JP2003222959A - Image reader and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize stable image reading that the luminance of an image is hardly changed even when a reading position is varied. <P>SOLUTION: The image reader is equipped with an original carrying means for carrying a sheet type original, and can read the original while carrying it. The reader has a briefly reading glass 4 for supporting the original at an image reading position, a reading means 5 arranged at a position opposed to the glass 4 and capable of reading the image of the original by radiating light to the original on the glass 4 from an illumination means 6, and a rotatable platen roller 12 provided at a position on an opposite side to the illumination means 6 and the reading means 5 oppositely to the glass 4, and is provided with a white sheet member 16 for reflecting light radiated from the illumination means 6 when reading the original while carrying it in the vicinity of the roller 12. <P>COPYRIGHT: (C)2003,JPO

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 scanner, a facsimile device,
In particular, the present invention relates to an image reading apparatus including a sheet conveying device that automatically conveys a sheet-shaped document to an image reading unit, and an image forming apparatus including the image reading apparatus.

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus provided in a digital copying machine, a printer, a facsimile, etc., automatically feeds a sheet-like document to the image reading apparatus. Document Feeder "
There is something that can be opened and closed freely.

As one of the reading methods by the image reading apparatus equipped with the ADF, the image reading means is fixed to a predetermined reading position of the platen glass provided in the image reading apparatus, and the original is moved at a constant speed on the reading position. A method is known in which an image is read by moving the image (hereinafter referred to as “flow reading”). This non-stop reading is
This is a technique used in many products as a reading method for processing a large number of sheet-shaped originals at high speed, which has the advantage that the original exchange speed can be increased.

In order to perform stable image reading at high speed in the flow-reading, it is necessary to prevent the original from floating from the platen glass at the reading position in order to prevent image blurring due to defocusing or fluttering of the original. As a method therefor, there is used a method of providing a platen roller which is rotationally driven at a predetermined interval with respect to the platen glass at the flow reading position. Compared with the method of suppressing the lifting of the document by the fixing member such as the guide plate at the scanning position, the scanning using the platen roller can reduce the lifting amount while reducing the conveyance load, and at a higher speed. High-quality image reading is possible.

FIG. 9 shows an example of a conventional image reading apparatus. The image reading apparatus shown in FIG. 9 uses a platen glass 100 for a method of placing and reading a document (hereinafter referred to as “book reading”), a flow-scanning glass 101 for a flow-scanning method, and both of the reading methods. A reading sensor 102 such as a contact image sensor, which is an image reading unit shared, is provided.

In the flow reading method, a platen roller is used.
104 are arranged at a predetermined interval with respect to the upper surface of the flow reading glass 101, and are rotationally driven at a predetermined speed. As a result, at the time of flow scanning, the document is stably conveyed while limiting the floating amount of the document from the upper surface of the flow scanning glass 101.

[0007]

In the flow reading using the platen roller 104, when the reading position, that is, the stop position of the reading sensor 102 varies with respect to the platen roller, the brightness level of the read image varies. There is. The cause of this phenomenon is explained by the schematic diagram of the conventional image reading apparatus shown in FIG.

FIG. 10 shows the path of the light emitted from the illumination means 105 in the book reading system shown in (a) and the flow reading system shown in (b). Here, for the sake of explanation, the path of the light emitted from the illumination means on one side and transmitted through the document is schematically shown by a chain double-dashed line. Further, the reading position in the flow-reading method is shown for a case in which the reading position is deviated from immediately below the center of the platen roller 104 to the upstream side in the document conveyance direction.

In the case of the book reading method shown in FIG. 10 (a), the light transmitted through the original 106 is reflected toward the reading sensor 102 by the white pressure plate 107 that presses the original 106 against the original table glass 100, and the back surface of the original is read. Irradiate. In contrast, Fig. 10 (b)
In the case of the flow-reading method shown in (1), the light transmitted through the original 106 is reflected by the white platen roller 104, but a part of it is reflected in the direction away from the reading sensor 102 due to the curvature of the platen roller 104.

