Time-of-flight of light calibration

• US 9,109,886 B1
• Filed: 10/09/2012
• Issued: 08/18/2015
• Est. Priority Date: 10/09/2012
• Status: Active Grant

• Current Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Original Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Inventors: Haskin, Menashe, Crump, Edward Dietz
• Primary Examiner(s): RATCLIFFE, LUKE D
• Application Number:
  US13/647,603
• Time in Patent Office: 1,043 Days
• Field of Search: 356 301- 315, 356 401- 41, 356 501- 551, 356 6- 22, 356/28, 356/28.5
• US Class Current: 1/1
• CPC Class Codes: G01C 3/08 Use of electric radiation detectors
• CPC Class Codes: G01S 17/003 Bistatic lidar systems; Multistatic lidar systems
• 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 17/66 Tracking systems using electromagnetic waves other than radio waves
• CPC Class Codes: G01S 17/86 Combinations of lidar systems with systems other than lidar, radar or sonar, e.g. with direction finders
• CPC Class Codes: G01S 17/894 3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
• CPC Class Codes: G01S 7/497 Means for monitoring or calibrating

Abstract

Calibration of devices may be performed to determine a relative location of the devices. The devices may be used to determine distances of surfaces within an environment. The calibration may be performed at different times and/or in response to triggering events to determine a relative location of each of the devices in an environment. After the relative location of the devices is known, the devices may be used to determine a distance of a surface within the environment. In various embodiments, a light sensor may identify a light emitter based on characteristics of the light emitted by the light emitter.

Claims

1. A system comprising:

a first unit having a first light emitter and a first time-of-flight (ToF) sensor;

a second unit having a second light emitter and a second ToF sensor;

a third unit having at least a third ToF sensor;

a plurality of links to provide communications between the first unit, the second unit, and the third unit;

one or more processors to perform acts including;

coordinating, using the plurality of links, operation of the first unit, the second unit, and the third unit;

determining relative locations of each of the first unit, the second unit, and the third unit by;

determining reference distances based at least in part on ToF values obtained by the first ToF sensor, the second ToF sensor, and the third ToF sensor based at least in part on a first pulse of light emitted in a first fixed direction by the first light emitter and a second pulse of light emitted in a second fixed direction by the second light emitter, the first pulse of light illuminating a field of view that includes the second ToF sensor and the third ToF sensor,

the reference distances determined between;

the first unit and the second unit,

the first unit and the third unit, and

the second unit and the third unit;

creating distance profiles using the reference distances, the distance profiles associated with locations of each of the first unit, the second unit, and the third unit, and

determining the relative locations of each of the first unit, the second unit, and the third unit based at least in part on the distance profiles; and

determining distance information associated with objects based at least in part on the ToF values obtained by one or more of the first ToF sensor, the second ToF sensor, or the third ToF sensor.

2. The system as recited in claim 1, wherein the first light emitter emits the first pulse of light that includes a first characteristic that associates the first pulse of light as being emitted from the first light emitter, and wherein the second light emitter emits the second pulse of light that includes a second, different characteristic that associates the second pulse of light as being emitted from the second light emitter, the first characteristic and the second characteristic having at least one of a different wavelength of light or a different modulation of light.

3. The system as recited in claim 1, wherein the one or more processors determine the relative locations of each of the first unit, the second unit, and the third unit in response to at least one of:

powering on the system,

a passage of a predetermined amount of time, or

movement of the first unit, the second unit, or the third unit.

4. The system as recited in claim 1, wherein the coordinating includes:

synchronizing a clock associated with each of the first unit, the second unit, and the third unit; and

determining a first time associated with the emitting of the first pulse of light and a second time associated with the emitting of the second pulse of light, and

wherein the determining reference distances is based at least in part on the first time and the second time.

5. A method comprising:

coordinating operation of a plurality of units to determine relative distance information, each unit including a light emitter and at least one light sensor;

performing, for each of the plurality of units;

emitting a pulse of light in a fixed direction from a light emitter in a unit, the pulse of light illuminating a field of view that includes each light sensor in other units of the plurality of units,

capturing the pulse of light by each light sensor in the other units,

determining, based at least in part on the pulse of light captured by light sensors in the other units, distances between the light sensors in the other units and the light emitter in the unit, and

determining a distance profile for each combination of the light emitter and the light sensors in the other units; and

determining a relative location of each of the plurality of units based at least in part on the distance profiles.

