JPH09179198A - Projection optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection optical device capable of saving space, improving the emitted light quantity of a light source and preventing dust from intruding into the periphery of a liquid crystal display board(LCD) by forming linearly polarized light illuminating the LCD by utilizing a polarizing beam splitter in the light source optical system of a liquid crystal projector. SOLUTION: Light (non-polarized light) emitted by a light source lamp 10 is divided into two in accordance with a polarized light component by an S-wave reflection mirror 30. The luminous flux (P-wave) transmitted through the mirror 30 is reflected to the same optical path by a total reflection mirror 32, and restored to the lamp 10. On the other hand, the lumious flux (S-wave) reflected by the mirror 30 is guided to a 1st condenser lens 12 through a total reflection mirror 34 and used as the illuminating light for the LCD 18. Thus, a polarizing plate which is set on the incident side of the LCD and is a heat generating source in the conventional device is not required and a cooling means is omitted. Then, hermetically sealing structure is obtained by housing a member such as the LCD 18 in a case 36 whereby the dust is prevented from attaching to the LCD 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection optical device, and more particularly to a projection optical device applied to a light source optical system of a liquid crystal projector.

[0002]

2. Description of the Related Art FIG. 2 is a block diagram of a projection optical device applied to a conventional liquid crystal projector, and FIG. 3 is an enlarged perspective view of the vicinity of the liquid crystal display plate. As shown in FIG. 2, the conventional projection optical device mainly includes a light source lamp 10, a first condenser lens 12 that collects light emitted from the light source lamp 10, and a pair of polarizing plates whose polarization planes are orthogonal to each other. 14, 16 and a liquid crystal display plate (hereinafter abbreviated as LCD) 18 provided between the pair of polarizing plates 14, 16.
A second condenser lens 20 for condensing the light transmitted through the polarizing plate 16 and a projection lens 22 for enlarging and projecting a display image. Each member is housed in a light shielding casing (not shown).

An arcuate lamp mirror 24 is provided behind the light source lamp 10, and the light emitted rearward from the light source lamp 10 is reflected forward by the lamp mirror 24. Also, the lamp mirror 24 is
Since a part of the light from the light source lamp 10 is absorbed to reach a high temperature, a fan 26 for cooling the light is provided. It should be noted that cooling the light source lamp 10 (light emitting portion) itself lowers the amount of light emission, so cooling the lamp itself is not preferable.

Further, the polarizing plate 14 provided on the incident side of the LCD 18 absorbs the polarized components other than the transmitted polarized component (for example, S-wave component) as heat, so that the temperature becomes high, and therefore the fan 28 for cooling the same is used. Is provided. With this configuration, the light emitted by the light source lamp 10 (non-polarized light)
Is efficiently radiated by the lamp mirror 24 toward the front of the lamp (left side in the drawing) and is incident on the polarizing plate 14 via the first condenser lens 12. Polarizing plate 14
As shown in FIG. 3, only the polarized component in the vertical direction is transmitted and the other polarized components are absorbed as heat. Liquid crystal display board 18
Means that when the applied electric field strength is 0, the plane of polarization of the vertically incident linearly polarized light is rotated by 90 degrees in the liquid crystal, and when the electric field strength exceeds a certain value, the plane of polarization of the linearly polarized light that has been incident is not rotated and remains as it is. To Penetrate. Therefore, light can be switched by the electric field strength applied to the liquid crystal and the polarizing plate 16 provided on the exit side.

The light transmitted through the polarizing plate 16 is enlarged and projected through the second condenser lens 20 and the projection lens 22 shown in FIG.

[0006]

However, the above-mentioned conventional projection optical apparatus has the fan 26 for cooling the lamp mirror.
And the cooling fan 28 for the polarizing plate 14 are required separately, and there is a drawback that the space becomes large and the cost is high. Further, since the polarizing plate 14 is cooled by the fan 28, an air flow is generated around the LCD 18 and the like, and L
There is also a problem that dust adheres to the CD 18 and other optical components.

The present invention has been made in view of the above circumstances, and can reduce the number of cooling fans to be installed to save space and enhance the luminous efficiency of a light source. An object of the present invention is to provide a projection optical device capable of preventing dust from entering.

