CN101206108A - Ultraprecise bifrequency interferometry system using real-time environment compensation process - Google Patents

Abstract

The invention provides a super-precision double-frequency interference measurement system using a real-time environment compensation method which can be used in the real-time environment compensation method of super-precision double-frequency interference measurement. The invention can simply be realized by adding an interferometer and a related reception element based on the prior double-frequency interference measurement without need other extra equipment; the invention has simple use, convenient computation, low cost and good real time, and also has good compensation effect to the frequency stabilization error caused by the instability of frequency difference of the laser.

Description

A kind of ultraprecise double frequency interferometer measuration system of using the real time environment compensation method

Technical field

The present invention relates to a kind of Range Measurement System, particularly a kind of double frequency interferometer measuration system.

Background technology

The double-frequency laser interferometry system is according to principle of optical interference, by optics and electronic fine-grained technology, can carry out the close displacement measurement of high speed and super precision, if with different annex combinations, can also carry out measurements such as length, speed, angle, flatness, linearity, have advantages such as measurement range is big, resolution is high, precision height.As a kind of ultraprecise non-contact measurement equipment, laser interferometry system all has purposes very widely in fields such as semiconductor manufacturing, precision machine tool processing, military aerospace, automobile making, measurement of coordinates.

Although two-frequency laser interferometer can reach the resolution of nanometer even Ya Nami, but its measuring accuracy is subjected to the influence of several factors, as environmental error, cosine error, Abbe error etc., the precision that reaches when causing actual measurement usually is a micron dimension, even poorer.This wherein, environmental error is again the main factor that influences measuring accuracy.

The reason that environmental error produces is to measure the overhead gas refractive index of light path in continuous fluctuation.Because what the double frequency interferometry provided is optical path difference between interferometer reference arm and the transfer arm, so its physical path length is that light path is divided by the mean refractive index of light beam by air on the path.In actual applications, through the fluctuation (especially when the motion platform moves back and forth) of the Yin Wendu of regular meeting, pressure and air-flow and change, cause measurement result error to occur along the air refraction of measuring route.Must real-Time Compensation correction in addition to this, to satisfy the ultra precise measurement demands of applications.

At present, a kind of compensation method is the ambient compensation instrument that utilizes special development, as difference index meter (the being also referred to as wavelength tracker) 10717A of Agilent company, but costs an arm and a leg; Another method is according to the environment temperature, humidity and the force value that record, calculate the wavelength variations situation in real time by Ai Dele (Edlen) formula, but this formula itself is exactly a kind of approximate data, also often adopt its reduced form during application, to avoid complicated calculating, this just inevitable meeting drawing-in system error, in addition, it is that unit carries out often with the second that the measurement of the temperature, pressure value of this method is upgraded, belong to " semireal time " bearing calibration, and powerless to the air turbulence of measuring in the light path; Also having a kind of method is the influence of determining environment along the velocity of sound of measuring route direct of travel by measuring simultaneously, " improve the method for the measurement of laser interferometer " (number of patent application CN99814090.2) as document, but this method has increased equipment cost undoubtedly; Another method similarly is to obtain refractive index by the optical path length of measuring two or more wavelength, as patent " structure of the dual wavelength heterodyne ineterferometer of make-up air disturbance " (application number CN99118742.3), but this method needs two and separates far measurement wavelength (normally multiple relation), and laser instrument has been proposed new requirement.

Summary of the invention

The object of the present invention is to provide a kind of ultraprecise double frequency interferometer measuration system of using the real time environment compensation method, realizing finishing in real time the correction of environmental error, the drift that the laser wavelength instability is caused also has good compensation effect and compensates.

In order to achieve the above object, the invention provides a kind of ultraprecise double frequency interferometer measuration system of using the real time environment compensation method, it comprises laser instrument, stellar interferometer, testee, first photoelectric apparatus, first counting circuit, this testee of irradiation reflected back into this stellar interferometer after the light beam that this laser instrument sends entered this stellar interferometer, the light beam of the interference of this stellar interferometer of process enters this first counting circuit, this laser instrument after this first photoelectric apparatus conversion, stellar interferometer, first photoelectric apparatus, first counting circuit constitutes measures light path.

