JPH03210548A - Projector - Google Patents

Abstract

PURPOSE:To make it possible to project light beams with high parallelism and to improve the using efficiency of light by providing the projector with a light guiding pipe capable of linearly expanding light beams converged upon one point in accordance with the advance of the light along the optical axis. CONSTITUTION:The projector is provided with a light source 10 having a fine light emitting size, a converging optical system including a mirror 20 for converging light beams from the light source 10 upon a point on the optical axis L and the light guiding pipe 30 for guiding the light converged upon one point in the direction of the optical axis L and linearly expanding the light in accordance with the advance of the light along the optical axis L. Thereby, light beams radiated from the light source 10 having the fine light emitting size are converged upon one point by the converging optical system such as a mirror 20 and the converged light is repeatedly reflected by the pipe 30 linearly expanded along the optical axis L, so that approximately parallel light beams can be obtained. Consequently, light with high parallelism can be projected, the using efficiency of light can be improved and the uniform illuminance distribution of an irradiated face can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a projector, and more particularly, to a projector suitably used as a backlight for a liquid crystal projector television.

[Technical Background] LCD projector televisions usually include an LCD screen, a backlight to illuminate the LCD screen, and a projection lens to magnify the transmitted light from the LCD screen and project it onto the screen. It is equipped with a system.

However, in order to form a good image on the screen, the light from the backlight needs to be perpendicularly incident on the entire surface of the LCD screen, and in order to achieve this,
It is necessary that the light projected from the backlight has high parallelism.

Conventionally, as shown in FIG. 6, a projector that projects highly parallel light has, for example, a short-arc metal halide lamp whose light emitting dimensions are adjusted so that its light emitting part is aligned with the focal point f of a parabolic mirror 80. A device in which a minute light source 10 is arranged is known. According to this projector, highly parallel light is projected from the parabolic mirror 80 along its optical axis. 50 is a liquid crystal screen.

[Problem to be solved by the invention]

However, the above-mentioned light projector has a drawback in that the light utilization rate is low. For example, when the light source 10 is a metal halide lamp, the light utilization rate is about 10%, and even for a xenon lamp with even smaller light emission dimensions, the light utilization rate remains at about 25%.

The reason why the light utilization rate is low in this projector is as follows.

(1) Strictly speaking, the light source 10 is not a point light source, but has a light emitting size above a certain level, so the parabolic mirror 80
The light reflected by the liquid crystal screen 50 will spread to the outside of the predetermined liquid crystal screen 50, and the peripheral light l will not be irradiated onto the liquid crystal screen 50. Parabolic mirror 80 and LCD screen 50
If the distance between the parabolic mirror 80 and the liquid crystal screen 50 is shortened, the projection rate to the liquid crystal screen 50 will be increased and the utilization rate of light will be increased. etc. are inserted, so it is not possible to bring the two very close together.

(2) The diameter of the parabolic mirror 80 is approximately the same as the size of the liquid crystal screen 50. This is because the parabolic mirror 80 has a large diameter when the parabolic mirror 80 has a large diameter.
The reflected light from the periphery of the parabolic mirror will not be irradiated onto the liquid crystal screen 50 even though it is projected parallel to the optical axis.On the other hand, if the aperture is small, the light reflected from the parabolic mirror itself will not be irradiated onto the liquid crystal screen 50. This is because the amount of light will decrease. This is an important problem because the size of the liquid crystal screen 5o is small in the case of small liquid crystal projectors, for which demand has been increasing recently.

Furthermore, conventional floodlights have a problem in that a uniform illuminance distribution cannot be obtained on the illuminated surface, such as the liquid crystal screen 50. This means that from the light source 10 and the parabolic mirror 80, $1 of light is emitted from the periphery! This is because a large amount of light is projected near the IL, and the illuminance distribution becomes non-uniform, being high near the optical axis and low at the periphery, as shown in FIG.

The present invention has been made based on the above-mentioned circumstances, and its objects are to be able to project highly parallel light, to have a high light utilization rate, and to provide uniform illuminance to the irradiated surface. The object of the present invention is to provide a floodlight that can obtain distribution.

