Abstract: The present invention provides an optical apparatus including an objective lens system for focusing optical radiation from a scene or object into an intermediate image and has at least one lens element which imposes a substantial degree of negative distortion on the intermediate image. The invention also provides a second lens system for focusing optical radiation from the intermediate image into a final image and an aperture stop for limiting the optical radiation forming the final image. The aperture stop is located between the final image region in which the final image is formed or to be formed and the lens element of the second lens system most distant from the final image region.

Abstract: A dual field-of-view objective system (40) which is inexpensive, has high transmission and is essentially achromatized and athermalized. The system (40) uses a silicon front lens A and all lens elements have positive temperature/refractive index change coefficient.