JP2016110720A - Light guide unit, luminaire including the same and image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress occurrence of illuminance unevenness on an irradiated surface, in a one-end part arrangement type luminaire.SOLUTION: A light guide unit 112 has a light guide body 111 having; an incident surface 115, an end surface 116 opposite to the incident surface 115; a light guide surface 117 longer in a first direction; and an emission surface 118 opposite to the light guide surface 117, and guides light, made incident from the incident surface 115, to the emission surface 118 through the light guide surface 117. The light guide unit includes: a first reflection member 114 opposite to the end surface 116; and a reflection part 121 reflecting, out of light reflected by the first reflection member 114, light having an incident angle smaller than a critical angle with respect to the emission surface 118, toward the inside of the light guide body 111.SELECTED DRAWING: Figure 3

Description

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

  Conventionally, an image reading apparatus employs an illumination device in which a light source such as an LED (Light Emitting Diode) or an EL (Electro Luminescence) element is disposed at one end (one end) in the longitudinal direction of the light guide. Yes. The light guide used in such a one-end arrangement type illumination device has an incident surface facing the light source, a light guide surface extending in the longitudinal direction, and an exit surface, and guides light incident from the incident surface. It is comprised so that it may guide to an output surface by a surface.

  Patent Documents 1 and 2 describe an illuminating device in which a diffuse reflector (white paint) is provided on an end surface opposite to an incident surface of a light guide. According to this illuminating device, the light emitted from the end face of the light guide can be reflected by the diffuse reflector and re-entered into the light guide, and the light guide efficiency can be improved.

JP 2010-103034 A Japanese Patent Laid-Open No. 11-84544

  However, in the illuminating devices described in Patent Documents 1 and 2, a part of the light reflected by the diffuse reflector is directly emitted from the emission surface without passing through the light guide surface. For this reason, an illuminance unevenness (illuminance deviation) in which a part of the illuminance is remarkably increased occurs in the original (illuminated surface) illuminated by the illumination device, and good image quality cannot be obtained.

  The objective of this invention is providing the light guide unit which can suppress generation | occurrence | production of the illumination intensity nonuniformity in a to-be-irradiated surface, an illuminating device provided with the same, and an image reader.

  In order to achieve the above object, a light guide unit according to one aspect of the present invention includes an incident surface, an end surface facing the incident surface, a light guide surface that is long in the first direction, and the light guide surface. A light guide unit that includes a light guide body including the light guide surface, and guides light incident from the light entrance surface to the light exit surface through the light guide surface, the light guide unit facing the end surface. A reflecting member and a reflecting portion that reflects light having an incident angle smaller than a critical angle with respect to the emission surface among the light reflected by the first reflecting member toward the inside of the light guide body; It is characterized by providing.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the illumination intensity nonuniformity in a to-be-irradiated surface can be suppressed in the illuminating device of a one end part arrangement type.

1 is a schematic diagram of a main part of an image reading apparatus according to Embodiment 1 of the present invention. The principal part enlarged view of the periphery of the illuminating device which concerns on Example 1 of this invention. The principal part schematic of the illuminating device which concerns on Example 1 of this invention. The figure for demonstrating the light distribution characteristic of Lambert light. The figure which shows the illumination intensity distribution by the illuminating device which concerns on Example 1 of this invention. The figure which shows the illuminating device and illuminance distribution which concern on the comparative example 1 of this invention. The principal part schematic of the illuminating device which concerns on Example 2 of this invention. The figure which shows the illumination intensity distribution by the illuminating device which concerns on Example 2 of this invention. The figure which shows the illuminating device and illuminance distribution which concern on the comparative example 2 of this invention. The principal part schematic of the illuminating device which concerns on Example 3 of this invention. The figure which shows the illumination intensity distribution by the illuminating device which concerns on Example 3 of this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Each drawing may be drawn on a different scale for convenience. Moreover, in each drawing, the same reference number is attached | subjected about the same member and the overlapping description is abbreviate | omitted.

[Example 1]
Hereinafter, the light guide unit according to the first embodiment of the present invention, the illumination device including the light guide unit, and the image reading device will be described in detail.

