Determination of the position of an optical lens in relation to a support or holder

Abstract

The present invention relates to the determination of the position of an optical lens, which is held by a lens holding element at a known lens surface of the optical lens, and to the processing and / or measurement and / or testing of a lens held in this manner. A computer-implemented method for determining a position of an optical lens (10) in relation to a lens holding element (16) while a first lens surface (12) of the optical lens (10) is pressed by means of a holding force onto an abutment region of the lens holding element (16) comprises: providing surface data of the first lens surface of the optical lens; providing surface data of the abutment region of the lens holding element; providing force action data of the holding force, which define at least a force-application point and a force direction of the holding force; providing a first contact point between the first lens surface and the abutment region of the lens holding element; virtually rotating the optical lens about a first axis of rotation, which extends through the first contact point and extends both perpendicularly to a force action axis, which extends through the force-application point and parallel to the force direction, and perpendicularly to the perpendicular of the first contact point on the force action axis, in the direction of a torque which is defined by the force action data for a rotation about the first axis of rotation until the first lens surface of the optical lens and the abutment region of the lens holding element form a second contact point; and virtually rotating the optical lens about a second axis of rotation, which extends through the first and the second contact point, in the direction of a torque which is defined by the force action data for a rotation about the second axis of rotation until the first lens surface of the optical lens and the abutment region of the lens holding element form a third contact point; and outputting the position of the optical lens resulting from the virtual rotations about the first and the second axis of rotation as the position to be determined.

Description

[0001] “DETERMINATION OF THE POSITION OF AN OPTICAL LENS RELATING TO A SUPPORT OR MOUNT”

[0002] Description

[0003] The present invention relates to the determination of the position of an optical lens which is held on a known lens surface of the optical lens by a lens holding element, as well as the processing or testing of a lens held in such a way.

[0004] Optical lenses typically have opposing lens surfaces which together produce the desired optical properties of the lens. In order to ensure the desired optical properties of such optical lenses with a high degree of accuracy, both the exact shape of each individual lens surface and their relative position to one another are crucial. Many, especially more complexly shaped, custom-fitted optical lenses, such as many high-quality spectacle lenses, are manufactured from lens blanks by mechanically machining or at least coating one or both of the opposing lens surfaces. For such steps during the manufacture of an optical lens, the optical lens is often held (e.g. blocked) at the other, opposite lens surface.

[0005] For example, in the manufacture of ophthalmic lenses, it is often customary to individually process at least the back surface (e.g., by grinding, polishing, milling, coating, etc.), while the semi-finished ophthalmic lens is held and manipulated by a corresponding lens holding element on the front surface. Initially, both the shape of the existing front surface of the ophthalmic lens blank and the desired final shape of the back surface, which is yet to be manufactured, are known in the coordinate system of the ophthalmic lens. The position (positioning and orientation) of the front and back surfaces relative to each other must also be precisely determined.

[0006] REPLACEMENT LEAF (RULE 26). This is also crucial for the desired optical effect. Especially with complexly shaped surfaces, such as progressive lenses, even small deviations in the relative position (positioning and / or orientation) of the two surfaces could have an unacceptably strong impact on the optical effects.

[0007] However, in order to manufacture the back surface in exactly this precise position (positioning and orientation) relative to the front surface, the precise position (position and direction / orientation) of the entire spectacle lens, especially the known front surface, relative to the holding element must be precisely determined. Since the precise position and orientation (e.g., relative to a corresponding processing or inspection tool) of an optical lens is often very important for processing or inspecting the lens surface(s) (including the edge), this information must be known for the state in which such a lens is held by the respective lens holding element.

[0008] An example of a possibility for determining the position of an optical lens during manufacturing is described in EP 3 437 797 A1. A coordinate transformation is found between a description in coordinates in a system of the lens and coordinates in a system of a mount by considering a plurality of point triplets and determining the optimal configuration from this plurality.

[0009] The object of the present invention is to further improve the quality of optical lenses or their optical characterization. This is achieved within the scope of the present invention by a method according to the independent claims. Preferred embodiments are the subject of the dependent claims.

[0010] Thus, in one aspect, the invention provides a computer-implemented method for determining a (stable) position (position and orientation) of an optical lens relative to a lens holding element while the optical lens is pressed against a contact area of ​​the lens holding element by a holding force with a (known) first lens surface. The first lens surface of the optical lens is at least partially in contact with the lens holding element. The lens holding element provides the contact area as a contact surface for this purpose.

