JP4946603B2 - Light guide and linear light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-guide body and a linear light source device that achieve space-saving while emitting light so as to prevent black streaks from appearing on a reading image even when a reading target has a thickness or a level difference. <P>SOLUTION: A rod-shaped light-guide body 1 is composed so that axial one end part is made as a light take-in part 3, the other end is made as a smooth face 4, and reflecting knurled-grooves 5 extending in an axial direction are formed in the side face. The side face facing the reflecting knurled-grooves 5 is made as a light emission face 9. Refracting knurled-grooves 10 are formed on the smooth-face side of the light emission face. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a linear light source device used as an illumination light source of an image reading apparatus used for a facsimile, a copying machine, an image scanner, a bar code reader or the like.

  2. Description of the Related Art In recent years, in an image reading apparatus such as a personal facsimile, a small and low power consumption LED is used as a light source of a reading light source device by improving output of a light emitting diode (hereinafter referred to as LED) and increasing sensitivity of a CCD sensor as a light receiving element. As it is becoming more commonly used. A conventional linear light source device having such an LED as a light source is designed to make light emitted from the light source incident on a light guide for the purpose of reducing the number of light sources and obtaining uniform illumination intensity. A configuration in which light is guided in a desired direction is known.

FIG. 10 is a diagram showing a configuration of a linear light source device disclosed in Japanese Patent Laid-Open No. 9-163080 as a conventional linear light source device.
The linear light source device includes a light guide 1 made of a transparent resin or the like and a light source 2 made of an LED. The light guide 1 is provided with a light capturing portion 3 at one end in the axial direction and a smooth surface 4 with a reflective film formed at the other end. The light source 2 is disposed so as to face the light capturing unit 3. A reflection knurl groove 5 extending in the axial direction is provided on the outer peripheral surface of the light guide 1 opposite to the irradiation direction. The reflection knurled groove 5 has a cut direction perpendicular to the axial direction, and a cross section along the axial direction has an isosceles triangle shape.
The light emitted from the light source 2 enters the light guide 1 from the light capturing portion, is repeatedly reflected in the light guide 1, is reflected by the reflection surface 6 of the reflective knurled groove 5, and has a predetermined angle. The light is emitted from the light guide 1.

Of the light emitted from the light source 2, the light α <b> 1 having a large incident angle with respect to the light capturing unit 3 is reflected by the reflecting surface 6 of the knurled groove 5 near the light capturing unit 3 (light α <b> 2). The light α1 having a large incident angle with respect to the light capturing portion 3 is emitted from the light guide 1 in a direction substantially perpendicular to the light emitting surface 9 because the incident angle with respect to the reflecting surface 6 of the knurled groove 5 is small (light α2). (Light α3).
On the other hand, of the light emitted from the light source 2, the light β1 having a small incident angle with respect to the light capturing unit 3 travels along the axial direction of the light guide 1 and is far from the light capturing unit 3 and close to the smooth surface 4. The light is reflected by the reflection surface 6 of the groove 5 (light β2). The light β1 having a small incident angle with respect to the light capturing portion 3 has a large incident angle with respect to the reflecting surface 6 of the knurled groove 5 (light β2), and is thus emitted from the light guide 1 with an angle inclined in the direction of the smooth surface 4 ( Light β3).

In the linear light source device shown in FIG. 10, light β3 having an angle inclined in the direction of the smooth surface 4 is emitted, and thus black streaks may occur in the read image. FIG. 11 is a partial cross-sectional view of the image reading apparatus showing the reading object 42 and the light beam in order to explain the shadow 44.
The image reading device is provided with a mounting surface 41 made of a light transmissive member so as to face the light emitting surface 9 of the linear light source device, and light emitted from the linear light source device is directed to the mounting surface 41. Irradiated. The image reading apparatus is used by placing a reading object 42 on which an image to be captured is described on a placement surface 41, and detects a projection image of the reading object 42 to obtain a reading image.
When a thick object such as a book is used as the reading object 42, a thickness is generated between the light irradiation surface of the reading object 42 and the document cover 43. Since the reading target 42 does not transmit light, the light β 3 _a that irradiates the end of the reading target 42 does not irradiate the document cover 43. The light β3 _b that irradiates with a slight shift in the axial direction from the light β3 _a that irradiates the end of the reading target 42 irradiates the document cover 43, but has an angle, and thus is shifted in the axial direction from the end of the reading target 42 Will be irradiated. Accordingly, _a shadow 44 that is not irradiated with light is formed between the light β3 _a and the light β3 _b , and appears as a black streak in the read image.
The same thing occurs when the reading object 42 has a step such as a broken line.

