CN104677305B - A kind of body surface three-dimensional method for reconstructing and system based on cross structure light - Google Patents

A kind of body surface three-dimensional method for reconstructing and system based on cross structure light Download PDF

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CN104677305B
CN104677305B CN201510071721.6A CN201510071721A CN104677305B CN 104677305 B CN104677305 B CN 104677305B CN 201510071721 A CN201510071721 A CN 201510071721A CN 104677305 B CN104677305 B CN 104677305B
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parameter
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CN104677305A (en
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吴珊珊
贺磊盈
武传宇
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浙江理工大学
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Abstract

The present invention relates to a kind of body surface three-dimensional method for reconstructing and system based on cross structure light.The three-dimensional rebuilding method and three-dimensional reconstruction system that purpose is to provide obtain the geometry parameter information of object by cross structure optical scanning object or body surface are rebuild, the situation that a word structure light marginal information can be avoided to lose, with preferably ageing.Technical scheme is:It is a kind of that the method that body surface three-dimensional is rebuild is realized based on cross structure light, it is characterised in that to comprise the following steps:Step 1:Calibration system parameter;Step 2:Extract optical losses;Step 3:Realize three-dimensional reconstruction;Step 4:The acquisition of object information.A kind of to realize the system that body surface three-dimensional is rebuild, including frame, mobile platform, screw mandrel and motor, the cross laser projector and video camera based on cross structure light, motor is connected with computer, and video camera is connected by image pick-up card with computer.

Description

A kind of body surface three-dimensional method for reconstructing and system based on cross structure light

Technical field

The present invention relates to optical engineering technical field, specifically a kind of body surface three-dimensional based on cross structure light is rebuild Method and system.

Background technology

Line-structured light three-dimensional values technology is mainly used in measurement object geometric parameter or recovers object depth information, and it has Noncontact, wide range, speed is fast, precision is high, algorithmic stability, it is easy to use, simple in construction the features such as.With science and technology constantly more New development, structure optical detection technique be progressively applied to industrial automatic detection, space flight and aviation, ergonomics, biologic medical and In food inspection.At present in line-structured light detecting system, be most widely used for a word structure light, such as Canadian scholar Samuel J.Lochner, which are applied to foot scan and produced, is available for medical model, Spain scholar Samuel verd ú Monitoring of opposite bag fermentation process etc. is realized with it.But a word structure light exist when with scanning object edge it is parallel when be easily lost Marginal information, or data volume, less need for defects such as Multiple-Scans, waits to improve when scanning interface is narrow.

The content of the invention

The purpose of the present invention is to propose to a kind of method and three-dimensional reconstruction that object dimensional reconstruction is realized based on cross structure light System, the geometric parameter that the three-dimensional rebuilding method and three-dimensional reconstruction system obtain object by cross structure optical scanning object is believed Breath is rebuild to body surface, the situation that a word structure light marginal information can be avoided to lose, with preferably ageing.

The technical solution adopted by the present invention is:It is a kind of that the method that body surface three-dimensional is rebuild is realized based on cross structure light, It is characterized in that comprising the following steps:

Step 1:Calibration system parameter, including the demarcation of cross structure optical parameter and direction of motion demarcation;

Step 2:Optical losses are extracted, two laser optical losses subpixel coordinates are obtained;

Step 3:Three-dimensional reconstruction is realized, by said system parameter calibration and Light stripes center extraction, laser plane institute is solved The body surface three-dimensional coordinate points scanned;

Step 4:The acquisition of object information, the geometric parameter of object is obtained by being fitted body surface three-dimensional coordinate points.

Preferably, in the step 1, the demarcation of cross structure optical parameter comprises the following steps:

Step 1-1:Convert the posture of target, video camera is shot under same posture without the/target image that has laser to irradiate Two width;

Step 1-2:Target image during for being irradiated without laser, utilizes the internal reference matrix of Zhang Zhengyou method calibrating cameras K and outer ginseng matrix [R | t];

Step 1-3:Camera mode is adjusted, the target image for having laser to irradiate is shot under high dynamic pattern, for band The target image of laser striation, the parameter of two laser planes is demarcated with step 1-4 method;

Step 1-4:There is the target image that laser irradiates using the segmentation of OTSU threshold methods first, extract two laser light rules Line;Two laser striation linear equations under image coordinate system are obtained secondly based on RANSAC algorithms, by slope to laser striation Classification;Then the projective plane equation and target plane equation under camera coordinate system are asked for, the space for obtaining laser striation is straight Line equation, so as to ask for laser plane normal direction [a, b, c]T;Finally distance using laser striation to laser plane is cost function, The object function for setting up optimization shown in following formula solves the parameter d of laser plane equation,

In the step 1, direction of motion demarcation comprises the following steps:

Step 1-5:Target is fixed on mobile platform and moved along a straight line, target figure during no laser irradiation is continuously shot As n (n>2) the outer ginseng matrix [R | t] of every two field picture, is obtained, with least square method to t fitting a straight lines, direction of motion ginseng is obtained Number.

