CN104713494B - The dual wavelength tuning interference testing device and method of Fourier transformation phase shift calibration - Google Patents
The dual wavelength tuning interference testing device and method of Fourier transformation phase shift calibration Download PDFInfo
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Abstract
Dual wavelength the invention discloses a kind of Fourier transformation phase shift calibration tunes interference testing device and method, test device is carried out at the same time work using the tunable laser of different centre wavelengths as light source, interference phase shift is realized, and utilize the moire map formed after detector acquisition two-way interference optical superposition by wavelength tuning.Time domain Fourier transformation first is carried out to the moire map that detector collects and analyzes each frequency component, completes the calibration to phase shift stepping-in amount, ensures the phase shift stepping-in amount under two kinds of wavelength；Secondly, phase shift is carried out according to calibrated phase shift stepping-in amount as two tunable laser of light source, collects the phase shift moire map for containing synthetic wavelength phase information；Finally, tested phase information is obtained using dual wavelength phase-shifting algorithm to phase shift moire map.The present invention can expand the face shape range of interferometry, and Single wavelength phase shift is demarcated without Additional passes, and light channel structure and fringe-pattern analysis algorithm are simple.
Description
Technical field
The present invention relates to interference of light testing field, the dual wavelength tuning interference of particularly a kind of Fourier transformation phase shift calibration
Test device and method.
Background technology
Optical interferometry is a kind of high-precision, highly sensitive metrology and measurement method, be widely used in plane, spherical surface and
Aspherical surface shape measurement, the measurement of sphere curvature radius and various lens, prism, optical system corrugated transmission quality
The measurement of a variety of physical quantitys such as measurement.Phase-shifting interference measuring technology is with its precision height, high degree of automation and in high-precision optical
It occupies an important position in detection.The basic principle of shift-phase interferometry is to introduce orderly position between two coherent lights of interferometer
It moves, changes the phase difference of reference light and test light to realize phase-modulation, when changing with reference to light path (or position phase), interference fringe
Position also make corresponding movement.In the process, the sampling of several array grids is carried out to interference pattern with photodetector, so
Frame memory is deposited after light intensity is digitized afterwards, phase point is asked according to the variation of light intensity according to certain mathematical model by computer
Cloth.
Phase-shifter is the critical component for realizing phase shift phase measuring method approach, and common phase shifting method has piezoelectric ceramics
(PZT) phase shift, rotatory polarization device (wave plate, polarizer) phase shift, mobile diffraction grating or tilt flat plate phase shift, wavelength phase shift
(change light source frequency of light wave by using tunable laser and realize phase shift) etc..The Phase shift precision of phase-shifter is to influence position mutually to survey
One of an important factor for accuracy of measurement.Therefore, the Accurate Calibration of phase-shifter or correction have highly important meaning in phase measurement
Justice.
Traditional phase-shifting interferometer has higher measurement accuracy and preferably when generally use single wavelength is as light source
Measurement reproducibility, but there are the smaller problems of its measurement range.If it is more than the noncontinuous surface of 0.5 wavelength to step height
Surface testing then will appear and be more than π more than its measurement range because being tested the larger phase difference for leading to adjacent pixel of step difference of height
The problem of, it can not correctly recover the height of step.
In order to expand the test scope of tradition phase-shifting interferometer, while retain the measuring accuracy of conventional dry interferometer, Yeou-
Yen Cheng et al. exist《Two-wavelength phase shifting interferometry》(APPLIED OPTICS,
24(23):4539-4543,1984) dual wavelength phase shift interference testing method is proposed in, by the phase data for analyzing Single wavelength
Difference obtains the larger synthetic wavelength phase data of wavelength, for the face shape that detection error is larger, expands traditional Single wavelength interference
The test scope of test.Compared with traditional Single wavelength interference testing, there are error amplification effects for dual wavelength phase shift interference testing method
Should, in order to solve this problem, Yeou-Yen Cheng et al. are then at it《Multiple-wavelength phase-
shifting interferometry》(APPLIED OPTICS,24(6):804-807,1985) proposed in a text with composite wave
Long phase data corrects Single wavelength phase data, expands the measurement range of Single wavelength shift-phase interferometry, while remain list again
The measuring accuracy of wavelength phase shift interference.For dual wavelength phase shift interference testing device generally using piezoelectric ceramics (PZT) phase shift, deposit
PZT Phase-shifting Errors problems at different wavelengths, Ribun Onodera exist《Two-wavelength interferometry
That uses a Fourier-transform method》(APPLIED OPTICS,37(34):It is carried in 7988-7994,1998)
The method of processing single frames dual wavelength moire map extraction synthetic wavelength phase is gone out, by existing to moire map
Each frequency component in frequency domain is detached, and is filtered out except λ1Positive first component and λ2Negative first component other than other frequencies
