MXPA00000850A - Field-customizable variable focal length lens - Google Patents

Abstract

A liquid-filled variable focus lens unit which comprises a liquid-filled variable focus capsule having a first set of predetermined optical characteristics and comprises a transparent wall member, a transparent distensible membrane (20), a layer of transparent liquid filling (26') the volume between the wall member and the distensible membrane and a fixed-focus rigid lens (23) exterior of and attached to the liquid-filled variable focus capsule and abutting the wall member, whereby the liquid-filled variable focus lens unit comprised of the liquid-filled variable focus capsule and the fixed-focus rigid lens possesses a second set of predetermined optical characteristics.

Description

VARIABLE, ADJUSTABLE FOCAL LENGTH LENS CUSTOMIZED IN FIELD BACKGROUND OF THE INVENTION This invention relates to variable focal length lenses filled with liquid, -particularly those used in eyeglasses. These lenses have been described in a number of prior patents, for example in U.S. Pat. No. 3,598,479 (right 1971), U.S. Pat. No. 5,138,494 (Kurtin 1972), and in the U.S. patent. No. 5,668,620 (Kurtin et al. 1997). In particular, this invention is directed to a construction that includes two conceptually distinct parts: (1) a capsule of variable focus (which is susceptible to mass production or in volume, since all the capsules of a certain style may be identical), and (2) a rigid, fixed focus lens that attaches to the variable focus capsule. The combination results in a lens unit that has the optical power to adjust to the requirements of a particular person for all viewing distances from far to near. The lens units described herein are particularly useful as eyeglass components, but it will be appreciated that other applications also exist.

