JP4609289B2 - Image reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus that optically reads an image of a document while conveying the document in one direction, and an image forming apparatus such as a copying machine and a printer including the image reading device.

  2. Description of the Related Art An electrophotographic image forming apparatus such as a copying machine or a printer is equipped with an image reading apparatus that optically reads a document image. As this type of image reading apparatus, conventionally, an image of a document conveyed along one surface of a plate-like slit glass is read by an optical reading means that is stationary while facing the other surface of the slit glass. A so-called document panning method that reads through a slit glass is known.

  In an image reading apparatus using the document panning method, only one line area of a reading sensor (usually a CCD line sensor is used) is used for reading on the slit glass. However, when dirt is generated, streak noise is generated in the entire image.

  Therefore, in Patent Document 1, a white background portion is provided on a guide member arranged with a gap with respect to one surface of the slit glass, and the whiteness of the shading plate read by the optical reading means and the guide member It is described that the stain of the slit glass is detected by comparing the whiteness of the background portion of the slit glass.

However, in the image reading apparatus described in Patent Document 1, since the dirt on the slit glass is detected against the white color provided on the guide member, black dirt can be detected, but white dirt cannot be detected. Had problems.
JP-A-11-213129

Accordingly, an object of the present invention is to detect not only black stains on the slit glass but also white or other color stains, and an original reading type image reading apparatus capable of suitably cleaning the stain on the slit glass, and An object is to provide an image forming apparatus.

In order to achieve the above object, the present invention provides:
In an image reading apparatus that reads an image of a document conveyed along one surface of a plate-shaped slit glass through the slit glass by an optical reading means that is stationary while facing the other surface of the slit glass.
A guide member having a background portion of at least two colors including white, and disposed with a gap with respect to one surface of the slit glass;
A white reference shading plate provided adjacent to the slit glass;
Wherein the optical reading means to read the reflection density of the background portion and the reflection density of the shading plate, the state of the reading position on the slit glass by comparing the reflection density of the reflection density and the background portion of the shading plate Control means for determining pass / fail;
A plurality of cleaning means for cleaning the slit glass;
Prepared,
The control means operates any one of the plurality of cleaning members according to the type of the background portion that has determined that the state of the reading position on the slit glass is not,
It is characterized by.

In the image reading apparatus according to the present invention, since the guide member for guiding the document on the slit glass is provided with at least two backgrounds including white, the reading position on the slit glass is determined based on the reflection density of the shading plate. Not only black stains but also other color stains can be reliably detected.

  In the image reading apparatus according to the present invention, the background portion provided on the guide member may be composed of a white portion and a black portion, or may be composed of a multi-tone gray scale. In this case, by moving the guide member, the white part and the black part can be moved to the reading position of the optical reading means, or each of the gray scale gradation parts can be moved to the reading position of the optical reading means. In other words, it may be configured. Of course, black stains can be detected by the white background portion, white stains can be detected by the black background portion, or gradation stains corresponding to gray scales can be detected.

  The background portion may be made of liquid crystal. In this case, black stains can be detected as the background of the white portion by making the liquid crystal transparent, and white stains can be detected by switching the liquid crystal to the light absorption state. It is also possible to perform detection similar to the gray scale by switching the liquid crystal to halftone.

Further, the image reading apparatus according to the present invention comprises a plurality of cleaning means for cleaning the slit glass. And when a control means determines with the state of the reading position on slit glass being no, a cleaning means is operated and the stain | pollution | contamination on slit glass is cleaned. Cleaning means is provided with a plurality of cleaning members, makes operation of one of a plurality of cleaning members according to the type of the background portion (i.e., the type of soiling). Since black stains are hard to remove such as glue, it is necessary to use a blade-like cleaning member, and white stains can be easily removed such as paper dust, so a brush-like cleaning member May be used.

Further, a warning may be generated when it is determined that the state of the reading position on the slit glass is NO. Such warning may be displayed on the operation panel of the image forming apparatus or notified to the user by voice.

  Embodiments of an image reading apparatus and an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings.

(Schematic configuration of image forming apparatus, see FIG. 1)
FIG. 1 shows a schematic configuration of a digital copying machine 100 as an embodiment of the present invention. The digital copying machine 100 includes an image reading device 110 that optically reads a document image and an image recording device 120 using electrophotography.

  The image reading device 110 is for reading an image of a document placed on the platen glass 116 and for reading an image of a document conveyed in the arrow X direction by the automatic document conveying device 117. The reading unit 6 includes a light source 111, a mirror 112, an imaging lens 113, and a CCD 114.

  In the stationary document reading mode, the reading unit 6 moves immediately below the document table glass 116 in the direction of the arrow X at a predetermined speed, and reads an image of the document placed on the document table glass 116. In the document panning mode, the reading unit 6 moves to the reading position A1 and is held stationary, and reads an image of the document conveyed by the automatic document conveying device 117.

