JPH10257256A - Original size detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a defect that an ADF(automatic document feeder) is completely closed till an image processing means starts its operation and the size of an original cannot be detected. SOLUTION: An engine CPU 71 starts an image read operation by a scanner section 2 in response to an activated opening/closing detection switch 80 and gives a signal that denotes start of image processing to an image processing device 73 via a signal line 78. The image processing device 73 applies processing to input image data from the scanner section 2 in response to a start signal from the engine CPU 71. Image data after the processing are stored in a memory 79 provided in the image processing device 73. When a main CPU 70 receives information of the activated opening/closing detection switch 80 from the engine CPU 71 via a communication line 72 after the image processing by the image processing device 73 is stopped, the main CPU 70 reads the image data stored in the memory 79 and discriminates the size of the original.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document size detecting device for detecting the size of a document set on a document table.

[0002]

2. Description of the Related Art In recent years, a so-called multifunction machine has been provided in which one image forming apparatus has a plurality of functions such as a copy function, a printer function, and a facsimile function. In general, a multifunction peripheral has an engine CPU that controls mechanical operations such as a scanner unit for reading a document image and a print unit for outputting an image on a predetermined sheet of paper, and performs a predetermined process on image data. And a main CPU that controls signal processing such as an image processing device and a facsimile function unit for achieving a facsimile function. The main CPU and the engine CPU communicate commands at regular intervals, and exchange necessary data between them.

Some of such multifunction peripherals have a function of detecting the size of a document set on a document table. Various techniques have been adopted as a technique for detecting the document size. For example, when a document cover for covering a document is closed after the document is set, an image of one line along the main scanning direction is read, and the size of the document is determined based on the read image data.

FIG. 6 shows a main CPU for detecting a document size.
FIG. 3 is a diagram showing a flow of control by an engine CPU. Referring to FIG. 6, before the user closes the document cover, the main CPU initializes data necessary for image processing performed by the image processing device. The main CPU is then on standby until a signal indicating that the document cover is closed is input from the engine CPU.

On the other hand, the engine CPU monitors the output of an open / close detection switch for detecting the opening / closing of the document cover.
The open / close detection switch is turned on when the angle between the document cover and the document table becomes equal to or less than a predetermined angle. The engine CPU turns on the light source for illuminating and scanning the original in response to the opening / closing detection switch being turned on. Light from the light source is reflected by the document and guided to the CCD sensor. The CCD sensor generates analog image data corresponding to the density of a document image based on the incident light. The analog image data is converted into digital image data representing the pixel density in 256 tones of 0 to 255 (FFh), for example, and then input to the image processing device.

The main CPU and the engine CPU communicate commands at a fixed period of, for example, 100 msec. The engine CPU determines that the document cover is closed by this communication (when the open / close detection switch is turned on). Is transmitted to the main CPU. Main CP
U responds to the signal input from the engine CPU,
Activate the image processing device. Then, predetermined processing is performed on the digital image data input thereafter by the image processing device. The processed image data is temporarily stored in a buffer memory or the like.

The main CPU reads out the image data stored in the buffer memory in a predetermined order, binarizes the read out digital image data with a predetermined threshold value, and firstly outputs low-level data (white data). ) Finds a portion where a predetermined number of data are continuous. And the main CP
U regards the found portion as a document edge, and determines the document size based on the position of the document edge.

[0008]

As described above, in the method of detecting the document edge and determining the document size based on the position of the document edge, the data processed by the image processing device includes the document cover. Must be data obtained before it is completely closed. This is because the surface of the document cover facing the document plate is usually formed in white, and when the document cover is completely closed, light from the light source is reflected by the document cover and enters the CCD sensor. This is because the portion is represented by white data and the edge of the document cannot be detected as described above.

However, the main CPU and the engine CPU
Are communicating at a constant period of 100 msec, a delay of up to 100 msec occurs from when the open / close detection switch is turned on to when a signal to the effect that the open / close detection switch is turned on is transmitted to the main CPU. there is a possibility. If this delay time is long, the fact that the open / close detection switch has been turned on is transmitted from the engine CPU to the main CPU, and when the main CPU operates the image processing device, the document cover is already completely closed. There is a risk.

To avoid such a problem, it is conceivable to shorten the cycle of command communication between the main CPU and the engine CPU. However, if the communication cycle is shortened, the load on both CPUs is increased by this communication, and the time required for other software processing may be prolonged, which may hinder control of other parts.

