APPARATUS FOR REMOVING AT LEAST ONE PORTION OF AT LEAST ONE COATING SYSTEM PRESENTING A MULTI-GLAZED WINDOW AND ASSOCIATED METHOD

Abstract

An apparatus for removing a portion of a coating system present in a multi-glazed window including: a decoating component to focus a laser source at a focus distance; two motors to move the decoating component along the X and Y axis; one optical system to detect on which interface the coating system is localized, and to estimate a distance between the decoating component and the detected interface; a third motor to control the position of the decoating component along a Z axis; and a displacement control unit of the third motor to displace the decoating component of a displacement distance equal to the difference between the estimated distance and said the distance in order to focus the decoating component on the detected interface.

Claims

1: An apparatus for removing at least one portion of at least one coating system present in a multi-glazed window comprising at least two glass panels alternatively separated by at least one interlayer, forming multiple interfaces (P1-P6); the apparatus comprising: a decoating means including a laser source and a lens array configured to focus the laser source at a focus distance (Fd); and two motors configured to move the decoating means along a plane (P), defined by a longitudinal axis X and a transversal axis Y; wherein the apparatus further comprises: one optical system configured to detect on which interface (P4) the coating system is localized, and to estimate a distance (Ed2) between the decoating means and the detected interface (P4); at least a third motor configured to control a position of the decoating means along a Z axis, orthogonal to the X and Y axis; a displacement control unit of the third motor configured to displace the decoating means of a displacement distance (Dd) equal to a difference between the estimated distance (Ed2) and the focus distance (Fd) in order to focus the decoating means on the detected interface (P4) of the at least one coating system.

2: The apparatus according to claim 1, wherein the apparatus further comprises: at least two fixing points configured to mount the apparatus on a first interface (P1) of the multi-glazed window; a support structure mounted on the at least two fixing points; a robot head mounted on the support structure movable by the two motors along the longitudinal axis X and the transversal axis Y relative to the support structure; and a shuttle, carrying the decoating means, mounted on the robot head movable by the third motor along the Z axis relative to the robot head.

3: The apparatus according to claim 2, wherein the optical system detects on which interface (P4) the coating system is localized by a near infrared unit comprising: at least one near infrared light source configured to emit an incident light (Icl) toward the multi-glazed window, and to generate a diffraction pattern (DifP) after refraction on the multi-glazed window; and at least one detector configured to measure an intensity of the light spots (Ils) of the diffraction pattern (DifP); wherein each light spot corresponds to an interface (P1-P6) in the multi-glazed window, and a spot of maximum intensity corresponds to the detected interface (P4) on which the coating system is localized.

4: The apparatus according to claim 3, wherein the near infrared unit is fixed relative to the support structure.

5: The apparatus according to claim 3, wherein the at least one near infrared light source is monochromatic with a wavelength between 700 and 1100 nm.

6: The apparatus according to claim 3, wherein the at least one detector of the near infrared unit corresponds to an array of photodiodes, a CMOS camera sensor or a 2D silicon detector.

7: The apparatus according to claim 3, wherein the estimation of a distance (Ed2) between the decoating means and the detected interface (P4) is obtained by a confocal unit comprising: at least one polychromatic light source configured to emit an incident light, punctual or in line, with several wavelengths toward the multi-glazed window, an optical element focalizing the incident light with different focus distances depending on the wavelength; and at least one detector configured to receive the light refracted by the multi-glazed window and detect the light intensity for each wavelength of the polychromatic light source; the wavelengths with intensity peak being the ones with a focus distance corresponding to an interface (P1-P6) in the multi-glazed window; the estimated distance (Ed2) being calculated based on the wavelength with intensity peak associated to the detected interface (P4).

8: The apparatus according to claim 7, wherein the at least one polychromatic light source (321) and the at least one detector are mounted on the shuttle with a fixed distance along the Z-axis from the decoating means.

