RU2519512C1 - Device to measure angular and linear coordinates of object - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: in a device to measure linear and angular coordinates of an object comprising an illuminator, a lens with a photodetector array connected to a data processing unit and set in the plane conjugated with the object, and a leading mark set on the object, the novelty consists in the fact that the leading mark is fitted by an illuminator switching on a light source, a condenser and a diffuser which are installed along the beam path, and two sighting elements forming ring and spot structures and spreaded along the optic axis, an optic path compensator is installed after the second structure along the beam path, the lens is made with variable focal length.

EFFECT: one-channel double-coordinate device to measure linear and angular coordinates of an object works in a wide range of distances with high accuracy and variable measurement range.

5 dwg

Description

The invention relates to the field of measuring equipment, to measuring devices characterized by remote optical measuring instruments, and can be used to solve problems requiring the simultaneous determination of two linear and two angular coordinates of an object at a constant distance from the object (alignment of composite shafts, assembly of large structures, tracking after the position of the object, pointing to the object).

Known devices having two two-coordinate measurement channels - angular and linear coordinates, using one lens, for example, a device for measuring angular and linear coordinates (Repot LLNL, UCRL-LR-105821-97-3, p. 187, figure 10), including two measuring channels. The first channel for measuring the angular coordinates of the object consists of a light source, a beam splitter, a lens, an autocollimation mirror with a scattering mark applied to it, and a matrix receiver of the angle measurement channel. The second channel for measuring the linear coordinates of the object includes a second matrix photodetector of the channel for linear measurements, located in the plane conjugated by the lens with the brand.

This device with a sufficiently high sensitivity, both to angular and linear movement of the object, has a number of significant drawbacks. This is primarily a small range of angular measurements, which is associated with the diameter of the entrance pupil of the lens at large distances to the object. At large distances to the object, the diameter of the entrance pupil of the lens is no longer determined by the necessary resolution (determined by the relative aperture of the lens), but by the required range of operation of the angle measuring channel, which, with an increase in the measurement range, leads to an increase in the dimensions of high-precision optical elements.

Other disadvantages of the device are the significant dimensions and complexity of the circuit associated with the presence of two separate channels of angular and linear measurements.

A known device for measuring angular and linear coordinates, selected by us as a prototype (US Pat. RU No. 2366893, IPC G01B 11/26, priority 02/19/2008).

The device includes a illuminator, a beam splitter located along the beam, a lens placed on the object’s mark and a matrix photodetector installed in the plane associated with the object with an information processing unit, the illuminator installed in the focal plane of the lens, and the mark made in the form of a segment of a focusing mirror located on a reflex surface, the focal length of the focusing mirror segment does not exceed the depth of the image space of the lens.

Due to the fact that the reflex surface of the brand returns a significant part of the light in the direction of the illuminator, and the focusing mirror reflects most of the rays so that they do not fall into the lens aperture, an image of the focusing mirror segment is formed in the image on the photodetector, the position of which relative to the coordinates of the photodetector matrix is used to calculate the linear coordinates of the object. The light reflected from the surface of the focusing mirror segment entering the aperture of the lens gives an image of an autocollimation point.

The images of the contour of the mirror segment and the autocollimation point of the mirror, spaced in depth, are projected by the lens into the plane of the photodetector. The position of the image of the autocollimation point of the mirror relative to the contour of the focusing mirror is used to calculate the angular coordinates of the object. The condition for a small error in measuring the angle is the correspondence of the focal length of the mirror segment to the depth of the sharply imaged lens space.

The device has a wide range of measurement of angular coordinates, an easy-to-manufacture design and small dimensions of a passive mark, which allows it to be placed on small objects. However, it is designed to operate with high accuracy at only one fixed distance, since the error depends on the scale of the image of the brand (inversely proportional to the size of the image) and the depth of the sharply imaged lens space.

We have proposed a single-channel two-coordinate device for measuring the angular and linear coordinates of an object, operating in a large range of distances with high accuracy and a variable measurement range.

We achieved such a technical result when, in a device for measuring the linear and angular coordinates of an object containing a illuminator, a lens with a photodetector array connected to an information processing device and installed in a plane that is paired with the object, and the measuring mark installed on the object is new, that the measuring mark is equipped with a illuminator, including a light source located along the beam, a condenser and a diffuser, and two sighting elements forming an annular and point structure and p znesennymi along the optical axis of the second beam structure along the optical motion compensator is installed, wherein the lens is formed with a variable focal length.

