DETERMINATION OF THE POSITION OF AN OPTICAL LENS IN RELATION TO A SUPPORT OR MOUNTING

Description

Description

[0001] The present invention relates to determining 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 such a held lens.

[0002] Optical lenses typically have opposing lens surfaces, which together create the desired optical properties of the lens. To ensure the desired optical properties of such lenses with high precision, both the exact shape of each individual lens surface and their relative position to each other are crucial. Many optical lenses, especially those with more complex shapes and custom designs, 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. During these steps in the manufacturing process, the optical lens is often held (e.g., blocked) by the opposing lens surface.

[0003] For example, in the production of spectacle lenses, it is often common practice to individually process at least the back surface (e.g., by grinding, polishing, milling, coating, etc.), while the semi-finished spectacle lens is held and manipulated by a corresponding lens holder at the front surface. In this process, both the shape of the existing front surface of the spectacle lens blank and the desired final shape of the back surface, which still needs to be manufactured, are known within the coordinate system of the spectacle lens. The position and orientation of the front and back surfaces relative to each other are also precisely defined. This is crucial for the desired optical effect.Especially with complex shaped surfaces, such as for progressive lenses (varifocal lenses), even small deviations in the relative position (positioning and / or orientation) of both surfaces to each other could have an unacceptably strong impact on the optical effects.

[0004] To manufacture the back surface in precisely this 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 accurately determined. Since the exact position and orientation (e.g., relative to a corresponding processing or testing tool) of an optical lens surface(s) (including the edge) is often crucial for processing or inspecting these surfaces, this information must be known for the state in which such a lens is held by the respective lens holding element.

[0005] An example of a method for determining the position of an optical lens during manufacturing is described in EP 3 437 797 A1. This involves finding a coordinate transformation between a description in coordinates in a system of the glass and coordinates in a system of a holder by considering a large number of point triplets and determining the optimal configuration from this large number.

[0006] 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.

[0007] Thus, in one aspect, the invention provides a computer-implemented method for determining a (stable) position (position and orientation) of an optical lens with respect 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 for this purpose.

[0008] The method according to the invention comprises providing surface data of the first lens surface of the optical lens. This first lens surface thus 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 sag values. The surface data of the first lens surface are provided, for example, as sag values ​​in a coordinate system of the lens in a database, in a file system, or via an interface to the computer executing 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 a customized surface optimization of a lens (e.g., a customized 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.The surface data of the first lens surface may have been transferred to a merchandise management system. Alternatively, the surface data of the first lens surface may also have been determined by (e.g., optical and / or mechanical / tactile) measurements of the lens surface and made available as (intermediately) stored data via a database or in a file system, e.g., of a measurement management system. Making the surface data of the first lens surface available thus preferably includes reading 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 executing the method according to the invention, as described above.

[0009] Furthermore, surface data of the contact area of ​​the lens retaining element are provided. This surface data can be provided, for example, as coordinates of surface points in a coordinate system of the lens retaining system in a database, a file system, or via an interface to the computer executing the method according to the invention. This surface data can also be stored as values ​​in a database or file system, e.g., a merchandise management system, and made available for the method described here. It can, for example, originate from type-specific technical data sets of the lens retaining element, e.g., provided by design drawings of the lens retaining element, or it can be measured directly on the actual lens retaining element.Providing the surface data therefore preferably includes reading the stored surface data from a data storage device and / or measuring the surface, e.g., using standardized coordinate measuring machines, wherein the measuring device or its control unit makes the measured surface data available to the computer that executes the method according to the invention, as described above.

