| 摘要 |
The invention relates to a dual-field (NF and WF) imaging system comprising an optronic detector (1) and an optical combination of narrow-field focal length FNF having, 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, that is to say situated upstream of the front lens, an intermediate focal plane (IFP). The optical combination has, on the optical axis, the following refractive groups: a convergent front group G1 of focal length F, where F<FNF/2, this group G1 comprising the front lens, a divergent field-change group G2 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 G3 imaging the IFP on the focal plane of the detector. The imaging system has a cooled IR2/IR3 detector and since the refractive groups have lenses, at least three different materials including CaF2 are used for the lenses of the front group G1.
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