JP4390520B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus.

  In a conventional image reading apparatus, a scanning method (original fixing / optical system moving method) in which an original is exposed and scanned when the optical system is moved with respect to a fixed original, and an original is moved with respect to a reading position in the optical system. It is divided into a sheet-through method (document moving / optical system fixing method) in which an original is exposed and scanned when moving at a predetermined speed. In either method, the optical system exposes the document through an optically transparent member such as contact glass.

  In an image forming apparatus provided with such an image reading apparatus, for example, an analog type that directly irradiates a photosensitive member with exposure light from an exposed scanned document, and exposure light from a document that is exposed and scanned using an imaging device such as a CCD. There is a digital type that acquires the image as digital image data. Recently, a digital type sheet-through method has been widely adopted because it is advantageous for reading a large original and performing various image processing thereafter.

  In an image reading apparatus that is a digital type and adopts a sheet-through method (hereinafter referred to as a digital image reading apparatus in this specification), an original is irradiated with exposure light through a slit having a predetermined width. A region of exposure light irradiated to the reading position through the slit (hereinafter referred to as reading exposure width) is narrow (for example, in a digital image reading apparatus having a reading density of 400 dpi, the reading exposure width is 25.4 / 400 = 0.0635 mm). ). In a digital image reading apparatus, when a foreign matter that is larger than the reading exposure width (for example, a diameter of 0.0635 mm or more in a digital image reading apparatus having a reading density of 400 dpi) adheres to the reading position, image data in a portion where the foreign matter has adhered. However, it is continuously read as black data regardless of the image on the document. Thereby, abnormalities such as so-called black stripes are likely to occur in the read image data.

  In order to solve such a problem, there has conventionally been an image reading apparatus in which a document is transported in a state of being floated on a contact glass to prevent dust from adhering or staying in an exposure unit (for example, Patent Document 1). reference).

  Note that in an analog type image reading apparatus, exposure is performed with a reading exposure width of 5 to 10 mm in both the scanning method and the sheet-through method. In an image forming apparatus including an analog type image reading apparatus employing a scanning method, if foreign matter such as dust adheres or stays at a reading position, a black spot corresponding to the size of the dust is generated. In addition, in an image forming apparatus including an image reading apparatus that employs an analog type and employs a sheet-through method, an image of a foreign matter portion becomes a blurred latent image, and does not become a clear image even if developed. For this reason, the adhesion of foreign matter to the reading position is not a problem in an analog type image reading apparatus.

JP-A-8-123157

  However, even in the technique described in Patent Document 1 described above, in a digital type image reading apparatus adopting a sheet-through method, when a sheet document is conveyed, dust, dust, and the like attached to the document are conveyed. May adhere to contact glass or the like. In such a case, the adhered foreign matter is continuously read as black (or white) data, and as a result, an abnormal image such as a black stripe (or white stripe) is generated in the acquired image data.

  An object of the present invention is to prevent the foreign matter from adhering to the contact glass and to prevent the foreign matter from staying on the contact glass even when the foreign matter adheres to the sheet document.

An image reading apparatus of the present invention is an optically transparent contact glass, an exposure optical system that exposes a reading position through the contact glass and receives exposure light that passes through the reading position, and is opposed to the contact glass. A document guide member provided such that a facing surface to be disposed passes through the reading position, a document transport mechanism that transports a sheet document in one direction between the contact glass and the document guide member, Air flow generating means for generating an air flow from the contact glass toward the document guide member and toward the sheet document conveyance direction by the document conveyance mechanism.

  Therefore, the sheet original conveyed between the contact glass and the original guide member by the original conveying mechanism is exposed by the exposure optical system while being pressed against the original guide member by the air flow generated by the air flow generating means. . At this time, the air flow generated by the air flow generating means flows between the sheet original and the contact glass from the upstream side to the downstream side in the sheet original conveying direction.

Preferred present invention, in the image reading apparatus, a gap of a predetermined spacing between the contact glass and the document guide member is formed.

  Accordingly, the foreign matter between the contact glass and the document guide member can be blown off by the air flow.

The present invention, in the image reading apparatus, the air flow generating means causes intermittently generating an air flow.

  Therefore, foreign matter between the contact glass and the document guide member can be blown off more effectively.

Preferred present invention, in the image reading apparatus, comprising a blowing duct having a blowing slit which opens toward the document guide member in the sheet original conveying direction upstream side of the contact glass, the air flow generating means, said An air flow from the blowing duct to the outside is generated through the blowing slit.

  Therefore, the operation of the invention according to claim 2 or 3 can be achieved with a configuration that is practically easy.

