A laser corner reflector
Patent Information
- Application Number
- CN202611530464.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-09-30
- Publication Date
- 2026-11-03
AI Technical Summary
Existing laser reflectors suffer from reduced ranging accuracy due to overlapping reflection fields caused by limited field of view or the presence of multiple corner prisms, making it difficult to achieve both high accuracy and a large field of view.
Design a cuboid laser corner reflector with five reflective surfaces and four base corners. Each base corner consists of three mutually orthogonal reflective surfaces. After the incident light passes through the cuboid structure, it returns via three reflections according to the reflection law of the corner prism, ensuring that only one base corner participates in each back reflection. Use transparent materials or high-reflectivity film materials to avoid multiple reflection points and overlapping fields of view.
It achieves high-precision and wide-field-of-view laser reflection, improves the range and accuracy of reflection angles, avoids the decrease in accuracy caused by pulse broadening, reduces calibration difficulty, and is suitable for satellite laser ranging, lidar and other fields.
Smart Images
Figure CN123029504A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the fields of optical components, laser ranging technology, lidar technology, and optical precision measurement technology, and specifically relates to a laser corner reflector, which has the characteristics of high precision and large field of view. Background Technology
[0002] Laser reflectors are the primary payload in laser ranging technology. Their function is to reflect the incident measurement light back along its original path from any direction within the field of view, enabling precise distance measurement in conjunction with a distant laser observation station. There are various types of laser reflectors, but the most commonly used is a solid block prism called a "cornerstone prism," such as... Figure 1 As shown, the cornerstone prism has an approximately tetrahedral structure, comprising three mutually perpendicular reflecting surfaces and a transmitting surface that can be cut into various shapes. The three mutually perpendicular reflecting surfaces can reflect the incident light beam three times in the opposite direction to the incident direction, thereby improving the laser reflection capability. It is widely needed in various high-precision ranging applications, especially in the field of satellite laser ranging.
[0003] In laser ranging, due to the relative attitude changes between the satellite and the ground station, the reflector often needs to have the largest possible measurable field of view (i.e., the range of incident directions that can be post-reflected), and the higher the accuracy of the reflector, the better.
[0004] Existing products mainly fall into two categories: single-piece corner cube prisms and arrays composed of multiple corner cube prisms. Single-piece corner cube prisms, such as... Figure 1 As shown, it has very high accuracy because current optical processing technology can ensure that the ranging error introduced by a single corner prism is far less than 1 mm. However, its disadvantage is that the reflected field of view is relatively limited. A corner prism array composed of multiple corner prisms, such as... Figure 2 As shown, the insufficient field of view can be compensated by the geometric arrangement of multiple corner prisms. However, there is often an overlap of reflected fields between the elements of the corner prism array, which causes the reflected light pulses in a specific direction to be indistinguishably broadened in the time domain, reducing the ranging accuracy. Summary of the Invention
[0005] The purpose of this invention is to provide a laser corner reflector to achieve high-precision and large-field-of-view backscattering.
[0006] To achieve the above objectives, the present invention provides a laser corner reflector, the main body of which is a cuboid structure with five reflecting surfaces and four base corners. Each base corner is composed of three mutually orthogonal reflecting surfaces, and the four base corners are regarded as corner pyramid prisms evenly distributed in four directions.
[0007] When the laser corner reflector is working, the incident light enters the cuboid structure through the top surface of the cuboid structure, and then returns along the original path after three reflections according to the reflection law of the corner prism; in each back reflection, only one of the four base corners participates in the back reflection.
[0008] The light-transmitting aperture of the laser corner reflector is the top surface of the cuboid structure.
[0009] The height of the cuboid structure is less than its length and width, and the height of the cuboid structure is its length in the direction normal to the incident light.
[0010] The main body of the laser corner reflector is a cuboid prism structure with an upper transmission surface; or, the main body of the laser corner reflector is a cuboid box structure with an opening on its top surface.
[0011] When the main body of the laser corner reflector is a cuboid prism structure, the cuboid prism structure is integrally formed.
[0012] When the main body of the laser corner reflector is a cuboid prism structure, the material of the cuboid prism structure is a transparent material.