The need for variable focus eyeglasses arises as people get older, because generally starting at the age of about 45, the lens in the human eye becomes unable to adjust enough to focus on nearby objects. After the onset of this condition of limited focal accommodation, called presbyopia, a single set of fixed-focus glasses will be found unsatisfactory for both distant and near vision, regardless of the user's general visual precision. Any correction (if any) may be required to correct a person's vision for distance, an additional amount of optical power (up to approximately three diopters) will be necessary to correct that person's vision for vision. The "near addition" required usually does not involve an astigmatic component. One solution to this problem is to fit presbyopia with glasses that have bifocal (or trifocal) lenses. In the most common form of bifocal lenses, the upper part is rectified to provide the user with the correct correction (if any) for distance vision, the lower part is corrected with the same correction plus an additional amount of power optics to focus on nearby objects This "close addition" represents at most three diopters of additional optical power.Using bifocal lenses in a pair of glasses allows a person to see distant objects clearly when viewed directly, and see nearby objects clearly looking down, instead of an abrupt change in the focal length between the top and bottom of the lens as in bi-or (tri-) focal lenses, other lens shapes have developed where the focal length changes gradually as the eye moves to see through different parts of the lens, these lenses are called "progressive addition lenses." Progressive lenses inherently suffer from having a limited distorted field of view. For these and other reasons, only a relatively small fraction of the potential market for multifocal eyeglasses is satisfied by the progressive ones. A major difficulty associated with all fixed multifocal lenses of the prior art (eg *, bifocal, trifocal and progressive) arises because various portions of the lenses employed have different focal lengths. Therefore, in order to focus on a particular object, it must be seen through the portion of the lens that has the focal length suitable for the distance of that object and this is not always convenient. For example, if you want to read the title of a book on a top shelf, you would find the person looking through the intended portion of a multifocal lens to see distant objects and the title of the book would not be focused. A variable focus lens filled with liquid avoids this and other problems associated with lenses that provide multiple fixed focuses. This is achieved by providing a lens unit with continuously variable focus, wherein the focal length is substantially constant over the entire field of the lens at each adjustment. The "near addition" required is provided by changing the lens shape as required. Variable focus lens units filled with eyeglass fluid are described in the prior art (for example in the aforementioned US patents) involving: (1) a rigid fixed focus lens, one side of which is configured to providing the distance correction of the user, (2) a layer of liquid against the other side of the rigid lens, and (3) a compliant or deformable membrane that limits the liquid side away from the rigid lens. If any of the liquid volume between the rigid lens and the membrane is increased (for example right '479) or the spacing between the rigid lens and the membrane is reduced (for example Kurtin' 494 and Kurtin et al. 620), the pressure of liquid will increase and the membrane will bulge outward in order to increase the optical power of the lens unit. The opposite action will result in a relaxation of the membrane and a decrease in optical power. Since each potential user of glasses requires their own prescription or prescription, the rigid lens must be rectified by considering a specific user. According to the designs of the pirevia technique, the rigid lens forms a boundary of the portion of the lens fluid, and must be incorporated at a very early stage in the assembly process. This creates a problem during production since after the rigid lens is installed, the units must be followed very carefully throughout the rest of the manufacturing process, to ensure that the individual units are identified and not confused. Programming production batches can also prove difficult. Therefore, with prior art designs, the circulating economies of assembling large quantities of identical products can be difficult to achieve. It is therefore an object of the present invention to facilitate the production of variable focus lens units for eyeglasses (and other applications) by providing a construction that includes a variable focus, fluid filled, self-contained capsule and a rigid lens of detachable fixed focus. The variable focus capsule can be manufactured and assembled without reference to the visual accuracy of the potential user of the glasses, and therefore "is more susceptible to mass production methods." COMPENDIUM OF THE INVENTION As noted above, in spectacle lenses of variable focus filled with liquid from the prior art, the rigid lens (which includes a corrective efferent to the visual accuracy at a distance of the intended user) forms a wall of the enclosure containing