JP2010177746A - Image reading unit and dust adhesion determination method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect dust adhered to the front surface of a contact glass at a reading section with a fixed reading position with high accuracy to quickly make a proper response such as cleaning. <P>SOLUTION: A reading roller 26 as a reference member faces a reading section 25. A first surface portion 26a of low density or high reflectivity (for example, white) of the reading roller 26 faces the reading section 25. The reading section 25 performs an image reading operation to acquire first image data. A second surface portion 26b of higher density or lower reflectivity (for example, black) than the first surface portion of the reading roller 26 faces the reading section 25, the reading section 25 performs an image reading operation to acquire second image data. Based on the first image data and the second image data, dust 40 adhered on a contact glass 36 at the reading section 25 is determined. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus that reads an image of a document conveyed in a sub-scanning direction in a main operation direction by a reading unit whose reading position is fixed, and in particular, dirt such as dust and dirt on an optical path read by the reading unit. The present invention relates to an image reading apparatus with good usability and a dust adhesion determination method thereof.

In an image reading process in a digital copying machine, a digital multi-function peripheral, a facsimile machine, a scanner device, etc., a document is set on a document table or a document feeder, the document is irradiated by a light source of a reading unit, and the reflected light is used as image information. An image is read on an optical reading element (input element) such as a CCD.
The image information of the original is usually taken line by line, and when the original is placed on a fixed original table, the light path of the reading unit and the optical path between the original and the input element are sequentially moved. When the document is moved by a feeding device or the like, the document is read by moving the document while fixing the light path of the reading unit and the optical path between the document and the input element.

That is, image information in the main scanning direction (original line direction) is determined by the reading timing of the input element and the original feed speed.
In the case of a conventional image reading apparatus using a reduction optical system, a white plate for generating white reference data (shading data) is often attached to contact glass on which an original is placed. In this case, the white plate is input. The optical path between the elements is in a closed space.

Therefore, since there is no fear that dirt or dust adheres to the white plate, adjustment for each reading element is performed at an appropriate timing when the power is turned on.
The reference sub-scanning position can be changed, and since several lines are normally averaged, more stable shading data can be generated.
This shading data is necessary for performing shading correction that eliminates luminance unevenness due to the characteristics of the optical system and the imaging system and corrects the brightness to be uniform throughout the main scanning direction.

  On the other hand, in the input element on the back side of the equal magnification optical system, the white reference white plate is fixed in a position opposite to the reading position (position where the document passes), and the white plate reading position (white reference reference position). Is always the same.

  An image reading apparatus using a contact image sensor conveys a document in contact with the contact glass, irradiates the conveyed document with light from the light source of the reading unit through the contact glass, and reflects the document by the document. The reflected light containing the image information is incident again on a photoelectric conversion element (for example, a charge coupled device (CCD)) through the contact glass, and photoelectric conversion is performed by the photoelectric conversion element, thereby reading an image of the document.

  In an image reading apparatus using such a contact image sensor, in order to correct fluctuations in the amount of light from a lamp and sensitivity variations of photosensitive pixels of a photoelectric conversion element such as a CCD, a white reference is conventionally used before reading a document. The original image data is subjected to shading correction by reading the plate and using the data when the white reference plate is read as the shading data.

  However, in the image reading apparatus using the contact image sensor, as described above, since the original is read while being conveyed in contact with the contact glass that is a transparent member, the original is attached to the original. Dust or toner or paper dust (collectively referred to as “dust”) tends to adhere to the surface of contact glass, etc. When these dust adheres to an optical path such as a white reference plate or contact glass, the read image data is displayed. When printing or printing, the dust appears as white stripes or black stripes in the image, which degrades the image quality.

  Therefore, as a method of avoiding image deterioration due to dust adhesion, a white reference plate can be moved relative to the reading position, and a portion of the white reference plate to which dust is attached is removed from the reading position. (See Patent Document 1).

However, the dust may adhere not only to the white reference plate but also to the contact glass of the contact image sensor.
In this case, if dust adheres to a portion corresponding to the reading position, even if the white reference plate is moved with respect to the reading position as in the conventional technique described above, the dust is read, and an image caused by dust adhesion is detected. Deterioration could not be avoided.

For dust adhering to the white reference plate, as a method for reducing the influence, by rotating the white roller with the white reference member as the white roller, the shading data is generated from the average value of the read data of a plurality of lines. However, it is possible to reduce the influence of garbage.
However, when dust adheres to the reading unit, it is read, and it has been impossible to avoid a reduction in image quality due to the occurrence of white or black lines.

  Accordingly, in view of the above problems, the present invention provides an image reading apparatus having a function of reading an image of a document conveyed in the sub-scanning direction in the main scanning direction by a reading unit having a fixed reading position. An object of the present invention is to detect dust attached to the glass surface with high accuracy so that appropriate measures such as cleaning can be quickly taken. This is not always the case when generating shading data.

In order to achieve the above object, the present invention provides an image reading apparatus having a function of reading an image of a document conveyed in the sub-scanning direction in the main scanning direction by a reading unit whose reading position is fixed as follows. It is characterized by comprising.
A reference member having a first surface portion having a low density or a high reflectance facing the reading portion and a second surface portion having a higher density or a lower light reflectance than the first surface portion, It is provided so as to be movable with respect to the reading unit.
When the reading unit does not read the image of the document, the reference member is set to the first position where the first surface portion faces the reading unit, and the reading unit is caused to perform an image reading operation. The first image data is acquired, and the reference member is set to the second position where the second surface portion faces the reading portion, and the reading portion is caused to perform an image reading operation to acquire the second image data. Provide means to do.
Further, there is provided determination means for determining whether dust is attached to the reading unit based on the first image data and the second image data.

  The determination means calculates a difference for each corresponding pixel of the first image data and the second image data, and dust is attached when the difference is less than or less than a preset value. It is good that it is a means to determine.

The means for acquiring the first image data obtains the first image data by averaging the image data of a plurality of line periods output from the reading unit when the reference member is at the first position. It is desirable that it is a means to do.
The means for acquiring the second image data obtains the second image data by averaging the image data of a plurality of line periods output from the reading unit when the reference member is at the second position. It is desirable that it is a means to do.

The first surface portion of the reference member is a white surface;
The means for obtaining the first image data is means for obtaining shading data, and the means for obtaining the second image data is means for obtaining dust detection data,
The determination unit may be a determination unit that determines whether dust is attached to the previous reading unit based on the shading data and the dust detection data acquired by the respective units.

The image reading apparatus according to the present invention may also be configured as follows with an image reading apparatus having the same function as the above-mentioned premise part.
A reference member having a first surface portion that is a white surface facing the reading portion and a second surface portion having a higher density or lower light reflectance than the first surface portion is disposed on the reading portion. To be movable.
When the reading unit is not reading an image of a document, the reference member is set to a first position where the first surface portion faces the reading unit, and the reading unit is caused to perform an image reading operation. Means for acquiring image data input from the reading unit and generating shading data; shading correction unit for correcting shading of the input image data input from the reading unit using the shading data; and the reference member The second surface portion is set to a second position facing the reading portion, the reading portion is caused to perform an image reading operation, and input image data input from the reading portion is subjected to shading correction by the shading correction means. Means for acquiring image data and generating dust detection data;
Further, there is provided determination means for determining whether dust is attached to the reading unit based on dust detection data generated by the means.

  The determination means compares the value of the dust detection data with the previous pixel for each pixel, and when the difference value exceeds a preset value or exceeds the preset value, And a means for detecting the dust attachment position based on the pixel position at that time.

When the input image data input from the reading unit is Din, the shading data is Dsh, the output image data subjected to the shading correction is Dout, and the number of bits of the image data is n,
Dout = Din / Dsh × (2 ⁿ −1)
It may be a means for performing a shading correction process by the calculation.
The preset value in the determination means is preferably a high level value close to the maximum value of the image data subjected to the shading correction.

