Patent ID: 11256073

Abstract:
A zoom lens system with a large zoom ratio is disclosed, which operates in a broad spectral range, including visible and infrared spectra. The zoom lens system comprises, in order from the object side to the image side, a positive first lens group, a negative second lens group, a positive third lens group, a positive fourth lens group, and a detection system, wherein zooming from a wide-angle end to a telephoto end is performed by axially moving the second and third lens groups. The system has a relatively long back focal length, and satisfies the following conditions: 0.2<|f2|/(fW*fT)½<2, 1<f4/|f2|<8, 0.3<|f2|/f3<1.5, where fW is the system focal length at the wide-angle end, fT is the system focal length at the telephoto end, (fW*fT)1/2 is the geometric mean of the two focal lengths, and fi is the focal length of the i-th lens group.