CN104976960A - Raindrop physical property observation method and device - Google Patents
Raindrop physical property observation method and device Download PDFInfo
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Abstract
The invention relates to a raindrop physical property observation method and device. The related method is based on an image processing technology, raindrops and noise are identified according to characteristic quantity like gray scale difference of a raindrop area and a non-raindrop area and a raindrop graphic structure, and then a binary raindrop graph is sketched, based on which raindrop images of the same name obtained through "snapshot" and "slow shot" are matched, and the position, the shape and trailing length of the raindrops are confirmed through design of a reasonable algorithm so that diameter and falling final speed of the raindrops are finally solved. The related device comprises a parallel light generation device, a projection curtain and image acquisition devices. The image acquisition devices comprise a first image acquisition device and a second image acquisition device. The exposure time of the first image acquisition device is less than that of the second image acquisition device. An observation view field is arranged between the parallel light generation device and the projection curtain. Parallel light irradiates the falling raindrops in the observation view field, raindrop projection is formed on the projection curtain, and the image acquisition devices acquire the raindrop projection.
Description
Technical field
The invention belongs to raindrop observation technology field, be specifically related to a kind of raindrop physical characteristics observation procedure and device.
Background technology
Raindrop are final products of macroscopic view, microprocess contradiction in cloud, although raindrop diameter is usual less than 6mm, but owing to usually having larger kinetic energy in raindrop descent, it is but very large to the hitting power of soil particle, can not ignore the Splash Erosion caused in soil erosion process.The physical characteristics of research raindrop is research soil water reservoir capacity dynamic processes, calculate the basic foundation of the work such as rainfall erosivity in land surface emissivity, also contribute to explaining in cloud and become rain mechanism, assessment artificial precipitation condition and validity check, therefore the research of raindrop physical characteristics receives the extensive attention of many scholars.
The parameter of reflection raindrop physical characteristics mainly contains rain drop shapes, diameter, landing end speed etc.The observation procedure of raindrop physical characteristics of the prior art has color spot, dough method, immersed method, kinetic energy impulse momentum method, Photographic technique etc.
Color-spot method is based on " the color spot size that raindrop are formed on same material is directly proportional to the particle size of raindrop " this supposition.The method is easy and simple to handle, with low cost, be still widely used so far, but in practice, raindrop splash down that what formed on filter paper is the pattern of the irregular band burr of a group pole of figure, make to estimate that Raindrop diameter relies on subjective experience to a great extent according to color spot shape.
Dough method refers to and connects Sheng raindrop with the container filling flour, and raindrop infiltrate flour forming surface powder ball, are then determined the size of raindrop by the weight of measuring surface powder ball.The process that dough method must have high Accuracy Electronic Balance to weigh, is not suitable for and measures the too little raindrop of particle diameter.
Immersed method connects Sheng raindrop with the container filling oil plant, determines the size of raindrop by measuring W/O pearl diameter, but the method is only applicable to measure the less droplet of particle diameter or raindrop.
Along with the development of electronic measurement technique, kinetic energy impulse sensor is adopted to measure the long-pending upper raindrop kinetic energy momentum of sensor section in rainfall field.Because impulse sensor limits by size, raindrop measure sectional area too little (several square centimeters), and then affect representativeness and accuracy that in the method, raindrop are measured; Separately there is sensor surface ponding, make the method to carry out Continuous Observation.
Existing Photographic technique can directly obtain raindrop image, but there is depth of field effect, and is confined to lab simulation rainfall research more, and cannot obtain the raindrop physical characteristics under natural precipitation condition.Visible, traditional raindrop physical characteristics measuring method ubiquity measuring accuracy is low, labour intensity is high, measure poor real, only can carry out the problems such as an example research.