The means for generating the shading data may be means for generating the shading data by averaging the image data of a plurality of line periods output from the reading unit when the reference member is at the first position. .
The means for generating dust detection data is means for generating the dust detection data by averaging the image data of a plurality of line periods subjected to shading correction by the shading correction means when the reference member is at the second position. Even better.

Each of the image reading devices preferably includes means for notifying the user when dust is determined to be attached by the determination means.
It is desirable that the reference member be in the first position also when the reading unit reads an image of the document.

The reference member is a cylindrical or columnar member, and a part of the outer circumferential surface of the outer circumferential surface forms the second surface portion in a strip shape along the axial direction, and the outer periphery excluding the second surface portion The surface may constitute the first surface portion made of a white surface.
In this case, during the period when the means for generating the shading data acquires image data from the reading unit and generates shading data, the first surface portion of the reference member faces the reading unit, and the dust detection During the period in which the data generation means acquires the image data shading corrected by the shading correction means and generates dust detection data, the second surface portion of the reference member is opposed to the reading portion. It is preferable to have rotating means for rotating the reference member in the circumferential direction.

Further, it is desirable that the rotating means rotate the reference member so that the first surface portion faces the reading portion even during a period in which the reading portion reads an image of the document.
Further, the cylindrical or columnar reference member can also function as a suppression roller that suppresses the floating of the document when the reading unit reads the image of the document.

The dust adhesion determination method in the image reading apparatus according to the present invention is a dust adhesion determination method for determining whether dust is attached to the reading unit in the image reading apparatus as described above. It is characterized by performing.
When the reading unit is not reading an image of a document, a first surface portion having a low reference member density or a high reflectance is opposed to the reading unit, and the reading unit is caused to perform an image reading operation. The second surface portion having a higher density or lower light reflectance than the first surface portion of the reference member is opposed to the reading portion, and the reading portion is caused to perform an image reading operation. 2 is acquired, and it is determined whether dust is attached to the reading unit based on the first image data and the second image data.

  At the time of the determination, a difference is calculated for each corresponding pixel between the first image data and the second image data, and dust is attached when the difference is less than or less than a preset value. Can be determined.

The first surface portion of the reference member is a white surface, shading data is acquired as the first image data, dust detection data is acquired as the second image data,
In the determination, it can be determined whether dust is attached to the reading unit based on the shading data and the dust detection data.

Alternatively, when the reading unit is not reading an image of a document, the reading unit is caused to perform an image reading operation in a state where the first surface portion made of a white surface of the reference member is opposed to the reading unit, Image data input from the reading unit is acquired to generate shading data, and thereafter, input image data input from the reading unit is subjected to shading correction using the shading data, and the second of the reference member is corrected. The image reading operation is performed by the reading unit with the surface portion facing the reading unit, and the input image data input from the reading unit is acquired with the shading correction by the shading correction unit. It is also possible to generate dust detection data.
In this case, it is determined whether dust is attached to the reading unit based on the dust detection data corrected for shading.

  In the determination, the value of the dust detection data is compared with the previous pixel for each pixel, and when the difference value exceeds or exceeds the preset value, dust is detected. It is possible to determine that it is attached, and to detect the attached position of dust based on the pixel position at that time.

When the input image data input from the reading unit is Din, the shading data is Dsh, the output image data subjected to the shading correction is Dout, and the number of bits of the image data is n.
Dout = Din / Dsh × (2 ⁿ −1)
It is good to carry out by the operation.

  First image data or shading acquired from the reading unit with the first surface portion having a low density or high reflectance of the reference member (a white surface when shading data is acquired) facing the reading unit The second surface portion having a higher density or lower light reflectance than the first surface portion of the reference member with respect to the data level is acquired from the reading portion in a state of facing the reading portion. Although the level of the second image data or dust detection data is lowered, the reading level of dust attached to the contact glass of the reading unit does not change.

Therefore, it is possible to determine whether dust is attached to the reading unit based on the first image data or shading data and the second image data or dust detection data.
Therefore, when the determination result indicates that dust is attached, it is possible to take appropriate measures such as notifying the user of the determination result and prompting cleaning without starting the image reading of the subsequent document. Degradation of image quality due to black streaks can be avoided.

When generating shading data and dust detection data, there are influences such as fluctuations in the amount of light of the light source in the reading unit and variations in sensitivity due to pixels of a photoelectric conversion element (sensor chip) such as a CCD. When the comparison is performed, the difference is small when the output level is small, and the difference is large when the output level is large, and the detection accuracy is lowered because it is necessary to give a certain range to the dust detection level.
Therefore, if the dust detection data is subjected to shading processing using the above-mentioned shading data, and dust adhesion is determined based on the dust detection data after the shading correction, the determination accuracy can be improved.

It is a figure which shows the structural example of the mechanism part of the image reading apparatus which is one Embodiment of this invention. 2 is a block diagram illustrating a configuration example of a control system of the image reading apparatus. FIG. FIG. 3 is a block diagram illustrating a configuration example of a main part of a control system of a second reading unit 25 in FIGS. 1 and 2. FIG. 4 is a view of a reading array unit including a light source unit 200 and a sensor chip 201 in a second reading unit 25 in FIG. 3 as viewed from the lower surface side of a contact glass 36 in FIG. 1. It is the figure which turned it upside down and was seen from the short or hand direction.

FIG. 6 is an explanatory diagram illustrating an example of a configuration in which a rotation position of a second reading roller that is a reference member facing the second reading unit is changed between generation of shading data and generation of dust detection data. FIG. 4 is a perspective view of the second reading roller 26 and a developed view thereof. FIG. 10 is an explanatory diagram illustrating an example of a configuration in which a slide position of a slide plate that is a reference member facing the second reading unit 25 is changed between generation of shading data and generation of dust detection data. The shading data D1 (n) generated in the state of FIG. 6 (a) or FIG. 7 (a) and the dust detection data D2 (n) generated in the state of FIG. 6 (b) or FIG. 7 (b). It is a curve figure which shows an example of main scanning output level distribution. FIG. 10 is a curve diagram showing a distribution regarding a main scanning position of a difference value between shading data D1 (n) and dust detection data D2 (n) in FIG. 9 for explaining a first embodiment of the dust detection function according to the present invention; FIG. 4 is a block diagram illustrating a circuit configuration example for realizing a first embodiment of a dust detection function of the image processing unit 204 in FIG. 3. FIG. 12 is a timing diagram showing changes in signals output from the controller 100 of FIG. 11.

It is a flowchart which shows an example of the dust detection process by the image process part shown in FIG. Curve diagram showing relationship between shading data Dsh, input image data Din corresponding to dust detection data, and dust detection data D (n) subjected to shading correction processing for explaining a second embodiment of the dust detection function according to the present invention. It is. It is a block diagram which shows the circuit structural example for implement | achieving 2nd Example of the dust detection function of the image process part 204 in FIG. FIG. 16 is a flowchart illustrating an example of dust detection processing by the image processing unit illustrated in FIG. 15. FIG. 16 is a timing diagram illustrating an example in which a gate signal D_GATE in each signal output from the controller 100 of FIG. 11 or FIG. 15 becomes active for a plurality of line periods.

It is a figure of the operation part which shows the example of a display at the time of dust detection. FIG. 10 is a curve diagram illustrating another example of shading data and dust detection data when dust is attached. FIG. 10 is a curve diagram showing still another example of shading data and dust detection data when dust is attached. It is explanatory drawing which shows the relationship between a 2nd reading part and a 2nd reading roller in detail. It is a perspective view which shows the photoelectric sensor which detects a 2nd reading roller and its rotation position.

