Optics: image projectors – Particular condenser
Reexamination Certificate
2003-02-27
2004-09-28
Mahoney, Christopher (Department: 2851)
Optics: image projectors
Particular condenser
C353S038000
Reexamination Certificate
active
06796662
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to an illumination optical system and a projector.
2. Description of Related Art
In related art projectors, illumination light emitted from an illumination optical system is modulated by a modulation device, such as a liquid crystal panel, according to image information, and the modulated illumination light is projected onto a screen, thereby performing image display.
In order to achieve a uniform in-plane illumination distribution of illumination light to illuminate the modulation device, such a related art projector adopts an integrator illumination optical system in which light emitted from a light source is divided into a plurality of sub-beams, and the sub-beams are superimposed near the modulation device.
FIG. 7
is a schematic of a related art integrator illumination optical system.
The illumination optical system
1000
shown in
FIG. 7
includes a light source device
1010
including a light source
1020
, an elliptic reflector
1030
, and an aspherical lens
1040
.
FIG. 7
also shows a first lens array
1050
, a second lens array
1060
, a superimposing lens
1070
, and an illumination area LA, such as a liquid crystal panel. The optical components are arranged relative to a light-source optical axis
1020
ax
(center axis of light flux emitted from the light source device
1010
). That is, the first lens array
1050
, the second lens array
1060
, and the superimposing lens
1070
are arranged substantially perpendicular to the light-source optical axis
1020
ax
so that the centers thereof are almost aligned with the light-source optical axis
1020
ax.
In the integrator illumination optical system
1000
, the light source
1020
has a light-emitting portion (arc) having a certain length along the light-source optical axis
1020
ax
, and is placed so that the center of the arc is disposed near a focal point (first focal point) F
1
closer to the elliptic reflector
1030
of two focal points of the elliptic reflector
1030
on the light-source optical axis
1020
ax
(the center axis of light flux emitted from the light source device
1010
). Light emitted from the light-emitting portion is reflected by a reflecting surface
1030
R of the elliptic reflector
1030
, and the reflected light is changed into light substantially parallel to the light-source optical axis
1020
ax
by the aspherical lens
1040
while traveling toward a second focal point F
2
, and enters the first lens array
1050
.
As shown in
FIG. 7
, the first lens array
1050
includes a plurality of cell lenses
1051
having a rectangular outline substantially similar to the shape of the illumination area LA and arranged in a matrix, and divides substantially parallel light from the light source device
1010
into a plurality of sub-beams by the plurality of cell lenses
1051
. The second lens array
1060
also includes a plurality of cell lenses
1061
having a rectangular outline and arranged in a matrix, in a manner similar to that in the first lens array
1050
, the cell lenses
1061
are provided corresponding to the cell lenses
1051
of the first lens array
1050
, and the plurality of sub-beams emitted from the cell lenses
1051
of the first lens array
1050
are collected on the corresponding cell lenses
1061
. The plurality of sub-beams emitted from the cell lenses
1061
of the second lens array
1060
are superimposed by the superimposing lens
1070
so as to illuminate the illumination area LA, such as a liquid crystal panel.
In this type of illumination optical system, when the parallelism of the light emitted from the light source
1020
is insufficient, the light cannot pass through the corresponding cell lenses
1051
and
1061
of the first lens array
1050
and the second lens array
1060
. Accordingly, the related art includes a technique of increasing the parallelism of light emitted from the light source device
1010
, which is disclosed in Japanese Unexamined Patent Application Publication No. 2000-347293, and which was invented by the present inventor.
On the other hand, some integrator illumination optical systems of such a type adopt a parabolic reflector that can simultaneously reflect and collimate light from the light source, without collimating light from the light source by the above-described combination of the elliptic reflector and the aspherical lens. However, in an illumination optical system using a parabolic reflector, as shown in
FIG. 9
, a reflecting surface
1080
R formed of a paraboloid of revolution of a parabolic reflector
1080
has an entrance angle &thgr; (angle around a light-source optical axis
1020
ax
), which allows light beams radially emitted from a light source
1020
to be guided to an aspherical lens
1040
, smaller than the entrance angle of the reflecting surface
1030
R formed of an ellipsoid of revolution of the elliptic reflector
1030
(
FIG. 9
shows a state in which light guiding to the aspherical lens
1040
is impossible because the entrance angle &thgr; is smaller than that of the reflecting surface
1030
R). Therefore, the light utilization efficiency in the parabolic reflector is lower than that in the elliptic reflector
1030
. Accordingly, the related art includes integrator illumination optical systems adopting elliptic reflectors.
In an illumination optical system using an elliptic reflector, however, the light intensity distribution is not uniform and tends to be biased toward the light-source optical axis, which causes the following problems.
FIG. 10
shows a state in which the light intensity distribution is biased.
FIG. 10
illustrates the loci of light beams radially emitted from the center of a light source of a light source device using a related art elliptic reflector, and shows the illuminance distribution in which the illuminance is high in a center portion near a light-source optical axis
1020
ax
and decreases away from the optical axis. For this reason, in the related art illumination optical system
1000
shown in
FIG. 7
adopting the elliptic reflector, although arc images
1062
formed on the second lens array
1060
should be contained in the cell lenses
1061
, as shown in FIG.
11
(
a
), they are offset in the center portion near the light-source optical axis
1020
a
, and extend into the cells on the peripheries of the cell lenses
1061
in which they should be contained, as shown in FIG.
11
(
b
).
Light beams that are not contained in the cell lenses
1061
of the second lens array
1060
, and extend therefrom cannot illuminate the illumination area and are useless, and this results in light loss. The light beams thus extending correspond to light beams that cannot pass through the corresponding lenses
1051
and
1061
of the first lens array
1050
and the second lens array
1060
. Although the light beams emitted from the aspherical lens
1040
should be caused to pass through the corresponding cell lenses
1051
and
1061
of the first and second lens arrays
1050
and
1060
by increasing the parallelism of the light beams in the above-described related art illumination optical system, in actuality, some of the light beams in the center portion near the light-source optical axis
1020
ax
still cannot pass therethrough, and a solution to this problem is desirable.
SUMMARY OF THE INVENTION
The present invention addresses or solves the above and/or other problems, and provides an illumination optical system and a projector that can efficiently utilize light from a light source by directing at least light beams in a center portion around a light-source optical axis, of light beams emitted from an aspherical lens, slightly outward rather than parallel to the light-source optical axis so that the light beams can pass through the corresponding lenses of first and second lens arrays.
An illumination optical system according to one exemplary embodiment of the present invention includes a light source; an elliptic reflector to reflect light from the light source; an aspherical lens having a concave aspherical surface to subs
Mahoney Christopher
Oliff & Berridg,e PLC
Seiko Epson Corporation
LandOfFree
Illumination optical system and projector does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Illumination optical system and projector, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Illumination optical system and projector will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3247186