RU2523780C1 - Opto-acoustic measurement of displacements - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: coherent light flux and movable periodic structure are produced in transparent medium located in displacement plane. Light flux is directed to transparent medium with movable periodic structure at preset angle selected subject to diffraction with the help of nonzero diffraction order formed by moving periodic structure. Measuring flux is formed. Reference flux is formed so that algebraic difference between reference and measuring fluxes aligned in the plane of periodic structure motion is proportional to periodic structure frequency. Said two fluxes are aligned in space. Then, interfering fluxes are converted into electric signal while periodic structure being looped with delayed feedback. Note here that light flux and moving periodic structure in transparent medium are formed in synchronous pulse medium. Parameters of pulse mode synchronisation are varied owing to control over time delay in feedback. Electric signal phase variations caused by displacements are compensated. Shifts in axis associated with periodic structure motion is defined by time delay.

EFFECT: higher precision of measurements, enhanced performances and higher resolution.

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Description

The invention relates to measuring technique, namely to laser interferometry, and can be used to control the accuracy of the movement of objects in the direction orthogonal to the coherent light flux, mainly in the field of machine and machine tools for controlling the movements of the working bodies of machine tools and measuring instruments.

In addition, the present invention can be used in the development and testing of instruments and devices of spacecraft (SC), for example, when aligning optical sensors of the SC, high-precision control of the geometry of the mirror panels and folding lobes of the expanding antenna and other complex elements. Moreover, in order to ensure the highest reliability of such measurements, it is necessary, as a rule, to use at least three alternative measurement methods.

, где λ - длина волны света, Λ_пав - длина ПАВ. Для возбуждения ПАВ подводится сигнал с несущей частотой f_A, амплитудно-модулированный другим сигналом с частотой f_м.The known method of optical sensing of surface acoustic waves (SAW) with a reference diffraction grating, which can be used to control the transverse displacements of objects / 1 /. A method implemented, for example, on the basis of an acousto-optical (AO) optical beam coordinate meter, consists of using an AO scale made on the basis of a substrate with a surfactant exciter and a reference phase diffraction grating. The latter is installed near the substrate at a distance

where λ is the wavelength of light, Λ _pav is the length of the surfactant. To excite the surfactant, a signal with a carrier frequency f _A , amplitude-modulated by another signal with a frequency f _{m, is} supplied.

The phase of the signal Δφ changes when the optical beam Δ1 is moved relative to the AO scale by Δφ-2πΔ1 / Λ _m , where Δ _m is the envelope period of the modulated signal on the surface of the sound duct, Δ1 is the beam offset along the scale.

In a device with an AO scale with a period of 100 μm, the resolution reached 2–5 μm.

The disadvantages of this method are the limitations of both the resolution and the value significantly exceeding the light length λ, and the field of use due to the use of the fragile highly sensitive AO scale as a movable element of the device.

A known method of measuring the spatial displacement of an object / 2 /, which consists in the formation of coherent radiation, which is divided into measuring and reference flows, form a periodic structure in a transparent medium, moving in two mutually perpendicular planes, the reference and reflected from the object measuring radiation flux direct onto a transparent medium with a moving periodic structure at an angle chosen from the condition of multi-order diffraction from each of the flows, while the measuring radiation flux They are 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 matching of the diffraction orders of these beams on a periodic structure so that the algebraic frequency difference of the diffraction orders combined in one of the directions of movement of the periodic structure, proportional to the frequency of the periodic structure in this direction, the interfering orders are diffracted x emissions into electrical signals, the parameters of which judge the displacement of the object.

