CN103148785A - Optics interference spectrum domain phase contrast B-scanner and measuring method thereof - Google Patents

Abstract

The invention discloses an optics interference spectrum domain phase contrast B-scanner and a measuring method of the optics interference spectrum domain phase contrast B-scanner are mainly used for measuring interior off-plane displacement distribution of a composite material construction part in a perspective mode. The optics interference spectrum domain phase contrast B-scanner is based on the optics interference principle, unfolds an interference spectrum of an interior tangent section of the composite material construction part by means of spatial modulation of a broadband light source on an image plane of a charge coupled device (CCD) camera, and works out the off-plane displacement distribution of the interior tangent section of the composite material construction part from phase-frequency characteristics of the optical spectrum. The optics interference spectrum domain phase contrast B-scanner can measure a transparent composite material construction part and an optical adiaphanous construction part in the perspective mode. The optics interference spectrum domain phase contrast B-scanner has the advantages of being high in measuring resolution ratio of an axial outline and off-plane displacement, high in measuring speed, and appropriate for mechanical property research and detection and identification of small defect of the composite material construction part.

Description

A kind of optical interference spectral domain phase place contrast B scanner and measuring method thereof

Technical field

The present invention relates to a kind of method and instrument of optical interferometry, particularly compound substance, transparent or semitransparent multi-layer resinous coating are carried out method and the instrument of three-dimensional acoplanarity displacement field distribution measurement.

Technical background

Along with the development of aerospace industry technology, the composite element of varying strength, rigidity and material is used more and morely.Because the complicated coupling effect between the various different materials components in inside and structure has been brought larger challenge to the analysis of its mechanical property and sign experimental technique, so need to have an X-rayed the inner mechanical quantity of measurement composite element: the experimental apparatus of three-D displacement field distribution and method.

Measure the distribution of composite element interior three-dimensional displacement field and have very strong practicality.Unstable due to manufacturing process, composite element produces inherent vice sometimes.In whole life cycle, although (the not impact of mechanical property on member of yardstick～0.01mm) has some but can be ascending to most of tiny flaw, causes at last component damage.Traditional detection mode is mainly by the component inside profile is measured, can't pick out the tiny flaw that those may have problems in the future, and perspective is measured the method for composite element internal displacement field distribution, can utilize the stress concentration phenomenon, directly observe and the hazard rating of assessment defective evolution process even, for research and the defects detection of composite element inside mechanical characteristic provides effective technological means.

In recent years, development along with computing machine and components and parts technology, several perspectives in succession occur and measured the method for composite element internal displacement field, mainly comprise: (1) digital body is correlated with (DVC): the simple in measurement system structure of the method, measuring accuracy is higher, but require the optical clarity of measurand high, fathom limited; (2) Magnetic resonance imaging: the method has very high measuring accuracy and axial resolution, but can't measure the member that metal is contained in inside; (3) X ray chromatography: the method has very strong penetration capacity, and shortcoming is system complex, and X ray has injury to human body, and resin-based materials is less in absorption and the reflection of X ray wave band, and image contrast is low; (4) neutron diffraction: similar with the X ray chromatography method, have stronger penetration capacity, shortcoming is the restriction that is subject to the first passage of neutron, spatial resolution is low; (5) optical wavelength interference scan method: the method can distribute to transparent, translucent or optical opacity composite element interior three-dimensional displacement field and carry out high-acruracy survey, axially three-D profile and displacement field Measurement Resolution are high, and shortcoming is that measuring speed is slower.

On the basis of comprehensive existing displacement field perspective measuring method, the present invention discloses a kind of new instrument and method for the three-dimensional acoplanarity displacement field measurement of composite inner, has realized that quick, the high precision perspective of composite element interior three-dimensional acoplanarity displacement field distribution measured.

Summary of the invention

The present invention discloses a kind of optical interference spectral domain phase place contrast B scanner and measuring method thereof, utilizes the spatial modulation of wideband light source and the phase-frequency characteristic of interference spectrum, the three-dimensional acoplanarity displacement distribution of carry out high resolving power, measuring at a high speed composite element inside.