[0010] In addition, force data relating to the holding force are provided to the computer executing the inventive method in a database, a file system, or via an interface. This data defines at least one point of force application and one direction of the holding force. This force data can be stored as values ​​in a database or file system, e.g., a merchandise management system, or it can be calculated for an application, e.g., by a calculation system, for example, if a clamping arm of the lens holding element is controllable and its position and force must be determined as a function of the lens and provided for the method described here. It can, for example, originate at least partially from type-specific technical data sets of the lens holding element, e.g., provided by design drawings of the lens holding element.Alternatively or additionally, the force application data can also be selected or entered, at least partially, by a user of the procedure described here, particularly via a user interface (e.g., a computer workstation). For example, a user could select (via an operator terminal) that gravity should act as the holding force and / or in which direction (e.g., relative to a coordinate system of the lens holding element) the holding force should act. Especially when considering the force exerted by gravity on the optical lens, at least the direction of the holding force can be automatically derived from a (predefined or user-entered) orientation of the lens holding element in space. The point of application of the force by gravity can then be calculated from the respective, instantaneous position of the lens relative to the lens holding element (e.g., as the coordinates of the lens's center of gravity in the lens's coordinate system).Providing the force effect data therefore preferably includes at least partially reading stored data from a data storage device and / or input by a user and / or calculation from stored and / or user-entered and / or pre-calculated data.

[0011] Finally, a first contact point is established between the first lens surface and the contact area of ​​the lens holding element. The establishment of this first contact point is preferably dependent on and adapted to the specific application in which the present invention is used. Examples and preferred embodiments are described in detail below.

[0012] Based on this data, the method involves virtually rotating the optical lens around a first axis of rotation. This axis passes through the (at least one) first contact point and is perpendicular to a force axis that runs through the point of force application and parallel to the force direction, as well as perpendicular to the perpendicular from the first contact point to the force axis. The rotation is directed towards a torque defined by the force data for rotation around the first axis. This virtual rotation can be performed in iterative, small steps. It continues until the first lens surface of the optical lens and the contact area of ​​the lens retainer form a second contact point.

[0013] Insofar as this description refers to "virtual" rotations and / or translations of a lens, it means in particular that no real lens is physically / mechanically moved, but that fixed points of the lens (especially surface points) in a given coordinate system (especially one 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).

[0014] Based on the first and second contact points, the optical lens is virtually rotated around a second axis of rotation, which passes through the first and second contact points, in the direction of a torque defined by the force data for rotation around the second axis of rotation, 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, particularly in iterative, small steps.

[0015] The two virtual rotations occur at least when the respective torques are not zero, i.e., when the axis of force 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, for example, terminate the calculation and determine the position of the optical lens to be the desired stable position.

[0016] Once the desired, stable position of the lens relative to the lens holding element is achieved, which can be characterized in particular by (at least) three contact points between the first lens surface and the contact area of ​​the lens holding element, this position can be output as the position to be determined. Thus, the method includes 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. This output can be provided, in particular, as a data set displayed on a screen and / or via 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 uniquely defines the position and / or orientation of the lens relative to the lens holding element in the (determined as stable) position. In particular, at least three translational (position) and three rotational coordinates (orientation) of the lens (relative to the lens holding element) are thus uniquely defined, directly or indirectly. If the lens exhibits symmetries that lead to invariances in the shape of the lens, it may be sufficient if the position to be determined defines fewer degrees of freedom to uniquely (sufficiently) describe the position of the optical lens. For example, in the case of a completely rotationally symmetric lens, it may be sufficient if the position to be determined uniquely defines only three translational and two rotational coordinates.The third coordinate, which describes the rotational symmetry, can be disregarded.

[0017] By determining the position of the optical lens relative to the lens holding element in this way, the second lens surface can also be uniquely determined relative to the lens holding element and thus also relative to the first lens surface. Depending on the process in which the present invention is applied, this is of corresponding benefit, as will be described below with some examples.

[0018] For example, the specific shape and position of the second lens surface (relative to the first lens surface) may initially be unknown during a measurement process. The goal of the measurement process may be to determine the shape and position of the second lens surface relative to the first lens surface. Measurement processes that directly measure only one lens surface (e.g., optically or mechanically) within a coordinate system of a corresponding measuring device are often technically much simpler, faster, and more cost-effective, and sometimes also more precise, than measurement processes that (must) measure both lens surfaces relative to a coordinate system of the measuring device and / or relative to each other. 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 very technically 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 particularly 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, especially if it is calibrated. The position of the first lens surface relative to the measuring device obtained by means of the method according to the invention, as well as the shape of the second lens surface and its position relative to the first lens surface, allow measurement methods to be simulated, for example, in a computational system, and thereby setpoint values ​​for the measurement to be determined. Examples of such measurement methods are transmission measurements such as those performed by vertex refractometers and automappers.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.