The disadvantages of this method are the limitations of functionality due to the ambiguity of measurements when determining the position of the beam; restriction of resolution in the directions of movement of the periodic structure;

Closest to the proposed invention is a method of measuring the displacements of an object / 3 /, selected as a prototype, in which coherent radiation is divided into measuring and reference flows, a periodic structure is formed 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 condition of multi-order diffraction from each of the fluxes, while 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 value of which is chosen from the condition of spatial alignment of the diffraction orders of these beams on a periodic structure so that the algebraic difference in the frequencies of the diffraction orders , combined in one of the directions of the movement of the periodic structure, is proportional to the frequency of the periodic structure in this direction, the interfering orders of diffracted radiation c. electric signals, each of the components of a periodic structure moving in one of two mutually perpendicular planes, is covered by positive feedback with a time delay, using as an signal controlling the formation of the corresponding component of the periodic structure, an electric signal obtained as a result of conversion diffracted on this component of the periodic structure of the measuring radiation flux, and about the displacement of the object along the axis, s knitted with the direction of movement of the periodic structure, judged by the proportional change in the frequency of the electrical signal.

This method increases the resolving power in the directions transverse (orthogonal) to the laser beam to ≈Λ _uz / _1214/4 /, which when using water-based light and sound pipe (at f≈8 MHz and Λ _uz ≈200 μm) was 0 , 2 microns. As can be seen, this method does not allow to achieve a resolution in the directions co-directed (collinear) to the laser beam up to ≈Λ / 1040≈0.6 nm / 5 / due to the fact that the ratio Λ _knots / λ can reach values ≈10-350 .

Also, the disadvantages of the prototype method include the limitations of the measurement range with the dimensions of the photodetector λ (≈1-2 mm) and functionality due to the ambiguity of measurements when determining the position of the beam.

The technical problem solved by the proposed method is to increase the accuracy of measuring the movement of objects in the direction orthogonal to the coherent light flux, expanding the functionality and range of measurements, as well as increasing the resolution.

This task is ensured by the fact that in the known acousto-optical method of measuring displacements, in which a coherent light flux and a moving periodic structure are formed in a transparent medium located in the displacement plane, the light flux is directed to a transparent medium with a moving periodic structure at a given angle selected from the diffraction condition using a non-zero diffraction order formed by a moving periodic structure, create a measuring flow, form a reference flow so that if the algebraic difference in the frequencies of the reference and measuring flows combined in the plane of motion of the periodic structure is proportional to the frequency of the periodic structure, the reference and measuring flows are spatially combined, the interfering flows are converted into an electrical signal, and the periodic structure is covered by feedback with a time delay, the new one is that the light flux and the moving periodic structure in a transparent medium are formed in a synchronous pulse mode, the sync parameters are changed onizatsii pulse mode by controlling the time delay in the feedback and compensate the phase variation of the electric signal arising from displacement, and the displacement along the axis associated with the movement direction of the periodic structure, is judged by the change in time delay.

The essence of the method is illustrated by the following drawings.

Figure 1 - block diagram of a device for measuring displacements that implements the proposed method;

Figure 2 - scheme of the interaction of light and ultrasound in the AO cell;

Figure 3 - timing diagrams of the device for measuring displacement.

A displacement measuring device for implementing the claimed method (FIG. 1) may include: a pulsed laser 1, a collimator 2, a triple prism 3 mounted on a carriage 4, a Mach-Zehnder interferometer 6, consisting of beam splitters 7 and 12, an optical circuit 8, a reflector 9, AO cells 10, aperture 13, photodetector 14, pulse interpolator 15, synchronization circuit 16, consisting of a generator 17, frequency dividers 18 and 21, pulse shapers 22 and 24, a phaser, 19, a delay line 20, an electronic key 23.

At the time of the light pulse T _{s, the} radiation of the pulsed laser 1 is converted by the collimator 2 into a collimated beam and is sent to the triple prism 3, which is mounted on the carriage 4, which moves along the controlled surface of the object 5. When the carriage 4 moves along the X axis, the triple prism 3 and reflected of the laser beam is make vertical displacement along the _y axis Y Δ1 corresponding to the deviation of the object 5. The reflected by the prism 3 triple-radiation illuminates the Mach-Zehnder interferometer 6, wherein the beam splitter 7 is divided into n two beams. The first beam (beam, stream) forms the supporting arm 1 of the interferometer _op , following the path: beam splitter 7 → optical scheme 8 → reflector 9 → beam splitter 12 (spatial alignment with diffraction order E (+1)) → aperture 13 → photodetector 14.

