RU2528109C1 - Pulsed laser location system - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: system comprises a pulsed laser, two one-dimensional scanning devices, an acoustooptical deflector, an output optical system, a computing device, an acoustooptical deflector control device, a prismatic beam splitter, a measurement channel, a photodetector array, a photodetector array lens and optical fibre bundles. At one end, the optical fibre bundles are tied to and face, through their ends, the photodetector arrays, and on the other side, fibres of each bundle are tied to straight lines which together form a straight line of fibres whose ends lie in the focal plane of the photodetector lens. The prismatic beam splitter is placed between the output of the acoustooptical deflector and the input of the output optical system. The optical input of the measurement channel is connected to the output of the prismatic beam splitter, and the output is connected to the angular error compensation input of the computing device.

EFFECT: reduced weight and size, high reliability and information value of the laser locator.

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Description

The invention relates to instrumentation, the technique of optical systems for viewing space and searching for obstacles and can be applied, in particular, in the technique of optical location, systems for constructing 3D images.

Currently, there are several most characteristic ways of obtaining images of objects and devices for their implementation, based on the illumination of the object by laser radiation.

According to the scanning methods and the ratio of the radiation patterns of the source and receiver, there are three options for constructing vision systems and ranging [V.E. Karasik, V.M. Orlov. Laser vision systems. M .: MSTU im. N.E. Bauman, 2001, p. 46-53].

In the first embodiment, the object is scanned by probing laser radiation with a narrow radiation pattern, and the registration of the radiation intensity reflected from various points on the surface of the object is carried out by means of a receiver with a wide radiation pattern.

When implementing the second method, scanning is absent, the object is illuminated by probe laser radiation with a wide radiation pattern, and the registration of the intensity of radiation reflected from various points on the surface of the object is carried out by means of a receiver with a narrow radiation pattern.

The implementation of the third method (Patent RU No. 2084925, priority 04/14/1995, IPC: G01S 17/06) differs from the implementation of the first two in that the object is scanned by probing laser radiation with a narrow radiation pattern, and the registration of radiation intensity reflected from various points the surface of the object is carried out by means of a receiver with a narrow radiation pattern, which is moved synchronously with the laser beam of illumination. This method and equipment that implements it have the greatest signal-to-noise ratio with the same initial data and have the greatest noise immunity from external factors.

Rotary mirror polyhedra - prisms and pyramids, which make it possible to achieve sufficiently large scan angles at a high repetition rate of time sweep over time and the formation of a high-quality energy distribution, are currently most widely used as line scanning devices in optical-location equipment. A rotational mirror is widely used for personnel scanning, the deflection angle of which is set by an electromechanical drive implemented, for example, on a stepper motor.

Such mechanical scanners implement a fiber optic locator described in the article "Hellas: Obstacle warning system for helicopters" K.R. SchuIz, S. Scherbarth, U. Fabry (Laser Radar Technology and Applications VII, Gary W. Kamerman, Editor, Proceedings of SPIE Vol. 4723 (2002) 2002 SPIE-0277-786 / X / 02), as well as fiber optic the scanner described in (Pat. RU No. 2302025, priority 06.12.2005, IPC: G02B 26/10, G02B 26/08).

The fiber-optic scanner consists of a horizontal scanning device made in the form of two mirrors tilted in opposite directions, which are mounted on the motor spindle and rotate synchronously. On both sides of the inclined mirrors on the same optical axis are the lenses of the transmitting and receiving channels, which are optically coupled to the ends of the fiber optic bundles mounted circumferentially into the fixed collectors. The second ends of the bundles are connected in two double-row rulers, and they are facing the scanning area. Optical fibers are mounted in the centers of the collectors. One central fiber of the transmitting channel is connected to the laser emitter, and a second central fiber of the receiving channel is connected to the radiation receiver.

