CN103134439A - Double-rotation optical wedge space phase shift method used for cutting speckle interference - Google Patents

Abstract

Disclosed is a double-rotation optical wedge space phase shift method used for cutting speckle interference. The double-rotation optical wedge space phase shift method used for cutting speckle interference is designed aiming at the dynamic measurement of plane deformation in the speckle interference measurement. Double holes are added in an imaging optical path, carrier frequency is introduced, thus the space phase shift requirements required by the phase extracting algorithm are met. A gap between the two holes is changed, the distance between adjusting imaging lens and an image plane is adjusted, thus control of size of phase shit quantity of the space can be achieved. Rotable and adjustable double optical wedges are arranged on the position of any one hole of the double holes. One beam of light ray of two beams of light rays passing the double holes deflects, thus two speckle fields on the image plane are caused to be mutually cut. A whole refraction angle of combining the double optical wedges is changed by revolving one of the optical wedges or by the relative revolving of the two optical wedges, thus regulation of the size of the cutting quantity is achieved.

Description

A kind of Dual-rotating light wedge space phase shifting method for speckle-shearing interferometry

Technical field

The present invention relates to from face distortion measurement technical field, the stress deformation or the thermal deformation that can be used for body surface detect, usually adopt the Surface profiling interferometric method from the face distortion measurement, the present invention solves is from the kinetic measurement problem of face deformation in the Surface profiling interferometric method.

Background technology

From face distortion measurement technical field, the Surface profiling interferometric method is one of the most frequently used measuring method, in order to calculate the phase information of measured object, usually needs to adopt phase-shift method.Wherein phase-shift method is divided into again two kinds of time-phase displacement method and spatial phase-shifting methods, the time-phase displacement method gathers image on time series, the general piezoelectric ceramics that adopts is as the phase shift driving element, form known phase poor between each width interferogram, obtain phase information to be measured by gathering 3 width or 3 width with epigraph simultaneous solution system of equations, this just requires measured object to keep stable in the process that phase shifted images gathers, and therefore is not suitable for measurement or the kinetic measurement of shorter object of strain time; And spatial phase-shifting method utilizes the mode of multichannel collecting, spatial mask or space carrier frequency phase shift to shorten acquisition time, and wherein the hyperchannel method utilizes a plurality of CCD cameras to gather simultaneously, and shortcoming is that cost is high, light path is complicated; It is a plurality of that the spatial mask method utilizes diffraction element and wave plate that light field is divided into, and respectively by the difference of CCD as quick regional record, it is had relatively high expectations to the light path installation accuracy; The space carrier frequency phase-shift method is by introducing carrier coded fringes in a speckle, make and form fixing phase differential between the CCD neighbor, this method only need gather a width interferogram, just can calculate phase information to be measured, is applicable to solve the measurement problem of quick stress deformation or dynamic deformation.

Summary of the invention

The objective of the invention is to study the method for introducing linear carrier frequency and shearing displacement adjusting in spatial phase shift Surface profiling interferometric method, be used for solving the measurement problem of the quick stress deformation of Surface profiling interferometric method or dynamic deformation, provide a kind of can implementation space carrier frequency phase shift and the adjustable scheme of shearing displacement, i.e. a kind of Dual-rotating light wedge space phase shifting method for speckle-shearing interferometry.

The present invention is based on the Mechanical Study On Young Interference theory, utilize diplopore to introduce carrier frequency and come the implementation space phase shift, and regulate the size of shearing displacement by the mode of dual rotary wedge.Be used for the dynamic practical application from face deformation of measurement in the Surface profiling interferometric method significant.The method utilizes diplopore to introduce linear carrier frequency, makes the interferogram that collects satisfy the required spatial phase shift condition of phase extraction algorithms, namely by diplopore, speckle field is modulated, and forms fixing phase differential between the neighbor of order collection image.Shearing is to realize by the mode that the position in a hole therein arranges circular two wedges, changes the angle of deviation of incident ray by rotating two wedges, can realize the adjusting of shearing displacement size.

Dual-rotating light wedge space phase shifting method for speckle-shearing interferometry provided by the invention comprises:

The introducing of 1st, spatial phase shift condition: utilize diplopore to introduce carrier frequency to satisfy the required spatial phase shift condition of phase extraction algorithms as phase-shifting element, the carrier frequency direction is the line direction of diplopore, the optical axis of system vertically passes through the point midway of diplopore line, diplopore is two circular holes that size is identical, and wherein the centre wavelength of the distance between the pitch-row of diplopore, imaging len and image planes, laser illuminator device and CCD's is to determine the major parameter of spatial phase shift amount as quick unit size.