, а фокусирующая линза преобразует новый диапазон поперечных смещений луча $$\Delta L_{у}^{\text{'}}$$

в диапазон угловых отклонений пучка ±γ на входе фотоприемника 14. Так как угловые отклонения пучка ±γ при пространственном совмещении с Е(+1) пучком приводят к изменениям периода интерференционной картины Λ_ик=λ/sinγ, то расстояние от оптической схемы 8 до фотоприемника 14 и, тем более, длина опорного плеча 1_оп должны быть такими, чтобы выполнялось условие ⌀_д<Λ_ик/2,5 /6/, где ⌀_д - диаметр диафрагмы. С учетом оптической схемы (Фиг.1) и, принимая, что для малых углов tgγ≈sinγ≈γ, правомерно записать условие 1_оп>2,5ΔL_у⌀_д/2mλ. Тогда при λ=0,6 мкм, m=6, ΔLу=30 мм и ⌀_д=0,1 мм получается 1_оп>1 м. Проведенный расчет позволил получить условие, при котором на выходе фотоприемника 14 возможно получить сигнал с высоким соотношением сигнал/шум /6/.The optical circuit 8 is a serial optical connection of a collimator and a focusing lens. The collimator reduces the entire range of lateral beam displacements by m times $$\Delta L_{\mathrm{at}}^{\text{'}\text{'}}=\Delta L_{\mathrm{at}}/m$$

and the focusing lens converts a new range of transverse beam displacements $$\Delta L_{\mathrm{at}}^{\text{'}\text{'}}$$

to the range of angular deviations of the beam ± γ at the input of the photodetector 14. Since the angular deviations of the beam ± γ when spatially aligned with the E (+1) beam lead to changes in the period of the interference pattern Λ _ik = λ / sinγ, the distance from the optical circuit 8 to the photodetector 14 and, moreover, the length of the supporting arm 1 _op must be such that the condition ⌀ _d <Λ _ik / 2.5 / 6 / is fulfilled, where ⌀ _d is the diameter of the diaphragm. Given the optical scheme (Figure 1) and, assuming that for small angles tgγ≈sinγ≈γ, it is legitimate to write the condition 1 _op > 2.5ΔL _y ⌀ _d / 2mλ. Then, at λ = 0.6 μm, m = 6, ΔLу = 30 mm and ⌀ _d = 0.1 mm, 1 _op > 1 m is obtained. The calculation performed allowed us to obtain a condition under which it is possible to obtain a signal with a high ratio at the output of photodetector 14 signal / noise / 6 /.

The second optical beam after the beam splitter 7 illuminates the AO cell 10 at an angle of incidence α _p . In each cycle, an ultrasonic pulse 11 (a moving periodic structure in a transparent medium) runs through the AO cell 10, which is, as it were, a running “diffraction window” for input radiation. If at the moment of the light pulse T _{sv the} positions of the beam illuminating the AO cell 10 and the “diffraction windows” spatially intersect, then a small, local part of the beam will diffract and form two diffraction orders: the first E (+1) and zero E (0). In this case, the zero diffraction order E (0) does not change the initial direction of motion, and the first diffraction order E (+1) deviates by the diffraction angle a _d and receives a frequency increment equal to the carrier frequency f ₁ . The values of α _p and α _d depend on the parameters of the diffraction mode selected in the AO cell 10. In this case, the beginning of the formed first diffraction order E (+1) is the center of the AO interaction, which can be taken as the middle of the traveling ultrasonic pulse 11.

