Patent 4298251 Issued on November 3, 1981. Estimated Expiration Date: September 14, 1999. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.
The system has a variator lens and a compensator lens which are mutually displaceable for varying the focal length of the optical system. In the normal zoom range, the focal length is adjustable between a telephoto condition and a wide angle condition, in accordance with the positions of the variator and compensator lenses. The system has macro capability in both a range beyond the extreme telephoto end of the zoom range and also in a range beyond the extreme wide angle end of the zoom range. In at least the macro range at the telephoto end, the slots in the camming sleeve for the variator and compensator lenses lie substantially in planes.