Head of display arrangements

Abstract

In an earlier Specification there is described and claimed a surveillance arrangement suitable for use in an aircraft wherein a television camera/display combination provides an image of the viewed scene, and infra-red detector means viewing part of the same scene provides brighten-up signals to effect a localized increase in intensity of the displayed image to highlight heat emitting targets in that part of the viewed scene; the resultant display is ultimately made available to the pilot via a HUD screen. This arrangement is not always satisfactory, and the present invention seeks a better solution by arranging for a target-emphasising visual effect to be generated and projected onto the HUD screen quite separately of the view of the scene, whether that view is obtained directly (through the HUD screen) or indirectly (from an image projected onto the HUD screen). Specifically, it provides a head-up display (HUD) system which includes means (2), preferably a scanning IR detector array, responsive to a radiation characteristic, preferably the IR output, of a target, within a scene viewed in operation on or through the HUD screen, for generating a signal (via 10,18,19) which causes a target-emphasizing visual effect (at 22, preferably a frame around the target position) to be projected onto the HUD screen separately of any scene viewed therethrough or of any image scene projected thereonto.