Design of double-group IR zoom lens

A 15× double-group linkage zoom lens was presented based on the 640×512 cooled FPA. Having two alternate components linked and moved together, double-group zoom structure has smoother cam curve, so the displacement of all components are smaller and the total length is shorter. The focal length rang is 30~450mm and wavelength is 3.7~4.8μm, F number is 4. This lens was placed at cold shield and 100% cold shield efficiency had reached. Moreover, detailed design and image quality were given by CODE V® optical software. After analysis, MTF approaches diffraction limit. The results show that this optical system has large zoom ratio, and excellent image quality.