JP6016077B2 - Linear light source device - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear light source device, and more particularly to a linear light source device used as an illumination light source of an image reading device used for a facsimile, a copying machine, an image scanner, a barcode reader, and the like. .

  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 due to an improvement in output of a light emitting diode (hereinafter referred to as LED) and advancement of a CCD sensor as a light receiving element. It is becoming used. For example, in Patent Document 1, an LED is arranged at an end of a linear light guide made of a light-transmitting resin, and light emitted from the LED is incident on the light guide to be reflected from the inside. There is known a linear light source device for reading an image, which is used as a linear light source by being emitted to the outside.

FIG. 6 is a longitudinal sectional view of the linear light source device described in Patent Document 2 which is a prior art document. The linear light source device includes a rod-shaped light guide 92, a light source 91 including an LED, and a reflecting member 93 surrounding the light source. The light guide 92 is provided with an emission surface 925 extending along the longitudinal direction, and a reflection groove portion 924 made up of concave and convex grooves is formed on the back surface facing the emission surface 925.
A protrusion 921 is provided at the end of the light guide 92 in the longitudinal direction. The light source 91 is disposed at a position facing the incident surface 922 which is one end surface of the protrusion 921 of the light guide 92, and the light emitted from the light source 91 passes through the incident surface 922 of the protrusion 921. The light is guided into 92. The guided light travels in the axial direction while being repeatedly reflected inside the light guide 92, and a part of the light is reflected by a plurality of concave and convex grooves provided in the reflective groove portion 924. The reflected light from the reflection groove 924 is emitted in the direction perpendicular to the longitudinal direction of the light guide 92 and is preferably applied to the document reading surface X of the document glass 6.

Japanese Patent No. 2693098 JP 2011-210530 A

FIG. 7 is a diagram showing the problems of the linear light source device as the prior art, and FIG. 7A shows the illuminance distribution in the longitudinal direction from the end to the center of the light guide of the conventional linear light source device. 7B shows an optical path inside the light guide of the light emitted from the light source, and FIG. 7C shows an optical path inside the light guide of the light reflected from the light source through the reflecting member, respectively. FIG.
The light emitted from the light source 91 passes through the vicinity of the end portion d from the incident surface 922 and is guided to the inside of the light guide 92. Therefore, the end portion of the light guide should originally have a larger amount of light than the inside. It is. However, as shown in FIG. 7A, in the conventional linear light source device, the amount of light is significantly reduced near the end d of the light guide. The cause is assumed to be as follows.

First, since there is a gap between the light source 91 and the light guide 92, the medium on the optical path is not constant, and the light emitted from the LED light source 91 is refracted by the incident surface 922 of the light guide 92. As shown in FIG. 7 (b), the light guided inward with respect to the optical path L1 ′ is refracted like the optical path L1, so that the center of the light guide 92 is located closer to the end d of the light guide 92 than the end d. It is reflected by the reflection groove 924 on the side.
Next, a protrusion 921 is formed at the end of the light guide 92, and the light guided by the incident surface 922 is totally reflected by the side surface of the protrusion 921, so the vicinity of the end of the light guide 92 The optical path L2 ′ toward the reflection groove 924 of d is totally reflected by the side surface of the protrusion 921 and follows the optical path L2. Further, as shown in FIG. 7C, the light guided from the LED light source 91 via the reflecting member 93 is also refracted by the incident surface 922 of the light guide 92 and follows the optical path L3 instead of the optical path L3 ′. Therefore, it is difficult for light to be guided to the concavo-convex groove near the end d of the light guide 92, and the amount of light emitted from the end d near the end is reduced.
The optical path L4 reflected near the opening of the reflecting member 93 is also not guided to the reflection groove 924 near the end d of the light guide 92 and cannot contribute to the amount of light emitted from the end.

  For the above reasons, the light intensity of the conventional linear light source device is reduced at the end of the light guide due to its configuration. For this reason, it is difficult to secure the required amount of light near the end of the light guide, and the effective light emission length of the light guide is shortened. Therefore, in order to ensure an effective light emission length, it is necessary to design an extra long light guide.

