JP2009111812A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reader capable of detecting even white dust. <P>SOLUTION: Platen glass 35 has a first main surface s1 positioned on the side of an original P and a second main surface s2 facing the first main surface s1. A planar light source 30 is provided on the side of the first main surface s1, and irradiates the platen glass 35 with light in the state that there is no original P present on the first main surface s1. A CCD 34 is provided on the side of the second main surface s2, and picks up the image of the platen glass 35 by the light which has passed through the platen glass 35. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image reading apparatus, and more particularly to an image reading apparatus used as an image input apparatus in a copying machine, a scanner, or the like.

  In the image reading apparatus, in order to improve the quality of the read image, the presence or absence of dust on the platen glass is detected before reading the document. Specifically, the detection of the presence or absence of dust is performed by the following method. FIG. 6 is a configuration diagram of a conventional sheet-through type image reading apparatus.

  First, the exposure lamp 102 provided for reading a document is turned on. Thereby, the light from the exposure lamp 102 passes through the platen glass 100 and irradiates the presser white plate 104. Thereafter, the light is reflected by the presser white plate 104, passes through the platen glass 100 again, is reflected by a mirror (not shown), and is guided to a CCD (Charge Coupled Device) (not shown). Thereby, an image of the presser white plate 104 is obtained.

  Here, when the dust D exists on the platen glass 100, a part of the light from the exposure lamp 102 is not reflected by the presser white plate 104 but by the dust D as shown by an arrow in FIG. reflect. The light reflected by the dust D is reflected by a mirror (not shown) and guided to a CCD (not shown). Thereby, an image of the presser white plate 104 on which the dust D is reflected is obtained. A control unit (not shown) analyzes this image and detects the presence or absence of dust D (see, for example, Patent Document 1).

However, in the image reading apparatus, when white dust such as paper dust exists on the platen glass 100, there is a problem that the control unit cannot accurately detect the presence or absence of the dust D. Specifically, in the image reading apparatus, the light reflected by the dust D is received by the CCD. Therefore, when the dust D is white, an image in which the white dust D is positioned in the presser white plate 104 is obtained. Therefore, even if the control unit analyzes the image, the control unit cannot distinguish the white dust D from the presser white plate 104 and cannot accurately detect the white dust D. As a result, when image reading is performed in the sheet-through type image reading apparatus, white streaks are formed in the read image as shown in the read image example shown in FIG.
JP 2000-349964 A

  Therefore, an object of the present invention is to provide an image reading apparatus that can accurately detect white dust.

  According to the present invention, in the image reading apparatus, a transparent plate having a first main surface located on the document side, a second main surface opposite to the first main surface, and the first main surface side. A light source that irradiates light to the transparent plate and light that has passed through the transparent plate in a state where the original is not present on the first main surface. And an image pickup means for picking up an image of the transparent plate.

  According to the present invention, since the light is irradiated from the first main surface side of the transparent plate, when the foreign matter exists on the transparent plate, the foreign matter forms a black shadow on the transparent plate. . Therefore, according to the present invention, when white dust is present on the transparent plate, the presence of the white dust can be detected by detecting the shadow of the white dust.

  In the present invention, the image forming apparatus may further include a determination unit that determines whether or not a foreign object exists on the transparent plate based on the image of the transparent plate captured by the imaging unit.

  In the present invention, the image forming apparatus further includes conveying means for conveying the original so as to pass through the reading position of the first main surface, and the imaging means picks up an image of the original that passes through the reading position. Good.

  In the present invention, further comprising a slider incorporating a reflecting member that reflects the light that has passed through the transparent plate and guides it to the imaging unit, and a moving unit that moves the slider to move the reading position, The moving means may move the reading position when the determining means determines that there is a foreign object at the reading position.

  In the present invention, further comprising a slider incorporating a reflecting member that reflects the light that has passed through the transparent plate and guides it to the imaging unit, and a moving unit that moves the slider to move the reading position, The moving means moves the plurality of sliders to move the reading position, and the imaging means takes an image of the transparent plate while the moving means moves the reading position, The determination unit may specify a position with the least foreign matter in the image of the transparent plate, and the moving unit may move the reading position to a position with the least foreign matter.

  In the present invention, the light source may be a planar light source.

