Patent Description:
When a user has been prescribed spectacle lenses with a new correction by an eye care professional, he usually selects a spectacle frame and associated spectacle lenses and wants to get his new eyeglasses if possible overnight.

However, manufacturing of optical elements like spectacle lenses has become more and more complex and the user has also a large amount of choices for example for the coatings applied to the lenses giving additional functions to the spectacle lenses.

Indeed, after grinding and polishing operations in order to shape the spectacle lenses to get the prescribed optical correction power of the optical element, specific treatments may be applied to the lenses according to the wishes of the user in order to enhance for example the vision comfort of the user and to protect the spectacle lenses against aggressions like for example scratches, dust and soiling materials.

Therefore, after grinding and polishing, several coatings are generally applied to the spectacle lenses like for example a hard coat, anti-reflective coatings or coatings with anti-soiling properties.

Indeed, most of nowadays manufactured spectacle lenses have an anti-reflective coating on both sides of their faces which provide to users an enhanced visual comfort, less fatigue and beautify the appearance of the user. In addition, anti-reflective coating increases the contrast resulting in a better sight of the user in particular when car driving.

Such anti-reflective coating is generally carried out in a coating station known in the state of the art as "box coater".

The execution of such an antireflection treatment involves subjecting optical elements or ophthalmic lens blanks to deposition of a stack of dielectrics under vacuum in an enclosure or chamber suitable for this purpose.

However, application of these coatings needs a perfect clean surface of the spectacle lenses. If this is not the case, the coatings applied may show defects and may peel off after a short period of time.

Therefore after polishing and/or grinding of the spectacle lenses, the latter are thoroughly cleaned once before being charged for example in a spin coater for application of a hard coat and a subsequent AR coating.

The applicant has observed that such a thorough cleaning of the optical elements might not be sufficient. Indeed, during polishing, the temperature of the optical elements raises and the polishing agent, which might be chemically active, in particular when exposed to a raised temperature of the optical element, may affect more in depth the surface to be coated later, in particular the longer the optical element stays in contact with the polishing agent.

This problem has also been observed especially when after polishing and/or grinding, the optical elements stay in a waiting loop before further treatment for example in a spin coater.

Therefore one object of the present invention is to improve the cleaning of the optical elements.

Nowadays, during nearly all steps of spectacles manufacturing, a human operator is involved to charge and discharge the optical elements to be processed in the relevant processing stations. The optical elements are charged and discharged between a tray containing a print out of the features of the future spectacle lenses and the processing station like a polishing station, a spin coating station, a box coater etc..

As consequence, although such operators are generally quite well trained, fatigue, stress or inattention may provoke errors in handling the different jobs of spectacle lenses leading to extended processing times or even optical elements to be scrapped.

Another object of the present invention concerns the automation of the whole spectacle manufacturing process. However, automation also implies that lenses may stay in a waiting loop for a certain time, for example for optimizing batches to be treated in a box coater or in case of process jam.

<CIT> discloses an opaque adhesive which can be used to secure the convex surface of a lens blank to a lens blocking piece.

From <CIT> there is known a method for manufacturing an optical element according to a prescription comprising the following steps: providing a combination of a block piece and a lens blank having a first face and a second face opposite to the first face, the lens blank being blocked with the first face on the block piece, surfacing and polishing the second face of the lens blank, cleaning the lens blank, hard coating the second face of said lens blank, degassing the lens blank, applying an AR-coating, deblocking the processed lens blank from said block piece. From <CIT> there is also known a manufacturing facility for manufacturing an optical element according to a prescription comprising: a first station configured for surfacing and polishing a second face of a lens blank blocked with its first face opposite to the second face on a block piece and a second station configured for hard coating the second face of the lens blank, means for degassing the lens blank, means for applying an AR-coating and a third station for deblocking the processed lens blank from said block piece for obtaining the optical element.

The present invention proposes a method for manufacturing optical elements according to a prescription where cleaning is improved.

To this extent, the present invention proposes a method for manufacturing an optical element according to a prescription as defined in claim <NUM>.

Thanks to the pre-cleaning step just after polishing / grinding, the polished optical element may be put on hold without problem for a certain time and even without further protection. In addition, the action of the polishing agent on the optical element is largely limited.

The method for manufacturing spectacle lenses according to a prescription according to the invention may comprise one or several of the following features taken alone or in combination:
According to one aspect, the lens blank is a semi-finished lens blank, the first face of the semi-finished lens blank presenting a hard coat and/or an AR coating.

The pre-cleaning step comprises for example a first washing step carried out with a warm cleaning fluid having a temperature comprised between <NUM>-<NUM>, preferentially between <NUM> and <NUM>.

The cleaning fluid consists for example of warm water free of additive chemical agents.

According to a further aspect, the water presents a hardness comprised between <NUM>-<NUM>° d. , in particular <NUM>-<NUM>° d.

