CN104899890A - Detection method based on polarized light imaging technology - Google Patents

Abstract

The invention relates to the technical field of image processing, and especially relates to a detection method and a detection device based on a polarized light imaging technology. According to the invention, polarized light imaging and intensity imaging principles are combined to fuse multi-source images, an enhanced fusion image is generated by utilizing complementation information in polarization image information and intensity image information, the details of the fusion image is more outstanding than that of any of polarization images and intensity images, and a new enhanced image deriving from the multi-source images is formed. The contrast of objective discrimination characteristics in the fusion image is far higher than the contrast of the objective discrimination characteristics in the intensity images, so that describing of relative scenes which is unable to obtained by a single image is realized, the limitation of the single image is overcome, the detection efficiency of objects to be detected is improved, and the accuracy of the detection efficiency is enhanced.

Description

Based on the detection method of polarized light imaging technique

Technical field

The present invention relates to a kind of technical field of image processing, particularly relate to a kind of detection method based on polarized light imaging technique.

Background technology

Dynamic Non-Destruction Measurement and non-damaged data, utilize the characteristics such as the sound of thing to be detected, light, magnetic and electricity, do not destroying under the prerequisites such as the original state of thing to be detected, chemical property, for obtaining the inspection method that physics, the chemical corps intelligences such as content, character or the composition relevant with article matter to be detected adopt, the existing lossless detection method being applied to industrial detection mainly contains mechanical type contact detection method and photo-electric non-contact detection method.Wherein mechanical type contact detection method is measured in the slippage of measured surface by the contact pilotage of instrument, this kind of method needs contact pilotage to carry out comprehensive engagement on the surface of thing to be detected, thus detection speed is slow, and easily scratch thing to be detected surface, cause secondary cut, photo-electric non-contact detection method is now widely used method, by analyzing the two dimensional image feature of testee, can realize quick, non-contact detecting.Existing non-contact detection method mainly adopts light intensity image checking and polarized light image checking, light intensity image checking is by light source irradiation thing to be detected, obtain the radiation intensity information on thing surface to be detected, and according to the flaw of thing to be detected in this radiation intensity information combining image Processing Algorithm detected image.Because thing surface blemish feature to be detected (as cut, surface is uneven, and smoothness is low) is usually more hidden, not easily present in intensity imaging system, this just for later image process brings larger pressure, not only can increase algorithm complexity, can reduce the detection efficiency of system equally.Polarized light image checking is that the target reflecting light by obtaining different polarization direction obtains target polarization information, target polarization parameter information is obtained by carrying out parsing to target polarization information, as degree of polarization, polarization angle etc., carry out Inversion Calculation according to target polarization parameter information and obtain object reconstruction figure, object reconstruction image comprises geometric configuration, surfaceness, texture, the polarization information of the physicochemical properties such as conductance, but there is certain difference in the surface of object reconstruction image and background on some polarization parameter and original image, compare intensity image, polarization parameter image readability is not good, need later stage decipher.

Summary of the invention

Thing surface blemish to be detected is detected in order to better utilize polarization characteristic, improve detection efficiency, the invention provides a kind of detection method based on polarized light imaging technique, by intensity imaging combine with technique polarized light imaging technique, intensity image basis utilizes carry out of polarization characteristic to thing surface blemish to be detected strengthen, improve detection efficiency and detection accuracy.

Based on a detection method for polarized light imaging technique, be applied to thing surface blemish to be detected and detect, wherein, comprise the steps,

Step S1, obtain the light intensity parameter on described thing surface to be detected in three predetermined angulars by a light intensity imaging device;

Step S2, obtain described thing surface image to be detected in three described predetermined angulars by a polarized light image-forming detecting system, forms the described surface image output that three light intensities are different;

Step S3, a computing unit described surface image different according to three light intensities obtains Stokes parameter and degree of polarization parameter P in conjunction with described light intensity parameter;

Step S4, described surface image is divided into several little images, calculates the average energy value of each described little image according to described Stokes parameter and degree of polarization parameter P,

Step S5, to choose the highest described little image of the average energy value be image to be fused;

Step S6, wavelet decomposition is carried out to the light intensity parameter I of described image to be fused and degree of polarization parameter P, obtain the low frequency coefficient of the light intensity parameter I of described image to be fused, the high frequency coefficient of light intensity parameter I, the low frequency coefficient of degree of polarization parameter P, the high frequency coefficient of degree of polarization parameter P respectively;

Step S7, the low frequency coefficient according to described light intensity parameter I, the high frequency coefficient of light intensity parameter I, the low frequency coefficient of degree of polarization parameter P, the high frequency coefficient of degree of polarization parameter P obtain low frequency coefficient to be fused, high frequency coefficient to be fused,

Step S8, carry out Image Reconstruction according to described high frequency coefficient to be fused and described low frequency coefficient to be fused, obtain fused images;

Step S9, Defect Detection is carried out to fused images.

