Centring apparatus and method

Abstract

The invention relates to a centering device comprising: - a chassis, - a support mounted on the chassis, the support being suitable for receiving an ophthalmic lens, and - a centering device mounted on the chassis, the centering device comprising: • a camera for acquiring an image of the ophthalmic lens when the ophthalmic lens is received on the support, and • a screen for displaying the image acquired by the camera and a centering target superimposed on said image, the centering target comprising two coaxial and parallel contour lines (150, 151).

Description

TECHNICAL FIELD

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

[0002] More particularly, the present invention relates to a centering device comprising:

[0003] - a chassis,

[0004] - a support mounted on the chassis, the support being suitable for receiving an ophthalmic lens, and

[0005] - a centering device mounted on the chassis, the centering device comprising:

[0006] • a camera for acquiring an image of the ophthalmic lens when the ophthalmic lens is received on the support, and

[0007] • a screen for displaying the image acquired by the camera and a centering target (also called "reticle") superimposed on said image. BACKGROUND

[0008] The technical part of the work of an optician comprising the mounting of a pair of ophthalmic lenses into the eyeglasses frame chosen by the customer can be divided into four main operations:

[0009] - acquiring the shape of the rim profile of the eyeglasses frame chosen by the customer,

[0010] - centering each ophthalmic lens, comprising the use of the centering marks provided thereon to determine the reference system of the lens, then the appropriate positioning of the rim profile acquired beforehand under the reference system of the lens, so that the lens is correctly positioned with respect to the corresponding eye of the customer and implements as much as possible the optical function of its design, as soon as it is edged to this profile and then mounted in its frame,

[0011] - blocking each lens, comprising the attachment of blocking accessories to the lens, so that the lens can be easily removed from the centering station, then engaged in the edging station, without loss of the reference system, then

[0012] - edging each lens, comprising the machining of the lens to the profile previously centered.

[0013] Here, the centering operation and the blocking operation are more particularly concerned.

[0014] These operations are generally carried out by the optician using a centering-blocking device.

[0015] These devices are generally constructed in the same way, with means for holding the ophthalmic lens, optical means for centering the ophthalmic lens, and blocking means for placing blocking accessories on the lens.

[0016] Applicant sells under reference Delta 2 an exemplary centering-blocking device. In this device, the optical centering means comprise a camera and a screen on which the optician can observe the lens superimposed on a centering reticle, thus allowing him to move the lens with respect to this reticle to center the lens correctly. The blocking means comprise, as such, an arm that is fixed and supports a blocking appendage. The lens support is movable along an axis parallel to the axis of the camera, so that when the lens is centered, the optician can press the lens and its support against the blocking appendage. The position of the blocking appendage on the lens then depends on the position of the lens with respect to the reticle.

[0017] This reticle generally has a cross shape, which is perfectly adapted when the lens marking comprises a point or a cross to be centered on the reticle.

[0018] But this reticle does not always guarantee a high precision when the lens marking is different.

[0019] Indeed, the lens marking is sometimes of a shape that makes the centering operation difficult to achieve. For example, the lens marking can be very numerous and distributed along concentric circles, the centers of which are not marked.

[0020] With such a lens marking, it is difficult for the optician to center the reticle on the center of the concentric circles, since this center is not marked. SUMMARY

[0021] In this context, the application provides a centering device as disclosed in the introduction, which has a reticle comprising two coaxial and parallel contour lines (called "centering target").

[0022] The shape of these contour lines depends on the shape of the lens marking. When the lens marking is formed by very numerous and distributed along concentric circles, the contour lines are circular and designed to be placed on either side of one of the concentric circles, thus making it possible to center the lens more accurately with respect to the reticle.

[0023] The principle of a reticle composed of at least two contour lines can be applied to a lens whose markings have a rounded shape, a square shape, or at least a closed shape (for example not a cross shape), or whose markings are distributed along a contour having a rounded shape, a square shape, or at least a closed shape (for example not a cross shape).

