RU14283U1 - DEVICE FOR DETERMINING THE GEOMETRIC CHARACTERISTICS OF THE SURFACE OF THE OBJECT - Google Patents

Abstract

1. A device for determining the geometric characteristics of the surface of an object, comprising a projector for generating a distribution of illumination on the surface of an object, consisting of a light source, a projection optical system and a holder for fixing and precision moving light transmitting plates that have a given distribution of light absorption coefficient, means for registering an image of the surface of an object, consisting of a lens and a matrix of photosensitive elements, and means d I process information from said matrix of photosensitive elements, characterized in that there are two said light transmitting plates, the distribution of the light absorption coefficient of one of the said plates being a set of bands whose intensity varies according to a sinusoidal law, and the distribution of the light absorption coefficient of the second of the said plates is set in such a way that allows for each point on the surface of the object to determine the number of the strip projected to this point from the said set polos.2. The device according to claim 1, characterized in that it further comprises means for determining the surface area of the object. The device according to claim 2, characterized in that the said means for determining the surface area of the object consists of a computer with a special software module. The device according to claims 1 to 3, characterized in that the second light-transmitting plate has an absorption coefficient distribution in the form of a step function k N, where k is some known coefficient, N is the strip number. The device according to claims 1 to 3, characterized in that

Description

Device for determining the geometric characteristics of the surface of an object

The device Д31Я for determining the geometric characteristics of the surface of an object is designed for non-contact optical measurements of the continuity of the shape of a surface (holes, grooves, etc.), for controlling the geometric characteristics of stable and slowly changing surfaces of objects, including surface areas, diagnosing the state of objects, and also supplying the initial data for machine control programs to recreate objects. It can also be used in architecture and sculpture (for digitizing the surface and estimating the flow rate of materials), robotics (vision systems), orthopedics, in the design and modeling of clothes.

In the proposed device, the determination of geometric characteristics of the surface is carried out by the following ofaz:

- the coordinates (x, y, z) of the surface points are determined, where x, y are the cosfdinates of the object point along a certain reference plane, and z is the distance between this surface point and the reference plane,

- from a set of co (fdinate (x, y, z) points of the surface of the object under study by means of calculations, the values of various geometrical) source characteristics of the object are found.

A non-contact three-digit digitization of the surface of an object is known (WO 96/12160, G 01 B 11/24), which consists of at least one project containing a light source and means for modulating and focusing the light into a system of bands on the surface of the object, a filament to obtain an image of the illuminated a projector of an object consisting of nabsra detectors, means for determining the phase of illumination at points of property, federal property for determining

IPC6 G01 at 11/24, G01 at 11/28

pfiod of the system of strips on the obtained surface and surface means and means for determining the three-coordinate coordinates of an object surface point from phase and pfiod. The phase determination is carried out in the following way: the whole part of the Pfiode N is established, at the points between the initial band and the band nearest to it, the illumination is interpolated by a sinusoidal function, then this {process occurs N-1 times between the following bands.

The disadvantages of this device are the obligatory presence of the initial band in the field of view, as well as the impossibility of using this method for surfaces with rafts, holes, and u)., Due to the fact that the applied procedure of stripping the nomf of the band requires the continuity of the observed bands.

A device for determining the absolute co-ordinates of an object (EP O 534 284 V1, G 01 V 11/24), consisting of a light source, a projection lattice, an optical system for projecting this lattice onto the surface of an object, an optical system for image forming the surface of an object, a detection system to determine the illumination at points on the surface of the object. The projection grill is rotatably or shear-mounted so that surface images can be obtained at several positions of the grill. From the obtained images, the absolute coordinates of the object are calculated.

The disadvantages of this device are as follows:

-when the projection grating rotates, there is a dependence of the measurement sensitivity on the location of the point of the surface to be measured, namely, on the distance between this point and the axis of rotation of the grating;

- when shifting the projection grating, it is necessary to count the order of the strip from the initial strip, while both the initial and intermediate stripes should be in the field of view, which does not allow the use of this device for surfaces with rafts.

Closest to the utility model is a device for measuring the contours of a three-dimensional object using one line (US patent No. 5612786, cl.

