JP2012034078A - Image reading device and image formation apparatus with the same - Google Patents

Abstract

An object of the present invention is to reduce the level of specularly reflected light that is specularly reflected on the surfaces of a document placing plate and a document guide plate and incident on a reading section without reducing the illumination level of the document.
An upper surface 44b of an original guide plate 44 is inclined at an inclination angle β with respect to upper and lower surfaces 43a and 43b of the original placement plate 43 and parallel to a straight transport path 63. The lower surface 44a of the document is flush with or parallel to the lower surface 43a of the document placing plate 43. For this reason, the incident angle α1 of the illumination light from the light source 46 of the first reading unit 45 to the document placement plate 43 and the incident angle α3 of the illumination light from the light source 46 of the first reading unit 45 to the document guide plate 44 (= matches α1). Therefore, if the incident angle α1 of the illumination light from the light source 46 of the first reading unit 45 to the document placement plate 43 is adjusted and optimized, the incidence angle α3 of the illumination light to the document placement plate 43 is simultaneously adjusted. Is also optimized.
[Selection] Figure 6

Description

  The present invention relates to an image reading apparatus that illuminates and reads a document, and an image forming apparatus including the image reading apparatus.

  This type of image reading apparatus reads an original and is used alone or mounted on a copying machine or the like. When used alone, an image of the read original is output to an external printer or the like, and when used in a copying machine, the read original image is copied by the copying machine.

  As such an image reading apparatus, an original placing plate and an original guide plate made of a light-transmitting glass plate and the like, and a reading unit that is moved below either the original placement plate or the original guide plate are provided. The reading unit is moved below the document placing plate, the document is placed on the document placing plate, and the reading unit illuminates and reads the document on the document placing plate, or the reading unit is a document. The reading unit illuminates and reads the document on the document guide plate while moving it below the guide plate and transporting and passing the document on the document guide plate. The reading unit includes a light source that illuminates the document, an image sensor (such as a CCD) that photoelectrically converts light reflected from the document, and the like.

  Here, the reflected light from the original incident on the image sensor is light irregularly reflected on the surface of the original. If light regularly reflected on the surface of the document placing plate or the document guide plate enters the image sensor, blooming occurs, and the image read by the image sensor is overexposed. Blooming is a phenomenon in which when a certain amount of light enters a light receiving element of an image sensor, the light receiving element is saturated and the generated charge overflows to surrounding light receiving elements.

  For this reason, the incident angle of light from the reading unit with respect to the surface of the document placement plate or document guide plate is adjusted, and the specularly reflected light that is regularly reflected on the surface of the document placement plate or document guide plate enters the image sensor. Or the level of specularly reflected light incident on the image sensor is lowered.

  In Patent Document 1, the amount of light from the light source is reduced and the light receiving element is not saturated to prevent blooming.

JP-A-7-203158

  By the way, in the image reading apparatus, when the incident angle of light from the reading unit with respect to the surface of the document placing plate matches the incident angle of light from the reading unit with respect to the surface of the document guide plate, both incident angles are set. At the same time, the specular reflection light regularly reflected on the surface of the document placement plate or the document guide plate is not incident on the image sensor, or the level of the regular reflection light incident on the image sensor is lowered. Can do.

  However, depending on the configuration of the image reading apparatus, the incident angle of light from the reading unit with respect to the surface of the document placing plate may not match the incident angle of light from the reading unit with respect to the surface of the document guide plate. In this case, even if one incident angle is optimized, the other incident angle is not optimized, and light regularly reflected on the surface of the document placing plate or the surface of the document guide plate easily enters the image sensor. Thus, the possibility of blooming increases.

  Further, when the blooming is prevented by reducing the light amount of the light source as in Patent Document 1, the illumination level on the document is lowered, and the document image read by the image sensor becomes dark.

  Accordingly, the present invention has been made in view of the above-described conventional problems, and is reflected regularly on the surfaces of the document placing plate and the document guide plate and incident on the reading unit without lowering the illumination level of the document. An object of the present invention is to provide an image reading apparatus capable of reducing the level of specular reflection light read in this manner, and an image forming apparatus including the same.

  In order to solve the above-described problem, an image reading apparatus according to the present invention moves a reading unit below a first light-transmitting plate, and reads a document placed on the first light-transmitting plate by the reading unit. A first reading mode in which reading is performed by illuminating through one light-transmitting plate, and the document is conveyed on the second light-transmitting plate by the reading unit by moving the reading unit below the second light-transmitting plate. An image reading apparatus that selectively sets a second reading mode in which reading is performed by illuminating through the second light-transmitting plate, the upper surface of the second light-transmitting plate relative to the upper surface of the first light-transmitting plate And the incident angle of the illumination light of the reading unit with respect to the first light transmitting plate is set so that the specularly reflected light regularly reflected by the first light transmitting plate does not return to the reading unit. In the second reading mode, the light is regularly reflected by the second light transmitting plate and returned to the reading unit. It is provided with optical means for reducing the level of specular reflection light to be read.

  In such an image reading apparatus of the present invention, the upper surface of the second light transmitting plate is inclined with respect to the upper surface of the first light transmitting plate. Therefore, the incident angle of the illumination light from the reading unit to the first light transmitting plate in the first reading mode, and the incident angle of the illumination light from the reading unit to the second light transmitting plate in the second reading mode And the incident angle of the illumination light with respect to the first light transmitting plate is set so that the specularly reflected light that is regularly reflected by the first light transmitting plate in the first reading mode does not return to the reading unit. Even if it is made suitable, the incident angle of the illumination light with respect to the second light transmitting plate cannot be made appropriate at the same time.

