Optical: systems and elements – Single channel simultaneously to or from plural channels
Reissue Patent
2001-10-24
2003-08-19
Mack, Ricky (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
C359S619000, C359S634000
Reissue Patent
active
RE038225
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection display apparatus with colored light combining means and a lighting optical system therefor.
2. Discussion of the Background
A cross dichroic prism is often used for projection display apparatus that project a color image on a projection screen. For example, in a transmissive liquid-crystal projector, the cross dichroic prism is utilized as colored light combining means that combines three colored rays of red, green, and blue and emits the composite light in a common direction. In a reflective liquid-crystal projector, the cross dichroic prism is utilized as colored light separation means that separated a beam of white light into three colored rays of red, green, and blue and also as colored light combining means that recombines modulated three colored rays and emits the composite light in a common direction. A known example of the projection display apparatus with the cross dichroic prism is disclosed in JAPANESE PATENT LAID-OPEN GAZETTE No. 1-302385.
FIG. 17
conceptually illustrates a main part of a projection display apparatus. The projection display apparatus includes three liquid-crystal light valves
42
,
44
, and
46
, a cross dichroic prism
48
, and a projection lens system
50
. The cross dichroic prism
48
combines three colored rays of red, green, and blue modulated by the three liquid-crystal light valves
42
,
44
, and
46
light and emits the composite light toward the projection lens system
50
. The projection lens system
50
focuses the composite light on a projection screen
52
.
FIG. 18
is a partly decomposed perspective view illustrating the cross dichroic prism
48
. The cross dichroic prism
48
includes four right-angle prisms which are bonded to one another via the respective right-angle surfaces by an optical adhesive.
FIG. 19
shows a problem arising in the case of utilizing the cross dichroic prism
48
. As shown in FIG.
19
(A), the cross dichroic prism
48
has a red light reflection film
60
R and a blue light reflection film
60
B which are arranged in a substantially X shape on an X-shaped interface formed by the right-angle surfaces of the four right-angle prisms. There is an X-shaped layer of optical adhesive
62
formed in the gaps between the four right-angle prisms. Both the reflection films
60
R and
60
B accordingly have gaps at a central axis
48
a of the cross dichroic prism
48
.
When a light beam passing through the central axis
48
a of the cross dichroic prism
48
is projected on the projection screen
52
, a dark line due to the central axis
48
a may be formed in the projected image. FIG.
19
(B) shows an example of the dark line DL. The dark line DL represents a relatively dark, linear area having a different color from that of the other part and is formed substantially on the center of the projected image. It is considered that the dark line DL is ascribed to scattering of rays and no-reflection of the red light and blue light in the gaps of the reflection films in the vicinity of the central axis
48
a. A similar problem arises in a cross dichroic mirror that includes two dichroic mirrors that are arranged in an X shape and respectively have selective reflection films, such as a red reflection film and a blue reflection film. In this case, a dark line due to a central axis of the mirror is formed in a projected image.
As described above, in the prior-art projection display apparatus, a dark line is formed substantially on the center of a projected image because of the central axis of the cross dichroic prism
48
or the cross dichroic mirror.
SUMMARY OF THE INVENTION
The object of the present invention is thus to solve the above problem in the prior art and make a dark line due to a central axis of an optical means inconspicuous, where the optical means includes two dichroic films arranged substantially in an X shape and may be a cross dichroic prism or a cross dichroic mirror.
The principle for solving the problem is described first with a concrete example shown in
FIGS. 1 through 4
. In the drawings, z direction denotes the direction of the course of light, x direction denotes the direction of 3 o'clock seen from the direction of the course of light (the z direction), and y direction denotes the direction of 12 o'clock. In the description below, the x direction represents the direction of rows and the y direction represents the direction of columns for the matter of convenience. Although the description of the principle is based on a concrete example for the better understanding, the present invention is not restricted to this concrete structure in any sense.
In a projection display apparatus, a lighting optical system with two lens arrays each including a plurality of small lenses (hereinafter referred to as an integrator optical system) as specified in WO94/22042 is known as the technique for dividing light from a light source into a plurality of partial light fluxes and thereby reducing an in-plane unevenness of the illuminance of light.
FIG. 1
shows the principle of forming a dark line when an integrator optical system is adopted in a projection display apparatus with a cross dichroic prism. FIGS.
1
(A-
1
) and
1
(B-
1
) show light fluxes (shown by the solid lines) passing through a plurality of small lenses
10
which are different in position in the x direction, that is, a plurality of small lenses
10
existing in different columns, and traces of their central optical axes (shown by the fine dotted lines). FIGS.
1
(A-
2
) and
1
(B-
2
) show the positions of dark lines DLa and DLb formed on a screen
7
.
A light flux emitted from a light source (not shown) is divided into a plurality of partial light fluxes by first and second lens arrays
1
and
2
each including the plurality of small lenses
10
. The light fluxes passing through the respective small lenses
10
included in the first and the second lens arrays
1
and
2
are converted to light fluxes parallel to the respective central axes of the partial light fluxes by means of a paralleling lens
15
. The partial light fluxes passing through the paralleling lens
15
are superposed on a liquid-crystal light valve
3
, so that a predetermined area is uniformly illuminated with the superposed light fluxes. Although only one liquid-crystal light valve
3
is shown in
FIG. 1
, the principle of the integrator optical stem and the principle of forming a dark line are also applicable to the her two liquid-crystal light valves.
FIG. 2
is a perspective view illustrating the appearance of the first and the second lens arrays
1
and
2
. Each of the first and the second lens arrays
1
and
2
includes the small lenses
10
that respectively have a substantially rectangular outline and are arranged in a matrix of M rows and N columns. In this example, M=10 and N=8. FIG.
1
(A-
1
) shows the trace of partial light fluxes passing through the small lenses
10
of the second column, whereas FIG.
1
(B-
1
) shows the trace of partial light fluxes passing through the small lenses
10
of the seventh column.
The light fluxes superposed on the liquid-crystal light valve
3
are subjected to modulation responsive to image information in the liquid-crystal light valve
3
and enter a cross dichroic prism
4
. The light flux output from the cross dichroic prism
4
is projected on the screen
7
via a projection lens system
6
.
As shown by the rough dotted lines in FIGS.
1
(A-
1
) and
1
(B-
1
), light fluxes passing through a central axis
5
(along the y direction in the drawing) of the cross dichroic prism
4
are projected at positions Pa and Pb on the screen
7
. As discussed previously in the prior art, scattering of the rays and no-reflection of the light to be reflected in the gaps between reflection films in the vicinity of the central axis
5
reduce the quantity of light passing through the vicinity of the central axis
5
. As shown in FIGS.
1
(A-
2
) and
1
(B
2
), the reduction causes dark lines DLa and DLb, which have the lower
Hashizume Toshiaki
Itoh Yoshitaka
Mack Ricky
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Seiko Epson Corporation
LandOfFree
Projection display and illuminating optical system for it does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Projection display and illuminating optical system for it, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Projection display and illuminating optical system for it will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3095539