EP2089755A2 - Verre progressif à indice gradient multicouche - Google Patents

Verre progressif à indice gradient multicouche

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Publication number
EP2089755A2
EP2089755A2 EP07861509A EP07861509A EP2089755A2 EP 2089755 A2 EP2089755 A2 EP 2089755A2 EP 07861509 A EP07861509 A EP 07861509A EP 07861509 A EP07861509 A EP 07861509A EP 2089755 A2 EP2089755 A2 EP 2089755A2
Authority
EP
European Patent Office
Prior art keywords
lens
refractive index
layer
gradient
vision
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07861509A
Other languages
German (de)
English (en)
Inventor
Donald A. Volk
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Publication of EP2089755A2 publication Critical patent/EP2089755A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
    • G02C7/00—Optical parts
    • G02C7/02—Lenses; Lens systems ; Methods of designing lenses
    • G02C7/06—Lenses; Lens systems ; Methods of designing lenses bifocal; multifocal ; progressive
    • G02C7/061—Spectacle lenses with progressively varying focal power
    • G—PHYSICS
    • G02—OPTICS
    • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
    • G02C2202/00—Generic optical aspects applicable to one or more of the subgroups of G02C7/00
    • G02C2202/12—Locally varying refractive index, gradient index lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02C—SPECTACLES; SUNGLASSES OR GOGGLES INSOFAR AS THEY HAVE THE SAME FEATURES AS SPECTACLES; CONTACT LENSES
    • G02C2202/00—Generic optical aspects applicable to one or more of the subgroups of G02C7/00
    • G02C2202/16—Laminated or compound lenses

Definitions

  • the present invention relates to a gradient index progressive addition spectacle lens that provides improved optical performance and a 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 refractive index gradient oriented transverse to a meridian of the lens that functions as a progressive intermediate vision zone between viewing portions of different refractive index that provide the refractive powers for corresponding vision portions of the lens.
  • the other layer(s) of the lens incorporates a generally constant or similarly changing refractive index.
  • Progressive addition spectacle lenses are visual aids used in the management of presbyopia, the condition wherein the accommodative function of the eye is partially or fully lost.
  • the Vision Council of America defines a progressive lens as a lens designed to provide correction for more than one viewing distance in which the power changes continuously rather than discretely.
  • the power change of a progressive lens may be derived by modifying the surface curvature of a lens or the refractive index of the optical material comprising the lens, or both.
  • a number of gradient index lens types have been proposed for use as progressive addition lenses.
  • These lenses provide a change or gradient of refractive power over what may be termed a progressive intermediate vision or transition zone of the lens through a corresponding change in refractive index of the optical media comprising the lens, theoretically providing the advantage of reducing or avoiding the astigmatism associated with non-rotationally symmetric aspheric surface contours common to conventional progressive addition lenses. Due to problems associated with these designs, including issues and difficulties relating to manufacturing, there has been no commercialization of gradient index progressive power lenses. In order to provide adequate power for both distance and near vision functioning, a significant amount of refractive index change in the optical material is required.
  • Ion exchange methods proposed by some to achieve a refractive index change, may tend to offer both an undesirable gradient index profile and less than the needed power change for a progressive addition spectacle lens. Lenses produced by diffusion methods likewise have failed to provide adequate add power or realize commercial success.
  • U.S. patent 3,485,556 to Naujokas describes a multifocal plastic ophthalmic lens wherein there is provided a major lens portion of one index of refraction and a minor lens portion of a different index of refraction with a uniform index gradient therebetween.
  • the plastic materials are produced by a process in which an interface is established between monomelic liquids and diffused over time in an isothermallycontrolled environment and then polymerized.
  • This lens at first appears to be capable of providing the stated distance and near vision properties.
  • a ray tracing of the lens in accordance with the parameters set forth in the patent shows that only when a significantly high plus power configuration is utilized can an add power of even 1 diopter be achieved.
  • Using the refractive indices of 1.5 and 1.6 identified in the patent a calculated plus power of 4.714 diopters is needed in the distance vision portion to achieve the only slightly greater power of 5.714 diopters in the near vision portion, thus the lens is useful only to those needing high plus power correction for distance vision.
  • a prescription incorporating cylinder power is produced on either the front or back surface, the cylinder power will vary and cause aberrations as a result of the changing refractive index.
  • U.S. patent 5,042,936 to Guilino et al. describes a progressive ophthalmic lens comprising a distance portion, the refractive power of which being designed for distance vision, a reading portion, the refractive power of which being designed for near vision, and an intermediate portion, in which the refractive power along the main line of vision at least partially increases continuously from the refractive power of the distance portion to the reading portion.
  • a refractive index of the lens material varies along the main line of vision at least in the intermediate portion so as to at least partially contribute to the increase in refractive power and correction of aberrations.
  • each of two progressive ophthalmic lenses in front of the left or right eye is provided with a main point of vision (distance reference point) Bf for distance vision and a main point of vision (near reference point) Bn for near vision.
  • distance reference point for distance vision
  • near reference point for near vision.
  • the refractive index function is a) solely a function of the coordinate y' so that by varying the refractive index, the increase in refractive power is produced only along the main meridian, or b) a function of the coordinate y'and x' so that not only the increase in refractive power along the main meridian, but also the correction of imaging errors on the main meridian and borne by the varying refractive index.
  • the index of refraction is shown in 4a to decrease below the main point for distance vision 4mm above the apex of the lens to the main point for near vision at the -14mm location, and well beyond.
  • the refractive index changes most dramatically below the -14mm mark to the -20mm mark (1.57 to 1.51 [.06 index units] over 6mm) and comparatively least above the -14mm mark to the 4mm point for distance vision (1.57 to 1.604 [.034 index units] over 18mm).
  • the so-called reading portion has the most increase in refractive power change, and therefore fits more the definition of the intermediate portion, and the intermediate portion, from 4mm to -14mm, has comparatively the least increase in refractive power change, and therefore fits more the definition of the reading portion.
  • a lens with altogether different refractive properties is needed to provide good optical qualities for a progressive ophthalmic lens.
  • U.S. patent 5,148,205 to Guilino et al. describes an ophthalmic lens having a front and an eye- facing boundary surface and a varying refractive index, which contributes to the correction of aberrations.
  • This patent describes a lens with a refractive index variation which depends on both the coordinate z lying in the direction of connecting axis of the apex of the lens and the coordinates x,y being perpendicular to the connecting axis, and therefore permits correcting aberrations and minimizing the critical lens thickness in a very simple manner.
  • the gradients may be utilized for generating an astigmatic and/or progressive refractive power, with the design of the surface not or only partially contributing to the astigmatic and/or progressive refractive power.
  • the bulk of the patent is directed to the use of what may be termed axial or modified axial refractive index gradients for the correction of aberrations and minimizing critical lens thickness.
  • U.S. patent 5,861,934 to Blum et al. describes a refractive index gradient lens comprising a composite of at least three different and separately applied layers, each layer having a different refractive index which allow for a progressive multifocal lens having a wide and natural progression of vision when looking from far to near.
  • a transition zone disposed between a base and an outer layer includes a distinct and separately applied transition layer or layers having an effective refractive index which is intermediate between the refractive indices of the base and outer layers, and preferably approximates the geometric mean of the refractive indices of the base and outer layers.
  • This transition zone may include multiple transition layers, with each transition layer having a different and distinct refractive index.
  • the refractive indices of the base, outer and transition layer(s) are each constant throughout their respective layers. Included within the lens design is a region of varying thickness which defines a progressive multifocal zone.
  • the technique of employing a transition zone having an intermediate refractive index is used in order to render the progressive multifocal area as invisible as possible.
  • the refractive indices of three transition layers in a transition zone may be about 1.54, 1.60 and 1.66 as the layers progress from the preform to the outer layer.
  • the gradient index does not contribute to the progressive power as in the previously mentioned prior art patents; rather, within the lens is a region of varying thickness which defines a progressive multifocal zone.
  • Patent 6,942,339 to Dreher describes a multifocal or progressive lens constructed with a layer of variable index material, such as epoxy, sandwiched in between two lens blanks.
  • the inner epoxy coating aberrator has vision zones configured to correct aberrations of the patient's eye and higher order aberrations.
  • the variable index coating that comprises the inner layer of this lens does not provide the progressive add power of the lens, rather as stated in the patent it corrects for aberrations of the patient's eye.
  • the lens has many of the limitations typical of aspheric progressive lenses.
  • a gradient index progressive spectacle lens that avoids the problems associated with the prior art lenses and which in particular has improved optical attributes.
  • the benefits are derived from a multi-layered lens incorporating a refractive index gradient that provides the required power variation for visualization over a range of viewing distances. It is therefore a main object of the present invention to provide a multi- layered progressive lens that comprises at least one layer incorporating a refractive index gradient that provides an area of progressive intermediate vision.
  • ⁇ t is another object of the invention to provide a gradient index progressive lens that comprises three layers, two adjacent layers incorporating a refractive index gradient profile and power sign opposite the other, and the third having a surface on which to incorporate a patient's prescription.
  • a progressive lens having continuous curvature and achieving increased power for progressive intermediate and near vision through a change of refractive index of the lens.
  • the character and magnitude of the refractive index gradient(s) results in a lens that can provide high add power and improved vision with minimal astigmatism in a thin configuration.
  • the lens of the present invention employs one or more refractive index gradient layers comprising a multi-layered lens.
  • the refractive index gradient profile corresponds to the regions of the lens that provide vision over the range of powers of the lens.
  • the refractive index gradient is oriented transverse to a meridian of the lens, generally from lens top to bottom, with a substantially constant refractive index from one surface of the layer to the other.
  • the refractive index gradient is defined by a rate of refractive index change ideally suited to provide smooth transitional power change through the progressive intermediate portion of the lens and generally follows the progression of a ⁇ ⁇ sine wave or sine wave like curve from maximum to minimum extrema ( ⁇ /2 to 3 ⁇ /2).
  • the rate of increase and decrease of refractive index change in the generally vertical orientation from the upper distance vision portion to the lower near vision portion of the lens provides a gradual increase and gradual decrease of power, while in a generally orthogonal direction along the gradient, there is substantially no change of refractive index.
  • the terms vertical and orthogonal in reference to the gradient index profile are general terms and do not designate an exact degree of orientation. Because refractive index and therefore lens power are generally constant in the defined orthogonal direction along the gradient, vision through the progressive intermediate vision portion of the lens is not restricted in width or limited to a corridor of vision as is the case with conventional aspheric progressive lenses, but rather, like the distance vision portion above it and the near vision portion below it, the effectiveness of the progressive intermediate vision portion will extend fully along its width.
  • the distance across the extent or span of the refractive index gradient defining the progressive intermediate lens portion should be great enough to provide meaningful optical performance, ranging from around 10mm to 20mm for example.
  • a lens according to the present invention may be produced with a minimum center and edge thickness.
  • a 48mm diameter lens providing '0' power through the distance portion of the lens and 2.5 diopters of add through the near vision portion of the lens may be a thin as 1.76mm center thickness and 1.13mm edge thickness.
