JP6183237B2 - Linear light source device for reading device - Google Patents

Description

  The present invention relates to a linear light source device for a document reading device used in devices such as a facsimile, a copying machine, and a scanner.

  Conventionally, for example, devices such as facsimiles, copiers, and scanners are equipped with a document reading device that includes a light source device that illuminates the document surface and reads character information and image information on the document surface by reflected light from the document surface. Has been.

  As a light source device for an original reading device, for example, an LED light source provided with an LED element is disposed at least one end of a rod-shaped light guide made of a translucent resin or the like, and light emitted from the LED light source A structure in which the light is propagated in the longitudinal direction of the light guide to irradiate the document surface is becoming mainstream. This is because, in such a so-called “side light type” linear light source device, a high-illuminance illumination region having a large width in the sub-scanning direction can be formed. Here, the “sub-scanning direction” refers to a moving direction when the light source device is moved relatively in a direction parallel to the document placement surface and perpendicular to the longitudinal direction of the light guide. For example, Patent Document 1 discloses a linear light source device in which LED light sources are disposed at both ends of a rod-shaped light guide.

  In the image reading unit, a light receiving element (for example, a CCD element) that receives the reflected light from the document surface is disposed at a central position in the longitudinal direction of the light guide so as to form a reduction optical system via a lens. According to the cosine fourth law, the lens has a characteristic that the light amount at the center in the main scanning direction (longitudinal direction of the light guide) is bright, but the light amount at the end is dark. In order to compensate for such lens characteristics, it is desirable to increase the amount of light at the end in the main scanning direction so that the light amount distribution on the light receiving element becomes uniform. Therefore, it is desirable that the light distribution in the main scanning direction (longitudinal direction of the light guide) of the linear light source device is such that the illuminance at both ends is higher than the illuminance at the center.

JP 2011-151440 A

In the linear light source device described above, the light distribution in the longitudinal direction of the light guide is obtained by combining light from one LED light source and light from the other LED light source. For this reason, when the brightness of the light from the LED light source is equal and has the same performance, the light distribution in the longitudinal direction of the light guide becomes a distribution that is symmetric with respect to the central position in the longitudinal direction. It is common to design as follows.
However, since there is a variation (individual difference) in the LED elements, when there is a difference in brightness (light quantity) between one LED element and the other LED element, the balance of the light distribution is broken, The light quantity ratio with respect to the center part of an edge part will deviate from the predetermined range. In addition, the lifetime characteristics of the LED elements are not uniform, and the amount of light varies as the lighting time elapses. This also breaks the balance of the light distribution. When the light distribution distribution changes as described above, there arises a problem that, for example, the illuminance of light with respect to the document surface is partially insufficient or the color balance is insufficient.

  The present invention has been made on the basis of the circumstances as described above, and even when there are individual differences in the light emitting elements themselves or when the light emitting state of the light emitting elements changes over time, An object of the present invention is to provide a linear light source device for a reading device capable of obtaining a light distribution characteristic.

The linear light source device for a reading device according to the present invention includes a rod-shaped light guide having a reflection portion and an emission portion that are opposed to each other along the longitudinal direction, and both end surfaces in the longitudinal direction of the light guide. The first light-emitting element and the second light-emitting element disposed opposite to each other, and the reflective portion of the light guide is adjacent to the concave-convex groove by forming a plurality of concave-convex grooves on the outer peripheral surface. In a linear light source device for a reading device constituted by a plurality of prism elements formed therebetween,
The individual prism elements constituting the reflection portion are formed so that a state satisfying the following conditions (A) and (B) is obtained.

Condition (A): The light distribution distribution curve in the longitudinal direction obtained when only one of the first light emitting element and the second light emitting element is lit has illuminance peaks at both ends.
Condition (B): In the light distribution curve in the longitudinal direction obtained when the first light-emitting element and the second light-emitting element are turned on under the condition that the light flux ratio is 1: 1, The longitudinal positions of the two illuminance peaks at both ends are xp and xp ′, the illuminance at the central position in the longitudinal direction is 100%, the illuminance at the position xp of the one illuminance peak is (100 + Axp)%, and the other When the illuminance at the illuminance peak position xp ′ is (100 + Axp ′)%, the light distribution in the longitudinal direction obtained when only one of the first light-emitting element and the second light-emitting element is turned on. The illuminance at the position xp of the one illuminance peak in the curve is in the range of (100-2 × Axp)% or more and (100 + 4 × Axp)% or less, and the illuminance at the position xp ′ of the other illuminance peak is (100-2 × Axp ')% or more, (100 + 4 × Axp' be a)% within the following range.

  In the linear light source device for a reading device according to the present invention, the one of the first light emitting element and the second light emitting element in the longitudinal light distribution distribution curve obtained when only one of the first light emitting element and the second light emitting element is turned on. The illuminance at the illuminance peak position xp is in the range of (100−Axp)% or more and (100 + 3 × Axp)% or less, and the illuminance at the other illuminance peak position xp ′ is (100−Axp ′)% or more. , (100 + 3 × Axp ′)% or less is preferable under the condition that the individual prism elements constituting the reflecting portion are formed under the condition that the state is within the range.

  Furthermore, in the linear light source device for reading device of the present invention, the inclination angle α with respect to the longitudinal direction of one optical plane facing the light emitting element on the proximal side in each prism element is the light emitting element on the distal side. Is preferably larger than the inclination angle β with respect to the longitudinal direction of the other optical plane.

