Radiation source detection.

摘要

Apparatus is provided for detecting a distant point source of radiation S with a low false alarm rate when set in a scene comprising adistribution of confusing sources of radiation. An image of the scene is formed as an array of picture elements OPE, each original picture element having a brightness value, which are transformed into array of processed picture elements PPE. Them brightness value of each processed picture element is compared with a threshold brightness level THR pre-assigned to that processed picture element, a point source being detected if the brightness value of any processed picture element exceeds the pre-assigned threshold brightness value. According to the invention an expectation of the range to the point source is obtained and the radiant intensity of the source is known. The attenuation of the source radiation by the atmosphere between the point source and the apparatus is calculated (22) and the expected processed picture element brightness value due to the point source calculated. A threshold brightness value THR based upon the expected processed picture element brightness value is then assigned to each processed picture element. The apparatus may be for use on board a ship at sea to detect an incoming sea-skimming missile comprising the source S.