CN103398675A - Three-dimensional measuring method for complex large object based on stripe period correction - Google Patents
Three-dimensional measuring method for complex large object based on stripe period correction Download PDFInfo
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Abstract
The invention discloses a three-dimensional measuring method for a complex large object based on stripe period correction. The measuring system comprises a projector, a measuring bracket, a camera, a computer and a reference plane, wherein the projector and the camera, on the same level, are placed on the measuring bracket, and are connected with the computer through wires respectively; an object to be detected is placed on the reference plane. The three-dimensional measuring method has the advantages that (1) a five-step phase moving method based on stripe period correction is proposed; (2) a time phase expansion method based on stripe period correction is proposed; (3) the operation is convenient and practical, and the high-accurate three-dimensional measuring of the complex and large object is realized.
Description
Technical field
The present invention relates to a kind of measuring method, relate in particular to a kind of complicated large three-dimensional measurement of objects method of based on fringe period, proofreading and correct.
Background technology
Grating project is widely used in the three-dimensional measurement of object, and the three-dimensional measurement technology is one of Key technology of modern manufacturing industry, is that light harvesting, mechanical, electrical and computer technology are in the new and high technology of one.It provides essential three-dimensional data for the product manufacturing, is widely used in the fields such as three-dimensional measurement, quality control, digital manufacturing, reverse-engineering and virtual manufacturing of various complex parts, has very high practical value.Adopt grating project to carry out the measurement of object dimensional pattern,, noncontact highly sensitive owing to having, the advantage such as real-time, become a kind of important measurement means of inspected object three-dimensional appearance.Grating project is that grating fringe is projected on measured surface, and grating fringe is modulated by carrier frequency in spatial domain.This modulation signal, through filtering and demodulation, obtains the phase information corresponding to the testee surface elevation, finally reconstructs the surface profile of testee.
When grating project was measured the three-D profile of object, it generally adopted the concurrent aces system of single projector and single camera.Projector is used for projection sinusoidal grating striped to the testee surface, and video camera is used for the striped imaging to by object, being modulated.But the concurrent aces system has following problem: when carrying out three-dimensional measurement, the sinusoidal grating fringe period on reference planes is a very important parameter, directly affects measurement result.When the projector oblique-angle projection, because projection ray disperses, the sinusoidal grating fringe period on reference planes there will be broadening, and it is not a definite value.PHASE DISTRIBUTION on reference planes is not linear distribution, to measurement, brings error, reduces measuring accuracy., for the measurement of wisp,, because the fringe period broadening is less, after having adopted calibration technique, can reach certain measuring accuracy.But for the measurement of larger object, for example 1-1.5 rice is long, and 1 meter object that left and right is wide is got over deviation from origin, and the fringe period broadening must be more serious, and measuring accuracy is lower.So the fringe projection technology of profiling is only applicable to the measurement of wisp, and object be placed near initial point relatively good, thereby limited its range of application.Fringe period broadening on reference planes becomes a major obstacle of fringe projection technology of profiling application.
External from state: due to the superiority of fringe projection technology of profiling and application prospect widely, Many researchers is studied it.The grating fringe cycle on reference planes is an important parameter, and many researchers conduct in-depth research it, has pointed out the problem of grating fringe period stretching, has done a lot of significant work.External pertinent literature record: the first, pointed out in the concurrent aces system, when the projector oblique-angle projection, when the uniform grating fringe of one-period projects on reference planes, the cycle is not a definite value, and has proposed a kind of Error Compensation Algorithm and revise.The second, analyze the relational expression that has obtained fringe period on virtual reference plane and reference planes.The 3rd, analyze the fringe period relation that has obtained projection plane and reference planes, and the employing least square method obtains the phase place on reference planes.The 4th, obtained relational expression between phase place and testee height according to geometric analysis.The 5th, for when measuring large object, the effective wavelength of fringe projection on reference planes can not be regarded the situation of a definite value as, the relationship between projection coordinate, object coordinates and three coordinates of camera coordinates of having derived.Obtain one and do not rely on the three-D profile of identical length and the mapping relations formula between phase place, eliminated because effective wavelength changes the measuring error that causes.
