Method for shaping optical lens

Abstract

The invention relates to a method for shaping an optical lens using a machining device equipped with: a blocking device for blocking the optical lens; the machining tool is used for machining the surface (S0) of the optical lens; and a force sensor adapted to measure a force (F) related to a force applied to the optical lens by a machining tool, the method comprising: a step of blocking the optical lens in said blocking device; and-a step of shaping an optical lens using said machining tool, in which step a value of said force is measured and said machining tool and / or said blocking means are / is controlled as a function of the measured value, characterized in that during said shaping step, said machining tool is controlled such that said optical lens is shaped. Such that the speed (V) of the point of contact between the optical lens and the machining tool remains substantially equal to a first preset constant (Vt) and such that the measured value of the force remains substantially equal to a second preset constant.

Description

Technical Field

[0001] The present invention relates generally to the field of eyewear.

[0002] More specifically, the present invention relates to a method for forming an optical lens using a machining device, which is equipped with: a blocking device for blocking the optical lens; a machining tool for machining the surface of the optical lens; and a force sensor suitable for measuring the force related to the force applied to the optical lens by the machining tool. Background Art

[0003] The technical part of an optician's work, which involves fitting a pair of ophthalmic lenses into the frames chosen by the client, can be divided into four main operations:

[0004] - Obtain the shape of the outline of the rim of the eyeglass frame selected by the customer,

[0005] - centering each ophthalmic lens, consisting in determining the reference system of the lens using the centering marks provided on the lens, and then suitably positioning the previously acquired profile of the bezel in the reference system of the lens, so that the lens, once edged to this profile and then mounted in its frame, is correctly positioned relative to the corresponding eye of the customer and satisfies as best as possible the optical function for which it was designed,

[0006] - Blocking each lens, including attaching a blocking accessory to the lens, allowing easy removal of the lens from the centering station and then engaging the lens in the edging station without losing the reference frame, and then

[0007] -Edging each lens involves machining the lens to the previously centered profile.

[0008] Prior to these operations, the optician obtains the client's prescription and selects a pair of semi-finished lenses based on this prescription. These semi-finished lenses are then surface-processed. In other words, one of the optical surfaces of these semi-finished lenses is machined so that the optical power of each lens corresponds to the client's needs, that is, to their prescription.

[0009] Here, machining operations (surfacing and edging) are of more particular interest.

[0010] These operations can be performed by an optician or in a lens factory.

[0011] Many methods are known to perform these operations.

[0012] For example, the edging operation is usually performed by the edging machine in several passes depending on the material of the lens to be edged. In each pass, the processing depth is calculated based on the average power consumed by the motor in the previous pass in order to reduce the time required to edge the lens.

[0013] This method is based on the assumption that the machining operation is repeatable and that the performance of the tool is constant over time.

[0014] But in reality, this assumption is wrong and as a result, the edge grinding machine cannot be utilized to its fullest potential.

[0015] The same problem can arise during surface preparation operations. Summary of the Invention

[0016] In this context, the present invention provides a solution that enables machining equipment to be used to its maximum capabilities in order to optimize productivity.

[0017] More particularly, the present invention relates to a method for shaping an ophthalmic lens using a machining device as defined in the introduction, and comprising:

[0018] - a step of blocking an ophthalmic lens in said blocking device; and

[0019] - a step of shaping an ophthalmic lens using said machining tool, during which the value of said force is measured and said machining tool and / or said blocking device is controlled as a function of the measured value,

[0020] Wherein, during the shaping step, the machining tool is controlled so that the speed of the contact point between the ophthalmic lens and the machining tool remains substantially equal to a first preset constant and so that the measured value of the force remains substantially equal to a second preset constant.

[0021] Thus, at each moment, the tool is driven in order to machine the ophthalmic lens at its maximum capacity.

[0022] Other preferred features of the present invention are as follows:

[0023] - During the forming step, the machining tool is always driven towards a target position, the distance of which relative to the surface is determined so that the measured value of the force remains substantially equal to a second preset constant.

[0024] - said distance is non-zero when said surfaces have to be machined at the contact point, and is zero otherwise.

[0025] - During said shaping step, said distance remains below or equal to a preset threshold.

[0026] - the surface is an optical surface of an optical lens, and the shaping step comprises machining the optical surface.

[0027] - said surface being an edge face of an optical lens, said shaping step comprising machining said edge face.