FIG. 12 is a diagram showing a configuration of a linear light source device disclosed in Japanese Patent Laid-Open No. 2003-97910 as a conventional linear light source device.
The light guide 1 and the light source 2 are stored in a space formed by the case 31 and the case lid 32. In order to refract the light emitted from the opening provided in the case lid 32, a deflection film 33 is provided. The deflection film 33 refracts and transmits outgoing light, and the refractive index is set according to the angle of the outgoing light. Specifically, the angle of the emitted light is canceled and the light is refracted so as to be perpendicular to the axial direction of the light guide 1. Since the light emitted from the linear light source device irradiates perpendicularly to the reading target, no shadow is generated that is not irradiated with light, and black stripes do not appear in the read image.

However, since the deflection film 33 is an extremely thin plate-like member, there is a problem that it is easily bent. If the deflection film 33 is only supported at both ends in the longitudinal direction, the deflection film 33 is bent at the center in the longitudinal direction. Assuming that the deflection film 33 is horizontal, the light is refracted so as to be perpendicular to the axis of the light guide 1. Therefore, when the deflection film 33 is bent, the light transmitted through the deflection film 33 is also bent. End up.
Therefore, for example, the deflection film 33 must be provided with a long slit in the plate-like case lid 32 so that the deflection film 33 is disposed between the slits so that it can be supported in the short direction. If such a structure is adopted, the apparatus becomes large, and it is not possible to meet the market needs for space saving for downsizing the entire document reading apparatus.
JP-A-9-163080 JP 2003-97910 A

  In view of the above-described problems, the present invention provides a light guide that emits light so that black stripes do not appear in a read image even when the reading target has a thickness or a step, and realizes space saving. It aims at providing a linear light source device.

The first invention of the present application is a rod-shaped light guide in which one end portion in the axial direction becomes a light capturing portion, the other end portion becomes a smooth surface, and a reflective knurled groove extending in the axial direction is formed on the side surface. the side opposite to the reflective knurls becomes a light emitting surface, characterized in that the refractive knurled grooves are formed on the smooth surface of the light emitting surface.
The second invention of the present application is characterized in that, in the first invention, the refractive knurled groove comprises a plurality of groove portions having a rectangular cross section in a cross section along the axial direction.
The third invention of the present application is characterized in that, in the first invention, the refractive knurled groove includes a plurality of groove portions having a triangular cross section in a cross section along the axial direction.
According to a fourth aspect of the present invention, in the first aspect, an angle formed by the light emitting surface and the surface having the light capturing portion is 90 ° or less.
Moreover, this-application 5th invention has the light guide as described in 1-4, and the light source provided facing the said light taking-in part of the said light guide.

  According to the light guide and the linear light source device according to the present invention, since the refractive knurled groove is formed on the smooth surface side of the light emitting surface, light is emitted from the linear light source device in two different directions in the axial direction. Therefore, even when the reading target has a thickness or a step, no shadow is generated on the document cover, and black stripes do not appear in the read image. In addition, since a separate member is not required to adjust the direction in which the emitted light travels, the linear light source device can be compactly accommodated to meet the market needs for space saving for downsizing the entire document reading device. Can do.

A first embodiment of the present invention will be described. FIG. 1 is a perspective view showing the configuration of the linear light source device of the present invention.
As shown in FIG. 1, the linear light source device includes a light guide 1 made of a transparent resin or the like and a light source 2 made of an LED. The light guide 1 is a cylindrical part, and is provided with a light capturing portion 3 at one end in the axial direction and a smooth surface 4 at the other end. A reflection knurl groove 5 extending in the axial direction is provided on the outer peripheral surface of the light guide 1, and a position facing the reflection knurl groove 5 is a light emitting surface 9. The reflective knurled groove 5 is formed with a plurality of groove portions 7 whose cutting direction is orthogonal to the axial direction of the light guide 1. The light exit surface 9 on the smooth surface side is provided with a refractive knurled groove 21 for the purpose of refracting light.