The above-mentioned detection method based on polarized light imaging technique, wherein, three predetermined angulars are defined as α 1, α 2, α 3 respectively; Three light intensity parameters form I respectively ₀(α 1), I ₀(α 2), I ₀(α 3), I ₀the light intensity parameter on the thing surface described to be detected that (α 1) obtains for α 1 polarization direction, I ₀the light intensity parameter on the thing surface described to be detected that (α 2) obtains for α 2 polarization direction, I ₀the light intensity parameter on the thing surface described to be detected that (α 3) obtains for α 3 polarization direction.

The above-mentioned detection method based on polarized light imaging technique, wherein, in described step S3, wherein, the computing formula of described Stokes parameter is:

$\left\{\begin{array}{c}I=\frac{2}{3}\left(I_o\right(\mathrm{\α}1)+I_o(\mathrm{\α}2)+I_o(\mathrm{\α}3\left)\right)\\ Q=\frac{2}{3}\left(2I_o\right(\mathrm{\α}1)-I_o(\mathrm{\α}2)-I_o(\mathrm{\α}3\left)\right)\\ U=\frac{2}{\sqrt{3}}\left(I_o\right(\mathrm{\α}2)-I_o(\mathrm{\α}3\left)\right)\\ V=0\end{array}\right.$

Wherein, I is light intensity parameter, and Q is the first polarization parameter, and U is the second polarization parameter, and V is circular polarization parameter, and because in natural light, V is less, value is zero;

The computing formula of described degree of polarization parameter P is:

$P=\frac{\sqrt{Q^2+U^2}}{I}$

Wherein, P is degree of polarization parameter.

The above-mentioned detection method based on polarized light imaging technique, wherein, in described step S4,

The computing formula of wherein said the average energy value is:

$E=\frac{1}{M\×N}\underset{x=1}{\overset{M}{\Σ}}\underset{y=1}{\overset{N}{\Σ}}I{(x,y)}^2$

Wherein: E is the average energy value, M is the length of each described little image, N is the width of each described little image, x be each described little image in the picture breakdown coordinate points in horizontal ordinate direction, y is that each described little image is in the picture breakdown coordinate points in ordinate direction.

The above-mentioned detection method based on polarized light imaging technique, wherein, in described step S6, also specifically comprises,

Step S61, carry out wavelet decomposition to the light intensity parameter I of described image to be fused and degree of polarization parameter P, Decomposition order is 1;

Step S62, obtain the low frequency coefficient (I of the light intensity parameter I of described image to be fused _lL), the high frequency coefficient (I of light intensity parameter I _lH, I _hL, I _hH),

Step S63, obtain the low frequency coefficient (P of the described degree of polarization parameter P of described image to be fused _lL), the high frequency coefficient (P of described degree of polarization parameter P _lH, P _hL, P _hH).

The above-mentioned detection method based on polarized light imaging technique, wherein, in described step S7, specifically comprises the steps,

Step S71, low frequency coefficient (I according to described light intensity parameter I _lL) with the low frequency coefficient (P of described degree of polarization parameter P _lL) obtain low frequency coefficient to be fused, described low frequency coefficient F to be fused _lLfusion formula be:

F _LL＝log(P _LL)·I _LL ⁿ

Wherein, n is I _lLindex, span is 0 ~ 1;

Step S72, high frequency coefficient (I according to described light intensity parameter I _lH, I _hL, I _hH) with the high frequency coefficient (P of described degree of polarization parameter P _lH, P _hL, P _hH) obtain high frequency coefficient F to be fused _h,

Wherein specifically comprise the steps,

High frequency coefficient (the I of step S721, definition light intensity parameter I _lH, I _hL, I _hH) be I _m; High frequency coefficient (the P of definition degree of polarization parameter P _lH, P _hL, P _hH) be P _m;

Step S722, set up light intensity parameter high frequency coefficient I _mwith described degree of polarization parameter P _mcorrelation coefficient M _i,P,

M _i,Pcomputing formula be:

$\left\{\begin{array}{c}{M}_{I,P}=\frac{2\[P_m\·I_m\]}{E_{HP}+E_{HI}}\\ E_{HP}={P_m}^2\\ E_{HI}={I_m}^2\end{array}\right.$

Wherein, E _hPfor the high frequency coefficient energy value of degree of polarization parameter P, P _mfor the high frequency coefficient of degree of polarization parameter P; E _hIfor the high frequency coefficient energy value of intensive parameter I, I _mfor the high frequency coefficient of light intensity parameter I;

Step S722, a default relative degree threshold value δ,

Step S723, calculate high frequency coefficient F to be fused according to described relative degree threshold value δ _h

