Laser grid projection device

Abstract

The invention discloses a laser grid projection device, which comprises a light source and a metasurface structure, and is characterized in that the light source is used for generating a laser beam; the metasurface structure is arranged on a light path of the laser beam, the metasurface structure comprises a substrate and a plurality of micro-nano structures formed on the surface of the substrate, and the metasurface structure is configured to receive the laser beam generated by the light source, regulate and control optical parameters of the laser beam through the plurality of micro-nano structures, and control the optical parameters of the laser beam through the micro-nano structures. And modulating an incident laser beam into emergent light with a target laser grid pattern, and projecting the target laser grid pattern. According to the laser grid projection device, the metasurface structure is adopted as a projection device, projection of a target laser grid pattern with a large field angle is achieved, meanwhile, the device is miniaturized, the integration degree is high, the device can be conveniently integrated into equipment such as a miniaturized robot, the response speed is high, and the cost is low.

Description

Technical Field

[0001] The present invention belongs to the field of optical technology, and in particular relates to a laser grid projection device based on a super surface structure. Background Art

[0002] The laser grid projection device is a key device in the laser grid projection technology. The basic principle of laser grid projection technology is to project a regular grid pattern through the laser grid projection device. When the grid pattern is projected onto the surface of an object, the three-dimensional topography of the object surface causes the grid pattern to deform. By capturing the deformed grid pattern and using three-dimensional information solving algorithms such as triangulation or phase measurement, the three-dimensional topography information of the object surface can be calculated.

[0003] Laser grid projection technology has a wide range of application scenarios. In industrial manufacturing, it can be used for the size measurement, shape inspection and quality inspection of precision parts. For example, laser grid projection technology is used to detect whether the shape of automotive parts meets the design specifications. By projecting a laser grid and analyzing its deformation, the three-dimensional data of parts can be quickly obtained to ensure their quality and accuracy; in the field of robot navigation, it can help robots obtain three-dimensional information of the external environment and help robots navigate and avoid obstacles autonomously while moving; in the field of 3D modeling, it can be used to create three-dimensional models of cultural relics; in the field of medical imaging, it can be used for the measurement of human morphology and medical diagnosis.

[0004] Traditional 3D measurement or 3D imaging technologies are divided into active and passive types. Active 3D imaging technologies include structured light projection imaging technology, laser radar ranging technology, and other technologies that actively project electromagnetic waves such as light waves and sound waves onto the object being measured; passive 3D imaging technologies include monocular vision imaging and binocular vision imaging. Laser grid projection technology is a type of active 3D imaging technology. Compared with other active or passive technologies, its advantages include large measurement angle, long working distance, small amount of 3D measurement solution calculation, and fast response speed. It can be used for target recognition of large-sized objects or machine vision obstacle avoidance.

[0005] Traditional laser grid projection devices mostly use large-sized equipment such as spatial light modulators, which do not meet the miniaturization and integration requirements in applications such as robots. The use of diffractive optical elements can reduce the size of laser grid projection devices, but the projection angle is limited by the working principle of the diffractive optical elements, and it is difficult to project a grid pattern with a large field of view with high quality. In addition, multiple overlays are required during the processing of the diffractive optical elements. The processing technology is complicated and easily produces overlay errors that affect the quality of the projection grid.

[0006] Metasurface is an emerging optical device in recent years with a sub-wavelength device size. According to its design principle, it can project a grid pattern with a maximum field of view of 180°, and the grid pattern has high diffraction efficiency and projection quality. During the processing of metasurface devices, only one graphic transfer needs to be completed to avoid the occurrence of overlay errors, and the processing technology is simple and efficient. In addition, the metasurface also has a high degree of design freedom. It can realize multi-dimensional light field control while projecting the laser grid, that is, it can realize multiple optical functions at the same time, such as polarization state control, amplitude control and dispersion control, etc., which not only meets the needs of miniaturization and integration of laser grid projection devices, but also provides potential for the future development of laser grid projection technology.

[0007] In general, laser grid projection technology is an accurate, efficient, non-contact 3D measurement technology with wide application potential. With the development of technology, its application scope and accuracy will continue to improve, bringing more innovation and convenience to all walks of life.

