Method and apparatus for centering ophthalmic lenses

Abstract

The present invention relates to a method for centering an ophthalmic lens (10) comprising several distinct patterns (12) located around a pattern-free region (13), the method being performed by a processing unit and comprising the steps of: acquiring at least one image of the ophthalmic lens; processing the image to detect the patterns; and inferring the position of a centering point (AC) therefrom. According to the present invention, after the processing step, only a portion of the patterns are selected as a function of their positions relative to the pattern-free region, and during the inference step, the centering point position is inferred from only the selected pattern positions.

Description

[Technical Field]

[0001] This invention generally relates to the field of eyeglasses.

[0002] More specifically, regarding a method for centering a particular ophthalmic lens, it is assumed that this lens includes several distinct patterns located around a pattern-free region.

[0003] More specifically, it is applied to myopia prevention lenses, and the pattern is formed by microlenses. [Background technology]

[0004] The technical part of an optician's job involves fitting a pair of ophthalmic lenses into eyeglass frames chosen by the customer, and can be broadly divided into the following four operations: - Obtaining the outer shape of the rim of the eyeglass frame selected by the customer. - Centering of each ophthalmic lens (determining the reference frame of the lens, then appropriately positioning the pre-acquired rim outline onto the reference frame of the lens, etching onto this outline, and then mounting it to the eyeglass frame, so that the lens is correctly positioned for the customer's corresponding eye and performs its designed optical function to the greatest extent possible), - Blocks for each lens (these are block accessories attached to the lenses, allowing them to be easily removed from the centering station and engaged with the etching station without losing the reference frame), - Edging of each lens (this involves machining the lens to match the pre-centered outer shape).

[0005] Here, the centering operation is of particular interest.

[0006] This procedure is usually performed by an optician using a centering device.

[0007] If the ophthalmic lens is a standard product, this procedure involves determining the position of the lens's optical center. This optical center must, in fact, be positioned in front of the patient's pupil.

[0008] However, if the lens is a myopia prevention lens (or more generally, if the lens exhibits a pattern on one of its optical surfaces, and that pattern is located around areas without a pattern), this operation is entirely different.

[0009] In fact, even if the optical center of this type of lens is offset from the center of this region, it is recommended to mount it so that the center of the free pattern region is positioned in front of the patient's pupil. Otherwise, the patient will naturally move their head or eyeballs so that their line of sight passes through the center of the region, thus maintaining this unnatural head position.

[0010] To determine the position of the center of this free pattern region, according to the international publication pamphlet No. 2022189352, it is known that an image of the lens to be centered is acquired using a camera, this image is processed to determine the center of each pattern, the position of the circle passing through these pattern centers is identified, and the position of the region center (which coincides with the center of the circle) is estimated from there.

[0011] The main drawback of this solution is that it only works if the pattern is distributed along a circle (or more generally along one or more given geometric shapes).

[0012] However, in practice, this process is difficult to perform because the geometric shape is unknown at the start of the centering operation. Furthermore, since some lenses have patterns randomly distributed across their optical surfaces, this process cannot be performed on all lenses. [Overview of the project] [Means for solving the problem]

[0013] In this regard, the present invention provides a method for acting on all lenses having a pattern located around a free pattern region.

[0014] This centering method is performed by the processing unit. - A step of acquiring at least one image of the ophthalmic lens, - A step of processing the image to detect the pattern, - A step of selecting only a portion of the aforementioned pattern as a function of their positions relative to the pattern-free region, - A step of inferring the position of the center alignment point (region center) from only the selected pattern positions, Includes.

[0015] In other words, it is possible to select the closest pattern from several patterns, such as a pattern-free area, and then infer the position of the center of this area. As a result, the lens can be centered relative to the center of this free pattern area, so that when it is attached to the eyeglass frame and worn by the wearer, the center of the lens's free pattern area is positioned in front of the wearer's pupil.

[0016] According to the present invention, this method is applicable to all lenses having patterns located in a free pattern region, regardless of the relative position of the patterns.

