Traps in displaying optical performances of a progressive-addition lens.
Typical traps when displaying the partial optical performances of a progressive-addition lens (PAL) are presented. The PAL is briefly described first. Then the ray-tracing software is described in detail. It permits the computation of the optical performance of the PAL in typical cases. For a reference PAL optical partial performances, which are computed in different cases, are displayed. The plots show that the performance depends on the computation conditions, that displaying only some areas of the partial performance may lead to traps for the characterization of the PAL, and that coma must be taken into account to obtain a precise measurement.
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