Method for polishing lenses

Abstract

The invention relates to a tool, to a device, to a method, and to a use for the zonal polishing of optical workpieces, wherein the tool has a preformed cap for forming a polishing surface and the tool is placed against the workpiece to be polished in such a way that the tilt angle of the axis of rotation of the tool to the normal of the contact surface on the workpiece and / or the size of the contact surface remains at least substantially constant.

Description

[0001] The present invention relates to a use of a tool for zonal polishing of optical workpieces, in particular lenses.

[0002] The present invention relates to the zonal polishing of optical workpieces. The tool (polishing tool) has a polishing surface that is or can be applied only partially to the workpiece to be polished in the area of ​​a contact surface. This contact surface is significantly smaller than the surface of the workpiece to be polished, particularly compared to the radial extent of the workpiece. "Zonal," in the context of the present invention, refers in particular to polishing with such a "small" contact surface. In contrast, so-called cup tools extend with their contact surface or contact edge over the entire radius of a workpiece surface to be polished.

[0003] With the proposed zonal polishing, it is also possible to polish aspherical and / or free-form surfaces or workpieces.

[0004] Mushroom-head polishing tools are particularly used for zonal polishing. A curved tool head supports a flexible or elastic polishing element to form a curved polishing surface. EP 1 796 872 B1, for example, shows such a tool. During polishing, the polishing surface of the tool partially rests against the workpiece in the area of ​​its contact surface, with the tilt angle between the surface normal of the contact surface and the tool's rotational axis continuously changing, so that the contact surface moves along a longitude on the tool.

[0005] Zonal polishing is used primarily for precision optics or workpieces with aspherical surfaces, such as mirrors or lenses, and especially for correcting manufacturing errors. Accordingly, it is important to enable the most precise and defined processing possible. Polishing always involves a certain amount of material removal from the workpiece.

[0006] DE 10 2004 047 563 A1 discloses a method for polishing a rotating workpiece using a tool comprising a rubber membrane or a ram with a glued-on polyurethane membrane. The exact design of the tool is not discussed in detail.

[0007] US 2013 / 0244553 A1 relates to a precision machining membrane for polishing workpiece surfaces. The membrane is first manufactured by lamination and then pressed into a concave embossed surface using a convex die, thereby curved the membrane. The membrane is used with a tool, with a pressure chamber provided between an end face of the tool and the curved membrane, which can be filled with a pressure-regulated fluid.

[0008] US 6,796,877 B1 relates to a polishing machine for polishing an optical workpiece. The polishing machine has two orthogonal pivoting mechanisms, by which a polishing head of the polishing machine can be pivoted. The polishing head can be tilted relative to the surface of the workpiece. The rotation speeds of the polishing head and the workpiece can be controlled.

[0009] EP 1 796 872 A1 relates to a method for polishing optical lenses. A tool can be tilted by an angle between the respective surface normal of a workpiece and the tool axis. This allows for both methods in which the angle remains constant throughout the entire movement along the workpiece surface and methods in which the relative angle increases continuously.

[0010] US 4,989,316 concerns the surface treatment of an ophthalmic lens blank. A cutting tool is moved along the surface of the workpiece to be machined at a constant rate, while the rotational speed of the blank is varied to keep the tangential speed of the blank constant relative to the tool.

[0011] US Pat. No. 5,320,006 relates to a method for manufacturing optical lenses. The rotation speed of the lens blank is increased while a cutting tool is moved in the direction of the tool's rotation axis.

[0012] US 2003 / 0017783 A1 relates to a toric tool for polishing an optical surface of a lens and a method for polishing an atoric surface using the tool. The tool comprises an elastic layer and a polishing layer adhered thereto, forming a toric surface for polishing. To polish an atoric surface, the elastic layer can be compressed and the polishing layer can be deformed.

[0013] JP 2000-071154 A relates to a manufacturing method for a polishing tool. A polishing foil is pressed onto a tool body.

[0014] The present invention is based on the object of specifying a use for the zonal polishing of optical workpieces, whereby a particularly precise or defined polishing of the respective workpiece, in particular also of an aspherical surface, is made possible with a preferably simple structure.

[0015] The above object is achieved by a use according to claim 1. Advantageous further developments are the subject of the subclaims.

[0016] According to a first aspect of the present invention, the tool used for zonal polishing has an elastic cap for forming a polishing surface or polishing pad, which cap sits or is tension-free on a curved head of the tool, preferably wherein the cap is pre-formed or shaped to adapt to the curvature of the head. In this way, a particularly defined spring behavior of the cap or the polishing surface formed thereby can be achieved in a simple manner. In particular, the pre-forming or shaping before attaching or gluing the cap to the tool head can prevent or at least minimize deformations, stresses, and the like in the cap material that otherwise occur during adaptation to the curvature, which are usually undefined.

