CN104713494A - Testing device and method for dual-wavelength tuning interference marked by Fourier transforming phase shifting - Google Patents

Abstract

The invention discloses a testing device and method for dual-wavelength tuning interference marked by Fourier transforming phase shifting. Tunable lasers with different central wavelengths are adopted by the testing device for serving as light sources to work at the same time, interference phase-shifting is achieved through wavelength tuning, and a detector is adopted for collecting a Moire fringe interference pattern formed after two paths of interference light are superposed. Firstly, the Moire fringe interference pattern collected by the detector is subjected to time-domain Fourier transforming to analyze each frequency component, the marking of phase-shifting step amount is completed, and the phase-shifting step amount under two kinds of wavelengths is guaranteed; secondly, the two tunable lasers serving as the light sources are subjected to phase shifting according to the marked phase-shifting step amount to collect and obtain a phase-shifting Moire fringe interference pattern including synthetic wavelength phase information; finally, the phase-shifting Moire fringe interference pattern is subjected to a dual-wavelength phase-shifting interference algorithm to obtain tested phase information. According to the testing device and method for the dual-wavelength tuning interference marked by the Fourier transforming phase shifting, the surface shape range measured by the interference can be broadened, additional optical paths are not needed in single wavelength phase-shifting marking, and the optical path structure and the interference pattern processing algorithm are simple.

Description

The tuning interference testing device and method of dual wavelength that Fourier transform phase shift is demarcated

Technical field

The present invention relates to interference of light field tests, the tuning interference testing device and method of dual wavelength of particularly a kind of Fourier transform phase shift demarcation.

Background technology

Optical interferometry is a kind of high precision, highly sensitive metrology and measurement method, be widely used in plane, sphere and aspheric surface shape measurement, the measurement of the multiple physical quantity such as measurement of the corrugated transmission quality of the measurement of sphere curvature radius and various lens, prism, optical system.Phase-shifting interference measuring technology is high with its precision, automaticity is high and occupy an important position in high-precision optical detects.The ultimate principle of shift-phase interferometry introduces orderly displacement between two coherent lights of interferometer, the phase differential changing reference light and test light realizes phase-modulation, when changing with reference to light path (or position phase), corresponding movement is also done in the position of interference fringe.In the process, with photodetector, interferogram is carried out to the sampling of several array grid, then deposit frame memory after light intensity digitizing, ask PHASE DISTRIBUTION according to certain mathematical model according to the change of light intensity by computing machine.

Phase-shifter is the critical component realizing phase shift phase measuring method approach, and common phase shifting method has piezoelectric ceramics (PZT) phase shift, rotatory polarization device (wave plate, polaroid) phase shift, mobile diffraction grating or tilt flat plate phase shift, wavelength phase shift (change light source frequency of light wave by adopting tunable laser and realize phase shift) etc.The Phase shift precision of phase-shifter is one of key factor affecting phase measurement precision.Therefore, phase-shifter Accurate Calibration or correct in phase measurement tool be of great significance.

Traditional phase-shifting interferometer has higher measuring accuracy and good measuring repeatability because usually adopting single wavelength as light source, but there is the less problem of its measurement range.If be greater than the surface testing of the noncontinuous surface of 0.5 wavelength to bench height, then there will be because of the tested step difference of height problem exceeding its measurement range that causes more greatly the phase differential of neighbor to be greater than π, correctly cannot recover the height of step.