  • a spraying technique using 2 or more spray guns each containing a mutually compatible resin of different refractive index, moving together along a linear or arcuate path and producing a combined deposit with overlapping or common deposit areas from between 10 to 20mm wide, for example, can create a varying blend of the component resins over the extent of the common deposit.
  • the overlapping or common section will comprise a varying volume of material from the adjacent guns, with the greatest amount of material from each gun closest to the center of its deposit area and the least amount furthest towards the edge of its deposit.
  • the composite resin material can be chemically or photo polymerized or otherwise cured.
  • Another gradient index production method involves a controlled diffusion process using a dissolvable polymer membrane that defines a predetermined interface shape that separates two optical resins of different refractive index, and which once dissolved by one or both of the optical resins provides a precise liquid interface for diffusion to commence.
  • a further method involves the use of dispersed particles of particular density that facilitate and accelerate the mixing, blending and diffusion process by their transport through the liquid complex by gravity, buoyancy or centrifugal force.
  • micron sized particles of high density are dispersed in the upper-most resin composition and through gravity fall and settle through the body of liquid, each particle introducing a small amount of an above portion resin of one refractive index into a below portion resin of a different refractive index, providing a thorough mixing and blending of the two adjacent liquids within an area and over an extent beneath the original interface. Once the particles fully settle out the liquid composition can be chemically or photo polymerized or otherwise cured.
  • the lens of the present invention may comprise two, three or multiple layers.
  • a layer of generally constant refractive index provides either a posterior or anterior surface on which to incorporate a patient's prescription.
  • reverse refractive index gradient profiles are used in adjacent plus power and minus power layers to effectively increase or double the refractive index difference, thereby providing a means of achieving high add values with lower or flatter curvatures and reducing lens thickness to a minimum. At least one pair of reverse gradient refractive index sections is required to achieve the increase in refractive index.
  • a refractive index gradient profile defines a maximum refractive index difference of .3, by using 1) a gradient refractive index layer wherein the high refractive index portion comprises the lower near vision portion of a plus power layer, in combination with 2) a reverse gradient refractive index layer wherein the high refractive index portion comprises the upper distance vision portion of an adjacent minus power layer, the effective refractive index difference is doubled to equal .6.
  • This very large index difference may be used advantageously to provide a high diopter progressive add power in a thin lens design in accordance with the present invention.
  • the lens consists of numerous thin layers of alternating refractive index gradient layers with reverse profiles and power values.
  • a 50mm diameter composite lens providing 2.5 diopters of add power may comprise 13 low curvature layers each having a critical thickness as low as .22mm while the overall lens thickness may approximate that of a standard lens of similar add power.
  • Plus power layers with an increasing refractive index and increasing plus power in one direction .22mm in center thickness alternate with adjacent minus power layers having an increasing refractive index and increasing minus power in the opposite direction, .22mm in edge thickness, thereby producing what may appear to be a piano power lens or window 1.5mm thick, but actually what is a progressive lens with substantial add power.
  • each layer is very thin and may be processed sequentially or independently, certain methods of manufacture that provide good blending results when thin sections are produced may be utilized to advantage.
  • the spraying method previously described is ideal for providing a thin layer of a gradient refractive index composition.
  • the density of one resin or monomer may be greater than the other, resulting in one sliding under the other by the pull of gravity. This problem can be avoided by limiting the volume of material applied and the time over which the spray application occurs when densities are substantially different.
  • Each layer may be fully or partially cured or polymerized after application, and prior to subsequent layer applications.
  • the base surface upon which the spray is applied comprises a material with desirable flexural characteristics it may be altered in shape the small amount needed to produce the necessary convex and concave curvatures required to impart the correct radius for each gelled or partially polymerized layer.
  • the thickness of an application layer may be limited.
  • some photo polymerization processes or materials provide suitable results only to limited depths of the resin or monomer.
  • Other processes designed to change the refractive index of a polymer such as electron beam irradiation or chemical treatment with a penetrating reactive diluent or swelling agent, may provide suitable results only to limited penetration depths or through relatively thin sections, thus the independent or sequential processing of very thin adjacent layers as described may be accomplished by these means.
  • the gradient index progressive lens takes the form of a doublet Fresnel lens comprising one or two gradient refractive index layers.
  • a Fresnel lens surface comprises numerous discontinuous coaxial annular sections each defining a slope corresponding to a continuous lens surface geometry, collapsed to form a surface of lower profile. Joining each annular section is a non-optically functional step that in conjunction with the refracting surfaces determines the overall geometry and lens thickness.
  • High plus and minus powered Fresnel lenses may be produced at a fraction of the thickness of conventional lenses, many with a maximum step height under .26mm.
  • a progressive lens of the present invention may be achieved in an extremely thin lens configuration.
  • spraying technique provides an ideal method of application of a gradient refractive index layer .3 to .4mm thick.
  • the use of two novel Fresnel lens designs providing increased efficiency and effectiveness of the present invention is described.
  • the lens of the present invention may be designed in a number of typical lens shapes or forms utilizing either spherical or aspheric curvatures.
  • shape or form is meant the general overall contour of the lens, that is, whether its front and back surfaces are flatter, having a lower value base curve, or more highly curved, with a higher value base curve.
  • Excellent optical quality may be obtained using spherical surfaces over a wide range of forms, with particular forms providing improved performance over others.
  • lens forms which are normally considered to be highly curved for spectacle lens applications tend to perform better and produce less marginal astigmatism at the standardized spectacle lens distance from the eye than less highly curved forms.
  • a particular corresponding form may provide the best performance.
  • the appropriate conic constant to aspherize those designs that require correction of marginal astigmatism aberration can be minimized and the optical quality for a wide range of base curves and prescriptions can be optimized, thereby widening the choice of lens forms and allowing flatter base curves to be used without compromise of optical quality.
  • a reduction in distortion or nonuniform magnification in the more highly powered portions of the lens may also be achieved.
  • Slight aspheric over-correction with a higher conic constant value or additional aspheric terms may be employed to further reduce lens thickness or change the magnification characteristics of the lens as desired.
  • FIG. s Ia, Ib and Ic are illustrative side views a first group of gradient index progressive lenses incorporating a single plus power refractive index gradient layer in a doublet lens configuration comprising concave, piano and convex internal surfaces.
  • FIG. 2 shows a graph of various gradient refractive index profiles.
  • FIG. s 3a, 3b and 3c illustratively show resin casting chambers incorporating dissolvable membranes separating resin portions.
  • FIG 4 shows a table of lens parameters of the lenses illustratively depicted in FIG.s Ia, Ib and Ic.
  • FIG. 5 is a chart showing lens radius relationship values for different refractive index valued lenses having a range of add powers.
  • FIG 6 shows a graph plotting anterior and posterior surface curvatures against internal surface curvature of the gradient refractive index lens.
  • FIG.s 7a, 7b, 7c and 7d illustratively show different orientation angles of a refractive index gradient lens layer.
  • FIG. 8 is an illustrative side view of a second group of gradient index progressive lenses incorporating a single minus power refractive index gradient layer in a doublet lens configuration comprising a concave internal surface.
  • FIG. 9 is an illustrative side view of a third group of gradient index progressive lenses incorporating a single posterior plus power refractive index gradient layer in a doublet lens configuration comprising a concave internal surface.
  • FIG.s 10a, 10b and 10c illustratively show side views of fourth group of gradient index progressive lenses incorporating a single posterior minus power refractive index gradient layer in a doublet lens configuration comprising concave, piano and convex internal surfaces.
  • FIG.s 11a and l ib illustratively show side views of a fifth group of gradient index progressive lenses incorporating two refractive index gradient layers in a doublet lens configuration comprising plus and minus power layers in both anterior and posterior positions.
  • FIG.s 12a and 12b illustratively show side views of a sixth group of gradient index progressive lenses incorporating two refractive index gradient layers in a triplet lens configuration comprising plus and minus power layers in both anterior and posterior positions and a third layer having a surface on which to incorporate a patient's prescription in both anterior and posterior positions.
  • FIG.s 13 is an illustrative side view of a gradient index progressive lens incorporating a refractive index gradient in the form of a doublet Fresnel lens.
  • FIG.s 14 illustrates the light pathways through a peripheral region of the Fresnel lens of FIG. 13.
  • FIG. 15 is an illustrative side view of a gradient index progressive lenses incorporating a refractive index gradient in the form of an optimized doublet Fresnel lens.
  • FIG.s 16 illustrates the light pathways through a peripheral region of the Fresnel lens of FIG. 15.
  • FIG. 17 is an illustrative side view of a gradient index progressive lenses incorporating a refractive index gradient in the form of an optimized triplet Fresnel lens in which the form of the lens is curved about the patient's eye.
  • FIG. 18 is an illustrative side view of a gradient index progressive lenses incorporating a refractive index gradient in the form of an optimized doublet Fresnel lens in which the form of the Fresnel lens is curved about the patient's eye.
  • FIG. 18a shows the lens of FIG. 18 with a protective layer.
  • FIG. 19 shows a gradient index section produced by creating a common area of sprayed deposits.
  • FIG 20 is an illustrative side view of a 14 layer gradient index progressive lens incorporating numerous refractive index gradient layers.
  • FIG. 21 illustrates an apparatus used to create a gradient index progressive lens layer of gradient refractive index by a spraying technique.
  • Fig. 22 illustrates the mixing of two liquids by particles descending through the interface separating the liquids.
  • anterior lens section A comprises a gradient refractive index layer and posterior section B comprises a generally constant refractive index layer of the lens.
  • anterior is meant a front position and further from the eye and by posterior is meant a rear position and nearer the eye.
  • Section A has plus power and section B has minus power.
  • the refractive index increases through the progressive intermediate vision portion of the lens from the distance vision portion to the near vision portion, therefore providing progressively increasing power for intermediate and near vision.
  • FIG Ia shows an embodiment wherein the internal interface curvature R2 is concave with respect to lens section A
  • FIG Ib shows a lens embodiment wherein the internal interface curvature is piano
  • FIG Ic shows a lens embodiment wherein the internal interface curvature is convex with respect to lens section A.
  • surface and layer designations for the three figures are shown in FIG Ia, and example gradient refractive index locations and extents are shown in FIG. Ib and FIG. Ic.
  • lens layer A is comprised of an optically transparent material having variable refractive index values. Al corresponds to the distance vision portion of the lens, A2 corresponds to the progressive intermediate vision portion of the lens and A3 corresponds to the near vision portion of the lens.
  • the progressive intermediate vision portion A2 is located between dotted lines 2 and 3 of the lens, which designate the lower aspect of the distance vision portion Al , whose refractive index is Nl , and the upper aspect of the near vision portion A3, whose refractive index is N3, respectively.