Work as M _i,Pduring > δ, $F_H=\{\begin{array}{ccc}{I}_H& if& E_{HI}\&GreaterEqual;E_{HP}\\ P_H& if& E_{HI}<E_{HP}\end{array},$

Work as M _i,Pduring < δ, F _h=ε _hIi _h+ ε _hPp _h,

${\mathrm{\&epsiv;}}_{HI}=\left\{\begin{array}{ccc}{\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{min}& if& E_I<E_P\\ {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{\max }& if& E_I\&GreaterEqual;E_P\end{array}\right.$

$\left\{\begin{array}{c}{\mathrm{\&epsiv;}}_{HP}=1-{\mathrm{\&epsiv;}}_{HI}\\ {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{\min }=\frac{1}{2}\&lsqb;1-\frac{1-M_{I,P}}{1-\mathrm{\&delta;}}\&rsqb;\\ {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{\max }=1-{\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{\min }\end{array}\right.$

Wherein ε _hPfor the weighting coefficient of degree of polarization parameter P, ε _hIfor the weighting coefficient of light intensity parameter I.

The above-mentioned detection method based on polarized light imaging technique, wherein, in described step 8, the reconstructing method of its image to be fused is:

$F_{LL}=H_r^{*}{H}_c^{*}{F}_{LL}+H_r^{*}{G}_c^{*}{F}_{LH}+G_r^{*}{H}_c^{*}{F}_{HL}+G_r^{*}{G}_c^{*}{F}_{HH},$

Wherein F _lLfor view data to be fused, h _r, H _c, G _r, G _cassociate matrix, F _lHbe the 1st layer of vertical direction high frequency imaging, F _hLbe the 1st layer of horizontal direction high frequency imaging, F _hHbe the 1st layer to angular direction high frequency imaging.

The above-mentioned detection method based on polarized light imaging technique, wherein, it is 0 ° that described predetermined angular is defined as α 1 respectively, and α 2 is 60 °, and α 3 is 120 °.

The above-mentioned detection method based on polarized light imaging technique, wherein, in described step 6, described wavelet decomposition is Mallat Wavelet Transformation Algorithm.

Compared with prior art, advantage of the present invention is:

Polarized light imaging and intensity imaging principle combine by the present invention, multi-source image (image that polarized light imaging obtains and the image that intensity imaging obtains) is merged, complementary information in polarization image information and intensity image information is utilized to generate the fused images of a width enhancing, the details of fused images is all more outstanding than a width any in polarization image and intensity image, what form a width enhancing has drawn the new images of multi-source image, in fused images, the contrast of target distinguishing characteristics is far above the contrast of target distinguishing characteristics in intensity image, thus obtain the description of the associated scenario that single image cannot obtain, overcome the limitation existing for single image, improve the detection efficiency of thing to be detected, enhance the accuracy of detection efficiency.

Accompanying drawing explanation

Fig. 1 is a kind of detection method schematic flow sheet based on polarized light imaging technique.

Embodiment

Below in conjunction with the drawings and specific embodiments, the invention will be further described, but not as limiting to the invention.

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, the every other embodiment that those of ordinary skill in the art obtain under the prerequisite of not making creative work, all belongs to the scope of protection of the invention.

It should be noted that, when not conflicting, the embodiment in the present invention and the feature in embodiment can combine mutually.

Below in conjunction with the drawings and specific embodiments, the invention will be further described, but not as limiting to the invention.

As shown in Figure 1, a kind of detection method based on polarized light imaging technique, is applied to thing surface blemish to be detected and detects, wherein, comprise the steps,

Step S1, obtain the light intensity parameter on thing surface to be detected in three predetermined angulars by a light intensity imaging device, predetermined angular is defined as α 1, α 2, α 3 respectively; Light intensity parameter comprises I ₀(α 1), I ₀(α 2), I ₀(α 3), wherein, I ₀the light intensity parameter on the thing surface to be detected that (α 1) obtains for α 1 polarization direction, I ₀the light intensity parameter on the thing surface to be detected that (α 2) obtains for α 2 polarization direction, I ₀the light intensity parameter on the thing surface to be detected that (α 3) obtains for α 3 polarization direction;

Step S2, obtain thing surface image to be detected in three predetermined angulars by a polarized light image-forming detecting system, the surface image forming three light intensities different exports;

Step S3, the computing unit surface image different according to three light intensities obtains Stokes parameter and degree of polarization parameter P in conjunction with described light intensity parameter;

Step S4, surface image is divided into several little images, calculates the average energy value of each little image according to Stokes parameter and degree of polarization parameter P,

Step S5, to choose the highest little image of the average energy value be image to be fused;