9: The apparatus according to claim 8, wherein apparatus comprises a calculation unit configured to: determine a number of the interfaces detected by the confocal unit in view of the number of wavelengths with intensity peak; estimate distances between the confocal unit and the interfaces (P1-P6); identify at least one most relevant interface (P4) corresponding to a spot of maximum intensity detected by the near infrared unit; retrieve a first estimated distance (Ed1) of the detected interface (P4) matching with the identified most relevant interface; calculate the estimated distance (Ed2) between the decoating means and the detected interface (P4) equal to a sum of the first estimated distance (Ed1) and a fixed distance (Df) between the confocal unit and the decoating means; and calculate the displacement distance (Dd) equal to a difference between the estimated distance (Ed2) and the focus distance (Fd).

10: The apparatus according to claim 2, wherein the shuttle is movable along the Z-axis between 100 and 500 mm away from the first interface of the multi-glazed window.

11: A method for removing at least one portion of at least one coating system present in a multi-glazed window with an apparatus according to claim 1; the method comprising the following steps: mounting the apparatus on a first interface (P1) of the multi-glazed window; using the optical system to detect on which interface (P4) the coating system is localized, and to estimate a distance (Ed2) between the decoating means and the detected interface (P4); moving the decoating means along said Z-axis in order to focus the decoating means on the detected interface (P4); and removing at least one portion of the coating system applied on the detected interface (P4) with the decoating means by displacing the decoating means along the X and Y-axis to etch a predetermined shape from the coating system.

12: The method according to claim 11, wherein, during the removing of at least one portion of the coating system, the position of the coating system is monitored in real time by the optical system to detect a difference between the estimated distance and the focus distance (Fd); when a difference is detected, the decoating means are moved the difference along the Z-axis in order to adjust the focus position of the decoating means to be coincident on the detected interface (P4).

13: The method according to claim 12, wherein the multi-glazed window comprises two coating systems applied on two different interfaces (P1-P6), the method comprises: using the optical system to detect a first interface (P1-P6) where a first coating system is applied, and estimate a first distance between the decoating means and the first detected interface (P1-P6); using the optical system to detect a second interface (P1-P6) where a second coating system is applied, and estimate a second distance between the decoating means and the second detected interface (P1-P6); moving the decoating means along the Z-axis to focus the decoating means on the first detected interface (P1-P6); modifying the first coating system applied on the first detected interface (P1-P6) with the decoating means by displacing the decoating means along said X and Y-axis to etch a predetermined shape from the first coating system; moving the decoating means along the Z-axis to focus the decoating means on the second detected interface (P1-P6); and modifying the second coating system applied on the second detected interface (P1-P6) with the decoating means by displacing the decoating means along the X and Y-axis to etch a predetermined shape from the second coating system.

14: The apparatus according to claim 3, wherein the at least one near infrared light source is monochromatic with a wavelength of 850 nm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0077] The different aspects of the present invention will now be described in more details, with reference to the appended drawings showing various exemplifying embodiments of the invention, which are provided by way of illustration and not of limitation. The drawings are a schematic representation and not true to scale. The drawings do not restrict the invention in any way. More advantages will be explained with examples.

[0078] FIG. 1 depicts a front view of an apparatus according to an embodiment of the invention mounted on a multi-glazed window;

[0079] FIG. 2 depicts a side view of the apparatus of FIG. 1;

[0080] FIG. 3 depicts a side view of a near infrared unit of the apparatus of FIG. 1;

[0081] FIG. 4 depicts a side view of a confocal unit of the apparatus of FIG. 1; and

[0082] FIG. 5 depicts a chart of the steps realized by a calculation unit of the apparatus of FIG. 1.

DETAILED DESCRIPTION

[0083] For a better understanding, the scale of each component in the drawing may be different from the actual scale. In the present specification, a three-dimensional coordinate system defined by three orthogonal axial directions is used, the longitudinal direction of the window 40 is defined as the X direction, the transversal direction is defined as the Y direction, and the normal direction to the window 40 is defined as the Z direction.

[0084] It is noted that the invention relates to all possible combinations of features recited in the claims or in the described embodiments.

