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WO1998038475A1 - Appareil permettant d'etalonner avec precision un intergerometre de mesure de la longueur - Google Patents

Appareil permettant d'etalonner avec precision un intergerometre de mesure de la longueur Download PDF

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Publication number
WO1998038475A1
WO1998038475A1 PCT/GB1998/000365 GB9800365W WO9838475A1 WO 1998038475 A1 WO1998038475 A1 WO 1998038475A1 GB 9800365 W GB9800365 W GB 9800365W WO 9838475 A1 WO9838475 A1 WO 9838475A1
Authority
WO
WIPO (PCT)
Prior art keywords
interferometer
length
artifact
optical length
etalon
Prior art date
Application number
PCT/GB1998/000365
Other languages
English (en)
Inventor
Noel William Frank Stephens
Original Assignee
Aberlink Technology Limited
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 Aberlink Technology Limited filed Critical Aberlink Technology Limited
Priority to AU59970/98A priority Critical patent/AU5997098A/en
Publication of WO1998038475A1 publication Critical patent/WO1998038475A1/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
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/0209—Low-coherence interferometers
    • 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
    • G01B9/0207—Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer
    • G01B9/02072—Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer by calibration or testing of interferometer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B2290/00—Aspects of interferometers not specifically covered by any group under G01B9/02
    • G01B2290/25—Fabry-Perot in interferometer, e.g. etalon, cavity