The present invention is achieved through the following technical solutions:

A kind of optical interference spectral domain phase place contrast B scanner as shown in Figure 1, is applicable to the research of composite element mechanical characteristic and the detection and identification of tiny flaw thereof, comprises successively low Coherent Wideband light source (1), convex lens L ₁(2), cylindrical mirror (3), spectroscope (4), polaroid (5), reference planes (6), tested composite element (7), convex lens L ₂(8), diffraction grating (9), convex lens L ₃(10), CCD camera (11) and computing machine (12).

The light path of instrument master apparent direction is as shown in Fig. 1 dotted line, and the biography photoimaging principle of its main apparent direction is: the broadband light that low Coherent Wideband light source (1) sends is through convex lens L ₁(2) become directional light after the collimation.Because cylindrical mirror on main apparent direction (3) is equivalent to planar lens, do not change the biography light direction, so after passing through spectroscope (4), directional light reflects respectively and is transmitted to tested composite element (7) and the reference planes (6) of interferometer two arms; After again passing through spectroscope (4) transmission and reflection from the reflected light of tested composite element (7) and reference planes (6), stack produces and interferes mutually.Because diffraction grating on main apparent direction (9) is equivalent to plane mirror, so interference light is by convex lens L ₂(8) and L ₃(10) after, parallel radiation looks like on the plane CCD camera (11).By polaroid (5) axially centered by it is rotated, can make two arm reflective light intensities close, thereby the contrast that guarantees interference image be the best.

Instrument is overlooked the direction light path as shown in Fig. 1 solid line, and its biography light principle of overlooking direction is: the broadband light that low Coherent Wideband light source (1) sends is through convex lens L ₁(2) after the collimation, parallel radiation arrives on cylindrical mirror (3).Be equivalent to convex lens owing to overlooking cylindrical mirror on direction (3), therefore after spectroscope (4) reflection, transmission, broadband light is focused into a luminous point at tested composite element (7) and reference planes (6) respectively, comprehensively lead, overlook two dimensions of light path, form a finishing tool of measuring the inner axial slices of composite element (7); The reflected light of tested composite element (7) and reference planes (6) is through after spectroscope (4) transmission and reflecting, at convex lens L ₂(8) under collimating effect, parallel broadband light is injected diffraction grating (9) with identical incident angle.Because diffraction grating (9), makes and only has the identical light of wavelength at convex lens L with different angle of diffraction diffraction different wave length ₃(10) under focussing force just can CCD camera (11) as the plane on specific y position imaging, therefore after the continuous broadband light of wavelength is passed through diffraction, at CCD camera (11) as the y direction on plane according to the wavelength continuous spreading, form Interferogram and also import computing machine (12) into.

B scanning refers to that the measurement each time of system can realize the measurement to the plane information of the inner tangent plane of tested composite element (7).

A kind of optical interference spectral domain phase place contrast B scanning survey method comprises the following steps:

1), the charger of use as shown in Fig. 2 (b) carries out slight pretension to tested composite element (7), record Interferogram at this moment;

2), use charger to apply feeding or loading to tested composite element (7), make it produce acoplanarity displacement, the Interferogram of record this moment;

3), with 1) and 2) two Interferograms that measure in step carry out respectively following Fourier transform: being radiated at CCD camera (11) as the interference spectrum on plane is:

$I\left(y\right)=\underset{p=1}{\overset{M}{\mathrm{\Σ}}}\underset{q=1}{\overset{M}{\mathrm{\Σ}}}\sqrt{I_p\·I_q}\·\exp [2\mathrm{\π}\·\frac{{\mathrm{\Λ}}_{\mathrm{pq}}}{\mathrm{\π}\·C}\·y+2{\mathrm{\Λ}}_{\mathrm{pq}}\·(k_c-\frac{D}{C})+{\mathrm{\φ}}_{\mathrm{pq}0}]$

Wherein I is interference light intensity, and y is the volume coordinate y of Fig. 1 system, the surperficial number of M for participating in interfering, I _pAnd I _pBe respectively the reflected light light intensity on p and q surface, Λ _pqBe the optical path difference between p and q surface, φ _pq0For the light phase place that reflex time produces on p and q surface changes, k _cBe the center wave number of low Coherent Wideband light source (1), C and D are constants:

