WO2019020800A1 - Procédé et dispositif de mesure optique de surfaces au moyen d'un capteur confocal - Google Patents

Procédé et dispositif de mesure optique de surfaces au moyen d'un capteur confocal Download PDF

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Publication number
WO2019020800A1
WO2019020800A1 PCT/EP2018/070439 EP2018070439W WO2019020800A1 WO 2019020800 A1 WO2019020800 A1 WO 2019020800A1 EP 2018070439 W EP2018070439 W EP 2018070439W WO 2019020800 A1 WO2019020800 A1 WO 2019020800A1
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WO
WIPO (PCT)
Prior art keywords
signal
light
optical system
confocal
confocal sensor
Prior art date
Application number
PCT/EP2018/070439
Other languages
German (de)
English (en)
Inventor
Johannes Frank
Gerd Jakob
Original Assignee
Nanofocus Ag
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nanofocus Ag filed Critical Nanofocus Ag
Priority to EP18756156.8A priority Critical patent/EP3658850A1/fr
Priority to CN201880057005.4A priority patent/CN111065884A/zh
Publication of WO2019020800A1 publication Critical patent/WO2019020800A1/fr

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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
    • 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
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G01B11/0608—Height gauges

Definitions

  • the invention relates to a method for the optical measurement of technical surfaces with the aid of a confocal sensor, wherein light of at least one light source is directed to the surface of a sample to be measured via an optical system. Moreover, the invention relates to a confocal sensor for carrying out the method, with at least one light source whose light is directed via an optical system to the surface to be measured of a sample.
  • confocal measurement technology In confocal measurement technology, light from a light source is usually focused onto the surface to be measured via a confocal filter, a beam splitter and an optical system.
  • a confocal filter e.g., a pinhole
  • the sensor shows a maximum signal when the surface is in focus. This allows the exact Z height of the surface to be determined.
  • a chromatically confocal sensor One method in which such mechanical elements can be dispensed with is the use of a chromatically confocal sensor.
  • the broadband spectrum of a light source (for example, white light) is directed onto the sample surface via an optical system with defined dispersion. Due to the dispersion, a longitudinal chromatic aberration is created, which allows each "light color" to be assigned a defined Z position on the sample surface, thus allowing the topography of the sample to be determined, so that mechanical scanning in the Z direction is no longer necessary.
  • the determination of the correct Z-position of the sample surface i.
  • the topography is done classically via a spectrometer.
  • the light reflected from the sample is spectrally analyzed, with the dominant wavelength corresponding to the Z position of the sample.
  • the used spectrometer lines can be read out with data rates of several kHz.
  • fast chromatic confocal sensors can be realized.
  • the readout speed of the spectrometer lines has its limits in the range of a few kHz and can not be further increased without further ado.
  • the invention is therefore based on the object to develop a method of the type mentioned so that high measurement rates are possible.
  • the optical system comprises an electrically controlled adaptive optic, wherein the focus of the optical system is varied by an electrical signal in the Z-direction and the light reflected back from the sample surface at least one photosensor is directed, the sensor signal being measured over time and the time and intensity of a signal maximum being determined and evaluated, the height Z of the surface being derived from the electrical signal at the time of the signal maximum.
  • an acousto-optical lens namely a tunable acoustic gradient index (TAG) lens, is suitable as adaptive optics (see A. Mermillod-Blondin, E.
  • TAG lens consists of a liquid-filled, cylindrical cavity which is excited radially with acoustic energy. This results in a periodic modulation in the liquid, correspondingly the refractive index varies and the lens continuously varies its focal length cyclically, with a frequency in the kHz to MHz range.
  • a TAG lens can be used in the optical system of the confocal sensor consisting of a cylindrical piezoelectric body as a cavity filled with liquid.
  • the piezoelectric body is supplied with the electrical signal, whereupon the position of the focus of the optical system in the Z-direction is varied.
  • the electrical signal can be generated by a function generator of a type known per se.
  • an adaptive optics comprising at least one modulation element which converts the electrical signal into a variation of the refractive index of a material irradiated by the light of the modulation element for varying the focus by utilizing the acousto-optic effect.
  • This modulation element may be a TAG lens of the type described above.
  • a purely optical "scanning" in the Z-direction takes place between the optical system and the sample surface.
  • the light incident on the sample surface is focused through the Z-region and reflected back and falls in the simplest case to one fast photodiode as a photosensor, with which the signal maximum is determined, wherein the adaptive optics is synchronized with respect to the time dependence of the focus position in the Z direction with a used electronic detection device, such that from the time course of the electrical signal that drives the adaptive optics, the focus position is determined in the signal maximum and thus can be closed to the height Z of the sample.
  • the electrical signal may be an AC voltage of high frequency in the range of 1 kHz to 10 MHz, preferably 10 kHz to 1 MHz, particularly preferably 50 kHz to 200 kHz, with which the acousto-optical lens is acted upon. Accordingly, the focus position in the Z direction is periodically varied between a maximum value and a minimum value. The measuring time per point of the sample surface is thus less than one microsecond.
  • the photosensor may be formed as a point sensor. However, it is also provided according to the invention that the light from the light source is split into a plurality of sub-beams and a multi-channel sensor, e.g. a (row or matrix) array of photodiodes is used.
  • a plurality of light sources can be used, wherein the back-reflected individual beams of the light sources are detected in parallel by means of a corresponding multi-channel photo sensor.
  • the detection of the sample topography can be further accelerated, in which the individual beams simultaneously scan a plurality of spaced-apart points on the sample surface.
