RU2556282C1 - Method of determining spatial orientation of object using optoelectronic system and corner reflector - Google Patents

Abstract

FIELD: physics, navigation.

SUBSTANCE: invention relates to remote determination of the spatial orientation of an object. In the method of determining the spatial orientation of an object using an optoelectronic system, a corner reflector is rigidly mounted on the object and its entrance plane is illuminated with a light beam along the sight line. The reflected light beam is projected by the lens of the optoelectronic system on the photosensitive layer of a matrix photodetector to form an image of the corner reflector, from which the spatial orientation of the object is determined in the form of angles of successively rotating the corner reflector about three mutually perpendicular axes. The entrance plane of the corner reflector is also illuminated with a light beam that has passed through a diaphragm which limits transmission of the entrance plane, wherein the periphery of said diaphragm does not merge into the diaphragm when turned by an angle of 180°. The reflected light beam is projected by the lens of the optoelectronic system on the photosensitive layer of a matrix photodetector completely, and the spatial orientation of the object is determined from the shape of the periphery of the image of the corner reflector.

EFFECT: broader functional capabilities of determining spatial orientation of objects in a wide range of distances.

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Description

The invention relates to measuring and location technology, and more specifically to remote sensing of the spatial orientation of an object, and can be used in information input devices, robotics, positioning, navigation and docking systems.

One way to remotely determine the orientation of an object in space is described in US Pat. No. 7,312,862 B2, dated December 25, 2007, G01B 11/26. In it, using a measuring system, six degrees of freedom of an object are determined by a block rigidly fixed on it containing an angular reflector. Three degrees of freedom, which determine the position of the object in space, are found as the distance to the top of the corner reflector and two angles of direction to it. These values are measured using a laser tracker or other functionally similar device. The three remaining degrees of freedom, which determine the orientation of the object in space, are determined by two collimation angles and a twist angle. For their measurement, an array photodetector (MFP) is located in the block of the corner reflector, and the top of the corner reflector is made in the form of an aperture that transmits radiation parallel to the light flux incident on it. The registration of the MPPU of the radiation transmitted by the aperture allows one to determine the collimation angles of the object's rotation; To measure the torsion angle, the corner reflector is labeled or an additional light source is used, the radiation of which is also detected by the MFP.

The disadvantages of this solution are the low reliability of the system and the limited range of acceptable conditions for its operation.

The closest in technical essence to the invention is a method for determining the spatial position of an object using an optoelectronic system (OES) and an angular reflector, described in patent US 7800758 B1, 09.21.2010, G01B 9/02, and selected as a prototype. In the known method, the orientation of the object in space is defined by three spherical coordinates, which are the distance to the corner reflector and two angles of direction to it. These values are determined using a laser tracker. The three degrees of freedom that determine the orientation of an object in space are the angles of successive rotation of the corner reflector around three mutually perpendicular axes. To determine these angles, an angular reflector is used, which is rigidly fixed to the object, then illuminated by a laser (light) beam directed along the line of sight coming out of the scanning module, optically connected to a fixed radiation source by an optical fiber bundle, while part of the light flux returned by the angular a reflector, they are sent to an optical system with a constant increase, forming on the MFPU located behind it a distribution of the light flux intensity in the region of the corner reflector. Due to manufacturing errors, the faces of the corner reflector have less reflectivity in the region of the ribs where they form the joints. If necessary, this effect can be further enhanced, for example, by increasing the thickness of the joints or darkening them. Therefore, the image of the corner reflector, formed as a result of projection of the light flux onto the surface of the photosensitive elements of the MFP, has the form of three dark lines corresponding to its edges. Using the obtained image, or rather, according to the slopes of the dark lines, as a result of solving the system of equations, the angles of successive rotation of the corner reflector around three mutually perpendicular axes are determined, which determine the spatial orientation of the object. The distribution of light on the MFP itself does not allow one to establish a one-to-one correspondence between the dark lines and the edges of the corner reflector. This correspondence can be established with the help of additional measures, for example, fixing the mark on the corner reflector. Otherwise, the orientation of the object in space is determined accurate to a twist angle of 120 °.

The disadvantage of the prototype is the limitation of the functionality to determine the spatial orientation of objects located in a wide range of distances, due to the direction of the part of the light flux returned by the corner reflector to the optical system with a constant increase, in addition, the use of an optical system with a constant increase requires focusing it during the measurement , which greatly complicates this method of determining orientation.

