A diffractive microstructure library management system, method, storage medium and optical element

Abstract

The application discloses a kind of diffractive microstructure library management system, method, storage medium and optical element applied to the field of diffractive optical element design, the transmission amplitude and phase of unit structure under different polarization states are simulated / measured, and polarization sensitivity index is calculated, the structure library index with "exclusive area / turning rule" is established, so that the unit structure that meets can be preferentially selected when generating prescription phase height field, to reduce the phase error and ghost risk caused by polarization, and output the data packet with version number, hash signature and audit field for cross-site replication, by introducing quantitative polarization sensitivity index, and actively screening unit structure that meets polarization sensitivity index meets set threshold in design stage, fundamentally reduce the dependence of diffractive optical element on incident light polarization state, so as to effectively reduce phase error, ghost and image quality degradation.

Description

Technical Field

[0001] This invention relates to the field of diffractive optical element design, and particularly to a diffractive microstructure library management system, method, storage medium, and optical element. Background Technology

[0002] Diffractive prescription lenses utilize micro- and nano-structures (unit structures) to modulate the phase of light waves, achieving refractive correction functions such as myopia, hyperopia, and astigmatism. The core of this technology lies in mapping the target phase distribution as a series of unit structure arrays with specific transmission characteristics.

[0003] In practical applications, the polarization state of incident light is typically uncontrollable and randomly changing. However, many micro / nano unit structures exhibit varying responses to light waves with different polarization states, meaning they possess polarization sensitivity. If a unit structure is polarization sensitive, the following problems arise: for the same target phase point, light waves with different polarization states will experience different effective phase modulations, causing the actual phase distribution to deviate from the design target; simultaneously, differences in transmission amplitude may lead to uneven light energy loss. These factors, in turn, cause problems such as image quality degradation, ghosting, and anomalous dispersion.

[0004] Traditional diffractive lens design methods rely heavily on designers' experience in selecting unit structures, lacking a systematic and large-scale evaluation and screening mechanism. In particular, they lack an engineering method capable of quantitatively assessing and proactively avoiding polarization sensitivity. Furthermore, in engineering practice, certain combinations of structural parameters may become "exclusive zones" due to manufacturing limitations, patent barriers, or other reasons. Existing technologies lack an integrated "bypass rule" to guide designs to automatically avoid these areas, and also lack a mechanism for versioning and traceable management of design data (such as structural libraries). Summary of the Invention

[0005] The core of this invention lies in solving the problems of high polarization sensitivity and lack of systematic management mechanism in the design of diffractive optical elements in the prior art by quantifying polarization sensitivity index and establishing a unit structure library that includes exclusive region management.

[0006] A diffraction microstructure library management system includes: a data acquisition module for acquiring or calculating optical response parameters of unit structures under different linear polarization states, wherein the optical response parameters include at least the transmission complex amplitude for the X-polarization state and the transmission complex amplitude for the Y-polarization state; an index calculation module for calculating the polarization sensitivity index of the unit structures based on the optical response parameters; an index construction module for constructing an index key for the unit structure library based on the target optical parameters and maintaining an exclusive region in the structure parameter space according to predefined rules, wherein unit structures in the exclusive region will be marked or excluded during retrieval; and an output module for encapsulating the unit structure library and its metadata into a data packet for output, wherein the data packet contains at least one of a version identifier, a hash signature, and an audit log field.

[0007] Furthermore, the polarization sensitivity index S_p is defined as the maximum value of the weighted sum of phase difference and amplitude difference over the target wavelength set λ, and its mathematical expression is: S_p=max_{λ∈Λ}(|φ_x-φ_y|+α·||t_x|-|t_y||) ); Here, α is a weighting coefficient used to balance the contributions of phase difference and amplitude difference to polarization sensitivity. When the polarization sensitivity index S_p is less than or equal to the preset threshold τ_p, the unit structure is determined to meet the polarization insensitivity requirement.

[0008] A method for generating microstructures of diffractive prescription lenses using the above system specifically includes the following steps: Step S1: Input the target phase distribution; Step S2: Based on the target phase and wavelength, search the unit structure library using the index key to obtain a set of candidate unit structures; Step S3: For each unit structure in the candidate unit structure set, obtain its polarization sensitivity index; Step S4: Filter the candidate unit structure set, filter the structures whose polarization sensitivity index meets the set threshold, and form a polarization-insensitive candidate subset; Step S5: Select the final cell structure from the polarization-insensitive candidate subset according to the preset optimization objective. The optimization objective includes optimizing at least one of phase error and process tolerance. Step S6: During the retrieval or filtering process, when the retrieved or filtered unit structure falls into the exclusive area, a detour rule is triggered. The detour rule includes redefining the retrieval parameters, jumping to an alternative index path, or marking the area as an area to be avoided. Step S7: Based on the result selected in step S5, generate a microstructure layout file corresponding to the target phase distribution and the corresponding structural parameter package.

