DIVING MASK WITH LENSES AND METHOD OF FABRICATING THE SAME

Abstract: A diving mask (10) having hemispherically-shaped lenses (12) mounted on a flexible gasket or portion (14) and fitted to the contours of a user's face. Laser scanning or topographic mapping is used to determine the contours of the user's face. Edges of the hemispherically-shaped lenses (12) are then shaped to fit the contours of the face. As a result, the spherical center of the lenses substantially coincides with the optical nodal point of the user's (24), or the center of rotation of the eyes. This virtually eliminates the phenomenon of underwater magnification-distortion caused by the difference in refractive indices of water and air.

Description: DIVING MASK WITH LENSES AND METHOD OF FABRICATING THE SAME CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of co-pending application. Serial No.08/114,551, filed August 30, 1993, and entitled "DIVING MASK WITH FITTED LENSES AND METHOD OF FABRICATING THE SAME," Which is a continuation-in-part of co-pending International Application No. PCT/US92/07321, filed August 28, 1992, entitled "DIVING MASK WITH FITTED LENSES AND METHOD OF FABRICATING THE SAME," which designated the U.S.; and which is a continuation-in-part of co-pending application,. Serial No. 07/750,988, filed August 28, 1991, and entitled "DIVING MASK WITH FITTED LENSES AND METHOD OF FABRICATING THE SAME." This application relies on Disclosure Document No. 351148, filed March 30, 1994. BACKGROUND OF THE INVENTION The present invention relates generally to underwater face masks and, more particularly, to underwater diving masks having eyepieces or lenses mounted on a flexible gasket. In the past, a variety of underwater face masks have been used for sporting and other activities such as skin and scuba diving. Early underwater face masks typically had several common features, including a contiguous air space shared by the diver t s nose and eyes, generally .flat, glass or plastic windows, eyepieces or ports fixed approximately perpendicularly to the wearer's straight-ahead viewing axis, and a flexible rubber or plastic support structure for holding the ports in position and trapping an air pocket against the wearer's face. A contiguous air pocket over both the wearer's nose and eyes, as opposed to a mask covering the eyes only, allows for equalizing pressure inside the mask with ambient water pressure as the wearer ascends and descends in the water. Such equalization is necessary to avoid injury to the wearer. Such conventional flat-window face mask share variety of shortcomings. The windows or eyepieces of conventional flat-window masks must be supported out from the face. Above and below water, the wearer's horizontal and vertical fields of view are severely limited by the flexible rubber or plastic structures providing such support, thereby creating a sense of "tunnel vision" and a closed-in, claustrophobic feeling. Above water, convention¬ al flat-window masks provide no more than a 140 degree horizontal by 90 degree vertical field of view. Below water, because of the refraction-induced magnification distortion of an air-water viewing system, discussed more fully hereinbelow, this field of view is effectively reduced to approximately 105 degrees horizontal by 67.5 degrees vertical. Additionally, conventional flat-window masks suffer quite significantmagnification-distortion problems fromthe difference in refractive indices between water and air. Specifically, objects viewed on an axis perpendicular to the window appear approximately 33% larger and 25% closer than they actually are. The magnification-distortion of objects viewed off-axis is even larger. Further, conventional flat-window masks create a significant amount of hydrodyna ic drag and present a significant risk of slipping off the wearer's face if hit by an unanticipated or oblique-angle wave or current. These and other flat-window mask problems have attempt¬ ed to be overcome, with less than satisfactory results, by spherically-shaped eyepieces or lenses used for underwater masks. For example, U.S. Patent Nos. 3,899,244, issued to Mulder on August 12, 1975, and 3,672,750, issued to Hagen on June 27, 1972, disclose underwater masks that use built- in corrective lenses in addition to spherically-shaped lenses to improve viewing under water. As such, these masks do not provide optimum viewing characteristics under wate without the use of additional corrective lenses. Othe single and multiple lens systems used for underwater fac masks that do not provide optimum viewing conditions are disclosed in U.S. Patent Nos. 3,944,345, issued to Decorato on March 16, 1976; 3,040,616, issued to Simpson on June 26, 1962; 2,088,262, issued to Grano on July 27, 1937; 2,928,097, issued to Neufeld on March 15, 1960; and 1,742,412, issued to O'Flanagan on January 7, 1930. U.S. Patent No. 4,607,398, issued to Faulconer on August 26, 1986, discloses a strap and retainer used for a diver's mask. U.S. Patent No. 3,051,957, issued to Chan on September 4, 1962, describes a diving mask having a support¬ ing device used to hold the eyeglasses of a diver. In addition, U.S. Patent No. 4,856,120, issued to Hart on August 15, 1989, describes a purge valve used for a diving mask and a deflector attached to the mask and used to channel air bubbles expelled during purging to the sides of the mask. Another purge valve used for a diver's mask is disclosed in U.S. Patent No. 4,241,898, issued to Segrest on December 30, 1980. SUMMARY OF THE INVENTION Accordingly, it is an object of this invention to provide a diving mask which furnishes improved viewing characteristics under water. It is another object of this invention to provide a diving mask which furnishes improved viewing characteristics under water, and may be used under water by divers who do not have to wear contact lenses or eyeglasses to correct eyesight when not under water. It is still another object of this invention to provide a diving mask which furnishes improved viewing characteris¬ tics under water, and may be used under water by divers while not wearing contact lenses which correct eyesight above water. It is still another object of this invention to provide a diving mask which furnishes improved viewing characteris¬ tics under water, and may be used under water by divers while wearing contact lenses which correct eyesight above water. It is still another object of this invention to provide a diving mask which may be used both above and under water. It is still another object of this invention to provide a diving mask which may be used both above and under water with additional corrective lenses if desired. It is still another object of this invention to provide a diving mask which furnishes a secure seal between the mask and a wearer's face. It is still another object of this invention to provide a method of fabricating such a diving mask. These and other objects and advantages are attained by a diving mask having hemispherically-shaped lenses mounted on a flexible gasket and fitted to the contours of a user's face. Laser scanning or topographical mapping is used to determine the contours of a user's face. The perimeter edges of the hemispherically-shaped lenses are then sized to fit the contours of the face. As a result, the spherical center of each of the hemispherically-shaped lenses substan¬ tially coincides with the optical nodal point of one of the user's eyes. This improvement virtually eliminates the phenomenon of underwater magnification-distortion caused by the difference in refractive indices of water and air. Improved horizontal and vertical fields of view are also provided by the hemispherically-shaped lenses. A secure seal is provided between the diving mask and a user's face by the flexible gasket. - Another embodiment of the diving mask is provided having a standard pair of hemispherically-shaped lenses mounted on a contoured portion of the mask which is fitted to the contours of a user's face. The contoured portion is mounted on a flexible gasket. In still another embodiment of the diving mask, the hemispherically-shaped lenses are designed so that the spherical center of curvature of each of the lenses εubstan- tially coincides with the center of rotation of one of a user's eyes. In still another embodiment of the diving mask, a shaft is mounted on the hemispherically-shaped lenses. The shaft is coupled to a pair of retractable corrective lenses, and may be used to lower the corrective lenses to a position in front of a user's eyes and to raise the lenses to a position above the eyes. The corrective lenses may be used by near- and far-sighted users. In still another embodiment of the diving mask, the hemispherically-shaped lenses are mounted on a support portion having a peripheral flange. The support portion, in turn, is mounted on a flexible gasket of selected size. The diving mask may have at least one purge valve in the support portion. In still another embodiment, a diving mask is provided having a purge valve in at least one of the hemispherically- shaped lenses. The purge valve is located at the front and bottom of the lens and in an area used to collect water which has leaked into the mask. The collecting area is angled to facilitate expelling water from the diving mask through the purge valve so that exhaust bubbles pass toward the back of the mask, away from the field of vision of a diver. In still another embodiment, the diving mask is provided with a bottom lens which facilitates drainage of water from the mask. The bottom lens may also be used for viewing both above and below the water. The diving mask may also have an additional lens mounted inside the mask which may be used by either nearsighted or farεighted divers. A member may be joined to the additional lens in order to provide trapped dry-air volume inside the mask. In still another embodiment of the diving mask, a baffle may be used with textured or coated surfaces in order to provide a translucent member for the purpose of eliminat¬ ing double vision. Also, the ends of the lenses may be bent or formed inwardly toward a diver's face in order to provide a reduced air volume inside the mask. In still another embodiment of the mask, hemispherically-shaped meniscus lenses are used to provide reduced weight and a reduced air volume inside the mask. The curvatures of the inner and outer surfaces of the meniscus lenses are chosen to produce an effective zero diopter value under water. The spherical centers of curvature of the meniscus lenses are located beneath the centers of a diver's eye in order to reduce the weight of the mask and to improve drainage. In still another embodiment of the diving mask, a perimeter clamp is used to clamp a conventional face seal to a support portion of the mask. Integral housings may be formed in the support portion for purge valves. Integral housings for the purge valves may also be formed in the perimeter clamp. A purge valve is provided for each lens. In still another embodiment, a diving mask is provided with a supplemental lens or lenses located in front of the hemispherically-shaped lenses for the purpose of holding water therein. The supplemental lens configuration provides above-water corrective lenses and hence clear vision when the diver raises his or her head out of water. The supplemental lens configuration comprises a thin-walled zero power transparent plastic or similar material member engaging the diving mask to form a water-tight seal. In