[0011] The method according to the invention comprises providing surface data of the first lens surface of the optical lens. This first lens surface therefore has a known surface shape which is defined by the surface data. In particular, the surface data of the first lens surface can be in the form of sagittal vertices. The surface data of the first lens surface are made available, for example, as sagittal vertices in a coordinate system of the lens in a database, in a file system or via an interface to the computer which carries out the method according to the invention. In particular, they can originate, for example, from standard lens data (e.g., the base curve of a spectacle lens) or from an individual surface optimization of a lens (e.g., an individual progressive spectacle lens). They can therefore be calculated in advance, for example, by a lens design program and stored in a database or in a file system, e.g.in a goods management system. Alternatively, the surface data of the first lens surface can also have been determined by (for example optical and / or mechanical / tactile) measurements of the surface of the lens and made available as (temporarily) stored data via a database or in a file system, e.g. of a measurement management system. Providing the surface data of the first lens surface thus preferably comprises reading out the stored surface data from a data storage device and / or measuring the first lens surface, e.g. using standardized area measuring devices such as Dual LensMapper, wherein the measuring device or its control unit makes the measured first lens surface available to the computer that carries out the method according to the invention, as described above.

[0012] In addition, surface data of the contact area of ​​the lens holding element is provided. The surface data of the contact area of ​​the lens holding element can be provided, for example, as coordinates of surface points in a coordinate system of the lens holding system in a database, in a file system or via an interface to the computer that carries out the method according to the invention. This surface data can also be present as stored values ​​in a database or a file system, e.g. of a goods management system, and made available for the method described here. For example, it can originate from type-specific, technical data sets of the lens holding element, e.g. given by design drawings of the lens holding element, or it can also have been measured directly on the specific lens holding element.The provision of the surface data thus preferably comprises reading the stored surface data from a data memory and / or measuring the surface, for example by means of standardized coordinate measuring machines, wherein the measuring machine or its control unit makes the measured surface data available to the computer which carries out the method according to the invention, as described above.

[0013] In addition, force effect data of the holding force are made available in a database, in a file system or via an interface to the computer that carries out the method according to the invention, which force effect data define at least one force application point and one force direction of the holding force. This force effect data can be present as stored values ​​in a database or a file system, e.g. of a goods management system, or it can be calculated for an application by e.g. a calculation system, for example when a clamping arm of the lens holding element is controllable and its position and force effect must be determined depending on the lens, and can be made available for the method described here. For example, it can originate at least partially from type-specific, technical data sets of the lens holding element, e.g. given by design drawings of the lens holding element.Alternatively or additionally, the force action data can also be selected or entered at least in part by a user of the method described here, in particular via a user interface (e.g., a screen workstation). For example, a user could select (by inputting data via an operating terminal) that gravity should act as the holding force and / or in which direction (e.g., with respect to a coordinate system of the lens holding element) the holding force should act. In particular, when taking the gravity of the optical lens into account, at least the direction of the holding force can result automatically from an orientation of the lens holding element in space (specified or entered by the user). The point of application of the force of gravity can then be calculated from the respective, current position of the lens relative to the lens holding element (e.g., as the coordinates of the center of gravity of the lens in the coordinate system of the lens).The provision of the force effect data thus preferably comprises at least partially a reading of stored data from a data memory and / or an input by a user and / or a calculation from stored data and / or data entered by a user and / or data calculated in advance.

[0014] Finally, a first contact point between the first lens surface and the contact area of ​​the lens holding element is provided. The provision of the first contact point is preferably dependent on and adapted to the specific application in which the present invention is used. Examples and preferred embodiments of this are described in more detail below.

[0015] Based on this data, the method comprises a virtual rotation of the optical lens about a first axis of rotation, which runs through the (at least one) first contact point and is both perpendicular to a force action axis, which runs through the force application point and parallel to the force direction, and perpendicular to the normal from the first contact point to the force action axis, in the direction of a torque, which is determined by the force action data for a rotation about the first axis of rotation. This virtual rotation can be carried out in particular in iterative, small steps. In any case, it continues until the first lens surface of the optical lens and the contact area of ​​the lens holding element form a second contact point with each other.

[0016] As far as this description refers to “virtual” rotations and / or translations of a lens, this means in particular that no real lens is physically / mechanically moved here, but that fixed points of the lens (in particular surface points) in a given coordinate system (in particular a system fixed to the lens holding element) are jointly computer-implemented and computationally transformed in such a way that this transformation describes, i.e. simulates, a real physical / mechanical rotation or translation of these fixed points together (and thus of the lens).

