JPH0983738A - Image reader, image reading method using this image reader and image forming device having this image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an image reader and an image forming device reducing adjusting time required when the reference of an original location is set and providing a reference location with high position precision. SOLUTION: The image signal showing the location of the reference display part of the developing indicator 24 outputted from a CCD sensor 48 is detected. Based on the picture element of the CCD sensor 48 to which the image signal showing the location of this developing indicator 24 is outputted and the image signal outputted from the picture element arranged at the reference location of the CCD sensor 48, the developing indicator 24 is moved to the reference location. The developing indicator 24 displays a location where an original should be set from the opening 22a of an original stopper 22 to an original table 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming an image on a photoconductor by an electrostatic photography process, developing the image with toner, and then outputting the image on a sheet.

[0002]

2. Description of the Related Art In an image forming apparatus using an electrostatic photography process, an image is formed on a photosensitive drum charged to a predetermined potential by using a photosensitive drum having photoconductivity and a developer containing toner. An image is formed by developing the electrostatic latent image obtained by providing the corresponding light with toner.

This type of image forming apparatus has a photosensitive drum as an image carrier.

Around the photosensitive drum, a charging device, a developing device, a transfer device and a cleaning device are arranged in order along the direction in which the photosensitive drum rotates. An exposure device that exposes image information on the surface of the photoconductor drum between the developing device and the charging device, and a fixing device that fixes the toner image developed by the developing device on a sheet are located at predetermined positions inside the image forming device. It is arranged. The image information provided to the exposure device is integrally arranged on the upper part of the device, or is converted into an electric signal by a reading device which is formed separately from the device and is connected via an interface, It is supplied to the exposure device.

In the photoconductor drum, a photoconductive layer such as selenium or OPC (Organic Photo-Conductor) is formed in a predetermined thickness on the surface of a conductor formed of aluminum or the like in a cylindrical shape. A drum-shaped optical semiconductor, which is irradiated with light while being charged to a predetermined potential, functions as a conductor only in the area where the light is irradiated, and a latent image corresponding to the exposed image information. Hold.

The reading device converts an original table holding an object to be read, that is, an original, an illumination lamp for illuminating the original set on the original table, and light reflected from the original illuminated by the illumination lamp into an electric signal. It has a CCD sensor and outputs image information recorded on a document as an electric signal. Many of the reading devices use a line CCD sensor that reads an image only in a predetermined direction.
Direction in which the reading pixel row of the line CCD sensor is extended
(Hereinafter referred to as the main scanning direction), the image of the document is extracted as an electric signal at a predetermined timing, and the document is placed in the direction orthogonal to the main scanning direction (hereinafter referred to as the sub scanning direction)
(Or, the position where the image information is read in the same way as the document is moved) is moved to take out the image of the document as an electrical signal in a fixed order.

The charging device has a charging wire for corona discharge, and a power supply device connected to the charging wire causes a charging wire to
By applying a voltage of 8 kilovolts, a surface potential of, for example, -700 volts is applied to the photosensitive drum.

The exposure device is a laser beam for irradiating light for changing the surface potential of the photosensitive drum at a position corresponding to image data stored in advance in the image memory or image data converted from image information of the original. An exposure device that forms an electrostatic latent image on a photosensitive drum from between a developing device and a charging device.

The developing device is disposed so as to face the developing position on the surface of the photosensitive drum, and a developer comprising a carrier for forming a magnetic brush on the photosensitive drum is formed on the photosensitive drum by frictionally charging the toner to a predetermined polarity. It has a developing roller which supplies to the electrostatic latent image and adheres only toner to the electrostatic latent image to form a toner image. The developing roller is formed by a rotatably formed cylindrical outer peripheral portion of a non-magnetic material and a magnet fixed at a predetermined position. Only provide the latent image.

The transfer device is composed of a corona discharge device similar to a charging device or a metal roller, and transfers the toner, that is, the toner image, provided to the electrostatic latent image on the photosensitive drum by the developing device along the rotation of the photosensitive drum. It is electrostatically attracted to the supplied paper and is transferred to the paper.

The fixing device is a pair of rollers each having a heater incorporated therein. The fixing device heats the paper and the toner while applying a predetermined pressure between the rollers to electrostatically adhere the paper to the paper. Toner is melted and fixed on the paper.

The cleaning device has a discharge lamp for irradiating the entire surface of the photosensitive drum with a light and a cleaner for scraping off the untransferred toner remaining on the surface of the photosensitive drum, and erases the residual charge remaining on the photosensitive drum. At the same time, the surface condition of the photosensitive drum is stabilized for the next image forming operation.

By the way, when the image of the original is read by the reading device, the readable effective read width varies depending on the combination of the original size, the copy magnification and the copy paper size. The document indicator shown is being used.

The document indicator is, for example, line C.
The reading pixel array of the CD sensor is arranged in a predetermined position at one end of the document table which is parallel to the extending direction, that is, the main scanning direction and is used as a reference when setting the document on the document table.

The document indicator is fixed to a belt or wire formed so as to be movable in the main scanning direction by, for example, a stepping motor.

The manuscript indicator moves a belt or a wire by a stepping motor in accordance with a reading effective width defined by a combination of a manuscript size, a copy magnification and a copy paper size, so that a predetermined position on the manuscript table is moved. Give instructions.

The original indicator is, for example, when the power of the image forming apparatus is turned on, when the timer mode is returned, when the paper jammed inside the apparatus is reset and reset, or when the developing device is replenished with toner. By resetting the secondary circuit inside the device represented by, the reference position is determined according to a predetermined routine.

[0018]

As an example of determining the reference position of the above-mentioned document indicator, a method of utilizing the characteristic of a stepping motor for moving the document indicator and a method of detecting the position of the document indicator by a sensor have been already proposed. ing.

A method of utilizing the characteristics of the stepping motor is, for example, to arrange a stopper at a predetermined position within a range where the document indicator is moved, and further rotate the stepping motor with the document indicator abutting against the stopper to perform stepping. Step out of motor (step out)
By doing so, the position of the stopper is used as a reference. However, the method using the position of the stopper as a reference has a problem that a click sound indicating that the stepping motor is out of step is generated. Further, since the stepping motor is rotated for several seconds assuming that the document indicator is moved from the position farthest from the stopper, there is a problem that the clicking sound is continued and the apparatus may be out of order. Needless to say, the movement time and the margin time for moving the document indicator to the position of the stopper increase the warm-up time at reset.