$C=\frac{-2\mathrm{\π}\·f_{L3}\{1+\tan {[\mathrm{si}{n}^{-1}(\frac{-2\mathrm{\π}}{k_{c}d}+\sin \mathrm{\α})+{\mathrm{\β}}_c]}^2\}}{{k_c}^{2}d\sqrt{1-{(\frac{-2\mathrm{\π}}{k_{c}d}+\sin \mathrm{\α})}^2}}$

$D=f_{L3}\·\tan [{\sin }^{-1}(\frac{2\mathrm{\π}}{k_{c}d}-\sin \mathrm{\α})-{\mathrm{\β}}_c]$

D is the grating constant of diffraction grating (9), and α is the incident angle of diffraction grating (9), β _cBe k _cCorresponding angle of diffraction, f _L3Be convex lens L ₃(10) focal length.After digital sample and windowing, the Fourier transform of interference spectrum:

$\tilde{I}\left(f\right)=F[w\left(y\right)\·I\left(y\right)\·\underset{n=-N/2}{\overset{N/2}{\mathrm{\Σ}}}(y-\mathrm{n\Δy})]$

W (y) and

Be respectively window function and sampling function, wherein Δ y is the sampled distance between adjacent two sampled points of finishing tool tangent plane y direction, and N is the maximum sampling number of the interior y direction of field range of finishing tool tangent plane.

Amplitude versus frequency characte after Fourier transform is:

$A\left(f\right)=\underset{p=1}{\overset{M}{\mathrm{\Σ}}}\underset{q=1}{\overset{M}{\mathrm{\Σ}}}\frac{\sqrt{I_p\·I_q}\sin [N\·\mathrm{\Δy}\·\mathrm{\π}(f\±\frac{{\mathrm{\Λ}}_{\mathrm{pq}}}{\mathrm{\π}\·C})]}{\mathrm{\Δy}\·\mathrm{\π}(f\±\frac{{\mathrm{\Λ}}_{\mathrm{pq}}}{\mathrm{\π}\·C})}$

Utilize amplitude versus frequency characte, the optical path difference between the inner p of tested composite element (7) and q surface can be used crest frequency f _pqBe expressed as:

Λ _pq＝π·C·f _pq

Because f _pqWith ∧ _pqLinear relationship, so f _pqCan characterize composite element (7) inner shaft to profile.

After Fourier transform, p, the q two axial acoplanarity displacement w of surface generation _pqThe interference spectrum phase-frequency characteristic of front and back is respectively:

${{\mathrm{\&phi;}}_{\mathrm{pq}}}^{\mathrm{wrap}}\left(f\right)={2\mathrm{\&Lambda;}}_{\mathrm{pq}}\&CenterDot;(k_c-\frac{D}{C})+{\mathrm{\&phi;}}_{\mathrm{<figure-callout\; id="0"\; label="pq"\; filenames="HSA00000847693000022.png,HSA00000847693000023.png"\; state="\{\{state\}\}">pq</figure-callout>}0}$

${{{\mathrm{\&phi;}}^{\&prime;}}_{\mathrm{pq}}}^{\mathrm{wrap}}\left(f\right)=2({\mathrm{\&Lambda;}}_{\mathrm{pq}}+w_{\mathrm{pq}})\&CenterDot;(k_c-\frac{D}{C})+{\mathrm{\&phi;}}_{\mathrm{<figure-callout\; id="0"\; label="pq"\; filenames="HSA00000847693000022.png,HSA00000847693000023.png"\; state="\{\{state\}\}">pq</figure-callout>}0}$

Phase differential is:

Δφ _pq ^wrap(f)＝φ′ _pq ^wrap(f)-φ _pq ^wrap(f)

Because the phase place that obtains after Fourier transform is-π is to the coiling phase place of π, so what calculate according to the coiling phasometer is the coiling phase differential.Through the jump of coiling phase place being added and subtracted 2 π of integral multiple, after separating coiling calculating, obtain the poor Δ f of unwrapped phase _pq ^Unwrap(f).At this moment, the axial acoplanarity displacement between p, q two surfaces is:

$w_{\mathrm{pq}}=\frac{C}{2(k_c\&CenterDot;C-D)}\&CenterDot;\mathrm{\&Delta;}{{\mathrm{\&phi;}}_{\mathrm{pq}}}^{\mathrm{unwrap}}\left(f\right)$

Following formula is exactly the phase place counter point that utilizes the phase calculation acoplanarity displacement before and after distortion between p, q two surfaces.This method loads Interferogram and the signal demodulation of the inner tangent plane of front and back composite element (7) by shooting, measure the acoplanarity displacement of the inner tangent plane of composite element (7).Advantage is highly sensitive, and the Measurement Resolution of acoplanarity displacement is ± λ/1000.

Description of drawings

Fig. 1 is the systematic schematic diagram of optical interference spectral domain phase place contrast B scanner; In figure, solid line and dotted line are respectively and overlook light path and the main light path of looking; The 1st, low Coherent Wideband light source, the 2nd, convex lens L ₁, the 3rd, cylindrical mirror, the 4th, spectroscope, the 5th, polaroid, the 6th, reference planes, the 7th, tested composite element, the 8th, convex lens L ₂, the 9th, diffraction grating, the 10th, convex lens L ₃, the 11st, CCD camera, the 12nd, computing machine.

Fig. 2 is tested composite element inner structure and charger; (a) tested composite element cut-away view; (b) charger; (c) the acoplanarity displacement distribution plan that produces after tested composite element loads.

Fig. 3 is the interference light intensity curve; I represents light intensity, and k represents wave number k axle.

Fig. 4 is amplitude-versus-frequency curve; OPD represents optical path difference, z representation space coordinate z axle.

Fig. 5 is S ₁S ₂(1.57mm), S ₂S ₃(0.4mm) and S ₁S ₃The poor curve of unwrapped phase (1.97mm); Phase differential when (a) applying 20 μ m feeding; Phase differential when (b) applying 40 μ m feeding; Pha represents phase place, and Sm represents the tested composite element of smooth surface, and Sp represents the tested composite element in speckle surface.

Fig. 6 is S before and after loading ₂, S ₃The acoplanarity displacement curve on surface; Relative acoplanarity displacement when (a) applying 20 μ m feeding; Relative acoplanarity displacement when (b) applying 40 μ m feeding; RD represents relative acoplanarity displacement.

Embodiment

The invention will be further described below in conjunction with experiment embodiment and accompanying drawing, but should not limit protection scope of the present invention.

As seen from Figure 1, the present invention includes: low Coherent Wideband light source (1), convex lens L ₁(2), cylindrical mirror (3), spectroscope (4), polaroid (5), reference planes (6), tested composite element (7), convex lens L ₂(8), diffraction grating (9), convex lens L ₃(10), CCD camera (11) and computing machine (12).In figure dotted line and solid line respectively the master of representative system look light path and overlook light path, because their biography photoimaging principle is different, so followingly respectively it is introduced.

The master of paper system looks light path.1), illumination section: low Coherent Wideband light source (Superlum Diodes. Ltd SLD-371-HP1) (1) sends the near infrared light of centre wavelength 840nm, bandwidth 50nm by optical fiber, through convex lens L ₁(2) (f _L1=60mm) become directional light after collimation, because the master looks light path central column face mirror (3) and is equivalent to planar lens, do not change the biography light direction, so after by 50: 50 spectroscope (4), directional light reflects respectively and is transmitted on tested composite element (7) and reference planes (6) on interferometer two arms.2), imaging moiety: after again passing through spectroscope (4) transmission and reflection from the reflected light of tested composite element (7) and reference planes (6), stack produces and interferes mutually.Because the master looks diffraction grating in light path (THORLABS GR25-1210) (9) and is equivalent to plane mirror, so interference light is by convex lens L ₂(8) and L ₃(10) (f _L2=150mm, f _L3=150mm) after, parallel radiation is on the picture plane of 1392 * 1040 CCD camera (dimension is looked the Digital image technology MV-VS141FM of company limited) (11) in pixel.By polaroid (5) axially centered by it is rotated, can make two arm reflective light intensities close, thereby the contrast that guarantees interference image be the best.