[0008] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention and should not be regarded as an acknowledgment or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art. Summary of the invention

[0009] The object of the present invention is to provide a laser grid projection device, which can miniaturize and integrate the laser grid projection device, so as to facilitate its integration into miniaturized robots and other equipment, and provide the robot with functions such as active detection of three-dimensional environment, such as avoiding obstacles in space and not destroying the surrounding environment during movement.

[0010] In order to achieve the above object, a technical solution provided by a specific embodiment of the present invention is as follows:

[0011] A laser grid projection device, characterized by comprising:

[0012] A light source for generating a laser beam;

[0013] A metasurface structure is arranged on the optical path of the laser beam, the metasurface structure includes a substrate and a plurality of micro-nano structures formed on the surface of the substrate, and the metasurface structure is configured to: receive the laser beam generated by the light source, regulate the optical parameters of the laser beam through the plurality of micro-nano structures, modulate the incident laser beam into an outgoing light having a target laser grid pattern, and project the target laser grid pattern.

[0014] In one or more embodiments of the present invention, the optical parameters of the laser beam include phase, amplitude and polarization state.

[0015] In one or more embodiments of the present invention, the laser beam includes one or more of a single-wavelength beam, a multi-wavelength beam, a visible light band beam, and an infrared band beam.

[0016] In one or more embodiments of the present invention, the laser grid projection device further comprises an optical component;

[0017] The optical component is arranged on the optical path of the laser beam and is located between the light source and the metasurface structure. The optical component is at least used to perform beam shaping and / or beam collimation and / or multi-wavelength beam coupling and / or polarization state regulation on the laser beam emitted by the light source, and make it incident on the metasurface structure.

[0018] In one or more embodiments of the present invention, the optical component includes a shaping unit and a collimating unit sequentially arranged along the optical path, the shaping unit is used to shape the laser beam into a Gaussian spot, and the collimating unit is used to collimate the Gaussian spot into parallel light.

[0019] In one or more embodiments of the present invention, the optical component further includes a beam combining unit disposed on the optical path of the laser beam and downstream of the collimating unit, wherein the beam combining unit is used to couple the multi-wavelength beams emitted by the plurality of light sources into the same optical path.

[0020] In one or more embodiments of the present invention, the optical component also includes a polarization control unit, which is arranged on the optical path of the laser beam and upstream of the metasurface structure, and the polarization control unit is used to adjust the polarization state of the laser beam to the polarization state required for projecting the target laser grid pattern.

[0021] In one or more embodiments of the present invention, the beam combining unit comprises a prism or a dichroic mirror; and / or,

[0022] The shaping unit comprises a spatial light filter, and the collimating unit comprises a collimating lens; and / or,

[0023] The polarization regulating unit includes a polarizer, a half-wave plate or a quarter-wave plate.

[0024] In one or more embodiments of the present invention, the phase of the micro-nano structure on the metasurface structure corresponds one-to-one to the phase of the target laser grid pattern to be projected.

[0025] In one or more embodiments of the present invention, the design method of the super surface structure is:

[0026] Determine the substrate material, micro-nano structure material and size parameters of the micro-nano structure of the super surface structure according to the wavelength of the laser beam, wherein the size parameters include height, length, width and period;

[0027] According to the size parameters of the target laser grid pattern, an iterative Fourier algorithm or its optimization algorithm or a derivative algorithm is used to convert the target laser grid pattern into a target amplitude, and the phase of the micro-nano structure on the metasurface structure is calculated and obtained; the size parameters include the field of view angle, the number of rows and the number of columns of the target laser grid pattern;

[0028] According to the corresponding relationship between the phase of the micro-nano structure and the angle of the micro-nano structure, the layout of the metasurface structure corresponding to the target laser grid pattern is obtained.

[0029] Compared with the prior art, the laser grid projection device of the present invention miniaturizes and integrates the laser grid projection device, making it easier to integrate it into miniaturized robots and other equipment, and providing the robot with functions such as active detection of three-dimensional environments, such as avoiding obstacles in space and not destroying the surrounding environment while moving.

[0030] The laser grid projection device of the present invention adopts a metasurface structure to project a target laser grid pattern, which can meet the requirements of a large field of view. For example, if a grid pattern with a field of view of 150° and 9 rows and 7 columns is required in an application scenario, a metasurface structure is specifically designed according to this requirement, which can meet the device adaptation in various application environments such as a large field of view.

