| 摘要 |
PURPOSE:To eliminate the jumping phenomenon of an image, by providing an area where the distortion or aberration is concentrated at the boundary between the farsight correction part and the shortsight correction part and thus eliminating the above-mensioned boundary. CONSTITUTION:A CR-39 lens having a lens diameter 72mm. and an additional degree 2.0 diop is taken as an example. The farsight correction part D is set at an area higher than the geometric center of the lens, and the part S where the distortion or aberration is concentrated is set at the lower part of the part D with about 8% area ratio to the entire part of the lens. Then the shortsight correction part N is set at the lower part of the section S. In such a way, the boundary line between the correction parts D and N is not visible from the external appearance of the lens. Furthermore no jumping phenomenon occurs when the wearer puts on the spectacles of such lenses, and no dust sticks to the lens since no difference of levels exists. |
