WO 2006/117544 PCT/GB2006/001597
1
Viewing Device
The present invention relates to viewing devices with
optically aligned lenses and particularly but not exclusively
devices such as spectacles.
Many optical devices with multiple lenses require variable
separation of the lenses from each other or the image plane
when focusing, magnifying or altering other characteristics
of the image. Uniocular devices can focus objects at varying
distances using mechanical devices such as threads, slides or
telescopic tubes. Binocular devices require two pairs of
lenses to be adjusted identically and simultaneously.
Binoculars usually consist of a pair of telescopic tubes
which are made to slide simultaneously and move by an
identical distance. This is achieved by a screw that is
placed between the tubes and drives both sides of the system
simultaneously.
Adjustable binocular systems have been applied to spectacles
to improve the viewing experience of the user. For example,
GB Patent No. 14,716 proposes an adjustable binocular system,
in which the bows of a front pair of spectacles slide in
sleeve portions on a rear pair of spectacles. As the bows of
the front pair of spectacles slide along the sleeves, the
separation between the two pairs of spectacles varies.
The binocular glasses of US Patent No. 3,420,599 incorporate
two adjustable levers pivotally connected to a front
spectacle frame which are also connected to a thread on a
rear spectacle frame via threaded sleeves. Rotation of the
thread moves the levers and varies the separation between the
two frames.

WO 2006/117544 PCT/GB2006/001597
2
In WO 03/083556 a gear wheel and roller mechanism is used to
ad-just the distance between nested lenses in a pair of
spectacles. Failing accommodation of the eye to view objects
at; varying distances (presbyopia) can be compensated with the
spectacles by making such adjustments.
Since most tasks (e.g. preparing a meal, reading music on a
stand, undertaking machine work or viewing plans) require
focusing of various object planes, a device for correcting
the failing accommodation should be adjustable to examine any
distance from the normal near point to infinity. A mechanism
that allows constant and easy adjustment, of the separation of
the lenses (particularly, simultaneous and identical
adjustments for both eyes) would enhance the usability of
such a viewing device.
Many aids for the visually disabled also require simultaneous
separation of two pairs of spectacle lenses.
Accordingly, the present invention provides a viewing device
comprising:
a pair of optically aligned (i.e. substantially coaxial)
lenses which are moveable relative to each other to vary the
gap between facing surfaces of the lenses, and
a linkage for controlling the relative motion, the
linkage including first and second elongate members which
crossover each other at a crossover pivot connection, the
first elongate member extending between a slidably moveable
pivot connection which is arranged to transmit relative
motion to the first lens of the pair and a pivot connection
which is arranged to transmit relative motion to the second
lens of the pair, and the second elongate member extending
between a slidably moveable pivot connection which is
arranged to transmit relative motion to the second lens and a

WO 2006/117544 PCT/GB2006/001597
3
pivot connection which is arranged to transmit relative
motion to the first lens;
wherein the connections are arranged such that the
linkage can open and close in a concertina- or scissor-like
fashion.
With such a viewing device it is possible to move one of the
lenses of the pair and cause relative motion between it and
the other lens. The linkage formed by the elongate members
and the connections allows continuous and easy adjustments to
be made to change the separation between the first and second
lens so that objects can be viewed at different distances.
However, at the same time, the linkage can provide precise
control over the relative positions of the lenses to
maintain, for example, optical alignment.
In general, the lenses will be held in respective supports.
Each connection transmitting relative motion to the first
lens can then be to a respective point on the support of that
lens. Similarly, each connection transmitting relative
motion to the second lens can be to a respective point on the
support of that lens. Thus the connections may be arranged
to transmit controlled relative motion to the lenses via the
supports. However, in other embodiments, the connections may
be made directly to. the lenses. Alternatively, the
connections may transmit the relative motion via other
intermediary bodies in addition to or instead of the
supports.
The position of the crossover pivot connection may be
moveable along one of the elongate members such that the
optical axis of one of the lenses can be tilted or angled
with respect to the optical axis of the other lens. Such
tilt can be useful, for example, to correct for astigmatism

