Patent Description:
It more particularly relates to a centering apparatus including:.

The technical part of the work of an optician, which consists in mounting a pair of ophthalmic lenses in a spectacle frame selected by a customer, may be split into four main operations:.

Here, the centering and blocking operations are more particularly of interest.

These operations are generally carried out by an optician, using a centering-blocking apparatus.

These apparatuses are generally configured in the same way, with means for holding the ophthalmic lens, optical means for centering the ophthalmic lens, and blocking means for depositing the blocking accessory on the lens.

An exemplary centering-blocking apparatus is sold by the Applicant under the reference Delta2. In this apparatus, the optical centering means include a camera and a screen on which the optician may observe the lens superposed on a centering reticle, thereby allowing him to move the lens with respect to this reticle so as to center it correctly. The blocking means for their part include an arm that is stationary and that supports the blocking accessory. The lens support is movable along an axis parallel to the axis of the camera, so that the optician can press the lens and its support towards the blocking accessory when the lens is centered. The position of the blocking accessory on the lens then depends on the position of the lens with respect to the reticle.

This reticle has usually a cross shape, that is perfectly adapted when the lens markings comprise a point or a cross to be centered on the reticle.

For instance, document <CIT> relates to a cup attaching apparatus for blocking a lens, comprising two cameras and a color monitor. The monitor displays the target lens shape, a cup figure having a circle shape, and a cross mark indicating the position of the optical center of the lens. This cross mark is displayed such that the center of a circle "O" depicted in the center conforms to the detected position of the optical center of the lens.

But this kind of reticle does not always guarantee a great precision when the lens markings are different.

Indeed, the lens markings have sometimes shapes that make the centering operation difficult to implement. For instance, lens markings can be round micro-engravings, very numerous, and distributed along concentric circles.

With such lens markings, it is difficult for the optician to center the reticle on the center of the concentric circles because this center is not marked.

In this context, the present invention provides a centering apparatus as as defined in claim <NUM>, having a reticle (named "centering target") that comprises two coaxial and parallel outlines.

These outlines have a shape that depends on the shape of the lens markings. When the lens markings are formed by round micro-engravings, very numerous, and distributed along concentric circles, these outlines are circular and designed to be placed on either sides of one of the concentric circles, which enables to center more accurately the lens relative to the reticle.

The principle of a reticle composed of at least two outlines could be applied to lenses whose micro-engravings have (or are distributed along a contour having) a round shape, a square shape, or at least an enclosing shape (not a cross for example).

Other preferred features of the invention are the following ones:.

The invention also applies to a method for centering an ophthalmic lens, as defined in claim <NUM>.

In a preferred embodiment, the ophthalmic lens comprises centering markings and the method comprises, before or during the step of manually modifying the position of the ophthalmic lens, a step of adjusting the distance between the two outlines as a function of the geometry of said centering markings.

Preferably, these two steps of manually modifying the position of the ophthalmic lens and of adjusting the distance between the two outlines are performed simultaneously by the optician. Indeed, the optician shall first position roughly the lens so that it could be possible to adapt the scale of the outlines to the size of the centering marks. When the scale of the outlines has been adapted, the optician can use them to position the lens more accurately.

In a preferred embodiment, the centering markings comprising patterns distributed along a contour centered on a point, the distance between said two outlines is adjusted so as to be comprised between once and twice the pattern width, said width being radially measured relative to said point.

In a preferred embodiment, the centering markings comprise patterns distributed along concentric circles, and each outline has a circular shape.

The following description with reference to the accompanying drawings, given by way of non-limiting example makes it clear what the invention consists in and how it can be reduced to practice.

<FIG> shows an example of centering-blocking apparatus <NUM>.

Such an apparatus is used by an optician to prepare an ophthalmic lens for edging to a given outline, with a view to mounting this ophthalmic lens in a spectacle frame selected by a customer.

This apparatus is generally used after the optician has acquired the shape of the outline C1 to which the lens must be edged (see <FIG>). This apparatus is then employed to carry out the operations of centering and blocking the ophthalmic lens.

The objective of the centering operation is to locate the frame of reference of the ophthalmic lens, and to determine the position that the aforementioned outline must occupy in this frame of reference so that the lens, once edged to this outline then mounted in the spectacle frame, is suitably centered facing the corresponding eye of the customer (in order to fulfil as best as possible the optical function for which it was designed).

