JPH1175025A - Picture reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely judge the size of an original by operating the first scanning of the main scanning direction of an original in a state that a platen cover is not closed, operating the second scanning of the main scanning direction of the original in a state that the platen cover is closed, and deciding the original size based on the line sensor outputs obtained by the second time scanning. SOLUTION: When a platen cover is about to be closed, an opening/closing detecting sensor 36 detects it, and communicates it to a controlling part 30. The controlling part 30 operates a picture reading part 3 for sky shot scanning (first scanning) in a state that the platen cover is not closed. After original information in the first scanning is read, when the platen cover is completely closed, the opening/closing detecting sensor 36 detects the second stage, and the controlling part 30 operates the reading part 3 for the second scanning. The controlling part 30 detects the changing point of a signal by a preliminarily set original edge part detection threshold based on first and second data stored in a memory 37, and judges the size of an original according to the maximum width of the plural changing points.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reader for converting image information into digital information. Especially,
The present invention relates to an automatic document size detection function using an image reading device. The image reading device is mounted on a digital copying machine, digital facsimile, image scanner, or the like.

[0002]

2. Description of the Related Art FIG. 7 is a diagram showing a configuration example of a conventional digital copying machine, and FIG. 8 is a diagram showing an external configuration example of the copying machine. In FIG. 8, reference numeral 26 denotes a paper feed tray for automatically feeding a document, and reference numeral 26a denotes a document insertion slot. Reference numeral 1 denotes a platen cover for holding an original, which also serves as an automatic paper feed mechanism (ADF). Reference numeral 19 denotes an upper tray for holding copy paper, 19a denotes a middle tray for holding copy paper, and 20 denotes a lower tray for holding copy paper. Reference numerals 24 and 25 denote large-capacity paper feed trays (LCT-1500) and large-capacity paper feed trays (L
CT-1000). Note that 1500 and 1000 indicate the number of sheets of copy paper accommodated.

In FIG. 7, reference numeral 40 denotes an operation unit for setting the number of copies of a copy sheet, setting a magnification, setting a selected sheet, and the like. Reference numeral 17 denotes a manual feed tray for manually feeding copy paper (not shown in FIG. 8). Reference numeral 1 denotes a platen cover (ADF), 2 denotes an exposure lamp for irradiating a document, and 3 denotes an image reading unit that receives reflected light from the document and reads it as an image signal.

[0004] Reference numeral 23 denotes an image processing unit which converts a document image read by the image reading unit 3 into digital data and then performs predetermined image processing. 4 denotes a photosensitive drum which receives the image signal processed by the image processing unit 23. 5 is an image writing unit for writing an image in the image writing unit 5. In the image writing unit 4, a polygon mirror 7 scans the emitted beam in the main scanning direction.

Next, the configuration near the photosensitive drum 5 will be described. A developing unit 6 for attaching toner to the electrostatic latent image formed on the photosensitive drum 5; a transfer pole 8 for transferring the toner image formed on the photosensitive drum 5 to copy paper;
9 is a PSL for removing the charge of the toner by simultaneous exposure to transfer.
It is. Reference numeral 10 denotes a separation pole for separating the copy sheet from the photosensitive drum 5, and reference numeral 12 denotes a transport unit that transports the separated copy sheet. A fixing unit 13 fixes the copy paper conveyed from the conveyance unit 12.

Reference numeral 14 denotes a cleaning unit for removing toner and the like remaining on the photosensitive drum 5 even after transfer, 15 a PCL for removing electric charges remaining on the surface of the photosensitive drum 5 before charging, and 16 a photosensitive member. These are band electrodes that uniformly charge the surface of the body drum 5.

19 is an upper tray for storing copy paper,
Reference numeral 20 denotes a lower tray for storing copy sheets. Reference numeral 18 denotes a paper feeding unit for feeding copy paper from these trays;
Is a second paper feed unit for feeding copy paper.