[0009] A diffractive prescription optical element, wherein the microstructure within its optically effective region is composed of unit structures from the unit structure library constructed according to claim 1, and all unit structures constituting the microstructure satisfy its polarization sensitivity index.

[0010] A computer-readable storage medium having a computer program stored thereon, characterized in that the computer program, when executed by a processor, implements the method described above for generating microstructures of diffractive prescription lenses.

[0011] Compared with the prior art, the advantages of this invention are: (1) This scheme introduces a quantified polarization sensitivity index and actively selects unit structures that meet the set threshold of the polarization sensitivity index during the design stage, thereby fundamentally reducing the dependence of diffractive optical elements on the polarization state of incident light, thus effectively reducing phase error, ghosting and image quality degradation.

[0012] (2) By maintaining exclusive areas and detour rules, structural parameter areas that are not suitable for use due to process or performance reasons can be automatically avoided, which improves the compliance and manufacturability of the design. By managing the structure library and design output through version number, hash signature and audit log, the consistency, integrity and traceability of design data are ensured, which facilitates team collaboration and knowledge accumulation. Attached Figure Description

[0013] Figure 1 This is a flowchart of the polarization-insensitive selection generation method of the present invention; Figure 2 This is a schematic diagram of the parameterized unit structure of the present invention; Figure 3 This is a schematic diagram of the data structure and index of the unit structure library of this invention; Figure 4 This is a schematic diagram illustrating how the polarization sensitivity index of this invention varies with structural parameters; Figure 5 These are example diagrams illustrating the shapes of several typical unit structures of this invention; Figure 6 This is a schematic diagram illustrating how the present invention achieves polarization insensitivity through orthogonal or rotating unit pairing; Figure 7 This is a schematic diagram of the mapping from the target phase to the cell index in this invention; Figure 8 This is a schematic diagram of the exclusive zone and bypass rules of the present invention; Figure 9 This is a comparison curve of the additional phase error under different polarization angles of the present invention; Figure 10 This is a schematic diagram illustrating the relationship between the data package, version, and deterministic derivation of this invention. Detailed Implementation

[0014] The technical solutions will now be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention.

[0015] First implementation method: Please see Figures 1-10 A diffraction microstructure library management system, comprising: The data acquisition module is used to acquire or calculate the optical response parameters (t_x, t_y, φ_x, φ_y) of the unit structure under different linear polarization states. The optical response parameters include at least the transmission complex amplitude (t_x, φ_x) for the X-polarization state and the transmission complex amplitude (t_y, φ_y) for the Y-polarization state; t_x and t_y represent the transmission amplitude of the unit structure for the X and Y polarization states, respectively; φ_x and φ_y represent the corresponding phases, respectively. The index calculation module is used to calculate the polarization sensitivity index S_p of the unit structure based on the optical response parameters; the index construction module is used to construct the index key of the unit structure library with the target optical parameters, and maintain the exclusive region Ω_{ex} in the structure parameter space according to predefined rules. The output module is used to encapsulate the unit structure library and its metadata into a data packet for output. The data packet contains at least one of the following fields: version identifier, hash signature, and audit log field.

