JP2002258421A - Image reader and image forming device with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader capable of preventing image degradation due to electrostatic noise with a simple constitution and to provide an image forming device with the image reader. SOLUTION: The image of a sheet put on platen glass 14 is read by moving an image reading means 18 disposed under the platen glass 14. Striking members 30 which come in contact with the platen glass 14 so as to keep a prescribed interval between the image reading means 18 and the platen glass 14 are attached to the image reading means 18 and the striking members 30 are formed from electrically conductive members.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus and an image forming apparatus having the same, and more particularly, to a structure for preventing electrostatic noise of image reading means.

[0002]

2. Description of the Related Art Conventionally, in an image reading apparatus such as a copying machine or an image scanner, an original or a book is placed on a platen glass and the original or a book (hereinafter referred to as a sheet) is placed.
Is read by moving image reading means provided below the platen glass. As such an image reading unit, there is an equal-magnification optical system using a Selfoc lens array (registered trademark) having a shallow depth of field of a lens.

In an image reading apparatus provided with such an image reading means, since the fluctuation of the distance between the platen glass and the lens array must be kept within about 0.5 mm, for example, abutting members are provided at both ends of the image reading means. Is provided, and the deflection of the distance is suppressed by urging the image reading means against the platen glass by a pressure spring or the like.

[0004]

However, in a conventional image reading apparatus having such a configuration and an image forming apparatus having the same, when reading an image on a sheet, the image reading means places the abutting member on the platen glass. Because of the movement while sliding, a charge due to frictional charging is generated on the glass surface and the abutting member.

[0005] When the charges thus generated are discharged, electrostatic noise is mixed into the photoelectric conversion elements and electric circuits arranged in the image reading means, and the image output may be disturbed. FIG. 4 is a schematic diagram showing an image defect caused by such discharge of electric charges.

[0006] Here, the same figure shows a uniform black image at the tip half,
This figure shows an enlarged view of the image output when using a document with a white image in the rear half, and as shown in FIG. Has irregular black spots.

In order to prevent the occurrence of image defects due to such discharge of electric charges, measures are taken to cover the image reading means with a conductive member such as a sheet metal or to perform a low resistance treatment on the back surface of the glass. In this case, the weight of the image reading means increases, the cost of the driving mechanism increases, and the cost of the platen glass increases. In addition, the component configuration becomes complicated, and the size of the apparatus increases.

Accordingly, the present invention has been made in view of such circumstances, and provides an image reading apparatus having a simple configuration capable of preventing an image defect due to electrostatic noise and an image forming apparatus having the same. It is intended to do so.

[0009]

According to the present invention, there is provided an image forming apparatus wherein a sheet is placed on a platen glass and an image of the sheet is read by moving an image reading means provided below the platen glass. In the reading device, an abutting member that abuts the platen glass on the image reading unit and maintains a predetermined interval between the image reading unit and the platen glass is provided, and the abutting member is formed of a conductive member. It is characterized by the following.

Further, the present invention is characterized in that the abutting member is urged to abut on the platen glass, and an upper end portion abutting on the platen glass has a spherical shape. .

Further, the present invention is characterized in that the abutment member has a volume resistivity of 10 ⁹ Ω · cm or less.

According to the present invention, there is provided an image forming apparatus comprising: an image reading device; and an image forming section for forming an image based on image information read by the image reading device. Are characterized by the following.

Further, as in the present invention, an image on a sheet placed on the platen glass is read by moving image reading means provided below the platen glass.
Then, an abutting member is provided for contacting the platen glass with the image reading means and maintaining a predetermined interval between the image reading means and the platen glass, and the abutting member is formed of a conductive member. .

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic sectional view of an image reading apparatus according to an embodiment of the present invention. In FIG. 1, reference numeral 14 denotes a platen glass, and 15 denotes a sheet (not shown) which is a sheet placed on the platen glass 14. On the platen glass 14. Reference numeral 18 denotes a document reading unit serving as image reading means. The document reading unit 18 is moved in a sub-scanning direction indicated by an arrow A by a driving device (not shown) with respect to the document placed on the platen glass 14. The original image is read.

On the other hand, FIG. 2 is a view showing the structure of the document reading unit 18. The document reading unit 18 is arranged in the frame 22 and movable in the vertical direction as shown in FIG. An image sensor unit 19 is provided.

