Electronic Device with Modulated Light Flash Operation for Rolling Shutter Image Sensor

Abstract

An electronic device ( 100 ) includes a modulated light projector ( 119 ) and an electronic rolling shutter (ERS) imaging camera ( 1302 ) having a sensor array ( 1306 ) with a set of pixel rows. The electronic device includes a controller ( 1304 ) to control the modulated light projector ( 119 ) to project a modulated light flash ( 1608, 1810, 2010 ) during capture of a first image frame ( 1606, 1806, 2006 ) by the sensor array. The controller is to initiate the modulated light flash while each pixel row of the set is exposed for gathering light and to terminate the modulated light flash before a pixel row of the set is exposed for capture of a next image frame by the sensor array. The electronic device further includes a processor ( 802 ) to determine modulated light image data ( 1320 ) based on the first image frame. The controller also may control the modulated light projector to refrain from projecting the modulated light flash during capture of a second image frame ( 1602, 1612, 1802, 1816, 2002, 2018 ), adjacent to the first image frame.

What is claimed is: 
     
         1 . An electronic device comprising:
 a modulated light projector;   an electronic rolling shutter (ERS) imaging camera having a sensor array with a set of pixel rows;   a controller to control the modulated light projector to project a modulated light flash during capture of a first image frame by the sensor array, wherein the controller is to initiate the modulated light flash while each pixel row of the set is exposed for gathering light and to terminate the modulated light flash before a pixel row of the set is exposed for capture of a next image frame by the sensor array; and   a processor to determine modulated light image data based on the first image frame.   
     
     
         2 . The electronic device of  claim 1 , wherein:
 the controller is to control the modulated light projector to refrain from projecting a modulated light flash during capture of a second image frame adjacent to the capture of the first image frame.   
     
     
         3 . The electronic device of  claim 2 , wherein:
 the ERS imaging camera captures the first image frame and the second image frame at a frame rate at least twice a nominal frame rate of the ERS imaging camera.   
     
     
         4 . The electronic device of  claim 2 , wherein:
 the processor is to determine the modulated light image data based on a comparison of the first image frame and the second image frame.   
     
     
         5 . The electronic device of  claim 1 , wherein:
 the controller is to control the ERS imaging camera to initiate exposure of the set of pixel rows substantially simultaneously for capture of the first image frame and to initiate the modulated light flash in response to the initiation of the exposure of the set of pixel rows substantially simultaneously.   
     
     
         6 . The electronic device of  claim 5 , further comprising:
 a mechanical shutter to terminate exposure of the set of pixel rows substantially simultaneously for capture of the first image frame; and   wherein the controller is to control the modulated light projector to terminate the modulated light flash prior to activation of the mechanical shutter for capture of the first image frame.   
     
     
         7 . The electronic device of  claim 1 , wherein the modulated light projector comprises:
 an array of one or more vertical cavity surface emitting laser (VCSEL) diodes;   an array of one or more lenses overlying the array of one or more VCSEL diodes; and   a diffractive optical element overlying the array of one or more lenses.   
     
     
         8 . A method comprising:
 capturing a first image frame at an electronic rolling shutter (ERS) imaging camera;   initiating a projection of a modulated light flash while each pixel row of a set of pixel rows of a sensor array of the ERS imaging camera is exposed for gathering light for the first image frame;   terminating the modulated light flash before a pixel row of the set is exposed for capture of a next image frame by the ERS imaging camera; and   determining modulated light image data based on the first image frame.   
     
     
         9 . The method of  claim 8 , further comprising:
 capturing a second image frame at the ERS imaging camera, the second image frame adjacent to the first image frame; and   refraining from projection of a modulated light flash during the capture of the second image frame.   
     
     
         10 . The method of  claim 9 , wherein:
 the first and second image frames are captured at a frame rate at least twice a nominal frame rate of the ERS imaging camera.   
     
     
         11 . The method of  claim 9 , wherein determining the modulated light image data based on the first image frame comprises:
 determining the modulated light image data based on a comparison of the first image frame and the second image frame.   
     
     
         12 . The method of  claim 8 , wherein:
 capturing the first image frame includes initiating exposure of the set of pixel rows substantially simultaneously; and   initiating the modulated light flash includes initiating the modulated light flash in response to the initiation of the exposure of the set of pixel rows substantially simultaneously.   
     
     
         13 . The method of  claim 12 , wherein:
 capturing the first image frame further includes terminating exposure of the set of pixel rows substantially simultaneously; and   terminating the modulated light flash includes terminating the modulated light flash prior to terminating exposure of the set of pixel rows substantially simultaneously.   
     
     
         14 . The method of  claim 13 , wherein terminating exposure of the set of pixel rows substantially simultaneously comprises:
 activating a mechanical shutter to terminate exposure of the set of pixels.   
     
     
         15 . The method of  claim 8 , further comprising:
 determining at least one spatial feature based on the modulated light image data.   
     
     
         16 . A method comprising:
 capturing, at an electronic rolling shutter (ERS) imaging camera, a set of image frames at a first frame rate;   capturing, at the ERS imaging camera, a first image frame and a second image frame at a second frame rate, the second frame rate greater than the first frame rate;   projecting a modulated light flash during the capture of the first image frame, a duration of the modulated light flash occurring while each pixel row of the ERS imaging camera is exposed for gathering light for the first image frame;   refraining from projection of a modulated light flash during the capture of the second image frame; and   determining modulated light image data based on a comparison of the first image frame and the second image frame.   
     
     
         17 . The method of  claim 16 , wherein determining the modulated light image data comprises:
 subtracting image content of the second image frame from image content of the first image frame.   
     
     
         18 . The method of  claim 16 , further comprising:
 displaying image content of the image frames of the set of image frames; and   refraining from displaying image content of the first image frame and the second image frame.   
     
     
         19 . The method of  claim 16 , wherein capturing the first image frame and the second image frame comprises:
 capturing the second image frame prior to capturing the first image frame.   
     
     
         20 . The method of  claim 16 , further comprising:
 determining at least one spatial feature based on the modulated light image data.