Diffractive optical element and method for manufacturing the same

Abstract

The embodiment of the present application discloses a kind of diffractive optical elements and preparation method thereof, the diffractive optical element includes optical element setting cavity, optical element setting cavity includes at least two layers of substrate and the connecting portion connected with substrate respectively;Diffractive optical element includes the optical structure arranged in optical element setting cavity, and optical structure includes diffractive structure and collimating structure.Adopt the diffractive optical element provided in the embodiment of the present application, the optical structure arranged in optical element setting cavity simultaneously includes diffractive structure and collimating structure, i.e. it is rich to adjust effect of light to optical element setting cavity.In comparison with the case that diffractive structure and collimating structure are separately arranged in prior art, the embodiment of the present application can reduce the production and processing difficulty of diffractive optical element, improve production efficiency and yield ratio etc., simultaneously, diffractive structure and collimating structure can also be avoided to be influenced by external factors such as environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of diffractive optics, in particular to a diffractive optical element and a preparation method thereof. BACKGROUND

[0002] With the development of intelligent manufacturing technology, robots are becoming more and more intelligent, and 3D vision is gradually replacing 2D vision and is widely used in various scenes of robot vision recognition. Compared with other 3D technology routes such as ToF and binocular structured light, 3D structured light has several times the precision advantage within the human-machine interaction distance, but considering the cost, currently 3D structured light only exists in high-end flagship products, and is limited by the design and processing difficulty of diffractive optical elements, which also limits the application of 3D structured light in large field angles (such as more than 90° scenes). How to reduce the cost and volume of 3D structured light modules under high performance requirements (high-quality diffraction patterns) and simultaneously improve the working field angle of 3D structured light is the only way to realize the popularization of 3D structured light.

[0003] 3D structured light usually includes a structured light projector and an infrared receiving module. The structured light projector emits infrared light spots with specific coding characteristics, which are projected on an object. The infrared camera receives the infrared light spots reflected by the object to form a structured light infrared image with specific coding characteristics. The current collected structured light infrared image is matched with the reference structured light infrared image with a known distance which is collected and saved in advance. The deviation of the pixels in the current structured light infrared image relative to the corresponding pixels in the reference structured light infrared image is obtained. Based on the principle of triangulation, the depth information of the entire image can be calculated by using the deviation of the pixel points in the image. Common structured light projectors mainly include a laser emitting light source, a collimating mirror and a diffractive optical element (DOE). The laser emitting light source usually has a vcsel (vertical cavity surface emitting laser), a hcsel (horizontal cavity surface emitting laser) and an eel (edge emitting laser). The light source emits light with a certain divergence angle, which is collimated into parallel light by the collimating mirror. The parallel light is replicated and diffused by the DOE to form a light spot with specific coding characteristics (hereinafter referred to as a structured light spot).

[0004] The existing structured light projector has a large structure volume. When the volume of the structured light projector is reduced, the preparation and assembly process of the diffractive optical element in the structured light projector is prone to various problems. SUMMARY

[0005] The diffractive optical element and the preparation method thereof provided by the embodiments of the present application set the optical structure in the cavity of the optical element to include both diffractive structures and collimating structures. Compared with the case where the diffractive structures and the collimating structures are separately set, the production and processing difficulty of the diffractive optical element can be reduced, and the production efficiency and yield can be improved.

[0006] In a first aspect, an embodiment of the present application provides a diffractive optical element, comprising an optical element setting cavity, the optical element setting cavity comprising at least two substrates and a connecting part connected to the substrates respectively;

[0007] The diffractive optical element comprises an optical structure arranged in the optical element setting cavity, the optical structure comprising a diffractive structure and a collimating structure.

[0008] Optionally, the diffractive optical element structure comprises at least one level of the diffractive structure, and one level of the diffractive structure and the collimating structure are arranged on different surfaces of the substrates respectively.

[0009] Optionally, the at least two substrates comprise a first substrate and a second substrate, and the optical structure is arranged in the optical element setting cavity defined by the first substrate and the second substrate.

[0010] Optionally, the at least one level of the diffractive structure comprises a first level of the diffractive structure, the first level of the diffractive structure is arranged on the surface of the first substrate, and the collimating structure is arranged on the surface of the second substrate.

[0011] Optionally, the at least one level of the diffractive structure comprises a first level of the diffractive structure and a second level of the diffractive structure.

[0012] The first level of the diffractive structure is arranged on the surface of the first substrate, and the collimating structure is arranged on the surface of the second substrate.

[0013] The second level of the diffractive structure is arranged on the surface of the collimating structure and located away from the surface of the second substrate.

[0014] Optionally, the at least one level of the diffractive structure comprises a first level of the diffractive structure and a second level of the diffractive structure.

[0015] The first level of the diffractive structure is arranged on the surface of the first substrate, and the collimating structure is arranged on the surface of the second substrate.

[0016] The second level of the diffractive structure is arranged on the surface of the first level of the diffractive structure and located away from the surface of the first substrate.

[0017] Optionally, the at least one level of the diffractive structure comprises a first level of the diffractive structure and a second level of the diffractive structure.

[0018] The first level of the diffractive structure is arranged on the surface of the first substrate, and the collimating structure and the second level of the diffractive structure are fused into one structure and arranged on the surface of the second substrate.

[0019] Optionally, the at least one level of the diffractive structure comprises a first level of the diffractive structure and a second level of the diffractive structure.

[0020] The first-order diffraction structure and the second-order diffraction structure are fused into one structure and arranged on the surface of the first substrate, and the collimating structure is arranged on the surface of the second substrate.

[0021] Optionally, the at least two substrates include a first substrate, a second substrate and a third substrate; the at least one diffraction structure includes a first-order diffraction structure and a second-order diffraction structure; the first-order diffraction structure is arranged in the optical element setting cavity defined by the first substrate and the second substrate, and the second-order diffraction structure is arranged in the optical element setting cavity defined by the first substrate and the third substrate.

[0022] Optionally, the diffraction structure includes at least one diffraction structure, and the diffraction structure includes a first-order diffraction structure and a second-order diffraction structure; the first-order diffraction structure, the second-order diffraction structure and the collimating structure are fused into one structure and arranged on the same surface of the substrate.

[0023] Optionally, the refractive index of the second substrate when powered is n1, and the refractive index of the second substrate when not powered is n2, wherein |n1-n2|>0.

[0024] The refractive index of the collimating structure is n3, wherein n1=n3.

[0025] Optionally, the diffractive optical element further includes a cavity filler for filling the optical element setting cavity.

[0026] The refractive index of the second substrate and the collimating structure when powered is n4, and the refractive index of the second substrate and the collimating structure when not powered is n5, wherein |n4-n5|>0.

[0027] The refractive index of the cavity filler is n6, wherein n4=n6.

[0028] Optionally, the collimating structure includes a Fresnel microstructure or a microlens array structure.

[0029] In a second aspect, an embodiment of the present application provides a preparation method of a diffractive optical element, applied to the diffractive optical element of any one of the first aspect, and the preparation method includes:

[0030] Providing at least two substrates;

[0031] Forming an optical element on the substrate, the optical element including a diffraction structure and a collimating structure;

[0032] Forming a connecting part on the substrate;

[0033] Attaching the at least two substrates through the connecting part to form an optical element setting cavity.

