Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
2001-07-15
2003-03-11
Adams, Russell (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S031000, C353S020000, C353S081000
Reexamination Certificate
active
06530663
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The invention relates to a projecting device, and more specifically, to a projecting device for displaying electrical images.
2. Description of the Prior Art
Please refer to FIG.
1
.
FIG. 1
is a perspective view of a prior art projecting device
10
of an LCD projector. The projecting device
10
comprises a light source
12
that produces a white light beam, a uniform illumination optical device
14
installed in front of the light source
12
for converging the white light emitted from the light source
12
, into a uniformly distributed rectangular light beam, a light separating device
16
for separating the rectangular light beam into red, green and blue color input light beams, a trichromic prism
18
having three input sides and an output slide for synthesizing the three input light beams into an output light beam, three modulating panels
20
each formed by a monochrome liquid crystal panel and separately installed in front of the three input sides of the trichromic prism
18
for modulating the three input light beams, three focusing lenses
17
,
19
and
21
separately installed in front of the three modulating panels
20
for focusing the three input light beams from the light separating device
16
onto the three modulating panels
20
, and a projecting lens
22
installed in front of the output side of the trichromic prism
18
for projecting the synthesized output light beam from the trichromic prism
18
onto a screen
24
. Each of the modulating panels
20
is formed by a transparent monochrome liquid crystal panel for displaying a monochrome image. The is trichromic prism
18
synthesizes the three monochrome images to form the output color image.
The light separating device
16
comprises a first dichroic mirror
26
for separating the red light from the rectangular light beam, a reflecting mirror
27
for reflecting the red light from the first dichroic mirror
26
onto the focusing lens
17
, a second dichroic mirror
28
for separating light reflected from the first dichroic mirror
26
by reflecting blue light to the focusing lens
19
, and two optical lenses
30
and two reflecting mirrors
32
for passing and reflecting green light to the focusing lens
21
.
FIG. 1
clearly shows that the distance traveled by the green light is much longer than that of the red and blue lights. Since traveling distances affect light intensities, the two optical lenses
30
installed in front of the two reflecting mirrors
32
are essential to converge the green light so as to compensate for the loss of its light intensity.
However, the installation of the two optical lenses
30
makes a structure of the light separating device
16
complicated and costly. It is therefore an important objective to provide a projecting device with a simple structure that can solve the problem of unequal traveling distances for the three color beams.
SUMMARY OF INVENTION
It is therefore a primary objective of the present invention to provide a projecting device to solve the above mentioned problem.
Briefly, in a preferred embodiment, the present invention provides a projecting device comprising:
an illumination device for emitting a polarized trichrome light comprising three primary colors with various polarization;
a first, second and third modulating device, each modulating, reflecting, and changing the polarization of its own distinct polarized monochrome light;
a light separating device having a first dichroic mirror, a first polarization beam splitting mirror, a second polarization beam splitting mirror, and a third polarization beam splitting mirror, the first dichroic mirror and the third polarization beam splitting mirror being arranged along a first diagonal direction, and the first and the second polarization beam splitting mirrors being arranged along a second diagonal direction perpendicular to the first diagonal direction; and
a first retarder film installed between the second and the third polarization beam splitting mirrors; wherein the first dichroic mirror separates the polarized trichrome light into a first polarized monochrome light and a polarized dichrome light, and transmits these two lights separately to the first and second polarization beam splitting mirror, the first polarization beam splitting mirror transmits the first polarized monochrome light to the first modulating device and transmits the modulated light reflected from the first modulating device to the third polarization beam splitting mirror, the second polarization beam splitting mirror separates the polarized dichrome light into second and third polarized monochrome lights which are directly transmitted to the second and third modulating devices, and then transmits the modulated lights reflected from the second and third modulating devices to the third polarization beam splitting mirror through the first retarder film, and the first retarder film changes the polarization of one of the modulated lights reflected from the second and third modulating devices, the modulated lights transmitted from the first and second polarization beam splitting mirrors are synthesized by the third polarization beam splitting mirror to form an output light beam.
It is an advantage of the present invention that the projecting device has a very simple structure.
It is another advantage of the present invention that the traveling distances of the three polarized light beams. are approximately equal and shorter than that of the prior art device.
These and other objects and the advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.
REFERENCES:
patent: 6089719 (2000-07-01), Lin
patent: 6183091 (2001-02-01), Johnson et al.
patent: 6247814 (2001-06-01), Lin
patent: 6364488 (2002-04-01), Lin
patent: 6375330 (2002-04-01), Mihalakis
patent: 2002/0003610 (2002-01-01), Park et al.
Adams Russell
Hsu Winston
Primax Electronics Ltd.
Sever Andrew
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