As a result, the amount of light that illuminates the original 106 from the back side decreases, and the brightness when the reflected light from the original 106 is read by the image sensor 109 via the lens 108 decreases. As the reading position moves away from just below the center of the platen roller 104, the amount of light reflected in the direction of the reading sensor 102 also decreases. Therefore, even if the same document is read, the brightness of the image further decreases. Further, the higher the light transmittance of the original 106, the greater the influence of this phenomenon.
The smaller the thickness of the sheet is, the more noticeable the decrease in luminance.

In order to read an image without being affected by the decrease in the brightness, it is necessary to accurately position the reading sensor 102 just below the center of rotation of the platen roller 104, which provides a brightness substantially equal to that of the book reading. There is.

However, the read sensor 102 is mounted on the platen roller 1 depending on the stop position accuracy of the read sensor 102 and the play of the hinge portion of the ADF 103 which is openably and closably attached.
Precise positioning with respect to 04 is difficult.

Further, dust is likely to adhere to the surface of the flow reading glass 101 just below the center of the platen roller 104 or on the downstream side in the document conveying direction. There is a problem that becomes. Therefore, the reading position is the platen roller 104.
It is desirable to set it slightly upstream from directly below the center.

Further, in order to prevent the generation of streak images due to dust on the flow-reading glass 101, the platen roller 104 is rotated while the document is not being conveyed, the image is read at the flow-reading reading position, and the flow is read. When the dust on the reading glass 101 and the dust on the surface of the platen roller 104 are distinguished, and the dust on the flow reading glass 101 is detected,
A method of moving the reading position has been proposed. When such a streak image preventing operation is performed, the reading position of the flow-reading is inevitably moved.

As described above, it is difficult to always position the flow reading position at the same position with respect to the platen roller 104 because of the influence of component accuracy and the operation of preventing the generation of streak images. In this case, the above-mentioned variation in luminance occurs.

The present invention is to solve the above-mentioned conventional problems, and an object thereof is to provide an image reading apparatus capable of stable image reading with little change in image brightness even when the reading position varies, and an image reading apparatus for the same. An image forming apparatus having the same is provided.

[0017]

A typical configuration according to the present invention for achieving the above object is provided with a document feeding unit for feeding a sheet-shaped document, and an image that can be read while the document is being transported. In a reading device, a transparent member supporting an original at an image reading position, and a reading unit capable of reading an original image by irradiating an original on the transparent member arranged at a position facing the transparent member with light from an illuminating unit. A rotatable rotator facing the transparent member at a position opposite to the illumination means and the reading means,
And a reflecting member for reflecting the light emitted from the illuminating means when the original is being read while being conveyed, is provided in the vicinity of the rotating body.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment] An image reading apparatus according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. 1 is a detailed cross-sectional explanatory view of the flow-reading section of the image reading device, FIG. 2 is an overall cross-sectional explanatory view of the image reading device, and FIG. 3 is a schematic explanatory diagram showing the luminance variation preventing effect of the reflecting member. FIG. 4 and FIG. 5 are graphs showing the relationship between the reading position of the flow reading and the brightness of the white background of the document.

[Overall Configuration of Image Reading Apparatus] As shown in FIG. 2, the image reading apparatus A according to the present embodiment has an ADF which is an automatic document feeder on the upper portion of the image reading section 1.
2 is installed.

The image reading section 1 can read an original by either a book reading method or a flow reading method. That is, a document table glass 3 for reading a book is provided on the upper surface of the image reading unit 1,
On one side of the original platen glass 3, a flow-reading glass 4 is provided as a transparent member for supporting a document for flow-reading.

Below the glass, a reading means 5 for reading the image written on the original is provided. The reading means 5 is arranged at an illuminating means 6 such as a xenon tube for illuminating an original on glass, a SELFOC lens 7 for forming an image of reflected light from the original, and an image forming position of the SELFOC lens 7. The contact image sensor 8 is integrally housed in a casing 9. Then, the casing 9 is abutted against the original table glass 3 or the flow reading glass 4 via an abutting member (not shown) having a high slidability, and the reading means 5 is arranged at a predetermined distance from the original surface. ing.