[0028] - said forming step comprises a roughing sub-step.

[0029] The shaping step comprises a finishing sub-step preceded by a roughing sub-step, the finishing sub-step comprising a grooving operation or a beveling operation or a milling operation and / or a chamfering operation and / or a polishing operation.

[0030] The present invention also relates to a machining device for machining an optical lens, the machining device comprising:

[0031] - a blocking device, which is used to block the optical lens;

[0032] - a machining tool for machining optical lenses;

[0033] a force sensor adapted to measure a force related to a force applied by a machining tool to the optical lens; and

[0034] - a processing unit for controlling said machining tool relative to said blocking means, said processing unit being programmed to implement the forming method described above.

[0035] Preferably, the force sensor comprises at least one unidirectional strain gauge. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The following description, given by way of non-limiting examples with reference to the accompanying drawings, makes clear what the invention consists of and the manner in which it can be put into practice.

[0037] In the attached figure:

[0038] - Figure 1 is a schematic diagram of a machining device suitable for implementing the lens machining method according to the present invention, the machining device comprising a machining tool and a device for blocking the lens,

[0039] - Figure 2 Shown Figure 1 The projections of the initial and final profiles of the lens shown, and

[0040] - Figure 3 :

[0041] ¤ In the first diagram, the variation of the radius of the edge surface of the ophthalmic lens, the variation of the target surface towards which the machining tool is driven, and the variation of the limit surface which must not be exceeded are shown,

[0042] ¤The second graph shows the variation of the force applied by the machining tool to the ophthalmic lens, and

[0043] ¤The third graph shows the variation in the speed of the contact point between the machining tool and the ophthalmic lens. DETAILED DESCRIPTION

[0044] The invention is applicable to machining any surface of an optical lens.

[0045] As used herein, the term "optical lens" generally refers to an article worn in front of the wearer's eye for purposes of improving or enhancing visual acuity, for protection from the environment, or for fashion. The lenses contemplated herein are ophthalmic lenses suitable for improving visual acuity.

[0046] More precisely, the present invention is applicable to machining the optical surfaces of ophthalmic lenses (known as surfacing) and to machining the edge surfaces of ophthalmic lenses (known as edging).

[0047] In the following it will be explained in detail how edging is performed. It will not be explained in detail how surface treatment is performed, as the skilled person will readily understand how to apply the following teaching to machining an optical surface of a lens.

[0048] Figure 1 An apparatus 200 is shown for edging an ophthalmic lens 20. The apparatus 200 comprises:

[0049] - means 202 , 203 for clamping the ophthalmic lens 20 ;

[0050] at least one tool 210 , 222 , 223 for machining an ophthalmic lens 20 ;

[0051] a force sensor 234 suitable for measuring the forces associated with the forces applied by the machining tools 210 , 222 , 223 to the ophthalmic lens 20 ; and

[0052] A unit 251 for controlling the movement of each machining tool 210 , 222 , 223 relative to the clamping device 202 , 203 .

[0053] The machining device 200 can take the form of any machine for cutting or removing material, which is capable of modifying the profile of the ophthalmic lens 20 so as to adapt it to the profile of the corresponding rim of the eyeglass frame chosen by the individual (hereinafter referred to as the "wearer" because he will be the wearer of this pair of frames in the future).

[0054] exist Figure 1 In the example schematically shown, the machining device 200 consists of an automatic grinding machine 200 (widely known as a digital grinder), as is known per se. In this case, this grinder comprises:

[0055] a shaker 201 mounted so as to pivot freely about a reference axis A5, practically a horizontal axis, on a carriage (not shown) and supporting an ophthalmic lens 20 to be machined;

[0056] at least one grinding wheel 210 mounted so as to pivot about a grinding wheel axis A6 parallel to the reference axis A5 and suitably driven in rotation by a motor (not shown);

[0057] A finishing module 220 , mounted to rotate about the grinding wheel axis A6 and equipped with tools 222 , 223 for finishing the ophthalmic lens 20 .

[0058] The pivoting mobility of the rocker 201 about the reference axis A5 is called retraction mobility ESC. It allows the ophthalmic lens 20 to be brought closer to the grinding wheel 210 until the former comes into contact with the latter.

[0059] This shaker 201 is equipped with two shafts 202 , 203 for clamping the ophthalmic lens 20 to be machined and for driving it in rotation, these shafts 202 , 203 corresponding to the aforementioned “clamping means”.

