JPH10311915A - Lighting equipment - Google Patents

Abstract

(57) [Problem] To provide an illuminating device that maintains good image quality of reflected light and has high illumination efficiency. SOLUTION: The illuminating device has a linear light source 1 and a plurality of slits 31 in which the light source is arranged on a side surface, the upper surface and the lower surface are substantially parallel, and the upper surface is formed of a different material or air at predetermined intervals. And a light guide 3 that is permanently arranged. Therefore, most of the light propagating inside the light guide is emitted from the light guide by total internal reflection at the slit formed in the light guide, and irradiates the reflection plate. The light enters the body, and in places other than the slits, the totally reflected light passes to the observer side, and does not hinder the observer's visual field in the slit portions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a printed matter such as a book or a photograph, an OA device such as a personal computer, a portable information terminal, a screen display device such as a portable video tape recorder, or a reflection type used for various monitors. The present invention relates to a lighting device used for a liquid crystal display device and the like.

[0002]

2. Description of the Related Art In recent years, personal computers, portable information terminals, video tape recorders, and the like have been reduced in size and portability, and reduction of power consumption of image display apparatuses has become an important issue. For this reason, there are many image display devices using a reflective liquid crystal display device. The reflection type liquid crystal display element obtains the brightness of the screen by reflecting external light such as sunlight and indoor light. However, sufficient brightness cannot be obtained on the screen in a place with little external light.
In view of this, there have been invented some reflection-type liquid crystal display devices provided with an illumination device capable of displaying a screen even in a place where external light is not sufficient. 1 shows an example of an illumination device attached to a reflective liquid crystal display element. FIG. 16 is a schematic sectional view of a conventional lighting device. As shown in FIG. 16, the conventional lighting device includes a light source 1, a reflector 2, a light guide 63, and a compensating plate 5.
Composed of The reflector 2 extends the distance from the light source 1 to the side surface of the light guide 63 in order to collimate the light emitted from the light source 1. The light guide 63 has a function of propagating the light beam introduced from the reflector 2 by total reflection, and a function of totally reflecting the light beam by the slope of the groove on the upper surface and illuminating the reflecting plate 4 by changing the angle of the light beam. The compensating plate 5 has a function of correcting distortion generated when the reflected light from the reflecting plate 4 passes through the light guide 63.

[0003]

However, in the conventional illuminating device, when the light transmitted from the light guide 63 to the compensator 5 is totally reflected on the upper surface of the compensator 5 and then enters the light guide 63 again, Since a part of the light beam is reflected on the slope of the groove on the upper surface of the light guide 63, there is a problem that the groove line is easily visible.
Further, in order to reduce the problem that the groove lines are easily visible, the light rays are collimated by the reflector 2, but the collimated light does not hit the slope of the groove of the light guide 63, and the light guide Because it is easy to reach the side opposite to the light source side of 63,
There is a problem that the lighting efficiency is low. Therefore, an object of the present invention is to solve the above-described problems, and an object of the present invention is to provide an illumination device in which groove lines are hardly seen, an image of reflected light is kept good, and illumination efficiency is high.

[0004]

Means for Solving the Problems and Their Functions In order to achieve the above object, the present invention is configured as follows.
According to the first aspect of the present invention, the light source includes a light source and a transparent substrate having the light source disposed on a side surface, and the transparent substrate is filled with a layer having a refractive index different from that of the transparent substrate. A plurality of slits are arranged at predetermined intervals on the surface or inside the lighting device. According to a second aspect of the present invention, there is provided the lighting device according to the first aspect, wherein an upper surface and a lower surface of the transparent substrate are substantially parallel. According to a third aspect of the present invention, in the first or second aspect, the refractive index of the transparent substrate is n, the refractive index of the material filling the slit with n _1, and the upper surface of the transparent substrate and the slit When the angle formed is θ and the viewing angle of the lighting device is β,

Θ <sin ⁻¹ (n ₁ / n) −sin ⁻¹ ｛(1 /
and n) providing an illumination device that satisfies the condition of sin (β)｝.

