JP2010277940A - Light guide body for linear light source device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide body for a linear light source device capable of stable copying, by forming the light guide body so that spread of light emitted to the outside of the light guide body from the vicinity of the light entrance plane of the light guide body where a light source such as an LED or the like is disposed becomes the same extent of spread of light emitted to the outside of the light guide body in a location away from the light entrance plane to uniform illuminance distributions of light emitted from several positions in the optical axis direction of the light guide body. <P>SOLUTION: This light guide body for the linear light source device includes an upper surface 3 formed along the optical axis of the light guide body 1 while having a cross section perpendicular to the optical axis, which is formed like an circular arc, and including a light emitting surface to emit light, a lower surface 5 disposed parallel to the upper surface 3 along the optical axis while including a reflecting surface 4 formed of recessed parts and projecting parts facing the upper surface 3, and a side surface 6 formed on the side part connecting the upper surface 3 and the lower surface 5, and an inclined surface 61 which approaches the center of the optical axis as it parts from the light source in the direction of the optical axis is provided on the side surface 6. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a light guide for a linear light source device, and more particularly to a linear light source used in an image reading device, which guides light from a light source such as an LED and emits linear light. The present invention relates to a light guide for a linear light source device.

In recent years, in an image reading apparatus such as a personal facsimile, by improving the output of the LED, a small and low power consumption LED is used as a light source, and as shown in Patent Document 1, the LED is disposed at the end of a rod-shaped light guide, There has been proposed an LED document illumination device that irradiates a document by guiding light from an LED with a light guide.
FIG. 8 is a diagram showing the configuration of the linear light source device for reading an original document described in FIG. 1 of Patent Document 1. In FIG. 8, 101 is a light guide, 102 is a light diffusing unit, and 103 is an LED. A light emitter 104, which is a light emitting surface.

Japanese Patent No. 2900799 Japanese Patent No. 2994148

  By the way, the linear light source device shown in FIG. 8 is incident on the light guide 101 from the LED and spreads in a plane orthogonal to the axial direction of the light emitted from the light guide 101. There is a problem that the position in the direction becomes narrower as the distance from the light emitter 103 increases. That is, when the light spread in the axial direction of the light emitted from the light guide 101 is different, when the light emitted from the light guide 101 is irradiated on the document and read by an optical reading element such as a CCD, Since an optical reading element such as a CCD has a narrow reading width, if the reading position of the CCD is slightly deviated, the intensity of light reflected from the document surface and incident on the CCD is determined by the position of the light guide 101 in the axial direction. Be influenced by different things.

This problem will be described in detail with reference to FIGS. FIG. 9 is a cross-sectional view along the longitudinal direction of the cylindrical light guide 202 of the linear light source device 201 according to the prior art.
As shown in the figure, the linear light source device 201 includes a cylindrical light guide 202, a light source 203 such as an LED facing the one end surface 204 in the longitudinal direction of the light guide 202, and a light guide 202. And the other end face 205 in the longitudinal direction. The light guide 202 is provided with a reflection groove 206 composed of a concave portion and a convex portion on an outer surface extending along the longitudinal direction. The reflection groove 206 is configured such that the cutting direction is orthogonal to the optical axis direction of the light guide 202. The light S emitted from the light source 203 enters from the one end surface 204 of the light guide 202 and is taken into the light guide 202. The light S taken into the light guide 202 is repeatedly reflected inside the light guide 202, reflected by the inclined surface of the reflection groove 206, and emitted from the light emission surface 207 facing the reflection groove 206 of the light guide 202. To do. As described above, the linear light S is emitted from the light emitting surface 207 along the longitudinal direction of the light guide 202.

  In the application of the image reading apparatus, the linear light S emitted from the light emitting surface 207 is received by an electronic light receiving element such as a CCD, for example. However, the illuminance distribution of the linear light S emitted from the light emitting surface 207 changes in the direction perpendicular to the optical axis at each position in the optical axis direction of the light guide 202. As described in paragraph 0004 of Patent Document 2, the reading position of the electron light receiving element may be shifted in the direction perpendicular to the axial direction of the light guide 202. There is a problem in that the amount of light received by the electronic light receiving element is affected by the change in the illuminance distribution.

