CN112132890A - Calibration method of digital grating projection measurement system for enlarging calibration space - Google Patents
Calibration method of digital grating projection measurement system for enlarging calibration space Download PDFInfo
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Abstract
The invention provides a calibration method of a digital grating projection measurement system for enlarging a calibration space, which comprises the following steps: s10: enlarging the calibration space; s20: and obtaining a relation model of world coordinates and camera pixel coordinates and phases. The invention firstly enlarges the calibration space, brings the measurement space except the calibration point into the calibration range, and establishes a relation model between world coordinates and camera pixel coordinates and phases in the space except the calibration point and the calibration point so as to avoid generating calibration errors.
Description
Technical Field
The invention relates to a calibration method of a digital grating projection system, in particular to a calibration method of a digital grating projection measurement system for enlarging a calibration space.
Background
The grating projection three-dimensional measurement technology is used as a hot field and an important direction of the optical three-dimensional measurement technology, and has a series of advantages of non-contact measurement, high measurement speed, high measurement precision and the like. With the development of scientific technology and the progress of industrial production in recent years, the grating projection measurement technology is more and more widely applied in the fields of industrial automatic detection, biomedical diagnosis, cultural relic reproduction, virtual reality realization, product quality control and the like. The system calibration is a basic link of the grating projection technology, and the accuracy and precision of the system calibration directly influence the accuracy and precision of the grating projection system measurement. Besides, the complexity and the executability of system calibration directly affect the application range and the universality of the measurement system.
With the development of optical measurement technology, grating projection measurement technology has become mature, and a plurality of different system calibration methods are presented. The traditional calibration method calibrates through calibrating accurate position parameters and direction parameters of a projector and a camera, the calibration is accurate, the operation is complex and tedious, and the calibration speed is slow. With the popularization of the Zhang Zhengyou camera calibration method, due to the similarity of the projector and the camera imaging model, the method of calibrating the projector as a 'reverse camera' is the most common calibration method of the grating projection system at present. The method has no external constraint on the structure of the system in the traditional calibration method, does not need to know the accurate position of the calibration plate in advance, and is widely used quickly due to the flexibility, easy operation and low cost. However, the problems with this approach are mainly: the error of the camera can be coupled into the calibration error of the projector; assume that the projector imaging is in focus. In practical situations, the projector is often out of focus to different degrees for various reasons, so that the system calibration method based on the Zhang friend calibration method and the 'inverse camera model' has calibration errors to different degrees at different depths.
Chinese patent application CN110849268A discloses a fast phase-height mapping calibration method, in which the phase-height mapping calibration mentioned in the patent is based on a geometric relationship derived from a specific geometric structure, and the resulting parameters are substantially the distance L between the CCD camera and the reference plane and the distance d between the CCD camera and the projector. However, the method needs to be based on the combination relationship of a telecentric lens and a specific system, the application range is not wide, calibration errors are easily generated due to defocusing of the projector, and besides, the calibration space is limited, namely, the calibration errors are difficult to avoid in the measurement space beyond the range of the calibration plate.
Disclosure of Invention
In view of this, the present invention provides a calibration method for a digital grating projection measurement system, which enlarges the calibration space, and solves the problems in the prior art that the calibration space is limited and the measurement space beyond the range of the calibration plate has calibration errors.
In order to solve the technical problems, the invention adopts the technical scheme that: a calibration method of a digital grating projection measurement system for expanding a calibration space comprises the following steps:
s10: enlarging a calibration space by obtaining coordinates under a world coordinate system and affine matrixes among the coordinates under an image coordinate system;
s20: and obtaining a relation model of world coordinates and camera pixel coordinates and phases.
Preferably, the method for expanding the calibration space comprises:
s101: obtaining coordinates of each calibration point on the known calibration plate under different positions under a world coordinate system and coordinates under an image coordinate system;
s102: obtaining coordinates of each calibration point in a world coordinate system and affine matrixes among the coordinates in an image coordinate system;
s103: and obtaining coordinates under a world coordinate system corresponding to the pixel points outside the calibration area of the known calibration plate according to the affine matrix.
