CN1932433A - Separating method for carrier frequency electronic speckle displacement field - Google Patents

Abstract

The invention provides the separation method of the carrier electronic speckle displacement field. The method is: it adds the reference path in the electronic speckle two-beam interference path to make the reference path share by the two beams; it imports the carrier modulation stripe by the deflection object, so the carrier stripe distorts adjusted by the object distortion. The two beams measure the distorting object independently to collect the stripe after the object distortion and get the two frame phase bitmap including the off-face displacement and the in-face displacement component information to separate the in-face displacement field and the off-face displacement field by computing the phase location. The invention can get the high precision measurement result, so it can provide a new way for measuring the deformation field component.

Description

The separation method of carrier frequency electronic speckle displacement field

Technical field

The present invention relates to the separation method of carrier frequency electronic speckle displacement field.

Background technology

In photodynamics was measured, time-phase displacement and carrier frequency modulation were two kinds of effective phase place quantitative measurment technology.Compare with phase-shifting technique, the method for interference fringe spatial modulation does not need accurate phase shift apparatus, and is low to the environmental requirement of measuring, and has the advantage of suitable kinetic measurement, and important value is arranged in actual applications.Because interference of light metering all is based on interference fringe and carries out that displacement field measures, the quality of interference fringe is very big to the influence of measurement result.Particularly the spatial modulation of interference fringe more needs the high-contrast striped, and this method is used more in holography and moire interference.The method of interference fringe spatial modulation also is introduced in the electronic speckle pattern interferometry, but the strong noise of speckle striped has limited the development of this technology.

Use the method for phase shifting electronic speckle and measure the existing report of two-dimension displacement component.The method measurement two-dimension displacement component of using carrier frequency electronic speckle yet there are no report.

Summary of the invention

The present invention is directed to existing electronic speckle and measure the deficiency that two-dimension displacement divides metering method, a kind of separation method of carrier frequency electronic speckle displacement field is provided, deformation field that can high-quality modulated object separates the acoplanarity displacement component of deformation of body with the in-plane displacement component, obtain high-precision measurement result.

The separation method of carrier frequency electronic speckle displacement field of the present invention is:

In twin-beam electronic speckle pattern interferometry light path, increase reference path, make this road reference light shared by two light beams; Introduce carrier modulation stripe by the deflection object, object loading back carrier fringe is subjected to the modulation of deformation of body and occurs bending and deformation, two-beam is measured deformable object independently of one another, gather the striped of deformation of body front and back, utilize fourier transform method, demodulation obtains comprising two amplitude phase diagrams of acoplanarity displacement and in-plane displacement component information respectively; Carrying out the phase bit arithmetic separates the in-plane displacement field with the acoplanarity displacement field.

Said method is introduced carrier modulation stripe by the deflection object, has the high advantage of fringe contrast.Utilization has the twin-beam electronic speckle pattern interferometry technology and the carrier modulation technology of same reference light path, in conjunction with Fourier transformation method, can the in-plane displacement field be separated with the acoplanarity displacement field by simple phase bit arithmetic.

The present invention increases the reference light system in double beam type electronic speckle pattern interferometry light path system, adopt the two light beams measured object that throws light on respectively during image acquisition, realized the striped modulation by deflection to Reference, obtained high-quality modulation stripe, utilize then Fourier transformation method respectively demodulation try to achieve the position phasor of two light beams when throwing light on respectively, from two width of cloth position phasors, isolate acoplanarity displacement field component and in-plane displacement field component through further calculating, obtain high-precision measurement result.This method provides a kind of new approach for the measurement of deformation field component.

Description of drawings

Fig. 1 is the twin-beam electronic speckle pattern interferometry carrier frequency modulation light path system diagram with same reference path.

Fig. 2 is the carrier fringe figure before the distortion of light beam first irradiating object among Fig. 1.

Fig. 3 is the carrier fringe of being modulated after light beam first irradiating object is out of shape among Fig. 1.

Fig. 4 is the carrier fringe figure before the distortion of light beam second irradiating object among Fig. 1.

Fig. 5 is the carrier fringe of being modulated after light beam second irradiating object is out of shape among Fig. 1.

The envelope position phasor (corresponding light beam first irradiating object) of Fig. 6 for demodulating by Fig. 2 and Fig. 3.

The envelope position phasor (corresponding light beam second irradiating object) of Fig. 7 for demodulating by Fig. 4 and Fig. 5.

