An attachment for bifocal eyeglasses including at least one eyeglass lens having a first correcting region providing corrected distant-vision and a second correcting region providing corrected near-vision, the attachment including a compensating lens sized and shaped for covering the second correcting region of the eyeglass lens without substantially covering the first correcting region of the eyeglass lens and providing optical compensation for the second correcting region so that corrected distant-vision is provided over substantially all of the first and second regions of the eyeglass lens; and an attachment for attaching the compensating lens to the eyeglasses.

FIELD OF THE INVENTION 
This invention pertains to an attachment for bifocal eyeglasses 
compensating for the region of a lens providing corrected near-vision so 
that distance corrected vision is achieved over all of the area of the 
bifocal lens. 
BACKGROUND OF THE INVENTION 
Multiple focus eyeglasses have been in common use for many years. The most 
prevalent version of multiple focus eyeglasses are bifocals in which one 
or both lenses include distinct regions providing vision corrections for 
forming focused images of objects at two distinct locations. In a typical 
bifocal lens, a first region provides a vision correction so that distant 
objects are observed in focus. In a second region of the bifocal lens, a 
different correcting region is-provided for viewing near images, for 
example, during reading. Eyeglasses with multiple focus lenses are handy 
because objects at different distances can be viewed in focus using the 
different correcting regions of the lenses without changing between 
separate pairs of distant-vision and near-vision eyeglasses. 
Although, in many instances, bifocals can be particularly useful, in some 
situations they can present an impediment to achieving some visual goal. 
Typically, the near-vision correction for reading is at the lower part of 
the lens and when it is desired to view a distant object looking downward, 
i.e., through the near-vision correcting region of the lens, some physical 
adjustment in head or eye position must be made in order to see the 
desired object in focus. Thus, certain activities, such as hunting and 
golfing, present dilemmas for those persons who wear bifocal lenses. For 
example, in hunting, when it is desired to view a distant target along a 
gun sight, the near-vision part of the bifocal lens is typically in the 
line of vision preventing accurate sighting. In golfing, when preparing to 
hit a teed ball or when taking other strokes, it is desirable to keep the 
head down. In that posture, it is difficult or impossible to view the ball 
through the distant-vision part of bifocal and, therefore, a golfer 
wearing bifocals has a tendency to change head position before and during 
his swing with a detrimental effect on the drive. 
One solution to the problem of attempting to view distant objects through 
the near correction region of a bifocal lens, other than adjusting the 
head position, is the provision of two pairs of glasses, one for 
near-vision viewing and one for distant-vision viewing. However, in 
activities such as golfing and hunting, it is necessary to carry out some 
activities while viewing near objects, e.g., selecting a club, inspecting 
a ball, and the like, or loading ammunition, cleaning a firearm or the 
like, and other activities while viewing distant objects, making repeated 
glasses changing a nuisance. Moreover, carrying of an additional pair or 
pairs of glasses can be annoying during sporting activities. 
Accordingly, it is desirable to provide some way of switching between 
conventional bifocal vision and distant-vision over all of an eyeglass 
lens viewing area without the necessity of changing glasses. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide an attachment for eyeglasses in 
which the near-vision correcting region of a bifocal lens can be readily 
and selectively converted to a distant-vision correction and similarly 
restored to a near-vision correction. 
It is a further object of the invention to provide an inexpensive eyeglass 
attachment for selectively and easily changing a near-vision correction of 
a bifocal lens to a distant-vision correction without substantial 
modification of the eyeglasses. 
An attachment for bifocal eyeglasses according to the invention includes at 
least one eyeglass lens having a first correcting region providing 
corrected distant-vision and a second correcting region providing 
corrected near-vision, a compensating lens sized and shaped for covering 
the second correcting region of the eyeglass lens without substantially 
covering the first correcting region of the eyeglass lens and providing 
optical compensation for the second correction region so that corrected 
distant-vision is provided over substantially all of the first and second 
regions of the eyeglass lens and means for attaching the compensating lens 
to the eyeglasses. 
