Comparison of four midwave (3-5 mu m) f2 objectives in the sense of their thermal performance

Passive athermalization of infrared (IR) imager objectives such as thermal goggles and binoculars which are exposed to variable atmospheric conditions is a critical issue. In this study, an athermal 50 mm f2 midwave objective design is compared with three similar commercially available objectives in terms of modulation transfer function (MTF) in Nyquist frequency under varying temperature conditions. The test setup constructed to enable the experimental comparison and the test process utilized are described. Finally, the results obtained are comparatively evaluated.