the preferred embodiment, the cavity formed by the supplemental lens may be filled through an opening with clear water and the opening • sealed with a non-porous material. Additionally, the upper edge of the supplemental lens may be open to permit water passage. The supplemental lens arrangement may also provide purge valves for dissipating water which collects in the mask. In still another embodiment, the diving mask having hemispherically-shaped lenses is provided with side wall lenses continuing from the hemispherically-shaped lenses to provide an outermost horizontal field-of-view. The side wall lenses extend from the hemispherically-shaped lenses to a visual horizontal peripheral line approximately perpendicular to the optical nodal point of each corresponding eye of said user's face. Each of the side wall lenses extend from approximately ten degrees to approximately zero degrees from the visual peripheral line. The side wall lenses comprise either an outer radius continuing the curvature of the outside of the hemispherically-shaped lenses, and an inner edge extending from the inside of said inner lens and substantially parallel to the outer radius so that the side wall lenses maintain generally uniform thickness, of an outer radius continuing the curvature of the outside of said hemispherically-shaped lenses and an inner edge extending from the inside of the inner lens and away from the inside of the inner lens, providing a secondary meniscus, lens thereby improving focusing characteristics at edges of the user's horizontal field of view. The various features of the present invention will be best understood together with further objects and advantages by reference to the following description of the preferred embodiments taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. l is a front elevational view of a diving mask with two generally hemispherically-shaped lenses mounted on a flexible gasket or portion and fitted to the face of a user, illustrating the principles of the present invention; FIG. 2 is a side elevational view of the diving mask of FIG. 1 shown worn on the head of the user; FIG. 3 is a partial cross-sectional view of the diving mask taken in the direction of arrows 3-3 shown in FIG. 1, illustrating how the spherical center of curvature of one of the hemispherically-shaped lenses substantially coincides with the optical nodal point of one of the user's eyes; FIG. 4 is a cross-sectional view of the diving mask taken in the direction of arrows 4-4 shown in FIG. 2 also showing how the spherical center of curvature substantially coincides with the optical nodal point; FIG. 5 is an enlarged detailed cross-sectional view of a skirt portion of the flexible gasket of the diving mask of FIG. l; FIG. 6 is an enlarged detailed cross-sectional view of the skirt portion showing how one of the hemispherically- shaped lenses is mounted on the skirt portion, and how apertures are provided in the skirt portion to allow water to fill a cavity in the skirt portion, helping to provide a cushioning effect against the user's face; FIG. 7 is a partial cross-sectional view of another embodiment of the diving mask having a turning shaft mounted on the hemispherically-shaped lenses, which may be used to lower retractable corrective lenses in front of a user's eyes; FIG. 8 is a partial cross-sectional view of the turning shaft and hemispherically-shaped lenses taken in the direction of arrows 8-8 shown in FIG. 7; FIG. 9 is a partial cross-sectional view of the diving mask, taken like FIG. 7, illustrating how the turning shaft may be used to raise the retractable corrective lenses from a position in front of the user's eyes, as shown in FIG. 7, to a position above the eyes; FIG. 10 is an exploded view of another embodiment of the diving mask having a standard pair of hemispherically- shaped lenses mounted on a contoured portion of the mask which is fitted to the contours of a user's face, and mounted on the flexible gasket; FIG. 11 is an exploded, enlarged, . detailed cross- sectional view of the skirt portion of the flexible gasket, the contoured portion of the mask and one of the hemispherically-shaped lenses, showing the contoured portion attached to the gasket; FIG. 12 is an enlarged detailed cross-sectional view, taken like FIG. 11, showing the hemispherically-shaped lens attached to the contoured portion; FIG. 13 is a front elevational view of another embodi- ment of the diving mask shown worn on the head of a user, having a pair of hemispherically-shaped lenses with purge valves therein mounted on the flexible gasket; FIG. 14 is a side elevational' view of the diving mask of FIG. 13; FIG. 15 is a partial cross-sectional view of the diving mask taken in the direction of arrows 15-15 shown in FIG. 13, illustrating how the hemispherically-shaped lenses may be connected to straps and the flexible gasket by a clamp and flange; FIG. 16 is a schematic representation illustrating how the spherical center of curvature of each of the hemispheri¬ cally-shaped lenses of FIG. 13 substantially coincides or aligns with the center of rotation of one of a user's eyes and falls within a predetermined acceptable zone of miε- alignment; FIG. 17 is a perspective view of another embodiment of the diving mask having a pair of hemispherically-shaped lenses mounted on a peripheral flange of a support portion of the mask; FIG. 18 is a partial cross-sectional view of another embodiment of a shaft shown mounted on the hemispherically- shaped lenses which may be used to raise and lower correc¬ tive lenses in front of a user's eyes; FIG. 19 is an enlarged cross-sectional view taken in the direction of arrows 19-19 shown in FIG. 18; FIG. 20 is a partial cross-sectional view of another embodiment of the diving mask taken in the direction of FIG. 4, showing a hemispherically-shaped lens having a bottom lens at the bottom of the hemispherically-shaped lens; FIG. 21 is an enlarged detailed view taken as indicated by arrows 21-21 shown in FIG. 20, showing how an O-ring may be used to provide a seal between the bottom lens and a peripheral flange of a support portion of the mask; FIG. 22 is an enlarged detailed view taken like FIG. 21 showing another way of using an 0-ring to provide a seal; FIG. 23 is a partial cross-sectional view of another embodiment of the diving mask taken like FIG. 20, showing a hemispherically-shaped lens with a bottom lens and another lens mounted inside the mask; FIG. 24 is a partial cross-sectional view taken like FIG. 20 showing a convexo-concave bottom lens; FIG. 25 is a partial cross-sectional view taken like FIG. 20 showing a plano-concave lens mounted inside a bottom lens; FIG. 26 is a partial cross-sectional view taken in the direction of FIG. 3, showing how an end portion of one of the hemispherically-shaped lenses may be contoured inwardly toward a diver's face in order to reduce the size of the diving mask and the trapped air space or volume within the mask; FIG. 27 is a partial cross-sectional view taken in the direction of FIG. 3, showing how a central translucent member may be attached to the hemispherically-shaped lenses where the lenses are joined together in order to prevent double vision; FIG. 28 is a partial cross-sectional view of another embodiment of the diving mask taken like FIG. 20, showing - a hemispherically-shaped lens with a bottom lens, and another lens of uniform thickness mounted inside the mask in order to provide a trapped dry-air space or volume inside the mask; FIG. 29 is a partial cross-sectional view of another embodiment of the diving mask taken like FIG. 20, showing a hemispherically-shaped lens with a bottom lens, and another convexo-concave lens mounted inside the mask in order to provide a trapped dry-air space or volume inside the mask; FIG. 30 is an enlarged detailed view of the bottom lens, with a plano-concave lens mounted therein, and of peripheral flange and support portion of the mask, showing how O-rings may be used to mount the plano-concave lens inside the bottom lens; FIG. 31 is a schematic representation of two hemis¬ pherically-shaped meniscus lenses of another embodiment of the diving mask having different outer and inner curvatures, each lens having spherical centers of curvature of its outer and inner surfaces that are coplanar, or that fall on a plane passing through the center of the eye of a user; FIG. 32 is a schematic representation of two hemisphe¬ rically-shaped meniscus lenses of another embodiment of the diving mask having different outer and inner curvatures, each lens having spherical centers of curvature of its outer and inner surfaces that are not coplanar; FIG. 33 is a schematic representation of a hemispheric¬ ally-shaped meniscus lens having a bottom lens, which illu¬ strates how changes in the effective diopter value of the meniscus lens can be matched with the type of bottom lens used for the diving mask, and illustrates how the spherical centers of curvature of the outer and inner surfaces of the meniscus lenses are located below the center of a diver's eye; FIG. 34 is a schematic representation of two different hemispherically-shaped meniscus lenses, illustrating the differences between a lens having spherical centers of curvature that are coplanar and a lens having spherical centers of curvature that are not coplanar; FIG. 35 is a side elevational view of a support por¬ tion, perimeter clamp and conventional flexible face seal of another embodiment of the diving mask, the support portion having a peripheral flange for mounting a pair of hemispherically-shaped lenses, and two integral housings for mounting purge valves; FIG. 36 is a front elevational view, showing the support portion and flexible face seal of FIG. 35; FIG. 37 is a bottom plan view of the support portion, perimeter clamp and flexible face seal of FIG. 35; FIG. 38 is an enlarged cross-sectional view of a part of the support portion of FIG. 5 and of one of the housings of the support portion, showing a purge valve mounted in the housing, and a hemispherically-shaped.lens mounted on the support portion; FIG. 39 is a front elevational view of two generally hemispherically-shaped meniscus lenses of the diving mask; FIG. 40 is a rear elevational view of the meniscus lenses of FIG. 39; FIG. 41 is a rear perspective view of the meniscus lenses of FIG. 39; FIG. 42 is a top plan view of the meniscus lenses of FIG. 30; FIG. 43 is a bottom plan view of the meniscus lenses of FIG. 39; FIG. 44 is a cross-sectional view taken in the direction of arrows 44-44 shown in FIG. 42; FIG. 45 is an exploded cross-sectional view of another embodiment of the diving mask taken across a perimeter clamp, flexible face seal, support portion and bottom lens, showing a housing in the clamp for mounting a purge valve; FIG. 46 is a top schematic plan view of a supplemental lens arrangement used in conjunction with two hemispherically-shaped meniscus lenses of an embodiment of the diving mask having different outer and inner curvatures, the supplemental lens arrangement providing a zero power lens and clear vision for a diver raising his or her head out of water; FIG. 47 illustrates a schematic side view of the supplemental lens arrangement; FIG. 48 is a top schematic plan view of the two hemispherically-shaped meniscus lenses of an embodiment of the diving mask having different outer and inner curvatures of the current invention; FIG. 49 is a top schematic plan view of the meniscus lenses of the current invention having an added pair