Patent Publication Number: US-2023133357-A1

Title: Reading apparatus, image forming apparatus, and reading method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2021-178140 filed Oct. 29, 2021. 
     BACKGROUND 
     (i) Technical Field 
     The present invention relates to a reading apparatus, an image forming apparatus, and a reading method. 
     (ii) Related Art 
     JP2008-028617A discloses an image sensor including a light source, a fluorescent substance that emits white light by light of the light source, an optical filter that blocks light on a longer wavelength side than a wavelength of a predetermined visible light region among the light from the fluorescent substance, a columnar light guide body that propagates the light passing through this optical filter and input to one end side, to the other end side, and emits the light emitted from a side surface to an irradiation target body, and a sensor IC that receives the light reflected from the irradiation target body and converts the light into an electric signal. 
     JP2012-239031A discloses an image sensor unit including a sensor substrate on which a light source, an image forming element that forms an image of reflected light from an illumination target object, and a photoelectric conversion element that converts the reflected light formed by the image forming element into an electric signal are mounted, in which a resin containing an infrared absorbing dye is provided in a light path between a light emitting surface of the light source and a light receiving portion of the photoelectric conversion element. 
     JP6732154B discloses an image reading apparatus including a light guide body extending in a main scanning direction in which light from a light source is incident on an end surface in the main scanning direction and the light is emitted to a reading target moving relatively in a sub-scanning direction, an optical filter provided between the end surface of the light guide body in the main scanning direction and the light source to block or attenuate light having a specific wavelength among the light emitted from the light source, a lens body that converges the reflected light reflected by the reading target and forms an image on a light receiving body that converts the reflected light into an electric signal, and a lens holder that holds the light guide body, the optical filter, and the lens body, in which the lens holder has a first positioning portion that determines a position in a height direction orthogonal to the main scanning direction and the sub-scanning direction and a position in the sub-scanning direction of the light guide body, and a second positioning portion that determines a position in the height direction orthogonal to the main scanning direction and the sub-scanning direction and a position in the sub-scanning direction of the optical filter. 
     SUMMARY 
     In a case where the optical filter blocks infrared light from the light source, red light in a red light region is also partially blocked depending on an emission angle of the light from the light source to the optical filter due to an angle dependence of the optical filter. For this reason, regarding the optical filter disposed parallel to the end surface of the light guide body, among light emitted from the light source at a high tilt angle, the red light is blocked, as compared with light emitted with a low tilt angle. Therefore, as compared with a center portion of the light guide body in a length direction, the light emitted from the light source with the low tilt angle passes through the optical filter and reaches, at an end portion of the light guide body in the length direction, the light emitted with the high tilt angle passes through the optical filter and reaches, the red light is insufficient and color unevenness occurs in the read image in the main scanning direction. 
     Aspects of non-limiting embodiments of the present disclosure relate to a reading apparatus, an image forming apparatus, and a reading method that prevents color unevenness from occurring in a read image in a main scanning direction, as compared with a case where an optical filter is disposed parallel to an end surface of a light guide body. 
     Aspects of certain non-limiting embodiments of the present disclosure overcome the above disadvantages and/or other disadvantages not described above. However, aspects of the non-limiting embodiments are not required to overcome the disadvantages described above, and aspects of the non-limiting embodiments of the present disclosure may not overcome any of the disadvantages described above. 
