RU2276795C2 - Device for determining direction towards a source of sound - Google Patents

Abstract

FIELD: tool-making industry.

SUBSTANCE: in device for determining direction to a source of sound, consisting of two photo-electric shadow devices and information processing systems, laser beams are directed at an angle of 90° to each other. In each photo-electric shadow device after focusing objective laser beam is split onto two laser beams, and these two laser beams go to two knives with mutually perpendicular edges. Edge of one of aforementioned knives in each photo-electric shadow device is parallel to plane, parallel to laser beams. Information, received from two photo-receivers, standing behind these knives, is utilized for maintaining similar sensitivity of both photo-electric shadow devices. Output signals from one of these photo-receivers and two other photo-receivers of photo-electric shadow devices are squared, amplified and added. Signal at output of adder is maintained constant due to loop of negative check connection from output of adder to inputs of amplifiers. On basis of signals at outputs of amplifiers with consideration of mutual phases of signal at outputs of photo-detectors by means of phase detectors and electronic computing machine, direction towards sound source is determined.

EFFECT: expanded functional capabilities of device.

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Description

The invention relates to the field of instrumentation, and in particular to devices for determining the direction to a sound source.

Known devices for determining the direction to the sound source (K. Clay, G. Medvin, Acoustic Oceanography, M., Mir, 1980, p. 170) using a ruler of n electro-acoustic transducers located at the same distance from each other. Electrical signals from the outputs of the converters are fed to n delay lines (see figure 1). By changing Δt (the difference in signal delays between adjacent delay lines), the signal delay τ = (n-1) Δt at the outputs of the delay lines is changed.

The direction to the sound source is determined by the maximum of the total signal from the outputs of the delay lines when Δt changes or by the maximum of the cross-correlation function. Direction angle to sound source

where Δt _max - Δt corresponding to the maximum signal;

Δl is the distance between the transducers;

s is the speed of sound. This device has the disadvantage that when the antenna moves in the medium, additional noise (in relation to the noise of the device and the medium) arises due to the flow around the protective cap of the antenna.

The use of shadow devices (TP), which detect the presence of a refractive index (density) gradient in a medium, is promising for recording a sound wave, since a light beam does not introduce changes into the medium. Beam Deflection Angle

where z is the direction perpendicular to the direction of the light beam;

n is the refractive index of the medium;

L is the length of the light beam in the medium.

- градиент показателя преломления по давлению.Where

- gradient of refractive index by pressure.

Typically, the angle θ is measured using a shadow instrument using a parallel light beam in the measurement volume, by changing the power of the light signal behind the knife, which is placed in the focus of the lens focusing the light beam, using a photodetector, the output of which changes the electric signal (M.A. Bramson, E.I. Krasovsky, B.V. Naumov, Marine Refractometry, L., Hydrometeoizdat, 1986, p. 183).

In the general case, with a diverging light beam in the measuring volume, the knife is placed after the focusing lens in the focus of the converging light beam, that is, in the image plane of the light-setting diaphragm, or for the laser beam in the plane of the minimum waist of the laser beam.

Known shadow photovoltaic device for recording pressure changes (L.A. Vasiliev, Shadow methods, M., Nauka, 1969, p.60). Using this device, without making changes to the environment, you can determine the presence of an acoustic wave, but you can not determine the direction to the sound source.

As a prototype, a shadow photoelectric device with double filtering of the light field was selected (M.A. Bramson et al. Marine refractometry, p.181).

Shadow device with double filtering of the light field, the structural diagram of which is shown in figure 2, contains: a light source (in this case, an incandescent lamp) 1, a condenser 2, a light aperture 3, lens 4, safety glasses 5, 6, focusing lens 7, a knife in the form of a half-plane 8, a matching lens 9, an aperture 10 placed in a plane optically conjugated with a plane located in the middle of the measurement volume (the volume located between the protective glasses), a photodetector 11.

The above-mentioned shadow device for recording pressure changes (M.A. Bramson et al. Marine refractometry, 1986, p. 183) differs from the shadow device with double filtration in that instead of aperture 10, a diaphragm is installed in front of the protective glass, which leads to increase the diffraction blur of the image of the light diaphragm in the plane of the knife.

Note that additional filtering leads to an expansion of the spatial frequency bandwidth. The described device with double filtration is a kind of devices that work according to the method of a knife and a slit. Using a laser as a light source increases the sensitivity of a shadow photovoltaic device (M.A. Bramson et al., Marine Refractometry, p. 179).

