JPH09270887A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To excellently read an image without image distortion, even when the distance from a predetermined reference face, such as an original placing face of an original platen up to an original face, is changed along with a read scanning direction. SOLUTION: A sensor 90 (original face state detection means) is mounted onto a 1st slider SL1, the sensor 90 is used to calculate a distance Δh (original face fold state) between an upper face of an original platen 5 and each part of the original face in real time during scanning of the original, and drive speeds V1 , V2 of the 1st slider SL1 and the 2nd slider SL2 are calculated in which the scanning speed of each part of the original and the optical path length from each part of the original face to an image forming lens 7, via reflecting mirrors M13, M21, M22 during scanning of the original face based on the distance Δh are kept constant and the 1st slider SL1 and the 2nd slider SL2 are driven at the drive speeds V1 , V2 .

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 mounted on a copying machine, an image scanner or the like, and more particularly, when it is placed on a platen like a folded portion of a book, the distance between each part of the document surface and the platen, or The present invention relates to an image reading apparatus having a function (book reading function) of correcting image distortion that occurs when the distance between each part of the document surface and a predetermined reference surface is not constant.

[0002]

2. Description of the Related Art Generally, in a copying machine, an image scanner or the like, a document image placed on a document table is read by a first slider equipped with an illumination lamp for illuminating a document on the document table and a first mirror. And a second with a second mirror
The slider scans the document while moving in parallel to the document table, guides the reflected light reflected on the document surface to the imaging lens by the first mirror and the second mirror, and reads the imaging light with an image sensor or the like. Alternatively, the imaging light is further guided to the photoconductor through the reflection mirror means. At this time, by moving the first slider and the second slider at a speed ratio of 2: 1, the optical path length of the image light of the document guided from the document surface to the imaging lens via the first mirror and the second mirror is constant. Then, a good image without image distortion is read.

However, as shown in FIG. 10, when a book 200 as a manuscript is placed on a transparent manuscript table 100 and a folding part 201 is provided on the manuscript table 100, the manuscript surface does not come into close contact with the manuscript table 100, that is, When the distance between the document table 100 and the document surface is not constant in the scanning direction, an image on the document surface raised from the document table 100 around the folding unit 201 is read by such an image reading device, and the read image is obtained. Image distortion such as shrinkage occurs, and the image cannot be read well.

To solve this problem, USP 498
0720 teaches a copying machine equipped with the following image reading device. In this image reading device, a first mirror mounted on a first slider is configured to be rotatable, the first slider is driven at a constant speed in a scanning direction, and detection is performed by a distance detection means mounted on the first slider. Based on the distance between the document surface and the document table, the first correction is performed to correct the magnification distortion in the moving direction of the first slider due to the lifting of the document.
The original image is read while compensating for the change in the conjugate length of the first mirror and the second mirror by changing the speed of the second slider while rotating the mirror.

Further, Japanese Patent Laid-Open No. 2821621/1993 teaches the following image forming apparatus in order to solve the above problems. This image forming apparatus has a distance detecting means for detecting the distance between the document surface and the document table, calculates the curvature of the document surface based on the detection result of this distance detecting means, and performs optical calculation according to the curvature. By correcting the copy magnification in the system scanning direction by the copy magnification correcting means, it is intended to obtain a good image without image distortion.

[0006]

However, USP49
In the image reading apparatus taught by 80720, a rotation mechanism for rotating the first mirror has to be newly provided on the first slider, and the number of parts used increases, the size increases, and the weight also increases. Driving burden increases. Also, the first
If the center of rotation of the mirror is not set to the center of gravity of the first mirror and the center of gravity of the first slider, the weight balance of the first slider fluctuates while the first slider is being driven, and the first slider may fluctuate in speed (uneven speed). ) Occurs. Even if the first mirror is arranged on the first slider so that the center of gravity and the center of rotation are aligned with each other, the speed fluctuation becomes larger than that in the case where the first mirror is fixed.

Further, the image forming apparatus taught by Japanese Patent Laid-Open No. 5-281621 requires new parts such as a copy magnification correcting means, which not only increases the size but also increases the cost.
Therefore, according to the present invention, an illumination lamp for illuminating a document on the platen and a first slider for mounting a first mirror and a second slider for mounting a second mirror scan the document while moving in parallel to the platen. Then, in the image reading apparatus in which the reflected light reflected on the document surface is guided to the imaging lens by the first mirror and the second mirror, from the predetermined reference surface such as the document mounting surface of the document table to the document surface. An image reading apparatus capable of performing good image reading without image distortion even when the distance changes along the reading scanning direction, and having a simple structure and capable of excellent image reading with less variation in slider speed. The challenge is to provide.

