| 摘要 |
<p>A gradient-index multifocal lens belonging to a group designed onthe basis of predetermined rules so that basic factors of gradient-index multifocal lenses, such as a far focal measurement position F and a nearfocal measurement position N, can be adapted to lenses for eyeglasses. Suppose that surface refractive power (in diopters) at the measurement position F is a base curve (Bi), that the difference in the surface refracting power between the measurement position F and the measurement position N is Di (in diopters), and that the width of a region is W(Di, Bi), where the value of surface mean additional refracting power along a sectional curve in a horizontal direction passing below the measurement position N is at least Di/2. When any two gradient-index multifocal lenses of Di=Da and Bi=B1, B2 are extracted from the group of the multifocal lenses, they satisfy the relation W(Da, B1) > W(Da, B2) when B1 > B2. Accordingly, a gradient-index multifocal lens with a wide field by view desirable to users of eyeglasses is provided without increasing the time and cost of prescription production.</p> |
