WO2023113646A1 - Device and method for receiving an optical signal reflected from a probed object - Google Patents

Abstract

The present invention relates to the field of receiving modulated optical signals and can be used, for example, in navigation, laser ranging, reflectometry and the detection of complex elongate objects having multiple component parts and being in motion relative to a signal receiver, in order to time synchronize optical lines, with synchronous detection of an optical signal. The invention makes it possible to create scanners (lidars) for remotely detecting metal items in crowds and undergrowth, to remote detect and determine the concentration of gases in air, and to create lidars capable of functioning in conditions of limited visibility (to the human eye). According to the invention, the device contains a unit for adjusting quantum efficiency according to the operating frequency of a sensor, and an assembly for generating a strobing adaptation signal.

Description

DEVICE AND METHOD OF RECEIVING OPTICAL

OF THE SIGNAL REFLECTED FROM THE SOUNDED OBJECT

The field of technology to which the invention belongs.

This invention relates to the field of receiving optical modulated signals, including signals used in measuring the time it takes a signal to travel a distance from a signal emitting source to an optical signal receiving device, in communication devices using pseudonoise optical signals, including a clock signal generator, an optical receiver a device operating in a non-linear mode, a matched filtering unit, a signal threshold detection module, and can be used, for example, in navigation, in laser ranging, reflectometry, locating complex extended objects that have many constituent elements and moving relative to the signal receiver, for time synchronization of optical lines with synchronous detection of an optical signal.

In this description, the following terms are used.

LIDAR (transliteration LIDAR English Light Identification Detection and Ranging - light detection and ranging) is a technology for obtaining and processing information about distant objects using active optical systems that use the phenomena of light reflection and its scattering in transparent and translucent media. Lidar, as a device, is at least an active optical range finder. Usually in Russia, such devices are called laser rangefinders and laser radars.

Optical radiation - electromagnetic waves, the lengths of which are in the range with conditional boundaries from 3000 pm to 0.25 pm.

PWB, Pseudo-random (pseudo-noise) sequences are completely deterministic digital sequences that appear random to an external observer.

M-sequences. An M-sequence is a recurrent sequence of order n modulo p, where p is a prime generated by the equation: y(j + n) = (a _o yi + n - 1) + "1/ + n - 2) + ^a ni /(0) modp A recurrent sequence of order n modulo p for any prime p and some combinations (^ takes values from the interval from 0 to p - 1, has the maximum possible minimum period equal to ^{p n} - 1.

An example of an M-sequence.

M-sequence of the first order modulo 37, period 37 ¹ - 1 = 36 is generated by the equation

(3 ₀ = 8; (3 _i+1 = (ao i) mod 37 where, and ₀ = 5;

Sequence /3

obtained from the first 37 members of this M-sequence.

[3= {8; 3; 15; 1 ; 5; 25; 14; 33; 17; eleven ; 18; 16; 6; thirty; 2; 10; 13; 28; 29; 34; 22; 36; 32; 12; 23; 4; 20; 26; 19; 21; 31; 7; 35; 27; 24; 9; 8}.

Binary, position modulated (PM) sequences. In foreign literature, such sequences are called - nonuniform trains, position modulated trains, non-uniformly spaced trains.

Sequences a = {ct _fc } of length L in which the members of the sequence take the values 0 and 1 and only N members of the sequence take the value equal to 1 .

The members of the sequence a with numbers (M * i + /3^ - /3 ₀ ), where i = 0,1,2, are equal to 1, and the remaining members of the sequence a are equal to 0. Such sequences are binary irregular sequences. The sequence /3 of length N, we will call the sequence of modulating shifts, and the sequence a - a binary position-modulated sequence (PM). An example of a /3 sequence is the M-sequence above.

Let us extend the ^sequence a so that for k < 0 v\ k > N - l and _k = 0, then the non-normalized ACF of the sequence ^a more than K for i 0. Such a sequence is called a sequence with the property "no more than K matches".

Binary sequences that have K=1 are called sequences with the "no more than one match" property.

For the examples discussed in the patent, the following is accepted: The numbering of the members of a binary sequence starts from the zero member.

• Members of a binary sequence with numbers j, for which the equality 0 = (J)' mod2 is true, are called members with even numbers.

• Members of a binary sequence with numbers j, for which the equality 1 = (J)' mod2 is true, are called members with odd numbers.