[0017] Preferably, the cap has a multi-layer structure and, in particular, comprises an intermediate element and a polishing element. This is beneficial for achieving the desired properties, particularly with regard to spring behavior, abrasion behavior, and polishing behavior.

[0018] In particular, the polishing element forms a polishing coating or a polishing film or polishing layer.

[0019] In the present invention, the polishing surface or the polishing coating formed by the cap or the polishing element preferably generally forms a polishing agent carrier for a polishing agent. The proposed polishing refers to polishing with a polishing agent, which is present or used in particular in the form of a suspension with polishing particles, such as extremely fine grains, particles, or the like. The polishing surface also serves, in particular, to transport the polishing agent into an active gap between the contact surface of the tool and the surface to be polished and / or to distribute or move it therein and / or to rub the polishing agent against the surface.

[0020] In particular, polishing reduces surface roughness and / or can remove cracks in the material that may have occurred during previous shaping, for example, through grinding. Material is removed in each process. The removed material is then transported away from the effective gap between the polishing surface and the surface to be polished by the tool or polishing surface, also by means of the polishing agent.

[0021] In general, the present invention relates in particular to the polishing of a workpiece using a tool and a polishing agent. However, polishing can alternatively be performed without a separate or additional polishing agent, but solely with the tool.

[0022] Depending on the polishing agent, the polishing surface can be either porous or non-porous and / or provided with a favorable surface structure or texture in order to achieve the desired polishing effect, particularly with a specific polishing agent for the respective workpiece material.

[0023] Preferably, the intermediate element and the polishing element are pre-shaped or machined to adapt to the curvature. The polishing element is then adapted to the shape of the intermediate element by prior shaping. This also allows stresses between the two elements to be avoided or at least minimized.

[0024] Pre-forming can be done, for example, by appropriate foaming or other primary forming to the desired shape.

[0025] The shaping is preferably carried out by material removal or mechanical machining of the cap or the elements forming the cap, in particular by milling and / or turning, for example from plate or solid material.

[0026] The polishing element is preferably designed to be substantially thinner than the intermediate element.

[0027] Preferably, the cap or intermediate element and the polishing element are glued on. This allows for a simple assembly.

[0028] Particularly preferably, the tool has a collar or other stop in the area of ​​the head for circumferential support and / or positioning of the cap. This contributes to simple and defined production.

[0029] When used as proposed, the tool is preferably used in a device and / or in a method.

[0030] Preferably, the device and method are characterized in particular by the fact that the diameter of the tool's contact surface on the workpiece and / or the tilt angle of the tool's rotational axis to the normal (surface normal) of the contact surface is / are kept at least substantially constant during the polishing of the workpiece, i.e., during the respective polishing process. This is conducive to defined polishing with, in particular, defined material removal.

[0031] Preferably, the tool is moved from one edge of the workpiece surface to be polished, across the center, and to the opposite side of the edge. This enables particularly uniform polishing, especially in the visually important and sensitive center of the workpiece. Stopping or ending the polishing process in the center usually results in uneven and / or undefined material removal.

[0032] Preferably, the indentation depth of the particularly elastically deformable polishing surface on the tool is preferably varied, controlled, or regulated by appropriately advancing the tool relative to the workpiece during the polishing process, particularly preferably depending on the radial position of the contact surface on the workpiece, the desired diameter of the contact surface, the (desired) contact pressure of the tool on the workpiece, and / or the profile of the workpiece, in particular the curvature of the workpiece in the region of the respective contact surface. This promotes defined polishing and defined material removal, while also enabling optimization of the time required for polishing.

[0033] Optionally, the distance between adjacent tracks of the preferably spiral polishing path of the contact surface on the workpiece or the surface to be polished is kept at least essentially constant. This promotes defined polishing or defined material removal.

[0034] According to a further aspect of the present invention, the rotational speed of the workpiece during one revolution is varied or controlled or regulated depending on the rotational position, a locally desired dwell time (polishing time), the diameter of the contact surface, the contact pressure of the tool on the workpiece, and / or the profile of the workpiece, particularly in the area of ​​the respective contact surface. This allows for optimal polishing with defined material removal and / or influencing or controlling, even taking into account the actual three-dimensional shape of the surface to be polished.