But this design has aberration distortions (astigmatism, coma) when the radiation direction through the lenses changes at an angle to the optical axis, which leads to radiation vignetting and, consequently, to radiation radiation losses both at the output and input channels of the device, and high accuracy is required production of collectors both in terms of the location of the optical fibers and the diameter of their location to ensure matching of the input and output channels of the collectors. Regardless of the degree of accuracy of the manufacture of mirrors, they are inherent in some assembly errors, in particular deviations from the given angles between the mirror faces and the axis of rotation of the polyhedron. All this leads to the need to increase the size of the faces of the polyhedron or to increase the aperture of the forming optics, both of which lead to an increase in the dimensions of the scanning device, and the need for a high scanning speed requires an increase in the rotation speed of the mirror polygon, which is technically impossible with large dimensions of the mirror polyhedron. Also, when the mirror surface is rotated, a linear geometric displacement of the beam in space occurs, which leads to uneven scanning speed and a decrease in the accuracy of beam positioning in the area of the scanned space.

A big drawback of laser locators with mechanical scanning of the angular radiation patterns of the transmitting and receiving channels is the limited information content and significant overall weight characteristics. The speed of line scanning is determined by the capabilities of mechanical scanners (engines) and changing it (increasing or decreasing) when changing application conditions, for example, when changing weather conditions - deteriorating visibility, is almost impossible. It is also almost impossible to increase the scanning speed to increase the frame refresh rate and increase the number of elements in the image line. The reliability of mechanical scanners, especially in a wide temperature range of use (in some cases, a laser locator is located outside the device) is insufficient.

The technical result of the invention is to increase the information content of the laser locator, reduce overall weight and weight characteristics, as well as increase reliability.

The technical result in the present invention is achieved by the fact that in a pulsed laser location system containing a pulsed laser, a single-axis scanning device, including an acousto-optical deflector and an output optical system of a transmitting channel, an optical lens of a photodetector, a single-axis scanning device in a second coordinate, orthogonal first coordinate, photodetector, computing device, as well as acoustoopt control unit a deflector, the control input of which is connected to the control output of the deflector of the computing device, and the output is connected to the control input of the deflector, the laser synchronization input being connected to the synchronization output of the computing device, a prismatic beam splitter, a measuring channel, an array of photodetectors including K photodetectors, the outputs of which connected to the measuring inputs of the range of the computing device, as well as To fiber optic bundles containing M fibers, which with one the first side are mounted together and facing the respective photodetectors, and on the other hand, the fibers of each bundle are mounted in single-line rulers, which together form a single-line ruler of MK fibers, the ends of which are facing the output of the optical lens of the photodetector and are located in its focal plane, a prism beam splitter placed between the output of the acousto-optical deflector and the input of the output optical system of the transmitting channel, the optical input of the measuring channel being connected to the second m output prismatic beam splitter, and the output is connected to the input of the compensation of angular errors of the computing device.

The introduction of an array of photodetectors, including K photodetectors, as well as K fiber optic bundles containing M fibers, which are mounted together on one side and facing the respective photodetectors, and on the other hand, the fibers of each bundle are mounted in single-line rulers that form a single-line a line of MK fibers, the ends of which are facing the output of the optical lens of the photodetector, which made it possible to reduce overall weight and weight characteristics, to increase reliability by eliminating Nia optomechanical horizontal scanner, and remove the restriction on the speed of horizontal scanning and correspondingly increase information content laser locator.

The introduction of a prism beam splitter located between the output of the acousto-optical deflector and the input of the output optical system of the transmitting channel, and the measuring channel, the optical input of which is connected to the second output of the prism beam splitter, and the output is connected to the input of the compensation of angular errors of the computing device, made it possible to increase the reliability of the locator when operating in the temperature range due to stabilization of the angular position of the scanning laser beam.

The applicant and the authors have not found in the patent and scientific literature of pulsed laser ranging systems made in this way.

Figure 1 shows the structural diagram of a pulsed laser location system.

