U.S. patent application number 10/492811 was filed with the patent office on 2005-01-27 for device and method for complete machining of lenses that are optically active on two sides.
Invention is credited to Buchenauer, Helwig, Kraemer, Klaus, Schneider, Gunter.
Application Number | 20050020186 10/492811 |
Document ID | / |
Family ID | 7702447 |
Filed Date | 2005-01-27 |
United States Patent
Application |
20050020186 |
Kind Code |
A1 |
Schneider, Gunter ; et
al. |
January 27, 2005 |
Device and method for complete machining of lenses that are
optically active on two sides
Abstract
A device for machining a lens which is optically active on two
sides includes a cutting and milling unit and/or a polishing unit
used to machine at least a first side of the lens. A re-clamping
unit is used to re-clamp the lens for machining on a second side of
the lens.
Inventors: |
Schneider, Gunter; (Marburg,
DE) ; Buchenauer, Helwig; (Dautphetal-Buchenau,
DE) ; Kraemer, Klaus; (Dautphetal-Friedensdorf,
DE) |
Correspondence
Address: |
Davidson Davidson & Kappel
14th Floor
485 Seventh Avenue
New York
NY
10018
US
|
Family ID: |
7702447 |
Appl. No.: |
10/492811 |
Filed: |
September 13, 2004 |
PCT Filed: |
October 15, 2002 |
PCT NO: |
PCT/EP02/11518 |
Current U.S.
Class: |
451/41 |
Current CPC
Class: |
B24B 13/005 20130101;
B24B 13/0037 20130101; B24B 13/0012 20130101 |
Class at
Publication: |
451/041 |
International
Class: |
B24B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 17, 2001 |
DE |
101 50 663.5 |
Claims
1-22. (canceled)
23. A device for machining a lens that is optically active on both
a first lens side and a second lens side, the device comprising: a
machining element configured to machine the lens; a first holding
device for clamping the lens in a first position so as to enable
the machining unit to machine the first side; a re-clamping unit
for re-clamping the lens from the first position to a second
position so as to enable the machining unit to machine the second
side; a positioning element; and a second holding device configured
to support the lens via the positioning element in relation to an
axial position of the lens.
24. The device as recited in claim 23, wherein the machining
element includes at least one of a cutting unit, a milling unit and
a polishing unit.
25. The device as recited in claim 23, wherein the second holding
device is connected to the re-clamping unit.
26. The device as recited in claim 23, wherein the positioning
element has at least one reference, the reference indicating at
least one of the first lens side, the second lens side and an
alignment of the lens.
27. The device as recited in claim 23, wherein the positioning
element is configured as a reference surface aligned relative to an
optical axis of at least one of the first lens side and the second
lens side.
28. The device as recited in claim 23, wherein the second holding
device includes at least two holding parts, each holding part
having a back stop associated with a reference surface.
29. The device as recited in claim 23, further comprising a support
part configured to be placed against the first lens side.
30. The device as recited in claim 29, wherein the support part has
a plastically and/or elastically deformable surface for placing
against the first lens side, the deformable surface.
31. The device as recited in claim 30, wherein the surface is
hardenable.
32. The device as recited in claim 30, wherein the surface includes
at least one of a binder and a filler.
33. The device as recited in claim 23, further comprising a marking
device for signing and/or marking the lens.
34. The device as recited in claim 23, further comprising a washing
device for washing and/or rinsing the lens is provided.
35. The device as recited in claim 26, wherein the reference
surface is disposed at least one of orthogonally and parallel
relative to an optical axis of one of the first lens side and the
second lens side.