If a sequence y of length L with the property “no more than K matches” contains terms equal to “1”, both with even and odd numbers, divide into two sequences: a, consisting of even-numbered members of the sequence y and the sequence

8, consisting of members of the sequence y with odd numbers, then it will be true that for sequences a and 8 the property “no more than K matches” is also satisfied, i.e. the level of side lobes of the non-normalized ACF of sequences a and 8 will not take values greater than TO.

An example of the formation and matched filtering of a binary PM sequence with the property of no more than one match.

From modulating sequence /3

of length N = 37 given in the example (M-sequence), we form the sequence

Li = 56 - 36 + 8 - 8 + 1 = 2017

Members (Zj with numbers M _r • i + - ? ₀ , where i = 0,1,2, . . N - 1 are equal to 1, and the remaining members are equal to 0. The sequence a has the property "no more than one match".

In FIG. 1 shows the scheme of formation and subsequent matched filtering of the PM sequence. The scheme consists of block 1 for the formation of the PM sequence a =

_LENGTH Block 1 contains thirty-six cascades connected in series 1.1.

The first input of cascade 1.1 is the input of block 1.

The second output of stage 1.1 of block 1 is the output of block 1. The first input of each next stage is connected to the first output of the previous stage, that is, the input of block 1.2 is connected to the first output of block 1.1, etc.

The second output of each cascade is connected to the second input of the previous cascade, that is, the second output of side 1.2 is connected to the second input of block 1.1, and so on.

The first output of the last thirty-sixth cascade 1.36 is connected to the second input of the same cascade 1.36.

Each stage consists of a discrete delay line (marked on the diagram as positions 1.1.2, 1.2.2, 1.3.2), etc., and one element that performs the disjunction operation (or), marked on the diagram as positions 1.1.1, 1.2.1 , 1.3.1 connected as shown in block diagram 1 in Fig. 1 . To form the PM sequence a and its subsequent matched filtering, a sequence is fed to the input of block 1, the zero (in the accepted numbering) member of which is equal to 1, and the remaining members of the sequence are equal to 0. Starting from zero to

- 1 cycle of operation of the device at the connection point of blocks 1 and 2 using the recording and display unit T1 of FIG. 1 we fix the sequence a. The binary sequence a is fed to the input of block 2 (consistent filtering block).

Figure 1 shows:

1 - block for the formation of the PM sequence a =

length

2 - matched filtering unit

1.1, 1.2, 1.3 ... 1.36 - cascades of block 1.

2.1, 2.2, 2.3, ... 2.36 - cascades of block 2.

Block 2 (matched filtering unit) consists of thirty-six cascades connected in series 2.1, 2.2, ... 2.36, connected in the same way as in block 1. Each cascade of block 2 consists of a discrete delay line (marked in the diagram of Fig.1 as 2.1. 2, 2.2.2, 2.3.3, ...2.36.2) and one addition element connected as shown in fig. 1 (marked in the diagram of Fig. 1 as 2.1 .1 , 2.2.1 , 2.3.1 , ... 2.36.1 )

Table 1. Formulas for determining the delays in the delay line of the cascades of blocks 1 and 2 in FIG. 1 .

Figure 2 (upper graph) shows a fragment of the response at the output of the matched filter of block 2, fixed by the registration and display unit T2 of Fig. 1 when applying to its input the sequence a fixed by block T1 of FIG. 1. (bottom graph).

As you can see, the position of the reference has eaten, and with the number

- 1 non-zero in sequence at the input of the matched filter (input of block 2) coincides with the (main) peak of the response at the output of the matched filter captured by block T2. The readings adjacent to the response peak will be called the response side lobes (peak) (there is a name in the literature side peaks), and the ratio of their maximum amplitude to the response peak amplitude will be called the UBL level of the side lobes (response). In the literature, the term side peak level is also used.

Modulating discrete sequence - a sequence of finite length, the numbers of members of which are confined to the numbers of time positions at which the lidar emits an optical pulse, if the member of the modulating sequence is different from zero.

T _mod - duration of the PIM signal time position fmod = /Tmod ~ modulation frequency of the emitted optical signal.

A member of the modulating sequence can be not only a binary value, (0 - not emitting, 1 - emitting), but an array of data, characterizing the shape, frequency, amplitude, phase, polarization of the emitted pulse, i.e., the given characteristics of the optical pulse.

