Optical device and document reading device

Abstract

To prevent both a reduction in the amount of light received by a light receiving unit and unevenness in the amount of light received by the light receiving unit when a light guide scatters light incident from an end face using a scatterer arranged in the direction in which the side face extends and then emits the light.SOLUTION: An optical device includes a light guide that scatters light incident from an end face using scatterers arranged in a direction in which the side faces extend and then outputs the light, a specular reflector that specularly reflects the light output from the light guide, a light receiving unit that receives the light reflected by the specular reflector, and a diffusion plate that diffuses and transmits the light output from the light guide such that the light enters the specular reflector and diffuses and transmits the light reflected by the specular reflector such that the light enters the light receiving unit.SELECTED DRAWING: Figure 10

Description

[Technical field]

[0001] The present invention relates to an optical device and a document reading device. [Background technology]

[0002] Patent document 1 describes an original reading device in which a reading guide member on which a background reflective member is arranged is attached so that its rear end portion downstream in the document transport direction can be lifted and tilted to a certain angle when the original being transported comes into contact with it, and the light guide has an exit surface that guides and emits light from the light source in a direction to be irradiated onto the background reflective member, and the width of the exit surface in the sub-scanning direction is set to a dimension that emits light that can be reflected by the background reflective member to be received by the light receiving unit even when the reading guide member is tilted. Patent document 2 describes an original reading device that is arranged in a state where light from a light source is reflected by a light receiving unit so that it passes through a reading position and is then received by the light receiving unit, and that is provided with a background reflection unit that reflects a greater amount of reflected light than the amount of original reflected light reflected by the original when no original is present, and the background reflection unit is configured by processing a mirror surface so as to reflect a lesser amount of reflected light than the amount of specular reflected light reflected by the mirror surface. Patent document 3 describes a document reading device that includes a light source that irradiates light onto a document passing through a reading position, a background section that is located opposite the light source across the document passing through the reading position, a first detection section that is located upstream of the reading position in the document transport direction and detects the leading edge of the document, a second detection section that detects the edge of the document from the difference in the amount of light from the light source reflected by the background section and the light reflected by the document, and a processing section that performs leading edge processing based on the result of the first detection section and tilt processing based on the result of the second detection section. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-019213 A [Patent Document 2] JP 2015-012347 A [Patent Document 3] JP 2015-023428 A Summary of the Invention [Problem to be solved by the invention]

[0004] When a light guide scatters light incident from an end face using a scatterer arranged in the direction in which the side face extends and then emits the light, the amount of light received by the light receiving unit is reduced. On the other hand, if an attempt is made to increase the amount of light, unevenness occurs in the amount of light received by the light receiving unit.

[0005] The object of the present invention is to prevent both a reduction in the amount of light received by the light receiving unit and unevenness in the amount of light received by the light receiving unit when a light guide scatters light incident from an end face using a scatterer arranged in the direction in which the side face extends and then emits the light. [Means for solving the problem]

[0006] The invention described in claim 1 is an optical device comprising a light guide that scatters light incident from an end face using scatterers arranged in the direction in which the side faces extend and then outputs the light, a specular reflector that specularly reflects the light output from the light guide, a light receiving unit that receives the light reflected by the specular reflector, and a diffuser that diffuses and transmits the light output from the light guide so that it enters the specular reflector and diffuses and transmits the light reflected by the specular reflector so that it enters the light receiving unit. The invention described in claim 2 is the optical device described in claim 1, wherein the diffuser plate includes a first layer having a first regular reflectance and a second layer having a second regular reflectance lower than the first regular reflectance, and the second layer is positioned facing the light receiving portion. An invention described in claim 3 is the optical device described in claim 2, in which the first layer is a backing coat layer, and the second layer is a light diffusing layer. The invention described in claim 4 is the optical device described in claim 1, further comprising a lens portion that guides light reflected by the specular reflector to the light receiving portion, and the specular reflector has a characteristic that prevents the light receiving portion from being located within the focal depth of the lens portion. The invention described in claim 5 is the optical device described in claim 4, in which the specular reflector has a recessed shape arranged in the direction in which the side surface of the light guide extends, thereby providing the above-mentioned characteristics. The invention described in claim 6 is an original reading device comprising a light source provided on the end face side of the light guide to irradiate light, a reading window through which an original document passes, and an optical device described in any one of claims 1 to 5, wherein the light receiving unit receives light emitted from the light guide and reflected by the original document when the original document passes through the reading window, and receives light reflected by the mirror reflector when the original document does not pass through the reading window. Effect of the Invention