of uniform thickness side wall lenses; and FIG. 50 is a top schematic plan view of the meniscus lenses of the current invention having an added pair of sidewallε providing formed to improve focusing characteristics at the most extreme edges of the field of view. DESCRIPTION OF THE PREFERRED EMBODIMENTS The following specification taken in conjunction with the drawings sets forth the preferred embodiments of the present invention in such a manner that any person skilled in the art can make or use the invention. The embodiments of -he invention disclosed herein are the best modes contemplated by the inventor for carrying out his invention .in a commercial environment, although it should be understood that various modifications can be accomplished within the parameters of the present invention. FIGS, l and 2 show a preferred embodiment of the diving mask 10 of the present invention. The diving mask 10 has two eyepieces, or generally hemispherically-shaped lenses 12, mounted on a flexible gasket or portion 14 of the mask 10. Each lens 12 may be a segment or portion of a sphere. It is important to note that each lens 12 may be smaller or larger than a hemisphere or may be only a segment or portion of a hemisphere. Therefore, "generally hemispherical¬ ly-shaped lenses" or "hemispherically-shaped lenses," as used herein, refers to lenses that are shaped like hemisphe¬ rically-shaped lens, or a portion thereof, or each such lens may be a segment or a portion of a spherically-shaped lens that is smaller or larger than one half of a sphere, or smaller or larger than a hemisphere. The lenses 12 are preferably made of plastic, glass, or the like. However, any transparent, optically clear material may be used for the lenses 12. The thickness of the lenses 12 preferably has a range of approximately from about 1/20-inch to about 1/2-inch. However, any thickness may be used. It is important to note that any minimum thickness that provides structural integrity may be used for the lenses 12. The diving mask 10 is secured to the face 16 of a user by straps 18 that are preferably fused or otherwise attached to the lenses 12 by, for example, members 17, or the like. As shown in FIGS. 1 and 3, the lenses 12 are preferably fused together at edge 20 adjacent the bridge of a user's nose. However, the lenses 12 may be separated by part of the flexible portion 14 running along the bridge of the user's nose (not shown), if desired. The flexible gasket or portion 14 is preferably made out of a flexible or elastic plastic or rubber material such as εilicone, neoprene, or the like. However, any other flexible material may be used for portion 14. A nose portion 22 of flexible portion 14 is also provided so that a seal is furnished between the user's face 16 and the diving mask 10, and an air space is provided between the lenses 12 and the user'ε eyes 24 and face 16 under the lenses 12. The air space provides air pressure inside the diving mask 10 which counteracts the ambient water pressure that exists outside the mask 10 when the user iε under water and protectε the user'ε eyes 24. As discussed below, the contours of the user'ε face are scanned or topographically mapped and the lenseε 12 are εhaped to cloεely fit the contours of the user'ε face 16. In order to provide optimum viewing characteristics under water, the edges or ends 42 of the lenses 12 (see FIG. 6) must closely fit the contours of a user'ε face 16 εo that the spherical center of curvature of the hemispherically- shaped lenses 12 substantially coincides with the optical nodal point 26 of the user's eyes 24 as illustrated by arrows 28 and 30 in FIGS. 3 and 4, respectively. When the spherical center of curvature and optical nodal point substantially coincide, this reεultε in virtually eliminat¬ ing the phenomenon of underwater magnification-distortion caused by the difference in refractive indices of water and air which causes objects to appear about 33% larger and about 25% closer than they actually are. In addition, such coinciding of the spherical center of curvature and optical nodal point provides hemispherically-shaped lenseε 12 that have a horizontal field of view of about 180 degrees and a vertical field of view of about 150 degrees. The outside diameter of the he iεpherically-εhaped lenεes 12 also determines the distance from the lenses 12 that a uεer'ε eye 24 must focus in order to see an image formed by an object under water. The theoretical baεiε for thiε is Snell'ε Law of Refraction, which for a baεic hemiεpherical lens and paraxial light rays may be expressed as: Ώ where n = the index of refraction of the medium in which the object is located; n l = the index of refraction of the lens; s «= the distance of the object from the outer surface of the lens; ε 1 « the location of the image formed from the outer surface of the lens; and R = the radius of curvature of the lens. Using n=1.34, the index of refraction of salt water, and n'el.49, the index of refraction of plexiglass, the following table indicates the distances from the front surface (cornea) of a user's eye 24 that the eye 24 must focus for different diameter hemispherically-εhaped lenεes having a lens thickness of .25 inches to clearly see the apparent image of an object located at different distances from the lenseε. All dimensions are presented in inches. The chart assumes a distance from a center of rotation 150 of a person's eye to the outer surface of the cornea to be .5 inch. The importance of the center of rotation 150 is discussed later in connection with FIGS. 15 and 16. Taking an example where n=1.34, the index of refraction of salt water; n l «l.49, the index of refraction of plexi- glaεε; R=2.75 incheε, the radiuε of curvature of a 5.5 inch diameter dome lens; and 6=22.75 inches, the distance from the lens' outer surface of an object 25 inches from an eye's corneal surface, the solution for ε 1 is -342.085 incheε; i.e., the image is formed 342.085 inches from the dome lens' outer surface on the opposite side relative to the object. The above equation is then εolved for this image using the inside surface of the dome lens in which s, the object diεtance, iε now -342.335 inches (compensating for the .25 inch thickness of the dome lens), n=1.49 (for the plexi- glaεε) , n ! «=l (for air), and R=2.5 inches (compensating for the .25 inch thickness of the dome lens). This results in a value for ε 1 of -4.991 inches, i.e., the image seen by the uεer iε 4.991.incheε from the inside surface of the dome lens toward the object. Add to thiε 2.5 incheε for the inεide radiuε of the dome lens, less the .5 inch for the diεtance from the center of rotation of the eyeball to the outer corneal εurface, to arrive at 6.991 inches, as indicated in the chart for a 5.5 inch diameter dome and a 25 inch object distance. The exterior diameter of the hemispherically-shaped lenses 12 preferably has a range of from about 4.25 inches to about 9 inches. However, any size diameter may be used for the lenses 12 depending on the wearer's vision, e.g., myopic wearers may opt for smaller sized domes. Referring now to FIGS. 5 and 6, a skirt portion 32 of the flexible portion 14 is shown having a body portion 35 with an elongated cavity 37 running the length thereof, flexible curved extensions 34 and edges 36 that contact the contours of a user's face 16 (see FIG. 3), and clevis arms 38 that extend away from the face 16. The clevis arms 38 form a channel 40 which engages the ends or edges 42 of the lenses 12 (see FIG. 6). The lenses 12 may be attached to channel 40 using any desirable method such as by force fitting, using adhesive, by fusion of the parts, welding, or by any suitable fastening or clamping means. The edges 42 of the lenses 12 are formed to match the contours of a user'ε face 16 (see FIG. 3) which are measured by scanning or topographical mapping as discussed below. A secure seal iε provided between the flexible gasket 14 and the user's face 16. The skirt portion 32 of the gasket 14 has a plurality of apertures 44 passing through body portion 35 and into elongated cavity 37. The apertures 44 preferably are spaced about 0.5 inch apart along cavity 37 and cause the cavity 37 to fill with water when a user iε under water, so that pressure inside the cavity 37 is equal to ambient water pressure, which provides a cushioning effect against the user's face 16. In order to fit the perimeter edges 42 of the lenses 12 to the contours of a user's face 16, laser scanning or topographical mapping may be used to accurately determine the contours of the face 16. Apparatus and technique which may be used for laser scanning a user'ε face are disclosed, for example, in U.S. Patent No. 3,636,250, isεued to Haeff on January 18, 1972, the diεclosure of which is hereby incorporated by reference. However, any available tech¬ nique, including any high-speed, optical scanning technique or topographical mapping technique, may be used to determine the contours of a user's face 16. FIGS. 10 through 12 εhow another embodiment of the diving mask 10 having a standard pair of hemispherically- shaped lenses 12 mounted on a contoured portion 46 of the mask 12. The contoured portion 46 iε attached to the εkirt portion 32 of the flexible gaεket 14, aε shown in FIGS, n and 12, with extension 48 of portion 46 engaging channel 58 formed by clevis arms 56 of the skirt portion 32 and edges or surfaces 50 and 52 of portion 46 being in contact with edges or surfaces 60 and 61 of εkirt portion 32. The contoured portion 46 may be attached to the εkirt portion 32 by force fitting, using adhesive, by fusion of the parts, or the like. Edges or surfaces 50 and 52 of -fche contoured portion 46 are shaped to closely fit the contours of a user'ε face 16 uεing laεer εcanning or topographical mapping aε dis¬ cussed above. Contoured portion 46 may be made out of plastic, or any desirable material, and edges 50 and 52 may be cut, shaped, molded or otherwise formed to fit the contours of the user'ε face 16. It is important to note that edges 50 and 52 and exten¬ sion 48 of the contoured portion 46 may have any desirable configurations or εhapeε, and the configuration and εhape of clevis arms 56 and channel 58 of the εkirt portion 32 may alεo be varied or designed to provide any desirable joint between portionε 32 and 46. The εkirt portion 32 preferably has the elongated cavity 37, apertures 44 and flexible curved extensions 34 discussed above. The standard pair of lenses 12 may be attached to the contoured portion 46 by engaging end or perimeter edge 62 of the lenses 12 in groove 54 provided in portion 46 by force fitting, using adhesive 64, by fusion of the parts, welding, or by any εuitable fastening or clamping means. Also, the configuration or εhape of end 62 and groove 54 may be varied to provide any desirable joint. A majority of divers may use the above described diving mask 10 because the preferred exterior diameter of the lenses 12 has a range of from about 4.25 inches to about 9.0 inches, resulting in focusing distances of from about 4.5 inches to about 16.0 inches in front of the diving mask. Moεt diverε will be able to focus their eyes within these distances. Therefore, most divers will be able to use the diving mask 10 without the need to use corrective lenses. The different sizes of hemispherically-shaped lenses 12 yield different effective diopter values under water. Diopter, as iε well known in the art, is a unit of measure- ment of the refractive power of lenses equal to the recipro¬ cal of