[0017] Other preferred features of the present invention are as follows: - The geometric center of each selected pattern is located, and the center alignment point is estimated from the location of the geometric center of the pattern. - The center point of the ophthalmic lens is determined, and the patterns are selected according to their positions relative to the said center point. - The patterns are sorted according to the angular position of the pattern with respect to the center point, each sorted pattern has a previous pattern and a next pattern, and each pattern where the distance to the center point is greater than the distance between the center point and each of the previous pattern and the next pattern is not selected (preferably, only when the angle between the line passing through the previous pattern and the current sorted pattern and the line passing through the next pattern and the current sorted pattern is less than a predefined threshold). - During the estimation step, a polygon passing through or touching the selected pattern is determined, and the centering point position is estimated from the shape of the polygon. - The centering point is the centroid of the polygon. - The axis of the lens is also estimated from the shape of the polygon. - The patterns are engraved on an ophthalmic lens, preferably forming microlenses. - The method includes · a step of locating the optical center of the ophthalmic lens, · a step of obtaining the shape of the outer profile where the ophthalmic lens is cut, · a step of positioning the outer profile with respect to the centering point. and includes. - The method includes a step of determining a parameter related to the prism defect due to the position of the optical center with respect to the centering point. - The method includes a step of determining a parameter related to the distribution of the patterns inside the outer profile. - The method includes a step of determining a parameter related to the surface inside the outer profile occupied by the patterns. - The optical center, the outer profile, the patterns, and the centering point are displayed on the screen together with the values of the parameters. - While the processing unit is updating the position of the outer profile and the values of the parameters, use a human - machine interface to manually move the centering point. - In one modified example, the method includes an automated step of moving the center alignment point according to the parameters.

[0018] The present invention also, - Chassis and, - Components that are mounted on the chassis and suitable for receiving ophthalmic lenses, - A centering means, mounted on the chassis and including an image sensor for acquiring an image of the ophthalmic lens when the ophthalmic lens is accepted into the component, - A processing unit programmed to perform the method defined above, This relates to a centering device, including one.

[0019] Detailed explanation of the example The following description, with reference to the accompanying drawings provided as non-limiting examples, clarifies the essence of the present invention and how it can be put into practice. [Brief explanation of the drawing]

[0020] [Figure 1] This is a schematic perspective view of one embodiment of a centering and blocking device suitable for performing the process according to the present invention. [Figure 2] Figure 1 is a schematic side view of the centering mechanism of the centering and blocking device shown in Figure 1. [Figure 3] Figure 1 is a front view of a first example of a lens that is centered by the centering and blocking device shown. [Figure 4] This is a zoomed-in view of a portion of the lens shown in Figure 3. [Figure 5] Figure 3 is a front view of the lens, showing geometric shapes. [Figure 6] Figure 1 is a front view of a second example of a lens centered by the centering and blocking device shown, with another geometric figure shown above it. [Figure 7] Figure 3 is a front view of the lens, with the contour to which the lens must be edged shown above it. [Modes for carrying out the invention]

[0021] The present invention relates to an ophthalmic lens intended to be attached to the rim of an eyeglass frame in order to form eyeglasses.

[0022] Figure 1 shows one embodiment of an optical machine (hereinafter referred to as "centering and blocking device 100") for preparing the ophthalmic lens from the viewpoint of its edging.

[0023] Therefore, this device is used for centering and blocking ophthalmic lenses.

[0024] When the shape of the contour from which the lens needs to be cut is known, the purpose of the "centering operation" is to identify the reference frame for the ophthalmic lens and determine the position within this reference frame that the contour should occupy. The positioning of the contour is performed so that when the lens is cut along this contour and mounted in the spectacle frame, it is properly centered and positioned for the corresponding eye of the spectacle wearer.

[0025] The purpose of the "block operation" is to place the block accessory 150 on the ophthalmic lens 10, thereby making it easier to grasp the ophthalmic lens 10 for transport from the centering and blocking device 100 to the cutting unit (hereinafter referred to as the "edging machine"), and on the other hand, providing a stable reference mark to indicate the position of the reference frame of the lens after transport.

[0026] The centering block device 100 shown in Figure 1 is automatic in the sense that the operation of locating the position of the lens reference frame and positioning the contour inside is performed automatically without the assistance of an optician. However, in a modified version, the centering block device used may be a manual one.