  Hereinafter, embodiments for carrying out the present invention will be specifically described with reference to the drawings. In this embodiment, a document to be read (hereinafter simply referred to as “document”) is conveyed to a fixed reading unit, and has an automatic document feeding (ADF) function for reading an image of the document while being conveyed at a predetermined speed. An example using an image reading apparatus will be described.

[Configuration example of image reading apparatus]
First, the configuration of an image reading apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a diagram illustrating a configuration example of a mechanism unit of the image reading apparatus, and FIG. 2 is a block diagram illustrating a configuration example of a control system of the image reading apparatus. In FIG. 2, illustration of the first reading unit 20 in FIG. 1 is omitted for convenience of illustration.

  This image reading apparatus includes a document setting unit A for setting a document bundle, a separation feeding unit B for separating and feeding documents one by one from the set document bundle, and a document fed thereby by the primary unit. A registration unit C which functions to abut and align and pull out and convey the aligned document, and the document conveyed thereby is turned, and the reading surface (image surface for a single-sided document, one for a double-sided document) A turn part D that conveys the surface (front surface) toward the reading side (downward), a first reading conveyance part E that reads the surface image of the document from below the contact glass, and a back image of the document (double-sided document) after reading. A second reading conveyance unit F for reading, a paper discharge unit G for discharging a document on which a front surface image or a double-sided image has been read out, and a stack unit H for stacking and holding the document after reading are configured.

  2 shows a second reading unit 25 in the second reading conveyance unit F, a controller for controlling the entire document reading apparatus, and various sensors 5, 6, 8, 11, 13, 15, 17 described later in FIG. The motors 101 to 105 of the drive unit that drives the document conveying operation, the operation unit 108, the main body control unit 111, the operation unit 108, and the like are provided.

  The document bundle 1 for image reading is set on the document table 2 including the movable document table 3 of the document setting unit A, and the user faces the document bundle 1 with the image surface (the front surface in the case of a double-sided document) facing upward. Set in state. Further, positioning of the document bundle 1 in the width direction (direction orthogonal to the transport direction) is performed by a side guide (not shown). The document set is detected by the set filler 4 and the document set sensor 5, and the detected information is transmitted from the controller 100 to the main body control unit 111 through an interface (hereinafter also referred to as “I / F”) 107.

Further, a document length detection sensor 30 or 31 provided on the table surface of the document table 2 (a reflection type sensor or an actuator type sensor that can detect even one document is used) is used to measure the length of the document in the conveyance direction. Is determined. In order to make this determination possible, it is necessary to have a sensor arrangement that can determine at least whether the document has the same vertical or horizontal size.
The movable document table 3 can be moved up and down in the directions a and b shown in FIG. 1 by a bottom plate raising motor 105 and is normally located at a home position (HP) detected by the bottom plate HP sensor 6. .

Thereafter, when the set filler 4 and the document set sensor 5 detect that the document has been set, the controller 100 receiving the detection information rotates the bottom plate raising motor 105 in the normal direction so that the top surface of the document bundle 1 is the pickup roller. The movable document table 3 is raised to a position where it contacts with 7.
The pickup roller 7 is operated in the c and d directions shown in FIG. 1 by a cam mechanism by the pickup motor 101, and the movable document table 3 is raised and pushed by the upper surface of the document on the movable document table 3 to be raised in the c direction. The upper limit can be detected by the appropriate paper feed position sensor 8.

A print key on the operation unit 108 is pressed, and a notification to that effect is sent to the main body control unit 111 via the I / F 106, and a document feed signal is transmitted from the control unit 111 to the controller 100 via the I / F 107. The pickup roller 7 is driven to rotate by the normal rotation of the paper feed motor 102 and picks up several (ideally one) originals on the original table 2. The rotation direction is a direction in which the uppermost document is conveyed (paper fed) to the paper feeding port.
The sheet feeding belt 9 is driven in the sheet feeding direction by the normal rotation of the sheet feeding motor 102, and the reverse roller 10 of the separation feeding unit B is rotated in the direction opposite to the sheet feeding direction by the normal rotation of the sheet feeding motor 102. The upper original and the lower original are separated, and only the uppermost original can be fed.

  More specifically, the reverse roller 10 is in contact with the paper feeding belt 9 at a predetermined pressure, and when the paper is in direct contact with the paper feeding belt 9 or through a single document, the reverse roller 10 rotates. Accordingly, when the document is rotated counterclockwise and two or more originals enter between the sheet feeding belt 9 and the reverse roller 10, the rotation force is set to be lower than the torque of the torque limiter. The reverse roller 10 is driven to rotate in the clockwise direction, which is the original driving direction, to push back the excess original, thereby preventing double feeding.

The original separated by the action of the paper feeding belt 9 and the reverse roller 10 is further fed by the paper feeding belt 9, the leading edge is detected by the abutting sensor 11 of the registration portion C, and further advances and stops. It hits the pull-out roller 12 that is.
The document hitting the pull-out roller 12 is sent by a predetermined distance from the detection time of the abutting sensor 11, and as a result, the document is fed while being pressed against the pull-out roller 12 with a predetermined amount of bending. By stopping the paper motor 102, the driving of the paper feed belt 9 is stopped, and a standby state is entered.

At this time, by rotating the pickup motor 101, the pickup roller 7 is retracted from the upper surface of the document, and the document is fed only by the conveying force of the paper feed belt 9, so that the leading edge of the document is in the nip of the upper and lower rollers of the pull-out roller 12. Enter and align the tip (skew correction).
The pull-out roller 12 has a skew correction function, and is a roller for conveying the skew-corrected document after separation to the intermediate roller 14, and is driven by the reverse rotation of the paper feed motor 102. At this time, the pull-out roller 12 and the intermediate roller 14 are driven, but the pickup roller 7 and the paper feed belt 9 are not driven.

A plurality of document width sensors 13 are arranged in the depth direction and detect the size in the width direction (main scanning direction) orthogonal to the transport direction of the document transported by the pull-out roller 12.
The length of the document in the conveyance direction is detected by detecting the leading edge and the trailing edge of the document with the butting sensor 11 and counting the output pulses of the paper feed motor 102 from the leading edge detection time to the trailing edge detection time. .
When the document is conveyed from the registration unit C to the turn unit D by driving the pull-out roller 12 and the intermediate roller 14, the conveyance speed at the registration unit C is higher than the conveyance speed at the first reading conveyance unit E. The processing time for setting and feeding the document to the first reading conveyance unit E is shortened.

When the leading edge of the document is detected by the reading entrance sensor 15, before the leading edge of the document enters the nip between the upper and lower roller pairs of the reading entrance roller 16, the document is decelerated to make the document transportation speed the same as the reading transportation speed. Simultaneously with the start, the reading motor 103 is driven forward to drive the reading inlet roller 16, the reading outlet roller 23, and the CIS outlet roller 27.
When the front end of the document is detected by the registration sensor 17, the controller 100 decelerates over a predetermined conveyance distance, temporarily stops the position before the reading position by the first reading unit 20, and sends the I / F 107 to the main body control unit 111. A registration stop signal is transmitted via

Thereafter, when the controller 100 receives a reading start signal from the main body control unit 111, the document whose registration has been stopped is accelerated so as to rise to a predetermined conveyance speed before the leading end reaches the reading position by the first reading unit 20. Then transported.
Then, at the timing when the leading edge of the document detected by counting the output pulses of the reading motor 103 reaches the reading position by the first reading unit 20, the controller 100 causes the main body control unit 111 to contact the first surface of the document ( Transmission of the gate signal indicating the effective image area in the sub-scanning direction on the front side is started, and is transmitted until the trailing edge of the document passes through the reading position by the first reading unit 20. Meanwhile, the first reading unit 20 reads the image on the first surface of the document through the contact glass (transparent glass piece) 35.

