CN101726257B - Multiple eye large range laser scanning measurement method - Google Patents

Abstract

The invention discloses a multiple large range laser scanning measurement method. The method uses multiple cameras which are arranged along the scanning line direction to perform stage imaging to a light knife and increases the total range of the field of vision by increasing the number of the cameras, thus achieving the aim of increasing the scanning efficiency. The length of the laser projecting line is increased correspondingly while the field of vision of cameras is increased so that the length of the light knife used for laser scanning can satisfy the demand of the field of vision for the multiple cameras. The method of the invention can be used to increase the efficiency of the laser scanning in multiple on the basis of not reducing the measurement accuracy.

Description

Multiple large range laser scanning measurement method

Technical field

The present invention relates to the method for laser scanning measurement three-D profile size, particularly a kind of method of utilizing multiple large range laser scanning to measure overall size.

Background technology

Along with the deep development of extremely manufacturing technology, the measuring technique under the extreme condition is also arisen at the historic moment.In manufacturing, assembling and the testing process of large-scale and ultra-large type mechanized equipment, the measurement of its physical dimension and morpheme error is the key factor that guarantees the equipment set quality.At present, mainly still be based on the measurement of coordinates technology such as large scale geometric measurements such as airframe, steamer hull, railroad cars.Under this measuring condition, the rational and effective terminal measuring method is the key point of system with device.

Its principal mode of currently used measuring terminals has a trigger-type, optical grating projection formula and laser scan type etc.With respect to length is several meters even tens meters the large scale and the measured workpiece of oversize, and its relative accuracy is had relatively high expectations, but the absolute precision requirement is very not high, thereby efficiency of measurement then seems very important.The point trigger-type is owing to only survey a point at every turn, though its precision is higher, efficient is too low; Optical grating projection formula efficient is higher relatively, but owing to be remote optical imagery, is measured environmental impact, and its measuring accuracy is lower, and is difficult in practice use; The laser scanning methods kind is more, and a scan-type, monochromatic light cutter scan-type, parallel many finishing tools scan-type and cross finishing tool scan-type are arranged at present.The measuring principle that laser scanning is adopted generally is the optical triangulation principle, promptly determine on the measured workpiece contour surface each point with respect to the end coordinates information of measuring terminals, obtain on the measured workpiece profile each point with respect to the positional information in global measuring space according to measuring terminals with respect to the position in global measuring space and attitude again by the geometric relationship between eye point, subpoint and the imaging three.

The laser projections light beam is a Line beam in the spot scan mode, forms a point when projecting on the workpiece profile, and this some imaging on video camera also can only become a point, and promptly each sampling can only be surveyed a point, and obviously efficient is too low.The laser projections light beam is a planar light beam in the monochromatic light cutter scan-type, projection forms straight line or curve on workpiece, and imaging also is a line on video camera, so be referred to as line sweep, owing to be imaged as a line, at every turn so its efficiency of measurement improves greatly than spot scan formula.If adopt a number on the every line is N, then its sampling efficiency has improved N doubly than some triggering and spot scan formula, but influenced by the camera field of view scope, and the incident line of scanning finishing tool is limited by the scope of video camera imaging, even finishing tool is long again, also can only use the local segment of finishing tool to carry out imaging.In order effectively to utilize the visual field of video camera, can adopt a plurality of finishing tool parallel sweeps, or the scanning of right-angled intersection finishing tool.The former utilizes one group of laser instrument projection parallel beam above measured workpiece, forms the imaging simultaneously of a plurality of finishing tools and measures simultaneously.In principle, owing to there is multi-stripe laser information, therefore every width of cloth image can be handled out the cross section profile information of a plurality of positions in every width of cloth measurement image, reaches the effect of measuring at a high speed with this.But because the spacing distance between its finishing tool is very little, there is uncertainty under certain conditions in the accurate identification of different finishing tools, and the efficient of its fractional scanning can not be brought up to the multiple of finishing tool number.Its inswept width of right-angled intersection finishing tool is identical with the monochromatic light cutter, with regard to its efficiency of measurement, is the same with the monochromatic light cutter.

Summary of the invention

The present invention is on the basis of further investigation laser scanning measurement technology, in conjunction with the characteristics that the measured workpiece stock size is very big and surface curvature is bigger in large scale and the oversize measurement, propose a kind of many orders and made up the method for laser scanning measurement on a large scale, can on the basis that does not reduce measuring accuracy, increase the efficient of laser scanning exponentially.

