JP6870557B2 - Image reader - Google Patents

Description

The present invention relates to an image reader, and more particularly to a technique for detecting the size of a document.

Some image reading devices have a function of detecting the size of a document placed on a document placing surface. As a means for detecting the size of the document in the main scanning direction, the light source is turned on just before the document holding member (for example, the document mat) is completely closed, and the size of the document is determined by the light incident on the scanning sensor that reads the document. There is something to detect. On the other hand, as a means for detecting the size of the original in the sub-scanning direction, a dedicated sensor (for example, a reflective sensor) is used in the area where the originals of various standard sizes (B5 size, A4 size, B4 size, etc.) are placed. Is installed, and the size of the document is detected based on the combination of the detection results from each sensor.

However, since the size of the document in the main scanning direction is detected by turning on the light source before the document holding member is completely closed, the reading sensor treats the external light from the lighting equipment mounted on the ceiling as ambient light. There is a risk that accurate detection will not be possible.

As an invention for solving such a problem, the following Patent Document 1 describes a contact glass (original document) in a state where the exposure lamp (light source) is not lit and a state in which the exposure lamp (light source) is lit when the document holding member is open. The manuscript placed on the mounting surface) is read by a CCD (Charge Coupled Device), and the manuscript is identified by identifying the part affected by ambient light based on the changes in the image data obtained by these readings. It is described that the size in the width direction (main scanning direction) of is accurately detected.

Japanese Unexamined Patent Publication No. 2001-147494

In the image reading device, when the document placed on the document placing surface is read by a scanning sensor such as a CCD while the document holding member is open, the outer margin of the document may be read in black. is there. In particular, reading a document such as an ID card (for example, a credit card) or a form (for example, a slip) is relatively often performed with the document holding member open.

In order to solve the situation where the outer margin of the original is read black, the existing extra-manuscript erasing function (the function of whitening the outer region of the original) can be executed as in the technique shown in Patent Document 1 above. It is conceivable to adopt a system, but the function is expensive and the cost increases.

Another method is to detect the size of the document placed on the document placement surface, set the scanning size of the document from the detected size of the document, and scan the document at the set scanning size. Although it is conceivable, in order to flexibly deal with the sizes of a wide variety of documents (particularly ID cards and forms) in the sub-scanning direction, a large number of dedicated sensors must be installed, which also increases the cost.

The present invention has been made in view of the above circumstances, and an object of the present invention is to enable accurate detection of the size of a document even when the document holding member is open, while suppressing an increase in cost.

When the document holding member is in the open state and the document is placed on the document placing surface, if the light source arranged below the document placing surface is turned on, the document on which the document is placed is placed. In the stationary area, the light emitted from the light source is reflected by the document, and in the area where the document does not exist, the light emitted from the light source is not reflected. Therefore, the size of the document can be detected by detecting the presence or absence of the reflected light by the reading sensor and specifying the document placing area. Specifically, the image data of the portion where the reflected light is incident on the reading sensor is a white image, and the image data of the other portion is a black image.

However, when the document holding member is open as described above, even in a region where the document does not exist, the light emitted from the light source is reflected by the document holding member and scattered, and the lighting equipment attached to the ceiling. External light from the above may enter the reading sensor as ambient light, and the image data of the portion other than the document placing area may become a white image.

The reading sensor is roughly classified into a CCD method and a CIS (Control Image Sensor) method, and the CIS method is more susceptible to ambient light than the CCD method. 1 and 2 are explanatory views for explaining the influence of ambient light. In each of FIGS. 1 and 2, (A) is a schematic view showing the positional relationship between the document holding member and the document placing surface, and (B) is a state in which the document holding member is open and the document is placed. It is a figure which showed an example of the image data obtained when the whole document placing surface was scanned without placing. Further, FIG. 1 shows a case where a CCD is adopted as a reading sensor, and FIG. 2 shows a case where CIS is adopted as a reading sensor.

The document mat 61, which functions as a document holding member, can be moved in contact with and detached from the upper surface of the platen glass 161 on which the document is placed, and can be opened and closed on one end side of the reading device (this is the back side of the device). It is supported. In FIG. 1B, the image data DA is image data obtained by turning on the light source provided in the reading sensor when a CCD is used as the reading sensor, and the vertical direction in the drawing is the sub-scanning direction. The left-right direction in the figure is the main scanning direction. The image indicated by the image data DA is an overall black image, and the white image WH extends in a strip shape in the sub-scanning direction at a position away from the back side of the platen glass 161. The white image part is a part affected by ambient light, but the part is relatively narrow.

