Overhead image-reading apparatus image processing method, and computer program product

• US 8,736,917 B2
• Filed: 03/08/2012
• Issued: 05/27/2014
• Est. Priority Date: 06/15/2011
• Status: Active Grant

• Current Assignee: PFU Limited (Fujitsu Limited)
• Original Assignee: PFU Limited (Fujitsu Limited)
• Inventors: Murata, Ikuo, Kado, Naofumi, Kameda, Hiroyuki
• Primary Examiner(s): Worku, Negussie
• Application Number:
  US13/415,194
• Publication Number:
  US 20120320430A1
• Time in Patent Office: 810 Days
• Field of Search: 358/474, 358/475, 358/501, 358/486
• US Class Current: 358/474
• CPC Class Codes: H04N 1/193 using electrically scanned linear arrays , e.g. linear CCD arrays
• CPC Class Codes: H04N 2201/0434 specially adapted for scanning pages of a book
• CPC Class Codes: H04N 2201/04787 by changing or controlling the addresses or values of pixels, e.g. in an array, in a memory, by interpolation
• CPC Class Codes: H04N 2201/04789 in the main-scan direction
• CPC Class Codes: H04N 2201/04793 using stored control or compensation data, e.g. previously measured data
• CPC Class Codes: H04N 2201/04794 Varying the control or compensation during the scan, e.g. using continuous feedback or from line to line

Abstract

An overhead image-reading apparatus includes a one-dimensional image sensor having imaging elements arranged in parallel to each other and is configured to change an angle between an optical axis of a light source and a medium to be read during reading of the medium, and the apparatus includes a correcting unit that corrects distortion in a main-scanning direction in read image data of the medium read by the apparatus.

Claims

1. An overhead image-reading apparatus comprising a one-dimensional image sensor, the overhead image-reading apparatus being configured to change an angle between an optical axis of a light source and a medium to be read during reading of the medium, the apparatus comprising:

a correcting unit that corrects distortion in a main-scanning direction in read image data of the medium read by the apparatus, wherein

the correcting unit corrects the distortion in the main-scanning direction based on a correction value corresponding to a sub-scanning position that is a reading position along a sub-scanning direction of the medium, and

the distortion to be corrected by the correcting unit is a barrel-shaped distortion caused by a change of an optical path length that is a distance between the one-dimensional image sensor and the medium to be read and that changes in accordance with the angle.

2. The overhead image-reading apparatus according to claim 1, wherein the correcting unit corrects the distortion in the main-scanning direction by using a correction table that stores a sub-scanning position and a correction value so as to correspond to each other.

3. The overhead image-reading apparatus according to claim 2, further comprising a correction table preparing unit that prepares the correction table.

4. An image processing method executed by an overhead image-reading apparatus including a one-dimensional image sensor, the overhead image-reading apparatus being configured to change an angle between an optical axis of a light source and a medium to be read during reading of the medium, the method executed by the overhead image-reading apparatus comprising:

a correcting step of correcting distortion in a main-scanning direction in read image data of the medium read by the apparatus, wherein

the correcting step corrects the distortion in the main-scanning direction based on a correction value corresponding to a sub-scanning position that is a reading position along a sub-scanning direction on the medium, and

the distortion to be corrected by the correcting step is a barrel-shaped distortion caused by a change of an optical path length that a distance between the one-dimensional image sensor and the medium to be read and that changes in accordance with the angle.

5. A computer program product having a non-transitory computer readable medium including programmed instructions for an overhead image-reading apparatus including a one-dimensional image sensor, the overhead image-reading apparatus being configured to change an angle between an optical axis of a light source and a medium to be read during reading of the medium, wherein

the instructions, when executed by the overhead image-reading apparatus, cause the overhead image-reading apparatus to execute a correcting step of correcting distortion in a main-scanning direction in read image data of the medium read by the apparatus, wherein

the correcting step corrects the distortion in the main-scanning direction based on a correction value corresponding to a sub-scanning position that is a reading position along a sub-scanning direction on the medium, and

the distortion to be corrected by the correcting step is a barrel-shaped distortion caused by a change of an optical path length that is changed between the one-dimensional image sensor and the medium to be read and that changes in accordance with the angle.