Note: Descriptions are shown in the official language in which they were submitted.
CA 02323672 2000-10-17
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A METHOD AND APPARATUS FOR AUTOMATIC
ATTACHMENT OF A FINISHING BLOCK TO A LENS
FIELD OF THE INVENTION
This invention relates to a method and apparatus for automatic attachment
of a finishing block to a lens, such as an ophthalmic lens.
BACKGROUND OF THE INVENTION
It is known in lens production that a lens that has been properly cut, ground,
polished and coated, proceeds to a finishing operation of edging where the
periphery of the lens is cut in an edging device, to conform a frame in which
it is to
be held. To properly position the lens within the edging device, a finishing
block is
attached to the lens at a location and orientation defined by reference
features on
o the lens, which is used for the fixation of the lens within the edging
device, keeping
the lens orientation as required.
In the past, finishing blocks were attached to lenses manually. However,
even for experienced and highly skilled lens makers, it was often difficult to
manually attach the block to the lens in proper registration with the
reference
~s features.
An apparatus for ophthalmic lens blocking is known in the art, wherein an
operator observing through a view port first positions the lens within the
apparatus
by manual aligning the reference features on the lens with an alignment
pattern in
the apparatus and, once the lens is properly positioned, the finishing block
is
2o attached to the lens at a location defined relative to the reference
features.
Clearly, visual comparing the reference features on a lens with the alignment
pattern in the apparatus and accurate manual positioning of the lens is a time
consuming process, which requires an experienced operator for proper lens
alignment. As any manual process, it may suffer from lens positioning
' CA 02323672 2000-10-17
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inaccuracies, which may subsequently cause incorrect use of spectacles. This
is
particularly critical for spectacles with progressive and bifocal ophthalmic
lenses.
Also, the necessity of visual comparison of the reference features on a lens
with the
alignment pattern makes the known apparatus non-suitable for use with lenses
where the reference features are invisible.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a
method for automatically determining a location and orientation of a finishing
block to be attached to a lens having either visible reference features or
invisible
o reference features associated with a predetermined or prescribed value of at
least
one optical characteristic of the lens, with respect to which reference
features said
location and orientation are in a predetermined geometric relationship. The
method
comprises the following steps:
(One) obtaining a graphic image of said lens if the reference features are
s distinguishable when imaged, or obtaining a mapping image of the lens
based on which said optical characteristic of the lens may be calculated, if
the reference features are non-distinguishable when imaged;
(Two) computer processing said graphic and/or said mapping image to derive
therefrom the coordinates of the reference features; and
20 (Three) determining said location and orientation of the finishing block
based
on their said predetermined geometric relationship with respect to said
reference features, using said coordinates of the reference features.
Thus, in accordance with the method of the present invention, graphic
images and optical characteristics of lenses are analyzed by a computer for
finding
2s the position of their reference features and for automatically attaching a
finishing
block to a lens in such a location and orientation relative to the reference
features,
as prescribed by the lens manufacturer or predetermined otherwise.
In the simplest case, the reference features may be in the form of pre-printed
marks indicating the location and orientation at which the finishing block is
to be
' CA 02323672 2000-10-17
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attached. For example, for a single vision lens, such marks may be in the
optical
center of the lens and along its cylinder axis. Similarly, the finishing block
mark
may be in the optical center of a bifocal lens with the orientation of the
finishing
block being defined relative to the position of the bifocal segment of the
lens. In a
s progressive lens, the finishing block mark is known to be in the form of a
printed
fitting cross.
Alternatively, the reference features may be in the form of other marks or
areas distinguishable when imaged, that are specific for different kinds of
lenses
and with respect to which the location and orientation of the finishing block
is
io prescribed. For example, in a bifocal lens, such a specific area is its
bifocal
segment, and in a progressive lens, hidden marks can be used.
If, however, a lens to which the finishing block is to be attached, has no
printed or other reference features that may be graphically imaged, mapping of
at
least one optical characteristic of the lens may be performed to derive the
reference
15 features therefrom, provided that the location and orientation of the
finishing block
relative to these signs have been prescribed. For example, for a single vision
lens,
optical power mapping enables determination of the optical center of the lens
where its prism power value is zero and of the orientation of the cylinder
axis
passing therethrough. In a single vision lens with spherical, cylindrical and
2o prescribed prism powers, the reference features may be a location where the
prism
power has a prescribed value and where the cylinder and prism axes have a
prescribed mutual angular orientation. In a progressive lens which has no
printed
reference features, spherical and cylinder power maps may be obtained, whereby
its
optical center may be determined and the precise positions of the far and near
25 vision points may be established according to the prescribed values and
prescribed
far and near inter-pupillary distances. All this will constitute the reference
features
of the progressive lens, based on which the location and orientation of the
finishing
block to be attached to the lens can be calculated, in accordance with an
original
prescription.
