Optical System
AssigneePilkington P.E. Limited
InventorIan Duguid Mearns
Life of this patent
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Abstract
A dual field optical system [20] comprises an objective [A, B,] which forms an intermediate image [10] and a relay [E, F,] which transfers radiation to a focal plane [12]. The objective [A, B] comprises a primary mirror [A] and a secondary mirror [B] arranged in the form of a Cassegrain system and is rendered dual-field by the provision of an alternative primary mirror [A.sup.1 ] which is axially movable between in-use and out-of-use positions. The primary mirror [A] forms part of a housing [J] for a linear actuator [15] which is connected by co-axial rods [14] to the alternative primary mirror [A.sup.1 ] so that the system is both compact and of low mass due to symmetry.
Claims4
An optical system comprising an objective which forms an intermediate image and a relay which transfers radiation from the intermediate image to a focal plane, wherein the objective comprises a principal concave primary mirror and a secondary mirror arranged generally in the form of a Cassegrain system and the optical system is rendered dual field by the provision of an alternative primary mirror which is axially movable between an out-of-use position adjacent the secondary mirror and an in-use position adjacent the intermediate image, where the principal concave primary mirror forms part of a housing for a linear actuator which is connected by co-axial rods to the alternative primary mirror.
Dependencies are inferred from the claim text.