[0007] According to the invention of claim 1, when a light guide scatters light incident from an end face using a scatterer arranged in the direction in which the side face extends and then emits the light, it is possible to prevent both a reduction in the amount of light received by the light receiving unit and unevenness in the amount of light received by the light receiving unit. According to the invention of claim 2, it is possible to further reduce the possibility that the amount of light received by the light receiving section becomes small. According to the invention of claim 3, it is possible to easily reduce the possibility that the amount of light received by the light receiving section becomes small. According to the invention of claim 4, it is possible to further reduce the possibility that the amount of light received by the light receiving section will be uneven. According to the invention of claim 5, it is possible to easily reduce the possibility that the amount of light received by the light receiving section will be uneven. According to the invention of claim 6, when a light guide scatters light incident from an end face using a scatterer arranged in the direction in which the side face extends and then emits the light, it is possible to prevent both a reduction in the amount of light received by the light receiving unit and unevenness in the amount of light received by the light receiving unit. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of a configuration of an image reading device according to an embodiment of the present invention. [Diagram 2]FIG. 2 is a perspective view showing an image reading unit according to the embodiment; [Diagram 3] FIG. 2 is an exploded perspective view showing an image reading unit according to the embodiment. [Figure 4] 4 is a cross-sectional view (cross-sectional view taken along line IV-IV in FIG. 5) showing an image reading unit in the present embodiment. [Diagram 5] 5 is a cross-sectional view (cross-sectional view taken along line VV in FIG. 4) showing an image reading unit in the present embodiment. [Figure 6] 4A and 4B are explanatory diagrams for explaining a diffusion pattern and light emitted from a light-emitting element in the present embodiment. [Figure 7] 1 is a first graph showing output values ​​of light reflected by a specular reflector. [Figure 8] 11 is a second graph showing output values ​​of light reflected by a specular reflector. [Figure 9] 11A and 11B are diagrams for explaining a dust detection and correction function. [Figure 10] 3A to 3C are diagrams illustrating an example of the configuration of a specular reflector in the present embodiment. [Figure 11] 13 is a graph showing the output value of light reflected by a specular reflector when a diffuser plate is disposed on the specular reflector. [Figure 12] 13 is a graph showing the output value of reflected light by a specular reflector when a backing coat layer is disposed on the image reading unit side. [Figure 13] 13 is a partially enlarged graph of the graph in FIG. 12. [Figure 14] 11 is a graph showing the output value of reflected light by a specular reflector when a light diffusion layer is disposed on the image reading unit side. [Figure 15] 15 is a partially enlarged graph of the graph in FIG. 14. [Figure 16] 13(a) and 13(b) are diagrams illustrating a modified example of the specular reflector in the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0010] [Image reader] 1 is a diagram showing an example of the configuration of an image reading device 60 according to the present embodiment. In the figure, H indicates the up-down direction and W indicates the device width direction. As shown in the figure, the image reading device 60 includes a first transparent plate 62 (so-called platen glass) on which a sheet of original G is placed when an image of the original G is read, and a second transparent plate 72 disposed on one side of the first transparent plate 62 in the device width direction (the left side in the figure). The first transparent plate 62 and the second transparent plate 72 are fitted into an upper portion of a housing 60A of the image reading device 60.

