Progressive multifocal lens and spectacles using same
First Claim
1. A progressive multifocal ophthalmic lens comprising first and second refractive surfaces, said first refractive surface having a central basic curve defined thereon which extends essentially vertically therealong and divides said first refractive surface into a left portion and a right portion, and including a far vision viewing zone in an upper portion for viewing mainly distant objects, a near vision viewing zone in a lower portion for viewing mainly nearby objects, and an intermediate vision viewing zone for viewing mainly intermediate objects between said far and near vision viewing zones, said far vision viewing zone and said near vision viewing zone each having an optical center and a clear vision viewing zone, a predetermined additional power being added between the optical center of the far vision viewing zone and the optical center of the near vision viewing zone along said central basic curve, the gradient G of the focal power variation between said optical center of the far vision viewing zone and said optical center of the near vision viewing zone satisfying the condition:
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space="preserve" listing-type="equation">G≦
ADD/20 (diopter/mm),wherein ADD is said additional power in units of diopter,the far vision viewing zone in the portion above said optical center of said far vision viewing zone having said clear vision viewing zone including said central basic curve and defined by the condition;
space="preserve" listing-type="equation">(n-1)×
|C1-C2|≦
0.5 (m.sup.-1),where n is the refractive index of the lens material, and C1 and C2 are the principal curvatures at each point on the refractive surface of the lens, and wherein m-1 =1/meter,the maximum width W (mm) of the said clear vision viewing zone in said far vision viewing zone satisfying the condition;
space="preserve" listing-type="equation">5≦
W≦
30 (mm).
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Accused Products
Abstract
Progressive multifocal ophthalmic lenses are provided having a far vision viewing zone, a near vision viewing zone and an intermediate vision viewing zone therebetween. A central basic curve extends essentially vertically through the far, intermediate and near vision viewing zones. The sizes of the zones and configuration of the zones are set by predetermined conditions and equations. The construction provides improved lenses for use especially where intermediate and near vision viewing is required.
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Citations
13 Claims
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1. A progressive multifocal ophthalmic lens comprising first and second refractive surfaces, said first refractive surface having a central basic curve defined thereon which extends essentially vertically therealong and divides said first refractive surface into a left portion and a right portion, and including a far vision viewing zone in an upper portion for viewing mainly distant objects, a near vision viewing zone in a lower portion for viewing mainly nearby objects, and an intermediate vision viewing zone for viewing mainly intermediate objects between said far and near vision viewing zones, said far vision viewing zone and said near vision viewing zone each having an optical center and a clear vision viewing zone, a predetermined additional power being added between the optical center of the far vision viewing zone and the optical center of the near vision viewing zone along said central basic curve, the gradient G of the focal power variation between said optical center of the far vision viewing zone and said optical center of the near vision viewing zone satisfying the condition:
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space="preserve" listing-type="equation">G≦
ADD/20 (diopter/mm),wherein ADD is said additional power in units of diopter, the far vision viewing zone in the portion above said optical center of said far vision viewing zone having said clear vision viewing zone including said central basic curve and defined by the condition;
space="preserve" listing-type="equation">(n-1)×
|C1-C2|≦
0.5 (m.sup.-1),where n is the refractive index of the lens material, and C1 and C2 are the principal curvatures at each point on the refractive surface of the lens, and wherein m-1 =1/meter, the maximum width W (mm) of the said clear vision viewing zone in said far vision viewing zone satisfying the condition;
space="preserve" listing-type="equation">5≦
W≦
30 (mm). - View Dependent Claims (2, 3, 4, 5, 6)
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7. Spectacles having at least one progressive multifocal lens set in a frame thereof, said progressive multifocal ophthalmic lens comprising first and second refractive surfaces, said first refractive surface having a central basic curve defined thereon which extends essentially vertically therealong and divides said first refractive surface into a left portion and a right portion, and including a far vision viewing zone in an upper portion for viewing mainly distant objects, a near vision viewing zone in a lower portion for viewing mainly nearby objects, and an intermediate vision viewing zone for viewing mainly intermediate objects between said far and near viewing zones, said far vision viewing zone and said near vision viewing zone each having an optical center and a clear vision viewing zone, a predetermined additional power being added between the optical center of the far vision viewing zone and the optical center of the near vision viewing zone along said central basic curve, the gradient G of the focal power variation between said optical center of the far vision viewing zone and said optical center of the near vision viewing zone satisfying the condition:
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space="preserve" listing-type="equation">G≦
ADD/20 (dopter/mm),wherein ADD is said additional power in units of diopter, the far vision viewing zone in the portion above said optical center of said far vision viewing zone having said clear vision viewing zone including said central basic curve and defined by the condition;
space="preserve" listing-type="equation">(n-1)×
|C1-C2|≦
0.5 (m.sup.-1),where n is the refractive index of the lens material, and C1 and C2 are the principal curvatures at each point on the refractive surface of the lens, and wherein m-1 =1/meter, the maximum width W (mm) of the said clear vision viewing zone in said far vision viewing zone satisfying the condition;
space="preserve" listing-type="equation">5≦
W≦
30 (mm). - View Dependent Claims (8, 9, 10, 11, 12, 13)
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Specification