An object of the present invention is to provide a copying machine or a facsimile machine in which a CPU to which an on / off signal from an open / close detection switch is input and a CPU for controlling an image processing device are separately provided. Another object of the present invention is to provide a document size detecting device capable of detecting a document size satisfactorily regardless of the cycle of command communication between the two CPUs.

[0012]

According to a first aspect of the present invention, there is provided an original size detecting apparatus for setting an original to be read from an image, a closed state covering the original table, and an original. A document cover displaceably provided in an open state in which a document can be set on the table, image reading means for reading an image of the document set on the document table and generating image data corresponding to the document density, and image reading means An image reading apparatus comprising: a first control unit for controlling the operation of the image processing unit; an image processing unit for performing predetermined image processing on the image data generated by the image reading unit; and a second control unit for controlling the operation of the image processing unit A document size detecting device adapted to detect a size of a document set on a document table, wherein the first control means transmits a predetermined signal from the first control means to the image processing means; A signal line connecting the image processing means, a switch detecting the switching of the document cover from open to closed, and a closing detection means for inputting the detection signal to the first control means; Document size determining means for determining the size of the document based on the image data, wherein the first control means responds to the input of the detection signal from the close detection means to the first control means. The operation is started, and a signal for starting an image processing operation required for document size detection is input from the first control unit to the image processing unit via a signal line.

According to the first aspect of the present invention, when the document size is detected, switching of the document cover from the open state to the closed state is detected, and the detection signal is sent from the close detection means to the first state. In response to the input to the control means, the first
The image reading operation is started under the control of the control means, and an operation start signal is input from the first control means to the image processing means via the signal line to start the image processing operation. That is, as soon as the close detecting means detects that the document cover is closed, the operation of the image processing means is started immediately.

Thus, data necessary for judging the size of the original is obtained from the time when the original cover is switched from the open state to the closed state by the close detecting means until the original cover is completely closed. can do. Therefore, unlike the prior art, the document cover is completely closed before the operation of the image processing means is started, and there is no problem that the edge of the document (document size) is not detected.

When the document size is detected, a signal indicating that the document cover is closed is given from the first control means to the second control means. In response to this signal, the second control means controls the operation of the image processing means. In the case of the configuration for starting, the command communication performed between the first control means and the second control means in order to obtain data necessary for determining the document size before the document cover is completely closed. It is necessary to shorten the cycle of. According to the above configuration, since the acquisition of data required for determining the document size and the second control unit are irrelevant, the cycle of command communication performed between the first control unit and the second control unit can be shortened. You don't have to.

Further, the invention according to claim 2 further includes storage means for holding the image data generated by the image processing means, wherein the document size determination means performs the image processing operation by the image processing means. 2. The apparatus according to claim 1, wherein the size of the document is detected based on the image data stored in the storage unit when the document is stopped.
The document size detection device described in FIG.

According to the second aspect of the present invention, since the determination of the document size by the document size determination means is performed based on the image data stored in the storage means, the operation of the image processing means is stopped by the document size determination means. It can be operated later at any timing.

[0018]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a schematic cross-sectional view showing an internal configuration of an image forming apparatus to which a document size detecting device according to an embodiment of the present invention is applied. FIG. 2 is a partial perspective view of the image forming apparatus shown in FIG.

This image forming apparatus is a so-called multifunction machine having a copying function, a facsimile function, and a printer function, and serves as an apparatus main body 1 and image reading means provided above the apparatus main body 1 for reading a document image. Scanner unit 2, an automatic document feeder (hereinafter, referred to as “ADF”) 3 mounted on the upper surface of the scanner unit 2, and an apparatus main body 1.
And a recording paper discharge unit 4 for receiving a recorded paper on which an image is recorded and discharged. As shown in FIG. 2, a display unit 51,
An operation unit 5 having various operation keys such as a ten key 52 and a start key 53 is arranged.

The ADF 3 is provided above the scanner unit 2 for automatically supplying a document to a transparent document table 21 disposed on the upper surface of the scanner unit 2. A
The DF 3 also serves as a cover for the document table 21, and the front side is opened upward, centering on the rear side, so that the document can be manually placed on the document table 21 (see FIG. 2). Also, as shown in FIG.
3 is provided with an open / close detection switch 80 for detecting the open / close state of the switch 3. The open / close detection switch 80 is turned off when the angle of the ADF 3 with respect to the upper surface of the scanner unit 2 exceeds a predetermined angle when the ADF 3 is opened and closed, and is turned on when the angle is smaller than the predetermined angle. .