Component obtains synthetic wavelength phase after inverse transformation, so as to avoid the different wave length Phase-shifting Errors of phase shift introducing, but single frames interference pattern
The precision that the precision of Processing Algorithm does not have phase shift to interfere is high.In terms of dual wavelength phase shift interference testing device, Michael
B.North-Morris exists《Phase-Shifting Multi-Wavelength Dynamic Interferometer》
(Proceedings of SPIE,Vol.5531:64-75, Bellingham, WA, 2004)) in devise a kind of dual wavelength and move
State interference checking device realizes the simultaneous phase-shifting under different wave length by the achromatism phase mask that Pixel-level is placed before CCD,
But its design processing request to mask plate is very high, and structure installation is complicated and follow-up processing is cumbersome.Youichi Bitou exist
《Two-wavelength phase-shifting interferometry using an electrically addressed
liquid crystal spatial light modulator》(APPLIED OPTICS,44(9):1577-1581,2005)
In propose opposite direction and the dual wavelength of unique step phase shift under two kinds of wavelength realized based on spatial light modulator (EA-SLM)
Phase shift interference testing device directly extracts synthetic wavelength phase data, but its device is because comprising a large amount of using tradition phase-shifting algorithm
Polarizer and diffraction element and structure seem complicated.D.G.Abdelsalam exists《Two-wavelength in-line
phase-shifting interferometry based on polarizing separation for accurate
surface profiling》(APPLIED OPTICS, 55 (33):It is devised in 6153-6161,2011) a kind of based on Mach
Damp Deccan relates to the two-wavelength-interferometer of light channel structure, and phase shift calibration error problem is then by using closed-loop control under different wave length
PZT realize what accurate phase shift under two kinds of wavelength solved, but its requirement to PZT is high and expensive.With it is above-mentioned from
Hardware aspect solves the problems, such as dual wavelength Phase-shifting Errors difference, and Joanna Schmit exist《Two-wavelength
interferometricwith a phase-step error-compensating algorithm》
(Optical Engineering,45(11):Two kinds of waves of solution from algorithm are proposed in 115602_1-115602_3,2006)
The method of PZT phase shift calibration error problems under long, using to 8 larger step Phase-shifting algorithms of the phase shift calibration error margin of tolerance come
Solve the phase value under two kinds of wavelength, but calculating process is complicated and the compensation of its Phase-shifting Errors there are certain ranges.Domestic aspect,
Tian Ailing et al. is in its patent《The surface shape detection apparatus and its detection method of a kind of large scale and high accuracy》(application number
201310044110.3) a kind of dual wavelength phase shift interference testing device is described in, is more than the one of 30nm using tunable range
A frequency-converted solid state laser realizes wavelength phase shift interference in two central wavelengths respectively, and needs to the interference pattern phase under two kinds of wavelength
Multiply the interference light intensity information that the moiré topography for being superimposed and obtaining low-pass filtering in frequency domain obtains including synthetic wavelength phase, finally
Synthetic wavelength phase is extracted using Phase-shifting algorithm.Test device only there are one frequency-converted solid state laser but is needed in two central wavelengths
Wavelength phase shift interference is realized respectively, therefore than relatively time-consuming.In addition, this method needs are low to the interference light intensity figure progress frequency spectrum of superposition
Pass filter processing, the selection of wave filter can reduce the precision of test data, and complex disposal process.
Invention content
The object of the present invention is to provide a kind of dual wavelength tuning interference testing device of Fourier transformation phase shift calibration and sides
Method is λ including centre wavelength1The first tunable laser (1), the first beam expanding lens (2) and the first collimating mirror (3), first point
Light prism (4), the second Amici prism (5), standard mirror (6), measured lens (7), centre wavelength λ2The second tunable laser
(8), the second beam expanding lens (9), the second collimating mirror (10), convergent lens (11), aperture (12), imaging len (13), CCD are visited
Survey device (14), wherein λ1≠λ2；Centre wavelength is set gradually as λ1The first tunable laser (1), the first beam expanding lens (2),
Optical axis where one collimating mirror (3), the first Amici prism (4) is primary optic axis；It sets gradually the second Amici prism (5), assemble
Optical axis where lens (11), aperture (12), imaging len (13), ccd detector (14) is the second optical axis；It sets gradually
Centre wavelength is λ2Tunable laser (8), the second beam expanding lens (9), the second collimating mirror (10), the first Amici prism (4),
Optical axis where two Amici prisms (5), standard mirror (6), measured lens (7) is third optical axis, primary optic axis, the second optical axis respectively with
Third optical axis is mutually perpendicular to；It is λ by centre wavelength1The wavelength that tunable laser (1) is sent out is λ1Laser light incident to first expand
Shu Jing (2), the first beam expanding lens (2) assemble incident small-bore directional light, and light beam becomes diverging after converging focal point
Spherical wave, spherical wave are incident to the first collimating mirror (3), the focus of the first collimating mirror (3) and the focus weight of the first beam expanding lens (2)
It closes, divergent spherical wave becomes the collimated light beam of collimation after the first collimating mirror (3) transmission, and the collimated light beam is through the first Amici prism
(4) the second Amici prism (5) is reflexed to, standard mirror (6) is incident to through the second Amici prism (5) and measured lens (7) forms
