparent support substrate or clamping frame. Using mechanical limiting edges, positioning pins, or reference grooves, a preliminary positional relationship is established between the first phase-type metasurface and the liquid crystal device on the geometric boundaries, thus completing coarse positioning. The purpose of coarse positioning is to reduce the relative positional deviation between the two from the millimeter or hundred-micrometer level to tens of micrometers or even smaller, so as to facilitate subsequent microscopic fine-tuning.

[0049] 3. Fine Alignment of Optical Marks. After coarse positioning, the alignment marks of the first phase-type metasurface and the liquid crystal device are simultaneously observed under a microscope or industrial vision system. Fine adjustments are made to the x-axis translation, y-axis translation, and in-plane rotation angle θz of the first phase-type metasurface relative to the liquid crystal device using a micro-displacement stage, gradually aligning the first and second alignment mark groups. In this embodiment, alignment is preferably performed in the following order: first, adjust the x and y-axis translations to make the alignment marks in the central region substantially coincide; then, adjust the in-plane rotation angle θz to simultaneously align the edge or corner alignment marks; finally, finely adjust the center position to eliminate secondary translation errors caused by rotation correction. Through the above process, the periodic array direction of the first phase-type metasurface is kept parallel to the pixel grid direction of the liquid crystal device, establishing a pixel-level correspondence between the two in the plane.

[0050] 4. Optical Feedback Fine-tuning. This embodiment further employs optical feedback for fine-tuning. Specifically, a preset test pattern, such as a uniform transmission pattern, a periodic phase pattern, or a blazed grating test pattern, is loaded onto the liquid crystal device; simultaneously, a collimated beam from a laser source illuminates the combination of the first phase-type metasurface and the liquid crystal device, and the output light field distribution is recorded in the far field or at the lens focal plane using a CCD, CMOS camera, or optical power detector, thereby achieving fine-tuning based on this feedback.

[0051] 5. After pixel-level alignment, the spacing between the first phase-type metasurface and the liquid crystal device is controlled and fixed for encapsulation. In this embodiment, the designed spacing between the first phase-type metasurface and the liquid crystal device is fixed at L1 = 200 μm. To ensure that this spacing remains consistent throughout the entire effective area, a transparent spacer support structure, such as micro-spacer pillars, glass microspheres, transparent support frames, or pre-fabricated thick gaskets, can be provided between the first phase-type metasurface and the liquid crystal device to control the spacing and improve parallelism. After completing pixel-level alignment and optical feedback fine-tuning, the first phase-type metasurface is fixed to the incident side of the liquid crystal device using transparent low-shrinkage optical adhesive, UV-curable adhesive, or a mechanical clamping frame. Preferably, the alignment state is maintained during the fixing process, and the target diffraction order, aperture utilization, or focal plane spot morphology is re-inspected after the adhesive has cured to confirm that the curing process has not introduced significant positional drift.

[0052] The pixel parameters further include the planar positions of the pixel opening region and the pixel dead region, and the first construction parameters include the cell period and the current guiding region; the first construction parameters for generating the first phase-type metasurface based on the pixel parameters further include: Generate the flow guiding region corresponding to the planar positions of the pixel opening region and the pixel dead region.

[0053] In this embodiment, the guiding region refers to the region on the first phase-type metasurface that completely corresponds to the dead zone position of the liquid crystal pixel. The first phase distribution calculated above is applied only in the guiding region, and the zero phase is maintained in the region corresponding to the opening region of the liquid crystal pixel. This design can minimize the modulation of the incident light in the opening region and ensure that the phase modulation and amplitude modulation functions of the liquid crystal device itself are not affected. It is suitable for scenarios with high modulation accuracy requirements, such as phase encoding and spatial light modulation.

[0054] In an optional embodiment of this application, the second construction parameter includes a second phase distribution; the step of generating the second construction parameter of the second phase-type metasurface based on the emitted light field characteristics modulated by the first phase-type metasurface includes: Define the target region in the preset focal plane or Fourier plane; Based on preset constraints, an iterative Fourier transform algorithm is used to repeatedly propagate the light field between the device surface of the second phase-type metasurface and the preset plane and iteratively update the second phase distribution until the preset convergence condition is reached; multi-dimensional evaluation indicators are used to characterize the overall performance of the system.