[0016] When constructing a specific diffraction microstructure library as described above: First, define the parameter space of the unit structure. For example, for a rectangular nanopillar unit, its parameters may include period p, width w, height h, rotation angle θ, etc. Figure 1 As shown; Within the limits of the technology, the parameter space is discretized and sampled into a grid. For each parameter combination (p,w,h,θ), electromagnetic simulation tools such as rigorous RCWA (frequency domain algorithm for solving the electromagnetic response of periodic micro-nano structures) and FDTD (numerical algorithm for solving the time-domain evolution of electromagnetic fields) are used, or actual measurements are taken, to calculate the transmission complex amplitudes of linearly polarized light in the X and Y directions at the target wavelength λ (or wavelength set λ), which are denoted as (t_x,φ_x) and (t_y,φ_y) respectively. Next, the polarization sensitivity index S_p of the unit structure is calculated according to the formula S_p=max_{λ∈Λ}(|φ_x-φ_y|+α·||t_x|-|t_y||), where λ is the target wavelength set and α is the weighting coefficient. At the same time, other optical performance parameters such as its average transmission efficiency and phase value φ_{avg} (e.g., (φ_x+φ_y) / 2) can be calculated. Then, database records are created. Each record uses a combination of optical performance parameters (such as target phase φ_{target}, wavelength λ, and substrate refractive index n) as its index key. Under the same index key, multiple combinations of unit structure parameters that meet the optical performance requirements are associated with their corresponding attributes such as S_p and efficiency, for example... Figure 2 As shown; When building the index, exclusive regions Ω_{ex} need to be predefined. Exclusive regions can be regions with known patent protection, extremely low process yields, or extremely high S_p values ​​within the parameter space. These regions are marked as "disabled" or "de-weighted" in the index, such as... Figure 8 As shown; Finally, the complete library data, indexes, and exclusive zone rules are packaged, assigned a version number (e.g., V1.0), a hash digest (e.g., SHA-256) of the data packet is calculated, and audit logs such as build time and creator are added to form a distributable data packet, such as... Figure 10 As shown.

[0017] Second implementation method: In this embodiment, a microstructure library for diffraction prescription lenses is constructed using the first implementation method of the diffraction microstructure library management system. Taking the rectangular nanopillar unit as an example, its parameter vector is denoted as (p,w,h,θ,n,λ), and it is discretely sampled in the parameter space shown in Table 1 below.

[0018] Table 1 Parameter Space

[0019] For each parameter combination, the transmission complex amplitude under X and Y linear polarization is calculated using RCWA. If necessary, FDTD is used to cross-check typical candidate structures. The polarization sensitivity index is calculated as S_p=max_{λ∈Λ}(|φ_x-φ_y|+α·||t_x|-|t_y||); in this embodiment, α is taken as 0.35, and the screening threshold τ_p is taken as 0.12.

[0020] The exclusive region Ω_ex consists of three categories of rules: first, unmanufacturable regions with a minimum gap of less than 70 nm; second, regions with an aspect ratio greater than 4.5 that significantly reduces process yield; and third, regions with a polarization sensitivity S_p higher than 0.12. The system records the exclusive region as "disabled" or "de-weighted" and writes it into the structure library version V1.3.2.

[0021] The third implementation method: Reference Figure 4 This embodiment provides a method for generating microstructures of diffractive prescription lenses using the system of the first embodiment, specifically including the following steps: Step S1: Input the target phase distribution φ^(x,y,λ) to be achieved, which is calculated by existing optical design software based on the refractive correction prescription; for each design point (or pixel) on the lens surface, execute step S2; Step S2: Based on the target phase φ^ and wavelength λ, a search is performed in the unit structure library using the index key to obtain a candidate unit structure set K: K={k_1,k_2,...,k_m}. These unit structures can approximately realize the target phase. The unit structures include composite unit structures formed by rotation pairing, used to reduce the phase response difference |φ_x-φ_y| between the X-polarized and Y-polarized states of the unit structure. Rotation pairing includes structure pairs formed by rotating the basic structure by 0° and 90° respectively. For specific unit structures, please refer to [link to relevant documentation]. Figure 5 For example: cross structure, ring structure and square hole structure; Step S3: For each unit structure k in the candidate unit structure set K, obtain its polarization sensitivity index S_{p,k}; Step S4: Filter the candidate unit structure set K, filter the unit structures whose polarization sensitivity index satisfies the set threshold S_{p,k}≤τ_p, and form a polarization-insensitive candidate subset, where τ_p is the preset threshold used to filter polarization-insensitive candidate structures.

[0022] Step S5: Select the final unit structure from the polarization-insensitive candidate subset according to the preset optimization objective. The optimal structure is selected by solving an optimization problem. The optimization objective includes at least one of the following: optimizing the phase error |φ_k-φ^*| and the process tolerance tolerance Tol_k. Step S6: If, during the retrieval or filtering process, a cell structure that has been retrieved or filtered falls into the exclusive region Ω_{ex}, a detour rule is triggered. The detour rule includes redefining the retrieval parameters, jumping to an alternative index path, or marking the region as a region to be avoided. For example, the system can automatically select a structure with a suboptimal cost function but not in the exclusive region, or record the event and prompt the designer.

[0023] Step S7: Based on the result selected in step S5, generate a microstructure layout file corresponding to the target phase distribution and a corresponding structure parameter package; when generating the structure parameter package, generate a structure index map, the structure index map representing the identifier of the unit structure selected at each position on the lens surface in the library. The structure index map is used to record the final structure ID used at each position on the lens surface.