[0060] The two shafts 202 , 203 are aligned with each other along a clamping axis A7 parallel to the axis A5 . These shafts 202 , 203 each have a free end facing each other, equipped with a head for clamping the ophthalmic lens 20 .

[0061] The first of the two shafts 202 is fixed against translation along the clamping axis A7 . In contrast, the second of the two shafts 203 is movable in translation along the blocking axis A7 in order to allow axial compression clamping of the ophthalmic lens 20 between the two clamping heads.

[0062] exist Figure 1 The grinding machine 200 schematically shown in FIG. 1 comprises only one cylindrical grinding wheel 210 .

[0063] In practice, the grinding machine comprises a set of grinding wheels coaxially mounted on a grinding wheel axis A6 , each grinding wheel being dedicated to a specific shaping operation of the ophthalmic lens 20 to be machined.

[0064] For roughing the lens, a roughing cylindrical grinding wheel is used. This roughing cylindrical grinding wheel is cylindrical, has a diameter greater than 10 cm, and comprises diamonds with a grit size between 100 and 500 μm, here equal to 300 μm.

[0065] To bevele a lens, which involves machining ribs along the edge face of the lens, a profiled grinding wheel (or "beveling grinding wheel") may be used that contains beveling grooves of dihedral cross-section.

[0066] For polishing the lenses, cylindrical grinding wheels and profile grinding wheels with the same geometry as the two grinding wheels mentioned above are used. These polishing grinding wheels have a particularly fine abrasive grit size.

[0067] The set of grinding wheels is carried by a slide (not shown) so as to move in translation along the grinding wheel axis A6. The translational movement of the slide carrying the grinding wheels is called "transmission" TRA.

[0068] Here, the grinding machine 200 also includes a connecting rod 230, one end of which is fixed to the shaker 201 and the other end of which is hinged relative to a nut 231 so as to pivot about an axis A8 parallel to the reference axis A5. This connecting rod 230 has a variable length (for this purpose, it includes Figure 1 Sliding system not shown).

[0069] The nut 231 is itself mounted for translational movement along a reset axis A9 perpendicular to the reference axis A5 (called reset mobility RES). The nut 231 is a tapped nut in threaded engagement with a threaded shank 232 aligned with the reset axis A9, driven in rotation by a motor 233.

[0070] When suitably clamped between the two shafts 202 , 203 , the ophthalmic lens 20 to be machined is brought into contact with one of the grinding wheels 210 , with the aim of performing an effective material removal.

[0071] The connecting rod 230 is equipped with a force sensor 234, here consisting of a unidirectional strain gauge mounted on a gauge support.

[0072] The gauge support is attached to the link 230 (and therefore to the shaker 201) and is designed to elastically deform when the lens comes into contact with the grinding wheel 210. It is this deformation that is measured and reflects the force applied by the grinding wheel 210 to the ophthalmic lens 20.

[0073] The measurement is reset when the lens 20 is not in contact with the grinding wheel 210. Therefore, when the link 230 is driven downward, once the lens comes into contact with the grinding wheel, this contact causes the support to deform, which is converted into a force (force F) by the strain gauge.

[0074] Here, the force sensor 234 is positioned to measure a substantially vertical machining force corresponding to the radial component of the force exerted by the ophthalmic lens 20 on the grinding wheel 210 or finishing tool 222 , 223 used.

[0075] In order to machine the ophthalmic lens 20 following a given contour, it is sufficient, on the one hand, to appropriately move the nut 231 along the reset axis A9 under the control of the motor 233 to control the reset movement RES and, on the other hand, to pivot the support shafts 202, 203 together about the clamping axis A7. The reset movement (and therefore the retraction movement of the shaker 201) and the rotational movement of the shafts 202, 203 are controlled and coordinated by the control unit 251, which is appropriately programmed for this purpose, so that all points of the contour of the ophthalmic lens 20 have the correct diameter.

[0076] According to the invention, the return movement is controlled in particular as a function of the machining force F measured by the strain gauge 234 .

[0077] The optional finishing module 220 has a pivoting mobility around the grinding wheel axis A6 , this mobility being denoted PIV. This mobility allows it to be brought closer to the ophthalmic lens 20 or moved further away from it.