[0031] The laser grid projection device, metasurface structure and other optical components of the present invention have the characteristics of low cost. At the same time, the generated target laser grid pattern has the characteristics of high light intensity and high quality. The deformed laser grid pattern can be collected without using a high-precision camera. In addition, the amount of data and calculation required for three-dimensional solution is small, and low-cost computing chips can meet the needs of three-dimensional information solution, which can greatly reduce the cost of the supporting system and provide development ideas for the wide application of portable three-dimensional imaging equipment.

[0032] The laser grid projection device of the present invention has the characteristic of fast response speed. After the device switch is turned on, the laser grid projection device of the present invention can quickly project the target laser grid pattern, so that the subsequent three-dimensional imaging method based on the projection of the target laser grid pattern can quickly calculate the relative position coordinates of the grid line intersections to complete the three-dimensional solution. The required data volume and calculation amount are small, and the supporting overall three-dimensional imaging system can quickly complete the three-dimensional information solution, which is convenient for robots and other equipment to make the next behavior judgment according to the implementation of the three-dimensional information.

[0033] The laser grid projection device of the present invention has the advantages of miniaturization, integration, large projection angle, high design freedom, low cost, high precision, fast response speed, etc.

[0034] The laser grid projection device of the present invention can project a target laser grid pattern with a large viewing angle by utilizing a metasurface structure, and can also customize the target laser grid pattern with parameters such as the number of rows and columns. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is a schematic structural diagram of a laser grid projection device in one embodiment of the present invention;

[0037] Figure 2 A single-wavelength target laser grid pattern projected by a laser grid projection device in one embodiment of the present invention;

[0038] Figure 3 A dual-wavelength target laser grid pattern projected by a laser grid projection device in one embodiment of the present invention;

[0039] Figure 4 A target laser grid pattern with a large viewing angle projected by a laser grid projection device in one embodiment of the present invention;

[0040] Figure 5a This is an uncorrected large field of view target laser grid pattern;

[0041] Figure 5b It is the corrected laser grid pattern of the target with large field of view;

[0042] Figure 6 is the corresponding relationship between the micro-nano structure angle and the phase of the super surface structure in Example 1 of the present invention;

[0043] Figure 7 The target laser grid pattern required to be projected in Example 1 of the present invention;

[0044] Figure 8 GS algorithm flow chart in Example 1 of the present invention;

[0045] Fig. 9 In the embodiment 1 of the present invention, the GS algorithm is used according to Figure 6 The metasurface structure phase calculated from the pattern;

[0046] Fig.10 This is a process diagram for preparing a metasurface device in Example 1 of the present invention. DETAILED DESCRIPTION

[0047] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0048] Metasurface is a new type of ultra-thin, flat optical device composed of an array of artificial subwavelength structures. It has electromagnetic properties that surpass those of natural materials. It manipulates light fields by designing the geometry and lateral dimensions of the micro-nanostructures on the substrate surface. It has powerful light field control capabilities, high-efficiency performance advantages, and easy-to-integrate volume advantages. It is one of the most promising technical approaches to replace traditional optical components.

[0049] Laser grid projection technology is a method of using laser projection to achieve 3D imaging and 3D measurement. This technology projects a grid-like laser pattern onto the surface of the target to be measured, then uses an optical sensor to capture the reflected image, analyzes and calculates the deformation of the grid pattern to generate 3D data. This technology has many applications and is widely used in industrial manufacturing, robot navigation, 3D modeling, medical imaging and other fields.

[0050] As mentioned in the background technology, the laser grid projection device is a key device in the laser grid projection technology.

[0051] However, the laser grid projection device in the prior art has the following disadvantages:

[0052] 1. Large size: Existing laser grid projection systems mostly use spatial light modulators and other devices to project laser grids, which cannot meet the miniaturization and integration requirements in applications such as robots.

[0053] 2. The field of view of the laser grid pattern is small; the main evaluation index of laser grid projection is the field of view, which can also be called projection angle or diffraction angle. Most miniaturized laser grid projection devices are diffractive optical elements, which regulate the phase of the light field through the optical path difference generated by the step structures at different heights on their surfaces. This phase regulation method makes it difficult to project laser grid patterns with large field of view.

