Least squares method for color misregistration detection and correction in image data

• US 6,859,228 B1
• Filed: 10/18/1999
• Issued: 02/22/2005
• Est. Priority Date: 10/18/1999
• Status: Expired due to Term

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Otsu, Makoto, Chang, William Ho
• Primary Examiner(s): Vu, Ngoc-Yen, Vu, Ngoc-Yen
• Assistant Examiner(s): Nguyen, Luong T
• Application Number:
  US09/419,602
• Time in Patent Office: 1,954 Days
• Field of Search: 348/263, 348/241, 348/269, 348/270, 382162-167, 358/1.9, 358/3, 358/26, 358/505, 358/461, 358/512, 358/520, 358/521, 358/518, 358/530, 358/540, 345/611
• US Class Current: 348/263
• CPC Class Codes: H04N 1/58 Edge or detail enhancement; Noise or error suppression, e.g. colour misregistration correction H04N1/62 takes precedence
• CPC Class Codes: H04N 23/15 Image signal generation with circuitry for avoiding or correcting image misregistration

Abstract

A method for color misregistration detection. Input image data is buffered and transferred to vector space. An examination window for a current pixel is established and foreground and background pixels within that window are selected. The current pixel is examined to determine if it is in an edge of a scanned object. If the current pixel is in an edge, it is deemed to have color misregistration. For pixels that have been deemed to have color misregistration, a correction value is determined and then adjusted prior to being applied to the pixel value.

Claims

1. A method for detecting and correcting color misregistration of input images, the method comprising:

buffering image data received from an image capture device in the form of color space data;

transferring said color space data to vector space;

establishing a window around and including a current pixel;

selecting foreground and background pixels in said window;

determining if said current pixel is in an edge of an object by determining if a gradient between the foreground pixel and the background pixel is higher than a gradient between the current pixel and the foreground pixel and a gradient between the current pixel and the background pixel;

designating said current pixel as having color misregistration if said current pixel is in an edge of an object;

determining a correction value by applying normal least square projection to said current pixel;

adjusting the correction value for said current pixel having color misregistration; and

applying said correction value to said current pixel having color misregistration.

2. The method as claimed in claim 1 wherein said method further includes initially determining if a pixel is on an edge, occurring before establishing a window.

3. The method as claimed in claim 1 wherein establishing a window further comprises establishing a window of 5 pixels in the sub-scan direction and 1 pixel in the main scan direction.

4. The method as claimed in claim 1, wherein determining if said current pixel is in an edge further comprises a luminance check on said current pixel.

5. The method as claimed in claim 1, wherein adjusting further comprises applying fuzzy logic to said correction value to adjust said correction value.

6. The method as claimed in claim 1, wherein said color space is RGB.

7. The method as claimed in claim 1, wherein said color space is CMY.

8. The method as claimed in claim 1, wherein said color space is CMYK.

9. The method as claimed in claim 1, wherein said color space is a luminance and chrominance color space.