Wavelength is λ1Laser tuning phase shift interference testing light path；It is λ by centre wavelength2The wavelength that tunable laser (8) is sent out is λ2
Laser light incident to the second beam expanding lens (9), the second beam expanding lens (9) assembles incident small-bore directional light, and light beam is through overconvergence
Become the spherical wave of diverging after focus, spherical wave is incident to the second collimating mirror (10), the focus of the second collimating mirror (10) and the
The focus of two beam expanding lens (9) overlaps, and divergent spherical wave becomes the collimated light beam of collimation after the second collimating mirror (10) transmission, this is flat
Row light beam is transmitted through the second Amici prism (5) through the first Amici prism (4), then after the second Amici prism (5) transmission, through standard
Mirror (6) and measured lens (7) form wavelength as λ2Laser tuning phase shift interference testing light path；Be incident to standard mirror (6) and by
The wavelength for surveying mirror (7) is respectively λ1And λ2Light through standard mirror (6) and measured lens (7) back reflection, then by the second Amici prism (5)
It is finally acquired successively by convergent lens (11), aperture (12), imaging len (13) by ccd detector (14) after reflection,
Form λ1And λ2Interfere the moire map acquisition light path after optical superposition.
The light splitting surface of first Amici prism (4) and the third optical axis included angle of horizontal direction are 135 °, the second Amici prism (5)
Light splitting surface and horizontal direction third optical axis included angle be 45 °.
The test method of dual wavelength tuning interference testing device based on Fourier transformation phase shift calibration, step are as follows：
Step 1：In striking rope type interference testing light path, using two tunable laser conducts of different centre wavelengths
Light source is carried out at the same time work, and carrying out wavelength tuning according to respective theoretical phase shift stepping-in amount realizes interference phase shift, utilizes CCD detection
Device collects a series of phase shift moire maps formed after two-way interference optical superposition, by being done to phase shift Moire fringe
It relates to after figure carries out time domain Fourier transformation and determines λ1And λ2Practical phase shift stepping-in amount under respective wavelength obtains real under two kinds of wavelength
The relationship of border phase shift stepping-in amount and laser power supply voltage change value, according to the practical phase shift stepping-in amount with it is electric with laser power supply
The relationship of change value is pressed to adjust laser power supply voltage value, it is respectively pi/2 and 3 to obtain practical phase shift stepping-in amount under two kinds of wavelength
Voltage value during pi/2 completes the phase shift stepping-in amount calibration under respective wavelength；
Step 2：Two tunable laser as light source are adjusted according to the voltage value obtained after being demarcated in step 1 to swash
Light device supply voltage, it is respectively pi/2 and 3 pi/2s to ensure the practical phase shift stepping-in amount under two kinds of wavelength, carries out wavelength phase shift into traveling wave
Long phase shift acquires two-way by detector and interferes the moire map formed after optical superposition, which contains synthesis
The phase information of wavelength；
Step 3：The Moire fringe phase-shift interference of ccd detector acquisition is obtained using dual wavelength phase-shifting algorithm
Tested phase information, is then mutually unpacked by position, solves the face shape information of tested surface.
Spectrum expression formula of the moire map after time domain Fourier transformation in above-mentioned steps one be：
Wherein f be frequency, A (f) be fundamental component, C1For λ1Positive primary frequency component under wavelength, C2For λ2Under wavelength
Positive primary frequency component,For C1Conjugation,For C2Conjugation, f1For λ1The frequency displacement that lower wavelength phase shift generates, i.e.,f2For λ2The frequency displacement that lower wavelength phase shift generates, i.e.,Δλ1、Δλ2For λ1And λ2Under wavelength change
Variable, h are interference cavity length.
In step 1 λ is extracted in the calibration of phase shift stepping-in amount1And λ2The method of practical phase shift stepping-in amount under respective wavelength
For：When phase shift is demarcated, centre wavelength λ1The first tunable laser according to λ1Phase shift stepping-in amount for pi/2 carries out wavelength shifting
Phase, centre wavelength λ2The second tunable laser according to λ2Phase shift stepping-in amount for π/(2n) carries out wavelength phase shift, wherein n
For positive integer, and n ≠ 1, therefore, λ in the frequency spectrum that moire map is obtained through time domain Fourier transformation1And λ2Frequency point
Amount is separated from each other, i.e. f in above formula1With f2It differs, then four frequency components of two kinds of wavelength are separated from each other in frequency spectrum, i.e. C1、C2、It is separated from each other, λ respectively is isolated by using bandpass filter1Positive primary frequency component C1And λ2Positive primary frequency
Component C2, inverse Fourier transform is carried out to it, solution obtains phase value, and the phase value obtained by two adjacent moments subtracts each other,
The practical phase shift stepping-in amount under two kinds of wavelength can be respectively obtained, according to be respectively offset from the degree of pi/2 and π/(2n) to voltage into
Row correction, obtains λ1And λ2Practical phase shift stepping-in amount is respectively the voltage value of pi/2 and π/(2n) under wavelength, is also just obtained in this way
Practical phase shift stepping-in amount is respectively the voltage value of pi/2 and 3 pi/2s under two kinds of wavelength, completes the calibration of dual wavelength phase shift stepping-in amount.
