Diffractive optical element and method for manufacturing same

Abstract

A method of manufacturing a diffractive optical element includes determining a phase distribution of the diffractive optical element based on a scalar GS algorithm, performing first binary quantization on the phase distribution in a first interval or a second interval obtained by Fourier transform, setting the phase distribution in the first interval as a first value, and setting the phase distribution in the second interval as a second value; the phase distribution in the first interval is set as a first value, the phase distribution in the second interval is set as a second value, the range size of the first interval is different from that of the second interval, so that the vector zero order of the large-angle beam splitting dot matrix is effectively reduced under the scalar design condition, and the sum of the range size of the first interval and the range size of the second interval is 2pi; and forming the diffractive optical element with a two-step structure according to the determined phase distribution of the diffractive optical element.

Description

Technical Field

[0001] The present invention generally relates to the field of diffractive optical technology, and in particular to a diffractive optical element and a manufacturing method thereof. Background Art

[0002] In 3D recognition systems such as binocular vision, structured light, and Tof, the depth recognition algorithm has high non-uniformity requirements for the projected scattered spot array, and the non-uniformity of the scattered spot array mainly depends on the beam splitting non-uniformity of the beam splitting device. Therefore, in the design process of the beam splitting device, it is necessary to make the energy of each beam splitting point as close as possible, that is, the non-uniformity of the dot array energy is as low as possible, which puts high requirements on the design method of the beam splitting dot array. The scalar GS algorithm can be used to design a dot array with low non-uniformity, but in the case of a large field of view (FOV), the characteristic size of the microstructure has reached the wavelength level. At this time, due to the existence of the vector effect, the (actual) zero order under the vector simulation is usually very high, which will make the dot array non-uniformity worse.

[0003] The contents of the background technology section are merely the technologies known to the inventors and do not necessarily represent the prior art in the field. Summary of the invention

[0004] In view of one or more deficiencies in the prior art, the present invention provides a diffractive optical element and a method for manufacturing the same.

[0005] According to one aspect of the present invention, there is provided a method for manufacturing a diffractive optical element, comprising:

[0006] Design of diffractive optical elements, including:

[0007] Determining an amplitude distribution of incident light of the diffractive optical element on a first plane and a target amplitude distribution of outgoing light of the diffractive optical element on a second plane, and presetting an initial phase distribution of the diffractive optical element, wherein the first plane is an incident plane of the diffractive optical element, and the outgoing light of the diffractive optical element is to form an optical pattern on the second plane;

[0008] Determining the phase distribution of the diffractive optical element based on a scalar GS algorithm includes:

[0009] Combining the initial phase distribution of the diffractive optical element with the amplitude distribution of the incident light in the first plane to perform Fourier transform, and then combining the phase distribution obtained by Fourier transform with the target amplitude distribution of the outgoing light in the second plane to perform inverse Fourier transform, thereby completing a first iterative process;

[0010] The phase distribution obtained by inverse Fourier transform is combined with the amplitude distribution of the incident light in the first plane to perform Fourier transform, and then the phase distribution obtained by Fourier transform is combined with the target amplitude distribution of the outgoing light in the second plane to perform inverse Fourier transform, thereby completing the second iterative process, and repeating the second iterative process, wherein, in at least one of the second iterative processes, the phase distribution obtained by Fourier transform and in the first interval or the second interval is first binary quantized, the phase distribution in the first interval is set to a first value, and the phase distribution in the second interval is set to a second value, the range size of the first interval is different from the range size of the second interval, so as to effectively reduce the vector zero order of the large-angle beam splitting point array under scalar design conditions, and the range size of the first interval and the range size of the second interval are 2π in total;

[0011] A diffractive optical element having a two-step structure is formed according to the determined phase distribution of the diffractive optical element.

[0012] According to an embodiment of the present invention, the amplitude distribution of the incident light on the first plane is determined according to a light source.

[0013] According to an embodiment of the present invention, a target amplitude distribution of the output light of the diffractive optical element in the second plane is determined according to a target optical pattern.

[0014] According to an embodiment of the present invention, the optical pattern is a beam splitting array.

[0015] According to an embodiment of the present invention, the target amplitude distribution of the outgoing light of the diffractive optical element in the second plane is determined according to the parameters of the target beam splitting point array.

[0016] According to an embodiment of the present invention, the parameter includes at least one of the field of view, resolution, and target light intensity distribution of the target beam splitting array.

[0017] According to an embodiment of the present invention, the range size of the first interval is greater than the range size of the second interval.

[0018] According to an embodiment of the present invention, the range of the first interval is greater than π.

[0019] According to an embodiment of the present invention, the range of the first interval is between 1.1π and 2π.

