|
Optical computing will have to meet the challenge of the tremendous progress actually made in the numerical field. We present prospective ideas towards the implementation of purely optical fast parallel Arithmetic and Logic Units (ALU). We first describe what could be envisionned as an electro-optical ALU system which would use a large adressable holographic memory. The corresponding (hypothetical) performance is shown to be not sufficient. The main idea which is proposed consists in trying to build processing units which can be "optically" connected together, without using any special propagating medium, or any special transducing property. As in instance, we describe an Elementary Optical Processing Unit (E.O.P.U.) based on a two-step diffraction principle. Then, a system is examined, in the aim of realizing a Purely Optical Parralel Processor (P.O.P.). Its principle would be based on a filtering process - FOUT filter - which is extended to the processing of 2 D. binary patterns, with a possible feedback implementation. The configuration of the system is studied in order to conceive the arithmetical and logical operations. It is also shown that such processors can present some associative performance. For the implementation, C.G.H. methods can be used. However, the real implementation of the filter leads to a singular problem which we have not been able to solve in general. In the last two sections, we finally propose simple logical operators based on Snell's law, and optical registers based on the propagation of very short light pulses in simple optical set-ups. The main characteristics of the proposed methods are due to the fundamental advantages of optics: speed, parallelism processing capabilities, connexion possibilities. However, severe limitations have been encountered all along the study, mostly due to the lack of non-linear possibilities. In general, these ideas will have to be tested in practice, regarding the available techniques, and particularly the possible development of integrated optical technologies.
|
