Design of large zoom ratio long-wave infrared zoom system with compound zoom method

The continuous zoom system with a large zoom ratio can search for a target in the wider field-of-view and distinguish a target at a further distance. As the range of focal length is limited for a traditional continuous zoom system, we present a compound zoom method to greatly increase the range of focal length for a traditional continuous zoom system. The compound zoom method combines the traditional zoom system with a dual field-of-view zoom system to achieve a large zoom ratio. The differential equation model of the compound zoom method is established. Based on this model, a long-wave infrared zoom system with a zoom ratio of 36 and F/1.6 is designed, and it has such advantages as large zoom ratio, simple mechanical structure, good image quality, and smooth cam curves.