On the other hand, the ADF 2 is attached to the upper portion of the image reading unit 1 so as to be openable and closable by a hinge or the like, and supplies a document to the image reading unit 1, and is in the form of a sheet stacked and placed on the document placing unit 10. Rollers 11a to 11f as document conveying means for conveying the documents one by one, a platen roller 12 as a rotating body for preventing the documents from rising from the scanning glass 4 at the time of scanning, and a document discharge for discharging the document after image reading A section 13 is provided.

In the case of the book reading method, the original placed on the original platen glass 3 is a white pressure plate attached to the ADF 2.
It is fixed by 14, and the document is read while driving the reading means 5 at a predetermined speed in the sub-scanning direction (left and right direction in FIG. 2). In the book reading method, the ADF 2 functions as a pressure plate that fixes the original on the original table glass 3.

In the case of the flow-reading method, the document placed on the document placing portion 10 of the ADF 2 is fed by the feeding roller 11a and is fed below the platen roller 12 at a predetermined speed by the feeding rollers 11b, 11c and 11d. Be transported to. The original is limited in its floating amount from the upper surface of the flow reading glass 4 by a platen roller 12 rotating at a predetermined rotation speed, and the reading means 5 stopped at a predetermined reading position is operated by the platen roller 12 and the upper surface of the flow reading glass 4. An image is read by irradiating the original conveyed between the sheets with light from the illumination unit 6. The document that has passed through the platen roller 12 is guided to the transport rollers 11e and 11f by the jump table 15 and discharged to the document discharge unit 13.

{Structure for Preventing Fluctuation of Luminance during Flow Reading} Next, a structure for preventing fluctuation of luminance during flow reading will be described. In the ADF 2 of this embodiment, as shown in FIG.
A white flexible sheet member 16 serving as a reflecting member is provided on the upstream side of the platen roller 12 in the document conveying direction. The white sheet member 16 is attached and arranged so as to be substantially parallel to the flow reading glass 4 with respect to a guide member that guides the document to the platen roller 12. The distance C2 between the white sheet member 16 and the flow reading glass 4 is larger than the distance C1 between the flow reading glass 4 and the surface of the platen roller 12, and the distance between the flow reading glass 4 and the rotation center of the platen roller 12 is large. It is arranged so as to be smaller than (C1 + R) (C1 <C2 <C1 + R).

The leading end position 17 where the sheet member 16 is closest to the platen roller 12 is located below the reading glass 5 when the direction of the rotating body (reading direction) is viewed from the reading position by the reading means 5, that is, perpendicular to the flow reading glass 4. When looking at the platen roller 12 and the white sheet member 16 located above in the direction, the white sheet member 16 is in the main scanning direction of the reading means 5 (longitudinal direction of the platen roller 12) in substantially the entire image reading range. It is arranged to hide a part of 12. Further, the reading position in the flow-reading method is set to a position where the surface of the platen roller 12 is read when the document is not conveyed.

The effect of preventing the brightness reduction by the white sheet member 16 of this embodiment will be explained with reference to the schematic diagram shown in FIG. FIG. 3 schematically shows a path of light emitted from one side (in the present embodiment, the left side) of the illumination means 6 and transmitted through the original. Further, the reading position in the flow-reading method is set to a position displaced from the position right below the center of rotation of the platen roller 12 to the upstream side in the document conveyance direction.

The light transmitted through the original 18 is white sheet member 16
It can be seen that the light is reflected in the direction of the reading means 5 and more light is emitted from the back surface of the document 18 than in the case of the conventional example shown in FIG. 10 (b). As a result, a decrease in brightness when the reading position is separated from just below the center of the platen roller 12 is reduced.

FIGS. 4 and 5 show the results of measuring the relationship between the reading position when the original is flow-read and the brightness (0 to 255 level) of the white background of the original. Note that FIG. 4 shows the measurement results in the case of the present embodiment in which the white sheet member 16 is attached, and FIG. 5 shows the measurement results in the case where the white sheet member 16 is not attached.

