JPH05288902A - Liquid prism - Google Patents

Abstract

PURPOSE:To prevent an image from being distorted owing to a liquid prism by reducing the vertical temperature irregularity of the liquid in the liquid prism and making the refractive index distribution uniform. CONSTITUTION:On the 1st incidence surface 6a of a prism container 6 filled with liquid, a heat absorbing member 13 is provided on the lower part of an unnecessary-light irradiating area S between circles A and B irradiated by a light source 1. When luminous flux with Gaussian distribution intensity is made incident from a light source 1, the liquid which is made warm on a prism center part by the light absorption of a polarizing plate 8, etc., rises by convection to generate a vertical temperature difference. The heat absorbing member 13, however, absorbs unnecessary light positively, so the liquid at the lower part in the prism container 6 can be heated and the liquid temperature at the lower part in the prism container 6 rises to approximate to the liquid temperature at the upper part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid prism used in an optical system having a light source of high brightness such as a projector, and in particular, a non-uniform refractive index caused by a vertical temperature distribution generated in the liquid prism. It relates to an improved liquid prism.

[0002]

2. Description of the Related Art Conventionally, in an optical system using a high-intensity light source, a liquid prism filled with a liquid is used as a measure against heat generation of an optical component due to absorption of light from the light source. For example, in the optical system of the display device using the reflective liquid crystal panel shown in FIG. 5, a liquid prism is used as the polarization prism.

In the figure, the light from the light source 1 is blue, green,
The red, dichroic mirrors 2, 2, 2 sequentially separate the lights, and the R, G, B lights are incident on the R, G, B liquid crystal panels 4 via the liquid prism 3. The polarized light of the reflected light from the liquid crystal panel 4 changes corresponding to the image of each liquid crystal panel 4, and only the light whose polarized light has changed is transmitted through the liquid prism 3 and guided to the projection lens 5. Then, the images of the R, G, and B liquid crystal panels 4 are projected and combined on the screen (not shown) by the three projection lenses 5.

As shown in FIG. 6, the liquid prism 3 comprises a rectangular cylindrical glass prism container 6 filled with a liquid 7 having a refractive index substantially the same as that of the prism container 6.
A polarizing plate 8 is provided on one side surface of the prism container 6 on the light source 1 side.
A polarizing mirror 9 that reflects the linearly polarized light that has passed through the polarizing plate 8 to the liquid crystal panel 4 is housed in the prism container 6.

[0005]

By the way, the liquid 7 filled in the liquid prism 3 includes ethylene glycol, glycerin, benzyl alcohol, etc., which have a large change in refractive index with temperature. According to the measurement, a change in the refractive index of 0.0003 to 0.0005 / degree occurs. Therefore, when the temperature unevenness occurs in the liquid 7 in the liquid prism 3, the uneven refractive index distribution appears.

However, in a projection type projector or the like, the light source 1 is a high brightness one such as a metal halide lamp in order to increase the brightness of the image, and the liquid prism 3 is irradiated with strong light. To be done. Therefore, the temperature rise of the liquid prism 3 is large due to the heat absorption by the polarizing plate 8 and the like. Moreover, the intensity of the luminous flux emitted from the light source 1 has a Gaussian distribution with a strong center. Therefore, the warmed liquid 7 in the central portion of the liquid prism 3 moves to the upper portion of the liquid prism 3 by convection, while the liquid 7 at the lower portion of the liquid prism 3 stays with little temperature rise and the liquid prism 3 Different temperature distributions occur in the vertical direction.

In the conventional example of FIG. 6, the light source 1 is turned on,
After the liquid prism 3 reached a thermal steady state, the temperature distribution of the liquid 7 in the liquid prism 3 in the vertical direction was measured, and it was as shown by the curve W in FIG. From this, a change in the refractive index due to the temperature unevenness occurs in the vertical direction of the liquid prism 3, and a correct image cannot be formed on the screen.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a liquid prism capable of reducing the temperature unevenness in the vertical direction in the liquid prism and achieving a uniform refractive index distribution. To do.

[0009]

In order to achieve the above object, the first liquid prism of the present invention comprises a light separating / combining means such as a polarizing mirror for separating and combining light beams in a prism container filled with liquid. A liquid prism provided, wherein a heat absorbing member is provided at a lower side portion of an irradiation area of unnecessary light irradiated to a peripheral portion of the first incident surface of the prism container on which a light flux from a light source is incident. Is.

The second liquid prism of the present invention is a liquid prism having a light separating / combining means such as a polarizing mirror for separating and combining the light beams in a prism container filled with the liquid. On the first incident surface of the prism container on which is incident, a reflecting member is provided in a region on the upper side of the irradiation area of unnecessary light irradiated to the peripheral portion thereof.

[0011]

In the first liquid prism of the present invention, since the absorbing member is provided in the lower part of the irradiation area of the unnecessary light incident on the first incident surface of the prism container, the unnecessary light is absorbed by this heat absorbing member. The liquid under the prism container can be heated by positively absorbing the liquid. Therefore, not only the liquid in the central portion is warmed by the light flux having a strong Gaussian distribution in the central portion, but also the liquid in the lower portion of the prism is warmed by the heat from the heat absorbing member, and the temperature difference between the upper and lower sides in the prism container decreases , The temperature distribution is flattened.

