Method for manufacturing laser beam splitting structure and laser beam splitting device

Abstract

The application provides a manufacturing method of a laser beam splitting structure and a laser beam splitting device, and relates to the technical field of laser sensors; the method comprises the following steps: determining an initial laser beam splitting structure according to the beam splitting quantity, the incident wavelength and the diffraction angle of an incident light beam, wherein the initial laser beam splitting structure comprises a substrate and a plurality of unit period structures, each unit period structure is perpendicular to the substrate and is arranged along a first direction of the substrate, and each unit period structure is formed by a plurality of dielectric layers arranged at intervals; and the structure parameters of the unit period structure are optimized by using a preset optimization algorithm to obtain a target laser beam splitting structure, wherein the energy difference between a plurality of split beams emitted by the incident light beam through the target laser beam splitting structure satisfies a preset uniformity condition, and the structure parameters comprise at least one of a dielectric layer width, a dielectric layer spacing and a dielectric layer depth. The laser beam splitting device manufactured by the manufacturing method of the laser beam splitting structure provided in the application can be applied to topography detection and three-dimensional structure point cloud reconstruction.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to, but are not limited to, the technical field of laser sensor, and particularly to a manufacturing method of laser beam splitting structure and a laser beam splitting device. BACKGROUND

[0002] In the application of topography detection and three-dimensional structure point cloud reconstruction, three-dimensional coordinates can be obtained through a structured light sensor, a binocular stereo vision system, etc. However, the structured light sensor, the binocular stereo vision system, etc. have certain requirements for the light environment. Strong or weak ambient light will affect the measurement accuracy, and the calculation complexity is high, which will affect the real-time performance. Therefore, in the related art, laser beam splitting structured light interference, phase measurement or multi-view information fusion are usually selected to obtain three-dimensional coordinate information of the object surface. Meanwhile, the miniaturization and integration of the laser beam splitting structure are utilized to meet the current measurement requirements of miniaturization and integration. However, in the related art, it is difficult for the laser beam splitting structure to split one beam into multiple beams while ensuring the uniformity of the split beam energy. Therefore, the effect of topography detection and three-dimensional structure point cloud reconstruction based on the laser beam splitting structure is not good. SUMMARY

[0003] The following is a summary of the subject matter of the detailed description herein. This summary is not intended to limit the scope of the claims. Embodiments of the present application provide a manufacturing method of laser beam splitting structure and a laser beam splitting device, which can ensure the uniformity of the split beam energy to be suitable for topography detection and three-dimensional structure point cloud reconstruction.

[0004] In a first aspect, a manufacturing method of laser beam splitting structure is provided according to embodiments of the present application, comprising:

[0005] obtaining a split beam number, an incident wavelength and a diffraction angle of an incident light beam;

[0006] determining an initial laser beam splitting structure according to the split beam number, the incident wavelength and the diffraction angle, the initial laser beam splitting structure comprising a substrate and a plurality of unit period structures, each unit period structure being perpendicular to the substrate and arranged along a first direction of the substrate, and each unit period structure being formed by a plurality of dielectric layers arranged at intervals;

[0007] optimizing a structure parameter of the unit period structure through a preset optimization algorithm to obtain a target laser beam splitting structure, wherein an energy difference between a plurality of split beams emitted by the incident light beam through the target laser beam splitting structure satisfies a preset uniformity condition, and the structure parameter comprises at least one of a dielectric layer width, a dielectric layer spacing and a dielectric layer depth.

[0008] Therefore, the above-mentioned embodiments of the present application have at least the following beneficial effects: the incident light beam is split by multiple unit period structures, and multiple phase abrupt points in the medium layer of each unit period structure can regulate the far-field split beam energy distribution. At this time, the initial laser beam splitting structure determined based on the split number, the incident wavelength, and the diffraction angle can meet the requirements of light splitting and diffraction angle. At the same time, by optimizing the structure parameters of the medium layer of a single unit period structure, it can be ensured that the energy difference between the split beams meets the uniformity requirement. Compared with related technologies, the laser beam splitting structure of the embodiments of the present application has better beam splitting uniformity and can be applied to topography detection and three-dimensional structure point cloud reconstruction.

[0009] According to some embodiments of the first aspect of the present application, the initial laser beam splitting structure is determined according to the split number, the incident wavelength, and the diffraction angle, including:

[0010] Half of the split number is taken as a medium layer number reference value, and the number of medium layers of a single period structure is determined according to the medium layer number reference value;

[0011] The initial phase of the central beam emitted by each unit period structure is determined, and the initial phase is less than 0.2;

[0012] According to the initial phase, the structure refractive index of the unit period structure, the incident wavelength, and the diffraction angle, the grating period, the diffraction order, and the initial medium layer depth are determined;

[0013] According to the incident wavelength, the diffraction order, and the split number, the number of units of the unit period structure is determined;

[0014] The initial medium layer width and the medium layer spacing in the unit period structure are determined;

[0015] According to the grating period, the number of medium layers, the number of units, and the initial medium layer width, the medium layer spacing, and the medium layer depth, the initial laser beam splitting structure is determined.

