Optical diffuser and method of designing the same

Abstract

The application relates to an optical diffusion sheet and a design method thereof, and relates to the technical field of optics. The optical diffusion sheet comprises a substrate and a microlens array arranged on the substrate; the microlens array comprises a plurality of seamless spliced sub-zones, each of the sub-zones comprises at least one microlens, and when the sub-zone comprises more than one microlens, two adjacent microlenses are seamlessly spliced; wherein the sub-zones at least comprise a first sub-zone and a second sub-zone, and the ratio of the first diameter of the first sub-zone to the first diameter of the second sub-zone is between 0.1 and 0.85, the first diameter is the average diameter of the circumscribed circle of all microlenses in the corresponding sub-zone, the first sub-zone is the sub-zone with the smallest first diameter in the microlens array, and the second sub-zone is the sub-zone with the largest first diameter in the microlens array. The optical diffusion sheet can effectively eliminate diffraction fringes and improve the uniformity of a light spot.

Description

Technical Field

[0001] This invention relates to the field of optical technology, and more specifically, to an optical diffuser and its design method. Background Technology

[0002] Optical diffusers are common beam shaping devices. The emitted light from a light source or optical system often needs to be homogenized and shaped by an optical diffuser before it can be fully utilized. Common optical diffusers include Gaussian diffusers (such as frosted glass), diffractive optical elements (DOEs), and microlens arrays (MLAs). Among them, Gaussian diffusers produce a Gaussian intensity distribution in the diffused spot. Although they are simple to manufacture, they have poor beam shaping freedom, and their optical uniformity and efficiency are not ideal. In contrast, DOEs and MLAs are two types of diffusers with superior performance. They can concentrate the energy of the beam within a given divergence angle and achieve a given intensity distribution, and are therefore widely used.

[0003] Among optical optical elements (DOEs), beam shaping is more flexible, theoretically capable of achieving beams of arbitrary shapes or distributions. However, it is more sensitive to manufacturing errors and is typically only suitable for single wavelengths. Furthermore, due to higher-order diffraction, DOEs have relatively low efficiency. Compared to DOEs, microlenses (MLAs) have attracted significant attention due to their lower manufacturing precision requirements, suitability for broadband light, and higher efficiency. However, regular MLAs exhibit strong diffraction effects, producing noticeable diffraction fringes in the emitted beam, affecting uniformity and thus reducing the imaging quality of the optical system. To improve diffraction fringes, existing technologies have proposed random microlens arrays (RMLAs), which utilize the non-periodicity of their structure to effectively eliminate diffraction fringes. However, current RMLAs still do not achieve ideal results in eliminating diffraction fringes, and the uniformity of the diffused beam needs further improvement. Summary of the Invention

[0004] The purpose of this invention is to provide an optical diffuser and its design method, which can effectively eliminate diffraction fringes and improve the uniformity of the light spot.

[0005] The embodiments of the present invention are implemented as follows:

[0006] In one aspect, the present invention provides an optical diffuser, comprising a substrate and a microlens array disposed on the substrate; the microlens array comprises a plurality of interconnected partitions, each partition comprising at least one microlens, and when a partition comprises more than one microlens, adjacent microlenses are seamlessly joined; wherein the partition comprises at least a first partition and a second partition, and the ratio of the first diameter of the first partition to the first diameter of the second partition is between 0.1 and 0.85, the first diameter being the average diameter of the circumcircle of all microlenses in the corresponding partition, the first partition being the partition with the smallest first diameter in the microlens array, and the second partition being the partition with the largest first diameter in the microlens array. This optical diffuser can effectively eliminate diffraction fringes and improve the uniformity of the light spot.

[0007] Optionally, the first partition includes multiple partitions spaced apart, and the second partition includes one partition, which is located at the intervals between the multiple first partitions.

[0008] Optionally, the second partition includes a plurality of spaced-apart partitions, and the optical diffuser also includes a plurality of third partitions respectively surrounding the periphery of the plurality of second partitions. The first partition includes one partition and is disposed at the gap between the plurality of third partitions. The first diameter of the third partition is greater than the first diameter of the first partition and smaller than the first diameter of the second partition.

[0009] Optionally, the boundaries of the microlens are random-shaped polygons, and the size and surface shape of the microlens are random.

[0010] Optionally, the substrate material and the microlens array material are any one of glass, resin and plastic, respectively.