[0008]

SUMMARY OF THE INVENTION To solve the above problems, the present invention is an image reading apparatus for optically scanning a document image, which comprises a document table on which a document is placed and a document table placed on the document table. An illuminating device for illuminating an original and a first mirror for guiding reflected image light from the original in a predetermined direction, and a first slider capable of reciprocating in parallel to the original table;
A second slider that mounts a second mirror that guides the image light from the mirror in a predetermined direction and can reciprocate in the same direction as the first slider; and a first slider that reciprocally drives the first slider.
A slider drive means, a second slider drive means for reciprocally driving the second slider independently of the first slider, a lens for forming image light from the second mirror, and a document table mounted on the original table. A document surface state detecting means for detecting a bent state of the surface of the document to be placed with respect to a predetermined reference surface, and a document at the time of scanning the document surface based on the state of each part of the document surface detected by the document surface state detecting means. The first slider and the second slider are driven so that the optical path length from each part of the surface to the lens through the first mirror and the second mirror and the scanning speed of each part of the document surface are maintained constant. There is provided an image reading apparatus comprising: a control unit that controls the operation of each of the first and second slider driving units.

The image reading apparatus according to the present invention further comprises, after the image forming lens, mirror means for guiding the image light to a photosensitive member which is an electrostatic latent image carrier, or
An image sensor including a CCD image pickup device can be provided after the imaging lens. The former image reading device can be applied to analog copying machines, and the latter image reading device can be applied to digital copying machines and image scanners.

The first slider driving means transmits the power of a linear motor capable of driving the first slider independently of the second slider and the power of the electric motor to the first slider via a transmission mechanism such as a wire / pulley mechanism. And so on. The same applies to the second slider driving means.
The platen may typically be a flat platen.

The number, position and orientation of the first reflecting mirrors mounted on the first slider and the number, position and orientation of the second reflecting mirrors mounted on the second slider can be appropriately determined. Regarding the “predetermined reference surface” for judging the document surface bending state according to the document surface state detecting means, for example, the document table is a flat table made of transparent glass,
In the case of a configuration in which a document is placed (face-down placement) with the document image to be read facing the table surface, the flat document table surface can be used as the predetermined reference surface. In addition, for example, in placing a document on a flat document table, in a configuration in which the surface opposite to the image to be read is placed toward the table (face-up placement), it is parallel to the document table surface. An appropriate surface can be the predetermined reference surface.

The "bent state of the document surface with respect to the predetermined reference surface" means that the portion of the document surface that is currently being scanned is in a state of being parallel or substantially parallel to the predetermined reference surface, or for scanning a document image. In the moving direction of the first and second sliders, the portion of the document surface is curved so as to gradually move away from the predetermined reference surface or gradually approaches (in other words, the predetermined reference surface of each portion of the document surface). Angle of inclination), how far the portion of the document surface is from the predetermined reference surface (or the position of the document surface portion with respect to the predetermined reference surface), and the like.

The "scanning speed of each part of the document surface" when the scanning speed of each part of the document surface is kept constant by the control means.
Also includes when the scanning speed is the scanning speed per unit area of the document surface portion. Of the surface to be scanned of the original placed on the original table (usually a flat table), a surface portion (usually a flat surface portion) substantially parallel to the predetermined reference surface.
With regard to (1), normally, the first slider is driven at a preset first slider scanning speed for scanning such a document surface portion, and the second slider is driven at a scanning speed ½ thereof.

Regarding the control means of the first and second slider driving means, regarding the scanning of the surface portion of the original placed on the original table which is to be scanned and which is substantially parallel to the predetermined reference surface. Drives the first slider and the second slider at a preset speed ratio (typically 2: 1),
Even when the document surface bending state detected by the document surface state detecting means exceeds a predetermined document surface bending state, the first slider and the second slider are set to the set speed ratio and the first slider is moved. The operations of the first and second slider driving means may be controlled so that the speed is maintained at a speed immediately before the predetermined original surface bending state is exceeded.

The document surface state detecting means is, for example, a distance sensor capable of detecting the distance between the predetermined reference surface and the document surface, or Doppler capable of detecting how fast the document surface moves away from (or approaches) the predetermined reference surface. A speed detector such as a speed detector utilizing the effect can be mentioned. When such a distance sensor is used, the control means calculates a change state (for example, a change state with respect to a predetermined time interval) of the distance from the predetermined reference surface to the document surface, which is obtained based on the detection result of the sensor, and changes the distance. First based on state
It is conceivable to configure so as to calculate the driving speed of the slider and the second slider.

When a speed detector is used, the control means calculates a speed change state (for example, a change state for a predetermined time interval) obtained by the speed detector, and based on the change state, the first It is conceivable that the drive speed of the second slider is calculated. The distance detection sensor and the speed detection sensor may be provided, for example, on the first slider or the second slider, or may be provided at a fixed position outside the slider.

In any case, the bending state of the document surface with respect to the predetermined reference plane can be detected by the document surface state detecting means in real time while the image is being read, or in advance, the entire reading range in the scanning direction can be detected. The bent state of the original is detected, the detection result is stored in a storage device or the like, and the bent state of the image reading position is taken out from the storage device or the like at any time during image reading. It is also possible to read the image while controlling the speed of the slider.

In the image reading apparatus according to the present invention, the distance from the predetermined reference surface (for example, the document table) to the document surface changes along the scanning direction when the document is placed on the document table like a book having a folded portion. The image of the original to be read is read as follows. When the control means receives a signal such as the start of image scanning, it controls the first slider driving means and the second slider driving means to drive the first slider and the second slider in the image scanning direction by the respective driving means.