During the first washing step, a rotating cleaning jet of cleaning fluid and pressured gas may be projected onto the surfaced and polished second face of the lens blank, the combination of the lens blank and the block piece rotating around its center axis during the first washing step.

The pre-cleaning step may further comprise a rinsing step with soft water having a hardness inferior to <NUM>° d. , in particular equal to <NUM>° d. carried out after said first washing step.

The pre-cleaning step may comprise further a subsequent first drying step carried out after the last of the first washing step or the rinsing step.

Said first drying step can comprise projection of a pressurized gas jet on the washed second face of the lens blank, the gas jet being centered with respect to the center axis of the lens blank.

According to a further aspect, after the first washing step and before the first drying step, the combination of the block piece and the lens blank is disposed in a transportation tray and the first drying step is carried out in a drying chamber separate from a washing chamber where the first washing step is carried out.

The pre-cleaned lens blanks may be disposed in a transportation tray and can be put on hold in a waiting position for further treatment, in particular if necessary.

According to another aspect, the deep cleaning step comprises a second washing step with warm cleaning fluid having a temperature comprised between <NUM>-<NUM>, preferentially <NUM>.

The warm cleaning fluid may consist of warm water which is free of additive chemical agents.

During the second washing step, a least a second and a third static cleaning jets of cleaning fluid and pressured gas can be projected respectively onto the surfaced and polished second face of the lens blank and onto the block piece, the lens blank being hold through at least three gripper arms and rotating around its center axis.

The static cleaning jets are for example projected under a pressure comprised between <NUM>-<NUM> bars, in particular <NUM> bars.

The deep cleaning step can comprise a drying step of the block piece carried out after the second washing step.

The deep cleaning step may further comprise a third washing step with warm deionized water having a temperature comprised between <NUM>-<NUM>, preferentially <NUM>, under high pressure comprised between 150bars and 200bars, in particular 180bars.

During the third washing step, the lens blank can rotate around its center axis and a fourth cleaning jet carrying out a swiveling or a translational movement may be projected towards the second face of the lens blank.

The invention also relates to a manufacturing facility for manufacturing an optical element according to a prescription as defined in claim <NUM>.

According to one aspect, the manufacturing facility further comprises a transfer system for conveyance of said combination of a block piece and a lens blank blocked with its first face on the block piece between the processing stations.

The first station comprises for example an automatic charger of said combination of a block piece and a lens blank on a transportation tray. The transfer system may comprise several second stations and a conveyor loop for supplying said second stations with lens blanks blocked on block pieces to be hard coated.

Other advantages and characteristics will appear with the reading of the description of the following figures:.

The embodiment(s) in the following description are only to be considered as examples.

In the present description, the terms "upstream" and "downstream" are used according the following meaning: a first station for a certain processing operation of an optical element is placed upstream with respect to a second station when the optical element undergoes first the operation in the first station and then another operation in the second station.

And a first station for processing a certain processing operation of an optical element is placed downstream with respect to a second station when the optical element undergoes first the operation in the second station and then another operation in the first station.

By "lens surfacing", it is understood in particular polishing, grinding or fine grinding and the overall object is to yield a finished spectacle lens so that the curvature of the first (in this instance convex) face cx and the curvature of the machined second (in this instance concave) face cc cooperate to yield desired optical properties according to a prescription of the user of the spectacle lenses.

In the figures may be shown a reference triad X-Y-Z, where X and Y are two horizontal axes perpendicular to each other and Z is a vertical axis perpendicular to X and Y.

In the present description, the term "semi-finished lens blank" is used. It is understood that the "semi-finished lens blank" is one of the starting points of the present method and will be transformed throughout different operations to achieve a finished lens blank or simply a finished lens. The term of "semi-finished lens blank" may be used even at the end of the operation in order to be sure to designate always the same objet that is transformed through the manufacturing process.

In <FIG> is shown an optical element <NUM> which is for example a lens blank, in particular a semi-finished lens blank SFB which is fixed to a block piece B.

A semi- finished lens blank SFB comprises for example a first face or front face cx, a second face also named back face cc opposite said first face cx, and an edge E between the first face cx and the second face cc.

The first face cx possesses a final curvature (not shown in the drawing) and is already coated, starting from a substrate comprised of, e.g., mineral glass, polycarbonate, PMMA, CR <NUM>, Trivex<®>, HI index, etc., as the case may be, with a standard hard coating HC, a standard antireflection coating AR on top of the hard coating HC, a standard top coating TC on top of the antireflection coating AR, and a special temporary grip coating GC on top of the top coating TC.

As is known per se, the antireflection coating AR comprises for example a stack of alternating antireflection layers of high index HIL and low index LIL with an outermost, in <FIG> lowest layer. The top coating TC is selected from a group comprising hydrophobic, oleophobic and dirt repelling coatings, as known.

The thickness of the temporary grip coating GC may range from <NUM> to <NUM>, preferably from <NUM> to <NUM>, and more preferably from <NUM> to <NUM>, in particular <NUM>.

