JP2003244439A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader having a through print eliminating function in which image processing can be simplified and a processing time can be shortened without requiring a large capacity for a storage device for storing undetermined image data. <P>SOLUTION: In respect to an original carried on an original carrier path 33, an image on its lower surface is read by a first read part 10 and at the same time, an image on its upper surface is read by a second read part 23. In the read image data, data equal to or lower than a prescribed gray level are eliminated by being replaced with a gray level value '0'. When a difference between the gray level data value of a pixel in data as an object to be corrected and the gray level value of a pixel in the data on the rear side exceeds a prescribed value and the gray level data value of the pixel in the data as the object to be corrected is smaller than the gray level data value of the pixel in the other data, the data value of the pixel in the data as the object to be corrected is replaced with a data value in the case of gray level '0'. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading device for reading an image on a document. In particular, the present invention relates to an improvement in an image reading apparatus having a show-through correction function that corrects image data on one side of a document using image data on the other side.

[0002]

2. Description of the Related Art Conventionally, in an image reading apparatus for reading an image of a document, image information read optically is converted into an electric signal and further converted into a digital signal. In this case, when an image having a high density is present on the surface (rear surface) on the back side of the image reading surface (front surface) of the document, so-called show-through occurs in which the image on the back surface is transparent to the front surface. In such a situation, the back side image data is mixed in the read image data,
The quality of the read image is significantly deteriorated.

In order to reduce the deterioration of the quality of the read image due to the show-through, conventionally, the density determination is performed using only the image information from one side (the image reading side), and the low density portion of a predetermined density or less is printed on the back side. A background removal process of determining that the image data is image data and uniformly deleting the low-density image data is performed.

However, when this background removal processing technique is used, when reading a document image of a relatively pale color tone such as a photograph, the low-density image data existing on the image reading surface is the image data on the back surface. Therefore, there is a problem that a part of the image data (image data to be acquired) on the image reading surface is removed due to the erroneous determination.

In order to solve this problem, Japanese Patent Laid-Open No. 11-
In Japanese Patent No. 317858, in addition to image information from one side (image reading surface), a document image on the other side (the surface on the back side of the image reading surface) is also read, and image information on the back side is used.
It is disclosed that density comparison is performed to more accurately reduce show-through.

In the technique disclosed in Japanese Patent Laid-Open No. 11-317858 mentioned above, the following reading operation is performed. First, the image on the front surface (image reading surface) of the original is read by the original reading unit, and one page of the obtained image data is stored in the image memory. Next, the original is turned over, the original is conveyed again to the original reading unit, the image on the back side is read, and the obtained image data is stored in the image memory. After that, the densities of the image data on the front surface and the image data on the back surface are compared with respect to the stored image data with reference to the origin coordinates that are the starting point of reading. As a result, the back image data in the image data obtained in the reading operation of the front image is specified, and this back image data is removed from the front image data to determine the final image data.

[0007]

However, in the technique disclosed in the above publication, in the image reading operation, the back surface image reading operation is performed after the front surface image reading operation, so that the final image data is determined. There was a problem that it took a long time to do. That is, when it is necessary to read only one side of a document, normally only one side needs to be read, whereas it is necessary to intentionally invert the document and read the back side to prevent show-through. Therefore, there is a problem that the reading time is twice or more as long as the case of reading only one side.

There is also a problem that a storage device having a relatively large storage capacity is required because it is necessary to store the respective image data on the front surface and the back surface of the document.

Further, since the front side image of the original is read and the back side image is read after the front side image of the original is read, when the original is conveyed again to the reading portion, a deviation of the conveying position of the original or an oblique feeding may occur. . Since it is not possible to compare the densities of the image data on the front surface and the image data on the back surface with this, it is necessary to perform image processing such as positional deviation correction for accurately aligning the positions of both image data. Therefore, not only does the entire image processing operation take a long time,
Since it is necessary to equip the apparatus with such an image processing function, the manufacturing cost of the apparatus increases.

The present invention has been made in view of these points, and does not require a large capacity in a storage device for storing unconfirmed image data, can easily perform image processing, and shorten processing time. It is an object of the present invention to provide an image reading apparatus having a show-through removal function capable of achieving the above.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention performs data correction for avoiding show-through by acquiring image information of both sides of a document. The image information on each side of the document is acquired substantially simultaneously by different reading means. As a result, the document reversing operation is not necessary, and the image processing such as the positional deviation correction in consideration of the conveyance position deviation and the oblique feeding accompanying the reversing operation is not necessary.

-Solution means-Specifically, first reading means for reading image information on one side of the document as first data, and second reading means for reading image information on the other side of the document as second data. The first data and the second data are compared by comparing the first data and the second data.
And a correction means for correcting at least one of the data. When the image information of the original is read, the first reading unit and the original are relatively moved to read the image information on one surface of the original by the first reading unit, and at the same time, the second reading unit and the original are relatively moved. The image information on the other side of the document is read by the second reading means.

According to this specific matter, when the document is read, the first reading means and the document are relatively moved to read one side of the document to obtain the first data. At the same time as this, the second
The reading unit and the original are relatively moved to read the other surface of the original to obtain the second data. As the relative movement here,
Examples include a case where the reading unit is fixed and the document is conveyed, a case where the document is fixed and the reading unit is moved, a case where the reading unit is moved and the document is conveyed, and the like. Then, the first data and the second data are compared, and the first data and the second data are compared.
Correct at least one of the data. Here, the correction performed by the correction unit includes, for example, an operation of removing a part of the image data in order to avoid the show-through. According to the solving means, the first reading means and the second reading means read different original images at substantially the same time, and the image data is corrected using the obtained data, so that, for example, the first data is read. The time required to read the original image necessary for correction may be the time required to read the image on one side. In other words, it is not necessary to perform “double reading of the original” such that the reading operation is performed on one side of the original and then the reading operation is performed on the other side. Therefore, the time for acquiring the data can be significantly shortened, and the data correction operation can be efficiently executed.

Further, since it is not necessary to invert the original in order to read the other side of the original after reading one side of the original, the paper feeding mechanism can be simplified. Furthermore, when comparing the data obtained by reading one side with the data obtained by reading the other side, there is no misalignment due to paper feeding, so the image processing functions such as "positional deviation correction" required in the prior art. The data can be corrected accurately without the need for ".