Linear array scanning method is in recent years applied gradually, and compared with said method, the method can directly measure raindrop diameter and speed, and then calculates raindrop kinetic energy accurately.But still there is error in various degree in these class methods, such as, OTT PARSIVEL laser raindrop spectrograph, two-dimensional video raindrop spectrometer etc. based on linear array scanning method directly can obtain the profile information of rainfall particle, but raindrop landing end speed is estimated according to rain drop shapes hypothesis, and can cause the distortion of particle image when particle exists horizontal shift through measured zone; In addition, this class methods sample space is little, more weak to the detectivity of small-particle.Such as, two-dimensional video raindrop spectrometer adopts twin-line array CCD and quadrature network, and sampling area is only 100mm × 100mm, and single CCD linear array comprises 512 pixels, and least resolution is 0.19mm.
Summary of the invention
For defect or the deficiency of prior art, an object of the present invention is to provide a kind of raindrop physical characteristics observation procedure.
Raindrop physical characteristics observation procedure provided by the invention comprises:
(1) utilize the first image acquisition device and the second image acquisition device to gather same rainfall scene, multiframe image in the same time period, the time shutter of described first image acquisition device is shorter than the time shutter of the second image acquisition device;
(2) geometric correction process is carried out to the image that the first image acquisition device and the second image acquisition device gather, make all images of step (1) gained be positioned at the same coordinate system;
(3) statistical filtering process is carried out to all images after step (2) process, the image containing raindrop is highlighted;
(4) image obtained step (3) carries out rolling filtering process:
If background pixel value is 0 in current pending image frame R, wait to judge that pixel value is 1; Then,
1. the pixel column of the right side edge being positioned at current pending image frame is moved on to the left side edge of current pending image frame, obtain right rolling image frame R
1;
2. the pixel column of the left side edge being positioned at current pending image frame is moved on to the right side edge of current pending image frame, obtain the dynamic image frame R that rolls left
2;
3. R*R is tried to achieve
1with R*R
2or operation values RES
1;
RES
1for the rolling filtering image of current pending image frame, or, to RES
(n-1)carrying out step 1. to 3. processing, obtaining RES
n, n be more than or equal to 2 natural number, RES
nfor the rolling filtering image of current pending image frame;
(5) binary conversion treatment is carried out to the image after step (4) process, obtain raindrop image;
(6) the raindrop image of foundation the first image acquisition device collection calculates the raindrop diameter of each raindrop in every width image; The raindrop image of foundation the first image acquisition device and the second image acquisition device collection calculates the raindrop landing end speed of each raindrop;
Described raindrop diameter is the geometric mean of the Second bobbin diameter that raindrop image maximum gauge is vertical with maximum gauge;
Described raindrop landing end speed is under synchronization, in the raindrop image of the second image acquisition device collection, to deduct the difference of diameter of raindrop B in the raindrop image that the first image acquisition device gathers poor divided by the time shutter of the first image acquisition device and the second image acquisition device for the diameter of the hangover image of raindrop A, and the raindrop image center of gravity of described raindrop B is arranged in the raindrop image of raindrop A.
Optionally, the acquisition frame rate of the first image acquisition device of the present invention and the second image acquisition device is 20 frame s
-1, the first image acquisition device time shutter was 1/4000s, and the second image acquisition device time shutter was 1/500s.
Optionally, step of the present invention (2) take target as reference, carries out geometric correction process to the image that the first image acquisition device and the second image acquisition device gather.
Optionally, in step of the present invention (5), the threshold value of binaryzation filtering process is 28-32.
Optionally, in step of the present invention (6), raindrop diameter is the maximum gauge of raindrop image; Or be the geometrical mean of each pixel and raindrop centroidal distance on raindrop image outer contour, or be the arithmetic average of each pixel and raindrop centroidal distance on raindrop image outer contour; Or be the equivalent diameter of a circle that raindrop image is corresponding.
The present invention additionally provides a kind of raindrop physical characteristics observation device simultaneously.
Device provided by the present invention comprises: directional light generating means, projection screen and image acquisition device, described image acquisition device comprises the first image acquisition device and the second image acquisition device, and the time shutter of described first image acquisition device is shorter than the time shutter of the second image acquisition device; For to observe visual field between described directional light generating means and projection screen; Directional light irradiates the whereabouts raindrop in observation visual field, and described projection screen is formed raindrop projection, and image acquisition device gathers raindrop projection.