Figure 2 for one line conditionally presents options for the position of the laser beams and fields of view for each fiber in the picture plane of the space under study for the case of discrete changes in the frequency of control of the deflector (figa), for the case of LFM signal control deflector (fig.2b) and for the case of irradiation with a laser beam of the field of view of the fibers with a pass of irradiation for the adjacent fiber (pigv).

Figure 3 shows the end view of the fiber optic bundles containing M = 19 fibers (figa) and containing M = 37 fibers (fig.2b), which are mounted on this side together and facing the ends to the corresponding photodetector.

The pulsed laser location system (Fig. 1) contains a pulsed laser 1, a single-axis scanning device 2, an acousto-optical deflector 3, a prism beam splitter 4, an output optical system of the transmitting channel 5, an acousto-optical deflector 6 control unit, a measuring channel 7, an optical lens of the photodetector 8, fiber optic bundles 9 ₁ -9 _K , an array of photodetectors 10 ₁ -10 _K , a computing device 11 and a single-axis scanning device 12. The bundles 9 ₁ -9 _K contain KM fibers 13 ₁ -13 _KM .

The output of the laser 1 through an acousto-optical deflector 3 and the first optical output of the prismatic beam splitter 4 is connected to the input of the output optical system of the transmitting channel 5. The second optical output of the prismatic beam splitter 4 is connected to the input of the measuring channel 7. The output of the measuring channel 7 is connected to the input of the compensation of angular errors of computing device 11 The output of the deflector control unit 6 is connected to the control input of the acousto-optical deflector 3. The input of the deflector control unit 6 is connected to the control output of the deflector torus calculation unit 11. Sign laser timing 1 is connected to the output of the synchronization of the computing device 11.

The output of the optical lens of the photodetector 8 through fiber optic bundles 9 ₁ -9 _{K is} connected to the array of photodetectors 10 ₁ -10 _K. The outputs of the photodetectors 10 ₁ -10 _{K are} connected to the measuring inputs of the range of the computing device 11.

The inputs / outputs of the scanner control of the computing device 11 are connected to the corresponding inputs / outputs of the single-axis scanning device 12.

The operation of the pulsed laser location system is as follows. The computing device 11 generates codes of the position of the laser beam along the line, which are fed to the input of the deflector control unit 6, and, with a time delay τ, which depends on the inertia of the acousto-optical deflector, the clock pulses supplied to the laser synchronization input 1. The deflector control unit 6, which is a synthesizer frequency, generates a high-frequency signal f _C , the frequency of which is proportional to the value of the received code of the position of the laser beam along the line. The high-frequency signal f _C applied to the acousto-optical deflector 3 excites acoustic waves in the deflector, in which diffraction of the laser beam incident on the deflector occurs.

The sync pulse applied to the synchronization input of laser 1 causes a short laser pulse to be generated, which, passing through the acousto-optical deflector 3, is deflected by an angle proportional to the value of the high-frequency signal f_FROM. Next, the deflected (diffracted) laser beam passes the output optical system of the transmitting channel 5 and increases the deflection angle in proportion to the angular increase in the output optical system of the transmitting channel 5. Next, the laser beam is reflected from the mirror of the single-axis scanning device 12 and is radiated into the viewing space.

A part of the laser beam deflected by the deflector 3 is diverted by the prism beam splitter to the second output and then it enters the measuring channel 7. In the measuring channel 7, the current angular position of the deflected laser beam is determined for a given (reference) position code. The value of the angular deviation of the current angular position of the deflected laser beam from the expected angular position for the given position code is calculated and this value is supplied to the computing device 11 for correcting the position codes in order to compensate for the angular scanning error due to the influence of the ambient temperature.