[0085] The following description relates to an building window unit but it's understood that the invention may be applicable to others fields like automotive or transportation windows which have to be attached such as train.

[0086] FIG. 1 depicts an apparatus 100 mounted on a multi-glazed window 40. As illustrated on FIGS. 2 and 3, the multi-glazed window 40 can be made with a complex of three glass panels 401, 403, 406 alternatively separated by two interlayers 402, 405.

[0087] For instance, at least one interlayer 402, 405 is a space filled by a gas like argon to improve the thermal isolation of the multi-glazed window 40. One interlayer 402, 405 can also be made of a transparent material, typically polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA) order to keep the glass panels 401, 403, 406 bonded together even when they are broken. These transparent materials can prevent the glass from breaking up into harmful large pieces.

[0088] The material of the glass panels 401, 403, 406 can be made of soda-lime silica glass, borosilicate glass or alumino silicate glass. However, a glass panel can also refer to other materials such as thermoplastic polymers, polycarbonates, used especially for automotive applications. Hence, references to glass throughout this application should not be regarded as limiting. The glass panels 401, 403, 406 can be manufactured by a known manufacturing method such as a float method, a fusion method, a redraw method, a press molding method, or a pulling method. In any case, each face of each glass panel 401, 403, 406 forms an interface P1-P6 of the window 40.

[0089] Moreover, the FIGS. 1 to 5 illustrate a very complex situation where the multi-glazed window 40 contains three glass panels 401, 403, 406. The invention can be used for simpler multi-glazed window comprising only two glass panels. In this case, the multi-glazed window comprises only the fours interfaces P1-P4.

[0090] According to the invention, glass panels of the multi-glazed window can be processed, ie annealed, tempered, . . . to respect with the specifications of security and anti-thief requirements.

[0091] Glass panels can be a clear glass or a coloured glass, tinted with a specific composition of the glass or by applying an additional coating or a plastic layer for example. In case of several glass panels, in some embodiments, each glass panels can be independently processed and/or coloured, . . . in order to improve the aesthetic, thermal insulation performances, safety, . . . . The thickness of the glass panels is set according to requirements of applications.

[0092] In some embodiments, glass panels of the multi-glazed window is at least transparent for visible waves in order to see-through and to let light passing through.

[0093] According to the invention, the glass panel can be formed in a rectangular shape in a plan view by using a known cutting method. As a method of cutting the glass panel, for example, a method in which laser light is irradiated on the surface of the glass panel to cut the irradiated region of the laser light on the surface of the glass panel to cut the glass panel, or a method in which a cutter wheel is mechanically cutting can be used. The glass panel can have any shape in order to fit with the application, for example a windshield, a sidelite, a sunroof of an automotive, a lateral glazing of a train, a window of a building, . . . .

[0094] In addition, said multi-glazed window can be assembled within a frame or be mounted in a double skin façade, in a carbody or any other means able to maintain a glazing unit. Some plastics elements can be fixed on the glazing panel to ensure the tightness to gas and/or liquid, to ensure the fixation of the glazing panel or to add external element to the glazing panel.

[0095] In the present embodiment, the rectangle includes not only a rectangle or a square but also a shape obtained by chamfering corners of a rectangle or a square. The shape of the glass panel in a plan view is not limited to a rectangle, and may be a circle or the like.

[0096] In some embodiments, the glass panel can be a laminated glass panel to reduce the noise and/or to ensure the penetration safety. The laminated glazing comprises glass panels maintained by one or more interlayers positioned between glass panels. The interlayers employed are typically polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA) for which the stiffness can be tuned.

[0097] These interlayers keep the glass panels bonded together even when broken in such a way that they prevent the glass from breaking up into large sharp pieces.

[0098] Typically, the glass panels 401, 403, 406 and the interlayers 402, 405 are low in reflectance for Radio Frequencies (RF) radiations. However, at least one coating system 404, which is high in reflectance for RF radiations, is localized on at least one interface P1-P6 of the window 40. Interfaces are commonly named Pi, where i starts from 1 where P1 represents the interface facing outside of the building where the multi-glazed window is mounted on and P6 facing inside of the building where the multi-glazed window is mounted on. The apparatus 100 of the invention is configured to remove at least one portion of this at least one coating system 404.

