WO2015096279A1 - High resolution heterodyne interferometric method and system - Google Patents

High resolution heterodyne interferometric method and system Download PDF

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Publication number
WO2015096279A1
WO2015096279A1 PCT/CN2014/072819 CN2014072819W WO2015096279A1 WO 2015096279 A1 WO2015096279 A1 WO 2015096279A1 CN 2014072819 W CN2014072819 W CN 2014072819W WO 2015096279 A1 WO2015096279 A1 WO 2015096279A1
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WO
WIPO (PCT)
Prior art keywords
retroreflector
measurement
beam splitter
frequency
linearly polarized
Prior art date
Application number
PCT/CN2014/072819
Other languages
French (fr)
Inventor
Jiubin Tan
Pengcheng HU
Peng Chen
Original Assignee
Harbin Institute Of Technology
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
Priority claimed from CN201310745318.8A external-priority patent/CN103743346B/en
Priority claimed from CN201310745960.6A external-priority patent/CN103743336B/en
Application filed by Harbin Institute Of Technology filed Critical Harbin Institute Of Technology
Publication of WO2015096279A1 publication Critical patent/WO2015096279A1/en

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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
    • G01B9/02001—Interferometers characterised by controlling or generating intrinsic radiation properties
    • G01B9/02002—Interferometers characterised by controlling or generating intrinsic radiation properties using two or more frequencies
    • G01B9/02003—Interferometers characterised by controlling or generating intrinsic radiation properties using two or more frequencies using beat frequencies
    • 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
    • G01B2290/15—Cat eye, i.e. reflection always parallel to incoming beam
    • 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
    • G01B2290/70—Using polarization in the interferometer

Definitions

  • the present invention relates to a high resolution heterodyne interferometric method and system, which can be used for measuring displacement of the target with high resolution and no periodic nonlinearity.
  • the heterodyne interferometer has been widely used in many precision machines and calibration services due to its large measuring range, high signal-to-noise ratio and high measurement precision.
  • high resolution, high speed and high accuracy measurements are required for many applications in order to produce small features. This initiates an improvement of the performance of the heterodyne interferometer to satisfy industrial demands.
  • a heterodyne interferometer with an acousto-optic modulator as a beam splitter was proposed by T. L. Schmitz and J. F. Beckwith in "Ascousto-optic displacement-measuring interferometer: a new heterodyne interferometer with Anstrom level periodic error" Journal of Modern Optics 49, pages 2105-2114.
  • this method can reduce the frequency and polarization mixing effects, the periodic nonlinearity is reduced and the precision and resolution are improved consequently. Nonetheless, its specific and complicated configuration limits the typically possible applications for measuring displacement.
  • One objective of the invention is to provide a heterodyne interferometric method and system, which is suitable for high resolution and high accuracy measurements.
  • a high resolution heterodyne interferometric method which comprises the steps of:
  • a high resolution heterodyne interferometric system is proposed.
  • the system is constructed of
  • a beam splitter provided for dividing two parallel laser beams with different frequencies _ and _/1 ⁇ 2 into reference beams and measurement beams;
  • a first retroreflector provided to reflect the reference beam with frequency _ back to said beam splitter
  • a second retroreflector provided to reflect the reference beam with frequency _ back to said beam splitter
  • a third retroreflector provided to reflect the measurement beam with frequency _ back to said beam splitter;
  • a fourth retroreflector provided to reflect the measurement beam with frequency f2 back to said beam splitter;
  • a first photodiode provided to detect one measurement signal of the heterodyne interferometric system
  • a second photodiode provided to detect the other measurement signal of the heterodyne interferometric system.
  • the measurement beam and the reference beam in this method and system are spatially separated, which eliminates the frequency and polarization mixing effects. As a result, the periodic nonlinearity is eliminated.
  • the measurement signals have opposite Doppler shift for the same target movement.
  • the resolution of the heterodyne interferometer is two times higher than the traditional heterodyne interferometer.
  • Fig. 1 construction of the high resolution heterodyne interferometric system proposed in preferred embodiment
  • Fig. 2 front view of the heterodyne interferometric system in Fig. 1;
  • Fig. 3 side view of the heterodyne interferometric system in Fig. 1;
  • a high resolution heterodyne interferometric system which comprises: a beam splitter 1 provided to divide two parallel laser beams with different frequencies fi and _ into reference beams and measurement beams; a first retroreflector 3 provided to reflect the reference beam with frequency fi back to said beam splitter 1; a second retroreflector 2 provided to reflect the reference beam with frequency _/1 ⁇ 2 back to said beam splitter 1; a third retroreflector 4 provided to reflect the measurement beam with frequency _ back to said beam splitter 1; a fourth retroreflector 5 provided to reflect the measurement beam with frequency _ back to said beam splitter 1; a first photodiode 6 provided to detect one measurement signal of the heterodyne interferometric system; a second photodiode 7 provided to detect the other measurement signal of the heterodyne interferometric system.
  • a high resolution heterodyne interferometric method which comprise the steps of:

Abstract

A high resolution heterodyne interferometric method and system are provided. The invention uses two parallel beams (8, 9) with different frequencies and the two parallel beams are oriented in diagonal position in the incident plane of the beam splitter (1); the invention generates two measurement signal with opposite Doppler shift. The structure is also balance. The measurement is insensitive to the thermal variation, and the periodic nonlinearity is essentially eliminated by using two separated beams. Therefore, the resolution is two times higher than the traditional interferometer.

Description

HIGH RESOLUTION HETERODYNE INTERFEROMETRIC METHOD AND SYSTEM
Technical field of the invention:
The present invention relates to a high resolution heterodyne interferometric method and system, which can be used for measuring displacement of the target with high resolution and no periodic nonlinearity.
Technical background
The heterodyne interferometer has been widely used in many precision machines and calibration services due to its large measuring range, high signal-to-noise ratio and high measurement precision. Nowadays, high resolution, high speed and high accuracy measurements are required for many applications in order to produce small features. This initiates an improvement of the performance of the heterodyne interferometer to satisfy industrial demands.
The periodic nonlinearity caused by frequency and polarization mixing effects limits the accuracy and resolution of a heterodyne interferometer. A lot of research has been done to reduce the periodic errors, However, periodic nonlinearity is originated from the frequency and polarization mixing effects in the light path which is inherent to the traditional heterodyne interferometer. As a result, for traditional heterodyne interferometers, it is hardly possible to realized high resolution and high precision displacement measurement.
A heterodyne interferometer with an acousto-optic modulator as a beam splitter was proposed by T. L. Schmitz and J. F. Beckwith in "Ascousto-optic displacement-measuring interferometer: a new heterodyne interferometer with Anstrom level periodic error" Journal of Modern Optics 49, pages 2105-2114. In this method can reduce the frequency and polarization mixing effects, the periodic nonlinearity is reduced and the precision and resolution are improved consequently. Nonetheless, its specific and complicated configuration limits the typically possible applications for measuring displacement.
A simpler heterodyne interferometer was proposed by Ki-Nam Joo, Jonathan D. Ellis, et al in (High resolution heterodyne interferometer without detectable periodic nonlinearity. Optics express/Vol.18, Issue 2/1159-1165 ) . In this interferometer has a reference beam and a measurement beam spatially separated to each other. This interferometer can eliminate the frequency and polarization mixing effects. The periodic nonlinearity is also eliminated and the precision is improved. In addition, the interferometer has a simple structure and which make it applicable to precision industrial engineering. Despite the benefit of the interferometer, the optical structure is not balanced and is therefore sensitive to the environment temperature variation.
In conclusion, all of the above existing methods and apparatuses are not suitable for high resolution and high accuracy measurements.
Summary of the invention
One objective of the invention is to provide a heterodyne interferometric method and system, which is suitable for high resolution and high accuracy measurements.
According to one aspect of the invention, a high resolution heterodyne interferometric method is proposed which comprises the steps of:
(a) providing a first linearly polarized laser beam with a first frequency fi and a second linearly polarized laser beam with a second frequency _ , wherein the first linearly polarized laser beam and the second linearly polarized laser beam is provided in parallel and spatially separated to each other;
(b) orienting the two linearly polarized laser beam diagonally in an incident plane of a beam splitter;
(c) dividing the first linearly polarized laser beam into a first reference beam and a first measurement beam by the beam splitter;
(d) dividing the second linearly polarized laser beam into a second reference beam and a second measurement beam by the beam splitter;
(e) directing the first reference beam to a first retroreflector by means of which it is reflected back to the beam splitter;
(f) directing the second reference beam to a second retroreflector by means of which it is reflected back to the beam splitter;
(g) directing the first measurement beam to a third retroreflector by means of which it is reflected back to the beam splitter;
(h) directing the second measurement beam to a fourth retroreflector by means of which it is reflected back to the beam splitter;
(i) adjusting the first retroreflector and the fourth retroreflector such that the first reference beam interferes with the second measurement beam to form a first measurement signal Iml;