Step S6, the light intensity parameter I treating fused images and degree of polarization parameter P carry out wavelet decomposition, obtain the low frequency coefficient of the light intensity parameter I of image to be fused, the high frequency coefficient of light intensity parameter I, the low frequency coefficient of degree of polarization parameter P, the high frequency coefficient of degree of polarization parameter P respectively;

Step S7, the low frequency coefficient according to light intensity parameter I, the high frequency coefficient of light intensity parameter I, the low frequency coefficient of degree of polarization parameter P, the high frequency coefficient of degree of polarization parameter P obtain low frequency coefficient to be fused, high frequency coefficient to be fused,

Step S8, carry out Image Reconstruction according to high frequency coefficient to be fused and low frequency coefficient to be fused, obtain fused images;

Step S9, Defect Detection is carried out to fused images.

Polarized light imaging and intensity imaging principle combine by the present invention, multi-source image (image that polarized light imaging obtains and the image that intensity imaging obtains) is merged, complementary information in polarization image information and intensity image information is utilized to generate the fused images of a width enhancing, the details of fused images is all more outstanding than a width any in polarization image and intensity image, what form a width enhancing has drawn the new images of multi-source image, in fused images, the contrast of target distinguishing characteristics is far above the contrast of target distinguishing characteristics in intensity image, thus obtain the description of the associated scenario that single image cannot obtain, overcome the limitation existing for single image, improve the detection efficiency of thing to be detected, enhance the accuracy of detection efficiency.

The above-mentioned detection method based on polarized light imaging technique, wherein, in step S3, wherein, the computing formula of Stokes parameter is:

$\left\{\begin{array}{c}I=\frac{2}{3}\left(I_o\right(\mathrm{\&alpha;}1)+I_o(\mathrm{\&alpha;}2)+I_o(\mathrm{\&alpha;}3\left)\right)\\ Q=\frac{2}{3}\left(2I_o\right(\mathrm{\&alpha;}1)-I_o(\mathrm{\&alpha;}2)-I_o(\mathrm{\&alpha;}3\left)\right)\\ U=\frac{2}{\sqrt{3}}\left(I_o\right(\mathrm{\&alpha;}2)-I_o(\mathrm{\&alpha;}3\left)\right)\\ V=0\end{array}\right.$

Wherein, I is light intensity parameter, and Q is the first polarization parameter, and U is the second polarization parameter, and V is circular polarization parameter, and because in natural light, V is less, value is zero;

The computing formula of degree of polarization parameter P is:

$P=\frac{\sqrt{Q^2+U^2}}{I}$

Wherein, P is degree of polarization parameter.

The above-mentioned detection method based on polarized light imaging technique, wherein, in step S4,

Wherein the computing formula of the average energy value is:

$E=\frac{1}{M\&times;N}\underset{x=1}{\overset{M}{\&Sigma;}}\underset{y=1}{\overset{N}{\&Sigma;}}I{(x,y)}^2$

Wherein: E is the average energy value, M is the length of each little image, and N is the width of each little image, x be each little image in the picture breakdown coordinate points in horizontal ordinate direction, y is that each little image is in the picture breakdown coordinate points in ordinate direction.

The above-mentioned detection method based on polarized light imaging technique, wherein, in step S6, also specifically comprises,

Step S61, the light intensity parameter I treating fused images and degree of polarization parameter P carry out wavelet decomposition, and Decomposition order is 1;

Step S62, obtain the low frequency coefficient (I of the light intensity parameter I of image to be fused _lL),

High frequency coefficient (the I of light intensity parameter I _lH, I _hL, I _hH),

Step S63, obtain the low frequency coefficient (P of the degree of polarization parameter P of image to be fused _lL), the high frequency coefficient (P of degree of polarization parameter P _lH, P _hL, P _hH),

The above-mentioned detection method based on polarized light imaging technique, wherein, in step S7, specifically comprises the steps,

Step S71, low frequency coefficient (I according to light intensity parameter I _lL) with the low frequency coefficient (P of degree of polarization parameter P _lL) obtain low frequency coefficient to be fused, low frequency coefficient F to be fused _lLfusion formula be:

F _LL＝log(P _LL)·I _LL ⁿ

Wherein, n is I _lLindex, span is 0 ~ 1;

Low frequency coefficient F to be fused _lLreflect the approximate of original image and evenness, concentrated the most information of original image, adopt modulation fusion method to obtain to low frequency coefficient.

