ADVANCED NOISE REDUCTION IN DIGITAL CAMERAS
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.