  Therefore, an optical means is provided, and when the reading unit is moved below the second light transmitting plate by the optical means, the level of the specular reflection light that is specularly reflected by the second light transmitting plate and returned to the reading unit. Is reduced.

  In the image reading apparatus of the present invention, the optical means is also used as the second light transmissive plate, and the second light transmissive plate has a lower surface that is flush with or parallel to the lower surface of the first light transmissive plate. It is a light plate.

  Even if the upper surface of the second light transmitting plate is inclined with respect to the upper surface of the first light transmitting plate, the lower surface of the second light transmitting plate is flush with or parallel to the lower surface of the first light transmitting plate. The incident angle of the illumination light from the reading unit with respect to the lower surface of the first light-transmitting plate matches the incident angle of the illumination light from the reading unit with respect to the lower surface of the second light-transmitting plate, and the direction of the first light-transmitting plate is At the same time, the orientation of the second light transmission plate is also optimized, so that any of the regularly reflected light regularly reflected by the lower surfaces of the first and second light transmission plates does not enter the reading unit. Alternatively, the level of regular reflection light incident on the reading unit can be lowered.

  Furthermore, in the image reading apparatus of the present invention, the optical means is an antireflection film formed on at least the lower surface of the second light transmitting plate.

  In this case, regardless of whether the incident angle of the illumination light from the reading unit with respect to the lower surface of the second light transmitting plate is optimized, the regular reflectance on the lower surface of the second light transmitting plate is reduced, The level of specular reflection light can be kept low.

  In the image reading apparatus of the present invention, the optical means is a mirror that first reflects the specularly reflected light that is read back to the reading unit at the reading unit, and the tilt angle of the mirror is the The angle exceeds 45 ° with respect to an imaginary line parallel to the upper surface of the second light transmitting plate.

  When the tilt angle of the mirror is increased in this way, the mirror is greatly tilted with respect to the incident direction of the specularly reflected light from the surface of the second light transmitting plate. The level of specular reflection light read by the unit is reduced.

  Furthermore, the image reading apparatus according to the present invention further includes control means for reducing the level of illumination light of the reading unit in the second reading mode than in the first reading mode.

  Thus, by reducing the level of illumination light of the reading unit in the second reading mode, the level of specularly reflected light read back to the reading unit can be more effectively reduced.

  The image reading apparatus of the present invention further includes a document transport path from a position above the first light-transmitting plate to the upper surface of the second light-transmitting plate, and the document transport path is the first transport path. It is inclined with respect to the upper surface of the light transmissive plate and is parallel to the upper surface of the second light transmissive plate.

  In the configuration in which the document transport path is provided so as to be inclined with respect to the upper surface of the first light-transmitting plate and parallel to the upper surface of the second light-transmitting plate, Since the upper surface of the two light transmitting plates is inclined, the incident angle of the illumination light from the reading unit with respect to the surface of the first light transmitting plate when the reading unit is moved below the first light transmitting plate, and the second light transmitting The incident angle of the illumination light from the reading unit with respect to the surface of the second translucent plate when the reading unit is moved below the plate does not match.

  On the other hand, an image forming apparatus of the present invention includes the image reading apparatus of the present invention. Such an image forming apparatus of the present invention also has the same effects as the image reading apparatus of the present invention.

  As described above, in the present invention, since the upper surface of the second light transmitting plate is inclined with respect to the upper surface of the first light transmitting plate, illumination from the reading unit for the first light transmitting plate in the first reading mode is performed. The incident angle of the light does not coincide with the incident angle of the illumination light from the reading unit with respect to the second light transmitting plate in the second reading mode, and the incident angle of the illumination light with respect to the first light transmitting plate is the first reading. Even if the specular reflection light regularly reflected by the first light transmission plate is set so as not to return to the reading unit in the mode, the incident angle of the illumination light with respect to the second light transmission plate is changed at the same time. It cannot be optimized. However, since the optical means is provided, the level of the specularly reflected light that is specularly reflected by the second light transmitting plate and returned to the reading unit when the reading unit is moved below the second light transmitting plate is adjusted. Can be reduced.

  For example, the optical means is a second light transmissive plate having a lower surface that is flush or parallel to the lower surface of the first light transmissive plate. Alternatively, it is an antireflection film formed on at least the lower surface of the second light transmitting plate. Alternatively, it is a mirror of the reading unit that is inclined at an angle exceeding 45 ° with respect to a virtual line parallel to the upper surface of the second light-transmitting plate and reflects specularly reflected light from the second light-transmitting plate. Furthermore, the second light-transmitting plate having a lower surface that is flush or parallel to the lower surface of the first light-transmitting plate, the antireflection film formed on at least the lower surface of the second light-transmitting plate, and an angle exceeding 45 ° The inclined mirrors may be appropriately combined.