  FIG. 1 is a schematic diagram (ZX sectional view) of a main part of an image reading apparatus 100 according to the present embodiment. The image reading apparatus 100 includes an illumination device 103, a reflection optical system 104, an image forming unit (image forming optical system) 106, and a light receiving unit 105, a carriage (reading unit) 107, a document table 102, And a drive unit 108. The illuminating device 103 according to the present embodiment is a one-end arrangement type illuminating device having a light guide unit in which a light source is arranged only at one end of a light guide. The one-end arrangement type illumination device is advantageous in that the number of light sources and the light emitting area can be reduced as compared with the both-end arrangement type illumination device in which the light sources are arranged at both ends of the light guide. is there.

  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, polyester resin, polycarbonate resin, or glass. The light receiving unit 105 includes an image sensor that receives a light beam from the document 101. As the image sensor, a CCD image sensor, a CMOS image sensor, or the like can be employed. These include 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, a line sensor of R pixels, a line sensor of G pixels, and a line sensor of B pixels. Sensors arranged in parallel to the rows may be used.

  The reflective optical system 104 includes a plurality of folding mirrors 104 a to 104 d that folds the light beam from the document 101 and guides it to the imaging unit 106. The imaging unit 106 is a reduction optical system that collects the light beam from the reflection optical system 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 (irradiated surface) of the document 101.

  The light beam emitted from the illuminating device 103 is reflected and diffused by the document surface of the document 101, and is guided to the image forming unit 106 by the first folding mirror 104 a to the fourth folding mirror 104 d of the reflection optical system 104. It is condensed on the light receiving 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. Image information read by the light receiving unit 105 is transmitted as an electric signal to an external device such as an image processing unit (not shown) or a personal computer through an interface.

  Note that when the carriage 107 scans the document surface, the relative positions of the members held by the carriage 107 do not change. Also, the relative position of the carriage 107 and the document 101 in the Z direction can be obtained by moving the document 101 instead of the carriage 107 or by moving both the carriage 107 and the document 101 by the drive unit 108 as a changing unit. May be changed. When the relative position is changed by moving only the document without moving the carriage 107, a document feeding roller, a feeding belt, or the like can be used as the changing means.

  Here, the illumination device 103 according to the present embodiment will be described in detail with reference to FIGS. 2 and 3. 2 is an enlarged view of the periphery of the illumination device 103 in FIG. 1, and FIGS. 3A and 3B are schematic views (perspective view and XY cross-sectional view) of a main part of the illumination device 103. FIG. The image reading apparatus 100 according to the present embodiment includes two identical illumination devices 103, and the respective illumination devices 103 are arranged symmetrically with the reading optical axis 109 interposed therebetween. Each illuminating device 103 includes a light guide unit 112 having a light guide 111 and a first reflecting member 114 and a light source 113, and guides a light beam emitted from the light source 113 to the reading area 110 in the document 101 by the light guide unit 112. Is shining.

  The light source 113 is disposed to face the incident surface 115 of the light guide 111, and includes a light emitting element indicated by a broken line in the drawing and a substrate indicated by a dotted line on which the light emitting element is mounted. Yes. As the light emitting element, an LED or EL element having a light emitting layer made of an inorganic semiconductor and / or an organic semiconductor 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. As an element that emits white light, a white light-emitting element called a power LED, a high-intensity LED, a high-intensity EL element, or the like can be used.

  As shown in FIGS. 2 and 3, the light guide 111 is long in the incident surface (one end surface) 115, the end surface (other end surface) 116 facing the incident surface 115, and the first direction (Y direction). The light guide surface 117 and the light exit surface 118 facing the light guide surface 117 are included. The light guide 111 is a bar-like member having a uniform shape in the first direction except for a notch 121 (details will be described later) formed on the end surface 116 side. The end surface 116 according to the present embodiment is a rough surface, and the light guide surface 117 is a diffusion surface on which a scattering pattern (white paint) for scattering (diffusing) a light beam is formed. In the light guide 111 according to the present embodiment, the length L in the first direction is 320 mm, the width of the light guide surface 117 (scattering pattern) (the length in the direction perpendicular to the first direction) D is 2.4 mm. , Height H = 6.0 mm.