Preferably, in the step 2, extracting optical losses and comprising the steps of:

Step 2-1:Laser light stripe is partitioned into using OTSU dual-threshold voltages;

Step 2-2:Initial laser optical losses are extracted using geometrical center method;

Step 2-3:The normal direction of striations, wherein Hessian such as following formula institutes are obtained by asking for Hessian matrixes Show,

G (x, y) is two-dimensional Gaussian function, and the corresponding characteristic vector of maximum of Hessian matrix exgenvalue absolute values is just It is normal direction;

Step 2-4:Laser optical losses subpixel coordinate is obtained by grey scale centre of gravity method;

Step 2-5:The normal direction obtained using Hessian matrixes determines to produce the laser plane of the striation, by normal The discontinuity in direction rejects the point of mistake.

Another technical scheme that the present invention is provided is:It is a kind of to realize what body surface three-dimensional was rebuild based on cross structure light System, including frame, by the rack-mounted mobile platform of horizontal guide rail, drive mobile platform screw mandrel and motor, The cross laser projector and video camera above mobile platform are fixed on, the motor is connected by motion control card and computer Connect, video camera is connected by image pick-up card with computer.

Beneficial effects of the present invention:

1st, the three-dimensional rebuilding method that provides of the present invention and system only need to a cross laser projector, a video camera and One conveyer, it is possible to reconstruct the surface of object, or the geometric parameter of measurand is obtained by reconstruction information, and And all demarcation of the present invention are all based on the plane target drone moved freely, it is adapted to field calibration, it is easy to operate;

2nd, the present invention is scanned to object using cross structure light, and information content increase, precision improve, reduces and needs to repeat Scan and increased workload, general industrial requirement can be met.

Brief description of the drawings

Fig. 1 is the schematic diagram for the three-dimensional reconstruction system that the present invention is provided.

Fig. 2 is the system framework figure for the three-dimensional reconstruction system that the present invention is provided.

Fig. 3 is the flow chart for the three-dimensional rebuilding method that the present invention is provided.

Fig. 4 is three floor map that the present invention need to be demarcated.

Fig. 5 is the schematic diagram that laser intersection of the present invention is fitted to laser plane.

Fig. 6 is the direction of motion demarcation schematic diagram of the present invention.

In figure:1st, scanned object (Aluminum cylindrical), 2, mobile platform, 3, the cross laser projector, 4, video camera, 5, meter Calculation machine.

Embodiment

The invention will be further described below, but the invention is not limited in following examples.

As shown in Figure 1, 2, the three-dimensional reconstruction system that the present invention is provided includes frame, is arranged on by horizontal guide rail in frame Mobile platform 2, the screw mandrel and motor that drive mobile platform, the cross laser projector 3 that is fixed on above mobile platform with And video camera 4, the motor is connected by motion control card with computer, and video camera is connected by image pick-up card with computer 5 Connect.Video camera shooting image is sent to computer through image pick-up card, and computer is rotated by motion control card controlled motor, by The time interval of motor speed and video camera shooting image calculates the relative movement distance for obtaining every two field picture jointly.Software is by scheming As processing routine, motion control program, the part of data analysis program three composition.

Scanned object (Aluminum cylindrical) 1 is fixed on mobile platform 2 by the present invention, the cross laser projector 3 and shooting Machine 4 is fixed on the steelframe above object, and motor drives ball-screw at the uniform velocity to rotate, and drives mobile platform to drive scanned object 1 horizontal motion, cross laser plane continuously sweeps testee 1, and camera acquisition a series of images is sent to computer 5, the reconstruction to body surface is realized by digital image processing techniques and coordinate system transformation.

The three-dimensional rebuilding method that above-mentioned three-dimensional reconstruction system is provided using the present invention realizes the reconstruction of body surface, the three-dimensional Method for reconstructing comprises the following steps:

(1) system parameter calibration:

1. line-structured light parameter calibration;

Target is moved freely, and shoots the target figure under different postures, to calibrating camera parameters and fitting laser plane, The width of target figure two with/without laser is shot under each posture.Target image during without laser, the internal reference to calibrating camera With outer ginseng, the band laser target image shot after camera mode is adjusted, to Calibration of Laser plane parameter.