1 is a cross-sectional view illustrating an image forming apparatus to which a first embodiment of an image reading apparatus of the present invention is applied. FIG. 2 is a perspective view showing an image reading device mounted on the upper part of the main body of the image forming apparatus 1 in FIG. 1. FIG. 3 is a cross-sectional view showing the image reading device of FIG. 2. It is a perspective view which shows the reading stand of the image reading apparatus of FIG. FIG. 5 is an enlarged cross-sectional view illustrating a periphery of a document guide plate and a periphery of a document placement plate in a comparative image reading apparatus. FIG. 3 is an enlarged cross-sectional view illustrating a periphery of a document guide plate and a periphery of a document placement plate in the image reading apparatus of FIG. 2. FIG. 10 is an enlarged cross-sectional view illustrating a periphery of a document guide plate and a periphery of a document placement plate in an image reading apparatus according to a second embodiment. It is a block diagram which shows the control system of the light source of the 1st reading part in the image reading apparatus of FIG. FIG. 10 is an enlarged cross-sectional view illustrating a periphery of a document guide plate and a periphery of a document placement plate in an image reading apparatus according to a third embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a sectional view showing an image forming apparatus to which the first embodiment of the image reading apparatus of the present invention is applied. The image forming apparatus 1 is a so-called multi-function machine having a scanner function, a copying function, a printer function, a facsimile function, and the like, and transmits an image of a document read by the image reading apparatus 2 to the outside (corresponding to a scanner function). The image of the read original or the image received from the outside is recorded and formed in color or single color on a recording sheet (corresponding to a copying function, a printer function, and a facsimile function).

  The image forming apparatus 1 includes an optical scanning device 11, a developing device 12, a photosensitive drum 13, a drum cleaning device 14, a charger 15, an intermediate transfer belt device 16, a fixing device 17, and a paper for printing an image on a recording paper. A transport path S, a paper feed tray 18, a paper discharge tray 19, and the like are provided.

  The image data handled in the image forming apparatus 1 uses data corresponding to a color image using each color of black (K), cyan (C), magenta (M), yellow (Y), or a single color (for example, black). This is in accordance with the monochrome image. For this reason, four each of the developing device 12, the photosensitive drum 13, the drum cleaning device 14, and the charger 15 are provided so as to form four types of toner images corresponding to the respective colors, and black, cyan, Four image stations Pa, Pb, Pc, and Pd are configured in association with magenta and yellow.

  Each photosensitive drum 13 has a photosensitive layer on the surface thereof. Each charger 15 is a charging means for uniformly charging the surface of each photosensitive drum 13 to a predetermined potential. In addition to a contact-type roller-type or brush-type charger, a charger-type charger. Is used.

  The optical scanning device 11 is a laser scanning unit (LSU) provided with a laser diode and a reflection mirror, and exposes the surface of each charged photosensitive drum 13 according to image data and corresponds to the image data on those surfaces. An electrostatic latent image is formed.

  Each developing device 12 develops the electrostatic latent image formed on the surface of each photosensitive drum 13 with toner of each color, and forms a toner image on the surface of these photosensitive drums 13. Each drum cleaning device 14 removes and collects toner remaining on the surface of each photosensitive drum 13 after development and image transfer.

  The intermediate transfer belt device 16 is disposed above each photosensitive drum 13 and includes an intermediate transfer belt 21, an intermediate transfer belt driving roller 22, a driven roller 23, four intermediate transfer rollers 24, and a belt cleaning device 25. ing.

  The intermediate transfer belt 21 is formed by forming a film having a thickness of about 100 μm to 150 μm into an endless belt shape. The intermediate transfer belt drive roller 22, the driven roller 23, each intermediate transfer roller 24, and the like stretch and support the intermediate transfer belt 21, and rotate the intermediate transfer belt 21 in the direction of arrow C.

  Each intermediate transfer roller 24 is rotatably supported in the vicinity of the intermediate transfer belt 21 and is pressed against the respective photosensitive drums 13 via the intermediate transfer belt 21.

  The toner images on the surfaces of the photosensitive drums 13 are sequentially transferred to the intermediate transfer belt 21 so as to form color toner images (each color toner image) on the intermediate transfer belt 21. Transfer of the toner image from each photosensitive drum 13 to the intermediate transfer belt 21 is performed by each intermediate transfer roller 24 that is in pressure contact with the back surface of the intermediate transfer belt 21. Each intermediate transfer roller 24 is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). Each intermediate transfer roller 24 is applied with a high-voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) in order to transfer the toner image. A high voltage is uniformly applied to the recording paper by the material.

  In this way, the toner images on the surfaces of the photosensitive drums 13 are stacked on the intermediate transfer belt 21 to become a color toner image indicated by the image data. This color toner image is conveyed together with the intermediate transfer belt 21 and transferred onto a recording sheet in a nip region between the intermediate transfer belt 21 and the transfer roller 26a of the secondary transfer device 26.

  The transfer roller 26a of the secondary transfer device 26 has a voltage (a high voltage having a polarity (+) opposite to the toner charging polarity (-)) for transferring the toner image of each color on the intermediate transfer belt 21 onto a recording sheet. Is applied. Further, in order to constantly obtain a nip region between the intermediate transfer belt 21 and the transfer roller 26a of the secondary transfer device 26, either the transfer roller 26a or the intermediate transfer belt drive roller 22 is made of a hard material (metal or the like). The other is made of a soft material such as an elastic roller (such as an elastic rubber roller or a foaming resin roller).