  Note that as the material of the light guide 111, a light-transmitting inorganic material such as glass, or a light-transmitting organic material such as an acrylic resin, a polyester resin, or a polycarbonate resin can be used. Further, the shape of the XZ cross section of the light guide 111 may be a circle, an ellipse, a polygon, or a combination thereof, and as shown in FIG. 3A, at least one side is a curve. A square (sector shape) may be used. The scattering pattern on the light guide surface 117 may be any pattern that can scatter the light beam. For example, the scattering pattern may be formed of a white or metallic glossy film made of resin or metal, or a group of fine protrusions. May be. Further, the shape of the scattering pattern is not limited to the continuous belt-like pattern shown in FIG. 3A, but may be a plurality of dot groups separated from each other.

  Furthermore, the light guide 111 includes a first reflection surface 119 and a second reflection surface 120 that connect the light guide surface 117 and the emission surface 118 as necessary. At this time, it is desirable that the shapes of the first reflecting surface 119 on the side closer to the reading optical axis 109 and the second reflecting surface 120 on the side far from the reading optical axis 109 are curved shapes having a condensing function. . Specifically, the first reflecting surface 119 and the second reflecting surface 120 are paraboloids or ellipsoids whose focal point positions coincide with the midpoint position of the light guide surface 117 in the ZX cross section. Have positive power. According to the first reflection surface 119 and the second reflection surface 120, the light beam scattered by the light guide surface 117 can be efficiently deflected toward the reading region 110. Therefore, it is possible to secure a sufficient amount of light in the reading area 110 and to secure an illumination area in the scanning direction (Z direction) where the amount of light is stable.

  As shown in FIG. 3B, the light S emitted from the light source 113 is incident on the inside of the light guide 111 from the incident surface 115 of the light guide 111 and directly or without passing through other surfaces. The light is totally reflected by at least one of the surfaces and reaches the light guide surface 117. The light S incident on the light guide surface 117 is Lambertian reflected (diffused) by the scattering pattern of the light guide surface 117 to become Lambertian light S1. Of the Lambertian light S 1, light incident on the exit surface 118 at an incident angle smaller than the critical angle (does not satisfy the total reflection condition on the exit surface 118) is emitted from the exit surface 118 and guided to the reading area 110 in the document 101. To be lighted. With this configuration, the reading area 110 can be linearly illuminated.

FIG. 4 is a diagram illustrating the light distribution characteristics of the Lambertian light S1. In FIG. 4, when the light distribution angle of the Lambertian light S1 with respect to the surface normal of the light guide surface 117 is α, and the maximum intensity of the Lambertian light S1 is I _o , the intensity I of the Lambertian light S1 is I = I _o. It is expressed as cos α. As shown in FIG. 4A, it can be seen that the Lambertian light S1 has a uniform light distribution characteristic. In addition, when the case where the light guide 111 is formed of an acrylic resin is considered, the critical angle at the exit surface 118 is 42.2 °. At this time, as shown in FIG. 4B, 67.2% of the Lambertian light S1 having a light distribution angle α smaller than the critical angle 42.2 ° is emitted from the emission surface 118. Become.

  The light S emitted from the light source 113 includes light that reaches the end surface 116 without being emitted from the emission surface 118. If the light is emitted from the end surface 116, a light amount loss occurs. Therefore, the light guide unit 112 according to the present embodiment includes a first reflecting member (diffuse reflector) 114 facing the end surface 116, and reflects the light emitted from the end surface 116 to reflect the inside of the light guide 111. In this case, the light is incident again. The Lambertian light S2 that is Lambert-reflected (diffused) by the first reflecting member 114 reaches the light guide surface 117 either directly or totally with no other surface, and reaches the light guide surface 117. It is Lambert-reflected and becomes Lambertian light S 1 and exits from the exit surface 118. With this configuration, it is possible to reduce the light emitted from the end face 116 and suppress the light amount loss.