For reaching above purpose, the present invention takes following technical scheme to be achieved:

A kind of multiple large range laser scanning measurement method comprises the steps:

(1) adopt a kind of measuring terminals, comprise framework, a side is provided with a laser light knife projector on this framework, is used for to workpiece projection plane light beam, and forms the long incident line on workpiece; Opposite side is provided with many orders digital camera on this framework, equidistantly arranges along long incident line direction, is used for the incident line is segmented into picture; Be provided with realtime graphic handles and the Communication Control center in this framework midfield, be used for the image-forming information of many orders digital camera is handled in real time, obtaining the coordinate information of the some cloud of workpiece profile on the incident line with respect to measuring terminals, and and the global calculation machine between operate synchronously and information passes mutually; Be provided with a plurality of hand-held mode location and attitude monitoring device around on framework, below framework, be provided with the airborne pattern retaining thread that is connected with the coordinate machine;

(2) terminal scanning is measured and is demarcated and the demarcation of terminal location attitude, wherein, under airborne pattern, the position T (X of terminal _T, Y _T, Z _T) and attitude R (α, beta, gamma) demarcate and to obtain by three coordinate measuring machine; Under hand-held mode, location on the terminal and attitude monitoring device only use as the target of host computer, and its position and attitude information are provided by host computer; Terminal scanning is measured and is demarcated, and then uses the virtual grid reflection method to demarcate;

(3) on the measuring workpieces surface finishing tool line arbitrfary point P with respect to the coordinate of measuring terminals.

If the optical center of video camera is the A point, the camera image sensor position is at the C point, laser projecting apparatus is at the B point, the perpendicular bisector of AB straight line is OD, vertical surface of the work, the intersection point of laser beam and camera optical axis is positioned on the perpendicular bisector OD, therefore, with the measuring terminals is that its X-axis of coordinate system that benchmark is set up is the DB direction, the Z axle is the DO direction, and Y-axis is the orientation of many orders digital camera then, and establishing AB length is c, the angle of laser beam and optical axis and AB is all β, the intersection point of surface of the work and laser beam is P, and the imaging point of P point on imageing sensor is P ', and P ' is s apart from the displacement that the optical axis center point O ' on the imageing sensor puts, and the focal length of camera lens is f, can get the coordinate position P of P point with respect to measuring terminals thus _C(X _C, Y _C, Z _C), its value is:

$X_C=c\·(\frac{\mathrm{Cos}\left(\mathrm{\α}\right)\mathrm{Sin}\left(\mathrm{\β}\right)}{\mathrm{Sin}(\mathrm{\α}+\mathrm{\β})}-0.5)$

$Z_C=c\·\frac{\mathrm{Sin}\left(\mathrm{\α}\right)\mathrm{Sin}\left(\mathrm{\β}\right)}{\mathrm{Sin}(\mathrm{\α}+\mathrm{\β})}$

Wherein:

$\mathrm{\α}=\mathrm{\β}-{\tan }^{-1}\left(\frac{s}{f}\right)$

If the finishing tool line go up a some P image in i (i=0,1,2,3 ...) on the individual camera image sensor, its picture point P ' is v apart from the camera optical axis distance, then the P point with respect to the Y of measuring terminals to coordinate is:

$Y_C=\frac{\mathrm{<figure-callout\; id="4"\; label="ib"\; filenames="H2009102544305E00021.png"\; state="\{\{state\}\}">ib</figure-callout>}}{4}+\frac{\mathrm{vcSin}\left(\mathrm{\&beta;}\right)}{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="H2009102544305E00011.png,H2009102544305E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="H2009102544305E00011.png,H2009102544305E00021.png"\; state="\{\{state\}\}">v</figure-callout>}}^2}\mathrm{Sin}(\mathrm{\&alpha;}+\mathrm{\&beta;})}$

(4) coordinate of arbitrfary point P in the global measuring space on the finishing tool line of measuring workpieces surface.If the coordinate of this P point in the global measuring space is P _G(X _G, Y _G, Z _G), its coordinate in end coordinates system is P _C(X _C, Y _C, Z _C), and the coordinate of measuring terminals in the global measuring space is T (X _T, Y _T, Z _T), attitude angle is R (α, a beta, gamma), then the coordinate of P point in the global measuring space can obtain through rotation and translation with its coordinate in terminal, i.e. P _GCan be expressed as:

$\left[\begin{array}{c}{X}_G\\ Y_G\\ Z_G\end{array}\right]=R\left[\begin{array}{c}{X}_C\\ Y_C\\ Z_C\end{array}\right]+T=\left[\begin{array}{ccc}{r}_0& r_1& r_2\\ r_3& r_4& r_5\\ r_6& r_7& r_8\end{array}\right]\left[\begin{array}{c}{X}_C\\ Y_C\\ Z_C\end{array}\right]+\left[\begin{array}{c}{X}_T\\ Y_T\\ Z_T\end{array}\right]$

Wherein R is a rotation matrix, and it is the trigonometric function combination of attitude angle (α, beta, gamma), and T is a translation vector, is that end coordinates is the position of initial point in global coordinate system, and two data messages are all provided by three coordinate measuring machine.

In the such scheme, described virtual grid reflection method is that measuring terminals is fixed on the three-dimensional automatic measurement machine, the laser light knife of terminal projects on the standard flat, utilize an auxiliary finishing tool and terminal finishing tool to intersect in addition again, drive three-dimensional coordinates measurement terminal finishing tool and auxiliary finishing tool are intersected, then the joining of two finishing tools constitutes a plane grid.

Described many orders digital camera, the time shutter synchronous triggering reaches sweep length b according to expection, and what establish imageing sensor is w as quick peak width, and length is kw, and k is that the Aspect Ratio coefficient generally is about 4/3, and lens focus is f, and then it should satisfy relational expression:

$\frac{w}{f}=\frac{\mathrm{bCos}\left(\mathrm{\&beta;}\right)}{2c}$

If pixel quantity is N on the Width, be kN then in length direction pixel quantity, can calculate theoretical resolution thus and be:

${\mathrm{\&Delta;}}_z=\frac{\mathrm{wl}}{\mathrm{kNf}}\mathrm{Sin}\left(\mathrm{\&beta;}\right)$

${\mathrm{\&Delta;}}_x=\frac{\mathrm{wl}}{\mathrm{kNf}}\mathrm{Cos}\left(\mathrm{\&beta;}\right)$

${\mathrm{\&Delta;}}_y=\frac{\mathrm{<figure-callout\; id="2"\; label="wc"\; filenames="H2009102544305E00011.png,H2009102544305E00021.png"\; state="\{\{state\}\}">wc</figure-callout>}}{2\mathrm{NfCos}\left(\mathrm{\&beta;}\right)}.$

Described many orders digital camera has adopted fixed aperture and electronic shutter and the method for regulating laser light knife brightness guarantees the exposure and the image quality of imaging.

Described laser light knife is handled and the grey scale change of Communication Control center according to the image that is obtained by realtime graphic, and the laser beam intensity of laser projections is suitably regulated.

The present invention uses multi-lens camera jointly a finishing tool to be carried out imaging along the scan-line direction arrangement, by increasing the video camera number, increases the overall field range of video camera, thereby reaches the purpose that improves scan efficiency.When camera field of view increased, the laser projections that correspondingly extends line length was so that the finishing tool length of laser scanning satisfies the visual field needs of multi-lens camera.

Because scanning finishing tool length of the present invention increases, the visual field of laser scanning increases, and adopts multi-lens camera that laser light knife is segmented into picture.Because each video camera is independently to the imaging of laser light knife in the multi-lens camera, its precision is identical with the monocular-camera measurement, in addition, the visual field of each video camera does not diminish yet, and sweep velocity does not reduce yet, therefore, compare with the single camera scan mode, its efficient has obtained significantly improving, and is for improving the especially efficient of oversize measuring three-dimensional profile of large scale, significant.

Large scale equipment such as aircraft, steamer etc., its profile is simple relatively, change of shape is slower, the curvature of the finishing tool curve that forms when therefore laser beam projects on the profile is big and curved transition is slower, this just means to use long finishing tool sweep trace and utilize multi-lens camera to carry out areal survey and is feasible, can form the vision blind area.

