CN107036555A - A kind of cross-axis optical grating projection measurement analogue system and its implementation - Google Patents

Abstract

The invention discloses a cross optical axis grating projection measurement simulation system (the so-called cross optical axis means that the mutual positions of the optical axis of the projector and the optical axis of the camera in the system are intersected, which overcomes the fact that the two optical axes must intersect in the existing simulation system. Because of the shortcomings of one point), using the windows system as the development platform, through the reverse ray tracing method, using the computer programming language, by writing the grating projection module, simulating the measured object and the workbench module, and the image acquisition module, the grating with high precision is realized. Projection measurement simulation system. The simulation system does not require that the optical axis of the projector and the optical axis of the camera intersect at one point, and can realize the simulation of the cross optical axis grating projection measurement system. The system can simulate the location of the shadow area of the object during the measurement process, and different discrimination methods are applied to the discrimination of the shadow area on the object surface and the shadow area on the workbench, which improves the accuracy and speed of shadow area discrimination .

Description

A simulation system for grating projection measurement with crossed optical axis and its realization method

technical field

The invention relates to a cross optical axis grating projection measurement simulation system and its realization method, more precisely, it is a structured light projection simulation system which uses a computer to simulate the grating modulation process in reality, and belongs to the field of structured light measurement.

Background technique

With the rapid development of science and technology and the continuous improvement of social productivity, the demand for measurement technology in various fields is also increasing, especially the requirements for its measurement method, measurement efficiency and measurement accuracy become more stringent. With computing technology. With the rapid development of optical measurement technology and digital image processing technology, three-dimensional shape measurement methods emerge in endlessly. Structured light measurement technology stands out among many measurement methods due to its advantages of non-contact and high precision.

The traditional contact three-dimensional measurement technology needs to touch the measured object through a mechanical probe, and obtain precise coordinate information on the surface of the object through the out point. The contact three-dimensional measurement technology has many advantages such as high measurement accuracy and no requirement on the color of the measured object, but there are also great disadvantages such as the measurement process takes a long time, and the mechanical probe will cause damage during the contact process with the object. Object surface contact deformation. More importantly, the surface shape of some objects is too complicated to be reached by mechanical probes, and the contact three-dimensional measurement technology for such objects cannot be measured.

Optical measurement technology is a non-contact three-dimensional measurement technology that can make up for the shortcomings of the above-mentioned contact three-dimensional measurement technology. The grating projection measurement technology is a very effective optical three-dimensional measurement technology. It projects the grating onto the surface of the object, causes deformation through the modulated grating on the surface of the object, and then uses the image collector to capture the deformed grating stripes, and finally demodulates them. The surface information of the object can be obtained. Due to the large amount of information, high efficiency and high accuracy of this technology, it has attracted much attention and has broad market prospects.

In order to use the fringe projection system (Fringe projection system, hereinafter referred to as FPS) to obtain the surface topography information of three-dimensional objects, it is best to use simulation to verify the design scheme before the experiment. Simulation can save the trouble of building an FPS platform, and the simulation is faster, more flexible, and can be used by others. The verification of FPS theory requires the establishment of a high-precision grating projection system, image collector, and experimental equipment calibration device. So it is necessary to develop a FPS simulation system as a replacement. Compared with building an FPS platform, the FPS simulation system not only has the advantages of high speed and economy, but also has higher flexibility and precision. In addition, it can also provide great convenience for system parameter setting and error analysis.

Many researchers have proposed optical simulation systems based on fringe projection technology. The simulation algorithms used in most literatures mainly use ray tracing techniques. At present, the ray tracing method is widely used in the field of optical simulation, but there are still many problems in the ray tracing method: first, due to the problem of Boolean union, the three-dimensional information is reduced to one dimension, resulting in two problems, the operation of three-dimensional objects It should be normalized, and the limited precision of machine calculations brings errors in the calculation of intersection points of lines and surfaces. Introducing a simple approximation regularization rule can ignore some small errors, but has some side effects. Second, many commonly used intersection algorithms have some obvious numerical problems due to the limitations of floating-point arithmetic. In particular, when light passes through a free-form surface, complex algorithms must be used to discuss different situations.