Furthermore, in the linear light source device for a reading device according to the present invention, the pitch of the prism elements constituting the reflection portion can be increased as it goes toward the center in the longitudinal direction.
Moreover, it can be set as the structure where the depth of the said uneven groove becomes small as it goes to the longitudinal direction center side.
Furthermore, the prism element constituting the reflection part includes a light absorption prism element in which the surface of one optical plane facing the light emitting element on the proximal side functions as a light absorption surface, and the arrangement of the light absorption prism element It can be set as the structure which becomes low as a density goes to a longitudinal direction center side.

  According to the linear light source device for a reading device of the present invention, there are individual differences in the brightness (light quantity) of the LED elements, or variations in the brightness (light quantity) of the LED elements over time. In addition, since the degree of peak fluctuation of the illuminance at both ends in the longitudinal direction of the light guide can be suppressed, the desired light distribution characteristic can be obtained with certainty.

It is sectional drawing which shows the outline of a structure in an example of the linear light source device for readers which concerns on the 1st Embodiment of this invention. It is sectional drawing perpendicular | vertical to the longitudinal direction of a light guide of the linear light source device for readers shown in FIG. It is an expanded sectional view which shows roughly the structure of the reflection part in the light guide of the linear light source device for readers shown in FIG. It is an idea figure which shows the ray tracing line of the light radiated | emitted from a LED light source. It is sectional drawing which shows the outline of a structure in an example of the linear light source device for readers which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the outline of a structure in an example of the linear light source device for readers which concerns on the 3rd Embodiment of this invention. It is a figure which shows the light distribution curve of the linear light source device for readers produced in Example 1. FIG. It is a figure which shows the light distribution distribution curve when only any one LED light source of the linear light source device for readers produced in Example 1 is lighted. It is a figure which shows the light distribution curve of the linear light source device for readers produced in Example 2. FIG. It is a figure which shows the light distribution distribution curve when only any one LED light source of the linear light source device for readers produced in Example 2 is made to light. 6 is a diagram illustrating a light distribution curve of a comparative linear light source device for a reading device manufactured in Comparative Example 1. FIG. It is a figure which shows the light distribution distribution curve when only any one LED light source of the linear light source device for comparative readers produced in the comparative example 1 is turned on.

  Hereinafter, embodiments of the present invention will be described in detail.

<First Embodiment>
FIG. 1 is a cross-sectional view schematically showing the configuration of an example of a linear light source device for a reading device according to the first embodiment of the present invention. 2 is a cross-sectional view perpendicular to the longitudinal direction of the light guide of the linear light source device for a reading device shown in FIG. FIG. 3 is an enlarged cross-sectional view schematically showing a configuration of a reflecting portion in the linear light source device for a reading device shown in FIG.
This linear light source device for a reading device is disposed so as to oppose a rod-shaped light guide body 10 in which both end faces 10a and 10b in the longitudinal direction are light receiving surfaces, and one end face 10a of the light guide body 10. The one end side LED light source 30a, the other end side LED light source 30b arranged to face the other end face 10b of the light guide 10, and a light guide support base 40 for supporting the light guide 10. ing.

The one-end-side LED light source 30a is a flat substrate 31a that is disposed opposite to the one-end surface 10a of the light guide 10 in the longitudinal direction, and a first light-emitting element mounted on one surface of the substrate 31a. The LED element 32a and the reflector 33a provided so as to surround the space between the one end face 10a of the light guide 10 and the LED element 32a.
The other end-side LED light source 30b is a flat substrate 31b that is spaced apart from the other end surface 10b of the light guide 10 in the longitudinal direction, and a second light emitting element mounted on one surface of the substrate 31b. The LED element 32b and the reflector 33b provided so as to surround the space between the other end face 10b of the light guide 10 and the LED element 32b.

The light guide 10 is a substantially cylindrical rod-like body, and an emission portion 11 having an arc-shaped light emission surface is formed along the longitudinal direction, and a reflection portion is formed on a circumferential surface facing the light emission surface. 15 is formed along the longitudinal direction. The light guide 10 is supported and fixed by a light guide support base 40 disposed so as to extend along the light guide 10 in a state where the light emission surface faces a predetermined direction.
The reflecting portion 15 of the light guide 10 includes a plurality of prism elements 20 formed between adjacent concave and convex grooves by forming a plurality of concave and convex grooves at positions spaced apart from each other in the longitudinal direction on the outer peripheral surface of the light guide 10. It is comprised by. In this example, the concavo-convex groove is constituted by, for example, a V-shaped groove 16 having a substantially V-shaped cross section, and each prism element 20 has a trapezoidal cross section. The depth D of the V-shaped groove 16 is a uniform size.

As a material constituting the light guide 10, for example, a translucent resin such as an acrylic resin, a polycarbonate resin, a cycloolefin copolymer (COC), and a cycloolefin polymer (COP) is used.
Moreover, as a material which comprises the light guide support stand 40, the light radiate | emitted outside the light guide 10 from places other than the output part 11 of the light guide 10 can be absorbed and shielded. For example, a polycarbonate resin or the like can be used. Moreover, what applied the coating which has a light absorptivity to the surface of a suitable base material can also be used.

