RU2579812C1 - Method for measurement of displacement (versions) - Google Patents

Abstract

FIELD: measurement technology.

SUBSTANCE: method of measuring displacements consists in formation on surface of quadrant photodetector two light fluxes, conversion of optical signals into electrical and determining coordinates of optical signals from electrical signals. Two additional light fluxes at interfaces of adjacent quadrants of photodetector and modulate orthogonal functions. Signals are separated from each light flux with each quadrant. Formed from selected signals difference signals proportional to difference of electric signals from each light flux from each pair of adjacent quadrants. From difference between difference signals of each pair of opposite adjacent quadrants is determined on movement, and from sum of all difference signals is determined on angle of twisting.

EFFECT: simple method and high measurement accuracy.

3 cl, 2 dwg

Description

The present invention relates to the field of measurement technology and is intended for measuring angular or linear displacements along two spatial coordinates and the twist angle.

Known devices for measuring angular and (or) linear displacements in two coordinates and the torsion angle (A.S. USSR No. 1146547, G01B 11/26, 03/23/1985; A.S. USSR No. 1435936, G01B 11/26, 07.11. 1988; A.S. USSR No. 1566206, G01B 11/26, 05.23.1990).

The disadvantage of the methods implemented in these devices is the need for complex optical systems, which leads to an increase in the dimensions, weight and cost of the devices.

The closest in technical essence to the proposed invention is a device for measuring the angular deviations of an object according to the USSR author's certificate No. 1211601, G01B 11/26, 02/15/1986, which allows to measure two angular coordinates and the twist angle.

The method used in the device consists in generating two light fluxes from the luminous grades mounted in the focal plane of the lens of the collimator of the transmitting optical system, forming on the quadrant photodetector using two collimators of the receiving optical system an image of the luminous grades, and judging by the offset image of the grades mutual angular deviations of the transmitting and receiving optical systems.

The disadvantage of this method is the need to use three lenses to implement the measurement function, which increases the size and complicates the device.

The technical result that this invention is directed to is the development of such a method that allows to simplify the device while maintaining the ability to measure two angular or linear displacements and the twist angle.

This problem is solved by the method of forming two light fluxes on the surface of a quadrant photodetector, converting optical signals into electrical signals and determining the coordinates of optical signals by electrical signals, characterized in that they form two additional light fluxes, the light fluxes are modulated with orthogonal functions, and the fluxes are formed at the interfaces adjacent quadrants of the photodetector, emit electrical signals from each light flux from each quadrant, form from x signals difference signals proportional to the difference of electric signals from each light flux from each pair of adjacent quadrant, by difference the difference signals of each pair of adjacent opposite quadrants judged move, and the sum of the difference signals is judged the angle of twisting.

In order to improve the measurement accuracy by stabilizing the flux power, a reference electrical signal is formed equal to the required value of the electrical signal from each light flux, signals proportional to the sum of the electrical signals of each light flux from each pair of adjacent quadrants are compared with the reference signal, and the light power is controlled by the results of the comparison flows to achieve equality of the total signals of the reference.

An option for solving the problem is a method consisting in forming two light fluxes on the surface of a quadrant photodetector, converting optical signals into electrical signals and determining the coordinates of optical signals by electrical signals, characterized in that two additional light fluxes are generated, light fluxes are modulated with orthogonal functions, and fluxes are formed at the boundaries section of adjacent quadrants of the photodetector, form differential signals proportional to the difference of the electrical signals from each pa s adjacent quadrants separated signals from each light flux from the difference signal from the difference between the allocated signals from each of adjacent pairs of opposite quadrants judged move, and the sum of all signals allocated to judge the twist angle.

The technical result provided by the above set of features is to simplify the method and device and improve the accuracy of measurement.

The essence of the method is illustrated in FIG. 1-2.

In FIG. 1 shows an optical diagram of a measuring structure.

In FIG. Figure 2 shows the projections of light fluxes from grades on the sensitive surface of a quadrant photodetector at various angular displacements.

A transmitting optical system containing a collimator 1 (Fig. 1), in the focal plane of which is mounted a block of luminous grades 2, forming four light fluxes. A possible shape and placement of marks is shown in view A (FIG. 1). Luminous fluxes arrive at the receiving optical system containing a collimator 3, in the focal plane of which a quadrant photodetector 4 is installed. The images of the grades on the photodetector are shown in view B (Fig. 1). Images of marks and quadrants of the photodetector are conditionally numbered, as shown in FIG. 2a, where the coordinate system of the photodetector x, y is also shown. Luminous fluxes form on the surface of the photodetector at the quadrants. The photodetector converts the optical signals of each light flux into electrical signals s11, s12, s22, s23, s33, s34, s44, s41. Here, the first index at s refers to the number of the light flux, and the second to the quadrant number of the photodetector (for example, s23 is the signal from the second light flux from the third quadrant). Each quadrant of the photodetector converts signals from two light fluxes; therefore, an electric signal from a quadrant consists of the sum of signals from two light fluxes. To extract the corresponding luminous flux from this sum of the signal, the luminous flux is modulated with orthogonal functions. The ability to extract a specific signal from the sum of orthogonally modulated signals is based on the properties of orthogonal functions.

If there are many orthogonal functions, for example, φ1 (t), φ2 (t), φ3 (t), φ4 (t), then

where (0, T) is the interval of orthogonality;

c is a constant (for c = 1, the set is called orthonormal).