Preferably, S101: the method for obtaining the coordinates of each calibration point on the known calibration plate under the world coordinate system at different positions comprises the following steps:
s1011: establishing a world coordinate system so that the world coordinate systemxoyThe faces are parallel to a known calibration plate,zthe axis is perpendicular to the known calibration plate;
s1012: perpendicular tozThe axes move the known calibration plate to obtain coordinates in the world coordinate system of each calibration point on the known calibration plate at different positions.
Preferably, the process of the coordinates in the image coordinate system of each calibration point on the known calibration plate at different positions is as follows: shooting the fringe projection images on the known calibration plate at different positions, establishing an image coordinate system, and extracting the coordinates of each calibration point on the known calibration plate at different positions under the image coordinate system.
Preferably, the affine matrix transformation process in step S102 is as follows:
wherein the content of the first and second substances,x w andy w is a coordinate under a world coordinate system of the center of a calibration point of a known calibration areaw pk Is/are as followsxAxis coordinate sumyThe coordinates of the axes are set to be,r、cthe center of a circle of a calibration point in a known calibration area is the coordinate of an image coordinate systemc pk ，MIs a 2 x 3 matrix, which is an affine transformation matrix.
Preferably, a relation model of world coordinates and phases of the camera pixels is obtained through a polynomial method.
Preferably, the process of obtaining a relation model of world coordinates and phases of the camera pixels by a polynomial method comprises:
s201: acquiring phase values at the circle centers of the calibration points on the dot calibration plate;
s202: performing polynomial fitting through least square according to the obtained image coordinate of any point in the image coordinate system in the calibration space, the corresponding phase value and the coordinate of the point in the world coordinate system to obtain a polynomial of the world coordinate system and the image coordinate system;
s203: and calculating a calibration result.
Preferably, a relation model of world coordinates and phases of camera pixels is obtained through an interpolation method.
Preferably, the process of obtaining a relation model of world coordinates and phases of the camera pixels by an interpolation method comprises:
S201，: acquiring phase values at the circle centers of the calibration points on the dot calibration plate;
S202，: according to the obtained image coordinate of any point in the image coordinate system in the calibration space, the corresponding phase value and the coordinate in the world coordinate system, the coordinate in the image coordinate systemr、c、φObtaining coordinates under a world coordinate system by axis three-dimensional interpolation;
S203，: and completing calibration.
Preferably, step S202，The method comprises the following steps:
S2021，: establishing a space coordinate system;
S2022，: obtaining coordinates of adjacent points of the points to be interpolated in a space coordinate system;
S2023，: in turn atr、c、φAnd (5) interpolating in the axial direction.
The invention has the advantages and positive effects that: the invention firstly enlarges the calibration space, brings the measurement space except the calibration point into the calibration range, and establishes a relation model between world coordinates and camera pixel coordinates and phases in the space except the calibration point and the calibration point so as to avoid generating calibration errors.
Drawings
FIG. 1 is a schematic diagram of the calibration system of the present invention;
FIG. 2 is a schematic structural diagram of a rectangular coordinate system established with the center of a circle of an upper left calibration point on a dot calibration plate as an origin according to the present invention;
FIG. 3 is a calculation process of extracting phases of different periods and taking absolute values by a four-step phase shift method according to the present invention;
FIG. 4 is a set-up spatial coordinate systemorcφAnd the point to be interpolatedp（r，c，φ) And (5) carrying out an interpolation process.
Detailed Description
For a better understanding of the present invention, reference is made to the following detailed description and accompanying drawings that illustrate the invention.
The invention provides a calibration method of a digital grating projection measurement system for expanding a calibration space, which comprises the following steps:
s10: enlarging a calibration space by obtaining coordinates under a world coordinate system and affine matrixes among the coordinates under an image coordinate system;
s20: and obtaining a relation model of world coordinates and camera pixel coordinates and phases.
In the prior art, a calibration plate is usually adopted to calibrate a system, the area of a calibration area is limited to a coverage area of a calibration point on the calibration plate, and areas except the calibration point cannot be used for calibration, so that a measurement space except the calibration point inevitably generates calibration errors.
The invention firstly enlarges the calibration space, brings the measurement space except the calibration point into the calibration range, and establishes a relation model between world coordinates and camera pixel coordinates and phases in the space except the calibration point and the calibration point so as to avoid generating calibration errors.