  • a single modulation element for example a single TAG lens, may be sufficient even in the case of parallel measurement with a plurality of partial or single beams.
  • a separate modulation element for example in the form of a plurality of TAG lenses arranged side by side, can be assigned to each of the partial beams or individual beams.
  • the detection device used to analyze the time-varying signal of the photosensor has an extreme value memory which follows the time-varying signal until an extremum of the signal is reached, a peak indicator signal being generated when the extremum is reached of which the time of the extremum and on the basis of which in turn the signal maximum associated focus position in the Z direction is detected.
  • the (absolute) signal maximum must be assigned to the peak indicator signal last generated during a variation cycle of the focus position.
  • the detection of multiple (local) signal maxima is possible with this method, for example, to determine the layer thickness distribution of a coating on the sample surface using the method according to the invention.
  • the optical system comprises an electrically controlled adaptive optics, wherein the focus of the optical system is varied by an electrical signal of a function generator in the Z-direction and the Reflected light back to the sample surface is directed to at least one photosensor, wherein the sensor signal by means of a detection means measured over time and the time of a maximum signal is determined, wherein the detection means is adapted to derive from the electrical signal at the time of the signal maximum, the height Z of the surface.
  • the light from the light source is directed onto the optical system after passing through a confocal filter (orifice hole), for example via a semitransparent mirror or a beam splitter cube
  • the light reflected back through the optical system passes through the semitransparent mirror onto the photosensor, through a light source
  • the light on the sensor becomes maximum when the light from the light source is focused on the surface of the sample due to the instantaneous focus position of the adaptive optics Focusing position shows the sensor signal a typical Signal tip (Confokalpeak). From the time of occurrence of this maximum signal can be determined at a known focus position (which is associated with the electrical signal at the relevant time), the height of the sample at the respective measurement position.
  • One possibility is to perform the device integrated fiber optic.
  • the light source, the photosensor and the optical system are connected to each other via optical fibers.
  • a laser is used as the light source.
  • suitable for the process is also any other light source.
  • a spectrally narrowband light source should be used to minimize measurement errors due to unavoidable chromatic aberration of the optical system.
  • the sample to be examined is moved relative to the confocal sensor in the X / Y direction, ie transversely to the direction of the light beam directed onto the sample surface, relative to the optical system, so that the surface is scanned in a grid pattern.
  • an X- / Y-adjustment can be used in a conventional manner.
  • a controllable deflection device for deflecting the light beam directed onto the sample surface can be used, in order in this way to scan the surface in a grid pattern.
  • Suitable deflection devices operating, for example, with movable mirrors are known in the art. So that the extremely high measured data rate and the associated signals can be evaluated correspondingly quickly, a detection device of the type described above is preferably used, which electronically analyzes the sensor signal, wherein the detection device has an extreme value memory, the time-varying signal until reaching an extremum the signal follows, in each case a peak indicator signal is generated when reaching the extremum, based on which Time of the extremum and on the basis of which, in turn, the instantaneous focus position of the optical system associated with the signal maximum is detected.
  • the mode of operation of the detection device in determining the signal maximum is described in the patent application DE 10 201 6 100 261, to which reference is made in its entirety.
  • the achievable high measuring rate opens up new fields of application for confocal measuring technology.
  • surface inspection is enabled in manufacturing processes where the sample is moved at a high feed rate (e.g., sheet rolling, film drawing).
  • the thickness of thin, transparent samples or transparent coatings can also be controlled with the fast implementation according to the invention, provided that the foil / layer top and bottom sides are within the measurement range of the sensor.
  • the light reflected at the sample becomes maximum at two different focus positions. From the spatial distance of the focus positions can be concluded on the layer thickness.
  • the list of applications is not complete by nature.
  • Figure 1 is a schematic representation of a sensor arrangement according to the invention.
  • FIG. 2 is a schematic representation of a sensor arrangement according to the invention in fiber-based design.
  • a confocal sensor is shown and generally designated by the reference numeral 1.
  • the essential components of this confocal sensor 1 are on the one hand a light source, preferably a suitable laser, which is provided with the reference numeral 2.
  • the laser 2 transmits its light through a confocal filter (pinhole) 3 via a beam splitter 4, which in the present example is a semitransparent mirror, onto an optical system 5 consisting of an objective 6 and a TAG lens 7.
  • the TAG lens is supplied with an electrical signal f (t), which is generated by a function generator 18.
  • the light is reflected back from the surface, passed through the optical system 5, the semitransparent mirror 4 through another pinhole 9 to a photosensor 10 which may be a single photodiode, its measured signal I (t) by means of detection means 1 1 is recorded and evaluated over time. The result is the intensity distribution as shown at 1 1.
  • FIG. 2 shows a fiber-based variant 12 of the sensor arrangement according to the invention. Corresponding components are designated by the same reference numerals as in FIG. 1.
  • the light source 2 is at its output connected via an optical fiber 13 to a fiber coupler 14. This is in turn coupled via a further fiber section 15 to a measuring head 16 comprising an adaptive optics in the form of a TAG lens 7 and an objective 6.
  • the fiber coupler 14 couples via another fiber section 17 to the photosensor 10, which thus receives the light reflected at the sample 8. Not shown is the required extraction and coupling optics for coupling out the light from the fiber section 15 or in the fiber section 15th

