Circuit and method for preventing laser jamming of night vision goggles

Abstract

A method for preventing laser jamming of night vision goggles having a gated image intensifier device and a display for displaying an intensified image of a scene. The method includes the steps of detecting laser pulses from a jamming laser source and producing respective electrical pulses in response thereto, and gating off the gated image intensifier device in synchronism with the electrical pulses in order to thereby prevent the laser pulses from affecting the intensified image of the scene displayed by the display. The step of gating off the gated image intensifier device is preferably carried out by using a phase locked loop to produce a PLL output signal synchronized with the laser pulses, conditioning the PLL output signal to produce a conditioned PLL output signal, comparing the conditioned PLL output signal with a prescribed reference voltage to generate a comparator output signal having a first level when the PLL output signal is greater than a prescribed reference voltage, and a second level when the PLL output signal is not greater than the prescribed reference voltage, generating a pulse train in response to the comparator output signal, and applying the pulse train to the gated intensifier device. The step of detecting laser pulses from the jamming laser source is preferably carried out by using a photodetector device to detect the laser pulses and to produce rounded electrical pulses corresponding to the detected laser pulses, and squaring the rounded electrical pulses to produce the electrical pulses, wherein the electrical pulses comprise square electrical pulses. Also disclosed is a circuit for implementing the above-described method for preventing laser jamming of night vision goggles.