Further, expanding the calibration space includes:
s101: obtaining coordinates of each calibration point on the known calibration plate under different positions under a world coordinate system and coordinates under an image coordinate system;
s102: obtaining coordinates of each calibration point in a world coordinate system and affine matrixes among the coordinates in an image coordinate system;
s103: and obtaining coordinates under a world coordinate system corresponding to the pixel points outside the calibration area of the known calibration plate according to the affine matrix.
Calibration space of traditional calibration methodVFrom the area S of the calibration area on the calibration plate and the distance moved by the calibration platehAre jointly determined, i.e.V =S·hThe calibration accuracy is inevitably reduced when the calibration space is exceeded, and the waste of camera pixels is also caused. The two ideas for enlarging the calibration space are provided, namely, the area of the calibration area is increasedSSecondly, increase the moving distance of the calibration plateh. Due to the distance of movementhLimited by the structure of the system and the formation of the guide rail of the displacement table, the increase is difficult, so the idea of the invention is to increase the area of the calibration areaS。
In the traditional method, the area of a calibration area is limited to the coverage area of a calibration point on a calibration plate, and the area except the calibration point cannot be used for calibration because the coordinate under a world coordinate system cannot be obtained; according to the invention, the coordinates of the pixel points outside the calibration area in the world coordinate system are obtained through affine transformation, so that the points outside the calibration area on the calibration plate are also used for calibration, and the area of the calibration area is increased.
According to the invention, the world coordinate system coordinates of each calibration point on the known calibration plate and the affine matrix of the image coordinate system coordinates are obtained, and the coordinates under the image coordinate system outside the calibration area of the known calibration plate can be collected by the camera, so that the collected coordinates under the image coordinate system outside the calibration area of the known calibration plate are subjected to affine transformation to obtain the coordinates under the world coordinate system of the pixel points outside the calibration area of the known calibration plate, and therefore, the pixel points outside the calibration area of the known calibration plate can also be used for calibration, the calibration area is increased, and the calibration result is more accurate.
Further, in a specific embodiment of the present invention, S101: the method for obtaining the coordinates of each calibration point on the known calibration plate under the world coordinate system at different positions comprises the following steps:
s1011: establishing a world coordinate system so that the world coordinate systemxoyThe faces are parallel to a known calibration plate,zthe axis is perpendicular to the known calibration plate;
s1012: perpendicular tozThe axes move the known calibration plate to obtain coordinates in the world coordinate system of each calibration point on the known calibration plate at different positions.
In this embodiment, as shown in fig. 1, the known calibration board is a dot calibration board 4, the dot calibration board 4 is provided with a plurality of calibration points with known parameters, and the calibration points are arranged in a matrix; the dot calibration plate 4 is placed on a precision displacement table 3 and moves under the driving of the precision displacement table 3, specifically, the precision displacement table 3 is provided with a fixed object carrying platform and a moving shaft capable of moving along the direction vertical to the object carrying plane, and the dot calibration plate 4 is placed on the object carrying platform of the precision displacement table 3 and moves along the direction vertical to the object carrying plane along with the object carrying platform; in this embodiment, the apparatus further comprises a camera 1 and a digital projector 2, wherein the camera 1 and the digital projector 2 are respectively fixed above the precision displacement stage 3 at an angle (for example, 30 degrees) independent of the precision displacement stage 3.
In this embodiment, the method further includes step S1010: the precision displacement table 3 is calibrated.
The precise displacement table 3 is calibrated by using a laser range finder, and the calibration aims to obtain the corresponding relation between the pulse number emitted by the laser range finder and the distance of the movement of the object carrying platform 3 along the direction vertical to the plane of the object carrying platform, such as fixing the pulse numberN p The distance of the precision displacement table 3 moving along the direction perpendicular to the plane of the object tablez p 。
Specifically, as shown in fig. 2, in the process of establishing the world coordinate system, the world coordinate system is madexoyThe face is parallel to the dot calibration plate 4,zthe axis is perpendicular to the dot calibration plate 4, and the purpose of this is to ensure that each calibration point on the dot calibration plate 4 is located during the movement of the dot calibration plate 4 in a direction perpendicular to its planexAxis coordinate andythe coordinates of the axes are not changed,zthe axis coordinate is the currentzThe axis coordinates plus the distance it has moved.
