Patent ID: 9025256
Filing Date: 2015-05-05
Classification: G02B

Abstract:
1. A non-reimaged optical system without an intermediate image plane and comprising: a first lens group comprising a first lens element having a positive power and a second lens element having a positive power; a second lens group comprising a first movable lens element having a negative power and a second movable lens element having a negative power, the second lens group being disposed adjacent the first lens group; a third lens group comprising a first third-group lens element having a positive power, a second third-group lens element having a positive power, a third third-group lens element having a positive power, and a fourth third-group lens element having a negative power, the third lens group being disposed adjacent the second lens group; and a detector disposed behind the third lens group and disposed within a cold shield for cooling the detector; wherein a pupil and an aperture stop of the non-reimaged optical system are located between the third lens group and the detector, external to the first lens group, the second lens group and the third lens group in combination, there being no lens groups positioned between the pupil and the detector, the pupil being disposed coincident with the cold shield and co-located with the aperture stop; and wherein the second lens group is movable respective to the first lens group and the third lens group along an optical axis extending between the first lens group and the detector so as to convert a configuration of the non-reimaged optical system between a narrow field of view (NFOV) configuration and a wide field of view (WFOV) configuration, the pupil being external to the first lens group, the second lens group, and the third lens group in both the NFOV configuration and the WFOV configuration.