When the white sheet member 16 is not provided, as shown in FIG. 5, the brightness of the white background portion of the original document greatly decreases as the reading position moves away from just below the center of rotation of the platen roller 12. On the other hand, when the white sheet member 16 is provided as in the present embodiment, as shown in FIG.
It can be seen that the decrease in brightness is small, and even if the reading position varies, the change in brightness can be suppressed to a level at which there is practically no problem.

The distance C2 between the white sheet member 16 and the flow reading glass 4 is larger than the distance C1 between the flow reading glass 4 and the platen roller 12 surface, and the center of rotation of the flow reading glass 4 and the platen roller 12 is set. Distance (C1 + R)
Since the white sheet member 16 is arranged so as to be smaller than that, the white sheet member 16 does not come into contact with the document 18 regulated by the platen roller 12, and the conveyance of the document 18 is obstructed, or the document surface is rubbed against dust. The light from the illumination means 6 is reflected.

Further, in this embodiment, when viewed from the reading position by the reading means 5 (in the direction of the platen roller 12), the white sheet member 16 hides a part of the platen roller 12 in almost the entire reading area. Because of the arrangement, the illumination unit 6 irradiates the light from the reading position, and the light transmitted through the document is surely reflected by the white sheet member 16 or the platen roller 12, so that the brightness is not lowered.

Further, since the white sheet member 16 is attached in parallel with the flow reading glass 4, the light transmitted through the document is reflected in the same manner as the light is reflected by the white pressure plate 14 in the case of book reading, and the light is read in book reading. Substantially no change in brightness occurs during flow reading.

The reading position at the time of flow reading is between the position just below the center of rotation of the platen roller 12 and the tip 17 of the white sheet member 16, that is, the position where the surface of the platen roller 12 is read when the original is not conveyed. Is set to, the dust on the scanning glass 4 and the platen roller
It is possible to detect the dust on the 12 and perform the detection operation, and high-quality image reading is performed while preventing the occurrence of streaks.
Further, by setting the reading position on the upstream side of the rotation center of the platen roller 12 in the document conveying direction, dust is unlikely to adhere to the platen roller 12.

Second Embodiment Next, a second embodiment of the image reading apparatus according to the present invention will be described with reference to FIGS. 6 and 7. 6 is a detailed cross-sectional explanatory diagram of the flow reading unit, and FIG. 7 is a schematic explanatory diagram showing the luminance variation preventing effect.

The present embodiment differs from the above-described first embodiment in that the first embodiment shows an example in which the white sheet member 16 is attached in parallel with the flow reading glass 4, but the white sheet member of the present embodiment. 16 is the distance from the scanning glass 4
That is, the platen roller 12 is arranged so that it becomes larger as it gets closer to the platen roller 12. Other configurations are similar to those of the first embodiment described above.

That is, as shown in FIG. 6, the distance between the white sheet member 16 and the flow-reading glass 4 is white so that the distance C4 at the downstream end is larger than the distance C3 at the upstream end in the document conveying direction. The sheet member 16 is obliquely attached. The minimum distance C3 between the white sheet member 16 and the flow-reading glass 4 is the flow-reading glass 4 and the platen roller 1.
2 Larger than the distance C1 from the surface and white sheet member 16
The maximum distance C4 between the flow reading glass 4 and the flow reading glass 4 is smaller than the distance (C1 + R) between the flow reading glass 4 and the center of the platen roller 12.

The effect of preventing the brightness reduction by the white sheet member 16 of the present embodiment will be explained with reference to the schematic diagram shown in FIG. FIG. 7 schematically shows a path of light emitted from the illumination means 6 on one side and transmitted through the document.