As the correcting operation of the correcting means, specifically,
In the first data and the second data, the data of the pixels that face each other on the front and back sides of the document are compared with each other to correct the data. According to this, only pixels corresponding to the same portion (pixels facing each other on the front and back sides of the document) are compared, so that the comparison procedure is simplified and the data processing operation can be speeded up.

Further, the first reading means and the second reading means are configured to read the image information at substantially close positions on the original at substantially the same time. According to this, the correction unit only memorizes the difference between the reading positions of the first reading unit and the second reading unit, and performs correction by comparing pixel data corresponding to the same portion of the document. You can
That is, for example, in order to correct the first data, it is not necessary to store all of the data for one side of the document as in the case of reading the other side of the document after reading one side of the document. Therefore, a storage device having a large storage capacity is not required.

Further, since the pixels at the same position may be compared as described above, according to the above configuration, it is possible to obtain the image data corrected at the same position before the reading of the entire document is completed.

In the above construction, the first reading means and the second reading means may read the same position on the original. However, in this case, since the same position is read by applying light from both sides, the show-through is emphasized. Therefore, as described above, when the positions are not the same but almost the same, the show-through is not emphasized, and the storage capacity required for the storage device can be reduced.

Further, the correction means can switch between a mode in which the first data and the second data are compared and only the first data is corrected, and a mode in which the first data and the second data are both corrected by the above comparison. Is configured. Therefore, for example, when it is necessary to read only one side, a mode in which only the first data is corrected is selected, and in this case, the first mode is selected.
It is possible to omit a wasteful process caused by correcting both the data and the second data.

Further, the correction means is constructed so that the following two modes can be switched. One is a mode in which when performing data correction, the data value of a pixel having a predetermined density or less in the data to be corrected is replaced with the data value when the density is “0” to remove the background. The other is a mode in which, when correcting data, the data value of a pixel having a predetermined density or less in the data to be corrected is treated as it is as the data value of the pixel and the background is left. By switching between the background removal mode and the mode for leaving the background, when it is desired to remove the background, for example, when reading a character original to be binarized, the background removal mode is selected and clear characters are selected. You can get the data. Further, for example, when it is desirable to leave the background, such as when reading a photo original, it is possible to faithfully read even a light photo original by selecting the mode for leaving the background.

Further, the data correction operation by the correction means will be described in detail. First, when the first data is to be corrected,
The difference (E in FIG. 5) between the density data value of the pixel of the first data and the density data value of the pixel of the second data opposite thereto exceeds a predetermined value (α in FIG. 5), and When the density data value of the pixel of the data is smaller than the density data value of the pixel of the second data, the data value of the pixel of the first data is replaced with the data value in the case of density "0". This operation procedure is the flow of steps S3, S4, S5 and S6 in the flowchart of FIG. On the other hand, similarly, when the first data is the correction target, the difference (E) between the density data value of the pixel of the first data and the density data value of the pixel of the second data opposite thereto is a predetermined value (α).
When the following is true (when NO is determined in step S4 of FIG. 5), or the difference (E) between the density data value of the pixel of the first data and the density data value of the pixel of the second data opposite thereto is predetermined. Even if it exceeds the value (α), if the density data value of the pixel of the first data is equal to or more than the density data value of the pixel of the second data (when determined as NO in step S5 of FIG. 5), The data value of the pixel of the first data is treated as it is as the data value of the pixel.

Further, as the data correction operation by the other correction means, when the first data is the correction target, the density data value of the pixel of the first data and the density data value of the pixel of the second data opposite thereto (E in FIG. 7) exceeds a first predetermined value (α in FIG. 7), and the density data value of the pixel of the first data is smaller than the density data value of the pixel of the second data. Sometimes, the difference (E) is subtracted from the density data value of the pixel of the first data, and the subtraction value (F in FIG. 7) is less than the second predetermined value (D in FIG. 7), and When the density data value of the pixel of the first data is equal to or larger than the second predetermined value (D), the data value of the pixel of the first data is replaced with the data value of the density “0”. In the flowchart of FIG. 7, this operation procedure includes steps S13, S14, S15, S16,
The flow is S17, S18, and S21. On the other hand, similarly, when the first data is to be corrected, the difference (E) between the density data value of the pixel of the first data and the density data value of the pixel of the second data opposite thereto is the first predetermined value. When (α) or less (when NO is determined in step S14 in FIG. 7), or the difference (E) between the density data value of the pixel of the first data and the density data value of the pixel of the second data opposite thereto (E )
Is greater than the first predetermined value (α), but the density data value of the pixel of the first data is equal to or higher than the density data value of the pixel of the second data (NO is determined in step S15 of FIG. 7). Time), the data value of the pixel of the first data is
The data value of the pixel is treated as it is.

By the data correcting operation by these correcting means, it is possible to realize the preferable correcting operation of the image data in consideration of the show-through. In particular, in the data correction operation by the latter correcting means, comparing the difference between the subtraction value (F) and the second predetermined value (D) means that the second predetermined value (D) is the background density. By doing so, it is determined whether the subtraction value (F), that is, the density of the surface to be read from which show-through has been removed, is D or more, and when the density of the original surface is smaller than D, the background is erased to "0". It decides whether to turn off.

[0024]

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

FIG. 1 and FIG. 3 are views showing the internal structure of the image reading apparatus (scanner apparatus) according to this embodiment.
This reading device is for reading an image of a document, and in particular, is capable of reading the front surface and the back surface of the document at the same time. In other words, the present reading device is a "static reading mode" in which the original is read while the original is read, a "running reading mode" in which an image of only one side of the original is read while the original is being conveyed, or an image on both sides of the original is being conveyed while the original is being conveyed. It is possible to perform image reading on a document by using a "double-sided reading mode (for double-sided reading in traveling reading mode)".

As shown in FIG. 1, the reading apparatus includes a lower housing 1, an upper housing 2, and a paper discharge tray 3.

Although not shown in FIG. 1, the reading apparatus also includes an operation unit (for example, a display unit including a liquid crystal display and buttons for setting), and the operation unit. The user can select, for example, the plurality of modes described above by operating the.

