PROGRESSIVE REFRACTIVE POWER LENS

摘要

The amount of asphericity delta to be added is defined as the sum of the optimal amount g(r) for the far distance viewing portion of a progressive refraction surface and the optimal amount h(r) for the near distance viewing portion and added to a progressive refraction surface in such a way that if the ratio of the amount g(r) to the amount h(r) is alpha : beta , the sum of alpha and beta may be equal to one. Hence, by adding an asphericity to a progressive power lens for correcting visual acuity so as to improve the optical performance or to reduce the thickness of the lens, optimal asphericity design can be applied not only to the principal meridian but also to the whole progressive refraction surface.