Acousto-optic tunable filter apparatus and method for detecting and

Abstract

A source of broad-band and/or narrow band optical radiation is detected and identified by apparatus including a pair of acousto-optical tunable filters which diffract from orthogonally polarized components of the optical radiation, a diffracted ordinary polarized beam and diffracted extraordinary beam, respectively. Undiffracted polarized radiation from the two AOTFs is combined and directed to a first detector which may comprise a small array such as a quadrant array. The diffracted ordinary and extraordinary polarized beams are directed to a second detector which is preferably a single large imaging array. A signal processor uses signals from the first detector generated by the undiffracted beams to detect the presence of the source, and polarized spectral signals from the large imaging array to identify the source of the radiation . A control unit generates radio frequency signals which can be rapidly varied in frequency to control wavelength of the polarized beams diffracted by the AOTFs. These radio frequency (rf) signals may be applied simultaneously, with or without amplitude modulation, or sequentially, to the AOTFs, and may be of the same or different frequencies. The rf drive may be withheld from the AOTFs to maximize the undiffracted beams for maximum range detection.