From domestic: domestic researcher also conducts in-depth research fringe projection technology of profiling and application thereof, and has obtained good achievement.Aspect the fringe period correction, the Related domestic documents record: the first, propose a kind of static phase measurement technology of profiling analysis reference planes of utilizing and blocked PHASE DISTRIBUTION, adopt iterative algorithm progressively to revise the method for projection grating fringe period.The second, a kind of method that obtains the uniform period striped on reference planes has been proposed.The 3rd, analyzed at projector and just thrown, when camera tilts to receive, the height of testee and the expression formula of height error.The 4th, a kind of concurrent aces projection measurement system of complicated face shape has been proposed, on the basis of having considered the fringe period broadening, discussed in detail the phase measurement principle of this system, the relation between physical surface shape and required phase place.Carried out a series of research on image point displacement error correction, lens distortion calibration, phase-shift method, system calibrating, phase unwrapping are wrapped up in and applied, made fruitful work, enrich with develop the theory of fringe projection technology of profiling.
When grating project was measured the three-D profile employing concurrent aces system of object, due to oblique-angle projection, broadening appearred in the grating fringe cycle on reference planes, and causing the cycle is not definite value, when testee is larger, to measurement, brings larger error.At present, home and abroad occurs that not yet a kind of measuring method can generate the serial sinusoidal grating striped (cycle is non-homogeneous) of each frequency five step phase shifts on the projector plane, this fringe projection is to the serial sinusoidal grating striped (cycle is even) that obtains each frequency five step phase shifts on reference planes, each frequency meet exponential sequence time phase the method for development striped frequency change rule, realize the high precision three-dimensional measurement of complicated large object.
Summary of the invention
The object of the present invention is to provide a kind of complicated large three-dimensional measurement of objects method of based on fringe period, proofreading and correct, this measuring method proposed the five step phase-shift methods of proofreading and correct based on fringe period and time phase method of deploying, realize that complicated large object high accuracy three-dimensional measures.
The present invention is achieved like this, and its measuring system comprises projector, measures support, video camera, computing machine, reference planes; It is characterized in that: projector and video camera are placed on to be measured on support; Projector, video camera connect computing machine with wire respectively; Object under test is placed on reference planes; Projector and video camera are sustained height, and projector optical axis and camera optical axis intersect at the O point, and the distance between them is d, and they are L to the distance of reference planes; P is the photocentre of projector, and p is the sinusoidal grating fringe period on reference planes; X is the x axle of reference planes, and X ' is the x axle on virtual reference plane, and this plane is vertical with the projector optical axis; X ' ' is the x axle on projector plane, and PA ' A is arbitrary throw light.
Comprise image pick-up card, projection software, Survey Software in computing machine of the present invention.
The present invention will carry out following work:
(1) the fringe period bearing calibration on reference planes.
(2) go on foot the theoretical model of phase-shift methods based on five of fringe period correction.
(3) proofread and correct based on fringe period time phase the method for development theoretical model.
(4) theoretical model of large three-dimensional measurement of objects.
The theoretical model of large three-dimensional measurement of objects comprises:
The correction of (1) image point displacement error;
(2) correction of lens distortion;
(3) set up the theoretical model of large three-dimensional measurement of objects.
Advantage of the present invention is: (1) has proposed the five step phase-shift methods of proofreading and correct based on fringe period; (2) method of deploying time phase of proofreading and correct based on fringe period has been proposed; (3) easy to operate, practical, realize complicated large object high accuracy three-dimensional measurement.
Description of drawings
Fig. 1 is work schematic diagram of the present invention.
Fig. 2 is the light channel structure schematic diagram of grating project measuring system of the present invention.
Fig. 3 is image point displacement error schematic diagram in the theoretical model of large three-dimensional measurement of objects of the present invention.
In the drawings, 1, projector 2, measure support 3, video camera 4, computing machine 5, reference planes 6, object under test.
Embodiment
As shown in Figure 1, the present invention implements like this and works, and its measuring system comprises projector 1, measures support 2, video camera 3, computing machine 4, reference planes 5; It is characterized in that: projector 1 and video camera 3 are placed on to be measured on support 2; Projector 1, video camera 3 connect computing machine 4 with wire respectively, comprise image pick-up card, projection software, Survey Software in computing machine 4; Object under test 6 is placed on reference planes 5.Projector 1 and video camera 3 are sustained height, and projector 1 optical axis and video camera 3 optical axis intersections are in the O point, and the distance between them is d, and they are L to the distance of reference planes 5; P is the photocentre of projector 1, and p is the sinusoidal grating fringe period on reference planes 5; X is the x axle of reference planes 5, and X ' is the x axle on virtual reference plane 5, and this plane is vertical with projector 1 optical axis; X ' ' is the x axle on projector 1 plane, and PA ' A is arbitrary throw light.
