JP3165497B2 - Liquid prism - Google Patents

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 high-luminance light source such as a projector, and more particularly to a liquid prism having a nonuniform 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 light source of high brightness, 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 an optical system of a display device using a reflective liquid crystal panel shown in FIG. 5, a liquid prism is used as a polarizing prism.

In FIG. 1, light from a light source 1 is blue, green,
The light is sequentially split by the red-reflecting dichroic mirrors 2, 2, and 2, and each of the R, G, and B lights enters the R, G, and B liquid crystal panels 4 via the liquid prism 3. The reflected light from the liquid crystal panel 4 changes its polarization corresponding to the image of each liquid crystal panel 4, and only the light whose polarization 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 a screen (not shown) by the three projection lenses 5.

[0006] As shown in FIG. 6, the liquid prism 3 is a rectangular cylindrical glass prism container 6 filled with a liquid 7 having substantially the same refractive index as the prism container 6.
A polarizing plate 8 is provided on one side of the prism container 6 on the light source 1 side.
And a polarizing mirror 9 that reflects linearly polarized light transmitted through the polarizing plate 8 to the liquid crystal panel 4 is accommodated in the prism container 6.

[0005]

By the way, ethylene glycol, glycerin, benzyl alcohol and the like are used for the liquid 7 filled in the liquid prism 3, and these have a large change in refractive index with respect to temperature. According to the measurement, a change in the refractive index of 0.0003 to 0.0005 / degree occurs. Therefore, the temperature unevenness occurs in the liquid 7 in the liquid prism 3, to appear as non-uniform refractive index distribution or <br/> intends.

However, in a projection type projector or the like, a light source 1 is of a high brightness such as a metal halide lamp for increasing the brightness of an image, and a strong light is applied to the liquid prism 3. Is done. Therefore, the temperature rise of the liquid prism 3 is large due to heat absorption by the polarizing plate 8 and the like. Moreover, the intensity of the light beam emitted from the light source 1 has a Gaussian distribution with a strong center. For this reason, the heated liquid 7 at the center in the liquid prism 3 moves to the upper part of the liquid prism 3 by convection, while the liquid 7 at the lower part of the liquid prism 3 remains without being heated so much. , Different temperature distributions occur in the vertical direction.

In the conventional example shown in FIG. 6, the light source 1 is turned on,
After the liquid prism 3 thermally reached the steady state, the temperature distribution in the vertical direction of the liquid 7 inside the liquid prism 3 was measured, and the result was shown by a curve B in FIG. For this reason, 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.

An object of the present invention is 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 temperature unevenness in a liquid prism in a vertical direction and achieving a uniform refractive index distribution. I do.

[0009]

To achieve SUMMARY OF to the above objects, the present invention relates to a liquid prism odor equipped with a polarizing Mirror for separating synthesized light beam to the prism in the container in which the liquid is filled
Further , a transparent partition is provided in the prism container so as to partition the prism container into the polarizing mirror side and the first incident surface side of the prism container into which the light beam from the light source enters.

[0010] Further , in the use state of the liquid prism, the end of the partition on the side of the direction of gravity when viewed from the center of the partition.
Part and the center opposite to the direction of gravity as viewed from the center.
It is preferable that a through hole is formed at an end of the partition to allow the liquid in the prism container to flow between the polarizing mirror and the first incident surface.

[0011]

The light beam incident on the first entrance surface of the prism container from the light source is separated and synthesized by the polarizing mirror and emitted out of the prism container.

During this time, light is absorbed by the prism container, the polarizing mirror, the liquid, etc., and the temperature of the liquid prism rises. In particular, the first incident surface side has a large amount of heat absorption and a large temperature rise. However, since the inside of the prism container is thermally divided by the partition, the temperature unevenness of the liquid in the prism generated by the rise of the liquid warmed by the Gaussian light flux is mainly limited to the first incident surface side, Temperature unevenness on the polarizing mirror side is reduced. Therefore, the use of liquid prisms
Non-uniformity of the refractive index distribution of the liquid prism due to temperature unevenness in the direction parallel to gravity in the use state is reduced.

[0013] Further, in the use state of the liquid prism, the end of the partition on the side of the direction of gravity when viewed from the center of the partition.
Part and the center opposite to the direction of gravity as viewed from the center.
When a through hole is provided at the end of the partition , the polarizing mirror side and the first
Inflow of liquid between the incident side, the outflow becomes possible, together with the high temperature and become a likely first incident surface side cooling is improved, the liquid
Temperature unevenness in the direction parallel to gravity in the use state of the body prism can also be reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. This embodiment is an example in which a liquid prism is used as a polarizing prism in an optical system of a projection type projector using a reflection type liquid crystal panel.