[0024] The diffractive optical element generated by the above method has a microstructure composed of a large number of units satisfying S_p≤τ_p, such as Figure 9As shown, within a polarization angle range of 0° to 90°, its phase error remains consistently lower than that of conventional designs, demonstrating excellent polarization insensitivity. This component enables the design of ultra-thin lenses with an aperture no greater than 50mm and a total thickness of less than 1mm.

[0025] This embodiment also provides a specific means of further reducing polarization sensitivity through unit structure pairing.

[0026] See Figure 6 For a target phase point, it is possible to use two or more unit structures to achieve it. An effective pairing method is to use a pair of identical basic structures with a rotation angle difference of 90° (e.g., one θ=0°, the other θ=90°).

[0027] Due to rotational symmetry, the responses of these two structures to X and Y polarizations are interchangeable. By interleaving these two structures on a subwavelength scale or by area-weighted mixing, the combined equivalent structure can be made to have a more consistent response to X and Y polarizations, thereby significantly reducing the |φ_x-φ_y| term and consequently reducing the overall S_p value.

[0028] When building the structure library, such paired structures can be modeled and their performance calculated as a special "composite unit," and then included in the library. In the selection generation method, such composite units will participate in the optimization selection as one of the candidates.

[0029] Fourth implementation method: This embodiment uses the system of the first implementation method and the method of the third implementation method to realize the generation of microstructure layouts based on structure libraries. The specific operations include: Input the target phase distribution φ*(x,y,λ) of a 25mm diameter diffraction prescription lens. Within the effective aperture, sample according to a 256×256 grid. For each sampling point, the system first performs a nearest neighbor search in the structure library based on the target phase value and the working wavelength to obtain the candidate unit structure set K.

[0030] For structure k in the candidate set, the system reads its S_p, average transmission efficiency, and process tolerance Tol_k, and performs a comprehensive evaluation according to J_k=||φ_k-φ*||²+γS_{p,k}+ηTol_k, where γ=0.50 and η=0.25. If a candidate structure falls into the exclusive region, a detour rule is triggered: adjacent phase buckets are searched again first; if no structure meets the conditions, the suboptimal structure that does not fall into the exclusive region is selected and a marker to be avoided is recorded.

[0031] Finally, the system outputs the GDSII layout, structure index diagram, and parameter data package (see...). Figure 10In this embodiment, the tie-break rule is set as follows: when the difference in cost functions among multiple candidate structures is less than 1×10⁻ 6 When multiple candidate structures have the same or similar cost functions, the structure with the smallest ID, the smallest rotation angle, and the smallest width w are selected in that order. This rule is used to ensure the determinism of the derived result when multiple candidate structures have the same or similar cost functions. The derived GDSII pattern was used to fabricate a diffraction prescription optical element sample on a transparent substrate using general micro / nano fabrication processes. The sample had an aperture of 25 mm and a total thickness of 0.85 mm. The sample was scanned at 550 nm with polarization angles from 0° to 90° to calculate and measure the additional phase error. The results of the additional phase error obtained from the polarization angle scan at 550 nm are available in [reference needed]. Figure 9 One curve corresponds to the conventional selection control group, and the other curve corresponds to the structure library selection results based on S_p constraints. For some target phase points, the system can combine a pair of basic structures with 90° oriented differences into a composite unit and arrange them alternately within the subwavelength scale. Taking a target phase barrel as an example, the S_p of the basic structure is 0.18 when used alone; after being rotated and paired by 0° / 90° and combined at a 1:1 area ratio, the S_p of the equivalent composite unit drops to 0.07.

[0032] During the search for candidate structures, the aforementioned composite unit is selected as one of the candidates for optimization. If its process tolerance and structural spacing meet the constraints, it can be given priority to further reduce polarization sensitivity.

[0033] The above description is merely a preferred embodiment of the present invention; it encompasses all the protection scope of the present invention. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in the present invention, based on the technical solutions and improved concepts of the present invention, should be covered within the protection scope of the present invention.