As shown in Figure 2, the light channel structure principle of grating project measuring system of the present invention is:
OFor initial point,
P(X 0 , 0, Z 0 ) be projector 1 position,
C(
0,0, Z 0 ) be video camera 3 positions,
P, C2 is sustained height.Testee 6 is lip-deep
DThe point with reference planes 5 on
APoint has identical phase place, namely
, testee 6 is lip-deep
DThe point with reference planes 5 on
BPoint images in same point on video camera 3, therefore have
In formula:
Frequency for projection gate on reference planes 5;
PSpace periodic for grating.By triangle
ABDWith triangle
PCDSimilar can obtaining
Wherein:
Z On 6 of testees
DThe height of point;
ABWith
PCThe expression line segment length.Due in actual light path
X 0 AB, following formula can be approximately
Wherein:
On testee 6 surfaces
DOn point and reference planes 5
BThe phase differential of point;
The coefficient relevant with light channel structure.
The present invention will carry out following work:
1, the fringe period bearing calibration on reference planes.
Purpose: generating period sinusoidal grating striped heterogeneous on projector 1 plane, this grating fringe projects on reference planes 5 uniform sinusoidal grating striped of the cycle that obtains.
When the projective amplification multiplying power is N, and the fringe period p on hypothetical reference plane 5 is in the situation of definite value, and the p value can be set in the grating fringe program, set up the mathematical relation of projector 1 plane phase place and coordinate X ' ':
Be and L, d, N, the function that X ' ' is relevant, and then obtain non-homogeneous sinusoidal grating striped of cycle on projector 1 plane.
2, go on foot the theoretical model of phase-shift methods based on five of fringe period correction.
Purpose: generate the sinusoidal grating striped (cycle is non-homogeneous) of five step phase shifts on projector 1 plane, this grating fringe projects on reference planes 5 the sinusoidal grating striped (cycle is even) that obtains five step phase shifts.
In the situation that the fringe period p on reference planes 5 proofreaied and correct as definite value, when on reference planes 5, striped is realized five step of standard phase shift, set up projector 1 plane X ' ' mathematical relation of coordinate and reference planes 5X coordinate.On this basis, research projector 1 plane phase place and the new mathematical relation of coordinate X ' ':
, wherein k is 0,1,2,3,4; And then obtain the sinusoidal grating striped of five on projector 1 plane step phase shift.
3, proofread and correct based on fringe period time phase the method for development theoretical model.
Purpose: the serial sinusoidal grating striped (cycle is non-homogeneous) that generates each frequency five step phase shifts on projector 1 plane, this fringe projection is to the serial sinusoidal grating striped (cycle is even) that obtains each frequency five step phase shifts on reference planes 5, each frequency meet exponential sequence time phase the method for development striped frequency change rule.
By
As seen, can change easily the grating fringe frequency f value of expectation on reference planes 5.Allow striped frequency on reference planes 5 according to 2
iThe rule of f changes successively.On the phase-shift method basis of based on fringe period, proofreading and correct, each striped frequency is realized five step phase shifts.Utilize the time phase method of development to obtain continuous phase.Time phase, the method for development can realize that the phase unwrapping of complicated face shape object wraps up in.At first solve the phase place of blocking of each different frequency striped
Be the phase place of blocking of f again according to frequency
Can demodulate accurately continuous phase
Namely
, and obtain on this basis the continuous phase of each time point
,
=
+
, wherein
=INT
, immediate integer is got in INT (*) expression, and k is the growth indices of frequency, and here k is 2.Method by recurrence just can solve last continuous phase like this.
4, the theoretical model of large three-dimensional measurement of objects.
The correction of (1) image point displacement error.
As shown in Figure 3: on testee 6, the world coordinate system coordinate of any point C is (Xc, Yc, Zc).Continuous phase poor of reference planes 5 images and the same pixel of body surface image due to the external phase potential difference, the reading images coordinate time, the plane picture coordinate that E is ordered is used as the plane picture coordinate that C is ordered, so the world coordinate system coordinate that the C that records is ordered is (X
E, Y
E, Zc).As seen X, error has appearred in the Y coordinate, this error is called the image point displacement error.When measuring larger object, must proofread and correct the image point displacement error.
, had by symmetry:
Here X
C, Y
C, Z
CIt is the world coordinates that C is ordered.Formula of Coordinate System Transformation is slightly different when the C point is in the right of initial point O.
(2) correction of lens distortion.
