JP2010011249A - Light guide and image sensor module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide easily manufacturable while uniformizing light quantity of each portion of linear light emitted from a light emitting surface, and an image sensor module having the light guide. <P>SOLUTION: The light guide 4 is elongated linearly as a whole, is formed into almost cylindrical shape and includes: a light incident surface 4A provided at an end portion in the main scanning direction x; a light reflecting surface 4B extending in the main scanning direction x to reflect light entering from the light entering surface 4A in an opposing direction z'; and a light emitting surface 4C for emitting light advancing from the light reflecting surface 4B as linear light extending in the main scanning direction x, wherein the light reflecting surface 4B is formed on a bottom portion of a recessed part 41 formed extending in the main scanning direction x. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light guide used for, for example, a flatbed scanner and an image sensor module.

  FIG. 6 shows an example of a conventional light guide and an image sensor module using the same (see, for example, Patent Document 1). The image sensor module X shown in the figure includes a substrate 91, a light source module 92, a plurality of sensor IC chips 93, a light guide 94, and a case 95. The substrate 91 is an insulating substrate, and a plurality of sensor IC chips 93 are arranged in the main scanning direction x. The light source module 92 includes an LED chip 92a that emits red light, green light, and blue light.

  The light guide 94 has a rod shape extending in the main scanning direction x, and is made of, for example, a transparent acrylic resin. The light guide 94 is formed with a light incident surface 94a, a light reflecting surface 94b, and a light emitting surface 94c. Light emitted from the light source module 92 is incident from the light incident surface 94a. The light reflecting surface 94b has a configuration in which a plurality of tapered grooves each extending in a direction perpendicular to the main scanning direction x are arranged at a predetermined pitch in the main scanning direction x. The light traveling in the light guide 94 is reflected toward the light exit surface 94c by these grooves of the light reflection surface 94b. Linear light extending in the main scanning direction x is emitted from the light emitting surface 94c. By irradiating the reading object with the linear light, the reflected light is received by the sensor IC chip 93. Thereby, the content described in the reading object can be taken in as electronic data.

  In the image sensor module X configured as described above, the light that has reached the groove of the light reflecting surface 94b is reflected by the tapered surface of the groove and travels in a substantially constant direction. If it does so, about the linear light radiate | emitted from the light-projection surface 94c, the peak of a some light quantity will arise with a groove pitch equivalent. In such a case, the illuminance of the entire length of the reading target in the main scanning direction x varies greatly, and the quality of an image obtained by reading the reading target is deteriorated. On the other hand, it is conceivable to make the amount of light of the linear light emitted by narrowing the groove pitch uniform. However, the light guide 94 is generally formed by injection molding. In order to narrow the groove pitch, high dimensional accuracy is required in the molding die. This makes it difficult to manufacture the mold, and in turn, makes it difficult to manufacture the light guide.

JP-A-9-275469

  The present invention has been conceived under the above-described circumstances, and is a light guide that can be easily manufactured while making the amount of light of the linear light emitted from the light exit surface uniform. It is an object to provide a body and an image sensor module including the light guide.

  The light guide provided by the first aspect of the present invention extends linearly as a whole and is formed in a substantially cylindrical shape. A light reflecting surface that extends and reflects light incident from the light incident surface toward the opposite emitting direction, and light emission that emits light traveling from the light reflecting surface as linear light extending in the longitudinal direction The light reflecting surface is provided at the bottom of a recess formed to extend in the longitudinal direction.

  According to such a structure, since the said light reflection surface is provided in the bottom part of the said recessed part, the boundary of the said light reflection surface and an other than that part can be prescribed | regulated correctly. Therefore, by providing the light reflecting surface with a uniform light scattering / reflecting function, it is possible to make uniform the amount of light in each part of the linear light emitted from the light emitting surface. In addition, since the light reflecting surface is formed so as to bite into the light guide, it is possible to reduce light that leaks to the outside of the light guide and to increase the amount of the linear light as a whole. ing.