36. A method for manufacturing a lens from a lens blank having a
first unworked side and a second unworked side, the method
comprising: clamping the lens blank in a lens receptacle rotatable
around a workpiece spindle axis; machining the first unworked side
so as to create a first optically active surface having a first
optical axis essentially coinciding with the workpiece spindle
axis; creating a clamping shoulder having a cylindrical lateral
surface and a ring-shaped bearing face, the clamping shoulder
serving as a positioning element, wherein a positioning axis of the
positioning element is defined by the lateral surface and the
bearing face and is disposed in a position that is one of
coinciding with the workpiece spindle axis, offset from the first
optical axis and tilted with respect to the first optical axis;
removing the lens blank from the lens receptacle; turning the lens
blank and reclamping the lens blank into one of the lens receptacle
and a further lens receptacle so that the positioning axis
coincides with the workpiece spindle axis; and machining the second
unworked side so as to create a second optical surface having a
second optical axis essentially coinciding with the workpiece
spindle axis.
37. A method for machining a lens having a first optically active
lens side and a second optically active lens side, the method
comprising: holding the lens in a first position using a first
holding device associated with the second lens side; machining at
least the first lens side with at least one of a cutting, milling
and polishing unit, wherein the machining includes forming a
positioning element having a reference indicating at least one of
the first lens side and the second lens side; grasping the lens
using a second holding device and aligning the lens relative to the
second holding device using the positioning element; removing the
lens from the first holding device after the grasping; reclamping
the lens from the first position to the second position so as to
enable a machining of the second side; and machining the second
side of the lens using at least one of a cutting unit and a
polishing unit.
38. The method as recited in claim 37, wherein the reference is a
reference surface and wherein the second holding device includes a
plurality of holding parts for grasping the lens in a radial
direction, the reference surface being disposed against at least
one holding part.
39. The method as recited in claim 38, wherein the plurality of
holding parts each include a back stop and the reference surface is
disposed against the back stop of the at least one holding
part.
40. The method as recited in claim 37, wherein the reference is a
reference surface disposed one of perpendicular and parallel to an
optical axis of the lens.
41. The method as recited in claim 36, further comprising disposing
a support part against the first side before the machining of the
second unworked side.
42. The method as recited in claim 36, further comprising placing
at least one of a marking and a signature at one of the first side
and the second side so as to aid in a subsequent alignment of the
lens.
43. The method as recited in claim 36, before the machining of the
second unworked side, applying a protective layer on the first
optical surface.
44. The method as recited in claim 43, further comprising washing
the first optical surface before applying the protective layer.
45. The method as recited in claim 43, wherein the protective layer
includes at least one of a protective film and a protective
coating.
46. The method as recited in claim 36, wherein after the machining
of the first unworked side and before removing the lens from the
lens receptacle, holding the lens using clamping jaws of a second
holding device.
47. The method as recited in claim 43, wherein the before or after
applying the protective layer, machining the edge is machined so as
to facilitate one of a later positioning of the lens and a later
attachment of the lens onto an eyeglass frame.
Description
[0001] The invention relates to a device for machining a lens that
is optically active on two sides, comprising a cutting, milling
and/or polishing unit that serves to machine at least a first side
of the lens, and it also relates to a method for machining a lens
that is optically active on two sides, with a cutting, milling
and/or polishing unit that serves to machine at least a first side
of the lens, whereby the lens is held by a first holding device
associated with a second side.
[0002] The prior-art methods make use of a lens blank made of
plastic or glass whose one side or first side already has the
final, optically active form. In the case of eyeglasses, this is
the front side, in other words, the side facing away from the eye,
which generally forms a spherical surface. Such lens blanks are
kept in stock in various graduations in terms of the radii of
curvature of the spherical surface. For purposes of grinding the
back surface or second side so as to obtain a toric lens, the lens
blank is mounted, that is to say, its front surface or first side
is attached to a blocking member that is clamped into the chuck of
a lens grinding machine.
[0003] In order to produce an individual lens that is adapted to
the multiple vision defects of a given person, the front or first
side is generally provided with an individualized progressive
surface by means of a cutting process. The term progressive surface
refers to a surface that, in partial areas, diverges from a
symmetrical--usually spherical--main surface so as to create a
progressive lens with near and far viewing areas and the
corresponding transition areas. In order to compensate for certain
vision defects, it is also necessary for the main surface of the
front surface or the first side to be tilted, offset and/or
phase-rotated relative to the back or second side.