[0017] Based on the first and second contact points, the optical lens is virtually rotated around a second rotation axis, which passes through the first and second contact points, in the direction of a torque determined by the force action data for rotation around the second rotation axis, until the first lens surface of the optical lens and the contact area of ​​the lens holding element form a third contact point. This virtual rotation can also be performed, in particular, in iterative, small steps.

[0018] The two virtual rotations occur at least when the respective torques are non-zero, i.e., when the axis of force action does not intersect the respective axis of rotation. This will generally be the case in practice. Only in exceptional cases, when this condition is not met, can the method abort the calculation and determine the position of the optical lens as the desired stable position.

[0019] As soon as the desired, stable position of the lens relative to the lens holding element is reached, which can be characterized in particular by (at least) three contact points of the first lens surface with the contact area of ​​the lens holding element, this position can be output as the position to be determined. Thus, the method comprises outputting the position (position and orientation) of the optical lens resulting from the virtual rotations about the first and second axes of rotation as the position to be determined. The output can be effected in particular in the form of an output of a data set via a screen and / or a computer-readable data interface for data transmission and / or data storage.Thus, outputting the position to be determined preferably comprises displaying and / or transmitting and / or storing position and / or orientation data that clearly defines the position and / or orientation of the lens relative to the lens holding element in the position determined (as stable). In particular, at least three translational (position) and three rotational coordinates (orientation) of the lens (relative to the lens holding element) are thereby clearly defined, directly or indirectly. If the lens has symmetries that lead to invariances in the shape of the lens, it may be sufficient if the position to be determined also defines fewer degrees of freedom in order to already describe the position of the optical lens clearly (enough). For example, in the case of a completely rotationally symmetrical lens, it may be sufficient if the position to be determined clearly defines only three translational and two rotational coordinates.The third coordinate, which describes the rotational symmetry, can be ignored.

[0020] By determining the position of the optical lens relative to the lens holding element in this way, the second lens surface can also be clearly determined relative to the lens holding element and thus also relative to the first lens surface. This is of corresponding benefit depending on the process in which the present invention is applied, as described below using several examples.

[0021] For example, for a measuring process the specific shape and position of the second lens surface (relative to the first lens surface) may initially be unknown. The aim of the measuring process may be to determine the shape and position of the second lens surface relative to the first lens surface. Measuring processes that directly measure only one lens surface (e.g. optically or mechanically) in a coordinate system of a corresponding measuring device are often technically much simpler, faster and more cost-effective, and sometimes also more precise, than measuring processes that (have to) measure both lens surfaces relative to a coordinate system of the measuring device and / or relative to one another. However, the method according to the invention makes it possible to determine the position and orientation of the first lens surface relative to the lens holding element very precisely.Since it is generally technically very simple to determine or adjust the position of the lens holding element relative to a measuring device very precisely, the method according to the invention enables a very simple and precise determination of the position of the first lens surface relative to the measuring device. This applies in particular if the lens holding element is a component of the measuring device or if the position of the lens holding element relative to the measuring device is known, in particular calibrated. By means of the position of the first lens surface relative to the measuring device obtained by means of the method according to the invention and the shape of the second lens surface as well as its position relative to the first lens surface, measuring methods can be simulated, for example in a calculation system, and target values ​​for the measurement can be determined in this way. Examples of these measuring methods are transmission measurements such as those using a lensmeter and automapper.Furthermore, when applying the method according to the invention, it may be sufficient to perform a measurement of the second lens surface (in the coordinate system of the measuring device) using the measuring device in order to determine the relative position of the second lens surface relative to the first lens surface. Examples of this are reflection measurements or area measurements, e.g., by scanning the lens surface.

[0022] In another exemplary application, in which a given second lens surface is to be processed (e.g., thinly coated) without significantly changing its shape (and position), in addition to the shape of the second lens surface, its position (position and orientation) relative to the first lens surface may already be known. For example, the goal may be to coat a complex, finished lens on the second lens surface, e.g., to apply a protective layer, an anti-reflective coating, a color, etc. In order to carry out this processing (e.g., coating) as precisely as possible, it may be advantageous to position and orient the second lens surface to be processed as precisely as possible relative to the processing device. For this purpose, the position of the optical lens relative to the processing device (or, conversely, a processing head, e.g.,spray head, of the processing device relative to the optical lens) can be adjusted as precisely as possible. The method according to the invention makes it possible to determine the position and orientation of the first lens surface relative to the lens holding element very precisely. However, insofar as the position of the second lens surface relative to the first lens surface is already known (specified) in this application example, the position of the second lens surface relative to the lens holding element is therefore also determined or can be determined. Since it is generally technically very simple to determine or adjust the position of the lens holding element relative to a processing device very precisely, the method according to the invention enables a very simple and precise adjustment of the position of the second lens surface relative to the processing device or the position of a processing head of the processing device relative to the second lens surface.This applies in particular if the lens holding element is a component of the processing device or if the position of the lens holding element relative to the processing device is known, in particular calibrated.