[0054] 3. High cost. Miniaturized and integrated laser grid projection devices use diffractive optical elements. To process the multi-layer step structure of the diffractive optical elements, multiple graphic transfer processes are required, which results in high manufacturing costs. Traditional three-dimensional imaging methods require high-resolution cameras to collect light field information. In addition, they require three-dimensional information solution chips that can process large amounts of data, which increases the cost of supporting equipment and cannot meet the cost control requirements of portable three-dimensional imaging devices.

[0055] 4. Slow response speed. Traditional 3D imaging methods such as stripe structured light or dot structured light require the acquisition of multiple frames of images or the completion of a large number of projection point matching and calculations, which reduces the speed of 3D information calculation and slows down the response speed of the overall system.

[0056] In order to solve the above problems, the present invention provides a laser grid projection device, which adopts a metasurface structure as a projection device to achieve the projection of a target laser grid pattern with a large field of view. At the same time, the device is miniaturized and highly integrated, which is convenient for integration into miniaturized robots and other equipment, and has a fast response speed and low cost.

[0057] like Figure 1 As shown, a laser grid projection device in an embodiment of the present invention includes a light source 10 and a metasurface structure 20. The light source 10 is used to generate a laser beam. The metasurface structure 20 is arranged on the optical path of the laser beam. The metasurface structure 20 includes a substrate and a plurality of micro-nano structures formed on the surface of the substrate. The metasurface structure 20 is configured to: receive the laser beam generated by the light source 10, regulate the optical parameters of the laser beam through a plurality of micro-nano structures on the surface of the substrate, modulate the incident laser beam into an outgoing light having a target laser grid pattern, and project the target laser grid pattern A.

[0058] The light source 10 provides a laser light source for the entire device. The light source 10 can be any type of laser, such as a VCSEL laser, a DFB laser, etc. The number of lasers can be 1, 2, or more. The power selection of the laser needs to meet the use requirements. For example, a camera or other acquisition device can clearly acquire the target laser grid pattern projected by the laser grid projection device.

[0059] The wavelength and quantity of the laser beam emitted by the light source 10 can be customized according to the target requirements. For example, the laser beam can be a single-wavelength beam, a multi-wavelength beam, a visible light band beam, an infrared band beam, or an integration of multiple of the above multiple beams. Figure 1 In the device diagram shown, the light source 10 is a single laser that emits a laser beam of a single wavelength.

[0060] After the metasurface structure 20 regulates the optical parameters of the laser beam, such as the phase, amplitude, and polarization state, the target laser grid pattern is projected. The phase of the micro-nano structure on the metasurface structure 20 corresponds one-to-one to the phase of the target laser grid pattern to be projected. The phase distribution of the micro-nano structure of the metasurface structure matches the target laser grid pattern and also matches the number of micro-nano structures. The shape of the micro-nano structure of the metasurface structure includes a cuboid, an ellipsoid, a cylinder, or an irregular cylinder. The projection mode of the metasurface structure can be transmission or reflection.

[0061] The design method of the super surface structure 20 is as follows:

[0062] First, the substrate material, micro-nano structure material and size parameters of the micro-nano structure of the super surface structure 20 are determined according to the wavelength of the laser beam; the size parameters include height, length, width and period.

[0063] The substrate material and micro-nano structure material of the super surface structure 20 match the wavelength of the light beam emitted by the light source, and a variety of materials can be selected according to the wavelength. The substrate size and micro-nano structure size are determined according to the design, and there are multiple design schemes. For example, a super surface structure working in the visible light band, the substrate material is SiO2, the thickness is 500μm, and the size is 200μm×200μm; the micro-nano structure material is TiO2, the height is 500nm, the length is 165nm, the width is 65nm, the period of each micro-nano structure is 200nm, and there are 1000×1000 micro-nano structures on the substrate. For another example, a super surface structure working in the infrared band, the substrate material and the micro-nano structure material can both be Si.

[0064] Secondly, according to the size parameters of the target laser grid pattern, an iterative Fourier algorithm or its optimization algorithm or a derivative algorithm is used to convert the target laser grid pattern into a target amplitude, and the phase of the micro-nano structure on the metasurface structure is calculated; the size parameters include the field of view angle, number of rows and number of columns of the target laser grid pattern.