Secondly introducing system overlooks light path.1), illumination section: pass through convex lens L by the broadband light that optical fiber sends ₁(2) after the collimation, parallel radiation to cylindrical mirror (3), is equivalent to convex lens (f owing to overlooking light path central column face mirror (3) _CL=150mm), therefore after spectroscope (4) reflection, transmission, broadband light is focused into a luminous point at tested composite element (7) and reference planes (6) respectively.Comprehensively lead, overlook two dimensions of light path, form a finishing tool of measuring the inner axial slices of composite element (7).2), imaging moiety: the reflected light of tested composite element (7) and reference planes (6) is through after spectroscope (4) transmission and reflecting, at convex lens L ₂(8) under collimating effect, parallel broadband light is injected diffraction grating (9) with identical incident angle.Because diffraction grating (9), makes and only has the identical light of wavelength at convex lens L by different angle of diffraction diffraction different wave length ₃(10) under focussing force just can CCD camera (11) as the plane on specific y position imaging.Therefore, after the continuous broadband light of wavelength is passed through diffraction, at CCD camera (11) as the y direction on plane according to the wavelength continuous spreading, form Interferogram and import in the middle of computing machine (12), Fig. 3 is the interference light intensity curve that extracts from Interferogram.

When total M the surperficial reflected light of measurand (7) and reference planes (6) interfered, the expression formula of interference spectrum was:

$I\left(y\right)=\underset{p=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{q=1}{\overset{M}{\mathrm{\&Sigma;}}}\sqrt{I_p\&CenterDot;I_q}\exp [2\mathrm{\&pi;}\&CenterDot;\frac{{\mathrm{\&Lambda;}}_{\mathrm{pq}}}{\mathrm{\&pi;}\&CenterDot;C}\&CenterDot;y+2{\mathrm{\&Lambda;}}_{\mathrm{pq}}\&CenterDot;(k_c-\frac{D}{C})+{\mathrm{\&phi;}}_{\mathrm{pq}0}],$

Wherein I is interference light intensity, and y is the volume coordinate y of Fig. 1 system, I _pAnd I _pBe respectively the reflected light light intensity on p and q surface, ∧ _pqIt is the optical path difference between p and q surface; φ _pq0For the light phase place that reflex time produces on p and q surface changes, k _c=7.48 * 10 ⁶/ m ^-1Be the center wave number of low Coherent Wideband light source (1), C and D are respectively constant:

$C=\frac{-2\mathrm{\&pi;}\&CenterDot;f_{L3}\{1+\tan {[\mathrm{si}{n}^{-1}(\frac{-2\mathrm{\&pi;}}{k_{c}d}+\sin \mathrm{\&alpha;})+{\mathrm{\&beta;}}_c]}^2\}}{{k_c}^{2}d\sqrt{1-{(\frac{-2\mathrm{\&pi;}}{k_{c}d}+\sin \mathrm{\&alpha;})}^2}},$

$D=f_{L3}\&CenterDot;\tan [{\sin }^{-1}(\frac{2\mathrm{\&pi;}}{k_{c}d}-\sin \mathrm{\&alpha;})-{\mathrm{\&beta;}}_c],$

D=1200 line/mm is the grating constant of diffraction grating (9), and α=80 ° are the incident angle of diffraction grating (9), β _c=-1.75 ° is k _cCorresponding angle of diffraction, f _L3=150mm is convex lens L ₃(10) focal length.After digital sample and windowing, the Fourier transform of interference spectrum:

$\tilde{I}\left(f\right)=F[w\left(y\right)\&CenterDot;I\left(y\right)\&CenterDot;\underset{n=-N/2}{\overset{N/2}{\mathrm{\&Sigma;}}}(y-\mathrm{n\&Delta;y})]$

W (y) and Be respectively window function and sampling function, wherein Δ y is the sampled distance between adjacent two sampled points of finishing tool tangent plane y direction, and N is the maximum sampling number of the interior y direction of field range of finishing tool tangent plane.