the focal length measured in meters. The following table lists the effective diopter values under water for different sizes of hemispherically-shaped lenses. For purposes of calculating the diopter values, the distance from the center of rotation 150 of a person's eye to the outer surface of the cornea was assumed to be 0.5 inch, the wall thickness of the lens 12 was assumed to be 0.075 inch, 1.34 was used for the index of refraction of salt water, and 1.586 was used for the index of refraction for the polycarbonate material which forms lenseε 12. As indicated in the above table, the preferred exterior diameter range of the lens 12 from about 4.25 inches to about 9.0 inches results in an effective negative diopter range under water of from about -5.3 to about -2.4. Effective negative diopter values for lenseε with exterior diameter sizes below 4.25 increase significantly and at a much faster rate aε the lenses get smaller. Therefore, most divers will not be able to use the smaller size of lenεes (i.e., below 4.25 incheε) without corrective lenseε, becauεe of the larger effective negative diopter values yielded by theεe εmaller lenεes under water. A majority of divers are represented by individuals who are under about 30 years of age and either have 20-20 vision or are near-sighted. These divers under 30 years of age have the ability to accommodate excessive negative diopter values because of the elasticity of the focuεing parts (muscle, etc.) of their eyes. Therefore, a majority of divers will be able to accommodate the negative diopter range of lenses 12 having an exterior diameter range of from about 4.25 incheε to about 9.0 incheε. Although the elaεticity of the focusing parts of an eye decreaεeε with age, some older divers will also be able to accommodate excessive negative diopter values. FIGS. 7 through 9 show yet another embodiment of the diving _αask 10 for use with corrective lenses having a turning shaft 66 which slidably and rotatably engages a sleeve 68 mounted to the hemispherically-shaped lenseε 12. The sleeve 68 engages a gasket 70 made out of a flexible material such aε rubber, or the like, which iε mounted in an aperture 72 in the lenεes 12. Flanges 74 of the gasket 70 engage the lenses 12 providing a seal between the gasket 70 and lenses 12. Flanges 76 of an upper portion 78 of the sleeve 68 bear against the gasket 70 helping to provide a seal. In addition, an 0-ring seal 77 is provided in upper portion 78 as shown in FIG. 8. Also, an annular portion 80 at the inside cylindrical surface of the gasket 70 engages an annular groove 82 in the outer cylindrical surface of the sleeve, providing a further seal. The rotating shaft 66 has a pin 84 attached to an upper portion 86 thereof which slidably engages an elongated slot 87 in the εleeve 68 so that the shaft 66 may be grasped by a knob 88 at the top of the shaft 66 and pulled upward. The shaft 66 alεo has a lower portion 90 which is connected to the upper portion 86 by a connecting member 92 having upper and lower balls 94 and 96, respectively, attached thereto. Upper ball 94 rotatably engages a εpherically-εhaped cavity 98 in the upper portion 86 of the shaft 66 so that a universal joint iε provided and upper portion 86 is free to rotate about its longitudinal axis. Another pin 100 is attached to the lower portion 90 of the shaft 66. This pin 100 also slidably engages elongated slot 87 in the εleeve 68 which also allows the lower portion 90 of the shaft 66 to be moved upward by pulling upward on the knob 88. Pin 100 alεo slidably engages elongated slots 102 in slotted arms 104. The slotted arms 104 are pivotally engaged at one end of each arm to pins 106 attached to lugs 108 at opposite slides of the sleeve 68. Elongated members 110 attached to a pair of retractable corrective lenses 112 are attached to the other ends of the slotted arms 104. In order to position the corrective lenses 112 in a position in front of a user's eyes 24 as shown in FIG. 7, the lower portion 90 is allowed to drop toward the bottom of the sleeve 68 until the bottom surface 114 of the knob 88 comes into contact with the top 116 of upper portion 78 of the sleeve 68. Alternatively, the different parts may be sized so that downward movement of the shaft 66 is stopped when pin 100 comes into contact with the lower end 118 of slot 87 in the sleeve 68. As the shaft 66 moves downward, the corrective lenses 112 rotate aε indicated by arrow 120 in FIG. 7 aε arms 104 pivot about pins 106 until the lenεes 112 reach a position in front of a user'ε eyes aε εhown. If the uεer wiεheε to move the lenses 112 away from his or her eyeε 24, thiε iε accomplished by pulling upward on knob 88 which causes shaft 66 to move upward and the lenseε 112 to rotate aε arms 104 pivot about pins 106 aε illustrated by arrow 122 εhown in FIG. 9. When pin 84 reaches the top end 124 of slot 87, the uεer may εimply rotate the upper portion 86 of shaft 66 by turning knob 88 until pin 84 engages horizontal slot 89 at the op end 124 of εlot 87. The εhaft 66 will then be held in place by pin 84 engaging εlot 89 and the lenεeε 112 will be moved to a poεition above the ueer's eyes 24. If the user wishes to lower the lenεeε 112 again to a position in front of his or her eyes 24, then knob 88 may be rotated εo that pin 84 disengages from εlot 89, and the lenses 112 may be lowered as described above. Another embodiment of a shaft 182 is shown in FIGS. 18 and 19. The εhaft 182 slidably engages a εleeve 178 mounted on the hemispherically-shaped lenses 12. The εleeve 178 engages gasket 70, which iε mounted in aperture 72 in the lenεes 12, as diεcuεεed above for the embodiment shown in FIGS. 7-9. An elongated member ill, attached to a pair of retract- able corrective lenses 112, passes through an aperture 188 in the shaft 182, near the lower end of the shaft 182. Member 111 may be welded to the shaft 182, or otherwise attached to shaft 182 by adhesive, or the like. The sleeve 178 has an elongated εlot 180 passing there- through, which allows the corrective lenses 112 to be raised and lowered, by grasping knob 88 at the top of the shaft 182, and by pulling upward or pushing downward on the knob 88. Downward movement of the lenseε 112 may be stopped by sizing the shaft 182 and sleeve 178 so that elongated member ill comes into contact with lower end 186 of the slot 180, or bottom surface 114 of the knob 88 comes into contact with the top 116 of upper portion 78 of the sleeve 178. The O-ring seal 77 holds the εhaft 182 in place when the corrective lenεes 112 are in an upward position, aε illustrated by dashed lines in FIG. 18. Any other desirable means may be used to hold the εhaft 178 in the upward position. FIGS. 13 through 15 show another embodiment of the diving mask 10 having a pair of hemispherically-shaped lenseε 12 with purge valves 126 therein mounted on the flexible gasket 14. A diver or uεer may expel or force any water inside the mask 10 through the purge valves .126 by exhaling through his or her nose. The purge valveε 126 are deεigned to permit air or fluid to flow from inεide the diving aεk 10 to outεide the maεk 10, but do not permit εuch flow into the mask 10. Thus, water may be purged from inside the diving maεk 10 through the valveε 126 without allowing leakage into the mask 10. Any suitable purge valve 126 may be used εuch aε the purge valve described in U.S. Patent No. 4,856,120, issued to Hart on August 15, 1989, the diεcloεure of which is hereby incorporated by reference thereto. One or more purge valves 126 may be used for the diving mask 10. For example, one valve 126 may be used for each lens 12. Alεo, only one purge valve 126 may be used for the diving mask 10, and a diver may tilt his or her head back and forth to move water from the lens 12 without the valve 126 to the lens 12 with the valve 126 prior to purging the water from the maεk 10. Each of the lenεeε 12 having one of the purge valves 126 preferably has a collecting area 128 near the front and bottom of such lens 12 as shown in FIG. 14. The collecting area 128 iε preferably formed aε εhown in FIG. 14, at angles 130 and 132 aε measured from horizontal and vertical lines, respectively. Angle 130 preferably has a range of from about 30 degrees to about 90 degrees, and angle 132 may be any εize up to about 60 degrees. However, angles 130 and 132 may vary as desired. Water that has entered the lens 12 of the diving mask 10 past the flexible gaεket 14 will move toward the bottom of the lenε 12 and into the collecting area 128. Angles 130 and 132, help to prevent collected water from εloshing out of the collecting area 128. Also, the location of the purge valve 126 at the bottom of the collecting area 128 and angles 130 and 132 help to direct bubbles formed when water iε exhauεted out the valve 126 toward the back of the diving mask 10, away from the field of vision of a diver. Angles 130 and 132 help to prevent water from εloshing or moving out of the collecting area 128 when a diver's head is in a vertical position as shown in FIG. 14, and when the diver iε in a prone εwimming poεition under water with hiε or her neck bent upward at approximately a 45 degree angle. If water trickles into the diving mask 10 while the diver is in a prone εwimming position and looking downward, the diver may purge water trapped inside the mask 10 through valve 126 by moving hiε or her head and/or neck upward at approximately a 45 degree angle, and then exhaling through hiε or her nose to force water out of the mask 10 through valve 126. FIG. 15 shows how the hemispherically-shaped lenses 12 may be connected to straps 18 and the f exible gasket 14 by a clamp 134 and alignment flange 136. The flange 136 may be molded or formed as an integral part of the lenses 12, or attached to ends or edges 138 of the lenses 12, which engage channel 137, as shown in FIG. 15, by adhesive, fusion, welding, or any suitable fastening means. The alignment flange 136 has extension 140. However, any suitable εhape or configuration may be used for the flange 136. End portion 142 of the flexible gasket 14 iε disposed in channel 144 of the clamp 134, folds around the extension 140, and is clamped between the flange 136 and extension 140. Clamp 134 may be attached to flange 136 by adhesive, welding, fastenerε, or any εuitable meanε. The εtrapε 18 are attached to extensions 146 of the clamp 134. As illustrated in FIG. 15, the lenses 12 are sized and mounted on the flexible gaεket 14 so that the spherical center of curvature of each of the lenses 12 with a radius 148 substantially falls on, or coincides with, the center of rotation 150 of the corresponding eye 24 of a diver surrounded by the lens 12. The center of rotation 150 of a person's eye 24 iε from about 0.5 inch to about 0.65 inch behind the front surface of the cornea. If the center of curvature of the lenses 12 substantially coincides with the center of rotation 150 of a diver's eyes 24, viewing distortion will be minimized when a diver's eyes 24 pan, tilt or rotate in their corresponding eye sockets. It is the intention of this invention that any εuitable meanε may be used to mount the lenses 12 on the flexible gasket 14 so that the center of curvature of the lenses 12 substantially coincides with the center of rotation 150 of the eyes 24 of a diver. As such, alignment of the centers of curvature and rotation may be achieved by fitting or forming the lenses 12 to match the contours of a diver's face 16, or a standard pair of lenses 12 may be mounted on a