Image reading apparatus, image reading method, and program for implementing the method

• US 8,018,629 B2
• Filed: 11/13/2007
• Issued: 09/13/2011
• 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
• Primary Examiner(s): Worku; Negussie
• Application Number:
  US11/939,021
• Publication Number:
  US 20080112023A1
• Time in Patent Office: 1,400 Days
• Field of Search: 358/474, 358/488, 358/497, 358/514, 358/461, 358/475, 358/509, 358/520, 382/289, 382/296, 382/202, 382/282, 382/290, 382/291
• US Class Current: 358/474
• 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 configured 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 configured to detect density changes of a sub-scanning direction of the read image obtained by said image sensor and to obtain boundary coordinate data of the image of the original based on the detected density changes,

wherein said boundary detecting unit comprises a differential data generating unit configured 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.

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

3. An image reading apparatus according to claim 2, comprising a circumscribing rectangle calculating unit configured to calculate a rectangle circumscribing the image of the original based on the boundary coordinate data and the detected skew angle.

4. An image reading apparatus according to claim 2, comprising a skew correcting unit configured to correct the skewed image of the original based on the skew angle.

5. An image reading apparatus according to claim 1, wherein said boundary detecting unit obtains binarized information by binarizing differential data of the sub-scanning direction of the read image to thereby obtain the boundary coordinate data based on the binarized information.

6. 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 density changes of a sub-scanning direction of the read image obtained by the image sensor and obtaining boundary coordinate data of the image of the original based on the detected density changes,

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.

7. An image reading method according to claim 6, further comprising a skew angle detecting step of detecting a skew angle of the image of the original based on the boundary coordinate data.

8. An image reading method according to claim 7, 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.

9. An image reading method according to claim 7, comprising a skew correcting step of correcting the skewed image of the original based on the skew angle.

10. An image reading apparatus according to claim 6, wherein said boundary detecting step obtains binarized information by binarizing differential data of the sub-scanning direction of the read image to thereby obtain the boundary coordinate data based on the binarized information.

11. A storage medium on which a computer-executable program is stored, said 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 for detecting density changes of a sub-scanning direction of the read image obtained by the image sensor and for obtaining boundary coordinate data of the image of the original based on the detected density changes,

wherein said boundary detecting module generates 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.