[0065] The calculation method used may also be an algorithm for optimizing phase distribution using a machine learning method.

[0066] Next, according to the correspondence between the phase of the micro-nano structure and the angle of the micro-nano structure, the layout of the metasurface structure corresponding to the target laser grid pattern is obtained.

[0067] Finally, the metasurface structure is fabricated according to the layout.

[0068] The following describes in detail the design and production method of the super surface structure 20 through specific embodiment 1.

[0069] First, a single-wavelength laser beam of 405 nm is selected as the light source. According to the incident wavelength of 405 nm, the substrate material of the supersurface structure is determined to be SiO2, the micro-nanostructure material of the supersurface structure is determined to be TiO2, and the size parameters of each micro-nanostructure are: height H is 500 nm, period P is 200 nm, length L is 165 nm, and width W is 65 nm. The phase of each micro-nanostructure can be controlled by rotating the structural angle. Among them, the corresponding relationship between the structural angle and the phase is as follows: Figure 6 shown.

[0070] Secondly, design the size parameters of the target laser grid pattern. For example, at a diffraction distance of 10 cm, the projection stripe width is 1 mm, with 10 grid lines horizontally and vertically. Figure 7shown.

[0071] Then, use Figure 8 The GS algorithm shown in FIG. 1 converts the target laser grid pattern into the target amplitude and calculates the phase. The calculated phase is the phase of the metasurface structure, as shown in FIG. Fig. 9 Specifically, step 1: According to the formula For the initial phase Step 2: Combine the transformed phase result with the target amplitude and perform an inverse diffraction transformation to confirm whether the acquired phase meets the requirements. If so, extract the phase If not, the phase result is combined with the incident light amplitude to replace the initial phase Repeat steps 1 and 2 until all phases meet the requirements. Fig. 9 That is, using the GS algorithm according to Figure 7 The phase of the metasurface structure obtained by calculation of the pattern.

[0072] Next, the determined micro-nano structure size parameters of the supersurface structure and the determined supersurface structure phase are combined to draw the supersurface structure electron beam exposure process layout. Exemplarily, the specific steps of the layout drawing program are as follows:

[0073] The first step is to determine the total number of micro-nano structures in the super-surface structure according to the micro-nano structure size and period P of the super-surface structure;

[0074] The second step is to establish a coordinate grid with the zero point of the layout as the center. The size of the grid coordinates is the same as the size of the period P, and the number and distribution method are the same as the number and position of the period;

[0075] The third step is based on Figure 6 The corresponding relationship between the phase and the structural angle is shown. According to the size parameters of the micro-nano structure length L and width W, the center of the rectangle is used as the grid center, the coordinates of the four vertices of each rectangle are calculated, and the vertices are connected according to the coordinates to complete the drawing of the rectangular pattern;

[0076] The fourth step is to generate a .cif format layout file for the graphic array, and combine the layout file with the overlay mark file in relative position to generate a .gds file to complete the electron beam layout drawing.

[0077] Finally, the super surface structure is fabricated according to the electron beam layout. Fig.10 shown.

[0078] Coating a photoresist layer 210 with a thickness of H on the surface of the substrate 200;

[0079] The photoresist layer 210 is patterned by electron beam exposure, wherein the mask used is an electron beam pattern, and after photolithography development, the removed photoresist area is consistent with the electron beam pattern;

[0080] Atomic layer deposition of TiO2220 on the surface of the patterned photoresist layer 210, wherein the deposition thickness of TiO2220 is not less than the thickness of the photoresist layer 210;

[0081] The TiO2220 beyond the surface of the photoresist layer 210 is etched away by ion beam etching technology;

[0082] The remaining photoresist layer 210 on the surface of the substrate 200 is removed by oxygen plasma bombardment to obtain a super surface structure 20 .

[0083] In the design process of the metasurface structure, higher transmittance and other evaluation indicators can be obtained by designing the size parameters of the micro-nanostructure. The iterative Fourier algorithm (GS algorithm) and its optimization algorithm or derivative algorithm are used to calculate the phase distribution of the micro-nanostructure on the metasurface structure. The calculation process is to first determine the field of view angle of the laser grid and the number of rows, columns and other parameters, and then solve the corresponding phase distribution according to the target grid. The metasurface phase distribution is matched one by one with the metasurface micro-nanostructure, the drawing of the metasurface structure layout is completed, and finally the metasurface structure is processed to obtain the laser grid projector.