According to a fourth aspect of the present invention, at least a light source, a transparent first substrate having the light source disposed on a side surface,
A transparent second substrate disposed on an upper surface of the first substrate, wherein the first substrate has a flat lower surface and a stepped slope having a predetermined interval at a predetermined interval. A plurality of second substrates, wherein a lower surface of the second substrate has a step-shaped slope arranged in the same shape as the slope of the upper surface of the first substrate, and the upper surface of the first substrate and the second surface Wherein the lower surface of the substrate is arranged at a predetermined interval. According to a fifth aspect of the present invention, there is provided the lighting device according to the fourth aspect, wherein a collimator is arranged at an exit of the light source. According to a sixth aspect of the present invention, in the fourth or fifth aspect, the refractive index of the first substrate is defined as n, and the refractive index of the material that bonds the first substrate and the second substrate is defined as n. when n ₂ and then, as the angle of the lower surface of the slope of the upper surface and the second substrate of the first substrate theta, and the viewing angle of the lighting device beta,

Equation 6 θ <sin ⁻¹ (n ₂ / n) −sin ⁻¹ ｛(1 /
and n) providing an illumination device that satisfies the condition of sin (β)｝.

According to a seventh aspect of the present invention, in the fifth or sixth aspect, the collimator disposed at the exit of the light source has a light exit angle of ± sin ^-1 [n * sin ｛90-θ-.
sin ^-1 (n ₂ / n)}]. According to an eighth aspect of the present invention, in any one of the fifth to seventh aspects, the collimator arranged at the exit of the light source has a flat light incident surface and a refractive index of the first substrate of n. The refractive index of the material that bonds the first substrate and the second substrate is n ₂ , the refractive index of the collimator is n _3, and a conical concave portion on the exit surface of the collimator is formed. The angle δ, which is half the vertex angle of the convex part, is

[Equation 7] sin ^-1 [n * sin ＊ 90-θ-sin
⁻¹ (n ₂ / n)｝] = 90−δ−sin ⁻¹ [n ₃ * sin
{90-δ-sin ^-1 (1 / n ₃ )}], the collimator has an illuminating device in which a plurality of inclined surfaces having an angle of + δ or an angle of -δ are provided on the exit surface of the collimator. I do. According to a ninth aspect of the present invention, in any one of the fifth to seventh aspects, the collimator arranged at the exit of the light source has a flat light incident surface and a refractive index of the first substrate of n. And the refractive index of the material that bonds the first substrate and the second substrate is n ₂ ,
The refractive index of the collimator and n _3, half the apex angle of the convex portion constituting the conical recess of the exit surface of the collimator δ is

Δ = sin ⁻¹ [n * sin ｛90−θ−sin
^-1 (n ₂ / n)}], the collimator has an illumination surface provided with a plurality of inclined surfaces having an angle of + δ or an angle of -δ.

According to the first to third aspects of the present invention, light emitted from the light source is incident on the transparent substrate and propagates in the transparent substrate while repeating total reflection. At this time, the light rays are divided into those that are totally reflected by the slits inside the transparent substrate and those that are transmitted, depending on the angle. The angle of the totally reflected light beam can be changed and becomes smaller than the total reflection angle, so that the light beam is emitted to the lower surface side of the transparent substrate.
Further, the transmitted light is totally reflected on the upper surface of the transparent substrate and subsequently propagates in the transparent substrate, so that the slit stripe of the transparent substrate is hardly visible. In addition, since a collimator, which is conventionally required for transmitting light through the slit and making the groove lines invisible, becomes unnecessary, almost all light rays are emitted to the lower side of the transparent substrate, so that illumination efficiency is good. Light emitted from the lower surface of the transparent substrate illuminates the object to be illuminated, and reflected light from the object to be illuminated is again incident on the transparent substrate.

## EQU9 ## θ <sin ⁻¹ (n ₁ / n) −sin
^{Since −1} {(1 / n) sin (β)}, a good image can be displayed without being affected by the viewing angle. As described above, it is possible to provide a lighting device in which groove lines are hardly seen and lighting efficiency is high.

According to the fourth to ninth aspects of the present invention, the light emitted from the light source is collimated by the collimator and introduced into the first substrate. Light incident on the first substrate is totally reflected on the slope of the first substrate, and is emitted to the lower surface side because the ray angle is smaller than the total reflection angle. In addition, light emitted from the lower surface of the first substrate illuminates an object to be illuminated, and reflected light from the object to be illuminated is incident again on the first substrate. There is no image distortion,