Thus, with the spatial intersection of the second optical beam formed after the beam splitter 7 and the “diffraction window”, the E (+1) radiation follows the following path: the “diffraction window” of the AO cell → the beam splitter 12 → the diaphragm 13 photodetector 14. The entire radiation path from the beam splitter 7, via the AO cell 10 and further to the photodetector 14 forms a measuring arm 1 _edited Mach-Zehnder interferometer 6 (Figure 2).

As a result of spatial alignment with a small angle γ and interference of pulsed different-frequency optical flows of the reference 1 _op and the measuring 1 _{cm of the} arms of the Mach-Zehnder 6 interferometer, a pulsed frequency measurement signal U _fp (t) ≅rect (t / T _sv ) is formed at the output of photodetector 14 sin (2πf ₁ t + (φо), where Δφ _о = 2π (1 _op -1 _out ) / λ, is the initial phase difference in the balanced Mach-Zehnder interferometer at Δ1 _у = 0. Next, the generated signal U _fp (t) follows the first input of the pulse interpolator 15.

The formation of electrical signals in the device is as follows (Figure 3). The generator 17 generates an electric signal U ₁ (t) = U _1m sin2πf ₁ t supplied to the first input of the phase shifter 19 and the input of the frequency divider 18. Frequency dividers 18 and 21 are used in the device to divide the frequency of the input signals by the division coefficient n, which is the same for both dividers, depends on the parameters of the device and for small angles of incidence α _p and diffraction α _d may be in the range [20; 40]. The frequency divider 18 creates at its output a signal U ₂ (t) = U _2m sin2πf ₂ t, where f ₂ = f _i / n, arriving at the second input of the pulse interpolator 15 and the input of the pulse shaper 24. The latter creates a signal in the form of short electric pulses U ₈ (t) = rect (t / T _CB ), leading to the generation of 1 pulses of light T _St. pulsed laser

At the second input of the phase shifter 19 from the pulse interpolator 15, a code N _dr is supplied that controls the phase shift (time delay) of the signal U ₁ (t). This unit allows for a smooth fractional change in the phase shift (φ _dr ) in the range from 0 to 2 l - (φ _dr = N _dr · δ _φ ), where δ _φ is the minimum discrete phase shift. The output signal of the phase shifter 19 U ₃ (t) = U _3m sin (2πf ₁ t + (φ _dr ) is supplied to the first input of the electronic switch 23 and to the input of the delay line 20.

The delay line 20 is a chain of delay elements connected in series, switched by a digital code N _c coming from the pulse interpolator 15. The minimum delay discrete is equal to the duration of the frequency period f1-T _min = 1 / f ₁ , and the total delay time is T _max = N _c · T _min = N _c / f1. Accordingly, the phase shift introduced by the delay is proportional to whole periods 2π-Δφ _c = 2πN _u . The sequential inclusion of the phase shifter 19 and the delay line 20 allows you to widely vary the total total phase shift (time delay) of the signal U ₄ (t) = U _4m sin (2πf ₁ t + ΔΨ), where ΔΨ = Δφ _c + Δφ _dr = 2πN _u + _{N, etc.} · δ _φ = N _O δ _φ, where N _u and _{N, etc.} - digital codes constituting the code N _O.

The signal U ₄ (t) leads to the creation at the output of the frequency divider 21 of the pulse signal U ₅ (t), with a frequency f ₂ = f ₁ / n, where n is the division coefficient. Then the pulse signal U ₅ (t) passes through the pulse shaper 21 and is converted into a signal U ₆ (t), consisting of electrical pulses. This signal goes to the second input of the electronic switch 23, as a result of which the signal U ₇ (t) ≅rect (t / Т _Uz ) (sin (2πf ₁ t + ΔΨ) in the form of electric pulses T _Uz filled with short pulses is formed at its output carrier frequency f _1. Pulses T _Uzn , arriving at the AO cell 10, excite in it the corresponding traveling ultrasonic pulses (moving periodic structures) 11 synchronized with light pulses T _St. In the description it is assumed that the carrier frequency is constant during measurements, f _t = const, and the durations of light and ultra ƃ pulses are in the ratio: T _RAS ≈4T _{communication.}

As a result of spatial alignment and interference of pulsed optical frequencies of different frequencies, as described earlier, the output of the photodetector 14 generates a pulse signal U _fp (t), which is a measuring signal and, as a feedback signal for the entire circuit, follows the first input of the pulse interpolator 15. The second input of the latter receives a pulse signal U ₁ (t) from the generator 17, which is the reference signal, and the signal U ₂ (t), which is supplied to its third input, is a gate signal for “starting measurements”.

