CN104504710B - Moore stripe recognition method and device for X-ray grating phase-contrast imaging - Google Patents
Moore stripe recognition method and device for X-ray grating phase-contrast imaging Download PDFInfo
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Abstract
The invention discloses a Moore stripe recognition method and device for X-ray grating phase-contrast imaging. The method includes the steps of 1, subjecting a Moore stripe image to be recognized to illumination unevenness correction; 2, filtering the Moore stripe image subjected to illumination unevenness correction; 3, binarizing the Moore stripe image filtered to obtain a binary image; 4, detailing the binary image to extract center lines of Moore stripes in the binary image; and 5, recognizing precision positions of the Moore stripes according to the extracted center lines of the Moore stripes. The Moore stripe recognition method and device has the advantages that calculation of the angle and direction of Moore stripes is automated, errors caused by subjective factors of an instrument user are avoided, instrument adjusting speed is greatly increased, and precision is well guaranteed.
Description
Technical field
The present invention relates to a kind of angle of stripe pattern and the automatic testing method in cycle, particularly, are related to X-ray grating
The angle and the automatic identifying method in cycle of the Moire fringe in phase contrast imaging device alignment procedures.
Background technology
Find that X-ray is worn because its is extremely strong in more than 100 years so far of X-ray first from Germany scientist roentgen in 1895
Thoroughly ability, is widely used in the imaging field of object.Traditional x-ray imaging method is mainly based upon suction of the object to X-ray
Receive, the final quality into image contrast for obtaining is heavily dependent on interior of articles each several part to X-ray absorption property difference
Size.In medical domain, because absorption of the human body soft tissue part to X-ray is little, this means that X-ray absorption is imaged
Approach application has significant limitation in the soft tissue lesionses diagnosis of human body.
From last century the nineties, with the development of third generation Synchrotron Radiation, Hard X-Ray Phase-Contrast Imaging
Technology is arisen at the historic moment.There are various X-ray phase contrast imaging technologies to be developed at present.Its mechanism briefly, is exactly
Make use of X-ray to penetrate the movement that its phase place occurs after object to be imaged.Compare absorption-contrast imaging, phase contrast imaging
Advantage be that same dose of X-ray penetrates soft tissue, the change that phase shift is produced absorbs the change for producing than transmitted intensity
Changing much bigger therefore resulting radioscopic image contrast will be greatly improved, referring to list of references [1].
X-ray grating stepping phase contrast imaging method is a kind of X-ray phase contrast method of the more maturation of development at present, by
The polychrome that produces using general X-ray production apparatus in it, incoherence light are imaged, and are widely adopted at present, referring to reference to text
Offer [2].The X-ray grating phase contrast imaging method for generally adopting now, is that Pfeiffer F et al. were carried first in 2006
Go out, the method is realized and completed phase contrast imaging on general X-ray production apparatus using the grating of three pieces of difference in functionalitys.Experiment
In, light source grating Main Function is that common X-ray source is divided into into a series of mutually incoherent line sources.Object sample is placed
Before phase grating, single X-ray line source is partially coherent, can produce Tabo effect with phase grating, is finally led to
The analysis grating being positioned over before detector is crossed, phase place change information is obtained, referring to list of references [3].
A key link for obtaining phase contrast image using the method is the alignment of phase grating and analysis grating, right
Accurate precision has significantly impact on the picture quality for obtaining.Alignment methods are：First adjustment analysis grating so as to grid stroke water
It is flat, afterwards by adjustment phase place grating so that the Taibo of phase grating is completely superposed just from imaging and analysis grating.It is right to judge
Whether standard completes to be to be imaged the Moire fringe angle and cycle judgement formed with analysis grating certainly according to the Taibo of phase grating.