The objective of the blocking operation is to place an accessory (called the "blocking accessory") on the ophthalmic lens, thereby making it easier to provide a stable coordinate system allowing the position of the frame of reference of the lens to be located after it has been transported from the centering-blocking apparatus <NUM> to an edging apparatus.

The ophthalmic lens <NUM> to be edged is shown in <FIG>. This lens has two optical faces (namely a convex front face and a concave back face) and an edge, the shape of which is initially circular. The shapes of the front and back faces of this ophthalmic lens <NUM> are designed such that the lens has optical characteristics allowing defects in the vision of the customer to be corrected.

Here, the ophthalmic lens <NUM> includes a first optical correction for providing correct vision to the wearer at a determined distance, and a second optical correction for changing the natural evolution of Myopia.

The first optical correction consists, in our example, in a spherical power for providing correct far vision to the wearer (for looking at objects situated at more than <NUM> meters). This first optical correction could also include a cylindrical and/or a prismatic power.

The optical center of the lens is defined as the point of the lens where the light rays are not deviated when they pass through the lens.

In a first embodiment, it can be assumed that the centering point P1 of the ophthalmic lens <NUM>, that is the point where the blocking accessory has to be deposited, is formed by this optical center.

In a second embodiment, the centering point P1 is formed by the geometric center (called "boxing center") of a virtual rectangular box circumscribing the outline C1 along which the lens will be edged.

In both embodiments, the centering and blocking apparatus <NUM> shall inform the edging apparatus in which point the blocking accessory is positioned.

The second optical correction provides an additional optical feature. This correction is specifically designed to limit or to stop the evolution of myopia.

In our example, the ophthalmic lens <NUM> contains to this end micro-lenses. Such an ophthalmic lens is described in document <CIT>.

The ophthalmic lens <NUM> is provided with centering markings <NUM> allowing its frame of reference to be located.

These markings may take the form of temporary marks printed in ink and/or permanent marks engraved into the lens (micro-engravings are spoken of).

Provisional markings generally allow the optical frame of reference of the lens to be suitably located prior to its mounting in the spectacle frame whereas permanent markings allow the nature and characteristics of the ophthalmic lens to be identified and, after the provisional markings have been removed, the exact location of said lens to be identified or reestablished.

Here, the ophthalmic lens <NUM> has only permanent markings for determining the centering point P1 of the lens.

As shown in <FIG>, these micro-engraved markings <NUM> are each round, they are very numerous, and they are distributed along concentric circles about the centering point P1 of the ophthalmic lens <NUM>.

The lens comprises more than three circles. Each circle comprises more than ten markings <NUM>.

The markings of a single circle have all the same diameter D2. Here, all the markings have the same diameter D2. This diameter is lower than <NUM>.

In the disclosed embodiment, these centering markings <NUM> are formed by the contours of the microlenses that are engraved in one of the optical faces of the lens to fulfill the second optical correction.

Here, and preferably, the ophthalmic lens <NUM> is intended to be centered and blocked manually.

As <FIG> shows, the centering-blocking apparatus <NUM> includes for this purpose at least:.

This centering-blocking apparatus may have several shapes. For instance, the holder could be fixedly mounted on the chassis and the blocking means could include a movable arm that is manually maneuverable so that the optician can force the arm to deposit the blocking accessory on the lens.

But in the shown embodiment, the blocking means <NUM> are fixedly mounted on the chassis <NUM>, and it is the holder <NUM> that is movably mounted on the chassis <NUM>.

The represented centering-blocking apparatus <NUM> can now be briefly described.

As <FIG> shows, in the described embodiment, the chassis <NUM> includes a dome <NUM>. This dome <NUM> has a sidewall the top face of which is apertured with a large circular aperture centered on a main axis A1 that here is vertical. It also includes a bottom that lies in a horizontal plane and that closes the back of the sidewall. It lastly includes, at mid-height, a false bottom <NUM>.

This false bottom <NUM> is visible through the large circular aperture <NUM>. It has in its center a circular hole centered on the main axis A1.

The blocking means <NUM> (which are designed to hold the blocking accessory <NUM>) includes a vertical shaft that is centered on the main axis A1. This vertical shaft has a lower end that is secured to the chassis and a free upper end for accommodating the blocking accessory <NUM>.

The holder <NUM> is a transparent and vertical tube mounted on the chassis <NUM> so as to be able to slide along the main axis A1.