the volume of liquid.Strongly, the rigid lens must -assembled to the unit at a very early stage, and safely before the unit is filled with liquid.In the present unit, the element having an optical power dependent on the intended user (here called a lens wafer) is not in contact with the unit. the liquid, and therefore it may be the last item installed.This structure allows full variable focus glasses to be assembled by method two of mass production and only be individualized for a particular user as the last stage, for example at the point of sale. In practicing the present invention, a variable focus "capsule" is manufactured first. This capsule is generally similar to a variable focus lens filled with liquid from the prior art, except that the custom-made rigid lens employed in the prior art is omitted and in place, for purposes of retaining the liquid in the capsule, there is a transparent wall member called "lens interface". The lens interface retains liquid, but as will be explained below, it does not affect the optical properties of the lens-complete unit. In other words, a variable focus capsule filled with liquid, as the term is used herein, it includes (1) a transparent wall member, (2) a transparent liquid layer and (3) a distensible membrane, relative to the front. Supply is also included to vary the pressure of the liquid, to cause the membrane to distend. The capsule has of course certain optical characteristics, but those characteristics do not require adjusting to the optical requirements of a intended user. They are generic in the sense that a simple capsule design can be used to satisfy the need of many users with widely varying prescription glasses. The lens interface, instead of being a customized piece depending on the intended user (ie, the rigid lens used in prior art designs), can be identical in all capsules of the same style. In order to adjust the optical requirements of a intended user, as a final step in the manufacturing process - possibly at the point of sale - a custom lens wafer is installed in the complete capsule, fully confining the interface of lens. The custom lens wafer has an appropriate surface (opposite the lens interface) to create a lens unit which in its distance position has the appropriate optical power to conform to the recipe for distance of the intended user. The capsule provides a continuously variable range of optical powers, such that the combination of capsule and rigid lens will allow the intended user to focus on any object from infinity to reading distance. Two embodiments of the invention are described in detail below. In one of the modalities, the lens interface is constituted by a thin membrane (called an interface membrane). "The interface membrane is limited to a support structure called a wafer support (since it also supports the lens wafer). that will be installed later.) The second mode has a lens interface that is molded integral with the wafer holder, In both cases, an identical lens interface can be used for all lenses of the same style, regardless of the user's visual precision. An individualized lens lens is subsequently placed in contact with the lens interface and held in place, creating a composite unit that has the optical characteristics required to result in a variable focus lens suitable for the intended user. THE DRAWINGS Figure 1 is a rear view (ie from the user's side) of a portion of a pair of glasses using lens units according to a first embodiment of the present invention; Figure 2 is a cross-sectional view; of the right eye lens unit from the glasses shown in Figure 1 taken at 2-2 of Figure 1. Figure 3 is a cross-sectional view of a second embodiment of a lens unit suitable for use in spectacles similar to those illustrated in Figure 1, the view is similar to that shown in Figure 2. DETAILED DESCRIPTION OF THE INVENTION Figure 1 illustrates a portion of a pair of Spl including variable focus lens units in accordance with The present invention Only the right lens unit is illustrated, the left lens unit is essentially an image in the mirror of the right unit For illustrative purposes, the invention will be described in the context or of a lens of the type described in the '494 and' 620 patents, but it will be appreciated that the principles are also applicable to the lens such as those described in the '479 patent as well as other constructions. Basically, a variable focus lens of the type described can be considered as a rigid fixed focus lens plus a liquid lens having variable power. The liquid lens is limited on one side by the rigid lens, and on the other side by a transparent distensible membrane, the space between the membrane and the rigid lens is filled with a transparent liquid. If the liquid lens moves closer to the membrane, the membrane will distend, becoming convex and increasing the optical power of the lens unit. On the contrary, if the lens moves away from the membrane, the membrane will become concave (or less convex) reducing the optical power of the unit. As seen in Figure 1, the illustrated glasses include a frame 10 to which pins (not shown) are connected. The frame is generally symmetric with respect to a nasal region 10 'and a pair of lens units are connected by screws or other means (not shown) on both sides of the nasal region 10 '.

