Abstract: Apparatus for efficiently modulating the output from an infrared radiation source is provided by a collector/collimator for collecting and collimating the output of the radiation source and a modulator including a stator and at least one rotor. The stator includes a disc of alternating opaque and transparent radial segments having means associated therewith for gathering the radiation from the source and passing substantially all of it to the transparent segments including optical wedges arranged on the opaque segments and a central reflector/collector. The rotor includes a disc of alternating transparent and opaque radial segments. A second rotor may be provided for adding a second modulation and comprises a disc of alternating opaque and transparent radial segments also having optical wedges arranged on the opaque segments and a central reflector.

Abstract: An infrared countermeasures system is provided by ganging a plurality of modulators each of which modulates the output of a radiant source to generate at least one collimated beam of radiation. The modulators are so disposed with respect to each other that the beams generated the reby are staggered in angular phase. When the modulators are rotated together they will provide at a point in space remote therefrom a signal comprising a burst of pulses followed by a dead time when no signal is present.