JPH01121821A - Illuminating device - Google Patents

Abstract

PURPOSE:To obtain a surface light source which is uniform, has high brightness and good directivity by imaging the real image at the exit end of a bundled fiber imaged by a lens as a virtual image in the space. CONSTITUTION:A luminous flux 35 emitted from a light source 1 is guided by the bundled fiber 3 to the exit end 5 of the bundled fiber. The exit end 5 is formed as the surface light source having good uniformity. The surface light source is imaged as the real image 11 in the space by using a lens 7. The real image 11 is imaged as the virtual image 13 in the space by using a lens 9. Namely, the virtual image 13 constitutes the uniform surface light source having the high brightness. A transparent display object such as liquid crystal display panel 37 is placed at the point P2 and the eye or camera is placed at the point P3. The same effect as the effect obtd. when the transparent display object is illuminated by the uniform surface light source having the high brightness existing at the point P1 is obtd. when said object is observed. The uniform surface light surface having the high brightness and the good directivity is thereby obtd.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a transmissive liquid crystal display device, and particularly to a transmissive liquid crystal display device in which the display of a transmissive liquid crystal display panel is directly observed with the naked eye or a camera without being projected onto a screen or the like. It relates to a lighting device that has a uniform, high brightness, and good directivity surface light source with an effective diameter of about 50 to 100 mmφ for use in liquid crystal display devices.

[Background of the invention]

In recent years, liquid crystal display panels have become increasingly dense and have high contrast, and have already been put into practical use as displays. However, since the liquid crystal display panel is a non-light-emitting element, it must not use external light. In particular, the pair of transparent substrates equipped with electrodes for driving the liquid crystal in the applicant's earlier Japanese Patent Application No. 165648/1983, A plurality of TNs each having substantially the same shape, each consisting of a TN-type liquid crystal layer sandwiched between the pair of transparent substrates and polarizing plates arranged on both sides of the pair of transparent substrates.
This is a 'v# type liquid crystal display panel in which two liquid crystal display panels are overlapped so that their corresponding electrodes completely overlap in the direction of the optical axis, and each liquid crystal display panel is simultaneously driven by the same ringing signal. When used, the contrast ratio can be greater than 1:1000, but the overall light transmittance is reduced and a particularly bright illumination device is required.

[Conventional technology and problems]

Conventionally, for rear illumination of a transmissive liquid crystal panel, it has been common to use a surface light emitting device such as an EL device, a lighting device using a lamp such as a fluorescent lamp as a surface light source, or a spot lamp.

However, although surface light emitting elements such as EL have good uniformity as a surface light source, their brightness is insufficient. Illumination devices that use lamps such as fluorescent lamps as surface light sources generally have much higher brightness than EL, but they are often still insufficient (and are generally less uniform as surface light sources.Light sources such as halogen bulbs) Spot lamps using 200-degree brightness can produce extremely high brightness, but if you try to create a uniform surface light source, the optical system becomes very complicated, and it is not advantageous to illuminate a large area. Installing a light diffusing plate allows for a simple configuration (for example, placing a point light source near the focal point of the lens and creating a parallel beam of light).

However, in this case, it is possible to obtain a uniform surface light source with a spot lamp (which looks like a point light source when observing the parallel light beam directly), but the diffuser plate causes many light rays to travel outside the field of view (
As a result, the amount of light is lost, or in the worst case, it becomes scattered noise light. This is particularly noticeable in the case of liquid crystal panels with relatively narrow viewing angles.

When light from a light source such as a halogen lamp is guided through a bundle fiber made by randomly bundling thin optical fibers, the output end face becomes a uniform and highly bright surface light source. They must be bundled together, making them very expensive, and the light emitted from the output end is diverging and has poor directivity.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an illumination device that solves the above-mentioned problems and can provide a uniform, high-luminance, and well-directed surface light source using a relatively inexpensive and simple method.

[Structure of the invention]

The configuration of the present invention includes a light source, a lens that forms an image of the light beam from the light source in space as a real image at the light guide bundle fiber and the output end of the bundle fiber, and a virtual image that converts the real image of the output end of the bundle fiber imaged by this lens. The structure consists of a lens that forms an image in space.

