JP2009212679A - Image reading apparatus and image forming apparatus - Google Patents

Abstract

In an image reading apparatus having a sheet-through method for reading original information by moving an original in the sub-scanning direction with a reading optical system fixed, the illumination system can be reduced in thickness, and the manufacturing cost can be reduced with low power consumption. The object is to illuminate the document surface efficiently without raising it.
A contact glass provided in a sheet-through reading unit in an image reading apparatus having a sheet-through type sheet-through reading unit that reads a document information by moving a document in a sub-scanning direction while fixing a reading optical system. Illuminating means for illuminating the original surface with a surface emitting light source elongated in the main scanning direction is provided on the surface through which the original passes.
[Selection] Figure 1

Description

  The present invention relates to an image reading apparatus and an image forming apparatus having a sheet-through method for reading original information by moving an original in a sub-scanning direction with a reading optical system fixed.

  An image reading device of a document reading unit of a facsimile or a digital copying machine reads reflected light of a document illuminated by an illumination system, forms an image on a line sensor that performs photoelectric conversion by an optical system, and converts the image information into a signal. In such an image reading apparatus, a document is placed on a contact glass, the document is pressed by a document pressing plate (pressure plate), scanned by an illumination system and an optical system (pressure plate method), and a sheet document is read. In order to improve work efficiency, the illumination system and the optical system do not move, and the original document is conveyed and read by an automatic document feeder (ADF) that automatically feeds the sheet document onto the document glass that is the exposure position of the optical system. (Sheet-through method).

  FIG. 10 is a conceptual diagram of a conventional optical image reading apparatus using three mirrors and a reduction imaging lens. Such an image reading apparatus includes contact glasses 2-1, 2-2, a first traveling body 3 having a first mirror 3-a, a second traveling having a second mirror 4-a and a third mirror 4-b. It comprises a body 4, a reduction imaging lens 5, a line sensor 6, an illumination system 7, and an ADF 8. When reading by the pressure plate method, the document is placed on the contact glass 2-2, the first traveling body 3 moves to the pressure plate reading start position 3-2, the second traveling body 4 moves to the pressure plate reading start position 4-2, The illumination light is reflected by the first mirror 3-a, then reflected by the first mirror 4-a and the second mirror 4-b, guided to the reduction imaging lens 5, and imaged on the line sensor 6. The When reading the longitudinal direction of the document, the first traveling body 3 moves at a speed to the reading position 3-3, and at the same time, the second traveling body 4 moves at a half speed of the first traveling body 3 to the reading position 4-3. And the entire document is read.

  On the other hand, in the case of the sheet through method, the illumination system 7, the first traveling body 3, and the second traveling body 4 are stopped at the position C, and the document 1 is contacted from the document tray A of the ADF 8 for sheet through. It is conveyed to the glass 2-1, and is conveyed at a constant speed at a point B on the contact glass. The document 1 is illuminated by the illumination system 7 and the illumination light of the document 1 is reflected by the first mirror 3-a of the first traveling body 3, and then the first mirror 4-a and the second mirror of the second traveling body 4. 4-b is reflected, guided to the reduction imaging lens 5, imaged on the line sensor 6, and document information is read.

  Illumination light sources used in image reading apparatuses include tube lamps such as xenon lamps and halogen lamps. However, the light sources consume a large amount of power and generate a large amount of heat. There is a problem that the temperature is raised. For this reason, LEDs that consume less power and generate heat have come to be used as new illumination light sources that replace tube lamps such as xenon lamps. However, since the LED is a point light source, it needs to be diffused and condensed, and an optical system for that purpose is required. For example, Patent Document 1 discloses an illumination unit that arranges LEDs in a row and illuminates a document through a light guide. In addition, as another known technique, Patent Document 2 discloses an illumination unit in which a long lens system is arranged in front of arranged LEDs to increase the concentration of illumination in a direction orthogonal to the LED arrangement. Has been. However, these conventional techniques have problems of adjustment and cost as the optical system becomes larger and the number of parts increases.