The upper end <NUM> of the holder <NUM> is circular and extends in a horizontal plane, such that it is suitable to support the ophthalmic lens <NUM>.

This holder <NUM> is more precisely mounted so as to be movable between:.

An elastic element, suitable for automatically returning the holder <NUM> to the centering position, is provided inside the dome <NUM>.

As a variant, the holder could comprise three protruding pins forming a tripod for accommodating the ophthalmic lens.

Advantageously, the centering means <NUM> are intended to observe the ophthalmic lens <NUM> along a viewing axis A2 that is parallel (here coincident) with the main axis A1.

As <FIG> shows, these centering means <NUM> include here means <NUM> for illuminating the ophthalmic lens <NUM> and means <NUM> for viewing the ophthalmic lens <NUM> illuminated by the illuminating means <NUM>.

The illuminating means <NUM> are distributed all around the holder <NUM>, so as to generate light of grazing incidence on the optical face of the lens that is placed on the holder <NUM> (here on the convex front face, in which the centering markings <NUM> are engraved).

These illuminating means <NUM> in this instance include a plurality of light-emitting diodes that are regularly distributed around the holder <NUM>.

The viewing means <NUM> comprise a mirror <NUM> that is inclined at <NUM>° with respect to the main axis A1 and that allows the image of the ophthalmic lens <NUM> to be redirected toward the objective <NUM> of a digital video camera <NUM>. This mirror <NUM> allows the centering-blocking apparatus <NUM> to be made more compact.

The digital video camera <NUM> is then designed to acquire an image of the ophthalmic lens <NUM> and to transmit it to a viewing screen <NUM> that is oriented toward the face of the optician. This viewing screen <NUM> may be of any kind (for instance LCD, TFT. It is preferably mounted onto the chassis <NUM> but it could be remoted from it.

Thus, the optician may observe in real-time on this viewing screen <NUM> the image of the ophthalmic lens <NUM>, in which the centering markings <NUM> provided on the lens clearly appear.

The centering-blocking apparatus also comprises a processing unit programmed to help the optician in centering the ophthalmic lens <NUM>.

To this end, the processing unit comprises a central processing unit (CPU), a memory and input/output components.

Thanks to its memory, the processing unit stores information used in the process described below. It stores in particular a computer application, consisting of computer programs comprising instructions, the execution of which allowing the implementation by the processing unit of the method described below.

This processing unit is connected to the viewing screen <NUM> so as to display a reticle superimposed to the images acquired by the camera <NUM>.

A reticle is defined as a centering target or as a fixed coordinate system that indicates the position of the blocking accessory <NUM>.

According to the invention, this reticle comprises two coaxial and parallel outlines <NUM>, <NUM>.

Each outline is preferably a line (a curve or a succession of segments) extending along a closed contour.

These outlines <NUM>, <NUM> are parallel in the sense in that the shortest distance between these two outlines is constant in any point all along the closed contour.

In practice, the outer outline <NUM> is the image of the inner outline <NUM> after a homothety.

Because in the embodiment shown in <FIG> the centering markings <NUM> comprise patterns distributed along concentric circles, each outline <NUM>, <NUM> here has a circular shape.

In a variant where the centering markings would comprise patterns distributed along concentric squares, each outline <NUM>, <NUM> would have a square shape.

These outlines <NUM>, <NUM> are displayed on the viewing screen <NUM> in the form of solid lines, but they could be displayed in the form of dotted lines or dashed lines.

These outlines extend along closed contours, but they could also be opened on a part of their contour.

It could be envisaged that the outlines have a size that cannot be changed. But in a preferred embodiment, the size of at least one of the outlines <NUM>, <NUM> is modifiable. Here the size of both outlines are modifiable.

This is preferable for the following reasons.

The size of the centering markings <NUM> displayed on the viewing screen <NUM> can vary because of scale modifications due to the lens power; so, depending on the lens spherical power, the distance between the outlines can change.

Moreover, lenses of different brands may show centering markings having different sizes, that is why it is advantageous to enable the size of the outlines to be scalable.

Here, the radius R1 of the inner outline <NUM> is adjustable and the distance D1 between the two outlines <NUM>, <NUM> is also modifiable.

Thanks to this, the two outlines <NUM>, <NUM> can be sized so that:.