Position-pulse modulation (PIM). If the modulating sequence is a binary PM sequence, then the sequence of emitted optical pulses modulated by it is called a position modulated sequence of (optical) pulses or a position-pulse modulated (PIM) sequence of (optical) pulses (PMPOI).

In foreign literature, such sequences of emitted pulses are called "PPM sequence". US Pat. No. 8,072,582 describes a closely related type of pulse train modulation called "pulse timing sequence, with pseudo-random timing".

The probing signal is a modulated sequence of optical pulses emitted by the lidar.

Quantum efficiency - the probability of generation of a single free carrier photon hitting the optical sensor, which will reach a high field region sufficient for impact ionization or the probability of sensor operation when a single photon hits the sensor surface.

Dynamic quantum efficiency - the ratio of the increase in the probability of triggering the sensor in the time interval T _d under the condition of increasing the number of photons q falling on the sensor surface in the time interval T _d , by the value of Lg|, to the value of Lg| when Aq/q is less than 0.1.

Dynamic conversion factor (dynamic sensitivity) photocurrent/power. For optical sensors operating in the power-to-photocurrent conversion mode, the dynamic conversion factor.

/^(W) = dl/dW , where I is the photocurrent, W is the radiation power incident on the sensor.

An example of such an optical sensor is a matrix silicon photomultiplier, referred to in foreign literature as SiPM.

The dynamic photocurrent/power conversion ratio also decreases with an increase in the radiation power coming to the sensor surface. The mode of detecting an optical signal by a quantum optical sensor, in which the “dynamic quantum efficiency” index is reduced by two or more or times, or the detection mode by an optical sensor operating in the power-to-photocurrent conversion mode, in which the dynamic photocurrent/power conversion coefficient is reduced by two or more more times, we will call the mode of operation of the sensor in the mode of saturation or limitation.

Saturation threshold - the minimum radiation power or the average number of photons for a given time interval arriving at the sensor at which the sensor operates in saturation (limitation) mode.

A resolvable object is an object or element/segment of an object that enters the beam target, in which the optical radiation emitted by the lidar transmitter is concentrated and into the beam target, in which the reflected radiation is concentrated, falling on the surface of the optical sensor of the lidar receiver.

ESR (Effective Scattering Surface) - is a quantitative measure of the property of a resolvable object to scatter part of the optical radiation towards the receiving sensor. The energy of the reflected probing signal arriving at the optical sensor is proportional to the RCS of the resolved object.

The received signal is a superposition of the reflected probing signals from the object/s, the distance to which/s is measured, and the reflected probing signals from other (objects) arriving at the surface of the optical sensor or sensors, if the optical sensor contains several receiving elements and noise emission.

In this superposition, the reflected optical signals arriving at the sensor surface can differ in intensity, including signals whose intensity is insufficient to resolve the object by the method with which the comparison is made, we will call "weak", the intensity signals of which on the sensor surface exceed the saturation threshold, we will call "strong" ( i.e. strong signals include those signals in which single optical pulses arriving at the sensor surface lead to its operation with a probability close to 1.0), and signals whose intensities on the sensor surface do not exceed the saturation threshold of the sensor, and at the same time are resolved using the method with which the comparison is made will be called "ordinary". Similarly, we will call the EPR of objects, and the objects themselves, generating reflected signals, as "weak", "strong", "ordinary".

Selectivity - the ability of a lidar to resolve (reliably determine the range to a probed object using a threshold detector) a probed object or a segment of an extended probed object that enters the beam target in the presence of other nearby objects (elements of a composite object) with large RCS and noise radiation in the beam target, hitting the surface of the receiving sensor. It can be said that if the peak of the response or peaks of the responses from the probed object/objects, or the element/elements of the object/objects are clearly distinguished on the reflectogram above the noise level, side lobes of the responses, then a lidar using a method or device that leads to obtaining a real trace uses a method that selectively resolves objects (elements of objects) and generates resolvable response peaks on the secondary trace.

Optical sensors operating in Geiger counter mode.

