JP3444997B2 - Image reading device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus used in a copying machine or the like, and more particularly to an image reading apparatus for reading an image of a document placed on a contact glass with an image sensor.

[0002]

2. Description of the Related Art As is well known, an image reading apparatus of this kind is used in, for example, a digital copying machine. The basic configuration of the digital copying machine is the image reading device,
Generally, a printer unit having a laser beam scanning device and an automatic document feeder are provided. Here, the automatic document feeder conveys the set originals one by one, sets them on the contact glass, and discharges the originals on the contact glass after the copying is completed. Further, the image reading device includes a light source including an illumination lamp and a reflecting mirror, and a first light source.
A first carriage equipped with a mirror, a second carriage equipped with a second mirror and a third mirror, an optical lens for forming an optical image sent through each mirror of the carriage, and the optical lens. An image pickup sensor such as a CCD (charge-coupled device) sensor that converts the formed optical image into an image signal is provided.

Further, in the above-mentioned printer section, during the copying operation, after the photosensitive drum is uniformly charged by the charging device by being rotationally driven by the driving section, image exposure by the digital image signal subjected to the image processing is performed by the laser. An electrostatic image is formed by a beam scanning device, and the electrostatic image on the photosensitive drum is transferred and developed on a sheet by a developing device.

In such a digital copying machine, at the time of reading a document, first, one set document is taken out by an automatic document feeder and conveyed, and placed on a contact glass. After that, the first carriage moves forward at a constant speed, and the second carriage moves forward following the first carriage at half the speed of the first carriage.
As a result, the document on the contact glass is optically scanned. The original on the contact glass is illuminated by a light source or the like, and the reflected light image is reflected by the first mirror, the second mirror, and the third mirror.
It is guided to an optical lens through a mirror, and an image is formed on the image sensor by this optical lens.

The image sensor photoelectrically converts the reflected light image of the formed document into an analog image signal, and the document is read. Then, after the reading of the document is completed, the first carriage and the second carriage return to the home position. Further, after the copying operation is completed, the original on the contact glass is discharged by the automatic original feeder, and the next original set is extracted and conveyed by the automatic original feeder and placed on the contact glass. To be done. In this way, the reading of the document is performed one after another. An analog image signal output from the image sensor is converted into a digital image signal by an analog / digital converter, and various image processing (binarization, multi-value conversion, floor conversion, etc.) is performed on a circuit board equipped with an image processing circuit. Adjustment processing,
Scaling processing, editing processing, etc.) is performed.

During the copying operation, in the printer section of the digital copying machine, the photosensitive drum is rotationally driven by the driving section so that it is uniformly charged by the charging device. The digital image signal image-processed by the image processing circuit is
An electrostatic image is formed on the photosensitive drum by the laser beam scanning device. Then, after the electrostatic image on the photosensitive drum is transferred to the transfer paper, the transfer paper having the transfer image is developed by the developing device and discharged onto the tray as a copy. By the above-mentioned work, the conventional digital copying machine makes a copy from the original.

By the way, in the above-mentioned image reading apparatus, in order to correct the illuminance on the image sensor surface and the output variation of each pixel of the image sensor (hereinafter referred to as "shading correction"), as shown in FIG. Scale 50
The white reference plate 502 is a part of the back surface of the contact glass 5
It is provided at a position 504 on the upper surface (generally equivalent to the document surface) of No. 03. Reference numeral 505 in FIG. 14 is the original scale 5.
01 indicates the end portion of the original document, and one end portion of the document comes into contact with the end portion 505. Further, in FIG. 14, reference numeral HP is a home position, and when starting reading, the first mirror of the first carriage is arranged at the home position HP.

Then, in the image reading apparatus 500,
As shown in FIG. 14, the home position H is set before reading the original placed on the contact glass 503.
It is determined that a predetermined distance Ls has elapsed from P, and the shading gate signal SLEAD is opened by a predetermined width S, so that the constant width S of the white reference plate 502 is read by the image sensor. In this way, the analog image signal obtained by reading with the image sensor is given to the image processing circuit to perform shading correction. Further, the image reading apparatus determines that the distance Lf has passed from the home position HP and opens the area determination gate signal FGATE that determines the original reading area by the distance F (the size of the original) to reflect the original. An optical image is given to the image sensor to read the original.

The range F in FIG. 14 varies depending on the document size, the transfer paper size, the scaling factor, and the like.
Further, the home position HP (reference position serving as a reference in the sub-scanning direction) is determined by detecting a specific position of the first carriage or the second carriage with a sensor such as a photo interrupter. Further, the image reading start position (distance Lf from the home position HP) can be adjusted in consideration of variations in the positions of the document scale 501 and the sensor (photo interrupter) for detecting the home position HP, component accuracy, and the like.

