JP2004320331A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-quality image reader having no setoff and generating no streaks on an image even when reading is applied to the thin double-sided printing image. <P>SOLUTION: A transparent cylindrical platen roller 4 and a cylindrical back ground plate 25 are supported through bearings 33 on a shaft 32. The transparent cylindrical platen roller 4 is closed with a cover 34 to internally prevent the cylindrical back ground plate 25 from adhesion of waste/dust or the like. Furthermore, the cylindrical back ground plate 25 is fixed to the shaft 32 and is rotated and driven by means of a motor 31 through a gear 29 fixed to the shaft 32 like the bearings 33. In reading a single-sided original, the cylindrical back ground plate 25 facing an original reading position is selectably retained on a white section. In the case of a double-sided original, the cylindrical back ground plate 25 facing the original reading position is selectably retained on a black section. Thus, the single-sided original has no decrease in contrast and the double-sided original is allowed reading having no setoff. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image reading apparatus, such as a facsimile, a copying machine, and a scanner, having a function of reading an image on a sheet document.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, for the purpose of effective use of resources and compression of information, double-sided printing has been widely performed on outputs of copiers, printers, and the like.
By the way, when the original on which double-sided printing has been performed is read by an image reading device such as an image scanner, a copying machine, and a facsimile, especially in the case of a double-sided original recorded on relatively thin paper, the image on the back side is transparent and the front side is read. It may be reflected in the image. This is a problem called “show-through”, and various techniques have been proposed as a countermeasure for this.
[Patent Document 1]
JP-A-9-247378 [Patent Document 2]
JP-A-2000-59569
[0003]
[Problems to be solved by the invention]
In Patent Document 1 and Patent Document 2, when reading a document having an image on both sides with a white background portion having a high reflectance and a black background portion having a low reflectance, the reading position of the document must be moved. Alternatively, by rotating or sliding the background surface, a black background portion having a low reflectance is set as a reading position to prevent the image on the back surface from being transparent.
However, in these conventional techniques, since the background plate is arranged in contact with the original, the background plate of the double-sided original may be stained by the original, and the background plate may become dirty. For this reason, a streak occurs in the image, which causes image deterioration. In particular, when dirt adhered to the white portion for shading correction, the occurrence of streaks was remarkable.
Accordingly, an object of the present invention is to provide a high-quality image reading apparatus that does not show off even when a thin double-sided printed image is read and that does not cause streaks in the image.
[0004]
[Means for Solving the Problems]
According to the first aspect of the present invention, there is provided an image reading apparatus comprising: a document conveying means for conveying a document onto a document glass serving as a document reading position; and a background plate serving as a background when reading the document at a position facing the document glass. The apparatus includes a cylindrical transparent platen roller for pressing a document against a document glass, and a detection sensor for detecting a color of the background plate, and the background plate is provided in a space inside the cylindrical transparent platen roller. The above object is achieved by being arranged as a cylindrical background plate.
According to a second aspect of the present invention, in the first aspect of the present invention, the cylindrical background plate has a white portion and a black portion formed on an outer peripheral surface thereof, and is rotatably supported.
[0005]
According to a third aspect of the present invention, in the first or second aspect of the invention, the cylindrical background plate detects a boundary between a white portion and a black portion by the detection sensor, and the white portion rotates during shading correction. While reading a white portion as a white reference for shading correction.
According to a fourth aspect of the present invention, in the first, second, or third aspect of the present invention, the white background and the black part are selectably positioned at the document reading position when reading the document. It is characterized by.
According to a fifth aspect of the present invention, in the first, second, third or fourth aspect of the present invention, the cylindrical background plate is sealed by the cylindrical transparent platen roller and a lid. And rotatably supported.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS.
FIG. 1 is a diagram showing an overall configuration of an image reading apparatus according to an embodiment of the present invention, and FIG. 2 is a diagram showing details thereof.
First, the operation of the image reading device will be described. The document 1 loaded on the document tray 21 is called by the call roller 22, and only the uppermost document 1 separated by the separation unit 23 is transported to the transport roller 2.
Then, as shown in FIG. 2, the document 1 is guided by guides 11 </ b> A and 12 by a transport roller 2 and is sent onto an ADF (automatic document feeder) reading glass 3. Thereafter, at a predetermined document reading position, the reflected light of the document 1 illuminated by the illumination lamp 6 is reflected by the first mirror 8, the second mirror 16, and the third mirror 17, and is reflected by the lens 18 through the lens 18. It is sent to a CCD (photoelectric conversion element) 19 provided on a reading substrate 20. Here, information of the original 1 is read by the CCD 19.
[0007]
At a position facing the ADF reading glass 3, a cylindrical transparent platen roller 4 is provided with a predetermined gap A (usually about 0.5 mm) from the ADF reading glass 3. The cylindrical transparent platen roller 4 regulates the original 1 from fluttering.
On the other hand, the opposing reflection plate 7 is provided to increase the illuminance of the document surface, and the first traveling body 9 has the illumination lamp 6, the opposing reflection plate 7, and the first mirror 8 mounted thereon. The second traveling body 15 has a second mirror 16 and a third mirror 17 mounted thereon.
After the information of the document 1 is read by the CCD 19, the document 1 is guided by the guide 11 </ b> B and is discharged to the discharge tray 24 by the discharge rollers 5.
