System for electronic compensation of beam scan trajectory distortion

• US 6,529,643 B1
• Filed: 12/21/1998
• Issued: 03/04/2003
• Est. Priority Date: 12/21/1998
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Banton, Martin E., Loce, Robert P., Harrington, Steven J.
• Primary Examiner(s): Mehta, Bhavesh
• Assistant Examiner(s): Kassa, Yosef
• Application Number:
  US09/217,224
• Time in Patent Office: 1,534 Days
• Field of Search: 382/300, 382/309, 382/293, 382/275, 382/294, 382/268, 382/317, 382/296, 382/289, 382/282, 382/274, 358/428, 358/258, 358/455, 358/525, 358/537, 358/538, 358/429
• US Class Current: 382/300
• CPC Class Codes: H04N 1/047 Detection, control or error compensation of scanning velocity or position H04N1/0402 and H04N1/17 take precedence
• CPC Class Codes: H04N 1/1135 for the main-scan only
• CPC Class Codes: H04N 1/12 using the sheet-feed movement or the medium-advance or the drum-rotation movement as the slow scanning component, e.g. arrangements for the main-scanningsheet-feed movement by translatory movement of a flat picture-bearing surface H04N1/1008; main-scanning using oscillating or rotating mirrors H04N1/113; using multi-element arrays H04N1/19
• CPC Class Codes: H04N 2201/02425 Self-adjusting arrangements, e.g. compensating for temperature fluctuations
• CPC Class Codes: H04N 2201/03162 Original guide plate
• CPC Class Codes: H04N 2201/04787 by changing or controlling the addresses or values of pixels, e.g. in an array, in a memory, by interpolation
• CPC Class Codes: H04N 2201/04789 in the main-scan direction
• CPC Class Codes: H04N 2201/04791 in the sub-scan direction

Abstract

A system for generating a warped contone image that compensates for beam scan trajectory distortions. The system includes an image buffer for storing a portion of a received contone image. An interpolation coefficient generator provides interpolation coefficients associated with a warped pixel within the warped contone image in response to an input identifying the warped pixel. A pixel interpolator is coupled to the image buffer and the interpolation coefficient generator and provides an output signal that identifies the warped pixel within the warped contone image. The pixel interpolator further retrieves pixels from the contone image stored in the image buffer using the interpolation coefficients and generates the warped pixel by combining the retrieved pixels into a single pixel value.

Claims

1. A system for generating a warped contone image that compensates for beam scan trajectory distortions, comprising:

an image buffer coupled to receive a contone image, said image buffer storing a portion of said contone image;

an interpolation coefficient generator providing an interpolation coefficient associated with a warped pixel within said warped contone image in response to an input signal uniquely identifying said warped pixel, said interpolation coefficient identifying a position within said image buffer that corresponds to the intersection of a position of the warped pixel along a beam scan trajectory of an output scanner with an ideal pixel grid describing a desired beam scan trajectory; and

a pixel interpolator coupled to said image buffer and said interpolation coefficient generator, said pixel interpolator providing said input signal uniquely identifying said warped pixel, retrieving pixels from said contone image stored in said image buffer in response to said interpolation coefficient associated with said warped pixel and generating a value for said warped pixel by combining said retrieved pixels into a single pixel value.

2. The system according to claim 1, wherein said interpolation coefficient generator stores an interpolation coefficient as an offset from a predetermined position within said contone image for a plurality of pixels along a beam scan trajectory.

3. The system according to claim 1, wherein said interpolation coefficient generator stores output position coordinates for said warped pixel.

4. The system according to claim 1, wherein said interpolation coefficient generator generates a compensated trajectory for said output scanner and identifies said interpolation coefficient from said generated trajectory.

5. The system according to claim 1, wherein said pixel interpolator combines said retrieved pixels into a single pixel by interpolating the values of the retrieved pixels.

6. The system according to claim 5, wherein said pixel interpolator performs a bilinear interpolation operation to combine the retrieved pixels into single pixel.

7. The system according to claim 1, wherein said pixel interpolator further retrieves tags associated with said retrieved pixels from said contone image stored in said image buffer and generates a warped tag based on a position of said warped pixel.