[0027] In the embodiments shown in Figures 1 and 2, the centering and blocking device 100 is - Chassis 101 and, - A workstation 102 fixed in the horizontal plane to the chassis 101 and equipped with a holder 103 for holding block accessories 150, - A centering means 110 (see Figure 2) for centering the lens, the means being fixed to the chassis 101 and comprising at least one image sensor 111 for acquiring an image of the lens, - A blocking means 120 for positioning a block accessory 150 on an ophthalmic lens 10, wherein the means is mounted so as to be movable on a chassis 101, - A processing unit 130 (see Figure 2) used to control the centering means and blocking means, It is equipped with.

[0028] The workstation 102 includes a transparent, planar support plate 104 on which the ophthalmic lens 10 is positioned. Here, this support plate forms a holder for the lens, but in the modified example shown in the figure, this holder 106 may be a separate component from the plate (for example, a rod with a widened head for supporting the lens).

[0029] The blocking means 120 includes an operating arm 121 that includes a carrier capable of gripping a block accessory 150 and placing it on the front surface of an ophthalmic lens 10 positioned on a transparent, flat support plate 104.

[0030] The operating arm 121 is self-propelled and has four degrees of freedom. Thus, it has the mobility to translate along a vertical axis V1 to move up or down in the direction of the planar support plate 104, and the mobility to rotate about this axis V1 to move away from or toward the planar support plate 104. Its carrier (invisible) has the mobility to translate radially with respect to this axis V1, and the mobility to rotate about an axis parallel to this axis V1 (to adjust the orientation of the block accessory relative to the arm).

[0031] The means for centering the ophthalmic lens 10 is designed, insofar as it relates, to determine the position of the reference frame of the ophthalmic lens 10 by the process disclosed below.

[0032] As shown in Figure 2, the centering means 110 includes on one side of the planar support plate 104 means for illuminating a lens placed on the planar support plate 104, and on the other side, an image sensor means for acquiring the emitted light.

[0033] The illumination means comprises a light source 112 that emits a light beam and a mirror 114 tilted at 45° that reflects this light beam toward the lens.

[0034] The image sensor means comprises an image sensor (in this case, a camera 111) and a mirror 113 tilted at 45° that reflects the light beam toward the camera 111.

[0035] The optical axis V2 of the centering means 110 is defined as the axis of the light beam passing through the ophthalmic lens 10.

[0036] In a modified configuration, the centering means may include a mirror on one side of the lens (downstream of the lens, considering the direction of light propagation), in which case the illumination means and image sensor means would be arranged together on the other side of the lens (upstream).

[0037] The processing unit 130 is programmed to center and block the ophthalmic lens 10.

[0038] For this purpose, the processing unit 130 comprises a central processing unit (CPU), memory, and input / output components.

[0039] The memory is used by the processing unit to store information used in the processes described below. In particular, the memory stores computer applications, which consist of computer programs containing instructions, and their execution enables the processing unit to perform the methods described below.

[0040] This processing unit 130 is connected to the centering means 110 and the blocking means 120.

[0041] It is also connected to a human-machine interface (in this case, a touchscreen 131) to allow opticians to input data useful for centering the lenses and controlling this centering operation.

[0042] Figure 3 shows the edged ophthalmic lens 10. This lens has two optical surfaces (i.e., a convex front surface and a concave back surface) and an edge 11, and its shape is initially circular.

[0043] This edge is intended to be machined to conform to the shape of the spectacle frame rim into which the lens must be mounted, once the lens has been edged.

[0044] The front and back shapes of this ophthalmic lens 10 are designed so that the lens has optical properties that enable it to correct the customer's vision defects.

[0045] Here, the ophthalmic lens 10 preferably includes at least a first optical correction to provide the wearer with correct visual acuity at a determined distance.

[0046] The first optical correction, in this example, is a spherical power to provide the wearer with correct distance vision (for seeing objects located more than 6 meters away). In variations, this first optical correction may include cylindrical and / or prism powers.

[0047] In this example, the optical center OC of the lens is defined as the point on the lens where light rays are not deflected as they pass through it (see Figure 7). This optical center can be determined, for example, by using a well-known Hartman apparatus.