A method of detecting with a sensor is, for example,
In this method, a home position sensor is arranged at a predetermined position within a range where the document indicator is moved, and the position of the document indicator is defined by the home position sensor.

However, this method also requires moving time for moving the document indicator to the home position sensor. Further, in this method, since there is a time difference between the detection of the document indicator by the home position sensor and the stop of the document indicator, in order to improve the stopping accuracy of the document indicator, the speed at which the document indicator is moved must be set. Need to decline. This causes a problem of further increasing the warm-up time at reset.

In any of the methods, a deviation from the position at which the image of the original is actually read occurs due to the variation in the mounting accuracy of the stopper or the home position sensor. There is a problem that the image obtained or read image is out of alignment.

In this case, when assembling the copying apparatus or the reading apparatus, it is necessary to perform an adjusting operation for matching the position of the image to be originally copied or read with the position of the copied or read image. In this adjustment work, the deviation between the image obtained by copying the original or the image obtained by reading the original and the position of the original set on the original table is measured, and an offset amount corresponding to the measured amount of deviation is set. However, there is a problem that an undesired time is required including the check after setting the offset amount.

An object of the present invention is to provide an image reading apparatus and an image forming apparatus that reduce the adjustment time required when setting the reference of the document position and provide high positional accuracy of the reference position. .

[0025]

SUMMARY OF THE INVENTION The present invention has been made based on the above problems, and has a platen on which a document is placed;
An original position display means for displaying the placement position of the original to be placed on the original table on the original placing surface side of the original table, and the original on the opposite side of the original placing surface of the original table. A position display member that moves in association with a change in the position displayed by the position display means, a light source that includes a moving region of the position display member, and illuminates a document on the document table, and the position display from the light source. Image signal forming means for receiving light supplied through the moving area of the member and the original to form an image signal, and the image when the light of the moving area of the position indicating member enters the image signal forming means. Detection means for detecting the position of the position display member from the image signal output by the signal forming means, and the document position display means so that the document position display means displays an appropriate position based on the detection result of the detection means. Control to control There is provided an image reading apparatus characterized by comprising a means.

According to the present invention, the original table on which the original is placed and the respective original positions of the originals of different sizes to be placed on the original table are set to the original placing surface side of the original table. A document position display member that is displayed by moving the document position, a moving unit that moves the document position display member along a predetermined direction, and a side opposite to the document mounting surface of the document table.
A position display member that moves in conjunction with a change in the position displayed by the document position display member, a light source that includes a moving region of the position display member, and illuminates a document on the document table, and a light source that emits light from the light source. Image signal forming means having a plurality of pixels for receiving light supplied through the moving area of the position display member and the original on the original table, the moving area of the position display member and the original Image forming means for guiding the light from the original on the table to the image signal forming means by scanning a predetermined range, and the image forming means for transmitting the light from the moving area of the position display member to the image signal forming means. When the light in the moving region of the position display member is incident on the drive means for moving the image forming means so as to guide it and the image signal forming means, the position of the position display member is determined from the image signal output by the image signal forming means. And a distance between the position of the position display member detected by the detecting means and a preset specific pixel of the image signal forming means, and corresponds to the calculated distance. And a control unit that regulates the movement amount of the movement.

Further, according to the present invention, the original document table on which the original document is placed and the original document placement position of the original document to be placed on the original document table are displayed on the original document placement surface side of the original document table. A position display means, a position display member on the side of the document table opposite to the document mounting surface, which moves in conjunction with a change in the position displayed by the document position display means, and a moving region of the position display member. A light source for irradiating the original on the original table with light, and image signal forming means for receiving light supplied from the light source through the moving area of the position display member and the original to form an image signal, An image forming unit that forms an image on an image carrier based on the image signal formed by the image signal forming unit, and the image signal when the light in the moving region of the position display member enters the image signal forming unit. From the image signal output by the forming means And a control unit for controlling the document position display unit so that the document position display unit displays an appropriate position based on the detection result of the detection unit. An image forming apparatus characterized by the above is provided.

Further, according to the present invention, the image information of the document placed on the document table is supplied to the image signal forming means including a plurality of pixels and receiving light to form an image signal. An image signal formed on the back surface of the document position display means for displaying the placement position of the document to be placed on the document table on the document placement surface side of the document table by using a light source for irradiating the document with light. The document position display means displays from the first position facing the white portion used as a reference for binarizing the threshold value of the output signal output by the forming means, on the side opposite to the document placing surface of the document table. Of the position display member that moves to the second position of the document position display means for resetting the reference position of the position display member that moves in association with the change of the position, and the image signal forming means outputs at the second position. The image signal indicating the position is detected and Based on the specific pixel of the image signal forming unit that outputs the image signal indicating the position of the position display member and the image signal output from the pixel arranged at the reference position of the image signal forming unit, the position display member is set as a reference. In order to move to the position, the moving means for moving the position display member is moved by a predetermined amount, and one end of the original is brought into contact. The image reading method is characterized in that the image of the document is read from the same reading start position by resetting the.

As described above, according to the present invention,
The original indicator indicating the second position in the direction orthogonal to the original stopper indicating the first position for setting the original on the original table is an output signal corresponding to the original indicator output by the CCD sensor and the original stopper. It is moved to a predetermined position based on the number of pixels between the position of the document indicator obtained by detecting the difference between the output voltage and the output signal and the pixel indicating the reference position of the CCD sensor.

Therefore, when the document is set on the document table, the positional deviation is reduced, and high reading accuracy can be obtained.

Further, in the image reading apparatus having a high reading resolution, it is possible to prevent the reading resolution from being undesirably lowered due to the displacement of the document indicator.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, the image forming apparatus, that is, the laser beam printer type digital copying apparatus 2 includes:
An image forming unit for copying image information corresponding to an image of an original on a recording sheet, that is, a copying apparatus main body 10, and an original D to be copied on an original mounting table, which will be described later, disposed on the copying apparatus main body 10 It is composed of an automatic feeder (hereinafter referred to as ADF) 100 that feeds the sheets one by one.

The copying apparatus main body 10 includes a document reading section 12 for reading the image information of the document D, and an image forming section 14 for forming an image based on the image data read by the document reading section 12 or the image data supplied from the outside. A sheet feeding section 16 for feeding a recording sheet holding the image formed by the image forming section 14, and a sheet conveying section for conveying the sheet on which the image formed by the image forming section 14 is transferred in a predetermined direction. Includes 18, etc.