  In the light source 2, for example, one or a plurality of blue LED elements are arranged inside a package made of a resin, the blue LED is fixed by a molding material and shielded from the outside air to protect, and the blue light from the blue LED is protected by a phosphor layer. Is converted to white light. In general, LED elements vary in light output, but when a plurality of LED elements are arranged in the light source 2, the light output of the light source 2 is not affected by the light output of each LED element, and is constant. Light output can be secured. The light source 2 is disposed so as to face the light capturing unit 3.

  The light emitted from the light source 2 has a light distribution of a cosine curve and is emitted toward the light guide 1. In general, when light is incident through different materials, light incident beyond a critical angle (an angle determined uniquely by each material) is totally reflected without loss. Light incident at an incident angle smaller than the critical angle is refracted and incident on a member having a small refractive index with a predetermined refraction angle. Since there is an air layer between the light source 2 and the light capturing unit 3, the only light that passes from the light capturing unit 3 into the light guide 1 is light that enters the light capturing unit 3 with a predetermined refraction angle. Thus, the light angle is within a certain range.

FIG. 2 is an enlarged cross-sectional view of the linear light source device of the present invention cut in the axial direction X. FIG.
The reflective knurled groove 5 is provided with a plurality of grooves 7 that are perpendicular to the axial direction X of the light guide and cut in the depth direction Y that proceeds from the reflective knurled groove 5 to the light emitting surface 9. A flat surface 8 is formed. The length of the flat surface 8 in the axial direction is reduced as the distance from the light capturing unit 3 increases. Further, the length of each groove portion 7 in the depth direction Y is formed so as to become deeper from the vicinity of the light capturing portion 3 toward the vicinity of the smooth surface 4.

  The refracting knurled groove 10 is provided on the smooth surface 4 side of the light emitting surface 9, the cutting direction is opposite to the depth direction Y, and a plurality of grooves 11 having a rectangular cross section in the cross section along the axial direction X are formed. ing. The light reflected by the reflective knurled groove 5 on the smooth surface 4 side enters the refractive knurled groove 10.

The light incident from the light source 2 reaches the reflection knurled groove 5 while reflecting the inner wall of the light guide 1. When the incident angle with respect to the reflecting surface 6 exceeds the critical angle, the light is totally reflected to the light emitting surface 9. The light travels from the light guide 1 to the outside. Light A <b> 1 having a large incident angle with respect to the light capturing unit 3 is reflected by the reflecting surface 6 of the reflective knurled groove 5 close to the light capturing unit 3. The incident light A <b> 1 is totally reflected in a direction substantially perpendicular to the light emitting surface 9 because the incident angle with respect to the reflecting surface 6 of the reflecting knurled groove 5 is small.
The light B1 having a small incident angle with respect to the light capturing part 3 travels along the axial direction of the light guide 1 and is reflected by the reflecting surface 6 of the reflecting knurled groove 5 far from the light capturing part 3 and close to the smooth surface 4. The Since the incident light B1 has a large incident angle with respect to the reflecting surface 6 of the reflecting knurled groove 5, the incident light B1 is reflected at an angle inclined in the axial direction X that proceeds from the light capturing portion 3 to the smooth surface 4.

  In the vicinity of the light capturing portion 3, the amount of light guided through the light guide 1 is large and tends to decrease as the distance increases, but the axial length of the flat surface 8 decreases as the distance from the light capturing portion 3 increases. In addition, by increasing the length in the depth direction Y of each groove portion 7 as it goes away from the vicinity of the light capturing portion 3, the amount of light reflected by the reflective knurled groove 5 is made uniform over the entire axial direction. Yes.