[0048] The ophthalmic lens 10 also exhibits several patterns 12 on at least one of its optical surfaces. These patterns 12 are designed so that the wearer is not aware of their presence. They are located around the entire periphery of the free pattern area 13 that the user is intended to see through.

[0049] In this example, each pattern 12 is formed by microlenses in relief relative to the rest of the optical surface of the lens, which locally corrects the refractive power of the lens.

[0050] In other words, here the lens exhibits a second optical correction to alter the natural progression of myopia. Pattern 12 is specifically designed to limit or halt this progression. Ophthalmic lenses with such patterns are described in international publication pamphlet 2019166654.

[0051] As shown in Figure 3, each of these patterns 12 is circular, and there are a great many of them. All patterns 12 have the same shape. Their diameters here are less than 1 mm.

[0052] In the illustrated embodiment, the pattern 12 is distributed along two coaxial circles. However, the pattern may be distributed on the optical surface of the lens in other ways. For example, in the modified form shown in Figure 6, the pattern 12 is randomly distributed on the surface of the lens, around the entire periphery of the free pattern area 13.

[0053] In this step, the region center AC can be defined as the geometric center of this region 13. As shown in Figure 5, this region center AC can be offset from the geometric center GC and / or the optical center OC of the lens.

[0054] The purpose is to position the region center AC in front of the wearer's pupil in order to center the lens.

[0055] Here, we can see that if the region center AC is offset from the optical center OC, this offset can generate a prism effect. In fact, in this case, the wearer will see through the zone of the deflected lens, which can be uncomfortable for the wearer.

[0056] Here, the ophthalmic lens 10 is intended to be automatically centered and blocked.

[0057] For this purpose, during the preceding steps, the ophthalmic lens 10 is positioned on the transparent plate 104, either manually or automatically, so that the convex front surface is away from this plate.

[0058] Next, during the first step, the processing unit 130 is programmed to acquire an image of the lens on the transparent plate using the camera 111. Such an image is shown in Figure 3.

[0059] Thanks to the centering mechanism 110 of the device, the edges 11 and pattern 12 of the ophthalmic lens 10 are visible in this image.

[0060] During the second step, this image is processed to locate the contours of each pattern 12.

[0061] Based on these contours, the processing unit 130 determines the position of the feature points of each pattern.

[0062] In a preferred embodiment, this feature point is the geometric center of pattern 12. Since each pattern 12 is circular, the feature point is the center of the circle.

[0063] During the third step, the processing unit 130 searches for patterns 12 adjacent to the free pattern area 13 and selects them.

[0064] These selections of pattern 12 can be carried out in various ways.

[0065] Here, during the first substep, patterns 12 are ordered as a function of the orientation of their centers around a central point that is (presumably) located in region 13.

[0066] Here, the center point considered is the geometric center GC of lens 10. In variations, it may be another point, for example, the optical center OC of the lens or the centroid of the pattern center.

[0067] As shown in Figure 4, the orientation of the center of pattern 12 is defined here by an angle α that falls between 0 and 360 degrees and is equal to 0 if the pattern center is located on the determined axis A0.

[0068] For simplicity, Figure 4 shows only the centers A1, A2, and A3 of the three patterns 121, 122, and 123, and their orientations α1, α2, and α3.

[0069] In the following, let N be the number of patterns, and any pattern 12 i Center A i , that direction is α i This is written as (where i ranges from 1 to N).

[0070] Next, during the second substep, the sorted patterns are processed in groups of three. The objective is to determine whether the central pattern is closer to the free pattern region 13 than the first and third patterns.

[0071] In other words, in a loop where i goes from 1 to N, there are three patterns 12 i , 12 i+1 , 12 i+2 Process pattern 12 i+1Determine whether it should be selected. To exclude this pattern from the selection, two cumulative conditions need to be satisfied.

[0072] The first one is that the angle between the line segment [12 i+1 12 i and the line segment [12 i+1 12 i+2 is less than 60°.

[0073] The second one is that the distance between the geometric center CG and pattern 12 i+1 is greater than the distance between the geometric center CG and pattern 12 i and greater than the distance between the geometric center CG and pattern 12 i+2 .