Optionally, directional light generating means of the present invention comprises light source and Fresnel Lenses, and the light that light source sends generates directional light after Fresnel Lenses.
Optionally, light source of the present invention is halogen pointolite.
Optionally, apparatus of the present invention also comprise target, and described target is the circular pattern be located on curtain.
Optionally, directional light generating means of the present invention is arranged in a waterproof case, and described projection screen and image acquisition device are arranged in a waterproof case.
Device of the present invention also can comprise data processing equipment, utilizes common computer and developing software of correspondence thereof to realize.
Compared with prior art, the invention has the advantages that:
(1) the present invention is water-saving irrigation, and in the systems such as artificially-simulated rainfall, the design and manufacture of shower nozzle provides detection means accurately; The present invention provides technical method and scope for research precipitation microscopic feature, calculating rainfall erosivity etc.;
(2) the present invention adopts the camera of two different exposure time to take pictures simultaneously, obtains the raindrop image of the same name of " static " and " hangover ", and then resolves raindrop physical characteristics parameter by computer image processing technology;
(3) technology such as rolling filtering that the present invention adopts can reject the noise in image effectively, efficiently.
(4) method of the present invention can also be measured the physical characteristics of the dissimilar precipitation particles such as snowflake, hail, not only can disclose the physical features of different precipitation particle, and help lend some impetus to the application of precipitation microscopic feature in Characteristics of Precipitation, the soil erosion and controlling mechanism assessment thereof etc.
Accompanying drawing explanation
Fig. 1 is raindrop image schematic diagram, and wherein (a) is static images, and (b) is hangover image;
Fig. 2 is device reference view of the present invention, wherein: the high-power pointolite of 1-, the luxuriant and rich with fragrance mirror of 2-optics, 3-projection screen, 4-high-speed capture camera, 5-low speed shooting camera, 6-camera synchronization controller, 7-image collection controls to resolve computing machine;
Fig. 3 is the image reference view in method processing procedure of the present invention, wherein: (a) raw video, and (b) statistical filtering, (c) rolling filtering, (d) binaryzation;
Fig. 4 is the raindrop image reference view after method process of the present invention, wherein: (a) " static " image; (b) " hangover " image, a
1and b
1be raindrop of the same name;
Fig. 5 is the frequency distribution of relative error, (a) diameter relative error; (b) landing end speed relative error.
Embodiment
The present invention is based on image processing techniques, the characteristic quantity such as gray difference, raindrop graphic structure according to raindrop region and non-raindrop region carries out identification to raindrop and noise, then the raindrop figure of binaryzation is delineated, mate the raindrop image of the same name that " snap " and " clapping slowly " obtains on this basis, and algorithm reasonable in design, determine the position of raindrop, shape and trailing length, finally resolve diameter and the landing end speed of raindrop.
" snap " and " clapping slowly " can generate two raindrop images, utilize the location target that observation visual field is laid, " static " raindrop image that snap is obtained and clap " hangover " raindrop image obtained slowly and normalize in the same coordinate system, same like this raindrop will be overlapping, and " hangover " of raindrop part also can show, afterwards just can identification raindrop of the same name according to the geometric shape of raindrop image.As shown in Figure 1, wherein, Fig. 1 (a) is " static " raindrop image when high-speed shutter is taken to raindrop image schematic diagram, " hangover " raindrop image when Fig. 1 (b) is the shooting of low no-delay gate.
In order to accurately calculate raindrop diameter, equivalent circular area mapping algorithm and geometric mean algorithm etc. can be adopted.The former refers to and the rain drop shapes of " static " is approximately circular, and closure area is considered as the area of a circle, instead pushes away corresponding diameter of a circle as raindrop diameter.Geometric mean algorithm refers to be found apart from two points farthest on the raindrop profile of " static ", its line is as raindrop maximum gauge, mid point through this diameter does vertical line, meet at 2 points on raindrop profile, distance between these 2 is raindrop Second bobbin diameter, and the geometric mean of maximum gauge and Second bobbin diameter is raindrop diameter.
