A metasurface-based laser scanning system
By designing a laser scanning system based on metasurfaces, and using a metasurface wedge prism and a mechanical device to rotate coaxially, the problems of large space occupation and centroid offset of traditional prism groups are solved, realizing the miniaturization and high-efficiency scanning of lidar, and supporting multi-wavelength control.
Patent Information
- Application Number
- CN202610393851.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-27
- Publication Date
- 2026-06-05
AI Technical Summary
Traditional prism arrays occupy most of the volume of a lidar system, and the problem of centroid misalignment is serious, making it difficult to meet the requirements of miniaturization and lightweighting in fields such as autonomous driving and intelligent robots.
A metasurface-based laser scanning system is adopted, which uses front and rear metasurface wedge prisms to form a prism group. Beam scanning is performed by coaxial rotation through an external mechanical device. The metasurface unit is composed of a substrate and nanopillars, and efficient beam scanning is achieved by combining a servo motor and a transmission gear set.
It achieves miniaturization and lightweighting of lidar, solves the problem of centroid offset in traditional prisms, enables a scanning range of 360° in the XY plane and ±40° along the Z axis, and supports the adjustment of different working wavelengths.
Smart Images
Figure CN122151342A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lidar scanning technology, specifically a laser scanning system based on metasurfaces. Background Technology
[0002] Metasurfaces achieve specific optical functions through the arrangement of unit structures, possessing characteristics such as small size, light weight, rich functionality, and ease of integration. They have broad application prospects in polarization conversion, holographic imaging, ultrathin lenses, and beam deflection. With the deepening research in the field of metasurfaces and the development of micro-nano fabrication technology, metasurfaces have provided entirely new solutions for the miniaturization and integration of optical systems in engineering applications.
[0003] Traditional scanning prism assemblies achieve arbitrary pointing of the beam within the scanning field of view through coaxial independent rotation. Due to their compact structure, high pointing accuracy, low power consumption, and rapid response, they are widely used in LiDAR, infrared countermeasures, and optical reconnaissance. The prism assembly employs a helical scanning method, which can meet requirements such as controllable field of view, controllable coverage, controllable cycle, and stable speed. In recent years, the development of autonomous driving technology and intelligent robots has placed higher demands on the miniaturization of LiDAR. In traditional LiDAR systems using prism assemblies as the scanning system, the traditional prism occupies most of the system's volume. Furthermore, because traditional prisms consist of two wedge-shaped prisms, the wedge prisms suffer from centroid asymmetry, and the rotation of the double wedge prisms exacerbates this centroid shift and further increases the space required for the scanning system. Summary of the Invention
[0004] To address the aforementioned problems, this invention designs a laser scanning system based on metasurfaces, which simplifies the design of the scanning system, makes it compact, and facilitates the miniaturization and weight reduction of lidar; at the same time, it solves the problem of centroid offset in traditional prisms.
[0005] The objective of this invention is achieved as follows: A metasurface-based laser scanning system includes a laser, a front metasurface wedge prism, and a rear metasurface wedge prism. The front and rear metasurface wedge prisms are arranged sequentially along the laser emission direction of the laser, forming a prism group. The front and rear metasurface wedge prisms can deflect incident light rays and rotate coaxially under the action of an external mechanical device to perform beam scanning.
[0006] In the aforementioned metasurface-based laser scanning system, both the front and rear metasurface wedge prisms are composed of multiple metasurface units. Each metasurface unit consists of a substrate and nanopillars on the substrate. The nanopillars are formed from a single material, with the center of the substrate and the center of the nanopillars overlapping, and the diameter of the nanopillars being smaller than the side length of the substrate.
[0007] In the aforementioned metasurface-based laser scanning system, the substrates of the metasurface units have the same size, the nanopillars have the same height, and the phase distribution of the metasurface units is related to the size, shape, and position of the nanopillars.
[0008] A coordinate system is established with the center of the front or rear metasurface wedge prism as the origin. In this coordinate system, the plane containing the front or rear metasurface wedge prism is the XY plane, and the laser incident direction is the Z-axis. The phase distribution of each metasurface unit of the front or rear metasurface wedge prism is then determined. φ ( x , y ) through formula φ ( x , y )= k * x * d *sin θ Calculated; where, ( x , y A phase unit is defined as the mesh position of the phase surface after meshing, taking into account the size of the metasurface unit. k The wave number of light in a vacuum is given by the wavelength. λ The calculation yields the following result: k =2 π / λ ; d Let be the base side length of the metasurface unit; θ The angle at which the incident light is deflected by the front metasurface wedge prism or the rear metasurface wedge prism.