  In addition, the toner image on the intermediate transfer belt 21 may not be completely transferred onto the recording paper by the secondary transfer device 26, and the toner may remain on the intermediate transfer belt 21. Causes color mixing. For this reason, the residual toner is removed and collected by the belt cleaning device 25. The belt cleaning device 25 is provided with, for example, a cleaning blade that contacts the intermediate transfer belt 21 and removes residual toner as a cleaning member, and the back side of the intermediate transfer belt 21 is driven by a driven roller 23 at a portion where the cleaning blade comes into contact. Is supported.

  The recording sheet is conveyed to the fixing device 17 after the color toner image is transferred in the nip region between the intermediate transfer belt 21 and the transfer roller 26 a of the secondary transfer device 26. The fixing device 17 includes a heating roller 31, a pressure roller 32, and the like, and sandwiches and conveys a recording sheet between the heating roller 31 and the pressure roller 32.

  The heating roller 31 is controlled so as to have a predetermined fixing temperature based on a detection output of a temperature detector (not shown), and the color transferred to the recording paper by thermocompression bonding the recording paper together with the pressure roller 32. The toner image is melted, mixed, and pressed, and thermally fixed to the recording paper.

  On the other hand, the paper feed tray 18 is a tray for storing recording paper, and is provided below the image forming apparatus 1 to supply the recording paper in the tray. The manual feed tray 7 is a tray on which recording paper is placed, and is provided on the side wall of the image forming apparatus 1 to supply the recording paper in the tray.

  In the image forming apparatus 1, an S-shaped sheet for feeding a recording sheet supplied from the paper feed tray 18 or the manual feed tray 7 to the sheet discharge tray 19 via the secondary transfer device 26 or the fixing device 17. A conveyance path S is provided. A sheet registration roller 34, a fixing device 17, a transport roller 35, a paper discharge roller 36, and the like are arranged along the paper transport path S.

  A paper pick-up roller 33 is provided at the end of the paper feed tray 18, and the recording paper is pulled out from the paper feed tray 18 one by one by the paper pick-up roller 33 and transported to the paper transport path S. A pickup roller 8 is provided at the end of the manual feed tray 7, and the recording paper is pulled out from the manual feed tray 7 one by one by the pickup roller 8 and sent out to the paper transport path S.

  The conveyance roller 35 is a small roller for promoting and assisting conveyance of the recording paper, and a plurality of sets are provided.

  The paper registration roller 34 temporarily stops the recording paper that has been conveyed, aligns the leading edge of the recording paper, and is placed on the intermediate transfer belt 21 in the nip region between the intermediate transfer belt 21 and the transfer roller 26a of the secondary transfer device 26. In order to transfer the color toner image onto the recording sheet, the recording sheet is conveyed in a timely manner in accordance with the rotation of each photosensitive drum 13 and the intermediate transfer belt 21.

  Further, the recording paper is fixed with a color toner image by the fixing device 17, passes through the fixing device 17, and is then discharged face down on the paper discharge tray 19 by the paper discharge roller 36.

  In addition, when printing not only on the front side of the recording paper but also on the back side, the recording paper is stopped by rotating the paper discharge roller 36 while the recording paper is being conveyed by the paper discharge roller 36 in the paper conveyance path S, and recording is performed. The paper is passed through the reverse path Sr, the front and back sides of the recording paper are reversed, the recording paper is guided to the paper registration roller 34, and the image is recorded and fixed on the back surface of the recording paper in the same manner as the front surface of the recording paper. The paper is discharged to the paper discharge tray 19.

  Next, the image reading device 2 mounted on the upper part of the main body of the image forming apparatus 1 in FIG. 1 will be described with reference to FIGS. 2, 3, and 4. 2 and 3 are a perspective view and a cross-sectional view showing the image reading device 2. FIG. 4 is a perspective view showing a reading table 41 of the image reading device 2.

  The image reading apparatus 2 includes a lower reading table 41 and an upper document conveying unit 42. The upper document transport section 42 is pivotally supported on the inner side of the lower reading table 41 by a hinge (not shown) and opened and closed by moving the front portion up and down. When the document conveying section 42 is opened, the document placing plate 43 and the document guide plate 44 of the reading table 41 are opened as shown in FIG. Both the document placing plate 43 and the document guide plate 44 are made of a glass plate having translucency. An original is placed on the original placement plate 43, and the original is conveyed on the original guide plate 44 and passes therethrough.

  The reading table 41 includes a document placing plate 43, a document guide plate 44, a first reading unit 45, and the like. The first reading unit 45 includes a light source 46, an imaging lens 47, a CCD (Charge Coupled Device) 48, first to fourth reflection mirrors 51 to 54, etc., and a document placement plate 43 and a document guide plate. 44, the original placed on the original placement plate 43 is read (first reading mode), and the original passing through the original guide plate 44 is read (second reading mode). ).

  In the first reading mode, the first reading unit 45 is moved below the document placing plate 43, the document conveying unit 42 is opened, the document is placed on the document placing plate 43, and the document conveying unit 42 is closed. . Then, while moving the first reading unit 45 in the sub-scanning direction Y by a distance corresponding to the document size at a constant speed, the document on the document placing plate 43 is illuminated by the light source 46, and the reflected light is first to first. The light is sequentially reflected by the four reflecting mirrors 51 to 54 and guided to the imaging lens 47. The imaging lens 47 condenses the reflected light from the document on the CCD 48 and forms an image on the surface of the document on the CCD 48. The CCD 48 repeatedly scans the image on the document surface in the main scanning direction X, and outputs an analog image signal of one main scanning line each time.

