| 摘要 |
In this lens, the curvature of the main meridian curve of power progression (MP) begins to vary from a point (A3) situated within the intermediate vision zone (VI) at a predetermined distance d1 from the point (A1) on the main meridian curve (MP) situated at the bottom of the far vision zone (VL), and it continues to vary down to a point (A4) situated in the near vision zone (VP) on an extension (MP') of the main meridian curve (MP), and at a predetermined distance d2 from the point (A2) on the main meridian curve (MP) situated at the top of the near vision zone (VP), with the curvature difference between the points (A2 and A4) having a predetermined value DELTA C. The values of d1, d2, and DELTA C are decreasing functions of the power addition A between the points (A1 and A2). |