(Description of Lower Housing 1) First, the structure of the lower housing 1 will be described. As shown in FIG. 1, the lower housing 1
Includes a first reading unit 10 as a first reading unit and a first contact glass 11. Then, as shown in FIG. 1, the first reading unit 10 includes a first scanning unit 12 and a second scanning unit 12.
Scanning unit 13, imaging lens 14, CCD (Charge c
It is provided with an oupled device 15 and a second contact glass 16.

The first contact glass 11 is a table on which a document to be read is placed in the "static reading mode".

The first scanning unit 12 of the first reading section 10
Exposes the original while moving along the first contact glass 11 from left to right in FIG. 1 at a constant speed V. Figure 1
Then, the respective positions Pos1 to Pos3 associated with the movement of the first scanning unit 12 are shown by solid lines.
The first scanning unit 12 includes a light source (exposure lamp) 50.
And a first reflection mirror 51 that guides the reflected light of the document to the second scanning unit 13 (see FIG. 3).

The second scanning unit 13 follows the first scanning unit 12 and moves at a speed of V / 2. The second scanning unit 13 includes second and third reflection mirrors 52 and 53 that guide the light from the first reflection mirror 51 to the CCD 15 via the imaging lens 14.

The image forming lens 14 forms an image of the reflected light from the third reflecting mirror 53 on the CCD 15.
The CCD 15 converts the light from the imaging lens 14 into an analog electric signal. The electric signals are converted into digital image data by image processing units 150 and 160 (see FIG. 2) described later and stored in the image memory 102, or output to an image forming apparatus such as a printer or an external device. It

A wire (not shown) is wound around the first scanning unit 12 and the second scanning unit 13 in order to synchronize their movements. The scanning units 12 and 13 are driven by a stepping motor (not shown) via the wire.

The first reading unit 10 reads a document placed on the first contact glass 11 and, as described later, a document conveyed by a member provided in the upper housing 2. It also has the function of reading the image.

When reading the original on the first contact glass 11, the first scanning unit 12 moves in the direction from the position Pos1 to the position Pos2 in FIG.
It moves by a predetermined distance according to the document size detected by the document size detecting means (not shown). On the other hand, when reading the conveyed document, the first scanning unit 12 is stopped at the position Pos3 in FIG. Further, during the standby time when it is not used, the first scanning unit 12 operates as shown in P in FIG.
Intermediate position between os1 and Pos3 (home position)
Has stopped.

Further, as shown in FIG. 3, a document placement reference plate (a placement reference plate for stationary documents) 41 is provided on the front side (left side in the figure) of the end of the first contact glass 11. .
The original placement reference plate 41 is used for the first contact glass 11
Indices indicating the size and placement direction of the document placed on are shown. Therefore, the user can easily place the document on the first contact glass 11 according to this index.

The shading of the CCD 15 (determination of the white level) is performed on the side of the first contact glass 11 opposite to the side on which the document placing reference plate 41 is provided, and facing the document placing reference plate 41. The 1st standard white board 42 used when carrying out () is provided. The first reference white plate 42 may be provided below the document placement reference plate 41 and above the first contact glass 11.

(Description of Upper Housing 2) Next, the structure of the upper housing 2 will be described. The upper housing 2 shown in FIG.
A mat 21, an original set tray 22, a second reading unit 23 as a second reading unit, and an opening door 24 are provided.

The upper housing 2 is upwardly moved with a hinge (not shown) provided between the upper housing 2 and the lower housing 1 on the back side (the back side of the drawing of FIG. 1) of the present reading device as a pivot. It is designed to rotate. As a result, in the present reading apparatus, as shown in FIG.
The upper surface of the first contact glass 11 and the upper surface of the second contact glass 16 can be opened from the front side of the paper.

The OC mat 21 is a mat for pressing a document placed at a position in which the upper mat 2 is pressed against the first contact glass 11 when the upper case 2 is closed.
The document set tray 22 is a table on which a document is placed when the "traveling reading mode" or "double-sided reading mode" is executed. The open door 24 is an openable / closable window provided in the upper housing 2 for adjusting the attachment state of the second reading unit 23.

The second reading section 23 includes the original set tray 22.
It is for reading the image of the original document conveyed from the original document conveying means 31, the contact image sensor unit (CI).
S: Contact Image Sensor) 32, a document feeding path 33, and a document discharging section 34.

The document conveying means 31 takes in a document placed on the document set tray 22 by rotating each roller and conveys the document on the document conveying path 33.

The document transport path 33 is a transport path constituted by the alignment roller pair 67 and the second contact glass 16 and between the upper document transport guide 70 and the second contact glass 16.

The upper original transport guide 70 is placed on the second contact glass 16. The horizontal position of the upper document transport guide 70 is set by the positioning protrusion 70a (see FIG. 3).

The close contact image sensor unit 32 includes the upper housing 2
And is for reading the upper image of the original document traveling on the original document transport path 33. Further, a light blocking member 90 is arranged on the first reading unit 10 side of the second contact glass 16. The second reference white plate 68 is provided on the lower surface of the second contact glass 16 and is used when performing the shading (determination of the white level) of the image sensor unit 32.

The document discharge section 34 discharges the document after the image is read by the contact image sensor section 32 to the discharge tray 3.

The paper discharge tray 3 of the present reading device is a base for discharging the document after the image is read.

(Description of Control System Configuration) Next, the control system in the present reading device will be described with reference to the block diagram of FIG.

The system controller 100 shown in FIG.
Controls the image processing relay unit 101 and the image memory 102 in addition to the reading control unit 110 via the bus B. By the above control, the system controller 100 controls the entire reading apparatus so that the reading operation of the document is appropriately performed.

The first light source control board 120 shown in FIG. 2 turns on / off the light source (first light source: xenon lamp) 50 of the first reading section 10 based on a signal from the reading control section 110. In addition, the second light source control board 130, based on the signal of the reading control unit 110, the contact image sensor unit 3
The second light source (second light source: LED array) 32a is turned on and off.

First reading scanning system drive motor control board 12
1 controls the first reading scanning system drive motor 122 based on the signal from the reading control unit 110 to move the first scanning unit 12 and the second scanning unit 13 in both left and right directions in FIG.