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According to another aspect of the present invention, there is provided an
apparatus for automatically determining a location and orientation of a
finishing
block to be attached to a lens having either visible reference features or
invisible
reference features associated with at least one optical characteristic of the
lens, with
respect to which reference features said location and orientation are in a
predetermined geometric relationship. The apparatus comprises:
- a support for carrying the lens;
- a reference features finder for obtaining a graphic image of said lens if
the
reference features are distinguishable when imaged, and/or obtaining a
io mapping image based on which said optical characteristic of the lens may be
calculated, if the reference features are non-distinguishable when imaged,
and
- a computer for processing the graphic and/or mapping image of the lens, to
derive therefrom the coordinates of the reference features and to determine
~s said location and orientation of the finishing block based on their said
predetermined geometrical relationship with the reference features and using
said coordinates of the reference features.
The reference features finder may comprise one or both of the imaging and
mapping branches. In the latter case, these branches may be arranged in one
2o common set-up to graphically image or map the lens along one optical axis
in either
imaging or mapping mode of the apparatus, or rather these branches may be in
the
form of two separate imaging and mapping stations of the apparatus.
The imaging branch of the reference features finder may be any appropriate
optics capable of providing graphic images in which printed or hidden
reference
25 features of a processed lens are clearly distinguishable. Such optics may
be based
on dark field or bright field lens illumination or it may be in the form of
shadow
imaging optics.
The mapping branch of the reference features finder may be any optics
capable of mapping at least one of the following optical characteristics of a
lens:
3o spherical power, cylindrical power, cylinder axis, prism power, prism axis,
coma,
' CA 02323672 2000-10-17
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and any local lens characteristic. Maps obtained by such optics may also
provide
information regarding geometrical lens layout, bifocal segment layout,
location of
far and near vision points, etc.
It should be noted that the use of imaging and mapping of lenses is well
s known for the purposes of optical shop testing. However, to the best of the
inventor's knowledge, none of the known techniques has ever been used for
automatic determination of the location and orientation of a finishing block
for its
automatic attachment to the lens, based on the automatic determination of
visible or
invisible reference features on the lenses.
io In view of the above, it is clear that the method and apparatus of the
present
invention cannot only serve for the automatic attachment of a finishing block
to a
lens but also may provide conventional mapping and lensmeter functions, with
the
possibility of printing out lenses' graphic images and optical maps. The
method and
apparatus of the present invention may also be used for determining
geometrical
is centers of lenses, finding lens edges and automatic lens-to-frame fitting.
The apparatus of the present invention may be compact and portable and it
can be placed on a table, workbench or other support and operated by a user
while
sitting. The user does not need to be particularly experienced.
The present invention is particularly useful for automated orienting and
2o attaching a finishing block to a lens, the periphery of which needs to be
cut and
finished in an edging device. It should be understood, however, that the
invention is
in no way limited to this particular application and can also be used to
attach a
holder or a surface block to a lens blank that is to be ground and polished.
