JP2016092523A - Linear light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear light source device high in uniformity of chromaticity as a whole without causing a large difference in the chromaticity distribution of a light guide body in a longitudinal direction, in a linear light source device including a light guide body formed of a light transmitting member and an LED disposed to face an incident end surface at an end part of the light guide body.SOLUTION: An incident end surface of a light guide body is provided with a long wavelength cut filter for a light having a small incident angle with respect to the incident end surface among lights from the LED, and/or a short wavelength cut filter for a light having a large incident angle with respect to the incident end surface.SELECTED DRAWING: Figure 1

Description

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

  In recent years, in the above-described image reading apparatus, a linear light source device using a small and low power consumption LED element is improved due to an improvement in output of an LED element (light emitting diode) and an increase in sensitivity of a CCD sensor as a light receiving element. For example, Japanese Patent Application Laid-Open No. 2008-216409 (Patent Document 1) discloses the technique.

The structure is shown in FIG. 6. In FIG. 6A, the linear light source device 1 includes a translucent rod-shaped light guide 2 made of acrylic resin or the like, and an LED ( The LED 3 is disposed opposite to the incident end face 2a of the light guide. The light guide 2 is provided with a reflecting portion 5 such as a prism along the longitudinal direction, and light incident from the incident end surface 2a of the light guide 2 repeats total reflection inside the light guide. Light that propagates and reaches the reflecting portion 5 during that time is taken out of the light guide and directed toward the document reading surface W. The substrate 4 is provided with a reflecting mirror 6 so as to surround the LED 3, and the light guide 2 and the substrate 4 are supported by a support base 7. At this time, a diffuse reflector 8 is provided between the light guide 2 and the support base 7, and plays a role of returning the light leaked from the light guide 2 into the light guide 2.
As shown in FIG. 6B, the light guide 2 has two reflecting portions 5 formed thereon, and the reflected light from the first reflecting portion 5a directly goes to the original reading surface W, and the second The reflected light from the reflecting portion 5 b is directed to the reflector member 20 arranged in parallel so as to face the light guide 2, and is reflected here toward the document reading surface W.

Thus, in such a linear light source device, the light chromaticity is determined by the output light from the one end side near the light source 3 of the light guide 2 and the output light from the other end side away from the light source 3. There was a bug that changed.
The light guide 2 absorbs the propagating light to a certain extent, but has a property of absorbing light components on the short wavelength side more particularly, and the longer the distance propagating through the light guide 2, the shorter the wavelength side. The absorption of light components increases. For this reason, when comparing the light emitted outside the light guide near the light source and the light emitted outside the light guide at a position away from the light source, the light component on the short wavelength side is more light in the latter. Since it is absorbed, it becomes a yellowish color with more components on the longer wavelength side as the distance from the light source increases. This causes a problem that linear light having a uniform color distribution in the longitudinal direction of the light guide cannot be obtained.

In order to solve such a problem, Japanese Patent Application Laid-Open No. 2011-249190 (Patent Document 2) discloses a technique for making a color distribution uniform using a filter.
FIG. 7 shows the structure, and by providing a plurality of filters 20 a, 20 b, 20 c whose transmittance varies in the longitudinal direction of the light guide 2 between the light guide 2 and the diffuse reflector 8. The color distribution in the longitudinal direction is intended to be uniform.
However, in this prior art, since a plurality of filters are attached in the longitudinal direction of the light guide, there is a problem that a member to be used becomes large and a member to be used for changing the transmittance becomes complicated. .

Japanese Unexamined Patent Application Publication No. 2011-210530 (Patent Document 3) discloses a technique in which a filter is provided on a reflecting mirror provided around a light source (LED).
The structure is shown in FIG. 8, and a filter 21 having a low transmittance of light in the long wavelength region (yellow) of light from the LED 3 is provided on the reflecting surface of the reflecting mirror 6 surrounding the light source (LED) 3. It is a thing.
However, the light distribution characteristic of the LED 3 has the highest light intensity in the direction perpendicular to the light emitting surface, and the light intensity decreases as the direction becomes horizontal to the light emitting surface. For this reason, even if a filter is provided in the horizontal direction of the light emitting surface as in Patent Document 2, it is difficult to adjust the chromaticity sufficiently in the longitudinal direction because wavelength conversion of light with high light intensity cannot be performed. There is a problem that there is.

JP 2008-216409 A JP 2011-249190 A JP 2011-210530 A

  In view of the above problems of the prior art, the present invention is a linear light source device including a light guide and an LED disposed opposite to an incident end face of the end of the light guide with a simple structure. It is an object of the present invention to provide a linear light source device that can achieve uniform color distribution in the longitudinal direction of a light body.

  In order to solve the above-described problem, the linear light source device according to the present invention has a long-wavelength cut for light having a small incident angle with respect to the incident end surface, out of light from the LED, on the incident end surface of the light guide. A filter and / or a short wavelength cut filter for light having a large incident angle with respect to the incident end face are provided.