[0010]

As described above, in the conventional image reading apparatus, the reading start position of the white reference plate (the distance Ls from the home position HP) is the position of the home position sensor such as the photo interrupter. To determine the position accuracy of the home position sensor itself, the carriage position detection accuracy by the home position sensor, the position accuracy between the home position sensor and the white reference plate, and the effects of temperature changes and equipment installation surfaces. There is a drawback that the reading start position of the white reference plate changes due to the positional deviation of each component when received.

Therefore, it is necessary to set the effective range of the white reference plate sufficiently wider than the reading region S so that the reading region S of the white reference plate does not deviate from the effective range of the white reference plate. Start position (home position H
It became necessary to adjust the distance Ls from P). As a solution to the above-mentioned problem, paying attention to the fact that the position accuracy can be secured because there are few components between the original scale and the white reference plate, and the reading start position of the white reference plate is set to the image reading start position. A method of determining based on the However, in this case, when the image reading device Lf is changed according to the user's convenience, the reading position of the white reference plate is also displaced at the same time.

Similarly to the reading start position of the white reference plate, the image reading start position (distance Lf from the home position HP) is determined based on the position of the home position sensor. The carriage position detection accuracy by the home position sensor, the position accuracy between the home position sensor and the document scale, and when the temperature change or the installation surface of the device affects the position of each component,
There arises a problem that the image reading start position fluctuates or shifts. Therefore, an object of the present invention is to provide an image reading apparatus that solves the above-mentioned problems, enables the white reference plate to be read reliably, and improves the accuracy of the image reading start position.

[0013]

An image reading apparatus according to claim 1 comprises a light source for exposing a document placed on a contact glass and a reflection mirror for obtaining a reflected light image of the document illuminated by the light source. In the image reading device, the first carriage, the second carriage for guiding the reflected light image from the first carriage to the optical lens, and the image sensor for photoelectrically converting the image formed by the optical lens are provided. A first gate signal defining shading data based on the distance or time from the first reference position to the end surface of the original scale as a second reference, and first means for creating the first gate signal based on the second reference. A second gate signal that defines the image reading area can be set to any value from the second reference.
And means for achieving the above object.

According to another aspect of the image reading apparatus of the present invention, the first means sets the distance from the predetermined first reference position to the second reference to L ₁ or the predetermined first reference position to the second reference position. Is t ₁ , the distance from the predetermined reference position until the first gate signal starts is Ls, or the time from the predetermined reference position until the first gate signal starts is ts,
The above object is achieved by setting L ₁ = Ls-constant or t ₁ = ts-constant. The image reading apparatus according to claim 3, wherein the second means sets the distance from the predetermined first reference position to the second reference to L ₁ or the time from the predetermined first reference position to the second reference. Is t ₁ , the distance from the predetermined first reference signal to the second reference is L _1, or the time from the predetermined first reference signal to the second reference is t ₁ , and the predetermined reference signal to the gate signal F Is a distance until the gate signal F starts from the predetermined reference signal or Ls.
When s, Ls = L ₁ + L ₂ or ts = t ₁
The above object is achieved by achieving + t ₂ .

In the image reading apparatus according to the fourth aspect, the above object is achieved by the fact that the reference signal corresponding to the predetermined first reference position is obtained based on the read data from the image sensor. In the image reading device according to the fifth aspect, the read data is obtained when the predetermined pattern provided on the contact glass is read, thereby achieving the object. In the image reading device according to the sixth aspect, the read data is obtained when the predetermined density provided on the contact glass is read, thereby achieving the object.

[0016]

In the image reading apparatus according to the first aspect of the invention,
By setting the reading start position of the white reference plate with the leading edge of the original scale as a reference, and setting the distance corresponding to the image reading start position and the image reading start position by the user, respectively. Even if the image reading position is changed according to the user's convenience, the reading area of the white reference plate does not change, and the effective range of the white reference plate need not be set wider than necessary. In the image reading device according to the second aspect of the present invention, since L ₁ = Ls-constant or t ₁ = ts-constant, the reading area of the white reference plate does not change.