WO 2006/117544 PCT/GB2006/001597
4
or to introduce a progressive (typically top to bottom)
varifocal effect. For additional adjustability, the position
of the crossover pivot connection may be moveable along both
of the elongate members.
In general, the pivot connection transmitting relative motion
to the first lens directly faces the pivot connection
transmitting relative motion to the second lens across the
gap between the lenses. Furthermore, the two slidably
moveable pivot connections generally face each other in the
same way. However, in some embodiments the connections may
be offset so that they do not face across the gap. Such an
arrangement also allows variable tilt or angulation between
the optical axes of the lenses to be introduced.
The elongate members of the linkage may be spaced apart at
the crossover connection to provide the linkage with
additional structural rigidity. Other embodiments of the
viewing device have a second linkage that is in a different
plane from the plane of the crossed elongate members of the
first linkage. The second linkage may have a similar
construction to the first linkage. The second linkage
provides increased structural rigidity whilst still
permitting the varying separation between the first and
second lenses. The structural rigidity of the viewing device
can be increased further if the plane of residence of the
second linkage is substantially orthogonal to that of the
first linkage.
The viewing, device may have an actuator mechanism for moving
the lenses relative to. each other. The actuator mechanism
may be operated by hand and may be in the form of a screw,
cam or any other means for moving the first and second lenses
apart or displacing the slidable pivots. The actuator

WO 2006/117544 PCT/GB2006/0U1597
5
mechanism allows the user to vary the separation between the
lenses without fouling the lenses. Furthermore, the
actuator mechanism may be motorised, electronic, pneumatic,
hydraulic or operated by any other automatic means to move
the two lenses. The mechanism may not act on the lenses
directly, but rather may act on e.g. lens supports or parts
of the linkage.
Preferably the viewing device further comprises a second pair
of optically aligned and relatively moveable lenses. A
binocular system such as this allows the device to be used on
spectacles, binoculars, loupes, binocular camera systems,
etc. Indeed, the viewing device is not limited to only two
pairs of lenses. Linkages may be applied to more than two
lenses in a lens group and more than two lens groups along
the same or different optical axes. The term "lens group"
defines a lens structure with two or more optical elements
aligned along an optical path. Furthermore, in binocular
viewing systems that include more than two optical elements
in the two lens groups, suitable adaptation of the linkage
structure may allow each lens to be separated differentially.
For example, the linkage may have further crossed elongate
members in addition to the first and second elongate members
that accommodate further optical elements and extend the
linkage, for example, in the manner of a lazy-tong.
Preferably the second pair of lenses is spaced from the first
pair of lenses such that a user can look through one pair of
lenses with one eye while looking through the other pair of
lenses with the other eye.
One linkage may control the relative motions of both pairs
but preferably each pair of optically aligned lenses has a
respective linkage for controlling the relative motion.

WO 2006/117544 PCT/GB2006/001597
6
The respective linkages may be openable and closeable
independently of each other whereby the lens separation
within one of the pairs of lenses may be altered
independently of the lens separation within the other. For
example, since both eyes are not typically identical in the
normal human subject, the correction required for each pair
of lenses may be different.
However, the respective linkages may be cooperatively
arranged such that opening or closing one of the linkages
results in corresponding movement from the other of the
linkages.
A cooperative arrangement may vary the angle between the
respective axes of the pairs of lenses as the linkages open
or close. In the normal human subject, the optical pathways
of the two eyes are not parallel and angle inwards during
accommodation to intersect at the object. Thus it is useful
for the viewing device to correspondingly adjust the angle
between the axes.
The viewing device may further comprise an alteration means
for altering the spacing between the pairs of lenses. This
is particularly useful when the device may have to be adapted
to the eye spacing of different users.
Preferably the viewing device is a pair of spectacles, for
example, spectacles to treat medical conditions of the eye
such as presbyopia, myopia, hypermetropia and astigmatism.
The invention will now be described by way of example with
reference to the accompanying drawings, wherein:

