JP2016051601A - Transparent material, luminaire, and image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transparent material, a luminaire, and an image reading device capable of restricting the loss of the illumination light amount while achieving miniaturization.SOLUTION: A transparent material 1 comprises: an entrance surface 2 and an emission surface 3 longer in a first direction; a light guide part 4 for guiding the light incident from the entrance surface 2; and a deflection part 5 for leading the light from the light guide part 4 to the emission surface 3, in which the deflection part 5 includes a first reflection plane 6 and a second reflection plane 7 that deflect light in a first cross section normal to the first direction; and the first reflection plane 6 is disposed at a position closer to the entrance surface 2 than the second reflection plane 7, so that in the first cross section, the angle defined by the surface normal of the entrance surface 2 and the surface normal of the first reflection plane 6 is larger than the angle defined by the surface normal of the entrance surface 2 and the surface normal of the second reflection plane 7.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a light guide used in an illumination device provided in an image reading device such as an image scanner, a facsimile machine, or a digital copying machine.

  2. Description of the Related Art As an illumination device provided in an image reading device, one having a light guide for guiding light from a light source to a document surface is known. Patent Document 1 employs a light guide that includes a deflecting surface that deflects light emitted from a light source in a direction parallel to the document surface toward the document surface, thereby reducing the size in the direction perpendicular to the document surface. A lighting device is described.

JP 2008-123766 A

  However, in the configuration described in Patent Document 1, since the light emitted from the light source is guided while being subjected to multiple reflections inside the light guide, it is incident on the deflection surface at various incident angles depending on the number of reflections. It will be. Therefore, light rays from the light source that have a small incident angle with respect to the deflection surface pass through the deflection surface without satisfying the total reflection condition, so that the amount of light reaching the document surface is reduced, resulting in a loss of illumination light quantity. End up.

  An object of the present invention is to provide a light guide, an illuminating device, and an image reading device that can reduce the amount of illumination light while realizing miniaturization.

  In order to achieve the above object, a light guide as one light guide surface of the present invention includes an incident surface and an output surface that are long in a first direction, and a light guide unit that guides light incident from the incident surface. A deflecting unit that guides light from the light guide unit to the emission surface, wherein the deflecting unit deflects light within a first cross section perpendicular to the first direction. The first reflecting surface is disposed closer to the incident surface than the second reflecting surface, and in the first section, the surface normal of the incident surface and the first reflecting surface The angle formed by the surface normal of the first reflecting surface is larger than the angle formed by the surface normal of the incident surface and the surface normal of the second reflecting surface.

  According to the present invention, it is possible to provide a light guide, an illuminating device, and an image reading device capable of suppressing the loss of the amount of illumination light while realizing miniaturization.

The principal part schematic of the light guide which concerns on embodiment of this invention. The principal part enlarged view of the deflection | deviation part which concerns on embodiment of this invention. 1 is a schematic view of a main part of an image reading apparatus according to an embodiment of the present invention. The principal part enlarged view of the periphery of the illuminating device which concerns on the Example of this invention. The figure for demonstrating the total reflection conditions in a light guide part. The figure for demonstrating the effect by a taper-shaped light guide part. The figure for demonstrating the relationship between the virtual image of a light source, and the frequency | count of reflection of the light in a light guide part. The figure which shows the light distribution characteristic of a light source.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In addition, in each figure, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

  FIG. 1 is a schematic view of a main part for explaining a light guide 1 according to this embodiment. FIG. 1A is a perspective view of the light guide 1 and FIG. The figure of the ZX cross section (1st cross section) perpendicular | vertical to a Y direction (1st direction) is each shown. As shown to Fig.1 (a), the light guide 1 is a translucent member long in a Y direction (1st direction), and organic materials, such as an acrylic resin and a polycarbonate resin, and inorganic materials, such as glass, are used. Become. The light guide 1 is held by a holding member 15 together with a light source 14 including a plurality of light emitting elements arranged in the Y direction.