[0019] In another exemplary application, where a given second lens surface is to be processed (e.g., thinly coated) without significantly altering its shape (and position), both the shape of the second lens surface and its position (position and orientation) relative to the first lens surface may already be known. For example, the goal might be to coat a complex, pre-shaped lens on the second lens surface, e.g., to apply a protective layer, an anti-reflective coating, a tint, etc. To perform this processing (e.g., coating) as precisely as possible, it can 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., a microscope) should be known.The 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. Since, in this application example, the position of the second lens surface relative to the first lens surface is already known (predetermined), the position of the second lens surface relative to the lens holding element is also determined or determinable. Because it is generally very easy 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 of 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.

[0020] In another exemplary application, where a second lens surface is to be machined (e.g., ground or milled) to conform its shape to a specific target, the position and orientation of the second lens surface relative to the first lens surface can also be known as a target for the manufacturing process. For example, the goal of the manufacturing process might be to produce a complexly shaped second lens surface in such a way that it ultimately occupies a precise position relative to the first lens surface. To perform this machining of the second lens surface (e.g., milling or grinding) as precisely as possible, it is crucial to be able to adjust the position of the optical lens (i.e., the first lens surface) relative to the manufacturing fixture (especially relative to a process head of the fixture, such as a milling or grinding head) as accurately 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. Since it is generally very easy to 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 very precisely, the method according to the invention enables a 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 produced 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, especially if it is calibrated. Insofar as, for such a manufacturing process, 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 forming) are also known and are to be used for controlling the manufacturing process (e.g., for determining the contact points of a process head at the beginning of the milling or grinding operation), the explanation for the machining process described above (e.g., coating) is applicable analogously.

[0021] 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 accurately relative to a corresponding machining tool.

[0022] The invention thus makes it possible to determine an optimal coordinate transformation, for example, through an iterative method. In contrast to the prior art, it is not necessary to compare multiple configurations. Rather, the method according to the invention is dynamically adaptive and therefore results in a much more precise and faster determination of the optimal coordinate transformation, particularly for complex lens surfaces.

[0023] Examples of lens holding elements include a block ring or a flat surface. This method is particularly suitable for spectacle lenses. The holding force can be, in particular, the lens's own gravity or a clamping arm that presses the lens against the contact area of ​​the lens holding element.

[0024] In particular, the method according to the invention is carried out in an iterative process, such that a coordinate transformation for determining the position (position and orientation) of the optical lens is found through each iteration. One aspect of the invention is that the spectacle lens is forced by all applied forces into a position in which all forces and torques are compensated by the contact of the first lens surface (e.g., the front or back surface of a spectacle lens) with the contact area of ​​the lens holding element. If the optical lens is not yet in this stable position, the forces and torques will cause it to move towards this stable position. Modeling this physical dynamic ensures that the optimal or stable position of the optical lens, and thus the optimal coordinate transformation, can be found.

[0025] Preferably, the method also includes, 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 is not located 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 passes at least through the contact point of the first, second, and third contact points that is closest to the projection point, in the direction of a torque which is determined by the force application 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 performed iteratively, whereby the contact point(s) (from the first, second, and third contact points) that is not contained in the further axis of rotation is discarded in subsequent iteration steps. Instead, a new configuration of three contact points is preferably sought iteratively until the projection point lies within the convex surface (triangle) formed by the three contact points.

[0026] In a preferred embodiment, the further axis of rotation passes through a further contact point formed by the first, second, and third contact points such that the contact point lying outside the further axis of rotation and the contact point formed by the further axis of rotation are separated from each other within the temporary contact plane. In other words, the further axis of rotation divides the temporary contact plane into two half-planes, with the contact point formed by the first, second, and third contact points lying outside the further axis of rotation in different half-planes. In this case, the contact point not traversed by the further axis of rotation is specifically discarded.

