System and method for roll-off correction in image processing
View Patent ↗A system and method is provided for processing a digital image. The system and method processes image data by correcting for roll-off variability in the digital image. The system and method corrects for roll-off in image data by determining for each pixel a roll-off contour in which the pixel resides and adjusting that pixel based upon its roll-off contour, which in turn, depends upon its location on the image plane.
1. A method of processing an a digital image, the method comprising the steps of:
receiving image data defining the image, the image data including a plurality of pixels;
defining a plurality of roll-off contours;
determining an offset from an optical axis for each pixel in the plurality of pixels;
determining for each pixel in the plurality of pixels which roll-off contour in the plurality of roll-off contours corresponds to the pixel from the offset for the pixel;
adjusting each pixel based on its corresponding roll-off contour, wherein the adjusting each pixel based on its corresponding roll-off contour comprises adjusting modulation transfer function of each pixel.
2. The method of claim 1 wherein each of the plurality of roll-off contours includes a plurality of linear segments that define the roll-off contour.
3. The method of claim 1 wherein each of the plurality of roll-off contours includes a plurality of linear segments that define an oval-type roll-off contour.
4. The method of claim 1 wherein each of the plurality of roll-off contours includes a plurality of linear segments that define a circle-type roll-off contour.
5. The method of claim 1 wherein the step of adjusting each pixel based on its corresponding roll-off contour comprises adjusting luminance of each pixel.
6. The method of claim 1 wherein the step of adjusting each pixel based on its corresponding roll-off contour comprises adjusting color of each pixel.
7. The method of claim 1 wherein the step of determining an offset from an optical axis for each pixel in the plurality of pixels comprises determining offset variables x and y representing horizontal and vertical offset components of each pixel, and wherein the step of determining for each pixel in the plurality of pixels which roll-off contour in the plurality of roll-off contours corresponds to the pixel comprises comparing x to y.
8. The method of claim 1 wherein the step of determining an offset from an optical axis for each pixel in the plurality of pixels comprises determining offset variables x and y representing horizontal and vertical offset components of each pixel, and wherein the step of determining for each pixel in the plurality of pixels which roll-off contour in the plurality of roll-off contours corresponds to the pixel comprises comparing x to 4y and selecting a roll-off contour defined by 5x/4 if x is greater than 4y, else comparing x to 2y and selecting a roll-off contour defined by x+y if x is greater than 2y, else selecting a roll-off contour defined by x/2+2y.
9. The method of claim 1 wherein the step of determining an offset from an optical axis for each pixel in the plurality of pixels comprises determining offset variables x and y representing horizontal and vertical offset components of each pixel, and wherein the step of determining for each pixel in the plurality of pixels which roll-off contour in the plurality of roll-off contours corresponds to the pixel comprises comparing x to y and selecting a roll-off contour defined by x+y/2 if x is greater than y, else selecting a roll-off contour defined by x/2+y.
10. The method of claim 1 wherein the step of determining an offset from an optical axis for each pixel in the plurality of pixels comprises determining offset variables x and y representing horizontal and vertical offset components of each pixel, and wherein the step of determining for each pixel in the plurality of pixels which roll-off contour in the plurality of roll-off contours corresponds to the pixel comprises comparing x to 6y and selecting a roll-off contour defined by 7x/16 if x is greater than 6y, else comparing x to 5y/2 and selecting a roll-off contour defined by 3(x+y)/8 if x is greater than 5y/2, else selecting a roll-off contour defined by x/8+y.
11. A method of processing an a digital image, the method comprising the steps of:
receiving image data defining the image, the image data including a plurality of pixels;
defining a plurality of roll-off contours;
determining an offset from an optical axis for each pixel in the plurality of pixels, wherein the step of determining an offset from an optical axis for each pixel in the plurality of pixels comprises determining offset variables x and y representing horizontal and vertical offset components of each pixel; and
determining for each pixel in the plurality of pixels which roll-off contour in the plurality of roll-off contours corresponds to the pixel from the offset for the pixel, wherein the step of determining for each pixel in the plurality of pixels which roll-off contour in the plurality of roll-off contours corresponds to the pixel comprises comparing x to 4y and comparing x to 2y; and
adjusting each pixel based on its corresponding roll-off contour.
12. A method of processing an a digital image, the method comprising the steps of:
receiving image data defining the image, the image data including a plurality of pixels;
defining a plurality of roll-off contours;
determining an offset from an optical axis for each pixel in the plurality of pixels, wherein the step of determining an offset from an optical axis for each pixel in the plurality of pixels comprises determining offset variables x and y representing horizontal and vertical offset components of each pixel; and
determining for each pixel in the plurality of pixels which roll-off contour in the plurality of roll-off contours corresponds to the pixel from the offset for the pixel, wherein the step of determining for each pixel in the plurality of pixels which roll-off contour in the plurality of roll-off contours corresponds to the pixel comprises comparing x to 6y and comparing x to 5y/2; and
adjusting each pixel based on its corresponding roll-off contour.