This point will be described in detail with reference to FIGS. 10 is a top view of the linear light source device 201 shown in FIG. 9 as viewed from the light emitting surface 207 side, and FIGS. 11A and 11B are axes of the linear light source device 201 shown in FIG. It is AA sectional drawing and BB sectional drawing of the surface orthogonal to a direction.
As shown in FIG. 10, the light S emitted from the light emission surface 207 of the light guide 202 is guided by the light S taken from the one end surface 204 inside the light guide 202. Are emitted as linear light extending from one end surface 204 to the other end surface 205. At this time, the light S taken into the light guide 202 has light S1 having a large angular component with respect to the axial direction of the light guide 202 on one end side 204 of the light guide 202, and this light S1. Is reflected by the reflection groove 206, it is emitted from the light emitting surface 207 as light S1 having a spread as shown in FIG. However, in the captured light S, most of the light S1 having a large angle component with respect to the axial direction of the light guide 202 is from the light emitting surface 207 between the one end surface 204 and the central portion of the light guide 202. It will be emitted. For this reason, the light S that reaches the other end face 205 side of the light guide 202 is only the light S <b> 2 having a small angle component with respect to the axial direction of the light guide 202. Therefore, the light S2 emitted from the light emitting surface 207 on the other end face 205 side of the light guide 202 is more than the light S1 emitted from the one end face 204 side of the light guide 202 as shown in FIG. Even the spread becomes a small light.

  That is, in such a linear light source device 201, the illuminance distribution of the cross section on the one end face 204 side in the longitudinal direction of the light guide 202 is different from the illuminance distribution of the cross section on the other end face 205 side. Therefore, when the linear light emitted from the light guide 202 is read along the longitudinal direction by an electron light receiving element (not shown), the illuminance distribution read along the central axis and the reading position of the electron light receiving element are The illuminance distribution at a position shifted in the lateral direction (Z-axis direction) from the central portion is different.

This point will be described in detail with reference to FIG. FIG. 12A shows the linear light source device 201 of FIG. 9 on the lower side of the paper, and the relative illuminance read by the electron light receiving elements X1 and X2 along the longitudinal direction of the linear light source device 201 on the upper side of the paper. The measurement results are shown. 12B and 12C are the same as the cross sections of FIGS. 11A and 11B, and show the reading positions of the electron light receiving elements X1 and X2 in each cross section.
As shown in FIGS. 12B and 12C, when the electron light receiving element X1 is positioned outside the central axis of the light guide 202, the electron light receiving element X1 along the central axis direction of the light guide 202. When the illuminance is read, the solid line in the upper side view of FIG. 12A is shown, and the relative intensity is constant. However, as shown in FIG. 12B, the light spread is large in the cross section on the one end face 204 side of the light guide 202, whereas the other of the light guide 202 is shown in FIG. 12C. In the cross section on the end face 205 side, the spread of light is small. For this reason, when the illuminance is read along the central axis direction of the light guide 202 in the electron light receiving element X2 moved in the lateral direction (X-axis direction in FIG. 12) from the outside of the central axis of the light guide 202, It becomes like the dotted line in the upper side view of FIG. 12A, and the relative strength of the light guide 202 decreases from the one end face 204 side toward the other end face 205 side. As described above, the linear light source device 201 according to the related art has a problem that the illuminance distribution in the longitudinal direction of the light guide 202 changes depending on the position read by the electron light receiving element.

  In view of the above problems, the object of the present invention is to spread the light emitted from the vicinity of the light incident surface of the light guide where a light source such as an LED is disposed to the outside of the light guide and away from the light incident surface. Illuminance distribution of light emitted from each position in the optical axis direction of the light guide by forming the light guide so that the spread of light radiated to the outside of the light guide at the same position is approximately the same It is an object of the present invention to provide a light guide for a linear light source device that can be made uniform and can be stably copied.

In order to solve the above-described problems, the invention according to claim 1 is a light that is formed along the optical axis of the light guide, the cross-sectional shape orthogonal to the optical axis is formed in an arc shape, and emits light. An upper surface including an emission surface, a lower surface including a reflecting surface composed of a concave portion and a convex portion that are arranged in parallel to the upper surface along the optical axis, and a side portion that connects the upper surface and the lower surface The light guide for a linear light source device is characterized in that the side surface has an inclined surface that approaches the optical axis center as the distance from the light source increases in the optical axis direction.
The invention according to claim 2 is the linear light source device according to claim 1, wherein a plurality of the inclined surfaces are provided on the side surface along the optical axis direction of the light guide. It is a light guide.
A third aspect of the present invention is the linear light source according to the first or second aspect, wherein the inclined surface has a linear cross-sectional shape orthogonal to the optical axis direction of the light guide. It is a light guide for apparatuses.