[0027] Alternatively or additionally, in another preferred embodiment or in another iteration step, the further axis of rotation runs both perpendicular to the force axis and perpendicular to the perpendicular from the contact point through which the axis of rotation passes to the force axis. In particular, in this case, both contact points not traversed by the further axis of rotation are discarded, and the (iterative) method preferably seeks two further contact points.

[0028] In a preferred embodiment, the point of application of the force is the center of gravity of the optical lens and the direction of the force is the vertical, i.e., the direction of the gravitational field (i.e., the direction of gravity).

[0029] The provision of the first contact point is preferably dependent on and 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 vertex refractometer or a Shack-Hartmann sensor is suitable as the measuring sensor. The location of the measuring sensor preferably defines two (horizontal) coordinates of the position of a reference point (e.g., the 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 (especially in the stable position to be determined) lie on a straight line that is, in particular, perpendicular to a support plane defined by the lens holding element.The angular coordinates of a rotation about this line can then be determined by aligning an internal coordinate system of the measuring sensor, e.g., a reference to a cylinder ash and / or a prism base of the optical lens.

[0030] For a block machining process, such as that used for milling, grinding, and / or polishing a lens, the first contact point could be provided such that the optical lens is aligned with respect to a block ring formed by the lens holding element. The center of the block ring defines, for example, two (horizontal) coordinates of a reference point (e.g., the lens center) relative to the block ring (specifically, relative to the block ring center). The first contact point could thus be provided with the objective of ensuring that the lens center and the block ring center lie on a straight line, specifically perpendicular to a support plane defined by the block ring. Angular coordinates of a rotation about this line can then be determined by alignment based on a reference defined by a cylindrical base and / or a prism base of the optical lens.

[0031] For determining the height of an optical lens, the specific choice of the first contact point is preferably subject to fewer boundary conditions, since preferably only the relative distance of the highest point of the second lens surface from a planar support formed by the lens holding element is determined, and this quantity is independent of the choice of the coordinate system and thus independent of the two horizontal (i.e., parallel to the planar support) translations and the rotation about the vertical (i.e., the perpendicular to the planar support).

[0032] In a preferred embodiment, providing a first contact point of the first lens surface with the contact area of ​​the lens holding element includes providing a target position for the optical lens relative to the lens holding element and specifying a starting value for the first contact point. The target position is preferably provided depending on and adapted to the application in which the method according to the invention is used, as has already been described by way of example. For selecting 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., a boundary curve of the optical lens when a concave first lens surface is positioned on a flat surface of the lens holding element, or the projection of the block ring onto the first lens surface.From this set of possible contact points, the starting value for the first contact point can be selected. This selection is also preferably made depending on and adapted to the application in which the inventive method is used. For example, when the front surface of a spectacle lens rests on a flat surface, the first contact point can be a point with the smallest swash level, and when the back surface of a spectacle lens rests on a flat surface, the first contact point can be a point with the largest swash level.

[0033] Furthermore, in this preferred embodiment, the method includes, after the virtual rotation of the optical lens about the second axis of rotation, 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 the required accuracy (i.e., within permissible tolerance deviations). If the target specification is met (or if 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 determining or needing to determine a correction value for the first contact point.

[0034] At least to the extent that a correction is made for the first contact point after the target specification has been identified as not being met, the virtual rotation about a first axis of rotation, the virtual rotation about a second axis of rotation, the verification of 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 carried out using a Newton method.

[0035] 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 machining device) is provided as a 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 a target specification. This is particularly advantageous in applications where, for example, a lens center is to be aligned relative to a sensor center of a measuring device or a tool center of a machining device.

[0036] Alternatively or additionally, preferably 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 provided as a target specification. This is particularly advantageous in applications where, 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.

