NZ784133A - Block-free lens support for lenses surfacing - Google Patents
Block-free lens support for lenses surfacing Download PDFInfo
- Publication number
- NZ784133A NZ784133A NZ784133A NZ78413322A NZ784133A NZ 784133 A NZ784133 A NZ 784133A NZ 784133 A NZ784133 A NZ 784133A NZ 78413322 A NZ78413322 A NZ 78413322A NZ 784133 A NZ784133 A NZ 784133A
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- New Zealand
- Prior art keywords
- lens
- support elements
- curvature
- seat
- supporting part
- Prior art date
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Abstract
The invention relates to a lens supporting part (100) for supporting a lens (L) in a surface machining process, in which one (L1) of two opposite side surfaces (L1, L2) of the lens (L) is processed. The lens supporting part (100) comprises a plurality of support elements (110) that are relatively moveable with respect to each other and that together form a lens seat (120) with a curvature for supporting the lens (L) on its other side surface (L2) against forces generated in the surface machining process. The lens supporting part (100) comprises an adjustment mechanism (130) for displacing during processing at least some of the support elements (110) relatively to each other to adjust the curvature of the lens seat (120) to a defined curvature independently from a lens (L) being seated on the support elements (110). The invention is also directed to a system (500) and a method for surface processing at least one of the side surfaces (L1, L2) of a lens (L) that utilize the lens supporting part (100) of the invention, respectively. veable with respect to each other and that together form a lens seat (120) with a curvature for supporting the lens (L) on its other side surface (L2) against forces generated in the surface machining process. The lens supporting part (100) comprises an adjustment mechanism (130) for displacing during processing at least some of the support elements (110) relatively to each other to adjust the curvature of the lens seat (120) to a defined curvature independently from a lens (L) being seated on the support elements (110). The invention is also directed to a system (500) and a method for surface processing at least one of the side surfaces (L1, L2) of a lens (L) that utilize the lens supporting part (100) of the invention, respectively.
Description
BLOCK-FREE LENS SUPPORT FOR LENSES SURFACING
Field of the invention
The present ion relates to a lens supporting part for ting a lens against forces
caused in a surface machining process, in which one of two opposite side surfaces of the lens is
processed. The invention also relates to a system and method for a lens surface machining
process, in which the lens supporting part is used, respectively.
Technical background
Any discussion of the prior art throughout the specification should in no way be
considered as an admission that such prior art is widely known or forms part of common general
knowledge in the field.
The manufacturing of modern custom-made eyeglass prescription lenses requires an
individualized machining process, in which it is not only possible to tailor lenses to a single
prescription recipe but also to the skull morphology of the customer as well as specific geometric
features of the frame chosen by the customer.
Commonly, lens blanks with different front ures are used in the cturing
process of lenses. Therein, lens blanks for divergent and for convergent lenses exist. Typically,
the front surface of a lens blank is finished so that no ment of the curvature or ing is
required on the front surface. The manufacturing process is started by choosing a lens blank with
a front e most suitable for the requirements of the ation. Thereafter, the rear surface
of the lens blank is processed to customize the lens, whereby a determination of how to process
the rear surface in order to generate a lens with the desired shape is based on the shape of the
front surface.
While it is an advantage of this approach that only one side has to be processed, it also
visualises the importance of the front surface maintaining its shape hout the entire
manufacturing process to arrive at a lens with the desired shape.
In the cturing process, the shape of the lens is adapted by generating (thickness)
differences in the curvature between the lens’ front and rear surface in order to change the way
the finished lens will change the course of light. The difference in curvature between the front
and rear surface of the lens leads to its corrective power. Accordingly, the location of areas of
different esses will vary depending on the customer. Unfortunately, the areas of ent
thicknesses show different mechanical reactions when being d to machining and clamping
forces. For examples, thin areas are more sensitive to the machining and clamping forces while
thicker areas are more resilient and thus, are less prone to being bent or deformed. Accordingly,
if such differences in the lens’ ability for dissipating mechanical stress are ted, it can lead
to irregularities in the power map of the lens and thereby, eventually to the production of a lens
that is out tolerance.
Therefore, there is a need to provide ient mechanical support to the front surface of
the lens while its rear e is machined in order to reduce the impact of the manufacturing
s on the lens quality.
In the prior art, this m has been addressed by attaching the front surface of the lens
blank to a surfacing block with a bonding material, such as an adhesive, e.g. resin, glue or low
melting alloy. Typically, the surfacing block remains attached to the lens throughout the entire
lens generation process and the various machines involved in the process have a universal
clamping system that facilitates to fix the surfacing block to the respective machine. Thereby, the
surfacing block can be used also for handling the lens and as reference point in all machining
steps. The surfacing block with the adhesive allows to keep a convex e stable under the
action of the machining forces and also against deformation caused by inner tensions in the lens
material. This known solution is most ly found in lens manufacturing applications.
However, such known solutions are disadvantageous, as they require connecting and
disconnecting the surfacing block from the lens, which is a complex and costly process that
becomes even more complicated when lenses of various shapes and curvatures are to be
ted. Also, they require the use of special blocking and de-blocking appliances as well as
special substances, such as adhesives, solvents, and water. Moreover, throughput times are
reduced. Accordingly, such solutions are not suitable for producing different lenses with
different curvatures and different power maps from lens blanks in quick succession.
In the prior art, attempts have been made to me some of these disadvantages by
using dedicated surfacing blocks that have a predefined curvature for receiving a lens blank with
exactly the same curvature. The lens blank can be attached to the surfacing block through the
application of suction forces.
While the problem of how to simplify ting and disconnecting the lens from the
surfacing block can be sed with this solution, a high number of such surfacing blocks
would be ed to provide a suitable surfacing block for every conceivable lens curvature.
Consequently, the shape of the surfacing block frequently does not fit to the lens blank. This
leads to manufacturing errors and a reduction in accuracy and quality of the finished lens
because the lens blank is insufficiently supported during the manufacturing process. er, it
was found that with this solution the strength of the vacuum is often icient for processing
the lens with high machining speeds.