In the image reading apparatus according to the third aspect of the invention, since Ls = L ₁ + L ₂ or ts = t ₁ + t ₂ is set, the image reading position is changed according to the usability of the user. be able to. In the image reading device according to the fourth aspect of the present invention, since the reference signal corresponding to the predetermined first reference position is obtained based on the read data from the image sensor, it is possible to improve the accuracy of the image reading start position. Variation is reduced. In the image reading device according to the invention of claim 5, since the read data is obtained when a predetermined pattern provided on the contact glass is read, the accuracy of the image reading start position is improved and the variation is reduced. ing. In the image reading apparatus according to the invention of claim 6, since the read data is obtained when a predetermined density provided on the contact glass is read, the accuracy of the image reading start position is improved and the image reading is varied. Has been reduced.

[0018]

The present invention will be described below with reference to the illustrated embodiments. 1 to 3 are diagrams for explaining a digital copying machine according to an embodiment of the present invention, and FIGS. 4 and 5 are diagrams for explaining a first embodiment of the present invention. First,
The basic configuration of the digital copying machine according to the present embodiment will be described with reference to FIGS. 1 to 3, and then the first embodiment will be described with reference to FIGS. 4 and 5.

FIG. 1 is an overall configuration diagram of a digital copying machine, FIG. 2 is an enlarged view of an image reading apparatus of the digital copying machine, and FIG. 3 is an enlarged perspective view of a printer section of the digital copying machine. Is. In FIG. 1, the digital copying machine is roughly composed of an image reading device 11, a printer unit 12 having a laser beam scanning device, and an automatic document feeder 13. Here, the automatic document feeder 13
The set originals are conveyed one by one and set on the contact glass 14, and the contact glass 14 after copying is completed.
The upper document is ejected.

As shown in FIG. 2, the document reading device 11 includes a light source including an illumination lamp 15 and a reflecting mirror 16 and a first light source.
A first carriage A equipped with a mirror 17 and a second carriage B equipped with a second mirror 18 and a third mirror 19 are provided. Further, the document reading device 11 is provided with a second
The color filter 20 that filters the reflected light image sent from the carriage B, the optical lens 21 that forms the reflected light image that has passed through this color filter 20, and the reflected light image that is formed by this optical lens 21 An image sensor (CCD sensor) 22 that converts an analog image signal
The circuit board 23 is equipped with a digital converter and an image processing circuit for image-processing a digital image signal converted by the analog / digital converter, and a cooling fan 24 for cooling the illumination lamp 15.

In this document reading device 11, when reading a document, the first carriage A moves forward at a constant speed, and the second carriage B follows the first carriage A at half the speed of the first carriage A. By moving forward, the original on the contact glass 14 is optically scanned, the original on the contact glass 14 is illuminated by the illumination lamp 15 and the reflecting mirror 16, and the reflected light image is reflected by the first mirror 17 and the second mirror 17. An image is formed on a CCD sensor 22 by a lens 21 via a mirror 18, a third mirror 19 and a color filter 20.

Further, the CCD sensor 22 photoelectrically converts the reflected light image of the formed original to output an analog image signal, and the circuit board 23 converts it into a digital image signal for image processing. Has become. After the image reading is completed, the first carriage A and the second carriage B move back to the home position HP position. In addition,
The CCD sensor 22 has three lines of C including red (R), green (G), and blue (B) filters.
A color original can be read by using a CD.

The printer unit 12 also forms a static image on the photoconductor drum 25 on which an electrostatic image is formed, a charging device 26 which uniformly charges the photoconductor drum 25, and the photoconductor drum 25. A laser beam scanning device 27, a developing device 28 for developing the electrostatic image formed on the photosensitive drum 25, a transfer device 30 for transferring the visible image formed on the photosensitive drum 25 onto a transfer sheet, A separation device 31 for separating the transfer paper from the photosensitive drum 25, a cleaning device 32 for wiping off the developer remaining on the photosensitive drum 25, paper feeding devices 33 to 35, and a registration roller 3.
6, a carrying device 37 for carrying the transfer paper, a fixing device 38 for fixing the visible image transferred to the transfer paper, and a tray 39 for placing a copy.

Next, the details of the laser beam scanning device 27 will be described with reference to FIGS. The laser beam scanning device 27 includes a semiconductor laser unit 40 fixed to the side surface of its housing, and a cylindrical lens 41 provided at a predetermined position on the output side of the semiconductor laser unit 40.
And a polygon mirror 42 provided at the center of one end side of this housing
A polygon motor 43 for rotating the polygon mirror 42, an fθ lens 44 provided slightly on the polygon mirror 42 side from the substantially central position of the housing, and a reflecting mirror 45 provided on the other end side of the housing. The housing is composed of a dustproof glass 46 provided below the reflecting mirror 45, a synchronization detecting mirror 47 provided at one end of the reflecting mirror 45, and a synchronization detecting sensor 48 receiving reflected light from the synchronization detecting mirror 47. ing.