Fig. 8 is the contour of equal displacement figure of isolated in-plane displacement component (u field).

Fig. 9 is the contour of equal displacement figure of isolated acoplanarity displacement component (w field).

Among the figure: 1, laser instrument, 2, variable spectroscope, 3, light beam third, 4, catoptron the third, 5, catoptron fourth, 6, beam expanding lens third, 7, semi-transparent semi-reflecting lens, 8, beam splitter, 9, the light beam first, 10, light beam second, 11, the catoptron first, 12, catoptron second, 13, video camera, 14, the beam expanding lens first, 15, beam expanding lens second, 16, rotation platform, 17, lens.

Embodiment

Embodiment

In double beam type electronic speckle pattern interferometry light path, increase by a reference path, and make this two bundles illumination light use this road reference light jointly.So just formed twin-beam electronic speckle pattern interferometry system with same reference path.

Light path system as shown in Figure 1, laser beam that laser instrument 1 sends be through variable spectroscope beam split, and light beam the third 3 shines on the semi-transparent semi-reflecting lens 7 behind catoptron the third 4, catoptron fourth 5 and beam expanding lens the third 6, through reflecting to form reference path.Be divided into equicohesive light beam first 9 and light beam second 10 behind the beam splitter of transmissive portions lease making combination, after catoptron first 11,12 reflections of catoptron second and beam expanding lens first 14, beam expanding lens second 15, shine on the measured object respectively, form the electronic speckle pattern interferometry system of double beam type.Measured object place by computer-controlled, can the platform 16 of accurate rotation on, scioptics 17 imagings, the speckle image of measured object is gathered by video camera 13.

The incident angle of two light beams is 47 °, tests on vibration isolators.Measured object is that periphery is fixing, the aluminium disks of center loaded.The thick of disk is 2mm, and diameter is 60mm, and the center loads with milscale.Disk is fixed on the platform 16, and the surface is coated with silver powder to strengthen reflectivity.Platform 16 can be made small deflection under the driving of stepper motor.Throws light on respectively by two light beams before the deformation of body, gather the original speckle image that an amplitude object do not load respectively and deposit in the computing machine.Subsequently, corresponding two light beams throw light on respectively and gather the image of object at other states, and each width of cloth image and first width of cloth image subtraction, and the result after subtracting each other is presented on the monitor in real time.Platform 16 rotation during this time drives the disk deflections can introduce carrier fringe, when object has distortion, carrier fringe be subjected to object distortion modulation and bend.

The interference fringe field becomes carrier fringe intensive, that contain deformation information after the linearity modulation.The carrier fringe of being modulated can be expressed as

I(x，y)＝a(x，y)+b(x，y)cos[Δφ(x，y)+2πf ₀x] (1)

Wherein, a (x y) is the background light intensity, b (x y) is streak amplitude, and b (x, y)/(x y) often is called fringe contrast to a, and (x, the y) phase change that causes for deformation of body promptly wait to ask a phase to Δ φ, and they all are the functions of locus.F in the formula ₀Be object deflection introduce along the axial spatial frequency of x.

${\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="A20061006897600085.png"\; state="\{\{state\}\}">f</figure-callout>}}_0=\frac{\mathrm{\&Delta;\&alpha;}(1+\cos \mathrm{\&theta;})}{\mathrm{\&lambda;}}---\left(2\right)$

Wherein, λ is used Wavelength of Laser, and θ is the angle of illumination light and body surface normal, and Δ α is the minute angle that object rotates.

By (1) formula as can be known, the phase-shift phase of the interference fringe of being modulated does not change in time, but with spatial variations.The light intensity expression (1) of carrier fringe on the x direction can be expressed as

I(x，y)＝a(x，y)+c(x，y)exp(j2πf ₀x)+c ^*(x，y)exp(-j2πf ₀x) (3)

Wherein, j represents imaginary part unit, and * represents the conjugation of plural number.C (x y) represents with plural form, for

$c(x,y)=\frac{1}{2}b(x,y)\exp \left[\mathrm{j\&Delta;\&phi;}(x,y)\right]---\left(4\right)$

(x, y) carrying out Fourier transform can obtain to light intensity I at the x direction of principal axis

H(f _x，y)＝A(f _x，y)+C(f _x-f ₀，y)+C ^*(f _x+f ₀，y) (5)

