JPH08321930A - Image reader - Google Patents

Abstract

PURPOSE: To prevent occurrence of black stripes in a reproduced image of a read image. CONSTITUTION: A mirror surface 20 of a 1st mirror 2 is shut from an external light by using a 1st transparent board 22 whose lengthwise direction is in parallel with a lengthwise direction of the 1st mirror 2 and in parallel with a contact glass face and close to the 1st mirror 2 between the 1st mirror 2 and a contact glass 7 and using a 2nd transparent board 22 whose lengthwise direction is in parallel with a lengthwise direction of the 1st mirror 2 orthogonal to the 2nd transparent board 22 close to the 1st mirror 2. Then a cleaning means 50 provided in the vicinity of a home position of the 1st mirror 2 is used to rub the surface of the 1st transparent board 21 to clean the surface by using the movement associated with the read scanning of the 1st mirror 2.

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.

[0002]

2. Description of the Related Art An image reading apparatus for reading an original image and converting it into data is known as an image scanner of various OA apparatuses, including a reading section of a digital electronic copying apparatus.

FIG. 4 (a) schematically shows only an essential part of an example of a conventionally known image reading apparatus of this kind.

A document 0 having an image to be read is flatly placed on a contact glass 7 provided on an upper portion of a housing 8 of the apparatus main body, and illuminated by a lamp 1 in a long slit shape in a direction orthogonal to the drawing. .

The reflected light flux from the illuminated portion of the original 0 is the first
It is reflected by the mirror 2 in a direction parallel to the contact glass 7. The light flux reflected by the first mirror 2 is reflected by the mirrors 3, 4
The image is reflected by a "folding mirror pair" constituted by the above and is incident on the imaging lens 5, and is imaged on the solid-state imaging device 6 such as CCD as an "image of the illuminated portion" of the original document 0.

The lamp 1 moves at a constant speed from the "position indicated by the solid line" to the "position indicated by the broken line" in the right direction to illuminate and scan the original 0. The first mirror 2 is the lamp 1
Together with the above, the document is read and scanned while moving at a constant speed from the position indicated by the solid line to the position indicated by the broken line.

The mirrors 3 and 4 forming the "folded mirror pair" have a speed half that of the first mirror 2 and
The position shown by the solid line is moved to the position shown by the broken line, and the "optical path length of the reflected light flux" from the document surface to the imaging lens 5 is kept constant.

By operating the solid-state image pickup device 6 while reading and scanning the original 0 in this manner, the image on the original 0 is read and converted into data (electric signal).

Such an image reading apparatus has the following problems.

That is, in such an image reading apparatus,
The image forming magnification of the image forming lens for forming the image of the original on the solid-state image pickup device is a “reduction ratio”, and the magnification is generally several 1 to 1/10.

As is well known, the "longitudinal magnification" of an imaging lens is "m ² " where the lateral magnification is m. If the lateral magnification of image formation in the above-mentioned imaging lens is 1/10, the longitudinal magnification will be 1/100.

On the other hand, from the surface of the contact glass 7 to the first
The optical distance to reach the effective part of the mirror 2 is usually 10 to 20 m.
m. Then, when the surface of the contact glass 7 and the light-receiving surface of the solid-state image sensor 6 are in a “conjugate relationship” at a reduction ratio of 1/10 by the imaging lens 5, the image of the effective portion of the first mirror is 0.01 ~ from the light receiving surface
A position separated by 0.02 mm, in other words, the solid-state image sensor 6
The image is formed in the very vicinity of the light receiving surface of.

Therefore, as shown in FIG. 4B, when dirt 200 is generated due to the adhesion of dust on the effective portion of the first mirror 2, an image of the dirt 200 is formed in the vicinity of the light receiving surface of the solid-state image sensor 6. When the white part of the original is read, the read information converted into data is changed as shown in FIG. 4C, and the read data of the stain 200 exceeds the “threshold”. Then, as shown in FIG. 4D, the reproduced image is not reproduced as “black stripes”, which significantly deteriorates the quality of the reproduced image.

Since the contact glass 7 is generally horizontal and the first mirror 2 is tilted with respect to the contact glass 7 and the mirror surface thereof faces upward, floating dust is likely to be accumulated and to be contaminated.

Since the mirrors 3 and 4 have a relatively long optical distance from the surface of the contact glass 7, the position where they are conjugate with the mirrors 3 and 4 by the imaging lens 5 is not the light receiving surface of the solid-state image sensor 6. Since the mirrors 3 and 4 are distant from each other, the image thereof is "blurred" at the light receiving surface position of the solid-state image pickup device 6 even if the mirrors 3 and 4 are dirty, and there is no problem of "black stripes" as described above.