Phase shift Moire fringe information in step 2 is：It is respectively λ with centre wavelength1And λ2Laser tuning light source simultaneously
Wavelength phase-shifting interference measuring is carried out, then the intensity signal I of kth step phase shift interference moiré topographykFor：
Wherein, k is the serial number of 4 frame Moire fringe phase-shift interferences, i.e. k=1,2,3,4, IaFor background light intensity, IbFor light intensity
Modulation degree, φ1Be wavelength be λ1Phase change amount, φ2Be wavelength be λ2Phase change amount, φeqFor synthetic wavelength number of phases
According to i.e. φeq=φ2-φ1, φeqContain the face shape information of tested surface.
It is to the dual wavelength phase-shifting algorithm of Moire fringe phase-shift interference processing in step 3：Due under two kinds of wavelength
Phase shift stepping-in amount be respectively pi/2 and 3 pi/2s, then in the intensity signal expression formula of kth step phase shift interference moiré topographyIn phase shift stepping-in amount for π, absolute value is unrelated with phase shift stepping-in amount, and includes composite wave appearance
The latter of positionIn phase shift stepping-in amount for pi/2, then be using similar traditional four-step phase-shifting algorithm
The phase of extractable synthetic wavelengtheqInformation, i.e.,Tested surface is obtained after phase unwrapping
Face shape information.
Step 1: the centre wavelength in step 2 is λ1The first tunable laser and centre wavelength be λ2Second can
The phase shift stepping-in amount of tuned laser can be exchanged with each other setting, as λ in step 11Phase shift stepping-in amount be π/(2n), λ2's
Phase shift stepping-in amount is pi/2, λ in step 21Phase shift stepping-in amount for 3 pi/2s, λ2Phase shift stepping-in amount be pi/2.
Compared with prior art, the present invention its remarkable advantage：
(1) phase shift misses under the different wave length generated for traditional dual wavelength phase shift interference testing device using PZT phase shifts
The problem of poor, respectively realizes frequency conversion wavelength phase shift, without pushing phase shift using two different tunable laser of centre wavelength
Device can control the accurate phase shift under different wave length, avoid the Phase-shifting Errors under the different wave length of PZT phase shifts introducing.
(2) it is worked successively using two kinds of wavelength light sources for traditional dual wavelength phase shift interference testing device, needs to divide successively
Not carry out phase shift calibration the problem of, worked at the same time using two different tunable laser of centre wavelength, by a series of
Phase shift moire map carries out time domain Fourier transformation and obtains the spectrum information of moire map, extracts in frequency spectrum
Each frequency component, obtains λ1And λ2Practical phase shift stepping-in amount under respective wavelength, computer distinguishes real time output control after processing
Tunable laser power supply processed controls λ1Tunable laser and λ2Tunable laser realize accurate wavelength phase shift, it is ensured that
λ1And λ2Phase shift be respectively pi/2 and 3 pi/2s, synchronously complete and the phase shift under dual wavelength demarcated, avoid because carrying out each wave
The interference pattern of each wavelength is demarcated and needs to respectively obtain in phase shift under long, directly handles phase shift moire map and realizes phase shift
Stepping-in amount is demarcated, without additional Single wavelength phase shift calibration light path.
(3) it needs to obtain in advance for the solution of traditional dual wavelength phase shift interference testing device synthetic wavelength phase data each
Phase data under wavelength, and the problem of the laser light source of two kinds of wavelength works respectively successively, it is different using centre wavelength
Two tunable laser work at the same time, and carry out wavelength tuning phase shift test, after being superimposed to two kinds of wavelength measurement interference patterns not
You are directly handled bar graph, extract synthetic wavelength phase data, and the extraction process of synthetic wavelength phase data is quick and easy.
Description of the drawings
Fig. 1 is that the dual wavelength of the Fourier transformation phase shift calibration of the present invention tunes the principle schematic of interference testing device.
Fig. 2 is that the dual wavelength based on Fourier transformation phase shift calibration of the present invention tunes the test method of interference testing device
Flow chart.