[0016] According to some embodiments of the first aspect of the present application, the optimization algorithm is a quasi-Newton algorithm; and the structure parameters of the unit period structure are optimized by the preset optimization algorithm to obtain a target laser beam splitting structure, including:

[0017] The width value constraint condition of the quasi-Newton algorithm is set to be that the medium layer spacing is greater than one-tenth of the incident wavelength, and less than the ratio of the grating period to the number of medium layers of a single unit period structure;

[0018] The depth value constraint condition of the quasi-Newton algorithm is set as a phase change amount provided by the medium layer depth being within 0.7π-2.3π;

[0019] The interval value constraint condition of the quasi-Newton algorithm is set as adjacent two medium layers not overlapping with each other.

[0020] The medium layer width, the medium layer interval and the medium layer depth of the unit period structure are synchronously optimized by the quasi-Newton algorithm through multiple iterations, to obtain the target laser beam splitting structure.

[0021] According to some embodiments of the first aspect of the present application, the iteration stop condition of the quasi-Newton algorithm comprises:

[0022] The intermediate light beams of the multiple light beams emitted by the initial laser beam splitting structure after each iteration optimization are all taken as reference light beams, and the reference light beams are adjacent to each other by a preset number of light beams.

[0023] According to the diffraction efficiency of each reference light beam, a uniformity error after the current iteration optimization is determined.

[0024] When the uniformity error is less than a preset error threshold for a preset number of iterations, the unit period structure obtained through the current iteration optimization is taken as a target unit period structure, and the target laser beam splitting structure is determined according to the target unit period structure.

[0025] According to some embodiments of the first aspect of the present application, the determination of the uniformity error after the current iteration optimization according to the diffraction efficiency of each reference light beam comprises:

[0026] The maximum diffraction efficiency and the minimum diffraction efficiency are determined from the diffraction efficiency of the multiple reference light beams.

[0027] The diffraction energy difference is determined according to the difference between the maximum diffraction efficiency and the minimum diffraction efficiency.

[0028] The total diffraction efficiency is determined according to the sum of the maximum diffraction efficiency and the minimum diffraction efficiency.

[0029] The uniformity error is obtained according to the ratio of the diffraction energy difference and the total diffraction efficiency.

[0030] In the second aspect, the laser beam splitting device is obtained by the manufacturing method of the laser beam splitting structure according to any one of the first aspect.

[0031] According to some embodiments of the second aspect of the present application, the width and the thickness of the unit period structure are proportional to the incident wavelength, and the minimum width of the medium layer in the unit period structure is inversely proportional to the incident wavelength.

[0032] According to some embodiments of the second aspect of the present application, when the number of beam splitting is 52 and the incident wavelength is 1080 nm, the width of the unit period structure is 547 um, the thickness of the unit period structure is 1200 nm; and the minimum width is 3.75 um.

[0033] According to some embodiments of the second aspect of the present application, when the number of beam splitting is 13 and the incident wavelength is 450 nm, the width of the unit period structure is 9 um, the thickness of the unit period structure is 442 nm; and the minimum width is 855 nm.

[0034] According to some embodiments of the second aspect of the present application, the widths of the adjacent two dielectric layers in the same unit period structure are different, and the unit period structure has at least two different dielectric layer intervals. BRIEF DESCRIPTION OF DRAWINGS

[0035] The accompanying drawings are included to provide a further understanding of the technical scheme of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical scheme of the present application, and do not constitute a limitation on the technical scheme of the present application.

[0036] Figure 1 is a flowchart of an embodiment of the method for manufacturing the laser beam splitting structure provided by the present application;

[0037] Figure 2 is a plan view of a 1x13 laser beam splitting structure obtained by the method for manufacturing the laser beam splitting structure provided by the present application;

[0038] Figure 3 is Figure 2 a structural schematic diagram of the laser beam splitting structure shown in FIG. 8;

[0039] Figure 4 is Figure 2 a distribution diagram of the diffraction efficiency of each order of the laser beam splitting structure shown in FIG. 8;

[0040] Figure 5 is a plan view of a 1x52 laser beam splitting structure obtained by the method for manufacturing the laser beam splitting structure provided by the present application;

[0041] Figure 6 is Figure 5 a structural schematic diagram of the laser beam splitting structure shown in FIG. 10;

[0042] Figure 7 is Figure 5 a distribution diagram of the diffraction efficiency of each order of the laser beam splitting structure shown in FIG. 10.