While both sliders are moving in the image scanning direction, the first
The illumination device mounted on the slider irradiates the original image with light, and the reflected light is guided to the lens by the first mirror arranged on the same optical axis and the second mirror mounted on the second slider. , The original image is scanned.
At that time, based on the bent state of each part of the document surface with respect to the predetermined reference plane detected by the document surface state detecting means at each position in the document scanning direction, the first mirror and the second mirror are provided from each part of the document surface.
The controller controls the first slider and the second slider at each position in the document scanning direction so that the optical path length from the mirror to the lens and the scanning speed of each part of the document surface are maintained constant.
The drive speed of each slider is calculated, and the first slider and the second slider are driven at the calculated drive speeds.

At this time, the first slider and the second slider are set in advance for the scanning of the surface portion of the original to be scanned placed on the original table which is substantially parallel to the predetermined reference surface. Although the document is driven at a speed ratio (typically 2: 1), even when the document surface bending state detected by the document surface state detecting means exceeds a predetermined document surface bending state (for example, a book folding portion). A portion where the distance from the predetermined reference surface is large, such as the inner portion of the first slider and the second slider at the set speed ratio and immediately before the speed exceeds the first slider speed. If the operations of the first and second slider driving means are controlled so that they are driven as they are, the driving speed of the first slider and the second slider may change sharply, or the second slider may start moving in the opposite direction. Ku, facilitates control of each slide.

The control means may be configured as follows. That is, as in the case where the folded portion of the book is placed at the scanning start position on the document table, when the document surface is already separated from the predetermined reference surface at the document scanning start position, the lens for image formation is formed from each part of the document surface. The second slider is moved in the scanning direction by a predetermined distance prior to the start of the original scanning so that the optical path length from the start of scanning to a predetermined constant optical path length is set, and then the first and the first scanning of the original is started. 2 The structure is such that the operation of the driving means for driving the sliders can be controlled.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an analog copying machine equipped with an image reading apparatus according to an embodiment of the present invention. FIG. 1 (A) is a schematic side view of the copying machine, and FIG.
FIG. 3 is a schematic plan view of the image reading device. FIG. 2 is an enlarged view of a first slider portion when a book is placed on a document table of the image reading apparatus.

This image reading device is provided with an original table 5 made of flat transparent glass. Below the original table 5, a first slider SL1 and a second slider S driven in parallel with the original table 5 are provided.
L2 is arranged, and an imaging lens 7 supported by a supporting means (not shown) is also arranged. In addition, the first,
Drive circuits 14 for the second sliders SL1 and SL2,
24 and a control unit 8 that controls the drive circuits 14 and 24.

The first slider SL1 has an illumination lamp 10 for illuminating an original placed on the original table 5 and emitting light in the visible range, a reflection mirror M11 for directing the illumination light of the illumination lamp 10 to the original, An M12, a reflection mirror M13 for guiding the reflected light from the document toward the second slider SL2, and a sensor 90 as a document surface state detecting means are mounted. As shown in FIG. 2, the sensor 90 uses light outside the visible range (in this example,
Illumination device 901 and illumination device 901 that can emit infrared rays
A light receiving device 902 that receives the light emitted from the device and reflected by the document surface and detects the intensity of the light is disposed below the reflection mirror M13. The reflection mirror M13 reflects the irradiation light in the visible range from the illumination lamp 10 reflected by the document surface, and transmits the irradiation light outside the visible range from the illumination device 901 of the sensor 90, and the sensor 90 is a reflection mirror. Even if it is arranged under M13, it does not hinder the document surface state detection of the sensor 90. The sensor 90 is connected to the control unit 8, and the distance Δh from the upper surface of the document table 5 to the document surface is based on the intensity of the reflected light from the document surface detected by the sensor 90.
(= H−h ₀ ) is calculated.

As shown in FIG. 1B, the first slider SL1 has a constant width in the direction perpendicular to its traveling direction, and has the bearing unit 11 at one end and the other end at the other end. Is provided with a support roller 12, the bearing unit 11 is externally fitted to the stator 3, and internally has a movable element coil and a hall element which is a position detection element used for controlling energization of the coil. Further, the roller 12 can run on the guide rail 4 parallel to the stator 3.

The stator 3 is a shaft type having a field magnet in which N poles and S poles are alternately arranged in the longitudinal direction, and together with a mover coil built in the bearing unit 11, the first slider. A linear motor that is a driving unit is configured. In this linear motor, slider position information in the longitudinal direction of the stator 3 is detected by an encoder scale 31 provided on the stator 3 and a detection element 111 of the encoder arranged in the bearing unit 11 at a position corresponding to the scale 31. it can. The encoder output is input to the first slider drive circuit 14 and the control unit 8. The first slider SL1 is servo-controlled by the drive circuit 14 and the control unit 8 based on the position information detected by the encoder.