Next, the overall operation of such a digital copying machine will be described. At the time of reading a document, first, one set document is taken out by the automatic document feeder 13 and conveyed, and placed on the contact glass 14. After that, the first carriage A moves forward at a constant speed, and the second carriage B moves forward following the first carriage A at half the speed of the first carriage A. As a result, the document on the contact glass 14 is optically scanned. The document on the contact glass 14 is illuminated by a light source or the like, and the reflected light image is reflected by the first mirror 17 and the second mirror 1.
8, guided to the optical lens 21 via the third mirror 19,
An image is formed on the CCD sensor 22 by the optical lens 21. The CCD sensor 22 photoelectrically converts the formed reflected light image of the document into an analog image signal, and the document is read.

After reading the original, the first carriage A and the second carriage B are moved to the home position HP.
Move back to the position. After the copying is completed, the original on the contact glass 14 is discharged by the automatic original feeder, and the next original set is taken out by one sheet and conveyed by the automatic original feeder.
Placed on top. In this way, the reading of the document is performed one after another. The analog image signal output from the CCD sensor 22 is converted into a digital image signal by an analog / digital converter mounted on the circuit board 23,
The image processing circuit mounted on the circuit board 23 performs various types of image processing (binarization, multi-value processing, gradation processing, scaling processing, editing processing, etc.).

Next, the document copying operation of the digital copying machine will be described. During the copying operation, in the printer unit 12 of the digital copying machine, the photosensitive drum 25 is rotationally driven by the driving unit so that the charging unit 26 uniformly charges the photosensitive drum 25. The digital image signal subjected to image processing by the image processing circuit mounted on the circuit board 23 is converted into an electrostatic image on the photosensitive drum 25 by the laser beam scanning device 27. The operation of the laser beam scanning device 27 will be described. A laser beam emitted from a semiconductor laser in the semiconductor laser unit 40 is converted into a parallel light beam by a collimating lens in the semiconductor laser unit 40, and is provided in the semiconductor laser unit 40. By passing through the aperture, it is shaped into a light beam of a fixed shape.

This light beam is compressed in the sub-scanning direction by the cylindrical lens 41 and enters the polygon mirror 42. The polygon mirror 42 has an accurate polygonal shape and is driven to rotate in a fixed direction by a polygon motor 43 at a fixed speed. The rotation speed of the polygon mirror 42 is determined by the rotation speed of the photosensitive drum 25, the writing density of the laser beam scanning device 27, and the number of faces of the polygon mirror 42. The laser beam entering the polygon mirror 42 from the cylindrical lens 41 is deflected by the reflecting surface of the polygon mirror and enters the fθ lens 44.
The fθ lens 44 converts the scanning light having a constant angular velocity from the polygon mirror 42 so that the photoconductor drum 25 scans at a constant velocity, and the laser beam from the fθ lens 44 passes through the reflecting mirror 45 and the dustproof glass 46. Photoconductor drum 25
Imaged above. The fθ lens 44 also has a surface tilt correction function.

Further, the laser beam that has passed through the fθ lens 44 is reflected by the synchronization detection mirror 47 outside the image area and guided to the synchronization detection sensor 48. Then, the detection signal of the synchronization detection sensor 48 provides a synchronization signal that serves as a reference for cueing in the main scanning direction. In this way, an electrostatic image is formed on the photosensitive drum 25 by the laser beam scanning device 27.

The electrostatic image on the photosensitive drum 25 is
It is transferred onto the transfer paper by the transfer device 30. After that, the transfer paper is separated from the photoconductor drum 25 by the separating device 31, and then conveyed to the developing device 38 by the conveying device 37. This transfer paper is developed by the developing device 38 and discharged onto the tray 39 as a copy. Further, the photosensitive drum 25 is cleaned by the cleaning device 32 after the transfer paper is separated, and the residual toner is removed. Through such work, the digital copying machine makes a copy.

Next, a first embodiment of the present invention will be described. FIG. 4 is a block diagram showing the first embodiment. Further, FIG. 5 is a diagram showing the positional relationship shown for explaining the operation of the first embodiment. 4 and 2, in the document reading device 11, the document scale 5 is used to correct the illuminance on the surface of the CCD sensor 22 and the output variation of each pixel of the CCD sensor 22 (shading correction).
The white reference plate 52 is provided on a part of the back surface of the contact glass 14
Is provided at a position 54 on the upper surface (almost equivalent to the document surface). Reference numeral 55 is an end portion of the original scale 51,
One end of the document comes into contact with this end 55.