  In addition, as shown in FIG. 1B, the light guide 1 guides light from the incident surface 2 on which light from the opposed light source 14 enters, the exit surface 3 from which light exits, and the incident surface 2. A light guide 4 that emits light and a deflecting unit 5 that guides light from the light guide 4 to the emission surface 3 are provided. The light guide unit 4 includes a first light guide surface 4 a and a second light guide surface 4 b that face each other and reflect light from the incident surface 2. Generally, since the refractive index of the translucent material used for the light guide is about 1.5, the light emitted from the light source 14 does not satisfy the total reflection condition at the interface between the air layer and the incident surface 2. All incident on the inside of the light guide 1. The light incident on the incident surface 2 from the light source 14 is guided in the direction (Z direction) perpendicular to the incident surface 2 while being totally reflected inside the light guide unit 4, and the direction of the emission surface 3 (X Direction). In this way, by adopting a configuration in which the optical path from the incident surface 2 to the output surface 3 is bent by the deflecting unit 5, the optical path length for spreading each light from the light source 14 in the Y direction is ensured while being covered. It becomes possible to reduce the length (height) in the direction perpendicular to the irradiation surface.

  Here, as shown in FIG. 1B, the deflecting unit 5 has a first reflecting surface 6, a second reflecting surface 7, and a third reflecting surface 8 that deflect light in the ZX cross section. doing. Further, when the two reflecting surfaces are compared with each other, the one closer to the incident surface 2 is arranged such that the inclination angle of the incident surface 2 with respect to the surface normal is smaller than the other. That is, in the ZX cross section, the angle formed by the surface normal of the incident surface 2 and the surface normal of the first reflective surface 6 (second reflective surface 7) is the surface normal of the incident surface 2 and the second normal. It is configured to be larger than an angle formed with the surface normal of the reflective surface 7 (third reflective surface 8).

  FIG. 2 is an enlarged view of the deflecting unit 5 in the light guide 1, in which the surface normal of the incident surface 2 is indicated by a one-dot chain line, and the surface normal of each reflecting surface is indicated by a broken line. As shown in FIG. 2, the angles formed by the surface normal of the incident surface 2 and the surface normals of the first reflecting surface 6, the second reflecting surface 7, and the third reflecting surface 8 are θ1, θ2, respectively. , And θ3, the condition of θ1> θ2> θ3 is satisfied.

  As described above, in this embodiment, the deflecting unit 5 in the light guide 1 is configured by a plurality of reflecting surfaces, and the angle formed between the incident surface 2 and the respective surface normals of the reflecting surfaces increases from the incident surface 2. It is set to be smaller. With this configuration, the light transmitted through the deflecting unit 5 without satisfying the total reflection condition among the light from the light guide unit 4 can be reduced, and the loss of the illumination light amount can be suppressed (details will be described later).

[Example]
Next, an example of the image reading apparatus including the light guide according to the above-described embodiment will be described in detail with reference to a schematic diagram (ZX cross-sectional view) of the main part in FIG. An image reading apparatus 100 according to this embodiment includes a reading unit (carriage) 107 that integrally holds an illumination device 103, a reflecting unit 104, an image forming unit 106, and a light receiving unit 105, a document table 102, and a driving unit. 108.

  The document table 102 is a table on which the document 101 is placed, and is made of a light-transmitting material such as acrylic resin, polycarbonate resin, or glass. The reflection unit 104 includes a plurality of folding mirrors 104 a to 104 d that folds the light from the document 101 and guides the light to the imaging unit 106. The light receiving unit 105 includes an image sensor that receives light from the document 101. The imaging unit 106 is a reduction optical system that collects the light from the reflection unit 104 on the light receiving surface of the light receiving unit 105 and forms an image based on image information of the document 101. The driving unit 108 includes a motor that generates a driving force for moving the carriage 107 in the Z direction (arrow direction in the drawing) that is parallel to the document surface of the document 101.