The second slider SL2 is equipped with reflection mirrors M21 and M22 for guiding the image light guided from the reflection mirror M13 to the imaging lens 7. Similarly to the first slider SL1, the second slider SL2 also has a constant width in a direction perpendicular to its traveling direction, and has a bearing unit 21 at one end and a support roller 22 at the other end. The bearing unit 21 is externally fitted to the stator 3 and has a mover coil and a hall element built therein. Further, the roller 22 can run on the guide rail 4 parallel to the stator 3. The stator 3 is common to the stator of the linear motor of the first slider SL1, and together with the mover coil built into the bearing unit 21, constitutes the linear motor that is the second slider driving means. The linear motor of the second slider SL2 is also a slider position in the longitudinal direction of the stator 3 due to the scale 31 of the encoder of the stator 3 and the detection element 211 of the encoder arranged in the bearing unit 21 at a position corresponding to this scale 31. Information can be detected. The encoder output is input to the second slider drive circuit 24 and the control unit 8. Second slider SL2
Also, similarly to the first slider SL1, the drive circuit 24 and the control unit 8 perform servo control based on the position information detected by the encoder.

The control unit 8 includes a CPU (central processing unit).
And an arithmetic processing unit. The control unit 8 receives the sensor 90.
The distance h from the optical device 902 to the document surface is input and
From the upper surface of the document table 5, which is the predetermined reference surface that has been sought, to the light receiving device
Distance h to 902₀The predetermined reference plane by subtracting
From the upper surface of the document table 5 to the document surface Δh (= h-
h ₀) Can be calculated.

Position information is further input to the controller 8 from encoders of the first slider SL1 and the second slider SL2, and the change state of the distance Δh in a predetermined minute time Δt is calculated together with the distance Δh. based on the change state, and calculates the driving velocity V ₁ and the driving velocity V ₂ of the second slider of the first slider SL1 for maintaining the scanning speed of the document surface each portion constant. This calculation method will be described later in detail. The drive speed V ₁ is converted into a first reference clock CLK1 having a frequency proportional to the speed and input to the first slider drive circuit 14. Similarly, the drive speed V _{2 is} also converted into the second reference clock CLK2 having a frequency proportional to the speed and is input to the second slider drive circuit 24.

The first slider drive circuit 14 is provided with an energizing circuit for energizing the mover coil of the first slider SL1 and a PLL control circuit, and a current flows through the mover coil by this energizing circuit. The 1-slider SL1 is driven. At this time, the current flowing through the mover is corrected by the PLL control circuit based on the phase difference between the first reference clock CLK1 and the position information of the encoder of the first slider SL1, so that the first slider has the frequency of the first reference clock CLK1. Is driven at a speed proportional to, that is, at the driving speed V ₁ calculated by the control unit 8.

The second slider SL2 is also controlled by the second reference clock CLK2 input to the second slider drive circuit 24 and the encoder feedback signal of the slider, the energizing circuit and the PLL control circuit of the drive circuit 24, and the first slider SL2. It is driven at a speed V ₂ in the same manner as the drive circuit 14. In the image reading apparatus of the present invention described above, when the document is placed on the document table 5 like a book having a folded portion, the distance from the predetermined reference surface (the upper surface of the document table 5) to the document surface is read and scanned. Image reading of a document that changes along a direction is performed as follows in a real-time method.

First, the standard set speed V ₀ of the first slider SL1 is set from the copying magnification (or reading magnification) input from the operation panel of a copying machine equipped with this image reading apparatus. When the distance Δh from the upper surface of the document table 5 of the predetermined reference surface to the document surface is Δh = 0,
That is, when the document image surface is in contact with the document table 5, the first slider SL1 is driven at the speed V ₁ = V ₀ . At this time, the speed of the second slider SL2 is V ₂ = V
It is driven by _{1/2 = V 0/2} .

When the distance Δh from the upper surface of the document table 5 which is a predetermined reference surface to the document surface is Δh> 0, that is, when the document surface is lifted from the document table 5, the reflection mirror M13 is reflected from each part of the document surface. , M21, M22, the optical path length to the imaging lens 7 and the scanning speed of each part of the document surface thereof are kept constant during document scanning.
Drive speed V ₁ of the second slider SL2 and drive speed V ₂ of the second slider SL2
Is calculated based on the changing state of the distance Δh.

The distance Δh is detected and calculated at every minute time interval Δt by the sensor 90 and the controller 8.
If the distance calculated one time before is Δh ′, and if the distance the first slider has moved during this Δt is L, then the velocities V ₁ and V ₂ are

[0035]

[Equation 1]

[0036]

[Equation 2]

It is calculated by The time interval Δt may be set arbitrarily according to the image reading accuracy, the copy magnification (driving speed), and the like. Further, in the image reading apparatus of this example, while the distance Δh from the upper surface of the document table 5 to the document surface exceeds the predetermined distance h _th , the speed V ₁ is the speed calculated before the time Δt. V ₁ 'maintaining and velocity V ₂ at this time is _{V 2 = V 1/2 =} V 1' to maintain / 2.

The velocities V ₁ and V ₂ calculated in this way
FIG. 3 illustrates how the first and second sliders SL1 and SL2 are driven by. FIG. 3A is a diagram showing a placed state of a book, and FIG. 3B is a diagram showing a relationship between the distance X in the scanning direction from the document scanning start position and the distance Δh from the document table 5 to the document surface. 3 (C) is a diagram showing the relationship between the time t from the start of document scanning and the distance Δh, FIG. 3 (D) is a diagram showing the relationship between the time t and the velocities V ₁ and V _2, and FIG. ) Is the time t and the moving distances X ₁ , X from the initial positions P _1S , P _{2S of the} respective sliders.
It is a diagram illustrating a _2.