Understand according to the relevant knowledge of Morie fringe, just can be approximate when Morie fringe is vertical and the cycle is equal and tends to infinity
Think that alignment is completed.And the angle of Morie fringe and cycle all foundation meat when being aligned in X-ray grating phase contrast imaging experiment at present
Eye judges that its drawback is that precision cannot ensure and speed is slower with personal subjective consciousness, referring to list of references [4].
List of references：
[1] Chapman L D, Tomlinson W C, Johnston R E, Washburn D, Pisano E, Gmur N,
Zhong Z, Menk R, Arfelli F, Sayers D 1997phys.med.biol.42 2015
[2] Atsushi MOMOSE, Recent Advances in X-ray Phase Imaging, Japanese
Journal of Applied Physics, Vol.44, No.9A, 2005, pp.6355-6367
[3] Franz Pfeiffer, TimmWeitkamp, Oliver Bunk, Christian David, Phase
retrieval and differentialphase-contrast imaging with low-brillianceX-ray
The APRIL 2006 of sources, nature physics VOL 2
[4] PavloBaturin, Mark Shafer, Optimization of grating-based phase-
Contrast imaging setup, Medical Imaging 2014：Physics of Medical Imaging,
Vol.9033,90334
The content of the invention
The accurate quick measuring and calculating in Morie fringe angle and cycle in order to realize X-ray grating phase contrast imaging alignment procedures,
So as to improving instrument alignment precision and obtaining high-quality phase contrast image.
The present invention proposes a kind of recognition methodss of the Morie fringe in X-ray grating phase contrast imaging, and it includes：
Step 1：The even amendment of uneven illumination is carried out to Morie fringe image to be identified；
Step 2：To being filtered through the even revised Morie fringe image of uneven illumination；
Step 3：Binaryzation is carried out to filtered Morie fringe image, binary image is obtained；
Step 4：The binary image is refined, to extract binary image in each Morie fringe initial position
Information；
Step 5：The exact position of each Morie fringe is recognized according to the initial position message of each Morie fringe for being extracted.
The invention allows for a kind of identifying device of the Morie fringe in X-ray grating phase contrast imaging, it includes：
Correcting module：The even amendment of uneven illumination is carried out to Morie fringe image to be identified；
Filtration module：To being filtered through the even revised Morie fringe image of uneven illumination；
Binarization block：Binaryzation is carried out to filtered Morie fringe image, binary image is obtained；
Refinement module：The binary image is refined, to extract binary image in each Morie fringe it is initial
Positional information；
Identification module：The accurate position of each Morie fringe is recognized according to the initial position message of each Morie fringe for being extracted
Put.
Compared with prior art, the scheme that the present invention is provided realizes the automatization of Morie fringe angle and direction calculating,
Error caused by the subjective factorss of the instrument user for avoiding, and instrument regulation speed greatly improves, and degree of accuracy is also obtained
Ensure well.
Description of the drawings
Fig. 1 is the composition schematic diagram of X-ray grating stepping phase contrast imaging system；
Fig. 2 is several exemplary relative positions of two blocks of gratings and corresponding Moire fringe schematic diagram；
Fig. 3 is the flow chart of the recognition methodss of the Morie fringe image in the present invention in X-ray grating phase contrast imaging；
Fig. 4 (a)-(e) is the recognition methodss for realizing the Morie fringe image in X-ray grating phase contrast imaging of the present invention
Software interface and process step schematic diagram.
Specific embodiment
To make the object, technical solutions and advantages of the present invention become more apparent, below in conjunction with specific embodiment, and reference
Accompanying drawing, the present invention is described in further detail.
It is as follows that Morie fringe produces principle：Understand that phase grating produces Grating self-imaging in talbot distance by Tabo effect,
Analysis grating is positioned over specific talbot distance by us, and the striped of the two is crossed to form Morie fringe, and by being positioned over analysis
Ccd detector behind grating is received and obtains original image.
Fig. 1 shows the composition of X-ray grating stepping phase contrast imaging system.As shown in figure 1, system from right to left according to
It is secondary for X-ray source, light source grating, test specimen, phase grating, analysis grating and ccd detector.