The position codes generated by the computing device 11 sequentially change from the smallest to the largest value with a given discreteness, thereby determining the range of variation of the magnitude of the high-frequency signal and, therefore, the angular scanning range of the laser beam along the line. The range of variation of the values of the high-frequency signal f _С is equal to Δf = f _max- f _min , where f _max and f _{min are the} highest and lowest frequencies of the deflector control 3. The extreme angular azimuthal positions of the diffracted laser beam are shown in Fig. 1. They correspond to the frequencies f _max and f _min . With a sequential discrete change in the frequency of control of the deflector 3 in this range, the diffracted laser beam in space forms a horizontal line containing N _S points, where N _D is the number of position codes in the sequence of line codes. The discrete change in the frequency ΔF _M control of the deflector 3 when switching neighboring points in this case is equal to the value ΔF _M = Δf / N _S. The position of this horizontal laser line in elevation is determined by the angular position of the mirror of the single-axis scanning device 12. According to the elevation angle (in the frame) due to the deflection of the scanning device 12, N _K discrete positions of the laser lines can be formed.

The lens of the photodetector 8, fiber 13 ₁ -13 _{K ,} fiber optic bundles 9 ₁ -9 _K and the array of photodetector 10 ₁ -10 _K have an instantaneous field of view for each photodetector 10 ₁ -10 _K , coupled with the angular position of the laser beam coming out of the single-coordinate scanning device 2 in the desired direction in the first coordinate, as shown in figa. Thus, for each laser pulse position code in the line, the fiber number from the set of fiber optic bundles 9 ₁ -9 _K is known, on which the laser pulse reflected from the distant object should be focused, and the number of the photodetector from the array of photodetectors 10 ₁ is also known -10 _K , to which the reflected signal will come.

The laser pulse reflected from the distant object is received by the lens of the photodetector 8 and, depending on the angle of arrival, it focuses on one of the fibers of the fiber optic bundles 9 ₁ -9 _K. The received laser stream through the fiber is directed to a single photodetector from an array of photodetectors 10 ₁ -10 _K and converted into an electric pulse, delayed by time τ _З = 2L / c relative to the radiation time, where L is the distance to a distant object, s is the speed of light .

Computing device 11 measures the time delay of the received laser pulse relative to the sync pulse (or, alternatively, relative to the light pulse emitted by the laser) and calculates the current distance in this direction to the reflective surface. The output of the computing device 11 is the current direction code for the line (azimuth), the current direction code for the frame (elevation angle taken from the sensor of the angular position of the mirror) and range. The current set of these data for one frame allows you to build a three-dimensional image of the space under study.

соответственно, по углу места и по азимуту. Дискрет изменения частоты управления дефлектором 3 в этом случае равен величине ΔF_М. Мгновенные угловые поля зрения фотоприемных устройств, с учетом каждого волокна из набора волоконно-оптических жгутов, равны φ_ПУ. Мгновенные угловые поля зрения, с учетом диаметра светопроводящего центра волокна, представлены на фиг.2 черными кругами. Круги с пунктирными линиями соответствуют угловым полям с учетом наружного диаметра волокон. Их число также равно М×К=N_S.Figure 2 for one line conditionally presents options for the position of the laser beams and fields of view for each fiber from a set of fiber optic bundles 9 ₁ -9 _K , which should be focused on the laser pulse reflected from a distant object in the picture plane of the space under study. On figa in the line laid M × K = N _S laser beams having angular divergence $${\varphi }_L^{\mathrm{At}M}\times {\varphi }_L^{\mathrm{BUT}3}$$

respectively, in elevation and azimuth. The discrete change in the frequency of control of the deflector 3 in this case is equal to the value ΔF _M. The instantaneous angular fields of view of the photodetectors, taking into account each fiber from the set of fiber optic bundles, are equal to φ _PU . Instant angular fields of view, taking into account the diameter of the fiber-conducting center of the fiber, are shown in Fig. 2 in black circles. Circles with dashed lines correspond to angular fields, taking into account the outer diameter of the fibers. Their number is also equal to M × K = N _S.