Known sensors (optical receiving elements) for detecting optical radiation SSPD (Superconducting Single-Photon Detector) or superconducting single-photon detectors operating at temperatures close to absolute zero and used to detect single photons and operating in the Geiger counter mode in the wavelength range from 250 to 3000 pt. An example of such a sensor is the sensor described in patent RU 2346357, published in 2009, based on thin-film superconducting structures. Such sensors are characterized by quantum efficiency up to 80-90%, time resolution up to 25 ps. On the basis of such receivers, integrated registration systems are created with dozens of channels (pixels). The disadvantage of using SSPD sensors is the need to cool the sensor to temperatures close to absolute zero.

Known sensors for detecting optical radiation InGaAs / InP SPAD (Indium Gallium Arsenide I Indium Phosphide Single-Photon Avalanche Diode) or Arsenide gallium-indium single-photon avalanche diodes based on, used to detect single photons operating in the Geiger counter mode in the wavelength range from 900 up to 1700 pt. Compared to superconducting single photon detectors, they do not require expensive cryogenic coolers. The main disadvantage of SPAD sensors is the high probability repeated triggering of the sensor after receiving an optical pulse in the time interval up to 100 ns, to compensate for this shortcoming, a special SPAD operation mode is used, called fast gating.

Fast gating (Ultra-short gating, extremely short gating) is an optical sensor operating mode in which the sensor is switched to the Geiger counter mode for very short time intervals of 100-200 ps. Fast gating allows to reduce the time during which the sensor is not ready for operation due to the transient processes occurring in it that occur as a result of receiving optical radiation in the Geiger counter mode and to reduce the probability of the sensor re-triggering (afterpulsing probability) during subsequent fast pulses after receiving optical radiation. gating of the optical sensor.

Fast gating can be done in a variety of ways. US Pat. No. 7,705,284 proposes a gating method and apparatus in which the sum of the bias voltage of the gating sinusoidal signal is applied to the anode of the diode. During each period of the strobe signal, a photon can be detected at the time interval in which the voltage at the anode of the diode exceeds the breakdown voltage and the diode is in an active state (ready to receive a photon). A signal representing a superposition of an avalanche signal and a sinusoidal signal is taken from the resistance in the diode cathode circuit. The avalanche signal is separated from the sinusoidal signal by a notch filter that suppresses the first harmonic of the sampling frequency. The disadvantages of this method include the fact that the instantaneous efficiency of photon reception in the time interval in which the voltage at the anode exceeds the breakdown voltage is not constant and is determined by the shape of the voltage at the anode, which changes according to a sinusoidal law. The gate time interval depends on the gate frequency and amplitudes of the bias voltage of the sinusoidal signal and the sinusoidal signal itself.

US Pat. No. 9,012,860 describes a method and apparatus for single photon reception in fast gating mode. The device contains two identical LTD diodes, to which a strobe signal in the form of a meander and a positive bias voltage are supplied through a signal divider to the cathodes of the diodes. The first APD diode is adopted as a radiation receiver, and the second is idle and is used as a source, identical to the first capacitive one. the transient process that occurs on the first APD when a strobe signal in the form of a meander is applied to it. The avalanche signal from the first LTD is extracted by subtracting from it the transient process formed on the second LTD. Due to the use of a square wave as a gating signal, the quantum efficiency in the time interval when the diode voltage exceeds the breakdown voltage is approximately constant. The time interval in which the diode is in the state of receiving a photon is almost independent of the meander amplitude and bias voltage. This method of reception is the most suitable for use in the described invention, but does not limit it.

Fast gating allows the sensor to receive optical radiation that enters the sensor only at gating intervals. T _d

Optical sensor. By optical sensor we mean a single optical sensor operating in the fast gating mode or a group of sensors operating in the fast gating mode.

Received optical signal, reflectograms. Under the received signal we mean the final discrete sequence formed in the process of receiving the optical signal. Each member of this sequence is formed based on the results of the operation of the sensor (or a group of optical sensors) at the corresponding time interval T _d

In our case, such a signal is also called the primary reflectogram or binary detection signal (sequence).

The secondary reflectogram is understood as the primary reflectogram processed by the matched filtering method. The secondary reflectogram is used to calculate the time delays of the optical signal reflected or generated by the probed object.

PC - a computer with software and interface modules designed to control the bench that simulates the operation of the lidar and to process the primary reflectograms generated by the bench to form auxiliary sequences of the bench blocks loaded into the memory.

Purpose of the invention.