Although the descent of raindrop is one become the process accelerated, be a kind of instantaneous measurement visualization technique due to what adopt in the present invention, therefore the subaerial descent of raindrop can be considered at the uniform velocity process.Phase differential between " hangover " raindrop image and " static " of the same name raindrop image is the displacement of these raindrop, just can obtain raindrop to land end speed by this distance divided by the time shutter difference of snap and slow shooting camera.Therefore, what calculate raindrop landing end speed focuses on calculating raindrop displacement.Inventor has devised two kinds of raindrop displacement computing method: outer contour extraction algorithm and line of centres algorithm.The former by extracting the enveloping outer enclosure of raindrop tracks, and then forms a closure, and the main shaft of this closure is the trailing length of raindrop, and the diameter that this length deducts corresponding " static " raindrop is the displacement of raindrop.The latter thinks that the center of gravity of raindrop motion track will be positioned at the central point of " hangover " rain drop shapes with maximum probability, and be uniform motion depending on raindrop, so the line of raindrop focus point and track focus point is the half of raindrop displacement.The former is combined closely with the treatment scheme of digitized video, and it just can extract the enveloping outer enclosure of raindrop in the process of raindrop binaryzation, makes this algorithm counting yield higher.
The determination methods of the present invention's raindrop of the same name is: in the hangover raindrop image of the raindrop A whether gathered at this moment second image acquisition device by the center of gravity that judges the raindrop image of the raindrop B that a certain moment first image acquisition device gathers, if so, then two raindrop are raindrop of the same name.
Physical size is obtained for obtaining raindrop, the invention provides a kind of concrete grammar is, take target as reference, geometric correction process is carried out to the image that the first image acquisition device and the second image acquisition device gather, namely projection screen spatially has physical size, spatially can demarcate, or/and be provided with target at projection screen; Secondly, because image and these two planes of projection screen have central projection relation, the transformation matrix between two planes can be resolved according to target locus, the calculating parameter that this transformation matrix is corrected as image geometry.With this transformation matrix raindrop image projecting to curtain spatially, make raindrop image and projection screen have consistent spatial measure size, like this process after all images can be positioned at the same space coordinate system.
The present invention adopts the imaging measurement technology of improvement, optional area array CCD particle imaging measuring technique, light path system and the imaging system of raindrop image is taken under have developed rainfall environment, based on Computer Vision Recognition technological development raindrop image capturing, digitized video correction, computer image deep treatment method, actual observation is carried out to raindrop or water droplet, especially analyzes raindrop or drop diameter and these two physical characteristics parameters of landing end speed.
The high frame per second that area array CCD particle imaging measuring technique utilizes CCD industry camera to have, high resolving power, the performance such as program-controlled carry out " snap " (time shutter is short) to landing raindrop and " clapping slowly " (time shutter is long) operates, gather raindrop " static " and " hangover " image of synchronization, determine its locus in specific time series and shape, and then resolve raindrop diameter and landing end speed.
Consider the tolerance of CCD camera imaging and the matching degree of camera and light source, inventor has selected powerful Philip silver soldier Halogen lamp LED, and it can produce the white light that a kind of colour temperature is about 4300K, and light directive property is obvious, can be similar to and regard pointolite as.At the initial stage of selecting light source, inventor has attempted different light sources, and what first select is LED, but too responsive to temperature due to it, causes its weak heat-dissipating, and easily occurs serious light decay, thus the light colour rendering that LED is sent is poor.Moreover inventor has selected a kind of electric arc etc. based on gas discharge, but due to its volume large, and intensity of illumination is little and be not finally used; In addition inventor additionally uses laser tube as pointolite, and its monochromaticity is good, high directivity, and in order to obtain the pointolite of high brightness, inventor has had a go at laser tube crystalline substance row, but is listed in as a crystalline substance in the process detected in field, and shockproof properties is poor, debug difficulties.
Below the specific embodiment that inventor provides, to be further explained explanation to technical scheme of the present invention.
