GB1062545A - Optical logic arrangement - Google Patents

Abstract

<PICT:1062545/C4-C5/1> An optical NOR circuit comprises a plurality of input light sources which are reflected into one or more light channels, the arrangement being such that an output light beam is obtained only when there is no light from any of the light sources. In Fig. 1 the beams from input sources L1-L3 are reflected by half-silvered mirrors Sp1-Sp3 on to a semi-conductor wafer H which is opaque to a particular wavelength when illuminated; light of this wavelength from source LZ is selected by a filter F1 and provides the output beam Stz1 when the wafer H is not illuminated from any of the inputs L1-L3. Apertured screens B1-B3 divide the light into the two channels, and the mirror Sp2 may be provided with an etched spot C which defines the output beam Stz1 and which provides an output beam St21 whenever there is an input from L2. In a modification, Fig. 3 (not shown), the light source L2 and semi-conductor wafer H are omitted, and the input light sources are directed on to a light detector (E) controlling a light source (S) which provides the output light beam Stz1. The units E and S may comprise a resistive photo-cell and neon lamp, or a photo transistor and Ga As Lamp. In another arrangement, Fig. 2 (not shown), input light beams (St4 and St5) are respectively reflected into a glass rod (Gs) forming the light channel by means of a set of shallow etched-out areas (Ae) and by means of a single groove (Ek) acting like a prism. The output beam may be split into two outputs by using a half-silvered mirror (Sp4, Fig. 4, not shown).