  In this embodiment, the first reflecting member 114 covered with white paint is provided outside the light guide 111. However, the present invention is not limited to this. For example, the first reflecting member 114 is provided on the end surface 116. For example, a configuration in which white paint as the one reflecting member 114 is directly applied may be employed. Further, when the end surface 116 is a rough surface (diffusion surface) as in this embodiment, the surface of the first reflection member 114 may be simply a reflection surface, and may not be a diffusion surface such as white paint. . That is, any configuration may be adopted as long as it is a configuration in which at least one of the end surface 116 and the first reflection member 114 forms a diffuse reflector.

  Here, in the Lambertian light S2, there is light S3 that is incident on the emission surface 118 at an incident angle smaller than the critical angle and is directly emitted from the emission surface 118 without passing through the light guide surface 117. If the light S3 is directly incident on the document 101 without passing through the light guide surface 117, the illuminance at that portion becomes extremely high, and a good image cannot be obtained.

  Therefore, the light guide unit 112 according to the present embodiment includes a reflection unit that reflects the light S3 from the first reflection member 114 toward the inside of the light guide 111. Specifically, in the light guide 111, a notch surface (notch portion) 121 that connects the end surface 116 and the emission surface 118 is provided as a reflecting portion. According to the cut surface 121, the light S3 can be prevented from being emitted from the emission surface 118 without passing through the light guide surface 117, and the light S3 can be guided to the light guide surface 117. It becomes possible to suppress the occurrence of unevenness.

  In this embodiment, the light guide 111 is directly provided with the reflection portion as the cut-out surface 121, so that it is not necessary to provide the reflection portion as a separate member, and the light guide 111 and the reflection portion can be formed integrally. The light guide unit 112 is downsized. The cut surface 121 is preferably a mirror surface (a mirror-finished surface), but is not limited to this as long as it reflects light. For example, not only the mirror-finished transmission surface as in the present embodiment, but also a reflection surface or a diffusion surface provided with a reflection film may be employed as necessary.

  FIG. 5 is a diagram illustrating the illuminance distribution on the document 101 illuminated by the illumination device 103 according to the present embodiment, and the horizontal axis indicates the position when the center is 0 mm in the Y direction of the document 101. The vertical axis represents the illuminance value in the document 101. As shown in FIG. 5, the illuminance distribution on the document 101 is substantially symmetric in the Y direction, and it can be seen that the occurrence of uneven illuminance is suppressed satisfactorily. In FIG. 5, the illuminance value increases toward the end in the Y direction in order to correct a decrease in illuminance at the end of the light receiving surface of the light receiving unit 105 due to the cosine fourth law. .

It is more desirable to configure so that the following conditional expression (1) is satisfied when the angle formed by the exit surface 118 and the notch surface 121 is θ ₁ .
125 ° <θ ₁ <155 ° (1)

In other words, when the inclination angle of the notch surface 121 with respect to the first direction is θ ₂ , it is desirable that the following conditional expression (2) is satisfied. However, θ ₂ = 180 ° −θ ₁ .
25 ° <θ ₂ <55 ° (2)

If the lower limit value of conditional expression (2) is not reached, light having a large light distribution angle out of the Lambertian light S2 passes through the cut surface 121 and leaks outside the light guide 111. If the upper limit value of conditional expression (2) is exceeded, light having a large light distribution angle in the Lambertian light S2 is refracted not through the notch surface 121 or at the notch surface 121 and is smaller than the critical angle. The light enters the light exit surface 118 and leaks to the outside of the light guide 111. Therefore, if conditional expressions (1) and (2) are not satisfied, illuminance loss and illuminance unevenness will occur. In the present embodiment, θ ₁ = 150 ° and θ ₂ = 30 ° satisfy the above-described conditional expressions (1) and (2).

  Here, the comparative example 1 with respect to a present Example is demonstrated. FIG. 6A is a main part schematic diagram (XY cross-sectional view) of the illumination device 603 according to the first comparative example. The illuminating device 603 according to Comparative Example 1 has a configuration corresponding to the illuminating device described in Patent Document 2 described above, and the present embodiment has the same configuration except that the light guide 611 does not have a notched surface. The configuration of the illumination device 103 is the same. In the illuminating device 603, since the light guide 611 does not have a notch surface, the light S3 cannot be directly emitted from the emission surface 618 without passing through the light guide surface 617. Therefore, as shown in FIG. 6B, the illuminance value at the end portion where the light S3 is incident on the original 101 is remarkably increased, and the illuminance distribution is uneven.