8. The system according to claim 1, wherein said pixel interpolator combines said retrieved pixels into said single pixel by generating an expanded pixel pattern for each retrieved pixel, determining an output position for said warped pixel with respect to said retrieved pixels and determining an expanded pixel pattern for said warped pixel.

9. The system according to claim 8, wherein said pixel interpolator further retrieves tags associated with said retrieved pixels from said contone image and wherein said expanded pixel patterns are generated as a function of said retrieved tags.

10. A printing system, comprising:

a print engine generating an output document in response to print ready data; and

an image processing system operating on image data representing an image to be printed to generate said print ready data, said image processing system including a warping processor for generating a warped contone image that compensates for pixel positioning errors introduced by an output scanner in said print engine, wherein said warping processor comprises;

an image buffer coupled to receive a contone image, said image buffer storing a portion of said contone image;

an interpolation coefficient generator providing an interpolation coefficient associated with a warped pixel within said warped contone image in response to an input uniquely identifying said warped pixel, said interpolation coefficient identifying a position within said image buffer that corresponds to the intersection of a position of the warped pixel along a beam scan trajectory of said output scanner with an ideal pixel grid; and

a pixel interpolator coupled to said image buffer and said interpolation coefficient generator, said pixel interpolator providing an output uniquely identifying said warped pixel, retrieving pixels from said contone image stored in said image buffer in response to said interpolation coefficient associated with said warped pixel and generating a value for said warped pixel by combining said retrieved pixels into a single pixel value.

11. The system according to claim 10, wherein said interpolation coefficient generator stores a compensated trajectory, said compensated trajectory identifying said pixel positioning errors relative to an ideal pixel grid.

12. The system according to claim 11, wherein said interpolation coefficient generator stores said compensated trajectory as a set of pixel offset values.

13. The system according to claim 10, wherein said pixel interpolator combines said retrieved pixels into a single pixel by interpolating the values of the retrieved pixels.

14. The system according to claim 13, wherein said pixel interpolator performs a bilinear interpolation operation to combine the retrieved pixels into single pixel.

15. The system according to claim 10, wherein said pixel interpolator further retrieves tags associated with said retrieved pixels from said contone image stored in said image buffer and generates a warped tag based on a position of said warped pixel.

16. The system according to claim 10, wherein said pixel interpolator combines said retrieved pixels into said single pixel by generating an expanded pixel pattern for each retrieved pixel, determining an output position for said warped pixel with respect to said retrieved pixels and determining an expanded pixel pattern for said warped pixel.

17. The system according to claim 16, wherein said pixel interpolator further retrieves tags associated with said retrieved pixels from said contone image and wherein said expanded pixel patterns for each retrieved pixel are generated as a function of said retrieved tags.

18. A method of realigning pixels within continuous tone image data to compensate for distortion in a beam scan trajectory of a first output scanner and improve image layer registration, comprising the steps of:

receiving said continuous tone image data, said received continuous tone image data comprising a plurality of scanlines;

identifying a warped pixel within a warped scanline;

identifying pixels within said received continuous tone image data that compensate for said distortion in said beam scan trajectory;

retrieving said identified pixel from said received continuous tone image data based on said desired output position; and

generating said warped pixel from said retrieved pixels.

19. The method of claim 18, wherein said step of identifying pixels within said received continuous tone image data comprises:

identifying said beam scan trajectory for said first output scanner;

identifying a desired beam scan trajectory; and

determining a compensated beam scan trajectory as a function said beam scan trajectory for said first output scanner and said a desired beam scan trajectory.

20. The said method of claim 19, wherein said step of generating said warped pixel from said retrieved pixels combines said retrieved pixels into a single pixel by interpolating between said retrieved pixels.

21. The said method of claim 19, wherein said step of generating said warped pixel from said retrieved pixels comprises:

generating expanded pixel patterns for said retrieved pixels;

determining an output position for said warped pixel with respect to said expanded pixel patterns;

determining an expanded pixel pattern for said warped pixel; and

determining a value for said warped pixel based on the expanded pixel pattern for said warped pixel.

22. The said method of claim 21, wherein said step of generating said warped pixel from said retrieved pixels further comprises retrieving tags from said received continuous tone image data and wherein said expanded pixel patterns are generated as a function of said retrieved tags.

23. The method of claim 22, wherein said desired beam scan trajectory matches a beam scan trajectory of a second output scanner.