     According to an aspect of the present disclosure, there is provided a reading apparatus including: a light source; a film-shaped optical filter that blocks light having a predetermined wavelength among light from the light source; and a cylindrical light guide body that guides light passing through the optical filter and incident on one end surface to the other end surface, and irradiates an irradiation target body with light emitted from a side surface, in which a diffusion pattern that diffuses the light is disposed on an opposite side not facing the irradiation target body, on the side surface of the light guide body, and the optical filter is disposed at a position facing the end surface of the light guide body to be tilted with respect to the end surface of the light guide body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiment(s) of the present invention will be described in detail based on the following figures, wherein: 
         FIG.  1    is a schematic configuration diagram illustrating an image forming apparatus according to a first exemplary embodiment of the invention; 
         FIG.  2    is a configuration diagram illustrating an image reading portion of the image forming apparatus according to the first exemplary embodiment of the invention; 
         FIG.  3    is a perspective view illustrating an image reading apparatus according to the first exemplary embodiment of the invention; 
         FIG.  4    is an exploded perspective view illustrating the image reading apparatus according to the first exemplary embodiment of the invention; 
         FIG.  5    is a cross-sectional view (cross-section of 10B-10B line in  FIG.  6   ) illustrating the image reading apparatus according to the first exemplary embodiment of the present invention; 
         FIG.  6    is a cross-sectional view (cross-section of 10A-10A line in  FIG.  5   ) illustrating the image reading apparatus according to the first exemplary embodiment of the present invention; 
         FIG.  7    is an explanatory diagram describing a diffusion pattern and light emitted from a light emitting element according to the first exemplary embodiment of the present invention; 
         FIG.  8    is an explanatory diagram describing a state in which an optical filter according to the first exemplary embodiment of the present invention is disposed to be tilted with respect to an end surface of a light guide body; 
         FIG.  9    is a diagram illustrating a spectral characteristic of a light receiving element according to the first exemplary embodiment of the present invention; 
         FIG.  10    is a diagram illustrating a spectral characteristic of the light emitting element according to the first exemplary embodiment of the present invention; 
         FIG.  11    is a diagram illustrating a spectral characteristic of the optical filter according to the first exemplary embodiment of the present invention; 
         FIG.  12    is a diagram illustrating the spectral characteristics of the image reading apparatus according to the first exemplary embodiment of the present invention; 
         FIG.  13    is a diagram illustrating relative values of an output distribution of red color in a case where an incident angle is changed with respect to a case where the optical filter according to the first exemplary embodiment of the present invention is not provided; 
         FIG.  14    is an explanatory diagram describing arrangement of a light guide body and an optical filter according to a second exemplary embodiment of the present invention; 
         FIG.  15    is an explanatory diagram describing arrangement of a light guide body and an optical filter according to a third exemplary embodiment of the present invention; 
         FIG.  16    is an explanatory diagram describing arrangement of a light guide body and an optical filter according to a fourth exemplary embodiment of the present invention; and 
         FIG.  17    is an explanatory diagram describing arrangement of a light guide body and an optical filter according to a fifth exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     First Exemplary Embodiment 
     Hereinafter, examples of exemplary embodiments of the present disclosure will be described with reference to the drawings. In each of the drawings, the identical or equivalent components and parts are given the same reference numerals. In addition, a dimensional ratio of the drawing is exaggerated for convenience of description, and is different from an actual ratio, in some cases. An arrow H as illustrated indicates an apparatus upward-downward direction (a vertical direction), an arrow W indicates an apparatus width direction (a horizontal direction), and an arrow D indicates an apparatus depth direction (a horizontal direction). 
     Overall Configuration 
     As illustrated in  FIG.  1   , an image forming apparatus  10  according to a first exemplary embodiment includes an accommodating portion  14  which accommodates a sheet member P as a recording medium from the lower side to the upper side in the apparatus upward-downward direction (the arrow H direction), a transport portion  16  which transports the sheet member P accommodated in the accommodating portion  14 , an image forming portion  20  which forms an image on the sheet member P transported from the accommodating portion  14  by the transport portion  16 , and an image reading portion  60  which reading the image formed on a document G, in this order. 
     Accommodating Portion 
     An accommodating member  26  capable of being pulled out from a housing  10 A of the image forming apparatus  10  toward the front side in the apparatus depth direction is provided in the accommodating portion  14 , and the sheet member P is loaded on the accommodating member  26 . Further, a delivery roll  30  which delivers the sheet member P at a highest level loaded on the accommodating member  26  to a transport path  28  constituting the transport portion  16  is provided in the accommodating portion  14 . 
     Transport Portion 
     The transport portion  16  is provided with a plurality of transport rolls  32  which transport the sheet member P along the transport path  28 . 
     Image Forming Portion 
     The image forming portion  20  is provided with four image forming units  18 Y,  18 M,  18 C, and  18 K of yellow (Y), magenta (M), cyan (C), and black (K). In the following description, in a case where it is not necessary to distinguish Y, M, C, and K, Y, M, C, and K may be omitted. 
     The image forming unit  18  of each color is detachable from the housing  10 A. The image forming unit  18  of each color includes an image holding body  36 , a charging roll  38  which charges a surface of the image holding body  36 , and an exposure device  42  which irradiates the charged image holding body  36  with exposure light. Further, the image forming unit  18  of each color includes a developing apparatus  40  which develops an electrostatic latent image formed by exposing the image holding body  36  charged by the exposure device  42  described above and visualizes the electrostatic latent image as a toner image. 
     In addition, the image forming portion  20  includes an endless transfer belt  22  which circulates in the arrow A direction in  FIG.  1   , and a primary transfer roll  44  which transfers the toner image formed by the image forming units  18  of each color to the transfer belt  22 . Further, the image forming portion  20  includes a secondary transfer roll  46  which transfers the toner image transferred to the transfer belt  22  to the sheet member P, and a fixing device  50  heats and pressurizes the sheet member P onto which the toner image is transferred to fix the toner image to the sheet member P. 