  Hereinafter, an image reading apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

(Overall configuration of image reading device)
FIG. 1 is a configuration diagram of an image reading apparatus 1 according to an embodiment of the present invention. The image reading apparatus 1 includes a document conveying unit 2 as a document conveying unit that conveys the document P so as to pass the reading position A, and a reading unit that optically reads an image of the document P conveyed at the reading position A. The image reading unit 3 includes the image reading unit 3. The image reading apparatus 1 includes a platen set method for reading an image of the document P placed on the platen glass 38 and a sheet-through method for reading an image of the document P conveyed on the platen glass 35 by the document conveying unit 2. Two types of image reading methods can be executed. In the present embodiment, since the image reading is performed by the sheet through method, the description of the platen set method is omitted.

  In the following, for simplicity of explanation, “the conveyance direction of the document P” is simply referred to as “conveyance direction”, “upstream side of the conveyance direction of the document P” is simply referred to as “upstream side”, and “ The “downstream side in the transport direction” is simply referred to as “downstream side”. Further, a direction perpendicular to the paper surface of FIG. 1 is defined as a “main scanning direction”.

  First, the configuration of the document conveying unit 2 will be described. The document transport unit 2 includes a paper feed tray 20, a pickup roller 21, a separating roller 22, a paper feed roller 23, a registration roller pair 24, a pre-reading roller pair 25, a post-reading roller pair 27, a paper discharge roller pair 28, and a paper discharge tray. 29 and a planar light source 30.

  A plurality of documents P are placed on the sheet feed tray 20. The pickup roller 21 picks up a part of a plurality of documents P. The separating roller 22 and the sheet feeding roller 23 separate and convey one by one when a plurality of documents P are picked up by the pickup roller 21. The registration roller pair 24 corrects the skew of the original P that has been conveyed one by one and conveys it to the pre-reading roller pair 25. The pre-reading roller pair 25 conveys the document P on the platen glass 35. After reading, the roller pair 27 conveys the original P that has passed over the platen glass 35 to the paper discharge roller pair 28. The paper discharge roller pair 28 discharges the original P conveyed from the roller pair 27 after reading onto the paper discharge tray 29.

  Next, the configuration of the image reading unit 3 will be described. The image reading unit 3 includes a first slider 31, a second slider 32, an imaging lens 33, a CCD 34, a platen glass 35, a step sheet 36, a scooping guide 37, a platen glass 38, a motor 39 and a control unit 40. The first slider 31 includes an exposure lamp 41 and a first mirror 42. The second slider 32 includes a second mirror 43 and a third mirror 44.

  The platen glass 35 is a transparent plate having a first main surface s1 positioned on the side of the original P that is conveyed at the reading position A, and a second main surface s2 that faces the first main surface s1. .

  The exposure lamp 41, the first mirror 42, the second mirror 43, the third mirror 44, the imaging lens 33 and the CCD 34 serve as reading means for optically reading the image of the document P conveyed at the reading position A. . Specifically, the exposure lamp 41 is arranged on the second main surface s2 side, plays a role of irradiating light to the reading position A, and is realized by, for example, a fluorescent lamp. The first mirror 42, the second mirror 43, and the third mirror 44 are arranged on the second main surface s 2 side, and serve to guide the light reflected by the document P conveyed to the reading position A to the imaging lens 33. Fulfill. Specifically, the first mirror 42 reflects the light reflected by the document surface conveyed to the reading position A in the left direction in FIG. The second mirror 43 reflects the light reflected by the first mirror 42 downward in FIG. The third mirror 44 reflects the light reflected by the second mirror 43 in the right direction in FIG.

  The imaging lens 33 is disposed on the second main surface s2 side, and plays a role of imaging the light reflected by the first mirror 42, the second mirror 43, and the third mirror 44 on the CCD 34. The CCD 34 is arranged on the second main surface s2 side, has a light receiving area for one line extending in the main scanning direction, can capture image data for one line extending in the scanning direction, and passes through the reading position A. Based on the light reflected at P, it plays a role as an image pickup means for picking up an image of the original P. Further, the CCD 34 converts the image of the original image formed by the imaging lens 33 into digital image data.

  The first slider 31 and the second slider 32 can translate in the transport direction. The moving speed of the first slider 31 is twice the moving speed of the second slider 32. As a result, even if the first slider 31 and the second slider 32 move, the optical distance from the reading position A to the CCD 34 does not change. The motor 39 serves as a moving unit that moves the first slider 31 and the second slider 32 to move the reading position A in the transport direction.

