Abstract: Significant features of interest of each pulse shape, amplitude and time of occurrence characteristics, are preserved in a detection circuit that (1) employs a tapped delay line as part of means for deriving a pedestal signal at the predicted current level of an input signal to the delay line, the level of the pedestal signal being determined by extrapolating the slope and level of a running segment of the past history of the input signal level to the delay line, (2) subtracts the derived pedestal signal level from the actual level of an applied input signal, comprised of pulses superimposed on an unknown and variable background signal, to produce a difference level, (3) indicates the occurrence of a pulse by this difference level being at least equal to a threshold level, (4) selectively applies the applied input signal as the input signal to the delay line when the difference level is below the threshold level, and (5) selectively applies the pedestal signal as an input signal to the delay line when the dif

Abstract: Apparatus for sun-interference suppression in optical imaging systems reduces the light flux density in the image of the sun in comparison to the light flux density of the scene image, thereby reducing the area of the scene image that is dominated by the sun. An illustrative reduction of 27:1 of the light flux density of the image of the sun compared to the light flux density of the image of the scene is accomplished by three filters formed of photochromic material positioned along the optical axis of the sun-interferences suppression apparatus behind an image-forming lens. The lens focuses the sunlight into a converging cone; the convergence of the cone of sunlight between photochromic filters provides intensification which enhances the darkening of subsequent photochromic filters. The positioning of the photochromic filters allows only the scene image within two (2) degrees of the center of the sun to be affected by the darkened photochromic glass.