  According to the present invention, the inclined surface formed along the axial direction of the light guide is formed so as to approach the optical axis central axis as it moves away from the light source disposed at the end of the light guide. The spread angle of the emitted light in the cross-sectional direction orthogonal to the optical axis can be controlled to be almost constant over the entire optical axis direction. As a result, the illuminance distribution of the light emitted from each position in the axial direction of the light guide can be made uniform, and a light guide for a linear light source device capable of stable copying can be provided.

It is a figure which shows the structure of the light guide for linear light source devices which concerns on 1st Embodiment. It is a figure which shows the short-axis irradiation distribution in the light guide for linear light source devices which concerns on 1st Embodiment. It is a figure which shows the structure of the light guide for linear light source devices which concerns on 2nd Embodiment. It is a figure which shows the short-axis irradiation distribution in the light guide for linear light source devices which concerns on 2nd Embodiment. It is a figure which shows the structure of the light guide for linear light source devices which concerns on 3rd and 4th embodiment. It is a figure which shows the structure of the light guide for linear light source devices which concerns on a prior art. It is a figure which shows the short-axis irradiation distribution in the light guide for linear light source devices shown in FIG. It is a figure which shows the structure of the linear light source device described in FIG. It is sectional drawing along the longitudinal direction of the cylindrical light guide of the linear light source device which concerns on a prior art. It is the top view seen from the light-projection surface side of the linear light source device shown in FIG. It is AA sectional drawing and BB sectional drawing of the surface orthogonal to the axial direction of the linear light source device shown in FIG. 9A shows the linear light source device 201 of FIG. 9 on the lower side of the paper, and shows the measurement result of the relative illuminance read by the electron light receiving elements X1 and X2 along the longitudinal direction of the linear light source device 201 on the upper side of the paper. (B) And (c) is the figure which showed the reading position of the electronic light receiving elements X1 and X2 in a light-guide cross section.

A first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a diagram illustrating a configuration of a light guide for a linear light source device according to the present embodiment.
As shown in the figure, the light guide 1 is formed along a light incident surface 2 on which light from a light source such as an LED (not shown) is incident, and along the optical axis of the light guide 1, and is orthogonal to the optical axis. The cross-sectional shape to be formed is an arc shape, and includes a top surface 3 including a light emitting surface that emits light, and a reflection composed of a concave portion and a convex portion that are arranged parallel to the top surface 3 along the optical axis. The lower surface 5 including the groove 4 and the side surface 6 formed on the side portion connecting the upper surface 3 and the lower surface 5 are formed. The side surface 6 is gradually centered on the optical axis as the distance from the light incident surface 2 increases in the optical axis direction. And has a long inclined surface 61 whose cross section orthogonal to the optical axis direction is linear. As shown in the figure, the curvature of the arc of the upper surface 3 is uniform in the optical axis direction of the light guide 1, or the distance between the upper surface 3 and the lower surface 5 is uniform in the optical axis direction of the light guide 1. It is configured. Further, for example, as shown in FIG. 9, the reflection groove 4 is configured in a prism shape including a concave portion and a convex portion whose cutting direction is orthogonal to the optical axis direction of the light guide 1. Further, the end 61 a of the inclined surface 61, which is a portion of the inclined surface 61 that runs in the direction opposite to the light incident surface 2 along the optical axis direction, is formed so that the end 61 a covers a part of the upper surface 3. The In the region of the upper surface 3 corresponding to the end 61a, most of the light does not reach the critical angle over the entire optical axis direction of the light guide 1, and no light is emitted outside the light guide 1.

  According to the light guide for a linear light source device of the present embodiment, the long inclined surface 61 is formed on the side surface 6 so as to gradually approach the center of the optical axis in the direction of the optical axis as the distance from the light incident surface 2 increases. As a result, the light incident on the light guide 1 can be reflected by the inclined surface 61. As a result, light having a large angle component with respect to the optical axis direction of the light guide 1 can be generated, and the spread angle of the light emitted from the upper surface 3 is almost uniform at any position in the optical axis direction. be able to. As a result, even if the reading position of an electronic light receiving element such as a CCD is slightly deviated in the direction perpendicular to the optical axis direction of the light guide 1, the influence of the change in illuminance distribution due to the deviation of the reading position is affected. The problem of affecting the amount of light received by the electron light receiving element can be solved.