     Image Reading Portion 
     As illustrated in  FIG.  2   , the image reading portion  60  includes a first transparent plate  62  (so-called platen glass) on which the document G is placed in a case where an image of one document G is read, and a second transparent plate  72  disposed on one side of the first transparent plate  62  in the apparatus width direction (left side in  FIG.  2   ). The first transparent plate  62  and the second transparent plate  72  are fitted in an upper portion of a housing  60 A in the image reading portion  60 . 
     Above the first transparent plate  62  and the second transparent plate  72 , an opening and closing cover  66  which opens or closes the first transparent plate  62  and the second transparent plate  72  is disposed. Inside the opening and closing cover  66 , a transport device  64  (so-called an ADF apparatus) which transports a plurality of documents G along the transport path  70  in the opening and closing cover  66  and passes the plurality of documents G through a document reading position R above the second transparent plate  72  is provided. 
     In addition, in a space  88  inside the housing  60 A, an image reading apparatus  100  which reads the image of the document G placed on the first transparent plate  62  and the image of the document G transported to the document reading position R by the transport device  64  is provided. Here, the image reading apparatus  100  is an example of a reading apparatus. 
     Further, the image reading portion  60  includes a drive apparatus  74  which drives the image reading apparatus  100  in the apparatus width direction. 
     As illustrated in  FIG.  2   , the drive apparatus  74  includes a shaft  76  extending in the apparatus width direction (a moving direction of the image reading apparatus  100 ) and a sliding member  78  which is attached to a lower surface of a housing  114  of the image reading apparatus  100  and which is slidably supported to the shaft  76 . 
     Further, the drive apparatus  74  includes a motor  80 , a drive pulley  84  which is rotationally driven by transmitting a drive force from the motor  80 , a driven pulley  86  which is driven and rotated, and an endless belt  82  winding around the drive pulley  84  and the driven pulley  86 . The drive pulley  84  is attached to one end of the shaft  76 , and the driven pulley  86  is attached to the other end of the shaft  76 . 
     Details of the image reading apparatus  100  will be described below. 
     Action of Image Forming Apparatus 
     In the image forming apparatus  10 , an image is formed as follows. 
     First, the image reading portion  60  reads an image of the document G. Specifically, in a case of reading the image of the document G transported by the transport device  64 , a drive force of the motor  80  (not illustrated) is transmitted via the endless belt  82 , and the image reading apparatus  100  moves to a transport reading position on the other side in the apparatus width direction and stops, as illustrated in  FIG.  2   . The image reading apparatus  100  disposed at the transport reading position reads the image of the document G transported by the transport device  64 . 
     Further, in a case of reading the image of the document G placed on the first transparent plate  62 , although not illustrated, the image reading apparatus  100  moves from a reading start position toward a reading end position in the apparatus width direction along the first transparent plate  62  by the drive apparatus  74 , while reading the image of the document G. 
     Subsequently, based on image information read by the image reading portion  60 , the exposure device  42  emits the exposure light on a surface of the image holding body  36  of each color charged by the charging roll  38  to form an electrostatic latent image (see  FIG.  1   ). 
     Therefore, the electrostatic latent image corresponding to the data is formed on the surface of the image holding body  36  of each color. Further, the developing apparatus  40  for each color develops this electrostatic latent image, and visualizes the electrostatic latent image as a toner image. Further, the toner image formed on the surface of the image holding body  36  of each color is transferred to the transfer belt  22  by the primary transfer roll  44 . 
     Therefore, the sheet member P delivered from the accommodating member  26  to the transport path  28  by the delivery roll  30  is delivered to a transfer position T at which the transfer belt  22  and the secondary transfer roll  46  come into contact with each other. At the transfer position T, the sheet member P is transported between the transfer belt  22  and the secondary transfer roll  46 , so that the toner image on the surface of the transfer belt  22  is transferred to the sheet member P. 
     The toner image transferred to the sheet member P is fixed to the sheet member P by the fixing device  50 . The sheet member P on which the toner image is fixed is output to an outside of the housing  10 A by the transport roll  32 . 
     Central Portion Configuration 
     Next, details of the image reading apparatus  100  will be described. 
     As illustrated in  FIGS.  3  to  7   , the image reading apparatus  100  includes a light emitting device  124  that irradiates the document G with light, a light receiving portion  117  that receives light, and a rod lens array  112  that guides light to the light receiving portion  117 , and a glass plate  122 . The document G is an example of an irradiation target body. The image reading apparatus  100  reads an image formed on the document G by using a known contact image sensor (CIS) method. 