[0016]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a new image reading apparatus capable of effectively preventing the generation of black stripes due to dirt on the first mirror. To do.

[0017]

SUMMARY OF THE INVENTION The image reading apparatus of the present invention is directed to "a document placed planarly on a contact glass having a horizontal document placement surface is provided so as to be inclined with respect to the contact glass. Is read and scanned by the first mirror that moves in close proximity to the first mirror, and the reflected light flux from the first mirror is moved to the imaging lens side by the folding mirror pair that is displaced in the same direction as the first mirror at a speed half that of the first mirror. The device reads the original image by reflecting so as to turn back and forming an image on the solid-state image pickup device by the image forming lens.

The original placing surface of the contact glass is "horizontal"
Needless to say, it means a “substantially horizontal state”, not a strictly horizontal state.

An image reading apparatus according to a first aspect of the invention has first and second transparent plates and a cleaning means.

In the "first transparent plate", the longitudinal direction is the first
It is arranged parallel to the longitudinal direction of the mirror, between the first mirror and the contact glass, parallel to the contact glass surface, and close to the first mirror.

The "second transparent plate" has a first in the longitudinal direction.
It is arranged parallel to the longitudinal direction of the mirror, orthogonal to the first transparent plate, and close to the first mirror.

The mirror surface of the first mirror is "closed to the outside" by using these first and second transparent plates.

The "cleaning means" is provided near the home position of the first mirror, and is means for rubbing and cleaning the surface of the first transparent plate by the movement of the first mirror during the reading and scanning.

The home position of the first mirror is shown in FIG.
In the example of (a), it is the “position indicated by the solid line” and / or the “position indicated by the broken line” of the first mirror 2.

The "antistatic film" may be formed on at least the surface of the second transparent plate of the first and second transparent plates (claim 2).

The above-mentioned cleaning means can be appropriately used as long as it can clean the surface of the first transparent plate by rubbing, and this can be used as a "static elimination brush" (claim 3).

In the image reading apparatus according to the fourth aspect,
A "dielectric resin material" is provided so as to surround the effective reflection surface area of the mirror surface of the first mirror.

Further, in the image reading apparatus according to the present invention, a "conductive film" is formed on a portion of the mirror surface of the first mirror outside the effective reflection surface area of the metal reflection film. The mirror surface of the first mirror is electrically set to the “grounded state” through the holder of the first mirror.

[0029]

According to the image reading apparatus of the present invention, since the mirror surface of the first mirror is closed to the outside by using the first and second transparent plates, the mirror surface of the first mirror is contaminated by dust. There is nothing to do.

Even if dust adheres to the surface of the first transparent plate, this "dust" is removed by the cleaning means.

Since the surface of the second transparent plate is substantially vertical, dust is unlikely to adhere to it. This "dust-resistant property" can be further effectively promoted by forming an antistatic film on the surface of the second transparent plate (claim 2).

The adhesion of dust to the mirror surface of the first mirror is caused by the movement of the first mirror during the reading and scanning, so that the mirror surface of the first mirror is frictionally charged by the air flow and the dust floating in the apparatus is electrically absorbed. There is part of the reason for doing this.

According to the fourth aspect of the present invention, the dielectric resin material is provided so as to surround the effective reflection surface area of the mirror surface of the first mirror, and the resin material is positively triboelectrically charged. The floating dust is positively adsorbed on the resin material to reduce the adhesion of dust to the mirror surface of the first mirror.

In the fifth aspect of the invention, the electric attraction of floating dust is prevented by electrically setting the mirror surface of the first mirror, which is formed by the metal reflection film, to the "grounded state".

[0035]

EXAMPLES Specific examples will be described below.

FIG. 1 (a) schematically shows only one characteristic part of one embodiment in which the invention according to claim 1 is applied to the image reading apparatus described with reference to FIG. 4 (a). Therefore, the same reference numerals as in FIG. 1 are used for those which are considered not to be confused.

FIG. 1A shows a state near the "home position" of the first mirror 2 in the image reading apparatus having the structure shown in FIG. 4A. In the state of the figure,
The first mirror 2 is in the home position. Reference numerals 1, 7,
8 are "lamps", respectively, as in FIG. 4 (a).
"Contact glass" and "housing of the device body" are shown.

The contact glass 7 has a substantially "horizontal document mounting surface", and the document 0 from which an image is to be read is
It is placed flat on the contact glass 7.