Specific embodiment
With reference to Fig. 1, the dual wavelength tuning interference testing device of a kind of Fourier transformation phase shift calibration of the present invention, including center
Wavelength is λ1The first tunable laser 1, the first beam expanding lens 2, the first collimating mirror 3, the first Amici prism 4, second light splitting rib
Mirror 5, standard mirror 6, measured lens 7, centre wavelength λ2The second tunable laser 8, the second beam expanding lens 9, the second collimating mirror 10,
Convergent lens 11, aperture 12, imaging len 13, ccd detector 14, wherein centre wavelength are λ1The first tunable laser
Optical axis where device 1, the first beam expanding lens 2, the first collimating mirror 3, the first Amici prism 4 is primary optic axis, the second Amici prism 5,
Optical axis where convergent lens 11, aperture 12, imaging len 13, ccd detector 14 is the second optical axis, centre wavelength λ2
The second tunable laser 8, the second beam expanding lens 9, the second collimating mirror 10, the first Amici prism 4, the second Amici prism 5, standard
Optical axis where mirror 6, measured lens 7 is third optical axis, and primary optic axis, the second optical axis are mutually perpendicular to respectively with third optical axis；Center
Wavelength is λ1The first tunable laser 1, the first beam expanding lens 2, the first collimating mirror 3, the first Amici prism 4, second light splitting rib
Mirror 5, standard mirror 6, measured lens 7 constitute wavelength as λ1Laser tuning phase shift interference testing light path, centre wavelength λ2Second
Tunable laser 8, the second beam expanding lens 9, the second collimating mirror 10, the first Amici prism 4, the second Amici prism 5, standard mirror 6, quilt
It surveys mirror 7 and constitutes wavelength as λ2Laser tuning phase shift interference testing light path, the second Amici prism 5, convergent lens 11, aperture light
Door screen 12, imaging len 13, ccd detector 14 constitute λ1And λ2Interfere the Moire fringe phase-shift interference acquisition light after optical superposition
Road is λ that is, by centre wavelength1The wavelength that tunable laser 1 is sent out is λ1Laser light incident to the first beam expanding lens 2, first expand
Mirror 2 assembles incident small-bore directional light, and light beam becomes the spherical wave of diverging after converging focal point, and spherical wave is incident to
First collimating mirror 3, the focus of the first collimating mirror 3 are overlapped with the focus of the first beam expanding lens 2, and divergent spherical wave is through the first collimating mirror 3
Become the collimated light beam of collimation after transmission, which reflexes to the second Amici prism 5 through the first Amici prism 4, through the
Two Amici prisms 5 are incident to standard mirror 6 and measured lens 7 forms wavelength as λ1Laser tuning phase shift interference testing light path；By
Centre wavelength is λ2The wavelength that tunable laser 8 is sent out is λ2Laser light incident to the second beam expanding lens 9, the second beam expanding lens 9 will enter
The small-bore directional light penetrated is assembled, and light beam becomes the spherical wave of diverging after converging focal point, and spherical wave is incident to the second standard
Straight mirror 10, the focus of the second collimating mirror 10 are overlapped with the focus of the second beam expanding lens 9, and divergent spherical wave is transmitted through the second collimating mirror 10
Become the collimated light beam of collimation afterwards, which is incident to 6 He of standard mirror through the first Amici prism 4 and the second Amici prism 5
Measured lens 7 forms wavelength as λ2Laser tuning phase shift interference testing light path；It is incident to the wavelength of standard mirror 6 and measured lens 7
For λ1And λ2Light wave through 7 back reflection of standard mirror 6 and measured lens, pass through convergent lens after being reflected by the second Amici prism 5 successively
11st, aperture 12, imaging len 13 finally form λ by the acquisition of ccd detector 141And λ2Interfere More's item after optical superposition
Line interferogram sampling light path.
The inclined-plane of the first above-mentioned Amici prism 4 and the third optical axis included angle of horizontal direction are 135 °, the second Amici prism 5
Inclined-plane and horizontal direction third optical axis included angle be 45 °.