[0011] An opening / closing cover 66 for opening or closing the first transparent plate 62 and the second transparent plate 72 is disposed above the first transparent plate 62 and the second transparent plate 72. Inside the opening / closing cover 66, a transport section 64 (so-called ADF) is provided for transporting a plurality of original documents G along a transport path 70 inside the opening / closing cover 66 and passing the original document G through an original document reading position R above the second transparent plate 72. The transport section 64 also includes a reading guide member 210 for guiding the original document G being transported along the transport path 70 to the original document reading position R and for guiding the original document G in the discharge direction after passing the original document reading position R. A mirror reflector 220 is provided on a part of the lower surface of the reading guide member 210 that faces the original document reading position R.

[0012] Also, an image reading unit 100 is provided in the internal space of the housing 60A, which reads an image of the original G placed on the first transparent plate 62 and an image of the original G transported to the original reading position R by the transport unit 64. Furthermore, the image reading device 60 is provided with a drive unit 74 which drives the image reading unit 100 in the device width direction.

[0013] The drive unit 74 includes a shaft 76 extending in the device width direction (the direction in which the image reading unit 100 moves) and a sliding member 78 attached to the lower surface of the housing 114 of the image reading unit 100 and slidably supported by the shaft 76.

[0014] Furthermore, the drive unit 74 includes a motor (not shown), a drive pulley 84 that is rotated by the driving force transmitted from the motor, a driven pulley 86 that is rotated by the motor, and an endless belt 82 that is wound 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.

[0015] The image reading unit 100 will be described in detail later.

[0016] In the image reading device 60, the image reading unit 100 reads an image of the original G as follows. Specifically, when reading an image of the original G transported by the transport unit 64, as shown in the figure, the image reading unit 100 moves to a transport reading position on the other side in the device width direction and stops there, by the driving force of a motor (not shown) being transmitted via the endless belt 82. Then, the image reading unit 100 arranged at the transport reading position reads an image of the original G transported by the transport unit 64.

[0017] In addition, when reading an image of the original G placed on the first transparent plate 62, although not shown, the image reading unit 100 moves in the device width direction from the reading start position toward the reading end position along the first transparent plate 62 by the drive unit 74 while reading the image of the original G.

[0018] Here, the image reading device 60 is an example of a document reading device.

[0019] [Image reading section] FIG. 2 is a perspective view showing the image reading unit 100 in the present embodiment. FIG. 3 is an exploded perspective view showing the image reading unit 100 in the present embodiment. Fig. 4 is a cross-sectional view showing the image reading unit 100 in this embodiment. Specifically, Fig. 4 is a cross-sectional view taken along line IV-IV in Fig. 5. Note that Fig. 4 also shows the second transparent plate 72 and the specular reflector 220, although they are not strictly speaking components of the image reading unit 100. 5 is a cross-sectional view showing the image reading unit 100 in the present embodiment. Specifically, FIG. 5 is a cross-sectional view taken along line VV of FIG. FIG. 6 is an explanatory diagram for explaining the diffusion pattern and the light emitted from the light emitting element in this embodiment. In these figures, H indicates the up-down direction, W indicates the width direction of the device, and D indicates the depth direction of the device.

[0020] 2 to 6, the image reading unit 100 has a light emitting unit 124 that irradiates light toward the document G, a light receiving unit 125 that receives the light, a rod lens array 112 that guides the light to the light receiving unit 125, and a glass plate 122. The image reading unit 100 is configured to read an image formed on the document G using a known CIS (Contact Image Sensor) method.

[0021] When reading an image of the document G transported by the transport unit 64, the image reading unit 100 is disposed below the second transparent plate 72 and directly below the specular reflector 220, as shown in FIG. 4. In this case, the document G transported by the transport unit 64 passes through the document reading position R on the second transparent plate 72. When the document G passes through the document reading position R on the second transparent plate 72, the document G reflects light emitted from a side surface 110B of the light guide 110, which will be described later. On the other hand, when the document G does not pass through the document reading position R on the second transparent plate 72, the specular reflector 220 reflects light emitted from a side surface 110B of the light guide 110, which will be described later.

