Temporally aligned exposure bracketing for high dynamic range imaging

Abstract

Apparatus and methods are provided to create high dynamic range images by passing an incoming image through a color-neutral separation prism having at least three channels to produce a corresponding number of full color fractionated images, each channel aligned with a corresponding image capturing device for which an ISO sensitivity is selected to simultaneously achieve a different exposure value for each fractionated image and image capturing device, referred to as exposure bracketing, and recombining the simultaneously collected fractionated images to create a high dynamic range image. The apparatus and methods may be used for still photography or motion pictures.

I claim: 
     
         1 . An optical imaging system comprising:
 a light aperture to receive incoming light from an external image;   a color-neutral separation prism having at least three full color light channels generated by one or more color-neutral internal partially-reflective boundaries, each of the internal partially-reflective boundaries adapted to reflect a selected fraction of the incoming light, the prism oriented to receive the incoming light along a first axis and pass a first fraction of the incoming light out a first light channel aligned with the first axis;   a plurality of image capturing devices corresponding to the at least three light channels, each of the image capturing devices positioned to receive the selected fraction of the incoming light from its corresponding light channel, including a first image capturing device corresponding to the first light channel and first fraction of incoming light;   wherein the ISO sensitivity of each image capturing device is selected in combination with the respective light fraction to achieve a respective exposure value, including at least a standard exposure value corresponding to the first light channel and first image capturing device, a second exposure value greater than the standard exposure value and corresponding to a second light channel and second image capturing device, and a third exposure value lesser than the standard exposure value and corresponding to a third light channel and third image capturing device, thereby creating at least three temporally aligned bracketed exposures of an image.   
     
     
         2 . The system of  claim 1 , further comprising an image processor in electronic communication with at least the plurality of image capturing devices to receive the bracketed exposures and combine them into a high dynamic range image. 
     
     
         3 . The system of  claim 1  wherein each of said image capturing devices further comprises an image detection sensor for said temporally aligned images. 
     
     
         4 . The system of  claim 2 , further comprising a tone-mapping processor in electronic communication with either or both of the image processor and image capturing devices. 
     
     
         5 . The system of  claim 1  wherein said three levels of exposure are about 14%, about 29% and about 57%, respectively, of the intensity of said incoming image. 
     
     
         6 . The system of  claim 1  wherein said three levels of exposure are about 5%, about 19% and about 76%, respectively, of the intensity of said incoming image. 
     
     
         7 . The system of  claim 1  wherein said three levels of exposure are about 1%, about 11% and about 88%, respectively, of the intensity of said incoming image. 
     
     
         8 . A method for creating a high dynamic range image, the method comprising
 receiving light from an incoming image through an aperture;   passing the received light through a color-neutral separation prism having at least three channels to create a corresponding number of full-spectrum fractionated images, each fractionated image comprising a pre-selected full color fraction of the received light;   directing each of the full color fractionated images from the at least three channels to a corresponding image capturing device;   selecting an ISO sensitivity for each image capturing device corresponding to its full color fractionated image to provide a different selected exposure value for each image capturing device;   causing the image capturing devices to simultaneously record their respective full color fractionated images at their corresponding selected exposure values;   passing the simultaneously recorded full color fractionated images to an image processor, wherein the image processor combines the at least three fractionated images having different exposure values into a single high dynamic range image of the incoming image.   
     
     
         9 . The method of  claim 9 , further comprising the step of tone mapping the high dynamic range image to an output media. 
     
     
         10 . The method of  claim 9 , wherein the recorded images are video images. 
     
     
         11 . The method of  claim 9  wherein the prism has three channels and the corresponding fractionated images are approximately 14%, 29% and 57%, respectively, of the light of the incoming image. 
     
     
         12 . The method of  claim 9  wherein the prism has three channels and the corresponding fractionated images are approximately 5%, 19% and 76%, respectively, of the light of the incoming image. 
     
     
         13 . The method of  claim 9  wherein the prism has three channels and the corresponding fractionated images are approximately 1%, 11% and 88%, respectively, of the light of the incoming image.