CN101871769B - Detection method of electronic speckles for synchronous carrier-frequency modulation in three-dimensional deformation field - Google Patents

Abstract

The invention provides a detection method of electronic speckles for synchronous carrier-frequency modulation in a three-dimensional deformation field. The method comprises the following steps: achieving short-distance illumination of three lasers and short-distance stack imaging on an object surface to be detected and a reference object surface by adopting a large-dislocation square prism; introducing carrier fringe patterns by deflecting the reference object surface, and then carrying out one-time modulation on a speckle interference fringe field lighted by the three lasers; when bending deformation occurs on the carrier fringe patterns under modulation of objection deformation after loading an object, independently measuring the deformed object by the three lasers, collecting the carrier fringe patterns before and after object deformation and the modulated carrier fringe patterns, and then respectively demodulating the carrier fringe patterns by a Fourier transform method to obtain a three-bitmap phase diagram containing off-plane and in-plane information; and finally carrying out phase operation to separate three components of a displacement field. By using the detection method, modulation of three speckle interference fringe fields by deflecting the reference object surface is achieved to obtain high-quality modulation fringe patterns. The method has the advantages of simple light path, relatively simple operation and high measuring precision.

Description

The electronic speckle detection method of 3 D deformation field carrier frequency modulation simultaneously

Technical field

The carrier frequency electronic speckle that the present invention relates to a kind of deformation field is interfered the detection method of three-D displacement component, belongs to the technical field that adopts carrier frequency electronic speckle interferometry deformation of body three-dimensional component.

Background technology

In photodynamics was measured, the ESPI measuring technique is the deformation field of Measuring Object accurately, had precision height, noncontact, to advantages such as the shock insulation requirement are low, in quiet, the kinetic measurement of object, was used widely.But the one dimension distortion that at present typical electronic speckle interference technology can only Measuring Object.Because the distortion of object is three-dimensional, usually needs the two dimension or the 3 D deformation component of Measuring Object.Time-phase displacement and carrier frequency modulation are 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 practical application.In available research achievements, use the method for phase shifting electronic speckle and measure the existing report of three-D displacement component.Use three and measure the light path existing report of electronic speckle method of carrier frequency modulation respectively, this method is modulated demodulation respectively respectively to three displacement components, and light path is complicated, in essence the still carrier frequency of one dimension modulation.Electronic speckle method to three disposable while modulation and demodulation of displacement component is not also appeared in the newspapers.

Summary of the invention

The present invention is directed to existing carrier frequency electronic speckle and measure the deficiency that three-D displacement divides metering method; The electronic speckle detection method of a kind of 3 D deformation field carrier frequency modulation simultaneously is provided; This method can high-quality while carrier frequency modulated object deformation field three displacement components, the disposable three-D displacement component that measures deformation of body.

The electronic speckle detection method of 3 D deformation of the present invention field carrier frequency modulation simultaneously is:

At the in parallel but discontiguous reference substance of measured object one side fixed placement one, the line at measured object center and large-misplacement square glass prism center equates with the beam splitting angle of large-misplacement square glass prism with the angle that the line at reference substance center and large-misplacement square glass prism center forms; A large-misplacement square glass prism is placed in the place ahead of measured object; Tested object plane and with reference to object plane through the large-misplacement square glass prism stacking image; A camera is placed in the large-misplacement square glass prism front; From throw light on simultaneously respectively tested object plane and with reference to object plane of different directions, the front of three laser instruments is equipped with a beam expanding lens with three laser instruments; Before the measured object distortion; With throw light on simultaneously respectively tested object plane and of three laser instruments with reference to object plane, gather the speckle interference image respectively, obtain three original tested object plane speckle interference images; With the reference substance deflecting facet; Gather three tested object plane speckle interference images more respectively,, obtain three tested object plane carrier fringe figure the tested object plane speckle interference image subtraction same laser instrument of correspondence, that reference substance deflecting facet front and back obtain; Keep reference substance deflecting facet state constant; Behind the measured object load deflection; Again with throw light on simultaneously respectively tested object plane and of three laser instruments with reference to object plane; Gather three tested object plane speckle interference images after measured object is out of shape respectively, three tested object plane speckle interference images and three original tested object plane speckle interference image subtractions with after the measured object distortion obtain three tested object plane modulated system carrier fringe figure; Three tested object plane modulated system carrier fringe figure combine with three tested object plane carrier fringe figure, utilize fourier transform method demodulation respectively, obtain three amplitude phase diagrams that comprise acoplanarity displacement and in-plane displacement component information of corresponding three laser illumination; Three amplitude phase diagrams are carried out the phase bit arithmetic obtain the three-D displacement field component.