  In the reading unit 6, the reflected light from the document surface is reduced and imaged on the light receiving surface of the CCD 114 by the lens 113 through the mirror 112 to obtain an analog electric signal subjected to photoelectric conversion for each line. For example, the resolution of the CCD 114 is 600 dpi in the main scanning direction Y, and the maximum document size is A3. The photoelectrically converted analog electrical signal is converted into digital data by the image processing unit 115, image processing such as scaling and image quality correction is performed, and the digital data is output to the LD drive unit 121.

  In the image recording apparatus 120, a charger 132, a laser scanning unit 133, a developing unit 134, a transfer unit 135, and a residual toner and residual charge cleaner 136 are arranged around a photosensitive drum 131 that is driven to rotate in the direction of arrow B. There is something set. An electrostatic latent image is formed on the photosensitive drum 131 based on the image data output from the LD drive unit 121, developed by the developing device 134, and developed on the paper fed from the paper feed cassettes 141 and 142. The transferred toner image is transferred. Thereafter, the sheet is conveyed to a fixing device 137 where toner is fixed and discharged onto a tray 138.

  The basic configuration and operation of the image reading device 110 and the image recording device 120 are well known in the art, and detailed descriptions thereof are omitted. Further, the image recording apparatus 120 may have a function of reproducing full color, and a full color machine usually has a configuration such as a tandem system. In the case of a full-color machine, the document reading device 110 separates and reads the image of the document line by line into the three primary colors RGB, and the basic configuration of this type of full-color reading device itself is well known.

(Image reading device, see FIGS. 2 and 3)
FIG. 2 shows details of the image reading device 110, particularly, an automatic document feeder 117 used in the document panning mode. The automatic document feeder 117 includes an upstream conveyance path 21 for feeding documents picked up one by one from a document tray (not shown) onto the slit glass 2, and a reading conveyance path 22 for conveying the documents on the slit glass 2. And a downstream conveyance path 23 for conveying the document onto a discharge tray (not shown).

  The upstream conveyance path 21 includes a pair of first conveyance rollers 1a and 1b and guide members 11a and 11b that are arranged to face each other with the sheet passing path at a predetermined interval. The reading conveyance path 22 includes an intrusion guide 12, a slit glass 2, a scooping guide 13, and upper guide members 3 a, 3 b, 3 c disposed above these at a predetermined interval. The slit glass 2 is a transparent glass plate elongated in the main scanning direction Y (direction perpendicular to the paper surface of FIG. 2) by the reading unit 6, and the upper surface 2a faces the upper guide member 3b with a predetermined interval. Yes. The downstream-side conveyance path 23 includes a pair of second conveyance rollers 5a and 5b and guide members 14a and 14b that are arranged to face each other with the sheet passing path at a predetermined interval. A shading plate 4 serving as a white reference is provided on the lower surface of the scooping guide 13.

  The upper guide member 3b is configured separately from the other upper guide members 3a and 3c, and is slidable in the sub-scanning direction X by, for example, a solenoid (not shown) (see FIG. 4C). Further, as shown in FIG. 3A, the lower surface of the upper guide member 3b is separately applied to a white background portion 31a and a black background portion 31d for detecting dirt at the reading position A1 on the slit glass 2. Yes. The white background portion 31 a is set to a color substantially equivalent to the white color of the shading plate 4. When the upper guide member 3b is in the normal position shown in FIGS. 2 and 4B, the white background 31a is opposed to the reading position A1, and when it is in the moving position shown in FIG. The background portion 31d is positioned opposite the reading position A1. The dirt detection operation by the background portions 31a and 31d will be described in detail later.

  Documents are supplied one by one from an unillustrated document tray to the upstream conveyance path 21 and are passed over the slit glass 2 of the reading conveyance path 22 by the first conveyance rollers 1a and 1b and the second conveyance rollers 5a and 5b. It is conveyed to the downstream conveyance path 23 and discharged onto a discharge tray (not shown). Here, the document passing through the reading conveyance path 22 is guided by the upper guide member 3a and the entry guide 12 and enters the upper surface 2a of the slit glass 2 at an obliquely downward angle. And it is conveyed along the upper surface 2a of the slit glass 2. FIG. Thereafter, the document is scooped up by the scooping guide 13, guided by the scooping guide 13 and the upper guide member 3c, and conveyed obliquely upward.

  At this time, the reading unit 6 is placed in a stationary state immediately below the lower surface 2b of the slit glass 2, and the image of the document conveyed on the slit glass 2 is read line by line at the reading position A1. The reading unit 6 is attached to a belt 8 wound in an endless manner between a pulley 9 that is rotationally driven by a motor 7 and a pulley 10 that is rotatably supported. The reading unit 6 reads the original reading position A1 and the shading plate 4. It is possible to move to the position A2 and stop at the positions A1 and A2.