The upper part of the copying apparatus main body 10 and the ADF
A document table (document table) 20 on which a document D to be copied is placed, that is, a document table 20 for holding the document D is disposed at a position of 100, which is opposed to a conveyance belt described later.

A document stopper 22 for defining the leading end position of the document D is arranged at one end of the document table 20. The rear surface of the document stopper 22, that is, the lower surface facing the illumination lamp described later, is defined to have a predetermined whiteness (brightness) in order to generate white light for correcting the threshold level of the CCD sensor described later. It is formed in white.

The document stopper 22 has a slit-shaped opening 22a which will be described later with reference to FIG. Opening 2
A document indicator 24 is arranged below 2a. The opening 22a is for preventing light passing through the opening 22a in the normal image forming operation, that is, light reflected from the original and light other than white light for correcting the threshold level from entering the CCD sensor 48. In addition, it is formed at a position farther from the end of the document table 20 than at the position where the document stopper 22 and the end of the document table 20 are in contact with each other.

Below the document table 20, it is arranged substantially parallel to the document table 20 and movably along the document table 20, and the information written on the document D is read out optically. A second carriage 4 that follows the carriage 30 and the first carriage 30 and transmits the information read by the carriage 30 to an information recording medium described later.
Contains 0.

The first carriage 30 has an illumination lamp 32 for illuminating the original document D, a reflector 34 for converging light from the illumination lamp 32 on the original document D and increasing illumination efficiency, and second reflection light from the original document D. A first mirror 36 that reflects the light toward the carriage 40 is arranged.

On the second carriage 40, the first mirror 36
A second mirror 42 that turns back the reflected light reflected from the original 90 ° and a third mirror 44 that turns back the reflected light from the document D that has been turned back through the second mirror 42 further 90 ° are arranged.

Below the first carriage 30 and within the plane including the optical axis of the third mirror 44 of the second carriage 40, an image forming lens 46 for converging the reflected light from the document D is provided. , And a CCD sensor 48 that thresholds the reflected light from the document D at a predetermined threshold level to perform photoelectric conversion, that is, binarizes it at a predetermined threshold value.

The image forming section 14 includes a drum-shaped photosensitive member, that is, a photosensitive drum 50, as an image bearing member, which is arranged in the center of the main body 10.

Around the photosensitive drum 50, a charging device 52 as a charging means for charging the photosensitive drum 50 to a predetermined surface potential, and an electrostatic device formed on the photosensitive drum 50 via a laser exposure device described later. A developing device 54 as a developing means for developing the latent image by supplying toner (not shown) to the latent image and a cleaning device for removing the toner remaining on the photosensitive drum 50 and removing the electric charge remaining on the photosensitive drum 50. 56 and the like are arranged in order along the direction in which the photosensitive drum 50 is rotated.

In the vicinity of the photoconductor drum 50 and upstream of the developing device 54 in the direction in which the photoconductor drum 50 is rotated, the photoconductor drum 50 charged to a predetermined potential by the charging device 52 is provided. On the other hand, an exposure position 58a to which a laser beam from a laser exposure device 58 which exposes a latent image corresponding to image data is irradiated is defined.

Further, the developing device 54 and the cleaning device 5
6 and the photosensitive drum 50 via the developing device 54.
A transfer roller 60 for transferring the latent image, that is, the toner image developed above, to a transfer target material such as a copy sheet P supplied from a cassette described later is arranged.

On the right side of the image forming unit 14, the image forming unit 1
The paper cassette 62a for storing the paper P for holding the image formed by the paper cassette 4 and a bypass tray 62b formed integrally with the cassette 62a are arranged above the paper cassette 62a. Below the cassette 62a, for example, a large-capacity cassette (hereinafter, a large capacity cassette, L
62c).

Between the paper cassette 62a and the large-capacity cassette 62c and the photosensitive drum 50, there is a cassette 62.
a paper feed roller 64a and an upper paper feed guide 66 that guide the paper P supplied from
a, and a lower paper feed roller 64b and a lower paper feed guide 66b that guide the paper P supplied from the LCC 62c toward the photosensitive drum 50 are arranged, respectively.
The bypass tray 62b is provided with a bypass feed roller 68 for guiding the paper P placed on the tray 62b to the upper paper feed roller 64a.

Between the paper feed guides 66a and 66b and the photoconductor drum 50, the paper P fed from the cassette 62a or the bypass tray 62b and the LCC 62c is temporarily stopped to correct the inclination of the paper P, and A registration roller 70 that is formed on the surface of the photosensitive drum 50 and that aligns the leading end positions of the image, that is, the toner image and the toner image that is conveyed toward the transfer roller 60 with the rotation of the photosensitive drum 50, is arranged.

The transfer roller 6 is provided on the left side of the image forming unit 14.
The fixing device 72 for fixing the image transferred to the paper P on the paper P to which the toner image is transferred from the photoconductor drum 50 by 0, and the toner image is transferred between the fixing device 72 and the transfer roller 60. A conveyance device 74 that sends the formed paper P toward the fixing device 72, and a branch that guides the paper P on which an image is fixed via the fixing device 72 to either the outside of the copying apparatus main body 10 or a paper reversing unit described later. A discharge roller 78 for sending the paper P guided to the outside of the copying apparatus main body 10 by the gate 76 and the branch gate 76 to the outside of the copying apparatus main body 10 and a tray 80 for holding the discharged paper P are arranged. .

Below the image forming section 14, the branch gate 7 is provided.
6, the sheet reversing section 9 for guiding the sheet P, which has been branched by the sheet P, to the registration rollers 70 again.
0 is arranged.

The sheet reversing section 90 guides the sheet P having an image already copied on one side thereof, and a reversing guide 91 and a reversing guide 9.
1 is stored at a predetermined interval, that is, a transport roller 92, a reversing guide 91, and a storage for temporarily storing the paper P guided by the transport roller 92, which are arranged at intervals defined depending on the size of the reversible paper P. A reverse paper feed roller 94 for transporting the paper P stored in the area 93 and the storage area 93 toward the registration roller 70, and guides the paper P pulled out from the rear end side by the reverse paper feed roller 94. The reversing paper feed guide 95 includes an intermediate conveyance roller 96 that propels the paper P passing through the reversing paper supply guide 95 toward the registration roller 70.

2 (a) and 2 (b) are a schematic plan view and a partial sectional view showing the structure of the document indicator.

As shown in FIG. 2A, the document indicator 24 is fixed at a predetermined position on an endless carrier 26 such as a toothed belt or a wire. Endless carrier 2
One end of 6 is rotatably supported by a pulley connected to the rotation shaft of a stepping motor (indicator motor) 28. As a result, the stepping motor 28
The document indicator 24 is reciprocated along the longitudinal direction of the document stopper 22 by rotating the document carrier 24 and moving the endless carrier 26.