[0024] Other preferred features of the application are the following features:

[0025] - at least one of the contour lines comprises a solid line,

[0026] - each contour line has a circular shape,

[0027] - each contour line has a square shape,

[0028] - the size of at least one contour line is modifiable,

[0029] - the distance between the contour lines is adjustable,

[0030] - the size of both contour lines is modifiable,

[0031] - the device comprises means for manually modifying the size of one of the contour lines displayed on the screen,

[0032] - the device comprises means for determining the shape of a centration mark located on the ophthalmic lens, and means for automatically modifying the size of the contour lines displayed on said screen as a function of the shape of the centration mark,

[0033] - the device comprises blocking means mounted on the chassis, said blocking means being suitable for receiving a blocking accessory arranged to be attached to the ophthalmic lens.

[0034] The invention also applies to a method for centration of an ophthalmic lens, comprising the steps of:

[0035] - positioning the ophthalmic lens on a support,

[0036] - acquiring, by a camera, an image of the ophthalmic lens received on the support,

[0037] - displaying the image acquired by the camera and a centration target superimposed on said image, said centration target comprising two coaxial and parallel contour lines, and

[0038] - manually modifying the position of the ophthalmic lens on the support.

[0039] In a preferred embodiment, the ophthalmic lens comprises a centration mark, and the method comprises, before or during the step of manually modifying the position of the ophthalmic lens, the step of adjusting the distance between the two contours as a function of the geometric shape of said centration mark.

[0040] Preferably, the two steps of manually modifying the position of the ophthalmic lens and adjusting the distance between the two contour lines are performed simultaneously by the optician. Indeed, the optician should first roughly position the lens so that the proportions of the contour lines can be adapted to the size of the centration mark. When the proportions of the contour lines are adjusted, the optician can use them to more accurately position the lens.

[0041] In a preferred embodiment, the centration mark comprises a pattern distributed along a contour centered on a point, the distance between the two contour lines being adjusted to be comprised between one and two times a width of the pattern, said width being measured radially with respect to said point.

[0042] In a preferred embodiment, the centring mark comprises a pattern distributed along a concentric circle, and each contour line has a circular shape. BRIEF DESCRIPTION OF DRAWINGS

[0043] The description that follows, given by way of non-limiting example with reference to the accompanying drawings, makes the nature of the present application clear and the manner in which it is to be implemented.

[0044] In the drawings:

[0045] - Figure 1 is a schematic view of a centring device according to the application; and

[0046] - Figure 2 is an example of a view of a screen display by the Figure 1 centring device shown in DETAILED DESCRIPTION

[0047] Figure 1 An example of a centring device 1 is shown.

[0048] Opticians use this device to prepare an ophthalmic lens for edging to a given contour, to mount this ophthalmic lens in a spectacle frame chosen by a customer.

[0049] This device is generally used after the optician has acquired the shape of the contour Cl to which the lens must be edged (see Figure 2 ). The device is then used to implement the operations of centring and blocking of the ophthalmic lens.

[0050] The purpose of the centring operation is to position the reference system of the ophthalmic lens, and to determine the position that the above-mentioned contour must occupy in this reference system, so that the lens, once edged to this contour and then mounted in a spectacle frame, is properly centred with respect to the corresponding eye of the customer (in order to achieve the optical function designed for it as much as possible).

[0051] The purpose of the blocking operation is to place an accessory, called a "blocking accessory", on the ophthalmic lens, so as to make it easier to provide a stable coordinate system, allowing the position of the reference system of the lens to be located after it has been transferred from the centring device 1 to the edging device.

[0052] Figure 2 An ophthalmic lens 100 to be edged is shown in . This lens has two optical faces, i.e. a convex front face and a concave back face, and an edge whose shape is initially circular. The shapes of the front and back faces of the ophthalmic lens 100 are designed so that this lens has optical properties that allow it to correct the vision defects of a customer.

[0053] Here, the ophthalmic lens 100 comprises a first optical correction for providing a wearer with corrected vision at a determined distance, and a second optical correction for modifying the natural progression of myopia.