[0099] Indeed, the coating system 404 can be a functional coating capable of either heating the surface of the windows 40, reducing the accumulation of heat in the interior of a building or a vehicle, or keeping the heat inside during cold periods for example. Although coating systems are thin and mainly transparent to the eyes.

[0100] The coating system 404 can be made of layers of different materials and at least one of this layer is electrically conductive. The coating system 404 of the present invention has an emissivity lower than 0.4. The coating system 404 of the present invention may comprise a metal-based low emissive coating system. These coatings are typically a system of thin layers comprising one or more, for example two, three or four, functional layers based on an infrared radiations reflecting material and at least two dielectric coatings, wherein each functional layer is surrounded by dielectric coatings. The coating system 404 of the present invention may in particular have an emissivity of at least 0.010. The functional layers are generally layers of silver with a thickness of a few nanometers, mostly about 5 to 20 nm. Concerning the dielectric layers, they are transparent and each dielectric layer is traditionally made of one or more layers of metal oxides and/or nitrides. For example, these different layers are deposited by means of vacuum deposition techniques such as magnetic field-assisted cathodic sputtering, more commonly referred to as “magnetron sputtering”. In addition to the dielectric layers, each functional layer may be protected by barrier layers or improved by deposition on a wetting layer.

[0101] For the coating system 404, a conductive film can be used. For instance, the conductive film can be a laminated film obtained by sequentially laminating a transparent dielectric, a metal film and a transparent dielectric. ITO, fluorine-added tin oxide (FTO) or the like can be used for that purpose. As for the metal film, it can be a film containing at least one main component selected from the group consisting of Ag, Au, Cu, and Al.

[0102] According to FIG. 1, the apparatus 100 is mounted on the first interface P1 of the window 40 with four suction pads 21 placed on the corners of the window 40. Two horizontal profiles 28 are fixed by two suction pads 21 and extend horizontally in the X direction. A transversal profile 29 is mounted movable in translation in the X direction on these two horizontal profiles 28.

[0103] The displacements of this transversal profile 29 are controlled by two synchronized motors 18 operating a pulley or a cog 25 and disposed on a first extremity of each horizontal profile 28. The other extremity of each horizontal profile 28 supports a pulley or a cog. A belt, a rope or a chain mounted on each horizontal profile 28 is stretched around the pulleys or the cogs of each extremity of the profiles 28. With the control of the motors 18, each belt, rope or chain rotates around the two pulleys or cogs, inducing the displacements in the X direction of the transversal profile 29.

[0104] The transversal profile 29 supports a robot head 36 movable in the Y direction relative to the transversal profile 29. The displacements of this robot head 36 are obtained by a motor 19 with a similar system comprising belt/rope/chain and pulley/cog.

[0105] In the embodiment of FIG. 1, using the motors 18, 19, the robot head 36 is then movable in the X and Y directions. Alternatively, the robot head 36 could be movable in the X and Y directions with one horizontal profile mounted over two transversal profiles. These directions X and Y form a plane P on which the robot head 36 is movable.

[0106] Even if the first interface P1 of the window 40 presents some default of evenness or a curved shape, the horizontal profiles 28 are placed at a sufficient distance from the suction pads 21 to obtain almost a plane P for the displacements of the robot head 36.

[0107] The robot head 36 is configured to carry the decoating means 31 of the coating system 404. Concerning the displacements in the directions X and Y of the decoating means 31 mounted over the robot head 36 to remove at least a portion of a coating system 404, the present invention is close to the invention described in the patent application WO 2015/050762 enclosed by reference.