Fig. 2 shows several exemplary relative positions and corresponding Moire fringe of analysis grating and phase grating.Such as Fig. 2 institutes
Show, the first row respectively scheme left side for analysis grating schematic diagram, right side for phase grating Taibo from be imaged, the second behavior they be superimposed
The Moire fringe for being formed afterwards.
As shown in figure 3, a kind of the invention discloses identification of the Morie fringe image in X-ray grating phase contrast imaging
Method, it includes：
Step 1：Stripe pattern is obtained, and the even amendment of uneven illumination is carried out to stripe pattern；Wherein, the stripe pattern can
Think Morie fringe, or general stripe pattern；
X-ray source in actual experiment is point source, thus the stripe pattern for obtaining to certainly exist uneven illumination even
Situation.Uneven light note makes image quality decrease, and display effect is deteriorated can more importantly affect follow-up Morie fringe meter
The precision of calculation.Therefore to the original image for obtaining, the present invention will carry out at first the even amendment of uneven illumination.
Understand that picture centre brightness is maximum for the feature of point source, each pixel brightness size is arrived for the pixel
The function of illumination central pixel point distance, gradually decays toward surrounding brightness, and the square distance inverse ratio for meeting point source irradiance is determined
The square distance inverse ratio cosine law of rule and point source irradiance.For this feature, the present invention proposes a kind of simple possible
Modification method.
The square distance law of reciprocity of point source irradiance, that is, the light intensity for assuming point source is Iθ, point source is to detector
The distance at irradiation center is I, then irradiate center illuminance and beAnd the square distance inverse ratio cosine of point source irradiance
Law, that is, assume point source irradiation position and shadow surface out of plumb, it will again be assumed that the light intensity of point source is Iθ, point source is to detector
The distance of plane is I, and point source and point of irradiation normal direction angle are θ, then irradiation position illuminance is
Assume that the gradation of image value matrix for obtaining is A=(a accordinglyij)m×n, illumination center pixel is apq, have
Here k is illuminance to the conversion coefficient of image intensity value, then be to any one position pixel gray value
Wherein I ' is distance of the light source to current pixel point (i, j) to be modified, therefore we can obtain current pixel
The gray value a of point (i, j)ij=apq·cos3θ.Accordingly, for pixel original gray value a on the image for obtainingij, Wo Menxiu
Just its gray value is a 'ij=aij/cos3θ, whereinAnd I can be calculated and measured, if to be modified
Current pixel point (i, j) to the distance at illumination center isI, j are taken in for original image
The pixel coordinate of preceding pixel point (i, j), p, q are the pixel coordinate of illumination center pixel (p, q), i.e.,
Therefore illumination centre coordinate (p, q) is specified in calculating, light source is measured to sensor distance I, to the pixel on image
(i, j) just can complete the even amendment of uneven illumination.
Step 2：Morie fringe image through the even amendment of uneven illumination is filtered.
Because the factors such as the restriction of actual environment condition, CCD self characters affect, the original image of acquisition exists unavoidably makes an uproar
Sound interference.The common noise of ccd image includes spiced salt noise, pulse noise, gaussian noise etc., in addition for the purpose of the present invention, light
The image of grid line is also noise information.Noise information can have a significant effect to successive image result, it is therefore desirable to image
It is filtered process.
Conventional image filtering method includes filter in spatial domain and frequency domain filtering.Filter in spatial domain is referred to directly to image
Pixel grey scale is processed, and is filtered according to the grey value characteristics of each pixel.Common filter in spatial domain method includes
Histogram equalization, median filtering method, mean filter method etc..Filter in spatial domain method simple, intuitive, but filter effect is often
It is not ideal enough, therefore frequency domain filtering method is preferentially adopted in the present invention.