  • the refractive index N2 of the progressive intermediate vision portion A2 increases from a lower refractive index value equal to that of Nl of portion Al adjacent A2 to a higher refractive index value equal to that of N3 of portion A3 adjacent A2, the gradient profile following a rate of change which is regular and continuous and which can be generally characterized across its extent as corresponding to the progression of a Vi sine wave or sine wave like curvature, from its ⁇ /2 to 3 ⁇ /2 position.
  • Posterior lens section B is comprised of an optically transparent material whose refractive index N4 is generally constant and which does not vary.
  • Anterior surface 4 of lens section A has a convex curvature with a radius value Rl
  • internal interface I has a curvature R2
  • posterior surface 5 of lens section B has a concave curvature with a radius value R3.
  • lens sections may be produced as preforms and bonded together using an optical cement, or a succeeding layer may be cast against and bonded to the surface of a preformed section.
  • preform is meant a solid or semi-solid shape formed prior to the casting or cementing of a lens section.
  • a perform lens section may be produced by thermoforming, molding, grinding, casting or other processes.
  • a selected value generally between 2.0 and -2.0
  • b l-(2a ⁇ )
  • c a *3 ⁇ ⁇ 2/4
  • Values of 'a' may be used to define various curves whose x,y coordinates correspond to the instantaneous refractive index of the gradient index layer at consecutive point along the extent of the gradient portion.
  • FIG. 2 shows a graph with 5 curvatures based on the above equation, plotting refractive index against Y.
  • Y is the distance in millimeters over the extent of the progressive intermediate vision portion of the lens from dotted line 2 to line 3 shown below lens centerline CL shown in FIG.s Ib and Ic.
  • Example values of 'a' chosen are as follows: -.3, 0, .1, .3 and .4.
  • a value of '0' defines a sine wave shape, and may be considered as a standard for the lens of the present invention, as the curve demonstrates a rate of increase and decrease of refractive index which are equal, this being the case as the upper and lower sine wave portions have symmetry.
  • a non-symmetrical 'modified' sine wave curve may be preferred, wherein the derivative of curvature at the extrema are also 0.
  • Modification using positive values of 'a' becomes of greater importance when the progressive intermediate vision portion of the lens is short, on the order of 10mm or less, in which case the concentrated refractive power change can cause a visual disturbance as the direction of gaze of the patient moves from the distance vision portion of the lens to the progressive intermediate vision portion of the lens.
  • the above-described sine wave models for the refractive index gradients have refractive index profiles that increase from a lower refractive index value equal to that of the adjacent portion with lower refractive index to that of the opposite adjacent portion with higher refractive index.
  • Such gradient index profiles may be produced using a number of different processing methods. Inter- diffusion of two monomers at a liquid interface or diffusion of one monomer into a partially polymerized or gelled monomer of a different refractive index are methods that have been shown to provide useful refractive index gradients with high refractive index difference values.
  • the interface Due to the fact that slight disturbances or irregularities at the liquid interface of two monomers or resins used in a diffusion process can result in undesirable properties or deformities in the final gradient index profile, it is very important that the interface have no irregularities or undesirable contours, including the meniscus that typically may form along the top surface of a liquid in a vessel, such as a lens casting chamber or mold that may be used in the diffusion/casting process. Especially if the viscosity of the liquid optical resin is high, the meniscus formed at the lens chamber and resin boundary will be highly curved. If the lens casting vessel is narrow in its interior dimension the meniscus can be continuous across the interface, and of course will remain if the material is partially polymerized to a gel state.
  • the interface generally should have a planar, cylindrical, or cylindro- aspheric, conical or similar shape, with the planar dimension extending perpendicular to the length of the interface, that is, through the lens.
  • Another similar problem relates to the application of one liquid monomer on top of or next to another and how to preserve the integrity of the interface during the application.
  • Both problems may be solved by utilizing a new diffusion method involving the use of a dissolvable polymer membrane as a separator within the casting chamber. Both resins may contact the separating membrane and following dissolution of the membrane by one or both of the resins, undergo inter-diffusion or diffusion of one resin into the other followed by full polymerization or curing of the resin complex mixture.
  • the membrane should be thick enough so that it withstands the weight or pressure of a first resin introduced prior to the addition of the second resin in the adjacent chamber portion on the opposite side of the membrane, but thin enough to dissolve within a desired period of time, for example within 1 hour.
  • a polymethylmethacrylate film membrane 0.012 to 0.025mm thick may provide the desired attributes.
  • a copolymer membrane having a refractive index as a mean or variable value between that of the high and low refractive index resins may also be used.
  • FIG. 3 a there is shown a casting chamber for the instant gradient index progressive lens including dissolvable membrane Ml sandwiched between vertical lens chamber sections Sl and S2.
  • Section Sl corresponds to the distance vision portion Al of the lens and section S2 corresponds to the near vision portion A2 of the lens.
  • Chamber Sl is filled with one refractive index resin and chamber S2 is filled with the other refractive index resin through ports Pl and P2 respectively. Only if the resin of a lower section is gel polymerized prior to the dissolving of the membrane may the density be less than that of the resin of an upper section, otherwise the resin having greater density should be placed in the lower portion to avoid undesirable mixing and resettling of the liquid resins once the membrane dissolves.
  • the resins have the same density either may be positioned in the upper or lower section, furthermore the sections may be positioned side by side.
  • the casting chamber may be tilted to insure air bubbles are allowed to escape through filling ports Pl and P2.
  • FIG. 3b in like manner shows a cylindrically shaped curved membrane used to create a curved interface. Curved membrane M2 is sandwiched between lens chamber sections S3 & S4 creating refractive index resin sections Nl and N2.
  • the membranes may be pitched in a forward or backward direction to create a sloped refractive index orientation angle. In such instances the mold chamber may be tilted to the same slope angle during the diffusion and polymerization processes to insure the interface maintains the desired slope angle.
  • the resins may be filled with the mold chamber tilted as described before in order to allow escape of air bubbles through the filling ports.
  • the chamber of FIG. 3b may be positioned and used in an upside down orientation to insure any residual air bubbles will not be trapped in the central area of the downward facing concavity of membrane M2, but instead will rise and follow the curvature of the membrane upward to the far left or right side of the mold chamber towards filling ports P3 and P4, out of the area of the optical portion of the lens.
  • An additional method to facilitate and quicken the creation of the refractive index blend involves the controlled mixing of resin or monomer solutions of different refractive index in a vessel or mold chamber such as the above-described membrane containing mold chamber.
  • a vessel or mold chamber such as the above-described membrane containing mold chamber.
  • two or more vertically or otherwise adjacent layered component resin solutions of different refractive index can be blended at their interface(s) through the use of fine particles, such as glass beads, dispersed in the top layer solution.
  • Figure 22 illustrates this process schematically in a vertically oriented mold arrangement.
  • particles P (not to scale) are shown as they begin their descent through the upper, liquid in the upper lens chamber section Sl toward and through the interface I (indicated by dashed lines in the middle of a mold chamber).
  • the particles P are shown as being concentrated in the upper portion of the top layer solution, but they could as well be dispersed evenly through the upper liquid. Either way, they slowly settle through the upper liquid and through the interface I. The particles settle through gravity or centrifugal force into and through the lower layer solution or solutions, and in so doing create a blend zone below the original interfacial level.
  • the particles may be up to 50 microns in diameter, for example, with the concentration of the particles, as well as their size being selected to control the extent of the blend. While the use of particles is illustrated in connection with forming a lens having two refractive indices joined by a blend, it can also be practiced with multiple blends in connection with the lens making techniques shown and described in connection with Figures 2b and 2c.
  • Gravity and centrifugal force are not the only forces and fields that may be used to move the particles through the layer(s) of solutions). With charged particles or particles influenced by magnetic fields, electric and/or magnetic fields may be used. However it is propelled, each falling and settling particle from the above layer solution drags with it a small amount of the above layer solution through the interface into the adjacent below layer solution where it is cleaned of the single component resin covering as it passes through the liquid. Not only does the particle carry the resin from the above layer solution to the adjacent below layer solution, it also micro-mixes the solution in the area it passes through. As stated, this method may be used in molding or casting chambers including or absent of the membrane system previously described. The process may also be implemented in a mold arrangement wherein the layered resin solutions are situated side by side, in which case a field other than gravity will be required to provide a sideways motion of the particles from one adjacent solution to the other.
  • lines 2 and 3 shown in FIG Ib and Ic may vary significantly in the Y direction.
  • Line 2 may be located 2mm below a centerline CL and line 3 may be 18mm below line 2, thereby providing a progressive intermediate vision portion whose span between the upper distance vision and lower near vision portions is 18mm,
  • line 2 may be 3mm below centerline CL and line 3 may be 10mm below line 2, thereby providing a progressive intermediate vision portion whose span between the upper distance vision and lower near vision portions is 1 Omm.
  • the extent of the progressive intermediate vision portion of the present lens may be made shorter than typically provided in aspheric progressive lenses without introducing vision degrading astigmatism typical of the aspheric progressive designs.
  • This particular attribute presents a significant advantage of the gradient index design taught by this disclosure over aspheric progressive lens designs.
  • a so-called 'softer' lens as taught by this disclosure is achieved when the Y extent of the progressive intermediate vision section is greater, as in the version with the 18mm span, and a so- called 'harder' design is achieved when the Y extent of the progressive intermediate vision section is reduced, as with the 10mm span.
  • the gradient profile follows a rate of change which is regular and continuous and which can be generally characterized across its extent as corresponding to the progression of a Vz sine wave or sine wave like curvature, from its ⁇ /2 to 3 ⁇ /2 position, thus there will no perceived discontinuity in the transition from distance to progressive intermediate to near vision.
  • FIG. 4 is a table listing relational values for spherical curvatures Rl, R2 and R3, representing example lenses illustratively depicted in FIG.s Ia, Ib and Ic.
  • Each of the lenses 1 through 7 has a constant edge thickness of 0.05mm for lens section A and a constant center thickness of .25mm for lens section B, with total lens center and edge thicknesses varying only slightly over the range of example lens forms as indicated in the table.
  • the two columns on the far right include conic constant values and additional information for aspheric versions of each of the examples.
  • FIG. 4 is a table listing relational values for spherical curvatures Rl, R2 and R3, representing example lenses illustratively depicted in FIG.s Ia, Ib and Ic.
  • Each of the lenses 1 through 7 has a constant edge thickness of 0.05mm for lens section A and a constant center thickness of .25mm for lens section B, with total lens center and edge thicknesses varying only slightly over the
  • conic constant designated CC
  • radius R radius
  • center thickness CT edge thickness ET in millimeters
  • radius R radius
  • edge thickness ET edge thickness
  • Radii, center thickness and edge thickness values pertain to spherical lens versions only.
  • Lenses 1 through 7 provide '0' diopters of power in the distance vision portion and 2.5 diopters of add power in the near vision portion of the lens. Add power of this and all other lenses is in terms of diopters and calculated as 1000/effective focal length.
  • the selection of '0' power in the distance vision portion of the lens represents a standard for distance vision assuming an emmetropic eye, and is calculated as equal to an effective focal length not less than +/-le+009.