  In a preferred embodiment of the present invention, the light reflecting surface is painted. The coating color is preferably white, for example. According to such a configuration, for example, a uniform light scattering / reflecting function can be easily imparted to the light reflecting surface by pouring paint into the recess.

  In a preferred embodiment of the present invention, the light reflecting surface is formed as a fine rough surface. According to such a configuration, a uniform light scattering reflection function can be imparted to the light reflecting surface.

  In a preferred embodiment of the present invention, the recess has a region where the width continuously expands as the distance from the light incident surface increases in the longitudinal direction. According to such a configuration, the amount of light reaching the light incident surface decreases as the distance from the light incident surface decreases, while the amount of light reflected by the light reflecting surface can increase as the distance from the light incident surface decreases. . For this reason, the said light guide can aim at equalization of the light quantity of the various places of the linear light emitted from the said light-projection surface.

  The image sensor module provided by the second aspect of the present invention accommodates the light guide provided by the first aspect of the present invention, the light source module facing the light incident surface, and the light guide. A case and a light receiving sensor arranged along the longitudinal direction and receiving linear light reflected by a reading object are provided. According to such a configuration, the content of the reading object can be read with a uniform color tone.

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

  1 and 2 show an example of an image sensor module according to the present invention, and FIGS. 3 to 5 show an example of a light guide according to the present invention. The image sensor module A of this embodiment includes a substrate 1, a light source module 2, a plurality of sensor IC chips 3, a light guide 4, a lens array 5, and a case 6. As shown in FIG. 2, for example, the image sensor module A reads the description content of the document Dc as image data while being relatively moved in the sub-scanning direction y with respect to the document Dc placed on the document table St. It is configured as.

  As shown in FIGS. 1 and 2, the substrate 1 is made of ceramic such as alumina or aluminum nitride, and has a long rectangular shape with the main scanning direction x as the long side direction and the sub-scanning direction y as the short side direction. Yes. The substrate 1 is attached to the lower end of the case 6 and is positioned with respect to the case 6. A plurality of sensor IC chips 3 are mounted on the substrate 1.

  The light source module 2 includes a light source substrate 20, a plurality of terminals 21, three LED chips 22, and a case 23. The light source substrate 20 has a rectangular shape, and is made of, for example, ceramic. Alternatively, the light source substrate 20 is made of a composite material of a reinforcing member and a polyimide resin, or a glass epoxy resin. The plurality of terminals 21 are for connecting the light source module 2 to the substrate 1. Each terminal 21 has a clip shape at one end. Each terminal 21 is attached to the light source substrate 20 by this clip-shaped portion. The three LED chips 22 emit red light, green light, and blue light, for example, and are mounted in series on the light source substrate 20. The case 23 is made of white resin, for example, and surrounds the three LED chips 22.

  The plurality of sensor IC chips 3 are semiconductor chips each having a rectangular shape in plan view, each having a light receiving portion (not shown), and is an example of a light receiving sensor referred to in the present invention. The plurality of sensor IC chips 3 are mounted on the substrate 1 along the main scanning direction x, and are arranged immediately below the lens array 5 as shown in FIG. The sensor IC chip 3 has a photoelectric conversion function and is configured to output an image signal having an output level corresponding to the amount of received light.

  As shown in FIGS. 3 to 5, the light guide 4 is a highly transparent member made of an acrylic resin such as PMMA (polymethyl methacrylate), and has a substantially cylindrical shape having a substantially circular cross section over its entire length. Has been. The light guide 4 is formed by, for example, injection molding using a mold, and has a light incident surface 4A, a light reflecting surface 4B, and a light emitting surface 4C. The light incident surface 4A is a surface for introducing light from the light source module 2 into the light guide 4 as shown in FIG. 1, and is constituted by one end surface of the light guide 4 in the main scanning direction x. . The light incident surface 4A has a mirror finish in order to prevent light from the light source module 2 from being scattered. In this embodiment, the light incident surface 4A has a gentle convex shape as shown in FIGS. ing. In the present embodiment, the light guide 4 has a total length of about 230 mm and a diameter of about 4 mm.