[0054] In our example, the first optical correction comprises a spherical power for providing the wearer with correct distance vision (for looking at objects located more than 6 meters away). This first optical correction can also comprise a cylindrical power and / or a prismatic power.

[0055] The optical center of the lens is defined as the point through which a light ray passes through the lens without being deviated.

[0056] In a first embodiment, it can be assumed that the centering point PI of the ophthalmic lens 100, i.e. the point at which the blocking attachment must be placed, is formed by this optical center.

[0057] In a second embodiment, the centering point PI is formed by the geometric center of a virtual rectangular box, called the “boxing center”, which circumscribes the profile CI along which the lens will be edged.

[0058] In these two embodiments, the centering device 1 should inform the edging device of the point at which the blocking attachment is located.

[0059] The second optical correction provides additional optical properties. This correction is specifically designed to limit or prevent the progression of myopia.

[0060] In our example, the ophthalmic lens 100 comprises for this purpose micro-lenses. Such an ophthalmic lens is described in document WO 2019166654.

[0061] The ophthalmic lens 100 is provided with centering marks 110 allowing to position its reference system.

[0062] These marks can take the form of temporary marks printed with ink and / or permanent marks engraved on the lens (the micro-engravings mentioned).

[0063] The temporary marks generally allow to properly position the optical reference system of the lens before mounting it into a spectacle frame, while the permanent marks allow to identify the properties and characteristics of the ophthalmic lens and to identify or reconstruct the exact position of said lens after removal of the temporary marks.

[0064] Here, the ophthalmic lens 100 only has permanent marks for determining the centering point PI of the lens.

[0065] As Figure 2 illustrated, these micro-engraved marks 110 are each rounded, they are very numerous and they are distributed along concentric circles around the centering point PI of the ophthalmic lens 100.

[0066] The lens comprises more than three circles. Each circle contains more than ten marks 110.

[0067] The marks of a single circle all have the same diameter D2. Here, all the marks have the same diameter D2. This diameter is less than 1 mm.

[0068] In the disclosed embodiments, the centring marks 110 are formed by the profile of a micro-lens engraved in one of the optical faces of the lens to implement a second optical correction.

[0069] Here and preferably, the ophthalmic lens 100 is intended to be centred and blocked manually.

[0070] As Figure 1 illustrated, to this end, the centring device 1 comprises at least:

[0071] - a chassis 10,

[0072] - a cradle 20 mounted on the chassis 10 and suitable for receiving the ophthalmic lens 100 (that is to say for supporting the ophthalmic lens or blocking it),

[0073] - a blocking device 30 mounted on the chassis 10 and suitable for receiving the blocking accessory 200, and

[0074] - a centring device 40 mounted on the chassis 10, comprising a sighting objective through which the optical reference frame of the ophthalmic lens 100 can be observed.

[0075] The centring device can have several shapes. For example, the cradle can be fixedly mounted on the chassis and the blocking device can comprise a movable arm which is manually manoeuvrable so that the optician can push the arm to place the blocking accessory on the lens.

[0076] But in the illustrated embodiment, the blocking device 30 is fixedly mounted on the chassis 10, while the cradle 20 is movably mounted on the chassis 10.

[0077] The illustrated centring device 1 can now be briefly described.

[0078] As Figure 1 illustrated, in the described embodiment, the chassis 10 comprises a dome 11. This dome 11 has a lateral wall the top face of which is open with a large circular aperture centred on a main axis Al which is vertical here. The dome also comprises a bottom which is in the horizontal plane and which closes the back face of the lateral wall. Finally, the dome comprises a false bottom 14 at an intermediate height.

[0079] The false bottom 14 is visible through the large circular aperture 12. The centre of the false bottom has a circular hole centred on the main axis Al.

[0080] The blocking device 30 (designed to hold the blocking accessory 200) comprises a vertical shaft centred on the main axis Al. This vertical shaft has a lower end fixed to the chassis and a free upper end for receiving the blocking accessory 200.

[0081] The support 20 is a transparent and vertical tube mounted on the chassis 10 so as to be able to slide along the main axis Al.

