Image reading device and image reading method for document detection

1 . An image reading device, comprising:

a first transport roller configured to transport a document in a predetermined transport direction;

a second transport roller provided downstream of the first transport roller in the transport direction and configured to transport the document in the transport direction;

a reading sensor provided downstream of the second transport roller and configured to read the document transported;

a document detection sensor provided, in the transport direction, between a position where the first transport roller comes into contact with the document and a position where the second transport roller comes into contact with the document, the document detection sensor being configured to detect the document; and

a control unit, wherein

the document detection sensor is located at a first position, the first position being a position away from an origin of the reading sensor by a first distance in a width direction intersecting the transport direction,

based on detection of the document by the document detection sensor, the control unit starts reading by the reading sensor,

when a size of the document is not specified, the control unit performs first identification processing of identifying, for image data generated as a reading result by the reading sensor and using a search line extending to a downstream end of the image data, a region of the document by detecting an edge of the document from the image data generated as the reading result by the reading sensor, and

when the size of the document is specified, the control unit performs second identification processing of searching the image data, at a position within a first range including the first position in the width direction, for a downstream end of the document from the downstream end of the image data toward upstream in the transport direction, and based on a position of the downstream end of the document identified by the searching, identifying as the region of the document a region corresponding to the size of the document specified, and

in the second identification processing, when the searching fails to identify the downstream end of the document from the image data, the control unit identifies a position away from the downstream end of the image data toward upstream by a fixed distance set in advance as a substitute for the downstream end of the document.

2 . The image reading device according to claim 1 , wherein

the second transport roller includes a roller on one side and a roller on the other side disposed spaced apart in the width direction and

the first range is included between the roller on the one side and the roller on the other side.

3 . The image reading device according to claim 1 , wherein

in the second identification processing, the control unit searches the image data for the downstream end of the document at the first position.

4 . The image reading device according to claim 3 , wherein

the control unit searches the image data for the downstream end of the document at the first position, and when the searching at the first position fails to identify the downstream end of the document, searches for the downstream end of the document at a second position within the first range, the second position being different from the first position.

5 . The image reading device according to claim 4 , wherein

the control unit searches the image data for the downstream end of the document at the second position, and when the searching at the second position fails to identify the downstream end of the document, searches for the downstream end of the document at a third position within the first range, the third position being on an opposite side of the second position with respect to the first position.

6 . The image reading device according to claim 1 , wherein

with a predetermined time shorter than a prescribed time required to transport the document from the document detection sensor to the reading sensor defined as a first time and

with a predetermined time longer than the prescribed time defined as a second time,

the control unit starts reading by the reading sensor at a timing at which the first time elapses since the document is detected by the document detection sensor and

in the second identification processing, the control unit searches for the downstream end of the document by using the image data generated by the reading in a period from when the reading by the reading sensor is started to when the second time minus the first time elapses.

7 . The image reading device according to claim 6 , wherein

the second time is a time having a length that permits reading from the downstream end of the document to a position upstream of the downstream end by 40 mm to 50 mm.

8 . The image reading device according to claim 1 , wherein

in the second identification processing, in a case in which the control unit searches for the downstream end of the document from the downstream end of the image data toward upstream, when a predetermined number of consecutive pixels correspond to a color of the document, the control unit identifies a position of a pixel farthest downstream of the predetermined number of consecutive pixels corresponding to the color of the document as the downstream end of the document.

9 . The image reading device according to claim 1 , wherein

in the second identification processing, the control unit searches the image data for the downstream end of the document at each of a plurality of positions within the first range, and identifies a position farthest downstream of downstream ends of the document identified by the searching at each of the plurality of positions as the downstream end of the document.

10 . An image reading method to be performed by an image reading device, the image reading device including:

a first transport roller configured to transport a document in a predetermined transport direction,

a second transport roller provided downstream of the first transport roller in the transport direction and configured to transport the document in the transport direction,

a reading sensor provided downstream of the second transport roller and configured to read the document transported, and

a document detection sensor provided, in the transport direction, between a position where the first transport roller comes into contact with the document and a position where the second transport roller comes into contact with the document, the document detection sensor being configured to detect the document,

the document detection sensor being located at a first position, the first position being a position away from an origin of the reading sensor by a first distance in a width direction intersecting the transport direction, the image reading method comprising:

based on detection of the document by the document detection sensor, starting reading by the reading sensor;

when a size of the document is not specified, performing first identification processing of identifying, for image data generated as a reading result by the reading sensor and using a search line extending to a downstream end of the image data, a region of the document by detecting an edge of the document from the image data generated as the reading result by the reading sensor; and

when the size of the document is specified, performing second identification processing of searching the image data, at a position within a first range including the first position in the width direction, for a downstream end of the document from the downstream end of the image data toward upstream in the transport direction, and based on a position of the downstream end of the document identified by the searching, identifying as the region of the document a region corresponding to the size of the document specified,

in the second identification processing, when the searching fails to identify the downstream end of the document from the image data, a control unit identifies a position away from the downstream end of the image data toward upstream by a fixed distance set in advance as a substitute for the downstream end of the document.

11 . An image reading device, comprising:

a first transport roller configured to transport a document in a predetermined transport direction;

a second transport roller provided downstream of the first transport roller in the transport direction and configured to transport the document in the transport direction;

a reading sensor provided downstream of the second transport roller and configured to read the document transported;

a document detection sensor provided, in the transport direction, between a position where the first transport roller comes into contact with the document and a position where the second transport roller comes into contact with the document, the document detection sensor being configured to detect the document; and

a control unit, wherein

the document detection sensor is located at a first position, the first position being a position away from an origin of the reading sensor by a first distance in a width direction intersecting the transport direction,

based on detection of the document by the document detection sensor, the control unit starts reading by the reading sensor,

when a size of the document is not specified, the control unit performs first identification processing of identifying, for image data generated as a reading result by the reading sensor and using a search line extending to a downstream end of the image data, a region of the document by detecting an edge of the document from the image data generated as the reading result by the reading sensor,

when the size of the document is specified, the control unit performs second identification processing of searching the image data, at a position within a first range including the first position in the width direction, for a downstream end of the document from the downstream end of the image data toward upstream in the transport direction, and based on a position of the downstream end of the document identified by the searching, identifying as the region of the document a region corresponding to the size of the document specified,

in the second identification processing,

setting as the region to be read by the reading sensor in a main scanning direction, a size corresponding to the document specified in the main scanning direction, and

when the document is inclined, searching for a plurality of downstream ends of the document, identifying, among the downstream ends, the one located farthest downstream as the downstream end of the document, and identifying a region of the document set along the transport direction from the downstream end toward an upstream region.

12 . The image reading device of claim 11 , wherein when the documents is skewed, a document region that is straight is aligned with the predetermined transport direction is extracted.