Bifocal ophthalmic lens constructed from birefringent material
US5073021A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Mar 17, 1989 |
| Grant date | Dec 17, 1991 |
| Priority date | — |
| Expiry date | Mar 17, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02C7/06
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
A dual focal length ophthalmic lens is formed from a birefringent material with its fast and slow axes perpendicular to the user's visual axis. The dual focal property arises due to the differing indices of refraction of the birefringent material for light polarized parallel to the fast and slow axes. Light emanating from far objects having one polarization and light emanating from near objects having the opposite polarization are both focused onto the user's retina. Depending upon which object is being viewed, an in-focus and a blurred image appear simultaneously on the user's retina. The ability of the user's eye/brain system to distinguish between the two images provides bifocal action from a single lens. The invention may take the form of a spectacle, contact, or intraocular implant lens.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.