[0035] The tool is preferably provided with a polishing surface formed from at least substantially closed pores, in particular wherein more than 1 or 5% (based on the surface area or number of pores) of the polishing surface is formed by pores with a size of more than 0.5 mm and / or more than 25 or 50% (based on the surface area or number of pores) is formed by pores with a size of less than 0.4 or 0.3 mm, particularly preferably less than 0.1 mm, and / or in particular wherein the size of the pores on the polishing surface is less than 1 mm, in particular less than 0.9 mm, and / or in particular wherein the polishing surface is not mechanically machined or dressed. The size of the pores is considered to be, in particular, the mean or maximum diameter. Tests have shown that such a polishing surface exhibits particularly good polishing properties, particularly when polishing precision optics or glass.

[0036] Particularly preferably, the polishing surface or the polishing coating or cap forming it is made of polyurethane or another suitable foam or plastic.

[0037] The tool is used for zonal polishing. Preferably, the tool is manufactured and prepared for the polishing device, thus eliminating the need for (further) conditioning or dressing of the polishing tool in a new state in the polishing machine, as is common, especially in precision machining.

[0038] Particularly preferably, the workpiece to be polished is first measured and errors can then be corrected by corrective polishing using the proposed tool, the proposed device or the proposed methods.

[0039] The proposed tool, the proposed device and / or the proposed methods can be used in particular for pre-polishing and / or corrective polishing.

[0040] Further aspects, features, advantages, and characteristics of the present invention will become apparent from the claims and the following description of a preferred embodiment with reference to the drawing. It shows: Fig. 1 is a schematic representation of a proposed device for polishing an optical workpiece, wherein various positions of a proposed tool with associated tool spindle are shown; Fig. 2 is a schematic section of the proposed tool; Fig. 3 is a schematic plan view of a surface of the workpiece to be polished, wherein a contact surface of the tool and the polishing path traveled on the workpiece are schematically indicated; and Fig. 4 is a partial enlargement of Fig. 1 to illustrate the tool head resting on the workpiece.

[0041] Fig. 1 shows in a schematic representation a proposed device 1 for in particular zonal polishing of an optical workpiece 2, in particular a lens, a mirror or the like, particularly preferably made of glass.

[0042] The device 1 is designed for polishing the workpiece 2 by means of a tool 3 according to the invention or another tool. The preferred structure of the proposed polishing tool 3 is described in particular with reference to Fig. 2 explained in more detail.

[0043] In the representation according to Fig. 1 the tool 3 is shown together with an associated tool spindle 13 of the device 1 in three different positions, in particular to illustrate the mobility of the tool 3 or a preferred process sequence.

[0044] The proposed tool 3 is shown in a schematic section in Fig. 2 It preferably comprises a carrier 4 with a curved head 5 and a particularly hemispherical or conical cap 6.

[0045] The cap 6 is preferably constructed in several layers and, in the example shown, preferably has an intermediate element 7 and a polishing element 8.

[0046] The tool 3, the cap 6 or its intermediate element 7 is attached to the head 5 of the tool 3, in particular glued thereto.

[0047] The cap 6 or its polishing element 8 forms a polishing surface 9.

[0048] The polishing surface 9 of the tool 3 or the cap 6 or the element 8 is preferably convexly curved, in particular geometrically similar to the head 5 or curved to match it and / or preferably spherical or hemispherical and / or conical.

[0049] The polishing element 8 is mounted on the intermediate element 7, in particular glued thereto.

[0050] Alternatively, the cap 6 can also be formed in one piece and / or manufactured in multiple layers by bi-injection or the like.

[0051] The cap 6 or the intermediate element 7 and / or the polishing element 8 is / are preferably made of plastic or foam and / or of an elastic and / or flexible material.

[0052] Particularly preferably, the intermediate element 7 is made of a preferably closed-cell foam, in particular of polyurethane.

[0053] The cap 6 or the intermediate element 7 preferably has a static modulus of elasticity under static continuous load of more than 0.5 N / mm 2< , preferably more than 1 N / mm 2< , in particular more than 1.5 N / mm 2< , and / or less than 30 N / mm 2< , preferably less than 15 N / mm 2< , in particular less than 7.0 N / mm 2< , and / or a dynamic modulus of elasticity under a dynamic continuous load of 10 Hz of more than 0.5 N / mm 2< , preferably more than 1 N / mm 2< , in particular more than 1.3 N / mm 2< , and / or less than 20 N / mm 2< , preferably less than 10 N / mm 2< , in particular less than 8.0 N / mm 2< , and / or a compression hardness at 10% deformation of more than 0.05 N / mm 2< , preferably more than 0.1 N / mm 2< , in particular more than 0.2 N / mm 2< , and / or less than 3 N / mm 2< , preferably less than 2 N / mm 2< , in particular less than 1 N / mm 2< , in each case measured in particular according to DIN 53513:1990-03.

[0054] The polishing element 8 is preferably made of a harder and / or stiffer material than the intermediate element 7.