[0009] The aforementioned metasurface-based laser scanning system, wherein the front metasurface wedge prism and / or the rear metasurface wedge prism are made of a metasurface as the main structure, fabricated by single-sided or double-sided micro-nano processing. In addition to deflection lines, the metasurface structure can also be specially designed to suppress reflection.
[0010] The aforementioned metasurface-based laser scanning system includes an external mechanical structure comprising a first servo motor and transmission gear set, a second servo motor and transmission gear set, a rear hollow gear, and a front hollow gear. The front metasurface wedge prism is mounted on the front hollow gear. The first servo motor and transmission gear set drive the front hollow gear to rotate, thereby rotating the front metasurface wedge prism. The rear metasurface wedge prism is mounted on the rear hollow gear. The second servo motor and transmission gear set drive the rear hollow gear to rotate, thereby rotating the rear metasurface wedge prism. Beam scanning is performed under the rotation of the front and rear metasurface wedge prisms.
[0011] The advantages of the laser scanning system based on metasurfaces in this invention are as follows: First, the use of metasurface devices instead of traditional prisms simplifies the design of the scanning system, making it more compact and facilitating the miniaturization and weight reduction of lidar. Second, by using metasurface devices instead of traditional prisms, the problem of centroid shift in traditional prisms is solved; Third, by using metasurface devices instead of traditional prisms, and by selecting different metasurface unit structures and parameter designs, it is possible not only to control the polarization sensitivity of the metasurface wedge prism, but also to achieve the control of different working wavelengths, making the design more flexible.
[0012] Fourth, the laser scanning system based on metasurfaces of this invention can achieve a scanning range of 360° in the XY plane and ±40° along the Z axis. Attached Figure Description
[0013] Figure 1 This is a schematic diagram of the structure of the metasurface-based laser scanning system of the present invention.
[0014] Figure 2 This is a schematic diagram of an external mechanical structure.
[0015] Figure 3 This is a three-dimensional structural diagram of the metasurface prism in this invention.
[0016] Figure 4 This is a schematic diagram of the front view structure of the metasurface prism in this invention.
[0017] Figure 5 This is a schematic diagram of the three-dimensional structure of a metasurface unit.
[0018] Figure 6 This is a schematic diagram of the main structure of a metasurface unit.
[0019] Figure 7 This is a normalized curve of the transmission phase coverage range of the metasurface unit.
[0020] Figure 8 This represents the correspondence between the emission azimuth angle and the relative rotation angle between the two metasurfaces.
[0021] Figure 9 This is a transmittance curve of a metasurface unit.
[0022] Figure 10 The simulation results are for the Z-axis beam scanning of a double-layer metasurface wedge prism with relative rotation.
[0023] Figure 11 This is a finished product of a metasurface wedge prism.
[0024] Figure 12Optical microscopic images of finished metasurface wedge prisms.
[0025] In the diagram: 1. Outer shell; 2. Laser; 3. First servo motor and transmission gear; 4. Second servo motor and transmission gear; 5. Rear metasurface wedge prism; 6. Front metasurface wedge prism; 7. Rear hollow gear; 8. Front hollow gear; 11. Coil; 12. Permanent magnet; 13. Loading frame. Detailed Implementation
[0026] The specific embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Specific Implementation Method 1 The specific implementation of the metasurface-based laser scanning system, such as Figure 1 As shown, enclosed by the outer shell 1, there are a laser 2, a front metasurface wedge prism 6, and a rear metasurface wedge prism 5. The front metasurface wedge prism 6 and the rear metasurface wedge prism 5 are arranged sequentially along the laser emission direction of the laser 2, forming a prism group. The front metasurface wedge prism 6 and the rear metasurface wedge prism 5 can deflect the incident light and rotate coaxially under the action of an external mechanical device to perform beam scanning.
[0028] Both the front metasurface wedge prism 6 and the rear metasurface wedge prism 5 are composed of multiple metasurface units. Each metasurface unit consists of a substrate and nanopillars on the substrate. The nanopillars are formed by processing a single material. The centers of the substrate and the nanopillars overlap, and the diameter of the nanopillars is smaller than the side length of the substrate.
[0029] The substrates of the metasurface units have the same size, the nanopillars have the same height, and the phase distribution of the metasurface units is related to the size, shape, and position of the nanopillars.
