CN104296667A - Micro electromechanical system in-plane displacement measuring method based on optimized box dimension image matching - Google Patents

Abstract

The invention provides an MEMS (Micro-Electro-Mechanical System) in-plane displacement measuring method based on fractal dimension and relates to the field of image matching techniques and MEMS dynamic measurement. The invention provides a new dimension calculating method-optimized box counting method through improving a differential box counting method and overcomes the defect that an 'empty box' exists in the differential box counting method; the new dimension calculating method is combined with an image matching technique to realize the whole pixel matching of an image; the matching is accurate to a sub-pixel level by using a fractal interpolation method; finally, the measurement of in-plane displacement is realized by the using the invariance principle of a matching area centroid.

Description

Based on the MEMS (micro electro mechanical system) in-plane displacement measurement method optimizing box counting dimension images match

Technical field

The invention belongs to MEMS dynamic measurement method research field, the measurement of MEMS in-plane displacement belongs to a content wherein.Be specifically related to the computing method of the images match method based on fractal dimension, fractal dimension.

Background technology

MEMS (micro electro mechanical system) (MEMS:Micro-electro-Mechanical Systems) is the research frontier of the multi-crossed disciplines developed on the basis of microelectronic technique, relates to various engineering technology and the science such as micro mechanics, microelectronics, control automatically, physics, chemistry, biology and materialogy.The technical development of MEMS opens a brand-new technical field and industry, adopt the microsensor that MEMS technology makes, microactrator, micro parts, Micromechanical Optics device, vacuum microelectronic device, power electronic devices etc. have volume little, quality is light, low in energy consumption, reliability is strong, be easy to intelligent, the advantages such as digitizing, so in aviation, space flight, automobile, biomedical, environmental monitoring, very wide application prospect is had in military and all spectra that almost people touch, this also makes MEMS become a n-th-trem relation n to develop to national science and technology, national defense safety and gordian technique of prosperous economy.The states such as U.S., day, Europe, Korea Spro, Singapore also all recognize that development MEMS is to the significance of international competition, treats MEMS and electronic information, Aero-Space etc. side by side as strategic high-tech.

In the testing research of MEMS, MEMS dynamic characteristic test is an important content.Micro-resonator, gyroscope, microsensor, microactrator, microelectronic component, micro-acceleration gauge and photoswitch etc. are had to the MEMS of movable member, its dynamic perfromance determines the key property of MEMS.By test, MEMS three-dimensional motion situation, material properties and Mechanics of Machinery parameter can be determined, can set up or verify its theoretical model and failure mechanism, instruct its Optimal Structure Designing, reduce batch production cost, advance MEMS industrialization process.Therefore the research of MEMS dynamic test Theories and methods has very important significance to micro-electromechanical system (MEMS) design, manufacture and reliability.

In the research of MEMS graphical analysis theory and means, in order to improve measuring accuracy and speed, the correlative character making full use of image becomes the emphasis in research.Self-similarity fractal is again making full use of unique potentiality in image correlation, so the present invention proposes a kind of based on fractal images match method in conjunction with fractal theory and image matching technology, then be used in MEMS in-plane displacement measurement, find the fractal characteristic with MEMS kinetic measurement target-as relevant in in-plane displacement, acquisition has the MEMS in-plane displacement measurement method of good measuring accuracy.Therefore the present invention has theory significance and the using value of reality.

At home and abroad, MEMS technique of dynamic measurement has obtained the great attention of many research institutions, the MEMS dynamic test set of the developments such as the Christian Rembe during UC Berkeley university of U.S. BSAC studies, be integrated with the micro-vision of stroboscopic and interference technique, adopt least square method and phase shift algorithm etc., three-dimensional real time kinematics and the dynamic structural deformations of MEMS can be tested, realize high-precision plane and out-of-plane motion measurement.The MEMS dynamic test system based on computation vision of research group's development of america's MIT micro-system laboratory professor Freeman leader.University Of Tianjin achieves large development in the research of MEMS dynamic characteristic test.The Central China University of Science and Technology thanks to brave monarch and waits employing integrated Strobed imaging, Computer go and micro-interference technology, have developed the three-dimensional quiet dynamic test system of MEMS, system can carry out the measurement of rigid motion in MEMS face, surface topography, vertical distortion and off-plane movement, and reaches nano-precision.More than study and do not use fractal theory or only fractal theory has been applied in the testing research of MEMS surface topography, multiplex in image correlation is matching method based on gray scale and feature, these methods are extremely responsive to aspects such as the grey scale change of image or rotations, therefore can there is larger measuring error.