  • the lenses of the present invention will require modification such as lab work when incorporating a patient's prescription, but as any prescription value is in terms of diopters departure from emmetropia, the basic reference of '0' power, corresponding to emmetropia, will be maintained for all calculations throughout this writing. All radii and power calculations are based on refractive index, nd, calculated at the helium d-line (587.56nm). Alteration of surface 5 to incorporate a patient's prescription needs or provide other function will modify both the distance and near vision power but will not change the add power provided by the lens.
  • the lenses have the additional following refractive index parameters:
  • N4 1.58
  • add powers, lens layer thicknesses and '0' power for distance maintained constant as stated, there may be seen an additional constant with regard to the relationship of Rl, R2 and R3 over a full range of possible lens forms, as exemplified, expressed as the curvature relationship and efficiency number or CREN, as listed in FIG. 4.
  • the CREN is a numeric value that defines the relationship between the radii of the surfaces of a lens constructed according to this disclosure, based on the '0' power standard described above and stated in terms of diopters.
  • each lens constructed according to this disclosure can be defined by a CREN number, and as such CREN values for all subsequent lens examples are listed with other defining lens parameters. It is the nature of the lens made following the precepts of this disclosure that it requires extra bulk or 'convexity' to provide add power through refractive index change in conjunction with a symmetrically rotational surface.
  • the CREN number may range from between 40 and 50 for lenses with add powers from 1 to 3.5 diopters, when the efficiency is lowest and the bulk is greatest, to between about 3 and 11 for the same add powers when the efficiency is highest and the bulk is least. Such a high efficiency value allows for a lens with minimal thickness.
  • the CREN may be calculated by the following formula:
  • the CREN may be determined by first canceling the added power or prescription value and then doing the calculation. Lenses having a low CREN are most desirable as their bulk and critical thickness will be least.
  • the CREN number is highest when the refractive index difference (RID) between the upper and lower aspects of the lens is least, on the order of 0.08 to .16, as shown at the top portion of the table, and lowest when the RID is greatest, on the order of .60 or greater, shown at the bottom portion of the table.
  • RID refractive index difference
  • Medium and high RID values can be obtained by using both very high and very low refractive index component optical resins together to create the gradient refractive index profile of section A.
  • the calculated values for Rl and R2 will be substantially the same, but R3 and therefore the calculated CREN value will be different with no change in the refractive index of section B.
  • identical values for R3 and CREN may be produced, nonetheless in order to achieve a low CREN value and superior optical quality the refractive index of layer B should be high.
  • Higher RID values may be obtained by using component optical resins with a greater refractive index difference.
  • a .32 RID value may be obtained by using a 1.42 low refractive index resin component in conjunction with a 1.74 high refractive index component to create the gradient refractive index profile.
  • the lens' RID value may also be increased in accordance with the methods taught by this disclosure to a value double the maximum value of the refractive index difference of two component resins, i.e. .64, by means outlined in the fifth and sixth embodiments.
  • FIG. 5 is a table listing the CREN values of a complement of lenses of the first embodiment according to the RID of the gradient refractive index layer(s) and add power of the lens.
  • the refractive index values for all calculations are those listed above with reference to FIG. 4.
  • Add powers in the table range from 1 to 3.5 diopters.
  • the CREN numbers for the example lenses above, having all parameters the same except for lens form, range from 18.436 to 18.729, and define the major portion of the 18.07 - 19.10 range listed in the category at the intersection of the .24 RID and the 2.5 diopter add.
  • the category range on the chart has been widened by 2% beyond the numerical range of the example lenses to 18.07 - 19.10 to include additional lens forms not included in FIG. 4.
  • the 18.07 - 19.10 CREN range represents a very usable but just medium efficiency group of gradient refractive index lenses of made following this disclosure.
  • the lower CREN number ranges representing the most efficient designs, are located where add power is least and RID values are greatest. Lower add powers obviously will require less refractive index change, just as with aspheric progressive lenses less curvature change is required.
  • the most efficient CREN category on the chart, 3.05 - 3.19 designates a total of approximately 3 diopters of bulk or 'gross sag' to provide 1 diopter of add.
  • the same 3.5 diopter add lens with the same .16 RID value having a concave internal interface R2 curvature of -400mm will have a convex Rl curvature of 42.739mm and a concave R3 curvature of -46.144mm and a CREN value of 40.07.
  • the steeper lens demonstrates better optical quality compared to the one with an Rl curvature of 80.0mm, from a cosmetic standpoint such a highly curved lens would likely be undesirable. Nonetheless each of the CREN ranges of FIG. 5 are calculated from a range of lens forms including steeper versions such as the one above.
  • CREN categories above 50, representing very inefficient designs, are not included in the chart as the thickness, weight and high curvature of lenses producing these CREN values will have limited usefulness.
  • the table also shows the approximate maximum RID of a first layer of gradient refractive index, or in the case where only one lens layer comprises a gradient refractive index, the maximum RID of the lens.
  • the demarcation, situated at the .32 RID level, is based on the use of available compatible optical resins having both extremely high and extremely low refractive indices. It is anticipated that other materials with both higher and lower refractive indices may be used to create a greater RID, and in such case the potential CREN may be lower. It is also possible, as previously mentioned, to use two gradient refractive index profiles in reverse orientation to increase the RID and lower the CREN. In such a case values beyond the first line and up to the 'Approximate maximum RID of the lens' will be applicable.
  • the additive RID may still surpass that of a lens with only one gradient refractive index layer with a maximum RID value, producing a very efficient and thin lens.
  • a family of lenses having various constants including refractive index, RID, add power, constant edge thickness of 0.05mm for lens layer A and a constant center thickness of .25mm for lens layer B, may assume a variety of shapes defined by a specific relationship between Rl, R2 and R3, calculated as the CREN value.
  • R2 must be a specific value to achieve the add power(s) and specified standard of '0' power through the distance vision portion of the lens. From FIG.s Ia, Ib and Ic and FIG. 4 it can be seen that over a range of possible lens shapes, R2 corresponds to Rl and R3 typically by exhibiting a bending in the direction of greater convexity (with respect to lens layer A) with flatter convex Rl and concave R3 curvatures and in the direction of greater concavity (with respect to lens layer A) with steeper convex Rl and concave R3 curvatures.
  • correction of the lens made following this disclosure with aspheric curvatures cannot provide optimal visualization for all lens portions as the power and therefore the amount of correction will vary across the lens.
  • less correction is required for the upper distance vision portion of the lens regardless of its form, therefore -conic constant values lower than those listed for the flatter form lenses may be selected so that some correction is achieved without loss of optical quality in the distance vision portion of the lens.
  • a somewhat steeper lens form requiring less aspheric correction may provide an alternative when the cosmetic appeal of a very flat lens is not the primary concern, and in the case of the example lenses of FIG. 4, lens #6, for example, would provide an excellent alternative to lens #7.
  • FIG. s 7a, 7b, 7c and 7d show four versions of the first exemplary lens following the teachings of this disclosure.
  • the orientation angles X of the refractive index gradient differ.
  • orientation angle of the refractive index gradient is meant the angle that defines at least a portion of a surface, such as a plane, that intersects the refractive index gradient in which there is substantially a constant refractive index.
  • Such a positive angle of tilt is on the order of 8°, with the upper distance portion of the lens pitched forward with respect to other areas of the lens, as shown in FIG. 7b.
  • a small tilt satisfy the orientation angle criteria with respect to the upper section of the progressive intermediate vision portion of the lens, it also may provide somewhat improved visualization of objects viewed through the lower portion of the lens, as the bundles of rays passing from a viewed object to the eye and passing through the lens do so at an angle more nearly normal to the surface location through which the light bundles are transmitted.
  • a second way to achieve a positive gradient index orientation angle is to tilt the gradient medium within the gradient index section to correspond more closely to the angle of gaze when a patient looks through a selected area of the progressive intermediate vision portion of the lens, as shown in FIG. 7c.
  • the orientation angle X may also vary through the progressive intermediate vision portion of the lens to correspond even more closely to the instantaneous angle of gaze through the entire gradient index portion, as shown in FIG. 7d where the orientation varies from approximately 8° to 18°. It is also possible to achieve the desired gradient index orientation angle by combining a forward pitch of the lens with a constant or variable tilt of the gradient medium with the lens.
  • the gradient index orientation angle is comparatively more important, when the gradient index portion comprises only the plus power portion of the lens (as specified in the present embodiment). In this case the patient gazing straight ahead will be looking through the thickest portion of the gradient index section.
  • the gradient index orientation angle is comparatively less important when the gradient index portion comprises only the minus power portion of the lens. In such a case the patient gazing straight ahead will be looking through the thinnest portion of the gradient index section.
  • a minus power transverse gradient index embodiment as described is shown in FIG.8.
  • Anterior lens section A comprises the gradient index section of the lens and section B comprises the generally constant refractive index section of the lens. Section A has minus power and section B has plus power.
  • the internal interface curvature R2 is concave.
  • the refractive index decreases through the progressive intermediate vision portion of the lens from the distance vision portion to the near vision portion, therefore providing progressively increasing power for intermediate and near vision.
  • Lens layer A in Figure 8 is comprised of an optically transparent material having variable refractive index values.
  • Al corresponds to the distance vision portion of the lens
  • A2 corresponds to the progressive intermediate vision portion of the lens
  • A3 corresponds to the near vision portion of the lens.
  • the progressive intermediate vision portion A2 is located between dotted lines 2 and 3 of the lens, which designate the lower aspect of the distance vision portion Al, whose refractive index is Nl, and the upper aspect of the near vision portion A3, whose refractive index is N3, respectively.
  • the refractive index N2 of the progressive intermediate vision portion A2 decreases from a higher refractive index value equal to that of Nl of portion Al adjacent A2 to a lower refractive index value equal to that of N3 of portion A3 adjacent A2, the gradient profile following a rate of change which is regular and continuous.
  • the refractive index orientation angle of 8° as shown indicated by dotted lines 2 and 3 is obtained by tilting the refractive index medium within the body of the lens, and the extent of the gradient refractive index progressive intermediate vision portion located between dotted lines 2 and 3 is 12mm.
  • Posterior lens section B in Figure 8 is comprised of an optically transparent material whose refractive index N4 is generally constant.
  • Anterior surface 4 of lens layer A has a curvature with a radius value Rl
  • internal interface I has a curvature R2
  • posterior surface 5 of lens section B has a curvature with a radius value R3.
  • values for Rl, R2 and R3 are based on the lens providing 0 power in the distance vision portion and 2.5 diopters of add power in the near vision portion of the lens.
  • orientation angle of the refractive index gradient in degrees designated OA
  • extent of the progressive intermediate vision portion in millimeters designated IE
  • refractive index CREN
  • radii and thickness values in millimeters.
  • N2 1.70 to 1.46 1.74 to 1.42 1.74 to 1.42
  • Figure 9 shows a doublet lens configuration of a third exemplary lens following the precepts of this disclosure.
