US 11,914,036 B2
Pulse width modulated integration for time of flight imaging
John Peter Godbaz, Sunnyvale, CA (US); Brock McCray Roland, San Bruno, CA (US); Rui Jin, Mountain View, CA (US); and Minseok Oh, Santa Clara, CA (US)
Assigned to Microsoft Technology Licensing, LLC, Redmond, WA (US)
Filed by Microsoft Technology Licensing, LLC, Redmond, WA (US)
Filed on Dec. 17, 2020, as Appl. No. 17/125,638.
Prior Publication US 2022/0201186 A1, Jun. 23, 2022
Int. Cl. G01S 17/10 (2020.01); G01S 7/483 (2006.01); G01S 17/26 (2020.01)
CPC G01S 17/10 (2013.01) [G01S 7/483 (2013.01); G01S 17/26 (2020.01)] 20 Claims
OG exemplary drawing
 
1. A method of operating a time-of-flight camera system comprising an illumination source and an image sensor, the image sensor comprising one or more sensor pixels each comprising an in-pixel memory, the method comprising:
operating the illumination source and the image sensor to control a plurality of integration cycles for a readout cycle by
performing a plurality of pulse width modulated (PWM) illumination cycles, each PWM illumination cycle separated from one or more adjacent PWM illumination cycles by a non-illumination cycle,
temporally modulating the illumination source during each PWM illumination cycle to emit temporally modulated light, the temporally modulated light being at different frequencies for at least two different PWM illumination cycles,
during each PWM illumination cycle, directing photocharge to the in-pixel memory for each pixel that is performing image integration, and
during each non-illumination cycle, conducting photocharge away from the in-pixel memory for each pixel that is performing image integration; and
during the readout cycle, for each pixel that performed image integration, reading a charge stored in the in-pixel memory.