The ultraprecise double frequency interferometer measuration system of this use real time environment compensation method also comprises compensation spectroscope, compensating interferometer instrument reference mirror, second photoelectric apparatus, second counting circuit and ambient compensation circuit, this compensation spectroscope is told a part with measuring beam and is entered behind this compensating interferometer instrument this compensating interferometer instrument that reflects back into through this reference mirror, interfering beam through this compensating interferometer instrument enters this second counting circuit after this second photoelectric apparatus conversion, the output signal of this first counting circuit and this second counting circuit is imported this ambient compensation circuit.

The propagation medium that is somebody's turn to do from the compensating interferometer instrument to this reference mirror is identical with the propagation medium that is somebody's turn to do from stellar interferometer to this testee.

Should the path from the compensating interferometer instrument to this reference mirror fix.

This compensating interferometer instrument is the single shaft interferometer.This compensating interferometer instrument can be a differential interferometer, also can be flat mirror interferometer, can also be linear interferometer.

In this measuring system, can also add the optical interference circuit that be used to measure identical with this measurement light path.

Can compensate the direction that adds catoptron adjustment compensation light path on the light path that spectroscope tells at this.

The ultraprecise double frequency interferometer measuration system of use real time environment provided by the present invention compensation method, only need increase an interferometer on the basis of traditional double frequency interferometry gets final product with relevant receiving element, need not other extras, use simple, convenience of calculation, expense is cheap, and real-time is good, and the unstable caused frequency stabilization error of laser instrument frequency difference is also had good compensation effect.

Description of drawings

Fig. 1 is the ultraprecise double frequency interferometer measuration system schematic diagram of use real time environment of the present invention compensation method;

Fig. 2 is three double frequency interferometer measuration systems of ultraprecise schematic diagram of use real time environment of the present invention compensation method;

In the accompanying drawing: 1, helium-neon laser; 2, compensation spectroscope; 3, stellar interferometer; 4, testee; 5, first photoelectric apparatus; 6, reflective mirror; 7, compensating interferometer instrument; 8, reference mirror; 9, second photoelectric apparatus; 10, first counting circuit; 11, second counting circuit; 12, ambient compensation circuit; 13, double frequency helium-neon laser; 14,50% spectroscope; 15,50% spectroscope; 16, reflective mirror; 17, single shaft interferometer; 18, single shaft interferometer; 19,50% spectroscope; 20, reflective mirror; 21, single shaft interferometer; 22, the single shaft interferometer that is used for compensating measure; 23, the motion platform of two sides plated film; 24, reflective mirror; 25, Photoelectric Detection receiver; 26, Photoelectric Detection receiver; 27, Photoelectric Detection receiver; 28, Photoelectric Detection receiver; 29, VME cabinet; 30, powerpc board card; 31, ambient compensation card; 32, Data Format Transform card; 33, the laser numbered card of diaxon; 34, the laser numbered card of diaxon; 35, motion platform controller; 36, main control.

Embodiment

Below in conjunction with accompanying drawing the specific embodiment of the present invention is further described.

Fig. 1 shows the ultraprecise double frequency interferometer measuration system schematic diagram of use real time environment of the present invention compensation method, this ultraprecise double frequency interferometer measuration system, comprise a frequency difference Stabilized He-Ne Laser 1, compensation spectroscope of coaxial successively placement 2, a stellar interferometer 3 and a testee 4 on the laser beam working direction; The light that compensation spectroscope 2 is told enters compensating interferometer instrument 7 and static reference mirror 8 behind reflective mirror 6.Interference light from stellar interferometer 3, with after first photoelectric apparatus 5,9 conversions of second photoelectric apparatus, send into first counting circuit 10 respectively from the interference light of compensating interferometer instrument 7, second counting circuit 11 is counted, and sends into ambient compensation circuit 12 then.