The present invention can be applicable to airborne pattern and hand-held mode.Under airborne pattern, can terminal be installed on the coordinate measuring machine by the retaining thread on the terminal, terminal and computing machine close together can directly insert the vision signal of multi-lens camera computing machine and handle generally speaking.Under hand-held mode, general terminal and main frame distance are far away, the transmission distortion of video image is serious, add its bumpy motion under the hand-held mode, many shortcomings of video imaging can not be compensated by obtaining movement velocity, therefore, vision signal must be handled on terminal in real time.Cloud data flow after the processing can significantly reduce, and can upload to host computer with cloud data this moment by wireless telecommunications.Under hand-held mode, the coordinate of cloud data is relative terminal on the measured workpiece, and the position of terminal and attitude change with respect to the global measuring space, therefore, must determine coordinate and the attitude of terminal in the global measuring space, just can cloud data be become the cloud data of global measuring volume coordinate by coordinate conversion.Coordinate conversion needs to dispose on the terminal global space positioning system and determines that its method is to determine with location on the tracking equipment end of scan and attitude monitoring device.

Description of drawings

Fig. 1 is a measuring terminals structural representation of the present invention.

Fig. 2 is a measuring terminals optical triangulation schematic diagram of the present invention.

Fig. 3 is cut apart synoptic diagram for measuring terminals multi-lens camera of the present invention visual field.

Embodiment

1. measuring terminals is formed.

As shown in Figure 1, the multiple large range laser scanning measuring terminals mainly is made up of five parts: the laser light knife projector 5, many heights of eye Accuracy Figure video camera 1, realtime graphic are handled and Communication Control center 3, hand-held mode location and attitude monitoring device 6, airborne pattern retaining thread 7, and the terminal framework is formed.

The function of the laser light knife projector 5 is to throw a planar light beam 4 to workpiece, and the incident line 8 that forms on workpiece is very long, and sweep length is very wide.Four orders (four) digital camera 1 is equidistantly arranged along the incident line 8 directions, and the incident line is segmented into picture, is fully used with the width that guarantees the incident line, thereby improves efficiency of measurement.Realtime graphic is handled with the image-forming information of the 3 pairs four order digital cameras 1 in Communication Control center and is handled in real time, obtaining the coordinate information of the some cloud of workpiece profile on the incident line 8 with respect to measuring terminals, and and the global calculation machine between operate synchronously and information passes mutually.Measuring terminals has two kinds of obtain manners with respect to the position and the attitude in global measuring space: airborne pattern and hand-held mode, under airborne pattern, be connected by the machinery of the retaining thread on the terminal framework 7 and coordinate machine and obtain, under hand-held mode, then obtain by 3 location and attitude monitoring device 6.

2. measuring principle

Fundamental measurement principle of the present invention is the optical triangulation principle.The purpose of measuring is to obtain on the surface of the work each point with respect to the coordinate in global measuring space, because the global space coordinate and the attitude of measuring terminals can be obtained by positioning system, therefore, as long as measure on the surface of the work finishing tool line each point with respect to the coordinate of measuring terminals.

As shown in Figure 2, the optical center of establishing video camera 1 is the A point, and the imageing sensor position is at the C point, and laser projecting apparatus 5 is at the B point.In when scanning, wish that terminal works face and surface of the work try one's best parallelly with anticollision, therefore, should make the perpendicular bisector OD of the AB straight line vertical surface of the work of trying one's best.During design, the intersection point of laser beam and camera optical axis being positioned on the perpendicular bisector OD, therefore, is that its X-axis of coordinate system that benchmark is set up is the DB direction with the measuring terminals, and the Z axle is the DO direction, and Y-axis then is the orientation of many orders digital camera, and initial point is the D point.If AB length is c, the angle of laser beam and optical axis and AB is all β, the intersection point of surface of the work and laser beam is P, and the imaging point of P point on CCD image sensor is P ', P ' is s apart from the displacement that the optical axis center point O ' on the imageing sensor puts, and the focal length of camera lens is f, can get the coordinate position P of P point with respect to measuring terminals thus _C(X _C, Y _C, Z _C), its value is:

$X_C=c\&CenterDot;(\frac{\mathrm{Cos}\left(\mathrm{\&alpha;}\right)\mathrm{Sin}\left(\mathrm{\&beta;}\right)}{\mathrm{Sin}(\mathrm{\&alpha;}+\mathrm{\&beta;})}-0.5)$

$Z_C=c\&CenterDot;\frac{\mathrm{Sin}\left(\mathrm{\&alpha;}\right)\mathrm{Sin}\left(\mathrm{\&beta;}\right)}{\mathrm{Sin}(\mathrm{\&alpha;}+\mathrm{\&beta;})}$

Wherein:

$\mathrm{\&alpha;}=\mathrm{\&beta;}-{\tan }^{-1}\left(\frac{s}{f}\right)$

If the finishing tool line go up a some P image in i (i=0,1,2,3 ...) on the individual camera image sensor, its picture point P ' is v apart from the camera optical axis distance, then the P point with respect to the Y of measuring terminals to coordinate is:

$Y_C=\frac{\mathrm{<figure-callout\; id="4"\; label="ib"\; filenames="H2009102544305E00021.png"\; state="\{\{state\}\}">ib</figure-callout>}}{4}+\frac{\mathrm{vcSin}\left(\mathrm{\&beta;}\right)}{\sqrt{{\mathrm{<figure-callout\; id="2"\; label="f"\; filenames="H2009102544305E00011.png,H2009102544305E00021.png"\; state="\{\{state\}\}">f</figure-callout>}}^2+{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="H2009102544305E00011.png,H2009102544305E00021.png"\; state="\{\{state\}\}">v</figure-callout>}}^2}\mathrm{Sin}(\mathrm{\&alpha;}+\mathrm{\&beta;})}$

It should be noted that Fig. 2,3 is the perspective projection model, its image distance is identical with focal length, and for the lens imaging model, its image distance is greater than focal length.In optical triangulation, because object distance is bigger, image distance is correspondingly smaller, when object distance during much larger than image distance, can think that image distance equals focal length.For the present invention, the object distance scope is about 100mm～300mm, and image distance is about about 10mm, therefore, can think that object distance is far longer than image distance, can be similar to focal length with image distance in formula, and the error that causes thus can compensate correction by system calibrating.

3. ray machine design

Because the measuring principle of this device is based on machine vision metrology, so its optics and physical construction must accurately design.

As shown in Figure 2, because working surface fluctuations and measuring terminals are far and near different at motion process middle distance workpiece, some P is apart from the distance X of measuring terminals _PHave certain variation, its variation range is defined as the measurement depth of field of terminal, and its size is denoted as 2h.Under hand-held mode, because the motion of staff is very not steady, and its custom of different operating personnel is also different, and the depth of field design of terminal must be enough big, to alleviate the requirement to operating personnel.

Reach sweep length b (Fig. 3) according to expection, select suitable imageing sensor and camera lens for use, what establish imageing sensor is w as quick peak width, and length is kw (relatively Chang Yong Aspect Ratio coefficient k is 4/3), and lens focus is f, and then it should satisfy relational expression:

$\frac{w}{f}=\frac{\mathrm{bCos}\left(\mathrm{\&beta;}\right)}{2c}$

If pixel quantity is N on the Width, be kN then in length direction pixel quantity, can calculate theoretical resolution of the present invention thus and be:

${\mathrm{\&Delta;}}_z=\frac{\mathrm{wl}}{\mathrm{kNf}}\mathrm{Sin}\left(\mathrm{\&beta;}\right)$

${\mathrm{\&Delta;}}_x=\frac{\mathrm{wl}}{\mathrm{kNf}}\mathrm{Cos}\left(\mathrm{\&beta;}\right)$

${\mathrm{\&Delta;}}_y=\frac{\mathrm{<figure-callout\; id="2"\; label="wc"\; filenames="H2009102544305E00011.png,H2009102544305E00021.png"\; state="\{\{state\}\}">wc</figure-callout>}}{2\mathrm{NfCos}\left(\mathrm{\&beta;}\right)}.$

Above formula provides is theoretical resolution for design reference, and the precision influence of actual device is also a lot, mainly contains the light integration period, lens aperture, object illumination of video camera etc.

Because scanning survey is motion measurement, during camera light integral time, video camera is in continuous motion, and the image error that causes thus is referred to as smear, and optical-integral-time is long more, and smear is serious more.Under airborne pattern, the influence of smear can reduce even eliminate by guaranteeing machine movement speed stationarity and speed is carried out precision calibration.But when hand-held mode,, can't demarcate compensation precision, therefore, reduce optical-integral-time and be only raising measuring accuracy effective means by speed because movement velocity is not steady.Present camera image sensor, the optical-integral-time of one two field picture mainly are subjected to two factor affecting: the illumination of measured target and the stop opening of camera lens.Illumination is high more, and stop opening is big more, and the time of its light integration can be short more.For the collection of ordinary video image, because object illumination is difficult to adjusting, and aperture is regulated the genus mechanical adjustment, and speed is slower, so the normal change electronic shutter time method that adopts is adjusted exposure, so the electronic shutter time is optical-integral-time.But influenced by the pixel quantity of imageing sensor and the speed of image processor, the short period of the time of its electronic shutter is limited.The present invention determines that the electronic shutter time method is: by calculating visual field size and measuring accuracy, select the imageing sensor of an amount of pixel quantity for use,, determine and fixing electronic shutter time by processor speed experiment, make it reach the shortest, to reduce the influence of image streaking to measuring accuracy.

