JPH01157687A - Projection type display device - Google Patents

Abstract

PURPOSE:To use a reflecting type light valve and, simultaneously, to obtain a full-color projecting type display device with a compact optical system and a little optical elements by using wavelength separating elements combined in a cross shape. CONSTITUTION:A cross-shaped wavelength separating element 101 is located in a position equivalent to respective reflecting type light valves 102. A projecting light 201 to be made incident on the reflecting type light valves 102 is emitted from a light source 103, and the light is separated from a modulated projecting light 203 by a separating means 202. The cross-shaped wave-shaped wavelength separating element 101 has two works to synthesize the modulating projecting light 203 two-dimensional-modulated by the light valves 102 corresponding to a color-separating light and, in addition, to separate the light source light to a color light. An image needs to be prepared so that the light valves reflected by the cross-shaped wavelength separating element 101 and the transmission light valves can be mutually made into mirror images. Thus, the light path length from respective reflecting type light valves 102 to a projecting lens can be made shortest, and the whole device can be made compact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the configuration of a projection display device that combines a plurality of reflective light valve images and projects a color image.

[Conventional technology]

A projection type display device using a conventional reflective light valve was published in 1988 by Dentsutsu ('6 Academic Conference, General National Conference Lecture Proceedings,
Volume 5, P, 66 (1983), JP-A-58-150
937; [Problems to be Solved] However, with the above-mentioned conventional technology, in cases such as full-color display that requires multiple wavelength separations, multiple wavelength separation elements must be arranged in series along the optical axis, and the entire device There was also a problem that the projection lens system had a long optical path between the projection lens and the light valve, requiring a long projection distance for enlarged projection.

Therefore, the present invention is intended to solve these problems, and its purpose is to provide a projection type display device that has a small number of optical elements and can perform large enlarged projection with a short projection distance. There is a particular thing.

Means for Solving Problem c] The projection type display device of the present invention uses a polarized beam beam as a means for separating the projection light source light and the modulated projection light.

It is characterized by having a twisted nematic liquid crystal as the display mode of the reflective light valve, and two types of wavelength separation elements placed at equivalent optical positions from each reflective light valve and combined in a cross shape.

[For production]

The basic configuration of the present invention is shown below. As shown in Figure 2,
A cross-shaped wavelength separation element 101 is connected to each reflective light valve 10.
It is placed in a position equivalent to 2. Projection light 201 entering the reflective light valve is emitted from light source 103 and separated from modulated projection light 203 by separation means 202 .

According to such a configuration, the optical path length from each reflection type light beam 1 to the projection lens becomes the shortest, and the entire apparatus becomes compact. In addition, the cross-shaped wavelength separation element not only separates the light source light into colored light, but also combines the modulated projection light that is two-dimensionally modulated by the light valve corresponding to the separated color light.
perform one function. Note that the images must be formed so that the light valve that receives reflection and the light bulb that receives transmission from the cross-shaped wavelength separation element are mirror images of each other.

〔Example〕

Embodiment 1 FIG. 1 is a configuration diagram of a projection type display device of the present invention. Two types of tichroic mirrors combined in a cross shape 10
7.108, three reflective light valves 102 are installed at optically equivalent positions. Projection light source 10
The projection light emitted from the polarizing beam splitter 101
The S-polarized light is reflected, and the P (li) light is transmitted.The polarizing beam splitter is a wideband type that works in the visible light range.The wavelength separation element is a very thin glass (for example, Corning Microsheet). It is a combination of a blue reflector (dashed line 107 in Figure 1) and a red reflector (solid line 108 in Figure 1) in a cross shape.109 focuses the projected light. 105 is a projection lens, and 106 is a screen.

Note that the wavelength separation element may be a cube-shaped prism coated with two different dichroic coatings. This is shown in FIG. The cube prism 301 also has the advantage that the cross portion of the coating 302 is less likely to be projected onto the screen.

The white S-polarized light reflected by the polarizing beam splitter is separated by the dichroic mirror into S-polarized color light, red on the top, blue on the bottom, and green on the left in FIG. The reflective light valve uses a 45° twisted nematic liquid crystal, and the director of the liquid crystal is aligned in the S polarization direction on the incident surface. Figure 4 shows a sectional view of the light valve used in the Honjitsu 74i PA, and Table 1 shows its specifications.

Table 1 Substrate TPT (thin film transistor) integrated active matrix liquid crystal 45°TN (twisted nematic) PCH (phenylcyclohexane) system liquid crystal layer cap Red 5.5μ Midorikawa 4.6μ Blue 3.8μ Reflector Pixel An aluminum electrode that also serves as an electrode (a passivation film is placed on the surface) Each pixel is driven by a thin film transistor 401, and when the voltage is zero, the incident S-polarized light reaches the reflective surface 402 with a 45° twist, and the optical path of reflection after reflection is changed. The light then exits from the incident surface again. Therefore, the polarized light at the time of emission becomes the S-polarized light at the time of incidence, and the S-polarized light is reflected by the polarizing beam splitter toward the light source and does not contribute to projection. Note that 403 is a liquid crystal layer, 404
is a transparent substrate, and 405 is a counter transparent electrode.