The image data DB shown in FIG. 2B is image data obtained by turning on the light source included in the reading sensor when CIS is adopted as the reading sensor. The image shown by the image data DB is a black image (gray image) BL at a distance LA or less from the back side of the platen glass 161 and a white image at other parts. The white image portion affected by the ambient light is relatively wide, but the range of the distance LA or less from the back side of the platen glass 161 is not a white image. Therefore, within this range, the document placement area can be specified even when the document holding member is open.

Further, as shown in FIG. 1 (B), even if the reading sensor is a CCD, the image indicated by the image data DA in the range of the distance LA or less from the back side of the platen glass 161 is also a black image. If it is inside, the document placement area can be specified even when the document holding member is open. Therefore, it can be said that the range is not affected by ambient light in terms of specifying the document placement area.

The image reading apparatus according to an aspect of the present invention includes a pressing member which is openably supported on the original Kono face, toward the document placed on the document placement surface, the main scanning direction A document reading unit that has a light source that emits light along the line, scans the document while moving the light source in the sub-scanning direction, receives reflected light from the document, and reads an image of the document. In the image data showing the document images at each position in the sub-scanning direction from the document scanning start position by the document scanning unit in the sub-scanning direction, an image of a predetermined value or less indicating a black image appears from the document scanning start position. The area up to the position in the sub-scanning direction is the image area in which the document is read, and the document size detection unit that detects the distance in the sub-scanning direction of the image area as the size of the document in the sub-scanning direction, and the operation unit. By correcting the image data obtained by reading by the operation reception unit that accepts user input and the document reading unit, the document up to a predetermined position that is inside the contour of the document image indicated by the image data. Based on the frame erasing processing unit that erases the surrounding image including the image portion and the document size detected by the document size detection unit, it is determined that the document placed on the document mounting surface is an ID card. In this case, or when the user's designation that the document to be read is an ID card is accepted by the operation reception unit, the range of erasure up to the predetermined position by the frame erasing processing unit is predetermined. When the document size detecting unit is in an open state where the document holding member is separated from the document placing surface, the document size detecting unit is provided with a limiting unit for reducing the value by the value of the image or prohibiting the erasing by the frame erasing processing unit. Using the image data obtained by reading by the document reading unit within a range of a predetermined distance in the main scanning direction from the one end side of the document mounting surface while the light source is lit. The size of the original is detected in the sub-scanning direction.

According to the present invention, in a state where the light source is lit when the document holding member is open, the document holding member is supported in advance with respect to the document placing surface from one end side of the apparatus main body. The size of the document in the sub-scanning direction is detected based on the image data obtained by scanning by the document reading unit within a predetermined distance range.

Since the place near the one end side of the document placing surface is not affected by the ambient light even when the document holding member is open, the document placing area in the sub-scanning direction can be accurately specified. Therefore, even when the document holding member is open, the size of the document in the sub-scanning direction can be accurately detected. Therefore, it is not necessary to newly install a dedicated sensor for detecting the size of the document in the sub-scanning direction, so that it is possible to suppress an increase in cost.

It is explanatory drawing for demonstrating the influence of ambient light. It is explanatory drawing for demonstrating the influence of ambient light. It is a functional block diagram which roughly showed the main internal structure of the image forming apparatus which comprises the image reading apparatus which concerns on 1st Embodiment of this invention. It is a perspective view which showed the appearance of the image forming apparatus which comprises the image reading apparatus which concerns on 1st Embodiment. An example of a state in which a manuscript is placed on a platen glass is shown, and is a view seen from above. It is explanatory drawing for demonstrating the method of detecting the size of a document in the main scanning direction. It is explanatory drawing for demonstrating the method of detecting the size of a document in a sub-scanning direction. It is explanatory drawing for demonstrating the method of detecting the size of a document in a sub-scanning direction. It is a functional block diagram which roughly showed the main internal structure of the image forming apparatus which comprises the image reading apparatus which concerns on 2nd Embodiment.

Hereinafter, the image reading device according to the embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a functional block diagram schematically showing a main internal configuration of an image forming apparatus including the image reading apparatus according to the first embodiment of the present invention, and FIG. 4 is a functional block diagram according to the first embodiment. It is a perspective view which showed the appearance of the image forming apparatus provided with the image reading apparatus.

