Multispectral Laser Warning with Single Aperture Based on Speckle Interferometry

Lasers used as designator and range finders, if detected can give early warning against potential threats. Informaiton about the direction of arrival, spectral content and temporal signature of the laser are needed to countermeasure effectively. Often times the laser radiation is a secondary reflection and not necessarily directed along the optical axis of the laser sensor. For a smart laser sensor to be useful it must have a very low false alarm rate, (FAR), with a high probability of detection, be light weight and integrate easily with existing systems. In essence, an ideal laser warning system should have the following attributes: 1) Low FAR 2) High probability of detection 3) Light weight 4) Low cost 5) Multispectral 6) Large dynamic range (~10 to the 8th power) 7) Through put sensitivty 8) CW and single pulse detection (10 nsec pulse width) 9) Detect scattered and direct laser signals A system designed to detect pulsed lasers may not be effective in detecting CW lasers if such a system is looking for the fast rise time and large peak power of the pulsed laser signal and does not have the sensitivity to detect the lower power of the CW laser. As will be described later in this proposal the PAT approach to laser warning can be used for both CW and pulsed lasers. Also the PAT approach to laser warning can tell the difference between direct and indirect laser signals, i.e., laser signals that enter the sensor directly verses scattered radiation will give different signal characteristics.