[0055] In this embodiment, the second phase distribution of the second phase-type metasurface is obtained through phase retrieval or constraint optimization, and solved using the Iterative Fourier Transform (IFTA) algorithm.

[0056] Specifically, in this application embodiment, a target region (ROI) is defined in a preset focal plane or Fourier plane. The target region refers to the area where the subsequent optical system can effectively receive and utilize light energy. Its size and shape are determined by the numerical aperture of the system and the application requirements. For example, in a structured light projection system, the target region is the effective imaging area of ​​the projection surface; in an interferometric measurement system, the target region is the detection surface area of ​​the interferometer.

[0057] The second phase distribution is solved by the Iterative Fourier Transform (IFTA) algorithm. The basic principle of this algorithm is to alternately perform optical field propagation calculations between the device surface of the second phase-type metasurface and the preset focal plane / Fourier plane. Preset constraints are applied to the focal plane, and only the phase information is updated on the device surface. After multiple iterations, the second phase distribution will gradually converge to the optimal solution that can meet the requirements of the target optical field distribution.

[0058] The convergence condition for the iterative process can be set to the number of iterations reaching a preset value, or the similarity between the light field distribution in the target area and the target distribution reaching a preset threshold, or the output change in multiple consecutive iterations being less than a preset value, etc.

[0059] In the iterative parameter optimization process, to comprehensively characterize the performance of the dual metasurface system, the following evaluation indicators can be used as the basis for judgment in the embodiments of this application: Define LCD aperture utilization rate This characterizes the proportion of energy entering the opening region of the liquid crystal device after passing through the first phase-type metasurface for current conduction. Its calculation formula is: ; in The light field at the incident surface of the liquid crystal device. This refers to the light field at the exit surface of the liquid crystal device.

[0060] Define intra-ROI similarity This characterizes the similarity between the system output distribution and the target distribution within the target region of the focal plane, and its calculation formula is: ; in Let I represent the target light intensity distribution, and let I represent the system output light intensity distribution. The summation range is the target region ROI.

[0061] Define global similarity It characterizes the similarity between the system output distribution and the target distribution across the entire focal plane. Its calculation formula is similar to that of the similarity within the ROI, but the summation range is the entire focal plane. This index is more sensitive to peripheral sidelobes and stray energy.

[0062] Define the proportion of external energy in ROI The energy leakage level outside the target area is characterized by the following formula: ; The summation range covers all areas outside the target area, and I represents the total light intensity of the entire focal plane. The smaller this value, the less energy leakage.

[0063] Define the energy percentage within the ROI It characterizes the degree of energy concentration within the target area, and its calculation formula is: .

[0064] During the parameter optimization process, multiple indicators mentioned above are optimized simultaneously. This requires not only maximizing the utilization rate of the LCD aperture, but also ensuring that the main lobe of the focal plane is as close as possible to the target distribution and minimizing energy leakage outside the ROI, so as to achieve a real improvement in the end-to-end available energy of the system.

[0065] The embodiments of this application use an iterative Fourier transform algorithm to solve the phase distribution of the second phase-type metasurface, which can flexibly adapt to different target light field distribution requirements. At the same time, through multi-dimensional system performance evaluation indicators, the light transmission efficiency and output light field quality of the system are fully quantified to ensure that the design results can meet the needs of practical applications.

[0066] In an optional embodiment of this application, the preset constraint conditions include at least one of the following: Within the target area, a target distribution constraint is applied to the output amplitude; the target distribution can be set to a quasi-Gaussian distribution, a flat-top distribution, or other custom distribution according to application requirements. For example, in a machine vision system that requires uniform illumination, a flat-top distribution can be set; in a laser processing system that requires high energy concentration, a quasi-Gaussian distribution can be set.

[0067] Outside the target region, a suppression constraint or a soft penalty constraint is applied to the output amplitude. The suppression constraint forces the optical field amplitude outside the target region to zero, while the soft penalty constraint multiplies the optical field amplitude outside the target region by a penalty coefficient less than 1. This constraint effectively suppresses sidelobes and stray energy, reduces energy leakage outside the target region, and increases energy concentration within the target region.