Alternative ons exist in the prior art that attempt to overcome the aforementioned
disadvantages by providing a surfacing block with a t for the front surface of the lens,
against which the lens blank is pressed by ting a suction force. The support has the ability
to copy the front curve of the lens blank once. After the step of deforming the lens support is
completed, the t is fixed so that its shape is kept in place for the rest of the subsequent
machining steps. Any further deformation of the lens support during the processing is not
possible with this known solution.
However, it has been found that this solution is insufficient for providing a lens that
achieves the required high quality standards. In particular, often the lens is insufficiently and
without the required cy supported by such surfacing blocks during the surface processing.
As a result, the lens is deformed by forces ng during the machining process. However, as
described above, the precision of the finished lens is dependent on the stability of the front
surface. Any deformation of the existing front surface that may be caused from machining the
lens can add errors to the final lens power.
Forces that could affect the lens arise either directly from the machining process, such as
forces generated by a suction or clamping system for securing the lens via its front surface or
machining/cutting forces. However, also inner tensions in the lens material can cause
deformations. Particularly, since the lens is relatively thin and of a deformable material, such
forces can have a strong impact on the shape of the surfaces of the lens.
For example, if inner tensions exist in an unprocessed lens blank, initially, they are
evenly distributed over the entire thickness of the raw lens blank and thus, do not have any or
have only a very small impact on the shape of the lens blank. However, during the machining
process, material is removed in parts of the lens blank while other parts are not processed yet.
Accordingly, tensions inside the processed lens blank are unevenly distributed and thus, can
generate deformations in the lens shape. Consequently, at the end of the machining process, the
final shape of the lens’ front surface will differ from the original shape, which -as described
above- was used lly for determining the processing steps of the rear surface. Thus, a power
map error results because the desired power map is based on the al) shape of the front
surface of the blank and not on the (deformed) shape of the ed lens. Figures 2 illustrate this
situation exemplarily by showing the shape of a lens (L) before starting a surface sing step
(Figure 2A) and the shape of the lens (L) at the end of the surface sing step (Figure 2B).
Ideally, the front surface (L2) would remain the same throughout the process while only the
shape of the rear surface (L1) changes from its original shape (L1) to the new shape (L11).
This may lead to the in Figures 2A and 2B arily illustrated phenomena that at the
beginning of the machining process of the lens’ rear e (L1), the lens blank (L) may match
the shape of the deformable t block (B100) perfectly (see Figure 2A) while at the end of a
processing step (see Figure 2B), not only the shape of the rear surface (L11) but also the shape of
the front surface (L2) may have changed so that a gap (G) between the front surface (L2) of the
lens (L) and the deformable support block (B100) exists. Thereby, the t capabilities of the
deformable support block (B100) for the lens (L) during subsequent surface processing is
reduced. This may lead to deformation of the front surface (L2) of the lens (L) through operating
forces during machining of the rear surface of the lens blank (L1, L11). Also, lens holding forces
generated with a suction pump can cause deformations.
Moreover, it has to be considered that deformable lens supports are commonly ed
with a rubber coating to avoid scratching the already finished front surface of the lens blank.
However, these rubber coatings may be subject to locally varying deformation under the effect of
operating forces and/or clamping forces, thereby introducing flexibility and instability in the
support of the lens blank during the machining process.
It is an object of the present invention to me or ameliorate at least one of the
disadvantages of the prior art, or to provide a useful alternative.
It is an object of the t invention to provide a part, system and method for
processing a surface of a lens that overcome the known disadvantages of the prior art,
respectively. Therein, it is a particular object of the ion to provide a rigid support for the
front surface of the lens that is actively adaptable throughout the processing of the lens and that
allows to t and to disconnect the lens from the support with minimal effort. Therein, it is a
particular object to provide a solution that is suitable for adjusting the lens support automatically
and in a short time.
These and other objects, which become apparent upon reading the description, are solved
by the subject-matter of the independent claims. The dependent claims refer to preferred
embodiments of the invention.
Summary of the invention
According to one aspect of the present invention, there is provided a lens supporting part
for supporting a lens in a e machining process, in which one of two opposite side surfaces
of the lens is processed, wherein the lens supporting part comprises
- a plurality of t elements being relatively moveable with respect to each other and
er forming a lens seat with a curvature for supporting the lens on its other side surface against
forces caused in the surface machining process, and
- an adjustment mechanism for displacing at least some of the plurality of support elements
relatively to each other during processing to adjust the ure of the lens seat to a defined
curvature ndently from a lens being seated on the support elements.
A first aspect of the present invention relates to a lens supporting part for supporting a
lens in a surface machining process, in which one of two opposite side surfaces of the lens is
processed. The lens supporting part comprises a plurality of support elements that are vely
moveable with respect to each other. The support elements form together a lens seat with a
ure for supporting the lens on its other side surface against forces caused in the surface
machining s. The lens supporting part r comprises an adjustment ism for
displacing at least some of the plurality of support elements relatively to each other during
processing to adjust the curvature of the lens seat to a defined curvature independently from a
lens being seated on the support elements.
In other words: the invention es a lens supporting part that is suitable for being
used in a surface machining process of a lens. The process may comprise, for example, any
ing or manufacturing step(s) for the generation of optical devices, such as roughing (i.e.
grinding of a lens surface to the approximate curvature and thickness), smoothing (i.e. grinding
of a lens surface to the exact curvature and thickness), polishing (i.e. making the lens smooth;
providing regular ission as well as specular reflection) and/or bevelling (i.e. g the
lens to the shape of eyeglass ). Generally, a “lens” may be understood, for example, as
any transmissive optical device that is adapted to change the course of light by refraction. For
example, the lens may be an ophthalmologic lens, such as corrective or iption lenses. The
lens may have two opposite side surfaces and a circumferential edge. Preferably, one of the two
side surfaces is processed (here referred to as “the one side surface) while the other one of the
two side surfaces of the lens (here referred to as “the other side surface) is supported by the lens
supporting part.
The lens supporting part comprises a plurality of e support elements that together
form a lens seat. The lens seat, for instance, may be a structure that acts as a base or centre for a
lens side e during the surfacing s. For example, the support elements may be
arranged and provided such that they contribute to parts or ns of a common surface or
frame structure, which has a curvature. The expression “curvature” may be understood, for
e, as a characteristic of a lens of having a (non-planar and/or) spherical contour in a
normal section of the lens along its optical axis. Therein, the curvature may be a measure to
determine the amount, by which a surface of the lens deviates from being a plane. For example,
in lens manufacturing, curvature may be understood as the reciprocal of a radius of a circle that
best fits a r of the lens in a normal section of the lens along its optical axis (e.g. the section
showing the lens optical e) and/or as a mean curvature of one of its side surfaces.