WO 2006/117544 PCT/GB2006/001597
7
Figs 1a and lb are schematic plan views of a first embodiment
of the invention in the closed and open positions
respectively,
Fig 2 is a schematic perspective view of a second embodiment
of the invention,
Fig 3 is a schematic side elevation of a third embodiment,
Fig 4 is a schematic side elevation of a fourth embodiment,
Fig 5 is a schematic side elevation of a fifth embodiment,
Fig 6 is a schematic perspective view of a sixth embodiment,
Fig 7 is a schematic front sectional elevation of a seventh
embodiment,
Figs 8a and 8b are schematic plan views of an eighth
embodiment in the closed and open positions respectively,
Figs 9a and 9b are schematic plan views of a ninth embodiment
in the closed and open positions respectively, and
Figs 10a and 10b are schematic plan views of a tenth
embodiment in the closed and open positions respectively, and
Figs 11a, 11b and 11c are schematic front, side and cross-
sectional views respectively of an eleventh embodiment in the
open position, Fig 11d is a schematic side view of the
eleventh embodiment in the closed position, and Fig 11e is a
further front view of the eleventh embodiment in the closed
position in use on a pair of spectacles.
Fig la shows a schematic plan view of a first embodiment of a
frame 1 for a pair of spectacles in a closed position. The
frame 1 has two linkages 2, 3 attached to a rear support

WO 2006/117544 PCT/GB2006/001597
8
crossbar 4 and to a front support crossbar 5. For clarity,
the lenses and the other parts of the frame of the spectacles
(such as the side arms) are not shown. However, each support
crossbar would support left and right lenses, the left lens
of the rear support crossbar 4 being optically aligned with
the left lens of the front support crossbar 5 to form a lens
pair, and the right lenses of the support crossbars forming a
similar lens pair. Thus linkage 2 controls the relative
motion between the lenses of the left pair and linkage 3
controls the relative motion between the lenses of the right
pair.
Linkage 2 is formed from two intersecting elongate members 6,
7 which are pivotally moveable relative to each other at
crossover pivot connection 8. The first elongate member 6
has a pivot connection 9 at the rear support crossbar 4 and a
slidably moveable pivot connection 10 at the front support
crossbar 5. The second elongate member 7 has a pivot
connection 11 at the front support crossbar 5 and a slidably
moveable pivot connection 12 at the rear support crossbar 4.
The connections permit relative motion to be transmitted to
the front and rear lenses of the left and right lens pairs.
Linkage 3 is the mirror image of linkage 2, and therefore,
the parts of linkage 3 have not been discussed in detail.
The sliding movement of connections 10, 12 is effected by
slides 13, 14 which respectively attach the elongate members
6, 7 to the ends of the rear and front support crossbars 4,
5. Support crossbars 4, 5 have a hollow box cross-section,
and the slides 13, 14 move inside the crossbars 4,5 along
their longitudinal axes when the linkages extend.
Fig 1b shows another schematic plan view of the first
embodiment with the frame 1 in an open position. When the

WO 2006/117544 PCT/GB2006/001597
9
rear support crossbar 4 is moved away from the front support
crossbar 5, the linkages 2, 3 control the relative motion
between the lenses of the left and right pairs. The elongate
members 6, 7 (i) move pivotally relative to support crossbars
4, 5 at the pivot connections 9, 11, (ii) move pivotally
relative to the slides 13, 14 at slidably moveable pivot
connections 10, 12, and (iii) move pivotally relative to each
other at pivot crossover connection 8. The relative pivotal
motion of the elongate members 6, 7 with respect to the
support crossbars 4, 5 causes the slides 13, 14 to move along
the longitudinal axis of the support crossbars towards the
centre of the support crossbars 4, 5. The overall effect is
concertina- or scissor-like opening of the linkages.
Thus the linkages 2, 3 force the support crossbars 4, 5 to
remain parallel and hence the front and rear lenses of each
lens pair remain optically aligned during and after the frame
adjustment. The linkages control the movement of the support
crossbars and control the lens separation within each lens
pair. Advantageously, motion produced at any point on a
support crossbar 4, 5 results in identical motion of the rest
of the crossbar.
Fig 2 shows a perspective view which is a variant of the
frame 1 of Fig 1. The same reference numbers are used for
eguivalent features between Figs 1 and 2.
In the second embodiment, linkage 2 has first and second
elongate members 6, 7 which are now fixed by pivot
connections 9, 11 at the ends of the rear and front support
crossbars 4, 5, and the slidably moveable pivot connections
10, 12 reside towards the centre of the rear and front
support crossbars 4,5.