  As described above, according to the light guide unit according to the present embodiment, it is possible to suppress the occurrence of illuminance unevenness on the irradiated surface in the one-end arrangement type illumination device.

[Example 2]
Hereinafter, a light guide unit, an illumination device including the same, and an image reading device according to a second embodiment of the present invention will be described in detail. Since the image reading apparatus according to the present embodiment is the same as the configuration of the image reading apparatus 100 according to the first embodiment except for the illumination device, the description thereof is omitted. FIG. 7 is a schematic diagram of a main part of the illumination device 203 according to the present embodiment, where FIG. 7A shows a perspective view, and FIG. 7B shows an XY cross-sectional view. The illumination device 203 according to the present embodiment is the same as the configuration of the illumination device 103 according to the first embodiment except for the light guide 211.

  As illustrated in FIG. 7, the light guide 211 includes an incident surface (one end surface) 215, an end surface (other end surface) 216 that faces the incident surface 215, a light guide surface 217 that is long in the first direction, and a light guide. An emission surface 218 opposite to the surface 217. The light guide 211 is a rod-like member that has a uniform shape in the first direction except for the notch 221 formed on the end face 216 side. In the light guide surface 217 according to the present embodiment, a plurality of cuts (grooves) in the direction perpendicular to the first direction (Z direction) are formed along the first direction. As shown in FIG. 7B, in the XY cross section, the light guide surface 217 is a sawtooth surface on which a plurality of concavo-convex structures arranged in the first direction are formed. Further, the emission surface 218 according to the present embodiment forms a part of a cylindrical shape, and has an arc shape in the ZX cross section.

  Similar to the light guide unit 112 according to the first embodiment, the light guide unit 212 according to this embodiment also includes the first reflecting member 214, and therefore does not emit light from the emission surface 218 and guides light reaching the end surface 216. It can be reflected toward the inside of the light body 211. Furthermore, since the light guide 211 according to the present embodiment includes the cut surface 221 that reflects the light S3 from the first reflecting member 214 toward the inside of the light guide 211, the light S3 is guided to the light guide. Direct emission from the emission surface 218 without passing through 217 can be suppressed. With this configuration, it is possible to suppress the occurrence of illuminance loss and illuminance unevenness.

  As shown in FIG. 8, the illuminance distribution on the document 101 according to the present embodiment is substantially symmetrical in the Y direction, and it can be seen that the occurrence of illuminance unevenness is well suppressed. Also in this embodiment, θ1 = 150 ° and θ2 = 30 °, which satisfies the above-described conditional expressions (1) and (2).

  Here, the comparative example 2 with respect to a present Example is demonstrated. FIG. 9A is a main part schematic diagram (XY cross-sectional view) of the illumination device 903 according to the comparative example 2. FIG. The illuminating device 903 according to Comparative Example 2 has a configuration corresponding to the illuminating device described in Patent Document 1 described above, and the present embodiment has the same configuration except that the light guide 911 does not have a notch surface. The configuration of the lighting device 203 is the same. In the lighting device 903, the light guide 911 does not have a cut-out surface, and thus the light S <b> 3 cannot be directly emitted from the emission surface 918 without passing through the light guide surface 917. For this reason, as shown in FIG. 9B, the illuminance value at the end portion where the light S3 is incident on the original 101 becomes remarkably high, resulting in unevenness in the illuminance distribution.

[Example 3]
Hereinafter, a light guide unit according to a third embodiment of the present invention, an illumination device including the same, and an image reading device will be described in detail. Since the image reading apparatus according to the present embodiment is the same as the configuration of the image reading apparatus 100 according to the first embodiment except for the illumination device, the description thereof is omitted. FIG. 10 is a schematic diagram of a main part of the illumination device 303 according to the present embodiment, where FIG. 10A shows a perspective view and FIG. 10B shows an XY cross-sectional view. The illumination device 303 according to the present embodiment has the same configuration as that of the illumination device 103 according to the first embodiment except for the light guide unit 312.