The lens supporting part r comprises an adjustment mechanism that is capable of
changing the position of at least one or more of the support ts relatively to each other such
that the curvature of the lens seat can be adapted to a desired new defined ure. Therein,
“defined curvature” may be understood, for example, as specifying the profile and/or contour of
the lens seat (e.g. when seen in a normal section of the lens along its optical axis) such that a
surface with a defined curvature radius (or mean curvature value) is constituted. Therein, the
defined curvature may be different from an initial (starting-)curvature of the other side surface.
The “adjustment mechanism” may be understood, for example, as a device, functional unit
and/or functionally linked group of components; which may actively manipulate or allow to
manipulate the respective support elements relatively to each other during processing to adjust
the curvature of the lens seat to a defined curvature independently from a lens being seated on
the support elements.
This capability of the adjustment mechanism is neither restricted by a lens being attached
to or supported/seated on the lens seat nor dependent on that a lens is attached to or
supported/seated on the lens seat.
Thereby, it is possible to actively adapt the curvature of the lens seat, which supports the
lens against mechanical stresses during a surface machining process, even during an ongoing
ing process as the curvature of the lens seat can be adjusted even when the lens is seated
on the lens seat. Thereby, it is possible to tailor the curvature of the lens seat not only to the
l curvature of the front surface of the lens but also to adapt the ure of the lens seat in
anticipation of upcoming and ongoing mechanical stresses during the surface processing as well
as of a ng ess profile of the lens. An adjustment of the curvature can be achieved
within the required accuracy . For example, in lens cturing applications there may
be a requirement that new relative positions of support elements can be set with an accuracy of 1
etre or below. Thereby, it is le to provide the lens with excellent support during the
entire manufacturing process so that the quality and accuracy of the finished lens can be
improved while power errors can be reduced or avoided.
Thus, the known problems and disadvantages of the prior art can be overcome with the
lens supporting part of the present invention.
According to a preferred embodiment of the invention, the adjustment mechanism may be
configured to move at least some (or all) of the plurality of support elements independently from
each other to obtain the defined curvature. Alternatively or onally, the adjustment
mechanism may be configured such that at least one (or preferably all) of the support elements
may be relatively movable to a lens being seated on the support elements. The support
element(s) may be freely movable between a position, where (one of) the t element(s) is
without direct contact with the other side surface of said lens, and a on, where the support
element is in direct contact with the other side surface of said lens.
Thereby, the position of each of the support elements with respect to the lens being seated
on the lens seat can be set freely. Thus, numerous different configurations of the support
elements with respect to each other and the lens can be defined. Accordingly, numerous
curvatures of the lens seat can be formed so that the lens can be mechanically supported by the
support elements throughout the surface machining s in different configurations. Thus,
with such configuration, the lens is less susceptible to ical stresses and deformations
during the manufacturing process so that the initial shape of the other side surface can be
maintained. Thereby, an improvement of the quality and accuracy of the finished lens can be
accomplished.
According to a r preferred embodiment of the invention, the adjustment ism
may be configured to move (e.g. slide) the respective support elements in a direction, which may
be transverse (e.g. orthogonal) to the lens seat to adjust the curvature of the lens seat.
Alternatively or additionally, the movement may be in a direction that is parallel to a holding
force for holding the lens on the lens supporting part to adjust the curvature of the lens seat.
Preferably, the t elements and/or the adjustment ism may be connectable to a
component for actuating at least one support element and/or each of the support elements to be
moved. Preferably, such actuation may be configured to actively adjust the curvature of the lens
seat. More preferred, the adjustment ism may be connectable to at least one actuator,
preferably to actuate (e.g. move or displace) the respective support t to be moved.
Thereby, the curvature can be adjusted more accurately and the lens can be supported
more effectively as the support ts are movable in directions that correspond with
directions of holding forces and machining forces, which have a high impact on affecting the
other side e of the lens during the e machining s. Hence, the quality of the
finished lens can be improved.
ing to a preferred embodiment of the invention, the support elements may each
have a distal end. Preferably, all (or at least some) distal ends together may form the lens seat.
The distal ends may each comprise or are made of an elastic material for supporting the lens.
Alternatively or additionally, the support elements may each extend along a longitudinal axis.
Preferably, the support elements may extend between the distal end and a proximal end.
Preferably, the proximal end may be le for being coupled to the adjustment mechanism.
Thereby, the other side surface of the lens can be protected from being scratched or
otherwise damaged during the surface machining process. Moreover, the adjustment mechanism
can be connected easily with the supporting elements.
According to a further preferred embodiment of the invention, at least one of the support
elements may form an outer circumferential sealing edge of the lens seat to allow for a
circumferential sealing of a lens being seated on the lens seat. Preferably, the outer
circumferential sealing edge may be provided at its distal end. Preferably, the at least one support
element, which forms the outer circumferential sealing edge, may be (provided) stationary and/or
fixed vely to other support elements and/or relatively to a lens being seated on the support
elements.
By providing g on an outer face of the structure formed by the support elements, it
is possible to seal a space between the support elements and the other side surface of the lens
from the outside. Thus, accidental damage of the other side surface of the lens through coolant or
material removed in the process can be averted. By providing the outer circumferential sealing
edge ble, it is possible to use the tive support element (forming the outer
circumferential sealing edge) as a reference edge for positioning and arranging the lens on the
lens supporting part. Thereby, manufacturing of the lens as well as the quality of the finished
lens can be improved.
According to a red ment of the invention, the lens ting part may
further comprise a vacuum unit. The vacuum unit may also be part of the system described
herein below, which then functions the same way. The vacuum unit may be fluidly connected to
the lens seat. atively or additionally, the lens seat may be configured to be fluidly
connectable to a/the vacuum unit to apply a vacuum in a suction space between the lens seat and
a lens being seated on the lens seat. Preferably, the vacuum unit and/or the fluid connection may
be provided for creating a g force for holding the lens on the lens seat upon a vacuum
being applied. Vacuum passages may be formed between at least some of the support ts
for ting the vacuum unit with the suction space (and/or with the lens seat).