Here, the image sensor unit 19 is provided with a light source 23 for irradiating the original on the platen glass 14 with light.
A lens array 21 for condensing reflected light from the original,
The CCD 20 is a photoelectric conversion element that forms an image of reflected light condensed by the lens array 21. In this embodiment, the CCD 20 has a pixel size of about 4 pixels.
The photoelectric conversion element is equivalent to 2 μm and 600 dpi, and has a line sensor formed by linearly arranging 5120 pixels.

In the image sensor unit 19 having such a configuration, the light emitted from the light source 23 is first reflected from the document and condensed by the lens array 21.
An image is formed on the CCD 20. Next, this reflected light is CCD
After being converted into analog data by 20, the data is transmitted to a circuit board (not shown) arranged in the image reading apparatus by a flexible cable (not shown) having high flexibility. After this,
After gain adjustment, A / D conversion, shading correction, γ correction, and the like are performed on the circuit board, the information is sent to a host computer as image information via a buffer RAM (not shown).

On the other hand, an urging spring 31 is disposed between the bottom surface of the frame 22 and the image sensor unit 19 as shown in FIG. Has been established.

The image sensor unit 19 is urged by an urging spring 31 so that the abutting member 31 comes into contact with the platen glass 14 so that the distance between the image sensor unit 19 and the platen glass 14 is set to a predetermined distance. So that you can keep it.

Here, the butting member 30 is formed of a conductive member such as POM. When the original reading unit 18 moves, the abutting member 30 for holding the interval between the image sensor unit 19 and the platen glass 14 at a predetermined interval is formed of a conductive member. Even if the member 30 comes into sliding contact with the platen glass 14 and charges are generated due to frictional charging, the charges are grounded via the biasing spring 31 or a ground mechanism (not shown). By setting the resistance of the abutting member to a volume resistivity of 10 ⁹ Ω · cm or less, the amount of charge due to friction can be reduced, and discharge can be prevented without providing a grounding mechanism.

This makes it possible to prevent image deterioration due to electrostatic noise with a simple configuration, and to reduce the weight of the image sensor unit 19 (original reading unit 18).

The upper end portion of the abutting member 30 which contacts the platen glass 14 has a spherical shape, and the original reading unit 18 can be moved smoothly by making the upper end portion have such a shape. While being able to
The contact area with the platen glass 14 can be reduced, and the amount of electric charge generated when the abutment member 30 trims the lower surface of the platen glass 14 can be reduced.

As described above, if noise is mixed in the image signal, the uniformity of the black portion is reduced and the white portion is fogged in the read image (FIG. 4).
When evaluating the noise component of such a read signal, a variance of noise with respect to the signal is used.

Here, for example, when the image signal value is subjected to 8-bit processing, if the variance of the signal value 10 (black area) is 4 or more, the uniformity of the black part is impaired, and the variance of the signal value 250 (white area) is reduced. When the value is 10 or more, fog becomes noticeable. Therefore, it is desirable for the image reading apparatus to have a variance value equal to or less than the above value.

Next, the dispersion values when the butting member 30 is formed of an insulating material and when it is formed of a conductive member will be described.

First, the dispersion value when the butting member is formed of an insulating type material will be described.

Here, when the original reading unit 18 having the butting member 30 formed of an insulating type material is moved at a reading scanning speed of about 30 mm / sec,
The image was not disturbed due to the generation of electrostatic noise due to friction between the abutting member 30 and the platen glass.

However, if the moving speed is set to 50 mm / sec with the recent increase in the speed of the device, the abutting member 3
Electrostatic noise is likely to occur due to frictional charging between the platen glass 0 and the platen glass 14, and the speed of the clock for driving the CCD 20 and the amount of original exposure light relatively decrease.
As a result, the variance value of the signal value 10 (black area) was about 5, and the variance value of the signal value 250 (white area) was about 18, and the fog image was particularly remarkable in the white portion, and a desirable image could not be obtained. .

Next, the dispersion value when the abutment member 30 is formed of a conductive POM having a volume resistivity of about 10 ⁹ Ω · cm will be described.

Here, the original reading unit 18 having the abutting member 30 is moved at a moving speed of 50 mm / sec.
, The variance value of the signal value 10 (black area) is about 3 and the variance value of the signal value 250 (white area) is increased despite the speeding up of the clock and the relative decrease in the exposure light quantity of the document. As a result, no particular problem occurred in the output image.

As described above, the abutment member 30 is formed of a conductive member, in particular, a conductive member having a volume resistivity of 10 ⁹ Ω · cm or less, which leads to an increase in size, complexity, and cost of the apparatus. In addition, it has been clarified that the generation of electrostatic noise due to sliding during document scanning can be suppressed, and a good read image can be obtained without disturbing the image read signal.