Studying the modulation process of grating stripes on the surface of an object is of great significance for studying the modulation method of gratings, studying the influence of system parameters on measurement, evaluating the pros and cons of algorithms, and determining reasonable technical solutions and system structures. However, the simulation methods of grating projection simulation systems that exist today are all based on the fact that two optical axes intersect at one point. If this method is still used to simulate the grating projection measurement system with crossed optical axes, the simulated result image Severe shape distortion will occur.

Contents of the invention

The technical problem to be solved by the present invention is to provide a cross-optical axis grating projection measurement simulation system and its implementation method, which are used to solve the problem of resultant image shape distortion in conventional grating projection simulation systems.

The technical solution adopted in the present invention is: a cross-optical axis grating projection measurement simulation system,

Using the windows system as the development platform, through the reverse ray tracing method, using the computer programming language, the grating projection module-Projecter, the simulated object to be measured-Object and the workbench module-plane R ₁ R ₂ R ₃ R ₄ , image acquisition module -Camera, realize the simulation model with grating projection measurement system, in which the optical axes of the simulated projector and camera have no intersection,

The grating projection module is used to simulate a projector to generate a grating fringe image, and set the grating modulation frequency and initial phase, so that the grating fringe image is projected onto the surface of the measured object;

The measured object and the workbench module are used to simulate the object to be measured and the test bench where the object is located;

The image acquisition module is used for simulating a camera to collect modulated grating stripes. After the simulated grating is projected onto the surface of an object, the grating stripes will be modulated by the surface of the object, resulting in deformation. The deformed grating fringe image is collected by simulating an industrial camera.

A method for realizing a cross optical axis grating projection measurement simulation system, comprising the following specific steps:

Step1, calculate the coordinates of the D point corresponding to the E point in the CCD array, wherein: the E point is the CCD pixel center, and the D point is the intersection of the extension line of the line segment EC and the reference plane R ₁ R ₂ R ₃ R ₄ ;

Step2. Calculate the coordinates of the intersection point A of the straight line CD and the surface of the object;

Step3. Transform the calculated coordinates of points A and D from the world coordinate system to the coordinate system of the projector to obtain the coordinates of points A' and D' in the coordinate system of the projector;

Step4. Calculate the x' coordinate of the intersection point B' of the straight line PA' and the projector reference plane and the x' coordinate of the intersection point W' of the straight line PD' and the projector reference plane according to the obtained coordinates of points A' and D';

Step5, calculate the intensity value of the pixel corresponding to point A and point D on the CCD array according to the x' coordinates of B' and W' in Step4;

Step6. Use the vector method to determine the area where shadows appear on the surface of the object;

Step7. Use the intersection number method to judge the area where the shadow appears on the plane R ₁ R ₂ R ₃ R ₄ .

In the step Step1, the principle of similar triangles is used for calculation, as follows:

Point E is a CCD pixel. The length and width of each pixel are represented by S _x and S _y respectively. The row and column of point E on the CCD array are represented by i and j respectively. The pixel E is connected to the optical center. The extension of the line EC intersects the surface of the object at point A, and intersects the plane R ₁ R ₂ R ₃ R ₄ at point D. According to the principle of similar triangles, the coordinates of point D can be calculated by formulas (1) and (2).

Among them, i represents the pixel in the i-th row, f represents the focal length of the camera, and l represents the distance from the optical center of the camera to the reference plane R ₁ R ₂ R ₃ R ₄ .

The coordinate calculation of the intersection point A of the straight line CD and the object surface in the step Step2 is calculated using the variable step size iterative method, as follows:

Since point A is on the straight line CD, according to the principle of similar triangles, we can obtain formulas (3), (4), and (5),

z _A ＝f(x _A ,y _A )(5)

In the three-dimensional space, use the iterative method to directly calculate the coordinates of the intersection point A. Point A is the intersection point between the straight line CD and the surface of the object. Suppose there is a point Q(x _q , y _q , z _q ) on the CD line, and the auxiliary line GH passes through point Q Perpendicular to the reference plane, H is the intersection point of the straight line GH and the reference plane, G is the intersection point of the straight line GH and the surface of the object, let h ₁ =QH, h ₂ =GQ, during the period h ₁ and h ₂ can be obtained by formula (6), formula ( 7) Calculated,

h ₂ ＝f(x _q ,y _q ) (7)