[Means to solve the problem]

The projector of the present invention includes a light source with a minute light emission dimension, a condensing optical system including a mirror that condenses light from the light source to a point on the optical axis, and lead in the direction of
It is characterized by a light guide pipe that expands linearly as it progresses along the optical axis.

[Effect]

Light emitted from a light source with minute emission dimensions is focused on a single point by a focusing optical system such as a mirror, and this focused light is passed through a light guide pipe that expands linearly along the optical axis. As the light is repeatedly reflected, it becomes a nearly parallel beam of light.

〔Example〕

Examples of the present invention will be specifically described below.

FIG. 1 is an explanatory cross-sectional view showing one embodiment of the projector of the present invention, and the projector has a first focal point f1 of an elliptical mirror 20 which itself functions as a condensing optical system.
A light source 10 made of a xenon lamp or the like with a minute light emitting size is arranged so that the light emitting part is located, and an elliptical mirror 20
A light guide pipe 30 that expands linearly as it advances along the optical axis is arranged along the optical axis.

The light guide pipe 30 has a cylindrical shape as a whole and has a light inlet 31 and a light outlet 32 at both ends.
The light outlet 320 expands along a straight line inclined at a relatively small angle θ with respect to the optical axis toward the light exit 32, and the area of the light exit 320 is larger than the area of the light entrance 31, and the inner surface is the entire surface of the light exit 320. It is considered a mirror surface with high reflectance.

This light guide pipe 30 is arranged so that the second focal point f2 of the elliptical mirror 20 is located slightly inward from the light entrance 31.

According to the above configuration, a part of the light from the light source 10 directly travels along the optical axis and passes through the light guide pipe 30, but most of the light is reflected towards the elliptical mirror 20. , the light is focused on one point at the second focal point f2 of the elliptical mirror 20. This focused light is reflected by the inner surface of the light guide pipe 30, guided toward the light outlet 32, and projected onto, for example, a liquid crystal screen 50 disposed at the light outlet 32 of the light guide pipe 30.

And the 1st rI! As shown in J, light having a large angle with respect to the optical axis from the condensing point (f2) passes through the light guide pipe 3.
However, since the light guide pipe 30 expands linearly as it advances along the optical axis, in one reflection by the inner surface of the light guide pipe 3o, after the reflection The angle β with respect to the optical axis of the light is smaller than the angle α with respect to the optical axis of the light before reflection, so that the light 5
The degree of parallelism to IL becomes higher. Here,
Since the angle of the inner surface of the light guide pipe 30 with respect to the optical axis at the reflection position is θ, the magnitude of β is β=α−2θ. Therefore, as the number of times the light is reflected by the light guide pipe 3o increases, the parallelism of the light becomes higher along the optical axis, and this light is projected from the light exit 32.

In addition, the light that would be emitted outward if the light guide pipe 30 did not exist is condensed by the light guide pipe 30 along the optical axis and guided to the light exit 32 as described above, so that the light The utilization efficiency of light is achieved, and at the same time, the closer the light exit 32 is, the more the light is mixed, so that the illuminance distribution on the liquid crystal screen 50 disposed at the light exit 32 is made sufficiently uniform. Become.

Since the light guide pipe 30 guides light from a so-called point light source that is condensed to one point, the diameter of the light entrance 31 can be made sufficiently small, so that the shape of the light exit 32 can be made relatively small. Since the present invention can sufficiently handle even small objects, it can be suitably applied to small-sized liquid crystal screens.

In the above description, the light emitted from the light source 10 that does not enter the light guide pipe 30 and is therefore not used is the light that travels outward from between the elliptical mirror 20 and the light guide pipe 30. Since the aperture of the elliptical mirror 2o is not restricted by the light guide pipe 30, by using the elliptical mirror 20 with a large aperture, this unused light can be significantly reduced. The utilization rate can be increased.