  In view of the above problems, the problem to be solved by the present invention is a linear light source device including a rod-shaped light guide, a light source including an LED, and a reflective member surrounding the light source. It is an object of the present invention to provide a linear light source device that prevents a significant light quantity decrease from occurring at the end.

The present invention employs the following means in order to solve the above problems.
That is, the gist of the present invention is that a diffuse reflection surface is provided on a part of the reflection member so that the amount of light does not decrease at the end of the light guide.

The present invention includes a rod-shaped light guide including a light emitting surface extending along a longitudinal direction and having a reflective groove portion formed of a concave and convex groove on a back surface facing the light emitting surface, and opposed to one end surface of the light guide. A concave portion that surrounds the light source, is attached to one end of the light guide, and expands from the light source toward the light guide in a cross-section along the longitudinal direction of the light guide. In the linear light source device having a reflection member having a shape, a specular reflection surface is provided on the inner surface of the reflection member, and a part of the reflection surface on the opening side of the reflection member is a diffuse reflection surface. It is characterized by being.
Further, the reflecting surface includes a frustoconical first reflecting surface whose diameter increases from the light source toward the light guide, and a cylindrical second reflecting surface formed continuously with the first reflecting surface. And at least a part of the second reflecting surface is a diffuse reflecting surface.
The second reflecting surface is a diffuse reflecting surface, and a part of the first reflecting surface is a diffuse reflecting surface formed continuously with the second reflecting surface.
The diffuse reflection surface is characterized in that the surface roughness is gradually increased as the light source approaches the light guide.

In the present invention, the concave-shaped reflecting member provided at the end of the light guide has a reflecting surface on the inner surface, and a part of the reflecting surface on the opening side of the reflecting member is a diffuse reflecting surface. Therefore, the reflected light from the diffuse reflection surface can be suitably guided to the reflection groove on the side of the light guide that is difficult to guide the light from the light source, and the light quantity at the end of the light guide is reduced. Can be suppressed.
Moreover, the illumination intensity of the longitudinal direction of a light guide can be adjusted more uniformly by changing the area and surface roughness of a diffuse reflection surface suitably.

The principal part sectional view of the linear light source device which shows a first embodiment concerning the present invention. Sectional drawing of the principal part of the linear light source device which shows 2nd embodiment concerning this invention. Sectional drawing of the principal part of the linear light source device which shows 3rd embodiment concerning this invention. BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram explaining the Example concerning this invention. The graph which shows the illumination distribution of the linear light source device concerning this invention. The longitudinal cross-sectional view which shows the conventional linear light source device. The schematic diagram for demonstrating the subject of the conventional linear light source device.

FIG. 1 is a cross-sectional view of the main part of the linear light source device according to the first embodiment of the present invention cut in the longitudinal direction. For convenience, hatched lines indicating the cross section of the light guide are not shown.
The linear light source device includes a light guide 2 that is a rod-shaped member, a light source 1 that is opposed to one end surface in the longitudinal direction of the light guide, and a concave shape that surrounds the light source 1 and is attached to one end of the light guide 2. The reflection member 3 is provided. A reflection surface 30 is provided on the inner surface of the reflection member 3 and functions to reflect the light emitted from the light source 1 and guide the reflected light to the inside of the light guide 2.

  The light source 1 includes an LED 11 that emits light and a hemispherical sealing body 12 that seals the periphery of the LED 11. A light-transmitting material is used for the sealing body 12, and a light-transmitting resin such as a silicone resin is used. Moreover, according to a use suitably, it is possible to adjust a light source color by apply | coating a phosphor to the sealing body 12, or adding inside. For example, when a blue light emitting diode is used as the LED 11, a yellow phosphor is sealed inside the sealing body 12. Thereby, the emitted light from the LED light source 1 is mixed with the blue light of the blue light emitting diode and the yellow light emitted by the yellow phosphor being excited, and white light can be obtained. Further, when an ultraviolet light emitting diode is used as the LED 11, high-luminance white light can be obtained by enclosing a white phosphor inside the sealing body 12.