Among them, z=f(x,y) is the function expression of the surface,

Let point D be the initial iterative point, and the initial step size s=1, iteratively search toward point C, and the results obtained after each iteration are as follows:

is the abscissa and ordinate of point Q obtained after n+1 iterations, k represents the ratio of the ordinate and abscissa of point Q, k=j/i, where i, j represent the abscissa and ordinate of the pixel at point E ,

Determine the stop point of the iteration, define three variables d ₁ , d ₂ , k _d , make the difference d ₁ = h ₁ -h ₂ calculated for the first time h ₁ , h 2 , and calculate h ₁ , h ₂ The difference d ₂ of h ₂ =h ₁ -h ₂ , let k _d =d ₁ ·d ₂ , this process re-assigns d ₁ and d ₂ once every iteration step, when point Q is on the DA line segment h ₁ >h ₂ (QH>GH), there is h ₁ -h ₂ <0; when point Q is on AC line segment, h ₁ >h ₂ , there is h ₁ -h ₂ >0; if the sign of k _d is nth Changes occur during iteration, indicating that Q point is on the DA line segment during the n-1 iteration, and Q point is on the AC line segment during the n-1 iteration, which means that the Q point has been iterated to the vicinity of the A point, and the Q point starts after exceeding the A point Reduce the value of the step size s and iterate in the opposite direction, set s=-s/2, and then use the above method to perform multiple iterations until |s|<0.001 and the iteration stops.

In the step Step4, according to the obtained A', D' point coordinates, calculate the x' coordinate of the intersection point B' of the straight line PA' and the projector reference plane and the x of the intersection point W' of the straight line PD' and the projector reference plane 'coordinates, as follows:

Points A', B', D', and W' correspond to points A, B, D, and W in the world coordinate system respectively. When observed in the coordinate system of the projector, point B' is the line PA and the plane R ₅ R ₆ R ₇ The intersection point of R ₈ , the straight line B'F' is perpendicular to the y'axis; the point W' is the intersection point of the straight line PD' and the plane R ₅ R ₆ R ₇ R ₈ , the straight line W'G' is perpendicular to the y' axis, according to similar triangles The principle can get formulas (10), (11), and then the x' coordinates of points B' and W' can be obtained,

Said step Step5 calculates the intensity value of the pixel corresponding to A point and D point on the CCD array according to the x' coordinates of B' and W' points in Step4, specifically as follows:

The pitch of the grating projected on the plane x'O'y' is λ, and the initial phase at point O' is set to 0, then the phases of the grating at point B' and point W' can be calculated by formulas (12) and (13) respectively get:

Among them, B'F'=x _B' , W'G'=x _W' ,

If there is an intersection point between the line ED and the object surface, the point E(i, j) on the CCD array represents the grating fringe intensity image modulated by the object surface, and the intensity of point E and B on the reference plane R ₅ R ₆ R ₇ R ₈ 'corresponds to the point intensity, and its intensity value can be calculated according to formula (14). If there is no intersection point between the line ED and the object surface, then the point E(i, j) on the CCD array represents the intensity of the grating stripes on the reference plane In the image, the intensity of point E corresponds to the intensity of point W' on the reference plane R ₅ R ₆ R ₇ R ₈ , and its intensity value can be calculated according to formula (15),

Among them, a represents the background light intensity, and b represents the maximum intensity of the projected grating.

Said step Step7, using the intersection number method to judge the area where the shadow appears on the reference plane, is as follows:

Point D on the plane can be seen by the camera at point D, but the light from the projector cannot be seen, so the intensity of point A seen by the camera is the black background light. For this case, the interpolation method is applicable, starting from point D , to iteratively search for point P, and determine how many intersection points there are between the line PD and the object surface. If there are more than one intersection points between the line PD and the object surface, then it can be determined that point D must be blocked by the object, and its light intensity It is equal to the background light intensity. The method of judging the number of intersection points is as follows:

H is a point on the line PD, let MH=h ₁ , MN=h ₂ , its size can be calculated by formula (16),