Large-misplacement square glass prism is Chinese patent document CN201364392 disclosed " a kind of large-misplacement square glass prism of realizing ESPI "; This large-misplacement square glass prism is made up of two right angle trigonometry prisms that ordinary optical glass grinds; Be coated with semi-transparent semi-reflecting film on the inclined-plane of one of them right angle trigonometry prism; The inclined-plane of these two right angle trigonometry prisms forms square glass prism with the optics glue bond together, and a reflecting surface of this square glass prism is the inclined-plane that grinds off a locking angle, and α is between 1 ° to 10 °; The face at the incident light place of square glass prism and the face at emergent light place are coated with anti-reflection film, and two reflectings surface all are coated with total reflection film.This large-misplacement square glass prism adopts ordinary optical glass to replace the calcite crystal of costliness in the prior art; Grind through square glass prism and to have realized ESPI the ordinary optical glass preparation; Simple in structure; Can be good at controlling splitting angle, the interference fringe quality of acquisition is good, realizes easily interfering.

The present invention adopts large-misplacement square glass prism to make measured object dignity and with reference to object plane stacking image closely, introduces carrier fringe through deflection with reference to object plane, to three disposable modulation of laser lighting interference field; The electronic speckle technology of 3 D deformation field carrier frequency modulation simultaneously in conjunction with Fourier transformation method, is measured when can realize three displacement components of deformation field.It is simple that this method has light path, operate simple relatively, the advantage that measuring accuracy is high.

Description of drawings

Fig. 1 is typical single beam illumination ESPI system light path synoptic diagram.

Fig. 2 is the ESPI system schematic of three-dimensional carrier frequency modulation.

Carrier fringe figure before testee distortion when Fig. 3 is first laser illumination.

Carrier fringe figure before testee distortion when Fig. 4 is second laser illumination.

Carrier fringe figure before testee distortion when Fig. 5 is the 3rd laser illumination.

When being first laser illumination, Fig. 6 modulated carrier fringe figure after the testee distortion.

When being second laser illumination, Fig. 7 modulated carrier fringe figure after the testee distortion.

When being the 3rd laser illumination, Fig. 8 modulated carrier fringe figure after the testee distortion.

Deformation of body envelope phase figure when Fig. 9 is first laser illumination.

Deformation of body envelope phase figure when Figure 10 is second laser illumination.

Deformation of body envelope phase figure when Figure 11 is the 3rd laser illumination.

Figure 12 is the bar graph of isolated in-plane displacement component (u field).

Figure 13 is the bar graph of isolated in-plane displacement component (v field).

Figure 14 is the bar graph of isolated acoplanarity displacement component (w field).

Embodiment

Obtain the displacement component value of deformation field, generally adopt the method for 3 illuminations, promptly change the incident angle in the following formula (1), and realize the measurement of three width of cloth fields of behaviour, calculate the component value of displacement field through phase splitting.The object example of 3 D deformation is usually met in engineering survey, and the free beam of processing with organic glass is the electronic speckle detection method that testee is explained the carrier frequency modulation simultaneously of 3 D deformation of the present invention field.

Typical single beam illumination ESPI system is as shown in Figure 1, comprises laser instrument, catoptron, beam expanding lens, lens, semi-transparent semi-reflecting lens and camera, measurement be the mixing field of deformation of body.When the incident angle of the illuminating bundle that incides the testee surface was θ, the phase change Δ φ that the testee surface deformation causes can be represented by displacement component and incident angle θ:

$\mathrm{\Δ\φ}=\frac{2\mathrm{\π}}{\mathrm{\λ}}[w(1+\cos \mathrm{\θ})+u\sin \mathrm{\θ}]---\left(1\right)$

In the formula (1), w representes the acoplanarity displacement of object, and u represents the in-plane displacement horizontal component of object, and λ is used Wavelength of Laser, and θ is the angle of illumination light and testee surface normal.

For the ESPI system of three-dimensional carrier frequency modulation, as shown in Figure 2, when having only first laser illumination, the phase change relational expression before and after the testee distortion can be derived as by (1) formula:

$\mathrm{\Δ\φ}=\frac{2\mathrm{\π}}{\mathrm{\λ}}[w(1+\cos {\mathrm{\θ}}_1)+u\sin {\mathrm{\θ}}_1]---\left(2\right)$

In like manner, for the interference system that has only second laser instrument or the 3rd laser illumination, the phase change relational expression before and after the testee distortion is respectively:

$\mathrm{\Δ\φ}=\frac{2\mathrm{\π}}{\mathrm{\λ}}[w(1+\cos {\mathrm{\θ}}_2)+u\sin {\mathrm{\θ}}_2]---\left(3\right)$

$\mathrm{\Δ\φ}=\frac{2\mathrm{\π}}{\mathrm{\λ}}[w(1+\cos {\mathrm{\θ}}_3)+v\sin {\mathrm{\θ}}_3]---\left(4\right)$

In above-mentioned (2), (3), (4) three formulas, u, v, w be the deformation component of corresponding testee on x, y, three change in coordinate axis direction of z respectively.θ ₁, θ ₂And θ ₃Be respectively the incident angle of three laser illumination objects, the big I of three angles obtains through the coordinate Calculation of beam expanding lens.Through simultaneous (2), (3), (4) three formulas, solve three-dimension deformation-quantity u, v, the w of testee.