When using a laser as a light source, the condenser 2 and lens 4 (see Fig. 2) are replaced by a telescopic system (collimator), which serves to increase the diameter of the collimated laser beam, which reduces the noise at the output of the photomultiplier caused by the scattering of the laser beam by particles located in measuring volume.

на плоскость, перпендикулярную оси светового пучка oz в среде, зависит от величины градиента давления и мощности звука. Величина этого отклонения:Experiments are known in which, using a shadow device, pressure changes created by artificial sources in the sea were recorded (report on Echo Research Institute, Research Institute FOOLIOS, St. Petersburg, 2001, inventory No. 4, p. 60), but using the described device You cannot determine the direction of the sound source. Indeed, for a parallel beam of light, the magnitude of the displacement of the image of the light diaphragm in the focus plane of the focusing lens (x`o y` plane in Fig. 2) in the direction parallel to the projection of the pressure gradient and the projection of the sound wave vector

to a plane perpendicular to the axis of the light beam oz in the medium depends on the magnitude of the pressure gradient and sound power. The magnitude of this deviation:

и осью oz,where φ is the angle between the gradient

and oz axis,

F is the focal length of the lens.

If the beam diverging in the measurement volume:

where F _p is the distance from the main plane of the focusing lens to the focus of the converging beam of light.

The value of the signal U at the output of the photodetector is proportional to the projection ρ on the axis oX`, perpendicular to the edge of the knife.

As a result:

на плоскость х` о y`).where θ is the angle between the axis ax` and the direction of movement of the focal spot (the angle between the axis ax` and the projection

on the plane x`o y`).

Obviously, the magnitude of the output signal U cannot determine the direction of the sound wave vector.

The aim of the invention is:

- expanding the capabilities of the shadow device to determine the direction to the sound source in a given half-space in which the values of one of the coordinates are always positive;

- determination of guide cosines and their corresponding angles defining this direction;

- reduction of noise of the acoustic antenna due to the use of a laser beam as a sensitive element, which does not introduce density changes in the medium.

This goal is achieved by the fact that in the device (figure 3), consisting of two photoelectric shadow devices, the laser beams of which are directed into the medium at an angle of 90 ° to each other, each of the two photoelectric shadow devices contains a laser, a collimator, a protective glass , a protective glass, a focusing lens, a beam splitter for dividing the laser beam into two laser beams, two knives in the form of a half-plane with mutually perpendicular edges mounted in each of the photoelectric shadow devices in after the beam splitter, one in two planes of the minimum constrictions of the laser beams on the optical axes of the laser beams obtained after the beam splitter, two matching lenses mounted one after each of these two knives, two photodetectors in each of the photoelectric shadow devices, mounted one after each of matching lenses in planes optically conjugated with the middle of the measuring volume located between the protective glasses, the outputs of the photodetectors are connected to the corresponding to adductors, the outputs of the quadrators are connected to the corresponding preamplifiers, the edge of one of the knives in each photoelectric shadow device is perpendicular to the plane parallel to the laser beams in the medium, two preliminary amplifiers (one in each photoelectric shadow device), connected through the quadrants to the outputs of the photodetectors, installed after matching lenses and knives with edges parallel to the plane parallel to the laser beams in the medium, connected to the subtracts by their outputs the output device of the subtractor device is connected to the second inputs of the preamplifiers of one of the photoelectric shadow devices, the output of the preamplifier of this photoelectric shadow device is not connected to the input of the subtractor, and the outputs of the preamplifiers of another photoelectric shadow device are connected to the terminal amplifiers, the outputs of the terminal amplifiers are connected to the adder and multi-channel analog-to-digital converter; the adder output is connected to the second inputs of the terminal amplifiers; the output of one of the two photodetectors installed after matching lenses and knives with edges parallel to the plane parallel to the laser beams in the medium is connected to the inputs of two phase detectors, the outputs of two other photodetectors corresponding to knives whose edges are perpendicular to the plane parallel to the second inputs are connected laser beams in the medium, the outputs of the phase detectors are connected to triggers, the outputs of which are connected to a multi-channel analog-to-digital converter, and the output of a multi-channel an A digital-to-digital converter is connected to the input of an electronic computer.