     Light Receiving Portion 
     The light receiving portion  117  has a light receiving substrate  102  and a plurality of light receiving elements  126  arranged in the apparatus depth direction. As illustrated in  FIG.  4   , a plate thickness direction of the light receiving substrate  102  has an upward-downward direction. The light receiving substrate  102  has a rectangular shape extending in the apparatus depth direction, as viewed from above, and is disposed below the housing  114 . Further, the plurality of light receiving elements  126  are mounted on an upper surface of the light receiving substrate  102 . 
     Rod Lens Array 
     The rod lens array  112  consisting of a transparent material (for example, glass) is formed in a rectangular parallelepiped shape extending in the apparatus depth direction, and is accommodated in a lens accommodating portion  114 B, which will be described below, in the housing, as illustrated in  FIG.  5   . The rod lens array  112  is configured to collect light emitted from a side surface  110 B of a light guide body  110 , which will be described below, and reflected from the document G on which the image is formed, in the light receiving element  126 . 
     Glass Plate 
     A plate thickness direction of the glass plate  122  has an upward-downward direction, and the glass plate  122  has a rectangular shape extending in the apparatus depth direction, as viewed from above. As illustrated in  FIG.  5   , the glass plate  122  is fixed to the housing  114  by a fixing section (not illustrated) in a state in which an edge portion of the glass plate  122  is in contact with a step portion  115  of the housing  114 , and is disposed to cover an upper surface of the housing  114 . 
     Light Emitting Device 
     Next, details of the light emitting device  124  will be described. 
     As illustrated in  FIGS.  4  and  5   , the light emitting device  124  includes the light guide body  110 , an irradiation portion  103 , and the housing  114  constituting the device main body. The light emitting device  124  has two light guide bodies  110 , and the respective light guide bodies  110  are arranged in parallel to be symmetrical with respect to a center of the housing  114  in the apparatus width direction. 
     Light Guide Body 
     As illustrated in  FIG.  4   , the light guide body  110  is formed in a cylindrical shape using a transparent material (for example, acrylic resin), and extends in the apparatus depth direction as a longitudinal direction. The light guide body  110  is accommodated in a light guide body accommodating portion  114 A (see  FIG.  5   ) which will be described below in the housing  114  (see  FIG.  4   ). Further, the light guide body  110  travels light incident on one end surface  110 A through an optical filter  130 , which will be described below, in the longitudinal direction, and irradiates the document G with the light emitted from the side surface  110 B. 
     Further, as illustrated in  FIGS.  5  to  7   , the light guide body  110  is provided with a diffusion pattern  111  that diffuses light incident from the end surface  110 A of the light guide body  110  and advances the light in the longitudinal direction, and emits the light toward the upper side of the rod lens array  112  (in an arrow B direction in  FIG.  5   ). Further, as illustrated in  FIG.  5   , the diffusion pattern  111  is disposed on an opposite side not facing the document G, on the side surface  110 B of the light guide body  110 . More specifically, on the side surfaces  110 B of the two light guide bodies  110 , the diffusion pattern  111  is disposed on the opposite side not facing the document G and on the side away from the other light guide body  110 . That is, the diffusion pattern  111  is displaced at a position at which a center of the fan-shaped diffusion pattern  111  illustrated in  FIG.  5    in the apparatus width direction passes through a center of the light guide body  110  and faces a document reading position R, not directly below the light guide body  110  in an apparatus downward direction. Further, as illustrated in  FIG.  7   , the diffusion pattern  111  is provided over the light guide body  110  in the longitudinal direction at predetermined intervals. Here, as an example, the diffusion pattern  111  is composed of solidified white paint, and diffuses light traveling inside the light guide body  110  toward the upper surface side (document G side) of the light guide body  110 . 
     Irradiation Portion 
     As illustrated in  FIG.  4   , the irradiation portion  103  includes wiring substrates  104 , an element substrate  106 , LED light emitting elements  128  (hereinafter, referred to as “light emitting elements  128 ”), and the optical filter  130 . 
     The wiring substrate  104  is a so-called flexible flat cable, and is provided in pairs, as illustrated in  FIG.  4   . A base end of one wiring substrate  104  is connected to an end portion of the light receiving substrate  102  on the back side (left side in  FIG.  4   ) in the apparatus depth direction, and a base end of the other wiring substrate  104  is connected to an end portion of the light receiving substrate  102  on the front side (right side in  FIG.  4   ) in the apparatus depth direction. 
