Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/0006—Working by laser beam, e.g. welding, cutting or boring taking account of the properties of the material involved
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
  • B23K26/352—Working by laser beam, e.g. welding, cutting or boring for surface treatment
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C23/00—Other surface treatment of glass not in the form of fibres or filaments
  • C03C23/0005—Other surface treatment of glass not in the form of fibres or filaments by irradiation
  • C03C23/0025—Other surface treatment of glass not in the form of fibres or filaments by irradiation by a laser beam
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/12—Optical coatings produced by application to, or surface treatment of, optical elements by surface treatment, e.g. by irradiation
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/0025—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical correction, e.g. distorsion, aberration
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/08—Mirrors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2101/00—Articles made by soldering, welding or cutting
  • B23K2101/34—Coated articles, e.g. plated or painted; Surface treated articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/30—Organic material
  • B23K2103/42—Plastics
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K2103/00—Materials to be soldered, welded or cut
  • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
  • B23K2103/52—Ceramics

Definitions

• the present invention relates to a method of microdeforming the front face of a thin piece.
• Such a part is delimited by a first face, called the front face, by a second face, called rear face, opposite the first face, and a peripheral portion, called periphery, which connects the first face to the second face.
• the greatest distance measurable on at least one of the first and second faces is greater than about five times, preferably eight times, the distance between the first and second faces.
• the invention applies in particular to the correction of the wave surface of a mirror, covered with a treatment or not, which, because of defects in polishing or treatment, does not meet the specifications of shape or flatness imposed on it.
• the objective then desired may be a minimization of the deformation or a local increase of this deformation.
• Correction of the flatness of the surface of a mirror-type optical component can be done during the polishing operation, through local retouching.
• the actual surface or the wave surface may be deformed due to polishing defects residues, applied layer stresses or treatment heterogeneities.
• optical treatments of the back face are used to counterbalance the changes related to the stresses of the layers deposited on the front face. In this case, a global spherical correction is obtained.
• One possible solution is to perform a correction of the front face by applying locally a material thickness using tools that use masks and robots.
• the present invention aims to overcome the disadvantages of the techniques mentioned above.
• the subject of the present invention is a process for microdeforming a first face of a thin piece, delimited by the first face, by a second face, opposite to the first face, and by a peripheral portion which connects the first face to the second face, the greatest distance measurable on the first face being greater than about five times, preferably eight times, the distance between the first and second faces, the method being characterized in that it applies to the second face or the peripheral part, a local treatment which causes a static microdeformation, fixed once and for all, of the first face, without applying any mechanical force to the thin piece.
• the thin piece is made of a material chosen from amorphous materials (especially glasses), metals, ceramics and plastics, and the microdeformation of the first face is a retouching local of this, obtained by applying a local treatment to the second face.
• the microdeformation is obtained by local glazing of the second face or of the peripheral part of the thin part, carried out by means of a laser.
• the wavelength of this laser can be adapted to the material to improve the laser-material interaction.
• a CO 2 laser emitting at 10.6 ⁇ m will preferably be used if the material is silica.
• the microdeformation is obtained by local machining of the second face or the peripheral portion of the thin piece.
• This local machining can be a local chemical machining, for example carried out by means of an ink jet machine.
• the local machining is performed by means of a device selected from lasers, ion guns and plasma jet devices.
• the local machining is carried out by means of a laser
• the microdeformation is obtained by a local deposition of at least one thin layer on the second face or on the peripheral portion of the thin piece.
• a control of the microdeformation of the first face is also carried out to check whether a desired microdeformation has been obtained, and if this is not the case, the same is repeated. local treatment of the second face or the peripheral portion until the desired microdeformation is obtained.
• a microdeformation determination device capable of supplying a signal representative of the microdeformation thus determined, and of controlling, by means of the signal, the device able to apply the local treatment, with a view to recommencing the local treatment until the desired microdeformation is obtained.