Step S72, high frequency coefficient (I according to light intensity parameter I _lH, I _hL, I _hH) with the high frequency coefficient (P of degree of polarization parameter P _lH, P _hL, P _hH) obtain high frequency coefficient F to be fused _h,

Wherein specifically comprise

High frequency coefficient (the I of step S721, definition light intensity parameter I _lH, I _hL, I _hH) be I _m; High frequency coefficient (the P of definition degree of polarization parameter P _lH, P _hL, P _hH) be P _m;

Step S722, high frequency coefficient F to be fused reflect the catastrophe characteristics of original image, to HFS respectively along horizontal direction, vertical direction with adopt coefficient weighted mean fusion rule to merge to angular direction.The high frequency coefficient of image after multi-resolution decomposition contains the detailed information of such as edge, region contour etc. in image.When fusion treatment, consider the correlativity between adjacent coefficient, set up light intensity parameter high frequency coefficient I _mwith described degree of polarization parameter P _mcorrelation coefficient M _i,P,

M ( _i, _p) computing formula be:

$\left\{\begin{array}{c}{M}_{I,P}=\frac{2\&lsqb;P_m\&CenterDot;I_m\&rsqb;}{E_{HP}+E_{HI}}\\ E_{HP}={P_m}^2\\ E_{HI}={I_m}^2\end{array}\right.$

Wherein, E _hPfor the high frequency coefficient energy value of degree of polarization parameter P, P _mfor the high frequency coefficient of degree of polarization parameter P;

E _hIfor the high frequency coefficient energy value of intensive parameter I, I _mfor the high frequency coefficient of light intensity parameter I;

Step S722, default a relative degree threshold value δ, relative degree threshold value δ according to actual selection, can not do concrete restriction herein.

Step S723, calculate high frequency coefficient F to be fused according to relative degree threshold value δ _h

Work as M _i,Pduring > δ, $F_H=\{\begin{array}{ccc}{I}_H& if& E_{HI}\&GreaterEqual;E_{HP}\\ P_H& if& E_{HI}<E_{HP}\end{array},$

Work as M _i,Pduring < δ, F _h=ε _hIi _h+ ε _hPp _h,

${\mathrm{\&epsiv;}}_{HI}=\left\{\begin{array}{ccc}{\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{min}& if& E_I<E_P\\ {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{\max }& if& E_I\&GreaterEqual;E_P\end{array}\right.$

ε _HP＝1-ε _HI

${\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{\min }=\frac{1}{2}\&lsqb;1-\frac{1-M_{I,P}}{1-\mathrm{\&delta;}}\&rsqb;,{\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{\max }=1-{\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{\min }$

Wherein ε _hPfor the weighting coefficient of degree of polarization parameter P, ε _hIfor the weighting coefficient of light intensity parameter I.

The above-mentioned detection method based on polarized light imaging technique, wherein, in step 8, the reconstructing method of its image to be fused is:

$F_{LL}=H_r^{*}{H}_c^{*}{F}_{LL}+H_r^{*}{G}_c^{*}{F}_{LH}+G_r^{*}{H}_c^{*}{F}_{HL}+G_r^{*}{G}_c^{*}{F}_{HH},$

Wherein F _lLfor view data to be fused, h _r, H _c, G _r, G _cassociate matrix, F _lHbe the 1st layer of vertical direction high frequency imaging, F _hLbe the 1st layer of horizontal direction high frequency imaging, F _hHbe the 1st layer to the relational expression between the high frequency imaging of angular direction.

The above-mentioned detection method based on polarized light imaging technique, wherein, it is 0 ° that predetermined angular is defined as α 1 respectively, and α 2 is 60 °, and α 3 is 120.

The above-mentioned detection method based on polarized light imaging technique, wherein, in step 6, wavelet decomposition is Mallat Wavelet Transformation Algorithm.

Enumerate a specific embodiment to explain:

CD is as thing to be detected, and the cut that optical disc surface has two places less, the degree of depth is about 0.5mm, and length is about 12mm.For obtaining stronger polarization information, select to test under fixing special light source incidence angle conditions.Gathered the original polarization frame of optical disc surface flaw respectively in three angles (0 °, 60 °, 120 °) by polarized light image-forming detecting system, and the image after gathering is handled as follows: obtain strength parameter I and degree of polarization parameter P, treat fused images and use the above-mentioned detection method based on polarized light imaging technique to obtain fused images F.

Effect is strengthened in order to verify to merge, using strength parameter I and degree of polarization parameter P as with reference to image, to the image of high light imaging, degree of polarization image and adopt the application to obtain fused images respectively computed image quality assessment parameter (comprising image information entropy, image averaging gradient, sharpness, contrast and Gauss three rank details average statistics amount) carry out image quality evaluation.

The computing formula of image information entropy is

$H=-\underset{i=0}{\overset{255}{\&Sigma;}}{p}_i\&CenterDot;{\log }_2\left(p_i\right),$

Wherein, pi is the probability that the gray level of i occurs, i is gray level, and H is image information entropy.

