Method for locally reducing row noise

1. A method for reducing row noise in image sensors, comprising:

defining a region W i centered on pixel P i of the i th column;

estimating Offset i on the basis of pixels within the region W i ; and

adding Offset i to the signal of pixel P i ,

wherein W i is a 2 dimensional region of odd number of pixels long and wide, a number of pixels in a row within the region W i being less than all pixels in the row.

2. A method for reducing row noise in image sensors, comprising:

defining a region W i centered on pixel P i of the i th column;

calculating A region (i), the average of the pixels in the row within region W i containing P i ;

calculating A region (i), the average of all the pixels in region W i ;

calculating Offset i by subtracting A line (i) from A region (i); and

adding Offset i to the signal of pixel P i ,

wherein W i is a 2 dimensional region of odd number of pixels long and wide.

3. A method for reducing row noise in image sensors, comprising:

defining a region W i centered on pixel P i of the i th column;

calculating, for each row inside region W i , the average pixel value A line (i), being an integer ranging between 1 and 2 u+1, u being an integer;

calculating Md(i), the median value of all the average pixel row values;

calculating Offset i by subtracting A line (u+1) from Md(i); and

adding Offset i to the signal of pixel P i ,

wherein W i is a 2 dimensional region of odd number of pixels long and wide.

4. The method of claims 1 , 2 , or 3 further comprising;

adding Offset i to the signal of one or more pixels immediately adjacent to pixel P i .

5. The method of claim 4 , wherein:

the pixel P i comprises a green pixel, the one or more pixels immediately adjacent to pixel P i comprising at least one of a blue and a green pixel neighboring the pixel P i .

6. The method of claims 1 , 2 , or 3 further comprising;

detecting whether or not pixel P i is located on a horizontal edge of an image; and

updating Offset i if P i is located on a horizontal edge of the image.

7. The method of claim 6 wherein the detecting step further comprises the steps of;

calculating the sum, S j , of signals for pixels in row j of the sensor;

calculating the sum, S j+2 , of signals for pixels in row j+2 of the sensor;

calculating the absolute value of the difference between S j and S j+2 ;

determining the ratio, R j+1 , of the absolute value of the difference between S j and S j+2 and the sum of S j and S j+2 ; and,

determining whether R j+1 is greater than some predetermined threshold value whereby pixel P i would likely lie on a horizontal edge of the image.

8. The method of claim 6 further comprising;

adding Offset i to the signal of one or more pixels immediately adjacent to pixel P i .