FIG. 2 shows the short-axis irradiation in the case where the spread of light emitted from the light guide 1 is arbitrary light intensity on the vertical axis, the center of the light guide 1 is 0 on the horizontal axis, and the distance from the center is taken. It is a figure which shows distribution. Here, the part with distance 0 on the horizontal axis shows the irradiated object side, that is, the part where the light spread angle becomes 0 degree. Each measurement point is a distance when the side where the LED is disposed as the light source on the light incident surface 2 of the light guide 1 is 0 mm, and the light spread angle at the positions of 90 mm, 180 mm, and 270 mm, respectively. Is shown.
As shown in the figure, according to the light guide for the linear light source device of the present embodiment, the light measured at each position of 180 mm and 270 mm with respect to the curve of the spread angle of the light measured at the position of 90 mm. It can be seen that the divergence angle curve agrees well. That is, it can be seen that there is no difference in the spread angle of the light emitted from each position of the light guide 1 in the optical axis direction.

Next, a second embodiment of the present invention will be described with reference to FIGS.
FIG. 3 is a diagram illustrating a configuration of a light guide for a linear light source device according to the present embodiment.
As shown in the figure, the light guide 1 is also formed along a light incident surface 2 on which light from a light source such as an LED (not shown) is incident, and along the optical axis of the light guide 1, and orthogonal to the optical axis. The cross-sectional shape to be formed is an arc shape, and includes a top surface 3 including a light emitting surface that emits light, and a reflection composed of a concave portion and a convex portion that are arranged parallel to the top surface 3 along the optical axis. The lower surface 5 including the groove 4 and the side surface 6 formed on the side connecting the upper surface 3 and the lower surface 5 are formed. A plurality of, for example, five inclined surfaces 611 to 615, which are formed so as to be close to each other and whose cross-sectional shape orthogonal to the optical axis direction is linear, are formed. As shown in the figure, the curvature of the arc of the upper surface 3 is uniform in the optical axis direction of the light guide 1 as in the case of FIG. 1, or the distance between the upper surface 3 and the lower surface 5 is the light guide. 1 in the direction of the optical axis.

  Also in the light guide for the linear light source device of the present embodiment, a plurality of inclined surfaces 611 to 615 are formed on the side surface 6 so as to gradually approach the center of the optical axis in the optical axis direction as the distance from the light incident surface 2 increases. As a result, the light incident on the light guide 1 can be reflected by the inclined surfaces 611 to 615. As a result, light having a large angle component with respect to the optical axis direction of the light guide 1 can be generated, and the spread angle of the light emitted from the upper surface 3 is almost uniform at any position in the optical axis direction. be able to. As a result, even if the reading position of an electronic light receiving element such as a CCD is slightly deviated in the direction perpendicular to the optical axis direction of the light guide 1, the influence of the change in illuminance distribution due to the deviation of the reading position is affected. The problem of affecting the amount of light received by the electronic light receiving element can be solved.

FIG. 4 is a diagram showing a short-axis irradiation distribution in which the spread angle of light emitted from the light guide 1 is shown in the same manner as in FIG. As in FIG. 2, each measurement point is a distance when the side where the LED is disposed as the light source on the light incident surface 2 of the light guide 1 is 0 mm, and the positions are 90 mm, 180 mm, and 270 mm, respectively. The spread angle of light at.
As shown in the figure, also in the light guide for the linear light source device of this embodiment, the spread of light measured at each position of 180 mm and 270 mm with respect to the curve of the spread angle of light measured at the position of 90 mm. The corner curves are in good agreement, and it can be seen that there is no difference in the spread of light emitted from each position of the light guide 1 in the optical axis direction.