[0055] The polishing element 8 is preferably thin-walled and / or foil-like.

[0056] The density - preferably according to DIN EN ISO 845:2009-10 - of the polishing element 8 is preferably more than 300 kg / m 3< , in particular more than 500 kg / m 3< , particularly preferably more than 700 kg / m 3< , and / or preferably less than 4000 kg / m 3< , in particular less than 3000 kg / m 3< , particularly preferably less than 2000 kg / m 3< .

[0057] The polishing element 8 or the cap 6 or polishing surface 9 preferably has a Shore hardness A of more than 5, in particular more than 10, particularly preferably more than 20, and / or preferably less than 90, in particular less than 80, particularly preferably less than 70, in particular according to DIN ISO EN 868:2003-10 or DIN ISO 7619-1:2012-02.

[0058] The polishing element 8 preferably has a thickness of more than 0.1 mm, in particular more than 0.3 mm, particularly preferably more than 0.4 mm, and / or preferably less than 3 mm, in particular less than 2 mm, particularly preferably less than 1 mm.

[0059] The thickness of the intermediate element 7 is preferably more than 2 mm and / or less than 10 mm, in particular approximately 3 to 7 mm.

[0060] The thickness of the intermediate element 7 is preferably at least 5 times, in particular about 10 times, the thickness of the polishing element 8 or more.

[0061] The cap 6, the intermediate element 7 and / or the polishing element 8 preferably each have an at least substantially constant thickness.

[0062] The polishing element 8 or the polishing surface 9 is preferably formed or manufactured from an open-cell or closed-cell plastic or composite material or the like.

[0063] In the illustrated example, the polishing element 8 is preferably made of a plastic film or polyurethane.

[0064] The cap 6 or the intermediate element 7 and / or polishing element 8 is / are preferably pre-shaped or machined internally and / or externally in order to adapt its shape to the curvature of the head 5 and / or to achieve a desired curvature or other shape, such as a sphere, i.e. before being attached to the tool 3 or head 5, its shape is adapted to that of the head 5, in particular provided with a complementary curvature to the head 5 or intermediate element 7.

[0065] The tool 3 or the head 5 preferably forms a solid or non-yielding surface made of metal or another suitable material for supporting and in particular also fastening the cap 6 or elements 7, 8 arranged thereon.

[0066] The shaping or shaping of the cap 6 or the intermediate element 7 and / or polishing element 8 is particularly preferably carried out mechanically, in particular by turning and / or milling.

[0067] It is particularly preferred to machine solid material to achieve the desired shape.

[0068] Mechanical processing has the advantage that a very uniform material layer can be produced without material compression, deformation or other material irregularities with the desired shape, here in particular a cap-like or spherical shape, or possibly also another shape.

[0069] Alternatively, the aforementioned shaping can also be carried out, for example, by appropriate foaming or other primary shaping.

[0070] The preformed or shaped cap 6 or correspondingly preformed or shaped elements 7 and 8 is or are attached to the tool 3 or head 5, in particular by gluing.

[0071] Particularly preferably, the polishing element 8 is attached to the intermediate element 7 by gluing. However, it can also be connected in other ways.

[0072] Particularly preferably, the cap 6 or the intermediate element 7 is or sits on the head 5 without tension.

[0073] According to the invention, "stress-free" is to be understood in particular as meaning that, in the applied state, no local material deformations or stresses occur in the material of the cap 6 or elements 7, 8 due to adaptation to the curvature, which would arise during the deformation to adapt to the curved shape and which (can) negatively influence a uniform and in particular defined spring and damping behavior of the cap 6 or elements 7, 8.

[0074] Preferably, the polishing element 8 should also be mounted tension-free in this sense, in particular in order to avoid any possible formation of wrinkles.

[0075] Particularly preferably, the polishing element 8 is adapted to the curvature of the outer side of the intermediate element 7 by appropriate pre-forming, in particular shaping, before being attached to or connected to the intermediate element 7.

[0076] The tool 3 or the cap 6 or the polishing element 8 or the polishing surface 9 is designed in particular such that a polishing agent (not shown) is transported over the polishing surface 9 and as a result the workpiece 2 can be machined and polished in a mechanical-chemical removal process, as already described at the beginning.

[0077] To facilitate the attachment and / or positioning of the cap 6 or elements 7, 8, the tool 3 or its carrier 4 preferably has a collar 10 or other stop, which projects in particular laterally from the head 5 and / or forms a preferably circumferential shoulder or the like.

[0078] The tool 3 or the carrier 4 preferably has a connecting section 11 and / or a stop 12 for the defined fastening or holding of the tool 3 on the associated tool spindle 13 or its tool chuck 14 or the like.