[0030] The working principle of the laser scanning system based on metasurfaces in this invention is as follows: Metasurface wedge prisms are analyzed and designed based on transport phase theory and geometric phase theory, both of which consist of an array structure composed of periodically arranged metasurface units. The transmittance and phase modulation capability of transport phase metasurface units are directly affected by the unit structure and its size, structural symmetry, and the periodicity of the unit; generally, the higher the structural symmetry, the less sensitive it is to polarization. Geometric phase metasurface units, on the other hand, are directly affected by the rotation angle of the nanopillars in terms of their phase response and polarization conversion efficiency.
[0031] Based on the aforementioned metasurface wedge prism, a prism group structure is formed by two metasurface wedge prisms. To improve overall scanning efficiency and avoid light leakage, the size of the front metasurface wedge prism 6 is slightly smaller than that of the rear metasurface wedge prism 5. Both metasurface wedge prisms can deflect the incident laser at a certain angle. The front metasurface wedge prism 6 deflects the perpendicularly incident laser at a certain angle and then obliquely incident it onto the rear metasurface wedge prism 5, achieving secondary deflection. Therefore, when the double-layer metasurface undergoes relative rotation and overall rotation, the beam deflected twice can achieve beam scanning along the Z-axis. Specific Implementation Method Two The metasurface-based laser scanning system in this specific embodiment, based on Specific Embodiment 1, is further defined as follows: the external mechanical structure includes a first servo motor and transmission gear set 3, a second servo motor and transmission gear set 4, a rear hollow gear 7, and a front hollow gear 8; the front metasurface wedge prism 6 is mounted on the front hollow gear 8, and the first servo motor and transmission gear set 3 drives the front hollow gear 8 to rotate, thereby driving the front metasurface wedge prism 6 to rotate; the rear metasurface wedge prism 5 is mounted on the rear hollow gear 7, and the second servo motor and transmission gear set 4 drives the rear hollow gear 7 to rotate, thereby driving the rear metasurface wedge prism 5 to rotate; beam scanning is performed under the rotation of the front metasurface wedge prism 6 and the rear metasurface wedge prism 5.
[0033] Taking the first servo motor and transmission gear set 3 driving the front hollow gear 8 to rotate, thereby driving the front metasurface wedge prism 6 to rotate, as an example; Figure 2 As shown, the transmission gear in the first servo motor and transmission gear set 3 meshes with the front hollow gear 8 in two ways: internal gear and external gear. By adjusting the speed of the servo motor, the speed of the front hollow gear 8 is controlled, thereby controlling the instantaneous relative angle between the front metasurface wedge prism 6 and the rear metasurface wedge prism 5. Specific Implementation Method 3 The metasurface-based laser scanning system in this specific embodiment is further defined based on the first specific embodiment: the external mechanical structure can also adopt a hollow arc motor to place the metasurface wedge prism on the loading frame 13, on which a permanent magnet 12 is fixed. After being energized, the interaction between the coil 11 and the permanent magnet 12 directly drives the loading frame 13. Specific Implementation Method Four The metasurface-based laser scanning system in this specific embodiment, based on the above specific embodiments, is further defined as follows: the front metasurface wedge prism 6 or the rear metasurface wedge prism 5 are both circular structures, such as... Figure 3 and Figure 4As shown, with the laser emission direction of laser 2 as the Z-axis, the front metasurface wedge prism 6 or the rear metasurface wedge prism 5 is placed perpendicular to the Z-axis, and the Z-axis passes through the center of the front metasurface wedge prism 6 or the rear metasurface wedge prism 5; along the Z-axis direction, the area of the front metasurface wedge prism 6 is smaller than that of the rear metasurface wedge prism 5, which helps to prevent light leakage and improve the efficiency of the scanning system, and a 5mm air gap is formed between the front metasurface wedge prism 6 or the rear metasurface wedge prism 5, forming a prism group structure; A coordinate system is established with the center of the front metasurface wedge prism 6 or the rear metasurface wedge prism 5 as the origin. In this coordinate system, the plane containing the front metasurface wedge prism 6 or the rear metasurface wedge prism 5 is the XY plane, and the laser incident direction is the Z-axis direction. The phase distribution of each metasurface unit of the front metasurface wedge prism 6 or the rear metasurface wedge prism 5 is then determined. φ ( x , y ) through formula φ ( x , y )= k * x * d *sin θ Calculated; where, ( x , y A phase unit is defined as the mesh position of the phase surface after meshing, taking into account the size of the metasurface unit. k The wave number of light in a vacuum is given by the wavelength. λ The calculation yields the following result: k =2 π / λ ; d Let be the base side length of the metasurface unit; θ The angle at which the incident light is deflected by the front metasurface wedge prism 6 or the rear metasurface wedge prism 5. Detailed Implementation Method Five The metasurface-based laser scanning system in this specific embodiment is further defined based on the above specific embodiments: The beam deflection angle is set to 20 degrees. Considering the processing accuracy of existing processing methods, the target phase is discretized using a step-by-step method to obtain the correspondence between the metasurface unit and the target phase. By matching the metasurface units one by one, the design of the metasurface wedge prism can be realized.