[0034] The diffraction optical element provided by the embodiment of the present application comprises an optical element setting cavity, the optical element setting cavity comprises at least two substrates and connecting parts connected with the substrates respectively; the diffraction optical element comprises optical structures arranged in the optical element setting cavity, and the optical structures comprise diffraction structures and collimation structures. The diffraction optical element provided by the embodiment of the present application is arranged in the optical element setting cavity and comprises diffraction structures and collimation structures at the same time, compared with the case that the diffraction structures and the collimation structures are arranged separately in the prior art, the diffraction optical element provided by the embodiment of the present application simultaneously realizes the functions of diffraction and collimation, which is equivalent to reducing the setting space of one collimation lens, and reduces the assembly difficulty and cost of the structured light projector. Meanwhile, the diffraction optical element adopts a closed optical cavity structure, which reduces the production difficulty of the diffraction optical element and protects the optical structures from pollution of the external environment. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0036] Figure 1 is a structural schematic diagram of a diffraction optical element in the prior art;

[0037] Figure 2 is a structural schematic diagram of a diffraction optical element provided by the embodiment of the present application;

[0038] Figure 3 is a structural schematic diagram of another diffraction optical element provided by the embodiment of the present application;

[0039] Figure 4 is a structural schematic diagram of another diffraction optical element provided by the embodiment of the present application;

[0040] Figure 5 is a top view structural schematic diagram of a diffraction optical element provided by the embodiment of the present application;

[0041] Figure 6 is a structural schematic diagram of another diffraction optical element provided by the embodiment of the present application;

[0042] Figure 7 is a structural schematic diagram of another diffraction optical element provided by the embodiment of the present application;

[0043] Figure 8 is a structural schematic diagram of another diffraction optical element provided by the embodiment of the present application;

[0044] Figure 9 is another structural diagram of a diffractive optical element provided by an embodiment of the present application;

[0045] Figure 10 is a structural diagram of a structured light spot provided by an embodiment of the present application;

[0046] Figure 11 is another structural diagram of a structured light spot provided by an embodiment of the present application;

[0047] Figure 12 is another structural diagram of a diffractive optical element provided by an embodiment of the present application;

[0048] Figure 13 is another structural diagram of a diffractive optical element provided by an embodiment of the present application;

[0049] Figure 14 is a flow chart of a preparation method of a diffractive optical element provided by an embodiment of the present application;

[0050] Figure 15 is a process chart of a preparation method of a diffractive optical element provided by an embodiment of the present application;

[0051] Figure 16 is a process chart of another preparation method of a diffractive optical element provided by an embodiment of the present application;

[0052] Figure 17 is a structural diagram of a connecting part provided by an embodiment of the present application;

[0053] Figure 18 is a process chart of another preparation method of a diffractive optical element provided by an embodiment of the present application. DETAILED DESCRIPTION

[0054] In order to make the objectives, technical solutions and advantages of the present application clearer, the following will combine the drawings in the embodiments of the present application, and describe the technical solutions of the present application completely through specific implementation manners. Obviously, the described embodiments are a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0055] Figure 1 is a structural diagram of a diffractive optical element in the prior art, referring to Figure 1As shown, the diffractive optical element 10' includes a diffractive substrate 100', and includes a diffractive structure surface 200' and a collimating structure surface 300' on both sides of the diffractive substrate 100', that is, by arranging two structure surfaces for adjusting light transmission on both sides of a diffractive substrate 100', the adjustment effect of the diffractive optical element 10' on light transmission can be enriched. That is, by realizing collimation and diffraction of light through a diffractive optical element 10', it is ensured that when collimation and diffraction are both arranged in a diffractive optical element 10' when the diffractive optical element 10' is applied to the field of 3D structured light, the occupied space of a collimating lens can be reduced, and the volume and assembly cost of the structured light projector. However, when the diffractive structure surface 200' and the collimating structure surface 300' are arranged on a diffractive substrate 100', unavoidable errors will occur during the preparation and assembly of the diffractive optical element 10', which will affect the transmission effect of the diffractive optical element 10' on light.

[0056] Specifically, integrating two structures, i.e., a diffractive structure and a collimating structure, on one diffractive substrate 100' increases the difficulty of the process, especially after the first structure is formed on the diffractive substrate 100', the second structure needs to be formed on the other side of the diffractive substrate 100', which is easy to damage the first structure, and also involves the alignment problem of the second structure with the first structure, and the stability problem of the production of the second structure, which will all reduce the production yield of the entire diffractive optical element 10'. Or, because the diffractive substrate 100' of the diffractive optical element 10' has very fine structures on both sides, when assembling the projector module, the automatic machine will attach the diffractive optical element 10' to a certain fixed surface, and the machine has the risk of scratching or damaging the structure, and at least one structure of this diffractive optical element 10' is exposed to the air, which is easy to be polluted by the environment, which may cause the efficiency of the diffractive optical element 10' to be lost, or even the serious situation of damaging the function of the entire diffractive optical element 10'.

[0057] To solve the above problems, the embodiment of the present application provides a diffractive optical element, which includes an optical element setting cavity, the optical element setting cavity includes at least two substrates and a connecting part connected with the substrates; the diffractive optical element includes an optical element arranged in the optical element setting cavity, and the optical element includes a diffractive structure and a collimating structure. The diffractive optical element provided by the embodiment of the present application has the diffractive structure and the collimating structure arranged in the optical element setting cavity at the same time, that is, the adjustment effect of the optical element setting cavity on light is enriched, and the processing difficulty and preparation cost of the diffractive optical element can be reduced, and the light adjustment effect of the diffractive optical element is ensured. Compared with the defects in the prior art mentioned above, arranging the diffractive structure and the collimating structure in the optical element setting cavity can avoid errors in the preparation or assembly process and damage the function of the entire diffractive optical element.

[0058] The above is the core idea of the present application, and the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0059] Figure 2 is a structural schematic diagram of a diffractive optical element provided by an embodiment of the present application, as shown in Figure 2 The diffractive optical element 10 provided by the embodiment of the present application includes an optical element setting cavity 100, the optical element setting cavity 100 includes at least two substrates 110 and connecting portions 120 connected with the substrates 110 respectively; the diffractive optical element 10 includes an optical structure 200 arranged in the optical element setting cavity 100, the optical structure 200 includes a diffractive structure 210 and a collimating structure 220.

[0060] The diffractive optical element 10 can combine a laser emitting source as a structured light transmitter in 3D structured light to realize three-dimensional accurate identification of a measured object. Specifically, a detection beam provided by the laser emitting source is adjusted by the diffractive optical element 10 to ensure that the detection beam is transmitted to the measured object according to a required requirement, and an infrared receiving module in 3D structured light captures the detection reflected by the measured object to complete identification of the measured object. Specifically, the diffractive optical element 10 has the optical structure 200 to adjust the light transmitted to the diffractive optical element 10.

[0061] Specifically, the diffractive optical element 10 provided by the embodiment of the present application includes an optical element setting cavity 100, as shown in Figure 2 The optical element setting cavity 100 includes at least two substrates 110 and connecting portions 120 connected with the substrates 110, that is, the substrates 110 and the connecting portions 120 constitute a closed space, that is, the optical element setting cavity 100. Exemplarily, the substrate 110 can be transparent glass or plastic material, and the embodiment of the present application does not specifically limit this. Only two substrates 110 are taken as an example for illustration in the figure, and based on actual process requirements, multiple substrates 110 can be arranged to constitute multiple optical element setting cavities 100, and the embodiment of the present application does not specifically limit this.

