Design method of diffractive optical elements for improving zeroth order diffraction effects

Abstract

The application provides a design method of a diffractive optical element for improving zero-order diffraction effect. Step S1: obtaining an initial diffractive optical element, using a scalar diffraction algorithm to obtain a phase distribution of the initial diffractive optical element to obtain an initial phase distribution; step S2: performing point array processing on the initial phase distribution to form a point array region, thereby forming a new diffractive optical element; step S3: calculating a processing depth according to a phase difference of the initial phase distribution; step S4: performing vector scanning on the processing depth of the initial diffractive optical element to obtain zero-order diffraction efficiency at different depths, and performing vector scanning on the processing depth of the new diffractive optical element to obtain zero-order diffraction efficiency at different depths; and step S5: comparing and analyzing the zero-order diffraction efficiency at different depths of the initial diffractive optical element and the new diffractive optical element. The application solves the problem of the influence of zero-order diffraction effect on imaging quality in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of diffractive optical manufacturing technology, in particular to a design method of a diffractive optical element for improving zero-order diffraction effect. BACKGROUND

[0002] Diffractive optical element (DOE) is a new optical element that has developed rapidly in recent years. It is usually composed of specific distribution of diffraction structure by semiconductor micro-nano processing technology, which can finely regulate the phase distribution of incident light wave front and generate interference at a certain distance (usually infinite or lens focal plane) to form a specific light intensity distribution. Beam shaping diffractive optical element can realize specified spot shape and energy distribution on the working plane. Among them, the zero-order diffraction effect is crucial to such uniform light diffractive optical element. Larger zero-order diffraction effect will cause a strong zero-order diffraction bright spot in the center of the target light field, which greatly reduces the imaging quality and uniform light effect of the diffractive optical element.

[0003] That is, the diffractive optical element in the prior art has the problem of zero-order diffraction effect affecting the imaging quality. SUMMARY

[0004] The main purpose of the present application is to provide a design method of a diffractive optical element for improving zero-order diffraction effect, so as to solve the problem of zero-order diffraction effect affecting the imaging quality of the diffractive optical element in the prior art.

[0005] In order to achieve the above-mentioned purpose, the present application provides a design method of a diffractive optical element for improving zero-order diffraction effect, comprising: step S1: obtaining an initial diffractive optical element, using a scalar diffraction algorithm to obtain the phase distribution of the initial diffractive optical element to obtain an initial phase distribution; step S2: performing point array processing on the initial phase distribution to form a point array region, thereby forming a new diffractive optical element; step S3: calculating the processing depth of the initial diffractive optical element according to the phase difference of the initial phase distribution; step S4: performing vector scanning on the processing depth of the initial diffractive optical element to obtain the zero-order diffraction efficiency at different depths, and performing vector scanning on the processing depth of the new diffractive optical element to obtain the zero-order diffraction efficiency at different depths; step S5: comparing and analyzing the zero-order diffraction efficiency of the initial diffractive optical element and the new diffractive optical element at different depths.

[0006] Further, in step S1, the initial phase distribution is a second-order phase distribution.

[0007] Further, in step S1, the initial phase distribution includes structure region and non-structure region which are interlaced with each other, and the point array region is selectively arranged in the structure region and the non-structure region.

[0008] Further, in step S2, the dot array region is only distributed in the non-structure region, and the dot array region is periodically distributed in the non-structure region; or the dot array region is only distributed in the structure region, and the dot array region is periodically distributed in the structure region; or the dot array region is globally distributed in the structure region and the non-structure region, and the dot array region is periodically distributed in the structure region and the non-structure region.

[0009] Further, in step S2, the dot array region is only distributed in the non-structure region, and the dot array region is randomly distributed in the non-structure region; or the dot array region is only distributed in the structure region, and the dot array region is randomly distributed in the structure region; or the dot array region is globally distributed in the structure region and the non-structure region, and the dot array region is randomly distributed in the structure region and the non-structure region.

