Dynamic information storage or retrieval – Systems having plural physically distinct independent tracks... – Common time base
Reexamination Certificate
1994-01-18
2003-04-08
Korzuch, William (Department: 2653)
Dynamic information storage or retrieval
Systems having plural physically distinct independent tracks...
Common time base
C369S112100, C369S124030
Reexamination Certificate
active
06545968
ABSTRACT:
FIELD OF THE INVENTION
The present invention pertains to the field of two-dimensional spatial light modulation.
BACKGROUND OF THE INVENTION
Optics is playing a greater and wider role in the fields of electronics, telecommunications, signal processing, and data storage. Light beams are preferable over electrical signals because of their high bandwidth and propagation speed. Rather than using conventional electrical signals, optical based systems employ light beams to convey and process information. In optical based systems, a light source, such as a laser, is modulated to convey the desired information. By implementing digital or analog modulation, the light beam can be used in a wide variety of different applications. Chief among these applications has been the generation of visual displays, optical signal processing, optical digital computing, laser printing, and storage of digital information, etc.
Although lasers can be modulated at rather high frequencies, many applications require even higher data rates. In an effort to increase the data rate, some prior art optical systems have implemented multiple light beams. By processing these multiple light beams in parallel, the overall speed of the system can dramatically be enhanced. And depending on the particular application, the number of light beams can range from tens to perhaps several thousands.
The disadvantage to utilizing multiple light beams is that a separate light source was typically required to generate each of these beams. Not only do these additional generators significantly increase the cost, but they also impact the reliability of the overall system. Moreover, these multiple generators increases the size of the packaging several fold.
Furthermore, prior art light modulation schemes have typically concentrated on the number of modulator array elements, rather than the element or total array modulation rate. Not that waveguide and PLZT ceramic devices operate only in transverse mode, whereas pockels effect devices operate in either transverse or longitudinal modes.
Thus, there is a need in the art for a light beam multiplication apparatus and method, whereby a single or a few light sources can be used to effectively create multiple light beams, each independently modulatable. It would also be preferable if such an apparatus and method could achieve a high throughput rate by implementing a fast, electrically driven modulator element array, comprised of a multiplicity of part independent modulators through each of which passes a single light-beam. It is further most beneficial if each throughput light-beam is diffraction limited.
SUMMARY OF THE INVENTION
The present invention pertains to an apparatus and method for generating a two dimensional array of diffraction limited modulated light beams for use in optical fiber telecommunications, optical signal processing, optical digital computing, laser printing, optical recording, etc. Basically, a laser diode and a collimator are used to generate a single collimated light beam. This collimated light beam is passed through a two dimensional holographic beam splitter. Thereupon, the holographic beam splitter produces a two dimensional divergent array of diffraction limited collimated light beams. These light beams are then independently modulated by a matched two dimensional array of electrooptic modulator elements to produce a two dimensional array of modulated light beams. The modulator array can be comprised of discrete micro optical Pockels modulators, waveguide structures, or an array of ferroelectric modulators using either bulk materials or a thin film layer deposited on a substrate. The resulting two dimensional array of modulated light beams can then be sent on to a recording medium or to an input plane to a next process.
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Feldman et al.,Iterative Encoding of High-Efficiency Holograms for Generation of Spot Arrays,Optics Letters, Optical Society of America, Washington D.C., May 15, 1989, vol. 14, No. 10, pp. 479-481.
Watabe et al.,Multi-Beam Read-Verifying Optical Head for Parallel Recording,Japanese Journal of Applied Physics Part 1, Nov. 1993, vol. 32, No. 11B, pp. 5406-5410.
Blakely , Sokoloff, Taylor & Zafman LLP
Chu Kim-Kwok
Korzuch William
Lots Technology, Inc.
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