Summary of the invention

For above deficiency of the prior art, the object of the present invention is to provide and a kind ofly improve the accuracy of images match and the MEMS (micro electro mechanical system) in-plane displacement measurement method of precision, technical scheme of the present invention is as follows:

Based on the MEMS (micro electro mechanical system) in-plane displacement measurement method optimizing box counting dimension images match, it comprises the following steps:

101, adopt CCD ccd image sensor to gather the image of MEMS (micro electro mechanical system), and pre-service is carried out to the image gathered;

102, a selected initial reference image, and a subarea interested and detected image S is selected in selected initial reference image, and detected image S is resolved into n secondary subarea S _i(i=1,2 ..., n);

103, on pretreated image, select the region identical with detected image S size shape in step 102 and image T to be detected in step 101, and detected image T is resolved into n secondary subarea T _i(i=1,2 ..., n);

104, to the secondary subarea S of the detected image S in step 102 _i(i=1,2 ..., n) and the secondary subarea T of detected image T _i(i=1,2 ..., n), adopt optimization box counting dimension counting method to calculate its fractal dimension, and be denoted as respectively and; represent the secondary subarea fractal dimension of detected image S, represent the secondary subarea fractal dimension of detected image S;

105, the secondary subarea fractal dimension of detected image S will obtained in step 104 and the secondary subarea fractal dimension of detected image S carry out dimension be correlated with, obtain correlation coefficient ρ;

106, when correlation coefficient ρ=1 or maximum and m≤ρ≤1 of ρ, in entire image, show the matching area image searched, and find the starting point P of this matching area; Otherwise return step 103 and carry out translation search;

107, in the region that P is adjacent, adopt fractal interpolation method to find sub-pix match point P ˊ, obtain matching area, and ask for the barycenter of area-of-interest and matching area, realize the measurement of MEMS (micro electro mechanical system) in-plane displacement.

Further, the optimization box counting dimension counting method specific implementation step in step 104 is as follows:

1) image is divided into the grid of r × r size, calculates the point set Z on each grid correspondence image gray surface _ij={ f ₁, f ₂, f ₃..., f _k;

2) to set Z _ijin each element f _icarry out s _i=fix (f _i/ r)+1 operation, obtain the S set={ s of its place cassette positions ₁, s ₂, s ₃..., s _k;

3) add up in S the element number only occurred once, determine the sum covering box needed for whole fractal pattern;

4) convert different size r, in like manner calculate required box sum, then be exactly fractal dimension with the slope that least square fitting obtains.

Further, the correlation coefficient ρ between the subarea S in step 105 and subarea T

$\mathrm{\ρ}=\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(d_{S_i}-\stackrel{\‾}{d_S})(d_{T_i}-\stackrel{\‾}{d_T})}{{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(d_{S_i}-\stackrel{\‾}{d_S})}^2\right]}^{1/2}{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(d_{T_i}-\stackrel{\‾}{d_T})}^2\right]}^{1/2}}---\left(2\right)$

Wherein, be respectively the average of i.

