Progressive addition lens
AssigneeEhs Lens Philippines, Inc.
InventorYohei Suzuki
Life of this patent
Estimating the term…
Abstract
There is provided a progressive addition lens capable of improving both of astigmatism and power error on a peripheral part of a distance area, including a distance area used for a distance vision, and other area different from the distance area, wherein at least one of an eyeball side surface of a wearer and an object side surface in the progressive addition lens is formed into an aspheric form, and when a prescription value T to be obtained from formula “S+C/2” expressed by a prescribed spherical power S and a cylindrical power C, is minus, the area where a power deviation ΔD of a spherical equivalent power D from the prescription value T goes negative, exists on principal sight line in the distance area.
Claims9
A progressive addition lens, comprising a distance area used for a distance vision, and other area different from the distance area, wherein at least one of an eyeball side surface of a wearer and an object side surface in the progressive addition lens is formed into an aspheric form, and when a prescription value T to be obtained from formula “S+C/2” expressed by a prescribed spherical power S and a cylindrical power C, is negative, the area where power deviation ΔD from the prescription value T of spherical equivalent power D goes negative, exists on principal sight line in the distance area.
A progressive addition lens, comprising a distance area used for a distance vision, and other area different from the distance area, wherein at least one of an eyeball side surface of a wearer and an object side surface in the progressive addition lens is formed into an aspheric form, and when a prescription value T to be obtained from formula “S+C/2” expressed by a prescribed spherical power S and a cylindrical power C is positive, the area where power deviation ΔD from the prescription value T of a spherical equivalent power D goes positive, exists on principal sight line in the distance area, wherein a point yc on the principal sight line which the spherical equivalent power D coincides with the prescription value T, exists in the distance area, and on the principal sight line in the distance area, the power deviation ΔD goes positive in the area that is nearer to other areas than point yc.
Dependencies are inferred from the claim text.