Amplitude versus frequency characte after Fourier transform is:

$A\left(f\right)=\underset{p=1}{\overset{M}{\mathrm{\&Sigma;}}}\underset{q=1}{\overset{M}{\mathrm{\&Sigma;}}}\frac{\sqrt{I_p\&CenterDot;I_q}\sin [N\&CenterDot;\mathrm{\&Delta;y}\&CenterDot;\mathrm{\&pi;}(f\&PlusMinus;\frac{{\mathrm{\&Lambda;}}_{\mathrm{pq}}}{\mathrm{C\&pi;}})]}{\mathrm{\&Delta;y}\&CenterDot;\mathrm{\&pi;}(f\&PlusMinus;\frac{{\mathrm{\&Lambda;}}_{\mathrm{pq}}}{\mathrm{\&pi;}C})}$

Utilize amplitude versus frequency characte, the optical path difference between the inner p of tested composite element (7) and q surface can be used crest frequency f _pqBe expressed as:

Λ _pq＝π·C·f _pq

Because f _pqWith ∧ _pqLinear relationship, so f _pqCan characterize composite element (7) inner shaft to profile, Figure 4 shows that the amplitude-versus-frequency curve after Fig. 3 interference signal Fourier transform.In Fig. 4, from left to right the horizontal ordinate of three interference peak signals represents respectively tested composite element (7) tangent plane S successively ₂S ₃, S ₁S ₂And S ₁S ₃Optical path difference between the surface in twos.Because the air gap layer S of composite element (7) ₂S ₃The standard thickness that fine gasket (KOOCZ00515-20) with 0.4mm separates formation, so the abscissa value that it is corresponding as the optical path difference reference standard, calculates other two peak value S ₁S ₂And S ₁S ₃Optical path difference between corresponding two groups of surfaces: 1.57mm and 1.97mm, with in advance identical for the test result of layers of material.

The maximum measuring depth of optical interference spectral domain phase place contrast B scanner is:

$\mathrm{\&Delta;}{\mathrm{\&Lambda;}}_{\max }=\frac{N\&CenterDot;\mathrm{\&pi;}}{2\&CenterDot;\mathrm{\&Delta;k}}$

The Measurement Resolution of axial profile is:

$\mathrm{\&Delta;}{\mathrm{\&Lambda;}}_{\min }=\frac{2\mathrm{\&pi;}}{\mathrm{\&Delta;k}}$

After bringing data into, the maximum axial that calculates the method single fathoms and is respectively 2.66mm and ± 26.6 μ m with the axial profile Measurement Resolution.In order to satisfy the needs of measuring the inner dark zone of composite element (7), the position that can regulate reference planes (6) changes the depth range of measuring.

When carrying out loading experiment, tested composite element (7) inner structure and charger are as shown in Figure 2.Measurand is intensity adjustable, the change rigidity composite element (7) that is made of glassy layer, air gap layer and resin bed three layer flat plate.The charger of tested composite element (7) is to be made of the φ 10mm vertical columns of two interval 60mm and a bulb screw micrometer, and it can carry out to member the stepping loading of accurate per step 0.01mm.

After Fourier transform, p, the q two axial acoplanarity displacement w of surface generation _pqThe interference spectrum phase-frequency characteristic of front and back is respectively:

${{\mathrm{\&phi;}}_{\mathrm{pq}}}^{\mathrm{wrap}}\left(f\right)={2\mathrm{\&Lambda;}}_{\mathrm{pq}}\&CenterDot;(k_c-\frac{D}{C})+{\mathrm{\&phi;}}_{\mathrm{<figure-callout\; id="0"\; label="pq"\; filenames="HSA00000847693000022.png,HSA00000847693000023.png"\; state="\{\{state\}\}">pq</figure-callout>}0}$

${{{\mathrm{\&phi;}}^{\&prime;}}_{\mathrm{pq}}}^{\mathrm{wrap}}\left(f\right)=2({\mathrm{\&Lambda;}}_{\mathrm{pq}}+w_{\mathrm{pq}})\&CenterDot;(k_c-\frac{D}{C})+{\mathrm{\&phi;}}_{\mathrm{<figure-callout\; id="0"\; label="pq"\; filenames="HSA00000847693000022.png,HSA00000847693000023.png"\; state="\{\{state\}\}">pq</figure-callout>}0}$

