JP2007221361A - Linear light source unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear light source unit capable of emitting emission light including uniform red, blue, green lights even around the light source unit. <P>SOLUTION: The linear light source unit provided with: a light source; and a light guide member 2 made of a type of transparent material, shaped thin and long, extended in the longitudinal direction, and including a light incidence face 2a for receiving light from the light source and a light emission face, is configured such that the light from the light source and made incident on the light incidence face 2a is emitted from the exit face while being traveled in the longitudinal direction, and is characterized in such that the light source includes a plurality of LEDs for emitting lights with different wavelengths and at least part of the light incidence face 2a is formed to be a roughened face 2d. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a linear light source device that is used, for example, in an image reading apparatus and emits linear light.

  The image reading apparatus is for converting the contents described on the original into an electrical signal as an image by irradiating the original with light and receiving the reflected light. In this image reading apparatus, a light source that emits linear light is often used. For example, such a linear light source device is also used in the image reading device described in Patent Document 1. FIG. 8 shows an example of a conventional linear light source device. The linear light source device X shown in the figure includes two light sources 91 and a light guide member 92. Each light source 91 is equipped with three LEDs 91B, 91G, and 91R for blue light, green light, and red light. FIG. 9 is a diagram showing the positional relationship between these three LEDs 91B, 91G, and 91R and the light incident surface of the light guide member. The light guide member 92 is made of translucent acrylic resin or the like, and has a shape extending in the left-right direction in FIG. The light guide member 92 has two light incident surfaces 92a, a reflecting surface 92b, and a light emitting surface 92c. The two light incident surfaces 92 a are located at both ends of the light guide 92 in the longitudinal direction. A light source 91 is disposed in front of each light incident surface 92a. Light from the light source 91 is introduced into the light guide member 92 from the light incident surface 92a. The reflection surface 92b is provided on the lower surface of the light guide member 92 in the drawing, and is a surface for reflecting light traveling in the longitudinal direction upward in the drawing in FIG. The light emitting surface 92c is a surface having an arcuate cross section extending in the longitudinal direction. The light reflected by the reflecting portion 92b is enhanced in directivity by the emission surface 92c to become linear light. This linear light is emitted upward in the drawing, and can illuminate a document to be read by the image reading apparatus.

  As shown in FIG. 9, in the light source 91, LED91R is arrange | positioned so that it may become a position away from the reflective surface 92b compared with two other LED91B and LED91G. In the present specification, for example, blue light emitted from the LEDs 91B, 91G, and 91R is represented as B, green light is represented as G, and red light is represented as R.

  In the prior art, in order to obtain uniform irradiation light from each LED 91B, 91G, 91R near the light source 91, each LED 91B according to the directivity characteristics of each LED 91B, 91G, 91R, the wavelength of B, G, R, etc. , 91G, 91R is tried to solve by adjusting the arrangement. However, since the wavelength of R is longer than the wavelengths of B and G, R has higher directivity than B and G. For this reason, it was difficult for R to reach the reflecting surface 92b unless it traveled a longer distance than B or G along the longitudinal direction. As a result, in the vicinity of the light source 91, R light is less likely to reach than B and G, and the amount of R light is smaller than B and G. Therefore, the length of the light emitting surface 92c in the longitudinal direction needs to be longer than the size of the reading target, which is a factor that hinders downsizing of the linear light source device X.

Japanese Patent Laid-Open No. 9-200439

  The present invention has been conceived under the circumstances described above, and it is an object of the present invention to provide a linear light source device capable of emitting red, blue and green light evenly in the vicinity of the light source.

  The linear light source device provided by the present invention is made of a light source and a translucent material, has an elongated shape, and has a light incident surface and a longitudinal direction for allowing light from the light source to enter. A light guide member having a light exit surface extending in a line, and a line configured to emit light from the light source incident on the light incident surface from the light exit surface while traveling in the longitudinal direction. The light source includes a plurality of LEDs that emit light having different wavelengths, and at least a part of the light incident surface is a rough surface.

  According to such a configuration, incident light that passes through the rough surface and enters the light guide member is scattered by the rough surface. For this reason, the directivity of the incident light is greatly reduced. Usually, in such a light guide member, a reflective surface is provided on the side opposite to the light emitting surface, and a part of the light hitting the reflecting surface travels toward the light emitting surface, and illumination The light is emitted as light. That is, the directivity of the incident light is reduced by the rough surface, so that the proportion of the light that reaches the reflecting surface in the vicinity of the incident surface of the incident light increases. As the amount of light reaching the reflecting surface increases, the amount of light emitted from the light emitting surface also increases. Therefore, the emission intensity in the vicinity of the light incident surface can be increased.