     The element substrate  106  is a so-called flexible printed circuit substrate, and a plate thickness direction of the element substrate  106  is the apparatus depth direction. As viewed from above, the element substrate  106  is a substrate having a rectangular shape as viewed from the apparatus depth direction, and is provided in pairs as illustrated in  FIG.  4   . One element substrate  106  is connected to a tip of one wiring substrate  104 , and the other element substrate  106  is connected to a tip of the other wiring substrate  104 . Further, the light emitting elements  128  arranged in the apparatus width direction are mounted on one surface of each element substrate  106 . The light emitting element  128  is an example of a light source. Here, the element substrate  106  may have flexibility. The flexibility means, for example, that a substrate having a width of 10 mm is supported in a cantilevered state, and a portion of 10 mm from a support end is pushed from above with a force of 9.8 N so that the amount of deflection becomes 1 mm or more. 
     As illustrated in  FIG.  6   , the light emitting element  128  is disposed on a surface of the element substrate  106  on the light guide body  110  side for each of the two light guide bodies  110  to face the end surface  110 A of the light guide body  110 . Each of the light emitting elements  128  emits light to irradiate the end surface  110 A with the light. 
     The optical filter  130  is disposed between the light emitting element  128  and the end surface  110 A of the light guide body  110 , and blocks light having a predetermined wavelength among the light from the light emitting element  128 , and is formed in a flat-plate film shape. Here, in the present exemplary embodiment, the optical filter  130  is a filter (IR Cut Filter) that blocks light having a predetermined wavelength, for example, light having a wavelength larger than approximately 670 nm such as infrared light. Further, as illustrated in  FIG.  5   , one optical filter  130  is disposed for the two light guide bodies. 
     In addition, as illustrated in  FIGS.  5  to  8   , the optical filter  130  is disposed at a position facing the end surface  110 A of the light guide body  110 , and is disposed to be tilted with respect to the end surface  110 A of the light guide body  110 . That is, the optical filter  130  is disposed to be tilted with respect to the end surface  110 A of the light guide body  110  such that a position of the optical filter  130  facing the diffusion pattern  111  side (apparatus downward direction) is farther from the light guide body  110  than a position of the optical filter  130  facing the document G side (apparatus upward direction). More specifically, as illustrated in  FIG.  8   , the optical filter  130  is disposed such that among angles formed by light from the light source and a normal line with respect to a plane of the optical filter  130 , an angle A on a side facing the diffusion pattern  111  side is smaller than an angle B on a side facing the document G side of the end surface  110 A of the light guide body  110 . 
     The point that the optical filter  130  is disposed to be tilted will be described in detail with reference to  FIGS.  9  to  13   . 
       FIG.  9    is a diagram illustrating an example of each spectral characteristic of a Blue sensor, a Green sensor, and a Red sensor provided in each light receiving element. The Blue sensor uses blue color (475 nm), green color (525 nm), and red color (640 nm) as predetermined reading colors. Although each sensor selectively receives light for each color, infrared light in the vicinity of reading of red color causes noise. Further, as illustrated in  FIG.  9   , a spectral sensitivity of the light receiving portion of a sensor chip 6 having a C-MOS configuration using a silicon semiconductor also receives light on the long wavelength side such as infrared rays. 
       FIG.  10    is a diagram illustrating a spectral characteristic of the light emitting element  128 . As illustrated in  FIG.  10   , the light source which consists of an LED also outputs infrared light on a longer wavelength side than red, and each sensor also receives the infrared light on the longer wavelength side than red, which affects an image quality. 
     The optical filter  130  is provided to remove such infrared light. As illustrated in  FIG.  11   , it can be seen that the optical filter  130  has a property of cutting red color (so-called blue shift) in a case where the optical filter  130  has 20 degrees with respect to the end surface  110 A of the light guide body  110  (angle C in  FIG.  8   ), as compared with a case where the optical filter  130  has 0 degrees parallel to the end surface  110 A of the light guide body  110  (angle C in  FIG.  8   ). Therefore, as illustrated in  FIG.  12   , regarding blue color or green color, even in a case where the degree of the optical filter  130  is changed from 0 degrees to 20 degrees with respect to the end surface  110 A of the light guide body  110 , the spectral characteristic is not changed or very slightly changed. Regarding red color, in a case where the degree is changed from 0 degrees to 20 degrees, the spectral characteristic is changed and the red color is cut. 
