EP2234758B1 - Method for preparing an ophthalmic lens with specific machining of the fitting rib thereof - Google Patents

Abstract

The invention relates to a method for preparing an ophthalmic lens (20) for mounting the same into the rim of a rimmed spectacles frame that comprises the step of acquiring a first longitudinal profile (27) of a groove of said rim, the step of blocking the lens in a holding means, and the step of trimming the ophthalmic lens using trimming means, during which the holding and trimming means are driven so that the ophthalmic lens is trimmed and includes a fitting rib extending along a second longitudinal profile (25; 26) derived from the first longitudinal profile. According to the invention, the method comprises the step of determining a second longitudinal profile of a singular portion (Z1) having a reduced curvature radius. Furthermore, during the trimming step, the holding and trimming means are driven so that the section of the fitting rib is locally narrowed in terms of width and/or height in said singular portion, and/or so that the setpoint of the trimming radius is reduced in said singular portion.

Description

TECHNICAL FIELD TO WHICH THE INVENTION REFERS

The present invention relates generally to the preparation of ophthalmic lenses for interlocking in circled spectacle frame surrounds.

TECHNOLOGICAL BACKGROUND

• l'acquisition de la forme des contours intérieurs des entourages de la monture,
• le centrage de chaque lentille qui consiste à positionner et à orienter convenablement chaque lentille en regard de chaque oeil du porteur, puis
• l'usinage de chaque lentille qui consiste à découper ou à détourer son contour à la forme souhaitée, compte tenu de la forme des entourages et des paramètres de centrage définis.

The technical part of the optician's profession is to mount a pair of corrective ophthalmic lenses on a frame of rimmed spectacles selected by a wearer. This assembly is broken down into three main operations:

• the acquisition of the shape of the inner contours of the frames of the frame,
• the centering of each lens which consists of positioning and orienting each lens correctly facing each eye of the wearer, then
• the machining of each lens which consists of cutting or contouring its contour to the desired shape, taking into account the shape of the surrounds and the defined centering parameters.

In the context of the present invention, it is more particularly interested in the first and third operations known as acquisition and machining. The practical objective of the optician is to cut the ophthalmic lens so that it can mechanically and aesthetically adapt to the shape of the corresponding entourage of the selected frame, while ensuring that the lens exercises at best the optical function for which it was designed.

The machining operation comprises in particular, in the case of rimmed frames, a beveling step for forming on the edge of the lens an interlocking rib, commonly called bevel, adapted to fit into a groove, commonly called a sucker, which runs along the inner face of the corresponding entourage of the mount. An example of implementation of this machining operation is for example presented in the document US 2001/036794 . considered as the closest state of the art.

In particular, the two acquisition and machining operations must be carried out carefully so that the lens can perfectly fit into its surroundings, effortlessly and "first time", that is to say without requiring resumption of machining.

To acquire the shape of the bezel, one generally uses a device contour reading device comprising a feeler which comes to raise the shape of the bezel. However, at the end of this probing, there are errors in raising the shape of the contour. These errors are inherent to the reading device which may have insufficient resolution, assembly defects or be damaged or unregulated. In addition, the deformations of the frame during the probing of the bezel (due to the support of the probe on the bezel) also generate errors.

At the end of the machining operation, there are also clipping errors, so that the effective shape of the edge of the lens does not correspond exactly to the desired shape. These errors are also inherent in the trimming apparatus which may have insufficient resolution, assembly defects or a worn-out wheel. In addition, the bending deformations of the lens (due to the support of the grinding wheel against the edge of the lens during its machining) also generate errors, as well as the phenomena of expansion of the lenses during their machining.

Ultimately, in view of these errors and inaccuracies, a lens thus machined has an outline that rarely corresponds exactly to the outline of the bezel of his entourage. It may then be too large, which forces the optician to perform a tedious resume of the machining of the bevel, or too small.

In order to increase the rate of correctly cut lenses "at first glance", it is known to correct the defects of acquisition and trimming devices, so as to increase their resolutions and that they take into consideration a larger number of parameters. It is also known to calibrate these devices at short intervals. However, these methods are long, complex and expensive to implement. The parameters currently taken into consideration are also not exhaustive. As a result, the rate of lenses correctly machined the first time is not so far satisfactory.

In addition, the lenses considered as mountable in their surroundings are, to a large extent, slightly too large compared to their surroundings, so that once nested in their surroundings, they are mechanically constrained. As a result, these lenses are weakened and their treatment layers are likely to degrade more rapidly. In addition, these mechanical stresses slightly modify the optical characteristics of the lenses, which can cause discomfort for the carriers.

It is also known to acquire the shapes of eyeglass frame surrounds by means of a database register having a plurality of records each associated with a spectacle frame pattern. However, due to manufacturing dispersions, it is observed that two spectacle frames of the same model never have exactly the same shape. Therefore, the shapes acquired in the database are generally slightly different from the actual shapes of the bezel crates selected by the wearer. As a result, the lenses machined according to these acquired shapes are not always mountable in the surroundings of the selected frame, so that it is often necessary to resume the machining of their interlocking ribs.

It is also known to acquire the shape of the bezel of an entourage of an eyeglass frame according to the previously acquired shape of the bezel of the other entourage of this eyeglass frame. However, due to manufacturing dispersions, it is observed that the two surrounds of a spectacle frame are never really symmetrical. Therefore, the shape deduced from a bezel is usually slightly different from the actual shape of this bezel. As a result, the lens machined as a function of this deduced shape is not always mountable in the corresponding surround of the frame, so that it is often necessary to resume machining its interlocking rib.

OBJECT OF THE INVENTION

In order to overcome the aforementioned drawbacks, the present invention provides a method of lens preparation that not only increases the rate of lenses properly machined the first shot, but also reduces the mechanical stress to which the lenses are subjected.

More particularly, methods for preparing an ophthalmic lens according to claims 1 and 7 are provided.

This compensates for errors inherent in the operation of reading and trimming devices, not by increasing the accuracy of the latter, but taking into account these errors when trimming each lens in areas of the interlocking rib particularly sensitive for assembling the lens with its mount.

These particularly sensitive areas are areas of interference between the bevel and the surrounding frame when the lens is interlocked in its surroundings. They correspond in this case singular very curved portions of the second longitudinal profile, that is to say, the projecting areas of the interlocking rib, of small radius of curvature. Therefore, trimming according to the invention of these protruding areas of the interlocking rib facilitates the interlocking of the lens in its surroundings. As a result, these singular portions of interference are so-called portions of freedom that induce a free play between the interlocking rib and the bezel.

The method according to the invention makes it possible in particular to determine with precision the positions of these singular portions of interference.

To trim the interlocking rib, it is possible to locally narrow the section of the engagement rib of the lens in these singular portions of the second longitudinal profile. We understand then that the nesting rib will be able to engage deeper in the bezel of the entourage at these singular portions. Therefore, if the lens has been mistakenly cut off in an outline that is slightly larger than the surrounding contour, this additional engagement depth will compensate for this clipping error.

To trim the interlocking rib, we can also calculate the shape of the second longitudinal profile particularly in the singular portions, so as to locally increase the radius of curvature of the second longitudinal profile to cause a decrease in its length. In this way, during the clipping step, the lens is locally milled more deeply to reveal, when mounting the lens in the surrounding area, a slight gap between the frame's surroundings and the edge of the frame. lens. Therefore, if the lens was mistakenly cut off in an outline that is slightly too big compared to the surrounding area, this slight space allows the entourage to locally deform to compensate for this clipping error.

In summary, the localized trimming of the interlocking rib in at least one of the singular portions of the second longitudinal profile makes it possible to reduce the difficulties of interlocking the lenses in their surroundings.

Preferably, said determining step excludes the search for said singular portion of the second longitudinal profile as a portion having a singular angular point or cusp.

By angular point is meant a point of the second longitudinal profile to which the two half-tangents form a non-flat angle. By curb point is meant a point of the second longitudinal profile to which the two half-tangents are opposite.

The search for singular portions of the second longitudinal profile is therefore not based on the irregularities in shape of the second longitudinal profile but rather on the variations of radius of curvature of this profile.

A second embodiment of the invention is presented in claims 3 and 9

The search for highly curved areas of the second longitudinal profile is thus achieved, not by analyzing the variations of radius of curvature of this profile, but rather by determining the points furthest from a central axis of the second profile. This axis will preferably be an optical axis or a geometric axis of the ophthalmic lens to be machined.

A third embodiment of the invention is presented in claims 4 and 10.

In this mode, the search for highly curved areas of the second longitudinal profile is made from a third longitudinal profile, for example in the form of a frame circumscribed to the second longitudinal profile. The use of this third longitudinal profile facilitates the identification of angular points or minimum radius of curvature or less than a threshold on this profile. In this way, it is easier to locate singular points on the second longitudinal profile. It is therefore also easier to identify singular portions of the second longitudinal profile at which it will trim the interlocking rib to facilitate assembly of the lens with its mount.