2s BRIEF DESCRIPTION OF THE DRAWINGS
In order to understand the invention and to see how it may be carried out in
practice, a preferred embodiment will now be described, by way of non-limiting
example only, with reference to the accompanying drawings, in which:
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Fig. 1 is a schematic illustration of an apparatus for automatic attachment of
a finishing block to a lens, according to the present invention;
Fig. 2 is a schematic illustration of an apparatus for automatic attachment of
a finishing block to a lens, according to one particular embodiment of the
present
invention;
Figs. 3, 4 and 5 are graphic images of lenses obtained by an apparatus of the
kind shown in Fig. 2;
Fig. 6 is a schematic illustration of an apparatus for automatic attachment of
a finishing block to a lens, according to another particular embodiment of the
o present invention;
Figs. 7 and 8 are mapping images of lenses obtained by an apparatus of the
kind shown in Fig. 6;
Figs. 9,10 and 11 are optical power maps of lenses obtained by an apparatus
of the kind shown in Fig. 6;
Is Fig. 12 is a schematic illustration of an apparatus for automatic
attachment
of a finishing block to a lens, according to a further particular embodiment
of the
present invention;
Fig. 13A is a schematic illustration of a blocking unit of the apparatus
shown in Fig. 1;
2o Fig. 13B is a schematic illustration of an alternative embodiment of the
blocking unit shown in Fig. 13A;
Figs. 14A and 14B are schematic illustrations of a finishing block
manipulator of the blocking unit shown in Fig. 13A; and
Figs. 15A and 15B are schematic illustrations of an apparatus for automatic
2s attachment of a finishing block to a lens, according to a still further
particular
embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Fig. 1 schematically shows an apparatus for determining a location and
orientation of a finishing block 1 to be attached to a lens A, and for the
attachment
' CA 02323672 2000-10-17
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of the finishing block 1 to the lens A, which lens has either visible
reference
features or invisible reference features associated with a predetermined or
prescribed value of at least one optical characteristic of the lens A. The
location
and orientation at which the finishing block 1 should be attached to the lens
A are
s in a prescribed or otherwise predetermined geometrical relationship with the
reference features.
As seen in Fig. 1, the apparatus has an optical axis O and it generally
comprises
a lens support plate 3 with a clamping device 4 for clamping the lens A, the
o lens support plate being movable in Y direction so as to bring the lens A
into
at least two working positions, of which one is an imaging position at the
optical axis O of the apparatus and the other one is a non-imaging position
remote from the optical axis O;
- a reference features finder designated generally as 5, for processing the
lens
15 A in its obtaining a graphic image of the lens A if the reference features
are
distinguishable when imaged and/or by obtaining a mapping image of the
lens based on which the above-mentioned optical characteristic of the lens
may be calculated, if the reference features are non-distinguishable when
imaged; and
20 - a blocking unit 10 with the finishing block in the form of a plastic or
metallic block with an adhesive pad 13 detachably attached to its end, and a
finishing block displacement mechanism generally designated as 14 capable
of moving the blocking unit 10 in X, Z and 8 directions to bring the
finishing block to the lens A at its non-imaging position, at a location and
25 orientation that are prescribed relative to the reference features of the
lens A.
The apparatus shown in Fig. 1 also comprises a main frame 12 carrying the
above components of the apparatus and it may have a housing to accommodate the
apparatus therein.
To enable the movement of the lens support plate 3 in the Y-direction, it is
3o provided with a driving motor 15 with a linear actuator. The finishing
block
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displacement mechanism 14 comprises driving motors 16 and 17 with linear
actuators and a driving motor 18 with a rotating actuator for respective
linear and
rotational displacement of the blocking unit 10.
The reference features finder 5 of the apparatus shown in Fig. 1 includes
s one of or both a lens imaging optics and a lens mapping optics, whose
components,
which are not shown specifically in Fig. 1, are located along the optical axis
O of
the apparatus on one or two sides of the lens support plate 3. The reference
features finders further includes an image acquisition device 20 to capture
images
from the lens imaging optics and/or lens mapping optics.
io The lens imaging optics may be any system capable of providing a high
quality graphic image of a lens with the reference features in the form of
printed or
hidden marks. For example, it may be optics with dark field or bright field
lens
illumination or it may be a shadow imaging optics.
The lens mapping optics may be any optics capable of providing a map of
~5 either of spherical power, cylindrical power, cylinder axis, prism power,
prism axis,
coma, or any local lens characteristic, from which the reference features may
be
derived. Such reference features may be coordinates of the optical center of a
lens,
orientation of its cylinder axis, coordinates of far and near vision points,
etc. The
lens mapping optics may be built in the form of shearing interferometer, moire
2o interferometer (see e.g. Takasaki, H., "Moire Topography," Appl. Opt., 9,
1467
(1970); Appl. Opt., 12, 845 (1973)), Shack - Hartmann test optical setup (see
e.g.
Shack R.B. & B.C. Platt "Production and Use of a Lenticular Hartmann Screen",
J.
Opt. Soc. Am., 61, 656 (1971)), or rather in the form of optical setup
disclosed in
co-pending Israel Patent Application No. 130465 for Grid Analysis Measuring &
2s Mapping (GAMMA) method.
