CN104359417B - Elliptical speckle generation method for large-viewing-field large-dip-angle measurement - Google Patents
Elliptical speckle generation method for large-viewing-field large-dip-angle measurement Download PDFInfo
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- CN104359417B CN104359417B CN201410647293.2A CN201410647293A CN104359417B CN 104359417 B CN104359417 B CN 104359417B CN 201410647293 A CN201410647293 A CN 201410647293A CN 104359417 B CN104359417 B CN 104359417B
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Abstract
The invention discloses an elliptical speckle generation method for large-viewing-field large-dip-angle measurement. The method includes the following steps that firstly, the size of each elliptical speckle area in a shot image is estimated according to the size of an image sub-area related to a measuring viewing field, and the density of the elliptical speckle areas in a printing page is determined according to the size of the set printing page and the estimated sizes of the elliptical speckle areas; secondly, according to the sizes of the elliptical speckle areas in the horizontal direction, long axis length is generated for each elliptical speckle randomly, and short axis length of each elliptical speckle is determined according to the included angle between a camera optical axis and the normal of the measured surface; thirdly, according to the sizes of the elliptical speckle areas and the long and short axis sizes of the elliptical speckles, the coordinates of an ellipse center pint are generated randomly for each elliptical speckle; fourthly, according to the coordinates of the center point, the long and short axis lengths and density of each elliptical speckle, an electronic speckle pattern corresponding to a speckle pattern coated on the measured surface is generated on the printing page.
Description
Technical field
The present invention relates to contactless deformation measurement field and in particular to a kind of for big visual field high inclination-angle measurement ellipse
Speckle generation method.
Background technology
In to testee surface displacement deformation isoparametric measurement related using digital picture, it is right that speckle pattern is used for
The coupling of measured surface feature and positioning, therefore, generate the premise bar that the good speckle pattern of recognition effect is whole measurement process
Part.
The speckle used in loading by means of digital image correlation method is to be made by the paint chequered with black and white in the injection of testee surface
Out.For large aircraft, because wing breadth is big, the visual field that therefore camera shoots is also larger, and this is for speckle pattern
Case proposes new requirement, that is, need, in the case of big visual field, to remain able to reflect the grey scale change of aerofoil surface.At this
In the case of kind, the method for the chequered with black and white speckle pattern of traditional direct spraying is inadvisable, and this method generates and preparation
Speckle is too little compared with measurement breadth, is displayed without the feature of speckle on image.Can not reflect when larger field
The grey scale change of aerofoil surface.
Spy is generated it is therefore desirable to pass through to calculate according to visual field and inclination angle in the environment of big visual field high inclination-angle is in due to camera
Sizing and the speckle pattern of shape, in order to mark point recognition and interpretation.Position according to camera arrangement and measured object chi
Very little information, index point and speckle is designed ovalisation according to a certain percentage, is relatively beneficial to follow-up accurately mate.
Content of the invention
In order to overcome the shortcomings of that traditional speckle measures on the high inclination-angle of camera big visual field, the invention provides a kind of for big
The speckle generation method of visual field high inclination-angle, can be efficiently completed the calculating of digital picture under this specific environment.
For reaching object above, the present invention employs the following technical solutions and is achieved：
A kind of oval speckle generation method for the measurement of big visual field high inclination-angle, comprises the following steps：
The first step, each the oval speckle regions of image subsection magnitude estimation according to being associated with measurement visual field size are being clapped
Take the photograph the size in image, and the size according to the printer page setting and the oval speckle regions size estimated determine oval dissipating
Density in printer page for the spot region；
Second step, according to oval speckle regions size in the horizontal direction, generates major axis at random for each oval speckle
Length, and the minor axis length of oval speckle is determined according to the angle between camera optical axis and tested surface normal；
The length shaft size of the 3rd step, the size according to oval speckle regions and each oval speckle, dissipates for each ellipse
Spot generates the coordinate of elliptical center point at random；
4th step, according to the center point coordinate of each oval speckle, length shaft length and speckle density, in printer page
Generate the electronic speckle pattern corresponding with the speckle pattern that will spray to measured surface.
