CN103712569B - Based on single image fast phase shift system and the method for detecting phases of deflection angle - Google Patents

Abstract

The invention discloses a kind of single image fast phase shift system and method based on deflection angle, it is characterized in that being irradiated to tested object plane by the object light of laser emitting forms laser speckle interferometry, the backhaul object light on measured object surface is projected on the target surface array of ccd video camera; The reference light of laser emitting is via collimator assembly and catoptron, be radiated on the target surface array of ccd video camera with angle [alpha], and with the formation laser interference phenomenon of backhaul object light on the target surface array of ccd video camera, the size of adjustment angle [alpha], make reference light on two adjacent pixels there is the optical path difference of 120 °, obtain the phase value of laser interference phenomenon according to the numerical evaluation of the adjacent phase vegetarian refreshments of three in the information of ccd video camera record.The present invention only uses a single image to realize fast phase and detects in speckle interference, without the need to the PZT displacement fine motion system needed for service time phase shifting method.

Description

Based on single image fast phase shift system and the method for detecting phases of deflection angle

Technical field

The present invention relates to a kind of speckle interference measuring system and method for detecting phases, particularly optics fast phase shift method, strain and the deformation measurement of each side such as machine-building, boat aviation sky, material and biology can be widely used in, the detection of fast offset field, deformation field, oscillator field can be realized, and the harmless non-cpntact measurement of material, framework and component.

Background technology

Digital speckle interference measuring technique (DigitalSpecklePatternInterferometry, DSPI) is an optical measurement method combining the technology such as laser, electronics and image procossing, has the advantages such as high precision, noncontact and measurement of full field.Therefore the measurement of each side such as machine-building, Aero-Space, material and biology is widely used in.

Fig. 4 is the existing speckle interference measuring system based on time-phase displacement, laser instrument 101 sends the laser prism 102 that is split and is divided into two-beam, light beam is after the first catoptron 103 and the first beam expanding lens 104 are irradiated to the surface of measured object 108, gathered by ccd video camera 110, transfer data in computing machine through video processing board-card 107; Second bundle light, as the target surface array being directly irradiated to ccd video camera with reference to light beam through the second catoptron 105 and the second beam expanding lens 106, is produced speckle interference with light beam, can be obtained the deflection of measured object by the phase measurement of interference fringe.Wherein be arranged in the second catoptron 105 piezoelectric actuator PZT below to adjust the second catoptron 105 by PZT driving circuit 109 and make every width image have constant phase shift, the phase place of interference fringe can be obtained by phase calculation.

In speckle interference is measured, the just intensity signal that ccd video camera obtains, intensity signal I1 (x, y) can be expressed as:

I ₁(x,y)=a(x,y)+b(x,y)cos[φ(x,y)](6)

In formula (6): a (x, y), b (x, y) and φ (x, y) represent background information, modulated amplitude and phase information respectively, just comprise the change information of measured object field in phase information φ (x, y).Directly cannot obtain phase information in measuring system, the light intensity signal relevant with phase place can only be obtained.Have three unknown quantity a (x, y) in formula (6), b (x, y) and φ (x, y), calculate φ (x, y), just needs at least three equations.In order to obtain phase information wherein, phase-shifting technique is grown up.

Phase-shifting technique (Phase-Shifting) is the Main Means of interference fringe phase detection techniques.Time-phase displacement method is mostly adopted to realize phase-detection at present, its principle obtains three equations by recording three width images, piezoelectric actuator PZT is adopted to drive catoptron to make the reference light in every width intensity image all have constant phase shift, such as: the wavelength by the fine motion of PZT being catoptron mobile 1/6 laser light wave at every turn, like this after three movements, through the reflection of catoptron, the phase place of the reference light of laser interference just creates the phase offset of 0 °, 120 ° and 240 °.Time-phase displacement method needs to gather multiple image and realize repeatedly phase shift with PZT in measuring process, and carry out phase calculation, usual measuring process needs the regular hour.Extract the light intensity data of same point in three width images, its principle as shown in Figure 5, obtains formula (7.1), formula (7.2) and formula (7.3) thus:

I ₁(x,y)=a(x,y)+b(x,y)cos[φ(x,y)](7.1)

I ₂(x,y)=a(x,y)+b(x,y)cos[φ(x,y)+120°](7.2)

I ₃(x,y)=a(x,y)+b(x,y)cos[φ(x,y)+240°](7.3)