[0068] In each iteration, the target amplitude is scaled to maintain energy consistency between the iterative target and the current light field. After each iteration, the total energy of the current light field remains consistent with the total energy of the initial light field. By scaling the target amplitude proportionally to match the total energy of the current light field, energy collapse or numerical instability during iteration can be avoided, ensuring stable convergence of the algorithm.

[0069] Within the target region, the target distribution is weighted and mixed with the original output field amplitude. This constraint is suitable for scenarios where it is necessary to preserve the original modulation characteristics of the liquid crystal device as much as possible. By adjusting the weighting coefficients, light field shaping can be achieved while avoiding additional distortion caused by excessive shaping, ensuring that the phase encoding and spatial light modulation functions of the liquid crystal device are not affected. This application embodiment, through multi-dimensional constraint design, can flexibly balance the relationship between energy concentration, sidelobe suppression, and modulation function preservation, enabling the design of the second phase-type metasurface to better adapt to the needs of different application scenarios and improve the system's versatility and applicability.

[0070] According to a second aspect of this application, a light field shaping apparatus is provided, comprising: A first phase-type metasurface is used to be disposed on the incident side of the liquid crystal device, and its first construction parameters are generated according to any of the above-mentioned light field shaping methods; A second phase-type metasurface is provided on the emission side of the liquid crystal device, and its second construction parameters are generated according to any of the above-described light field shaping methods.

[0071] Specifically, both the first phase-type metasurface and the second phase-type metasurface are ultra-thin planar optical elements with a thickness of only a few hundred nanometers. They can be closely fitted to liquid crystal devices or maintain a predetermined distance without significantly increasing the size and weight of the system.

[0072] The first phase-type metasurface is located on the incident side of the liquid crystal device, responsible for deflecting dead-zone energy into the aperture region; the second phase-type metasurface is located on the emitting side of the liquid crystal device, responsible for angular spectrum and wavefront reshaping of the emitted light field. Working together, they achieve the dual goals of improving light transmission efficiency and ensuring light field quality. This device can be directly integrated as a standalone optical component into various liquid crystal modulator-based optical systems.

[0073] The light field shaping device of this application embodiment has a simple structure, small size, and light weight. It does not require changes to the structure and driving method of existing liquid crystal devices and can be directly attached to both sides of the liquid crystal device as an external optical layer, enabling rapid upgrades and modifications to existing systems. It has extremely high engineering application value and promotional significance. Furthermore, the light field shaping device of this application embodiment also has similar technical effects to the aforementioned light field shaping method, which will not be elaborated upon here.

[0074] In an optional embodiment of this application, both the first phase-type metasurface and the second phase-type metasurface are composed of a substrate and a superatomic array arranged on the substrate; the substrate material is selected from at least one of silicon, silicon dioxide, silicon nitride, germanium, and titanium dioxide, and the superatomic structure is selected from at least one of cylinder, ring, and rectangular pillar.

[0075] Specifically, the selection of substrate materials mainly considers the transmittance and refractive index at the working wavelength. For example, in the visible light band, silicon dioxide and silicon nitride have high transmittance and suitable refractive index, making them ideal substrate materials; in the near-infrared and mid-infrared bands, silicon and germanium have higher refractive indices, enabling the realization of more compact superatomic structures.

[0076] Superatoms are the basic building blocks of metasurfaces. Their geometric parameters determine their ability to modulate the phase of incident light. By adjusting the geometric dimensions of superatoms, continuous phase modulation in the range of 0 to 2π can be achieved while maintaining high transmission efficiency.

[0077] The embodiments of this application use a meta-atom array structure to achieve phase modulation, which has the advantages of high modulation efficiency, high phase control accuracy, and compatibility with existing semiconductor processes. It can realize the mass production of high-performance, low-cost metasurface devices and is suitable for large-scale industrial applications.

[0078] According to a third aspect of this application, a light field shaping system is provided, comprising: A light source and collimation assembly are used to output a collimated incident beam; any of the above-mentioned light field shaping devices are disposed on the emission side of the light source and collimation assembly along the light propagation direction. A liquid crystal device is disposed between the first phase-type metasurface and the second phase-type metasurface of the light field shaping device; The lens and focal plane detection assembly is located on the output side of the light field shaping device and is used to receive and record the output light field after it has been processed by the light field shaping device.