An attachment according to the invention may include hooks engaging the 
bridge or temples of eyeglass frames and, most preferably, includes a 
hinge for rotating the compensating lens to a use position in front of the 
eyeglass lens and for rotating the compensating lens away from the 
eyeglass lens to a storage position. Further, more preferably, the hinge 
includes a detent for releasably retaining the compensating lens in 
selected positions. Further, an attachment according to the invention 
includes a lens connected by a bendable support to an eyeglass attachment 
element for adjustment of the lens to cover the near-vision correcting 
region of the eyeglass lens accurately. Most preferable, the attachment 
includes as many compensating lenses as there are bifocal lenses in the 
eyeglasses. Further, according to another embodiment of the invention, the 
attachment may be permanently attached to the eyeglass frames.

DESCRIPTION OF PREFERRED EMBODIMENTS 
FIGS. 1a and 1b show a pair of eyeglasses 1 with a bifocal-compensating 
eyeglass attachment according to an embodiment of the invention attached 
to the eyeglasses. In FIG. 1a, the compensating attachment is shown in a 
storage position and in FIG. 1b, the compensating attachment is shown in 
the use position. In these figures, the conventional eyeglasses 1 include 
two correcting lenses 2, each of which is a bifocal lens. Each bifocal 
lens 2 includes a first correcting region 3 providing corrected 
distant-vision and a second correcting region 4 providing corrected near 
or reading vision. As is conventional with bifocal lenses, each correcting 
region has a particular prescription, generally expressed in diopter 
units. Although like numbers are given to each of the correcting regions 
in each of the two lenses, ordinarily the distant and near corrections for 
each lens are different. The eyeglasses 1 include side portions, i.e., 
temples, 5 and a bridge 6 that provides support for the lenses 2. 
The bifocal-compensating eyeglass attachment 10 includes a pair of 
attaching structures 11, generally in the shape of hooks, that mount the 
attachment 10 on the bridge 6 of the eyeglass frames. Most preferably, two 
attaching structures are provided. An axle 12 extends parallel to the 
lenses 2 and is mounted on the attaching structures 11. A rotatable frame 
including compensating lens-supporting elements 13 and, preferably, a 
bridging member 14 is rotatingly mounted on the axle 12, forming a hinge. 
A compensating lens mounting member 15 is attached at the end of each of 
the lens-supporting elements 13 and a compensating lens 16 is attached to 
each of the compensating lens mounting elements 15. 
In the view of FIG. 1a, the compensating lenses 16 are out of the line of 
view of the wearer of the eyeglasses 1, i.e., are stored. In the view of 
FIG. 1b, the rotatable frame has been rotated about the axle 12 so that 
the compensating lenses 16 are placed adjacent respective near-vision 
correcting regions 4 of the lenses 2. 
Preferably, the sizes and shapes of the compensating lenses 16 are 
substantially the same as those of the corresponding near-vision 
correcting regions 4. Most preferably, the compensating lenses are aligned 
to cover those corresponding near-vision correcting regions as accurately 
as possible without covering substantially any part of the corresponding 
distant-vision correcting region 3. Conventionally, the refracting powers 
of the near-vision correcting regions 4 are larger than the refracting 
powers of the first correcting regions 3 that correct images of distant 
objects. For example, in diopters, a typical distant-vision correction for 
hyperopia is +4 with an additional correction of +2 diopters for the 
near-vision correction. The compensating lens 16 has a refracting power 
opposite that of the near-vision correcting region 4 that the lens 16 
changes, sufficient to reduce the refracting power of the near-vision 
correction region to that of the distant-vision correcting regions 3. For 
instance, in the foregoing example, the compensating lens 16 has a power 
of -2 diopters. Thus, the net correction of a near-vision correcting 
region 4 and the compensating lens 16 is +4 diopters, the same power as 
the distant-vision correcting region 3. Therefore, when a compensating 
lens 16 is placed in front of and adjacent a corresponding near-vision 
correcting region, the same refracting power, the refracting power of the 
distant-vision correcting region 3, is produced over all the area of the 
lens 2. In other words, the entire lens 2 functions as if it were a 
distant-vision correcting lens only. Although the specific example 
pertains to only one correcting lens and compensating lens pair, just as 
each of the lenses 2 typically has a different refracting power, so the 
compensating lenses 16 is usually of different powers, chosen so that the 
respective near-vision corrections are compensated to the desired 
distant-vision corrections for each of the lenses 2. 