The light transmitted through the original 18 is white sheet member 16
Is reflected in the direction of the reading means 5. Since the white sheet member of the present embodiment is arranged so as to be inclined with respect to the flow reading glass 4, it has an effect of condensing the light transmitted through the document 18 in the direction of the reading unit 5, and is shown in FIG. More light is emitted from the original than the flow scanning unit of the first embodiment.
It can be seen that 18 is illuminated from the back. This allows
The decrease in brightness when the reading position is separated from just below the center of rotation of the platen roller 12 is further reduced, and stable image reading with little change in brightness is performed even when the reading position varies.

Not only when the white sheet member 16 is tilted, but also when the illumination means 6 is formed into a concave curved surface shape, the light from the illumination means 6 is more effectively focused on the reading means 5. Like

[Third Embodiment] Although the above-described embodiment has been described with reference to the image reading apparatus, as shown in FIG.
The present invention can be applied to an image forming apparatus C such as a copying machine in which the image reading apparatus A and the image recording apparatus B are integrated.

FIG. 8 is an overall schematic explanatory view of the image forming apparatus, and the image reading apparatus A has the same configuration as that described in the first embodiment. The image recording device B records an image based on the image data read by the image reading device A, the image data read from another image reading device, or the like.

That is, when an image recording signal is input, one of the sheet storage units 19a, 19b, 19c, 19d and the recording medium set in the tray 19e is selected as the feeding unit 20.
a, 20b, 20c, 20d, 20e and the conveying roller 31 are driven to convey to the image forming means to form an image.

The image forming means includes a photoconductor drum 21 and a charger 22 for uniformly charging the surface of the photoconductor drum 21.
An exposing means 23 for selectively exposing the surface of the photosensitive drum 21 charged by the charger 22 according to image information, and an electrostatic latent image formed on the photosensitive drum 21 by the exposing means 23. A developing device 24 for developing a toner image to form a toner image to be transferred onto a conveyed recording medium;
A transfer charger 25 for transferring the toner image developed on the surface of 21 to a recording medium, a separation charger 26 for separating the recording medium on which the toner image is transferred from the photosensitive drum 21, and a toner image A cleaner 27 for removing the toner remaining on the photosensitive drum 21 after the transfer is provided, and an image is formed on a recording medium by an electrophotographic method.

Then, the recording medium on which the image has been formed is conveyed by the conveying section.
The toner image is conveyed to a fixing device 29 by 28, and the toner image is heated and fixed, and then discharged to a discharge tray 30.

As described above, by constructing the image forming apparatus C by integrating the image reading apparatus A and the image recording apparatus B, it is possible to effectively reduce the variation in brightness when the original is scanned in the same manner as the above-described embodiment. By preventing this, stable image reading can be performed, and based on this, high-quality image formation can be performed at high speed.

[Other Embodiments] In the above-described embodiment,
An example in which a contact image sensor is used as the image reading means is described, but a folding mirror and CC
A type using D or a type in which the reflected light from the original is guided to the surface of the photoconductor of the image forming apparatus by a folding mirror and directly exposed.

Further, in the above-described embodiment, in order to avoid the influence of dust on the flow reading glass 4, the reading position is set to the upstream side in the original conveying direction with respect to the position just below the center of rotation of the platen roller 12, and the reading position is set to the upstream side. A white sheet member 16 is provided.
However, since the attachment of dust to the flow reading glass 4 changes depending on the document transport path shape and the like, the downstream side of the document transport direction from immediately below the center of rotation of the platen roller 12 is set as the reading position, and reflection is performed accordingly. A white sheet member 16 which is a member may be provided on the downstream side, the flow reading position is set on both sides sandwiching the position right below the center of rotation of the platen roller 12, and the white sheet member 16 is provided on the upstream side and the downstream side in the document conveying direction. May be.

Further, in the above-mentioned embodiment, the white sheet member that easily reflects light is used as the reflecting member, but the reflecting member is not limited to this, and the member that can effectively reflect the light from the illumination means 6 is used. If

[0051]

As described above, according to the present invention, since the reflecting member for reflecting the light emitted from the illuminating means when the document is read while being conveyed is provided, the light transmitted through the document is read by the image reading means. The light is reflected in the direction of and the document is illuminated from the back side. Therefore, even if the reading position of the flow reading varies, it is possible to perform stable image reading with little change in the brightness of the image.

