Methods and systems for increasing the range of time-of-flight systems by unambiguous range toggling
A method of operating a time of flight system includes detecting first optical signals comprising a first frequency having a first unambiguous range, the first optical signals reflected from a target, processing the first optical signals to determine a first estimated distance to the target, and generating an output frame comprising a true distance to the target based on the first estimated distance and a second estimated distance to the target, wherein the second estimated distance was used to generate a previous output frame.
1. A method of operating a time of flight system comprising:
detecting first optical signals comprising a first frequency having a first unambiguous range, the first optical signals reflected from a target;
processing the first optical signals to determine a first estimated distance to the target; and
generating an output frame comprising a corroborated distance to the target based on the first estimated distance and a second estimated distance to the target, wherein the second estimated distance was used to generate a previous output frame,
wherein the second estimated distance is generated by processing second optical signals comprising a second frequency having a second unambiguous range, different from the first unambiguous range, and
wherein determining the corroborated distance to the target comprises comparing a calculated difference between the first estimated distance to the target and the second estimated distance to the target to a calculated difference between the first unambiguous range and the second unambiguous range.
2. The method of claim 1 , wherein the second estimated distance is generated by processing second optical signals comprising a second frequency having a second unambiguous range, different from the first unambiguous range.
3. The method of claim 2 , wherein the previous output frame is generated after the processing of the second optical signals, and
wherein the first optical signals are processed after generating the previous output frame.
4. The method of claim 2 , wherein the first optical signals are processed during a first subframe of the output frame, and
wherein the second optical signals are processed during a second subframe of the previous output frame, prior to the first subframe.
5. The method of claim 1 , wherein determining the true corroborated distance to the target comprises adjusting the first estimated distance based on a calculated difference between the first estimated distance and the second estimated distance.
6. The method of claim 1 , wherein the first estimated distance to the target is determined using first phase shifts in the first optical signals.
7. The method of claim 2 , wherein the first optical signals and the second optical signals are detected by individual detector elements of a detector array.
8. The method of claim 1 , wherein the first frequency is a combination of a plurality of frequencies, the combination of the plurality of frequencies having the first unambiguous range.
9. The method of claim 1 , wherein the target is one of a plurality of targets, and
wherein the first estimated distance to the target is one of an array of estimated distances to the plurality of targets generated during a first subframe.
10. A Time of Flight (ToF) system comprising:
an emitter array comprising a first plurality of emitters configured to emit first optical signals and a second plurality of emitters configured to emit second optical signals;
a detector array that is configured to:
detect the first optical signals comprising a first frequency having a first unambiguous range, the first optical signals reflected from a target;
detect the second optical signals comprising a second frequency having a second unambiguous range, different from the first unambiguous range; and
a control circuit configured to:
process the first optical signals to determine a first estimated distance to the target;
process the second optical signals to determine a second estimated distance to the target; and
generate an output frame comprising a corroborated distance to the target based on the first estimated distance and a second estimated distance to the target, wherein the second estimated distance was used to generate a previous output frame.
11. The ToF system of claim 10 , wherein the previous output frame is generated after the processing of the second optical signals, and
wherein the first optical signals are processed after generating the previous output frame.
12. The ToF system of claim 10 , wherein determining the corroborated distance to the target comprises adjusting the first estimated distance based on a calculated difference between the first estimated distance and the second estimated distance.
13. The ToF system of claim 10 , wherein the true corroborated distance to the target is a first sum of the first estimated distance and a first multiple of the first unambiguous range and/or a second sum of the second estimated distance and a second multiple of the second unambiguous range, and
wherein responsive to determining that subtracting the second estimated distance from the first estimated distance results in a positive number, the second multiple is calculated by the equation
( TD 1− TD 2))/( UR 2− UR 1)
where UR 1 is the first unambiguous range, UR 2 is the second unambiguous range, TD 1 is the first estimated distance, and TD 2 is the second estimated distance.
14. The ToF system of claim 10 , wherein the control circuit is further configured to determine the first estimated distance to the target using first phase shifts in the first optical signals.
15. The ToF system of claim 10 , wherein the first frequency is a combination of a plurality of frequencies, the combination of the plurality of frequencies having the first unambiguous range.
16. The ToF system of claim 10 , wherein the target is one of a plurality of targets, and
wherein the first estimated distance to the target is one of an array of estimated distances to the plurality of targets generated during a first subframe.
17. A control circuit for determining a distance to a target, the control circuit configured to perform operations comprising:
controlling transmission of first optical signals at a first modulation frequency having a first unambiguous range in a first subframe to obtain a first estimated distance to a target; and
generating an output frame comprising a corroborated distance to the target based on the first estimated distance and a second estimated distance to the target, wherein the second estimated distance was used to generate a previous output frame,
wherein the second estimated distance is generated by processing second optical signals comprising a second frequency having a second unambiguous range, different from the first unambiguous range, and
wherein determining the corroborated distance to the target comprises comparing a calculated difference between the first estimated distance to the target and the second estimated distance to the target to a calculated difference between the first unambiguous range and the second unambiguous range.
18. The control circuit of claim 17 , wherein the previous output frame is generated after the processing of the second optical signals, and
wherein the first optical signals are processed after generating the previous output frame.
19. The control circuit of claim 17 , wherein the control circuit is further configured to determine the first estimated distance to the target based on a calculated duration between the transmission of the first optical signals and a detection of the first optical signals by a detector after being reflected by the target.
20. A method of operating a time of flight system comprising:
emitting, by an emitter array comprising a first plurality of emitters configured to emit first optical signals and a second plurality of emitters configured to emit second optical signals, the first optical signals and the second optical signals;
detecting the first optical signals comprising a first frequency having a first unambiguous range, the first optical signals reflected from a target;
processing the first optical signals to determine a first estimated distance to the target;
generating a first output frame comprising a first corroborated distance based on the first estimated distance;
detecting the second optical signals comprising a second frequency having a second unambiguous range, different from the first unambiguous range, the second optical signals reflected from the target;
processing the second optical signals to determine a second estimated distance to the target; and
generating a second output frame comprising a second corroborated distance based on the first estimated distance and the second estimated distance to the target.
21. The method of claim 20 , wherein generating the second output frame comprises generating the second corroborated distance by adjusting the second estimated distance to the target based on a comparison of the second estimated distance to the first estimated distance.