Further, in <FIG> reference sign CB designates a combination of the above lens blank SFB and a block piece B for holding the lens blank SFB for processing thereof as will be described here beneath.

As to the structure and function of a currently preferred block piece B explicit reference is being made at this point to document <CIT> of the present applicant.

Such block piece B, which can be used in thin film coating processes under vacuum conditions, typically has a basic body made from a plastic material, with a workpiece mounting face F for attachment of the lens blank SFB with the aid of a blocking material M on one side, and a clamping portion C on the other side which is configured to be grasped by an elastic blocking means or robotized units (detailed later on in the description) during transport or different processing steps. Clamping portion C has a cylindrical portion CY and a frustoconical shape (truncated cone) CF.

Generally speaking, during lens processing, the lens blank SFB is blocked on the basic body of the block piece B in a machine or apparatus for processing of the lens blank SFB, and to provide in particular for reliable and secure mounting to the processing equipment throughout the whole process while avoiding damage and/or deformation to the lens blank SFB.

As far as a presently preferred blocking material M is concerned, which is applied directly onto the "temporary grip coating GC of the lens blank SFB" or to the mounting face F of the block piece B and preferably comprises an adhesive curable by UV or visible light that is liquid in an un-polymerized state, explicit reference is being made at this point to document <CIT> of the present applicant. In order to enhance the bonding effect, the workpiece mounting face F of the block piece B may be plasma treated prior to applying the blocking material M onto the workpiece mounting face F.

During manufacturing of spectacle lenses, the second face cc of the lens blank SFB needs to be processed.

However, in alternative embodiments, one may consider that second face cc possesses a final curvature and is already coated. In this case the lens blank SFB is fixed and blocked with its second face cc on the block piece B and the first face cx shall be processed.

In <FIG> is illustrated an example of a flowchart of a method for manufacturing an optical element <NUM> according to a prescription and in <FIG> is shown in a schematic way a possible embodiment of a related manufacturing facility <NUM> configured to carry out such a method.

Hereafter, the method according the invention is described step by step in following also different processing stations in the manufacturing facility <NUM>.

In a first step S1, there is provided a combination CB of block piece B and the lens blank SFB blocked with its first face cx on the block piece B.

In this case, for example two combinations CB relating to one prescription of one user may be provided in an associated transportation tray <NUM>. The transportation tray <NUM> as well as the two combinations CB may be identified and associated to specific processing jobs to each of the lens blanks SFB in the management system <NUM> (see in <FIG>) which is represents a control system with implemented control functions/software of manufacturing facility <NUM>, the specific processing jobs corresponding the prescription of the spectacle lenses to be manufactured starting from the lens blanks SFB.

Each transportation tray <NUM> contains in general two lens blanks to be processed and may be specifically identified for example by a tray identification tag or a lens identification tag. Such a tray identification tag or lens identification tag may be a RFID tag or a barcode /matrix code. Different tag readers and/or writers are for example disposed in particular along conveyors <NUM>, <NUM>-L and at the entry and/or exit of a specific processing station. Such identification tags allow localizing and directing the transportation trays <NUM> within the manufacturing facility <NUM>, as well as monitoring and tracking of the process operations. Thus, the management system <NUM> is configured to route the transportation trays <NUM> between the different processing stations and to monitor and track the processing operations.

Furthermore, each identification tag is associated with job data for processing the lens blanks contained in the associated transportation tray <NUM> in order to obtain final lenses that are in conformity with a prescription and wishes of a user, in particular the prescribed optical correction power and specific treatments applied to the lenses according to the wishes of the user in order to enhance for example the vision comfort of the user and to protect the spectacle lenses against aggressions like for example scratches, dust and soiling materials.

For example, one data matrix code or an RFID tag may be fixed to the transportation tray <NUM>. Or one data matrix code or a RFID tag may be fixed to the clamping portions C of the block pieces B. An RFID tag may be mounted within an internal cavity of the block piece B, which is for example aligned with the optical axis OA. This allows the management system <NUM> at any time to locate the lens blanks SFB, to know the status of the process operations that have been already realized and that need to be realized, and to convey the lens blanks SFB to the next, if applicable, "available" processing station. At the entry of a specific processing station, a lens blank SFB may be refused if a specific processing operation was not carried out. At the output of a specific processing station, data may be generated and associated with the identification tag or written into such an identification tag (in particular a RFID tag), when a processing operation has been successfully been carried out.

Other identifications means may be employed as well.

Then the combinations CB of block piece B and the lens blank SFB are conveyed to a first station <NUM> which is a polishing and pre-cleaning station, configured for carry out.

The transfer between sub-unit <NUM>-<NUM> and <NUM>-<NUM> may be carried out by a robotized unit <NUM> schematically represented in <FIG>.