[0079] Particularly preferably, the tool 3 is clamped or fastened to the tool spindle 13 by means of the tool chuck 14. The stop 12 serves, in particular, to define a defined axial position of the tool 3 on the tool spindle 13 or on the tool chuck 14. However, other design solutions are also possible.

[0080] Preferably, tools 3 with different curvature radii of the head 5 or the cap 6 or the polishing surface 9 are used depending on the shape of the surface 2A to be polished.

[0081] The radius of curvature of the polishing surface 9 is preferably more than 2 mm, in particular more than 3 mm or 5 mm, and / or preferably less than 1000 mm, in particular less than 500 mm, particularly preferably less than 100 mm, preferably depending on the (maximum) curvature of the surface 2A to be polished and / or the desired application. In corrective polishing, tools 3 with smaller radii of curvature, preferably less than 100 mm, are used.

[0082] The distance of the polishing surface 9, in particular at the intersection point with the rotation axis R, to the stop 12 is preferably the same for all tools 3, even if they have different curvatures or curvatures.

[0083] The proposed device 1 has the tool spindle 13 for rotating the associated or clamped tool 3 about a rotation axis R, as shown in Fig. 1 indicated.

[0084] The rotation speed is preferably about 1000 to 5000 revolutions per minute.

[0085] The rotation speed is preferably controlled or regulated.

[0086] Preferably, the rotation speed is kept constant during the polishing process. However, it is also possible in principle to change the rotation speed during a polishing process or to adapt the rotation speed to a particular tool 3 and / or workpiece 2 or for each polishing process.

[0087] The rotation of tool 3 preferably occurs without detecting the angle of rotation. Therefore, it is not a controlled rotation axis in the sense of a CNC control.

[0088] The tool spindle 13 and thus the tool 3 can be pivoted about a pivot axis B. In particular, this is a controlled or regulated pivot axis or CNC axis, also called a rotary axis. In particular, the pivot position is recorded. This enables defined pivoting, as exemplified by the three different positions in Fig. 1 shown.

[0089] In the example shown, the pivot axis B runs transversely and in particular perpendicular to the rotation axis R or the drawing plane.

[0090] The pivot axis B is preferably arranged as close as possible to the tool 3 or to the polishing surface 9 and / or to the tool chuck 14.

[0091] The device 1 has a workpiece drive 15, in particular a workpiece spindle, for the workpiece 2, so that the workpiece 2 to be polished can be rotated about the rotation axis C with a defined angular position.

[0092] Preferably, the workpiece 2 is held or coupled to the workpiece drive 15 at a defined angular position by means of a holder 16, such as a block piece, and / or by means of a chuck.

[0093] The rotation axis C is, in particular, a controlled or regulated axis or a CNC axis, also called a rotary axis. Preferably, the rotation angle position is also recorded here. Particularly preferably, an angle-dependent variation of the rotation speed is enabled, even within one revolution.

[0094] The rotational speed of the workpiece drive 15 or of the workpiece 2 is generally variable, in particular, for example, from approximately 10 or 20 revolutions per minute (for polishing at the edge 2C of the side 2A of the workpiece 2 to be polished) up to approximately 2000 to 3000 revolutions per minute (for polishing in the area of ​​the center 2B of the workpiece 2).

[0095] The C-axis preferably runs in a plane with the rotation axis R (independent of the pivot position of the tool spindle 13) and / or transversely or perpendicularly to the pivot axis B.

[0096] The workpiece drive 15 and thus the workpiece 2 are preferably linearly movable or adjustable in the Z direction, as in Fig. 1 indicated. The adjustment is carried out in particular by means of a slide and adjustment drive (not shown) or the like.

[0097] The Z-axis preferably runs parallel to the C-axis and / or transversely or perpendicularly to the swivel axis B.

[0098] The tool spindle 13 and thus the tool 3 are preferably adjustable transversely in the X-direction, in particular by means of a carriage (not shown) and an associated drive. This carriage then preferably also carries the B-axis and the corresponding pivot drive for pivoting the tool spindle 13.

[0099] The X-axis and Z-axis are preferably designed as controlled or regulated axes or as CNC axes or linear axes, so that precise positioning in the X and Z directions is possible.

[0100] The X-axis preferably runs transversely or perpendicularly to the C-axis, B-axis and / or Z-axis.

[0101] The X-axis preferably runs in or parallel to the common plane of the C-axis and R-axis.

[0102] The axes can also be stacked or distributed differently. For example, the Z-axis can be assigned to the tool spindle 13 instead of the workpiece drive 15. Alternatively or additionally, it is also possible for the B-axis and / or X-axis to be implemented on the workpiece side rather than on the tool side.