The image forming apparatus 1 is a multifunction device having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes a control unit 10, a document feeding unit 6, a document reading unit 5, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, an operation unit 47, and a mat open / close detection sensor 51.

A case where the document reading operation is performed by the image forming apparatus 1 will be described. The document reading unit 5 optically reads the image of the document conveyed by the document feeding unit 6 or the document placed on the platen glass 161 and generates image data. The image data generated by the document reading unit 5 is stored in an image memory or the like (not shown). The platen glass 161 is an example of a document placing surface within the scope of claims.

Further, the document feeding section 6 is configured to be openable and closable on the upper surface of the document reading section 5 by a hinge or the like, and the document feeding section 6 is provided with a document mat 61 and reads a document placed on the platen glass 161. In some cases, it functions as a document holding member cover. The document reading unit 5 is provided with a mat open / close detection sensor 51 for detecting the open / closed state of the document mat 61. The manuscript mat 61 is an example of a manuscript holding member within the scope of claims.

The document reading unit 5 has a light source that emits light toward the document placed on the platen glass 161 along the main scanning direction, and moves the light source line by line in the sub-scanning direction to move the document. It scans and receives the reflected light from the document to read the image of the document. Either a CCD (Charge Coupled Device) or a CIS (Contact Image Sensor) may be adopted for the document reading unit 5, but in the present embodiment, a case where a CCD is adopted will be described.

A case where the image forming operation is performed by the image forming apparatus 1 will be described. Based on the image data generated by the document reading operation, the image data received from the computer as an external device connected to the network, and the like, the image forming unit 12 records as a recording medium to be fed from the paper feeding unit 14. Form a toner image on paper.

The fixing portion 13 fixes the toner image on the recording paper by thermocompression bonding, and the fixing treatment of the recording paper is discharged to the discharge tray 151. The paper feed unit 14 includes a paper feed cassette.

The operation unit 47 receives instructions such as an image formation operation execution instruction from the operator for various operations and processes that can be executed by the image forming apparatus 1. The operation unit 47 includes a display unit 473 that displays operation guidance and the like to the operator. The display unit 473 is a touch panel, and the operator can operate the image forming apparatus 1 by touching the buttons and keys displayed on the screen.

The control unit 10 includes a processor, a RAM (Random Access Memory), a ROM (Read Only Memory), and a dedicated hardware circuit. The processor is, for example, a CPU (Central Processing Unit), an ASIC (Application Specific Integrated Circuit), an MPU (Micro Processing Unit), or the like. The control unit 10 includes a control unit 100, an operation reception unit 101, and a document size detection unit 102.

The control unit 10 functions as a control unit 100, an operation reception unit 101, and a document size detection unit 102 by operating according to a control program stored in the HDD 92 (Hard disk drive). However, the control unit 100 and the like can be configured by hardware circuits, regardless of the operation according to the control program by the control unit 10. Hereinafter, the same applies to each embodiment unless otherwise specified.

The control unit 100 controls the overall operation of the image forming apparatus 1. The control unit 100 is connected to a document feeding unit 6, a document reading unit 5, an image forming unit 12, a fixing unit 13, a paper feeding unit 14, an operation unit 47, an HDD 92, and a mat open / close detection sensor 51, and drives each of these units. Perform control, etc.

The operation reception unit 101 receives an operation input from the user via the operation unit 47.

The document size detection unit 102 detects the size of the document placed on the platen glass 161.

FIG. 5 shows an example of a state in which the original is placed on the platen glass 161 and is viewed from above. The original M1 (for example, an ID card) is placed along the back corner C1 of the platen glass 161. Indicates the state in which it is being used. The back side is one end side of the main body of the image forming apparatus 1 in which the document mat 61 is supported openly and closably with respect to the document placing surface. Hereinafter, a means for detecting the size of the document will be described by taking as an example a case where the size of the document M1 placed on the platen glass 161 is detected according to the back corner C1.

(1) When there is a user instruction to start scanning the document M1 placed on the platen glass 161 while the document mat 61 is open.

(1-1) Detection of the size of the document M1 in the main scanning direction will be described.