[0011] Optionally, the refractive index of the substrate and / or the refractive index of the microlens array are between 1.1 and 5.0.

[0012] Optionally, the optical diffuser also includes a capping layer located on the side of the microlens array away from the substrate. The capping layer is made of any one of glass, resin, and plastic, and the absolute value of the difference between the refractive index of the capping layer and the refractive index of the microlens array is greater than 0.1.

[0013] Optionally, the optical diffuser may further include a silver or aluminum reflective layer, which may be deposited on either the substrate or the microlens array.

[0014] Optionally, the surface shape of the microlens is a freeform surface, and the surface shape of the microlens satisfies the following height formula:

[0015]

[0016] in, c is the radius of curvature, K is the conic coefficient, and A iare the coefficients of the polynomial, where m and n are both integers, both m and n are greater than or equal to 0, and 1≤m+n≤20.

[0017] In another aspect, the present invention provides a design method for an optical diffuser, the method comprising: dividing a design area of ​​a substrate into multiple design units of the same size; randomly dividing each design unit so that each design unit contains at least one design block; irregularizing the boundary of each design block so that the boundary of each design block is polygonal; optimizing the surface shape of each design block according to the incident parameters of the incident light and the parameters of the outgoing light spot, and obtaining multiple microlenses according to the surface shape of each design block and the boundary of the corresponding design block, wherein adjacent microlenses are seamlessly spliced ​​together; wherein microlenses in different regions are respectively clustered to form multiple partitions, and multiple partitions are seamlessly spliced ​​together to form a microlens array; and placing the microlens array on a substrate to obtain an optical diffuser, wherein the ratio of the first diameter of the first partition and the first diameter of the second partition of the microlens array is between 0.1 and 0.85, the first diameter is the average diameter of the circumcircle of all microlenses in the corresponding partition, the first partition is the partition with the smallest first diameter in the microlens array, and the second partition is the partition with the largest first diameter in the microlens array.

[0018] The beneficial effects of this invention include:

[0019] The optical diffuser provided in this application includes a substrate and a microlens array disposed on the substrate. The microlens array includes multiple interconnected partitions, each partition including at least one microlens, and when a partition includes more than one microlens, adjacent microlenses are seamlessly joined. Each partition includes at least a first partition and a second partition, and the ratio of the first diameter of the first partition to the first diameter of the second partition is between 0.1 and 0.85. The first diameter is the average diameter of the circumcircle of all microlenses in the corresponding partition. The first partition is the partition with the smallest first diameter in the microlens array, and the second partition is the partition with the largest first diameter in the microlens array. By arranging the microlens array of the optical diffuser in the above form and setting the ratio of the first diameter of the first partition to the first diameter of the second partition between 0.1 and 0.85, this application, through the regional alternating distribution of microlenses of varying sizes, can further increase the randomness of the structure. Through the mutual cancellation of diffraction fringes between large and small lenses, it can significantly improve the diffraction fringes of the light spot and enhance the uniformity of the diffused light spot compared to existing technologies. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is one of the structural schematic diagrams of the optical diffuser provided in the embodiments of the present invention;

[0022] Figure 2 This is one of the structural schematic diagrams of a microlens array provided in an embodiment of the present invention;

[0023] Figure 3 This is a second schematic diagram of the structure of the microlens array provided in an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of the structure of a microlens array provided for the prior art;

[0025] Figure 5 for Figure 4 The distribution of the emitted light spot of the provided microlens array under 940nm wavelength laser irradiation;

[0026] Figure 6 This is the third schematic diagram of the structure of the microlens array provided in the embodiment of the present invention;

[0027] Figure 7 for Figure 6 The distribution of the emitted light spot of the provided microlens array under 940nm wavelength laser irradiation;

[0028] Figure 8 This is a second schematic diagram of the structure of the optical diffuser provided in an embodiment of the present invention;

[0029] Figure 9 A flowchart illustrating the design method of the optical diffuser provided in an embodiment of the present invention;

[0030] Figure 10 This is one of the schematic diagrams illustrating the design process of an optical diffuser provided in an embodiment of the present invention;

[0031] Figure 11 A schematic diagram of boundary irregularities provided for an embodiment of the present invention;

[0032] Figure 12 This is the second schematic diagram illustrating the design process of the optical diffuser provided in an embodiment of the present invention.

