Polishing device for polishing concave lens faces of optical lenses, and method for operation thereof

Abstract

A polishing device for polishing curved lens faces of optical lenses has a workpiece holder for receiving an optical lens and a polishing tool. The polishing tool has a support element, an elastic substructure and a curved polishing surface on the elastic substructure. The polishing tool, with the polishing surface, is driven in a rotating manner about a rotation axis, the workpiece holder being driven in a rotating manner about a first axis, in order to rotate the optical lens. A distance between the workpiece holder and the polishing tool is adjustable along a second axis. An offset between the workpiece holder and the polishing device is adjustable along a third axis, which is aligned transversely in relation to the first axis. A pitch angle between the rotation axis and the first axis is adjustable by tilting about a fourth axis. A method of operating the device is also disclosed.

Claims

1. A polishing device (1) for polishing curved lens faces (101) of optical lenses (100), the polishing device (1) having a workpiece holder (10) for receiving an optical lens (100) and having a polishing tool (20), the polishing tool (20) having a support element (21) with a curved polishing surface (23), being driven in a rotating manner about a rotation axis (R), either the curved lens face (101) being concave and the curved polishing surface (23) being convex, or the curved lens face (101) being convex and the curved polishing surface (23) being concave, the workpiece holder (10) being driven in a rotating manner about a first axis (A1), in order to rotate the optical lens (100), a distance (z) between the workpiece holder (10) and the polishing tool (20) being adjustable along a second axis (A2), an offset (x) between the workpiece holder (10) and the polishing device (20) being adjustable along a third axis (A3), which is aligned transversely in relation to the first axis (A1), wherein the curved polishing surface (23) is located on an elastic substructure (22) of the polishing tool (20), a pitch angle (W) between the rotation axis (R) and the first axis (A1) is adjustable by tilting about a fourth axis (A4), when there is an optical lens (100) received in the workpiece holder (10), the polishing tool (20) can be placed, according to the pitch angle (W), obliquely on the curved lens face (101), and a strip-type contact area (F) can be realized between the polishing surface (23) and the curved lens face (101) as a result of deformation of the elastic substructure (22), and the pitch angle (W) between the rotation axis (R) and the first axis (A1) being such a magnitude that the polishing surface (23) is partially raised from the curved lens face (101) and a portion of the polishing surface (23) floats above the lens face (101) at a lateral distance from the contact area.

2. The polishing device (1) as claimed in claim 1, wherein the strip-type contact area (F) extends at both ends (E1, E2) as far as a circumferential edge (103) of the curved lens face (101).

3. The polishing device (1) as claimed in claim 1, further comprising an electric controller, wherein during a polishing process, the speed of rotation of the workpiece holder (10) about the first axis (A1), the distance (z) between the workpiece holder (10) and the polishing tool (20) along the second axis (A2), the offset (x) between the workpiece holder (10) and the polishing tool (20) along the third axis (A3), and the pitch angle (W) between the rotation axis (R) and the first axis (A1), by tilting about the fourth axis (A4), are driven by the electric controller in an interpolating manner.

4. The polishing device (1) as claimed in claim 3, wherein the pitch angle (W) is regulated, by the electric controller, to a value at which a maximally uniform contact pressure force is present over the length of a strip-type contact area (F) between the polishing surface (23) and the curved lens face (101).

5. The polishing device (1) as claimed in claim 1, wherein the second axis (A2) and the third axis (A3) are mechanically coupled to the workpiece holder (10).

6. The polishing device (1) as claimed in claim 1, wherein the fourth axis (A4) is mechanically coupled to the polishing tool (20).