[0020] According to an embodiment of the present invention, the range of the first interval is between 1.9π and 2π.

[0021] According to an embodiment of the present invention, the first value is 0 and the second value is π.

[0022] According to an embodiment of the present invention, in at least one of the second iteration processes before performing the first binary quantization, a second binary quantization is performed on the phase distribution obtained by Fourier transform and in a third interval or a fourth interval, and the phase distribution in the third interval is set to a third value, and the phase distribution in the fourth interval is set to a fourth value, and the range size of the third interval and the range size of the fourth interval are both less than π.

[0023] According to an embodiment of the present invention, the range size of the third interval and the range size of the fourth interval increase with an increase in the number of iterations.

[0024] According to an embodiment of the present invention, the range size of the third interval and the range size of the fourth interval gradually increase from zero.

[0025] According to an embodiment of the present invention, the range size of the third interval and the range size of the fourth interval are both smaller than 0.6π.

[0026] According to an embodiment of the present invention, the range size of the third interval and the range size of the fourth interval are both smaller than 0.3π.

[0027] According to an embodiment of the present invention, the range size of the third interval is equal to the range size of the fourth interval.

[0028] According to an embodiment of the present invention, the third interval and the fourth interval are symmetrically distributed.

[0029] According to an embodiment of the present invention, the third value is 0, and the fourth value is π.

[0030] According to another aspect of the present invention, a diffractive optical element is provided, which is manufactured by the above method.

[0031] According to an embodiment of the present invention, the convex areas on the surface of the diffractive optical element are not distributed continuously.

[0032] By the method for manufacturing a diffractive optical element provided by the present invention, the vector zero order of a large-angle beam splitting lattice is effectively reduced under scalar design conditions. Specifically, by introducing the first binary quantization in the second iterative process, or further introducing the second binary quantization, a stepped DOE phase with a higher zero order under scalar simulation is forced to be obtained, so that the zero order of the vector simulation is within the target level range, thereby effectively reducing the non-uniformity of the output light field. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0034] Figure 1 A schematic flow chart of a method for manufacturing a diffractive optical element according to an embodiment of the present invention is shown.

[0035] Figure 2 The embodiment of the present invention is shown Figure 1 A schematic flow chart of step S1 is shown.

[0036] Figure 3 The embodiment of the present invention is shown Figure 2 A schematic flow chart of step S12 is shown.

[0037] Figure 4 A schematic structural diagram of a diffraction optical system according to an embodiment of the present invention is shown.

[0038] Figure 5 A schematic flow chart of a scalar GS algorithm according to an embodiment of the present invention is shown.

[0039] Figure 6 The phase distribution according to the embodiment of the present invention is shown. An example of performing the first binary quantization.

[0040] Figure 7 The phase distribution according to the embodiment of the present invention is shown. An example of performing the second binary quantization.

[0041] 8(a), (b), (c), and (d) are schematic diagrams showing comparative examples of scalar GS iteration processes according to embodiments of the present invention.

[0042] 9(a), (b), and (c) are schematic diagrams showing an application example of a scalar GS iteration process according to an embodiment of the present invention.

[0043] FIG. 10 ( a ) and ( b ) show phase diagrams of a diffractive optical element (DOE) designed according to the comparative example shown in FIG. 8 and vector simulation results thereof.

[0044] FIG. 11 ( a ) and ( b ) show the phase diagram of the diffractive optical element (DOE) designed according to the application example shown in FIG. 9 and the vector simulation results thereof.

[0045] Fig.12 Schematic diagrams showing target beam splitting point arrays of the comparative example shown in FIG. 8 and the application example shown in FIG. 9 are shown.

[0046] 13(a) and (b) are schematic diagrams showing a vector simulation process in two cases according to an embodiment of the present invention. DETAILED DESCRIPTION

[0047] As can be seen from the background art, in the prior art, under the condition of a large field of view (FOV), due to the existence of a vector effect, there is a problem of deterioration of the non-uniformity of the lattice.

