Single frequency time of flight de-aliasing
A system and method are disclosed for determining a depth map using TOF with low power consumption. In order to disambiguate, or de-alias, the returned distance(s) for a given phase shift, the system may emit n different frequencies of light over n successive image frames. After n frames of data are collected, the distances may be correlated by a variety of methodologies to determine a single distance to the object as measured over n image frames. As one frequency may be emitted per image frame, the depth map may be developed while consuming low power.
1. A depth imaging system comprising:
an optical energy emitter configured to emit light over a range of frequencies;
an array of pixel detectors configured to receive light from the optical energy emitter after reflection off of an object; and
a processor determining phase shift data in light of a first frequency, a second frequency and a third frequency received in a pixel detector of the array of pixel detectors, light of the first frequency received in the pixel detector in a first frame and not a second or third frame, light of the second frequency received in the pixel detector in the second frame and not the first or third frames, and light of the third frequency received in the third frame and not the first or second frames, the processor de-aliasing the phase shift data to determine a distance to the object indicated by the first and second frequencies at a first time, and the processor de-aliasing the phase shift data to determine a distance to the object indicated by the first and second frequencies at a second time subsequent to the first time.
2. The system of claim 1 , wherein one of the first, second and third frequencies has a single distance associated with the measured phase shift within a predefined range of distances between objects in a scene and the depth imaging system.
3. The system of claim 1 , wherein one of the first, second and third frequencies has multiple distances associated with the measured phase shift within a predefined range of distances between objects in a scene and the depth imaging system.
4. The system of claim 1 , the processor reusing the first and second frequencies at times subsequent to the first and second times to de-alias the phase shift data.
5. The system of claim 1 , the optical energy emitter emitting light between 50 MHz and 100 MHz.
6. A capture device of a target recognition, analysis, and tracking system, the capture device comprising:
an RGB camera; and
a depth imaging system, comprising:
an optical energy emitter configured to emit light over a range of frequencies,
an array of pixel detectors configured to receive the light from the an optical energy emitter configured to emit after reflection off of an object, and
a processor determining phase shift data in light of a plurality of different frequencies received in a pixel detector of the array of pixel detectors in a plurality of successive frames, each frequency of the plurality of different frequencies received in a different frame of the plurality of successive frames, the processor dealiasing the phase shift data to determine a distance to the object indicated by first and second frequencies of the plurality of different frequencies at a first time, and the processor de-aliasing the phase shift data to determine a distance to the object indicated by the second frequency and a third frequency of the plurality of different frequencies at a second time different than the first time.
7. The capture device of claim 6 , the processor determining phase shift data in light of a fourth frequency received in the pixel detector, the processor dealiasing the phase shift data to determine a distance to the object indicated by at least the third and fourth frequencies at a third time different than the first and second times.
8. The capture device of claim 6 , the processor determining phase shift data in light of the first and second frequencies by taking sample captures at 0° and 90°.
9. The capture device of claim 6 , the processor determining phase shift data in light of the first and second frequencies by taking sample captures at 0°, 90°, 180°, 270°.