, где λ - длина волны лазерного излучения, υ - скорость акустических волн в дефлекторах. При дифракции лазерного пучка в акустооптическом дефлекторе число разрешимых положений пучка на выходе дефлектора N_d по критерию Релея равно N_d=Δf×τ, где Δf - полоса рабочих частот, τ - постоянная времени дефлектора, вычисляемая из соотношения: τ=d₀/υ, где d₀ - световая апертура дефлекторов, d - скорость акустических волн в дефлекторе. Полный угол сканирования лазерного пучка φ_СК на выходе дефлектора равен величине φ_СК=N_d×φ_пад, где φпад - угловая расходимость падающего лазерного пучка.Modern designs of acousto-optical deflectors due to the skewing of the input and output faces are implemented in such a way that the incident laser beam and the laser beam diffracted at the central operating frequency f _{0 are} aligned. The center of the scanning angle corresponds to the control frequency of the deflector f ₀ = (f _max + f _min ) / 2. The frequency range of control of the deflectors Δf = f _max -f _min determines the angular size of the raster $${\varphi }_{\mathrm{FROM}\mathrm{TO}}=\frac{\lambda }{\upsilon }\Delta f$$

where λ is the wavelength of laser radiation, υ is the speed of acoustic waves in the deflectors. When a laser beam is diffracted in an acousto-optical deflector, the number of resolvable beam positions at the deflector output N _d according to the Rayleigh criterion is N _d = Δf × τ, where Δf is the operating frequency band, τ is the deflector time constant calculated from the relation: τ = d ₀ / υ where d ₀ is the light aperture of the deflectors, d is the speed of acoustic waves in the deflector. The total scanning angle of the laser beam φ _SK at the output of the deflector is equal to φ _SK = N _d × φ _pad , where φpad is the angular divergence of the incident laser beam.

и будет засвечивать по азимуту несколько полей зрения фотоприемных устройств, как представлено на фиг.2б. В этом случае одновременно измеряется дальность до объекта по нескольким направлениям. Лазерная строка в этом случае будет содержать R лазерных полосок (фиг.2б), число которых равно R=Δf/ΔF_Б. Закон изменения частоты высокочастотного сигнала управления дефлектором во времени для каждой лазерной полоски 1…R может быть представлен в виде $$f_{С}(t)=f_{\min }+k\frac{\Delta F_{Б}}{\tau }t$$

, где k=1…R, t - текущее время. Очевидно, что девиация частоты ΔF_Б не должна превышать величины ΔF_{Б мах}≤Δf/К, иначе от одного лазерного импульса на одном фотоприемном устройстве от двух волокон соседних жгутов будут приняты отраженные сигнала из двух направлений.When the deflector control frequencies are linearly changed (a linear frequency modulation signal is a LFM signal), the diffracted laser beam angularly broadens along the scanning direction (Bondarenko D.A., Karasik V.E., Semenkov V.P. Study of the mode of laser beam diffraction on a linear frequency-modulated acoustic wave in an anisotropic acousto-optic deflector // Bulletin of MSTU named after NE Bauman. Special issue "Modern problems of optical engineering. 2011. P.31-41). If, during the time τ, before applying a sync pulse causing the appearance of a laser pulse, a chirp signal with a frequency deviation ΔF _{B is} applied to the deflector 3, then the diffracted laser beam will have an angular size $${\varphi }_B=\frac{\lambda }{\upsilon }\Delta f_B$$

and it will illuminate in azimuth several fields of view of photodetectors, as shown in figb. In this case, the distance to the object is measured simultaneously in several directions. The laser line in this case will contain R laser strips (fig.2b), the number of which is equal to R = Δf / ΔF _B. The law of change in the frequency of the high-frequency deflector control signal in time for each laser strip 1 ... R can be represented as $$f_{\mathrm{FROM}}(t)=f_{\min }+k\frac{\Delta F_B}{\tau }t$$

, where k = 1 ... R, t is the current time. Obviously, the frequency deviation ΔF _B should not exceed ΔF _{B max} ≤ Δf / K, otherwise, reflected signals from two directions will be received from two fibers of adjacent bundles from a single laser pulse on a single photodetector.