Therefore, an illumination unit using organic electroluminescence (organic EL) has been invented as a light source capable of surface emission. In Patent Document 3, two surface light sources are arranged close to each other to illuminate a document surface, a space is provided between the two surface light sources, and document surface information is read from the space. However, considering that the illumination light from the surface light source is brightest on the center of the light emitting surface and the position where the document information is read is at the end of the light emitting surface, the surface light source is actually used for reading the document information. The illumination light from is hardly used, and the illumination efficiency is very poor. Therefore, as a conventional technique for increasing the illumination efficiency, Patent Document 4 aims to increase the amount of illumination light at a position where document information is read by arranging a reflective member on a surface light source. Patent Document 5 aims to illuminate the original surface by forming a large number of microprisms on the light emitting surface of a surface light source to enhance the orientation of the light emitting direction. Further, Patent Document 6 proposes an illumination unit in which a surface emitting light source is directly arranged on the back surface of the contact glass (the opposite side on which the document is conveyed).
JP 2006-025303 A JP-A-2005-278132 JP 2000-115470 A JP 2007-13913 A Japanese Patent Laid-Open No. 6-217083 JP 2006-60528 A

  However, in general, it can be assumed that the light emitting surface has a Lambert light distribution, and considering the amount of light irradiated on the original surface, it becomes darker in inverse proportion to the square of the distance to the original surface. When the reflecting member is arranged between the light emitting surface and the document reading position, the light emitting surface is arranged away from the document reading position, so that the illuminance on the surface of the document is likely to be dark, and when the configuration is such that light is collected on the reflecting member Adjustment is difficult because the illuminance of the document surface is generated by adjusting the position of the reflecting member. Furthermore, the illumination system itself becomes large and it is difficult to reduce the size. Further, when a large number of minute prisms are formed, the manufacturing cost is increased, and the prism unit is formed, so that the illumination unit is separated from the document surface, so that the document surface illuminance becomes dark and the proof efficiency is poor. Further, when the light source is arranged on the back surface of the contact glass, the illumination unit is integrated with the contact glass. Therefore, the light source is used in the image reading apparatus in which the illumination unit scans under the contact glass as shown in FIG. Is difficult.

  In recent years, there is an increasing demand for reducing the height direction of the reading optical system, and accordingly, there is an increasing demand for a thinner illumination system. In order to reduce the thickness of the illumination system, it is necessary to make the light source as close to the original surface as possible. For example, as shown in FIG. 11, it is necessary to illuminate the contact light at a large angle with respect to the contact glass in order to bring the illumination light closer to the contact glass as shown in FIG. When the illumination light is incident at a large angle as described above, there is a problem that total reflection occurs in the contact glass when the illumination light is emitted from the contact glass to the air, and the document cannot be illuminated.

  The present invention has been made in view of the above problems. In a sheet-through method for reading original information by moving an original in the sub-scanning direction with a reading optical system fixed, an illumination system without increasing manufacturing costs. An object of the present invention is to reduce the thickness of the original and efficiently illuminate the document surface with power saving.

  In order to solve the above-described problems, an image reading apparatus according to the present invention is an image reading apparatus having a sheet-through type sheet-through reading unit that reads a document information by fixing a reading optical system and moving the document in the sub-scanning direction. The surface of the contact glass provided in the sheet-through reading means that passes the original is provided with an illuminating means that illuminates the original with a surface light source that is long in the main scanning direction.

  The illuminating means is organic electroluminescence formed directly on the contact glass.

  The illuminating means is arranged with an angle inclination.

  The illumination means is characterized in that the light amount is variable between the light source central portion and the peripheral portion, and the image formation light amount is kept uniform regardless of the angle of view.

  A plurality of illumination means are provided to face each other in the sub-scanning direction.

  The illuminating means is white light.