An original setting surface 31 on which an original to be read by the scanner unit 2 is set is provided on the upper surface of the ADF 3.
Are formed. In FIG. 1, a document inlet 32 is formed on the left side of the document setting surface 31, and a document outlet 33 is formed on the right side of the document setting surface 31. Further, the ADF 3 is provided with a transport belt 34 for arranging a document at a predetermined position on the document table 21. The transport belt 34 is provided so as to face the document table 21 when the ADF 3 is closed.
The surface opposite to is white.

When a document is set on the document table 21 using the ADF 3, the document is set on the document setting surface 31 with the ADF 3 closed, and a start key 53 provided on the operation unit 5 is pressed. . Then, the documents set on the document setting surface 31 are taken in one by one from the document inlet 32, and are arranged on the document table 21 by the transport belt 34. Then, after the document image is read by the scanner unit 2, the document image is sent out from the document table 21 by the transport belt 34 and discharged from the document discharge port 33. At this time, the size of the original is, for example, the original setting surface 31 of the ADF 3.
Is detected based on the outputs of the plurality of reflection sensors arranged in the first and second sensors.

On the other hand, when the original is manually set on the original platen 21, the front side of the ADF 3 is
Expose 1 Then, the document is transferred to, for example,
After the document is set in accordance with the left rear corner of the ADF 3, the front side of the ADF 3 is pulled down and the document table 21 is covered with the ADF 3. Thereafter, when the start key 53 is pressed, the document image is read by the scanner unit 2. At this time, the size of the document set on the document table 21 is detected by executing a document size detection process described later.

The scanner section 2 is provided with a light source 22 for illuminating a document on a document table 21. Light source 22
Is constituted by, for example, a fluorescent tube elongated in the main scanning direction (the front-back direction in FIG. 1), and is configured to be reciprocally displaceable below the document table 21 in the sub-scanning direction (left-right direction in FIG. 1). . The light generated from the light source 22 is
Is reflected by The reflected light is reflected by a first reflecting mirror 23 that moves together with the light source 22, and its optical path is turned back by a second reflecting mirror 25 and a third reflecting mirror 26 fixed to a moving frame 24 before being incident on a CCD sensor 27. Is done.
The CCD sensor 27 generates analog image data based on the incident light.

The apparatus main body 1 is provided with a printing unit 10 for outputting an image on a predetermined sheet. Printing unit 10
1 includes a cylindrical photoreceptor 11 that is rotated at a constant speed clockwise in FIG. 1 at the time of image output, a main charger 12, a developing device 13, and a transfer roller 14 that are sequentially arranged along the rotation direction of the photoreceptor 11. And the main charger 1
A laser scanning unit 15 that exposes the surface of the photoconductor 11 with laser light is provided between the developing unit 2 and the developing device 13.

The photoconductor 11 is driven to rotate, and the surface of the photoconductor 11 uniformly charged by the main charger 12 is exposed by the laser beam from the laser scanning unit 15. The laser scanning unit 15 corresponds to image data created by the scanner unit 2 as described above, image data input via a communication line, and image data input from an external device such as a personal computer (not shown). The surface of the photoreceptor 11 is exposed by the modulated laser light. As a result, an electrostatic latent image corresponding to the image to be output is formed on the surface of the photoconductor 11. The photoreceptor 11 on which the electrostatic latent image is formed next faces the developing device 13, and the electrostatic latent image is developed into a toner image. As the photoconductor 11 further rotates, the toner image formed on the surface of the photoconductor 11 faces the transfer roller 14.

On the other hand, the apparatus main body 1 is provided with paper feed cassettes 61 and 62 each capable of storing a plurality of sheets. In synchronization with the above-described toner image forming operation in the printing unit 10, a sheet according to the document size and the copy magnification is fed out onto the transport path 63 from one of the sheet feeding cassettes 61 and 62. The sheet fed out onto the conveyance path 63 is temporarily stopped by the registration roller 64, and then fed toward the photoconductor 11 at a timing when the toner image on the surface of the photoconductor 11 is aligned with the transfer roller 14. Then, by the operation of the transfer roller 14, the photosensitive member 1
The toner image on one surface is transferred to the fed sheet.

