Patent ID: 7012759
Filing Date: 2006-03-14
Classification: G02B

Abstract:
1. An infrared zoom lens system for forming a final image of an object, said system having an object side and an image side and forming a first intermediate real image between the object and the final image, said system comprising in order from the object side to the image side: a first optical unit including at least two lens elements and located between the object and the first intermediate real image, said unit comprising at least one optical subunit which is moved to change the magnification of the first intermediate real image; and a second optical unit including at least two lens elements and located between the first intermediate real image and the final image, at least a portion of which is moved to change the magnification of the final image; wherein at least said two lens elements of said first optical unit and said two lens elements of said second optical unit are crystalline; and wherein the zoom lens system has a zoom ratio of at least 10 to 1.