[0023] In another example application, in which a second lens surface to be manufactured is to be machined (e.g. ground or milled) by adapting its shape to a specified target, in addition to the shape of the second lens surface, its position (position and orientation) relative to the first lens surface can also already be known as the target of the manufacturing process. For example, the goal of the manufacturing process can be to manufacture a complex-shaped second lens surface in such a way that it ultimately assumes an exact position relative to the first lens surface. In order to be able to carry out this machining of the second lens surface (e.g. milling or grinding) as precisely as possible, it is important to be able to adjust the position of the optical lens (i.e. the first lens surface) relative to the manufacturing device (in particular relative to a process head of the manufacturing device, such as a milling or grinding head) as precisely as possible.The method according to the invention makes it possible to very precisely determine the position and orientation of the first lens surface relative to the lens holding element. Since it is generally technically very simple to very precisely determine or adjust the position of the lens holding element relative to a manufacturing device (e.g., grinding or milling machine) or the position of a process head (e.g., milling or grinding head) of the manufacturing device relative to the lens holding element, the method according to the invention enables very simple and precise adjustment of the position of the first lens surface relative to the manufacturing device such that the second lens surface to be manufactured by the manufacturing device then assumes the desired position relative to the first lens surface.This applies particularly if the lens holding element is a component of the manufacturing device or if the position of the lens holding element relative to the manufacturing device is known, in particular calibrated. To the extent that, in addition to the shape and position of the second lens surface to be manufactured, the initial shape and position of the second lens surface (i.e., before its deformation) are known for such a manufacturing process and are to be used to control the manufacturing process (e.g., to determine the contact points of a process head at the beginning of the milling or grinding process), the embodiments for the machining process described above (e.g., coating) are applicable analogously.

[0024] The present invention thus makes it possible to determine the position and orientation of the optical lens (i.e., its lens surfaces) relative to the lens holding element very reliably and precisely. This also allows the optical lens to be positioned very precisely relative to a corresponding machining tool.

[0025] The invention thus makes it possible to determine an optimal coordinate transformation, for example, using an iterative method. Unlike the prior art, this eliminates the need to compare multiple configurations. Rather, the method according to the invention is dynamically adaptive and thus results in a much more accurate and faster determination of the optimal coordinate transformation, especially for complex lens surfaces.

[0026] Examples of lens holding elements include a blocking ring or a flat support. The preferred optical lenses used in this method are particularly suitable for spectacle lenses. The holding force can be provided by the optical lens's own gravity or by a clamping arm that presses the optical lens against the contact area of ​​the lens holding element.

[0027] In particular, the method according to the invention is carried out in an iterative process, so that a coordinate transformation for determining the position (position and orientation) of the optical lens is found through iteration. One idea of ​​the invention is that the spectacle lens is forced by all exerted forces into a position in which all forces and torques are compensated by the contact of the first lens surface (e.g. front or back surface of a spectacle lens) on the contact area of ​​the lens holding element. If the optical lens is not yet in this stable position, the optical lens will move towards this stable position due to the forces and torques. Modeling this physical dynamics ensures that the optimal or stable position of the optical lens and thus the optimal coordinate transformation can be found.

[0028] Preferably, the method also comprises, if a projection point resulting from a projection of the force application point along the force direction onto a temporary contact plane through the first, second and third contact points does not lie within a triangle formed by the first, second and third contact points, a virtual rotation of the optical lens about a further axis of rotation, which runs at least through that contact point from the first, second and third contact points which is closest to the projection point, in the direction of a torque which is determined by the force action data for a rotation about the further axis of rotation, until the first lens surface of the optical lens and the contact area of ​​the lens holding element form a further contact point.This step is particularly preferably carried out iteratively, wherein the contact point or contact points (from the first, second and third contact points) which are not contained in the further axis of rotation are discarded in the further iteration steps. Instead, a new constellation of three contact points is preferably searched for iteratively until the projection point lies within the convex surface (triangle) formed by the three contact points. In a preferred embodiment, the further axis of rotation runs through a further contact point from the first, second and third contact points in such a way that the contact point from the first, second and third contact points lying outside the further axis of rotation and the projection point are separated from one another by the further axis of rotation within the temporary contact plane.In other words, the additional rotation axis divides the temporary contact plane into two half-planes, with the projection point and the contact point outside the additional rotation axis, consisting of the first, second, and third contact points, lying in different half-planes. In this case, this contact point, which is not traversed by the additional rotation axis, is discarded.

