JP2003023531A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce influence due to dust or scratches adhered to a white reference part at shading correction, and to improve maintenance performance by reducing the frequency of cleaning of the white reference part. SOLUTION: A white reference part is shaped like a roller, and the white reference part is rotated, while reference density is read so as to reduce the influence of dust or scratches.

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 such as a copying machine, a facsimile and a scanner.

[0002]

2. Description of the Related Art FIG. 3 is a sectional view showing a conventional image reading apparatus. In FIG. 3, 1 is an image reading device,
Reference numeral 2 is an original reading unit using a flow-reading method, and 3 is an automatic document feeder for feeding a sheet original to the original reading unit. The automatic document feeder 3 includes a document placing section 4 on which a plurality of sheet documents can be placed, a pickup roller 5 for taking out the sheet documents one by one, a separation roller pair 6 for separating the multi-fed sheet documents, and a sheet document. Transporting rollers 7, 8, 9, 10 for transporting the sheet to the discharge rollers via the document reading unit 2.
And the paper discharge roller pair 11 described above.

The image reading apparatus 1 is composed of a first mirror stand 20, a second mirror stand 21, a lens barrel 22, and a CCD sensor 23 as a scanning optical section. The first mirror stand 20 has an exposure lamp 2 for illuminating the original surface.
4, the reflection shade 25, the direction of the reflected light of the irradiated original 45
A first mirror 26 is provided that changes the degree and guides it to the second mirror. The second mirror base 21 is provided with a second mirror 27 and a third mirror 28 that turn back the reflected light incident from the first mirror base by 180 degrees. Second mirror stand 21
The reflected light that has been reflected by the lens passes through the lens barrel 22 and CC
An image is formed by the D sensor 23. The first mirror base 20 and the second mirror base 21 are supported by rails (not shown) and can move on the rails. Also, the first mirror stand 2
The 0 and the second mirror base 21 are driven by a wire, a drive shaft, a pulley, a stepping motor and the like (not shown) so that the optical path length from the document surface to the CCD sensor 23 is always constant.

During flow reading, the first mirror base 20 is temporarily fixed substantially below the flow reading contact glass 29.

Next, the operation of the above conventional image reading apparatus will be described. First, while the image reading apparatus 1 is on standby, the first mirror base 20 is on standby at the shading position shown in FIG.

Here, when a reading start in the flow reading mode is instructed from an operation unit (not shown), the exposure lamp 24 is turned on to illuminate the white reference portion 30 for shading, and variations in the light amount distribution at both ends and the center of the document, Data for performing shading correction, such as variations in the amount of transmitted light between the center and the periphery of the lens and variations in the sensitivity of light receiving elements in the CCD, is detected, and shading correction is performed by a CPU (not shown).

After that, the first mirror base 20 and the second mirror base 21 are moved in the direction of arrow B by the driving of the stepping motor and stopped at the document reading section 2. At this time,
The exposure lamp 24 remains on.

After that, the document feeding operation is started. First, the pickup roller 5 rotates to take out the original sheet, the separating roller pair 6 separates the multi-feed sheet, and the conveying rollers 7, 8 and 9 convey the sheet to the flow reading contact glass 29 of the image reading unit 2. And the manuscript sheet is
The exposure lamp 24 is irradiated while being conveyed on the flow reading contact glass 29. The reflected light is guided to the lens by the first, second and third mirrors 26, 27 and 28 and forms an image on the CCD sensor 23. CCD sensor 2
The image signal of the original read by 3 is converted into a signal for exposing the photoconductor when copying. Further, when transmitting by facsimile, it is converted into a predetermined digital signal and sent to the telephone line.

Thereafter, the original sheet is conveyed by the conveying rollers 7, 8,
The sheet 9 is further transported to the downstream side by the sheet discharge rollers 9 and 10 and discharged onto the sheet discharge tray by the sheet discharge roller pair 11. Document placing section 5
When all the originals placed on the sheet are ejected and a series of reading operations are completed, the exposure lamp 24 is turned off, and the first mirror table 20 and the second mirror table 21 return to the shading position again and stop.

The shading correction will be briefly described below. When a CCD sensor is used as the image reading element, even if an original having a uniform density is read in the main scanning direction, the output of the CCD for the original does not always have a uniform value. The reason is as follows.

1. The light amount of document illumination differs between the center and both ends.

2. In the concavo-convex combined lens, the amount of light transmitted through the lens differs between the center and the periphery.

3. The sensitivity of the light receiving element in the CCD varies.

Shading correction is to detect variations in CCD output due to these and multiply each output of the CCD by a predetermined correction coefficient so that all outputs for reading the same density become uniform.

In such shading correction, the correction is premised on that the density of the white reference portion is constant. Therefore, if there is dust or scratches on the white reference part,
The amount of illumination light, the amount of light transmitted through the lens, and CC
Correction that is not related to the correction of D sensitivity variation is performed,
Image defects occur. Specifically, if black dust adheres to a part of the white reference portion, the read value will be closer to black than it should be. When the shading correction is performed based on that, the output of the CCD pixel corresponding to the dust adhering portion is corrected to be whiter than it should be, and appears as white streaks in the image when a halftone original having a uniform density is read. . Moreover, since such a streak is fixed pattern noise that appears uniformly from the beginning to the end of the image, even a slight level of noise is very noticeable.

In order to prevent such image defects due to dust and scratches on the white reference portion, there have been proposed means for avoiding the influence of dust and scratches. For example, JP-A-9-186
In No. 56, the peripheral surface of the document conveying roller of the document feeding device is also used as the white reference portion, and when the document is not conveyed, the peripheral surface of the document conveying roller which is the white reference portion is read and the light amount data is output. A method has been proposed.

