Code domain power control for structured light

• US 9,846,943 B2
• Filed: 03/03/2016
• Issued: 12/19/2017
• Est. Priority Date: 08/31/2015
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Nash, James Wilson, Atanassov, Kalin Mitkov, Lindner, Albrecht Johannes
• Primary Examiner(s): Strege, John
• Application Number:
  US15/060,028
• Publication Number:
  US 20170061634A1
• Time in Patent Office: 656 Days
• CPC Class Codes: G01B 11/22 for measuring depth
• CPC Class Codes: G01B 11/2513 with several lines being projected in more than one direction, e.g. grids, patterns
• CPC Class Codes: G06F 18/22 Matching criteria, e.g. proximity measures
• CPC Class Codes: G06F 18/24 Classification techniques
• CPC Class Codes: G06T 7/50 Depth or shape recovery
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: G06V 30/224 of printed characters having additional code marks or containing code marks

Abstract

Systems and methods for controlling structured light laser systems are disclosed. One aspect is a structured light system. The system includes a memory device configured to store a depth map. The system further includes an image projecting device including a laser system configured to project codewords. The system further includes a receiver device including a sensor, the receiver device configured to sense the projected codewords reflected from an object. The system further includes a processing circuit configured to retrieve a portion of the depth map and calculate expected codewords from the depth map. The system further includes a feedback system configured to control the output power of the laser system based on the sensed codewords and the expected codewords.

Claims

1. A structured light system, comprising:

a memory device configured to store a depth map;

an image projecting device including a laser system configured to project codewords;

a receiver device including a sensor, the receiver device configured to sense the projected codewords reflected from an object;

a processing circuit configured to retrieve at least a portion of the depth map stored in the memory device and calculate expected codewords from the depth map; and

a feedback system configured to control an output power of the laser system based on the sensed codewords and the expected codewords.

2. The structured light system of claim 1, wherein the processing circuit is further configured to update the depth map based on the sensed codewords, and wherein the memory device is further configured to store the updated depth map.

3. The structured light system of claim 2, wherein the feedback system is configured to determine a code domain statistic comparing the sensed codewords with the expected codewords, and wherein the feedback system controls the output power of the laser system based at least in part on the determined code domain statistic.

4. The structured light system of claim 3, wherein the code domain statistic quantifies symbol classification accuracy.

5. The structured light system of claim 4, wherein the code domain statistic is the square of the difference in intensity means divided by the sum of the intensity variances.

6. The structured light system of claim 5, wherein the processing circuit is further configured to calculate expected symbols from the depth map and/or previously received codewords;

the processing circuit further configured to assign each received intensity value to the corresponding expected symbols, the processing circuit further configured to calculate a mean intensity value for each symbol, the processing circuit further configured to calculate a variance intensity value for each symbol, and the processing circuit further configured to calculate the code domain statistic as the square of the difference in intensity means divided by the sum of intensity variances.

7. The structured light system of claim 3, wherein the code domain statistic quantifies codeword detection accuracy.

8. The structured light system of claim 7, wherein the code domain statistic is the percent of received codewords that match expected codewords.

9. The structured light system of claim 8, wherein the processing circuit is further configured to compare received codewords to expected codewords, the processing circuit is further configured to calculate the percentage of correctly received codewords, wherein correctly received codewords correspond to expected codewords.

10. The structured light system of claim 3, wherein the code domain statistic quantifies basis function accuracy.

11. The structured light system of claim 10, wherein the code domain statistic is the percent of received basis functions that match expected basis functions.

12. The structured light system of claim 11, wherein the processing circuit is further configured to calculate expected basis functions from the depth map and/or previously received codewords;

the processing circuit further configured to compare received basis functions to expected basis functions, and the processing circuit further configured to calculate the percentage of correctly received basis functions, wherein correctly received basis functions correspond to expected basis functions.

13. The structured light system of claim 3, wherein the feedback system is configured to control an output power of the laser system iteratively to converge to a maximum value for the code domain statistic.

14. A method of controlling laser power in a structured light system, comprising:

storing a depth map with a memory device;

projecting codewords with a laser system;

sensing the projected codewords reflected from an object with a receiver sensor;

retrieving a portion of the depth map from the memory device;

calculating expected codewords from the depth map; and

controlling output power of the laser system based on the sensed codewords and the expected codewords.

15. The method of claim 14, further comprising:

updating the depth map based on the sensed codewords; and

storing the updated depth map with the memory device.

16. The method of claim 14, further comprising:

determining a code domain statistic comparing the sensed codewords with the expected codewords; and

controlling output power of the laser system based at least in part on the determined code domain statistic.

17. The method of claim 16, wherein the code domain statistic quantifies symbol classification accuracy.

18. The method of claim 17, wherein the code domain statistic is the square of the difference in intensity means divided by the sum of the intensity variances.

19. The method of claim 18, further comprising:

calculating expected symbols from the depth map and/or previously received codewords;

assigning each received intensity value to the corresponding expected symbols;

calculating a mean intensity value for each symbol;

calculating a variance intensity value for each symbol; and

calculating the code domain statistic as the square of the difference in intensity means divided by the sum of the intensity variances.

20. The method of claim 16, wherein the code domain statistic quantifies codeword detection accuracy.

21. The method of claim 20, wherein the code domain statistic is the percent of received codewords that match expected codewords.

22. The method of claim 21, further comprising:

comparing received codewords to expected codewords; and

calculating the percentage of correctly received codewords, wherein correctly received codewords correspond to expected codewords.

23. The method of claim 16, wherein the code domain statistic quantifies basis function accuracy.

24. The method of claim 23, wherein the code domain statistic is the percentage of received basis functions that match expected basis functions.

25. The method of claim 24, further comprising:

calculating expected basis functions from the depth map and/or previously received codewords;

comparing received basis functions to expected basis functions, and

calculating the percentage of correctly received basis functions, wherein correctly received basis functions correspond to expected basis functions.

26. The method of claim 16, further comprising controlling an output power of the laser system iteratively to converge to a maximum value for the code domain statistic.

27. A structured light system, comprising:

means for storing a depth map;

means for projecting codewords;

means for sensing the projected codewords reflected from an object;

means for retrieving a portion of the depth map from the means for storing a depth map;

means for calculating expected codewords from the depth map; and

means for controlling output power of the projecting means based on a comparison between the sensed codewords and the expected codewords.

28. The structured light system of claim 27, wherein the storing means comprises a memory device, wherein the project means comprises a laser system, wherein the sensing means comprises a receiver sensor, wherein the retrieving means comprises a processing circuit, wherein the calculating means comprising the processing circuit, and wherein the controlling means comprises a feedback system.

29. The structured light system of claim 27, further comprising:

means for determining a code domain statistic comparing the sensed codewords with the expected codewords; and

means for controlling output power of the laser system based at least in part on the determined code domain statistic.

30. A non-transitory computer-readable medium storing instructions that when executed cause a processor to perform a method of controlling output power of a laser system of a structured light system, the method comprising:

;

storing a depth map with a memory device;

projecting codewords with the laser system;

sensing the projected codewords reflected from an object with a receiver sensor;

retrieving a portion of the depth map from the memory device;

calculating expected codewords from the depth map; and

controlling output power of the laser system based on the sensed codewords and the expected codewords.