[0033] Icons: 10-substrate; 20-microlens array; 21-section; 211-first section; 212-second section; 213-third section; 216-microlens; 30-capsule. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0037] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0038] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0039] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0040] Please refer to Figures 1 to 3 This embodiment provides an optical diffuser, which includes a substrate 10 and a microlens array 20 disposed on the substrate 10. The microlens array 20 includes a plurality of seamlessly joined partitions 21, each partition 21 including at least one microlens 216, and when a partition 21 includes more than one microlens 216, adjacent microlenses 216 are seamlessly joined. Each partition 21 includes at least a first partition 211 and a second partition 212, and the ratio of the first diameter of the first partition 211 to the first diameter of the second partition 212 is between 0.1 and 0.85. The first diameter is the average diameter of the circumcircle of all microlenses 216 in the corresponding partition 21. The first partition 211 is the partition 21 with the smallest first diameter in the microlens array 20, and the second partition 212 is the partition 21 with the largest first diameter in the microlens array 20. This optical diffuser can effectively eliminate diffraction fringes and improve the uniformity of the light spot.

[0041] The materials of the substrate 10 and the microlens array 20 can be any one of glass, resin and plastic.

[0042] Optionally, the refractive index of the substrate 10 and / or the refractive index of the microlens array 20 can be between 1.1 and 5.0. Exemplarily, the refractive index of the substrate 10 and the refractive index of the microlens array 20 can be 1.1, 1.2, 1.5, 1.8, 2.0, 2.2, 2.5, 3.0, 4.0, or 5.0, etc., and will not be listed in this application.

[0043] The microlens array 20 includes multiple partitions 21, which are seamlessly connected. Each partition 21 includes one or more microlenses 216. When a partition 21 includes two or more microlenses 216, adjacent microlenses 216 should be seamlessly connected.

[0044] Furthermore, in this embodiment, partition 21 includes at least a first partition 211 and a second partition 212, and the ratio of the first diameter of the first partition 211 to the first diameter of the second partition 212 is between 0.1 and 0.85, wherein the first diameter is the average diameter of the circumcircle of all microlenses 216 in the partition 21. The first partition 211 is the partition 21 with the smallest first diameter in the microlens array 20, and the second partition 212 is the partition 21 with the largest first diameter in the microlens array 20. That is, in the microlens array 20, there exists a partition 21 with the largest first diameter and another partition 21 with the smallest first diameter, and the ratio of the smallest first diameter to the largest first diameter is between 0.1 and 0.85.

[0045] Furthermore, in this embodiment, the first diameters of two adjacent partitions 21 are different. Alternatively, the first diameters of two adjacent partitions 21 may be different, and in the two adjacent partitions 21, the circumcircle diameter of any microlens 216 in the partition 21 with the larger first diameter is larger than the circumcircle diameter of all microlenses 216 in the other partition 21 (of course, this is merely an example provided in this application and is not a limitation thereof). In this embodiment, in two adjacent partitions 21, generally smaller microlenses 216 are clustered into one partition 21, and generally larger microlenses 216 are clustered into another partition 21. Thus, the optical diffuser provided in this application is composed of smaller microlenses 216 clustered into one or more partitions 21, and larger microlenses 216 are also clustered into one or more partitions 21. Thus, by distributing microlenses 216 of varying sizes in alternating regions, this application can further increase the randomness of the structure. Through the mutual cancellation of diffraction fringes between larger and smaller microlenses 216, compared to a typical RMLA, it can significantly improve the diffraction fringes of the light spot and enhance the uniformity of the diffused light spot.

[0046] Please refer to Figure 4 and Figure 5 , Figure 4 It is a top view of the RMLA provided by existing technology. Figure 5 for Figure 4 The provided diagram shows the distribution of the emitted light spot of the RMLA under 940nm wavelength laser irradiation; Figure 6 This is a top view of the RMLA provided in this application. Figure 7 yes Figure 6The provided diagram shows the distribution of the emitted light spot of the RMLA under 940nm wavelength laser irradiation. It can be seen that the existing optical diffuser (which is simply a seamless splicing of multiple randomly distributed microlenses 216) has a divergence angle of approximately 60°×60°, which is relatively uniform overall, but slight horizontal and vertical stripes can still be observed. In contrast, the optical diffuser provided in this application (the microlens array 20 of this optical diffuser includes two sections 21, each with randomly sized and shaped microlenses 216; however, the diameter of the microlenses 216 in one section 21 is generally larger, with an average diameter (i.e., the first diameter) of 35µm, while the diameter of the microlenses 216 in the other section 21 is generally smaller, with an average diameter (i.e., the first diameter) of 20µm) also appears relatively uniform under 940nm wavelength laser irradiation, but compared to... Figure 5 The horizontal and vertical stripes have been significantly improved, and the overall light spot is more uniform.