By Simultaneous Equations, the PHASE DISTRIBUTION φ (x, y) that can obtain laser interference of solving an equation is as follows:

$\mathrm{\φ}(x,y)=\arctan \frac{\sqrt{3}[I_3(x,y)-I_2(x,y)]}{2I_1(x,y)-I_2(x,y)-I_3(x,y)}---\left(8\right)$

Time-phase displacement method is current most widely used method for detecting phases, but the impact that method is subject to ambient vibration, temperature variation and measured piece skew itself is larger, therefore to the stability of measured piece, there is very high requirement, because the method needs to realize multistep phase shift by PZT, and need collection three width image, just can calculate, therefore cannot meet the requirement of modern industry Quick Measurement.Temporal phase-shifting method is confined to the measurement to static or quasistatic position phase.Spatial phase shift method then can carry out dynamic phase measurement.The Spatial phase measurement method of current employing generally adopts porous diffraction, adds the method for Fourier conversion to obtain stripe pattern.But its optical system is comparatively complicated, higher to request detector, therefore realizes dynamic speckle in the urgent need to the simple and rapid Method for Phase Difference Measurement of one and measure.

Summary of the invention

Technical matters to be solved by this invention avoids weak point existing in above-mentioned prior art, a kind of single image fast phase shift system based on deflection angle and method for detecting phases are provided, the large-scale speckle that adjustment laser interference generates, make it in spatial domain, cover the pixel of a lot of ccd array, by the phase calculation of single pixel and its adjacent pixels, only need gather the phase diagram that single image can obtain optical interference, to dynamically and obtain the phase information of speckle under Quick Measurement, the traditional speckle measurement of effective solution cannot realize the problem that rapid deformation is measured.Do not need in gatherer process to use PZT to carry out phase shift to reference light, simplify the structure of acquisition system, reduce the error of phase shift from error source.

Technical solution problem of the present invention adopts following technical scheme:

The design feature that the present invention is based on the single image fast phase shift system of deflection angle is: System's composition comprises laser instrument, variable nd optical filter, beam expanding lens, collimator assembly, aperture diaphragm, imaging len, catoptron, Amici prism and ccd video camera;

The emergent light of described laser instrument is divided into object light and reference light by variable nd optical filter, the surface that described object light is irradiated to measured object after beam expanding lens expands forms laser speckle interferometry, and via hole diameter diaphragm and imaging len are projected on the target surface array of ccd video camera the backhaul object light on measured object surface successively; Described reference light is reference collimation laser via collimator assembly collimation, described reference collimation laser is radiated on the target surface array of ccd video camera through catoptron and Amici prism, and on the target surface array of ccd video camera, form laser interference phenomenon with described backhaul object light, by the distribution of light intensity information of laser interference phenomenon described in described ccd video camera record;

By being arranged on the angle fine-adjustment mechanism under catoptron, adjustment is with reference to the irradiating angle of collimation laser, during to make the normal angulation α with reference to the direction of illumination of collimation laser and ccd video camera target surface array, adjacent two pixels exist the optical path difference of 120 °, obtains the phase value of described laser interference phenomenon according to the numerical evaluation of three adjacent phase vegetarian refreshments in the distribution of light intensity information of described ccd video camera record.

The present invention utilizes the feature based on the method for detecting phases of the single image fast phase shift system of deflection angle to be carry out in accordance with the following steps:

Step one, the adjustment size of aperture diaphragm and the spatial relation of imaging len and ccd video camera, realize the control to the speckle size of the laser speckle interferometry obtained by ccd video camera collection, guarantee that each speckle at least covers three neighbor pixels of described ccd video camera target surface array;

The direction of illumination of step 2, adjustment reference collimation laser, when guaranteeing the angled α of normal with reference to direction of illumination and the described ccd video camera target surface array of collimation laser, the optical path difference of existence 120 ° on adjacent two pixels of described ccd video camera target surface array;

Step 3, at any time, uses the distribution of light intensity information of ccd video camera record current time, with I _{(M-1, N)}, I _{(M, N)}and I _{(M+1, N)}represent the distribution of light intensity information of three continuous image vegetarian refreshments respectively, (M, N) represents the coordinate of pixel at described ccd video camera target surface array, then have:

$I_{(M-1,N)}=a_{(M-1,N)}+b_{(M-1,N)}\cos [{\mathrm{\φ}}_{(M,N)}-\frac{\mathrm{\π}}{3}]---\left(1\right)$