Image information entropy weighs image information to enrich an important indicator of degree, the size of the entropy of fused images represent the average information that image comprises number.By the details expressive ability that relatively can draw image to image information entropy.The size of entropy reflects the number of the quantity of information that image carries, and entropy is larger, illustrates that the quantity of information of carrying is larger.

The computing formula of image averaging gradient is

$g=\frac{1}{(M-1)(N-1)}\underset{i=1}{\overset{(M-1)(N-1)}{\&Sigma;}}\sqrt{\&lsqb;{\left(\frac{\&part;Dx}{\&part;x}\right)}^2+{\left(\frac{\&part;Dy}{\&part;y}\right)}^2\&rsqb;/2}$

Wherein, image X-direction derivative, it is image Y-direction derivative.

Average gradient is that the index of responsive reflection image to minor detail contrast and texture variations feature representation ability is general, and g is larger, and image level is more, and fused image is more clear, merges to reach to put forward high-resolution object.

Sharpness computation formula is

$\stackrel{\&OverBar;}{g}=\frac{1}{MN}\underset{i=1}{\overset{M}{\&Sigma;}}\underset{j=1}{\overset{N}{\&Sigma;}}\sqrt{I_x^2(i,j)+I_y^2(i,j)}$

Wherein, I here _xand I _ybe respectively the difference of image I in x and y direction, i is X-direction coordinate figure in image, and j is Y-direction coordinate figure in image.The sharpness of image represents with average gradient, and sharpness shows that more greatly the details such as image texture are more obvious, is more easy to observe.

The computing formula of the contrast gray-scale value contrast of object and background (in the image) is:

$C=\frac{|E\left(\underset{(x,y)\&Element;R}{W_T(x,y)}\right)-E\left(\underset{(x,y)\&Element;R}{W_B(x,y)}\right)|}{E\left(\underset{(x,y)\&Element;R}{W_T(x,y)}\right)+E\left(\underset{(x,y)\&Element;R}{W_B(x,y)}\right)}\&times;100\%$

Wherein W _t(x, y), W _b(x, y) is respectively target and background image intensity value, and R is selected zone, and E is mathematical expectation, and C is the gray-scale value contrast of object and background in image.

The concrete formula of Gauss three rank details average statistics amount is:

$\left\{\begin{array}{c}{c}_{3f}=\frac{1}{MN}\underset{i=1}{\overset{N}{\&Sigma;}}\underset{j=1}{\overset{M}{\&Sigma;}}{m}_{3f}(i,j)-3m_{1f}(i,j)m_{2f}(i,j)+2{m_{1f}}^2(i,j)\\ m_{1f}(i,j)=\frac{1}{{(2Q+1)}^2}\underset{K=-Q}{\overset{Q}{\&Sigma;}}\underset{l=-Q}{\overset{Q}{\&Sigma;}}f(i+K,j+l)\\ m_{2f}(i,j)=\frac{1}{{(2Q+1)}^2}\underset{K=-Q}{\overset{Q}{\&Sigma;}}\underset{l=-Q}{\overset{Q}{\&Sigma;}}{f}^2(i+K,j+l)\\ m_{3f}(i,j)=\frac{1}{{(2Q+1)}^2}\underset{K=-Q}{\overset{Q}{\&Sigma;}}\underset{l=-Q}{\overset{Q}{\&Sigma;}}{f}^3(i+K,j+l)\end{array}\right.$

Wherein, c _3ffor Gauss three rank details average statistics amount, m _1f(i, j) is the local mean value in the picture in (i, j) the little field of putting, m _2f(i, j) is the second moment of image f (i, j), m _3f(i, j) is the third moment of image f (i, j), and K is the departure of coordinate i, and Q is image template size, and i is X-direction coordinate figure in image, and j is Y-direction coordinate figure in image, and l is the departure of coordinate j.

Gauss three rank details average statistics metering method does not need original image for referencial use, insensitive to white Gaussian noise, can reflect the signal to noise ratio (S/N ratio) of image preferably, wherein defines the larger picture quality of numerical value higher.

Table 1 is image, the degree of polarization image of high light imaging and adopts the fused images of the application's acquisition to distinguish the picture appraisal result of computed image quality assessment parameter.

Table 1 picture appraisal result

Can find from table 1 picture appraisal result:

(1) information entropy comparing strength parameter image, degree of polarization parametric image and fused images can be found out, fused images is compared degree of polarization parametric image information entropy and improved a lot.Compared with degree of polarization parametric image, the quantity of information of fused images obtains enhancing;

(2) average gradient of the fused images obtained through blending algorithm is greatly improved, and improves overall sharpness, and the detail section reflecting image obtains enhancing;

(3) from the result of the contrast of optical disc surface flaw and intact optical disc surface, in fused images, target contrast is far above strength parameter image;

(4) from visual effect, fused images remains the scene information in strength parameter image, highlights the detailed information of optical disc surface flaw in degree of polarization parametric image simultaneously;

(5) visible according to Gauss three rank details average statistics amount result of calculation, the picture quality after fusion is all better than the strength parameter image before merging and degree of polarization parametric image;

(6) detection and indentification that enhancing result is easier to optical disc surface flaw is merged.