[0037] In this specific implementation, when the metasurface wedge prism is working, the incident laser is input from one side of the substrate and passes through the metasurface structure. Since the metasurface structure has good phase modulation capability and phase coverage, the corresponding transmission phase can be obtained by adjusting the diameter of the silicon nanopillars.
[0038] The metasurface wedge prism is composed of several metasurface units, each with the same structure consisting of a substrate and nanopillars, with the substrate and nanopillars overlapping at their centers. Based on different requirements for operating wavelength and polarization conditions, the metasurface units employ different design schemes. This specific embodiment is implemented under two different parameters, as follows: Parameter 1: A pure silicon metasurface operating at a wavelength of 10.6µm, wherein the metasurface unit is composed of a substrate of a single material and nanopillars, such as... Figure 5 As shown, the substrate is square with a side length of 4µm, and the nanopillar is cylindrical with a height of 12µm. Both are made of silicon material. The radius of the silicon nanopillar is between 0.75µm and 1.25µm. Cylinders with different radii have different phase responses. The phase response of the metasurface unit is controlled by adjusting the radius of the silicon nanopillar to realize the beam deflection function of the wedge prism metasurface.
[0039] Parameter 2: A titanium dioxide metasurface operating at a wavelength of 632.8 nm, wherein the metasurface units of the titanium dioxide metasurface are designed based on the geometric phase principle, such as... Figure 6 As shown, the substrate is square with a side length of 400 nm and is made of silicon dioxide. The nanopillars are cuboid in shape, with a height of 500 nm, a length of 370 nm, and a width of 95 nm. Based on the geometric phase principle, cuboids with different rotation angles have different phase responses. The phase response of the metasurface unit is controlled by adjusting the rotation angle of the cuboids to achieve the beam deflection function of the wedge prism metasurface.
[0040] like Figure 7 The figure shown is a phase coverage curve of the metasurface unit in this specific embodiment. Figure 7 (a) Figure 7 (b) corresponds to parameter one and parameter two respectively, where, Figure 7 (a) The horizontal axis represents the radius of the silicon nanopillars, and the vertical axis represents the normalized phase response. Within the radius range of 0.75µm to 1.25µm, the phase coverage reaches 2π. Figure 7 (b) The horizontal axis represents the rotation angle of the titanium dioxide nanopillar, and the vertical axis represents the normalized phase response. Within the rotation angle range of 0° to 180°, the phase coverage reaches 2π.
[0041] A scanning simulation of a peripheral Z-axis incident laser was performed on the scanning system designed in this specific embodiment. The two metasurfaces rotated relative to each other from 0 to 180 degrees, and the direction of the deflected beam could be determined by... Figure 9 Chinese azimuth θ and φ To express. Figure 8This refers to the correspondence between the emission azimuth angle and the relative rotation angle of the two metasurfaces in the two embodiments of this specific implementation.
[0042] In parameter one, the relative rotation angle and azimuth angle of the double supersurfaces θ and φ The correspondence is as follows Figure 9 As shown, it is represented as: φ =0.5* δ θ =43-0.0165* δ -0.002* δ ^2+(3.76E-6)* δ ^3 in θ and φ It is the azimuth angle. δ Let be the relative rotation angle between the two metasurfaces.
[0043] In parameter two, the relative rotation angle and azimuth angle of the double supersurfaces θ and φ The correspondence is as follows Figure 10 As shown, it is represented as: φ =90.5-0.5* δ θ =0.335* δ -(2.44E-4)* δ ^2-(4.25E-6)* δ ^3 in θ and φ It is the azimuth angle. δ Let be the relative rotation angle between the two metasurfaces.
[0044] Because of the opposite rotation directions, the corresponding relationships exhibit opposite trends; both sets of parameters achieve a maximum deflection angle of approximately 40 degrees between the deflected beam direction and the positive Z-axis. Since the metasurface wedge prism structure is highly symmetrical, only the 0-180 degree correspondence is given; the 180-360 degree correspondence exists symmetrically. When the entire double-layer metasurface rotates, its beam deflection direction for the incident laser also rotates accordingly, causing the deflected beam to rotate 360° around the positive Z-axis, achieving a beam scan with a field of view of 80 degrees along the positive Z-axis.