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] (5)

Wherein, a (x y) is the background light intensity, b (x y) is streak amplitude, and b (x, y)/(x y) is commonly referred to fringe contrast to a, and (x, the phase change that y) 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.

$f_0=\frac{\mathrm{\Δ\α}(1+\cos \mathrm{\θ})}{\mathrm{\λ}}---\left(6\right)$

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

Can know that by (1) formula the phase-shift phase of the interference fringe of being modulated does not change in time, but with spatial variations.The light intensity expression (5) 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) (7)

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

$c(x,y)=\frac{1}{2}b(x,y)\exp \left[\mathrm{j\Δ\φ}(x,y)\right]---\left(8\right)$

(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) (9)

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:

$\mathrm{\Δ\φ}(x,y)={\tan }^{-1}\frac{\mathrm{Im}\left[c(x,y)\right]}{\mathrm{Re}\left[c(x,y)\right]}---\left(10\right)$

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 (10), need separate the envelope computing could be with its serialization.

The ESPI system of three-dimensional carrier frequency modulation is as shown in Figure 2; Comprise three laser instruments, three beam expanding lenss, large-misplacement square glass prism and camera (comprising lens), large-misplacement square glass prism adopts Chinese patent document CN201364392 disclosed " a kind of large-misplacement square glass prism of realizing ESPI ".LASER Light Source is the He-Ne laser instrument, and optical source wavelength is 0.6328 μ m.Reference substance faces and closely is placed on the testee next door.Testee is the free beam that organic glass is processed, and it is long to be 150.0mm, high 19.5mm, thick 18.5mm.The span that loads is 70.0mm.In the free beam surfaces coated with water paint to strengthen its reflectivity.The central axis (surface normal) of choosing testee is the z axle, sets up three-dimensional system of coordinate xyz.By step motor drive, can do small deflection with reference to object plane in x-z direction, y-z direction.Select the approximately equalised laser instrument of three power, light intensity 1, laser instrument 2 and laser instrument 3.The beam expanding lens 1 of laser instrument 1 front and the beam expanding lens 2 of laser instrument 2 fronts are arranged on the x axle, and are distributed in z axle two side positions; 3 of the beam expanding lenss of laser instrument 3 fronts are arranged on the y axle positive axis, make the approximate coplane of the beam expanding lens that lays respectively at three laser instrument the place aheads in the xoy face.Simultaneously, the laser beam sent of laser instrument 1, laser instrument 2 and laser instrument 3 becomes θ respectively with z axle (testee surface normal) ₁, θ ₂And θ ₃On the z in testee dead ahead axle, be placed with large-misplacement square glass prism, be used to receive thing light and reference light.Place video camera before the large-misplacement square glass prism.Thing light and reference light produce speckle interference through large-misplacement square glass prism in the stack of CCD target surface, interfere speckle image to insert computing machine through CCD, carry out data processing through digital image processing system.In order to have more generality, three laser instruments are arbitrarily apart from the distance of xyz coordinate origin O, and promptly the position of three laser instruments has randomness.The incident angle of each laser beam is confirmed with respect to the coordinate values of testee by each each beam expanding lens of laser instrument the place ahead.

At first, laser instrument 1, laser instrument 2 and laser instrument 3 be respectively from level and vertical three different directional lighting measured object and reference substances, and three laser instruments and imaging system form big shearing ESPI system respectively.Gather the speckle interference image respectively, obtain the speckle interference image of three original tested object planes of corresponding laser instrument 1, laser instrument 2 and laser instrument 3 illuminations; Gather three width of cloth speckle interference images behind the reference substance deflecting facet more respectively.The speckle interference image subtraction of corresponding same laser instrument obtains three width of cloth carrier fringe figure.Carrier fringe figure during laser instrument 1 illumination is as shown in Figure 3, and the carrier fringe figure during laser instrument 2 illuminations is as shown in Figure 4, and the carrier fringe figure during laser instrument 3 illuminations is as shown in Figure 5.