In the first reading / scanning system position sensor group 123, the first scanning unit 12 has a home position, Pos1 and Ps.
When arranged in os2 and Pos3, the reading control unit 11
The reference position signal is output to 0.

In the above structure, the reading control section 110 is
A reference position signal of the first scanning system position sensor group 123,
The position of the first scanning unit 12 is calculated based on the number of steps of the first reading scanning system drive motor 122. And
By controlling the first reading and scanning system drive motor 122 in the forward and reverse directions,
The scanning units 12 and 13 are moved back and forth.

The drive motor control board 140 of the automatic document feeder (document transport means 31, document discharge section 34) controls the drive motor 141, which is a stepping motor, to be turned on and off in response to a signal from the reading control section 110, thereby automatically The driving system of the document feeder is driven to transmit the driving force to the above-mentioned alignment roller pair 67 and other conveying rollers. In addition, the drive motor 14
In No. 1, the rotation speed can be changed by the pulse rate from the drive motor control board 140.

The document discharge sensor 59, the document set detection sensor 62, and the feeding timing sensor 65 (see FIG. 1) transmit a document presence / absence signal to the reading control unit 110 when the document reaches the position of the sensor. On the other hand, the reading control unit 1
Reference numeral 10 calculates whether or not the document is conveyed at an appropriate timing by means of a document presence / absence signal from these sensors 59, 62 and 65 and a timer. If the document is not conveyed properly, a jam or the like is generated. The signal is transmitted to the system controller 100 via the bus B.

The roller clutch group 142 includes the reading control unit 1
A signal from 10 is turned on / off to switch each drive system of the automatic document feeder to connection or non-connection to stop or rotate the drive system.

(Image Signal Processing Operation) Next, the processing of an electrical image signal obtained by reading scanning when the present reading apparatus performs single-sided reading or double-sided reading in the above-described configuration will be described.

As shown in FIG. 2, an electric image signal (hereinafter referred to as an image signal) obtained by the CCD (first photoelectric conversion element) 15 and the image sensor section (second photoelectric conversion element: CIS) 32 is The image is transmitted to the image processing units 150 and 160, subjected to predetermined image processing, and then transmitted to the image processing relay unit 101, and further image processing (region separation process, spatial filter process based on the region separation result, After halftone processing such as error diffusion and resolution conversion processing),
The image memory 10 is distinguished for each page via the bus B.
Stored in 2.

The image processing units 150 and 160 include analog signal processing units 151 and 161, and A / D conversion units 152 and 1.
62, shading correction units 153, 163, filter processing units 154, 164, density conversion units 155, 165, line buffers 156, 166, and data comparison processing units (correction means in the present invention) 157, 167.
Each element of the image processing units 150 and 160 operates under the control of the reading control unit 110.

The analog signal processing sections 151 and 161 respectively perform level conversion processing, sample hold processing and signal amplification processing on the image signals input from the CCD 15 and the contact image sensor section 32, and the A / D conversion section 152. , 162. Since the CCD 15 and the contact image sensor unit 32 are different in light source light amount, photoelectric conversion efficiency, output signal level, and the like, dedicated analog signal processing units 151 and 161 are individually provided for the CCD 15 and the contact image sensor unit 32, respectively. Has been.

A / D (analog / digital) converter 15
Reference numerals 2 and 162 denote digital conversion of the analog image signals input from the analog signal processing units 151 and 161, and the quantized image signals are shaded correction units 153 and 16 respectively.
Output to 3.

The shading correction units 153 and 163 are
The quantized image signals input from the A / D conversion units 152 and 162 are subjected to black reproduction and white reproduction, and output to the filter processing units 154 and 164.

The black reproduction means that the implicit output of the CCD 15 or the contact image sensor unit 32 is sampled and stored, and this is read data, which is the CCD 15 at the time of reading the original.
Alternatively, it is a process of eliminating the influence of the implicit output by subtracting from the image signal output from the contact image sensor unit 32.

The white reproduction means that the image signal at the time of reading the original is normalized for each pixel on the basis of the image signal for each pixel when the reference white plates 42, 68 having uniform reflectance are read, and the uneven light amount and the optical signal are read. This is a process of correcting the influence of components and the variation in pixel sensitivity of the first photoelectric conversion element 15 and the second photoelectric conversion element 32.

Filter processing section (filter processing means) 15
Reference numerals 4 and 164 denote predetermined filtering processing, specifically spatial filtering processing, based on the coefficients for determining the filter characteristics set by the reading control unit 110, on the image signals input from the shading correction units 153 and 163. By emphasizing the high frequency components of the image, the “blurring” of the image is restored. That is, the image signals output from the CCD 15 and the contact image sensor unit 32 include optical components such as lenses and mirrors, aperture aperture of the light receiving surface of the CCD 15 and the image sensor unit 32, transfer efficiency of the CCD 15 and the contact image sensor unit 32, and the like. MTF (Modu due to afterimage, integration effect due to physical scanning, and uneven scanning)
There is deterioration of the relation transfer function), and the filter processing units 154 and 164 compensate for the deterioration of the MTF.

As described above, since the degree of deterioration of the MTF differs greatly depending on the CCD 15 and the contact image sensor section 32, an appropriate filtering process is performed. Also, MT
Since the deterioration of F is more prominent in the high frequency region, the filter processing units 154 and 164 are
By applying the enhancement processing, "blurring" is restored and the image quality is improved. Filter processing units 154 and 16
The filter processing 4 is different depending on whether the input image signal is the image signal from the CCD 15 or the image signal from the contact image sensor unit 32.

Density conversion unit (density conversion means, binarization means)
Reference numerals 155 and 165 are for performing density conversion on the image signals filtered by the filter processing units 154 and 164. For example, when the image signals are communicated by facsimile, or the printing condition is designated as binary. When the image signal is binarized, the image quality is improved by performing density conversion according to a predetermined density characteristic if the printing condition is multi-valued such as a photographic image.

The density converters 155 and 165 are connected to the RAM (Ra
An ndom access memory) control unit and a RAM (both not shown) are provided, and the input image signal is used as address data for R
By reading the table value stored in the lookup table for data conversion set in AM,
Data conversion is performed to perform density conversion processing.