[0043] Reference signs:

[0044] Unit cycle structure 100, air layer 110, dielectric layer 120. DETAILED DESCRIPTION

[0045] For the purpose of the present application, technical solutions and advantages, the following will be further described in detail in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not intended to limit the present application.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing the embodiments of the present application only and is not intended to limit the present application. The terms "first", "second", "third", "fourth" and the like (if any) in the specification and the above drawings of the present application are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0047] In addition, the described features, structures or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, many specific details are provided to give a sufficient understanding of the embodiments of the present disclosure. However, those skilled in the art will realize that the technical solutions of the present disclosure can be practiced without one or more of the specific details, or other methods, components, devices, steps, etc. can be used. In other cases, well-known methods, devices, implementations or operations are not shown or described in detail to avoid obscuring the aspects of the present disclosure.

[0048] The following is a brief description of the technical terms involved in the embodiments of the present application:

[0049] Diffractive angle refers to the angle between the incident beam and the emergent beam due to the diffraction effect after the laser passes through the beam splitter structure.

[0050] Full angle of beam splitting refers to the angle range covered by the required beam after beam splitting in the process of laser beam splitting.

[0051] In the application of topography detection and three-dimensional structure point cloud reconstruction, three-dimensional coordinates can be obtained through a structured light sensor, a binocular stereo vision system, etc. However, the structured light sensor, the binocular stereo vision system, etc. have certain requirements for the light environment, and the measurement accuracy will be affected by too strong or too weak ambient light. In addition, the calculation complexity is high, and the real-time performance will be affected. Therefore, in the related art, laser beam splitting structured light interference, phase measurement or multi-view information fusion are usually selected to obtain three-dimensional coordinate information of the surface of an object. Meanwhile, the miniaturization and integration of the laser beam splitting structure are utilized to meet the current demand for miniaturization and integration of measurement. However, in the related art, it is difficult for the laser beam splitting structure to split one beam of light into multiple beams of light while ensuring the uniformity of the split beam energy. Therefore, the effect of topography detection and three-dimensional structure point cloud reconstruction based on the laser beam splitting structure is not good. Based on this, the embodiment of the present application provides a manufacturing method of a laser beam splitting structure and a laser beam splitting device, which can be applied to topography detection and three-dimensional structure point cloud reconstruction.

[0052] In a first aspect, referring to Figure 1 The manufacturing method of the laser beam splitting structure according to the embodiment of the present application comprises the following steps:

[0053] In step S100, the number of split beams, the incident wavelength and the diffraction angle of the incident light beam are obtained.

[0054] In step S200, an initial laser beam splitting structure is determined according to the number of split beams, the incident wavelength and the diffraction angle. The initial laser beam splitting structure comprises a substrate and a plurality of unit period structures. Each unit period structure is perpendicular to the substrate and arranged along a first direction of the substrate. Each unit period structure is formed by a plurality of dielectric layers arranged at intervals.

[0055] In step S300, the structure parameters of the unit period structure are optimized by a preset optimization algorithm to obtain a target laser beam splitting structure. The energy difference between the multiple split beams emitted by the target laser beam splitting structure satisfies a preset uniformity condition. The structure parameters include at least one of the dielectric layer width, the dielectric layer spacing and the dielectric layer depth.

[0056] Therefore, the incident light beam is split by the plurality of unit period structures 100, and the plurality of phase abrupt points are realized by the dielectric layers 120 in each unit period structure 100 to regulate the energy distribution of the far-field split beam. At this time, the initial laser beam splitting structure determined based on the number of split beams, the incident wavelength and the diffraction angle can meet the requirements of light splitting and diffraction angle. Meanwhile, the structure parameters of the dielectric layer 120 of the single unit period structure 100 are optimized to ensure that the energy difference between the split beams emitted satisfies the uniformity requirement. The laser beam splitting structure of the embodiment of the present application has better splitting uniformity and can be applied to topography detection and three-dimensional structure point cloud reconstruction.

[0057] The embodiments of the present application do not limit how to determine the initial laser beam splitting structure, which can be determined by a person skilled in the art based on optical principles and reverse design methods, and will not be described here.

[0058] Each dielectric layer 120 in the unit period structure 100 forms a phase jump point, and the incident light beam entering each unit period structure 100 is jointly affected by multiple phase jump points to realize the regulation of the spot energy distribution of the far-field split beams. Each unit period structure 100 is the same, and adjacent two unit period structures 100 do not overlap each other, and the air layer 110 is arranged between adjacent two unit period structures 100. The unit period structure 100 is periodically arranged on the base. In order to guarantee the uniformity of beam splitting and achieve the expected number of beam splitting, the number of dielectric layers 120 in the unit period structure 100 can be constrained according to the uniformity of beam splitting and the number of beam splitting, wherein the more the required number of beam splitting is, the more the number of dielectric layers is. In order to meet the periodicity requirement, in some embodiments, the number of unit period structures 100 arranged along the first direction should be at least greater than or equal to 3.

