JPH0927889A - Document reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an abnormal image from being generated by carrying an original without being placed onto a contact glass plate and avoiding adhesion of dusts to a read position. SOLUTION: A contact glass plate 21 is arranged so that an upper side of the contact glass 21 is placed downward with respect to a line A tying contact points between an original carrying roller pairs 16 and original carrying roller pairs 17 with the contact glass 21 in between and a gap G of 1mm or over is formed between a backup roller 24 and the contact glass 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a document reading apparatus used in a facsimile machine, a copying machine or the like, and more particularly, to prevent deterioration of the quality of a read image of a document due to dust or the like adhering to contact glass. The present invention relates to a document reading device that can perform.

[0002]

2. Description of the Related Art Some facsimile machines, copiers and the like are equipped with a document reading device in which an image is read by a fixed reading portion while a document is being conveyed (for example, Japanese Patent Laid-Open No. 63-63). For example, FIG. 5 shows such a document reading device.

In FIG. 5, reference numeral 1 denotes a contact glass, and the contact glass 1 has a pair of rollers 2a and 2a.
The original is nipped and conveyed by the first conveying roller pair 2 composed of b. The original document conveyed to the contact glass 1 is illuminated by a light source (not shown), and the illumination light is reflected by the original document to pass through the lens 3 to C
Read by CD4.

A white backup roller 5 also serving as a reference reflector for shading correction is provided above the contact glass 1. The backup roller 5 has a reflection density of 0.03 to 0.08 (reflectance of 93 to 83%). ) Is set. The original document that has been read on the contact glass 1 is carried out from the glass 1 by a second pair of transport rollers 6 composed of a pair of rollers 6a and 6b, and is discharged to a discharge tray (not shown). .

The upper surface of the contact glass 1 is disposed substantially on the same plane (L ₀ = 0) as the line connecting the facing surfaces of the first and second conveying roller pairs 2 and 6, and the backup roller 5 is also provided. G ₀ between the contact glass and contact glass 1 is 0.1
It is set to about 0.2 mm, and the original is conveyed while being pressed against the contact glass 1 by the backup roller 5.

Here, the gap G ₀ between the backup roller 5 and the contact glass 1 is set to about 0.1 to 0.2 mm so that when the original has a curl or a fold, the original is protected by the backup roller 5. This is for pressing the contact glass 1 and making it substantially flat so that the space between the surface image surface of the original and the lens 3 is always kept constant. By doing so, it is possible to prevent the document from floating from the contact lens 1, and to prevent the bit shift of the seam of the image and the loss of the image.

[0007]

However, in such a conventional image reading apparatus, the gap G ₀ between the backup roller 5 and the contact glass 1 is 0.1 to 0.2 mm.
Therefore, when the dust D adheres to the reading surface on the contact glass 1 as shown in FIG. 6 (FIG. 6 is an exaggerated view for easy understanding of the adhered state of the dust D). 7), when the original P as shown in FIG. 7A is read, the original image data shown in FIG.
The straight black data d as shown in (b) is generated.

That is, a reading density of 400 is commonly used in a moving-document-type digital document reading apparatus.
With dpi (dote per inch), the reading exposure width is 25.4 / 400.
= 63.5 μm, which is very narrow, and when dust of 63.5 μm or larger adheres to this portion and stays there, the portion was read as black data d regardless of the image on the document. If dust is not deposited on the contact glass 1 and is conveyed along with the document P, the image is reproduced as a black dot corresponding to the size of the dust and does not become a straight line, but as described above, the conventional image reading apparatus is used. Has a very small gap G ₀ between the backup roller 5 and the contact glass 1 of 0.1 to 0.2 mm,
Since the original P is pressed onto the glass 1 by the backup roller 5 at a position where the original P is connected to the contact glass 1 by a perpendicular line from the center line of the backup roller 5, the glass 1
The dust adheres and accumulates on the top.