To this end, the distance D1 between the two outlines <NUM>, <NUM> has to be adjusted so as to be comprised between once and twice the diameter of the engraved microlenses.

In this position, the optician is sure to have well centered the lens relative to the blocking accessory <NUM>.

In a first embodiment, the apparatus <NUM> comprises an HMI (Human-Machine Interface) enabling the optician to manually modify the sizes of the outlines <NUM>, <NUM> displayed on the viewing screen <NUM>.

This HMI can be formed by the screen if the latter is a touch screen. In this embodiment, two buttons associated to each outline are displayed, one for increasing the size of the associated outline and the second to decrease its size.

In a second embodiment, the processing means are programmed to:.

More specifically, the processing means are programmed to determine in a first step, the shape and the position of each centering marking <NUM>.

Then, they determine if some of the centering markings are distributed along a closed contour.

If it is not the case, a cross-shape reticle is displayed on the screen. The exact shape of this reticle depends on the shape of the centering markings. In other words, the shape of the reticle depends on the lens kind:.

If it is the case, the processing means determine the shape of the detected closed contour (here, this shape is circular). Then, they determine the mean diameter of one of the detected circles along which markings are distributed, and the diameters of these markings. Finally, they display on the screen two outlines <NUM>, <NUM> adapted to the shapes of the centering markings.

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

To center and then block the ophthalmic lens <NUM>, the centering-blocking apparatus <NUM> is used by the optician in the following way.

In a first step, the optician loads a blocking accessory <NUM> on the vertical shaft.

In a second step, the optician deposits the ophthalmic lens <NUM> on the upper end <NUM> of the holder <NUM>, in such a way that the convex front face of the lens bears against this holder <NUM>.

At this step, the camera <NUM> acquires images of the lens and these images are displayed on the viewing screen <NUM>. These images are displayed together with the two outlines <NUM>, <NUM>.

In the second embodiment, the sizes and shapes of the two outlines <NUM>, <NUM> are automatically modified to be adapted to the shape of the centering markings <NUM>.

In a third step, the optician manually moves the ophthalmic lens transversely, i.e. by sliding it over the holder <NUM>, until the ophthalmic lens <NUM> is placed on the axis of the blocking accessory <NUM>. To do this, the optician observes the images of the ophthalmic lens <NUM> on the viewing screen <NUM>, which images are displayed in superposition with the outlines <NUM>, <NUM>. The optician then seeks in this step to place the two outlines <NUM>, <NUM> on each side of a single circle of centering markings <NUM>.

At this step, in the first embodiment, the sizes of the two outlines can be manually modified by the optician in order to achieve this aim.

Once this position has been reached, the optician presses the ophthalmic lens <NUM> downward, while taking care not to move it transversely, so as to lower the holder <NUM>. This operation allows the lens to bear against a double-sided self-adhesive provided on the blocking accessory <NUM>. In this way, the latter automatically bonds to the lens, in a desired position (with a precision better than half a millimeter).

The present invention is in no way limited to the embodiment described and shown.

In particular, it would be possible to automate the blocking operation, by equipping the holder with a pneumatic or mechanical maneuvering mechanism, and by equipping the centering-blocking apparatus with electronic means for controlling this maneuvering mechanism.

This invention also applies to an automatic blocking system (having a motorized arm that can deposit the blocking accessory to a specific point of the lens and having centering means helping the optician with the camera's help to manually position the lens taking into account this blocking point). According to another variant of the invention, the holder could take a different form from that shown in the figures. It could thus take the form of a tripod mounted so as to be able to slide on the chassis in a plane orthogonal to the main axis A1.

Claim 1:
A centering apparatus (<NUM>) including:
- a chassis (<NUM>),
- a holder (<NUM>) mounted on the chassis (<NUM>), which is suitable for receiving an ophthalmic lens (<NUM>), and
- centering means (<NUM>) mounted on the chassis (<NUM>), which include:
• a camera (<NUM>) for acquiring images of the ophthalmic lens (<NUM>) when received on the holder (<NUM>), and
• a screen (<NUM>) for displaying the images acquired by the camera (<NUM>) and a centering target superimposed onto said images,
characterized in that said centering target comprises two coaxial and parallel outlines (<NUM>, <NUM>), and wherein the size of at least one outline (<NUM>, <NUM>) is modifiable so that the distance between the outlines (<NUM>, <NUM>) is adjustable.