7. A method for operating a polishing device (1) comprising: a workpiece holder (10) for receiving an optical lens (100) and having a polishing tool (20), the polishing tool (20) having a support element (21) with a curved polishing surface (23), being driven in a rotating manner about a rotation axis (R), either the curved lens face (101) being concave and the curved polishing surface (23) being convex, or the curved lens face (101) being convex and the curved polishing surface (23) being concave, the workpiece holder (10) being driven in a rotating manner about a first axis (A1), in order to rotate the optical lens (100), a distance (z) between the workpiece holder (10) and the polishing tool (20) being adjustable along a second axis (A2), an offset (x) between the workpiece holder (10) and the polishing device (20) being adjustable along a third axis (A3), which is aligned transversely in relation to the first axis (A1), wherein the curved polishing surface (23) is located on an elastic substructure (22) of the polishing tool (20), a pitch angle (W) between the rotation axis (R) and the first axis (A1) is adjustable by tilting about a fourth axis (A4), when there is an optical lens (100) received in the workpiece holder (10), the polishing tool (20) can be placed, according to the pitch angle (W), obliquely on the curved lens face (101), and a strip-type contact area (F) can be realized between the polishing surface (23) and the curved lens face (101) as a result of deformation of the elastic substructure (22), and the pitch angle (W) between the rotation axis (R) and the first axis (A1) being such a magnitude that the polishing surface (23) is partially raised from the curved lens face (101) and a portion of the polishing surface (23) floats above the lens face (101) at a lateral distance from the contact area, the method comprising the following steps: a) receiving an optical lens (100) with the workpiece holder (10), b) placing the polishing tool (20), with the polishing surface (23), on the curved lens face (101), c) rotating the polishing tool (20) about the rotation axis (R), d) performing a polishing operation, by driving in an interpolating manner the speed of rotation of the workpiece holder (10) about the first axis (A1), the distance (z) between the workpiece holder (10) and the polishing tool (20) along the second axis (A2), the offset (x) between the workpiece holder (10) and the polishing tool (20) along the third axis (A3), and the pitch angle (W) between the rotation axis (R) and the first axis (A1), by tilting about the fourth axis (A4), wherein the polishing tool (20) is placed, according to the pitch angle (W), obliquely on the curved lens face (101), and a strip-type contact area (F) is realized between the polishing surface (23) and the curved lens face (101) as a result of deformation of the elastic substrate (22), and the pitch angle (2) between the rotation axis (R) and the first axis (A1) being of such a magnitude that the polishing surface (23) is partially raised from the curved lens face (101) and a portion of the polishing surface (23) floats above the lens face (101) at a lateral distance from the contact area.

8. The method as claimed in claim 7, wherein the driving in the interpolating manner takes into account, as a first objective function, the pitch angle (W) at which a maximally uniform contact pressure force is present over the length of the strip-type contact area (F) between the polishing surface (23) and the curved lens face (101).

9. The method as claimed in claim 8, wherein the driving in the interpolating manner takes into account, as a second objective function, the strip-type contact area (F) between the polishing surface (23) and the curved lens face (101) that extends at both ends (E1, E2) as far as a circumferential edge (103) of the curved lens face (101).

10. The method as claimed in claim 7, wherein the driving in the interpolating manner takes into account, as a third objective function, a contact pressure force that is maximally uniform over a revolution of the optical lens (100).

11. The method as claimed in claim 7, wherein the driving in the interpolating manner takes into account, as a fourth objective function, a constant removal profile in the strip-type contact area (F) between the polishing surface (23) and the curved lens face (101).

12. The method as claimed in claim 7, wherein, for each revolution of the optical lens (100) about the first axis (A1), the pitch angle (W) between the rotation axis (R) and the first axis (A1) is tilted to and fro twice about the fourth axis (A4).

13. The method as claimed in claim 7, wherein, for each revolution of the optical lens (100) about the first axis (A1), the offset (x) between the workpiece holder (10) and the polishing tool (20) along the third axis (A3) oscillates to and fro twice.

14. The method as claimed in claim 7, wherein the rotating of the polishing tool (20) about the rotation axis (R) is effected at a constant rotational speed, between starting-up and decelerating.

Description

(1) Further features, details and advantages of the invention are disclosed by the wording of the claims and by the following description of exemplary embodiments, on the basis of the drawings. These are shown in:

(2) FIG. 1 a section through a portion of a polishing device;

(3) FIG. 2 a perspective view of a polishing device having two working planes;

(4) FIG. 3 a schematic diagram to illustrate the contact area of a polishing tool placed with a pitch angle on the lens face, and

(5) FIG. 4 a perspective view of a polishing device according to FIG. 2, but represented with a frame, housing and secondary equipment for automated operation.