The image signal having the determined density is processed by the data comparison processing units 157 and 167, which will be described later, and then relayed by the image processing relay unit 101 to be stored in the image memory 102. Further, at this time, the image may be output to the image forming apparatus while being stored in the image memory 102.

The image signal stored in the image memory 102 is read by the system controller 100 at a predetermined timing and output to the image output device 103. The image output device 103 is an electrophotographic type, an inkjet type,
An image is formed on a recording medium such as paper by a thermal transfer method or the like, but is not particularly limited.

(Image Reading Operation) An image reading operation of the present reading apparatus having the above-mentioned configuration will be described below mainly with reference to FIG.

As described above, the reading apparatus is set so that one of the "static reading mode", the "running reading mode", and the "double-sided reading mode" is input from the operation unit 104 (FIG. 2). It is supposed to be done by.

The "static reading mode" is a mode in which the image is read while the document is kept still, and the image is read by the first reading unit 10 in the lower housing 1.

In this "static reading mode", only one side can be read. Then, when the one side is read, the first reading unit 10 is used to read the document.
At this time, the first scanning unit 12 of the first reading unit 10
First, the home position (Pos3 and Pos1 in FIG. 1)
It is located in the position between and). Then, the reading control unit 11
In response to the instruction of 0, the document placed on the first contact glass 11 is scanned from the position of Pos1 and moves to the Pos2 side together with the second scanning unit 13. This allows the CCD 15 to receive the reflected light corresponding to the original image. In this way, the first reading unit 10
Reads an image formed on the lower surface (front surface) of a stationary document.

The "running reading mode" is a mode in which an image is read while a document is being conveyed, and the second reading inside the upper housing 2 is performed.
An image is read by the reading unit 23 or the first reading unit 10 in the lower housing 1.

In the "running reading mode", both single-sided reading and double-sided reading can be selected. Here, only the single-sided reading will be referred to as the "running reading mode", and the double-sided reading will be simply referred to as the "double-sided reading mode".

In the "running reading mode", only the first reading section 10 is used for reading the document (the second reading section 23 also performs the reading operation when the show-through is prevented by the one-sided reading. The reading operation is similar to that in the "double-sided reading mode" described later). When this mode is instructed, the first scanning unit 12 of the first reading unit 10 moves from the position of the home position to the position of Pos3 and stops, and the stopped state is maintained as it is to read the traveling document. To do. Then, in response to an instruction from the reading control unit 110, the CCD 15 reads the image of the document conveyed through the document conveyance path 33 via the second contact glass 16 from below. That is, the first reading unit 10 reads the image formed on the lower surface (front surface) of the document. (To prevent show-through, the second reading unit 23
The image formed on the upper surface (back surface) of the original is read. However, only the read image data on the front side after the show-through prevention processing is corrected is output).

On the other hand, the "double-sided reading mode" is a mode in which images on both sides of the original are read while the original is being conveyed, and reading is performed by using both the first reading section 10 and the second reading section 23 at the same time. It has become.

In the "double-sided reading mode", both the first reading section 10 and the contact image sensor section 32 are used for reading the original. At this time, the first reading unit 1
The first scanning unit 12 of 0 is stopped at the position of Pos3 in FIG. 1 as in the case of the single-sided mode of the “traveling reading mode” described above.

In this embodiment, the deviation L (see FIG. 3) between the reading point A of the first reading section 10 and the reading point B of the second reading section 23 is set to about 17 mm.

Then, in response to an instruction from the reading control unit 110, the first reading unit 10 reads the image of the document conveyed through the document conveyance path 33 via the second contact glass 16 from below. Similarly, the contact image sensor unit 32
Reads the image formed on the upper surface (back surface) of the conveyed document from the upper side.

As described above, in the "double-sided reading mode" of the present reading apparatus, the first reading section 10 and the contact image sensor section 32 simultaneously read the images on both the front and back sides of the conveyed document from the vertical direction.

In the above configuration, for example, the deviation L of the reading point may be set to 0 mm. In this case, the reading start timing and the reading end timing for both sides of the original can be made to completely match, but the first reading unit 10 and the second reading unit 23
The interference with the image becomes large, and the show-through occurs more significantly, which makes it difficult to remove the show-through. In addition, the second reference white plate 68 for shading correction of the second reading unit 23 becomes an obstacle, and a complicated structure having a function of inserting and removing the second reference white plate in the optical path must be provided. In order to avoid these, in the present embodiment,
A deviation L having a predetermined dimension is provided between the reading points A and B.

Further, as the deviation L is made larger than that in the above example, the interference between the first reading unit 10 and the second reading unit 23 is reduced and the show-through is reduced. As the capacity of the storage device for storing the fixed image data increases, the time required for the processing increases.

Regarding the capacity of the above storage device, the line buffers 156 and 166 have the following characteristics if L is "0".
The line buffer 156 for the first reading unit and the line buffer 166 for the second reading unit both read and read
All you need is a line. When L is not “0” as in the above example, the reading unit (first reading unit 10 in the present embodiment) in which image data is first generated when reading both sides of the document.
The capacity of the line buffer 156 of the
It suffices to increase the line amount (L × resolution) proportional to That is, if the resolution is 600 dpi, (17
× 600 ÷ 25.4≈402) Therefore, 403 lines are needed. Even in this case, it suffices to have two lines of the reading unit (the second reading unit 23 in this embodiment) in which the image data is generated with a delay.

In the above "double-sided reading mode",
For example, as shown in the explanatory diagram of FIG. 8, the first reading unit 10 and the contact image sensor unit 32 may both move without the document being conveyed. Although not shown, the document may be conveyed and both the first reading unit 10 and the contact image sensor unit 32 may move.

(Image Information Correction Operation) The reading apparatus according to the present embodiment corrects the image information read by the above-described operation using the data comparison processing units 157 and 167 as described below. .

The present reading apparatus according to the present embodiment can select and switch between the "background removal mode" and the "background removal mode" when performing double-sided reading. In other words, when reading images on both sides in order to prevent show-through in the "running reading mode" for performing single-sided reading described above,
"Background removal mode" for each of the two-sided image reading in the "double-sided reading mode"
, And "mode for leaving the background" can be selected and switched.

Below, in the "double-sided reading mode",
The image correction operation in the "background removal mode" and the "background removal mode" will be described in detail.