[0013] The cuboid structure has a high-reflectivity film coated on all five planes except the top transmissive surface.
[0014] The rectangular structure is not coated.
[0015] The laser corner reflector serves as a reflective target for a laser ranging system or a laser link-building system.
[0016] When the laser corner reflector of this invention is in operation, the incident light enters the cuboid prism structure through the top surface of the cuboid prism structure, and then returns along the original path after three reflections according to the reflection law of the pyramidal prism. In each back reflection, only one of the four pyramidal prisms participates in the back reflection. Therefore, compared with the current mainstream laser reflectors, it has a higher reflective angle range and higher reflection accuracy, and is a type of laser reflector that combines high precision and a large field of view.
[0017] Specifically, compared to a single-piece corner prism, the laser corner reflector of this invention significantly improves the field of view. The five planes on the prism, excluding the transmission surface, can form three mutually perpendicular planes over a wide incident angle range, effectively reflecting incident light in the opposite direction. The blind zone is narrow, reaching a solid angle range close to that of a hemisphere. Compared to a corner prism array, its cuboid structure ensures that there are no multiple reflection points at any incident angle, theoretically avoiding the accuracy degradation caused by pulse broadening. Furthermore, the cuboid prism is a one-piece manufactured structure, eliminating measurement accuracy issues and adjustment problems associated with reflection points, and reducing calibration difficulty in precision measurements. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of a typical pyramidal prism.
[0019] Figure 2 This is a schematic diagram showing the position of the laser corner reflector of the present invention and the corresponding bottom corner, which is regarded as a corner prism;
[0020] Figure 3 This is a schematic diagram of the beam reflection trajectory of the laser corner reflector of the present invention;
[0021] Figures 4A-4C This is a schematic diagram showing the effective reflective area of an existing triangularly cut corner prism. Figure 4A The diagram shows the area S of overlap between the projection of the aperture of a cornerstone prism along the direction of the refracted beam and its virtual image in mirror space. Figure 4B The reflection process of the light beam within the overlapping area S is shown. Figure 4C The cross-sectional area S' of the reflected light beam after refraction and exiting the cornerstone prism is shown;
[0022] Figure 5 It is an angular distribution diagram of the normalized effective reflective area of an existing single corner cube prism;
[0023] Figures 6A-6F These are angular distribution diagrams of the normalized effective reflective area of laser corner reflectors according to various embodiments of the present invention; wherein, Figure 6A This is an angular distribution diagram of the normalized effective reflective area of a laser corner reflector with an aspect ratio of 2:2:1. Figure 6B This is an angular distribution diagram of the normalized effective reflective area of a laser corner reflector with an aspect ratio of 10:10:6. Figure 6C This is an angular distribution diagram of the normalized effective reflective area of a laser corner reflector with an aspect ratio of 10:10:7. Figure 6D This is an angular distribution diagram of the normalized effective reflective area of a laser corner reflector with an aspect ratio of 10:10:8. Figure 6E This is an angular distribution diagram of the normalized effective reflective area of a laser corner reflector with an aspect ratio of 10:10:9. Figure 6F This is an angular distribution diagram of the normalized effective reflective area of a laser corner reflector with an aspect ratio of 10:10:10.
[0024] Figure 7 It is a geometric diagram showing the relationship between a satellite equipped with a laser corner reflector and a laser ranging station. Detailed Implementation
[0025] like Figure 2 and Figure 3As shown, the present invention provides a laser corner reflector 10. The main body of the laser corner reflector is a cuboid prism structure, which has an upper transmission surface and four bottom corners 11 with orthogonal planes. The four bottom corners are used as corner pyramid prisms evenly distributed in four directions.
[0026] When the laser corner reflector is in operation, the incident light enters the cuboid prism structure through the top surface of the cuboid prism structure, and then returns along the original path after three reflections according to the reflection law of the corner prism. Thus, within the field of view, light beams from any incident direction can complete the back reflection of the light beam along the original path.