When the control unit 100 determines that the document mat 61 is open based on the detection signal obtained from the mat open / close detection sensor 51, the operation reception unit 101 reads the document M1 placed on the platen glass 161. Upon receiving the start user instruction, by controlling the operation of the document scanning unit 5, the document M1 placed on the platen glass 161 is placed at the document scanning start position (the document scanning start position () without turning on the light source of the document scanning unit 5. For example, a line extending in the main scanning direction, for example, one line is read from the position near the back corner C1 in the sub-scanning direction, and the image data obtained by reading by the document reading unit 5 is stored as comparative image data.

Subsequently, the control unit 100 turns on the light source of the document reading unit 5 by controlling the operation of the document reading unit 5, and turns off the document M1 placed on the platen glass 161 in the main scanning direction. One line, which has the same number of lines, is read, and the image data obtained by reading by the document reading unit 5 is taken in. The document size detection unit 102 compares the captured image data with the image data as comparative image data, and detects the size of the document M1 in the main scanning direction.

For example, the document size detection unit 102 compares the captured image data with the image data as comparative image data, and identifies the area where the data is different as the document placement area, so that the document M1 in the main scanning direction Detects the size of.

FIG. 6A is an example of image data D1 as comparative image data obtained by reading by the document reading unit 5 without turning on the light source in a state where the document M1 is placed on the platen glass 161. FIG. 6B shows an example of image data D2 obtained by reading by the document reading unit 5 by turning on the light source while the document M1 is placed on the platen glass 161.

In the image shown by the image data D1 as the comparative image data, the portion P1 in which the ambient light is incident on the reading sensor is a white image, and the other portions are black images. On the other hand, the image data D2 includes not only the portion P1 in which the ambient light is incident on the reading sensor, but also the portion in which the reflected light emitted from the light source and reflected on the document M1 (not shown) is incident on the reading sensor. P2 is also a white image.

Therefore, the document size detection unit 102 compares the image data D1 and the image data D2, and identifies a region (part P2) in which the data is different between the image data D1 and the image data D2 as the document placement region. The document size detection unit 102 detects the distance S1 (the length of the portion P2) from the back side of the platen glass 161 (not shown) as the size of the document M1 in the main scanning direction.

(1-2) Detection of the size of the document M1 in the sub-scanning direction will be described.

When the control unit 100 determines that the document mat 61 is open based on the detection signal obtained from the mat open / close detection sensor 51, the operation reception unit 101 starts reading the document placed on the platen glass 161. When the user's instruction is received, the light source of the document reading unit 5 is turned on by controlling the operation of the document reading unit 5, and the document reading unit 5 is read from the document scanning start position in the sub-scanning direction. The document reading operation is performed while moving in the sub-scanning direction to the end of the contact glass 161 in the sub-scanning direction opposite to the start position.

Subsequently, as shown in FIG. 7, the control unit 100 is within a predetermined distance L1 (for example, about 3 mm) from the back side of the platen glass 161 in a state where the light source is lit (in the figure). , The area indicated by the diagonal line), the image data obtained by scanning by the document scanning unit 5 is captured. The document size detection unit 102 detects the size of the document in the sub-scanning direction by specifying the document placing area (the area up to the rear end of the document) in the sub-scanning direction based on the captured image data. The above range is a range that is not affected by ambient light when the light source is turned on and the document reading unit 5 reads the document while the document mat 61 is open. The distance L1 indicating the range is determined in advance by an experiment, and is determined, for example, to be equal to or less than the distance LA shown in FIG.

FIG. 8 shows that the document M1 is read by the document reading unit 5 within a predetermined distance L1 from the back side of the platen glass 161 by turning on the light source while the document M1 is placed on the platen glass 161. It is a figure which showed an example of the obtained image data D3.

In the image indicated by the image data D3, the portion P3 in which the reflected light reflected by the document M1 is incident on the reading sensor is a white image (when the document M1 is blank), and the other portions P4 are It becomes a black image. That is, since the portion of the platen glass 161 from the document reading start position on the left side to the distance S2 becomes white, the document size detecting unit 102 detects the distance S2 as the size of the document M1 in the sub-scanning direction. For example, the document size detection unit 102 has a predetermined value (for example, 256) indicating a black image from the document scanning start position in the image data D3 indicating the document image at each position in the sub-scanning direction from the document scanning start position. In the case of gradation, the area up to the position in the sub-scanning direction in which the following images appear 20) is defined as the image area in which the document M1 is read, and the sub-scanning direction distance of the area is detected as the size in the sub-scanning direction of the document M1. ..

(2) When the document mat 61 is closed.

(2-1) Detection of the size of the document M1 in the main scanning direction will be described.

