Bifocal ophthalmic lens constructed from birefringent material
AssigneeEnvironmental Research Institute of Michigan
InventorJoseph C. Marron
Life of this patent
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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.
Claims9
An ophthalmic lens formed of birefringent material supported with its central axis coincident with the user's visual axis and with the fast and slow axes of the birefringent material perpendicular to the visual axis, so as to provide one focal length for light polarized parallel to the fast axis and a second focal length for light polarized parallel to the slow axis.
An ophthalmic lens formed of a birefringent material supported with its central axis coincident with the user's visual axis and with the fast and slow axes of the birefringent material perpendicular to the visual axis, the lens having one focal length for light polarized parallel to the fast axis and a second focal length for light polarized parallel to the slow axis, whereby the lens acts in conjunction with the visual system of the user to produce focused images for both far and near objects on the user's retina.
An ophthalmic lens having a first segment formed of non-birefringent material and adapted to provide a focal length for viewing objects far from the user;
- and including a second segment formed of a birefringent material with the fast and slow axes of the birefringent material being perpendicular to the visual axis through the second segment of the lens, and providing two focal lengths for viewing objects near to the user, whereby a trifocal action is realized with a lens having only two segments.
Dependencies are inferred from the claim text.