The usual way of frequency domain filtering method is：First image is carried out into fast Fourier transform, choose frequency domain filtering function and enter
Row filtering, by filtered image Fourier inversion is carried out, and obtains filtered image, so as to filter noise, improves image
Quality.
When phase grating and analysis grating can form Moire fringe when interfering, it is assumed that in X, Y plane, coordinate points table
It is shown as (x, y), the cycle of two blocks of gratings is respectively d1And d2, make the grid line and Y of first block of grating i.e. phase grating or analysis grating
Axle is parallel, and second block of grating analyzes grating or the grid line of phase grating is into θ angle clockwise with Y-axis, it is assumed that two grating gaps are
Zero, the Fourier transformation of the penetration function of first block of grating is f1(T), the Fourier transformation of the penetration function of second block of grating is
f2(T), they are in the interference field light distribution that space is formed：
Wherein, x, y are the coordinate of arbitrfary point on Morie fringe, and T is the Fourier transformation cycle；a01, anFor first block of grating
The Fourier Transform Coefficients of penetration function, a02, amFor second piece of grating penetration function Fourier Transform Coefficients, analyze and understand, on
Formula equation the right Section 1 does not contain phase factor, and it represents bias light, and Section 2 contains frequency contentIt comprises first
Block grating is the structural information of phase grating, and Section 3 contains frequency contentIt comprises second block of grating and analyze grating
Structural information, and Section 4 contain two gratings and frequency and difference frequency component, belong to Morie fringe information.Therefore Section 1 and the
Four useful informations for needing to retain for us, Section 2 and Section 3 need to filter.Certainly, the image for actually obtaining is included
More complicated noise frequency composition, all should be filtered in filtering.
The picture frequency information characteristics of analysis according to more than, present invention employs the combination filter that a kind of low pass is combined with band logical
Ripple device, low pass is used to leach background component, and band logical is to leach Moire fringe information.Wave filter species, can select in the present invention
Ideal filter, exponential filter, the fertile husband's wave filter of Bart etc. are selected, wherein ideal filter form is relatively simple and effect reaches
To requiring, therefore for the preferential method for adopting of the invention.I.e. filter function is H (u, v), is had
Wherein r1For low pass filter filter radius, r2For band-pass filter radius, u, v are to put on filtering level
Coordinate, u0, v0For bandpass filtering centre coordinate.
Therefore assume that filter wavefront image information Fourier transformation is F (u, v), filtered image Fourier transformation should for G (u,
V)=F (u, v) H (u, v), to it Fourier inversion is carried out, and obtains filtered image.
Step 3：Binaryzation is carried out to having carried out filtered original image.
Binaryzation is exactly as its name suggests to divide the image into area-of-interest and region two parts of loseing interest in.In the present invention,
Image bright rays is area-of-interest, represents the area-of-interest with 1 after binaryzation, and other regions are represented with 0.Base
It is very ripe in the image binaryzation method of Image Segmentation Theory, the method for typically now adopting for threshold division, threshold value
Changing partitioning algorithm mainly has two steps：It is determined that need segmentation threshold and segmentation threshold is compared to divide picture with pixel value
Element.Threshold division method includes local thresholding method, Global thresholding, manual threshold method etc., wherein determining that suitable threshold value is
The key of image segmentation, and the extracting method of threshold value is also varied.Different threshold segmentation methods are suitable for different characteristic
Image, the present invention needs image information to be processed relatively easy, and through pretreatment, picture quality is also relatively good, therefore
Most of threshold segmentation method is all suitable for.
Step 4：The area-of-interest of image is refined after to having carried out binaryzation, to extract the first of image Morie fringe
Beginning positional information.
Through above-mentioned process, image information has been greatly simplified, but it is an object of the present invention to obtains the essence of Morie fringe
True position, it is therefore desirable to further extract the positional information of Moire fringe, i.e. image thinning.Image thinning extracts image
Trunk information, so that Moire fringe is extracted as an example, exactly obtains the center point coordinate and angle of Morie fringe.