[0004] In order to produce the progressive surface, until now, the
back surface of the lens blank has been attached to a blocking
member by means of a metallic paste. The lens thus mounted is then
clamped in the head of a tool spindle so that it can be machined.
Since the lens blank is attached directly to the blocking member,
the tilt, the offset and/or the phase-position has to be taken into
account during the mounting by attaching the lens blank to the
blocking member so that it is tilted or offset. As a result, the
mounting procedure is quite time-consuming. Moreover, a separate
machine is needed for this purpose. In spite of all due caution,
this additional step entails a certain degree of imprecision that
cannot be avoided.
[0005] A machine for the production of lenses is already known from
European Patent EP 0 849 038 A3. This machine has a cutting unit
and a polishing unit for machining one side of a lens. Complete
machining of the lens on both sides is not mentioned.
[0006] U.S. Pat. No. 5,205,076 describes a method with which,
likewise while the first side of the lens blank for a contact lens
made of plastic is being machined, a lateral surface is machined
but there is not a bearing face with which the turned lens blank
could then be clamped. It is evident that the axis of the lateral
surface coincides with the workpiece spindle axis, as a result of
which the lens blank does not tilt when the lens blank is placed
into a holding device in order to machine the second side, as a
result of which the method is not suitable for producing lenses in
a simple manner when the optical axes of both sides do not
coincide.
[0007] The invention is based on the objective of creating and
configuring a device and a method in such a way that a complete
machining of the lens on both sides is ensured.
[0008] This objective is achieved according to the invention in
that a re-clamping unit is provided for re-clamping the lens from
the first side to the second side for purposes of machining the
second side of the lens. In this manner, it is achieved that the
lens, after the first side has been machined, is held or clamped on
this side, whereby the unworked second side is separated from a
receptacle adapter and subsequently machined. The machining of the
first side using a receptacle adapter has the advantage that,
irrespective of the shape of the first surface to be produced,
optimal space conditions exist during the machining step. As an
alternative, the lens can also be clamped directly via its
cylindrical basic shape in order to be machined.
[0009] For this purpose, it is also advantageous for the
re-clamping unit to have a second holding device for the lens and
for the lens to be supported relative to the second holding device
via at least one positioning element, whereby the positioning
element has a reference indicating the first side and/or the second
side of the lens and/or its alignment. The reference between the
positioning element and the first side serves to align the lens in
the second holding device relative to an optical axis of the first
side. In this process, the positioning element is generated when
the first side is machined in the same clamping set-up. As a
positioning element, it is also possible to use the first side or
the first holding surface or the support part that serves to
machine the first side. The relationship between this first holding
surface or support part and the first side is given. The
relationship between the first side and the second side is present
anyway. After being clamped by the second holding device, the
support part is then removed. A robot arm can also be used as the
second holding device or for re-clamping.
[0010] Moreover, it is advantageous for the positioning element to
be configured as a reference surface, whereby the reference surface
is aligned relative to an optical axis of the first side and/or of
the second side. The reference surface here is a part of the edge
of the lens that is left behind after the first side of the lens
has been machined. During or after the machining of the second
side, this reference surface is ground away. In addition to this
one reference surface, it is also advantageous to have a second
reference surface that is likewise generated within the scope of
the machining process for the first side of the lens. The second
reference surface can be configured as a side surface or lateral
surface of the lens and it is arranged perpendicular to the
reference surface, that is to say, essentially parallel to the
optical axis of the first side and/or of the second side. In the
ideal case, the reference surface configured as a side surface
constitutes the outer surface of the lens that subsequently goes
into a frame, i.e. the lens does not have to undergo any further
edge machining. The first holding surface or the support part that
serves to machine the first side or else the axis position of the
robot that fixes the lens position can also be used as the
positioning element.
