Low profile lidar scanner with polygon mirror

• US 10,571,567 B2
• Filed: 04/27/2018
• Issued: 02/25/2020
• Est. Priority Date: 11/22/2017
• Status: Active Grant

• Current Assignee: Luminar Technologies, Inc.
• Original Assignee: Luminar Technologies, Inc.
• Inventors: Campbell, Scott R., Eichenholz, Jason M., Russell, Austin K., Hughes, John G.
• Primary Examiner(s): Ratcliffe, Luke D
• Application Number:
  US15/965,197
• Publication Number:
  US 20190154836A1
• Time in Patent Office: 669 Days
• CPC Class Codes: G01S 17/08 for measuring distance only indirect measurement G01S17/46; active triangulation systems G01S17/48
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/87 Combinations of systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/931 of land vehicles
• CPC Class Codes: G01S 7/4813 Housing arrangements
• CPC Class Codes: G01S 7/4817 relating to scanning
• CPC Class Codes: G02B 26/101 with both horizontal and vertical deflecting means, e.g. raster or XY scanners colour television using laser beams scanning a display screen H04N9/3129
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence
• CPC Class Codes: G02B 26/123 Multibeam scanners, e.g. using multiple light sources or beam splitters
• CPC Class Codes: G02B 26/125 Details of the optical system between the polygonal mirror and the image plane G02B26/123, G02B26/127 take precedence; F-Theta lenses G02B13/0005
• CPC Class Codes: G02B 27/0955 Lenses lenses per se G02B3/00
• CPC Class Codes: G02B 27/0977 Reflective elements
• CPC Class Codes: G02B 27/1086 operating by diffraction only
• CPC Class Codes: G02B 27/30 Collimators
• CPC Class Codes: G02B 5/0841 comprising organic materials, e.g. polymers
• CPC Class Codes: G02B 5/09 Multifaceted or polygonal mirrors , e.g. polygonal scanning mirrors; Fresnel mirrors
• CPC Class Codes: G02B 5/1857 using exposure or etching means, e.g. holography, photolithography, exposure to electron or ion beams
• CPC Class Codes: G02B 5/22 Absorbing filters G02B5/201 - G02B5/208 take precedence
• CPC Class Codes: G02B 7/1821 for rotating or oscillating mirrors
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 27/14643 : Photodiode arrays; MOS imagers
• CPC Class Codes: H01L 27/14647 : Multicolour imagers having a stacked pixel-element structure, e.g. npn, npnpn or MQW elements
• CPC Class Codes: H01L 27/14694 : The active layers comprising only AIIIBV compounds, e.g. GaAs, InP

Abstract

A lidar system comprises a light source configured to emit light, a scanner configured to direct the emitted light to scan a field of regard of the lidar system in accordance with a scan pattern, a receiver configured to detect the light scattered by one or more remote targets, and a controller configured to control motion of at least the second mirror to modify the scan pattern. The scanner includes a rotatable polygon mirror having a block having a first wall, a second wall, and reflective surfaces extending between the first and second walls, the reflective surfaces being angularly offset from one another along a periphery of the block. The scanner also includes a polygon mirror axle extending into the block through at least one of the first and second walls, about which the block rotates, and a second mirror pivotable along an axis orthogonal to the polygon mirror axle.

Claims

1. A lidar system comprising:

a light source configured to emit light;

a scanner configured to direct the emitted light to scan a field of regard of the lidar system in accordance with a scan pattern, the scanner including;

a rotatable polygon mirror having a block having a first wall, a second wall, and a plurality of reflective surfaces extending between the first and second walls, the reflective surfaces being angularly offset from one another along a periphery of the block,

a polygon mirror axle extending into the block through at least one of the first and second walls, about which the block rotates, and

a second mirror pivotable along an axis orthogonal to the polygon mirror axle;

a receiver configured to detect at least a portion of the emitted light scattered by one or more remote targets;

a controller configured to control motion of at least the second mirror to modify the scan pattern; and

a housing at least partially enclosing one or more of the light source, the scanner, the receiver, and the controller, wherein the rotation of the polygon mirror imparts a flow of air through the housing to provide cooling to components enclosed within the housing.

2. The lidar system of claim 1, wherein:

the polygon mirror directs the emitted light to the second mirror at different orientations of the polygon mirror to generate a different respective scan line for each of the plurality of reflective surfaces, and

the second mirror pivots to distribute the scan lines across the field of regard.

3. The lidar system of claim 2, wherein to modify the scan pattern, the controller varies a rate at which the second mirror pivots to increase or decrease a distance between at least some of the scan lines.

4. The lidar system of claim 2, wherein to modify the scan pattern, the controller varies a range within which the second mirror pivots to modify at least one of a horizontal or vertical angular dimension of the field of regard.

5. The lidar system of claim 4, wherein the second mirror is configured so as to pivot over a range of allowable motion larger than a range corresponding to at least one of the horizontal or vertical angular dimension of the field of regard, so as to define a maximum range of allowable motion larger than a range within which the second mirror pivots during a scan, wherein the controller selects different portions of the maximum range of allowable motion as the range within which the second mirror pivots, in accordance with modifications of the scan pattern.

6. The lidar system of claim 1, further comprising a drive belt and a drive-belt motor to impart oscillating motion to the second mirror, wherein the drive-belt motor is coupled to the second mirror via the drive belt.

7. The lidar system of claim 6, wherein to modify the scan pattern, the controller modifies a drive signal supplied to the drive-belt motor.

8. The lidar system of claim 1, wherein the controller regulates a speed of rotation of the polygon mirror to keep the speed of rotation substantially constant.

