# US 2014/0192386 A1 · Document reading unit, image forming apparatus incorporating same, and method of detecting original document using with same

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- Number: US 2014/0192386 A1
- Document ID: US20140192386A1
- Status: Published application
- Kind: A1
- Application number: 14/141,555
- Filed: 2013-12-27
- Published: 2014-07-10
- Earliest claimed: 2013-01-08
- Assignees: Ricoh Company, Ltd.
- Inventors: Masatoshi ISHIDA
- Web page: https://patentgrep.com/patent/US20140192386A1

## CPC

- H04N 1/00689: {Presence}
- H04N 1/00708: {Size or dimensions}
- H04N 1/0071: {Width}
- H04N 1/00713: {Length}
- H04N 1/00734: {Optical detectors}
- H04N 1/00737: {using the scanning elements as detectors}
- H04N 1/00748: {Detecting edges, e.g. of a stationary sheet}
- H04N 1/0075: {Detecting a change in reflectivity}
- H04N 1/00753: {of a sheet relative to a particular backgroud}
- H04N 1/02815: {Means for illuminating the original, not specific to a particular type of pick-up head}
- H04N 1/1061: {Details relating to flat picture-bearing surfaces, e.g. transparent platen}
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A document reading unit included in an image forming apparatus and operated with a method of detecting an original document, includes an original document table, a moving irradiation unit having multiple block light sources moving in a sub scanning direction while irradiating the original document, an image sensor receiving reflected light, and a controller that starts a length specifying operation with the moving irradiation unit located at a position facing the original document, sequentially turns on the block light sources, obtains an amount of reflected light under lighting conditions of each block light sources, and determines the length of the original document in the main scanning direction. While the moving irradiation unit is moving in the sub scanning direction, the image sensor receives the reflected light on a region of the original document in the sub scanning direction under each lighting condition during the length specifying operation.

## Claims

### Claim 1

A document reading unit comprising:
an original document table on a surface of which an original document is placed;
a moving irradiation unit having multiple block light sources aligned in a main scanning direction of a surface of the original document and to move in a sub scanning direction that is a direction along the surface of the original document table and perpendicular to the main scanning direction while irradiating light emitted by the multiple block light sources to the original document placed on the original document table and obtaining reflected light reflected on the original document;
an image sensor to receive reflected light from the original document irradiated by the moving irradiation unit and read an image formed on the original document; and
a controller configured to perform a length specifying operation to specify a length of the original document in the main scanning direction,
wherein the controller starts the length specifying operation in a state in which the moving irradiation unit is located at a position facing the original document placed on the original document table, sequentially turns on the multiple block light sources one by one, obtains an amount of reflected light received by the image sensor under respective lighting conditions of the multiple block light sources, and determines the length in the main scanning direction of the original document based on the obtained amount of reflected light,
wherein the controller causes the image sensor to receive the reflected light reflected on a region having a width in the sub scanning direction of the original document placed on the original document table under the multiple lighting conditions during the length specifying operation while causing the moving irradiation unit to move in the sub scanning direction.

### Claim 2 (depends on 1)

The document reading unit according to claim 1, wherein, in the length specifying operation, the controller turns on a first block light source of the multiple block light sources to obtain the amount of reflected light by the image sensor in a unit moving time period in which a speed of movement of the moving irradiation unit is increasing to a given speed after the start of movement of the moving irradiation unit.

### Claim 3 (depends on 2)

The document reading unit according to claim 2, wherein, in the length specifying operation, the controller causes the moving irradiation unit to emit the light and the image sensor to receive the reflected light for a first time period to obtain data of the received amount of reflected light under a lighting condition in which a second block light source that is different from the first block light source is turned on while the moving irradiation unit is moving at the given speed,
wherein, in the length specifying operation, the controller causes the moving irradiation unit to emit the light and the image sensor to receive the reflected light for a second time period that is greater than the first time period to obtain data of the received amount of reflected light under a lighting condition in which the first block light source is turned on during the unit moving time period.

