JP3202710B2 - Dichroic prism for LCD projector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dichroic prism used in a three-panel liquid crystal projector.

[0002]

2. Description of the Related Art When a presentation is made using a personal computer and a liquid crystal projector, a light image from the liquid crystal projector is displayed on a screen 1 as shown in FIG.
At the same time, it is proposed that the liquid crystal projector receives infrared light (Ir) from the infrared light source 3 of the pointing rod 2 indicating the position on the screen 1 at the liquid crystal projector side and performs position analysis or the like with a personal computer.

When this is realized by a three-panel liquid crystal projector, as shown in FIG. 1, only infrared light (Ir) is reflected on the front side of a main dichroic prism M for synthesizing light of three colors of green, red and blue. It is conceivable to arrange auxiliary dichroic prisms S to be juxtaposed.

In this case, the dichroic prism M is
It is a hexahedron as a whole, formed by intersecting a red reflection film 4R and a blue reflection film 4B at right angles. The first surface M1 is a green light (G) incident surface, and the second surface is perpendicular to the first surface M1. M2 is a red light (R) incident surface, and a third surface M3 opposite to the second surface M2.
Is the blue light (B) incident surface, and the fourth surface on the opposite side to the first surface M1.
The surface M4 is an emission surface of the combined green light, red light and blue light.

Further, the dichroic prism S is also a hexahedron as a whole, and the first surface S1 is an incident surface of green light, red light and blue light synthesized by the dichroic prism M, and an opposite surface to the first surface S1. The fourth surface S4 is a surface on which infrared light (Ir) from the infrared light source 3 is incident, and the infrared reflection film 5 is formed at an angle of 45 degrees with respect to the fourth surface S4. The infrared light reflected by the infrared reflecting film 5 is
The light emitted from the fifth surface S5, which is perpendicular to the first and fourth surfaces, is received by an infrared light receiving element (not shown). The green light, red light, and blue light incident from the first surface S1 are reflected by infrared light. The light passes through the film 5 and exits from the fourth surface S4.

[0006]

However, according to such a structure, the distance from the liquid crystal panel of the liquid crystal projector to the lens becomes large, which is disadvantageous in optical performance. In addition, since the distance between the lens and the liquid crystal panel must be equal to the distance between the lens and the infrared light receiving element, the infrared light receiving element is separated from the prism S having the infrared reflective film 5 and the projector body becomes very large. .

[0007] The object of the present invention is to address such a problem.
An object of the present invention is to provide a dichroic prism for a liquid crystal projector which does not require a separate prism for detecting infrared rays from the outside in a three-panel liquid crystal projector.

[0008]

A dichroic prism for a liquid crystal projector according to the present invention is obtained by integrating two dichroic prisms in FIG. 1 into one. That is, this dichroic prism is a hexahedron as a whole, the first surface is a green light incident surface, the second surface perpendicular to the first surface is a red light incident surface, and the third surface opposite to the second surface is a third surface. The blue light incident surface and the fourth surface opposite to the first surface are the combined green light, red light and blue light emission surfaces, and are the infrared light incident surfaces. On the other hand, an infrared reflecting film is formed at an angle of 45 degrees, and the fifth surfaces perpendicular to the first to fourth surfaces are infrared emission surfaces.

[0009]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

A dichroic prism P according to the present invention
Is a hexahedron as a whole, as shown in FIGS. 2 and 3, formed by intersecting a red reflection film 6R and a blue reflection film 6B at right angles, and a first surface P1 is an incident surface of green light (G). , The first surface P1
Is perpendicular to the second surface P2, the red light (R) incident surface, the second surface P
A third surface P3 opposite to the second surface P2 is a blue light (B) incident surface, a green light combined with a fourth surface P4 opposite to the first surface P1;
It is an emission surface for red light and blue light, and infrared (I
r) is the incident surface. The infrared reflection film 6Ir is formed at an angle of 45 degrees with respect to the fourth surface,
Fifth surfaces P5 perpendicular to the fourth to fourth surfaces are infrared emission surfaces. Among them, the red reflection film 6Ir has a property of transmitting infrared rays, unlike the red reflection film of a general dichroic prism.

[0011] External infrared rays (Ir) transmitted through a lens (not shown) of the liquid crystal projector enter from the fourth surface P4 of the dichroic prism P, are reflected by the infrared reflecting film 6Ir, and are reflected from the fifth surface P5. The light is emitted and directed to an infrared light receiving element (not shown).

[0012]

According to the present invention, the dichroic prism for synthesizing the three colors of green, red and blue also serves as a prism for guiding infrared light from the outside to the infrared light receiving element. And the distance from the lens to the infrared light receiving element can be made equal, and the distance from the liquid crystal panel to the lens has the same advantage as the conventional three-panel liquid crystal projector.

[Brief description of the drawings]

FIG. 1 is an optical system diagram of a reference example in which an auxiliary dichroic prism that reflects only infrared light is arranged in front of a main dichroic prism that combines three colors of green, red, and blue.

FIG. 2 is a configuration diagram of a dichroic prism according to the present invention.

FIG. 3 is a layout view of a reflection film of the dichroic prism according to the present invention.

[Explanation of symbols]

P dichroic prism P1 to P5 First to fifth surfaces of dichroic prism
Surface 6R Red reflective film 6B Blue reflective film 6Ir Infrared reflective film

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G02F 1/13 505 G02B 5/20 G02F 1/1335

Claims (1)

(57) [Claims] 1. A hexahedron as a whole, wherein a first surface is a green light incident surface, a second surface perpendicular to the first surface is a red light incident surface, and a third surface opposite to the second surface is a blue light incident surface. And the fourth surface opposite to the first surface is a combined green light, red light, and blue light emission surface and an infrared light incidence surface. A dichroic prism for a liquid crystal projector, wherein an infrared reflection film is formed at an angle of 45 degrees, and a fifth surface perpendicular to each of the first to fourth surfaces is an infrared emission surface.