[0048] In order to solve the technical problem, the present invention provides a method for manufacturing a diffractive optical element, comprising:

[0049] Design of diffractive optical elements, including:

[0050] Determining an amplitude distribution of incident light of the diffractive optical element on a first plane and a target amplitude distribution of outgoing light of the diffractive optical element on a second plane, and presetting an initial phase distribution of the diffractive optical element, wherein the first plane is an incident plane of the diffractive optical element, and the outgoing light of the diffractive optical element is to form an optical pattern on the second plane;

[0051] Determining the phase distribution of the diffractive optical element based on a scalar GS algorithm includes:

[0052] Combining the initial phase distribution of the diffractive optical element with the amplitude distribution of the incident light in the first plane to perform Fourier transform, and then combining the phase distribution obtained by Fourier transform with the target amplitude distribution of the outgoing light in the second plane to perform inverse Fourier transform, thereby completing a first iterative process;

[0053] The phase distribution obtained by inverse Fourier transform is combined with the amplitude distribution of the incident light in the first plane to perform Fourier transform, and then the phase distribution obtained by Fourier transform is combined with the target amplitude distribution of the outgoing light in the second plane to perform inverse Fourier transform, thereby completing the second iterative process, and repeating the second iterative process, wherein, in at least one of the second iterative processes, the phase distribution obtained by Fourier transform and in the first interval or the second interval is first binary quantized, the phase distribution in the first interval is set to a first value, and the phase distribution in the second interval is set to a second value, the range size of the first interval is different from the range size of the second interval, so as to effectively reduce the vector zero order of the large-angle beam splitting point array under scalar design conditions, and the range size of the first interval and the range size of the second interval are 2π in total;

[0054] A diffractive optical element having a two-step structure is formed according to the determined phase distribution of the diffractive optical element.

[0055] In the technical solution of the present invention, by introducing the first binary quantization in the second iterative process, a stepped DOE phase with a higher zero order under scalar simulation is forced to be obtained, so that the zero order of the vector simulation is within the target level range, that is, the vector zero order of the large-angle beam splitting point array is effectively reduced under scalar design conditions, thereby effectively reducing the non-uniformity of the output light field.

[0056] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0057] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0058] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0059] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0060] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply means that the first feature is lower in level than the second feature.

[0061] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0062] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0063] Figure 1 FIG. 2 is a schematic flow chart of a method for manufacturing a diffractive optical element according to an embodiment of the present invention. Figure 1 As shown, the method may include the following steps:

[0064] S1: designing a diffractive optical element to determine a phase distribution of the diffractive optical element;

[0065] S2: forming the diffractive optical element according to the determined phase distribution of the diffractive optical element.

[0066] It should be noted that when light is incident on the surface of the diffractive optical element, the surface structure of the diffractive optical element modulates the initial phase distribution of the incident light (i.e., the phase distribution before modulation). The phase distribution of the diffractive optical element characterizes the surface structure of the diffractive optical element, and thus the diffractive optical element can be formed accordingly.

[0067] Figure 2 The embodiment of the present invention is shown Figure 1 The schematic flow chart of step S1 is shown in FIG. Figure 2 As shown, step S1 may include the following steps:

[0068] S11: determining an amplitude distribution of incident light of the diffractive optical element in a first plane and a target amplitude distribution of outgoing light of the diffractive optical element in a second plane, and presetting an initial phase distribution of the diffractive optical element;

[0069] S12: Determine the phase distribution of the diffractive optical element based on a scalar GS algorithm.

[0070] In step S11, the first plane is the incident plane of the diffractive optical element, and the outgoing light of the diffractive optical element is to form an optical pattern on the second plane.

[0071] It should be noted that the initial phase distribution of the diffractive optical element is preset, and the phase distribution of the diffractive optical element can be finally determined through multiple iterations described below, and the phase distribution of the diffractive optical element characterizes the surface structure of the diffractive optical element.

[0072] In some embodiments of the present invention, the amplitude distribution of the incident light in the first plane is determined according to a light source.

[0073] It should be noted that the amplitude of light is related to the vibration characteristics of the light source. The amplitude of light is also related to factors such as the medium in which the light propagates, and the amplitude will decay as the propagation distance increases.

[0074] In some embodiments of the present invention, a target amplitude distribution of the output light of the diffractive optical element in the second plane is determined according to a target optical pattern.

[0075] It should be noted that the intensity of light is proportional to the square of the amplitude. The target optical pattern represents the target light intensity distribution on the target plane (ie, the second plane), and therefore, the target amplitude distribution on the target plane can be determined.

[0076] In some embodiments of the present invention, the optical pattern is a beam splitting array.

[0077] By distributing the initial phase of incident light through the surface structure of the diffractive optical element according to some embodiments of the present invention, a beam splitting lattice of, for example, a laser beam splitting pattern can be obtained.

[0078] In some embodiments of the present invention, a target amplitude distribution of the outgoing light of the diffractive optical element in the second plane is determined according to parameters of a target beam splitting point array.

[0079] Specifically, the parameters include at least one of the field of view, resolution, and target light intensity distribution of the target beam splitting array.