[0078] The finishing tools 222 , 223 equipped in the finishing module 220 here particularly include a grooved disk 222 suitable for generating grooves along the edge surface of the ophthalmic lens 20 , and a milling cutter 223 suitable for chamfering the sharp edge of the ophthalmic lens 20 .

[0079] These finishing tools 222, 223 are mounted so as to rotate about a given axis and are driven in rotation by a motor housed in a base 224, which is itself mounted so as to pivot about an axis A10 orthogonal to the grinding wheel axis A6 on the finishing module 220. This pivoting mobility of the base 224 about the axis A10, known as finishing mobility FIN, allows an optimal orientation of the tools 222, 223 relative to the lens.

[0080] The control unit 251 is an electronic and / or computing system. The control unit includes a processing unit (such as a CPU) or a controller, or any combination thereof. The control unit also includes a memory and various input and output interfaces.

[0081] The processing unit is suitable for receiving information due to its input interface, such as the shape of the initial profile 21 of the lens ( Figure 2 ), the shape of the final profile 22 of the lens, the lens material, etc.

[0082] The control unit 251 stores, thanks to its memory, a computer application consisting of a computer program comprising instructions, the execution of which by the processor enables the processing unit to implement the method described hereinafter.

[0083] The control unit 251 is adapted, due to its output interface, to control:

[0084] - a motor for driving the translational movement of the second axis 203;

[0085] - a motor for driving the two shafts 202 , 203 in rotation;

[0086] - a motor for driving the slide carrying the grinding wheels in translation with its transmission mobility TRA;

[0087] - a motor 233 for driving the nut 231 in translation with its return mobility RES;

[0088] a motor for driving the finishing module 220 in rotation with its pivoting mobility PIV; and

[0089] A motor for driving the base 224 of the finishing tools 222 , 223 in rotation with its finishing mobility FIN.

[0090] The grinding machine 200 also includes a human machine interface 252 ("HMI"), which here includes a display screen 253, a keyboard 254, and a mouse 255, which are adapted to communicate with the control unit 251. The HMI 252 allows a user to input values, such as the material of the lens, on the display screen 253 so that the tools of the grinding machine 200 can be appropriately controlled.

[0091] exist Figure 1 In the embodiment of the present invention, the control unit 251 is implemented on a desktop computer connected to the grinding machine 200. Of course, as a variant, the software part of the grinding machine can be implemented directly on the electronic circuit of the grinding machine. The software part of the grinding machine can also be implemented on a remote computer that communicates with the grinding machine via a private or public network (for example using IP (Internet) communication protocol).

[0092] Figure 2 The projection of an initial profile 21 of a lens 20 to be machined into a principal plane (eg the plane of the initial profile 21 ) is shown.

[0093] The figure also shows a projection of the final contour 22 of the lens 20 after machining. This final contour 22 corresponds, for example, to the bottom of a bezel of the rim of an individually chosen spectacle frame, this bezel being suitable for receiving the machined lens.

[0094] Figure 2 Also shown is a "box system" of the final outline 22. As is known, the box system comprises a box 23, which is a rectangle drawn around the projection of the final outline 22, the box having two horizontal sides.

[0095] The center of the frame 23 is called the frame center. The lens is here to be blocked between the two axes 202, 203 so that the blocking axis A7 passes through the frame center.

[0096] Before machining the ophthalmic lens 20 , the control unit 251 acquires the geometry of the final profile 22 .

[0097] Here, the final contour 22 takes a plurality of points P that characterize the shape of the final contour 22. i A set of triplets corresponding to the cylindrical coordinates (r i ,θ i ,z i ) in the form of (wherein i is an integer from 1 to N, N is equal to 360, for example).

[0098] These coordinates may be obtained from a database accessible to the optician, or by using an imaging device comprising image capture means and image processing means, adapted to process photographs of sample lenses delivered with the spectacle frames, or by feeling the bottom of the bezel of the frame chosen by the individual.

[0099] The lens is then subjected to a centering operation followed by a blocking operation.

[0100] These two operations are well known to those skilled in the art and do not form part of the subject matter of the present invention, so they are only briefly described.

[0101] During the centering operation, the position of the mark or marks etched on the lens is determined and the desired position of the final profile 22 is derived therefrom (so that after the lens has been shaped according to this profile and fitted in the chosen frame, its optical center is correctly positioned relative to the corresponding eye of the spectacle wearer).

