Design of a SWIR optical zoom system for surveillance

We have designed a SWIR(Short Wavelength Infrared) optical zoom system for surveillance. The focal length of the optical zoom system was 50mm to 500mm for a 640x512 pixel detector. The spot diameter of the optical system was about less than 30um concerning the pixel pitch of the SWIR detector. The MTF of the optical system was about 0.3 at the edge field of view. In field test we have proved to be able to get the image of a target in 1.5 times longer distance than visibility range by using our optical system with a SWIR detector at the focal length of 300mm.