[0022] Here, the second transparent plate 72 is an example of a reading window portion through which the document passes. Also, the specular reflector 220 is an example of a specular reflector that specularly reflects the light emitted from the light guide.

[0023] The light receiving unit 125 has a light receiving substrate 102 and a plurality of light receiving elements 126 arranged in the device depth direction. As shown in Fig. 3, the light receiving substrate 102 has a plate thickness direction in the up-down direction. When viewed from above, the light receiving substrate 102 has a rectangular shape extending in the device depth direction, and is disposed below the housing 114. In addition, a plurality of light receiving elements 126 are mounted on the upper surface of the light receiving substrate 102.

[0024] Furthermore, when original G has passed through original reading position R on second transparent plate 72, light receiving unit 125 receives light that is emitted from side surface 110B of light guide 110 (described later) and reflected by original G. On the other hand, when original G has not passed through original reading position R on second transparent plate 72, light receiving unit 125 receives light that is emitted from side surface 110B of light guide 110 (described later) and reflected by specular reflector 220.

[0025] Here, the light receiving unit 125 is an example of a light receiving unit that receives light reflected by a specular reflector. Also, the light receiving unit 125 is an example of a light receiving unit that receives light emitted from the light guide and reflected by the document when the document passes through the reading window, and receives light reflected by the specular reflector when the document does not pass through the reading window.

[0026] The rod lens array 112 is made of a transparent material (e.g., glass), is formed in a rectangular parallelepiped shape extending in the device depth direction, and is housed in a lens housing section 114B of a housing 114 as shown in Fig. 4. When an original G passes through an original reading position R on the second transparent plate 72, the rod lens array 112 is configured to collect light that is emitted from a side surface 110B of the light guide 110 described later and reflected by the original G, on the light receiving element 126. On the other hand, when an original G does not pass through an original reading position R on the second transparent plate 72, the rod lens array 112 is configured to collect light that is emitted from a side surface 110B of the light guide 110 described later and reflected by a specular reflector 220, on the light receiving element 126.

[0027] Here, the rod lens array 112 is an example of a lens section that guides the light reflected by the specular reflector to the light receiving section.

[0028] The glass plate 122 has a thickness direction in the up-down direction and is rectangular in shape extending in the device depth direction when viewed from above, as shown in Fig. 3. Then, the glass plate 122 is fixed to the housing 114 by a fixing means (not shown) with the edge of the glass plate 122 in contact with the step portion 115 of the housing 114, as shown in Fig. 4, and is disposed so as to cover the upper surface of the housing 114.

[0029] 3 and 4, the light-emitting unit 124 has a light guide 110, an irradiation unit 103, and a housing 114 constituting the device main body. The light-emitting unit 124 has two light guides 110, which are arranged in parallel to be symmetrical with respect to the center of the housing 114 in the device width direction.

[0030] 3, the light guide 110 is formed in a cylindrical shape using a transparent material (e.g., acrylic resin) and extends with its longitudinal direction aligned with the depth direction of the device. The light guide 110 is accommodated in a light guide accommodating section 114A of a housing 114. The light guide 110 causes light incident on one end face 110A to travel in the longitudinal direction, and irradiates light exiting from a side face 110B onto a document G.

[0031] 4 to 6, the light guide 110 is provided with a diffusion pattern 111 that diffuses the light incident from the end surface 110A of the light guide 110 and causes it to travel in the longitudinal direction, and also emits the light toward the upper side of the rod lens array 112 (in the direction of the arrow B in FIG. 4). As shown in FIG. 4, the diffusion pattern 111 is disposed on the side surface 110B of the light guide 110 opposite to the original G. More specifically, the diffusion pattern 111 is disposed on the side surface 110B of the two light guides 110 opposite to the original G and away from the other light guide 110. That is, the diffusion pattern 111 is disposed not directly below the light guide 110 in the device downward direction, but at a position where the center of the fan-shaped diffusion pattern 111 in the device width direction passes through the center of the light guide 110 and faces the document reading position R. 6, the diffusion patterns 111 are provided at predetermined intervals along the longitudinal direction of the light guide 110. Here, the diffusion patterns 111 are formed of solidified white paint, for example, and diffuse the light traveling inside the light guide 110 to direct it toward the upper surface side (document G side) of the light guide 110. Alternatively, a prism may be used as the diffusion pattern 111.