Lens aperture is regulated and is belonged to mechanical adjustment, and speed is slower, and is easy to wear, and long-time stability are difficult to guarantee, in addition, can cause the video camera depth of field to change after aperture is regulated, thereby range and precision are measured in influence.Therefore the present invention adopts the mode of fixed aperture.Simultaneously, reduce the aperture of aperture as far as possible, can increase the depth of field like this, improve the sharpness of image.

Because lens aperture and electronic shutter have all been fixed, but exposure must be regulated, the present invention uses intensity adjustable laser instrument, and realtime graphic is handled with the Communication Control center and can be changed according to the brightness of the image that is obtained, and the laser beam intensity of laser projections is suitably adjusted.

What must propose is, the video camera time shutter is longer relatively, and the camera motion stationarity is difficult to guarantee, if the moment of each video camera exposure is asynchronous, the time of exposure is unequal, must cause the position of imaging on the imageing sensor not and quality inconsistent.If the time shutter is the longest to be that frame period and video camera frame frequency are 25, then its time shutter is 40ms, and establishing sweep velocity is 10mm/s, then because the asynchronous maximum error that causes of frame can reach 0.4mm.Obviously, such error is difficult to accept for precision measurement.For this reason, the time shutter of each lens camera must carry out synchronously.In the present invention, the time shutter of each lens camera is identical, and exposes synchronously with external trigger.

4. system calibrating

The coordinate of intersection point P in the global measuring space of surface of the work and laser beam is P _G(X _G, Y _G, Z _G), the coordinate in end coordinates system is P _C(X _C, Y _C, Z _C), and the coordinate of measuring terminals in the global measuring space is T (X _T, Y _T, Z _T), attitude angle is R (α, a beta, gamma), and then the coordinate of P point in the overall situation can obtain through rotation and translation with its coordinate in terminal, and promptly PG can be expressed as:

$\left[\begin{array}{c}{X}_G\\ Y_G\\ Z_G\end{array}\right]=R\left[\begin{array}{c}{X}_C\\ Y_C\\ Z_C\end{array}\right]+T=\left[\begin{array}{ccc}{r}_0& r_1& r_2\\ r_3& r_4& r_5\\ r_6& r_7& r_8\end{array}\right]\left[\begin{array}{c}{X}_C\\ Y_C\\ Z_C\end{array}\right]+\left[\begin{array}{c}{X}_T\\ Y_T\\ Z_T\end{array}\right]$

Wherein R is a rotation matrix, and it is the trigonometric function combination of attitude angle (α, beta, gamma).T is a translation vector, is that end coordinates is the position of initial point in global coordinate system.

The measuring accuracy of optics videographic measurment depends primarily on imaging precision, but because the nonlinear quantization error of the optical imaging concept error of videographic measurment, image digitazation and optical system make ideal model and actual conditions differ greatly in the various errors of processing and installation process is produced.In addition, along with the difference of system-operating environment and time, the state of system also can change, and its measuring accuracy also can be affected.Therefore, when measuring accuracy was not high, the ideal model that can directly use in the measuring principle to be given, but for high-acruracy survey, its ideal model can only be as design references, and can not be directly used in the calculating net result.Like this, can only simulate its actual mathematical model accurately by the method for system calibrating, thereby try to achieve accurate measurement result.This shows that system calibrating is the precondition and guarantee that measuring system realizes high-acruracy survey.

System calibrating divides terminal scanning to measure demarcation and the terminal location attitude is demarcated.Under airborne pattern, (for example be installed on the three coordinate measuring machine) location information of terminals T (X _T, Y _T, Z _T) and attitude information R (α, beta, gamma) obtain by global measuring machine (three coordinate measuring machine); Under hand-held mode, location on the terminal and attitude monitoring device only use as the target of host computer, and its position and attitude information are provided by host computer, and therefore, the terminal location attitude is demarcated and is not described in detail in this.It is a lot of that terminal scanning is measured scaling method, and commonly used have calibrated bolck standardization, inclined-plane standardization, standard ball standardization and a grid standardization etc., and the present invention uses the virtual grid mapping calibrating method.Its method is that measuring terminals is fixed on the three-dimensional automatic measurement machine, the laser light knife of terminal projects on the standard flat, utilize an auxiliary finishing tool and terminal finishing tool to intersect in addition again, driving three-dimensional coordinates measurement makes terminal finishing tool and auxiliary finishing tool intersect on different X, Y, Z position, then the joining of two finishing tools constitutes a plane grid, because the three-dimensional position is provided by coordinate measuring machine, its precision can well be guaranteed, so the precision of plane grid can be guaranteed.