In order to expand the test specification of tradition phase-shifting interferometer, retain the measuring accuracy of conventional dry interferometer simultaneously, the people such as Yeou-Yen Cheng are at " Two-wavelength phase shifting interferometry " (APPLIEDOPTICS, 24 (23): 4539-4543,1984) dual wavelength movable phase interfere method of testing is proposed in, the larger synthetic wavelength phase data of wavelength is obtained by the phase data difference of analysis list wavelength, be used for the larger face shape of metrical error, expand the test specification of traditional Single wavelength interference testing.Compared with traditional Single wavelength interference testing, there is error enlarge-effect in dual wavelength movable phase interfere method of testing, in order to address this problem, the people such as Yeou-Yen Cheng are subsequently at its " Multiple-wavelength phase-shifting interferometry " (APPLIED OPTICS, 24 (6): 804-807,1985) propose in a literary composition with synthetic wavelength phase data correction Single wavelength phase data, expand the measurement range of Single wavelength shift-phase interferometry, remain again the measuring accuracy of Single wavelength movable phase interfere simultaneously.Piezoelectric ceramics (PZT) phase shift is generally adopted for dual wavelength movable phase interfere proving installation, deposit PZT Phase-shifting Errors problem at different wavelengths, Ribun Onodera is at " Two-wavelength interferometry that uses a Fourier-transform method " (APPLIED OPTICS, 37 (34): 7988-7994,1998) method that process single frames dual wavelength moire map extracts synthetic wavelength phase place is proposed in, by being separated each frequency component of moire map in frequency domain, filtering is except λ ₁positive first component and λ ₂negative first component beyond other frequency components, obtain synthetic wavelength phase place after inverse transformation, thus the different wave length Phase-shifting Errors avoiding phase shift to introduce, but the precision of single frames fringe-pattern analysis algorithm there is no the precision of movable phase interfere high.Dual wavelength movable phase interfere proving installation aspect, Michael B.North-Morris is at " Phase-Shifting Multi-WavelengthDynamic Interferometer " (Proceedings of SPIE, Vol.5531:64-75, Bellingham, WA, 2004) a kind of dual wavelength dynamic interference pick-up unit is devised), the simultaneous phase-shifting under different wave length is realized by the achromatism phase mask placing Pixel-level before CCD, but it is very high to the design processing request of mask plate, structure installment is complicated and follow-up process is loaded down with trivial details.Youichi Bitou is at " Two-wavelengthphase-shifting interferometry using an electrically addressed liquid crystal spatiallight modulator " (APPLIED OPTICS, 44 (9): 1577-1581, 2005) propose in and achieve reverse direction under two kinds of wavelength and the dual wavelength movable phase interfere proving installation of unique step phase shift based on spatial light modulator (EA-SLM), adopt tradition phase-shifting algorithm extracting directly synthetic wavelength phase data, but its device is because comprising a large amount of polarizer and diffraction element, and structure seems complicated.D.G.Abdelsalam is at " Two-wavelength in-linephase-shifting interferometry based on polarizing separation for accurate surfaceprofiling " (APPLIED OPTICS, 55 (33): 6153-6161,2011) a kind of two-wavelength-interferometer based on Mach Zehnder optical interference circuit structure is devised in, under different wave length, phase shift calibration error problem is then by adopting the accurate phase shift of the PZT of closed-loop control realization under two kinds of wavelength to solve, but it is high and expensive to the requirement of PZT.From above-mentioned to solve dual wavelength Phase-shifting Errors problem from hardware aspect different, Joanna Schmit is at " Two-wavelength interferometric with a phase-step error-compensatingalgorithm " (Optical Engineering, 45 (11): 115602_1-115602_3,2006) method solving the PZT phase shift calibration error problem under two kinds of wavelength from algorithm is proposed in, adopt the 8 step Phase-shifting algorithm larger to phase shift calibration error margin tolerance to solve phase value under two kinds of wavelength, but complicated and its Phase-shifting Errors of computation process compensate and there is certain scope.Domestic aspect, the people such as Tian Ailing describe a kind of dual wavelength movable phase interfere proving installation in its patent " a kind of surface shape detection apparatus of large scale and high accuracy and detection method thereof " (application number 201310044110.3), the frequency-converted solid state laser adopting tunable range to be greater than 30nm realizes wavelength movable phase interfere two central wavelength respectively, and need to be multiplied to the interferogram under two kinds of wavelength to superpose the interference light intensity information that the moiré topography low-pass filtering in frequency domain obtained obtains comprising synthetic wavelength phase place, finally adopt Phase-shifting algorithm to extract synthetic wavelength phase place.Proving installation only has a frequency-converted solid state laser but needs to realize wavelength movable phase interfere respectively two central wavelength, therefore more consuming time.In addition, the method needs to carry out frequency spectrum low-pass filtering treatment to the interference light intensity figure of superposition, and the selection of wave filter can reduce the precision of test data, and complex disposal process.

Summary of the invention

The object of this invention is to provide the tuning interference testing device and method of dual wavelength that a kind of Fourier transform phase shift is demarcated, comprising centre wavelength is λ ₁the first tunable laser (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 be λ ₂the 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 λ ₁≠ λ ₂, setting gradually centre wavelength is λ ₁the first tunable laser (1), the first beam expanding lens (2), the first collimating mirror (3), the first Amici prism (4) place optical axis be primary optic axis, set gradually the second Amici prism (5), convergent lens (11), aperture (12), imaging len (13), ccd detector (14) place optical axis be the second optical axis, setting gradually centre wavelength is λ ₂tunable 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), measured lens (7) place optical axis be the 3rd optical axis, primary optic axis, the second optical axis are mutually vertical with the 3rd optical axis respectively, be λ by centre wavelength ₁the wavelength that tunable laser (1) sends is λ ₁laser be incident to the first beam expanding lens (2), the small-bore directional light of incidence is assembled by the first beam expanding lens (2), light beam becomes the spherical wave dispersed after converging focal point, spherical wave is incident to the first collimating mirror (3), the focus of the first collimating mirror (3) overlaps with the focus of the first beam expanding lens (2), divergent spherical wave becomes the parallel beam of collimation after the first collimating mirror (3) transmission, this parallel beam reflexes to the second Amici prism (5) through the first Amici prism (4), being incident to standard mirror (6) and measured lens (7) through the second Amici prism (5), to define wavelength be λ ₁laser tuning movable phase interfere optical system for testing, be λ by centre wavelength ₂the wavelength that tunable laser (8) sends is λ ₂laser be incident to the second beam expanding lens (9), the small-bore directional light of incidence is assembled by the second beam expanding lens (9), light beam becomes the spherical wave dispersed after converging focal point, spherical wave is incident to the second collimating mirror (10), the focus of the second collimating mirror (10) overlaps with the focus of the second beam expanding lens (9), divergent spherical wave becomes the parallel beam of collimation after the second collimating mirror (10) transmission, this parallel beam is transmitted through the second Amici prism (5) through the first Amici prism (4), again after the second Amici prism (5) transmission, defining wavelength through standard mirror (6) and measured lens (7) is λ ₂laser tuning movable phase interfere optical system for testing, the wavelength being incident to standard mirror (6) and measured lens (7) is respectively λ ₁and λ ₂light through standard mirror (6) and measured lens (7) back reflection, successively through convergent lens (11), aperture (12), imaging len (13) after being reflected by the second Amici prism (5) again, finally gathered by ccd detector (14), define λ ₁and λ ₂moire map after interference light superposition gathers light path.