[0011] It is also advantageous for the second holding device to
have at least two holding parts, each having at least one back stop
associated with at least one reference surface. The uniform
configuration of the back stop and of the holding part ensures a
precise positioning of the lens without an additional reference
between the back stop and the holding part. The back stop of the
lens receptacle is configured as a counter-surface to the ring
surface or to the reference surface of the lens blank and it
extends perpendicular to the workpiece spindle axis.
[0012] Moreover, in a preferred embodiment of the solution
according to the invention, it is provided that there is a support
part that can be placed against the first side of the lens, whereby
the support part has a plastically and/or elastically deformable
surface that can be placed against the first side of the lens and
said surface is made of binder and/or filler and/or else it can be
hardened. Thus, the lens is provided with a support that allows the
second side to be machined. The hardening of the surface or
adhesive makes it possible to mount the lens without any
pre-stressing so that the second side can be machined in a
reproducible manner.
[0013] It is likewise advantageous to have a device for signing
and/or marking the lens. This ensures the proper positioning of the
lens in its later receptacle within a component such as, for
example, an eyeglass frame. This signing can be done either in a
cutting unit by means of a tool and/or in a re-clamping unit by
means of a laser. In addition, the marking also serves to position
the lens relative to the holding device, if the relationship has
not already been ensured by means of the re-clamping device during
the re-clamping.
[0014] Furthermore, it is advantageous to have a washing and/or
rinsing device for the lens. The first side of the lens can thus be
cleaned before it is re-clamped and the completely machined lens
can be cleaned before being removed. The washing and/or rinsing
device here is provided in a polishing unit.
[0015] Moreover, it is advantageous for the reference surface to be
arranged orthogonally or parallel to the optical axis of the first
side and/or of the second side of the lens. Here, the orthogonally
arranged reference surface serves to attain a vertical alignment,
whereby the reference surface arranged in parallel determines the
radial position of the lens. It is also possible to ensure the
alignment of the lens in the vertical and in the radial directions
by means of a shaping surface.
[0016] The objective is achieved by the following process steps:
clamping the lens blank into a lens receptacle or holding device
that can be rotated around a workpiece spindle axis. Machining a
first optically active surface having an optical axis on the first
side of the lens blank. Creating a clamping shoulder having a
cylindrical lateral surface whose axis lies essentially in the
workpiece spindle axis, whereby this step can also be carried out
before the first optically active surface is machined.
[0017] Removing and turning the lens blank that has been thus
machined, clamping the turned lens blank on the clamping shoulder
into the previously used lens receptacle or into another one,
machining a second optical surface having an optical axis on the
second side of the lens blank, whereby the optical axis of this
surface is offset or tilted relative to the optical axis of the
first surface.
[0018] In this method, the tilt or the offset is taken into account
when the sides, especially the second side, are machined, that is
to say, the movement path of the tool not only takes the actual
progressive surface into account but also the tilt of the main
surface. Although this method is certainly feasible, it requires a
very dynamic servomotor for the tool, since the latter has to
traverse larger stroke amplitudes because the main surface is
tilted with respect to the workpiece spindle axis.
[0019] Therefore, another method calls for the following steps.
Clamping the lens blank into a lens receptacle that can be rotated
around a workpiece spindle axis. Machining a first optically active
surface having an optical axis on the first side of the lens blank,
whereby the optical axis of this surface lies essentially in the
workpiece spindle axis. Creating a clamping shoulder having a
cylindrical lateral surface and a ring-shaped bearing face, whereby
the axis defined by the lateral surface and by the ring surface is
offset and/or tilted with respect to the optical axis of the first
optically active surface, whereby this step can also be carried out
before the first optically active surface is machined. Removing and
turning the lens blank that has been thus machined. Clamping the
turned lens blank into the previously used lens receptacle or into
a different one, so that the axis of the clamping shoulder
coincides with the workpiece spindle axis. Machining a second
optical surface having an optical axis on the second side of the
lens blank, whereby the optical axis of this surface likewise lies
essentially in the workpiece spindle axis. The slant or offset of
the lens blank needed in each case for machining the second side
can consequently be obtained by machining a clamping shoulder whose
axis is tilted and/or offset relative to the optical axis of the
first optical surface so that the turned lens blank can be clamped
so as to be tilted and/or offset. The second surface is now
machined, whereby its optical axis coincides with the workpiece
spindle axis. This makes it considerably easier to guide the tool;
it merely has to follow a path that, for the most part, follows the
symmetrical main surface. Elevations or depressions that define the
progressive surface only constitute minor deviations that can
easily be calculated into the movement path. All in all, this leads
to smaller strokes of the tool in the axial direction than if the
tilt or an offset still had to be additionally machined. Therefore,
both methods have in common the fact that they can dispense with
the need for the time-consuming blocking procedure which requires
an additional machine and which is quite error-prone.