  The light reflecting surface 4B directs the light traveling along the main scanning direction x from the light incident surface 4A toward the light emitting surface 4C provided to face the light reflecting surface 4B in the direction z ′ (emitting direction). It is a surface for reflecting along. As shown in FIGS. 3 to 5, the light reflecting surface 4 </ b> B is provided at the bottom of the recess 41. The recess 41 has a strip shape with a substantially rectangular cross section extending in the main scanning direction x. In this embodiment, the bottom part of the recessed part 41 is made into flat form, and the light reflection surface 4B which has a light-scattering function is formed by giving the white coating 42 to this bottom part part. The white paint 42 is formed, for example, by application using a dispenser. The white coating 42 can also be formed by a method using an ink jet or a method of pouring paint.

  In the present embodiment, the concave portion 41 is formed such that its width dimension (dimension in the direction y ′) continuously spreads uniformly as the distance from the light incident surface 4A increases. The width dimension of the recess 41 is, for example, 0.2 to 0.85 mm. In the present embodiment, the recess 41 has a depth of about 0.2 to 0.5 mm. In FIG. 5, an example of a path of light reflected by the light reflecting surface 4 </ b> B provided at the bottom of the concave portion 41 is indicated by a virtual line.

  The light exit surface 4C is a surface that emits light toward the document Dc, and extends in the main scanning direction x. From the light emitting surface 4C, linear light extending in the main scanning direction x and traveling along the z ′ direction is emitted.

  The lens array 5 is for focusing the light reflected by the document Dc on the plurality of sensor IC chips 3 at the same erect magnification. The lens array 5 includes a block-shaped holder extending in the main scanning direction x and a plurality of lenses arranged along the main scanning direction x. These lenses extend in a direction z whose optical axis is perpendicular to both the main scanning direction x and the sub-scanning direction y.

  The case 6 is made of synthetic resin and has a substantially block shape extending in the main scanning direction x. The case 6 accommodates the substrate 1, the light source module 2, the plurality of sensor IC chips 3, the light guide 4, and the lens array 5.

  Next, the operation of the light guide 4 having the above configuration and the image sensor module A including the light guide 4 will be described.

  According to this embodiment, the light emitted from the light source module 2 and traveling through the light guide 4 is reflected by the light reflecting surface 4B and emitted from the light emitting surface 4C. The light reflecting surface 4B to which the white coating 42 is applied has a uniform light scattering reflection function along the main scanning direction x, and linear light emitted from the light emitting surface 4C is in the main scanning direction x. The amount of light in each place is almost uniform over the entire length range. Therefore, it is possible to read the description content of the document Dc as image data having a uniform color tone.

  Moreover, in this embodiment, since the light reflection surface 4B is provided in the bottom part of the recessed part 41, the boundary of the light reflection surface 4B and another part can be prescribed | regulated correctly. For this reason, even in the light guide 4 having a substantially circular cross section, the boundary between the light reflecting surface 4B and other portions can be accurately defined. This is suitable for making the amount of light of the linear light emitted from the light emitting surface 4C uniform.

  Furthermore, as shown in FIG. 5, since the light reflecting surface 4B is formed so as to bite into the light guide 4, the light irregularly reflected by the light reflecting surface 4B hardly leaks to the outside of the light guide 4. Further, the light leaking from the light guide 4 travels along the z ′ direction. For this reason, the light guide 4 can emit brighter linear light because of less wasted light. Therefore, the image sensor module A including the light guide 4 can preferably read the description content of the document Dc with brighter linear light.