As shown in FIG. 2B, the document indicator 24 is formed so as to be visible from above the document table 20 through the opening 22a of the document stopper 22.

At a predetermined position on the surface of the document indicator 24 which is visible from the opening 22a of the document stopper 22, a document position display portion 24G showing a position where the document is to be set on a document table 20 described later with reference to FIG. Has been formed. Note that the document position display section 24G is, for example, as shown in FIG.
As shown in (a) to FIG. 4 (c), the shape itself is formed by a structure indicating a position, or a band or linear marking or coloring.

At a predetermined position on the rear surface of the document indicator 24, for example, at the center, a reference with a band or linear marking or a density gradient described later with reference to FIGS. 5 (a) to 5 (f). Display 24a to 2
4f is prepared. It should be noted that the reference display portions 24a to 24f and the document position display portion 24G of the document indicator 24 are provided.
The distance between and is defined as “0” or a predetermined offset amount uniquely given at the time of manufacturing. Therefore, by detecting the positions of the reference display portions 24a to 24f and moving the reference display portions 24a to 24f to predetermined positions, the position where the document is to be set on the document table 20 is visually recognized from the opening 22a of the document stopper 22 by the document position display portion 24G. Is displayed. By using the CCD sensor 48 already incorporated in the image reading unit 12 as a detection device for detecting the positions of the reference display portions 24a to 24f, an independent detection device can be omitted.

FIG. 3 is a block diagram showing a control block of a main part of the laser beam printer type digital copying apparatus shown in FIG.

As shown in FIG. 3, the copying machine 2 has a CPU 102 as a main controller.

The CPU 102 stores a ROM (Read Only Memory) 10 in which initial data for initial operation of the apparatus main body 10 of the copying apparatus 2 is stored.
4 and a RAM (random memory) for temporarily storing data such as copy magnification and the number of copies input from an operation panel (not shown), or input operating conditions.
Access memory 106 is connected. Note that R
It goes without saying that the OM 104 also stores a reset routine used to reset the reference position of the document indicator shown in FIG.

The CPU 102 also has an NVM (nonvolatile memory) 108 for storing initial setting data relating to the operation of the apparatus main body 10 and elapsed time data such as the total number of copies (prints) in which the photosensitive drum 50 is used. It is connected.

The CPU 102 instructs the motor drive circuit 110 to rotate the photosensitive drum 50, rotates a main motor (not shown) at a predetermined speed, and rotates the photosensitive drum 50 at a predetermined speed. Similarly, the CPU 102 rotates the developing motor (not shown) at a predetermined speed to rotate the developing roller of the developing device 54.

The CPU 102 also turns on the illumination lamp 32 of the first carriage 30 at a predetermined timing by giving a predetermined instruction to the lamp regulator 112, and the fixing device 7 via the heater lighting circuit 114.
The fixing temperature provided by the heater lamp 2 (not shown) is set within a predetermined range.

Further, the CPU 102 moves the document indicator 24 installed in a predetermined position of the document stopper 22 in a predetermined direction via the document indicator control unit 122.

The document indicator control unit 122 is
Reference display portions 24a to 24x of the document indicator 24
6 for detecting the position of the document, and a position control circuit 126 for controlling a stepping motor 28 for rotating the endless transport body 26 to move the document indicator 24 to a predetermined position. And a CCD sensor 48 of the image reading unit 12 by the position detecting unit 124.
After reading the current position of the document indicator 24 from the output of the document indicator 2, the stepping motor 28 is rotated in a predetermined direction so that the document position display section 24G displays the position where the document should be set on the document table 20.
4 is moved to a predetermined position.

The CPU 102 further gives a predetermined instruction to the motor drive circuit 110 and controls a servo motor (not shown) to move the first and second carriages 30 and 40 of the image reading unit 12 along the original table 20. Move the image of the original set on the original table 20 to CC
Guide to the D sensor 48. As a result, the illumination lamp 32
The image information of the document illuminated by is photoelectrically converted by the CCD sensor 48. The first and second carriages 30 and 40 remove paper jammed in the apparatus when the apparatus 2 is powered on, when the apparatus returns from the timer mode, as described later with reference to FIG. When the reference position is determined according to a predetermined routine by resetting the data of the secondary circuit inside the apparatus, which is represented by the time of resetting the toner or the time of supplying toner, etc. First and second carriages 30 and 40 used for reading image information
Is moved to a position farther from the end of the manuscript table 20 than the movement start position, that is, to the manuscript indicator calibration position below the manuscript stopper 22.

The image information of the original taken into the light receiving surface (not shown) of the CCD sensor 48 is converted into a digital signal via the analog-digital (A / D) conversion circuit 130 of the image signal processing unit 120, and shading correction is performed. The circuit 132 corrects the deviation caused by the difference in the amount of light between the central portion and the peripheral portion, and temporarily stores it in the line memory 134.

The image information of the original document stored in the line memory 134 is stored in the buffer memory 1 of the image processing unit 140.
42, the laser beam emitted from the laser exposure device 58 as predetermined image processing and image output via the image processing circuit 144 and the image editing unit 146 is converted into controllable print data, and stored in the page memory 148. Stored.

Further, the CPU 102 uses the charging power source device 15
By inputting a predetermined control amount for 2, the charging device 52
Control the magnitude of the high voltage supplied to the corona wire (not shown). The grid bias voltage supplied to the grid (not shown) of the charging device 52 is supplied by extracting a part of the voltage discharged by a corona wire (not shown) through a zener diode (not shown).

Further, the CPU 102 inputs a predetermined control amount to the bias power source device 154, so that the developing device 5
The developing roller of No. 4 is provided with a predetermined developing bias voltage.

The CPU 102 also supplies a predetermined transfer voltage to the transfer roller 60 by inputting a predetermined control amount to the transfer bias power supply device 160.

The CPU 102 further inputs a predetermined control voltage to a predetermined tap (not shown) of the mechanical controller 170 so that, for example, the cleaning device 5
6, a blade solenoid (not shown) is operated to bring a cleaning blade (not shown) into contact with the surface of the photosensitive drum 50, or a clutch (not shown) integrally assembled with one end of the registration roller 70 is driven at a predetermined timing. To do.

4 (a) to 4 (c) are schematic views showing the configuration of the document position display portion of the document indicator.