On the other hand, in the analog type document reading apparatus, both the structure for moving the document and the structure for moving the optical system have a relatively large width of 5 to 10 mm (width of the exposure area in the document conveying direction). Since the original is exposed in the slit area and the latent image is not formed on the photoconductor unless the original and the photoconductor move in synchronism, even if the above-mentioned minute dust adheres to the contact glass, the optical system will With moving structures, black spots correspond to the size of the dust, and with moving structures, a minute latent dust is not clearly read and becomes a blurred latent image, which is not an image when developed. The above problem does not occur.

Therefore, it is desired to solve the above-mentioned problems in the original moving type digital image reading apparatus having the backup roller 5. Therefore, according to the first and second aspects of the present invention, by providing a relatively large gap between the backup roller and the contact glass, the original can be conveyed without being pressed against the contact glass and dust can be present at the reading position. It is an object of the present invention to provide an original reading device which can prevent an abnormal image from being formed by preventing adhesion.

According to the third and fourth aspects of the invention, even when a relatively large gap is provided between the backup roller and the contact glass, the original is made substantially flat and curling, wrinkles, folds, etc. are prevented. It is an object of the present invention to provide a document reading device capable of preventing the bit shift of the seam of images and the loss of images.

[0012]

According to the first aspect of the present invention,
In order to solve the above problems, a first conveying roller pair that nips and conveys an original to a contact glass, an original reading unit that is provided below the contact glass and reads an original conveyed on the contact glass, and a contact. A backup roller which is provided above the glass and constitutes a white reference during reading, which rotates in sliding contact with the original conveyed on the contact glass, and which is provided on the downstream side of the contact glass in the original conveying direction and passes through the contact glass. A second pair of conveying rollers for nipping a document and carrying it out from the glass;
In a document reading apparatus including the contact glass, the contact glass is arranged such that the upper surface of the contact glass is located below the line connecting the contact points of the first conveying roller pair and the second conveying roller pair, and a backup is provided. The feature is that a gap is formed between the roller and the contact glass.

In this case, the contact glass is retracted below the original conveying path (the line connecting the contact point of the first conveying roller pair and the contact point of the second conveying roller pair), and there is a gap between the original and the contact glass. Is formed, dust is less likely to collect between the backup roller and the contact glass, and
Since the original is not pressed against the contact glass by the backup roller, dust does not adhere to the contact glass. As a result, formation of abnormal images is prevented.

According to a second aspect of the invention, in order to solve the above-mentioned problems, in the invention of the first aspect, the gap is set to 1
It is characterized by being set to mm or more. In that case, the backup roller reliably prevents the original from being pressed against the contact glass, and reliably prevents dust from adhering to the contact glass.

In order to solve the above-mentioned problems, the invention according to claim 3 is the same as in the invention according to claim 1 or 2, in which the second conveying roller pair is conveyed with respect to the conveying speed of the first conveying roller pair. It is characterized in that the speed is increased and the carrying force of the first carrying roller pair is made stronger than the carrying force of the second carrying roller pair. In that case, when the document is nipped by the first and second transport roller pairs, the document is pulled by the second transport roller pair and becomes substantially flat. As a result, even if a relatively large gap is provided between the backup roller and the contact glass, curl, wrinkles, folds, etc. do not occur in the original document, and bit shift or image loss of the seam of the image occurs. There is no.

In order to solve the above-mentioned problems, a fourth aspect of the present invention is the invention of the first or second aspect, in which the outer diameter of the driving side roller of the first conveying roller pair is set to be larger than the outer diameter of the driving side roller.
The outer diameter of the drive-side roller of the pair of transport rollers is increased, and the driven-side roller of the second pair of transport rollers is made of plastic. In that case,
Since the rotation speed of the second conveyance roller pair is faster than the rotation speed of the first conveyance roller pair, and the driven roller of the second conveyance roller is made of plastic that easily slips on the document, The document transport force of the first transport roller pair is stronger than the document transport force of the transport roller pair.