  As the light receiving unit 105, a CCD (Charge Coupled Devices) image sensor, a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or the like can be employed. They are a line sensor in which a large number of pixels are arranged in the Y direction, a line sensor in which a large number of RGB pixels are arranged in a line in the Y direction, and each line sensor of R, G, and B pixels is arranged in three lines in parallel. It may be a sensor.

  The light emitted from the illuminating device 103 is reflected and diffused by the original surface of the original 101, guided to the imaging unit 106 by the first folding mirror 104 a to the fourth folding mirror 104 d of the reflecting unit 104, and received by the light receiving unit 105. Focused on the surface. Then, by moving the carriage 107 in the Z direction by the driving unit 108, the carriage 107 can scan the original surface of the original 101 in the Z direction. As a result, the light receiving unit 105 can read the image information of the entire original surface of the original 101. The image information read by the light receiving unit 105 is transmitted through an interface to an image processing unit (not shown) or an external device such as a personal computer.

  Note that when the carriage 107 scans the document surface, the relative positions of the members held by the carriage 107 do not change. Further, the drive unit 108 moves the document 101 instead of the carriage 107 or moves both the carriage 107 and the document 101 to change the relative position of the carriage 107 and the document 101 in the Z direction. Also good. In the case where the relative position is changed by moving only the document without moving the carriage 107, it is possible to use a driving unit that drives a feeding roller, a feeding belt, or the like that transports the document.

  FIG. 4 is an enlarged view of the periphery of the illumination device 103 in FIG. The illuminating device 103 includes the light guide 1 and the light source 14 described above, and the light emitted from the light source 14 is read by the light guide 1 on a reading area 112 (reading of the imaging unit 106) on the original surface (irradiated surface) of the original 101. The light is guided to the region on the optical axis 111. The light source 14 is disposed so as to face the incident surface 2 of the light guide 1 and includes a plurality of light emitting elements arranged in the Y direction as shown in FIG. As the light emitting element, an LED (Light Emitting Diode) having a light emitting layer made of an inorganic semiconductor or an organic semiconductor, an EL (Electro Luminescence) element, or the like is used. The generated light is preferably white light, but is not limited thereto, and light such as red, green, and blue may be used.

  FIG. 5 is a diagram for explaining a state in which light emitted from the light source 14 is refracted and reflected on each surface of the light guide 1. Here, the case where the light guide surfaces 4a and 4b are parallel to each other is shown for convenience. As shown in FIG. 5 (a), the light emitting surface of the light source 14 and the incident surface 2 of the light guide 1 are arranged close to each other via an air layer and facing each other. Therefore, as shown in FIG. 5B, the light emitted from the light source 14 is refracted at the interface between the air layer and the incident surface 2. Since the light guide 1 according to the present embodiment is made of acrylic resin and has a refractive index of 1.49, the light emitted from the light source 14 satisfies the total reflection condition at the interface between the air layer and the incident surface 2. Without being incident on the inside of the light guide 1.

Here, when the incident angle of light with respect to the incident surface 2 is θi ₁ and the refraction angle is θo ₁ , from the law of refraction,
sin θi ₁ = 1.49 sin θo ₁
The following formula is satisfied. At this time,
0 ° ≦ | θi ₁ | ≦ 90 °
Because
0 ° ≦ | θo ₁ | ≦ 42.155 ° (1)
Thus, it can be seen that the maximum value of the refraction angle θo ₁ is 42.155 °. Actually, since there is no light having an incident angle θi ₁ of 90 °, the refraction angle θo ₁ is less than 42.155 °.

