Background technology
Interference fringe method in liquid medium electric field measurement field because its rapidity, intuitive, real-time are compared additive method and are had larger superiority and be progressively widely adopted.
Adopt the principle of interference fringe method measurement liquid medium electric field roughly as follows:
Under uniform electric field, due to the electric birefringence character of some liquid medium, reference beam in light path and the phase differential between measuring beam change, thus on imaging device, interference fringe can present and moves in parallel, therefore, interference image after utilizing imageing sensor (Charge-coupled Device, CCD) device to take respectively not apply voltage and applying voltage, can calculate the outer size executing electric field by the displacement of striped and light and shade fringe spacing.
But there is following problem in the use of above-mentioned interference the Schlieren method:
The interference image utilizing CCD device to take is carrying out in pretreated background image, needs the target striped before optional m igration, then identifies target striped in pressurization image and locates, could calculate electric field intensity exactly according to stripe shift amount.In the prior art, paper " interference fringe detects the image processing method of fine motion displacement " (" intelligent computer and application ", 1st volume the 4th phase, in Dec, 2011), sketched the pretreatment process of interference image, wherein the treatment scheme of interference fringe comprises removal background and noise, binaryzation, refinement, displacement calculating etc.; Paper " Processing Algorithm based on the Mach-Zehnder interference fringe picture that CCD gathers " describes the computing method of width of fringe (" applied optics ", the 26th volume the 2nd phase, in March, 2005).But, for the field-induced displacement of interference fringe under uniform electric field, not to how to choose target striped and identify the solution that the target striped after moving provides in prior art, cause the implementation calculating electric field intensity according to stripe shift amount not strong.
Summary of the invention
Based on this, the invention reside in and choosing and recognition methods of target striped in interference fringe method is provided, intelligent processing method can be carried out to the interference fringe image obtained under uniform electric field, choose rapidly and identify that target striped is to calculate electric field intensity according to stripe shift amount exactly.
According to an aspect of the present invention, provide choosing and recognition methods of target striped in a kind of interference fringe method, it comprises: apply the background image before voltage under obtaining uniform electric field, extract the skeleton line of bright fringe in described background image; A bright fringe is chosen as target striped in described background image; Pixel range is set according to described target striped, and obtains the reference line coordinate of described pixel range mid point; Apply the described pressurization image after voltage under obtaining uniform electric field, extract the skeleton line of bright fringe in described pressurization image; In described pressurization image, the reference line passing perpendicularly through described pixel range mid point is set, and obtains the mobile row-coordinate of described reference line and each striped intersection point; Calculate the difference of described mobile row-coordinate and described reference line coordinate, the striped that difference is less than preset range be mobile after described target striped.
According to another aspect of the present invention, choosing and recognition system of target striped in a kind of interference fringe method is provided, comprise image preprocess apparatus, apply the background image before voltage under can obtaining uniform electric field respectively and apply the pressurization image after voltage, and extracting the skeleton line of bright fringe in the skeleton line of bright fringe in described background image and described pressurization image; Pixel range selecting device, can arrange pixel range according to target striped selected in described background image and in described pressurization image, arrange the reference line passing perpendicularly through described pixel range mid point; Target fringe counting method device, the mobile row-coordinate of each striped and described reference line intersection point in the reference line coordinate of pixel range mid point described in described background image and described pressurization image can be obtained respectively, calculate the difference of described mobile row-coordinate and described reference line coordinate, the fringe counting method that difference is less than preset range be mobile after described target striped.
Choosing with recognition methods and system by arranging pixel range and in the mode arranging reference line in image according to pixel range of pressurizeing in background image of this target striped, the identification of target striped in pressurization image can be determined according to the position relationship between striped and reference line, thus can rapidly, localizing objects striped exactly, thus the displacement of target striped can be obtained exactly, laying a good foundation for calculating electric field intensity according to stripe shift amount, in interference fringe electric field measurement field, there is important practical significance.
Embodiment
For making object of the present invention, technical scheme and advantage clearly understand, below in conjunction with the drawings and the specific embodiments, the present invention is described in further detail.Should be understood that, embodiment described herein only in order to explain the present invention, does not limit protection scope of the present invention.
Refer to Fig. 1, be choosing and recognition methods of target striped in the interference fringe method that one embodiment of the invention provides, it comprises: apply the background image before voltage under obtaining uniform electric field, extracts the skeleton line of bright fringe in background image; A bright fringe is chosen as target striped in background image; Pixel range is set according to target striped, and obtains the reference line coordinate of pixel range mid point; Apply the pressurization image after voltage under obtaining uniform electric field, extract the skeleton line of bright fringe in pressurization image; In pressurization image, the reference line passing perpendicularly through pixel range mid point is set, and obtains the mobile row-coordinate of reference line and each striped intersection point; Calculate the mobile row-coordinate of each striped and the difference of reference line coordinate, the striped that difference is less than preset range be mobile after target striped.
