JPH0728014A - Image projection device - Google Patents

Abstract

PURPOSE:To provide an inexpensive image projection device excellent in image quality by constituting the device so as to make the direction wide in visual angle of characteristics of a liquid crystal panel to coincide with a specific direction. CONSTITUTION:A light source 2 is constituted of a lamp 2a and a reflector 2b. By the light source 2, the reflection type liquid crystal panel 1 is illuminated. By the liquid crystal panel 1, an image light is reflected by controlling a reflection light according to an image signal and a video signal for every pixel. The reflection light (image light) is enlarged and projected on a screen through a projection lens 3. This device is constituted so as to make the direction wide in the visual angle characteristics of the liquid crystal panel to coincide with the direction along a surface formed by the optical axis 4 of the illuminating light and the optical axis 5 of the reflection light. Thus, in spite of that the optical axis 4 of the illuminating light and the optical axis 5 of the reflection light have a prescribed angle between them, a high contrast projection image is provided. Further, it is prefered that an irradiation light is made incident with <=20 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image projection device such as a liquid crystal projector, and more particularly to an image projection device using a reflective liquid crystal panel.

[0002]

2. Description of the Related Art An image projection apparatus of this type has already been disclosed in Japanese Patent Laid-Open No. 61-61.
-13385 and the like. Here, the illumination light projection direction and the reflected light emission direction from the liquid crystal panel are the same,
The illumination light and the reflected light were separated by a beam splitter.

[0003]

However, in the above-mentioned conventional example, since a prism processed product such as a beam splitter is used, there is a drawback that the cost becomes extremely high.

[0004]

Therefore, in the present invention, the illumination light projection direction and the reflected light emission direction from the liquid crystal panel are different and have a predetermined angle, and the illumination light optical axis and the reflected light optical axis are formed. By configuring such that the direction of wide viewing angle characteristics of the liquid crystal panel is aligned with the direction along the plane, a low-cost image projection apparatus with high image quality can be configured.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the basic construction of an embodiment of the present invention. Reference numeral 2 denotes a light source composed of a lamp 2a and a reflector 2b, which illuminates the reflective liquid crystal panel 1. The liquid crystal panel 1 reflects the image light by controlling the reflected light for each pixel according to the image signal and the video signal, and the reflected light (image light) is passed through the projection lens 3 to a screen or the like (not shown). Is enlarged and projected.

FIG. 2 shows a top view of the liquid crystal panel 1, and 6 shows the liquid crystal molecules therein. This liquid crystal panel is a reflective liquid crystal panel using TN liquid crystal, and its liquid crystal molecules 6 are tilted with respect to the panel 1 as shown in the drawing. Arrows EF and GH indicate the directions of the polarization axes of the upper and lower deflectors, and arrows AB and CD indicate the horizontal and vertical directions of the panel 1, respectively. Further, a reflection plate is installed below the lower polarizing plate.

3 and 4 show viewing angle characteristics of the liquid crystal panel 1 in the AB and CD directions, respectively. In the case of the tilt of the liquid crystal molecules as described above, a wider viewing angle characteristic can be obtained in the CD direction. Here, the viewing angle characteristic means the relationship between the incident angle of illumination light and the contrast, and the fact that the incident angle shows a negative value means that the incident side and the reflecting side are reversed.

Therefore, in this example, as shown in FIG. 1, the CD direction having a wide viewing angle characteristic of the liquid crystal panel 1 coincides with the direction along the surface formed by the illumination light optical axis 4 and the reflected light optical axis 5. Is configured. Therefore, in this example, although the illumination light optical axis 4 and the reflected light optical axis 5 have a predetermined angle, a projected image with high contrast can be obtained. In this embodiment, it is preferable that the incident angle of the illumination light is 20 ° or less as shown in FIG.

By the way, in this example, by using a liquid crystal panel provided with a mosaic color filter, it is possible to cope with full-colorization, and while making use of this basic structure, three sheets corresponding to the three primary colors of RGB are used. Full color can also be achieved by using a monochrome liquid crystal panel and a color separation / color synthesis optical system.

The reflection type liquid crystal panel that can be used here is not limited to the TN liquid crystal used in this example, and HFE mode liquid crystal, ferroelectric liquid crystal or the like may be used.

[0011]

As described above, in constructing an image projection apparatus using a reflective liquid crystal panel, the illumination light projection direction and the reflected light emission direction from the liquid crystal panel have a predetermined angle, and the illumination light light is emitted. By configuring the axis so that the direction having a wide viewing angle characteristic of the liquid crystal panel coincides with the direction along the surface formed by the optical axis of the reflected light, an image projection apparatus with high image quality can be configured at low cost.

[Brief description of drawings]

FIG. 1 is a basic configuration diagram showing an embodiment of an image projection apparatus according to the present invention.

FIG. 2 is a top view of the reflective liquid crystal panel of FIG.

FIG. 3 is a diagram showing viewing angle characteristics of a reflective liquid crystal panel.

FIG. 4 is a diagram showing viewing angle characteristics of a reflective liquid crystal panel.

[Explanation of symbols]

 1 ... Reflective liquid crystal panel 2 ... Light source 3 ... Projection lens 4 ... Illumination optical axis 5 ... Reflected optical axis 6 ... Liquid crystal molecule

Claims (1)

[Claims] 1. An image projection apparatus using a reflective liquid crystal panel, wherein an illumination light projection direction and a reflected light emission direction from the liquid crystal panel have a predetermined angle, and an illumination light optical axis and a reflected light optical axis are formed. An image projection apparatus, characterized in that a direction having a wide viewing angle characteristic of a liquid crystal panel is aligned with a direction along a plane.