Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
2001-08-30
2002-06-04
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S621000, C359S622000, C359S623000
Reexamination Certificate
active
06400510
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a uniform illumination optical device, and more particularly, to a uniform illumination optical device with a concave lens.
2. Description of the Prior Art
Please refer to
FIG. 1
, which is a diagram of a prior art uniform illumination optical device
10
. The uniform illumination optical device
10
, applied in a projection device, is used to provide a uniform illumination of light L produced from a light source
11
. The uniform illumination optical device
10
comprises a beam splitting device
12
for converting the light L from the light source
11
into a plurality of parallel beams I, and a beam condenser
14
for condensing the parallel beams I to form a more uniform condensed light L* than the light from the light source
11
.
As shown in
FIG. 1
, the beam splitting device
12
comprises a plurality of first dispersing lenses
16
, and a plurality of second dispersing lenses
18
that correspond to the first dispersing lenses
16
. The first dispersing lenses
16
are flat-convex lenses used for converting the transmitted light L from the light source
11
into the plurality of beams I. Similarly, the second dispersing lenses
18
are flat-concave lenses located outside a focus of the first dispersing lenses
16
, and transmit the received beams I to the beam condenser
14
.
The beam condenser
14
comprises a first condensing lens
20
and a second condensing lens
22
. The first condensing lens
20
is a flat-concave lens located behind the second dispersing lenses
18
of the beam splitting device
12
for receiving the beams I transmitted from the beam splitting device
12
. The second condensing lens
22
is a convex lens located behind the first condensing lens
20
for receiving the beams I transmitted from the first condensing lens
20
. As shown in
FIG. 1
, the beams I gradually converge to form the condensed light L* after passing the first and second condensing lenses
20
and
22
.
Generally speaking, the light L transmitted from the light source
11
is not uniform. Therefore, the beams I generated from the light L are also not uniform. Nevertheless, the beams I are condensed to form the condensed light L*. Overall, the condensed light L* is more uniform than the light L transmitted from the light source
11
.
When designing a small-sized projection device, to improve the overall performance of the device, a designer strives to achieve a short optic path, a small beam size W, and light that is parallel. A shorter optic path leads to a smaller projection device. If the beam size W is small, the actual size of the lenses, dichroic mirrors, and polarization beam splitters are decreased, which reduces the overall size of the device and lowers costs as well. In addition, dichroic mirrors, reflective liquid crystal display panels, and transmissive liquid crystal display panels all generally have a fixed range of angles for incident light. If each incident beam is parallel, the beams will have a smaller incident angle within the limiting range of allowed incident angles.
Please refer to
FIG. 2
, which is a diagram of an optic path for transmitted light from the uniform illumination device
10
incident upon a dichroic mirror
24
. Two beams I′, I″″ generated from the light L are taken as an example. If the two beams I′, I″″ are not parallel, their corresponding incident angles &thgr;′, &thgr;″″ will be different for the dichroic mirror
24
. Because the dichroic mirror
24
has a limitation on the incident angle, incident angles &thgr;′, &thgr;″″ exceeding this limitation influence the final display quality. Typically, a more expensive device, such as a coating dichroic mirror, is used to solve this problem.
Designing a short optic path, a smaller beam size, and parallel light beams according to the prior art uniform illumination device
10
is very difficult. As shown in
FIG. 1
, the second dispersing lens
18
is usually located behind the focus of the first dispersing lens
16
, and is used to disperse the beams transmitted from the first dispersing lens
16
. The optic path between the second dispersing lens
18
and the first dispersing lens
16
, therefore, must be longer than the length of the focus of the first dispersing lens
16
. Taking the second condensing lens
22
as an example, the curvature of the second condensing lens
22
must be large for a smaller beam size W. However, a larger curvature makes transmitted beams converge towards the optic center so that the transmitted beams are no longer parallel. The design of the prior art uniform illumination device
10
is thus incapable of simultaneously satisfying the demands for a short optic path, a smaller beam size, and parallel beams.
SUMMARY OF INVENTION
It is therefore a primary objective of the present invention to provide a uniform illumination device with a concave lens to solve the above-mentioned problem.
Briefly, the claimed invention provides a uniform illumination device comprising a beam splitting device for converting the light from the light source into a plurality of parallel beams, and a beam condenser for condensing the parallel beams to form a more uniform condensed light than the light from the light source. The beam condenser further comprises a first condensing lens made of a convex lens and a second condensing lens made of a concave lens. When the parallel beams transmitted from the beam splitting device pass through the first condensing lens of the beam condenser, the parallel beams converge to the central axis. On the other hand, when the parallel beams pass through the second condensing lens, the parallel beams converge with axes that are parallel with the central axis. In the end, the parallel beams transmitted from the beam splitting device through the first condensing lens and the second condensing lens mix to form the more uniform condensed light.
It is an advantage of the present invention that, with the concave lens, the uniform illumination device can satisfy the demands of having a short optic path, a smaller beam size, and the desired parallel beams.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in the various figures and drawings.
REFERENCES:
patent: 5241416 (1993-08-01), Mitsutake et al.
patent: 5786939 (1998-07-01), Watanabe
patent: 6075648 (2000-06-01), Yamamoto et al.
patent: 6246526 (2001-06-01), Okuyama
patent: 6283615 (2001-09-01), Takahashi
patent: 6330112 (2001-12-01), Kaise et al.
Acer Communications and Multimedia Inc.
Epps Georgia
Hsu Winston
O'Neill Gary
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