Choosing with recognition methods by arranging pixel range and in the mode arranging reference line in image according to pixel range of pressurizeing in background image of this target striped, the identification of target striped in pressurization image can be determined according to the position relationship between striped and reference line, thus can rapidly, localizing objects striped exactly.
Wherein, the background image before voltage is applied under obtaining uniform electric field by interference fringe method, extract the step of the skeleton line of bright fringe in background image, and the pressurization image applied under acquisition uniform electric field after voltage, extract the step of the skeleton line of bright fringe in pressurization image, the pressurization image that can taken the background image before not applying voltage respectively by CCD device and be applied after voltage, then carries out pretreated mode realization respectively to background image and pressurization image.Wherein, execute alive mode and for apply 9kv surge voltage under 3mm spacing plate electrode, pressurization image can be obtained at peak value place.Pretreated mode at least comprises image intensifying and SUSAN filtering two pretreatment operation, then extracts the skeleton line of all bright fringes by binary map method, is presented on former figure by skeleton line.SUSAN filtering algorithm is a kind of filtering algorithm of holding structure, its essence is the weighted filtering utilizing similar comparison function and Gaussian function product as weight.Obtain background image and pressurization image its pre-service by existing techniques in realizing, can not repeated them here in the concrete mode obtaining bright fringe skeleton line.
Choose in the step of a bright fringe as target striped in background image, following four principles are preferably considered in choosing of target striped, first, be positioned at the striped in the centre position of entire image, the second, the striped that width of fringe is relatively large, 3rd, the striped that relatively high, the mixed and disorderly branch of contrast is relatively less, the 4th, transitions smooth is without the striped of breakpoint.Wherein, four principles freely can measure sanction according to actual conditions, and the situation that can all simultaneously meet is optimal situation.Preferably, target striped can also choose the bright fringe being positioned at centre position in three adjacent bright fringes.Choose more suitable target striped by the way, can disturbing factor be reduced, improve recognition efficiency and the accuracy of target striped in whole method.
Arranging pixel range according to target striped, and obtaining in the step of reference line coordinate of pixel range mid point, pixel range is choose scope wide as far as possible along striped bearing of trend to both sides from the center of target striped.Usually, striped can slightly curved shape, and arranging pixel range can the center of target striped be middle strokes and dots horizontal line, and horizontal length covers the part of target striped zone line transitions smooth without breakpoint as far as possible.Pixel range choose two end regions as far as possible avoiding the curvature of target striped larger.The mid point of pixel range is positioned on target striped, and as far as possible near the center of target striped.Preferably, the mid point of pixel range and the center superposition of target striped.The row-coordinate of pixel range mid point is reference line coordinate y
0.
In pressurization image, arrange and pass perpendicularly through the reference line of pixel range mid point, and obtain in the step of the mobile row-coordinate of reference line and each striped intersection point, reference line is through the mid point of pixel range, and vertical with pixel range.The length of reference line arranges and should make it as far as possible can be crossing with the striped in entire image, thus conveniently determine the intersection point of each striped and reference line, to obtain the row-coordinate of each intersection point, because each striped in pressurization image forms after move of stripe in background image, therefore, for ease of describing, the row-coordinate of the intersection point of each striped and reference line is called mobile row-coordinate y
i(i=1,2,3 ... k, k are the quantity of bright fringe in image).
In the calculating mobile row-coordinate of each striped and the difference of reference line coordinate, the striped that difference is less than preset range be mobile after target striped step in, described preset range is determined according to the character of liquid medium electric field, its usually satisfied following formula of condition:
|y
0-y
i|<d/2;
Wherein, y
0for reference line coordinate the row-coordinate of pixel range mid point (in the background image), y
ifor mobile row-coordinate the row-coordinate of the intersection point of each striped and reference line (in the pressurization image), d is the spacing of adjacent two bright fringes.As in the present embodiment, mobile row-coordinate and reference line coordinate are subtracted each other, wherein y1-y0=88, y2-y0=50, y3-y0=90, and the spacing of adjacent two bright fringes is 124 pixels, in the image that therefore pressurizes row-coordinate be the striped of y2 be mobile after target striped.
In the interference fringe method provided by the present embodiment, target striped chooses and recognition methods, intelligent processing method can be carried out to the interference fringe image obtained under uniform electric field, quickly positioning target striped, laying a good foundation for calculating electric field intensity according to stripe shift amount, in interference fringe electric field measurement field, there is important practical significance.
