MEASURING AND REMOVING THE CORRUPTION OF TIME-OF-FLIGHT DEPTH IMAGES DUE TO INTERNAL SCATTERING

Depth imagers can implement time-of-flight operations to measure depth or distance of objects and systematically remove measured light which can corrupt the depth or distance measurement. A depth imager can emit light onto a scene and sense light reflected back from the objects in the scene using an...

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Hauptverfasser: DEMIRTAS, Sefa, BARNES, Erik D, MATHY, Charles
Format: Patent
Sprache:eng ; fre ; ger
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Zusammenfassung:Depth imagers can implement time-of-flight operations to measure depth or distance of objects and systematically remove measured light which can corrupt the depth or distance measurement. A depth imager can emit light onto a scene and sense light reflected back from the objects in the scene using an array of sensors. Timing of the reflected light hitting the array of sensors gives information about the depth or distance of objects in the scene. In some cases, corrupting light that is outside of a field of view of a pixel in the array of sensors can hit the pixel due to internal scattering or internal reflections occurring in the depth imager. A technique for effectively getting arbitrarily short pulses is disclosed which involves two light pulses of width TLof the same shape but shifted in time by some delay time td. The first emitted light (e.g., plot 1002) starts at t = 0, and has a duration of TL. The second emitted light starts at t = td, and has a duration of TL. The duration TLis significantly greater than td. The second emitted light pulse has a second start time that is delayed by a pre-determined time tdrelative to the first start time. When the second emitted light is subtracted from the first emitted light, the difference (e.g., plot 1006) would appear as a short positive pulse 1010 of width td, followed by a short negative pulse 1020 of width td. A charge storage unit can be controlled by sensor signal (e.g., plot 1008), to start sensing light at -t1and for a duration of Ts. It is possible to make two measurements: (1) a first measurement with the first emitted light and the sensor signal starting to sense at -t1and turning off at some time before the negative pulse 1020, and (2) a second measurement with the second emitted light and the sensor signal start sensing at -t1and turning off at some time before the negative pulse 1020. It is possible to obtain a measurement as if a short light pulse of width tdwas used by (1) performing two measurements with the same sensor signal (e.g., plot 1008) with light pulses which are slightly delayed with respect to each other, and (2) obtaining a difference of the two measurements. Using this technique, arbitrarily small light pulses can be simulated, even if the driver or the light source cannot output short light pulses directly. This resulting measurement can thus capture corrupting light and background light.