• FIGS. 1A to 1E schematically illustrate a first example of the invention
• FIGS. 2A to 2E schematically illustrate a second example of the invention
• FIGS. 3A to 3E schematically illustrate a third example of the invention
• FIGS. 4A to 4E schematically illustrate a fourth example of the invention
• the present invention is a method of microdeforming the front face of a thin piece (whose aspect ratio is preferably about 8: 1 or more), thanks to a suitable surface treatment, performed on the back side , even the periphery, of the room.
• the treatment modifies the tensions of this superficial layer.
• the invention has a static correction function which makes it possible, if necessary, to recover a discarded part, to correct the effect of the constraints of a hard treatment and to compensate the edge effects of machining or cutting. And in some cases, the invention can replace a polishing under constraints.
• the correction or rather a microcorrection, is called static. This means that this microcorrection is fixed once and for all; it will not correct surface modifications, related to thermal variations for example.
• Such a correction is opposed to a dynamic correction, for which corrections are made in real time and can change over time.
• the originality of the invention lies in the fact that the corrections are made on the rear face, by different methods that do not generate pressure on the part. These methods may include laser machining, ion machining, plasma machining, chemical etching, or local thin film processing.
• the corrections can be global, in which case their corrective actions will be perceived on the whole of the part, or punctual, that is to say local, the system used to perform them being addressable locally.
• the particularity of the aforementioned methods lies in the fact that they are not developed in the field of polishing or in the field of surface treatment.
• the invention allows the correction of surface defects (generally thicknesses because a hollow corresponds to an extra thickness of material around this hollow).
• the applied treatment will be local and will have a spatial extension, that is to say a width, and an intensity, that is to say a depth, which will depend on the desired correction.
• the principle of the invention consists in using the relaxation or the creation of stresses to locally modify the surface of a thin piece. It suffices to act locally on the rear face of this piece to observe a modification of the front face thereof.
• parts consisting of square glass substrates, 50 mm in side and 4 mm in thickness, whose two faces have been optically polished and whose front faces have been measured using an interferometer.
• the pieces were placed in turn in a frame allowing an interferometric measurement over an area of 40 mm x 40 mm.
• substrate of FIG. 1A a vertical line 6 according to a median
• substrate of FIG. 2A a line 8 along a diagonal
• substrate of FIG. 3A two lines inclined at 45 ° and connecting the midpoints of the sides, and
• - substrate of Figure 4A a square area 12 of about 5 mm side, located approximately in the center of the substrate.
• the front faces of the four substrates were then remeasured and subtracted the measurements obtained after machining the measurements obtained before machining.
• PV represents the peak-to-valley difference and RMS represents the root mean square.
• pix represents the number of pixels (in abscissa and ordinate).
• FIG. 1B shows the result of the measurement of the front face of the substrate of FIG. 1A before the machining of the rear face of this substrate (first measurement); in the case of FIG. 1B, PV is 0.089 ⁇ m and RMS is 0.013 ⁇ m.
• FIG. 1C shows the result of the measurement of the front face of the substrate of FIG. 1A after the machining of the rear face of this substrate (second measurement); in the case of FIG. 1C, PV is 0.203 ⁇ m and RMS is 0.039 ⁇ m.
• Figure 1D shows the modification of the front face, that is to say the first measurement ( Figure 1B) minus the second measurement ( Figure 1C); in the case of FIG. 1D, PV is 0.170 ⁇ m and RMS is 0.028 ⁇ m.
• Figure 1E shows a profile of this change.
• Distance represents the width (in pixels) of the measured area, corresponding to about 40 mm; and Height represents a variation of height (in ym).
• FIG. 2B shows the result of the measurement of the front face of the substrate of FIG. 2A before the machining of the rear face of this substrate (first measurement); in the case of FIG. 2B, PV is 0.083 ⁇ m and RMS is 0.013 ⁇ m.
