CN103489186A - Spatial position matching method of dynamic interferometer child interferograms - Google Patents

Abstract

The invention discloses a spatial position matching method of dynamic interferometer child interferograms. According to the method, a phase correlation method is used for determining spatial position matching errors of the child interferograms of a dynamic interferometer. The method comprises the following steps that spatial phase shifting interferograms of the dynamic interferometer are collected, the child interferograms of the spatial phase shifting interferograms are divided into child images with the same size, each child image comprises a whole child interferogram at a corresponding position; one of the child images is used as a standard, the phase correlation method is used for determining spatial position matching errors of the interferograms in other child images and the child interferogram in the standard child image; according to the spatial position matching errors, the phase position formula is corrected, and spatial position matching of the child interferograms is completed. The method improves the automation level of dynamic interferometer spatial position matching, lowers influence on spatial position matching caused by light split ratio, image gradation and other factors, and has strong applicability.

Description

The locus matching process of the sub-interferogram of dynamic interferometer

Technical field

The invention belongs to interference of light metering field, particularly the locus matching process of the sub-interferogram of dynamic interferometer.

Background technology

Thereby dynamic interferometer is widely used among the on-line measurement of optics processing site due to its good resistance to shock.Yet no matter present stage is to adopt the many CCD of single CCD to gather the dynamic interferometer of interferogram, although light splitting means different (prismatic decomposition, one-dimensional grating light splitting, two-dimensional quadrature grating beam splitting) but all have the locus matching problem of phase-shift interference.The locus method for registering adopted at present generally can be divided into following two kinds:

A kind of is the space-artifact position registration.This scheme often adds certain sharp keen target (as needle point) in the light path before light splitting, due to each image device after light splitting, all to this target imaging, the picture of this target is arranged in sub-interferogram.Will be in four width interferograms take out separately, artificially identify the most advanced and sophisticated of target picture and read this most advanced and sophisticated position coordinates in sub-interferogram, because these coordinate points are same points on space actually, utilize these coordinates to carry out sub-interferogram locus coupling.The method does not need to carry out the consideration on algorithm, but higher to sharp keen target imaging quality requirements, and the identification of the sharp keen target in four width interferograms is comprised to human factor, and automaticity is not high.

Another kind is to adopt the method for image correlation to carry out spatial registration.This scheme generally first adopts certain means to make the same image of sub-hot spot imaging, be that sub-hot spot has identical gray level image to distribute, adopt the image correlation parameter to mate evaluating as locus, by the related operation of image, realize the locus coupling between each subgraph.The method depends on gradation of image, and reliability easily is subject to the interference of image quality, light splitting ratio error factors.

Summary of the invention

The object of the present invention is to provide the locus matching process of the sub-interferogram of dynamic interferometer that a kind of precision is high, reliability is strong, convenient, as to realize efficiently dynamic interferometer neutron interferogram locus coupling.

The technical scheme that realizes the object of the invention is: the locus matching process of the sub-interferogram of a kind of dynamic interferometer comprises the following steps:

Step 1, gather the spatial Phase-shifting Method interferogram of dynamic interferometer, and each the sub-interferogram in the partition space phase-shift interference be the subimage that size is identical, and each sub-picture pack contains the whole sub-interferogram of correspondence position;

Step 2, the wherein width subimage of usining, as benchmark, adopts phase correlation method to determine the locus matching error of other subimage neutron interferogram and benchmark subimage neutron interferogram;

Step 3, according to the locus matching error, revise the locus coupling that the phase place formula completes each sub-interferogram.

Compared with prior art, its remarkable advantage is in the present invention: (1) has largely improved the automaticity of dynamic interferometer locus coupling, eliminates the impact that human factor causes the locus coupling; (2) reduce the impact that the factors such as light splitting proportional error, gradation of image cause the locus coupling, improved reliability; (3) method is quick and easy, and not additional any ancillary hardware, is applicable to the dynamic interferometer that great majority adopt the light splitting scheme.

Below in conjunction with accompanying drawing, the present invention is described in further detail.

The accompanying drawing explanation

Fig. 1 is the hardware experiments device schematic diagram of the locus matching process of the sub-interferogram of dynamic interferometer of the present invention.

Fig. 2 is the spatial Phase-shifting Method interferogram that dynamic interferometer of the present invention records, and comprises A, B, C, tetra-sub-interferograms of D.

