Image sensor that uses a temperature sensor to compensate for dark current

Abstract

An image sensor that has a temperature sensor. The temperature sensor senses the temperature of a pixel array of the image sensor. The sensed temperature is used to scale a dark frame image generated by the pixel array. The scaled dark frame image is subtracted from a light image frame generated by the pixel array. The scaled dark image frame compensates for temperature variations in the pixel array. The scaled dark image frame may be generated by multiplying the dark frame by a scale factor(s). The scale factor may be computed from an equation or determined from a look-up table. The equation or look-up table may compensate for thermal gradients across the pixel.

1 . An image sensor, comprising: 
 a pixel array;    a temperature sensor that senses a temperature of said pixel array;    a dark frame estimator coupled to said pixel array and said temperature sensor, said dark frame estimator multiplies a dark image frame generated by said pixel array with a scale factor determined from a look-up table to create a scaled dark image frame, said look-up table provides a different scale factor for at least two different pixels of said pixel array, wherein said scale factors are a function of a temperature measured by said temperature sensors; and    a combiner coupled to said dark signal estimator and said pixel array, said combiner combines the scaled dark image frame with a light image frame generated by said pixel array.    
     
     
         2 . The image sensor of  claim 1 , further comprising a memory coupled to said pixel array.  
     
     
         3 . The image sensor of  claim 1 , further comprising a memory coupled to said temperature sensor.  
     
     
         4 . The image sensor of  claim 1 , wherein said different scale factors are also dependent on exposure time.  
     
     
         5 . An image sensor, comprising: 
 pixel array means for generating a dark image frame and a light image frame;    temperature sensor means for sensing a temperature of said pixel array means during the dark image frame and the light image frame;    dark frame estimator means for multiplying the dark image frame with a scale factor, said scale factor is determined from a look-up table to create a scaled dark image frame, said look-up table provides a different scale factor for at least two different pixels of said pixel array, wherein said scale factors are a function of a temperature measured by said temperature sensor means; and    combiner means for combining the scaled dark image frame with the light image frame.    
     
     
         6 . The image sensor of  claim 5 , wherein said different scale factors are also dependent on exposure time.  
     
     
         7 . A method for dark signal reduction in an image sensor, comprising: 
 sensing a temperature of a pixel array that generates a light image frame;    scaling a dark image frame in accordance with the sensed temperature with a plurality of scale factors that are dependent on the sensed temperature and are provided by a look-up table to generate a scaled dark image frame, at least two different pixels of the pixel array having a different scale factor; and,    combining the scaled dark image frame with the light image frame.    
     
     
         8 . The method of  claim 7 , wherein the dark image frame is scaled by multiplying the dark image frame with the scale factor.  
     
     
         9 . A program storage medium that can cause a processor to provide dark signal reduction in an image sensor system, comprising: 
 a processor readable storage medium that causes a processor of an image sensor system to scale a dark image frame based on a temperature of a pixel array sensed during the generation of light image frame with a plurality of scale factors that are dependent on the sensed temperature and are provided by a look-up table to generate a scaled dark image frame, at least two different pixels of the pixel array having a different scale factor, and combine the scaled dark image frame with the light image frame.    
     
     
         10 . The storage medium of  claim 9 , wherein the dark image frame is scaled by multiplying the dark image frame with a scale factor.