The task to which the invention is directed is to improve remote measurement of the degrees of freedom of an object, determining its orientation in space, using an ECO and an angular reflector.

This problem is solved due to the fact that in the known method, the corner reflector is rigidly fixed on the object, its input face is illuminated with a light beam along the line of sight, the reflected light beam is projected onto the photosensitive layer of the MFP for the image of the corner reflector, which determines the spatial the orientation of the object in the form of angles of successive rotation of the corner reflector relative to three mutually perpendicular axes, while the input face of the corner reflector To illuminate with a light beam passing through a diaphragm restricting the transmission of the input face, the perimeter of which does not change into itself when turned through an angle of 180 °, the reflected light beam is completely projected using the OES lens onto the photosensitive layer of the MFP, and the spatial orientation of the object is determined by the shape of the image perimeter reflector.

The technical result provided by the given set of features is to expand the functionality of determining the spatial orientation of objects located in a wide range of distances.

The invention is illustrated by the following drawings:

figure 1 shows a device for implementing the inventive method;

figure 2 is a diagram of a device for measuring orientation;

on figa presents a diagram of the formation of a beam of rays in the plane of the receiver;

on figb shows examples of images indicating the pixels of the photodetector;

on figv-3e illustrates the formation of the image of the corner reflector on the MFP;

on figa demonstrated the correspondence of the cross-sectional shape of the light beam incident on the input face of the corner reflector, each set of angles of its orientation;

on figb shows a change in the shape of the cross section of the light beam at different angles of orientation of the corner reflector;

figure 5 explains the method of restoring the rotation angles of the corner reflector from its image on the MFP.

The claimed method for determining the spatial orientation of an object (see Fig. 1) is implemented by a device 1, which is an ECO, designed to work with a corner reflector 2, rigidly fixed to the object. This device allows you to measure up to six degrees of freedom in your own XYZ coordinate system. Corner reflector 2 is made, for example, in the form of a regular trihedral pyramid, the side faces of which have the shape of a triangle with an angle at the top of the pyramid 90 °, with a diaphragm applied to its base (not shown in the drawing), the perimeter of which does not transform into itself when turned at an angle 180 ° (for example, such a diaphragm may have the shape of a triangle). As an object 3, a joystick is depicted which rotates at some angles (orientation angles) around three mutually perpendicular axes passing through the vertex A of the reflector 2, while the vertex A of the reflector 2 itself can move in space as A → A 'along the path B. The device 1 includes an orientation unit 4 and may include a range measuring unit 5, beam splitters 6, 7, and a positioning unit 8 that controls the scanning mirror 9, which processes the mismatch angles of the line of sight (LP) using drives equipped with azimuth 10 and angle 11 sensors "angle code" controlled by the positioning unit 8, generating a signal for working out the angle of misalignment of the drug.

Figure 2 shows a diagram of an orientation unit 4, consisting of a block of a radiator 12 containing a radiation source 13 and a collimator 14, a beam splitter 15, a block of a radiation receiver 16 including an optical system 17 focusing a parallel beam of rays incident on it, and an MPPU 18, and also a control and processing unit 19, calculating the orientation angles of the object 3, connected to the input with the output of the radiation receiver unit 16, and the output to the actuator.

The principle of image formation in the orientation unit 4 (Fig. 3) and determining, according to the shape of the image perimeter, the angular reflector of the spatial orientation of the object (Fig. 4a, b) will be described below.

The claimed method operates as follows.

Block 4 determines the orientation of the object 3. A parallel light beam emerging from block 4, formed by a radiation source 13 (LED or laser diode), a collimator 14 and reflected by a beam splitter 15, passes through a beam splitter 6, after which it is mixed with a beam emerging from a range measuring unit 5 is passed through a beam splitter 7, hits a scanning mirror 9, is reflected from its surface and passes through the input window of the device 1 in the direction of the corner reflector 2. Upon reaching the last, the light beam is reflected in brotherly direction, penetrates through the input window of the device 1 and, reflected from the scanning mirror 9, falls on the beam splitter 7, where it is divided into two components - the transmitted beam and reflected reflected in the positioning unit 8. In the positioning unit 8 by the image shift of the light beam returned with an angular reflector, relative to the position of the beam emitted by block 5, a drug mismatch signal is generated for the elevation and azimuthal drives, on the shafts of which the corresponding sensors l-code ”11 and 10. Using the drives, the scanning mirror 9 is positioned so that the LV of the device 1, combined with the emitted beam, is directed exactly to the top of the corner reflector 2. Thus, the positioning unit allows you to track the movement of the top A → A ′ of the corner reflector 2 in space along trajectory B and determine the direction angles of the drug to its peak A. The returned light beam passing through the beam splitter 7 enters the beam splitter 6, where it is divided into transmitted and reflected beams. The last one is sent to the range measuring unit 5, which determines the distance to the vertex A of the corner reflector 2 using one of the methods described in known sources (see, for example, US Pat. No. 7,800,758 B1 and the references therein).