[0010] Further, in step S2, only the outer peripheral edge portion of the non-structure region is provided with the dot array region, so that the dot array region is in a strip shape; or only the outer peripheral edge portion of the structure region is provided with the dot array region, so that the dot array region is in a strip shape; or only the outer peripheral edge portions of the non-structure region and the structure region are provided with the dot array region.

[0011] Further, in step S2, the dot array region includes a plurality of pixel point structures, so that the new diffractive optical element has a plurality of columnar structures.

[0012] Further, in step S2, the dot array processing includes one or more of a global random addition algorithm, a global periodic addition algorithm, an expansion algorithm, and an erosion algorithm.

[0013] Further, in step S1, the initial diffractive optical element is a Fresnel diffractive optical element or a Fraunhofer diffractive optical element.

[0014] Further, in step S5, after comparison and analysis, the depth bandwidth corresponding to the low zero-order diffraction efficiency of the new diffractive optical element is more than twice the depth bandwidth corresponding to the low zero-order diffraction efficiency of the initial diffractive optical element.

[0015] The design method of the diffractive optical element for improving the zero-order diffraction effect comprises the following steps: S1, obtaining an initial diffractive optical element, and using a scalar diffraction algorithm to obtain a phase distribution of the initial diffractive optical element to obtain an initial phase distribution; S2, performing point array processing on the initial phase distribution to form a point array region, thereby forming a new diffractive optical element; S3, calculating a processing depth of the initial diffractive optical element according to a phase difference of the initial phase distribution; S4, performing vector scanning on the processing depth of the initial diffractive optical element to obtain zero-order diffraction efficiencies at different depths, and performing vector scanning on the processing depth of the new diffractive optical element to obtain zero-order diffraction efficiencies at different depths; and S5, comparing and analyzing the zero-order diffraction efficiencies at different depths of the initial diffractive optical element and the new diffractive optical element.

[0016] The present application is directed to the strong zero-order diffraction effect in the diffractive optical element, the point array processing is performed on the initial phase distribution to form a point array region, thereby forming a phase distribution with the point array region, and then a new diffractive optical element with the corresponding phase distribution can be obtained, through comparison verification and analysis, the new diffractive optical element obtained by the method successfully realizes the elimination of the strong zero-order diffraction bright spot, the central zero-order diffraction bright spot of the target diffraction field is eliminated, the light uniformity effect and the imaging quality are improved, and the corresponding processing depth bandwidth is also greatly expanded. The present application realizes the elimination of the zero-order diffraction through the small processing and change of the point array processing, and does not cause large differences in energy of other diffraction orders except the zero-order, thereby ensuring the overall imaging quality, and the minimum zero-order diffraction efficiency can be as low as about 0.05%. BRIEF DESCRIPTION OF DRAWINGS

[0017] The accompanying drawings, which form a part of the present description, are included to provide a further understanding of the application and are incorporated in and constitute a part of this application. The embodiments of the present application, and their

[0018] Figure 1 A flow chart of the design method of the diffractive optical element for improving the zero-order diffraction effect of one optional embodiment of the present application is shown;

[0019] Figure 2 A schematic diagram of an initial diffractive optical element, an initial phase distribution and a target diffraction light field of the present application are shown;

[0020] Figure 3 A setting mode of a point array region in an initial phase distribution of one optional embodiment of the present application is shown;

[0021] Figure 4 A setting mode of a point array region in an initial phase distribution of another optional embodiment of the present application is shown;

[0022] Figure 5 The setting of the point array region in the initial phase distribution of another optional embodiment of the application is shown;

[0023] Figure 6 The zero-order diffraction efficiency curves of the initial diffractive optical element and the new diffractive optical element at different depths are shown;

[0024] Figure 7 The window diffraction efficiency curves of the initial diffractive optical element and the new diffractive optical element at different depths are shown;

[0025] Figure 8 The diffraction light field distribution of the initial diffractive optical element and the new diffractive optical element at different depths is shown.

[0026] Among them, the above-mentioned drawings include the following reference signs:

[0027] 10, light source; 20, collimating lens; 30, initial diffractive optical element; 41, structure region; 42, non-structure region; 51, pixel point structure. DETAILED DESCRIPTION

[0028] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0029] It should be noted that, unless otherwise specified, all technical and scientific terms used in the present application have the same meaning as generally understood by those skilled in the art to which the present application belongs.

