Abstract: A modulated infrared source is disclosed in which spatial modulation is accomplished by the sweeping of an infrared beam past a point in space. In one embodiment close to 100% of the energy from the infrared source is focused by rotating optics including parabolically shaped reflectors about the source such that energy losses due to the modulation technique are minimized due to a single reflection of the energy from the IR source. The speed of the rotation of the reflective optics is minimized while maintaining sufficiently high modulation frequencies by the provision of four beams from a single source. In another embodiment a squirrel cage reflecting system is provided in which the energy from the IR source is reflected twice.