[0047] Generally speaking, the smaller the particle diameter of microlens 216, the more pronounced the diffraction tends to be. (Comparison) Figure 4 and Figure 6 , Figure 6 The structure is equivalent to in Figure 4 Based on the existing technology, microlenses 216 with smaller particle diameters are introduced, but the emitted light spot is more uniform. Therefore, it can be strongly demonstrated that the optical diffuser provided in this application can indeed effectively improve diffraction fringes.

[0048] In summary, the optical diffuser provided in this application includes a substrate 10 and a microlens array 20 disposed on the substrate 10. The microlens array 20 includes a plurality of interconnected partitions 21, each partition 21 including at least one microlens 216, and when a partition 21 includes more than one microlens 216, two adjacent microlenses 216 are seamlessly connected. The partition 21 includes at least a first partition 211 and a second partition 212, and the ratio of the first diameter of the first partition 211 to the first diameter of the second partition 212 is between 0.1 and 0.85. The first diameter is the average diameter of the circumcircle of all microlenses 216 in the corresponding partition 21. The first partition 211 is the partition 21 with the smallest first diameter in the microlens array 20, and the second partition 212 is the partition 21 with the largest first diameter in the microlens array 20. This application sets the microlens array 20 of the optical diffuser in the above form, and sets the ratio of the first diameter of the first partition 211 and the first diameter of the second partition 212 to between 0.1 and 0.85. In this way, by distributing the microlenses 216 of different sizes in different regions, this application can further increase the randomness of the structure. By canceling out the diffraction fringes of the large and small lenses, the diffraction fringes of the light spot can be significantly improved compared with the prior art, and the uniformity of the diffused light spot can be enhanced.

[0049] Optionally, the microlenses 216 in the aforementioned partition 21 can be any one or more of convex lenses or concave lenses. That is, the microlenses 216 in each partition 21 can all be convex lenses, all be concave lenses, or may contain both convex and concave lenses simultaneously.

[0050] Please refer to Figure 2 In one feasible embodiment, the first partition 211 includes a plurality of partitions spaced apart, the second partition 212 includes one partition, and the second partition 212 is disposed at the gap between the plurality of first partitions 211.

[0051] exist Figure 2 In this design, the first partition 211 comprises three parts, each of which is composed of a plurality of relatively small microlenses 216 (the first diameter of the first partition 211 may be 20 μm); the second partition 212 comprises one part, which is composed of a plurality of relatively large microlenses 216 (i.e., the microlenses 216 of the second partition 212 are relatively large compared to the microlenses 216 of the first partition 211. For example, the first diameter of the second partition 212 may be 60 μm).

[0052] Please refer to Figure 3 In another feasible embodiment, the second partition 212 includes a plurality of partitions spaced apart, and the optical diffuser also includes a plurality of third partitions 213 respectively surrounding the periphery of the plurality of second partitions 212. The first partition 211 includes one partition, and the first partition 211 is disposed at the gap between the plurality of third partitions 213. The first diameter of the third partition 213 is greater than the first diameter of the first partition 211 and smaller than the first diameter of the second partition 212.

[0053] exist Figure 3 In this design, four second partitions 212 are included, each containing only one large-particle-diameter microlens 216. For example, the first diameter of each second partition 212 is 40 μm. Four third partitions 213 are annular regions surrounding the second partitions 212, each enclosing one second partition 212. One first partition 211 is included, positioned at the gaps between the multiple third partitions 213. For example, the first diameter of the third partition 213 can be 28 μm. One first partition 211 is also included, filling the gaps between the four third partitions 213. For example, the first diameter of the first partition 211 can be 20 μm.

[0054] It should be understood that the above two configurations of partition 21 are merely examples provided in this application and are not intended to limit the configuration of partition 21.

[0055] Furthermore, it should be noted that in this embodiment, the boundary of the microlens 216 is a polygon of random shape, and the size and surface shape of the microlens 216 are random.