Further, as shown in FIG. 5A, the incident angle of light with respect to the light guide surfaces 4a and 4b is 90 ° −θo ₁ . At this time, from the above equation (1),
47.845 ° ≦ | 90 ° −θo ₁ | ≦ 90 ° (2)
Therefore, it can be seen that the minimum value of the incident angle of light with respect to the light guide surfaces 4a and 4b is 47.845 °. Further, as shown in FIG. 5C, when the critical angle satisfying the total reflection condition for the light incident on the light guide surfaces 4a and 4b is θi ₂ , the law of refraction
1.49 sin θi ₂ = sin 90 °
To satisfy
θi ₂ = 42.155 ° (3)
It becomes. From equations (2) and (3), since the incident angle of all the light incident on the light guide surfaces 4a and 4b is larger than the critical angle, all the light incident from the incident surface 2 is transmitted through the light guide surfaces 4a and 4b. The total reflection condition is satisfied. Therefore, the light incident on the light guide surface 4a and the light guide surface 4b is guided to the deflecting unit 5 while being reflected (multiple reflection) a plurality of times. By appropriately setting the length of the light guide unit 4 in the Z direction, it is possible to ensure a sufficient optical path length to spread the light from each light emitting element, and to uniformly distribute the Y direction on the document surface. It is possible to form a uniform illuminance distribution.

  Furthermore, as shown in FIG. 4, the light guide surfaces 4 a and 4 b according to the present embodiment are arranged so that the distance between the light guide surfaces 4 a and 4 b increases as the distance from the incident surface 2 increases in the ZX cross section. That is, the light guide 4 has a shape (taper shape) having a taper angle (an angle formed by the first light guide surface 4a and the second light guide surface 4b) in the ZX cross section. FIG. 6 is a diagram showing a case where the light guide surface 4a in FIG. 5A has a taper angle α. By providing the light guide surface 4a with a taper angle, the critical angle at the light guide surface 4a is reduced, and the total reflection condition is more easily satisfied.

  In this embodiment, since the LED is used as the light source 14, the light emitted radially from the light emitting surface enters the incident surface 2 while spreading according to the light distribution characteristics. At this time, the light B from the incident surface 2 is incident on the light guide surface 4a at an incident angle θi + α and is reflected at a reflection angle θi + α. Therefore, the sum of the incident angle and the reflection angle is compared with the case where there is no taper angle. And increase by 2α. Therefore, the traveling direction of the light B approaches the traveling direction of the light A emitted perpendicularly from the light emitting surface of the light source 14 (the surface normal direction of the incident surface 2). That is, since the light distribution angle of the light source 14 is apparently narrowed (narrowed), the light guide unit 4 can obtain a condensing action (convergence action) due to its tapered shape.

  According to this light guide unit 4, light from the incident surface 2 can be efficiently condensed on each reflecting surface of the deflecting unit 5, and linear illumination that is long in the Y direction and short in the Z direction on the document surface. Since the region can be formed, the reading region 112 can be efficiently illuminated. The light condensing effect and the degree of narrowing of the light guide 4 are determined by the taper angle and the number of reflections. That is, the greater the number of reflections at the light guide 4, the narrower the light distribution angle of the light source 14 and the greater the light condensing action in the ZX cross section. Therefore, the light reflected last from the first light guide surface 4 a out of the light from the incident surface 2 enters the position closer to the incident surface 2 in the deflecting unit 5 as the number of reflections by the light guide unit 4 increases. However, the incident angle becomes smaller (approaching normal incidence). This will be described in detail with reference to FIG.

  In FIG. 4, a part of the light guided by the light guide 1 is shown as light rays 9 to 13. A light beam 9 is a light beam emitted in a direction (Z direction) perpendicular to the light emitting surface of the light source 14, and directly enters the second reflecting surface 7 without passing through the light guide surface 4a and the light guide surface 4b, and is totally reflected. And guided to the exit surface 3. The light beams 10 and 11 are light beams reflected once by the light guide unit 4, and the light beams 12 and 13 are light beams reflected by the light guide unit 4 three times. The light beams 10 and 12 are the light beams finally reflected by the first light guide surface 4a in the light guide unit 4, and the light beams 11 and 13 are finally transmitted by the second light guide surface 4b in the light guide unit 4. The reflected light. The light beam 10 is incident on the second reflecting surface 7, the light beam 12 is incident on the first reflecting surface 6, and the incident angle of the light beam 12 is smaller than the incident angle of the light beam 10. That is, the light beam that is finally reflected by the first light guide surface 4a is incident at a smaller incident angle at a position closer to the incident surface 2 in the deflecting unit 5 as the number of reflections by the light guide unit 4 increases. Will do.