Wherein, A (f _x, y) obtain by background light intensity and low-frequency noise conversion.With suitable wave filter with A (f _x, y) and C ^*(f _x+ f ₀, y) filter, obtain C (f _x-f ₀, it is moved on to initial point after y) and becomes C (f _x, y), do again inverse fourier transform obtain c (x y), can obtain PHASE DISTRIBUTION:

$\mathrm{\&Delta;\&phi;}(x,y)={\tan }^{-1}\frac{\mathrm{Im}\left[c(x,y)\right]}{\mathrm{Re}\left[c(x,y)\right]}---\left(6\right)$

Wherein, Re and Im represent to get real and imaginary part.The envelope position phase of the variation that is main value in [π, π] that is obtained by formula (6), need separate the envelope computing could be with its serialization.

When the light beam A illuminated objects, phase of light wave changes and the deformation of body pass is

${\mathrm{\&Delta;\&phi;}}_A(x,y)=\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}[w(1+\cos \mathrm{\&theta;})+u\sin \mathrm{\&theta;}]---\left(7\right)$

Wherein w be deformation of body along the acoplanarity displacement on the z direction of principal axis, u is that deformation of body is along the in-plane displacement on the x direction of principal axis.What as seen, measure is mixing field.During for light beam second 10 illuminated objects, what obtain is the mixing field of acoplanarity displacement field (w field) and in-plane displacement field (u field) equally, promptly

$\mathrm{\&Delta;}{\mathrm{\&phi;}}_B(x,y)=\frac{2\mathrm{\&pi;}}{\mathrm{\&lambda;}}[w(1+\cos \mathrm{\&theta;})-u\sin \mathrm{\&theta;}]---\left(8\right)$

With formula (7) and formula (8) addition with subtract each other, can get acoplanarity displacement field and in-plane displacement field.

${\mathrm{\&Delta;\&phi;}}_A(x,y)+{\mathrm{\&Delta;\&phi;}}_B(x,y)=\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}w(1+\cos \mathrm{\&theta;})---\left(9\right)$

${\mathrm{\&Delta;\&phi;}}_A(x,y)-{\mathrm{\&Delta;\&phi;}}_B(x,y)=\frac{4\mathrm{\&pi;}}{\mathrm{\&lambda;}}u\sin \mathrm{\&theta;}---\left(10\right)$

By formula (9) and formula (10) as seen, as long as the phase change of deformation of body when obtaining light beam first 9 and 10 irradiations of light beam second respectively, then simple plus and minus calculation is carried out mutually in this two width of cloth position, just acoplanarity displacement field and in-plane displacement field can be separated.

The carrier fringe that obtains during light beam first 9 irradiating objects before and after loading as shown in Figure 2, the modulated carrier striped is as shown in Figure 3.The carrier fringe that obtains during light beam second 10 irradiating objects before loading as shown in Figure 4, the modulated carrier striped is as shown in Figure 5.Utilize fourier transform method to demodulate deformation of body position phase Δ φ respectively _AWith Δ φ _B, the envelope position phasor that Fig. 6 and Fig. 7 demodulate when being respectively light beam first 9 and light beam second 10 illumination measured objects.Fig. 6 and Fig. 7 are separated envelope respectively obtain continuous position phasor, two continuous phasors are added and subtracted separable horizontal shift component phase figure of going out in back and acoplanarity displacement phase diagram mutually.Fig. 8 is the profile diagram of isolated in-plane displacement component (u field), and Fig. 9 is the profile diagram of isolated acoplanarity displacement component (w field).

By the result as seen, utilize the carrier fringe contrast height of the method introducing of deflection object, effectively the deformation field of modulated object.In conjunction with Fourier transformation method, this method can effectively be separated mixing field.

Claims (1)

1, a kind of separation method of carrier frequency electronic speckle displacement field is characterized in that: increase reference path in twin-beam electronic speckle pattern interferometry light path, make this road reference light shared by two light beams; Introduce carrier modulation stripe by the deflection object, object loading back carrier fringe is subjected to the modulation of deformation of body and occurs bending and deformation, two-beam is measured deformable object independently of one another, gather the striped of deformation of body front and back, utilize fourier transform method, demodulation obtains comprising two amplitude phase diagrams of acoplanarity displacement and in-plane displacement component information respectively; Carrying out the phase bit arithmetic separates the in-plane displacement field with the acoplanarity displacement field.

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