Thereby, a space with air pressure below atmospheric pressure can be generated between
the lens and the lens supporting part. This allows to secure and/or fix the lens to the lens
supporting part by (active) force application so that it is possible to reversibly connect and
disconnect the lens from the lens supporting part. In particular, it is no longer necessary to block
and to de-block the lens at the beginning or the end of the lens manufacturing process. Thus, the
above uration facilitates ted processing of lenses with high throughput rates. By
applying the suction force or vacuum through preferably evenly spread passages, deformation of
the other side surface of the lens during processing can be avoided. Moreover, it is possible to
adapt the strength of the holding force locally so that deformations caused by holding forces can
be minimized.
According to a preferred embodiment of the invention, the adjustment mechanism may
comprise at least one actuator, such as an electric motor or pneumatic cylinder. Preferably, the
actuator may be suitable and/or ured for displacing the support elements relatively to each
other. The actuator may also be part of the system described herein below, which then functions
the same way; then the adjustment mechanism may be configured to be connectable to (e.g. the)
at least one actuator. Moreover, the adjustment mechanism may comprise a blocking part that is
movable between a first position, where the support elements are fixed in their relative position
to each other (and preferably to a lens being seated on the lens seat), and a second position,
where the support elements are vely movable with respect to each other (and preferably to a
lens being seated on the lens seat). For example, the blocking part may be a movable clamp.
Thereby, the support elements can be actively moved between different positions and can
be fixed in different positions so that the curvature of the lens seat can be varied and ed
with sufficient rigidity in each of the ent arrangements of the support elements.
Preferably, the actuator may be controllable and/or comprise a sensor unit, such as an
encoder, for determining positional information, e.g. a ve on of the actuator.
Thereby, it is possible to provide the lens supporting part with a closed loop control as the
positional information can be used to check and verify a position of a support element. In case of
deviations between a d and actual position, it is possible to adjust (actively) the position of
the respective support element.
According to a r preferred embodiment of the ion, the t elements may
be formed and/or arranged in a ring shape. ably, the support elements may be rings having
a plurality of (differing) ring ers and/or may be coaxially arranged to form the lens seat.
Thereby, the support elements can be provided as simple structures that could correspond
with a spherical shape of a lens. Also, the support elements can be arranged concentrically so
that the ure of a sphere can be mirrored with high precision. Therein, the lens can be
arranged such that its optical axis may correspond with the common centre of the ring
arrangement. Hence, accuracy and precision, by which the ure of the lens seat can be
adapted with respect to the lens seated on the lens seat, can be ed. Also, the number of
parts can be reduced as each ring forms a circumferential section of the lens seat, which reduces
structural and control xity.
According to a preferred embodiment of the invention, the adjustment mechanism may
further comprise (for each of the support elements to be moved) a connecting ism to
(directly or indirectly) transmit (or transfer) an actuation force of an actuator to the tive
support element. Preferably, the actuation force may be transferred such that said support
element is linearly moved. The or may be the y mentioned or or a different
actuator.
Thereby, it is possible to displace the individual support elements with respect to each
other with simple and highly effective technical means. Also, it is le to introduce
additional stiffness into the system so that the rigidity of the lens seat is improved, thereby
improving the support provided to the lens against mechanical stresses during the manufacturing
process. Moreover, the individual support elements can be moved with high accuracy and
precision.
According to a preferred embodiment of the invention, at least one (or preferably all) of
the support elements may be made of a rigid material, such as metal or plastic material, which
preferably has a tensile ess between 150 MPa and 250 MPa.
Alternatively or additionally, at least one (or preferably all) of the support elements may
comprise or be made of a material with a surface hardness that ranges between a surface
hardness found with hard plastic and the one found with hardened steel.
For example, a hard plastic material may have a e hardness ranging from 40 to 100
ShD, preferably 60 to 70 ShD. Therein, the surface hardness of rubber and plastic is quantified
with the scale (commonly used unit abbreviations: ShA and ShD), which is defined in
industrial norms, such as ASTM D2240. In comparison, hardened steel may have a surface
hardness ranging from 50 HRC to 70 HRC, preferably 62 HRC. Therein, the e hardness is
quantified with the Rockwell scale (HRC), which is defined in industrial norms, such as ISO
6508.
Preferably, the distal end of (each of) the support elements may comprise or be made of
an elastic al for ting the lens. For example, rubber may be used. ably, the
c material may be provided as a coating or a separate element that is e to each of the
distal ends. Alternatively or additionally, it is also conceivable that a single cover element may
be provided for covering each of the distal ends. Preferably, the al used for covering or
coating the distal ends of the support elements may have a surface hardness that ranges n
a surface hardness found with soft rubber and the one found with soft plastic. Preferably, the
surface hardness of soft rubber may be 40 ShA to 100 ShA, preferably 50 ShA to 60 ShA. The
surface hardness of soft plastic may be 40 ShD to 100 ShD, preferably 60 ShD to 70ShD.
Thereby, the support elements are provided with high rigidity so that the support
elements can act as a rigid wall for the lens during the surface machining process. Also, the
resistance to vibrations can be improved.
In a further preferred embodiment of the present invention, the adjustment mechanism
may be configured such that – during processing - at least some of the plurality of support
ts are displaceable relatively to each other to adjust the curvature of the lens seat to a
(new) defined curvature independently from a lens being seated on the support elements.
In a preferred embodiment of the present invention, the lens supporting part may be
configured such that at least some of the support elements and/or the adjustment mechanism
is/are ely) controllable by a control unit (e.g. through the adjustment mechanism).
In a further preferred embodiment of the present ion, the adjustment mechanism
may be configured to ce – during processing - at least some of the plurality of support
elements relatively to each other to a d ure and/or to a curvature that is defined by a
control unit, preferably such that the curvature of the lens seat may change during processing.
Preferably, the control unit may be (functionally) connected to the adjustment mechanism
preferably so that the adjustment mechanism converts a control signal from the control unit into
relative displacement of the support elements. Preferably, the adjustment mechanism may
comprise the control unit. Alternatively or additionally, the control unit may be configured to
send a control command to an (or each of the) actuator(s) (preferably of the adjustment
mechanism) that may convert the command into an sponding) actuation of the actuator.