The light splitting surface of the first Amici prism (4) and the 3rd optical axis included angle of horizontal direction are 135 °, and the light splitting surface of the second Amici prism (5) and the 3rd optical axis included angle of horizontal direction are 45 °.

Based on the method for testing of the tuning interference testing device of dual wavelength that Fourier transform phase shift is demarcated, step is as follows:

Step one: in striking rope type interference testing light path, adopt two tunable laser of different centre wavelength to carry out work as light source simultaneously, carry out wavelength tuning according to respective theoretical phase shift stepping-in amount to realize interfering phase shift, the a series of phase shift moire map formed after utilizing ccd detector to collect the superposition of two-way interference light, determine λ after carrying out time domain Fourier transform to phase shift moire map ₁and λ ₂actual phase shift stepping-in amount under respective wavelength, the relation of actual phase shift stepping-in amount and laser power supply voltage change value under obtaining two kinds of wavelength, according to this actual phase shift stepping-in amount with regulate laser power supply magnitude of voltage with the relation of laser power supply voltage change value, magnitude of voltage when actual phase shift stepping-in amount is respectively pi/2 and 3 pi/2 under obtaining two kinds of wavelength, the phase shift stepping-in amount completed under respective wavelength is demarcated;

Step 2: two tunable laser as light source regulate laser power supply voltage according to the magnitude of voltage obtained after demarcation in step one, ensure that the actual phase shift stepping-in amount under two kinds of wavelength is respectively pi/2 and 3 pi/2s, carry out wavelength phase shift and carry out wavelength phase shift, the moire map formed after gathering the superposition of two-way interference light by detector, this interferogram contains the phase information of synthetic wavelength;

Step 3: adopt dual wavelength phase-shifting algorithm to obtain tested phase information to the Moire fringe phase-shift interference of ccd detector collection, then unpacked mutually by position, solve the face shape information of tested surface.

The spectrum expression formula of moire map in above-mentioned steps one after time domain Fourier transform is:

$I\left(f\right)=A\left(f\right)+C_1\exp (f-f_1)\text{+}{C}_1^{\text{*}}\exp (f+f_1)+C_2\exp (f-f_2)+C_2^{*}\exp (f+f_2)$

Wherein f is frequency, and A (f) is fundamental component, C ₁for λ ₁positive primary frequency component under wavelength, C ₂for λ ₂positive primary frequency component under wavelength, for C ₁conjugation, for C ₂conjugation, f ₁for λ ₁the frequency displacement that lower wavelength phase shift produces, namely f ₂for λ ₂the frequency displacement that lower wavelength phase shift produces, namely Δ λ ₁, Δ λ ₂for λ ₁and λ ₂under changed wavelength, h is that interference cavity is long.

In step one phase shift stepping-in amount demarcation in extract λ ₁and λ ₂the method of the actual phase shift stepping-in amount under respective wavelength is: phase shift timing signal, and centre wavelength is λ ₁the first tunable laser according to λ ₁for the phase shift stepping-in amount of pi/2 carries out wavelength phase shift, centre wavelength is λ ₂the second tunable laser according to λ ₂for the phase shift stepping-in amount of π/(2n) carries out wavelength phase shift, wherein n is positive integer, and n ≠ 1, therefore, and λ in the frequency spectrum that moire map obtains through time domain Fourier transform ₁and λ ₂frequency component separated from one another, the f namely in above formula ₁with f ₂not etc., then in frequency spectrum, four frequency components of two kinds of wavelength are separated from one another, i.e. C ₁, c ₂, be separated from each other, adopt bandpass filter to isolate λ respectively ₁positive primary frequency component C ₁and λ ₂positive primary frequency component C ₂, inverse Fourier transform is carried out to it, solves and obtain phase value, the phase value obtained by two adjacent moment is subtracted each other, can obtain the actual phase shift stepping-in amount under two kinds of wavelength respectively, the degree according to departing from pi/2 and π/(2n) respectively corrects voltage, obtains λ ₁and λ ₂under wavelength, actual phase shift stepping-in amount is respectively the magnitude of voltage of pi/2 and π/(2n), and under so also just obtaining two kinds of wavelength, actual phase shift stepping-in amount is respectively the magnitude of voltage of pi/2 and 3 pi/2s, completes dual wavelength phase shift stepping-in amount and demarcates.