Wherein, the distance B between the pitch-row d of described diplopore, imaging len and image planes ' and spatial phase shift amount δ three between relation determine according to as follows:

The phase-shift phase that diplopore is introduced spatial phase shift can be expressed as

$\mathrm{\δ}=\frac{2\mathrm{\π}}{\mathrm{\λ}}\frac{d}{D^{\′}}{x}^{\′}---\left(1\right)$

Wherein λ is the centre wavelength of laser illuminator device, and x ' is as the coordinate figure on X ' direction on the plane;

The formula of determining distance between measured object and imaging len and diplopore screen is

$\frac{1}{D^{\′}}-\frac{1}{-(\mathrm{\ΔD}+D_0)}=\frac{1}{f^{\′}}---\left(2\right)$

Wherein Δ D is the distance that diplopore shields lens, makes Δ D try one's best little of to reduce the overall dimensions of system, D ₀Be the distance between measured object and diplopore screen, f ' is the focal length of imaging len;

The average-size of the speckle on image planes is regulated by the size of controlling diplopore, and its expression formula is

$\mathrm{\σ}=1.22\frac{\mathrm{\λ}{\mathrm{\Δ}}^{\′}}{a}---\left(3\right)$

Wherein D ' is the distance of imaging len to image planes, i.e. image distance; A is the diameter in the upper hole of diplopore screen, and the diameter in hole should be less than the length of the diplopore line of centres.

2nd, the adjusting of shearing displacement: the two wedges that can regulate rotation are placed in any hole site in diplopore, and the two wedges of order cover a hole wherein; Two wedges are the wedge of identical two overlapping placements,, form and shear thereby be through the light in two holes two pictures that mutually stagger on imaging surface respectively the Deflection of light effect due to wedge; By rotating one of them wedge or making two wedges relatively rotate the whole refraction angle that changes the two wedges of combination, realize the adjusting of shearing displacement size.

In the amount regulative mode of described shearing, definite foundation of shearing displacement size is as follows:

For single wedge, its angle of deviation computing formula is

θ ₀=β(n-1)（3）

Wherein β is the refraction angle of wedge, and n is the refractive index of wedge;

With the two overlapping placements of wedge, parallel and when placing in the same way, the angle of deviation of generation is maximal value when the principal section of two wedges, equal two wedge angle of deviation and; At this moment one of them wedge is turned clockwise 90 °, another wedge is rotated counterclockwise 90 °, the parallel reverse placement in the principal section of two wedges, and the angle of deviation of this moment is 0; And with one of them wedge rotation

Another opposite spin

The expression formula of the angle of deviation that produces is

Total angle of deviation that two wedges produce is relevant to the relatively rotation place of the angle of deviation of single wedge and two wedges.The formula of determining object plane shearing displacement size is

D wherein ₀Be the distance between object plane and diplopore screen, x is the coordinate figure of any point P on directions X on object plane, x _PartiallyBe the coordinate figure of equivalent point P' on directions X on object plane after the two wedge deflections of light process of ordering from P.

Advantage of the present invention and good effect:

The present invention proposes a kind of Dual-rotating light wedge space phase shifting method for speckle-shearing interferometry, the method adopts the space carrier frequency phase-shift method, simplified the gatherer process of phase shifted images, each state that changes for measured object only need to gather 1 width interferogram, just phase result be can calculate, the measurement of shorter object of stress deformation time or the kinetic measurement of object are applicable to; The size that the two wedges of circular rotating can be regulated shearing displacement within the specific limits makes the present invention can adapt to the requirement of different measuring sensitivity.

Description of drawings

Fig. 1 is a kind of Dual-rotating light wedge space phase shift interference measuring system schematic diagram for speckle-shearing interferometry, and in figure, 1 is imaging len, the 2nd, and the diplopore screen, the 3rd, the diplopore of the line of centres on directions X, the 4th, rotate adjustable pair of wedge, the 5th, object plane, X ₀O ₀Y ₀Diplopore screen plane, place, the 6th, as the plane.

Fig. 2 is the two wedge schematic diagram of combination, the 7th, and wedge 1,8th, wedge 2,9th, the optical axis of two wedges.

