| 摘要 |
PURPOSE:To obtain a good field of view without making a chromatic aberration of a near use part perceptive by making a prism prescription whose base bottom direction is 90 degrees, which does not aim at a diagonal view correction, in the near use part of a progressive multifocus lens. CONSTITUTION:A prism prescription whose base bottom direction is 90 degrees, which does not aim at a diagonal view correction is applied equally to left and right lenses as shown by a full line, to the near use part of a progressive multifocus lens having a near view correcting prescription in a far use part area shown by a dotted line in the figure. In a graph for showing a prism distribution, a vertical axis and the right direction of a horizontal axis show a lens position and a prism quantity Pup of 90 degrees of the base bottom direction, respectively, but by inserting a prism Pt of 90 degrees of the base bottom direction, the prism quantity increases at a position A of the far use part, but no chromatic aberration is perceived within Pg of a chromatic aberration limit, and it made equal to the limit quantity Pg, therefore, no chromatic aberration of the near use part is perceived, and a good field of view can be obtained. |