[0082] The upper end 22 of the support 20 is circular and extends in a horizontal plane, so that it is suitable for supporting the ophthalmic lens 100.

[0083] More precisely, the support 20 is mounted so that it can move between:

[0084] - a centring position, in which the ophthalmic lens 100 resting on the upper end 22 of the support 20 is at a distance from the blocking appendix 200, and

[0085] - a blocking position, in which the ophthalmic lens 100 rests on the blocking appendix 200.

[0086] An elastic element suitable for automatically returning the support 20 to the centring position is provided inside the dome 11.

[0087] As a variant, the support can comprise three projecting pins forming a tripod for receiving the ophthalmic lens.

[0088] Advantageously, the centring device 40 is intended to view the ophthalmic lens 100 along a viewing axis A2 parallel to (here coinciding with) the main axis Al.

[0089] As Figure 1 illustrated, the centring device 40 here comprises means 50 for illuminating the ophthalmic lens 100 and means 60 for viewing the ophthalmic lens 100 illuminated by the illumination means 50.

[0090] The illumination means 50 are all distributed around the support 20 so as to produce a grazing incidence of light on the optical face of the lens placed on the support 20 (here the convex face on which the centring marks 110 are engraved).

[0091] In this case, the illumination means 50 comprise a plurality of light-emitting diodes regularly distributed around the support 20.

[0092] The viewing means 60 comprise a mirror 63 inclined by 45° with respect to the main axis Al and allowing to redirect the image of the ophthalmic lens 100 towards the objective 61 of a digital video camera 62. This mirror 63 makes the centring device 1 more compact.

[0093] The digital video camera 62 is then designed to acquire the image of the ophthalmic lens 100 and to transmit it to a viewing screen 70 oriented towards the face of the optician. This viewing screen 70 can be of any kind (for example LCD, TFT...). This viewing screen is preferably mounted on the chassis 10 but can be remote from it.

[0094] The optician can thus observe in real time on this observation screen 70 an image of the ophthalmic lens 100 in which the centration marks 110 placed on the lens are clearly displayed.

[0095] The centration device also comprises a processing unit programmed to help the optician to center the ophthalmic lens 100.

[0096] To this end, the processing unit comprises a central processing unit (CPU), a memory and input / output means.

[0097] Thanks to its memory, the processing unit stores information used in the processes described below. The memory notably stores a computer application constituted by a computer program comprising instructions, the execution of which allows the processing unit to implement the method described below.

[0098] The processing unit is connected to the observation screen 70 to display the reticle superimposed on the image acquired by the video camera 62.

[0099] The reticle is defined as a centration target or as a fixed coordinate system indicating the position of the blocking accessory 200.

[0100] According to the application, the reticle comprises two coaxial and parallel contour lines 150, 151.

[0101] Each contour line is preferably a line (curve or series of line segments) extending along a closed contour.

[0102] The contour lines 150, 151 are parallel in the sense that the shortest distance between the two contour lines is constant at any point along the entire closed contour.

[0103] In practice, the outer contour line 151 is an image of the inner contour line 150 after a similar expansion.

[0104] Because the centration marks 110 comprise a pattern distributed along concentric circles in the embodiment shown, each contour line 150, 151 has a circular shape here. Figure 2 In a variant in which the centration marks would comprise a pattern distributed along concentric squares, each contour line 150, 151 would have a square shape.

[0105] The contour lines 150, 151 are displayed in the form of solid lines on the observation screen 70, but they can be displayed in the form of dotted or dashed lines.

[0106] The contour lines extend along a closed contour, but can also be open over a portion of their contour.

[0107]

[0108] ​It is conceivable that the size of the contour lines cannot be modified. But in the preferred embodiment, the size of at least one of the contour lines 150, 151 is modifiable. Here, the size of both contour lines is modifiable.

[0109] This is preferred for the following reasons.

[0110] The size of the centration marks 110 displayed on the observation screen 70 can vary due to the scale modification induced by the lens power; thus, depending on the spherical power of the lens, the distance between the contour lines can change.