  Thus, in the above-described linear light source device for a reading device, the individual prism elements 20 constituting the reflecting portion 15 are formed so that a state satisfying the following conditions (A) and (B) is obtained. Yes.

Condition (A):
The light distribution curve in the longitudinal direction of the light guide 10 obtained when any one of the LED element 32a in the one end side LED light source 30a and the LED element 32b in the other end side LED light source 30b is lit alone is Each has an illuminance peak.
However, the illuminance peak obtained when either one is lit alone is a condition that the luminous flux ratio of the LED element 32a in the one end side LED light source 30a and the LED element 32b in the other end side LED light source 30b is 1: 1. It is not necessary to match the two illuminance peaks at both ends in the light distribution curve in the longitudinal direction of the light guide 10 obtained when the light is turned on.
Further, the “illuminance peak” means that the illuminance rises higher than the peripheral illuminance in the longitudinal direction, and thus is viewed as a peak, and does not necessarily mean that it is higher than the illuminance at the longitudinal center position.
For example, referring to FIG. 8, in the light distribution distribution curve (a) indicated by a solid line obtained when the LED element 32a in the one-end-side LED light source 30a is lit alone, the one-end-side near, for example, −140 mm. It has an illuminance peak, for example, an illuminance peak at the other end in the vicinity of 140 mm.

Condition (B):
Light distribution in the longitudinal direction of the light guide 10 obtained when the LED element 32a in the one-end-side LED light source 30a and the LED element 32b in the other-end-side LED light source 30b are turned on under the condition that the luminous flux ratio is 1: 1. In the curve, the longitudinal positions of the two illuminance peaks at both ends are set as xp and xp ′, respectively.
The illuminance at the longitudinal position xp of one illuminance peak is (100 + Axp)%, and the illuminance at the longitudinal position xp ′ of the other illuminance peak is (100 + Axp ′)%.
At this time, the light distribution curve in the longitudinal direction obtained when any one of the LED element 32a in the one end side LED light source 30a and the LED element 32b in the other end side LED light source 30b is lit alone is the center in the longitudinal direction. When the illuminance at the position is 100%, the illuminance at the longitudinal position xp is in the range of (100−2 × Axp)% or more and (100 + 4 × Axp)% or less, and at the longitudinal direction position xp ′. Illuminance shall be in the range of (100-2 × Axp ′)% or more and (100 + 4 × Axp ′)% or less.
For example, referring to FIG. 7, a solid line obtained when the LED element 32a in the one-end-side LED light source 30a and the LED element 32b in the other-end-side LED light source 30b are turned on under the condition that the luminous flux ratio is 1: 1. In the light distribution curve (α) shown in FIG. 1, the longitudinal positions of the two illuminance peaks at both ends are set as xp and xp ′ (here, positions near −140 mm and +140 mm, respectively). The illuminance at the longitudinal center position is 100%, the illuminance at the longitudinal position xp of one illuminance peak is (100 + Axp)%, and the illuminance at the longitudinal position xp ′ of the other illuminance peak is (100 + Axp ′). %.
At this time, as shown in FIG. 8, the illuminance at the longitudinal position xp in the longitudinal light distribution curve (a) obtained when the LED element 32a in the one-end-side LED light source 30a is lit alone is (100− 2 × Axp)% or more and 100 + 4 × Axp)% or less, and the illuminance at the longitudinal position xp ′ is (100−2 × Axp ′)% or more and (100 + 4 × Axp ′)% or less. It is inside.
Further, the illuminance at the longitudinal position xp in the longitudinal light distribution curve (b) obtained when the LED element 32b in the other-side LED light source 30b is lit alone is (100-2 × Axp)% or more, The illuminance at the longitudinal position xp ′ is in the range of (100−2 × Axp ′)% or more and (100 + 4 × Axp ′)% or less.
In the above, the light distribution distribution curves are all based on the LED elements at the initial lighting time. For example, when the brightness of the LED elements varies at the initial lighting time, the light distribution distribution curve shown in FIG. In (α), the value of the illuminance peak position with high illuminance is used.

  Furthermore, in the above-described linear light source device for a reading device, an arrangement obtained when any one of the LED element 32a in the one end side LED light source 30a and the LED element 32b in the other end side LED light source 30b is lit alone. The light distribution curve is such that the illuminance at the longitudinal position xp is (100−Axp)% or more and (100 + 3 × Axp)% or less when the illuminance at the center position in the longitudinal direction is 100%. The individual prism elements 20 constituting the reflecting portion 15 under the condition that the illuminance at the longitudinal position xp ′ is in the range of (100−Axp ′)% or more and (100 + 3 × Axp ′)% or less. Is preferably formed.

  The structure of the reflection unit 15 will be described in detail. The reflection unit 15 of the light guide 10 in the linear light source device for a reading device according to the first embodiment includes a plurality of prism elements 20 having the same shape. The pitch (formation pitch of the V-shaped groove 16) is formed in a state of increasing from the end toward the center in the longitudinal direction. The reflecting portion 15 is configured such that the prism elements 20 are formed substantially symmetrically with respect to the center position of the light guide 10.