An obvious way to increase the efficiency of resolving target elements with “weak” EPR is to increase the energy of probing optical pulses, which makes it possible to increase the signal-to-noise ratio on the surface optical sensor. But often an increase in energy requires significant material costs or technically, at this level of technology, is not feasible. At the same time, relatively accessible methods for generating optical radiation are known, which have limitations in terms of peak power, and sources, such as laser diodes, optical-terahertz converters, for example, using the Dember effect [DOI: 10.1364/OL.428599].

The use of such sources of pulsed terahertz radiation in conjunction with terahertz radiation receivers (see, for example, SSPD) in the fast gating mode using the technical solutions described in this patent makes it possible to create scanners (lidars) for remote detection of metal objects and determining their shape, for example , in a crowd of people, in thickets in the presence of fog, for remote determination of low concentrations of gases in the atmosphere, etc.

The purpose of this invention is to ensure the detection of all elements of the probed object in the case when the energy of the emitted optical pulses is insufficient to provide reliable resolution of the probed objects and there are time limits for resolving these objects. Preferably, the time required for resolution does not exceed one probing cycle.

Or, in other words, the task is to improve the selectivity of the resolution of probed objects with limited probing signal power and/or probing signal duration.

Disclosure of the invention.

Based on this original observation, the present invention mainly aims to provide an apparatus for receiving an optical signal, including a clock signal generator connected to an optical receiver operating in a non-linear mode, a matched filtering unit, a signal threshold detection module, allowing, by at least smooth out at least one of the above disadvantages, namely, to ensure the detection of all elements of the probed object in the case when the energy of the emitted optical pulses is insufficient to ensure reliable resolution of the probed objects known methods and there are limitations on the time of probing, which is the technical problem of the present invention.

To achieve this goal, the device includes a clock signal generator 17.1, a quantum efficiency adjustment unit based on the average frequency of sensor responses 108-2, and a gating adaptation signal generator 105.

Due to these advantageous characteristics, it becomes possible to reduce the time of probing, to carry out probing of all elements of the probed object that fall into the target of the probing beam at the same time.

The invention also relates to methods for receiving an optical signal, in which a clock signal is generated, a signal reflected from a resolvable object is received by an optical receiver 17.2 operating in a non-linear mode, having a matched filtering unit 17.3 and a threshold signal detection module 17.4.

In order to ensure the detection of all elements of the probed object in the case when the energy of the emitted optical pulses is insufficient to ensure reliable resolution of the probed objects and there are restrictions on the probing time, it is proposed, according to the invention, it is necessary to add a step in which the gate signal is adapted , regulate the quantum efficiency by the frequency of the sensor operation.

Due to these advantageous characteristics, it becomes possible to reduce the time of probing, to carry out probing of all elements of the probed object that fall into the target of the probing beam at the same time.

There is a variant of the invention in which the formation of the gating adaptation signal is carried out in the process of probing based on the results of matched filtering of a fragment of the probing PI sequence or a separate probing pilot signal, which makes it possible to estimate the time delays of the reflected signal from the elements of the probed object about "strong" RCS.

Thanks to these advantageous characteristics, it becomes possible to refuse the use of an additional optical path necessary for the formation of the gating adaptation signal. Brief description of the drawings.

Other features and advantages of the present invention will clearly appear from the description below, by way of illustration and without being restrictive, with reference to the accompanying figures, in which:

Figure 1 shows the block diagram of the PIM sequence generation a =

and its matched filtering.

Figure 2 depicts fragments of discrete sequences captured and displayed by blocks T2 (upper graph) and T1 (lower graph). The abscissa indicates the operation cycles of the device of FIG. 1 .

Figure 3 is a graph explaining a method for generating a gate pulse signal.

Figure 4 shows options for the possible timing of the strobes (strobe pulses) relative to the received PIM sequence of (optical) pulses.

- graph A - schematically depicts two fragments of the received PIM signal, containing four time positions of the signal, even time positions are marked with the sign "0", odd ones with the sign "1".

- graphs B, C, D, E schematically display periodic gating signals, differing only in their position in time relative to the beginning of the even time positions of the signal.

Figure 1 shows a graph, where the abscissa of graphs B, C, D, E plots the numbers of samples of the binary sequence obtained by the method considered in the example. On the ordinates of the graphs B, C, D, E, the amplitudes of the readings are plotted, the binary sequence obtained by the method considered in the example, differing in the position of the gating signals, the variants of which are shown in the graphs B, C, D, E in figure 4.

