Optics: image projectors – Polarizer or interference filter
Reexamination Certificate
1999-10-20
2001-06-19
Dowling, William (Department: 2851)
Optics: image projectors
Polarizer or interference filter
C353S033000, C349S009000
Reexamination Certificate
active
06247814
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projecting device, and more particularly, to a projecting device for displaying electronic images.
2. Description of the Prior Art
Please refer to FIG.
1
.
FIG. 1
is a schematic diagram of a projecting device
10
of an LCD projector according to the prior art. The projecting device
10
comprises a light source
12
, a uniform illumination optical device
14
, a light-separating device
16
, a trichromatic prism
18
, three modulating devices
20
, a projecting lens
22
and three focussing lenses
17
,
19
and
21
. The light source
12
produces a white beam of light. The uniform illumination optic device
14
installed in front of the light source
12
converges the light emitted from the light source
12
into an approximately square-shaped beam with a uniformly distributed illumination. The light-separating device
16
separates the square-shaped beam into red (R), green (G) and blue (B) color input beams. The approximately square-shaped trichromatic prism
18
, having three input sides
18
a
and an output side
18
b,
combines the red (R), green (G) and blue (B) input beams into an output beam. The three modulating devices
20
are installed in front of their associated input sides
18
a
of the trichromatic prism
18
to modulate the three input beams. The three focusing lenses,
17
,
19
and
21
, separately installed in front of the three modulating devices
20
, focus the three input beams from the light-separating device
16
onto the three modulating devices
20
. The projecting lens
22
installed in front of the output side
18
b
of the trichromatic prism
18
projects the combined output beam from the trichromatic prism
18
onto a screen
24
. Each modulating device
20
consists of a transparent monochromatic liquid crystal display panel used to display a monochromatic image. The trichromatic prism
18
combines the three monochromatic images to form the output color image.
The light-separating device
16
comprises a first dichroic mirror
26
to separate the red light from the square-shaped white beam from the uniform illumination optic device
14
. A reflecting mirror
27
reflects the red light from the first dichroic mirror
26
onto the focusing lens
17
. The remaining light reflects from the dichroic mirror
26
to a second dichroic mirror
28
that separates out the blue light and reflects it to the focusing lens
19
. Two optical lenses
30
and two reflecting mirrors
32
pass and reflect the remaining 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 light. 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 its loss of intensity.
However, the installation of the two optical lenses
30
makes the 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 THE INVENTION
It is therefore a primary objective of the present invention to provide a projecting device to solve the above mentioned problems.
In a preferred embodiment, the present invention provides a projecting device comprising:
a light source for generating a polarized trichromatic beam which comprises red, green and blue beams of the same polarization;
first, second and third modulation units, each modulation unit being used for modulating a polarized monochromatic beam and changing its polarization by reflection;
an optic module comprising first and third polarization beam splitter mirrors and a second dichromatic mirror, the first and third polarization beam splitter mirrors being aligned approximately along a flat surface, the second dichromatic mirror being perpendicular to the flat surface; and
an input lens set installed between the light source and the optic module comprising a fourth dichromatic mirror used for separating the polarized trichromatic beam into a polarized monochromatic beam and a polarized bichromatic beam, and a retarder film used for converting the polarization of one polarized monochromatic beam within the polarized bichromatic beam into another polarization, the polarized monochromatic beam and polarized bichromatic beam being input into the optic module in two mutually perpendicular directions;
wherein the polarized monochromatic beam is transmitted to the first polarization beam splitter mirror and the polarized bichromatic beam is transmitted to the third polarization beam splitter mirror, the first polarization beam splitter mirror transmits the monochromatic beam to the first modulation unit and transmits the first modulated beam reflected from the first modulation unit to the second dichromatic mirror, and the third polarization beam splitter mirror separates the polarized bichromatic beam into two polarized monochromatic beams which are separately transmitted to the second and third modulation units, and then transmits the second and third modulated beams reflected from the second and third modulation units to the second dichromatic mirror, and the second dichromatic mirror combines the first, second and third modulated beams to form an output beam.
It is an advantage of the present invention that the distances traveled by the red, green and blue beams are approximately equal and very short. So the projecting device
40
does not need to use extra lenses and mirrors and is simpler in structure, less expensive and more efficient.
This and other objectives 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 which is illustrated in the various figures and drawings.
REFERENCES:
patent: 4749259 (1988-06-01), Ledebuhr
patent: 4842374 (1989-06-01), Ledebuhr
patent: 5105265 (1992-04-01), Sato et al.
patent: 5153752 (1992-10-01), Kurematsu et al.
patent: 5274968 (1994-01-01), Haven et al.
patent: 6113239 (2000-09-01), Sampsell et al.
patent: 6183091 (2001-02-01), Johnson et al.
Dowling William
Hsu Winston
Primax Electronics Ltd.
LandOfFree
Projecting device for displaying electronic images does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Projecting device for displaying electronic images, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Projecting device for displaying electronic images will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2445504