Refer to Fig. 2, for choosing and recognition system of target striped in the interference fringe method that another embodiment of the present invention provides, comprise image preprocess apparatus 10, under obtaining uniform electric field respectively, apply the pressurization image after the background image before voltage and applying voltage, and extract the skeleton line of bright fringe in background image and the skeleton line of bright fringe in pressurization image; Pixel range selecting device 20, for arranging pixel range and arrange the reference line passing perpendicularly through pixel range mid point in pressurization image according to target striped selected in background image; Target fringe counting method device 30, for the mobile row-coordinate of each striped and reference line intersection point in the reference line coordinate of pixel range mid point in respectively background extraction image and pressurization image, calculate the mobile row-coordinate of each striped and the difference of reference line coordinate, the fringe counting method that difference is less than preset range be mobile after target striped.
Choosing of this target striped also comprises image collecting device 40 with recognition system, for the pressurization image gathering the background image before applying voltage and apply after voltage, and sends image preprocess apparatus to.This image collecting device can be ccd image sensor, its can at least 100000fps sampling rate collection and transmit interference fringe image.
Image preprocess apparatus 10, pre-service is carried out respectively to obtain the skeleton line of bright fringe in image to background image and pressurization image, wherein pretreated mode at least comprises image intensifying and SUSAN filtering two pretreatment operation, then extract the skeleton line of all bright fringes by binary map method, skeleton line is presented on former figure.Image preprocess apparatus can for being equiped with the computer system of the software processing image by the way.
Please refer to Fig. 3, pixel range selecting device 20, comprises the indexing unit 21 that can draw marking line in background image and pressurization image.Concrete, the zone line of the target striped that indexing unit 21 can be selected in background image draws horizontal line as pixel range along the bearing of trend of target striped, wherein horizontal length covers the part of target striped zone line transitions smooth without breakpoint as far as possible, and avoids the region that target striped two ends curvature is larger.The mid point of pixel range is positioned on target striped, and as far as possible near the center of target striped.Preferably, the mid point of pixel range and the center superposition of target striped.Indexing unit can also do the straight line in vertical pixel interval as reference line using the mid point of pixel range in pressurization image.The length of reference line arranges and should make it as far as possible can be all crossing with the striped in entire image.
Wherein, choosing of the target striped in background image manually can be chosen by operating personnel, also automatically can be chosen by software.As shown in Figure 4, if choose target striped by automatically choosing mode, then choosing of this target striped also comprises target striped selecting device 50 with recognition system.Choosing of target striped mainly considers following four principles, the first, is positioned at the striped in the centre position of entire image, the second, the striped that width of fringe is larger, the 3rd, the striped that relatively high, the mixed and disorderly branch of contrast is relatively less, the 4th, transitions smooth is without the striped of breakpoint.Wherein, when manually choosing target striped, four principles freely can measure sanction according to actual conditions, and the situation that can simultaneously meet is optimal situation.Automatically choose, according to actual conditions, different priorities can be set to four principles and realize.Preferably, target striped can also choose the bright fringe being positioned at centre position in three adjacent bright fringes.
Target fringe counting method device 30, the coordinate reading unit 31, the calculating that comprise display read pixel point row-coordinate are selected the computing unit 32 of the row-coordinate difference of pixel and judge whether difference belongs to the judging unit 33 in preset range according to the result of calculation of computing unit 32.Wherein, described preset range is determined according to the character of liquid medium electric field, its following formula of condition usually met:
| y
0-y
i| < d/2; Wherein, y
0for the reference line coordinate row-coordinate of pixel range mid point (namely in background image), y
ifor mobile row-coordinate the row-coordinate of the intersection point of each striped and reference line (namely pressurize in image), d is the spacing of adjacent two bright fringes.
The spacing of described adjacent two bright fringes reads the row-coordinate value of pixel on adjacent two bright fringes respectively by coordinate reading unit 31, calculate difference and obtain by computing unit 32.This target fringe counting method device 30 can determine the target striped of movement quickly and accurately according to the judged result of judging unit 33, thus the displacement of target striped can be obtained exactly, laying a good foundation for calculating electric field intensity according to stripe shift amount, in interference fringe electric field measurement field, there is important practical significance.
The foregoing describe the specific embodiment of the present invention, it describes comparatively concrete and detailed, but therefore can not be interpreted as limitation of the scope of the invention.For the person of ordinary skill of the art, without departing from the inventive concept of the premise, can also make some distortion and improvement, these all belong to protection scope of the present invention.