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WO1989008825A1 - Agencement de determination de la longueur d'onde ou de l'indice de refraction - Google Patents

Agencement de determination de la longueur d'onde ou de l'indice de refraction Download PDF

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Publication number
WO1989008825A1
WO1989008825A1 PCT/EP1989/000255 EP8900255W WO8908825A1 WO 1989008825 A1 WO1989008825 A1 WO 1989008825A1 EP 8900255 W EP8900255 W EP 8900255W WO 8908825 A1 WO8908825 A1 WO 8908825A1
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WO
WIPO (PCT)
Prior art keywords
partial
beams
pair
frequency
beam splitter
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/EP1989/000255
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German (de)
English (en)
Inventor
Ernst LÖBACH
Gerhard Leuchs
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Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Publication of WO1989008825A1 publication Critical patent/WO1989008825A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
    • G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
    • G01J9/0246—Measuring optical wavelength
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
    • G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J9/00—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength
    • G01J9/02—Measuring optical phase difference; Determining degree of coherence; Measuring optical wavelength by interferometric methods
    • G01J2009/0207—Double frequency, e.g. Zeeman

Definitions

  • the invention relates to a device for determining the wavelength of light beams in a medium or the refractive index of this medium, with at least two dimensional standards of different lengths, each of which has a different geometric path difference of two Partial beam bundle formed in a beam splitter defines, wherein one of the partial beam bundles of such a partial beam bundle passes through a distance defined by the associated measuring standard in the medium, and in which an at least one photoelectric detector device is provided, with which the two recombined partial beam bundles each are formed in a partial beam bundle formed output beams can be analyzed.
  • the wavelength prevailing in a medium (hereinafter referred to as air wavelength for short) is often determined by mechanically displacing an auxiliary reflector by a distance defined by a measure of embodiment, the displacement path being simultaneously measured interferometrically in units of the air wavelength.
  • a comparison provides the searched air wavelength even at completely unknown frequency and completely unknown refractive index of the medium.
  • the above condition for the initial wavelength uncertainty obviously depends on the length of the material measure. (If the above inequality is adhered to, it is also said that the "wavelength lies in the free spectral range of the material measure".) If the material measure has a short length, the requirement for the initial wavelength uncertainty is advantageously low. On the other hand, the measuring accuracy that can be achieved with a short measuring standard is also less than with a long one.
  • the object of the invention is to provide an inexpensive and compact device of the type mentioned at the beginning, with which the wavelength in a medium (or, if the frequency is known, the refractive index of the medium therefrom) without the use of movable components even with a relatively large one wavelength uncertainty can be immobilized quickly and extremely precisely.
  • the material measures are static material measures, the length of which does not change in operation, in that a device is provided for generating two light beams of different frequencies, one partial beam from the light beam of the one frequency and one partial beam of a partial beam pair and a partial beam from the light beam of the other frequency each represent the other partial beam of a pair of partial beams, and that the photoelectric detector means has a phase detector which detects vibration in each output beam.
  • the device according to the invention works heterodyne, that is to say with two different frequencies of known frequency difference.
  • This allows the use of simple, completely static material measures (etalons), eg mirrors arranged at a certain fixed distance.
  • etalons eg mirrors arranged at a certain fixed distance.
  • the phase position of the beat oscillation is measured, which arises when a partial beam of one frequency with the partial beam of the other frequency, a path difference or a phase shift against the one by running over a distance defined in the medium by the respective dimensions Partial beams are experienced, recombined and superimposed.
  • the method according to the invention is based on the knowledge that the directly immeasurable phase shift of two rapidly oscillating partial beams, which depends on the difference in the path of these partial beams, is reflected in the phase position of the beat oscillation, which is approximately in the megahertz range, which can be easily detected with today's electronic devices. From the phase position of the beat oscillation one knows the phase position of the two partial beams of a partial beam pair and thus their optical path difference. Together with the known geometrical path difference determined by the respective measuring standard, the air wavelength of the partial beam bundle guided in the medium begins, provided the initial wavelength uncertainty for the respective measuring standard lies in the free wavelength range ( ⁇ / ⁇ ⁇ / 2l). Starting from the smallest measuring standard (low requirement for initial wavelength uncertainty), increasingly longer measuring standards (in which the same air conditions prevail) can be used to gradually specify the air wavelength.
  • the device according to the invention for determining the wavelength can be used particularly advantageously in heterodyne-operated interferometer arrangements, where the device for generating two light beams is different Frequency is already part of the interferometer itself, i.e. two light beams of different frequencies already exist.
  • the device according to the invention can, however, also be used in homodyne (operated at a frequency) arrangement, in that from the interferometer light beam by means of a suitable device, for example by means of an acousto-optical crystal, two light beam beams of different frequencies for heterodyne operation according to the invention tiered etalons are formed.
  • the frequencies of the two different frequency light beams must be known. This can be done by using a frequency standard as the light source, or by a suitable addition to the stepped etalons, for example by a quartz etalon, which will be explained in more detail later.