Fig. 3 is that the object plane shearing displacement calculates schematic diagram, O(0, y, 0) be the coordinate figure initial point, A(d/2, y, 0) by on the corresponding object plane in the center in the hole that rotating double-optical wedge is set a bit, P(x, y, 0) be any point on object plane, P'(x', y, 0) be the shearing point on the object plane corresponding with the P point.

Fig. 4 is the assembling schematic diagram of test specimen, and test specimen is a round rubber plate, and in figure, 10 is round rubber plates, the 11st, and metal binding, the 12nd, metal substrate, the 13rd, stress loading circular hole.

Fig. 5 is the interference image that collects when measured object is measured.

Fig. 6 is the wrapped phase result of a series of kinetic measurements, and wherein figure (a) ~ (i) is respectively from reference to constantly counting, through the interferogram and the resulting wrapped phase figure of reference interferogram calculating that collected in 1 ~ 9 second.

Embodiment

A kind of Dual-rotating light wedge space phase shifting method for speckle-shearing interferometry provided by the invention is implemented as follows:

The first, selecting wavelength X is that the laser instrument of 650nm throws light on to measured object as light source.Use pin hole to carry out filtering to the light beam from laser emitting, then utilize 40 * microcobjective laser is expanded to increase lighting area.

The second, utilize diplopore to introduce the required spatial phase shift condition of phase extraction algorithms as phase-shifting element, namely by diplopore, speckle field is modulated, form fixing phase differential between the neighbor of order collection image.Measured object plane, diplopore screen, two wedge, imaging len, as the position relationship between the plane as shown in Figure 1, the distance between the distance between the pitch-row of diplopore, imaging len and image planes, the focal length of imaging len, measured object and imaging len, the parameters such as size of diplopore are determined by formula (1), formula (2) and formula (3): in order to introduce 2 π/3pixel ^-1The spatial phase shift amount, selecting the centre distance d of diplopore is 1.5mm, calculates distance B between imaging len and image planes ' be 44.65mm by formula (1); Select focal distance f ' for the imaging of carrying out of the lens of 35mm, calculate object distance Δ D+D by formula (2) ₀Be 162mm, consider that lens have certain thickness, making the distance, delta D between diplopore screen and imaging len is 7mm, and measured object is to the distance B of diplopore screen ₀Be 155mm, namely working distance is 155mm; Adopt three step spatial phase shift arithmetics need to make a speckle cover at least 3 pixels on CCD, upward the diameter a in hole should be less than 1.83mm can to calculate the diplopore screen by formula (3), because the diameter in hole can not be greater than the diplopore wire length, so the diameter a of selecting hole is 1.2mm.

Three, adopt rotating double-optical wedge as shearing elements, realize the adjusting of shearing displacement, two wedge schematic diagram as shown in Figure 2, its array mode is with two overlapping placements of identical wedge, two wedges can be rotated to regulate around central axis the size of shearing displacement.The use refraction angle is the wedge of 2 °, as definite working distance D ₀During for 155mm, the range of adjustment that calculates shearing displacement Δ x according to formula (6) is 0 ~ 5.95mm.

Four, the calculating of the collection of interference image and deformation phase place.dynamically the measuring object of deformation is that the effective coverage is the rubber slab of diameter 50mm, be characterized in producing elastic deformation after being subject to stress loading, as shown in Figure 4 measured object is fixed, wherein with sheet metal as the fixing substrate of test specimen, the circular hole that it is 10mm that metal base plate central authorities open a diameter, test specimen is loaded from the sheet metal back by circular hole, with the even spreading glue in the rubber slab back side to prevent its slip, utilize the metal binding that rubber slab is rolled tight and is fixed by screws on metal base plate, wherein metal binding central openings diameter is 50mm, metal base plate utilizes clamping device to be fixed on optical table.The mode of back stress loading is adopted in the measurement of rubber test specimen, rubber slab generation elastic deformation after stress application, carry out continuous acquisition in process to rubber slab recovery deformation after stress is cancelled, choose deformation larger position as with reference to constantly the time, although rubber slab is the process that deformation recovers with respect to the Equilibrium position, with respect to being in reference to position rubber slab constantly the state that occurs from face deformation.The interferogram that CCD collects as shown in Figure 5, its intensity expression formula is:

Wherein A (x ', y ') is background intensity, B (x ', y ') be modulate intensity,