[0108] In addition to the elements disclosed in this patent application WO 2015/050762, the invention comprises a shuttle 22, on which the decoating means 31 are mounted, movable in the Z direction relative to the robot head 36. The displacements of the shuttle 22 in the Z direction are preferably more accurate than the displacements of the robot head 36 in the X and Y directions. For instance, as depicted in FIG. 2, the shuttle 22 can be mounted on two guiding rods 24 and an endless screw 23 movable by a motor 20 fixed on the robot head 36. The endless screw 23 drives a nut fixed on the shuttle 22 in order to obtain a very precise displacement of the shuttle 22 and thus a very precise displacement of the decoating means 31 in the Z direction relative to the coating system 404. For instance, the shuttle 22 can be movable between 100 and 500 mm away from the window 40.

[0109] Indeed, the decoating means 31 include a laser source 311 and a lens array 312 with a focal point localized at a focus distance Fd. According to the invention, the laser source 311 corresponds to the point where the laser beam is generated in direction to the lens array 312. Before this point, the laser beam can be generated by an optical generator and transmitted from this optical generator to the laser source 311 through an optical fiber. Thus, when the invention recites that the decoating means 31 are mounted on the shuttle 22, only the lens array 312 and the end of the optical fiber forming the laser source 311 can be mounted on the shuttle 22 when the optical generator is distant from the shuttle 22.

[0110] To maximize the efficiency of the decoating means 31 on the coating system 404, the focal point must be precisely positioned on the coating system 404. Thus, the distance Ed2 between the decoating means 31 and the coating system 404 must be equal to the focus distance Fd of the decoating means 31.

[0111] To this end, the invention proposes to use at least one optical system 32-33 to detect on which interface P4 the coating system 404 is localized, and to estimate a distance Ed2 between said decoating means 31 and the detected interface P4. A calculating unit 17 can then compare the distance Ed2 with the focus distance Fd and a displacement control unit 27 can then displace the decoating means 31 to focus the laser beam on the coating system 404 i.e to match the distance Ed2 between the decoating means 31 with the focus distance Fd of the decoating means 31.

[0112] Preferably, the displacement control unit 27 controls the motors 18-20 with the help of three different signals ComX, ComY and ComZ. Hence, the shuttle 22 is displaceable along the three directions of space X, Y and Z.

[0113] In order to obtain a detection of the interface P4 on which the decoating system 404 is localized, it is possible to use two different optical systems: a near infrared unit 33 and a confocal unit 32.

[0114] The confocal unit 32 consists of two sub-parts: confocal and chromatism. The confocal side requires at least a polychromatic light source 321 and a detector 322.

[0115] Preferably, the polychromatic light source 321 and the detector 322 are mounted on the shuttle 22. As the laser source 311, the polychromatic light source 321 can be generated by an optical generator and transmitted from this optical generator to the shuttle 22 through an optical fiber. Additionally, the detector 322 can also contain an optical fiber fixed on the shuttle 22 to acquire and transmit the reflected beam.

[0116] The polychromatic light source 321 is focused on the multi-glazed window 40 via a pinhole 323, for example a mask with a minuscule hole, and an array of lenses 324. A beam is reflected on a boundary between two layers with a different refractive index. The refracted beams travel via the lenses 324, 325 and a beam splitter 326 to the detector 322, in front of which there is also a pinhole 327.

[0117] As a consequence, everything in the sample which is not in focus is also not displayed on the detector 322.

[0118] These reflected beams fall outside of the tiny hole. Thus, the detector 322 can only see something that is in perfect focus because the pinhole 327 of the detector 322 blocks all other reflections, whether they are to the left or to the right, higher or lower. Therefore, the confocal unit 32 provides a sharp focus area for the interfaces P1-P6 of the multi-glazed window 40.

[0119] Then, there is the chromatic side. The way a lens 326 focuses light depends on the wavelength. When using a positive lens 326, red light is the least refracted. Thus, the focal point lies too far from the lens 326. Violet light is, however, strongly deflected and has its focal point closer to the lens 326. Using a polychromatic light source 321 that contains a broad spectrum of wavelengths on such a lens 324, a rainbow of focal points is developed.