[0030] In the present application, unless otherwise specified, the orientation words such as "up, down, top, bottom" are generally directed to the directions shown in the drawings, or are directed to the vertical, perpendicular or gravity directions of the components themselves; similarly, for the convenience of understanding and description, "inner, outer" refers to the inner and outer relative to the contour of the components themselves, but the above orientation words are not used to limit the present application.

[0031] In order to solve the problem of the influence of zero-order diffraction effect on imaging quality in the prior art diffractive optical element, the present application provides a design method of a diffractive optical element for improving the zero-order diffraction effect.

[0032] As Figures 1 to 8As shown, the design method for a diffractive optical element used to improve the zero-order diffraction effect includes: Step S1: Obtain an initial diffractive optical element 30, and use a scalar diffraction algorithm to obtain the phase distribution of the initial diffractive optical element 30 to obtain an initial phase distribution; Step S2: Perform point array processing on the initial phase distribution to form a point array region, thereby forming a new diffractive optical element; Step S3: Calculate the processing depth of the initial diffractive optical element 30 based on the phase difference of the initial phase distribution; Step S4: Perform vector scanning on the processing depth of the initial diffractive optical element 30 to obtain the zero-order diffraction efficiency at different depths, and simultaneously perform vector scanning on the processing depth of the new diffractive optical element to obtain the zero-order diffraction efficiency at different depths; Step S5: Compare and analyze the zero-order diffraction efficiencies of the initial diffractive optical element 30 and the new diffractive optical element at different depths.

[0033] This application addresses the strong zero-order diffraction effect in diffractive optical elements by performing a dot array processing on the initial phase distribution to form a dot array region. This results in a phase distribution with a dot array region, leading to a new diffractive optical element with a corresponding phase distribution. Through comparative verification and analysis, the new diffractive optical element obtained by this method successfully eliminates strong zero-order diffraction bright spots, thereby eliminating the central zero-order diffraction bright spot in the target diffraction field, improving homogenization and imaging quality, and significantly expanding the corresponding processing depth bandwidth. This application eliminates zero-order diffraction through minute processing and changes in the dot array, without causing significant energy differences in other diffraction orders besides the zero order, ensuring overall imaging quality. Furthermore, the lowest zero-order diffraction efficiency of this invention can be as low as approximately 0.05%.

[0034] It should be noted that the scalar diffraction algorithm mentioned above, namely the GS algorithm, is a common basic algorithm in DOE design. The main steps are to solve the DOE phase distribution through forward and inverse Fourier transforms, also known as the IFTA algorithm (Iterative Fourier Transform Algorithm).

[0035] In step S1, the initial phase distribution is a second-order phase distribution, i.e., it only has 0-phase and π-phase. The initial phase distribution is imported into Matlab software, and software algorithms are used to add single-pixel structures 51 or multiple pixel structures 51 to form a dot array region. In step S2, the algorithms for forming the dot array region mainly include one or more of the following: global random addition algorithm, global periodic addition algorithm, expansion algorithm, and erosion algorithm. By constructing a phase distribution with a dot array region, a strong central zero-order diffraction bright spot is successfully eliminated while ensuring a high level of overall homogenization effect and imaging quality for the circular diffraction spot. Furthermore, the DOE processing depth bandwidth corresponding to the low zero-order diffraction effect is also increased.

[0036] Global random addition algorithm: the point array region is randomly added in the whole initial phase distribution, where no pi phase structure is added in the structure area 41, only 0 phase structure is added, no 0 phase structure is added in the non-structure area 42, only pi phase structure is added. In other words, the diffractive optical element after adding the point array region still maintains the second-order phase distribution 0 and pi.

[0037] Global periodic addition algorithm: the added point array region is uniformly distributed in the whole initial phase distribution with a certain period, and only the point array region in a single period has a difference on the pixel structure 51. Similarly, no pi phase structure is added in the structure area 41, only 0 phase structure is added, no 0 phase structure is added in the non-structure area 42, only pi phase structure is added. In other words, the diffractive optical element after adding the point array region still maintains the second-order phase distribution 0 and pi.