## EQU10 ## θ <sin ⁻¹ (n ₁ / n) −sin ⁻¹ ｛(1
/ N) sin (β)｝, a good image can be displayed without being affected by the viewing angle. In addition, the light exit angle of the collimator is ±
Within {90−θ−sin ⁻¹ (n ₁ / n)}, all the light rays emitted from the light source are totally reflected on the slope of the first substrate, and can illuminate the object to be illuminated. Good lighting efficiency. As described above, it is possible to provide a lighting device in which groove streaks are hardly seen, image quality of reflected light is kept good, and lighting efficiency is high.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a lighting device according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic diagram of a cross section of a lighting device according to a first embodiment of the present invention. In the lighting device according to the first embodiment of the present invention, the angle at which the observer views the lighting device from above (hereinafter, referred to as a viewing angle) is β. In FIG. 1, reference numeral 1 denotes a light source, for example, a fluorescent lamp such as a hot-cathode tube or a cold-cathode tube, or a light-emitting diode that is linearly arranged;
Alternatively, it is formed by forming an incandescent lamp or an organic light emitting material into a linear shape, and is disposed on the side surface of the light guide 3. In FIG. 1, reference numeral 2 denotes a reflector which is arranged so as to cover the light source 1, and whose inner surface is configured to have a high reflectance and a low diffusivity. For example, a reflector having a high reflectance such as silver or aluminum is deposited on a resin sheet, and the sheet is adhered to a thin metal plate or a resin sheet to form a reflector. When the light source 1 is a fluorescent lamp, it is desirable that the gap between the light source 1 and the reflector 2 is filled with a material having a refractive index close to 1.5 of glass. Further, it is desirable that the side surface thickness of the light guide 3 on the light source 1 side and the height of the reflector 2 be the same. The reason is that the light guide 3 is desirably thin, but the lower limit of the thickness is the height of the reflector 2 for the sake of incidence efficiency. In FIG. 1, reference numeral 3 denotes a transparent substrate (hereinafter referred to as a light guide) made of quartz, glass, a transparent resin, for example, an acrylic resin, or polycarbonate. The upper surface and the lower surface of the light guide 3 are substantially parallel, and the light guide 2 is substantially rectangular when viewed from the upper surface.
The side surface and the upper surface and the side surface and the lower surface of the light guide 3 form an angle of approximately 90 degrees, respectively. A slit 3 is provided on the upper surface of the light guide 3.
1 is formed.

FIG. 2 shows a detailed view of the slit 31 portion. The slit 31 extends substantially parallel to the longitudinal direction of the light source 1. The inside of the slit 31 is filled with a material having a low refractive index, and is made of, for example, air or a fluorine-based resin. Further, the slit 31 sets the refractive index of the light guide to n.
And then, the refractive index of the inner slit and n _1, the slit 31
When the angle between the light guide and the upper surface of the light guide is θ, and the viewing angle is β,

[Equation 11] θ <sin ⁻¹ (n ₁ / n) −sin ⁻¹ ｛(1
/ N) sin (β)｝. In the first embodiment, the light guide material is PMM
And A (Polymethylmetacrylate), an inner slit and air, since the viewing angle is 40 degrees, n = 1.5, n ₁
= 1, β = 40, the angle θ between the slit 31 and the upper surface
Was 16 degrees. Also, the length 33 of the slit 31 is set to 50
μm, and the pitch 32 of the slit 31 was 200 μm. When the viewing angle β = 30, θ = 22.34 °. In FIG. 1, reference numeral 4 denotes a reflection plate. The reflection plate 4
For example, it means printed matter such as books and photographs, OA equipment such as a personal computer, a portable information terminal, a screen display device such as a portable video tape recorder, or a reflective liquid crystal display device used for various monitors.

Next, the propagation of light in the light guide 3 will be described with reference to FIG. The light incident on the light guide 3 is a light having a radiation distribution of ± sin ^-1 (1 / n) according to Snell's law, where n is the refractive index of the light guide 3. Most of the above-mentioned materials of the light guide 3 have a refractive index of 1.42 or more, so that the radiation distribution is in a range of ± 44.77 degrees. By the way, the light guide 3 has an upper surface and a lower surface that are substantially parallel to each other, and the side surface and the upper surface and the side surface and the lower surface, which are incident surfaces to the light guide 3, respectively, form an angle of approximately 90 degrees. When the reflected light is incident on the upper surface or the lower surface, the minimum value of the incident angle is 90-44.77 = 45.23 degrees. Refractive index is 1.
When the angle is 42 or more, the total reflection angle is 44.77 degrees or less, so that light incident from the side surface is totally reflected on the upper surface and the lower surface. In a portion of the light propagating through the light guide 3 other than the vicinity of the slit 31, the light is totally reflected by the flat portions on the upper and lower surfaces of the light guide 3. The slit 31 is divided into a light beam that is transmitted according to the angle of the light beam and a light beam that is totally reflected.
As shown in FIG. 3, when an angle between the light beam and the upper surface of the light guide 3 is α,

When α> 90−θ−sin ⁻¹ (n ₁ / n), the light passes through the slit 31 and

When α <90−θ−sin ⁻¹ (n ₁ / n), the light is totally reflected by the slit 31.