The first and second sliders SL1 and SL2 are moved from the slider initial positions P _1S and P _2S to the original scanning start position (positions of X = 0 and t = 0 on the horizontal axis of each figure in FIG. 3). Speeds V ₁ = V ₀ , V ₂ = V ₀ /
Accelerate to 2. The first slider SL1 maintains V ₁ = V ₀ while the distance Δh is Δh = 0, and decelerates in a portion where the document surface rises (a portion where Δh increases).
While Δh exceeds a predetermined threshold value h _th , the speed immediately before that is maintained, and when the original surface sinks (the portion where Δh decreases) accelerates, Δh = 0. Then, V ₁ = V ₀ , and the speed is maintained until the document scanning end position.

Further, the second slider SL2 during distance Delta] h is Delta] h = 0 is maintained at V ₂ = V _0/2, the document surface is lifted by going portion (Delta] h is going portion increases) accelerating the , and Δh is greater than the _{h th V 2 = V 1/} 2 next, Δ
In the part where the document surface sinks past the section where h exceeds h _th (the part where Δh decreases), deceleration and acceleration are performed,
Delta] h = 0 and V ₂ = V _0/2 becomes when became to maintain the speed up document scanning end position.

As described above, the first and second sliders SL1 and S
While L2 is moving under the document table 5 in parallel with the document table 5 while changing its moving speed, the irradiation light of the illumination lamp 10 is placed on the document table 5 by the reflection mirrors M11 and M12. A reflection mirror M13 in which the image light reflected by the document is directed toward the document and is arranged on the same optical axis,
It is guided to the lens 7 by M21 and M22, and the lens 7
The image-forming light imaged by is further guided to the exposure position on the photoconductor drum 6 by the reflection mirror M3.

The photosensitive drum 6 is driven in the direction of the arrow in FIG. 1A by a driving means (not shown) at a constant standard speed V ₀ of the first slider SL1 when the copy magnification is 1/1. Further, around the photoconductor drum 6, a charging charger 61, a developing device 62, a transfer charger 63, a separation charger 64, a cleaner 65, and a main eraser 66 are arranged. The charged surface of the photoconductor drum arrives at the exposure position, where it is imagewise exposed to form an electrostatic latent image.

Then, the electrostatic latent image formed by the image light guided to the exposure position is developed by the developing device 62 into a visible toner image, and the toner image is sent to the transfer position. At this time, the copy sheet is supplied to the transfer position by a sheet feeding unit (not shown). The toner image is transferred onto the supplied copy paper by the transfer charger 63, and the paper is separated from the photosensitive drum 6 by the separation charger 64. The separated sheet is conveyed to a fixing device (not shown) by a conveying unit (not shown), the toner image is fixed on the sheet by the device, and the sheet is discharged to the outside of the copying machine.

Toner remaining on the surface of the photosensitive drum 6 without being transferred to the copy sheet at the transfer position is cleaned by the cleaner 6
5, and the main eraser 66 erases the residual charges on the surface of the photoconductor drum 6 to prepare for the next image forming process. In addition, the first and second sliders SL
After reading the image, the first and SL2 are returned to the slider initial positions P _1S and P _2S to prepare for the next image reading.

Even if the distance h _th is exceeded, the speeds V ₁ , V ₂
May be the speed calculated by the equations 1 and 2, and the manner in which the first and second sliders SL1 and SL2 are driven in this case is illustrated in FIG. FIG. 4 (A) is a diagram showing a placed state of the book, and FIG. 4 (B) is a time t and speeds V ₁ and V.
FIG. 4 (C) is a diagram showing the relationship with ₂ and time t and the distance X ₁ X ₂ from the initial position of each slider.

However, even if the distance h _th is exceeded, the speeds V ₁ , V
_{If 2} is the speed calculated by the formula 1 and the formula 2, the speed change becomes steep at the folding position of the book, or the second slider S
L2 may start moving in the opposite direction. Therefore, the distance h _th
If it exceeds, the speed immediately before exceeding the first slider speed is maintained as described above, and the second slider speed is reduced to 1 /
It is desirable to be 2.

Further, in the above description, the case where the book placed on the document table is in contact with the document table and the document surface at the document scanning start position has been described.
As shown in (A), the image reading apparatus of the present invention can also be applied to the case where there is a folded portion of the book at the document scanning start position and the document surface gradually approaches the document table 5. FIG. 5 illustrates how the first slider and the second slider are driven at this time. FIG. 5A is a diagram showing a state where the book is placed, FIG. 5B is a diagram showing a relationship between the distance X from the document scanning start position and the distance Δh from the document table to the document surface, and FIG. 5D is a diagram showing the relationship between the time t from the start of document scanning and the distance Δh, and FIG. 5D shows the time t and the first slider and the second slider.
Slider graph showing a relationship each of the driving speed V _1, V _2, FIG. 5 (E) is the time t and the initial position P _1S of each slider,
Is a diagram illustrating a distance X ₁ X ₂ from P _2S.

