The underwater image which does not receive the influence of reflection from the aircraft electricity the system null which is detected optically

摘要

An electro-optical detection system for detecting objects (12) embedded within a partially transmitting medium comprises means (20) to receive electro-magnetic radiation in two close spectral channels (28, 212): a signal channel (212) where the wavelength and bandwith of the signal channel are optimised to correspond to the peak of transmission of the medium and a reference channel (28) where the wavelength and bandwidth are selected to correspond to a spectral region where attenuation in the medium is high. The signal and reference channels are then subtracted (213) so as to remove the effect of reflected radiation from the signal channel (212). The signal is processed digitally (218) to provide an enhanced image of the field of view. In a particular arrangement for detecting objects underwater a CCD TV camera (20) is used with three separate CCD detector arrays providing concurrent red (R), green (G), blue (B) output signals. The green and blue signals are combined in an adjustable ratio to provide the image signal to match the prevailing conditions of the partially transmitting sea. A notch filter is employed to cut out light in a spectral band between the signal and reference channels.