[0103] However, it is desirable to distribute the axes on the tool side and workpiece side to enable greater machining accuracy.

[0104] The device 1 is in particular a polishing machine or CNC machine with X, Z, B and C axes.

[0105] Preferably, the X-axis and / or the B-axis run horizontally.

[0106] Particularly preferably, the C-axis and / or the Z-axis runs vertically.

[0107] Particularly preferably, the polishing tools 3 are each located with their polishing surfaces 9 at the level of or near the B-axis, so that the contact surface A can be pivoted with as little radius as possible.

[0108] The B-axis is preferably spaced less than 100 or 50 mm, in particular less than 30 or 15 mm, particularly preferably less than 10 mm from the polishing surface 9 or contact surface A, in particular from the intersection point of the rotation axis R with the polishing surface 9. In particular, this distance is preferably at least substantially the same even for tools 3 with different radii of curvature of the polishing surface 9.

[0109] The B-axis intersects the rotation axis R preferably within the cap 6 or polishing surface 9.

[0110] By appropriate relative adjustment, in particular by moving in X and Z directions and by pivoting around the B axis, the tool 3 can be moved in particular as indicated by arrow W in Fig. 1 and in Fig. 3 schematically indicated over the workpiece 2 or the surface 2A to be polished.

[0111] Particularly preferably, the tool 3 is moved from an edge 2C of the workpiece 2 or the surface 2A towards the center 2B and beyond this to the opposite side of the edge 2C, as in Fig. 1 and 3 This avoids interrupting or terminating the polishing process in the center 2B area, as is common in the prior art, and thus enables or ensures more optimal processing or more defined material removal.

[0112] During polishing, the polishing surface 9 of the tool 3 only partially rests with a contact surface A on the workpiece 2 to be polished or its surface 2A, as is particularly shown in Fig. 4 schematically shown, which is a partial enlargement of the dotted circle area of Fig. 1 represents.

[0113] The contact surface A is preferably at least substantially circular, whereby this (also) depends on the three-dimensional shape of the surface 2A. In the schematic plan view according to Fig. 3 , the contact surface A, with which the polishing surface 9 rests on the workpiece 2 or its surface 2A, is also indicated.

[0114] Preferably, the surface normal N intersects the rotation axis R of the tool 3 at a (relative) tilt angle K, as in Fig. 1 and 4indicated. In particular, polishing with the tool 3 is carried out in such a way that the contact surface A is located off-center with respect to the rotation axis R on the polishing surface 9. In other words, work or polishing is carried out (preferably always) with a tilt angle K of more than 0°, in particular more than 2°, particularly preferably more than 5° or 10°, and / or preferably less than 50°, in particular less than 30°, particularly preferably less than 25°.

[0115] Particularly preferably, the tilt angle K is kept constant during the respective polishing process. This is achieved by appropriately pivoting the tool spindle 13 or the tool 3. The pivot angle S (angle of the rotation axis R to the C-axis) then varies accordingly along the tool path W, as shown schematically in Fig. 1 indicated, for example from a small swivel angle S in the left position via a medium swivel angle S in the middle position to a large swivel angle S in the right position.

[0116] A polishing process in the sense of the present invention refers in particular to the complete polishing of the surface 2A of the workpiece 2 to be polished with a tool 3. In such a process, as already explained, the tool path W is preferably traversed or followed by the tool 3 while, on the one hand, the tool 3 and, on the other hand, the workpiece 2 rotate.

[0117] During the polishing process, the contact surface A or its center AM then sweeps over the surface 2A to be polished in a particularly spiral-shaped polishing path P, as in Fig. 3 However, this is only indicated schematically. The spiral polishing path P is traversed once when the tool 3 or the contact surface A moves from the edge region 2C to the center 2B or to the rotation axis C. The same or a corresponding spiral polishing path P is then traversed again when the tool 3 or the contact surface A continues to move outward from the center 2B to the edge region 2B, following the tool path W.

[0118] Particularly preferably, the device 1 is designed in such a way or a control or regulation is carried out in such a way that a uniform spiral or an at least substantially constant distance PA between adjacent polishing tracks PS of the polishing path P is achieved or traversed, as in Fig. 3 The distance PA is therefore particularly preferably kept at least essentially constant. However, the distance PA can alternatively vary, particularly depending on the workpiece radius at which the center of the contact surface is (straight) located.

[0119] Particularly preferably, the diameter AD of the contact surface A is at least 10 or 20 times larger than the spiral spacing or spacing PA of adjacent polishing tracks PS.

[0120] Preferably, the tool 3 rotates opposite to the workpiece 2. However, a rotation in the same direction is also possible.

[0121] Preferably, tool 3 rotates (much) faster than workpiece 2.