  The amount of light that enters from the light incident surface 4A and reaches each place in the light guide 4 tends to decrease as the distance from the light incident surface 4A increases. On the other hand, in the present embodiment, the width of the light reflecting surface 4B increases as the distance from the light incident surface 4A increases as described above. For this reason, the light guide 4 can preferably achieve a uniform amount of light at various locations of the linear light emitted from the light emitting surface 4C.

  In the present embodiment, the light reflecting surface 4B can be formed relatively easily by pouring the white paint into the recess 41.

  The light guide and the image sensor module according to the present invention are not limited to the above-described embodiments. The specific structure of each part of the light guide and the image sensor module according to the present invention can be varied in design in various ways.

  In the above embodiment, the width of the recess 41 is formed so as to be continuously and uniformly widened. However, a part of the recess 41 may have a constant width region. For example, considering that the amount of light reaching the light incident surface 4A is sufficiently large, the end portion of the recess 41 closer to the light incident surface 4A may be a narrow constant width region. Further, in consideration of the light that travels in the main scanning direction x and reaches the end surface, and is reflected and returned from the end surface, the end portion farther from the light incident surface 4A in the concave portion 41 has a wide constant width region. It is good.

  Moreover, it is good also as a structure where the recessed part 41 in which the light reflection surface 4B is provided changes a width | variety in steps as it distances from the light-incidence surface 4A. Moreover, it may replace with the structure in which the recessed part 41 was provided in series in the longitudinal direction of the light guide 4, and you may provide several recessed part so that it may isolate | separate in the said longitudinal direction.

  Moreover, in the said embodiment, although the white coating 42 is used for the light reflection surface 4B, the color of coating can be set freely and the light guide 4 radiate | emits the linear light according to the color of coating. It is possible.

  Moreover, in the said embodiment, although the white coating 42 is given to the recessed part 41, by making the part corresponding to the bottom face of the recessed part 41 in the metal mold | die which forms the light guide 4 into a fine rough surface, the recessed part 41 is provided. You may form a bottom face in a fine rough surface.

It is principal part sectional drawing which shows an example of the image sensor module which concerns on this invention. It is sectional drawing which follows the II-II line | wire of FIG. It is principal part sectional drawing which shows an example of the light guide which concerns on this invention. It is a principal part bottom view which shows an example of the light guide which concerns on this invention. It is sectional drawing which follows the VV line of FIG. It is principal part sectional drawing which shows an example of the conventional image sensor module.

Explanation of symbols

A Image sensor module Dc Document (reading object)
St Document placement table x Main scanning direction (longitudinal direction)
y Sub-scanning direction y 'direction z direction z' direction (outgoing direction)
1 Substrate 2 Light source module 3 Sensor IC chip (light receiving sensor)
4 Light guide 5 Lens array 6 Case 20 Light source substrate 21 Terminal 22 LED chip 41 Recess 42 White coating 4A Light incident surface 4B Light reflecting surface 4C Light emitting surface

Claims (6)

It extends in a straight line as a whole and is formed in a substantially cylindrical shape.
A light incident surface provided at an end in the longitudinal direction, a light reflecting surface that extends in the longitudinal direction and reflects light incident from the light incident surface toward an opposite emitting direction, and travels from the light reflecting surface A light emitting surface that emits the emitted light as linear light extending in the longitudinal direction,
The light guide, wherein the light reflecting surface is provided at a bottom of a recess formed to extend in the longitudinal direction.   The light guide according to claim 1, wherein the light reflecting surface is coated.   The light guide according to claim 2, wherein the coating is white.   The light guide according to claim 1, wherein the light reflecting surface is formed on a fine rough surface.   5. The light guide according to claim 1, wherein the recess has a region whose width continuously expands as the distance from the light incident surface increases in the longitudinal direction.   A light guide according to any one of claims 1 to 5, a light source module facing the light incident surface, a case accommodating the light guide, arranged along the longitudinal direction, and depending on a reading object An image sensor module, comprising: a light receiving sensor that receives the reflected linear light.

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