  • Anterior lens section A in Figure 9 comprises a generally constant refractive index section of the lens and section B comprises the gradient index section of the lens. Section A has minus power and section B has plus power.
  • the internal interface curvature R2 is concave with respect to lens section A.
  • the refractive index increases through the progressive intermediate vision portion of gradient lens section B from the distance vision portion to the near vision portion, therefore providing progressively increasing power for intermediate and near vision.
  • posterior lens layer B in Figure 9 is comprised of an optically transparent material having variable refractive index values.
  • Bl corresponds to the distance vision portion of the lens
  • B2 corresponds to the progressive intermediate vision portion of the lens
  • B3 corresponds to the near vision portion of the lens.
  • the progressive intermediate vision portion B2 is located between dotted lines 2 and 3 of the lens, which designate the lower aspect of the distance vision portion Bl, whose refractive index is Nl, and the upper aspect of the near vision portion B3, whose refractive index is N3, respectively.
  • the refractive index N2 of the progressive intermediate vision portion B2 increases from a lower refractive index value equal to that of Nl of portion Bl adjacent B2 to a higher refractive index value equal to that of N3 of portion B3 adjacent B2, the gradient profile following a rate of change which is regular and continuous.
  • Anterior lens section A is comprised of an optically transparent material whose refractive index N4 is generally constant and which does not vary.
  • Anterior surface 4 of lens section A has a curvature with a radius value Rl
  • internal interface I has a curvature R2
  • posterior surface 5 of lens section B has a curvature with a radius value R3.
  • the refractive index orientation angle of 8° as shown indicated by dotted line 2 is obtained by tilting the lens with respect to the angle of gaze of the patient. Both lenses have a progressive intermediate vision extent of 1 Omm.
  • Values for Rl , R2 and R3 are based on the lens providing 0 power in the distance vision portion and 2.0 diopters of add power in the near vision portion of the lens.
  • N2 1.46 to 1.70 1.46 tol.70
  • FIG.s 10a, 10b and 10c show three doublet lens configurations of a fourth exemplary lens constructed according to the teachings of this disclosure.
  • anterior lens section A comprises a generally constant refractive index section of the lens
  • section B comprises the gradient index section of the lens.
  • Section A has plus power
  • section B has minus power.
  • the refractive index decreases through the progressive intermediate vision portion of gradient refractive index lens section B from the distance vision portion to the near vision portion, therefore providing progressively increasing power for intermediate and near vision.
  • FIG 1 Oa shows an exemplary lens wherein the internal interface curvature R2 is concave
  • FIG 10b shows an exemplary lens wherein the internal interface curvature is piano
  • FIG 10c shows an exemplary lens wherein the internal interface curvature is convex.
  • Posterior lens layer B in Figures 10a - c is comprised of an optically transparent material having variable refractive index values.
  • Bl corresponds to the distance vision portion of the lens
  • B2 corresponds to the progressive intermediate vision portion of the lens
  • And B3 corresponds to the near vision portion of the lens.
  • the progressive intermediate vision portion B2 is located between dotted lines 2 and 3 of the lens.
  • Line 2 designates the lower aspect of the distance vision portion Bl, whose refractive index is Nl; line 3 designates the upper aspect of the near vision portion B3, whose refractive index is N3, respectively.
  • the refractive index N2 of the progressive intermediate vision portion B2 decreases from a higher refractive index value equal to that of Nl of portion Bl adjacent B2 to a lower refractive index value equal to that of N3 of portion B3 adjacent B2, the gradient profile following a rate of change which is regular and continuous.
  • Anterior lens section A is comprised of an optically transparent material whose refractive index N4 is generally constant.
  • Anterior surface 4 of lens section A has a curvature with a radius value Rl
  • internal interface I has a curvature R2
  • posterior surface 5 of lens section B has a curvature with a radius value R3.
  • the refractive index orientation angle of 8° as shown indicated by dotted lines 2 and 3 is obtained in FIG. 10b by tilting the lens with respect to the angle of gaze of the patient.
  • the lens of FIG. 10c has a combined 4° forward pitch of the lens and 4° tilt of the refractive index medium within the lens, thereby providing a total 8° orientation angle slope. Both lenses have a progressive intermediate vision extent of 8mm.
  • Relational values for Rl, R2 and R3, representing example lenses illustratively depicted in FIG.s 10a, 10b and 10c, are listed below along with refractive index values.
  • the lens examples provide '0' power in the distance vision portion and 2.5 diopters of add power in the near vision portion of the lens.
  • N2 1.72 to 1.44 1.72 to 1.44 1.72 to 1.44
  • FIG.s 11a and 1 Ib show two doublet lens configurations defining fifth and sixth exemplary lenses made following the teachings of this disclosure. In these examples only one figure each, rather than three, will be used to illustrate the range of forms possible for each, it having been established through previous embodiments and examples that lenses with concave, piano and convex internal interface surfaces can be made following this disclosure's teachings.
  • both anterior lens section A and posterior lens section B comprise gradient refractive index portions of the lens.
  • the refractive index difference ⁇ RID) of each layer may be additively combined, resulting in a RID value well beyond what may be achieved by a single gradient refractive index layer, thereby providing a means of achieving high add values with lower or flatter curvatures and reducing lens thickness, as will be seen in the following embodiments and examples.
  • lens section A has plus power and lens section B has minus power.
  • the refractive index of anterior lens section A increases through its progressive intermediate vision portion from the distance vision portion to the near vision portion, and the refractive index of posterior lens section B decreases through its progressive intermediate vision portion from the distance vision portion to the near vision portion this arrangement provides progressively increasing power for intermediate and near vision.
  • Lens layer A is comprised of an optically transparent material having variable refractive index values. Al corresponds to the distance vision portion of the lens, A2 corresponds to the progressive intermediate vision portion of the lens, and A3 corresponds to the near vision portion of the lens.
  • the progressive intermediate vision portion A2 is located between dotted lines 2a and 3 a of the lens.
  • Line 2a designates the lower aspect of the distance vision portion Al , whose refractive index is Nl
  • line 3a designates the upper aspect of the near vision portion A3, whose refractive index is N3.
  • the refractive index N2 of the progressive intermediate vision portion A2 increases from a lower refractive index value equal to that of Nl of portion Al adjacent A2 to a higher refractive index value equal to that of N3 of portion A3 adjacent A2, the gradient profile following a rate of change which is regular and continuous.
  • Lens layer B is comprised of an optically transparent material having variable refractive index values.
  • Bl corresponds to the distance vision portion of the lens
  • B2 corresponds to the progressive intermediate vision portion of the lens
  • B3 corresponds to the near vision portion of the lens.
  • the progressive intermediate vision portion B2 is located between dotted lines 2p and 3p of the lens, which designate the lower aspect of the distance vision portion Bl, whose refractive index is N4, and the upper aspect of the near vision portion B3, whose refractive index is N6, respectively.
  • the refractive index N5 of the progressive intermediate vision portion B2 decreases from a higher refractive index value equal to that of N4 of portion Bl adjacent B2 to a lower refractive index value equal to that of N6 of portion B3 adjacent B2, the gradient profile following a rate of change which is regular and continuous.
  • dotted lines 2a and 3a and 2p and 3p representing respectively refractive index gradient portions of lens sections A and B are aligned to provide cooperating and aligned vision portions of the lens.
  • alignment is meant that the refractive index gradients share a common level and extent. It also means that the surfaces defining the orientation angles of the upper and lower aspects of the two refractive index gradients generally coincide.
  • the refractive index gradient orientation angle of the example lenses is 8°, produced by tilting the refractive index mediums within the body of the lens, and the extent of the progressive intermediate vision portions is 14mm.
  • Anterior surface 4 of lens section A has a curvature with a radius value Rl
  • internal interface I has a curvature R2
  • posterior surface 5 of lens section B has a curvature with a radius value R3.
  • Relational values for Rl, R2 and R3, representing example lenses with concave, piano and convex internal interface curvatures are listed below along with the associated CREN values, refractive indices, lens thicknesses and optional conic constant values.
  • the three lens examples provide '0' power in the distance vision portion and 2.5 diopters of add power in the near vision portion of the lens.
  • N2 1.44 to 1.70 1.44 to 1.70 1.44 to 1.70
  • N5 1.70 to 1.44 1.70 to 1.44 1.70 to 1.44
  • Example #1 Example #2
  • Example #3 Three additional lens examples shown below provide '0' power in the distance vision portion and 3.5 diopters of add power in the near vision portion of the lens.
  • N2 1.42 to 1.74 1.42 to 1.74 1.42 to 1.74
  • N5 1.74 to 1.42 1.74 to 1.42 1.74 to 1.42
  • section A has minus and section B has plus power.
  • the refractive index of anterior lens section A decreases through its progressive intermediate vision portion from the distance vision portion to the near vision portion, and the refractive index of posterior lens section B increases through its progressive intermediate vision portion from the distance vision portion to the near vision portion.
  • This arrangement provides progressively increasing power for intermediate and near vision.
  • Lens layer A is comprised of an optically transparent material having variable refractive index values. Al corresponds to the distance vision portion of the lens, A2 corresponds to the progressive intermediate vision portion of the lens, and A3 corresponds to the near vision portion of the lens.
  • the progressive intermediate vision portion A2 is located between dotted lines 2a and 3a of the lens.
  • Line 2a designates the lower aspect of the distance vision portion Al, whose refractive index is Nl
  • line 3a designates the upper aspect of the near vision portion A3, whose refractive index is N3.
  • the refractive index N2 of the progressive intermediate vision portion A2 decreases from a higher refractive index value equal to that of Nl of portion Al adjacent A2 to a lower refractive index value equal to that of N3 of portion A3 adjacent A2, the gradient profile following a rate of change which is regular and continuous.
  • Lens layer B in Figured 1 Ib is comprised of an optically transparent material having variable refractive index values.
  • Bl corresponds to the distance vision portion of the lens
  • B2 corresponds ' to the progressive intermediate vision portion of the lens
  • B3 corresponds to the near vision portion of the lens.
  • the progressive intermediate vision portion B2 is located between dotted lines 2p and 3p of the lens.
  • Line 2p designates the lower aspect of the distance vision portion Bl, whose refractive index is N4, and line 3p designates the upper aspect of the near vision portion B3, whose refractive index is N6.
  • the refractive index N5 of the progressive intermediate vision portion B2 increases from a lower refractive index value equal to that of N4 of portion Bl adjacent B2 to a higher refractive index value equal to that of N6 of portion B3 adjacent B2, the gradient profile following a rate of change which is regular and continuous.
  • dotted lines 2a and 3a and 2p and 3p representing, respectively, refractive index gradient portions of lens sections A and B are misaligned to provide a modified rate of change of power of the lens.
  • misalignment is meant the refractive index gradients do not share a either a common level or extent, or both. It also means that the planes defining the orientation angles of the upper and lower aspects of the two refractive index gradients do not coincide.
  • Refractive index gradients of adjacent lens sections may be misaligned such that one refractive index gradient is displaced either above or below the level of the refractive index gradient of the adjacent section.