In a particular embodiment, the fine displacement stage 3 is marked in an initial positionp 0 In the process of establishing a world coordinate system, the precision displacement table 3 is firstly adjusted to an initial positionp 0 The dot calibration plate 4 is fixed on a precise displacement table, and the plane world coordinate system of the dot calibration plate 4 is usedxoyThe center of the circle of the upper left calibration point on the circular point calibration plate 4 is used as the originoThe direction of the row and the column parallel to the calibration dot matrix isx w A shaft,y w The axial direction, perpendicular to the direction of the calibration plate, isz w World coordinate system established in axial directionox w y w z w 。
Since the parameters of the dot calibration plate 4 are known, the initial position is determinedp 0 The coordinates of the center of each calibration point on the circular point calibration plate 4 in the world coordinate system are knownw p0 （x w ，y w ，z w ) Indicating that the dot calibration plate 4 is in the initial positionp 0 World coordinate system coordinatesw p0 （x w ，y w ，z w ) While a sinusoidal fringe pattern is projected onto the dot calibration plate 4 with the digital projector 2 and then a picture is taken with the camera 1.
Further, according to the result of the calibration in step S1010, the dot calibration plate 4 moves with the precision displacement table 3kA fixed number of pulsesN P The coordinates of the points on the dot calibration plate 4 in the world coordinate system are also knownw pk Indicating that the calibration plate 4 moves with the precision displacement table 3kA fixed number of pulsesN P When the world coordinate system coordinates arew pk （x w ，y w ，z w +kz p ) While a sinusoidal fringe pattern is projected onto the dot calibration plate 4 with the digital projector 2 and then a picture is taken with the camera 1.
By analogy, the precise displacement table is madeN PThe pulse is a movement interval and moves to the position in sequencep 1 Position ofp 2 …, positionp n (wherein,ntaking appropriate values according to specific conditions), then any position is adoptedp k （k = 1， 2，…，n) The coordinate under the world coordinate system of the center of each calibration point on the corresponding dot calibration plate 4 isw pk （x w ，y w ，z w + kz p ) Is collected to obtainp 0 Location is shared internallyn+ 1 fringe projection images at different positions.
Then, an image coordinate system is established according to the stripe projection images shot at different positions, and coordinates of each calibration point on the dot calibration plate 4 at different positions under the image coordinate system are extracted.
In a particular embodiment, the dots are for example in the upper left corner of the imageo c In the row and column directions of the imagerA shaft,cEstablishing an image coordinate system by the axis; extracting when the dot calibration plate 4 moves to different positions along with the precision displacement table 3 through an algorithmp k Then, the center of each calibration point on the calibration plate 4 of the round point in the collected picture is in the image coordinate systemo c rcCoordinates of lower, notedc pk （r，c）。
Because the coordinates under the image coordinate system and the coordinates under the world coordinate system of the circle centers of all the calibration points on the circular point calibration plate 4 are known, the known points are used for solving affine matrixes, and the affine transformation is carried out through the affine matrixes to obtain the coordinates under the world coordinate system corresponding to the pixel points on the image outside the calibration area on the calibration plate, so that the points outside the calibration area can be used for calibration, and the calibration space can be expanded by expanding the calibration area.
Further, in the process of obtaining the affine matrix, the coordinates of the calibration point in the world coordinate system are recorded asw pk The coordinates of the pixels outside the calibration area in the world coordinate system are recorded asw opk The coordinates of the index point in the image coordinate system are recorded asc pk And the coordinates of the pixel points outside the calibration area in the image coordinate system are recorded asc opk 。
Firstly, according to the coordinates of the calibration point on the dot calibration board 4 in the world coordinate systemw pk And coordinates in the image coordinate systemc pk Obtaining a matrix M by a least square method, wherein the affine transformation principle is as follows:
wherein the content of the first and second substances,x w andy w coordinates in the world coordinate system being the centre of the calibration pointw pk The first two items of (a) and (b),r、cis the coordinate of the center of a circle of the calibration point under the image coordinate systemc pk ，MIs a 2 x 3 matrix called affine transformation matrix.