[0111] Moreover, different brands of lenses can show centration marks with different sizes, which is why it is advantageous to make the size of the contour lines scalable.

[0112] Here, the radius R1 of the inner contour line 150 is adjustable, and the distance D1 between the two contour lines 150, 151 is also modifiable.

[0113] As a result, the size of the two contour lines 150, 151 can be set so that:

[0114] - the individual circles of the centration marks 110 extend between them, and

[0115] - the two contour lines are tangent to all the centration marks 110 of the circle.

[0116] To this end, the distance D1 between the two contour lines 150, 151 must be adjusted to be comprised between one and two times the diameter of the engraved micro-lens.

[0117] In this position, the optician must have well centered the lens with respect to the blocking accessory 200.

[0118] In a first embodiment, the device 1 comprises an HMI (Human Machine Interface) enabling the optician to manually modify the size of the contour lines 150, 151 displayed on the observation screen 70.

[0119] If the screen is a touch screen, this HMI can be formed by this screen. In this embodiment, two buttons are displayed associated with each contour line, one button for increasing the size of the associated contour line and a second button for decreasing its size.

[0120] In a second embodiment, the processing means are programmed to:

[0121] - process the image of the lens acquired to identify the features of the centration marks 110, and

[0122] - automatically modify the size and / or the shape of the contour lines 150, 151 displayed on the screen 70 as a function of these features.

[0123] More specifically, the processing means are programmed to determine the shape and the position of each centration mark 110 at a first step.

[0124] Then, the processing means determine whether the partial centration marks are distributed along a closed contour.

[0125] If this is not the case, a cross reticle is displayed on the screen. The exact shape of this reticle depends on the shape of the centration marks. In other words, the shape of the reticle depends on the lens type:

[0126] - single focus,

[0127] - progressive,

[0128] - multi-focal (an example of a bi-focal lens is a single focus lens fitted with a near vision lens pasted on the front face of the single focus lens),

[0129] - executive (an example of an executive lens is a bi-focal lens in which the near vision correction is performed by the bottom part of the lens and the far vision by the upper part of the lens, said parts being separated by a line),

[0130] - interview (an example of an interview lens is a progressive lens which does not have a far vision correction, but only a near vision correction and a mid vision correction).

[0131] If this is the case, the processing means determine the shape of the detected closed contour (here, the shape is circular). Then, the processing means determine the average diameter of one of the detected circles along which the marks are distributed, and the diameters of these marks. Finally, the processing means display on the viewing screen two contour lines 150, 151 adapted to the shape of the centration marks.

[0132] In other words, in this second embodiment, the processing means are programmed to propose a reticle shape adapted to the current lens family and selected among six different shapes.

[0133] To center the ophthalmic lens 100, then to block it, the optician uses the centration device 1 in the following way.

[0134] At a first step, the optician loads the blocking accessory 200 on the vertical shaft.

[0135] At a second step, the optician places the ophthalmic lens 100 on the upper end 22 of the holder 20 in such a way that the convex front face of the lens rests on this holder 20.

[0136] At this step, the camera 60 acquires images of the lens, and these images are displayed on the viewing screen 70. These images are displayed with the two contour lines 150, 151.

[0137] In a second embodiment, the size and shape of the two contour lines 150, 151 are automatically modified to adapt to the shape of the centring mark 110.

[0138] At a third step, the optician manually moves the ophthalmic lens laterally, i.e. by sliding the ophthalmic lens on the support 20, until the ophthalmic lens 100 is placed on the axis of the blocking attachment 200. To do this, the optician observes the images of the ophthalmic lens 100 on the viewing screen 70, these images being displayed with the superimposition of the contour lines 150, 151. The optician then tries to place the two contour lines 150, 151 on each side of the single circle of the centring mark 110 at this step.

[0139] At this step, in the first embodiment, the optician can manually modify the size of the two contour lines to achieve this aim.

[0140] Once this position has been reached, the optician presses the ophthalmic lens 100 down while taking care not to move the ophthalmic lens laterally to lower the support 20. This operation allows the lens to rest on the double-sided self-adhesive provided on the blocking attachment 200. In this way, the blocking attachment is automatically bonded to the lens in the desired position (with a precision better than half a millimetre).