  In the second reading mode, the first reading unit 45 is moved and positioned below the document guide plate 44, and the document is transported on the document guide plate 44 in the sub-scanning direction Y by the document transport unit 42. When a document passes over the document guide plate 44, the light source 46 of the first reading unit 45 illuminates the document surface via the document guide plate 44, and the reflected light from the document surface is reflected by the first reading unit 45. Reflected sequentially by the fourth reflecting mirrors 51 to 54 and led to the imaging lens 47, the reflected light from the document surface is condensed on the CCD 48 by the imaging lens 47, and an image of the document surface is formed on the CCD 48. The image on the document surface is repeatedly scanned in the main scanning direction X by the CCD 48 to read the image on the document surface.

  Further, the image on the back side of the document can be read by the second reading unit 55 built in the document conveying unit 42. The second reading unit 55 is disposed above the document guide 44, and similarly to the first reading unit 45, the light source 46, the imaging lens 47, the CCD (Charge Coupled Device) 48, and the first to fourth. Reflecting mirrors 51 to 54 are provided. When the original is conveyed in the sub-scanning direction Y by the original conveying unit 42 and passes between the original guide plate 44 and the reading guide plate 56 (made of a light-transmitting glass plate or the like), the second reading unit 55 The back side of the document is illuminated by the light source 46 via the reading guide plate 56, and the reflected light is sequentially reflected by the first to fourth reflecting mirrors 51 to 54 and guided to the imaging lens 47. The imaging lens 47 condenses the reflected light from the back side of the document on the CCD 48, forms an image on the back side of the document on the CCD 48, and the CCD 48 repeatedly scans the image on the back side of the document in the main scanning direction X. Read the back image.

  Furthermore, it is possible to simultaneously read the front and back of the document passing over the document guide plate 44 by the first reading unit 45 and the second reading unit 55.

  The original image read by the CCD 48 of the first reading unit 45 and the second reading unit 55 is output from the CCD 48 as an analog image signal, and the analog image signal is A / D converted into a digital image signal. The digital image signal (image data) is subjected to various image processing and then sent to and received by the optical scanning device 11 of the image forming apparatus 1, and the image forming apparatus 1 records an image on a recording sheet. The paper is output as a copy original.

  On the other hand, the document conveying unit 42 includes a bottom plate 61 that holds down the document on the document placing plate 43 when the document conveying unit 42 is closed, a bottom plate 61, and a document tray 62 disposed above the document placing plate 43, A straight conveyance path 63 that extends linearly from the document tray 62 via the document guide plate 44, a curved conveyance path 64 that branches from the middle of the straight conveyance path 63 and curves upward, and is provided on the end side of the curved conveyance path 64. The first document discharge tray 65 and the second document discharge tray 66 provided on the end side of the straight conveyance path 63 are provided.

  The document tray 62 includes a fixed tray 62 a and an elevating tray 62 b, and is inclined so as to become lower as it approaches the straight conveyance path 63. The document is placed on the fixed tray 62a or the lifting tray 62b, and the leading end side is placed on the lifting tray 62b. The elevating tray 62b incorporates an elevating mechanism (not shown), and is normally lowered. When the document is placed, the elevating tray 62b is raised until the leading edge of the document comes into contact with the pickup roller 67.

  In the straight conveyance path 63, a pickup roller 67 is disposed at the start end thereof, a discharge roller 68 is disposed at the end thereof, and a plurality of conveyance rollers 69 and registration rollers 71 are disposed in the middle thereof. In the curved conveyance path 64, a discharge roller 72 is disposed at the end thereof, and a conveyance roller 69 is disposed in the middle thereof. Further, a switching claw 73 is disposed at a branch point between the straight conveyance path 63 and the curved conveyance path 64.

  Normally, the switching claw 73 is positioned by rotating clockwise around its axis 73a as shown by a solid line. In this state, when the second reading mode is set and the document is placed on the document tray 62, the raising / lowering tray 62b is raised until the leading edge of the document comes into contact with the pickup roller 67, and the pickup roller 67 rotates and the pickup roller 67 rotates. The document is pulled out from the document tray 62 by the roller 67 and sent to the straight conveyance path 63. In the straight conveyance path 63, the document is conveyed by the conveyance roller 69, the leading edge of the document is abutted against the registration roller 71, and the document is moved between the document guide plate 44 and the reading guide plate 56 by the registration roller 71. The document is further conveyed to the curved conveyance path 64 by the switching claw 73, and the document is conveyed to the first document discharge tray 65 via the conveyance roller 63 and the discharge roller 72 and discharged.

  During the conveyance of the original, the front side or the back side of the original is read by the first reading unit 45 or the second reading unit 55.

  When reading an image of a thick paper original (thickness of about 0.8 mm) such as a photo, a postcard, a card, or a business card, the switching claw 73 is rotated counterclockwise around its axis 73a as indicated by a dotted line. Positioned. In this state, when the second reading mode is set and a thick paper document is placed on the document tray 62, the lifting tray 62b is raised until the leading edge of the thick paper document contacts the pickup roller 67. It is pulled out from the document tray 62 and sent to the straight conveyance path 63. In the straight conveyance path 63, the thick paper original is conveyed by the conveyance roller 69, the leading edge of the thick paper original is abutted against the registration roller 71, and then the thick paper original is aligned between the original guide plate 44 and the reading guide plate 56 by the registration roller 71. Then, the sheet is further conveyed to the second document discharge tray 66 via the switching claw 73 and the discharge roller 68 and discharged.