Step 5：The exact position of Morie fringe is recognized according to the initial position message of the Morie fringe for being extracted.
The striped initial position message extracted through micronization processes has substantially met precision needs, but in order to further
Precision is improved, the present invention proposes a kind of iterative calculation method based on gray variance weight, to recognize the accurate of Morie fringe
Position.The method is specially：
Step 51：The initial position message of current Morie fringe to be identified is obtained, if its central point is (x0, y0), length is
L, angle is θ0；
Step 52：Setting iterative calculation number of times, calculates angle of eccentricity α and line quantity n, with (x0, y0) centered on, l is length
Spend, to the left and right each tilt alpha draws n bar straight lines；
Step 53：If the variance of pixel gray value is followed successively by σ on each straight line1, σ2, σ3... ..., σ2n.Simultaneously by retouching before
State and understand, the straight line drift angle β of each line correspondencesiAlso it is not difficult to calculate, such asClass successively
Push away.
Step 54：According to the size of pixel gray level variance on each bar straight line, to each bar linear angle of inclination weight is givenAccording to formula
The new angle of calculated current Morie fringe to be identified；
Step 55：According to the iterative calculation number of times of step 52 setting, repeat step 52 arrives step 54 iterative process, most
The exact position of current Morie fringe to be identified is obtained eventually, and the exact position of the current Morie fringe to be identified includes currently treating
The center point coordinate and angle of identification Morie fringe, the center point coordinate is still the initial position message obtained in step 4
In center point coordinate, and angle be through step 51-55 optimization after angle.
The precise position information of each Morie fringe can be obtained by repeating step 5, and according to each Morie fringe
Center point coordinate can obtain cycle of Morie fringe.
Step 6：Instrument calibration judgement up to standard.
For calculated each bar Morie fringe, then on the basis of its central point, with the abscissa phase of adjacent center point
Subtract, calculate their cycle.According to being actually needed, to angle and cycle set allowable error, when instrument is adjusted to a certain state
When, if calculated angle and cycle are all up to standard, it is possible to think that instrument alignment has been completed.
The recognition methodss of the above-mentioned Morie fringe of the present invention can pass through LabVIEW programming realizations.
The present invention writes software using LabVIEW, realizes above-mentioned algorithm (note：LabVIEW is upper should to be provided with " vision
With motion " module).All of image processing process is all based on what image intensity value was carried out, so should use " IMAQ first
ImageToArray " functions convert images into gray value two-dimensional matrix.
Image irradiation amendment part.Light source to sensor distance and illumination center are input quantity, pixel position coordinateses
And pixel gray value is read in from image, and by as described before formula is brought into
Revised gradation of image matrix is obtained, utilizes " IMAQ ArrayToImage " function that revised image is obtained.Separately
Outward we can intuitively observe correction effect with the 3-D view of " curved surface " function drawing image gray matrix.
The Mixed-Programming Technology of LabVIEW and MATLAB is used in this part of image filtering.LabVIEW and MATLAB is programmed
Have the advantages that oneself is original, the graphic programming mode of LabVIEW can allow developer to focus more on algorithm itself, and
The graphics process workbox of MATLAB is then integrated with many image processing functions, brings great convenience to image procossing, because
LabVIEW and MATLAB are combined programming by this can greatly improve our programming efficiency.The mixing of LabVIEW and MATLAB
Programming realization method is varied, and the method adopted in the present invention is adjusted for " MATLAB script " node used in LabVIEW
With MATLAB, it is located at " mathematics ＞ scripts and formula ＞ script node ＞ MATLAB scripts ", inserts after the node to the left
Addition input, right side addition output, input MATLAB processes code in node, you can use, simple and convenient.