Approaches to the design of the sighting elements of the annular and point structure and the compensators of the optical stroke are known.

The figure 1 shows a functional diagram of the device, where the brand illuminator with a light source 1, a condenser 2, a diffuser 3, a ring structure 4 brands, a dot structure 5 brands, a compensator 6 optical travel lens 7 with a variable focal length, a matrix photodetector 8, block 9 information processing.

The figure 2 shows the image of the brand in the determination of linear and angular coordinates with a small increase in "roughly" (a) and a large increase in "exactly" (b).

The figure 3 shows an example of a specific implementation, where the brand illuminator with a light source 1, a condenser 2, a diffuser 3, a ring structure 4 brands, a dot structure 5 brands, a compensator 6 optical path, a lens 7 with variable focal length, a matrix photodetector 8, block 9 information processing, prisms 10, 12, shafts 11, 13. Devices for mounting prisms and alignment of the brand and the receiving part are not shown.

The figure 4 shows the results of measuring the angular displacements of the object. The graph shows the dependence of the measured angle in the angle. min (along the ordinate axis) from a given angle in the angle. min (abscissa).

The figure 5 shows the results of measuring the linear displacements of the object. The graph shows the dependence of the measured transverse displacement in microns (along the ordinate axis) on a given displacement in microns (along the abscissa axis).

The device operates as follows.

The mark is mounted on the object, the lens 7 with the matrix photodetector 8 is mounted coaxially with the mark (the object and alignment devices are not shown) and focused on the sighting structures of the mark. The light source 1 through the condenser 2 and the diffuser 3 illuminates the annular structure 4 and the point structure 5, the optical path compensator 6 located between the point-oriented sight structures of the brand located behind the point structure 5, brings the images of the structures of brands 4 and 5 into a single image plane on the photodetector 8.

When measuring the angle, the compensator 6 of the optical path, in addition to bringing the image of the target structures into a single plane in this design with marks spaced along the axis, began to perform an additional function - increasing the accuracy of measuring the angular coordinate by increasing the image offset of the point structure 5 relative to the ring structure 4 when the mark is tilted. The additional offset is proportional to the angle and length of the compensator.

Using a lens with a variable focal length 7 sets the maximum possible increase in the image of the brand.

The thickness of the glass (transparent material) of the compensator 6 is determined by the well-known formula as

$$\text{h}=\text{L / n-1}\text{,}\text{(one)}$$

where h is the thickness of the compensator, mm;

L is the distance along the axis between the target structures, mm;

n is the refractive index of the glass at the working wavelength.

Due to the fact that the mark structures are spaced along the axis, it becomes possible to measure the relative angular coordinates of the mark, for which purpose the position of the center of the image of the point structure of the mark 5 relative to the center of the ring structure of the mark 4 shown on the same photodetector 8 is used.

The image obtained from the photodetector 8 at different magnification of the lens 7 is shown in figure 2.

Data from the photodetector 8 is transmitted to the information processing unit 9 (computer).

To measure the two relative linear coordinates of the brand, the position of the center of the image of the ring structure of the brand 4 relative to the coordinates of the matrix photodetector 8 is used.

The transverse shift of the mark relative to the coordinates of the matrix receiver is defined as

$${\Delta }_m={\Delta }_{\mathrm{and}}*D/D_{\mathrm{and}},\left(2\right)$$

where Δ _m is the shift of the mark, mm;

Δ _and - image offset ring structure 4 brands, mm;

D is the diameter of the ring structure 4 brands, mm;

D _and - the diameter of the image of the ring structure 4 brands, mm;

D / D _and - increase in the optical system.

The diameter of the image of the ring structure 4 of the brand and the position of its center relative to the coordinates of the matrix are determined by known algorithms.

The relative angular coordinates of the brand at small angles are defined as $$\varphi =\sigma {\text{* D}}_{\text{and}}\text{/ D * (L}+\text{h / n)}\text{(3)}$$

Where

φ is the angular coordinate, rad

σ is the displacement of the center of the image of the point structure of the 5th mark relative to the center of the ring structure of the 4th mark, mm,

D is the diameter of the ring structure 4 brands, mm,

D _and - the diameter of the images of the ring structure 4 brands, mm,

L is the distance between the sighting structures of the brand, mm,

h is the length of the compensator, mm

n is the refractive index of the compensator material.

The diameter of the image of the annular structure 4 of the brand and the position of its center, the position of the center of the point structure 5 of the brand are determined by known algorithms.