Thus, using the found direction angles to the vertex A of the corner reflector and the distance to it, the position of the vertex A in space is determined. The orientation of the object in space is determined by the image of the corner reflector 2, formed in the orientation unit 4 by the returned light beam passing through the beam splitter 6.

The principle of image formation of the corner reflector 2 on the matrix photodetector 18 of the block 16 of the OES 1 is presented in figure 3. The radiation receiver unit 16 is arranged in such a way that its optical system 17 focuses the returned parallel beam of rays falling into it, passing through the beam splitter 15, into a plane that does not coincide with the plane of the photosensitive surface of the matrix radiation receiver. For reasons of reducing the dimensions of the receiver, it is preferable that this beam is focused beyond the plane of the receiver, as shown in figa. The distance between the focus plane and the receiver plane determines the image size of the corner reflector. As well as the size of the receiver 18 itself, this distance can vary widely depending on the requirements for the accuracy of measurements and the power of the radiation source.

The diameter D of the entrance pupil of block 16 of OES 1 is selected from the condition D≥l, where l is the maximum distance between two points of the diaphragm perimeter of the input face of the corner reflector, we note that if we apply the claimed method for diverging beams of rays:

- the luminous flux of the emitter unit 12, reflected from the beam splitter 15;

- the returned luminous flux that has passed the beam splitter 6;

- direct luminous flux transmitted through the beam splitter 6,

then this condition passes into the condition D≥2 · l. With this choice of the entrance pupil, the image of the corner reflector on the matrix photodetector changes depending on the angles of its rotation, examples of images indicating the pixels of the photodetector are shown in Fig.3b. The distance between the focusing plane and the plane of the photodetector is set in such a way as to enable image shape recognition for any angle of rotation of the corner reflector. As a rule, for this it is enough that the maximum distance between different points of the image is at least 10-15 pixels. With an increase in this distance, the recognition accuracy of the image shape and, therefore, the whole method increases.

Fig.3c-e illustrates how the image of the corner reflector 2 is formed as a result of projecting the light beam reflected from it on the matrix photodetector 18. Using the ECO, let the corner reflector, the input face of which has the shape of an equilateral triangle, sequentially rotate at some angles around three mutually perpendicular axes (figv). In this case, the intersection of the axis of the ray falling at the top of the corner reflector passes from the orthocenter of the input face to some point B, see Fig. 3d, d. The location of point B on the input face depends on the angles of rotation of the corner reflector and its design. The shape of the light flux returned by the corner reflector in the plane of its input face is determined by point B as follows. It is necessary to expand an equilateral triangle restricting the transmission of the input face by 180 °, and then move the resulting expanded triangle so that its orthocenter occupies a position symmetrical to the original relative to point B, see fig.3d. The luminous flux returned by the corner reflector in the plane of the input face has the form of the intersection of the unfolded and displaced equilateral triangle with the original one. The plane of the input face of the corner reflector during its rotation has a certain inclination relative to the plane of the radiation receiver, Fig.3e. Therefore, the final image of the corner reflector is determined by projecting the shape of the light flux, found as shown in Fig. 3d, onto the plane of the radiation matrix detector 18, followed by scaling to the desired size.