Therefore filter in this part, we use MATLAB script nodes, revised gradation of image matrix to utilize
" fft2 " function in MATLAB realizes fast two-dimensional Fourier transformation, from front panel input filter centre coordinate and filtering half
Footpath size, completes filter function structure.Image uses afterwards after filtering " ifft2 " to realize Fourier inversion, after being filtered
Image.
Binarizing portion.Filtered image realizes binaryzation in the part, the part we be integrated with " local threshold
Method " " automatic threshold method " and " manual threshold method " three kinds of methods.Wherein " local thresholding method " use " IMAQ Local
Threshold " functions realize that " automatic threshold method " use " IMAQ AutoBThreshold 2 " function is realized, and " manual threshold
Value method " use " IMAQ Threshold " function is realized.Concrete |input paramete needed according to each function and picture situation by
Operator is input into.
Image thinning determines that two parts are constituted by refinement and striped initial position in fact.The refinement of image uses " IMAQ
Skeleton " functions realize that stripe pattern can just obtain the venation of striped after processing using the function.But venation image may
Bending occurs, the problems such as burr is more, and its more specific location information also cannot determine, therefore and then we use " IMAQ
Find Straight Edges 2 " functions are realizing primarily determining that for fringe position.The function is originally for searching graph line
Edge, but we are applied to the image after refinement, and by arranging appropriate parameter, it just can realize searching in image
Straight line, and the function of linear position and angle is returned, therefore can be used for primarily determining that for fringe position.
The accurate calculating section of fringe position mainly uses " IMAQ Line Profile " function, and the function can be to image
The upper a certain straight line specified returns pixel gray value variance size on the straight line.Obtain concrete after variance calculating according to previously retouching
That what is stated removes programming realization.
The allowable error of front panel input angle and variance again after the determination of striped exact position, by each fringe position and mark
Standard is contrasted, you can judge whether angle and cycle are up to standard, and indicates respectively angle and cycle in front panel two boolean's lamps of setting
Result of determination, represents up to standard so that lamp is bright.
Fig. 4 (a)-(e) is shown in a kind of X-ray grating phase contrast imaging alignment procedures proposed in the embodiment of the present invention not
The angle and the automatic identifying method in cycle of your striped realizes that said method proposed by the present invention is also applied for arbitrarily containing with software
The fringe counting method of stripe pattern.It is divided into five steps when being embodied as to complete.
As shown in Fig. 4 (a) step one, the first step is the even amendment of uneven illumination.First measure light source to detector distance simultaneously
Input.Original Morie fringe image is read in, Three-Dimensional Gray figure is converted into and is observed its gray feature, according to the knot observed
Really, the abscissa and vertical coordinate at illumination center are set gradually, runs software, the uneven illumination of image is even can be corrected.Repair
Image and its Three-Dimensional Gray figure after just is also shown in software, helps us to observe correction effect.In addition we can lead to
Cross click " storage corrected parameter " button to preserve current amendment setting.
As shown in Fig. 4 (b) step 2, second step is image filtering.The revised image of illumination is input, input picture elder generation
Carry out two-dimensional fast fourier transform, the frequency domain figure after output transform as be easy to we observe the frequency content of needs residing for position
Put.According to the image result observed, the abscissa vertical coordinate and filter radius size of three filtering points of wave filter are determined successively,
Runs software exports filtered frequency domain figure picture and its inverse transformation after being provided with, and can see the filter effect of image, parameter
Setting can be finely tuned again.In addition we can preserve current amendment and arrange by clicking on " storage filtering parameter " button.
As shown in Fig. 4 (c) step 3, the 3rd step is image binaryzation.Image after input filter, selects a kind of binaryzation
Method.Here the method that we select is the Niblack methods in local thresholding method, and design parameter is set to, and Niblack deviates
Coefficient is 0.2, and calculation window size is multiplied by 32 pixels for 32 pixels.We can also select according to picture quality in practical operation
Other binarization methods are obtaining best binaryzation effect.
