Cooperative targets for optical imaging sensors and tof cameras for space relative measurements

Abstract

The application provides a cooperative target for spatial relative measurement, which is suitable for optical imaging sensors and TOF cameras, and comprises a target plate for fixing a plurality of sub-targets arranged in a staggered manner; the sub-targets comprise near-field active light targets, far-field active light targets, far-field passive light reflection targets, near-field passive light reflection targets and single-point targets; the near-field active light targets and the far-field active light targets are respectively used for alignment of the optical imaging sensors; and the far-field passive light reflection targets, the near-field passive light reflection targets and the single-point targets are respectively used for alignment of the TOF cameras. The application has the advantages of small size and high integration, and can simultaneously provide measurement requirements for two different types of sensors, and the sub-targets do not interfere with each other and serve as backups, thereby improving the reliability of rendezvous and docking measurement.

Description

Technical Field

[0001] This invention belongs to the field of aerospace docking relative measurement, specifically involving a cooperative target for an optical imaging sensor and a TOF camera used for space relative measurement. Background Technology

[0002] Traditional space station rendezvous and docking measurement missions typically employ a combination of lidar and optical imaging sensors. This combination uses targets that occupy a large area and is constrained by the interface structure, often leading to layout difficulties and spatial obstruction issues. Furthermore, the optical imaging sensor, as the only device for high-precision pose measurement at the end point, lacks backup methods and has relatively low reliability. Summary of the Invention

[0003] The purpose of this invention is to provide a cooperative target device that can simultaneously meet the measurement requirements of optical imaging sensors and TOF measurement cameras when facing the rendezvous and docking between small spacecraft. It can provide measurement requirements for both types of sensors across the entire range, and the two different types of targets serve as backups for each other, greatly improving the lifespan and reliability of space applications.

[0004] To achieve the above objectives, the present invention provides a cooperative target for spatial relative measurement, applicable to optical imaging sensors and TOF cameras, comprising: a target plate for fixing multiple sub-targets that are misaligned; the sub-targets include: a near-field active light target, a far-field active light target, a far-field passive reflective target, a near-field passive reflective target, and a single-point target; the near-field active light target and the far-field active light target are used for aligning the optical imaging sensor; the far-field passive reflective target, the near-field passive reflective target, and the single-point target are used for aligning the TOF camera.

[0005] Preferably, the near-field active light target includes at least four first low targets and at least one first high target; each of the first low targets has the same height and is installed on the same plane, so that each of the first low targets is coplanar, for coarse calculation of pose information.

[0006] Preferably, the near-field active light target includes four first low targets and two first high targets. The four first low targets are divided into two groups of two, and the two groups of first low targets are symmetrically arranged on the target plate along the line connecting the first high targets, forming a symmetrical crab claw structure that does not cause optical interference between them.

[0007] Preferably, the far-field active light target includes at least five second low targets of the same height and at least one second high target; wherein, three of the second low targets are collinear, and the other two second low targets are located on opposite sides of the collinearity, and the connecting line of the two second low targets intersects the collinearity; the position of the second high target is not fixed, and it can be set at any position on the target plate without obstructing other sub-targets and without being obstructed itself.

[0008] Preferably, both the near-field active light target and the far-field active light target are composed of light-emitting components; the first light-emitting aperture and the first light-emitting port of each first low target and each first high target in the near-field active light target are consistent; the second light-emitting aperture and the second light-emitting port of each second low target and each second high target in the far-field active light target are consistent.

[0009] Preferably, the near-field passive reflective target includes: at least 4 third low targets and at least 1 third high target; each of the third low targets has the same height and is installed on the same plane, so that each of the third low targets is coplanar.

[0010] Preferably, the near-field passive reflective target includes four third low targets and two third high targets. The four third low targets are divided into two groups of two, and the two groups of third low targets are symmetrically arranged on the target plate along the line connecting the third high targets, forming a symmetrical crab claw structure that does not cause optical interference between them.

