| 摘要 |
A progressive-power multifocal lens whose far-vision portion dioptric power is minus, which has, along a principal meridian curve, a far-vision correction portion, a near-vision correction portion, a progressive-power portion between the far-vision correction portion and the near-vision correction portion. Where a base curve is represented by BC; a mean surface refracting power at an arbitrary point on the progressive-power multifocal surface, located at a distance of x (mm) from a far-vision portion eyepoint in the horizontal direction in wear of spectacles and located at a distance of y (mm) from the far-vision portion eyepoint in the vertical direction in wear of spectacles, by P (x,y) (diopter); and a mean surface additional refracting power obtained by subtracting the base curve BC from the mean surface refracting power, by DELTAP(x,y){=P(x,y)-BC} (diopter);the lens fulfills the condition ofin a region which satisfies 15<=(x2+y2)½<=20 in the far-vision correction portion.
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