WO 2006/117544 PCT/GB2006/001597
10
Cylindrical slides 18, 19 carry the slidably moveable pivot
connections and reside in respective channels 16, 17 formed
within the support crossbars 4, 5. Thus as slides 10, 19
move along the channels 16, 17, the elongate members 6, 7
move pivotally relative to the slides and the crossbars. The
second embodiment provides the additional advantage that the
device is more compact since the slidably moveable
connections do not protrude beyond the ends of the crossbars.
Fig 3 shows a side elevation of a third embodiment of the
invention. This embodiment is the same as the first
embodiment except that the inside opposing faces of the first
and second elongate members 6, 7 are spaced apart by a spacer
21 surrounding crossover pivot connection 8. This
arrangement ensures that the first and second elongate
members 6, 7 are moveable in spaced, parallel planes. The
third embodiment has increased structural rigidity and the
linkages have additional resistance to twisting forces.
Fig 4 shows a side elevation of a fourth embodiment in
accordance with the invention. The fourth embodiment
combines the third embodiment with a second linkage for
providing increased structural rigidity. The second linkage
permits controlled relative motion between the front and rear
optically aligned lenses of each lens pairs. The plane of
residence of the second linkage 31 is different, and
typically orthogonal, to the plane of residence of the first
linkages 2, 3. Typically, the first linkages are in a
horizontal plane, and the second linkage is in a vertical
plane.
The second linkage 31 is of similar construction to the first
linkages 2, 3. It has first and second elongate members 32,
33 connected by a crossover pivot connection 34. The first

WO 2006/117544 PCT/GB2006/001597
11
elongate member 32 is attached to a rear strut 35 extending
perpendicularly from the rear support crossbar 4. The second
elongate member 33 is attached to a front strut 36 extending
perpendicularly from the front support crossbar 5. The first
elongate member 32 has a pivot connection 37 at the rear
strut 35 and slidably moveable pivot connection 310 at the
front strut 36. The second elongate member 33 has a pivot
connection 38 at the front strut 36 and slidably moveable
pivot connection 39 at the rear strut 35. The struts 35, 36
can provide support for the lenses of the right and/or loft
lens pairs.
The slide movement of connections 39, 310 is effected by
slides 311/312 in a similar fashion to the sliding movement
in the first linkages. Thus as the separation of the rear
and front support crossbars 4, 5 varies, the movement of the
second linkage provides controlled separation between the
front and rear lenses of each lens pair. However, the second
linkage ensures that the lenses remain in a plane orthogonal
to the plane in which the crossed elongate members of the
first linkages 2, 3 reside.
A fifth embodiment of the invention, as shown in Fig 5,
incorporates the features of the fourth embodiment and
further permits the face of one of the lenses of a pair to be
tilted with respect to the face of the other lens of the
pair. With reference to WO 03/083556, this can provide a
progressive varifocal correction, i.e. the focal length of
the lens system shortens from top to bottom, allowing nearer
objects to be viewed during down-gaze.
The second linkage 31 has first and second intersecting
elongate members 32, 33 that are connected by a. slidably
moveable pivot crossover connection 41. At their