[0020] When the description of the invention refers to an optical
axis of a progressive surface, this means an axis that describes
the mean curvature of the progressive surface and that orients
itself towards the optical axis of the underlying symmetrical main
surface.
[0021] As explained, the clamping shoulder has a cylindrical
lateral surface and a ring-shaped bearing face that runs
perpendicular thereto. The lateral surface is grasped by tongs or
holding parts of a lens receptacle or of a holding device in order
to hold the lens blank so that it cannot rotate, whereby the
bearing face lies on the back stops of the holding part. Since the
surface normal of the bearing face is tilted with respect to the
blank axis and since the upper end or back stop of the holding
parts or their back stop lies in a counter-surface running
perpendicular to the workpiece spindle axis, the lens blank is held
in the lens receptacle in such a way that its axis is tilted with
respect to the workpiece spindle axis.
[0022] The main surface axes of the two sides have to be matched
with each other. This can also be taken into account with the
clamping shoulder in that a phase marking that interacts
mechanically or optically with a corresponding counter-marking on
the lens receptacle is integrated into the clamping shoulder. This
makes it possible to place the lens blank phase-precisely into the
lens receptacle so that the control unit, which knows the relative
position of the workpiece spindle relative to the machining tool,
also receives information about the phase alignment of the lens
blank and can thus effectuate phase-correct machining of the second
side.
[0023] Due to the tilting of the axis of the lateral surface,
undercuts are formed on one side of the lens so that a turning tool
that is stepped or offset with respect to the blank axis is used in
order to create the clamping shoulder.
[0024] Moreover, when the first side is being machined, one or more
line markings or signatures can be incorporated that make it
possible to adjust and check the angular positions of the two
optical surfaces relative to each other for machining the second
side. Such line markings, also called signatures, are also applied
onto the second side. The line markings contain especially
information about the position of the main and secondary axes of
the lens main surface. Markings on both sides are needed primarily
for edge machining of eyeglass lenses that have to be placed with
phase-precision into eyeglass frames.
[0025] The objective is also achieved in that the cutting procedure
provides the lens with a positioning element having a reference
indicating the first side and/or the second side and in that, after
the cutting and/or polishing of a first side and before the lens is
removed from the first holding device or before the detachment of
the first holding device, said lens is grasped by the second
holding device and aligned relative to said second holding device
by means of the positioning element. The positioning element here
can also be incorporated into the clamping shoulder as a phase
marking so that a phase-precise placement of the turned lens blank
is possible.
[0026] The polishing--in addition to the usual mechanical and
chemical machining--also comprises extremely fine diamond machining
or machining without additives, only with water. In this manner,
minute cutting marks are reworked and removed.
[0027] In this process, a receptacle adapter that is optionally
arranged on the second side of the lens for the machining of the
first side is detached from the second side of the lens and the
second side of the lens is machined by means of the cutting and/or
polishing unit.
[0028] If no further positioning element is formed by the cutting
process, then the first side or the first receiving surface or
support part for machining the first side serves as a positioning
element for machining the second side.
[0029] Furthermore, it is advantageous for the lens to be clamped
in the radial direction by holding parts of the second holding
device, whereby the positioning element of the lens configured as a
reference surface is laid against at least one holding part or one
back stop of the holding part. The back stop here is point-shaped,
line-shaped or flat so that the reference surface can be laid
against it.