  When reading an image of a single-sided document, the document that has passed through the first reading and conveying unit E is conveyed to the paper discharge unit G via the second reading unit 25 of the second reading and conveying unit F. At this time, when the controller 100 detects the leading edge of the document by the paper discharge sensor 24, the paper discharge motor 104 is driven to rotate forward to rotate the paper discharge roller 28. Further, by counting the output pulses of the paper discharge motor 104 from the detection of the leading edge of the document by the paper discharge sensor 24, the paper discharge motor 104 of the paper discharge motor 104 immediately before the trailing edge of the document comes out of the nip between the upper and lower roller pairs of the paper discharge roller 28. Control is performed so that the document discharged onto the discharge tray 29 constituting the stack portion H does not jump out by reducing the driving speed.

  The first reading roller 19 also serves as a white reference member for obtaining shading data in the first reading unit 20 as well as a function as a roller for suppressing the floating of the document in the first reading unit 20. Further, the first reading roller 19 faces the reading unit (in this case, the first reading unit 20) so that the surface having a predetermined uniform light reflectance faces the reading unit, and the distance from the reading unit is increased. It can also serve as a reference member used in the present invention that can be changed.

  When reading an image on a double-sided document, the controller 100 detects the leading edge of the document with the paper discharge sensor 24 and then counts the output pulses of the reading motor 103, so that the document is placed at a reading position by the second reading unit 25. At the timing when the leading edge arrives, the controller 100 starts transmitting a gate signal indicating an effective image area in the sub-scanning direction on the second side (back side) of the document to the main body control unit 111, and the reading position of the second reading unit 25 Is sent until the trailing edge of the document is removed. Meanwhile, the second reading unit 25 reads the image on the second surface of the document through the contact glass (transparent glass piece) 36.

  The second reading roller 26 also serves as a white reference member for obtaining shading data in the second reading unit 25, as well as a function as a roller for suppressing the floating of the document in the second reading unit 25. Further, the second reading roller 26 faces the reading unit (in this case, the second reading unit 25) with a predetermined uniform light reflectance surface directed toward the reading unit, and the distance from the reading unit is increased. It also serves as a reference member used in the present invention that can be changed.

FIG. 3 is a block diagram illustrating a configuration example of a main part of a control system of the second reading unit 25 in FIGS. 1 and 2. Since the control system of the first reading unit 20 has the same configuration, the description thereof is omitted.
The second reading unit 25 includes a light source unit 200 including an LED array, a fluorescent lamp, a cold cathode tube, or the like.

  A plurality of sensor IC chips (hereinafter abbreviated as “sensor chips”) 201 arranged in the main scanning direction (direction corresponding to the document width direction), and a plurality of amplifier circuits 202 individually connected to the sensor chips 201. And a plurality of A / D converters 203 (abbreviated as “A / D” in the drawing) 203 individually connected to each amplifier circuit 202.

Furthermore, an image processing unit 204, a frame memory 205, an output control circuit 206, and an I / F circuit 207 are also provided.
Each of the plurality of sensor chips 201 is provided with a photoelectric conversion element called a 1 × contact image sensor and a condensing lens.

A lighting signal is sent from the controller 100 to the light source unit 200 before a document (not shown) enters the reading position by the second reading unit 25.
Thereby, the light source unit 200 is turned on, and the light is emitted toward the second surface of the document (not shown). The reflected light reflected by the second surface of the document is condensed on the photoelectric conversion element by the condenser lens in the plurality of sensor chips 201 and read as image information by the photoelectric conversion element. Image information read by each sensor chip 201 is amplified by an amplifier circuit 202 and then converted into digital image information by an A / D converter 203.

  The digital image information is input to the image processing unit 204 and subjected to shading correction, and then temporarily stored in the frame memory 205. Thereafter, the data is converted into a data format acceptable by the main body control unit 111 by the output control circuit 206, and then output to the main body control unit 111 via the I / F circuit 207. Note that a timing signal for notifying the timing at which the leading edge of the document reaches the reading position by the second reading unit 25 (image data after that timing is treated as valid data), a light source lighting signal, a power source, etc. Is output.

The main body control unit 111 includes an operation unit 108 having various operation keys and a display for operating the image reading apparatus, and an image that performs processing such as displaying, printing, storing, and transmitting the read image data. A processing circuit is connected.
FIG. 4 shows a reading array unit including the light source unit 200 and the sensor chip 201 in the second reading unit 25, and is a view seen from the lower surface side of the contact glass 36 in FIG. FIG. 5 is a view in which the top and bottom are reversed and viewed from the short or hand direction, and the contact glass 36 is not shown.

The four LED substrates 401a to 401d shown in FIG. 4 correspond to the light source unit 200 in FIG. 3, and the light emitted from them is two that extend in parallel with the main scanning direction (direction corresponding to the width direction of the document). The light guides 402a and 402b are incident from both ends, light is reflected and diffused therein, and a strip-shaped light beam is emitted to the document 405 through the contact glass 36 shown in FIG. 1 (see FIG. 5).
Then, the reflected light from the document 405 is photoelectrically converted by the 1 × sensor array 404 corresponding to the sensor chip 201 of FIG. 3 through the SLA 403 which is a condenser lens (see FIG. 5).

  The distance (A in FIG. 5) between the document 405 and the second reading unit 25 through the contact glass 36 is configured so that the light beam can be most concentrated on the document 405. Even if the original density is the same, the reflected light from the original 405 becomes smaller if the position A is changed in a direction away from the optimum distance.

[Basic configuration for dust detection]
A basic configuration example for detecting dust adhering to the surface of the contact glass 36 of the second reading unit 25 on the document conveying side according to this embodiment will be described with reference to FIGS.
As described above, the second reading roller 26 serves as a roller for suppressing the floating of the document in the second reading unit 25. However, when the second reading unit 25 does not read the image of the document, the second reading roller 25 It serves as both a white reference member for acquiring shading data and a reference member for carrying out the present invention.

The second reading roller 26 also serving as the reference member is provided opposite to and in close proximity to the contact glass 36 of the second reading unit 25, and the first surface portion 26a having a low density or high reflectance and the first surface thereof. And a second surface portion 26b having a higher density or lower light reflectance than the portion 26a, and is provided so as to be movable with respect to the second reading portion 25.
FIG. 6 shows a first reference member that faces the second reading unit 25 at the time of generating shading data as the first image data (a) and at the time of generating dust detection data as the second image data (b). 2 is an explanatory diagram showing an example of a configuration for changing the rotational position of a reading roller 26. FIG.

  In the example shown in FIG. 6, the second reading roller 26 is a columnar member (may be cylindrical) as shown in FIG. 7A, and its outer peripheral surface is shown in FIG. As shown in a developed state, a part of the circumferential direction (its circumferential length is indicated by C) is formed in a band shape along the axial direction (its axial length is indicated by L), for example, as a black second surface portion 26b, Most of the outer peripheral surface excluding the second surface portion is a white first surface portion. When the second reading roller 26 does not serve as a white reference member for acquiring shading data, the first surface portion 26a is a relatively bright intermediate surface other than white, a mirror surface or a glossy surface having a high light reflectance. You may make it. The second surface portion 26b is not limited to black, and may be a gray or chromatic surface having a high density or a non-reflective surface having a low light reflectance.

  In the example shown in FIG. 6, when generating the shading data shown in FIG. 6A, the second reading roller 26 is moved so that the white first surface portion 26 a is in the first position facing the second reading portion 25. Turn in the direction shown. When generating dust detection data shown in (b), the second reading roller 26 is rotated in the direction indicated by the arrow so that the black second surface portion is in the second position where the second reading portion 26 faces the second reading portion 25. Move.

