BACKGROUND OF THE INVENTION Prior art attempts to make diving masks are best represented in U.S. Patent Nos. 3,055,256 issued September 25, 1962 to John H. Andreson, Jr., Patent No. 3,672,750, issued June 27, 1972 to Kenneth G. Hagen and Patent No. 3,320,018 issued May 16, 1967 to Max H. Pepke. The Andreson '256 patent discloses a mask for divers with imperfect vision which includes a conventional mask frame in which is mounted a spherical lens, conventionally aligned. The Hagen *750 patent discloses a diving mask with curved lenses for each eye, with a centre of curvature for each lens at the eyeball of the user. The Hagen mask should be custom made for each category of user to locate the specific eye points (eg. optical centres and eye depth) properly; a universally acceptable mask cannot be made according to the teachings of Hagen. Further, it has been found that only slight shifting of the Hagen mask on the user's face distorts one's vision to such an extent that nausea may result. For this reason, then, such a diving mask is fundamentally unacceptable.

Pepke "018 is relevant at Figure 20, showing a diving mask, again with spherical lenses having separate centres of curvature but located at the pupils of the eyes of the user, rather than at the centres of the eyeballs. The Pepke mask suffers the same deficiencies as Hagen's; the teachings of the Pepke patent cannot be used to produce a universally acceptable, distortionless vision mask but only individual masks, custom made for each category of diver user.

Remaining prior art disclosures are remote. U.S. Patent No's 2,876,766 issued March 10, 1959 to Dimitri Rebikoff et al and 3,010,108 issued November 28, 1961 to Melvin H. Sachs illustrate diving mask lenses curved laterally and vertically. However, neither patent even remotely

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suggests a mask lens curvature specifically designed and configured to provide distortionless vision underwater. The distortions inherent in such unspecified curvatures have also been found to dangerously cause nausea to users. U.S. Patent No's 2,952,853 issued September 20, 1960 to Howard A. Benzel and 3,027,562 issued April 3, 1962 to James K. idenor are more remote and simply show diving masks curved in a single plane only; vision distortion is only exacerbated by such a construction, not alleviated. U.S. Patent No. 3,483,569 issued to Israel Armendariz is similar. Again, the safety-threatening condition of diver nausea is inherent in these designs.

More exotic disclosures of attempts to provide magnification-free underwater vision are provided by U.S. Patent No's. 3,040,616, issued June 26, 1962 to George R. Simpson and 4,373,788 issued February 15, 1983 to M. Linton Herbert. These patents disclose dual 'focal point' lenses structures with air chambers behind the lenses in the former patent and a filling and draining bladder structure in the latter to permit readjustment of several lenses. Clearly, both designs are unfavourably complex and impractical.

Other prior art disclosures directed to attempt to improve certain aspects of underwater vision and/or provide diving mask myopia-correction lenses include U.S. Patent No's 2,928,097 issued March 15, 1960 to Lester N. Neufeld, 3,051,957 issued September 4, 1962 to Chester C. Chan and French Patent No. 1,374,010 issued August 24, 1964 to Jean-Louis Marro and an article entitled "Visual Problems of Skin Diving" by James R. Gregg, Skin Diver Magazine, April 1961, reprinted in The Optometric Weekly, July 13, 1961, pp. 1381-1388.

What the prior art fails to disclose is a diving mask having a lens configured to provide substantially distortion free underwater vision, a major portion of the mask lens being curved so that the apparent magnification of images underwater is less than that observed through a conventional, flat lens plate, certain portions of the lens being further curved to

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eliminate or mitigate pincushion-type distortion. Further, the prior art also fails to disclose an improved application for a simple spherical mask lens which is incorporated into a skirt narrow enough to allow the user's nose to extend forwardly of the lens and whereby the optical axis is tilted in a forward vertical plane.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is a principal object of the invention to provide an enhanced peripheral vision mask or other underwater vision device having a faceplate lens major surface created from a specified aspherical, an ellipsoid or paraboloid configuration to improve underwater vision by reducing pincushion-type or barrel-type distortion and magnification.

It is a further object of the invention to provide a low volume, enhanced peripheral vision mask created from the combination of a narrow skirt which allows a portion of the user's nose to extend forwardly of a faceplate lens major surface created from a sphere configuration, the main optical axis of such sphere being tilted out of alignment in a forward vertical plane with respect to the general optical axis of forward-pointing eyes of the user.

It is another object of the invention to provide a diving mask having a faceplate lens curved in a predetermined manner so that vision underwater appears to be more closely similar to vision in air.

It is a further object of the invention to provide a diving mask having a faceplate lens of simplified, uncomplicated structure which is low in cost of manufacture yet provides substantially distortion free underwater vision.

It is yet a further object of the invention to provide an uncomplicated and substantially distortion-free magnifying dive mask.