The image acquisition device 20 is equipped with an imaging camera lens
22 that may be a CCD, TV or still camera, CID or CMOS camera, having an
optical axis coinciding with the optical axis O of the apparatus, for
projecting an
image of the processed lens A obtained by the lens imaging optics and/or lens
3o mapping optics on a light-detecting element of the imaging camera (CCD, CID
or
' CA 02323672 2000-10-17
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CMOS chip). The camera lens 22 is preferably built in the form of a
telecentric or
telescopic type camera lens with a high depth of focus providing the imaging
of the
front surface of the lens A in practically parallel rays. However, other types
of
camera lenses may be used.
The apparatus shown in Fig. 1 further comprises a computer 24 with a frame
grabber 25 via which it is connected to the output of the image acquisition
device
20, I/O board 26, a display 27 and keyboard 28 through which the user may
input in
the computer identification and prescribed information regarding the lens A to
be
processed and selectively control various functions of the apparatus. The
computer
0 24 has appropriate software for:
- controlling the overall performance of the apparatus;
- processing graphic and mapping images obtained from the lens imaging and
lens mapping optics for determining exact coordinates of the reference
features of the lens A as well as its form, dimensions, orientation and any
is other needed information concerning the lens;
- determining, based on the pre-determined geometrical relationship with
respect to the reference features and using the coordinates of the reference
features, coordinates of the location and orientation at which the finishing
block 1 is to be attached to the lens A; and
20 - manipulating the support plate 3 and the blocking unit 10 to attach the
finishing block 1 to the lens A at the location and orientation thereof
determined by the computer.
When the apparatus is designed for lens-to-frame fitting, the computer 24 is
preferably provided with an interface enabling its receiving data from a frame
25 tracer device, to further process both the lens graphic or mapping image
and the
data from the frame tracer, to enable automatic frame fitting into lens
patterns in
any prescribed manner.
Figs. 2, 6 and 12 illustrate different embodiments of the apparatus generally
illustrated in Fig. 1, where particular designs of reference features finder
are used
3o for processing lenses having different kinds of the reference features.
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In the apparatus shown in Fig. 2, the reference features finder 5 includes a
lens imaging optics (not designated) and it is intended to process lenses in
which
the reference features has a geometrically distinguishable form. Thus, the
reference
features may be in the form of printed marks indicating the location and
orientation
s at which the finishing block 1 should be attached to the lens A.
Alternatively, the
reference features may be in the form of other printed marks, or hidden marks
in
progressive lenses, or bifocal segment in bifocal lenses, relative to which
the
location and orientation at which the finishing block 1 is to be attached to
the lens
is prescribed or predetermined otherwise.
io In the apparatus shown in Fig. 2, the lens imaging optics is in the form of
a
self-compensating imaging shadowgraphy optical setup as described in EP 0 856
728, incorporated herein by reference. The lens imaging optics has an
illumination
means in the form of a point source of radiation 31 providing suitable
preferably
wide divergence of radiation illuminating the lens A along the optical axis O.
It is
~5 desirable that the point source of radiation 31 has minimal possible
dimensions,
whereby high resolution of measurements may be obtained. For example, the
point
source 31 may be in the form of a diode laser 32 with a focusing optics 33 and
pinhole 34. The lens imaging optics further comprises a beam-deflecting
element
36, a collimating lens 38 and a projecting screen 40. The beam-deflecting
element
20 36 may be in the form of an ordinary beam-sputter. The projecting screen 40
may
be in the form of a diffusing or luminescent or phosphorescent surface or any
kind
of back-scattering surface. The camera lens 22 is in optical coincidence with
the
radiation source 31, i.e. they are optically equidistant from the optical
element A.
When the lens imaging optics is operated, the collimating lens 38 collimates
25 the radiation beam from the radiation source 31 and, in cooperation with
the
camera lens 22, provides the imaging of the lens A in parallel rays. The
processed
lens A illuminated by the collimated incident radiation forms on the
projecting
screen 40 a shadow pattern. Distribution of brightness in the shadow pattern
depends on the optical power of the lens A and on local power and transparency
3o deviations produced by the reference features of the lens. Since the camera
lens 22
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is in the optical coincidence with the point source of radiation 31, the rays
forming
the image of the lens A propagate along the same optical path as the incident
rays
illuminating the lens A. As a result, relative dimensions of the reference
features
and their disposition relative to the edges of the lens A remain undistorted
in the
image of the shadow pattern obtained by the image acquisition device 20, i.e.
they
are exactly the same as in the lens surface. This enables the computer 24 to
calculate the coordinates of the reference features 24 and to subsequently
determine
the location and orientation at which the finishing block 1 is to be attached
to the
lens A. Examples of images of the shadow patterns from a bifocal lens and from
a
o progressive lens with printed and hidden marks on their surfaces are shown
on
Figs. 3, 4 and 5 respectively.