  In a preferred embodiment of the present invention, the light incident surface is provided at one end in the longitudinal direction of the light guide member and is orthogonal to the longitudinal direction. Further, the plurality of LEDs are arranged in series along the emission direction of the light emission surface, and a portion of the light incident surface opposite to the light emission surface is the rough surface. According to such a configuration, since the rough surface is formed in a portion of the light emitting surface close to the reflecting surface, the light emitting surface preferably acts on a light source facing a position away from the light emitting surface.

  Further, in a preferred embodiment of the present invention, the plurality of LEDs include a blue light LED, a green light LED, and a red light LED, and the three LEDs are on the light emitting surface side. To LED for blue light, LED for green light, and LED for red light. According to such a configuration, the LED for red light having relatively high directivity can be brought close to the rough surface. More preferably, at least a portion of the light incident surface that directly faces the red light LED is the rough surface. The portion facing the green light LED may be further roughened. According to such a configuration, light having strong directivity can be suitably diffused by passing through the rough surface, and the directivity can be reduced.

  Furthermore, in a preferred embodiment of the present invention, the surface of the light guide member opposite to the light exit surface is a rough surface near the light incident surface. According to such a configuration, the light diffused on the light incident surface is irregularly reflected by the newly provided rough surface. In the case of reflection by a smooth surface, the reflected light retains a component that travels in the longitudinal direction and is unlikely to travel near the light incident surface. However, if it is irregular reflection, the amount of light traveling toward the light exit surface in the vicinity of the light incident surface can be relatively increased. Further, the light guide member is often used while being covered with a reflecting member, but the newly provided rough surface also has a function of alleviating reflection by the reflecting member.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

  Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the drawings.

  FIG. 1 shows a cross-sectional view along the longitudinal direction of an image reading apparatus B provided with an example of a linear light source device according to the present invention. 2 is a cross-sectional view taken along the line II-II in FIG. As shown in FIGS. 1 and 2, the image reading device B includes a linear light source device A, a case 4, a substrate 5, a rubber connector 6, a glass cover 7, a light receiving element 8, and a lens array 9. Configured. The image reading device B is a device that reads a document on a reading line extending along the longitudinal direction of the image reading device B. A linear light source apparatus A according to the present invention is an apparatus for illuminating the reading line, which includes a light source 1, a light guide member 2, and a reflecting member 3.

  In FIG. 4, the top view which made the surface in which LED of the light source 1 was installed the front was shown. FIG. 5 shows a view of the light source 1 as seen from the back surface of FIG. The light source 1 includes three LEDs 1B, 1G, and 1R for blue light, green light, and red light, and a terminal group 1a. The light source 1 is arranged so that the light emitting surfaces of the LEDs 1B, 1G, and 1R face one side surface of the light guide member 2. As shown in FIG. 4, the LEDs 1B, 1G, and 1R are installed on a straight line along the lower left direction in the figure in the order of the LEDs 1B, 1G, and 1R from the upper side. The terminal group 1a is for conducting with a wiring pattern installed on the substrate 5 through the rubber connector 6.

  The light guide member 2 is formed of, for example, an acrylic transparent resin such as PMMA, and has an elongated shape having a certain dimension in the longitudinal direction of the image reading apparatus B. As shown in FIGS. 1 and 2, the light guide member 2 includes a light incident surface 2a, a reflective surface 2b, and a light emitting surface 2c. FIG. 3 is a perspective view of the vicinity of the light incident surface 2 a of the light guide member 2.

  The light incident surface 2a is a portion disposed opposite to the light emitting surface of the light source 1, and is formed at one end along the longitudinal direction of the light guide member 2, as shown in FIG. As shown in FIG. 3, a rough surface 2d is formed on the side of the light incident surface 2a in contact with the reflecting surface 2b by, for example, shaving with a file. The region where the rough surface 2d is formed is shown in FIG. 3 and FIG. 5 as a hatched portion by a solid line or a broken line. According to FIG. 5, the rough surface 2d is formed in a region facing the LEDs 1G and 1R, and is not formed in a region facing the LED 1B. In the present embodiment, the rough surface 2d has a surface roughness equivalent to Ayamadai Co., Ltd .: grain pattern type AH0-949s or AH0-1003s.

  The reflection surface 2b extends along the longitudinal direction of the light guide member 2, and is formed in a mirror shape so that light traveling from the inside of the light guide member 2 to the reflection surface 2b is folded back into the light guide member 2. Further, it is one side surface of the light guide member 2. On the reflecting surface 2b, irregularities such as grooves are formed at regular intervals along the longitudinal direction of the light guide member 2, and when reflecting light, a part thereof is irregularly reflected. In addition, as shown in FIG. 3, a rough surface 2e is formed in the vicinity of the light incident surface 2a of the reflecting surface 2b by, for example, shaving with a file. A region on the reflection surface 2b to which the rough surface 2e is applied is indicated by a hatched portion in FIG. In this rough surface 2e, irregular reflection is more likely to occur than in other regions of the reflective surface 2b where the uneven portions are formed.