In the plan view of FIG. 1 and the side view of FIG. 2, reference numeral 1 denotes a high-luminance light source such as a metal halide lamp, and a liquid prism 10 is provided in front of the light source 1. The liquid prism 10 has a prism container 11 made of glass having a rectangular cylindrical shape, and the prism container 11 is filled with a liquid 7 having a refractive index substantially equal to that of the prism container 11. The lower portion of the prism container 11 is mounted on a support (not shown) via a support 12, and a cooling unit 13 is formed on the upper portion of the prism container 11.

The polarizing plate 8 is provided in the prism container 11.
And the polarizing mirror 9 are stored in a state of being immersed in the liquid 7. The polarizing plate 8 is provided in parallel with the first incident surface 11a, which is one side surface of the prism container 11 on which the light beam from the light source 1 is incident, and slightly away from the first incident surface 11a. The polarizing mirror 9 is arranged at a predetermined angle with respect to the first incident surface 11a so as to reflect linearly polarized light transmitted through the polarizing plate 8 and make it enter the liquid crystal panel 4.

A transparent glass plate partition 14 is provided upright between the polarizing plate 8 and the polarizing mirror, and the partition 14 allows the inside of the prism container 11 to have a polarizing plate chamber 15 for accommodating the polarizing plate 8 and a polarizing mirror 9. And a polarization mirror chamber 16 for storing the same. Further, slit-shaped through holes are formed above and below the partition 14 to allow the liquid 7 to flow between the polarizing plate chamber 15 and the polarizing mirror chamber 16.

A light beam from the light source 1 enters the first incident surface 11a, passes through the polarizing plate 8, is converted into linearly polarized light, is reflected by the polarizing mirror 9, exits the liquid prism 10, and enters the liquid crystal panel 4. Irradiated. The light radiated to the liquid crystal panel 4 and reflected from the liquid crystal panel 4 is a luminous flux whose polarization has changed in accordance with the image of the liquid crystal panel 4, and only the light of the portion whose polarization has changed is the light of the liquid prism 10. The light passes through the polarizing mirror 9 and is introduced into the projection lens 5 and 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 as in FIG. Is projected on the screen and synthesized.

As described above, while the light beam from the light source 1 passes through the liquid prism 10, light is absorbed by the polarizing plate 8, the polarizing mirror 9, and the like, and the inside of the prism container 11 is heated.
Since the intensity distribution of the luminous flux from the light source 1 is Gaussian, the heating of the liquid 7 is large at the center of the luminous flux, and the convection of the heated liquid 7 causes a temperature difference in the vertical direction of the liquid 7.

However, in this embodiment, since the inside of the prism container 11 is separated into the polarizing plate chamber 15 and the polarizing mirror chamber 16 by the partition 14, the solution 7 in the polarizing plate chamber 15 having the polarizing plate 8 with much heat absorption is provided. The convection and the uneven temperature in the vertical direction caused by the convection are not directly transmitted to the polarizing mirror chamber 16 side. That is, the polarizing plate chamber 15 and the polarizing mirror chamber 16 are thermally shut off by the partition 14, so that they are hardly affected by the mutual thermal influence. For this reason, the temperature unevenness in the vertical direction of the liquid 7 due to the heating from the polarizing plate 8 having the largest heat absorption is limited to the polarizing plate chamber 15 and the polarizing mirror chamber 1
The temperature unevenness in the vertical direction in 6 is reduced. Therefore, the unevenness of the refractive index distribution due to the temperature unevenness in the vertical direction of the liquid 7 is improved as a whole of the liquid prism 10, and the image of the liquid crystal panel 4 can be accurately formed on the screen. Will be improved.

Further, through holes 17 are formed above and below the partition 14, so that the liquid 7 can flow between the polarizing plate chamber 15 and the polarizing mirror chamber 16, and both the polarizing plate 8 and the polarizing mirror 9 are vertically spaced. Is provided, the flow of the liquid 7 makes the liquid prism 10 uniform in temperature, the cooling effect is enhanced, and the temperature unevenness is reduced.