Reference numeral HP is a home position (reference position in the sub-scanning direction), and the first mirror 17 of the first carriage A is located at the home position HP when reading is started. . Also,
The document reading device 11 is provided with a scanner control unit 101 including, for example, a one-chip CPU (central processing unit), and the scanner control unit 101 is used by the document reading device 1.
The operation within 1 is controlled. A home position sensor 102 composed of a photo interrupter or the like is connected to the scanner control unit 101.

The home position sensor 102 is arranged at the home position HP and can detect, for example, whether the first mirror 17 is located at the home position HP. The scanner control unit 101 includes a stepping motor 103 for moving the first carriage A and the like, and an illumination lamp 1 provided between the illumination lamp 15 and the power supply 104.
The flashing circuit 105 for controlling the flashing of 5 is connected. Further, the scanner control unit 101 has a counter 1 for counting the pulses supplied to the stepping motor 103.
06 and the operation panel 107 are connected.

Further, the scanner control section 101 can receive a reading start command ST given from the main body. In addition, the scanner control unit 101 is capable of forming a shading gate signal SLEAD instructing capture of shading data and an area defining gate signal FGATE defining a reading area. The output of the CCD sensor 22 is connected to the signal processing circuit 111. The output of the signal processing circuit 111 is
It is connected to the analog / digital (A / D) converter 112. The output of the A / D converter 112 is connected to one input terminal of each of the first gate circuit 113 and the second gate circuit 114.

The shading gate signal SLEAD is applied from the scanner controller 101 to the other inverting input terminal of the first gate circuit 113.
Further, the other inverting input terminal of the second gate circuit 114 is supplied from the scanner control unit 101 to the area defining gate signal FG.
ATE is provided. The output terminal of the first gate circuit 113 is connected to the shading correction circuit 115. The output terminal of the second gate circuit 114 is connected to the image processing circuit 116.

Next, the operation of the first embodiment will be described. The reading start command ST from the main body is the original reading device 11
Then, the scanner control unit 101 creates a reference signal based on the detection signal from the home position sensor 102 and activates the blinking circuit 105 to turn on the illumination lamp 15. Further, the stepping motor 103
To start the movement of the first carriage A and the like. On the other hand, along with the reference signal, the drive pulse of the stepping motor 103 is counted by the counter 106. The scanner control unit 101 causes the shading gate signal SLEAD to fall by a constant width after the count value of the counter 106 reaches the predetermined moving distance Ls. This allows the CCD
The image signal from the sensor 22 is input to the shading correction circuit 115. Therefore, the shading correction circuit 115 can correct the CCD sensor 22.

Further, the shading gate signal SLEA
Since D is started up after a predetermined width has passed, the first
The gate circuit 113 will be closed. After that, when the scanner control unit 101 determines that the distance Lf from the value of the counter 106 to the leading end position of the read image area has been reached, the area defining gate signal FGATE is turned off and the reading determined by the operation panel 107 or the like is performed. After the area defining gate signal FGATE falls by the range, the area defining gate signal FGATE rises. Therefore, while the area defining gate signal FGATE is at the low level (“L”), the CCD sensor 22 and the signal processing circuit 11 are operated.
The image signal that has passed through 1 and the A / D converter 112 is supplied to the image processing circuit 116 via the second gate circuit 114. In this embodiment, Ls · Lf can be set with _two independent parameters L ₁ and L ₂ as represented by the following formulas 1 and 2.

[0038]

[Formula 1] Ls = L ₁ −const (constant value)

[0039]

[Formula 2] Lf = L ₁ + L ₂

Here, the distance L ₁ is set at the time of factory shipment of the apparatus, and is normally determined so as to coincide with the front end portion 55 of the original scale 51 on the reading start side in the sub-scanning direction. The value of const is determined from the positional relationship between the tip portion 55 of the original scale 51 and the white reference plate 52 for taking in shading data, and is determined in consideration of component accuracy. The distance L ₂ can be set by the user from the operation panel 107 or the like according to the convenience of use, and L ₂ = 0 at the time of normal shipping.
Is set to. The distance L ₁ is the distance from the home position HP to the leading end 55 of the original scale 51 (see FIG. 4).