If the image coordinate of the target surface of video camera is that (u, v), the coordinate of the relative video camera of net point is P to P ' on the standard flat _C(X _C, Y _C, Z _C), the mapping relations between these two planes can be represented with a square recurrence polynomial of degree n:

$X_C=X(u,v)=\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}\underset{i=0}{\overset{n-j}{\mathrm{\&Sigma;}}}{a}_{\mathrm{ij}}{u}^i{v}^j$

$Y_C=Y(u,v)=\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}\underset{i=0}{\overset{n-j}{\mathrm{\&Sigma;}}}{b}_{\mathrm{ij}}{u}^i{v}^j$

$Z_C=Z(u,v)=\underset{j=0}{\overset{n}{\mathrm{\&Sigma;}}}\underset{i=0}{\overset{n-j}{\mathrm{\&Sigma;}}}{c}_{\mathrm{ij}}{u}^i{v}^j$

Wherein, (u, v) each intersection point of coordinate system constitutes M * N dot matrix on the CCD target surface.X _C, Y _CWith Z _CError function E X, EY and EZ be:

$E_X=\underset{k=0}{\overset{M}{\mathrm{\&Sigma;}}}{(X_k-X)}^2$

$E_Y=\underset{k=0}{\overset{N}{\mathrm{\&Sigma;}}}{(Y_k-Y)}^2$

$E_Z=\underset{k=0}{\overset{N}{\mathrm{\&Sigma;}}}{(Z_k-Z)}^2$

a _Ij, b _IjAnd c _IjCan be by formula $\frac{\&PartialD;E_x}{\&PartialD;a_{\mathrm{ij}}}=0,$ $\frac{\&PartialD;E_x}{\&PartialD;a_{\mathrm{ij}}}=0,$ $\frac{\&PartialD;E_z}{\&PartialD;c_{\mathrm{ij}}}=0$ Try to achieve.

More than demarcate is imageing sensor, camera lens, laser light knife to video camera and the composite calibration of measuring the depth of field, after demarcation finishes, the coordinate that utilizes the cloud data relative measurement terminal that calibration result calculates is exactly accurate, again the coordinate T (X of the terminal that provides according to the global calculation machine _T, Y _T, Z _T) and attitude angle R (α, beta, gamma) can determine that by coordinate transform the arbitrfary point is with respect to the coordinate in global measuring space on the measured workpiece.

Claims (4)

1. a multiple large range laser scanning measurement method is characterized in that, comprises the steps:

(1) adopt a kind of measuring terminals, comprise framework, a side is provided with a laser light knife projector on this framework, is used for to workpiece projection plane light beam, and forms the long incident line on workpiece; Opposite side is provided with many orders digital camera on this framework, equidistantly arranges along long incident line direction, is used for the incident line is segmented into picture; Be provided with realtime graphic handles and the Communication Control center in this framework midfield, be used for the image-forming information of many orders digital camera is handled in real time, obtaining the coordinate information of the some cloud of workpiece profile on the incident line with respect to measuring terminals, and and the global calculation machine between operate synchronously and information passes mutually; Be provided with a plurality of hand-held mode location and attitude monitoring device around on framework, below framework, be provided with the airborne pattern retaining thread that is connected with the coordinate machine;

(2) the measuring terminals scanning survey is demarcated and the demarcation of measuring terminals position and attitude, wherein, under airborne pattern, the position T (X of measuring terminals _T, Y _T, Z _T) and attitude angle R (α, beta, gamma) demarcate and to obtain by three coordinate measuring machine; Under hand-held mode, location on the measuring terminals and attitude monitoring device only use as the target of host computer, and its position and attitude information are provided by host computer; The measuring terminals scanning survey is demarcated, and then uses the virtual grid reflection method to demarcate;