Phase shift Moire fringe information in step 2 is: be respectively λ with centre wavelength ₁and λ ₂laser tuning light source carry out wavelength phase-shifting interference measuring, then the intensity signal I of kth step movable phase interfere moiré topography simultaneously _kfor:

$I_k=I_a+I_b\cos [\frac{1}{2}({\mathrm{\φ}}_1+{\mathrm{\φ}}_2)+\mathrm{k\π}]\×\cos [\frac{1}{2}{\mathrm{\φ}}_{\mathrm{eq}}+\frac{1}{2}\mathrm{k\π}]$

Wherein, k is the sequence number of 4 frame Moire fringe phase-shift interferences, i.e. k=1,2,3,4, I _afor background light intensity, I _bfor intensity modulation degree, φ ₁be wavelength be λ ₁phase change amount, φ ₂be wavelength be λ ₂phase change amount, φ _eqfor synthetic wavelength phase data, i.e. φ _eq=φ ₂-φ ₁, φ _eqcontain the face shape information of tested surface.

Be: because the phase shift stepping-in amount under two kinds of wavelength is respectively pi/2 and 3 pi/2s that then kth walks in the intensity signal expression formula of movable phase interfere moiré topography to the dual wavelength phase-shifting algorithm of Moire fringe phase-shift interference process in step 3 in phase shift stepping-in amount be π, its absolute value and phase shift stepping-in amount have nothing to do, and comprise latter one of synthetic wavelength phase place in phase shift stepping-in amount be pi/2, then adopt similar traditional four step phase-shifting algorithms can extract the phase of synthetic wavelength _eqinformation, namely the face shape information of tested surface is obtained after phase unwrapping.

Centre wavelength in step one, step 2 is λ ₁the first tunable laser and centre wavelength be λ ₂the phase shift stepping-in amount of the second tunable laser mutually can exchange setting, be λ in step one ₁phase shift stepping-in amount be π/(2n), λ ₂phase shift stepping-in amount be pi/2, λ in step 2 ₁phase shift stepping-in amount be 3 pi/2s, λ ₂phase shift stepping-in amount be pi/2.

The present invention compared with prior art, its remarkable advantage:

(1) problem of Phase-shifting Errors under the different wave length produced for the employing PZT phase shift of traditional double wavelength movable phase interfere proving installation, two different tunable laser of centre wavelength are adopted to realize the phase shift of frequency conversion wavelength separately, without the need to promoting phase shifting device, the accurate phase shift under different wave length can be controlled, the Phase-shifting Errors under the different wave length avoiding PZT phase shift to introduce.

(2) two kinds of wavelength light sources are adopted to work successively for traditional double wavelength movable phase interfere proving installation, need the problem of carrying out phase shift demarcation successively respectively, adopt two different tunable laser of centre wavelength to work simultaneously, by carrying out to a series of phase shift moire map the spectrum information that time domain Fourier transform obtains moire map, extract each frequency component in frequency spectrum, obtain λ ₁and λ ₂actual phase shift stepping-in amount under respective wavelength, computing machine real time output control tunable laser power supply respectively after process, control λ ₁tunable laser and λ ₂tunable laser realize accurate wavelength phase shift, guarantee λ ₁and λ ₂phase shift stepping-in amount be respectively pi/2 and 3 pi/2s, synchronously complete and the phase shift under dual wavelength is demarcated, avoid because the phase shift carried out under each wavelength is demarcated and need to obtain respectively the interferogram of each wavelength, direct process phase shift moire map realizes phase shift stepping-in amount and demarcates, and demarcates light path without the need to the phase shift of attach list wavelength.

(3) solve for traditional double wavelength movable phase interfere proving installation synthetic wavelength phase data the phase data that needs obtain under each wavelength in advance, and the problem that the laser light source of two kinds of wavelength works successively respectively, adopt two different tunable laser of centre wavelength to work simultaneously, carry out wavelength tuning phase shift test, moiré topography after two kinds of wavelength measurement interferogram superpositions is directly processed, extract synthetic wavelength phase data, the leaching process of synthetic wavelength phase data is simple fast.

Accompanying drawing explanation

Fig. 1 is the principle schematic of the tuning interference testing device of dual wavelength that Fourier transform phase shift of the present invention is demarcated.

Fig. 2 is the method for testing process flow diagram of the tuning interference testing device of dual wavelength based on Fourier transform phase shift demarcation of the present invention.