In this example, for example, the region from the end surface position of the light guide 10 to the center position is divided into two regions L1 and L2, and the formation pitch of the prism elements 20 in each of the regions L1 and L2 (the formation pitch of the V-shaped groove 21) ) Increases from the end of the light guide 10 toward the longitudinal center position (p1 <p2). An intermediate region may be set between the end region L1 and the central region L2.
A ratio (p1 / p2) between the formation pitch p1 of the V-shaped groove 16 in the end region L1 and the formation pitch p2 of the V-shaped groove 16 in the central region L2 is, for example, 0.15 to 0.85.
Further, the interval between the m-th (m + 1) -th prism element 20 and the (m + 1) -th prism element 20 counted from the end of the light guide 10 is formed with a pitch pm, and the (m + 1) -th prism element. And the (m + 2) -th prism element as the formation pitch p (m + 1), the light guide 10 may be configured such that pm <p (m + 1) toward the longitudinal center position.

Each prism element 20 has an inclination angle α with respect to the longitudinal direction of one optical plane 21 facing the proximal LED light source, with respect to the longitudinal direction of the other optical plane 22 facing the distal LED light source. It is preferable to have a shape larger than the inclination angle β. In FIG. 3, the prism element 20 formed on one end side from the longitudinal center position of the light guide 10 is shown. With such a configuration, a part of the light incident on one optical plane 21 from the proximal LED light source is transmitted and the distal LED light source is transmitted to the other optical plane 22. Most of the incident light can be reflected. Therefore, when any one of the LED light sources is lit alone, a light distribution distribution curve can be obtained in which the illuminance at the end opposite to the end of the lit LED light source is locally increased. (See, for example, FIG. 8.) When the two LED light sources are turned on together, the desired light distribution curve can be reliably obtained as a whole.
The inclination angle α with respect to the longitudinal direction of the first optical plane 21 is preferably, for example, 80 to 90 °, and the inclination angle β with respect to the longitudinal direction of the second optical plane 22 is, for example, 5 to 15 °. It is preferable.

  In the above-described linear light source device for a reading device, as shown in FIG. 4, for example, light from the one-end-side LED light source 30a is reflected directly or by the reflector 33a and one end surface of the light guide 10 10a. The light incident on the one end face 10 a of the light guide 10 is guided in the longitudinal direction by the light guide 10. At this time, a part of the light incident on one optical plane 21 in each prism element 20 located at one end side from the center position in the reflecting portion 15 is reflected by the one optical plane 21 and The reflected light is emitted from the light exit surface of the light guide 10. Further, all the other light incident on the one optical plane 21 is transmitted through the prism element 20, is emitted to the outside of the light guide 10, and is diffused by the light guide support base 40. Further, most of the light incident on the prism element 20 located on the other end side from the center position is reflected by the other optical plane 22 of the prism element 20, and the reflected light is the light exit surface of the light guide 10. It is emitted from.

  On the other hand, the light from the other end side LED light source 30b is reflected directly or by the reflector 33b and enters the other end face 10b of the light guide 10. Light incident from the other end surface 10 b of the light guide 10 is guided in the longitudinal direction by the light guide 10. At this time, a part of the light incident on one optical plane 21 of the prism element 20 positioned on the other end side from the center position is reflected by the one optical plane 21 and the reflected light is guided. The light exits from the light exit surface of the body 10. Further, all the other light incident on the one optical plane 21 is transmitted through the prism element 20, is emitted to the outside of the light guide 10, and is diffused by the light guide support base 40. Further, most of the light incident on the prism element 20 located at one end side from the center position is reflected by the other optical plane 22 of the prism element 20, and the reflected light is reflected from the light emitting surface of the light guide 10. Emitted.

  As described above, in this linear light source device for a reading device, the light from the proximal LED light source that is incident on one optical plane 21 that faces the proximal LED light source of each prism element 20. By passing through the prism element 20, the peak illuminance at the end portion, which is originally high, is suppressed to be small. And since the arrangement | positioning density of the prism element 20 is made high in the edge part of the light guide 10, such an effect can be acquired reliably. On the other hand, the light from the distal LED light source that is incident on the other optical plane 22 facing the distal LED light source in each prism element 20 is reflected by the other optical plane 22 to be light. Although it is emitted from the emission surface, the light density of the light guide 10 is reflected by the other optical plane 22 because the arrangement density of the prism elements 20 is high at the end of the light guide 10. The amount of light emitted from the emission surface increases.

  Thus, according to the reader device configured as described above, even when any one of the LED light sources is lit alone, the illuminance is also observed at the end on the side opposite to the lit LED light source side. Can be obtained locally (having an illuminance peak). For this reason, even when there is an individual difference in the brightness (light quantity) of the LED elements 32a and 32b or when the brightness (light quantity) of the LED elements 32a and 32b varies over time, the light guide Since the degree of illuminance peak fluctuation at both ends in the longitudinal direction of 10 can be suppressed to be small, the desired light distribution characteristic can be obtained with certainty.

<Second Embodiment>
FIG. 5 is a cross-sectional view schematically illustrating a configuration of an example of a linear light source device for a reading device according to the second embodiment of the present invention.
This linear light source device for a reading device is the same as that of the linear light source device for a reading device according to the first embodiment, except that the structure of the reflecting portion of the light guide is different. It has the same configuration as the linear light source device for reading device.