Fig. 3 is the phase-shift interference of Spatial Mismatch, and wherein (a), (b), for two width subimages after cutting apart, (c) are the coordinate system of image (a), (b).

Fig. 4 is the dynamic interferometer movable phase interfere map space matching result based on grating beam splitting in embodiment 1.

Embodiment

Below in conjunction with drawings and the specific embodiments, the present invention is described in further detail.

Dynamic interferometer can collect several width simultaneously and have the fixedly sub-interferogram of amount of phase shift, thereby organizes sub-interferogram and can resolve the face shape that PHASE DISTRIBUTION to be measured is determined measured piece from this.Adopt the dynamic interferometer of light splitting scheme generally to collect the mutually sub-interferogram of four amplitude shifts, be respectively I ₁(x, y), I ₂(x, y), I ₃(x, y), I ₄(x, y), the phase shift phasor magnitude is pi/2, if not Existential Space location matches error, tested phase place can be solved by following formula:

If yet Existential Space location matches error is calculated phase place by (1) formula and will be introduced measuring error.

In conjunction with Fig. 1～4, the locus matching process of the sub-interferogram of dynamic interferometer of the present invention, utilize the locus of the sub-interferogram of phase place related algorithm implementation space phase shift to mate, and comprises the following steps:

Step 1, gather the spatial Phase-shifting Method interferogram of dynamic interferometer, and each the sub-interferogram in the partition space phase-shift interference be the subimage that size is identical, and each sub-picture pack contains the whole sub-interferogram of correspondence position, is specially:

In conjunction with Fig. 1, place standard spherical mirror in the dynamic interferometer test arm, make the axial distance of standard spherical mirror and dynamic interferometer equal the radius-of-curvature of standard spherical mirror, at this moment can collect the spatial Phase-shifting Method interferogram by CCD, the inclination of adjusting axial defocusing and standard spherical mirror makes the closed fringe number of each sub-interferogram all be less than 3, and closed center all is positioned at the field of view center of corresponding sub-interferogram; Gather spatial Phase-shifting Method interferogram now, wherein comprise some sub-interferograms, if take Fig. 2 as example, wherein comprise A, B, C, D tetra-width interferograms, as shown in Figure 3, the sub-interferogram of each in the partition space phase-shift interference is the subimage that size is identical, each sub-picture pack is containing the whole sub-interferogram of correspondence position, Fig. 3 (a), 3 (b) are two width subimages after cutting apart, and in figure, the white edge scope comprises corresponding locus, and does not mate the locus of known two width interferograms.

Step 2, the wherein width subimage of usining, as benchmark, adopts phase correlation method to determine the locus matching error of other subimage neutron interferogram and benchmark subimage neutron interferogram, and detailed process is as follows:

(1) choose wherein a width subimage as benchmark subimage f ₀(x, y), by benchmark subimage f ₀(x, y) and another width subimage f ₁(x, y) carries out Fourier transform under as Fig. 3 (c) at the same coordinate system:

$\begin{array}{c}{F}_0(u,v)=\mathrm{FFT}\left\{f_0(x,y)\right\}\\ F_1(u,v)=\mathrm{FFT}\left\{f_1(x,y)\right\}\end{array}---\left(2\right)$

(2) determine F ₀(u, v) and F ₁the phase place correlation matrix of (u, v), and the phase place correlation matrix is obtained to Spatial Mismatch function C (x, y) do inverse Fourier transform:

$C(x,y)={\mathrm{FFT}}^{-1}\left\{\frac{F_0{(u,v)}^{*}{F}_1(u,v)}{\left|F_0(u,v)\right|\left|F_1(u,v)\right|}\right\}---\left(3\right)$

In formula ^*f ₁(u, v) is F ₁the conjugation of (u, v);

(3) find coordinate (Δ x, Δ y) corresponding to Spatial Mismatch function C (x, y) maximal value, be subimage f ₁(x, y) neutron interferogram and benchmark subimage f ₀the locus matching error of (x, y) neutron interferogram:

(Δx,Δy)=Findcoordinate{max{C(x,y)}} (4)

In formula, Findcoordinate means to find coordinate computation;

(4), according to the method for (1)～(3), determine successively the locus matching error of other subimage neutron interferogram and benchmark subimage neutron interferogram.