[0038] Expansion algorithm: a non-global addition algorithm, the main method is to keep the structure area 41 in the initial phase distribution unchanged, and add a random pi phase point array region on the periphery of the structure area 41, that is, to expand the structure area outward, that is, the expansion algorithm.

[0039] Erosion algorithm: a non-global addition algorithm, the main method is to keep the non-structure area 42 in the initial phase distribution unchanged, and add a random 0 phase point array region on the periphery of the non-structure area 42, that is, to expand the non-structure area outward, at this time, corresponding to the inward erosion of the structure area, that is, the erosion algorithm.

[0040] As shown in Figure 2 The light emitted by the light source 10 irradiates the diffractive optical element, and then a corresponding diffractive light field is obtained. The light source 10 can be a collimated plane wave light source 10 or a Gaussian distributed laser light source 10. The diffractive light spot obtained in the final diffractive light field can be a uniform circular spot, but is not limited thereto. In step S1, the scalar diffraction algorithm is used to obtain the second-order phase distribution of the initial diffractive optical element 30 to obtain the initial phase distribution. The theoretical depth corresponding to the phase difference of the initial phase distribution and the refractive index of the material of the initial diffractive optical element 30 at the wavelength of the test light source 10 is calculated, and the depth is processed for testing. The test depth meets the requirements. The optical performance is characterized, and it can be seen that although the uniform light effect of the target diffractive light field is good, as described in the background art, a bright zero-order diffraction spot appears in the center of the diffractive field. Figure 2 The upper right is the initial phase distribution, and the lower is the target diffractive light field. By performing a certain range of vector scanning on the processing depth, a diffractive light field with low zero-order diffraction effect can be obtained above the theoretical depth.

[0041] As shown in Figure 2The light source 10 is a 660nm laser light source, which is parallel incident to the surface of the initial diffractive optical element 30 after collimating lens 20, and then diffractive plane imaging. Corresponding to the theoretical processing depth, the diffractive field uniform light effect is excellent, the overall uniformity is good, but the zero-order diffraction effect is obvious, and there is a strong zero-order diffraction bright spot in the central of the diffractive field.

[0042] The initial phase distribution of the present application is a second-order phase distribution, that is, only 0 phase and π phase. When the dot array region is arranged, it can be periodically arrayed in the 0 phase in the π phase, or periodically arrayed in the π phase in the 0 phase; or it can be randomly distributed in the 0 phase in the π phase, or randomly distributed in the π phase in the 0 phase.

[0043] As shown in Figures 2 to 5 , in step S1, the initial phase distribution includes a structure region 41 and a non-structure region 42 interlaced with each other, the structure region 41 and the non-structure region 42 are complementary, and the dot array region is selectively arranged in the structure region 41 and the non-structure region 42. The dot array region can be distributed in the whole region or locally distributed in the edge region.

[0044] Figures 3 to 5 Different distribution forms of the dot array region are shown respectively, and each figure includes three specific distribution schematic diagrams, and only a partial enlarged view is shown in the upper right corner of each distribution schematic diagram.

[0045] In an optional embodiment of the present application, in step S2, as shown in the first figure of Figure 3 , the dot array region is only distributed in the whole region of the non-structure region 42, and the dot array region is periodically and regularly distributed in the non-structure region 42; or, as shown in the second figure of Figure 3 , the dot array region is only distributed in the whole region of the structure region 41, and the dot array region is periodically and regularly distributed in the structure region 41; or, as shown in the third figure of Figure 3 , the dot array region is distributed in the whole region of the structure region 41 and the non-structure region 42, and the dot array region is periodically and regularly distributed in the structure region 41 and the non-structure region 42.