[0011] Preferably, the far-field passive reflective target includes at least five fourth low targets of the same height and at least one fourth high target; wherein, three fourth low targets are collinear, and the other two fourth low targets are located on opposite sides of the collinearity, and the connecting line of the two fourth low targets intersects the collinearity; the position of the fourth high target is not fixed, and it can be set at any position on the target plate without obstructing other sub-targets and without being obstructed itself.

[0012] Preferably, both the near-field passive reflective target and the far-field passive reflective target are composed of glass microsphere reflective stickers and a fixing structure. The fixing structure is fixedly mounted on the target plate, and the glass microsphere reflective stickers are fixed on the fixing structure. The glass microsphere reflective stickers are made of diffuse reflective material. The third light-emitting aperture of each third low target and each third high target in the near-field passive reflective target is consistent. The fourth light-emitting aperture of each fourth low target and each fourth high target (42) in the far-field passive reflective target is consistent.

[0013] Preferably, the TOF camera single-point target is composed of a corner cube prism with a reflective surface size of Φ20mm and a divergence angle of no more than ±5°. Its position is not fixed and can be set at any position on the target plate 1 without obstructing other sub-targets or being obstructed by them, in order to reflect the laser emitted by the TOF camera.

[0014] In summary, compared with traditional rendezvous and docking cooperative targets, the cooperative target of the optical imaging sensor and TOF camera for space relative measurement of the present invention has the following beneficial effects: (1) The present invention uses a combination of optical imaging sensor and TOF camera for space relative measurement. In the measurement process of 100m to 0.3m in the whole measurement segment, they can be backed up to each other, and there is overlap between the measurement segments in the far field and near field, which improves the measurement reliability; (2) The cooperative target provided by the present invention has the characteristics of small size and high integration. By combining active light-emitting target and passive reflective target, the applicable scenarios in space are improved, and it can be deployed in a small area. It is not only suitable for large rendezvous and docking measurement tasks of space station, but also applicable to the relative measurement needs between other small spacecraft; (3) The present invention deploys five targets for different application scenarios on a 600mm*600mm honeycomb aluminum plate, and fully analyzes the occlusion relationship between targets at different angles and distances. It can simultaneously meet the measurement needs of optical imaging sensor and TOF camera. At the same time, considering the long life application needs in space, the key targets have redundant designs. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall structure of the cooperative target of the optical imaging sensor and the TOF camera for spatial relative measurement according to the present invention.

[0016] Figure 2 This is a far-field active optical target configuration diagram of the optical imaging sensor in the cooperative target of the optical imaging sensor for spatial relative measurement and the TOF camera of the present invention.

[0017] Figure 3 This is a far-field passive target configuration diagram of the TOF camera in the cooperative target of the optical imaging sensor and the TOF camera for spatial relative measurement of the present invention. Detailed Implementation

[0018] The following will be combined with the appendix in the embodiments of the present invention. Figure 1 ~Attached Figure 3 The technical solutions, structural features, objectives and effects achieved in the embodiments of the present invention will be described in detail.

[0019] It should be noted that, in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only the expressly listed elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0020] This invention provides a cooperative target for an optical imaging sensor and a TOF camera (depth imaging camera) for spatial relative measurements, such as... Figures 1-3 As shown, the cooperative target includes: a target plate 1 for fixing multiple sub-targets arranged in a staggered manner; the sub-targets include: a near-field active light target 2, a far-field active light target 3, a far-field passive reflective target 4, a near-field passive reflective target 5, and a single-point target 6; the near-field active light target 2 and the far-field active light target 3 are used for aligning the optical imaging sensor; the far-field passive reflective target 4, the near-field passive reflective target 5, and the single-point target 6 are used for aligning the TOF camera. By mixing and staggering the active light target of the optical imaging sensor and the passive reflective target of the TOF camera on the target plate 1, the active light target and the passive reflective target can work simultaneously without interfering with each other. When the cooperative target is working, a constant current power supply is required for the active light target (including the near-field active light target 2 and the far-field active light target 3), while the passive reflective target does not require power.