Reference numeral 27 denotes a paper discharge tray for receiving copy paper on which an image has been transferred, reference numeral 21 denotes an ADU paper discharge / transport unit for returning the copy paper during double-sided copying, and reference numeral 22 denotes an ADU paper discharge / conveyance.
This is an ADU sheet feeding / conveying unit that returns the copy sheet conveyed from the conveying unit 21 to the entrance of the photosensitive drum while turning it upside down. Reference numeral 24 denotes a first large capacity paper feed tray (LCT-150
0) and 25 are the second large capacity paper feed trays (LCT-100).
0).

Reference numeral 30 denotes a control unit for controlling the overall operation of the image forming apparatus. As the control unit 30, for example, a microprocessor is used. An operation unit for setting the number of copies, enlargement magnification, copy density, manual setting of paper type, etc., and notifying the control unit 30. Here, the operation unit is shown outside the apparatus for simplicity, but specifically, FIG.
As shown in (1), the ADF 1 is usually provided on the mounting surface together with a copy number setting button, an enlargement magnification selection button, a paper selection button, and the like.

As the operation section 40, for example, a keyboard or a function key is used. Control unit 30
Thus, a control signal for driving the motor for rotating the photosensitive drum 5, a control signal for driving the conveyance system to specify the conveyance speed, a control signal for specifying the fixing temperature of the fixing unit 13, and the like are output. The operation of the device configured as described above will be described below.

A general copying operation will be described below. A document is placed on the ADF 1, the document is exposed by the exposure lamp 2, and optical image information is read by the image reading unit 3. As the reading element, for example, a CCD is used. The detection signal of the CCD is sent to the image processing unit 23,
After being converted into digital image data, the image processing unit 2
In step 3, predetermined correction and image processing are performed. The output of the image processing section 23 is sent to the image writing section 4 after being converted into an analog signal.

The photoreceptor drum 5 is formed by applying an OPC photoreceptor on the drum, is electrically grounded, and is driven and rotated clockwise by a motor (not shown). The band electrode 16 uniformly charges the peripheral surface of the photosensitive drum 5. Prior to the charging, exposure is performed by an exposure device (for example, PCL) 15 using a light emitting diode or the like, and static electricity on the peripheral surface of the photosensitive drum is removed.

After the photosensitive drum 5 is uniformly charged, the image writing unit 4 performs image exposure based on the image signal from the image processing unit 23. The image writing section 4 uses a laser diode (not shown) as a light emitting light source to scan the optical path by bending the optical path through a rotating polygon mirror 7 via a rotating polygon mirror 7. To form

A developing section 6 containing a developer composed of black toner and a carrier is provided on the peripheral edge of the photosensitive drum 5, and a developing sleeve (not shown) which contains a magnet and rotates while holding the developer. ) Is developed. The developer is transported to a development area. A predetermined AC bias voltage and a predetermined DC voltage are superimposed and applied between the developing sleeve and the photosensitive drum 5 in the developing area. As a result, the toner that has been given the opportunity to leave the carrier,
It adheres to a portion lower than the DC potential and visualization is performed.

On the other hand, the upper tray 19 or the lower tray 20
Alternatively, the manual feed tray 17 or the first large capacity paper feed tray (L
CT-1500) 24 or the second large-capacity paper tray (L
The copy paper conveyed from the CT-1000) 25 is fed to the transfer area by the conveyance system when the transfer timing is adjusted. In the transfer area, an image is transferred by the transfer pole 8 while a copy sheet is held on the peripheral surface of the photosensitive drum 5 in synchronization with the transfer timing.

Next, the charge on the photosensitive drum 5 is changed to PSL 9
The copy paper is separated by the separation pole 10 and transported to the fixing unit 13 by the transport unit 12, and the toner is welded by heating and pressing the heat roller and the pressure roller.
The paper is discharged via a paper discharge roller and accumulated in the paper discharge tray 27. If necessary, the transfer of the original image transferred to the front surface is returned to the entrance of the photosensitive drum 5 via the ADU paper discharge / transport unit 21, and the original image is also transferred to the back surface.

On the other hand, the photosensitive drum 5 from which the copy paper has been separated is pressed against the blade of the cleaning unit 14,
The residual toner is removed and cleaned, and the charge is removed by the PCL 15 and charged by the band electrode 16 again to prepare for the next image forming process.