An advantageous characteristic of the invention is presented in claim 17.

The surrounds of metal spectacle frames are generally provided, close to the branches of the frame (temporal zones), barrels allowing them to open to accommodate a cutout ophthalmic lens. It is observed that these barrels generate a discontinuity of the bezel (and therefore the first longitudinal profile) which generates local mechanical stresses on the lens, or even which prevent the nesting rib of the lens to properly fit into its bezel. Here, thanks to the invention, the trimming of the interlocking rib in the first singular portion compensates for this discontinuity.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

The description which follows, with reference to the appended drawings, given by way of non-limiting example, will make it clear what the invention consists of and how it can be achieved.

• la figure 1 est une vue en perspective d'un appareil de lecture de contours de drageoirs de montures de lunettes ;
• la figure 2 est une vue schématique d'une lentille ophtalmique maintenue dans un appareil de détourage pourvu d'une meule de biseautage ;
• les figures 3 à 5 sont des vues de côté de trois meules de biseautage ;
• la figure 6 est une vue de face d'une lentille ophtalmique non détourée, sur lequel est représenté le contour final qu'elle présentera après détourage;
• les figures 7 et 8 sont des vues en coupe des tranches de deux lentilles ophtalmiques détourées selon deux modes de réalisation différents du procédé selon l'invention ;
• la figure 9 est une vue d'une image d'une lentille ophtalmique non détourée sur laquelle sont superposées des images du contour final et d'un curseur ;
• la figure 10 est une vue du contour final après détourage d'une lentille ophtalmique et d'une forme déduite de ce contour final par homothétie ;
• la figure 11 est une vue du contour final après détourage d'une lentille ophtalmique et d'un cadre boxing de ce contour final ;
• la figure 12 est une vue du contour final après détourage d'une lentille ophtalmique et d'une forme polygonale déduite de ce contour final ; et
• la figure 13 est une vue du contour final après détourage d'une lentille ophtalmique.

In the accompanying drawings:

• the figure 1 is a perspective view of a device for reading bezel contours of spectacle frames;
• the figure 2 is a schematic view of an ophthalmic lens held in a trimming apparatus provided with a beveling wheel;
• the Figures 3 to 5 are side views of three beveling wheels;
• the figure 6 is a front view of an ophthalmic lens not cut off, on which is represented the final outline it will present after clipping;
• the Figures 7 and 8 are sectional views of the slices of two ophthalmic lenses cut according to two different embodiments of the method according to the invention;
• the figure 9 is a view of an image of a non-cutout ophthalmic lens on which images of the final contour and a cursor are superimposed;
• the figure 10 is a view of the final contour after trimming an ophthalmic lens and a shape deduced from this final contour by homothety;
• the figure 11 is a view of the final contour after trimming an ophthalmic lens and a boxing frame of this final contour;
• the figure 12 is a view of the final contour after trimming an ophthalmic lens and a polygonal shape deduced from this final contour; and
• the figure 13 is a view of the final contour after trimming an ophthalmic lens.

The present invention aims to facilitate and improve the preparation of an ophthalmic lens for its nesting in a surrounding of a spectacle frame.

We will therefore be more particularly interested in rimmed glasses frames 10 ( figure 1 ) having two surrounds 11 which are connected to each other by a bridge and which are each equipped with a branch. Conventionally, each surround 11 is internally traversed by a groove, generally in the form of a dihedron, commonly called bezel 11. This bezel extends along a first curvilinear longitudinal profile called acquired longitudinal profile 27.

This acquired longitudinal profile 27 corresponds to one of the strands of the bezel which extends on one and / or the other of the sides of this bezel and which is substantially parallel or coincides with the bottom ridge of this bezel.

Each surround 11 is further closed by a barrel crossed by a screw which allows to tighten the lens in the entourage so as to correctly immobilize it in the mount.

As shown in figure 2 the ophthalmic lens 20 has a convex front face 21 and a concave rear face 22, as well as a peripheral edge 23 whose initial contour 28 ( figure 6 ) is generally circular.

As shown by Figures 6, 7 and 8 , this ophthalmic lens 20 is intended to include after machining its edge 23 an engagement rib 24 extending along a second longitudinal profile 25; 26 curvilinear, called longitudinal profile deduced, whose shape is calculated to allow the interlocking of the ophthalmic lens 20 in the surrounding 11 corresponding to the spectacle frame 10.

This longitudinal profile deduces 25; 26 corresponds to a line running along the edge 23 of the lens and which joins a defined point of each cross section of the nesting rib 24. Each of these points is here defined by a rule which is uniform for the whole cross sections of the interlocking rib 24. By way of example, the longitudinal profile 25; 26 corresponds to one of the strands of the interlocking rib 24 which extends on one and / or the other of the flanks of this interlocking rib and which is substantially parallel or coincident with the vertex of the rib nesting.

As shown on the figure 11 a box frame 60 can be defined with respect to the longitudinal profile deduced.

This boxing frame 60 can be defined as the rectangle which, on the one hand, is circumscribed to the orthogonal projection of the longitudinal profile deduced in the plane of the initial contour 28, and which, on the other hand, has two parallel sides intended for extend horizontally when the frame 10 supporting the lens 20 will be carried by the wearer.

This boxing frame 60 has, at the intersection of its two diagonals, a geometric center C1 through which passes a central axis A1 optical and geometric lens ( figure 2 ). The central axis A1 considered is substantially normal to the plane which is tangential to the front optical face 21 of the lens and which passes through the point of the front optical face 21 whose orthogonal projection in the plane of the initial contour 28 is the geometric center C1.

Device

To prepare such a lens, it is known to use a contour reading device 1 such as, for example, the one shown in FIG. figure 1 .

This apparatus comprises a top cover 2 covering the set of the apparatus with the exception of a central upper portion accessible to the user, in which the eyeglass frame 10 is arranged.

The contour reading apparatus 1 is intended to record the shape of the contours of the bezels 11 of the surroundings of this spectacle frame 10.

It comprises for this purpose a set of two jaws 3, one of which is movable, which are provided with movable studs 4 for clamping between them the spectacle frame 10 in order to immobilize it.

In the space left visible by the upper central opening of the cover 2, a frame 5 is visible. A plate (not visible) can move in translation on the frame 5 along a transfer axis D. On this plate is rotatably mounted a turntable 6. This turntable 6 is adapted to take two positions on the transfer axis D1, opposite each of the two frames of the spectacle frame 10.

The turntable 6 has an axis of rotation B1 defined as the normal axis to the front face of the turntable 6 and passing through its center. It is adapted to pivot about this axis relative to the plate. The turntable 6 further comprises an oblong slot 7 in the form of an arc of a circle through which a probe 8 protrudes. This probe 8 comprises a support rod 8A with an axis perpendicular to the plane of the front face of the turntable 6 and, at its free end, a feeler pin 8B with an axis perpendicular to the axis of the support rod 8A. This finger 8B is intended to follow by sliding or possibly rolling the bottom of the bezel of each of the two surrounds of the spectacle frame 10, moving along the light 7.

The contour reading apparatus 1 comprises actuating means (not shown) adapted, firstly, to slide the support rod 8A along the lumen 7 in order to modify its radial position R with respect to the B1 rotation axis of the turntable 6, a second part, to vary the TETA angular position of the turntable 6 about its axis of rotation B1, and, thirdly, to position the feeler finger 8B of the probe 8 at an altitude Z more or less important with respect to the plane of the front face of the turntable 6. Each point palpated by the end of the feeler finger 8B of the probe 8 is then located in a corresponding coordinate system R, TETA, Z. The coordinates of this point probed are then noted ra _i , tetaa _i , za _i .

The contour reading apparatus 1 furthermore comprises an electronic and / or computer device 9 making it possible, on the one hand, to drive the actuating means of the contour reading apparatus 1, and, on the other hand, to acquire and to record the coordinates ra _i , tetaa _i , za _i of the end of the feeler finger 8B of the probe 8.

To prepare the ophthalmic lens 20, it is also known to use a trimming apparatus 30 which is not the subject of the present invention. Such a clipping apparatus, well known to those skilled in the art, is for example described in the document US 6,327,790 or marketed by the Applicant under the trademark Kappa CTD.

As shown in figure 2 such a trimming apparatus generally comprises support means here formed by shafts 31 for holding and rotating the ophthalmic lens 10 around a locking pin A1. Such a trimming apparatus further comprises trimming means here formed by a machining tool 32 rotatably mounted about an axis of rotation A2 which is here substantially parallel to the locking axis A1, but which could also be inclined relative to this axis. The machining tool 32 and / or the shafts 31 are provided with two relative mobilities, including a radial mobility that makes it possible to modify the spacing between the axis of rotation A2 and the blocking axis A1, and translational mobility. axial along an axis parallel to the blocking axis A1.