[0046] In another optional embodiment of the present application, in step S2, as shown in the first figure of Figure 4 , the dot array region is only distributed in the whole region of the non-structure region 42, and the dot array region is randomly distributed in the non-structure region 42; or, as shown in the second figure of Figure 4 , the dot array region is only distributed in the whole region of the structure region 41, and the dot array region is randomly distributed in the structure region 41; or, as shown in the third figure of Figure 4 , the dot array region is distributed in the whole region of the structure region 41 and the non-structure region 42, and the dot array region is randomly distributed in the structure region 41 and the non-structure region 42.

[0047] In another optional embodiment of the present application, the dot array region can be edge-localized. In step S2, as shown in the first drawing of FIG. 4, only the outer peripheral portion of the non-structure region 42 is provided with the dot array region, so that the dot array region is in a strip shape; or, as shown in the second drawing of FIG. 4, only the outer peripheral portion of the structure region 41 is provided with the dot array region, so that the dot array region is in a strip shape; or, as shown in the third drawing of FIG. 4, only the outer peripheral portions of the non-structure region 42 and the structure region 41 are provided with the dot array region, so that the dot array region is in a strip shape. When the dot array region is edge-localized, the dot array region can be randomly distributed in a π phase. Figure 5 In another optional embodiment of the present application, the dot array region can be edge-localized. In step S2, as shown in the first drawing of FIG. 4, only the outer peripheral portion of the non-structure region 42 is provided with the dot array region, so that the dot array region is in a strip shape; or, as shown in the second drawing of FIG. 4, only the outer peripheral portion of the structure region 41 is provided with the dot array region, so that the dot array region is in a strip shape; or, as shown in the third drawing of FIG. 4, only the outer peripheral portions of the non-structure region 42 and the structure region 41 are provided with the dot array region, so that the dot array region is in a strip shape. When the dot array region is edge-localized, the dot array region can be randomly distributed in a π phase. Figure 5 In another optional embodiment of the present application, the dot array region can be edge-localized. In step S2, as shown in the first drawing of FIG. 4, only the outer peripheral portion of the non-structure region 42 is provided with the dot array region, so that the dot array region is in a strip shape; or, as shown in the second drawing of FIG. 4, only the outer peripheral portion of the structure region 41 is provided with the dot array region, so that the dot array region is in a strip shape; or, as shown in the third drawing of FIG. 4, only the outer peripheral portions of the non-structure region 42 and the structure region 41 are provided with the dot array region, so that the dot array region is in a strip shape. When the dot array region is edge-localized, the dot array region can be randomly distributed in a π phase. Figure 5 In another optional embodiment of the present application, the dot array region can be edge-localized. In step S2, as shown in the first drawing of FIG. 4, only the outer peripheral portion of the non-structure region 42 is provided with the dot array region, so that the dot array region is in a strip shape; or, as shown in the second drawing of FIG. 4, only the outer peripheral portion of the structure region 41 is provided with the dot array region, so that the dot array region is in a strip shape; or, as shown in the third drawing of FIG. 4, only the outer peripheral portions of the non-structure region 42 and the structure region 41 are provided with the dot array region, so that the dot array region is in a strip shape. When the dot array region is edge-localized, the dot array region can be randomly distributed in a π phase.

[0048] Specifically, the dot array region includes a plurality of pixel point structures 51. After the dot array region is provided in the initial phase distribution, the structure of the entire diffractive optical element is changed, and the pixel point structure 51 in the phase distribution corresponds to a columnar structure of the diffractive optical element, that is, after the dot array region is provided in the initial phase distribution, the new diffractive optical element obtained has a plurality of columnar structures. Since the diffractive optical element of the present application is in the micro-nano level, a single pixel point structure 51 is a structure point in the nano level, and the size of the pixel point structure 51 of the present application is 100 nm. It should be noted that the above columnar structure is not a cylinder but a polygonal column, specifically a quadrangular column; the cross section of the columnar structure is a quadrilateral, specifically a square, not a circle.

[0049] Of course, the initial phase distribution can also be grid partitioned to form a plurality of blocks, and the number of pixel point structures 51 in one block does not exceed 5*5, so as to ensure the diffraction stability of the diffractive optical element.

[0050] In an optional embodiment of the present application, the initial diffractive optical element 30 is a Fresnel diffractive optical element.

