WO2009098126A1 - Interféromètre - Google Patents

Interféromètre Download PDF

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Publication number
WO2009098126A1
WO2009098126A1 PCT/EP2009/050716 EP2009050716W WO2009098126A1 WO 2009098126 A1 WO2009098126 A1 WO 2009098126A1 EP 2009050716 W EP2009050716 W EP 2009050716W WO 2009098126 A1 WO2009098126 A1 WO 2009098126A1
Authority
WO
WIPO (PCT)
Prior art keywords
light source
pulse
interferometer
light
interferometer according
Prior art date
Application number
PCT/EP2009/050716
Other languages
German (de)
English (en)
Inventor
Matthias Fleischer
Jonathan Becker
Original Assignee
Robert Bosch Gmbh
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 Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Publication of WO2009098126A1 publication Critical patent/WO2009098126A1/fr

Links

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
    • G01B9/02055—Reduction or prevention of errors; Testing; Calibration
    • G01B9/02062—Active error reduction, i.e. varying with time
    • G01B9/02067—Active error reduction, i.e. varying with time by electronic control systems, i.e. using feedback acting on optics or light
    • G01B9/02069—Synchronization of light source or manipulator and detector
    • 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
    • G01B9/02001—Interferometers characterised by controlling or generating intrinsic radiation properties
    • G01B9/02012—Interferometers characterised by controlling or generating intrinsic radiation properties using temporal intensity variation
    • G01B9/02014—Interferometers characterised by controlling or generating intrinsic radiation properties using temporal intensity variation by using pulsed light
    • 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
    • G01B9/02075—Reduction or prevention of errors; Testing; Calibration of particular errors
    • G01B9/02076—Caused by motion

Definitions

  • the invention relates to an interferometer according to the preamble of claim 1.
  • Interferometers are interferometric measuring devices used for precision measurements such as length measurements, refractive index measurements, angle measurements and spectroscopy.
  • a light emission of a light source is split into two coherent partial beams, which are later superimposed again.
  • a measurement object is mounted in one of the partial beams.
  • the superimposed partial beams are directed to a camera (sensor), wherein an interference pattern is imaged on the camera chip.
  • the interference pattern is determined by the difference of the optical paths, which have covered the two partial beams to the union.
  • Interferometers are highly sensitive devices which are susceptible to external disturbances in the form of oscillations, whereby interferometers are in practice provided with corresponding mechanical vibration dampers.
  • Known interferometers are usually with constant light sources, such as lasers, halogen lamps or
  • the object of the invention is to propose an interferometer which is less susceptible to vibrations.
  • the invention is based on the idea of pulsed operation of the at least one light source of the, in particular flat, measuring interferometer, ie to provide a light pulse break between two consecutive light pulses.
  • a weakening of the interference contrast can be avoided, as is unavoidable in unmodulated light sources due to (external) vibrations, since with unmodulated light sources, different signal components intersect with one another.
  • this Ausstoffn in a trained according to the concept of the invention interferometer advantageously prevented.
  • the life of the light source increases because its temperature development is lower due to the pulsed operation.
  • a higher wavelength stability is also obtained.
  • the interferometer is provided with, for example, a transistor comprising, synchronization means which control the light source in response to a trigger signal.
  • the synchronization means are designed such that they synchronize the transmission of a light pulse by the light source with a trigger signal.
  • the trigger signal it is possible to further reduce the susceptibility of the interferometer to vibrations.
  • attenuation of the interference contrast in particular, can be avoided, as occurs with unmodulated light sources.
  • the synchronized pulsing of the light source eliminates the artifacts associated with unmodulated light source interferometers by the camera interlacing.
  • the light source comprises at least one LED.
  • the light source can be formed as a single LED or as a collection of LEDs.
  • the synchronization means always release the power supply for the at least one light source as soon as the synchronization means detect a trigger signal.
  • the synchronization means comprise an electronic switch which is closed as soon as a trigger signal is detected.
  • the trigger signal thus forms a start or release signal for the electrical power supply of the light source.
  • the synchronization means may comprise an integrated circuit or a transistor, wherein in the case of the provision of a transistor preferably the base of the transistor is controlled by means of the trigger signal.
  • Particularly preferred is an embodiment of the synchronization means as an operational amplifier.
  • an embodiment is advantageous in which the synchronization means are designed such that at the beginning of each image frame (frame or field) a light pulse is emitted by the light source. This will block the pulsing of the light source from the camera, i. the camera chip, in particular a CCD chip, not registered.
  • the trigger signal is an integral part of the video signal or is generated based on the video signal.
  • the synchronization means are designed to monitor the video signal. It is also possible that the trigger signal is not or not directly generated in connection with the video signal.
  • the synchronization with an external trigger signal makes it possible to use the particular areal-type interferometer for further applications, such as the measurement of oscillations or of moving components.
  • the trigger signal is formed by an image frame synchronization pulse of the video signal, or generated on the basis of the image frame synchronization pulse.
  • the frame synchronization pulse signals (encodes) the beginning of a new picture (frame).
  • the pulse duration of the light pulse emitted from the light source and / or the pulse pause length is not fixed, but adjustable / is.
  • the pulse pause between two temporally successive light pulses is significantly longer than the actual light pulse.
  • the pulse duration (pulse length) of the light pulse is between about 0.5 ms and about 2 ms.
  • the pulse duration is preferably selected or selectable from a value range between approximately 0.8 ms and approximately 1.3 ms.
  • the synchronization means preferably comprise a counter which is started by the trigger signal or loaded with a defined value. When overflow of the counter, ie when a predetermined or predetermined value, the counter and the light pulse is stopped / stopped. The stopping / stopping of the light pulse preferably takes place by interrupting the power supply of the at least one light source.
  • FIG. 1 shows a schematic structure of an interferometer with pulsed synchronized light source
  • Fig. 2 a Michelson interferometer with pulsed synchronized light source.
  • Fig. 1 is a possible construction of a flat-type interferometer 1, comprising a designed as an LED light source 2, shown.
  • the light source 3 emits light pulses 3, wherein the light pulses 3 with a video signal 4 of a camera 5 (sensor) are synchronized.
  • the camera used is a CCD camera with a frame rate of 25 Hz, ie with 25 image frames per second.
  • the pulse duration of the light pulses in the embodiment shown is about 1 ms, whereas the Image duration of an image frame of the camera 5 takes about 40 ms.
  • the pulse pauses between two light pulses thus last about 39 ms.
  • a light pulse 3 emitted by the light source 2 impinges on a beam splitter 6 which splits the light pulse 3 into two coherent partial light pulses 7, 8, wherein a measurement object 9 to be measured is arranged in the upper partial light pulse 7 in the plane of the drawing.
  • the partial light pulses 7, 8 are redirected via mirrors 10, 11 and combined to a beam splitter 12 and directed to a camera 5 designed as a digital camera, which outputs a video signal 4.
  • the video signal 4 is monitored by means of synchronization means 14, which have the function of an electronic switch in the embodiment shown. If a trigger signal integral with the video signal 4 is detected by the synchronization means 14, a power supply 13 for the light source 2 is released for a predetermined or predefinable time, ie a circuit is closed (for a limited time), so that a (limited) of the light source 2 Light pulse 3 is sent out.
  • an image frame synchronization pulse of the video signal 4 which marks the beginning of a new image frame, is used as a triggering circuit for enabling the power supply 13.
  • 25 light pulses per second are emitted by the light source 2 at a frame rate of 25 Hz mentioned in the sequence. Due to the synchronization of the light pulses 3 with the image frames of the video signal 4, individual light pulses 3 are not registered by the camera 5 and do not disturb the evaluation of the detected interference pattern as a result. Rather, the prevent short, synchronized light pulses attenuation of the interference contrast.
  • the obtained interferometer 1 is less susceptible to external disturbances in the form of vibrations. Therefore, can be dispensed with a mechanical vibration damping, or the vibration damping can be at least easier and thus cheaper to run as in known interferometers with continuously operated light source.
  • FIG. 2 shows a preferred embodiment of a Michelson interferometer 1.
  • the structure differs from the exemplary embodiment shown in FIG. 1 essentially in that only a single beam splitter 6 is provided which divides the light pulse 3 into two coherent partial light pulses 7, 8 and also recombines and feeds the camera 5.
  • the partial light pulse 8 strikes behind the beam splitter 6 on a mirror 10, which reflects the partial light pulse 8 back to the beam splitter 6, which deflects the partial light pulse 8 by 90 ° to the camera 5.
  • the partial light pulse 7 is reflected by the measurement object 19 to be measured back onto the beam splitter 6 and radiates straight through it onto the camera 5.
  • the synchronization means 14 and the video signal 4 are also in the Michelson interferometer shown coupled.