[0120] The confocal unit 32 combines this light property with the existing confocal properties. Because each wavelength has its own focal point, the colour that the detector 322 receives is a very precise measurement of the distance to the reflective surface P1-P6.

[0121] After all, there is only one wavelength in which the focal point exactly coincides with a reflective surface. The result of a scan over the interfaces P1-P6 of the multi-glazed window 40 is a colour-coded micro-topography.

[0122] The detector 322 behind the pinhole 327 or a calculating unit 17 can decode this information and transform the wavelengths detected to distances between the confocal unit 32 and the interfaces P1-P6 of the multi-glazed window 40. With perfect points on the pinholes 321, 327, a Dirac function should appear on the wavelengths detected by the detector 322. However, in practice, this is not feasible.

[0123] Even if the pinholes 321, 327 have a very small diameter, approximately 1.8 microns, a Gaussian curve is obtained for each wavelength detected and the distance of each interface P1-P6 is estimated from the peak wavelengths. Indeed, the confocal unit 32 can achieve a resolution of 7 nanometres with a single measurement. If necessary, the precision could be improved by multiple measurements with movement of the confocal unit 32.

[0124] Indeed, the confocal unit 32 provides a measure Iλ of the variation of the intensity I of the peak for different wavelengths.

[0125] Preferably, the polychromatic light source 321 and the detector 322 are fixed on the shuttle 22 with a distance Df along said Z-axis from the decoating means 31. For instance, this fixed distance Df could be 60 mm.

[0126] The near infrared unit 33 is simpler. This near infrared unit 33 also comprises a light source 331 and a detector 332. The light source 331 is preferably monochromatic with a wavelength comprised between 700 and 1100 nm, preferably 850 nm. The detector 332 corresponds to an array of photodiodes, a CMOS camera sensor or a 2D silicon detector.

[0127] The light source 331 shines on the window 40 with an angle α. The transparency of the window 40 induces a reflection of the light in the form of a diffraction pattern DifP emitted by the light source 331 on each interfaces P1-P6 of the window 40.

[0128] The detector 332 then collects the diffraction pattern DifP. Due to the angle formed between the light source 331 and the detector 332, the detector 332 can observe different spots at different positions depending on the corresponding reflecting interface P1-P6. Moreover, the interface P4 where the coating system 404 is localized reflects more strongly than the other interfaces P1-P3, P5-P6. Indeed, the near infrared unit 33 provides a picture Its where different spots with variable intensity are visible.

[0129] Thus, the confocal unit 32 and the near infrared unit 33 are configured to send the measures a and Its to a calculating unit 17 implemented inside the displacement control unit 27.

[0130] Alternatively, when an unknown coating system composition is applied on the multi-glazed window, a coating type detector means can also be used to adapt directly some parameters of the laser, such as the power of the laser, when the apparatus is mounted on said window to optimize the decoating. This means avoids to configure such parameters of the laser before the mounting.

[0131] As depicted in FIG. 5, the calculating unit 17 is configured to calculate a displacement distance Dd based on the measures a and Its and two constants Df and Fd. The first constant Df corresponds to the fixed distance between the decoating means 31 and the confocal unit 32. In this example, the first constant Df is 60 mm. The second constant Fd corresponds to the focusing distance of the decoating means 31. In this example, the second constant Fd is 160 mm.

[0132] In a first step 101, the calculating unit 17 uses the measure a to determine the number of interfaces P1-P6 detected by the confocal unit 32. Thus, each wavelength peak is associated to a number of interfaces. Using the confocal and the chromatic sides of the confocal unit 32, the calculating unit 17 can then estimate the distance between the confocal unit 32 and each of the detected interfaces, during step 102.