WO 2006/117544 PCT/GB2006/001597
12
intersection, the second elongate member 33 has a slot 42 in
which the slidably moveable pivot crossover connection 41 can
move along the second elongate member 33. The front
orthogonal strut 36 is attached by a pivot 43 to the front
support crossbar 5. When the position of the slidably
moveable pivot crossover connection 41 is adjusted, the front
orthogonal strut 36 rotates about pivot connection 43 and the
angle between the optical axis of the front lens changes with
respect to the optical axis of the rear lens.
A sixth embodiment, as shown in Fig 6, incorporates the
fourth embodiment and provides improved structural rigidity
to the spectacles by using two, joined together, second
linkages instead of one. Again, the second linkages are in a
different (typically orthogonal) plane to the plane of the
first linkages. The connections of the additional second
linkage are similar to the second linkage in the fourth
embodiment. For clarity, the support bars 4, 5 are shown in
Fig 6 with intermittent lines.
The arrangement of the connections of the first linkages 2, 3
is the same as the second embodiment. However, the support
crossbars 4, 5 are cut away and their cross section forms an
"L" shape to provide space at their centres to attach the
second linkages 51, 52. Thus the slides (not shown) carrying
the slidably moveable pivot connections (not shown) move in
the centre of the support crossbars 4, 5 in a shallow channel
50.
The rear and front support crossbars 4, 5 have tubular
elements 59, 510, 511, 512 extending perpendicularly to the
plane of residence of the crossed elongate members of the
first linkages 2, 3.

WO 2006/117544 PCT/GB2006/001597
13
The tubular elements 59, 510, 511, 512 accommodate respective
arms of two inverted U-shaped portions 513, 514. The second
linkages 51, 52 are joined i) in their pivot connections with
the rear and front support crossbars 4, 5 via sleeve portions
515, 516 and ii) in the inverted U-shaped portions 513, 514
at the ends of which they make slidably moveable pivot
connections 517, 518, 519, 520.
When the separation between support crossbars 4, 5 varies,
the elongate members 53, 55 of second linkage .51 and the
elongate members 54, 56 of second linkage 52 pivot relative
to each other at respective crossover pivot connections 57,
58 (structurally, elongate members 53 and 54 are the arms of
one U-shaped rod whose central section extends through sleeve
portion 515, and elongate members 55 and 56 are the arms of
another U-shaped rod whose central section extends through
sleeve portion 516). The sliding movement of the connections
517, 518, 519, 520 is accomplished by the arms of inverted U-
shaped portions 513, 514 moving in the tubular elements 59,
510, 511, 512. Thus, as the two support crossbars 4, 5 move
towards each other, the slidably moveable pivot connections
517, 518, 519 520 permit relative pivotal motion between the
"U" portions and the elongate members. Hence, the slidably
moveable pivot connections 517, 518, 519, 520 move down so
that the middle sections of the U-shaped portions 513, 514
approach or meet the support crossbars 4, 5.
The sixth embodiment of the spectacle frames.shown in Fig 6
provides further structural rigidity whilst allowing
controlled relative movement of the front and rear lenses of
the left and right lens pairs. Optionally, the first
linkages 2, 3 may be omitted, as the central assembly formed
by the second linkages 51, 52 can provide sufficient rigidity

WO 2006/117544 PCT/GB2006/001597
14
on its own to maintain the lenses in their appropriate
relative positions.
In addition, the tubular elements 59, 510, 511, 512 can be
used to support the lenses. When a user wears the spectacles
the U-shaped portions 513, 514 bridge the user's nose.
Fig 7 shows a front sectional elevation of a seventh
embodiment that is a variant of the first embodiment. The
seventh embodiment allows the spacing between the lens pairs
to be altered to accommodate for eye spacing of different
users by having a stiff central pivot 61 in support crossbars
4, 5. However, by angling crossbars 4, 5 at pivot 61,
linkages 2 and 3 adopt different planes of residence, which
gives further stability to the lenses in the vertical plane.
Fig 8a shows an eighth embodiment of the invention in a
closed position. This embodiment allows the independent
relative movement of the lenses of the pairs.
The frame 1 has a first front support bar 71 and a second
front support bar 72 that replace the front support crossbar
in the first embodiment. Moreover, the first and second
elongate members 73, 74 of the first linkage 2 are of
different lengths and are pivotally moveable at connections
75, 76 which are offset so that they do not face each other
across the gap between the respective pair.
Fig 8b shows the eighth embodiment in the open position. The
effect is similar to that achieved by the sliding of the
pivot connection 41 in the fifth embodiment, i.e. the angle
between the optical axes of the lenses is varied, although.,
the angular variation is now in a different plane and is
achieved by a different mechanism. The other of the first
linkages 3 is a mirror image of the first linkage 2. Minor

