EP0961669B1 - Method for finishing spectacle lenses, and related device - Google Patents

Description

The invention relates to a method for touching up spectacle lenses after a first size of it, of the kind according to which, with a view to a new passage of this glass of glasses on a grinder we implant on it a block of gripping proper to its installation on such a grinder. Such a process is conventionally used by opticians for the precise adaptation of a lens to a glasses frame of their client. The invention also relates to the device associated.

Spectacle lenses are produced in the form of parts which are substantially circulars ensuring a certain optical correction. They are then cut by the manufacturer or optician depending on the shape of the spectacle frame chosen by the customer. It is clear that the size must be carried out taking into account both the shape of the frame and the position of the user's eyes. The optical center of glass must indeed be correctly placed in front of the eye, to produce the desired mink correction.

Most often, the size is carried out slightly beyond the size dimensions initially requested, and a touch-up is necessary to adapt the lens perfectly to the frame, especially in the case of frames metal.

It is then for the optician to carry out the retouching size of the glass according to the same constraints of shape and optical center, and in an interval of time naturally limited by the client's desire to quickly recover their glasses.

Certain machines, fully automated, make it possible to carry out roughing, finishing and retouching the glass without removing it from its initial size support. This is the case of the machine proposed by the document EP-A-0 706 439, according to the preamble of claim 7.

However, in current practice, the glass is most often dismantled from its original size support, to try the lens on the frame, and the defect is only detected then. Likewise, it is more and more common that the optician no longer cuts the glass directly, but transmits the measurements corresponding to a frame and a client to the lens manufacturer, who delivers the lens to him cut and bizarre, disassembled from its size support, this glass in front then possibly be retouched.

Two retouching methods are currently used. The first one consists of a "judged" retouch by the optician, by resizing all or part of the contour of the glass, with obvious disadvantages of lack of precision of the form of partial decentering of the optical center relative to the eye of the user.

The second method is to use an automated machine that requires on the part of the optician to center (orientation) and center (position) the lens precisely, then implant the grip block on the glass at a specific point taking into account the position of the user's eye. The optician then proceeds probing by a mechanical or digital contour reader of the final shape sought for the lens, corresponding to the customer's frame. The reader of contour then controls the grinding of the blocked glass and placed on the grinder according to the desired final form. This method is complex and time consuming, and any error in positioning is reflected after grinding on the final shape of the glass.

As for the invention, it relates to a method for retouching spectacle lens, quick to use, allowing precise touch-up of the glass.

To this end, the invention provides a method for touching up a glass of glasses after a first size thereof, according to claim 1.

It is understood that this method makes it possible to compensate for an offset position of the block on the glass by the optician, thanks to the reading of the form, which serves as a reference for own grinding, instead of using as a reference, as well as in art front, the center of the glass, which therefore had to be determined with precision as we said.

The invention also relates to a device for implementing a method according to the preceding description, according to claim 7.

• la figure 1 est une représentation schématique du principe de lecture de contour du verre,
• la figure 2 est une représentation de la forme finale recherchée pour le verre,
• la figure 3 est une schématisation de la trajectoire de meulage pour la retouche du verre selon la forme finale recherchée.

The description and the drawing of a preferred embodiment of the invention, given below, will make it possible to better understand the aims and advantages of the invention. It is clear that this description is given by way of example, and is not limiting. In the drawings,

• FIG. 1 is a schematic representation of the principle of reading the contour of the glass,
• FIG. 2 is a representation of the final shape sought for the glass,
• FIG. 3 is a diagram of the grinding trajectory for touching up the glass according to the final shape sought.

For the implementation of the process, the optician has a device of implantation of grip block on glass of retouching bezel, of a contour reading device 2, for example of a mechanical nature, and of a lens glass grinder, these various means being of a conventional nature in the field and therefore not detailed here further.

When touching up a spectacle lens 1 that was initially assumed to be too cut large, a gripping block 3, which is for example in the form of a "acorn" is first of all fixed by the optician at any point 4, preferably close to the center of the glass 5, and the glass 1 is thus secured an axis A substantially perpendicular to its reference plane.

The glass is then fixed in the contour reader 2 (figure 1), around its block 3 for example, in any orientation characterized by axes 6, 7. In the case of a mechanical contour reader, a probe 8 raises the read form 9 of the glass, during a rotation of the glass 1 around the axis A, thus determining a function of type R = f (α), where R is the distance from the point read to the axis A, and α the angle of rotation of the lens from its initial locking position. The information of form read 9 from the glass, obtained by this probe 8 is transmitted to a control unit, which is conventionally a computer integrated into the reader outline 2.

The final shape 10 sought for the glass is also stored with a known manner in the control unit, and is for example defined (Figure 2), of a hand, by a point 11 called "boxing center", which corresponds to the center of a rectangle 12 in which the desired final shape is inscribed, said rectangle having main directions 13, 14 corresponding to the vertical and the horizontal of the mount in wear position by the user, on the other hand, by two axes perpendicular for example in the directions 13, 14 of the rectangle in which the final form sought 10 is entered, finally by a function in coordinates polar R1 = f1 (β), with R1 distance from the point of the desired final form of glass 1 at its center 11 for a rotation β around the theoretical axes 13, 14.