FIG. 4A shows a first example of the document position display portion 24G of the document indicator 24. FIG.
Referring to (a), the document position display portion 24G of the document indicator 24 has a marker 24m formed so as to be visible from above the document table 20 through the opening 22a of the document stopper 22.

The marker 24m is displayed on the manuscript table 2 by the user.
The line width is defined as a predetermined line width that is defined according to the allowable value of the positional deviation when the document is set to 0 or the reading resolution of the image reading unit 12. The marker 24m is formed by applying or printing a colorant on a protrusion or groove integrated with the document indicator 24 or by sticking a tape-shaped colorant. Further, the marker 24m is the original indicator 2
A colorant may be applied or printed or a tape-shaped colorant may be attached to the surface of No. 4.

FIG. 4B shows a second example of the document position display portion 24G of the document indicator 24. FIG.
Referring to (b), the document position display portion 24G of the document indicator 24 has a protrusion 24t formed along the direction in which the opening 22a of the document stopper 22 extends to have a width substantially equal to the width of the opening 22a. ing. Also, the protrusion 24
A marker 24m is formed at a predetermined position of t by a method similar to that of the first example shown in FIG. According to this structure, when the document indicator 24 is moved along the opening 22a of the document stopper 22, the document position display portion 24G is prevented from undesirably tilting with respect to the perpendicular line of the end of the document table 20. It Therefore, the original table 2
The display accuracy of the position where the original should be set to 0 is improved.

FIG. 4C shows a third example of the document position display portion 24G of the document indicator 24. FIG.
Referring to (c), the document position display portion 24G of the document indicator 24 is arranged in a direction orthogonal to the direction in which the opening 22a of the document stopper 22 extends so that the front end is slightly exposed from the end of the document table 20. It has a reference display bar 24b extended to the. Further, a marker 24m is formed at the tip of the reference display bar 24b by the same method as in the first example shown in FIG. 4 (a).

With this structure, it is possible to prevent an undesired increase in the deviation between the document and the document indicator 24 that occurs when the user sets the document on the document table 20. Therefore, the display accuracy of the position where the document should be set on the document table 20 is improved. As a result, the image reading unit 1
It is possible to provide a highly accurate reading start position that matches the reading resolution of 2.

5 (a) to 5 (f) are schematic views showing various examples of the reference display portion of the document indicator.

FIG. 5A shows a first example of the reference display portion of the document indicator. Referring to FIG. 5A, the reference display portion 24 a of the document indicator 24 is illuminated by the illumination lamp 32 that illuminates the document set on the document table 20, so that a white portion on the back surface of the document stopper 22 is displayed. It is colored in a predetermined color that can provide different amounts of reflected light. The reference display portion 24a is formed by applying protrusions or grooves integrally formed on the document indicator 24 or coloring them by applying or printing a coloring agent, or by pasting a tape-like coloring agent.

FIG. 5B shows a second example of the reference display portion of the document indicator. Referring to FIG. 5B, the reference display portion 24b of the document indicator 24 has a predetermined color capable of providing a reflected light amount different from that of the white portion on the back surface of the document stopper 22 and has a density gradient. According to this configuration, a special output signal waveform is output, as will be described later in signal detection, so that the reference position is more clearly indicated.

FIG. 5C shows a third example of the reference display portion of the document indicator. Referring to FIG. 5C, the reference display portion 24c of the document indicator 24 is a protrusion integrally formed on the document indicator 24 with a predetermined width. In this example, the coloring as the reference display portion 24c is
It becomes unnecessary. In this case, by making the material of the reference display portion 24c darker than the white portion on the back surface of the document stopper 22, it is possible to eliminate painting or printing or tape sticking, which often causes a cost increase.

FIG. 5D shows a fourth example of the reference display portion of the document indicator. Referring to FIG. 5D, the reference display portion 24d of the document indicator 24 is a protrusion integrally formed on the document indicator 24 with a predetermined width. In this example, the reference display portion 24d of the document indicator 24 is formed of a material having substantially the same color as the white portion on the back surface of the document stopper 22. Therefore, it is possible to eliminate painting or printing or tape sticking, which often causes a cost increase. In this example, the CCD
When the document lamp 22 is illuminated by the illumination lamp 32 to obtain the reference position output supplied to the sensor 48, the position where the illumination light is irradiated is the opening 22a of the document stopper 22.
The first carriage 30 is moved so that That is, since the amount of reflected light from the opening 22a of the document stopper 22 is lower than that of the white portion of the document stopper 22, special coloring or the like is applied to both the document stopper 22 and the document indicator 24. It becomes unnecessary.

FIG. 5E shows a fifth example of the reference display portion of the document indicator. Referring to FIG. 5 (e), the reference display portion 24e of the document indicator 24 is illuminated by the illumination lamp 32 that illuminates the document set on the document table 20, so that the reference display part 24e becomes a white part on the back surface of the document stopper 22. It is colored in a predetermined color that can provide different amounts of reflected light. Note that the reference display unit 24e is a tolerance value of the positional deviation when the user sets a document on the document table 20 or a reading resolution of the image reading unit 12 at a predetermined position of a protrusion integrally formed on the document indicator 24. The colorant is applied or printed in a width corresponding to a predetermined line width defined according to. The reference display section 24e
May be formed by applying a tape-shaped coloring agent.

FIG. 5F shows a sixth example of the reference display portion of the document indicator. Referring to FIG. 5 (f), the reference display portion 24 f of the document indicator 24 has a white portion on the back surface of the document stopper 22 with a reflection area capable of providing approximately the same amount of reflected light as the white portion on the back surface of the document stopper 22. Is colored in a predetermined color capable of providing a different amount of reflected light. It should be noted that the white portion of the reference display portion 24f is the allowable value of the positional deviation when the user sets the original on the original table 20 or the image reading at a predetermined position of the protrusion integrally formed on the original indicator 24. It is formed to have a predetermined line width defined according to the reading resolution of the portion 12. According to this configuration, a special output signal waveform is output, as will be described later in signal detection, so that the reference position is more clearly indicated.

FIG. 6 is a schematic block diagram showing an example of the position detection unit of the document indicator control unit.

The document indicator control unit 122 includes
Based on the output signal from the CCD sensor 48, FIG.
Based on the outputs from the position detection unit 124 and the position detection unit 124 that detect the positions of the reference display units 24a to 24f shown in FIGS.
To move the stepping motor 28 to the reference position.
Position control circuit 12 for rotating the motor in a predetermined direction by a predetermined number of pulses
Have six.

