JP3369895B2 - Projection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection device for irradiating a liquid crystal panel with strong light having a vibrating plane of light and irradiating an image of the liquid crystal panel on a screen or the like.

[0002]

2. Description of the Related Art The projection device shown in FIG. 7 is known. The light from the light source (1) is polarized beam splitter.
By (2), part or all of the S-wave that is vertically polarized is reflected, and the P-wave that is horizontally polarized and part of the S-wave pass. The passing light irradiates the liquid crystal panel (4),
The image of (4) is illuminated with irradiation light and is projected onto the screen (8) by the projection lens (7). The polarizing beam splitter (2) usually uses a prism in many cases, but in view of cost reduction, the one shown in FIG. 6 has been proposed.

In this, a plurality of glass plates (30) (30) are stacked to form a glass plate group (3), and the glass plate group (3) is formed.
Is tilted according to the Brewster's angle. Here, the Brewster angle means an angle θ represented by n = tan θ, where n is the refractive index of the glass plate (30), and the normal direction of the glass plate (30) and the incident light are , When the Brewster angle θ is set, 100% of P wave is transmitted and about 1 of S wave is transmitted for each glass plate (30).
It is empirically known to reflect 5%. Therefore, in the glass plate group (3) in which 4 to 5 glass plates (30) are stacked, 100% of the P wave is transmitted and 50% of the S wave is reflected (see JP-A-3-10218). Polarizing beam splitter
(2) is a pair of glass plate groups (3) (3a) arranged vertically
The upper end and the lower end of the are abutted. In this way, a group of glass plates that combines a plurality of glass plates (30) (30)
By constructing the polarization beam splitter (2) with (3), the cost is reduced.

[0004]

As is well known, incident light is
When it enters the glass plate (30), it refracts and advances. In FIG.
Light entering the lower end of the upper glass plate group (3a) is refracted upward, and light entering the upper end of the lower glass plate group (3) is refracted downward. When the light hits the end face of the glass plate (30), it is diffusely reflected and hardly passes through the glass plate group (3). Therefore, in the abutting portion of both glass plate groups (3) and (3a), there is a shaded portion where almost no light passes, as indicated by the diagonal lines. Because of this part, the light utilization efficiency decreases,
When illuminated on the screen (8), the screen becomes dark. An object of the present invention is to narrow such a shadow portion in a polarization beam splitter in which a group of glass plates are connected.

[0005]

[Means for Solving the Problem] From the light source (1) and the light source (1)
Of all the P-waves and a part of the S-waves of the light, a liquid crystal panel (4) illuminated by the light passing through the polarization beam splitter (2), and a projection lens ( 7) and a polarizing beam splitter (2), a glass plate group (3) (3) (where the normal line is inclined with respect to the optical axis by a Brewster's angle, a plurality of glass plates (30) (30) In a projection device in which 3a) are vertically arranged, a polarization beam splitter
In (2), a plurality of glass plate groups (3) and (3a) are arranged vertically,
Of a pair of vertically adjacent glass plates (3) (3a), a first glass plate group whose upper end faces the adjacent glass plate group
The upper end of (3) faces the projection direction, and the lower end of the second glass plate group (3a) faces the projection direction.
(5) The first glass plate group, which is displaced along the direction, is arranged.
The upper end of (3) and the lower end of the second glass plate group (3a) overlap each other along the optical axis (5) direction.

[0006]

Operation and effect Polarizing beam splitter according to the present invention
In the case of (2), since the upper and lower glass plate groups (3) and (3) are arranged so as to be offset from each other in the projection direction, they pass beneath the second glass plate group (3) located above. Even if the light is
The light can enter the surface of the glass plate (30) located closest to the light source (1) of the first glass plate group (3) and can pass through the glass plate group (3). Therefore, the width of the incident light that cannot pass through the end portions of the upper and lower glass plate groups (3) (3) and becomes a shadow can be made narrower than that of the conventional configuration, and thus the shadowed portion at the time of emission can be obtained. Width can be reduced

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION An example of the present invention will be described below with reference to the drawings. The same configurations as the conventional one will be described using the same reference numerals. FIG. 1 is a side view of the projection device. light source
The light from (1) is reflected by the reflector (10), travels straight, and enters the polarization beam splitter (2). A part of P wave and S wave of the incident light is allowed to pass through the polarization beam splitter (2), and a part of S wave is reflected. The light passing through the polarization beam splitter (2) enters the liquid crystal panel (4), and the image on the liquid crystal panel (4) is displayed on the screen (8) by the projection lens (7). Normally a liquid crystal panel
A polarizing plate is provided immediately before (4), but if only the P wave is allowed to pass by only the polarizing plate, most of the light from the light source (1) irradiates the polarizing plate, The temperature rises. Therefore, there is a possibility that the polarizing plate may be damaged.
In order to prevent this fear, the P wave and a part of the S wave are separated in advance on the upstream side of the polarizing plate.