  Since the straight conveyance path 63 is substantially straight, it is possible to quickly convey a thick paper document without causing a jam or the like.

  By the way, in the image reading apparatus 2, the first reading unit 45 reads the document on the document placing plate 43 and the document guide plate 44, and thus the first reading unit 45 performs a high operation on the document placing plate 43. It is necessary to match the document reading position in the vertical direction with the document reading position in the height direction on the document guide plate 44 so that the first reading unit 45 is in focus at any document reading position. The document tray 62 is positioned higher than the document placement plate 43. The straight conveyance path 63 of the document conveyance unit 42 extends linearly from the document tray 62 positioned higher than the document placement plate 43 to the document guide plate 44 having the same height as the document placement plate 43. Accordingly, the straight conveyance path 63 is inclined so as to be lower on the document guide plate 44 side.

  Therefore, the upper surface of the document guide plate 44 that forms a part of the straight conveyance path 63 and the lower surface of the reading guide plate 56 are also inclined. Specifically, when the upper surface of the document placement plate 43 that directly overlaps the surface of the document is used as a reference, the upper surface of the document guide plate 44 and the lower surface of the reading guide plate 56 are inclined with respect to the upper surface of the document placement plate 43.

  Here, if a flat document guide plate 44A as shown in FIG. 5 is employed, the document reading position P1 in the height direction on the document placement plate 43 by the first reading unit 45 and the document guide plate 44A. It is assumed that the document reading position P2 in the height direction above coincides, and the document guide plate 44A is inclined at an inclination angle β with respect to the document placement plate 43. In this case, the incident angle α1 of illumination light from the light source 46 of the first reading unit 45 to the document placement plate 43 and the incident angle α2 of illumination light from the light source 46 of the first reading unit 45 to the document guide plate 44A (= α1-β) is different. Accordingly, the specularly reflected light emitted from the light source 46 of the first reading unit 45 and specularly reflected by the lower surface 43a of the document placing plate 43 is combined with the first to fourth reflecting mirrors 51 to 54 of the first reading unit 45 and the coupling. Even if the incident angle α1 of the illumination light to the document placement plate 43 is adjusted and optimized so that it does not enter the CCD 48 via the lens 47, the incident angle α2 of the illumination light to the document guide plate 44A is not changed. Will not be justified. Therefore, the specularly reflected light irradiated from the light source 46 of the first reading unit 45 and specularly reflected by the lower surface of the document guide plate 44A is reflected by the first to fourth reflecting mirrors 51 to 54 and the coupling lens of the first reading unit 45. It enters the CCD 48 via 47.

  The reflected light from the document incident on the CCD 48 is light that is irregularly reflected on the surface of the document. If specularly reflected light regularly reflected by the lower surface of the document guide plate 44A is incident on the CCD 48, blooming occurs, and an image read by the CCD 48 is overexposed.

  Therefore, in the image reading apparatus 2 of the first embodiment, the lower surface 44a of the document guide plate 44 is flush with or parallel to the lower surface 43a of the document placement plate 43 as shown in FIG. Further, the upper surface 44 b of the document guide plate 44 is inclined at an inclination angle β with respect to the upper and lower surfaces 43 a and 43 b of the document placement plate 43, and is parallel to the straight conveyance path 63. For this reason, the longitudinal cross-sectional shape of the document guide plate 44 is substantially triangular. Further, the document reading position P1 in the height direction on the document placement plate 43 by the first reading unit 45 and the document reading position P2 in the height direction on the document guide plate 44 coincide with each other.

  In such a configuration in which the document guide plate 44 is disposed, the incident angle α1 of the illumination light from the light source 46 of the first reading unit 45 to the document placement plate 43 and the document guide plate 44 from the light source 46 of the first reading unit 45. The incident angle α3 (= α1) of the illumination light with respect to is coincident. Therefore, the specularly reflected light regularly reflected by the lower surface 43 a of the document placing plate 43 is prevented from entering the CCD 48 via the first to fourth reflecting mirrors 51 to 54 and the coupling lens 47 of the first reading unit 45. If the incident angle α1 of the illumination light to the document placement plate 43 is adjusted and optimized, the incident angle α3 of the illumination light to the document placement plate 43 is also optimized at the same time. Accordingly, the specularly reflected light regularly reflected by the lower surface of the document guide plate 44 does not enter the CCD 48 via the first to fourth reflecting mirrors 51 to 54 and the coupling lens 47 of the first reading unit 45.

  For this reason, blooming does not occur in both the first and second reading modes.

  Although regular reflection also occurs on the upper surface 44b of the document guide plate 44, the illumination light is sequentially reflected by the lower surface 44a, the upper surface 44b, and the lower surface 44a of the document guide plate 44 and then passes through the lower surface 44a. The amount of specularly reflected light that is specularly reflected by the upper surface 44b and incident on the first reading unit 45 is small, and this specularly reflected light is unlikely to cause blooming.

  In addition, since the illumination light from the light source 46 is incident only on the reading guide plate 56 for the second reading unit 55, if only the incident angle of the illumination light to the reading guide plate 56 is adjusted and optimized, blooming occurs. Can be prevented.

  FIG. 7 is an enlarged sectional view showing the periphery of the document guide plate and the periphery of the document placement plate in the second embodiment of the image reading apparatus of the present invention.