The present invention proposes big visual field high inclination-angle measurement speckle preparation method it is adaptable to using number under high inclination-angle measuring environment
The related situation to testee Surface Creation speckle of word image, has advantages below：(1) can be big according to measurement breadth
Little, by being calculated suitable speckle size and distribution density；(2) because this method generates view picture speckle image, with tradition
Small breadth speckle spraying compare, on tested surface the geomery of speckle be easier control, speckle finely make digital picture
The precision of identification and coupling improves.
Brief description
Fig. 1 is the diagram of 1: 10 measurement model；
Fig. 2 is the flow chart of the speckle generation method according to embodiments of the invention for big visual field high inclination-angle；
Fig. 3 is the schematic diagram of camera imaging rule；
Fig. 4 is the schematic diagram of the imaging angle according to embodiments of the invention and oval Size calculation；
Fig. 5 is the schematic diagram determining elliptical center point coordinate in the x direction in oval speckle regions；
Fig. 6 (a) is the schematic diagram of the speckle of different ovalitys and density；
Fig. 6 (b) is the oval speckle elongating design；
Fig. 7 is that true wing paint and bushing are sprayed with the simulation design sketch after speckle.
Specific embodiment
Below in conjunction with accompanying drawing, embodiments of the present invention is described in detail.
In the present embodiment, as the typical application scenarios of big visual field high inclination-angle, measured with the dynamic deformation of certain big aircraft
Illustrate as a example process.Measurement obtains the size of aircraft：50 meters of the span, 47 meters of captain, machine is high 15 meters, leading edge sweep 24
Degree.As shown in figure 1, building 1: 10 half side wing measurement model indoors, wherein wing can be simulated using plastic plate, and can
To simulate wing deformation using irregularly waving.Because the measurement breadth of the present embodiment is larger, so for small breadth application
Traditional speckle of occasion is no longer applicable.In the present embodiment, elliptical speckles can be adopted.
As shown in Fig. 2 being used for the oval speckle generation method of big visual field high inclination-angle measurement according to an embodiment of the invention,
Comprise the following steps：
The first step, each the oval speckle regions of image subsection magnitude estimation according to being associated with measurement visual field size are being clapped
Take the photograph the size in image, and the size according to the printer page setting and the oval speckle regions size estimated determine oval dissipating
Density in printer page for the spot region.
Specifically, following sub-step can be included：
(1) pixel size that each oval speckle regions takies in the picture is determined according to image subsection size；
(2) the rectangle chi that oval speckle regions take is determined according to each pixel corresponding actual size during camera imaging
Very little；
(3) rectangular dimension of the size according to the printer page setting and oval speckle regions occupancy determines oval speckle area
Density in printer page for the domain.
Image subsection size can be the image subsection size of digital picture selection when carrying out correlation computations, and, can
To envision, image subsection is divided into size identical rectangular area one by one, each oval speckle is just arranged in such a
In rectangular area, that is, so-called " oval speckle regions ".Taking x direction (horizontal direction) as a example it is assumed that image subsection is 30*30 pixel
Size, if x direction comprises 4 oval speckle regions in image subsection, each oval speckle regions is in the x of this image subsection
7 pixels are accounted on direction.
As shown in figure 3, (unless otherwise stated, the unit acquiescence of each variable according to camera imaging rule, can be calculated as follows
For mm)：
Assume camera CCD chip a size of a*b, camera resolution is k pixel * l pixel, lens focus are f, shooting distance
For L, then shooting breadth under this shooting distance for this camera is：
Single pixel in the corresponding actual size in x direction is：
Because oval speckle regions account for 7 pixels in x direction, so oval speckle regions are in x direction
A size of 7*m.If the printer page size selecting is w*h, then the density in x direction for the oval speckle regions is：
Process on y direction is similar with x direction, repeats no more.
