Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
  • G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
  • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
  • G01B9/02056—Passive reduction of errors
  • G01B9/02057—Passive reduction of errors by using common path configuration, i.e. reference and object path almost entirely overlapping
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/08—Measuring arrangements characterised by the use of optical techniques for measuring diameters
  • G01B11/12—Measuring arrangements characterised by the use of optical techniques for measuring diameters internal diameters
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B11/00—Measuring arrangements characterised by the use of optical techniques
  • G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
  • G01B9/00—Measuring instruments characterised by the use of optical techniques
  • G01B9/02—Interferometers
  • G01B9/02049—Interferometers characterised by particular mechanical design details
  • G01B9/0205—Interferometers characterised by particular mechanical design details of probe head
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/24—Coupling light guides
  • G02B6/26—Optical coupling means
  • G02B6/262—Optical details of coupling light into, or out of, or between fibre ends, e.g. special fibre end shapes or associated optical elements

Definitions

• the present invention relates to a device for analyzing the surface condition of the inside of a tube, and in particular a small inner diameter tube.
• optical interferometric analysis devices that can measure the roughness of a surface with a precision of one nanometer.
• An example of such a device is described in the French patent application No. 0859091 (B9031) applicants.
• FIG 1 shows Figure 1 of the aforementioned patent application.
• An optical source 1 sends a beam light, for example a laser beam, towards the surface 2 of an object to be analyzed by means of an optical fiber 3 comprising a core 4 and an optical cladding 5.
• the laser beam forms a light spot on the object 2 .
• the light beam is returned to the fiber on the one hand by the end surface 7 of the fiber, on the other hand by the object 2, towards a separator 8 and a detector 9. level detec tor ⁇ , one can observe an interference between light reflected from the fiber end and the light reflected by the object.
• the surface of the object is generally orthogonal to the axis of the output beam of the fiber, and if the fiber is moved so that its end remains in a plane parallel to the plane of the object, a variation of the Interference figure and this variation makes it possible to determine the topography of the object.
• This device makes it possible to accurately analyze the state of flat surfaces. We would like to be able to analyze with the same precision the inner surface of a tube.
• an object of an embodiment of the present invention is to provide a device adapted to measure the topo ⁇ graphy of the inner surface of a very small diameter tube with a very high resolution.
• Another object of an embodiment of the present invention is to provide a simple device compatible with existing optical fiber interferometric analysis devices.
• an embodiment of the present invention provides an optical device for interferometric analysis of the surface state of the inside of a tube, comprising an optical fiber whose free end is sharpened and then bevelled. at its single core, the bevelled surface being metallized, so that only a portion of the The surface of the fiber core contributes to the return of the incident beam perpendicular to the axis of the fiber.
• the metallization material is gold.
• the device further comprises means for filtering the interference signal removing frequencies resulting from moving ⁇ of the optical fiber.
• the present invention provides a method for interferometric analysis of the surface condition of the inner surface of a tube, comprising the steps of introducing an end of an optical fiber into the tube, the end of the fiber being cut in a point and then bevelled at its single core, the beveled surface being metallized, so that only a portion of the surface of the core of the fiber contributes to the return of the incident beam perpendicularly to the axis of the fiber; moving the optical fiber in translation and rotation; and detecting the interference signal between a light wave reflected by the optical fiber and a wave returned by the inner surface of the tube.
• the device further comprises a step of filtering the interference signal to eliminate the frequencies resulting from the displacement of the optical fiber.
• FIG. 1 previously described, schematically represents an optical device for interferometric analysis of the topography of a surface to be analyzed
• FIG. 2 represents the end of an optical fiber of a device for interferometric analysis of the topography of the inner surface of a tube
• FIG. 3 illustrates an alternative embodiment of a device for interferometric analysis of the topography of the inner surface of a tube
• FIGS. 4A and 4B illustrate a device for interferometric analysis of the topography of the inner surface of a tube according to an embodiment of the present invention. detailed description
• FIG. 2 represents the end of an optical fiber of a device for interferometric analysis of the topography of the inner surface of a tube.
• An optical fiber 3, only one end is shown, comprises a heart 4, 5 an optical cladding coating the heart 4 and a protective sheath 6 surroun ⁇ rant the cladding 5.
• the end of the optical fiber is stripped by removing a portion of the protective sheath to form a portion of bare optical fiber.
• the core 4 and the optical cladding 5 are, for example, of differently doped silicon oxides.
• the end of the bare optical fiber is beveled at an angle of about 45 °.
• the bevel is covered with a reflective layer 10, for example a metalli ⁇ that and more particularly a layer of gold.
• the reflective layer on the bevel it is possible for example to expose the end of the bare optical fiber to a source of evaporation or sputtering.
• the evaporation and the spray being directional, all the surfaces of the optical fiber naked opposite the source are covered by the reflecting layer ⁇ health, as illustrated in the figure.
• an adhesion layer such as chromium or titanium and the reflective layer may be gold or 1 aluminum.
• the light return mode of FIG. 2 is particularly advantageous with respect to prior structures as described for example in the US patent application 2010/0220369. In fact, it is avoided to add to the existing system a reflecting mirror, this reflecting mirror being incorporated into the fiber by means of its bevel size as indicated above.
