SU1765691A1 - Method of measuring object displacement 9237, ,1167 vehicle heel pickup - Google Patents

Description

one

(21) 4816509/28

(22) 04.19.90

(46) 09/30/92. Bul Number 36

(71) Moscow Machine Tool Institute

(72) V.Y.Teleshevsky and N.A.Yakovlev

(56) USSR Copyright Certificate Mg 572646, cl. G 01 B 11/00, 1977.

USSR author's certificate Ns 1610252, cl. G 01 B 11/00, 1988. (54) METHOD OF MEASURING OBJECT DISPLACEMENTS

(57) The invention relates to a measurement technique. The aim of the invention is to improve accuracy by using frequency as an information parameter. The reference and reflected measurement streams of coherent radiation are directed to a moving periodic structure formed in a transparent medium, orienting them from the condition of multi-stream diffraction. The measuring flux is divided into three beams, orienting them from the condition of spatial combination of the diffraction orders of these beams on a periodic structure in such a way that the algebraic

Since the difference in frequency in one direction of motion of the periodic structure is proportional to the frequency of the periodic structure in this direction, the interfering orders of the diffracting radiation are converted into electrical signals. Each component of a periodic structure moving in one of two mutually perpendicular planes is covered with positive feedback in a time delay using these electrical signals as control for the formation of a corresponding periodic structure. It is shown that the implementation of this positive feedback provides a proportional dependence of the displacement of an object along the axis related to the direction of motion of the periodic structure on the frequency change of the corresponding electrical signal, i.e. allows for displacements along the coordinates associated with the directions of motion of the periodic structure as an informative parameter to use the frequency, which provides a positive effect in the form of an increase in accuracy. 4 il.

cl

with

XI and about o

The invention relates to a measuring technique and can be used to control the accuracy of linear movements of objects, such as the working bodies of machine tools and measuring devices,

A known method for measuring the phase shift of light waves is that the monochromatic coherent radiation of the reference and measuring channels of the interferometer is directed to a periodic structure created by the emitter in the propagation medium of ultrasonic waves at an angle that provides multi-diffraction from each radiation and transforms the interfering diffracted waves. radiation into an electrical signal whose frequency is determined by the algebraic difference of the numbers of the interfering orders, and zovy shift is a phase shift of light waves.

The disadvantage of this method is the impossibility of measuring spatial movements.

The closest to the technical essence of the present invention is a method for measuring the spatial movement of an object, which consists in forming coherent radiation, which is divided into measuring and reference flows, forming a periodic structure in a transparent medium, moving in two mutually perpendicular planes, reference and reflected from the object measuring radiation fluxes are directed to a transparent medium with a moving periodic structure at an angle chosen from the conditions of multiple orders This diffraction is from each of the streams, and the measuring radiation flux is divided into three beams, oriented so that one of the beams forms equal angles with the other two in two mutually perpendicular planes, the magnitude of which is chosen from the condition of spatial alignment of the orders diffraction of these beams on a periodic structure in such a way that the algebraic difference of the frequencies of the diffraction orders combined in one of the directions of motion of the periodic structure is proportional to the frequency of the periodic structure In this direction, transform the interfering orders of the diffracted radiation into electrical signals, the parameters of which judge the displacement of the object.

However, the disadvantage of this method is the low resolution of devices for measuring movement in the directions of motion of a periodic structure.

The aim of the invention is to improve the accuracy of movement measurements.

This is achieved by separating coherent radiation into measurement and reference fluxes, forming a periodic structure in a transparent medium, moving in two mutually perpendicular planes, and measuring and reflecting radiation fluxes from the object directed to the transparent medium with a moving periodic structure at an angle chosen from the condition of multi-diffraction from each of the streams, and the measuring radiation flux is divided into three beams, oriented so that one of the beams forms with two In two mutually perpendicular planes, equal angles, the magnitude of which is chosen from the condition of spatial combination of diffraction orders of these beams on a periodic structure in such a way that the algebraic difference of the frequencies of diffraction orders combined in one of the directions of motion of the periodic structure, is proportional to the frequency of the periodic structure in this direction, the interfering orders of the diffracted radiation are converted into electrical signals, each of the components of the periodic structure The drivers moving in one of two mutually perpendicular planes are covered with positive feedback with a time delay, using as a signal controlling the formation of the corresponding component of the periodic structure, an electrical signal obtained as a result of the measurement of the diffracted on the component of the periodic structure of the measuring radiation flux, and the displacement of an object along the axis related to the direction of motion of the periodic structure is judged by proportional frequency change s electric signal.

Figure 1 shows the beam propagation scheme; figure 2 - diagram of the device that implements the proposed method.