The first mirror 2 has a strip shape whose longitudinal direction is orthogonal to the drawing, and its mirror surface 20 is provided so as to be inclined 45 degrees with respect to the contact glass 7 and is integrated with the lamp 1 at the time of reading. And moves closer to the contact glass 7 to "scan" the document 0.

The light flux reflected by the first mirror 2 is shown in FIG.
As described in connection with (a), it is reflected back to the imaging lens side by the folding mirror pair that is displaced in the same direction as the first mirror 2 at a speed of 1/2 of the first mirror, To form an image on the solid-state image sensor. Then, the solid-state image sensor converts the document image into data.

In FIG. 1 (a), reference numerals 21 and 22 respectively indicate "first and second transparent plates". First
Also, both the second transparent plates 21 and 22 have a strip shape whose longitudinal direction is the direction orthogonal to the drawing.

The first transparent plate 21 has a longitudinal direction parallel to the longitudinal direction of the first mirror 2, and between the first mirror 2 and the contact glass 7, parallel to the contact glass surface and close to the first mirror 2. Will be deployed.

The second transparent plate 22 has a longitudinal direction parallel to the longitudinal direction of the first mirror 2, and is arranged orthogonal to the first transparent plate 21 and close to the first mirror 2.

The first and second transparent plates 21 and 22 close the mirror surface 20 of the first mirror 2 to the outside as shown. Although not shown, both end portions (both end portions in the direction orthogonal to the drawing) of the space having a triangular cross section surrounded by the first mirror 2 and the first and second transparent plates 21 and 22 are suitable side plates ( It may be transparent or may not be transparent), so that the mirror surface 20 is sealed to the outside and dust from the outside does not adhere.

At the time of image reading, the light flux from the original 0 enters the mirror surface 20 of the first mirror 2 through the first transparent plate 21 and is reflected, and then passes through the second transparent plate 22 and is not shown. Turn back to the mirror pair.

In FIG. 1 (a), reference numeral 50 designates a charge eliminating brush (claim 3) as "cleaning means". As shown in the figure, the static elimination brush 50 is held by an appropriate holding means at the home position position of the first mirror 2, and the tip of the brush is the first in the direction orthogonal to the drawing.
The upper surface of the transparent plate 21 is in contact with the transparent plate 21 in the longitudinal direction thereof.

At the time of image reading, the first mirror 2 is integrated with the lamp 1 and moves to the right in the figure to read and scan the original. At that time, the first transparent plate with respect to the static elimination brush 50 is used. By the relative movement of 21, the first transparent plate 21
The upper surface of is cleaned with a static elimination brush and static electricity is eliminated. Even after the image reading is completed and the first mirror 2 returns to the home position, the cleaning and discharging of the first transparent plate 21 by the discharging brush 50 is performed.

As described above, since the first transparent plate 21 is cleaned and neutralized by the static elimination brush 50 every time an image is read, the transparent plate 21 is less likely to electrically adsorb floating dust. Further, even if the floating dust accumulates, it is removed by cleaning with the static elimination brush 50.
Therefore, the first transparent plate 21 does not become dirty and does not affect image reading.

Further, since the second transparent plate 22 has a substantially vertical surface, dust is unlikely to adhere to it.

Therefore, in this embodiment, it is possible to effectively prevent the occurrence of "black stripes" in the reproduced image due to the dirt on the mirror surface of the first mirror 2.

As described above, the second transparent plate 22 has a substantially vertical surface, which is originally "hard to attach dust".
As shown in (b), if the antistatic film 22A is formed on the surface of the second transparent plate 22, the second transparent plate 22 will not be electrically charged and dust will not be electrically adsorbed. The transparent plate 22 becomes "harder to stain".

FIG. 2 shows only the characteristic portion of one embodiment in which the invention according to claim 4 is applied to the image reading apparatus described with reference to FIG.

That is, the "framed" member 30 made of a dielectric resin material is provided so as to surround the "effective reflection surface area" of the mirror surface 20 of the first mirror 2.

The member 30 made of a resin material is formed, for example, by a "plastic mold".

Since the member 30 is dielectric, it is easily charged by the air flow during the reading and scanning by the first mirror 2. Therefore, when the floating dust approaches the mirror surface 20 of the first mirror 2, it is electrically adsorbed by the charged member 30.
As a result, the adhesion of dust to the mirror surface 20 of the first mirror 2 is prevented.

FIG. 3 is a diagram for explaining one embodiment in which the invention according to claim 5 is applied to the image reading apparatus described with reference to FIG.

The mirror surface 20 of the first mirror 2 shown in FIG.
A is a "metal reflection film" and is conductive (the mirror surface 20 of the second mirror in the embodiments of FIGS. 1 and 2 is also generally a metal reflection film).

