Optics: eye examining – vision testing and correcting – Spectacles and eyeglasses – Ophthalmic lenses or blanks
Patent
1992-10-22
1995-04-25
Sugarman, Scott J.
Optics: eye examining, vision testing and correcting
Spectacles and eyeglasses
Ophthalmic lenses or blanks
351161, 351172, 359494, 359495, 359497, 623 6, G02C 706, G02C 704, G02B 530, A61F 216
Patent
active
054103754
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a bifocal lens means made of birefringent material the birefringent material being a polymer which has been made birefringent by an orienting process by stretching under defined conditions, the material exhibiting an ordinary refractive index n.sub.O and an extraordinary refractive index n.sub.e after the orienting process, the lens means exhibiting two powers D.sub.min, D.sub.max necessary for a specific optical application, the powers being measured for the lens system being immersed in a medium of refractive index n.sub.m.
Birefringent multifocal lens systems are disclosed in EP 0 308 705 A2 or in U.S. Pat. No. 4,981,342. These lens systems comprise birefringent and/or isotropic lens components or single lenses, such that at least two powers of the lens system can be given predetermined values in independence of the material properties of the lens components of the lens system. It is shown that a lens system has to comprise at least one birefringent lens component and at least one isotropic of another birefringent lens component in order to provide at least two arbitrarily selected powers. It was further shown that at least two birefringent lens components and at least one isotropic or another birefringent lens component are required in order to provide at least three arbitrarily selected powers etc. In general, it was shown that in a lens system consisting of M birefringent lens components the number N.sub.free of independently selectable powers is N.sub.free =M. It is further shown in the above European patent application and U.S. Pat. No. (equation 23) that at least another birefringent or isotropic lens component has to be added to the M birefringent lens components in order to provide N.sub.free =M+1 independently selectable powers.
It is an object of the invention to provide structurally simple ophthalmic lens means which exhibits two different powers D.sub.max, D.sub.min which may be preselected in complete independence of one another.
According to the invention this is achieved in that the lens means is a birefringent single lens and in that the birefringent of the birefringent material is so adjusted by means of the orienting process that for the value of the birefringence .delta.n=n.sub.e -n.sub.O either equation ##EQU1## is satisfied.
A specific embodiment of the invention is a simultaneous vision bifocal intraocular ophthalmic lens being immersed in a medium, which exhibits at least two deliberately preselectable or necessary power.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a single birefringent lens 10 according to this invention being made of a birefringent material the birefringence .delta.n of which is given by ##EQU2## where D.sub.max and D.sub.min are just the powers necessary for a optical application. By choosing this birefringence it is achieved that the single lens exhibits the two desired, i.e. preselected powers D.sub.max and D.sub.min when the lens is immersed in a medium 40 of refractive index n.sub.m ; the crystal optic axis 100 of lens 10 is perpendicular with the lens axis 30; light rays 20 incident in parallel with lens axis 30 are refracted by the lens 10 such that resultant light rays 21 and 22 are produced; rays 21 are focussed to focal point 31, rays 22 are focussed to focal point 32; focal point 31 corresponds to the maximum power D.sub.max of lens 10, focal point 32 corresponds to the minimum power D.sub.min of lens 10.
FIG. 2 is a birefringent lens system according to this invention; birefringent lenses 11 and 12 are fabricated from the same birefringent lens material; crystal optic axis 101 of lens 11 and crystal optic axis 102 of lens 12 are both perpendicular to axis 30 of both lenses 11 and 12; the angle between crystal optic axis 101 and crystal optic axis 102 is .beta.. conditions, the material exhibiting an ordinary refractive index n.sub.o and an extraordinary refractive index n.sub.e after the orienting process, characterized in that the birefringence of the birefringent material is so adjusted by means of the orienting process
REFERENCES:
patent: 3391053 (1968-07-01), Kolb
patent: 4227950 (1980-10-01), Spycher
patent: 4679918 (1987-07-01), Ace
patent: 4793703 (1988-12-01), Fretz, Jr.
patent: 5064712 (1991-11-01), Fretz, Jr.
patent: 5073021 (1991-12-01), Marron
patent: 5116684 (1992-05-01), Fretz, Jr. et al.
patent: 5142411 (1992-08-01), Fiala
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