Folded zoom lenses: a review of patent literature

Folded zoom lenses offer an interesting opportunity for a review of patent literature: they are of a reasonable complexity that the designs are likely to be instructive, they offer a small range of design constraints because of the standardization of CMOS imager sizes and the mechanical constraints imposed on DSC cameras, and there is enough recent activity in awarded patents that a representative sample of contemporary designs can be collected. This paper presents a review of recent patent literature for folded zoom lenses. Zemax models were built for the designs disclosed in 67 patents. For this large set of models, the distribution of paraxial properties and lens materials is presented. For the most-common design constraints, two particularly-similar disclosed designs are compared in detail. Engineering differences between the two disclosed designs are compared to differences in patent claims directed to the disclosed designs; the patents' claims are shown to omit, at least for these two patents, some design differences that seem important from an engineering point of view.