The position detector 124 outputs an output voltage corresponding to the amount of reflected light of the white part of the document stopper 22 output via the analog-digital (A / D) conversion circuit 130 and the shading correction circuit 132 and a reference (not shown). A comparator for comparing with a reference voltage ref supplied from the voltage generator, a feedback circuit for stabilizing the light quantity of the illumination light generated from the illumination lamp 32 by referring to the output from the comparator, and a peak value from the output of the comparator. And a reflected light from the document indicator 24 included in the output of the reflected light from the white portion (or the opening 22a) of the document stopper 22 is detected. Further, the position detection unit 124 samples the output voltage output from each pixel of the CCD sensor 48 according to the required reading accuracy by the sampling method described below, and the sampling voltage shown in FIGS. The positions of the reference display portions 24a to 24f shown in (f) are detected. The position detector 124 may detect a position where the output passed through the A / D conversion circuit 130 exceeds a threshold level defined by a predetermined magnitude. Further, the change point may be obtained by differentiating the output of the CCD sensor 48 by a differentiating circuit. 7 (a) to 7 (f)
Is the CCD of the image reading unit by the position detecting unit shown in FIG.
6 is a timing chart showing a method of reading the current position of the document indicator from the output signal of the sensor. The horizontal axis of each chart corresponds to the longitudinal position of the CCD sensor 48, that is, the main scanning direction. The vertical axis in each chart shows the output voltage of the CCD sensor 48.

FIGS. 7 (a) to 7 (f) respectively show the output signals of the position detecting portions corresponding to the reference display portions of the document indicators shown in FIGS. 5 (a) to 5 (f). The respective timing charts show the output voltage from the pixels defined based on all of the outputs of the pixels of the CCD sensor 48 or at predetermined intervals according to the required reading accuracy.

For example, the output signal of the CCD sensor 48 corresponding to the reference display portion 24a shown in FIG.
As shown in (a), the document stopper 2
An output voltage different from the reflected light from the white part 2 is obtained. This reduces the necessity of taking out all the outputs of the respective pixels of the CCD sensor 48 at the time of sampling, so that the detection time required for detecting the reference position can be reduced. In this case, the reading resolution is C
It is reduced as compared with the method of extracting all of the outputs of each pixel of the CD sensor 48. On the other hand, the width of the reference display portion 24a is 1
Sampled at intervals less than / 2.

The output signal of the CCD sensor 48 corresponding to the reference display portion 24b shown in FIG. 5 (b) is reflected from the white portion of the document stopper 22 in a relatively wide section, as shown in FIG. 7 (b). An output voltage different from that of light is obtained. Needless to say, the output signal of the CCD sensor 48 is
Corresponds to a concentration gradient of 4b. This not only can reduce the detection time required for detecting the reference position at the time of sampling, but is also useful for erroneous detection due to noise or the like.

The output of the CCD sensor 48 shown in FIG. 7 (c) is almost the same as the example shown in FIG. 7 (a) except for the magnitude of the output voltage. Therefore, the cost can be reduced by using the reference display portion 24c shown in FIG.

In the output of the CCD sensor 48 shown in FIG. 7D, the output voltage corresponding to the area of the reference display portion 24d is projected as compared with the area voltage corresponding to the opening 22a of the document stopper 22. In this method, as described above, the cost of the document stopper 22 and the document indicator is reduced.

The output signal of the CCD sensor 48 corresponding to the reference display portion 24e shown in FIG. 5 (e) is reflected from the white portion of the document stopper 22 in a relatively narrow section as shown in FIG. 7 (e). An output voltage different from that of light is obtained. This means that all the outputs of each pixel of the CCD sensor 48 are taken out at the time of sampling, so that a higher reading resolution can be provided as compared with the example shown in FIGS. 7A to 7D. In this case, at least the reference display unit 24
It is sampled at intervals smaller than the width of e.

According to FIG. 7 (f), the output signals of the CCD sensor 48 corresponding to the reference display section 24f shown in FIG. 5 (f) are the white color of the document stopper 22 immediately before and after the reference display section 24f. The output voltage is different from the reflected light from the section. Therefore, in sampling, not only the detection time required for detecting the reference position can be shortened, but also it is useful for erroneous detection due to noise or the like.

FIG. 7G shows an example of the differential output obtained by differentiating the output signal from the CCD sensor shown in FIG. 7A as an example.

FIG. 8 is a flowchart showing the reset operation of the document indicator.

As described above, the original indicator 2
Reference numeral 4 denotes a time when a power source (not shown) of the image forming apparatus 2 is turned on, a time when the timer mode is returned, a time when a sheet jammed in the apparatus 2 is reset and reset, or a time when the developing device 54 is replenished with toner. By resetting the secondary circuit inside the representative device 2, that is, when any of the covers (not shown) of the device 2 is opened or closed, the original reference position is reset in accordance with a predetermined routine.

More specifically, by resetting the secondary circuit inside the device 2, the servo motor (not shown) is rotated in a predetermined direction according to the drive current from the motor drive circuit 110 under the control of the CPU 102, and the first The first carriage 30 is moved to a position where the illumination lamp 32 of the carriage 30 can illuminate the white portion of the document stopper 22, that is, the home position (STP1).

Subsequently, a predetermined instruction is given to the lamp regulator 112 by the control of the CPU 102, and the illumination lamp 32 of the first carriage 30 is turned on at a predetermined voltage. As a result, the white portion of the document stopper 22 is illuminated and the reflected light is guided to the CCD sensor 48. The reflected light of the white portion of the document stopper 22 guided by the CCD sensor 48 is converted into a digital signal by the A / D converter 130 and supplied to the shading correction circuit 132. As a result, the correction amount of the shading correction circuit 132 is calibrated (STP2).

Then, the reference position of the document indicator 24 is reset.

First, the servomotor (not shown) is rotated in a predetermined direction by the drive current from the motor drive circuit 110 under the control of the CPU 102, and the first carriage 30 stopped at the home position is moved to the original table 20.
Is moved by a predetermined amount in the direction away from the end of the. That is,
The illumination lamp 32 of the first carriage 30 serves as the document stopper 2
It is moved to a position where the vicinity of the second opening 22a can be illuminated.
(STP3).

Subsequently, the illumination lamp 32 of the first carriage 30 which has been moved to a predetermined position for resetting the reference position of the document indicator 24 is turned on, and the rear faces of the document indicator 24 and the document stopper 22 are illuminated.
(STP4).

