JPH05323121A - Projection type display device - Google Patents

Abstract

PURPOSE:To obtain excellent polarization characteristics since a polarizing plate, etc., put in a housing together with filling liquid is uniformly cooled without directivity and neither curves nor has strain by itself and the temperature distribution of the whole polarization beam splitter is made uniform. CONSTITUTION:The projection type display device is equipped with the polarization beam splitter which polarizes and splits the light emitted by a light source, and the polarization beam splitter consists of the housing 60h formed of a transparent material, a transparent flat plate 60g which has a polarizing film arranged in the housing so as to obtain a specific angle of incidence, the liquid 60L which is charged in the housing and nearly equal in refractive index to the housing, and a polarizing plate 60p which is arranged on the upstream part of the transparent plate 60g, provided with the polarizing film in the housing on the incidence path of the light emitted by the light source so that both surfaces of the polarizing plate contact the liquid 60L.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection type display device having a projection optical system, and more particularly to a projection type display device characterized by a polarization beam splitter for receiving and polarizing a light beam emitted from a light source.

[0002]

2. Description of the Related Art As a conventional projection type display device, there is one using a reflection type photoconductive type liquid crystal light valve.
Shows an example of the configuration. In the figure, a reflective photoconductive liquid crystal light valve 1 is coupled to a front face of a CRT (cathode ray tube) 2. The CRT writes the image displayed on its front face to the photoconductive layer of each photoconductive liquid crystal light valve through the optical fiber layer. Birefringence occurs in the liquid crystal layer in accordance with the potential of the photoconductive layer, and the shade of the projected image is formed.

On the other hand, a light beam emitted from a light source 3 such as a metal halide lamp passes through a cold mirror 4 and a condenser lens 5 and enters a polarizing beam splitter 6.
The P-polarized component of this incident light passes through the polarization beam splitter 6. Most of the S-polarized light component is bent in the traveling direction by the polarization beam splitter 6 and enters the photoconductive liquid crystal light valve 1. The polarization beam splitter used here is a cube in which one of the two right-angled prisms is provided with a polarizing film on one of the inclined surfaces and the two are bonded to each other. Further, a polarizing plate 7 is provided upstream of the polarization beam splitter 6 to increase the degree of polarization.

Here, if the liquid crystal layer of the photoconductive type liquid crystal light valve 1 has a birefringence corresponding to the image of the CRT, the liquid crystal layer of the photoconductive type liquid crystal light valve is reflected by the reflected light reflected by the photoconductive type liquid crystal light valve. The S polarization component is converted into a P polarization component according to the refractive index. Then, the P-polarized component in the reflected light passes through the polarization beam splitter 6 as it is, so that the P-polarized component, that is, the image by the projection light is projected on the screen 9 through the projection lens 8. In this way, the liquid crystal layer forms an optical switch.

When using a high-intensity light source such as such a metal halide lamp, since optical elements such as a polarization beam splitter and a polarization plate are arranged in the housing of the projection type display device, the polarization plate and the polarization beam splitter are used. A lot of extra light that is not polarized even after passing through (hereinafter referred to as leak light) reaches the downstream optical system, and finally is converted into heat. The polarizing plate 7 upstream of the polarization beam splitter 6 is generally attached to the outer surface of the polarization beam splitter 6 having a large heat capacity in order to prevent heat.

However, since the polarizing plate 7 absorbs about 60% of light, its polarization characteristics are deteriorated by heat. Further, since the polarization beam splitter made of glass has a high light absorption rate and retardation occurs due to internal stress strain due to heat, its polarization effect is limited. Also, since the light quantity distribution of the luminous flux from the metal halide lamp is high in the central part,
Due to heat, the central part of the polarizing plate deteriorates before the surroundings. The polarizing plate 7 is cooled by air to prevent such heating, but only air can be blown along the surface of the polarizing plate 7, and sufficient cooling has not been achieved.

[0007]

SUMMARY OF THE INVENTION In view of the above problems of the prior art, an object of the present invention is to provide a polarizing beam splitter capable of preventing heating by light from a light source and obtaining a sufficient degree of polarization. It is to provide a projection display device.