When the control unit 100 determines that the document mat 61 is about to be completely closed based on the detection signal obtained from the mat open / close detection sensor 51, the control unit 100 controls the operation of the document reading unit 5 to control the document reading unit 5. The light source is turned on, and the document M1 placed on the platen glass 161 is read from the document reading start position by a line extending in the main scanning direction, for example, one line.

Subsequently, the control unit 100 captures the image data obtained by scanning by the document scanning unit 5, and the document size detecting unit 102 detects the size of the document M1 in the main scanning direction based on the captured image data. ..

In the place where the document M1 exists, the light emitted from the light source is reflected by the document M1, and in the place where the document M1 does not exist, the light emitted from the light source is not reflected by the document M1. Therefore, by detecting the presence or absence of reflected light with the reading sensor, the document placement area in the main scanning direction can be specified, and the size of the document M1 in the main scanning direction can be detected.

The light source is turned on immediately before the original mat 61 is completely closed to detect the size of the original M1 in the main scanning direction. When the light source is turned on after the original mat 61 is completely closed, the original M1 is detected. This is because even in the portion where the document is not placed, the light is reflected by the document mat 61 and is erroneously detected as the reflected light from the document M1.

(2-2) Detection of the size of the document M1 in the sub-scanning direction will be described.

The document size detection unit 102 determines the document size in the sub-scanning direction of the document M1 from the information indicating the main scanning direction size and the sub-scanning direction size for a predetermined standard document size, and determines the document in the detected main scanning direction. Determine the original size in the sub-scanning direction corresponding to the size.

For example, the document size detection unit 102 determines that the document M1 is an ID card when the size of the document in the main scanning direction is 53.98 mm and matches the length of the short side of the ID card, which is a standard document size. Judging, the size of the document in the sub-scanning direction is determined to be 85.60 mm. In this case, the document size detection unit 102 holds 53.98 mm and 85.60 mm (international standard (ISO7810)) as the main scanning direction size and the sub scanning direction size for the ID card, which is a standard document size. It shall be.

Further, when the size of the document in the main scanning direction is 210 mm and matches the length of the short side of the A4 size, the document size detecting unit 102 determines that the document M1 is the A4 size and determines that the document M1 is in the sub-scanning direction. The size of the original is determined to be 297 mm. In this case, it is assumed that the document size detection unit 102 has 210 mm and 297 mm as the main scanning direction size and the sub scanning direction size for the standard document size A4 size.

According to the first embodiment, the document reading unit 5 reads the document mat 61 within a predetermined distance L1 from the back side of the platen glass 161 while the light source is lit when the document mat 61 is open. By specifying the document placement area in the sub-scanning direction based on the image data obtained in the above, the size of the document M1 in the sub-scanning direction is detected.

Since the place near the back side of the platen glass 161 is not affected by the ambient light even when the document mat 61 is open, the document placement area in the sub-scanning direction can be accurately specified. Therefore, even when the document mat 61 is open, the size of the document M1 in the sub-scanning direction can be accurately detected. Therefore, it is not necessary to newly install a dedicated sensor for detecting the size of the document M1 in the sub-scanning direction, so that an increase in cost can be suppressed. Further, the size of the document M1 in the main scanning direction can be accurately detected without being affected by the ambient light.

According to the document size detection process shown in the above embodiment, the above-mentioned accurate document size detection is possible regardless of whether the document reading unit 5 adopts the method of CCD or CIS.

By the way, some existing copiers and the like are equipped with a system capable of executing a frame erasing processing function for erasing the periphery of the original M1, but in the case of an ID card, various information is described up to all four edges. When a process of erasing the periphery of the original M1 is performed by the frame erasing process, the frame erasing process erases the surrounding image up to a position slightly inside the contour of the scanned document image. Since it is often a setting, important information may be erased.

Therefore, as a second embodiment, as shown in FIG. 9, the control unit 10 may include a frame erasing processing unit 103 and a limiting unit 104.

The frame erasing processing unit 103 performs the existing frame erasing process described above. The frame erasing processing unit 104 corrects the image data obtained by scanning by the document scanning unit 5, so that the document image portion up to a predetermined position (for example, 5 mm) that has entered the inside of the contour of the document image. It is a setting to erase the surrounding image of the original image including.