[0074] If these two conditions are not satisfied, pattern 12 i+1 is excluded from the selection. Otherwise, it is selected.

[0075] This process can be carried out in a single loop (where i goes from 1 to N) or in a continuous loop (by repeating the loop at least twice).

[0076] Here, as shown in FIGS. 5 and 6, the selected patterns are only black patterns (in FIG. 5, the patterns distributed on the smaller-diameter circle).

[0077] During the fourth step, the processing unit determines the shape of the polygon 16 that passes through or is adjacent to each of the selected patterns 12.

[0078] One can also consider the polygon formed by the vertices centered on the selected pattern 12.

[0079] However, here, as shown in FIGS. 5 and 6, the polygon 16 to be considered is a polygon that touches the pattern 12 and does not enclose these patterns.

[0080] In a variation, we can also consider closed curves instead of polygons or any other geometric figures, if they pass through or are adjacent to each of the selected patterns 12.

[0081] During the fifth step, the processing unit determines the geometric center of this polygon 16 (for example, its center of mass or more generally its centroid), which is considered the region center AC.

[0082] As shown in Figure 6, the processing unit 130 can also determine the orientation (if any) of the center alignment axis B0, which is the longitudinal axis of the free pattern region 13. For this purpose, it determines, for example, the orientation α of the longest diagonal of the polygon.

[0083] The position of the region center AC and the orientation of the center alignment axis B0 (if present) define the reference frame of lens 10.

[0084] Therefore, as shown in Figure 7, the processing unit 130 can position the final outline 14 (which the lens must be edged along) on ​​the image of the lens 10.

[0085] This final outline 14 is defined by its own reference frame (rim reference frame). This reference frame is characterized by a point ("pupil point") and an axis inclination (if present).

[0086] More precisely, we can first define a boxing 18, which is a virtual rectangular box with two horizontal sides, surrounding the final outer shape 14 (taking into account the outer shape of the rim in the mounting configuration).

[0087] The pupillary point is located relative to the box 18 by two distances: the height of the pupil relative to the bottom of the box 18, and a width equal to half the distance between the wearer's pupils.

[0088] In other words, the pupillary point has a fixed position relative to the final outline 14.

[0089] As a result, in order to center the lens, the processing unit 130 positions the final outline 14 such that the pupil point of the final outline 14 coincides with the region center AC (so that the lens is well centered with respect to the wearer's eye when mounted on the spectacle frame). If present, this final outline 14 is oriented such that the centering axis A0 satisfies a predetermined requirement (e.g., parallel to the lower edge of the box 18).

[0090] At this step, we can assume that the lens is properly centered and ready for edging.

[0091] However, in a preferred embodiment, several checks are performed before etching the lens.

[0092] For this purpose, the processing unit 130 first displays an image of the type shown in Figure 7 on the touchscreen 131 (without boxing 18 and lines 16, 17).

[0093] This image includes a photograph of lens 10, i.e., a large circle corresponding to the initial contour 11 of the lens (before etching), and a small circle corresponding to the contour of pattern 12.

[0094] This image also includes the optical center OC of the lens, identified by the first crosshair. It also includes the region center AC, identified here by the second crosshair.

[0095] Finally, this image includes the final outline 14 of the lens, i.e., the contour that can be used to edge the lens.

[0096] In a preferred embodiment, other data is also displayed on the touchscreen 131.

[0097] Here, all of the following data is displayed, but in variations, only some of it may be displayed. In other variations, other data may also be displayed.

[0098] The first piece of data is the distance between the optical center OC and the region center AC. In fact, as explained above, this distance generates the prism degree, so knowledge of this distance is important to ensure that the proposed configuration does not have too many unpleasant effects on the wearer.

[0099] The second data point is linked to the first data point and the refractive power of the lens, and represents the prism defect perceived by the wearer when viewed through the central AC of the region.

