Smiths Industries Plc

George Mann

A head-up display system for an aircraft has a display unit which projects a display of symbology representing the aircraft flight parameters onto a separately mounted partially-transparent reflector positioned in front of the aircraft pilot, so that the pilot sees an image of the display against the external scene. The display unit has a sensor which receives an image of the display via the reflector. The sensor responds to displacement of this image from a reference established with respect to the display unit, caused by movement of the reflector relative to the display unit, and the display is correspondingly modified to compensate for such movement. The display unit may include a cathode-ray tube for providing the display which can be modified by adjustment of the deflection of the cathode-ray beam. In this case the reference established with respect to the display unit may be an instantaneous point image of the cathode-ray beam. A light source may be mounted with the display unit and the sensor may be arranged to respond additionally to displacement of an image of this light source received via the reflector. The light source may be located at a position spaced from the center of the display. Two sensors may be provided in the display unit, one of which receives an image of the display directly from within the unit, and the other of which receives an image of the display via the reflector, the display being modified in accordance with the difference between the outputs of the two sensors. The sensors may each be formed by a matrix array of photo-responsive devices.

Display systems

A head-up display system in a military aircraft provides projection of flight and weapon-aiming information into the pilot's line-of-sight through a partially-transparent reflector. The pilot operates a button firstly when he recognizes a target viewing through the display and then again when he fixes his eye on an aiming marker in the display. On each occasion of button operation a measure of his eye position is entered into the system to derive coordinates of the identified target related to the marker position in the display, for generation of the appropriate shifts to move the marker into register with the identified target. The measure of eye position is provided in each case by analysis of video-signal waveforms derived by a vidicon camera that is carried on the pilot's helmet and scans reflection in the helmet-visor of the pilot's eye as illuminated, also by reflection in the visor, from an infra-red source. The analysis involves determination from the video signals of successive line-scans of the eye-image, of the boundaries of the iris (or pupil) in relation to both the frame and line time-bases, and computation therefrom of coordinates of the centerpoint of the pupil. Compensation for head movement in the interval between the two measurements of eye position is provided in accordance with variation during that interval of the phasing (in the time-bases) of response to two arrays of point-sources mounted on said reflector.

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Winchcombe, United Kingdom

George Mann