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Publication of NL108245CpublicationCriticalpatent/NL108245C/xx
G02B15/00—Optical objectives with means for varying the magnification
G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
G02B15/142—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having two groups only
G02B15/1421—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective having two groups only the first group being positive