Actually, according to the configuration shown in Figure 1, a xenon lamp with a light emission dimension of 2+n+r+ and a rated power consumption of 150W was used as the light source lO, and an elliptical mirror with a focal length of 12 years, a focal length of 120111ff+, and an aperture of 80 mm was used. 20
and the length is 200ITll'111, the dimensions of the light inlet 31 are 20 mm x 15 mm, and the dimensions of the light outlet 32 are 40 mm.
x3Qmm, and a light guide pipe 30 having a 95% reflectance mirror on the inner surface, the light utilization rate is extremely high at 50%, and the liquid crystal placed at the light exit 32 A high degree of parallelism was achieved, with the angle of incidence on the surface 50 being within 10 degrees with respect to the optical axis, and a sufficiently uniform illuminance distribution was obtained as shown in FIG.

In the above, the light emission dimension of the light source 10 is specifically 2 to 1
Preferably, it is within the range of 0 mm. If the light emission dimensions of the light source 10 are too large, the dimensions of the light condensing point will become large, which is not preferable. Therefore, as the light filO, it is preferable to use a short arc discharge lamp such as a metal halide lamp in addition to the above-mentioned xenon lamp.

Instead of the elliptical mirror 20, it is also possible to use another condensing optical system that has the function of condensing the light from the light source 10 to one point. For example, as shown in FIG. A condensing optical system can also be constructed by a parabolic mirror 60 that is combined so as to be positioned at , and a lens 61 that condenses light parallel to the optical axis from the parabolic mirror 6o to one point. Furthermore, using a parabolic mirror, the light source lO
A similar function can also be obtained by arranging the light emitting part at a position slightly displaced backward from the focal point of the parabolic mirror.

In the light guide pipe 30, it is preferable that the angle θ of the peripheral wall of the pipe with respect to the optical axis is usually within the range of 3 degrees to 30 degrees. It is not necessary that this angle be the same on the entire circumferential wall, and the shapes of the light entrance 31 and the light exit 32 are not particularly limited either.

FIG. 4 shows another embodiment of the present invention. In this example, the light leakage prevention device is provided with a light leakage prevention device whose inner surface is a reflective surface and which expands as it approaches the light source 10 following the light inlet 31 of the light guide pipe 30. A cylinder body 40 is provided. According to this configuration, among the light emitted from the light source 10, the light directed between the mirror and the light guide pipe 30 constituting the condensing optical system is directed into the light guide vibrator 30 by the light leakage prevention cylinder 40. As a result, an even higher light utilization rate can be obtained.

FIG. 5 shows still another embodiment of the present invention, in which the optical axis is bent by a deflection mirror 70 which is a plane reflecting mirror. Further, an infrared cut filter 71 is provided in the middle of the light guide vibrator 30. In this way, the light guide pipe 30 can be used to provide an auxiliary optical system.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a light source with a minute emission dimension, a focusing optical system including a mirror that focuses light from the light source onto one point on the optical axis, and a focusing optical system including a mirror that focuses light from the light source onto one point on the optical axis. The structure is composed of a light guide pipe that guides the light in the direction of the optical axis and expands linearly as it travels along the optical axis, so it is possible to project highly parallel light and also improve the light utilization rate. It is possible to provide a projector that has high brightness and can provide a uniform illuminance distribution on the illuminated surface.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is an explanatory sectional view showing the configuration of an embodiment of the present invention;
FIG. 2 is a curve diagram showing the illuminance distribution by an example of the projector of the present invention, FIG. 3 is an explanatory cross-sectional view showing a modified example of the condensing optical system in the present invention, and FIGS. 4 and 5 are respectively according to the present invention. FIG. 6 is an explanatory sectional view showing the main part of another embodiment, FIG. 6 is an explanatory sectional view showing the structure of a conventional projector, and FIG. 7 is a curve diagram showing the illuminance distribution by the projector of FIG. 1G...Light source 20...Elliptical mirror 30
...Light guiding pipe 31...Light inlet 32...Light outlet 40...Cylinder for light leakage prevention 50...LCD screen 60...Parabola mirror 61...Lens 70...Direction change Mirror 71...Infrared cut filter

Claims (1)

[Claims] 1) A light source with minute emission dimensions, a condensing optical system including a mirror that condenses the light from the light source to a point on the optical axis, and guides the light condensed to the one point in the direction of the optical axis. , a light projector comprising a light guide pipe that expands linearly as it advances along the optical axis.