The light transmitted through the slit 31 is transmitted to the light guide 3
Is totally reflected by the flat portion on the upper surface of the substrate and propagates again. The light ray totally reflected by the slit 31 is emitted from the lower surface of the light guide 3, and the incident angle on the lower surface is {90− (2θ + α)}, and according to Snell's law,

When 90− (2θ + α) <sin ⁻¹ (1 / n), the light is emitted from the lower surface of the light guide 3 to illuminate the reflector 4. As described above, the illumination device of the first embodiment illuminates the reflector 4, but since the light emitted from the light source 1 does not need to be collimated, the total reflection rate at the slit 31 is high, and the reflector is efficiently illuminated. 4 can be illuminated. Also,
Since the light transmitted through the slit 31 propagates through the light guide 3 again, there is an effect that the groove lines are hardly seen.

Next, the propagation of reflected light after illuminating the reflector 4 will be described with reference to FIG. The light beam illuminated from the light guide 3 illuminates the reflector 4 and returns reflected light. The reflected light re-enters the light guide 3 from the lower surface, and is emitted from the upper surface of the light guide 3 as it is except near the slit 31. In the vicinity of the slit 31, assuming that the angle of incidence of the reflected light on the lower surface of the light guide 3 is γ,

[Equation 15] θ + sin ⁻¹ {(1 / n) sin (γ)}>
At the time of sin ⁻¹ (n ₁ / n), the light is totally reflected by the slit 31. For this reason, when the reflected light 41 is incident from the lower surface of the light guide 3 at an angle γ, γ>
When β, the light is totally reflected by the slit 31 and does not reach the observer, but when γ ≦ β, the light passes through the slit 31 and reaches the observer. This and the angle θ of the slit 31

(16) θ <sin ⁻¹ (n ₁ / n) −sin ⁻¹ ｛(1
/ N) sin (β)｝, the reflected light is not totally reflected at the slit 31 within the range of the viewing angle ± β, so that a good image can be obtained without obstructing the visual field of the observer.

As described above, according to the first embodiment, it is possible to provide a lighting device in which the groove of the light guide 3 is difficult to see, the image of the reflected light is kept good, and the lighting efficiency is high. is there. In addition, since uniform illumination is possible and it is not necessary to collimate the light emitted from the light source 1, the size of the reflector 2 can be reduced, and the height of the reflector 2 and the height of the side surface of the light guide 3 can be reduced as described above. Are approximately equal, the thickness of the side surface of the light guide 3 can be reduced according to the height of the reflector 2. In the first embodiment, the slits 31 are arranged on the upper surface of the light guide 3, but between the upper surface and the lower surface of the light guide 3 as shown in FIG. 11, or the light guide as shown in FIG. The light guide 3 may be disposed obliquely from the upper surface to the lower surface of the light guide 3 as shown in FIG. In the first embodiment, the light guide 3
Although the upper surface and the lower surface are parallel, they need not be parallel. Further, in the first embodiment, the pitch 32 of the slits 31 is set at equal intervals. Lighting can be obtained. The same effect can be obtained by increasing the length 33 of the slit 31 as the distance from the light source 1 of the light guide 3 increases. The same effect can be obtained even if the angle θ of the slit 31 increases as the distance from the light source 1 increases.

Hereinafter, a lighting device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a schematic diagram of a cross section of the lighting device according to the second embodiment of the present invention.
The lighting device according to the second embodiment of the present invention has a viewing angle β
And In FIG. 5, the light source 1 and the reflector 2 are the first
This is the same as the embodiment. In FIG. 5, reference numeral 30 denotes a light guide as an example of a first transparent substrate, and reference numeral 6 denotes a compensator as an example of a second transparent substrate disposed on the light guide 30. Reference numeral 5 denotes a collimator disposed between the light source 1 and the light guide 30, and collimates the light emitted from the light source 1.
Assuming that the angle of the stepped slope 131 on the upper surface of the light guide 30 is θ, the refractive index of the light guide 30 is n, and the refractive index of the material between the light guide 30 and the compensator 6 is n ₂ , the collimator 5 is ± sin ⁻¹ [n * sin ｛90−θ−sin
⁻¹ (n ₂ / n)}]. For example, β = 40, n
= 1.5, n ₂ = 1, θ = 16 °, and the emission characteristic of the collimator 5 is ± 52.13 °. Also, β
= 30, n = 1.5, and n ₂ = 1, θ = 22.3
4 and the emission characteristic of the collimator 5 is ± 40.85 °. The structure of the collimator 5 can be realized by, for example, a plano-convex cylindrical lens satisfying the above-mentioned emission characteristics. Further, the collimator 5 may be a diffraction grating. If the viewing angle β of the illumination device is large, the collimator 5
The collimator 5 need not be provided because the emission characteristic angle is large.

