Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
2001-01-19
2003-07-01
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S490020
Reexamination Certificate
active
06587275
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a light beam polarization apparatus, and more particularly to a light beam polarization converter for electro-optical devices, such as liquid crystal projection displays.
DESCRIPTION OF THE PRIOR ART
With the advent of the information technology (IT) age, there is an increasing demand for various electro-optical displays, such as liquid crystal projection type displays. In this type of display, the light source is not inherently integrated, and thus an external source may be required for image display. As the demand for higher quality displays increases, it is becoming more and more important that the utilization efficiency of light sources be enhanced. A conventional way to increase efficiency is to convert the non-polarized light beams of a light source into linearly polarized light beams having a single polarization state, as disclosed in, for example U.S. Pat. No. 5,122,895 to Takanashi et al., wherein a conventional converter, the so-called P-S converter is disclosed. The P-polarized light component refers to the optical component of the electric field oscillation direction that is parallel to the plane of the incident light beam. The S-polarized light component is the optical component perpendicular to that plane.
As shown in prior art
FIG. 1
, in a conventional liquid crystal projection type display, the light beam emitted from a light source
10
is projected through a projection lens onto a screen (not shown) through the processing of a parallelizing lens
11
, a diffusion plate
12
, a P-S converter
13
, color-splitting lenses
14
and
15
, a reflecting mirror
16
and respective liquid crystal displays
301
,
302
and
303
. The main function of the P-S converter
13
is to reduce the optical loss of light beams when screened through the liquid crystal elements
301
,
302
and
303
for specific polarization.
FIG. 2
shows a schematic perspective view of a conventional P-S converter
70
. The non-polarized light beams I emitted from a light source travels upward from the bottom side of the P-S converter
70
, and is converted therein and thereby emitted from the top side of the P-S converter
70
as a single S-polarized state light beam.
FIG. 3
shows a typical optical path of a light beam in a conventional P-S converter. One light beam (designated “I
1
”) of a plurality of light beams emanating from the light source is representative. The light beam I
1
is incident to the P-S converter through an anti-reflection film
70
, and then subsequently becomes a light beam I
2
having both P- and S-polarization states. The light beam I
2
is then incident on a polarization splitting film
73
with a P-component I
4
penetrating through and a S-component I
3
being reflected. The P-component I
4
is converted by a half-wave plate
78
and further travels through an anti-reflection film
79
as a light beam I
6
of a single S-polarization state. The S-component I
3
reflected by the splitting film
73
is further reflected by a highly reflective film
75
and then penetrates through an anti-reflection film
77
as a light beam I
6
of a single S-polarization state.
Since the effect of polarization conversion described above may not be obtained if the light beam emitted from the light source is incident to the portion
81
as shown in
FIG. 3
, the conventional P-S converter only achieves efficiency of at best 50% in converting the polarization state of light beams. In addition, the configuration of conventional P-S converters is very complicated and carries relatively high manufacturing costs. It is also known in the art that a display incorporating such a conventional converter is notorious for high power consumption.
SUMMARY OF THE INVENTION
In view of the above problems, the principal object of the present invention is to provide a light beam polarization converter for converting an illumination source into a single polarization light source, which reduces the optical loss in light beam output, is suitable for mass production, and decreases manufacturing costs.
Another object of the present invention is to provide a light beam polarization converter for converting an illumination source into a single polarization light source, which is easily integrated with conventional devices and achieves highly efficient polarization conversion.
To achieve these objects, the present invention provides a light beam polarization converter for converting an illumination light source having a plurality of polarization states into a polarization light source, comprising
an under plate having undulated lower and upper surfaces in conjugate to each other for converging and parallelizing the light beams respectively;
a substrate having an upper surface and a ridged lower surface disposed on the under plate;
a phase retardation film of high reflectivity disposed partially on the lower surface of the substrate; and
a polarization splitting film disposed on the upper surface of the substrate, providing transmission of predetermined polarization states and reflection of predetermined polarization states of the illumination light source.
Another light beam polarization converter in accordance with the present invention is similar to the converter described above except that the phase retardation film is not included therein, and the lower surface of the substrate functions to proceed total reflection of the light beams, such that the conversion of the polarization states can be achieved.
The present invention further provide a light beam polarization converter for converting an illumination light source having a plurality of polarization states into a polarization light source, comprising
an under plate having undulated lower and upper surfaces in conjugate to each other for converging and parallelizing the light beams respectively;
a substrate having a ridged upper surface and a ridged lower surface disposed on the under plate;
a phase retardation film of high reflectivity disposed partially on the lower surface of the substrate;
an upper cover having a ridged lower surface, substantially complementary to the ridged upper surface of the substrate and facing therewith, and an upper surface; and
a thin film disposed between the upper cover and the substrate, the index of refraction thereof is different from that of the substrate.
Another light beam polarization converter in accordance with the present invention is similar to the converter described above except that the phase retardation film is not included therein, and the lower surface of the substrate functions to proceed total reflection of the light beams, such that the conversion of the polarization states can be achieved.
In order to enhance the optical performance, the ridge pitches between ridges on the upper and lower surfaces of the substrate and on the lower surface of the upper cover may be constant or not, and the direction of the polarized light beams reflected by the polarization splitting film or by the thin film and the upper cover should not be parallel to that of the ridge lines on the upper surface of the substrate, thus allowing greater freedom of converter design. Moreover, the undulations, such as cylindrical, spherical or non-spherical undulations, on the upper and lower surfaces of the under plate should be corresponding to each other in a conjugate way to ensure the light beams passing through in parallel, and thus enhance the transmitting efficiency of light beams passing through the converter. The ridged lower surface of the substrate is designed for total reflection of the light beams so as to proceed or even further enhance the conversion of the polarization states of the light beams.
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patent: 3213753 (1965-10-01), Rogers
patent: 5751480 (1998-05-01), Kitagishi
patent: 5757547 (1998-05-01), Rodman et al.
patent: 6104536 (2000-08-01), Eckhardt
patent: 6147802 (2000-11-01), Itoh et al.
patent: 6335051 (2001-01-01), Kausch et al.
patent: 6262842 (2001-07-01), Ouderkirk et al.
patent: 6373630 (2002-04-01), Lee et al.
Lee Chih-Kung
Lee Shu-Sheng
Lin Chih-Ting
Tang Ching-Heng
Epps Georgia
Harrington Alicia M.
Slight Opto-Electronics Co., Ltd.
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