contoured portion of the mask 10 fitted or formed to match the contours of the diver's face 16, all as described in the above discussion. In addition, predetermined sizes may be selected for the flexible gasket 14, clamp 134 and flange 136 in order to mount different sizes of lenses 12 on the diving mask 10 so that the centers of curvature and rotation are aligned within an acceptable zone of misalignment, as discussed below. FIG. 16 iε a εchematic representation illustrating how the spherical center of curvature of each of the hemiεpheri- cally-ehaped lenεeε 12 of the preεent invention is intended to substantially coincide or align with the center of rotation 150 of a diver's eye 24, and falls within a predetermined acceptable zone of misalignment illustrated by region 152, which represents both horizontal and vertical misalignment. The optical nodal point 26 of a diver's eyes 24 is the point at which the spherical center of curvature of the lenεeε 12 εhould align or coincide with if the eyeε 24 do not pan, tilt or rotate in their eye εockets. The optical nodal point 26 is about 7 mm behind the front surface of the cornea of an eye. However, because a diver's eyes 24 move in their εockets, the spherical center of curvature of the lenses 12 εhould align or coincide with the center of rotation 150 of the diver's eyeε 24 to achieve optimum viεion through the lenεeε 12. It iε the intention of the preεent invention to εubεtantially align the centerε of curvature and rotation 15 in order to achieve improved viεion through the hemiεpherically-εhaped lenεes 12 of the diving mask 10. Radiuε 154 shown in FIG. 16 represents a particular εize lenε 12 having a εpherical center of curvature that coin- cides with the center of rotation 150 of an eye 24. Radii 156 and 160 represent two other sizes of lenses 12 having centerε of curvature 158 and 162, respectively, that do not coincide exactly with the center of rotation of the eye 24. However, the centers of curvature 158 and 162 fall within the predetermined acceptable zone of misalignment of the present invention represented in FIG. 16 by the three dimensional region 152. "Substantially" coincides or aligns with, as used herein, meanε that the spherical center of curvature of a lens 12 falls within the predetermined acceptable zone of misalignment represented by region 152 so that improved vision is provided by the lens 12. The two hemispherically-shaped lenses 12 are joined along edge 20. As a result, the distance 164 between edge 20 and the bridge 166 of a diver's nose 168 εhould be minimized to prevent viεion distortion through the lenseε 12 due to edge 20. Preferably, distance 164 has a range of from about 1 cm to about 50 cm. The present invention will allow a majority of diverε to uεe standard lenses 12 mounted on the diving mask 10 that have centers of spherical curvature that fall within the predetermined acceptable zone of misalignment or within region 152. However, larger diameter lenseε 12 will provide a larger predetermined acceptable zone of misalignment than smaller diameter lenεeε 12. Therefore, for purposes of the present invention, the exterior diameter of the lenses 12 preferably has a range of from about 4.25 inches to about 9 inches. FIG. 17 showε another embodiment of the diving maεk 10 having a pair of hemispherically-shaped lenses 12 mounted on a peripheral flange 174 of a support portion 169 of the mask 10. The support portion 169 has a portion 170 that is clamped (by, e.g., clamp 134), or is otherwise fastened to the flexible gasket 14. Portion 169 also has another portion 171 which covers nose portion 22 of gasket 14 that fits around a user'ε nose, an upward nose portion 176 connected to portion 171, and portion 172 which connects peripheral flange 174 to portions 170 and 176. The support portion 169 εhown in FIG. 17 may be fabri¬ cated aε an integral piece, such as by using molding techniques and plastic or other suitable material, or the various parts of portion 169 may be attached together. The support portion 14 may be used with selected sizes of lenseε 12 and flexible gaskets 14, and designed so that the spherical center of curvature of each lens 12 substantially coincides with the optical nodal point of a user'ε eye, or with the center of rotation of a user's eye, or falls within a predetermined acceptable zone of misalignment, as de¬ scribed above. Alεo, purge valveε 126 may be uεed in the εupport portion 169 of FIG. 17 and portion 169 may have a collecting area 128, like area 128 εhown in FIG. 14. It iε intended that different εizes (or standard sizeε) of flexible gaskets 14 may be selected and used with the lenses 12 and εupport 169, and different sizes (or standard εizeε) of flexible gaeketε 14 may be εelected and used with the lenεeε 12 and εupport 169, εo that the εpherical center of curvature of each lenε 12 substantially coincides with the optical nodal point of a uεer'ε eye, or with the center of rotation of a uεer'ε eye, or fallε within a predetermined acceptable zone of miεalignment, as described above. It is important to note that the εizeε of the flexible gasket 14, clamp 134 and flange 136 may be chosen to fit or accommodate any desirable εize lenε 12. Nearεighted diverε may uεe ε aller εize lenεes 12. If deεired, the diving maεk 10 of FIGS. 13 through 17 may be used with the corrective lenseε of FIGS. 7 through 9, and 18. Any combination of features disclosed in this application may be uεed for the diving maεk 10. The hemispherically-εhaped lenses 12 of the diving mask 10 may be uεed with a full face maεk, or a helmet which covers the head of a diver. Alεo, each lens of a diving maεk may compriεe only a small portion or segment of the hemispherically-shaped lens 12. Therefore, the lenses of a conventional mask may be replaced by εuch εmall portion of lens 12. FIG. 20 shows still another embodiment of the diving mask 10 having hemispherically-shaped lenses 12 mounted on the peripheral flange 174 of the support portion 169 of the maεk 10. Preferably, each one of the lenses 12 haε a bottom lenε 190 at the bottom of the lens 12. The bottom lens 190 preferably is integrally formed (molded) as part of the lens 12. Alternatively, the diving mask 10 may be manufactured with only one of its two lenses 12 having the bottom lens 190. The lens 190 shown in FIG. 20 iε a flat or plano-plano lens 192. A flange portion 194 attaches the lens 190 to the larger lens 12, so that the flat surfaces of the lens 190 are perpendicular to a diver's line of sight represented by line 196 in FIG. 20. The lens 190 may extend any desirable diεtance or length along the bottom of the hemispherically- shaped lens 12. Also, if desired, the lens 190 may conform with the contour or εhape of lens 12. For example, lens 190 may be a portion or section of a larger hemispherically-εhaped lenε. The plano-plano flat lens 192 of FIG. 20 would provide a magnified image, or an image larger than the image seen through the hemispherically-shaped lenε 12. As a result, presbyopic, or farεighted diverε, who have difficulty focuεing their eyes 24 close to the mask 10, may use the bottom lens 190 to inspect small objects held close to the mask 10 under water, which will magnify the εize of the objects. Locating the bottom lenses 190 at the bottom of the hemispherically-shaped lenses 12 forms a collecting area 198, which aids in draining water toward the purge valves 126. Furthermore, the collecting area 198 keeps water from flowing into the lenεeε 12 when a diver tilts his or her head in a downward direction in order to look εtraight down. FIGS. 21 and 22 show how the bottom lens 190 may be mounted on the peripheral flange 174 using an O-ring seal 200 between the lens 190 and flange 174. An o-ring seal 200 may also be used at the top of the lens 12 between the lens 12 and flange 174. However, any type of εuitable seal may be used in place of the O-ring seal 200. Channels or grooves 202 and 204 may be used in the lens 192 and flange 174, respectively, for the O-ring seal 200. If deεired, channel 206 may be used in the flange 174 as shown in FIG. 22. The lens 12 and bottom lens 190 may be mounted to the peripheral flange 174 using any suitable clamping or fastening means. Alternatively, O-ring seals 200 may be omitted, and the lenseε 12 and 190 may be attached to the flange 174 by adheεive, fuεion of the partε, welding, or by any suitable means. Channels or grooves 202 and 204 may have any desirable εhape or configuration εuch aε rectangu¬ lar, concave, etc. The diving maεk 10 may alεo be manufactured with bottom lenεes 190 which may be used by nearsighted diverε. Three such bottom lenses 190 are εhown in FIGS. 24, 25 and 30. In FIG. 24, a convexo-concave lenε 208 has an inside concave surface 212 and an outside convex surface 210, which yield a negative diopter value. The lenε 208 may be uεed by nearsighted divers to see clearly when in or out of the water. The lens 208 may be fastened to the lens 12 and peripheral flange 174 by adhesive, fuεion of the parts, welding, clamping, or by any suitable fastening means. Alternatively, lens 208 may be integrally molded as part of lens 12. The bottom lens 190 of FIG. 25 has-a plano-plano flat lens 192 and a plano-concave lens 214 (having an inside concave surface 216) fastened to the flat lenε 192. Any εuitable means may be uεed to faεten the lenεes 192 and 214 together, such as adhesive, fusion of the parts, welding, or the like. The combination of lenses 192 and 214 yields a negative diopter value, which allows nearsighted divers to see clearly through the lens 190 of FIG. 25 when the diving mask 10 is being worn above or below water. Another bottom lenε 190 used for the diving mask 10 is shown in FIG. 30 which allows different corrective lenses 216 with positive or negative diopter values to be removably installed in the bottom lens 190. Flat lens 192 has posi- tioning portions 218 at its inside flat surface 220. Por¬ tions 218 may be molded as part of lens 192, or may be attached to surface 220. As such, portions 218 may be made out of a material such as plastic or glass, or a resilient material such as rubber, neoprene, silicone, or the like. Portions 218 are sized εo that a gap or diεtance 226 will be maintained between εurface 220 and flat surface 222 of lenε 216, resulting in a trapped εpace 226 when lens 216 is installed in bottom lens 190. In order to allow excesε fluid to eεcape as lens 216 iε installed, portionε 218 do not extend completely around or along channel 198. Corrective lens 216 has a groove 228 which extends around the periphery or perimeter of the lens 216. Corre- εponding grooveε 230 and 232 exist in flange portion 194 and peripheral flange 174, reεpectively. A εeal 234 fits in grooves 228, 232 and 234, and is used to keep fluid in trapped εpace 226, when lens 216 is installed in bottom lens 19, aε deεcribed below. The bottom lens 190 design of FIG. 30 allows a diver to conveniently and quickly install lens 216 in order to yield a desirable positive or negative diopter value for the lens 190. A plano-concave lens 216 with concave surface 224 iε εhown in FIG. 30. However, any deεirable type lens may be uεed for lenε 216, εuch aε plano-convex lens, etc. Space 226 iε filled with fluid prior to inεtallation of lenε 216 in order to avoid a trapped air space between lenses 192 and 216. Snapping lens 216 into place in bottom lens 190 with a trapped air εpace will cauεe problemε, becauεe air compresses as a diver descends under water, and expands as the