(3) on the measuring workpieces surface finishing tool line arbitrfary point P with respect to the coordinate of measuring terminals, if the optical center of video camera is the A point, the camera image sensor position is at the C point, the laser light knife projector is at the B point, the perpendicular bisector of AB straight line is OD, vertical surface of the work, the intersection point of laser beam and camera optical axis is positioned on the perpendicular bisector OD, therefore, be that its X-axis of coordinate system that benchmark is set up is the DB direction with the measuring terminals, the Z axle is the DO direction, Y-axis then is the orientation of many orders digital camera, if AB length is c, the angle of laser beam and optical axis and AB is all β, and the intersection point of surface of the work and laser beam is P, and the imaging point of P point on imageing sensor is P ', the displacement of the optical axis center point O ' point of P ' on the imageing sensor is s, and the focal length of camera lens is f, can get the coordinate position P of P point with respect to measuring terminals thus _C(X _C, Y _C, Z _C), its value is:

$X_C=C\&CenterDot;(\frac{\mathrm{Cos}\left(\mathrm{\&alpha;}\right)\mathrm{Sin}\left(\mathrm{\&beta;}\right)}{\mathrm{Sin}(\mathrm{\&alpha;}+\mathrm{\&beta;})}-0.5)$

$Z_C=C\&CenterDot;\frac{\mathrm{Sin}\left(\mathrm{\&alpha;}\right)\mathrm{Sin}\left(\mathrm{\&beta;}\right)}{\mathrm{Sin}(\mathrm{\&alpha;}+\mathrm{\&beta;})}$

Wherein:

$\mathrm{\&alpha;}=\mathrm{\&beta;}-{\tan }^{-1}\left(\frac{s}{f}\right)$

If the some P that goes up of finishing tool line images on i the camera image sensor, i=0,1,2,3, Its picture point P ' is v apart from the camera optical axis distance, and then the P point with respect to the Y of measuring terminals to coordinate is:

$Y_C=\frac{\mathrm{ib}}{4}+\frac{\mathrm{vcSin}\left(\mathrm{\&beta;}\right)}{\sqrt{f^2+v^2}\mathrm{Sin}(\mathrm{\&alpha;}+\mathrm{\&beta;})},$

Wherein b is a sweep length;

(4) coordinate of arbitrfary point P in the global measuring space on the finishing tool line of measuring workpieces surface, establishing the coordinate of this P point in the global measuring space is P _G(X _G, Y _G, Z _G), its coordinate in the measuring terminals coordinate system is P _C(X _C, Y _C, Z _C), and the coordinate of measuring terminals in the global measuring space is T (X _T, Y _T, Z _T), attitude angle is R (α, a beta, gamma), then the coordinate of P point in the global measuring space can obtain through rotation and translation with its coordinate in measuring terminals, i.e. P _GCan be expressed as:

$\left[\begin{array}{c}{X}_G\\ Y_G\\ Z_G\end{array}\right]=R\left[\begin{array}{c}{X}_C\\ Y_C\\ Z_C\end{array}\right]+T=\left[\begin{array}{ccc}{r}_0& r_1& r_2\\ r_3& r_4& r_5\\ r_6& r_7& r_8\end{array}\right]\left[\begin{array}{c}{X}_C\\ Y_C\\ Z_C\end{array}\right]+\left[\begin{array}{c}{X}_T\\ Y_T\\ Z_T\end{array}\right]$

Wherein R is a rotation matrix, and it is the trigonometric function combination of attitude angle R (α, beta, gamma), and T is a translation vector, is the position of measuring terminals coordinate origin in global coordinate system, and two data messages are all provided by three coordinate measuring machine.

2. multiple large range laser scanning measurement method as claimed in claim 1, it is characterized in that, described virtual grid reflection method is that measuring terminals is fixed on the three-dimensional automatic measurement machine, the laser light knife of measuring terminals projects on the standard flat, utilize the laser light knife of an auxiliary finishing tool and measuring terminals to intersect in addition again, drive three-dimensional coordinates measurement the laser light knife of measuring terminals and auxiliary finishing tool are intersected, then the joining of two finishing tools constitutes a plane grid.

3. multiple large range laser scanning measurement method as claimed in claim 1 is characterized in that, described many orders digital camera adopts fixed aperture and electronic shutter and the method for regulating laser light knife brightness guarantees the exposure and the image quality of imaging.

4. multiple large range laser scanning measurement method as claimed in claim 1, it is characterized in that, described laser light knife is handled and the grey scale change of Communication Control center according to the image that is obtained by realtime graphic, and the laser beam intensity of laser projections is suitably regulated.

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