The sheet on which the toner image has been transferred is
6 and a fixing device 18 including a pressure roller 17.
The toner on the sheet is fixed on the sheet by heating by the heat roller 16 and pressing by the pressure roller 17. The sheet after the fixing process is discharged by a discharge roller 19 to a recording sheet discharge section 4 formed on the upper surface of the apparatus main body 1. FIG.
FIG. 2 is a block diagram showing an electrical configuration of the apparatus main body 1.

The main body 1 of the apparatus has a main CPU 70 for overall control of each section of the image forming apparatus shown in FIG. 1, and an engine CPU 71 for controlling operations of mechanical parts such as the scanner section 2 and the print section 10. Provided. The main CPU 70 and the engine CPU 71 are connected by a command communication line 72 and have a predetermined cycle (for example, 100
The necessary control data is exchanged between each other by the command communication being performed within 200 msec.

The apparatus main body 1 includes an image processing device 73 (corresponding to image processing means) for performing predetermined processing on image data generated by the scanner unit 2, a modem 74 and an NCU (Network Control Unit). And a facsimile function unit 76 including the facsimile unit 75. The facsimile function unit 76 is connected to the main CPU 70, and image data received from the external communication line 77 is input to the main CPU 70 via the facsimile function unit 76. When an external device (not shown) such as a personal computer is connected to the apparatus main body 1, image data created by the external device is input to the main CPU 70.

When a copy image of a document set on the document table 21 (see FIG. 1) is formed on paper, the engine CPU
The scanner unit 2 is controlled by 71, and analog image data based on the reflected light from the original is generated by the CCD sensor 27 (see FIG. 1). The generated analog image data is converted into digital image data representing the density of each pixel in 256 gradations of, for example, 0 to 255 (FFh), and then input to the image processing device 73.

On the other hand, the main CPU 70 sends a signal to the image processing device 73 to start image processing. The image processing device 73 starts image processing in response to the start signal from the main CPU 70. Main CPU 70
Generates a command necessary for drive control of the printing unit 10 based on the image data processed by the image processing device 73 and gives the command to the engine CPU 71. The engine CPU 71 controls the printer unit 10 based on a command given from the main CPU 70 to output an image corresponding to the document image on a sheet.

As described above, when a document image is read in order to obtain a copy image, the operation of the image processing device 73 is controlled by the main CPU 70 as the second control means. However, if the size of the document set on the document table 21 is detected, the image processing device 7
The operation 3 is controlled by the engine CPU 71. One of the features of this embodiment is that the operation of the image processing device 73 at the time of detecting the document size is controlled by the engine CPU 71 as first control means.
The configuration for this will be described with reference to FIG.

Engine CPU 71 and Image Processing Device 7
3 is connected by a communication line 78. Further, an on / off signal from an opening / closing detection switch 80 for detecting opening / closing of the ADF 3 is input to the engine CPU 71. In response to the input of the ON signal from the open / close detection switch 80, the engine CPU 71 controls the scanner unit 2 to read an image of one line of the document, and starts / stops image processing via the communication line 78. A signal to the effect is given to the image processing device 73. The image processing device 73 processes the one-line image data generated by the scanner unit 2 and stores the processed data in a memory 79 provided in the image processing device 73. And the main CPU 7
0 determines the document size based on one line of image data stored in the memory 79.

Main CPU 7 at the time of document size detection
FIG. 4 shows the flow of the document size detection process in order to describe the operation of the engine CPU 71 and the engine CPU 71 in more detail. The document size detection process is performed on the document table 21 (see FIG. 1).
This is a process for automatically detecting the size of the document placed above, and is executed when the user opens the ADF 3 (see FIG. 1) and manually sets the document on the document table 21. .

Referring to FIGS. 3 and 4, main CPU
Reference numeral 70 performs initial settings of data necessary for image processing performed by the image processing device 73 before the document is set on the document table 21 and the ADF 3 is closed. Main CPU 70
Permits initialization of the image processing device 73, and then allows the operation start and stop of the image processing device 73 to be controlled by the engine CPU 71 thereafter.
Thereafter, the main CPU 70 is in a standby state until a signal indicating that the ADF 3 has been closed is input from the engine CPU 71.