Upon the arrival of the gate pulse U ₂ (t), the pulse interpolator 15 starts converting the phase difference between the signals U _fn (t) and U ₁ (t) into a digital code N _o , the highest bits of which are the code N _c , and the lower ones - N _etc. The digital code N _o is output and is simultaneously used as feedback signals N _u and N _etc. Depending on the values of the two code components N _c and N _dr in the phase shifter 19 and the delay line 20, proportional time delays (phase shifts) are introduced, which, together changing the total phase shift ΔΨ, shift the “diffraction window” and compensate for the phase shift of the interferometer imbalance, arising due to transverse displacements of the beam Δ1y.

A description of the operation of the device is made taking into account the use of the Bragg diffraction mode. However, it is permissible to use light diffraction in the Raman-Nat mode. It is also assumed that, with a short duration of light pulses T _{sv, the} displacements of the traveling ultrasonic pulse 11 are minimal and do not lead to significant “smearing”, expansion of the first diffraction order E (+1).

The value of the division coefficients n of the frequency dividers 18 and 21, which is in the range from 20 to 40, is selected from the calculation of small angles of incidence α _p and diffraction α _d . However, depending on various parameters of the device, primarily from the AO cell 10 used, the value of n may differ from those previously selected.

Figure 1 and Figure 2 shows the scheme of the Mach-Zehnder interferometer 6, in which the flow of the supporting arm 1 _op formed by the beam splitter 7 is spatially aligned and interferes with the first diffraction order E (+1). Despite this, in the proposed method, it is possible to use the zero diffraction beam E (0) as the reference flow.

In the claimed method, the synchronization mode of lighting (light pulses T _sv ) and excitation (ultrasound pulses T _sv ) AO cells is used. Due to the stroboscopic effect for each light pulse, the displacements of the ultrasonic pulse are minimal, therefore it is assumed that in each illumination cycle a fixed "diffraction window" is formed with its own small local area and the center of AO interaction (figure 2). Transverse beam displacements Δ1 _{near the} “diffraction window” lead to a shift in the center of AO interaction and, as a result, to co-directional (collinear) displacements of the optical flux Δ1 "and Δ1 'in the measuring arm of the interferometer. The unbalance signal appears as an additional phase shift of light waves Δφ _{sv is} converted into a compensating phase mismatch of the synchronization mode, which shifts the “diffraction window” in order to balance the changes in Δφ _sv (that is, a measuring balancing method is implemented):

_{Communication} Δφ = ΔΨ.

The expression for φ _sv ((sv is written in the form:

,

,

и

- фазовые сдвиги, возникающие от изменения оптических путей Δ1" и Δ1', соответственно, Δ1' - изменения оптического пути до центра АО взаимодействия (от светоделителя 7 до бегущего ультразвукового импульса 11), Δ1" - изменения оптического пути после центра АО взаимодействия (от бегущего ультразвукового импульса 11 до светоделителя 12).Where

and

- phase shifts arising from changes in the optical paths Δ1 "and Δ1 ', respectively, Δ1' - changes in the optical path to the center of AO interaction (from the beam splitter 7 to the traveling ultrasonic pulse 11), Δ1" - changes in the optical path after the center of AO interaction (from traveling ultrasonic pulse 11 to the beam splitter 12).