[0084] In the above technical solution, if the divergence angle of the laser beam emitted by the light source 10 is small, it does not need to be shaped by an optical component, and can be directly incident on the metasurface structure to obtain the target laser grid pattern. However, if the divergence angle of the laser beam emitted by the light source 10 does not meet the use requirements, an optical component with a corresponding wavelength or band should be used to collimate the laser beam emitted by the light source 10.

[0085] In one embodiment, the laser grid projection device further includes an optical component 30. The optical component 30 is disposed on the optical path of the laser beam and is located between the light source 10 and the metasurface structure 20. The optical component 30 is at least used to perform beam shaping and / or beam collimation and / or multi-wavelength beam coupling and / or polarization state regulation on the laser beam emitted by the light source 10, and make it incident on the metasurface structure 20.

[0086] by Figure 1 As shown in the example, when the light source 10 is a single laser and emits a single-wavelength laser beam, the optical component 30 includes a shaping unit 31 and a collimating unit 32 arranged in sequence along the optical path. The shaping unit 31 is preferably a spatial light filter, which is used to shape the laser beam into a circular Gaussian spot. The collimating unit 32 is preferably a collimating lens, which is used to collimate the circular Gaussian spot into parallel light, which is then incident on the metasurface structure 20.

[0087] like Figure 2As shown, Figure 2 This is a single-wavelength target laser grid pattern projected by a laser grid projection device in one embodiment of the present invention, wherein the laser emitted by the light source 10 is a single-wavelength laser of 405 nm, and the field of view angle is 120°.

[0088] When the light source 10 is a plurality of lasers (not shown) emitting multi-wavelength laser beams, the function of the optical component 30 should also include shaping the multi-wavelength laser beams and coupling them to the same optical path to be incident on the metasurface structure. Therefore, the optical component 30 also includes a beam combining unit, which is arranged on the optical path of the laser beam and is located downstream of the collimating unit 32. The beam combining unit is preferably a prism or a dichroic mirror, which is used to couple the multi-wavelength beams emitted by multiple light sources to the same optical path. For example, each laser is equipped with a shaping unit 31 and a collimating unit 32 to shape the beam, and then the multiple laser beams are coupled to the same optical path through the beam combining unit to be incident on the metasurface structure 20.

[0089] like Figure 3 As shown, Figure 3 This is a dual-wavelength target laser grid pattern projected by a laser grid projection device in an embodiment of the present invention, wherein the laser emitted by the light source 10 is a dual-wavelength laser of 405 nm and 532 nm, and the field of view angle is 120°.

[0090] The metasurface structure 20 can realize grid pattern projection with a large field of view by utilizing the discontinuous characteristics of its surface phase mutation.

[0091] like Figure 4 As shown, Figure 4 This is a target laser grid pattern with a large viewing angle (150°) projected by a laser grid projection device in one embodiment of the present invention.

[0092] It is understandable that when the target laser grid pattern has a large field of view, the phase distribution calculated using the GS algorithm or its optimization algorithm will cause the projected laser grid pattern to produce a pincushion distortion, making the laser grid unable to work properly. In this case, the target laser grid pattern should be corrected before using the GS algorithm or its optimization algorithm to calculate the phase of the metasurface structure, for example, the target laser grid pattern and the intensity distribution are approximately transformed according to the Rayleigh-Sommerfeld diffraction integral.

[0093] refer to Figure 5a and Figure 5b As shown, specifically, the coordinate value of each pixel is calculated according to the coordinate transformation formula to obtain the corrected coordinate value, and then the intensity value of the original pixel coordinate is assigned to the intensity of the corrected coordinate, so that the corrected grid pattern can be obtained.

[0094] Among them, the relationship between the corrected (approximately post-diffraction plane) coordinates (u', v') and the original coordinates (u, v) is: The intensity change of the complex amplitude function after correction is: Where z is the distance between the incident plane and the diffraction plane, and r is the distance between a point on the approximated device and a sampling point on the projection lattice.