[0037] In another aspect, the invention provides a method for processing at least one lens surface of an optical lens, comprising: Providing an optical lens with a first lens surface having known surface properties and a second lens surface to be machined; blocking the lens with the first lens surface on a lens holding element, wherein the position (position and orientation) of the optical lens relative to the lens holding element is determined by a method described herein, in particular according to one of the preferred embodiments described herein; and machining the second lens surface while the optical lens is held in the determined position relative to the lens holding element by the lens holding element.

[0038] The invention is described in more detail below with reference to preferred embodiments and the accompanying drawings. These drawings show: Fig. 1 a schematic representation of an optical lens held by a lens holding element; Fig. 2A and 2B schematic representations of virtual constellations between an optical lens and a lens holding element during a method according to the invention.

[0039] Fig. 1 Figure 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, which are made available to the method according to the invention. The surface data are provided, for example, as sags 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. 1The coordinate system (x'-y'-z') of the spectacle lens is shown (the y'-axis runs into the plane of the drawing). The exact shape of the second lens surface 14 does not need to be known for the method of determining the position and orientation of the spectacle lens. The aim is to determine the exact position and orientation, and in particular (up to) three translational and (up to) three rotational parameters, of the spectacle lens 10 relative to a lens holding element 16, which holds the spectacle lens. The lens holding element 16 has a contact area 18 against which the spectacle lens 10 is positioned with its 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 are formed between the lens surface 12 and the mounting area 18, forming a triangle through whose area an axis of force, with which the spectacle lens 10 is pressed against the lens holding element, passes.

[0040] In Fig. 1A coordinate system (xyz) is also shown (the y-axis runs into the plane of the drawing), which is fixed within the system of the lens holding element. The exact coordinates of the first lens surface 12 in this coordinate system in its stable position depend in particular on the surface shape of the first lens surface 12 and the shape of the contact area 18. The aim 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., specifically within 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.

[0041] Fig. 2Figure 1 schematically shows several virtual, temporary positions during the determination of the (to be determined, 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. Surface data of the contact area 18 of the lens retaining element 16 are also provided. The method is intended to determine stable contact between the spectacle lens 10 and the lens retaining element 16 when a force acts on the spectacle lens, pressing the spectacle lens 10 with its first lens surface 12 against the contact area 18 of the lens retaining element 16. For this purpose, force application data of the holding force are also provided, defining at least one point of force application 20 and one direction 22 of the holding force.The schematically depicted 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 influence of its own gravity. The center of gravity of the spectacle lens 10 can thus be provided as the point of force application 20. In the illustrated embodiment of... Figs. 1 and 2 The lens protrudes laterally beyond the attachment area 18. Alternatively, the attachment area 18 could also protrude laterally beyond the lens.

[0042] Furthermore, 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 occurs 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.

[0043] The method can particularly preferably 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 to 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, for example, be chosen 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 user position).Initially, a position is chosen in which the spectacle lens, with its first lens surface 12 to be held by the lens holding element 16, touches the contact area 18, 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 lens's contact. A corresponding initial virtual position with the first contact point 30-1 is, in particular, shown in . Fig. 2A schematically represented.

[0044] The following steps are then preferably carried out, particularly recursively: The first contact point 30-1 is identified as the pivot point. When the resulting torque with respect to this pivot point is 0, the recursive procedure is terminated.

[0045] If the torque is not 0, it generates a direction of rotation in which the spectacle lens rotates, holding the pivot point in place. The rotation continues until at least a second contact point 30-2 of the lens surface 12 of the spectacle lens 10 is formed with the contact area 18 of the lens retaining element 16. This virtual configuration is in Fig. 2B The diagram shows a schematic representation. The rotation is taken into account in the coordinate transformation. The process continues recursively using the two identified points of tangency.

[0046] If two points of contact exist, these points define an axis of rotation. If the resulting torque about this axis of rotation is zero, the recursive process ends. If the torque is not zero, it determines a rotation. This rotation is performed with a fixed axis of rotation 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 is then continued with these three points of contact.