[0079] Specifically, the light source and collimation assembly are used to generate a collimated incident beam with high brightness and high uniformity, which can be achieved by using a laser light source, an LED light source, or other coherent / incoherent light source in combination with a collimating lens group.

[0080] The first phase-type metasurface of the light field shaping device performs the first phase modulation on the incident beam, deflecting the dead zone energy into the aperture region of the liquid crystal device; the liquid crystal device modulates the amplitude or phase of the light transmitted through the aperture region, realizing programmable light field control. The second phase-type metasurface modulates the emitted light from the liquid crystal device in a second phase, compensating for wavefront distortion and concentrating energy into the target region. The detection component can specifically be a lens and focal plane detection component, used to focus the modulated light onto the focal plane and detect the light field distribution on the focal plane for system performance testing and calibration.

[0081] The light field shaping system in this application embodiment can be widely used in fields such as programmable amplitude masks, phase modulation, structured light projection, machine vision lighting, and interferometry.

[0082] The light field shaping system of this application has similar technical effects to the light field shaping method and apparatus described above, and will not be described in detail here.

[0083] In one specific embodiment, refer to Figure 2 As shown, the system in this embodiment includes, in sequence along the light propagation direction: a light source and collimation component 1, a first phase-type metasurface 2, a transmissive liquid crystal device 3, a second phase-type metasurface 4, and a lens and focal plane detection component 5.

[0084] The incident light is a collimated Gaussian beam, and the working wavelength is fixed. The distance between the first phase-type metasurface and the incident surface of the liquid crystal device is fixed at... The focal plane is formed by a lens, and the focal length of the lens is fixed. The pixel period of a liquid crystal device is fixed as follows: The fill factor is fixed at FF = 0.58. If the pixel opening is represented as a square opening, then the side length of the opening is: The dead zone half-width is: =4.29μm, meaning the ring area outside the pixel aperture area is considered a dead zone occlusion / absorption area.

[0085] The phase gradient intensity coefficient and power exponent parameters were determined by parameter scanning to be γ=0.6 and s=3, respectively. Based on the aforementioned optical shaping method, the first phase distribution of the first phase-type metasurface and the second phase distribution of the second phase-type metasurface were determined, as detailed below. Figure 3 and Figure 4 As shown.

[0086] To transform the ideal continuous first and second phase distributions into fabricable discrete metasurface structures, this embodiment further establishes a library of superatomic structures operating at a wavelength of 633 nm. The superatomic structures in the library are as follows: Figure 5 As shown, substrate material Medium column material Each superatomic unit in the structure library has a preset combination of geometric parameters: unit period p = 350 nm, cylinder radius 50-120 nm, inner diameter of annulus 30-80 nm, outer diameter of annulus 50-120 nm, side length of rectangular prism 50-320 nm, and superatomic height. To ensure the metasurface has extremely high transmittance, a coating process is applied to the metasurface. The coating material is titanium dioxide, and the thickness is... Each set of geometric parameters is scanned one by one, and the transmission amplitude and phase delay of each superatomic unit at the working wavelength are calculated using full-wave electromagnetic simulation, forming a mapping database of "geometric parameters - transmission amplitude - phase response". The structure library covers the transmission phase range from 0 to 2π, while ensuring that the transmission amplitude is as high as possible and changes smoothly to reduce the additional losses and wavefront errors caused by discrete mapping.

[0087] After obtaining the phase distributions of the ideal phase-type first-phase metasurface and the second-phase metasurface, the device surface is discretized into a superatomic mesh corresponding to the actual fabrication process. For each discrete location in the mesh, its target phase value is read, and the superatomic unit in the structure library that has the transmission phase closest to the target phase and whose transmission amplitude meets a preset threshold condition is selected as the actual structure at that location. This completes the conversion from a continuous phase layout to a discrete superatomic arrangement layout, forming the actual device layouts of the first-phase metasurface and the second-phase metasurface, respectively.