• the end of the optical fiber is placed in a tube 11 which is the object whose inner surface it is desired to analyze.
• the optical fiber 3 is positioned in the tube 11 so that the axis of the fiber is substantially coincident with that of the tube.
• a light beam 12 for example that of a laser emitting in the visible range, is injected into the optical fiber 3.
• the beam is reflected by the reflective layer 10 and propagates transversely to the axis of the optical fiber in the opposite direction to the bevel.
• the beam forms on the inner surface of the tube a light spot of height d2.
• the beam is returned to the fiber on the one hand by the interface 14 between the optical fiber and the air, on the other hand by the tube 11.
• the evolution of the interference pattern can be measured during the displacement of the optical fiber in translation and in rotation along the axis of the tube 11.
• the displacement of the interference fringes reflects the variation in distance between the end ⁇ Beveled fiber optic and analyzed surface.
• a measurement of the topology of the inner surface of the tube is obtained.
• the device proposed here has a resolution of the order of a few nanometers for the radial distances between the cut end of the optical fiber and the analyzed surface.
• the spatial resolution that is to say in the directions of the illuminated surface of the tube, is substantially equal to the dimensions of the light spot, substantially the dimensions of the core 4 of the optical fiber (currently 3 to 5 ym for a fiber adapted to guide visible light).
• FIG. 3 illustrates a first variant of the embodiment illustrated in FIG. 2, aimed at improving the spatial resolution.
• An optical fiber 3 is cut in double bevel.
• the double bevel consists of two chamfers 20a and 20b SYME ⁇ tric in the example shown.
• a reflective layer 22 covers the bevel 20b. Contrary to what is shown in the figure, the angle formed by the two bevels is chosen so that the portion of the light beam reflecting on the bevel 20b of the fiber orthogonal to its axis.
• an incident laser beam 24 is divided into a reflected beam 26 on the bevel 20b and a transmitted beam 28 through the bevel 20a. Only the reflected beam 26 is useful for interferometric analysis of the inner surface of the tube. It will be ensured that the transmitted beam 28 is not returned to the fiber.
• This reflected beam 26 forms on the inner surface of the tube a light spot of height d3.
• the light beam is returned to the fiber on the one hand by the interface 29 between the core 4 and the air, on the other hand by the tube 11.
• the spatial resolution of the device is increased relative to that of the device illustrated in FIG. 2.
• the height d 3 of the light spot on the tube is divided by two in relation to the height. d2 since only half of the laser beam is reflected on the layer 22.
• the equivalent of a diaphragm is made which limits the dimensions of the light spot on the surface of the tube.
• the double bevel according to which the end of the fiber is cut can be asymmetrical. In this case, if it is the smaller surface bevel that is metallized, the spatial resolution is further increased.
• FIGS. 4A and 4B FIG. 4B being an enlarged view of a portion of FIG. 4A, illustrate a second variant of the embodiment illustrated in FIG. 2, also aimed at improving the spatial resolution according to one embodiment of this embodiment. invention.
• an optical fiber 3 comprising a core 4, an optical sheath 5 surrounding the core and a protective sheath 6 surrounding the optical sheath 5, the end of the optical fiber being stripped by eliminating a portion of the protective sheath to form a portion of bare fiber.
• the fiber is cut in an extremely sharp fashion, so that a pointed end 30 of the core 4 protrudes substantially beyond the limit of the optical cladding 3. Then the fiber is cut to form a flat part. only on the pointed end 30 of the core 41, as shown. Then, as before, a reflective layer 33 is shaped so as to cover the side of the fiber having the flat portion 31. The angle of the flat portion 31 is chosen so that light entering the optical fiber and striking this flat part 31 is reflected to form an output beam 36 orthogonal to the general direction of the fiber. On the other hand the light arriving on the part 34 of the heart is lost (it is reflected in direc ⁇ tions from which it will not be returned in the fiber).
• the output beam 36 has a diameter d4 which, as will be understood, can be adjusted in a chosen manner depending on the distance to the tip of the fiber to which the flat has been formed. In practice, the dimensions of the half-wavelength of the incident light can be provided for the reflecting surface 31.
• the optical fiber is rotated and rotated at a constant speed. If the fiber is off-center, it appears during rotation a variation in distance between the fiber and the tube, even if the tube has a perfectly regular relief. In other words, the interference signal measured is modulated by the rotation frequency of the fiber.
• means for filtering the interference signal are provided to eliminate the rotation frequency of the optical fiber.
• the filtering means may for example be a high-pass filter since the signals corresponding to the topology of an analyzed surface have a high frequency relative to the rotation frequency of the fiber. Filtering can be done with signal processing software.
• the diameter of a bare optical fiber is of the order of 100 microns, and the diameter of the protec ⁇ sheath is of the order of 250 to 600 microns. If the tube is of very small diameter, only the stripped end of the fiber is introduced.
• the device proposed here can make measurements on tubes of internal diameter less than one millimeter.
• the device proposed here makes it possible to carry out measurements on tubes of very variable lengths, of a few millimeters to a few centimeters, such as syringes or catheters.
• the emission wavelength of the laser, the type of optical fiber and the material of the reflective layer will be selected according to the desired performance of the device.
• a displacement in rotation and in translation of the fiber relative to the tube it may be easier to move the tube relative to the fiber.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Length Measuring Devices By Optical Means (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

Country Status (4)

Family Cites Families (13)

• 2011
  • 2011-08-16 FR FR1157347A patent/FR2979143B1/fr not_active Expired - Fee Related
• 2012
  • 2012-08-13 EP EP12758564.4A patent/EP2745071A1/de not_active Withdrawn
  • 2012-08-13 WO PCT/FR2012/051886 patent/WO2013024229A1/fr active Application Filing
  • 2012-08-13 US US14/238,897 patent/US20150124260A1/en not_active Abandoned

Non-Patent Citations (1)

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