[0030] For this purpose, it is also advantageous for the reference
surface to be arranged perpendicular or parallel to an optical axis
of the lens and for a support part to be laid against the first
side. The support part has a plastic-elastic surface that is
hardened after being applied so that the lens is supported
stress-free.
[0031] Moreover, it is advantageous for a marking and/or signature
to be placed onto or incorporated into the first side and/or the
second side for purposes of a subsequent alignment of the lens,
whereby after the first side has been machined, a protective layer
or a protective film is placed on said first side. The signing here
can be done directly by means of a laser before the re-clamping or
else during the cutting or milling process. In addition to the
simplified subsequent positioning of the lens in the component or
eyeglass frame, the marking also serves for positioning the lens
relative to the holding device insofar as the relationship is not
ensured by the re-clamping device during the re-clamping. Due to
the signing, the phase position of the lens relative to another
lens or to the eyeglass frame or to the re-clamping device is
ensured.
[0032] It is also advantageous for the lens to be washed after the
first side has been machined or after the polishing and before the
application of the protective layer or protective film and for the
first side and/or the second side to be provided with a coating.
For practical reasons, the coating of both sides simultaneously is
of great significance.
[0033] Furthermore, it is advantageous if, after the first side has
been machined and before the lens has been removed from the first
holding device, it is held by the clamping jaws of the second
holding device. In this manner, the positioning of the lens
relative to the first holding device can be transferred to the
second holding device. The use of signatures and/or markings can be
eliminated.
[0034] For this purpose, it is advantageous for the lens to be
removed from a receptacle adapter after the first side has been
machined and/or to be detached from a support part after the second
side has been machined. This ensures the machining and completion
of the lens after the appertaining machining step.
[0035] Finally, it is advantageous if, before or after the coating,
the edge is machined for purposes of the later positioning and
attachment of the lens onto the eyeglass frame. Due to the edge
machining after the coating, critical coating areas in the edge
region are removed and special attachment modalities are created in
the form of shape-rounding, grooving or drilling of the lens for
attachment to the eyeglass frame.
[0036] Additional advantages and details of the invention are
explained in the patent claims and in the description and they are
depicted in the figures. The drawings show the following:
[0037] FIG. 1 a schematic diagram of a lens with a receptacle
adapter on the second side;
[0038] FIG. 2 a schematic diagram of a lens with a support part and
clamping jaws;
[0039] FIG. 3 a schematic diagram of a complete machining unit with
a cutting and/or milling unit, a polishing unit and a re-clamping
unit;
[0040] FIGS. 4-9 the consecutive steps for machining a lens from a
lens blank.
[0041] The lens 1 shown in FIG. 1 has an optically active first
side 1.1 and a side 1.2 that is to be machined. According to FIG.
1, the lens 1 is connected to a workpiece spindle (not shown here)
of a cutting and milling unit 7 via a receptacle adapter 6 and a
receptacle journal 6.1. In an embodiment (not shown here), the
cylindrical lens is accommodated directly in the workpiece
spindle.
[0042] According to FIG. 1, the lens 1 is glued onto the receptacle
adapter 6 so that the first side 1.1 of the lens 1 can be machined.
Aside from the lens shape generated on the first side 1.1 with the
resultant optical axis 1.3, the lens 1 also has a reference surface
4.1 that is arranged orthogonally to the optical axis 1.3. The
reference surface 4.1 is part of the still remaining material of
the former blank lens 1 that is machined according to FIG. 2 in
another machining step to form the second side 1.2 of the lens 1.
In addition to the reference surface 4.1, there is a side surface
4.2 that is arranged perpendicular to the reference surface 4.1 and
that likewise has a reference to the optical axis 1.3.
[0043] According to FIG. 2, the lens is turned so that the already
machined first side 1.1 of the lens 1 can be held by a two clamping
jaws 3.1, 3.2 of a second holding device 3 of a re-clamping unit 2.