The reflecting portion 15 of the light guide 10 in this example has a plurality of prisms formed between adjacent concave and convex grooves by forming a plurality of concave and convex grooves at a predetermined pitch in the longitudinal direction on the outer peripheral surface of the light guide 10. It is constituted by the element 20.
The concave / convex groove is formed of, for example, a V-shaped groove 16 having a substantially V-shaped cross section, and the depth of the V-shaped groove 16 is formed so as to decrease toward the center in the longitudinal direction. Therefore, a prism element 20 having a trapezoidal cross section, for example, is formed between the adjacent V-shaped grooves 16, and the height of each prism element 20 decreases from the end toward the center in the longitudinal direction.
The reflecting portion 15 is configured such that the prism elements 20 are formed substantially symmetrically with respect to the center position of the light guide 10.

Each prism element 20 has an inclination angle α with respect to the longitudinal direction of one optical plane 21 facing the proximal LED light source, with respect to the longitudinal direction of the other optical plane 22 facing the distal LED light source. It is preferable to have a shape larger than the inclination angle β.
The inclination angle α with respect to the longitudinal direction of one optical plane 21 is preferably, for example, 80 to 90 °, and the inclination angle β with respect to the longitudinal direction of the other optical plane 22 is, for example, 5 to 15 °. preferable.

In this linear light source device for a reading device, light from the one-end-side LED light source 30a is incident on the one end surface 10a of the light guide 10 either directly or after being reflected by the reflector 33a. The light incident on the one end face 10 a of the light guide 10 is guided in the longitudinal direction by the light guide 10. At this time, a part of the light incident on one optical plane 21 in each prism element 20 positioned on one end side from the center position is reflected by the one optical plane 21 and the reflected light is guided. The light is emitted from the light exit surface of the light body 10. Further, all the other light incident on the one optical plane 21 is transmitted through the prism element 20, is emitted to the outside of the light guide 10, and is diffused by the light guide support base 40. Further, most of the light incident on the prism element 20 located on the other end side from the center position is reflected by the other optical plane 22 of the prism element 20, and the reflected light is the light exit surface of the light guide 10. It is emitted from.
On the other hand, the light from the other end side LED light source 30b is reflected directly or by the reflector 33b and enters the other end face 10b of the light guide 10. Light incident from the other end surface 10 b of the light guide 10 is guided in the longitudinal direction by the light guide 10. At this time, a part of the light incident on one optical plane 21 of the prism element 20 positioned on the other end side from the center position is reflected by the one optical plane 21 and the reflected light is guided. The light exits from the light exit surface of the body 10. All other light incident on the one optical plane 21 is transmitted through the prism element 20 and emitted to the outside of the light guide 10 and diffused by the light guide support 40. Further, the light incident on the prism element 20 positioned on one end side from the center position is reflected by the other optical plane 22 of the prism element 20, and the reflected light is emitted from the light emitting surface of the light guide 10. .

As described above, in this linear light source device for a reading device, the light from the proximal LED light source that is incident on one optical plane 21 that faces the proximal LED light source of each prism element 20. A part of the light is transmitted through the prism element 20, so that the peak illuminance at the end portion that is originally high is suppressed to be small. And since the height of the prism element 20 is large at the end of the light guide 10, the amount of light transmitted through the prism element 20 increases toward the end, and this effect is ensured. Can be obtained. On the other hand, most of the light from the distal LED light source incident on the other optical plane 22 facing the distal LED light source in each prism element 20 is reflected by the other optical plane 22. However, since the prism element 20 has a large height at the end of the light guide 10, the light guide 10 is reflected by the other optical plane 22. The amount of light emitted from the light exit surface increases.
Therefore, a state satisfying the above conditions (A) and (B) can be obtained also by the structure of the reflecting portion 15 as described above.

  Thus, according to the linear light source device for a reading device having the above-described configuration, when any one of the LED light sources is lit alone, the end on the side opposite to the lit LED light source side is used. Also, it is possible to obtain a light distribution curve in which the illuminance is locally increased (has an illuminance peak). For this reason, even when there is an individual difference in the brightness (light quantity) of the LED elements 32a and 32b or when the brightness (light quantity) of the LED elements 32a and 32b varies over time, the light guide Since the degree of illuminance peak fluctuation at both ends in the longitudinal direction of 10 can be suppressed to be small, the desired light distribution characteristic can be obtained with certainty.

<Third Embodiment>
FIG. 6 is a cross-sectional view schematically illustrating a configuration of an example of a linear light source device for a reading device according to the third embodiment of the present invention.
This linear light source device for a reading device is the same as that of the linear light source device for a reading device according to the first embodiment, except that the structure of the reflecting portion of the light guide is different. It has the same configuration as the linear light source device for reading device.

  The reflecting portion 15 of the light guide 10 in this example has a plurality of prisms formed between adjacent concave and convex grooves by forming a plurality of concave and convex grooves at a predetermined pitch in the longitudinal direction on the outer peripheral surface of the light guide 10. It is composed of elements. The reflecting portion 15 is configured such that prism elements are formed substantially symmetrically with respect to the center position of the light guide 10.

  The concave / convex groove is constituted by, for example, a V-shaped groove 16 having a V-shaped cross section, and the depth of the V-shaped groove 16 is uniform.

