John C Weldon

US Patent:

60056835, Dec 21, 1999

Filed:

Dec 5, 1997

Appl. No.:

8/985475

Inventors:

Myungsae Son - Rancho Santa Fe CA
John M. Weldon - San Diego CA

Assignee:

Hewlett-Packard Company - Palo Alto CA

International Classification:

H04N 104
H04N 140
G06K 936

US Classification:

358488

Abstract:

A technique for document edge detection in an optical scanning system. The document is placed against an over-sized neutral background. A linear optical sensor array is used to provide successive lines of pixel data representing the luminance of detected pixel areas. Commencing from one end of the line of pixel data, for successive current pixels being tested, a group of n adjacent pixel values is correlated with a successive group of n adjacent pixel values to provide a correlation value for the current pixel. One of the groups is assumed to contain only background pixels, and their luminance is approximated to be equal to the average luminance over the entire background. If the correlation value exceeds a threshold constant, the current pixel is chosen to be an edge in this line of pixels. Data from several lines is processed to find corresponding edges for each line, and the line edges are subjected to a least squares fit to calculate the location of the document edge. The left and right edge of the document can be found using this technique.