To increase the refresh rate of frames, it is possible to form a horizontal scan not only by sequentially illuminating adjacent instantaneous fields of the forming receiving device, but by skipping one, two, or several illumination positions, as shown in Fig. 2c. For a number of applications, all of the above options for the formation of horizontal scanning can be applied to optimize the resulting image of the picture plane.

Laser 1 operating in a pulsed mode can be implemented on an active element made of garnet with neodymium and pumped by semiconductor laser diodes. An acousto-optical modulator, for example, a commercially available MZ-321M having a control signal frequency of 80 MHz, can be installed inside the resonator. An embodiment of such a laser is described in the book (V.V. Bezotosny et al. Highly efficient compact Nd ³⁺ : YAG - a laser at a wavelength of 1.064 μm, operating in continuous and pulsed modes, with diode pumping and Q-switching by an acousto-optic gate. Quantum electronics, t. 35, No. 6 (2005), 507-510). Such a laser provides a diffraction divergence of the laser radiation at the output, and in the pulsed mode the pulse repetition rate reaches 200 kHz. With a laser exit aperture of 4.5 mm, the angular divergence of the laser radiation will be about 0.3 mrad.

When constructing a pulsed laser location system with other wavelengths, a laser based on an active element made of garnet with neodymium and pumped by semiconductor laser diodes and intracavity nonlinear conversion of radiation into second harmonic (λ = 0.53 μm) or with parametric intracavity conversion can be used as a laser in a wavelength safe for eyes (λ = 1,57 microns). It is possible to use fiber lasers with an eye-safe wavelength of λ = 1.54 μm.

As a deflector 3 of a pulsed laser location system, acousto-optic deflectors with a light and sound pipe from paratellurite (TeO ₂ ) can be used. Such deflectors can scan laser radiation in the visible region (for example, 0.53 μm) and the near infrared region of the spectrum (for example, 1.064 μm), including in the spectrally safe region of ~ 1.5 μm. When implementing the design of the deflector with the Brewster angle (Patent RU No. 2462739, priority 08/08/2011, IPC: G02F 1/33) for laser radiation with a wavelength of 1.064 μm and a frequency range of control of the deflector λf = 32 MHz, a full scan angle of 6 , 6 degrees. The central operating frequency f0 is equal to 80 MHz. For the light aperture of the deflector 9 mm, the deflector time constant is τ ~ 14 μs, and the number of resolved states of the deflector by the Rayleigh criterion is Nd ~ 450. The diameter of the laser beam at the input of such a deflector is about 4.5 mm.

When using the deflector 3 with the above parameters and the output optical system of the transmitting channel 5, having a magnification of 5, a laser beam scan of 33 degrees is provided at the output of the pulsed laser location system. The output optical system of the transmitting channel 5, it is advisable to implement a cylindrical. In this case, the angular divergence of the laser radiation at the output of the pulsed laser ranging system will be about 0.3 mrad × 1.5 mrad, and the large angular divergence of the laser beam corresponds to the scanning direction of the laser beam (Fig. 2a).

The deflector control unit 6 can be implemented on a standard frequency synthesizer chip, for example, AD9954YSVB, which has a built-in fast frequency scanning circuit, the output of which is connected to a broadband power amplifier, implemented, for example, on a standard RA07H0608V chip. When using a laser with a wavelength of 1.064 μm, the output power of the high-frequency signal of the deflector control unit 6 in the deflector control frequency range Δf = f _max -f _min = 96 MHz ... 64 MHz = 32 MHz should be about 5 W. Modern frequency synthesizers have a two-byte frequency setting code, which allows you to very accurately position the angular position of the laser beam during scanning. For example, setting the range code of the position of the laser beam along the line equal to 8192 ± 4096, in order to provide the above frequency range for controlling the deflector 80 ± 16 MHz, it is realistic to obtain 8192 angular discretes for positioning the laser beam along the line.