  Further, color separation means is provided in the optical path of the reading optical system, and document information is read in full color.

  Furthermore, the illumination means is provided with a protection means for preventing deterioration due to dirt or the like.

  The protection unit is a document guide for direct contact between the document and the illumination unit.

  In addition, an image forming apparatus according to the present invention includes the above-described image reading apparatus.

  According to the present invention, in the sheet-through method, it is possible to reduce the thickness of the illumination system, to efficiently illuminate the original surface without increasing the manufacturing cost and saving power. In comparison, since the light source can be brought close to the original and strong illumination light can be obtained, it is possible to cope with high-speed reading.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  FIG. 1 is a conceptual diagram of an image reading apparatus according to an embodiment of the present invention. In an image reading apparatus having a sheet-through image reading method, a surface light source 9 is formed on the surface of a contact glass 2-1. When reading a document by the sheet-through method, the document is transported by the ADF 8 and illuminated by the surface light source at the position B, and the illumination light is reflected by the first mirror of the first traveling body 3-1. In the same manner as above, an image is formed on the line sensor by the optical system. In the case of the pressure plate method, the original is illuminated using the illumination system 7 provided in the first traveling body as in the conventional case, and the original information is read.

  In this way, by arranging the surface emitting light source on the surface through which the document surface of the contact glass passes, the illumination light does not pass through the contact glass even when the light source is brought close to the distance to the document. In addition, since the reflection component on the exit surface is eliminated and total reflection does not occur, it is possible to illuminate the document without loss of light quantity. Since the document surface illuminance is inversely proportional to the distance between the light source and the document, it is possible to secure the document surface illuminance without increasing the light amount of the light source by bringing the light source closer to the document. In addition, by making the shape of the surface light source long in the main scanning direction, the light emission area can be increased, and the illuminance on the original surface on the original surface can be efficiently reduced without using a special condensing means. It is possible to raise. Further, since no image forming means such as a lens or a prism is required, it is advantageous for miniaturization.

  FIG. 2 shows an example of a sheet-through type image reading apparatus using a CCD-integrated optical system. In the sheet-through method, the optical system stops at position 8-1, the sheet document conveyed by the ADF is illuminated by the illumination system, and the illumination light of the document is reflected by the five mirrors M1 to M5. The image is guided to the reduction imaging lens 5 and imaged on the line sensor 6 by the imaging lens, and the document information is read. In the case of the pressure plate method, the optical system moves to position 8-2, and the document information is scanned by scanning the document.

  In addition, as shown in FIG. 3, reading by the sheet-through method when using an equal magnification imaging type optical system, the optical system having the equal magnification imaging element 10 stops at a position 9-1. The sheet original conveyed by the ADF is illuminated by an illumination system, and is imaged on the equal magnification sensor 11 by the equal magnification image forming element 10, and the document information is read. In the case of the pressure plate method, the optical system moves to the position 9-2, scans the document, and is similarly read.

  FIG. 4 is a conceptual diagram of an organic EL. A cathode layer, an electron injecting and transporting layer, a light emitting layer, a hole injecting and transporting layer, and an anode layer are formed on the substrate, and a protective layer for protecting each layer from scratches and humidity is formed. The electron transport layer, the light emitting layer, and the hole transport layer are all formed of an organic material, and the anode layer is an organic EL using a transparent electrode of indium tin oxide (ITO), and the anode is a transparent electrode. Emits light from the layer side.

  By tilting the contact glass at an arbitrary angle, the light emitting surface of the surface light source can be directed in a direction in which the original can be efficiently illuminated, and the illumination light rate can be improved. FIG. 5 is a diagram showing a method of tilting the contact glass at an arbitrary angle. In (A), the whole is inclined by θ. There are a method of inclining only a part as shown in (B) and a method of curving the whole as shown in (C). Of course, it is also possible to bend only a part.