In the above-mentioned digital copying machine, an automatic document size detecting function is realized by using the image reading section 3. The outline of this function is as follows. When the operator places the document on the platen glass and closes the platen cover, or when the operator places the document on the platen glass and performs a copying operation, the image reading unit 3 is used to read the document image in the sub-scanning direction. Read several lines (in the vertical direction of the document).

If the background of the read original is white and the image is read without closing the platen cover, the portion other than the original becomes a sky shot (in a state where an image outside the image forming range of the optical system is read). Therefore, one of the main scanning directions (horizontal direction of the document) output from the image reading unit 3
The output signals for the lines are as shown in FIG. In the figure, the horizontal axis is the main scanning direction, and the vertical axis is the detection signal (luminance).
It is. The output of the line sensor increases when the image is bright, and decreases when the image is dark.

The apparatus stores in advance information on the usable original paper width (correspondence between the original paper width and the number of pixels) so that the output detected by a predetermined threshold value (original edge detection threshold) can be obtained. The width of the document most suitable for the width (number of pixels) of the signal change point (points A and B in FIG. 9) can be specified.

If such a method is developed in the vertical direction of a document, the length of the document can be specified, and the size of the document is determined. However, in this case, it is necessary to scan the image reading unit 3 by the length of the document, so that it takes time to specify the document size. Therefore, for the purpose of shortening the detection time, an optical position detection sensor or the like may be separately used for detecting the document in the vertical direction (sub-scanning direction).

[0022]

In the above-mentioned specific operation of the original size, if the original has a black background, only a black signal is output from the image reading section 3 as shown in FIG. A problem occurs that the width of the document cannot be detected from the signal. Further, in the above-described specific operation of the document size, the signal processing from the image reading unit 3 may be performed using information subjected to so-called “thinning processing” in order to improve processing speed and reduce the amount of processing information. .

For example, 400 dpi (dot / inch)
When the image reading unit 3 having the resolution of 1 performs the thinning-out process for taking in information of one pixel for every 16 pixels, an image having a width of about 63 μm is taken in at an interval of about 1 mm.

With such a setting, when an original having lines arranged at regular intervals (for example, 1 mm intervals) such as graph paper is read, there is a possibility that the original may be indeterminate to either white or black depending on the place where the original is placed. There is a problem when performing APS.

FIG. 11 is an explanatory diagram of occurrence of a defect. This is the case of reading with a sky shot. The vertical axis is the main scanning direction, and the horizontal axis is the detection signal. The circles in the figure are sampling points for thinning. If the sampling point happens to overlap the black portion of the graph paper, the output of the line sensor will be in a low state as shown in the figure, making it difficult to determine the width of the document.

The present invention has been made in view of the above problems, and has as its object to provide an image reading apparatus capable of reliably determining the size of a document.

[0027]

According to the present invention, there is provided an image reading apparatus for reading image information recorded on an original, comprising: a line sensor for receiving optical information from the original and converting the optical information into an electric signal; An A / D converter for converting the output of the line sensor into digital data; and a control unit for controlling at least the image reading process. The first unit in the main scanning direction of the original in a state where the platen cover is not closed is provided. And then performs a second scan of the document in the main scanning direction with the platen cover closed. The control unit determines the size of the document based on the line sensor output obtained by these two scans. Is determined.

According to the configuration of the present invention, the size of the original is reliably determined by performing the first scan with the platen cover closed and the second scan with the platen cover closed. can do.

In this case, a detecting means for detecting the opening / closing of the platen cover is provided. When the detecting means detects that the platen cover is about to be closed, the first scanning is performed, and then the platen cover is completely closed. The second scanning is performed when the close is detected.

According to the configuration of the present invention, the time when the operator attempts to close the platen cover is detected, the sky shot scanning is performed, and then the scanning is performed with the platen cover closed, thereby reducing the size of the original. The determination can be made reliably.

Further, the control unit determines the document size by receiving one of the output of the line sensor by the first scan and the output of the line sensor by the second scan. I have.

According to the structure of the present invention, when an operator performs an original reading operation with the platen cover opened, or when an operator performs an original reading operation with the platen cover closed, The document size can be determined from the information on only the first scan or the information on only the second scan.