The reflected light from the back surface of the document indicator 24 and the document stopper 22 illuminated in step STP4 is guided by the CCD sensor 48 of the image reading section 12 to the reference display section 24a or 24f on the back surface of the document indicator 24. The change in the amount of reflected light provided by either one is detected by the CCD sensor 48 (STP5). The positions of the reference display portions 24a to 24f of the document indicator 24 guided by the CCD sensor 48 in step STP5 are obtained by the position detection unit 124 of the document indicator control unit 122 described in detail with reference to FIG. 6 (STP).
6). In this case, for example, the peak value of the reflected light is detected according to the characteristic of the position detection unit 124 (STP6
a), thresholding the output signal of the CCD sensor 48 at a predetermined threshold level (STP6b), and differentiating the output of the CCD sensor 48 by a differentiating circuit to obtain a change point (STP6c).

Next, the number of pixels existing between the current position of the document indicator 24 obtained via the position detection unit 124 and the reference pixel of the CCD sensor 48 stored in advance in the NVM 108 is calculated. The CCD sensor 48
When the device 2 is assembled, the reference pixel of is set according to the mounting error of the CCD sensor 48 and the deviation between the mounting position peculiar to the CCD sensor 48 and the pixel at the beginning (or the reference position), and then the NVM 108. It goes without saying that it will be remembered. Then, the document indicator 24
Of the number of pixels existing between the current position of the image sensor and the reference pixel of the CCD sensor 48, the original size, the paper size, the copy magnification, and the automatic paper selection or the automatic magnification selection input from the operation panel (not shown). The original reference position condition resulting from the mode is input, and the stepping motor 28
The amount of rotation that should rotate the CPU is calculated by the CPU 102.
(STP7).

Subsequently, C is set so as to satisfy the rotation amount of the stepping motor 28 obtained in step STP7.
Under the control of the PU 102, the drive current of the number of steps corresponding to the rotation amount of the stepping motor 28 is supplied from the motor drive circuit 110 to the stepping motor 28. As a result, the document indicator 24 is moved from the current position to the CCD.
It is moved to a predetermined position corresponding to the reference pixel of the sensor 48. In this case, since the document indicator 24 is directly moved from the current position to a predetermined position corresponding to the reference pixel of the CCD sensor 48, the time required for the document indicator 24 to move can be minimized. S
TP8).

As described above, according to the method of setting the reference position of the document indicator 24 shown in FIG. 5 and the document indicator 24 shown in FIG. The reference position of the document indicator 24 can be easily reset only by obtaining the number of pixels between the current position of the document indicator 24 detected by the CCD sensor 48 and the reference pixel of the CCD sensor 48.

FIG. 9 is a flow chart showing a modification of the reset operation of the document indicator shown in FIG.

Referring to FIG. 9, step STP is performed in the same manner as the reset operation of the document indicator shown in FIG.
In step 11, the first carriage 30 is moved to the home position, and in step STP12, the shading correction circuit 13
The correction amount of 2 is corrected.

Subsequently, in step STP13, the illumination lamp 32 of the first carriage 30 is moved to a position where it can illuminate the vicinity of the opening 22a of the document stopper 22, and step S
The rear surface of the document indicator 24 and the document stopper 22 is illuminated by TP14.

Next, in step STP15, the reference display portion 24a or 24 on the rear surface of the document indicator 24 is displayed.
The change in the amount of reflected light provided by either f is CC
The position is detected by the D sensor 48, and the positions of the reference display portions 24a to 24f of the document indicator 24 are obtained by the position detection portion 124 in step STP16.

Thereafter, at step STP17, the CPU 102 obtains the number of pixels existing between the current position of the document indicator 24 and the reference pixel of the CCD sensor 48 and the rotation amount for rotating the stepping motor 28.

The drive current of the number of steps to be supplied to the stepping motor 28 corresponding to the rotation amount of the stepping motor 28 obtained in step STP17 is supplied,
The document indicator 24 is the CCD sensor 4 from the current position.
Directly moved to a predetermined position corresponding to 8 reference pixels
(STP18).

Then, steps STP15 to STP18 are repeated according to the reading resolution given to the image reading section 12, and the reference position of the document indicator 24 is finely adjusted (STP19).

As described above, according to the method of setting the reference position of the document indicator 24 shown in FIG. 5 and the document indicator 24 shown in FIG. The reference position of the document indicator 24 can be easily reset only by obtaining the number of pixels between the current position of the document indicator 24 detected by the CCD sensor 48 and the reference pixel of the CCD sensor 48.
Further, in the example shown in FIG. 9, since the reference position of the document indicator 24 is finely adjusted according to the reading resolution given to the image reading unit 12, the document indicator 24 is adjusted.
The high reading resolution provided to the reading unit 12 is not sacrificed due to the undesired shift of the reference position of.

[0115]

As described above, according to the present invention, the original indicator that indicates the second position in the direction orthogonal to the original stopper that indicates the first position for setting the original on the original table is the CCD. Number of pixels between the position of the document indicator obtained by detecting the difference in output voltage between the output signal of the document indicator output by the sensor and the output signal of the document stopper and the pixel indicating the reference position of the CCD sensor Is moved to a predetermined position.

Therefore, displacement of the original when setting the original on the original table is reduced, and high reading accuracy can be obtained.

Further, in the image reading apparatus having a high reading resolution, it is possible to prevent the reading resolution from being undesirably lowered due to the displacement of the document indicator.

Further, the cost of parts of the apparatus is reduced and the waiting time required when the reference position of the document indicator is reset is reduced.

[Brief description of drawings]

FIG. 1 is a schematic view showing an image forming apparatus incorporating a document indicator according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing the periphery of a document indicator and a document stopper of the image forming apparatus shown in FIG.

FIG. 3 is a block diagram showing a control block of a main part of the image forming apparatus shown in FIGS. 1 and 2.

FIG. 4 is a schematic diagram showing an example of a document position display unit applied to the document indicator shown in FIG.

5 is a schematic diagram showing an example of a reference display unit applied to the document indicator shown in FIG.

FIG. 6 is a schematic block diagram showing an example of a position detection unit of a document indicator control unit.

7 is a timing chart showing the output of the CCD sensor corresponding to the reference display portion of the document indicator shown in FIG.

8 is a flowchart showing an operation of resetting the position of a document indicator with reference to the output of the CCD sensor shown in FIG.

9 is a flowchart showing another example of the operation of resetting the position of the document indicator shown in FIG.