Further, in Japanese Patent Laid-Open No. 10-56542, a CCD output value read from a reference color member is collated with a threshold value, and a pixel having an output value lower than the threshold value is detected to have dust and the reading position is moved. Is proposed.

[0018]

However, the above-mentioned conventional proposals have the following problems, respectively.

First, in the shading method disclosed in Japanese Patent Application Laid-Open No. 9-18656, since the outer periphery of the document conveying roller also serves as the white reference portion, dirt is likely to adhere to the white reference portion. Therefore, if the cleaning work is not frequently performed, accurate shading correction cannot be performed, and correct image density cannot be obtained.

On the other hand, in the detection method disclosed in Japanese Patent Laid-Open No. 10-56542, a method is used in which a certain threshold value is provided for the CCD output and a normal pixel and an abnormal pixel are discriminated by comparison with the threshold value. Therefore, depending on the setting of the threshold value, it is not possible to deny the possibility of making an erroneous determination in pixels with abnormal output near the threshold value due to small dust or scratches.

[0021]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has the following configurations (1) and (2) and is used for shading correction of an image reading apparatus. It is characterized in that the reference portion is of a rotating roller type.

(1) In an image reading apparatus equipped with a line image sensor and a density reference member for shading correction, the density reference portion has a roller shape and is rotatably supported, and at the time of reading for shading correction. An image reading apparatus, wherein the density reference unit is rotated.

(2) The image reading apparatus according to (1) above, further comprising a cleaning member that comes into contact with the density reference portion.

With the above structure, dust and scratches attached to the white reference portion do not remain in one place, and the influence of dust and scratches attached to the white reference portion on shading correction can be reduced.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of the present invention will be described below with reference to the drawings. Note that the description of the configuration of the image reading apparatus that overlaps with the conventional example will be omitted.

FIG. 1 is a sectional view showing an image reading apparatus embodying the present invention. The first mirror stand 20 includes an exposure lamp 24, a reflection shade 25, and a first mirror 26. In addition, the second mirror base 21 includes a second mirror 27 and a third mirror 28. The read information is folded back by these first to third mirrors and guided to a lens and a CCD (not shown).

A roller-shaped white reference member (white reference roller) 41 is provided between the flow reading contact glass 29 and the platen glass 40. The white reference roller 41 is rotatably supported at the front and the back of the apparatus, and is controlled to rotate at the time of reading shading correction. The driving force of the white reference roller 41 is supplied by a dedicated drive motor (not shown).

With the above-described structure, in the image reading apparatus of this embodiment, the white reference roller 41 for shading correction rotates during correction reading, so that dirt or scratches may be attached to the outer peripheral surface of the white reference roller 41. Even if it does, the effect will be diminished and the CCD will not return an abnormal reflection density.

Further, in the present embodiment, the white reference roller 41 is a member independent of the document conveyance,
Unlike the conventional example, the outer peripheral surface of the white reference roller 41 is not contaminated by the document. Therefore, the frequency of cleaning the white reference portion is reduced, and serviceability and maintainability are greatly improved.

(Second Embodiment) FIG. 2 is a sectional view showing a second embodiment of the present invention.

In the first embodiment, the effect was reduced by rotating it, but in order to completely remove the effect of dust adhering to the white reference roller on the shading correction, the surface of the roller should be cleaned. I had no choice but to remove it.

On the other hand, in the second embodiment, the cleaning roller 42 which is driven to rotate while being in contact with the surface of the white reference roller 41 is provided. The surface of the cleaning roller 42 is subjected to an adhesive treatment, and by rotating while being in contact with the surface of the white reference roller 41, an effect of removing dust adhering to the white reference roller 41 is exerted. The removed dust is retained on the cleaning roller 42 side by virtue of its viscous property and never returns to the surface of the white reference roller 41 again.

With the above-described structure, the white reference roller 41 is always stripped of dust by the cleaning roller 42, so that the cleaning frequency can be further reduced as compared with the first embodiment. The serviceability and maintainability are further improved. Even if dust that cannot be removed by the cleaning roller 42 adheres to the white reference roller 41, the white reference roller 41 rotates during the shading correction reading as in the first embodiment. Can minimize the effect on shading correction.

[0034]

As described above, according to the present invention,
The following effects can be obtained.

1. Since the roller-shaped white reference portion rotates during the shading correction reading, it is possible to reduce the influence of dust and scratches on the correction.

2. Since the white reference roller is installed independently of the document conveyance, the white reference roller is not contaminated by the document, the frequency of cleaning the white reference roller is reduced, and the maintainability is improved.

3. By bringing the cleaning roller into contact with the white reference roller, the white reference roller can always obtain a surface cleaning action during rotation.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing a conventional example.

[Explanation of symbols]

1 Image reading device 2 Document reading section 3 Automatic document feeder 4 Document placing section 5 Pickup roller 6 Separation roller pair 7, 8, 9, 10 Transport rollers 11 Paper ejection roller pair 20 1st mirror stand 21 Second mirror stand 22 Lens barrel 23 CCD sensor 24 exposure lamp 25 reflective shade 26 First Mirror 27 Second mirror 28 Third mirror 29 Flow reading contact glass 30 White reference part 40 platen glass 41 White reference member (white reference roller) 42 Cleaning roller

Claims (2)

[Claims] 1. An image reading apparatus comprising a line image sensor and a density reference member for shading correction, wherein the density reference section is in the shape of a roller and is rotatably supported. An image reading device characterized in that a density reference unit is rotated. 2. The image reading apparatus according to claim 1, further comprising a cleaning member that comes into contact with the density reference portion.