Next, when a voltage is applied and the tie lefter of the liquid crystal rises in the direction of the electric field, the S-polarized incident light undergoes birefringence in the optical path back and forth in the cell, and the output light becomes elliptically polarized light. However, if a high voltage is applied, the tie-lefter will completely rearrange itself in the direction of the electric field, so this must be avoided. In the polarizing beam splitter, only pixels to which a polarizing voltage is applied that transmits and projects P-polarized light are displayed brightly.

The light bulb using a thin film transistor used here is manufactured by Nikkei Electronics L-Lonics No. 351 (1984).
)P, has the structure shown in 21.1, and the pixel electrode is formed of a reflective metal electrode.

The metal electrode preferably uses an inert metal such as chromium, or is preferably made of aluminum or the like with a transparent protective thin film provided thereon. Furthermore, by placing an insulating layer on top of the wiring electrode and placing the pixel electrode on top of it, it is also possible to effectively utilize the pixel area.

In the manner described above, a voltage is applied to each pixel according to image information to form an image. After the above-mentioned image formation is performed in each of the red, blue, and green light valves, the colors are synthesized by a tichroic mirror or a tichroic prism, and the polarized beam splitter transforms the image into an intensity-modulated image@projected light onto the screen. image on top.

Embodiment 2 Embodiment 2 is a simple matrix light valve using a 270° twisted nematic liquid crystal as a reflective light valve. This high twist angle nematic liquid crystal mode was developed as STN (super twisted nematic) mode in 1985, SID DIGEST.
P, 120, or similar mode for 1986 S
ID DIGEST'P, 122.

Since the STN mode switches light using an ECB (field effect birefringence) type, the wavelength dependence of the switching ratio cannot be ignored. However, even a simple linear matrix, which has excellent threshold characteristics with respect to voltage, has the advantage of being able to drive many pixels. In this embodiment, as shown in FIG.
In order to divide the G and B wavelength regions into three light valves,
A reduction in the switching ratio for broadband wavelength light can be avoided. Table 2 shows the specifications of the reflective light valve used in this example, and FIG. 5 shows its cross-sectional structure. 5
01 is a reflecting plate that reflects incident light. 502 is TN
The liquid crystal layers 503 and 504 are X and Y electrodes. In the case of FIG. 5, the reflection plate is provided on the outside of the panel, but it may also be installed on the inside of the panel, serving also as the Y-side electrode. Furthermore, since the optical path is twice that of the transmission type, the retardation setting is half that of the transmission type.

Table 2 Display mode 270°TN (STN) simple matrix polarizing element Polarizing beam splitter liquid crystal PCI (phenylcyclohexane) mixture Δn 0.09 Liquid crystal layer gap Red 5.5μ Midorikawa 4.6μ Blue 3. 8μ reflective plate Aluminum surface reflective treatment mirror image
Prime number 600 x 400 - In this embodiment, the liquid crystal layer gap is changed according to the wavelength range in charge, or the same effect can be produced by adjusting the Δn of the liquid crystal.

The liquid crystal light valve is driven in the same manner as a normal S'FN to form an image. The method of color composition of images is performed in the same manner as in the first embodiment.

〔Effect of the invention〕

As described above, according to the present invention, by using wavelength separation elements combined in a cross shape, a full-color projection display device can be realized with a compact optical system and a small number of optical elements even if a reflective light valve is used. Furthermore, since the distance between the light valve and the projection lens can be shortened, projection can be performed over a short distance even at the same projection magnification.

Furthermore, by using twisted nematic liquid crystal, it is possible to provide a projection type display device with high contrast and excellent halftone expression.

Furthermore, by using a simple 7-trix display with excellent multiplex link properties, cost reduction can be achieved.

Furthermore, basically only one light source is required for projection, and this method is advantageous in terms of maintenance costs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a projection type display device of the present invention. FIG. 2 is a schematic diagram of the projection type display device of the present invention. FIG. 3 is a configuration diagram of a projection type display device (using a dichroic prism) of the present invention. FIG. 4 is a sectional view of the TPT reflective light valve. FIG. 5 is a sectional view of the STN simple matrix reflective light valve. 101...Polarizing beam splitter 102...Reflection type light valve (consisting of twisted nematic liquid crystal) 103...Projection light source 105...Projection lens and above Applicant Seiko Epson Corporation

Claims (1)

[Claims] In a projection display device consisting of a plurality of reflective light valves for image formation, a wavelength separation element for combining colored light, a projection optical system, and an illumination optical system, polarized light is used as a means to separate the projection light source light and the modulated projection light. The display mode of the beam splitter and reflective light valve is characterized by having a twisted nematic liquid crystal and two types of wavelength separation elements placed at equivalent optical positions from each reflective light valve and combined in a cross shape. Projection type display device.