[0122] In order to achieve a similar or, if possible, identical dwell time of the tool 3 or the contact surface A over a surface area of ​​the surface 2A, the rotation speed of the workpiece 2 and, consequently, the movement speed of the workpiece 2 along the tool path W are increased starting from the edge 2C to the center 2B and then reduced again towards the edge, while the rotation speed of the tool 3 remains constant.

[0123] Alternatively or additionally, the rotational speed of the workpiece 2 can also be varied during one revolution, in particular depending on the rotational position, the diameter AD of the contact surface A, the contact pressure of the tool 3 on the workpiece 2, the indentation depth E of the polishing surface 9, and / or the profile of the workpiece 2, in order to achieve particularly uniform material removal or a desired polishing result. This allows, in particular, highly precise polishing.

[0124] Particularly preferably, the device 1 is designed in such a way, or the proposed method is implemented in such a way, that the size or diameter AD of the contact surface A is kept at least substantially constant during the polishing process. This promotes uniform and defined material removal.

[0125] The size or diameter AD of the contact surface A is also determined in particular by the Fig. 4 The schematically indicated indentation depth E of the polishing surface 9 is determined by appropriate advancement of the tool 3 during the polishing process, but also depends on the surface shape of the workpiece 2, in particular the respective curvature conditions and the curvature of the polishing surface 9.

[0126] By varying the feed of the tool 3 during the polishing process, the indentation depth E of the polishing surface 9 and thus also the size or diameter AD of the contact surface A are varied accordingly.

[0127] Particularly preferably, the indentation depth E of the polishing surface 9 is varied by appropriately advancing the tool 3 during a polishing process such that, in particular, even with different curvatures of the surface 2A to be polished, particularly preferably with an aspherical surface 2A, an at least substantially constant diameter AD of the contact surface A is achieved. This is conducive to uniform or defined material removal throughout the entire polishing process.

[0128] Alternatively, it can also be provided that the diameter AD of the contact surface A decreases from the edge 2C to the center 2B and increases in the opposite direction.

[0129] The speed of the C-axis, i.e. the rotational speed of the workpiece 2, is preferably derived from calculated dwell times of the contact surface A over certain partial areas of the surface 2A to be polished.

[0130] To correct local rotationally asymmetrical defects of the surface 2A to be polished, the path speed or rotational speed of the workpiece 2 is preferably varied within one revolution. This allows different polishing or dwell times to be achieved, particularly within one revolution, depending on the required defect correction.

[0131] The speed of the X-axis is adjusted in particular so that the desired constant spiral pitch (PA) or spacing between adjacent polishing tracks (PS) remains constant per revolution. Accordingly, the feed rate in the X-direction is directly linked to the speed or number of revolutions of the C-axis, or vice versa.

[0132] Preferably, the optimal dwell time of the tool 3 or the contact surface A is determined in advance using a simulation in local areas on the surface 2A to be polished. Subsequently, the corresponding path positions and path speeds are determined from the calculated local dwell times.

[0133] The optimal indentation depth E of the polishing surface 9 or the infeed of the tool 3 on the workpiece 2 is optimally determined depending on the tool 3 and the geometry of the surface 2 to be polished, in particular by means of corresponding calculations, estimates and / or measurements, wherein the indentation depth E is adjusted during the polishing process in particular so that the diameter AD of the contact surface A remains as constant as possible.

[0134] The proposed polishing tool 3 is characterized in particular by a cap 6 or a cap structure with defined spring and damping properties. Thus, the size of the contact surface A can be very precisely influenced by the indentation depth E.

[0135] The indentation depth E is preferably more than 0.1 mm and / or less than 0.8 mm.

[0136] The size or diameter AD of the contact surface A is preferably more than 1 mm, in particular more than 3 mm, and / or less than 25 mm, in particular less than 15 or 10 mm.

[0137] Particularly preferably, zonal polishing of the workpiece 2 is carried out. "Zonal" is to be understood as meaning that the contact surface A is significantly smaller than the surface 2A of the workpiece 2 to be polished, in particular compared to the radial extent of the workpiece 2. Particularly preferably, the mean or largest diameter AD of the contact surface A is significantly smaller than the mean or largest radius of the workpiece 2. Particularly preferably, the mean or largest radius of the workpiece 2 is at least a factor of 2, 3 or 5 larger than the mean or largest diameter AD of the contact surface A.

[0138] During polishing, additional parameters can be taken into account, as explained in particular in DE 10 2009 004 787 A1, which is hereby cited as a supplementary disclosure in this regard.

[0139] The device 1 also has, in particular, a feed for polishing agents (not shown), as is usual in polishing machines, so that the polishing agent can be fed in the desired manner during polishing.