       FIG.  13    is a diagram illustrating relative values of an output distribution of red color from a center (0 mm) to an end portion (+150 mm, -150 mm) of the light guide body  110  in the longitudinal direction, in a case where the optical filter  130  is provided parallel to the end surface  110 A of the light guide body  110  (with IRCF) , in a case where the optical filter  130  is tilted by 5 degrees with respect to the end surface  110 A of the light guide body  110  (IRCF 5 degrees), and in a case where the optical filter  130  is tilted by 10 degrees with respect to the end surface  110 A of the light guide body  110  (IRCF 10 degrees), based on a case where the optical filter  130  is not provided (without IRCF). Here, since the light guide body  110  has a length corresponding to an A3 paper size (297 mm × 420 mm), the length is approximately 300 mm. Further, in a case where the optical filter  130  is tilted by 5 degrees with respect to the end surface  110 A of the light guide body  110 , the optical filter  130  facing the lower surface side of the light guide body  110  is tilted by 5 degrees to be separated from the end surface  110 A of the light guide body  110  (angle C in  FIG.  8   ), based on a case where the optical filter  130  is provided parallel to the end surface  110 A of the light guide body  110 . 
     As illustrated in  FIG.  13   , in a case where the optical filter  130  is provided parallel to the end surface  110 A of the light guide body  110  (with IRCF), the output of the reddest color is the smallest. Specifically, at the center (0 mm) of the light guide body  110  in the longitudinal direction, the output distribution of red color is not changed or is very slightly changed even in a case where the optical filter  130  is not provided (without IRCF). Meanwhile, the output distribution of red color becomes smaller as a distance from the center (0 mm) is increased, and the output distribution becomes approximately -18% from the vicinity of approximately 70 mm (+70 mm, -70 mm) to the end portion (+150 mm, -150 mm). Specifically, even in a case where the optical filter  130  is tilted by 5 degrees with respect to the end surface  110 A of the light guide body  110  (IRCF 5 degrees), in the same manner as the case where the optical filter  130  is provided parallel to the end surface  110 A of the light guide body  110  (with IRCF) , at the center (0 mm) of the light guide body  110  in the longitudinal direction, the output distribution of red color is not changed or is very slightly changed even in a case where the optical filter  130  is not provided (without IRCF). Meanwhile, the output distribution of red color becomes smaller as a distance from the center (0 mm) is increased, and the output distribution becomes approximately -14% from the vicinity of approximately 70 mm (+70 mm, -70 mm) to the end portion (+150 mm, -150 mm). In this manner, a difference in output distribution of red color between the center and the end portion of the light guide body in the longitudinal direction becomes color unevenness. 
     On the other hand, unlike the case where the optical filter  130  is provided parallel to the end surface  110 A of the light guide body  110  (with IRCF) and the case where the optical filter  130  is tilted by 5 degrees with respect to the end surface  110 A of the light guide body  110  (IRCF 5 degrees), in a case where the optical filter  130  is tilted by 10 degrees with respect to the end surface  110 A of the light guide body  110  (IRCF 10 degrees), the output distribution of red color becomes smaller even in a case where the distance from the center (0) is increased, and is only approximately -7%. From this, it can be seen that it is desirable that the optical filter  130  is tilted by, for example, approximately 10 degrees with respect to the end surface  110 A of the light guide body  110 . The optical filter  130  may be tilted by 10 degrees or more. 
     Housing 
     As illustrated in  FIG.  4   , the housing  114  has a box shape extending in the apparatus depth direction. As illustrated in  FIG.  5   , in the housing  114 , a pair of light guide body accommodating portions  114 A in which a pair of light guide bodies  110  are respectively accommodated, and a lens accommodating portion  114 B which is formed between the pair of light guide body accommodating portions  114 A and in which the rod lens array  112  is accommodated are formed. Further, a substrate accommodating portion  114 C in which the element substrate  106  and a part of a pressing member  120  are accommodated are formed in the housing  114 . 
     As illustrated in  FIGS.  4  and  5   , the pair of light guide body accommodating portions  114 A are formed side by side in the apparatus width direction, and each light guide body accommodating portion  114 A extends in the apparatus depth direction. Further, a cross-section of each light guide body accommodating portion  114 A intersecting in the longitudinal direction has a semicircular shape with an upper opening. 
     As illustrated in  FIG.  5   , the lens accommodating portion  114 B is formed between the pair of light guide body accommodating portions  114 A in the apparatus width direction, and goes through in the upward-downward direction. The lens accommodating portion  114 B is formed with a pair of projections  116  that support an end portion of a lower surface of the rod lens array  112  in the apparatus width direction. 