  The document passing through the reading conveyance path 22 is guided along the upper surface 2a of the slit glass 2 by the upper guide member 3b so as not to deviate from the focus position of the reading unit 6, and is optically transmitted through the transparent slit glass 2. The image can be read with high accuracy.

  Further, the digital copying machine 100 includes a CPU 30 as a control unit. The CPU 30 not only exchanges signals with the operation panel 40 but also controls each unit of the image reading device 110 and the image recording device 120 to read from the reading unit 6. A signal is input and the motor 7 is also controlled. Further, detection of dirt on the slit glass 2, which will be described below, cleaning instructions for dirt, and warning of dirt detection if necessary.

(Dirt detection control, see FIGS. 4 to 7)
The image reading apparatus 110 having the above configuration is controlled by the CPU 30 as follows, and detects dirt on the slit glass 2. First, as shown in FIG. 4A, before reading a certain original, the motor 7 is driven to move the reading unit 6 to a position A2 facing the lower side of the shading plate 4. The reflection density (whiteness read value Dsh) of the shading plate 4 by the reading unit 6 in one line in the main scanning direction at this position A2 is obtained (step S1 in FIG. 5).

  Next, as shown in FIG. 4B, the motor 7 is driven to move the reading unit 6 to the document reading position A1. Then, the reflection density (white background portion reading value Dg1) of the white background portion 31a of the upper guide member 3b transmitted through the slit glass 2 by the reading unit 6 in one line in the main scanning direction at the position A1 is obtained (step in FIG. 5). S2).

  Next, the two reading values Dsh and Dg1 are compared to determine whether the dirt state at the reading position A1 of the slit glass 2 is good (step S3 in FIG. 5). Specifically, the reading value Dg1 of the white background portion 31a at the document reading position A1 is lower than the reading value Dsh of the shading plate 4 where the slit glass 2 is dirty. FIG. 6 shows a waveform of the read value Dg1 when there is a stain of a size c at the position b in the main scanning direction and the read value drop a occurs.

  Therefore, the quality of the upper surface 2a of the slit glass 2 is determined according to whether or not there is a portion where the reading value Dg1 at the image reading position A1 is equal to or less than a certain value d from the level of the reading value Dsh of the shading plate 4. be able to. That is, if Dsh−Dg1 ≦ d at all locations in one line, it is determined that the slit glass 2 is not dirty (YES in step S3 in FIG. 5). If Dsh-Dg1> d even at one location, it means that black stain has been detected (NO in step S3 in FIG. 5, step S4).

  Next, a solenoid (not shown) is driven to move the upper guide member 3b one step to the left as shown in FIG. 4C (step S5 in FIG. 5). Accordingly, the black background portion 31d provided on the lower surface of the upper guide member 3b faces the image reading position A1 by the reading unit 6. Then, the reflection density (black background portion read value Dg2) of the black background portion 31d transmitted through the slit glass 2 by the reading unit 6 in one line in the main scanning direction at the position A1 is obtained (step S6 in FIG. 5).

  Next, the two reading values Dsh and Dg2 are compared to determine whether the dirt state at the reading position A1 of the slit glass 2 is good (step S7 in FIG. 5). Specifically, the reading value Dg2 of the black background portion 31d at the document reading position A1 rises at a portion where the slit glass 2 has white stains with respect to the reading value Dsh of the shading plate 4. FIG. 7 shows a waveform of the read value Dg2 in the case where a stain having a size of f exists at the position g in the main scanning direction and the read value rises e.

  Therefore, the quality of the upper surface 2a of the slit glass 2 is determined according to whether or not there is a portion where the read value Dg2 at the image reading position A1 is equal to or higher than a certain value h from the level of the read value Dsh of the shading plate 4. be able to. That is, if Dsh−Dg2 ≧ h at all locations in one line, it is determined that the slit glass 2 is not dirty (YES in step S7 in FIG. 5). If Dsh-Dg2 <h even at one location, it means that white stain has been detected (NO in step S7 in FIG. 5, step S8).

  By the above control, white stain as well as black stain can be detected. If the difference between the two reading values Dg1, Dg2 and the reference reading value Dsh is not more than a certain amount d and not less than h, the state of the slit glass 2 at the reading position A1 is “good”, that is, the glass surface It is determined that dirt and scratches are within an acceptable range. On the other hand, if the difference exceeds a certain amount d or less than a certain amount h even at one position in reading one line, the state at the reading position A1 of the slit glass 2 is “No”, that is, the glass surface. It is determined that the dirt and scratches of the product exceed the allowable range.