Phase differential is:

Δφ _pq ^wrap(f)＝φ′ _pq ^wrap(f)-φ _pq ^wrap(f)

Because the phase place that obtains after Fourier transform is-π is to the coiling phase place of π, so what calculate according to the coiling phasometer is the coiling phase differential.Through the jump of coiling phase place being added and subtracted 2 π of integral multiple, after separating coiling calculating, obtain the poor Δ f of unwrapped phase _pq ^Unwrqp(f), as shown in Figure 5.At this moment, the axial acoplanarity displacement between p, q two surfaces is:

$w_{\mathrm{pq}}=\frac{C}{2(k_c\&CenterDot;C-D)}\&CenterDot;\mathrm{\&Delta;}{{\mathrm{\&phi;}}_{\mathrm{pq}}}^{\mathrm{unwrap}}\left(f\right)$

Following formula is exactly the phase place counter point that utilizes the phase calculation acoplanarity displacement before and after distortion between p, q two surfaces.This method loads Interferogram and the signal demodulation of the inner tangent plane of front and back composite element (7) by shooting, measure the acoplanarity displacement of the inner tangent plane of composite element (7).Advantage is highly sensitive, and the Measurement Resolution of acoplanarity displacement is ± λ/1000.

After the poor curve low-pass filtering of the unwrapped phase of Fig. 5 different loads, multiply by scale-up factor C/2 (k _cC-D), draw S ₁S ₂And S ₁S ₃Acoplanarity displacement and the product curve of refractive index, because the refractive index of air is 1, the refractive index of glass is 1.45, so obtain S ₁S ₂And S ₁S ₃The acoplanarity displacement curve.The inner acoplanarity displacement situation of tested composite element (7) as shown in Fig. 2 (c), by the load mode of the structure of composite element (7) and supported at three point as can be known, as resin bed S ₃After compressive deformation, due to the iris action that air gap layer is transmitted power, load will directly pass on the support cylinder of glassy layer opposite side along resin bed and glassy layer supported on both sides, so S ₃The surface has produced larger acoplanarity displacement, S ₂Small translation has occured, i.e. slight compression, S ₁Keep static.Before and after loading, reference surface S ₁Be not subjected to displacement, so S ₁S ₂Acoplanarity displacement be exactly S ₂Acoplanarity displacement, S ₁S ₃Acoplanarity displacement be exactly S ₃Acoplanarity displacement, S ₂, S ₃The acoplanarity displacement curve as shown in Figure 6.

It should be noted that the position that applies feeding is z=-5mm, and surveyed area is z=0mm～3.5mm, thus the place that maximum occurs in surveyed area be distance z=-5mm nearest z=0mm place.According to Fig. 6, work as S ₃When the surface was subject to the loading feeding of 20 μ m, the acoplanarity displacement of 7 μ m had occured in the z=0mm place; When being subject to the loading feeding of 40 μ m, the acoplanarity displacement of 13.2 μ m has occured in the z=0mm place.The linear relationship that loads between the amount of feeding and acoplanarity displacement variable quantity has verified that phase place contrasts the conclusion of algorithm.

As shown in Figure 6, due to the speckle surface to the scattering of light effect, cause speckle composite surface material member (7) to separate the level and smooth degree of the rear curve of coiling not as smooth surface composite element (7), but in the situation that load is identical, the speckle that measures is surperficial close with the smooth surface acoplanarity displacement, the B scanner and the measuring method thereof that have proved the contrast of optical interference spectral domain phase place can be used for the acoplanarity displacement that perspective is measured transparent and the inner tangent plane of optical opacity composite element (7), and good reproducibility.

Claims (8)

1. an optical interference spectral domain phase place contrast B scanner, comprise low Coherent Wideband light source (1), convex lens L1 (2), cylindrical mirror (3), spectroscope (4), polaroid (5), reference planes (6), tested composite element (7), convex lens L successively ₂(8), diffraction grating (9), convex lens L ₃(10), CCD camera (11) and computing machine (12).