Slightly more than half of a pair of glasses is illustrated in Figure 1, only the lens unit on the right side (11) is shown. A cross-sectional view of a first embodiment of a lens unit according to the present invention is illustrated in Figure 2. The support structure of the lens unit is constituted by a front ring 12 and rear ring 13; the front ring 12 is firmly secured to the frame 10, and the rear ring 13 is hingedly connected with the front ring 12 on the ear 14 (which can be seen in Figure 1). The hinges may be any of several types, with torsional bends currently being preferred. A tongue 15 on the rear ring 13, remote from the hinges, is coupled to an actuator 16. By moving the slider 17 of the actuator 16 causes the tongue 15 to move towards and away from the front ring 13. The front ring structure as illustrated, includes a circularizing membrane holder 18 (as described in the '620 patent mentioned above), a retainer 19 and a transparent distensible membrane 20. The membrane 20 (under tension, is attached to the retainer, which in turn, it is connected to the front ring 12, preferably by laser welding.The rear ring structure includes the ring 13 itself, a wafer support 21, an interfacing membrane 22 and a lens wafer 23. The wafer support 21 attached to the ring 13, either by mechanical means or adhesives.A possible method of joining the support member 21 to ring 13 is to use an epoxy adhesive. Since this joint can be subjected to great stresses as the ambient temperature varies, it is preferred that a circumferential groove 27 in the ring 13 be cut at its joint with the support member 21, to provide a mechanical restraint against axial movement, if the joint Epoxy is detached from the back ring. The interface membrane 22 is connected to the front of the wafer support 21, preferably by adhesive means, with the membrane under tension. The wafer surface of the lens 23 abutting the interface membrane 22 is preferably slightly convex, for example with a spherical radius of approximately 101.6 cm (40"), such that when assembled, the wafer will press against the membrane and will expel any trapped air Optionally, a small amount of liquid between the surfaces when the wafer is assembled to the lens unit will help to expel air Ideally, this liquid should have substantially the same refractive index as the wafer In order to avoid internal reflections, as will be explained below, the shape of the inner surface of the lens wafer 23 does not affect the optical properties of the lens unit and is significant only in that it facilitates proper assembly. of the lens 23 is held in the wafer holder 21 and against the interface membrane 22, by a plurality of adhesive plugs 24. Other methods for connecting The wafer of the lens to the wafer support is of course possible. The front and rear ring structures are connected by a circumferential elastomer seal 25, forming a closed volume 26 which is filled with a transparent liquid (here denoted by the number 26 '). "Preferably, the lens wafer 23, the wafer support member 21, the interface membrane 22, the filling liquid 26 ', the membrane support 18 and the compliant membrane 20 are all transparent and preferably have substantially the same refractive index. , it is not essential that the wafer support 21 and the membrane support 18 are transparent, but it is preferred that they be transparent.The reason for preferring that the indexes correspond is that if all the elements in the line of sight of the user have the same refractive index, there will be no annoying internal reflections, and also the interfaces between the various elements will be substantially invisible to other people. achieved by manufacturing the solid polycarbonate parts, the sarán membranes using appropriate high index silicone oil as the liquid refill. Since the silicone oil is connected to most of the rubbers, the seal 25 is preferably molded from a fluorosilicone elastomer, which attacks the majority of the rubbers that are not thus attacked. ~~ The light that travels through the regions of constant refractive index, travels in a straight line (even though the region is constituted by several physically different parts, as in the lens unit described above). Therefore, with index-adjusted parts, regardless of the shapes of the individual internal parts, there can be no distortion or optical power generated within the lens unit. The optical power of the lens unit is therefore a function only of (1) the difference in index between the elements of the lens unit and the surrounding medium (air) and (2) the shapes of the external surfaces of the lens. lens unit. For cosmetic reasons, it is preferred that the curvature of the surface of the compliant membrane 20 be positive and sufficient to present a pleasing appearance. A minimum curvature corresponding to an approximate optical power of +0.5 diopters, has been found to be cosmetically satisfactory. The minimum curvature occurs when the lens unit is adjusted for distance vision. If the user does not require remote sensing correction, the outer surface 28 of lens J-23 is rectified at an optical offset power of -0.5 diopter, such that the new optical power of the lens unit (when adjusted for distance view) is 0. If the user requires a -correction for distance vision, this correction, including both spherical and astigmatic components (-0.5 wax diopter) is ground on the surface 28. Moving the slider 17 from the position away to the reading position, causes the actuator 16 to move the tongue 15, which in turn causes the rear ring structure to tilt toward the front ring structure. Since the liquid filling is sensitively incompressible, this movement causes the distensible membrane 20 to bulge, increasing the optical power of its surface and adding a spherical reading addition to the lens unit. Functionally, the lens unit described is identical to the units described in the '494 and' 620 patents referred to above. The difference is in the construction of the present invention, which allows the assembly sequence to be such that the correction of the proposed user can be incorporated into the assembly at a very late stage of the production cycle instead of one of the first stages. It will be appreciated that this flexibility in the manufacturing sequence is of tremendous utility, since it allows volume production of identical capsules, with the proposed user's accessory (when adding a lens wafer) as a final stage. The final assembly of the lens wafer to the glasses may in fact be divorced from the rest of the manufacturing sequence, and be performed by optometrists, opticians or optical laboratories at a later date. Figure 3 illustrates a second embodiment of the invention, which is similar to the first embodiment, but which uses a rigid transparent wall as a lens interface (ie to retain the liquid in the capsule) instead of a membrane. Figure 3 is a sectional view taken in the same place as Figure 2, but showing the construction of the second embodiment. Instead of the interface between the lens wafer and the filling liquid as a third membrane, the wafer support (31) is molded so as to provide an integral barrier for filling the liquid. If desired, the surface 32 can be molded flat, but the interface surface 3_4 between the wafer of the lens 33 and the wafer support 31 is preferably somewhat concave, as illustrated (exaggerated for clarity). The circumference of the Tente wafer 33 can be placed in a recess in the wafer support 31 as illustrated in Figure 3, or alternatively the interface surface 34 can intersect the back surface of the wafer support as convenient. While the wafer of the lens and the wafer support can be assembled as described in connection with the first embodiment, it is preferred that they are connected by an optical cement layer between the wafer of the lens and the wafer support. The procedure may begin by placing a small amount of optical cement that cures the light having the appropriate refractive index in the center of the disc-shaped recess that forms in the wafer support 31 and then dropping the lens wafer 33 in the recess, in the wafer support. If the surfaces are clean, the surface tension will cause the cement to circulate outward until it covers the whole area of the lens, after which the exposure to light (of the appropriate wavelength) will cure the cement. Instead of a light curing cement, heat-cured cements, chemicals or moisture can be used to achieve the same result. What has been invented is a construction for a variable focus lens filled with liquid, which is susceptible to mass production techniques, but nevertheless it is suitable for use in glasses that must fit people with different vision characteristics. No doubt modifications and adaptations of the invention will occur to those skilled in the art. These modifications and "adaptations are intended within the terms and spirit of the following claims and therefore are intended to be covered in this manner.