-Mode for removing background- First, the "background removal mode" will be described.

FIG. 4 shows the read image data and the corrected data. FIG. 4A shows a part of the image data obtained by reading one side (front side) of the document.
In this figure, the lower part shows the density of the read image data in each pixel, and the upper part shows the density value (density data value).

FIG. 4B shows a part of image data obtained by reading the other surface (back surface) of the original. Also in this figure, the lower part shows the density of the read image data in each pixel, and the upper part shows the density value.

In FIGS. 4A and 4B, the fact that the data are arranged side by side represents the position of the pixel data on the document. Therefore, data having the same horizontal position represents the same position on the front and back sides of the document.

By the correction operation described below, the read image data is corrected as shown in FIGS. 4 (c) and 4 (d).

Here, the correction operation will be described with reference to the flowchart of FIG. First, in step S1, the reading operation is started simultaneously for the front and back images of the document.

In step S2, the image data of the Nth line obtained by reading is input from the line buffers 156 and 166 to the data comparison processing units 157 and 167.

That is, when comparing the front and back pixel densities at the same location as in the present embodiment, one is used as the target pixel density data and the other is used as the reference pixel density data, and the data from the line buffers 156 and 166 is used. Comparison processing unit 15
When data is read to 7, 167, one of them is read from the opposite direction. Generally, the reference pixel density data is read out in the reverse direction.
FIG. 4B shows a state in which the reference pixel density data (backside read image data) is read out in the reverse direction. As a result, in FIGS. 4A and 4B, vertically adjacent pixels in the drawing are pixels that face each other on the front and back sides of the document.

In step S3, data having a predetermined density D (here, D = 25 is set) or lower is removed by replacing it with the density value "0" as the background removal. For the other pixels, the density difference E is calculated by comparing with the density value of the corresponding pixel on the back surface.

In step S4, the set value α (here, α
= 100) and the density difference E is larger than that. If the density difference E is larger than the set value α, the process proceeds to step S5. If the density difference E is smaller than the set value α, it is determined that it is not show-through, and the process proceeds to step S8.

In step S4, the density difference E is larger than the set value α.
If it is determined that the value of is larger than that of the pixel on the front surface (pixel of interest), it is determined in step S5 whether or not the density value of the pixel on the opposite surface is smaller than that of the pixel on the opposite surface. If the density value of the pixels on the front surface is smaller than the density value of the pixels on the back surface, it is determined in step S6 that the image data on the front surface is due to show-through, and the density value of the pixels on the front surface is "0". Is output. If the density value of the pixels on the front surface is larger than the density value of the pixels on the back surface, it is determined that it is not show-through, and the process proceeds to step S8.

If it is determined in step S6 that the density value of the front surface pixel is "0" because of the show-through, step S6 is performed.
In 7, it is judged whether or not the read N-th line is the last line. In the case of the last line, the process ends. If it is not the final line, the process returns to step S2 and the same process as described above is performed on the next line.

If it is determined in step S4 or step S5 that the image is not the show-through image, the read data is output as it is in step S8. And
The process proceeds to step S7 described above.

By the above operation, the correction is performed by comparing the data on the front side with the data on the back side for each line of the original read for each pixel of the line.

As a result of the above operation, FIG. 4 (a), (b)
The corrected read data shown in FIG.
It shows in (d).

The explanatory view of FIG. 4C shows data after the image data shown in FIG. 4A is corrected by the above-mentioned operation using the image data shown in FIG. 4B. is there. That is, it is the image data of the surface without the influence of show-through. For example, in the third data from the left, the density value of the front side is “100” and the density value of the back side is “2” before the correction.
55 ", which is determined to be show-through by the above operation, and the density value is set to" 0 "in FIG. 4C.

The explanatory view of FIG. 4 (d) shows the data after the image data shown in FIG. 4 (b) is corrected by the above-mentioned operation using the image data shown in FIG. 4 (a). is there. That is, the image data on the back surface is obtained by eliminating the influence of show-through (the image on the front surface is transparent to the back surface side). For example, in the third data from the left, the value of the front surface is “100” and the value of the back surface (the surface to be corrected) is “255” before the correction. Is set to the value "255" as it is.

As described above, the "background removal mode"
In the above, since the density of the predetermined density level D = 25 or less is erased before the determination, it is suitable for reading a character original, for example.

-Mode for leaving the background- Next, the “base leaving mode” will be described.

FIG. 6 shows the read image data and the corrected data. 6A and 6B respectively show a part of the image data obtained by reading one side (front side) of the document and a part of the image data obtained by reading the other side (back side) of the document. 4 (a) and 4 (b).

By the correction operation described below, the read image data is corrected as shown in FIGS. 6 (c) and 6 (d).

Here, the correction operation will be described with reference to the flowchart of FIG. First, in step S11, the reading operation is started simultaneously for the front and back images of the document.

In step S12, the image data of the Nth line obtained by the reading is stored in the line buffers 156 and 166.
Is input to the data comparison processing units 157 and 167.

That is, when comparing the front and back pixel densities at the same location as in the present embodiment, one is used as the target pixel density data and the other is used as the reference pixel density data, and the data from the line buffers 156 and 166 is used. Comparison processing unit 15
When data is read to 7, 167, one of them is read from the opposite direction. Generally, the reference pixel density data is read out in the reverse direction.
Similar to FIG. 4B, FIG. 6B shows a state in which the reference pixel density data is read from the reverse direction. As a result, in FIGS. 6A and 6B, vertically adjacent pixels in the drawing are pixels that face each other on the front and back sides of the document.

In step S13, unlike the above-mentioned "background removal mode", all the pixels are compared with the density values of the corresponding pixels on the back surface without performing the background removal, and the density difference E is obtained.

In step S14, it is determined whether or not the density difference E is larger than the set value α (here, α = 100 is set). When the density difference E is larger than the set value α,
It proceeds to step S15. If the density difference E is smaller than the set value α, it is determined that it is not the show-through, and the process proceeds to step S23.

When it is determined in step S14 that the density difference E is larger than the set value α, the density value of the front surface pixel (target pixel) is smaller than the density value of the opposite back surface pixel in step S15. It is determined whether or not. If the density value of the pixels on the front surface is larger than the density value of the pixels on the back surface, it is determined that it is not show-through, and the process proceeds to step S23.