In situations where a person who normally wears bifocal glasses wishes to 
dispense with the near-vision correction, retaining over the entire field 
of view the distance vision correction, that result is easily achieved by 
swinging the rotatable frame to place the compensating lenses 16 in front 
of the near-vision correcting regions 4. Thus, a golfer can tee off while 
viewing the ball in focus without having to adjust his head to a 
particular posture to enable a clear view of the ball. Likewise, a hunter 
can sight a target without changing glasses or adopting an awkward head 
position. When those golfing, hunting, and like activities are completed, 
the compensating lenses 16 can be swung out of the way to the storage 
position without changing eyeglasses to restore the desired bifocal vision 
for other activities, such as keeping score and loading ammunition. When 
these vision options are no longer desired, the compensating attachment 
can be removed from the glasses by detaching the attaching structures 11 
from the bridge 6. 
The lens mounting members 15 for mounting the compensating lenses 16 are 
entirely conventional. Those mounting members may employ an adhesive or 
rivets, for example, as typically used with rimless or thin metal frame 
glasses commonly available so as not to unduly obscure the vision of the 
wearer of the eyeglasses 1 with the compensating lenses are in the use 
position. Likewise, the compensating lens supporting elements 13 of the 
rotatable frame are shown, for simplicity, in FIGS. 1a and 1b as linear 
elements. Those elements may be wires, rods, or tubes that have a sinuous 
region around the nose piece of the eyeglass frames to minimize obscuring 
of the lenses 2. Those supporting elements 13 may be resilient, e.g. 
plastic, or, preferably, are bendable in order to permit precise 
adjustment of the compensating lenses 16 for placement directly opposite 
the near-vision correcting regions 4. The bridging member 14 of the 
rotatable frame is an optional stabilizing strut that may optionally 
include a tab 17, shown only in FIG. 1a, that may be grasped with a finger 
and/or fingernail in order to aid in the rotation of the frame while 
moving the compensating lenses 16 between the storage and use positions. 
The invention provides important advantages over the prior art. The 
invention is directly usable with existing bifocal eyeglasses that the 
user conventionally wears. An inverse arrangement in which a pair of 
distant-vision eyeglasses are fitted with an attachment including 
"flip-down" lenses providing near-vision or bifocal viewing is undesirable 
because a second pair of eyeglasses (distant-vision only) is required, the 
user still has to change eyeglasses to his conventional bifocals after use 
of the single vision eyeglasses, and the more common viewing arrangement 
requires the use of additional lenses, the less desirable of the two 
viewing options. 
The attaching structures 11 and the mechanism for moving the compensating 
lenses between stored and use positions may employ any known structures 
serving those functions. For example, structures similar to conventionally 
available detachable sunglasses for use with eyeglasses may be employed. 
The axle 12 may be part of the rotatable frame and the attaching 
structures 4 may include a barrel or groove receiving the axle. The 
frictional engagement of the axle and barrel or groove may be sufficient 
to retain the compensating lenses in storage and use positions in spite of 
head movement by the wearer of the eyeglasses. However, because of the 
weight of the compensating lenses and, for convenience, most preferably, 
the attaching structures and the mechanism providing rotational movement 
of the frame include a detent or other releasable means for releasably 
holding the compensating eyeglass attachment in the storage and use 
positions. The particular axle and rotating barrel arrangement of the 
embodiment of FIG. 1a is further illustrated in FIG. 2b. As seen there, 
the compensation lens supporting element 13 extends from a barrel 18 
through which the axle 11 passes. 
