Optical: systems and elements – Collimating of light beam
Reexamination Certificate
2000-05-01
2001-09-18
Epps, Georgia (Department: 2873)
Optical: systems and elements
Collimating of light beam
C359S629000, C359S558000, C359S559000, C359S291000, C359S292000
Reexamination Certificate
active
06292304
ABSTRACT:
The present application is based on Korean Application No. 99-37104 filed on Sep. 2, 1999, herein incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for generating an independent coherent beam array from a single light source, and more particularly, to an apparatus for generating an independent coherent beam array in which beams are independently switched for recording and reading operations.
2. Description of the Related Art
FIG. 1
illustrates a conventional coherent beam array adapted in a holographic memory, which has been suggested in U.S. Pat. No. 4,988,153. In the coherent beam array, a plurality of vertical cavity surface emitting laser (VCSEL) diodes
14
form a two-dimensional laser diode array
12
as a light source. An XY selector
16
allows for selective electrical activation of a single or several VCSEL diodes in sequence.
The output beam from the selected VCSEL diode is converted into a collimated beam by a collimating lens
20
. The position of the selected VCSEL diode, the X-Y coordinate of the selected VCSEL diode on the two-dimensional laser diode array
12
, causes a small change in the incident angle of the collimated beam upon a holographic recording medium
10
.
Images can be written to or read from the holographic recording medium
10
by collimated beams generated from the coherent beam array. During recording, an image
40
is presented on an image light source
42
and is recorded through a recording collimating lens
46
on the recording medium
10
. The writing angle &thgr;
W
between the collimated beams respectively from the collimating lens
42
and the recording collimating lens
46
, which are incident upon the recording medium
10
, is varied, which allows multiple independent images to be superimposed and sequentially written to the recording medium
10
. Although not illustrated, during reading, images recorded on the recording medium
10
are read out only by the collimated beam, of which the incident angle upon the recording medium
10
for reading is the same as that of the reference collimated beam.
The coherent beam array generating apparatus having the above-mentioned configuration can be applied to holographic information storing devices or displays, for optical interconnections therein, which require several tens to several hundreds of light sources. The manufacture of the VCSEL
12
is technically difficult, particularly in controlling the heat generated from laser diodes thereof and in maintaining the uniformity in the intensity of laser beams as well as irradiation angle of the laser beams, which increases the manufacturing cost and produces a low yield.
SUMMARY OF THE INVENTION
To solve the above problems, it is an object of the present invention to provide an apparatus for generating an independent coherent beam array from a single light source, in which coherent beams can be independently activated for recording and reading operations.
The above object of the present invention is achieved by an apparatus for generating an independent coherent beam array, comprising: a single light source; a first collimating lens for collimating the beam emanated from the light source; a phase grating for splitting the collimated beam from the first collimating lens into a plurality of diffraction beams; a Fourier transform lens for focusing the diffraction beams from the phase grating into beam spots by Fourier transformation; a reflective spatial light modulator for selectively reflecting the beam spots from the Fourier transform lens; a polarizing beam splitter for passing the beam spots from the Fourier transform lens toward the reflective spatial light modulator, and changing the path of the beams reflected by the reflective spatial light modulator; and a second collimating lens for collimating the beams reflected by the reflective spatial light modulator and incident via the polarizing beam splitter.
Preferably, assuming that grating periods for the X- and Y-axis directions of the phase grating are d
x
and d
y
, respectively, and the wavelength of the beam emanated from the light source is &lgr;, the focal length of the Fourier transform lens is f, the distances between spots focused onto the reflective spatial light modulator in the X-axis and Y-axis directions, S
x
and S
y
, respectively, are expressed by equations
S
x
=
λ
f
d
x
S
y
=
λ
f
d
y
.
Also, the reflective spatial light modulator may be constructed of a micro-mirror reflector or a reflective liquid crystal display panel.
REFERENCES:
patent: 4877297 (1989-10-01), Yeh
patent: 4988153 (1991-01-01), Paek
patent: 5121228 (1992-06-01), Paek
patent: 5497254 (1996-03-01), Amako
patent: 5740276 (1998-04-01), Tomoko
Kim Ji-deog
Lee In Young
Lee Suk-han
Burns Doane Swecker & Mathis L.L.P.
Epps Georgia
O'Neill Gary
Samsung Electronics Co,. Ltd.
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