  The light exit surface 2c extends along the longitudinal direction of the light guide member 2, and guides a part of the light traveling from the inside of the light guide member 2 to the light exit surface 2c toward the reading line. It is one side of the optical member 2. The light exit surface 2c is formed in an arc shape in cross section and functions as a lens in order to focus light onto the reading line. As shown in FIG. 2, the light emitting surface 2c is a side surface opposite to the reflecting surface 2b.

  The reflection member 3 is made of, for example, a white synthetic resin, and is housed in the case 4 and serves as a holder for the light guide member 2 as shown in FIG. The reflecting member 3 is provided to return light leaking from the light guide member 2 into the light guide member 2. For this reason, the light guide member 2 is formed so as to cover substantially the entire surface excluding the light incident surface 2a and the light emitting surface 2c.

  The case 4 is made of, for example, a synthetic resin and is formed in a long box shape along the longitudinal direction. The case 4 has an opening on the substantially entire upper surface portion in FIG. 1 and an opening on the bottom surface portion. The main part of the image reading apparatus B is accommodated in the case 4.

  The substrate 5 is made of, for example, epoxy resin or ceramic, is fitted into the bottom of the case 4, and has the light receiving element 8 mounted thereon. Although not shown, a wiring pattern for mounting the light receiving element 8 or supplying power to the light source 1 is formed on the substrate 5. A connector terminal for connecting the wiring pattern and an external control device is also mounted.

  A plurality of light receiving elements 8 are arranged on the substrate 5 in a row extending in the longitudinal direction of the image reading apparatus B. The light receiving element 8 photoelectrically converts the received light and outputs it as an electrical signal through the wiring pattern.

  The rubber connector 6 is, for example, a rubber case for conducting the wiring pattern and the terminal group 1a of the light source 1 and incorporating a conducting member therein. The rubber connector 6 is used by being press-fitted between the light source 1 and the substrate 5.

  The glass cover 7 is made of transparent glass, and is formed so as to fit into the opening of the upper surface portion of the case 4 in FIG. A reading document can be placed on the glass cover 7.

  The lens array 9 is for focusing the light reflected by the original on the reading line onto the light receiving element 8. As the lens array 9, for example, a large number of lenses capable of focusing an original image at an erecting equal magnification are arranged in the longitudinal direction.

  The image reading device B is a device that reads a document fed using, for example, a pressure roller on a reading line along the longitudinal direction, and outputs it as an electrical signal. That is, first, light emitted from the light source 1 is introduced into the light guide member 2 from the light incident surface 2a. The light introduced from the light incident surface 2a travels radially inside the light guide member 2 around the light traveling along the longitudinal direction. Among these lights, part of the light irregularly reflected on the reflecting surface 2b reaches the light emitting surface 2c directly, and part of the light reaches the light emitting surface 2c through reflection on the other side surface. A part of the light reaching the light emitting surface 2c is emitted as linear light toward the reading line due to the lens effect of the light emitting surface 2c. The linear light can illuminate the entire length of the reading line. The light reflected by the original sent on the reading line is focused on the light receiving element 8 by the lens array 9. By outputting an electrical signal according to the amount of light sensed by the light receiving element 8, the image reading apparatus B can read the document as an electrical signal. Further, the electrical signal can be output through a wiring pattern formed on the substrate 5.

  In order for the image reading apparatus B to appropriately read a color original, each of B, G, and R that illuminates the original needs to be substantially uniform over the entire length of the reading line. That is, the light guide member 2 needs to be configured so that the light from the three LEDs 1B, 1G, and 1R is uniform over almost the entire length of the reading line.

  Hereinafter, effects of the linear light source device X incorporated in the image reading device B will be described.

  In general, light having a longer wavelength has a lower refractive index, and is therefore relatively difficult to diffuse and has higher directivity. For this reason, the arrangement of the LEDs in the light source 1 is LEDs 1R, 1G, and 1B in order from the closest to the reflecting surface 2b. That is, since light with a longer wavelength is less likely to reach the reflecting surface 2b that is parallel to the main light traveling direction, the LED that emits light with a longer wavelength is disposed closer to the reflecting surface 2b.

  Further, since the rough surface 2d is formed in the region of the light incident surface 2a facing the LEDs 1R and 1G, the light emitted from the LEDs 1R and 1G is diffused by the rough surface 2d when entering the light guide member 2. The Due to the diffusion by the rough surface 2d, the proportion of light reaching the reflecting surface 2b in the vicinity of the light incident surface 2a in the light emitted from the LEDs 1R and 1G increases. In addition, a rough surface 2e is formed on the reflecting surface 2b in the vicinity of the light incident surface 2a. On the rough surface 2e, the light traveling from the light guide member 2 is irregularly reflected. As a result, part of the light emitted from the LEDs 1R and 1G and traveling to the rough surface 2e reaches the light emitting surface 2c immediately adjacent to the light incident surface 2a by irregular reflection. That is, for example, in normal reflection by the reflecting member 3 or the like, light tends to travel in the right direction in the drawing in FIG. 3, but in irregular reflection, light having a component in the left direction in the drawing in FIG. 3 is also generated. Since B originally tends to diffuse, a part thereof reaches the rough surface 2e without passing through the rough surface 2d, and can reach the light emitting surface 2c immediately adjacent to the light incident surface 2a.