The light guide 2 has a protruding portion 21 formed at one end in the longitudinal direction. An incident surface 211 for taking in light from the light source is provided on the end face of the projecting portion 21, and the incident surface 211 is arranged to face the light source 1 so that direct light from the light source is suitably taken in. The protrusion 21 is inserted from the opening side of the reflecting member 3, and the incident surface 211 of the light guide 2 and the light source 1 are held in an opposing arrangement. Since a gap is formed between the protruding portion 21 and the reflecting member 3, the light taken from the incident surface 211 is easily totally reflected by the side surface 212 of the protruding portion 21. Therefore, the light taken in from the incident surface 211 is guided to the inside of the light guide 2 while being totally reflected by the side surface 212 of the protrusion 21.
On the side surface of the light guide 2 excluding the protrusions, a light emitting surface 25 extending along the longitudinal direction is provided, and a reflection groove portion 24 including a plurality of concave and convex grooves 23 is formed on a surface facing the light emitting surface 25. An uneven groove is formed in the longitudinal direction of the light guide 2. The concavo-convex groove 23 has a substantially trapezoidal shape, and the light guided from the incident surface 211 can be preferably reflected to the exit surface 25 side.
As the material of the light guide 2, a material that transmits white light is used. Examples thereof include materials such as acrylic resin, cycloolefin polymer resin, and polycarbonate resin.

  The reflecting member 3 is a member having a bottomed concave shape, and includes an LED light source 1 inside and is attached to one end portion of the light guide 2. A reflecting surface 30 is formed on the inner surface of the reflecting member 3, and the light emitted from the light source 1 can be preferably reflected toward the incident surface 211 of the light guide 2. The shape of the reflection surface 30 is increased in diameter from the light source 1 toward the light guide 2, the light source 1 is provided on the small diameter side, and the protruding portion 21 of the light guide 2 is disposed on the large diameter side. The As an example, the reflecting surface 30 of the reflecting member 3 shown in FIG. 1 has a frustoconical first reflecting surface 31 whose diameter increases from the LED light source 1 toward the light guide 2, and the first reflecting surface. 31 and a cylindrical second reflecting surface 32 formed continuously, and at least a part of the second reflecting surface 32 is a diffuse reflecting surface 5a subjected to roughening.

  The reflecting surface 30 has a mirror-finished surface, and is formed with both a mirror-reflecting surface that is a main portion of the first reflecting surface and a diffuse reflecting surface 5a that is obtained by roughing the surface. The diffuse reflection surface 5a is provided on the reflection surface 30 on the large diameter side (light guide body side in FIG. 1) of the reflection member 3, and the specular reflection surface is a reflection on the small diameter side (LED light source side in FIG. 1). It is provided on the surface 30. As shown in the above configuration, the diffuse reflection surface 5 a is provided on the opening side of the reflection member 3, and the amount of light at the end of the light guide 2 can be increased. Further, the specular reflection surface is provided on the small diameter side of the reflection member 3, and the light from the LED light source 1 can be suitably guided into the light guide 2. When a significant light amount decrease is observed at the end portion of the light guide 2, the light amount decrease at the end portion can be more preferably prevented by widening the area of the diffuse reflection surface 5 a.

  In the reflecting member 3 according to the present invention, the diffuse reflecting surface 5 a is formed on the reflecting surface 30 on the opening side of the reflecting member 3. The light reflected by the diffuse reflection surface 5a is uniformly scattered in the surroundings, and the light is suitably guided also to the end portion of the light guide where it is difficult for the light from the light source to reach. Therefore, the amount of radiated light at the end of the light guide increases, and a significant reduction in the amount of light near the end of the light guide 2 can be suppressed. The diffuse reflection surface 5 a is formed only in the vicinity of the opening side of the reflection member 3. For example, when the diffuse reflection surface 5a is formed in the vicinity of the small diameter side (the LED light source side in FIG. 1) of the reflecting member 3, it becomes impossible to suitably guide light into the light guide 2 and guide the light. The light quantity at the center of the body 2 is reduced. In addition, if the ratio of the diffuse reflection surface 5a in the reflection surface 30 is large, the amount of light may be attenuated due to multiple scattering, so care must be taken.