[0051] Or in another optional embodiment of the present application, the initial diffractive optical element 30 is a Fraunhofer diffractive optical element.

[0052] It should be noted that in the design of the diffractive optical element, the scalar diffraction theory is an approximate theory, which has different applicable conditions: Fresnel approximation and Fraunhofer approximation, the main difference lies in the diffraction distance of the diffracted field to the diffractive optical element, and the corresponding DOE phase solved by using the approximate condition is the Fresnel diffractive optical element or the Fraunhofer diffractive optical element. Fresnel and Fraunhofer represent the approximate method of the scalar diffraction theory used in solving the diffractive optical element, and are not a specific shape and structure of the optical element.

[0053] In step S5, after comparative analysis, the depth bandwidth corresponding to the lower zero-order diffraction efficiency of the new diffraction optical element is more than twice that of the lower zero-order diffraction efficiency of the initial diffraction optical element 30.

[0054] Specifically, such as Figure 6 As shown, the zero-order diffraction efficiency curves of the initial diffraction optical element 30 and the new diffraction optical element at different depths are illustrated. Constructing a point array region within the initial phase distribution can further reduce the zero-order diffraction efficiency and expand the corresponding depth range; relatively speaking, the overall diffraction performance of the two does not show a significant difference. Figure 6 As can be seen, below the zero-order diffraction efficiency of 0.2%, the overall diffraction field is uniformly distributed with no obvious bright spot in the center. The initial diffraction optical element 30 can only be obtained in a very small range of 10nm, and the efficiency is close to 0.2%. The new diffraction optical element not only has a lower zero-order diffraction efficiency, but also the depth range below the zero-order diffraction efficiency of 0.2% is widened to about 30nm.

[0055] like Figure 7 As shown, the window diffraction efficiency curves of the initial diffraction optical element 30 and the new diffraction optical element at different depths are displayed. The data in the figure shows that the overall window diffraction efficiency decreased by only about 0.6%, with a relative difference of only about 0.008%, which can be considered almost no change. Figure 8 As shown, the diffraction field distribution of the initial diffraction optical element 30 and the new diffraction optical element at different depths is illustrated. The upper right corner of the figure shows a magnified view near the zeroth order. As can be seen from the figure, the new diffraction optical element not only further reduces its zeroth-order diffraction efficiency, but also increases the depth bandwidth corresponding to the low zeroth-order diffraction efficiency from approximately 10 nm initially to approximately 25 nm, expanding by more than two times.

[0056] Specifically, the processing depth of a diffractive optical element without a zero-order diffraction bright spot can be obtained through vector scanning; however, the depth bandwidth of its lower zero-order diffraction effects is relatively narrow, such as... Figure 6 , Figure 8 This only occurs within a depth range of approximately 10 nm. However, the new diffractive optical element containing a dot array region not only further reduces its zero-order diffraction efficiency, but also increases the depth bandwidth corresponding to the low zero-order diffraction efficiency to approximately 25 nm, more than doubling the range.

[0057] It should be noted that the specific structure of the phase distribution with the point array region to the diffractive optical element of the present application mainly relates to the processing technology, and the present application focuses on the design of introducing the point array region in the second-order phase distribution. The specific process flow is as follows: obtaining the phase distribution diagram with the point array region, then generating the gds processing drawing, then selecting the substrate glass, uniformly coating the photoresist (this process controls the design depth), and finally laser lithography exposure to generate the master plate, then the master plate is nano-imprinted to form the sub-plate, and a new diffractive optical element is formed.

[0058] In order to eliminate the adverse effects of the zero-order diffraction effect of the diffractive optical element (DOE), there are mainly two existing technical solutions. One is to introduce a refractive optical element (generally a lens), to form a catadioptric optical system with the diffractive optical element, to separate the zero-order diffraction point from the target field by focusing with a positive lens, or to increase the divergence of the light source 10 by using a negative lens, no matter which one, it increases the complexity of the optical system. The second is to realize it by superimposing diffractive optical elements, the main principle of which is to design a phase elimination phase for the zero-order diffraction field on the phase of the target field diffractive optical element, and to superimpose the two diffractive optical elements. This method has certain requirements for design and processing capacity. In view of this, the present application aims to change the internal phase structure distribution of the initial diffractive optical element 30 corresponding to the target light field, which realizes the elimination of the zero-order diffraction effect under the guarantee of the design of the single-piece diffractive optical element.