9. The lidar system of claim 1, further comprising:

a motor configured to impart rotation to the polygon mirror axle, the motor including a rotor disposed at least partially inside the block.

10. The lidar system of claim 1, wherein the controller is configured to modify the scan pattern on a frame-by-frame basis, each frame corresponding to a complete scan of the field of regard of the lidar system.

11. The lidar system of claim 1, wherein the second mirror includes a pivot mirror block having a reflective surface facing the polygon mirror, the center of gravity of the pivot mirror block being displaced closer to the reflective surface than to a wall of the second mirror opposite the second surface.

12. The lidar system of claim 1, wherein each reflective surface of the block is joined to adjacent reflective surfaces of the block along a drag-reducing, non-sharp edge.

13. The lidar system of claim 1, wherein a width of the second mirror is greater than a width of each of the reflective surfaces, measured along a common axis, wherein the width of the second mirror limits the field of regard of the lidar system along the horizontal dimension.

14. The lidar system of claim 1, wherein the light source is a first light source, and the light emitted by the first light source corresponds to a first beam of light;

the lidar system further comprising;

a second light source configured to emit a second beam of light; and

a plurality of optical elements configured to direct the first and second beams of light respectively to two different reflective surfaces of the rotatable polygon mirror.

15. The lidar system of claim 14, wherein:

the scanner scans the first beam of light and the second beam of light to define a first field of regard and a second field of regard, respectively, and

the first field of regard and the second field of regard in combination define the field of regard of the lidar system.

16. The lidar system of claim 1, wherein the receiver includes an avalanche photodiode (APD).

17. An optical scanner configured to direct light in accordance with a scan pattern to scan a field of regard, the optical scanner comprising:

a rotatable polygon mirror having a block having a first wall, a second wall, and a plurality of reflective surfaces extending between the first and second walls, the reflective surfaces being angularly offset from one another along a periphery of the block;

a polygon mirror axle extending into the block through at least one of the first and second walls, about which the block rotates;

a second mirror pivotable along an axis orthogonal to the polygon mirror axle within an available range, wherein the second mirror includes a pivot mirror block having a reflective surface facing the polygon mirror, the center of gravity of the pivot mirror block being displaced closer to the reflective surface than to a wall of the second mirror opposite the second surface, and the pivot mirror block of the second mirror includes a layer with a honeycomb structure;

a first motor configured to impart rotation to the polygon mirror axle; and

a second motor configured to impart oscillating motion to the second mirror within an operational range smaller than the available range;

wherein the second motor modifies the operational range of the second mirror in response to a drive signal.

18. The optical scanner of claim 17, wherein the second motor moves the operational range upward or downward along a vertical dimension within the available range in response to the drive signal.

19. The optical scanner of claim 17, wherein the second motor increases the operational range within the available range in response to the drive signal.

20. The optical scanner of claim 17, wherein the polygon mirror directs light to the second mirror at different orientations of the polygon mirror to generate a different respective scan line for each of the plurality of reflective surfaces, and the second mirror pivots to distribute the scan lines across the field of regard.

21. The optical scanner of claim 20, wherein in response to the drive signal, the second motor modifies the oscillating motion imparted to the second mirror so as to increase or decrease a distance between at least some of the scan lines.

22. The optical scanner of claim 17, wherein the first motor is configured to rotate the polygon mirror at a substantially constant speed of rotation.

23. The optical scanner of claim 17, wherein the rotatable polygon mirror is configured to receive a first beam of light at a first one of the plurality of reflective surfaces and concurrently receive a second beam of light at a second one of the plurality of reflective surfaces.

24. The optical scanner of claim 23, configured to scan the first beam of light and the second beam of light to define a first field of regard and a second field of regard, respectively;

wherein the first field of regard and the second field of regard in combination define the field of regard.

25. A lidar system comprising:

a light source configured to emit light;

a scanner configured to direct the emitted light to scan a field of regard of the lidar system in accordance with a scan pattern, the scanner including;

a rotatable polygon mirror having a block having a first wall, a second wall, and a plurality of reflective surfaces extending between the first and second walls, the reflective surfaces being angularly offset from one another along a periphery of the block,

a polygon mirror axle extending into the block through at least one of the first and second walls, about which the block rotates, and

a second mirror pivotable along an axis orthogonal to the polygon mirror axle, wherein the second mirror includes a pivot mirror block having a reflective surface facing the polygon mirror, the center of gravity of the pivot mirror block being displaced closer to the reflective surface than to a wall of the second mirror opposite the second surface, and the pivot mirror block of the second mirror includes a layer with a honeycomb structure;

a receiver configured to detect at least a portion of the emitted light scattered by one or more remote targets; and

a controller configured to control motion of at least the second mirror to modify the scan pattern.

26. A lidar system comprising:

a light source configured to emit light;

a scanner configured to direct the emitted light to scan a field of regard of the lidar system in accordance with a scan pattern, the scanner including;

a rotatable polygon mirror having a block having a first wall, a second wall, and a plurality of reflective surfaces extending between the first and second walls, the reflective surfaces being angularly offset from one another along a periphery of the block,

a polygon mirror axle extending into the block through at least one of the first and second walls, about which the block rotates, and

a second mirror pivotable along an axis orthogonal to the polygon mirror axle;

a receiver configured to detect at least a portion of the emitted light scattered by one or more remote targets;

a controller configured to control motion of at least the second mirror to modify the scan pattern; and

a housing at least partially enclosing one or more of the light source, the scanner, the receiver, and the controller, wherein at least a portion of the second mirror extends above the rotatable polygon mirror, and only a region extending from a lower edge of the second mirror to a top of the housing projects prominently from a surface of a body of a vehicle on which the lidar system is deployed.