The present apparatus selects central wavelength lambda1Tunable laser 1 and λ for 687nm2Tunable laser 8 for 633nm is made
For light source, wherein tunable wavelength ranging from 682~692nm of the first tunable laser 1, tunable laser 8 it is adjustable
Resonance wave length ranging from 632.5~635nm, specific test process are as follows：
Step 1：Using central wavelength lambda1Tunable laser 1 and λ for 687nm2Tunable laser 6 for 633nm
Work is carried out at the same time, wherein tunable laser 1 carries out wavelength tuning according to pi/2 theory phase shift stepping-in amount and realizes interference phase shift,
Second tunable laser 8 carries out wavelength tuning according to the theoretical phase shift stepping-in amount of π/(2n) and realizes interference phase shift, by phase shift
λ is calculated after carrying out time domain Fourier transformation in moire map1And λ2Practical phase shift stepping-in amount under respective wavelength, root
Voltage is corrected according to the degree for being respectively offset from pi/2 and π/4, obtains λ1And λ2Practical phase shift stepping-in amount is respectively pi/2 under wavelength
With the voltage value of π/4, the voltage value that practical phase shift stepping-in amount under two kinds of wavelength is respectively pi/2 and 3 pi/2s has also just been obtained in this way,
Complete the calibration of dual wavelength phase shift stepping-in amount；
Step 2：As the first tunable laser 1 of light source and the second tunable laser 8 according to being demarcated in step 1
The voltage value that obtains afterwards adjusts laser power supply voltage, ensures that the practical phase shift stepping-in amount under 687nm wavelength is pi/2,633nm waves
Practical phase shift stepping-in amount under long is 3 pi/2s, carries out wavelength phase shift, passes through shape after the acquisition two-way interference optical superposition of ccd detector 14
Into moire map, which contains the phase information of synthetic wavelength；
Step 3：The Moire fringe phase-shift interference acquired to ccd detector 14 is obtained using dual wavelength phase-shifting algorithm
It to tested phase information, is then mutually unpacked by position, finally solves the face shape information of tested surface.
Wherein, the phase shift moire map information in step 1 is：It is respectively λ with centre wavelength1And λ2Laser tune
Humorous light source is carried out at the same time wavelength phase-shifting interference measuring, then the intensity signal of kth step phase shift interference moiré topography is：
Wherein, k is the serial number of 4 frame Moire fringe phase-shift interferences, i.e. k=1,2,3,4, IaFor background light intensity, IbFor light intensity
Modulation degree, h (x, y) are interference cavity length, and h (x, y) contains the face shape information of tested surface, φeqFor synthetic wavelength phase data, i.e.,δ1、δ2Respectively λ1And λ2Phase shift stepping-in amount, and Its
Middle Δ λ1、Δλ2For λ1And λ2Under changed wavelength.Frequency spectrum table of the Moire fringe phase-shift interference after time domain Fourier transformation
It is up to formula：
Wherein f be frequency, A (f) be fundamental component, C1、C2Respectively λ1And λ2Positive primary frequency component under wavelength,Respectively C1And C2Conjugation, f1For λ1The frequency displacement that lower wavelength phase shift generates, i.e.,f2For λ2Lower wavelength moves
The frequency displacement mutually generated, i.e.,H is interference cavity length.When phase shift is demarcated, centre wavelength λ1The first tunable laser
Device and centre wavelength are λ2The second tunable laser according to λ1And λ2The phase shift stepping-in amount of respectively pi/2 and π/(2n) carries out
Wavelength phase shift, wherein n are positive integer, and n ≠ 1, therefore, in the frequency spectrum that moire map is obtained through time domain Fourier transformation
λ1And λ2Frequency component be separated from each other, i.e. f in above formula1With f2Differ, then in frequency spectrum two kinds of wavelength four frequency components that
This separation, i.e. C1、C2、It is separated from each other, λ respectively is isolated by using bandpass filter1Positive primary frequency component C1And λ2
Positive primary frequency component C2, inverse Fourier transform is carried out to it, solution obtains phase value, obtained by two adjacent moments
Phase value subtracts each other, and the practical phase shift stepping-in amount under two kinds of wavelength can be respectively obtained, according to the journey for being respectively offset from pi/2 and π/(2n)
Degree is corrected voltage, obtains λ1And λ2Practical phase shift stepping-in amount is respectively the voltage value of pi/2 and π/(2n) under wavelength, in this way
Also the voltage value that practical phase shift stepping-in amount under two kinds of wavelength is respectively pi/2 and 3 pi/2s has just been obtained, has completed dual wavelength phase shift step
Input is demarcated.
With centre wavelength it is respectively λ in step 21And λ2Laser tuning light source according to the phase shift stepping demarcated in step 1
Amount carries out being carried out at the same time wavelength phase-shifting interference measuring, i.e. λ1And λ2Phase shift stepping-in amount be respectively pi/2 and 3 pi/2s, then kth step phase shift
Interference moiré topography intensity signal be：
Wherein, k is the serial number of 4 frame Moire fringe phase-shift interferences, i.e. k=1,2,3,4, IaFor background light intensity, IbFor light intensity
Modulation degree, φeqFor synthetic wavelength phase data, i.e. φeq=φ2-φ1, φeqContain the face shape information of tested surface.In step 3
To Moire fringe phase-shift interference processing dual wavelength phase-shifting algorithm be：Due to the phase shift stepping-in amount difference under two kinds of wavelength
For pi/2 and 3 pi/2s, then kth step phase shift is interfered in the intensity signal expression formula of moiré topographyIn
Phase shift stepping-in amount is π, and absolute value is unrelated with phase shift stepping-in amount, and includes the latter of synthetic wavelength phaseIn phase shift stepping-in amount for pi/2, then using the i.e. extractable synthesis of similar traditional four-step phase-shifting algorithm
The phase of wavelengtheqInformation, i.e.,The face shape information of tested surface is obtained after phase unwrapping.