(j) adjusting the second retroreflector and the third retroreflector such that the second reference beam interferes with the first measurement beam to form a second measurement signal lm2,
(k) detecting the two measurement signals Imi, Im2 by a first photodiode and a second photodiode respectively, and calculating the displacement of the subject being measured.
According to a second aspect the present invention, a high resolution heterodyne interferometric system is proposed.
The system is constructed of
a beam splitter provided for dividing two parallel laser beams with different frequencies _ and _/½ into reference beams and measurement beams;
a first retroreflector provided to reflect the reference beam with frequency _ back to said beam splitter;
a second retroreflector provided to reflect the reference beam with frequency _ back to said beam splitter;
a third retroreflector provided to reflect the measurement beam with frequency _ back to said beam splitter;
a fourth retroreflector provided to reflect the measurement beam with frequency f2 back to said beam splitter;
a first photodiode provided to detect one measurement signal of the heterodyne interferometric system;
a second photodiode provided to detect the other measurement signal of the heterodyne interferometric system.
The features and advantages of this invention are shown as detailed below:
(1) The measurement beam and the reference beam in this method and system are spatially separated, which eliminates the frequency and polarization mixing effects. As a result, the periodic nonlinearity is eliminated.
(2) The measurement signals have opposite Doppler shift for the same target movement. The resolution of the heterodyne interferometer is two times higher than the traditional heterodyne interferometer.
(3) The structure of the proposed heterodyne interferometer is balanced and not sensitive to the environment temperature change. BRIEF DESCRIPTION OF THE DRAWINGS
IN THE DRAWINGS,
Fig. 1 : construction of the high resolution heterodyne interferometric system proposed in preferred embodiment;
Fig. 2: front view of the heterodyne interferometric system in Fig. 1;
Fig. 3: side view of the heterodyne interferometric system in Fig. 1;
Specification of piece numbers in Fig. 1 :
1 beam splitter,
2 second retroreflector,
3 first retroreflector,
4 third retroreflector,
5 fourth retroreflector,
6 first photodiode,
7 second photodiode,
8 laser beam with frequency },
9 laser beam with frequency _ .
PREFERRED EMBODIMENTS OF THE INVENTION
As shown in Fig.l, a high resolution heterodyne interferometric system, which comprises: a beam splitter 1 provided to divide two parallel laser beams with different frequencies fi and _ into reference beams and measurement beams; a first retroreflector 3 provided to reflect the reference beam with frequency fi back to said beam splitter 1; a second retroreflector 2 provided to reflect the reference beam with frequency _/½ back to said beam splitter 1; a third retroreflector 4 provided to reflect the measurement beam with frequency _ back to said beam splitter 1; a fourth retroreflector 5 provided to reflect the measurement beam with frequency _ back to said beam splitter 1; a first photodiode 6 provided to detect one measurement signal of the heterodyne interferometric system; a second photodiode 7 provided to detect the other measurement signal of the heterodyne interferometric system.
As shown in Fig.1—3, a high resolution heterodyne interferometric method, which comprise the steps of:
(a) providing two parallel laser beams which are linearly polarized laser beam and with different frequencies fi and f ,
(b) orienting the two laser beams in diagonal position in the incident plane of a beam splitter, as shown in Fig.2;
(c) dividing the laser beam with frequency _ into a reference beam and a measurement beam by the beam splitter;
(d) dividing the laser beam with frequency _ into a reference beam and a measurement beam by the beam splitter;
(e) directing the reference beam with frequency ] to a first retroreflector by means of which it is reflected back to the beam splitter;
(f) directing the reference beam with frequency _/} to a second retroreflector by means of which it is reflected back to the beam splitter;
(g) directing the measurement beam with frequency fi to a third retroreflector by means of which it is reflected back to the beam splitter;
(h) directing the measurement beam with frequency _/½ to a fourth retroreflector by means of which it is reflected back to the beam splitter;
(i) adjusting the first retroreflector and the fourth retroreflector such that the reference beam with frequency fi interferes with the measurement beam with frequency whereby a first measurement signal lmi is generated;
(j) adjusting the second retroreflector and the third retroreflector such that the reference beam with frequency _/½ interferes with the measurement beam with frequency _ whereby a second measurement signal Im2 is generated;
(k) detecting the two measurement signals Imi, Im2 by a first photodiode and a second photodiode respectively, and calculating the displacement of the measuring subject.