These are only preferred embodiment of the present invention; not thereby embodiments of the present invention and protection domain is limited; to those skilled in the art; should recognize and all should be included in the scheme that equivalent replacement done by all utilizations instructions of the present invention and diagramatic content and apparent change obtain in protection scope of the present invention.

Claims (9)

1., based on a detection method for polarized light imaging technique, be applied to thing surface blemish to be detected and detect, it is characterized in that, comprise the steps,

Step S1, obtain the light intensity parameter on described thing surface to be detected in three predetermined angulars by a light intensity imaging device;

Step S2, obtain described thing surface image to be detected in three described predetermined angulars by a polarized light image-forming detecting system, forms the described surface image output that three light intensities are different;

Step S3, a computing unit described surface image different according to three light intensities obtains Stokes parameter and degree of polarization parameter P in conjunction with described light intensity parameter;

Step S4, described surface image is divided into several little images, calculates the average energy value of each described little image according to described Stokes parameter and degree of polarization parameter P,

Step S5, to choose the highest described little image of the average energy value be image to be fused;

Step S6, wavelet decomposition is carried out to the light intensity parameter I of described image to be fused and degree of polarization parameter P, obtain the low frequency coefficient of the light intensity parameter I of described image to be fused, the high frequency coefficient of light intensity parameter I, the low frequency coefficient of degree of polarization parameter P, the high frequency coefficient of degree of polarization parameter P respectively;

Step S7, the low frequency coefficient according to described light intensity parameter I, the high frequency coefficient of light intensity parameter I, the low frequency coefficient of degree of polarization parameter P, the high frequency coefficient of degree of polarization parameter P obtain low frequency coefficient to be fused, high frequency coefficient to be fused,

Step S8, carry out Image Reconstruction according to described high frequency coefficient to be fused and described low frequency coefficient to be fused, obtain fused images;

Step S9, Defect Detection is carried out to fused images.

2. the detection method based on polarized light imaging technique according to claim 1, is characterized in that, three predetermined angulars are defined as α 1, α 2, α 3 respectively; Three light intensity parameters form I respectively ₀(α 1), I ₀(α 2), I ₀(α 3), wherein I ₀the light intensity parameter on the thing surface described to be detected that (α 1) obtains for α 1 polarization direction, I ₀the light intensity parameter on the thing surface described to be detected that (α 2) obtains for α 2 polarization direction, I ₀the light intensity parameter on the thing surface described to be detected that (α 3) obtains for α 3 polarization direction.

3. the detection method based on polarized light imaging technique according to claim 2, is characterized in that, in described step S3, wherein, the computing formula of described Stokes parameter is:

$\left\{\begin{array}{c}I=\frac{2}{3}\left(I_o\right(\mathrm{\&alpha;}1)+I_o(\mathrm{\&alpha;}2)+I_o(\mathrm{\&alpha;}3\left)\right)\\ Q=\frac{2}{3}\left(2I_o\right(\mathrm{\&alpha;}1)-I_o(\mathrm{\&alpha;}2)-I_o(\mathrm{\&alpha;}3\left)\right)\\ U=\frac{2}{\sqrt{3}}\left(I_o\right(\mathrm{\&alpha;}2)-I_o(\mathrm{\&alpha;}3\left)\right)\\ V=0\end{array}\right.$

Wherein, I is light intensity parameter, and Q is the first polarization parameter, and U is the second polarization parameter, and V is circular polarization parameter, and because in natural light, V is less, value is zero;

The computing formula of described degree of polarization parameter P is:

$P=\sqrt{\frac{Q^2+U^2}{I}}$

Wherein, P is degree of polarization parameter.

4. the detection method based on polarized light imaging technique according to claim 1, is characterized in that, in described step S4,

The computing formula of wherein said the average energy value is:

$E=\frac{1}{M\&times;N}\underset{x=1}{\overset{M}{\&Sigma;}}\underset{y=1}{\overset{N}{\&Sigma;}}I{(x,y)}^2$

Wherein: E is the average energy value, M is the length of each described little image, N is the width of each described little image, x be each described little image in the picture breakdown coordinate points in horizontal ordinate direction, y is that each described little image is in the picture breakdown coordinate points in ordinate direction.