Embodiment

Composition graphs 1, the tuning interference testing device of dual wavelength that the phase shift of a kind of Fourier transform of the present invention is demarcated, comprising centre wavelength is λ ₁the first tunable laser 1, first beam expanding lens 2, first collimating mirror 3, first Amici prism 4, second Amici prism 5, standard mirror 6, measured lens 7, centre wavelength be λ ₂the second tunable laser 8, second beam expanding lens 9, second collimating mirror 10, convergent lens 11, aperture 12, imaging len 13, ccd detector 14, wherein centre wavelength is λ ₁the optical axis at the first tunable laser 1, first beam expanding lens 2, first collimating mirror 3, first Amici prism 4 place be primary optic axis, the optical axis at the second Amici prism 5, convergent lens 11, aperture 12, imaging len 13, ccd detector 14 place is the second optical axis, and centre wavelength is λ ₂the second tunable laser 8, second beam expanding lens 9, second collimating mirror 10, first Amici prism 4, second Amici prism 5, standard mirror 6, measured lens 7 place optical axis be the 3rd optical axis, primary optic axis, the second optical axis are mutually vertical with the 3rd optical axis respectively; Centre wavelength is λ ₁the first tunable laser 1, first beam expanding lens 2, first collimating mirror 3, first Amici prism 4, second Amici prism 5, standard mirror 6, measured lens 7 to constitute wavelength be λ ₁laser tuning movable phase interfere optical system for testing, centre wavelength is λ ₂the second tunable laser 8, second beam expanding lens 9, second collimating mirror 10, first Amici prism 4, second Amici prism 5, standard mirror 6, measured lens 7 to constitute wavelength be λ ₂laser tuning movable phase interfere optical system for testing, the second Amici prism 5, convergent lens 11, aperture 12, imaging len 13, ccd detector 14 constitute λ ₁and λ ₂moire fringe phase-shift interference after interference light superposition gathers light path, is namely λ by centre wavelength ₁the wavelength that tunable laser 1 sends is λ ₁laser be incident to the first beam expanding lens 2, the small-bore directional light of incidence is assembled by the first beam expanding lens 2, light beam becomes the spherical wave dispersed after converging focal point, spherical wave is incident to the first collimating mirror 3, the focus of the first collimating mirror 3 overlaps with the focus of the first beam expanding lens 2, divergent spherical wave becomes the parallel beam of collimation after the first collimating mirror 3 transmission, this parallel beam reflexes to the second Amici prism 5 through the first Amici prism 4, and being incident to standard mirror 6 and measured lens 7 through the second Amici prism 5, to define wavelength be λ ₁laser tuning movable phase interfere optical system for testing; Be λ by centre wavelength ₂the wavelength that tunable laser 8 sends is λ ₂laser be incident to the second beam expanding lens 9, the small-bore directional light of incidence is assembled by the second beam expanding lens 9, light beam becomes the spherical wave dispersed after converging focal point, spherical wave is incident to the second collimating mirror 10, the focus of the second collimating mirror 10 overlaps with the focus of the second beam expanding lens 9, divergent spherical wave becomes the parallel beam of collimation after the second collimating mirror 10 transmission, and this parallel beam is incident to standard mirror 6 and measured lens 7 through the first Amici prism 4 and the second Amici prism 5, and to define wavelength be λ ₂laser tuning movable phase interfere optical system for testing; The wavelength being incident to standard mirror 6 and measured lens 7 is λ ₁and λ ₂light wave through standard mirror 6 and measured lens 7 back reflection, successively through convergent lens 11, aperture 12, imaging len 13 after being reflected by the second Amici prism 5, finally by ccd detector 14 gather define λ ₁and λ ₂moire map after interference light superposition gathers light path.

The inclined-plane of the first above-mentioned Amici prism 4 and the 3rd optical axis included angle of horizontal direction are 135 °, and the inclined-plane of the second Amici prism 5 and the 3rd optical axis included angle of horizontal direction are 45 °.

This device selects central wavelength lambda ₁for tunable laser 1 and the λ of 687nm ₂for the tunable laser 8 of 633nm is as light source, wherein the tunable wavelength scope of the first tunable laser 1 is 682 ~ 692nm, and the tunable wavelength scope of tunable laser 8 is 632.5 ~ 635nm, and concrete test process is as follows:

Step one: adopt central wavelength lambda ₁for tunable laser 1 and the λ of 687nm ₂for the tunable laser 6 of 633nm carries out work simultaneously, wherein tunable laser 1 carries out wavelength tuning realization interference phase shift according to the theoretical phase shift stepping-in amount of pi/2, second tunable laser 8 is carried out wavelength tuning according to the theoretical phase shift stepping-in amount of π/(2n) and is realized interfering phase shift, after carrying out time domain Fourier transform to phase shift moire map, calculate λ ₁and λ ₂actual phase shift stepping-in amount under respective wavelength, the degree according to departing from pi/2 and π/4 respectively corrects voltage, obtains λ ₁and λ ₂under wavelength, actual phase shift stepping-in amount is respectively the magnitude of voltage of pi/2 and π/4, and under so also just obtaining two kinds of wavelength, actual phase shift stepping-in amount is respectively the magnitude of voltage of pi/2 and 3 pi/2s, completes dual wavelength phase shift stepping-in amount and demarcates;

Step 2: regulate laser power supply voltage according to the magnitude of voltage obtained after demarcating in step one as the first tunable laser 1 of light source and the second tunable laser 8, ensure that the actual phase shift stepping-in amount under 687nm wavelength is pi/2, actual phase shift stepping-in amount under 633nm wavelength is 3 pi/2s, carry out wavelength phase shift, the moire map formed after gathering the superposition of two-way interference light by ccd detector 14, this interferogram contains the phase information of synthetic wavelength;

Step 3: adopt dual wavelength phase-shifting algorithm to obtain tested phase information to the Moire fringe phase-shift interference that ccd detector 14 gathers, then unpacked mutually by position, finally solve the face shape information of tested surface.