The transfer between sub-unit <NUM>-<NUM> and <NUM>-<NUM> may be carried out by a robotized unit <NUM> configured to dispose the combination CB of the pre-cleaned lens blank SFB and the block piece B in a tray <NUM> that is able to travel on conveyor <NUM> to sub-unit <NUM>-<NUM> as schematically represented in <FIG>.

The robotized units <NUM> or <NUM> may be qualified as automatic chargers / unchargers and comprise for example a gripping arm to grasp the block piece B and to transfer the combination CB of the pre-cleaned lens blank SFB and the block piece B for example in a processing station or out of the latter. This allows that the lens blank SFB is never touched during processing allowing high process safety, process speed and quality.

The polishing and surfacing sub-unit <NUM>-<NUM> will not be described in detail. An example of a possible polishing sub-unit <NUM>-<NUM> is disclosed in <CIT> in the name of the present applicant.

An example of a first washing station in pre-cleaning sub-unit <NUM>-<NUM> which is a first washing station <NUM>, is presented in <FIG>.

As already stated first washing station <NUM> corresponds to sub-unit <NUM>-<NUM> and is integrated in the first station <NUM>. In an alternative, the first washing station may also be a stand-alone unit disposed downwards a polishing station.

The washing station <NUM> comprises two washing containers <NUM> in order that two combinations CB may be pre-cleaned at the same time, but separately.

Each washing container <NUM> comprises a rotating projection nozzle <NUM> disposed on the bottom <NUM> of the washing container <NUM> and projecting upwards toward the top.

On the top <NUM> of the washing container <NUM> is installed a rotatable holder <NUM> gripping the block piece B in a manner that the combination CB of lens blank SFB is hanging top down in face of the rotating projection nozzle <NUM>.

During first washing step S3-W, a rotating cleaning jet <NUM> of a warm cleaning fluid, in particular warm water and pressured gas is projected onto the surfaced and polished second face cc of the lens blank SFB.

The first washing step S3-W is carried out with a warm cleaning fluid having a temperature comprised between <NUM>-<NUM>, preferentially between <NUM> and <NUM>. The warm water is free of additive chemical agents. Warm water has a better washing efficiency. The selected temperature range for the warm water is high enough to get a good washing efficiency and in particular good evacuation of any polish particles and slurry on the second face cc but not too high for causing damages to the first face cx of the lens blank SFB or to the glue for blocking the lens blank SFB on the block piece B.

In order to obtain a good washing efficiency, the water presents a hardness comprised between <NUM>-<NUM>° d. = deutsche Härte = German hardness ; <NUM>°d. = <NUM>,<NUM> mmol/l of alkaline mineral ions), in particular <NUM>-<NUM>° d.

After this first washing step S3-W, a rinsing step S3-R is realized with soft water having a hardness inferior to <NUM>° d. , in particular equal to <NUM>° d. The soft water is for example at room temperature and needs not to be heated. This rinsing step S3-R is optional and in general shorter than the first washing step S3-W, for example <NUM>-<NUM> for the first washing step S3-W and about <NUM> for the rinsing step S3-R.

Once washed, the top <NUM> of the washing containers <NUM> turn around about <NUM>° and robotized unit <NUM> places the combinations CB of the lens blank SFB and block piece B in an associated transport tray <NUM> to convey them on conveyor <NUM> to sub-unit <NUM>-<NUM> which is depicted more in detail in <FIG> as drying station <NUM>. In the transportation tray <NUM>, the combination CB of lens blank SFB and block piece B are placed top up, meaning that the block piece B cooperates with the base plate of the transportation tray <NUM>, the second face cc being directed upwards.

The drying station <NUM> (which corresponds to the sub-unit <NUM>-<NUM> when integrated into the first station <NUM>), comprises a drying chamber <NUM> that is traversed by the conveyor <NUM>.

On the top plate <NUM> of the drying chamber are installed two jet nozzles <NUM> for projection of a pressurized gas jet on the washed second face cc of the lens blank SFB. For drying, the transportation tray <NUM> is stopped in the drying chamber <NUM> in order that the gas jets are centered with respect to the center axis of the lens blanks SFB. The pressurized gas is for example filtered air according to the international standard ISO <NUM>-<NUM>:<NUM> [<NUM>:<NUM>:<NUM>] for inert gases and containing particles of less than <NUM>. The applied pressure is between <NUM>-<NUM> bars, in particular <NUM> bars.

When coming out of the drying station <NUM>, the second face cc of the lens blank SFB is sufficiently cleaned in order that polish agents and slurry are removed and cannot alter anymore the second face cc of the lens blank SFB.

The second face cc is therefore clean enough to be put on hold if necessary, for example in case processes jam occurs or in a waiting position of a transportation system, i.e. for optimizing and grouping several processing jobs.

After this pre-cleaning including the first washing step S3 and the drying step S4, the combination CB of the lens blank SFB and the block piece B is conveyed, disposed in its associated tray <NUM>, to a conveyor loop <NUM>-L.

