Method and apparatus for measuring angular resolution of multi-beam lidar

1. A method for measuring an angular resolution of a multi-beam lidar, the multi-beam lidar comprising a center axis and at least one laser emitter, each laser emitter of the at least one laser emitter rotating around the center axis, the method comprising:

acquiring, when a checkerboard calibration plate is scanned by the multi-beam lidar, an image of the checkerboard calibration plate photographed by a camera;

identifying a checkerboard in the image, and determining a physical length characterized by a unit pixel of the image based on shape and length information of each checker in the checkerboard calibration plate;

determining a center light spot and a light spot pair in the image, the center light spot being an image of a laser beam perpendicular to the checkerboard calibration plate among laser beams emitted by the at least one laser emitter in the image, and the light spot pair being two images of two laser beams emitted by two adjacent laser emitters of at least two laser emitters in the image;

determining an angle between a laser beam corresponding to each light spot of the light spot pair and a laser beam corresponding to the center light spot based on the physical length characterized by the unit pixel, the determined center light spot and the determined light spot pair; and

determining the angular resolution of the multi-beam lidar based on the determined angle between the laser beam corresponding to the each light spot of the light spot pair and the laser beam corresponding to the center light spot.

2. The method according to claim 1 , wherein the determining an angle between a laser beam corresponding to each light spot of the light spot pair and a laser beam corresponding to the center light spot based on the physical length characterized by the unit pixel, the determined center light spot and the determined light spot pair comprises:

determining the angle for the each light spot of the light spot pair as follows: determining a pixel distance between the each light spot and the center light spot in an axial direction, the axial direction being a direction of a projection of the center axis on the checkerboard calibration plate; determining a distance between a projection of the laser beam corresponding to the each light spot on the checkerboard calibration plate and a projection of the laser beam corresponding to the center light spot on the checkerboard calibration plate based on the determined pixel distance and the physical length characterized by the unit pixel; and determining the angle between the laser beam corresponding to the each light spot and the laser beam corresponding to the center light spot based on the determined distance.

3. The method according to claim 2 , wherein the center axis is parallel to the checkerboard calibration plate; and

the determining the angle between the laser beam corresponding to the each light spot and the laser beam corresponding to the center light spot based on the determined distance comprises:

calculating a ratio of the determined distance to a distance between the checkerboard calibration plate and the center axis; and

determining an arctangent angle of the calculated ratio as the angle between the laser beam corresponding to the each light spot and the laser beam corresponding to the center light spot.

4. The method according to claim 3 , wherein the determining the angular resolution of the multi-beam lidar based on the determined angle between a laser beam corresponding to each light spot of the light spot pair and a laser beam corresponding to the center light spot comprises:

calculating an angular difference between an angle between a laser beam corresponding to a light spot of the light spot pair and the laser beam corresponding to the center light spot and an angle between a laser beam corresponding to another light spot of the light spot pair and the laser beam corresponding to the center light spot; and

defining the calculated angular difference as the angular resolution of the multi-beam lidar.

5. The method according to claim 1 , wherein the camera is an infrared camera.

6. An apparatus for measuring an angular resolution of a multi-beam lidar, the multi-beam lidar comprising a center axis and at least one laser emitter, each laser emitter of the at least one laser emitter rotating around the center axis, the apparatus comprising:

at least one processor; and

a memory storing instructions, the instructions when executed by the at least one processor, cause the at least one processor to perform operations, the operations comprising:

acquiring, when a checkerboard calibration plate is scanned by the multi-beam lidar, an image of the checkerboard calibration plate photographed by a camera;

identifying a checkerboard in the image, and determining a physical length characterized by a unit pixel of the image based on shape and length information of each checker in the checkerboard calibration plate;

determining a center light spot and a light spot pair in the image, the center light spot being an image of a laser beam perpendicular to the checkerboard calibration plate among laser beams emitted by the at least one laser emitter in the image, and the light spot pair being two images of two laser beams emitted by two adjacent laser emitters of at least two laser emitters in the image;

determining an angle between a laser beam corresponding to each light spot of the light spot pair and a laser beam corresponding to the center light spot based on the physical length characterized by the unit pixel, the determined center light spot and the determined light spot pair; and

determining the angular resolution of the multi-beam lidar based on the determined angle between the laser beam corresponding to the each light spot of the light spot pair and the laser beam corresponding to the center light spot.

7. The apparatus according to claim 6 , wherein the determining an angle between a laser beam corresponding to each light spot of the light spot pair and a laser beam corresponding to the center light spot based on the physical length characterized by the unit pixel, the determined center light spot and the determined light spot pair comprises:

determining the angle for the each light spot of the light spot pair as follows: determining a pixel distance between the each light spot and the center light spot in an axial direction, the axial direction being a direction of a projection of the center axis on the checkerboard calibration plate; determining a distance between a projection of the laser beam corresponding to the each light spot on the checkerboard calibration plate and a projection of the laser beam corresponding to the center light spot on the checkerboard calibration plate based on the determined pixel distance and the physical length characterized by the unit pixel; and determining the angle between the laser beam corresponding to the each light spot and the laser beam corresponding to the center light spot based on the determined distance.

8. The apparatus according to claim 7 , wherein the center axis is parallel to the checkerboard calibration plate; and

the determining the angle between the laser beam corresponding to the each light spot and the laser beam corresponding to the center light spot based on the determined distance comprises:

calculating a ratio of the determined distance to a distance between the checkerboard calibration plate and the center axis; and

determining an arctangent angle of the calculated ratio as the angle between the laser beam corresponding to the each light spot and the laser beam corresponding to the center light spot.

9. The apparatus according to claim 8 , wherein the determining the angular resolution of the multi-beam lidar based on the determined angle between a laser beam corresponding to each light spot of the light spot pair and a laser beam corresponding to the center light spot comprises:

calculating an angular difference between an angle between a laser beam corresponding to a light spot of the light spot pair and the laser beam corresponding to the center light spot and an angle between a laser beam corresponding to another light spot of the light spot pair and the laser beam corresponding to the center light spot; and

defining the calculated angular difference as the angular resolution of the multi-beam lidar.

10. The apparatus according to claim 6 , wherein the camera is an infrared camera.

11. A non-transitory computer storage medium storing a computer program for measuring an angular resolution of a multi-beam lidar, the multi-beam lidar comprising a center axis and at least one laser emitter, each laser emitter of the at least one laser emitter rotating around the center axis, the computer program when executed by one or more processors, causes the one or more processors to perform operations, the operations comprising:

acquiring, when a checkerboard calibration plate is scanned by the multi-beam lidar, an image of the checkerboard calibration plate photographed by a camera;

identifying a checkerboard in the image, and determining a physical length characterized by a unit pixel of the image based on shape and length information of each checker in the checkerboard calibration plate;

determining a center light spot and a light spot pair in the image, the center light spot being an image of a laser beam perpendicular to the checkerboard calibration plate among laser beams emitted by the at least one laser emitter in the image, and the light spot pair being two images of two laser beams emitted by two adjacent laser emitters of at least two laser emitters in the image;

determining an angle between a laser beam corresponding to each light spot of the light spot pair and a laser beam corresponding to the center light spot based on the physical length characterized by the unit pixel, the determined center light spot and the determined light spot pair; and

determining the angular resolution of the multi-beam lidar based on the determined angle between the laser beam corresponding to the each light spot of the light spot pair and the laser beam corresponding to the center light spot.