As shown in Fig. 4 (d) step 4, the 4th step is image thinning.Image after binaryzation, can in image used as input
To delimit the scope for needing refinement and measuring.The option that straight line is searched is more, and " refinement direction ", can be with according to depending on stripe direction
Left and right directions, it is also possible to above-below direction, " kernel size " input minima, " number of lines " is most in line options
Amount is bigger with including all of straight line, and other specification default value just can be with.It can also be as needed adjusted in practical operation
His parameter setting is obtaining more preferable effect.The striped number for detecting is exported in the lower right corner of software interface.
As shown in Fig. 4 (e) step 5, the 5th step is that striped is calculated and qualification determination.The straight line information that step 4 finds
Such as fringe center dot position information, angle and line segment length information are input to the step, filter in step 2 according to straight line information
Line calculating is carried out on the image for obtaining afterwards.The angle and number of line is input into by software operator, after the completion of calculating, final
To streak line will include in filtered image in red line form.We export the angle information of every stripe and each
Cycle information between striped, and it is shown in a program in the form of cartogram, convenient observation.We arrange again angle
The allowable error Δ in allowable error δ (being qualified within ± δ ° of angle) and cycle is (if the meansigma methodss in cycle areCycle
It is qualified within pixel), if the angle of each stripe is qualified with the cycle will to light boolean's display lamp.Finally collect each stripe letter
Breath, then the overall angle of decision-making system and the cycle it is whether up to standard, if up to standard light boolean's lamp, two lamps all light i.e. system alignment
Complete, if it is not, selecting suitable calibration steps according to stripe angle and the distribution situation in cycle, continue to adjust stop position,
The each step work of repetition.
Particular embodiments described above, has been carried out further in detail to the purpose of the present invention, technical scheme and beneficial effect
Describe in detail bright, it should be understood that the foregoing is only the specific embodiment of the present invention, be not limited to the present invention, it is all
Within the spirit and principles in the present invention, any modification, equivalent substitution and improvements done etc. should be included in the protection of the present invention
Within the scope of.
Claims (8)
1. the recognition methodss of the Morie fringe in a kind of X-ray grating phase contrast imaging, it includes：
Step 1：The even amendment of uneven illumination is carried out to Morie fringe image to be identified；
Step 2：To being filtered through the even revised Morie fringe image of uneven illumination；
Step 3：Binaryzation is carried out to filtered Morie fringe image, binary image is obtained；
Step 4：The binary image is refined, to extract binary image in each Morie fringe initial bit confidence
Breath；
Step 5：The exact position of each Morie fringe is recognized according to the initial position message of each Morie fringe for being extracted；
Wherein step 5 is specifically included：
Step 51：The initial position message of current Morie fringe to be identified is obtained, if the central point of current Morie fringe to be identified
For (x0, y0), length is l, and angle is θ0；
Step 52：Setup algorithm angle of eccentricity α and line quantity n, with (x0, y0) centered on, l is length, is respectively inclined to the left and right
α draws n bar straight lines；
Step 53：If the variance of pixel is followed successively by σ on each straight line1, σ2, σ3... ..., σ2n, then the straight line of each line correspondences is calculated
Drift angle βi；
Step 54：According to the size of pixel gray level variance on each bar straight line, to each bar linear angle of inclination weight is givenAnd according to formula
The new angle of calculated current Morie fringe to be identified；
Step 55：According to the iterative calculation number of times of step 52 setting, repeat step 52 arrives step 54 iterative process, final to obtain
To the exact position of current Morie fringe to be identified.
The method of claim 1, wherein 2. fixed according to the square distance inverse ratio of point source irradiance in the step 1
The square distance inverse ratio cosine law of rule and point source irradiance, to the Morie fringe image the even amendment of uneven illumination is carried out.
3. method as claimed in claim 2, wherein, the optional position in the step 1 on revised Morie fringe image
Pixel gray value is calculated as below：
Wherein, aijWith a 'ijRespectively described mole bar
With revised grey scale pixel value before any pixel (i, j) is corrected on print image, I is point source to Morie fringe image detection
The distance of device irradiation position, p and q are respectively the pixel coordinate of illumination center pixel (p, q).
