JPH041350B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is arranged on the back side of a transmissive image display device,
The present invention relates to an illumination device that uniformly illuminates an image display element from the back side.

Prior Art Transmissive image display devices using image display elements such as liquid crystals use an illumination device as shown in FIG. 7, for example, in order to brightly and uniformly illuminate the image display elements from the back side. .

That is, the light source 1 is placed below the linear light source 1.
A reflector plate 2 with a parabolic cross-sectional shape is provided to efficiently condense the light emitted from the light source 1, and a diffuser plate provided above the light source 1 allows the direct light from the light source 1 and the reflected light from the reflector plate 2 to be reflected from the light source 1. 3, the back surface of the image display element 4 placed in parallel on the diffuser plate 3 is illuminated.

Problems to be Solved by the Invention In such a conventional lighting device, the reflector 2
Since the cross-sectional shape of is a parabola, a part of the light from the light source 1 reflected by the reflection plate 2 is irradiated onto the diffuser plate 3 almost perpendicularly. This reflector 2
If the diffuser plate 3 is irradiated with only the reflected light from the diffuser plate 3, the luminance distribution of the diffuser plate 3 will be nearly uniform. However, since the diffuser plate 3 is irradiated with direct light from the light source 1 in addition to the reflected light, the brightness distribution is a combination of the direct light and the reflected light as shown in FIG. Since the brightness is high and the brightness decreases toward the end of the diffuser plate 3, the brightness of the image display element 4 becomes non-uniform.

As a method to make the brightness distribution of the diffuser plate 3 uniform,
It is conceivable to block the direct light from the light source 1, or to change the diffusion plate 3 to a material with high diffusion properties (one that approximates a perfect diffusion surface as much as possible: for example, opal glass), but in either case, the light source This is undesirable because it lowers the efficiency of using light in step 1.

Therefore, the present invention makes the luminance distribution of the diffuser plate uniform without reducing the efficiency of using light from the light source.

Means for Solving the Problems The technical means of the present invention for solving the above problems is that, in addition to the direct light from the light source and the reflected light from the reflective member, it also uses transmitted light that passes through the interior of the reflective member. By combining these, the aim is to make the luminance distribution of the diffuser plate uniform.

Effect The effect of this technical means is as follows.
That is, a reflective member having the functions of both a reflective mirror and a light guide is provided below the light source, direct light from the light source is irradiated near the center of the diffuser plate, and the reflected light from the surface of the reflective member is directed to the diffuser plate. Irradiates the entire area. The process up to this point is the same as the conventional technology. Furthermore, by irradiating the transmitted light from the inside of the reflective member (light guide) to the portion where the brightness of the diffuser plate normally decreases, that is, to both ends of the diffuser plate, the direct light from the light source and the reflective member can be separated from each other. Since the reflected light and transmitted light can be irradiated onto the diffuser plate in a well-balanced manner, a uniform brightness distribution can be achieved.

Embodiment Hereinafter, a first embodiment of the present invention will be described based on the accompanying drawings.

In FIG. 1, reference numeral 5 indicates a linear light source (for example, a fluorescent lamp, etc.).
A diffusion plate 6 is provided parallel to the tube axis direction.
Furthermore, there is an image display element 7 placed above the diffuser plate 6 in parallel with the diffuser plate 6, and the diffuser plate 6 and the image display element 7 are disposed close to each other with an interval of several mm. On the other hand, a reflecting member 8 whose cross-sectional shape is partially a parabola is provided below the light source 5, and the light source 5 is placed at the focal point of this parabola.

The material of the reflective member is transparent acrylic resin,
As shown in FIG. 2, the structure is as shown in FIG. A metal vapor-deposited aluminum film is applied to the part excluding the part (which is transparent even with the width of It serves as a reflecting mirror for total reflection in the direction. The interior of the reflecting member 8 is a light guide in which the light incident thereon is repeatedly reflected by the wall surface and transmitted through, and a part of the light from the light source 5 is made to enter from A to both ends of the diffuser plate 6. The structure is such that the area is irradiated with light.

By configuring the lighting device as described above,
Of the light irradiated from the light source 5, the diffuser plate 6 contains the directly irradiated light (direct light), the light reflected by the reflective mirror of the aluminum metal vapor deposited film on the surface of the reflective member 8 (reflected light), and light that passes through the reflecting member 8 while being repeatedly reflected (transmitted light)
As a result, the luminance distribution on the diffuser plate 6 becomes as shown in FIG. 3.

In FIG. 3, A is the brightness distribution due to direct light from the light source 5, B is the brightness distribution due to the reflected light from the reflective member 8, C is the brightness distribution due to the transmitted light from the reflective member 8, and A, B, By combining C, the target brightness distribution D can be obtained.