According to FIG. 2, the second side 1.2 is now facing upwards and
the receptacle adapter 6 has been removed. The second side 1.2 is
freely accessible in this position and can be machined. The
position of the lens 1 relative to the workpiece spindle (not shown
here) according to FIG. 1 and the position of the lens 1 relative
to the holding part 3.1 are maintained here.
[0044] The lens 1 lies with its reference surface 4.1 on a back
stop 3.3 or back stop 3.3' of the clamping jaw 3.2 or of the
clamping jaw 3.1 and is thus aligned with the optical axis 1.3 of
the first side 1.1. The optical axis 1.3 now runs approximately
parallel to a workpiece spindle (not shown here) or parallel to the
side surface 4.2 of the first side 1.1. Here, the side surface 4.2
serves to determine the position relative to the radial alignment
of the lens 1. The lens 1 is held by the clamping jaws 3.1, 3.2 in
the radial direction via the side surface 4.2.
[0045] In order to support the lens for purposes of machining the
second side 1.2, a support part 5 is provided that has a surface
5.1 that can be hardened, such as an adhesive. The support part 5
is connected via a receptacle journal 5.2 to a workpiece spindle
(not shown here). The surface 5.1 here is elastically-plastically
deformable and can be placed or pressed from below against the lens
1 or against the first side 1.1 by means of the clamping jaw 3.1 so
as to clamp the lens 1. Thus, the surface 5.1 adapts to the
geometry of the first side 1.1 of the lens 1 and offers sufficient
support after the hardening.
[0046] According to FIG. 3, a complete machining unit 10 has a
cutting and milling unit 7, followed by a polishing unit 8, a
re-clamping unit 2 and a coating unit 9. After the first side 1.1
has been machined in the cutting and milling unit 7, the lens is
transferred to the polishing unit 8. After being polished, the lens
1 is washed in the polishing unit 8, turned by the re-clamping unit
2 as shown in FIGS. 1, 2 and transferred to the cutting and milling
unit 7 so that the second side 1.2 can be machined. Then the second
side 1.2 is polished and washed in the polishing unit 8. In the
re-clamping unit 2, the lens 1 is detached from the receptacle
adapter 6 after the first side 1.1 has been machined or detached
from the support part 5 after the second side 1.2 has been machined
and held by the clamping jaws 3.1, 3.2.
[0047] As desired, after the washing, a unit or a station is
provided for coating the lens 1 with a protective layer or a
protective film such as a plastic film so that the surface of the
already machined first side 1.1 is not damaged during the machining
of the second side 1.2.
[0048] After the cutting or milling and the polishing of the first
side 1.1 and/or of the second side 1.2, the lens is signed in the
re-clamping unit 2, for example, by means of a laser, and/or it is
transferred to the coating unit 9, from which it emerges completely
machined.
[0049] FIG. 4 shows a cylindrical lens blank 1 with a first side
1.1 and a second side 1.2, both of which extend perpendicular to
the blank axis 1.4. The lens blank 1 is clamped in a lens
receptacle 3 of a workpiece spindle (not shown here), said lens
receptacle 3 having holding part or tongs 3.1, 3.2, so that the
blank axis 1.4 coincides with the workpiece spindle axis.
[0050] According to FIG. 5, first of all, the optically active
surface of the first side 1.1 is machined with a turning tool 11.
In the simplest case, the optically active surface 1.1 is a
spherical surface whose optical axis 1.3 coincides with the blank
axis 1.4. However, a progressive surface can already be created
here as well, whereby the optical axis 1.3 is the axis of the main
surface of the progressive surface. The machining is carried out
with a rapidly rotating workpiece spindle, whereby the turning tool
11 is moved up and down corresponding to the rotation of the
workpiece spindle while said tool is slowly moved in the radial
direction. In order to prevent excessive acceleration of the tool
in the axial direction, the turning motion or rotation can be
slowed down, if so desired, in those areas displaying considerable
changes in the local curvature. The workpiece spindle axis is thus
a controlled, that is to say, phase-regulated axis.