[0080] Figure 3 The embodiment of the present invention is shown Figure 2 FIG. 1 is a schematic flow chart of step S12. Figure 3 As shown, step S12 may include the following steps:

[0081] First iterative process S121: combining the initial phase distribution of the diffractive optical element with the amplitude distribution of the incident light in the first plane to perform Fourier transform, and then combining the phase distribution obtained by Fourier transform with the target amplitude distribution of the outgoing light in the second plane to perform inverse Fourier transform;

[0082] Second iterative process S122: combining the phase distribution obtained by inverse Fourier transform with the amplitude distribution of the incident light in the first plane to perform Fourier transform, and then combining the phase distribution obtained by Fourier transform with the target amplitude distribution of the outgoing light in the second plane to perform inverse Fourier transform;

[0083] Repeat the second iteration process S122. In at least one second iteration process S122, the phase distribution obtained by Fourier transform and in the first interval or the second interval is first binary quantized, the phase distribution in the first interval is set to a first value, and the phase distribution in the second interval is set to a second value, the range size of the first interval is different from the range size of the second interval, so as to effectively reduce the vector zero order of the large-angle beam splitting point array under the scalar design condition, and the range size of the first interval and the range size of the second interval are 2π in total.

[0084] It should be noted that when light is incident on the surface of the diffractive optical element, the surface structure of the diffractive optical element modulates the initial phase distribution of the incident light (i.e., the phase distribution before modulation). The incident light is usually regarded as a plane wave, so the initial phase distribution of the incident light does not need to be considered in the calculation.

[0085] The phase distribution obtained by inverse Fourier transform in the last second iteration process S122 (i.e., the last inverse Fourier transform) is finally determined as the phase distribution of the diffractive optical element. The phase distribution of the diffractive optical element characterizes the surface structure of the diffractive optical element, so that the diffractive optical element can be formed based on this.

[0086] In particular, in at least the last second iteration process S122, the phase distribution obtained by Fourier transform is subjected to the first binary quantization processing, so that the phase distribution of the diffractive optical element finally determined is also binary, and therefore, the diffractive optical element (DOE) has a two-step structure.

[0087] The at least one second iteration process S122 in which the first binary quantization processing is performed does not have a strict quantization convergence condition, and it is basically sufficient to perform such a second iteration process S122 more than ten times.

[0088] In addition, it should be noted that the range of the continuous phase distribution is (0, 2π). In optics, one phase value corresponds to one physical thickness, and the DOE microstructure is processed by a two-step processing method, so it is equivalent to having only two physical thicknesses, which is equivalent to corresponding to two phase values. Therefore, it is necessary to divide the continuous phase distribution (0, 2π) into two quantization intervals in order to quantize them into two values ​​(i.e., hard quantized phase), so the two quantization intervals add up to 2π. Because the range of the continuous phase distribution is (0, 2π), taking the middle value π of (0, 2π), the two intervals can be assigned 0 and π respectively, which achieves better results than assigning non-π values.

[0089] In the embodiment of the present invention, the two quantization intervals are not the same size, that is, one interval is larger than the other interval, which is a result obtained by the inventor after continuous attempts. Assuming that the pixel of the DOE is 1001x1001 and the resolution is 500nm, usually, these 100,000 pixels are evenly distributed within 0~2π, so if the two quantization intervals are the same size, then 50,000 pixels will be quantized to 0 and 50,000 pixels will be quantized to π, half of the area to half. In this case (0 and π phase areas each occupy half), the scalar simulation has a lower zero level, but the vector simulation zero level (real zero level) is higher. If the vector zero level is to be lower, the scalar zero level must be higher. Through simulation experiments, it is found that if the quantization interval range of the assigned π is relatively small, the vector zero level will be relatively low. Therefore, it is necessary to set a quantization interval larger than the other quantization interval.

[0090] In some embodiments of the present invention, the range size of the first interval is greater than the range size of the second interval.

[0091] It should be noted that the two quantization intervals are not of the same size, that is, one interval is larger than the other interval. Therefore, the range size of the first interval may be larger than the range size of the second interval, and vice versa, the range size of the second interval may also be larger than the range size of the first interval.

[0092] Specifically, the range of the first interval is greater than π.

[0093] The sum of the two quantization intervals is 2π, so the larger quantization interval must be greater than π.

[0094] More specifically, the first interval ranges from 1.1π to 2π.

[0095] The larger quantization interval is preferably greater than 1.3π.

[0096] More specifically, the first interval ranges from 1.9π to 2π.

[0097] According to the results of simulation experiments, the range size of the first interval is preferably around 1.99π.

[0098] More specifically, the first value is 0, and the second value is π.