diver ascends. As the air expands, this may cause lens 216 to unseat or come loose from bottom lens 190. Also, trapped air may condense during diving, causing moisture buildup on lenses 192 and 216, which may result in fogging. Alεo, Newton ringε—or diffraction lineε of interference—may occur due to differences in pressure, which could cause lenseε 192 and 216 to contact each other, making it difficult to see through the bottom lens 190. The above problems may be solved by installing the lens 216, for example, in a bucket of distilled water. A diver may simply use his or her fingers to push the corrective lens 216 into place in the bottom lens 190 so that seal 234 is engaged in grooves 228, 230 and 232, and the distilled water fills the εpace 226. Other suitable fluid may be used instead of the distilled water. The lens 216 may be removed from the bottom lens 190 using a suction-cup tool, and replaced with another lens 216. FIG. 23 showε another embodiment of the diving maεk 10, which may be uεed for farεighted or presbyopic diverε. A convexo-concave lenε 236 with a positive diopter value is mounted inside the mask 10 for each lens 12 to either the peripheral flange 174 or εupport portion 169, or to b th theεe partε. Any εuitable means may be used to mount the lens 236, εuch as adhesive, welding, fusion of the parts, clamping of the parts, etc. The lens 236 has convex and concave surfaces 238 and 240, respectively, and may have any desirable positive diopter value to meet the needs of a diver. A bottom lens 190 may be used with the maεk 10. The bottom of lens 236 is cut off, molded, or formed at 244, as εhown in FIG. 23, εo that a diver's line of sight 196 through the bottom lens 190 is not obstructed by the lens 236. A diver cannot see clearly above water through lenses 12 when wearing the diving mask 10 of FIG. 23 with positive diopter value lens 236. However, the plano-plano lens 192 or bottom lens 190 is a zero diopter lens above water, which allows a diver to εee clearly through lenε 190 above water. Locating the bottom lenses 190 at the bottom of the hemispherically-shaped lens 12 provides significant advan- tageε. Prior to jumping into the water from a boat, a diver uεt be able to glance down to ensure that no obstacles or other diverε are in the way. While wearing the diving maεk 10, a diver may easily look downward through the bottom lenses 190 prior to jumping into the water. Also, while floating upright in the water and looking toward a boat or the shore, a diver typically tilts his or her head in a backward direction to keep water out of his or her mouth. Clear vision is provided through the bottom lenεeε 190 of the diving maεk 10 while the diver tiltε his or her head backward. Water which has seeped into the diving mask 10 may enter air space 246 between convex surface 238 of lens 236 and inside surface 242 of the hemispherically-εhaped lenε 12. Aε a reεult, water dropletε may form on surfaces 238 and 242, causing optical diεtortion through the lenseε 12 and 236. Thiε problem iε εolved by the embodiment of the diving maεk 10 εhown in FIG. 29, having a member 252 attached to each lenε 236 near end 244 and to the lens 12 near flange portion 194, so as to not obstruct a diver's line of sight through bottom lens 190. Member 252, lens 236 and lens 12 form a trapped dry-air space 248 inside the diving maεk 10. Aε a reεult, water iε not allowed to enter εpace 248, preventing moiεture droplets from forming on surfaceε 238 and 242 and diεtorting the diver'ε viεion. The trapped dry-air εpace 248 provides important advantageε. Space 248 causes the diving mask 10 to float, aiding retrieval of the maεk when dropped or eeparated from a diver. Aε a reεult of the trapped dry-air εpace 248, the internal air volume of the diving maεk 10 is reduced, making it easier for a diver to clear the mask 10 of water that has seeped into the mask 10. Also, dry-air εpace 248 reduces the amount of air volume required to compensate for hyper- baric pressure when descending under water. FIG. 28 shows yet another embodiment of the diving mask 10 having a transparent wall 250 of uniform thickness, which forms trapped dry-air space 248. Member 252 is attached to member 250 and to lens 12 near flange portion 194. Wall 250 is used for each lens 12, and may be used to support a positive diopter lens (not shown) , which may be attached to wall 250 using any suitable means εuch aε adhesive^ fuεion of parts, clamping, welding, or the like. Note that the bottom lenεeε 190 of FIGS. 23 through 25 and 28 through 30 have collecting areas 198. As shown in FIG. 26, the ends 253 of the hemiεpherically-εhaped lenεes 12 may be formed or curved toward a diver's head. Ends 253 decrease the external dimenεionε of the diving maεk 10, reducing the internal trapped-air volume of the mask 10. Formed endε 253 will only create minor diεtortion of viεion in the most extreme 10 degree angle of view. Another embodiment of the diving maεk 10 is εhown in FIG. 27. This embodiment has a translucent baffle 251 attached near edge 20 where the hemiεpherically-εhaped lenεeε 12 are joined. The baffle 251 is positioned parallel to a straight-ahead field-of-view through the mask 10. The εideε of the baffle 251 may be textured aε repreεented by numeral 254, or may be coated by any εuitable material, which will provide a translucent baffle that allows light to pass through the baffle, but not the detail of an image. The translucent baffle 251 preventε double viεion which occurε in the center ost stereoscopic field of view when large εize lenses 12 are uεed, and when the left eye 24 εeeε through the right lens 12, and the right eye 24 sees through the left lens 12. A vast majority of divers currently wear contact lenseε when uεing their diving masks under water. There is a need for a diving maεk 10 that can be used to provide improved viewing characteristics under water, and may be used by divers under water while vearing contact lenses which correct eyesight above water. Such a mask 10 could be used by both a diver who does not need contactε or eyeglaεεeε, or by a diver who needε corrective lenses to see clearly above water. FIG. 31 schematically represents two generally hemispherically-shaped meniscus lenseε 256 used for another embodiment of the diving maεk 10, which would allow diverε with 20-20 viεion and divers wearing contact lenses to see clearly under water. Each lens 256 has outer and inner surfaces 258 and 260, respectively, having different curvatures. A schematic representation of two other generally hemispherically-shaped meniscuε lenses 262 uεed for εtill another embodiment of the diving maεk 10 is shown in FIG. 32. Each lens 262 alεo haε outer and inner surfaces 258 and 266, respectively, having different curvatures. Note that lenses 256 and 262 have the same outside surfaceε 258. The lenses 262 may alεo be uεed in a diving maεk 10, which can be uεed under water by diverε with 20-20 viεion and diverε wearing contact lenεeε. The curvatures of outer surface 258 and inner εurfaceε 260 and 266 of the lenεeε 256 and 262 are εized to yield an effective zero diopter value under water. As a result, a diver with 20-20 vision, or vision corrected by contact lenseε, may then use the diving mask 10 to see clearly under water. Lenεes 256 and 262 are designed by first selecting an outer surface 258 of a particular curvature, and then varying the curvature of the inner εurfaceε 260 and 266 to yield lenεeε 256 and 262 having a zero diopter value under water. FIG. 34 iε a εchematic repreεentation of meniεcuε lenses 256 and 262. The spherical centers of curvature 268 and 270 of the outer and inner εurfaceε 258 and 260, respectively, of lens 256 are coplanar, or fall on a plane 271 pasεing through the center 272 of a diver'ε eye 24. For practical purposes, the center of an eye 24 may be consid¬ ered to be the center of rotation 150 of the eye 24. Also, the εpherical centerε of curvature 268 and 270 are located distances 274 and 276, respectively, behind the center 272 of eye 24. As a result, lens 256 is located closer to a diver's face 16. This effectively reduces the trapped air volume inside the diving mask 10 and the size of the mask 10. The spherical centers of curvature 268 and 278 of the outer and inner surfaces 258 and 266, respectively, of lens 262 are not coplanar, or do not fall on a plane 271 pasεing through the center 272 of a diver'ε eye 24. The εpherical center of curvature 278 of inner εurface 266 iε located a diεtance 180 behind the center 272 of eye 24. Alεo, note that εpherical center of curvature 278 of inner εurface 266 iε offεet a diεtance 281 from center of curvature 270 of the inner εurface 260, εuch that line 283, passing through centers 268 and 278 forms an angle 285 with line 271. Preferably, angle 285 has a range of from about zero degrees to about 15 degrees. However, angle 285 may have any desired value. Surfaces 284 and 286 of lenεeε 256 and 262, reεpective- ly, may be textured or coated with any εuitable material to provide a tranεlucent effect in order to prevent double viεion, aε explained above. Meniεcus lens 256 has a thickness 264 that is larger than the maximum thickness 282 of meniscus lens 262. As a result, lens 262 is lighter than lens 256. The curvature of inside εurface 266 of lenε 262 causes a slight degree of coma, or a slight distortion where a fringe iε produced, for peripheral vision. However, such coma effect is so minimal to almost be imperceptible. For an outer surface 258 diameter of 5.5 inches, the thickness 264 of lenε 256 is about 20 mm, and the thickness of lens 262 iε about 16.3 mm. The radius of inner surface 260 iε about 120 mm, and the radius of inner surface 266 is about 126 mm. The main curvatures of εurfaceε 260 and 266 are alεo chosen (designed) εo that the lenseε 256 and 262 provide increaεed peripheral viεion. Note in FIG. 34 that the interεection of outer surface 258 and inner surface 260 of lens 256 at 288 is slightly above a line 292 passing in front of the eyes 24 (or corneas) of a diver. Also, the intersection of outer εurface 258 and inner surface 266 of lens 262 at 290 approximately falls on line 290, providing optimal peripheral viεion. It iε the intention of the invention to provide increaεed peripheral vision for the diving mask 10. The lenεes 256 and 262 preferably provide in-focus peripheral viεion in a range of from about 90 degrees to about 180 degrees. It iε the intention of thiε invention to provide a diving maεk 10 uεing the meniscus lens 256 or 262, which furnishes optimal peripheral viεion and decreased trapped air εpace inside the mask, while still furnishing clearances for a diver's face. The meniscus lenseε 256 and 262 described above, having an outside εurface 258 with a 5.5 inch diameter furnishes the above-mentioned advantages. FIG. 33 schematically illustrates how changes in the effective diopter value of the meniscus lens 256 (or 262) can be matched with the type of bottom lens 190 used for the diving maεk 10. For a meniscus lens 256 yielding a zero diopter value under water, a plano-plano bottom lens 290 would be needed. For a meniscus lenε 256 having a poεitive diopter value under water, a plano-convex bottom lens 190 would be used for the diving maεk 10. A plano-concave bottom lens 190 would be required for a meniscuε lenε 256 yielding a negative diopter value under water. The lenses 256 and 262 are designed so that the centers of εpherical curvature 294 of the outside and inside surfaceε 258, 260 and 266 of the