Definitions

  • This invention relates to apparatus for precise length measurement calibration.
  • Diode lasers are inexpensive, small and compact, efficient, and will run on low voltage current drives. Their main disadvantages are: propensity to mode hopping; wavelength changes with temperature
  • their lasing cavities are sensitive to small amounts of light reflected back into the cavity, for example off optical surfaces; and the coherence of their emitted light is restricted.
  • This invention is aimed at calibrating relatively unstable incremental length measuring apparatus and is specifically, but not exclusively, directed towards calibrating laser based length measuring interferometers which use diode lasers. This invention addresses the problem of achieving high accuracy when using a relatively unstable laser wavelength. It also, by default, eliminates the need
  • optical cell which acts as standard length artifact or optical length artifact (OLA).
  • OVA optical length artifact
  • a suitable beam may be
  • the cell produces collimating light emitted from, for example, a standard light emitting diode of the Gallium Aluminium Arsenide type, or a filament lamp.
  • the cell operates by (although not exclusively) interference to impose a cyclically varying intensity profile across the wavelength spectrum of the light it transmits.
  • a cell capable of producing this effect is a Fabry Perot etalon. The appropriate spectral properties are
  • a Fabry Perot etalon cell imposed on the beam after passing it through a Fabry Perot etalon cell.
  • Perot etalon is a multi-beam interferometer and as such produces a non-sinusoidal
  • a two beam interferometer A two beam interferometer
  • the Fabry Perot etalon provides a convenient means of producing the desired effect.
  • An advantage of the Fabry Perot etalon is that a fixed mass of gas (air) may conveniently be sealed in a volume between its two reflectors (between which multiple reflections occur). This means that the optical path between the two reflectors (which defines the length of the optical artifact) will not be affected by changes in atmospheric conditions to a very high degree of accuracy. The only significant change
  • optical path length will be due to thermal expansion of the etalon which is accurately predictable using for example fused silica spacers.
  • Erskine and Holmes use two similar, fixed path difference, interferometers in tandem.
  • a low coherence light beam passes through each of the interferometers in turn with a measurement arm situated between the two interferometers.
  • Measurement ranges of laser based interferometers are inherently linear because they in effect count in wavelengths of
  • wavelength of light from diode lasers is prone to vary with small changes in temperature and drive current, typically 70 parts per million per degree Celsius.
  • the wavelength can be different each time the diode is switched on and stabilised at a fixed temperature and drive current.
  • the wavelength of the laser light is not actually required to be known, prior to taking measurements, in this invention. This is a distinguishing feature of the
  • a cyclically varying spectral profile may alternatively be produced using any suitable stable filtering means, for example, Sole or Lyot filter types.
  • a broad band (white light) light source has very low coherence and as such
  • the spectrum of broad band light is modified by first passing it through a filter, such as an interferometer of fixed path difference, for example a Fabry Perot etalon, then subsequent positions of detectable interference are found at path differences
  • a filter such as an interferometer of fixed path difference, for example a Fabry Perot etalon
  • This invention requires detectable interference to occur at at least two path differences, one of which may be the zero path condition, in order to derive at least two reference signatures.
  • the physical separation of any two reference may be the zero path condition, in order to derive at least two reference signatures.
  • the finesse of the Fabry Perot etalon may be any suitable finesse of the Fabry Perot etalon.
  • Low finesse is also an advantage in terms of transmission of broad band radiation, which is proportional to the inverse of the finesse of the etalon.
  • spectral composition of a light source may also be understood with reference to the field of Fourier transform spectroscopy.
  • apparatus for precise length measurement calibration comprising a linear length measuring interferometer
  • a measurement beam having a broad spectral band source, a collimating means for producing a collimated incident beam, a beam splitter for producing part beams which, in use, pass along a reference arm and a measurement arm of the interferometer respectively, a reference reflector for reflecting the part beam passing along the reference arm, a measurement
  • combining means for recombining the part beams reflected by the reference reflector and the measurement reflector, the measurement reflector being moveable to provide a measuring range; an optical length artifact for modifying the spectral composition of the incident beam or of one of the part beams or of a recombined beam in a way that imposes a cyclically varying spectral intensity with changing wavelength across the broad spectral range of the light source; and fringe detection means providing at least two reference signatures throughout the measuring range spaced apart by an amount determined by the optical length artifact.
  • FIG. 1 illustrates the salient features of one embodiment of the invention
  • FIG. 2 illustrates another embodiment of the invention
  • FIG 3 shows typical reference signatures generated in the detection means of Figures 1 and 2
  • Figure 4 shows a Fabry Perot etalon adapted as an optical length artifact with sealed cavity
  • Figure 5 shows a Fabry Perot etalon whose cavity is exposed to atmospheric changes
  • Figure 6 shows modified broad spectral band after transmission through the
  • Figure 7 shows one embodiment of the invention incorporating a laser based
  • Figure 8 shows an alternative site for the optical length artifact
  • Figure 9 shows a further site for the optical length artifact
  • Figure 10 shows another embodiment of the invention incorporating a laser based length measuring interferometer
  • FIG 11 shows the salient features of the preferred embodiment.
  • Figure 12 shows the optical length artifact in the reference arm, reflecting light directly back to the beam splitter/combiner.
  • a light emitting diode is collimated by lens 2 before being modified by an optical length artifact 11 in the form of a Fabry Perot etalon shown in Figures 4 and 5.
  • the Fabry Perot etalon imposes a cyclically varying profile across the broad spectral band of the light source as illustrated in Figure 6.
  • the light After being modified by its passage through the Fabry Perot etalon, the light enters a measuring interferometer of the Michelson type, having a beam splitter 4 for producing part beams 5R and 5M
  • reflector 7M is movable over a measurement range 10. Normally, a measuring
  • interferometer of this type produces detectable fringes only over a small measuring range, typically 5-10 microns, when using a broad spectral band source.
  • a small measuring range typically 5-10 microns
  • short bursts of detectable fringes are produces at several places along the measuring range 10, as illustrated in Figure 3.
  • the central maxima of the detectable fringes is located by
  • the Fabry Perot etalon 11 may be used as an optical length artifact in two distinct ways: either a fixed mass of gas is sealed in the etalon cavity as illustrated in
  • the former can be used in conjunction with atmospheric monitoring to enable a correction to be made to measured displacements.
  • the Fabry Perot etalon cell In the preferred embodiment of the invention, the Fabry Perot etalon cell
  • FIG. 5 comprises two partially reflecting and partially transmitting surfaces 21,24 which may be plane or configured as a confocal resonator, supported on an appropriate substrates 20, for example fused silica.
  • the partially reflecting surfaces 21,24 may be plane or configured as a confocal resonator, supported on an appropriate substrates 20, for example fused silica.
  • mirrors are spaced apart by a convenient distance (eg. 50 mm) by a spacer tube 22 also fabricated in fused silica.
  • the etalon mirrors are
  • An air filter 25 is located in the breather tube to prevent contamination of the etalon mirrors.
  • Figure 4 shows the mirror substrates hard sealed 23, or fused, to the spacer
  • Fused silica is cited for its low and predictable coefficient of thermal
  • mirror substrates Any other material with appropriate properties may be used for mirror substrates and spacer tube.
  • the measured distance between successive reference signatures is an optical distance in the measuring range which is precisely equal to the optical separation between the etalon mirrors. If the etalon is sealed, as shown in Figure 4, its optical length only varies with the thermal expansion of its mirror spacer. Its optical length must therefore be determined at an accurately known temperature, so
  • the length is always equal to the separation of successive reference signatures in the measuring range. In this case either: the physical length (not optical length) of the
  • etalon must be measured at a known temperature; or the separation between reference signatures in the measuring range accurately determined using an auxiliary precision interferometer, for example an atmospheric corrected Iodine stabilised helium-neon
  • Figure 2 shows a length measuring interferometer incorporating an
  • the optical length artifact shown in Figure 2 represents any form of two beam fixed path difference interferometer.
  • the general fixed path interferometer may be variations or combinations of any of the following types: Michelson
  • interferometer This is facilitated using cube corner retroreflector 7R and 7M in the reference arm 6R and measurement arm 6M respectively.
  • Retroreflectors in the respective arms of the interferometer are, used
  • Cube corner reflectors may also be used to spatially separate the
  • the retroreflectors 7R and 7M are 90 degree porro type reflecting prisms.
  • FIGS 8 and 9 show alternative sites for the optical length artifact in the
  • Figure 10 shows the combining of the laser and broad band beams prior to entering the measuring interferometer, and their subsequent separation prior to their respective fringe detection.
  • beam combiner 18 and separator 17 are
  • optical length artifact could be located between the beam combiner 8 and the separator 17 instead of in the incident beam or the reference
  • FIG 11 shows the preferred embodiment of the invention in which the
  • etalon is located in the reference arm of a Michelson interferometer.
  • Michelson interferometer In the preferred
  • the etalon is reflective, which returns the light back along the same path in the reference arm.
  • the measuring arm of the interferometer has a corresponding
  • Such an arrangement is commonly referred to as a double pass interferometer and has the advantage that, once set up, fringe visibility is unaffected by lateral displacement or rotation of cube corner retroreflectors in either arm of the interferometer. Because it is double path, interference signatures produced in the Michelson interferometer by virtue of the etalon are separated in distance along the measuring arm by half the length of the etalon.
  • Figure 12 shows an embodiment of the invention in which the optical length artifact is located in the reference arm, with its mirrors reflecting light back to the beam splitter/recombiner, without the use of additional reflecting surfaces in the reference arm.
  • This embodiment retains double pass in the measuring arm which benefits from displacement tolerance of the associated retroreflector.
  • the beam combiner 8 used in the preferred embodiment of this invention, and also in any laser length measuring interferometer used in conjunction with this invention, is a non-polarising type proposed by Raines and Downs (Optica Acta,
  • Phase quadrature signals are used for up and down incremental counting and form the basis of position measurement known in the art.
  • the 90 degree phase delay is also useful when deriving a reference
  • the fringe detection means 9 detects fringes
  • the laser length interferometer is calibrated by counting the number of
  • the invention may be adapted for use with polarising length measuring interferometers known in the art.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Instruments For Measurement Of Length By Optical Means (AREA)