In the measuring channel 7, the current angular position of the deflected laser beam is determined at a certain position code, for example, equal to 8192, corresponding to the center frequency of the deflector control frequency range f ₀ = 80 MHz. The diffracted laser beam is partially reflected by the prism beam splitter 4 to the second output and then goes to the measuring channel 7. The measuring channel is a telephoto lens with a photodetector in its focal plane, for example, a CCD array containing 256 elements. An image of a laser beam is built on a CCD line. The focus of the lens and the dimensions of the CCD line are selected so that the image of the laser beam covers two to three dozen elements of the line and under normal conditions is approximately in the center of the line. The center of the laser beam is defined as the average value of the numbers of the illuminated elements of the line. When the ambient temperature changes, the position of the image of the laser beam on the elements of the CCD line will change due to a change in the diffraction angle of the laser beam in the deflector and, calculating in the computing device 11 a new average value of the numbers of the illuminated elements of the line, it is easy to determine the amount of compensation for the temperature drift of the deflector. Such an operation takes fractions of a ms in time and can be performed both before the operation of the pulsed laser location system and during operation.

The design of the lens of the photodetector 8 may be similar to the known fiber optic locators.

The fibers of the optical fiber bundles 9 ₁ -9 _K (Fig. 1) on one side facing the photodetector are arranged in a circle. An example of laying for 19 and 37 fibers is shown in figa and figb respectively. The fiber laying diameter d _B for the above cases is 5d _B and 7d _B , where d _B is the outer diameter of the fiber. The fibers of the optical fiber bundles 9 ₁ -9 _K, on the other hand, facing the lens of the photodetector 8, are laid out in a ruler, as shown in Fig. 1: at the beginning of the ruler, the first fibers of all bundles are stacked, then the second fibers of all bundles, etc. . Fiber optic bundles 9 ₁ -9 _K can be made of optical fibers, for example, with an external diameter d _B = 200 μm and a diameter of the central light guide part d _C = 160 μm. The stacking diameter db for the above cases is 1.0 mm and 1.4 mm.

As a photodetector, a set of single avalanche photodiodes can be used, as well as a line of avalanche photodiodes, the geometric dimensions of the photosensitive areas of which will provide laser radiation from the output of a fiber optic bundle. The diameter of the photosensitive pads D _{Ф of} avalanche photodiodes should exceed the fiber stacking diameter d _B by 10-40 percent and for the above cases, avalanche photodiodes with pads with a diameter of 1.5 mm and 2.0 mm can be used. With the introduction of a special optical system for focusing laser radiation from the output of a fiber optic bundle, the diameter of the pads can be reduced.

The number K of the used photodetectors in locators with a large angular field of view is advisable to choose equal to 8 or 10 pcs. Depending on the problem being solved, their number may be different.

When K = 8, the number of fibers in the bundle M = 37 and the outer diameter of the fibers is 200 μm, the linear dimensions d _{F of the} fibers facing the lens of the photodetector 8 and laid in a line are d _F = 59.2 mm. The number of fibers and, therefore, the number of angular solvable elements in the row is equal to N _S = 296.

. Для φ_F=15 градусов и вышеприведенных данных F_ПУ=110,0 мм. Мгновенное угловое поле зрения φ_В системы импульсной лазерной локации зависит от диаметра волокна, фокусного расстояния объектива фотоприемного устройства и определяется выражением φ_В=d_С/F_ПУ. Для вышеприведенного примера φ_В=1,45 мрад.With the angular field of view of the pulsed laser ranging system along a line equal to 2φ _F , the focal length F of the _{PU of the} objective of the photodetector 8 should be equal $$F_{P\mathrm{At}}=\frac{d_F}{2tg{\varphi }_F}$$

. For φ _F = 15 degrees and the above data, F _PU = 110.0 mm. The instantaneous angular field of view φ _V of a pulsed laser location system depends on the fiber diameter, the focal length of the objective of the photodetector and is determined by the expression φ _B = d _C / F _PU . For the above example, φ _B = 1.45 mrad.