Let point D be the initial iterative point, carry out iterative calculation toward the direction of P, set the iterative step size as s=1, use formula (17) to carry out iterative search,

in, is the abscissa and ordinate of point Q obtained after n+1 iterations,

Define four variables d ₁ , d ₂ , k _d , n, let the first calculation of the difference between h ₁ and h ₂ be d ₁ =h ₁ -h ₂ , and calculate the values of h ₁ and h ₂ after iterating on point Q Difference d ₂ ＝h ₁ -h ₂ , let k _d ＝d ₁ ·d ₂ , this process re-assigns d ₁ and d ₂ once every iteration step, let n=0, if k _d <0, execute n=n+1, follow this method to iteratively calculate from point D to point P until the iteration stops at point P. If the final result is that the value of n is the number of intersection points, if n≥1, it can be obtained The straight line PD has an intersection point, so it can be judged that the point D is in the shaded area. At this time, the background light intensity can be used to assign a value to the point E corresponding to the point D on the CCD array.

The beneficial effects of the present invention are:

1. Easy to use

In order to use the fringe raster projection system (FPS) to obtain the surface topography information of three-dimensional objects, it is best to use simulation to verify the design scheme before the experiment. Simulation can save the trouble of building an FPS platform, and the simulation is faster, more flexible, and can be used by others. The verification of FPS theory requires the establishment of a high-precision grating projection system, image collector, and experimental equipment calibration device. Compared with building an FPS platform, the FPS simulation system not only has the advantages of high speed and economy, but also has higher flexibility and precision. In addition, it can also provide great convenience for system parameter setting and error analysis.

2. Cross optical axis grating projection measurement simulation

The so-called crossed optical axis means that the mutual positions of the optical axis of the projector and the optical axis of the camera in the system are intersected, which overcomes the shortcoming that the two optical axes must intersect at one point in the existing simulation system. The simulation methods of grating projection simulation systems that exist today are all based on the fact that two optical axes intersect at one point. If this method is still used to simulate the grating projection measurement system with crossed optical axes, the simulated result image will be Severe shape distortion occurs. The proposed method solves the problem of image shape distortion in the previous grating projection simulation system.

Description of drawings

Fig. 1 is a schematic diagram of the system of the present invention;

Fig. 2 is the two-dimensional schematic diagram of point A (line and curved surface intersection point) calculated by iterative method;

Figure 3 A point algorithm flow chart;

Fig. 4 is a three-dimensional schematic diagram of the coordinates of each point in the projector coordinate system;

Fig. 5 is a two-dimensional schematic diagram of the shadow area discrimination method on the plane R ₁ R ₂ R ₃ R ₄ ;

Fig. 6 is a flow chart of the implementation method of the grating projection simulation system with crossed optical axes in the present invention.

detailed description

The present invention will be further elaborated below in conjunction with the embodiments and accompanying drawings, but the protection content of the present invention is not limited to the stated scope.

Embodiment: Referring to Fig. 1-Fig. 6, a kind of cross optical axis grating projection measurement simulation system adopts 64-bit win7 operating system, Intel(R) Core(TM) i5-2410M CPU@2.30 processor, 4GB memory, selects C ++Builder6.0 is the development software. Through the reverse ray tracing method, using C++ language, by writing the grating projection module-projecter, simulating the object to be measured and the workbench module, and the image acquisition module-camera (where point C is the optical center of the camera), a grating projection measurement system is realized A simulation model for ; where the optical axes of the simulated projector and camera do not need to intersect. In the embodiment, the simulation system parameters are selected as follows: the CCD pixel is 800x600, the camera focal length f=1.5mm, the pixel size s _x =0.0032mm, s _y =0.0032mm, the distance l between the camera and the reference plane R ₁ R ₂ R ₃ R ₄ = 100mm, the distance l` between the projector and the reference plane R ₅ R ₆ R ₇ R ₈ = 150mm, the installation position of the projector: xp = -150mm, yp = 0mm, zp = 100mm.