Fig. 6 illustrates another embodiment of the apparatus of the present
invention where the reference features finder 5 includes a lens mapping optics
(not
designated) for measuring and mapping optical power of lenses, and it is
intended
i5 to process lenses in which the reference features are not geometrically
distinguishable when imaged such as explained above with reference to Fig. 2.
In
such lenses and depending on their type, the reference features which may be
coordinates of the optical center of a lens, orientation of its cylinder axis,
coordinates of far and near vision points, etc, are to be derived from the
mapping
2o images or optical power maps, based on which the location and orientation
are to
be determined, at which the finishing block 1 should be attached to the lens.
In the apparatus shown in Fig. 6, the lens mapping optics comprises a
diffusive light source 52 stationary mounted on the main frame 12, and a
contrast
mapping pattern 54 on a pattern supporting plate 56. The diffusive light
source 52
25 may be of any type capable of giving a relatively uniform illumination of
the
processed lens A from below, and it is preferably in the form of back light
illuminating LED matrix with a diffusive element. The mapping pattern 54 may
be
printed or engraved on a substrate made of a transparent or translucent
material
such as mineral glass, milky glass, ground glass or paper. The pattern may be
in the
3o form of number of regularly ordered points, lines or circles of known
dimensions
CA 02323672 2000-10-17
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and at known mutual dispositions, concentric circular pattern with radial
lines,
staggered arranged squares, regular grid with highlighted origin lines or the
like.
The mapping pattern 54 with its supporting plate 56 are moveably mounted
on a slider 58 with a linear actuator 59 driven by a motor 60, providing their
s movement up and down along the axis Z. This enables the apparatus to process
lenses in a wide range of optical powers, so that the higher the power of a
lens, the
less the distance thereto from the mapping pattern 54.
In the apparatus shown in Fig. 6, the camera lens 22 has a narrow, preferably
pin-hole, entrance pupil (not shown).
io When the lens mapping optics of the apparatus shown in Fig. 6 is operated,
the radiation from the illuminator 52 illuminating the pattern 54 and being
scattered
thereby, passes through the lens A towards the camera lens 22. Though each
point
of the pattern 54 is illuminated by a wide range of light rays from the
diffusive
illuminator 52, only those that are focused at the entrance pupil of the
camera lens
is 22 will pass therethrough to the image acquisition device 20, producing
thereby an
image of each point of at least a portion of the pattern and, consequently, an
optical
power map of the lens A. Ray tracing in this case is mathematically equivalent
to
the ray tracing of the Shack - Hartmann method known to those skilled in the
art,
and the mathematics developed for this method may be applied to method of
power
2o measurement providing results similar to those of the Shack - Hartmann
method.
Examples of mapping images recorded by a CCD camera in testing of ophthalmic
lenses using lens mapping optics of the kind described above are shown in
Figs. 7
and 8. These Figures represent images of a pattern, which is a regular squared
grid,
recorded through a bifocal lens with the base spherical and cylindrical power
and a
2s segment additional power (Fig. 7) and recorded through a progressive lens
(Fig. 8).
The computer 24 is provided in the apparatus shown in Fig. 6, with a
dedicated software to process the mapping pattern image obtained as described
above, to identify the pattern control points and/or lines and to compare
their
measured coordinates and/or form with those of a pattern image produced
without
3o the lens A and stored in the computer's memory. The measured deformation of
the
CA 02323672 2000-10-17
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pattern image caused by the lens A enables the calculation therefrom of the
lens's
refractive properties. Spherical power results in the magnification of the
pattern and
cylinder power results in its deformation with the direction of the
deformation
indicating the orientation of the cylinder axis. Prismatic power results in
parallel
displacement of points of the pattern image relatively to their position
stored in the
computer memory. Direction of the displacement indicates the prism axis
orientation. Prismatic power is to be calculated by means of the following
formula:
Z=100 ~ r-R
B
io where r and R are radial coordinates of a ray impinging the lens A and the
pattern
54 respectively, B is a distance between the lens A and the pattern.