FIG. 3 is a projection view in which the light guide 1 of the present invention is cut in the depth direction Y along the line segment AA ′ shown in FIG. 2. A solid line indicates the shape of the light guide 1 in the line segment AA ′, and a broken line indicates the groove portion 7 of the reflective knurled groove 5 and the groove portion 11 of the refractive knurled groove 10.
The cross-section in the depth direction of the light guide 1 is not a perfect circle, and a linear portion is provided in part. When viewed from the entire light guide 1, a horizontal plane extending in the axial direction is provided on the outer peripheral surface. The reflective knurled groove 5 is provided on this horizontal plane. This is because the horizontal plane can facilitate highly accurate groove processing.
The reflective knurled groove 5 forms a groove portion 7 having a cut of the same length in the depth direction Y over the width direction Z. In the plan view of the depth direction Y and the width direction Z, the groove 7 has a trapezoidal shape.
The refractive knurled groove 10 is formed to face the reflective knurled groove 5 in the depth direction Y. It is preferable to form the central part of the refractive knurled groove 10 in the width direction Z and the central part of the reflective knurled groove 5 in the width direction Z so as to face the depth direction Y. The refracting knurled groove 10 is provided on the outer peripheral surface of the arc-shaped light guide 1 serving as the light exit surface 9, and the same length is cut from the light exit surface 9 toward the axial center of the light guide 1. Groove portion 11 is formed. In the projection view of the plane in the depth direction Y and the width direction Z, the groove portion 11 has a fan shape. Since the refracting knurled groove 10 is formed on the extension of the light emitting surface 9, it is preferable to form the groove 11 by cutting so as to form a fan shape.

The light guide 1 is for emitting light in a line shape, and is designed so that light is emitted from the light emitting surface 9. The refractive knurled groove 10 provided on the smooth surface 4 side of the light emitting surface 9 is provided to transmit the light A reflected by the reflective knurled groove 5 when it is emitted from the inside of the light guide 1 to the outside. ing. Therefore, even if the refractive knurled groove 10 is provided at a location where the light is totally reflected on the outer peripheral surface of the light guide 1 and guided again into the light guide 1 like the light B, the object cannot be achieved. In order to facilitate processing, it is preferable to form the refractive knurled grooves 10 only in necessary portions.
As described above, when the incident angle is larger than the critical angle θ _C , the incident light B is totally reflected without loss. The light A that is reflected from the central portion in the width direction of the reflective knurled groove 5 and can be emitted to the outside of the light guide 1 is when the angle θ is smaller than the critical angle θ _C. Therefore, when both ends in the width direction of the groove portion 11 of the refractive knurled groove 10 are S and T and the central axis of the light guide 1 is O, a line connecting one end S of the refractive knurled groove 10 in the width direction Z and the axial center O. The angle θ _a formed by the segment SO and the line segment TO connecting the other end T in the width direction Z of the refractive knurled groove 10 and the axis center O is preferably 4θ _C or less. In addition, θ _a is preferably 8/3 · θ _C or more so that a sufficient amount of light can pass through the refractive knurled groove 10.

FIG. 4 is an enlarged cross-sectional view of the refractive knurled groove 10 cut in the axial direction X.
The refractive knurled groove 10 is provided with a groove portion 11 having a rectangular cross section in a cross section cut in the axial direction X. The groove portion 11 includes a side surface 12 on the light capturing portion side, a bottom surface 13, and a side surface 14 on the smooth surface side, and a top surface 15 is formed between the groove portion 11 and the groove portion 11.
A description will be given of how light (A1, B1, C1) reflected by the reflective knurled groove 5 is transmitted through the refractive knurled groove 10 using ray tracing.
The light A1 passes through the bottom surface 13 and is refracted in the axial direction X and is emitted to the outside of the light guide 1 to become light A2. The light A2 passes through the side surface 14 on the smooth surface side, is refracted in the axial direction X, enters the light guide 1, and becomes light A3. The light A3 is transmitted through the side surface 12 on the light capturing portion side, is refracted in the direction opposite to the axial direction X, is emitted to the outside of the light guide 1, and becomes light A4. The light A4 travels in a direction inclined from the depth direction Y to the axial direction X.
The light B1 is transmitted through the top surface 15, refracted in the axial direction X, and emitted to the outside of the light guide 1 to become light B2. The light B2 travels in a direction inclined from the depth direction Y to the axial direction X.
The light C1 is totally reflected from the side surface 12 on the light capturing portion side to become light C2. The light C2 passes through the top surface 15 and is refracted in the direction opposite to the axial direction X, and is emitted to the outside of the light guide 1 to become light C3. The light C3 travels in a direction inclined from the depth direction Y in the direction opposite to the axial direction X.
The lights A4 and B2 have an angle inclined in the axial direction X from the depth direction Y, while the light C3 has an angle inclined in the opposite direction of the axial direction X from the depth direction Y. Therefore, the light A4 and B2 having an angle inclined in the axial direction X and the light C3 having an angle inclined in the opposite direction to the axial direction X are emitted from the refractive knurled groove 10.