Second step, according to oval speckle regions size in the horizontal direction, generates major axis at random for each oval speckle
Length, and the minor axis length of oval speckle is determined according to the angle between camera optical axis and tested surface normal.
Wherein, the size (i.e. the length of transverse) in x direction for each oval speckle is random generates, and is beneficial to the later stage and makes
With during images match.But, this size can not be too small, otherwise can make to occur larger blank between adjacent speckle
Region, and make the overall speckle pattern printing inharmonious, it is unfavorable for image procossing；Meanwhile, nor too big, otherwise
The oval speckle in adjacent rectangle region can be made to occur overlapping.In one example, can be by the length of oval speckle major axis
It is set as random value between 0.5-1 times of described ellipse speckle regions size in the horizontal direction.
As shown in figure 4, when the angle of camera and camera optical axis and measured surface normal direction is θ, size r on x direction is (i.e.
Oval major axis) it is not changed in, and the size (i.e. oval short axle) on y direction is r*cos θ.That is, the length of ellipse
Axis scale is to be determined by the angle of camera optical axis and measured surface normal direction.
The length shaft size of the 3rd step, the size according to oval speckle regions and each oval speckle, dissipates for each ellipse
Spot generates the coordinate of elliptical center point at random.
The speckle of aerofoil surface mainly contains density and two parameters of ovality, and its Midst density is used for describing printer page
In speckle number, ovality namely major and minor axis ratio.In addition to density and ovality, cloth in printer page for the oval speckle
Office is also affected by elliptical center point position.Therefore, oval speckle to be drawn, except according to the random ellipse generating of preceding step
Speckle major and minor axis are in addition it is also necessary to determine the coordinate of speckle central point so that the oval speckle generating is seated in currently oval speckle area
In domain, in order to avoid overlapping with other speckles.
As shown in figure 5, the determination of oval speckle central point is also random.Still taking x direction as a example, if m-th on x direction
The major semiaxis size of speckle is b1, a width of 2b of the rectangular area that speckle is located, then the x at the center of this m-th oval speckle sits
It is marked on (m-1) * 2b+b1(m+1) * 2b-b1Between random value.In the same manner it may be determined that the center of this oval speckle is in y direction
On coordinate.
4th step, according to the center point coordinate of each oval speckle, length shaft length and speckle density, in printer page
Generate the electronic speckle pattern corresponding with the speckle pattern that will spray to measured surface.
The distribution situation of speckle in printer page, the speckle pattern of different densities and ovality can be checked in preview region
As shown in Fig. 6 (a).In actual applications, density and two parameters of ovality can also be changed.A kind of ellipse elongating design dissipates
Shown in spot such as Fig. 6 (b).
Generate the step after electronic speckle pattern, can include：Processed for speckle leakage based on this speckle electronics pattern
The bushing of print；Carry out paint spraying using this bushing in measured surface to prepare required speckle.Below it is briefly described.
The speckle electronics pattern generating can save as file, such as PS file.This document can also be converted into PDF lattice
Formula, carries out data transfer to facilitate.This file is sent to machining center to manufacture bushing.Target speckle with white background stain
As a example, take size, thickness, hardness suitable non-black sheet plastic to be processing object, by speckle oval on electronics pattern pair
Should cut away in the region in mould plate.Special material and ink-jet can also be chosen, after speckle pattern completes to print, due to chemistry
Speckle regions are corroded into sky by reaction automatically.In the application scenarios of the present embodiment, as simulated experiment, can will print
Cardboard is directly considered as having sprayed the wing of speckle.Fig. 7 is that true wing paint and bushing are sprayed with the simulation after speckle
Effect.In actual measurement, camera, after the demarcation of ground, sprays speckle pattern using bushing on aircraft wing, fuselage, empennage
Case.Speckle due to printing is white background stain, so first covering one layer of uniformly white dumb light paint in tested region, then covers
Bushing, is painted at the hole of bushing with black matte paint.