A cross optical axis grating projection measurement simulation system, comprising the following specific steps:

Step1, calculate the coordinates of the D point corresponding to the E point in the CCD array, the E point is the CCD pixel center, and the D point is the intersection of the extension line of the line segment EC and the reference plane R ₁ R ₂ R ₃ R ₄ ;

Step2. Calculate the coordinates of the intersection point A of the straight line CD and the surface of the object;

Step3. Transform the calculated coordinates of points A and D from the world coordinate system to the coordinate system of the projector to obtain the coordinates of points A' and D' in the coordinate system of the projector;

Step4. Calculate the x' coordinate of the intersection point B' of the straight line PA' and the projector reference plane and the x' coordinate of the intersection point W' of the straight line PD' and the projector reference plane according to the obtained coordinates of points A' and D';

Step5, calculate the intensity value of the pixel corresponding to point A and point D on the CCD array according to the x' coordinates of B' and W' in Step4;

Step6. Use the vector method to determine the area where shadows appear on the surface of the object;

Step7. Use the intersection number method to judge the area where the shadow appears on the reference plane;

Further, use similar triangle principle to calculate in described step Step1, specifically as follows: As shown in Figure 1, point E is a CCD pixel, and the length and width of each pixel are represented by S _x and S _y respectively, and point E is at The row and column on the CCD array are represented by i and j respectively. The extension line of the line EC connecting the pixel E and the optical center intersects the surface of the object at point A, and intersects the plane R ₁ R ₂ R ₃ R ₄ at point D. According to the principle of similar triangles, formulas (1) and (2) can be drawn to calculate the coordinates of point D,

Among them, i represents the pixel in the i-th row, f represents the focal length of the camera, and l represents the distance from the optical center of the camera to the reference plane R ₁ R ₂ R ₃ R ₄ .

Further, the coordinate calculation of the intersection point A between the straight line CD and the surface of the object in Step 2 is calculated using the variable step size iterative method, specifically as follows: as shown in Figure 1, since point A is on the straight line CD, according to the principle of similar triangles, we can get Formulas (3), (4), (5) are given.

z _A ＝f(x _A ,y _A )(5)

Since the above formula cannot be used to directly calculate the coordinate of the intersection point A in three-dimensional space, an iterative method is used for numerical calculation. As shown in Figure 2, point A is the intersection point of straight line ED and the surface of the object. Imagine that there is a point Q(x _q , y _q , z _q ) on the straight line CD, and the auxiliary line GH passing through point Q is perpendicular to the reference plane, and H is the straight line GH and The intersection point of the reference plane, G is the intersection point of the straight line GH and the surface of the object, let h ₁ =QH, h ₂ =GQ, mid-term h ₁ , h ₂ can be calculated by formula (6) and formula (7) respectively,

h ₂ ＝f(x _q ,y _q ) (7)

Let point D be the initial iterative point, and the initial step size s=1, iteratively search toward point C, and the results obtained after each iteration are as follows:

is the abscissa and ordinate of point Q obtained after n+1 iterations, k represents the ratio of the ordinate and abscissa of point Q, k=j/i, where i, j represent the abscissa and ordinate of the pixel at point E ,

Determine the stop point of the iteration, define three variables d ₁ , d ₂ , k _d , make the difference d ₁ = h ₁ -h ₂ calculated for the first time h ₁ , h 2 , and calculate h ₁ , h ₂ The difference of h ₂ is d ₂ =h ₁ -h ₂ , let k _d =d ₁ ·d ₂ , and the values of d ₁ and d ₂ are re-assigned at each iteration step of this process. When the Q point is on the DA line segment, h ₁ >h ₂ (QH>GH), there are h ₁ -h ₂ <0; when the Q point is on the AC line segment, h ₁ >h ₂ , there are h ₁ -h ₂ >0 ; If the sign of k _d changes at the nth iteration, it means that the Q point is on the DA line segment at the n-1th iteration, and the Q point is on the AC line segment at the n-1th iteration, which means that the Q point has been iterated to A point nearby. After point Q exceeds point A, start to reduce the value of the step size s and iterate in the opposite direction, let s=-s/2, and then use the above method to perform multiple iterations until |s|<0.001 iteration stops, and the obtained Q The point is intersection point A. The flow chart of point A algorithm is shown in Figure 3.