[0029] Alternatively or additionally, in another preferred embodiment or in another iteration step, the additional axis of rotation runs both perpendicular to the force action axis and perpendicular to the normal from the contact point through which the axis of rotation runs to the force action axis. In this case, in particular, both contact points not traversed by the additional axis of rotation are discarded, and the (iterative) method preferably searches for two additional contact points.

[0030] In a preferred embodiment, the force application point is the center of gravity of the optical lens and the force direction is the vertical, i.e. the direction of the gravitational field (i.e. the direction of gravity).

[0031] The provision of the first contact point preferably depends on and is adapted to the specific application in which the present invention is used. For example, for a measuring method, the first contact point can be determined such that the lens is to be aligned with respect to a measuring sensor. A lensmeter or a Shack-Hartmann sensor can be used as the measuring sensor. The location of the measuring sensor preferably defines two (horizontal) coordinates of the position of a reference point (e.g. lens center) relative to the lens holding element and thus relative to the measuring device (e.g. relative to a sensor center). The provision of the first contact point could thus be carried out with the objective that the lens center and the sensor center (particularly in the stable position to be determined) lie on a straight line that is particularly perpendicular to a support plane defined by the lens holding element.Angular coordinates of a rotation around this straight line can then be determined by aligning an internal coordinate system of the measuring sensor, e.g. reference of a cylinder base and / or a prism base of the optical lens.

[0032] For a blocking process, such as can be used for milling, grinding, and / or polishing a lens, the first support point could be provided such that the optical lens is aligned with respect to a blocking ring formed by the lens holding element, wherein a blocking ring center, for example, defines two (horizontal) coordinates of a reference point (e.g., lens center) relative to the blocking ring (in particular relative to the blocking ring center). Thus, the first contact point could be provided with the objective that the lens center and the blocking ring center lie on a straight line, which is in particular perpendicular to a support plane defined by the blocking ring. Angular coordinates of a rotation about this straight line can then be defined by the alignment based on a reference specification by a cylindrical shank and / or a prism base of the optical lens.

[0033] For the determination of the overall height of an optical lens, the concrete choice of the first contact point is preferably linked to fewer boundary conditions, since here preferably only the relative distance of the highest point of the second lens surface from a plane support formed by the lens holding element is determined and this value is independent of the choice of the coordinate system and thus independent of the two horizontal translations (i.e. parallel to the plane support) and the rotation around the vertical (i.e. the perpendicular to the plane support).

[0034] In a preferred embodiment, providing a first contact point of the first lens surface with the contact region of the lens holding element comprises providing a target specification for the position of the optical lens relative to the lens holding element and specifying a starting value for the first contact point. The target specification is preferably provided as a function of and adapted to the application in which the method according to the invention is used, as has already been described by way of example. To select the starting value of the first contact point, the lens holding element is preferably described in the coordinate system of the optical lens by a set of possible contact points, e.g. an edge curve of the optical lens when positioning a concave first lens surface on a flat support of the lens holding element or the projection of the blocking ring onto the first lens surface.The starting value for the first contact point can be selected from this set of possible contact points. This selection is also preferably made depending on and adapted to the application in which the method according to the invention is used. For example, when a front surface of a spectacle lens rests on a flat support, a point with the smallest sagittal height can be selected as the first contact point, and when a rear surface of a spectacle lens rests on a flat support, a point with the largest sagittal height can be selected as the first contact point.

[0035] Furthermore, in this preferred embodiment, after the virtual rotation of the optical lens about the second axis of rotation, the method comprises checking the resulting position of the optical lens for compliance with the target specification; and determining a correction value for the first contact point if the target specification is not met to a required accuracy (i.e., within permissible tolerance deviations). If the target specification is met (or a deviation is within a permissible tolerance), the method can preferably output the position of the optical lens resulting from the virtual rotations about the first and second axes of rotation as the position to be determined, without a correction value for the first contact point being or having to be determined.