  • the orientation angle for each refractive index gradient of the example lenses is 8°, produced by a forward pitch of the lens as previously described, and the extent of each progressive intermediate vision portions is 10mm.
  • Anterior surface 4 of lens section A has a curvature with a radius value Rl
  • internal interface I has a curvature R2
  • posterior surface 5 of lens section B has a curvature with a radius value R3.
  • Relational values for Rl, R2 and R3, representing example lenses with concave, piano and convex internal interface curvatures are listed below along with the associated CREN values, refractive indices, lens thicknesses and optional conic constant values.
  • the three lens examples provide '0' power in the distance vision portion and 3.0 diopters of add power in the near vision portion of the lens.
  • N2 1.74 to 1.42 1.74 to 1.42 1.74 to 1.42
  • N5 1.42 to 1.74 1.42 to 1.74 1.42 to 1.74
  • FIGs. 12a and 12b show two triplet lens configurations defining sixth and seventh exemplary lenses constructed following the teachings of this disclosure. Again in these examples only one figure each, rather than three, will be used to illustrate the range of forms possible for each.
  • the lenses have the same defining characteristics and identified refractive index sections Nl, N2, N3, N4, N5 and N6 of the prior fifth and sixth examples of FIG. 11a and l ib respectively, wherein both anterior lens section A and posterior lens section B comprise gradient refractive index portions of the lens.
  • the lens examples in Figures 12a and 12b incorporate a third bonded lens layer C on which to provide a patient's prescription.
  • posterior lens section C comprises an optically transparent material whose refractive index N7 is generally.
  • lens section C is positioned adjacent lens section B and is therefore the posterior-most layer of the lens.
  • lens section C is positioned adjacent lens section A, and is therefore the anterior-most layer of the lens.
  • lens section C may be positioned adjacent either lens section A or lens section B.
  • lens blank form the lens of Figure 12a may be formed with lens section C thick enough to allow a wide range of patient prescriptions to be processed into the finished lens.
  • Final center thickness of lens section C may be as low as .25mm.
  • Relational values for Rl, R2, R3, and R4 for the two embodiments representing example lenses with various internal interface curvatures R2 are listed below along with the associated CREN values, refractive indices, lens thicknesses and optional conic constant values.
  • the equation to determine the CREN number has been modified to include values corresponding to the additional lens layer C, and is expressed in surface diopters as follows:
  • Dl, D3 and D4 are the absolute values of the surface diopters of Rl, R3 and R4 respectively, and the sign of D2, which is the surface diopter power of R2, is positive when its curvature is convex with respect to lens section A and negative when its curvature is concave with respect to lens section A.
  • D3-D4 is an unsigned value.
  • both lens portions A and B share more or less equally in providing the progressive add power of the lens. It is also possible to slightly increase the CREN and optical performance efficiency of the lens by increasing the thickness of lens section C to a value greater than the .25mm center thickness listed above. By so doing some of the lens curvatures flatten slightly, although overall thickness of the lens is increased, so there is a trade off of sorts. To provide improved optical performance, increase the CREN efficiency and to reduce lens thickness and bulk a center thickness for lens section C may preferably be between .25 and 1.Omm.
  • center thickness of lens section C may exceed lmm.
  • edge thickness of lens section C and of the entire lens will increase.
  • a center thickness of .5mm has been selected for lens section C.
  • an R4 value for lens section C equal to the R3 value of lens section B, when section C is adjacent section B, and equal to the Rl value of lens section A, when section C is adjacent section A, is used in the examples below.
  • portions A and B are opposite in both power sign and gradient refractive index profile orientation, the opportunity exists to increase, up to double, the refractive index difference or RID value of the lens by approximately a 50% power sharing of the two portions.
  • the percentage shift may favor either lens section A or lens section B.
  • a shift in favor of lens section A would result in an increase in the surface diopter power and center thickness of lens section A and a decrease in the surface power and edge thickness of lens section B.
  • the percentage shift can be partial or even equal 100%, in which case lens section A will be doing all the work, and be quite a bit steeper, and lens section B will essentially become a piano lens, contributing nothing to the add function of the lens.
  • the lens is essentially the same as the lens of the first example wherein there is only one section comprising the gradient refractive index portion of the lens.
  • lenses of the sixth and seventh exemplary lenses may have CREN numbers ranging from a maximum efficiency value, resulting from the optimal sharing and combining of both add generating lens portions A and B, to approximately that of a lens with only one section incorporating a gradient refractive index.
  • the CREN value in parenthesis represents the CREN value when section A is providing 100% of the add power and section B provides none
  • the CREN value in parenthesis represents the CREN value when section B is providing 100% of the add power and section A provides none.
  • the CREN value for each lens example may range between these two values based on the percentage each portion contributes to the add power of the lens.
  • Orientation angle OA and progressive intermediate portion extent IE are the same as in the example lenses of FIG.s 11a and 1 Ib, and are not listed with the example lens parameters below.
  • the lenses provide '0' power in the distance vision portion and 3.5 diopters of add power in the near vision portion of the lens.
  • N2 1.46 to 1.70 1.46 to 1.70 1.46 to 1.70
  • N3 1.70 1.70 1.70
  • N5 1.70 to 1.46 1.70 to 1.46 1.70 to 1.46
  • N2 1.42 to 1.74 1.42 to 1.74 1.42 to 1.74
  • N5 1.74 to 1.42 1.74 to 1.42 1.74 to 1.42
  • FIG.s 13 through 18 show an additional exemplary lenses constructed following the teachings of this disclosure. They have multi-layered Fresnel lenses incorporating a gradient refractive index.
  • a Fresnel lens surface comprises numerous discontinuous coaxial annular sections each defining a slope corresponding to a continuous lens surface geometry, collapsed to form a surface of lower profile. Joining each optically functional annular section is a non-optically functional step, also in the form of an annulus, that in conjunction with the refracting surfaces determines the overall geometry and lens thickness.
  • each annulus comprising a non-optically functional step may be oriented at an angle substantially equal to that of the light rays passing through that point on the lens from points in the field corresponding to the line of sight of the patient and proceeding to the patient's eye.
  • the pupil When the patient looks straight ahead, the pupil is located approximately 16mm behind the back surface of the spectacle lens, whereas the center of rotation of the eye is approximately 28.5mm behind the back surface of the spectacle lens. Either location, or any point in between may be used to determine the slope angles of the steps and excellent results may be achieved. Furthermore, improved results may be achieved by selecting any point posterior of the lens greater than about 15mm as the location defining the exit pupil. A distance of 21mm from the back surface of the lens for the location of the exit pupil results in an approximately equal angular error of the non-optical step of about 8° for the two extremes of the eye orientation stated with reference to peripheral rays directed to that location.
  • each step may equal the angle of refracted rays passing through the lens at the location of the step and proceeding from the lens to the exit pupil.
  • Each step may be visualized as one of a series of annular right circular concentric conical sections formed by the intersection of conical surfaces and the lens body, as the conical surfaces, following at least to some degree the pathway of the refracted light rays proceeding through the lens, form their apices at the 21mm distance mentioned or other distances posterior of the back surface of the lens.
  • the second step that may be taken to improve the Fresnel lens performance of the present invention is to bond the defined adjacent lens layer to the Fresnel surface as a cast layer, thereby limiting or entirely eliminating Fresnel diffraction and reflection of one portion, either the upper distance or lower near vision portion, and substantially reducing diffraction and reflection in the other portion, while providing protection of the vulnerable Fresnel geometry.
  • the refractive index of the bonded portion is equal to that of the Fresnel preform, the function of the Fresnel as well as its visibility and any resulting visual degradation are completely eliminated.
  • Such an area of the doublet Fresnel lens will act as a single index optical window and is ideal for the distance vision portion of the lens.
  • the refractive index of the bonded portion providing progressive add power may be somewhat close to that of the preform. The higher the power, the less refractive index difference there need be.
  • the refractive index of the bonded add portion may be greater or lesser than that of the preform, yielding a plus or minus power, depending on whether the Fresnel preform is positive or negative in power.
  • Figure 13 shows a doublet fresnel lens configuration defining an eighth exemplary lens constructed following the teachings of this disclosure.
  • the non-optically functional steps are normal to the form of the lens, and do not correspond to the described exit pupil, hi the figure, lens section A comprises the generally constant refractive index section of the lens, and lens section B comprises the gradient refractive index section of the lens. Separately, section A has minus power and section B has plus power.
  • the refractive index increases through the progressive intermediate vision portion of gradient lens section B from the distance vision portion to the near vision portion, therefore providing progressively increasing power for intermediate and near vision.
  • Rl, R2 and R3 are the absolute values of the surface radii, and R2 is the diopter curvature form (R2f) of the Fresnel, independent of its actual surface power.
  • CREN value is 6, indicating some bulk or gross sag to the lens.
  • CREN values for the Fresnel lens of the present example generally range from 0 to 20, and are listed with the associated lens parameters for each example Fresnel lens.
  • posterior lens layer B is comprised of an optically transparent material having variable refractive index values.
  • Bl corresponds to the distance vision portion of the lens
  • B2 corresponds to the progressive intermediate vision portion of the lens
  • B3 corresponds to the near vision portion of the lens.
  • the progressive intermediate vision portion B2 is located between dotted lines 2 and 3 of the lens, which designate the lower aspect of the distance vision portion Bl, whose refractive index is Nl, and the upper aspect of the near vision portion B3, whose refractive index is N3, respectively.
  • the refractive index N2 of the progressive intermediate vision portion B2 increases from a lower refractive index value equal to that of Nl of portion Bl adjacent B2 to a higher refractive index value equal to that of N3 of portion B3 adjacent B2, the gradient profile following a rate of change which is regular and continuous.
  • Anterior lens layer A is a Fresnel perform lens comprised of an optically transparent material whose refractive index N4 is generally constant and which does not vary.
  • Anterior surface 4 of lens layer A has a curvature Rl which is piano
  • internal Fresnel interface I has a form R2f, which is generally flat, an equivalent Fresnel radius R2r with respect to lens section A and a conic constant value CC
  • posterior surface 5 of lens section B has a curvature R3 which is piano.
  • the lens provides '0' power in the distance vision portion and a high dioper add power in the near vision portion of the lens, listed below.
  • Surface 4 may be modified to incorporate a patient's prescription or both surfaces 4 and 5 may be modified to provide a meniscus curvature form.
  • Example #1 Example #2 Example #3 Example #4
  • N2 1.491 to 1.58 1.498 to 1.58 1.498 to 1.56 1.498 to 1.55
  • R2r -24.68 -24.68 -24.68 -24.68
  • FIG. 14 is an enlargement of two optically functional slopes 6 and 7 along with interconnecting non-optically functional steps 8, 9 and 10, 11. of internal Fresnel interface R2r of FIG. 13, indicated by the arrows.
  • a significant amount of the bundles 12 and 13 is clipped or obstructed by steps 8, 9 and 10, 11 and as a result the lens is quite inefficient in its periphery.