Preferred present invention, in the image reading apparatus, comprising a suction duct having a suction slit which opens toward the document guide member in the sheet original conveying direction downstream side of the contact glass, the air flow generating means, said An air flow from the outside to the inside of the suction duct is generated through the suction slit.

  Accordingly, the foreign matter blown off by the air flow from the upstream side of the reading position between the contact glass and the document guide member can be removed from between the contact glass and the document guide member.

Preferred present invention, in the image reading apparatus, the outlet slit and the suction slit, the imaginary straight line in the opposite direction between said document guide member in the reading position the contact glass connecting said suction slit and the outlet slit A reading position is provided on the contact glass side.

  Therefore, it is possible to prevent the sheet original from coming into contact with the contact glass and to reliably press the sheet original against the original guide member.

Preferred present invention, in the image reading apparatus, the duct guides the transport position of the sheet original by the outer surface of the document guide member.

  Therefore, it is possible to suppress an increase in the size of the image reading apparatus.

Preferred present invention, in the image reading apparatus, wherein the duct is shaped in the contact glass and integral.

  Therefore, it is possible to suppress the enlargement of the image reading apparatus and to reduce the number of parts.

According to the image reading apparatus of the present invention, the foreign material between the sheet original and the contact glass is prevented while the sheet original is exposed to the original guide member to prevent the sheet original from contacting the contact glass. Can be blown away from the upstream side toward the downstream side in the sheet document conveying direction, so that even when foreign matter is attached to the sheet original, the foreign matter is prevented from adhering to the contact glass and the foreign matter is contacted. It can prevent staying on glass. Further, since the sheet original is exposed while being pressed against the original guide member, it is possible to adjust the focus when reading the sheet original, so that the quality of the read image can be improved.

According to a preferred invention, in the image reading apparatus, it is possible to blow away foreign matter between the contact glass and the document guide member by the air flow, cleaning work to remove foreign matter between the contact glass and the document guide member Can be made unnecessary.

According to the present invention, in the image reading apparatus, it is possible to blow away foreign matter between the contact glass and the document guide member more effectively, more reliably remove the foreign matter between the contact glass and the document guide member can do.

According to a preferred invention, in the image reading apparatus, by practically simple configuration can achieve the effect of the invention of claim 2 wherein.

According to a preferred invention, in the image reading apparatus, for removing foreign matter blown off by the air flow from the upstream side of the reading position between the contact glass and the document guide member from between the contact glass and the document guide member Therefore, it is possible to more reliably prevent foreign matter from staying between the contact glass and the document guide member.

According to a preferred invention, in the image reading apparatus, together with the sheet original is prevented from coming into contact with the contact glass, so the sheet original can be securely pressed against and abut the document guide member, the reading with respect to the sheet document position Can be surely passed, and an image with good quality in focus can be obtained.

According to a preferred invention, in the image reading apparatus, the size of the image reading apparatus can be suppressed.

According to a preferred invention, in the image reading apparatus, it is possible to suppress upsizing of the image reading apparatus, it is possible to reduce the number of components.

  An embodiment of the present invention will be described with reference to the drawings. This embodiment shows an application example to a digital image reading apparatus as an image reading apparatus.

  FIG. 1 is a cross-sectional view showing a schematic configuration near a reading position of a digital image reading apparatus according to an embodiment of the present invention. The digital image reading apparatus 1 of the present embodiment includes an automatic document feeder (hereinafter referred to as ADF) 2 as a document transport mechanism. The ADF 2 sequentially feeds the sheet document 4 placed on the document feeding table 3 from the uppermost sheet document 4 on the document feeding table 3 into the ADF 2 by the feeding roller 5. Although not shown in FIG. 1, a document separation belt and a roller for separating the sheet document 4 placed on the document feeding table 3 one by one are provided in the vicinity of the feeding roller 5. ing.

  The sheet document 4 fed into the ADF 2 is fed so as to pass the reading position S by the transport roller 6 and the driven roller 7, and is placed on the paper discharge tray 10 by the paper discharge roller 8 and the driven roller 9. The paper is ejected.

  Although the description is omitted because it is a known technique, the digital image reading apparatus reads the image information of the sheet original 4 when the sheet original passes through the reading unit.

  A document width detection sensor and a length sensor (not shown) are provided on the document feeder 3 (or the vicinity thereof). The size of the sheet document 4 sent from the ADF is detected by these document width detection sensors and length sensors.

  Below the ADF 2, a reading device 11 that reads an image of a sheet document is arranged. The reading device 11 has a contact glass 12 provided on the upper surface of the housing 11a. The contact glass 12 of the present embodiment is made of an optically transparent material. The contact glass 12 protrudes upward in FIG. 1 from the upper surface of the housing 11a.