In addition, in case the transportation tray <NUM> or the block piece B are equipped with an identification tag, data may be generated and associated with the specific identification tag that the pre-cleaning step has been carried out successfully for the concerned combination CB of the lens blank SFB and the block piece B.

Connected to this conveyor loop <NUM>-L are for example three second stations <NUM> configured for deep-cleaning the second face of a lens blank SFB blocked with its front side on a block piece B and for hard coating the second face cc.

The second station <NUM> is for spin coating in order to apply a hard coat on the second face cc of the lens SFB including two upstream located washing stations for deep-cleaning the surface of the second face cc.

In case the transportation tray <NUM> or the block piece B presented at the entry of the second station <NUM> are equipped with an identification tag which is not associated with data stating that the pre-cleaning step has been carried out successfully for the concerned combination CB of the lens blank SFB and the block piece B, such transportation tray <NUM> or combination CB of the lens blank SFB may be refused or sorted out by the management system <NUM> or the second station <NUM> itself.

One of the second stations <NUM> is detailed in <FIG> in having three sub-units: sub-unit <NUM>-<NUM> (a second washing station <NUM>), sub-unit <NUM>-<NUM> (a third washing station <NUM>) and sub-unit <NUM>-<NUM> which is a spin coating unit.

The second washing station <NUM> (sub-unit <NUM>-<NUM>) is in particular dedicated to clean the block piece B of the combination CB. This is especially important to ensure that the same block piece B can be used several times. This cleaning step prevents severe accumulation of residual polishing slurry and therefore contamination in downstream vacuum processes.

In the second washing station <NUM>, the combination CB of the lens blank SFB and the block piece B is mounted on a rotational holder <NUM> having on a rotating base <NUM> three upwards directed and pivoting gripper arms <NUM> that enter into contact with the clamping portion C of the block piece B. The pivoting gripper arms <NUM> are configured to pivot inwards for centering and holding the combination CB in order that the optical axis is aligned with the rotation axis of the rotating base <NUM>.

Several static projection nozzles <NUM> and <NUM> are mounted on a support structure <NUM> having a general circular form with its center aligned with the rotation axis of the rotating base <NUM>. Static projection nozzles <NUM> are directed from above to the second face cc of the lens blank SFB and static projection nozzles <NUM> (one of the two nozzles is slightly hidden on the figure) are directed from beneath to the block piece B of the combination CB.

A second washing step S5-W, carried out in the second washing station <NUM>, is realized with a warm cleaning fluid consisting for example of warm water and having a temperature comprised between <NUM>-<NUM>, preferentially <NUM> which is for example free of additive chemical agents. The cleaning fluid like warm water may contain an alkali soap additive having a PH value comprised between <NUM>-<NUM>, in particular equal to <NUM>,<NUM> +/-<NUM>. Such alkali soap additive allows improving adhesion of the subsequent coatings.

Pressurized gas, for example filtered air is added in the water/cleaning jets <NUM>, <NUM> in order increase its energy and improve the cleaning impact and enhance cleaning efficiency.

During this second washing step S5-W, a least one, but in the present example several second <NUM> and third <NUM> static cleanings jet of warm cleaning fluid like warm water and pressured gas are projected respectively by the static projection nozzles <NUM> and <NUM> onto the surfaced and polished second face cc of the lens blank SFB and onto the block piece B while the lens blank SFB is hold through at least three gripper arms <NUM> in contact with the block piece B and rotating around its center axis. The static cleaning jets <NUM>, <NUM> are projected under a pressure comprised between <NUM>-<NUM> bars, in particular <NUM> bars.

A static drying nozzle <NUM> (mounted in front of one of the projection nozzles <NUM> and hiding the latter) is also mounted on support structure <NUM>. Static drying nozzle <NUM> is directed, like static projection nozzle <NUM>, from beneath to the block piece B of the combination CB. This ensures the dryness of the block piece B which is necessary before vacuum coating.

Thus, after the second washing step S5-W, a drying step S5-D of the block piece B is realized by projecting pressured drying gas like filtered air through drying nozzle <NUM> in direction of the rotating combination CB, in particular in direction of the rotating block piece B.

A third washing step S6 is applied and the combination CB of lens blank SFB and block piece B is transferred automatically with a robotized unit (not shown) to sub-unit <NUM>-<NUM> corresponding to the third washing station <NUM>.

In <FIG> is shown an, example of a third washing station <NUM> comprising an optical element holder <NUM> for holding the optical element <NUM> and a first drive <NUM> for rotating the optical element holder <NUM> around a rotation axis "7A", the rotation axis "7A" coinciding with the optical axis "OA" of the optical element <NUM> when held by the optical element holder <NUM>.

The optical element holder <NUM> is configured to cooperate with the clamping portion C of the block piece B.

The first drive <NUM> comprises for example a not shown electrical motor. Reference <NUM> designates the rotational guide for a vacuum suction unit for holding the block piece B and that is coupled via a not shown magnetic coupling to the electrical motor.