Each prism element has the same height as each other, for example, an inclination angle α with respect to the longitudinal direction of one optical plane 21 facing the proximal LED light source, and the distal LED light source. The other optical plane 22 has a shape in which the inclination angle β with respect to the longitudinal direction is the same.
In this example, the prism element includes one whose optical plane 21 facing the proximal LED light source 21 also functions as a light transmitting surface, and one optical plane facing the proximal LED light source. 21 includes a light absorption prism element 20a that functions as a light absorption surface. And the reflection part 15 is formed in the state which the arrangement | positioning density of the light absorption prism element 20a becomes low as it goes to the longitudinal direction center side.
The light absorbing prism element 20a is configured, for example, by coating the surface of one optical plane 21 facing the proximal LED light source with, for example, black ink.

  In this linear light source device for a reading device, light from the one-end-side LED light source 20a is incident on the one end surface 10a of the light guide 10 either directly or after being reflected by the reflector 33a. The light incident on the one end face 10 a of the light guide 10 is guided in the longitudinal direction by the light guide 10. At this time, the light incident on one optical plane 21 of the light absorption prism element 20 a located at one end side from the center position is absorbed by the one optical plane 21. Further, a part of the light incident on one optical plane 21 in the prism elements 20 other than the light absorbing prism element 20a is reflected by the one optical plane 21, and the reflected light is light of the light guide 10. The light is emitted from the emission surface. Further, all the other light incident on one optical plane 21 is transmitted through the prism element 20 and emitted to the outside of the light guide 10 and diffused by the light guide support 40. Further, most of the light incident on the other optical plane 22 in all the prism elements 20 including the light absorption prism element 20 a positioned on the other end side from the center position is reflected by the other optical plane 22. The reflected light is emitted from the light exit surface of the light guide 10.

  On the other hand, the light from the other end side LED light source 30b is reflected directly or by a reflector and enters the other end face 10b of the light guide 10. Light incident from the other end surface 10 b of the light guide 10 is guided in the longitudinal direction by the light guide 10. At this time, the light incident on one optical plane 21 in the light absorption prism element 20 a located on the other end side from the center position is absorbed by the one optical plane 21. Further, a part of the light incident on one optical plane 21 in the prism elements 20 other than the light absorbing prism element 20a is reflected by the one optical plane 21, and the reflected light is light of the light guide 10. The light is emitted from the emission surface. Further, all the other light incident on one optical plane 21 is transmitted through the prism element 20 and emitted to the outside of the light guide 10 and diffused by the light guide support 40. Further, most of the light incident on the other optical plane 22 in all the prism elements 20 including the light absorption prism element 20 a positioned at one end side from the center position is reflected by the other optical plane 22. The reflected light is emitted from the light exit surface of the light guide 10.

As described above, in this linear light source device for a reading device, the proximal light incident on one optical plane 21 facing the LED light source on the proximal side in all the prism elements 20 including the light absorbing prism element 20a. Most of the light from the LED light source on the side is absorbed by one optical plane 21 of the light-absorbing prism element 20a and the light guide support base 40, so that the peak illuminance at the end portion that is originally high is suppressed small. The Rukoto. And since the arrangement | positioning density of the light absorption prism element 20a is made high in the edge part of the light guide 10, such an effect can be acquired reliably. On the other hand, most of the light from the distal LED light source that is incident on the other optical plane 22 facing the distal LED light source in all the prism elements 20 including the light absorbing prism element 20a, The light is reflected by the optical plane 22 and emitted from the light exit surface.
Therefore, a state satisfying the above conditions (A) and (B) can be obtained also by the structure of the reflecting portion 15 as described above.

  Thus, according to the linear light source device for a reading device having the above configuration, even when any one of the LED light sources is lit alone, the end on the side opposite to the end on the side of the lit LED light source The light distribution distribution curve in which the illuminance is locally high (has an illuminance peak) can be obtained. For this reason, even when there is an individual difference in the brightness (light quantity) of the LED elements 32a and 32b or when the brightness (light quantity) of the LED elements 32a and 32b varies over time, the light guide Since the degree of illuminance peak fluctuation at both ends in the longitudinal direction of 10 can be suppressed to be small, the desired light distribution characteristic can be obtained with certainty.

  Specific examples of the present invention will be described below, but the present invention is not limited to these examples.

<Example 1>
With reference to the configuration shown in FIGS. 1 to 3, a linear light source device for a reading device according to the present invention having the following specifications was produced.
[Light guide support base (40)]
Material: Acrylic resin [LED light source (30a, 30b)]
LED element (32a, 32b): emitting white light [light guide (10)]
Dimensions: Full length 340 mm, outer diameter 5 mm, cylindrical material: Acrylic resin Uneven groove: V-shaped groove, depth 0.2 mm, end region (L1) pitch (p1) 2.5 mm, central region (L2) pitch (P2) 4mm
Cross-sectional shape of prism element: trapezoidal shape, tilt angle (α) of one optical plane in the range of 80 to 90 °, tilt angle (β) of the other optical plane in the range of 5 to 15 °

