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2-D Coherent Optical Dynamic Processor

Objective

The objective of COOP was to develop and implement an optical processor for pattern recognition based on the most recent technological developments. The feasibility of parallel optical signal processing was to be demonstrated using a spatial light modulator (electrically and/or optically), a solid-state laser, and non-linear components based on the Four Wave Mixing (FWM) process, allowing real-time modification of the correlation function or alternatively matched filters. By improving the spatial light modulator a corresponding improvement in processor performance was expected, leading ultimately to a resolution of 1200 x 1200 pixels, in parallel, at a standard TV frame-rate.
The system was to be demonstrated and evaluated on a robotic application.
The objective was to develop and implement an optical processor for pattern recognition based on the most recent technological developments. The feasibility of parallel optical signal processing was demonstrated using a spatial light modulator, a solid state laser, and nonlinear components based on the four wave mixing (FWM) process, allowing real time modification of the correlation function or alternatively matched filters. A process for growing high optical quality bismuth silicon oxide (BSO) crystals of 50 mm diameter was developed. Electrically addressed spatial light modulators and optically addressed spatial light modulators were realised. Exploratory studies on the next generation of supported liquid membrane (SLM) led to the development of 2-dimensional arrays of quantum wells. Two system architectures were studied systems using dynamic correlation (continuous or pulsed);
and systems using filtering algorithms. Pulsed correlation showed good stability and reproducibility. However, due to the low level of maturity of this technology and its complexity, the second option was considered when building the industrial prototype. Various filtering techniques were considered and experimented on. Due to limitations of technology, the pure nonredundant filtering techniques (well suited for the robotic application) could not be implemented. Instead, simpler optically produced matched spatial filters, implemented in a single 4 channel filter, were used. In this way a correlator coupled to a robot was developed for pattern recognition purposes. It resulted in a very good recognition rate, good determination of the position, but rather poor angle measurement. The main difficulty encountered in the multichannel approach was the simultaneous alignment of all the channels. Despite these difficulties, the system is equivalent to a 200 Mips processor.
Excellent results on both materials on components were obtained:
-a process for growing high optical quality BSO crystals of 50 mm diameter was developed
-electrically addressed (TFT/liquid crystal) spatial light modulators were realised
-Optically addressed (BSO/ liquid crystal) spatial light modulators were realised. The BSO/LC valves were initially addressed by CRT and later by a TFT/LC matrix, giving significant improvements.
-More exploratory studies on the next generation of SLMs led to the development of 2-D arrays of quantum wells.
Furthermore, two system architectures were studied and experimented on:
-systems using dynamic correlation (continuous or pulsed)
-systems using filtering algorithms.
Pulsed correlation showed good stability and reproducibility. However, due to the low level of maturity of this technology and its complexity, the second option was considered when building the industrial prototype.
Various filtering techniques were considered and experimented on.
Due to limitations of technology, the pure non-redundant filtering techniques - well-suited for the robotic application - could not be implemented. Instead, simpler optically produced matched spatial filters, implemented in a single four-channel filter, were used.
In this way a correlator coupled to a robot was developed for pattern recognition purposes. It resulted in a very good recognition rate, good determination of the position, but rather poor angle measurement. The main difficulty encountered in the multichannel approach was the simultaneous alignment of all the channels.
Despite these difficulties, the system is equivalent to a 200 Mips processor; improvements could lead to an operating frequency of 1 KHz (a requirement of HDTV) and an increased number of channels (parallelism).
Exploitation
In this project various techniques and technologies were developed and tested either by simulation or experimentation.
The results obtained are of great value for the progress of optical processing which, by its very nature, allows real-time and wave-band applications.
Moreover, a first prototype working in an industrial environment has been developed and experimented on. It is the initial step in the attempt to develop robust low-cost systems based on optical processing.

Coordinator

THOMSON CSF
Address
Rue Camille Des Moulins
92132 Issy-les-moulineaux
France

Participants (3)

GEC-Marconi Materials Technology Ltd
United Kingdom
Address
Elstree Way
WD6 1RX Borehamwood
Thomson CSF
France
Address
Domaine De Corbeville
91404 Orsay
UNIV LIBRE DE BRUXELLES
Belgium
Address
Avenue F.d. Roosevelt Bp 122
1050 Brussels