Wherein, the phase shift moire map information in step one is: be respectively λ with centre wavelength ₁and λ ₂laser tuning light source carry out wavelength phase-shifting interference measuring simultaneously, then the intensity signal of kth step movable phase interfere moiré topography is:

$I_k=I_k+I_K\cos [\frac{2\mathrm{\πh}(x,y)}{{\mathrm{\λ}}_1}+\frac{2\mathrm{\πh}(x,y)}{{\mathrm{\λ}}_2}+\frac{1}{2}k({\mathrm{\δ}}_1+{\mathrm{\δ}}_2)]\×\cos [{\mathrm{\φ}}_{\mathrm{eq}}+\frac{1}{2}k({\mathrm{\δ}}_1+{\mathrm{\δ}}_2)]$

Wherein, k is the sequence number of 4 frame Moire fringe phase-shift interferences, i.e. k=1,2,3,4, I _afor background light intensity, I _bfor intensity modulation degree, h (x, y) for interference cavity long, h (x, y) contains the face shape information of tested surface, φ _eqfor synthetic wavelength phase data, namely δ ₁, δ ₂be respectively λ ₁and λ ₂phase shift stepping-in amount, and wherein Δ λ ₁, Δ λ ₂for λ ₁and λ ₂under changed wavelength.The spectrum expression formula of Moire fringe phase-shift interference after time domain Fourier transform is:

$I\left(f\right)=A\left(f\right)+C_1\exp (f-f_1)\text{+}{C}_1^{\text{*}}\exp (f+f_1)+C_2\exp (f-f_2)+C_2^{*}\exp (f+f_2)$

Wherein f is frequency, and A (f) is fundamental component, C ₁, C ₂be respectively λ ₁and λ ₂positive primary frequency component under wavelength, be respectively C ₁and C ₂conjugation, f ₁for λ ₁the frequency displacement that lower wavelength phase shift produces, namely f ₂for λ ₂the frequency displacement that lower wavelength phase shift produces, namely h is that interference cavity is long.Phase shift timing signal, centre wavelength is λ ₁the first tunable laser and centre wavelength be λ ₂the second tunable laser according to λ ₁and λ ₂the phase shift stepping-in amount being respectively pi/2 and π/(2n) carries out wavelength phase shift, and wherein n is positive integer, and n ≠ 1, therefore, and λ in the frequency spectrum that moire map obtains through time domain Fourier transform ₁and λ ₂frequency component separated from one another, the f namely in above formula ₁with f ₂not etc., then in frequency spectrum, four frequency components of two kinds of wavelength are separated from one another, i.e. C ₁, c ₂, be separated from each other, adopt bandpass filter to isolate λ respectively ₁positive primary frequency component C ₁and λ ₂positive primary frequency component C ₂, inverse Fourier transform is carried out to it, solves and obtain phase value, the phase value obtained by two adjacent moment is subtracted each other, can obtain the actual phase shift stepping-in amount under two kinds of wavelength respectively, the degree according to departing from pi/2 and π/(2n) respectively corrects voltage, obtains λ ₁and λ ₂under wavelength, actual phase shift stepping-in amount is respectively the magnitude of voltage of pi/2 and π/(2n), and under so also just obtaining two kinds of wavelength, actual phase shift stepping-in amount is respectively the magnitude of voltage of pi/2 and 3 pi/2s, completes dual wavelength phase shift stepping-in amount and demarcates.

λ is respectively with centre wavelength in step 2 ₁and λ ₂laser tuning light source according in step one demarcate phase shift stepping-in amount carry out wavelength phase-shifting interference measuring, i.e. λ simultaneously ₁and λ ₂phase shift stepping-in amount be respectively pi/2 and 3 pi/2s, then the intensity signal of kth step movable phase interfere moiré topography is:

$I_k=I_a+I_b\cos [\frac{1}{2}({\mathrm{\φ}}_1+{\mathrm{\φ}}_2)+\mathrm{k\π}]\×\cos [\frac{1}{2}{\mathrm{\φ}}_{\mathrm{eq}}+\frac{1}{2}\mathrm{k\π}]$

Wherein, k is the sequence number of 4 frame Moire fringe phase-shift interferences, i.e. k=1,2,3,4, I _afor background light intensity, I _bfor intensity modulation degree, φ _eqfor synthetic wavelength phase data, i.e. φ _eq=φ ₂-φ ₁, φ _eqcontain the face shape information of tested surface.Be: because the phase shift stepping-in amount under two kinds of wavelength is respectively pi/2 and 3 pi/2s that then kth walks in the intensity signal expression formula of movable phase interfere moiré topography to the dual wavelength phase-shifting algorithm of Moire fringe phase-shift interference process in step 3 in phase shift stepping-in amount be π, its absolute value and phase shift stepping-in amount have nothing to do, and comprise latter one of synthetic wavelength phase place in phase shift stepping-in amount be pi/2, then adopt similar traditional four step phase-shifting algorithms can extract the phase of synthetic wavelength _eqinformation, namely the face shape information of tested surface is obtained after phase unwrapping.

