IMAGE READING APPARATUS, CONTROL METHOD THEREFOR, AND PROGRAM

• US 20110043873A1
• Filed: 08/03/2010
• Published: 02/24/2011
• Est. Priority Date: 08/19/2009
• Status: Active Grant

• Current Assignee: Canon Hi-Tech Limited (Canon Inc.)
• Original Assignee: Canon Hi-Tech Limited (Canon Inc.)
• Inventors: Maruo, Masaru
• Granted Patent: US 8,482,818 B2
• Time in Patent Office: Days
• US Class Current: 358/475
• CPC Class Codes: H04N 1/0071 Width
• CPC Class Codes: H04N 1/00713 Length
• CPC Class Codes: H04N 1/00745 Detecting the leading or trailing ends of a moving sheet
• CPC Class Codes: H04N 1/00748 Detecting edges, e.g. of a stationary sheet
• CPC Class Codes: H04N 1/00755 Detecting an interruption of light
• CPC Class Codes: H04N 1/00795 Reading arrangements details of scanning heads H04N1/024; scanning arrangements therefor H04N1/04
• CPC Class Codes: H04N 1/00814 according to a detected condition or state of the reading apparatus, e.g. temperature
• CPC Class Codes: H04N 1/00816 Determining the reading area, e.g. eliminating reading of margins
• CPC Class Codes: H04N 1/00997 Light control, e.g. shielding from ambient light or preventing light leakage
• CPC Class Codes: H04N 1/40056 Circuits for driving or energising particular reading heads or original illumination means H04N1/401, H04N1/407 take precedence

Abstract

There is provided an image reading apparatus and a control method therefor, which can suppress the influence of external light, and obtain an appropriate read image. To accomplish this, the image reading apparatus executes a Light-on reading processing for turning on an LED and causing a sensor to read an original document on a original platen at the first resolution, and a Light-off reading processing for turning off a light source and causing the sensor to read the original document on the original platen at the second resolution. In accordance with the influence of external light in an Light-off mode image read by the Light-off reading processing, the image reading apparatus removes the influence of external light in a Light-on mode image read by the Light-on reading processing.

Claims

1. An image reading apparatus comprising:

a original platen on which an original document is placed;

a light source that emits light toward the original document on said original platen;

a sensor that reads an image of the original document on said original platen;

a reading unit that executes a Light-on reading processing for turning on said light source and causing said sensor to read the original document on said original platen at a first resolution, and a Light-off reading processing for turning off said light source and causing said sensor to read the original document on said original platen at a second resolution;

an image processing unit that removes an influence of external light included at a reading position outside the original document in a Light-on mode image read by the Light-on reading processing, in accordance with an influence of external light included at a reading position outside the original document in a Light-off mode image read by the Light-off reading processing; and

a specifying unit that specifies a boundary between the inside and outside of the original document on said original platen based on the Light-on mode image in which said image processing unit has removed the influence of external light.

2. The apparatus according to claim 1, wherein the Light-off reading processing reads at the second resolution lower than the first resolution.

3. The apparatus according to claim 1, wherein before removing the influence of external light from the Light-on mode image, said image processing unit converts the Light-on mode image with the first resolution into an image with the second resolution.

4. The apparatus according to claim 3, wherein said specifying unit further specifies a position and a size of the original document on said original platen based on the specified boundary.

5. The apparatus according to claim 4, further comprising an adjustment unit that adjusts the position and size of the original document specified by said specifying unit in accordance with a difference between the first resolution and the second resolution.

6. The apparatus according to claim 4, wherein said specifying unit

comprises a detection unit that detects an end portion of the read original document by determining, at two end portions of each line in a main scan direction of said sensor, whether there exists a pixel having a brightness equal to or higher than a predetermined threshold with respect to the image in which said image processing unit has removed the influence of external light, and

specifies the boundary on said original platen based on a detection result by said detection unit.

7. The apparatus according to claim 1, wherein the specifying unit specifies coordinates of four corners of the original document from the Light-on mode image in which said image processing unit has removed the influence of external light.