Figure 3 shows the optical and structural diagrams of the proposed optical-electronic device for determining the direction to the sound source, which contains: lasers 1, 22, collimators 2, 23, protective glasses 3, 4, 24, 25, focusing lenses 5, 26, beam splitters 6, 27, knives 7, 10, 28, 34 in the form of half-planes, matching lenses 8, 11, 29, 35, photodetectors 9, 12, 30, 36, quadrants 13, 19, 31, 37, preamplifiers 14, 20 , 32, 38, terminal amplifiers 15, 21, 33, adder 16, multi-channel analog-to-digital converter 17, subtractor 18, phase detectors 39, 40, flip-flops 41, 42, electronic computer 43.

Between the protective glasses are the measurement volumes.

Laser beams of lasers 1, 22 of two photoelectric shadow devices (nodes 1, 2, 3, 4, 5, 6, 7, 8, 9, 19, 20, 10, 11, 12, 13, 14 - the first photoelectric shadow device) and (nodes 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 34, 35, 36, 37, 38 - the second photoelectric shadow device) fall on the collimators 2, 23, where they expand to reduce interference from light scattering particles from the measuring volume. Having passed the protective glasses 3, 24, the measurement volume and the protective glasses 4, 25, the laser beams directed into the medium at an angle of 90 ° to each other are focused by lenses 5, 26, and each of the laser beams is divided into two converging laser beams by beam splitters 6, 27, after which the laser beams fall on two knives 7, 10 of one photoelectric shadow device, and accordingly, on two knives 28, 34 of another photoelectric shadow device, installed so that their edges in each photoelectric shadow device are mutually perpendicular, and the edge of one of the knives in each photoelectric shadow device was perpendicular to the plane parallel to the laser beams in the medium, after knives 7, 10 the laser beams pass through the corresponding matching lenses 8, 11 to the respective photodetectors 9, 12 in one photoelectric shadow device and, respectively, after knives 28, 34 through the respective matching lenses 29, 35 to the respective photodetectors 30, 36 in each other matching photoelectric shadow device.

In the coordinate system, in which the axis ox coincides with the direction in the medium of the laser beam from the laser 22, the axis oy coincides with the direction in the medium of the laser beam from the laser 1, and the axis oz is perpendicular to the laser beams, the photodetector 9 senses a change in light proportional to the projection of the displacement of the laser waist the beam on the axis oX, the photodetector 12 senses a change in light proportional to the projection of the displacement of the laser beam on the axis oz, the photodetector 30 senses a change in light proportional to the projection of the displacement of the laser waist beam on the axis oy, the photodetector 36 senses a change in light proportional to the projection of the movement of the waist of the laser beam on the axis oz (see figure 4). The signals at the outputs of the photodetectors 12, 36 are always correlated, since the laser beams through the corresponding matching lenses 11, 35 fall on the photodetectors 12, 36 after the knives 10, 34 with edges perpendicular to the oz axis and parallel to the plane parallel to the laser beams in the medium.

The instantaneous values of the electrical signals at the outputs of the photodetectors of the device contain complete information about the directions of deviations of the constrictions of the laser beams in the planes of the knives and the direction of the wave vector, opposite to the direction directed to the sound source.

After the quadrants, information about the phase of the electrical signals is lost, and three vectors corresponding to the direction of the sound source correspond to three modules of projection values on the coordinate axis of the vector, which are located in four sectors of the half-space (see figure 5):

- sector I is bounded by the xoz plane, the yoz plane, and the first quadrant of the xoy plane;

- sector II is bounded by the xoz plane, the yoz plane, and the second quadrant of the xoy plane;

- sector III is bounded by the xoz plane, the yoz plane, and the third quadrant of the xoy plane;

- sector IV is bounded by the xoz plane, the yoz plane, and the fourth quadrant of the xoy plane.

A line parallel to the projection of the sound wave vector onto the xoz plane and passing through the origin is located in a quadrant of the xoz plane, depending on whether the in-phase or out-of-phase signals at the outputs of photodetectors 9 and 12 are.

In the xoz plane, the first quadrant is between the axes ox and oz, the second is between the axes o (s) and oz.

In the yoz plane, the first quadrant is between the oy and oz axes, and the second is between the o (-y) and oz axes.

Indeed, a knife with a symmetry axis parallel to the z axis overlaps (darkens) the third and fourth quadrants of the xoz plane, and a knife with a symmetry axis parallel to the x axis overlaps (darkens) the second and third quadrants of the xoz plane (Figs. 6, 7).