According to the linear light source device of the present invention, since the filters having different wavelengths to be cut according to the incident angle are provided on the incident end face of the light guide, the incident angle from the LED is small, and the longitudinal direction of the light guide Since the long wavelength component (yellow component) of light reaching a distant area is cut in advance to obtain light with a lot of short wavelength components (blue component), the short wavelength component (blue component) is propagated through the light guide. Even if the component) is absorbed, the chromaticity of the light emitted to the outside of the light guide is balanced with the chromaticity of the light emitted from the region close to the LED.
In addition, for the same purpose, light that is emitted from the region having a large incident angle from the LED and close to the longitudinal direction of the light guide to the outside of the light guide is cut in advance in the short wavelength component (blue component) and long wavelength. By making the light with a large amount of component (yellow component), the light propagating to the region far from the LED of the light guide, even if the long wavelength component (yellow component) increases, the longitudinal direction of the light guide Then, the chromaticity is uniform.

Sectional drawing (A) of the linear light source device of this invention, and its XX transverse cross-sectional view (B). Sectional drawing (A) of the other Example of this invention, and its XX cross-sectional view (B). Sectional drawing (A) of the further another Example of this invention, and the XX transverse cross-sectional view (B). Explanatory drawing explaining the principle of this invention. The graph showing the effect of this invention, (A) Conventional example, (B) This invention. Conventional linear light source device. Another conventional linear light source device. Still another conventional linear light source device.

Before describing the embodiment of the present invention, first, the principle of the present invention will be described with reference to FIG.
As shown in FIG. 4A, the light rays from the LED 3 are considered by being classified according to the incident angle α with respect to the incident end face 2a of the light guide. That is, light incident on the incident end face 2a is a light beam group X having a small incident angle α1 (hereinafter referred to as a small angle light beam group X) and a light beam group Y having a large incident angle α2 (hereinafter referred to as a large angle light beam group Y). ).
Among these, as shown in FIG. 4B, since the angle formed by the small-angle light beam group X with the outer surface of the light guide 2 is small, the light guide on the side close to the incident end face 2 a of the light guide 2. 2 There are few components emitted to the outside, and many components propagate to a far region in the longitudinal direction, and are emitted here. The illuminance distribution is schematically shown in FIG.
On the other hand, as shown in FIG. 4C, since the large-angle light ray group Y has a large angle with the outer surface of the light guide 2, a large amount of components are emitted to the outside of the light guide in the region near the incident end face 2a. Is done. The illuminance distribution is shown in FIG.

In this way, the light beam group X having a small incident angle α1 propagates over a long distance in the light guide 2, but the light guide 2 emits light on the shorter wavelength side of the light, that is, They have the property of absorbing the blue component, and when emitted from the end portion far from the incident end face 2a of the light guide 2, it has a yellowish chromaticity with many long wavelength components.
At this time, the large-angle light ray group Y emitted near the incident end face 2a is less influenced by absorption by the light guide 2, and its chromaticity is substantially the light emitted from the LED 3. For this reason, the emitted light from the light guide 2 is different in chromaticity in the longitudinal direction.

An embodiment of the present invention will be described based on the above knowledge.
As shown in FIG. 1, a long wavelength cut filter (hereinafter also referred to as a blue filter) 10 that cuts light on the long wavelength side of white light from the LED 3 is provided on the incident end face 2 a of the light guide 2. . The blue filter 10 is provided in a region for light (small-angle light beam group X) having a small incident angle α1 with respect to the incident end face 2a of the light guide 2 out of the light from the LED 3.
The white light from the LED 3 is composed of light emitted from the LED element (having a peak wavelength near 450 nm) and light emitted from a yellow phosphor provided around it (having a peak wavelength near 550 nm). Even if the blue filter 10 is a filter that absorbs light of 500 nm to 600 nm, such as a correction filter for color photographing, the purpose can be sufficiently achieved.
Thereby, since the long wavelength component (yellow component) is cut in advance for the light of the small-angle light ray group X propagating to a distance far from the incident end face 2a in the light guide 2, when traveling in the light guide 2. Even if the short wavelength component (blue component) is absorbed in the light, the light emitted from the light guide becomes white light in which the yellow component and the blue component are balanced, and the incident end face 2a of the light guide 2 The chromaticity is not significantly different from the light emitted from the vicinity of the.

FIG. 2 shows another second embodiment. In this embodiment, a short wavelength cut filter (which cuts light on the short wavelength side of white light from the LED 3) is formed on the incident end face 2 a of the light guide 2. (Hereinafter also referred to as a yellow filter) 11 is provided. The yellow filter 11 is provided in an annular region for light having a large incident angle α2 with respect to the incident end face 2a of the light guide 2 among the light from the LED 3 (large-angle light beam group Y).
In this embodiment, contrary to the first embodiment, the blue component of the light having a large incident angle is cut, and the light emitted from the vicinity of the incident end surface 2a of the light guide 2 is changed to light having a large yellow component. Even if the light propagating through the light guide 2 and exiting from the region far from the incident end face 2a is absorbed by the blue component to become yellowish light, a large chromaticity change is not caused between them. Is.