Advantage of the present invention and beneficial effect as follows:

In the present invention, the research of fractal dimension computing method realizes the key based on fractal dimension images match.The situation that the present invention is directed to traditional differential box counting method existence " empty packet " defect is analyzed, a kind of preferably fractal dimension computing method is newly proposed by improving---optimum box dimension (Optimal Box Counting Method, OBC), make the fractal dimension of calculating more accurate.Then this dimension computing method is used in image matching technology, utilizes fractal dimension correlativity to find the template position after moving, thus realize the in-plane displacement measurement of MEMS.To sum up theoretical research, the present invention proposes a kind of MEMS in-plane displacement measurement method based on optimum box counting dimension images match.The new fractal dimension computing method proposed overcomes the defect that differential box counting method exists " empty packet ", make to try to achieve fractal dimension closer to theoretical dimension, then be used in images match method by fractal, images match is carried out with fractal dimension, improve the accuracy of coupling, recycling fractal interpolation method, realizes the images match of sub-pixel, thus measurement is accurate to sub-pixel.

Accompanying drawing explanation

Fig. 1 is the algorithm flow chart that the present invention adopts fractal dimension;

Fig. 2 Integer Pel level images match schematic diagram;

Fig. 3 Integer Pel level images match process flow diagram;

Fig. 4 is based on the sub-pix images match process flow diagram of fractal dimension;

Fig. 5 MEMS in-plane displacement measurement realize block diagram.

Embodiment

The invention will be further elaborated to provide an infinite embodiment below in conjunction with accompanying drawing.But should be appreciated that, these describe just example, and do not really want to limit the scope of the invention.In addition, in the following description, the description to known features and technology is eliminated, to avoid unnecessarily obscuring concept of the present invention.

Fractal dimension is the basic parameter that fractal geometry describe fractal characteristic, and therefore it is also the basis of the images match based on fractal dimension.The method calculating fractal dimension has multiple, as Pixel-Covering Method, and blanket method, differential box counting method etc.The general type calculating fractal dimension is shown below:

$d=\underset{\mathrm{\ϵ}\→0}{\lim }[\log N\left(\mathrm{\ϵ}\right)/\log \left(\frac{1}{\mathrm{\ϵ}}\right)]$

(1)

In formula, ε is the length of side of small cubes, and the total small cubes number covered required for tested fractal pattern is removed in N (ε) expression with corresponding length of side small cubes, and the form of calculation of a lot of fractal dimension is all the distortion of formula (1).

What the present invention used is new dimension computing method---the optimum box dimension proposed.The method adopts the dividing mode of differential box counting method to divide plane grid, and process flow diagram is shown in Fig. 1, and specific implementation step is as follows:

1) image is divided into the grid of r × r size, calculates the point set Z on each grid correspondence image gray surface _ij={ f ₁, f ₂, f ₃..., f _k}

2) to set Z _ijin each element f _icarry out s _i=fix (f _i/ r)+1 operation, obtain the S set={ s of its place cassette positions ₁, s ₂, s ₃..., s _k}

3) add up in S the element number only occurred once, determine the sum covering box needed for whole fractal pattern.

4) convert different size r, in like manner calculate required box sum, then be exactly fractal dimension with the slope that least square fitting obtains.

Image matching technology is target localization is substantially the most also the most frequently used method.In many measuring system of pictures, the accurate location of target is a key issue.The present invention proposes the images match method based on fractal dimension according to this key character of fractal self similarity, and coupling schematic diagram is as Fig. 2.Selected our interested subarea S in reference picture before change, the more selected subarea T all identical with subarea S size and shape arbitrarily in reference picture after change.Subarea S is resolved into n secondary subarea S _i(i=1,2 ..., n), and make each S is calculated respectively by the dimension computing method proposed _ifractal dimension in like manner, in the same way T subarea is resolved into n time subarea T _i(i=1,2 ..., n), make and calculate each subarea T _ifractal dimension according to the correlation principle of mathematical statistics, the correlation coefficient ρ between subarea S and subarea T

$\mathrm{\ρ}=\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(d_{S_i}-\stackrel{\‾}{d_S})(d_{T_i}-\stackrel{\‾}{d_T})}{{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(d_{S_i}-\stackrel{\‾}{d_S})}^2\right]}^{1/2}{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(d_{T_i}-\stackrel{\‾}{d_T})}^2\right]}^{1/2}}---\left(2\right)$

Wherein, be respectively average.As Fig. 2, ρ equal 1 or maximum and close to 1 time find the match point P of subarea starting point O, to determine matching area figure T (namely template S and T mates).Coupling process flow diagram as shown in Figure 3.