In operation, the rotational speed of the optical element is comprised between <NUM>-<NUM> revolutions /minute, in particular <NUM> RPM.

The third washing station <NUM> further comprises a cleaning nozzle <NUM> configured to project a cleaning jet <NUM> of a cleaning liquid, in particular a cleaning liquid like water towards the optical element <NUM> and may be disposed beneath the optical element holder <NUM> (<FIG>).

Thus, the cleaning jet <NUM> is projected in a general upward direction along the vertical axis z.

As shown in particular in <FIG>, the cleaning nozzle <NUM> is mounted on a second drive <NUM> for moving the cleaning nozzle <NUM> in order that the cleaning jet <NUM> impacts successively different locations on the optical element <NUM> during cleaning operation.

More specifically, the second drive <NUM> is connected to a controller unit <NUM> and is configured to apply a swivel movement (arrows <NUM> on <FIG>) to the cleaning nozzle <NUM>. Controller unit <NUM> comprises for example one or more processors, memories containing a specific program or software and components to communicate in a network allowing for example to receive instructions, in particular job data.

Thanks to the rotational movement of the optical element holder <NUM> and the back and forth swiveling movement of the cleaning nozzle <NUM>, the cleaning jet <NUM> impacts successively all locations on the optical element <NUM> during cleaning operation, developing thus the best cleaning impact. The amplitude and frequency of the swivel movement is controlled by controller unit <NUM>. The swivel movement of the cleaning nozzle is in particular controlled in a way that it moves only to the very circumference of the optical element <NUM> and does not exceed its circumference. In other words, the swivel movement is depending on the individual geometry of the optical element (like the diameter) and is adjusted automatically for example according to job data related to the optical element <NUM>. This leads to faster processing and enhanced throughput of the third washing station <NUM>.

Typically, projection of the cleaning liquid only starts after start of rotation of the optical element <NUM> and the start or zero position of the cleaning nozzle <NUM> is off the center of the optical element <NUM> in order to avoid damage due to the high pressure cleaning jet <NUM> which might occur because the center of the optical element <NUM> can be considered as nearly static.

As an example for application of a swiveling movement to the cleaning nozzle <NUM>, the second drive <NUM> comprises a swiveling axis <NUM> orientated perpendicular to the rotation axis "7A" of the optical element holder <NUM> and the cleaning nozzle <NUM> is centered with respect to the rotation axis "7A" of the optical element holder <NUM>.

Preferentially, the swiveling axis <NUM> might be hollow to serve at the same time as feeding pipe for the cleaning liquid.

The optical element holder <NUM> and the cleaning nozzle <NUM> are housed in a cleaning chamber <NUM>.

In a bottom part of the cleaning chamber <NUM> is disposed a suction pipe <NUM> for aspiration or suction and evacuation of the cleaning liquid after having impacted the optical element <NUM> for cleaning. To this extent, an exhaust fan <NUM> is connected to the suction pipe <NUM>. A constant exhaust or suction prevents defects in the hard coat caused by water droplets which can re-deposit on the surface of the optical element <NUM> if a foggy environment in the cleaning chamber <NUM> is present.

The cleaning chamber <NUM> comprises a bottom cylinder <NUM> supporting the cleaning nozzle <NUM> and a separable lid <NUM> supporting the optical element holder <NUM>.

As can be seen on <FIG>, the swiveling axis <NUM> traverses the bottom cylinder <NUM> and is supported by two bearings <NUM> mounted in the wall of the bottom cylinder <NUM>.

One first end <NUM> of the swiveling axis <NUM> comprises a connector <NUM> for connecting the hollow swiveling axis <NUM> to a pump unit <NUM> (<FIG>).

The other second end <NUM> of the swiveling axis <NUM> is connected to the second drive <NUM>.

In the present case, the second drive <NUM> comprises an electrical motor <NUM> connected to and controlled by the controller unit <NUM>. The electrical motor has an output shaft <NUM> which is connected by a belt <NUM> to a disk <NUM> fixed to the second end <NUM> of the swiveling axis <NUM>.

The third washing station <NUM> further comprises a separate drying nozzle <NUM> which is also mounted on the second drive <NUM> and is configured to project, after cleaning, a drying jet 749A of a drying gas (for example filtered air) towards the optical element <NUM>.

The drying nozzle <NUM> is for example a tube allowing to limit divergence of the drying jet 749A and having an inner diameter of less than <NUM> to which can be applied pressurized drying gas of about <NUM>-<NUM> bars, in particular <NUM>-<NUM> bars. The pressurized gas is for example filtered air according to the international standard ISO <NUM>-<NUM>:<NUM> [<NUM>:<NUM>:<NUM>] for inert gases and containing particles of less than <NUM>.

The drying nozzle <NUM> is coupled and fixed to the cleaning nozzle <NUM>, slightly offset with respect to the latter, and points in a direction parallel to said cleaning nozzle <NUM>.