If the line parallel to the projection of the sound wave vector onto the xoz plane and passing through the origin is in the first quadrant of the xoz plane (Fig.6) (the angle ζ is positive), then when the sound pressure (and the gradient of the refractive index) changes, the waist of the laser beams on two mutually perpendicular knives simultaneously come out of the shade and at the same time darken.

If the line parallel to the projection of the sound wave vector onto the xoz plane is in the second quadrant (Fig. 7) (the angle ζ is negative), then when the waist of the laser beam on the knife with the axis of symmetry parallel to the z axis leaves the shadow, then the waist of the laser beam on a knife with an axis of symmetry parallel to the x axis, is darkened.

Thus, the electrical signals at the outputs of the photodetectors in the first case change in phase, and in the second in antiphase, which indicates the quadrant in which there is a straight line passing through the origin and parallel to the projection of the sound wave vector onto the xoz plane.

Similarly, a line parallel to the projection of the wave vector onto the yoz plane and passing through the origin is located in a quadrant of the yoz plane, depending on whether the in-phase or out-of-phase signals at the outputs of photodetectors 30 and 36 are.

The nature of the signals for the first and second cases is illustrated in table 1.

TABLE 1. Knives are located in a plane parallel to xoz Knives are located in a plane parallel to yoz Laser beam waist position Signals at the output of photodetectors Laser beam waist position Signals at the output of photodetectors I quadrant xoz in phase I quadrant yoz in phase II quadrant xoz out of phase II quadrant yoz out of phase

So, the amplitudes and mutual phases of the electrical signals at the outputs of the photodetectors contain information about the directions of projections of the sound wave vector on the xoz and yoz planes and, thus, about the direction to the sound source.

An electrical circuit, the structure of which is included in FIG. 3, processes this information and determines the direction of the sound wave vector in a given half-space, regardless of the magnitude of the sound signal, fluctuations in laser power and changes in the transparency of optical parts (mainly protective glasses). The signals from the outputs of the photodetectors 9, 12, 30, 36 are squared respectively by the squares 19, 13, 31, 37, from the outputs of which the signals are respectively fed to the inputs of the preliminary amplifiers 20, 14, 32, 38 and amplified.

The signals from the outputs of the preamplifiers 14, 38, correlated with each other, since they correspond to photodetectors 12, 36, standing respectively after the matching lenses 11, 35 and knives 10, 34 with edges parallel to the plane parallel to the laser beams in the medium, are fed to the inputs of the subtracting device 18, the signal from the output of the subtracting device is fed to the second inputs of the preamplifiers 32, 38 of one of the photoelectric shadow devices on the optical and structural diagram of the device (Fig. 3), consisting of nodes: 22, 23, 24, 25, 26, 2 7, 28, 29, 30, 31, 32, 34, 35, 36, 37, 38; as a result of this action, the above (second) photoelectric shadow device becomes equivalent with respect to the optical wedge in its measuring volume to the first photoelectric shadow device, consisting of nodes of the optical and structural diagrams: 1, 2, 3, 4, 5, 6, 7, 8, 9, 19, 20, 10, 11, 12, 13, 14; equivalence ensures proportionality of electrical signals at the output of the preamplifiers 20, 32, 14 to the squares of the projections of the wave vector on the x, y, z axis, regardless of the change in laser power and the contamination of protective glasses (as well as collimators and focusing lenses); the signals from the outputs of the preamplifiers 14, 20, 32 are respectively supplied to the inputs of the terminal amplifiers 15, 21, 33 and after amplification are summed in the adder 16, the negative feedback signal from the output of the adder is fed to the second inputs of the terminal amplifiers 15, 21, 33; this feedback provides a constant signal at the output of the adder 16, due to which the signals at the output of the terminal amplifiers 15, 21, 33 will be normalized to the pre-set value of the output voltage of the adder and are proportional to the squares of the guiding cosines cos ² α, cos ² β, cos ² γ where α is the angle between the direction of the wave vector and the axis o (-x), β is the angle between the direction of the wave vector and the axis o (-y), γ is the angle between the direction of the wave vector and the axis o (-z); angles α, β, γ determine the direction to the sound source; the signals from the outputs of the terminal amplifiers 15, 21, 33 are fed to the inputs of a multi-channel analog-to-digital converter 17; the signals from the outputs of the photodetectors 9, 12 are fed to the inputs of the phase detector 39, the signals from the outputs of the photodetectors 12, 30 are fed to the inputs of the phase detector 40; the signals from the outputs of the phase detectors 39, 40 are respectively supplied to the inputs of the triggers 42, 41, which are triggered when the input signals exceed the zero level, and from their outputs the signals are fed to the inputs of the multi-channel analog-to-digital converter 17, from the output of the multi-channel analog-to-digital converter They come in the form of an electronic computer, in which the values of cos ² α, cos ² β, cos γ ² with the numbers quadrants which contain the projection of the sound wave vector in the plane and xoz yoz (wherein the numbers to adrantov determined by signals at the outputs of flip-flops 41 and 42) are determined by the magnitude of the direction cosines cos α, cos β, cos γ (and guide angles α, β, γ).