  Here, the configuration near the reading position A will be described in more detail with reference to FIG. FIG. 2 is a diagram illustrating a configuration of the image reading apparatus 1 in the vicinity of the reading position A.

  Around the platen glass 35, a reading guide 51 and a scooping guide 37 for scooping up the document P that has passed the reading position A are arranged. Further, in order to prevent the document P being conveyed from directly touching the platen glass 35, the stepped sheet 36 has a stepped portion C on the surface of the platen glass 35 on the document P side upstream of the reading position A. It is provided to be formed. As a result, the stepped portion C, which is the edge portion of the stepped sheet 36, is provided on the upstream side of the reading position A, and forms a surface higher than the surface of the platen glass 35 on the original P side (the upper surface of the stepped sheet 36). To come.

  In this image reading apparatus 1, the document P conveyed rightward while sliding on the upper surface of the step sheet 36 by the pre-reading roller pair 25 and the post-reading roller pair 27 has a reading position A at a predetermined height depending on the thickness of the step sheet 36. Therefore, it is conveyed in a non-contact state with the platen glass 35, and an image of the original is read by the reading means through the platen glass 35. Since there is a gap between the document surface and the platen glass 35, adhesion of adhesive foreign matter such as correction liquid to the platen glass 35 is suppressed.

  By the way, in the image reading apparatus 1, the planar light source 30 is provided on the first main surface s <b> 1 side of the platen glass 35 in order to be able to detect white dust D such as paper dust that has been difficult to detect. . More specifically, the planar light source 30 is attached to the document conveying section 2 so as to face the first main surface s1 of the platen glass 35. The planar light source 30 irradiates the platen glass 35 with light in a state where the document P does not exist on the first main surface s 1 of the platen glass 35. The planar light source 30 is realized by, for example, an organic EL element or an inorganic EL element.

  The light irradiated by the planar light source 30 passes through the platen glass 35. At this time, as shown in FIG. 2, if dust D exists on the reading position A of the platen glass 35, part of the light irradiated by the planar light source 30 is absorbed by the dust D. As a result, a black shadow of dust D is formed on the platen glass 35.

  Thereafter, the first mirror 42, the second mirror 43, and the third mirror 44 serve to guide the light transmitted through the platen glass 35 to the imaging lens 33. Specifically, the first mirror 42 reflects the light transmitted through the platen glass 35 in the left direction in FIG. The second mirror 43 reflects the light reflected by the first mirror 42 downward in FIG. The third mirror 44 reflects the light reflected by the second mirror 43 in the right direction in FIG.

  The imaging lens 33 plays a role of imaging the light reflected by the first mirror 42, the second mirror 43 and the third mirror 44 onto the CCD 34. The CCD 34 captures an image of one line extending in the main scanning direction at the reading position A of the platen glass 35 by the light transmitted through the platen glass 35. Further, the CCD 34 converts the image of the platen glass 35 formed by the imaging lens 33 into digital image data.

  The control part 40 is comprised by CPU, for example. Based on the image data of the image at the reading position A of the platen glass 35 imaged by the CCD 34, it serves as a determination means for determining whether or not dust D exists on the reading position A of the platen glass 35. Specifically, the control unit 40 performs well-known image analysis on the image data, and determines whether or not the black shadow of the dust D is included in the image data. Thereby, the control unit 40 can detect the white dust D. Note that the control unit 40 may be provided in the image reading apparatus 1 or may be provided in an image forming apparatus to which the image reading apparatus 1 is connected.

(Operation of image reader)
The operation of the image reading apparatus 1 configured as described above will be described below with reference to the drawings. The operation of the image reading apparatus 1 described below is a dust detection operation on the platen glass 35, and is performed, for example, when the image reading apparatus 1 is turned on or immediately before the image of the document P is read. FIG. 3 is a flowchart showing an operation performed by the control unit 40 in the dust detection operation.

  When the dust detection operation is started, the control unit 40 causes the CCD 34 to capture an image at the reading position A of the platen glass 35 (step S1). More specifically, the control unit 40 causes the planar light source 30 to irradiate the platen glass 35 with light without causing the document transport unit 2 to transport the document P. Thereby, the light passes through the platen glass 35, passes through the first mirror 42, the second mirror 43, the third mirror 44, and the imaging lens 33, and enters the CCD 34. Based on this light, the CCD 34 captures an image of one line extending in the main scanning direction at the reading position A of the platen glass 35 and outputs the image data of the image to the control unit 40.