[0059] The structure parameters represent the size of the dielectric layer 120, and the size of the dielectric layer 120 includes at least one of the dielectric layer width, the dielectric layer spacing, and the dielectric layer depth, wherein the dielectric layer spacing represents the interval distance between adjacent two dielectric layers 120 in the same unit period structure 100, and the interval distance between any two adjacent dielectric layers 120 in the same unit period structure can be different. The dielectric layer depth represents the distance from the side of the dielectric layer 120 away from the base to the side close to the base. The dielectric layer width represents the width of a single dielectric layer 120 along the arrangement direction. The dielectric layer widths of different dielectric layers 120 can be different.

[0060] For example, referring to FIG. 1, Figure 2 , Figure 2 The laser beam splitting structure includes three unit period structures 100, wherein each unit period structure 100 includes four dielectric layers 120, and each unit period structure 100 is composed of dielectric layer 120->air layer 110->dielectric layer 120->air layer 110->dielectric layer 120->air layer 110->dielectric layer 120 from left to right; the air layer 110 is arranged between adjacent two unit period structures 100, thereby forming a periodic structure.

[0061] The tuning algorithm is an algorithm for solving an unconstrained optimization problem, and the embodiments of the present application do not limit what the tuning algorithm is. For example, the tuning algorithm is a quasi-Newton algorithm, thereby obtaining the structure parameters satisfying the uniformity condition.

[0062] The embodiments of this application do not impose restrictions on the uniformity conditions. For example, in some embodiments, the energy difference between multiple beams can be set to be less than or equal to a preset uniformity threshold. In other embodiments, the energy change trend between multiple beams can be set to be less than a preset uniformity threshold. Those skilled in the art can selectively set these conditions according to the actual situation.

[0063] For example, taking a 1×13 laser beam splitting structure as an example, refer to... Figure 2 As shown, multiple dielectric layers 120 are vertically positioned on a cuboid base and stacked in a stepped planar manner with a dielectric-air-dielectric structure. This results in varying numbers and effects of beam splitting within a single stacked unit periodic structure 100, creating a horizontally stacked array of random line-shaped pixel pillars of different numbers and widths. Furthermore, these random line-shaped pixel pillars are arranged periodically along the x-axis (i.e., the arrangement direction of the dielectric layers 120). Figure 2 As shown, the pixel pillars (i.e., dielectric layers 120) of each unit periodic structure 100 are stacked into four lines of varying widths. The dielectric layer widths, from left to right, are narrow-wide-narrow-wide. The first and second pixel pillars have the narrowest spacing (i.e., the smallest dielectric layer spacing), while the third and fourth pixel pillars have the widest spacing (i.e., the largest dielectric layer spacing). Simultaneously, the first pixel pillar is the narrowest in terms of dielectric layer width, and the second pixel pillar is the widest. The fourth pixel pillar is connected to the air layer 110 in the periodic arrangement (i.e.,... Figure 2 (as shown in the white area), thus satisfying the requirement that each unit periodic structure 100 is arranged periodically. At this time, based on this laser beam splitting structure, a single-wavelength beam can be split, and the incident beam passes through... Figure 2 In the laser beam splitting structure shown, each pixel column within the structure forms a phase abrupt change point. The incident beam is affected by the combined effect of multiple phase abrupt change points, thereby regulating the energy distribution of the far-field beam splitting spot. The number of beam splits and the full beam splitting angle meet the expected requirements. By optimizing the structural parameters of a single unit periodic structure 100 and combining the output of the entire laser beam splitting structure to optimize the stopping conditions, the target laser beam splitting structure can achieve good beam energy distribution uniformity.

[0064] Understandably, the initial laser beam splitting structure is determined based on the number of beams, the incident wavelength, and the diffraction angle, including:

[0065] Half of the number of beams is used as a reference value for the number of dielectric layers, and the number of dielectric layers in a single periodic structure is determined based on the reference value for the number of dielectric layers.

[0066] Determine the initial phase of the central beam emitted from each unit periodic structure; the initial phase is less than 0.2.

[0067] According to the initial phase, the structural refractive index of the unit period structure, the incident wavelength and the diffraction angle, the grating period, the diffraction order and the initial medium layer depth are determined;

[0068] According to the incident wavelength, the diffraction order and the number of beamsplitting, the number of units of the unit period structure is determined;

[0069] The initial medium layer width and the medium layer spacing in the unit period structure are determined;

[0070] According to the grating period, the number of medium layers, the number of units, and the initial medium layer width, the initial medium layer spacing and the initial medium layer depth, the initial laser beam splitting structure is determined.

[0071] It can be understood that according to the phase formula and the grating equation The grating period, the diffraction order and the initial medium layer depth of the incident light beam in the case of perpendicular incidence can be determined; wherein, represents the initial phase, represents the incident wavelength; represents the structural refractive index; represents the medium layer depth; represents the grating period; represents the diffraction angle corresponding to the diffraction order; represents the diffraction angle.