  The diffuse reflection surface 5a formed on the reflection surface 30 is not necessarily subjected to the same rough surface processing. For example, the diffuse reflection surface 5a can be formed so that its surface roughness gradually increases as it goes from the LED light source to the light guide.

  As the material of the reflecting member 3, for example, a metal material such as aluminum or an alloy material such as stainless steel is used. These metal materials and alloy materials can be mirror-finished to form a reflecting surface, and can be roughened to form a diffuse reflecting surface that diffuses and reflects light in multiple directions. The diffuse reflection surface desirably has at least a surface roughness of Ra 0.8 or more (Ra: JIS B 0601-1994). When the surface roughness is lower than Ra0.8, the function as a diffusion surface becomes poor, and the effect of the present invention cannot be obtained. In addition, when a material having poor reflection characteristics such as resin or ceramics is used as the material of the reflecting member 3, the reflecting surface can be formed by applying or vapor-depositing a reflecting material on the inner surface of the reflecting member 3.

FIG. 2 is a cross-sectional view of a main part of a linear light source device showing a second embodiment of the present invention. The basic structure of the second embodiment of the present invention is substantially the same as that of the linear light source device shown in FIG. 1, and the same reference numerals as those shown in FIG.
The reflecting member 3 shown in FIG. 2 includes a first reflecting surface 31 having a truncated cone shape whose diameter increases from the light source 1 toward the light guide 2, and a cylindrical first reflecting surface 31 continuously formed on the first reflecting surface 31. The second reflection surface 32 is a diffuse reflection surface 5b having a roughened surface, and a part of the first reflection surface 31 is diffusely reflected continuously with the second reflection surface 32. Surface 5b is formed.
With the above-described configuration, the diffuse reflection surface 5b is formed not only on the second reflection surface 32 but also on a part on the first reflection surface 31 side, and it is more preferable to prevent the light amount at the end of the light guide 2 from being reduced. Can do.

  FIG. 3 is a cross-sectional view of a main part of a linear light source device showing a third embodiment of the present invention. 3, the same reference numerals as those in FIG. 1 are assigned to the same members. The reflecting member 3 shown in FIG. 3 is a member having a bottomed concave shape, and includes an LED light source 1 inside, and is attached to one end portion of the light guide 2. A reflecting surface 30 is formed on the inner surface of the reflecting member 3, and the shape thereof is formed into a concave curved surface shape whose diameter is gradually reduced from the opening of the reflecting member 3. With the above configuration, the light emitted from the LED light source 1 is preferably reflected toward the incident surface 211 of the light guide 2.

  The shape of the reflection surface 30 is increased in diameter from the light source 1 toward the light guide 2, the light source 1 is provided on the small diameter side, and the protruding portion 21 of the light guide 2 is disposed on the large diameter side. The The reflecting surface 30 is formed with both a specular reflecting surface obtained by mirroring the surface and a diffuse reflecting surface 5c obtained by roughing the surface. The diffuse reflection surface 5c is provided on the reflection surface on the large diameter side (light guide body side in FIG. 3) of the reflection member, and the specular reflection surface is provided on the reflection surface on the small diameter side (LED light source side in FIG. 3). It has been. As shown in the above configuration, the diffuse reflection surface 5 c is provided on the opening side of the reflection member 3, and the amount of light at the end of the light guide 2 can be increased. Further, the specular reflection surface is provided on the small diameter side of the reflection member 3, and the light from the LED light source 1 can be suitably guided into the light guide 2. When a significant light amount reduction is observed at the end portion of the light guide 2, the light amount reduction at the end portion can be suppressed by widening the area of the diffuse reflection surface 5 c.

  The diffuse reflection surface 5c formed on the reflection surface 30 is not necessarily subjected to the same rough surface processing. For example, the diffuse reflection surface 5c can be formed so that its surface roughness gradually increases as it goes from the LED light source 1 to the light guide 2.