     As illustrated in  FIG.  4   , the substrate accommodating portions  114 C are formed in pairs on the back side and the front side in the apparatus depth direction with respect to the light guide body accommodating portion  114 A, and each substrate accommodating portion  114 C goes through in the upward-downward direction, as illustrated in  FIG.  6   . Specifically, the substrate accommodating portion  114 C is formed between wall portions  119  at both ends of the housing  114  in the longitudinal direction and the light guide body accommodating portion  114 A, and a flange  118  that comes into contact with a lower end of the element substrate  106  from below is formed below the substrate accommodating portion  114 C. 
     Second Exemplary Embodiment 
     Next, a second exemplary embodiment will be described with reference to  FIG.  14   . 
     In the first exemplary embodiment described above, one optical filter  130  is provided at each of both ends of the light guide body  110 , and one optical filter  130  is disposed with respect to the two light guide bodies  110 , on one side and the other side of the light guide body  110 . Meanwhile, in the second exemplary embodiment, two optical filters  130  are provided at each of both ends of the light guide body  110 , and the optical filter  130  is disposed for each light guide body  110 . 
     A portion different from the first exemplary embodiment described above will be generally described, and the description will be simplified or omitted for the duplicate portion. 
       FIG.  14    is a schematic explanatory diagram describing arrangement of the light guide body  110  and the optical filter  130  according to the present exemplary embodiment. 
     In the present exemplary embodiment, as illustrated in  FIG.  14   , one optical filter  130  is disposed for each end surface  110 A of the two light guide bodies  110 . In this manner, a size of the optical filter  130  can be made smaller than a size of the optical filter  130  in a case where one optical filter  130  is disposed for the two light guide bodies  110 . Further, the point that the optical filter  130  is disposed to be tilted has the same manner as the first exemplary embodiment described above (see  FIG.  6   ). 
     Third Exemplary Embodiment 
     Next, a third exemplary embodiment will be described with reference to  FIG.  15   . 
     In the second exemplary embodiment described above, the optical filter  130  is disposed to be tilted with respect to the end surface  110 A of the light guide body  110  such that a position facing the diffusion pattern  111  side (apparatus downward direction) is farther from the light guide body  110  than a position facing the document G side (apparatus upward direction). Meanwhile, in the third exemplary embodiment, the optical filter  130  is disposed to be tilted with respect to the end surface  110 A of the light guide body  110  such that a position facing the diffusion pattern  111  side and away from the other optical filter  130  is further from the light guide body  110  than a position facing the document G side. 
     A portion different from the second exemplary embodiment described above will be generally described, and the description will be simplified or omitted for the duplicate portion. 
       FIG.  15    is a schematic explanatory diagram describing arrangement of the light guide body  110  and the optical filter  130  according to the present exemplary embodiment. 
     In the present exemplary embodiment, as illustrated in  FIG.  15   , the optical filter  130  is disposed to be tilted with respect to the end surface  110 A of the light guide body  110  such that a position facing the diffusion pattern  111  side and away from the other optical filter  130  is farther from the light guide body  110  than a position facing the document G side. Specifically, the flat-plate optical filter  130  is disposed such that a central side corner portion  130 A of the optical filter  130  is closest to the end surface  110 A of the light guide body  110 , and an end portion side corner portion  130 B is farthest from the end surface  110 A of the light guide body  110 , in the flat-plate optical filter  130 . Therefore, red color of light emitted to the diffusion pattern  111  side is not cut and reaches the diffusion pattern  111 . The light reaching the diffusion pattern  111  is diffused and emitted to the document G, so that the document G can be read without color unevenness. 
     Fourth Exemplary Embodiment 
     Next, a fourth exemplary embodiment will be described with reference to  FIG.  16   . 
     In the first to third exemplary embodiments described above, the optical filter  130  is formed on a flat plate. Meanwhile, in the fourth exemplary embodiment, the optical filter  130  is formed in a substantially semi-cylindrical shape having a side surface facing the end surface  110 A of the light guide body  110 . 
     A portion different from the first exemplary embodiment to the third exemplary embodiment described above will be generally described, and the description will be simplified or omitted for the duplicate portion. 
       FIG.  16    is a schematic explanatory diagram describing arrangement of the light guide body  110  and the optical filter  130  according to the present exemplary embodiment. 