lenses are located below the centers 272 of a diver's eye 24, when the lenses are viewed vertically as shown in FIG. 33. Center 294 repre¬ sents either of the centers 268, 270 and 278 shown in FIG. 34. Locating center 294 below center 272 of the eye results in reduced weight for the lenses 256 and 262 because the thicker portion of the lenseε iε located near the bottom lens 190, and is reduced in size to form bottom lens 190. Alεo, as discussed below, drainage is improved due to locating center 294 below the center 272 of the eye 24. FIGS. 35 through 38 show a support portion 169, perimeter clamp 296 and conventional flexible face seal 298 of another embodiment of the diving maεk 1.0. The support portion has a peripheral flange 174 for mounting a pair of hemiεpherically-εhaped lenseε 12 (which may be meniscus lenses) , and two integral housings 300 used for mounting purge valve 126 (see FIG. 38) . Aε best shown in FIGS. 36 and 38, an opening 302 is formed in support portion 169 which allows water to drain from inside the maεk 10 through purge valve 126. A diver may exhale, forcing the water through opening 302 and out of the maεk through purge valve 126. The purge valve 126 iε angled to direct air bubbles away from the diver's field of view toward the back of the maεk 10. The εupport portion 169 haε one integral houεing 300 for each lenε 12, i.e., two purge valveε are used with the mask as shown in FIGS. 36 and 37. FIG. 45 shows another embodiment of the diving mask 10 using a perimeter clamp 304 having integral housings 306 formed in the clamp for the purpose of mounting purge valveε 126. The perimeter clamp 296 εerves the dual functions of mounting the face seal 298 to the εupport portion 169, and mounting the lenεes 12, including the bottom lenseε 190, to the εupport portion. The perimeter clamp 296 may be a bezel clamp and iε uεed to clamp the face εeal 298 to the εupport portion 169. The perimeter clamp 304 and εupport portion 169 have grooves 308 and 310, respectively, which engage extensions 312 integrally formed in the face seal 298. As shown in FIG. 45, the support portion 169, face εeal 298, and perimeter clamp 304 are generally formed to engage each other. These partε can be formed in any deεirable manner in order to engage each other. Preferably, clamp 304 haε a flange portion 314 which engages a flange portion 316 of the bottom lens 190. Preferably, one of the housings 306 is used for each lens 12 of the maεk. As described above, the housings are angled to direct air bubbles away from the diver's field of view toward the back of the mask 10. FIGS. 39 through 44 εhow two generally hemiεpherically-εhaped meniεcuε lenses 262 of the diving mask 10. Note that each lens 262 haε an integrally formed bottom lenε 190. Bottom lens 190 may be a portion or segment of a larger hemiεpherically-εhaped lenε. However, lenε 190 may have any other deεirable εhape, aε explained above, e.g., plano-plano, plano-convexo, etc. Note that the top 318 of the pair of lenεeε 262 iε formed to fit the εupport portion 169 of the maεk 10. However, top portion 318 may have any desirable εhape. The bottom lenεes 190 are formed to provide collecting areas 198 for draining water inside the mask. As diεcuεsed above in connection with FIG. 33, the εpherical centers of curvature 268 and 278 of the lenses 262 are located below the centers 272 of a diver's eyes. As best illustrated in FIG. 44, this locates the thicker portions of the lenses 262 near the collecting areas 198, and helps to reduce the weight of the lenses. Also,. ecause, the thicker portions of the lenseε 262 are located near areas 198, thiε facilitates drainage into the collecting areas. As explained above, surfaceε 286 may be textured or coated to provide translucent surfaces in order to prevent double viεion. Meniscus lenses may be uεed for the diving mask instead of lenses 262, described above. When the user iε under water, the diving maεk ιo deεcribed hereinabove provideε optimum viewing characteriεticε underwater. However, when the uεer raiεeε hiε or her head and the diving maεk 10 above water, the primary meniεcuε lenεeε deεcribed hereinabove yield.a very εtrong poεitive diopter effect, which inhibitε. viεion beyond a range of approximately eighteen incheε. FIG. 46 preεentε a top plan view of a εingle supplemental lens 300 which attaches to the diving mask 10 for purposeε of providing the user with clear viεion when the uεer raiεes his or her head above water. The two hemispherically- shaped meniscus lenses 301 having different inner and outer radii of curvature are described hereinabove in reference to FIGS. 23-44. The supplemental lens 300 is formed of a thin-walled transparent material having zero power. Once the diver enters the water, the cavity 304 fills with water and provides the diver with the beneficial aspectε of the diving mask 10 described hereinabove, specifically the elimination of underwater magnification-distortion caused by the differences in refractive indices of water and air. The diver views an image through the hemispherically-shaped lenses 301, the water filled cavity 304, and the supplemental lens 300, and the ambient water outside the supplemental lens 300. As the supplemental lens 300 is constructed of a transparent material providing zero power, no optical distortion occurs. When under water, the thin walls of the transparent supplemental lens 300 are effectively invisible, yielding no power and no distortion. The supplemental lens 300 may be constructed of a different glass or plastic material than the hemispherically-shaped lenses 301 εo that the supplemental lenses 300 may be replaced when scratches or other abrasions occur. The preferred material for the supplemental lens 300 is acrylic, but any material which is relatively transparent in water may be used. Acrylic provideε the additional benefit of being transparent to scratcheε and abrasions when underwater, as εuch imperfectionε tend to fill with water and become practically imperceptible. The εupplemental lenε may be joined to the diving maεk 10 by any conventional engagement means, εuch as clips, a ridge surrounding the supplemental lens and a corresponding receiving channel within the diving mask 10, or any other suitable means for joining plastic members and concurrently providing a water tight seal. The supplemental lens 300 may alεo be permanently affixed to the diving mask 10 by epoxy or other permanent adhesive, a molded bar surrounding the periphery of the εupplemental lenε, or εome other commonly known permanent joining methods. When the εupplemental lenε 300 iε joined to the mask 10, cavity 304 is formed and water may be stored therein. Storage of water in cavity 304 provides the beneficial dioptric effect missing when the diver εurfaceε and uses the diving mask 10 out of water. Both left εupplemental lenε 305 and right εupplemental lenε 303 are formed to approximately conform with the curvature of the left and right portions of the outer radius of both hemiεpherically-εhaped lenses 301, respectively. Thiε curvature of the εupplemental lens 300 preserves the hydrodynamic shape of the diving mask 10. Center supplemental lenseε 302 are curved to provide zero power in conjunction with water filling the cavity 304 and dependant on the refraction of water, the thicknesε of the center εupplemental lenεes 302, the radii of the outer edge of the hemispherically-shaped lenses 301 and the inner edge of center εupplemental lenεeε 302, which relate to the εize of cavity 304. The curvature of the center εupplemental lenεeε iε determined by the εtandard lenεmaker formula. To produce the required dioptric effect above water using this standard lensmaker formula, the center εupplemental lenses 302 are tilted slightly inward. Cavity 304 may be filled using various means. As shown in FIG. 46, the preferred embodiment consists of a water-tight cork 306 used in connection with hole 307 in εupplemental lens 300. Any commonly known flexible water¬ tight material may be used for cork 306. The user initially removes cork 306 from hole 307 and fills cavity 304 with water through hole 307. Alternately, a hole and cork may be located within hemiεpherically-εhaped lenεeε 301 and the cavity 304 filled from the inεide of the diving maεk 10. FIG. 47 εhowε the εupplemental lenε 300 having a curved upper portion 308 and a curved lower portion 309 εubstantially parallel to the curvature of the .outer edge of hemispherically-shaped lens 301, again to provide a beneficial hydrodynamic effect. An alternate means for filling cavity 304 is to provide an opening between curved upper portion 308 and hemispherically-εhaped lens 301. Such an arrangement provides a cupping effect for a user raising his or her head above water, but may serve to collect turbid water in cavity 304 and obstruct both underwater and above water viεion. FIG. 48 illuεtrateε a pair of hemiεpherically-εhaped meniεcus lenses 301 having visual gaps 320 and 321. The visual gaps 320 and 321 typically consiεt of εectionε of contoured portion 46 of diving maεk 10, inhibiting the peripheral vision of the diver and providing an approximately 160 degree horizontal field of view. The division between the visual horizontal peripheral line 325 perpendicular to the optical nodal point of each correεponding eye 24 of the uεer iε approximately ten degreeε on each εide. In order to provide 180 degree viεibility to the user, additional εide lenεeε are incorporated into diving mask 10. FIG. 49 illustrateε two εide wall lenses 351 and 355. Outer side wall lens edge 352 continues the curvature of the outer edge of hemiεpherically-εhaped lenεes 301 and inner side wall lens 353 runs substantially parallel to outer side wall lens 352 and adjoins hemispherically-shaped lenεes 301 at first joint 354. These εide wall lenses 353 and 355 provide a zero power wall within ten degree visual gaps 320 and 321. A user viewing an object through the lens configuration shown in FIG. 49 would see a 180 degree field of view, however the outermost field-of-view through the side wall lenεeε 353 and 355 would be out of focus, since underwater this lens configuration would yield a negative dioptric effect. Although the configuration is out of focus, the lens configuration produces no fragmentation of objects viewed through the εide wall lenεeε 353 and 355. FIG. 50 illuεtrateε an alternate embodiment of the eniεσuε lenε and εide wall lens configuration εhown in FIG. 49. The hemiεpherically-εhaped lenεeε 301 have affixed thereto a pair of enhanced focuε εide wall lenεeε 356 and 360. The enhanced focuε εide wall lenεeε have an outer εurface 357 and an inner εurface 358 formed to conεtitute a secondary meniεcuε lenε which improveε focuεing at the outermoεt points of the user'ε field of viεion. The inner εurface 358 adjoinε the hemiεpherically shaped lenseε 301 at edge 359. Any suitable optical material may be used for the lenses 12, 256, 262, and 301, such aε polycarbonate, glass, or any other refractive material. Any parts or features of the diving mask 10 described above may be used in combination with any other partε. The above description discloεes the preferred embodiments of the present invention. However, perεonε of ordinary εkill in the art are capable of numerouε modificationε once taught theεe principleε. Accordingly, it will be underεtood by thoεe εkilled in the art that changeε in form and detailε may be made to the above-detailed embodimentε without departing from the spirit and scope of the invention.