Abstract

Appareil utile pour étalonner des interféromètres laser de mesure de la longueur au moyen d'une source (1) de lumière à large bande spectrale dont la composition spectrale est modifiée par un filtre (11). La lumière traverse un interféromètre de mesure de la longueur et des salves courtes de franges sont alors détectées à plus d'un endroit sur une plage (10) de mesure. Dans la forme de réalisation préférée de cette invention le filtre est un interféromètre de Fabry-Pérot dans lequel la séparation des miroirs définit l'intervalle sur la plage de mesure entre lequel sont détectées les salves de franges. Les salves de franges sont transformées en signatures de référence électriques par un dispositif de détection (9) des franges et leurs positions sont définies avec une précision extrême par un circuit de détection électronique connu. La séparation des salves courtes de franges détectables dans la plage de mesure correspond précisément à la séparation des miroirs de l'étalon Fabry-Pérot. La longueur de la cavité de l'étalon définitpar conséquent un artéfact de longueur optique à l'aide duquel on étalonne la plage (10) de mesure.
PCT/GB1998/000365 1997-02-25 1998-02-05 Appareil permettant d'etalonner avec precision un intergerometre de mesure de la longueur WO1998038475A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU59970/98A AU5997098A (en) 1997-02-25 1998-02-05 Apparatus for precise length measurement calibration

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9703928A GB9703928D0 (en) 1997-02-25 1997-02-25 Apparatus for precise length measurement calibration
GB9703928.3 1997-02-25

Publications (1)

Publication Number Publication Date
WO1998038475A1 true WO1998038475A1 (fr) 1998-09-03