[0102] During the blocking operation, the lens is clamped between the shafts 202, 203 of the edger 200 by means of a clamping attachment which is adhesively bonded to the lens in a central position on the frame center so that the frame center is centered on the clamping axis A7.

[0103] Then, forming is performed in two operations, a roughing operation and a finishing operation.

[0104] For roughing the lens, a roughing cylindrical grinding wheel 210 is used to roughly reduce the radius of the lens 20 to the shape of the final profile 22. More precisely, the shafts 202, 203 and the rocker 201 are here controlled relative to each other so that for each angular position θ of the lens about the clamping axis A7 i Reduce the radius of the lens to a radius r equal to the final profile 20 i length.

[0105] To finish the lens, a "bevel" or groove or any suitable form is formed on the edge face of the lens using a profiled grinding wheel and / or any other finishing tool, and the resulting edge is polished.

[0106] The present invention is applicable to both steps. However, in the following, only how to perform the roughing step will be described (the other step is performed in the same manner).

[0107] During this step, the grinding wheel 210 follows a path (for example in a spiral) about the clamping axis A7 relative to the lens 20. The lens 20 is thus machined in several passes about the clamping axis A7.

[0108] According to the present invention, a roughing step is performed in order to reduce the time required to machine the edge of the lens 20 .

[0109] For this reason, Figure 3 As shown, during the roughing step:

[0110] - The value F of the force F is measured by the sensor 234 meas ,

[0111] - The rotation of the shafts 202, 203 is controlled so that the machining speed V remains substantially equal to a first preset constant V t ,and

[0112] - The torque applied by the motor 233 is continuously regulated so that the measured value F of the force F meas Maintain substantially equal to the second preset constant F t .

[0113] Here, “machining speed V” is defined as the speed of the contact point Pc in a reference frame attached to the ophthalmic lens 20. In other words, the machining speed is the speed of the contact point between the ophthalmic lens 20 and the machining tool 210.

[0114] The machining speed therefore depends on the angular speed of the shafts 202, 203 and on the distance between the axis A7 and the contact point Pc.

[0115] The first preset constant V t The value of is determined on the basis of various tests in order to have a satisfactory compromise between machining time and the appearance of the finished lens. In practice, the first preset constant may have two values, namely 70 mm / s or 14 mm / s, depending on the material to be machined. The second preset constant F t The value of is determined based on various tests to provide a satisfactory compromise between machining time and the appearance of the finished lens. In practice, the second preset constant may have a value between 1.5 kg and 2.2 kg. This value may depend on the material to be machined.

[0116] For example, the more "soft" material a lens has, the faster the lens will tend to be machined, given the same applied force.

[0117] As long as the distance between the axis A7 and the contact point Pc is known, the machining speed can be kept constant.

[0118] Keeping the force F constant is more difficult, since its value is not known in advance and needs to be measured (and always corrected). Figure 3 The force F is shown relative to the second preset constant F t There are minor changes in the reason. These changes are kept small, that is, less than the preset constant F t 5% of.

[0119] As long as there is material left to be machined and the distance D remains below the threshold value Δ, the force F will remain more constant. If Δ is reached, the force F will tend to decrease.

[0120] To drive the motor 233 so as to keep the force F constant, for example a feedback loop and a PID controller may be used.

[0121] However, in preferred embodiments, the method is performed in other ways.

[0122] Figure 3 In the upper graph a first curve S0 is shown which shows the radius r of the edge face of the lens as a function of the angle θ at any moment of machining the edge of the lens. i Example of a variation: Above this curve is shown the grinding wheel 210 at this moment in time.

[0123] Also shown in this upper graph is a second curve S showing the position towards which the wheel is driven. t This diagram shows that at each moment (that is, for each angular position θ of the shafts 202, 203 i), the motor 233 is controlled to attempt to pull the grinding wheel 210 toward the axis A7 by a non-zero distance D relative to the edge surface of the lens.

[0124] The greater the distance D, the more powerful the motor 233 (and the greater the force F).

[0125] For safety reasons, at any moment, the distance D is kept below or equal to a preset threshold value Δ (as shown by the third curve S on the upper graph). l This threshold value Δ depends, for example, on the material of the lens. Due to this safety, the machining of the edge surface of the lens remains of good quality.

[0126] This distance D is zero (a zero value) when the edge surface of the lens does not need to be machined at the contact point Pc, and is non-zero (a non-zero value) otherwise.