For stellar interferometer, under starting condition, the physical pathway L of measurement ₀, initial wavelength X ₀, the fringe number XL in extended resolution N and the corresponding initial air ₀The pass be:

L ₀＝XL ₀×λ ₀/N

The measurement fringe number reading of the pairing measurement light path of stellar interferometer this moment is 0.

And for the compensating interferometer instrument, under starting condition, the physical pathway C of measurement ₀, initial wavelength X ₀, the fringe number XC in extended resolution N and the corresponding initial air ₀The pass be:

C ₀＝XC ₀×λ ₀/N

The measurement fringe number reading of the pairing compensation light path of compensating interferometer instrument this moment also is 0.

The actual value of remembering certain moment wavelength is λ.For the pairing compensation light path of compensating interferometer instrument, the currency that note is measured fringe number is XC, because reference mirror is static all the time, physical pathway does not change, and then has:

C ₀＝(XC ₀+XC)×λ/N

So:

$\frac{\mathrm{\λ}}{N}=\frac{C_0}{{\mathrm{XC}}_0+\mathrm{XC}}$ (formula one)

For the pairing measurement light path of stellar interferometer, the currency that note is measured fringe number is XL, then the physical path length that moves of testee should for:

L+L ₀＝(XL ₀+XL)×λ/N

Substitution formula one then has:

$L=\frac{L_0+\mathrm{XL}\·({\mathrm{\λ}}_0/N)}{C_0+\mathrm{XC}\·({\mathrm{\λ}}_0/N)}\·C_0-L_0$

Obviously, as long as the measurement light path of compensating interferometer instrument has identical environmental baseline with the measurement light path of stellar interferometer, just can accurately obtain the physical path length of testee actual displacement.And calculate simply, can fully guarantee the real-time requirement.

Fig. 2 shows three double frequency interferometer measuration systems of ultraprecise schematic diagram of use real time environment of the present invention compensation method, comprise a double frequency helium-neon laser 13, three 50% spectroscopes 14,15,19, two reflective mirrors 16,20,3 single shaft interferometers 17 that are used to measure, 18,21, a single shaft interferometer 22 that is used for compensating measure, the motion platform 23 of a two sides plated film, a static reflective mirror 24, four Photoelectric Detection receivers 25,26,27,28, a VME cabinet 29, the built-in laser numbered card 33 of 30, two diaxons of a powerpc board card, 34, an ambient compensation card 31,35, one main controls 36 of one blocks of data format conversion card, 32, one motion platforms controller.

In order to obtain better measuring accuracy, the compensating interferometer instrument has been selected differential interferometer for use, and stellar interferometer has been selected flat mirror interferometer for use.In addition, compensating interferometer instrument 22 and static mirror 24 are fixed on the same block of invar plate, to reduce the influence of environmental change to the two distance as far as possible.During work, the ambient compensation card reads count value X1 (corresponding to stellar interferometer 17), X2 (corresponding to stellar interferometer 18), Y (corresponding to stellar interferometer 21) and C (corresponding to compensating interferometer instrument 22) with the fixed sample interval T from two laser numbered cards 33,34.During the note initialization, the dead Cheng Changdu of X1, X2, Y correspondence is respectively DX1, DX2, DY, and the difference measurement distance of compensating interferometer instrument is DC, and the beam separation between the stellar interferometer 17 and 18 is M, and initial wavelength is λ ₀, extended resolution is N, then pass through environmental correction after, displacement situation x, y and the Rz of motion platform are respectively:

$x=\frac{\frac{X1+\mathrm{<figure-callout\; id="2"\; label="X"\; filenames="S2007101724284E00011.png"\; state="\{\{state\}\}">X</figure-callout>}2}{2}\&CenterDot;\mathrm{DC}-\frac{\mathrm{DX}1+\mathrm{<figure-callout\; id="2"\; label="DX"\; filenames="S2007101724284E00011.png"\; state="\{\{state\}\}">DX</figure-callout>}2}{2}\&CenterDot;C}{\mathrm{DC}+C\&CenterDot;({\mathrm{\&lambda;}}_0/N)}\&CenterDot;\frac{{\mathrm{\&lambda;}}_0}{N}$

$y=\frac{Y\&CenterDot;\mathrm{DC}-\mathrm{DY}\&CenterDot;C}{\mathrm{DC}+C\&CenterDot;({\mathrm{\&lambda;}}_0/N)}\&CenterDot;\frac{{\mathrm{\&lambda;}}_0}{N}$

$\mathrm{Rz}=\frac{(X2-X1)\&CenterDot;\mathrm{DC}-(\mathrm{DX}2-\mathrm{DX}1)\&CenterDot;C}{[\mathrm{DC}+C\&CenterDot;({\mathrm{\&lambda;}}_0/N)]\&CenterDot;M}\&CenterDot;\frac{{\mathrm{\&lambda;}}_0}{N}$

This computation process is finished in the ambient compensation plate.The displacement result that calculating provides through sending into controller behind the Data Format Transform plate (be not necessary, decide on the control unit interface situation), can be finished ultraprecise motion control task.Actual measurement shows that the precision of this environment compensation method is better than 0.15ppm, satisfies the needs of ultraprecise observing and controlling fully.It can also be seen that from technical scheme of the present invention the present invention not only can finish the error correction to environmental perturbation in real time, and the unstable caused error of laser instrument frequency difference is also had good compensation effect.

Claims (7)

1. ultraprecise double frequency interferometer measuration system of using the real time environment compensation method comprises:

Laser instrument;

Stellar interferometer;

Testee;

First photoelectric apparatus;

First counting circuit;

The described testee of irradiation reflected back into described stellar interferometer after the light beam that described laser instrument sends entered described stellar interferometer, the light beam of the interference of the described stellar interferometer of process enters described first counting circuit after described first photoelectric apparatus conversion, described laser instrument, stellar interferometer, first photoelectric apparatus, first counting circuit constitute measures light path;

It is characterized in that, also comprise:

The compensation spectroscope;

The metrophia compensation interferometer;

Reference mirror;

Second photoelectric apparatus;

Second counting circuit; With

The ambient compensation circuit;

Described compensation spectroscope is told a part with measuring beam and is entered behind the described compensating interferometer instrument through the described compensating interferometer instrument of reflecting back into of described reference mirror, interfering beam through described compensating interferometer instrument enters described second counting circuit after described second photoelectric apparatus conversion, the output signal of described first counting circuit and described second counting circuit is imported described ambient compensation circuit.

2. the ultraprecise double frequency interferometer measuration system of use real time environment according to claim 1 compensation method is characterized in that: described propagation medium from the compensating interferometer instrument to described reference mirror is identical with described propagation medium from stellar interferometer to described testee.

3. the ultraprecise double frequency interferometer measuration system of use real time environment according to claim 1 compensation method is characterized in that: described path from the compensating interferometer instrument to described reference mirror is fixed.

4. the ultraprecise double frequency interferometer measuration system of use real time environment according to claim 1 compensation method is characterized in that: described compensating interferometer instrument is the single shaft interferometer.

5. the ultraprecise double frequency interferometer measuration system of use real time environment according to claim 4 compensation method is characterized in that: described compensating interferometer instrument can be a differential interferometer, also can be flat mirror interferometer, can also be linear interferometer.

6. the ultraprecise double frequency interferometer measuration system of use real time environment according to claim 1 compensation method is characterized in that: in the described measuring system, can also add the optical interference circuit that be used to measure identical with described measurement light path.

7. the ultraprecise double frequency interferometer measuration system of use real time environment according to claim 1 compensation method is characterized in that: the direction that can add catoptron adjustment compensation light path on the light path that described compensation spectroscope is told.

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