[0095] The optical components of the above two technical solutions are suitable for the case where the target laser grid pattern is a centrally symmetrical pattern. However, it is understandable that the target laser grid pattern may not be a centrally symmetrical pattern.

[0096] Therefore, when the target laser grid pattern is not a centrally symmetrical pattern and the micro-nanostructure design principle of the metasurface structure is the geometric phase principle, the polarization state of the laser beam incident on the metasurface structure needs to be left-handed circularly deflected or right-handed circularly deflected. At this time, the optical component 30 also includes a polarization control unit (not shown), which is arranged on the optical path of the laser beam and is located upstream of the metasurface structure 20. The polarization control unit is preferably a polarizer, a half-wave plate, and a quarter-wave plate, which is used to adjust the polarization state of the laser beam to the polarization state required for projecting the target laser grid pattern. The selection of the optical element of the polarization control unit should match the wavelength, and high transmission efficiency should be guaranteed under single-wavelength conditions. Under multi-wavelength conditions, high transmission efficiency should be guaranteed while ensuring the accuracy of the polarization state of each wavelength.

[0097] The number of rows and columns in the target laser grid pattern to be projected can be designed according to the requirements, and can be an irregular or asymmetrical pattern. At the same time, the thickness of each grid line and the distance between grid lines can be exactly the same, partially the same, or completely different.

[0098] Compared with the prior art, the laser grid projection device of the present invention miniaturizes and integrates the laser grid projection device, making it easier to integrate it into miniaturized robots and other equipment, and providing the robot with functions such as active detection of three-dimensional environments, such as avoiding obstacles in space and not destroying the surrounding environment while moving.

[0099] The laser grid projection device of the present invention adopts a metasurface structure to project a target laser grid pattern, which can meet the requirements of a large field of view. For example, if a grid pattern with a field of view of 150° and 9 rows and 7 columns is required in an application scenario, a metasurface structure is specifically designed according to this requirement, which can meet the device adaptation in various application environments such as a large field of view.

[0100] The laser grid projection device, metasurface structure and other optical components of the present invention have the characteristics of low cost. At the same time, the generated target laser grid pattern has the characteristics of high light intensity and high quality. The deformed laser grid pattern can be collected without using a high-precision camera. In addition, the amount of data and calculation required for three-dimensional solution is small, and low-cost computing chips can meet the needs of three-dimensional information solution, which can greatly reduce the cost of the supporting system and provide development ideas for the wide application of portable three-dimensional imaging equipment.

[0101] The laser grid projection device of the present invention has the characteristic of fast response speed. After the device switch is turned on, the laser grid projection device of the present invention can quickly project the target laser grid pattern, so that the subsequent three-dimensional imaging method based on the projection of the target laser grid pattern can quickly calculate the relative position coordinates of the grid line intersections to complete the three-dimensional solution. The required data volume and calculation amount are small, and the supporting overall three-dimensional imaging system can quickly complete the three-dimensional information solution, which is convenient for robots and other equipment to make the next behavior judgment according to the implementation of the three-dimensional information.

[0102] The laser grid projection device of the present invention has the advantages of miniaturization, integration, large projection angle, high design freedom, low cost, high precision, fast response speed, etc.

[0103] The thickness of the metasurface structure is usually 500μm, and the length and width are usually 200μm×200μm. The light source can use a semiconductor laser chip, and the size of the optical component can also be determined according to the quality of the light source. Therefore, the entire laser grid projection device can be packaged as a chip integrated into the circuit board, which can greatly reduce the size of the device compared to traditional laser grid projectors.

[0104] Due to the optical control mechanism of the metasurface structure, the laser grid projection device based on the metasurface structure can project a target laser grid pattern with a large field of view, which can meet the requirements of the three-dimensional imaging system in application environments that require a large field of view.

[0105] The laser grid projection device of the present invention can project a high-quality target laser grid pattern, and can also realize beam deflection, polarization state control, dispersion control and other functions on this basis. The projected target laser grid pattern can be flexibly customized according to the application environment, and a single wavelength or multiple wavelengths can be selected to increase the amount of three-dimensional information obtained.

[0106] Compared with the existing diffractive optical elements that require multiple engravings during the processing, the metasurface structure can be formed with only one processing, and the device processing cost is low. In addition, the device requires low-quality supporting equipment, and the system can complete the three-dimensional information solution by using a low-resolution camera and a small-capacity data processing chip combination.

