A GATED VIEWER FOR TARGET RECOGNITION IN ADVERSE ATMOSPHERIC CONDITIONS

 

It was shown with a transmissometer and a contrast radiometer designed at SRDE that forward and backscatter can degrade the recognition of a target when it is illuminated by a continuous light source. In a 100 metre dark tunnel a target situated behind light scattering screens was illuminated by a very brief of pulse of light emitted by a laser. The delay time was adjusted before the viewer was switched on to receive the pulse of light reflected from the target. The back-scattered light was then excluded from the viewer and the signal to noise ratio of the signal reflected from the target to the scattered light noise from the screens was changed from less than unity to a value where the target was recognisable. By changing the delay time before the viewer was switched on and also the time for which the viewer was switched on it was possible to change the image of the target from a bright object to a silouhette. Image storage techniques required to prolong or to capture the transient images were then developed at SRDE.