As described above, the polarization beam splitter (2) has a plurality of glass plate groups (3c) (3a) (3) (3b) which are formed by stacking several glass plates (30) (30) on top of each other. It will be lined up. Each glass plate group (3) is tilted with respect to the optical axis (5) direction, and the glass plate groups (3a) (3) vertically adjacent to each other form a chevron shape. In FIG. 1, the glass plate groups (3c) (3a) (3) (3b) are arranged in upper and lower four stages, but they may be four or more stages or four or less stages. Figure 2
FIG. 3 is a perspective view showing a state in which the polarization beam splitter (2) is viewed obliquely from above, and FIG. The polarizing beam splitter (2) consists of a group of glass plates in the frame (6).
(3) (3) is provided, and both end faces of the glass plate group (3) are framed.
It is clamped by the holding plates (60) (60) constituting (6). Presser plate
The (60) has a recessed portion (61) which is recessed one step, and the recessed portion (61) has a contact surface (62) in contact with a corner of the glass plate group (3) and a glass plate group.
It has a receiving surface (63) in contact with the surface end of (3). The glass plate group (3) is positioned near one of the contact surfaces (62). The corner between the contact surface (62) and the receiving surface (63) is the glass plate group (3).
If the glass plate group (3) cannot be properly attached if the glass plate group (3) is convex toward, a notch (64) is provided at the corner in order to accurately attach the glass plate group (3).

The glass plate group (3) has an end portion with one contact surface (6
2) With the receiving surface (63) in contact with each other, as shown in FIGS. 3 and 4, insert the pressing piece (65) from the outside of the frame body (6),
The pressing piece (65) is pressed and sandwiched by the end surface and the receiving surface (63), and is fixed in the frame body (6). That is, glass plate group (3)
It is not necessary to fix the glass plate group (3) with an adhesive or the like at the time of attaching, and the workability is good. Also, glass plate group (3)
Is brought into contact with the contact surface (62) and the receiving surface (63) to be accurately positioned.

FIG. 5 is an enlarged side view of a part of the glass plate group (3) in the polarization beam splitter (2). The glass plate group (3) is configured by stacking a plurality of glass plates (30) (30), and each glass plate (30) has the Brewster angle with respect to the normal direction to the optical axis (5) direction. Just leaning. A pair of vertically adjacent glass plate groups (3a) (3) have their tip portions facing each other, and the glass plate groups (3a) (3) are stacked with the glass plates (30) (30) being displaced. The glass plate (30) is displaced closer to the optical axis (5) as the glass plate (30) located closer to the projection direction of light is. The reason for this is as shown in FIG. ) Is aligned, the glass plate (30) closest to the light source (1)
This is because the light incident on the lower end of the is diffusely reflected on the way and does not pass through the glass plate group (3). The second glass plate group (3a) located on the upper side of the first glass plate group (3) whose upper end is inclined in the light projection direction has its lower end tilted in the light projection direction. . The upper end of the first glass plate group (3) is located closer to the light projection direction side than the lower end of the second glass plate group (3) and is the upper end of the first glass plate group (3). The portion and the lower end of the second glass plate group (3) overlap each other in the projection direction.

In FIG. 5, the light incident on the lower end of the second glass plate group (3a) located on the upper side is refracted upward and proceeds. However, when the light is incident on the lower end of the second glass plate group (3a), the light has not reached the upper end of the first glass plate group (3), and the second glass plate group (3a) is not reached. The light goes straight below (3a). The light that has passed below the second glass plate group (3a) enters the upper end of the first glass plate group (3),
It bends downward and advances.

With the above structure, the conventional glass plate group (3) (3
It is possible to narrow the range of the shadow part generated at the abutting part of a). This will be described below. Light refracts in the glass plate (30) and travels, so it is the most light source
(1) Light incident on the lower end of the glass plate (30) closer to the glass plate cannot pass through the glass plate (30) and is diffusely reflected. Therefore,
As shown in FIG. 6, only the light separated from the optical axis (5) by a certain distance m or more passes through the glass plate (30). In the conventional polarization beam splitter (2), the upper and lower glass plate groups (3) and (3) are butted against each other, so that the upper and lower glass plate groups (3) and (3) can pass through. The width L of the incident light that becomes a shadow at the time of emission is about twice the width m of the incident light that cannot pass through one glass plate group (3).