About this linear light source device for readers, one end side LED light source (30a) and the other end side LED light source (30b) are turned on under the condition that the luminous flux ratio is 1: 1, and from the central axis of the light guide (10). When the light distribution in the longitudinal direction of the light guide (10) at a position spaced by 6.2 mm in the vertical direction was measured, a light distribution distribution curve (α) indicated by a solid line in FIG. 7 was obtained. In this light distribution curve (α), there is a peak at one end side in the longitudinal direction position (xp) near −140 mm with respect to the center position, and at the longitudinal direction position (xp ′) near 140 mm with respect to the center position. There was a peak at the other end, and the peak illuminance was about 120% (Axp, Axp′≈20%) when the illuminance at the center position was 100%.
Further, when the light distribution when the one-end-side LED light source (30a) was lit alone was measured by the same method as described above, a light distribution distribution curve (a) indicated by a solid line in FIG. 8 was obtained. . Furthermore, when the light distribution when the other end side LED light source (30b) is lit alone is measured by the same method as described above, a light distribution curve (b) indicated by a one-dot chain line in FIG. 8 is obtained. It was.
Thus, in the above-described linear light source device for a reading device, one end side in the light distribution curve obtained when one of the one end side LED light source (30a) and the other end side LED light source (30b) is turned on. The illuminance at the peak longitudinal position (xp) is in the range of (100−2 × Axp)% or more and (100 + 4 × Axp)% or less, and the illuminance at the other end side peak longitudinal position (xp ′) is , (100-2 × Axp ′)% or more and (100 + 4 × Axp ′)% or less.

  In the above linear light source device for reading device, the one end side LED light source (30a) and the other end side LED light source (30b) are turned on under the condition that the luminous flux ratio is 1: (1/2), and the same method as above Thus, when the light distribution in the longitudinal direction of the light guide (10) was measured, a light distribution curve (β) indicated by a broken line in FIG. 7 was obtained. At this time, each peak at both ends is higher than the central illuminance (100%).

<Example 2>
In the linear light source device for a reading device manufactured in Example 1, the present invention has the same configuration as that manufactured in Example 1 except that the structure of the reflecting portion of the light guide is changed as follows. A linear light source device for a reading device according to the above was manufactured.
[Reflecting part (15)]
Concave and convex groove: V-shaped groove, depth 0.2 mm, end region (L1) pitch (p1) 2.5 mm, central region (L2) pitch (p2) 4 mm
Cross-sectional shape of prism element (20): trapezoidal shape, tilt angle (α) of one optical plane: 80 to 90 °, tilt angle (β) of other optical plane: 5 to 15 °

With respect to the linear light source device for the reading device, the light distribution when the one end-side LED light source and the other end-side LED light source are both turned on by the same method as in Example 1 is measured. A light distribution curve (α) was obtained. In this light distribution curve (α), one end side peak exists at a position of −140 mm with respect to the center position, and the other end side peak exists at a position of 140 mm with respect to the center position. When the illuminance was 100%, the magnitude was about 120% (Axp, Axp′≈20%).
Further, when the light distribution was measured when the one-end-side LED light source was lit alone, a light distribution distribution curve (a) indicated by a solid line in FIG. 10 was obtained. Furthermore, when the light distribution was measured when the other-end LED light source was lit alone, a light distribution curve (b) indicated by a one-dot chain line in FIG. 10 was obtained.
Thus, in the above-described linear light source device for a reading device, the longitudinal position of the one end side peak in the light distribution curve obtained when one of the one end side LED light source and the other end side LED light source is turned on ( The illuminance at xp) is in the range of (100−Axp)% or more and (100 + 3 × Axp)% or less, and the illuminance at the longitudinal position (xp ′) of the other end side peak is (100−Axp ′)%. As described above, it was confirmed that it was within the range of (100 + 3 × Axp ′)% or less.

  In the above-described linear light source device for a reading device, the one end side LED light source and the other end side LED light source are turned on under the condition that the luminous flux ratio is 1: (1/3). When the light distribution in the longitudinal direction was measured, a light distribution curve (β) indicated by a broken line in FIG. 9 was obtained. At this time, each peak at both ends is higher than the central illuminance (100%).

<Example 3>
In the linear light source device for a reading device manufactured in Example 1, with reference to the configuration shown in FIG. 6, the structure of the reflection part of the light guide was changed as follows, and was manufactured in Example 1. A linear light source device for a reading device according to the present invention having the same configuration as the above was manufactured.
[Reflecting part (15)]
Irregular groove: V-shaped groove, pitch 4 mm, depth: 0.05 to 0.4 mm (end side 0.3 to 0.4 mm, center side 0.05 to 0.15 mm), concave and convex groove depth Is formed so as to become smaller toward the center in the longitudinal direction. Sectional shape of prism element: trapezoid, inclination angle (α) of one optical plane 80 to 90 °, inclination angle (β) 5 of the other optical plane ~ 15 °

  Also in this linear light source device for a reading device, the longitudinal position of one end side peak in the light distribution curve obtained when either one end side LED light source (30a) or the other end side LED light source (30b) is turned on. The illuminance of (xp) is in the range of (100-2 × Axp)% or more and (100 + 4 × Axp)% or less, and the illuminance at the longitudinal direction position (xp ′) of the other end side peak is (100-2). It was confirmed that it was in the range of not less than × Axp ′)% and not more than (100 + 4 × Axp ′)%.

<Comparative Example 1>
In the linear light source device for a reading device manufactured in Example 1, a diffusion extending along the longitudinal direction of the light guide on the opposite side of the light emitting surface of the light guide without forming a reflection portion on the light guide A comparative linear light source device for a reading device having the same configuration as that manufactured in Example 1 was prepared except that the sheet was arranged. As the diffusion sheet, a sheet in which a diffuse reflection surface using TiO ₂ was provided on the surface of the base material made of PET resin in contact with the light guide.