[0072] Since the initial phase, the structural refractive index, the incident wavelength and the required diffraction angle are known, a set of initial grating period, diffraction order and initial medium layer depth can be obtained based on the phase formula and the grating equation.

[0073] The grating period represents the distance between the medium layer 120 in a unit period structure and the repeated medium layer 120 in the next unit period structure. The smaller the grating period, the larger the diffraction angle, thereby resulting in a larger diffraction full angle.

[0074] By taking half of the number of beamsplitting as a reference value of the number of medium layers, the tuning efficiency of the tuning algorithm can be improved, and the target laser beam splitting structure meeting the uniformity condition can be obtained faster.

[0075] The present application does not limit how the initial medium layer width and the medium layer spacing are determined. For example, in some embodiments, the initial medium layer width and the medium layer spacing are determined by dividing the total width of the target laser beam splitting structure, the number of units and the number of medium layers. In other embodiments, the initial medium layer width and the medium layer spacing can also be set based on empirical values.

[0076] It can be understood that the optimization algorithm is a quasi-Newton algorithm; the structure parameters of the unit period structure are optimized by the preset optimization algorithm to obtain a target laser beam splitting structure, including:

[0077] The width value constraint condition of the quasi-Newton algorithm is set to be greater than one-tenth of the incident wavelength and less than the ratio of the grating period to the number of dielectric layers of a single unit period structure;

[0078] The depth value constraint condition of the quasi-Newton algorithm is set to be within 0.7π-2.3π of the phase change provided by the dielectric layer depth;

[0079] The spacing value constraint condition of the quasi-Newton algorithm is that the adjacent two dielectric layers do not overlap;

[0080] The dielectric layer width, dielectric layer spacing and dielectric layer depth of the unit period structure are simultaneously optimized by the quasi-Newton algorithm through multiple iterations to obtain the target laser beam splitting structure.

[0081] In some embodiments, when the diffraction full angle is less than 20 degrees, the depth value constraint condition of the quasi-Newton algorithm is set to be within 0.7π-1.3π of the phase change corresponding to the dielectric layer depth, and in some embodiments, when the diffraction full angle is greater than or equal to 20 degrees, the depth value constraint condition of the quasi-Newton algorithm is set to be within 1.3π-2.3π of the phase change corresponding to the dielectric layer depth. For example, when the diffraction full angle is 10 degrees, the depth corresponding to 0.7π is selected as the dielectric layer depth for iteration operation. For example, when the diffraction full angle is 15 degrees, the depth corresponding to 1.3π is selected as the dielectric layer depth for iteration operation. For example, when the diffraction full angle is 20 degrees, 1.3π can be selected as the dielectric layer depth for iteration operation, or 2.3π or 2.0π can be selected as the dielectric layer depth for iteration operation. At this time, according to The depth value range can be limited.

[0082] The adjacent two dielectric layers do not overlap, including the adjacent two dielectric layers 120 within the same unit period structure, and the two dielectric layers 120 adjacent to each other and arranged in the adjacent two unit period structures.

[0083] Therefore, by setting the above width value constraint condition, depth value constraint condition and spacing value constraint condition, the convergence speed of the quasi-Newton algorithm can be improved. The specific calculation process of the quasi-Newton algorithm is not described herein.

[0084] It can be understood that the iteration stopping condition of the quasi-Newton algorithm includes:

[0085] The intermediate light beams of the plurality of light beams emitted by the initial laser beam splitting structure after each iteration optimization are all used as reference light beams;

[0086] determine the uniformity error after the current iteration optimization according to the diffraction efficiency of each reference beam;

[0087] When the uniformity error is less than the preset error threshold for a preset number of iterations, the unit period structure obtained after the current iteration optimization is taken as the target unit period structure, and the target laser beam splitting structure is determined according to the target unit period structure.

[0088] The error threshold represents the maximum value of the uniformity error when the uniformity requirement is met. It can be set according to experience. The error threshold is not limited in the embodiments of the present application, for example, in some embodiments, the error threshold is set to 1e-5. For example, in some embodiments, when the uniformity error obtained for 15 times is less than 1e-5, it is considered that the optimal adjustment has been reached, and the structure parameters of the current structure are taken as the structure parameters of the target unit period structure, so that the target laser beam splitting structure can be determined.

[0089] The preset number is not limited in the embodiments of the present application, for example, it is set to 3, and 3 beams are selected from the left and right sides of the middle beam as reference beams. The middle beam is a beam located in the middle position of the plurality of beams. By selecting a preset number of beams as reference beams, the operation process can be simplified, and the energy of the middle beam can be avoided to be too concentrated, so that the spot of the beam is not uniform.

