Comparison study of a multispectral zoom lens using standard and novel optical materials

We demonstrate two broadband multispectral infrared (3.5-11.5 μm), zoom (3×) systems with focal lengths adjustable from 50 mm to 150 mm. Both systems are successful in meeting the modulation transfer function (MTF) requirement of 20 lp/mm. The difference between the two designs is that one employs novel infrared-transparent glasses that permit the designer to achieve an improved system performance with dramatically fewer lens elements. The impact of these materials on the design performance is discussed in terms of MTF and chromatic focal shift as a function of temperature, and we conclude with a brief description of these new glasses and their optical functionality.