After the measured object distortion, gather three width of cloth speckle interference images more respectively, the original object plane speckle interference image subtraction of this three width of cloth image and corresponding same laser illuminator device obtains the carrier fringe figure that three width of cloth are modulated.Carrier fringe receives the modulation of deformation of body and bends.The carrier fringe of being modulated during laser instrument 1 illumination is as shown in Figure 6, and the carrier fringe of being modulated during laser instrument 2 illuminations is as shown in Figure 7, and the carrier fringe of being modulated during laser instrument 3 illuminations is as shown in Figure 8.

Corresponding each laser illuminator device has two width of cloth bar graphs: carrier fringe figure before the deformation of body and the carrier fringe figure that is modulated behind the deformation of body.Utilize the fourier transform method demodulation, obtain a width of cloth envelope phase figure who comprises acoplanarity displacement and in-plane displacement component information of this laser illumination.Three laser illumination obtain three width of cloth envelope phase figure altogether.Deformation of body envelope phase figure during laser instrument 1 illumination is as shown in Figure 9, and the deformation of body envelope phase figure during laser instrument 2 illuminations is shown in figure 10, and the deformation of body envelope phase figure during laser instrument 3 illuminations is shown in figure 11.Fig. 9, Figure 10, Figure 11 are object mixed deformation field, separate envelope and utilization formula (2), formula (3) and formula (4) calculating, the separable PHASE DISTRIBUTION that obtains the deformation component on x, y, three change in coordinate axis direction of z, the i.e. field of behaviour of displacement component u, v, w through phase place.Contrast for ease is reconstructed into the form of bar graph according to the isolated field of behaviour, and the bar graph of in-plane displacement u field is shown in figure 12, and the bar graph of in-plane displacement v field is shown in figure 13, and acoplanarity displacement w field bar graph is shown in figure 14.

The present invention utilizes the electronic speckle system of three beam lasers illuminations, adopts large-misplacement square glass prism to make testee and with reference to object plane stacking image closely, introduces carrier fringe through deflection with reference to object plane, to three disposable modulation of laser lighting interference field; Utilize fourier transform method, demodulation obtains comprising three width of cloth position phasors from face and in-plane displacement information respectively; Carry out three components of phase computing separation displacement field.Characteristics are that modulation is disposable to the carrier frequency of three speckle interference fringe field of deformation of body; Three displacement components of deformation field are to calculate from mixing displacement field, are not to measure respectively.

Claims (1)

1. the electronic speckle detection method of 3 D deformation field carrier frequency modulation simultaneously; It is characterized in that: at the in parallel but discontiguous reference substance of measured object one side fixed placement one, the line at measured object center and large-misplacement square glass prism center equates with the beam splitting angle of large-misplacement square glass prism with the angle that the line at reference substance center and large-misplacement square glass prism center forms; A large-misplacement square glass prism is placed in the place ahead of measured object; Tested object plane and with reference to object plane through the large-misplacement square glass prism stacking image, a camera is placed in the large-misplacement square glass prism front, with three laser instruments from throw light on simultaneously respectively tested object plane and of different directions with reference to object plane; The front of three laser instruments is equipped with a beam expanding lens; The central axis of choosing testee is the z axle, sets up three-dimensional system of coordinate xyz, and the beam expanding lens of first laser instrument front and the beam expanding lens of second laser instrument front are arranged on the x axle; And be distributed in z axle two side positions; The beam expanding lens of the 3rd laser instrument front then is arranged on the y axle positive axis, on the z in testee dead ahead axle, places large-misplacement square glass prism, is used to receive thing light and reference light; Before the measured object distortion; With throw light on simultaneously respectively tested object plane and of three laser instruments with reference to object plane, gather the speckle interference image respectively, obtain three original tested object plane speckle interference images; With the reference substance deflecting facet; Gather three tested object plane speckle interference images more respectively,, obtain three tested object plane carrier fringe figure the tested object plane speckle interference image subtraction same laser instrument of correspondence, that reference substance deflecting facet front and back obtain; Keep reference substance deflecting facet state constant; Behind the measured object load deflection; Again with throw light on simultaneously respectively tested object plane and of three laser instruments with reference to object plane; Gather three tested object plane speckle interference images after measured object is out of shape respectively, three tested object plane speckle interference images and three original tested object plane speckle interference image subtractions with after the measured object distortion obtain three tested object plane modulated system carrier fringe figure; Three tested object plane modulated system carrier fringe figure combine with three tested object plane carrier fringe figure, utilize fourier transform method demodulation respectively, obtain three amplitude phase diagrams that comprise acoplanarity displacement and in-plane displacement component information of corresponding three laser illumination; Three amplitude phase diagrams are carried out the phase bit arithmetic obtain the three-D displacement field component.

Images