Therefore, when the original is sandwiched between the first and second conveying roller pairs, the original is pulled by the second conveying roller pair and becomes substantially flat. As a result, even if a relatively large gap is provided between the backup roller and the contact glass, curl, wrinkles, folds, etc. do not occur in the original document, and bit shift or image loss of the seam of the image occurs. There is no.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are views showing an embodiment of a document reading apparatus according to the present invention. First, the configuration will be described. In FIG. 1, an upper unit case 13 is supported above a document table 12 on which a document 11 is placed by a support shaft (fixed to a side plate of the main body structure of the document reading device) 14 so as to be vertically swingable. A transparent contact glass 21 is disposed in front of the document table 12 (on the left side in FIG. 1), and below the contact glass 21, a lamp 23, a lens 25, and a light receiving member such as a CCD constituting a document reading unit. 26 are provided.

A backup roller 24 which is supported by the upper unit case 13 and rotates clockwise in FIG. 1 is disposed above the contact glass 21. On the right side of the contact glass 21, there are arranged a document conveying roller pair 15 and a document conveying roller pair 16 which is a first conveying roller pair,
The contact glass 21 has a second portion on the downstream side of the document 11 in the conveying direction.
A document conveying roller pair 17 as a conveying roller pair is arranged.

The original 11 on the original table 12 is conveyed by a pair of conveying rollers.
It is sandwiched by 15, 16 and 17 and passes over the contact glass 21 while being conveyed to the left side in FIG. 1, and is illuminated by the lamp 23 at the illumination position L at this time. The reflected light from the illuminated document 11 is received by the lens 25 by the light receiving member 26.
The light is focused on the upper side, and the light receiving member 26 reads the image of the original.

In this case, when the original 11 is inserted on the original table 12 and the first sensor 27 provided in the upper unit case 13 detects this, the original conveying roller pairs 15, 16, 17 and the backup roller 24 rotate. At the beginning, the lamp 23 lights up. When the leading edge of the conveyed document 11 is detected by the second sensor 28, the conveyance speed of the document 11 changes to the conveyance speed according to the preselected magnification. After that, when the leading edge of the document 11 is detected by the registration sensor 29, the reflected light from the backup roller 24 at the exposure position L is read by the light receiving member 26.

The surface of the backup roller 24 is pre-painted in white, and the reflection density of this roller 24 is about 0.03 to 0.08.
It is set to (reflectance 93-83%). The read reflected light data of the backup roller 24 is A / D converted,
The shading correction data is stored in a shading RAM (not shown). Thereafter, the original 11 is conveyed on the contact glass 21 and is conveyed between the contact glass 21 and the backup roller 24, and is illuminated by the lamp 23 at the illumination position L during that time, and the reflected light at that time is received by the lens 25 by the light receiving member. The image of the original is reduced and focused on the light receiving member 26, and is read.

The original document 11 for which the reading and scanning has been completed is ejected to the paper ejection tray 30 by the original document conveyance roller pair 17. The image data of the scanned original is displayed on the lamp 23
In order to correct the decrease in the light amount due to the cos ⁴ rule and the uneven sensitivity of each pixel of the light receiving member 26, the shading correction data is used for correction. The upper case unit 13 is swung upward about the support shaft 14 so as to release the surfaces of the original table 12 and the contact glass 21 by a predetermined angle.
By this release, maintenance work such as cleaning of the conveying roller pairs 15, 16, 17, the document table 12, the sensors 27 to 29, the contact glass 21 and the like, handling of documents having troubles in transportation, replacement of the lamp 23 and the like can be performed easily. You can
A cover 32 is provided around the illumination lamp 23, the lens 25 and the light receiving member 26 to protect these members from dust.