[0059] Obviously, the above-described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0060] It should be noted that the terms used herein are only intended to describe specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, they indicate the presence of the features, steps, operations, devices, components and / or combinations thereof.

[0061] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0062] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A design method of a diffractive optical element for improving a zeroth order diffraction effect, characterized by, The method comprises the following steps: Step S1: obtaining an initial diffractive optical element (30), and using a scalar diffraction algorithm to obtain a phase distribution of the initial diffractive optical element (30) to obtain an initial phase distribution; Step S2: performing point array processing on the initial phase distribution to form a point array region, thereby forming a new diffractive optical element; the point array processing comprises one or more of a global random addition algorithm, a global period addition algorithm, an extension algorithm, and an erosion algorithm; Step S3: calculating a machining depth of the initial diffractive optical element (30) according to a phase difference of the initial phase distribution; Step S4: performing vector scanning on the machining depth of the initial diffractive optical element (30) to obtain a zero-order diffraction efficiency at different depths, and performing vector scanning on the machining depth of the new diffractive optical element to obtain a zero-order diffraction efficiency at different depths; Step S5: comparing and analyzing the zero-order diffraction efficiencies of the initial diffractive optical element (30) and the new diffractive optical element at different depths.

2. The design method of a diffractive optical element for improving a zeroth order diffraction effect according to claim 1, characterized in that, In the step S1, the initial phase distribution is a second-order phase distribution.

3. The method of designing a diffractive optical element for improving zero-order diffraction effects according to claim 1, wherein In the step S1, the initial phase distribution comprises a structure region (41) and a non-structure region (42) which are interwoven with each other, and the point array region is selectively arranged in the structure region (41) and the non-structure region (42).

4. The design method of a diffractive optical element for improving a zeroth order diffraction effect according to claim 3, characterized in that, In the step S2, the point array region is only distributed in the non-structure region (42) and is periodically distributed in the non-structure region (42); or the point array region is only distributed in the structure region (41) and is periodically distributed in the structure region (41); or the point array region is globally distributed in the structure region (41) and the non-structure region (42), and is periodically distributed in the structure region (41) and the non-structure region (42).

5. The method of designing a diffractive optical element for improving zero-order diffraction effects according to claim 3, wherein In the step S2, the point array region is only distributed in the non-structure region (42) and is randomly distributed in the non-structure region (42); or the point array region is only distributed in the structure region (41) and is randomly distributed in the structure region (41); or the point array region is globally distributed in the structure region (41) and the non-structure region (42), and is randomly distributed in the structure region (41) and the non-structure region (42).

6. The method of designing a diffractive optical element for improving zero-order diffraction effects according to claim 3, wherein In the step S2, only the outer peripheral portion of the non-structure region (42) is provided with the point array region, so that the point array region is in a strip shape; or only the outer peripheral portion of the structure region (41) is provided with the point array region, so that the point array region is in a strip shape; or only the outer peripheral portions of the non-structure region (42) and the structure region (41) are provided with the point array region.

7. The method of designing a diffractive optical element for improving zero-order diffraction effects according to claim 1, wherein In the step S2, the point array region comprises a plurality of pixel point structures (51), so that the new diffractive optical element has a plurality of columnar structures.

8. The method of designing a diffractive optical element for improving zero-order diffraction effect according to claim 1, wherein, In the step S1, the initial diffractive optical element (30) is a Fresnel diffractive optical element or a Fraunhofer diffractive optical element.

9. The method of designing a diffractive optical element for improving zero-order diffraction effects according to claim 1, wherein, In the step S5, after the comparative analysis, the depth bandwidth corresponding to the low zero-order diffraction efficiency of the new diffractive optical element is more than doubled relative to the depth bandwidth corresponding to the low zero-order diffraction efficiency of the initial diffractive optical element (30).

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