[0127] like Figure 3 As shown in the last graph of FIG, when the distance D is not zero, the distance is calculated so that the measured value of the force F remains substantially equal to the second preset constant F t .

[0128] For this purpose, the measured value F of the force F meas With the second preset constant F t The distance D is calculated by multiplying the error between them by the gain K. The larger the error, the larger the distance D (the distance D is limited to a preset threshold Δ).

[0129] In a variant, the distance D (depending on which the motor 203 is controlled) can be read in a database.

[0130] In this variant, the database includes, for example, three data fields (i.e., three columns). The first field is associated with the measured value of force F; the second field is associated with the distance D to be applied when the lens is made of plastic material; and the third field is associated with the distance D to be applied when the lens is made of glass material. Each record (i.e., each row) of the database corresponds to a measurement value interval. The values ​​in the second and third fields of the database are predetermined, for example, by the manufacturer of the grinding machine 200.

[0131] In other words, in this variant, the distance D is read in the record (ie in a row) that matches the measured value of the force F, in the second field or in the third field (depending on the lens material).

[0132] It will be noted that in this variant, the values ​​registered in the database are determined according to the grinding machine used and the tool used.

[0133] This distance D is then converted into a command sent to the motor 233 .

[0134] The invention is in no way limited to the described and shown embodiments.

[0135] For example, as explained above, finishing operations (beveling, polishing, etc.) can be performed in the same manner with the other tools of the grinding machine, that is, by maintaining the machining speed equal to a first preset constant and keeping the measured value of the force F substantially equal to a second preset constant.

Claims

1. A method for shaping an optical lens (20) using a machining device (200), the machining device being equipped with: a blocking device (202, 203) for blocking the optical lens (20); a machining tool (210) for machining a surface (S0) of the optical lens (20); and a force sensor (234) adapted to measure a force (F) associated with a force applied by the machining tool (210) to the optical lens (20), the method comprising: - a step of blocking the optical lens (20) in the blocking device (202, 203); as well as - a step of shaping the optical lens (20) using the machining tool (210), in which step the value of the force (F) is measured and the machining tool (210) and / or the blocking means (202, 203) are controlled according to the measured value, During the forming step, the blocking means (202, 203) are controlled so that the measured value of the force (F) remains substantially equal to a second preset constant (F t ), The invention is characterized in that, during the forming step, the blocking device (202, 203) is also controlled so that the speed (V) of the contact point (Pc) between the optical lens (20) and the machining tool (210) is kept substantially equal to a first preset constant (V t ),and During the forming step, the machining tool (210) is always driven towards a target position, the distance (D) of the target position relative to the surface (S0) being determined so that the measured value of the force (F) remains substantially equal to the second predetermined constant (F t ).

2. The method for forming according to claim 1, wherein Said distance (D) is non-zero when said surface (S0) has to be machined at said contact point (Pc), and is zero otherwise.

3. The method for forming according to claim 1 or 2, wherein: During the shaping step, the distance (D) remains below or equal to a preset threshold (Δ).

4. The method for forming according to any one of claims 1 to 3, wherein The surface (S0) belongs to the optical surface of the optical lens (20), and the forming step includes machining the optical surface.

5. The method for forming according to any one of claims 1 to 3, wherein The surface (S0) belongs to the edge surface of the optical lens (20), and the forming step includes machining the edge surface.

6. The method for forming according to claim 5, wherein The forming step includes a rough machining sub-step.

7. The method for forming according to claim 5 or 6, wherein The shaping step comprises a finishing sub-step, which is preceded by a roughing sub-step, and which comprises a grooving operation or a beveling operation or a milling operation and / or a chamfering operation and / or a polishing operation.

8. A machining device (200) for machining an optical lens (20), the machining device comprising: - a blocking device (202, 203), the blocking device being used to block the optical lens (20); - a machining tool (210), which is used to machine the optical lens (20); a force sensor (234) adapted to measure a force (F) associated with a force applied by the machining tool (210) to the optical lens (20); and a processing unit for controlling the machining tool (210) relative to the blocking means (202, 203), Characterized in that the processing unit is programmed to implement the forming method according to any one of claims 1 to 7.

9. The machining apparatus (200) according to claim 8, wherein: The force sensor (234) includes at least one unidirectional strain gauge.

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