When the density value of the front surface pixel is smaller than the density value of the rear surface pixel in step S15, the density difference E is subtracted from the density value of the front surface target pixel in step S16 to obtain the difference F.

For example, when the density value on the front surface is x and the density value on the back surface is y, the density difference E = y−x, and the difference F here is F = x−E = 2x−y. And means the value obtained by removing the show-through density value from the surface density value.

In step S17, the previous step S16
The difference F obtained in step 1 is compared with a predetermined density value D (here, D = 25 is set). If the difference F is less than the density value D, the process proceeds to step S18. If the difference F is greater than or equal to the density value D, the process proceeds to step S22.

Here, the meaning of comparing the difference F with the predetermined value D is that D is the background density. Therefore, it is determined whether F, that is, the density of the surface from which show-through has been removed, is D or more, and the original surface is determined. If the density is higher than D, it is lowered to the background density, and if it is lower than D, it is erased to "0".

If the difference F is less than the density value D in step S17, the density value of the front target pixel is compared with the predetermined value D in step S18. When the density value of the front target pixel is D or more, the process proceeds to step S19. If the density value of the front target pixel is less than D, the process proceeds to step S21.

If the density value of the target pixel on the front surface is D or more in step S18, the density value of the target pixel is output as D ("25" in this embodiment) in step S19. Then, the process proceeds to step S20.

On the other hand, if the density value of the front target pixel is less than D in step S18, the value of the target pixel is output as "0" in step S21. That is,
In this case, it is determined to be the show-through. Then, the process proceeds to step S20.

If the difference F is greater than or equal to the density value D in step S17, the value of the front target pixel is output as F in step S22.

For example, when the density value on the front surface is x and the density value on the back surface is y, the density difference E = y−x, and the difference F here is F = x−E = 2x−y. Therefore, F is the value of the front surface from which the show-through is subtracted, and is therefore the density value of the target pixel. The base is not removed here.

If the difference E between the front surface and the back surface is larger than the set value α in step S14, or if the value of the front surface pixel is smaller than the back surface in step S15, it is determined that there is no influence of show-through. In step S23, the image data is output as it is with the density as the final density.

In step S20 performed after step S19, step S21, step S22, or step S23, it is judged whether or not the read line N at this time is the last line to be read. If it is the final line, the process ends. If it is not the final line, the process returns to step S12 and the comparison process is performed for the next line.

By the above operation, the correction is performed by comparing the data on the front side with the data on the back side for each line of the original read for each pixel of the line.

As a result of the above operation, FIG. 6 (a), (b)
The corrected read data shown in FIG.
It shows in (d).

The explanatory view of FIG. 6C shows data obtained by correcting the image data shown in FIG. 6A by the above-mentioned operation using the image data shown in FIG. 6B. is there. For example, in the third data from the left, the density value of the front surface is “100” and the density value of the back surface is “255” before the correction, but it is determined to be the base area by the above operation. In 6 (c), the density value is "25".

The explanatory view of FIG. 6 (d) shows the data after the image data shown in FIG. 6 (b) is corrected by the above-mentioned operation using the image data shown in FIG. 6 (a). is there. For example, in the third data from the left, the density value of the front side is 100 and the density value of the back side is “255” before the correction, and the value “255” as it is in FIG. It is said that

According to the above arrangement, for example, as shown in the photograph,
It is possible to correct even a document having gradation and low density, which is important as image data to be acquired.

The two modes described above can be switched according to the user's selection, for example, from the operation unit 104. Also, in the device that can be automatically set,
The image data of the read document may be automatically identified and the mode may be automatically switched, or the image data may be divided into regions and the read image data may be generated in a mode suitable for each divided region.

In the above description, the "background removal mode" and "background leaving mode" in the "double-sided reading mode" have been described. In the above operation, each mode can be similarly switched in the "running reading mode" in which one-sided reading is performed. In this case, the correction operation is performed only for the one-sided image data to be read. That is, in FIG. 4, when the correction operation is performed only on the image data on the front surface of the document, only the image data shown in FIG. 4C is obtained as the correction result. Similarly, in FIG. 6, when the correction operation is performed only on the image data on the front surface of the document,
As the correction result, only the image data shown in FIG. 6C is obtained.

(Effect of Embodiment) As described above,
In the present exemplary embodiment, both the first reading unit 10 and the second reading unit 23 are simultaneously used for an image reading apparatus that performs data correction that avoids show-through by acquiring image information of both sides of the document. The image information of the surface is acquired. Therefore, the time required to acquire the image data can be significantly shortened, and the data correction operation can be efficiently executed. Further, since it is not necessary to reverse the original in order to read the other surface of the original after reading one surface of the original, the paper feeding mechanism can be simplified. further,
When comparing the data scanned on one side with the data scanned on the other side, there is no misalignment due to paper feed. Therefore, the "image processing function such as misregistration correction" required in the prior art was used. Data can be corrected accurately without needing to.

(Other Embodiments) In the above embodiment,
The case where the present invention is applied as a scanner device has been described. The present invention is not limited to this, and can be applied to a double-sided original reading unit such as a copying machine or a facsimile machine.

[0137]

As described above, according to the present invention, the image information of each side of the original is different from that of the image reading apparatus which performs the data correction for avoiding the show-through by acquiring the image information of both sides of the original. The reading means obtains the information at substantially the same time. As a result, since it is possible to obtain the image information of each side at substantially the same time and perform the data correction operation, it is not necessary to store all of the data for one side of the document in memory, and a large storage device is required. do not do. In addition, "double-reading of the original", such as performing the reading operation on one side of the original and then the reading operation on the other side
Since it is not necessary, the time for acquiring data can be significantly shortened, and the data correction operation can be efficiently executed. In addition, in the case of the conventional one that "reads the original twice", there is a possibility that the original may be misaligned in the transport position or skewed. Therefore, it is necessary to correct the misalignment to accurately align the positions of both image data. It was necessary to have a function to perform the image processing of. In the present invention, since the "double reading of the original" is not performed, it is not necessary to equip the apparatus with such an image processing function, and the manufacturing cost of the apparatus can be reduced.