[0032] Here, the diffusion pattern 111 is an example of a scatterer arranged in the direction in which the side surface extends. Also, the light guide 110 is an example of a light guide that scatters light incident from an end face with a scatterer and emits the light.

[0033] As shown in FIG. 3, the irradiation section 103 has a wiring board 104, an element board 106, and an LED light-emitting element 128 (hereinafter, "light-emitting element 128").

[0034] The wiring boards 104 are so-called flexible flat cables, and a pair of wiring boards 104 are provided as shown in Fig. 3. One wiring board 104 has a base end connected to an end of the light receiving board 102 on the rear side in the device depth direction (left side in the figure), and the other wiring board 104 has a base end connected to an end of the light receiving board 102 on the front side in the device depth direction (right side in the figure).

[0035] The element substrate 106 is a so-called flexible printed circuit board (Flexible Printed Circuits), and the thickness direction is the device depth direction. The element substrate 106 is a substrate that is rectangular when viewed from the device depth direction, and is accommodated in a substrate accommodation section 114C of the housing 114 as shown in FIG. 3, and is provided as a pair. One element substrate 106 is connected to the tip of one wiring substrate 104, and the other element substrate 106 is connected to the tip of the other wiring substrate 104. In addition, light emitting elements 128 arranged in the device width direction are mounted on one surface of each element substrate 106. The light emitting elements 128 are provided on the end surface side of the light guide and are an example of a light source that irradiates light. Here, the element substrate 106 may be flexible. The flexibility means, for example, that a substrate with a width of 10 mm is supported in a cantilever state, and a portion 10 mm from the support end is pressed from above with a force of 9.8 N, and the deflection amount is 1 mm or more.

[0036] 6, the light emitting elements 128 are disposed on the surface of the element substrate 106 facing the light guides 110, for every two light guides 110, so as to face the end faces 110A of the light guides 110. Each of the light emitting elements 128 emits light and irradiates the end faces 110A with light.

[0037] [Background of this embodiment] In such an image reading device 60, when the conveying unit 64 conveys the document G along the conveying path 70, the document G may be inclined. To cope with such a case, the image reading device 60 may have a function of mechanically correcting the inclination of the document G (hereinafter, "mechanical skew correction function"). The mechanical skew correction function corrects the inclination of the leading edge of the document G by abutting the document G against a stopped roller to create a loop, thereby suppressing the variation in the timing at which each part of the leading edge of the document G arrives at the document reading position R. However, this mechanical skew correction function has a problem in that it generates an impact sound when the leading edge of the document G collides with the roller, and an impact sound when creating and releasing a loop of the document G.

[0038] To cope with such a problem, the image reading device 60 may have a function of detecting the inclination angle of the document G by image processing and correcting the inclination angle. However, the inclination angle of the document G cannot be detected unless there is a difference equal to or greater than a predetermined standard between the output value of the reflected light from the document G when the document G passes through the document reading position R and the output value of the reflected light from the specular reflector 220 when the document G does not pass through the document reading position R. Specifically, since the output value of the reflected light from a white document G is close to 240 LSB in the case of an 8-bit 256-level output, for example, the output value of the reflected light from the specular reflector 220 needs to be a higher value than that.

[0039] However, when an illumination system is adopted in which the light emitting element 128 irradiates light from the end surface 110A of the light guide 110 as in the above-mentioned image reading device 60, the output of the light from the light guide 110 is low, and therefore the output of the reflected light by the specular reflector 220 is also low. Also, in order to speed up image reading or deepen the focal depth, it is required to increase the output of the reflected light, but the above-mentioned image reading device 60 cannot meet such a requirement.