Therefore, for example,

Based on this expression, an orthogonal filter is constructed to extract a specific signal from the sum of the orthogonal signals. The filter contains a multiplier of the sum of the signals to the allocated signal and integrator.

There are many types of orthogonal functions, such as, for example, harmonic functions of multiple frequencies, Walsh functions, etc. A particular (and simplest) case of orthogonal functions is a periodic sequence of groups of pulses that do not coincide in time on the interval of orthogonality (period).

Thus, it becomes possible to extract signals from each quadrant of the signals from the corresponding luminous flux s11, s12, s22, s23, s33, s34, s44, s41.

With mutual deviations of the transmitting and receiving optical systems by the angles Δα and Δβ (Fig. 1), the image grades on the photodetector will shift respectively in the x and y coordinates by Δx and Δy (Fig. 2b). The amount of displacement is associated with angular deviations and focal length f of the collimator 2 by the relations

In turn, as can be seen from FIG. 2b, the signal difference Δs1 = s11-s12 and, accordingly, Δs3 = s33-s34 is proportional to the offset Δx, and the signal difference Δs2 = s22-s23 and, accordingly, Δs4 = s44-s41 is proportional to the offset Δy.

When the transmitting and receiving optical systems rotate by the twist angle γ (Fig. 1), the image of the marks on the photodetector will also be rotated through the angle γ (Fig. 2c). The image of the marks on the photodetector will shift, and, as can be seen from the figure, the signal difference Δs1 = s11-s12, Δs2 = s22-s23, Δs3 = s33-s34, Δs4 = s44-s41 will be proportional to the offset due to the rotation by the angle γ.

Since these difference signals are also proportional to the linear displacements Δx and Δy, in order to distinguish the signals due to linear displacements from the signals due to twisting, the resulting signals Δsx and Δsy proportional to the linear displacements Δx and Δy are formed as the difference of the signals of the difference pairwise opposite quadrant photodetector:

Moreover, as follows from FIG. 2c, with a clean turn through the angle γ without offsets Δx and Δy, the signals s11 = s33, s12 = s34, s22 = s44, s23 = s41 and, in accordance with (3), the resulting signals Δsx = Δsy = 0.

According to the measurement results Δsx and Δsy using (2) determine the angular displacement Δα and Δβ.

The resulting signal Δsg, proportional to the twist angle γ, is formed as the sum of all difference signals:

Δsg = Δs1 + Δs2 + Δs3 + Δs4 = (s11-s12) + (s22-s23) + (s33-s34) + (s44-s41). (four)

If the power of the light flux is unstable, i.e. can change over time, then to stabilize them, total signals from adjacent quadrants can be formed, proportional to the power of each light flux and independent of movements.

s _sum1 = s11 + s12,

s _sum2 = s22 + s23,

s _sum3 = s33 + s34,

s _sum4 = s44 + s41. (5)

These signals are compared with the reference (reference) signal s _ref and, if the total signals differ from the reference signal, the power of the corresponding luminous flux is adjusted until the equality s _sum1 = s _sum2 = s _sum3 = s _sum4 = s _ref . Thus, the stability of the power of the light flux is achieved.

If the power of the light flux is stable enough, then this procedure can be excluded and use the second version of the method. This option differs from the first in that the signals from the quadrants of the photodetector are first subtracted from each other, and then the signal from the corresponding light flux is extracted using the orthogonal filter from the resulting mixture of signals. This allows you to reduce the number of orthogonal filters, but this eliminates the possibility of regulating the power of light fluxes.

The inventive method for measuring displacements can be used in tracking tracking systems for mismatches and in accurate positioning systems. In addition to angular displacements, it is possible to measure linear displacements and the twist angle. In this case, a system of two rigidly coupled collimators 1 and 3 (Fig. 1) can be considered as a projection lens and move and rotate the block of grades 2 or the photodetector 4. In any of these cases, linear displacements Δx and Δy will be measured using the signals Δsx and Δsy and twist angle γ according to the signal Δsg.

Claims (3)

1. The method of measuring displacements, which consists in forming two light fluxes on the surface of a quadrant photodetector, converting optical signals into electrical signals and determining the coordinates of optical signals by electric signals, characterized in that two additional light fluxes are generated, light fluxes are modulated with orthogonal functions, and fluxes are formed at the boundaries section of the adjacent quadrants of the photodetector, emit electrical signals from each light flux from each quadrant, form from the selected Signal difference signals proportional to the difference of electric signals from each light flux from each pair of adjacent quadrant, by difference the difference signals of each pair of adjacent opposite quadrants judged move, and the sum of the difference signals is judged the angle of twisting. 2. The method according to p. 1, characterized in that they form a reference electrical signal equal to the required value of the electrical signal from each light flux, signals proportional to the sum of the electrical signals of each light flux from each pair of adjacent quadrants are compared with the reference signal and according to the results of comparison adjust the power of the light flux until the equality of the total signals to the reference. 3. A method of measuring displacements, which consists in forming two light fluxes on the surface of a quadrant photodetector, converting optical signals into electrical signals and determining the coordinates of optical signals in electrical signals, characterized in that two additional light fluxes are generated, light fluxes are modulated with orthogonal functions, and fluxes are formed at the boundaries section of adjacent quadrants of the photodetector, form differential signals proportional to the difference of the electrical signals from each pair of adjacent quadrants, extract signals from each luminous flux from difference signals, according to the difference of the extracted signals from each pair of opposite adjacent quadrants, movement is judged, and the torsion angle is judged by the sum of all selected signals.

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