As shown in FIG. 2 which is a cross-sectional view of the surface of the lens 25 passing through the optical axis, two sets of optical systems including the lens 25 are arranged along the main scanning direction of the original. The image information of the document 11 is separately read by the two light receiving members 26. In FIG. 2, a lens 25 and a light receiving member 26 are arranged along two optical axes 32, respectively. The original 11 is transferred between the contact glass 21 and the backup roller 24. Guide rollers 33 are rotatably supported at both ends of the backup roller 24. In the past, the gap between the backup roller 24 and the contact glass 21 was set to about 0.1 to 0.2 mm, so a small amount of dust accumulated between the backup roller 24 and the contact glass 21
This garbage has adhered to 21. In the present embodiment, this is solved by the structure specifically shown in FIG.

In FIG. 3, the original conveying roller pair 16 is composed of a driving roller 16a and a driven roller 16b,
The driven roller 16b is made of a rubber roller and is pressed against the driving roller 16a by a spring 40 so as not to hinder the rotation. Further, the document conveying roller pair 17 is a driving roller 17
a and a driven roller 17b. The driven roller 17b is made of a plastic roller and is pressed against the driving roller 17a by a spring 41 so as not to hinder the rotation.

Further, the outer diameter of the driving roller 17a is formed larger than the outer diameter of the driving roller 16a, and the pair of original conveying rollers is set to the conveying speed V ₁₆ of the original conveying roller pair ₁₆ .
The transport speed V ₁₇ of ₁₇ is faster. On the other hand, the contact glass 21 is arranged such that the upper surface of the contact glass 21 is located below the line A connecting the contact points of the document conveying roller pair 16 and the document conveying roller pair 17.
Is separated from the upper surface of the contact glass 21 by a distance H. In addition, the backup roller 24 and the contact glass 21
A gap G is formed between them, and this gap G is set to at least 1 mm or more. Therefore, the conveyance path of the document 11 is positioned L below the line A connecting the contact points of the driving roller 16a and the driven roller 16b and the contact points of the driving roller 17a and the driven roller 17b. In FIG. 2, reference numeral 35 is a pulley for transmitting power to the backup roller 24 from a driving member such as a motor (not shown) via a belt, and 36 is a one-way clutch.

As described above, in the present embodiment, the upper surface of the contact glass 21 is located below the line A connecting the contact points of the document conveying roller pair 16 and the document conveying roller pair 17 provided with the contact glass 21 sandwiched therebetween. Like contact glass 21
And a gap G of 1 mm or more is formed between the backup roller 24 and the contact glass 21, the contact glass 21 is retracted below the conveyance path of the document 11 (below the line A by L). Can be manuscript
It is possible to form a gap between the contact glass 21 and the contact glass 21 to prevent dust from accumulating between the backup roller 24 and the contact glass 21.

Further, as shown in FIG. 4, since the original 11 is not pressed against the contact glass 21 by the backup roller 24 when the original 11 is conveyed, it is possible to prevent dust from adhering to the contact glass 21. . As a result, it is possible to prevent abnormal images from being formed. Further, the outer diameter of the driving roller 17a of the document feeding roller pair 17 is set larger than the outer diameter of the driving roller 16a of the document feeding roller pair 16, and the driven roller 17b of the document feeding roller pair 17 is made of plastic. Therefore, for the rotation speed V ₁₆ of the document transport roller pair ₁₆ , the document transport roller pair 17
The rotational speed V ₁₇ of the original conveying roller pair 16 can be increased, and the driven roller 17b is made of plastic that easily slips on the original 11, so that the original conveying roller pair 16 can detect the original conveying force of the original conveying roller pair 17 against the original conveying force of the original conveying roller pair 17. The carrying force can be increased.

Therefore, the document 11 is fed to the document feed roller pair 16,
When the document 11 is nipped by the pair 17, the document 11 can be pulled by the pair of transport rollers 17 to be substantially flat as shown in FIG. As a result, even if a relatively large gap G is provided between the backup roller 24 and the contact glass 21, the original 11
It is possible to prevent curls, wrinkles, folds, and the like from occurring, and it is possible to prevent occurrence of bit shift and image loss at seams of images.