Claims: I CLAIM : 1. A method of fabricating a diving mask comprising the steps of: forming two hemispherically-εhaped lenεes; and mounting said lenses on a flexible portion so that a spherical center of curvature of each of said lenses when mounted on said flexible portion εubεtantially coincides with an optical nodal point of a corresponding eye of said user'ε face. 2. The method of fabricating a dive maεk of Claim 1, further comprising the step of: forming at least one supplemental lens to engage said diving mask and form a cavity between said diving mask and each supplemental lens, wherein said cavity may be filled with and hold liquid. 3. An underwater diving mask comprising: a flexible gasket; two generally hemispherically-εhaped lenεes mounted on said flexible gasket; and means for releasably securing said diving mask to a face of a user, said hemispherically-shaped lenses being mounted on said flexible gasket so that a spherical center of curvature of each of said hemispherically-εhaped lenεeε εubεtantially coincides with a center of rotation of a corresponding eye of said uεer'ε face. 4. The diving mask of Claim 3 further comprising retractable corrective lenseε mounted to εaid diving maεk. 5. The diving maεk of Claim 3 further co priεing a εupplemental lenε that engageε εaid diving maεk forming a cavity between said diving mask and said εupplemental lenε. 6. The diving maεk of Claim 5 further compriεing a hole and εtopping mechaniεm located in εaid hemiεpherically-shaped lenses. 7. The diving mask of Claim 5 further comprising a hole and stopping mechanism located in said supplemental lens. 8. The diving mask of Claim 3 further comprising side wall lenses continuing from said hemispherically- shaped lenses, said side wall lenses extending from said hemispherically-εhaped lenεeε to a visual horizontal peripheral line approximately perpendicular to the optical nodal point of each corresponding eye of said user'ε face. 9. The diving mask of Claim 8 wherein each of said side wall lenseε extend from approximately ten degrees to approximately zero degrees from said visual peripheral line. 10. The diving mask of Claim 8 wherein said side wall lenses comprise: an outer radius continuing the curvature of the outside of said hemispherically-shaped lenses; and an inner edge extending from the inside of said inner lens and substantially parallel to εaid outer radiuε, wherein εaid side wall lenseε maintain generally uniform thickness. 11. The diving mask of Claim 10 wherein said side wall lenses and hemispherically-shaped lenses are shaped to subεtantially fit said contours of said user's face using laser scanning techniqueε. 12. The diving mask of Claim 8 wherein said side wall lenses comprise: an outer radius continuing the curvature of the outside of said hemispherically-εhaped lenεeε; and an inner edge extending from the inside of said inner lens and away from the inside of the inner lenε, wherein said side wall lenses provide a secondary meniscuε lenε thereby improving focuεing characteriεticε at edges of the user'ε horizontal field of view. 13. The diving mask of Claim 12 wherein said side wall lenεes and hemispherically-shaped lenseε are shaped to substantially fit said contours of said user's face using laser scanning techniques. 14. The diving mask of Claim 3 further comprising at least one purge valve located in εaid diving mask. 15. An underwater diving mask comprising: two generally hemispherically-shaped lenses; and means for mounting said lenses on a face of a user so that a spherical center of curvature of each of said lenses substantially coincides with a center of rotation of a corresponding eye of said user. 16. The diving mask of Claim 15 further compriεing retractable corrective lenεeε mounted to εaid diving maεk. 17. The diving maεk of Claim 15 further comprising a supplemental lens that engages said diving mask forming a cavity between said diving mask and said supplemental lens. 18. The diving mask of Claim 15 further comprising side wall lenses continuing from said hemispherically- shaped lenses, said side wall lenseε extending from εaid hemispherically-shaped lenses to a visual horizontal peripheral line approximately perpendicular to the optical nodal point of each corresponding eye of said user'ε face. 19. The diving maεk of Claim 18 wherein each of εaid εide wall lenεes extend from approximately ten degrees to approximately zero degrees from said visual peripheral line. 20. An underwater diving mask comprising: a flexible gasket; two generally hemispherically-shaped lenses mounted on said flexible gasket; means for releasably securing said diving mask to a face of a user; and at least one purge valve located in said diving mask so that bubbles formed when water is expelled from said mask pass away from a field of vision of said user. 21. The diving mask of Claim 20 further comprising retractable corrective lenseε mounted to εaid diving maεk. 22. The diving maεk of Claim 20 further compriεing a εupplemental lens that engages said diving mask forming a cavity between said diving mask and said supplemental lens. 23. The diving mask of Claim 20 further comprising side wall lenses continuing from said hemispherically- shaped lenses, said side wall lenses extending from said hemispherically-shaped lenses to a visual horizontal peripheral line approximately perpendicular to the optical nodal point of each corresponding eye of said user's face. 24. The diving mask of Claim 23 wherein each of said side wall lenses extend from approximately ten degrees to approximately zero degreeε from said visual peripheral line. 25. The diving mask of Claim 23 wherein one of said lenseε has a collecting area, said at least one purge valve being located in said collecting area. 26. A method of fabricating a diving mask comprising the steps of: selecting two hemispherically-shaped lenses of a predetermined size; selecting a flexible gasket of a predetermined size to fit a user'ε face; selecting a support portion of a predetermined size; attaching said support portion to said flexible gasket; and mounting said lenses on said support portion so that a spherical center of curvature of each of said hemispherically-shaped lenses subεtantially coincideε with a center of rotation of a corresponding eye of said user's face. 27. The method of fabricating a diving mask of Claim 26, further comprising the stepε of: εelecting at least one supplemental lens to engage said diving mask and form a a cavity between said diving mask and each supplemental lens; and mounting said supplemental lens on εaid diving maεk so that liquid may be situated within said cavity. 28. An underwater diving mask comprising: two generally hemispherically-εhaped lenses; a translucent baffle attached to said lenseε; and meanε for mounting εaid lenses on a face of a user so that a spherical center of curvature of each of said lenses substantially coincides with a corresponding eye of said user. 29. The diving mask of Claim 28 further comprising a supplemental lenε that engageε εaid diving maεk forming a cavity between εaid diving mask and εaid εupplemental lens. 30. The diving mask of Claim 28 further comprising side wall lenses continuing from said hemispherically- εhaped lenses, said side wall lenseε extending from εaid hemiεpherically-εhaped lenεeε to a viεual horizontal peripheral line approximately perpendicular to the optical nodal point of each corresponding eye of said user's face. 31. An underwater diving mask comprising: two generally hemispherically-shaped meniscus lenses designed to provide a zero diopter value under water, each of said lenses providing an in-focus peripheral vision of more than ninety degrees; and means for mounting εaid lenses on a face of a user. 32. The diving mask of Claim 31 further comprising a εupplemental lens that engages said diving mask forming a cavity between said diving mask and said supplemental lens. 33. The diving mask of Claim 31 further comprising side wall lenεes continuing from said hemiεpherically- εhaped lenεeε, εaid εide wall lenεes extending from said hemispherically-shaped lenseε to a viεual horizontal peripheral line approximately perpendicular to the optical nodal point of each correεponding eye of εaid uεer'ε face. 34. The diving maεk of Claim 31 wherein each of εaid lenεeε has inner and outer surfaceε of different curvature. 35. An underwater diving maεk comprisilng: two lenses; at least one purge valve mounted in said mask and located in at least one of said lenseε; and means for mounting said lenseε on a face of a uεer. 36. The diving maεk of Claim 35 wherein εaid two lenεeε are generally hemiεpherically-εhaped. 37. The diving mask of Claim 35 wherein said mask comprises two purge valves, with one purge valve located in each lens.

Inventors: KRANHOUSE JON, KRANHOUSE, JON
Applicants: KRANHOUSE JON, KRANHOUSE, JON
Application year: 1996
Main classification: G02C1
IPC codes: A63B33, B63C11, G02C1, G02C7