Optical: systems and elements – Polarization without modulation – By relatively adjustable superimposed or in series polarizers
Reexamination Certificate
2001-06-13
2002-05-07
Shafer, Ricky D. (Department: 2872)
Optical: systems and elements
Polarization without modulation
By relatively adjustable superimposed or in series polarizers
C359S490020, C359S487030, C359S634000, C359S247000, C359S250000, C359S256000, C353S020000, C353S031000, C349S005000, C348S756000
Reexamination Certificate
active
06384972
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a projection display, more particularly to one that includes three polarization beam splitter prisms.
2. Description of the Related Art
In a conventional projection display, beam splitter prisms are employed to separate a light beam into red, blue and green primary color components to facilitate independent control of the characteristics of the latter and to achieve the effect of optimum contrast.
FIG. 1
illustrates a conventional projection display
1
that incorporates four polarization beam splitter prisms. In the conventional projection display
1
, a P-polarization light beam
2
is processed before providing the same to a projection lens
20
. The projection lens
20
has an optical axis that is parallel to an input axis of the light beam
2
. The light beam
2
includes a first (green) color component
21
, a second (blue) color component
22
, and a third (red) color component
23
.
In order to achieve independent control of the color components
21
,
22
,
23
, the components of the conventional projection display
1
are generally arranged into first and second rows. The first row is aligned with the input axis of the light beam
2
. The second row is aligned with the optical axis of the projection lens
20
. The components in the first row, in an order from left to right and with the light beam
2
coming from the left, include a first light polarization selector
10
, a first polarization beam splitter prism
11
, a second light polarization selector
12
, a second polarization beam splitter prism
13
, and a first reflective light valve
14
. The components in the second row, in an order from left to right and with the projection lens
20
disposed at the right, include a second reflective light valve
15
, a third polarization beam splitter prism
16
, a fourth polarization beam splitter prism
17
, and a third light polarization selector
18
. A fourth light polarization selector
19
is disposed between the second and fourth polarization beam splitter prisms
13
,
17
. A third reflective light valve
29
is disposed on one side of the second polarization beam splitter prism
13
opposite to the fourth light polarization selector
19
.
The operation of the conventional projection display
1
when the first, second and third reflective light valves
14
,
15
,
29
are in an active (ON) state is as follows: When the P-polarization light beam
2
passes through the first light polarization selector
10
, the polarization state of the first color component
21
will be changed from P-polarization to S-polarization. Thereafter, the S-polarization first color component
21
will be reflected by the first polarization beam splitter prism
11
toward the third polarization beam splitter prism
16
, and will be further reflected by the third polarization beam splitter prism
16
toward the second reflective lightvalve
15
. Because the second reflective light valve
15
is in the active (ON) state, the polarization state of the first color component
21
will be changed from S-polarization to P-polarization, and the P-polarization first color component
21
will be reflected back to the third polarization beam splitter prism
16
. The P-polarization first color component
21
then passes through the third polarization beam splitter prism
16
, the fourth polarization beam splitter prism
17
, and the third light polarization selector
18
such that the polarization state of the first color component
21
is changed to S-polarization prior to reaching the projection lens
20
.
As the P-polarization first color component
21
passes through the third and fourth polarization beam splitter prisms
16
,
17
, about 10% thereof will form polarized light leakage components
211
,
212
. However, the polarized light leakage components
211
,
212
have reflected paths that are transverse to the optical axis of the projection lens
20
and therefore do not reach the projection lens
20
. As such, when the second reflective light valve
15
is in the active (ON) state, the polarized light leakage components
211
,
212
that are attributed to the first color component
21
will not be projected by the projection lens
20
so as not to affect the output image quality.
After the P-polarization second and third color components
22
,
23
pass through the first light polarization selector
10
, they will be allowed to pass directly through the first polarization beam splitter prism
11
so as to reach the second light polarization selector
12
. As the P-polarization second color component
22
passes through the second light polarization selector
12
, the polarization state thereof will change from P-polarization to S-polarization. Thereafter, the S-polarization second color component
22
will be reflected by the second polarization beam splitter prism
13
toward the third reflective light valve
29
. Because the third reflective light valve
29
is in the active (ON) state, the polarization state of the second color component
22
will be changed from S-polarization to P-polarization, and the P-polarization second color component
22
will be reflected back to the second polarization beam splitter prism
13
. The P-polarization second color component
22
then passes through the second polarization beam splitter prism
13
so as to reach the fourth light polarization selector
19
. As the P-polarization second color component
22
passes through the fourth light polarization selector
19
, the polarization state thereof will change from P-polarization to S-polarization prior to reaching the fourth polarization beam splitter prism
17
. The fourth polarization beam splitter prism
17
reflects the S-polarization second color component
22
to enable the latter to pass through the third light polarization selector
18
and reach the projection lens
20
.
As the P-polarization second color component
22
passes through the second polarization beam splitter prism
13
, a polarized light leakage component
221
will be formed. However, since the polarized light leakage component
221
is reflected by the second polarization beam splitter prism
13
so as not to reach the projection lens
20
, the output image quality will not be affected thereby.
The P-polarization third color component
23
from the first light polarization selector
10
will be allowed to pass through the first polarization beam splitter prism
11
, the second light polarization selector
12
and the second polarization beam splitter prism
13
so as to reach the first reflective light valve
14
. Because the first reflective light valve
14
is in the active (ON) state, the polarization state of the third color component
23
will be changed from P-polarization to S-polarization, and the S-polarization third color component
23
will be reflected back to the second polarization beam splitter prism
13
. The S-polarization third color component
23
is then reflected by the second polarization beam splitter prism
13
so as to pass through the fourth light polarization selector
19
and reach the fourth polarization beam splitter prism
17
. The fourth polarization beam splitter prism
17
reflects the S-polarization third color component
23
to pass through the third light polarization selector
18
prior to reaching the projection lens
20
.
As the P-polarization third color component
23
passes through the first and second polarization beam splitter prisms
11
,
13
, polarized light leakage components
231
will be formed. However, since the polarized light leakage components
231
are reflected so as not to reach the projection lens
20
, the output image quality of the conventional projection display
1
will not be affected thereby.
Referring to
FIG. 2
, the paths of the color components
21
,
22
,
23
of the light beam
2
when the first, second and third reflective light valves
14
,
15
,
29
of the conventional projection display
1
are in an inactive (OFF) state are as follows:
1. The P-polarization first color c
Prokia Technology Co., Ltd.
Shafer Ricky D.
Trop Pruner & Hu P.C.
LandOfFree
Projection display with three polarization beam splitter prisms does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Projection display with three polarization beam splitter prisms, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Projection display with three polarization beam splitter prisms will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2886870