Above content is to further describe it is impossible to assert with reference to specific preferred embodiment is made for the present invention
The specific embodiment of the present invention is only limitted to this, for general technical staff of the technical field of the invention, is not taking off
On the premise of present inventive concept, some simple deduction or replace can also be made, all should be considered as belonging to the present invention by institute
The scope of patent protection that the claims submitted to determine.
Claims (5)
1. a kind of oval speckle generation method for the measurement of big visual field high inclination-angle, comprises the following steps：
The first step, according to each the oval speckle regions of image subsection magnitude estimation being associated with measurement visual field size in shooting figure
As in size, and the size in shooting image according to the size of printer page setting and the oval speckle regions estimated
Determine oval density in printer page for the speckle regions；
Second step, according to oval speckle regions size in the horizontal direction, generates long axis length at random for each oval speckle,
And the minor axis length of oval speckle is determined according to the angle between camera optical axis and tested surface normal；
The length shaft size of the 3rd step, the size according to oval speckle regions and each oval speckle, for each oval speckle with
Machine generates the coordinate of elliptical center point；
4th step, according to the center point coordinate of each oval speckle, length shaft length and speckle density, generates in printer page
The electronic speckle pattern corresponding with the speckle pattern that will spray to measured surface.
2. generation method as claimed in claim 1 is in the first step, big according to the image subsection being associated with measurement visual field size
The little step estimating each size in shooting image for the oval speckle regions includes：
(1) pixel size that each oval speckle regions takies in the picture is determined according to image subsection size；
(2) rectangular dimension that oval speckle regions take is determined according to each pixel corresponding actual size during camera imaging.
3. generation method as claimed in claim 1, in second step, according to oval speckle regions size in the horizontal direction,
Generate long axis length at random for each oval speckle to include：The length of oval speckle major axis is set as in described ellipse speckle area
Random value between 0.5-1 times of domain size in the horizontal direction.
4. generation method as claimed in claim 1, in second step, true according to the angle between camera optical axis and tested surface normal
The minor axis length of fixed ellipse speckle is specially：If the major axis of ellipse is r, camera optical axis are θ with the angle of tested surface normal, then ellipse
The short axle of circle is r*cos θ.
5. generation method as claimed in claim 1, wherein, the 3rd step includes：
If the major semiaxis size of m-th speckle is b on x direction1, speckle be located rectangular area a width of 2b, then this m-th ellipse
The x coordinate at the center of circle speckle is in (m-1) * 2b+b1(m+1) * 2b-b1Between random value.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106610279A (en) * | 2015-10-27 | 2017-05-03 | 中国飞行试验研究院 | Digital photogrammetry method under large inclination angle |
| CN107270818B (en) * | 2017-06-05 | 2019-04-09 | 南京大学 | A method of utilizing monitoring CCD the real time measure laser probe and plane of illumination spacing walk-off angle degree |
| CN109458943B (en) * | 2018-11-07 | 2020-11-06 | 中国电子科技集团公司第三十八研究所 | DIC technology random speckle generation method |
| CN111951151B (en) * | 2020-07-24 | 2022-09-06 | 南京理工大学 | Speckle pattern headgear design method for three-dimensional human head model measurement |
| CN112200203B (en) * | 2020-11-04 | 2022-04-05 | 西安交通大学 | Matching method of weak correlation speckle images in oblique field of view |
| CN113188453B (en) * | 2021-04-30 | 2022-11-01 | 东北电力大学 | Speckle generating device for film structure non-contact displacement and strain measurement |
| CN113446999A (en) * | 2021-06-30 | 2021-09-28 | 同济大学 | Networking construction method of high-speed video measurement system |
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