  An exposure optical system 13 is provided in the housing 11a. The exposure optical system 13 includes an exposure lamp 14, a mirror 15, a lens 16, a reading sensor CCD 17, and the like. The reading sensor CCD 17 of the present embodiment is a full color CCD. In the exposure optical system 13, the exposure lamp 14 irradiates light to a reading position S, which will be described later, and is reflected from the reading position S and bent toward the lens 16 by the mirror 15, and the reading sensor CCD 17 passes through the lens 16. An optical path leading to is formed.

  A document guide member 18 is provided at a position where light from the exposure lamp 14 is irradiated. The document guide member 18 is provided to face the contact glass 12 with a predetermined gap from the contact glass 12. In the present embodiment, the reading position S is a position where the light from the exposure lamp 14 is irradiated on the document guide member 18.

  When the sheet document 4 is read by the digital image reading apparatus 1, the sheet document 4 is exposed by the exposure optical system 13 while the sheet document 4 is conveyed by the ADF 2. The reading sensor CCD 17 performs photoelectric conversion based on the amount of light reflected from the sheet original 4 imaged on the reading sensor CCD 17 during the exposure, and generates image data. Note that generation of image data by the reading sensor CCD 17 is a known technique, and thus description thereof is omitted. Incidentally, since the reading CCD sensor of this embodiment is a full color CCD, the image data after photoelectric conversion is separated into red (R), green (G), and blue (B) colors. Although illustration and description are omitted because it is a known technique, the image signal of each color is subjected to processing such as A / D conversion by an image processing circuit, and thereafter various image processing is performed by an image processing unit.

  In the digital image reading apparatus 1 of the present embodiment, a blowout duct 20 having a blowout slit 19 is provided on the upstream side (left side in FIG. 1) in the sheet document conveying direction from the contact glass 12. The blowing slit 19 is provided so as to open toward the document guide member 18 (upper side in FIG. 1).

  A suction duct 22 having a suction slit 21 is provided downstream of the contact glass 12 in the sheet document conveying direction (left side in FIG. 1). The suction slit 21 is provided so as to open toward the document guide member 18.

  The blowout duct 20 and the suction duct 22 are formed integrally with the contact glass 12. For this reason, in this Embodiment, the blowing duct 20 and the suction duct 22 are also formed of the optically transparent material. In the blowing duct 20 and the suction duct 22, the outer surface facing the document guide member 18 performs a guide function for guiding the transport position of the sheet document 4. Thus, when the sheet document 4 is transported, the sheet document 4 can be transported so as to pass through a target path.

  In the blowing duct 20, air flow generating means realized by a fan, a compressed air pump, or the like that feeds air from the blowing slit 19 to the outside of the blowing duct 20 is provided at both ends in the front and back direction in FIG.

  In the present embodiment, air flow generating means realized by a fan or a compressed air pump or the like is provided at both ends of the blowout duct 20, but the present invention is not limited to this, and a compressed air pump, a compression tank, It is good also as an air flow generation | occurrence | production means which sends out air intermittently to the exterior of the blowing duct 20 from the blowing slit 19 by providing an air valve and opening and closing an air valve intermittently.

  In the case where an air flow generating means for intermittently sending air from the blowing slit 19 to the outside of the blowing duct 20 is used, even if there is a foreign substance between the contact glass 12 and the document guide member 18, this foreign substance is removed. It can be easily blown away.

  In the digital image reading apparatus 1 of the present embodiment, when reading the image of the sheet document 4, the air flow generating means generates an air flow from the blow duct 20 to the outside through the blow slit 19. As a result, an air flow is generated between the contact glass 12 and the document guide member 18 from the upstream side to the downstream side in the sheet material conveyance direction. Here, since the blowing slit 19 is opened toward the document guide member 18 in the vicinity of the contact glass 12, the sheet material between the contact glass 12 and the document guide member 18 is blown out through the blow slit 19. It is pressed against the document guide member 18 by the air flow from the duct 20 toward the outside. As a result, the sheet document 4 is exposed while being pressed against the document guide member 18.

  Thus, according to the digital image reading apparatus 1 of the present embodiment, the sheet original 4 is prevented from coming into contact with the contact glass 12 by exposing the sheet original 4 while being pressed against the original guide member 18. However, since the foreign matter between the sheet original 4 and the contact glass 12 can be blown from the upstream side to the downstream side in the sheet original conveying direction, this foreign matter is also present when the foreign matter adheres to the sheet original 4. Can be prevented from adhering to the contact glass 12 and this foreign matter can be prevented from staying on the contact glass 12.