The trimming apparatus 30 further comprises an electronic and / or computer device (not shown) which is provided, on the one hand, with communication means with the electronic and / or computer device 9 of the contour reading device. 1, and, secondly, means for controlling the mobilities of the shafts 31 and of the machining tool 32. This electronic and / or computer device makes it possible in particular to control, for each angular position of the lens 20 around of the locking pin A1, the radial spacing between the machining tool 32 and the locking pin A1, as well as the axial position of the edge 23 of the lens relative to the working surface of the machining tool 32.

As shown more particularly in figure 3 , the machining tool 32 is in this case constituted by a main wheel 33 of shape, that is to say having hollow, in the manner of a negative, a machining profile complementary to that to obtain relief on the edge 23 of the lens to be machined. More particularly, this main grinding wheel 33 is here of revolution about the axis of rotation A2 and is provided with a bevelling groove 34 capable of forming on the edge of the lens 20 the interlocking rib 24 ( figure 7 ) of complementary shape. The diameter of the main grinding wheel will preferably be less than 25 millimeters.

This interlocking rib 24 is most often made to present, in cross section, a profile in the form of a dihedral, that is to say in the shape of an inverted V, which is why the interlocking rib 24 is commonly called bevel. Of course, this interlocking rib may have, in cross section, different shapes, for example a semi-circular or rectangular shape.

Alternatively and with reference to figure 4 it can be provided that the machining tool comprises a wheel set comprising, in addition to the aforementioned main wheel 33, an auxiliary beveling wheel 35 provided with a beveling groove 36 of depth and / or width less than less 0.05 millimeter to the depth and / or width of the beveling groove 34 of the main grinding wheel 33. This small beveling groove 36 may for example have a depth and width less than 0.3 millimeters to the depth and to the width of the beveling groove 34 of the main grinding wheel 33.

In another variant, as shown by figure 5 it can be provided that the machining tool 32 comprises a grinder 37 having a cylindrical central portion 40 of revolution about the axis of rotation A2, and, on either side of this central portion 40, two portions of end 38, 39 conical of revolution about the axis of rotation A2 and arranged back-to-back. These two end portions 38, 39 will then be able to successively machine the two sides of the engagement rib 24 of the ophthalmic lens 20. Of course, it will also be possible for these two end portions to be arranged facing each other. at a distance from each other.

The machining tool may be of another type. It may in particular be formed by a cutter or a knife rotatably mounted about the axis of rotation A2. Knife means a tool having, in the manner of a flat wick, a central shaft on each side of which extend radially in the same plane, two blades adapted to machine the wafer of the ophthalmic lens.

Preparation process

For the implementation of the method according to the invention, with reference to the figure 1 firstly, the eyeglass frame 10 chosen by the future wearer is fixed in the reading apparatus 1. For this, the frame is inserted between the studs 4 of the jaws 3, so that each of the frames of the frame is ready. to be palpated along a path starting by the insertion of the probe 8 between the two studs 4 enclosing the lower part of the entourage to be probed, then following the bezel 11 of this entourage to cover its entire length.

More precisely, the electronic and / or computer device 9 defines as zero the angular position and the altitude of the probe 8 when the feeler finger 8B is disposed between the two aforementioned studs 4.

Once the spectacle frame 10 is fixed and the feeler 8 in contact with the bezel 11, the electronic and / or computer device 9 controls the rotation of the turntable 6 so that the feeler finger 8B of the probe 8 moves continuously along the bottom of the bezel 11.

The preservation of the contact of the feeler finger 8B with the bottom of the bezel 11 is provided by the actuating means which exert on the probe 8 a radial return force directed towards the bezel 11. This radial return force thus makes it possible to avoid that the feeler finger 8B goes up along one or other of the sides of the bezel 11 and that it leaves the bezel.

Consequently, the feeler 8 is controlled in angular position around the axis of rotation B and is guided according to its radial coordinate and according to its altitude thanks to the shape here V of the bezel 11.

The electronic and / or computer device 9 then falls during the rotation of the turntable 6 the spatial coordinates ra _i , tetaa _i , za _i of a plurality of points of the acquired longitudinal profile 27 of the bezel 11, for example 360 points, to memorize a precise digital image of the outline of this bezel. This image, in orthogonal projection in the plane of the initial contour 28, is represented in dotted line on the figure 6 .

Alternatively, it could be provided that the probe comes to feel, in a discrete manner, a predefined number of points of the bezel to raise the spatial coordinates of these points.

In another variant, these spatial coordinates ra _i , teta _i , z _{i i} can be acquired by means of a database register. In this variant, the database register comprises a plurality of records each associated with a referenced type of spectacle frames (that is to say a given spectacle frame model). More specifically, each record includes an identifier that corresponds to the referenced type of spectacle frames, and an array of values referencing, for example, the spatial coordinates of 360 characteristic points of the shape of a longitudinal profile of the bezel of an eyeglass frame. referenced type. Thus, to acquire these spatial coordinates ra _i , tetaa _i , za _i , the user can search the database for the record whose identifier corresponds to the eyeglass frame selected by the wearer (for example by means of the code -barre of the mount). Then, The values referenced in this recording will then be read and transmitted to the electronic and / or computer device of the trimming apparatus 30. A disadvantage generally found when using this acquisition method is that, since two frames of the same type do not show that rarely exactly the same shape, the spatial coordinates acquired in the database can be slightly different from the real coordinates of the corresponding points of the bezel. However, the method according to the invention will make it possible to compensate for these differences, so that the lens is easily mountable in the frame selected by the wearer.

According to another variant, the acquisition of coordinates of points of the acquired longitudinal profile can be carried out in a plane, for example on a picture of the wearer. In this variant, during a first operation, a digital photograph of the wearer equipped with his spectacle frame is acquired. Then, during a second operation, the acquired image is taken from the shape of the inner contour of each surrounding of the spectacle frame, for example by means of an image processing software. We thus deduce the coordinates ra _i , tetaa _i of a plurality of points of the acquired longitudinal profile.

During a second step, a computational instruction of the ophthalmic lens to be inserted in the palpated surround of the eyeglass frame 10 is calculated.

This calculation step may be performed by computing means of the electronic and / or computer device hosted by the contour reading device 1 or by those of the trimming apparatus 30, or by those of any other device capable of communicate with one and / or both of these devices 1.30.

During this second step, the calculation means develop, as a function of the spatial coordinates ra _i , tetaa _i , za _i points acquired longitudinal profile 27 on the bezel 11, a set of clipping radius and an axial setpoint clipping of the ophthalmic lens 20. These instructions are elaborated so that the lens is cut off, on its edge 23, a profiled interlocking rib 24 having a desired section and extending according to the longitudinal profile deduced ( figure 6 ), which here corresponds to the top of the edge of the interlocking rib 24 to be machined.

The deduced longitudinal profile 25 is here defined by 360 points whose spatial coordinates are denoted rs _j , tetas _j , zs _j .

• Pour i = j et j allant de 1 à 360,
• rs_j = ra_i + k ; tetas_j = tetaa_i ; zs_j = za_i + g(tetas_j).

The longitudinal profile deduced 25 is deduced from the acquired longitudinal profile 27 in the sense that it is defined to be either confused with it, or removed from it by an almost constant distance. More precisely, the coordinates rs _j , tetas _j , zs _j of the 360 points of the derived longitudinal profile 25 are calculated from the coordinates ra _i , tetaa _i , za _i of the 360 points of the acquired longitudinal profile 27 according to the following mathematical law:

• For i = j and j ranging from 1 to 360,
• rs _j = ra _i + k; tetas _j = tetaa _i ; zs _j = za _i + g (tetas _j ).

The constant k is calculated conventionally according to the architectures of the contour reading apparatus 1 and the contouring apparatus 30, as well as to the shapes of the cross sections of the bezel of the surround of the frame and the bevelling groove of the main grinding wheel 33. This constant k makes it possible in particular to take into account the fact that, once the lens is nested in the surrounding area, the top of the interlocking rib (corresponding to the longitudinal profile deduced 25) is never in contact the bottom of the bezel (corresponding to the acquired longitudinal profile 27) but is slightly offset from the latter.

The function g (tetas _j ) can be chosen to be zero or constant or variable, to take into account a possible difference between the general camber of the lens and the bezel of the frame. The choice of this function makes it possible in particular to modify the position of the interlocking rib on the peripheral edge 23 of the lens, such that the interlocking rib extends along the front optical face of the lens. or rather in the middle of his slice.

During a third step, the calculation means proceed to the detection of at least one singular portion Z1-Z5 of the longitudinal profile deduced 25.

This detection will subsequently machine the ophthalmic lens 20 so that its nesting rib 24 is ideally in contact with the bezel outside the singular portions and out of contact with this bezel in these singular portions. It is thus understood that the interlocking rib 24 will be machined in a conventional and uniform manner out of the singular portions of the longitudinal profile 25 deduced, so that the nesting rib 24 fits into the bezel 13, and it will be machined in a particular and non-uniform manner in the singular portions of the longitudinal profile deduced 25, so that ideally the nesting rib 24 does not fit completely into the bezel 13 at these singular portions.