(6) FIG. 1 shows, in a section through a portion of a polishing device 1, how the polishing of a concave lens face 101 of an optical lens 100 is effected by means of a polishing tool 20.

(7) The polishing device 1 is composed of two corresponding units. The first unit in this case comprises the receiver and motion kinematics of the optical lens 100, with a workpiece holder 10. The second unit relates to the polishing tool 20 and its motion kinematics.

(8) The polishing tool 20 has a support element 21 and an elastic substructure 22 between a convex polishing surface 23 and the support element 21. The polishing tool 20, with the polishing surface 23, in this case is driven in a rotating manner about a rotation axis R. In particular, the polishing tool 20 is rotatably mounted on a tool holder, in this case, in particular, a tool drum 50. Also disposed here is a spindle drive 35, by means of which the polishing tool 20 is driven about the rotation axis R.

(9) The tool drum 50, in turn, is driven so as to be rotatable about a fourth axis A4. This rotation is used to set and regulate, by means of a fourth drive A4, on the one hand, a pitch angle W of the polishing tool 20 relative to the optical lens 100 and, on the other hand, to enable the use of differing polishing tools, which are disposed on the circumference of the tool drum 50.

(10) In this case, the rotation axis R and the fourth axis A4 intersect perpendicularly. This renders the motion kinematics particularly simple. However, this intersection is not absolutely necessary. Also conceivable, alternatively, are a non-perpendicular alignment and/or a spaced-apart arrangement.

(11) In summary, the polishing tool 20 thus rotates about the rotation axis R, and can be aligned and adjusted by adaptation of the pitch angle W to the lens face 101. These are the only adjustable axes and degrees of freedom of the polishing tool 20. Thus, no cardanically mounted polishing disk is provided.

(12) The workpiece holder 10 is driven in a rotating manner about the first axis A1, in order to rotate the optical lens 100 about its center. For this purpose, the optical lens 100 may be connected, in particular by its back side 102, either by material bonding to a so-called block piece, or a vacuum holder is used, which holds the optical lens 100 on the back side of the lens 102 by means of a vacuum.

(13) In respect of the optical lens 100, the diameter D2 of the lens face 101, the circumferential edge 103 and the surface curvature K2 of the lens face 101 are also identified.

(14) Furthermore, the motion kinematics of the workpiece holder 10 is also represented schematically. Firstly, the workpiece holder 10 has a first drive 31, for effecting a rotation about the first axis A1. By means of a second drive 32, the workpiece holder 10 can be moved back and forth along a second axis A2. In this case, the second axis A2 is coaxial with the first axis A1. A simple motion kinematics is thereby achieved. Additionally provided is a third drive 33, by means of which the workpiece holder 10 can be moved back and forth laterally; this, in particular, transversely, and in particular perpendicularly, in relation to the second axis A2. These are the only three axes of motion of the workpiece holder 10. Moreover, the first axis A1 is aligned perpendicularly through the center of the concave lens face 101.

(15) It is preferred that the fourth axis A4 intersects perpendicularly the plane spanned by the second and third axis A2, A3. Moreover, preferably, the rotation axis R and the first axis A1 also intersect each other.

(16) Thus, in this case, the first axis A1, the second axis A2 and the third axis A3 are mechanically coupled to the workpiece holder 10, i.e. these three axes determine the degrees of freedom of the workpiece holder 10. The fourth axis A4 and the rotation axis R are mechanically coupled to the polishing tool 20, i.e. they determine the degrees of freedom of the polishing tool 20.

(17) The first axis A1 and the rotation axis R are to be disposed, as described, in order to effect the rotations of the lens 100 and of the polishing tool 20. On the other hand, alternatively, it is possible in principle for the second axis A2 and the third axis A3 to be mechanically coupled to the polishing tool 20, and/or for the fourth axis A4 to be mechanically coupled to the workpiece holder 10.