### Claim 4 (depends on 3)

The document reading unit according to claim 3, wherein, in the length specifying operation, the controller receives the light by the image sensor under the respective multiple lighting conditions in the unit moving time period and causes the time of receiving the light by the image sensor under the multiple lighting conditions to be gradually reduced.

### Claim 5 (depends on 1)

The document reading unit according to claim 1, wherein the controller causes each emission intensity of the multiple block light sources in the length specifying operation to be lower than each emission intensity of the multiple block light sources in an image reading operation to read the image of the original document.

### Claim 6 (depends on 1)

The document reading unit according to claim 1, further comprising:
an original document pressing unit to press the original document placed on the original document table against the surface of the original document table; and
an open/close detecting unit to detect an open/close operation of the original document pressing unit with respect to the original document table,
wherein the controller starts the length specifying operation based on a result that the open/close detecting unit detects the close operation of the original document pressing unit.

### Claim 7 (depends on 1)

An image forming apparatus comprising:
the document reading unit according to claim 1; and
an image forming unit to form an image on a recording medium based on an image reading result obtained by the document reading unit.

### Claim 8

A method of detecting an original document comprising:
placing the original document on a surface of an original document table;
reading data of an image of the original document,
the reading comprising:
emitting light to the original document from a moving irradiation unit comprising multiple block light sources aligned in a main scanning direction along the surface of the original document table;
obtaining reflected light reflected on the original document;
moving the moving irradiation unit along the surface of the original document in a sub scanning direction that is perpendicular to the main scanning direction to an original document reading start position; and
receiving the reflected light of the original document by an image sensor; and
performing a length specifying operation to specify a length of the original document in the main scanning direction,
the performing comprising:
starting the length specifying operation in a state in which the moving irradiation unit is located at a position facing the original document placed on the original document table;
turning on the multiple block light sources one by one;
obtaining an amount of received light obtained by the image sensor under respective lighting conditions; and
determining the length of the original document in the main scanning direction based on the amount of reflected light.

### Claim 9 (depends on 8)

The method of detecting the original document according to claim 8, wherein the performing the length specifying operation further comprises:
turning on a first block light source of the multiple block light sources; and
obtaining the amount of reflected light in a unit moving time period in which a speed of movement of the moving irradiation unit is increasing to a given speed after the start of movement of the moving irradiation unit.

### Claim 10 (depends on 9)

The method of detecting the original document according to claim 9, wherein the performing the length specifying operation further comprises:
causing the moving irradiation unit to emit the light and the image sensor to receive the reflected light for the first time period to obtain data of the received amount of reflected light under a lighting condition in which a second block light source that is different from the first block light source is turned on while the moving irradiation unit is moving at the given speed; and
causing the moving irradiation unit to emit the light and the image sensor to receive the reflected light for a second time period that is greater than the first time period to obtain data of the received amount of reflected light under a lighting condition in which the first block light source is turned on during the unit moving time period.

### Claim 11 (depends on 10)

The method of detecting the original document according to claim 10, wherein the performing further comprises:
receiving the light by the image sensor under the respective multiple lighting conditions in the unit moving time period; and
causing the time of receiving the light by the image sensor under the multiple lighting conditions to be gradually reduced.

### Claim 12 (depends on 8)

The method of detecting the original document according to claim 8, wherein the performing further comprises causing each emission intensity of the multiple block light sources in the length specifying operation to be lower than each emission intensity of the multiple block light sources in an image reading operation to read the image of the original document.

### Claim 13 (depends on 8)

The method of detecting the original document according to claim 8, further comprising:
pressing the original document placed on the original document table against the surface of the original document table;
detecting an open/close operation of the original document pressing unit with respect to the original document table; and
starting the length specifying operation based on a result that the close operation of the original document pressing unit is detected.