1385383 Modulating light RESEARCH FRONTIERS Inc 30 March 1972 [31 March 1971] 15163/72 Heading H4F In a light valve wherein particles suspended in a fluid are controllably aligned by an electric and/or magnetic field to vary the optical transmission or reflection characteristics of the valve, thermal convection currents are used to produce fluid flow in the valve and prevent agglomeration of the particles. As described, one or more conduits connect opposite edges of the valve, being disposed externally of, or formed integrally with, the valve. In use the fluid flow in the valve is vertical or horizontal, heat from an electric, convective or radiant heat source being applied to a part of the system where upwards fluid flow obtains, e.g. in the conduit or below a vertical valve. Alternatively, if for example the valve forms a window in a building, an external conduit may be disposed within or without the building, the temperature differential between the building and the atmosphere producing convective flow. The particles may be light absorptive, or reflective, dichroic, polarizing, birefringent, metallic or non-metallic. They may be of herapathite, graphite, mica, garnet red, aluminium, periodicles of alkaloid sulphate salts.
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