  • Lens example #1 in Figure 14 comprises a Fresnel prefom A with a negative focal length of 50mm, refractive index N4 of 1.491, Fresnel radius R2r of -24.68mm, and conic constant of -.631.
  • This preform is combined with a .4mm thick cast Fresnel layer B comprising an Nl refractive index of 1.491 , an N2 gradient refractive index ranging from 1.491 to 1.58 and an N3 refractive index of 1.58.
  • the lens provides 3.5 diopters of progressive add power. Two rays are selected at peripheral angles of 35° and 45° degrees directed to the above described exit pupil.
  • the surface slope is 44.67° and has a calculated step depth of .25095mm over a selected groove width of .254mm.
  • the surface slope is 32.51° and has a calculated step depth of .16210mm over the groove width of .254mm.
  • the 26.59° ray shows losses from interference of the .25095mm tall (outer) step annulus resulting in 49.5% light reduction
  • the 35° ray shows losses from interference of the .16210mm tall (outer) step annulus resulting in a 25% light reduction.
  • optical materials with similar Abbe values should be selected, or materials with compensating Abbe characteristics may be selected to correct chromatic aberration.
  • FIG. 15 shows a doublet Fresnel lens configuration of a ninth lens constructed following the teachings of this disclosure identical to the prior Fresnel lens of FIG. 13 except that the annular step slopes have been corrected as described to minimize obstruction of light rays especially through the periphery of the lens.
  • the surface radii, refractive indices, lens section powers, thickness and add power of the lens are the same as listed for example #1 lens relating to FIG. 13.
  • FIG. 16 is an enlargement of two optically functional slopes 6 and 7 along with interconnecting non-optically functional steps 8, 9 and 10, 11 of internal Fresnel interface R2r of FIG. 15, indicated by the arrows.
  • the internal Fresnel interface surface I is generally flat as is typical of most commercially available Fresnel lenses, but the form of the lens may be other than flat, for example with surfaces Rl and R3 curved in meniscus form to resemble a standard ophthalmic lens.
  • the lens thickness will increase as a result of increased center thickness of section A and increased edge thickness of section B. By using low diopter curvatures, the thickness increase will be within reasonable limits.
  • FIG. 17 shows a tenth exemplary lens constructed following the teachings of this disclosure.
  • the Figure 17 lens is a triplet Fresnel lens incorporating a third bonded lens layer C.
  • internal Fresnel interface surface I is generally flat and the form of the lens as above described is meniscus and resembles a standard ophthalmic lens.
  • the lens may incorporate non-optically functional steps which are normal to the plane of the lens or which are angled and corrected as described above in connection with Figures 15 and 16.
  • lens section A comprises a Fresnel preform of generally constant refractive index
  • lens section B comprises the gradient refractive index section of the lens
  • lens section C comprises a 2 nd preform. Separately, section A has minus power, section B has plus power, and section C has minus power.
  • the refractive index increases through the progressive intermediate vision portion of gradient lens section B from the distance vision portion to the near vision portion, therefore providing progressively increasing power for intermediate and near vision.
  • Gradient refractive index lens layer B functions as an optical cement between lens layers A and C.
  • Bl corresponds to the distance vision portion of the lens
  • B2 corresponds to the progressive intermediate vision portion of the lens
  • B3 corresponds to the near vision portion of the lens.
  • the progressive intermediate vision portion B2 is located between dotted lines 2 and 3 of the lens, which designate the lower aspect of the distance vision portion Bl, whose refractive index is Nl, and the upper aspect of the near vision portion B3, whose refractive index is N3, respectively.
  • the refractive index N2 of the progressive intermediate vision portion B2 increases from a lower refractive index value equal to that of Nl of portion Bl adjacent B2 to a higher refractive index value equal to that of N3 of portion B3 adjacent B2, the gradient profile following a rate of change which is regular and continuous.
  • Anterior lens layer A is a Fresnel preform lens comprising an optically transparent material whose refractive index N4 is generally constant .
  • Posterior lens layer C is a preform lens with a refractive index N5.
  • Internal surface 5 of lens section C has a curvature R3 which may be flat or just slightly convex with respect to lens section C in order to facilitate an air bubble free bond in conjunction with the gradient refractive index optical cement comprising section B.
  • Anterior surface 4 of lens layer A has a curvature Rl which is convex
  • internal Fresnel interface I has a form R2f, which is generally flat, an equivalent Fresnel radius R2r with respect to lens section A and a conic constant value CC
  • posterior surface 6 of lens section C has a curvature R4 which is concave.
  • Surface 4 or 6 may be modified to incorporate a patient's prescription.
  • the 3 diopter convex curvature of surface 4 and concave curvature of surface 6 provide a meniscus lens form typical of ophthalmic lenses. Center and edge thicknesses in a 50mm diameter lens having the following parameters are well within reasonable limits for an ophthalmic lens and are listed below.
  • the lens provides '0' power in the distance vision portion and 3.265 diopters of add power in the near vision portion of the lens. Higher refractive index preforms will result in a significantly thinner lens, allowing for higher curvatures for surfaces 4 and 6.
  • Fresnel examples may be produced with either or both sections comprising the gradient refractive index sections of the lens as with previous embodiments of this writing, although it is preferred that only one section comprise a gradient refractive index in the Fresnel lens versions.
  • an lens similar to the fifth and sixth exemplary lenses wherein both sections comprise a gradient refractive index, and the progressive intermediate portions are misaligned may provide a modified rate of change of power as desired.
  • the Fresnel preform may have either plus or minus power and be positioned as either the anterior or posterior lens layer.
  • the refractive index of one portion of the gradient refractive index layer may be the same as or different than its counterpart of the adjacent bonded layer.
  • the inner Fresnel surface may typically be flat with the overall form of the lens being either flat or curved.
  • Figure 18 shows a doublet fresnel lens configuration of an eleventh exemplary lens constructed following the precepts of this disclosure.
  • the Figure 18 lens incorporates a curved internal Fresnel surface R2, as well as curved surfaces Rl and R3.
  • the Fresnel lens form incorporates a corrected geometry of the non-optically functional step as previously described in addition to a curved surface R2 that allows a meniscus form to be used without an increased CREN value and added thickness of the lens.
  • the curvature of R2 may approximate that of Rl or R3.
  • R2 in conjunction with Rl and R3 may also provide a more highly curved lens such that the pathways of the light rays within the body of the lens are substantially perpendicular to the Fresnel form and therefore the non-optically functional steps are as well normal to the Fresnel form.
  • the one case in which this occurs is when the radius of posterior surface 5 is approximately equal to the distance to the exit pupil. This translates to a curvature of 47.6 diopters which by most standards would be excessively steep for an ophthalmic lens. Therefore it is preferred that the curvature R2 be reduced to a value typical of base curves of standard ophthalmic lenses, for example 200mm (5 diopter curve) and the step angles be corrected accordingly.
  • Section A in Figure 18 comprises the gradient refractive index section of the lens and section B comprises the generally constant refractive index section of the lens. Separately, section A has minus power and section B has plus power.
  • the refractive index decreases through the progressive intermediate vision portion of gradient index lens section A from the distance vision portion to the near vision portion, therefore providing progressively increasing power for intermediate and near vision.
  • Lens layer A is comprised of an optically transparent material having variable refractive index values.
  • Al corresponds to the distance vision portion of the lens
  • A2 corresponds to the progressive intermediate vision portion of the lens
  • A3 corresponds to the near vision portion of the lens.
  • the progressive intermediate vision portion A2 is located between dotted lines 2 and 3 of the lens.
  • Lien 2 designates the lower aspect of the distance vision portion Al, whose refractive index is Nl
  • line 3 designates the upper aspect of the near vision portion A3, whose refractive index is N3.
  • the refractive index N2 of the progressive intermediate vision portion A2 decreases from a higher refractive index value equal to that of Nl of portion Al adjacent A2 to a lower refractive index value equal to that of N3 of portion A3 adjacent A2, the gradient profile following a rate of change which is regular and continuous.
  • Posterior lens layer B is a Fresnel preform lens comprised of an optically transparent material whose refractive index N4 is generally constant .
  • Anterior surface 4 of lens layer A has a curvature Rl which is convex
  • internal Fresnel interface I has a form R2f which is concave and an equivalent Fresnel radius R2r with respect to lens section A and a conic constant value CC
  • posterior surface 5 of lens section B has a curvature R3 which is concave.
  • the extent of the progressive intermediate portion IE is 16mm.
  • the lens provides '0' power in the distance vision portion and 2.278 diopters of add power in the near vision portion of the lens.
  • Surface 5 may be modified to incorporate a patient's prescription.
  • the gradient refractive index portion of the above described flat- form Fresnel lenses of FIG. s 13, 15 and 17 may be produced using the spraying method previously described, wherein two spray guns moving together in a linear or arcuate path each spray a deposit of one of the refractive index resins onto the Fresnel preform surface in such a manner as to produce an overlapping or common deposit from between 4 to 20mm wide or greater across the extent of the lens.
  • a thin vertical separator wall positioned between the spray guns and above the pooling resin deposits, oriented in line with the direction of the spray guns' movement, separates the distance and near vision portions and blocks unwanted spray from each gun from depositing in the adjacent portion.
  • the extent of the overlap or blend area may be increased or decreased and easily controlled primarily by adjusting the direction and pattern of spray of the guns and secondarily by adjustment of the height of the separator wall.
  • the spray process may continue as the guns continue their back and forth linear or arcuate motion, insuring an even distribution and volume of resin material is deposited over the Fresnel lens surface.
  • the spraying process further insures that thorough mixing of the two resins occurs in the blend area by the massaging and mixing action of the existing pooled deposit caused by the impact of both the resin mist and air pressure of the spray guns.
  • the spraying apparatus described with respect to FIG. 20 may be used to accomplish the above-described spraying procedure.
  • FIG. 19 shows 2 sprayed deposit areas including an overlapping or common area incorporating the gradient index mixture. Both spray pattern deposits in this case are circular, but may be differently shaped, such as elliptical.
  • Circular deposit A and circular deposit B share common area A+B wherein a varying amount of each resin contributes to the composition over the common area extent represented by line AB. Due to the linear or arcuate motion and path of the guns in the direction LP, as well as the varying chord lengths CL of each circular deposit within A+B (parallel to LP), the resin mixture and therefore the refractive index of the composition will demonstrate a smooth, continuous and regular rate of change in a direction perpendicular to LP, closely following the progression of a portion of a sine wave form from its ⁇ /2 to 3 ⁇ /2 positions.
  • the lens may be fully cured or polymerized and subsequently machined or processed as desired, or a protective layer or additional section, such as lens section C of FIG. 17 or 18a, may be applied to the liquid resin surface and polymerized, creating a permanently bonded layer.
  • a removable casting member may be applied to the upper most resin surface followed by polymerization and subsequent removal to create an optical quality surface such as 5 indicated in FIG. 13.