Preferably, the control unit may comprise anyone of the features of a control unit of a system
described below.
Thereby, it is possible to provide a lens supporting part that is ly controlled so that
the curvature of the seat for supporting the lens during processing can be adjusted during
processing. Thus, unlike in the ons of the prior art, where the seat can be ed only
once before the start of the processing, with the above configuration the curvature can be
adjusted continuously.
A further aspect of the invention relates to a system for surface processing of at least one
of two opposite side surfaces of a lens. The system comprises a lens supporting part for
supporting the lens during the surface machining s as described above. The system r
comprises a surface processing unit for processing the one side surface of the lens. For example,
the surface processing unit may be a lens cutting or lens polishing device. The system also
comprises a surface information supply unit for supplying a ry of the other side surface of
the lens. The surface ation supply unit may be a camera, a pressure sensor or a laser
, for example, for identifying the geometry of the other side surface of the lens.
Alternatively or additionally, the surface information supply unit may be, for example, an
interface to a se. The system further comprises a control unit for determining and setting a
defined curvature of the lens seat based on the supplied geometry of the other side surface of the
lens and for controlling the adjustment mechanism to displace the support elements relative to
each other to obtain the defined curvature of the lens seat.
Preferably, the surface information supply unit may be a (digital) database that, for
example, may be stored on the control unit. For example, the geometry of the other side surface
may be stored in a memory of the control unit as a p table. The lens curvature of the other
side surface may be stored in a database as an information. The information stored in the
database may be a measured value (e.g. fied by a sensor) or may be a value coming from
the manufacturer’s se. The supplied geometry may comprise actual/measured values
and/or may comprise corrected values, such as, for example, a (pre-) compensated values with
the compensation amount being based on measured values. Preferably, the information
(geometry, data) from the information supply unit may be supplied (provided or transferred) to
the control unit h a data connection, e.g. a wire or soldering. For example, the operator
may scan at the begin of processing a barcode on the lens blank and derive corresponding
information from the surface information supply unit on the geometry of the other side surface of
the lens blank based on the barcode information.
Preferably, the control unit may be configured to determine a (target) position for each of
the support elements before and/or during processing based on the information (i.e. the
geometry) supplied by the e information supply unit. For example, an algorithm may be
executed on the control unit in order to determine such ons. Therein, for example, while not
being excluded, the algorithm may be configured such that positions for the support elements are
returned that may be different from ons that lead to replicating the curvature of the other
side surface of the lens. Preferably, the control unit may control the adjustment mechanism to
adjust the position of the respective support elements (with respect to each other and/or with
respect to a lens being seated on the lens seat).
The system comprises all advantages and benefits that were bed in detail above. In
particular, by supplying the geometry of the other side surface of the lens, for example by
ement or through a database, it is possible to adapt the t of the lens based on the
actual (real/measureable) shape of the other side surface of the lens in a state, when the lens is
not being subjected to any external forces, such as holding or machining . Moreover, the
geometry (e.g. dimensions, contours, parameters and/or functions describing the
shape/geometrical characteristics of the other side e) can be used to ate and/or
establish how the adjustment ism is to be controlled in order to obtain a desired curvature
by displacing the (at least some of the) support elements. Thus, it is possible to take geometrical
peculiarities of the lens into consideration so that a d shape of the lens can be obtained with
high precision and quality since the structure ting the lens can be adapted in accordance
with the actual shape of the lens. Thus, unlike in the prior art, it is not necessary to accept that
power errors, which result from imperfections of the other side surface of the lens, inevitably
exist. Instead, these initial faults of the lens blanks can be detected and corrected by adapting the
processing of the one side surface.
According to a preferred embodiment of the invention, the control unit may be
configured to (continuously) determine and set the d curvature of the lens seat. Preferably,
determining and setting the defined curvature may be based on detected process parameters, like
mechanical stresses occurring during a processing step, and/or a desired shape for the finished
lens.
Thereby, it is possible to actively adapt the curvature of the lens seat ing on a
momentary (actual) state of the lens so that consistent support can be provided.
According to a further preferred embodiment of the invention, the system may further
comprise a spindle for rotating the lens supporting part during the surface machining process.
Preferably, the lens supporting part and the spindle may be arranged coaxially. Additionally or
alternatively, the lens ting part and the spindle may be detachably coupled to each other.
Thereby, it is possible to rotate the lens relatively to the surface processing unit so that
the tion of the lens can be achieved with conventional lens manufacturing machinery.
Moreover, the lens supporting part can be d and decoupled from the spindle so that it is
possible to use the lens supporting part as well as the system of the invention in an already
ng lens manufacturing environment.
As already mentioned herein above, the above-mentioned actuator(s) and/or vacuum unit
may be part of the system with the functions and advantages as described before.
A r aspect of the invention relates to a method for surface processing at least one of
two te side surfaces of a lens. The method comprises the step of providing the above
described system for surface processing at least one of two opposite side surfaces of a lens. A
geometry of the other side e of the lens is supplied (e.g. provided with the surface
information supply unit). A d curvature of the lens seat is determined and set based on the
supplied geometry of the other side surface of the lens (e.g. with the control unit). The curvature
of the lens seat is adjusted independently from a lens being seated thereon to obtain the defined
curvature of the lens seat (e.g. with the adjustment mechanism and/or during processing). The
lens is supported with its other side surface on the lens seat through (by) its defined curvature.
The at least one side surface of the lens is processed to a desired shape (e.g. with the surface
processing unit).
Preferably, the lens may be attached to the lens seat by activating a suction force or
vacuum as a holding force (e.g. with a or the vacuum unit). More preferred, the lens may be
centred on the lens seat. According to a preferred embodiment of the invention, during the
sing step, the defined curvature of the lens seat may be continuously determined, set
and/or adjusted. For example, the d curvature of the lens seat may be continuously
determined and set based on detected process parameters. Process parameter may be mechanical
stresses occurring during a processing step, positional information ined by sensors of the
actuators, and/or a desired shape for the finished lens. Preferably, the defined curvature may be
ined and set (e.g. based on one or all of these process parameters) such that a curvature of
the other side surface of the lens at the beginning of the processing is maintained. The curvature
of the lens seat may be adjusted independently from the lens being seated thereon to obtain the
d curvature of the lens seat.