[0133] The relation between the wavelengths and the distance can be calibrated with several measurements on reference samples. As a result, the calculating unit 17 can fulfil the following table with the number of each detected interface and the distance between the confocal unit 32 and each detected interface:

TABLE-US-00001 d1 180 mm d2 190 mm d3 195 mm d4 205 mm d5 225 mm d6 230 mm

[0134] If the window 40 is thicker than the resolution depth of the confocal unit 32, the motor 20 can be used in this step to move the confocal unit 32 along the Z axis and improve the depth of the analysis inside the window 40. Obviously, if the confocal unit 32 is moved, the moving distance must be added to the new measures obtained by the calculating unit 17 in order to detect all of the interfaces P1-P6 of the window 40.

[0135] At this stage, the calculating unit 17 doesn't know where the coating system 404 is positioned inside the window 40. Thus, a third step 103 is used to identify on witch interface P1-P6 the coating system 404 is localized with the measure Its of the near infrared unit 33. This measure Its presents a picture with multiple spots where a larger spot corresponds to the reflection of most of the near infrared light.

[0136] The spot illustrated on the left side of the picture corresponds to the reflection on the first interface P1 and the second spot from the left side of the picture corresponds to the reflection on the second interface P2 . . . . The fourth spot from the left side of the picture is covered by the larger spot of the picture meaning that the coating system 404 is localized on the fourth interface P4. The intensity of the spot detected after the larger spot are smaller compared to the intensity of the first spots because the coating system 404 has reflected most of the light emitted by the near infrared source 331.

[0137] To detect the interface where the coating system 404 is localized, the calculating unit 17 can thus count the number of spots detected before the largest spot. At the end of this step 103, the calculating unit 17 knows that the spot of the maximum intensity corresponds to the fourth spot detected by the near infrared unit 33.

[0138] The step 104 permits to match the results of the analysis of the measures Iλ and Ils. Thus, the calculating unit 17 is configured to retrieve the distance to the fourth interface detected by the confocal unit 32.

[0139] At the end of this stage, the calculating unit 17 can estimate the distance Ed1 between the confocal unit 32 and coating system 404. According to this example, this distance Ed1 corresponds to 205 mm.

[0140] Knowing the distance Df between the decoating means 31 and the confocal unit 32, the step 105 calculates the estimated distance Ed2 between the decoating means 31 and the coating system 404. According to this example, this distance Ed2 corresponds to Ed1−Df=205−60=145 mm.

[0141] The displacement distance Dd can then be calculated, on a last step 106, with the difference between the estimated distance Ed2 and the focus distance Fd. According to this example, this displacement distance Dd is calculated at Ed2−Fd=145−160=−15 mm. Thus, the displacement control unit can control the motor 20 to move the shuttle 22 on the right direction along 15 mm in order to focus the decoating means 31 on the coating system 404.

[0142] This displacement Dd can be used at a preliminary stage of a process of decoating prior to the use of the lase source 311.

[0143] For instance, a process of decoating a window 40 contains a first step where the apparatus 100 is mounted on the first interface P1 of a window 40. After the first step, the optical system 32-33 and the displacement control unit 27 are used to position the shuttle 22 in order to focus the decoating means 31 on the detected interface P4.

[0144] At the end of this preliminary stage, the decoating means 31 can be used to remove at least one portion of the coating system 404 by displacing the decoating means 31 along the X and Y-axis in order to etch a predetermined shape from said coating system 404.

[0145] After the preliminary stage, the optical system 32-33 and the displacement control unit 27 can also be used to focus, in real time, the decoating means 31 on the coating system 404 during the displacements along the X and Y-axis. Thus, the apparatus 100 can overcome default of evenness and permits to decoat curved multi-glazed window.

[0146] Moreover, if the window 40 presents two coating systems 404 applied on two different interfaces, the optical system 32-33 and the displacement control unit 27 can be used to move the position the shuttle 22 in order to focus the decoating means 31 on the second coating system 404 after the decoating of the first coating system 404.

[0147] Indeed, the invention permits to improve the existing processes of decoating a multi-glazed windows 40. This invention can be used for multiple kind of multi-glazed windows including at least one coating system 404, where the position and the thickness of the glass panels 401, 403, 406 and the position of the coating system 404 can vary. Moreover, the invention is able to work when the multi-glazed window is already mounted on a structure.