  Next, the control unit 40 performs image analysis on the image data to determine whether or not the image at the reading position A of the platen glass 35 includes a black shadow of the dust D (step S2). . Hereinafter, the determination will be described with reference to FIG. FIG. 4 is a graph showing the number of gradations in the pixels arranged in the main scanning direction at the reading position A. The horizontal axis indicates the position of the pixels arranged in the main scanning direction at the reading position A, and the vertical axis indicates the gradation number. As the tone number increases, the color approaches white, and as the tone number decreases, the color approaches black.

  When acquiring the image data from the CCD 34, the control unit 40 detects the gradation number of each pixel of the image data. When the gradation number of each pixel is visualized, a graph shown in FIG. 4 is obtained. When the image data includes a pixel having a gradation number lower than the predetermined gradation number, the control unit 40 determines that the black shadow of the dust D is included in the image of the platen glass 35. . For example, when the predetermined gradation is set to 200, it can be understood that dust D is present at three positions of the reading position A on the platen glass 35 in FIG.

  In step S2, if the black shadow of dust D is not included (No), this process ends. In this case, the control unit 40 determines that there is no dust D at the reading position A on the platen glass 35, and accepts an instruction to read the original P input thereafter. On the other hand, if the black shadow of dust D is included in step S2 (Yes), the process proceeds to step S3.

  When the black shadow of the dust D is included, the control unit 40 determines that the dust D exists at the reading position A of the platen glass 35 and drives the motor 39 to drive the first slider 31 and the second slider. 32 is moved in the transport direction (step S3). As a result, the reading position A also moves in the transport direction. The amount of movement of the reading position A in the transport direction in step S3 is preferably about 12 pixels, for example. This is because if the movement amount is too small, the dust D detected in step S2 may be detected again. In addition, if the movement amount is too large, the reading position A protrudes from the platen glass 35. After step S3, the process returns to step S1. Thereafter, the control unit 40 repeats the operations of Steps S1 to S3 until no dust D is detected. As a result, the reading position A can be set at a position where no dust D exists.

(effect)
As described above, according to the image reading device 1, when dust D exists on the reading position A of the platen glass 35 by irradiating light from the first main surface s1 side of the platen glass 35, The dust D forms a black shadow on the platen glass 35. Therefore, the image reading apparatus 1 can detect the presence of the white dust D by detecting the shadow of the white dust D even when the white dust D exists on the reading position A of the platen glass 35. Is possible.

  Further, the image reading apparatus 1 moves the reading position A when the dust D is detected on the reading position A of the platen glass 35. Therefore, the image reading apparatus 1 can read the image of the document P in a state where the dust D does not exist on the reading position A.

  Since the planar light source 30 is a planar light source, the incident angle of light does not change even if the reading position A is moved. Therefore, it is possible to obtain stable dust D detection accuracy in the image reading apparatus 1.

(Modification)
The image reading apparatus according to the present invention is not limited to the above embodiment, and can be changed within the scope of the gist. Hereinafter, an image reading apparatus according to a modification will be described with reference to the drawings. Since the configuration of the image reading apparatus according to the modification is the same as that of the image reading apparatus 1 according to the first embodiment, the description thereof is omitted.

  The image reading apparatus 1 according to the modified example captures an image of the platen glass 35 while moving the reading position A by moving the first slider 31 and the second slider 32 to the motor 39 in the dust detection operation. The entire image of the platen glass 35 is captured. Then, the image reading apparatus 1 sets the position with the least amount of dust D as the reading position A based on the entire image of the platen glass 35. Hereinafter, a dust detection operation of the image reading apparatus 1 according to the modification will be described with reference to the drawings. FIG. 5 is a flowchart showing an operation performed by the control unit 40 in the dust detection operation.

  When the dust detection operation is started, the control unit 40 drives the motor 39 to move the first slider 31 and the second slider 32 so that the reading position A is located on the most upstream side of the platen glass 35. . Next, the control unit 40 causes the CCD 34 to capture an image at the reading position A of the platen glass 35 (step S11). The operation performed by the image reading apparatus 1 in step S11 is the same as step S1 in FIG.

  Next, the control unit 40 determines whether or not all the imaging of the platen glass 35 has been completed (step S12). More specifically, the control unit 40 determines whether or not the reading position A has been moved to the most downstream side of the platen glass 35. If the imaging of the platen glass 35 has not been completed (No), the process proceeds to step S13. On the other hand, when all the imaging of the platen glass 35 is completed (Yes), the process proceeds to step S14.