Be the space carrier frequency on the X' direction,

Shearing phase distribution for reflection measured object positional information.Interference fringe picture is recorded and is stored as digital picture by CCD, wherein the intensity of (i, j) pixel record is:

In formula, i=1,2,3 ... m; J=1,2,3 ... n, wherein m * n is the pixel count of interference image that CCD gathers.Greater than 3 pixels, (i, j) has identical background intensity, fringe contrast and phase place to be measured between (i+1, j) and neighbors such as (i+2, j) due to the speckle average-size, and the intensity distributions of corresponding pixel points is expressed as:

Can obtain (i, j) some shearing phase by formula (9) is distributed as:

Can be obtained the PHASE DISTRIBUTION of each point on interference image by formula (10), respectively gather a width interferogram before and after measured object produces deformation, variation phase can be expressed as:

Wherein

With

Be corresponding phase place before and after object deformation,

What reflect is distributing from face deformation derivative of measured object.Fig. 6 (a) ~ (i) is respectively from reference to constantly counting, through the interferogram and the resulting wrapped phase figure of reference interferogram calculating that collected in 1 ~ 9 second.

Claims (1)

1. Dual-rotating light wedge space phase shifting method that is used for speckle-shearing interferometry is characterized in that:

The introducing of 1st, spatial phase shift condition: utilize diplopore to introduce carrier frequency to satisfy the required spatial phase shift condition of phase extraction algorithms as phase-shifting element, the carrier frequency direction is the line direction of diplopore, the optical axis of system vertically passes through the point midway of diplopore line, diplopore is two circular holes that size is identical, and wherein the centre wavelength of the distance between the pitch-row of diplopore, imaging len and image planes, laser illuminator device and CCD's is to determine the major parameter of spatial phase shift amount as quick unit size;

Distance B between the pitch-row d of described diplopore, imaging len and image planes ' and spatial phase shift amount δ three between relation determine according to as follows:

The phase-shift phase that diplopore is introduced spatial phase shift can be expressed as

$\mathrm{\δ}=\frac{2\mathrm{\π}}{\mathrm{\λ}}\frac{d}{D^{\′}}{x}^{\′}---\left(1\right)$

Wherein λ is the centre wavelength of laser illuminator device, and x ' is as the coordinate figure on X ' direction on the plane;

The average-size of the speckle on image planes is regulated by the size of controlling diplopore, and its expression formula is

$\mathrm{\σ}=1.22\frac{\mathrm{\λ}{\mathrm{\Δ}}^{\′}}{\mathrm{\α}}---\left(2\right)$

Wherein D ' is the distance of imaging len to the picture plane, i.e. image distance; A is the diameter in the upper hole of diplopore screen, and the diameter in hole should be less than the length of the diplopore line of centres, i.e. the pitch-row d of diplopore;

2nd, the adjusting of shearing displacement: the two wedges that can regulate rotation are placed in any hole site in diplopore, and the two wedges of order cover a hole wherein; Two wedges are the wedge of identical two overlapping placements,, form and shear thereby be through the light in two holes two pictures that mutually stagger on imaging surface respectively the Deflection of light effect due to wedge; By rotating one of them wedge or making two wedges relatively rotate the whole refraction angle that changes the two wedges of combination, realize the adjusting of shearing displacement size;

In the regulative mode of described shearing displacement, definite foundation of shearing displacement size is as follows:

For single wedge, its angle of deviation computing formula is

θ ₀=β(n-1)（3）

Wherein β is the refraction angle of wedge, and n is the refractive index of wedge;

With the two overlapping placements of wedge, parallel and when placing in the same way, the angle of deviation of generation is maximal value when the principal section of two wedges, equal two wedge angle of deviation and; At this moment one of them wedge is turned clockwise 90 °, another wedge is rotated counterclockwise 90 °, the parallel reverse placement in the principal section of two wedges, and the angle of deviation of this moment is 0; And with one of them wedge rotation

Another opposite spin

The expression formula of the angle of deviation that produces is

Total angle of deviation that two wedges produce is relevant to the relatively rotation place of the angle of deviation of single wedge and two wedges;

The formula of determining object plane shearing displacement size is

D wherein ₀Be the distance between object plane and diplopore screen, x is the coordinate figure of any point P on directions X on object plane, x _PartiallyBe the coordinate figure of equivalent point P' on directions X on object plane after the two wedge deflections of light process of ordering from P.

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