The second drive <NUM> is configured for moving the drying nozzle <NUM> in order that the drying jet 749A impacts successively different locations on the optical element <NUM> during drying operation.

As for the cleaning, the second drive <NUM> is configured to apply a swivel movement (arrows <NUM> on <FIG>) to the drying nozzle <NUM>.

Thanks to the rotational movement of the optical element holder <NUM> and the back and forth swiveling movement of the drying nozzle <NUM>, the drying jet 749A impacts successively all locations on the optical element <NUM> during drying operation, developing thus the best drying impact.

Thus, after the third washing step S6, the optical element <NUM> can be dried efficiently due to its rotation on the optical element holder <NUM> and drying jet 749A. The swivel movement of the drying nozzle <NUM> is in particular controlled in the same way as the cleaning nozzle <NUM> so that it moves only to the very circumference of the optical element <NUM> and does not exceed the circumference of the latter. In other words, the swivel movement is depending on the individual geometry of the optical element <NUM> and is adjusted automatically according to job data related to the optical element <NUM>.

This feature increases the product yield rate because it avoids potential re-deposition of water droplets from the walls of the cleaning chamber <NUM>. Indeed, if the drying jet exceeds the circumference of the optical element <NUM>, it is likely to hit the wet walls of the cleaning chamber <NUM> and may recontaminate the optical element <NUM> with cleaning liquid.

The cleaning liquid of the cleaning jet <NUM> comprises deionized water (DI water) from a deionized water tank <NUM> (<FIG>). A lens drying additive may be added to the deionized water. Such a lens drying additive may be of the family of alcohols.

The third washing station <NUM> may further comprise a heater <NUM> installed downstream the pump unit <NUM> for heating the deionized water, in particular to a temperature comprised between <NUM> and <NUM>, for example <NUM>.

The pump unit <NUM> comprises a piston operated pump unit <NUM>, in particular a pneumatic high pressure pump which is equipped with a stroke number monitoring unit <NUM>. Such a stroke number monitoring unit <NUM> may comprise an induction loop to measure the displacements of the piston in the piston operated pump unit <NUM>.

The working pressure and output of the piston operated pump unit for the cleaning jet is comprised between <NUM>-200bars, in particular about 180bars.

The stroke rate of the piston operated pump unit <NUM> is for example comprised between <NUM> and <NUM> strokes/min, in particular <NUM> strokes /min.

The stroke number monitoring unit <NUM> counts the number of strokes of the piston operated pump unit <NUM> in order to detect potential clogging of the cleaning nozzle <NUM> which would lead to high product rejection rates. This feature is especially helpful when running a fully automated manufacturing of optical elements <NUM>. Once the number of strokes is out of a defined range (for example +/- <NUM>% of a reference value), the third washing station <NUM> will stop processing and an operator will be prompted to maintain or change the cleaning nozzle <NUM>.

One understands that the here disclosed third washing station <NUM> allows a very efficient cleaning of optical elements <NUM> in order to prepare the surface of the optical element <NUM> to be hard coated.

As an example, the whole cleaning and drying cycle lasts only about <NUM>-<NUM>.

The optical elements <NUM> are then auto-loaded in particular when the optical element holder <NUM> is equipped with clamping means for cooperation with clamping portion C of the block piece B.

Then the combination CB of lens blank SFB and block piece B is transferred to sub-unit <NUM>-<NUM> which is a spin coating unit and where a spin coating step S7 for application of a hard coat is applied and cured on the second face cc of the lens blank SFB.

After spin-coating in sub-unit <NUM>-<NUM>, the coated lens blank SFB with the block piece B are transferred with a robotized unit <NUM> on a transportation tray <NUM> in order to be conveyed to a tunnel oven <NUM> for application of a degassing step S8. The transportation tray <NUM> used may be a new one and in this case the management system <NUM> of the manufacturing facility <NUM> will associate the transportation tray <NUM> to the combinations CB of lens blank SFB and block piece disposed in the transportation tray <NUM>.

After the tunnel oven <NUM> and degassing step S8, the blanks SFB blocked on block piece B are transferred to a vacuum box coater <NUM> for application of an anti-reflection coating (AR-coating) in step S9.

In <FIG>, three vacuum box coaters <NUM> are represented. The management system <NUM> of the manufacturing facility <NUM> is configured in order to group lens blanks SFB that need the same AR-coating.

To this extend, the transportation trays <NUM> are conveyed to a vacuum box coater <NUM> and uncharged by robotized units <NUM> which will load automatically sector elements of the vacuum box coaters <NUM> also designated as coating station with reference to <FIG>.

<FIG> shows a cross sectional view of an example of a coating station <NUM> (vacuum box coater <NUM> in <FIG>) for application in particular of an AR coating to the face cc of the lens blank SFB during an AR coating step S9.

The coating station <NUM> is disposed downstream the degassing tunnel oven <NUM>.