[Explanation of symbols]

2 ... Copying device (image forming device), 10 ... Copying device main body,
12 ... Original reading section, 14 ... Image forming section, 16 ... Paper feeding section, 18 ... Paper feeding section, 20 ... Document table, 22 ... Document stopper, 24 ... Document indicator, 26 ... Endless carrier, 28 ... Stepping motor ( (Indicator motor)
, 30 ... First carriage, 32 ... Illumination lamp, 34 ...
Reflector, 36 ... First mirror, 40 ... Second carriage, 42 ... Second mirror, 44 ... Third mirror, 46 ... Imaging lens, 48 ... CCD sensor, 50 ... Photoconductor drum (photoconductor), 52 ... Charging Device (charging means), 54 ... Developing device, 56 ... Cleaning device, 58 ... Laser exposure device,
58a ... Exposure position, 60 ... Transfer roller, 70 ... Registration roller, 72 ... Fixing device, 100 ... ADF, 102 ... C
PU, 104 ... ROM, 106 ... RAM, 108 ... Non-volatile memory, 110 ... Motor drive circuit, 112 ... Lamp regulator, 114 ... Heater lighting circuit, 120 ... Image signal processing unit, 122 ... Original indicator control unit,
Reference numeral 124 ... Position detector, 126 ... Position control circuit, 130 ...
Analog-digital (A / D) conversion circuit, 132 ... Shading correction circuit, 134 ... Line memory, 140
... image processing unit, 142 ... buffer memory, 144
Image processing circuit, 146 ... Image editing unit, 148 ... Page memory, 152 ... Charging power supply device, 154 ... Bias power supply device, 160 ... Transfer bias power supply device, 170 ... Mechanical controller.

Claims (10)

[Claims] 1. A manuscript table on which a manuscript is placed, and manuscript position display means for displaying the manuscript position on which the manuscript should be placed on the manuscript table on the manuscript mounting surface side of the manuscript table. On the side of the document table opposite to the document placement surface, a position display member that moves in association with a change in the position displayed by the document position display means, and a moving area of the position display member are included on the document table. A light source that irradiates the document with light, an image signal forming unit that receives the light supplied from the light source through the moving region of the position display member and the document, and forms an image signal. A detector for detecting the position of the position display member from the image signal output by the image signal forming unit when light in the moving region of the position display member is incident, and the document position based on the detection result of the detector. The display means the proper position display Image reading apparatus characterized by comprising a control means for controlling the document position display means to perform, the. 2. A manuscript table on which a manuscript is to be placed and manuscripts of different sizes to be placed on the manuscript table are moved on the manuscript mounting surface side of the manuscript table by moving the respective manuscript positions. A document position display member to be displayed, a moving means for moving the document position display member along a predetermined direction, and a position of the position displayed by the document position display member on the opposite side of the document placing surface of the document table. A position display member that moves in association with a change, a light source that includes a moving region of the position display member, and illuminates a document on the document table, and a moving region of the position display member from the light source and the document table. The image signal forming means having a plurality of pixels for receiving the light supplied through the upper original and forming an image signal, the moving area of the position display member and the light from the original on the original table are set to a predetermined value. By scanning the range Image forming means for guiding the image forming means to the image signal forming means, drive means for moving the image forming means so that the image forming means guides light from the moving region of the position display member to the image signal forming means, and the image signal Detecting means for detecting the position of the position indicating member from the image signal output by the image signal forming means when the light in the moving area of the position indicating member enters the forming means; and the detecting means detected by the detecting means. Control means for determining a distance between the position of the position display member and a preset specific pixel of the image signal forming means, and defining the movement amount of the movement in correspondence with the determined distance. An image reading device characterized by the above. 3. The control means detects the position of the position display member guided to the image signal forming means by the image forming means by obtaining the peak of the image signal output from the image signal forming means. The image reading apparatus according to claim 2, wherein: 4. The position display member guided by the image forming means to the image signal forming means by binarizing the image signal output from the image signal forming means by a predetermined threshold value. The image reading device according to claim 2, wherein the position of 5. The position display guided by the image forming means by the image forming means by obtaining a change point obtained by differentiating the image signal output from the image signal forming means. The image reading apparatus according to claim 2, wherein the position of the member is detected. 6. A document table on which a document is placed, and a document position display means for displaying a document placement position of the document to be placed on the document table on the document placement surface side of the document table. On the side of the document table opposite to the document placement surface, a position display member that moves in association with a change in the position displayed by the document position display means, and a moving area of the position display member are included on the document table. A light source for irradiating the original with light, an image signal forming means for receiving the light supplied from the light source through the moving area of the position display member and the original, and forming an image signal, and the image signal forming means. Image forming means for forming an image on an image carrier based on the formed image signal, and an image output by the image signal forming means when light in the moving region of the position display member enters the image signal forming means. The position of the position display member from the signal An image comprising: detection means for detecting; and control means for controlling the document position display means so that the document position display means displays an appropriate position based on the detection result of the detection means. Forming equipment. 7. The position display member guided by the image forming means to the image signal forming means by binarizing an image signal output from the image signal forming means by a predetermined threshold value. 7. The image forming apparatus according to claim 6, wherein the position of is detected. 8. The position display guided by the image forming means by the image forming means by obtaining a change point obtained by differentiating the image signal output from the image signal forming means. The image forming apparatus according to claim 6, wherein the position of the member is detected. 9. The control means controls the position display means guided by the image forming means to the image reading means by obtaining a change point obtained by differentiating an output signal output from the image reading means. The image forming apparatus according to claim 6, wherein the position is detected. 10. A document is irradiated with light in order to supply image information of a document placed on a document table toward an image signal forming means including a plurality of pixels and receiving light to form an image signal. Output signal output from the image signal forming means formed on the back surface of the document position display means for displaying the placement position of the document to be placed on the document table on the document placement surface side of the document table. Is interlocked with the change in the position displayed by the document position display means from the first position opposite to the white portion used as a reference for binarizing the threshold of Move to the second position of the document position display means for resetting the reference position of the position display member to be moved,
An image signal indicating the position of the position display member output from the image signal forming unit is detected at the second position, and the specific pixel and image signal of the image signal forming unit from which the image signal indicating the position of the position display member is output. Based on the image signal output from the pixel arranged at the reference position of the forming means, in order to move the position display member to the reference position, the moving means for moving the position display member is moved by a predetermined amount and the original document is moved. Image reading, characterized in that the image of the original is read from the same reading start position by resetting the reference position of the position display member for pointing the other end of the original orthogonal to the original position display means with which one end is in contact. Method.