[0021] To ensure the compactness and miniaturization of the target layout, the target plate 1 is set to 600mm×600mm in this embodiment by comprehensively optimizing parameters such as measurement distance, luminous power of near-field active light target 2 and far-field active light target 3, and occlusion relationship between sub-targets.

[0022] Among them, such as Figure 1As shown, the near-field active light target 2 of the optical imaging sensor includes at least four first low targets 21 and at least one first high target 22 of the same height. Each of the first low targets 21 has the same height and is mounted on the same plane (i.e., on the target plate 1), thus making each of the first low targets 21 coplanar for coarse calculation of pose information. The first high target 22 is used to improve the calculation accuracy of pose information. In this embodiment, the near-field active light target 2 includes four first low targets 21 and two first high targets 22. The four first low targets 21 are divided into two groups, and the two groups of first low targets 21 are symmetrically arranged on the target plate 1 along the line connecting the first high targets 22. That is, two first low targets 21 are respectively arranged on both sides of the first high target 22, forming a symmetrical and non-optically interfering crab claw structure, effectively utilizing the limited layout space. The near-field active light target 2 (including a first low target 21 and a first high target 22) is composed of LEDs or other light-emitting components, and the first light-emitting aperture and the emission power of the first light-emitting port of each first low target 21 and each first high target 22 in the near-field active light target 2 are consistent. In this embodiment, a specially designed LED is used as the near-field active light target 2. It should be noted that in this embodiment, if the alignment accuracy meets the requirements, only one first high target 22 is needed, and the other can be used as a redundancy design.

[0023] Among them, such as Figure 1 and Figure 2 As shown, the optical imaging sensitive far-field active light target 3 includes at least five second low targets 31 of the same height and at least one second high target 32; each of the second low targets 31 has the same height and is mounted on the same plane (i.e., on the target plate 1), thus making each of the second low targets 31 coplanar. The position of the second high target 32 ​​is not fixed; it can be set at any position on the target plate 1 without obstructing other sub-targets or itself. The position distribution of the second low targets 31 is set using an coded method, such as... Figure 2 As shown, three second low targets 31 are collinear (i.e., on a straight line), and two other second low targets 31 are located on opposite sides of the collinearity, with the connecting line between these two second low targets 31 intersecting the collinearity. The far-field active light target 3 (including the second low target 31 and the second high target 32) is the same as the near-field active light target 2, composed of LEDs or other light-emitting components, and the second emission aperture and the emission power of the second emission port of each second low target 31 and each second high target 32 ​​in the far-field active light target 3 are consistent.

[0024] Specifically, in this embodiment, such as Figure 2As shown, the far-field active optical target 3 includes five second low targets 31 (namely, second low target 311, second low target 312, second low target 313, second low target 314, and second low target 315) and two second high targets 32 (namely, second high target 321 and second high target 322); the distribution positions of the five second low targets 31 are as follows... Figure 2 As shown, the second low target 311, the second low target 312, and the second low target 313 are collinear and intersect the line connecting the second low target 314 and the second low target 315 at point P. The second low target 311, the second low target 312, point P, and the second low target 313 form a fixed cross ratio combination. Let the length of the line segment between the second low target 311 and the second low target 312 be L1, the length of the line segment between point P and the second low target 313 be L2, the length of the line segment between point P and the second low target 312 be L3, and the length of the line segment between the second low target 311 and the second low target 313 be L4. Then the first cross ratio CR1 = (L1·L2) / (L3·L4). The first cross ratio CR1 is a photographic invariant. Since the line connecting the second low target 314 and the second low target 315 must intersect the collinearity of the second low target 311, the second low target 312, and the second low target 313, there must be an intersection point P. Therefore, the position of point P can be determined by the first cross ratio CR1 of this invariant. This invariant can then be used to determine the position coordinates of five coplanar points (i.e., the second low target 311, the second low target 312, the second low target 313, the second low target 314, and the second low target 315). This allows for the calculation of a coarse pose information. By using a back-projection algorithm combined with the target calibration information, the position coordinates of all far-field active light targets 3 can be determined, thus achieving the goal of target plate 1 search and matching and improving the success rate of search and matching. It should be noted that since the positions of the second low targets 314 and 315 are uncertain, determining point P through the first cross ratio CR1, provided that the second low targets 314 and 315 do not obstruct other sub-targets and are not obstructed themselves, is sufficient to determine the positions of the second low targets 314 and 315 by ensuring that the line connecting them passes through point P.