Computing device 11 can be implemented, for example, on the control microcontroller STM 32F407, which has a high clock frequency, a significant number of peripheral units - DACs and ADCs, external interfaces of various types, as well as large RAM and ROM.

A single-coordinate scanning device at the second coordinate 12, as in the known fiber-optic scanners, can be implemented on the basis of a scanning mirror with a stepper motor and a sensor for the angular position of the mirror.

Compare the proposed pulsed laser location system and the well-known fiber-optic scanners.

In known fiber-optic scanners, the forming device for generating a flow of pulsed laser radiation in the desired direction along the first coordinate (transmitter lens) practically corresponds to the forming receiving device, which ensures the transmission of pulsed laser radiation reflected from the object to the photodetector (receiver lens), since they are optically matched with optical fibers through which laser radiation is transmitted and received. These lenses are quite large in weight and size. The light aperture of such a lens is at least 50 mm. In the proposed system there is only one lens (receiving). The transmitting part is equipped with a small-sized optical system with an aperture of 10-15 mm, which reduces the overall weight characteristics.

The implementation of a high-speed scanning line device based on an acousto-optical deflector increased the reliability of the system by eliminating a mechanical scanner having a dependence of parameters in a wide temperature range of use. In particular, freezing of the grease of the scanner at low temperatures is difficult to eliminate electronically.

In known fiber-optic scanners, the frequency of updating information is not more than 3 Hz and it is practically impossible to change it. It is determined by the laser repetition rate, which is 60 kHz in analogs, the number of fibers in a horizontal scanning device, equal to 100-120, and the number of lines when performing a single-scan scanning with a single-axis scanning device. The number of lines in the frame is approximately 200.

In the proposed system of pulsed laser location, an acousto-optical deflector allows you to change the angular divergence of the laser radiation in the scanning direction using a linearly frequency-modulated deflector control signal. In this case, it is possible to simultaneously receive reflected laser pulses from several instantaneous fields of view. In the proposed implementation example, this gives an increase in the frequency of updating information up to 8 times, or, at a lower frequency of updating information, allows to increase the information content of the frame by increasing the resolution in rows.

We also note that the acousto-optical deflector allows you to generate a laser line not only by sequentially illuminating adjacent instantaneous fields of the forming receiving device, but in another way, for example, by skipping one or two positions of the neighboring illumination in a row, forming a different structure of neighboring rows, but increasing the frequency frame updates, i.e. informational content of the system.

Claims (1)

A pulsed laser location system comprising a pulsed laser, a single-axis scanning device including an acousto-optical deflector and an output optical system of a transmitting channel, an optical lens of a photodetector, a single-coordinate scanning device in a second coordinate, orthogonal to the first coordinate, a photodetector, a computing device, and also an acousto-optical deflector control unit, the control input of which is connected to the control output deflector of the computing device, and the output is connected to the control input of the deflector, and the laser synchronization input is connected to the synchronization output of the computing device, characterized in that a prismatic beam splitter, a measuring channel, an array of photodetectors, including K photodetectors, the outputs of which are connected to the measuring inputs, are introduced into it the range of the computing device, as well as K fiber optic bundles containing M fibers, which are mounted on one side and facing end to the respective photodetector, and on the other hand, the fibers of each bundle are mounted in single-line rulers, which in total form a single-line ruler of MK fibers, the ends of which face the output of the optical lens of the photodetector and are located in its focal plane, the prism beam splitter is placed between the output of the acousto-optical deflector and the output output optical system of the transmitting channel, and the optical input of the measuring channel is connected to the second output of the prism beam splitter, and the output is connected nen with the input of compensation of angular errors of the computing device.

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