[0045] like Figure 11 The image shown is a finished product of the metasurface wedge prism designed in this specific embodiment. Its diameter is 25mm, and it is made of all-silicon material using a laser direct-write processing technology. Figure 12The image shows a microscopic view of the metasurface wedge prism under an optical microscope, revealing distinct nanopillars and periodic structures.
[0046] The above results demonstrate that this specific embodiment achieves beam scanning control of incident lasers with wavelengths of 10.6µm and 632.8nm through micro-nano structure design. Simulation results show that this lidar scanning system can achieve beam scanning within a 360° range in the XY plane and a ±40° range along the Z-axis. Furthermore, it allows for system design under other wavelengths and beam scanning ranges by changing the design and selection of the metasurface micro-nano unit structure.
[0047] It should be noted that the front metasurface wedge prism 6 or / and the rear metasurface wedge prism 5 are made of metasurface as the main structure, and are fabricated by single-sided or double-sided micro-nano processing. In addition to deflection lines, their metasurface structure can also play a role in suppressing reflection through special design.
[0048] It should also be noted that the above description is only a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar alternative features unless otherwise specified. All features or steps in all methods or processes disclosed may be combined in any way except for mutually exclusive features and / or steps.
Claims
1. A laser scanning system based on metasurfaces, characterized in that: It includes a laser (2), a front metasurface wedge prism (6) and a rear metasurface wedge prism (5). The front metasurface wedge prism (6) and the rear metasurface wedge prism (5) are arranged sequentially along the laser emission direction of the laser (2) to form a prism group. The front metasurface wedge prism (6) and the rear metasurface wedge prism (5) can deflect the incident light and rotate coaxially under the action of an external mechanical device to perform beam scanning.
2. The laser scanning system based on metasurfaces according to claim 1, characterized in that: The front metasurface wedge prism (6) and the rear metasurface wedge prism (5) are both composed of multiple metasurface units. Each metasurface unit is composed of a substrate and a nanopillar on the substrate. The nanopillar is formed by processing a single material. The center of the substrate and the nanopillar overlaps, and the diameter of the nanopillar is smaller than the side length of the substrate.
3. The laser scanning system based on metasurfaces according to claim 1, characterized in that: The substrates of the metasurface units have the same size, the nanopillars have the same height, and the phase distribution of the metasurface units is related to the size, shape, and position of the nanopillars.
4. The laser scanning system based on metasurfaces according to claim 3, characterized in that: A coordinate system is established with the center of the front metasurface wedge prism (6) or the rear metasurface wedge prism (5) as the origin. In the coordinate system, the plane where the front metasurface wedge prism (6) or the rear metasurface wedge prism (5) is located is the XY plane, and the laser incident direction is the Z-axis direction. Then, the phase distribution of each metasurface unit of the front metasurface wedge prism (6) or the rear metasurface wedge prism (5) is... φ ( x , y ) through formula φ ( x , y )= k * x * d *sin θ Calculated; in,( x , y A phase unit is defined as the mesh position of the phase surface after meshing, taking into account the size of the metasurface unit. k The wave number of light in a vacuum is given by the wavelength. λ The calculation yields the following result: k =2 π / λ ; d Let be the base side length of the metasurface unit; θ The angle of deflection of incident light by the front metasurface wedge prism (6) or the rear metasurface wedge prism (5).
5. A laser scanning system based on metasurfaces according to claim 2, characterized in that: The front metasurface wedge prism (6) and / or the rear metasurface wedge prism (5) are made of metasurface as the main structure and are fabricated by single-sided or double-sided micro-nano processing. In addition to deflection lines, the metasurface structure can also be specially designed to suppress reflection.
6. The laser scanning system based on metasurfaces according to claim 1, characterized in that: The external mechanical structure includes a first servo motor and transmission gear set (3), a second servo motor and transmission gear set (4), a rear hollow gear (7), and a front hollow gear (8); the front metasurface wedge prism (6) is mounted on the front hollow gear (8), the first servo motor and transmission gear set (3) drives the front hollow gear (8) to rotate, and then drives the front metasurface wedge prism (6) to rotate; the rear metasurface wedge prism (5) is mounted on the rear hollow gear (7), the second servo motor and transmission gear set (4) drives the rear hollow gear (7) to rotate, and then drives the rear metasurface wedge prism (5) to rotate; beam scanning is performed under the rotation of the front metasurface wedge prism (6) and the rear metasurface wedge prism (5).