FIG. 8 shows a slide plate that is a reference member facing the second reading unit 25 when the shading data that is the first image data is generated (a) and when the dust detection data that is the second image data is generated (b). It is explanatory drawing which shows the example of a structure which changes the slide position.
In the example shown in FIG. 8, a slide plate 46 is provided as a reference member so as to face and approach the contact glass 36 of the second reading unit 25 and linearly move in parallel therewith. One half of the moving direction (arrow direction) constitutes a white first surface portion 46a, and the other half constitutes a second surface portion 46b covered with black.

Also in this case, when the slide plate 46 does not serve as a white reference member for acquiring shading data, the first surface portion 46a is a mirror surface having a relatively bright intermediate color other than white, a high light reflectance, or the like. It may be a glossy surface. The second surface portion 46b is not limited to black, and may be a gray or chromatic surface having a high density or a non-reflective surface having a low light reflectance.
In the example shown in FIG. 8, when the shading data shown in FIG. 8A is generated, the slide plate 46 is positioned in the direction indicated by the arrow so that the white first surface portion 46 a faces the second reading portion 25. Slide to. Further, at the time of dust detection data generation shown in (b), the slide plate 46 is slid in the direction indicated by the arrow so that the black second surface portion 46 b is at the second position facing the second reading portion 25.

This slide plate 46 is guided by guide members on both sides, and one end in the longitudinal direction is pulled by a spring, and is normally held at the first position shown in FIG. 8A, and only when dust detection data is detected. An end can be pulled with a plunger etc., and it can be constituted so that it may be in the 2nd position shown in (b).
The slide plate 46 is transported if the white first surface portion 46a faces the second reading unit 25 even when the second reading unit 25 reads an image of the document. In addition to guiding the original, it is possible to prevent the image from being deteriorated due to show-through in the case of a thin original.

  Here, the density is higher on the main scanning reading line on the outer surface of the contact glass 36 of the second reading unit 25 than the first surface portion (white) 26a or 46a of the second reading roller 26 or the slide plate 46 (reflection). When the dust 40 is attached, the second reading unit 25 causes the second reading roller 26 shown in FIG. 6A or the slide plate 46 shown in FIG. Detected when the shading data, which is the first image data generated by detection in the state at the position, and the second reading roller 26 or slide plate 46 shown in FIG. An example of the main scanning output level distribution of the dust detection data that is the second image data generated in this way is shown in FIG.

When the shading data is generated, the second reading roller 26 or the slide plate 46 having the white first surface portion facing the second reading portion 25 is the black second surface portion when dust detection data is generated. Since 26b or 46b is controlled to the second position facing the second reading unit 25, the dust detection data level is lower than the shading data as shown in FIG.
However, only the data level of the portion of dust 40 near the black adhering to the contact glass 36 of the second reading unit is the same level because both are extremely low and the distance does not change.

[First embodiment of dust detection function]
A first embodiment of the dust detection function (dust adhesion determination method) according to the present invention will be described with reference to FIGS. When the shading data that is the first image data at each position of the main scan in FIG. 9 is D1 (n) and the dust detection data that is the second image data is D2 (n), D1 (n ) -D2 (n) value distribution with respect to the main scanning position is shown by a solid line in FIG. Here, n is the order from one end to the other end of the main scanning range of the sensor chip 201 (corresponding to the condensing lens SLA403 in FIG. 4) arranged in the main scanning range shown in FIG. This corresponds to the read pixel position in the scanning direction.

The same applies to the case where the above-described slide plate 46 is used as the reference member. Hereinafter, an example in which the second reading roller 26 is used will be described.
Even if the second reading roller 26 moves, the position of the dust 40 and the reflectance thereof do not change. Therefore, the portion where the dust 40 is attached becomes D1 (n) ≈D2 (n), and D1 (n) −D2 (n ) ≈0 or very small value. Therefore, when D1 (n) −D2 (n) is compared with a preset dust detection threshold level th and becomes a value less than or less than that, dust adheres to the second reading unit 25. It can be judged.
Note that the larger the difference in density between the outer peripheral surface of the second reading roller 26 and the dust adhering to the second reading unit 25, the easier it is to determine the adhering of the dust.

Here, the dust detection operation described above will be described in more detail with reference to FIG. 11 which is a block diagram showing the configuration of the image processing unit 204 in FIG. 3, the tongue chart of FIG. 12, and the flowchart of FIG.
The image processing unit 204 illustrated in FIG. 11 includes a shading correction circuit 701, a shading data generation circuit 702, a dust detection data generation circuit 703, and a dust detection circuit 704. Further, the line synchronization signal LSYNC, the shading data gate signal S_GATE, and the dust detection gate signal D_GATE shown in FIG. 12 are input from the controller 100, and the dust detection signal D_DTCT is output from the dust detection circuit 704 to the controller 100.

Image data Din input from the A / D converter 203 of FIG. 3 to the image processing unit 204 is input to the shading correction circuit 701, the shading data generation circuit 702, and the dust detection data generation circuit 703.
When the second reading unit 25 is not reading the image of the document, the shading data generating circuit is in a period of the gate signal S_GATE = “L” from the controller 100 with the second reading roller 26 in the first position. In 702, shading data is generated from the average value of the image data Din of a plurality of lines. The position of the second reading roller 26 at this time is the first position when the shading data is generated as shown in FIG.

Since the shading data includes dark noise and light shot noise, the output level can be stabilized by averaging the image data Din of a plurality of lines and generating the shading data, and the dust detection accuracy can be improved. .
The shading correction circuit 701 performs shading correction on the image data Din input thereafter with the shading data, and outputs image data Dout having a uniform main scanning output level distribution.

Further, dust detection data is generated by the dust detection data generation circuit 703 during the period of the gate signal D_GATE = “L” from the controller 100. The position of the second reading roller 26 at this time is the second position at the time of dust detection data generation shown in FIG.
The dust detection circuit 704 detects a level difference between the shading data D1 (n) and the dust detection data D2 (n) for each pixel, and a difference within a predetermined dust detection width (less than the threshold level value th in FIG. 8 or In the case of the following), the controller 100 notifies the controller 100 that there is dust as a dust judgment signal D_DTCT = “L”.

  According to the flowchart of FIG. 13, when the dust detection process is started when the second reading unit 25 is not reading an image of a document, the controller 100 first sets the gate signal S_GATE = “L” in step S1 and the shading data. The generation circuit 702 acquires image data Din (by image reading in the state of FIG. 6A) by the first reading method and stores it as shading data D1 (n) that is the first image data.

Thereafter, in step S <b> 2, the second reading roller 26 is moved to the position shown in FIG. 6B and separated from the second reading unit 25.
In step S3, the controller 100 sets the gate signal D_GATE = “L”, and the dust detection data generation circuit 703 obtains the image data Din by the second reading method (by reading the image in the state of FIG. 6B). Then, it is stored as dust detection data D2 (n) which is the second image data.

  Next, in step 4, the dust detection circuit 704 calculates a level difference D1 (n) −D2 (n) between the shading data D1 (n) and the dust detection data D2 (n) for each pixel, and sets a predetermined threshold level value. Compare with th. When D1 (n) −D2 (n) <th (less than th), the process proceeds to step S5 to set the dust determination signal D_DTCT = “L”, notifies the controller 100 that dust is present, and ends the process. If D1 (n) −D2 (n) ≧ th up to the last pixel in step 4, the processing is terminated with the dust determination signal D_DTCT = “H”, and dust adhesion is not detected. Note that it may be determined that there is dust when D1 (n) −D2 (n) ≦ th (th or less).

  3 is notified to the main body control unit 111 of FIG. 3, and the main body control unit 111 displays it on the display of the operation unit 108 or generates a warning sound. To inform the user to prompt cleaning of the contact glass 36 of the second reading unit. It is desirable not to start reading an image of a document until the display is reset after cleaning, or the apparatus is turned off and then turned on again, and the dust detection process results in the determination that no dust is attached.