[0056] Please refer to the reference again. Figure 8 Optionally, the optical diffuser also includes a cover layer 30 located on the side of the microlens array 20 away from the substrate 10, the refractive index of the cover layer 30 being different from that of the microlens array 20.

[0057] The capping layer 30 covers the microlens array 20. Optionally, the capping layer 30 is made of any one of glass, resin, and plastic. Furthermore, the capping layer 30 and the microlens array 20 have a refractive index difference.

[0058] For example, the absolute value of the difference between the refractive index of the capping layer 30 and the refractive index of the microlens array 20 is greater than 0.1. In this way, the capping layer 30 can protect the microlens array 20.

[0059] Alternatively, the optical diffuser may further include a silver or aluminum reflective layer (i.e., a silver reflective layer or an aluminum reflective layer), which is deposited on either the substrate 10 or the microlens array 20. That is, the silver or aluminum reflective layer can be deposited on the substrate 10 or on the microlens array 20. For example, the silver or aluminum reflective layer can be deposited on the upper or lower surface of the substrate 10, or it can be deposited on the upper or lower surface of the microlens array 20.

[0060] Optionally, the surface profile of the microlens 216 is a freeform surface, and the surface profile of the microlens 216 satisfies the following height formula:

[0061]

[0062] in, c is the radius of curvature, K is the conic coefficient, and A i are the coefficients of the polynomial, where m and n are both integers, both m and n are greater than or equal to 0, and 1≤m+n≤20.

[0063] Please refer to the reference again. Figure 9 In another aspect, the present invention provides a method for designing an optical diffuser, the method comprising:

[0064] S100: Divide the design area of ​​the substrate into multiple design units of the same size.

[0065] It should be noted that the design method for the optical diffuser provided in this application is intended to design the optical diffuser described above.

[0066] The substrate is the substrate of the microlens array 20.

[0067] S200. Each design unit is randomly divided so that each design unit contains at least one design block.

[0068] That is, after dividing the substrate into multiple design units of the same size, each design unit is then randomly divided, so that each design unit includes at least one design block. The size of each design block is randomly set. For example... Figure 10 As shown, some design units are divided into four design blocks, while others are divided into sixteen design blocks. The specific division method can be determined by those skilled in the art. Figure 10 This is just an example.

[0069] S300. Irregularize the boundary of each design block so that the boundary of each design block is polygonal.

[0070] Figure 11 The diagram illustrates a method for creating irregular boundaries. This involves rotating, translating, and scaling the existing boundary lines, then adding new connecting lines to create irregular boundary lines. Figure 11 The line segment (1) in the diagram is the supplementary connecting line. There are various ways to handle the irregularity of the boundary line, as long as the effect of boundary irregularity can be achieved, this application does not limit this.

[0071] After irregularizing the boundaries of each design block, multiple design blocks with an irregular distribution can be obtained, such as... Figure 12 As shown.

[0072] S400: Optimize the surface shape of each design block according to the incident parameters of the incident light and the parameters of the emitted light spot, and obtain multiple microlenses 216 according to the surface shape of each design block and the boundary of the corresponding design block. Adjacent microlenses 216 are seamlessly spliced ​​together. Among them, microlenses 216 in different regions are respectively gathered to form multiple partitions 21, and multiple partitions 21 are seamlessly spliced ​​together to form a microlens array 20.

[0073] In this embodiment, when optimizing the surface shape of the design block, the surface shape of each design block can be defined as a freeform surface, and satisfies the following height function formula:

[0074]

[0075] in, c is the radius of curvature, K is the conic coefficient, and A i are the coefficients of the polynomial, where m and n are both integers, both m and n are greater than or equal to 0, and 1≤m+n≤20.

[0076] Based on the incident light conditions and the requirements of the emitted light spot, the optimization objective for each design block is that its emitted light spot constitutes part of the overall light spot. Since the size and shape of each design block are random, the surface shape of each optimized design block is also random. After obtaining the optimized surface shape, multiple microlenses 216 can be obtained based on the surface shape of each design block and the corresponding boundary of the design block. At this time, the top view of the microlens 216 should also be consistent with... Figure 12 The top view structure shown is the same.

