Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
1997-11-06
2001-01-23
Dowling, William (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S037000, C353S098000
Reexamination Certificate
active
06176585
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection apparatus, adapted for use for example in a color liquid crystal projector which projects image information, displayed on an optical modulating element such as a color liquid crystal display panel, onto a screen in a magnified manner.
2. Related Background Art
There have been proposed various color liquid crystal projectors, which projects the optical information, displayed on a liquid crystal panel serving as an optical modulating element, onto a screen. Among such projectors, an optical system for use in a liquid crystal projector employing a transmissive liquid crystal apparatus is disclosed for example in the Japanese Patent Laid-open Application No. 61-99118.
FIG. 28
is a schematic view of the optical system proposed in the above-mentioned patent application.
Referring to
FIG. 28
, the light emitted from a light source
1
is converted by a reflector (parabolic mirror)
2
into a substantially parallel light beam, which then enters a dichroic mirror
34
transmitting the green (G) light and reflecting the green (G) and red (R) lights. The G and R lights reflected by the dichroic mirror
34
enters a dichroic mirror
35
, which reflects the green (G) light and transmits the red (R) light. The G light beam reflected by the dichroic mirror
35
illuminates a liquid crystal panel
14
for the G light while the R light beam transmitted by the dichroic mirror
35
illuminates a liquid crystal panel
15
for the R light. Also the blue light beam transmitted by the dichroic mirror
34
illuminates, via mirror
36
, a liquid crystal panel
16
for the B light. The light beams transmitted by the liquid crystal panels
14
,
15
,
16
are respectively modulated by the image information of respective colors. The light beams from the liquid crystal panels
14
,
16
are synthesized by a dichroic mirror
37
which transmits the blue light beam and reflects the green light beam. Also the red light beam from the liquid crystal panel
15
enters, via a mirror
38
, a dichroic mirror
38
which transmits the red light beam and reflects the blue and green light beams.
The red, blue and green light beams are synthesized by the dichroic mirror
39
to provide a full color image, which is projected through a projection optical system
22
onto a screen
23
. In the liquid crystal panels
14
,
15
,
16
there is employed, for example, twisted nematic (TN) liquid crystal or super-twisted nematic (STN) liquid crystal.
FIG. 29
is a schematic view of an optical system for a color liquid crystal projector, employing the transmissive liquid crystal apparatus, as proposed in the Japanese Patent Laid-open Application No. 1-131593.
Referring to
FIG. 29
, the light emitted from a light source
1
is converted by a reflector (parabolic mirror)
2
into a substantially parallel light beam, which then enters a dichroic mirror
341
reflecting the blue (B) and transmitting the green (G) and red (R) lights. The light beam transmitted by the dichroic mirror
341
enters a dichroic mirror
35
′, which transmits the green light and reflects the red light. The green light beam transmitted by the dichroic mirror
35
′ illuminates a liquid crystal panel
14
for the green light while the red light beam reflected by the dichroic mirror
35
′ illuminates, via mirrors
38
,
41
, a liquid crystal panel
15
for the red light. Also the blue light beam reflected by the dichroic mirror
34
′ illuminates, via mirrors
36
,
40
, a liquid crystal panel
16
for the blue light.
The light beam transmitted by the liquid crystal panels
14
,
15
,
16
are respectively modulated by the image information of respective colors, and enter a cross dichroic prism
42
wherein they are synthesized as a full-color image. The cross dichroic prism
42
is composed of a cross-shaped combination of a dichroic mirror transmitting the green light beam and reflecting the blue light beam and a dichroic mirror transmitting the green light beam and reflecting the red light beam. The full-color image synthesized in the cross dichroic prism
42
is projected through a projection optical system
22
onto a screen
23
.
FIG. 30
is a schematic view of an optical system for a color liquid crystal projector, employing a reflective liquid crystal apparatus, as disclosed in the Japanese Patent Laid-open Application No. 6-265842. This optical system is called a Schlieren optical system.
Referring to
FIG. 30
, the light emitted from a light source
1
is converted by a reflector (parabolic mirror)
2
into a substantially parallel light beam, then reflected by a mirror
36
, and is condensed by a condenser lens
4
so as to form an image of the light source in the vicinity of a mirror
43
positioned at a diaphragm aperture of the projection optical system
22
. The light beam reflected by the mirror
43
is emitted toward a plano-convex lens
44
, converted therein into a parallel light beam, then separated by a cross dichroic prism
42
into the light beams of three colors which respectively illuminate reflective liquid crystal panels
25
,
26
,
27
of the respective wavelength regions.
The light beams respectively modulated by the reflective liquid crystal panels
25
,
26
,
27
are synthesized by a cross dichroic prism
42
into a full-color image, which is condensed by a plano-convex lens
44
, then transmitted by a diaphragm
28
and projected through a projection optical system
22
onto a screen
23
.
The liquid crystal panel contains, for example, polymer liquid crystal of dispersion type, which becomes transparent in case of displaying a white level, thereby reflecting the light beam, but scatters the light beam in case of displaying a black level. The light reflected by the liquid crystal panels and color synthesized by the cross dichroic prism
42
is condensed by the plano-convex lens
44
in the vicinity of the diaphragm
28
of the projection optical system
22
. The light beam reflected by the liquid crystal panel is mostly transmitted by the aperture of the diaphragm
28
and displays the white level on the screen
23
through the projection optical system
22
, while the light beam scattered by the liquid crystal panel is transmitted, only by a very limited portion, by the aperture of the diaphragm
28
, thereby displaying the black level on the screen
23
.
As explained in the foregoing, the light scattering in the liquid crystal is utilized to display the image information, which is projected by the projection optical system onto the screen.
FIGS. 31A and 31B
are respectively an entire view and a schematic partial view of a color liquid crystal projector proposed in the Japanese Patent Laid-open Application No. 4-428, wherein liquid crystal panels
14
,
15
,
16
are respectively illuminated with the R, G and B lights. The light beams from the liquid crystal panels, illuminated with the respective color lights are condensed by auxiliary lenses
17
,
18
,
19
in the vicinity of the entrance pupil EnP of a projection lens
30
. The light beam from the auxiliary lens
18
is directly entered into a projection optical system
22
, while that from the auxiliary lens
17
is guided thereto via a mirror
20
, and that from the auxiliary lens
19
is guided thereto via a mirror
21
. The projection optical system
22
projects images, displayed on the liquid crystal panels
14
,
15
,
16
onto a screen
23
.
In
FIGS. 31A and 31B
, there are illustrated principal rays Pr
1
, Pr
2
, Pr
3
at the center for the respective projection systems, and three rays for each of the projection systems. The optical axis of the auxiliary lens
18
of the central projection system B coincides with that of the projection lens
32
, and the optical axes of the auxiliary lenses
17
,
19
of the peripheral projection systems A, C are perpendicular to the optical axis of the projection lens.
The entrance pupil EnP of the projection lens is positioned at the crossing point of the optical axes of the three auxiliary lenses, an
Koyama Osamu
Kuramochi Junko
Sugawara Saburo
Canon Kabushiki Kaisha
Dowling William
Morgan & Finnegan , LLP
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