As described above, in this embodiment, the distance L ₁ from the predetermined reference position (home position HP) to the leading end 55 of the original scale 51 is used as the second reference, and the shading gate signal (first 1 gate signal) SLEAD is created based on the second reference (L ₁ ). That is, at the position where the above formula 1 is satisfied,
The shading gate signal SLEAD is started to fall, the gate signal SLEAD is lowered by a predetermined width, and then the gate signal SLEAD is raised again.

Further, in the present embodiment, the area defining gate signal (second gate signal) FGAT which defines the image reading area.
E can be set to any value from the second reference (L ₁ ). That is, the area defining gate signal FGA
After falling TE at a predetermined distance Lf and falling the gate signal FGATE by a predetermined width F, the gate signal FG is again set.
I am trying to launch ATE. Further, Lf is the distance L ₂ when the operation panel 1
It can be set arbitrarily from 07 and the like. In this example,
As described above, since the reading position of the white reference plate does not change even if the image reading start position is changed according to the usability of the user, the effective range of the white reference plate can be narrowed.

Also, the trouble of adjusting the reading start position of the white reference plate in the manufacturing process is eliminated. In addition, in the above-mentioned embodiment, the equations 1 and 2 are described by using the distance, but they may be performed by time like the following equations 3 and 4.

[0044]

(3) ts = t ₁ -const (constant value)

Here, ts represents the start time point of the shading gate signal SLEAD from the reference position HP, and t ₁ represents the time from the reference position HP to the leading end 55 of the original scale 51.

[0046]

## EQU4 ## tf = t ₁ + t ₂

However, tf is a start time of the area defining gate signal FGATE from the reference position HP, and t ₂ is a time which can be arbitrarily set from the operation panel 107 or the like. In this case, the timer is operated from the time when the first carriage A starts moving from the reference position HP, and
When the above condition is established, the shading gate signal SLEAD and the area defining gate signal FGA are output from the scanner control unit 101.
It suffices to output TE.

Next, a second embodiment will be described with reference to FIGS. Here, FIG. 6 is an explanatory diagram showing a configuration for creating the reference position signal of the second embodiment. Figure 7
It is a top view showing the composition for creating the reference position signal of the 2nd example. FIG. 8 shows a CCD used in the second embodiment.
6 is a time chart showing an example of a partial signal from the sensor 22, in which the horizontal axis represents time t and the vertical axis represents data of a predetermined pixel.

In the second embodiment, the reference position signal is formed by the detection signal from the home position sensor 102 in the circuit configuration of FIG. 4, but instead of this, for example, the detection data of the CCD sensor 22 is fetched. The reference position signal is thus formed. Specifically, the output of the A / D converter 112 is set to the scanner control unit 10.
1, and the scanner control unit 101 forms a reference position signal by paying attention to signals of some pixels.

Therefore, the white reference plate 52 is provided below the left original scale 51, and the pattern 56 is arranged on the contact glass 14 at a position to be read prior to the white reference plate 52 on the original scale 51. ing. In the actual operation, when the reading start command ST is sent from the main body to the signal processing circuit 111, the scanner control unit 101 causes the blinking circuit 1 to operate.
05 is activated to turn on the illumination lamp 15. Next, the scanner control unit 101 drives the stepping motor 103 to start the movement of the first carriage A and the like, but crosses the center of the pattern 56 on the contact glass 14 to CC.
When read by the D sensor 22, the pixel output of the CCD sensor 22 shows the time t from the first “L ₁ ”, as shown in FIG.
The next “L ₂ ” is output after 1 and “L ₃ ” is output after time t ₂ has passed from this “L ₂ ”.

The scanner control unit 101 compares the output pattern with a pattern having a value stored in advance and the interval of the black portion as a reference, and when it is determined that they match, the reference position is based on the reading position indicated by HPS in the drawing. Creating a signal. According to the second embodiment, since the predetermined reference position signal is obtained from the read data of the CCD sensor 22, the number of components involved from the position where the data for generating the predetermined reference signal is read to the document leading end position is reduced. Therefore, the accuracy of the reading start position is improved. In addition, it is possible to remove components such as the home position sensor 102, so that the cost can be reduced.

Next, a third embodiment of the present invention will be described. 9 and 10 are views for explaining the third embodiment of the present invention. FIG. 9 is a plan view showing the pattern on the contact glass, and FIG. 10 is an explanatory view showing the pattern of the read data. As shown in FIG. 9, the white reference plate 52 of the original scale 51 is provided on the contact glass 14.
The pattern 57 is arranged at a position where it can be read in advance. As shown in FIG. 9, this pattern 57 is made up of black B and white W based on a diagonal line of a quadrangle.