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BRIEF DESCRIPTION OF THE DRAWINGS

These, and further objects of the invention will become readily apparent by reference to the following detailed specification and drawings in which:

Figure 1 is a perspective view of one embodiment of the invention being worn by a user;

Figure 2 is a top plan view of the diving mask shown in Figure 1 and drawn to a larger scale;

Figure 3 is a perspective view showing the generation of a diving mask faceplate lens from a sphere, and the faceplate's subsequent tilting, in a forward vertical plane, out of alignment with the sphere's main optical axis, whereby the diver's normal forward vision would remain on the original axis;

Figures 4A and 4B are lateral and vertical section views, respectively, taken through a lens generated from a sphere and taken along Lines 4A-4A and 4B-4B of Figures 1 and 2 respectively;

Figures 5A and 5B are section views similar to Figures 4A and 4B, showing a lens generated from an aspherical configuration such as, for example, specific-radius spherical in the centre and a smaller radius/radii group towards the edge portions;

Figures 6A and 6B are section views similar to Figures 4A and 4B showing a lens generated either from an ellipsoid or other aspherical surface having a similarly decreasing radius of curvature outwardly from a centre point or points;

Figure 7 is a perspective view of another embodiment of the invention;

Figures 8, 9 and 10 are perspective, diagrammatic views showing generation of a faceplate lens from a short axis ellipsoid, long axis ellipsord and paraboloid, respectively; and

Figure 11 is a largely diagrammatic view of a magnifying diving mask with a specified aspherical surface

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where radius of curvature generally increases towards the edges, for example, paraboloid-type.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings by reference character, and particularly Figures 1 and 2 thereof, an embodiment of the invention is shown including a simple faceplate lens 10 carried by a thin profile surrounding skirt 12. The low profile of skirt 12, with a portion of the user's nose extending forwardly of the lens, combined with curved faceplate lens 10 provides a streamlined mask of low internal volume. Also, the construction permits the lens 10 to be as close to the face and eyes of the user as comfort and practicality will permit, so that peripheral vision is further enhanced in part by expected mathematical effect. In the case of simple spherical lenses, however, there is noted an additionally further, unexpected, disproportionate, geometrically synergistic effect which plays an extended role of enhancing peripheral vision beyond the relevant prior art teachings.

Faceplate lens 10 may be made from material generated from any one of a wide variety of geometric shapes. Unlike prior art faceplate lenses, it has been found possible to create a lens which is virtually distortion free and substantially devoid of pincushion-type or barrel-type distortion. Pincushion distortion occurs as the field of vision is viewed anywhere except generally straight ahead and increases as the field is viewed farther and farther from generally straight ahead. For example, parallel straight lines, horizontal and vertical, appear to acquire increasingly more distance between them with increasing distance from the field of view's central portion.

It has long been desired to create an acceptable dive mask wherein vision underwater appears the same as unobstructed in air, in other words, a mask having a lens that reduces the magnifying effect of water viewed through the air

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inside the mask and at the same time provides continuous and truly substantial peripheral vision.

With reference to Figure 3, I have found that a suitable mask can be made by combining a narrow supporting skirt which positions the lens so that a portion of the user's nose extends forwardly from the lens, with a lens of transparent material created from a spherical surface. Thus, a lens 14 is shown having a single radius of curvature across the entire surface thereof, the centre of curvature of the sphere being well behind the eyeballs of the user. This lens, in combination with the aforementioned new positioning is in direct contradistinction to prior art dive masks which are intended to eliminate the visual magnification present by being underwater, such masks teaching either dual curved lenses having centres of curvature at the centres of the user's eyeballs or at the user's pupils, or in another example the single curved lens failing to be combined with the peripheral-vision-enhancing positioning described above, which produces an unexpected, disproportionate and synergistic geometrical effect. (In a computer model, for instance, I found that an average user, whose eyes possess 70 mm optical centres, would receive only a 7 " per side angular increase of spherical over flat side peripheral vision in the case of a larger volume mask where pupil-to-lens distance is 2.2" to keep the user's nose behind the lens. Unexpectedly, however, it was found that the same user and lens type configured in a low-volume mask with the user's nose protruding forwardly of the lens and a pupil-to-lens distance of 1.0" gains, not 7°, but 13° disproportionately more increase in side peripheral vision, or a total of 26° for both sides. Geometrically speaking, this occured because the low-volume mask's eyepoint is more perpendicularly placed in relation to the middle point of the window of angular increase provided by a spherical lens over flat, thus effectively widening such a window.) In a preferred embodiment, the radius of curvature of the sphere 16 will be in a range of from five to about seventeen inches or more and, more preferably, on the order of about

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nine-to-twelve inches. This provides a diving mask lens wherein the user appears to see objects underwater much the same as he would in air, without the typical magnification created by the fact that the index of refraction of water is about 1.33 whereas that of air is 1. A further finding with relation to the simple spherical lens, with centre of curvature 16A in the drawing, is that, despite the common practice of ensuring uniform alignment in an optical system, it is possible to gain advantage by tilting the mask lens in a forward vertical plane out of parallel alignment with the main optical axis, line 16A-16B, while the general optical axes of forward-pointing eyes of the user remain parallel to the original axis line 16A-16B. This produces further meaningful gains in field-of-view and yet appears, unexpectedly, to not upset user eye comfort as long as certain conditions are met, including, firstly, the forward vertical plane tilting is kept under the limit of approximately 5"-25°, represented in the drawing as angle 16C, and, secondly, no tilting occurs in a horizontal plane in order to preserve a common eye-to-lens distance for both left and right eyes of the user, and, thirdly, the radius of curvature of the lens remains greater than approximately 5|".