The light guide 30 is made of quartz, glass, transparent resin,
For example, an acrylic resin or polycarbonate is used as a material. FIG. 6 shows a detailed view of the light guide 30. The lower surface of the light guide 30 is flat, and the upper surface is a stepped slope 13.
1 are arranged at predetermined intervals. Each slope 131 is substantially parallel to the longitudinal direction of the light source 1. Slope 13
The angle of 1 is θ, the refractive index of the material of the light guide 30 is n, and the refractive index of the material between the light guide 30 and the compensator 6 is n _2.
When the viewing angle is β, the angle θ of the slope 131 is

## EQU17 ## θ <sin ⁻¹ (n ₂ / n) −sin ⁻¹ ｛(1
/ N) sin (β)｝. The pitch 32 of the slope 131 may be reduced as the distance from the light source 1 of the light guide 30 increases. Slope 1
The length 33 of the light guide 31 may be increased as the distance from the light source 1 of the light guide 30 increases. Further, the angle θ of the slope 131 may be increased as the distance from the light source 1 increases. Also,
The light guide 30 is substantially rectangular when viewed from above. The compensator 6 is made of quartz, glass, transparent resin, for example, acrylic resin, polycarbonate, or the like. The lower surface of the compensator 6 has a stepped slope 61 arranged in the same shape as the slope 131 of the upper surface of the light guide 30, and the upper surface is flat. The upper surface of the light guide 30 and the lower surface of the compensator 6 are arranged at a predetermined interval. In FIG. 5, reference numeral 4 denotes a reflector. The reflection plate 4 is, for example, a printed matter such as a book or a photograph, an OA device such as a personal computer, a portable information terminal,
Or a screen display device such as a portable video tape recorder, a reflective liquid crystal display device used for various monitors, and the like.

Next, the propagation of light in the light guide 30 according to the second embodiment will be described with reference to FIG. The light incident on the light guide 30 propagates while being totally reflected at a flat portion on the upper surface or the lower surface of the light guide 30 at a place other than the vicinity of the slope 131 of the light guide 30. In the vicinity of the inclined surface 131 of the light guide 30, the light beam is divided into a light beam that is transmitted according to the angle of the light beam and a light beam that is totally reflected. Let n be the refractive index of the light guide 30,
The refractive index of the material between the light guide 30 and the compensator 6 is n ₂ ,
The angle between the lower surface of the light guide 30 and the light beam is α, and the light guide 3
Assuming that the angle of the slope 131 of 0 is θ,

When α> 90−θ−sin ⁻¹ (n ₂ / n), the light passes through the slope 131 of the light guide 30,

When α <90−θ−sin ⁻¹ (n ₂ / n), the light is totally reflected by the slope 131 of the light guide 30.

The light transmitted through the inclined surface 131 of the light guide 30 is reflected after reaching the opposite side of the light source 1 of the compensator 6, so that it is more likely to be emitted to the observer side, thereby deteriorating the illumination efficiency. . However, the emission characteristic of the collimator 5 of the light source 1 is ± sin ⁻¹ [n * sin ｛90−θ−sin ⁻¹ (n
₂ / n)}], the light beam incident on the light guide 30 is within ± {90−θ−sin ⁻¹ (n ₂ / n)}, and thus satisfies the expression (19). Therefore, most of the light rays are totally reflected by the slope 131 of the light guide 30 and illuminate the reflector 4. Therefore, the light emitted from the light source 1 can efficiently display the reflection plate 4. In addition, in order to efficiently illuminate the reflection plate 4 in this manner, the amount of light transmitted through the slope 131 of the light guide 30 to the observer side is small.
There is an effect that the groove line is difficult to see.