[0040] In the previous example, the final output was shown as 256 levels of gradation, but in the stages prior to the final output, processing may be done with more levels, for example 10-bit, 1024 levels of gradation, and then rounded down to 8-bit, 256 levels of gradation as the final output; for the sake of explanation below, we will use 10-bit output. 7 is a first graph showing the output value of the reflected light by the specular reflector 220. Here, the output value of the reflected light is measured using the specular reflector 220 of the existing technology. In order to detect the inclination angle of the document G, the output value of the reflected light by the specular reflector 220 needs to be about 400 LSB, but in the first graph, it is clear that the output of the reflected light is insufficient, as it does not reach about 400 LSB.

[0041] 8 is a second graph showing the output value of the reflected light by the specular reflector 220. Here, the output value of the reflected light is measured using a specular reflector 220 of existing technology with a higher reflectance. In the second graph, it can be seen that the output value of the reflected light by the specular reflector 220 reaches about 400 LSB, but unevenness in the amount of light (hereinafter simply referred to as "unevenness") occurs due to the projection of the diffusion pattern 111 (areas M1 and M2).

[0042] That is, there is no specular reflector 220 in the existing technology that does not cause a shortage of reflected light output and does not cause unevenness.

[0043] Additionally, in recent years, image reading devices 60 may have a function of detecting and correcting dust on second transparent plate 72 (hereinafter, referred to as a "dust detection and correction function"). 9 is a diagram for explaining the dust detection and correction function. When dust is present on the second transparent plate 72, streaks S appear in the conveying direction at the same location in the width direction of the image of the document G as shown in the figure. In this case, the dust detection and correction function determines that such streaks S are caused by dust on the second transparent plate 72, and removes them by image processing.

[0044] On the other hand, if the reflectance of the specular reflector 220 is increased so that the lower limit of the area where unevenness occurs (areas M1 and M2 in FIG. 8) exceeds the target value, the inclination of the original G can be detected, but the unevenness cannot be distinguished from the streaks S in FIG. 9, and the dust detection and correction function cannot detect dust.

[0045] [Specular Reflector of the Present Embodiment] 10 is a diagram showing a configuration example of the specular reflector 220 in this embodiment. As shown in the figure, a diffusion plate 230 is arranged on the image reading unit 100 side of the lower surface of the specular reflector 220 in this embodiment. In addition, in the diffusion plate 230, a light diffusion layer 234 is provided on the image reading unit 100 side of the base material 232, and a backing coat layer 236 is provided on the specular reflector 220 side of the base material 232.

[0046] When the specular reflector 220 and the diffuser 230 are combined in this manner, the light emitted from the light guide 110 passes through the diffuser 230, and the light reflected by the specular reflector 220 passes through the diffuser 230 again. In other words, the light passes through the diffuser 230 twice. This makes it possible to increase the output of the light reflected by the specular reflector 220 and reduce unevenness caused by this reflected light.

[0047] Here, the diffusion plate 230 is an example of a diffusion plate that diffuses and transmits the light emitted from the light guide to make it enter the specular reflector, and diffuses and transmits the light reflected by the specular reflector to make it enter the light receiving unit. The portion including the light guide 110, the specular reflector 220, the diffusion plate 230, and the light receiving unit 125 is an example of an optical device.

[0048] 11 is a graph showing the output value of the reflected light by the specular reflector 220 when the diffuser 230 is disposed on the specular reflector 220. In this graph, it can be seen that the output value of the reflected light by the specular reflector 220 reaches the target value of about 400 LSB.

[0049] Incidentally, in FIG. 10, it is also possible to dispose the light diffusing layers 234 on both sides of the base material 232, but in that case, the output of the reflected light by the specular reflector 220 would be insufficient. Also, in FIG. 10, it is possible to arrange the backing coat layer 236 on the image reading unit 100 side of the substrate 232 and the light diffusion layer 234 on the specular reflector 220 side of the substrate 232, but in that case too, the reflected light output by the specular reflector 220 would be insufficient. Therefore, in this embodiment, the surface of the diffusion plate 230 that is less reflective, i.e., the surface with a low regular reflectance, is disposed on the image reading unit 100 side. Specifically, the light diffusion layer 234 is disposed on the image reading unit 100 side of the substrate 232, and the backing coat layer 236 is disposed on the specular reflector 220 side of the substrate 232.