WO 2006/117544 PCT/GB2006/001597
15
adjustments to the geometry of the linkages allow the angle
between the optical axes to change as a function of the
separation within each lens pair. Thus, the frame 1 allows
the controlled independent relative movement of each lens
pair relative to the other lens pair. Of course, if each
connection was exactly opposite its corresponding connection
on the facing crossbar, independent motion of the two
linkages would be achieved, while the lenses of each pair
remained parallel.
7A ninth embodiment of the invention is shown in Figs 9a and
9b. By connecting the two first linkages 2, 3 cooperative
convergence of the two optical axes is achieved.
The frame 1 has a first linkage 2 that is connected between a
first front support bar 71 and a first rear support bar 81
and the other first linkage 3 is connected between a second
front support bar 72 and a second rear support bar 82. The
first and second rear bars 81, 82 are fixed to a third rear
bar 83 by pivot connections 84, 89. The arrangement of the
connections 9, 11, 10, 12 is the same as the first
embodiment. However, the first elongate member 6 of the
first linkage 2 and the second elongate member 8 6 of the
other first linkage 3 extend beyond the pivot connections 9,
87 to meet at crossover pivot connection 88.
Fig 9a shows the frame 1 in the closed position where the
respective axes 90, 91 of the lens pairs are parallel. As
the front bars 71, 72 are separated from the rear bars 81,
82, the rear bars 81, 82 move about pivot connections 84, 89
on the third bar 83.. Thus the two first linkages 2, 3 move
pivotally relative to each other about connections 84, 88, 89
so that the axes 90, 91 converge at a point in front of the
user as shown in Fig 9b. However within the pairs of lenses,

WO 2006/117544 PCT/GB2006/001597
16
the front and back lenses remain aligned and parallel and the
inter-lens spacing is adjusted by an identical amount.
Figs 10a and 10b show a tenth embodiment of the invention
providing an alternative method of cooperatively converging
the axes of the lens pairs. Whereas crossover pivot
connection 88 between elongate members of adjacent linkages
faces away from the user in the ninth embodiment, the
corresponding connection 97 faces towards the user in the
tenth embodiment. Furthermore, the front bars 71, 72 and the
rear bars 81, 82 are connected by cross braces 92. The first
brace 93 of cross braces 92 is connected to the pivot
connection 9 on the first front bar 71, and to the pivot
connection 94 on the second rear bar 82. The second brace 95
of cross braces 92 is connected to the pivot connection 11 on
the first rear bar 81 and to the pivot connection 96 on the
second front bar 72. The second elongate member 7 of the
first linkage 2 and the first elongate member 98 of the
second linkage 3 extend beyond the respective pivot
connections 94, 11 to meet at crossover pivot connection 97.
As the frame 1 moves from the closed position in Fig 10a to
the open position in Fig 10b, the angle between the axes 90,
91 changes such that they converge to a point in front of the
user. Furthermore, as the separation within the lens pairs
increases, the angle between braces 95, 93 changes, reducing
the distance between the pivot connections on the front bars
9 and 96 (and between the connections on the rear bars 11 and
94 to a lesser extent) and thus the distance between the two
pairs of lenses. This reduction of the distance between the
lenses is advantageous, as it allows the axes 90, 91 to
remain centred on the user's eyes.