(18) As a result of these or the stated alternative arrangements and degrees of freedom of the workpiece holder 10 and of the polishing tool 20, it is now possible to adjust and regulate a distance z between the workpiece holder 10 and the polishing tool 20, along the second axis A2. At the same time, an offset x between the workpiece holder 10 and the polishing tool 20, along the third axis A3, which is aligned transversely in relation to the first axis A1, can be adjusted and regulated. In addition, the pitch angle W between the rotation axis R and the first axis A1 can be actively adjusted and regulated, by means of the fourth drive 34, by tilting about the fourth axis A4.

(19) It is thereby possible for the polishing tool 20 to be placed obliquely on the concave lens face 101, in such a manner that only a portion of the polishing surface 23 comes into contact with the concave lens face 101. This contact area F is represented by an overlap between the polishing tool 20 and the optical lens 100. In reality, the elastic substructure 22 deforms. Another portion of the polishing surface 23 is raised from the lens face 101. It floats to a certain extent above the lens face 101. This also affects, in particular, the center in the middle M of the polishing surface 23 around the rotation axis R.

(20) As a result of deformation of the elastic substructure 22, a strip-type contact area F, in particular, is realized between the polishing surface 23 and the concave lens face 101, as explained in greater detail in the following with reference to FIG. 3. The more strongly the polishing tool 20 is pressed against the lens face 101, the greater the contact pressure force becomes, and the wider the contact area F becomes. Both correlate with the removal rate. Moreover, the removal rate is also determined by the rotational speed of the polishing tool 20 about the rotation axis R and by the rotational speed of the optical lens 100 about the first axis A1.

(21) By an electric controller it is now possible, during a polishing process, in particular exclusively, for the speed of rotation of the workpiece holder 10 about the first axis A1, the distance z between the workpiece holder 10 and the polishing tool 20 along the second axis A2, the offset x between the workpiece holder 10 and the polishing tool 20 along the third axis A3, and the pitch angle W between the rotation axis R and the first axis A1, by tilting about the fourth axis A4
to be driven in an interpolating manner. This, in particular, in that the rotating drive of the workpiece holder 10 about the first axis A1 by means of the first drive 31 is regulated by the control means, the adjustment of the distance z between the workpiece holder 10 and the polishing tool 20 along the second axis A2 by means of the second drive 32 is regulated by the electric controller, the adjustment of the offset x between the workpiece holder 10 and the polishing tool 20 along the third axis A3 by means of the third drive 33 is regulated by the electric controller, and the adjustment of the pitch angle W between the rotation axis R and the first axis A1 by means of the fourth drive 34 is regulated by the electric controller.

(22) During a polishing process, in particular exclusively, the rotational speed of the first drive 31, the position of the second drive 32, the position of the third drive 33, and the position of the fourth drive 34
are driven in an interpolating manner by the electric controller. Possible, in particular, is an interpolation that performs an interpolating motion of the second, third and fourth axis A2, A3, A4 over each revolution of the lens blank 100 about the first axis A1.

(23) On the other hand, the rotational speed of the convex polishing surface 23 about the rotation axis R is preferably held to a constant rotational speed by the spindle drive 35. This rotational speed is preferably to be selected, in any case, so as to be of such a speed that, owing to the rotational inertia, a rapid modulation of the rotational speed is not possible. A rotational speed of between 600 and 1500 revolutions per minute is to be preferred.

(24) In addition, the rotational speed at which the polishing tool 20 rotates about the rotation axis R between starting-up and decelerating should be greater than the maximum rotational speed of the rotation of the workpiece holder 10 about the first axis A1. In particular, during the polishing operation, values of between 0 and 100 revolutions per minute are appropriate as a maximum rotational speed of the rotation of the workpiece holder 10 about the first axis A1.

(25) The pitch angle W is regulated by the electric controller, insofar as possible, to a value at which there is a maximally uniform contact pressure force present over the length of the strip-type contact area F between the polishing surface 23 and the concave lens face 101. The greater the local surface curvature K2 of the lens face 101, therefore, the greater the pitch angle W will be.

