Multi-layered multifocal lens with blended refractive index
View Patent ↗The lens of the present invention relates to multifocal spectacle lenses, including bifocal and trifocal lenses, with improved cosmetic appearance, optical performance and wide visual field. The lens comprises a plurality of axially layered and bonded lens sections of continuous curvature at least one of which has a changing refractive index incorporating a refractive index blend area oriented transverse to a meridian of the lens. The blend eliminates visibility of the joining area of adjacent portions of generally constant refractive index and the abrupt magnification shift and image jump typical of segmented multifocal lenses. The areas of generally constant refractive index provide the refractive powers for corresponding discrete vision portions of the lens. The other layer(s) of the lens incorporates a constant or similarly changing refractive index.
1. A multifocal ophthalmic lens for use by a patient, said lens formed of at least two layers, one having a positive power and the other having a negative power, one of the two layers being a first layer and having two adjacent portions, one portion with a first, substantially constant refractive index and the other portion with a second, substantially constant refractive index, and a blended region extending transverse to a meridian of the lens and forming a transition between the adjacent portions with a refractive index that varies continuously between the first and second refractive indices, the transition having a width selected to be too narrow to provide a useful zone of vision.
2. The lens of claim 1 , the two layers each having surfaces of continuous curvature.
3. The lens of claim 1 , the other of said two layers being a second layer and being shaped to provide, in combination with the first layer, a vision-correcting prescription.
4. The lens of claim 3 wherein one portion corresponds to a first zone of vision of the patient and the other portion corresponds to a second zone of vision of the patient, the zones of vision being selected from a group consisting of a distance vision zone, an intermediate vision zone and a near vision zone.
5. The lens of claim 1 , wherein the two layers comprise Fresnel lenses and wherein the interface of the two layers comprises the Fresnel surfaces.
6. The lens of claim 5 wherein the Fresnel surfaces have non-optically functional steps at least some of which are conical and wherein the apices of the conic steps are located posterior of the posterior surface of the lens thereby providing increased light transmission from peripheral field points through the lens to the patient's eye.
7. The lens of claim 6 wherein the apices of the conic steps are 16-28.5 mm behind the posterior surface of the lens.
8. The lens of claim 5 wherein the other of said two layers being a second layer and the second layer has a substantially constant index of refraction which is substantially the same as the index of refraction of the one portion of the first layer.
9. The lens of claim 1 wherein the second layer includes two adjacent portions, one portion with a first, substantially constant refractive index and the other portion with a second, substantially constant refractive index, and a blended region extending transverse to said meridian forming a transition between the adjacent portions with a refractive index that varies continuously between the first and second refractive indices, the transition having a width selected to be too narrow to provide a useful zone of vision, and wherein the first and second layers are oriented with respect to each other in a positional relationship selected from the group consisting of a) having at least part of the portion of the first layer having a lower refractive index aligned along a line of sight of the patient with at least part of the portion of the second layer having a higher refractive index and b) having at least part of the portion of the first layer having a higher refractive index aligned along a line of sight of the patient with at least part of the portion of the second layer having a lower refractive index.
10. The lens of claim 9 including a third layer, the third layer being shaped to provide, in combination with the first and second layers, a vision-correcting prescription.
11. The lens of claim 1 wherein the first layer has an anterior surface and a posterior surface each generally transverse to a line of sight of the patient through the lens, the transition having an extent between the anterior and posterior surfaces wherein through said extent is defined a surface that has a substantially constant index of refraction at least a portion of which is generally aligned with the line of sight of the patient through the lens.
12. The lens of claim 11 wherein the transition of the first layer has a positional relationship with the transition of the second layer selected from the group consisting of a) being substantially aligned along a line of sight through the lens so as to form a first alignment of portions comprising the first layer's lower refractive index portion and the second layer's higher refractive index portion and a second alignment of portions comprising the first layer's higher refractive index portion and the second layer's lower refractive index portion and b) being offset so as to form a first partial alignment of portions comprising the first layer's lower refractive index portion and the second layer's higher refractive index portion, a second partial alignment of portions comprising the first layer's higher refractive index portion and the second layer's lower refractive index portion and a third partial alignment of portions between the transitions of the first and second layers comprising portions selected from the group consisting of a) the first layer's lower refractive index portion and the second layer's lower refractive index portion and b) the first layer's higher refractive index portion and the second layer's higher refractive index portion.
13. The lens of claim 12 wherein said at least two layers each have anterior and posterior surfaces each generally transverse to a line of sight of the patient through the lens, the transition having an extent between the anterior and posterior surfaces wherein through said extent is defined a surface that has a substantially constant index of refraction at least a portion of which is generally aligned with the line of sight of the patient through the lens.