[0036] At least to the extent that a correction is made for the first contact point after the target specification has been detected as non-compliance, the virtual rotation around a first axis of rotation, the virtual rotation around a second axis of rotation, the checking for compliance with the target specification, and, if necessary, the determination of a correction value for the first contact point are performed iteratively until compliance with the target specification is determined. Preferably, the determination of the correction value for the first contact point can be performed using a Newton method.

[0037] Preferably, at least one coordinate of a target position of at least one reference point of the optical lens (e.g., a lens center) relative to the lens holding element (and thus, in particular, relative to a measuring or processing device) is provided as the target specification. Particularly preferably, two coordinates of the target position of the at least one reference point of the optical lens relative to the lens holding element are provided as the target specification. This is particularly advantageous in applications in which, for example, a lens center is to be aligned relative to a sensor center of a measuring device or a tool center of a processing device.

[0038] Alternatively or additionally, at least one coordinate of a target orientation of the optical lens relative to the lens holding element (and thus in particular relative to a measuring or processing device) is preferably provided as a target specification. This is particularly advantageous in applications in which, for example, a reference axis of a cylindrical effect and / or a prism base is to be aligned relative to a measuring device or a processing device.

[0039] In a further aspect, the invention provides a method for processing at least one lens surface of an optical lens, comprising:

[0040] Providing an optical lens having a first lens surface with known surface data and a second lens surface to be machined;

[0041] Blocking the lens with the first lens surface on a lens holding element, wherein the position (position and orientation) of the optical lens with respect to the lens holding element is determined by a method described here, in particular according to one of the preferred embodiments described here; and

[0042] Machining the second lens surface while the optical lens is held by the lens holding member in the predetermined position relative to the lens holding member.

[0043] The invention will be further described below using preferred embodiments with reference to the accompanying drawings.

[0044] Fig. 1 is a schematic representation of an optical lens held by a lens holding element;

[0045] Fig. 2A and 2B are schematic representations of virtual constellations between an optical lens and a lens holding element during a method according to the invention.

[0046] Fig. 1 shows an exemplary positioning of a spectacle lens 10 as an example of a preferred optical lens, which has a first lens surface 12 and a second lens surface 14. Surface data are known at least for the first lens surface and are made available to the method according to the invention. The surface data are made available, for example, as sagittal angles in a coordinate system (x'-y'-z') of the spectacle lens in a database. In particular, they can originate, for example, from standard lens data (e.g., base curves) or from an individual surface optimization of a spectacle lens. Fig. 1 shows the coordinate system (x'-y'-z') of the spectacle lens (the y' axis extends into the plane of the drawing). The exact shape of the second lens surface 14 does not have to be known for the method for determining the position and orientation of the spectacle lens.The aim is to determine the exact position (position and orientation), i.e. in particular (up to) three translational and (up to) three rotational parameters, of the spectacle lens 10 relative to a lens holding element 16 that holds the spectacle lens. The lens holding element 16 has a contact area 18 on which the spectacle lens 10 is arranged with the first lens surface 12 and against which the spectacle lens is pressed. This results in direct contact between the first lens surface 12 and the contact area 18. This position is naturally stable if, for example, at least three contact points arise between the lens surface 12 and the contact area 18, which form a triangle through whose surface an axis of the force with which the spectacle lens 10 is pressed against the lens holding element passes.

[0047] Fig. 1 also shows a coordinate system (xyz) (y-axis extends into the plane of the drawing), which is firmly defined in the system of the lens holding element. The exact coordinates of the first lens surface 12 in this coordinate system in the stable position depend in particular on the surface shape of the first lens surface 12 and the shape of the contact area 18. The goal is to determine this exact position of the first lens surface 12 and thus of the entire spectacle lens 10 relative to the lens holding element (i.e. in particular in the coordinate system of the lens holding element). For this purpose, the surface data of the spectacle lens, which are initially provided in the coordinate system of the spectacle lens (x'-y'-z'), can be transformed into the coordinate system of the lens holding system (xyz).In particular, the individual (virtual) rotations and translations of the spectacle lens (i.e. the transformed surface data) can then be carried out in these coordinates.

[0048] Fig. 2 schematically shows some virtual, temporary positions during the determination of the (stable) position of the spectacle lens. For this purpose, surface data of the known first lens surface 12, in particular in a coordinate system of the spectacle lens 10, are provided. Furthermore, surface data of the contact area 18 of the lens holding element 16 are provided. The method is intended to determine stable contact between the spectacle lens 10 and the lens holding element 16 upon the action of a force on the spectacle lens, which force presses the spectacle lens 10 with the first lens surface 12 against the contact area 18 of the lens holding element 16. For this purpose, force effect data of the holding force are also provided, which define at least one force application point 20 and a force direction 22 of the holding force.The schematically illustrated embodiment describes a configuration in which the spectacle lens is placed on a horizontal support surface (contact area 18 of the lens holding element 16) under the effect of its own gravity. The center of gravity of the spectacle lens 10 can thus be provided as the force application point 20. In the illustrated embodiment of Figs. 1 and 2, the spectacle lens protrudes laterally beyond the contact area 18. Alternatively, the contact area 18 could also protrude laterally beyond the spectacle lens.