Next, the result of performing temperature measurement on the liquid prism 10 of this embodiment will be described. As the liquid 7, a mixture of benzyl alcohol and glycerin was used. Light source 1
Was turned on, and the temperature was measured after the liquid prism 10 reached a steady state thermally. FIG. 4 shows the outside air temperature at point a in the vicinity of the liquid prism 10 and each part b of the liquid prism 10.
9 shows the temperature of the liquid 7 at points 〜 to g. As shown, the vertical temperature difference of the liquid 7 in the polarizing plate chamber 15 is 1
Although the temperature was 3.4 ° C., the vertical temperature difference of the deflection mirror chamber 16 was greatly reduced to 3.7 ° C. Further, from this measurement, the temperature distribution in the polarizing mirror chamber 16 is as shown by the curve A in FIG. 3, and the temperature unevenness is greatly improved as compared with the curve B showing the temperature distribution in the conventional liquid prism 3. You can see that there is.

In the above embodiment, the polarizing plate 8 is housed in the polarizing plate chamber 15 while being separated from the first incident surface 11a. However, the polarizing plate 8 may be attached to the first incident surface 11a.
In order to prevent the heat of the liquid prism 10 from being dissipated to the support base via the support 12, the support 12
A heat insulating material may be used, or an air layer may be formed. Although the above embodiment is an example applied to a liquid prism, it can also be applied to a spectral prism or a color separation / combination prism provided with a dichroic mirror as a light separation / combination unit in a prism container.

In each of the above embodiments, the present invention is applied to an optical system of a projection type projector, but may be applied to other optical systems such as various projectors and projection televisions.

[0026]

As described above, according to the present invention, the interior of the prism container filled with the liquid is thermally divided into the polarizing mirror side and the first incident surface side by providing the partition. Therefore, the usage state in the liquid prism caused by receiving the light flux of Gaussian distribution intensity from the light source
The temperature unevenness in the direction parallel to the gravitational force is limited to the first incident surface that is easily heated, and the temperature unevenness on the polarizing mirror side is reduced. Therefore, when the liquid prism is in use,
The unevenness of the refractive index distribution of the entire liquid prism due to the temperature unevenness in the direction parallel to the applied gravity is reduced, the distortion of the image by the liquid prism is improved, and the image quality of a projection television or the like using the liquid prism of the present invention is improved. Can be achieved.

[0027] In use of the liquid prism, the end of the partition on the side of the direction of gravity when viewed from the center of the partition.
And the relevant side on the side opposite to the direction of gravity when viewed from the center.
By providing a through-hole at the end of the cut , liquid can flow between the polarizing mirror side and the first incident surface side. The liquid prism can be cooled, the temperature of the liquid prism can be equalized, the cooling effect of the liquid prism can be enhanced, and the use condition of the first incident surface side can be improved.
Temperature unevenness in the direction parallel to the gravity in the state can also be reduced.

[Brief description of the drawings]

FIG. 1 is a plan sectional view showing an 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 side sectional view of the liquid prism of FIG.

FIG. 3 is a diagram showing a vertical temperature distribution in a liquid prism of the embodiment of FIG. 1 in comparison with a vertical temperature distribution of a conventional liquid prism.

FIG. 4 is a view showing the result of measuring the temperature of each part of the liquid prism of FIG. 1;

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

FIG. 6 is a plan sectional view showing a part of the optical system of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Light source 2 ... Dichroic mirror 3, 10 ... Liquid prism 4 ... Liquid crystal panel 5 ... Projection lens 6, 11 ... Prism container 7 ... Liquid 8 ... Polarizing plate 9 ... Polarizing mirror 11a ... 1st entrance surface 14 ... Partition 15 ... Polarized Plate room 16: Polarizing mirror room 17: Through hole

Continuation of the front page (56) References JP-A-3-120503 (JP, A) JP-A-4-320202 (JP, A) JP-A-2-502588 (JP, A) (58) Fields surveyed (Int .Cl. ⁷ , DB name) G02B 5/06 G02B 5/04 G02B 5/30

Claims (2)

(57) [Claims] 1. A liquid prism provided with a polarizing mirror for separating and synthesizing a light beam in a prism container filled with liquid, wherein the light beam from the polarizing mirror side and a light source enters the prism container. A liquid prism, wherein a transparent partition is provided for partitioning the container from the first incident surface side of the container. 2. A through hole for allowing liquid to flow in the prism container between the polarizing mirror side and the first incident surface side is provided with the partition in a state where the liquid prism is used.
End of the partition on the side of the direction of gravity when viewed from the center of
The partition on the side opposite to the direction of gravity when viewed from the center
The liquid prism according to claim 1, wherein the liquid prism is formed at each end of the liquid prism.