Multiple field of view changing apparatus for an optical system

摘要

A three field of view change apparatus has a cubic carousel 1 mounted for rotation about a rotation axis 2 which is coincident with a diagonal of the carousel 1. The rotation axis 2 makes an angle of 54.736 DEG with a fixed optical axis 5 so that carousel 1 can be rotated to cause the fixed optical axis 5 to pass through the centres of any two opposed faces of the carousel 1. Optical components 14 are arranged on opposed faces of the carousel 1 and can be swung into alignment with the optical axis by rotating the carousel.