WO 2006/117544 PCT/GB2006/001597
17
Figs 11a, 11b and 11c are schematic front, side and cross-
sectional views respectively of an eleventh embodiment in the
open position. The cross-section of Fig 11e is along line A-
A of Fig 11a.
This embodiment has two, side-by-side and joined together
linkages 51', 52' which have similarities with the joined
together second linkages 51, 52 of the sixth embodiment
described above in relation to Fig 6. Thus linkage 51' has a
first elongate member 53' with a lower front, slidably
moveable pivot connection 518' and linkage 52' has a first
elongate member 54' with a lower front, slidably moveable
pivot connection 519' . However, structural rigidity is
improved by forming the first elongate members 53' and 54' as
the opposing sides of a planar rectangular body 551, the body
having a central hole..
The structural rigidity is further improved by forming the
other elongate members of linkages 51', 52' as a unitary,
planar, central body 550 which penetrates the central hole of
rectangular body 551.
A pin 552 traverses central body 550 and the opposing sides
of rectangular body 551 to form the crossover pivot
connections of the two linkages.
Two inverted U-shaped portions 513', 514' perform effectively
the same functions as inverted U-shaped portions 513, 514 of
the sixth embodiment, cylindrical holes 512' (only one being
visible in the view of Fig 11b) in which the arms of the
inverted U-shaped portion 514' are slidable being formed in
front plate 5', and cylindrical holes 59' (only one being
visible in the view of Fig 11b) in which the arms of the
inverted U-shaped portion 513' are slidable being formed in
facing rear plate 4' . These holes correspond to tubular

WO 2006/117544 PCT/GB2006/001597
18
elements 59, 510, 511, 512 of the sixth embodiment. In Fig
11a, front plate 5' is omitted for clarity.
The lower front, slidably moveable pivot connections 518',
519' are formed by turning in the ends of the arms of the
inverted U-shaped portion 514' and engaging the ends with
corresponding recesses 560, 561 in rectangular body 551.
Likewise, lower rear, slidably moveable pivot connections
517' (only one being visible in the view of Fig 11c) are
formed to either side of central member 550 by turning in the
ends of the arms of the inverted U-shaped portion 513' and
engaging the ends with corresponding recesses in central
member 550. More particularly, central body 550 is I-shaped,
the recesses being formed in the ends of the lower portion
(hidden behind rectangular body 551, but indicated with
dotted lines in Fig 11a) of the I.
Respective upper, front pivot connections 553 of the linkages
51', 52' are formed by pin 555 which extends across the upper
portion of the I-shaped central body 550 to fit into
corresponding recesses in front plate 5'. Similarly,
respective upper, rear pivot connections 554 (only one being
visible in the view of Fig 11c) of the linkages 51', 52' are
formed by pin 558 which extends across the top side of
rectangular body 551 to fit into corresponding recesses in
rear plate 4' .
Fig 11d is a schematic side view of the eleventh embodiment
in the closed position. Front plate 5' and rear plate 4'
have tapered central portions (shown in the cross-sectional
view of Fig 11c) which accommodate central body 550 and
rectangular body 551 in the closed position.
Fig.11e is a further front view of the eleventh embodiment in
the closed position in use on a pair of spectacles.

WO 2006/117544 PCT/GB2006/001597
19
Conveniently, the rear 4' and front 5' plates in which the
arms of the inverted U-shaped portions 513', 5.14' are
slidable being adapted to form the bridge of the spectacles.
The viewing device of the present invention is particularly
adapted for adjusting the nested lenses described in WO
03/083556. Thus the optically aligned lenses of the present
invention may provide a lens structure in which:
• The or each pair of optically aligned lenses arc nested
such that the gap between the facing surfaces of the
lenses is a cleft of variable width, one of the lenses
having a divergent refracting surface and the other
having.a convergent refracting surface.
• The maximum width of the cleft may be less than the
focal length of the refracting surface of the first of
the lenses through which viewed light travels, and
preferably the maximum width of the cleft is less than
one half or one quarter of this focal length.
• One of the lenses may have a concave surface within
which nests a convex surface of the other of the lenses,
the cleft being created between said surfaces.
• The lenses may be arranged so that viewed light travels
through the concave and convex surfaces in that order.
• The facing surfaces of the lenses may have complementary
shapes so that when they are brought into precise
juxtaposition, the cleft between them is virtually
eliminated.
• The refracting surfaces may be of substantially equal
and opposite focusing power.