  In addition, by making the light amount near the periphery of the light source higher than the vicinity of the center, for example, when a reduction imaging lens is used as a reading optical system, the aperture efficiency of the reduction imaging lens and the cosine fourth law can be used. Even in a reading optical system in which the amount of imaged light decreases according to the angle of view, the amount of imaged light on the line sensor can be kept uniform regardless of the angle of view. As a method in that case, for example, as shown in FIG. 6, the wiring density in the vicinity of the periphery of the cathode layer and the anode layer can be realized by wiring higher than the vicinity of the center. The hatched portion in the figure is the layout of the wiring formed in the cathode layer or anode layer. Light emitted from the light-emitting layer is strong in the vicinity of the wiring, and the amount of light emitted decreases as the distance from the wiring increases. Is possible.

  FIG. 7 is a schematic view when a plurality of surface light sources are arranged facing each other in the sub-scanning direction. As shown in the figure, by arranging a plurality of light sources, even when a document has a pasting portion, it is possible to illuminate without causing a shadow of the pasting portion, and high-quality reading is possible. At this time, the surface light source does not need to be arranged at a fixed interval unless the reading position is blocked. Further, the distance from the reading position may be arranged symmetrically or asymmetrically in the sub-scanning direction. That is, the surface light source can be arranged in any state in which the shadow of the bonded original does not appear. Further, it is possible to incline the whole or a part as shown in FIG. 7B, or to curve as shown in FIG. At this time, the left and right angles θ1 and θ2 may be the same or different.

  Furthermore, the surface light source of the image reading apparatus according to the embodiment of the present invention is white light, and a color separation function is provided in an arbitrary optical path of the reading optical system, whereby document information can be read in full color. As a method of making the organic EL white light, white light can be obtained by color-converting light emitted from one light emitting layer with a phosphor placed in the next layer. As another method, white light can be obtained by stacking a plurality of light emitting layers that emit light having different wavelengths, and a white light source obtained by various other methods can be used. For color separation, a color separation prism or a filter is selectively inserted between the reading lens and the CCD to separate colors into R, G, and B, and a light receiving element having R, G, and B filters is one chip. Any method can be used, such as a method of using three-line CCDs arranged in three rows and separating the colors into three primary colors by forming a color image on the light receiving surface.

  In the embodiment of the present invention, since the surface light source is on the surface of the contact glass, when the document directly contacts the surface light source, the surface light source is contaminated, etc. Problems such as vertical stripes occur. Therefore, as shown in FIG. 8, the above problem can be solved by providing the document guide 103 so that the document does not directly contact the surface light source. Further effects can be expected by applying a protective sheet or coating to the entire surface of the contact glass or the surface light source.

  FIG. 9 is an example of a laser printer using the embodiment of the present invention. The laser printer 100 has a photoconductive photosensitive member formed in a cylindrical shape as a latent image carrier 111. Around the latent image carrier 111, a charging roller 112 as a charging unit, a developing device 113, a transfer roller 114, and a cleaning device 115 are provided. A corona charger can also be used as the charging means.

  Further, an optical scanning device 117 that performs optical scanning with a laser beam (LB) is provided, and exposure by optical writing is performed between the charging roller 112 and the developing device 113, and the fixing device 116, A cassette 118, a registration roller pair 119, a paper feed roller 120, a conveyance path 121, a paper discharge roller pair 122, a tray 123, and a transfer paper P as a recording medium are provided.

  When image formation is performed, the image carrier 111, which is a photoconductive photoconductor, is rotated at a constant speed in the clockwise direction, and the surface thereof is uniformly charged by the charging roller 112. An electrostatic latent image is formed upon exposure to the image. The formed electrostatic latent image is a so-called negative latent image, and the image portion is exposed. This electrostatic latent image is reversely developed by the developing device 113, and a toner image is formed on the image carrier 111.