[0088] For regions with large phase errors, local error minimization or neighborhood smoothing constraints can be further introduced to reduce scattering and sidelobe enhancement caused by phase quantization. Since the function of the first phase-type metasurface is to redirect the light energy corresponding to the pixel dead zone of each liquid crystal device pixel unit to the pixel aperture region of that pixel, the phase functional region of the first phase-type metasurface and the pixel period of the liquid crystal device satisfy a one-to-one correspondence. In other words, the cell period of the first phase-type metasurface is preferably consistent with the pixel period of the liquid crystal device, and the guiding region in its layout is strictly registered in planar position with the pixel dead zone and aperture region of the liquid crystal device. This is to avoid the problem that light energy that should be guided to the aperture region of the pixel may be shifted to neighboring pixels due to excessive alignment error, resulting in increased crosstalk, enhanced focal sidelobes, and decreased overall utilization.

[0089] In this embodiment, the first phase-type metasurface and the second phase-type metasurface are aligned with the liquid crystal device at the pixel level, including lateral alignment and angular alignment. Lateral alignment means that the center of the periodic array of the first phase-type metasurface coincides with the center of the pixel array of the liquid crystal device in the x and y directions; angular alignment means that the periodic direction of the first phase-type metasurface is parallel to the pixel grid direction of the liquid crystal device to avoid cumulative misalignment in the row and column directions.

[0090] In this embodiment, simulations are used to calculate the liquid crystal device without the aforementioned first phase-type metasurface and second phase-type metasurface. =0.5900, =0.4968. The system after adding the first-phase metasurface and the second-phase metasurface. , Define the overall available energy ratio of the system. It can be calculated that when the first phase-type metasurface and the second phase-type metasurface are introduced, the available energy of the entire optical system is 1.527 times that of the original liquid crystal device.

[0091] Figure 6 The point spread function (PSF) of the original Gaussian light is shown in the Gaussian light incident system, the PSF with only a liquid crystal device, the PSF with only a first phase-type metasurface, and the PSF with both a first and a second phase-type metasurface. Figure 6 It can be seen that the available light energy increases when only the first phase metasurface is added, and the available light energy increases when both the first and second phase metasurfaces are added, while the far-field spot morphology is restored to an approximately Gaussian distribution. This result shows that adding the first and second phase metasurfaces significantly improves the light energy utilization rate.

[0092] In an optional embodiment of this application, when the system needs to simultaneously support at least two optical field modulation tasks such as focusing and deflection, the step of generating the second construction parameters of the second phase-type metasurface based on the characteristics of the emitted optical field modulated by the first phase-type metasurface further includes: Construct target amplitude functions for multiple target optical field modulation tasks respectively.

[0093] Specifically, for systems that simultaneously support single-focus focusing and multiple-angle beam deflection, a Gaussian target amplitude function with a peak value at the center of the focal plane is constructed for the focusing state, and a Gaussian target amplitude function with a peak value at the theoretical deflection position is constructed for each deflection state. All target amplitude functions are normalized to ensure comparability between different tasks.

[0094] During the iterative update process, the phase distributions of multiple target optical field modulation tasks are weighted and summed.

[0095] During the iteration process, the phase distributions of multiple target optical field modulation tasks are weighted and summed to generate a shared phase-type second phase distribution that supports multiple tasks.

[0096] By using a single second-phase metasurface to simultaneously meet the compensation requirements of multiple tasks, there is no need to design and replace metasurface devices separately for each task, which can significantly reduce system cost and complexity, and reduce system size.

[0097] In an optional embodiment of this application, the formula for determining the weighted sum includes: ; in, The second phase distribution constructed on the second phase-type metasurface during the k-th iteration update; To focus on task weights, The weight for each deflection task is M, where M is the number of deflection tasks. This represents the phase distribution corresponding to the focusing task in the k-th iteration; Let be the phase distribution corresponding to the m-th deflection task in the k-th iteration.

[0098] Specifically, the formula constructs a second phase distribution by weighted summation of the complex optical fields obtained from solving multiple tasks individually.