On the other hand, the engine CPU 71 monitors the output of the open / close detection switch 80 for detecting whether the ADF 3 is open or closed. This open / close detection switch 80 is, as described above,
It is turned on when the angle formed between the ADF 3 and the document table 21 is smaller than a predetermined angle. Engine CPU
Reference numeral 71 denotes a light source 22 provided in the scanner unit 2 (FIG. 1) in response to the opening / closing detection switch 80 being turned on.
(See). At this time, the light source 22 remains stopped at the home position (the position shown in FIG. 2), and one line along the main scanning direction of the document is illuminated by the light from the light source 22, and an image of one line is read. .

The light applied to the document is reflected on the document surface and guided to the CCD sensor 27. Also, immediately after the open / close detection switch 80 is turned on, the ADF 3 is not in contact with the document table 21, so that the light applied to the portion other than the document (document table 21) is radiated to the outside. CCD sensor 2
7 generates analog image data based on the incident reflected light. The analog image data is obtained by setting each pixel density of the original portion to 0 to 255 (FFh).
The image data is converted into digital image data represented by 56 gradations, and the portion other than the original is converted into “255 (FFh)”. The converted digital image data is provided to the image processing device 73.

The engine CPU 71 turns on the light source 22 to start reading the image data, and the signal line 78
, A signal to start image processing is input to the image processing device 73. Since the start and stop of the operation of the image processing device 73 are controlled by the engine CPU 71 in advance, the image processing device 73 responds to the start signal from the engine CPU 71 by the input digital signal. A predetermined process is performed on the image data. The processed image data is stored in the memory 79 provided in the image processing device 73.
The contents of the memory 79 are rewritten one after another until the operation of the image processing device 73 is stopped.

When a predetermined time (for example, 25 to 75 msec) has elapsed since the opening / closing detection switch 80 was turned on,
The engine CPU 71 gives a signal to the effect that image processing is to be stopped to the image processing device 73 via a signal line 78. In response, the image processing by the image processing device 73 is stopped. At this time, data immediately before the operation of the image processing device is stopped is stored in the memory 79, and this data is used for determining the document size.

During the predetermined time from when the open / close detection switch 80 is turned on to when the image processing is stopped, the ADF 3 is placed on the document table 2 after the open / close detection switch 80 is turned on.
The time is set in consideration of the time required for the amount of light generated from the light source 22 to reach a steady state within the time required to come into contact with 1. The engine CPU 71 notifies the main CPU 70 that the open / close detection switch 80 has been turned on by command communication performed after the image processing by the image processing device 73 is stopped. The main CPU 70 having the function of the size judging means reads out the image data stored in the memory 79 in a predetermined order, binarizes the read out image data with a predetermined threshold value, and first sets the low-level data ( A portion where white data) continues for a predetermined number of data is found. Then, the main CPU 70
The found portion is regarded as the document edge, and the document size is determined based on the position of the document edge.

The original size is specifically determined as follows. Referring to FIG. 5, lengths La, Lb, and Lc of portions other than the original on one line indicated by a two-dot chain line differ depending on the original size. Therefore, ROMs (not shown) connected to the main CPU 70 have lengths La and L.
The numbers of image data respectively corresponding to b and Lc are stored in advance in association with the document sizes A4, B4 and A3, respectively.

When the document edge is detected as described above, the number of data from the image data corresponding to the pixel at the most upstream side in the main scanning direction to the image data corresponding to the pixel at the document edge is counted. You. Then, the counted number of image data is compared with the number of image data stored in the ROM to determine the document size. For example,
If the counted number of image data is substantially equal to the number of data corresponding to the length La, it is determined that the document set on the document table 21 is A4.

As described above, in the document size detection processing according to this embodiment, the scanner unit 2 is controlled by the engine CPU 71 in response to the signal indicating that the ADF 3 is to be closed being input from the open / close detection switch 80 to the engine CPU 71. Is controlled to start the image reading operation, and an operation start signal is input from the engine CPU 71 to the image processing device 73 via the signal line 78 to start the image processing operation. That is, depending on the user, ADF
When the switch 3 is closed, the operation of the image processing device 73 starts immediately when the open / close detection switch 80 is turned on.

As a result, data necessary for determining the document size can be obtained before the ADF 3 is completely closed. Therefore, unlike the related art, the ADF 3 does not come into contact with the document table 21 until the operation of the image processing device 80 is started, so that a problem that the document edge (document size) cannot be detected does not occur. .