When the CCD sensor 22 is read across the center of the pattern 57, the output signal from the CCD sensor 22 shows a pattern in which "L" and "H" follow the center value, as shown in FIG. Become. Therefore, the scanner control unit 101 compares this pattern with a previously stored pattern using the density and the width as a reference, and when it determines that they match, the scanner control unit 101 determines the reference position signal with the reading position indicated by the symbol HPS in the drawing as a reference. Creating. In the third embodiment, since the read data is obtained when the predetermined pattern 57 provided on the contact glass 14 is read, the number of components up to the leading end 55 of the original scale 51 is reduced. The accuracy of the reading start position is improved, and moreover, erroneous recognition can be prevented by reading a predetermined pattern.

Next, a fourth embodiment will be described. 11 and 12 are for explaining the fourth embodiment. Here, FIG. 11 is a plan view of a pattern used in the fourth embodiment, and FIG. 12 is an explanatory diagram of read data obtained in the fourth embodiment, in which the horizontal axis indicates time t,
R axis CCD sensor, G CCD sensor, B CC
The respective output signals of the D sensor are shown. This 4th
In this embodiment, the CCD sensor 22 is a three-line CCD for R, G, and B. In this case, FIG.
The predetermined density pattern 58 provided on the contact glass 14 as shown in FIG. 4 has a specific color. Here, the color of the scale is gray and the color of the color pattern is blue. In this case, as in the third embodiment, the pixel output of the CCD sensor 22 which is read across the center of the pattern 58 has the lowest level of the R image signal, as shown in FIG. The image signal for G has a low level, and the image signal for B has a high level.

In the scanner control unit 101, such an output pattern is compared with a prestored pattern based on color balance and width, and when it is determined that they match,
The reference position signal is created with reference to the reading position indicated by the symbol HPS in the drawing. According to the fourth embodiment, the components related to the leading end portion (original leading end position) 55 of the manuscript scale 51 are obtained when the predetermined color pattern 58 provided on the contact glass 14 is read. As a result, the accuracy of the reading start position is improved, and erroneous recognition can be prevented by reading a predetermined color.

Next, a fifth embodiment of the present invention will be described. FIG. 13 is a perspective view showing the fifth embodiment. In this fifth embodiment, each pattern 5 shown in each of the above embodiments is used.
6 to 58 are arranged as a pattern 60 on the left original scale 51 as shown in FIG. That is, in the original scale 51, as shown in FIG.
The pattern 60 is arranged at a position where it can be read in advance. Here, the pattern 60 may be, for example, the same geometric pattern 56 as that of the second embodiment, the pattern 57 of the third embodiment, or the density pattern 58 of the fourth embodiment.

As a modification, the pattern 60 may be the color pattern 58 as in the fourth embodiment. Further, the manuscript scale 51 is made of a resin material, and the pattern 5
2 and the pattern 60 may be formed by two-color molding. According to the fifth embodiment, since the read data is obtained when the predetermined density provided on the scale is read, the components related to the leading end position of the document are eliminated and the accuracy of the read start position is improved. Further, by reading the predetermined density, erroneous recognition can be prevented.

Further, according to the fifth embodiment, since the read data is obtained when a predetermined color provided on the scale is read, there is no component related to the leading end position of the document, so that the read start position is obtained. Accuracy is improved, and erroneous recognition can be prevented by reading a predetermined color.
Further, in the fifth embodiment, the predetermined pattern or the predetermined color provided on the original scale 51 is formed by two-color molding, so that the original scale 51 is provided with a mark or an accessory for generating a reference signal. Since there is no need to add it, processing costs, processing time, and assembly time can be reduced.

[0059]

As described above, according to the first aspect of the invention, the reading start position of the white reference plate is set with reference to the leading end of the original scale and the distance corresponding to the image reading start position is set. By enabling each setting and the image reading start position by the user, the reading area of the white reference plate does not change even if the image reading position is changed according to the user's convenience, and the effective range of the white reference plate Need not be set wider than necessary. According to the second aspect of the invention, since L ₁ = Ls-constant or t ₁ = ts-constant, the reading area of the white reference plate is changed even if the reading position of the image is changed according to the usability of the user. Does not fluctuate. In the invention according to claim 3, Ls =
Since L ₁ + L ₂ or ts = t ₁ + t ₂ is set, the image reading position can be changed according to the usability of the user. According to the invention of claim 4,
Since the reference signal corresponding to the predetermined first reference position is obtained based on the read data from the image sensor, there is no component related to the position of the leading edge of the document, and the accuracy and variation of the image reading start position are improved. It can be reduced. In the invention according to claim 5, since the read data is obtained when a predetermined pattern provided on the contact glass is read, it is possible to improve the accuracy of the image reading start position and reduce variations. In the invention of claim 6, the read data is
Since it is obtained when the predetermined density provided on the contact glass is read, it is possible to improve the accuracy and the variation of the image reading start position, and reduce the erroneous recognition.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of a digital copying machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an enlargement of a document reading device of the digital copying machine of FIG.

