Electronic image registration for a scanner

• US 6,999,209 B2
• Filed: 05/26/2004
• Issued: 02/14/2006
• Est. Priority Date: 09/23/1998
• Status: Expired due to Fees

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Tse, Francis K., Kelly, Nancy R., Nagarajan, Ramesh
• Primary Examiner(s): Williams, Kimberly
• Assistant Examiner(s): Worku, Negussie
• Application Number:
  US10/854,010
• Publication Number:
  US 20040212853A1
• Time in Patent Office: 629 Days
• Field of Search: 358/488, 358/486, 358/474, 358/496, 358/497, 358/494, 382/199, 382/266, 382/267, 382/268, 382/287, 382/289, 382/293, 355/218
• US Class Current: 358/474
• CPC Class Codes: G06T 3/608 by skew deformation, e.g. two-pass or three-pass rotation
• CPC Class Codes: G06V 10/24 Aligning, centring, orientation detection or correction of the image
• CPC Class Codes: H04N 1/3878 Skew detection or correction

Abstract

A system electronically registers an image on an input document. The system includes a scanner for generating an image data stream representing an electronic image of the image on the input document and an edge detecting circuit for detecting edge data within the image data stream. A circuit detects a first corner of a leading edge of the input document based on the detected edge data and for establishing a first coordinate value therefrom and a second corner of a leading edge of the input document based on the detected edge data and for establishing a second coordinate value therefrom. The system further determines a minimum and maximum location for a leading edge of the scanned document and determines a minimum and maximum location for a trailing edge of the scanned document. An image window is generated representing valid image data to processed and rendered based on the minimum and maximum location for a leading edge of the scanned document, the minimum and maximum location for a trailing edge of the scanned document, the first coordinate value, and the second coordinate value.

Claims

1. A method for electronically registering an input document, comprising:

(a) generating an image data stream representing a captured image, the captured image including the input document, the image data stream being partition into a plurality of scan lines of image data;

(b) detecting if the scan line of image data contains an edge of the input document and generating leading edge data and trailing edge data therefrom;

(c) establishing, when a scan line of image data containing an edge of the input document is detected and no corner of the input document has been established, a first corner of the input document based on the generated leading edge data and trailing edge data corresponding to the scan line of image data containing an edge of the input document;

(d) establishing a second corner of the input document from generated leading edge data, the establishing of the second corner of the input document including,

(d1) determining, after the first corner of the input document has been established and a scan line of image data containing an edge of the input document is detected, if the generated leading edge data is less than a first threshold value,

(d2) determining if the generated leading edge data represents a corner when it is determined that the generated leading edge data is less than the first threshold value, and

(d3) establishing the second corner of the input document based on the generated leading edge data when it is determined that the generated leading edge data represents a corner;

(e) establishing a third corner of the input document from generated trailing edge data, the establishing of the third corner of the input document including,

(e1) determining, after the first corner of the input document has been established and a scan line of image data containing an edge of the input document is detected, if the generated trailing edge data is greater than a second threshold value,

(e2) determining if the generated trailing edge data represents a corner when it is determined that the generated trailing edge data is greater than the second threshold value, and

(e3) establishing the third corner of the input document based on the generated trailing edge data when it is determined that the generated trailing edge data represents a corner; and

(f) establishing, when the generated trailing edge data is less than the second threshold value and the generated leading edge data is greater than the first threshold value, a fourth corner of the input document, after the first corner of the input document has been established and a scan line of image data containing an edge of the input document is detected, based upon current generated edge data.

2. The method as claimed in claim 1, further comprising:

(g) creating an electronic scanning window enclosing all four corners of the input document.

3. The method as claimed in claim 1, further comprising:

(g) creating an electronic scanning window within all four corners of the input document.

4. The method as claimed in claim 1, wherein the generated edge data is determined from averaging image data over a predetermined number of pixels.

5. The method as claimed in claim 1, wherein the leading generated edge data represents as a transition from image data representing a background of a platen cover to image data representing an edge of the input document.

6. The method as claimed in claim 1, wherein the leading generated edge data represents as a transition from image data representing a background of a constant velocity transport device to image data representing an edge of the input document.

7. The method as claimed in claim 1, wherein the trailing generated edge data represents as a transition from image data to image data representing an edge of the input document to image data representing a background of a platen cover.

8. The method as claimed in claim 1, wherein the trailing generated edge data represents as a transition from image data to image data representing an edge of the input document to image data representing a background of a constant velocity transport device.