Further, in the step Step4, according to the calculated A', D' point coordinates, calculate the x' coordinate of the intersection point B' of the straight line PA' and the projector reference plane and the intersection point W of the straight line PD' and the projector reference plane The x' coordinates of ' are as follows: as shown in Figure 4 (A', B', D', W' correspond to A, B, D, W in the world coordinate system respectively), observed in the projector coordinate system, B' Point is the intersection point of line PA and plane R ₅ R ₆ R ₇ R ₈ , line B'F' is perpendicular to the y'axis; point W' is the intersection point of line PD' and plane R ₅ R ₆ R ₇ R ₈ , line W 'G' is perpendicular to the y' axis. According to the principle of similar triangles, formulas (10) and (11) can be obtained, and then the x' coordinates of points B' and W' can be obtained.

Further, said step Step5 calculates the intensity value of the pixel corresponding to point A and point D on the CCD array according to the x' coordinates of B' and W' in Step4, specifically as follows: on the plane x'O'y' The pitch of the projected grating is λ, and the initial phase of point O' is set to 0, then the phases of the grating at point B' and point W' can be calculated by formulas (12) and (13) respectively:

where, B'F'=x _B' , W'G'=x _W' ,

If there is an intersection point between the line ED and the object surface, the point E(i, j) on the CCD array represents the grating fringe intensity image modulated by the object surface, and the intensity of point E and B on the reference plane R ₅ R ₆ R ₇ R ₈ ' Corresponding to the intensity of the point, its intensity value can be calculated according to the formula (14). If there is no intersection point between the line ED and the object surface, the point E(i, j) on the CCD array represents the grating fringe intensity image on the reference plane, the intensity of point E and W on the reference plane R ₅ R ₆ R ₇ R ₈ ' Corresponding to the intensity of the point, its intensity value can be calculated according to the formula (15).

Among them, a represents the background light intensity, and b represents the maximum intensity of the projected grating.

Further, said step Step7, using the intersection number method to judge the area where the shadow appears on the reference plane, is as follows:

As shown in Figure 5, point D on the workbench plane can be seen by the camera at point D, but cannot be illuminated by the light of the projector, so the intensity of point A seen by the camera is the black background light. For this kind of situation, this patent uses an interpolation method to judge the shadow area, starting from point D, iteratively searching to point P, judging how many intersection points there are between the straight line PD and the object surface, if the intersection point of the straight line PD and the object surface If there are more than one, it can be determined that point D must be blocked by an object, and its light intensity is equal to the background light intensity. The method of judging the number of intersection points is as follows:

As shown in Fig. 5, H is a point on the straight line PD, let MH=h ₁ , MN=h ₂ , and its size can be calculated by formula (16).

Let point D be the initial iterative point, carry out iterative calculation in the direction of P, set the iterative step size as s=1, and use formula (17) to carry out iterative search.

in, are the abscissa and ordinate of point Q obtained after n+1 iterations.

Define four variables d ₁ , d ₂ , k _d , n, let the first calculation of the difference between h ₁ and h ₂ be d ₁ =h ₁ -h ₂ , and calculate the values of h ₁ and h ₂ after iterating on point Q Difference d ₂ ＝h ₁ -h ₂ , let k _d ＝d ₁ ·d ₂ , this process re-assigns d ₁ and d ₂ once every iteration step, let n=0, if k _d <0, execute n=n+1, follow this method to iteratively calculate from point D to point P until the iteration stops at point P. If the final result is that the value of n is the number of intersection points, if n≥1, it can be obtained The straight line PD has an intersection point, so it can be judged that point D is in the shadow area. At this time, we can use the background light intensity to assign a value to point E corresponding to point D on the CCD array. The implementation method flow of the system is shown in FIG. 6 .

The present invention is described through a specific implementation process. Without departing from the scope of the present invention, various transformations and equivalent substitutions can be made to the present invention. Therefore, the present invention is not limited to the disclosed specific implementation process. Anyone familiar with the technology Those skilled in the art within the technical scope disclosed in the present invention, the simple changes of the technical solutions that can be clearly obtained should fall within the protection scope of the present invention.

Claims (7)

1. The utility model provides a crossing optical axis grating projection measurement simulation system which characterized in that:

the windows system is used as a development platform, a grating projection module projector, a simulated Object-Object and a workbench module-plane R are compiled by a back light tracing method and a computer programming language₁R₂R₃R₄And an image acquisition module-Camera, implementing a simulation model with a raster projection measurement system, wherein the optical axes of the simulated projector and Camera do not have an intersection point,

the grating projection module is used for simulating a projector to generate a grating stripe image, and setting a grating modulation frequency and an initial phase so as to project the grating stripe image to the surface of a measured object;

the measured object and workbench module is used for simulating an object to be measured and an experiment table where the object is located;

the image acquisition module is used for acquiring modulated grating stripes by the analog camera, the grating stripes can be modulated by the surface of the object after the analog grating is projected onto the surface of the object, so that deformation is generated, and the image of the deformed grating stripes is acquired by the analog industrial camera.