[0099] Through simulation experiments, it is found that if the quantization interval range of the assigned value π is relatively small, the zero level of the vector will be relatively low. Therefore, a larger quantization interval is assigned the value 0, and a smaller quantization interval is assigned the value π.

[0100] In some embodiments of the present invention, during at least one of the second iterations before performing the first binary quantization, a second binary quantization is performed on the phase distribution obtained by Fourier transform and in a third interval or a fourth interval, and the phase distribution in the third interval is set to a third value, and the phase distribution in the fourth interval is set to a fourth value, and the range size of the third interval and the range size of the fourth interval are both less than π.

[0101] It should be noted that the second iteration process S122 for performing the second binary quantization process is a transition stage between continuous phase iteration and hard quantization phase iteration (i.e., soft quantization phase iteration), and the value range of the continuous phase distribution is (0, 2π). According to experience, setting the range of the third interval and the fourth interval to be less than π will make the iteration process more stable. Moreover, there is no connection between the soft quantization interval range and the hard quantization interval range, which can make the DOE scalar after hard quantization have a higher zero order, while the vector zero order is lower.

[0102] In an optional solution of the present invention, the light effect is further improved by performing the second binary quantization in at least one second iterative process S122 before the at least one second iterative process S122 in which the first binary quantization is performed, that is, adding a transition stage between the continuous phase iteration and the hard quantization phase iteration.

[0103] Specifically, the range size of the third interval and the range size of the fourth interval increase with the increase of the number of iterations.

[0104] As a transition stage, soft quantization phase iteration needs a gradual transition process. The quantization range cannot be too large at once, otherwise the light effect will become worse. The range of the two quantization intervals needs to be increased little by little with the number of iterations, not too fast. Generally speaking, the number of soft quantization iterations can reach more than a hundred times.

[0105] Specifically, the range size of the third interval and the range size of the fourth interval gradually increase from zero.

[0106] The soft quantization phase iteration process follows the continuous phase iteration process, so it is best to gradually increase from zero. Generally speaking, after the continuous phase iteration process converges (that is, after the evaluation value curve basically tends to be flat), the soft quantization phase iteration process begins.

[0107] Preferably, the range size of the third interval and the range size of the fourth interval are both smaller than 0.6π.

[0108] More preferably, the range size of the third interval and the range size of the fourth interval are both smaller than 0.3π.

[0109] Simulation experiments show that when the range of the third and fourth intervals is around 0.2π or 0.3π, the optimized DOE has a lower vector zero order.

[0110] Specifically, the range size of the third interval is equal to the range size of the fourth interval.

[0111] According to experience, with this setting, the iteration process will be more stable.

[0112] More specifically, the third interval and the fourth interval are symmetrically distributed.

[0113] According to experience, with this setting, the iteration process will be more stable.

[0114] More specifically, the third value is 0, and the fourth value is π.

[0115] Keeping it consistent with the amplitude of the hard quantization interval, this assignment can minimize the loss of light effect caused by stepping.

[0116] Figure 4 FIG. 2 shows a schematic structural diagram of a diffraction optical system according to an embodiment of the present invention. Figure 4 As shown, the optical axis of the system and the z-axis of the coordinate systems of planes S1 and S2 are consistent, the z-axis is perpendicular to the x1-axis and y1-axis in plane S1, and the x1-axis and y1-axis in plane S1, plane S1 is the incident plane (i.e., the first plane) where the diffractive optical element (DOE) is located, plane S2 is the diffraction output surface (i.e., the second plane), and the distance between planes S1 and S2 is z.

[0117] The light field distribution function of plane S1 is:

[0118] Among them, A1(x1,y1) is the amplitude distribution of the incident light in plane S1, is the phase distribution of the diffractive optical element.

[0119] The light field distribution function of plane S2 is:

[0120] Among them, A2(x2,y2) is the target amplitude distribution of the outgoing light in plane S2, is the phase distribution of plane S2.

[0121] Figure 5 FIG. 4 shows a schematic flow chart of a scalar GS algorithm according to an embodiment of the present invention. Figure 5 As shown, take any As the initial phase distribution of the incident surface S1, combined with the amplitude A1(x1, y1) of the incident light on the plane S1, the complex amplitude of the incident light on the incident surface S1 is obtained At this time k=0.

[0122] like Figure 5 As shown, for U 1,k (x1, y1) is Fourier transformed from the incident surface S1 to the output surface S2 to obtain the complex amplitude Take U′ 2,k Phase distribution of (x2,y2) Combined with the target amplitude distribution A2(x2,y2) of the outgoing light in plane S2, a new light field distribution function is obtained At this time, k=k+1.