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004033986A1 (fr) * 2002-10-11 2004-04-22 Agilent Technologies, Inc. Controle d'interferometre
EP1696201A1 (fr) * 2005-02-23 2006-08-30 Leica Geosystems AG Compensation du bruit de phase pour un interféromètre de mesure d'une distance absolue
CN104237894A (zh) * 2013-06-18 2014-12-24 赫克斯冈技术中心 距离改变的干涉测量确定
US9645044B2 (en) 2014-09-30 2017-05-09 Corning Optical Communications LLC Controlled-contact method of measuring insertion loss in optical fiber connectors
DE102017101580A1 (de) 2017-01-26 2018-07-26 Picofine GmbH Messkopf für ein Laserinterferometer und betreffendes Messverfahren
CN108827162A (zh) * 2018-09-10 2018-11-16 中国计量大学 基于电容传感器的法布里珀罗标准具微位移测量系统的线性度比对装置和方法
CN109000567A (zh) * 2018-10-22 2018-12-14 中国计量大学 基于psd的法布里珀罗标准具微位移测量系统的线性度比对装置和方法
WO2019191698A3 (fr) * 2018-03-30 2019-12-05 Si-Ware Systems Spectromètre auto-référencé

Citations (2)

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Publication number Priority date Publication date Assignee Title
DE1204838B (de) * 1960-11-24 1965-11-11 Olympus Optical Co Interferenz-Komparator
WO1990011485A1 (fr) * 1989-03-21 1990-10-04 Tabarelli, Werner Dispositif generateur de lumiere

Patent Citations (2)

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Publication number Priority date Publication date Assignee Title
DE1204838B (de) * 1960-11-24 1965-11-11 Olympus Optical Co Interferenz-Komparator
WO1990011485A1 (fr) * 1989-03-21 1990-10-04 Tabarelli, Werner Dispositif generateur de lumiere

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
M KERNER: "Wellenlängenstabilisierte Interferometer", TM TECHNISCHES MESSEN, vol. 57, no. 6, June 1990 (1990-06-01), MÜNCHEN DE, pages 227 - 234, XP000132777 *

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2004033986A1 (fr) * 2002-10-11 2004-04-22 Agilent Technologies, Inc. Controle d'interferometre
US7423760B2 (en) 2002-10-11 2008-09-09 Agilent Technologies, Inc. Method and apparatus for monitoring an interferometer
EP1696201A1 (fr) * 2005-02-23 2006-08-30 Leica Geosystems AG Compensation du bruit de phase pour un interféromètre de mesure d'une distance absolue
WO2006089845A1 (fr) * 2005-02-23 2006-08-31 Leica Geosystems Ag Compensation du bruit de phase pour mesure de distance absolue par interferometrie
US7619719B2 (en) 2005-02-23 2009-11-17 Leica Geosystems Ag Phase noise compensation for interferometric absolute rangefinders
CN104237894A (zh) * 2013-06-18 2014-12-24 赫克斯冈技术中心 距离改变的干涉测量确定
EP2816315A1 (fr) * 2013-06-18 2014-12-24 Hexagon Technology Center GmbH Détermination interférométrique de changement de distance à l'aide d'une diode laser, de détection de largeur de bande élevée et de traitement rapide de signal
US9310178B2 (en) 2013-06-18 2016-04-12 Hexagon Technology Center Gmbh Interferometric determination of distance change with laser diode, high bandwidth detection and fast signal processing
US9645044B2 (en) 2014-09-30 2017-05-09 Corning Optical Communications LLC Controlled-contact method of measuring insertion loss in optical fiber connectors
DE102017101580A1 (de) 2017-01-26 2018-07-26 Picofine GmbH Messkopf für ein Laserinterferometer und betreffendes Messverfahren
WO2019191698A3 (fr) * 2018-03-30 2019-12-05 Si-Ware Systems Spectromètre auto-référencé
US11085825B2 (en) 2018-03-30 2021-08-10 Si-Ware Systems Self-referenced spectrometer
CN108827162A (zh) * 2018-09-10 2018-11-16 中国计量大学 基于电容传感器的法布里珀罗标准具微位移测量系统的线性度比对装置和方法
CN108827162B (zh) * 2018-09-10 2023-08-18 中国计量大学 基于电容传感器的法布里珀罗标准具微位移测量系统的线性度比对装置和方法
CN109000567A (zh) * 2018-10-22 2018-12-14 中国计量大学 基于psd的法布里珀罗标准具微位移测量系统的线性度比对装置和方法
CN109000567B (zh) * 2018-10-22 2023-08-18 中国计量大学 基于psd的法布里珀罗标准具微位移测量系统的线性度比对装置和方法

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Publication number Publication date
GB9703928D0 (en) 1997-04-16
AU5997098A (en) 1998-09-18

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