The "placement" by the computer of the final form sought 10 in the read form 9 (FIG. 3) is carried out by means known to a person skilled in the art, and for example by using a minimum distance search algorithm of the form read 9 to the final form sought 10. It is clear that the form read 9 is assumed to be close to the desired shape 10.

We finally obtain a grinding function R2 = f2 (α) corresponding to the transformation of the function f1 of final form 10 in the coordinate system 11, 13, 14 into a function around mark 4, 6, 7.

Based on these results, the computer controls the grinding, carried out on a part or all of the outline of the glass 1, in a conventional manner.

As can be understood on reading the description, the process has an advantage of simplicity of use for the optician, and saving of time overall, the time to read the contour and calculate the trajectory correction of grinding being largely compensated by the elimination of the centering time and orientation of the glass by the optician.

We presented in the description a fixing by acorn, which is classic in this domain. The fact remains that any type of fixing of the glass is satisfactory for the invention, insofar as it guarantees a fixed position of the glass relative to the grinding machine. A suction cup attachment is thus usable without modifying the process.

In a variant of positioning of the final shape sought 10 in the form read 9, an algorithm for determining the main axes of inertia and center of inertia of the two forms is usable, since the form read is assumed to be close to the final form sought 10, with only a few minor contour corrections.

In another variant, the probe and the grinder are integrated within of the same machine, so that the reading axis and the grinding axis are confused.

The scope of the present invention is not limited to the details of the forms of embodiment above considered by way of example, but on the contrary extends to modifications defined in the appended claims.

Claims (13)

1. A method of finishing a spectacle lens (1) after first cutting thereof and removal of the lens from its first cutting support, of the kind in which, for a further passage of the spectacle lens through a grinding machine, a holding block (3) is fitted to it for holding it in place on the grinding machine, characterized in that the block (3) is fitted at any point (4) of the spectacle lens, preferably close to its centre (5), the lens (1) is fixed into the contour reading device around said block (3) in any orientation, the contour of the spectacle lens (1) is read to obtain a read shape (9) for the spectacle lens, the read shape (9) is compared to the required final shape (10) by placing the required final shape (10) in the read shape (9), a grinding function is established allowing for the difference between the read shape (9) and the final shape (10) and the grinding machine is controlled accordingly.
2. A method according to claim 1, characterized in that, with any orientation of the lens (1) in the contour reading device being characterized by two axes (6, 7) defining with said fixing point (4) a first system of axes (4, 6, 7), a function of the type R=f(α) is determined on reading the contour, where R is the distance from the point read to an axis (A) relative to which the lens (1) was fixed during fitting of the holding block (3), and α is the angle the lens has rotated from its initial fixed position.
3. A method according to claim 2, characterized in that the required final shape (10) for the lens (1) is defined by a function of the type R1=f(β), where R1 is the distance from the point of the required final shape (10) of the lens (1) to its centre (11), known as "centre boxing", and β is the angle rotated about theoretical axes (13, 14) defining with the centre boxing (11) a second system of axes (11, 13, 14).
4. A method according to claim 3, characterized in that said grinding function is of the type R2=f2(α) and corresponds to the conversion of the function f1 in the second system of axes (11, 13, 14) into a function in the first system of axes (4, 6, 7).
5. A method according to any of claims 1 to 4, characterized in that the read shape (9) is compared to the required final shape (10) using an algorithm to find the minimum distance from the read shape (9) to the required final shape (10).
6. A method according to any of claims 1 to 5, characterized in that the read shape (9) is compared to the required final shape (10) using an algorithm for determining the principal axes of inertia and the centre of inertia of the read shape (9) and of the required final shape (10).
7. A machine for implementing a method according to any of claims 1 to 6, including a grinding machine, a device to implant a holding block (3) on the spectacle lens (1), a contour reading device (2), a grinding machine control unit including means for storing the read shape and the required final shape, characterized in that it includes a computer able to place the required final shape in the read shape, for comparing the two shapes and establishing a grinding function allowing for the difference between the two shapes.
8. A machine according to claim 7, characterized in that the holding block (3) is an acorn.
9. A machine according to claim 7, characterized in that the holding block (3) is a sucker.
10. A machine according to any of claims 7 to 9, characterized in that it includes digital means for reading the contour of the spectacle lens (1).
11. A machine according to any of claims 7 to 9, characterized in that it includes mechanical means for reading the contour of the spectacle lens (1).
12. A machine according to any of claims 7 to 11, characterized in that the contour reading means include means for positioning the lens (1) by means of its holding block (3).
13. A machine according to any of claims 7 to 12, characterized in that the reading and grinding axes are one and the same.

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