WO 2006/117544 PCT/GB2006/001597
20
• Both of the outer lens surfaces may be substantially
planar.

21
Claims
1. A viewing device comprising:
a pair of optically aligned lenses which are moveable
relative to each other to vary the gap between facing
surfaces of the lenses, and
a linkage for controlling the relative motion, the
Linkage including first and second elongate members which
crossover each other at a crossover pivot connection, the
first elongate member extending between a slidably moveable
pivot connection which is arranged to transmit relative
motion to the first lens of the pair and a pivot connection
which is arranged to transmit relative motion to the second
lens of the pair, and the second elongate member extending
between a slidably moveable pivot connection which is
arranged to transmit relative motion to the second lens and a
pivot connection which is arranged to transmit relative
motion to the first lens;
wherein the connections are arranged such that the
Linkage can open and close in a concertina- or scissor-like
fashion.
2. A viewing device according to claim 1, wherein the
position of the crossover connection is,moveable along at
least one of the elongate members to tilt one of the Lenses
relative to the other lens.
3. A viewing device according to claim 1 or 2, further
comprising a second linkage for controlling the relative
motion, the crossed elongate members of the second linkage
residing in a different plane from the crossed elongate
members of the first linkage.

22
4. A viewing device according to claim 3, wherein the plane
of residence of the crossed elongate members of the second
Linkage is substantially orthogonal to the plane of residence
of the crossed elongate members of the first linkage.
5. A viewing device according to any one of the previous
claims, further comprising an actuator mechanism for moving
the lenses relative to each other.
6. A viewing device according to any one of the previous
claims further comprising a second pair of optically aligned
and relatively moveable lenses.
7. A viewing device according to claim 6, wherein the second
pair of lenses are spaced from the first pair of lenses such
that a user can look through one pair of lenses with one eye
while looking through the other pair of lenses with the other
eye .
8. A viewing device according to claim 6 or 7, wherein each
pair of optically aligned lenses has a respective linkage for
controlling the relative motion.
9. A viewing device according to claim 8, wherein the
respective linkages are openable and closable independently
of each other.
10. A viewing device according to claim 9, wherein the
respective linkages are cooperatively arranged such that
opening or closing one of the linkages results in
corresponding movement from the other of the linkages.
11. A viewing device according to claim 10, wherein the
cooperative arrangement varies the angle between the
respective axes of the pairs of lenses as the linkages open
or close.

23
12. A viewing device according to any one of claims 6 to 11,
further comprising alteration means for altering the spacing
between the pairs of lenses.
13. The viewing device of any one of the previous claims
which is a pair of spectacles.
14. The viewing device of any one of claims 1 t.o 12 which is
a hand-held optical instrument, such as a pair of binoculars.
15. The viewing device of any one of claims 1 to 12 which is
a laboratory optical instrument, such as a microscope and
preferably a binocular microscope.

A viewing device comprises: a pair of optically aligned lenses which are
moveable relative to each other to vary the gap between facing surfaces of
the lenses, and a linkage for controlling the relative motion. The linkage
includes first and second elongate members which crossover each other at a
crossover pivot connection. The first elongate member extends between a
slidably moveable pivot connection which is arranged to transmit relative
motion to the first lens of the pair and a pivot connection which is arranged
to transmit relative motion to the second lens of the pair. The second
elongate member extends between a slidably moveable pivot connection
which is arranged to transmit relative motion to the second lens and a pivot
connection which is arranged to transmit relative motion to the first lens.
The connections are arranged such that the linkage can open and close in a
concertina- or scissor-like fashion.