356/376), intended for measuring three-dimensional cosfdinate points on the surface contours of an object. The device consists of a project illuminating the surface of the object, which contains a slide with a possibility to line up a line, the intensity of the lines changes according to a sinusoidal law, telecamps, using which the surface is made from the surface, and computational file. Computational federation is intended for obtaining from a surface image of a preliminary phase distribution containing the phases of each of the many cells that are in accordance with the points of the object, phase recovery, and converting the nabf of the restored phases into a set of three-coordinate coordinates of the surface of the object. The phase recovery procedure, designed to separate the nymph band, is performed by minimizing the increments in the coordinates of the surface at neighboring points. In the calculations, calibration parameters are used, the values of which are set during the 1st calibration procedure.

To determine the braids of the data of the surface points, it is necessary to obtain at least three images of the object, which differ in a certain phase shift, which is created by the location of the camera located in the camera, and the mentioned slide with a set of lines is fixed in the camera. For the perception of the absolute phase, and therefore absolute cosdinates, one line from this set of lines is marked.

The disadvantage of this arrangement is that the assumption is that there is only one label in the field: phenium, you can unambiguously number all the visible lines at all points of the surface, and the phase recovery procedure used imposes restrictions on many surfaces, the shape of the squares can be changed. The method cannot be used to modify the characteristics of the surface without creating a solid system of bands in the field of view.

The objective of the utility model is to measure the geometric characteristics of visible complex profiles with a non-contact optical method, including sharp edges, holes, and parts of the surface that are not interconnected or

belonging to different objects.

This problem is solved in that in the device containing the projector, designed to form the distribution of illumination on the surface of the object and consisting of a light source, a projection optical system and a diffuser, designed to fix and precision move light transmitting plates having a given separation of the light absorption coefficient, a fund for recording the image of the surface of an object, consisting of a lens and a matrix of photosensitive elements, and a file for processing information from the aforementioned matrices of light-sensitive elements, which allow us to measure the intensity of the light incident on each element of the aforementioned matrix, there are two light-transmitting plates, the distribution of the light absorption coefficient of one of these plates being a set of bands, the intensity changing according to a sinusoidal law, and the distribution of the light absorption coefficient of the second of the plates is set in such an order that allows for each surface point of an object to determine the nomf of the strip projected to this point from the mentioned set of bands.

The device may additionally provide for the separation of the surface area of the object. This tool can consist of a computer with a special software module.

In a light-transmitting plate, the absorption coefficient may have the distribution in the ffm of the step function k N, where k is some known coefficient, N is the band nph, or in the form H (f), where f is the phase, f is the monotonous non-continuous function , 1 derivative kotfsoy does not accept zero value.

The means for operating the information from the above-mentioned matrix of photosensitive elements may consist of a computer and a controller for inputting the computer images.

The proposed device allows you to extend the phase shift method to the measurement of surfaces of complex shape, srffzhayuschie steps, sharp 1faya, otvfstiya and sections

surfaces that are not interconnected and belonging to different objects, with the possibility of determining the absolute positions of all surface areas. This is achieved through the use of an additional distribution of illumination intensity, which allows the simultaneous processing of all registered images to obtain an unambiguous absolute value of the phase of the sinusoidal distribution for each surface point outside of DF5TIMI points or surface areas, which removes restrictions on the complexity of the shape of the imaged surface.

The utility model is illustrated by the drawing, which depicts a obzid view of the device.

A device for determining the geometrical characteristics of the surface of an object 1 consists of a projector 2, means for recording the image of the surface of the object to be measured, for example, telecamp 3 with a CCD - matrix 4, control 5 for digitizing images, a computer 6 for storing and processing of isophage and precise control of the position of slide 7 in 1ofektfa 2. The surface of object 1 should be in the field of illumination of the projector 2 and in the field of view of the telecamp 3.

The projector 2 has a light source, a slide holder, which enables the precision movement of slide 7 in the direction pfpendicular to the direction of transmitted light, and a lens.

Slide 7 is a light transmitting plate; a predetermined distribution of the light absorption coefficient is preformed. The day of determining the coordinates of the surface points of object 1 requires two separation: one — periodic with a sinusoidal profile of the bands, one — additional — non-periodic, such that it allows for each point on the surface of object 1 to determine the meter of the strip projected onto this point from the first distribution when maintenance of images of the surface of object 1 registered when projecting onto it these distributions. This additional distribution may take the form of a step function with a step width equal to pfiode

The distribution, or the form of myotonia function, does not take zero values, or another form that allows you to determine the band num. Next, we consider the option when this separation has the form of a linear function.