     In the present exemplary embodiment, as illustrated in  FIG.  16   , the optical filter  130  is formed in a substantially semi-cylindrical shape, and the side surface of the substantially semi-cylindrical shape is disposed toward the end surface  110 A of the light guide body  110 . Here, as illustrated in  FIG.  16   , the substantially semi-cylindrical shape has a center of the cylinder as the light emitting element  128 , and is formed in a curved shape such that angles D formed by light emitted from the light emitting element  128  to the optical filter  130  and a normal line with respect to a plane of the optical filter  130  are the same. The angles at which the light emitted from the light emitting element  128  is incident on the optical filter  130  are substantially the same regardless of a position. Therefore, an angle dependence of the optical filter  130  is not affected, red color light blocked by the optical filter  130  is not biased, and color unevenness is prevented from occurring in a read image in a main scanning direction. 
     The optical filter  130  formed in the substantially semi-cylindrical shape may be disposed as one with respect to the two light guide bodies as in the first exemplary embodiment, or may be disposed for each light guide as in the second exemplary embodiment or in the third exemplary embodiment. 
     Fifth Exemplary Embodiment 
     Next, a fifth exemplary embodiment will be described with reference to  FIG.  17   . 
     In the first to third exemplary embodiments described above, the optical filter  130  is formed on a flat plate. Meanwhile, in the fifth exemplary embodiment, the optical filter  130  is formed in a spherical crown shape projecting toward the end surface  110 A of the light guide body  110 . 
     A portion different from the first exemplary embodiment described above will be generally described, and the description will be simplified or omitted for the duplicate portion. 
       FIG.  17    is a schematic explanatory diagram describing arrangement of the light guide body  110  and the optical filter  130  according to the present exemplary embodiment. 
     In the present exemplary embodiment, as illustrated in  FIG.  17   , the optical filter  130  is formed in a spherical crown shape projecting toward the end surface  110 A of the light guide body  110 . Here, in the same manner as in the fourth exemplary embodiment described above, the spherical crown shape has a center of the sphere as the light emitting element  128 , and is formed in a curved shape such that the angles D formed by light emitted from the light emitting element  128  to the optical filter  130  and a normal line with respect to a plane of the optical filter  130  are the same. The angles at which the light emitted from the light emitting element  128  is incident on the optical filter  130  are substantially the same regardless of a position. Therefore, an angle dependence of the optical filter  130  is not affected, red color light blocked by the optical filter  130  is not biased, and color unevenness is prevented from occurring in the read image in the main scanning direction. 
     The optical filter  130  formed in a spherical crown shape is disposed for each light guide body, as in the second exemplary embodiment or the third exemplary embodiment. 
     Sixth Exemplary Embodiment 
     Next, a sixth exemplary embodiment will be described. 
     In the first to fifth exemplary embodiments described above, the optical filter  130  is disposed to be tilted. Meanwhile, in the sixth exemplary embodiment, the diffusion pattern  111  disposed on the central side of the light guide body in the longitudinal direction is formed by printing with an ink that absorbs infrared light. 
     A portion different from the first exemplary embodiment to the fifth exemplary embodiment described above will be generally described, and the description will be simplified or omitted for the duplicate portion. 
     In the present exemplary embodiment, the diffusion pattern  111  disposed on the central side of the light guide body  110  in the longitudinal direction is formed by printing with an ink that absorbs infrared light. Here, the central side of the light guide body  110  in the longitudinal direction is a portion at which red color is output more strongly than the other portions, for example, a portion of +50 mm, -50 mm from a center of the light guide body  110  in the longitudinal direction (see  FIG.  13   ). By absorbing the infrared light of the portion at which the red color of the light guide body  110  is output more strongly than the other portions, a difference of an output of red color with the end portion side, at which red color is output smaller than the central side, is reduced to prevent color unevenness from occurring in the read image in the main scanning direction. 
     In the present exemplary embodiment, the optical filters  130  according to the first to fifth exemplary embodiments described above may be disposed, or the optical filters  130  may not be disposed. 
     Further, in the present exemplary embodiment, the diffusion pattern  111  disposed on the central side of the light guide body  110  in the longitudinal direction is not limited to the case of printing with an ink that absorbs infrared light. Before printing the diffusion pattern  111 , the infrared light absorbing ink may be applied to the central side of the light guide body  110  in the longitudinal direction, in a printing region of the diffusion pattern  111 . 
     The exemplary embodiment of the present invention is not limited to the exemplary embodiment described above, and various modifications and applications are possible without departing from the gist of the exemplary embodiment of the present invention. 
     For example, in the exemplary embodiments described above, the two light guide bodies  110  are provided, and one or three or more light guide bodies  110  may be provided. 
     Further, the light emitting elements  128  are disposed on both end sides of the light guide body  110  to irradiate the light guide body  110  with light, and the present invention is not limited to this. The light emitting element  128  may be disposed on only any one side. 
     The foregoing description of the exemplary embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.