• FIG. 2C shows the result of the measurement of the front face of the substrate of FIG. 2A after the machining of the rear face of this substrate (second measurement); in the case of FIG. 2C, PV is 0.229 ⁇ m and RMS is 0.047 ⁇ m.
• Figure 2D shows the modification of the front face, that is to say the first measurement ( Figure 2B) minus the second measurement ( Figure 2C); in the case of FIG. 2D, PV is 0.211 ⁇ m and RMS is 0.038 ⁇ m.
• Figure 2E shows a profile of this change.
• FIG. 3B shows the result of the measurement of the front face of the substrate of FIG. 3A before the machining of the rear face of this substrate (first measurement); in the case of FIG. 3B, PV is 0.089 ⁇ m and RMS is 0.010 ⁇ m.
• FIG. 3C shows the result of the measurement of the front face of the substrate of FIG. 3A after the machining of the rear face of this substrate (second measurement); in the case of FIG. 3C, PV is 0.169 ⁇ m and RMS is 0.024 ⁇ m.
• Figure 3D shows the modification of the front face, that is to say the first measurement ( Figure 3B) minus the second measurement ( Figure 3C); in the case of FIG. 3D, PV is 0.145 ⁇ m and RMS is 0.017 ⁇ m.
• FIG. 4B shows the result of the measurement of the front face of the substrate of FIG. 4A before the machining of the rear face of this substrate (first measurement); in the case of FIG. 4B, PV is 0.102 ⁇ m and RMS is 0.014 ⁇ m.
• FIG. 4C shows the result of the measurement of the front face of the substrate of FIG. 4A after the machining of the rear face of this substrate (second measurement); in the case of FIG. 4C, PV is 0.141 ⁇ m and RMS is 0.019 ⁇ m.
• FIG. 4D shows the modification of the front face, that is to say the first measurement (FIG. 4B) minus the second measurement (FIG. 4C); in the case of FIG. 4D, PV is 0.110 ⁇ m and RMS is 0.011 ⁇ m.
• Figure 4E shows a profile of this change.
• the surface of the front face has been modified, according to the respective directions 6, 8 and 10, or according to the zone 12, which have been machined by laser to demonstrate the validity of the invention. Induced deformations naturally depend on the material, its thickness and the machining performed.
• FIG. 5 illustrates another example of
• the piece 14 shows a thin piece 14 which is delimited by its front face 16, its rear face 18 and its periphery 20.
• the largest measurable distance on the front face is at least eight times the distance between the faces 16 and 18.
• the report aspect ratio is at least 8: 1.
• the piece 14 is made of glass and has the shape of a cylinder of diameter D and thickness E, with D> 8E.
• the front face has a defect of curvature.
• a laser 22 is used, for example an Nd: YAG type laser, which operates at 3Cu or 4 (0 and emits radiation 24 at length wave of 355 nm (3 (0) or 266 nm (4 (D).
• the laser 22 is provided with means 26 for moving and orienting. With these means, the orientation of the laser 22 is changed and the orientation of the laser 22 is applied to apply the following treatment to the rear face 18 of the part 14 by means of the radiation 24: either a spot machining or a machining in a circle whose radius and depth depend on the deformity to be corrected and the properties of the material.
• the radiation 24 either a spot machining or a machining in a circle whose radius and depth depend on the deformity to be corrected and the properties of the material.
• this treatment has the effect of eliminating or minimizing the curvature.
• the front face 16 is then checked, for example using a Fizeau or Michelson type interferometer 28, or a Shack-Hartmann type wavefront analyzer, or a fringe projection system. Moiré type, to check that the defect has been corrected. If this is not the case, we start over treatment of the rear face 18 until the correction is made.
• the control can be done "open loop". Then, the laser 22 is operated independently of the interferometer 28.
• a signal provided by the interferometer 28 is used, this signal being representative of the microdeformation caused to the front face 16 during the local processing of the rear face 18 by the laser 22, to control this laser 22 as well as the displacements and the orientation of the latter, by means of appropriate electronic control means 30.