[0008]

A projection type display device according to the present invention is a projection type display device comprising a polarization beam splitter for polarizing and separating light emitted from a light source, wherein the polarization beam splitter is transparent. A case made of a material, a transparent flat plate having a polarizing film arranged to form a predetermined incident angle in the case, and a refractive index filled in the case and substantially equal to the case. A liquid, and a polarizing plate disposed in the housing and fixed on the upstream side of the transparent flat plate provided with the polarizing film in the incident path of the light emitted from the light source so that both surfaces thereof are in contact with the liquid. Is characterized by.

[0009]

In the projection type display device according to the present invention, the incident light emitted from the light source is the casing of the polarization beam splitter,
It reaches a flat plate coated with a polarizing film through a liquid, a polarizing plate, and a liquid, and the P-polarized component of the incident light goes straight on,
Only the S-polarized component can be changed in direction.

In the light incident process, the light incident on the polarizing plate is absorbed by the polarizing plate body except for a single vibration component. Then, the energy of the absorbed light is converted into heat in the polarizing plate. The heat converted here tries to be conducted and transferred so as to be stably in an equilibrium state, but since both surfaces of the polarizing plate are in contact with a liquid having a larger heat capacity than gas etc., heat transfer is smoothly performed, The temperature rise of the polarizing plate itself is prevented. Also, the natural convection of the liquid makes this heat transfer effect more effective.

The light that has passed through the polarizing plate is further received by the glass plate and the glass housing, but since the housing is filled with the liquid, the local temperature rise is prevented and the initial polarization characteristics are reduced. Retained.

[0012]

FIG. 2 is a diagram showing the structure of a polarization beam splitter in a projection type display apparatus according to an embodiment of the present invention. In the figure, such a polarization beam splitter has, for example, a rectangular parallelepiped housing 60h made of a transparent material such as glass, and the housing 60h is filled with a transparent liquid 60L. In consideration of the refractive index of the liquid, a transparent flat plate 60g such as a glass plate on which a multilayer film having polarization characteristics is vapor-deposited is erected upright on the diagonal line of the housing 60h. In addition, in order to clarify the position of the flat plate 60g, the drawing is drawn by separating the upper surface member of the housing 60h.

Further, in the housing 60h, a polarizing plate 6 is provided upstream of the flat plate 60g in the incident path of the light emitted from the light source.
0p is arranged so that both surfaces thereof are in contact with the liquid 60L. As a method of fixing the polarizing plate 60p, the side surface thereof is directly fixed to the housing (for example, both side surfaces of the polarizing plate are fitted and fixed in a groove provided in the housing) or via a separate fixing means described later. You may fix it.

The liquid 60L filled in the housing is
It must be transparent, and in addition, low toxicity and low volatility (vapor pressure), high flash point, and cost performance are taken into consideration. For example, ethylene glycol C ² H ⁶ O ² (refractive index n = 1.43) and glycerin C ³ H ⁵ O ³ (n = 1.474) are used as matching liquids for CRT projection. Also suitable for liquids. Other liquids include benzyl alcohol C ⁷ H ⁸ O (n = 1.54).

3 and 4 show the polarizing plate 60p shown in FIG.
FIG. 3 shows an embodiment in which the fixing means is fixed by using a separate fixing means, FIG. 3 is a sectional view in a state where it is incorporated in a polarization beam splitter, and FIG. 4 is a perspective configuration diagram of the fixing means alone. Is shown. As shown in FIG. 4, a groove 70b is provided inside the U-shaped frame 70a, and the polarizing plate 60p can be fitted into the groove 70b.

On the other hand, in the case of being incorporated in the polarization beam splitter 60, the fixing means 70 in which the polarizing plate 60P is inserted as shown in FIG. 3 may be fixed to the light incident side inner surface of the housing 60h. 5 and 6 show another embodiment in which the polarizing plate 60p shown in FIG. 2 is fixed by using a separate fixing means, and FIG. 5 is a sectional view showing a state where the polarizing plate 60p is incorporated in a polarization beam splitter. FIG. 6 is a perspective view showing the fixing means alone and the polarizing plate.