6. The method as recited in claim 5, wherein the pulse of light is reflected off a surface prior to capture by the light sensors in the other units.

7. The method as recited in claim 5, wherein the coordinating the operation includes synchronizing the plurality of units to operate using same time intervals, the coordinating performed using at least one of a radio link or a wired link that provides communication between the plurality of the units.

8. The method as recited in claim 5, wherein the light emitter emits light that includes a characteristic that associates the pulse of light as being emitted from the respective light emitter.

9. The method as recited in claim 8, wherein the characteristic is at least one of a wavelength of the pulse of light or a modulation of the pulse of light.

10. The method as recited in claim 5, wherein the relative location of each of the light emitter and the light sensors in the plurality of the units is extrapolated to determine the relative location of each of the plurality of the units.

11. The method as recited in claim 5, wherein the performing is initiated in response to powering on at least a portion of a system that includes the plurality of the units.

12. The method as recited in claim 5, wherein the performing is initiated in response to at least one of movement of one of the plurality of the units or a passage of a predetermined amount of time.

13. The method as recited in claim 5, wherein the light sensor is a time-of-flight (ToF) sensor, and wherein the determining the distances between the ToF sensor in the other units and the light emitter in the unit is performed by determining relative distance information detected by the ToF sensor.

14. The method as recited in claim 5, wherein the relative location of each of the plurality of units is based on intersections of the distance profiles.

15. The method as recited in claim 5, further comprising determining distance information associated with objects based on time-of-flight (ToF) values obtained by the plurality of units.

16. The method as recited in claim 5, further comprising:

adding an additional unit that includes at least one additional light sensor; and

determining the relative location of the additional unit by;

capturing, by the at least one additional light sensor and at different times, light emitted by two different light emitters of the plurality of units,

determining additional distance profiles associated with the additional unit by determining, based at least in part on the pulse of light captured by the at least one additional light sensor, distances between the additional unit and the two different light emitters of the plurality of units, and

determining a relative location of the additional unit and the plurality of units based at least in part on the additional distance profiles.

17. A method comprising:

coordinating operation of a plurality of units to perform relative distance calculations, the plurality of units each including at least one of a light emitter or a light sensor;

determining distances between each of the plurality of units by, for each pair of units, emitting a pulse of light in a fixed direction from the light emitter in one unit and capturing the pulse of light by the light sensor in at least two other units; and

determining relative locations of each of the plurality of units relative to each other based at least in part on the determined distances.

18. The method as recited in claim 17, wherein each light emitter emits light that includes a characteristic that associates the pulse of light as being emitted from the respective light emitter.

19. The method as recited in claim 18, wherein the characteristic is at least one of a wavelength of the pulse of light or a modulation of the pulse of light.

20. The method as recited in claim 17, wherein the determining the distances is initiated in response to at least one of powering on a system that includes the plurality of the units or detecting movement of one of the plurality of the units.

21. The method as recited in claim 17, wherein the coordinating the operation is performed by exchanging signals between the plurality of units using at least one of radio links or wired links that provide communication between the plurality of the units.

22. The method as recited in claim 17, wherein the pulse of light is reflected off a surface after being emitted by the light emitter and prior to capture by the light sensor.

23. The method as recited in claim 17, wherein the light sensor is a time-of-flight (ToF) sensor, and wherein the determining the distances between the ToF sensor in the other units and the light emitter in the unit is performed by determining relative distance information detected by the ToF sensor.

24. The method as recited in claim 17, further comprising using the plurality of units to determine distance information associated with objects after determining the relative locations of the plurality of the units.

25. The method as recited in claim 17, further comprising creating distance profiles using the determined distances, the distance profiles associated with locations of each of the plurality of units, and wherein the determining the relative locations of each of the plurality of units relative to each other based is based at least in part on intersections of the distance profiles.