Further, in the second liquid prism of the present invention, since the reflecting member is provided in the upper portion of the irradiation area of the unnecessary light incident on the first incident surface of the prism container, the first incident surface Unnecessary light incident on the upper side can be reflected by the reflecting member, and the incident heat on the upper side of the prism container is reduced. For this reason,
The fluid warmed by the Gaussian luminous flux rises due to convection, and the temperature unevenness in which the upper side of the prism container becomes hot is reduced.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. First, a first embodiment of the present invention will be described with reference to FIGS. This embodiment is an example in which a liquid prism is applied as a polarizing prism to an optical system of a projection type projector using a reflection type liquid crystal panel.

In the perspective view of FIG. 1 and the plan sectional view of FIG. 2, reference numeral 1 denotes a high-intensity light source such as a metal halide lamp. A liquid prism 10 is provided in front of the light source 1, and both sides of the liquid prism 10 are provided. The liquid crystal panel 4 and the projection lens 5 are arranged so as to sandwich this. The liquid prism 10 has a rectangular cylindrical cylindrical glass container 6, and the prism container 6 is filled with a liquid 7 having a refractive index substantially the same as that of the prism container. As the liquid 7, a mixed liquid of ethylene glycol, glycerin, benzyl alcohol, or the like is used.

A cooling unit 11 is formed on the upper portion of the prism container 6 and a support 12 is formed on the lower portion of the prism container 6.
And is placed on a support (not shown) via the. A heat insulating material is used for the support 12 so that the heat of the prism container 6 does not escape to the support base side. Or support 12
You may make it form the air layer for heat insulation in. Also,
A polarizing plate 8 is attached to the inner surface of the first incident surface 6a, which is one side surface of the prism container 6 irradiated with the light flux from the light source 1. Further, in order to reflect the linearly polarized light that has passed through the polarizing plate 8 and make it enter the liquid crystal panel 4, a polarizing mirror 9 is provided in the liquid 7 at a predetermined angle with respect to the first incident surface 6a.

The light beam from the light source 1 which is vertically incident on the first incident surface 6a of the prism container 6 has a cross-sectional shape indicated by a circle A and has a Gaussian distribution intensity. A portion of the light flux irradiated on the first incident surface 6a that can reach the liquid crystal panel 4 and be effectively used as an image is the light flux inside the circle B. Therefore, the luminous flux between the circle A and the circle B is unnecessary light, and the annular irradiation area S between the circle A and the circle B in the luminous flux irradiation area of the first incident surface 6a is the unnecessary light irradiation area. Is. The first incident surface 6a corresponding to the lower side portion of the unnecessary light irradiation area S
The endothermic surface or endothermic member 13 is formed by applying a black paint having a good endothermic property.

Next, the operation of this embodiment will be described. Light source 1
Is incident on the first incident surface 6a, passes through the polarizing plate 8 to be linearly polarized light, and then is reflected by the polarization mirror 9.
The liquid prism 10 is emitted to irradiate the liquid crystal panel 4. The light emitted to the liquid crystal panel 4 and reflected from the liquid crystal panel 4 is a light flux whose polarization is changed in accordance with the image on the liquid crystal panel 4, and only the light of the portion whose polarization is changed is the liquid prism 10. The light is transmitted through the polarization mirror 9 of FIG. 1 and introduced into the projection lens 5, and is projected on a screen (not shown).

A color separation optical system such as a dichroic mirror is provided between the light source 1 and the liquid prism 10, and an image on each of the R, G and B liquid crystal panels 4 is projected onto each projection lens 5. It is designed to be projected and synthesized on the screen by.

As described above, while the light flux from the light source 1 passes through the liquid prism 10, light is absorbed by the polarizing plate 8, the polarizing mirror 9, etc., and the liquid 7 in the prism container 6 is heated. Since the intensity distribution of the light flux from the light source 1 is Gaussian, the heating of the liquid 7 is large at the central portion of the light flux, and a rise in temperature due to convection of the heated liquid 7 causes a temperature difference in the vertical direction of the liquid 7, An attempt is made to shift to the temperature distribution as shown by the curve W in FIG.

However, in this embodiment, since the heat absorbing member 13 is provided below the first entrance surface 6a of the prism container 6, the heat absorbing member 13 positively absorbs unnecessary light emitted from the light source 1. Therefore, the liquid 7 under the prism container 6 can be heated. Further, since the support 12 below the prism case 6 has a heat insulating structure, the heat radiation from the bottom of the prism case 6 is small. Therefore, the liquid temperature in the lower portion of the prism container 6 rises and approaches the liquid temperature in the upper portion of the prism container 6, and the temperature distribution of the liquid 7 in the vertical direction is flattened as shown by the curve I in FIG. Therefore, the unevenness of the refractive index distribution due to the vertical temperature unevenness in the prism container 6 is reduced, the image of the liquid crystal panel 4 can be accurately formed on the screen, and the image quality of the projection television or the like is improved. Become.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, a reflecting member 14 is provided on the first incident surface 6a instead of the heat absorbing member 13 in the first embodiment. A thin plate made of metal or the like having high reflectivity is used as the reflecting member 14, and this is attached to the upper portion of the unnecessary light irradiation area S. It should be noted that a metal thin film may be formed on the glass plate serving as the first incident surface 6 to serve as the reflecting member.

