Patent US 4,209,255

An aiming point locating system has a single LED mounted on the helmet of a pilot in an aircraft and can be used to designate a point on a cockpit display, or the like, without touching the display. An optical device located in front of the LED tapers the energy pattern from the LED so that a sufficiently varying energy field reaches photodiodes located adjacent the display. The photodiodes are oriented toward the pilot so that they respond directly to the tapered energy field thus allowing greater accuracy in electrically identifying the pilot's aiming point on the display. A two stage switch actuated by the pilot has a partially depressed stage causing a visible aiming reticle to appear on display and a fully depressed stage activating the emitter to obtain an electrical output from the photodiodes. Monopulse processing of the signals from the photodiodes is used to create varying X-Y signals which directly correspond to the coordinates of the point on the display viewed by the pilot.