Next, third and fourth embodiments of the present invention will be described with reference to FIG.
FIG. 5A is a diagram illustrating a configuration of a light guide for a linear light source device according to the third embodiment. As illustrated in FIG. 5A, the linear light source device of the first and second embodiments. Compared to the light guide for the light source, the side surface 6 formed on the side connecting the upper surface 3 and the lower surface 5 is formed so as to gradually approach the center of the optical axis in the optical axis direction as the distance from the light incident surface 2 increases. A curved surface 62 having a curved cross-sectional shape perpendicular to the optical axis direction is formed.
Moreover, FIG.5 (b) is a figure which shows the structure of the light guide for linear light source devices which concerns on 4th Embodiment, As shown in the figure, the linear form of 1st-3rd embodiment is shown. Compared with the light guide for the light source device, the side surface 6 formed on one side connecting the upper surface 3 and the lower surface 5 is formed so as to gradually approach the center of the optical axis as the distance from the light incident surface 2 increases. An inclined surface 63 is formed.
Also in the light guides for the linear light source devices of the third and fourth embodiments, light having a large angular component with respect to the optical axis direction of the light guide 1 can be generated, and light emitted from the upper surface 3 can be generated. The divergence angle can be made substantially uniform at any position in the optical axis direction. As a result, even if the reading position of an electronic light receiving element such as a CCD is slightly deviated in the direction perpendicular to the optical axis direction of the light guide 1, the influence of the change in illuminance distribution due to the deviation of the reading position is affected. The problem of affecting the amount of light received by the electronic light receiving element can be solved.

For comparison with the light guide for linear light source device of the present invention, the light guide for linear light source device according to the prior art will be described with reference to FIGS.
FIG. 6 is a diagram showing a configuration of a light guide for a linear light source device according to the prior art. As shown in FIG. 6, this light guide 301 receives light from a light source such as an LED (not shown). A light incident surface 302 that is formed along the optical axis of the light guide 301, a cross-sectional shape that is orthogonal to the optical axis is formed in an arc shape, and includes an upper surface 303 that includes a light emitting surface that emits light, and an upper surface 303. A lower surface 305 including a reflection groove 304 composed of a concave portion and a convex portion facing the upper surface 303 and parallel to the optical axis, and a side surface 306 formed on a side portion connecting the upper surface 303 and the lower surface 305. Therefore, the side surface 306 is different in that the inclined surfaces 61, 611 to 615, 63 and the curved surface 62 which are shown in the light guide for the linear light source device of the first to fourth embodiments are not formed. To do.

FIG. 7 shows the short-axis irradiation in the case where the spread of light emitted from the light guide 301 is arbitrary light intensity on the vertical axis, the center of the light guide 301 is 0 on the horizontal axis, and the distance from the center is taken. It is a figure which shows distribution. Here, the part with distance 0 on the horizontal axis shows the irradiated object side, that is, the part where the light spread angle becomes 0 degree. Each measurement point is a distance when the side where the LED is disposed as a light source on the light incident surface 302 of the light guide 301 is 0 mm, and the spread of light at the positions of 90 mm, 180 mm, and 270 mm, respectively. Show.
As shown in the figure, according to the light guide for a linear light source device according to the prior art, the spread of light measured at each position of 180 mm and 270 mm with respect to the curve of the spread of light measured at a position of 90 mm. It can be seen that the curves are very different. That is, it can be seen that there is a large difference in the spread of light emitted from each position of the light guide 301 in the optical axis direction, and a large attenuation occurs in the illuminance in the optical axis direction. When such a light guide for a linear light source device according to the prior art and a light guide for a linear light source device according to the first to fourth embodiments of the present invention are compared, the present invention relates to a line according to the prior art. It can be seen that the light guide for the light source device has an effect that cannot be achieved.

DESCRIPTION OF SYMBOLS 1 Light guide 2 Light incident surface 3 Upper surface 4 including a light-projection surface 4 Reflecting groove 5 Lower surface 6 Side surface 61 Inclined surface 61a End part 611-615 of the inclined surface 61 Inclined surface 62 Curved surface 63 Inclined surface

Claims (3)

An upper surface formed along the optical axis of the light guide, the cross-sectional shape orthogonal to the optical axis is formed in an arc shape, and includes a light emitting surface that emits light,
A lower surface including a reflective surface composed of a concave portion and a convex portion disposed parallel to the upper surface along the optical axis and facing the upper surface;
A line formed on a side portion connecting the upper surface and the lower surface, and the side surface has an inclined surface that approaches the optical axis center as the distance from the light source increases in the optical axis direction. -Shaped light source for light source device.   The light guide for a linear light source device according to claim 1, wherein a plurality of the inclined surfaces are provided on the side surface along an optical axis direction of the light guide. 3. The light guide for a linear light source device according to claim 1, wherein the inclined surface has a linear shape in a cross section perpendicular to the optical axis direction of the light guide. 4.