Differential electron-projection method for measuring a surface shape of the object

 

The invention relates to measurement devices, and in particular to methods for measuring the shape and movements of the object surface. The invention consists in projecting synthesized in the computer reference grid representing the alternating bands of light and dark, scanning the grid digital camera. Comparing the received image with the synthesized mesh and characterization of the surface at each point. Effect: increase the accuracy of the surface shape and the increasing automation of the control process. 3 Il.

The invention relates to measurement devices, and in particular to methods for measuring the shape and movements of the surface of the object.

A method of obtaining a moiré pattern, which gives qualitative information about the surface of the object, based on the design of the image grid from slide on the surface of the object, and then adding the obtained image of the grid on the surface of an object with another grid in front of the object [1].

The disadvantage of this method is its complexity, the difficulty of obtaining results in real time.

The known method for motion measurement, osnovannymi bands of light and getting moire patterns and counting the number of moiré patterns [2].

The disadvantage of this method is the low accuracy and complexity.

Known electron-projection method for measuring the shape and movements of the object surface [3] , which is the closest to the claimed consists in the fact that the grid from slide projected on the surface of the object so that the dark line was crossed by the main optical axis of the projector, and the main optical axis of the projector and the cameras intersect at a point on the surface of the object obtained using the camcorder raster object is introduced into the computer, where it is compared with the pre-formed imaginary raster and the results of the comparison determine the surface shape of the object.

The disadvantage of this method is the lack of accuracy and the dependence of the result on the angle between the main optical axes of the projector and video camera.

The problem to be solved in the proposed method, associated with the automated monitoring of surface production facilities. The technical result is achieved by using the described method increases the precision of the surface of an object, also increases the degree of automates the three video systems by combining the axes of the projector and camera at the point on the object surface, then carry out the projection of this surface with the projector grid with alternating light and dark lines, synthesize imaginary raster computer, put it with the adopted camera work pattern and define obtained by moiré picture taking into account the previously established correlation parameters of the surface of the object, and the parameters of the synthesized computer projected on the surface of the object reference grid and imaginary raster programmatically change and imaginary raster turn relative to its original position angle in the plane of the projection axis of the projector.

In Fig. 1 shows a structural diagram for the implementation of the proposed method. It contains the control object 1 with designed for him by the grid, a digital projector 2, the digital video camera 3, a controller 4, the actuator 5, the personal computer 6, the plane of the imaginary raster 7 and rotated by the anglethe imaginary plane raster 8.

The proposed method is implemented as follows.

Using the computer 6 is synthesized grid view (set the grid spacing, the width of the bright and dark bands, the angle of rotation in the plane of the design), which is ZAT what about their main optical axis are focused at point a on the surface of the object. Is determined by the anglebetween the main optical axis of the projector 2 and the camera 3 and the distance L from the projector 2 to the point A. the Image projected on the surface of the object grid (raster work) is taken by the camera 3 and transmitted to the computer 6. After that, the computer 6 is synthesized second grid (imaginary raster) 7, spaced from the surface of an object at a distance of LIn. Later in the computer 6 using a special program is turning imaginary raster 7 relative to the point In lying on the axis of the projector, in the plane perpendicular to this axis, on the corner. Then in the computer 6 overprint working and rotated by the angleimaginary raster 8, getting moire patterns and the calculation on the specified dependencies of the parameters of the surface of the test object.

Consider theoretical background for the development of this method. The formation of moiré patterns (the phenomenon of mechanical interference) is possible in the following cases: 1) two superimposed grid of straight parallel lines with the same steprotated relative to each other by the angle; 2) overlap DV the PTA between them; 3) are superimposed grid with different step and rotated relative to each other by the angle(the case in question).

When overlaying two grids with spacing between lines, respectively1and2as shown in Fig.2, disposed at angles1and2to the axis of the abscissa x, moiré patterns are formed with a step S and rotated to the x-axis by the angle. At this fair the following expressions.

The angle of inclination of the moire fringes to the x-axis is determined from the following expression:and does not depend on with1and C2(distance from the origin to the first line of the corresponding grid). Therefore, when the parallel movement of one or both lines, the angle of inclination of the moire fringes is not changed. The rotation of the moire fringes can be obtained only by relative rotation imposed systems of lines.

Cut, clip moire stripe on the y axis, is defined as:Distance moiré patterns from the origin:Step strips S is determined by the formula:
=1-2= 0, then step moire fringes is equal to:
S =12/1-2,
i.e., the smaller the difference between the steps of the mesh, the greater the step moiré patterns S, so it is advisable to reduce the step S to improve the accuracy of control. If the angle between the grids (0) the increase in the latter will lead to a reduction step S. Therefore, programmatically varying parameters1and2andyou can increase the resolution of the method.

As follows from Fig.2 and Fig.3 vectordetermining the displacement in the direction perpendicular to the grid increments1(in the coordinate system x1,1), is [4]:

where To order strips(-1, 0, 1,...),the grid spacing and band with K= 0 passes through the point of rotation (Fig.1), which is I formula according to the method of [3] and represents the change of the distance from the plane of the imaginary raster to the surface.

Thus, each moire stripe carries information about the vector sum of the displacements - (W+U) (Fig.3). The vector W is determined from the pattern of bands produced by the electron-projection method [3]. i.e. when applying in the computer scanned projection grid with an imaginary raster (both grid parallel to each other). The vector U is formed by the rotation of the imaginary raster angle(unlike the provisions of the imaginary raster in [3]).

Therefore, to obtain the actual topology of the surface, defined by the vector W, it is necessary after treatment of the bands of the received picture (W+U) subtract the "imaginary" move U created due to rotation of the imaginary raster

Taking into account [3, 4], we have:
W = (h+K)sin= (h+K)sin(arccos(U/W+U)),
where
where- step lines of the original mesh in the projector,
mg- the scale of the projection grid in the plane of the "imaginary" raster
1and2- angles, respectively illumination and observation control raster
mg=(Lp-fg)/fg,
where Lp=L-LIn- Russ is a career.

Sources of information
1. Theocaris So moiré patterns in the study of deformations. - M.: Mir, 1972. - S. 25-38.

2. Domrachev Century, and other Circuitry digital converters movements. Reference manual / Century, Domrachev, C. R. Matveevskaya, Y. S. Smirnov. - M.: Energoatomizdat, 1987, S. 14-15.

3. A. C. 2065570 EN, IPC 6 G 01 21/00, publ. 20.08.96. Bull. 23. Kucheruk C. I., Popov A. M., Kolesnikov A. C. Electron-projection method for measuring the shape and movements of the surface of the object (the prototype).

4. Durelli A., Park, C. deformation Analysis using moire /Lane. from English. Ushakov B. N. - M.: Mir, 1974. - S. 46-58.


Claims

A method of measuring a surface shape of the object, comprising pre-configuring the video by combining the axes of the projector and camera at the point on the surface of the object projected onto the surface using the projector grid with alternating light and dark lines, the synthesis of imaginary raster computer, add it to the accepted camera work pattern and the definition received a moiré pattern with regard to previously established correlations of the parameters of the object surface, characterized in that the parameters of synthesized computer projected on powershotdigital its original position angle in the plane of the projection axis of the projector.

 

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