3D depth point cloud from timing flight of 2D scanned light beam pulses

• US 9,285,477 B1
• Filed: 01/21/2014
• Issued: 03/15/2016
• Est. Priority Date: 01/25/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Smith, Scott T., Last, Matthew E., Valko, Edward A.
• Primary Examiner(s): Ratcliffe, Luke
• Application Number:
  US14/160,382
• Time in Patent Office: 784 Days
• Field of Search: 356 301- 315, 356 401- 41, 356 501- 515, 356 6- 22
• US Class Current: 1/1
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01S 17/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 17/42 Simultaneous measurement of distance and other co-ordinates indirect measurement G01S17/46
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 7/4817 relating to scanning

Abstract

A light detection and ranging (LIDAR) system has an emitter which produces a sequence of outgoing pulses of coherent collimated light that transmitted in a given direction, a mirror system having a scanning mirror that is positioned to deflect the outgoing pulse sequence towards a scene, and a detector collocated with the emitter and aimed to detect a sequence of incoming pulses being reflections of the outgoing pulses that are returning from said given direction and have been deflected by the scanning mirror. An electronic controller communicates with the emitter and the detector and controls the scanning mirror, so that the outgoing pulses scan the scene and the controller computes a radial distance or depth for each pair of outgoing and incoming pulses and uses the computed radial distance to provide a scanned 3D depth map of objects in the scene. Other embodiments are also described.

Claims

1. A light detection and ranging system comprising:

an emitter which produces an outgoing pulse sequence of coherent collimated light;

a mirror system having a scanning mirror that is positioned to deflect the outgoing pulse sequence;

a compensation mirror positioned to further deflect the outgoing pulse sequence after it is deflected by the scanning mirror, the compensation mirror having a surface with a first curvature at an edge of the compensation mirror that is different from a second curvature at a center of the compensation mirror;

a detector collocated with the emitter and aimed to detect an incoming pulse sequence that is a reflection of the outgoing pulse sequence; and

electronic circuitry that is coupled to communicate with the emitter and the detector and to control the scanning mirror, so that the outgoing pulse sequence scans a scene and the electronic circuitry computes a radial distance for each pair of outgoing and incoming pulses and uses the computed radial distance to provide a scanned 3D depth map of objects in the scene.

2. The system of claim 1 wherein the compensation mirror comprises a field of view expanding panoramic mirror.

3. The system of claim 1 wherein the scanning mirror is a MEMS 2-axis scanning mirror having a single mirror surface that tilts so that the outgoing pulse sequence covers the scene.

4. The system of claim 1 wherein the emitter comprises a pulsed laser.

5. The system of claim 1 wherein the first curvature is a convex curvature, and the second curvature is either a reduced convex curvature or a concave curvature.

6. The system of claim 1 wherein the first curvature causes an effective increase in an angular velocity of the outgoing pulse sequence after it is deflected by the scanning mirror when the scanning mirror is moving with a low angular velocity.

7. The system of claim 6 wherein the second curvature causes an effective decrease in the angular velocity of the outgoing pulse sequence after it is deflected by the scanning mirror when the scanning mirror is moving with a high angular velocity.

8. The system of claim 1 wherein the first curvature and the second curvature of the compensation mirror together cause 1) an effective increase in an angular velocity of the outgoing pulse sequence after it is deflected by the scanning mirror when the scanning mirror is moving with a low angular velocity, and 2) an effective decrease in the angular velocity of the outgoing pulse sequence after it is deflected by the scanning mirror when the scanning mirror is moving with a high angular velocity.

9. The system of claim 1 wherein the first curvature and the second curvature of the compensation mirror together cause a reduction of pincushion distortion otherwise present in a full sweep pattern of the outgoing pulse sequence after it is deflected by the scanning mirror.

10. The system of claim 1 wherein:

the emitter illuminates the scanning mirror off-axis when the scanning mirror is in its un-actuated orientation; and

the compensation mirror is shaped to reduce pincushion distortion created by the angle of emitter illumination.

11. The system of claim 1 wherein an overall shape of the compensation mirror simultaneously 1) changes an angular velocity of the outgoing pulse sequence after it is deflected by the scanning mirror moving with a changing angular velocity to be constant, and 2) reshapes the outgoing pulse sequence after it is deflected by the scanning mirror moving into an essentially rectangular sweep pattern.

12. A method for providing a scanned 3D depth map of objects in a scene, comprising:

producing an outgoing pulse sequence of coherent collimated light;

moving one or more reflective surfaces to deflect the outgoing pulse sequence;

deflecting the outgoing pulse sequence coming from the one or more reflective surfaces towards the scene using a non-moving compensation mirror having a surface with a first curvature at an edge of the compensation mirror that is different from a second curvature at a center of the compensation mirror; and

detecting an incoming pulse sequence that is a reflection of the outgoing pulse sequence;

computing a plurality of radial distances based on time of flight between each of a plurality of outgoing pulses and corresponding incoming pulses;

providing the computed plurality of radial distances as part of a scanned 3D depth map of objects in the scene.

13. The method of claim 12 wherein the compensation mirror is a field of view expanding panoramic mirror.

14. The method of claim 12 wherein the first curvature is a convex curvature, and the second curvature is either a reduced convex curvature or a concave curvature.

15. The method of claim 12 wherein the first curvature causes an effective increase in an angular velocity of the outgoing pulse sequence after it is deflected by the one or more reflective surfaces when the one or more reflective surfaces are moving with a low angular velocity.

16. The method of claim 15 wherein the second curvature causes an effective decrease in the angular velocity of the outgoing pulse sequence after it is deflected by the one or more reflective surfaces when the one or more reflective surfaces are moving with a high angular velocity.

17. The method of claim 12 wherein the first curvature and the second curvature of the compensation mirror together cause an effective increase in an angular velocity of the outgoing pulse sequence after it is deflected by the one or more reflective surfaces when the one or more reflective surfaces are moving with a low angular velocity, and cause an effective decrease in the angular velocity of the outgoing pulse sequence after it is deflected by the one or more reflective surfaces when the one or more reflective surfaces are moving with a high angular velocity.

18. The method of claim 12 wherein the first curvature and the second curvature of the compensation mirror together cause a reduction of pincushion distortion otherwise present in a full sweep pattern of the outgoing pulse sequence after it is deflected by the one or more reflective surfaces.

19. The method of claim 12 wherein:

an emitter illuminates the one or more reflective surfaces off-axis at an angle of emitter illumination when the one or more reflective surfaces are in their un-actuated orientations; and

the compensation mirror is shaped to reduce pincushion distortion created by the angle of emitter illumination.

20. The method of claim 12 wherein an overall shape of the compensation mirror simultaneously changes an angular velocity of the outgoing pulse sequence to be constant after the outgoing pulse sequence is deflected by the one or more reflective surfaces moving with a changing angular velocity, and reshapes the outgoing pulse sequence into an essentially rectangular sweep pattern after it is deflected by the one or more reflective surfaces.