Next, the propagation of reflected light after illuminating the reflector 4 will be described with reference to FIG. The light beam illuminated from the light guide 30 illuminates the reflector 4 and returns reflected light. The reflected light re-enters the light guide 30 from the lower surface, and the slope 1 of the light guide 30 is
The light is emitted from the upper surface as it is except near 31. In the vicinity of the inclined surface 131 of the light guide 30, when the incident angle of the reflected light on the lower surface of the light guide 30 is γ,

[Equation 20] θ + sin ⁻¹ {(1 / n) sin (γ)}>
At the time of sin ⁻¹ (n ₂ / n), the light is totally reflected by the slope 131 of the light guide 30. For this reason, when the reflected light 41 is incident from the lower surface of the light guide at an angle γ, when γ> β, it is totally reflected on the slope 131 and does not reach the observer, but when γ ≦ β, it passes through the slope 131. To reach the observer. This and the angle θ of the slope 131 of the light guide 30 are:

[Equation 21] θ <sin ⁻¹ (n ₂ / n) −sin ⁻¹ ｛(1
/ N) sin (β)｝, the reflected light is not totally reflected at the slope 131 of the light guide 30 within the range of the viewing angle ± β, and therefore does not hinder the field of view of the observer, resulting in a good image. Can be obtained.

As described above, according to the second embodiment, it is possible to provide an illuminating device in which the groove of the light guide 30 is hardly seen, the image of the reflected light is kept good, and the illumination efficiency is high. . In the second embodiment, the groove is formed in a step shape, but may be an arbitrary curve as shown in FIG. In the second embodiment, the pitch 32 of the slope 131 is set to be equal. However, if the pitch 32 becomes smaller as the light guide 30 becomes farther from the light source 1,
There is little difference in brightness between a place near and far from the light source 1 and uniform illumination can be obtained. Further, the same effect can be obtained by increasing the length 33 of the slope 131 as the distance from the light source 1 of the light guide 30 increases. In addition, the angle θ of the slope 131 is
The same effect can be obtained by increasing the distance as the distance increases. Also, as shown in FIG. 17, the upper surface of the compensator 6 and the light guide 3
The same effect can be obtained even if the lower surfaces of 0 are not parallel. The same effect can be obtained even if the upper surface of the compensator 6 is a curved surface as shown in FIG.

Hereinafter, a lighting device according to a third embodiment of the present invention will be described. The structure of the third embodiment of the present invention is almost the same as that of the second embodiment, and only the structure of the collimator 5 is different. The structure of the collimator 5 according to the third embodiment will be described with reference to FIG. The light incident surface 51 of the collimator 5 is a flat surface. The exit surface 52 of the collimator 5 has a structure in which a plurality of conical concave portions having a vertex angle 2δ are provided. Light guide 30
Is n, the refractive index of the material that bonds the light guide 30 and the compensator 6 is n _2, and the refractive index of the collimator 5 is n ₃ , δ is

## EQU22 ## sin ^-1 [n * sin ｛90-θ-sin ^-1
(N ₂ / n)｝] = 90−δ−sin ⁻¹ [n ₃ * sin
{90−δ−sin ⁻¹ (1 / n ₃ )}].

Next, the operation of the collimator 5 will be described with reference to FIG. When a light beam emitted from the light source 1 is incident on the incident surface 51 of the collimator 5, its radiation distribution becomes ± sin ^-1.
(1 / n ₃ ). Therefore, the angle of the light beam incident on the inclined surface 52 on the exit side of the collimator 5 is geometrically determined, and the minimum incident angle value i _min is

(23) where i _min = 90−δ−sin ⁻¹ (1 / n ₃ ), and the maximum value of the incident angle i _max is

I _max = 90 The angle of the light beam emitted from the collimator 5 is obtained from Snell's law, and the minimum value o _{min of the} emission angle with respect to the slope 52 on the emission side is:

## EQU25 ## where o _min = sin ^-1 {n ₃ * sin (i _min )}, and the maximum output angle o _max is

## _EQU26 ## where o _max = 90.

Since the exit side slope 52 is inclined with respect to the optical axis by δ, the maximum exit angle ω _max is

Ω _max = 90−δ−o _min and the emission angle minimum value ω _min is:

Ω _min = −δ. That is,

Ω _max = 90−δ−sin ⁻¹ [n ₃ * sin
{90-δ-sin ^-1 (1 / n ₃ )}]

Ω _min = −δ.

When the angle of the slope 131 of the light guide 30 is θ and the refractive index of the material between the light guide 30 and the compensator 6 is n ₂ , the required emission characteristics of the collimator 5 are ± 2.
sin ⁻¹ [n * sin ｛90−θ−sin ⁻¹ (n ₂ /
n)｝]. δ is sin ⁻¹ [n * sin ｛9
0−θ−sin ⁻¹ (n ₂ / n)｝] = 90−δ−sin
^-1 [n ₃ * sin {90-δ-sin ^-1 (1 / n ₃ )}]
Ω _max = (the emission characteristic of the collimator 5), and satisfies the desired emission characteristic. For example, viewing angle β = 30, n = 1.5, n ₂ = 1,
When n ₃ = 1.5, θ = 22.4, the necessary emission characteristic is 40.85 °, and when δ = 46.2 °, the emission angle is ω _max = + 40.81 °. , Ω _min = −
46.2 °, and desired emission characteristics of the collimator 5 can be obtained. Also, δ = sin ⁻¹ [n * sin−90−θ−
sin ⁻¹ (n ₂ / n)｝], δ = 40.85 °, ω _max = + 38.10 °, ω _{min in the} above example.
= −40.85 °, the desired emission characteristics of the collimator 5 can be obtained. Under the above conditions, δ is 40.85 °
The value may be any value not less than 46.2 °.