[0062] Further, the optical structure 200 is arranged in the optical element arrangement cavity 100, and the optical structure 200 further comprises the diffraction structure 210 and the collimation structure 220, wherein the diffraction structure 210 and the collimation structure 220 can be microstructure surfaces. Moreover, the optical element arrangement cavity 100 is a closed cavity structure, i.e. the diffraction structure 210 and the collimation structure 220 are arranged in the optical element arrangement cavity 100 in a closed manner. In other words, the optical structure 200 for adjusting light is arranged in the closed optical element arrangement cavity 100, i.e. the functions of diffraction and collimation are integrated on the diffraction optical element 10. Through the design of the diffraction optical element 10, the space of the structured light projector and the manufacturing cost can be saved. Moreover, the arrangement of the optical structure 200 in the closed optical element arrangement cavity 100 can also avoid the diffraction structure 210 or the collimation structure 220 from being damaged or contaminated by the external environment during the manufacturing and assembly of the diffraction optical element 10, so as to ensure the transmission effect of the diffraction optical element 10 on light.

[0063] In summary, the diffraction optical element provided by the embodiment of the present application can reduce the production and processing difficulty of the diffraction optical element, improve the production efficiency and yield, and also avoid the influence of external factors such as environment on the diffraction structure and the collimation structure, so as to ensure the transmission effect of the diffraction optical element on light and better application of the diffraction optical element in structured light.

[0064] With reference to the foregoing Figure 2 As shown, the diffraction structure 210 comprises at least one level of diffraction structure 210, and the one level of diffraction structure 210 and the collimation structure 220 are arranged on different surfaces of the substrate 110.

[0065] Specifically, the optical structure 200 includes at least one level of diffraction structure 210, that is, by increasing the diffraction order of the diffraction structure 210, that is, by providing a multi-level diffraction structure 210, the maximum diffraction angle of the diffractive optical element 10 can be improved, that is, the field of view angle of the diffractive optical element 10 is improved, and the diffractive optical element 10 is applied to the structured light projector of the structured light, which has a larger field of view angle. Further, the optical element setting cavity 100 includes at least two substrates 110, and the at least one level of diffraction structure 210 and the collimating structure 220 are arranged on the surfaces of different substrates 210, respectively, that is, the diffraction structure 210 and the collimating structure 220 are both located in the closed optical element setting cavity 100, in other words, the diffractive optical element 10 integrates the collimating and diffraction functions through the optical element setting cavity 100, and the two are located on different substrates 110. In the process of assembling the two substrates 110, it can be ensured that the diffraction structure 210 and the collimating structure 220 located on any substrate 110 will not be damaged by the external environment, and the functions of diffraction and collimation of the diffractive optical element 10 are guaranteed. For example, referring to Figure 2 It is shown that the optical structure 200 includes only one level of diffraction structure 210, that is, only the positional relationship between the diffraction structure 210 and the collimating structure 220 is represented, and the diffraction order and the like are not specifically limited.

[0066] Continuing to refer to Figure 2 It is shown that the at least two substrates 110 include a first substrate 110A and a second substrate 110B, and the optical structure 200 is arranged in the optical element setting cavity 100 defined by the first substrate 110A and the second substrate 110B.

[0067] Specifically, the optical element setting cavity 100 includes at least two substrates 110, that is, the first substrate 110A and the second substrate 110B, in other words, the first substrate 110A and the second substrate 110B together with the connecting part 120 form a closed optical element setting cavity 100. Further, referring to Figure 2 It is shown that the at least one level of diffraction structure 210 and the collimating structure 220 included in the diffraction structure 210 are both arranged in the optical element setting cavity 100 defined by the first substrate 110A and the second substrate 110B, that is, the diffractive optical element 10 can realize the functions of collimation and diffraction in one optical element setting cavity 100, and when the diffractive optical element 10 is used as a structured light projector, the space of one collimating lens can be reduced, thereby reducing the occupied space of the structured light projector.

[0068] Figure 3 is another structural schematic diagram of a diffractive optical element provided by an embodiment of the present application, Figure 4 is another structural schematic diagram of a diffractive optical element provided by an embodiment of the present application, Figure 5 is a top view structural schematic diagram of a diffractive optical element provided by an embodiment of the present application, referring toFigures 2 to 5 As shown, the at least one level of diffraction structure 210 includes a first level of diffraction structure 210A, and the collimating structure 220 is arranged on the surface of the second substrate 110B.

[0069] Specifically, referring to Figures 2 to 3 As shown, the first level of diffraction structure 210A is arranged on the surface of the first substrate 110A, and the collimating structure 220 is arranged on the surface of the second substrate 110B, i.e. the arrangement positions of the first level of diffraction structure 210A and the collimating structure 220 are specifically described, so as to realize the functions of collimation and diffraction of the closed optical element arrangement cavity 100.

[0070] Optionally, the collimating structure 220 includes a Fresnel microstructure or a microlens array structure.

[0071] Further, referring to Figure 2 and Figure 3 As shown, the collimating structure 220 includes a Fresnel microstructure, so as to realize the collimation adjustment of the passing light. Referring to Figure 2 As shown, the collimating structure 220 includes a stepped Fresnel microstructure, referring to Figure 3 As shown, the collimating structure 220 includes a continuous Fresnel microstructure. Referring to Figure 4 As shown, the collimating structure 220 can also include a microlens array structure, i.e. a spherical microlens array structure or an aspherical microlens array structure, which is not specifically limited in the embodiments of the present application.

[0072] Further, the diffractive optical element 10 can also include some protective film layers to ensure the stability of the diffractive optical element 10. Exemplarily, the protective film layers can be arranged on the side of the second substrate 220 away from the first substrate 210, or on the side of the first substrate 210 away from the second substrate 220, i.e. on the outside of the optical element arrangement cavity 100. Referring to Figure 5 As shown, a transparent conductive layer 400 is coated on the side of the second substrate 220 away from the first substrate 210, and the resistance value of the transparent conductive layer 400 is monitored in real time to monitor whether the diffractive optical element 10 is damaged, so that the projector is immediately turned off when the diffractive optical element 10 is damaged, so as to stop the work of the projector and avoid hurting the human eye, thereby playing a safety monitoring role. Further, the protective film layer can also be a fingerprint-resistant film layer and a polarized film layer, etc., so as to enrich the functions of the diffractive optical element 10 applied in the structured light field, which is not specifically limited in the embodiments of the present application.

[0073] Figure 6 is another structural schematic diagram of a diffractive optical element provided by the embodiments of the present application, Figure 7 is another structural schematic diagram of a diffractive optical element provided by the embodiments of the present application, Figure 8This is a schematic diagram of another diffractive optical element provided in an embodiment of the present invention. Figure 9 This is a schematic diagram of another diffractive optical element provided in an embodiment of the present invention. Figure 10 This is a schematic diagram of a structured light spot provided in an embodiment of the present invention. Figure 11 This is a schematic diagram of another structured light spot provided in an embodiment of the present invention, for reference. Figures 6 to 11 As shown, at least one diffraction structure 210 includes a first-order diffraction structure 210A and a second-order diffraction structure 210B.

[0074] Specifically, the diffraction equation in the process of light diffraction is: dsinθ=mλ, where d is the grating period of the diffraction optical element, θ is the diffraction angle, and m is the diffraction order. To design a large diffraction angle, i.e., the field of view of the diffraction optical element, the diffraction order can be increased. However, in the existing technology, the design difficulty of the diffraction optical element increases with the larger the diffraction order. Furthermore, as the diffraction angle increases, or the diffraction order increases, the structured light spot formed by diffraction will exhibit obvious pincushion distortion, causing the distribution density of the structured light spot around it to gradually decrease, making it impossible to effectively identify the target light spot. In addition, the uniformity between different orders is poor (uniformity is defined as the ratio of the difference between the highest and lowest light intensities in each diffraction order to the sum of the values; the lower the index value, the better the performance), all of which will affect the accuracy of three-dimensional ranging. Therefore, it is difficult to meet the performance requirements when designing and manufacturing according to the conventional single-layer diffraction structure.