Next, an image forming apparatus provided with the image reading device having such a configuration will be described.

FIG. 3 is a diagram illustrating a schematic configuration of a copying machine as an example of such an image forming apparatus.

Here, the copying machine includes an image reading device 10 and an image forming section 11 for forming an image based on image information read by the image reading device 10 as shown in FIG. This copier has a process speed of 7
It operates at 5 mm / sec and can copy A4 portrait size at 12 sheets per minute. The image reading apparatus 10 has a reading speed of 75 mm / sec and a resolution of 600 dpi × 600 d.
pi and the maximum reading size A4.

In such a copying machine, a signal output from the image reading apparatus 10 by the above-described process is sent to an image processor, which is an image processing unit (not shown), and then subjected to a predetermined image processing. Thus, the image information is converted into optimal image information, and is temporarily stored in a memory or sent to the image forming unit 11 directly.

On the other hand, in the image forming section 11, first, based on the image information sent from the image processor, the exposure means 8 irradiates the surface of the photosensitive drum 1 which has been charged in advance by the charging means 6 with laser light 9. To form an electrostatic latent image on the surface of the photosensitive drum.

Next, the electrostatic latent image is developed by the developing means 2 using toner, and the recording paper P is transported between the photosensitive drum 1 and the transfer means 3 in accordance with the rotation of the photosensitive drum 1. Then, the toner image on the photosensitive drum 1 is transferred.
After that, the recording paper P is guided to the fixing unit 7, and the recording paper P is heated and pressed in the fixing unit 7,
The toner image is fixed as a permanent image and is discharged onto the discharge tray 16.

The image reading apparatus 10 uses the original reading unit 18 provided with the abutting member 30 having a volume resistivity of 10 ⁹ Ω · cm as described above. Even when a document having a white image (reflection density 0.08) in the rear half is read, the variance of the signal value 10 (black area) is about 3 and the signal value 2
The variance of 50 (white area) was about 8, and there was no particular problem in the output image, and a good image was obtained.

On the other hand, when a conventional abutment member made of an insulating member is used, when the above-described original is read, the variance of the signal value 10 (black area) is 1.
The variance of the signal value 250 (white area) is about 0, and the white spot-shaped pattern is irregularly generated in the black part and the black fog is irregularly generated in the white part as shown in FIG. Was.

As described above, the image reading apparatus 10 provided with the original reading unit 18 having the butting member 30 formed of a conductive member, more preferably a conductive member having a volume resistivity of 10 ⁹ Ω · cm or less, is used as a copier. By using it for an image forming apparatus, it is possible to suppress the generation of electrostatic noise due to sliding when scanning a document and to disturb an image reading signal from a CCD without increasing the size, complexity, and cost of the apparatus. And a good output image could be obtained.

Further, even when the image is read by a facsimile or a copying machine in which it is difficult for the user to perform image correction, the image is hardly disturbed by noise, so that unnecessary facsimile communication costs and consumption of transfer materials, toners, etc. Can be suppressed.

[0043]

As described above, according to the present invention, the abutting member provided on the image reading means and for maintaining the predetermined distance between the image reading means and the platen glass is formed by the conductive member. This makes it possible to prevent image defects due to electrostatic noise with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a document reading unit of the image reading apparatus.

FIG. 3 is a diagram illustrating a schematic configuration of a copying machine as an example of an image forming apparatus including the image reading device.

FIG. 4 is a schematic diagram showing an example of an image defect in a conventional image reading apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Image reading apparatus 11 Image forming part 14 Platen glass 18 Document reading unit 19 Image sensor unit 22 Frame 30 Abutment member 31 Urging spring

Claims (4)

[Claims] 1. An image reading apparatus, wherein a sheet is placed on a platen glass and an image of the sheet is read by moving an image reading means provided below the platen glass. An abutting member that abuts on the platen glass to maintain a predetermined interval between the image reading unit and the platen glass, and the abutting member is formed of a conductive member. . 2. The image according to claim 1, wherein the abutting member is urged to abut on the platen glass, and an upper end portion abutting on the platen glass has a spherical shape. Reader. 3. The volume resistivity of the abutment member is 10 ^9.
2. The image reading apparatus according to claim 1, wherein the resistance is equal to or less than Ω · cm. 4. An image forming apparatus comprising: an image reading device; and an image forming unit that forms an image based on image information read by the image reading device. The image reading device according to claim 1, An image forming apparatus according to any one of the preceding claims.