  Here, as in the configuration described in Patent Document 1 described above, if the deflecting unit 5 is to be configured with only one reflecting surface, the inclination of the reflecting surface is more of the light rays emitted from the light source 14. It is necessary to set so that a light beam having a high intensity (light quantity level) satisfies the total reflection condition. Therefore, a case is considered in which a virtual reflecting surface 6 ′ as shown in FIG. 4 is provided so that the light beam 9 emitted perpendicularly from the light emitting surface of the light source 14 is equal to the inclination of the second reflecting surface 7 that is totally reflected. . At this time, as described above, the light beam reflected by the light guide unit 4 a number of times and finally reflected by the first light guide surface 4a is incident on the virtual reflection surface 6 'closer to the incident surface 2. become. Therefore, a light ray that does not satisfy the total reflection condition and passes through the virtual reflection surface 6 ′ is generated like the light ray 12 ′. Therefore, the light ray that reaches the document surface is reduced, and the amount of illumination light is lost.

  Therefore, in the present embodiment, as described above, the deflecting unit 5 is composed of a plurality of reflecting surfaces (planes), and the angle formed between the incident surface 2 and the surface normal of each reflecting surface is the incident surface 2. It is set so that it gets smaller as it gets away from. With this configuration, the inclination of the corresponding reflecting surface can be appropriately set according to the number of reflections of the light beam in the light guide unit 4, so that the light beam that does not satisfy the total reflection condition can be reduced. That is, even a light beam that is reflected a number of times by the light guide unit 4 and finally reflected by the first light guide surface 4 a is totally reflected by the first reflection surface 6 disposed at a position close to the incident surface 2. Thus, the light can be guided to the exit surface 3 like the light beam 12. As a result, it is possible to suppress the loss of the illumination light quantity on the document surface.

  By making the exit surface 3 convex, it is possible to have a condensing function in the ZX cross section, so that a sufficient amount of illumination light can be secured even when the document 101 is lifted from the document table 102. become. In addition, as shown in FIG. 2, when the angle formed by the surface normal of the incident surface 2 and the surface normal of each reflection surface is set so as to satisfy the condition of θ1> θ2> θ3, two adjacent reflections The angle formed by the surfaces (θ1 + θ2, θ2 + θ3) is less than 180 °. As a result, the light condensing action in the ZX cross section can be given to the deflection unit 5 as well. Therefore, not only the shape of the exit surface 3 but also the arrangement of the reflecting surfaces can be adjusted to control the light collection effect and the illuminance distribution, so the degree of freedom in designing the light guide 1 can be increased. become.

FIG. 7 is a diagram for explaining the relationship between the virtual image of the light source 14 and the light reflected by the light guide unit 4. Here, the position of the virtual image of the light source 14, the trajectory of light, the scale of each member, and the like are changed from actual ones for convenience. As shown in FIG. 7, each of the light that is multiple-reflected by the light guide unit 4 and emitted toward the deflecting unit 5 can be regarded as light emitted from a virtual image of the light source 14 arranged in the X direction. Here, when the length of the light guide unit 4 in the Z direction is L and the half value of the height of the light guide unit 4 in the X direction is h, it corresponds to the light reflected n times on the light guide surfaces 4a and 4b. The height h (n) from the surface normal of the incident surface 2 of the virtual image is
h (n) = 2 × h × n
The following formula is satisfied. Further, the exit angle θ (n) of the light reflected from the light guide surfaces 4a and 4b n times from the light guide unit 4 is:
θ (n) = atan (n × h / L)
It can be expressed by the following formula.