  • the gradient refractive index portion of the above described curved form Fresnel lens of FIG. 18 may be produced in a similar manner using a two gun spraying system producing a composite refractive index gradient area.
  • the sprays are deposited on a flat surface with flexural characteristics to the desired thickness, for example .35mm thick.
  • the resins may be partially polymerized to a gel state.
  • the flexible surface may be deformed or relaxed to a curvature corresponding to the Fresnel preform and subsequently pressed against the perform and polymerized to permanently bond the gelled layer to the Fresnel surface.
  • Layer C incorporating the flexible surface may remain as part of the lens, as shown in FIG. 18a, or be removed and reused or disposed of.
  • the flexible surface as stated may be relaxed to the desired curvature or by mechanical or other means, for example by a vacuum forming process, be caused to deform to the desired curvature.
  • Figure 20 shows a 12th exemplary lens constructed following the precepts of this disclosure.
  • the Figure 20 lens is a gradient index progressive lens which incorporates numerous layers with gradient refractive index profiles and power signs each opposite that of adjacent layers.
  • a pair of gradient refractive index profiles may be used in adjacent plus power and minus power layers effectively to increase or double the refractive index difference, thereby providing a means of achieving high progressive add values with lower or flatter curvatures and reduced lens thickness.
  • the present embodiment works on the same principle but utilizes numerous paired layers of low curvature and thickness to achieve a similar result. Film layers .3mm thick or less may be combined in various numbers to produce a corresponding progressive add value.
  • anterior lens section A comprises a generally constant refractive index layer and sections B, C, D and E comprise gradient refractive index layers of the lens. There are six C sections and five D sections. Sections B and E are equal in power and added together constitute an additional D section. Paired sections C and D are opposite and equal in power. Section A has plus power and compensates for a negative 'add' power of the upper distance vision portion of the lens, section B has plus power, sections C have minus power, sections D have plus power and section E has plus power.
  • the refractive index decreases through the progressive intermediate vision portion of gradient refractive index lens section C from the distance vision portion to the near vision portion, and increases through the progressive intermediate vision portion of gradient refractive index lens section D from the distance vision portion to the near vision portion, therefore providing complexed and progressively increasing power for intermediate and near vision.
  • Lens layer A is comprised of an optically transparent material whose refractive index Nl is generally constant.
  • Lens layer B is comprised of an optically transparent material having variable refractive index values.
  • Bl corresponds to the distance vision portion of the lens and has a refractive index value N2
  • B2 corresponds to the progressive intermediate vision portion and has a gradient refractive index value N3
  • B3 corresponds to the near vision portion of the lens and has a refractive index value N4.
  • Lens layer C is comprised of an optically transparent material having variable refractive index values.
  • Lens layer D is comprised of an optically transparent material having variable refractive index values.
  • Dl corresponds to the distance vision portion of the lens and has a refractive index value N8
  • D2 corresponds to the progressive intermediate vision portion and has a gradient refractive index value N9
  • D3 corresponds to the near vision portion of the lens and has a refractive index value NlO.
  • Lens layer E is comprised of an optically transparent material having variable refractive index values.
  • El corresponds to the distance vision portion of the lens and has a refractive index value Nl 1
  • E2 corresponds to the progressive intermediate vision portion and has a gradient refractive index value N 12
  • E3 corresponds to the near vision portion of the lens and has a refractive index value Nl 3.
  • Refractive index gradient portions N3, N6, N9 and Nl 2 are located between dotted lines 2 and 3 defining the progressive intermediate vision portion of the lens.
  • Anterior surface 4 of lens layer A has a convex curvature with a radius value Rl
  • internal interface surface 5 has a radius R2
  • internal interface surfaces 6 have a radius R3
  • internal interface surfaces 7 have a radius R4, and posterior surface 8 has a radius R5.
  • Lens sections C and D share curved interfaces 6/R3 and 7/R4.
  • R3 is concave and R4 is convex with respect to section A. Because adjacent internal interface surfaces are opposite in curvature the CREN value for a lens according to this example may be calculated simply by adding the absolute surface diopter powers of all surfaces.
  • the refractive index orientation angle of 8° as shown is obtained by misaligning each successive refractive index gradient an incremental amount.
  • values for all the radii are based on the lens providing 0 power in the distance vision portion and 2.5 diopters of add power in the near vision portion of the lens.
  • N3 1.41 to 1.74
  • N12 1.41 to 1.74
  • the above described lens may be produced by processing each lens layer independently of the others in a sequential order using for example the spraying method above described with respect to the FIG.s 13, 15, 17 and 18 in conjunction with a deformable base with desirable flexural characteristics.
  • FIG. 21 shows a spraying apparatus that may be used to process the lens layers comprising two spray guns Sl and S2 that deliver separately the 1.74 and the 1.41 refractive index materials respectively.
  • the guns move together in a linear motion and path LP, each spraying resin deposits S 1.41 and S 1.74 onto base surface B and producing a combined overlapping or common deposit 14mm wide.
  • a thin vertical separator wall W positioned between the spray guns and above the pooling resin deposits, oriented in line with the direction of the spray guns' movement, divides the distance portion D and near portion N and blocks unwanted spray US from each gun from depositing in the adjacent portion while helping to control the amount of each sprayed resin that passes underneath and beyond it to mix with the adjacent sprayed resin portion.
  • the extent of the common deposit or blend area may be increased or decreased and easily controlled primarily by adjusting the direction and pattern of spray of the guns and secondarily by adjusting the height of the separator wall. Assuming a cone angle spray from each gun of 30°, a convergent tilt of 15° for each gun, a spray distance of 63mm from gun tip to deposit surface, a gun tip to gun tip separation of 56mm and separator wall height of 12mm above the deposit surface, a 14mm wide gradient index section may be produced.
  • Separator wall W serves mainly to prevent unwanted spray US from depositing but within limits may be adjusted to control the width of the gradient index portion.
  • the wall may include an opening along its lower extent connected to a vacuum source that draws accumulated resin build up away from the sprayed area and off the wall W in order to prevent dripping of material from the wall into the deposit.
  • Flexible and deformable base B is the surface on which the first resin layer is sprayed, and above which is the vertical separator wall W.
  • the deformable base B is mounted on base support cylinder BS, which has an upper wall portion R that extends above base B and which acts as a container for the sprayed resins.
  • Deformable base B comprises a thin plastic, glass or stainless steel member that through mechanical or other means may be caused to change curvature. During each spray application a change of curvature is induced in base B which in turn creates the curvature of each internal interface as a new layer is applied.
  • vacuum line VL provides a partial and controllable vacuum from a vacuum source to vacuum chamber VC and provides suction means to draw deformable base B downward to create a concave curvature.
  • line VL is pressurized to create an atmospheric pressure environment in chamber VC and provides pressure means to push deformable base B upward to create a convex curvature.
  • R3 and R4 have a sagittal depth of 0.0974mm over 50mm, only a small amount of surface change is needed to cause base B to assume the needed radius of curvature.
  • a variable thickness of base B may be used to insure that a surface of continuous and useful optical curvature, for example, a spherical curvature, is achieved when the base is deformed.
  • the first composite layer Bl is initially applied when the base B is maintained in a flat condition.
  • base surface B may be progressively steepened in concavity to its final curvature, as indicated in the drawing, as the spray layer thickness is achieved, thus the change of curvature progresses in concert with the build up of the applied resin layer.
  • wall W may be removed.
  • the liquid surface of the sprayed resin layer will settle and self-level after which it can be photo polymerized to a gel state.
  • a flat or slightly convex casting surface may be applied to the unpolymerized resin layer to precisely control the surface contour.
  • a convex casting surface is used to avoid entrapment of air bubbles when applied to the air- exposed surface of the sprayed resin composition.
  • the resin layer may then be gel polymerized and afterward the upper casting surface removed.
  • the top most surface of the gel cured deposit becomes the base Bl on which the second sprayed layer is applied, therefore any minor adjustments in curvature needed may be made to base B to provide a flat surface Bl on which to apply the second layer.
  • a second sprayed resin layer may then be applied to the flat surface, although this time with the spray guns or lens rotated 180° to achieve an opposite refractive index profile orientation.
  • base surface B may be progressively reduced in concave steepness and gradually be made convex to its final steepness as the spray layer thickness is achieved, thus again the change of curvature progresses in concert with the build up of the applied resin layer, creating each new curved interface radius with a corresponding change of curvature of base B.
  • the top surface of the sprayed liquid resin may be finished as previously described.
  • the spray guns or lens may be repeatedly rotated 180° to achieve an opposite refractive index profile orientation for each additional layer having corresponding alternating plus or minus power. Each rotation may also include an incremental offset to achieve the refractive index orientation angle indicated by dotted lines 2 and 3.
  • the final polymerization from gel to solid should be undertaken with the base material surface and top surface in a flat state.
  • the final layer A may be produced as a preform and bonded to the composite multi-layered lens, or it may be cast onto surface B or E and polymerized.
  • the above-described spraying technique may also be used.
  • a greater sprayed thickness deposit will be required. If the density of the two refractive index materials sprayed is substantially different, the heavier material may settle beneath the lighter material by the pull of gravity if single spray applications of great thickness are applied.
  • periodic gel polymerization or partial curing of thin applied layers may be undertaken. For example, applied layers .25mm thick may be sequentially gel polymerized until the final layer thickness is achieved.
  • an upper casting surface need not be applied to each of the sequential spray deposits to create a perfectly flat surface as additional spray coatings of the same refractive index profile orientation will be applied.
  • These lenses of greater thickness and steeper curvature may also utilize a deformable base to facilitate the spray production process and to provide the required radius.
  • a removable casting surface may be applied to the upper most surface followed by final polymerization and subsequent removal.
  • the casting surface may comprise an additional permanently bonded lens section serving as a protective layer.

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Abstract

L'invention concerne un verre de lunettes d'addition progressif à indice gradient qui offre une meilleure performance optique et un champ visuel large. Le verre comporte une pluralité de sections de verre axialement stratifiées et collées ayant une courbure continue, et au moins une de ces sections possède un gradient d'indice de réfraction orienté transversalement au méridien du verre pour fonctionner en tant que zone de vision intermédiaire progressive entre des parties de visibilité qui possèdent différents indices de réfraction pour fournir les puissances réfractives aux parties de vision correspondantes du verre. La ou les autres couches du verre possèdent un indice de réfraction généralement constant ou changeant de manière similaire.
EP07861509A 2006-10-25 2007-10-25 Verre progressif à indice gradient multicouche Withdrawn EP2089755A2 (fr)

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US85446906P 2006-10-25 2006-10-25
PCT/US2007/022615 WO2008051592A2 (fr) 2006-10-25 2007-10-25 Verre progressif à indice gradient multicouche

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MX2009004328A (es) 2009-11-13
CN101681028A (zh) 2010-03-24
JP2010507834A (ja) 2010-03-11
WO2008051592A3 (fr) 2008-08-21
WO2008051592A2 (fr) 2008-05-02
WO2008051592A8 (fr) 2008-06-26

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