Embodiment 1:
The raindrop physical characteristics observation device of this embodiment comprises optical projection system, acquisition system and acquisition control system, specifically comprise six working cells, be respectively pointolite, optics luxuriant and rich with fragrance mirror, projection screen, CCD industrial camera, camera synchronization controller and terminal, as shown in Figure 2.This system can realize the function such as Real-time Collection, information extraction, storage of image data.
Optical projection system primary responsibility provides the parallel light field of reliable, stable a, sufficient intensity for acquisition system.This system is made up of 5 large modules: Philip silver soldier Halogen lamp LED, focal length are the Fresnel condenser of 220mm, H7 ceramic high-temperature resistant socket, four-core water joint, optical projection shell and related accessory.
It is about 4300K that Philip silver soldier Halogen lamp LED can produce a kind of colour temperature, and the obvious white light of light directive property, can myopia be pointolite, power be 55w; The light post filtering that Fresnel condenser receiving station light source sends becomes the area source (20cm × 20cm) of high brightness, the high depth of parallelism, and then irradiates observation visual field (20cm × 20cm × 20cm).
The collection of acquisition system primary responsibility image, the acceptance of trigger pip, the transmission etc. of image.This system is composed as follows: two German BASLER acA 1600-20gm cameras, RJ45 gigabit network interface water joint, four-core water joint, projection screen, direct supply, acquisition module shell and related accessory.Wherein, two CCD industrial camera resolution are 1624pixels × 1234pixels; Projection screen is canescence, and adopt the PVC material of high light transmittance to make, thickness is 0.55mm, and angle of visibility reaches 180 °, and gain coefficient is 2.0, and light transmissibility is extremely strong, is enough to the sharpness ensureing picture.
Projection screen adopts special PVC material (U.S. produces tygon and applies rear-projection Screen Cloth) to make, and curtain thickness is 0.55mm, and visible angle reaches 180 degree, and gain coefficient is 2.0 times, ensure that the sharpness of picture.The leading indicator of this curtain: (1) gain beta τ >=5-0.6; (2) effective °-110 °, scattering angle 2 α τ >=30; (3) aggregative index κ τ=60-116; (4) curtain face requires do not have speck; (5) curtain face resolving power 60-80 line right/mm feature.
Raindrop can imaging on projection screen by the moment of observation visual field, and camera is observed in the behind of curtain.The circular target of a circle black is laid at projection screen edge, and being in order to calibration camera on the one hand, is for the correction of post-digital image provides standard on the other hand.The order of acquisition system and the transmission of data all adopt TCP/IP procotol, synchronous triggering, kilomega network hardware interface to build.
Gather synchronous control system to be used for managing image collecting module, be responsible for the order transmitting-receiving, management, the transmission of high-level efficiency data etc. of image collection computing machine.Gather synchronization control module to be made up of D-Link gigabit five-port switch, synchronous trigger board, four-core Aviation Connector, serial ports conversion equipment, collection synchronization control module shell and related accessory.D-Link gigabit five-port switch is used for the high-speed transfer of digitized video, the high telecommunication management of low speed camera and the association of main control computer; Synchronous trigger board is responsible for the power supply, serial ports synchronizing signal order transmitting-receiving, acquisition frame rate control etc. of high low speed camera.In gatherer process, operating personnel link digitized video acquisition module and image collection computer for controlling accordingly, coordinate optical projection system and image acquisition system can carry out the observation of raindrop physical characteristics.
Embodiment 2:
(1) test design and statistical study
Within on September 20th, 2014, utilize the system acquisition raindrop image of embodiment 1 the 14:00-15:00 time period in the afternoon, terminate to carry out omnidistance digitized video collection to rainfall from rainfall, collect 4327 two field pictures altogether, the wherein effective raindrop image of 779 width, the complete acquisition probability that therefore raindrop are right is 18.0%.High speed camera and low speed collected by camera frame per second are 20 frame s
-1, the time shutter is respectively 1/4000s and 1/500s.