[0123] Next, if Figure 5 As shown, for U 2,k+1 (x2, y2) performs an inverse Fourier transform from the output surface S2 to the incident surface S1, and we get Take U′ 1,k+1 Phase distribution of (x1,y1) replace After replacement, continue to iterate and repeat the above steps.

[0124] As an example, combining Figure 5 The first binary quantization of the present invention refers to the phase distribution Binary quantization is performed on the entire area, which can also be called hard quantization. Figure 6 The phase distribution according to the embodiment of the present invention is shown. An example of performing the first binary quantization (ie, hard quantization).

[0125] like Figure 6 As shown, the hard quantization parameter Q represents the range size of the interval represented by the dotted arc (i.e., the first interval). The range size of the interval represented by the dotted arc (i.e., the first interval) is larger than the range size of the interval other than the interval represented by the dotted arc (i.e., the first interval) (i.e., the second interval), that is, Q>π, and all phase values ​​in the interval represented by the dotted arc (i.e., the first interval) are assigned to 0 (i.e., the first value), and all phase values ​​in the interval other than the interval represented by the dotted arc (i.e., the first interval) (i.e., the second interval) are assigned to π (i.e., the second value).

[0126] As an example, combining Figure 5 The second binary quantization of the present invention refers to the phase distribution Binary quantization is performed on the local area of ​​​​the image, which can also be called soft quantization. Figure 7 The phase distribution according to the embodiment of the present invention is shown. An example of performing the second binary quantization (ie, soft quantization).

[0127] like Figure 7 As shown, the interval represented by the left dotted arc (i.e., the third interval) and the interval represented by the right dotted arc (i.e., the fourth interval) are symmetrically distributed, that is, the range sizes of the intervals represented by the two dotted arcs (i.e., the third interval and the fourth interval) are equal, and the soft quantization percentage coefficient R represents the percentage of the range size of the interval represented by any dotted arc (i.e., the third interval or the fourth interval) to π, and the range sizes of the intervals represented by the two dotted arcs (i.e., the third interval and the fourth interval) are both less than π, that is, R<100%, and the phase values ​​of the interval represented by the left dotted arc (i.e., the third interval) are all assigned to 0 (i.e., the third value), and the phase values ​​of the interval represented by the right dotted arc (i.e., the fourth interval) are all assigned to π (i.e., the fourth value).

[0128] The present invention also provides a diffractive optical element, which is manufactured by adopting any one of the above methods.

[0129] Optionally, the raised areas on the surface of the diffractive optical element are not distributed continuously.

[0130] 8(a), (b), (c), and (d) are schematic diagrams showing comparative examples of scalar GS iteration processes according to embodiments of the present invention.

[0131] In the comparative example, combined Figure 5 , for the phase distribution taken The first 100 iterations are continuous phase iterations, the 101st to 300th iterations are soft quantization phase iterations, and the 301st to 401st iterations are hard quantization phase iterations, thereby obtaining the phase distribution of the diffractive optical element.

[0132] In the 101st to 300th soft quantization phase iteration process of the comparative example, the range of the third interval and the fourth interval can be gradually increased from 0 to π, that is, the soft quantization percentage coefficient R can reach 100%. As shown in Figures 8(a), (b), and (c), from the 101st to the 201st and then to the 300th, the range of the intervals represented by each group of dotted arrows (i.e., the third interval and the fourth interval) is getting larger and larger.

[0133] As shown in Fig. 8(d), during the 301st hard quantization phase iteration, the range of the first interval assigned a value of 0 (i.e., the first value) is equal to the range of the second interval assigned a value of π (i.e., the second value), that is, the hard quantization parameter Q is equal to π.

[0134] Figs. 9(a), (b), and (c) show schematic diagrams of application examples of the scalar GS iteration process according to embodiments of the present invention.

[0135] Similarly, in the application example, in combination with Figure 5 , for the taken phase distribution continuous phase iterations are performed for the first 100 times, soft quantization phase iterations are performed for the 101st - 300th times, and hard quantization phase iterations are performed for the 301st - 401st times, so as to obtain the phase distribution of the diffractive optical element.

[0136] During the 101st - 300th soft quantization phase iteration process of the application example, the range of the third interval and the fourth interval can gradually increase from 0 to R*π. As shown in Figs. 9(a) and (b), from the 101st to the 300th time, the range of the interval (i.e., the third interval and the fourth interval) represented by each group of dashed arrows becomes larger and larger. However, compared with Fig. 8(c), the soft quantization percentage coefficient R in Fig. 9(b) is smaller, preferably R < 60%, more preferably R < 30%, for example, R = 10%.