The rules for determining the angles α, β, γ, taking into account the numbers of sectors in which the vectors are located that determine the direction to the sound source, and the potentials at the outputs of the triggers, are given in table 2.

Table 2. Trigger number
figure 3 Trigger output potential Sector number α β γ 42 one I α ₀ β ₀ γ ₀ 41 one 42 0 II π - α ₀ β ₀ γ ₀ 41 one 42 0 III π - α ₀ π - β ₀ γ ₀ 41 0 42 one IV α ₀ π - β ₀ γ ₀ 41 0

α ₀ = arccos√cos ² α; β ₀ = arccos√cos ² β; γ ₀ = arccos√cos ² γ.

The proposed device allows you to determine the direction to the sound source in half space by the values of the directing cosines cos α, cos β, cos γ. Compared with an antenna made of a matrix of electro-acoustic transducers, in the proposed device, the direction to the sound source can be determined using a single two-channel optoelectric transducer. And most importantly, in the proposed device, a significant reduction in the influence of running noise can be achieved in comparison with an antenna made in the form of a matrix of electro-acoustic transducers.

Enumeration of figures.

Figure 1. A device for determining the direction to a sound source using a line of electro-acoustic transducers.

Figure 2. Block diagram of a shadow device with double filtering of the light field.

Figure 3. The optical and structural diagrams of the proposed optoelectronic device for determining the direction to the sound source.

Figure 4. The projection of the movement of the laser beam waist on the z axis.

Figure 5. Four sectors of half space.

6. The signals at the output of the photodetectors in phase.

7. Signals at the output of photodetectors in antiphase.

Claims (1)

A device for determining the direction to a sound source, consisting of two photoelectric shadow devices, laser beams of which are directed in the medium at an angle of 90 ° to each other, each of two photoelectric shadow devices contains a laser, a collimator, two protective glasses in series, between which the measurement volumes are located , a focusing lens, a beam splitter for dividing the laser beam into two laser beams, two knives, edges mutually perpendicular to each other, and installed after the LEDs of the detector one at a time on the optical axes of the separated laser beams in two planes of the minimum diameter of the laser beam waist, two matching lenses, installed one after each of these two knives, two photodetectors in each of the photoelectric shadow devices, installed one after each of the matching lenses in planes optically paired with the middle of the measuring volume located between the protective glasses, the outputs of the photodetectors are connected to the corresponding quadrants, the outputs of the quad tori are connected to the corresponding preamplifiers, characterized in that the edge of one of the knives in each photoelectric shadow device is perpendicular to the plane parallel to the laser beams in the medium, two preliminary amplifiers (one in each photoelectric shadow device), connected via quadrants to the outputs of the photodetectors installed after matching lenses and knives with edges parallel to the plane parallel to the laser beams in the medium, connected to the subtractor by their outputs device, the output of the subtractor is connected to the second inputs of the preamplifiers of one of the photoelectric shadow devices, the output of the preamplifier of this photoelectric shadow device is not connected to the input of the subtractor, and the outputs of the preamplifiers of another photoelectric shadow device are connected to the terminal amplifiers, the outputs of the terminal amplifiers are connected to the adder and multi-channel analog-to-digital converter, the adder output is connected to the second inputs ok of finite amplifiers, the output of one of the two photodetectors installed after matching lenses and knives with edges parallel to the plane parallel to the laser beams in the medium is connected to the inputs of two phase detectors, the outputs of two other photodetectors corresponding to knives whose edges are perpendicular are connected to the second inputs the plane parallel to the laser beams in the medium, the outputs of the phase detectors are connected to the triggers, the outputs of which are connected to a multi-channel analog-to-digital converter, and the output a multi-channel analog-to-digital converter is connected to the input of an electronic computer.

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