[0141] The application is in no way limited to the embodiments described and illustrated.

[0142] In particular, the blocking operation can be automated by equipping the support with a pneumatic or mechanical handling mechanism, and by equipping the centring device with electronic means for controlling this handling mechanism.

[0143] The application is also applicable to an automatic blocking system (with a motorised arm that can place the blocking attachment on a specific point of the lens, and with a centring device that helps the optician to manually position the lens taking into account this blocking point with the help of a camera). According to another variant of the application, the support can take a form that is different from that illustrated in the figures. Thus, the support can take the form of a tripod that is mounted so as to be able to slide on a base in a plane that is orthogonal to the main axis Al.

[0144] According to another variant of the application, the centring device can be operated automatically to centre and block the lens (without the help of the optician). With such a device, the use of the two contour lines makes it possible to centre the lens more accurately by the processing means.

Claims

1. A centering apparatus (1) comprising: - a chassis (10), - a holder (20) mounted on the chassis (10), the holder being suitable for receiving an ophthalmic lens (100), and - a centering device (40) mounted on the chassis (10), the centering device comprising: - means (50) for illuminating the ophthalmic lens (100), - a camera (60) for acquiring an image of the ophthalmic lens (100) when the ophthalmic lens is received on the holder (20), and - a screen (70) for displaying the image acquired by the camera (60) and a centering target superimposed on the image, characterized in that the centering target comprises two coaxial and parallel contour lines (150, 151), and in that the size of the overall shape contained by at least one of the contour lines (150, 151) is modifiable so that the distance between the contour lines (150, 151) is adjustable.

2. Centering device (1) according to claim 1, wherein At least one of the contour lines (150, 151) comprises a solid line.

3. Centering device (1) according to claim 1, wherein Each contour line (150, 151) has a circular shape.

4. Centering device (1) according to claim 1, wherein Each contour line (150, 151) has a square shape.

5. Centering device (1) according to claim 1, wherein The size of the overall shape contained by both contour lines (150, 151) is modifiable.

6. The centering apparatus (1) according to claim 5, comprising means for manually modifying the size of the overall shape contained by one of the contour lines (150, 151) displayed on the screen (70).

7. The centering apparatus (1) according to claim 5, comprising means for determining the shape of a centering mark (110) located on the ophthalmic lens (100), and means for automatically modifying the size of the overall shape contained by the contour lines (150, 151) displayed on the screen (70) as a function of the shape of the centering mark (110).

8. The centering apparatus (1) according to claim 1, comprising a blocking device (30) mounted on the chassis (10), the blocking device being suitable for receiving a blocking accessory (200) arranged to be attached to the ophthalmic lens (100).

9. A method for centering an ophthalmic lens, the method comprising the steps of: - positioning the ophthalmic lens (100) on a holder (20), - acquiring an image of the ophthalmic lens (100) received on the holder (20) by a camera (60), and - displaying the image acquired by the camera (60) and a centering target superimposed on the image, - manually modifying the position of the ophthalmic lens (100) on the holder (20), characterized in that the centering target comprises two coaxial and parallel contour lines (150, 151), and in that the size of the overall shape contained by at least one of the contour lines (150, 151) is modifiable so that the distance between the contour lines (150, 151) is adjustable, before the step of manually modifying the position of the ophthalmic lens.

10. The method of claim 9, wherein, The ophthalmic lens (100) comprises a centration mark (110), and wherein the method comprises a step of adjusting the distance between the two contour lines (150, 151) as a function of the geometry of the centration mark (110).

11. The method of claim 10, wherein, The centration mark (110) comprises a pattern distributed along a contour centered on a point (Pl), the distance between the two contour lines (150, 151) being adjusted to be comprised between one and two times a pattern width, the width being measured radially with respect to the point (Pl).

12. The method of claim 10, wherein, The centration mark (110) comprises a pattern distributed along a concentric circle, each contour line (150, 151) having a circular shape.

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