In a system for real-time coherent optical filtering of visual imagery which encompasses a laser and a set of lenses for transmitting a visual target image of an input, a Fabry-Perot interferometer for filtering the target image to produce a filtered target image at an output having a predetermined bandwidth of spatial frequency information, the improvements relate to the output being in the form of a low-light level video system capable of detecting the filtered image even when at a low level of luminance, and a laser adjustable in operating power between low and high levels and in operating wavelength within a wide range for adjusting the bandwidths of the interferometer between narrow and broad ranges.