The sections of the interlocking rib 24 which are expected to be in contact with the bezel 13 are called bearing sections, while the sections of the nesting rib 24 which are expected to be in contact with the bezel 13 are called freedom sections. These sections of freedom are so named because if the lens is not properly cut and has a contour too large compared to that of the entourage 11 corresponding, this entourage is free to deform at these sections of freedom to marry the shape of the nesting rib. In this sense, the singular portions could also be called portions of freedom.

More particularly, the calculation means proceed to the detection of at least one singular point P1-P5 to which the derived longitudinal profile has a minimum radius of curvature or less than a threshold, and then they deduce the position of at least one singular portion Z1-Z5 of the longitudinal profile deduced as a portion within 5 millimeters of or containing the singular point P1-P5.

In order to determine the positions of the singular points P1-P5, the calculation means determine the radii of curvature Rc _j of the longitudinal profile deduced at the level of its 360 previously defined points.

The calculation of these radii of curvature can be achieved in various ways, in two or three dimensions.

Here, the calculation of the radii of curvature is made in two dimensions, in the plane of projection of the longitudinal profile deduced 25 represented on the figure 6 , by ignoring the coordinates zs _j of the points of the longitudinal profile deduced 25.

avec

• a₀ = (bo - bi) / (b₂ - b₃) ;
• a₁=b₁-b₂.a₀ ;

où

• b₀ = (c₀ ² - c₁ ² + c₂ ²- c₃ ²) / (2.c₂ - 2.c₃) ;
• b₁ = (c₁ ² - c₄ ² + c₃ ² - c₅ ²) /(2.c₃ - 2.c₅) ;
• b₂ = (c₁ - c₄) / (c₃ c₅) ;
• b₃ = (c₀-c₁)/(c₂-c₃) ;

et où

• c₀ = rs_j+1 . cos (tetas_j+1) ;
• c₁ = rs_j . cos (tetas_j) ;
• c₂ = rs_j+1. sin (tetas_j+1) ;
• c₃ = rs_j . sin (tetas_j) ;
• c₄ = rs_j-1 . cos (tetas_j-1) ;
• c₅ = rs_j-1 . sin (tetas_j-1).

The calculation of the radius of curvature Rc _j of the longitudinal profile deduced at each point P _j is carried out as follows: $$\mathrm{R}{\mathrm{vs}}_{\mathrm{j}}\mathrm{=}{\left[{\left(\mathrm{r}{\mathrm{s}}_{\mathrm{j}}\mathrm{.}\cos \left(\mathrm{teta}{\mathrm{s}}_{\mathrm{j}}\right)\mathrm{-}{\mathrm{at}}_{\mathrm{0}}\right)}^{\mathrm{2}}\mathrm{+}{\left(\mathrm{r}{\mathrm{s}}_{\mathrm{j}}\mathrm{.}\sin \left(\mathrm{teta}{\mathrm{s}}_{\mathrm{j}}\right)\mathrm{-}{\mathrm{at}}_{\mathrm{1}}\right)}^{\mathrm{2}}\right]}^{\mathrm{1}\mathrm{/}\mathrm{2}}\mathrm{,}$$

with

• a ₀ = (bo - bi) / (b ₂ - b ₃ );
• a ₁ = b ₁ -b ₂ .a ₀ ;

or

• b ₀ = (c ₀ ² - c ₁ ² + c ₂ ² - c ₃ ² ) / (2.c ₂ - 2.c ₃ );
• b ₁ = (c ₁ ² - c ₄ ² + c ₃ ² - c ₅ ² ) /( 2.c ₃ - 2.c ₅ );
• b ₂ = (c ₁ - c ₄ ) / (c ₃ c ₅ );
• b ₃ = (c ₀ -c ₁ ) / (c ₂ -c ₃ );

and or

• c ₀ = rs _{j + 1} . cos (tetas _{j + 1} );
• c ₁ = rs _j . cos (tetas _j );
• c ₂ = rs _{j + 1} . sin (tetas _{j + 1} );
• c ₃ = rs _j . sin (tetas _j );
• c ₄ = rs _j-1 . cos (tetas _j-1 );
• c ₅ = rs _j-1 . sin (tetas _j-1 ).

avec f = df(tetas_j)/d(tetas_j) et f" = d²f(tetas_j)/d(tetas_j)².As a variant, in order to determine each radius of curvature, the calculation means can deduce from the coordinates of the 360 points of the deduced longitudinal profile 25, a function f (tetas _j ) representative of the longitudinal profile deduced 25, in polar coordinates and twice differentiable. The calculation of each radius of curvature will then be performed using the formula: $$\mathrm{R}{\mathrm{vs}}_{\mathrm{j}}\mathrm{=}{\left({\mathrm{f}}^{\mathrm{\text{'}}\mathrm{2}}\mathrm{+}{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="imgf0001.png"\; state="\{\{state\}\}">f</figure-callout>}}^{\mathrm{2}}\right)}^{\mathrm{3}\mathrm{/}\mathrm{2}}\mathrm{/}\left(\mathrm{2.}{\mathrm{f}}^{\mathrm{\text{'}}\mathrm{2}}\mathrm{+}{\mathrm{f}}^{\mathrm{2}}\mathrm{-}\mathrm{f}\mathrm{.}{\mathrm{f}}^{\mathrm{"}}\right),$$

with f = df (tetas _j ) / d (tetas _j ) and f "= d ² f (tetas _j ) / d (tetas _j ) ² .

In any case, the calculation means then proceed to the determination of the positions of the singular points P1-P5 of the longitudinal profile deduced 25.

For this purpose, the calculation means compare the values of the 360 calculated radii of curvature Rc _j with a threshold value and select the points at which the calculated radius of curvature is less than this threshold value.

Preferably, this threshold value is predetermined and stored in the calculation means. It is then chosen less than 20 millimeters, here equal to 10 millimeters.

As a variant, this threshold value may be determined as a function of the calculated values of the radii of curvature Rc _j . In other words, the threshold value can be chosen as a function of the overall shape of the longitudinal profile deduced 25, or even according to the shape of the acquired longitudinal profile 27. By way of nonlimiting examples, the threshold value can be chosen according to the average and / or the standard deviation and / or the median of the 360 calculated radii of curvature Rc _j . It may also be chosen equal to the smallest radius of curvature calculated, so that it allows to select a single point of the longitudinal profile deduced 25, namely the point where the curvature of this profile is maximum. It can also be chosen equal to the Nth smallest calculated radius of curvature (with N less than 360, typically between 5 and 60), so that it allows to select N points of the longitudinal profile deduced 25, namely the N points. where the curvature of this profile is maximum.

Be that as it may, the comparison of the radii of curvature Rc _j calculated with this threshold value makes it possible to record at least one singular point on the longitudinal profile deduced at which the radius of curvature of the profile is less than this threshold value.

Generally, sets of several neighboring points, at which the radius of curvature of the profile is less than this threshold value, are thus raised. The calculation means define a single singular point P1-P5 by set of points, namely the central point of this set of points.

Then, the calculation means define the singular portions Z1-Z5 as the areas of the longitudinal profile deduced 25 which are centered on these singular points P1-P5 and which have a length of between 5 and 10 millimeters, here equal to 8 millimeters.

As shown on the figure 6 , the calculation means determine five singular portions spaced apart from each other.

Finally, during a fourth and last step, the ophthalmic lens 20 is locked between the shafts 31 of the shaping device 30 and the ophthalmic lens 20 is cut off by this shaping device 30.

During this step, the support shafts 31 of the lens and / or the trimming tool 32 are controlled such that the deduced longitudinal profile has, in at least one singular portion Z1-Z5, a specific deviation E1 with respect to acquired longitudinal profile 27 such as to increase its radius of curvature and / or so that the section of the engagement rib 24 is locally narrowed in width and / or height on at least one singular portion Z1-Z5.

As described below, the lens will be specifically bevelled in each singular portion Z1-Z5.

Alternatively, it will be possible to provide the bevel specifically in only certain singular portions. Consider, to choose which one or which singular portions will be specifically beveled, the longitudinal profile deduced as a whole. It has a temporal zone that corresponds to the area around the frame at which is fixed one of the branches of the eyeglass frame, and a nasal area that corresponds to the area of the entourage of the frame at the level of which is fixed the bridge of the eyeglass frame. Then, if one chooses to bevel the lens specifically in only one of the singular portions Z1-Z5, the singular portion Z2 selected will be the one closest to the zone of attachment of the branch on the entourage (in this case the temporal area of the longitudinal profile deduced 25). If one chooses to bevel the lens specifically in two of the singular portions Z1-Z5, the singular portions Z2, Z3 selected will be, for one of them, the one closest to the temporal zone of the longitudinal profile deduced. , and, for the other of them, the one closest to the nasal zone of the longitudinal profile deduced 25. Thus, if, because of the welding of the branches and the bridge on the entourage, the bezel is locally deformed in the areas temporal and / or nasal, the two singularly bevelled singular portions will be confused or located near these temporal and / or nasal areas.