[0050] Fig. 12 is a graph showing the output value of the reflected light by the specular reflector 220 when the backing coat layer 236 is disposed on the image reading unit 100 side. Fig. 13 is a graph showing a partial enlargement of the graph in Fig. 12. These graphs show that some unevenness remains when the backing coat layer 236 is disposed on the image reading unit 100 side.

[0051] Fig. 14 is a graph showing the output value of the reflected light by the specular reflector 220 when the light diffusion layer 234 is disposed on the image reading unit 100 side. Fig. 15 is a graph showing a partial enlargement of the graph in Fig. 14. These graphs show that almost no unevenness remains when the light diffusion layer 234 is disposed on the image reading unit 100 side.

[0052] In the above, the surface of the backing coat layer 236 is used as the highly reflective surface, the surface of the light diffusion layer 234 is used as the less reflective surface, and the light diffusion layer 234 is arranged to face the light receiving unit 125 side, but this is not limited to the above. More generally, the surface of a first layer having a first regular reflectance may be used as the highly reflective surface, and the surface of a second layer having a second regular reflectance lower than the first regular reflectance may be used as the less reflective surface, and the second layer may be arranged to face the light receiving unit side. In this case, the backing coat layer 236 is an example of the first layer, and the light diffusion layer 234 is an example of the second layer.

[0053] [Modification of specular reflector] In a modification of the specular reflector 220 in this embodiment, a recess is provided on the image reading unit 100 side of the specular reflector 220 along the longitudinal direction of the light guide 110. In other words, this modification of the specular reflector 220 uses the recess to increase the apparent distance and blur the image, thereby eliminating unevenness.

[0054] 16(a) and (b) are diagrams for explaining modified examples of the specular reflector 220 in this embodiment. 13A is a diagram showing a case where no recess is provided on the side of the specular reflector 220 facing the image reading unit 100. In this case, the light is focused on the light receiving unit 125, causing unevenness. 13B is a diagram showing a case where a recess is provided on the image reading unit 100 side of the specular reflector 220. In this case, the distance from the specular reflector 220 to the rod lens array 112 becomes longer, the light on the light receiving unit 125 spreads, and unevenness is reduced.

[0055] 16(a) and (b), the specular reflector 220 is disposed at the same position in the vertical direction. However, in order to emphasize that the distance from the specular reflector 220 to the rod lens array 112 is longer in (b) than in (a), the specular reflector 220 in (b) is shown disposed at a higher position in the vertical direction than the specular reflector 220 in (a).

[0056] In the above, a recess is provided on the image reading unit 100 side of the specular reflector 220 along the longitudinal direction of the light guide 110, but this is not limiting. The specular reflector 220 may have any property that prevents the light receiving unit 125 from being located within the focal depth of the rod lens array 112. In the above, a method of arranging a recess in the direction in which the side surface of the light guide 110 extends is used as an example of a method for providing the specular reflector 220 with such a property.

[0057] In this modified example of the specular reflector 220, a sheet-like diffuser 230 may be attached along the recesses of the specular reflector 220. In addition, even if a recess is not provided in the specular reflector 220, a recess may be provided in the reading guide member 210 to which the specular reflector 220 is attached, and sheet-like objects may be attached to the reading guide member 210 along the recess as the specular reflector 220 and the diffusion plate 230.