Centre wavelength in above-mentioned steps one, step 2 is λ ₁the first tunable laser and centre wavelength be λ ₂the phase shift stepping-in amount of the second tunable laser mutually can exchange setting, be λ in step one ₁phase shift stepping-in amount be π/(2n), λ ₂phase shift stepping-in amount be pi/2, λ in step 2 ₁phase shift stepping-in amount be 3 pi/2s, λ ₂phase shift stepping-in amount be pi/2.

Claims (8)

1. the tuning interference testing device of dual wavelength of Fourier transform phase shift demarcation, is characterized in that: comprising centre wavelength is λ ₁the first tunable laser (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 be λ ₂the 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 λ ₁≠ λ ₂, setting gradually centre wavelength is λ ₁the first tunable laser (1), the first beam expanding lens (2), the first collimating mirror (3), the first Amici prism (4) place optical axis be primary optic axis, set gradually the second Amici prism (5), convergent lens (11), aperture (12), imaging len (13), ccd detector (14) place optical axis be the second optical axis, setting gradually centre wavelength is λ ₂tunable 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), measured lens (7) place optical axis be the 3rd optical axis, primary optic axis, the second optical axis are mutually vertical with the 3rd optical axis respectively, be λ by centre wavelength ₁the wavelength that tunable laser (1) sends is λ ₁laser be incident to the first beam expanding lens (2), the small-bore directional light of incidence is assembled by the first beam expanding lens (2), light beam becomes the spherical wave dispersed after converging focal point, spherical wave is incident to the first collimating mirror (3), the focus of the first collimating mirror (3) overlaps with the focus of the first beam expanding lens (2), divergent spherical wave becomes the parallel beam of collimation after the first collimating mirror (3) transmission, this parallel beam reflexes to the second Amici prism (5) through the first Amici prism (4), being incident to standard mirror (6) and measured lens (7) through the second Amici prism (5), to define wavelength be λ ₁laser tuning movable phase interfere optical system for testing, be λ by centre wavelength ₂the wavelength that tunable laser (8) sends is λ ₂laser be incident to the second beam expanding lens (9), the small-bore directional light of incidence is assembled by the second beam expanding lens (9), light beam becomes the spherical wave dispersed after converging focal point, spherical wave is incident to the second collimating mirror (10), the focus of the second collimating mirror (10) overlaps with the focus of the second beam expanding lens (9), divergent spherical wave becomes the parallel beam of collimation after the second collimating mirror (10) transmission, this parallel beam is transmitted through the second Amici prism (5) through the first Amici prism (4), again after the second Amici prism (5) transmission, defining wavelength through standard mirror (6) and measured lens (7) is λ ₂laser tuning movable phase interfere optical system for testing, the wavelength being incident to standard mirror (6) and measured lens (7) is respectively λ ₁and λ ₂light through standard mirror (6) and measured lens (7) back reflection, successively through convergent lens (11), aperture (12), imaging len (13) after being reflected by the second Amici prism (5) again, finally gathered by ccd detector (14), define λ ₁and λ ₂moire map after interference light superposition gathers light path.

2. the tuning interference testing device of dual wavelength of Fourier transform phase shift demarcation according to claim 1, it is characterized in that: the light splitting surface of the first Amici prism (4) and the 3rd optical axis included angle of horizontal direction are 135 °, the light splitting surface of the second Amici prism (5) and the 3rd optical axis included angle of horizontal direction are 45 °.

3., based on the method for testing of the tuning interference testing device of dual wavelength of Fourier transform phase shift demarcation according to claim 1, it is characterized in that, step is as follows:

Step one: in striking rope type interference testing light path, adopt two tunable laser of different centre wavelength to carry out work as light source simultaneously, carry out wavelength tuning according to respective theoretical phase shift stepping-in amount to realize interfering phase shift, the a series of phase shift moire map formed after utilizing ccd detector to collect the superposition of two-way interference light, determine λ after carrying out time domain Fourier transform to phase shift moire map ₁and λ ₂actual phase shift stepping-in amount under respective wavelength, the relation of actual phase shift stepping-in amount and laser power supply voltage change value under obtaining two kinds of wavelength, according to this actual phase shift stepping-in amount with regulate laser power supply magnitude of voltage with the relation of laser power supply voltage change value, magnitude of voltage when actual phase shift stepping-in amount is respectively pi/2 and 3 pi/2 under obtaining two kinds of wavelength, the phase shift stepping-in amount completed under respective wavelength is demarcated;

Step 2: two tunable laser as light source regulate laser power supply voltage according to the magnitude of voltage obtained after demarcation in step one, ensure that the actual phase shift stepping-in amount under two kinds of wavelength is respectively pi/2 and 3 pi/2s, carry out wavelength phase shift and carry out wavelength phase shift, the moire map formed after gathering the superposition of two-way interference light by detector, this interferogram contains the phase information of synthetic wavelength;

Step 3: adopt dual wavelength phase-shifting algorithm to obtain tested phase information to the Moire fringe phase-shift interference of ccd detector collection, then unpacked mutually by position, solve the face shape information of tested surface.