As described above, by using the third embodiment, it is possible to realize the collimator 5 that satisfies the emission characteristics required for the light guide 30, and to obtain the same effects as those of the second embodiment. In the third embodiment, the emission surface 52 of the collimator 5 is used.
Is a conical concave portion having an apex angle of 2δ, but may be a conical protrusion having an apex angle of 2δ. Further, instead of the conical shape, a polygonal pyramid having a vertex angle of 2δ may be used. In addition, FIG.
A parallel groove having a vertex angle 2δ as shown in FIG.

[0026]

As described above, according to one embodiment of the present invention, a light source, for example, a linear light source is disposed on the side surface of a flat light guide, and a slit is formed inside the light guide substantially parallel to the light source. By arranging the light guide so as to extend, most of the light propagating inside the light guide is emitted from the light guide by total reflection at a slit formed in the light guide, and an example of an illuminated object The reflector can be illuminated, and the light is not totally reflected at the slit, and the transmitted light propagates inside the light guide again, so that the groove lines are difficult to see, and the reflected light from the reflector has no distortion. Since the light is transmitted to the observer, it is possible to maintain good image quality of the reflector. Further, since it is not necessary to collimate the light emitted from the light source, the size of the illumination device can be reduced, and all the light is emitted from the light guide by total reflection at the slit, so that the illumination efficiency is high. Further, by arranging the slits at a predetermined angle, a difference in luminance between the slit portion and the portion other than the slit portion in the field of view of the observer is small, and it is possible to maintain good image quality of reflected light.

According to another aspect of the present invention, a light source, for example, a linear light source is disposed on a side surface of a light guide as an example of the first transparent substrate, and light emitted from the light source is collimated by a collimator. The light guide has a second surface in which a lower surface is flat and an upper surface is provided with a stepped slope at a predetermined angle, and an upper surface is flat and a lower surface is provided with a groove having the same shape as the light guide.
By bonding a compensating plate as an example of a transparent substrate to the light guide, most of the light propagating inside the light guide is totally reflected by the stepwise slope of the light guide. The light can be emitted from a light body to irradiate a reflecting plate as an example of an illuminated object. In addition, because of the presence of the compensating plate, the reflected light from the reflecting plate is transmitted without distortion to the observer side, so that good image quality of the reflecting plate can be maintained. In addition, since the light emitted from the light source is collimated at a predetermined angle by the collimator, the light is not transmitted from the light guide to the compensator, and the reflector can be efficiently illuminated. Streaks are difficult to see. In addition, by setting the step-like slope at a predetermined angle, the difference in luminance between the step-like slope portion and the portion other than the slope portion within the field of view of the observer is small, and it is possible to maintain good image quality of reflected light. . Further, according to still another aspect of the present invention, it is possible to realize a collimator that satisfies the emission characteristics required for the light guide, and it is also possible to obtain the effects of the above-described aspect.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a cross section of a lighting device according to a first embodiment of the present invention.

FIG. 2 is a schematic view showing an arrangement of slits in the first embodiment.

FIG. 3 is a diagram for explaining light propagation in a light guide according to the first embodiment;

FIG. 4 is a diagram for explaining the propagation of reflected light within the light guide according to the first embodiment.

FIG. 5 is a schematic diagram of a cross section of a lighting device according to a second embodiment of the present invention.

FIG. 6 is a diagram for explaining light propagation in a light guide according to a second embodiment.

FIG. 7 is a diagram for explaining light propagation in a light guide according to a second embodiment.

FIG. 8 is a diagram for explaining propagation of reflected light within a light guide according to a second embodiment.

FIGS. 9A and 9B are a schematic cross-sectional side view and a plan view of a collimator according to a second embodiment.

FIG. 10 is a diagram for explaining the operation of the collimator according to the second embodiment.

FIG. 11 is a schematic cross-sectional view of a modification of the illumination device according to the first embodiment of the present invention.

FIG. 12 is a schematic cross-sectional view of another modification of the illumination device according to the first embodiment of the present invention.

