Color misconvergence measurement using a common monochrome image

• US 6,198,514 B1
• Filed: 02/27/1998
• Issued: 03/06/2001
• Est. Priority Date: 02/27/1998
• Status: Expired due to Term

• Current Assignee: Apple Inc.
• Original Assignee: Apple Computer Incorporated (Apple Inc.)
• Inventors: Wong, Min Keat, Lee, Kwang Wee
• Primary Examiner(s): HSIA, SHERRIE Y
• Application Number:
  US09/031,837
• Time in Patent Office: 1,103 Days
• Field of Search: H04/N 1.702, H04/N.322, H04/N.323, H04/N.326, H04/N.928, 348/180, 348/184, 348/189, 348/190, 348/191, 348/657, 348/658, 348/745, 348/746, 348/747, 348/800, 348/806, 348/807, 348/181, 250/205, 315/368.11, 315/368.12
• US Class Current: 348/807
• CPC Class Codes: H04N 17/04 for receivers

Abstract

Accurate measurements of the misconvergence of a color CRT are obtained using a monochrome CCD camera or the like and a common image. In accordance with one embodiment of the invention, color misconvergence of a color video display is determined using a monochrome camera, by capturing a monochrome image of an output display displayed on the color video display. For each of multiple different colors, information from the monochrome image is processed to identify a displayed feature or feature pattern of that color, and a position of that displayed feature or feature pattern is determined. Then a difference in position of a feature or feature pattern of a first color and a feature or feature pattern of a second color is determined. The effects of color crosstalk, video/image jitter, and lens distortion are all eliminated or minimized.

Claims

1. A method of determining color misconvergence of a color video display using a monochrome camera, the method comprising the steps of:

capturing a single monochrome image of an output display displayed on the color video display;

for each of a plurality of different colors, distinguishing a displayed feature or feature pattern of that color by processing information from the single monochrome image, and determining a position of said displayed feature or feature pattern; and

determining a difference in position of a feature or feature pattern of a first color and a feature or feature pattern of a second color.

2. The method of claim 1, wherein the output display includes a background region of a background color that is a primary color and a white line extending across the background region.

3. The method of claim 2, wherein a brightness of the white line is greater than a brightness of the background region.

4. The method of claim 2, wherein distinguishing comprises distinguishing a feature or feature pattern of said background color based on a brightness characteristic thereof.

5. The method of claim 4, wherein distinguishing further comprises distinguishing features or feature patterns of remaining primary colors based on positional relationships of those features or feature patterns to said feature or feature pattern of said background color.

6. The method of claim 2, wherein horizontal misconvergence is determined, with the white line being a vertical white line, and wherein said feature pattern is a group within said image of at least three pixels of a given primary color having substantially the highest brightness of all pixels of that color within a row of image pixels.

7. The method of claim 6, wherein the position of the group of pixels is determined in a weighted fashion taking into account the relative brightness of the pixels.

8. The method of claim 7, wherein the position of the group of pixels is determined to be the peak of a curve passing through the points x1, y1;

x2, y2; and

x3, y3;

wherein x1, x2 and x3 correspond, respectively, to the x position of the pixels and y1, y2 and y3 correspond, respectively, to the brightness of the pixels.

9. The method of claim 8, wherein the curve is a parabola.

10. The method of claim 2, wherein vertical misconvergence is determined, with the white line being a horizontal white line, and wherein said feature is a pixel of a given primary color having substantially the highest brightness of all pixels of that color within a vertical swath of image pixels.

11. The method of claim 1, wherein said monochrome image is captured using a monochrome CCD camera.