The light that has entered the light guide 1 from the light source 2 is guided in the axial direction X while repeating total reflection on the side surface of the light guide 1, but the light D 1 guided in the axial direction X is light. When incident on the side surface 12 of the take-in portion side, the incident angle to become smaller than the critical angle theta _C, resulting in emitted to the outside of the light guide 1 is transmitted through the side surface 12 of the light intake side. When such light increases, it becomes impossible to guide the light incident from the light source 2 into the light guide 1 in the axial direction X, and the light emitted from the light emitting surface 9 on the smooth surface side decreases. .
Therefore, the refractive knurled groove 10 is provided on the smooth surface side of the light emitting surface 9 so that the light incident on the light guide 1 can be efficiently guided in the axial direction X.

  When the distance between the grooves 11 and the depth, and the length of the bottom surface 13 and the top surface 15 in the axial direction X are substantially the same throughout the refractive knurled groove 10, the width of the groove 11, That is, the relationship between the axial direction X length P of the bottom surface 13 and the height of the groove 11, that is, the length H in the depth direction of the side surface 12 on the light capturing portion side and the side surface 14 on the smooth surface side is H / P Is preferably 2.1 or more and 3.7 or less. If comprised in this way, when light A1, B1, C1 reflected by the reflective knurl groove | channel 5 inclines 15 to 25 degrees with respect to the depth direction Y and injects into the refractive knurl groove | channel 10, it will incline in the axial direction X. This is because the light flux ratio between the light beams A4 and B2 having the same angle and the light beam C3 having the angle inclined in the opposite direction to the axial direction X can be made uniform.

FIG. 5 is a partial cross-sectional view of the image reading apparatus showing a state where the light beams A4 and C3 are irradiated onto the reading object 42. FIG.
The lights A4 and C3 transmitted through the refractive knurled groove 10 shown in FIG. 4 are emitted to the outside of the light guide 1 and irradiate the reading object 42 shown in FIG. The image reading device is provided with a mounting surface 41 made of a light transmissive member so as to face the light emitting surface 9 of the linear light source device, and light emitted from the linear light source device is directed to the mounting surface 41. Irradiated. The image reading apparatus is used by placing a reading object 42 on which an image to be captured is placed on a placement surface 41, and detecting a projection image of the reading object 42 placed on the placement surface 41. And
When a thick object such as a book is used as the reading object 42, a thickness is generated between the light irradiation surface of the reading object 42 and the document cover 43. Since the reading target 42 does not transmit light, the light A4 having an angle component inclined in the axial direction X does not irradiate the document cover 43 when the end of the reading target 42 is irradiated. However, since the light C3 having an angle inclined in the direction opposite to the axial direction X can irradiate a portion of the document cover 43 where the light A4 cannot be irradiated, a shadow that is not irradiated with light does not occur.
The same applies to the case where the reading target 42 has a step such as a broken line.

  Therefore, by forming the refractive knurled groove 10 on the smooth surface side of the light emitting surface 9, light having two different angle components in the axial direction X can be emitted toward the reading object 42 from the linear light source device. Therefore, even when the reading target 42 has a thickness or a step, no shadow is generated on the document cover 43, and black stripes do not appear in the read image. In addition, since a separate member is not required to adjust the direction in which the emitted light travels, the linear light source device can be compactly accommodated to meet the market needs for space saving for downsizing the entire document reading device. Can do.