Then, the image coordinates of the pixel points outside the calibration area of the dot calibration plate 4 are brought inc opk Can obtain the coordinates under the corresponding world coordinate systemw opk In (1)xAxial coordinatex opk Andyaxial coordinatey opk As follows:
the corresponding world coordinate system coordinatesw opk Comprises the following steps:
wherein the content of the first and second substances,z pk is the lower z-axis coordinate of the world coordinate system of the calibration area on the calibration plate.
In this embodiment, the coordinates in the world coordinate system of the pixel points other than the calibration point on the dot calibration plate 4 are obtained by the affine matrixw opk Therefore, the pixel points except the calibration point on the dot calibration plate 4 can also be used as the calibration points for calibration, and the calibration range is enlarged.
Further, in a specific embodiment of the invention, a relation model of world coordinates and phases of camera pixels is obtained by a polynomial method, which includes the following steps:
s201: acquiring phase values at the circle centers of the calibration points on the dot calibration plate 4;
s202: performing polynomial fitting through least square according to the obtained image coordinate of any point in the image coordinate system in the calibration space, the corresponding phase value and the coordinate of the point in the world coordinate system to obtain a polynomial of the world coordinate system and the image coordinate system;
s203: and calculating a calibration result.
Further, in the implementation, phase values are obtainedφThe method comprises two steps of phase extraction and phase unwrapping.
Specifically, the phase extraction process includes: the digital projector 2 projects four fringe patterns with 1/4 periods of phase difference to the dot calibration plate 4I 1，I 2，I 3AndI 4as given by the following equation.
Wherein the content of the first and second substances,Arepresents the average gray level of the image,Bwhich represents the degree of modulation,Trepresenting the period of the sinusoidal fringe, the main phaseφ 0The calculation method of (a) is given by the following formula:
due to the phase obtained at this timeφ 0Discontinuous and not true phase, it is necessary to unwrapp its phase to true phase by phase unwrapping algorithmφThe phase unwrapping method used in the present invention is a multi-period method, i.e. the projection periods are respectivelyT，2T，4T，…，2 k ·T，…，2 n ·TWhereink = 0， 1，2， …， nAnd ensuring that the fringe of the last period is less than or equal to 1 complete period in the area acquired by the camera, extracting the phases of different periods by a four-step phase shift method, taking an absolute value, and then sequentially performing the following operations, wherein a program block diagram is shown in fig. 3. Wherein the content of the first and second substances,φ(k) Represents a period of2 k ·TExtracting the phase of the sine fringe pattern to obtain the absolute value of the phase;φrepresenting the phase values during the unwrapping calculation, the final result being the phase unwrapped values.
Further, the calibration points obtained in the previous step are in different positions on the calibration platep k World coordinates of timew k (coordinates in world coordinate System outside the calibration areaw opk And calibrating coordinates under the world coordinate system in the regionw pk Composition) of the coordinates in the coordinate system of the image acquired by the camerac k (coordinates in the image coordinate System outside the calibration area)c opk And coordinates under the image coordinate system in the calibration areac pk Composition) and phase values obtained by phase calculationφ(ii) a Polynomial fitting using least squares calculations yields the following relationships:
wherein the content of the first and second substances,f N()(r, c, φ)，g N()(r, c, φ) Andh N()(r, c, φ) So as to maker，c，φIs a linear polynomial combination with the highest degree of the multivariate variable being N. For simplicity of expression, the quadratic multivariate linear regression is taken as an example, then
Wherein the content of the first and second substances,b x k,，b y k,andb z k,（k = 1, 2, …, 10) respectivelyf (2)(r, c, φ)，g (2)(r, c, φ) Andh (2)(r, c, φ) The coefficients of the terms in the expression.
The final calibration result obtained by the least square calculation can be expressed as follows.
Wherein the content of the first and second substances,b x ，b y andb z respectively correspond tof N()(r, c, φ)，g N()(r, c, φ) Andh N()(r, c, φ) The coefficients of the respective terms of the polynomial.