  If the imaging of the platen glass 35 has not been completed, the control unit 40 drives the motor 39 to move the first slider 31 and the second slider 32 by a predetermined amount downstream in the transport direction (step) S13). As a result, the reading position A also moves in the transport direction by a predetermined amount. After step S13, the process returns to step S11. Thereafter, the control unit 40 repeats the operations of Steps S11 to S13 until the reading position A is located on the most downstream side of the platen glass 35. Thereby, the control unit 40 can acquire image data of substantially the entire surface of the platen glass 35.

  In step S14, the control unit 40 determines the reading position A based on the image data (step S14). The processing performed in step S14 is as follows. First, the control unit 40 performs image analysis on the image data, and determines whether or not the image of the entire surface of the platen glass 35 includes a black shadow of the dust D. The determination in step S14 is substantially the same as the determination performed by the control unit 40 in step S2 of FIG. However, in step S2, image analysis is performed on the image data for one line in the main scanning direction, whereas in step S14, image analysis is performed on the entire platen glass 35 image. Next, the control unit 40 identifies the position where the dust D is the least in the platen glass 35 and determines the position as the reading position A. Thereafter, the process proceeds to step S15.

  Next, the control unit 40 moves the first slider 31 and the second slider 32 by the motor 39, and moves the reading position A to the position where the dust D specified in step S14 is the least (step S15). As a result, the reading position A can be set at a position where dust D is the least.

  In step S11 to step S13, an image of the entire platen glass 35 is captured, but the image capturing range is not limited to this. The image reading device 1 only needs to capture at least the entire range of the platen glass 35 that can be used for imaging.

  Although the sheet-through type image reading apparatus 1 has been described, the planar light source 30 can also be applied to a platen set type image reading apparatus. When the planar light source 30 is attached to the platen set type image reading apparatus, it is necessary to attach the planar light source 30 to the document conveying unit 2 so as to face the platen glass 38 in FIG.

1 is a configuration diagram of an image reading apparatus according to an embodiment of the present invention. It is the figure which showed the structure of the image reading apparatus in the reading position vicinity. It is the flowchart which showed the operation | movement which a control part performs in dust detection operation | movement. It is the graph which showed the gradation number in each pixel arranged in the main scanning direction in the reading position. It is the flowchart which showed the operation | movement which a control part performs in dust detection operation | movement. It is a block diagram of a conventional sheet-through type image reading apparatus. It is the figure shown to the example of a reading image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reading apparatus 2 Document conveying part 3 Image reading part 30 Planar light source 31 1st slider 32 2nd slider 35,38 Platen glass 39 Motor 40 Control part 42 1st mirror 43 2nd mirror 44 3rd mirror A Reading position D Garbage P Document s1 First main surface s2 Second main surface

Claims (6)

A transparent plate having a first main surface located on the document side, and a second main surface facing the first main surface;
A light source that is provided on the first main surface side and that irradiates light to the transparent plate in a state where the original does not exist on the first main surface;
An imaging unit that is provided on the second main surface side and that captures an image of the transparent plate with light that has passed through the transparent plate;
Providing
An image reading apparatus characterized by the above. Based on the image of the transparent plate captured by the imaging unit, a determination unit that determines whether or not a foreign object exists on the transparent plate,
To provide further,
The image reading apparatus according to claim 1. Conveying means for conveying the document so as to pass the reading position of the first main surface;
In addition,
The imaging means captures an image of the document passing through the reading position;
The image reading apparatus according to claim 2. A slider that incorporates a reflective member that reflects the light that has passed through the transparent plate and guides it to the imaging means;
Moving means for moving the reading position by moving the slider;
Further comprising
The moving means moves the reading position when the determining means determines that there is a foreign object at the reading position;
The image reading apparatus according to claim 3. A slider that incorporates a reflective member that reflects the light that has passed through the transparent plate and guides it to the imaging means;
Moving means for moving the reading position by moving the slider;
Further comprising
The moving means moves the plurality of sliders to move the reading position;
The imaging means captures an image of the transparent plate while the moving means moves the reading position,
The determination means identifies a position having the least foreign matter in the image of the transparent plate,
The moving means moves the reading position to a position where the foreign matter is the least;
The image reading apparatus according to claim 3, wherein: The light source is a planar light source;
The image reading apparatus according to claim 1, wherein the image reading apparatus is an image reading apparatus.

Images