As shown in FIG. 6, two pins 80b are provided on the upper surface of the pair of linear members 80a in the axial direction, and each pin 80b comprises a head portion 80bh and a neck portion 80bk. On the other hand, when it is incorporated in the polarization beam splitter 60, as shown in FIG.
The pin 80b is fixed to a corner of the light incident side inner surface of the polarizing plate 60p, and the pin 80b is fitted into the circular hole 61a of the hole 61 provided in the polarizing plate 60p. Move and fix 60p.

The means for fixing the polarizing plate 60p is not limited to the above embodiment, but the polarizing plate 60p
Any means may be used as long as both sides of p can come into contact with the liquid and have excellent heat resistance and do not affect the polarization characteristics. As can be seen from the above description, in the polarization beam splitter according to the present invention, the space inside the housing is divided into three regions by the flat plate 60g provided with the polarizing film and the polarizing plate 60p, but each space is completely divided. If it is possible to move the liquid 60L that is filled with the fluidity instead of being hermetically closed, the temperature distribution becomes uniform due to the natural convection of the liquid, and the distortion of the components due to the generation of partial thermal stress. Does not occur, and the initial polarization characteristics can be maintained.

[0019]

As described above, according to the projection type display device of the present invention, a liquid crystal having a refractive index substantially equal to that of the housing is filled in a housing formed of a transparent material, and a polarizing film is formed. Since both surfaces of each of the transparent flat plate having a transparent plate and the polarizing plate separately provided for increasing the degree of polarization are in contact with the liquid over the entire area, each of the both surfaces is uniformly cooled by the liquid, It is possible to prevent warpage and distortion due to thermal stress caused by the temperature gradient between the two surfaces.

Further, even if the filled liquid has a partial temperature rise due to heat transfer from a polarizing plate or the like, its natural convection has the effect of stabilizing the temperature distribution in a uniform equilibrium state. The temperature distribution becomes uniform even for the entire splitter, and as a result, good polarization characteristics with less internal distortion can be obtained. As a result, it is possible to obtain a projection type display device with good image quality.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a conventional projection type display device using a reflection type.

FIG. 2 is a perspective view showing a configuration of a polarization beam splitter according to the projection type display device of the present invention.

FIG. 3 is a cross-sectional view showing a state in which a polarizing plate is arranged and fixed in a housing via a fixing means of an embodiment.

FIG. 4 is a perspective view of the fixing means alone shown in FIG.

FIG. 5 is a cross-sectional view showing a state in which a polarizing plate is arranged and fixed in a housing through a fixing means of an embodiment.

FIG. 6 is a perspective configuration diagram of the fixing means alone shown in FIG.

[Explanation of symbols]

 1 Photoconductive Liquid Crystal Light Valve 2 CRT 3 Light Source 4 Cold Mirror 5 Condenser Lens 8 Projection Lens 9 Screen 60 Liquid Filling Polarization Beam Splitter 60g Transparent Flat Plate with Polarizing Film 60h Housing 60L Liquid 60P Polarizing Plate 61 Hole 61a Circular Hole 61b Length Hole 70 Fixing means 70a U-shaped frame 70b Groove 80 Fixing means 80a Straight member 80b Pin 80bh Head 80bk Neck

Claims (2)

[Claims] 1. A projection type display device comprising a polarization beam splitter for polarization-separating light emitted from a light source, wherein the polarization beam splitter includes a housing made of a transparent material, and a housing formed in the housing. A transparent flat plate having a polarizing film arranged to form a predetermined incident angle, a liquid filled in the housing and having a refractive index substantially equal to that of the housing, and emitted from the light source in the housing. A projection type display device comprising: a polarizing plate whose both surfaces are arranged and fixed so as to be in contact with the liquid at an upstream side of a transparent flat plate provided with the polarizing film in a light incident path. 2. The means for arranging and fixing the polarizing plate so that both surfaces thereof come into contact with the liquid is fixed by fitting the polarizing plate into the fixing means fixed in the housing. Item 1. The projection display device according to item 1.