[0090] The uniformity error is used to represent the energy difference between the beams, which can be determined by the mean square deviation, or by the extreme value of the diffraction efficiency of the beam, which can be selected and set according to the actual needs of those skilled in the art.

[0091] It can be understood that the uniformity error after the current iteration optimization is determined according to the diffraction efficiency of each reference beam, including:

[0092] The maximum diffraction efficiency and the minimum diffraction efficiency are determined from the diffraction efficiency of the plurality of reference beams;

[0093] The diffraction energy difference is determined according to the difference between the maximum diffraction efficiency and the minimum diffraction efficiency;

[0094] The total diffraction efficiency is determined according to the sum of the maximum diffraction efficiency and the minimum diffraction efficiency;

[0095] The uniformity error is obtained according to the ratio of the diffraction energy difference and the total diffraction efficiency.

[0096] For example, the uniformity error is The formula is:

[0097] ;

[0098] wherein diffraction efficiency of the diffraction order, that is, the smaller the uniformity error is, the smaller the energy difference between the beam splitting spots is, the more uniform the energy distribution is, and the total diffraction efficiency a proportion of the total energy of the required diffraction order in the energy of the light source. diffraction efficiency, diffraction efficiency.

[0099] Therefore, the laser beam splitting structure of the above-mentioned embodiments of the present application realizes phase modulation of the incident light by changing the width of each medium layer 120 and the medium layer spacing in each unit period structure 100, obtains the required beam splitting effect, improves the beam splitting uniformity, and meets the required beam splitting function. At the same time, the structure based on the medium layer 120-air-medium layer 120 in a single unit period structure 100 is arranged, so that the number of beam splitting and the beam splitting effect in a single unit period structure 100 are stacked to present random line type pixel column structures with different numbers and different widths. The embodiments of the present application can form multiple phase mutation points in each unit period structure 100 to regulate the energy distribution of the far field beam splitting spot, thereby realizing phase modulation of the incident light, ensuring the uniformity of the energy distribution of the beam splitting spot, and at the same time, the size of the unit period structure 100 ensures the beam splitting angle, thereby realizing beam splitting. Therefore, the embodiments of the present application have the advantages of large beam splitting angle, good beam splitting uniformity, etc., and are suitable for the field of three-dimensional structured light, etc.

[0100] In a second aspect, the laser beam splitting device according to the embodiments of the present application comprises a laser beam splitting structure; the laser beam splitting structure is obtained by the following steps:

[0101] obtaining the beam splitting number, the incident wavelength and the diffraction angle of the incident light beam;

[0102] determining an initial laser beam splitting structure according to the beam splitting number, the incident wavelength and the diffraction angle, wherein the initial laser beam splitting structure comprises a substrate and a plurality of unit period structures 100, each unit period structure 100 is arranged perpendicular to the substrate and along the first direction of the substrate, and each unit period structure 100 is formed by a plurality of medium layers 120 arranged at intervals;

[0103] optimizing the structure parameters of each unit period structure 100 of the initial laser beam splitting structure until the energy difference between the plurality of split beams of the incident light beam passing through the initial laser beam splitting structure meets a preset uniformity condition;

[0104] obtaining a target laser beam splitting structure according to the structure parameters after stopping optimization.

[0105] Therefore, the splitting of the incident light beam is performed by the plurality of unit period structures 100, and the plurality of phase abrupt points are realized by the dielectric layers 120 in each unit period structure 100, so that the far-field split beam energy distribution can be regulated, at this time, the initial laser beam splitting structure determined based on the splitting number, the incident wavelength, and the diffraction angle can meet the requirements of light splitting and diffraction angle, and by optimizing the structure parameters of the dielectric layer 120 of the single unit period structure 100, it can be ensured that the energy difference between the split beams meets the uniformity requirement. Compared with related technologies, the laser beam splitting structure of the embodiment of the present application has better beam splitting uniformity and can be applied to topography detection and three-dimensional structure point cloud reconstruction.

[0106] It can be understood that the width and thickness of the unit period structure 100 are proportional to the incident wavelength, and the minimum width of the dielectric layer 120 in the unit period structure 100 is inversely proportional to the incident wavelength.

[0107] By adjusting the dielectric layer width and the dielectric layer spacing based on the fact that the width and thickness of the unit period structure 100 are proportional to the incident wavelength, and the minimum width of the dielectric layer 120 in the unit period structure 100 is inversely proportional to the incident wavelength, the optimization process can be simplified.

[0108] In some embodiments, the dielectric layer width can be adjusted first, and then the dielectric layer spacing can be adjusted.

[0109] The thickness of the unit period structure 100 represents the height of the dielectric layer 120 protruding from the surface of the substrate. The height of each dielectric layer 120 can be the same.