The device contains a monochromatic light source 7, a collimator 8, a beam splitter 9, a radiation shaper 10, a measuring reflector 11, a reference reflector 12, an optical wedge 13, a stop diaphragm 14, a light modulator 15, an optical system 18, photodetectors 4.5, 6, narrowband amplifiers 19, 20, 21, phase meter device 20, frequency meters 21, 22, electronic generator 15 and key 16.

The method is carried out as follows.

The laser radiation 7 through the collimator 8 is directed to the beam splitter 9 of the Michelson interferometer and is divided into two light beams of the measuring and reference channels - IT and EO. The radiation of the measuring channel passes through the imaging unit 10, where it is divided into three luminous fluxes: E1, E2, EZ and directed to the measuring corner reflector 11 mounted on the object 30,

Reflected from the measuring 11 and the reference 12 corner reflectors, the light emitted by the EI and EO are spatially combined on the beam splitter 9 at an angle a defined by the double optical wedge 13 of the reference light wave and directed through the diaphragm 14 to the light modulator 17,

whereby radiators 2 and 3 create a moving structure with periodic structure 1 in the form of two ultrasonic waves moving in a transparent medium mutually perpendicularly at the frequency O) specified by the generator 15.

The signal Uo of the generator 15 through the switch 16 is fed to the ultrasound emitters 2 and 3. One of the light fluxes, E1, forms with two other E2 and E3 in two mutually perpendicular planes equal angles a, which ensure the spatial alignment of the diffraction orders of the output spectra E1, E2 and E1, EZ, the algebraic difference of the frequencies of which is proportional to the frequency of excitation of the periodic structures on axes m X and Y respectively

In this scheme, the proportionality coefficient is equal to one. The interfering orders of the diffraction spectra of E3 (0), E1 (-1) and E2 (0), E2 (+1) are directed to the photovoltaics 4 and 5, which separate the electrical measuring signals U3 and U2 at the corresponding frequency Q).

The radiation of the reference channel EO is directed to the periodic structure 1 at an angle a to the radiation of the measuring channel in one of the planes, and the interfering orders of the diffraction spectra of the reference and measuring channel E0 (0) and E1 (-1) are directed to the photoconverter 6, which extracts an electrical signal U1 with a frequency QD.

Fig. 3 shows the location of the zero diffraction orders of radiation, which are focused on the photoreception plane by the optical system 18. The dark dots indicate the photoreceivers installed in the overlap zones of the zero and first orders. Axes X and Y show the direction of motion of periodic structures.

Figure 4 shows the optical scheme of the radiation shaper 10. It contains two beam-splitting cubes 25, 26, four triple prisms 27, two optical wedges 28, 29. The wedges 28 and 29 specify the angles between the beams E1, E2 and E1, E3 in two mutually perpendicular planes. The rays are combined on the beam-splitting faces of the cubes 25 and 26 and directed to the object of measurement.

In the process of measuring the movement of an object along the Z axis, the phase change of the measuring channel of the interferometer will be:

d (p 2 p d Z :, where dZ is the increment of the Z coordinate;

I is the wavelength of a monochromatic source.

When the object 30 moves along the axis X and Y, a transverse displacement of the measuring beam EI, reflected from the measuring corner reflector 11, occurs. In this case, a transverse displacement of the light beams E1, E2, E3 of the measuring channel along the periodic structure 1 occurs, the propagation directions of which coincide with the axes X and Y. Phase shifts dpx and dp y, occurring in the first order, of the measuring channel when the coordinates X and Y of the acousto-optic interaction change by the value of dX and dY are respectively:

v3B

,

V3b

where V3e is the speed of ultrasonic waves in a transparent modulator medium;

Q) is the frequency of excitation of the periodic structure.

As a result of interference (optical heterodyning) of different frequencies from wind waves at the intakes of the 6, 5, and 4 receivers, electrical signals are received in TC, the phase change of which is proportional to the change in the coordinates Z, X and Y, respectively. Electrical signals are described by the expressions:

U1 Uosin (Q, t + dpz + dpx), (4)

U2 Uosin (+ d (p x), (5)

U3 UQSin (Јit + dpy), (6) where Uo is the amplitude value of the voltage of the output electrical signal.

When switching the key 16 to the second position, the generator 15 is turned off, the electrical signals U2 and U3 through the amplifiers 20 and 19 through the feedback circuits through the key 16 arrive at the excitation of radiators 2 and 3, creating a periodic structure moving in the X and Y directions respectively, they also form a closed loop for converting the measurement information in the form of a storage (adder) of frequency shifts caused by a change in the X and Y coordinates in time:

 Qo dX Q UH

v3B d t

V3b

(7)

  Qo d Y ° Y z it:; ri-

d t v3B dtv3B

(eight)

where Vx, Vy are the velocities of the object moving in the X and Y directions;

d Qx, d Q y - changes in the circular frequency of the periodic structure in the directions X and Y.