According to a first embodiment of the invention, during this step of trimming, the support shafts 31 of the lens and / or the trimming tool 32 are controlled so that the longitudinal profile deduced 26 has, in each singular portion Z1-Z5 considered, a specific difference E1 with respect to the acquired longitudinal profile 27 of a nature to increase its radius of curvature (see figure 6 ).

More particularly, during the trimming step, the shafts 31 and / or the trimming tool 32 are controlled so that the longitudinal profile deduced 26 is deductible from the acquired longitudinal profile 27 by a mathematical law which, on the singular portions Z1-Z5, differs from the rest of the longitudinal profile 26 deduced, so that the average radius of curvature of each singular portion Z1-Z5 of the longitudinal profile deduced 26 is increased relative to the mean radius of curvature that this singular portion Z1- Z5 would have presented if the given mathematical law had been, on this singular portion Z1-Z5, the same as for the remainder of the longitudinal profile deduced 26.

In other words, the calculation means determine a new longitudinal profile deduced 26, coinciding with the initial calculated longitudinal profile initially calculated except in each singular portion Z1-Z5. Consequently, the aforementioned mathematical law is uniform (and corresponds to the mathematical formula for deducing the longitudinal profile deduced as a function of the acquired longitudinal profile 27) outside the singular portions Z1-Z5, and is non-uniform in each singular portion.

To obtain the coordinates of the new longitudinal profile deduced 26 in each singular portion Z1-Z5, the calculation means reduce the values of the radial coordinates rs _j of the points of the initial derived longitudinal profile which are located in the singular portion Z1 considered.

More specifically, in a first step, the calculation means reduce the value of the radial coordinate rs _j of each singular point P1-P5 by a value between 0.05 and 0.3 millimeters, here equal to 0.1 millimeter . Then, in a second step, the calculation means adjust the radial coordinates rs _j of the other points of the singular portions Z1-Z5 considered so that the new longitudinal profile deduced 26 extends continuously without angular points and no cusp. In this way, the gap between the new profile longitudinal curve 26 and the acquired longitudinal profile 27 is constant and equal to k out of the singular portions, and is variable in each singular portion. Thus, the gap between the initial derived longitudinal profile and the newly derived longitudinal profile 26 is at least one point greater than 0.05 millimeters and is in any case less than 0.3 millimeters.

Finally, the lens is cut off in a conventional manner according to the new longitudinal profile deduced 26, by means of the main grinding wheel 33. In this way, the interlocking rib 24 presents at the end of this step a uniform section, it is that is to say of invariable form on all of its length.

So, as shown in figure 7 at the end of this trimming, the top of the interlocking rib has, in each singular portion Z1-Z5 considered, a profile 24A which extends at a distance from the locking pin A1 closer than that to which would have extended if the lens had been beveled according to the initial longitudinal profile (profile 24B). In this way, when the probing of the surround of the frame and / or the trimming of the lens are imperfectly made and that, therefore, the contour of the lens is slightly too large compared to the contour of the entourage, the specific beveling allows the lens to remain mountable in the environment, without this assembly generates mechanical stresses detrimental to the life of the ophthalmic lens 20.

Advantageously, it will be possible, after the determination step, to memorize the shape of the new longitudinal profile deduced 26 in a database register. For this purpose, the register may comprise a plurality of records each of which is associated with a referenced type or model of glasses frames and contains the shape of a new longitudinal profile deduced 26 common to such frames. or this model. The storage in the register of the shape of the new longitudinal profile deduced 26 will then be performed by searching in this register a record corresponding to the mount concerned and by writing in this record the shape of the new longitudinal profile deduced 26.

In this way, when subsequently trimming an ophthalmic lens for mounting in a mount of the same type or the same model, the calculating means can acquire in the register the shape of this new longitudinal profile 26 deduced, so to directly machine the lens according to this profile.

According to a second embodiment of the invention, during the trimming step, the support shafts 31 of the lens and / or the trimming tool 32 are piloted according to the initial longitudinal profile deduced, so as to achieve a profiled nesting rib 24, that is to say of uniform section, except in each singular portion Z1-Z5 where they are controlled to reduce only the size of the section of this interlocking rib 24.

This embodiment has a particular advantage. Indeed, as shown in figure 8 the fact of only decreasing the size of the interlocking rib section without modifying the target trim radius of the lens (i.e. without locally modifying the longitudinal profile deduced on the singular portions) allows to ensure that the position of the foot of the interlocking rib (part of the edge of the lens bordering the interlocking rib) remains locally unchanged. After mounting the lens in its surroundings, the foot of the nesting rib 24 will then extend close to the inner face of the frame of the spectacle frame, as on the rest of the lens surround, without creating any unsightly interstice between the edge of the lens and the mount at the level of singular portions.

Preferably, the trimming of the lens comprises a first machining phase of the interlocking rib 24 with a uniform section along the longitudinal profile deduced 25 and a second trimming phase of the interlocking rib 24 on each singular portion Z1- Z5 of the longitudinal profile deduced 25.

Here, the first machining step being carried out by means of the main grinding wheel 33 of shape (shown in FIG. figure 3 ) while the second phase is performed using the auxiliary grinding wheel 35 (shown in FIG. figure 4 ).

For this, the beveling groove 36 of the auxiliary beveling wheel 35 is brought into contact with the engagement rib 24 of the ophthalmic lens 20, at one of the ends of a first singular portion. Then the support shafts 31 of the lens and / or the trimming tool 32 are controlled so that the engagement rib 24 of the lens is trimmed along the entire length of this singular portion, then over the entire length of the other singular portions. As shown in figure 8 , this control is provided so that the profile of the engagement rib 24, at each singular point P1-P5, has a height and / or a width less than 0.05 millimeters and at most 0 , 3 millimeters relative to the height and / or the width of the interlocking rib 24 outside the singular portions. This control is further provided so that the engagement rib 24 has no discontinuity, particularly at the ends of each singular portion Z1-Z5.

Moreover, it can be seen that, if the section of the interlocking rib 24 has been narrowed in height, the longitudinal profile deduced 25 along which this nesting rib 24 extends is slightly deformed at said singular portions.

Alternatively, the trimming of the interlocking rib 24 may be made differently. For example, it can be achieved using the main grinding wheel 33 during a second pass, moving it in a direction substantially parallel to the locking pin A1, transversely offset relative to the longitudinal profile. deduced 25. For this, during the second pass, the support shafts 31 of the lens and / or the trimming tool 32 will be controlled in each singular portion Z1-Z5 considered so as to shift progressively axially (following the locking pin A1) relative to their position during the first pass. Thus, during this second pass, one of the flanks of the engagement rib 24 will be machined by one of the flanks of the beveling groove 34 of the main grinding wheel 33, which will have the effect of reducing the height and the width of the interlocking rib 24 in each singular portion under consideration.

Alternatively, the trimming of the interlocking rib 24 can be achieved by means of a cylindrical portion of the main grinding wheel 33, by planing the top of the interlocking rib 24, so as to break its vertex edge. , or even so as to locally remove the interlocking rib 24. In this variant, only the height of the interlocking rib will be modified.

In another variant, the realization of the interlocking rib 24 and its trimming can be performed simultaneously.

Thus, during the beveling of the lens by the main grinding wheel 33, the support shafts 31 of the lens and / or the trimming tool 32 may be controlled so as to present axial reciprocating movements (along the blocking axis A1 ). Thus, these reciprocating movements will plan the two flanks of the nesting rib.

To cut off the lens so that the narrowing of the engagement rib 24 is made simultaneously with the formation of this interlocking rib, it is also possible to use the grinder shown in FIG. figure 5 by machining this interlocking rib 24 in two successive phases, including a machining phase of a first of its flanks and a machining phase of a second of its flanks.

For this purpose, in a first step, the electronic and / or computer device of the trimming apparatus 30 co-ordinates the radial mobility of the grinder relative to the shafts 31 to position a first conical end portion 39 of the grinder 37 against the edge of the lens, on the side of its front face. Then, the grinder 37 and the support shafts 31 of the lens are piloted to form the front flank of the engagement rib 24. Here, this control is provided so that the leading edge of the engagement rib 24 is formed to a constant distance from the front face of the lens, except in singular portions where it deviates from the front face.

In a second step, the electronic and / or computer device of the trimming apparatus 30 co-ordinates the radial mobility of the grinder relative to the shafts 31 to position a second conical end portion 38 of the grinder 37 against the slice. the lens, on the side of its back side. Then, the grinder 37 and the support shafts 31 of the lens are piloted to form the trailing edge of the engagement rib 24. Here, this control is provided so that the trailing edge of the interlocking rib 24 is formed to a constant distance from the front face of the lens, except in the singular portions where it approaches the front face.

In this way, the ophthalmic lens is beveled so that its interlocking rib 24 has a local narrowing of height and / or width in each singular portion Z1-Z5.