[0075] For details, please refer to Figures 6 to 9 As shown, at least one diffraction structure 210 includes a first-order diffraction structure 210A and a second-order diffraction structure 210B, that is, a two-order diffraction structure 210 is designed in the diffraction optical element 10, which can be a reference. Figure 6 or Figure 7 The layered design shown can also be used as a reference. Figure 8 or Figure 9 The designs shown, which integrate the elements into a single structure, can all improve the overall diffraction order of the diffraction optical element 10, thus increasing the field of view of the diffraction optical element 10 as a projector. Compared to using a single-layer diffraction structure to achieve the same diffraction order, the distortion of the diffraction spot pattern is smaller and the uniformity is better.

[0076] For example, refer to Figure 10, the diffraction effect structure light spot pattern generated by the diffractive optical element 10 can be known, when the diffractive optical element 10 includes the first-order diffractive structure 210A and the second-order diffractive structure 210B, the originally designed 9*9 order diffractive structure 210 can be divided into two 3*3 order diffractive structures 210 to realize, that is, equivalent to adding a layer of diffractive structure 210, the diffraction orders of the two layers of diffractive structures 210 can also be 1*9 and 9*1 collocation, which is not limited here, as long as the total copy number is 81. The embodiment of the application does not specifically limit the order of the diffractive structure 210, that is, 9*9 is an example, and other diffraction orders such as 11*11 can also be used. Specifically, refer to Figure 10 As shown in the figure, the wire frame A represents a point light source provided outside the diffractive optical element 10. The light source can also be a dot matrix light source. Here, a single point light source is used for illustration. The wire frame B represents a schematic diagram of the structured light spot after the point light source passes through the collimation structure 220 and is diffracted by the first-order diffractive structure 210A. The wire frame C represents a schematic diagram of the structured light spot after the second-order diffractive structure 210B. It should be noted again that the dashed wire frame in the figure is only used for division and does not exist in the actual structured light spot diagram. That is, the diffraction order of the light spot after one diffraction is small, and the diffraction angle is small. The diffraction structure 210 can be designed based on the scalar theory of light waves. The diffraction structure 210 has small design and processing difficulty, small diffraction pattern distortion, and good uniformity, but only 9 diffraction light spot patterns exist. After the light passes through two diffractive structures 210, 81 diffraction light spot patterns are formed. The diffraction order of the light spot passing through each diffractive structure 210 alone is small, but the diffractive optical element 10 provided by the embodiment of the application calculates the sum of the diffraction orders of the two diffractive structures 210. In other words, the diffraction order and the diffraction angle of each diffractive structure 210 are smaller than those of a single layer of diffractive microstructure, the design difficulty of the diffractive structure 210 is reduced, the diffraction pattern distortion is small, and the uniformity is good. The design difficulty of the diffractive optical element 10 is greatly reduced by using two layers of diffractive structures 210 in combination, and the imaging quality of the large-angle diffraction pattern is improved.

[0077] Further, refer to Figure 10 As shown in the figure, the light passes through the first-order diffractive structure 210A and the second-order diffractive structure 210B to form a regular structured diffraction light spot. Refer to Figure 11 As shown in the figure, the light passes through the first-order diffractive structure 210A and the second-order diffractive structure 210B to form a regular structured diffraction light spot. Refer to Figure 11Another light spot diagram of the single-point light source provided by the application after passing through two layers of 3*3 diffraction structures 210 is shown in the figure. The first-level diffraction structure 210A is designed to be offset by 1 / N sub-mode size, where N can be any number greater than 1. The second-level diffraction structure 210B is designed to be offset by 1 / M sub-mode size, where M can be any number greater than 1. The values of M and N can be set according to the actual simulation of the randomness of the light spot. When the single-point light source passes through the second-level diffraction structure 210B, it becomes 9 first sub-modes B with a certain offset in the vertical direction Y. After passing through the second-level diffraction structure 210B again, the second sub-mode C with a certain offset in the Y direction is generated, that is, the original 9 points are copied into 9 sub-patterns with a certain offset in the Y direction, a total of 81 points. Of course, the offset design can also be offset in the X direction, which is not described one by one here. In addition, only one of the first microstructure surface and the second microstructure surface can be designed to be offset. That is, a variety of structural light spot arrangement modes are provided, which can ensure that the structural infrared image formed by the 3D structural light transmitted to the infrared receiving module by the diffraction optical element 10 has diversity, that is, it helps to improve the subsequent identification accuracy of the surface information of the measured object. The embodiments of the application do not make specific descriptions here.

[0078] Optionally, as shown in Figure 6 , the first-level diffraction structure 210A is arranged on the surface of the first substrate 110A, and the collimating structure 220 is arranged on the surface of the second substrate 110B. The second-level diffraction structure 110B is arranged on the surface of the collimating structure 220 and is located away from the surface of the second substrate 110B.

[0079] Specifically, on the basis that the first-level diffraction structure 210A is arranged on the surface of the first substrate 110A and the collimating structure 220 is arranged on the surface of the second substrate 110B, the diffraction optical element 10 further comprises a second-level diffraction structure 110B. As shown in Figure 6 , the second-level diffraction structure 110B is arranged on the surface of the collimating structure 220 and is spaced apart from the first-level diffraction structure 210A. In the case of two diffraction structures 210, it is necessary to ensure that they do not interfere with each other in a contact manner, and at the same time, the first-level diffraction structure 210A, the second-level diffraction structure 210B and the collimating structure 220 are arranged in the same optical element setting cavity 100. When the diffraction optical element 10 is used as a structural light projector, the space of one collimating lens can be reduced, thereby reducing the occupied space of the structural light projector.

[0080] Optionally, as shown in Figure 7 , the first-level diffraction structure 210A is arranged on the surface of the first substrate 110A, and the collimating structure 220 is arranged on the surface of the second substrate 110B. The second-level diffraction structure 210B is arranged on the surface of the first-level diffraction structure 210A and is located away from the surface of the first substrate 110B.

[0081] Specifically, the first-order diffractive structure 210A is arranged on the surface of the first substrate 110A, and the collimating structure 220 is arranged on the surface of the second substrate 110B, and the diffractive optical element 10 further comprises a second-order diffractive structure 210B. As shown in FIG. 2B, the second-order diffractive structure 210B is arranged on the surface of the first-order diffractive structure 210A, and there is a distance between the second-order diffractive structure 210B and the collimating structure 220, that is, in the case of implementing the two diffractive structures 210, there is no contact interference between the collimating structure 220 and the added second-order diffractive structure 210B, and meanwhile, the first-order diffractive structure 210A, the second-order diffractive structure 210B and the collimating structure 220 are arranged in the same optical element setting cavity 100, which can reduce the space of one collimating lens when the diffractive optical element 10 is used as a structured light projector, and further reduce the occupied space of the whole structured light projector. Figure 7

[0082] Optionally, as shown in FIG. 2C, the first-order diffractive structure 210A is arranged on the surface of the first substrate 110A, and the collimating structure 220 and the second-order diffractive structure 210B are fused into one structure and arranged on the surface of the second substrate 110B. Figure 8

