Projector

Details Projector Projector

2001-12-27

2003-03-25

Dowling, William (Department: 2851)

Optics: image projectors

Polarizer or interference filter

C353S031000, C349S009000

Reexamination Certificate

active

06536902

ABSTRACT:

This application claims the benefit of the Korean Application No. P2000-84717 filed on Dec. 28, 2000, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projector.
2. Background of the Related Art
The projector enlarges, and projects a small picture on a small display inside of the projector by using a lens system to a large sized screen, to display a large sized picture. There are a front projection type in which the picture is displayed on a front face of the screen, and a rear projection type in which the picture is displayed on a rear face of the screen. As a typical one of the latter, there is the projection television. As the small display in the projector that displays the small picture, LCD (Liquid Crystal Display) and DMD (Digital Micromirror Device), and the like are employed. The LCD is provided with a polarization beam converter for displaying the picture by using a linearly polarized light.
FIG. 1
illustrates a related art projector.
Referring to
FIG. 1
, the related art projector is provided with a lamp
1
for emitting a beam of light, a parabolic reflector
2
for reflecting the beam to forward of the lamp
1
, a polarization beam converter for transmitting an ‘S’ wave, and converting ‘P’ wave into ‘S’ wave and transmitting the converted ‘S’ wave among the beam from the parabolic reflector
2
, first to third illumination lenses
10
,
12
, and
14
for focusing the beam polarized into a particular polarized light at the polarization beam converter, a color switch
16
for transmitting only a particular beam among the beams from the third illumination lens
14
, a polarization beam sprite prism
18
for supplying a color light from the color switch
16
to a display
22
, and the beam reflected at the display
22
to a projection lens
20
, a display
22
for displaying a picture by reflecting the color light from the polarization beam sprite prism
18
in response to a video signal, and a projection lens
20
for enlarging the beam of the picture from the display
22
, and projecting to a distance.
The beam of light from the lamp
1
is directed to the polarization beam converter by the parabolic reflector
2
. The polarization beam converter transmits the S wave, and converts and transmits P wave among the beam from the parabolic reflector
2
.
To do this, the polarization beam converter is provided with a first lens array
4
, a second lens array
6
, and a polarization beam sprite array
8
facing a light output surface of the second lens array
6
. The first lens array
4
, or the second lens array
6
focuses the beam of light including the P wave and the S wave to a plurality of focusing points.
To do this, the first, or second lens array
4
, or
6
has a matrix of a plurality of lenses. The polarization beam sprite array
8
transmits ‘S’ wave, and converts the P wave into the S wave, and transmits the converted S wave, both from the second lens array
6
. To do this, the polarization beam sprite array
8
provided with polarization beam split planes
24
and reflection planes
26
, and half wave plates
28
attached to light output surfaces of the polarization beam split planes
24
as shown in FIG.
2
.
The polarization beam split plane
24
transmits only the P wave and reflects the S wave among the white light from the second lens array
6
. The P wave transmitted through the polarization beam split plane is converted into an S wave by the half wave plate
28
. On the other hand, the S wave reflected at the polarization beam split plane
24
is reflected at the reflection plane
26
.
That is, the entire beam of light including the P wave and the S wave passed through the polarization beam sprite array
8
is converted into the S wave. The beam of light converted into the S wave at the polarization beam converter passes through the first to third illumination lenses
10
,
12
, and
14
in succession. The first to third illumination lenses
10
,
12
, and
14
focus the beam of light converted into the S wave onto the color switch
16
.
The color switch
16
splits red, green, and blue colors in succession so that one display cell has red, green, and blue colors. To do this, the color switch
16
filters a particular color light according to a variation of a voltage signal applied. In this instance, the color light passed through the color switch
16
is converted into the P wave from the S wave, and directed to the polarization beam sprite prism
18
. The P wave color light from the color switch
16
to the polarization beam sprite prism
18
transmits a split plane
30
, and directed to the display
22
.
The display
22
reflects the P wave color light transmitted through the polarization beam sprite prism
18
according to a video signal, to produce a picture beam with picture information. In this instance, as shown in
FIG. 3A
, the P wave color light reflected at the display
22
is converted into the S wave when no electric signal is applied thereto.
The picture beam converted into the S wave at the display
22
is reflected at the split plane
30
of the polarization beam sprite prism
18
, and directed to the projection lens
20
. To do this, the split plane
30
of the polarization beam sprite prism
18
transmits the P wave, and reflects the S wave as shown in
FIGS. 4A and 4B
. Accordingly, the polarization beam sprite prism
18
transmits the P wave from the color switch
16
, and reflects the S wave from the display
22
toward the projection lens
20
. The projection lens
20
enlarges the picture beam from the polarization beam sprite prism
18
, and projects to a screen at a distance.
In the meantime, as shown in
FIG. 3B
, the display
22
transmits the P wave color light from the polarization beam sprite prism
18
is if there is an electrical signal applied thereto. Therefore, no beam of light is incident on the projection lens
20
when there is the electrical signal applied to the display
22
. The projection lens
20
enlarges the picture beam from the polarization beam sprite prism
18
, and projects onto a screen at a distance therefrom.
However, the color switch
16
for splitting the color light from the beam of light in the related art projector has a poor light efficiency caused by poor light transmission performance. A color wheel may be employed in place of the color switch
16
.
However, for employing the color wheel in the related art projector, an optical system that converges the beam of light and an optical system that diverges the beam of light are required. Moreover, the polarization beam converter in the related art projector requires lens arrays
4
, and
6
each having a plurality of lenses.
However, the lens array
4
or
6
with the plurality of lenses has optical losses between the lenses. A number of the lenses in the lens array
4
or
6
may be reduced for reducing the optical loss, but that increases a thickness of the polarization array to push the cost up. Moreover, since an optical conversion efficiency is significantly dependent on an alignment of the lens arrays
4
, and
6
, assembly of the projector requires much time.
In addition to this, the related art projector has the lamp with the parabolic reflector
2
for providing parallel lights to the polarization beam converter. The lamp with the parabolic reflector
2
has an optical efficiency poorer than a lamp
34
with an elliptic reflector
32
as shown in FIG.
5
.
It will be explained in detail assuming that a diameter of the parabolic reflector
2
is Dp and a diameter of the elliptic reflector is De. The lamp
1
with the parabolic reflector
2
directs the beam of light forward in parallel, i.e., the parabolic reflector
2
is required to have a slope for directing the beam from the lamp
1
forward in parallel.
On the other hand, the lamp
34
with an elliptic reflector
32
directs the beam of light such that the beam is focused at a plane in front of the lamp
34
. Accordingly, the elliptic reflector
32
is required to have a slope greater than the par

Affiliated with

Also associated with

Rating

Projector does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Projector, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Projector will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3035183