[0047] If three or more points of contact are found, it is checked whether the resulting force acts within the convex shape created by these three or more points of contact. This establishes the stable optimal position of the spectacle lens, since the resulting torque about each axis through two points of contact can be compensated by resting on an additional point of contact. If this stable position is not found, the line connecting the at least three points of contact that is closest to the resulting force is determined—that is, the torque about an axis through two points of contact that cannot be compensated by resting on an additional point of contact—and the procedure is carried out recursively, removing the points of contact not lying on the connecting line.

[0048] After completion, a coordinate transformation is found through the recursive application of the rotations in the coordinate transformation, which describes the transition from the coordinate system used to describe the glass geometry to the coordinate system used to describe the support.

[0049] As an example, the following considers an algorithm for determining the plane of contact for a spectacle lens, i.e., the back surface rests on a horizontal plane. The resulting force is given by the weight force acting at the center of gravity of the spectacle lens. The contact plane is preferably perpendicular to this force and forms the contact area of ​​the lens retainer. In a first step, the contact plane with respect to the spectacle lens is defined such that it also touches a point on the back surface (first surface) of the spectacle lens. Then, the recursion described above is performed, 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 complete when, for example, the force is 1.At least three points of contact between the lens and the support plane exist, and these describe a convex hull containing the projection of the center of mass perpendicular to the support plane. For example, with a toric back surface, it is possible that the points of contact and the projection of the center of mass lie on a straight line in the support plane, meaning the lens rests 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 lens on only one point of contact occurs, for example, when determining the planar support of a rotationally symmetric, biconvex lens.

Claims

1. A computer-implemented method for determining a position of an optical lens (10) relative to a lens holding member (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 member (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 member (16); - Providing force action data of the holding force, which define at least one force application point (20) and a 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 is defined by the first contact point (30-1) and is both perpendicular to a force axis, which runs through the force application point (20) and parallel to the force direction (22), and perpendicular to the perpendicular from the first contact point (30-1) to the force action axis, in the direction of a torque determined by the force action data for 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); - virtual rotation of the optical lens (10) about a second axis of rotation, which is defined by the first (30-1) and second contact points (30-2) in the direction of a torque determined by the force action data for 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 - Outputting the position of the optical lens (10) resulting from the virtual rotations about the first and second axes of rotation as the position to be determined.

2. 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 points, does not lie within a triangle formed by the first (30-1), second (30-2) and third contact points: - virtual rotation of the optical lens (10) about a further axis of rotation, which runs at least through the contact point from the first (30-1), second (30-2) and third contact points that is closest to the projection point, in the direction of a torque that is determined by the force effect data for rotation about the additional 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 an additional contact point.

3. 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 points such that the contact point lying outside the further axis of rotation from the first (30-1), second (30-2), and third contact points and the projection point through the further axis of rotation are separated from each other within the temporary contact plane.

4. Method according to claim 2, wherein the further axis of rotation runs both perpendicular to the axis of force and perpendicular to the perpendicular from the contact point through which the axis of rotation runs to the axis of force.

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. Method according to 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 specification for the position of the optical lens (10) relative to the lens holding element (16); and - specifying a starting value for the first contact point (30-1), wherein the method, after virtually rotating the optical lens (10) about the second axis of rotation, further comprises: - checking the resulting position of the optical lens (10) for compliance with the target value; and - determining a correction value for the first contact point (30-1) if the target specification is not met, and wherein the method of virtually rotating about a first axis of rotation, virtually rotating about a second axis of rotation, checking for compliance with the target specification, and, if necessary, determining a correction value for the first contact point (30-1) are performed iteratively until compliance with the target specification is determined.

7. Method according to claim 6, wherein the determination of a correction value for the first contact point (30-1) is performed using a Newton method.

8. 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. Method for processing at least one lens surface of an optical lens (10), comprising: - providing an optical lens (10) with a first lens surface (12) with known surface data and a second lens surface (14) to be processed; - blocking the lens (10) with the first lens surface (12) on a lens holding element (16), wherein the position of the optical lens (10) relative to the lens holding element (16) is determined using a method according to one of claims 1 to 9; - machining the second lens surface (14) while the optical lens (10) is held by the lens holding element (16) in the determined position relative to the lens holding element (16).