  FIG. 8 is a diagram illustrating light distribution characteristics (directional characteristics of emitted light) of the light source (LED) 14 according to the present embodiment. Here, the emission angle when the angle of the surface normal passing through the center of the emission surface of the light source 14 with respect to the emission surface is 0 °, and the luminous intensity with respect to the emission angle (the light intensity level when the emission angle is 0 ° is 100). Relative value). When the light source 14 is an ideal light source that emits light with the same brightness regardless of the radiation angle, the light distribution is circular, and when the radiation angle is θ, the luminous intensity can be expressed as cos θ. That is, the luminous intensity of the ideal light source is smaller than the luminous intensity on the surface normal in proportion to the apparent light emitting area when the light source is viewed from the direction in which the radiation angle increases. At this time, the radiation angle (half-value angle) when the luminous intensity becomes the maximum half-value (50) is 60 °. On the other hand, in this embodiment, the light source 14 has an elliptical orientation distribution as shown in FIG. 8, and therefore the half-value angle γ0 is 51 °.

Here, consider a case where the inclination of the first reflecting surface 6 in the deflecting unit 5 is set so that the light beam satisfying the half-value angle γ0 satisfies the total reflection condition on the first reflecting surface 6. Relationship between an incident angle θi ₃ when light having a half-value angle γ 0 is incident on the first reflecting surface 6 and an angle θ 1 formed by the surface normal of the incident surface 2 and the surface normal of the first reflecting surface 6. Is
θi ₃ = θ1-γ0
It becomes. At this time, when the inclination θm = 0 ° of the first reflecting surface 6 with respect to the surface normal of the incident surface 2, that is, θ1 = 90 °,
θi ₃ = 90 ° -51 ° = 39 °
It becomes. Considering in the same manner as described above with reference to FIG. 5, in order for the light having the half-value angle γ0 to satisfy the total reflection condition on the first reflecting surface 6,
42.155 ° ≦ θi ₃
Must be
42.155−39 = 3.155 ° ≦ θm
It is necessary to incline the first reflecting surface 6 so as to satisfy the above. That is, in order for light having a high luminous intensity (light whose emission angle is a half-value angle or less) among the light emitted from the light source 14 to satisfy the total reflection condition in the deflecting unit 5,
93.2 ° ≦ θ1
It is desirable to set the inclination of the first reflecting surface 6 so as to satisfy the following condition. That is, the angle formed by the surface normal of the incident surface 2 and the surface normal of the first reflecting surface 6 may be set to be 93.2 ° or more.

  As described above, according to the present embodiment, the deflecting portion 5 in the light guide 1 is configured by a plurality of reflecting surfaces, and the angle formed between the incident surface 2 and the respective surface normals of the reflecting surfaces is separated from the incident surface 2. It is set to be smaller. That is, the inclination of each reflecting surface is set so that each light satisfies the total reflection condition according to the number of times the light from the incident surface 2 is reflected by the light guide 4. With this configuration, light transmitted through the deflecting unit 5 without satisfying the total reflection condition among the light from the light guide unit 4 can be reduced, and loss of the illumination light amount can be suppressed.

[Modification]
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various combination, a deformation | transformation, and a change are possible within the range of the summary.

  For example, in the above-described embodiment, the deflecting unit has three reflecting surfaces. However, the configuration is not limited thereto, and a configuration having two or four or more reflecting surfaces may be adopted. However, the configuration in which the deflecting unit has more reflecting surfaces can be set so that more light rays appropriately satisfy the total reflection condition, and the light collecting action in the ZX cross section can be controlled more appropriately. Therefore, a configuration having three or more reflecting surfaces is desirable.

  In the above-described embodiment, the angle formed by the surface normal of the incident surface and the surface normal of each reflecting surface is set so as to decrease as the distance from the incident surface increases. is not. That is, in order to satisfy the total reflection condition of the light ray incident on the reflecting surface disposed closer to the incident surface, at least the surface normal of the reflecting surface disposed near the incident surface and the surface of the incident surface What is necessary is just to set large the angle which a normal makes. For example, in FIG. 2, each reflecting surface is arranged so as to satisfy θ1> θ2> θ3, but may be arranged so that θ2 ≦ θ3. However, if the angle formed by the surface normal of the reflecting surface arranged far from the incident surface and the surface normal of the incident surface is too large, the light condensing action of the deflecting unit and the miniaturization of the light guide can be reduced. Since it becomes small, it is preferable to comprise as mentioned above.