[0049] In addition, an initial position of the spectacle lens 10 relative to the lens holding element 16 is determined, at which a first contact point 30-1 results between the first lens surface 12 and the contact area 18. This first contact point 30-1 is provided in particular in the coordinate system (xyz) of the lens holding element 16.

[0050] Particularly preferably, the method can be carried out in this coordinate system. The coordinate system is preferably defined as a right-handed coordinate system in which the z-axis is directed in the opposite direction of the force acting on the optical lens (e.g., spectacle lens 10). The x-axis is perpendicular to the z-axis and is otherwise freely selectable. In particular, it can be selected, for example, relative to (e.g., perpendicular to) an (initial) axis of the coordinate system used to describe the spectacle lens geometry (e.g., a y'-axis, which can represent a vertical axis of the spectacle lens in a wear position).Initially, a position is selected in which the spectacle lens touches the contact area 18 with the first lens surface 12, which is to be held by the lens holding element 16, thus defining an initial coordinate transformation from the coordinate system used to describe the spectacle lens geometry and the coordinate system used to describe the contact of the spectacle lens. A corresponding initial virtual position with the first contact point 30-1 is schematically illustrated in particular in Fig. 2A.

[0051] Thereafter, the following steps are preferably carried out, in particular recursively: The first contact point 30-1 is identified as the pivot point. If the resulting torque with respect to this pivot point is 0, the recursive process is terminated. If the torque is not 0, it generates a direction of rotation in which the spectacle lens is rotated, whereby the pivot point is held. The rotation is continued until at least a second contact point 30-2 of the lens surface 12 of the spectacle lens 10 with the contact area 18 of the lens holding element 16 is created. This virtual constellation is schematically illustrated in Fig. 2B. The rotation is taken into account in the coordinate transformation. The process continues recursively with the two contact points found.

[0052] If two points of contact exist, these points define an axis of rotation. If the resulting torque about this axis of rotation is 0, the recursive process is terminated. If the torque is not 0, it determines a rotation. This rotation is performed with the axis of rotation fixed until at least a third point of contact is found on the surface of the lens. The rotation is taken into account in the coordinate transformation. The recursive process continues with these three points of contact.

[0053] Once three or more contact points have been found, a check is carried out to determine whether the resulting force acts within the convex shape created by the three or more contact points. This means that the stable, optimal position of the lens has been found, since the resulting torque about each axis through two contact points can be compensated for by supporting the lens at another contact point. If this stable position cannot be found, the closest connecting line to the resulting force between the at least three contact points is determined, i.e. the torque about an axis through two contact points that cannot be compensated for by supporting the lens at another contact point. The process is carried out recursively, removing the contact points not on the connecting line.

[0054] Once completed, the recursive application of the rotations in the coordinate transformation results in a coordinate transformation that describes the transition from the coordinate system used to describe the lens geometry to the coordinate system used to describe the support. As an example, the following algorithm for determining the flat support for a spectacle lens, i.e. the back surface rests on a horizontal plane, is considered. The resulting force is given by the weight acting at the center of gravity of the spectacle lens. The support plane is preferably perpendicular to this force and forms the contact area of ​​the lens holding element. In a first step, the support plane is defined with respect to the spectacle lens in such a way that it also touches a point on the back surface (first surface) of the spectacle lens.The recursion described above is then carried out, whereby the resulting torque can be determined by the weight force at the center of gravity with respect to the described pivot point or axis of rotation. The recursion is terminated when, for example, there are at least three points of contact between the spectacle lens and the support plane and these describe a convex hull within which the projection of the center of gravity perpendicular to the support plane is contained. With a toric back surface, for example, it is possible that the points of contact and the projection of the center of gravity lie on a straight line in the support plane and thus the spectacle lens comes to rest on only two points of contact. This is an example of the termination condition of the recursion with two points of contact and a resulting torque of 0. A rest position of the spectacle lens on only one point of contact is given, for example, when the flat support of a rotationally symmetric, biconvex spectacle lens is determined.