Data from the photodetector 8 is transmitted to EMV 9, where the linear and angular relative coordinates of the brand are determined by formulas 2 and 3.

An example of a specific implementation.

As an example of a specific embodiment of the device, its use in a system for measuring shaft decentration is shown (see FIG. 3). To measure the decentration (misalignment) of the shafts, it is necessary to determine the mutual slope and mutual displacement of the shaft axes in two coordinates. The method of measuring decentration is known and includes installing on the shafts in the region of the coupling of the base prisms (a prism whose edge is a dihedral angle parallel to the axis of the cylindrical generatrix of the shaft) on which the measuring devices are mounted. The technique includes synchronous rotation of the shafts by four angles - 0, 90, 180, 270 angles. hail, and measuring the linear and angular displacements of the shaft axes in these positions. Known methods with synchronous rotation of the shafts to other angles (at least three), characterized by more complex formulas for calculating decentration and less accuracy. They are used when it is impossible to rotate 270 angles. hail.

A brand with a source 1, a condenser 2, a diffuser 3, an annular and dotted structure 4, 5, a transparent rod 6 is mounted on one shaft 11 using a prism 10. A lens with a variable focal length 8 and an array photodetector are installed on the other shaft 13 using a prism 12 9.

The range of measurement of linear displacements depends on the image scale of the annular structure of 4 marks. Therefore, at the first stage, with large initial errors in the alignment of the shafts, such an increase in the lens 7 with a variable focal length is chosen so that with a simultaneous rotation of the shafts by 360 angles. hail, images of the brand structures remained in the field of view of the photodetector 8. The rough relative linear and angular displacements of the shaft axes are calculated from the coordinates of the images of the ring 4 and point structures 5 of the brand.

Then, coarse linear and angular displacements of the shafts are eliminated by displacement of the bearing assemblies of the shafts by a known method.

After practicing coarse linear and angular displacements, the magnification of the lens 7 with a variable focal length is changed to the maximum possible (so that the image of the ring structure of the 4 brand occupies the maximum possible area of the photodetector 8), and the relative linear and angular displacement is determined using the same method with high precision flanges of shafts.

After that, the final precision installation of the bearing units of the shafts is carried out according to a known method.

Thus, using a single single-channel two-coordinate device for measuring angular and linear coordinates, the shaft decentration parameters are determined in a large range and in a limited range with high accuracy. The device operates in a wide range of distances between the centered shafts.

In the device mockup, a visible-spectrum LED (wavelength 635 nm), a television lens V27Z9535M from Computer, Japan, with a variable focal length of 9.5-256 mm and a light diameter of 80 mm, are used as illuminator 1. The distance from the lens to the brand is 400-5000 mm, the diameter of the ring structure of the 4 brands is 80 mm, the distance between the structures of the brand is 50 mm.

As a photodetector, a digital camera with a 6.4 × 5.2 mm format matrix of the VAC-135 type manufactured by EMU, St. Petersburg was used. Data from the matrix photodetector is transmitted to a Pentium-4 type computer and processed using known correlation algorithms for searching the diameter and center of the image coordinates of the ring structure 4 and the image coordinate center of the point structure 5 relative to the coordinates of the matrix photodetector 8. Then, the obtained image coordinates are converted to relative linear and angular brand coordinates using the above dependencies 2 and 3.

On the created layout, the basic parameters of the device were determined (operating range, sensitivity to angular and linear movements of the object). For measurements, a stand was used, which allows one to set linear (1 μm) and angular (5 arcsec) mark movements with high accuracy.

With accurate measurements (maximum magnification), the error in the channel for measuring angular coordinates is not more than 0.5 angles. min, in the channel for measuring linear coordinates - not more than 15 microns.

Thus, a remote single-channel two-coordinate device for measuring angular and linear coordinates using a mark with spaced apart sighting structures with compensation of the optical path between them is proposed, which has a large range of working distances, high accuracy and a large measuring range of relative linear and angular coordinates.

Claims (1)

A device for measuring linear and angular coordinates of an object, comprising a illuminator, a lens with an array photodetector connected to an information processing device and mounted in a plane that is paired with the object, and a measuring mark mounted on the object, characterized in that the measuring mark is equipped with a illuminator including a light source, a condenser and a diffuser, and two sighting elements forming an annular and point structure and spaced along the optical axis, behind the second structure an optical path compensator is installed about the beam path, while the lens is made with a variable focal length.

Images