[0110] It can be understood that, as shown in Figure 5 and Figure 6 , when the splitting number is 52 and the incident wavelength is 1080 nm, the width of the unit period structure 100 is 547 um, and the thickness of the unit period structure 100 is 1200 nm; the minimum width is 3.75 um.

[0111] The minimum width is the minimum width of the dielectric layer 120 in the same unit period structure 100. As shown in Figure 5 and Figure 6 , the splitting number is 52, the number of unit period structures 100 is 3, the width of each unit period structure 100 is 547 um, and the thickness of each unit period structure 100 is 1200 nm; the minimum width of the dielectric layer 120 is 3.75 um.

[0112] It can be understood that, as shown in Figure 2 and Figure 3 , when the splitting number is 13 and the incident wavelength is 450 nm, the width of the unit period structure 100 is 9 um, and the thickness of the unit period structure 100 is 442 nm; the minimum width is 855 um.

[0113] As shown in Figure 2 and Figure 3 , the number of beam splitting is 13, the number of unit period structures 100 is 3, the width of each unit period structure 100 is 9um, and the thickness of each unit period structure 100 is 442nm; the minimum width of the dielectric layer 120 is 855nm.

[0114] It can be understood that the dielectric layer width of adjacent two dielectric layers in the same unit period structure 100 is different, and at least two different dielectric layer spacings exist in the same unit period structure 100.

[0115] It can be understood that the dielectric layer 120 and the substrate of the unit period structure 100 are both made of light-transmitting materials.

[0116] The light-transmitting materials used by the unit period structure 100 and the substrate can be the same or different, and the embodiments of the present application do not limit this. In some embodiments, the light-transmitting material used by the dielectric layer 120 in the unit period structure 100 is one of glass, plastic, optical resin and the like; and the light-transmitting material used by the substrate is one of glass, plastic, optical curing glue and the like.

[0117] Exemplarily, taking the dielectric layer 120 as fused quartz, a 1x13 (i.e. the number of beam splitting is 13) laser beam splitting structure, a total beam splitting angle of 34.8°, and an incident wavelength of the incident light beam of 450nm as an example, as shown in Figure 2 and Figure 3 , according to the number of beam splitting, the incident wavelength and the diffraction angle of the incident light beam, it is determined that the number of unit period structures 100 in the initial laser beam splitting structure is 3, the number of dielectric layers 120 in each unit period structure 100 is 4, and the thickness of the unit period structure 100 is 442nm. At this time, the dielectric layer width of a single unit period structure 100 is optimized, and after stopping the optimization, the minimum width of the dielectric layer 120 is 855nm; the width of a single unit period structure 100 is 9um. At this time, as shown in Figure 2 , each unit period structure 100 has four pixel columns stacked with different widths, the widths of the pixel columns are narrow-wide-narrow-wide from left to right, and from the left, the first pixel column and the second pixel column are spaced the narrowest, the third pixel column and the fourth pixel column are spaced the widest, and at the same time, the first pixel column is the narrowest and the second pixel column is the widest in the dielectric layer width. The fourth pixel column is connected with air medium in the periodic arrangement (i.e. the white area shown in Figure 2 ), so that the properties of the periodic arrangement can be met. Wherein, the optimized laser beam splitting structure has a higher diffraction efficiency and a good uniformity error while meeting the total beam splitting angle of 34.8°. Wherein, the diffraction efficiency is as shown in Figure 4The uniformity error can reach 11.6%.

[0118] As shown in the example, the medium layer 120 is fused quartz, the laser beam splitting structure is 1x52 (i.e., the number of beam splitting is 52), the full angle of beam splitting is 11.5°, and the incident wavelength of the incident light beam is 1080nm. Figure 5 and Figure 6 As shown, according to the number of beam splitting of the incident light beam, the incident wavelength, and the diffraction angle, the number of unit period structures 100 in the initial laser beam splitting structure is determined to be 3, and the number of medium layers 120 in each unit period structure 100 is 27; the thickness of the unit period structure 100 is 1200nm. At this time, the width of the medium layer of a single unit period structure 100 is optimized, and after stopping the optimization, the minimum width of the medium layer 120 is 3.75um. The width of the unit period structure 100 is 547um. At this time, as shown, the unit period structure 100 has a plurality of pixel columns with different widths stacked, and the phase control meeting the requirements is realized by using different line widths in the wide-narrow-wide-narrow manner, thereby realizing the energy control of the light beam and meeting the diffraction performance requirements of high uniformity. Among them, the optimized laser beam splitting structure meets the full angle of beam splitting of 11.5°, and has high diffraction efficiency and excellent uniformity error. As shown, the diffraction efficiency can reach 82.97%, and the uniformity error can reach 0.67%. Figure 5 Figure 7

[0119] The above is a specific description of the preferred embodiments of the present application, but the present application is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or replacements without departing from the spirit of the present application, and these equivalent modifications or replacements are all included in the scope defined by the claims of the present application.​​