The method that the parameter of video camera can be proposed by Zhang Zhengyou realizes that it not only avoids traditional scaling method requirement High, cumbersome the shortcomings of, and precision is high, and robustness is stronger.Its obtained outer ginseng matrix [R | t] it is assumed to be formula 1, internal reference square Battle array K is assumed to be formula 2.Fx, fy are focal length, (u0,v0) it is ideal image coordinate, R is rotating vector, and t is translation vector.

Formula 1

Formula 2

Demarcation to laser plane parameter can be realized by following 3 step:

1) OTSU threshold method segmentation figure pictures are used, laser striation is extracted.Based on RANSAC algorithms, (stochastical sampling is unanimously calculated Method) least square line fitting is carried out to the laser spots filtered out, obtain corresponding laser linear equation.Because there is two to swash Light straight line, therefore delete and RANSAC and Algorithm of fitting a straight line are repeated after the point filtered out for the first time, you can obtain two laser straight lines Equation, calculates the slope of two laser straight lines, the laser straight line of all shooting images is divided into the class of A, B two by slope.

2) the projective plane equation and target plane equation (such as Fig. 4) under camera coordinate system are calculated.Two planes of simultaneous Equation obtains the space line equation such as formula 3, i=1 of laser striation, 2,3 ..., n, and n is acquired image number.Because this is straight Line is located on laser plane, so the direction vector of straight line is orthogonal with the normal vector of laser plane.Make the parameter side of laser plane Journey is ax+by+cz+d=0 (wherein a2+b2+c2=1), n equation is obtained by n width images, simultaneous obtains overdetermined linear system Formula 4, is represented to obtain formula 5 with matrix form.Matrix A singular value decomposition is obtained:A=U Σ VT, wherein V last row to Measure v3The as solution of the system of homogeneous linear equations.

Formula 3

Formula 4

Formula 5

3) the normal direction F of laser plane is so far obtainedL[a b c].As shown in figure 5, laser projecting apparatus is fixed, target is converted Target posture, each posture and laser plane have an intersection, known the space equation of every laser intersection, straight line is intended It is combined into plane and can obtain laser plane equation.

Distance using striation straight line to laser plane is cost function, and the object function for setting up optimization solves laser plane side The parameter d of journey.Simultaneous video camera origin obtains laser rays to the linear equation and laser space line equation 6 of image end points The three-dimensional coordinate information of two end points of section obtains line segment length L.(u, v) is image coordinate in formula, and (x, y, z) is required video camera Three-dimensional coordinate under coordinate system.

Formula 6

Linear equation is converted into parametric form (formula 7) and is brought into the quadratic equation with one unknown that formula 8 can obtain d, is obtained Minimum is exactly required parameter d.

Formula 7

Formula 8

2. the direction of motion is demarcated;

Video camera shooting once can only obtain the three-D profile information on two sections, it is necessary to additional one-dimensional scanning information Whole surface information can be obtained.Target is fixed on a mobile platform, control leading screw direction of rotation shoots 5 width above pictures. Know the internal reference matrix K of video camera, can calculate and obtain the corresponding outer ginseng matrix [R of each moment targeti|ti], i=1,2, 3 ..., n, n are acquired image number.Mobile platform as shown in Figure 6 moves for rectilinear direction, therefore target is not present rotation and joined Amount, it is each outer join in spin matrix R close to identical, and translation vector t be in target plane origin under camera coordinate system Expression, fitting a straight line is carried out to the translation vector at each moment with least square method, mobile platform is obtained relative to video camera The direction of motion [t1 t2 t3]T

(2) optical losses are extracted:

1) object shot easily forms three peak characters if metal materials such as aluminum, steel, that is, is divided into the laser light rule Halation that line, laser are formed in material surface, three layers of background, striation striped can be partitioned into using OTSU dual-threshold voltages.

2) in order to improve real-time, initial optical losses need to first be obtained, in the acquisition algorithm of center striped, look for row or Geometric center point on column direction is fastest.Therefore the initial center position of striation is extracted using geometrical center method.

3) obtain the normal direction of initial center point with Hessian matrixes, Hessian matrix exgenvalue absolute values it is very big It is exactly normal direction to be worth corresponding characteristic vector.Then the sum weight in normal forward direction and inverse direction, uses grey scale centre of gravity method Just it can determine that the position of sub-pixel optical losses.Hessian matrixes can be obtained by formula 9, and g (x, y) is two-dimensional Gaussian function.Gray scale Focus point (xi,yi) can be obtained by formula 10.

Formula 9

Formula 10

4) normal direction obtained using Hessian matrixes determines to produce the laser plane of the striation, by normal direction Discontinuity rejects the point of mistake.

(3) three-dimensional reconstruction is realized:

The reference frame of the present invention is camera coordinate system, and it is the coordinate on image that above-mentioned steps, which obtain optical losses, (u, v) is, it is necessary to the coordinate (x being converted under camera coordinate systemc,yc,zc).Simultaneous camera coordinates are tied to image coordinate The transfer equation and laser plane equation 11 of system, you can solve the body surface three-dimensional coordinate points that laser plane is scanned.