[0008]

In order to achieve the above object, the present invention achieves the above object by dividing a light source lamp and a polarization beam splitter which divides non-polarized light emitted from the light source lamp into linearly polarized lights having vibrating planes orthogonal to each other. And one of the linearly polarized light split by the polarization beam splitter is vertically incident, the linearly polarized light is reflected in the same optical path as the incident light path, and is returned to the light source lamp by a total reflection mirror and the polarization beam splitter. A condenser lens that collects the other linearly polarized light, a liquid crystal display plate that is illuminated by the linearly polarized light that is condensed by the condenser lens, and is arranged on the exit side of the liquid crystal display plate and condensed by the condenser lens. A polarizing plate that transmits linearly polarized light having an oscillation plane orthogonal to the linearly polarized light and a lens that magnifies and projects the light that has passed through the polarizing plate is provided. It is characterized in.

According to the present invention, the light emitted from the light source lamp is split by the polarization beam splitter into two linearly polarized lights having vibrating planes orthogonal to each other. One of them, linearly polarized light, is reflected by the total internal reflection mirror, returns through the same path to reach the light source lamp, and warms the light source lamp.
As a result, the temperature of the light source lamp rises and the light amount of the light source increases. The other linearly polarized light split by the polarization beam splitter is condensed by a condenser lens and illuminates the liquid crystal display panel. When the vibrating surface of the light passing through the liquid crystal display plate and the transmission direction of the polarizing plate arranged on the emission side of the liquid crystal display plate coincide with each other, the light passes through the polarizing plate. Then, the light passing through the polarizing plate is enlarged and projected forward by the projection lens.

As described above, since the linearly polarized light for illuminating the liquid crystal display plate is produced by the polarization beam splitter, the polarizing plate on the incident side of the pair of polarizing plates required before and after the liquid crystal display plate is unnecessary. Becomes By omitting the polarizing plate on the incident side, heat is not generated from the portion concerned, so that cooling means (fan or the like) for cooling the polarizing plate on the incident side is not necessary, and the surroundings of the liquid crystal display plate are eliminated. It becomes possible to store in a case and have a closed structure. By adopting such a sealed structure, it is possible to prevent dust from adhering to the liquid crystal display panel or the like.

When the light source lamp has a lamp mirror, it is sufficient to provide only one fan for cooling the lamp mirror as a cooling means.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a projection optical apparatus according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a plan view showing an embodiment of a projection optical apparatus according to the present invention. The same parts as those of the conventional projection optical apparatus shown in FIG. 2 are designated by the same reference numerals, and the duplicated description will be omitted.

In the projection optical apparatus shown in the figure, a light source lamp (for example, a metal halide lamp) 10 is arranged in a light-shielding casing (not shown), and an arc-shaped lamp mirror 24 is provided behind the light source lamp 10 (on the left side in the figure). Is provided. A fan 26 is provided on the back side of the lamp mirror 24.
Is provided, and the lamp mirror 24 that absorbs part of the light from the light source and becomes high in temperature is cooled.

In front of the light source lamp 10, an S-wave reflection mirror (corresponding to a polarization beam splitter) 30 is arranged with its reflection surface fixed at an angle of 45 degrees with respect to the optical axis. The S-wave reflecting (P-wave transmitting) mirror 30 reflects only the S wave of the incident non-polarized light source light downward by 90 degrees in the figure, and generates a P wave having a vibration surface orthogonal to the vibration surface of the S wave. Permeate in the straight direction on the right side of the figure.

On the right side of the S-wave reflecting mirror 30 in the figure,
The total reflection mirror 32 has a reflection surface arranged at right angles to the optical axis. Therefore, the light flux (P-wave) transmitted through the S-wave reflection mirror 30 is vertically incident on the total reflection mirror 32, reflected by the total reflection mirror 32 in the same path, and is reflected by the light source lamp 10.
Is to be returned to. On the other hand, a total reflection mirror 34 is disposed 90 degrees below the S-wave reflection mirror 30 in the figure with its reflection surface fixed at an angle of 45 degrees with respect to the optical axis. The light beam (S wave) reflected 90 degrees downward in the drawing is guided to the first condenser lens 12 via the total reflection mirror 34 and used as illumination light for the LCD 18.

S reflected by the total reflection mirror 34
On the traveling optical axis of the wave, a first condenser lens 12, an LCD 18, a polarizing plate 16 and a second condenser lens 20 are arranged in this order from the right side of the drawing, and a projection lens 22 is provided in front of it. The first condenser lens 12, LC
Each member of D18, the polarizing plate 16, and the second condenser lens 20 is housed and hermetically sealed in a case 36 so that dust is not mixed from the outside.