[0025] Among them, such as Figure 1As shown, the layout of the near-field passive reflective target 5 of the TOF camera and the near-field active light target 2 of the optical imaging sensor is consistent, including: at least 4 third low targets 51 of the same height and at least 1 third high target 52; each of the third low targets 51 has the same height and is installed on the same plane (i.e., on the target plate 1), thus making each of the third low targets 51 coplanar; in this embodiment, the near-field passive reflective target 5 includes 4 third low targets 51 and 2 third high targets 52, and the 4 third low targets 51 are divided into two groups, and the two groups of third low targets 51 are symmetrically arranged on the target plate 1 along the line connecting the third high targets 52, that is, 2 third low targets 51 are respectively arranged on both sides of the third high target 52, forming a symmetrical crab claw structure that does not form optical interference with each other. The near-field passive reflective target 5 (including a third low target 51 and a third high target 52) ​​is composed of a 50-mesh glass microsphere reflective sticker and a fixing structure. The fixing structure is fixedly mounted on the target plate 1, and the glass microsphere reflective sticker is fixed on the fixing structure. The glass microsphere reflective sticker is made of diffuse reflective material, and the third light-emitting aperture of each third low target 51 and each third high target 52 in the near-field passive reflective target 5 is consistent. In this embodiment, the heights of the two third high targets 52 are consistent, the heights of the four third low targets 51 are consistent, and they are installed on the same plane (i.e., the target plate 1). The position of the TOF camera near-field passive reflective target 5 is determined by the installation position of the TOF camera. The geometric center of the TOF camera near-field passive reflective target 5 is on the optical axis of the TOF camera and does not form optical interference with other sub-targets.

[0026] Among them, such as Figure 1 and Figure 3 As shown, the far-field passive reflective target 4 of the TOF camera includes at least five fourth low targets 41 of the same height and at least one fourth high target 42; all the fourth low targets 41 are of the same height and are mounted on the same plane (i.e., on the target plate 1), thus making all the fourth low targets 41 coplanar. The position of the fourth high target 42 is not fixed; it can be located at any position on the target plate 1 without obstructing other sub-targets or itself. The positional distribution of the fourth low targets 41 is set using the same coding method as the far-field active light target 3 of the optical imaging sensor, such as... Figure 3 As shown, three fourth low targets 41 are collinear (i.e., on a straight line), and two other fourth low targets 41 are located on opposite sides of the collinearity, with the connecting line of these two fourth low targets 41 intersecting the collinearity. Similarly, the far-field passive reflective target 4 is also composed of glass microsphere reflective stickers and a fixing structure. Through this fixing structure, the glass microsphere reflective stickers are fixed at designated positions on the target plate 1, and the fourth light-emitting port of each fourth low target 41 and each fourth high target 42 in the far-field passive reflective target 4 is consistent.