[0099] Focus on task weight and deflection task weights It can be adjusted according to actual needs. For example, when the system is mainly used for focusing, it can be set to... Greater than This allows for higher energy concentration in the focused state; when the system needs to support multiple deflection tasks in a balanced manner, all settings can be configured. Equal. By adjusting the weighting coefficients, performance trade-offs can be flexibly made between different tasks to meet different application requirements. In this embodiment, the preferred choice is: , This indicates that in joint optimization, the focused state is given higher weight, while multiple deflection states are also taken into account.

[0100] The embodiments of this application achieve efficient solution of multi-task shared phase through the above method. The calculation process is simple and the convergence speed is fast. It can quickly obtain the second phase type metasurface phase distribution that meets the requirements of multiple tasks, while ensuring that the performance of each task can reach the expected level.

[0101] In one specific embodiment, the second phase-type metasurface needs to simultaneously support four tasks: single-focus focusing, beam deflection task one with a discrete period Ng=4, beam deflection task two with a discrete period Ng=6, and beam deflection task three with a discrete period Ng=8. Based on this, the second phase-type metasurface in this embodiment adopts a shared phase design approach, that is, using a single metasurface to meet the compensation requirements of multiple tasks, rather than designing separate second phase-type metasurfaces for each task.

[0102] The goal of focusing missions is to form an approximately Gaussian main peak at the center of the focal plane, while the goal of beam deflection missions is to achieve their respective theoretical deflection positions. A localized main peak is formed nearby, while sidelobes and unwanted energy leakage outside the target region are suppressed as much as possible. A normalized target amplitude function is constructed for each task. and ,in, This represents the Gaussian distribution of the target under focused conditions. This represents the target distribution centered on the target deflection position under the m-th beam deflection state. All of the above target distributions are preferably normalized to maintain comparability between different tasks during numerical iteration, and then the second phase distribution is constructed using the aforementioned weighted summation method during the IFTA iteration process.

[0103] The MS2 obtained in the above embodiment is used to compensate for the angular spectral spread and wavefront distortion introduced by the MS1 diffracting, enabling the system to maintain good focusing and beam deflection performance at the focal plane even with a significant increase in light transmittance. Simulation results show that although the LCD aperture utilization rate is significantly improved after introducing MS1, the focusing quality and target order energy concentration decrease without introducing MS2. After further introducing the shared phase type MS2 designed according to the above method, the focal spot size of the system is reduced, the energy concentration near the focal point is improved, and the target order diffraction efficiency under multiple deflection states is restored to a level close to or slightly higher than that when only the LCD is used.

[0104] Under the parameters used in this embodiment, Figure 7 The paper presents the one-dimensional PSF and full width at half maximum (FWHM) sizes of the original LCD, the LCD with only MS1 added, and the LCD with MS1+MS2. The results demonstrate that the MS1+MS2 dual metasurface system can effectively concentrate the focused light spot and increase its energy in focusing scenarios while improving the effective fill factor. Figure 8 Three different angle deflection scenarios are presented, demonstrating that the dual metasurface system's ability to achieve angle deflection remains unaffected by increasing the effective fill factor. Specifically, the focusing efficiency in the focused state increases from 0.33058 when using only MS1 to 0.46104; in the beam deflection state, , and The target order diffraction efficiencies reached 0.2324, 0.2291, and 0.2408, respectively. Combined with the effect of MS1 on improving light transmittance, it can be explained that the MS2 design method described in this embodiment does not simply increase a single peak value, but rather, based on "more light passing through the LCD," reallocates this additional light energy to the preset focal range and target deflection order, thereby improving the system's end-to-end effective output capability.

[0105] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0106] The embodiments, implementation methods, and related technical features of this application can be combined and substituted for each other without conflict.

[0107] The above are merely preferred embodiments of this application and are not intended to limit this application in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method for shaping an optical field, characterized in that, include: Obtain the pixel parameters of the liquid crystal device; The first construction parameters of the first phase-type metasurface are generated according to the pixel parameters, wherein the first phase-type metasurface is used to be disposed on the incident side of the liquid crystal device to construct a lateral phase gradient toward the pixel opening region in the pixel dead zone, so that the light energy that originally falls into the pixel dead zone is deflected into the adjacent pixel opening region. The second construction parameters of the second phase-type metasurface are generated based on the characteristics of the emitted light field modulated by the first phase-type metasurface. The second phase-type metasurface is used to be disposed on the emission side of the liquid crystal device to perform angular spectrum and wavefront reshaping on the light field emitted by the liquid crystal device. The first construction parameter and the second construction parameter are output to prepare the corresponding metasurface device using the first construction parameter and the second construction parameter.