4. the method as described in any one of claim 1-3, wherein, step 2 is specifically included：
Step 21：Fast Fourier transform is carried out to described through the even revised Morie fringe image of uneven illumination；
Step 22：Result from after fast Fourier transform is chosen frequency domain filtering function and is filtered；
Step 23：Image after frequency domain filtering is carried out into Fourier inversion, filtered Morie fringe image is obtained.
5. method as claimed in claim 4, wherein, the frequency domain filtering function adopted in step 22 is expressed as below：
Wherein r1For low pass filter filter radius, r2For band-pass filter radius, u, v are the coordinate put on filtering level,
u0, v0For bandpass filtering centre coordinate.
6. the method for claim 1, wherein the exact position of current Morie fringe to be identified includes described in step 5
The central point and angle of current Morie fringe to be identified.
7. method as claimed in claim 6, wherein, the method also includes：
Step 6：Judge whether to reach instrument calibration according to the angle of calculated each Morie fringe and Morie fringe cycle
Standard.
8. the identifying device of the Morie fringe in a kind of X-ray grating phase contrast imaging, it includes：
Correcting module：The even amendment of uneven illumination is carried out to Morie fringe image to be identified；
Filtration module：To being filtered through the even revised Morie fringe image of uneven illumination；
Binarization block：Binaryzation is carried out to filtered Morie fringe image, binary image is obtained；
Refinement module：The binary image is refined, to extract binary image in each Morie fringe initial position
Information；
Identification module：The exact position of each Morie fringe is recognized according to the initial position message of each Morie fringe for being extracted；
Wherein, the identification module recognizes as follows the exact position of each Morie fringe：
The initial position message of current Morie fringe to be identified is obtained first, if the central point of current Morie fringe to be identified is
(x0, y0), length is l, and angle is θ0；
Setting iterative calculation number of times, calculates angle of eccentricity α and line quantity n, with (x0, y0) centered on, l is length, to the left and right
Each tilt alpha draws n bar straight lines；If the variance of pixel is followed successively by each straight line, σ1, σ2, σ3... ..., σ2n, then each straight line pair is calculated
The straight line drift angle β for answeringi；
According to the size of pixel gray level variance on each bar straight line, to each bar linear angle of inclination weight is givenAnd according to formula
The new angle of calculated current Morie fringe to be identified；
According to the iterative calculation number of times of above-mentioned setting, the above-mentioned iterative process of repetition, current to be identified mole of bar is finally given
The exact position of stricture of vagina.
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| CN107346553A (en) * | 2016-05-06 | 2017-11-14 | 深圳超多维光电子有限公司 | The determination method and apparatus of stripe information in a kind of image |
| CN107807139B (en) * | 2016-09-05 | 2020-04-24 | 天津工业大学 | Dual-energy X-ray phase contrast imaging system without stepping device and implementation method thereof |
| CN107085000B (en) * | 2017-04-17 | 2020-06-16 | 深圳先进技术研究院 | X-ray grating phase contrast imaging automatic calibration system and method |
| WO2019056309A1 (en) * | 2017-09-22 | 2019-03-28 | Shenzhen United Imaging Healthcare Co., Ltd. | Method and system for generating a phase contrast image |
| CN108876845B (en) * | 2018-06-14 | 2022-02-25 | 歌尔股份有限公司 | Fresnel pattern center determining method and device |
| CN108988786B (en) * | 2018-07-18 | 2019-09-10 | 西安电子科技大学 | Photovoltaic cell efficiency figure compresses measuring device and measuring method |
| CN112287942A (en) * | 2020-10-20 | 2021-01-29 | 哈尔滨理工大学 | Binarization method suitable for non-uniform illumination condition |
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