  • FIG. 1 shows an embodiment of the device according to the invention as a wavelength determination device in an interferometer arrangement for determining the displacement of a movable component
  • FIG. 2 shows another embodiment of the device according to the invention as an absolute refractometer.
  • the laser interferometer arrangement shown in FIG. 1 works according to the so-called heterodyne method, in which two partial beams with slightly different frequencies are used.
  • a laser diode 1 emits monochromatic, infrared light, which is collected by the lens 2 and focused on the acousto-optical crystal 3.
  • the downstream lens 4 aligns the two partial beams in parallel.
  • a beam splitter 5 which has a semi-transparent mirror layer, which is formed by the half-mirrored diagonal surface of a cube made of glass, directs a part of both partial beams in the direction of the measuring interferometer component 6, in which the partial beam f 1 and that on the movable component 7 via a connecting rod connected reflector 8 running other partial beam are superimposed and fed to a photodetector 9 which is connected to an electronic evaluation device 9 '.
  • Said measuring interferometer component 6 consists only of two semi-transparent mirror surfaces which are arranged for protection within quartz glass bodies.
  • the amplitude of the total radiation impinging on the photodetector 9 changes with the resting vibration frequency ⁇ f of the two partial beams, which is counted in the evaluation device 9 '.
  • ⁇ f which is approximately 50 MHz, can be measured directly and precisely.
  • the resulting change in the floating frequency received by the photodetector 9 compared to the resting floating frequency is a measure of the instantaneous displacement speed, which over time integrates the displacement distance of the reflector 8 in units of the existing wavelength in the medium (refractive index n) on the measurement path (hereinafter briefly Air wavelength, although media other than air are also conceivable).
  • Air wavelength the existing wavelength in the medium (refractive index n) on the measurement path
  • the material measure 11a with the greatest length d 1 is arranged closest to the entry point 14 of the two light beams of different frequencies f 1 , f 2 into the device 10.
  • the different intensity losses in the individual measuring standards due to the different lengths of the material measures can also be compensated for by differently transmissive beam splitter layers, so that the output beam bundles 15a-d to the respectively assigned photo detectors 16a-d of the photoelectric detector device 17 have approximately the same intensity.
  • the beam splitters 12a-d which in the present exemplary embodiment each have two beam splitter layers arranged at right angles to one another and at 45 to the light beam bundles f 1 , f 2 entering the device in parallel, a partial beam bundle pair of different frequencies is formed, with a partial beam bundle pair ( Frequency f 2 ) a distance d determined by the respective material measure 11a or 11b or 11c. passes through in the medium.
  • the partial beam bundles now having a certain optical path difference are superimposed and fed together as output beam bundles 15a-d to the associated photodetector 16a-d.
  • a partial beam of rays continues through the beam splitter layers of the beam splitters 12a-c to the next beam splitter 12b-d.
  • the photoelectric detector device 17 detects the phase positions of the beat oscillations present in the output beams 15a-c, specifically in the present exemplary embodiment relative to the phase positions of the reference beat vibrations present in the output beams 15d. Since the beam splitters 12a-d are constructed essentially the same (the beam splitter layers are each embedded in quartz glass), the glass paths are the same and the phase positions of the beat vibrations in the output beams 15a-c relative to the phase position of the reference beat vibration in the output beam 15d, where the mirror 13d is direct attached to the beam splitter 12d, give directly by covering the distances d i in the medium Refractive index n caused phase shifts of the partial beam of frequency f 2 . From these phase shifts, the known wavelength in the medium can be determined, if d i 's are known.
  • the result of the present wavelength determination is fed to the evaluation device 9 ', which then displays the displacement distance ⁇ x in meters or otherwise communicates it.
  • a particular advantage of the device according to the invention is in addition to the high measurement accuracy in the completely static structure, which does not require moving parts.
  • the glass bodies of the individual beam splitters 12a-d are joined together directly over flat surfaces
  • the device according to the invention can not only be used to determine the air wavelength alone, but - with a known frequency of the light beam - in an absolute refractometer, as shown in FIG. 2.
  • FIG. 2 differs from the arrangement shown in FIG. 1 essentially by the omission of the components 5, 6, 7, 8, 9 and 9 'and by the addition of the device according to the invention by a quartz etalon 23 with a known refractive index n QUARTZ together with the associated mirror 24, the beam splitter 25 and the
  • the frequency of the partial beams is in the additional evaluation circuit can be determined (the refractive index of the quartz is known) and from this, with a known air wavelength, the desired refractive index of the medium n.
  • This refractometer has an extremely compact structure compared to known refractometers. In particular, no vacuum pumps are necessary. The refractive index can also be determined in real time.
  • the determination of the refractive index with a single additional quartz etalon, as described above, is unambiguous if the refractive index of the air (or in general of the medium), for example according to the parameter method, is so far roughly known that the quartz etalon is in the free wavelength range.
  • the invention is of course not limited to the exemplary embodiments shown. Both the number and the structure of the dimensional structures and beam splitters can vary within the scope of the invention.
  • the device according to the invention can also be used in arrangements other than those shown, either for determining the air wavelength or the refractive index of a medium.
  • a frequency standard is also conceivable and possible as a light source, as a result of which the device according to the invention becomes an absolute refractometer.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Instruments For Measurement Of Length By Optical Means (AREA)