In this embodiment, from the light source 1 to the first incident surface 6
Since the unnecessary light emitted to the upper side of a is reflected by the reflecting member 14, heat input from the upper side of the prism container 6 is prevented. Therefore, the liquid temperature above the prism container 6 can be lowered. Further, by making the support 12 have a heat insulating structure as in the above-described embodiment, it is possible to reduce heat radiation from the bottom of the prism container 6 and raise the liquid temperature under the prism container 6. Therefore, in this example,
The vertical temperature distribution of the liquid 7 in the prism container 6 is shown in FIG.
It is flattened as shown by the curve II.

Although the liquid prism is applied to the polarizing prism in the first and second embodiments, a spectral prism or a color separating / combining prism having a dichroic mirror as a light separating / combining means in the prism container is shown. It may be applied to. In the first embodiment, the heat absorbing member 13 is the black paint applied to the first incident surface 6a. However, a heat absorbing substance may be added to the glass plate of the first incident surface 6a, or the heat absorbing plate may be added. May be attached to the first incident surface 6a to form a heat absorbing member. Further, the polarizing plate 8 may be attached to the outer surface of the glass plate of the first incident surface 6a. Further, both the heat absorbing member 13 of the first embodiment and the reflecting member 14 of the second embodiment may be provided on the first incident surface 6a to further reduce the temperature unevenness. It should be noted that since light is absorbed and reflected by the first incident surface of the prism container of the present invention with respect to unnecessary light, there is no adverse effect on the projector image or the like.

Further, in each of the above-mentioned embodiments, the constitution is applied to the optical system of the projection type projector, but it can be applied to the optical system of other various projectors, projection televisions and the like.

[0025]

As is apparent from the above description, according to the first liquid prism of the present invention, the first liquid incident surface of the first entrance surface of the prism container on which the luminous flux from the light source is incident is located below the unnecessary light irradiation area. Since the heat absorbing member is provided, it is possible to accelerate the heating of the lower portion of the prism container by positively absorbing unnecessary light with the heat absorbing member, and it is possible to raise the liquid temperature of the lower portion of the prism container. Therefore, the vertical liquid temperature difference caused by receiving the light flux of Gaussian distribution intensity from the light source is reduced,
The temperature unevenness is reduced and the refractive index distribution of the liquid prism is made uniform. Therefore, the image distortion and the like due to the liquid prism are improved, and the image quality of a projection television or the like can be improved by using this liquid prism.

Further, according to the second liquid prism of the present invention, since the reflecting member is provided on the upper side of the unnecessary light irradiation area of the first incident surface, it is unnecessary to make the incident on the upper side of the first incident surface. Light can be reflected by the reflecting member, heat input from the upper side of the prism container can be prevented, and the liquid temperature above the prism container can be reduced. Therefore, the temperature unevenness in the vertical direction in the prism container caused by the irradiation of the Gaussian light flux is improved, the refractive index of the liquid prism is made uniform, and the image quality of a projection television or the like using this liquid prism can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment in which a liquid prism of the present invention is applied to an optical system of a projection type projector using a reflection type liquid crystal panel.

FIG. 2 is a plan sectional view of FIG.

FIG. 3 is a side view showing a second embodiment of the liquid prism of the present invention.

FIG. 4 is a diagram showing the temperature distribution in the vertical direction in the prism for comparison between the liquid prism of the present invention and the conventional liquid prism.

FIG. 5 is a perspective view showing an optical system of a liquid crystal projector using a conventional liquid prism.

6 is a plan sectional view showing a part of the optical system of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Dichroic mirror 3, 10 ... Liquid prism 4 ... Liquid crystal panel 5 ... Projection lens 6 ... Prism container 7 ... Liquid 8 ... Polarizing plate 9 ... Polarizing mirror 11 ... Cooling part 12 ... Support 13 ... Endothermic member 14 ... Reflection Material A, B ... Circle S ... Irradiation area of unnecessary light

Claims (2)

[Claims] 1. A liquid prism having a light separating / combining means such as a polarizing mirror for separating and combining light beams in a prism container filled with a liquid, wherein a first incident surface of the prism container into which a light beam from a light source is incident. A liquid prism, wherein a heat absorbing member is provided in a lower portion of an irradiation area of unnecessary light with which the peripheral portion is irradiated. 2. A liquid prism having a light separating / combining means such as a polarizing mirror for separating and combining light beams in a prism container filled with a liquid, wherein a first incident surface of the prism container into which a light beam from a light source is incident. A liquid prism characterized in that a reflecting member is provided in a region on an upper side of an irradiation area of unnecessary light irradiated to the peripheral portion thereof.