JPH0622824Y2 - LCD projector device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a liquid crystal projector device for projecting light of a short arc discharge lamp reflected by a concave mirror onto a liquid crystal plate.

[Prior art and its problems]

For example, a xenon short arc discharge lamp has a small arc bright spot formed at the tip of the cathode during lighting and is close to a point light source, and it is possible to easily diffuse or concentrate light using an optical system. In addition, since it has the advantages of high brightness and excellent color rendering properties, it has attracted attention as a light source for liquid crystal projector devices and has been put to practical use. In such a liquid crystal projector device, as shown in FIG. 1, the xenon short arc discharge lamp 1 is arranged such that its arc bright point K coincides with the focal point F of the parabolic concave mirror 2, and the parabolic concave mirror 2 is reflected almost in parallel. Light is projected on the liquid crystal plate 3. Then, the image formed by the light passing through the liquid crystal plate 3 is projected on the screen through a projector lens (not shown). Here, since the liquid crystal plate 3 is vulnerable to heat and malfunctions when the temperature becomes high, the concave mirror 2 has a multilayer film 21 in which a high refractive index layer and a low refractive index layer are alternately arranged on the inner surface thereof, and a xenon short arc is formed. A cold mirror is used that transmits the heat rays emitted from the discharge lamp 1 rearward and reflects visible light.

By the way, the light that enters at the small incident angle θ ₁ and is reflected by the top side 2a of the concave mirror 2 mainly irradiates the central portion of the liquid crystal plate 3, and the light that enters at the large incident angle θ ₂ and reflected by the opening side 2b is The peripheral part of the liquid crystal plate 3 is mainly irradiated. On the other hand, multilayer film
Reference numeral 21 reflects or transmits light in a specific wavelength range according to the optical film thicknesses of the high refractive index layer and the low refractive index layer, but its optical interference action depends on the incident angle θ of the light on the multilayer film 21. That is, the wavelength range of reflection or transmission differs depending on the incident angle θ. FIG. 2 shows TiO ₂ coated with 42 layers
/ SiO ₂ layer, the incident wavelength at an incident angle of 0 ° is 47
Incident of a multilayer film in which a second multilayer film that reflects light in a predetermined wavelength range centering on 620 nm light is overlaid on a first multilayer film that reflects light in a predetermined wavelength range centering on 0 nm light Although it exhibits angle dependence, the reflected light shifts to the short wavelength side as the incident angle θ increases. That is, in FIG. 1, the light that mainly irradiates the peripheral portion of the liquid crystal plate 3 has a large incident angle θ ₂ , so that the light of 650 nm or more is small. Next, FIG. 3 shows an example in which the spectral distributions at the peripheral portion and the central portion of the liquid crystal plate 3 were actually measured. In the range of 600 nm or more, the solid line indicates the intensity of the central portion by a dotted line. The strength of the peripheral portion shown is low. As a result, there is a problem that the central part and the peripheral part of the image projected on the screen have different color tones, the peripheral part is bluish and the color temperature is high, and the central part is reddish.

Therefore, for example, if the number of layers of the multilayer film is increased to widen the reflection region and the light with a large incident angle shifts to the short wavelength side so as not to reach the visible light region, the above-mentioned problems can be solved,
The overall film thickness is increased, the heat resistance of the multilayer film is reduced, and the cost is increased.

[Purpose of device]

Therefore, the present invention, without increasing the number of layers of the multilayer film,
An object of the present invention is to provide a liquid crystal projector device capable of obtaining a beautiful image with no color tone variation in the central portion and the peripheral portion of the screen.

[Constitution of the device and its action]

In the liquid crystal projector device of the present invention, the multilayer film formed of the high-refractive index layer and the low-refractive index layer formed on the inner surface has a thin film on the top side and a thick concave film on the opening side. It is characterized by comprising a short arc discharge lamp arranged so that the points coincide with each other, and a liquid crystal plate on which the reflected light of the concave mirror is projected.

That is, the film thickness of the multilayer film formed on the inner surface of the concave mirror is
Since the opening side is thicker than the top side, the incident angle from the arc bright spot of the short arc discharge lamp is large and the light reflected on the opening side has less "deviation" to the short wavelength side, For example, even in the visible light region with a wavelength of 600 nm or more, the incident angle is small and the intensity is almost equal to the intensity of light reflected on the top side. Therefore, variations in color tone between the central portion and the peripheral portion of the screen are eliminated, and a beautiful image can be obtained.

〔Example〕

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

The basic configuration of the liquid crystal projector device according to the present invention is the first
As shown in the figure, the thickness of the multilayer film 21 is thin on the top side 2a where the incident angle θ is small, as shown in the film thickness ratio in Table 1.
The opening side 2b side where the incident angle θ is large is thick.

Here, the multilayer film 21 is made of Ti coated in 42 layers.
Λ is formed on the first multilayer film that is composed of an O ₂ / SiO ₂ layer and reflects light in a predetermined wavelength range centered on light having a wavelength of λ ₀ nm.
_A second multilayer film that reflects light in a predetermined wavelength range centering on 0'nm light is laminated and coated, and the number of layers is the same as that of the conventionally used multilayer film. Then, the film thickness ratio is represented by the ratio of the film thickness in the region of θ = 20 ° to 1. FIG. 5 shows the case where the multilayer film 21 is incident at a film thickness ratio of 1.00 at θ = 20 ° (shown by a solid curve) and is incident at a film thickness ratio of 1.10 at θ = 60 °. The calculated values of the reflectance in the case (displayed by a dotted curve) are shown, but both have almost the same reflection characteristics.

Next, FIG. 4 shows an example in which the spectral distributions at the peripheral portion and the central portion of the liquid crystal plate 3 are actually measured. The intensity of the central portion shown by the solid line is different from that of the peripheral portion shown by the dotted line. 60
It is almost the same in the range of 0 nm or more, and it can be understood that the effect is great by comparison with FIG. 3 of the conventional example.

[Effect of device]

As described above, the liquid crystal projector device of the present invention is provided with a concave mirror in which the thickness of the multilayer film formed of the high refractive index layer and the low refractive index layer formed on the inner surface is thick on the opening side even on the top side, and the concave mirror. Since it is equipped with a short arc discharge lamp arranged so that the arc bright spot coincides with the focal point of, and a liquid crystal plate onto which the reflected light of the concave mirror projects, the angle of incidence of the arc bright spot of the short arc discharge lamp on the concave mirror The reflectance is almost the same regardless of the size. Therefore, the spectral distribution of the light irradiating the liquid crystal plate is almost equal in the central part and the peripheral part,
The central part and the peripheral part of the screen have the same color tone, and a beautiful image can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a liquid crystal projector device, FIG. 2 is an explanatory diagram of incident angle dependence of reflectance, FIGS. 3 and 4 are explanatory diagrams of spectral distribution, and FIG. 5 is an explanatory diagram of reflectance. . 1 ... Short arc discharge lamp, K ... Arc bright spot 2 ... Concave mirror, 21 ... Multilayer film, 2a ... Top side 2b ... Aperture side, F ... Focus, 3 ... Liquid crystal plate

Claims (1)

[Scope of utility model registration request] 1. A concave mirror having a thin film on the apex side and a thick concave film on the opening side, and the arc luminescent spot coincides with the focal point of the concave mirror. And a short arc discharge lamp arranged to
A liquid crystal projector device comprising: a liquid crystal plate onto which reflected light from a concave mirror is projected.