I _(M,N)=a _(M,N)+b _(M,N)cos[φ _(M,N)](2)

$I_{(M+1,N)}=a_{(M+1,N)}+b_{(M+1,N)}\cos [{\mathrm{\φ}}_{(M,N)}+\frac{\mathrm{\π}}{3}]---\left(3\right)$

In formula (1), formula (2) and formula (3), a _{(M-1, N)}, a _{(M, N)}, a _{(M+1, N)}represent the background light intensity of its corresponding coordinate pixel respectively, b _{(M-1, N)}, b _{(M, N)}, b _{(M+1, N)}represent the modulated amplitude of its respective pixel point respectively, φ _{(M, N)}for the phase value of described laser interference phenomenon; Because described speckle size covers at least three pixels, therefore, the light intensity under same speckle and modulated amplitude are similar to thinks equal, and the above-mentioned formula of simultaneous (1), (2) and (3) solve, then have:

${\mathrm{\φ}}_{(M,N)}=\arctan \frac{\sqrt{3}[I_{(M-1,N)}-I_{(M+1,N)}]}{{2I}_{(M,N)}-I_{(M-1,N)}-I_{(M+1,N)}}---\left(4\right)$

Step 4, apply distortion to measured object, the phase value of laser interference phenomenon of two different conditions before not calculating measured object distortion respectively in the same time and after being out of shape, subtracting each other by phase value, in conjunction with optical maser wavelength, obtains the true strain of measured object:

$D_{(M,N)}=\frac{\mathrm{\λ}({\mathrm{\φ}}_{1(M,N)}-{\mathrm{\φ}}_{2(M,N)})}{2\mathrm{\π}}---\left(5\right)$

In formula (5), D _{(M, N)}for the emergent light wavelength that the distortion of measured object, λ are laser instrument, φ _{1 (M, N)}and φ _{2 (M, N)}laser interference phase place before being respectively measured object distortion and after distortion.

Compared with the prior art, beneficial effect of the present invention is embodied in:

1, the present invention adopts novel easy space phase shifting method, the irradiating angle changing reference beam realizes the change of phase place, without the need to the PZT hardware system of Conventional temporal phase-shifting technique, because this simplify system architecture and cost, reaching the object that rapid data obtains, laying the foundation for realizing measuring real-time.

2, the present invention owing to realizing phase shift in single image, therefore only need to gather the phase place that single image just can calculate interference fringe, could phase place be calculated without the need to gathering three width images in traditional phase-shifting technique, also greatly reducing measuring process and time, also reaching the object of Quick Measurement.

Accompanying drawing explanation

Fig. 1 is the fast phase shift light path system pie graph that the present invention is based on single image;

Label in Fig. 1: 1 laser instrument, 2 variable nd optical filters, 3 beam expanding lenss, 4 collimator assemblies, 5 aperture diaphragms, 6 imaging lens, 7 measured objects, 8 reflective mirrors, 9 is ccd video camera, 10 Amici prisms;

Fig. 2 is the speckle interference schematic diagram at the change beam deflection angle that the present invention adopts;

Fig. 3 is the ultimate principle that in the single image that adopts of the present invention, three adjacent pixels realize phase calculation;

Fig. 4 is existing digital speckle interference measuring system schematic diagram;

Label in Fig. 4: 101 laser instruments, 102 Amici prisms, 103 first catoptrons, 104 first beam expanding lenss, 105 second catoptrons, 106 second beam expanding lenss, 107 video processing board-cards, 108 measured objects, 109PZT driving circuit, 110CCD video camera;

Fig. 5 is existing time-phase displacement method schematic diagram;

Embodiment

See Fig. 1, in the present embodiment, comprise laser instrument 1, variable nd optical filter 2, beam expanding lens 3, collimator assembly 4, aperture diaphragm 5, imaging len 6, catoptron 8, Amici prism 10 and ccd video camera 9 based on the System's composition of the single image fast phase shift system of deflection angle.

In the present embodiment, the emergent light of laser instrument 1 is divided into object light and reference light by variable nd optical filter 2, the surface that object light is irradiated to measured object 7 after beam expanding lens 3 expands forms laser speckle interferometry, and via hole diameter diaphragm 5 and imaging len 6 are projected on the target surface array of ccd video camera 9 the backhaul object light on measured object surface successively; Reference light collimates as the larger reference collimation laser of diaphragm diameter via collimator assembly 4, be radiated on the target surface array of ccd video camera 9 with reference to collimation laser through catoptron 8 and Amici prism 10, and on the target surface array of ccd video camera 9, form laser interference phenomenon with backhaul object light, by the distribution of light intensity information of ccd video camera 9 recording laser interference.