Claims (14)

1. - A variable focus lens unit filled with liquid, characterized in that it comprises: a variable focus capsule filled with liquid having a first set of pre-determined optical characteristics and constituted by: (i) a transparent wall member; (ii) a transparent compliant member; and (iii) a transparent liquid layer that fills the volume between the wall member and the compliant membrane; and a rigid fixed-focus lens exterior of and connected to the variable focus capsule filled with liquid and butt-confined to the wall member, whereby the variable focus lens unit fills with liquid constituted by the variable-focus capsule filled with liquid and the rigid lens of fixed focus, they possess a second set of predetermined optical characteristics.

2. A variable focus lens unit filled with liquid according to claim 1, characterized in that the surface of the rigid lens that abuts the wall member has a convex shape.

3. - A variable focus lens unit filled with liquid according to claim 2, characterized in that the rigid lens is connected to the lens capsule by a layer of transparent cement between the rigid lens and the wall member.

4. - A variable focus lens unit filled with liquid according to claim 2, characterized in that the portion of the lens capsule filled with liquid that abuts the rigid lens is rigid.

5. - A variable focus lens unit filled with liquid according to claim 1, characterized in that the transparent wall member is a thin flexible membrane. 6 - A variable focus lens unit filled with liquid according to claim 1, characterized in that the rigid lens is adhesively connected to the lens capsule around the periphery of the rigid lens. 7. A variable focus lens unit filled with liquid according to claim 1, characterized in that it also includes a liquid film between the rigid fixed focus lens and the transparent wall member. 8. A variable focus lens unit filled with liquid, characterized in that it comprises: a closed chamber having opposite outer walls, the opposite outer walls of the chamber comprising a transparent wall member and a distensible member; a clear liquid that fills the camera; means for varying the pressure of the transparent liquid in the chamber; and a rigid fixed-focus lens exterior to the chamber and abutting the transparent wall member. 9. - A variable focus lens unit filled with liquid according to claim 8, characterized in that the means for varying the transparent liquid pressure comprises means for changing the spacing between the transparent wall member and the distensible membrane. 10. A variable focus lens unit filled with liquid according to claim 8, characterized in that the rigid lens surface that abuts the transparent wall member is convex and also includes a layer of transparent cement between the rigid lens. and the transparent wall member. 11. A variable focus lens unit filled with liquid according to claim 8, characterized in that it also includes a liquid film between the rigid lens and the transparent wall member. 12. A variable focus lens unit filled with liquid according to claim 8, characterized in that the transparent wall member is a thin flexible member. 13. - A variable focus lens unit filled with liquid according to claim 8, characterized in that the transparent wall member is rigid. 14. - A variable focus lens unit filled with liquid according to claim 13, characterized in that the transparent wall member has a concave shape -