Figure 6 shows a diagram of the generation and subsequent matched filtering of the PIM sequence.

Figure 7 depicts a fragment of the filter response (from cycle 74000 to cycle 76750) at the output matched at point T2 of Fig.6 (on the registration device and display T2) and at the output of the notch filter at point T3 of Fig 6 (on the registration device and display of T3). Figure 8 depicts a functional diagram of the stand for imitation of the receiving and transmitting paths of the lidar, without the functional blocks for processing reflectograms implemented programmatically in a PC.

Figure 9 depicts the robot of the block for the formation of the modulating binary PM sequence.

Figure 10 depicts the operation of the gating adaptation signal generator 105.

Figure 11 schematically depicts the device of the block for simulating a complex probed object (CISO).

Figure 12 schematically depicts the relationship of samples in the binary detection sequence (plot E in Fig. 12) with gate time intervals (plot D) and clock timing (plot B).

Figure 13 shows a functional diagram of signal processing and generation implemented in PC software.

Figures 14 and 15 show fragments of the Z trace obtained after processing the primary traces by matched filtering and the corresponding fragments of the 5*Y auxiliary sequence.

In FIG. 16 shows a possible diagram of the optical path of the gating adaptation signal generator.

Implementation of the invention.

Let us show how the quantum efficiency of the sensor is controlled in the fast gating mode. The probability of operation of an optical sensor for T _d from the number of photons with a Poisson time distribution for materials [DOS: 10.1049 / e!: 19840411 ] can be represented as a simple equation (1)

(1 ) Р _c = 1 - (1 - P _dc )exp(-^) , where

P _dc - the probability of sensor operation in the absence of radiation on the surface. sensor for a time interval T _d (dark count probability), - quantum efficiency, tu - the average number of photons that hit the sensor for a time interval T _d .

Equation (1) can be conveniently represented as (2)

(2) Р _c = 1 - exp(— (my + ?y _dc )) , where

In the practical application of this equation, the number of photons that hit the sensor surface during the gating time T _d consists of photons of the noise component (subscript N) AND the actual signal component (subscript s)

(3) rj = TJ _N + Tj _s

From a practical point of view, the spontaneous operation of the sensor, expressed by the variable jy _dc , can be considered as an element of the noise component in the detected signal, despite the fact that it is associated with the internal nature of the sensor.

It is known that P _dc and, accordingly, jy _dc in the high-speed gating mode increases when the indicator is increased by increasing the bias voltage on the LTD operating in the Geiger counter mode, increasing the operating temperature of the sensor, and reducing the time elapsed from the moment of the previous sensor operation to the start of a new gating.

In practice, the noise component jy _w is actually the sum of the average number of noise photons that hit the sensor surface during the gating time, denoted here as r^ _n , and the value jy _dc , which characterizes the intrinsic noise of the sensor. jy _w is the equivalent number of noise photons.

(4) rj _N = i) _fn + T] _dc

The probability of sensor operation during the gating time in the absence of a signal optical pulse hitting the sensor surface can be expressed by the equation:

(5) P _CN = 1 - exp(- < fjy _w )

The probability of sensor operation during the gating time when a signal optical pulse hits the sensor surface can be expressed by the equation:

(6) P _cs = 1 - exp(

where S/N = i _s h _N .

The increase in the probability of sensor operation when an optical signal hits the sensor surface can be defined as Р _ds = P _cs - P _CN

The presence of the gain allows you to extract from the detected optical signal by matched filtering, information about the time of the start of arrival at the optical sensor of the PIMPOI, for example, reflected from the element of the probed object. With matched filtering of one PIM sequence, the S/N ratio in the sample - peak response at the output of a discrete matched filter will be increased compared to the ratio under detection conditions.

Let us denote the S/N ratio under the detection conditions as (S/N)t _n

The signal component of the response at the output of the matched PIM sequence filter can be estimated as the mathematical expectation of the value of the response peak count at the output of the matched filter equal to MR _DS , where M is the number of optical pulses received in the gating mode and contributing to the formation of the matched filtering response peak, and the noise component, as standard deviation of 8 output samples of the matched filter when applying to its input a sequence obtained by detecting only the noise component .