8. The apparatus according to claim 1, further comprising:

an opening/closing cover that is attached to said original platen so as to be openable/closeable, and presses the original document against said original platen; and

a detection unit that detects a state in which said opening/closing cover is closed or opened,

wherein when reading the original document on said original platen, said reading unit executes only the Light-on reading processing if said detection unit detects that said opening/closing cover is closed, and executes the Light-on reading processing and the Light-off reading processing if said detection unit detects that said opening/closing cover is opened.

9. The apparatus according to claim 1, further comprising a setting unit that sets a reading region for reading the original document,

wherein when reading the original document on said original platen, said reading unit executes only the Light-on reading processing if said setting unit has set the reading region, and executes the Light-on reading processing and the Light-off reading processing if said setting unit has not set the reading region.

10. The apparatus according to claim 1, further comprising a unit that executes processing for flicker on at least one or more of the Light-off mode image obtained by the Light-off reading processing, the Light-on mode image obtained by the Light-on reading processing, and the image in which said image processing unit has removed the influence of external light.

11. The apparatus according to claim 1, further comprising an opening/closing cover that is attached to said original platen so as to be openable/closeable, and is in contact with the original document on said original platen in an open state,

said opening/closing cover comprises a front cover and a rear cover which are connected with each other, and is foldable in a direction in which surfaces of the front cover and the rear cover to be in contact with the original document come close to each other,

wherein when reading the original document in a state in which said opening/closing cover is opened, said image processing unit removes a reflection of a front end portion of said front cover.

12. The apparatus according to claim 11, wherein if continuous regions each having a brightness equal to or higher than a predetermined threshold have a dimension equal to or shorter than a predetermined threshold in a sub-scan direction at two end portions in the main scan direction in the Light-on mode image, said image processing unit determines that the continuous regions include the reflection of the front end portion of said front cover, and removes the reflection in the continuous regions.

13. The apparatus according to claim 1, further comprising a notifying unit that notifies, when reading the original document, an operator that the original document is being read.

16. The apparatus according to claim 1, wherein said image processing unit comprises a correction unit that corrects a shift between reading positions of the Light-on mode image and the Light-off mode image.

17. The apparatus according to claim 16, wherein said correction unit

comprises a storage unit that stores, in advance, a shift amount between the reading positions of the Light-on mode image and the Light-off mode image which have been read by said reading unit, and

corrects the shift between the reading positions based on the shift amount stored in said storage unit before said image processing unit removes the influence of external light.

18. The apparatus according to claim 16, further comprising a partial light source that is located near said original platen, and emits light toward part of the reading position,

wherein said correction unit

comprises a partial light source specifying unit that specifies, as the shift amount between the reading positions, a shift amount between positions, at which said partial light source is reflected, in the Light-on mode image and the Light-off mode image which have been read by said reading unit, and

corrects the shift between the reading positions in accordance with the shift amount specified by said partial light resource specifying unit between the positions at which said partial light source is reflected, before said image processing unit removes the influence of external light.

19. The apparatus according to claim 18, wherein said correction unit removes the reflection of said partial light source in the Light-on mode image and the Light-off mode image.

20. The apparatus according to claim 16, wherein said correction unit

comprises an edge detection unit that detects edges of document regions in the Light-on mode image and the Light-off mode image, and a region specifying unit that specifies document regions in the Light-on mode image and the Light-off mode image, which are obtained based on the edges detected by said edge detection unit, and

corrects the shift between the reading positions in accordance with a shift between the document regions specified by said region specifying unit in the Light-on mode image and the Light-off mode image before said image processing unit removes the influence of external light.

14. A control method for an image reading apparatus, comprising:

executing a Light-on reading processing for turning on a light source which emits light toward an original document on a original platen and causing a sensor to read an image of the original document on the original platen at a first resolution, and a Light-off reading processing for turning off the light source and causing the sensor to read the original document on the original platen at a second resolution;

removing an influence of external light included at a reading position outside the original document in a Light-on mode image read by the Light-on reading processing, in accordance with an influence of external light included at a reading position outside the original document in a Light-off mode image read by the Light-off reading processing; and

specifying a boundary between the inside and outside of the original document on the original platen based on the Light-on mode image in which the influence of external light has been removed in the removing step.

15. A computer-readable storage medium storing a computer program for causing a computer or a control unit of an image reading apparatus to execute the control method for the image reading apparatus according to claim 14.