Patent ID: 8369008

Claim:
A dual-field (NF and WF) imaging system comprising an optronic detector and an optical combination of narrow-field focal length F NF having, on an optical axis: a front lens, a narrow-field entrance pupil situated in the vicinity of the front lens, a real wide-field entrance pupil, situated upstream of the front lens, an intermediate focal plane (IFP), the optical combination comprising, on the optical axis, the following refractive groups: a convergent front group G 1 of focal length F, where F<F NF /2, this group G 1 comprising the front lens, a divergent field-change group G 2 that can move along the optical axis, this group being situated upstream of the IFP in NF configuration and downstream of the IFP in WF configuration, a relay group G 3 imaging the IFP on the focal plane of the detector, wherein the detector is a cooled IR2/IR3 detector, and in that, since the refractive groups comprise lenses, at least three different materials including CaF 2 are used for the lenses of the front group G 1 .