According to another variant, the electronic and / or computer device of the trimming apparatus 30 may control the radial mobility of the machining tool and / or the shafts 31 so as not only to reduce in width and / or height the section of the interlocking rib 24 on each singular portion but also to machine the feet of the interlocking rib 24 (by determining the shape of a new longitudinal profile from the longitudinal profile deduced, according to a method of the type of the one mentioned above).

Advantageously, it will be possible to record the shape of the longitudinal profile deduced in a record of the database register, as well as the positions of the singular portions on this profile.

More precisely, after having determined the spatial coordinates of this longitudinal profile deduced and the positions of the singular portions and / or the singular points, the electronic and / or computer device of the trimming apparatus 30 can transmit these data to the register so that he memorizes them in a recording whose identifier corresponds to the frame of glasses selected by the holder or in a new ad hoc record. This recording can then be read later to cut another lens intended to be mounted in a mount of the same type.

Furthermore, following the shaping of this first ophthalmic lens, it will be possible to trim a second ophthalmic lens for mounting in a second surround of said spectacle frame 10, forming on its edge a nesting rib generally. profiled. This rib will then be made so that it follows a symmetrical longitudinal profile of the longitudinal profile deduced 25 and so that each of its sections has a shape identical to that of the corresponding section (by symmetry) of the interlocking rib 24 of the first lens.

Thanks to the invention, if the two surrounds of the spectacle frame 10 are not perfectly symmetrical while the two lenses have been machined symmetrically, the lenses will remain mountable in their respective surroundings.

This invention will find a particularly advantageous application to lens preparation processes implemented by customers (opticians) called "outsourcers" subcontracting the manufacture and trimming of lenses.

More specifically, it will be possible here to consider, on the one hand, a client terminal installed on the client side for the control of lenses, and, on the other hand, a manufacturer terminal installed on the side of a lens manufacturer for the manufacture and trimming of lenses.

The client terminal comprises computer means for recording and transmitting control data of the ophthalmic lens 20, for example via an IP communication protocol (Internet type). This control data includes visual correction prescription data (eg optical power, centering data, etc.) and mount data.

The terminal-manufacturer comprises meanwhile computer means for receiving and recording the order data transmitted by the terminal-client. It further comprises a device for manufacturing the ophthalmic lens in accordance with the prescription data, provided for example with means for molding the lens and / or for machining at least one of the optical faces of the lens. It also includes a device for trimming this ophthalmic lens in accordance with the data relating to the frame. This device In particular, the clipping path is designed to implement the previously described blocking and clipping steps, according to one or other of the presented embodiments.

For the implementation of the process for preparing the lens according to the invention, the step of acquiring the acquired longitudinal profile 27 comprises three successive operations.

During a first so-called determination operation, the client determines a reference of the spectacle frame 10.

During a second so-called transceiver operation, the client terminal transmits control data of a lens (integrating said reference) and the terminal-manufacturer receives this data.

The third operation is carried out by means of a database register equipping the terminal-manufacturer, each record of which is associated with a type of spectacle frames 10 and contains, on the one hand, a reference of this type of frames, and, on the other hand, the shape of an acquired longitudinal profile which is common to all frames of this type. During this third so-called search operation, the manufacturer searches in this register, using the reference acquired during the first operation the shape of the longitudinal profile of the bezel of the corresponding frame. In this way, it can then implement the previously described method, by determining in particular the position of the singular portions of the acquired longitudinal profile.

Thus the manufacturer can exploit these spatial coordinates to cut the ophthalmic lens to the desired shape, without physically having the frame in which the lens is intended to be nested. Furthermore, the method according to the invention will make it possible to compensate for possible errors in acquiring the shape of the longitudinal profile and / or machining of the lens, so that the lens will be easily mountable "at first glance" in the frame selected by the wearer. This advantage is decisive here since it avoids returning the lens to the manufacturer for resumption, which is always expensive and time-consuming referral.

As a variant, provision may be made for the acquisition step of the acquired longitudinal profile 27 to comprise a step of determining by the customer the shape of a longitudinal profile of the bezel 11, namely that of the acquired longitudinal profile 27, and a step of transmitting and receiving control data comprising the shape of the acquired longitudinal profile 27. In this variant, the determination of the positions of the singular portions on the longitudinal profile acquired 27 may be carried out indifferently by the manufacturer or by the customer.

In another embodiment of the invention shown in the figure 9 the determination of each singular portion Z6 of the derived longitudinal profile may be performed manually by the operator.

For this purpose, a man-machine interface, including in particular a screen 51, is made available to the operator. This screen 51 will preferably be tactile and accompanied by a stylus allowing the operator to interact precisely with the screen 51. The interface is further equipped with an electronic device able, on the one hand, to communicate with the user. electronic device and / or computer of the contour reading device 1 or with that of the trimming apparatus 30, and, secondly, to display images on the screen.

The electronic device is particularly adapted to display on the screen 51 an image of the contour 24 of an ophthalmic lens 20 not cut-out, an image representing two buttons 52, 53 respectively provided with a symbol "+" and an acronym "-", an image of a cursor 50 in the form of a circle and an image of a numerical value 54 corresponding to the radius R1 of the cursor 50. It is further adapted to display an image of the longitudinal profile deduced 25.

Then, to determine the positions of the singular portions Z6 of the derived longitudinal profile 25, when the spatial coordinates of the 360 points of the derived longitudinal profile 25 have been calculated, these coordinates are transmitted to the electronic device of the screen 51 which determines, as a function of these coordinates, the shape of the longitudinal profile deduced 25 and which displays this shape on the touch screen 51.

Then, the operator adjusts the radius R1 of the cursor 50 by pressing one or other of the two buttons 52, 53 with his stylus. The choice of the value of the radius R1 allows the operator to set a threshold radius of curvature.

The initial value of the radius R1 of the slider 50 is initially set at 10 millimeters and can thus be modified in a range of values between 5 and 20 millimeters.

Once this radius R1 adjusted, the operator with the stylus navigates, as shown on the figure 9 , the slider 50 in such a way that the circular edge of this slider runs along the longitudinal profile deduced 25. The electronic device of the screen 51 is here adapted to assist the operator by guiding the slider so as to maintain a point contact between the circular edge of the slider 50 and the longitudinal profile deduced 25.

When the operator believes that the shapes of the slider 50 and profile In the longitudinal equation, the operator selects the portion of the longitudinal profile deduced in which the cursor is located, for example by "double clicking" with the stylus on the touch screen 51.

The shapes are considered here as "concordant" when the cursor has two points of contact with the longitudinal profile deduced 25. In fact, the portions of the longitudinal profile in which the cursor has two points of contact have a radius of curvature less than radius of the cursor, that is to say below the threshold determined by the operator. These portions therefore correspond to the singular portions Z6 of the longitudinal profile deduced 25. These singular portions Z6 are then defined as the portions situated between the two points of contact of the slider 50 with the longitudinal profile deduced 25.

Preferably, the selected portions are then displayed in color so that the operator can visually validate his selection.

The spatial coordinates of the points belonging to the singular portions Z6 are then transmitted to the trimming apparatus 30, so that the latter diverts the lens specifically in these singular portions.

In other embodiments of the invention represented on the Figures 10 to 12 the determination of each singular portion of the derived longitudinal profile may be made considering not the shape of the derived longitudinal profile 25 or the acquired longitudinal profile 27, but rather the shape of a third longitudinal profile 60; 61; 62 deduced from either of these two longitudinal profiles 25, 27 according to a deduction rule given and distinct from these two longitudinal profiles.

More particularly, after having determined this third longitudinal profile, the calculation means establish an association between each point of this third longitudinal profile 60; 61; 62 and each point of the longitudinal profile deduced 25 according to a given rule of correspondence, then they determine the positions of the singular portions of the longitudinal profile deduced 25 as portions less than 5 millimeters from or containing a singular point whose associated point on said third longitudinal profile 60; 61; 62 is angular or has a minimum radius of curvature or less than a threshold.

According to the alternative embodiment of the method according to the invention shown in the figure 10 the determination of each singular portion of the derived longitudinal profile is performed on a third longitudinal profile 62 deduced from this profile by a mathematical calculation of homothety.

More precisely, after having determined the spatial coordinates of the 360 points of the longitudinal profile deduced 25, the calculation means deduce from these coordinates the coordinates of 360 points of the third longitudinal profile 62.