The S/N on for the peak response at the output of the matched filter can be written as,

(8) (S/N) _out = VM(exp(-(l + ( )in)

The maximum no (S/N) _out is reached if the condition (S/N) _tn > 1 is satisfied and

for 0 < (5//V) _£n < 1 .

It follows from equation (10) that at (S/N)t _n < 1 and given T] _N at the optimal quantum efficiency of the quantum efficiency at which the exponent (S/N) _out is maximum, the probability of the sensor triggering from the noise component in the time interval T _d will be P _CN ~ 0.63 « 1 - e ^-1 , and from equation (9) it follows that with an increase in the ratio (S / N) _in should decrease inversely proportional to (S / N) t _n and with (S / N) _in > 5 is P _CN ~ l/(5//V) _£n .

An example of estimating the average frequency of sensor activations

PIMPOI contains N ≈ 500 optical pulses of these pulses, only a part in the amount of M=200 in time to reach the sensor surface coincides with the time intervals of high-speed gating of the sensor. The duration of PIMPOI is 20000/ ₅ , where f _g is the sampling frequency of the sensor. The average number of photons in each optical pulse arriving at the surface sensor is 1 . r/ _s = 1 , The singal/noise ratio is defined as the ratio of the average number of photons in the optical pulse arriving at the sensor surface during the gating interval to the equivalent average number of noise photons arriving at the sensor surface during the gating interval (S/N _n = 1 , 0.

Then, according to equation (9), it is necessary to set the sensor equal to or not higher than 0.69/1 = 69%, set = 25% as the maximum achievable for this type of sensors.

For = 25% we get that

MP _{& C} \u003d MP _CS - P _CN ) \u003d M (0.39 - 0.22) \u003d 0.17 M

(S / N _out \u003d 0.17 / 0.42 VM "\u003d 0.42 "14.14 \u003d 5.87 in this case, the average sensor actuation frequency f _c will be f _c \u003d (P _CN (20000-M) / 20000 + P _CS M/20000) f _g =

= (0.22*(20000-M)/20000 +0.39*M/20000) f _g « 0.22

As can be seen from the above example, the average frequency of sensor responses is determined mainly by the value of P _CN , determined by the noise component, and it, in turn, is determined by equation (5) by the product T] _N . With an increase in the ratio (S/N)t _n , the value of P _CN decreases, which requires more time to estimate the average frequency of sensor triggers f _c , therefore, it is advisable to use the method when S/N) _in is not more than 5, preferably not more than 3.

Thus, given: the noise level T] _N on the sensor and the minimum operating ratio S/N) _in, to optimize S/N) _out at the output of the matched filter, it is necessary to maintain a fixed average over time t sensor actuation frequency by adjusting the quantum efficiency of the sensor. Such regulation can be implemented, for example, using a bias voltage amplitude control loop V _bias supplied in total with a rectangular gating signal to an LPD diode operated in the Geiger counter mode or by directly regulating the gating voltage. A figure explaining the method of generating the strobe signal is shown in FIG. 3. Table 2 3.

The time t is defined as the time sufficient to determine the average relative frequency of sensor responses with an acceptable error. Since the average relative frequency of sensor responses is determined by the quantum efficiency of the sensor, as the time t increases, the fluctuations in the quantum efficiency of the sensor will also decrease. In fact, the control loop maintains the average frequency of sensor responses close to the control setpoint through the control action on the quantum efficiency of the sensor, but the changes in the control action must be smooth and provide a minimum relative fluctuation of the quantum efficiency during the control process. Relative fluctuations in the steady-state control mode within ± 5% of the average steady-state value does not significantly affect the technical characteristics of the receiving path of the lidar or other device using the considered method.

This control loop (adjustment assembly) can be used in high-speed gating of an optical sensor, for example, according to the method described in US patent US 9012860. Sensor gating adaptation.

Adaptive gating can be used to reduce sensor false alarms associated with an effect known as "after-pulsing probability" (APP) described for example in B [DOI: 10.1155/2018/9585931].

Indeed, there is a problem that increasing the sensor by increasing the voltage amplitude at the moments of the sensor operation in the Geiger counter mode leads to an increase in the so-called. false positives of the sensor, both permanently and additionally at the time interval necessary for the complete restoration of the sensor parameters.