Claims

1. A method for fabricating a laser beam splitting structure, characterized in that, The method comprises: acquiring a splitting number, an incident wavelength, and a diffraction angle of an incident light beam; determining an initial laser beam splitting structure according to the splitting number, the incident wavelength, and the diffraction angle, the initial laser beam splitting structure comprising a substrate and a plurality of unit period structures, each of the unit period structures being arranged perpendicularly to the substrate and along a first direction of the substrate, and each of the unit period structures being formed by a plurality of dielectric layers arranged at intervals; optimizing structure parameters of the unit period structures by a preset optimization algorithm to obtain a target laser beam splitting structure, wherein an energy difference between a plurality of split beams of the incident light beam passing through the target laser beam splitting structure satisfies a preset uniformity condition, and the structure parameters comprise at least one of a dielectric layer width, a dielectric layer interval, and a dielectric layer depth; wherein the determining of the initial laser beam splitting structure according to the splitting number, the incident wavelength, and the diffraction angle comprises: taking half of the splitting number as a dielectric layer number reference value, and determining a dielectric layer number of a single period structure according to the dielectric layer number reference value; determining an initial phase of a central beam of each of the unit period structures, the initial phase being less than 0.2; determining a grating period, a diffraction order, and an initial dielectric layer depth according to the initial phase, a structure refractive index of the unit period structure, the incident wavelength, and the diffraction angle; determining a unit number of the unit period structure according to the incident wavelength, the diffraction order, and the splitting number; determining an initial dielectric layer width and the dielectric layer interval in the unit period structure; determining the initial laser beam splitting structure according to the grating period, the dielectric layer number, the unit number, and the initial dielectric layer width, the dielectric layer interval, and the dielectric layer depth.

2. The method of claim 1, wherein The optimization algorithm is a quasi-Newton algorithm; and the optimization of the structure parameters of the unit period structures by the preset optimization algorithm to obtain the target laser beam splitting structure comprises: setting a width value constraint condition of the quasi-Newton algorithm as the dielectric layer interval being greater than one-tenth of the incident wavelength and being less than a ratio of the grating period to a dielectric layer number of a single unit period structure; setting a depth value constraint condition of the quasi-Newton algorithm as a phase variation amount provided by the dielectric layer depth being within 0.7π-2.3π; setting an interval value constraint condition of the quasi-Newton algorithm as adjacent two dielectric layers not overlapping each other; synchronously optimizing the dielectric layer width, the dielectric layer interval, and the dielectric layer depth of the unit period structure by the quasi-Newton algorithm for multiple iterations to obtain the target laser beam splitting structure.

3. The method of claim 2, wherein the laser beam splitting structure is formed by a process comprising: The iteration stop condition of the quasi-Newton algorithm comprises: taking a preset number of split beams adjacent to a middle split beam of a plurality of split beams of the initial laser beam splitting structure after each iteration optimization as reference split beams; determining a uniformity error after a current iteration optimization according to diffraction efficiencies of the reference split beams. When the uniformity error is less than a preset error threshold for a preset number of iterations, a unit period structure obtained by the current iteration is taken as a target unit period structure, and the target laser beam splitting structure is determined according to the target unit period structure.

4. The method of claim 3, wherein The uniformity error after the current iteration is determined according to the diffraction efficiency of each reference beam: The maximum diffraction efficiency and the minimum diffraction efficiency are determined from the diffraction efficiency of the plurality of reference beams; The diffraction energy difference is determined according to the difference between the maximum diffraction efficiency and the minimum diffraction efficiency; The total diffraction efficiency is determined according to the sum of the maximum diffraction efficiency and the minimum diffraction efficiency; The uniformity error is obtained according to the ratio of the diffraction energy difference to the total diffraction efficiency.

5. A laser beam splitting device, characterized by The laser beam splitting structure obtained by the method of any one of claims 1-4. The width and thickness of the unit period structure are directly proportional to the incident wavelength, and the minimum width of the dielectric layer in the unit period structure is inversely proportional to the incident wavelength.

6. The laser beam splitting device according to claim 5, characterized in that When the number of beam splitting is 52 and the incident wavelength is 1080 nm, the width of the unit period structure is 547 um, the thickness of the unit period structure is 1200 nm, and the minimum width is 3.75 um.

7. The laser beam splitting device according to claim 6, characterized in that When the number of beam splitting is 13 and the incident wavelength is 450 nm, the width of the unit period structure is 9 um, the thickness of the unit period structure is 442 nm, and the minimum width is 855 nm.

8. The laser beam splitting device according to claim 6, characterized in that The dielectric layer widths of adjacent dielectric layers in the same unit period structure are different, and at least two different dielectric layer spacings exist in the same unit period structure.

9. The laser beam splitting device according to claim 5, wherein, ​

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