For more accurate lens power measuring and mapping, images of the
mapping pattern are to be taken in two different positions thereof, and their
analysis
is to be performed by the comparison of the measured coordinates of the
control
points of the two pattern images with those of the corresponding pattern
images
obtained without the lens A and stored in the computer memory. Thereby, there
may be calculated coordinates of any reference points on the processed lens A
having prescribed optical characteristics, e.g. prescribed local power, as
well as the
mutual orientation of its local cylinder and prism axes, and consequently, the
location and orientation at which the finishing block 1 should be attached to
the
lens A.
The output of the apparatus working in the lens power mapping mode may
be presented in the form of topographical spherical and cylindrical power
maps, as
shown in Figs. 9 to 11. Figs. 9 and 10 show respective spherical and
cylindrical
power maps of an ophthalmic progressive lens, and Fig. 11 shows a prism power
map of a single vision lens. More details of the lens mapping optics of the
above
kind may be found in the counterpart Israeli application No. 130465
incorporated
herein by reference.
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Fig. 12 illustrates an apparatus according to a further particular embodiment
of the present invention, where the reference features finder includes both
the lens
imaging branch as in the embodiment of Fig. 2 and the lens mapping branch as
in
the embodiment of Fig. 6. The lens imaging branch allows the determination of
s exact geometrical position of the lens A and its reference features that are
in the
form of printed or hidden marks if the lens A is a progressive lens, bifocal
segment
if the lens A is a bifocal lens, and a geometrical center if the lens A is a
single
vision lens. It also enable the determination of the shape and dimensions of
the
lens A. The lens mapping branch allows for determining optical features of the
lens
io such as spherical, cylindrical and prism power at every point of the lens,
cylinder
and prism axis directions and exact coordinates of the optical center of the
lens,
which all may constitute the lens's reference features. The combination of the
lens
graphical imaging and lens mapping branches in one apparatus as shown in Fig.
12
enables the determination of the reference features and, consequently, of the
i5 coordinates of the location and orientation at which the finishing block 1
should be
attached to the lens A, for all possible lens types.
In the apparatus of the Fig. 12, the optical components of the reference
features finder 5 that are located above the lens A are basically as in the
embodiment of Fig. 2, and those located below the lens A are basically as in
the
2o embodiment of Fig. 6 with the difference that in addition to the mapping
pattern 54
disposed below the lens A, the apparatus includes a diffusing or back
scattering
screen 70 having a non-working position 70' remote from the optical axis O and
a
working position 70" on the optical axis O above the mapping pattern 54. To
this
end, the screen 70 is mounted on a slider 72 driven by a motor 74 enabling the
25 displacement of the screen 70 in the Y-direction.
With reference to Figs. 13A, 13B, 14A and 14B, there will be described in
more details the blocking unit 10 carrying the finishing block 1, and
mechanisms
providing relative displacement between the blocking unit 10 and the lens
support
plate 3, used in the embodiments of the apparatus of the present invention,
3o described above.
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Fig. 13A shows the lens support plate 3 movably mounted on sliders 76
whose linear actuator 78 is driven by the motor 15, providing the movement of
the
lens support plate 3 along the axis Y Fig. 13A further shows the finishing
block
displacement mechanism 14 comprising a slider 80 carrying the blocking unit 10
and connected with a linear actuator 82 driven by the motor 17, to provide the
movement of the blocking unit 10 along the axis Z. The finishing block
displacement mechanism 14 also comprises a slider 84 carrying the slider 80
with
its linear actuator 82 and the motor 17, and connected with a linear actuator
86
driven by the motor 16 to provide the movement of the finishing block 10 along
the
io axis X. The finishing block displacement mechanism 14 further comprises the
motor 18 accommodated within the blocking unit 10 and having a shaft (not
seen)
on which the finishing block 1 is detachably attached by a spring coupling 87,
to
provide the rotational movement of the finishing block 1 in the 0-direction
around
the axis Z.
i5 As seen in Figs. 14A and 14B, the blocking unit 10 is further provided with
a finishing block manipulator 88 enabling the rotation of the blocking unit 10
between its vertical working position in which the pad 13 faces downwardly
towards the lens A to which the finishing block 1 is to be attached, and a non-
working upper position in which the pad 13 faces the operator, thereby
enabling the
2o finishing block manual loading in a position convenient to the operator. To
this end,
the manipulator 88 includes an axle 90 on which the blocking unit 10 is
fixedly
mounted, a roll 92 attached to the blocking unit 10 and a wedge 94 mounted on
the
slide 84 or stationary fixed on the apparatus main frame (not seen in Figs.