By being arranged on the angle fine-adjustment mechanism under catoptron 8 in the present embodiment, the irradiating angle of adjustment reference collimation laser, to make the optical path difference two adjacent pixels existing 120 °; See Fig. 2, during normal angulation α with reference to the direction of illumination of collimation laser and ccd video camera 9 target surface array, reference collimation laser is H in the wavelength difference of adjacent two pixels of ccd video camera 9 target surface array, adjustment angle [alpha], make H be λ/3, thus meet the optical path difference of existence 120 ° on two adjacent pixels.The phase value of laser interference phenomenon is obtained according to the numerical evaluation of three adjacent phase vegetarian refreshments in the distribution of light intensity information that ccd video camera 9 records.

Carry out in accordance with the following steps based on the method for detecting phases of the single image fast phase shift system of deflection angle in the present embodiment:

Step one, the adjustment size of aperture diaphragm 5 and the spatial relation of imaging len 6 and ccd video camera 9, realize the control of the speckle size to the laser speckle interferometry being gathered acquisition by ccd video camera 9, guarantee that each speckle at least covers three neighbor pixels of ccd video camera 9 target surface array;

Step 2, see Fig. 2, in the present embodiment, adjustment is with reference to the direction of illumination of collimation laser, when guaranteeing the angled α of normal with reference to direction of illumination and the ccd video camera 9 target surface array of collimation laser, the optical path difference of existence 120 ° on adjacent two pixels of ccd video camera 9 target surface array;

Step 3, at any time use ccd video camera 9 record the distribution of light intensity information of current time, with I _{(M-1, N)}, I _{(M, N)}and I _{(M+1, N)}represent the distribution of light intensity information of three continuous image vegetarian refreshments respectively, (M, N) represents the coordinate of pixel at ccd video camera 9 target surface array, then have:

$I_{(M-1,N)}=a_{(M-1,N)}+b_{(M-1,N)}\cos [{\mathrm{\φ}}_{(M,N)}-\frac{\mathrm{\π}}{3}]---\left(1\right)$

I _(M,N)=a _(M,N)+b _(M,N)cos[φ _(M,N)](2)

$I_{(M+1,N)}=a_{(M+1,N)}+b_{(M+1,N)}\cos [{\mathrm{\φ}}_{(M,N)}+\frac{\mathrm{\π}}{3}]---\left(3\right)$

In formula (1), formula (2) and formula (3), a _{(M-1, N)}, a _{(M, N)}, a _{(M+1, N)}represent the background light intensity of its corresponding coordinate pixel respectively, b _{(M-1, N)}, b _{(M, N)}, b _{(M+1, N)}represent the modulated amplitude of its respective pixel point respectively, φ _{(M, N)}for the phase value of laser interference phenomenon.Because speckle size covers at least three pixels, therefore, light intensity under same speckle and modulated amplitude are similar to thinks equal, see Fig. 3, by calculating the distribution of light intensity information of three continuous image vegetarian refreshments of any time in the present embodiment, simultaneous formula (1), (2) and (3) solve, then have:

${\mathrm{\φ}}_{(M,N)}=\arctan \frac{\sqrt{3}[I_{(M-1,N)}-I_{(M+1,N)}]}{{2I}_{(M,N)}-I_{(M-1,N)}-I_{(M+1,N)}}---\left(4\right)$

Step 4, apply distortion to measured object, the phase value of laser interference phenomenon of two different conditions before not calculating measured object distortion respectively in the same time and after being out of shape, subtracting each other by phase value, in conjunction with optical maser wavelength, obtains the true strain of measured object:

$D_{(M,N)}=\frac{\mathrm{\λ}({\mathrm{\φ}}_{1(M,N)}-{\mathrm{\φ}}_{2(M,N)})}{2\mathrm{\π}}---\left(5\right)$

In formula (5), D _{(M, N)}for the distortion of measured object, λ are optical maser wavelength, φ _{1 (M, N)}and φ _{2 (M, N)}laser interference phase place before being respectively measured object distortion and after distortion.

