Illumination – Light modifier – Refractor
Reexamination Certificate
2000-04-07
2001-09-04
Quach, Y. (Department: 2875)
Illumination
Light modifier
Refractor
C362S333000, C362S336000
Reexamination Certificate
active
06283615
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an illumination apparatus having a collimator lens, and more particularly to an illumination apparatus having a collimator lens that converts a convergent light beam to a collimated light beam.
In the past, a projection display apparatus was known such that a light emitted by an illumination apparatus illuminates a spatial light modulator and the light modulated by the spatial light modulator is projected onto a screen so as to display a picture image thereon.
Upon investigation by the inventor of the present invention, a configuration described below is presented.
As shown in
FIG. 1
, a light emitted from a light source
39
between a pair of opposing electrodes
37
of a light bulb
21
is reflected by a mirror
23
, after which it is converted to a collimated light beam by a collimator lens
25
, and enters into an integrator
31
having a first fly-eye lens
27
and a second fly-eye lens
29
.
The fly-eye lenses
27
and
29
of the integrator
31
, as observed from the direction of the optical axis O shown in
FIG. 1
, have tiny lens segments
27
e
and
29
e
, respectively, arranged in a matrix. The integrator
31
is configured so that each spot image of the light bulb
21
by the lens segments
27
e
of the first fly-eye lens
27
is correspondingly formed at the lens segments
29
e
of the second fly-eye lens
29
. When viewed from the left side in the direction of the optical axis O in
FIG. 1
, each spot image
32
of the light bulb
21
formed at the lens segments
29
e
of the second fly-eye lens
29
appears as shown in FIG.
2
.
Returning to
FIG. 1
, the light exiting from the second fly-eye lens
29
passes through a condenser lens
33
, and then enters into a spatial light modulator
35
.
The spatial light modulator
35
is an element that, by use of the birefringence of a liquid crystal, for example, imparts light modulation to its incident light in accordance with a video signal. In this case, the light from the light-collecting lens
33
is reflected by the spatial light modulator
35
as it is modulated thereby, so that the reflected light forms a video image on a screen (not shown in the drawing).
As shown in
FIG. 1
, the above-noted collimator lens
25
in general has simple spherical curved surfaces at its light entrance and exit surfaces.
SUMMARY OF THE INVENTION
However, upon further making more detailed investigation of the above-presented illumination apparatus, the inventor has found out the following technical facts.
Firstly, as shown in
FIG. 3
, together with the above-described collimator lens
25
, while a light beam exiting therefrom and propagating in a region A near the optical axis O is converted into a collimated light beam with relatively good precision, each light exiting from the collimator lens
25
and propagating in regions B and C that are distant from the optical axis C exhibits a tendency to gradually broaden outward as it propagates from the collimator lens
25
along the direction of the optical axis C.
In order to compensate for such broadening of the light beam, an attempt was made to appropriately shift the optical axes of the lens segments
27
e
of the first fly-eye lens
27
shown in
FIG. 1
in a direction perpendicular thereto, for example. However, when the optical axes of the lens segments
27
e
are shifted in this way, steps occurs between adjacent lens segments
27
e
, and these steps cause so-called sags at the edge parts of the first fly-eye lens
27
when the lens
27
is manufactured. Additionally, the trueness to sphericity of the lens segments
27
e
is lowered, and non-uniformity occurs in the radius of curvature of the lens segments
27
e
. When the collimator lens
25
is used in the illumination apparatus, these phenomena cause mass production problems such as a worsening of yield and, because sag cannot be completely eliminated, there is even a lowering of the illumination efficient itself.
Accordingly, in accordance with the above-described investigation, it is an object of the present invention to provide an illumination apparatus which is suitable for mass production and which features a high illumination efficiency, using a collimator lens that performs precise conversion of a light beam entering thereinto in order to generate a collimated light beam, even at locations distant from the optical axis, that is, regardless of the distance from the optical axis.
An Illumination apparatus according to the present invention is provided with a light source, a mirror that reflects a light emitted by the light source and converts it to a convergent light beam, and a collimator lens that collimates the convergent light beam reflected by the mirror to a collimated light beam. Here, the collimator lens is provided with a region positioned at a central region with respect to an optical axis and having a negative focal distance, and a plurality of concentric annular regions centering with respect to the optical axis and having focal distances different from each other.
REFERENCES:
patent: 1393573 (1921-10-01), Ritter
patent: 2143435 (1939-01-01), Dietrich
patent: 2215900 (1940-09-01), Bitner
patent: 2853599 (1958-09-01), Kliegl
patent: 07174974 (1995-07-01), None
Nath Gary M.
Nath & Associates PLLC
Quach Y.
Victor Company of Japan , Limited
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