When acquiring the data necessary for determining the document size, the operation of the image processing device 73 is controlled by the engine CPU 71 and
It has nothing to do with U70. Therefore, the main CPU 70 and the engine CPU 7 need to acquire data necessary for determining the document size before the ADF 3 is completely closed.
It is not necessary to shorten the cycle of the command communication performed between the communication device 1 and the device.

Further, the image data necessary for determining the document size is stored in a memory 79 provided in the image processing device 73 before the engine CPU 71 notifies the main CPU 70 that the open / close detection switch 80 has been turned on.
Is stored in Therefore, the determination of the document size by the main CPU 70 can be performed at an arbitrary timing after the operation of the image processing device 73 is stopped. therefore,
The cycle of command communication between the main CPU 70 and the engine CPU 71 can be extended within a range that does not affect software processing executed by the main CPU 70 and the engine CPU 71 other than the document size detection processing.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the main CPU responds to the fact that the open / close detection switch has been turned on from the engine CPU to the main CPU.
Are configured to read image data from a memory. However, not limited to this configuration, the engine CP
The state of the signal line connecting U and the image processing device is periodically checked by the main CPU, and the main CPU responds to detecting that a signal to stop the image processing is input from the engine CPU to the image processing device. Then, the image data may be read from the memory.

Further, in the above-described embodiment, the configuration in which the automatic document feeder which also serves as the document cover for covering the document is provided has been described as an example. It may be a cover. Further, in the above-described embodiment, the case where the document size detecting device according to the present invention is applied to a multifunction peripheral having a copy function, a facsimile function, and a printer function has been described as an example. The present invention is applicable to an image reading apparatus such as a copying machine and a facsimile machine.

In addition, various changes can be made within the scope described in the claims.

[0051]

According to the first aspect of the invention, there is no problem that the document cover is completely closed and the size of the document is not detected before the operation of the image processing means is started. . Further, since the acquisition of data required for determining the document size and the second control means are irrelevant, it is necessary to shorten the cycle of command communication performed between the first control means and the second control means. Absent.

According to the second aspect of the present invention, the determination of the document size by the document size determination means is performed based on the image data stored in the storage means. It can be operated later at any timing.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an internal configuration of an image forming apparatus to which a document size detecting device according to an embodiment of the present invention is applied.

FIG. 2 is a partial perspective view of the image forming apparatus shown in FIG.

FIG. 3 is a block diagram illustrating an electrical configuration of an apparatus main body provided in the image forming apparatus illustrated in FIG.

FIG. 4 is a diagram showing a flow of operations of a main CPU and an engine CPU when detecting a document size.

FIG. 5 is a diagram for explaining the principle of document size detection.

FIG. 6 is a diagram showing a conventional example of an operation flow of a main CPU and an engine CPU at the time of document size detection.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Device main body 2 Scanner part 3 Automatic document feeder (ADF) 22 Light source 27 CCD sensor 70 Main CPU 71 Engine CPU 72 Command communication line 73 Image processing device 78 Communication line 79 Memory 80 Open / close detection switch

Claims (2)

[Claims] An original cover for setting an original from which an image is to be read; an original cover movably provided between a closed state covering the original table and an open state in which an original can be set on the original table; Image reading means for reading an image of a set document and generating image data corresponding to the document density;
An image comprising first control means for controlling the operation of the image reading means, image processing means for performing predetermined image processing on image data generated by the image reading means, and second control means for controlling the operation of the image processing means A document size detection device applied to a reading device for detecting the size of a document set on a document table, comprising: a first control unit for transmitting a predetermined signal from the first control unit to the image processing unit; A signal line connecting to the image processing means, a closing detection means for detecting the switching of the document cover from open to closed, and inputting the detection signal to the first control means; Document size determining means for determining the size of the document based on the image data, wherein the first control means reads the image in response to the detection signal being input from the close detection means to the first control means. The document size is characterized in that the operation of the document taking means is started and a signal for starting an image processing operation required for document size detection is inputted from the first control means to the image processing means via a signal line. Detection device. 2. The image processing apparatus according to claim 1, further comprising a storage unit configured to store image data generated by the image processing unit, wherein the document size determination unit stores the image data in the storage unit when the image processing operation by the image processing unit is stopped. 2. The document size detecting device according to claim 1, wherein the size of the document is detected based on the stored image data.