14A and
14B). Such a construction provides for the rotation of the finishing block
25 manipulator 88 for 80° - 100° around the axle 90 upon the
slide 80 moving along
the axis Z, and fixation of the manipulator 88 in the upper position as it is
shown on
Fig. 14B. This non-working position should normally be the blocking unit's
starting
position when it is loaded with the finishing block and it should also be
taken by
the blocking unit 10 after the finishing block has been attached to the lens
A.
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It should be mentioned regarding the displacement mechanisms that they
may have any appropriate design different from that described above with
reference
to Figs. 13A, 14A and 14B, providing the relative linear and rotational
displacement between the lens support plate 3 and the finishing block 1. For
example, as shown in Fig. 13B, the lens support plate 3 may be build in the
form of
an X-Y table 100 provided with linear actuators and motors enabling its
displacement in X and Y directions, and with the mechanism enabling the
rotation
of the lens A in 8 direction. In this case, the blocking unit 10 may be
displaceable
only in Z direction. Also, both the lens support plate and the finishing block
may
io have only linear displacement mechanisms, whilst the provision of their
relative
rotational displacement may be avoided by means of the registration of the
lens's
orientation and subsequent use of the registered data when a finishing
operation is
performed on the lens.
Also, the actuators and the motors used in providing the above
is displacements may be of any suitable kind. For example, the actuators 82,
86 and
96 may be built in the form of a timing belt, a rack-and-pinion, a screw-and-
nut
actuator, or the like. The motors 15, 16, 17 and 18 may be of any appropriate
kind
but, preferably, the motors 15, 16 and 18 responsible for the displacements in
X, Y
and A directions are stepped or servo motors, and the motor 17 is a DC motor.
2o The motors 15, 16, 17 and 18 are all connected to the computer 24 via the
interface board 26 and they are controlled by the computer to perform the
above
described displacements in their due time.
In operation, an initial state of the apparatus, according to the embodiments
described with reference to Figs. 1, 2, 6 and 12, has the lens support plate 3
and the
25 blocking unit 10 in their non-working positions. The non-working position
of the
lens support plate 3 is with its lens clamping device 4 open, and the non-
working
position of the blocking unit 10 is away from the optical axis O of the
apparatus.
For processing the lens A, the operator manually loads the finishing block 1
with
the adhesive pad 13 into the blocking unit 10 and places the lens A on the
support
3o plate 3, where it is fixed by the lens clamping device 4. The finishing
block 1 has a
' CA 02323672 2000-10-17
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horizontal reference line (not seen in the drawings) it is loaded by the
operator so
that the reference line is oriented in a pre-determined manner. The operator
further
inputs into the computer 24, via the keyboard 28, all necessary information
about
the lens to be processed. If the lens is to be edged, the information
regarding the
s frame in which it is to be mounted is also to be introduced in the computer.
This
can be accomplished by providing the computer, for example, with a job number
corresponding to a particular lens and particular frame shape. The computer 24
correlates the specified job number with the data regarding the frame stored
in
memory or gets the relevant information from a frame tracer or any other
external
io source. The computer memory is also loaded with the information regarding
the
location and orientation at which the finishing block is to be attached to the
lens,
relative to the reference features on the lens. The operator initiates the
apparatus
via the keyboard 28. The support plate 3 moves the lens A into its imaging
position
where its geometrical center is located in the proximity of the optical axis O
of the
I5 apparatus. Then the reference features finder 5 processes the lens A by
graphically
imaging the lens A if it is of the kind that its reference features are
distinguishable
when imaged, or by obtaining a mapping image of the lens A, if it is of the
kind
that its reference features are non-distinguishable when imaged. The graphic
image
of the lens and/or its mapping image are transferred via the frame grabber 25
to the
2o computer 24 which analyzes them according to the dedicated program to
determine
the reference features and the edges of the lens A, to compare the dimensions
of the
lens and the position of its reference features with the shape, dimensions and
the
central point position of the frame to fit the processed lens to the frame.
The
computer further uses this information to calculate the location at which the
25 finishing block 1 has to be attached to the processed lens A and the
angular
orientation of the finishing block 1.
