PubMed · 66538
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D Epstein, B Philipson. 1977-04-02. Problems with contact lenses.. https://doi.org/10.1016/s0140-6736(77)92191-2
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A method is proposed which may prove useful as an aid in the design of non-spherical surfaces with desired multifocal properties. More specifically, if an axially symmetrical surface is described by a polynomial then the coefficients of this polynomial can be found such that optical path lengths between given object and image points are nearly constant over desired portions of the surface. Three examples are given. One of the examples, a 'trifocal' surface, is compared to an aberration-free two-segment concentric bifocal contact lens.
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