Automatic contrast and brightness control system for thermal image apparatus integrated into an aircraft

DETAILED DESCRIPTION It is an object of the invention to improve the automatic contrast and brightness control for thermal image apparatus of aircraft during roll movements of the aircraft.
The control system of the invention is for the automatic contrast and brightness control for thermal image apparatus of a FLIR-system integrated into an aircraft.
The FLIR-system includes a TV-monitor on which an FLIR-image having an evaluation window is formed.
The control system includes: circuit means for fixing the shape of the evaluation window; actual-value forming means for forming the actual values for contrast and brightness; and, displacing circuit means for displacing the window in dependence upon the content of the FLIR-image as defined by the actual values.
In an advantageous embodiment of the invention, the form of the window corresponds to an isosceles triangle which, in normal flight, is arranged in the FLIR-image so that its base extends over the entire width of this image and is spaced from the lower edge of the image to the extent that the scenes, which change rapidly because of the speed of the aircraft, extend and the apex of the isosceles triangle extends to the horizon line.
The form of the window as having a triangular form is described here only as being exemplary.
This window could also have other forms adapted to the scenes over which the aircraft flies and adapted to the flight conditions.
What is important for the advantageous use of the invention is however the displaceability of the window in the FLIR-image which is undertaken in correspondence to the image content determined by the contrast and brightness control system.
With the suitably selected and pregiven form of the evaluation window for the contrast and brightness control and by means of its automatically controlled displacement, the condition is prevented that the cold sky enters the evaluation window during roll movements up to approximately 90.
degree.
and unfavorably influences the contrast and brightness control