The location of the finishing block and its orientation relative to the
reference features of the lens depend on the type of the lens A to which it is
to be
attached, and the manner of their determination depends on the kind of the
3o reference features that the lens has, as follows:
' CA 02323672 2000-10-17
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- for a single vision lens in which reference features are in the form of
three
marked points indicating the optical center of the lens and the orientation of
its cylinder axis, the location of the finishing block will preferably be at
the
central point of the lens with the finishing block's horizontal reference line
being parallel to a line passing through the marked points or at a prescribed
angle thereto; in this case , the apparatus should preferably be used with the
reference features finder in the form of the lens imaging optics as in Figs. 2
and 12;
- for a single vision lens in which no references signs are marked, the
to finishing block should be located at the optical center which is determined
by the apparatus in which the reference features finder is in the form of the
lens mapping optics as in Figs. 6 and 12, at a location on the lens where the
prism power has zero value or at a point having a prescribed disposition
relative to the optical center, and with the orientation of the finishing
block's
~5 horizontal reference line along the cylinder axis or at a prescribed angle
thereto;
- for a single vision lens without marked reference features and with
prescribed spherical, cylindrical and prism powers and prescribed angle
between the cylinder and prism axes, the apparatus should be used in which
2o the reference features finder is in the form of the lens mapping optics as
in
Figs. 6 and 12, for determining a location with the prism power of a
prescribed value and with a prescribed angle between the cylinder and prism
axes, with respect to which the location and orientation of the finishing
block is subsequently calculated in accordance with a prescription of lens
25 manufacture;
- for a bifocal lens where the bifocal segment is preferably used as the
reference features, the apparatus should preferably be used with the
reference features finder in the form of the lens imaging optics as in Figs. 2
and 12, to determine the exact position and orientation of the bifocal
3o segment, with respect to which the location and orientation of the
finishing
' CA 02323672 2000-10-17
-19-
block are subsequently calculated in accordance with a prescription of lens
manufacture;
- for a progressive lens in which the reference features are in the form of
printed fitting cross and central line, the apparatus should preferably be
used
with the reference features finder in the form of the lens imaging optics as
in
Figs. 2 and 12, and the location of the finishing block will be on the fitting
cross with the horizontal reference line of the finishing block being parallel
to the lens central line;
- for a progressive lens which has no printed reference features, hidden marks
o may be used as reference features, and the apparatus should preferably be
used with the reference features finder in the form of the lens imaging optics
as in Figs. 2 and 12, for determining the lens orientation by finding the
precise positions of the hidden marks, with respect to which the location and
orientation of the finishing block is subsequently calculated in accordance
i5 with a prescription of lens manufacture;
- for a progressive lens which has no printed or hidden reference features,
the
apparatus should be used in which the reference features finder is in the
form of the lens mapping optics as in Figs. 6 and 12, for determining the
optical center of the lens based on its spherical and cylinder power maps,
2o determining the lens orientation by finding the precise positions of its
far
and near vision points according their prescribed values and prescribed far
and near interpupillary distances, with respect to which the location and
orientation of the finishing block is subsequently calculated in accordance
with a prescription of lens manufacture.
25 Figs. 15A and 15B illustrate a further embodiment of an apparatus
according to the present invention, for processing pairs of lenses and their
frame
fitting. In this embodiment, the reference features finder 5 may be of any
design
described above or any other appropriate design.
The apparatus has a lens support plate 110 and a blocking unit 111. The
3o support plate 110 is movable along axis X and the blocking unit 111 is
moveable in
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Y and Z directions. The lens support plate 110 has two independent clamping
devices 112 and 114, which are capable of clamping both lenses A 1 and A2 and
spectacle frames Fl and F2.
Processing spectacle frames F1 and F2 results in accurate frame shape and
s interpupillary distance measurements and processing lenses A1 and A2 results
in
the attachment thereto of the finishing blocks at locations and orientations
determined inter alia based on the measurements of the frames.
The configuration of the apparatus as shown in Figs. 15A and 15B, enables
processing of lens pairs and spectacle frames in the manner described above
with
io reference to Figs. 2, 6 and 12 and thereby enables lens-to-frame fitting
without
additional information regarding the frames.
The method and apparatus according to the present invention and,
particularly, their optical setups and their displacement mechanisms may have
features different from those in the examples described above, within the
scope of
is the claims.