[0027] To ensure that all four base corners 11 with orthogonal planes can achieve back-reflection of the beam along its original path, the height of the cuboid prism structure is less than its length and width. The height of the cuboid prism structure is its length along the normal direction of the incident light. While the length, width, and height of the cuboid prism structure are not strictly required, the aperture of the equivalent pyramidal prism is limited by the minimum of its length, width, and height; therefore, different length and width values are unnecessary. The maximum reflectible angle of the entire reflector is negatively correlated with the height of the cuboid, so the recommended value for the height should be slightly less than its length and width to increase the aperture of the equivalent pyramidal prism. The aperture is the plane on which the laser beam is transmitted and emitted; it is the only plane besides the three reflecting surfaces and is typically categorized as circular, triangular, or hexagonal based on different common cutting methods. In this embodiment, the aperture of the laser corner reflector is its upper transmission surface and is square in shape.
[0028] The far-field diffraction characteristics of reflected light are mainly controlled by optical design and precision optical processing technology to control the dihedral angles of the three orthogonal planes of the reflection vertex, which is a conventional processing technology for corner cube prisms.
[0029] The cuboid prism structure itself determines the process of the incident light's orientation change (i.e., the projection of the incident light onto the transmission surface rotates with the normal to the transmission surface). This ensures that in each back reflection, only one of the four corner prisms participates in the back reflection. Therefore, there is no overlap of the fields of view of multiple corner prisms in a partial corner prism array, which would cause simultaneous reflection and result in broadened echo signals, i.e., decreased accuracy. Although some corner prism arrays can be designed with a sparser array element arrangement in terms of direction to eliminate field of view overlap, multiple corner prisms still have the problem of insufficient assembly accuracy. However, the integrated structural design of the cuboid prism and current optical processing capabilities can ensure that the geometric positional accuracy of the four reflection points reaches or even exceeds 0.1mm. This characteristic allows the reflection accuracy of the cuboid reflector to reach a level comparable to that of a single corner prism.
[0030] The reflection field of view typically refers to the range of incident light rays within which a laser reflector can achieve back reflection, and can be determined by the angular distribution diagram of the effective reflective area. The effective reflective area measures the size of the cross-section of the incident beam that is effectively reflected. For example... Figures 4A-4C As shown, the effective reflective area of the reflector is determined by the overlapping area of the projection of the aperture along the optical axis and the mirror image of the aperture. Figures 4A-4C This is a schematic diagram of the effective reflective area of an existing triangularly cut corner prism.
[0031] Figure 5 This is an angular distribution diagram of the normalized effective reflective area of an existing single corner cube prism (circular cut, material refractive index 1.46). The radial coordinate is the incident angle, the circumferential coordinate is the azimuth angle, and the color bars display the percentage ratio of the effective reflective area to the maximum value across all angles. Figure 5 As shown, the effective reflective area of a single corner cube prism drops to half of its peak value at an incident angle of around 20°, and decreases to a negligible level above 40°.
[0032] Figure 6A This is an angular distribution diagram of the normalized effective reflective area of a laser corner reflector (length:width:height ratio 2:2:1, material refractive index 1.46) according to an embodiment of the present invention. The radial coordinate is the incident angle, the circumferential coordinate is the azimuth angle, and the numbers displayed by the color bars are the percentage ratios of the effective reflective area to the maximum value of all angles. Compared with existing single corner prisms, such as Figure 6A As shown, the effective reflective area of the laser corner reflector of this invention has a much larger distribution range with the incident angle. The direction of relatively strong reflection is not near the normal incident (i.e., 0° incident) direction, which is rarely used in actual moving target applications, but is evenly distributed in four fan-shaped areas, with considerable intensity over a large incident angle range, and only a narrow cross-shaped blind zone. Figure 6A As shown, under this parameter combination, the laser corner reflector of the present invention has a large reflective area in most directions within the incident angle range of approximately 30°-75°. The incident angle refers to the incident angle of the light beam incident on the upper transmission surface.
[0033] like Figures 6A-6FAs shown, the length, width, and height of the cuboid prism structure affect the applicable range of incident angles. Therefore, in some preferred embodiments, the height of the cuboid prism structure is smaller than its length and width. The height of the cuboid prism structure is its length along the normal direction of the incident light, thereby increasing the field of view. In other embodiments, the length, width, and height of the cuboid prism structure can be in any ratio, and the upper surface does not necessarily have to be a square; it can be rectangular, meaning the length and width can be different. However, the smaller the height relative to the length and width, the larger the field of view. But if the difference between the length, width, and height is too large, it will limit the reflective area provided per unit volume weight, because the reflective area is largely determined by the shortest side.