(Glass surface cleaning and warning)
Here, when the state determination result of the slit glass 2 is “No”, the CPU 30 operates a cleaning unit (not shown) to clean the slit glass 2 from dirt. The cleaning means includes, for example, a brush-like cleaning member and a blade-like cleaning member that can move in the long side direction of the slit glass 2, and operates any one of the plurality of cleaning members according to the type of dirt. In other words, since black-colored stains are difficult to remove such as glue, a blade-like cleaning member is used, and white-colored stains are paper dust and other stains that can be easily removed. Use to clean.

  Further, since black-type stains are often uncleanable by the cleaning member, an indication that there is dirt on the operation panel 40 or a warning to that effect may be given. Only a display warning or an audio warning may be given, and the user may be prompted to clean. If the mounting of the cleaning means is omitted, an increase in cost can be suppressed.

(See gray scale, Fig. 3 (B))
In the above-described embodiment, an example in which the detected background portion of two colors (the white background portion 31a and the black background portion 31d) is provided on the lower surface of the upper guide member 3b is shown in FIG. 3B. Thus, it may be composed of a multi-tone gray scale. That is, a white background portion 31a, a background portion 31b having a density of 30%, a background portion 31c having a density of 60%, and a black background portion 31d arranged in parallel in the sub-scanning direction X on the lower surface of the upper guide member 3b are used as the detected background portion. be able to. In this case, the upper guide member 3b may be moved in four steps in the sub-scanning direction X in accordance with the background portions 31a to 31d. The white background portion 31a can detect black stains, the black background portion 31d can detect white stains, and can also detect gradation stains corresponding to the halftone background portions 31b and 31c.

(Use of liquid crystal)
Further, the non-detection background portion may be a liquid crystal embedded in the lower surface of the upper guide member 3b. In this case, black dirt can be detected as the background of the white portion by making the liquid crystal transparent, and white dirt can be detected by switching the liquid crystal to the light absorption state. It is also possible to perform detection similar to the gray scale by switching the liquid crystal to halftone. When liquid crystal is used, it is not necessary to move the upper guide member 3b when detecting dirt.

(Other examples)
The image reading apparatus and the image forming apparatus according to the present invention are not limited to the above-described embodiments, and can be variously modified within the scope of the gist thereof.

1 is a schematic configuration diagram showing an embodiment of an image forming apparatus (digital copying machine) according to the present invention. 1 is an elevational view showing an embodiment of an image reading apparatus according to the present invention. (A), (B) is a top view which shows the to-be-detected background part used with the said image reading apparatus, respectively. (A), (B), (C) is an elevational view showing the operating state of the image reading device. It is a flowchart figure which shows the control procedure of the dirt detection in the said image reading apparatus. It is a graph which shows the detection waveform at the time of black dirt detection. It is a graph which shows the detection waveform at the time of white dirt detection.

Explanation of symbols

2 ... Slit glass 3b ... Upper guide member 4 ... Shading plate 6 ... Reading unit 30 ... CPU
31a to 31d ... detected background part 40 ... operation panel 100 ... digital copying machine 110 ... image reading device 120 ... image recording device

Claims (7)

In an image reading apparatus that reads an image of a document conveyed along one surface of a plate-shaped slit glass through the slit glass by an optical reading means that is stationary while facing the other surface of the slit glass.
A guide member having a background portion of at least two colors including white, and disposed with a gap with respect to one surface of the slit glass;
A white reference shading plate provided adjacent to the slit glass;
Wherein the optical reading means to read the reflection density of the background portion and the reflection density of the shading plate, the state of the reading position on the slit glass by comparing the reflection density of the reflection density and the background portion of the shading plate Control means for determining pass / fail;
A plurality of cleaning means for cleaning the slit glass;
Prepared,
The control means operates any one of the plurality of cleaning members according to the type of the background portion that has determined that the state of the reading position on the slit glass is not,
An image reading apparatus. The background part consists of a white part and a black part,
The white part and the black part can be moved to the reading position of the optical reading means by moving the guide member,
The image reading apparatus according to claim 1. The background portion is composed of a multi-tone gray scale,
By moving the guide member, gray scale gradation portions can be moved to the reading position of the optical reading device, respectively.
The image reading apparatus according to claim 1.   The image reading apparatus according to claim 1, wherein the background portion is made of liquid crystal. Wherein, when it is determined that whether the state of the reading position on the slit glass, the image reading apparatus according to any one of claims 1 to 4, characterized in that to generate a warning. An image forming apparatus comprising the image reading device according to claim 5 , wherein the warning is displayed on an operation panel. An image forming apparatus comprising the image reading device according to claim 5 , wherein the warning is issued by voice.

Images