Claims

1. A diffraction microstructure library management system, characterized in that, include: The data acquisition module is used to acquire or calculate the optical response parameters (t_x, t_y, φ_x, φ_y) of the unit structure under different linear polarization states. The optical response parameters include at least the transmission complex amplitude (t_x, φ_x) for the X polarization state and the transmission complex amplitude (t_y, φ_y) for the Y polarization state. The index calculation module is used to calculate the polarization sensitivity index S_p of the unit structure based on the optical response parameters; the index construction module is used to construct the index key of the unit structure library with the target optical parameters, and maintain the exclusive region Ω_{ex} in the structure parameter space according to predefined rules. The output module is used to encapsulate the unit structure library and its metadata into a data packet for output. The data packet contains at least one of the following fields: version identifier, hash signature, and audit log field.

2. The system according to claim 1, characterized in that, The polarization sensitivity index S_p is determined by the following formula: S_p=max_{λ∈Λ}(|φ_x-φ_y|+α·||t_x|-|t_y||), where λ is the target wavelength set and α is the weighting coefficient.

3. The system according to claim 1, characterized in that, In the index building module, the index key contains at least the target phase value and the operating wavelength.

4. The system according to claim 1, characterized in that, The exclusive region is a subset of the parameter space defined based on at least one of the following: patent protection scope, manufacturing process constraints, or polarization sensitivity index.

5. The system according to claim 1, characterized in that, The hash signature generated by the output module is a cryptographic hash digest calculated based on the content of the data packet.

6. The system according to claim 1, characterized in that, The audit log fields include at least one of the following: packet creation time, creator identifier, and modification history.

7. The system according to claim 1, characterized in that, The system supports versioned management of the unit structure library and supports rolling back to historical versions.

8. A method for generating microstructures of diffractive prescription lenses using the system according to any one of claims 1-7, characterized in that, Specifically, the following steps are included: Step S1: Input the target phase distribution; Step S2: Based on the target phase and wavelength, search the unit structure library using the index key to obtain a set of candidate unit structures; Step S3: For each unit structure in the candidate unit structure set, obtain its polarization sensitivity index; Step S4: Filter the candidate unit structure set, and select structures that meet the set threshold to form a polarization-insensitive candidate subset; Step S5: Select the final cell structure from the polarization-insensitive candidate subset according to the preset optimization objective. The optimization objective includes at least one of phase error and process tolerance. Step S6: During the retrieval or filtering process, when the retrieved or filtered unit structure falls into the exclusive area, a detour rule is triggered. The detour rule includes redefining the retrieval parameters, jumping to an alternative index path, or marking the area as an area to be avoided. Step S7: Based on the result selected in step S5, generate a microstructure layout file corresponding to the target phase distribution and a corresponding structural parameter package.

9. The method according to claim 8, characterized in that, During the retrieval or filtering process, if the unit structure involved falls into the exclusion zone, a detour rule is executed, which includes re-retrieval, selection of alternative structures, or marking.

10. The method according to claim 8, characterized in that, In the step of determining the final selected unit structure, the selection is made by an optimization algorithm. The objective function of the optimization algorithm considers at least two of the following: phase matching error, polarization sensitivity index, and process tolerance.

11. The method according to claim 8, characterized in that, The step of retrieving the candidate unit structure set adopts the nearest neighbor search algorithm.

12. The method according to claim 8, characterized in that, The unit structure includes a composite unit structure formed by rotational pairing, which is used to reduce the phase response difference |φ_x-φ_y| between the X-polarized state and the Y-polarized state of the unit structure.

13. The method according to claim 8, characterized in that, The rotation pairing includes structural pairs formed by rotating the base structure by 0° and 90° respectively.

14. The method according to claim 8, characterized in that, The generated microstructure layout is a GDSII format or bitmap format file.

15. The method according to claim 8, characterized in that, In S7, when generating the structural parameter package, a structural index map is generated. The structural index map represents the identifier of the unit structure selected at each position on the lens surface in the library.

16. A diffractive prescription optical element, characterized in that, The microstructure within its optically effective region is composed of unit structures from the unit structure library constructed according to any one of claims 1-7, and the unit structures that make up the microstructure all satisfy their polarization sensitivity index S_p≤τ_p, where τ_p is a preset threshold.

17. The optical element according to claim 16, characterized in that, The aperture of the optical element is no greater than 50 mm.

18. The optical element according to claim 16, characterized in that, The total thickness of the optical element is less than 1 mm.

19. The optical element according to claim 16, characterized in that, Within the range of incident light polarization angle from 0° to 90°, the additional phase error caused by polarization at each point within the effective area of ​​the optical element is less than the preset image quality error threshold.

20. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the method as described in any one of claims 8-15.

21. The storage medium according to claim 20, characterized in that, When the computer program is executed by the processor, it can deterministically derive the same microstructure generation results based on the same input conditions and the same version of the structure library.

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