FIG. 2a schematically illustrates one embodiment of an attaching structure 
11. That attaching structure includes a hook 20 having an extending end 21 
that is preferably resilient so that the bridge 6 of the eyeglass frame, 
possibly including a portion of a lens 2, is grasped securely by the hook 
20. The resilience of the end 21 aids in attachment and detachment of the 
hook 20 as well as the grasping function. The hook 20 may be lined or 
coated with a resilient material, such as a plastic foam or sleeve (not 
shown), in order to increase the gripping power and frictional force of 
the hook 20. The side 22 of the hook 20 opposite the end 21 includes a 
clevis, the slot of which receives a compensating lens-supporting element 
13. A pin 23 passes through the clevis and the lens-supporting member 13 
so that the lens-supporting member 13 can rotate relative to the hook 20. 
A resilient stop pin 24 penetrates through the supporting element 13 and 
functions, with the side 22 of the hook 20, as a detent mechanism. The 
side 22 and the location of the resilient pin 24 relative to the location 
of the pin 23 determines when the pin 24 will contact and engage the side 
22. By properly choosing the shape and dimensions of the side 22 of the 
hook 20, the resilient pin 24 will frictionally engage the side 22 in the 
position shown in FIG. 2a and when the supporting element 13 is rotated 
180.degree. relative to the position shown in FIG. 2a. In other words, the 
resilient pin 24 can releasably lock the supporting element 13 in the use 
and storage positions of the compensating eyeglass attachment. By altering 
the dimensions of the hook so that the pin 24 securely engages the side 22 
of the hook 20 when the supporting element is rotated 90.degree. from the 
position shown in FIG. 2a, a different storage position from that shown in 
FIG. 1a can be produced. In that alternative storage location, the 
compensating lenses 16 are generally perpendicular to the lenses 2. The 
rotating frame and attaching structure may be made of any suitable 
materials, such as metals or plastics, although metals may be preferred at 
least for the lens-supporting elements 13 since metal supporting elements 
can be bent to adjust the positions of the compensating lenses relative to 
the near-vision correcting regions 4 of the lenses 2. 
FIGS. 3a and 3b are cross-sectional views of the axle and barrel 
arrangement of FIG. 2b, taken along line 4--4, showing two alternative 
retaining, i.e., detent, mechanisms for releasably maintaining the 
rotatable frame 13 and compensating lenses 16 in the storage and use 
positions without inadvertent release or undue movement. In the structure 
shown in FIG. 3a, the inside surface of the barrel 18' includes four 
projections 30 symmetrically spaced on the inside surface of the barrel 
18'. The axle 11', at least within the barrel 18', has a generally square 
cross-section with rounded corners. The axle 11' and the projections 30 on 
the inside surface of the barrel 18' are dimensioned, considering their 
respective resiliencies, so that the axle 11' is retained relatively 
firmly in the position shown in FIG. 3a but, upon the application of a 
sufficient torque, can be rotated. During rotation, the rounded corners of 
the axle 11' and the projections 30 are mutually compressed and, after 
further rotation, the compression ends so that the arrangement shown in 
FIG. 3a is restored. The embodiment of FIG. 3a permits the storage and use 
positions to be 90.degree. apart, for example, a storage position under 
and adjacent the visor of a hat. If, as in the embodiment of FIGS. 1a and 
1b, the storage and use positions are 180.degree. apart, the detent 
mechanism of FIG. 3a can also be used, although it might be simplified. 
