Dual video camera system for scanning hardcopy documents

• US 6,493,469 B1
• Filed: 06/28/1999
• Issued: 12/10/2002
• Est. Priority Date: 06/28/1999
• Status: Expired due to Term

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Taylor, Michael J., Newman, William M.
• Primary Examiner(s): Tran, Phuoc
• Assistant Examiner(s): Bayat, Ali
• Application Number:
  US09/340,748
• Time in Patent Office: 1,261 Days
• Field of Search: 382/284, 382/289, 382/290, 382/296, 382/294, 382/199, 382/200, 382/154, 358/450
• US Class Current: 382/284
• CPC Class Codes: H04N 1/1903 Arrangements for enabling electronic abutment of lines or areas independently scanned by different elements of an array or by different arrays
• CPC Class Codes: H04N 1/195 the array comprising a two-dimensional array or a combination of two-dimensional arrays
• CPC Class Codes: H04N 1/19584 Combination of arrays
• CPC Class Codes: H04N 1/19594 using a television camera or a still video camera
• CPC Class Codes: H04N 2201/0436 Scanning a picture-bearing surface lying face up on a support H04N2201/0434 takes precedence; using cylindrical picture bearing surfaces H04N1/06; with manual scanning H04N1/107
• CPC Class Codes: H04N 7/142 Constructional details of the terminal equipment, e.g. arrangements of the camera and the display

Abstract

A face-up document scanning apparatus stitches views from multiple video cameras together to form a composite image. The document scanning apparatus includes an image acquisition system and a frame merger module. The image acquisition, which is mounted over the surface of a desk on which a hardcopy document is placed, has two video cameras for simultaneously recording two overlapping images of different portions of the hardcopy document. By overlapping a portion of the recorded images, the document scanning apparatus can accommodate hardcopy documents of varying thickness. Once the overlapping images are recorded by the image acquisition system, the frame merger module assembles a composite image by identifying the region of overlap between the overlapping images. The composite image is subsequently transmitted for display on a standalone device or as part of a video conferencing system.

Claims

1. A document scanning apparatus, comprising:

an image acquisition system for simultaneously recording parts of a hardcopy document positioned face-up on a surface;

the parts of the hardcopy document being recorded without perspective distortion in a first image and a second image by said image acquisition system;

a portion of each of the parts of the hardcopy document recorded in the first image and the second image recording an identical segment of the hardcopy document; and

a frame merger module for forming a composite image of the hardcopy document by stitching the first image and the second image together at the portions in each image that record the identical segment of the hardcopy document;

said frame merger module identifying the portion in the first image and the portion in the second image by computing correlation values of high gradient images of the first image and the second image for different regions of overlap between the first image and the second image.

2. The document scanning apparatus according to claim 1, wherein said frame merger module further comprises:

means for incrementally overlapping the first image and the second image by a predefined number of pixels to define regions of overlap between the first image and the second image;

means for computing a correlation value for identifying a degree of similarity between overlapping pixels in each of the regions of overlap; and

means for identifying a maximum correlation value from the correlation values for each of the regions of overlap computed by said computing means to identify the regions of overlap for forming the composite image.

3. The document scanning apparatus according to claim 2, wherein said identifying means forms the composite image using a region of overlap identified for a previous set of images recorded by said image acquisition system when none of the correlation values for each of the regions of overlap exceeds a predefined maximum value.

4. The document scanning apparatus according to claim 1, wherein said image acquisition system further comprises a first camera for recording the first image and a second camera for recording the second image.

5. The document scanning apparatus according to claim 4, wherein said image acquisition system further comprises an adjustment for aligning opposing sides of the first image with opposing sides of the second image.

6. The document scanning apparatus according to claim 4, wherein said image acquisition system further comprises an adjustment for correcting differences in scale between images recorded with the first camera and images recorded with the second camera.

7. The document scanning apparatus according to claim 4, wherein said image acquisition system further comprises an adjustment for defining a maximum document thickness.

8. The document scanning apparatus according to claim 4, wherein said image acquisition system further comprises an adjustment for rotating the first image relative to the second image.

9. The document scanning apparatus according to claim 1, further comprising a display for viewing the composite image of the hardcopy document.

10. The document scanning apparatus according to claim 1, further comprising an image enhancement module for enhancing the composite image of the hardcopy document output from said frame merger module.

11. The document scanning apparatus according to claim 1, further comprising means for computing a high gradient image for the first image and a high gradient image for the second image,

wherein the high gradient image for the first image and the high gradient image for the second image are computed with:

means for binarizing the first image and the second image; and

means for locating edge pixels by setting to black only those pixels in the binarized first image and the binarized second image with white neighbors in an overlap direction.

12. A method for operating a document scanning apparatus, comprising the steps of:

simultaneously recording, with an image acquisition system, parts of a hardcopy document positioned face-up on a surface;

said recording step recording the parts of the hardcopy document without perspective distortion in a first image and a second image;

a portion of each of the parts of the hardcopy document recorded in the first image and the second image recording an identical segment of the hardcopy document; and

forming, with a frame merger module, a composite image of the hardcopy document by stitching the first image and the second image together at the portions in each image that record the identical segment of the hardcopy document;

said forming step identifying the portion in the first image and the portion in the second image by computing correlation values of high gradient images of the first image and the second image for different regions of overlap between the first image and the second image.

13. The method according to claim 12, wherein said stitching step further comprises the steps of:

incrementally overlapping the first image and the second image by a predefined number of pixels to define regions of overlap between the first image and the second image;

computing a correlation value for identifying a degree of similarity between overlapping pixels in each of the regions of overlap; and

identifying a maximum correlation value from the correlation values for each of the regions of overlap computed by said computing step to identify the regions of overlap for forming the composite image.

14. The method according to claim 13, said identifying step forms the composite image using a region of overlap identified for a previous set of images recorded by said recording step when none of the correlation values for each of the regions of overlap exceeds a predefined maximum value.

15. The method according to claim 12, wherein said recording step further comprises the step of recording the first image with a first camera and the second image with a second camera.

16. The method according to claim 15, wherein said recording step further comprises the step of aligning two sides of the first image and two sides of the second image.

17. The method according to claim 15, wherein said recording step further comprises the step of correcting differences in scale between images recorded with the first camera and images recorded with the second camera.

18. The method according to claim 15, wherein said recording step further comprises the step of defining adjusting the height of the document acquisition system relative to the surface on which the hardcopy document is positioned to define a maximum document thickness.

19. The method according to claim 15, wherein said recording step further comprises the step of rotating the first image relative to the second image.

20. The method according to claim 12, further comprising the step of viewing the composite image of the hardcopy document on a display.

21. The method according to claim 12, further comprising the step of computing a high gradient image for the first image and a high gradient image for the second image;

wherein the high gradient image for the first image and the high gradient image for the second image are computed by;

binarizing the first image and the second image; and

locating edge pixels by setting to black only those pixels in the binarized first image and the binarized second image with white neighbors in an overlap direction.