FIG. 3 is a perspective view showing a configuration of a laser beam scanning device of a digital copying machine.

FIG. 4 is a block diagram showing a first embodiment.

FIG. 5 is an explanatory diagram for explaining the operation of the first embodiment.

FIG. 6 is a side view showing the pattern arrangement of the second embodiment.

FIG. 7 is a plan view showing a pattern arrangement of a second embodiment.

FIG. 8 is a time chart showing an image signal obtained in the second embodiment.

FIG. 9 is a plan view showing a pattern arrangement of a third embodiment.

FIG. 10 is a time chart showing an image signal obtained in the third embodiment.

FIG. 11 is a plan view showing the pattern arrangement of the fourth embodiment.

FIG. 12 is a time chart showing an image signal obtained in the fourth embodiment.

FIG. 13 is a perspective view showing a pattern arrangement and the like of a fifth embodiment.

FIG. 14 is an explanatory diagram showing a part of a conventional document reading apparatus.

[Explanation of symbols]

11 Document reading device 12 Printer section 13 Automatic document feeder 14 Contact glass 15 Lighting lamp 16 Reflector 17 First Mirror 18 Second mirror 19 Third mirror 21 Optical lens 22 CCD sensor (imaging sensor) 23 circuit board 25 photoconductor drum 26 Charging device 27 Laser beam scanning device 28 Developing device 30 transfer device 31 Separator 38 Developing device A first carriage B second carriage 51 manuscript scale 52 White reference plate 54 Top surface position 55 Edge 56-58 patterns 60 patterns 101 Scanner control unit 102 Home position sensor 103 stepping motor 105 flashing circuit 106 counter 107 Operation panel 111 Signal processing circuit 112 Analog / Digital (A / D) Converter 113 First Gate Circuit 114 second gate circuit 115 Shading correction circuit 116 Image processing circuit 500 image reading device 501 manuscript scale 502 White reference plate 503 contact glass 505 Original scale edge

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Koho Shijo 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) Reference JP-A-4-261269 (JP, A) JP 5-14609 (JP, A) JP-A-5-91259 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04N 1/401

Claims (6)

(57) [Claims] 1. A first carriage having a light source for exposing a document placed on a contact glass and a reflecting mirror for obtaining a reflected light image of the document illuminated by the light source, and reflected light from the first carriage. Second to guide the image to the optical lens
In an image reading apparatus including a carriage and an image sensor that photoelectrically converts an image formed by the optical lens, a distance or time from a predetermined first reference position to an end surface of a document scale is used as a second reference. , A first means for creating a first gate signal defining shading data based on the second reference, and a second gate signal defining an image reading area to an arbitrary value from the second reference. An image reading apparatus comprising a second unit that can be set. 2. The first means is a distance L _{1 from a} predetermined first reference position to a second reference or a time t ₁ from a predetermined first reference position to a second reference, The distance from the predetermined reference position to the start of the first gate signal is Ls
Alternatively, assuming that the time from the predetermined reference position until the first gate signal starts is ts, L ₁ = Ls-constant, or
The image reading apparatus according to claim 1, wherein t ₁ = ts-constant. 3. The second means is a distance L _{1 from a} predetermined first reference position to a second reference or a time t ₁ from a predetermined first reference position to a second reference, The distance from the predetermined first reference signal to the second reference is L ₁ or the time from the predetermined first reference signal to the second reference is t ₁ , until the gate signal F starts from the predetermined reference signal The distance of Ls
Alternatively, when the time from the predetermined reference signal to the start of the gate signal F is ts, Ls = L ₁ + L ₂ or t
The image reading apparatus according to claim _{1, wherein} s = t ₁ + t ₂ . 4. The image reading apparatus according to claim 1, wherein the reference signal corresponding to the predetermined first reference position is obtained based on the read data from the image sensor. 5. The image reading apparatus according to claim 4, wherein the read data is obtained when a predetermined pattern provided on the contact glass is read. 6. The image reading apparatus according to claim 4, wherein the read data is obtained when a predetermined density provided on the contact glass is read.