Patent EP0109753A2 successfully refreshed from Google Patents.
EP0109753A2
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EP
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Bifocal contact lens comprising a plurality of concentric zones
Assignee: PBH Inc
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Filing: 1983-10-14
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Granted: —
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Expires: 2003-10-14
Abstract
Abstract A bifocal contact lens has diffractive power added to the basic refractive power provided by the material of the lens (2) and the basic curvature of its front and rear surfaces (3 and 1). The diffractive power arises from concentric zones, each providing an asymmetric retardation of light across the zone width to direct design wavelength light predominantly into a required order and sign of diffraction, while other wavelength light is predominantly transmitted at zero order. Design wavelength light from an object at one distance can then be focused by way of diffraction of that order and sign, and other wavelength light from an object at another distance can be focused by way of zero order transmission. Preferably the zones are defined, and the asymmetric retardation provided, by a rear surface contour having steps but which approximates to the required basic curvature.
Inventors
- 👤 Michael Harold Freeman
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-07 09:36
CPC Classifications
G; G02; G02C; G02C7/00; G02C7/02; G02C7/04; G02C7/041; G02C7/044; G02B; G02B5/00; G02B5/18; G02B5/1876; G02C7/042; G02C2202/00; G02C2202/20
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
155 words
A bifocal contact lens having diffractive power, comprising a plurality of concentric zones arranged so as to cause diffraction of light transmitted through the lens, characterised in that each zone provides an asymmetric retardation of light across the zone width in a manner which directs light of a design wavelength predominantly into a required order and sign of diffraction at the expense of transmission at zero order and at the expense of transmission at the opposite sign of said required order of diffraction, while light of another wavelength displaced from said design wavelength is predominantly transmitted at zero order in preference to said required order and sign of diffraction, whereby light of said design wavelength from an object at one distance can be focused by way of said required order and sign of diffraction and light of said other wavelength from an object at another distance can be focused by way of zero order transmission.
Claim 2
Dependent Claim
155 words
A bifocal contact lens having diffractive power, comprising a plurality of concentric zones arranged so as to cause diffraction of light transmitted through the lens, characterised in that each zone provides an asymmetric retardation of light across the zone width in a manner which directs light of a design wavelength predominantly into a required order and sign of diffraction at the expense of transmission at zero order and at the expense of transmission at the opposite sign of said required order of diffraction, while light of another wavelength displaced from said design wavelength is predominantly transmitted at zero order in preference to said required order and sign of diffraction, whereby light of said design wavelength from an object at one distance can be focused by way of said required order and sign of diffraction and light of said other wavelength from an object at another distance can be focused by way of zero order transmission.
Claim 3
Dependent Claim
17 words
A lens according to Claim 1 in which said required order of diffraction is first order diffraction.
Claim 4
Dependent Claim
35 words
A lens according to Claim 1 or Claim 2 in which the zones are defined, and the asymmetric retardation is provided, by the surface contour of the lens, and preferably by the rear surface contour.
Claim 5
Dependent Claim
19 words
A lens according to any preceding claim in which the zones are defined by steps in the lens surface.
Claim 6
Dependent Claim
25 words
A lens according to any preceding claim in which the asymmetric retardation is provided by a stepped surface contour having stepped areas across each zone.
Claim 7
Dependent Claim
24 words
A lens according to any of Claims 1 to 4 in which the asymmetric retardation is provided by a smooth curve across each zone.
Claim 8
Dependent Claim
53 words
A lens according to any preceding claim whose diffractive power is additional to refractive power provided by the material of the lens and the basic curvature of its front and rear surfaces, and in which any surface contour superimposed on the base curve is in a manner which effectively retains the basic curvature.
Claim 9
Dependent Claim
31 words
A lens according to Claim 7 and Claim 5, in which the stepped areas across each zone each have a radius of curvature the same as that of the base curve.
Claim 10
Dependent Claim
55 words
A lens according to Claim 7 and Claim 6 and Claim 4, in which the smooth curve across each zone has a radius of curvature which differs from that of the base curve but the step size at the zone edge is such as to give general conformation of the surface to the basic curvature.
Claim 11
Dependent Claim
20 words
A lens according to any preceding claim having a surface contour produced by cutting, and preferably by a computer-controlled lathe.
References Cited (Backward Citations)
No citation records indexed.
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