Next, the operation of the projection optical device constructed as described above will be described. The light (non-polarized light) emitted from the light source lamp 10 is efficiently emitted toward the front of the lamp (leftward direction in the drawing) by the lamp mirror 24 arranged behind the light source lamp 10. This non-polarized light is divided into two by the S-wave reflection mirror 30 according to the polarization component. That is, S
The light beam (P wave) that has passed through the wave reflection mirror 30 is reflected by the total reflection mirror 32, returns through the same optical path, and reaches the light source lamp 10. As a result, the light emitting portion of the light source lamp 10 is warmed and the amount of light emitted from the light source is increased.

On the other hand, the light beam (S wave) reflected by the S wave reflection mirror 30 enters the condenser lens 12 via the total reflection mirror 34 and becomes the illumination light of the LCD 18. At this time, since the non-polarized light emitted from the light source lamp 10 is already linearly polarized by only the S wave because it is reflected by the S wave reflection mirror 30, it is necessary for the conventional projection optical system shown in FIG. The incident side polarization plate 14 of the LCD 18 is unnecessary. Conventionally, the incident-side polarization plate 14 has been a heat source by absorbing as heat the components other than the transmitted polarization component (for example, S-wave component), and a fan 28 for cooling this.
However, in the present embodiment, the cooling fan 28, which is installed for the heat generation of the polarization plate 14 on the incident side, is not necessary, and the space can be saved.

Further, in the projection optical apparatus shown in FIG. 1, since the polarizing plate 14 serving as a heat source does not exist, the first condenser lens 12, the LCD 18, the polarizing plate 16, and the second condenser lens 12.
The condenser lens 20 can be housed in the case 36 to form a closed structure. This can prevent dust from entering from the outside.

[0020]

As described above, according to the projection optical apparatus of the present invention, the light emitted from the light source lamp is split into two linearly polarized lights having vibrating planes orthogonal to each other by the polarization beam splitter, and a liquid crystal display is provided. Since the linearly polarized light for illuminating the plate is created, the polarizing plate on the incident side of the pair of polarizing plates provided before and after the liquid crystal display plate is not required. Therefore, a cooling means such as a fan for cooling the incident side polarization plate is not required, and space can be saved, and the periphery of the liquid crystal display plate can be housed in a case to form a sealed structure. Become. By adopting such a sealed structure, it is possible to prevent dust from adhering to the liquid crystal display panel or the like.

When the light source lamp is provided with a lamp mirror, only one fan for cooling the lamp mirror may be provided. Furthermore, of the two linearly polarized lights split by the polarization beam splitter,
Since the light flux not used for illumination of the liquid crystal display plate is reflected by the total reflection mirror and returned to the same light path to reach the light source lamp, the light source lamp is warmed and the light emission amount of the light source increases.

[Brief description of the drawings]

FIG. 1 is a plan view showing an embodiment of a projection optical device according to the present invention.

FIG. 2 is a plan view showing the configuration of a conventional projection optical device.

FIG. 3 is an enlarged perspective view of a liquid crystal display unit of a conventional translucent optical device.

[Explanation of symbols]

 10 ... Light source lamp 12 ... 1st condenser lens 14, 16 ... Polarizing plate 18 ... Liquid crystal display board 20 ... 2nd condenser lens 22 ... Projection lens 30 ... S wave reflection mirror (polarization beam splitter) 32, 34 ... Total reflection mirror 36 …Case

Claims (3)

[Claims] 1. A light source lamp, a polarization beam splitter that splits non-polarized light emitted from the light source lamp into linearly polarized light beams having vibration planes orthogonal to each other, and one linearly polarized light beam split by the polarizing beam splitter. A total reflection mirror that is vertically incident, reflects the linearly polarized light in the same optical path as the incident optical path, and returns it to the light source lamp; a condenser lens that collects the other linearly polarized light split by the polarization beam splitter; and the condenser lens. A liquid crystal display panel illuminated by linearly polarized light condensed by the polarized light, and a polarized light which is disposed on the exit side of the liquid crystal display plate and transmits linearly polarized light having an oscillation plane orthogonal to the linearly polarized light condensed by the condenser lens. A projection optical device comprising: a plate; and a lens that magnifies and projects the light that has passed through the polarizing plate. 2. The projection optical apparatus according to claim 1, wherein the liquid crystal display plate and the polarizing plate are housed and hermetically sealed in a case. 3. The light source lamp has a lamp mirror,
The projection optical apparatus according to claim 1, further comprising a fan that cools the lamp mirror.