A second embodiment of the present invention will be described. FIG. 6 is an enlarged cross-sectional view of the light guide 1 of the present invention cut in the axial direction X.
The second embodiment is obtained by changing the shape of the groove portion 11 of the refractive knurled groove 10 in the linear light source device of the first embodiment.
The refracting knurled groove 10 is provided on the smooth surface 4 side of the light emitting surface 9, the cutting direction is opposite to the depth direction Y, and a plurality of groove portions 11 having a triangular cross section in the cross section along the axial direction X are formed. ing. The light reflected by the reflective knurled groove 5 on the smooth surface 4 side enters the refractive knurled groove 10.
Similarly to the refractive knurled groove 10 of the first embodiment, the refractive knurled groove 10 of the second embodiment also has a fan-shaped groove portion 11 that is cut toward the center direction of the light guide 1 and has a width direction. Is formed so as to face the central portion in the width direction of the reflective knurled groove 5 in the depth direction.

FIG. 7 is an enlarged cross-sectional view of the refractive knurled groove 10 cut in the axial direction X.
The groove portion 11 of the refractive knurled groove 10 includes a light transmitting surface 17 that is a side surface on the light capturing portion side and a switching surface 16 that is a side surface on the smooth surface side that is the other side surface of the light transmitting surface 17. The switching surface 16 is preferably formed so as to be substantially parallel to the traveling direction of the light reflected by the reflective knurled groove 5. With this configuration, the light reflected by the reflective knurled groove 5 can be refracted by allowing almost all of the light to enter the light transmission surface 17 without entering the switching surface 16. Further, the inclination angle θ _b of the light transmission surface 17 indicates an angle when the light transmission surface 17 is rotated clockwise from the opposite direction 180 ° to the light transmission surface 17, and the angle of the light reflected by the reflection knurled groove 5. It is preferable to adjust by. For example, the reflected light reflected knurls 5, toward the smooth surface 4 side, the angle of tilt in smooth surface direction is increased, by increasing the inclination angle theta _b of the light transmitting surface 17, of the light guide 1 The light can be refracted so as to be substantially perpendicular to the axial direction.

The light A <b> 1 reflected by the reflection knurled groove 5 and guided to the refractive knurled groove 10 enters the light transmission surface 17. Angle of incidence with respect to the light transmission surface 17 of the light A1 is the theta _1. Since the refractive index of the light guide 1 is larger than that of the atmosphere, the emission angle θ ₂ of the light A 2 that is refracted through the light transmission surface 17 is larger than the incident angle θ ₁ . Since the perpendicular L of the light transmission surface 17 is inclined in the axial direction X, the outgoing light A2 of the light transmission surface 17 is refracted so as to travel in the opposite direction of the axial direction X. If the inclination angle theta _b of the light transmitting surface 17 and 40 ° to 65 °, the emitted light A2 is proceed in a preferred direction.

FIG. 8 is a partial cross-sectional view of the image reading apparatus showing a state in which the light beam A <b> 2 is irradiated on the reading object 42.
When the groove portion 11 having a triangular cross section is formed in the refractive knurled groove 10, the light A <b> 2 emitted from the light transmission surface 17 of the groove portion 11 is refracted so as to travel in the direction opposite to the axial direction X. The light A2 emitted from the refracting knurled groove 10 is directed to irradiate the end portion of the reading object 42, so that no shadow is generated on the document cover 43. In addition, since a separate member is not required to adjust the direction in which the emitted light travels, the linear light source device can be compactly accommodated to meet the market needs for space saving for downsizing the entire document reading device. Can do.

A third embodiment of the present invention will be described. FIG. 9 is an enlarged cross-sectional view of the light guide 1 of the present invention cut in the axial direction X. FIG.
The third embodiment, in the linear light source device of the second embodiment, in which the angle theta _d of a surface having a light emitting surface 9 and the light take-in portion 3 is configured to be 90 ° or less is there. The angle formed between the surface on which the reflective knurled grooves 5 are formed and the surface having the light capturing portion 3 is 90 °.