FIG. 13 is a schematic cross-sectional view of still another modification of the illumination device according to the first embodiment of the present invention.

FIG. 14 is a schematic cross-sectional view of an example of a lighting device according to a second embodiment of the present invention.

15A and 15B are a schematic cross-sectional side view and a plan view of a collimator of a lighting device according to a third embodiment of the present invention.

FIG. 16 is a schematic view of a cross section of a conventional lighting device.

FIG. 17 is a schematic cross-sectional view of a modification of the illumination device according to the second embodiment of the present invention.

FIG. 18 is a schematic cross-sectional view of another modification of the illumination device according to the second embodiment of the present invention.

DESCRIPTION OF SYMBOLS 1 Light source 2 Reflector 3 Light guide 4 Reflector 5 Collimator 6 Compensator 30 Light guide 31 Slit 32 Slit pitch 33 Slit length 41 Reflected light 51 Collimator entrance surface 52 Collimator exit surface 131 Slope

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Watanabe 1006 Kazuma Kadoma, Kadoma City, Osaka Inside Matsushita Electric Industrial Co., Ltd.

Claims (9)

[Claims] 1. A light source, comprising: a light source; and a transparent substrate disposed on a side surface of the light source, wherein the transparent substrate is filled with a layer having a refractive index different from that of the transparent substrate. A lighting device, wherein a plurality of slits (31) are arranged at predetermined intervals on the surface or inside. 2. The lighting device according to claim 1, wherein an upper surface and a lower surface of the transparent substrate are substantially parallel. 3. The refractive index of the transparent substrate (3) is n,
Wherein the refractive index of the material that satisfies the slit and n _1, the angle between the upper surface of the transparent substrate and the slits and theta, when the viewing angle of the lighting device and beta, Equation 1] θ <sin ^-1 ( n ₁ / n) −sin ⁻¹ ｛(1 /
The lighting device according to claim 1, wherein a condition of n) sin (β)｝ is satisfied. 4. A transparent first substrate (30) having at least a light source (1), a side surface of the light source, and a transparent second substrate (6) disposed on an upper surface of the first substrate. The first substrate has a flat lower surface, and a plurality of slopes (131) having a stepped upper surface are arranged at predetermined intervals, and the second substrate has a lower surface. A step-shaped slope is arranged in the same shape as the slope of the upper surface of the first substrate, and the upper surface of the first substrate and the lower surface of the second substrate are arranged at a predetermined interval. A lighting device, comprising: 5. The lighting device according to claim 4, wherein a collimator (5) is arranged at an exit of the light source. 6. The refractive index of the first substrate is n, the refractive index of the materials bonded to the second substrate and the first substrate and n _2, the upper surface of said first substrate And when the angle of the slope of the lower surface of the second substrate is θ and the viewing angle of the illumination device is β, θ <sin ⁻¹ (n ₂ / n) −sin ⁻¹ ｛(1) /
The lighting device according to claim 4, wherein the condition of n) sin (β)｝ is satisfied. 7. The collimator (5) disposed at the exit of the light source has a light exit angle of ± sin ⁻¹ [n * sin ｛9].
7. The lighting device according to claim 5, wherein the angle is within a range of 0−θ−sin ⁻¹ (n ₂ / n)｝]. 8. A collimator (5) disposed at an exit of the light source has a flat light incident surface, the refractive index of the first substrate is n, and the first substrate and the second substrate are provided. Is n ₂ , the refractive index of the collimator is n _3, and the exit surface (5
The angle δ which is a half of the vertex angle of the convex portion constituting the conical concave portion of 2) is given by: sin ⁻¹ [n * sin ｛90−θ−sin]
⁻¹ (n ₂ / n)｝] = 90−δ−sin ⁻¹ [n ₃ * sin
{90-δ-sin ⁻¹ (1 / n ₃ )}], wherein the collimator has a plurality of inclined surfaces having an angle of + δ or an angle of −δ on the exit surface thereof. The lighting device according to any one of claims 7 to 10. 9. A collimator (5) disposed at an exit of the light source has a flat light incident surface, the refractive index of the first substrate is n, and the first substrate and the second substrate are provided. Is n ₂ , the refractive index of the collimator is n _3, and the exit surface (5
The angle δ which is half of the apex angle of the convex portion forming the conical concave portion of 2) is expressed as follows: δ = sin ⁻¹ [n * sin ｛90−θ−sin
^-1 (n ₂ / n)｝], wherein the collimator is provided with a plurality of inclined surfaces having an angle of + δ or an angle of -δ on the output surface of the collimator. Lighting equipment.