Prescription lens carrier

A protective optical device is disclosed. The device includes a transparent shield for protecting a portion of the wearers face and a device for mounting an ophthalmic lens in the transparent shield. The mounting device includes an aperture through the transparent shield, a wall surrounding the aperture and extending forwardly from the shield to a front edge, and a shoulder surrounding the front edge for securing an ophthalmic lens to the front edge. The device allows standard ophthalmic lens to be securely mounted in a protective shield and minimizes the number of lens surfaces of the device.

TECHNICAL FIELD The present invention pertains to the art of protective 
optical devices. 
BACKGROUND OF THE INVENTION 
In situations wherein a prescription lens user must also use a device 
having a plano protective lens, e.g. scuba mask, gas mask, respirator, it 
is desirable to mount the prescription lens in the protective device to 
provide an optical system. Conventional methods for mounting the 
prescription lenses include mounting the prescription lens behind or in 
front of the plano lens or by cementing the prescription lens to the plano 
lens. 
Each of the conventional mounting methods have disadvantages. 
A prescription lens mounted behind or in front of plano lens may become 
dislodged during use. If a prescription lens mounted behind the plano 
lens, i.e. between the plano lens and the wearers eye, becomes dislodged, 
the wearer must remove the protective device in order to remount the 
prescription lens. The prescription lens may cause discomfort or injury 
while dislodged by contacting the wearers facial features. If a 
prescription lens mounted in front of the plano lens becomes dislodged, 
the prescription lens may be lost. 
Mounting a prescription lens in back of or in front of a plano lens 
juxtaposes a number of lens surfaces, which the wearer must look through. 
The optical performance of an optical system having a plurality of 
juxtaposed lens surfaces is compromised by reflections within the system. 
Performance may be improved by using expensive antireflective coatings. 
Cementing the prescription lens to a plano lens requires a special 
prescription lens design whenever every lens in the series has the same 
back curve, i.e. a series of plus toric lenses. Such lenses are not 
standard in the ophthalmic industry and typically it would not be cost 
effective to stock a wide prescription range of such lenses for such a 
restricted purpose. 
SUMMARY OF THE INVENTION 
A protective optical device is disclosed. The device includes a transparent 
means for protecting a portion of a wearers face and a means for mounting 
an ophthalmic lens in the transparent means. The means for mounting 
comprises an aperture through the transparent means, a wall surrounding 
the aperture and extending forwardly from the transparent means to a front 
edge, a means for securing the ophthalmic lens to the front edge. The 
device of the present invention allows standard ophthalmic lenses to be 
securely mounted in a protective device and minimizes the number of lens 
surfaces that the wearer must look through.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 shows a front view of the protective ophthalmic device of the 
present invention. The device includes a transparent shield 2, and an 
ophthalmic lens 4 mounted on the shield 2. The shield 2 may comprise any 
transparent material, e.g. a glass, a thermoset polymer or a thermoplastic 
polymer. The lens 4 may be any ophthalmic lens, e.g. a plano lens, a 
positive power lens or a negative power lens. The ophthalmic device of the 
present invention may be mounted in any conventional form of protective 
headgear, e.g. a scuba mask, a respirator or a gas mask, to provide a 
protective device having prescription ophthalmic lenses. 
FIG. 2 shows a cross sectional view of a first embodiment of the present 
invention taken along line 2--2 in FIG. 1. The shield 2 has an inner 
surface 6 and an outer surface 8. The shield 2 includes a convex wall 
portion 10, an annular wall portion 12 and an attachment member 14 for 
mounting the shield 2 in protective headgear (not shown). The annular wall 
portion 12 extends forwardly from the convex wall portion 10 to a front 
edge 16 and surrounds an aperture formed in the convex wall portion 10. An 
annular step 18 having a back surface 20 and a peripheral surface 22 is 
formed at the intersection of inner surface 6 and front edge 16 of shield 
2. 
Lens 4a is a positive power lens having a front surface 24, a back surface 
26 and a peripheral surface 28 between the front and back surfaces 24, 26. 
An annular step 30 having a back surface 32 and a peripheral surface 34 is 
defined around the perimeter of lens 4a at the intersection of the back 
surface 26 and the peripheral surface 28. Step 18 of shield 2 engages step 
30 of lens 4a to locate the lens 4a relative to the shield 2. 
FIG. 3 shows a cross sectional view of a second embodiment of the present 
invention, taken along line 3--3 in FIG. 1. 
Lens 4b is a negative power lens having a front surface 36, a back surface 
38 and a peripheral surface 40 between the front and back surfaces 36 and 
38. An annular step 42 having a back surface 44 and a peripheral surface 
46 is formed around the perimeter of lens 4b at the intersection of back 
surface 38 and peripheral surface 40. The step 18 of shield 2 engages the 
step 42 of lens 4b to locate lens 4b relative to the shield 2. 
In either of the embodiments shown the engagement between the shield 2 and 
the lens 4 may be maintained by any convenient means. For example, the 
lens 4 may be retained in engagement with shield 2 by an interference fit 
between the shield 2 and the lens 4, by a mechanical clamp, or by an 
adhesive bond between the lens 4 and the shield 2. Preferably, the lens 4 
is retained in engagement with shield 2 by adhesive bond between the 
shield 2 and the lens 4. 
While preferred embodiments have been shown and described, various 
modifications and substitutions may be made thereto without departing from 
the spirit and scope of the invention. Accordingly, it is to be understood 
that the present invention has been described by way of illustrations and 
not limitations.