Abstract

L'invention concerne un interféromètre (1) comprenant une source lumineuse (2) et une caméra (5) produisant un signal vidéo (4), en particulier une caméra numérique, pour enregistrer une figure d'interférence. Selon l'invention, la source lumineuse (2) peut fonctionner en mode pulsé. Dans un mode de réalisation spécifique, les impulsions lumineuses sont synchronisées avec les images de la caméra.
PCT/EP2009/050716 2008-02-08 2009-01-22 Interféromètre WO2009098126A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102008008559.6 2008-02-08
DE200810008559 DE102008008559A1 (de) 2008-02-08 2008-02-08 Interferometer

Publications (1)

Publication Number Publication Date
WO2009098126A1 true WO2009098126A1 (fr) 2009-08-13

Family

ID=40410204

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2009/050716 WO2009098126A1 (fr) 2008-02-08 2009-01-22 Interféromètre

Country Status (2)

Country Link
DE (1) DE102008008559A1 (fr)
WO (1) WO2009098126A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110128551A1 (en) * 2008-04-30 2011-06-02 Matthias Fleischer Interferometric system and method for adjusting a path difference

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001082786A2 (fr) * 2000-05-03 2001-11-08 Flock Stephen T Imagerie optique de structures anatomiques internes et de biomolecules
US6556305B1 (en) * 2000-02-17 2003-04-29 Veeco Instruments, Inc. Pulsed source scanning interferometer
WO2007066465A1 (fr) * 2005-12-07 2007-06-14 Kabushiki Kaisha Topcon Instrument de mesure d'image optique

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10321887A1 (de) 2003-05-07 2004-12-02 Universität Stuttgart Robuster optischer Sensor und Verfahren zur Hochgeschwindigkeits-Detektion

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6556305B1 (en) * 2000-02-17 2003-04-29 Veeco Instruments, Inc. Pulsed source scanning interferometer
WO2001082786A2 (fr) * 2000-05-03 2001-11-08 Flock Stephen T Imagerie optique de structures anatomiques internes et de biomolecules
WO2007066465A1 (fr) * 2005-12-07 2007-06-14 Kabushiki Kaisha Topcon Instrument de mesure d'image optique
EP1970694A1 (fr) * 2005-12-07 2008-09-17 Kabushiki Kaisha TOPCON Instrument de mesure d'image optique

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20110128551A1 (en) * 2008-04-30 2011-06-02 Matthias Fleischer Interferometric system and method for adjusting a path difference
US8625103B2 (en) * 2008-04-30 2014-01-07 Robert Bosch Gmbh Interferometric system and method for adjusting a path difference

Also Published As

Publication number Publication date
DE102008008559A1 (de) 2009-08-13

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