[0033]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic circuit diagram showing an embodiment of the present invention, and mainly shows the configuration of an image reading unit. The same components as those in FIG. 7 are denoted by the same reference numerals. In the figure, reference numeral 30 denotes a control unit for controlling at least an image reading process, for example, a microprocessor. Reference numeral 37 denotes a memory provided in the control unit 30 for storing various information. The memory 37 can be provided outside the control unit 30 instead of inside as shown in the figure. The memory 37 stores the document size (for example, A3, A
4, B3, B4, B5, etc.) in the width direction (the number of pixels) is stored.

A line sensor 31 converts optical original information into an electric signal, for example, a CCD. 32 is the C
An A / D converter 33 that converts the output of the CD line sensor 31 into digital data, and an image processing circuit 33 that receives the output of the A / D converter 32 and performs image processing. As the image processing circuit 33, for example, an LUT (Look Up Table) or the like in which a relation between an input and an output is stored is used.

A pulse width modulator 34 receives the output of the image processing circuit 33 and performs pulse width modulation (PWM) according to the gradation, and 35 drives the laser by receiving the output of the pulse width modulator 34. It is a laser drive unit. The laser driving section is provided to the image writing section 4 (see FIG. 7).

Reference numeral 36 denotes an open / close detection sensor for detecting that the platen cover is closed. The open / close detection sensor comprises a microswitch or the like which is turned on in two stages. Is turned on and the second stage switch is turned on when completely closed. Further, apart from this configuration, two micro switches may be provided according to the number of stages.

An operation unit 40 sets copy conditions such as the number of copies, copy density, and magnification. Open / close detection sensor 3
The reference numeral 6 is provided, for example, near the opening / closing fulcrum of the platen cover as shown in FIG. The outputs of the open / close detection sensor 36 and the operation unit 40 are given to the control unit 30. The control unit 30
Is a CCD line sensor 31, an A / D converter 32,
The operation of the pulse width modulator 34 and the operation of the laser driver 35 are controlled. To explain the operation of the device configured as described above,
It is as follows.

First, the operator places the document 41 on the platen glass 42 as shown in FIG. When the platen cover 1 is to be closed, the opening / closing detection sensor 36 detects that the platen cover 1 is about to be closed at the time when the platen cover 1 is closed to a certain extent, and notifies the control unit 30. The control unit 30 operates the image reading unit 3 in this state, and performs a sky shot scan in a state where the platen cover 1 is not closed (first scan). This scanning is performed for several lines in the sub-scanning direction. Then, the average of the obtained image data of several lines is obtained.

At this time, the reflected image of the document 41 is formed on the CCD line sensor 31 via the optical system, and the CCD line sensor 31 converts a light signal into an electric signal. CCD
The output of the line sensor 31 is decimated, enters the subsequent A / D converter 32, and is converted into digital image data.
Here, the reason for thinning out the output of the CCD line sensor 31 is as follows.
This is because the mode is not the mode for reading the document information but the mode for determining the size of the document. It suffices if there is data of the number of pixels required to determine the size of the document 41. Therefore, it is sufficient to provide a predetermined number of sampling points in the main scanning direction and read the image. The output of the A / D converter 32 is sent to the control unit 30 and stored in the memory 37.

After reading the document information by the first scanning, when the platen cover 1 is completely closed, the opening / closing detection sensor 36 detects the second stage, and the control unit 30 is notified. Then, the control unit 30 operates the image reading unit 3 to perform scanning (second scanning). This scanning is also performed for several lines in the sub-scanning direction. At this time, the image signal read by the CCD line sensor 31 is thinned out and input to an A / D converter 32, which converts the image signal into digital image data. Memory 37
Is stored.

Next, the control unit 30 stores the image data obtained by the first scanning, which is stored in the memory 37,
Based on the image data obtained by the second scan, a change point of the signal is detected by a preset document edge detection threshold, and the document size is determined by the maximum width (number of pixels) of the plurality of change points. There are various states of the document 41 as shown in FIG. FIG. 3A shows a state in which the background of the document at the position where the width of the document is detected is white.
Indicates a state in which a part of the original is black (the area indicated by hatching), and (c) indicates a state in which the background of the original is black. In each case, the control unit 30 determines the document size by the following operation.

