| 摘要 |
PURPOSE:To smooth the distribution of astigmatism, by specifying the curvature of a transverse section which is the line of intersection of a plane perpendicular to a main meridian curve and the refracting surface of a lens. CONSTITUTION:The way of dividing a long distance part area, an intermediate distance part area, and a close distance part area is the same as before, but the different point is that curves C1 and C2 which are boundary lines among those three areas have projection parts on the long distance part area side and close distance area side when extending from the main meridian curve to the outer circumference of the lens. Variation in angle K on respective sections M-M9 and variation in the vcurvature of the transverse section in the intermediate part area are shown in a figure. A broken line in the figure shows conventional one; in this invention, the variation in angle K on sections M3, M4, M5, and M6 where the boundary lines C1 and C2 in the center part area project upward and downward becomes gentle and the variation rates are nearly equalized to each other. |