  The cassette 118 storing the transfer paper P is detachable from the main body of the image forming apparatus 100. When the transfer paper P is mounted as shown in the drawing, the uppermost sheet of the stored transfer paper P is fed by the paper supply roller 120. The leading edge of the fed transfer paper P is captured by the registration roller pair 119. The registration roller pair 119 feeds the transfer paper P to the transfer unit in time with the toner image on the image carrier 111 moving to the transfer position. The transferred transfer paper P is superimposed on the toner image at the transfer portion, and the toner image is electrostatically transferred by the action of the transfer roller 114. The transfer paper P to which the toner image has been transferred is sent to the fixing device 116, where the toner image is fixed by the fixing device 116, passes through the conveyance path 121, and is discharged onto the tray 123 by the paper discharge roller pair 122. .

  The surface of the image carrier 111 after the toner image is transferred is cleaned by a cleaning device 115 to remove residual toner and paper dust. In an image forming apparatus that forms a latent image on the latent image carrier 111 by optical scanning and obtains a desired recorded image by visualizing the latent image, the present invention is used as an optical scanning device that optically scans the latent image carrier 111. The latent image carrier 111 is a photoconductive photoconductor, and an electrostatic latent image is formed by uniform charging and optical scanning, and the formed electrostatic latent image is visualized as a toner image. The

  The present invention has been described above by the preferred embodiments of the present invention. While the invention has been described with reference to specific embodiments, various modifications and changes may be made to the embodiments without departing from the broad spirit and scope of the invention as defined in the claims. Obviously you can. In other words, the present invention should not be construed as being limited by the details of the specific examples and the accompanying drawings.

1 is a configuration diagram of an image reading apparatus according to an embodiment of the present invention. 1 is a configuration diagram of an image reading apparatus according to an embodiment of the present invention. 1 is a configuration diagram of an image reading apparatus according to an embodiment of the present invention. It is a structural example of organic EL. It is a figure which shows the angle inclination of contact glass. It is an example of wiring of a surface light source. It is the example of arrangement | positioning of the surface emitting light source which concerns on embodiment of this invention. 1 is a configuration diagram of an image reading apparatus according to an embodiment of the present invention. 1 is a configuration diagram of a laser printer according to an embodiment of the present invention. It is a block diagram of the conventional image reading apparatus. It is a schematic diagram of illumination light.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Document 2-1 Sheet-through contact glass 2-2 Pressure plate contact glass 3 First traveling body 4 Second traveling body 5 Reduction imaging lens 6 Line sensor 7 Illumination system 8 ADF
9 Surface light source 101 Surface light source 102 Conveying roller 103 Document guide 104 Auxiliary conveying roller 105 Contact glass holder

Claims (10)

In an image reading apparatus having a sheet-through-type sheet-through reading unit that fixes a reading optical system and moves an original in a sub-scanning direction to read original information.
An image reading apparatus comprising: illumination means for illuminating a document surface with a surface emitting light source elongated in a main scanning direction on a surface of the contact glass provided in the sheet-through reading unit through the document.   2. The image reading apparatus according to claim 1, wherein the illuminating means is organic electroluminescence directly formed on a contact glass.   The image reading apparatus according to claim 1, wherein the illumination unit is arranged with an angle inclination.   4. The lighting device according to claim 1, wherein the illumination unit has a variable amount of light between a light source central portion and a peripheral portion, and keeps the image formation light amount uniform irrespective of the angle of view. Image reading apparatus.   5. The image reading apparatus according to claim 1, wherein a plurality of the illumination units are provided to face each other in the sub-scanning direction.   The image reading apparatus according to claim 1, wherein the illumination unit is white light. Furthermore, color separation means is provided in the optical path of the reading optical system,
The image reading apparatus according to claim 1, wherein the document information is read in full color.   The image reading apparatus according to claim 1, further comprising a protection unit that prevents the illumination unit from being deteriorated by dirt or the like.   The image reading apparatus according to claim 1, wherein the protection unit is a document guide for direct contact between the document and the illumination unit.   An image forming apparatus comprising the image reading apparatus according to claim 1.

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