4. the method for testing of the tuning interference testing device of dual wavelength based on Fourier transform phase shift demarcation according to claim 3, is characterized in that: the spectrum expression formula of the moire map in step one after time domain Fourier transform is:

$I\left(f\right)=A\left(f\right)+C_1\exp (f-f_1)\text{+}{C}_1^{\text{*}}\exp (f+f_1)+C_2\exp (f-f_2)+C_2^{*}\exp (f+f_2)$

Wherein f is frequency, and A (f) is fundamental component, C ₁for λ ₁positive primary frequency component under wavelength, C ₂for λ ₂positive primary frequency component under wavelength, for C ₁conjugation, for C ₂conjugation, f ₁for λ ₁the frequency displacement that lower wavelength phase shift produces, namely f ₂for λ ₂the frequency displacement that lower wavelength phase shift produces, namely Δ λ ₁, Δ λ ₂for λ ₁and λ ₂under changed wavelength, h is that interference cavity is long.

5. the method for testing of the tuning interference testing device of dual wavelength of demarcating based on Fourier transform phase shift according to claim 3, is characterized in that: in step one phase shift stepping-in amount demarcation in extract λ ₁and λ ₂the method of the actual phase shift stepping-in amount under respective wavelength is: phase shift timing signal, and centre wavelength is λ ₁the first tunable laser according to λ ₁for the phase shift stepping-in amount of pi/2 carries out wavelength phase shift, centre wavelength is λ ₂the second tunable laser according to λ ₂for the phase shift stepping-in amount of π/(2n) carries out wavelength phase shift, wherein n is positive integer, and n ≠ 1, therefore, and λ in the frequency spectrum that moire map obtains through time domain Fourier transform ₁and λ ₂frequency component separated from one another, the f namely in above formula ₁with f ₂not etc., then in frequency spectrum, four frequency components of two kinds of wavelength are separated from one another, i.e. C ₁, c ₂, be separated from each other, adopt bandpass filter to isolate λ respectively ₁positive primary frequency component C ₁and λ ₂positive primary frequency component C ₂, inverse Fourier transform is carried out to it, solves and obtain phase value, the phase value obtained by two adjacent moment is subtracted each other, can obtain the actual phase shift stepping-in amount under two kinds of wavelength respectively, the degree according to departing from pi/2 and π/(2n) respectively corrects voltage, obtains λ ₁and λ ₂under wavelength, actual phase shift stepping-in amount is respectively the magnitude of voltage of pi/2 and π/(2n), and under so also just obtaining two kinds of wavelength, actual phase shift stepping-in amount is respectively the magnitude of voltage of pi/2 and 3 pi/2s, completes dual wavelength phase shift stepping-in amount and demarcates.

6. the method for testing of the tuning interference testing device of dual wavelength based on Fourier transform phase shift demarcation according to claim 3, is characterized in that: the phase shift Moire fringe information in step 2 is: be respectively λ with centre wavelength ₁and λ ₂laser tuning light source carry out wavelength phase-shifting interference measuring, then the intensity signal I of kth step movable phase interfere moiré topography simultaneously _kfor:

$I_k=I_a+I_b\cos [\frac{1}{2}({\mathrm{\φ}}_1+{\mathrm{\φ}}_2)+\mathrm{k\π}]\×\cos \frac{1}{2}\mathrm{k\π}]$

Wherein, k is the sequence number of 4 frame Moire fringe phase-shift interferences, i.e. k=1,2,3,4, I _afor background light intensity, I _bfor intensity modulation degree, φ ₁be wavelength be λ ₁phase change amount, φ ₂be wavelength be λ ₂phase change amount, φ _eqfor synthetic wavelength phase data, i.e. φ _eq=φ ₂-φ ₁, φ _eqcontain the face shape information of tested surface.

7. the method for testing of the tuning interference testing device of dual wavelength based on Fourier transform phase shift demarcation according to claim 3, it is characterized in that: in step 3 to the dual wavelength phase-shifting algorithm of Moire fringe phase-shift interference process be: because the phase shift stepping-in amount under two kinds of wavelength is respectively pi/2 and 3 pi/2s, then kth walks in the intensity signal expression formula of movable phase interfere moiré topography in phase shift stepping-in amount be π, its absolute value and phase shift stepping-in amount have nothing to do, and comprise latter one of synthetic wavelength phase place in phase shift stepping-in amount be pi/2, then adopt similar traditional four step phase-shifting algorithms can extract the phase of synthetic wavelength _eqinformation, namely the face shape information of tested surface is obtained after phase unwrapping.

8. the method for testing of the tuning interference testing device of dual wavelength based on Fourier transform phase shift demarcation according to claim 3, is characterized in that: the centre wavelength in step one, step 2 is λ ₁the first tunable laser and centre wavelength be λ ₂the phase shift stepping-in amount of the second tunable laser mutually can exchange setting, be λ in step one ₁phase shift stepping-in amount be π/(2n), λ ₂phase shift stepping-in amount be pi/2, λ in step 2 ₁phase shift stepping-in amount be 3 pi/2s, λ ₂phase shift stepping-in amount be pi/2.