In this case, the drive control is performed after the second slider is moved from the initial position P _2S to the position P _2S 'as shown in FIG. 5 (E) before the reading scanning is started. In addition,
When it is found that the folded portion is at the image reading start position during the standard reading operation, the above-described processing may be performed to restart the reading, or, for example, the first reading may be performed.
It is also possible to install a sensor near the tip of the slider in the image scanning direction and determine whether or not the folding is at the image reading start position before the reading is started.

The position of the document surface state detecting means in the document scanning direction is not limited to the document reading position below the reflection mirror M13 in which the sensor 90 shown in FIG. 1 is arranged. For example, as shown in FIG. 6, it is conceivable to set the distance L ₀ ahead of the document reading position in the document scanning direction. The image reading apparatus shown in FIG. 6 uses the same sensor 90 as the apparatus of FIG. 1 as the document surface state detecting means, and this sensor 90 is also connected to the control unit 8. FIG.
6 is substantially the same as the image reading apparatus of FIG. 1 except for the position of the sensor 90, and FIG.
It is a schematic side view of a slider part. In addition, parts having substantially the same structure and operation as the parts of the apparatus shown in FIG.
The same reference numerals as in FIG. 1 are attached.

Also in this apparatus, the predetermined reference surface is the upper surface of the document table 5, the sensor 90 can detect the distance h from the position of the sensor 90 to the document surface, and the predetermined reference surface (upper surface of the document table 5) which is obtained in advance. By subtracting the distance h ₀ from the upper surface of the document table 5 to the document surface Δh (= h−h
₀ ) can be calculated. The distance h is detected by a minute time interval Δt.
The time interval Δt is detected for each time and can be arbitrarily determined according to the accuracy of image reading and the like.

The first slider is set at the standard set speed V ₀ during the time N · Δt that is N times (N is an arbitrary integer) the distance L ₀ from the document reading position in the document scanning direction to the distance detection position. When approximated to the driven distance, the distance Δh ′ between the upper surface of the original table 5 and the original at the image reading position can be approximated to the distance between the upper surface of the original table 5 and the original calculated N times before. , The drive speeds V ₁ and V ₂ of the second slider are given by
If equation 3 and equation 4 below are used instead of equation 2, the operation is substantially the same as that of the apparatus shown in FIG.

[0052]

(Equation 3)

[0053]

(Equation 4)

The means for detecting the distance between the predetermined reference surface and the document surface is not limited to the distance sensor 90 shown in FIG. 1, but a line sensor may be adopted. Another embodiment of the present invention using a line sensor is shown in FIG. This image reading apparatus is substantially the same as the apparatus shown in FIG. 1 except that a line sensor is provided in place of the sensor 90 which is the document surface state detecting means in the apparatus shown in FIG. FIG. 7A shows the first slider SL1 of this device.
A schematic side view of the portion, and FIG. 7B is a schematic plan view of the portion. Parts having substantially the same structure and operation as those of the device shown in FIG. 1 are designated by the same reference numerals as those in FIG.

In this apparatus, the line sensor 91 as the document surface state detecting means is installed by being supported by the support member 15 in a posture perpendicular to the bearing unit 11 of the first slider SL1, and the line sensor 91 is the first. Slider SL1
Driven with Also in this apparatus, the predetermined reference surface is the upper surface of the original table 5 as in the apparatus shown in FIG. 1, and the line sensor 91 detects the distance Δh between the upper surface of the original table 5 and the original surface of the predetermined reference surface, Send to control unit. Except for this, the apparatus has the same configuration as that of the apparatus shown in FIG. 1, and this apparatus can also read an image in the same manner as the apparatus shown in FIG.

Next, FIG. 8 shows still another embodiment of the present invention using a line sensor. This image reading apparatus is substantially the same as the apparatus shown in FIG. 1 except that a line sensor is provided in place of the sensor 90 which is the document surface state detecting means in the apparatus shown in FIG. FIG. 8 is a schematic side view of the device. Parts having substantially the same structure and operation as those of the device shown in FIG. 1 are designated by the same reference numerals as those in FIG.

In this apparatus, a plurality of line sensors 92, which are the document surface state detecting means, are installed vertically on the document table 5 by a supporting member 51. Line sensor 92
Are arranged at equal intervals of L in the document scanning direction, and the number is determined by the maximum document scanning distance. Also in this apparatus, the predetermined reference surface is the upper surface of the original table 5 as in the apparatus shown in FIG. 1, and each line sensor 92 detects the distance Δh between the upper surface of the original table 5 and the original surface of the predetermined reference surface. , Send to the control unit. Except for this, the configuration is substantially the same as that of the apparatus shown in FIG. 1, and this apparatus can also read an image in the same manner as the apparatus shown in FIG.

The document surface state detecting means for detecting the bent state of the document surface with respect to the predetermined reference plane is limited to the sensor for detecting the distance as in the apparatus shown in FIGS. 1, 6, 7, and 8. Instead, the speed detector can detect how fast the document surface moves away from (or approaches) the predetermined reference surface. Examples of this speed detector include a laser Doppler speed detector.