With such configurations of the method, it is possible to achieve all advantages and
benefits of the invention that were described in detail above. Also, it is possible to improve the
quality and accuracy of the lens generated in the surface machining process.
According to a further preferred embodiment of the ion, the processing step may
comprise a lens surface rough g step. In the lens surface rough cutting step, the lens may be
secured on both side surfaces between the lens supporting part and an additional g .
The additional holding device may preferably be arranged opposite of the lens supporting part
with respect to the lens (seated on the lens seat). Preferably, a finishing step may exist, where the
lens is secured only by the lens supporting part.
Thereby, additional support is provided to the lens during a processing step, in which
cutting forces are at a high level. Thus, it can be ensured that the lens is well supported on the
lens support part and that machining forces are counteracted by the lens t.
Further aspects of the present ion relate to a (ophthalmologic) lens produced with
the method of the invention and a use of the system for ing a (ophthalmologic) lens.
Unless the context clearly requires otherwise, throughout the ption and the claims,
the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as
opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not
limited to”.
Brief description of drawings
Further features, advantages and objects of the ion will become apparent for the
skilled person when reading the following detailed description of embodiments of the invention
and when taking in conjunction with the figures of the enclosed drawings.
In case numerals were omitted from a figure, for example for reasons of clarity, the
corresponding features may still be present in the figure.
Figure 1 shows schematically a lens in a front view and a side view in the beginning
and the end of surface processing.
Figure 2A shows tically a side view of the tion between a lens and a
surfacing block of the prior art at the beginning of a surface machining process.
Figure 2B shows tically a side view of the connection between a lens and a
surfacing block of the prior art at the end of a surface machining process.
Figure 3 shows schematically an embodiment of a lens supporting part according to
the present invention.
Figure 4 shows schematically an embodiment of a system of the present invention
with a simplified illustration of a further embodiment of the lens supporting part according to the
present invention.
Detailed description
Figure 1 shows exemplary profiles of a lens L at the beginning and the end of a surface
machining s. s 2A and 2B illustrate known challenges that exist in connecting a lens
L with a support block B100 known from the prior art and that were described in more detail
above. Figures 3 and 4 show different aspects of different embodiments of the present ion.
For instance, a first aspect of the invention s to a lens supporting part 100 according
to the invention. ments of the lens supporting part 100 are illustrated in Figures 3 and 4.
The lens supporting part 100 is suitable for supporting lens L in a surface machining process. For
example, the lens supporting part 100 may be a jig, a chuck, a workpiece holder, and/or an
r suitable to be used in a lens surfacing process.
The lens L comprises two opposite side surfaces L1, L2. This is exemplarily illustrated in
all s. In the surface machining process, one side surface L1 of the lens L is to be
processed. At the end of the processing, the lens L may have a newly shaped one side surface
L11. This is exemplarily illustrated in Figure 1. Preferably, the lens L may comprise a
ferential edge L3 that extends between the two side surfaces L1, L2. Preferably, the lens L
may be made of a transparent and/or translucent material, e.g. a plastic material, such as
polycarbonate, or glass. More red, the lens L may be a lens blank. Preferably, one side
surface of the lens blank (e.g. its back surface) may be used for customization in a surface
machining process while the other side surface of the lens blank (e.g. its front surface) may be
already in its finished state, i.e. may comprise already its intended curvature and may be already
polished. The lens L may comprises a coating for polarisation or light blocking. r, this is
only an e and the lens L may be a lens blank with both side surfaces requiring surface
processing. The lens L may comprise side surfaces L1, L2 that may be convex and/or concave.
The lens L may comprise an optical axis OA that may be a normal of a symmetry plane of the
lens L. The lens L may comprise spherically shaped side surfaces L1, L11, L2. It is also
conceivable that the lens L has more than one optical axis or ently shaped side es L1-
The lens supporting part 100 comprises a plurality of support elements 110. In Figures 3
and 4, the lens supporting part 100 is exemplarily illustrated with six support elements 110.
However, this is only an example and the lens supporting part 100 may comprise any number of
support ts 110 greater or equal than two. Preferably, the support elements 110 may each
extend along a udinal axis. Moreover, (each or some of) the support elements 110 may
preferably extend between a distal end 111 and a proximal end 112. This is exemplarily
illustrated in Figures 3 and 4. The support elements 110 may have a ring shape. For e, the
support elements 110 may be long hollow shafts. Each of the ring-shaped support elements 110
may have a different diameter and may be arranged coaxially as exemplarily illustrated in
Figures 3 and 4. r, this is only an e and the support ts 110 may have
various shapes and may be arranged differently. For instance, the support elements 110 may be
slats or plates that preferably they may be arranged in a circle such that they all are directed
towards a common centre. Preferably, at least one (or all) of the support elements 110 may be
made of a rigid al, such as metal (e.g. stainless steel) or a hard plastic. The support
elements 110 may have a e stiffness between 150 MPa and 250 MPa. Preferably,
material(s) used for the support elements 110 may have a surface hardness in the range between
surface harnesses found with hard steel (e.g. 62 HRC) and hard plastic material (e.g. 60-70 ShD).
Moreover, the support elements 110 may each have their distal end 111 made of an
elastic material for supporting and/or contacting the lens L. For example, a material with a
surface hardness ranging between the surface hardness found for soft rubber (e.g. 60 ShA) and
soft plastic material (e.g. 60-70 ShD) may be used for the distal end 111. For example, the
support ts 110 may have a rubber coating or gasket provided on their respective distal end
111 to avoid scratching the other side surface L2 when the support elements 110 come into
contact with the lens L as exemplarily illustrated in Figures 3 and 4.
The support elements 110 are relatively le with respect to each other. Moreover,
the support elements 110 form together a lens seat 120 with a curvature for supporting the lens L
on its other side surface L2 against forces caused in the surface machining process. Preferably,
each of the distal ends 111 together may form the lens seat 120. Figures 3 and 4 illustrate
exemplarily that by increasing the number of t ts 110 it may be possible to increase
the resolution for g the ure of the lens seat 120. In Figures 3 and 4, the lens seat 120
is exemplarily shown with a convex shaped surface that is formed by the distal ends 111 of the
support elements 110. Each of the support elements 110 may be ed relatively movable to
the lens L when the lens L is seated on the t elements 110.
