PROGRESSIVE POWER LENS AND DESIGN METHOD FOR THE PROGRESSIVE POWER LENS
A progressive power lens including a far vision part and a near vision part (wherein an average power of a far vision measurement reference point is minus) including: an object side surface including a first element, and an eyeball side surface including a second element cancelling the first element. The first element includes an element of a tonic surface or an element of an atoric surface by which horizontal surface power is larger than vertical surface power at a fitting point positioned at a lower end of the far vision part. The far vision part includes an element by which the vertical surface power in a first coordinate of a principal sight line intersecting the fitting point is smaller than the vertical surface power in a second coordinate of the principal sight line whose distance from the fitting point surpasses the distance between the first coordinate and the fitting point.
1 . A progressive power lens comprising:
a far vision part; and
a near vision part;
wherein an average power of a far vision measurement reference point is minus,
the progressive power lens further comprising:
an object side surface including a first surface element; and
an eyeball side surface including a second surface element which cancels the first surface element,
the first surface element comprising:
an element of a tonic surface or an element of an atoric surface by which a horizontal surface power is larger than a vertical surface power at a fitting point positioned at a lower end of the far vision part; and
in the far vision part, an element by which the vertical surface power in a first coordinate of a principal sight line passing through the fitting point, is smaller than the vertical surface power in a second coordinate of the principal sight line whose distance from the fitting point is larger than a distance between the first coordinate and the fitting point.
2 . The progressive power lens according to claim 1 , wherein in the near vision part, the first surface element includes the element by which the vertical surface power in a third coordinate of the principal sight line is smaller than the vertical surface power in a fourth coordinate of the principal sight line whose distance from the fitting point is larger than a distance between the third coordinate and the fitting point.
3 . The progressive power lens according to claim 1 , wherein in an intermediate region positioned between the far vision part and the near vision part, the first surface element further includes an element by which the vertical surface power in a fifth coordinate of the principal sight line is smaller than the vertical surface power in a sixth coordinate of the principal sight line whose distance from the fitting point is larger than a distance between the fifth coordinate and the fitting point.
4 . The progressive power lens according to claim 1 , wherein in the far vision part, the first surface element includes an element by which the vertical surface power at an arbitrary point on the principal sight line whose distance from the fitting point is a prescribed value or less, is equal to the vertical surface power at the fitting point.
5 . The progressive power lens according to claim 1 , wherein in the element by which the vertical surface power in the first coordinate is smaller than the vertical surface power in the second coordinate, a variation rate of the vertical surface power between the first coordinate and the second coordinate is 0.05 D/mm or more, wherein D indicates diotor.
6 . The progressive power lens according to claim 1 , wherein in the element by which the vertical surface power in the first coordinate is smaller than the vertical surface power in the second coordinate, the variation rate of the vertical surface power between the first coordinate and the second coordinate is 0.07 D/mm or more and 0.10 D/mm or less.