• the local processing of the rear face 18 is thus recommenced until the correction of the defect of the front face 16.
• the present invention can be applied to thin parts such as telescope mirrors or optical microcomponents.
• the aspect ratio is in all cases of the order of 5: 1 or greater than 5: 1.
• the piece is made of glass.
• the invention is not limited to the treatment of parts made of such a material. It allows for example to perform a local retouch of the front face of parts, by actions on the rear face thereof, in the case where these parts are made of amorphous materials such as glass, or metals, or ceramics or plastics.
• the invention is not limited to the use of a laser, whose wavelength, power and the repetition rate can be adapted according to the material, in order to locally machine the rear face (or the periphery) of a thin piece.
• the local treatment applied in accordance with the invention is not limited to laser machining: in the invention, it is possible to use a chemical machining for locally machining the rear face (or the periphery) of the part, by example by using an inkjet machine.
• This use can be a clean means (chemical attack by an acid for example) or a complementary means of laser machining, in order to optimize the deposition of light energy through the deposition of inks or other substances, so to optimize the absorption of the laser radiation by the rear face (or the periphery) of the room.
• the implementation of the invention can also be carried out using an ion gun, or a plasma jet, for locally machining the rear face (or the periphery) of the part.
• the invention can also be implemented by using a local coating of the rear face (or the periphery) of the part, this coating consisting of one or more thin layers.
• These layers and their location are chosen according to the amplitude of the correction to be made and the position of the fault to be corrected.
• This deposition of thin layers can be performed by masking, with PVD or Sol-Gel techniques, or by inkjet.
• Fizeau or Michelson-type interferometers or Schack-Hartmann-type wavefront analyzers, or moire-type fringe projection systems, to assist in the correction of the surface of the front of the room.
• This system can be open-loop or closed-loop with the chosen implementation device.
• the invention therefore proposes the use of a static method for modifying the surface state of the front face of a component, independently of the steps prior to the production of the component.
• This method can be used to compensate for the effect of the stresses induced by the presence of thin layers on the front face of the component. It is known in fact that such thin layers tend to render the convex components in general.
• This method can also be used to compensate edge effects related to machining or cutting steps of a part.
• the present invention is not limited to the local treatment of the rear face of a thin part, in order to cause a microdeformation of the front face of the part: to cause this microdeformation, it is also possible to apply the local treatment to the periphery of the room.
• document WO 2004/036316 already discloses a method of microdeforming a thin optical element. According to this method, the rear face of the element is illuminated, which heats and deforms it.
• the microdeformation performed is static, fixed once and for all.
• the process disclosed by this document belongs, for its part, to a completely different category, that of dynamic correction methods. Indeed, for heating, it uses laser diodes or lasers that deliver surface powers of the order of 1 W. cm "2 , in order not to increase the temperature by more than 20 ° C. This surface power of the order of 1 W. cm -2 is much lower than the power required for a glaze or laser ablation for example (In the order of 10 3 to 10 9 W.cm -2 .) Furthermore, the invention is not limited to the application of a local treatment to the only rear face of a part, nor to the the use of a laser.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Engineering & Computer Science (AREA)
• General Physics & Mathematics (AREA)
• Plasma & Fusion (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
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• Geochemistry & Mineralogy (AREA)
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• Organic Chemistry (AREA)
• Laser Beam Processing (AREA)
• Optical Elements Other Than Lenses (AREA)

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• 2009
  • 2009-10-12 FR FR0957112A patent/FR2951281B1/fr not_active Expired - Fee Related
• 2010
  • 2010-10-11 US US13/501,694 patent/US9375805B2/en not_active Expired - Fee Related
  • 2010-10-11 WO PCT/EP2010/065164 patent/WO2011045260A1/fr not_active Ceased
  • 2010-10-11 JP JP2012532628A patent/JP2013507651A/ja active Pending
  • 2010-10-11 EP EP10762937A patent/EP2488902A1/de not_active Withdrawn

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