  Note that the image reading apparatus according to the above-described embodiment has a configuration including only one illumination device. However, for example, a configuration in which two illumination devices are arranged symmetrically with the reading optical axis in between may be adopted. . Alternatively, a configuration in which two light exit surfaces are provided on the light guide and a reflecting member is disposed on the opposite side across the reading optical axis may be employed. In this case, the light beam emitted from one emission surface can be guided directly to the document surface, and the light beam emitted from the other emission surface can be deflected by the reflecting member and guided to the document surface.

DESCRIPTION OF SYMBOLS 1 Light guide 2 Incident surface 3 Outgoing surface 4 Light guide part 5 Deflection part 6 1st reflective surface 7 2nd reflective surface

Claims (16)

A light guide comprising an entrance surface and an exit surface that are long in the first direction, a light guide portion that guides light incident from the entrance surface, and a deflection portion that guides light from the light guide portion to the exit surface. Body,
The deflection unit includes first and second reflection surfaces that deflect light in a first cross section perpendicular to the first direction,
The first reflecting surface is disposed closer to the incident surface than the second reflecting surface,
In the first cross section, the angle formed by the surface normal of the incident surface and the surface normal of the first reflecting surface is the surface normal of the incident surface and the surface normal of the second reflecting surface. A light guide characterized by being larger than the angle formed by   The light guide according to claim 1, wherein the deflecting unit includes three or more reflecting surfaces including the first and second reflecting surfaces.   The angle formed by the surface normal of the incident surface and each surface normal of the three or more reflecting surfaces in the first cross section decreases as the distance from the incident surface decreases. 2. The light guide according to 2.   4. The light guide according to claim 2, wherein the first reflecting surface is disposed at a position closest to the incident surface among the three or more reflecting surfaces. 5.   5. The light guide according to claim 1, wherein inclinations of the first and second reflecting surfaces are set based on critical angles thereof. 6.   6. The light guide according to claim 1, wherein the light guide unit includes first and second light guide surfaces facing each other in the first cross section. 7.   The inclination of the first and second reflecting surfaces varies depending on the number of reflections of light that is directly incident on the first light guide surface from the incident surface on the light guide unit. The light guide according to 1.   8. The light guide according to claim 6, wherein the first and second light guide surfaces are arranged so that a distance between the first and second light guide surfaces increases as the distance from the incident surface increases.   The first reflection surface and the second light guide surface are arranged adjacent to each other, and light incident on the first reflection surface from the first light guide surface without passing through another surface. 9. The light guide body according to claim 6, wherein light having the highest number of reflections at the light guide portion is totally reflected by the first reflection surface. 10.   The angle between the surface normal of the incident surface and the surface normal of the first reflection surface in the first cross section is 93.2 ° or more. The light guide according to any one of the above.   An illumination device comprising: a light source; and the light guide according to claim 1 that guides light emitted from the light source to an irradiated surface.   The lighting device according to claim 11, wherein the light source includes a plurality of light emitting elements arranged in the first direction.   The lighting device according to claim 12, wherein the plurality of light emitting elements are arranged to face the incident surface through air.   The illumination device according to any one of claims 11 to 13, a light receiving unit that receives light from the irradiated surface, and an imaging unit that guides light from the irradiated surface to the light receiving unit. An image reading apparatus comprising:   The image reading apparatus according to claim 14, further comprising a carriage that integrally holds the illumination device, the light receiving unit, and the imaging unit.   The image reading apparatus according to claim 15, further comprising a drive unit configured to change a relative position between the irradiated surface and the carriage in a direction parallel to the irradiated surface.

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