Further, in another specific embodiment of the present invention, a relation model of world coordinates and phases of camera pixels is obtained by an interpolation method, which includes:
S201，: acquiring phase values at the circle centers of the calibration points on the dot calibration plate;
S202，: according to the obtained image coordinate of any point in the image coordinate system in the calibration space, the corresponding phase value and the coordinate in the world coordinate system, the coordinate in the image coordinate systemr、c、φObtaining coordinates under a world coordinate system by axis three-dimensional interpolation;
S203，: and completing calibration.
Wherein step S201，: the method for acquiring the phase value at the center of each calibration point on the circular point calibration plate and the method for acquiring the phase value at the center of each calibration point on the circular point calibration plate through the step S201 in the polynomial method are as follows: the method for obtaining the phase value at the center of each calibration point on the dot calibration plate 4 is the same, and is not repeated again.
Further, step S202，Further comprising:
S2021，: establishing a space coordinate system;
S2022，: obtaining coordinates of adjacent points of the points to be interpolated in a space coordinate system;
S2023，: in turn atr、c、φAnd (5) interpolating in the axial direction.
In the implementation process, the coordinates in the world coordinate system are acquiredw k (x w , y w , z w ) The method of (1) is as follows:
the calibration points obtained in the previous step are in different positions on the calibration platep k World coordinates of timew k (coordinates in world coordinate System outside the calibration areaw opk And calibrating coordinates under the world coordinate system in the regionw pk Composition) of the coordinates in the coordinate system of the image acquired by the camerac k (coordinates in the image coordinate System outside the calibration area)c opk And coordinates under the image coordinate system in the calibration areac pk Composition) and phase values obtained by phase calculationφ；
According to the coordinates of any point in the image coordinate system in the calibration spacec k (r，c) And corresponding phase valueφRespectively obtaining the coordinate values under the world coordinate systemx w 、y w 、z w . As shown in FIG. 4, a spatial coordinate system is establishedorcφPoint of contactp(r, c,φ) For the point to be interpolated, the interpolation process needs 8 adjacent points to participate according to the principle of three-dimensional linear interpolation, and the coordinates of points 1-8 in the figure are shown in the following table:
TABLE 1 coordinate values of neighboring points
First, atrLinear interpolation in the axial direction:
wherein the content of the first and second substances,mis convenient to usex w Ory w Orz w ，Represents a particularr,c,φCoordinates under a world coordinate system corresponding to the values;m(r)、m(r i )、m(r i+1) Representsc, φHave the same valuerDifferent in valuemThe value is obtained. As a result, a plane 1 can be obtained, and the r-axis values of all points on the plane are allr。
Then, the coordinates of points 9-12 in the c-axis direction are linearly interpolated as shown in Table 2.
TABLE 2 coordinate values of adjacent points on plane 1
Interpolate as follows:
wherein the content of the first and second substances,mis convenient to usex w Ory w Orz w ，Represents a particularr，c，φCoordinates under a world coordinate system corresponding to the values;m(r, c)、m(r,c i )、m(r, c i+1) Represents a r-axis value ofr，φSame value and different c-axis valuemThe value is obtained. As a result, a straight line 1 having c-axis values of all points is obtainedc。
Finally, inφLinear interpolation in the axial direction. The coordinates of points 13 and 14 are respectively: (r,c, φ i )、(r,c, φ i+1 ). Interpolate as follows:
wherein the content of the first and second substances,mis convenient to usex w Ory w Orz w ，Represents a particularr,c,φThe value corresponds to the coordinate under the world coordinate system.
So far, the image coordinate of any point in the image coordinate system can be usedc k (r, c) And corresponding phase valueφObtaining the coordinates of the world coordinate systemw k (x w , y w , z w ) And the calibration of the whole system is completed.
The embodiments of the present invention have been described in detail, but the description is only for the preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made within the scope of the present invention should be covered by the present patent.
Claims (9)
1. A calibration method of a digital grating projection measurement system for expanding a calibration space is characterized in that: the method comprises the following steps:
s10: enlarging the calibration space;
s20: obtaining a relation model of world coordinates, camera pixel coordinates and phases;
the method for expanding the calibration space comprises the following steps:
s101: obtaining coordinates of each calibration point on the known calibration plate under different positions under a world coordinate system and coordinates under an image coordinate system;
s102: obtaining coordinates of each calibration point in a world coordinate system and affine matrixes among the coordinates in an image coordinate system;
s103: and obtaining coordinates under a world coordinate system corresponding to the pixel points outside the calibration area of the known calibration plate according to the affine matrix.
