Rapid Synchronized Lighting and Shuttering

Abstract

This document describes various apparatuses and techniques for rapid synchronized lighting and shuttering. These apparatuses and techniques are capable of capturing two images, where one of the images integrates multiple exposures during which an image area is illuminated by a light source and another of the images integrates multiple exposures during which the image is not illuminated by the light source. The image area can be illuminated by rapidly flashing the image area with the light source and synchronizing a shutter to permit one image sensor to capture an image when the image area is illuminated and another image sensor to capture the image area when the image area is not illuminated. These two images can be captured concurrently or nearly concurrently, thereby reducing or eliminating motion artifacts. Further, these apparatuses and techniques may do so with slow and relatively low-cost cameras and relatively low computational costs.

What is claimed is: 
     
         1 . A controller configured to:
 synchronize flashing of a light source and shuttering of a shutter effective to enable capture of a first image integrating multiple exposures during which the light source is flashed and a second image integrating multiple exposures during which the light source is not flashed; and   provide the first image and the second image, the first image and the second image usable to determine a net image in which one or more additional light sources other than the light source are excluded.   
     
     
         2 . A controller as recited in  claim 1 , wherein the controller is further configured to synchronize flashing of a second light source of the one or more additional light sources, the second light source excludable from the net image. 
     
     
         3 . A controller as recited in  claim 1 , wherein the light source is an LED or laser diode and a flash rate of the LED or laser diode is at least 60 Hz. 
     
     
         4 . A controller as recited in  claim 3 , wherein the flash rate of the LED or laser diode is at least twice as fast as an image-capture rate at which the first and second images are captured. 
     
     
         5 . A controller as recited in  claim 3 , wherein the controller is further configured to synchronize the shuttering of the shutter at a shuttering rate of at least as fast as the flash rate. 
     
     
         6 . A controller as recited in  claim 1 , wherein the shutter includes a beam splitter, a polarizer, and a ferro-electric polarization retarder and the controller is further configured to control the beam splitter, the polarizer, and the ferro-electric polarization retarder as part of synchronizing the flashing of the light source and the shuttering of the shutter. 
     
     
         7 . A controller as recited in  claim 1 , wherein the controller is computer hardware operating without computer-readable instructions or a processor. 
     
     
         8 . A controller as recited in  claim 1 , wherein the controller includes computer-executable instructions and further is configured to determine the net image by comparing the first image and the second image. 
     
     
         9 . A controller as recited in  claim 1 , wherein the controller is configured to synchronize flashing of the light source and shuttering of the shutter effective to enable capture of the first image by a first image sensor and capture of the second image by a second image sensor. 
     
     
         10 . A controller as recited in  claim 1 , wherein the controller is further configured to:
 synchronize flashing of a second light source and shuttering of a second shutter effective to enable capture of a third image integrating multiple exposures during which the second light source is flashed and a fourth image integrating multiple exposures during which the second light source is not flashed; and   provide the third and fourth images, the first image, the second image, the third image, and the fourth image usable to determine placement of a moving object in three dimensions based on a first shadow of the moving object created by the light source and a second shadow of the moving object created by the second light source.   
     
     
         11 . A controller as recited in  claim 1 , wherein the first image, the second image, and the net image include a finger, hand, arm, or body and the controller is further configured to determine a gesture performed by the finger, hand, arm, or body based on the net image. 
     
     
         12 . A method comprising:
 rapidly flashing an object with a first light source, the object illuminated by a second light source in addition to the first light source;   synchronizing shuttering to the rapid flashing, the synchronized shuttering effective to enable capture of a first image integrating multiple exposures during the flashes and a second image integrating multiple exposures not during the flashes; and   comparing the first image and the second image effective to create a net image, the net image showing the object illuminated by the first light source but not illuminated by the second light source.   
     
     
         13 . A method as recited in  claim 12 , wherein synchronizing shuttering causes a first mechanical shutter to open prior to or during each flash of the rapid flashes and close prior to or during each flash of the rapid flashes, the first mechanical shutter interposed between the object and a first image sensor, and wherein synchronizing shuttering causes a second mechanical shutter to open when or after each flash of the rapid flashes ceases and close prior to or when each flash of the rapid flashes begins, the second mechanical shutter interposed between the object and a second image sensor. 
     
     
         14 . A method as recited in  claim 12 , wherein the object is a finger, hand, arm, body, or stylus and further comprising determining a gesture based on the net image. 
     
     
         15 . A method as recited in  claim 14 , wherein the second light source is light generated by a computer screen over which the finger, hand, arm, body, or stylus performs the gesture. 
     
     
         16 . A method as recited in  claim 12 , wherein comparing the first image and the second image effective to create the net image subtracts the second image from the first image. 
     
     
         17 . A method as recited in  claim 12 , wherein rapidly flashing the object is performed non-periodically effective to cause one of the first or second images to be an integration of longer exposures that the other of the first or second images. 
     
     
         18 . A computing device comprising:
 a first light source configured to flash at a flash rate;   a shutter configured to shutter at least twice as fast as the flash rate;   a computer screen having a second light source; and   a controller configured to:
 synchronize flashing of the first light source and shuttering of the shutter effective to enable capture of a first image integrating multiple exposures during which the first light source is flashed and a second image integrating multiple exposures during which the first light source is not flashed and the second light source is provided; and 
 provide the first image and the second image, the first image and the second image usable to determine a net image in which the second light source is excluded. 
   
     
     
         19 . A computing device as recited in  claim 18 , wherein the computing device further includes:
 one or more processors; and   one or more computer-readable storage memory having computer-executable instructions thereon that, responsive to execution by the one or more processors, perform an act comprising determining, based on the net image, a gesture performed by an object captured in the net image.   
     
     
         20 . A computing device as recited in  claim 19 , wherein the object is a finger, hand, arm, or body and the gesture performed by the object is over the computer screen.