(26) For the purpose of operating a polishing device 1, the following steps, in particular, are performed: a) receiving an optical lens 100 by means of the workpiece holder 10, b) placing the polishing tool 20, with the polishing surface 23, on the concave lens face 101, c) rotating the polishing tool 20 about the rotation axis R, d) performing a polishing operation by driving in an interpolating manner the speed of rotation of the workpiece holder 10 about the first axis A1, the distance z between the workpiece holder 10 and the polishing tool 20 along the second axis A2, the offset x between the workpiece holder 10 and the polishing tool 20 along the third axis A3, and the pitch angle W between the rotation axis R and the first axis A1, by tilting about the fourth axis A4.

(27) This means that, during the polishing operation, precisely four axes interpolate with one another, namely, the first, second, third and fourth axis A1, A2, A3, A4. The rotational speed about the rotation axis R it taken into account (if at all) as a constant input variable.

(28) According to the method, it is possible for the driving in an interpolating manner to take into account, as a first objective function, a pitch angle W at which a maximally uniform contact pressure force is present over the length of a strip-type contact area F between the polishing surface 23 and the concave lens face 101. In addition, regulation can be effected such that the driving in an interpolating manner generates, as a third objective function, a contact pressure force that is maximally uniform over one rotation of the optical lens 100.

(29) Moreover, the driving in an interpolating manner may pursue, as a second objective function, a strip-type contact area F between the polishing surface 23 and the concave lens face 101 that extends at both ends E1, E2 as far as a circumferential edge 103 of the concave lens face 101. A lens edge that surrounds the concave lens face 101 and that does not require polishing is insignificant.

(30) As described above, the removal rate also depends on the rotational speeds, in particular on the velocity vectors in the contact area F. The velocity vectors can be determined, besides the local contact pressure force, solely on the basis of the positions of the workpiece holder 10, the polishing tool 20 and the surface shape of the lens face 101. This enables the driving in an interpolating manner to take into account, as a fourth objective function, a maximally constant removal profile in the contact area F between the polishing surface 23 and the concave lens face 101.

(31) FIG. 2 shows a perspective view of a polishing device 1 having two working planes. Located in the working plane that is foremost in the direction of the image are a workpiece holder 10 and a polishing tool 20 according to the section shown in FIG. 1. For reasons of clarity, only some of the technical features are denoted by references here.

(32) In particular, it can be seen that the workpiece holder 10 holds an optical lens 100 that is machined by means of the polishing tool 20. The polishing tool 20 is composed of a support element 21, an elastic substructure 22 mounted thereon, and a polishing surface 23 on the elastic substructure 22.

(33) As also in FIG. 1, the workpiece holder 10 can be displaced along the second axis A2, to enable regulation of a distance z between the workpiece holder 10 and the polishing tool 20. An offset x between the workpiece holder 10 and the polishing tool 20 can also be regulated, by displacing the workpiece holder 10 along the third axis A3. At the same time, the workpiece holder 10, including an optical lens 100, is rotated about a first axis A1.

(34) On the other side, the polishing tool 20 is driven in a rotating manner about a rotation axis R. In addition, the tool drum 50, on which the polishing tool 20 is mounted so as to be rotatable about the rotation axis R, can be rotated about a fourth axis A4, in order to regulate the pitch angle W of the polishing tool 20 on the lens 100.

(35) In respect of the further details relating to the workpiece holder 10 and the polishing tool 20, reference is made to the description above relating to FIG. 1.

(36) It can furthermore be seen from FIG. 2 that there is also an optional, second working plane. The latter is realized such that it is functionally identical to the front working plane. Two lenses 100, 100a can thus be machined simultaneously and in an identical manner. In particular, the working planes are fixedly connected to one another in respect of the degrees of freedom of the workpiece holder 10, 10a and of the polishing tool 20, 20a. The working planes also share the drives, such that the workpiece holders 10, 10a and the polishing tools 20, 20a move synchronously.