5. the detection method based on polarized light imaging technique according to claim 1, is characterized in that, in described step S6, also specifically comprises,

Step S61, carry out wavelet decomposition to the light intensity parameter I of described image to be fused and degree of polarization parameter P, Decomposition order is 1;

Step S62, obtain the low frequency coefficient (I of the light intensity parameter I of described image to be fused _lL), the high frequency coefficient (I of light intensity parameter I _lH, I _hL, I _hH),

Step S63, obtain the low frequency coefficient (P of the degree of polarization parameter P of described image to be fused _lL), the high frequency coefficient (P of degree of polarization parameter P _lH, P _hL, P _hH).

6. the detection method based on polarized light imaging technique according to claim 5, is characterized in that, in described step S7, specifically comprises the steps,

Step S71, low frequency coefficient (I according to described light intensity parameter I _lL) with the low frequency coefficient (P of described degree of polarization parameter P _lL) obtain low frequency coefficient to be fused, described low frequency coefficient F to be fused _lLfusion formula be:

F _LL＝log(P _LL)·I _LL ⁿ

Wherein, n is I _lLindex, span is 0 ~ 1;

Step S72, high frequency coefficient (I according to described light intensity parameter I _lH, I _hL, I _hH) with the high frequency coefficient (P of described degree of polarization parameter P _lH, P _hL, P _hH) obtain high frequency coefficient F to be fused _h,

Wherein specifically comprise

High frequency coefficient (the I of step S721, definition light intensity parameter I _lH, I _hL, I _hH) be I _m; High frequency coefficient (the P of definition degree of polarization parameter P _lH, P _hL, P _hH) be P _m;

Step S722, set up light intensity parameter high frequency coefficient I _mwith described degree of polarization parameter P _mcorrelation coefficient M _i,P,

M _i,Pcomputing formula be:

$\left\{\begin{array}{c}{M}_{I,P}=\frac{2\&lsqb;P_m\&CenterDot;I_m\&rsqb;}{E_{HP}+E_{HI}}\\ E_{HP}={P_m}^2\\ E_{HI}={I_n}^2\end{array}\right.$

Wherein, E _hPfor the high frequency coefficient energy value of degree of polarization parameter P, P _mfor the high frequency coefficient of degree of polarization parameter P;

E _hIfor the high frequency coefficient energy value of intensive parameter I, I _mfor the high frequency coefficient of light intensity parameter I;

Step S722, a default relative degree threshold value δ,

Step S723, calculate high frequency coefficient F to be fused according to described relative degree threshold value δ _h

Work as M _i,Pduring > δ, $F_H=\{\begin{array}{ccc}{I}_H& if& E_{HI}\&GreaterEqual;E_{HP}\\ P_H& if& E_{HI}<E_{HP}\end{array},$

Work as M _i,Pduring < δ, F _h=ε _hIi _h+ ε _hPp _h,

${\mathrm{\&epsiv;}}_{HI}=\left\{\begin{array}{ccc}{\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{min}& if& E_I<E_P\\ {\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}}_{max}& if& E_I\&GreaterEqual;E_P\end{array}\right.$

$\left\{\begin{array}{c}{\mathrm{\&epsiv;}}_{HP}=1-{\mathrm{\&epsiv;}}_{HI}\\ \stackrel{\&OverBar;}{\mathrm{\&epsiv;}}\min =\frac{1}{2}\&lsqb;1-\frac{1-M_{I,P}}{1-\mathrm{\&delta;}}\&rsqb;\\ \stackrel{\&OverBar;}{\mathrm{\&epsiv;}}\max =1-\stackrel{\&OverBar;}{\mathrm{\&epsiv;}}\min \end{array}\right.$

Wherein ε _hPfor the weighting coefficient of degree of polarization parameter P, ε _hIfor the weighting coefficient of light intensity parameter I.

7. the detection method based on polarized light imaging technique according to claim 6, is characterized in that, in described step 8, the reconstructing method of its image to be fused is:

$F_{LL}=H_r^{*}{H}_c^{*}{F}_{LL}+H_r^{*}{G}_c^{*}{F}_{LH}+G_r^{*}{H}_c^{*}{F}_{HL}+G_r^{*}{G}_c^{*}{F}_{HH},$

Wherein F _lLfor view data to be fused, h _r, H _c, G _r, G _cassociate matrix, F _lHbe the 1st layer of vertical direction high frequency imaging, F _hLbe the 1st layer of horizontal direction high frequency imaging, F _hHbe the 1st layer to angular direction high frequency imaging.

8. the detection method based on polarized light imaging technique according to claim 1, is characterized in that, it is 0 ° that described predetermined angular is defined as α 1 respectively, and α 2 is 60 °, and α 3 is 120 °.

9. the detection method based on polarized light imaging technique according to claim 1, is characterized in that, in described step 6, described wavelet decomposition is Mallat Wavelet Transformation Algorithm.