The present invention will be explained below based on the drawings. FIG. 1 shows an example of the configuration according to the present invention. For simplicity, it is assumed that the lenses 7 and 9 are thin single lenses and each effective diameter is determined by the lens diameter.

A light beam 35 emitted from a light source 1 such as a halogen lamp, an arc lamp, or a laser beam is guided by a bundle fiber 6 to an output end 5 of the bundle fiber. Since the bundle fiber 3 is made up of thin independent fibers bundled at random, the output end 5 becomes a surface light source with very good uniformity.

This surface light source is converted into a real image 11 using a lens 7 with a focal length f.
image in space.

Note that 15 indicates an optical axis. At this time, a and b in FIG. 1 satisfy the relationship of equation (1) below, which is a known lens imaging formula.

Further, in this case, the imaging magnification becomes -(b/a).

The real image 11 of the output end 5 of the bundle fiber has a focal length f
The image is formed in space as a virtual image 16 using two lenses.

At this time, c and d in FIG. 1 satisfy the relationship of equation (2) below.

cdf.

Further, the imaging magnification is (d/c). Note that the condition for forming a virtual image is O(c (f'2).

In conclusion, bundle fiber 6, which is a uniform surface light source,
The output end 5 of is multiplied by -(b d / ac ) and imaged as a virtual image 16 at point P in the figure.

In other words, this virtual image 16 serves as a uniform, high-brightness surface light source. Further, since the light rays from the virtual image 16 are almost condensed by the lens 9, the directivity is good.

In Figure 1, a transmissive display object such as a liquid crystal display panel 67 is placed as a spatial light modulator at 22 points, and 23 points in the figure that satisfy the following equation (3) (that is, these 23 points are When observing a transmissive display object by placing the eye or a camera at the pupil (which becomes the pupil), the same effect can be obtained as if the transmissive display object were illuminated by a uniform, high-brightness surface light source located at point P in the figure. Furthermore, the number of observation points does not need to be 25.

Note that field lenses having a focal length r that satisfies the relationship of equation (4) below may be inserted at 24 points in the figure. In this case, optical performance such as light utilization efficiency is generally improved.

b c f.

[Embodiments of the invention]

FIG. 2 shows an embodiment of the present invention. A beam 65 of the emitted light from the l.logen lamp 17 is efficiently guided to the bundle fiber 27 using a parabolic mirror 19 and a lens 21. The bundle fiber 27 has an effective diameter of 10 mm, and the lens 26 has a focal length of 50 mm and an effective diameter of about 47 mm.
+rmo lens 25 has a focal length of 250 mm and an effective diameter of approximately 8 mm.
It is 0 φ.

The positional relationship of each component is the output end 2 of the bundle fiber.
The distance g from 9 to the lens 26 is 58+ot.

The distance from the lens 26 to the virtual image 31-j is 345 mm,
The distance i from the virtual image 61 to the lens 25 is 75.5 m, and the distance j from the lens 25 to the exit pupil 66 is 616.6 m.
+o+yell.

When such a configuration is adopted, when observing the direction of the light source from the position of the exit pupil 66, it is imaginary II! 61, a surface light source of about 80 mm diameter with uniform and high brightness (good directivity) is observed.

〔Effect of the invention〕

As is clear from the above description, according to the lighting device of the present invention, a large-area surface light source with high brightness, uniformity, and good directivity can be obtained by an inexpensive and simple method.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of the configuration of a lighting device according to the present invention, and FIG. 2 is a schematic diagram showing an embodiment of the lighting device according to the present invention. 1...Light source, 6.27...Bundle fiber, 5.29.
...Output end, 7.9.21.26.25...Lens, 11.
... Real image, 16.61 ... Virtual image, 15 ... Optical axis, 17 ... Halogen lamp, 19 ... Parabolic mirror, 66... Exit pupil, 65... Luminous flux, 67... Liquid crystal display panel. Patent applicant: Citizen Watch Co., Ltd.

Claims (1)

[Claims] In an illumination device for a spatial light modulator in a device in which light modulated by a spatial light modulator is directly observed with the naked eye or with an imaging device such as a television camera, a light source, a bundle fiber that guides a light flux from the light source, It is characterized by being composed of a lens that forms an image of the output end of the bundle fiber as a real image in space, and a lens that forms a real image of the output end of the bundle fiber that is imaged by the lens as a virtual image in space. lighting equipment.