[0137] As shown in Fig. 9(c), during the 301st hard quantization phase iteration, the range of the first interval assigned a value of 0 (i.e., the first value) is larger than the range of the second interval assigned a value of π (i.e., the second value). That is, compared with Fig. 8(d), the hard quantization parameter Q in Fig. 9(c) is larger, preferably 1.1π < Q < 2π, more preferably 1.9π < Q < 2π, for example, Q = 1.993π.

[0138] Figs. 10(a) and (b) show the phase diagram (i.e., phase distribution) of the diffractive optical element (DOE) designed according to the comparative example shown in Fig. 8 and its vector simulation results, where the soft quantization percentage coefficient R = 100% and the hard quantization parameter Q = π. Figs. 11(a) and (b) show the phase diagram (i.e., phase distribution) of the diffractive optical element (DOE) designed according to the application example shown in Fig. 9 and its vector simulation results, where the soft quantization percentage coefficient R = 10% and the hard quantization parameter Q = 1.993π. Fig.12 Schematic diagrams of the target beam splitting lattice of the comparative example shown in Figs. 8(a), (b), (c), (d) and the application example shown in Figs. 9(a), (b), (c) are shown.

[0139] Other design parameters include:

[0140] Target design lattice FOV: 100°x75°,

[0141] Wavelength: 940nm,

[0142] Design resolution: 100nm x 100nm, pixel 5001x5001,

[0143] DOE microstructure size: 0.5mm x 0.5mm,

[0144] The material refractive index of DOE is 1.5063, and the optimal structural depth corresponding to the zero-order vector (i.e., step depth) is about 1.1um.

[0145] about Figure 10(b) , 11(b) The vector simulation results shown are as follows: the horizontal axis is the beam splitting point, and the sorting method is Fig.12 The beam splitting point array diagram shown is obtained by sorting from top to bottom and then from right to left; the vertical axis is efficiency, which represents the energy of each beam splitting point / the energy of the incident laser.

[0146] Compared with the phase diagram of the diffractive optical element shown in FIG10( a ), the light-colored portion (corresponding to the convex region of the diffractive optical element) in the phase diagram of the diffractive optical element shown in FIG11( a ) is not continuously distributed.

[0147] Compared with the vector simulation result shown in FIG10( b ), the vector simulation result shown in FIG11( b ) effectively degrades the vector zero order of the large-angle beam splitting array, thereby effectively reducing the non-uniformity of the output light field.

[0148] 13(a) and (b) are schematic diagrams showing a vector simulation process in two cases according to an embodiment of the present invention.

[0149] Based on the two-step (0 and π) phase distribution designed in the above embodiment, after the material (refractive index n) of the diffractive optical element is selected, the initial height of the step, that is, the initial depth of the step, is obtained by calculating the formula h0=λ / (2*(n-1)), λ refers to the wavelength incident to the DOE, and n refers to the refractive index of the material of the DOE. As shown in Figure 13(a) or Figure 13(b), the light beam passes through the air structure of the DOE and the material of the DOE to reach the surface of the step, and they have different phases. Since the refractive index of air is 1 and the refractive index of the material is n, it can be calculated that the phases of the air part and the material part at the step surface are 2πh0 / λ and 2nπh0 / λ respectively, and the phase difference between the two values ​​is π.

[0150] Specifically, for example, as shown in Figure 13(a), assume that the light beam is incident from above onto plane 1 at the top of the DOE step. At this time, the phase distribution of the light wave in the entire plane 1 is uniform. Then the light beam passes through the air structure and material structure of the DOE step respectively to reach plane 2 at the bottom of the step. At this time, the phase difference between the material part and the air part at the bottom of the step is π. The material part at the bottom of the step corresponds to phase π, and the air part at the bottom of the step corresponds to phase 0.

[0151] For another example, as shown in FIG13( b ), assume that the light beam is incident from below onto plane 2 at the bottom of the DOE step. At this time, the phase distribution of the light wave in the entire plane 2 is uniform. Then the light beam passes through the air structure and material structure of the DOE step respectively to reach plane 1 at the top of the step. At this time, the phase difference between the material part and the air part at the top of the step is π. The material part at the top of the step corresponds to phase π, and the air part at the top of the step corresponds to phase 0.

[0152] After the phase distribution is structured as above, it is imported into the electromagnetic simulation platform written based on the FDTD algorithm. After the complex amplitude distribution at the step surface (i.e., plane 2 at the bottom of the step shown in Figure 13 (a) or plane 1 at the top of the step shown in Figure 13 (b)) is simulated, the energy distribution of each beam splitting point is obtained through the propagation algorithm from the near field to the far field, that is, the diffraction efficiency of each order in the far field. Simulations are performed at different depths near h0, such as h0±50nm, and then the optimal depth when the vector zero order is the ideal value is determined.