Claims

Claims What is claimed is:
1. A high resolution heterodyne interferometric method, which comprises the steps of:
(a) providing a first linearly polarized laser beam with a first frequency _ and a second linearly polarized laser beam with a second frequency _/½ , wherein the first linearly polarized laser beam and the second linearly polarized laser beam is provided in parallel and spatially separated to each other;
(b) orienting the two linearly polarized laser beam diagonally in an incident plane of a beam splitter;
(c) dividing the first linearly polarized laser beam into a first reference beam and a first measurement beam by the beam splitter;
(d) dividing the second linearly polarized laser beam into a second reference beam and a second measurement beam by the beam splitter;
(e) directing the first reference beam to a first retroreflector by means of which it is reflected back to the beam splitter;
(f) directing the second reference beam to a second retroreflector by means of which it is reflected back to the beam splitter;
(g) directing the first measurement beam to a third retroreflector by means of which it is reflected back to the beam splitter;
(h) directing the second measurement beam to a fourth retroreflector by means of which it is reflected back to the beam splitter;
(i) adjusting the first retroreflector and the fourth retroreflector such that the first reference beam interferes with the second measurement beam to form a first measurement signal lmi,
(j) adjusting the second retroreflector and the third retroreflector such that the second reference beam interferes with the first measurement beam to form a second measurement signal Im2;
(k) detecting the two measurement signals Imj , Im2 by a first photodiode and a second photodiode respectively, and calculating the displacement of the subject being measured.
2. A high resolution heterodyne interferometric system, which comprises:
a beam splitter (1) provided for dividing two parallel laser beams with different frequencies _ and _/½ into reference beams and measurement beams; a first retroreflector (3) provided to reflect the reference beam with frequency _ back to said beam splitter (1);
a second retroreflector (2) provided to reflect the reference beam with frequency f2 back to said beam splitter (1);
a third retroreflector (4) provided to reflect the measurement beam with frequency _ back to said beam splitter (1);
a fourth retroreflector (5) provided to reflect the measurement beam with frequency _/½ back to said beam splitter (1);
a first photodiode (6) provided to detect one measurement signal of the heterodyne interferometric system;
a second photodiode (7) provided to detect the other measurement signal of the heterodyne interferometric system.
PCT/CN2014/072819 2013-12-23 2014-03-03 High resolution heterodyne interferometric method and system WO2015096279A1 (en)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
CN201310745318.8A CN103743346B (en) 2013-12-23 2013-12-23 Based on diagonal angle incident light laser heterodyne interference measurement method and the device of prism of corner cube
CN201310745960.6 2013-12-23
CN201310745960.6A CN103743336B (en) 2013-12-23 2013-12-23 Based on diagonal angle incident light laser heterodyne interference measurement method and the device of right-angle prism
CN201310745318.8 2013-12-23

Publications (1)

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WO2015096279A1 true WO2015096279A1 (en) 2015-07-02

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5793487A (en) * 1994-08-02 1998-08-11 Canon Kabushiki Kaisha Optical interference system for performing interference measurement using wavelength
US6483593B1 (en) * 1999-08-10 2002-11-19 The Boeing Company Hetrodyne interferometer and associated interferometric method
CN101067546A (en) * 2006-06-20 2007-11-07 哈尔滨工业大学 Method and apparatus for reducing heterodyne interference nonlinear error first harmonic component
WO2010030179A1 (en) * 2008-09-11 2010-03-18 Technische Universiteit Delft Laser interferometer

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5793487A (en) * 1994-08-02 1998-08-11 Canon Kabushiki Kaisha Optical interference system for performing interference measurement using wavelength
US6483593B1 (en) * 1999-08-10 2002-11-19 The Boeing Company Hetrodyne interferometer and associated interferometric method
CN101067546A (en) * 2006-06-20 2007-11-07 哈尔滨工业大学 Method and apparatus for reducing heterodyne interference nonlinear error first harmonic component
WO2010030179A1 (en) * 2008-09-11 2010-03-18 Technische Universiteit Delft Laser interferometer

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