Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
2000-02-15
2003-10-21
Adams, Russell (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S034000, C353S037000, C353S098000, C353S099000, C349S005000, C349S007000, C349S008000, C359S838000
Reexamination Certificate
active
06634755
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an illuminating device and a projector using the same, and is suitable for a color liquid crystal projector for enlarging and projecting, for example, images of three colors displayed on three liquid crystal panels onto a screen.
2. Related Background Art
There have heretofore been proposed various liquid crystal projectors for enlarging and projecting an image made by a liquid crystal light valve or the like onto a screen.
In the projector of this kind, three image display elements are illuminated with three color lights R, G and B obtained by color-separating a light from a light source, and images of three colors R, G and B are displayed by these three image display elements. The images (color lights) by the image display elements are color-combined and are projected onto a screen or the like by a projection lens.
When in this construction, a cross dichroic prism of a construction in which surfaces having dichroic film intersect with each other is used for color combination, there is a case where one of optical path lengths of three color lights for illumination from the light source to the image display elements is longer than the other two optical path lengths or a case where two optical path lengths are longer than remaining one optical path length.
In a projector disclosed in Japanese Laid-Open Patent Application No. 63-116123, an optical path bending plane mirror is provided in the longest one of optical paths of lights of three colors. This is often used in a construction for directing the light from a light source directly to an image display element.
In this case, there has been the problem that in the longest optical path, the light diverges and the utilization efficiency of light is reduced relative to the other short optical paths. Against such a problem, U.S. Pat. No. 5,626,409 discloses a construction as shown in
FIG. 9
of the accompanying drawings wherein an illuminating system for illuminating an image display element is provided with a so-called integrator
103
comprising a lens array constructed into the form of a matrix, and a relay system comprising a convex lens and a plane mirror is provided to produce a uniform illuminating area so that a first uniform illuminating area produced in an optical path by the integrator
103
and the image display element may be made conjugate with an optical path longer than the other optical paths in a color separating system.
In
FIG. 9
, the reference numeral
101
designates a light source such as a metal halide lamp or a mercury lamp. The reference numeral
102
denotes a reflector having a reflecting surface comprising a parabolic surface or an elliptical surface. The reference numeral
103
designates an integrator comprising a first lens array
1031
and a second lens array
1032
.
The reference numeral
104
denotes a polarization converting element which converts a non-polarized incident light into a predetermined linearly polarized light and emits it. The reference numeral
105
designates a color separating system comprising dichroic mirrors
1051
and
1052
. The reference numerals
1071
and
1072
denote mirrors. The reference numeral
108
designates a relay system having lenses
1081
,
1082
and
1083
and mirrors
1084
and
1085
.
The reference characters
110
R,
110
G and
110
B denote image display elements for colors R, G and B comprising liquid crystal panels (light valves). The reference numeral
111
designates a cross dichroic prism. The reference numeral
112
denotes a projection lens having positive refractive power and for enlarging and projecting images displayed by the image display elements
110
R,
110
G and
110
B.
The reference numeral
106
designates a condensing lens for condensing the diffused light from the polarization converting element
104
onto the image display elements
110
R,
110
G and
110
B. The reference characters
109
G and
109
R denote condenser lenses for condensing the illuminating light onto the projection lens, and the lens
1081
of the relay system
108
also has the same role as that of these condenser lenses.
In recent years, in projectors such as color liquid crystal projectors, the downsizing thereof has been desired, and an illuminating optical system for illuminating an image display element has also been downsized. In the case of the color projector as shown in
FIG. 9
, it is effective for the downsizing of the illuminating system to shorten the longest relay optical path (B optical path) of the optical paths of three color lights.
However, to shorten the optical path of the relay system
108
while maintaining the conjugate relation between the uniform illuminating area formed in the optical path of R and the image display element, the refractive power (positive) of the lenses
1081
and
1082
constituting the relay system
108
must be strong.
The relay system
108
is such that the second relay lens
1082
for adjusting at least the conjugate relation is provided in the central portion of the relay system, the first relay lens
1081
for producing a plurality of light source images produced near the first uniform illuminating area by the lens array
103
near the second relay lens is provided near the uniform illuminating area, the third relay lens
1083
working as a condenser lens for the projection lens in the relay system is provided near the image display element, and the two plane mirrors
1084
and
1085
for bending the optical path are provided between the relay lenses.
Strengthening the refractive power of a lens to shorten the optical path is strengthening the refractive power of the first, second and third relay lenses
1081
,
1082
and
1083
.
However, if this is done, there is also the problem that the radius of curvature of each relay lens becomes small and the thickness of the lens is increased and the reduction in transmittance by the absorption of the interior of the lens cannot be neglected and after all, the quantity of light is reduced.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide an illuminating device and a projector in which a reduction in quantity of light is small.
A first aspect of the present invention is an illuminating device in which a light from a light source separated into three color lights differing in optical path from one another by a color separating system, and light modulating elements conforming to the respective color lights are illuminated with the color lights, wherein at least one of the optical paths of the three color lights has therein an optical system for converging and reflecting the color light passing therethrough without using any converging lens.
A second aspect of the present invention is an illuminating device in the first aspect wherein only the longest one of the three optical paths or only the remaining two optical paths except the shortest optical path have the reflecting system therein.
A third aspect of the present invention is an illuminating device in which a light from a light source is separated into three color lights differing in optical path from one another by a color separating system, and light modulating elements are illuminated with the respective color lights, wherein two of the three optical paths are equal in optical path length to each other and longer in optical path length than the remaining one optical path, and each of the two optical paths has therein an optical system for converging and reflecting the color light passing therethrough without using any converging lens.
A fourth aspect of the present invention is an illuminating device in the first, second or third aspect wherein the reflecting optical system has a plurality of concave mirrors separate from each other or connected to each other.
A fifth aspect of the present invention is an illuminating device in the first, second, third or fourth aspect wherein the reflecting optical system has a concave mirror of a shape free of axis-symmetry (non-rotational symmetry).
A sixth aspect of the presen
Kodama Hiroyuki
Okuyama Atsushi
Sugawara Saburo
Adams Russell
Canon Kabushiki Kaisha
Koval Melissa J.
Morgan & Finnegan L.L.P.
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