Similar to the first embodiment, the control unit 10 operates according to the control program stored in the HDD 92 to control the control unit 100, the operation reception unit 101, the document size detection unit 102, the frame erasing processing unit 103, and the limitation. It functions as a unit 104. However, the control unit 100 and the like can be configured by hardware circuits, regardless of the operation according to the control program by the control unit 10.

In the limiting unit 104, the size of the original M1 placed on the platen glass 161 is a predetermined size, for example, the size of an ID card, based on the original size detected by the original size detecting unit 102, and the original M1 Is an ID card, or when the operation reception unit 101 accepts a user's designation that the document M1 to be read is, for example, an ID card, the distance from the outline of the document image to the predetermined position is reached. The distance is reduced by a predetermined value (for example, when the distance to the predetermined position is 5 mm, the predetermined value is set to 2 mm), or the distance is predetermined from the outline of the original image. The erasing process up to the position is prohibited.

As a result, when the original M1 is determined to be an ID card, or when the user instructs "ID copy", for example, the erasing range is narrowed from 5 mm to 3 mm, or the erasing is prohibited. Therefore, it is possible to avoid erasing important information existing in the vicinity of the outline of the original image.

Further, the present invention is not limited to the configuration of the above-described embodiment, and various modifications can be made. Further, in the above-described embodiment, a multifunction device is used as an embodiment of the image reading device according to the present invention, but this is only an example, and has, for example, a copy function, a facsimile function, a scanner function, and the like. Other image reading devices may be used.

Further, in the above-described embodiment, the configuration and processing shown by the above-described embodiment with reference to FIGS. 1 to 9 are merely one embodiment of the present invention, and the present invention is not intended to be limited to the configuration and processing.

1 Image forming device 5 Document reading unit 51 Mat open / close detection sensor 61 Document mat 100 Control unit 101 Operation reception unit 102 Document size detection unit 103 Frame erasing processing unit 104 Limiting unit 161 Platen glass

Claims (4)

A pressing member which is openably supported on the original Kono surface,
It has a light source that emits light along the main scanning direction toward the document placed on the document placing surface, and scans the document while moving the light source in the sub-scanning direction to scan the document. A document reader that receives reflected light from the light source and reads the image of the document.
In the image data showing the document images at each position in the sub-scanning direction from the document scanning start position by the document scanning unit in the sub-scanning direction, an image of a predetermined value or less indicating a black image appears from the document scanning start position. The area up to the position in the sub-scanning direction is the image area in which the document is read, and the document size detection unit that detects the distance in the sub-scanning direction of the image area as the size of the document in the sub-scanning direction .
An operation reception unit that accepts user input from the operation unit,
By correcting the image data obtained by scanning by the document scanning unit, the surrounding image including the document image portion up to a predetermined position that is inside the contour of the document image indicated by the image data is erased. Frame erasing processing unit and
A user who determines that the document placed on the document placing surface is an ID card based on the document size detected by the document size detector, or that the document to be read is an ID card. When the designation by the operation receiving unit is received by the operation receiving unit, the range of erasing to the predetermined position by the frame erasing processing unit is reduced by a predetermined value, or the frame erasing processing unit performs the above. Equipped with a restriction part that prohibits erasure,
The document size detecting unit is in the main scanning direction from the one end side of the document mounting surface in a state where the light source is lit when the document holding member is in an open state away from the document mounting surface. An image reading device that detects the size of a document in the sub-scanning direction by using the image data obtained by scanning by the document reading unit within a range of a predetermined distance. The image reading device according to claim 1, wherein the predetermined distance range is a predetermined range that is not affected by ambient light. Further, the document size detecting unit opens the image data obtained by reading by the document reading unit and the document pressing member in a state where the light source is not lit when the document pressing member is open. When the light source is lit, the image data obtained by reading by the document reading unit is compared with the image data, and the area that is different in the image data portion is specified as the document placing area. The image reading device according to claim 1 or 2, wherein the size of the original is detected in the main scanning direction. The document size detection unit further turns on the light source immediately before the document holding member is completely closed, and is based on image data obtained by scanning by the document reading unit while the light source is lit. To detect the size of the document in the main scanning direction,
When the document size detection unit detects the size of the document in the main scanning direction, the document size in the sub-scanning direction of the document is set to the size in the main scanning direction for a predetermined standard document size and the size in the main scanning direction. The image reading device according to any one of claims 1 to 3, wherein the size of the document in the sub-scanning direction corresponding to the detected size of the document in the main scanning direction is determined from the information indicating the size in the sub-scanning direction.

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