The cylindrical background plate 25 is provided inside the cylindrical transparent platen roller 4 and is rotatably supported. Then, the boundary between the white portion and the black portion is detected by the sensor 26, and the white portion or black is selectively held at the document reading position when reading the document.
[0008]
At the time of shading correction, the white portion is read while the cylindrical background plate 25 rotates, but the sensor 26 detects the boundary between the white portion and the black portion, and only the white portion of the rotating cylindrical background plate 25 is detected. Is controlled to perform shading.
Since the cylindrical background plate 25 is provided inside the cylindrical transparent platen roller 4, it is possible to prevent dirt and the like of the document from adhering to the cylindrical background plate 25.
[0009]
FIG. 3 is a diagram illustrating details of the cylindrical transparent platen roller 4 and the cylindrical background plate 25.
The cylindrical transparent platen roller 4 and the cylindrical background plate 25 are supported on a shaft 32 via a bearing 33. The cylindrical transparent platen roller 4 is hermetically sealed by a lid 34 so that dust and dirt do not adhere to the cylindrical background plate 25.
The cover 34 is integrally provided with a gear portion, and is rotatably driven by the motor 28 via the gear 27.
The cylindrical background plate 25 is fixed to a shaft 32, and is driven to rotate by a motor 31 via a gear 29 similarly fixed to the shaft 32.
In this embodiment, even if the diameter of the cylindrical transparent platen roller 4 is made smaller, the cylindrical background plate 25 can be arranged inside the transparent platen roller 4 and the size of the device can be reduced.
[0010]
Further, at the time of shading correction, correction is performed based on white read data for several lines, but if there is unevenness in the white portion on the read line, the influence of the unevenness appears on the image. In order to avoid the influence of such unevenness, the correction is usually made based on the average data of several to several tens of parts while moving the white background plate, but this cannot be done with the fixed background plate. Therefore, by performing shading correction while rotating the white portion, it is possible to perform high-quality image reading that is not affected by density unevenness of the white background plate.
Further, in this embodiment, when reading a single-sided document, the cylindrical background plate 25 facing the document reading position is placed in a white portion, and in the case of a double-sided document, the cylindrical background plate 25 facing the document reading position is placed in black. By selectively holding the originals in the copy unit, it is possible to perform reading without show-through on double-sided originals without lowering the contrast of single-sided originals.
[0011]
【The invention's effect】
According to the first aspect of the present invention, the background plate is provided inside the cylindrical transparent platen roller, so that the background plate is not stained by the original, and a high quality image having no streaks in the read image. Image reading can be performed.
According to the second aspect of the present invention, even if the diameter of the cylindrical transparent platen roller is made smaller, the background plate can be disposed inside the roller and the size of the device can be reduced.
[0012]
According to the third aspect of the invention, by performing shading correction while rotating the white portion, it is possible to perform high-quality image reading that is not affected by density unevenness of the white background plate.
According to the fourth aspect of the invention, in the case of a single-sided document, the cylindrical background plate facing the document reading position can be selected as a white portion, and in the case of a double-sided document, the background plate facing the document reading position can be selected as a black portion. Therefore, reading without show-through can be performed on a double-sided original without lowering contrast in a single-sided original.
[0013]
According to the fifth aspect of the present invention, the surface of the cylindrical background plate is sealed so that paper dust, dust, and dust do not adhere to the surface of the cylindrical background plate. It can be performed.
[Brief description of the drawings]
FIG. 1 is a diagram showing the overall structure of an image reading apparatus according to the present invention.
FIG. 2 is a diagram illustrating details of an image reading apparatus.
FIG. 3 is a view showing details of a cylindrical transparent platen roller and a cylindrical background plate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Original 2 Conveying roller 3 ADF reading glass 4 Cylindrical transparent platen roller 5 Discharge roller 6 Illumination lamp 7 Opposite reflector 8 First mirror 9 First running body 11A Guide 11B Guide 12 Guide 15 Second running body 16 Second Mirror 17 Third mirror 18 Lens 19 CCD
REFERENCE SIGNS LIST 20 image reading board 21 document tray 22 call roller 23 separation unit 24 discharge tray 25 cylindrical background plate 26 sensor 27 gear 28 motor 29 gear 31 motor 32 shaft 33 bearing 34 lid

Claims (5)

Document transport means for transporting a document onto a document glass serving as a document reading position;
In an image reading apparatus including a background plate serving as a background when reading a document at a position facing the document glass,
A cylindrical transparent platen roller for pressing the original against the original glass,
And a detection sensor for detecting the color of the background plate,
The image reading device according to claim 1, wherein the background plate is disposed as a cylindrical background plate in a space inside the cylindrical transparent platen roller. 2. The image reading apparatus according to claim 1, wherein the cylindrical background plate has a white portion and a black portion formed on an outer peripheral surface and is rotatably supported. The cylindrical background plate detects a boundary between a white portion and a black portion by the detection sensor, and reads the white portion as a white reference for shading correction while rotating the white portion during shading correction. The image reading device according to claim 1. 4. The image reading apparatus according to claim 1, wherein said cylindrical background plate selectively positions a white portion and a black portion at a document reading position when reading the document. The said cylindrical background plate is rotatably supported in the state sealed by the said cylindrical transparent platen roller and a lid, The Claim 1, Claim 2, Claim 3 or Claim 4 characterized by the above-mentioned. The image reading device according to claim 1.

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