(37) A further optional detail of the embodiment according to FIG. 2 is that the tool drum 50, in each of the working planes, has a plurality of polishing tools, in particular in this case four, in particular, differing polishing tools 20, 20a, 20b, 20c, 20d, 20e, 20f, 20g. The third to eighth polishing tools 20b, 20c, 20d, 20e, 20f, 20g may also be polishing disks that have a cardanic compensating joint. These polishing disks then bear against the lens faces of the lenses 100, 100a and oscillate about the cardanic compensating joint.

(38) FIG. 3 shows a schematic diagram to illustrate the contact area F of a polishing tool 20 placed with a pitch angle on a lens face 101 of an optical lens 100.

(39) Of the lens face 101, the circumferential edge 103, the surface curvature K2 and the diameter D2 are also identified. An optical transition line shows that the already pre-machined lens 100 has a toric lens face 101. This means that the lens face 101 to be polished is oval, or elliptical. Two crescent-shaped edge regions do not need to be polished concomitantly.

(40) Cross-hatching then indicates, in particular, the contact area F between the polishing surface 23 and the lens face 101. This contact area is in the form of a strip, and extends at both ends E1, E2 as far as a circumferential edge 103 of the concave lens face 101. With other regions, the polishing surface 23 projects beyond the circumferential edge 103 at the ends E1, E2. The figure does not show the parts of the polishing surface 23 that float above the lens face 101, as shown in FIG. 1.

(41) Additionally identified are the movements of the lens 100 about the first axis A1 and along the axis A3.

(42) FIG. 4 shows a perspective view of a polishing device 1 according to FIG. 2, but represented with a frame 41, housing 40 and secondary means for automated operation.

(43) The frame 41 supports both the polishing tool 20 and the workpiece holder 10. The entire tool drum 50, together with the polishing tool 20 and the workpiece holder, are disposed inside the housing 40. On the front side, the housing 40 has an inspection window and a flap, or door. The drives 31, 32, 33, 34 are clearly visible in the representation of FIG. 4. The first drive 31 drives the workpiece holder 10 in a rotating manner about the first axis A1.

(44) The second and the third drive 32, 33 are realized as cross slides, such that the displacements for regulating the offset x and the distance z can be regulated.

(45) Also shown is a transport rail 42, via which lenses 100a that have been pre-machined in an automated manner are provided and removed again after machining.

(46) A loading means 43 is used to remove the lenses 100, 100a from the transport rail 42, before the polishing operation, and load them into the workpiece holder 10. After polishing, they are taken back out of the workpiece holder 10 by means of the loading means 43 and deposited on the transport rail 42 for removal.

(47) The invention is not limited to one of the embodiments described above, but may be modified in various ways.

(48) In particular, the above descriptions also apply to an optional modification, in which the curved lens face 101 is convex and the curved polishing surface 23 is concave. In particular, in the tool drum 50, polishing tools 20b, 20c having a concave polishing surface 23 may also be used in addition to the polishing tools 20, 20a. Concave and convex lens faces 101 can then be machined in the same polishing device 1.

(49) All features and advantages arising from the claims, the description and the drawing, including structural design details, spatial arrangements and method steps, may be essential for the invention, both separately and in the most diverse combinations.

(50) TABLE-US-00001 List of references 1 polishing device 10 workpiece holder 10a second workpiece holder 20 polishing tool 20a second polishing tool 20b third polishing tool 20c fourth polishing tool 20d fifth polishing tool 20e sixth polishing tool 20f seventh polishing tool 20g eighth polishing tool 21 support element 22 elastic substructure 23 convex polishing surface 31 first drive (first axis) 32 second drive (second axis) 33 third drive (third axis) 34 fourth drive (fourth axis) 35 spindle drive 40 housing 41 frame 42 transport rail 43 loading means 50 tool drum 100 optical lens 100a second optical lens 101 lens face 102 back side of lens 103 circumferential edge A1 first axis (rotation) A2 second axis (distance) A3 third axis (offset) A4 fourth axis (pitch angle) D1 diameter (polishing surface) D2 diameter (lens face) E1 first end (strip-type contact area) E2 second end (strip-type contact area) F strip-type contact area K1 surface curvature (polishing surface) K2 surface curvature (lens face) M center (polishing surface) R rotation axis W pitch angle z distance x offset