JPH02211418A - Optical device - Google Patents

Abstract

PURPOSE:To simplify the constitution of the projection type optical system and to reduce the size thereof by using space modulating elements in a reflection mode by optical reflecting elements and executing optical path sepn. by polarized light separating elements. CONSTITUTION:The optical system is constituted, successively from the side near a light source 101, of a polarizer 102, the polarized light separating element 103, a color separating element 104, the 1st to 3rd space modulating elements 108 to 110, and the 1st to 3rd optical reflecting elements 105 to 107 corresponding thereto. The color light of a lamp 501 is polarized to linearly polarized light by the polarizing plate 102 and is separated to red, green and blue by a dichroic prism 104 at the time of projection. These light rays are modulated by the respectively corresponding space modulating elements 108 to 110 and are then reflected by the optical reflecting elements 105 to 107 so as to be synthesized by the polarized separating element 103. The synthesized light is imaged onto a screen 503 by a projecting lens 502. The constitution is, therefore, simplified and the device is miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the configuration of an optical system of a projection type display device using a field effect spatial modulation element, typified by a liquid crystal light valve.

[Prior Art 1 The configuration of the optical system of a conventional projection display device is shown in FIG.
Colored light emitted from the lamp 501 is separated into three colors of red, green, and blue by dichroic mirrors 601 and 602. The respective lights are transmitted through spatial modulation elements 608, 611, and 61.
After being modulated by 4, dichroic mirrors 605 and 60
6 and is imaged onto a screen 503 by a projection lens 502.

In FIG. 4, 603 and 604 are reflecting mirrors for bending the optical path, and 607.609.610.612.
6i3.615 is a polarizing plate used in combination with a spatial modulation element to modulate light.

[Means for Solving the Problem 1] However, the above-mentioned conventional technology has the problem that the entire device becomes large because the number of elements constituting the optical system is large and their spatial arrangement is wasteful. was there.

SUMMARY OF THE INVENTION The present invention is intended to solve these problems, and an object of the present invention is to provide a small-sized projection display device with a simple configuration.

[Means to solve the problem]

The optical device of the present invention includes a light source 101 as shown in FIG.
From the side closest to Second and third spatial modulation elements 1
08, 109, and 110, and the first, second, and third light reflecting elements 105, 106, and 10 corresponding to the three spatial modulation elements.
7 is arranged.

Furthermore, regarding the first, second, and third spatial modulation elements,
Just before or after that, the quarter wave plate 201.20
2.203 is added.

Furthermore, the first, second, and third spatial modulation elements are comprised of liquid crystal light valves.

[Function 1] According to the above configuration of the present invention, the spatial modulation element is used in the reflection mode by the light reflection element, and the optical path is separated by the polarization element and the polarization separation element, so that the optical system becomes small.

〔Example〕

FIG. 3 shows a projection type display device using the optical device of the present invention.

The colored light emitted from the lamp 501 becomes linearly polarized light (referred to as P polarized light) by the action of the polarizing plate 102, and the colored light emitted from the polarizing prism 10
3 and reaches the dichroic prism 104. Due to the action of the prism, colored light is separated into red, green, and blue.
The corresponding liquid crystal light valves 108.109.
1.10 then mirror 105.106.10
7't' is reflected and passes through the dichroic prism 104 again to reach the polarizing prism 103. At this time, the polarization of the colored light is approximately S due to the action of the liquid crystal light valve.
It is polarized light. Therefore, due to the action of the polarizing prism 103, the colored light is reflected and imaged onto the screen 503 via the projection lens 502.

FIG. 5 is a diagram showing the operation of the liquid crystal light valve. The liquid crystal light valve 301 is a 45° TN cell, and the product Δnd of birefringence Δn and thickness d is.

The brightness contrast is set to be sufficiently high. The light valve 301 receives linearly polarized light 30 of P polarization.
4 is incident, the polarized light 304 passes through the light valve 301 twice by the mirror 302, so that a light 305 close to S-polarized light is obtained (Fig. 5(a)). When applied, the polarizing effect of the light valve disappears, so light close to P-polarized light is obtained (
Figure 5(b)).

FIG. 6 is a diagram showing the operation of a liquid crystal light valve having a different structure, which is used in the configuration shown in FIG. 3 with a quarter-wave plate added. The liquid crystal light valve has a structure in which the long axes of molecules are aligned in the same direction and the product Δnd of birefringence Δn and thickness d satisfies the following formula.

Δnd = (1/4 + m/2) L where 1m is an integer of 0 or more. Further, the long axis direction of the molecule is set to form approximately 45° with the direction of the incident linearly polarized light.

To the light valve 301, via a quarter wavelength plate 401,
When P-polarized linearly polarized light 304 is incident, the polarized light 304 passes twice through a quarter-wave plate and a light valve having the same effect as a quarter-wave plate, respectively, by the mirror 302.
Light 305 close to P-polarized light is obtained (Figure 6(a))
. Furthermore, when a voltage 303 is applied to the light valve, the birefringence effect of the light valve disappears, so that light close to S-polarized light is obtained (FIG. 6(b)).

Note that although a liquid crystal light valve is used as an example of the spatial modulation element here, this is only one example.

[Effects of the Invention] As described above, according to the present invention, spatial modulation is performed in reflection mode by the light reflection element! The polarization state of the light is controlled by the birefringence effect of the spatial modulation element, and the optical path is separated by the polarization separation element, so the optical device can be made smaller without sacrificing conventional performance. It becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an optical device of the present invention. FIG. 2 is a perspective view showing the optical device of the present invention. FIG. 3 is a perspective view showing an embodiment of the optical device of the present invention. FIG. 4 is a perspective view showing a conventional optical device. FIGS. 5(a) and 5(b) are diagrams showing the operation of a liquid crystal light valve in an embodiment of the present invention. Figures 6(a) and (b3 are diagrams showing the action of a liquid crystal light valve with a different structure in one embodiment of the present invention. ...Light source...Polarizer...Polarization separation element...Color light separation Element...Light reflecting element 106, LOT, l08, 109, 110, 201, 202, 203, 501, 502, 503, 607, 608, 609, 301, 302, 303, 401, light reflecting element・Light Reflective element, spatial modulation element, spatial modulation element, spatial modulation element, 1/4 wavelength root, 174 wavelength plate, l/4 wavelength plate, lamp, projection lens, screen, polarizing plate, spatial modulating element, polarizing plate, liquid crystal light Valve-to-voltage/wave plate No. 1 Kasumi J3 Fig. 2 ≠ Fig. 85 country (2) No. 6121 (^) 8sri2 (b) 4ot1/# long plate 16 times (S)

Claims (3)

[Claims] (1) In an optical device that separates, modulates, and combines light,
a polarizing element, a polarization separation element, a color separation element, a first, a second,
An optical device comprising a third spatial modulation element and first, second, and third light reflection elements corresponding to the three spatial modulation elements. (2) The optical device according to claim 1, further comprising a quarter-wave plate added immediately before or after the first, second, and third spatial modulation elements. (3) The optical device according to claim 1, wherein the first, second, and third spatial modulation elements are comprised of liquid crystal light valves.