The coordinate system is chosen in such a way that the z axis is directed from object 1 to telecamp 3, the x axis lies in a plane pfpendicular to the labeling of the sinusoidal bands on slide 7, the axis at the perpendiculars on the z and x axes. In this case, telecamp 3 by rotation around the z axis can be set so that the x and y axes are parallel to the edges of the rectangular image recorded by telecamp 3.

The transmission of light by a slide with pfiodic distribution can be described by the formula

I (h) / Io (l + cos (27ih / D)) / 2, (1)

where I (h) is the intensity of the light transmitted through the point of the slide with the co-ordinate h along the X axis, measured from some point, natfimf, 1st slide of the slide,

1o - light intensity without slide,

D - Pfiod of dissection.

As an example of an additional distribution, select a linear function. Then the transmission of light by such a slide can be described by the formula:

I (h) / Io-h / L, (2)

where L is the slide displacement in the x axis direction.

Use of the device is carried out by the following ofaz.

The surface of the object 1 will be placed in the lighting field of the projector 2 and at the same time in the field of telecamp 3.

The lens of the projector 2 is adjusted so that the plane of the image created by the lens on the slide 7 is aligned with the surface of the object 1. This setting allows you to establish a one-to-one correspondence between points

slide and surface points of the object 1.

On the surface of object 1 using project h) a 2, the pfiodic distribution of the light intensity is projected, which is a set of bands whose intensity varies according to a sinusoidal law.

Telecamphus 3 (Fig. 1) is directed to the surface of the object 1 at a certain angle not equal to zero in the lighting labeling by the projector 2, which allows one to observe a deformed picture of the bands. If the surface of the object 1 is flat, the projected stripes will form an even lattice similar to the one emitted. In the case of an object of arbitrary shape, a curvature of the strip system will occur, the larger the more the object differs from the plane and the larger the angle in between the directions of lighting and observation.

In this case, the lens of the camera 3 must be configured so that the image of the object 1 created by this lens falls exactly on the CCD matrix 4, then there must be a one-to-one correspondence between the surface points of the object 1 and the cells of the CCD matrix 4.

It is also suggested that the distances between object 1 and project 2 and object 1 and camera 3 are quite large compared to the lenses of projector 2 and camera 3 and the dimensions of object 1, so that, within a certain error, the projection and observation directions are the same for each point properties of the object 1.

Using a camera 3, an image of the surface of the object 1 is obtained, digitized using a controller 5 and stored using a computer 6.

The procedure of toffing the periodic distribution and recording the corresponding image of the surface of the object 1 is repeated M times (at least three times), each time shifting slide 7 with this distribution in the direction perpendicular to the stripes and the labeling of the transmitted light by a controlled amount within the strip. To facilitate further calculations, this value should be given constant and equal to D

(m-l) / M, where m is the shift, m О, 1, 2, .... Then, when projecting three periodic distributions, the shift will be 1/3 of the period.

Under the assumption that the image-digitizing system operates in a linear mode, that is, the image brightness in the corresponding cell of matrix 4 is specifically dependent on the illumination of this cell, these three iso-phages will be described by the following formulas;

8о (Пх, Пу) В (Пх, Пу) + К (п, Пу) 1о (1 + cos (27th (nx, ny) / D)) / 2,

Si (n, Pu) B (Px, Pu) + K (n, Pu) 1 ° (1 + cos (271 h (n, Pu) / 0 + 271/3)) / 2, (3)

S2 (Пх, Пу) В (Пх, Пу) + К (Пх, Пу) 1о (1 + cos (27С b (Пх, Пу) / В +)) / 2,

where So, Si, S2 - image space in the cell with coordinates (Px, Pu),

K is the coefficient of performance taking into account the fraction of light that entered the cell of matrix 4 after scattering from a point on the surface of object 1, the sensitivity of the cell to light, the amplification of the electrical signal, and the coefficient during analog-to-digital conversion,

B - contribution to the brightness of the image in the same cell, due to background lighting (1 fomé projector 2).

Next, an additional distribution of the light intensity is projected once onto the surface of the object 1 with the help of project 2, allowing for each point of the said surface to determine the number of the strip from the aforementioned strip nbsp, and similarly receive and save an additional image of this surface.