[0140] The proposed tool 3, the proposed device 1, and / or the proposed method can be used in particular for polishing precision optics or aspherical surfaces or other optical workpieces, wherein the surface shape can preferably be measured before polishing, allowing a desired surface shape to be achieved by polishing. This is also referred to as corrective polishing.

[0141] In particular, polishing can be carried out with an accuracy of 10 to 100 nm.

[0142] Tools 3 with smaller radii of curvature of the polishing surface 9, in particular with radii of curvature of less than 100 mm, particularly preferably less than 50 mm, are preferably used for correction purposes.

[0143] Tools 3 with larger radii of curvature of the polishing surface 9, in particular up to 1000 mm, are preferably used for pre-polishing.

[0144] After optimal pre-polishing, the surface to be machined is preferably measured 2A and then corrective polishing is carried out.

[0145] The proposed device 1 and the proposed methods can in principle be used for both pre-polishing and corrective polishing. Bezugszeichenliste:

[0146] 1 Fixture 2 Workpiece 2A Surface of the workpiece 2B Center of the workpiece 2CRedge of the workpiece 3 Tool 4 Carrier 5 Head 6 Cap 7 Intermediate element 8 Polishing element 9 Polishing surface 10 Collar 11 Connecting section 12 Stop 13 Tool spindle 14 Tool chuck 15 Workpiece drive 16 Holder AContact surface ADDiameter of the contact surface AMCenter point of the contact surface BSwivel axis CRotational axis of the workpiece EIndentation depth KKip angle NNormal PPolishing path PADistance between polishing marks PSPolishing mark RRotational axis of the tool SSwivel angle WTool path XLinear axis ZLinear axis

Claims

1. Use of a tool (3) for zonal polishing of a surface (2A) of an optical workpiece (2), in particular a lens, wherein the tool (3) has a curved head (5) and an elastic cap (6) arranged thereon to form a polishing surface (9), wherein the cap (6) is stress-free on the head (5), wherein the tool (3) with its curved polishing surface (9) is swiveled and / or advanced relative to the workpiece (2), so that the polishing surface (9) of the rotating tool (3) is placed partially by indentation in the area of a contact surface (A) against the rotating workpiece (2) that is to be polished, wherein the contact surface (A) traverses a polishing path (P) on the workpiece (2), wherein the rotational speed of the workpiece (2) is varied during a rotation depending on the rotating position, the locally desired dwell time, and / or the profile of the workpiece (2).

2. Use according to claim 1, characterized in that the indentation depth (E) of the polishing surface (9) is varied by advancing the tool (3) during the polishing of the workpiece (2) depending on the radial position of the contact surface (A) on the workpiece (2).

3. Use according to claim 1 or 2, characterized in that the diameter (AD) of the contact surface (A) is kept at least essentially constant by variation of the indentation depth (E).

4. Use according to claim 1, characterized in that the diameter (AD) of the contact surface (A) decreases starting from an edge (2C) to the center (2B) of the surface (2A) and increases in the opposite direction.

5. Use according to one of the preceding claims, characterized in that the distance (PA) between adjacent tracks (PS) of the polishing path (P) is kept at least essentially constant.

6. Use according to one of the preceding claims, characterized in that the center (AM) of the contact surface (A) traverses a spiral polishing path (P) on the workpiece (2).

7. Use according to one of the preceding claims, characterized in that the rotational speed of the workpiece (2) increases starting from a polishing on the edge (2C) to the center (2B) of the surface (2A) and decreases in the opposite direction.

8. Use according to one of the preceding claims, characterized in that the tilt angle (K) of the axis of rotation (R) of the tool (3) to the normal (N) of the contact surface (A) is kept at least essentially constant during the polishing of the workpiece (2).

9. Use according to one of the preceding claims, characterized in that the contact surface (A) is significantly smaller than the surface (2A) of the workpiece (2).

10. Use according to one of the preceding claims, characterized in that the rotational speed of the tool (3) during the polishing process is kept constant.

11. Use according to one of the preceding claims, characterized in that the tool (3) rotates faster than the workpiece (2).

12. Use according to one of the preceding claims, characterized in that the cap (6) is bonded to the head (5).

13. Use according to one of the preceding claims, characterized in that the tool (3) has a connecting portion (11) and a stop (12) for defined fastening and / or holding of the tool (3) on an assigned tool spindle (13).

14. Use according to one of the preceding claims, characterized in that the cap (6) is built up of multiple layers, and / or has an intermediate element (7) and a polishing element (8).

15. Use according to one of the preceding claims, characterized in that the tool (3) is moved from an edge (2C) of the surface (2A) over the center (2B) of the workpiece (2) to the opposite side of the edge (2C).

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