  Hereinafter, specific examples of the present invention will be described.

<Example 1>
According to the configuration shown in FIG. 4, a linear light source device according to the present invention was manufactured under the following conditions.
Light guide (2): full length (L ₂ ) 336 mm, diameter (D ₂ ) φ5.6 mm,
Protrusion (21): distance (L ₂₁ ) 2 mm, diameter (D ₂₁ ) φ 4.8 mm,
First reflective surface (31): distance (L ₃₁ ) 2.25 mm, diameter (D ₃₁ ) φ 5.4 mm to 3.52 mm,
Second reflecting surface (32): distance (L ₃₂ ) 2 mm, diameter (D ₃₂ ) φ5.4 mm,
Rough surface machining position (5): Distance (L ₅ ) 2.57 mm
Surface roughness (5s): Ra0.8

<Conventional example 1>
A linear light source device having the same configuration as in Example 1 was produced except that a diffuse reflection surface was formed on the first reflection surface and the second reflection surface.

FIG. 5 is a diagram showing the measurement results of the illuminance distribution in the longitudinal direction from the end portion to the center portion of the light guide for the linear light source devices of Example 1 and Conventional Example 1. The distance L shown in FIG. 5 corresponds to L ₂ shown in FIG. 4 and indicates the distance from the end of L ₂ to the center. The illuminance distribution of the light guide was measured by installing an illuminometer at a position 8 mm away from the light exit surface of the light guide and scanning the illuminometer in the longitudinal direction. As the illuminance meter, an illuminance meter T-10M (manufactured by Konica Minolta) was used.
As shown in FIG. 5, it was confirmed that Conventional Example 1 has low illuminance at the end portion of the light guide, and the light guide end portion has lower illuminance than the central portion. On the other hand, in Example 1, no significant decrease in illuminance was observed at the end of the light guide, and it was confirmed that the illuminance higher than the central portion of the light guide was maintained. By making the reflecting surface provided in the opening of the reflecting member a diffuse reflecting surface,
This is because the reflected light is preferably guided to the reflection groove near the end of the light guide, and the amount of emitted light at the end is increased.

  The linear light source device according to the present invention prevents a local light amount from falling by forming not only a specular reflection surface but also a diffuse reflection surface on the reflection surface of the reflection member, and a wider effective light emission length. Can be secured.

1 Light source 11 LED
DESCRIPTION OF SYMBOLS 12 Sealing body 2 Light guide 21 Protruding part 211 Incident surface 212 Side surface 23 Concavity and convexity groove 24 Reflective groove part 25 Outgoing surface 3 Reflective member 30 Reflective surface 31 First reflective surface 32 Second reflective surface 5 Diffuse reflective surface 6 Original glass 91 Light source 92 Light guide 921 Protruding portion 922 Incident surface 924 Reflecting groove portion 925 Output surface d Near end portion 93 Reflecting member

Claims (4)

A rod-shaped light guide having a light exit surface extending along the longitudinal direction and having a reflection groove formed of a concavo-convex groove on a surface facing the light exit surface, and a light source disposed to face one end surface of the light guide Have
A line provided with a reflective member having a concave shape that surrounds the light source and is attached to one end of the light guide, and expands from the light source toward the light guide in a cross section along the longitudinal direction of the light guide. A light source device,
A specular reflection surface is provided on the inner surface of the reflection member,
A part of the reflection surface on the opening side of the reflection member is a diffuse reflection surface. The reflecting surface includes a truncated cone-shaped first reflecting surface that increases in diameter from the light source toward the light guide, and a cylindrical second reflecting surface formed continuously with the first reflecting surface. And
The linear light source device according to claim 1, wherein at least a part of the second reflecting surface is a diffuse reflecting surface. The second reflecting surface is a diffuse reflecting surface,
The linear light source device according to claim 2, wherein a part of the first reflection surface is a diffuse reflection surface that is continuous with the second reflection surface.   4. The linear light source device according to claim 1, wherein the diffuse reflection surface is formed so that the surface roughness gradually increases as it approaches the light guide from the light source. 5.

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