[0100] The third data is an estimate of the additional power given by the pattern (forming the microlens). This estimate can be given by a value (in diopters) or a color (this color may, for example, fill in a small circle). According to this value, the following explanation can be given: The microlens creates an image in front of the retina (the wearer is not aware of this image). Unconsciously, the eye muscles constantly exert force on the eyeball, attempting to deform it so that the retina can see this image. This constant force over many years shortens the length of the eyeball and inhibits the progression of myopia in the patient. In other words, this third data is an indicator for opticians that is linked to the lens and provides information about its quality.

[0101] The fourth data point is the percentage of the inner zone of the final contour 14 that is covered by pattern 12. In fact, this value is a relevant criterion for determining whether the lens can perform the function of a myopia prevention lens.

[0102] The fifth data point is the balance of the pattern between the nasal and temporal sides of the final contour 14.

[0103] The sixth data point is the balance of the pattern between the upper and lower parts of the final contour 14.

[0104] These values ​​are also relevant to determining whether the lens can perform its function as a myopia prevention lens.

[0105] To determine these balances, the processing unit 130 can proceed with processing in various ways.

[0106] Here, the processing unit 130 divides the zone inside the final contour 14 into four parts by two orthogonal lines 16 and 17 that intersect at the region center AC (see Figure 7).

[0107] In a preferred embodiment, vertical lines 17 and horizontal lines 16 (parallel to the lower edge of the box 18) are used. The processing unit 130 then calculates the proportion of each part of the inner zone of the final contour 14 that is covered by the pattern 12, and thus estimates the found balance as a percentage.

[0108] More precisely, the processing unit 130 determines a first balance between the temporal region and the nasal region (on both sides of the vertical line 17), and a second balance between the upper region and the lower region (on both sides of the horizontal line 16).

[0109] In this step, the processing unit 130 is programmed to give the optician the possibility of changing the position of the pupil point relative to the region center AC in order to correct the final position of the contour 14 relative to the lens 10.

[0110] For this purpose, the optician can use, for example, arrows displayed on the touchscreen 131.

[0111] As the optician moves the pupil point, the final position of contour 14 and all the aforementioned data are recalculated in real time through a loop process.

[0112] The objective of the optician is to arrive at the final configuration resulting from compromise, which is based on the following observations.

[0113] Wearers of myopia-preventive lenses will naturally move their eyeballs or head so that their line of sight precisely passes through the center of the free pattern area 13. Taking this natural behavior into account, the optician attempts to keep the pupil point in its original position (on the area center AC). However, since this area center AC is distinctly different from the optical center OC, prism defects may appear. Therefore, the optician must try to find a good compromise between the following: - Prism defects (should be minimized as much as possible), - The distance between the pupillary point and the center AC of the region (should be as small as possible), - The proportion of the optical surface occupied by pattern 12 (should be greater than a predetermined threshold), - A balanced distribution of patterns between the upper and lower parts of the surface, and - A balanced distribution of patterns between the nasal and temporal sides of the surface.

[0114] The optimal position for the final contour 14 can be reached manually by the optician by moving this contour using the arrows on the touchscreen 131.

[0115] However, the processing unit 130 can also be programmed to help the optician find a good compromise by taking into account all the aspects that need to be considered.

[0116] For example, values ​​that do not meet a given requirement can be colored red.

[0117] In the modified version, the processing unit can propose at least one compromise.

[0118] At the end of this process, the pupil point forms the center alignment point of the lens 10, which is the point on the lens that will be located in front of the pupil of the wearer's eye.

[0119] Finally, the last step is to block the ophthalmic lens 10 using the blocking accessory 150.

[0120] For this purpose, the optician mounts the block accessory 150 on the vertical axis of the holder 103.

[0121] Next, the block arm 121 is moved by the processing unit 130 to grasp the block accessory 150 and place it in front of the lens.

[0122] In a preferred embodiment, the block accessory 150 is positioned at the pupillary point.

[0123] The present invention is by no means limited to the embodiments described and illustrated.

[0124] In particular, this process can be applied when a standard lens (without microlenses) is shown with a pattern such as a drawing in which these lenses are engraved.