[0153] By the method for manufacturing a diffractive optical element provided by the present invention, the vector zero order of a large-angle beam splitting lattice is effectively reduced under scalar design conditions. Specifically, by introducing the first binary quantization in the second iterative process, or further introducing the second binary quantization, a stepped DOE phase with a higher zero order under scalar simulation is forced to be obtained, so that the zero order of the vector simulation is within the target level range, thereby effectively reducing the non-uniformity of the output light field.

[0154] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for manufacturing a diffractive optical element, comprising: Design of diffractive optical elements, including: Determining an amplitude distribution of incident light of the diffractive optical element on a first plane and a target amplitude distribution of outgoing light of the diffractive optical element on a second plane, and presetting an initial phase distribution of the diffractive optical element, wherein the first plane is an incident plane of the diffractive optical element, and the outgoing light of the diffractive optical element is to form an optical pattern on the second plane; Determining the phase distribution of the diffractive optical element based on a scalar GS algorithm includes: Combining the initial phase distribution of the diffractive optical element with the amplitude distribution of the incident light in the first plane to perform Fourier transform, and then combining the phase distribution obtained by Fourier transform with the target amplitude distribution of the outgoing light in the second plane to perform inverse Fourier transform, thereby completing a first iterative process; The phase distribution obtained by inverse Fourier transform is combined with the amplitude distribution of the incident light in the first plane to perform Fourier transform, and then the phase distribution obtained by Fourier transform is combined with the target amplitude distribution of the outgoing light in the second plane to perform inverse Fourier transform, thereby completing the second iterative process, and repeating the second iterative process, wherein, in at least one of the second iterative processes, the phase distribution obtained by Fourier transform and in the first interval or the second interval is first binary quantized, the phase distribution in the first interval is set to a first value, and the phase distribution in the second interval is set to a second value, the range size of the first interval is different from the range size of the second interval, so as to effectively reduce the vector zero order of the large-angle beam splitting point array under scalar design conditions, and the range size of the first interval and the range size of the second interval are 2π in total; A diffractive optical element having a two-step structure is formed according to the determined phase distribution of the diffractive optical element.

2. The method according to claim 1, characterized in that The amplitude distribution of the incident light on the first plane is determined according to the light source.

3. The method according to claim 1, characterized in that A target amplitude distribution of the output light of the diffractive optical element in the second plane is determined according to the target optical pattern.

4. The method according to claim 1, characterized in that: The optical pattern is a beam splitting array.

5. The method according to claim 4, characterized in that The target amplitude distribution of the outgoing light of the diffractive optical element in the second plane is determined according to the parameters of the target beam splitting point array.

6. The method according to claim 5, characterized in that The parameters include at least one of the field of view, resolution, and target light intensity distribution of the target beam splitting array.

7. The method according to claim 1, characterized in that The range size of the first interval is greater than the range size of the second interval.

8. The method according to claim 7, characterized in that The range of the first interval is greater than π.

9. The method according to claim 8, characterized in that The first interval ranges from 1.1π to 2π.

10. The method according to claim 9, characterized in that The first interval ranges from 1.9π to 2π.

11. The method according to claim 7, characterized in that The first value is 0, and the second value is π.

12. The method according to claim 1, characterized in that During at least one of the second iterations before performing the first binary quantization, a second binary quantization is performed on the phase distribution obtained by Fourier transform and in the third interval or the fourth interval, and the phase distribution in the third interval is set to a third value, and the phase distribution in the fourth interval is set to a fourth value, and the range size of the third interval and the range size of the fourth interval are both less than π.

13. The method according to claim 12, characterized in that The range size of the third interval and the range size of the fourth interval increase with the increase of the number of iterations.

14. The method according to claim 13, characterized in that The range size of the third interval and the range size of the fourth interval gradually increase from zero.

15. The method according to claim 12, characterized in that The range size of the third interval and the range size of the fourth interval are both smaller than 0.6π.

16. The method according to claim 15, characterized in that The range size of the third interval and the range size of the fourth interval are both smaller than 0.3π.

17. The method according to claim 12, characterized in that The range size of the third interval is equal to the range size of the fourth interval.

18. The method according to claim 17, characterized in that The third interval and the fourth interval are symmetrically distributed.

19. The method according to claim 12, characterized in that The third value is 0, and the fourth value is π.

20. A diffractive optical element, characterized in that: It is manufactured by the method according to any one of claims 1 to 19.

21. The diffractive optical element according to claim 20, characterized in that: The convex areas on the surface of the diffractive optical element are not distributed continuously.

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