  As shown in FIG. 10A, the light guide 311 according to the present embodiment has the same configuration as that of the light guide 111 according to the first embodiment, except that the light guide 311 does not have a cut surface. And as shown in FIG.10 (b), the light guide unit 312 is used as a reflection part which reflects the light S3 from the 1st reflection member 314 toward the inside of the light guide 311 instead of a notch surface. A second reflecting member 321 is provided to face the end of the exit surface 318 on the end surface 316 side. Specifically, white paint as the second reflecting member 321 is provided so as to cover a range of 3 mm from the outermost end portion of the emission surface 318 on the end surface 316 side.

  According to the second reflecting member 321, similarly to the cut-out surface 121 according to the first embodiment, it is possible to suppress the light S <b> 3 from being directly emitted from the emission surface 318 without passing through the light guide surface 317. . As shown in FIG. 11, the illuminance distribution on the document 101 according to this embodiment is substantially symmetric in the Y direction, and it can be seen that the occurrence of illuminance unevenness is well suppressed.

  In addition, although the present Example employ | adopts the structure which applied the white paint as the 2nd reflective member 321 directly to the edge part of the output surface 318, this invention is not limited to this. For example, the second reflecting member 321 may be provided at an interval with respect to the end of the emission surface 318. Further, the end of the emission surface 318 may be a rough surface (diffusion surface), and the surface of the second reflection member 321 may be a simple reflection surface. That is, any configuration may be adopted as long as the diffuse reflector is formed by at least one of the end portion of the emission surface 318 and the second reflecting member 321 facing the end portion. At this time, the first reflecting member 314 and the second reflecting member 321 may be integrally formed.

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

  For example, the shape of the light guide is not limited to that in the above-described embodiments as long as light from the incident surface can be guided to the document surface. Moreover, you may change the density of the scattering pattern formed in the light guide surface which concerns on Example 1 and 3 mentioned above to a 1st direction as needed.

  In the image reading apparatus according to each of the embodiments described above, the two illumination devices are arranged symmetrically with the reading optical axis in between, but the present invention is not limited to this configuration. For example, a configuration may be adopted in which two illumination surfaces are provided in one lighting device and a reflecting member is arranged instead of the other lighting device. 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 111 Light guide 112 Light guide unit 114 1st reflection member 115 Incident surface 116 End surface 117 Light guide surface 118 Output surface 121 Reflection part

Claims (13)

A light guide including an incident surface, an end surface facing the incident surface, a light guide surface long in the first direction, and an exit surface facing the light guide surface, is incident from the incident surface A light guide unit that guides light to the exit surface through the light guide surface;
A first reflecting member facing the end surface;
Of the light reflected by the first reflecting member, a reflecting portion that reflects light having an incident angle smaller than a critical angle with respect to the emission surface toward the inside of the light guide,
A light guide unit comprising:   The light guide unit according to claim 1, wherein the reflection portion is a cut-out surface that connects the end surface and the emission surface. When the angle formed by the exit surface and the notch surface is θ ₁ ,
125 ° <θ ₁ <155 °
The light guide unit according to claim 2, wherein the following condition is satisfied.   The light guide unit according to claim 2, wherein the cut-out surface is a transmission surface.   2. The light guide unit according to claim 1, wherein the reflection portion is a second reflection member facing an end portion of the emission surface on the end surface side.   The light guide unit according to claim 5, wherein the second reflecting member is white paint.   The light guide unit according to claim 5 or 6, wherein the first reflecting member and the second reflecting member are integrally formed.   The light guide unit according to claim 1, wherein the first reflecting member is white paint.   The light guide unit according to claim 1, wherein the end surface is a rough surface.   An illumination apparatus comprising: a light source; and a light guide unit that guides light emitted from the light source to a document, wherein the light guide unit is the light guide unit according to claim 1. .   The illumination device according to claim 10, comprising: a light receiving unit that receives light from the original; and an imaging unit that collects light from the original on a light receiving surface of the light receiving unit. Image reading device.   The image reading apparatus according to claim 11, further comprising a carriage that holds the illumination device, the light receiving unit, and the imaging unit.   The image reading apparatus according to claim 12, further comprising a drive unit that changes a relative position between the document and the carriage in a direction parallel to the document.

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