  As described above, the light guide member 2 is configured such that any of B, G, and R can reach the light exit surface 2c immediately adjacent to the light incident surface 2a. Therefore, the light emitting surface 2c of the light guide member 2 can emit light uniformly over almost the entire length in the longitudinal direction of B, G, and R.

  6 and 7 show the relationship between the longitudinal position on the light exit surface 2c and the exit luminance. FIG. 6 shows the results when a light guide member that does not have the rough surface 2d and the rough surface 2e is used. FIG. 7 shows the result when the light guide member 2 having the rough surface 2d and the rough surface 2e is used. The rough surface 2d and the rough surface 2e are rough surfaces having a surface roughness equivalent to Ayamadai Co., Ltd .: grain pattern type AH0-949s or AH0-1003s. In FIGS. 6 and 7, the position in the longitudinal direction represents each position on the light emitting surface by the number of dots from the light incident surface side.

  Comparing FIG. 6 and FIG. 7, in the case of FIG. 7, the emission luminance of R is increased in the vicinity of 0 dots compared to the case of FIG. That is, it can be seen that by forming the rough surface 2d and the rough surface 2e, a wider area of the light emitting surface 2c can provide uniform illumination light. This makes it possible to reduce the size of the light guide member 2 and, accordingly, to reduce the size of the image reading apparatus.

  The linear light source device according to the present invention is not limited to the above-described embodiment. The specific configuration of each part of the linear light source device according to the present invention can be varied in design in various ways. For example, various forms are possible, such as forming the rough surface 2d only in a region facing R, or not forming the rough surface 2e.

It is sectional drawing in alignment with the longitudinal direction of the image reading apparatus provided with an example of the linear light source device which concerns on this invention. It is sectional drawing which follows the II-II line of FIG. It is a principal part perspective view of the light guide member in an example of the linear light source device which concerns on this invention. It is a schematic plan view of the light source in an example of the linear light source device according to the present invention. It is a figure which shows the positional relationship of the light source and light guide member in an example of the linear light source device which concerns on this invention. It is the figure which showed the relationship between the longitudinal direction position and emitted luminance in the linear light source device of a comparative example. It is the figure which showed the relationship between a longitudinal direction position and emitted luminance in the linear light source device shown in FIG. It is a figure which shows the positional relationship of the light source and light guide member in the conventional linear light source device. It is a figure which shows the positional relationship of three LED in the conventional linear light source device, and the light-incidence surface of a light guide member.

Explanation of symbols

A Linear light source device B Image reading device 1B Blue LED
1G Green LED
1R LED for red
DESCRIPTION OF SYMBOLS 1 Light source 1a Terminal 2 Light guide member 2a Light incident surface 2b Reflective surface 2c Light output surface 2d, 2e Rough surface 3 Reflective member 4 Case 5 Substrate 6 Rubber connector 7 Glass cover 8 Light receiving element 9 Lens array

Claims (6)

A light source;
A light guide member made of a light-transmitting material, having an elongated shape, and having a light incident surface for allowing light from the light source to enter and a light emitting surface extending along the longitudinal direction. And
A linear light source device configured to emit light from the light exit surface while proceeding in the longitudinal direction with light from the light source incident on the light incident surface,
The light source includes a plurality of LEDs that emit light having different wavelengths.
The linear light source device according to claim 1, wherein at least a part of the light incident surface is a rough surface. The light incident surface is provided at one end in the longitudinal direction of the light guide member, and is orthogonal to the longitudinal direction,
The plurality of LEDs are arranged in series along the emission direction of the light exit surface,
The linear light source device according to claim 1, wherein a portion of the light incident surface opposite to the light emitting surface is the rough surface. The plurality of LEDs include a blue light LED, a green light LED, and a red light LED,
The linear light source device according to claim 2, wherein the three LEDs are arranged in the order of the blue light LED, the green light LED, and the red light LED from the light emitting surface side.   The linear light source device according to claim 3, wherein at least a portion of the light incident surface facing the red light LED is the rough surface.   The linear light source device according to claim 4, wherein a portion of the light incident surface that faces the green light LED is further roughened.   6. The linear light source device according to claim 2, wherein a portion of the light guide member opposite to the light emitting surface is a rough surface near the light incident surface.

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