[0051] According to FIG. 6, a clamping shoulder 4 is created in the
same clamping set-up. This clamping shoulder 4 consists of an
encircling step 4.3 with a lateral surface 4.2 and a ring surface
4.1 running perpendicular thereto. It is crucial for the clamping
shoulder 4 to be tilted with respect to the blank axis 1.4 and thus
with respect to the optical axis 1.3 of the optically active
surface 1.1 of the first side, in other words, for the surface
normal of the ring surface 4.1, that is, the axis 12 of the
clamping shoulder, to be tilted with respect to these axes. As a
matter of principle, the step 4.3 can also be configured to be
additionally offset with respect to the optical axis 1.3. In order
to be able to machine the step 4.3, a laterally offset turning tool
11 is used so as to also be able to machine the areas that are in
the form of undercuts.
[0052] The machining of the first side 1.1 of the lens blank 1 is
thus completed. It is now removed from the clamping set-up and
turned over, and then, with the first side 1.1 facing downwards, it
is once again placed into the clamping set-up phase-precisely by
using a phase marking in the form of a line marking. Such a marking
can be dispensed with if the re-clamping is carried out in a
controlled manner, that is to say, if the phase position of the
lens 1 with respect to the spindle is known and if, thanks to the
controlled movement of the transfer tool 3, this information is not
lost, so that the turned lens 1 is once again placed
phase-precisely into the chuck of a phase-regulated spindle. Here,
as is shown in FIG. 7, the lens blank 1 is grasped at the step 4.3,
whereby the tongs 3.1, 3.2 of the lens receptacle 3 grasp the
lateral surface 4.2 and hold the lens blank 1 so that it cannot
rotate. At the same time, the ring surface 4.1 lies on the upper
end of the tongs 3.1, 3.2 so that the blank axis 1.4 is tilted with
respect to the workpiece spindle. The second side 1.2 of the lens
blank 1, which is now facing upwards, runs tilted with respect to
the workpiece spindle.
[0053] According to FIG. 8, the second side 1.2 facing upwards is
now machined into a progressive surface, that is the second optical
surface 1.2, whereby its optical axis 1.4 coincides with the
workpiece spindle axis and is thus tilted or optionally offset with
respect to the optical axis 1.3 of the first side 1.1.
[0054] In order for the angle alignment of the two optical surfaces
1.1, 1.2 to have the desired value, during the machining of the
first side 1.1, a line marking is created that is taken into
account when the second side 1.2 is being machined. Before the
cutting process begins, the lens blank 1 is aligned on the basis of
the line marking. At the same time, it constitutes the starting
point for the machining of the second side 1.2.
[0055] As soon as the second side 1.2 has also been machined, the
lens that has been made from the lens blank 1 is removed from the
lens receptacle 3 and its edges are machined, whereby at least the
material area that forms the ring surface of the clamping
set-up--shown here with double crosshatching--is removed.
List of Reference Numerals
[0056] 1 lens
[0057] 1.1 first side, first optical surface
[0058] 1.2 second side or optical surface, progressive surface
[0059] 1.3 optical axis
[0060] 1.4 optical axis, blank axis
[0061] 2 re-clamping unit
[0062] 3 second holding device, lens receptacle, transfer tool
[0063] 3.1 holding part, clamping jaw, tongs
[0064] 3.2 holding part, clamping jaw, tongs
[0065] 3.3 back stop, counter-surface
[0066] 3.3' back stop, counter-surface
[0067] 4 clamping shoulder
[0068] 4.1 positioning element, reference surface
[0069] 4.2 side surface, lateral surface
[0070] 4.3 step
[0071] 5 support part
[0072] 5.1 surface
[0073] 5.2 receptacle journal
[0074] 6 receptacle adapter
[0075] 6.1 receptacle journal
[0076] 7 cutting and milling unit
[0077] 8 polishing unit
[0078] 9 coating unit
[0079] 10 complete machining unit
[0080] 11 turning tool
[0081] 12 axis of the clamping shoulder
* * * * *