Centre wavelength in above-mentioned steps one, step 2 is λ1The first tunable laser and centre wavelength be λ2
The phase shift stepping-in amount of two tunable laser can be exchanged with each other setting, as λ in step 11Phase shift stepping-in amount for π/
(2n), λ2Phase shift stepping-in amount for pi/2, λ in step 21Phase shift stepping-in amount for 3 pi/2s, λ2Phase shift stepping-in amount be pi/2.
Claims (6)
- A kind of 1. test method of the dual wavelength tuning interference testing device of Fourier transformation phase shift calibration, which is characterized in that institute The dual wavelength tuning interference testing device for stating Fourier transformation phase shift calibration includes centre wavelength for λ1The first tunable laser Device (1), the first beam expanding lens (2) and the first collimating mirror (3), the first Amici prism (4), the second Amici prism (5), standard mirror (6), Measured lens (7), centre wavelength λ2The second tunable laser (8), the second beam expanding lens (9), the second collimating mirror (10), assemble Lens (11), aperture (12), imaging len (13), ccd detector (14), wherein λ1≠λ2；Setting gradually centre wavelength is λ1The first tunable laser (1), the first beam expanding lens (2), the first collimating mirror (3), the optical axis where the first Amici prism (4) For primary optic axis；Set gradually the second Amici prism (5), convergent lens (11), aperture (12), imaging len (13), CCD Optical axis where detector (14) is the second optical axis；Centre wavelength is set gradually as λ2Tunable laser (8), second expand Where mirror (9), the second collimating mirror (10), the first Amici prism (4), the second Amici prism (5), standard mirror (6), measured lens (7) Optical axis for third optical axis, primary optic axis, the second optical axis are mutually perpendicular to respectively with third optical axis；It is λ by centre wavelength1It is tunable The wavelength that laser (1) is sent out is λ1Laser light incident to the first beam expanding lens (2), the first beam expanding lens (2) will be incident small-bore Directional light is assembled, and light beam becomes the spherical wave of diverging after converging focal point, and spherical wave is incident to the first collimating mirror (3), the The focus of one collimating mirror (3) is overlapped with the focus of the first beam expanding lens (2), and divergent spherical wave becomes after the first collimating mirror (3) transmission Into the collimated light beam of collimation, which reflexes to the second Amici prism (5) through the first Amici prism (4), through second point Light prism (5) is incident to standard mirror (6) and measured lens (7) forms wavelength as λ1Laser tuning phase shift interference testing light path； It is λ by centre wavelength2The wavelength that tunable laser (8) is sent out is λ2Laser light incident to the second beam expanding lens (9), second expand Mirror (9) assembles incident small-bore directional light, and light beam becomes the spherical wave of diverging after converging focal point, and spherical wave is incident To the second collimating mirror (10), the focus of the second collimating mirror (10) is overlapped with the focus of the second beam expanding lens (9), and divergent spherical wave is through Become the collimated light beam of collimation after two collimating mirrors (10) transmission, which is transmitted through second point through the first Amici prism (4) Light prism (5), then after the second Amici prism (5) transmission, wavelength is formd as λ through standard mirror (6) and measured lens (7)2Swash Magic eye phase shift interference testing light path；The wavelength for being incident to standard mirror (6) and measured lens (7) is respectively λ1And λ2Light through standard Mirror (6) and measured lens (7) back reflection, then pass through convergent lens (11), aperture successively after being reflected by the second Amici prism (5) (12), imaging len (13) are finally acquired by ccd detector (14), form λ1And λ2Moire fringe after interference optical superposition is done Relate to figure acquisition light path；The step of the method, is as follows：Step 1：In striking rope type interference testing light path, using two tunable laser of different centre wavelengths as light source Work is carried out at the same time, carrying out wavelength tuning according to respective theoretical phase shift stepping-in amount realizes interference phase shift, is adopted using ccd detector Collection obtains a series of phase shift moire maps formed after two-way interference optical superposition, by phase shift moire map λ is determined after carrying out time domain Fourier transformation1And λ2Practical phase shift stepping-in amount under respective wavelength, obtains actually moving under two kinds of wavelength The relationship of phase stepping-in amount and laser power supply voltage change value, according to the practical phase shift stepping-in amount with changing with laser power supply voltage The relationship of variate adjusts laser power supply voltage value, and to obtain practical phase shift stepping-in amount under two kinds of wavelength be respectively pi/2 and 3 pi/2s When voltage value, complete under respective wavelength phase shift stepping-in amount calibration；Step 2：Two tunable laser as light source adjust laser according to the voltage value obtained after being demarcated in step 1 Supply voltage, it is respectively pi/2 and 3 pi/2s to ensure the practical phase shift stepping-in amount under two kinds of wavelength, carries out wavelength phase shift and carries out wavelength shifting Phase acquires two-way by detector and interferes the moire map formed after optical superposition, which contains synthetic wavelength Phase information；Step 3：The Moire fringe phase-shift interference of ccd detector acquisition is tested using dual wavelength phase-shifting algorithm Then phase information is mutually unpacked by position, solve the face shape information of tested surface.