The light incident from the light source 2 includes light that travels directly from the light capturing unit 3 to the reflecting surface 6 of the reflecting knurled groove 5, but is guided toward the smooth surface 4 while reflecting the inner wall of the light guide 1. After that, there is also light that travels to the reflecting surface 6 of the reflecting knurled groove 5. Like the light A1, if incident from the light source 2 to the light incident surface 9 proceeds to a light emitting surface 9, the incident angle theta ₁ with respect to the light emitting surface 9 is greater than the critical angle with the member of the light guide 1, the light Total reflection at the exit surface 9. The light A2 totally reflected by the light exit surface 9 has an exit angle θ ₂ equal to the incident angle θ ₁ , but the light exit surface 9 is inclined from the surface on which the reflective knurled grooves 5 are formed. angle theta ₃ is increased with respect to the knurled grooves 5.

As described above, the angle θ ₃ with respect to the reflection knurled groove 5 can be increased every time the light is totally reflected on the light emitting surface 9, so that the light is guided toward the smooth surface 4 while reflecting the light emitting surface 9. The incident angle of the light with respect to the reflecting surface 6 of the reflecting knurled groove 5 is smaller than that of the light traveling directly from the light capturing unit 3 to the reflecting surface 6 of the reflecting knurled groove 5. The light incident on the reflecting surface 6 near the smooth surface 4 is reflected by the reflecting surface 6 because the guided light reflected by the light emitting surface 9 is added to the direct light from the light capturing unit 3. The light generally has a smaller angle component in the axial direction X than when θ _d is 90 °. Therefore, the problem that the incident angle with respect to the reflecting surface 6 of the reflecting knurled groove 5 increases as the distance from the light capturing unit 3 increases can be reduced.

As described above, if the angle θ _d formed by the light emitting surface 9 and the surface having the light capturing portion 3 is configured to be 90 ° or less, the light reflected by the reflecting surface 6 of the reflecting knurled groove 5 is Since the angle component in the axial direction X is reduced as a whole, the angle that must be refracted by the refractive knurled groove 10 is also reduced. Possible range of the inclination angle theta _b of the light transmitting surface 17 becomes easily design widely.

The perspective view which shows the structure of the linear light source device of this invention. Expanded sectional view of the linear light source device of the present invention Projection view of the light guide of the present invention cut in the radial direction Enlarged sectional view of the refractive knurled groove of the present invention Partial sectional view of the image reading apparatus showing a state in which the light beam is irradiated on the reading target Expanded sectional view of the linear light source device of the present invention Enlarged sectional view of the refractive knurled groove of the present invention Partial sectional view of the image reading apparatus showing a state in which the light beam is irradiated on the reading target Expanded sectional view of the linear light source device of the present invention Sectional drawing which shows the structure of the conventional linear light source device Partial sectional view of the image reading apparatus showing a state in which the light beam is irradiated on the reading target Sectional drawing which shows the structure of the conventional linear light source device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light guide 2 Light source 3 Light taking-in part 4 Smooth surface 5 Reflective knurled groove 6 Reflective surface 7 Groove part 8 Flat surface 9 Light-emitting surface 10 Refractive knurled groove 11 Groove part 31 Case 32 Case cover 33 Deflection film 41 Mounting surface 42 Reading Target 43 Document cover

Claims (5)

In a rod-shaped light guide body in which one end in the axial direction becomes a light capturing portion, the other end becomes a smooth surface, and a reflective knurled groove extending in the axial direction is formed on the side surface.
Light guide, wherein the side facing the reflective knurls becomes a light emitting surface, the refractive knurled grooves are formed on the smooth surface of the light emitting surface.
2. The light guide according to claim 1, wherein the refractive knurled groove includes a plurality of grooves having a rectangular cross section in a cross section along the axial direction. 2. The light guide according to claim 1, wherein the refractive knurled groove includes a plurality of groove portions having a triangular cross section in a cross section along the axial direction. The light guide according to claim 1, wherein an angle formed between the light emitting surface and the surface having the light capturing portion is 90 ° or less. 5. A linear light source device comprising: the light guide according to claim 1; and a light source provided to face the light capturing portion of the light guide.

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