2. A realization method of a cross optical axis grating projection measurement simulation system is characterized in that: the method comprises the following specific steps:

step1, calculating the coordinates of a point D corresponding to the point E in the CCD array, wherein: point E is the center of CCD pixel, point D is the extension line of line segment EC and reference plane R₁R₂R₃R₄The intersection point of (a);

step2, calculating the coordinates of the intersection point A of the straight line CD and the surface of the object;

step3, transforming the coordinates of the points A and D obtained from the world coordinate system into the projector coordinate system to obtain the coordinates of the points A 'and D' in the projector coordinate system;

step4, calculating the x 'coordinate of the intersection point B' of the straight line PA 'and the projector reference plane and the x' coordinate of the intersection point W 'of the straight line PD' and the projector reference plane according to the calculated point coordinates A 'and D';

step5, calculating the intensity values of the pixels corresponding to the points A and D on the CCD array according to the x ' coordinates of B ' and W ' in Step 4;

step6, judging the area where the shadow appears on the surface of the object by using a vector method;

step7, judging plane R by using intersection point number method₁R₂R₃R₄Upper shaded areas.

3. The method for implementing the cross optical axis grating projection measurement simulation system according to claim 2, wherein: in the Step1, a similar triangle principle is used for calculation, which is specifically as follows:

the E point is CCD picture element, the length and width of each picture element are respectively S_x，S_yTo show that the row and column of point E on CCD array are respectively represented by i, j, the extended line of the connecting line EC of the image element E and the optical center intersects with the surface of the object at point A, and the extended line intersects with the plane R₁R₂R₃R₄Intersecting with the D point, obtaining the coordinates of the D point by formulas (1) and (2) according to the similar triangle principle,

where i denotes the pixel in the ith row, f denotes the camera focal length, and l denotes the camera center to the reference plane R₁R₂R₃R₄The distance of (c).

4. The method of claim 3, wherein the simulation system comprises: the coordinate calculation of the intersection point a of the straight line CD and the object surface in Step2 is calculated by using a variable Step size iterative method, which specifically comprises the following steps:

since point a is on the straight line CD, we can derive equations (3), (4), (5) according to the principle of similar triangles,

z_A＝f(x_A,y_A) (5)

directly calculating the intersection point A in the three-dimensional space by adopting an iteration methodIn the notation, point A is the intersection of the line CD and the surface of the object, assuming that there is a point Q (x) on the CD line_q，y_q，z_q) The Q-point-crossing auxiliary line GH is perpendicular to the reference plane, H is the intersection point of the straight line GH and the reference plane, G is the intersection point of the straight line GH and the object surface, and H is the order of the intersection point of the straight line GH and the object surface₁＝QH，h₂Long term GQ, term h₁，h₂Can be respectively calculated by formula (6) and formula (7),

h₂＝f(x_q,y_q) (7)

wherein, z ═ f (x, y) is a function expression of a curved surface,

and (3) taking the point D as an initial iteration point, setting the initial step length s as 1, performing iteration search in the direction of the point C, and obtaining the following results after each iteration is performed:

is the abscissa and ordinate of the Q point obtained after n +1 iterations, k represents the ratio of the ordinate and the abscissa of the Q point, k is j/i, where i, j represent the abscissa and the ordinate of the E point pixel,

determining iteration stop point, defining three variables d₁、d₂、k_dLet h be calculated for the first time₁、h₂Difference d of₁＝h₁-h₂H is calculated after the Q point iteration₁、h₂Difference d of₂＝h₁-h₂Let k_d＝d₁·d₂The process will repeat d once again for each iteration step₁、d₂Assignment of valueOnce, h when the point Q is on the DA line segment₁＞h₂(QH > GH) having h₁-h₂Less than 0; when the Q point is on the AC line segment h₁＞h₂Has the following advantages₁-h₂Is greater than 0; if k is_dThe sign of (a) is changed in the nth iteration, which indicates that the Q point is on the DA line segment in the nth-1 iteration and the Q point is on the AC line segment in the nth-1 iteration, namely, the Q point is already iterated to the vicinity of the A point, the value of the step length s is reduced after the Q point exceeds the A point, the iteration is carried out in the opposite direction, so that s is equal to-s/2, and then the iteration is carried out for multiple times by using the method until | s | is less than 0.001, and the iteration is stopped.

