Timing of multiplexed sensor phase measurements in a depth camera assembly for depth determination using fringe interferometry

Abstract

A depth camera assembly (DCA) determines distances between the DCA and objects in a local area within a field of view of the DCA. The DCA projects a series of sinusoidal patterns into the local area DCA and captures images of the sinusoidal patterns via a sensor. Each pixel of the augmented sensor includes a plurality of charge bins, and charge accumulated by a photodiode of a pixel during different time intervals (e.g., times when different sinusoidal patterns are emitted) is stored in a different charge storage bin. Charge may be retrieved from different charge storage bins to determine depth from the DCA.

1 . A method comprising:
 determining an illumination source is emitting a first periodic illumination pattern during a first time interval;   during the first time interval, communicating to a sensor a first control signal opening a first transfer gate coupling a photodiode of a pixel to a first charge storage bin and other control signals closing other transfer gates coupling the photodiode of the pixel to other charge storage bins apart from the first charge storage bin;   determining the illumination source is emitting a second periodic illumination pattern having a different spatial phase shift during a second time interval; and   during the second time interval, communicating to the sensor a second control signal opening up a second transfer gate coupling the photodiode of the pixel to a second charge storage bin and other control signals closing other transfer gates coupling the photodiode of the pixel to other charge storage bins apart from the second charge storage bin.   
     
     
         2 . The method of  claim 1 , further comprising:
 communicating an additional control signal to the sensor that closes the first transfer gate to decouple the photodiode of the pixel to the first charge storage bin while other transfer gates coupled to the photodiode of the pixel remain closed within a threshold time interval from a time when the illumination source stopped emitting the first periodic illumination pattern.   
     
     
         3 . The method of  claim 2 , further comprising:
 determining an additional time interval when the illumination source is emitting the first periodic illumination pattern; and   communicating an alternative control signal to the sensor opening an additional transfer gate to couple the photodiode of the pixel to an additional charge storage bin while the first transfer gate and other transfer gates coupled to the photodiode of the pixel remain closed in response to determining the illumination source is emitting the first periodic illumination pattern during the additional time interval.   
     
     
         4 . The method of  claim 3 , further comprising:
 communicating a further control signal to the sensor closing the additional transfer gate to decouple the photodiode of the pixel to the additional charge storage bin while the first transfer gate and other transfer gates coupled to the photodiode of the pixel remain closed within the threshold time interval from the time when the illumination source stopped emitting the first periodic illumination pattern.   
     
     
         5 . The method of  claim 3 , further comprising:
 determining an alternative time interval when the illumination source is emitting the first periodic illumination pattern; and   communicating a further control signal to the sensor opening an alternative transfer gate to couple the photodiode of the pixel to an alternative charge storage bin while the first transfer gate, the additional transfer gate, and other transfer gates coupled to the photodiode of the pixel remain closed in response to determining the illumination source is emitting the first periodic illumination pattern during the alternative time interval.   
     
     
         6 . The method of  claim 1 , wherein each pixel further comprises a drain coupled to the photodiode by a shutter. 
     
     
         7 . The method of  claim 6 , further comprising:
 providing a signal to the sensor opening the shutter for charge accumulated by the photodiode to be directed to the drain within a threshold time interval from a time when the illumination source stopped emitting the first periodic illumination pattern.   
     
     
         8 . The method of  claim 1 , further comprising:
 communicating control signals to the sensor opening different transfer gates at different times corresponding to emission of the first periodic illumination pattern by the illumination source.   
     
     
         9 . The method of  claim 1 , further comprising:
 emitting different periodic illumination patterns at different times; and   communicating control signals to the sensor that open different transfer gates at times when the illumination source emits different periodic illumination patterns.   
     
     
         10 . The method of  claim 1 , further comprising:
 combining charge accumulated in each of a plurality of charge storage bins coupled to the photodiodes.   
     