The coating station <NUM> comprises a vacuum chamber <NUM> that is connected to a vacuum pump system <NUM>. On the bottom of the vacuum chamber <NUM> is disposed a vaporization source <NUM>.

During coating, a not shown vaporization material is heated, for example by an electric heating device or an electron beam source in order to vaporize or sublimate the vaporization material (schematically shown by arrows <NUM>) that will be deposited on the optical elements <NUM>, in particular the face cc of the lens blank SFB.

The coating station <NUM> further comprises an optical elements holder device <NUM> which is hanging from the top wall <NUM> of the vacuum chamber <NUM> and is connected, through a rotation axis <NUM>, to a drive motor <NUM> configured to rotate (arrows <NUM>) the optical elements holder device <NUM>.

Rotation of the optical elements holder device <NUM> during coating ensures averaging spatial inhomogeneity of the vaporization cone during coating.

As can be seen on <FIG>, the optical elements holder device <NUM> comprises one or several metal sheet carrier(s) <NUM> having a plurality of holes <NUM>, such as circular holes, and presenting the shape of a dome or a part of a dome in order to put all optical elements <NUM> to the same distance with respect to the vaporization source <NUM>.

In <FIG> is shown in dotted lines a dome frame <NUM> configured to support four different metal sheet carriers <NUM>, only one of them is shown with having holes <NUM>.

As can be seen on <FIG>, the optical elements <NUM> are mounted in a releasable manner upside down in the optical elements holder device <NUM>. Thus in <FIG>, one can see the backside of the block piece B, the lens blank SFB pointing in direction towards the vaporization source <NUM>.

In order to allow easy mounting of the optical elements <NUM> blocked on the block piece B, an elastic blocking means <NUM> associated to each hole <NUM> is fixed to the metal sheet carrier <NUM>.

This can be seen more in detail in <FIG> which is a schematic view in cross section of a part of a metal sheet carrier <NUM> and an optical element <NUM> fixed on a block piece B.

According to this embodiment, the elastic blocking means <NUM> comprises an O-ring <NUM> of elastic material, like i.e. a fluoroelastomer like VITON (registered trademark) by the company DuPont.

A fluoroelastomer as elastic material has the advantage to withstand the vacuum conditions during coating and not to contaminate the coating process.

In order to mount the optical element <NUM> with its associated block piece B into a hole <NUM>, the robotized unit <NUM> only has to grasp or to pick up the block piece B on its lateral sides and to insert it by pushing along arrow <NUM> into the hole <NUM>. The movement to insert the block piece B into the hole <NUM> is quite simple so that there is no problem for a programmed robotized unit <NUM> to realize such mounting instead of a human operator.

As the internal diameter of the O-ring <NUM> is slightly smaller than the largest diameter of the clamping portion C, the O-ring <NUM> will be radially compressed and will hold the block piece B by friction regularly contacting the block piece B on all the circumference of the hole <NUM>. The O-ring <NUM> will then clamp the block piece B in a releasable manner and block the block piece B in a centered position such that the lens blank SFB is hold in a predetermined position for coating.

After AR-coating, the nearly finished lens blanks SFB are recharged by a robotized unit <NUM> in a transportation tray <NUM> and conveyed to a third station <NUM> configured to deblock with a water jet the lenses from the block piece B during a deblocking step S10. The thus processed lens blank SFB becomes the optical element <NUM> having the optical properties and functions according to the prescription and/or order of the end user.

As one may understand, the manufacturing facility <NUM> for manufacturing an optical element <NUM> according to a prescription allows a very efficient process that is less time consuming, enhancing the quality and nearly suppresses all possibilities of errors of human operators. In addition, the lens blank is never touched during all the processing steps.

Claim 1:
Method for manufacturing an optical element (<NUM>) according to a prescription comprising the following steps :
- providing (S1) a combination (CB) of a block piece (B) and a lens blank (SFB) having a first face (cx) and a second face (cc) opposite to the first face (cx), the lens blank (SFB) being blocked with the first face (cx) on the block piece (B),
- surfacing and polishing (S2) the second face (cc) of the lens blank (SFB),
- cleaning (S3-W/-R-S6) the lens blank (SFB),
- hard coating (S7) the second face (cc) of said lens blank (SFB),
- degassing (S8) the lens blank (SFB),
- applying (S9) an AR-coating (AR) in a vacuum box coater (<NUM>),
- deblocking (S10) the processed lens blank (SFB) from said block piece (B),
wherein said cleaning step comprises
- a pre-cleaning step (S3-S4) carried out in a first station (<NUM>) including a finishing drying step allowing the lens blank (SFB) to be put on hold, the pre-cleaning being applied after the polishing and is configured to remove polish agents and slurry, and
- a deep cleaning step(S5-W/-D-S6) carried out in a second station (<NUM>) prior to the hard coating step (HC), the deep cleaning being applied prior to the hard coating which is carried out in the second station (<NUM>).