[0083] Specifically, the first-order diffractive structure 210A is arranged on the surface of the first substrate 110A, and the collimating structure 220 is arranged on the surface of the second substrate 110B, and the diffractive optical element 10 further comprises a second-order diffractive structure 210B. As shown in FIG. 2B, the second-order diffractive structure 210B is arranged on the surface of the first-order diffractive structure 210A, and there is a distance between the second-order diffractive structure 210B and the collimating structure 220, that is, in the case of implementing the two diffractive structures 210, there is no contact interference between the collimating structure 220 and the added second-order diffractive structure 210B, and meanwhile, the first-order diffractive structure 210A, the second-order diffractive structure 210B and the collimating structure 220 are arranged in the same optical element setting cavity 100, which can reduce the space of one collimating lens when the diffractive optical element 10 is used as a structured light projector, and further reduce the occupied space of the whole structured light projector. Figure 8

[0084] ​​​For example, the optical structure comprises: the first diffractive structure 210A disposed on the surface of the first substrate 110A, the collimating structure 220 and the second diffractive structure 210B fused into one structure and disposed on the surface of the second substrate 110B. The actual design is equivalent to still having two layers of diffractive structures 220. When designing the phase distribution of the diffractive structure surface with a large field of view angle, the design difficulty of the double-layer diffractive structure surface is smaller than that of the single-layer diffractive structure surface. For the specific process of fusing the collimating structure 220 and the second diffractive structure 210B into one structure, for example, the phase distribution function of the designed collimating structure 220 is t(x, y), the phase distribution function of the first diffractive structure 210A is ψ(x, y), and the phase distribution function of the second diffractive structure 210B is φ(x, y). The overall phase distribution function of the collimating structure 220 and the second diffractive structure 210B fusion structure can be χ(x, y) = t(x, y) + φ(x, y). Through the phase distribution function, the overall fluctuation profile function of the designed collimating structure 220 and the second diffractive structure 210B fusion structure can be obtained: S(x, y) = (χ(x, y) * λ) / (2π * (n b -n a )), wherein n b corresponds to the refractive index of the material used by the collimating structure 220 and the second diffractive structure 210B fusion structure as a whole, n a corresponds to the refractive index of the cavity filler material disposed in the cavity 100 of the optical element, and λ is the working wavelength of the transmitted light.

[0085] Optionally, as shown in Figure 9 , the first diffractive structure 210A and the second diffractive structure 210B are fused into one structure and disposed on the surface of the first substrate 110A, and the collimating structure 220 is disposed on the surface of the second substrate 110B.

[0086] Specifically, on the basis of the first diffractive structure 210A disposed on the surface of the first substrate 110A and the collimating structure 220 disposed on the surface of the second substrate 110B, the diffractive optical element 10 increases the second diffractive structure 210B. Referring to Figure 9As shown, the second-order diffraction structure 210B is fused with the first-order diffraction structure 210A into one structure and arranged on the same surface, that is, the second-order diffraction structure 210B and the first-order diffraction structure 210A are fused into one structure surface and located on the surface of the first base material 110A, further realizing that the structure fused by the first-order diffraction structure 210A and the second-order diffraction structure 210B and the collimating structure 220 are arranged in the same optical element setting cavity 100, compared with arranging two layers of diffraction structures 210 and one layer of collimating structures 210, here, two layers of diffraction structures 210 are fused into one structure surface, one layer of structure surface is reduced. Without increasing the difficulty of structure surface design, the diffraction effect of the diffractive optical element 10 is ensured, and the integration of the diffractive optical element 10 is higher, and the volume can be made smaller.

[0087] For example, the optical structure 200 includes: the first-order diffraction structure 210A and the second-order diffraction structure 210B fused into one structure arranged on the surface of the first base material 110A, and the collimating structure 220 arranged on the surface of the second base material 110B, and the actual design is equivalent to still having two layers of diffraction structures 120. In the case of meeting the phase distribution when designing a large field of view angle of the diffraction structure 210, the design difficulty of the double-layer diffraction structure 210 is smaller than that of the single-layer diffraction structure 210, in other words, in the case of meeting the same field of view angle, the design difficulty of the two diffraction structures 210 provided by the embodiment of the present application is smaller than that of one diffraction structure. For the specific design process of fusing the first-order diffraction structure 210A and the second-order diffraction structure 210B into one structure, for example, the phase distribution function of the first-order diffraction structure 210A is ψ(x, y), and the phase distribution function of the second-order diffraction structure 210B is φ(x, y), and the phase distribution function of the fused structure of the first-order diffraction structure 210A and the second-order diffraction structure 210B can be: ξ(x, y) = ψ(x, y) + φ(x, y). Through the phase distribution function, the surface relief profile function of the fused structure of the first-order diffraction structure 210A and the second-order diffraction structure 210B can be obtained: S(x, y) = (ξ(x, y) * λ) / (2π * (n b -n a )), wherein n b corresponds to the refractive index of the material used by the fused structure of the first-order diffraction structure 210A and the second-order diffraction structure 210B, n a corresponds to the refractive index of the cavity filler material in the optical element setting cavity 100, and λ is the working wavelength of the transmitted light.

[0088] Further, Figure 12 is another structure diagram of a diffractive optical element provided by the embodiment of the present application, referring to Figure 12As shown in the figure, the at least two layers of substrates 110 include a first substrate 110A, a second substrate 110B and a third substrate 110C; the at least one level of diffractive microstructure 210 includes a first level of diffractive structure 210A and a second level of diffractive structure 210B; the first level of diffractive structure 210A is arranged in the optical element setting cavity 100 / 100A defined by the first substrate 110A and the second substrate 110B, and the second level of diffractive structure 210B is arranged in the optical element setting cavity 100 / 100B defined by the first substrate 110A and the third substrate 110C.

[0089] Specifically, referring to Figure 12 As shown in the figure, the optical element setting cavity 100 includes the first substrate 110A, the second substrate 110B and the third substrate 110C, and two optical element setting cavities 100 can be formed. Specifically, the first substrate 110A and the second substrate 110B together with the connecting part 120 form a closed optical element setting cavity 100 / 100A, and the first substrate 110A and the third substrate 110C together with the connecting part 120 form a closed optical element setting cavity 100 / 100B. Further, referring to Figure 12 As shown in the figure, the two levels of diffractive structures 210 are arranged in the two optical element setting cavities 100 defined by the first substrate 110A, the second substrate 110B and the third substrate 110C, that is, the diffractive optical element 10 can realize the functions of collimation and diffraction, and the optical structure 200 in the diffractive optical element 10 is arranged in the closed optical element setting cavity 100, which ensures the stability of the diffractive optical element 10.

[0090] Figure 13 It is another structure diagram of a diffractive optical element provided by an embodiment of the present application, referring to Figure 13 As shown in the figure, the diffractive structure 210 includes at least one level of diffractive structure 210, the diffractive structure 210 includes a first level of diffractive structure 210A and a second level of diffractive structure 210B, the first level of diffractive structure 210A, the second level of diffractive structure 210B and the collimating structure 220 are fused into one structure and arranged on the same substrate 110 surface.