Observe in the image obtained and comprise raindrop information and noise information, illumination is lower, as shown in Fig. 3 (a), and the appearance of raindrop in observation visual field is random, therefore inventor is considered as stochastic variable the image greyscale of raindrop, in a long time sequence, explore the statistical nature of this variable, that finally determines this pixel intensity is distributed as normal distribution.On this basis, calculate each pixel in image space and, along the statistical parameter of time shaft, then assess its probability occurred, if the probability distribution of pixel intensity is outside three times of fiducial intervals (99%) with statistical parameter, then be considered as raindrop image, otherwise be background video.Detect raindrop image by statistical filtering to highlight, the raindrop image after statistical filtering is as shown in Fig. 3 (b).
The distribution spatially of discrete noise is random, as long as a therefore random sequence difference locus in arrangement, their similarity just declines rapidly.Utilize this characteristic, the imaging results that statistical filtering obtains is carried out left and right rolling line by line along transverse axis, the image after rolling is multiplied with raw video.Now for a line image sequence on transverse axis to the right, 1 rolling operation left, process and the result of rolling filtering are described.
With pending image wherein one behavior example, suppose that R is the sequence containing raindrop and noise point, wherein 5-9 position is raindrop pixel bit, all the other be 1 continuous flag figure place be less than 5 be noise pixel bit, in sequence, 0 represents background pixel position.R sequence is done to the computing of rolling and rolling to the right left:
R＝1010111110010000110100010
Obtain after the right rolling of R:
R
1＝0101011111001000011010001
R obtains after rolling left and moving:
R
2=0101111100100001101000101R is multiplied by R
1obtain RR as follows:
RR＝R*R
1＝0000011110000000010000000
R is multiplied by R
2obtain RL as follows:
RL＝R*R
2＝0000111100000000100000000
RL and RR carries out logical OR computing and obtains RES
1, to recover the original shape and structure of raindrop, RES
1as follows:
RES
1＝RL|RR＝0000111110000000110000000
The raindrop resolution of this embodiment is 5 pixel bit, if be less than 5 pixel bit, be considered as noise, in order to eliminate isolated noise pixel bit as far as possible, retain raindrop pixel bit, aforesaid operations need carry out the image after 5 rolling filtering process continuously as shown in Fig. 3 (c), and described carrying out continuously refers to RES for 5 times
1for new handling object, obtain RES2 after carrying out aforesaid operations process, obtain RES by that analogy
2, RES
3, RES
4, RES
5, Fig. 3 (c) is depicted as RES
5.In order to eliminate isolated noise pixel bit as far as possible, retain raindrop pixel bit, the raindrop resolution of this embodiment is 5 pixel bit, RES
5if in be less than 5 pixel bit (namely value is that the number of the continuous image vegetarian refreshments of 1 is less than 5); be considered as noise.
Image after above-mentioned filtering process, overall binarization method is adopted to delineate the raindrop image of binaryzation, namely the threshold value that setting one is overall, in this embodiment, threshold value arranges 28-32, the pixel value of the pixel group being greater than this threshold value is set as white, and the pixel value being less than the pixel group of this threshold value is set as black.On this basis, utilize " convex closure problem " algorithm, travel through whole raindrop imagery zone, compare by pixel, finally obtain the raindrop image of binaryzation, as shown in Fig. 3 (d).
Data acquisition SPSS software carries out statistical study, utilizes SigmaPlot software to chart.The foundation of mathematical model and the concrete steps of inspection are: 646 raindrop measurement results sorted by raindrop diameter size, and be divided into two data samples by odd even numbering, modeling and test samples can be made like this can to cover the dynamic range of raindrop diameter change, improve model prediction accuracy.Wherein odd number is used for opening relationships, and even numbers is used as Sample.Raindrop landing end speed and raindrop diameter adopt linear fit, and with the raindrop landing end speed data detection forecast model of actual measurement, calculate mean square deviation (root mean squared error, RMSE), precision of prediction (prediction accuracy, PA) valuation prediction models is carried out with relative error (relative error, RE).Above-mentioned parameter computing formula is as follows:
X in formula
i-the analogue value
-measured value
The average of mean-simulated items
(2) raindrop physical characteristics Parameter analysis
Table 1 gives the statistical nature of raindrop diameter and landing end speed.As can be seen from Table 1, raindrop distribution is based on median particle, namely the raindrop of diameter within the scope of 1.0-3.0mm account for 86.53% of total sample number, and small rain droplets (diameter <1.0mm) and large raindrop (diameter >3.0mm) account for 7.74% and 5.73% of total sample number respectively.Raindrop diameter fluctuation range is 0.31-4.03mm, and average is 2.00mm, and its coefficient of variation is 1.33%.Raindrop landing end speed fluctuation range is 0.05-8.03ms
-1, average is 3.52ms
-1, the coefficient of variation is 2.10%.