Next, a second embodiment of the present invention will be described.
FIG. 4 shows a second embodiment, in which the reflective member 9
is composed of a reflector 10 and a reflector 11.

In this embodiment, the reflector 10 and the reflector 1
1, each uses a reflective mirror made of an aluminum plate with high specularity, and the cross-sectional shape of each mirror is a parabola. At the focal point of this parabola, a linear light source 5 (for example, a fluorescent lamp) is arranged as in the first embodiment. A diffuser plate 6 is provided above the light source 5 in parallel to the tube axis direction of the light source 5, and further above the diffuser plate 6 is an image display element 7 placed parallel to the diffuser plate 6. The diffuser plate 6 and the image display element 7 are arranged close to each other with an interval of several mm, and the specifications and positional relationships of the components of the light source 5, the diffuser plate 6, and the image display element 7 are based on the first one. It is the same as the example.

On the other hand, the reflection member 9 is provided below the light source 5, and the reflection plate 10 and the reflection plate 11 are arranged at an appropriate interval so that the space between the reflection plate 10 and the reflection plate 11 is hollow. This gives it the effect of a light guide. Further, in the reflecting plate 10 facing the light source 5, a rectangular opening is provided directly below the light source 5 (portion B in FIG. 4) along the tube axis direction of the light source 5, as shown in FIG. light source 5
A part of the light enters from this opening, and is reflected between the reflector 10 and the reflector 11, and then reaches the diffuser plate 6.
The structure is such that both ends of the beam are irradiated.

By configuring the lighting device as described above,
Of the light emitted from the light source 5, the diffuser plate 6 contains the directly emitted light (direct light), the light reflected by the reflector 10 of the reflection member 9 (reflected light), and the light emitted from the reflector 10. The light that is a combination of the light (transmitted light) that is repeatedly reflected with the reflection plate 11 is irradiated, and the luminance distribution on the diffuser plate 6 becomes as shown in FIG. In FIG. 6, E is the brightness distribution due to direct light from the light source 5, F is the brightness distribution due to the light reflected from the reflective plate 10 of the reflective member 9, and G is the brightness distribution due to the reflected light from the reflective plate 10 and the reflective plate 11 of the reflective member 9. This is the brightness distribution due to the transmitted light between
By combining F and G, the target brightness distribution H can be obtained.

Note that although highly specular aluminum plates were used for the reflector 10 and the reflector 11 constituting the reflective member 9, a reflector made of acrylic resin or the like with aluminum vapor-deposited may be used instead of the aluminum plate. It has a similar effect.

Furthermore, in the first and second embodiments, a straight tube fluorescent lamp was used as the light source 5;
Linear light sources such as cold cathode discharge lamps and segmented halogen bulbs, as well as tungsten lamps and
A device in which multiple LEDs or the like are connected in a linear manner may also be used.

Effects of the Invention The present invention has a structure in which a reflecting member whose surface facing the light source is a reflecting mirror and whose interior is a light guide is provided below the light source. By irradiating both ends of the diffuser plate with the transmitted light, it is possible to prevent a decrease in brightness at both ends of the diffuser plate, which has been a problem with conventional lighting devices, and achieve a uniform brightness distribution.

In addition, among the light emitted from the light source, the direct light, the reflected light from the reflective mirror on the surface of the reflective member, and the transmitted light from inside the reflective member can all be irradiated onto the diffuser plate, so the light from the light source The efficiency of use is excellent.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of a lighting device according to a first embodiment of the present invention, FIG. 2 is a perspective view of a reflecting member in the lighting device of the first embodiment, and FIG. 3 is a diagram showing the structure of a lighting device according to the first embodiment. FIG. 4 is a cross-sectional view showing the configuration of the lighting device in the second embodiment of the present invention, and FIG. 5 is a diagram showing the reflective member in the lighting device of the second embodiment. Perspective view, No. 6
The figure is a brightness distribution characteristic diagram of the diffuser plate in the illumination device of the second embodiment, FIG. 7 is a sectional view showing the configuration of the conventional illumination device, and FIG. 8 is a brightness distribution characteristic diagram of the diffuser plate in the conventional illumination device. It is. 5...Light source, 6...Diffusion plate, 7...Image display element, 8 and 9...Reflection member, 10 and 11...
…a reflector.

Claims (1)

[Claims] 1. A linear light source, a reflecting member provided below the light source to reflect and transmit a portion of the light from the light source, and a reflecting member provided above the light source to reflect direct light from the light source and the reflecting member. 1. An illumination device for a transmissive image display device, comprising a diffuser plate to which reflected light and transmitted light are irradiated, the surface of the reflecting member being a reflecting mirror, and the interior of the reflecting member being a light guide.