Exposure control for an imaging system

Abstract

A device that analyzes an image. The device includes a circuit that receives an image that includes a plurality of pixels. The circuit creates a histogram of the image and analyzes the histogram to determine an acceptable exposure of the image. The histogram may include a plurality of bins versus a population of pixels associated with each bin. By way of example, the bins may be associated with an intensity of light. The images and histograms may include data defined by low dynamic range number of bits and/or an extended dynamic range number of bits. Certain features and criteria of the image may be determined and analyzed to determine whether the image has an acceptable exposure. If the image is unacceptable, an exposure characteristic can be changed and the process can be repeated until an acceptable image is obtained.

What is claimed is: 
     
         1 . A method for generating an image for a scene from a first image of the scene and a second image of the scene, the first image having a first exposure value and including a first pixel, the second image having a second exposure value smaller than the first exposure value and including a second pixel, comprising:
 generating, at a third exposure value intermediate between the first and second exposure values, a third image from at least the first and second images, mapping a first intensity value of the first pixel from the first exposure value to the third exposure value and mapping a second intensity value of the second pixel from the second exposure value to the third exposure value.   
     
     
         2 . The method of  claim 1 , where said generating the third image includes clamping the second intensity value. 
     
     
         3 . The method of  claim 1 , further comprising:
 forming, prior to said generating the third image, a low dynamic range histogram from at least the first and second images for an exposure value intermediate between the first and second exposure values.   
     
     
         4 . The method of  claim 3 , where the low dynamic range histogram is formed via an extended dynamic range histogram formed from at least the first and second images. 
     
     
         5 . The method of  claim 1 , wherein the third image is generated via an extended dynamic range image that is generated from at least the first and second images. 
     
     
         6 . The method of  claim 5 , further comprising:
 forming an extended dynamic range histogram from the extended dynamic range image; and,   forming a low dynamic range histogram from the extended dynamic range histogram.