A Discharge Illuminant for Optical Systems capable of either Continuous or Flash Operation

Abstract

IT is sometimes desired to illuminate an object in an optical system at one level for general examination and at a momentarily higher level for photographic recording. The development of a combined flash and continuous source lamp offers a novel method for doing this. The high-pressure mercury-vapour compact-source lamp, the characteristic high brightness of which is well known, has successfully been used under pulse conditions to provide high levels of illumination for high-speed ciné photography^1,2; this type of lamp has also been used as a condenser flash-discharge source to give high-intensity short-duration flashes of light. Recently a small xenon discharge lamp has been developed which provides a useful amount of light for such purposes as photo-micrography, and can, in addition, be switched at will from the steady arc to a condenser flash-discharge with a flash duration of less than 50 microsec. The xenon discharge gives excellent colour rendering under both conditions of operation.