  This dust detection process is performed when the second reading unit 25 is not reading an image of a document, for example, when the image reading device is turned on, or at least one before or after starting a document reading job. When the ADF is opened / closed, the document is set, or the like, or a plurality of conditions may be used. If reading quality is important even if productivity is lowered, it is desirable to execute it every scan. These dust detection processing start conditions may be arbitrarily selected by the user from the operation unit 108.

[Second Embodiment of Dust Detection Function]
A second embodiment of the dust detection function (dust adhesion determination method) according to the present invention will be described with reference to FIGS.
In this embodiment, shading data (here, Dsh) when dust is attached on the main scanning reading line of the contact glass 36 of the second reading unit 25 and dust detection data (here, ( The input image data Din at the time of image reading in the state of b) is as shown in FIG. 14A, and Dsh and Din are shading data D1 as the first image data shown in FIG. This corresponds to (n) and dust detection data D2 (n) which is the second image data.
With this shading data Dsh and the input image data Din at the time of dust detection, dust detection data D (n) subjected to shading correction processing as shown in FIG. 12B can be generated.

The shading correction calculation is performed by the following equation.
Dout = Din / Dsh × (2 ⁿ −1)
Dsh: Shading data Din: Input image data “ ⁿ ” of the above “2 ⁿ ” is the number of bits of the image data, “8” if it is 8-bit data, and “2 ⁿ ” is “256”.

When this shading correction calculation is performed for each pixel, since the ratio is substantially constant at Din <Dsh in the pixels where dust is not attached, the calculation output Dout is substantially constant, but dust is attached. Since the ratio of Din≈Dsh and the ratio is almost “1” in the case of 8-bit data, the value of the pixel is around “255”, and other parts are shown in FIG. More protruding and larger.
From the dust detection data D (n) subjected to the shading correction process, it is possible to detect the presence or absence of dust and the position in the main scanning direction when it is attached.

  FIG. 15 is a block diagram showing a circuit configuration example for realizing the second embodiment of the dust detection function of the image processing unit 204 in FIG. Since the image processing unit 204 is configured by a circuit having the same name as the image processing unit 204 of the first embodiment shown in FIG. 11, the same reference numerals are used.

  The image processing unit 204 differs from the image processing unit 204 of the first embodiment shown in FIG. 11 in that input image data Din is input only to the shading correction circuit 701 and the shading data generation circuit 702 to generate dust detection data. The circuit 703 receives Dout as an output of the shading correction circuit 701 and generates dust detection data D (n) subjected to the shading correction processing therefrom. The dust detection circuit 704 determines whether or not dust is attached from the dust detection data D (n) shown in FIG. 12B, and if it is determined that dust is attached, The difference is that the position in the main scanning direction is also detected.

The operation of the dust detection process will be described with reference to the flowchart of FIG.
When the process shown in FIG. 16 is started when the second reading unit 25 is not reading an image of a document, the controller 100 first sets the gate signal S_GATE = “L” in step S11, and the shading data generation circuit 702 performs the first processing. Image data Din is acquired by the reading method (by reading the image in the state of FIG. 6A), and shading data Dsh is generated and stored from the average value of a plurality of lines in the period of S_GATE = “L”.
Thereafter, in step S <b> 12, the second reading roller 26 is moved to the position shown in FIG. 6B and separated from the second reading unit 25.

Then, when the controller 100 sets the gate signal D_GATE = “L” in step S13, the shading data generation circuit 702 uses the second reading method (by reading the image in the state of FIG. 6B) and shading with the image data Din. by the shading data Dsh from the data generating circuit 702 performs a correction operation of ^{Dout = Din / Dsh × (2} n -1), and input the output Dout is the dust detection data generating circuit 703, in FIG. 14 (b ) To generate and store dust detection data D (n) corrected for shading.

  Next, in step 14, the dust detection circuit 704 calculates the level difference D (n−1) −D (n) from the value of the dust detection data subjected to the shading correction to the data value of the previous pixel for each pixel. Then, it is compared with a preset threshold level value th (different from the threshold level value th of the second embodiment). When D (n−1) −D (n)> th (a value exceeding th), the process proceeds to step S5 to set the dust determination signal D_DTCT = “L” and output the value of n to the controller 100. Then, the presence of dust is notified, and the dust attachment position (the nth pixel from one end) in the main scanning range is notified, and this processing is terminated.

If D (n−1) −D (n)> th is not satisfied up to the last pixel in step 14, the process ends with the dust determination signal D_DTCT = “H”, and no dust adhesion is detected. It will be. Note that it may be determined that there is dust when D (n−1) −D (n) ≧ th (th or more).
The method of notifying the user when dust adhering (with dust) is detected and the execution timing of this dust detection processing are the same as in the case of the first embodiment described above.
According to this embodiment, the attachment of dust can be detected with higher accuracy, and the attachment position can also be detected in units of pixels.

[Common changes]
In the first and second embodiments described above, as shown in the timing chart of FIG. 17, the dust detection gate signal D_GATE output from the controller 100 is activated for a plurality of line periods, and the image data in the period of D_GATE = “L”. If dust detection data is generated from (averaged) the average value, stable dust detection data from which noise has been removed can be generated.

  Further, the operation unit 108 shown in FIG. 3 includes various operation key groups 108a including a reading start key and a numeric keypad and a display unit 108b using a liquid crystal display panel as shown in FIG. When the controller 100 notifies the operation unit 108 of dust detection via the main body control unit 111 of FIG. 3, a display such as “There is dust in the ADF. Please clean.” Is displayed on the display unit 108a. Thus, the user can be prompted to clean.

  In each of the embodiments described above, an example in which the outer peripheral surface of the second reading roller 26 is white and dust of a color close to black adheres to the contact glass 36 of the second reading unit 25 has been described. When such dust is attached, shading data and dust detection data as shown in FIG. 19 are acquired. Even in this case, the level of the image data of the pixel at the position where dust is attached does not change due to the movement of the second reading roller 26, and the levels of the shading data and the dust detection data are almost the same.

  Further, the second reading roller 26 or the slide plate 46 is not used as a white reference member, the outer peripheral surface is made relatively light gray, and white dust such as paper dust adheres to the contact glass 36 of the second reading unit 25. In such a case, shading data and dust detection data as shown in FIG. 20 are acquired. In this case, the level of the image data of the pixel at the position where dust is attached does not change due to the movement of the second reading roller 26 or the slide plate 46, and is always a high level. The bell is almost the same.

  As described above, in any case, the level of the image data of the pixel at the position where dust is attached is not changed by the movement of the second reading roller 26 or the slide plate 46, and the shading data which is the first image data. Since the level of the dust detection data as the second image data is almost the same, if the difference is taken as in the first embodiment, the pixel data at the position where the dust is attached is almost zero. Therefore, the adhesion of dust can be detected.

Even when dust detection data that has been subjected to shading correction is generated as in the second embodiment, the values of the shading data Dsh and the input image data at the time of dust detection are substantially the same at the pixel where dust is attached. Therefore, the ratio becomes substantially “1”, and the output of Dout = Din / Dsh × (2 ⁿ −1) by the shading correction calculation increases in a peak shape. By comparing it with a preset value or by taking the difference from the value of the previous pixel for each pixel and comparing it with a preset value, dust adhesion and even the position is detected. can do. In this manner, the adhesion can be detected in the same manner regardless of the color and density of the dust.

  Further, in each of the above-described embodiments, the case where the adhesion of dust to the contact glass 36 of the second reading unit 25 illustrated in FIG. 1 has been described, but the dust on the contact glass 35 of the first reading unit 20 is also described. Of course, the present invention can be similarly applied to the detection of adhesion.