However, the polarization beam splitter of this example
In (2), since the upper and lower glass plate groups (3a) and (3) are arranged so as to be offset from each other in the projection direction, the light that has passed directly under the second glass plate group (3a) located on the upper side is Even if there is,
As shown in FIG. 1, the light is incident on the surface of the glass plate (30) located closest to the light source (1) of the first glass plate group (3),
You can go through (3). Therefore, the width L of incident light which cannot pass through the upper and lower glass plate groups (3) and (3) and becomes a shadow can be made substantially equal to the width m of incident light which cannot pass through one glass plate group (3). . That is, by narrowing the width of the incident light that becomes a shadow, the width of the portion that becomes a shadow at the time of emission can be reduced. At the lower end of the glass plate group (3) and the upper end of the glass plate group (3b) located below the glass plate group (3), incident light is refracted downward and upward, respectively, as shown in FIG. . Therefore, the shaded area formed by the incident light is narrow, which poses no practical problem.

In order to verify the above, the applicant prototyped a polarizing beam splitter (2) in which upper and lower glass plate groups (3) and (3) are displaced from each other along the projection direction. For trial production,
Three glass plates (30) having a plate thickness of about 1.0 mm and made of a glass material having a refractive index of about 1.5 were used. Therefore, the Brewster angle θ is about 57 degrees from the above equation. The width m of the incident light that cannot pass through one glass plate group (3) is 0.36 m
m. Conventional polarization beam splitter (2) shown in FIG.
At this time, the width L of the incident light that becomes a shadow at the time of emission is 0.72
mm, and the width of the shadow is 3.6 mm. However, in the polarization beam splitter (2) according to the present example, the width L of the incident light that becomes a shadow at the time of emission is 0.36 mm, and the width of the shadow is 3.2 mm. Applicant is a group of upper and lower glass plate (3)
The width of the shadow was measured by preparing two types of the glass plate (30) located closest to the light source (1) in (3) with a vertical interval P of 38.8 mm and 37.4 mm. But 3.
It was the same as 2 mm. Therefore, it was demonstrated that the width of the shadow does not change even if the interval P varies.

Contrary to the above example, the upper glass plate group
The lower end of (3a) may be located closer to the projection direction than the upper end of the lower glass plate group (3).

The above description of the embodiments is for explaining the present invention, and should not be construed as limiting the invention described in the claims or limiting the scope. The configuration of each part of the present invention is not limited to the above-mentioned embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims.

[Brief description of drawings]

FIG. 1 is a side view of a projection device.

FIG. 2 is a perspective view of a polarization beam splitter.

FIG. 3 is a cross-sectional view of FIG. 2 viewed from the direction A.

FIG. 4 is a side view showing a state where a pressing piece is attached to a pressing plate.

FIG. 5 is a side view showing the arrangement of glass plate groups in the polarization beam splitter.

FIG. 6 is a side view showing an arrangement of glass plate groups in a conventional polarization beam splitter.

FIG. 7 is a side view of a conventional projection device.

FIG. 8 is a diagram showing an optical path in a glass plate group in which the end faces of the glass plates are aligned.

[Explanation of symbols]

(1) Light source (2) Polarizing beam splitter (3) Glass plate group (4) LCD panel (6) Frame body (62) Abutting surface (63) Receiving surface

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Claims (2)

(57) [Claims] 1. A light source (1) and P of light from the light source (1)
A polarizing beam splitter (2) for passing all of the waves and a part of the S waves, a liquid crystal panel (4) illuminated by the light passing through the polarizing beam splitter (2), and a projection lens (7). , The polarization beam splitter (2) is composed of a plurality of glass plates (30) whose normals are inclined by Brewster's angle with respect to the optical axis.
In the projection device in which the glass plate groups (3) and (3a) in which the (30) are superposed are vertically arranged, the polarization beam splitter (2) includes a plurality of glass plate groups (3).
The upper end of the first glass plate group (3) in which the upper end of the pair of vertically adjacent glass plates (3) (3a) faces the adjacent glass plate group (3a) Is a second glass plate group having the projection direction and the lower end facing the projection direction.
It is arranged so as to be displaced along the optical axis (5) direction from the lower end of (3a), and the upper end of the first glass plate group (3) and the second glass plate group.
The lower end of (3a) is a projection device characterized in that they overlap each other along the optical axis (5) direction. 2. A receiving surface (63) for supporting and supporting each glass plate group (3) in a frame body (6), the frame body (6) being in contact with and supporting an end of the glass plate group (3). Projection device according to claim 1, comprising a contact surface (62).