We denote by Tx and TU the time of the ultrasonic wave passing the distances Ho and YO from the emitters 2 and 3 to the acousto-optic interaction zone. Multiplying the numerator and denominator of expressions (7) and (8) by Тх and Тu, respectively, we get:

, (9)

AO

(1Q)

about

where Ho, YO are the distances from the emitters 3 and 2 to the acousto-optic interaction zone.

Electrical signals U1, U2, U3 can be described by the expressions:

U1 Uosin (Q3t + dQxt + - pdZ), (11)

U2 Uosin (Q, t + dQxt), (12) U3 Uosin (+ dQyt). (13) As can be seen from formulas (11), (12), (13), for measuring the coordinate dZ, the phase of the electrical signal U1 can be measured using the signal U2 as a reference. The change in the phase of the signal U1 is multiplied by the value I / 2 l and the corresponding change in the coordinate dZ is obtained. For this, the signal U1 is fed through the narrowband amplifier 21 to the phase meter device 24 together with the signal U2.

Measuring the frequency of the signals U2 and U3 before and after moving along the X and Y coordinates find the movements dX and dY

(14)

,

ABOUT,

(15)

The signals U2 and U3 are fed to frequency meters 23 and 22,

The use of the method will provide an increase in the accuracy and location of the linear displacement meter in the direction of ultrasound propagation by increasing the measurement accuracy of the informative parameter frequency.

FORUMAWLAH AND ISLANDS

The method of measuring the displacements of an object, which consists in forming coherent radiation, which is divided into measuring and reference flows, forms in a transparent medium a periodic structure moving in mutually perpendicular planes, the reference and reflected measuring radiation flows from an object are directed to a transparent Wednesday

with a moving periodic structure at an angle chosen from the conditions of multi-diffraction diffraction from each of the streams, the measuring radiation flux is divided into three beams oriented so that

one of the beams forms equal angles with the other two in two mutually perpendicular planes, the magnitude of which is chosen from the condition of spatial combination of the diffraction order of these beams on the periodic structure in such a way that the algebraic difference of frequencies combined in one of the directions of motion of the periodic structure is proportional to frequency of periodic structure in

In this direction, the interfering orders of diffracting radiation are converted into electrical signals, according to the parameter of which an object is displaced, characterized in that, in order to increase

each component of a periodic structure moving in one of two mutually perpendicular planes is covered by a positive feedback with a time delay;

as a signal controlling the formation of the corresponding component of the periodic structure, the electrical signal obtained by converting the measured radiation flux diffracted on this component, and displacing the object along the axis associated with the direction of motion of the periodic structure is judged proportional to change the frequency of the electrical signal.

FIG. 2

B, l;

FIG.

zo

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EO

27 25 2726

FIG. four

About f /

/ Ј

Fiyo.Z

27 29 Yu

Claims (1)

Claim A method for measuring object displacements, which consists in generating coherent radiation, which is divided into measuring and reference flows, form a periodic structure in a transparent medium moving in mutually perpendicular planes, the reference and reflected radiation flows from the object are directed to a transparent medium with a moving periodic structure at an angle selected from the conditions of multi-order diffraction from each of the flows, the measuring radiation flux is divided into three beams oriented t k, that one of the beams forms equal angles with the other two in two mutually perpendicular planes, the value of which is selected from the condition of spatial alignment of the diffraction orders of these beams on the periodic structure in such a way that the algebraic difference in frequencies combined in one of the directions of the periodic structure is proportional the frequency of the periodic structure in this direction, the interfering orders of diffracting radiation are converted into electrical signals, the parameter of which is judged and an object, characterized in that, in order to improve accuracy, each of the components of the periodic structure moving in one of two mutually perpendicular planes is covered by positive feedback with a time delay, an electrical signal is used as a signal that controls the formation of the corresponding component of the periodic structure obtained as a result of the conversion of the measuring radiation flux diffracted on this component of the periodic structure, and about the displacement of the object along the axis, associated with the direction of movement of the periodic structure, judged by the proportional change in the frequency of the electrical signal. FIG. 2 At Fig.Z Fig. H Compiled by N. Yakovlev Editor T. Loshkareva Tehred M. Morgenthal Proofreader N.Korol Order 3379 Mintage Subscription VNIIIPI of the State Committee for Inventions and Discoveries under the State Committee for Science and Technology of the USSR 113035, Moscow, Zh-35, Raushskaya nab., 4/5 Production and Publishing Combine Patent, Uzhgorod, 101 Gagarin St. Z / 4