     
         11 . A non-transitory computer-readable storage medium comprising stored instructions, the instructions when executed by a processor of a device, cause the device to:
 determine an illumination source is emitting a first periodic illumination pattern during a first time interval;   during the first time interval, communicate to a sensor a first control signal opening a first transfer gate coupling a photodiode of a pixel to a first charge storage bin and other control signals closing other transfer gates coupling the photodiode of the pixel to other charge storage bins apart from the first charge storage bin;   determine the illumination source is emitting a second periodic illumination pattern having a different spatial phase shift during a second time interval; and   during the second time interval, communicate to the sensor a second control signal opening up a second transfer gate coupling the photodiode of the pixel to a second charge storage bin and other control signals closing other transfer gates coupling the photodiode of the pixel to other charge storage bins apart from the second charge storage bin.   
     
     
         12 . The non-transitory computer-readable storage medium of  claim 11 , further comprising stored instructions that when executed cause the device to:
 communicate an additional control signal to the sensor that closes the first transfer gate to decouple the photodiode of the pixel to the first charge storage bin while other transfer gates coupled to the photodiode of the pixel remain closed within a threshold time interval from a time when the illumination source stopped emitting the first periodic illumination pattern.   
     
     
         13 . The non-transitory computer-readable storage medium of  claim 12 , further comprising stored instructions that when executed cause the device to:
 determine an additional time interval when the illumination source is emitting the first periodic illumination pattern; and   communicate an alternative control signal to the sensor opening an additional transfer gate to couple the photodiode of the pixel to an additional charge storage bin while the first transfer gate and other transfer gates coupled to the photodiode of the pixel remain closed in response to determining the illumination source is emitting the first periodic illumination pattern during the additional time interval.   
     
     
         14 . The non-transitory computer-readable storage medium of  claim 13 , further comprising stored instructions that when executed cause the device to:
 communicate a further control signal to the sensor closing the additional transfer gate to decouple the photodiode of the pixel to the additional charge storage bin while the first transfer gate and other transfer gates coupled to the photodiode of the pixel remain closed within the threshold time interval from the time when the illumination source stopped emitting the first periodic illumination pattern.   
     
     
         15 . The non-transitory computer-readable storage medium of  claim 13 , further comprising stored instructions that when executed cause the device to:
 determine an alternative time interval when the illumination source is emitting the first periodic illumination pattern; and   communicate a further control signal to the sensor opening an alternative transfer gate to couple the photodiode of the pixel to an alternative charge storage bin while the first transfer gate, the additional transfer gate, and other transfer gates coupled to the photodiode of the pixel remain closed in response to determining the illumination source is emitting the first periodic illumination pattern during the alternative time interval.   
     
     
         16 . The non-transitory computer-readable storage medium of  claim 11 , wherein each pixel further comprises a drain coupled to the photodiode by a shutter. 
     
     
         17 . The non-transitory computer-readable storage medium of  claim 16 , further comprising stored instructions that when executed cause the device to:
 provide a signal to the sensor opening the shutter for charge accumulated by the photodiode to be directed to the drain within a threshold time interval from a time when the illumination source stopped emitting the first periodic illumination pattern.   
     
     
         18 . non-transitory computer-readable storage medium of  claim 11 , further comprising stored instructions that when executed cause the device to:
 communicate control signals to the sensor opening different transfer gates at different times corresponding to emission of the first periodic illumination pattern by the illumination source.   
     
     
         19 . non-transitory computer-readable storage medium of  claim 11 , further comprising stored instructions that when executed cause the device to:
 emit different periodic illumination patterns at different times; and   communicate control signals to the sensor that open different transfer gates at times when the illumination source emits different periodic illumination patterns.   
     
     
         20 . non-transitory computer-readable storage medium of  claim 11 , further comprising stored instructions that when executed cause the device to:
 combine charge accumulated in each of a plurality of charge storage bins coupled to the photodiodes.