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Microscoopes, Condenser (AREA)

Abstract

L'invention concerne un procédé et un dispositif de mesure optique de surfaces techniques au moyen d'un capteur confocal, de la lumière d'une source lumineuse (2) étant dirigée sur la surface (8) à mesurer d'un échantillon, par l'intermédiaire d'un système optique (5, 16). Selon l'invention, ledit système optique (5, 16) comprend une optique (7) adaptative à commande électrique, le foyer du système optique (5, 16) pouvant être modulé par un signal électrique (f(t)) dans la direction Z. La lumière réfléchie par la surface d'échantillon (8) est déviée vers au moins un photocapteur (10), le signal de capteur étant mesuré au cours du temps au moyen d'un système de détection (11) et l'instant d'un maximum du signal étant déterminé. Le système de détection (11) déduit du signal électrique, à l'instant du maximum de signal, la hauteur Z de la surface (8).
PCT/EP2018/070439 2017-07-27 2018-07-27 Procédé et dispositif de mesure optique de surfaces au moyen d'un capteur confocal WO2019020800A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP18756156.8A EP3658850A1 (fr) 2017-07-27 2018-07-27 Procédé et dispositif de mesure optique de surfaces au moyen d'un capteur confocal
CN201880057005.4A CN111065884A (zh) 2017-07-27 2018-07-27 借助于共焦传感器进行光学的表面测量的方法和设备

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
DE102017116993.8 2017-07-27
DE102017116993 2017-07-27
DE102017130211.5 2017-12-15
DE102017130211.5A DE102017130211A1 (de) 2017-07-27 2017-12-15 Verfahren und Vorrichtung zur optischen Oberflächenmessung mit Hilfe eines konfokalen Sensors

Publications (1)

Publication Number Publication Date
WO2019020800A1 true WO2019020800A1 (fr) 2019-01-31

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EP (1) EP3658850A1 (fr)
CN (1) CN111065884A (fr)
DE (1) DE102017130211A1 (fr)
WO (1) WO2019020800A1 (fr)

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EP4113054A1 (fr) * 2021-07-02 2023-01-04 Stiftung für Lasertechnologien in der Medizin und Messtechnik an der Universität Ulm Ilm Dispositif de mesure pour le mesurage optique d'un objet

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WO2020221818A1 (fr) 2019-05-02 2020-11-05 Inproq Optical Measurement Gmbh Procédé et dispositif de contrôle de roues dentées
WO2020221859A1 (fr) 2019-05-02 2020-11-05 Inproq Optical Measurement Gmbh Procédé et dispositif de vérification de surface
CN112797937B (zh) * 2021-03-31 2021-08-13 苏州天准科技股份有限公司 一种非接触式测量设备
CN113108696A (zh) * 2021-04-06 2021-07-13 合肥埃科光电科技有限公司 一种光源波长扫描光谱共焦传感器

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WO2016001840A1 (fr) * 2014-07-03 2016-01-07 Align Technology, Inc. Appareil et procédé de mesure optique de topographie de surface
DE102016100261A1 (de) 2016-01-08 2017-07-13 Nanofocus Ag Verfahren zur elektronischen Analyse eines zeitlichen veränderlichen Signals

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WO2016001840A1 (fr) * 2014-07-03 2016-01-07 Align Technology, Inc. Appareil et procédé de mesure optique de topographie de surface
DE102016100261A1 (de) 2016-01-08 2017-07-13 Nanofocus Ag Verfahren zur elektronischen Analyse eines zeitlichen veränderlichen Signals

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MERMILLOD-BLONDIN A ET AL: "High-speed varifocal imaging with a tunable acoustic gradient index of refraction lens", OPTICS LETTERS, OPTICAL SOCIETY OF AMERICA, US, vol. 33, no. 18, 15 September 2008 (2008-09-15), pages 2146 - 2148, XP001516916, ISSN: 0146-9592, DOI: 10.1364/OL.33.002146 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4113054A1 (fr) * 2021-07-02 2023-01-04 Stiftung für Lasertechnologien in der Medizin und Messtechnik an der Universität Ulm Ilm Dispositif de mesure pour le mesurage optique d'un objet

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CN111065884A (zh) 2020-04-24
EP3658850A1 (fr) 2020-06-03
DE102017130211A1 (de) 2019-01-31

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