[0091] Specifically, the optical structure 200 includes at least one diffractive structure 210, i.e. by increasing the diffraction order of the diffractive structure 210, the diffraction angle of the diffractive optical element 10 can be increased, i.e. the field of view angle of the diffractive optical element 10 used in the projector is increased. For example, if the optical structure 200 includes two diffractive structures 210, i.e. a first-order diffractive structure 210A and a second-order diffractive structure 210B, by increasing the diffraction order, the diffraction angle can be increased compared to the case of only one diffractive structure 210, i.e. the field of view angle of the diffractive optical element 10 used in the projector is increased, and the diffraction effect of the diffractive optical element 10 is further improved. Further, the optical element setting cavity 100 includes at least two substrates 110, which are used to realize the closed optical element setting cavity 100. Further, at least one diffractive structure 210 and the collimating structure 220 can be arranged on the same surface of the substrate 210, which can ensure that the diffractive structure 210 and the collimating structure 220 are located in the closed optical element setting cavity 100. In other words, the diffractive optical element 10 integrates the collimating and diffractive functions through the optical element setting cavity 100, and the two functions are integrated into the same structure and arranged on the same surface of the same substrate 110. During the assembly of the two substrates 110, it can be ensured that the two diffractive structures 210, i.e. the first-order diffractive structure 210A and the second-order diffractive structure 210B, located on any one of the substrates 110 are also located on the same surface, i.e. the volume of the optical element setting cavity 100 in the diffractive optical element 10 can be further reduced. For example, if the phase distribution function of the collimating structure 220 is t(x, y), the phase distribution function of the first-order diffractive structure 210A is ψ(x, y), and the phase distribution function of the second-order diffractive structure 210B is φ(x, y), then the phase distribution function of the integrated structure can be φ(x, y) = t(x, y) + ψ(x, y) + φ(x, y). Through the phase distribution function, the surface relief profile function of the integrated structure can be obtained as S(x, y) = (φ(x, y) * λ) / (2π * (n b -n a )), where n b is the refractive index of the material corresponding to the integrated structure, n a is the refractive index of the material corresponding to the cavity filler, and λ is the working wavelength. Overall, the diffractive optical element 10 has both diffractive and collimating functions.

[0092] Referring back to Figure 2 , the refractive index of the second substrate 110B when energized is n1, and the refractive index of the second substrate 110B when not energized is n2, where |n1-n2|>0; the refractive index of the collimating structure 220 is n3, where n1=n3.

[0093] Specifically, when the diffractive optical element 10 is used for 3D structured light and used for scanning and identifying the object to be measured, the 3D structured light includes a structured light transmitter (including the diffractive optical element 10) infrared receiving module, a flood illuminator, and a color receiving module. The infrared receiving module receives the structured light projected by the structured light transmitter to obtain a structured light spot pattern with a structure feature, and a depth map is obtained by algorithm analysis. The infrared receiving module can also receive uniform infrared light projected by the flood illuminator to obtain a uniform infrared map. The color receiving module obtains a color map. The uniform infrared map and the color map can be used for face detection, face framing, face feature comparison, and face recognition in different scenes. The depth map adds face depth information, and can be used for live detection and effectively cope with planar attack means. In the field of face recognition, the 3D structured light imaging module has two light sources, a structured light transmitter and a flood illuminator, which has a high production cost and a large volume after assembly, limiting the application scenarios of the 3D structured light.

[0094] Further, the embodiment of the present application enriches the function of the diffractive optical element 10 by designing the diffractive optical element 10 to place the optical structure 200 including the criteria and the diffraction function in the closed optical element setting cavity 100, and can reduce the device and assembly cost of the overall assembly of the structured light module.

[0095] Further, the above-mentioned infrared receiving module can receive the uniform infrared light projected by the flood illuminator while receiving the structured light projected by the structured light transmitter. The diffractive optical element 10 provided by the embodiment of the present application can emit structured light and uniform infrared light by dynamically adjusting the refractive index of the substrate 110.

[0096] Reference Figure 2As shown, the material of the second substrate 110B of the diffractive optical element 10 can be a kind of electro-refractive index variable material, under the action of an applied electric field, the refractive index of the material can change, such as commonly used electro-optic materials: lithium niobate crystal (LiNbO3), lithium tantalate crystal (LiTaO3), potassium niobate (KTN), lead titanate, etc. That is, the refractive index of the second substrate 110B when powered on is n1, and the refractive index of the second substrate 110B when not powered on is n2, wherein |n1-n2|>0. Further, the refractive index of the collimating structure 220 is n3, wherein n1=n3, that is, the refractive index of the collimating structure 220 is the same as the refractive index of the second substrate 110B when powered on. The specific process is: when a certain voltage is applied to the second substrate 110B, the refractive index of the second substrate 110B material changes in accordance with the refractive index of the collimating structure 220, which is equivalent to the collimating structure 220 having no beam collimating function at this time, and the laser beam still enters the diffractive structure 210 with a certain divergence angle after passing through the second substrate 110B and the collimating structure 220. At this time, the light beam emitted after passing through the diffractive structure 210 is a uniform piece of infrared light, which can replace the original flood illuminator. In this way, by controlling the voltage applied to the second substrate 110B, the diffractive optical element 10 can project a structured light spot or uniform infrared light, and one projector can simultaneously realize the functions of the original two projectors, saving one flood illuminator and further saving cost and reducing the size of the diffractive optical element 10. For example, referring to Figures 2 to 4 As shown, the refractive index of the collimating structure 220 can be adjusted to achieve the projection effect of two kinds of light. Furthermore, by adjusting the refractive index of the material in the diffractive optical element 10, the diffractive optical element 10 with multiple diffractive functions in one optical element setting cavity 100 can also be applied, for example, referring to Figures 6 to 9 and Figure 13 As shown, by adjusting the change of the refractive index between the collimating structure 220 and the second substrate 110B, the projection effect of two kinds of light can be achieved. Further, by adjusting the refractive index of the material in the diffractive optical element 10, the diffractive optical element 10 with multiple diffractive functions in two optical element setting cavities 100 can also be applied, for example, referring to Figure 12 The embodiments of the present application do not make specific limitations on this.

[0097] Continuing to refer to Figure 2 As shown, the diffractive optical element 10 further includes a cavity filler 500 for filling the optical element setting cavity 100; the refractive index of the second substrate 110B and the collimating structure 220 when powered on is n4, and the refractive index of the second substrate 110B and the collimating structure 220 when not powered on is n5, wherein |n4-n5|>0; the refractive index of the cavity filler 500 is n6, wherein n4=n6.

[0098] The DOE 10 further comprises a cavity filler 500, which protects the structure in the DOE 10. The cavity filler 500 can be air, vacuum, glue or polymer, etc. When the cavity filler 500 is vacuum, the structure is isolated from air, preventing the oxidation reaction or other corrosion of the structure caused by the particles in the air. When the cavity filler 500 is glue or polymer, the adhesion between the two substrates is increased, and the structural reliability of the entire DOE 10 is enhanced.

