IMAGE READING APPARATUS, IMAGE READING METHOD, AND PROGRAM FOR IMPLEMENTING THE METHOD

• US 20080112023A1
• Filed: 11/13/2007
• Published: 05/15/2008
• Est. Priority Date: 11/13/2006
• Status: Active Grant

• Current Assignee: Canon Hi-Tech Limited (Canon Inc.)
• Original Assignee: Canon Hi-Tech Limited (Canon Inc.)
• Inventors: Watanabe, Hirotaka
• Granted Patent: US 8,018,629 B2
• Time in Patent Office: Days
• US Class Current: 358/514
• CPC Class Codes: H04N 1/00681 Detecting the presence, position or size of a sheet or correcting its position before scanning H04N1/047 takes precedence; mode signalling H04N1/333; skew detection or correction in image signals H04N1/3878
• CPC Class Codes: H04N 1/00718 Skew
• CPC Class Codes: H04N 1/00721 Orientation
• CPC Class Codes: H04N 1/00726 Other properties of the sheet, e.g. curvature or reflectivity

Abstract

An image reading apparatus in which the position of the boundary between an image of an original and a background image, as well as a skew and the size of the image of the original, can be accurately detected even with dust on a line image sensor or on an opposing member opposite to the line image sensor. An image formed on an original is read by a reading unit, and an opposing member is arranged at a position opposite to the reading unit. A plate glass distances the original from the opposing member. Shadow portions of the read image is detected from changes in a sub-scanning direction of pixel data of a read image generated based on output from the reading unit, and boundary coordinate data of the image of the original is obtained.

Claims

1. An image reading apparatus comprising:

an image sensor adapted to read an image formed on an original;

an opposing member that is arranged at a position opposite to said image sensor;

a distancing member that distances the original from said opposing member; and

a boundary detecting unit adapted to detect, from changes in a sub-scanning direction of pixel data of a read image generated based on output from said image sensor, shadow portions of the read image and to obtain boundary coordinate data of the image of the original.

2. An image reading apparatus according to claim 1, further comprising an original size detecting unit adapted to detect the size of the original based on the boundary coordinate data.

3. An image reading apparatus according to claim 1, wherein said distancing member comprises a transparent member distancing the original from said opposing member.

4. An image reading apparatus according to claim 1, wherein said boundary detecting unit comprises a differential data generating unit adapted to generate differential data by performing at least one of differentiation and quadratic differentiation on a pixel data sequence of the sub-scanning direction of the read image, and detects a boundary based on the differential data.

5. An image reading apparatus according to claim 1, further comprising a skew angle detecting unit adapted to detect a skew angle of the image of the original based on the boundary coordinate data.

6. An image reading apparatus according to claim 5, comprising a circumscribing rectangle calculating unit adapted to calculate a rectangle circumscribing the image of the original based on the boundary coordinate data and the detected skew angle.

7. An image reading apparatus according to claim 5, comprising a skew correcting unit adapted to correct the skewed image of the original based on the skew angle.

8. An image reading method applied to an image reading apparatus comprising an image sensor that reads an image formed on an original, an opposing member that is arranged at a position opposite to the image sensor, and a distancing member that distances the original from the opposing member, the method comprising a boundary detecting step of detecting, from changes in a sub-scanning direction of pixel data of a read image generated based on output from the image sensor, shadow portions of the read image and obtaining boundary coordinate data of the image of the original.

9. An image reading method according to claim 8, further comprising an original size detecting step of detecting the size of the original based on the boundary coordinate data.

10. An image reading method according to claim 8, wherein said boundary detecting step comprises generating differential data by performing at least one of differentiation and quadratic differentiation on a pixel data sequence of the sub-scanning direction of the read image and detecting a boundary based on the differential data.

11. An image reading method according to claim 10, further comprising a skew angle detecting step of detecting a skew angle of the image of the original based on the boundary coordinate data.

12. An image reading method according to claim 11, comprising a circumscribing rectangle computing step of computing a rectangle circumscribing the image of the original based on the boundary coordinate data and the skew angle.

13. An image reading method according to claim 11, comprising a skew correcting step of correcting the skewed image of the original based on the skew angle.

14. A program for causing a computer to implement an image reading method applied to an image reading apparatus comprising an image sensor that reads an image formed on an original, an opposing member that is arranged at a position opposite to the image sensor, and a distancing member that distances the original from the opposing member, the program comprising a boundary detecting module of detecting, from changes in a sub-scanning direction of pixel data of a read image generated based on output from the image sensor, shadow portions of the read image and obtaining boundary coordinate data of the image of the original.