13. A method of processing a digital image, the method comprising the steps of:
receiving image data defining the image, the image data including a plurality of pixels;
defining a first plurality of roll-off contours, each of the first plurality of roll-off contours including a first plurality of linear segments that define the roll-off contour;
determining for each pixel in the plurality of pixels which roll-off contour in the first plurality of roll-off contours corresponds to the pixel;
adjusting luminance of each pixel based on its corresponding roll-off contour in the first plurality of roll-off contours;
defining a second plurality of roll-off contours, each of the second plurality of roll-off contours including a second plurality of linear segments that define the roll-off contour;
determining for each pixel in the plurality of pixels which roll-off contour in the second plurality of roll-off contours corresponds to the pixel; adjusting color of each pixel based on its corresponding roll-off contour in the second plurality of roll-off contours;
defining a third plurality of roll-off contours, each of the third plurality of roll-off contours including a third plurality of linear segments that define the roll-off contour;
determining for each pixel in the third plurality of pixels which roll-off contour in the third plurality of roll-off contours corresponds to the pixel; and
adjusting modulation transform function of each pixel based on its corresponding roll-off contour in the third plurality of roll-off contours.
14. The method of claim 13 wherein the step of determining for each pixel in the plurality of pixels which roll-off contour in the first plurality of roll-off contours corresponds to the pixel comprises determining an offset from an optical axis for each pixel in the plurality of pixels, and wherein the step of determining for each pixel in the plurality of pixels which roll-off contour in the second plurality of roll-off contours corresponds to the pixel comprises determining an offset from the optical axis for each pixel in the plurality of pixels; and wherein the step of determining for each pixel in the plurality of pixels which roll-off contour in the third plurality of roll-off contours corresponds to the pixel comprises determining an offset from an optical axis for each pixel in the plurality of pixels.
15. The method of claim 13 wherein the step of determining for each pixel in the plurality of pixels which roll-off contour in the first plurality of roll-off contours corresponds to the pixel comprises determining offset variables x and y representing horizontal and vertical offset components of each pixel and comparing x to 4y and selecting a roll-off contour defined by 5x/4 if x is greater than 4y, else comparing x to 2y and selecting a roll-off contour defined by x+y if x is greater than 2y, else selecting a roll-off contour defined by x/2+2y.
16. The method of claim 13 wherein the step of determining for each pixel in the plurality of pixels which roll-off contour in the first plurality of roll-off contours corresponds to the pixel comprises determining offset variables x and y representing horizontal and vertical offset components of each pixel and comparing x to y and selecting a roll-off contour defined by x+y/2 if x is greater than y, else selecting a roll-off contour defined by x/2+y.
17. A method of processing a digital image, the method comprising the steps of:
receiving image data defining the image, the image data including a plurality of pixels;
determining for each pixel if the pixel is likely corrupt by comparing each pixel to a plurality of neighboring pixels;
replacing each pixel determined to be likely corrupt with a statistical function of a plurality of nearby pixels;
converting the plurality of pixels to a format that includes a luminance component, a first color component and a second color component;
defining a first plurality of luminance roll-off contours, each of the first plurality of luminance roll-off contours including a first plurality of linear segments that define the luminance roll-off contour;
determining for each pixel in the plurality of pixels which luminance roll-off contour in the first plurality of luminance roll-off contours corresponds to the pixel;
adjusting luminance component of each pixel based on its corresponding roll-off contour in the first plurality of roll-off contours; defining a second plurality of color roll-off contours, each of the second plurality of color roll-off contours including a second plurality of linear segments that define the color roll-off contour;
determining for each pixel in the plurality of pixels which color roll-off contour in the second plurality of roll-off contours corresponds to the pixel; adjusting first and second color components of each pixel based on its corresponding color roll-off contour in the second plurality of roll-off contours;
defining a third plurality of MTF roll-off contours, each of the third plurality of MTF roll-off contours including a third plurality of linear segments that define the roll-off contour; determining for each pixel in the third plurality of pixels which MTF roll-off contour in the third plurality of roll-off contours corresponds to the pixel; and
adjusting MTF of luminance components of each pixel based on its corresponding MTF roll-off contour in the third plurality of roll-off contours.
18. A processor, tangibly embodying a program of instructions to perform method steps for digital image processing, comprising the machine executed steps of:
receiving image data defining the image, the image data including a plurality of pixels; defining a plurality of roll-off contours;
determining an offset from an optical axis for each pixel in the plurality of pixels; determining for each pixel in the plurality of pixels which roll-off contour in the plurality of roll-off contours corresponds to the pixel from the offset for the pixel;
adjusting each pixel based on its corresponding roll-off contour, wherein the adjusting each pixel based on its corresponding roll-off contour comprises adjusting modulation transfer function of each pixel.