Based on the above formulas and taking into account the optical scheme (Figure 2), we obtain:

N _{O = ΔΨ / δ φ = 2π (} Δ1 " and _{Δ1 ') / λ · δ φ} = 2π (Δ1 _y [sec (α _n + α _d) -ctg (α _n + α _d] / λ · δ _φ,

where α _p + α _d are the angles of incidence and diffraction in the AO cell, respectively, δ _φ is the minimum discrete of the compensating phase mismatch ΔΨ.

As seen from this formula, the obtained dependence implements "the absolute encoder" for transverse displacements Δ _y ray and the full range of phase mismatch ΔΨ N and _O correspond to code offsets within the beam range _at ΔL. This extends the functionality.

When using JSC cells with α _n + α _d = 45 ° formula is converted to the form: N _O = 2πΔ1 _y / λ · δ _φ, from which a single photon (N _out = 1) equal to δ _φ = 1 °, resolution is ~ 1.7 nm. As you can see, the resolution of the proposed method is more than 100 times the prototype. A further decrease in the sum of α _p + α _d contains a reserve for increasing the resolution.

As follows from the algorithm of the proposed method, the first diffraction order E (+1) formed in the AO cell is spatially stabilized at any position of the illuminating beam. Therefore, the entire range of transverse displacements of the beam Δ1 _y increases from the size of the photodetector 1-2 mm (as in the prototype) to the sizes determined by the expression (Figure 2):

ΔL _y = h _aom -d _p -l _aom tgα _p ,

where h _aom and l _aom are the height and width of the AO cell, respectively, d _n is the diameter of the optical beam.

Based on the above equations, in order to increase the measurement range ΔL _y and increase the resolution, it is necessary to select such a diffraction mode in the AO cell in order to reduce α _p + α _d . As follows from / 7 /, AO cells based on uniaxial and biaxial crystals operating in the anisotropic diffraction mode are best suited for these requirements. For for such AO cells / 8 / at small angles α _p and α _d, the measurement range ΔL _y can reach 10 ÷ 30 mm, which is 5-15 times more than that of the prototype.

According to the algorithm of the device, the value of T _St should not be more than 1-2 cycles of the carrier frequency f ₁ -T _St <(1-2) / f ₁ . When using AO cells based on a paratellurite crystal (Te0 ₂ ), as in / 8 /, with f ₁ = 25 MHz, v _knot ≈600 m / s and l _aom (1 cm), the temporal measurement parameters will be as follows:

T _b <40 ÷ 80 ns, measurement cycle (for small angles α _p , α _d (p, (d) T _c > l _aom tg · α _p / v _uz ≈1.5 · 10 ^-6 s. The obtained values are acceptable when using the most common pulsed lasers, for example, as in / 9 /.

The maximum "transverse" speed v _{y max} under the condition of two measurements per period (wavelength K) according to the Nyquist criterion, taking into account the previously defined parameters, is equal to v _{y max} = λ / 2Т _ц ≈0.2 m / s. As you can see, the obtained value is proportional to the maximum "longitudinal" velocities v _{x max} = 0.2-0.3 m / s, for example, as for the NR-5525A (5526A) or IPL-30 (30K1, 30K2) / 6 / interferometers.

As follows from the algorithm of the device, the measurement time of the pulse interpolator should not exceed the duration of the light pulse - T _St <40 ÷ 80 ns. The practical implementation of such a pulsed interpolator is possible with the introduction of the synchronization mode, gating in the designs of interpolators widely used in interferometers with a phase output, for example, as in / 10 /.

The introduction of the phase shift can be carried out, for example, by using a digital phase shift driver with a positive or negative sign, in manual or automatic modes. For the current level of development of phasemetry circuitry, it is possible for 8 control binary bits to achieve the minimum discrete value δ _φ ≈1.41 °. For phase shift of the signal in the proposed device, it is also possible to use a digital-to-analog converter with voltage-controlled phase shifters, for example, Merrimac model PSFM-4-30 with an accuracy of 1 ° ÷ 5 ° / 11 / or the use of phase-locked loop systems.

