Optics: image projectors – Reflector
Reexamination Certificate
1997-10-14
2001-07-17
Dowling, William (Department: 2851)
Optics: image projectors
Reflector
C353S102000
Reexamination Certificate
active
06260974
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image projecting apparatus for enlargingly projecting an image formed by an optical modulating device such as a liquid crystal panel on a display surface such as a screen.
2. Related Background Art
An optical system for a liquid crystal projector using a reflection type liquid crystal device is proposed in Japanese Patent Application Laid-Open No. 6-265842. This optical system is known as the Schlieren optical system. The prior art optical system will be explained with reference to FIG.
1
.
Referring to
FIG. 1
, light beams from a light source
1
are substantially collimated by a paraboloidal reflector
2
(a paraboloidal mirror) and, after being reflected by a mirror
3
, a light source image is formed in the vicinity of a reflecting mirror
7
disposed in a position of an aperture stop
13
of a projection lens
14
. The light beams reflected by the reflecting mirror
7
outgo toward a plano-convex lens
8
and become parallel light beams through the plano-convex lens
8
. The light beams are then separated into the light beams of three colors R, G, B by a cross dichroic prism
9
, on the light beams in the respective colors (wavelength bands) illuminate reflection type liquid crystal display panels
10
,
11
,
12
.
The respective color light beams modulated by the reflection type liquid crystal panels
10
,
11
,
12
are color-synthesized as the reflected light beams having image information again by the cross dichroic prism
9
, and converged by the plano-convex lens
8
. Then, the converged light beams pass through an aperture of the aperture stop
13
and are projected onto a screen
15
via the projection lens
14
.
The liquid crystal panels
10
,
11
,
12
, within which polymer dispersion type liquid crystals are sealed, control directions of liquid crystal particles by electric fields so as to reflect incident light beams by becoming transparent when displaying a white level and scatter the incident light beams when displaying a black level. The light beams, which have been reflected by the liquid crystal panel and color-synthesized by the cross dichroic prism
9
, are converged in the vicinity of the aperture stop
13
of the projection lens
14
by the plano-convex lens
8
. Most of the light beams reflected by the liquid crystals pass through the aperture of the aperture stop
13
. After traveling through the projection lens
14
, they are displayed as the white level on the screen
15
. However, an extremely small quantity of the whole light beams scatter by the liquid crystals just pass through the aperture of the aperture stop
13
and therefore appear as the black level on the screen
15
.
According to the prior art, however, there arises a problem in which a color ununiformity and a luminance ununiformity of the light source occur on the screen. Further, the light source image formed by the reflector exhibits a rotation symmetry, and hence there might be a large loss of light quantity when illuminating a rectangular liquid crystal panel, resulting in such a problem that the luminance on the screen decreases.
It can be considered that an integrator is introduced in order to solve this problem, however, the light source image formed at the aperture of the aperture stop
13
of the projection lens
14
is destined to be enlarged only by simply disposing the integrator, and the quantity of the light passing through the aperture of the aperture stop
13
decreases when displaying the white level. Further, when aperture of the stop is widened to prevent the reduction in the optical quantity, the contrast is destined to be declined. Thus, the integrator effective for decreasing the color ununiformity and the luminance ununiformity on the screen is no good in terms of compatibility with the Schlieren optical system.
SUMMARY OF THE INVENTION
It is a primary object of the present invention, which obviates the problems described above, to provide an image projecting apparatus capable of reducing a color ununiformity and a luminance ununiformity of projection image on a screen and obtaining a bright and high contrast of projection image by corners of the screen.
It is another object of the present invention to provide an improved illuminating apparatus.
According to one aspect of the present invention, an image projecting apparatus comprises an optical element having a first end surface, a second end surface and a reflection surface for connecting the first and second surfaces and constructed so that light beams are incident on the first end surface, and at least some of the light beams are reflected by the reflecting surface and outgone from the second end surface. The image projecting apparatus also comprises a reflection type optical modulating device for modulating the light beams outgoing from the second end surface, and a projection optical system for projecting an image of the reflection type optical modulating device onto a screen. The first end surface of the optical element is provided with a light source or a light source image. A position of the first end surface of the optical element and a position of a stop of the projection optical system are set in a conjugate relationship. A position of the second end surface of the optical element and a position of the reflection type optical modulating device are set in the conjugate relationship.
According to another aspect of the present invention, an image projecting apparatus comprises a light source, converging means for converging light beams from the light source and forming a light source image, and an optical means having a first end surface, a second end surface and a reflecting surface for connecting the first and second end surfaces, and constructed so that the light beams from the light source are incident on the first end surface, and at least some of the light beams are reflected by the reflecting surface and outgone from the second end surface.
The image projecting apparatus also comprises a light beam deflecting element for deflecting the light beams from the second end surface of the optical element and guiding the deflected light beams to the reflection type optical modulating device, a projection lens for projecting an image of the reflection type optical modulating device onto a screen, and a condenser lens for converging the light beams modulated by the reflection type optical modulating device at a position of a stop of the projection lens, the light beam deflecting element being disposed in the vicinity of the position of the stop of the projection lens. The first end surface of the optical element is disposed in a position where the light source image is formed. A position of the first end surface of the optical element and a position of the light beam deflecting element are set in a conjugate relationship. A position of the light beam deflecting element and the position of the stop of the projection lens are set in the conjugate relationship. A position of the second end surface of the optical element and the position of the reflection type optical modulating device are set in the conjugate relationship.
According to still another aspect of the present invention, an image projecting apparatus comprises an optical element having a first end surface, a second end surface and a reflection surface for connecting the first and second surfaces and constructed so that light beams are incident on the first end surface, and at least some of the light beams are reflected by the reflecting surface and emerge from the second end surface. The image projecting apparatus also comprises an optical modulating device for modulating the light beams outgoing from the second end surface, and a projecting element for projecting an image of the optical modulating device onto a display surface such as screen. Sizes of the first and second end surfaces of the optical element are made different from each other. The first end surface of the optical element is supplied with a light source or a light source image. A position o
Canon Kabushiki Kaisha
Dowling William
Morgan & Finnegan L.L.P.
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