A conductive film 25 is formed on a part of the mirror surface 20A outside the effective reflection surface area. The conductive film 25 is
For example, as shown in FIG. 3B, the mirror surface 2 of the first mirror
It is formed at the longitudinal end of 0A, and in this embodiment, it is provided so as to surround the first mirror at the end as shown in FIG. 3 (a).

In FIG. 3C, reference numeral 40 indicates a "holder of the first mirror". The holder 40 is "conductive". Both ends of the first mirror 2 in the longitudinal direction are fixed to the holder 40 by springs 41 made of a conductive metal such as phosphor bronze (one side is not shown).
Directly contacts the holder 40 and the spring 41. Since the holder 40 is generally in contact with a metallic member, the mirror surface 20A is eventually "grounded" through the conductive film 25 and the holder 40.

Therefore, the mirror surface 20A is effectively prevented from being charged, and the dust floating in the image reading device is not electrically attracted to the mirror surface 20A and does not stain the mirror surface 20A.

Although each of the above embodiments has been described as an example of application to the image reading device described with reference to FIG. 4A, the structure of the image reading device is limited to that of FIG. 4A. It goes without saying that it is not a thing. Also, setting the original on the contact glass may be done manually,
It may be performed using an automatic document feeder (so-called “ADF”).

[0062]

As described above, according to the present invention, a novel "image reading device" can be provided. Since the image reading apparatus of the present invention is configured as described above, the dirt on the first mirror can be effectively prevented, and the "reproduced image caused by dirt on the mirror surface of the first mirror 2" which has been a problem in the past. It is possible to effectively prevent the occurrence of "black stripes" in the.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention.

FIG. 2 is a diagram for explaining another embodiment of the present invention.

FIG. 3 is a diagram for explaining another embodiment of the present invention.

FIG. 4 is a diagram for explaining a conventional technique and its problems.

[Explanation of symbols]

 1 Lamp 2 1st mirror 21 1st transparent plate 22 2nd transparent plate 50 Static elimination brush (cleaning means)

Claims (5)

[Claims] 1. A document placed flat on a contact glass having a horizontal document placement surface is read by a first mirror which is provided inclined with respect to the contact glass and moves close to the contact glass. The light beam reflected by the first mirror is scanned and reflected by the pair of folding mirrors that are displaced in the same direction as the first mirror at a speed half that of the first mirror so as to be folded back toward the imaging lens side to form the image. An image reading apparatus for reading an original image by forming an image on a solid-state imaging device with a lens, wherein a longitudinal direction is parallel to a longitudinal direction of the first mirror, and a contact glass is provided between the first mirror and the contact glass. A first transparent plate disposed parallel to the surface and close to the first mirror, and having a longitudinal direction parallel to the longitudinal direction of the first mirror and orthogonal to the first transparent plate. A second transparent plate disposed in the vicinity of the first mirror, and a second transparent plate provided near the home position of the first mirror, and slides on the surface of the first transparent plate by the movement of the first mirror accompanying the reading scan. An image reading apparatus comprising: a cleaning unit for rubbing and cleaning, wherein the mirror surface of the first mirror is closed to the outside by using the first and second transparent plates. 2. The image reading apparatus according to claim 1, wherein an antistatic film is formed on at least a surface of the second transparent plate of the first and second transparent plates. 3. The image reading device according to claim 1, wherein the cleaning unit is a charge eliminating brush. 4. A document placed flat on a contact glass having a horizontal document placement surface is read by a first mirror which is provided inclined with respect to the contact glass and moves close to the contact glass. The light beam reflected by the first mirror is scanned and reflected by the pair of folding mirrors that are displaced in the same direction as the first mirror at a speed half that of the first mirror so as to be folded back toward the imaging lens side to form the image. In an image reading device for reading an original image by forming an image on a solid-state image pickup device with a lens, a dielectric resin material is provided so as to surround the effective reflection surface area of the mirror surface of the first mirror. An image reading device characterized by. 5. A document placed flat on a contact glass having a horizontal document placement surface is read by a first mirror that is inclined with respect to the contact glass and moves close to the contact glass. The light beam reflected by the first mirror is scanned and reflected by the pair of folding mirrors that are displaced in the same direction as the first mirror at a speed half that of the first mirror so as to be folded back toward the imaging lens side to form the image. In an image reading apparatus for reading an original image by forming an image on a solid-state image pickup element with a lens, a conductive coating is formed on a part of the mirror surface of the first mirror outside the effective reflection surface area, and the conductive film is formed. An image reading apparatus in which the mirror surface of the first mirror is electrically grounded through a protective film and a holder of the first mirror.