The speed detector can be installed, for example, at the position of the sensor 90 of the device shown in FIG. 1 instead of the sensor 90, and the speed detector can be used by connecting it to the control unit. At this time, when the speed Vh detected by the speed detector is constant, that is, when the document is in contact with the document table 5,
If default speed of the first slider SL1 determined from the copying magnification, etc. is assumed to be V _0, the first slider SL1 is driven at a speed V ₁ = V _0, also the second slider SL2 speed V ₂ = V It is driven by _{1/2 = V 0/2} .

When the speed Vh detected by the speed detector changes, that is, when the document is lifted from the document table 5, the first slider SL1 and the second slider SL2 are used.
The respective driving speeds V ₁ and V ₂ of the above may be calculated by the following equations 5 and 6 instead of the equations 1 and 2. Also in this case, the reflection mirrors M13, M21, M
The optical path length through 22 to the imaging lens 7 and the scanning speed of each part of the document surface are kept constant during document scanning. The velocity Vh detected by the velocity detector is detected at each minute time interval Δt, and in the equations 5 and 6, the driving velocity of each of the first slider SL1 and the second slider SL2 calculated one time before is represented by V. ₁ ', V ₂ '

[0061]

(Equation 5)

[0062]

(Equation 6)

In this case also, the speed detected by the speed detector
Vh is a predetermined speed Vh _thWhile exceeding
Is the speed V₁Is the speed V calculated just before that₁’
Is maintained, and at this time, the speed V_TwoIs V_Two= V₁／ 2
You may have it. There is also a speed detector
The position to be placed is not limited to the position below the reflection mirror M13.
Instead, for example, as shown in FIG.
-Place the speed detector 93 on the extension of the optical path of the image light to M3.
You may put it. FIG. 9 is a diagram showing an arrangement position of the speed detector.
And the image reading with the speed detector 93 arranged in this way
The picking device operates substantially similar to the device shown in FIG.
You. In this case, the reflection mirror M3 reflects the image light in the visible range.
However, the information to the speed detector 93 should be passed.
You.

It is also possible to dispose the distance detection sensor 90 described above at the same position as this speed detector. In the image reading apparatus of the present invention described above, even if the distance between the predetermined reference surface (the upper surface of the document table 5 in the apparatus of FIG. 1) and the document surface changes along the scanning direction, the first slider, The second slider is driven at a driving speed calculated so that the optical path length from each part of the document surface to the imaging lens and the scanning speed of each part of the document surface are constant, so that a good image is read without image distortion. be able to. In addition, the apparatus according to the present invention can perform excellent image reading with a simple structure such as only installing the document surface state detecting means in the conventional image reading apparatus. further,
Since the reflecting mirror for guiding the image light to the lens mounted on the first slider and the second slider is fixed to each slider, it is not necessary to provide a component such as a driving device for rotating the reflecting mirror, and therefore it is simpler. With such a configuration, the number of parts is small, the device is not enlarged, and the reflection mirror is fixed, so that the speed fluctuation of the slider is suppressed to be smaller than that of the conventional slider having the reflection mirror rotating mechanism, which is good. You can read various images.

In the above embodiment, an example in which the image reading device of the present invention is mounted on an analog copying machine has been described.
The apparatus of the present invention can be installed in a digital copying machine or an image scanner. Further, although linear motors are used as the first and second slider driving means in the above-described embodiments, power of the rotary motor and a transmission mechanism for transmitting the power may be used. Further, the type of motor can be a servo motor or a stepping motor. These drive circuits may be hardware circuits including a PLL control circuit as in this example, or may be servo-controlled by software.

Further, in the above embodiment, the case where the original is placed so-called face down is described.
In the case of so-called face-up placement, the document surface is often bent because there is no member for pressing the document surface, and it is particularly effective to apply the present invention in such a case. Further, not only the book but also the case where the original has unevenness or a curved surface in the image scanning direction, the image can be read well as in the case of a folded book. In the case of a flat original, image reading is performed in the same manner as an image reading apparatus having no book reading function.

The book reading function of the present invention may be operated at all times, or may be operated only when selected by the user, operator, or the like.

[0068]

According to the present invention, the illumination lamp for illuminating a document on the platen and the first slider having the first mirror and the second slider having the second mirror move in parallel to the platen. In the image reading apparatus that scans the document while guiding the reflected light reflected from the document surface to the image forming lens by the first mirror and the second mirror, a predetermined reference surface such as the document mounting surface of the document table. Even if the distance from the document surface to the document surface changes along the scanning direction, good image reading can be performed without image distortion. Moreover, with a simple configuration, the speed of the slider can be evenly reduced and good image reading can be performed. It is possible to provide an image reading apparatus capable of performing the image reading.

For scanning the surface of the document placed on the document table which is to be scanned and is substantially parallel to the predetermined reference plane, the first slider and the second slider are driven at a preset speed ratio. However, even when the bent state of the document surface detected by the document surface state detecting means exceeds a predetermined bent state of the document surface, the first slider and the second slider are moved at the set speed ratio and at the first slider speed. When the operations of the first and second slider driving means are controlled so as to drive at a speed immediately before exceeding the predetermined original surface bending state, the original surface bending state is continuous, for example, at a book folding position. Even when it does not change, the control of each slider becomes easy without the driving speed of the first slider and the second slider changing sharply and the second slider not moving in the opposite direction.

