Time-of-flight calculations using a shared light source

• US 8,988,662 B1
• Filed: 10/01/2012
• Issued: 03/24/2015
• Est. Priority Date: 10/01/2012
• Status: Active Grant

• Current Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Original Assignee: Rawles, LLC (Amazon.com, Inc.)
• Inventors: Haskin, Menashe, Weatherford, William Thomas, Crump, Edward Dietz
• Primary Examiner(s): Alsomiri, Isam
• Assistant Examiner(s): Abraham, Samantha K
• Application Number:
  US13/632,570
• Time in Patent Office: 904 Days
• Field of Search: 356/3.01, 356/4.01, 356/5.01, 356/5.09, 356/9, 356/28.5
• US Class Current: 356/5.01
• 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 17/894 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

Abstract

In some embodiments, distances associated with a surface may be calculated using time-of-flight (ToF) of a plurality of pulses of light occurring at a predetermined frequency. Reflected light from a light emitter may be captured by two or more light sensors. At least one light sensor may be located in a sensor pod that is separate from the light emitter, which may be housed in an emitter pod with or without a light sensor. The sensor pod may be synchronized with the emitter pod to enable ToF of light distance calculations. The calculated distance may be used to determine movement of a surface and/or one or more pixels of a surface. In some instances, the calculated distance may be used to identify a profile of a surface, which may then be used associate the profile with an object, a command, or another association.

Claims

1. A system comprising:

an emitter unit including;

a light emitter to emit light in pulses having predetermined time intervals;

a first light sensor to capture light that is emitted from the light emitter and reflected off a surface;

one or more processors to calculate a first distance between the first light sensor and the surface and a second distance between a second light sensor and the surface based at least in part on a ratio of light captured during two consecutive instances of the time intervals, the one or more processors to create a profile of the surface based at least in part on the first distance and the second distance; and

an emitter unit communications port to broadcast a synchronization signal to synchronize the second light sensor with the light emitter to operate during the time intervals, and to receive data indicating a ratio of light captured during the two consecutive instances of the time intervals by the second light sensor; and

a sensor unit including;

the second light sensor, located separate from the emitter unit, to capture light that is emitted from the light emitter and reflected off the surface, the second light sensor being synchronized with the light emitter using the synchronization signal to operate during the time intervals; and

a sensor communications port to receive the synchronization signal from the emitter unit communications port and to transmit information indicating the ratio of light captured by the second light sensor during the two consecutive instances of the time intervals to the one or more processors using the emitter unit communications port.

2. The system of claim 1, wherein the first light sensor captures light as energy that is stored in two storage devices, each of the storage devices associated with a different one of the two consecutive time intervals, and wherein the ratio is based at least in part on the energy stored during the two consecutive instances of the time intervals.

3. The system of claim 1, wherein the emitter unit includes a clock to generate the synchronization signal, the synchronization signal to synchronize the time intervals across each of the first light sensor, the second light sensor and the light emitter.

4. The system of claim 1, wherein a field of view of the second light sensor is different than a field of view of the first light sensor.

5. The system of claim 1, wherein a field of view of the second light sensor at least partially overlaps a field of view of the first light sensor to create an overlapped portion, and wherein the one or more processors remove outlier data from the overlapped portion.

6. The system as recited in claim 1, wherein the one or more processors create the profile using location information of a group of pixels, the group of pixels including at least a first pixel located at the first distance and a second pixel located at the second distance.

7. One or more computer-readable media storing computer-executable instructions that, when executed by one or more processors, cause the one or more processors to perform acts comprising:

receiving sensor data from a first unit having a light emitter and at least a first light sensor, the sensor data including light captured from the light emitter during time intervals and used to determine a first distance associated with a surface that reflects light emitted by the light emitter, the first distance determined based at least in part on the sensor data received from the first unit;

receiving sensor data from a second unit having at least a second light sensor, the second unit being synchronized with the first unit to operate during the time intervals, the sensor data including light captured from the light emitter during the time intervals and used to determine a second distance associated with the surface that reflects light emitted by the light emitter, the second distance determined based at least in part on the sensor data received from the second unit;

calculating the first distance and the second distance based at least in part on the sensor data from the first unit and the sensor data from the second unit; and

creating a profile of the surface based at least in part on the first distance and the second distance.

8. The one or more computer-readable media storing computer-executable instructions of claim 7, wherein the first and second distances are calculated at least in part using a ratio of light captured during two consecutive instances of the time intervals.

9. The one or more computer-readable media storing computer-executable instructions of claim 7, wherein the sensor data from the first unit corresponds to light reflected from a first portion of the surface and the sensor data from the second unit corresponds to light reflected from a second portion of the surface that is different than the first portion of the surface.

10. The one or more computer-readable media storing computer-executable instructions of claim 7, wherein the sensor data from the first unit corresponds to light reflected from a first portion of the surface and the sensor data from the second unit corresponds to light reflected from a second portion of the surface, wherein the second portion at least partially overlaps the first portion of the surface to create an overlapped portion, and wherein the acts further comprise removing outlier data in the overlapped portion.