When the background of the document is white (corresponding to FIG. 3A) In this case, the image detected by the CCD line sensor 31 is as shown in FIG. (A) shows a sky shot state (first scan), and (b) shows a state in which the platen cover 1 is closed (second scan).

In the sky shot scanning shown in (a), the CCD output is high (high level) only in the document portion, and the portions other than the document are dark (low level). In the case of the second scan shown in (b), the color of the back surface of the platen cover 1 is set to white in the area other than the original, so that the CCD
The output is high and cannot be distinguished from the edge of the document (not detectable). However, by this when comparing with a predetermined threshold value detection signal in sky shot scan shown in (a) (copy edge detection threshold), the width of the original document ₍₁ point A and B ₁ point) can be recognized Therefore, it can be recognized that the distance W between the points A ₁ and B ₁ is the width of the document.

Specifically, C of the CCD line sensor 31
The document width information can be obtained from the output of the CCD line sensor 31 by referring to the relationship between the number of CD elements and the document type and the document width stored in the memory 37 in advance. The same applies to the case where pixels are read out with thinning. It is sufficient to determine in advance how much the distance between the thinned pixels corresponds to the document distance.

When the background of the document is partially black (FIG. 3
In this case, the image detected by the CCD line sensor 31 is as shown in FIG. (A) shows a sky shot state (first scan), and (b) shows a state in which the platen cover 1 is closed (second scan).

In the sky shot scanning, since the left end of the document is black, the CCD output is low, and the low level range is apparently widened as shown in FIG. That is, the range of the high level of the document is narrowed.

On the other hand, the second scanning with the platen cover 1 closed
Then, in the sky shot, the low level area is the platen
The signal of the part that reads the back of cover 1 turns white
Thus, the characteristics shown in FIG. So in this case
Shows the point A detected at the first scan in FIG.
₁, B₁And point A detected in the second scan of (b)_Two, B_TwoBut
Is detected. Thus, more than two document edge candidates
Is detected, the outermost (the widest candidate)
Is adopted. Therefore, the document size is point A _TwoFrom
Point B_TwoCan be obtained as a distance W to the object.

When the background of the original is black (corresponding to FIG. 3C) In this case, the image detected by the CCD line sensor 31 is as shown in FIG. (A) shows a sky shot state (first scan), and (b) shows a state in which the platen cover 1 is closed (second scan).

In the sky shot scanning, since the left and right edges of the original are dark, the CCD output becomes low, and apparently at a low level as shown in FIG. That is, the high-level range of the document cannot be detected.

Meanwhile, in the second scan closing the platen cover 1, since the dark parts of the original is detected as shown in (b), the distance W between the A ₂ points and B ₂ points (b) document Can be recognized.

When the width of the document is determined in this manner, the control unit 3
0 indicates that the document width is a document of a specific size (for example, A4 or A3) when there is the same or almost the same width direction data as compared with the width direction data of the document stored in the memory 37. ).

Further, by combining with information of an optical sensor (not shown) for detecting the length of the original, the original size (for example, A4) can be specified. In the above-described embodiment, by performing the first scan with the platen cover closed and the second scan with the platen cover closed, it is possible to reliably determine the width of the document. it can.

In this embodiment, the time when the operator attempts to close the platen cover is detected by the open / close detection sensor to perform sky shot scanning, and then scanning is performed with the platen cover closed. Thus, the width of the document can be reliably determined.

In this embodiment, the microprocessor of the control unit 30 processes the information stored in the memory 37 for realization, but it may be realized by adding hardware for performing the same processing.

In the above-described embodiment, the case where the width of the document in the main scanning direction is obtained is taken as an example. However, the present invention can be similarly applied to the document in the sub-scanning direction. In this case, since the width information and the length information of the document are added, the size of the document can be reliably determined without installing an optical sensor or the like. However, since it is necessary to scan the document after the document is placed and before the platen cover closes, it is necessary to take measures such as increasing the scanning speed.