Step 3, according to the locus matching error, revise the locus coupling that the phase place formula completes each sub-interferogram.Take that to collect the mutually sub-interferogram of four amplitude shifts be example, establish subimage f ₁(x, y), f ₂(x, y), f ₃(x, y) neutron interferogram and benchmark subimage f ₀the locus matching error of (x, y) neutron interferogram is respectively (Δ x ₁, Δ y ₁), (Δ x ₂, Δ y ₂), (Δ x ₃, Δ y ₃), the tested phase place of revising

can be solved by following formula:

Below in conjunction with specific embodiment, the present invention is described in further detail.

Embodiment 1

The dynamic interferometer of utilization based on grating beam splitting realized the locus coupling of sub-interferogram, and this interferometer utilizes a two-dimensional quadrature grating to generate the spatial Phase-shifting Method interferogram of 2 * 2 arrays.

Step 1, used the proving installation shown in Fig. 1, and wherein dynamic interferometer is the dynamic interferometer based on grating beam splitting, gathers the spatial Phase-shifting Method interferogram, as shown in Figure 4 interferogram is divided into to four number of sub images, number consecutively 0,1,2,3.

Step 2, using subimage 0 as benchmark, adopt phase correlation method to determine that subimage 1,2,3 neutron interferograms are respectively (26 with respect to the locus matching error of benchmark subimage 0 neutron interferogram,-20), (12 ,-17), (17,19), Fig. 4 has shown the space matching result of interferogram 0 with interferogram 1,2,3.

Step 3, according to the locus matching error, revise the locus coupling that the phase place formula completes each sub-interferogram.Phase place formula to be measured is revised:

In sum, the locus matching process of the sub-interferogram of dynamic interferometer of the present invention, utilize the locus coupling of the sub-interferogram of phase place related algorithm implementation space phase shift, largely improve the automaticity of dynamic interferometer locus coupling, eliminated the impact that human factor causes the locus coupling; Reduce the impact that the factors such as light splitting proportional error, gradation of image cause the locus coupling, improved reliability; The method is quick and easy, and not additional any ancillary hardware, is applicable to the dynamic interferometer that great majority adopt the light splitting scheme.

Claims (3)

1. the locus matching process of the sub-interferogram of dynamic interferometer, is characterized in that, comprises the following steps:

Step 1, gather the spatial Phase-shifting Method interferogram of dynamic interferometer, and each the sub-interferogram in the partition space phase-shift interference be the subimage that size is identical, and each sub-picture pack contains the whole sub-interferogram of correspondence position;

Step 2, the wherein width subimage of usining, as benchmark, adopts phase correlation method to determine the locus matching error of other subimage neutron interferogram and benchmark subimage neutron interferogram;

Step 3, according to the locus matching error, revise the locus coupling that the phase place formula completes each sub-interferogram.

2. the locus matching process of the sub-interferogram of dynamic interferometer according to claim 1, is characterized in that, the closed fringe number of described each the sub-interferogram of step 1 all is less than 3, and closed center all is positioned at the field of view center of corresponding sub-interferogram.

3. the locus matching process of the sub-interferogram of dynamic interferometer according to claim 1, it is characterized in that, the described employing phase correlation method of step 2 is determined the locus matching error of other subimage neutron interferogram and benchmark subimage neutron interferogram, and detailed process is as follows:

(1) choose wherein a width subimage as benchmark subimage f ₀(x, y), by benchmark subimage f ₀(x, y) and another width subimage f ₁(x, y) carries out Fourier transform under the same coordinate system:

F ₀(u,v)=FFT{f ₀(x,y)}

F ₁(u,v)=FFT{f ₁(x,y)}

(2) determine F ₀(u, v) and F ₁the phase place correlation matrix of (u, v), and the phase place correlation matrix is obtained to Spatial Mismatch function C (x, y) do inverse Fourier transform:

$C(x,y)={\mathrm{FFT}}^{-1}\left\{\frac{F_0{(u,v)}^{*}{F}_1(u,v)}{\left|F_0(u,v)\right|\left|F_1(u,v)\right|}\right\}$

In formula ^*f ₁(u, v) is F ₁the conjugation of (u, v);

(3) find coordinate (Δ x, Δ y) corresponding to Spatial Mismatch function C (x, y) maximal value, be subimage f ₁(x, y) neutron interferogram and benchmark subimage f ₀the locus matching error of (x, y) neutron interferogram:

(Δx,Δy)=Findcoordinate{max{C(x,y)}}

In formula, Findcoordinate means to find coordinate computation;

(4), according to the method for (1)～(3), determine successively the locus matching error of other subimage neutron interferogram and benchmark subimage neutron interferogram.

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