This statement in the case of a linear distribution described by fs formula (2) will be described by the following formula:

SL (Пх, Пу) В (Пх, Пу) + 2 К (Пх, Пу) 1о h (Пх, Пу) / L. (4)

The obtained isophazes (3) and (4) are processed to obtain preliminary and resultant phase distributions containing phases corresponding to surface points. The hepatic phase distribution of the phase within the band

sinusoidal distribution, i.e. they do not exceed 2k. The resulting phase distribution contains phases relative to a certain starting point, for example, corresponding to the edge of the slide projected onto object 1.

The treatment is as follows. The system of equations (3) is solved for each isophage cell relative to B, K and h, however, since h is under the sign of the function cos, it can be found only up to a constant of type 27iN, where N is an integer. We denote by h the value of h located in the interval О h D. Thus, a preliminary phase distribution of h (Пх, Пу) is obtained.

The resulting phase distribution is related to the preliminary phase distribution by the formula

h (Px, Pu) h (Px, Pu) + N (Px, Pu) D (5)

N О1 is separated from the estimate of the true value h of the quantity h obtained from equation (4) by substituting B and K found from solving the system of equations (3);

 (Пх, Пу) (SL (Пх, Пу) - В (Пх, Пу)) L / К (n,%). (6)

From (5) and (6), N (nx,%) is obtained, rounding up the whole result of calculations by) the formula:

K (Px, Pu) - {(Px,%) - h (Px,%)) / D. (7)

The resulting phase distribution is found by substituting O1 cobbled up to an integer value of N (nx, Pu), found by formula (7), in formula (5).

The estimated value of h (Px,%), obtained from (6), is inappropriately taken for the final, because the parameter L (the magnitude of the slide along the x axis), located in the denominator, is very large, and, accordingly, the measurement accuracy is low. A separate determination of the fractional and integer part of the phase h (Пх, Пу) allows one to determine the accuracy of measurements.

Then, from the above-mentioned resulting phase distribution, the absolute coordinates of the surface points of the object 1 are obtained using the preliminary calibration data.

During calibration, a relationship is established between the coordinates x, y, z of the object’s points, the image cell numbers, they fall into these points, and the full phases of the pfiodiological separation of h at these points. In the simplified case of a slide projector 2 and a camera 3 infinitely remote from the object 1, this relationship is established by the dependencies:

X P ki

Z Пх ks + Пу k4 + h (Пх, Пу) ks.

The parameters ki - ks are determined during measurements on the test object.

Because the optical parameters of the system are the same during measurements and calibration, relations (8) are used to obtain absolute cosfdinates of the surface points of object 1.

The values of various geometric characteristics of the surface of an object are found from the set of coordinates of the points on the surface of the object under study by calculation.

For example, the calculation of surface area is as follows. The surface points, the coordinates of the kotfs are delimited, is a grid. This grid is first divided into quadrangles, the vertices of the Kotsshs are the nearest points located within the studied area of the surface, and then the diagonals of these quadrangles are trident. From the coordinates of the vertices of these triangles, their areas are determined, which are then summed.

y nyk2.)

Claims (6)

1. A device for determining the geometric characteristics of the surface of an object, comprising a projector for generating a distribution of illumination on the surface of an object, consisting of a light source, a projection optical system and a holder for fixing and precision moving light transmitting plates that have a given distribution of light absorption coefficient, means for registering an image of the surface of an object, consisting of a lens and a matrix of photosensitive elements, and means d I process information from said matrix of photosensitive elements, characterized in that there are two said light transmitting plates, the distribution of the light absorption coefficient of one of the said plates being a set of bands whose intensity varies according to a sinusoidal law, and the distribution of the light absorption coefficient of the second of the said plates is set in such a way that allows for each point on the surface of the object to determine the number of the strip projected to this point from the said set bands.  2. The device according to claim 1, characterized in that it further comprises means for determining the surface area of the object.  3. The device according to claim 2, characterized in that the said means for determining the surface area of the object consists of a computer with a special software module.  4. The device according to claims 1 to 3, characterized in that the second light-transmitting plate has an absorption coefficient distribution in the form of a step function k N, where k is a certain known coefficient, N is the strip number.  5. The device according to claims 1 to 3, characterized in that the second light-transmitting plate has an absorption coefficient distribution in the form f (φ), where φ is the phase, f is a monotonic continuous function, the derivative of which does not take a zero value. 6. The device according to claims 1-5, characterized in that the means for processing information from said matrix of photosensitive elements consists of a computer and a controller for inputting images into the computer.