In the above-described embodiment, the case of forming an image with a single color toner is taken as an example. However, the present invention is not limited to this, and the above-described image forming process is repeated by the number of toners. The same applies to machines. In the case of color image formation, yellow (Y),
Magenta (M), cyan (C), and black (K) toners are used.

If a copy start is instructed with the platen cover open, the second scan (the state in which the platen cover is closed) cannot be detected, and only the detection result of the first scan is detected. May be used to detect the width of the document. Similarly, if the operator puts the original on the platen glass and turns on the power while performing the copy operation with the platen cover closed, the first scan cannot be detected.
The width of the document may be detected only by the detection result of the second scan.

Further, in the above-described embodiment, the case where the present invention is applied to a copying machine is taken as an example. However, the present invention is not limited to this, The present invention can be similarly applied to other types of image reading apparatuses, for example, facsimile apparatuses and image scanners that read image information from a personal computer or the like.

The line sensor used is not limited to a CCD sensor, but may be any photoelectric conversion element.

[0060]

As described above in detail, according to the present invention, in an image reading apparatus for reading image information recorded on an original, a line sensor for receiving optical information from the original and converting the optical information into an electric signal is provided. An A / D converter for converting the output of the line sensor into digital data, and a control unit for controlling at least image reading processing.
The first scanning in the main scanning direction of the original is performed with the platen cover not closed, and the second scanning in the main scanning direction of the original is performed with the platen cover closed. By determining the document size based on the line sensor output obtained by two scans, the size of the document can be reliably determined without installing a special document size detection device.

In this case, detecting means for detecting the opening / closing of the platen cover is provided. When the detecting means detects that the platen cover is about to be closed, the first scanning is performed, and then the platen cover is completely closed. When it is detected that the platen cover has been closed, the second scan is performed to detect a point in time when the operator attempts to close the platen cover, perform a sky shot scan, and then perform a scan with the platen cover closed. Thus, the size of the document can be reliably determined.

Further, the control section receives one of the output of the line sensor by the first scan and the output of the line sensor by the second scan to determine the size of the original, and When the document reading operation is performed with the platen cover opened, or when the document reading operation is performed with the platen cover closed, the information on only the first scanning or the second The document size can be determined from the information of only the scanning.

As described above, according to the present invention, it is possible to provide an image reading apparatus capable of reliably determining the size of a document.

[Brief description of the drawings]

FIG. 1 is a schematic circuit diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an open / closed state of a platen cover.

FIG. 3 is a diagram illustrating a state of a document.

FIG. 4 is an explanatory diagram (1) of document width detection.

FIG. 5 is an explanatory diagram (2) of document width detection.

FIG. 6 is an explanatory diagram (3) of document width detection.

FIG. 7 is a diagram illustrating a configuration example of a copying machine.

FIG. 8 is a diagram illustrating an example of an external configuration of a copying machine.

FIG. 9 is a diagram illustrating an output signal waveform of an image reading unit.

FIG. 10 is an explanatory diagram (1) of occurrence of a defect.

FIG. 11 is an explanatory diagram (2) of occurrence of a defect.

[Explanation of symbols]

 Reference Signs List 31 CCD line sensor 32 A / D converter 33 Image processing circuit 34 Pulse width modulation unit 35 Laser drive unit 36 Open / close detection sensor 40 Operation unit

Claims (3)

[Claims] 1. An image reading apparatus for reading image information recorded on an original, comprising: a line sensor for receiving optical information from the original and converting it into an electric signal; and an A / D for converting an output of the line sensor into digital data. A converter for performing a first scan in the main scanning direction of the original in a state where the platen cover is not closed, and a state where the platen cover is closed. A second scanning of the document in the main scanning direction, and the control unit determines the document size based on the line sensor output obtained by these two scans. 2. A detecting means for detecting opening and closing of the platen cover, wherein the detecting means detects that the platen cover is about to be closed, performs the first scan, and then completely closes the platen cover. 2. The image reading apparatus according to claim 1, wherein the second scanning is performed when the detection is performed. 3. The apparatus according to claim 1, wherein the control unit receives one of an output of the line sensor by the first scan and an output of the line sensor by the second scan to determine a document size. The image reading device according to claim 1.