When the above-mentioned L is set to 0 or more, the original 11 can be surely brought into close contact with the backup roller. Further, in this embodiment, the driven roller is made of a plastic roller so that the conveying force of the original conveying roller pair 16 is increased with respect to the original conveying roller pair 17, but the driven roller of the original conveying roller pair 17 is driven. The roller 17b is made of a rubber roller, and the pressing force of the spring 40 for pressing the driven roller 16b is set larger than the pressing force of the spring 41 for pressing the driven roller 17b. Thus, the conveying force of the document conveying roller pair 16 may be increased.

[0031]

According to the first and second aspects of the present invention, the contact glass is positioned below the original conveying path (the line connecting the contact point of the first conveying roller pair and the contact point of the second conveying roller pair). By retracting, a gap can be formed between the original and the contact glass. Therefore, it is possible to prevent dust from accumulating between the backup roller and the contact glass, and it is possible to prevent the backup roller from pressing the original document against the contact glass. Can be prevented. As a result, it is possible to prevent abnormal images from being formed. The gap is preferably set to 1 mm or more.

According to the third and fourth aspects of the present invention, even if a relatively large gap is provided between the backup roller and the contact glass, it is possible to prevent the original from curling, wrinkling, folding or the like. Therefore, it is possible to prevent the occurrence of bit shift and image loss at the seams of the images.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment of a document reading apparatus according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a diagram showing a positional relationship between a pair of first and second conveying rollers, a backup roller and a contact glass according to an embodiment.

FIG. 4 is a diagram illustrating a state in which a document according to an embodiment is conveyed.

FIG. 5 is a diagram showing a positional relationship between a pair of conventional first and second conveyance rollers, a backup roller, and contact glass.

FIG. 6 is a diagram showing a state in which dust adheres between a conventional document and a backup roller.

FIG. 7A is a diagram showing a document before being read by a conventional image reading device, and FIG. 7B is image data of the document read when dust adheres to and stays on the contact glass or image data thereof is formed. It is a figure which shows the recorded recording paper.

[Explanation of symbols]

11 Original 16 Original transport roller pair (first transport roller pair) 17 Original transport roller pair (second transport roller pair) 16a, 17a Drive roller 16b, 17b Driven roller 21 Contact glass 23 Lamp (original reading part) 24 Backup Roller 25 Lens (original reading part) 26 Light receiving member (original reading part) G Gap A Line connecting the contact points of the first conveying roller pair and the second conveying roller pair

Claims (4)

[Claims] 1. A first conveying roller pair for nipping and conveying a manuscript to a contact glass, a manuscript reading section provided below the contact glass for reading a manuscript conveyed on the contact glass, and above the contact glass. A backup roller that is provided and configures the white reference for reading, and rotates in sliding contact with the original conveyed on the contact glass, and a downstream side of the contact glass in the original conveyance direction, and clamps the original that has passed through the contact glass. And a second conveying roller pair that is carried out from the glass. In the document reading apparatus, the contact glass of the contact glass is connected to the line connecting the contact points of the first conveying roller pair and the second conveying roller pair. Place the contact glass so that the upper surface is located below, and form a gap between the backup roller and the contact glass. An original reading device characterized by the above. 2. The document reading apparatus according to claim 1, wherein the gap is set to 1 mm or more. 3. The conveying speed of the second conveying roller pair is made higher than the conveying speed of the first conveying roller pair, and
3. The document reading apparatus according to claim 1, wherein the conveying force of the first conveying roller pair is made stronger than the conveying force of the second conveying roller pair. 4. The outer diameter of the driving side roller of the second conveying roller pair is made larger than the outer diameter of the driving side roller of the first conveying roller pair, and the driven side of the second conveying roller pair. The original reading device according to claim 1 or 2, wherein the roller is made of plastic.