  Further, by exposing the sheet original 4 while pressing the sheet original 4 against the original guide member 18 provided so as to pass through the reading position, it is possible to adjust the focus when the sheet original 4 is read. The quality of the read image can be improved.

  Further, in the digital image reading apparatus 1 of the present embodiment, when reading the image of the sheet document 4, an air flow (negative pressure) is generated from the outside into the suction duct 22 through the suction slit 21 by the air flow generating means. Let As a result, the air flow from the upstream side to the downstream side in the sheet material conveyance direction can be made more reliable between the contact glass 12 and the document guide member 18. Accordingly, foreign matter blown off by the air flow from the upstream side of the reading position S between the contact glass 12 and the document guide member 18 can be removed from between the contact glass 12 and the document guide member 18. It is possible to prevent foreign matter from staying between the contact glass 12 and the document guide member 18.

  Here, the suction slit 21 opens toward the document guide member 18 in the vicinity of the contact glass 12, and the blowout slit 19 and the suction slit 21 further include the document guide member 18 and the contact glass 12 at the reading position S. The reading position S is located closer to the contact glass 12 than the virtual straight line (left and right direction in FIG. 1) connecting the blowing slit 19 and the suction slit 21 in the opposite direction (up and down direction in FIG. 1). Therefore, the sheet document 4 can be reliably pressed against the document guide member 18 while preventing the sheet document 4 from contacting the contact glass 12. As a result, the sheet document 4 reliably passes through the reading position, so that the focus can be stabilized and a good quality image can be obtained.

  Further, according to the present embodiment, since a gap with a predetermined interval is formed between the document guide member 18 and the contact glass 12, foreign matter between the contact glass 12 and the document guide member 18 is caused by the air flow. Can be blown off more reliably, and this eliminates the need for a cleaning operation to remove foreign matter between the contact glass 12 and the document guide member 18.

  The duct portion 6B that sucks air toward the downstream portion in the conveyance direction is provided in the conveyance outlet guide in the reading downstream portion in order to prevent the dust blown off from the original from collecting on the right side in the drawing. , Sucking trash.

  The digital image reading apparatus according to the present embodiment is used together with a printer engine that performs an image forming operation based on image data, and causes the printer engine to perform an image forming operation based on image data read by the digital image reading apparatus. It is also possible to function as a copying machine. The printer engine and the copying apparatus including the printer engine can be easily realized by a known technique, and thus the description thereof will be omitted. Examples of the image forming method in the printer engine include an electrophotographic method and an inkjet method. Various known techniques can be applied.

  In such a copying apparatus, the quality of the image is suppressed by controlling the drive of the printer engine based on the image data subjected to various image processing by the image processing unit of the digital image reading apparatus. A good image can be obtained by copying.

It is sectional drawing which shows schematic structure of the reading position vicinity of the digital image reading apparatus of one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image reader 2 Document conveying mechanism 4 Sheet document 13 Exposure optical system 18 Document guide member 19 Blowing slit 20 Blowing duct 21 Suction slit 22 Suction duct

Claims (8)

Optically transparent contact glass,
An exposure optical system for receiving the exposure light passed through the reading position while exposing the reading position through the contact glass,
A document guide member provided so that a facing surface facing the contact glass passes through the reading position;
A document conveying mechanism that conveys a sheet document in one direction between the contact glass and the document guide member;
A blow slit for generating an air flow from the upstream side in the sheet document conveying direction from the contact glass; and a suction slit for sucking an air flow from the downstream side in the sheet document conveying direction from the contact glass; An air flow generating means for generating an air flow toward the guide member and in the sheet document conveying direction by the document conveying mechanism,
The blowout slit and the suction slit are provided so that the reading position is located on the contact glass side from a virtual straight line connecting the blowout slit and the suction slit,
The air flow generation means is an image reading device that intermittently generates an air flow during conveyance of the sheet original .   The image reading apparatus according to claim 1, wherein a gap having a predetermined interval is formed between the document guide member and the contact glass. It said air flow generating means includes an image reading apparatus according to claim 1 or 2, wherein an air valve for feeding intermittently air from the blowing slit. The image reading apparatus according to claim 1, wherein the airflow generation unit includes a blowout duct that supplies an airflow to the blowout slit. The image reading apparatus according to claim 1, wherein the air flow generation unit includes a suction duct that sucks an air flow from the suction slit. The image reading apparatus according to claim 1, wherein outer surfaces of the blowout duct and the suction duct facing the document guide member have a guide function for guiding a sheet document . The image reading apparatus according to claim 1, wherein the blowout duct and / or the suction duct is formed integrally with the contact glass. A copying machine comprising: the image reading apparatus according to claim 1; and a printer engine that performs an image forming operation based on image data read by the image reading apparatus.

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