High or while measuring large object for accuracy requirement, need to consider camera lens one, second order radial distortion and tangential distortion, realize the correction of lens distortion.
k
1, k
2For camera lens one, the second order coefficient of radial distortion, p
1, p
2Be one, second order tangential distortion coefficient.The normalized image coordinate of the spatial point that (x, y) arrives for actual observation, (x ', y ') are the normalized image coordinate of desirable spatial point.k
1, k
2, p
1, p
2These distortion factors are demarcated and are obtained by video camera 3.
(3) set up the theoretical model of large three-dimensional measurement of objects.
Considered camera lens one, on the basis of second order radial distortion and tangential distortion, set up the relation of image coordinate system and world coordinate system.On this basis, then consider the image point displacement error, set up the theoretical model of large three-dimensional measurement of objects.
(u v), is obtained by high computational formula (1) for certain point coordinate on image
So, only need to obtain X, the Y value of this point.Utilization, with the relation of image coordinate system and the world coordinate system of lens distortion calibration, obtains the coordinate (X, Y) of world coordinate system.Consider image point displacement error correction, this world coordinate system coordinate is [(1-h/L) X, (1-h/L) Y, h] again.
Claims (4)
1. complicated large three-dimensional measurement of objects method of based on fringe period, proofreading and correct, its measuring system comprises projector, measures support, video camera, computing machine, reference planes; It is characterized in that measuring method is: projector and video camera are placed on to be measured on support; Projector, video camera connect computing machine with wire respectively; Object under test is placed on reference planes; Projector and video camera are sustained height, and projector optical axis and camera optical axis intersect in a bit; X is the x axle of reference planes, and X ' is the x axle on virtual reference plane, and this plane is vertical with the projector optical axis, and X ' ' is the x axle on projector plane.
2. a kind of complicated large three-dimensional measurement of objects method of based on fringe period, proofreading and correct according to claim 1, is characterized in that: comprise image pick-up card, projection software, Survey Software in computing machine.
3. a kind of complicated large three-dimensional measurement of objects method of based on fringe period, proofreading and correct according to claim 1 is characterized in that the present invention will carry out following work:
(1) the fringe period bearing calibration on reference planes;
(2) go on foot the theoretical model of phase-shift methods based on five of fringe period correction;
(3) proofread and correct based on fringe period time phase the method for development theoretical model;
(4) theoretical model of large three-dimensional measurement of objects.
4. a kind of complicated large three-dimensional measurement of objects method of based on fringe period, proofreading and correct according to claim 3 is characterized in that the theoretical model of large three-dimensional measurement of objects comprises:
The correction of (1) image point displacement error;
(2) correction of lens distortion;
(3) set up the theoretical model of large three-dimensional measurement of objects.
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| CN104154879A (en) * | 2014-08-18 | 2014-11-19 | 河北工业大学 | Non-uniform stripe segmented generation method |
| CN104154879B (en) * | 2014-08-18 | 2017-01-25 | 河北工业大学 | Non-uniform stripe segmented generation method |
| CN104457614A (en) * | 2014-11-11 | 2015-03-25 | 南昌航空大学 | Stripe reflection three-dimensional measurement method based on binary stripe defocusing |
| CN105180837A (en) * | 2015-08-28 | 2015-12-23 | 河北工业大学 | Transverse non-uniform striped partition generation method |
| CN105300317A (en) * | 2015-10-28 | 2016-02-03 | 南昌航空大学 | Three-dimensional measurement method on the basis of projection of sinusoidal stripes and triangular wave stripes |
| CN110268223A (en) * | 2017-03-07 | 2019-09-20 | 欧姆龙株式会社 | Three-dimensional shape measuring device, three-dimensional shape measuring method and program |
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| CN109186492B (en) * | 2018-08-14 | 2020-04-24 | 博众精工科技股份有限公司 | Three-dimensional reconstruction method, device and system based on single camera |
| CN110849268A (en) * | 2019-12-10 | 2020-02-28 | 南昌航空大学 | Quick phase-height mapping calibration method |
| CN110849268B (en) * | 2019-12-10 | 2021-07-06 | 南昌航空大学 | Quick phase-height mapping calibration method |
| CN111174730A (en) * | 2020-01-07 | 2020-05-19 | 南昌航空大学 | Rapid phase unwrapping method based on phase encoding |
| CN112799094A (en) * | 2020-12-24 | 2021-05-14 | 江苏烽禾升智能科技有限公司 | Optical system for three-dimensional imaging test |
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