[0125] In the above embodiment, the pupil point is offset from the region center AC after the region center is located by the polygon 16. However, in modifications not included in the present invention, it may be possible to locate the region center AC according to a method different from the method described above, and then shift the pupil point in the same way as described above. In fact, this region center AC can be located by another method, such as those described in European Patent No. 3943240 or International Publication No. 2022189352. [Explanation of Symbols]

[0126] 10 Ophthalmic Lenses 11. Initial contour, edge 12 patterns 13 Free Pattern Area 14. Outline, shape 100 Block Device 101 Chassis 102 Workstations 103 Holder 104 Flat support plate 106 Holder 110 Centering means 111 Image sensors, cameras 112 Light source 113 Miller 114 Mirror 120 Blocking means 130 processing units 131 screens, touchscreen 150 Block Accessories

Claims

1. A method for centering an ophthalmic lens (10) comprising several distinct patterns (12) located around a pattern-free region (13), wherein the method is performed by a processing unit, and - A step of acquiring at least one image of the ophthalmic lens (10), - A step of processing the image to detect the pattern (12), - A step of inferring the position of the center alignment point (AC) from the pattern (12), Includes, After the processing step, only a portion of the pattern (12) is selected as a function of the position of the pattern (12) relative to the pattern-free region (13), During the estimation step, the center alignment point (AC) position is estimated solely from the selected pattern (12) position. A method characterized by the following.

2. The geometric center (A) of each selected pattern (12) １ A ２ A ３ The position of the center alignment point (AC) is determined, and the position of the geometric center (A) of the pattern is determined. １ A ２ A ３ The method according to claim 1, as inferred from the location of ).

3. The method according to claim 1, wherein the center point (GC) of the ophthalmic lens (10) is determined, and the pattern (12) is selected according to the position of the pattern (12) relative to the center point (GC).

4. The pattern (12) is sorted according to the angular position (α １ , α ２ , α ３ ) with respect to the center point (GC), and each sorted pattern (12) has a previous pattern and a next pattern. For each pattern (12) in which the distance to the center point (GC) is greater than the distances between the center point and each of the previous pattern and the next pattern, if the angle between the line passing through the previous pattern and the current sorted pattern and the line passing through the next pattern and the current sorted pattern is less than a predefined threshold value, it is not selected. The method according to claim 3.

5. The method according to claim 1, wherein during the estimation step, a polygon (16) that passes through or touches the selected pattern (12) is determined, and the center alignment point (AC) position is estimated from the shape of the polygon (16).

6. The method according to claim 5, wherein the center point (AC) is the centroid of the polygon (16).

7. The method according to claim 5, wherein the axis (B0) of the ophthalmic lens is also inferred from the shape of the polygon (16).

8. The method according to claim 1, wherein the pattern (12) is engraved on the ophthalmic lens to preferably form a microlens.

9. - A step of locating the optical center (OC) of the ophthalmic lens (10), - A step of obtaining the shape of the outer shape (14) of the ophthalmic lens (10) that is cut, - A step of positioning the outer shape (14) with respect to the center alignment point (AC), The method according to claim 1, including the method described in claim 1.

10. The method according to claim 9, comprising the step of determining parameters relating to prism defects resulting from the position of the optical center (OC) with respect to the center alignment point (AC).

11. The method according to claim 9, further comprising the step of determining parameters relating to the distribution of the pattern (12) inside the outer shape (14).

12. The method according to any one of claims 9 to 11, comprising the step of determining parameters relating to the inner surface of the outer shape (14) occupied by the pattern (12).

13. The method according to claim 10, wherein the optical center (OC), the outline (14), the pattern (12), and the centering point (AC) are displayed on a screen (131) along with the parameter values, and the centering point (AC) is manually moved using a human-to-human interface while the processing unit updates the position of the outline and the parameter values.

14. The method according to claim 10, comprising an automatic step of moving the center alignment point (AC) according to the parameters.

15. A centering device (100), - Chassis (101) and, - A component (102) that is attached to the chassis (101) and is suitable for receiving an ophthalmic lens (10), - A centering means (110) is mounted on the chassis (102) and includes an image sensor (111) for acquiring an image of the ophthalmic lens (10) when the ophthalmic lens (10) is received in the component (102), Includes, A centering device (100) also comprising a processing unit (130) programmed to perform the method described in claim 1.

Images