Claims

Patent claims 1. A computer-implemented method for determining a position of an optical lens (10) with respect to a lens holding element (16) while the optical lens (10) is pressed by a holding force with a first lens surface (12) against a contact area (18) of the lens holding element (16), comprising: Providing surface data of the first lens surface (12) of the optical lens (10); Providing surface data of the contact area (18) of the lens holding element (16); Providing force effect data of the holding force, which define at least one force application point (20) and one force direction (22) of the holding force; Providing a first contact point (30-1) of the first lens surface (12) with the contact area (18) of the lens holding element (16); virtually rotating the optical lens (10) about a first axis of rotation, which runs through the first contact point (30-1) and both perpendicular to a force action axis, which runs through the force application point (20) and parallel to the force direction (22), and perpendicular to the normal from the first contact point (30-1) to the force action axis, in the direction of a torque, which is determined by the force action data for a rotation about the first axis of rotation, until the first lens surface (12) of the optical lens (10) and the contact area (18) of the lens holding element (16) form a second contact point (30-2);virtually rotating the optical lens (10) about a second axis of rotation, which runs through the first (30-1) and the second contact point (30-2), in the direction of a torque which is determined by the force action data for a rotation about the second axis of rotation, until the first lens surface (12) of the optical lens (10) and the contact area (18) of the lens holding element (16) form a third contact point; and; Output the virtual rotations around the first and second The position of the optical lens (10) resulting from the axis of rotation is considered to be the position to be determined.

2. The method according to claim 1, further comprising, if a projection point resulting from a projection of the force application point (20) along the force direction (22) onto a temporary contact plane through the first (30-1), second (30-2) and third contact point does not lie within a triangle formed by the first (30-1), second (30-2) and third contact point: virtually rotating the optical lens (10) about a further axis of rotation which runs at least through that contact point from the first (30-1), second (30-2) and third contact point which is closest to the projection point, in the direction of a torque which is determined by the force action data for a rotation about the further axis of rotation, until the first lens surface (12) of the optical lens (10) and the contact area (18) of the lens holding element (16) form a further contact point.

3. The method according to claim 2, wherein the further axis of rotation runs through a further contact point from the first (30-1), second (30-2) and third contact point such that the contact point from the first (30-1), second (30-2) and third contact point lying outside the further axis of rotation and the projection point are separated from one another by the further axis of rotation within the temporary contact plane.

4. The method according to claim 2, wherein the further axis of rotation extends both perpendicular to the force action axis and perpendicular to the normal from the contact point through which the axis of rotation extends to the force action axis.

5. Method according to one of claims 1 to 4, wherein the force application point (20) is the center of gravity of the optical lens (10) and the force direction (22) is the vertical.

6. The method according to any one of the preceding claims, wherein providing a first contact point (30-1) of the first lens surface (12) with the contact area (18) of the lens holding element (16) comprises: Providing a target for the position of the optical lens (10) relative to the lens holding element (16); and Presetting a starting value for the first contact point (30-1), wherein the method after the virtual rotation of the optical lens (10) about the second axis of rotation also comprises: Checking the resulting position of the optical lens (10) for compliance with the target specification; and Determining a correction value for the first contact point (30-1) if the target specification is not met, and wherein in the method the virtual rotation about a first axis of rotation, the virtual rotation about a second axis of rotation, the checking for compliance with the target specification and, if appropriate, the determination of a correction value for the first contact point (30-1) are carried out iteratively until compliance with the target specification is determined.

7. The method according to claim 6, wherein the determination of a correction value for the first contact point (30-1) is carried out by means of a Newton method.

8. The method according to claim 6 or 7, wherein at least one coordinate of a target position of at least one reference point of the optical lens (10) relative to the lens holding element (16) is provided as the target specification, wherein preferably two coordinates of the target position of the at least one reference point of the optical lens (10) relative to the lens holding element (16) are provided as the target specification.

9. Method according to one of claims 6 to 8, wherein at least one coordinate of a target orientation of the optical lens (10) relative to the lens holding element (16) is provided as a target specification.

10. A method for processing at least one lens surface of an optical lens (10), comprising: Providing an optical lens (10) having a first lens surface (12) with known surface data and a second lens surface (14) to be machined; Blocking the lens (10) with the first lens surface (12) at a Lens holding element (16), wherein the position of the optical lens (10) with respect to the lens holding element (16) is determined by a method according to one of claims 1 to 9; Processing the second lens surface (14) while the optical lens (10) is held in the specific position relative to the lens holding element (16).

Images