[0077] S500. A microlens array 20 is disposed on a substrate 10 to obtain an optical diffuser, wherein the ratio of the first diameter of the first partition of the microlens array 20 to the first diameter of the second partition is between 0.1 and 0.85, the first diameter is the average diameter of the circumcircle of all microlenses 216 in the corresponding partition 21, the first partition is the partition with the smallest first diameter in the microlens array 20, and the second partition is the partition with the largest first diameter in the microlens array 20.

[0078] Additionally, it should be noted that the material and refractive index of the microlens 216 can be referred to the description above.

[0079] The above description is merely an optional embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An optical diffuser, characterized in that, The system includes a substrate and a microlens array disposed on the substrate. The microlens array includes multiple seamlessly joined partitions, each partition including at least one microlens, and when a partition includes more than one microlens, adjacent microlenses are seamlessly joined. Each partition includes at least a first partition and a second partition, and the ratio of the first diameter of the first partition to the first diameter of the second partition is between 1 / 3 and 4 / 7. The first diameter is the average diameter of the circumcircle of all microlenses in the corresponding partition. The first partition is the partition with the smallest first diameter in the microlens array, and the second partition is the partition with the largest first diameter in the microlens array. The first partition includes multiple partitions spaced apart, and the second partition includes one partition, which is disposed at the gaps between the multiple first partitions. Alternatively, the second partition may include a plurality of spaced-apart partitions, and the optical diffuser may further include a plurality of third partitions respectively surrounding the periphery of the plurality of second partitions. The first partition may include one partition, and the first partition may be disposed at the gap between the plurality of third partitions. The first diameter of the third partition is greater than the first diameter of the first partition and less than the first diameter of the second partition.

2. The optical diffuser according to claim 1, characterized in that, The boundary of the microlens is a polygon of random shape, and the size and surface shape of the microlens are random.

3. The optical diffuser according to claim 1, characterized in that, The substrate and the microlens array are made of glass or resin, respectively.

4. The optical diffuser according to claim 1 or 3, characterized in that, The refractive index of the substrate and / or the refractive index of the microlens array are between 1.1 and 5.

0.

5. The optical diffuser according to claim 1, characterized in that, The optical diffuser also includes a cover layer located on the side of the microlens array away from the substrate. The cover layer is made of glass or resin, and the absolute value of the difference between the refractive index of the cover layer and the refractive index of the microlens array is greater than 0.

1.

6. The optical diffuser according to claim 1, characterized in that, The optical diffuser also includes a silver or aluminum reflective layer, which is deposited on either the substrate or the surface of the microlens array.

7. The optical diffuser according to claim 1, characterized in that, The microlens has a freeform surface, and its surface shape satisfies the following height formula: ， in, Where c is the radius of curvature, K is the conic coefficient, and A is... i The coefficients of the polynomial are m and n, where m and n are both integers, m and n are both greater than or equal to 0, and 1 ≤ m + n ≤ 20.

8. A method for designing an optical diffuser, characterized in that, include: The substrate design area is divided into multiple design units of the same size; Each design unit is randomly divided so that each design unit contains at least one design block; The boundaries of each design block are made irregular so that the boundaries of each design block are polygonal; The surface shape of each design block is optimized based on the incident parameters of the incident light and the parameters of the outgoing light spot. Multiple microlenses are obtained based on the surface shape of each design block and the boundary of the corresponding design block. Adjacent microlenses are seamlessly spliced ​​together. Microlenses in different regions are respectively clustered to form multiple partitions, and multiple partitions are seamlessly spliced ​​together to form a microlens array. The microlens array is disposed on a substrate to obtain an optical diffuser, wherein the ratio of the first diameter of the first partition and the first diameter of the second partition of the microlens array is between 1 / 3 and 4 / 7, the first diameter is the average diameter of the circumcircle of all microlenses in the corresponding partition, the first partition is the partition with the smallest first diameter in the microlens array, and the second partition is the partition with the largest first diameter in the microlens array; the first partition includes a plurality of partitions spaced apart, the second partition includes one partition, and the second partition is disposed at the gap between the plurality of first partitions; Alternatively, the second partition may include a plurality of spaced-apart partitions, and the optical diffuser may further include a plurality of third partitions respectively surrounding the periphery of the plurality of second partitions. The first partition may include one partition, and the first partition may be disposed at the gap between the plurality of third partitions. The first diameter of the third partition is greater than the first diameter of the first partition and less than the first diameter of the second partition.

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