[Specific Example of Second Reading Roller]
Here, a specific configuration example of the second reading roller illustrated in FIG. 6 will be described with reference to FIGS. 21 and 22.
As shown in FIG. 21, a second reading roller 26 having a cylindrical shape (which may be a columnar shape) having a plurality of surfaces whose outer peripheral surfaces are different in density is provided facing the contact glass 36 of the second reading unit 25. Yes. At least one of the surfaces, in this example, the circumferential range 26 (SH) and the range 26 (Y), is a white first surface portion 26 a that is a density for shading data. As the surface width in the direction, a surface range 26 (SH) used when generating shading data and a surface range 26 (Y) necessary when reading a document are secured.

Also, as shown in FIG. 22, a part of the outer peripheral surface is a second surface portion 26b for acquiring dust detection data having a predetermined width and a low reflectance over the entire length in the axial direction.
A rotation shaft 209 passes through the center of the second reading roller 26, and a gear 210 to which a rotational driving force is transmitted from a stepping motor (not shown) is fixed to a projecting end of the rotation shaft 209. Can be rotated. A filler 211 for controlling the rotational position of the second reading roller 26 is provided in the radial direction on the other end protruding portion of the rotation shaft 209 on the opposite side (position rotated by 180 °) from the second surface portion 26b. It is attached to extend. Further, a transmissive photoelectric sensor 212 is provided so as to sandwich the filler 211 at the lowermost part so as to detect the filler 211 at a position directly below.

Therefore, the second reading roller 26 rotates, the second surface portion 26b is positioned directly above as shown in FIG. 22, and the second surface portion 26b is the second reading portion as shown in FIG. 25, the light emitting part and the light receiving part of the photoelectric sensor 212 are shielded from light by the filler 211, so that the stepping motor (not shown) is detected and the rotation of the second reading roller 26 is stopped. This position is set as the home position of the second reading roller 26.
From the home position, a predetermined pulse for the stepping motor is set in each of the range 26 (SH) and the range 26 (Y), and the rotation amount of the second reading roller 26 is controlled by the pulse amount.

  When a gate signal for shading operation is transmitted from the main body control unit 111 shown in FIG. 3, the stepping motor is driven by a predetermined number of pulses from the home position, which is the detection position of the filler 211 by the photoelectric sensor 212, and the second The rotation of the reading roller 26 is controlled so that the range 26 (SH) of the white first surface portion 26 a is located at a position facing the second reading portion 25. From there, the second reading unit 25 performs an image reading operation to acquire shading data of a plurality of lines (first reading method).

Thereafter, if the stepping motor is driven reversely by the same number of pulses, the photoelectric sensor 212 detects the filler 211, and the second surface portion 26 b having a high density of the second reading roller 26 and a low reflectance becomes the second reading portion 25. The second reading unit 25 performs an image reading operation within the range, and acquires dust detection data for several lines (second reading method).
The shading data and dust detection data are sent to the image processing unit 204, and the presence / absence of dust is determined as described above.

  After the dust detection data is acquired, the left end portion of the second reading roller 26 faces the opposite portion of the second reading portion 25 in FIG. 21 in the circumferential range 26 (Y) of the first surface portion 26a when the reading of the document starts. The second reading roller 26 is rotationally controlled so as to reach the position, and waits until a gate signal for starting document reading by the second reading unit 25 is received.

When the gate signal is input, the second reading unit 25 starts reading. During the reading, the second reading roller 26 rotates in the document conveyance direction (when the document is conveyed from left to right in FIG. 21, the second reading roller 26 rotates to the right). Control is performed so that one document is read by the second reading unit 25 while (Y) faces the second reading unit 25. Therefore, the rotation speed v of the second reading roller 26 at the time of document reading is: document reading time (document length / conveyance linear speed) = ty, width in the circumferential direction of the range 26 (Y) in the first surface portion 26a. Is by, v = by / ty.
At this time, the second reading roller 26 rotates while suppressing the back surface of the document conveyed along the contact glass 36 of the second reading unit 25 to prevent the document from being lifted. The distance to the surface is not changed, and clear image reading is always possible.

  As described above, when reading the image of the document by the second reading unit 25, the portion 26 (Y) (preferably white, having the same density as the portion 26 (SH) used when the second reading roller 26 acquires the shading data is used. A portion of a range different from the portion used for acquiring shading data) is used while acquiring shading data of the first surface portion 26a by performing reading while rotating the portion in the document transport direction so as to face the second reading portion 25. The portion (SH) can be protected from contamination by the original. Further, since reading is performed at a portion having the same density (preferably white) as the portion used when acquiring shading data, it is possible to prevent image deterioration due to show-through.

  The image reading apparatus and dust adhering determination method according to the present invention are not limited to the above-described embodiments, and an image of a document conveyed in the sub-scanning direction by a reading unit with a fixed reading position is displayed in the main scanning direction. A first surface portion having a low density or a high reflectance facing the reading unit and a second surface having a higher density or a lower light reflectance than the first surface portion. A reference member having a surface portion of the reference member is provided so as to be movable with respect to the reading portion. When the reading portion is other than reading an image of a document, the first surface portion is opposed to the reading portion. In the first position, the reading unit performs an image reading operation to acquire first image data, and the reference member is set in the second position where the second surface portion faces the reading unit, and the reading is performed. The image reading operation to the second image Get the data, it is sufficient to determine whether dust on the reading section on the basis of the first image data and the acquired second image data is attached.

  The first image data acquired from the reading unit with the first surface portion having a low density or high reflectance of the reference member (a white surface when shading data is acquired) facing the reading unit. A second image acquired from the reading portion with the second surface portion having a higher density or lower light reflectance than the first surface portion of the reference member facing the reading portion. Although the data level is lowered, the reading level of dust adhering to the contact glass of the reading unit does not change. Therefore, it is possible to determine whether dust is attached to the reading unit by various methods based on the first image data and the second image data.

  The shape and moving means of the reference member can be variously changed, and in addition to those described in the embodiment, for example, a rectangular tube or a prismatic rotating member having a plurality of portions having different concentrations or reflectances on the surface, or a disc Rotating (rotating) members such as a fan shape or a fan blade shape or a radiating blade shape, or a front / back reversing member may be used. This reference member can also be used as a white reference member for acquiring shading data, a holding roller or a holding plate that suppresses the floating of the document when the image is read by the reading unit, or a guide member that guides the conveyance of the document. You can also.

  The present invention can be used for an image reading unit of an image forming apparatus such as a digital copying machine, a digital multifunction peripheral, and a facsimile machine, and an image reading apparatus such as a scanner device. Particularly, in an image reading apparatus having an automatic document feeder (ADF) and having a function of sequentially reading an image of a document conveyed in the sub-scanning direction by the ADF by a reading unit in a state where the reading position is fixed. Therefore, it is possible to detect dust adhering to the reading unit in a timely manner so that the user can quickly take appropriate measures such as prompting the user to clean.When the scanned image data is displayed or printed, It is possible to prevent streaks or black streaks from appearing in the image and degrading the image quality.

