Optical: systems and elements – Lens – With light limiting or controlling means
Reexamination Certificate
1999-04-12
2001-02-13
Mack, Ricky (Department: 2873)
Optical: systems and elements
Lens
With light limiting or controlling means
C359S618000, C353S037000, C353S097000
Reexamination Certificate
active
06188529
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projecting apparatus suitable for, e.g., a color liquid crystal projector for enlarging and projecting image information displayed on one or a plurality of optical modulation elements such as liquid crystal panels on a screen or the like.
2. Related Background Art
A variety of color liquid crystal projectors for projecting image information displayed on a liquid crystal panel as an optical modulation element on a screen are conventionally proposed. An optical system for a liquid crystal projector using a transmission liquid crystal is proposed, i.e., Japanese Laid-Open Patent Application No. 61-99118.
FIG. 1
is a view schematically showing the optical system of this prior art.
Referring to
FIG. 1
, light emitted by a light source
1
is roughly collimated by a reflector
2
(parabolic mirror) and incident on a dichroic mirror
34
which transmits the blue light component (B light component) and reflects the green light component (G light component) and the red light component (R light component). The C and R light components reflected by the dichroic mirror
34
enter a dichroic mirror
35
which reflects the green light component (G light component) and transmits the red light component (R light component). The green light component reflected by the dichroic mirror
35
illuminates a liquid crystal panel
14
for G light, and the red light component transmitted through the dichroic mirror
35
illuminates a liquid crystal panel
15
for R light. The blue light component transmitted through the dichroic mirror
34
illuminates a liquid crystal panel
16
for B light.
The light beams transmitted through the liquid crystal panels
14
,
15
, and
16
are modulated in accordance with image information in units of colors. The light beams from the liquid crystal panels
14
and
16
are synthesized by a dichroic mirror
37
which transmits a blue light component and reflects a green light component. The red light component from the liquid crystal panel
15
passes through a mirror
38
and reaches a dichroic mirror
39
which transmits a red light component and reflects blue and green light components.
The red, blue, and green light components are synthesized by the dichroic mirror
39
into a full-color image. This full-color image is projected on a screen
23
through a projection optical system
48
. The liquid crystal panels
14
to
16
use, e.g., a twisted nematic (TN) liquid crystal or a super twisted nematic (STN) liquid crystal.
FIG. 2
is a view schematically showing an optical system for a color liquid crystal projector using a transmission liquid crystal proposed in Japanese Laid-Open Patent Application No. 1-131593.
Referring to
FIG. 2
, light emitted by a light source
1
is roughly collimated by a reflector
2
(parabolic mirror) and incident on a dichroic mirror
34
′ which reflects a blue light component (B light component) and transmits a green light component (G light component) and a red light component (R light component). The light components transmitted through the dichroic mirror
34
′ are incident on a dichroic mirror
35
′ which transmits the green light component and reflects the red light component. The green light component transmitted through the dichroic mirror
35
′ illuminates a liquid crystal panel
14
for green, and the red light component reflected by the dichroic mirror
35
′ illuminates a liquid crystal panel
15
for red through mirrors
38
and
41
. The blue light component reflected by the dichroic mirror
34
′ illuminates a liquid crystal panel
16
for blue through mirrors
36
and
40
.
The light beams transmitted through the liquid crystal panels
14
,
15
, and
16
are modulated in accordance with image information in units of colors. The light beams reach a cross dichroic prism
42
and synthesized into a full-color image. The cross dichroic prism
42
is formed by crossing a dichroic mirror for transmitting a green light component and reflecting a blue light component and a dichroic mirror for transmitting a green light component and reflecting a red light component. The full-color image synthesized by the cross dichroic prism
42
is projected on a screen
23
through a projection optical system
48
.
FIGS. 3 and 4
are views schematically showing color projectors each using an optical system for synthesizing a full-color image without using a plurality of flat dichroic mirrors or prisms, which are proposed in Japanese Laid-Open Patent Application No. 4-428.
In
FIG. 3
, transmission liquid crystal panels
14
,
15
, and
16
are illuminated with light beams in corresponding wavelength bands. Light beams transmitted through the liquid crystal panels and modulated according to image information in units of colors are brought to a focus near the stop of a projecting lens
48
through field lenses
45
,
46
, and
47
arranged behind the liquid crystal panels. Tilted mirrors
20
and
21
are inserted near the stop of the projecting lens
48
at an interval. The light beam transmitted through the liquid crystal panel
14
passes between the two mirrors.
The liquid crystal panel
15
and the field lens
46
are decentered from each other by a distance s and so are the liquid crystal panel
16
and the field lens
47
. The light beam transmitted through the liquid crystal panel
15
is deflected through the field lens
46
and reflected by the mirror
20
.
Similarly, the light beam transmitted through the liquid crystal panel
16
is deflected through the field lens
47
and reflected by the mirror
21
. The color light components are transmitted through the projecting lens
48
, synthesized into a full-color image, and projected on a screen
23
.
In
FIG. 4
, the positions of each liquid crystal panel and a corresponding field lens are reversed to those in FIG.
3
. In this case as well, a liquid crystal panel
15
and a field lens
46
′ are decentered from each other by a distance s', and so are a liquid crystal panel
16
and a field lens
47
′. The light beam deflected through the field lens
46
′ is focused, transmitted through the liquid crystal panel
15
, and reflected by a mirror
20
.
Likewise, the light beam deflected through the field lens
47
′ is focused, transmitted through the liquid crystal panel
16
, and reflected by a mirror
21
. The color light components are transmitted through a projecting lens
48
, synthesized into a full-color image, and projected on a screen
23
.
FIG. 5
is a view schematically showing an optical system for a color liquid crystal projector using the reflection liquid crystal proposed in Japanese Laid-Open Patent Application No. 6-265842. This optical system is called a Schlieren optical system.
Referring to
FIG. 5
, light emitted by a light source
1
is roughly collimated by a reflector
2
(parabolic mirror), reflected by a mirror
36
, and condensed through a condenser lens
4
to form a light source image near a reflection mirror
43
arranged at the position of the aperture stop of a projecting lens
48
. The light beam is reflected by the reflection mirror
43
toward a plano-convex lens
44
, collimated by the plano-convex lens
44
, and separated into three colors by a cross dichroic prism
42
. The three color light components respectively illuminate reflection liquid crystal panels
25
,
26
, and
27
of the corresponding wavelength bands.
The light beams modulated by the reflection liquid crystal panels
25
to
27
are synthesized into a full-color image by the cross dichroic prism
42
. The full-color image is focused by the plano-convex lens
44
, passes through a stop
28
, and is projected on a screen
23
through the projecting lens
48
.
A liquid crystal, e.g., a polymer dispersed liquid crystal is sealed in each liquid crystal panel. When the white level is to be displayed, the liquid crystal panel becomes transparent to reflect an incoming light beam. In displaying the black level, it scatters the light beam. The
Koyama Osamu
Kuramochi Junko
Sugawara Saburo
Canon Kabushiki Kaisha
Mack Ricky
Morgan & Finnegan , LLP
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