For the claimed method to work, it is necessary that the perimeter of the diaphragm bounding the input face of the corner reflector does not go into itself when turned through 180 °. From the whole variety of diaphragms that meet this condition, it is advisable to single out, on the one hand, the most technologically advanced for manufacturing and use, and, on the other hand, the most simple from the point of view of recognition. Two such apertures are shown in FIG. The first of them has the shape of an equilateral triangle. It is this shape that the input face of the corner reflector is made in its pure form without any modifications aimed at reducing its size. Fig. 4a shows how the shape of the returned light flux changes in the plane of the input face of the corner reflector, having the shape of an equilateral triangle. In the center of FIG. 4a, the input face itself (equilateral triangle) and the shape of the returned light flux through it (shaded hexagon) in the absence of the angle of rotation of the corner reflector are shown. Around the central image are the forms of the returned light flux for the rotation angles of the corner reflector, schematically represented by the circuit 20 in the upper left corner of FIG. The radius of the circle shown in diagram 20 sets the amount of displacement at given rotation angles of the point of intersection of the beam falling at the top of the corner reflector with the input face. The direction of the segment sets the direction of displacement for the image 0, located on figa to the right of the Central. The remaining images correspond to the rotation of the segment on the circuit 20 counterclockwise with a resolution of 45 ° at angles of 45 °, 90 °, ..., 315 °, respectively. Fig. 4a shows that each set of orientation angles of the corner reflector corresponds to its own form of the returned light flux through its input face and, therefore, its image on the photodetector matrix 18. Thus, the orientation angles of the corner reflector can be restored from its image. Note that the orientation angles are restored accurate to a twist angle of 120 °.

Fig. 4b shows a change in the shape of the returned light flux at different angles of orientation of the corner reflector, the transmission of the input face of which is limited to a hexagon obtained from an equilateral triangle by truncating its vertices. The perimeter of such a diaphragm also does not transform into itself when turned through 180 ° and is obtained naturally if the truncated parts of an equilateral triangle are used to mount the corner reflector. The arrangement of the images in FIG. 4b is the same as in FIG. 4a. Fig. 4b shows that the stronger the vertices of an equilateral triangle are truncated, the narrower the range of determined orientation angles. So, for example, the images 21 and 22 in Fig. 4b, corresponding to the positions 225 ° and 315 ° in the circuit 20, are visually practically indistinguishable. At the same time, images 23 and 24 in Fig. 4a, corresponding to the same positions 225 ° and 315 ° in the circuit 20, are clearly distinguishable even by eye. Note that this restriction on the range of angles to be determined, as well as the limitation that the claimed method determines the orientation of an object with an accuracy of twisting angle of 120 °, can be eliminated by introducing additional marks into the block of the corner reflector, which is known in public sources, for example, patents US 7312862 B2 and US 7800758 B1.

The restoration of the orientation angles of the corner reflector from its image on the MFP is performed, for example, as shown in Fig. 5. First, all edges of the image constituting its perimeter are detected. Then these edges are divided into two groups, so that the edges included in each of the groups do not have common points. From the intersections of the lines defined by the edges of each group, find the points C, D, E and C ', D', E ', respectively. In this case, the lines SS ', DD', EE 'form in the vicinity of the point of intersection exactly the same configuration as the lines that determine the orientation of the corner reflector in US Pat. No. 7,800,758 B1. The dependence of the slopes of the lines SS ', DD', EE 'on the orientation angles of the corner reflector is determined by the system of equations given in US 7800758 B1. Solving this system, find the orientation angles of the corner reflector 2 and object 3 in space.

Supplementing the data of block 4 on the orientation of the object in space with data on the range of block 5 and data on the direction angles of block 8, up to six degrees of freedom of the object are found on which the corner reflector is fixed. The present invention allows to determine the orientation of the object in a simpler way, in more difficult operating conditions, in a much wider range of distances.

Claims (1)

A method for determining the spatial orientation of an object using an optical-electronic system (OES) and an angular reflector, which consists in the fact that:
- the corner reflector is rigidly fixed to the object,
- the input face of the corner reflector illuminate along the line of sight,
- the reflected light beam using an OES lens is projected onto the photosensitive layer of a multi-site photodetector (MFP) to form an image of the corner reflector,
the spatial orientation of the object in the form of angles of successive reversal of the corner reflector relative to three mutually perpendicular axes is determined by the image of the corner reflector on the MFP, characterized in that
- the entrance face of the corner reflector is illuminated in such a way that the diaphragm restricting the transmission of the input face completely diverges into the light beam, the perimeter of which does not transform into itself when turned through an angle of 180 °,
- the reflected light beam using the OES lens is projected onto the photosensitive layer of the MFP completely;
- and the spatial orientation of the object in the form of rotation angles of the corner reflector is determined by the shape of the perimeter of the image of the corner reflector.

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