• Pour j allant de 1 à 360, $$\mathrm{r}{\mathrm{h}}_{\mathrm{j}}\mathrm{=}\mathrm{r}{\mathrm{s}}_{\mathrm{j}}\mathrm{.}\exp \left(\mathrm{-}\mathrm{0}\mathrm{,}\mathrm{5.}\left(\mathrm{r}{\mathrm{s}}_{\mathrm{j}}\mathrm{-}\mathrm{rmin}\right)\mathrm{/}\left(\mathrm{rmax}\mathrm{-}\mathrm{rmin}\right)\right);\mathrm{teta}{\mathrm{h}}_{\mathrm{j}}\mathrm{=}\mathrm{teta}{\mathrm{s}}_{\mathrm{j}}\mathrm{;}\mathrm{z}{\mathrm{h}}_{\mathrm{j}}\mathrm{=}\mathrm{z}{\mathrm{s}}_{\mathrm{j}}\mathrm{.}$$
  

For this purpose, given the coordinates rs _j , tetas _j , zs _j of a point T _j 1 of the longitudinal profile deduced 25 and the coordinates rh _j , tetah _j , zh _j of a corresponding point T _j 2 of the third profile longitudinal 62, the coordinates rh _j , tetah _j , zh _j 360 points of this third longitudinal profile are calculated according to the following formulas:

• For j ranging from 1 to 360, $$\mathrm{r}{\mathrm{h}}_{\mathrm{j}}\mathrm{=}\mathrm{r}{\mathrm{s}}_{\mathrm{j}}\mathrm{.}\exp \left(\mathrm{-}\mathrm{0}\mathrm{,}\mathrm{5.}\left(\mathrm{r}{\mathrm{s}}_{\mathrm{j}}\mathrm{-}\mathrm{rmin}\right)\mathrm{/}\left(\mathrm{rmax}\mathrm{-}\mathrm{rmin}\right)\right);\mathrm{teta}{\mathrm{h}}_{\mathrm{j}}\mathrm{=}\mathrm{teta}{\mathrm{s}}_{\mathrm{j}}\mathrm{;}\mathrm{z}{\mathrm{h}}_{\mathrm{j}}\mathrm{=}\mathrm{z}{\mathrm{s}}_{\mathrm{j}}\mathrm{.}$$
  

In this formula, the constant rmax corresponds to the coordinate rs _j of the point of the longitudinal profile deduced 25 farthest from the blocking axis A1 and the constant rmin corresponds to the coordinate rs _j of the nearest point of the longitudinal profile deduced 25 of the locking pin A1.

• rh_j = rs_j + v, avec v une constante quelconque.

Of course, the coordinates rh _j points of the third longitudinal profile 62 may be calculated differently, for example by means of the following formula:

• rh _j = rs _j + v, with v any constant.

Be that as it may, once these coordinates have been calculated, the calculation means determine the radii of curvature of the third longitudinal profile 62 at its 360 points.

Then, during a comparison step, the computation means compare these radii of curvature with a determined threshold in order to locate on the third longitudinal profile 62 at least one point P17 of small radius of curvature.

Finally, the calculation means deduce from the coordinates of this point P17 those of the singular point P7 corresponding to the longitudinal profile deduced 25. The calculation means then determine, as has been explained above, the position of at least one singular portion. Z7 of the longitudinal profile deduced 25, centered on this singular point P7.

According to the alternative embodiment of the method according to the invention shown in the figure 11 , the determination of each singular portion of the longitudinal profile deduced 25 is carried out by means of a third longitudinal profile circumscribed to the longitudinal profile deduced 25. This third longitudinal profile corresponds here boxing frame 60.

More precisely, after having acquired the spatial coordinates rs _j , tetas _j , zs _j of 360 points of the longitudinal profile deduced 25, the calculation means of the device deduce from these coordinates the geometry of boxing frame 60.

The calculation means then establish a rule of correspondence between the points of this boxing frame 60 and the points of the longitudinal profile deduced 25. For this purpose, a point of the longitudinal profile deduced 25 is defined as being associated with a point of the boxing frame 60 if these two points have the same angular position around the blocking axis A1, that is to say if these two points are located on the same straight line through the blocking axis A1.

Then, the calculation means determine the coordinates of four angular points P20, P21, P22, P23 boxing frame 60, that is to say here the coordinates of the four corners of the frame.

The calculation means deduce the coordinates of the four singular points P10, P11, P12, P13 associated. On the figure 11 these four singular points P10, P11, P12, P13 correspond to the points of intersection of the diagonals of the boxing frame 60 with the longitudinal profile deduced 25. These four singular points P10, P11, P12, P13 are located near the strongly curved zones of the longitudinal profile deduced 25.

Consequently, the calculation means can deduce from the coordinates of these four singular points the positions of four singular portions Z10, Z11, Z12, Z13 curved of the longitudinal profile deduced 25.

According to the alternative embodiment of the method according to the invention shown in the figure 12 , the determination of each singular portion of the deduced longitudinal profile is carried out by means of a third polygon-shaped profile 61 inscribed in the longitudinal profile deduced 25.

This polygon is chosen to have at least 10 sides of equal lengths whose ends belong to the longitudinal profile deduced 25.

Of course, alternatively, this polygon may be chosen to be limited to the longitudinal profile deduced 25, so that each of its sides is tangent to the longitudinal profile deduced 25.

In any event, the calculation means then establish a rule of correspondence between the points of this polygon 61 and the points of the longitudinal profile deduced 25. For this purpose, a point of the longitudinal profile deduced 25 is defined as being associated with a point of the polygon 61 if these two points have the same angular position around the blocking axis A1, that is to say if these two points are located on the same straight line through the blocking axis A1.

Then, during a calculation step, the calculation means determine the ALPHA angles at the junction of each of the sides of the polygon.

During a comparison step, the calculation means compare these angles with a predetermined threshold preferably between 150 and 175 degrees. They deduce the position of at least one junction point P14 from two sides of the polygon which is particularly angular. This junction point P14, which here belongs to the longitudinal profile deduced 25, is then located near a strongly curved portion of this profile.

Consequently, the calculation means can deduce from the coordinates of this junction point P14 the position of a curved singular portion Z14 of the derived longitudinal profile 25.

According to another embodiment of the invention shown in the figure 13 the determination of each singular portion of the derived longitudinal profile can be made by selecting singular portions Z15, Z16 of the derived longitudinal profile which are less than 5 millimeters from or containing a singular point P15, P16 whose distance from the blocking pin A1 is maximum or greater than a threshold.

More particularly here, the calculation means select from among the 90 points of the upper left dial of the longitudinal profile deduced 25 (the index points j ranging from 91 to 180) and from the 90 points of the upper right dial of this longitudinal profile deduced 25 (the index points j ranging from 181 to 270), the point of each dial farthest from the blocking axis A1 (that is, the point of each dial having a maximum radial coordinate). These two points are then located near strongly curved parts of the longitudinal profile deduced 25.

The calculation means then deduce the positions of the two singular portions Z15, Z16 of the longitudinal profile deduced 25, which are defined here as the portions of the profile of 10 millimeters in length, centered on the two points P15, P16.

Claims (18)

1. A method of preparing an ophthalmic lens (20) for mounting in a surround of an eyeglass frame (10), the method comprising:

   • an acquisition step of acquiring a first longitudinal profile (27) of said surround;

   • a blocking step of blocking the ophthalmic lens (20) in support means (31); and

   • an edging step of edging the ophthalmic lens (20) by edging means (32), during which the support means (31) and/or the edging means (32) are controlled in such a manner that the ophthalmic lens (20) is edged to have an engagement ridge (24) on its edge face (23) that is generally profiled with a desired section and that extends along a second longitudinal profile (25) that is derived from the first longitudinal profile (27);

   the method being characterized in that it includes a determination step of determining at least one singular portion (Z1-Z5) of the second longitudinal profile (25) as a portion that is situated at less than 5 millimeters from or that contains a singular point (P1-P5) at which the second longitudinal profile (25) presents a radius of curvature that is at a minimum or less than a threshold; and
   in that during the edging step, the support means (31) and/or the edging means (32) are controlled in such a manner that the section of the engagement ridge (24) is reduced in width and/or height over said singular portion (Z1-Z5).
2. A method according to the preceding claim, wherein said determination step excludes searching for said singular portion (Z1-Z5) of the second longitudinal profile (25) as a portion that presents a singular point (P1-P5) that is a geometrical singularity, i.e. an angular point or a cusp.
3. A method of preparing an ophthalmic lens (20) for mounting in a surround of an eyeglass frame (10), the method comprising:

   • an acquisition step of acquiring a first longitudinal profile (27) of said surround;

   • a blocking step of blocking the ophthalmic lens (20) in support means (31); and

   • an edging step of edging the ophthalmic lens (20) by edging means (32), during which the support means (31) and/or the edging means (32) are controlled in such a manner that the ophthalmic lens (20) is edged to have an engagement ridge (24) on its edge face (23) that is generally profiled with a desired section and that extends along a second longitudinal profile (25) that is derived from the first longitudinal profile (27);

   the method being characterized in that it includes a determination step of determining at least one singular portion (Z1-Z5) of the second longitudinal profile (25) as a portion that is situated at less than 5 millimeters from or that contains a singular point (P1-P5) situated at a distance from an axis of the ophthalmic lens (20) passing inside the second longitudinal profile (25) that is at a maximum or greater than a threshold; and
   in that during the edging step, the support means (31) and/or the edging means (32) are controlled in such a manner that the section of the engagement ridge (24) is reduced in width and/or height over said singular portion (Z1-Z5) .
4. A method of preparing an ophthalmic lens (20) for mounting in a surround of an eyeglass frame (10), the method comprising:

   • an acquisition step of acquiring a first longitudinal profile (27) of said surround;

   • a blocking step of blocking the ophthalmic lens (20) in support means (31); and

   • an edging step of edging the ophthalmic lens (20) by edging means (32), during which the support means (31) and/or the edging means (32) are controlled in such a manner that the ophthalmic lens (20) is edged to have an engagement ridge (24) on its edge face (23) that is generally profiled with a desired section and that extends along a second longitudinal profile (25) that is derived from the first longitudinal profile (27);

   the method being characterized in that, it takes into consideration a third profile (60; 61; 62) derived from the first or the second longitudinal profile (25, 27) in application of a given derivation rule, the third profile being distinct from said first and second longitudinal profiles (25, 27) and each point thereof being associated with a point of the second longitudinal profile (25) in application of a given correspondence rule, and it includes a determination step of determining at least one singular portion (Z1-Z5) of the second longitudinal profile (25) as a portion that is situated at less than 5 millimeters from or that contains a singular point (P1-P5) for which the associated point on said third longitudinal profile (60; 61; 62) is angular or presents a radius of curvature that is at a minimum or that is less than a threshold; and
   in that during the edging step, the support means (31) and/or the edging means (32) are controlled in such a manner that the section of the engagement ridge (24) is reduced in width and/or height over said singular portion (Z1-Z5).
5. A method according to any preceding claim, wherein the width and/or the height of the section of the engagement ridge (24) are, at at least one point of each singular portion, reduced by at least 0.05 millimeters.
6. A method according to the preceding claim, wherein the width and the height of the section of the engagement ridge (24) are, at each point in each singular portion, reduced by at most 0.3 millimeters.
7. A method of preparing an ophthalmic lens (20) for mounting in a surround of an eyeglass frame (10), the method comprising:

   • an acquisition step of acquiring a first longitudinal profile (27) of said surround;

   • a blocking step of blocking the ophthalmic lens (20) in support means (31); and

   • an edging step of edging the ophthalmic lens (20) by edging means (32), during which the support means (31) and/or the edging means (32) are controlled in such a manner that the ophthalmic lens (20) is edged to have an engagement ridge (24) on its edge face (23) that is generally profiled with a desired section and that extends along a second longitudinal profile (26) that is derived from the first longitudinal profile (27);

   the method being characterized in that it includes a determination step of determining at least one singular portion (Z1-Z5) of the second longitudinal profile (26) as a portion that is situated at less than 5 millimeters from or that contains a singular point (P1-P5) at which the second longitudinal profile (26) presents a radius of curvature that is at a minimum or less than a threshold; and
   in that during the edging step, the support means (31) and/or the edging means (32) are controlled in such a manner that the second longitudinal profile (26) is derivable from the first longitudinal profile (27) by a mathematical relationship that, over said singular portion (Z1-Z5), differs from the remainder of the second longitudinal profile (26) in such a manner that the mean radius of curvature of said singular portion (Z1-Z5) of the second longitudinal profile (26) is increased relative to the mean radius of curvature that said singular portion (Z1-Z5) would have presented if the given mathematical relationship had been the same over said singular portion (Z1-Z5) as for the remainder of the second longitudinal profile (26).
8. A method according to the preceding claim, wherein said determination step excludes searching for said singular portion (Z1-Z5) of the second longitudinal profile (26) as a portion that presents a singular point (P1-P5) that is a geometrical singularity, i.e. an angular point or a cusp.
9. A method of preparing an ophthalmic lens (20) for mounting in a surround of an eyeglass frame (10), the method comprising:

   • an acquisition step of acquiring a first longitudinal profile (27) of said surround;

   • a blocking step of blocking the ophthalmic lens (20) in support means (31); and

   • an edging step of edging the ophthalmic lens (20) by edging means (32), during which the support means (31) and/or the edging means (32) are controlled in such a manner that the ophthalmic lens (20) is edged to have an engagement ridge (24) on its edge face (23) that is generally profiled with a desired section and that extends along a second longitudinal profile (26) that is derived from the first longitudinal profile (27);

   the method being characterized in that it includes a determination step of determining at least one singular portion (Z1-Z5) of the second longitudinal profile (26) as a portion that is situated at less than 5 millimeters from or that contains a singular point (P1-P5) situated at a distance from an axis of the ophthalmic lens (20) passing inside the second longitudinal profile (26) that is at a maximum or greater than a threshold; and
   in that during the edging step, the support means (31) and/or the edging means (32) are controlled in such a manner that the second longitudinal profile (26) is derivable from the first longitudinal profile (27) by a mathematical relationship that, over said singular portion (Z1-Z5), differs from the remainder of the second longitudinal profile (26) in such a manner that the mean radius of curvature of said singular portion (Z1-Z5) of the second longitudinal profile (26) is increased relative to the mean radius of curvature that said singular portion (Z1-Z5) would have presented if the given mathematical relationship had been the same over said singular portion (Z1-Z5) as for the remainder of the second longitudinal profile (26).
10. A method of preparing an ophthalmic lens (20) for mounting in a surround of an eyeglass frame (10), the method comprising:

    · an acquisition step of acquiring a first longitudinal profile (27) of said surround;

    · a blocking step of blocking the ophthalmic lens (20) in support means (31); and

    · an edging step of edging the ophthalmic lens (20) by edging means (32), during which the support means (31) and/or the edging means (32) are controlled in such a manner that the ophthalmic lens (20) is edged to have an engagement ridge (24) on its edge face (23) that is generally profiled with a desired section and that extends along a second longitudinal profile (26) that is derived from the first longitudinal profile (27);

    the method being characterized in that, it takes into consideration a third profile (60; 61; 62) derived from the first or the second longitudinal profile (26, 27) in application of a given derivation rule, the third profile being distinct from said first and second longitudinal profiles (26, 27) and each point thereof being associated with a point of the second longitudinal profile (26) in application of a given correspondence rule, and it includes a determination step of determining at least one singular portion (Z1-Z5) of the second longitudinal profile (26) as a portion that is situated at less than 5 millimeters from or that contains a singular point (P1-P5) for which the associated point on said third longitudinal profile (60; 61; 62) is angular or presents a radius of curvature that is at a minimum or that is less than a threshold; and
    in that during the edging step, the support means (31) and/or the edging means (32) are controlled in such a manner that the second longitudinal profile (26) is derivable from the first longitudinal profile (27) by a mathematical relationship that, over said singular portion (Z1-25), differs from the remainder of the second longitudinal profile (26) in such a manner that the mean radius of curvature of said singular portion (Z1-Z5) of the second longitudinal profile (26) is increased relative to the mean radius of curvature that said singular portion (Z1-Z5) would have presented if the given mathematical relationship had been the same over said singular portion (Z1-Z5) as for the remainder of the second longitudinal profile (26).
11. A method according to any one of claims 7 to 10, wherein the singular portion (Z1-Z5) of the second longitudinal profile (26) presents, relative to the shape that said portion would have presented if the mathematical relationship had been the same over the singular portion (Z1-Z5) as for the remainder of said second longitudinal profile (26), a departure at at least one point that is greater than 0.05 millimeters.
12. A method according to the preceding claim, wherein the singular portion (Z1-Z5) of the second longitudinal profile (26) presents, relative to the shape that said portion would have presented if the mathematical relationship had been the same over the singular portion (Z1-Z5) as for the remainder of said second longitudinal profile (26), a departure that is less than 0.3 millimeters.
13. A method according to any one of claims 7 to 12, wherein the edging means (32) and/or the support means (31) are controlled in such a manner that at the end of the edging step, the engagement ridge (24) presents a section of uniform shape along the second longitudinal profile (26).
14. A method according to claim 4 or claim 10, wherein said third longitudinal profile is a polygon that is circumscribed (60) or inscribed (61) relative to the first or second longitudinal profile (25; 26, 27).
15. A method according to claim 4 or claim 10, wherein said third longitudinal profile is a homothety (62) of the first or the second longitudinal profile (25; 26, 27) .
16. A method according to any one of claims 1, 4, 7, and 10, wherein said threshold is less than 20 millimeters, and is preferably equal to 10 millimeters.
17. A method according to any preceding claim, wherein, for the second longitudinal profile (25; 26) including at least two singular portions (Z1-Z5) including a first singular portion (Z2) that is the closest to a temple portion of the second longitudinal profile (25; 26), the support means (31) and/or the edging means (32) are controlled in such a manner that the section of the engagement ridge (24) is reduced locally in width and/or in height at least in the first singular portion (Z2) and/or in such a manner that the second longitudinal profile (26) is derived by said different mathematical relationship at least in the first singular portion (Z2).
18. A method according to any preceding claim, wherein each singular portion (Z1-Z5) of the second longitudinal profile (25; 26) is centered on said singular point (P1-P5) and presents a length of less than 10 millimeters.

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