[Brief description of drawings]

FIG. 1 is a diagram showing an image reading apparatus mounted on an analog copying machine according to an embodiment of the present invention, FIG. 1A is a schematic side view of the apparatus shown together with a photoconductor of the copying machine, and FIG. B) is a schematic plan view of the device.

FIG. 2 is an enlarged view of a first slider portion when a document book is placed on a document table.

3A and 3B are diagrams showing how the first and second sliders are driven. FIG. 3A is a diagram showing a placed state of a document book, and FIG. 3B is a distance X from a document scanning start position. FIG. 3 is a diagram showing the relationship between the distance Δh from the document table to the document surface, FIG. 6C is a diagram showing the relationship between the time t from the start of document scanning and the distance Δh, and FIG. Slider speeds V ₁ and V ₂
And (E) is a diagram showing the time t and the distances X ₁ X ₂ from the initial positions P _1S and P _{2S of the} respective sliders.

4A and 4B show other driving states of the first and second sliders. FIG. 4A is a diagram showing a placed state of a document book, and FIG. 4B is a time t from the start of document scanning and a first state. , A diagram showing the relationship between the velocities V ₁ and V _{2 of} the second slider, and FIG. 7C is a diagram showing the time t and the moving distance of each slider from the initial position.

5A is a diagram showing another placement state of a document book, and FIG. 5B shows a relationship between a distance X from a document scanning start position and a distance Δh from a document table to a document surface. The figure, figure (C) is the figure which shows the relationship between time t and distance deltah, figure (D) is time t
And the velocity V ₁ and V _{2 of} the first and second sliders. FIG. 6E shows time t and initial positions P _1S and P _{1 of} each slider.
Is a diagram illustrating a distance X ₁ X ₂ from _2S.

FIG. 6 is a schematic side view of a part of an image reading apparatus according to another embodiment of the present invention.

7A and 7B are diagrams showing an image reading apparatus using a line sensor according to still another embodiment of the present invention, FIG. 7A is a schematic side view of a portion of the apparatus, and FIG. 7B is a portion of the apparatus. It is a schematic plan view.

FIG. 8 is a partial schematic side view of an image reading apparatus using a line sensor according to still another embodiment of the present invention.

FIG. 9 is a partial schematic side view of an image reading apparatus using a speed detector according to still another embodiment of the present invention.

FIG. 10 is a diagram showing a state in which a book is placed on a document table.

[Explanation of symbols]

SL1 first slider 10 illumination lamp (illumination device) 11 first slider bearing unit 111 first slider encoder detection element 12 support roller 14 first slider drive circuit (first slider drive means) 15 support members M11, M12 Reflecting mirror M13 Reflecting mirror (first reflecting mirror) SL2 Second slider 21 Second slider bearing unit 211 Second slider encoder detection element 22 Support roller 24 Second slider drive circuit (second slider drive means) M21, M22 reflection mirror (second reflection mirror) 3 stator 31 encoder scale 4 guide rail 5 document table 6 photoconductor drum 61 charging charger 62 developing unit 63 transfer charger 64 separation charger 65 cleaner 66 main eraser 7 imaging lens 8 control unit 0 sensor (original surface state detection means) 901 illumination device 902 receiving device 91, 92 a line sensor (the document surface state detecting means) 93 speed detection meter (the original surface state detection means)

Claims (2)

[Claims] 1. An image reading apparatus for optically scanning a document image, comprising a document table on which the document is placed, an illuminating device for illuminating the document placed on the document table, and a reflection image from the document. The first slider, which is equipped with a first mirror that guides light in a predetermined direction and is capable of reciprocating in parallel with the document table, and the second mirror, which is used to guide image light from the first mirror in a predetermined direction, are mounted on the first slider. A second slider that can reciprocate in the same direction as the slider, a first slider driving unit that reciprocally drives the first slider, and a second slider that reciprocally drives the second slider independently of the first slider. Slider driving means, a lens for forming image light from the second mirror, a document surface state detecting means for detecting a bending state of a surface of a document placed on the document table with respect to a predetermined reference plane, and the document Surface condition Based on the state of each part of the document surface detected by the output means, the optical path length from each part of the document surface to the lens through the first mirror and the second mirror during the scanning of the document surface and the scanning speed of each part of the document surface And a control means for controlling the operation of each of the first and second slider driving means so as to drive the first slider and the second slider so as to maintain a constant value. Reader. 2. The control means controls the first slider and the second slider to scan a surface portion of a document placed on the document table which is to be scanned and which is substantially parallel to the predetermined reference surface. The first slider and the second slider are set even when the original surface bending state detected by the original surface state detecting means is driven at a predetermined set speed ratio and exceeds the predetermined original surface bending state. The speed ratio and the first
The first and second sliders are driven so that the slider speed is maintained at the speed immediately before the predetermined original surface bending state is exceeded.
The image reading apparatus according to claim 1, wherein the operation of the slider driving means is controlled.