[0034] like Figure 7 As shown, the laser corner reflector of this invention combines high precision with a large receiving field of view. Therefore, the laser corner reflector can be applied in fields such as satellite laser ranging, lidar, laser guidance, and large-scale industrial deformation monitoring. For example, for an artificial satellite S with precise orbit determination requirements, this type of laser corner reflector can be installed on the satellite S's usual ground-facing side, and its large receiving field of view can cover most of the incident laser angle from the ground laser ranging station O'. The laser corner reflector can also be installed on the external target of the lidar or on the target being guided. Furthermore, the installation location of the laser corner reflector is not limited to the three locations mentioned above: the satellite's usual ground-facing side, the external target of the lidar, and the target on the target being guided. The laser corner reflector of this invention can be used as a reflective target for any other laser ranging system or laser link-establishing system.
[0035] The material of a cuboid prism structure can be any transparent material suitable for making transmissive lenses, such as various optical glasses, fused silica, etc., or it can be a hollow cuboid box structure composed of five reflective surfaces other than the top plane. Its essence lies in the pyramidal prism structure enclosed by the bottom reflective surface and the four side reflective surfaces of the cuboid.
[0036] In this embodiment, the cuboid prism structure is integrally formed, and five planes other than the top transmissive surface are coated with high-reflectivity films. In another embodiment, the cuboid prism structure is not coated. Since high-efficiency back reflection can be achieved by relying on the principle of total internal reflection of the prism, although the range of high reflectivity directions is limited, the uncoated cuboid prism also has the characteristics of a wider range of reflectable angles and higher reflection accuracy. The reflection process of the light beam is similar to that of a coated corner cube prism.
[0037] In another embodiment, the cuboid structure is not a single prism; its main body is a cuboid box structure composed of five reflecting surfaces other than the top surface, and it has an opening on its top surface. The beam reflection process and working principle are consistent with the cuboid prism structure. That is to say, the laser corner reflector must at least be a cuboid structure (specifically, it can be a cuboid prism structure or a cuboid box structure), and have five reflecting surfaces and four base corners. Each base corner is composed of three mutually orthogonal reflecting surfaces, and the four base corners are regarded as four evenly distributed corner pyramid prisms.
[0038] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A laser corner reflector, characterized in that, Its main body is a cuboid structure with five reflecting surfaces and four base corners. Each base corner is composed of three mutually orthogonal reflecting surfaces, and the four base corners are regarded as corner prisms evenly distributed in four directions.
2. The laser corner reflector according to claim 1, characterized in that, When the laser corner reflector is working, the incident light enters the cuboid structure through the top surface of the cuboid structure, and then returns along the original path after three reflections according to the reflection law of the corner prism; in each back reflection, only one of the four base corners participates in the back reflection.
3. The laser corner reflector according to claim 1, characterized in that, The light-transmitting aperture of the laser corner reflector is the top surface of the cuboid structure.
4. The laser corner reflector according to claim 3, characterized in that, The height of the cuboid structure is less than its length and width, and the height of the cuboid structure is its length in the direction normal to the incident light.
5. The laser corner reflector according to claim 1, characterized in that, The main body of the laser corner reflector is a cuboid prism structure with an upper transmission surface; or, the main body of the laser corner reflector is a cuboid box structure with an opening on its top surface.
6. The laser corner reflector according to claim 5, characterized in that, When the main body of the laser corner reflector is a cuboid prism structure, the cuboid prism structure is integrally formed.
7. The laser corner reflector according to claim 5, characterized in that, When the main body of the laser corner reflector is a cuboid prism structure, the material of the cuboid prism structure is a transparent material.
8. The laser corner reflector according to claim 1, characterized in that, The cuboid structure has a high-reflectivity film coated on all five planes except the top transmissive surface.
9. The laser corner reflector according to claim 1, characterized in that, The rectangular structure is not coated.
10. The laser corner reflector according to claim 1, characterized in that, The laser corner reflector serves as a reflective target for a laser ranging system or a laser link-building system.