A: Document setting unit B: Separating and feeding unit C: Registration unit D: Turn unit E: First reading and conveying unit F: Second reading and conveying unit G: Paper discharging unit H: Stack unit 1: Document bundle 2: Document table
19: 1st reading roller 20: 1st reading part 25: 2nd reading part 26: 2nd reading roller 26a: 1st surface part 26b: 2nd surface part 35, 36: Contact glass 40: Dust 46: Slide Plate 46a: First surface portion 46b: Second surface portion

100: Controller 108: Operation unit 111: Main body control unit
113: Image processing circuit 200: Light source unit 201: Sensor chip 202: Amplifier circuit 203: A / D converter 204: Image processing unit 205: Frame memory 206: Output control circuit 207: I / F circuit 5: Output circuit 6:
701: Shading correction circuit 702: Shading data generation circuit 703: Dust detection data generation circuit 704: Dust detection circuit

JP 2002-290685 A

Claims (23)

In an image reading apparatus having a function of reading an image of a document conveyed in the sub-scanning direction in the main scanning direction by a reading unit whose reading position is fixed,
A reference member having a first surface portion having a low density or high reflectance facing the reading unit and a second surface portion having a higher density or lower light reflectance than the first surface portion, Provided to be movable with respect to the reading unit,
When the reading unit is not reading an image of a document, the reference member is set to a first position where the first surface portion faces the reading unit, and the reading unit is caused to perform an image reading operation. Means for acquiring the image data, and the reference member is set to the second position where the second surface portion faces the reading portion, and the reading portion is caused to perform an image reading operation to acquire the second image data. Means to
An image reading apparatus comprising: a determination unit that determines whether dust is attached to the reading unit based on the first image data and the second image data.   The determination unit calculates a difference for each corresponding pixel of the first image data and the second image data, and dust is attached when the difference is less than or less than a preset value. The image reading apparatus according to claim 1, wherein the image reading apparatus is a unit that determines that the image is present.   The means for acquiring the first image data obtains the first image data by averaging the image data of a plurality of line periods output from the reading unit when the reference member is at the first position. The image reading apparatus according to claim 1, wherein the image reading apparatus is a means for performing the above operation.   The means for acquiring the second image data obtains the second image data by averaging the image data of a plurality of line periods output from the reading unit when the reference member is at the second position. The image reading apparatus according to claim 3, wherein the image reading apparatus is a means for performing the processing. The first surface portion of the reference member is a white surface;
The means for obtaining the first image data is means for obtaining shading data, and the means for obtaining the second image data is means for obtaining dust detection data,
The determination unit is a determination unit that determines whether dust is attached to the reading unit based on the shading data and the dust detection data acquired by each of the units. 5. The image reading device according to any one of items 1 to 4. In an image reading apparatus having a function of reading an image of a document conveyed in the sub-scanning direction in the main scanning direction by a reading unit whose reading position is fixed,
A reference member having a first surface portion that is a white surface facing the reading portion and a second surface portion having a higher density or lower light reflectance than the first surface portion is disposed on the reading portion. To be movable,
When the reading unit is not reading an image of a document, the reference member is set to a first position where the first surface portion faces the reading unit, and the reading unit performs an image reading operation. Means for acquiring image data input from the image generation unit, generating shading data, shading correction unit for correcting the shading of input image data input from the reading unit using the shading data, and the reference member Image data obtained by causing the reading unit to perform an image reading operation with the second surface portion facing the reading unit in a second position, and input image data input from the reading unit being subjected to shading correction by the shading correction unit To generate dust detection data by acquiring
An image reading apparatus comprising: determination means for determining whether dust is attached to the reading unit based on dust detection data generated by the means.   The determination means compares the value of the dust detection data with the previous pixel for each pixel, and when the difference value exceeds a preset value or exceeds the preset value, The image reading apparatus according to claim 6, wherein the image reading apparatus detects that the dust is attached and detects a dust attached position based on the pixel position at that time. The shading correction means, when the input image data input from the reading unit is Din, the shading data is Dsh, the output image data after shading correction is Dout, and the number of bits of the image data is n,
Dout = Din / Dsh × (2 ⁿ −1)
The image reading apparatus according to claim 6, wherein the image reading apparatus is a means for performing a shading correction process by the calculation of   The image reading apparatus according to claim 6, wherein the preset value in the determination unit is a high level value close to a maximum value of the image data subjected to the shading correction. .   The means for generating the shading data is means for generating the shading data by averaging the image data of a plurality of line periods output from the reading unit when the reference member is at the first position. The image reading apparatus according to claim 6, wherein the image reading apparatus is characterized in that:   The means for generating dust detection data is means for generating the dust detection data by averaging the image data of a plurality of line periods subjected to shading correction by the shading correction means when the reference member is at the second position. The image reading apparatus according to claim 10, wherein:   12. The image reading apparatus according to claim 1, further comprising means for notifying a user of dust when it is determined by the determination means that dust is attached. 13. Reader.   13. The image reading apparatus according to claim 1, further comprising means for keeping the reference member in the first position even when the reading unit reads an image of a document. An image reading apparatus.   The reference member is a cylindrical or columnar member, and a part of the outer circumferential surface of the outer circumferential surface constitutes the second surface portion in a band shape along the axial direction, and the second surface portion is excluded. The image reading apparatus according to claim 6, wherein the outer peripheral surface constitutes the first surface portion formed of a white surface. The image reading apparatus according to claim 14.
During the period when the means for generating the shading data acquires image data from the reading unit and generates shading data, the first surface portion of the reference member faces the reading unit and generates the dust detection data. The reference member so that the second surface portion of the reference member faces the reading unit during a period in which the image data corrected by the shading correction unit is acquired and the dust detection data is generated. An image reading apparatus comprising a rotating means for rotating the lens in the circumferential direction.
.   The image according to claim 15, wherein the rotation unit rotates the reference member so that the first surface portion faces the reading unit even during a period in which the reading unit reads an image of a document. Reader.   The cylindrical or columnar reference member also functions as a restraining roller that suppresses floating of the document when the reading unit reads the image of the document. The image reading apparatus described. (Method claim)
A dust adhesion determination method for determining whether dust is attached to the reading unit in an image reading apparatus that reads an image of a document conveyed in the sub-scanning direction in a main scanning direction by a reading unit having a fixed reading position. Because
When the reading unit is not reading an image of a document, a first surface portion having a low reference member density or a high reflectance is opposed to the reading unit, and the reading unit is caused to perform an image reading operation. The second surface portion having a higher density or lower light reflectance than the first surface portion of the reference member is opposed to the reading portion, and the reading portion is caused to perform an image reading operation. 2 image data,
A dust adhesion determination method for an image reading apparatus, comprising: determining whether dust is attached to the reading unit based on the first image data and the second image data.   In the determination, a difference is calculated for each corresponding pixel between the first image data and the second image data, and dust is attached when the difference is less than or less than a preset value. The dust adhesion determination method in the image reading apparatus according to claim 18, wherein the determination is made as follows. The first surface portion of the reference member is a white surface,
Obtaining shading data as the first image data, obtaining dust detection data as the second image data,
20. The dust adhesion in the image reading apparatus according to claim 18, wherein, in the determination, it is determined whether dust is attached to the reading unit based on the shading data and the dust detection data. Judgment method. In an image reading apparatus that reads an image of a document conveyed in the sub-scanning direction in a main scanning direction by a reading unit whose reading position is fixed, dust for detecting whether dust is attached to the reading unit is detected. An adhesion determination method,
When the reading unit is not reading an image of a document, the reading unit is caused to perform an image reading operation with the first surface portion made of a white surface of the reference member facing the reading unit. The image data input from the unit is acquired to generate shading data, and then the input image data input from the reading unit is subjected to shading correction using the shading data, and the first surface portion of the reference member An image reading operation is performed on the reading unit with the second surface portion having a higher density or lower light reflectance facing the reading unit, and the input image data input from the reading unit is subjected to the shading. The image data corrected by the shading by the correction means is acquired to generate dust detection data,
A dust adhesion determination method in an image reading apparatus, wherein it is determined whether dust is attached to the reading unit based on the dust detection data.   In the determination, the value of the dust detection data is compared with the previous pixel for each pixel, and dust is detected when the difference value exceeds a preset value or more than the preset value. The dust adhesion determination method according to claim 21, wherein the dust adhesion position is detected based on the pixel position at that time and the dust adhesion position is detected based on the pixel position at that time. When the input image data input from the reading unit is Din, the shading data is Dsh, the output image data subjected to the shading correction is Dout, and the number of bits of the image data is n.
Dout = Din / Dsh × (2 ⁿ −1)
23. The dust adhesion determination method in the image reading apparatus according to claim 21, wherein the dust adhesion determination method is performed by the following calculation.

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