[0058] [Note] (((1))) a light guide that scatters light incident from an end face of the light guide by a scatterer disposed in a direction in which the side face of the light guide extends, and outputs the light; a specular reflector that specularly reflects the light emitted from the light guide; a light receiving unit that receives light reflected by the specular reflector; a diffusion plate that diffuses and transmits the light emitted from the light guide to be incident on the specular reflector, and diffuses and transmits the light reflected by the specular reflector to be incident on the light receiving unit; An optical device comprising: (((2))) The optical device described in (((1))), wherein the diffuser plate includes a first layer having a first regular reflectance and a second layer having a second regular reflectance lower than the first regular reflectance, and the second layer is arranged to face the light receiving portion. (((3))) the first layer is a backing coat layer; The optical device according to (((2))), wherein the second layer is a light diffusing layer. (((4))) The light receiving device further includes a lens portion that guides the light reflected by the specular reflector to the light receiving portion, The optical device described in (((1))), wherein the specular reflector has a property that prevents the light receiving portion from being located within the focal depth of the lens portion. (((5))) The optical device described in (((4))), wherein the specular reflector has a concave shape arranged in a direction in which the side surface of the light guide extends, thereby achieving the above characteristic. (((6))) a light source provided on the end surface side of the light guide and configured to irradiate light; a reading window through which the document passes; An optical device according to any one of ((1)) to (((5))) Equipped with The light receiving unit receives light emitted from the light guide and reflected by the original when the original passes through the reading window, and receives light reflected by the mirror reflector when the original does not pass through the reading window.

[0059] According to the invention (((1))), when a light guide scatters light incident from an end face using a scatterer arranged in the direction in which the side face extends and then emits the light, it is possible to suppress both a reduction in the amount of light received by the light receiving unit and the occurrence of unevenness in the amount of light received by the light receiving unit. According to the invention (((2))), the possibility that the amount of light received by the light receiving section will be reduced can be further reduced. According to the invention (((3))), the possibility that the amount of light received by the light receiving section will be reduced can be easily reduced. According to the invention (((4))), it is possible to further reduce the possibility that the amount of light received by the light receiving section will become uneven. According to the invention (((5))), the possibility of unevenness in the amount of light received by the light receiving section can be easily reduced. According to the invention (((6))), when a light guide scatters light incident from an end face using a scatterer arranged in the direction in which the side face extends and then emits the light, it is possible to prevent both a reduction in the amount of light received by the light receiving unit and the occurrence of unevenness in the amount of light received by the light receiving unit. [Explanation of symbols]

[0060] 60...image reading device, 100...image reading section, 110...light guide, 110A...end face, 110B...side face, 111...diffusion pattern, 112...rod lens array, 125...light receiving section, 128...light emitting element, 220...mirror reflector, 230...diffusion plate, 232...base material, 234...light diffusion layer, 236...backing coat layer

Claims

1. a light guide that scatters light incident from an end face of the light guide by a scatterer disposed in a direction in which the side face of the light guide extends, and outputs the light; a specular reflector that specularly reflects the light emitted from the light guide; a light receiving unit that receives light reflected by the specular reflector; a diffusion plate that diffuses and transmits the light emitted from the light guide to be incident on the specular reflector, and diffuses and transmits the light reflected by the specular reflector to be incident on the light receiving unit; An optical device comprising:

2. The optical device of claim 1 , wherein the diffuser plate includes a first layer having a first regular reflectance and a second layer having a second regular reflectance lower than the first regular reflectance, the second layer being arranged to face the light receiving portion.

3. the first layer is a backing coat layer; The optical device of claim 2 , wherein the second layer is a light diffusing layer.

4. The light receiving device further includes a lens portion that guides the light reflected by the specular reflector to the light receiving portion, The optical device of claim 1 , wherein the specular reflector has a property that prevents the light receiving portion from being located within a depth of focus of the lens portion.

5. The optical device according to claim 4 , wherein the specular reflector has a recessed shape arranged in a direction in which the side surface of the light guide extends, thereby providing the characteristic.

6. a light source provided on the end surface side of the light guide and configured to irradiate light; a reading window through which the document passes; An optical device according to any one of claims 1 to 5; Equipped with The light receiving unit receives light emitted from the light guide and reflected by the original when the original passes through the reading window, and receives light reflected by the mirror reflector when the original does not pass through the reading window.

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