  Similar to the image reading apparatus 2 of the first embodiment, the image reading apparatus 2 of the second embodiment is applied to the image forming apparatus 1 of FIG. 1 and is generally configured as shown in FIGS. Instead of the document guide plate 44, a document guide plate 81 is applied.

  As shown in FIG. 7, the document guide plate 81 has a flat plate shape in which a lower surface 81a and an upper surface 81b are parallel, and an antireflection film (AR coating) AR is formed on the lower surface 81a. As is well known, the antireflection film AR reduces the reflectance of light, and various types such as a silica coat are provided. Therefore, they can be appropriately selected and applied.

  Here, since the document guide plate 81 has a flat plate shape, the lower surface 81 a and the upper surface 81 b of the document guide plate 81 are inclined at an inclination angle β with respect to the document placement plate 43. Further, the document reading position P1 in the height direction on the document placement plate 43 by the first reading unit 45 coincides with the document reading position P2 in the height direction on the document guide plate 44A.

  When the document guide plate 81 has a flat plate shape, as described above with reference to FIG. 5, the incident angle α1 of the illumination light from the light source 46 of the first reading unit 45 to the document placement plate 43, and the first Unlike the incident angle α2 (= α1-β) of the illumination light from the light source 46 of the first reading unit 45 to the document guide plate 44A, the specularly reflected light that is regularly reflected by the lower surface 43a of the document placement plate 43 is the first. Even if the incident angle α1 of the illumination light to the document placement plate 43 is adjusted and optimized so that it does not enter the CCD 48 of the reading unit 45, the incident angle α2 of the illumination light to the document guide plate 81 is so adjusted. Not optimized.

  However, since the antireflection film AR is formed on the lower surface 81a of the document guide plate 81, the illumination light of the light source 46 of the first reading unit 45 is incident on the lower surface 81a of the document guide plate 81 at an incident angle α2. Most of the illumination light is transmitted through the antireflection film AR and the lower surface 81a of the document guide plate 81, and only a small amount of the illumination light is reflected by the antireflection film AR or the lower surface 81a of the document guide plate 81, and the first reading unit. It is incident on 45 CCDs 48. For this reason, blooming does not occur.

  On the other hand, in the second embodiment, not only the document guide plate 81 is applied, but also the amount of illumination light of the light source 46 of the first reading unit 45 is changed between the first reading mode and the second reading mode.

  FIG. 8 is a block diagram showing a control system of the light source 46 of the first reading unit 45. In FIG. 8, a control unit 82 controls the image reading apparatus 2 in an integrated manner, and includes a CPU, a RAM, a ROM, various interfaces, and the like. The reading drive unit 83 moves the first reading unit 45 below one of the document placement plate 43 and the document guide plate 44, or moves the first reading unit 45 below the document placement plate 43 in the sub-scanning direction Y. Are moved at a constant speed by a distance corresponding to the document size. The input operation unit 84 includes, for example, a plurality of input keys and a liquid crystal display device.

  For example, when the document on the document placement plate 43 is detected by the sensor 85, the control unit 82 selects the first reading mode, controls the reading drive unit 83, and places the first reading unit 45 on the document placement. When the reading operation is instructed by an input operation of the input operation unit 84, the first reading unit 45 is moved below the document placing plate 43 in the sub-scanning direction Y by a distance corresponding to the document size. While moving at a constant speed, the first reading unit 45 is controlled to read the document on the document placing plate 43. Alternatively, when the document on the document tray 62 is detected by the sensor 85, the control unit 82 selects the second reading mode, controls the reading driving unit 83, and moves the first reading unit 45 to the document guide plate 44. When reading is instructed by an input operation of the input operation unit 84, the document conveying unit 42 is controlled to control the first reading unit 45 while the document is being conveyed, and the document guide plate The document passing over 44 is read.

  In addition, when the control unit 82 selects either the first reading mode or the second reading mode, the control unit 82 adjusts and sets the amount of illumination light of the light source 46 of the first reading unit 45 according to the selected reading mode. Specifically, the amount of illumination light in the second reading mode is reduced from the amount of illumination light in the first reading mode. Thus, in the second reading mode, the amount of illumination light is reduced, the amount of specularly reflected light that is regularly reflected on the lower surface of the document guide plate 81 and is incident on the CCD 48 of the first reading unit 45 is further reduced, and blooming is performed. Is more reliably prevented.

  However, the amount of illumination light in the second reading mode is set such that the brightness of the original image read by the CCD 48 of the first reading unit 45 is not significantly reduced.

  If the antireflection film AR is also formed on the upper surface 81b of the document guide plate 81, the amount of regular reflection light from the upper surface 81b of the document guide plate 81 is reduced, and this regular reflection light causes blooming. Is almost gone.

  FIG. 9 is an enlarged sectional view showing the periphery of the document guide plate and the periphery of the document placement plate in the third embodiment of the image reading apparatus of the present invention.

  Similar to the image reading device 2 of the first embodiment, the image reading device 2 of the third embodiment is applied to the image forming device 1 of FIG. 1 and is configured as shown in FIGS. Instead of the document guide plate 44, a document guide plate 81 is applied to change the inclination angle γ of the first reflection mirror 51 in the first reading unit 45.