[0107] The target laser grid pattern projected by the laser grid projection device of the present invention can achieve a size of hundreds of microns, can complete three-dimensional information resolution of hundreds of microns, and is suitable for fine three-dimensional modeling and detection.

[0108] The three-dimensional imaging system based on the laser grid projection device does not need to be in direct contact with the object being measured, thus avoiding physical damage to the surface of the object being measured, and is suitable for measuring fragile or complex surfaces.

[0109] The three-dimensional imaging system based on the laser grid projection device can complete the three-dimensional data solution of a large area using a single frame image, that is, the system has a fast response speed and is suitable for real-time detection and measurement of dynamic scenes.

[0110] The laser grid projection device of the present invention can project a target laser grid pattern with a large viewing angle by utilizing a metasurface structure, and can also customize the target laser grid pattern with parameters such as the number of rows and columns.

[0111] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0112] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A laser grid projection device, characterized in that: include: A light source for generating a laser beam; A metasurface structure is arranged on the optical path of the laser beam, the metasurface structure includes a substrate and a plurality of micro-nano structures formed on the surface of the substrate, and the metasurface structure is configured to: receive the laser beam generated by the light source, regulate the optical parameters of the laser beam through the plurality of micro-nano structures, modulate the incident laser beam into an outgoing light having a target laser grid pattern, and project the target laser grid pattern.

2. The laser grid projection device according to claim 1, characterized in that: The optical parameters of the laser beam include phase, amplitude and polarization state.

3. The laser grid projection device according to claim 1, characterized in that: The laser beam includes one or more of a single-wavelength beam, a multi-wavelength beam, a visible light band beam, and an infrared band beam.

4. The laser grid projection device according to claim 1, characterized in that: The laser grid projection device also includes an optical component; The optical component is arranged on the optical path of the laser beam and is located between the light source and the metasurface structure. The optical component is at least used to perform beam shaping and / or beam collimation and / or multi-wavelength beam coupling and / or polarization state regulation on the laser beam emitted by the light source, and make it incident on the metasurface structure.

5. The laser grid projection device according to claim 4, characterized in that: The optical component comprises a shaping unit and a collimating unit which are sequentially arranged along the optical path, the shaping unit is used to shape the laser beam into a Gaussian light spot, and the collimating unit is used to collimate the Gaussian light spot into parallel light.

6. The laser grid projection device according to claim 5, characterized in that: The optical component further comprises a beam combining unit, which is arranged on the optical path of the laser beam and located downstream of the collimating unit. The beam combining unit is used for coupling the multi-wavelength beams emitted by the plurality of light sources into the same optical path.

7. The laser grid projection device according to claim 6, characterized in that: The optical component also includes a polarization control unit, which is arranged on the optical path of the laser beam and located upstream of the metasurface structure. The polarization control unit is used to adjust the polarization state of the laser beam to the polarization state required for projecting the target laser grid pattern.

8. The laser grid projection device according to claim 7, characterized in that: The beam combining unit comprises a prism or a dichroic mirror; and / or, The shaping unit comprises a spatial light filter, and the collimating unit comprises a collimating lens; and / or, The polarization regulating unit includes a polarizer, a half-wave plate or a quarter-wave plate.

9. The laser grid projection device according to claim 1, characterized in that: The phase of the micro-nano structure on the metasurface structure corresponds one-to-one to the phase of the target laser grid pattern to be projected.

10. The laser grid projection device according to claim 1, characterized in that: The design method of the super surface structure is: Determine the substrate material, micro-nano structure material and size parameters of the micro-nano structure of the super surface structure according to the wavelength of the laser beam, wherein the size parameters include height, length, width and period; According to the size parameters of the target laser grid pattern, an iterative Fourier algorithm or its optimization algorithm or a derivative algorithm is used to convert the target laser grid pattern into a target amplitude, and the phase of the micro-nano structure on the metasurface structure is calculated and obtained; the size parameters include the field of view angle, the number of rows and the number of columns of the target laser grid pattern; According to the corresponding relationship between the phase of the micro-nano structure and the angle of the micro-nano structure, the layout of the metasurface structure corresponding to the target laser grid pattern is obtained.

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