The descriptive statistic of table 1 raindrop diameter and landing end speed
Raindrop landing end speed is along with the increase of raindrop diameter is in linearly increasing trend (R significantly
2=0.8585, P<0.001)).Obtain speed empirical relationship after carrying out linear fit and see formula (4).The scope of application of this empirical equation is 0.31mm<D<4.03mm, all inapplicable for this equation of less or larger raindrop.
V=2.5746D-1.6443 (R
2=0.8585, P<0.001) V-raindrop landing end speed (ms in (4) formula
-1)
D-raindrop diameter (mm)
The speed that matching obtains is slightly less than Altas (V=9.65-10.3e
(-0.6D)) and Brandes (V=-0.1021+4.932D-0.9551D
2+ 0.07934D
3-0.002362D
4) speed that obtains of empirical relationship matching.Based on the raindrop diameter value of 323 test samples of actual measurement, regression equation (4) is utilized to calculate corresponding raindrop landing end speed, then regretional analysis is carried out with measured value, can find out, the slope of the raindrop landing measured value of end speed and the equation of linear regression of the analogue value, up to 0.88, shows that measured value and predicted value are comparatively identical.Raindrop diameter is respectively 82.96% and 27.07% to the precision of prediction of raindrop landing end speed and relative error.
Comparative example:
In order to detect precision and the accuracy of raindrop physical characteristics observation procedure, this embodiment has carried out the unrestrained experiment of steel ball.Experiment employing diameter is 3 kinds of spherical steel balls of standard of 2.0mm, 2.5mm and 3.0mm, sentencing initial velocity in distance scope 1.70m, 2.45m and 3.00m height (h) is respectively zero to trickle down, the steel ball of often kind of specification goes up repetition 3 times at various height, observation steel ball diameter in various situations and falling speed.Due to steel ball be with initial velocity be zero trickle down, be freely falling body depending on steel ball, its at any one time theory landing end speed
The result of the actual diameter of steel ball, theoretical landing end speed and particle imaging measuring method be analyzed (table 2), result shows that diameter of the steel ball relative error fluctuation range is 1.32-6.36%, and average is 3.71%; Steel ball landing end speed relative error maximal value is 9.65%, and minimum value is 0.28%, and average is 2.83%.In addition, inventor has carried out diameter and the analysis of frequency distribution of speed relative error to steel ball sample, find that the relative error of most of Sample diameter and speed is less, detect in sample at 3555, there is the relative error of 2756 Sample diameter below 10%, account for 78% of total sample number, have the sample of 84% simultaneously, its landing end speed relative error <5%.Above result shows, the prediction accuracy of this measuring method to test samples data reaches higher level, can observe the raindrop physical characteristics in rainfall accurately.
The observation of table 2 material object contrasts with particle imaging measurement result
Measured value: means standard deviation; Relative error: 100% × | measured value-actual value |/actual value
The relative error average of diameter of the steel ball is 3.71%, and wherein the sample number of relative error below 10% accounts for 78% of total sample number; The relative error average of steel ball landing end speed is 2.83%, and the sample number of relative error below 5% accounts for 84% (Fig. 5) of total sample number.This result shows that particle imaging measuring technique observational error is less, and it can observe raindrop physical characteristics parameter effectively, fast, economically.