2. The method according to claim 1, characterized in that, The first construction parameters include a first phase distribution, and the pixel parameters include a dead half-width. The step of generating the first phase-type metasurface based on the pixel parameters includes determining the first phase distribution based on the dead half-width, wherein the formula for determining the first phase distribution includes: ， ； ， ； in, For any point within the dead zone The shortest distance from this point to the pixel opening region; For wave number, The operating wavelength; , L1 is the designed spacing between the first phase-type metasurface and the incident surface of the liquid crystal device; s is the phase gradient intensity coefficient; γ is the power exponent parameter; and w is the dead zone half-width.

3. The method according to claim 2, characterized in that, The pixel parameters also include the pixel period and the planar positions of the pixel opening region and the pixel dead region; the first construction parameters include the cell period and the current guiding region; the first construction parameters for generating the first phase-type metasurface based on the pixel parameters further include: Generate the cell period that matches the pixel period; Generate the flow guiding region corresponding to the planar positions of the pixel opening region and the pixel dead region.

4. The method according to claim 1, characterized in that, The second construction parameters include a second phase distribution; the second construction parameters for generating the second phase-type metasurface based on the emitted light field characteristics modulated by the first phase-type metasurface include: A target region is defined in a preset plane of the second phase-type metasurface, wherein the preset plane includes a focal plane or a Fourier plane; Based on preset constraints, the light field is repeatedly propagated between the device surface of the second phase-type metasurface and the preset plane, and the second phase distribution is iteratively updated until the preset convergence condition is reached.

5. The method according to claim 4, characterized in that, The preset constraints include at least one of the following: Within the target region, a target distribution constraint is applied to the output amplitude; Outside the target region, a suppression constraint or a soft penalty constraint is applied to the output amplitude; In each iteration update, the target amplitude is scale-matched to maintain energy consistency between the iterative target and the current light field; Within the target area, the target distribution is weighted and mixed with the original output field amplitude.

6. The method for shaping the optical field of dual metasurfaces according to claim 4, characterized in that, The second construction parameters for generating the second phase-type metasurface based on the emitted light field characteristics modulated by the first phase-type metasurface further include: Construct target amplitude functions for multiple target optical field modulation tasks respectively; During the iterative update process, the phase distributions of multiple target optical field modulation tasks are weighted and summed to obtain the second phase distribution.

7. The method for shaping the optical field of dual metasurfaces according to claim 6, characterized in that, The target optical field modulation task includes a focusing task and a deflection task; the formula for determining the weighted summation includes: ； in, The second phase distribution constructed on the second phase-type metasurface during the k-th iteration update; To focus on task weights, The weight for each deflection task is M, where M is the number of deflection tasks. This represents the phase distribution of the focusing task in the k-th iteration; Let be the phase distribution of the m-th deflection task in the k-th iteration.

8. A light field shaping device, characterized in that, include: A first phase-type metasurface is provided on the incident side of a liquid crystal device, and its first construction parameters are generated according to the method of any one of claims 1 to 7. A second phase-type metasurface is provided on the emission side of the liquid crystal device, and its second construction parameters are generated according to the method of any one of claims 1 to 7.

9. The apparatus according to claim 8, characterized in that, Both the first phase-type metasurface and the second phase-type metasurface are composed of a substrate and a superatomic array arranged on the substrate; the substrate material is selected from at least one of silicon, silicon dioxide, silicon nitride, germanium, and titanium dioxide, and the superatomic structure is selected from at least one of cylinder, ring, and rectangular pillar.

10. A light field shaping system, characterized in that, include: The light source and collimation assembly are used to output a collimated incident beam; The light field shaping device as described in claim 8 or 9 is disposed on the emission side of the light source and collimation assembly along the light propagation direction; A liquid crystal device is disposed between the first phase-type metasurface and the second phase-type metasurface of the light field shaping device; The detection component is located on the output side of the light field shaping device and is used to receive and record the output light field after it has been processed by the light field shaping device.

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