JPH052237B2 - - 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 parallel to 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. If only the reflected light from the reflector 2 is irradiated onto 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 reflector and a light guide is provided below the light source, and direct light from the light source is irradiated near the center of the diffuser plate. The reflected light from the paraboloid (which is a reflective surface) is applied to the entire area of the diffuser plate. Furthermore, the transmitted light that has entered the interior of the reflective member (light guide) from a plurality of slopes (transmitting surfaces) provided alternately with paraboloids on the surface of the reflective member,
By irradiating the parts where the brightness of the diffuser plate normally decreases, that is, both ends of the diffuser plate, the direct light from the light source and the reflected light and transmitted light from the reflecting member can be irradiated onto the diffuser plate in a well-balanced manner. This makes it possible to achieve a uniform brightness distribution.

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, at the lower part of the light source 5, a reflecting member 8 is provided, which has a parabolic cross-sectional shape (paraboloid) and a wedge-shaped surface formed by an inclined plane and a flat surface. A light source 5 is placed at the focal point.

The material of the reflective member 8 is transparent acrylic resin, and the portion of the surface facing the light source 5 has a Fresnel shape in which a plurality of paraboloids, slopes, and flat surfaces are alternately arranged at regular intervals, as shown in FIG. be. All parts except the slope and plane, the part directly under the light source 5 (part A in Figs. 1 and 2), and the exit surface of transmitted light (part B in Figs. 1 and 2) It has a metal vapor-deposited aluminum film attached to it and has the function of a reflecting mirror. Further, all of the slopes are arranged in a direction perpendicular to the focal point of the paraboloid, and a part of the light emitted from the light source 5 passes through the slopes and enters the interior of the reflecting member 8. It's getting old. Furthermore, inside the reflecting member 8, there is a light guide member in which the light incident thereon is repeatedly reflected by the wall surface and transmitted through the light guide member, and a diffuser plate is provided that allows part of the light from the light source 5 to enter from A and the slope. The structure is such that both ends of the tube are irradiated.

By configuring the illumination device as described above and setting the width a of the paraboloid and the width b of the slope of the reflecting member 8 to appropriate values as shown in FIG.
Of the light irradiated from the reflecting member 8, there are two types: directly irradiated light (direct light), light reflected by a parabolic reflecting mirror provided on the surface of the reflecting member 8 (reflected light), and light irradiated from the reflecting member 8. The light that is a combination of the part A and the light that enters from the slope and passes through the reflection member 8 while repeating reflection (transmitted light) is irradiated in a well-balanced manner, and the brightness distribution on the diffuser plate 6 is It will look like Figure 3. In Figure 3, A is the light source 5
, B is the brightness distribution due to the reflected light from the reflecting member 8, C is the brightness distribution due to the transmitted light from the reflecting 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 11 have a parabolic cross-sectional shape (paraboloid), are made of highly specular aluminum, and have the function of a reflector. . At the focal point of this paraboloid, 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 as to form a hollow space between the reflection plate 10 and the reflection plate 11.
and the reflecting plate 11 function as a light guide.

Further, the reflection plate 10 facing the light source 5 is provided with a plurality of rectangular openings (forming a flat transmission surface) along the tube axis direction of the light source 5, as shown in FIG. , the parabolic reflecting mirror portions and the apertures are alternately arranged at regular intervals. A part of the light from the light source 5 enters through this opening,
The light is reflected between the reflector plate 10 and the reflector plate 11 and is irradiated onto both ends of the diffuser plate 6.

By configuring the illumination device as described above and setting the width c of the paraboloid and the width d of the opening of the reflecting member 9 to appropriate values as shown in FIG. Among the irradiated lights, directly irradiated light (direct light), light reflected by the paraboloid of the reflecting plate 10 of the reflecting member 9 (reflected light), and incident from the opening of the reflecting plate 10 Then, the light that is a well-balanced combination of the light (transmitted light) that is repeatedly reflected between the reflector 10 and the reflector 11 is irradiated, and the brightness distribution on the diffuser plate 6 is as shown in FIG. become. 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 paraboloid of the reflecting plate 10 of the reflecting member 9, and G is the brightness distribution due to the reflecting plate 10 of the reflecting member 9. This is the brightness distribution due to the transmitted light that enters from the opening and is repeatedly reflected between the reflector 10 and the reflector 11.
By combining the two images, the target luminance distribution image 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 the drawing]

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 reflective 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 sectional view showing the configuration of the lighting device according to the second embodiment of the present invention, and FIG. 5 is a diagram showing the reflective member of the lighting device according to the second embodiment. Perspective view, No. 6
The figure is a brightness distribution characteristic diagram of a diffuser plate of a lighting device in the second embodiment, FIG. 7 is a sectional view showing the configuration of a conventional illumination device, and FIG. 8 is a brightness distribution characteristic diagram of a diffuser plate in a conventional illumination device. It is. 5... Light source, 6... Diffusion plate, 7... Image display element, 8
and 9...reflection member, 10 and 11...reflection plate.

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. A diffuser plate is provided to which reflected light and transmitted light are irradiated, and the surface of the reflecting member has a shape in which a plurality of parabolic reflecting surfaces and sloped or planar transmitting surfaces are sequentially arranged at regular intervals. An illumination device for a transmissive image display device, wherein the interior of the reflective member is a light guide.