Abstract: The invention comprises a modular illumination system comprising at least one mounting strip; one or more emitter strips each having an outwardly directed face in use through which infra red light may be transmitted; one or more printed circuit boards each carrying a plurality of infra red light emitting diodes; and one or more contact elements. The system is such that the or each emitter strip can interconnect with a mounting strip to form a conduit through which a power supply bus may be carried. Each contact element is adapted to complete an electrical connection between the power supply bus and a printed circuit board mounted behind the outwardly directed face of the emitter strip. The system is easily assembled and is advantageously used to provide a source of covert illumination for security or other monitoring purposes.

Abstract: A phosphate glass doped with copper in an amount of less than 2% by weight is formed to produce a lens for use on external aircraft lights. The glass attenuates infra red radiation to a degree where it does not pose a danger of temporarily blinding a pilot wearing night vision goggles yet remains visible. The glass has little appreciable effect on light transmission in the visible spectrum. Conveniently, the glass can be formed by slumping at a softening temperature against a mold to produce intricate lens shapes. In addition, the glass is able to withstand conventional toughening processes.