JPH0566476A - Illuminating device - Google Patents

Abstract

PURPOSE:To improve the utilization efficiency of a light source for irradiating a liquid crystal display board, etc. CONSTITUTION:A light beam 3 from the light source 1 and a light beam 3 reflected by a reflection mirror 2 are condensed by a condenser lens 4, and transmitted through a 1/4 wavelength plate 5. Then, the light beam 7 which is made incident on a polarizing device 6 and polarized in a vertical direction, for example, is transmitted and the light beam 8 which is polarized in a horizontal direction is reflected. The reflected light beam 8 is made incident on the 1/4 wavelength plate and becomes a circularly polarized light beam 9. The light beam 9 is reflected by the reflection mirror and becomes a circularly polarized light beam 10 whose rotating direction is inverted, and it is made incident on the 1/4 wavelength plate and becomes a light beam 11 polarized in the vertical direction, then it is transmitted through the polarizing device and outputted together with the light beam 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a light valve using a liquid crystal display panel or the like, and when vertically polarized light is required for illumination of the liquid crystal display panel or the like, the light from the light source is vertically polarized light. And horizontally polarized light, and converts the horizontally polarized light into vertically polarized light for output.

[0002]

2. Description of the Related Art In a liquid crystal display panel or the like used for a light valve, only light polarized in one direction is used, and light polarized in the other direction is not used. That is,
When the liquid crystal display plate 31 uses, for example, vertically polarized light 35 (upward and downward arrows), as shown in FIG. 3, a polarizing filter that transmits only vertically polarized light in front of the liquid crystal display plate 31.
32 is arranged, and only the light transmitted through the polarization filter 32 is incident on the liquid crystal display element, and the light incident on the liquid crystal display element to which a required drive signal is not applied is 90 in the horizontal direction (marked by a black dot in a circle). It is output after passing through the polarization filter 34 which is polarized and transmitted, and which transmits horizontally polarized light 36 arranged next to the liquid crystal display plate 31. Since the light from the light source 33 is a mixture of polarized components in all directions, if only the light of the polarized component in the vertical direction is used, the light utilization rate is up to 1/2. Efficiency is low.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. For example, when light polarized in the vertical direction is required, light polarized in the vertical direction from the light source is transmitted as it is, The light polarized in the horizontal direction is separated, once converted to circularly polarized light through the quarter-wave plate, and the circularly polarized light is reflected by a reflecting mirror to be circularly polarized light with the rotation direction reversed, It is an object of the present invention to provide an illuminating device which converts the light into the vertically polarized light which is incident on the quarter-wave plate and outputs the light together with the vertically polarized light from the light source.

[0004]

In order to solve the above-mentioned problems, the present invention provides, for example, a polarizer which transmits vertically polarized light from a light source and reflects horizontally polarized light orthogonal thereto, and a polarizer. Circularly polarized light reflected by the reflecting mirror, which is composed of a quarter-wave plate that receives horizontally polarized light from the same and converts it into circularly polarized light, and a reflecting mirror that reflects the circularly polarized light from the quarter-wave plate. The present invention provides an illuminating device configured to output the above-mentioned light along with the vertically polarized light through a 1/4 wavelength plate and a polarizer.

[0005]

With the above-described structure, in the illuminating device according to the present invention, for example, when vertically polarized light is required, the vertically polarized light from the light source is transmitted and the horizontal direction orthogonal thereto is transmitted. A polarizer that reflects light that is polarized in the direction is provided, and the light that is polarized in the horizontal direction and reflected by the polarizer is converted into circularly polarized light through a quarter-wave plate, and this circularly polarized light is reflected by a reflecting mirror. The circularly polarized light whose rotation direction is reversed by the reflection of the light is converted into the light which is incident on the ¼ wavelength plate and is polarized in the vertical direction, and is transmitted through the polarizer together with the light polarized in the vertical direction from the light source and output. .

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a lighting device according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a conceptual diagram of an embodiment of a lighting device according to the present invention. In the figure, 1 is a light source, which emits light polarized in all directions. A reflecting mirror 2 reflects the light from the light source 1 or the like in the optical axis direction. A condenser lens 4 condenses the light 3 from the light source 1 and the reflecting mirror 2. Reference numeral 5 denotes a quarter wavelength plate, which delays the light incident through the condenser lens 4 by a quarter wavelength. Reference numeral 6 denotes a polarizer, which is composed of a slit grating, a laminated polarizer, a prism, or the like, and is divided into light 7 polarized in the vertical direction and light 8 polarized in the horizontal direction orthogonal thereto, for example, polarized in the vertical direction. Light 7
And transmits light 8 which is polarized in the horizontal direction.