[0099] Referring to Figure 2 The second substrate 110B and the collimating structure 220 are made of an electro- refractive index variable material, which changes the refractive index under the action of an applied electric field. The commonly used electro-optic materials include lithium niobate crystal (LiNbO3), lithium tantalate crystal (LiTaO3), potassium niobate-tantalate (KTN), lead titanate, etc. The refractive index of the second substrate 110B and the collimating structure 220 when powered is n4, and the refractive index of the second substrate 110B and the collimating structure 220 when not powered is n5, where |n4-n5|>0. Further, the refractive index of the material of the cavity filler 500 is n6, where n4=n6, i.e. the refractive index of the cavity filler 500 is the same as the refractive index of the second substrate 110B and the collimating structure 220 when powered. The specific process is as follows: when a certain voltage is applied to the second substrate 110B and the collimating structure 220, the refractive index of the second substrate 110B and the collimating structure 220 changes in accordance with the refractive index of the cavity filler 500, which is equivalent to the collimating structure 220 having no beam collimating function at this time. The laser beam still enters the diffraction structure 210 at a certain divergence angle after passing through the second substrate 110B, the collimating structure 220 and the cavity filler 500. At this time, the light beam emitted after passing through the diffraction structure 210 is a uniform piece of infrared light, which can replace the original flood illuminator. In this way, by controlling the voltage applied to the second substrate 110B and the collimating structure 220, the DOE 10 can project a structured light spot or uniform infrared light. One projector can simultaneously realize the functions of the original two projectors, saving one flood illuminator and further saving cost and reducing the size of the DOE 10. Figures 2 to 4 As shown in FIG. 6, different types of collimating structures 220 can achieve the projection effect of two types of light by adjusting the refractive index. Further, by adjusting the refractive index of the material in the DOE 10, the DOE 10 with multiple levels of diffraction function in the cavity 100 can also be applied, as shown in FIG. 7. Figures 6 to 9 and Figure 13As shown, the projection effect of the two lights is achieved by adjusting the change between the refractive index of the collimation structure 220 and the second substrate 110B and the refractive index of the cavity filler 500. Further, by adjusting the refractive index of the material in the diffractive optical element 10, the diffractive optical element 10 can also be applied to realize a multi-level diffractive function in the optical element setting cavity 100. For reference Figure 12 The embodiments of the present application do not make specific limitations on this.

[0100] Based on the same inventive concept, the embodiments of the present application also provide a preparation method of a diffractive optical element, Figure 14 is a flowchart of a preparation method of a diffractive optical element provided by the embodiments of the present application. The preparation method comprises the following steps:

[0101] S110, providing at least two substrates.

[0102] Exemplarily, the substrate can be transparent glass or plastic material, and the embodiments of the present application do not make specific limitations on this. By providing at least two substrates, the optical element setting cavity can be formed, so as to ensure that the diffractive optical element can set the structure including the collimation and diffractive functions in the optical element setting cavity, and ensure the effect of the diffractive optical element on the light transmission.

[0103] S120, forming an optical structure on the substrate, the optical structure including a diffractive structure and a collimation structure.

[0104] Further, the optical structure is prepared on the substrate, that is, the diffractive structure and the collimation structure are formed on the substrate for forming the optical element setting cavity. Specifically, the diffractive structure and the collimation structure can be made by directly etching, laser direct writing or plasma direct writing technology on the corresponding substrate, or the photoresist can be spin-coated on the substrate, and the nano-imprint can be made, or the precise injection molding process can be used, and the corresponding substrate can be glass material (such as quartz), plastic material (such as PC, PMMA) and the like, and the embodiments of the present application do not make specific limitations on this.

[0105] S130, forming a connecting part on the substrate.

[0106] S140, laminating the at least two substrates through the connecting part to form the optical element setting cavity.

[0107] Further, the connecting part is formed on the substrate, which is used to realize the lamination connection of the two adjacent substrates, and further ensure the formation of the optical element setting cavity. Exemplarily, the connecting part can be a dam adhesive, which ensures the close contact of the two adjacent substrates, and further ensures the airtightness of the optical element setting cavity. The embodiments of the present application do not make specific limitations on the specific material of the connecting part.

[0108] Further, for reference Figure 5As shown, in order to ensure accurate alignment of different substrates 110, the diffractive optical element 10 further comprises alignment marks 700. When the substrates 110 are bonded, the alignment marks 700 can ensure the accuracy of the bonding of the substrates 110, and further ensure the alignment accuracy of the structure in the optical element setting cavity, and further ensure the transmission effect of the light of the diffractive optical element 10.

[0109] Optionally, taking the example that the diffractive optical element comprises two substrates, i.e. a first substrate and a second substrate, the preparation process of the diffractive optical element is exemplified.

[0110] Exemplarily, Figure 15 is a process diagram of a preparation method of a diffractive optical element provided by an embodiment of the present application, referring to Figure 15 As shown, the preparation process comprises:

[0111] At least two substrates 110 are provided, i.e. a first substrate 110A and a second substrate 110B.

[0112] The diffractive structure 210 is directly formed on the first substrate 110A, and the collimating structure 220 is directly formed on the second substrate 110B. That is, the diffractive structure 210 and the collimating structure 220 are respectively formed on the surfaces of different substrates 200.

[0113] The connecting part 600 is formed on the first substrate 110A or the second substrate 110B. The connecting part 600 can include the dam glue 610 and the ultraviolet glue 620. Specifically, the dam glue 610 can be formed on the substrate 110 by exposure and development or dispensing. Further, the thickness of the dam glue 610 is greater than the sum of the heights of the two structures of the diffraction structure 210 and the collimating structure 220. The dam glue 610 can be designed according to the pushing force between the two substrates 110 after bonding. Generally, the pushing force between the two substrates 110 after bonding is required to be greater than 1.5 kgf, and the thickness of the dam glue 610 is 20-30 um. The dam glue 610 is preferably a glue with low flowability and low curing temperature. By setting the dam glue 610, the two substrates can be bonded, and the dam glue 610 can also be used as a dam to prevent the subsequent bonding glue from flowing to the structure. Further, the area inside the dam glue 610 can be filled with the ultraviolet glue 620. Preferably, silicate (SiO2, Al2O3, feldspar powder, coal gangue, etc.) can be added to the ultraviolet glue 620 to increase the viscosity of the ultraviolet glue 620 and improve the air tightness and structural reliability of the seal. The dam glue 610 and the ultraviolet glue 620 are cured by heat or light, and the curing temperature of the dam glue 610 and the ultraviolet glue 620 is preferably controlled within 200°C to avoid affecting the substrate 110 and the structure on the substrate 110. Then, the area 800 is cut by a suitable cutting technology (such as knife cutting, laser cutting, etc.), and the substrate 110 is cut into a plurality of single optical structures 200. At this time, the diffractive optical element 10 is a closed optical element with a cavity, which can protect the structure from external force or environmental pollution.

[0114] Exemplarily, Figure 16 is a process diagram of another preparation method of a diffractive optical element provided by an embodiment of the present application, Figure 17 is a structural schematic diagram of a connecting part provided by an embodiment of the present application, referring to Figure 16 and Figure 17 , the preparation process includes:

[0115] At least two substrates 110 are provided, i.e., the first substrate 110A and the second substrate 110B.

[0116] A plurality of first grooves 910 are prepared on the first substrate 110A, and a plurality of second grooves 920 are prepared on the second substrate 110B. Further, the diffraction structure 210 is prepared between the plurality of first grooves 910, and the collimating structure 220 is prepared between the plurality of second grooves 920. In the design and processing, the positions and sizes of the grooves of the two substrates 110 need to be one-to-one corresponding, so as to ensure that the structures on the first substrate 110A and the optical structures on the second substrate 110B are aligned on the optical axis at the same time, and the positions of the grooves on the two substrates 110 are also one-to-one aligned. That is, the alignment accuracy of the diffractive optical element is improved.