Due to the change not necessarily Integer Pel level of MEMS image, in order to improve matching precision further, present invention employs the images match that fractal interpolation method realizes sub-pixel, coupling process flow diagram is shown in Fig. 4.

Because region barycenter has principle of invariance, after therefore obtaining the image matched with subarea interested in the dynamic sequence figure of the present invention after change, ask for the region barycenter in two subareas respectively, ask for in-plane displacement amount according to region barycenter, realize block diagram and see Fig. 5.

These embodiments are interpreted as only being not used in for illustration of the present invention limiting the scope of the invention above.After the content of reading record of the present invention, technician can make various changes or modifications the present invention, and these equivalence changes and modification fall into the scope of the claims in the present invention equally.

Claims (3)

1., based on the MEMS (micro electro mechanical system) in-plane displacement measurement method optimizing box counting dimension images match, it is characterized in that: comprise the following steps:

101, adopt CCD ccd image sensor to gather the image of MEMS (micro electro mechanical system), and pre-service is carried out to the image gathered;

102, a selected initial reference image, and a subarea interested and detected image S is selected in selected initial reference image, and detected image S is resolved into n secondary subarea S _i(i=1,2 ..., n);

103, on pretreated image, select the region identical with detected image S size shape in step 102 and image T to be detected in step 101, and detected image T is resolved into n secondary subarea T _i(i=1,2 ..., n);

104, to the secondary subarea S of the detected image S in step 102 _i(i=1,2 ..., n) and the secondary subarea T of detected image T _i(i=1,2 ..., n), adopt optimization box counting dimension counting method to calculate its fractal dimension, and be denoted as respectively and; represent the secondary subarea fractal dimension of detected image S, represent the secondary subarea fractal dimension of detected image S;

105, the secondary subarea fractal dimension of detected image S will obtained in step 104 and the secondary subarea fractal dimension of detected image S carry out dimension be correlated with, obtain correlation coefficient ρ;

106, when correlation coefficient ρ=1 or maximum and m≤ρ≤1 of ρ, in entire image, show the matching area image searched, and find the starting point P of this matching area; Otherwise return step 103 and carry out translation search;

107, in the region that P is adjacent, adopt fractal interpolation method to find sub-pix match point P ˊ, obtain matching area, and ask for the barycenter of area-of-interest and matching area, realize the measurement of MEMS (micro electro mechanical system) in-plane displacement.

2. the MEMS (micro electro mechanical system) in-plane displacement measurement method based on optimizing box counting dimension images match according to claim 1, is characterized in that: the optimization box counting dimension counting method specific implementation step in step 104 is as follows:

1) image is divided into the grid of r × r size, calculates the point set Z on each grid correspondence image gray surface _ij={ f ₁, f ₂, f ₃..., f _k;

2) to set Z _ijin each element f _icarry out s _i=fix (f _i/ r)+1 operation, obtain the S set={ s of its place cassette positions ₁, s ₂, s ₃..., s _k;

3) add up in S the element number only occurred once, determine the sum covering box needed for whole fractal pattern;

4) convert different size r, in like manner calculate required box sum, then be exactly fractal dimension with the slope that least square fitting obtains.

3. the MEMS (micro electro mechanical system) in-plane displacement measurement method based on optimizing box counting dimension images match according to claim 1, is characterized in that: the correlation coefficient ρ between the subarea S in step 105 and subarea T

$\mathrm{\ρ}=\frac{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}(d_{S_i}-\stackrel{\‾}{d_S})(d_{T_i}-\stackrel{\‾}{d_T})}{{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(d_{S_i}-\stackrel{\‾}{d_S})}^2\right]}^{1/2}{\left[\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{(d_{T_i}-\stackrel{\‾}{d_T})}^2\right]}^{1/2}}---\left(2\right)$

Wherein, be respectively average.