Real image mode variable magnification finder
Patent 5970266 Issued on October 19, 1999. Estimated Expiration Date: 
February 20, 2018. 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.
February 20, 2018. 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.Patent ReferencesReal image type variable magnification viewfinder optical system Patent #: 5257129 InventorAssigneeApplicationNo. 026533 filed on 02/20/1998US Classes:396/379, Zoom359/432, Variable magnification359/676With variable magnification (e.g., zoom type)ExaminersPrimary: Blankenship, Howard B.Attorney, Agent or FirmForeign Patent References
International ClassG03B 013/10Foreign Application Priority Data1997-02-20 JPAbstractA real image mode variable magnification finder includes an objective system having a positive refracting power, an image erecting optical system for erecting an image formed by the objective system, and an eyepiece system having a positive refracting power. The objective system is composed of a first lens unit of a negative biconcave lens, a second lens unit of a positive lens, and a third lens unit of a positive meniscus lens with a convex surface directed toward the image side. The first lens unit is fixed and the second and third lens units are moved along the optical axis, thereby changing the magnification of the finder. In this way, the real image mode variable magnification finder of wide-angle design can be provided which is compact in size, has a high variable magnification ratio, and exhibits excellent performance for correction for aberration. | |