[0117] The connecting portion 600 is formed in the first groove 910 of the first substrate 110A or the second groove 920 of the second substrate 110B. Further, the connecting portion 600 is formed by bonding the first substrate 110A and the second substrate 110B through the isolation element 630. The material of the isolation element 630 can be glass, resin, ceramic or metal, etc. The isolation element 630 is a planar substrate structure arranged by a plurality of isolation columns 630A and a plurality of through holes 630B. The size of the isolation element 630 matches the size of the first substrate 110A and the second substrate 110B. The position of the isolation column 630A corresponds to the position of the groove on the first substrate 110A or the second substrate 110B. In order to prevent the overflow of the ultraviolet glue 620, the length and width of the isolation column 630A are slightly larger than the size of the groove. Figure 16 As shown in the figure, the connecting portion 600 is formed in the second groove 920 of the second substrate 110B. The second groove 920 is designed to prevent the ultraviolet glue 620 from flowing to the optical structure surface and affecting the optical performance of the optical structure. When designing the width of the second groove 920, the width required for subsequent cutting and slicing needs to be reserved. In addition, the width of the second groove 920 needs to ensure that the dispensing amount is sufficient to make the pushing force between the two bonded substrates 110 greater than a certain value. Generally, the pushing force between the two bonded substrates 110 is required to be greater than 1.5 kgf. The conventional width of the second groove 920 can be designed to be 200-450 um, and the depth of the second groove 920 is 20-50 um. Further, the connecting portion 600 can also be bonded in the first groove 910 of the first substrate 110A, which is not specifically shown in the figure. Then, the cutting area 800 is cut by a suitable cutting technology (such as knife cutting, laser cutting, etc.), and the substrate 110 is cut into a plurality of single optical structures 200. At this time, the diffractive optical element 10 is a closed optical element setting cavity, which can protect the structure from external force or environmental pollution.

[0118] Exemplary, Figure 18 is a process diagram of another preparation method of a diffractive optical element provided by an embodiment of the present application, referring to Figure 18 As shown in the figure, the preparation process includes:

[0119] At least two substrates 110 are provided, i.e. the first substrate 110A and the second substrate 110B.

[0120] A plurality of first protrusions 930 are prepared on the second substrate 110B. The collimating structure 220 is prepared between the plurality of first protrusions 930. A plurality of first grooves 910 are prepared on the first substrate 110B. And the diffractive structure 210 is prepared between the plurality of first grooves 910. Referring to Figure 18The first protrusion 903 and the first groove 910 are aligned and attached to ensure the accurate close between the first substrate 110A and the second substrate 110B, and further ensure the alignment of the structure on the first substrate 110A and the optical structure on the second substrate 110B. The depth of the first groove 910 is greater than the sum of the height of the diffraction structure 210 and the collimating structure 220, so that the first groove 910 and the first protrusion 930 are aligned and attached without affecting the diffraction structure 210 and the collimating structure 220. Further, to ensure that the first substrate 110A and the second substrate 110B are aligned and attached based on the first groove 910 and the first protrusion 930, and to prevent the overflow of the ultraviolet glue 620 between the first groove 910 and the first protrusion 930, the transverse size of the first protrusion 930 is greater than the transverse size of the first groove 910, and the transverse size is parallel to the direction of the substrate 110. At the same time, the width of the first groove 910 needs to ensure that the ultraviolet glue 620 is sufficient to make the pushing force between the two substrates 110 after attachment greater than a certain value, and generally requires that the pushing force between the two substrates 110 after adhesion is greater than 1.5 kgf. The conventional first groove 910 width can be designed to be 200-450um, and the first groove 910 depth is 20-50um. The specific values are not limited in the embodiment of the application. Further, the protrusion can also be prepared on the first substrate 110B, and the groove can be prepared on the second substrate 110A, which is not limited in the embodiment of the application. It should be noted that the diffraction structure 210 and the collimating structure 220 prepared on the substrate 110 can be completed by semiconductor lithography process, nano-imprinting process and precision injection molding process, and the embodiment of the application does not limit the specific process. Further, the substrate 110 is cut into a plurality of single diffraction optical elements 10 by a suitable cutting technology (such as knife cutting, laser cutting, etc.), and at this time the diffraction optical element 10 is a closed optical element setting cavity 100, which can protect the structure from external force or environmental pollution.

[0121] In summary, the preparation method of the diffraction optical element provided in the embodiment of the application simultaneously includes the diffraction structure and the collimating structure in the optical element setting cavity, which is equivalent to reducing the setting space of one collimating lens, and reduces the assembly difficulty and cost of the structured light projector. At the same time, the diffraction optical element adopts a closed optical cavity structure, which reduces the production difficulty of the diffraction optical element and protects the optical structure from the pollution of the external environment.

[0122] Note that the above merely describes preferred embodiments of the present application and the principles of the technology applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, modifications and substitutions can be made without departing from the scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the claims.

Claims

1. A diffractive optical element, characterized by The optical element setting cavity comprises at least two layers of substrates and connecting parts connected with the substrates respectively; The diffractive optical element comprises optical structures set in the optical element setting cavity, and the optical structures comprise diffractive structures and collimating structures; the diffractive optical element structure comprises at least one level of the diffractive structures, and the diffractive structures comprise first level diffractive structures and second level diffractive structures; The at least two layers of the substrates comprise a first substrate and a second substrate; the collimating structures are set on the surface of the second substrate; the first level diffractive structures and the second level diffractive structures are set in the space defined by the first substrate and the collimating structures; The refractive index of the second substrate when energized is n1, and the refractive index of the second substrate when not energized is n2, wherein |n1-n2|>0; the refractive index of the collimating structure is n3, wherein n1=n3.

2. The diffractive optical element of claim 1, wherein, There is one level of the diffractive structures and the collimating structures respectively set on different surfaces of the substrates, and the first level diffractive structures and the second level diffractive structures are located on one side of the collimating structures.

3. The diffractive optical element of claim 1, wherein, The first level diffractive structures are set on the surface of the first substrate, and the collimating structures are set on the surface of the second substrate; The second level diffractive structures are set on the surface of the collimating structures and located on the side away from the surface of the second substrate.

4. The diffractive optical element of claim 1, wherein, The first level diffractive structures are set on the surface of the first substrate, and the collimating structures are set on the surface of the second substrate; The second level diffractive structures are set on the surface of the first level diffractive structures and located on the side away from the surface of the first substrate.

5. The diffractive optical element of claim 1, wherein, The first level diffractive structures are set on the surface of the first substrate, and the collimating structures and the second level diffractive structures are fused into one structure and set on the surface of the second substrate.

6. The diffractive optical element of claim 1, wherein, The first level diffractive structures and the second level diffractive structures are fused into one structure and set on the surface of the first substrate, and the collimating structures are set on the surface of the second substrate.

7. The diffractive optical element of claim 1, wherein, The first level diffractive structures, the second level diffractive structures and the collimating structures are fused into one structure and set on the same surface of the substrates.

8. The diffractive optical element of claim 1, wherein, The collimating structures comprise Fresnel microstructures or microlens array structures.

9. A method of manufacturing a diffractive optical element, applied to the diffractive optical element according to any one of claims 1 to 8, characterized by, The preparation method comprises: Providing at least two layers of substrates; the substrates comprise a first substrate and a second substrate, a plurality of first grooves are prepared on the first substrate, and a plurality of second grooves are prepared on the second substrate; wherein the positions and sizes of the first grooves and the second grooves correspond one by one; Forming optical elements on the substrates, the optical elements comprise diffractive structures and collimating structures; the diffractive structures are prepared between a plurality of the first grooves, and the collimating structures are prepared between a plurality of the second grooves; forming a connecting part on the substrate; wherein the connecting part is formed in the first groove or in the second groove; the connecting part is attached between the first substrate and the second substrate by an isolation element; the isolation element comprises a plurality of isolation columns and a plurality of through holes, the plurality of isolation columns and the plurality of through holes are arranged at intervals, the length and width dimensions of the isolation columns are greater than the dimensions of the first groove, and the length and width dimensions of the isolation columns are greater than the dimensions of the second groove; attaching at least two layers of the substrate through the connecting part to form an optical element setting cavity.

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