At least one of the t elements 110 may preferably form at its distal end 111 an
outer circumferential sealing edge 113 of the lens seat 120. For example, the circumferential
sealing edge 113 may be a (rubber) gasket, such as an O-ring. The circumferential sealing edge
113 may allow for a circumferential sealing of the lens L being seated on the lens seat 120 as
exemplarily illustrated in Figure 3. Preferably, the support element 110 that forms the outer
ferential sealing edge 113 may be fixed relatively to other support elements 110 and
preferably also to the lens L when being seated on the support elements 110. This is shown by
way of example in s 3 and 4.
Preferably, the support element(s) 110 that form(s) the outer circumferential sealing edge
113 may form a main body of the lens supporting part 100. However, the main body may be
formed by a separate ent instead. For example, the main body may be a cartridge or a
container. The main body may be arranged to be coupled to a machine or system for surface
processing. Preferably, the support elements 110 may be arranged inside the main body around a
common axis. Therein, the support elements 110 may be preferably arranged such that for
processing they may be brought in alignment with a rotational axis RA of a machine spindle (e.g.
later described spindle 540). Figures 3 and 4 indicate this exemplarily. Preferably, the lens L
may be ed on the lens seat 120 such that its optical axis is aligned with the rotational axis
Preferably, the lens supporting part 100 may further comprise a vacuum unit 200. The
vacuum unit 200 may be a vacuum ejector, a displacement or kinetic vacuum pump, for
example. In Figure 4, the vacuum unit 200 is exemplarily yed as part of a system 500,
which will be described in more detail below. The vacuum unit 200 may be fluidly connected
/connectable to the lens seat 120 to apply a vacuum in a suction space 210 between the lens seat
120 and the lens L being seated on the lens seat 120. This is exemplarily rated in Figure 3.
With the vacuum unit 200, a g force for holding r securing) the lens L on the lens
seat 120 may be created. Therein, the lens supporting part 100 may comprise at least one vacuum
passage 115 for connecting the vacuum unit 200 with the lens seat 120 and the suction space
210. In Figure 3, the vacuum passages 115 are exemplarily shown as being formed between at
least some of the support elements 110 for connecting the vacuum unit 200 with the lens seat
120. Therein, the support elements 110 may be arranged with a small gap between each other. In
Figure 4, the vacuum passage 115 is exemplarily shown as a single duct that leads to the centre
of the lens seat 120 and that may be provided as a through hole in one of the support elements
The lens supporting part 100 further comprises an adjustment mechanism 130 for
displacing at least some of the plurality of support elements 110 relatively to each other during
processing to adjust the curvature of the lens seat 120 to a defined ure independently from
a lens L being seated on the support ts 110. The adjustment ism 130 is
exemplarily illustrated in Figures 3 and 4. Preferably, the adjustment mechanism 130 may be
configured to move at least some of the plurality of support elements 110 independently from
each other to obtain the d curvature.
The support elements 110 may be coupled to the adjustment mechanism 130 via their
proximal ends 112. Therein, for example, the adjustment mechanism 130 may comprise a
connecting mechanism 140. For example, the connecting mechanism 140 may (mechanically
and/or electrically) link the support element 110 with the ment mechanism 130. For
instance, the connecting mechanism 140 may convert or transfer an actuation (e.g. a l
motion or a force) of the adjustment mechanism 130 to the (individual) support elements 110.
The connecting mechanism 140 may define the kinematics n the adjustment mechanism
130 and the support t 110. The connecting mechanism 140 is exemplarily illustrated in
Figures 3 and 4 as connecting portion between the t elements 110 and corresponding
actuators 300 for displacing, e.g. during processing, at least some of the t elements 110.
Preferably, each of the support elements 110 may be displaced through the connecting
mechanism 140 directly/indirectly transmitting an actuation force of the actuators 300 to the
corresponding support element 110, e.g. so that the respective support element 110 may be
linearly moved. For example, in one of its simplest configurations, the connecting mechanism
140 may be a mechanical connection, such as a screw connection, between the ment
mechanism 130 and the respective support element 110.
As mentioned above, the adjustment mechanism 130 or the system 500 may comprise at
least one actuator 300. In general, the actuator 300 may be a component that is configured to
(actively) generate a (mechanical or ical) force for actuating (i.e. displacing, for example,
in a controlled/defined manner) the support elements 110 (to be moved). n, the actuator
300 may be a different component depending, for example, on the design of the adjustment
mechanism 130 and/or the connecting mechanism 140. ably, at least one actuator 300 may
be provided for each of the support elements 110 that is to be displaced during the surface
ing process. The or 300 may be an electric motor, such as illustrated in Figures 3
and 4, or it may be a pneumatic cylinder or a piezo motor. r, it is also vable that
the actuator 300 may be a mechanical break or an eddy current break. These are only es
and do not represent a complete enumeration. Preferably, the actuator 300 may be controllable,
for example by a computational unit or machine control unit (such as later described control unit
530). The actuator 300 may comprise a sensor unit 310 for determining positional information,
such as a relative position of the actuator 300 with respect to the lens L or with respect to the
outer circumferential sealing edge 113. For example, the actuator 300 may be battery powered
and/or may be llable through a wireless receiver for receiving control commands from the
machine control unit. The actuator(s) 300 may be arranged relatively movable and/or static (i.e.
fixed/immovable) relative to the support elements 110 preferably in operation.
Preferably, the adjustment mechanism 130 may be configured to move the respective
support ts 110 in a ion, which is transverse (e.g. orthogonal) to the lens seat 120, in
order to adjust the curvature of the lens seat 120. In the examples illustrated in Figures 3 and 4,
the adjustment mechanism 130 is configured to move the respective support elements 110 in a
direction parallel to the g force for g the lens L on the lens supporting part 100,
which is generated by the vacuum unit 200. Preferably, the adjustment mechanism 130 and/or
the support elements 110 may be configured to slide.