[0027] Specifically, in this embodiment, such as Figure 3 As shown, the far-field passive reflective target 4 includes five fourth low targets 41 (namely fourth low target 411, fourth low target 412, fourth low target 413, fourth low target 414, and fourth low target 415) and two fourth high targets 42 (namely fourth high target 421 and fourth high target 422); the distribution positions of the five fourth low targets 41 are as follows... Figure 3 As shown, the fourth low target 411, the fourth low target 412, and the fourth low target 413 are collinear and intersect the line connecting the fourth low target 414 and the fourth low target 415 at point Q. The fourth low target 411, the fourth low target 412, point Q, and the fourth low target 413 form a fixed cross ratio combination. Let the line segment length between the fourth low target 411 and the fourth low target 412 be L5, the line segment length between point Q and the fourth low target 413 be L6, the line segment length between point Q and the fourth low target 412 be L7, and the line segment length between the fourth low target 411 and the fourth low target 413 be L8. Then the second cross ratio CR2 = (L5·L6) / (L7·L8). The second cross ratio CR2 is also a photographic invariant. Since the line connecting the fourth high target 421 and the fourth high target 422 must intersect the collinearity of the four low targets 411, the fourth low target 412, and the fourth low target 413, there must be an intersection point Q. Therefore, the position of point Q can be determined by the second cross ratio CR2 of this invariant. This invariant can then be used for target search and matching. Specifically, the position coordinates of five coplanar points (i.e., the fourth low target 411, the fourth low target 412, the fourth low target 413, the fourth low target 414, and the fourth low target 415) can be determined using this invariant. A coarse pose information can then be calculated. By using a back-projection algorithm combined with the target calibration information, the position coordinates of all far-field active light targets 3 can be determined, thus achieving the goal of target plate 1 search and matching. It should be noted that since the positions of the fourth high targets 421 and 422 are uncertain, the second cross ratio CR2 is used to determine point Q. Provided that the fourth high targets 421 and 422 do not obstruct other sub-targets and are not obstructed themselves, the position of the fourth high targets 421 and 422 is determined as long as the line connecting them passes through point Q.

[0028] The TOF camera's single-point target 6 is composed of a cornerstone prism with a reflective surface size of Φ20mm and a divergence angle of no more than ±5°. Its position is not fixed; it can be positioned anywhere on the target plate 1 to reflect the laser emitted by the TOF camera, provided it does not obstruct other sub-targets and is not itself obstructed. Furthermore, the TOF camera collects the reflected laser, and based on the optical path difference, it can calculate the line-of-sight distance and line-of-sight angle at long distances.

[0029] In practical applications, for the optical imaging sensor, in the distance range of 100m to 8m, the far-field camera of the optical imaging sensor performs imaging calculations on the far-field active light target 3; in the distance range of 20m to 0.3m, the near-field camera of the optical imaging sensor performs imaging calculations on the near-field active light target 2. For the TOF camera, in the distance range of 100m to 10m, the TOF camera emits a laser at the single-point target 6, and the TOF camera uses the measured echo to measure the line-of-sight angle and line-of-sight distance; in the distance range of 15m to 2.5m, the TOF camera emits a laser to illuminate the far-field passive reflective target 4, and uses the grayscale imaging function of the TOF camera to image the target, completing the target search and pose calculation; in the distance range of 3m to 0.3m, the grayscale imaging function of the TOF camera is also used to image the near-field passive reflective target 5, completing the target search and pose calculation. To ensure calculation accuracy and improve product stability, the cooperative target disclosed in this invention fully considers the reusability of far-field and near-field targets. At the algorithm level, it can utilize all sub-targets within the field of view for calculation, thereby improving calculation accuracy.

[0030] In summary, compared with the prior art, the optical imaging sensor and TOF camera cooperative target for spatial relative measurement provided by the present invention have the advantages of small size and high integration, and can simultaneously provide measurement requirements for two different types of sensors. Moreover, each sub-target does not interfere with each other and serves as a backup for the others, thereby improving the reliability of rendezvous and docking measurements.