11. The one or more computer-readable media storing computer-executable instructions of claim 7, wherein:

the surface is a surface of an object,

the sensor data from the first unit corresponds to light reflected from a first portion of the surface of the object and the sensor data from the second unit corresponds to light reflected from a second portion of the surface of the object, wherein the second portion of the surface of the object includes part of the surface of the object that is different than the first portion of the surface of the object, and

the acts further comprise determining a depth of the object based at least in part on (i) the first distance calculated based at least in part on the light reflected from the first portion of the surface of the object and (ii) the second distance calculated based at least in part on the light reflected from the second portion of the surface of the object.

12. The one or more computer-readable media storing computer-executable instructions of claim 7, wherein the acts further comprise causing synchronization by exchanging a synchronization signal between the second unit and the first unit using at least one of radio communications or optical communications.

13. The one or more computer-readable media storing computer-executable instructions of claim 7, wherein the light emitter is a first light emitter, and wherein the acts further comprise sending commands to the first light emitter and a second light emitter to alternate emission of light between the first light emitter and the second light emitter to cause receipt of sensor data for a portion of the surface otherwise obscured by an object when the object is situated between the first light emitter and the portion of the surface.

14. The one or more computer-readable media storing computer-executable instructions of claim 7, wherein the creating the profile further comprises:

determining a first location of a first pixel based at least in part on the first distance;

determining a second location of a second pixel based at least in part on the first distance; and

creating the profile based at least in part on at least the first location of the first pixel and the second location of the second pixel.

15. A system comprising:

an emitter unit including a light emitter and at least a first light sensor synchronized with the light emitter to operate during time intervals, the at least the first light sensor to detect light emitted by the light emitter and reflected from a surface during at least two of the time intervals, the detected light used to calculate a first distance between the at least the first light sensor and the surface;

a sensor unit including at least a second light sensor, synchronized with the light emitter to operate during the time intervals and located separate from the emitter unit, the at least the second light sensor to detect light emitted by the light emitter and reflected from the surface during at least two of the time intervals, the detected light used to calculate a second distance between the at least the second light sensor and the surface; and

a processor to create a profile of the surface based at least in part on the first distance and the second distance.

16. The system of claim 15, wherein the emitter unit includes an emitter unit communications port that exchanges data with a sensor communications port included in the sensor unit, the exchanged data to provide synchronization of the time intervals by an exchange of at least one of optical signals or radio waves.

17. The system of claim 15, wherein a field of view of the at least the second light sensor is different than a field of view of the at least the first light sensor.

18. The system of claim 15, wherein a field of view of the at least the second light sensor at least partially overlaps a field of view of the at least the first light sensor to create an overlapped portion, and wherein the emitter unit removes outlier data from the overlapped portion.

19. The system of claim 15, wherein emitter unit uses the first distance and the second distance to track movement of one or more surfaces or one or more objects.

20. The system of claim 15, wherein the light emitter is a first light emitter, and further comprising a second light emitter that emits light in alternation with the first light emitter, the second light emitter to cause illumination of a portion of the object that is not illuminated by the first light emitter, the second light emitter included in the sensor unit and synchronized to operation during the time intervals.

21. The system of claim 15, wherein the processor creates the profile using locations of pixels that are located by at least the first distance and the second distance.

22. A method comprising:

calculating a first distance associated with a surface using sensor data collected by a first unit having a light emitter and at least a first light sensor synchronized with the light emitter to operate during time intervals, the sensor data collected by the first unit indicating measurements of light emitted by the light emitter and reflected off the surface during at least two different intervals of the time intervals;

calculating a second distance associated with the surface using sensor data from a second unit having at least a second light sensor synchronized with the light emitter to operate during the time intervals, the sensor data from the second unit indicating measurements of light emitted by the light emitter and reflected off the surface during the at least two different intervals of the time intervals; and

creating a profile of the surface based at least in part on the first distance and the second distance.

23. The method of claim 22, wherein the sensor data from the first unit corresponds to light reflected from a first portion of the surface and the sensor data from the second unit corresponds to light reflected from a second portion of the surface that is different than the first portion of the surface.

24. The method of claim 22, wherein the sensor data from the first unit corresponds to light reflected from a first portion of the surface and the sensor data from the second unit corresponds to light reflected from a second portion of the surface, wherein the second portion at least partially overlaps the first portion of the surface to create an overlapped portion, and further comprising removing outlier data in the overlapped portion.

25. The method of claim 22, wherein:

the surface is a surface of an object,

the sensor data from the first unit corresponds to light reflected from a first portion of the surface and the sensor data from the second unit corresponds to light reflected from a second portion of the surface, wherein the second portion of the surface includes part of the surface of the object that is different than the first portion of the surface of the object, and

further comprising determining a depth of the object based at least in part on (i) the first distance calculated based at least in part on the light reflected from the first portion of the surface of the object and (ii) the second distance calculated based at least in part on the light reflected from the second portion of the surface of the object.

26. The method of claim 22, wherein the creating the profile further comprises aggregating distance information from a plurality of distances that include at least the first distance and the second distance.

27. The method of claim 26, wherein the profile includes at least one of a persistent shadow or a persistent omission due to orientations of one or more of the light emitter, the first light sensor, or the second light sensor.