The adjustment mechanism 130 may be configured to temporarily block (freeze) the
nt of the support elements 110. Therein, the ment mechanism 130 may comprise a
blocking part that may be movable between a first position, where the support elements 110 are
fixed in their relative position to each other (and preferably also to the lens L when being seated
on the lens seat 120), and a second position, where the support elements 110 are relatively
movable with respect to each other (and ably also to the seated lens L). Preferably, the
blocking part may be a movable clamp. atively, it is also conceivable that the actuators
300 block any further movement of the support elements 110 without ing a corresponding
l signal.
A further aspect of the present invention relates to a system 500 for surface processing at
least one of the two opposite side surfaces L1, L2 of the lens L. The system 500 is exemplarily
illustrated in Figure 4. For example, the system 500 may be a machine for surface processing of
lenses.
The system 500 comprises the lens supporting part 100 as described above. Unlike in
Figure 3, the actuators 300 may be provided as part of the system 500. However, this is only an
example.
Furthermore, the system 500 comprises a surface processing unit 510 for sing at
least the one side surface L1 of the lens L. For example, the surface processing unit 510 may be a
drill, a lens cutting or a lens polishing device. In Figures 3 and 4, the surface sing unit 510
is exemplarily illustrated as a tool bit. However, this is only an example and other tools for
roughing, polishing, ing can be used instead.
The system 500 further comprises a surface ation supply unit 520 for supplying a
geometry of at least the other side surface L2 of the lens L. The surface information supply unit
520 may be a camera, a pressure sensor or a laser sensor. However, it is also conceivable that the
e information supply unit 520 may be a database or an interface, such as a connector or
data link, to a database. Preferably, the surface information supply unit 520 may be a contactless
sensor such as exemplarily illustrated in Figure 4. The surface ation supply unit 520 may
be arranged outside of or (e.g. integrally provided) within the lens supporting part 100.
The system 500 further comprises a (preferably “the” aforementioned) control unit 530
for determining and setting a defined curvature of the lens seat 120 based on the supplied
geometry of the other side surface L2 of the lens L and for controlling the adjustment mechanism
130 to displace the support elements 110 relative to each other to obtain the defined curvature of
the lens seat 120. For example, the control unit 530 may be a e l device as
exemplarily rated in Figure 4. However, it is also conceivable that the control unit 530 may
be part of the control unit of one of the actuators 300 (e.g. a servomotor). For example, the
control unit 530 may comprise the surface information supply unit 520, e.g. the surface
information supply unit 520 may be the memory of the control unit 530 or it may be mounted on
the control unit 530.
Preferably, the control unit 530 may be configured to (continuously) determine and set
the defined curvature of the lens seat 120. For this, the control unit 530 may comprise signal
connections that connect the individual ents of the system 500 with the control unit 530.
This is arily illustrated in Figure 4. For example, the actuator 300 may transmit to the
control unit 530 positional information 311 that is determined by the sensor unit 310 of the
actuator 300 or by a te sensor provided in the system 500. Further, the control unit 530
may be configured to set and adapt the level and/or application location of the suction force or
vacuum created by the vacuum unit 200. Also, the control unit 530 may be configured to
(continuously) determine and set the d curvature of the lens seat 120 based on the (so)
detected process parameters, but also on mechanical stresses occurring during a processing step
and/or a desired shape for the finished lens L. Therefore, the l unit 530 may be connected
to the surface information supply unit 520, e.g. via a signal connection.
Preferably, the system 500 may further comprise a spindle 540 for rotating the lens
supporting part 100 during the e machining process along the rotational axis RA. This is
exemplarily illustrated in Figure 4 but also indicated in Figure 3. The lens supporting part 100
may be part of the spindle 540. Alternatively, the lens supporting part 100 may be arranged
coaxially and is detachably coupled thereto as exemplarily illustrated in Figure 4. The control
unit 530 may be connected to the spindle 540, e.g. via a signal connection, to control and set the
onal speed during surface processing.
A further aspect of the present ion relates to a method for surface sing at
least one of the two te side surfaces L1, L2 of the lens L.
The method comprises a step, in which the above described system 500 is provided to
facilitate surface processing at least one of the two opposite side surfaces L1, L2. A geometry of
at least one of the two side surfaces L1, L2 of the lens L is supplied preferably with the surface
information supply unit 520. Based on the so supplied geometry of the respective side surface
L1, L2, a d curvature of the lens seat 120 is determined and set, preferably by the control
unit 530. The curvature of the lens seat 120 is adjusted (e.g. during processing) independently
from the lens L being seated thereon to obtain the d ure of the lens seat 120,
preferably by the adjustment mechanism 130. The lens L is supported on the lens seat 120 with
its defined curvature at the side e L1, L2 that is not processed.
The lens L may be attached to the lens seat 120 by activating a suction force or vacuum
as a holding force, ably with the vacuum unit 200. Preferably, when attaching the lens L on
the lens seat 120, the lens L may be centred on the lens seat 120 through the suction force or
vacuum pulling the lens L onto the outer circumferential sealing edge 113 into the right position.
For e, the lens seat 120 may be provided with ures of a self-centring mechanism for
the lens L.
The at least one side surface of the lens L to be processed is processed to a desired shape,
preferably with the surface processing unit 510.
Preferably, during the processing step, the defined curvature of the lens seat 120 may be
continuously determined and set based on detected process parameters, like ical stresses
occurring during the processing step, the onal information 311 ined by the sensor
unit 310, and/or based on a desired shape for the finished lens L. For example, by setting the
defined curvature the adjustment mechanism 130 may be (actively) controlled to displace at least
some of the support elements 110 relatively to each other.
Preferably, the control unit 530 may be ured such that a curvature of the side
surface L2 of the lens L (which is not to be processed) is maintained in its shape at the start of
the processing. Alternatively or additionally, during the (still ongoing) sing step, the
curvature of the lens seat 120 may be adjusted independently from the lens L being seated
thereon to obtain the defined curvature of the lens seat 120. Therein, the processing step may
comprise a lens surface rough cutting step, where the lens L is secured on both side surfaces L1,
L2 between the lens supporting part 100 and an additional holding device (not illustrated). The
additional holding device may be arranged opposite of the lens supporting part 100 with respect
to the lens L seated thereon. For completeness and clarification purposes, reference is made to
WO
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP21151489.8 | 2021-01-14 |
Publications (1)
Publication Number | Publication Date |
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NZ784133A true NZ784133A (en) | 2022-01-28 |
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