Derivation of Depth Information from Time-of-Flight (TOF) Sensor Data

Abstract

A time-of-flight sensor includes: a light source for emitting periodic light bursts in the direction of one or more objects; and an array of optical sensing elements for detecting light reflected from the one or more objects and generating sensor data corresponding to the detected light. A distance calculator determines depth information of the one or more objects by: determining an approximate phase shift of the reflected light relative to the emitted light based on a first frame of the sensor data and a second frame of the sensor data; calculating an incremental phase shift of the reflected light relative to the emitted light based on a linear relationship between the first frame and the second frame regarding the approximate phase shift; and combining the approximate phase shift and the incremental phase shift to determine an actual phase shift of the reflected light relative to the emitted light.

Claims

1. A time-of-flight sensor, comprising: a light source configured to emit periodic light bursts in the direction of one or more objects; an array of optical sensing elements configured to detect light reflected from the one or more objects; and a distance calculator configured to receive sensor data corresponding to the detected light from the array of optical sensing elements and configured to determine depth information of the one or more objects by: determining a rough phase shift of the reflected light relative to the emitted light based at least in part on a first frame of the sensor data and a second frame of the sensor data; calculating an incremental phase shift of the reflected light relative to the emitted light based at least in part on a linear relationship between the first frame and the second frame with respect to the rough phase shift; combining the rough phase shift and the incremental phase shift to determine an actual phase shift of the reflected light relative to the emitted light; and determining the depth information based on the actual phase shift.

2. The time-of-flight sensor according to claim 1, wherein the first frame of the sensor data is acquired during a plurality of first sensing cycles, and the second frame of the sensor data is acquired during a plurality of second sensing cycles, the second sensing cycles being phase-shifted relative to the first sensing cycles.

3. The time-of-flight sensor according to claim 2, wherein the rough phase shift is determined based at least in part on a phase shift between the first sensing cycle and the second sensing cycle.

4. The time-of-flight sensor according to claim 1, wherein the distance calculator is to determine the rough phase shift based at least in part on whether the first frame of the sensor data includes a positive value or a negative value and whether the second frame of the sensor data includes a positive value or a negative value.

5. The time-of-flight sensor according to claim 4, wherein the rough phase shift: is equal to 0° when the first frame of the sensor data includes a positive value and the second frame of the sensor data includes a positive value; is equal to 90° when the first frame of the sensor data includes a negative value and the second frame of the sensor data includes a positive value; is equal to 180° when the first frame of the sensor data includes a negative value and the second frame of the sensor data includes a negative value; and is equal to 270° when the first frame of the sensor data includes a positive value and the second frame of the sensor data includes a negative value.

6. The time-of-flight sensor according to claim 1, wherein the rough phase shift includes a value of 0°, 90°, 180°, or 270°.

7. The time-of-flight sensor according to claim 6, wherein the linear relationship depends on the value of the rough phase shift.

8. The time-of-flight sensor according to claim 7, wherein the first frame represents a real component of the sensor data, and the second frame represents an imaginary component of the sensor data, and wherein the incremental phase shift: Equal when the value of the approximate phase shift is 0° Equals when the value of the approximate phase shift is 90° Equals when the value of the approximate phase shift is 180° and Equals when the value of the approximate phase shift is 270° 9. The time-of-flight sensor according to claim 1, wherein the distance calculator is further configured to: determine a real component of the sensor data based on a difference between the first frame and a third frame of the sensor data; determining an imaginary component of the sensor data based on a difference between the second frame and the fourth frame of the sensor data; and determining the approximate phase shift at least in part based on whether the real component includes a positive or negative value and whether the imaginary component includes a positive or negative value.

10. The time-of-flight sensor of claim 9, wherein the distance calculator is to further calculate the incremental phase shift based on a linear relationship between the real component and the imaginary component of the approximate phase shift.

11. A method for determining depth information,[[]]END]] comprising: receiving sensor data from an array of optical sensing elements configured to detect light reflected from one or more objects; determining an approximate phase shift of the reflected light relative to corresponding light bursts periodically emitted in the direction of the one or more objects based at least in part on a first frame of the sensor data and a second frame of the sensor data; calculating an incremental phase shift of the reflected light relative to the emitted light based at least in part on a linear relationship between the first frame and the second frame of the approximate phase shift; combining the approximate phase shift and the incremental phase shift to determine an actual phase shift of the reflected light relative to the emitted light; and determining depth information for the one or more objects based on the actual phase shift.

12. The method of claim 11, further comprising: acquiring a first frame of the sensor data during a plurality of first sensing cycles; and acquiring a second frame of the sensor data during a plurality of second sensing cycles, the second sensing cycles being phase-shifted relative to the first sensing cycles.

13. The method of claim 12, wherein the approximate phase shift is determined at least in part based on a phase shift between the first sensing cycle and the second sensing cycle.

14. The method of claim 11, wherein the determination of the approximate phase shift comprises: determining whether a first frame of the sensor data includes a positive or negative value; and determining whether a second frame of the sensor data includes a positive or negative value.

15. The method of claim 14, wherein the approximate phase shift: is equal to 0° when a first frame of the sensor data includes a positive value and a second frame of the sensor data includes a positive value; is equal to 90° when a first frame of the sensor data includes a negative value and a second frame of the sensor data includes a positive value; is equal to 180° when a first frame of the sensor data includes a negative value and a second frame of the sensor data includes a negative value; and is equal to 270° when a first frame of the sensor data includes a positive value and a second frame of the sensor data includes a negative value.

16. The method of claim 11, wherein the approximate phase shift includes a value of 0°, 90°, 180°, or 270°, and the linear relationship depends on the value of the approximate phase shift.

17. The method of claim 16, wherein the first frame represents a real component of the sensor data, and the second frame represents an imaginary component of the sensor data, and wherein the incremental phase shift: Equals when the value of the approximate phase shift is 0° Equals when the value of the approximate phase shift is 90° Equals when the value of said approximate phase shift is 180° and Equals when the value of the approximate phase shift is 270° 18. The method of claim 11, wherein the determination of the approximate phase shift further comprises: Determine a real component of the sensor data based on a difference between the first frame and the third frame of the sensor data; and Determine an imaginary component of the sensor data based on a difference between the second frame and the fourth frame of the sensor data, wherein the approximate phase shift is determined at least in part based on whether the real component includes a positive or negative value and whether the imaginary component includes a positive or negative value.

19. The method of claim 18, wherein an incremental phase shift is calculated based on a linear relationship between the real component and the imaginary component with respect to the approximate phase shift.

20. A sensing device, comprising: a processing system; and a memory that stores instructions that, when executed by the processing system, cause the sensing device to: receive sensor data from an array of optical sensing elements configured to detect light reflected from one or more objects; determine an approximate phase shift of the reflected light relative to a corresponding optical burst periodically emitted in a direction of the one or more objects based at least in part on a first frame of the sensor data and a second frame of the sensor data; calculate an incremental phase shift of the reflected light relative to the emitted light based at least in part on a linear relationship between the first frame and the second frame with respect to the approximate phase shift; combine the approximate phase shift and the incremental phase shift to determine an actual phase shift of the reflected light relative to the emitted light; and determine depth information for the one or more objects based on the actual phase shift.

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