Formula 11

Obtain three-dimensional coordinate point (xc,yc,zc) after, need to add the translational movement ability of relative first two field picture per frame coordinate Obtain actual coordinate.The pace for controlling leading screw is 8mm/s, is obtained by video camera caller per two field picture relative to the The shooting time interval S of one two field picture, obtains every frame displacement dis.Direction of motion demarcation obtains motion vector [t1 t2 t3], The actual coordinate for obtaining each point by formula 12 is (x 'c,y’c,z’c)。

Formula 12

(4) acquisition of object information:

Body surface that laser scans each three-dimensional coordinate information for putting is can obtain according to above-mentioned steps.If scanning pair As the object for regular geometric shapes, the geometric parameter of object can be obtained by being fitted body surface three-dimensional coordinate points, such as long, Width, height, radius etc..If sweep object is irregularly shaped object, three-dimensional reconstruction can be realized to it, recover its surface information.Still need Bright is:The present invention obtains more object geometry by cross structure optical scanning object so as to a relative word structure light Parameter information, the three-dimensional coordinate point that computer is fitted body surface by these geometry parameter informations is existing mature technology, Do not describe in detail herein, the algorithm software needed for computer can be write by common program staff.

Finally it should be noted that listed above is only specific embodiment of the invention.It is clear that the invention is not restricted to Above example, can also there is many variations.One of ordinary skill in the art can directly lead from present disclosure All deformations for going out or associating, are considered as protection scope of the present invention.

Claims (1)

1. a kind of realize the method that body surface three-dimensional is rebuild based on cross structure light, it is characterised in that comprises the following steps:
Step 1:Calibration system parameter, including the demarcation of cross structure optical parameter and direction of motion demarcation;
Step 2:Optical losses are extracted, two laser optical losses subpixel coordinates are obtained;
Step 3:Three-dimensional reconstruction is realized, by said system parameter calibration and Light stripes center extraction, laser plane is solved and is scanned The body surface three-dimensional coordinate points arrived;
Step 4:The acquisition of object information, the geometric parameter of object is obtained by being fitted body surface three-dimensional coordinate points;
In the step 1, the demarcation of cross structure optical parameter comprises the following steps:
Step 1-1:Convert the posture of target, video camera is shot under same posture without the/width of target image two that has laser to irradiate;
Step 1-2:Target image during for being irradiated without laser, using Zhang Zhengyou method calibrating cameras internal reference matrix K and Outer ginseng matrix [R | t];
Step 1-3:Camera mode is adjusted, the target image for having laser to irradiate is shot under high dynamic pattern, for band laser The target image of striation, the parameter of two laser planes is demarcated with step 1-4 method;
Step 1-4:There is the target image that laser irradiates using the segmentation of OTSU threshold methods first, extract two laser light stripes; Two laser striation linear equations under image coordinate system are obtained secondly based on RANSAC algorithms, by slope to laser striation point Class;Then the projective plane equation and target plane equation under camera coordinate system are asked for, the space line of laser striation is obtained Equation, so as to ask for laser plane normal direction [a b c]T;Finally the distance using laser striation to laser plane is built as cost function The object function for making optimization shown in formula solves the parameter d of laser plane equation,
<mrow> <mi>F</mi> <mrow> <mo>(</mo> <mi>d</mi> <mo>)</mo> </mrow> <mo>=</mo> <msubsup> <mo>&amp;Integral;</mo> <mn>0</mn> <mi>L</mi> </msubsup> <mfrac> <mrow> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <msup> <mrow> <mo>(</mo> <mi>a</mi> <mi>x</mi> <mo>+</mo> <mi>b</mi> <mi>y</mi> <mo>+</mo> <mi>c</mi> <mi>z</mi> <mo>+</mo> <mi>d</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> </mrow> <msqrt> <mrow> <msup> <mi>a</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mi>b</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mi>c</mi> <mn>2</mn> </msup> </mrow> </msqrt> </mfrac> <mi>d</mi> <mi>t</mi> </mrow>
In formula:A, b, c are respectively the coefficient of x, y, z in parametric equation ax+by+cz+d=0,
Wherein a2+b2+c2=1, d are the parameter of laser plane equation;
L is the length of laser line segment;
In the step 1, direction of motion demarcation comprises the following steps:
Step 1-5:Target is fixed on mobile platform and moved along a straight line, target image n during no laser irradiation is continuously shot , wherein n>2, the outer ginseng matrix [R | t] of every two field picture is obtained, with least square method to t fitting a straight lines, direction of motion ginseng is obtained Number.
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