[0031] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A cooperative target for spatial relative measurements, suitable for optical imaging sensors and TOF cameras, characterized in that, include: The target plate (1) is used to fix multiple sub-targets that are misaligned; the sub-targets include: near-field active light target (2), far-field active light target (3), far-field passive reflective target (4), near-field passive reflective target (5) and single-point target (6). The near-field active optical target (2) and the far-field active optical target (3) are used for optical imaging sensor alignment, respectively. The far-field passive reflective target (4), the near-field passive reflective target (5), and the single-point target (6) are used for TOF camera alignment, respectively. The near-field active light target (2) includes four first low targets (21) and two first high targets (22). The four first low targets (21) are divided into two groups, and the two groups of first low targets (21) are symmetrically arranged on the target plate (1) along the line connecting the first high targets (22) to form a symmetrical crab claw structure that does not form optical interference with each other. The near-field passive reflective target (5) includes four third low targets (51) and two third high targets (52). The four third low targets (51) are divided into two groups, and the two groups of third low targets (51) are symmetrically arranged on the target plate (1) along the line connecting the third high targets (52) to form a symmetrical crab claw structure that does not form optical interference with each other. The far-field active light target (3) includes at least 5 second low targets (31) of the same height and at least 1 second high target (32); wherein, 3 second low targets (31) are collinear, and the other 2 second low targets (31) are located on both sides of the collinearity and the connecting line of the 2 second low targets (31) intersects the collinearity; The far-field passive reflective target (4) includes at least 5 fourth low targets (41) of the same height and at least 1 fourth high target (42); wherein, 3 fourth low targets (41) are collinear, and the other 2 fourth low targets (41) are located on both sides of the collinearity and the connecting line of the 2 fourth low targets (41) intersects the collinearity; The near-field active light target (2), far-field active light target (3), near-field passive reflective target (5), far-field passive reflective target (4) and single-point target (6) are staggered on the target plate (1) so that the active light target and the passive reflective target can work simultaneously without interfering with each other.

2. The cooperative target for spatial relative measurement as described in claim 1, characterized in that, The near-field active light target (2) includes at least four first low targets (21) and at least one first high target (22); each of the first low targets (21) has the same height and is installed on the same plane, so that each of the first low targets (21) is coplanar, for coarse calculation of pose information.

3. The cooperative target for spatial relative measurement as described in claim 1, characterized in that, The position of the second high target (32) is not fixed. It can be set at any position on the target plate (1) without obstructing other sub-targets or being obstructed itself.

4. The cooperative target for spatial relative measurement as described in claim 2 or 3, characterized in that, Both the near-field active light target (2) and the far-field active light target (3) are composed of light-emitting components; The first light-emitting aperture and the emission power of the first light-emitting port of each first low target (21) and each first high target (22) in the near-field active light target (2) are consistent; The second light-emitting aperture and the second light-emitting power of the second low target (31) and each second high target (32) in the far-field active light target (3) are consistent.

5. The cooperative target for spatial relative measurement as described in claim 1, characterized in that, The near-field passive reflective target (5) includes at least four third low targets (51) and at least one third high target (52); each of the third low targets (51) has the same height and is installed on the same plane, so that each of the third low targets (51) is coplanar.

6. The cooperative target for spatial relative measurement as described in claim 1, characterized in that, The fourth high target (42) is not fixed in position. It can be set at any position on the target plate (1) without obstructing other sub-targets or being obstructed itself.

7. The cooperative target for spatial relative measurement as described in claim 5 or 6, characterized in that, The near-field passive reflective target (5) and the far-field passive reflective target (4) are both composed of glass microsphere reflective stickers and a fixing structure. The fixing structure is fixedly set on the target plate (1), and the glass microsphere reflective stickers are fixed on the fixing structure. The glass microsphere reflective stickers are made of diffuse reflective material. The third light-emitting aperture of each third low target (51) and each third high target (52) in the near-field passive reflective target (5) is consistent; The fourth light outlet of each fourth low target (41) and each fourth high target (42) in the far-field passive reflective target (4) is consistent.

8. The cooperative target for spatial relative measurement as described in claim 1, characterized in that, The TOF camera single-point target (6) is composed of a corner cube prism with a reflective surface size of Φ20mm and a divergence angle of no more than ±5°. Its position is not fixed. It can be set at any position on the target plate 1 without obstructing other sub-targets or being obstructed, and is used to reflect the laser emitted by the TOF camera.

Images