  In FIG. 9, assuming a virtual line Q parallel to the top surface 43 b of the document placing plate 43 as a reference, the inclination angle γ of the first reflecting mirror 51 is an angle formed with respect to the virtual line Q. Thus, the angle exceeds 45 ° (= 45 ° + θ) (θ> 0 °). Further, the position and inclination angle of the second to fourth reflection mirrors 52 to 54, the position and orientation of the imaging lens 47, the position and orientation of the CCD 48, and the like are changed in accordance with the inclination angle γ of the first reflection mirror 51. Thus, the light reflected by the first reflecting mirror 51 is sequentially reflected by the second to fourth reflecting mirrors 52 to 54 so as to be accurately incident on the CCD 48 via the imaging lens 47.

  Here, in the image reading device 2 of the first and second embodiments, as shown in FIGS. 3 and 7, the inclination angle γ of the first reflecting mirror 51 is set to 45 ° or an angle smaller than 45 °. Yes. This is because the optical path of the light reflected by the first reflecting mirror 51 is set parallel to (or parallel to) the upper surface 43b of the document placing plate 43 (parallel to the sub-scanning direction Y), and the second to second optical paths following the optical path. This is to simplify the positioning and setting of the optical path of the fourth mirrors 52 to 54 → the coupling lens 47 → the CCD 48.

  However, when the inclination angle γ of the first reflecting mirror 51 is set to 45 ° or smaller than 45 °, the incident light is reflected in the incident direction of the regularly reflected light reflected by the lower surface 81a or the upper surface 81b of the document guide plate 81. The first reflecting mirror 51 faces and the amount of the specularly reflected light reflected by the first reflecting mirror 51 increases, the amount of the specularly reflected light incident on the CCD 48 also increases, and blooming is likely to occur.

  On the other hand, when the inclination angle γ of the first reflecting mirror 51 is set to an angle exceeding 45 ° (= 45 ° + θ) as in the image reading device 2 of the third embodiment, the lower surface 81a or the upper surface of the document guide plate 81 is set. Since the first reflection mirror 51 is greatly inclined with respect to the incident direction of the regular reflection light reflected by 81b, the amount of the regular reflection light reflected by the first reflection mirror 51 is reduced, and the regular reflection incident on the CCD 48 is reduced. The amount of light is also reduced and blooming does not occur.

  In the image reading apparatus 2 of the third embodiment as well, the control system shown in FIG. 8 is applied, and the amount of illumination light in the second reading mode is higher than the amount of illumination light in the first reading mode. May be reduced. Thereby, in the second reading mode, the amount of specularly reflected light that is specularly reflected by the lower surface of the document guide plate 81 and incident on the CCD 48 of the first reading unit 45 is further reduced, and blooming is more reliably prevented.

  As mentioned above, although preferred embodiment and modification of this invention were described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. It is understood.

  For example, the first, second, and third embodiments can be appropriately selected and combined, thereby effectively reducing the level of specularly reflected light that is incident on and read from the CCD 48 of the first reading unit 45. can do.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image reading device 11 Optical scanning device 12 Developing device 13 Photosensitive drum 14 Drum cleaning device 15 Charger 16 Intermediate transfer belt device 17 Fixing device 18 Paper feed tray 19 Paper discharge tray 41 Reading stand 42 Document conveying portion 43 Original plate (first translucent plate)
44 Document guide plate (second translucent plate)
45 First reading section 46 Light source 47 Imaging lens 48 CCD
55 Second Reading Unit 63 Straight Conveyance Path 64 Curved Conveyance Path

Claims (7)

A first reading mode in which the reading unit is moved below the first light-transmitting plate, and the original placed on the first light-transmitting plate by the reading unit is illuminated and read through the first light-transmitting plate; The second reading unit moves the reading unit below the second translucent plate and illuminates and reads the document conveyed on the second translucent plate by the reading unit through the second translucent plate. An image reading apparatus for selectively setting a mode,
The upper surface of the second light transmitting plate is inclined with respect to the upper surface of the first light transmitting plate;
The incident angle of the illumination light of the reading unit with respect to the first light transmitting plate is set so that the specularly reflected light regularly reflected by the first light transmitting plate does not return to the reading unit,
An image reading apparatus comprising: optical means for reducing a level of specularly reflected light that is specularly reflected by the second light transmitting plate and returned to the reading unit in the second reading mode. The image reading apparatus according to claim 1,
The optical means is the second light transmitting plate that is also used as the second light transmitting plate and has a lower surface that is flush or parallel to the lower surface of the first light transmitting plate. apparatus. The image reading apparatus according to claim 1,
The image reading apparatus according to claim 1, wherein the optical means is an antireflection film formed on at least a lower surface of the second light transmitting plate. The image reading apparatus according to claim 1,
The optical means is a mirror that first reflects specularly reflected light read back to the reading unit at the reading unit,
The image reading apparatus according to claim 1, wherein an inclination angle of the mirror is an angle exceeding 45 ° with respect to a virtual line parallel to the upper surface of the second light transmitting plate. The image reading apparatus according to any one of claims 1 to 4,
An image reading apparatus comprising: control means for reducing the level of illumination light of the reading unit in the second reading mode than in the first reading mode. An image reading apparatus according to any one of claims 1 to 5,
A document transport path from a position above the first light transmissive plate to the upper surface of the second light transmissive plate;
An image reading apparatus, wherein the document transport path is inclined with respect to the upper surface of the first light-transmitting plate and parallel to the upper surface of the second light-transmitting plate.   An image forming apparatus comprising the image reading device according to claim 1.

Images