About the linear light source device for reading device for comparison, when the light distribution was measured when both the one-end side LED light source and the other-end side LED light source were turned on by the same method as in Example 1,
A light distribution curve (α) indicated by a solid line in FIG. 11 was obtained. In this light distribution curve (α), one end side peak exists at a position of −140 mm with respect to the center position, and the other end side peak exists at a position of 140 mm with respect to the center position. When 100%, the peak illuminance was about 120% (Axp, Axp′≈20%).
Further, when the light distribution when the one-end-side LED light source was lit alone was measured by the same method as described above, a light distribution distribution curve (a) indicated by a solid line in FIG. 12 was obtained. Furthermore, when the light distribution when the other-end LED light source was lit alone was measured by the same method as described above, a light distribution distribution curve (b) indicated by a one-dot chain line in FIG. 12 was obtained.
Thus, in the comparative linear light source device for reading device, the light distribution curve obtained when one of the one-end-side LED light source and the other-end-side LED light source is lit is the lit LED There is an illuminance peak at the end on the light source side, and the illuminance tends to gradually decrease toward the end on the opposite side, and the illuminance is (100-2 × Axp)% or more at each of both ends. It is confirmed that there is no illuminance peak in the range of (100 + 4 × Axp)% or less and in the range of (100-2 × Axp ′)% or more and (100 + 4 × Axp ′)% or less. It was.

  In the above linear light source device for reading device, the one-end LED light source and the other-end LED light source are turned on under the condition that the luminous flux ratio is 1: (1/2), and the light is guided by the same method as described above. When the light distribution in the longitudinal direction of the light body was measured, a light distribution distribution curve (β) indicated by a broken line in FIG. 11 was obtained. At this time, the peak on one side is lower than the central illuminance (100%).

  As is clear from the above results, according to the linear light source device for a reading device according to the present invention, even if there is a difference in the light emission state (brightness) of the one end side LED light source and the other end side LED light source. It was confirmed that the light amount ratio with respect to the center portion of the end portion can be maintained within a predetermined range, and the desired light distribution characteristic can be obtained.

DESCRIPTION OF SYMBOLS 10 Light guide 10a One end surface 10b Other end surface 11 Output part 15 Reflection part 16 V-shaped groove 20 Prism element 20a Light absorption prism element 21 One optical plane 22 The other optical plane 30a One end side LED light source 30b The other end side LED Light source 31a, 31b Substrate 32a, 32b LED element 33a, 33b Reflector 40 Light guide support base

Claims (6)

A rod-shaped light guide having a reflecting portion and an emitting portion formed along the longitudinal direction so as to face each other, and a first light emitting element disposed to face each of both end faces in the longitudinal direction of the light guide And a second light emitting element, wherein the reflecting portion of the light guide is configured by a plurality of prism elements formed between adjacent concave and convex grooves by forming a plurality of concave and convex grooves on the outer peripheral surface. In the linear light source device for reading device,
Condition (A): The light distribution distribution curve in the longitudinal direction obtained when only one of the first light emitting element and the second light emitting element is lit has illuminance peaks at both ends.
Condition (B): In the light distribution curve in the longitudinal direction obtained when the first light-emitting element and the second light-emitting element are turned on under the condition that the light flux ratio is 1: 1, The longitudinal positions of the two illuminance peaks at both ends are xp and xp ′, the illuminance at the central position in the longitudinal direction is 100%, the illuminance at the position xp of the one illuminance peak is (100 + Axp)%, and the other When the illuminance at the illuminance peak position xp ′ is (100 + Axp ′)%, the light distribution in the longitudinal direction obtained when only one of the first light-emitting element and the second light-emitting element is turned on. The illuminance at the position xp of the one illuminance peak in the curve is in the range of (100-2 × Axp)% or more and (100 + 4 × Axp)% or less, and the illuminance at the position xp ′ of the other illuminance peak is The individual prism elements constituting the reflection portion are formed so that a state in a range of (100-2 × Axp ′)% or more and (100 + 4 × Axp ′)% or less is obtained. A linear light source device for a reading device.   The illuminance at the position xp of the one illuminance peak in the longitudinal light distribution curve obtained when only one of the first light-emitting element and the second light-emitting element is turned on is (100−Axp). )% Or more and (100 + 3 × Axp)% or less, and the illuminance at the position xp ′ of the other illuminance peak is within the range of (100−Axp ′)% or more and (100 + 3 × Axp ′)% or less. 2. The linear light source device for a reading device according to claim 1, wherein the individual prism elements constituting the reflecting portion are formed under a condition that the following state is obtained.   The inclination angle α with respect to the longitudinal direction of one optical plane facing the light emitting element on the proximal side in each prism element is more than the inclination angle β with respect to the longitudinal direction of the other optical plane facing the light emitting element on the distal side. The linear light source device for a reading device according to claim 1, wherein the linear light source device is large.   4. The linear light source device for a reading device according to claim 3, wherein the pitch of the prism elements constituting the reflecting portion increases toward the center in the longitudinal direction.   The linear light source device for a reading device according to claim 3, wherein the depth of the concave and convex grooves decreases toward the center in the longitudinal direction.   The prism element constituting the reflection part includes a light absorption prism element in which the surface of one optical plane facing the light emitting element on the proximal side functions as a light absorption surface, and the arrangement density of the light absorption prism elements is long. The linear light source device for a reading device according to claim 1, wherein the linear light source device for the reading device is lowered toward the center in the direction.

Images