Advanced noise reduction in digital cameras

Abstract

A noise reduction apparatus is presented that includes groups of one or more serially connected non-linear filter units. Each of the filter unit groups are driven by decimated input image data at a different level of decimation and the output of at least one of these groups serves as one of a plurality of inputs to another group driven at a different decimation level.

1 . An image noise reduction apparatus comprising groups of one or more serially connected non-linear filter units; wherein each of said filter unit groups are driven by decimated input image data at a different level of decimation; and wherein the output of at least one of said groups serves as one of a plurality of inputs to another group driven at a different decimation level. 
     
     
         2 . The noise reduction apparatus of  claim 1 , wherein the filter units are implemented in hardware. 
     
     
         3 . The noise reduction apparatus of  claim 1 , wherein the filter units are implemented in software. 
     
     
         4 . The noise reduction apparatus of  claim 1 , wherein the filter units are edge preserving filters. 
     
     
         5 . The noise reduction apparatus of  claim 1 , wherein the filter units are sigma class filters. 
     
     
         6 . The noise reduction apparatus of  claim 1 , wherein each of said filter units use the same filtering algorithm. 
     
     
         7 . The noise reduction apparatus of  claim 1 , wherein the input image data is image data from a digital camera. 
     
     
         8 . The noise reduction apparatus of  claim 1 , wherein the input image data is image data from a video camera. 
     
     
         9 . The noise reduction apparatus of  claim 1 , further comprising:
 a first non-linear filter element connectable to be driven by said input image data, filter the image data, and determine an indication of uniformity of the image data; and   a blend module connectable to receive the filtered image data from the first non-linear filter element, the indication of uniformity, and an interpolated output of one of said groups and form a combination of the filtered image data from the first non-linear filter element and the interpolated output of said one of said groups, wherein the combination is responsive to the indication of uniformity.   
     
     
         10 . The noise reduction apparatus of  claim 9 , wherein the combination is a linear combination. 
     
     
         11 . The noise reduction apparatus of  claim 9 , wherein the indication of uniformity of the image data around a pixel is determined for an N by N neighborhood of the pixel, where N is an odd integer. 
     
     
         12 . The noise reduction apparatus of  claim 1 , wherein said another group driven at a different decimation level further includes a blend module that forms a combination of the output of the last of the serially connected filter units therein and an interpolated version of said output of at least one of said groups. 
     
     
         13 . A method of performing a noise reduction operation on input image data, comprising:
 decimating the input image data to a plurality of different levels of decimation;   for each level of decimation, filtering the decimated image data by a group of one or more serially connected non-linear filter units; and   providing the output of at least of one said groups as one of a plurality of inputs to another of the groups at a different level of decimation.   
     
     
         14 . The method of  claim 13 , wherein the filter units are implemented in hardware. 
     
     
         15 . The method of  claim 13 , wherein the filter units are implemented in software. 
     
     
         16 . The method of  claim 13 , wherein the filter units are edge preserving filters. 
     
     
         17 . The method of  claim 13 , wherein the filter units are sigma class filters. 
     
     
         18 . The method of  claim 13 , wherein each of said filter units use the same filtering algorithm. 
     
     
         19 . The method of  claim 13 , wherein the input image data is image data from a digital camera. 
     
     
         20 . The method of  claim 13 , wherein the input image data is image data from a video camera. 
     
     
         21 . The method of  claim 13 , further comprising:
 filtering the input data image with a first non-linear filter element;   determining an indication of uniformity of the image data; and   forming a combination of the filtered image data from the first non-linear filter element and the interpolated output of said one of said groups, wherein the combination is responsive to the indication of uniformity.   
     
     
         22 . The method of  claim 21 , wherein the combination is a linear combination. 
     
     
         23 . The method of  claim 21 , wherein the indication of uniformity of the image data around a pixel is determined for an N by N neighborhood of the pixel, where N is an odd integer. 
     
     
         24 . The method of  claim 13 , further comprising:
 interpolating said output of at least of one said groups; and   forming a combination of the output of the last of the serially connected filter units of said another of the groups at a different level and the interpolated output of at least one of said groups.