[Brief description of drawings]

FIG. 1 is a block diagram of an image reading apparatus according to a first embodiment of the present invention.
It is a detailed sectional view of a flow reading unit.

FIG. 2 is a sectional view of the image reading apparatus according to the first embodiment of the present invention.

FIG. 3 shows the image reading device according to the first embodiment of the present invention,
It is a schematic diagram which shows the brightness fluctuation prevention effect.

FIG. 4 is a graph showing the relationship between the reading position of the flow reading and the brightness of the white background of the original in the image reading apparatus according to the first embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the reading position of the flow-reading and the brightness of the white background portion of the document when the white sheet member is not provided.

FIG. 6 shows an image reading apparatus according to a second embodiment of the present invention,
It is a detailed sectional view of a flow reading unit.

FIG. 7 shows an image reading apparatus according to a second embodiment of the present invention,
It is a schematic diagram which shows the brightness fluctuation prevention effect.

FIG. 8 is a sectional view of an image forming apparatus according to a third embodiment of the present invention.

FIG. 9 is a cross-sectional view of an image reading device according to a conventional technique.

FIG. 10 is a schematic diagram showing a luminance variation factor of an image reading apparatus according to a conventional technique.

[Explanation of symbols]

A ... Image reading device B ... Image recording device C ... Image forming apparatus 1 ... Image reading unit 2 ... ADF 3… Platen glass 4… Scanning glass 5 ... Reading means 6 ... Lighting means 7 ... Selfoc lens 8 ... Image sensor 9… Casing 10… Original section 11a-11f ... Roller 12… Platen roller 13-Document output section 14… White plate 15… Jump platform 16… White sheet material 17… Tip position 18 ... manuscript 21 ... Photosensitive drum 22 ... Charger 23 ... Exposure means 24 ... Developer 25… Transfer charger 26 ... Separation charger 27 ... Cleaner 28… Transport section 29… Fixer 30… Ejection tray 31… Conveyor rollers

Claims (9)

[Claims] 1. An image reading apparatus comprising a document feeding unit for feeding a sheet-shaped document and capable of reading the document while feeding the document, and a transparent member for supporting the document at an image reading position; and a transparent member facing the transparent member. And a reading unit capable of reading a document image by irradiating an original on the transparent member with light from an illuminating unit, and a position opposite to the illuminating unit and the reading unit facing the transparent member. A rotatable rotating body, and a reflecting member for reflecting the light emitted from the illuminating means when the document is read while being conveyed, is provided in the vicinity of the rotating body. Image reading device. 2. The distance between the reflecting member and the transparent member is
The image reading apparatus according to claim 1, wherein the distance is smaller than the distance between the transparent member and the center of rotation of the rotating body and larger than the distance between the transparent member and the surface of the rotating body. 3. The tip end position of the reflecting member closest to the rotating body is such that the reflecting member is substantially in the entire reading area of the reading means when the direction of the rotating body is seen from the reading position by the reading means. The image reading device according to claim 1, wherein the image reading device is arranged at a position where a part of the rotating body is hidden. 4. The reflecting member is arranged in parallel with the transparent member.
The image reading device described in any one of 1. 5. The reflection member is arranged so that a distance from the transparent member increases as the distance from the rotating member increases.
The image reading device described in any one of 1. 6. The image reading device according to claim 1, wherein the reflecting member is a flexible white sheet. 7. The reading position for reading the original while being conveyed is set to a position where the surface of the rotating body is read when the original is not being conveyed. The image reading device according to any one of items. 8. The image reading apparatus according to claim 7, wherein a reading position for reading the original while conveying the original is upstream of a rotation center of the rotating body in the original conveying direction. 9. An image forming apparatus, comprising an original document conveying means for conveying a sheet-shaped original document, capable of recording information read by an image reading device capable of reading while conveying the original document on a recording medium. An image forming apparatus, comprising: the image reading apparatus according to claim 8; and an image forming unit for recording an image on a recording medium.