Claims (10)
1. a raindrop physical characteristics observation procedure, is characterized in that, method comprises:
(1) utilize the first image acquisition device and the second image acquisition device to gather same rainfall scene, multiframe image in the same time period, the time shutter of described first image acquisition device is shorter than the time shutter of the second image acquisition device;
(2) geometric correction process is carried out to the image that the first image acquisition device and the second image acquisition device gather, make all images of step (1) gained be positioned at the same coordinate system;
(3) statistical filtering process is carried out to all images after step (2) process, the image containing raindrop is highlighted;
(4) image obtained step (3) carries out rolling filtering process:
If background pixel value is 0 in current pending image frame R, wait to judge that pixel value is 1; Then,
1. the pixel column of the right side edge being positioned at current pending image frame is moved on to the left side edge of current pending image frame, obtain right rolling image frame R
1;
2. the pixel column of the left side edge being positioned at current pending image frame is moved on to the right side edge of current pending image frame, obtain the dynamic image frame R that rolls left
2;
3. R*R is tried to achieve
1with R*R
2or operation values RES
1;
RES
1for the rolling filtering image of current pending image frame, or, to RES
(n-1)carrying out step 1. to 3. processing, obtaining RES
n, n be more than or equal to 2 natural number, RES
nfor the rolling filtering image of current pending image frame.
(5) binary conversion treatment is carried out to the image after step (4) process, obtain raindrop image;
(6) the raindrop image of foundation the first image acquisition device collection calculates the raindrop diameter of each raindrop in every width image; The raindrop image of foundation the first image acquisition device and the second image acquisition device collection calculates the raindrop landing end speed of each raindrop;
Described raindrop diameter is the geometric mean of the Second bobbin diameter that raindrop image maximum gauge is vertical with maximum gauge;
Described raindrop landing end speed is under synchronization, in the raindrop image of the second image acquisition device collection, to deduct the difference of diameter of raindrop B in the raindrop image that the first image acquisition device gathers poor divided by the time shutter of the first image acquisition device and the second image acquisition device for the diameter of the hangover image of raindrop A, and the raindrop image center of gravity of described raindrop B is arranged in the raindrop image of raindrop A.
2. raindrop physical characteristics observation procedure as claimed in claim 1, it is characterized in that, the acquisition frame rate of described first image acquisition device and the second image acquisition device is 20 frame s
-1, the first image acquisition device time shutter was 1/4000s, and the second image acquisition device time shutter was 1/500s.
3. raindrop physical characteristics observation procedure as claimed in claim 1, it is characterized in that, step (2) take target as reference, carries out geometric correction process to the image that the first image acquisition device and the second image acquisition device gather.
4. raindrop physical characteristics observation procedure as claimed in claim 1, is characterized in that, in step (5), the threshold value of binaryzation filtering process is 28-32.
5. raindrop physical characteristics observation procedure as claimed in claim 1, is characterized in that, in described step (6), raindrop diameter is the maximum gauge of raindrop image; Or be the geometrical mean of each pixel and raindrop centroidal distance on raindrop image outer contour, or be the arithmetic average of each pixel and raindrop centroidal distance on raindrop image outer contour; Or be the equivalent diameter of a circle that raindrop image is corresponding.
6. a raindrop physical characteristics observation device, it is characterized in that, device comprises: directional light generating means, projection screen and image acquisition device, described image acquisition device comprises the first image acquisition device and the second image acquisition device, and the time shutter of described first image acquisition device is shorter than the time shutter of the second image acquisition device; For to observe visual field between described directional light generating means and projection screen; Directional light irradiates the whereabouts raindrop in observation visual field, and described projection screen is formed raindrop projection, and image acquisition device gathers raindrop projection.
7. raindrop physical characteristics observation device as claimed in claim 6, it is characterized in that, described directional light generating means comprises light source and Fresnel Lenses, and the light that light source sends generates directional light after Fresnel Lenses.
8. raindrop physical characteristics observation device as claimed in claim 6, it is characterized in that, described light source is halogen pointolite.
9. raindrop physical characteristics observation device as claimed in claim 6, it is characterized in that, described device also comprises target, and described target is the circular pattern be located on curtain.
10. raindrop physical characteristics observation device as claimed in claim 6, it is characterized in that, described directional light generating means is arranged in a waterproof case, and described projection screen and image acquisition device are arranged in a waterproof case.
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