Abstract

Un agencement de détermination de la longueur d'onde de faisceaux de rayons de lumière dans un milieu ou de l'indice de réfraction dudit milieu comprend au moins deux corps stationnaires de mesure (11a, 11b, 11c) de différentes longueurs dont chacun détermine un trajet géométrique différent pour deux faisceaux partiels de rayons formés par une lame séparatrice. Chaque faisceau partiel de rayons (f2) d'une telle paire de faisceaux partiels de rayons parcourt dans le milieu un trajet (d1, d2, d3) déterminé par le corps de mesure correspondant (11a, 11b ou 11c). Deux faisceaux de rayons de lumière présentent des fréquences différentes (f1, f2). Un des faisceaux partiels de rayons de chaque paire de faisceaux partiels de rayons est formé par le faisceau de rayons de lumière ayant la fréquence (f1), et l'autre faisceau partiel de chaque paire de faisceaux partiels est formé par le faisceau de rayons de lumière ayant l'autre fréquence (f2). Un détecteur photoélectrique détermine la relation de phases de pleurage de chaque faisceau de rayons de sortie (15a-c) formé par superposition et par recombinaison des deux faisceaux partiels de rayons de chaque paire de faisceaux partiels de rayons. Cette relation de phases constitue une mesure de la différence entre les trajets optiques de chaque faisceau partiel de rayons d'une paire de faisceaux partiels de rayons.
PCT/EP1989/000255 1988-03-11 1989-03-11 Agencement de determination de la longueur d'onde ou de l'indice de refraction Ceased WO1989008825A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT0066288A AT390836B (de) 1988-03-11 1988-03-11 Einrichtung zur wellenlaengebestimmung bzw. brechzahlbestimmung
ATA662/88 1988-03-11

Publications (1)

Publication Number Publication Date
WO1989008825A1 true WO1989008825A1 (fr) 1989-09-21

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Application Number Title Priority Date Filing Date
PCT/EP1989/000255 Ceased WO1989008825A1 (fr) 1988-03-11 1989-03-11 Agencement de determination de la longueur d'onde ou de l'indice de refraction

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EP (1) EP0357754A1 (fr)
AT (1) AT390836B (fr)
WO (1) WO1989008825A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2425338C2 (ru) * 2009-08-17 2011-07-27 Общество с ограниченной ответственностью "Телеком-прибор" (ООО "Телеком-прибор") Быстродействующий измеритель длины волны лазерного излучения для волоконно-оптических систем передачи информации

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4309108A (en) * 1977-01-17 1982-01-05 The Perkin-Elmer Corporation Analyzer for coherent radiation
GB2148497A (en) * 1983-10-20 1985-05-30 Seiko Instr & Electronics Liquid refractometer

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5742824A (en) * 1980-08-28 1982-03-10 Rikagaku Kenkyusho Method and device for sequential determination of light wavelength

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4309108A (en) * 1977-01-17 1982-01-05 The Perkin-Elmer Corporation Analyzer for coherent radiation
GB2148497A (en) * 1983-10-20 1985-05-30 Seiko Instr & Electronics Liquid refractometer

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Applied Physics B. Photophysics and Laser Chemistry, Band 38, Nr. 1, September 1985, Springer-Verlag (Berlin, DE), R. Castell et al.: "The accuracy of laser wavelength meters", Seiten 1-10 *
Patent Abstracts of Japan, Band 6, Nr. 112 (P-124)(990), 23. Juni 1982; & JP-A-5742824 (RIKAGAKU KENKYUSHO) 10. März 1982 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2425338C2 (ru) * 2009-08-17 2011-07-27 Общество с ограниченной ответственностью "Телеком-прибор" (ООО "Телеком-прибор") Быстродействующий измеритель длины волны лазерного излучения для волоконно-оптических систем передачи информации

Also Published As

Publication number Publication date
EP0357754A1 (fr) 1990-03-14
ATA66288A (de) 1989-12-15
AT390836B (de) 1990-07-10

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