2. The calibration method of the digital grating projection measurement system with the enlarged calibration space of claim 1, wherein: s101: the method for obtaining the coordinates of each calibration point on the known calibration plate under the world coordinate system at different positions comprises the following steps:
s1011: establishing a world coordinate system so that the world coordinate systemxoyThe faces are parallel to a known calibration plate,zthe axis is perpendicular to the known calibration plate;
s1012: perpendicular tozThe axes move the known calibration plate to obtain coordinates in the world coordinate system of each calibration point on the known calibration plate at different positions.
3. The calibration method of the digital grating projection measurement system with the enlarged calibration space according to claim 1 or 2, wherein: the process of the coordinates under the image coordinate system of each calibration point on the known calibration plate under different positions is as follows: shooting the fringe projection images on the known calibration plate at different positions, establishing an image coordinate system, and extracting the coordinates of each calibration point on the known calibration plate at different positions under the image coordinate system.
4. The calibration method of the digital grating projection measurement system with the enlarged calibration space of claim 1, wherein: the affine matrix transformation process in step S102 is:
wherein the content of the first and second substances,x w andy w is a coordinate under a world coordinate system of the center of a calibration point of a known calibration areaw pk Is/are as followsxAxis coordinate sumyThe coordinates of the axes are set to be,r、cthe center of a circle of a calibration point in a known calibration area is the coordinate of an image coordinate systemc pk ，MIs a 2 x 3 matrix, which is an affine transformation matrix.
5. The calibration method of the digital grating projection measurement system with the enlarged calibration space of claim 1, wherein: and obtaining a relation model of world coordinates, camera pixel coordinates and phases by a polynomial method.
6. The calibration method of the digital grating projection measurement system with the enlarged calibration space of claim 5, wherein: the process of obtaining a relation model of world coordinates and camera pixel coordinates and phases by a polynomial method comprises the following steps:
s201: acquiring phase values at the circle centers of the calibration points on the dot calibration plate;
s202: performing polynomial fitting through least square according to the obtained image coordinate of any point in the image coordinate system in the calibration space, the corresponding phase value and the coordinate of the point in the world coordinate system to obtain a polynomial of the world coordinate system and the image coordinate system;
s203: and calculating a calibration result.
7. The calibration method of the digital grating projection measurement system with the enlarged calibration space of claim 1, wherein: and obtaining a relation model of world coordinates, camera pixel coordinates and phases by an interpolation method.
8. The calibration method of the digital grating projection measurement system with the enlarged calibration space of claim 7, wherein: the process of obtaining a relation model of world coordinates and camera pixel coordinates and phases by an interpolation method comprises the following steps:
S201，: acquiring phase values at the circle centers of the calibration points on the dot calibration plate;
S202，: according to the obtained image coordinate of any point in the image coordinate system in the calibration space, the corresponding phase value and the coordinate in the world coordinate system, the coordinate in the image coordinate systemr、c、φObtaining coordinates under a world coordinate system by axis three-dimensional interpolation;
S203，: and completing calibration.