Figures 4A and 4B illustrate such a lens 14 in horizontal and vertical cross-section.

Figures 5A and 5B, similar to Figures 4A and 4B, illustrate an even more satisfactory lens surface 18 wherein, for example, a central, major portion 20 is spherical and the outer, upper and lower edges become specified aspherical or ellipsoidal in configuration as is indicated at 22. This more pronounced curvature at portions 22 assists in reducing the pincushion-type distortion phenomenon discussed above. These views also illustrate that the lens 20 could alternatively be generated as an aspherical surface of specified, incrementally decreasing radii beginning from a centre axis or centre point or points, the latter of which is illustrated in dotted lines in Figure 5A.

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Figures 6A and 6B, similar to Figures 4A and 4B, show a lens 24 generated from an ellipsoidal surface; such a lens also assists in reducing the pincushion distortion phenomenon. These views also illustrate that the lens 24 could alternatively be generated as an aspherical surface of specified, incrementally decreasing radii, beginning from a centre axis 26 or central point or points, the latter of which is illustrated in dotted lines in figure 6A. In any event, pincushion distortion is reduced in lenses 20 and 24 because the angles of incidence of incoming light rays, particularly from the direction of the more peripheral areas of the faceplate lens, are closer to being at right angles to tangents drawn at the lens surface than is the case with single-radius spherical lenses and conventional flat faceplate lenses of any readily available diving mask. Also, the outer areas of reduced radius provide a further reduced image size in those areas which effect appears to also contribute in reducing pincushion distortion.

Turning now to Figures 8, 9 and 10, faceplate lenses generated from other geometric forms are illustrated. Figure 8 illustrates a lens 28 generated from the surface of an ellipsoid 30 created by rotating an ellipse about its short axis 32. Here, it should be noted that the lens may be taken radially from the axial portion of ellipsoid 30 so that curvature of the lens away from its centre axis (e.g., 32, Figure 8) is uniform.

In Figure 9 a lens 34 is generated from the surface of an ellipsoid 36 created by rotating an ellipse about its long axis 38. In this case, the lens may be taken radially from the long rather than short axial portion of ellipsoid 36 as is roughly illustrated.

In Figure 10, the surface is a paraboloid 40 created by rotating a parabola about is axial centreline 42 and the lens 44 may be taken from the axial portion of paraboloid 40 as is roughly illustrated.

Figure 7 illustrates another embodiment of the invention comprising a pair of faceplate lenses 46, 48 mounted

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in a mask skirt 50. Preferably, lenses 46 and 48 are generated from a continuous smooth curved surface as in the embodiments discussed above. For example, if generated by a spherical surface, lenses 46 and 48 will have the same radius of curvature and common centre of curvature, somewhat behind the eyes of the user. If desired, lenses 46 and 48 could be displaced somewhat from a true imaginary common spherical surface so as to provide two distinct centres of curvature, one for each lens, but each well behind the eyes of the wearer.

A magnifying dive mask 64 is illustrated in Figure 11, including a faceplate lens 66 in a frame 68, which lens may be selected from any of the lenses of the previously described embodiments except spherical, but is mounted in reverse, so that the convex surface of lens 66 is adjacent the user's face, rather than the concave side as in the previous embodiments. Distortion can be eliminated or mitigated in this type of mask by selecting a lens which possesses multiple radii of curvature where the radii lengths generally increase with increasing distance away from a central point or points, as in a paraboloid, for instance.

In all of the embodiments discussed, preferably the lens material is of uniform thickness but in certain applications it may be desirable to vary the material thickness and/or composition. Also, it is desired that the lens structure be rather rigid so that predetermined visual properties of any selected lens are not varied or altered by bending, e.g., when a mask is placed on the face of the user.

While the present invention has been shown and described as applied to a diving mask, it is to be understood that it may also be incorporated in a diving helmet, a full face diving mask, or other underwater vision/optical device for divers.

While this invention has been described as having a preferred design, it is understood that it is capable of further modifications, uses and/or adaptations of the invention and following in general the principles of the

invention and including such departure from the present disclosure as come within known or customary practice in the art to which the present invention pertains, and as may be applied to central features herein before set forth, and fall within the scope of the invention or the limits of the claims appended hereto.

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