FIG. 3b shows an alternative arrangement in which a barrel 18" includes 
four recesses 31 equally spaced apart on the inside surface of the barrel 
18". The axle 11", at least within the barrel 18", is generally elliptical 
in shape so than the ends of the ellipse can engage an opposed pair of the 
recesses 31. Again, considering the elasticity and resilience of the 
materials from which the barrel 18" and axle 11" are made, the dimensions 
of the recesses 31, the inside surface of the barrel 18", and the 
elliptical axle 11" are chosen so that the axle can rotate within the 
barrel in response to a sufficient torque yet "seat" in the recesses to 
provide the desired releasable retention of the axle 11" in storage and 
use positions. When the storage and use positions of the compensating 
lenses 16 are 180.degree. apart, then only a single pair of recesses 31 is 
required. However, if it is desirable to provide a storage position 
90.degree. from the use position, two pairs of recesses 31 are preferably 
used. 
The detent mechanisms of FIGS. 2a, 3a, and 3b are not exclusive. Other 
means of releasably holding the compensating eyeglass attachment in 
storage and use positions can be devised and may include springs or other 
additional members. However, it is desirable that the releasable rotation 
arrangement be kept as simple and lightweight as possible. 
Yet another embodiment of a compensating eyeglass attachment in which the 
attachment is more permanently fixed to eyeglass frames is illustrated in 
FIGS. 4a and 4b. As shown there, each compensating lens 16 mounted on a 
respective compensating lens mounting member 15 is attached by a support 
41 to the temple 6 of the eyeglasses 1. The support 41 is mounted 
rotatingly in the eyeglass frames so that each compensating lens 16 can be 
brought into a use position opposite the corresponding near-vision region 
3 of a lens 2, as shown in FIG. 4b. When near-vision compensation is no 
longer required, then the compensating lenses 16 can be rotated to a 
storage position, as illustrated in FIG. 4a. The attachment between the 
supports 41 and the temple 6 may be a simple journal bearing or may have a 
more complex structure with a detent mechanism, for example, using the 
barrel and axle arrangement described above with respect to other 
embodiments. The support 41 may be plastic or another convenient material. 
Preferably, the support 41 is a metal wire or other bendable material so 
that the positioning of the compensating lenses with respect to the 
near-vision correcting regions and of the lenses 2 can be adjusted as 
necessary. While the embodiment of FIG. 1a has the advantage of 
simultaneously moving both lenses between storage and use positions, the 
storage position of the embodiment of FIGS. 4a and 4b may be more 
convenient in some instances than the storage position of the embodiment 
of FIG. 1a, even though an additional pair of eyeglasses may be required. 
The embodiment of FIGS. 4a and 4b preferably include a permanent 
attachment of the compensating lens support 41 to the eyeglass temple. The 
attachment may be made by drilling a hole in-the frames and inserting, 
with an adhesive, if necessary, a barrel receiving the rotatable support 
41. Alternatively, the support 41 might simply be inserted in the hole 
provided an end of the support is flattened or a retaining element is 
fitted on the support, such as a nut, to avoid unintentional withdrawal of 
the support 41. Similar embodiments functioning as shown in FIGS. 4a and 
4b including clips or hooks that respectively attach a single compensating 
lens at a side of the eyeglass frames also could be made. 
While the invention has been particularly described with respect to 
bifocals, it is equally applicable to multi-focus lenses of greater 
complexity such as trifocals and to graded bifocals so long as the 
correction of the compensating lens, in combination with the near-vision 
correction, provides the distant-vision correction. In some instances, 
only a single compensating lens may be provided for a pair of correcting 
lenses 2 with the other lens either missing or replaced by a 
non-correcting lens if monocular distance vision is sufficient for a 
particular activity. 
The invention has been described with respect to certain preferred 
embodiments. Various additions and modifications within the spirit of the 
invention will appear to those of skill in the art from the foregoing 
description. Accordingly, the scope of the invention is limited solely by 
the following claims.