FIG. 2 is a conceptual diagram of another embodiment of the lighting device according to the present invention. In the figure, reference numeral 21 denotes a polarizer, which is arranged such that the incident surface forms a required angle with respect to the optical axis from the light source 1, and which vertically polarizes light 7 and horizontally polarizes light 8.
Is separated and, for example, the light 7 polarized in the vertical direction is transmitted,
The light 8 polarized in the horizontal direction is reflected upward. A reflecting mirror 22 reflects the light 8 from the polarizer 21 toward the polarizer 21.

Next, the operation of the lighting device according to the present invention will be described. In the case of FIG. 1, directly from the light source 1 or the reflecting mirror 2
The light 3 reflected by is condensed by the condenser lens 4 and
The light enters the quarter wave plate 5 and is transmitted therethrough. This transmitted light is light that is polarized in all directions like the light from the light source 1. This light 3 enters the polarizer 6. The polarizer 6 transmits, for example, light 7 polarized in the vertical direction and reflects light 8 polarized in the horizontal direction orthogonal thereto. The reflected light 8 enters the quarter-wave plate 5 and is converted into circularly polarized light 9. This light 9 is reflected by the reflecting mirror 2 and becomes circularly polarized light 10 of which the rotation direction is reversed, enters the quarter wavelength plate 5, and is polarized in the vertical direction.
It is converted to 11, transmitted through the polarizer 6 and output together with the light 7. This light is made incident on the liquid crystal display plate or the like and is generated as image light corresponding to the drive signal applied to the liquid crystal display plate.

In the case of FIG. 2, since the polarizer 21 transmits the light 7 polarized in the vertical direction from the incident light 3 and reflects the light 8 polarized in the horizontal direction in a direction different from the axis of the incident light 3, the incident light 3 is incident. It is arranged at a required angle (Brewster angle) with respect to the optical axis. As a result, the light 8 which is reflected by the polarizer 21 and is polarized in the horizontal direction is incident on the reflecting mirror 22 disposed at a required position facing the polarizer 21, is reflected, and is incident on the polarizer 21. Then, the light is reflected by the polarizer 21 toward the quarter-wave plate 5, and thereafter, it is converted into the light 11 which is polarized in the vertical direction through the same path as in the case of FIG.

[0010]

As described above, according to the illumination device of the present invention, most of the light from the light source polarized in all directions is converted into the light polarized in the same direction and then output. Therefore, when it is used as a light source for illuminating a light valve using a liquid crystal display plate or the like, the amount of light incident on the liquid crystal display plate is approximately double that in the conventional case using the same light source, and the light utilization efficiency is improved. The image quality is remarkably improved and a bright image can be obtained with a small light source.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an embodiment of a lighting device according to the present invention.

FIG. 2 is a conceptual diagram of another embodiment of the lighting device according to the present invention.

FIG. 3 is a conceptual diagram of an example of a conventional lighting device.

[Explanation of symbols]

 1 Light Source 2 Reflector 4 Condenser Lens 5 1/4 Wave Plate 6 Polarizer 7 Light Polarized Vertically 8 Light Polarized Horizontally 9 Light Circularly Polarized 10 Light Circularly Polarized 11 Light Polarized Vertically 21 Polarized Container 22 reflector

Claims (2)

[Claims] 1. A polarizer that transmits a first linearly polarized light from a light source and reflects a second linearly polarized light orthogonal to the first linearly polarized light, and a second polarizer from the polarizer. 1/4 wavelength plate that converts linearly polarized light into circularly polarized light and 1
And a first reflecting mirror that reflects circularly polarized light from the / 4 wavelength plate, and transmits circularly polarized light from the first reflecting mirror through the ¼ wavelength plate and through the polarizer to the first linearly polarized light. A lighting device configured to output together with light. 2. A second reflecting mirror for reflecting the light of the second linearly polarized light reflected by the polarizer toward the polarizer is provided, and the light from the second reflecting mirror is divided into ¼ by the polarizer. The illumination device according to claim 1, wherein the illumination device is configured to reflect toward the wave plate.