Claims (1)

1., based on a method for detecting phases for the single image fast phase shift system of deflection angle, the System's composition of the described single image fast phase shift system based on deflection angle comprises laser instrument (1), variable nd optical filter (2), beam expanding lens (3), collimator assembly (4), aperture diaphragm (5), imaging len (6), catoptron (8), Amici prism (10) and ccd video camera (9); The emergent light of described laser instrument (1) is divided into object light and reference light by variable nd optical filter (2), the surface that described object light is irradiated to measured object (7) after beam expanding lens (3) expands forms laser speckle interferometry, and via hole diameter diaphragm (5) and imaging len (6) are projected on the target surface array of ccd video camera (9) the backhaul object light on measured object surface successively; Described reference light is reference collimation laser via collimator assembly (4) collimation, described reference collimation laser is radiated on the target surface array of ccd video camera (9) through catoptron (8) and Amici prism (10), and on the target surface array of ccd video camera (9), form laser interference phenomenon with described backhaul object light, the distribution of light intensity information of described laser interference phenomenon is recorded by described ccd video camera (9); By being arranged on the angle fine-adjustment mechanism under catoptron (8), adjustment is with reference to the irradiating angle of collimation laser, during to make the normal angulation α with reference to the direction of illumination of collimation laser and ccd video camera (9) target surface array, adjacent two pixels exist the optical path difference of 120 °, obtains the phase value of described laser interference phenomenon according to the numerical evaluation of three adjacent phase vegetarian refreshments in the distribution of light intensity information that described ccd video camera (9) records;

Described method for detecting phases carries out as follows:

Step one, the size of adjustment aperture diaphragm (5) and the spatial relation of imaging len (6) and ccd video camera (9), realize the control of the speckle size to the laser speckle interferometry obtained by ccd video camera (9) collection, guarantee that each speckle at least covers three neighbor pixels of described ccd video camera (9) target surface array;

The direction of illumination of step 2, adjustment reference collimation laser, when guaranteeing the angled α of normal with reference to direction of illumination and described ccd video camera (9) the target surface array of collimation laser, the optical path difference of existence 120 ° on adjacent two pixels of described ccd video camera (9) target surface array;

Step 3, at any time, uses the distribution of light intensity information of ccd video camera (9) record current time, with I _{(M-1, N)}, I _{(M, N)}and I _{(M+1, N)}represent the distribution of light intensity information of three continuous image vegetarian refreshments respectively, (M, N) represents the coordinate of pixel at described ccd video camera (9) target surface array, then have:

$I_{(M-1,N)}=a_{(M-1,N)}+b_{(M-1,N)}cos\[{\mathrm{\φ}}_{(M,N)}-\frac{\mathrm{\π}}{3}\]---\left(1\right)$

I _(M,N)＝a _(M,N)+b _(M,N)cos[φ _(M,N)](2)

$I_{(M+1,N)}=a_{(M+1,N)}+b_{(M+1,N)}cos\[{\mathrm{\φ}}_{(M,N)}+\frac{\mathrm{\π}}{3}\]---\left(3\right)$

In formula (1), formula (2) and formula (3), a _{(M-1, N)}, a _{(M, N)}, a _{(M+1, N)}represent the background light intensity of its corresponding coordinate pixel respectively, b _{(M-1, N)}, b _{(M, N)}, b _{(M+1, N)}represent the modulated amplitude of its respective pixel point respectively, φ _{(M, N)}for the phase value of described laser interference phenomenon; Because described speckle size covers at least three pixels, therefore, the light intensity under same speckle and modulated amplitude are similar to thinks equal, and the above-mentioned formula of simultaneous (1), (2) and (3) solve, then have:

${\mathrm{\φ}}_{(M,N)}=arctan\frac{\sqrt{3}\[I_{(M-1,N)}-I_{(M+1,N)}\]}{2I_{(M,N)}-I_{(M-1,N)}-I_{(M+1,N)}}---\left(4\right)$

Step 4, apply distortion to measured object, the phase value of laser interference phenomenon of two different conditions before not calculating measured object distortion respectively in the same time and after being out of shape, subtracting each other by phase value, in conjunction with optical maser wavelength, obtains the true strain of measured object:

$D_{(M,N)}=\frac{\mathrm{\λ}({\mathrm{\φ}}_{1(M,N)}-{\mathrm{\φ}}_{2(M,N)})}{2\mathrm{\π}}---\left(5\right)$

In formula (5), D _{(M, N)}for the emergent light wavelength that the distortion of measured object, λ are laser instrument, φ _{1 (M, N)}and φ _{2 (M, N)}laser interference phase place before being respectively measured object distortion and after distortion.