9. The calibration method of the digital grating projection measurement system with the enlarged calibration space of claim 8, wherein: step S202，The method comprises the following steps:
S2021，: establishing a space coordinate system;
S2022，: obtaining coordinates of adjacent points of the points to be interpolated in a space coordinate system;
S2023，: in turn atr、c、φAnd (5) interpolating in the axial direction.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113847874A (en) * | 2021-08-20 | 2021-12-28 | 天津大学 | Vision-based displacement direction calibration method for displacement table |
| CN114234847A (en) * | 2021-12-08 | 2022-03-25 | 苏州恒视智能科技有限公司 | Grating projection system and automatic correction and compensation method for grating phase shift height measurement |
| CN115601231A (en) * | 2022-11-22 | 2023-01-13 | 南京后摩智能科技有限公司（Cn） | Image processing method and device, hardware accelerator, chip and equipment |
Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102183216A (en) * | 2011-03-14 | 2011-09-14 | 沈阳飞机工业（集团）有限公司 | Three-dimensional measurement method and device based on linear structured light |
| CN103528543A (en) * | 2013-11-05 | 2014-01-22 | 东南大学 | System calibration method for grating projection three-dimensional measurement |
| CN106408556A (en) * | 2016-05-23 | 2017-02-15 | 东南大学 | Minimal object measurement system calibration method based on general imaging model |
| CN106500626A (en) * | 2015-09-08 | 2017-03-15 | 东南大学 | A kind of mobile phone stereoscopic imaging method and three-dimensional imaging mobile phone |
| CN107146256A (en) * | 2017-04-10 | 2017-09-08 | 中国人民解放军国防科学技术大学 | Camera marking method under outfield large viewing field condition based on differential global positioning system |
| EP3238447A1 (en) * | 2014-12-22 | 2017-11-01 | Cyberoptics Corporation | Updating calibration of a three-dimensional measurement system |
| CN108225737A (en) * | 2017-12-06 | 2018-06-29 | 天津大学 | A kind of novel optical lens measurement method |
| CN110793464A (en) * | 2019-10-17 | 2020-02-14 | 天津大学 | Large-field-of-view fringe projection vision three-dimensional measurement system and method |
| CN111652943A (en) * | 2020-05-29 | 2020-09-11 | 浙江四点灵机器人股份有限公司 | Defocusing digital fringe projection calibration device and method |
| CN111811433A (en) * | 2020-07-15 | 2020-10-23 | 河北工业大学 | Structured light system calibration method and device based on red and blue orthogonal stripes and application |
-
2020
- 2020-11-26 CN CN202011343343.XA patent/CN112132890B/en active Active
Patent Citations (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102183216A (en) * | 2011-03-14 | 2011-09-14 | 沈阳飞机工业（集团）有限公司 | Three-dimensional measurement method and device based on linear structured light |
| CN103528543A (en) * | 2013-11-05 | 2014-01-22 | 东南大学 | System calibration method for grating projection three-dimensional measurement |
| EP3238447A1 (en) * | 2014-12-22 | 2017-11-01 | Cyberoptics Corporation | Updating calibration of a three-dimensional measurement system |
| CN106500626A (en) * | 2015-09-08 | 2017-03-15 | 东南大学 | A kind of mobile phone stereoscopic imaging method and three-dimensional imaging mobile phone |
| CN106408556A (en) * | 2016-05-23 | 2017-02-15 | 东南大学 | Minimal object measurement system calibration method based on general imaging model |
| CN107146256A (en) * | 2017-04-10 | 2017-09-08 | 中国人民解放军国防科学技术大学 | Camera marking method under outfield large viewing field condition based on differential global positioning system |
| CN108225737A (en) * | 2017-12-06 | 2018-06-29 | 天津大学 | A kind of novel optical lens measurement method |
| CN110793464A (en) * | 2019-10-17 | 2020-02-14 | 天津大学 | Large-field-of-view fringe projection vision three-dimensional measurement system and method |
| CN111652943A (en) * | 2020-05-29 | 2020-09-11 | 浙江四点灵机器人股份有限公司 | Defocusing digital fringe projection calibration device and method |
| CN111811433A (en) * | 2020-07-15 | 2020-10-23 | 河北工业大学 | Structured light system calibration method and device based on red and blue orthogonal stripes and application |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113847874A (en) * | 2021-08-20 | 2021-12-28 | 天津大学 | Vision-based displacement direction calibration method for displacement table |
| CN114234847A (en) * | 2021-12-08 | 2022-03-25 | 苏州恒视智能科技有限公司 | Grating projection system and automatic correction and compensation method for grating phase shift height measurement |
| CN114234847B (en) * | 2021-12-08 | 2024-01-30 | 苏州恒视智能科技有限公司 | Grating projection system and grating phase shift height measurement automatic correction compensation method |
| CN115601231A (en) * | 2022-11-22 | 2023-01-13 | 南京后摩智能科技有限公司（Cn） | Image processing method and device, hardware accelerator, chip and equipment |
| CN115601231B (en) * | 2022-11-22 | 2023-03-10 | 南京后摩智能科技有限公司 | Image processing method and device, hardware accelerator, chip and equipment |
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