The proposed acousto-optical method for measuring displacements allows to increase the accuracy of measuring the displacements of objects in the direction orthogonal to the coherent light flux (laser beam), and to bring the resolution to ~ 1-5 nm, as well as expand the range of measured transverse displacements to ~ 10-30 mm, which allows you to do without the use of alternative measurement methods to increase the reliability of measurements. Moreover, the implementation of the proposed method can be carried out on the basis of devices known from the prior art.

Information sources

1. Komotsky V.A., Kotyukov M.V. Acousto-optic optical beam coordinate meter. // Autometry. - 1991, - No. 5. - p. 110-113 (analogue).

2. A. p. No. 1610252 IPC G01B 11/00. A method of measuring the spatial displacements of an object // Teleshevsky V.I., Yakovlev N. A., Ignatov S.A. Publ. in BI No. 44, 1990 (analogue).

3. A.S. No. 1765691 IPC G01B 21/00. A method of measuring the displacements of an object. Teleshevsky V.I., Yakovlev N.A. // Publ. in BI 1992, No. 36 (prototype).

4. Yakovlev N.A. Construction of laser systems for measuring displacement along three coordinates based on the acousto-optic transformation of measurement information. Abstract. diss. for a job. academic degree, Ph.D. 11/05/16. M., 1991.

5. Ignatov S.A. Increasing the resolution of laser measuring systems for monitoring GPS equipment by acousto-optoelectronic information processing. Abstract. diss. for a job. academic degree, Ph.D. 11/05/16. M., 1987.

6. Ivanov V.A. Privalov V.E. The use of lasers in precision mechanics. St. Petersburg, Polytechnic, 1993.

7. Balakshiy V.I., Martynova M.V., Rumyantsev A.A. Diffraction of light by an acoustic pulse. / Yuptika and spectroscopy, 1998, vol. 84, No. 5, pp. 860-866.

8. Balakshiy V.I., Ghazaryan A.V. Acousto-optic stabilization of the laser beam direction. // Quantum Electronics, 1998, v.25, No. 11, p. 988-992.

9. Acousto-optical scanner based on a running acoustic LFM lens // Vovk Yu.M., Zatolokin V N., Rudakov IB and other Autometry, No. 1, p. 54-62.

10. RF patent No. 2016381 IPC G01B 21/00. A method for automatic interpolation of the interference order and a device for its implementation // Mikhalchenko EP, Ryumin AV, Yakovlev N.A. Publ. in BI No. 13, 1994.

11. Erlich M., Philips L., Wagner J. Voltage-controlled acousto-optic phase shifter / Instruments for scientific research. Russian translation of "Review Scientific Instrument" 1988, No. 11, pp. 57-59.

Ehrlich M.J., Philips L.C., Wagner J.W. Voltage-controlled acousto-optic shifter / 7 Review Scientific Instrument 59, 1988, No.11, pp.2390-2392.

Claims (1)

The acousto-optic method of measuring displacements, in which a coherent light flux and a moving periodic structure are formed in a transparent medium located in the displacement plane, the light flux is directed to a transparent medium with a moving periodic structure at a given angle selected from the diffraction condition using a non-zero diffraction order formed moving periodic structure, create a measuring flow, form a reference flow so that the algebraic difference in the frequencies of the reference and measure The total fluxes combined in the plane of motion of the periodic structure were proportional to the frequency of the periodic structure, spatially combine the reference and measuring fluxes, transform the interfering fluxes into an electric signal, and the periodic structure is covered by feedback with a time delay, characterized in that the light flux and the moving periodic structure in a transparent medium, they are formed in a synchronous pulse mode, the parameters of the synchronization of the pulse mode are changed by controlling the times a delay in the feedback and compensate for changes in the phase of the electric signal arising due to displacements, and the displacement along the axis associated with the direction of movement of the periodic structure is judged by the change in the time delay.

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