2. a kind of optical interference spectral domain phase place according to claim 1 contrasts the B scanner, it is characterized in that: the instrument master looks and comprises successively low Coherent Wideband light source (1), convex lens L in index path ₁(2), the cylindrical mirror (3), spectroscope (4), polaroid (5), reference planes (6), tested composite element (7), the convex lens L that are equivalent to planar lens ₂(8), the diffraction grating (9), the convex lens L that are equivalent to plane mirror ₃(10), CCD camera (11) and computing machine (12).

3. a kind of optical interference spectral domain phase place according to claim 1 contrasts the B scanner, it is characterized in that: instrument is overlooked and is comprised successively low Coherent Wideband light source (1), convex lens L in index path ₁(2), the cylindrical mirror (3), spectroscope (4), polaroid (5), reference planes (6), tested composite element (7), the convex lens L that are equivalent to convex lens ₂(8), have diffraction grating (9), the convex lens L of different wave length with different diffraction angle diffraction ₃(10), CCD camera (11) and computing machine (12).

4. a kind of optical interference spectral domain phase place contrast B scanner according to claim 1, is characterized in that: the above low Coherent Wideband light source (1) of utilized bandwidth 10nm in illumination path.

5. a kind of optical interference spectral domain phase place contrast B scanner according to claim 1, is characterized in that: the convex lens L of imaging optical path ₂(8) and convex lens L ₃(10) comprise a diffraction grating (9) between.

6. an optical interference spectral domain phase place contrasts B scanning survey method, it is characterized in that comprising the following steps:

1), tested composite element (7) is carried out slight pretension, record Interferogram at this moment;

2), tested composite element (7) is loaded, make it produce acoplanarity displacement, the Interferogram of record this moment;

3), with 1) and 2) two Interferograms that measure in step carry out respectively Fourier transform, get phase-frequency characteristic poor, the three-dimensional acoplanarity displacement field distribution of calculating tested composite element (7).

7. a kind of optical interference spectral domain phase place according to claim 6 contrasts the B scan method, it is characterized in that: utilize the crest frequency of interference spectrum amplitude versus frequency characte to calculate the inner three-D profile distribution of tested composite element (7):

Optical path difference between the inner p of tested composite element (7) and q surface can be by the amplitude versus frequency characte upward peak frequency f of correspondence _pqObtain

Λ _pq＝π·C·f _pq

Wherein C is constant:

$C=\frac{-2\mathrm{\&pi;}\&CenterDot;f_{L3}\{1+\tan {[\mathrm{si}{n}^{-1}(\frac{-2\mathrm{\&pi;}}{k_{c}d}+\sin \mathrm{\&alpha;})+{\mathrm{\&beta;}}_c]}^2\}}{{k_c}^{2}d\sqrt{1-{(\frac{-2\mathrm{\&pi;}}{k_{c}d}+\sin \mathrm{\&alpha;})}^2}}$

f _L3Be convex lens L ₃(10) focal length, k _cBe the center wave number of low Coherent Wideband light source (1), d is the grating constant of diffraction grating (9), and α is the incident angle of diffraction grating (9), β _cBe k _cCorresponding angle of diffraction.

8. a kind of optical interference spectral domain phase place contrast B scan method according to claim 6 is characterized in that: the coiling phase difference f that utilizes the interference spectrum phase-frequency characteristic of the inner p of tested composite element (7) before and after loading, q two surperficial stressed front and back _pq ^Wrap(f), after separating through 2 π that the jump of coiling phase place added and subtracted integral multiple the calculating of reeling, obtain the poor Δ f of unwrapped phase _pq ^Unwrap(f); Use the inner acoplanarity displacement of the tested composite element of the poor calculating of unwrapped phase (7) to distribute:

$w_{\mathrm{pq}}=\frac{C}{2(k_c\&CenterDot;C-D)}\&CenterDot;\mathrm{\&Delta;}{{\mathrm{\&phi;}}_{\mathrm{pq}}}^{\mathrm{unwrap}}\left(f\right)$

Wherein C and D are constant:

$D=f_{L3}\&CenterDot;\tan [{\sin }^{-1}(\frac{2\mathrm{\&pi;}}{k_{c}d}-\sin \mathrm{\&alpha;})-{\mathrm{\&beta;}}_c].$

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