FIG. 3 shows still another third embodiment, which is a combination of the first and second embodiments. That is, the incident end face 2a of the light guide 2 has a long wavelength cut filter (blue filter) 10 that cuts light on the long wavelength side of white light from the LED 3, and a short wavelength cut filter that cuts light on the short wavelength side. (Yellow filter) 11 is provided.
The blue filter 10 is provided in a region corresponding to the small angle light beam group X of the light incident on the light guide 2, and the yellow filter 11 is provided in an annular region corresponding to the large angle light beam group Y, respectively. It is what.
With respect to the function, the chromaticity change of the emitted light in the longitudinal direction of the light guide 2 is suppressed by having both the functions of the first and second embodiments.

A specific numerical example of the first embodiment of the present invention will be described below.
<Light guide>
Material: Acrylic resin, total length 340mm, diameter φ5mm
Reflection part: Consists of a plurality of recesses arranged in the longitudinal direction <Light source>
LED arranged opposite the incident end face of the light guide
LED element: 1 mm square LED element emits blue light and excites yellow phosphor on its optical axis to obtain white light by mixing blue of LED element and yellow of phosphor. LED element and yellow phosphor are R1. Sealed with a 3 mm hemispherical translucent silicone resin lens Distance between the resin lens and the incident end face of the light guide: 1.15 mm
<Reflector>
Conical shape (conical angle of 30 °) made of aluminum that expands toward the incident end face side <Blue filter>
Disc shape with a diameter of 3 mm. Concentrically arranged on the incident end face of the light guide Absorbs the long wavelength component (500-600 nm) in the white light from the LED

The above-described linear light source device of the present invention was incorporated in a reading device as shown in FIG. 6B, and compared with a device incorporating the conventional linear light source device shown in FIG.
<Optical arrangement>
The optical arrangement at that time is as follows.
The distance from the central axis of the light guide 2 in the horizontal direction to the document reading axis is 6.2 mm.
The reflector member 20 is a long rectangular plate-like plane mirror. The vertical and horizontal dimensions are 10 mm x 320 mm, and the inclination angle with respect to the horizontal plane (original placement surface) is 60 °.
Vertical distance from the central axis of the light guide to the document placement surface 12mm
In the optical arrangement described above, the light receiving portion of the spectroscope installed on the document placement surface was moved along the longitudinal direction of the light guide 2 and the spectral distribution (chromaticity) at each position was measured.

The results are shown in FIG. 5, in which FIG. 5 (A) incorporates the conventional linear light source device shown in FIG. 6, and FIG. 5 (B) shows the linear light source device of the present invention shown in FIG. It is crowded.
As can be seen from FIG. 5A, in the prior art, the chromaticity differences Δx and Δy both increase with distance from the incident end face of the light guide.
On the other hand, as can be seen in FIG. 5B, in the present invention, the fluctuation widths of the chromaticity changes Δx and Δy are both kept small.

  In the above-described embodiment, the LED is described as being provided on one end face of the light guide. However, the LED may be provided on both end faces of the light guide. In that case, the long-wavelength cut filter and / or the short-wavelength cut filter are also provided on both end faces of the light guide body on which the LEDs are arranged to face each other.

  As described above, in the present invention, in the linear light source device including the light guide and the LED disposed opposite to the incident end face of the end portion of the light guide, the incident end face of the light guide has By providing a long wavelength cut filter for light having a small incident angle and / or a short wavelength cut filter for light having a large incident angle among the light from the LED, the incident end face of the light guide is provided. It is possible to suppress a large chromaticity difference between light emitted to the outside from a near region and light emitted to the outside from a region far from the incident end surface through the light guide body, and the length of the light guide The chromaticity distribution in the direction can be made uniform.

DESCRIPTION OF SYMBOLS 1 Linear light source device 2 Light guide 2a Incident end surface 3 LED
4 Substrate 5 Reflector 5a First Reflector 5b Second Reflector 6 Reflector 7 Support Base 10 Long Wavelength Cut Filter (Blue Filter)
11 Short wavelength cut filter (yellow filter)
20 Reflector member α1 Small incident angle α2 Large incident angle X Small angle ray group Y Large angle ray group

Claims (1)

In a linear light source device including a light guide body made of a translucent member and an LED disposed to face an incident end face of an end portion of the light guide body,
On the incident end surface of the light guide, a long wavelength cut filter for light having a small incident angle with respect to the incident end surface, and / or light having a large incident angle with respect to the incident end surface, out of the light from the LED. A linear light source device, characterized in that a short wavelength cut filter is provided.

Images