- 2. the test of the dual wavelength tuning interference testing device according to claim 1 based on Fourier transformation phase shift calibration Method, it is characterised in that：Spectrum expression formula of the moire map after time domain Fourier transformation in step 1 be：Wherein f be frequency, A (f) be fundamental component, C1For λ1Positive primary frequency component under wavelength, C2For λ2Positive one under wavelength Grade frequency component,For C1Conjugation,For C2Conjugation, f1For λ1The frequency displacement that lower wavelength phase shift generates, i.e.,f2 For λ2The frequency displacement that lower wavelength phase shift generates, i.e.,Δλ1、Δλ2For λ1And λ2Under changed wavelength, h is interference cavity It is long.
- 3. the test of the dual wavelength tuning interference testing device according to claim 1 based on Fourier transformation phase shift calibration Method, it is characterised in that：In step 1 λ is extracted in the calibration of phase shift stepping-in amount1And λ2Practical phase shift stepping-in amount under respective wavelength Method be：When phase shift is demarcated, centre wavelength λ1The first tunable laser according to λ1Phase shift stepping-in amount for pi/2 carries out Wavelength phase shift, centre wavelength λ2The second tunable laser according to λ2Phase shift stepping-in amount for π/(2n) carries out wavelength phase shift, Wherein n is positive integer, and n ≠ 1, therefore, λ in the frequency spectrum that moire map is obtained through time domain Fourier transformation1And λ2Frequency Rate component is separated from each other, i.e. f in above formula1With f2It differs, then four frequency components of two kinds of wavelength are separated from each other in frequency spectrum, i.e., C1、C2、It is separated from each other, λ respectively is isolated by using bandpass filter1Positive primary frequency component C1And λ2Positive level-one frequency Rate component C2, inverse Fourier transform is carried out to it, solution obtains phase value, the phase value phase obtained by two adjacent moments Subtract, the practical phase shift stepping-in amount under two kinds of wavelength can be respectively obtained, according to being respectively offset from the degree of pi/2 and π/(2n) to voltage It is corrected, obtains λ1And λ2Practical phase shift stepping-in amount is respectively the voltage value of pi/2 and π/(2n) under wavelength, is also just obtained in this way Practical phase shift stepping-in amount is respectively the voltage value of pi/2 and 3 pi/2s under two kinds of wavelength, completes the calibration of dual wavelength phase shift stepping-in amount.
- 4. the test of the dual wavelength tuning interference testing device according to claim 1 based on Fourier transformation phase shift calibration Method, it is characterised in that：Phase shift Moire fringe information in step 2 is：It is respectively λ with centre wavelength1And λ2Laser tuning Light source is carried out at the same time wavelength phase-shifting interference measuring, then the intensity signal I of kth step phase shift interference moiré topographykFor：Wherein, serial numbers of the k for 4 frame Moire fringe phase-shift interferences, i.e. k=1,2,3,4, IaFor background light intensity, IbFor intensity modulation Degree, φ1Be wavelength be λ1Phase change amount, φ2Be wavelength be λ2Phase change amount, φeqFor synthetic wavelength phase data, That is φeq=φ2-φ1, φeqContain the face shape information of tested surface.
- 5. the test of the dual wavelength tuning interference testing device according to claim 1 based on Fourier transformation phase shift calibration Method, it is characterised in that：It is to the dual wavelength phase-shifting algorithm of Moire fringe phase-shift interference processing in step 3：Due to two Phase shift stepping-in amount under kind wavelength is respectively the intensity signal expression formula of pi/2 and 3 pi/2s, then kth step phase shift interference moiré topography InIn phase shift stepping-in amount for π, absolute value is unrelated with phase shift stepping-in amount, and includes synthetic wavelength The latter of phaseIn phase shift stepping-in amount for pi/2, then use similar traditional four-step phase-shifting algorithm The phase of i.e. extractable synthetic wavelengtheqInformation, i.e.,Tested surface is obtained after phase unwrapping Face shape information.
- 6. the test of the dual wavelength tuning interference testing device according to claim 3 based on Fourier transformation phase shift calibration Method, it is characterised in that：Step 1: the centre wavelength in step 2 is λ1The first tunable laser and centre wavelength be λ2 The phase shift stepping-in amount of the second tunable laser can be exchanged with each other setting, as λ in step 11Phase shift stepping-in amount for π/ (2n), λ2Phase shift stepping-in amount for pi/2, λ in step 21Phase shift stepping-in amount for 3 pi/2s, λ2Phase shift stepping-in amount be pi/2.
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