5. The method of claim 4, wherein the simulation system comprises: in Step4, the x 'coordinate of the intersection point B' of the straight line PA 'and the projector reference plane and the x' coordinate of the intersection point W 'of the straight line PD' and the projector reference plane are calculated from the obtained coordinates of the points a 'and D', as follows:

points A ', B ', D ' and W ' respectively correspond to A, B, D, W points in a world coordinate system, and the point B ' is a straight line PA and a plane R when observed in a projector coordinate system₅R₆R₇R₈The straight line B ' F ' is perpendicular to the y ' axis; point W 'is a straight line PD' and a plane R₅R₆R₇R₈The intersection point of the straight line W 'G' is vertical to the y 'axis, the formulas (10) and (11) can be obtained according to the similar triangle principle, then the x' coordinates of the points B 'and W' can be obtained,

6. the method of claim 5, wherein the simulation system comprises: in the Step5, the intensity values of the pixels corresponding to the points a and D on the CCD array are calculated according to the x ' coordinates of the points B ' and W ' in Step4, which is specifically as follows:

the grating pitch projected on the plane x 'O' y 'is λ, and the initial phase of the O' point is 0, then the grating phases at the B 'point and the W' point can be calculated by the equations (12) and (13), respectively:

wherein, B' F ═ x_B'，W'G'＝x_W',

If the line ED has an intersection with the object surface, the point E (i, j) on the CCD array represents the intensity image of the grating fringe modulated by the object surface, the intensity of the point E and the reference plane R₅R₆R₇R₈The intensity of the point B' above corresponds to the intensity value calculated according to equation (14), and if there is no intersection between the line ED and the object surface, the point E (i, j) on the CCD array represents the grating fringe intensity image on the reference plane, the intensity of the point E and the reference plane R₅R₆R₇R₈The intensity of the point W' above corresponds to its intensity value, which can be calculated according to equation (15),

where a represents the background light intensity and b represents the maximum intensity of the projection grating.

7. The method of claim 6, wherein the simulation system comprises: step7, judging the area where the shadow appears on the reference plane by using an intersection number method, which is specifically as follows:

for the point D on the plane, the camera can see the point D, but the light of the projector can not be illuminated, so the intensity of the point A seen by the camera is the black background light, the interpolation method is applied to the situation, the iterative search is carried out from the point D to the point P, a plurality of intersection points are judged between the straight line PD and the object surface, if the intersection points between the straight line PD and the object surface are more than 1, the point D can be judged to be blocked by the object, the light intensity is equal to the background light intensity, and the method for judging the number of the intersection points is as follows:

h is a point on the straight line PD, let MH be H₁，MN＝h₂The size of which can be calculated by equation (16),

taking the point D as an initial iteration point, performing iterative calculation in the direction of P, setting the iteration step length as s to be 1, performing iterative search by using a formula (17),

wherein, is the abscissa and ordinate of the Q point obtained after n +1 iterations,

four variables d are defined₁、d₂、k_dN, let h be calculated for the first time₁、h₂Difference d of₁＝h₁-h₂H is calculated after the Q point iteration₁、h₂Difference d of₂＝h₁-h₂Let k_d＝d₁·d₂The process will repeat d once again for each iteration step₁、d₂Assigning once, making n equal to 0, if k_dIf n is less than 0, executing n to n +1, and sequentially carrying out iterative calculation from the point D to the point P according to the method until the point P stops the iteration, if the final obtained result is that the value of n is the number of intersection points, if n is more than or equal to 1, the straight line PD can be obtained to have intersection points, so that the point D can be judged to be in a shadow area, and at the moment, the point E corresponding to the point D on the CCD array can be assigned by using the background light intensity.