Further, when the first reading means and the second reading means read the image information at the positions substantially close to each other on the original at substantially the same time, the correcting means is the first reading means and the second reading means. Only by memorizing the difference in the reading position between and, the pixel data corresponding to the same portion of the document can be compared and corrected. Therefore, the first
In order to correct the above data, it is not necessary to store all the data for one side of the document as in the case of reading the other side of the document after reading one side of the document.
Therefore, a storage device having a large storage capacity is not required.

Further, when it is possible to switch between a mode in which the first data and the second data are compared to correct only the first data and a mode in which both the first data and the second data are corrected by the above comparison can be switched. Is a wasteful image processing operation, in which it is possible to avoid correcting both the first data and the second data by selecting a mode in which only the first data is corrected when only one side needs to be read. It is possible to speed up the processing operation by not performing.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall internal configuration of an image reading apparatus according to an embodiment.

FIG. 2 is a block diagram showing a configuration of a control system of the image reading apparatus.

FIG. 3 is a diagram showing a configuration of a peripheral portion of a scanning unit of the image reading apparatus.

FIG. 4 shows each image data in a mode of removing a background, (a) shows read image data of a document surface,
FIG. 7B is a diagram showing read image data on the back side of the document, FIG. 7C is a diagram showing image data on the front side of the document after correction, and FIG. 8D is a diagram showing image data on the back side of the document after correction.

FIG. 5 is a flowchart showing a procedure of an image data correction operation in a background removal mode.

FIG. 6 shows each image data in a mode of leaving a background, (a) shows the read image data on the front side of the document, and (b) shows the image data.
FIG. 4A is a diagram showing read image data on the back side of the document, FIG. 7C is a diagram showing image data on the front side of the document after correction, and FIG. 8D is a diagram showing image data on the back side of the document after correction.

FIG. 7 is a flowchart showing a procedure of an image data correction operation in a background leaving mode.

FIG. 8 is a diagram showing an internal configuration of an image reading apparatus configured such that a first reading unit and a contact image sensor unit both move to read an image.

[Explanation of symbols]

10 First Reading Unit (First Reading Means) 23 Second Reading Unit (Second Reading Unit) 157,167 Data comparison processing unit (correction means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/19 H04N 1/12 Z F term (reference) 5B047 AA01 BB03 BC05 BC09 BC11 BC14 CA04 CB22 DA10 DC09 5B057 AA11 BA02 CA02 CA08 CA12 CA16 CB02 CB08 CB12 CB16 CE11 DA17 DB02 DB05 DB09 DC22 DC32 DC36 5C072 AA01 BA02 BA03 CA02 DA02 DA04 EA05 EA07 UA20 WA02 5C077 LL05 PP15 PP25 PP47 PQ12 PQ20 PQ23 SS01 TT06

Claims (7)

[Claims] 1. A first reading means for reading image information on one side of a document as first data, a second reading means for reading image information on the other side of the document as second data, the first data and the second data. And a correction unit that corrects at least one of the first data and the second data by comparing the data with the data, and when the image information of the document is read, the first reading unit and the document are relatively moved to read the document. When the image information on one side of the document is read by the first reading unit, the second reading unit and the document are relatively moved at the same time, and the image information on the other side of the document is read by the second reading unit. Image reading device. 2. The image reading apparatus according to claim 1, wherein the correction unit corrects the data by comparing the data of pixels facing each other on the front and back sides of the document in the first data and the second data. An image reading device characterized by being configured. 3. The image reading apparatus according to claim 2, wherein the first reading unit and the second reading unit are configured to read the image information at substantially close positions on the document at substantially the same time. Image reading device. 4. The image reading apparatus according to claim 1, 2 or 3, wherein the correction unit compares the first data and the second data with each other to determine the first data.
An image reading apparatus, which is configured to be switchable between a mode for correcting only data and a mode for correcting both the first data and the second data by the above comparison. 5. The image reading apparatus according to claim 1, wherein the correction unit, when correcting the data, has a data value of a pixel having a predetermined density or less in the correction target data. Is replaced with the data value in the case of the density “0” to remove the background, and when the data is corrected, the data value of the pixel having a predetermined density or less in the data to be corrected is directly stored in the pixel. The image reading apparatus is configured so that it can be switched between a mode in which it is treated as a data value of and the background is left. 6. The image reading apparatus according to any one of claims 1 to 5, wherein, when the correction means sets the first data as a correction target, the correction data is the density data value of the pixel of the first data. When the difference between the density data value of the pixel of the second data facing it and the density data value of the pixel of the first data is smaller than the predetermined value, and the density data value of the pixel of the first data is smaller than the density data value of the pixel of the second data, While replacing the data value of the pixel of the first data with the data value in the case of the density “0”, when the first data is the correction target, the density data value of the pixel of the first data is opposed to the density data value of the pixel. When the difference between the density data value of the pixel of the second data and the predetermined value or less, or the density data value of the pixel of the first data and the second opposite
Even if the difference between the data and the density data value of the pixel exceeds a predetermined value, if the density data value of the pixel of the first data is equal to or higher than the density data value of the pixel of the second data, the pixel of the first data An image reading apparatus configured to handle a data value as it is as a data value of the pixel. 7. The image reading apparatus according to any one of claims 1 to 5, wherein, when the correction means sets the first data as a correction target, the correction data is the density data value of the pixel of the first data. The difference from the density data value of the pixel of the second data facing it exceeds the first predetermined value, and the density data value of the pixel of the first data is smaller than the density data value of the pixel of the second data. Sometimes, the difference is subtracted from the density data value of the pixel of the first data, the subtracted value is less than the second predetermined value, and the density data value of the pixel of the first data is the second predetermined value. When the above is the case, the data value of the pixel of the first data is replaced with the data value of the density “0”, while the density of the pixel of the first data is changed when the first data is the correction target. The density data of the data value and the pixel of the second data opposite to it Data value is less than or equal to the first predetermined value,
Alternatively, even if the difference between the density data value of the pixel of the first data and the density data value of the pixel of the second data opposite thereto exceeds the first predetermined value, the density data value of the pixel of the first data becomes the second value. An image reading apparatus characterized in that, when the density data value of the pixel of the data is equal to or more than the data value of the pixel, the data value of the pixel of the first data is treated as it is as the data value of the pixel.