The number of false alarms induced by the reception of optical pulses from "strong" and "ordinary" or "strong" signals can be reduced by turning off the sensor from the Geiger counter mode at the moments when optical pulses reflected from objects with strong and ordinary EPR are expected to hit the sensor surface ( strong and ordinary signals).

The strobe signal applied to the sensor can be adapted based on a priori information about the moments when optical "strong" and "ordinary" optical pulses arrive at the sensor surface.

An obvious application of adaptive gating is to turn off the receiving sensor at time intervals delayed from the optical pulse emission time intervals by the time required for the optical pulse to travel from the optical pulse transmitter to the sensor surface. For example, this is required in cases where the sensor and the transmitter of optical pulses use a common transmit-receive optical path. In this case, adaptive gating can be implemented by adapting the signal by performing a conjunction operation on the gating signal (“1” - there is sensor gating, “0” - there is no sensor gating) and the inverted signal emitting optical pulses (“1” - there is no emission of an optical pulse on gating interval, "0" - is the emission of an optical pulse at the gating interval).

Example #1

Imagine a PIM signal that is modulated by the PM sequence a from the example: “An example of the formation and matched filtering of a binary PM sequences with at most one match property. The number of non-zero terms with even-numbered terms in the sequence a is close to the number of odd-numbered terms.

The duration of the pulses in the PIM signal is T _p = 10 ps.

PIM signal modulation frequency f _mod = 5 GHz

Modulation period of the PIM signal T _o \u003d l / f _mO d \u003d 200 ps

This PIM signal is fed to the synchronous detection device, which is also supplied with a periodic signal of strobe pulses with a period of T _d = 400 ps. (gate signal frequency f _g = 2.5 GHz). The duration of the strobing pulses (strobes) T _d = 205 ps , which corresponds to the period of strobing increased pulse duration in the detected PIM signal.

The synchronous detection device works according to the following principle:

- if at least one PIM pulse of the sequence or its fragment with a duration of at least the duration of the optical pulse and the strobe (strobe) pulse coincides in time, a logical unit with a duration of 200 ps is formed along the trailing edge of the strobe, followed by a logical "zero", with a duration of 200 ps;

- otherwise (if there is no coincidence or the coincidence in time of the strobe and the optical pulse is less than the duration of the PIM signal pulse), two logical zeros with a duration of 200 ps are formed on the trailing edge of the strobe. Thus, a binary sequence is formed, with a clock transition time of 200 ps.

Let's call this method of receiving binary signal detection.

The sequence formed in the described manner is fed in cycles to the matched filter - block 2, which is shown in Fig. 1 .

It is obvious to the specialist that since every second sample in the processed sequence is a “0” signal, then when processing the signal, the number of addition operations can be halved and the frequency of performing streaming operations necessary to implement matched filtering can be halved. However, since the purpose of this patent is not to reduce the addition operations in matched filtering, a simplified description of the filtering devices is used in the description. In FIG. 4 schematically shows how the time position of the gates relative to the start of the even time positions of the PIM signal pulses affects the shape of the output binary sequence (binary detection signal). By even time positions we mean time positions that are confined to the even members of the sequence a, by odd ones, which are confined to the odd members of the sequence a.

In FIG. 4 (plot A) schematically shows a fragment of the received PIM signal containing four time positions of the pulses (zero (even), first (odd), second (even) and j-th (odd)). In place of the zero (even) and j-th (odd) time positions of the pulses, the received pulses are displayed, in the place of the first (odd) and second (even) positions, the absence of the received pulse is displayed.

In FIG. 4 (plots B, C, D, E) are schematic representations of periodic gating signals, differing only in their position in time relative to the start of the even time positions of the pulses. So, the gate signal "B" ensures the gate of only even time positions of the pulses, and the gate signal "E" - only the odd positions of the pulses. Signal "C" provides gating of even positions and partially odd ones. The "D" signal provides gating for odd positions and partially even ones.

In FIG. 5. shows the signals (fragments of discrete sequences - reflectograms) at the output of the matched filter considered in the example - block 2, which is shown in FIG. 1 with impulse x-coy a ⁼

obtained by applying to its input discrete sequences obtained during binary detection of the PIM signal considered in this example, with options for the position of the gates relative to the time positions of the code (B, C, D, E) shown in Fig. 4.

Designations of variants of the relative position of the gates in Fig. (B, C, D, E) correspond to the notation obtained at the output of the matched filter fragments of discrete sequences.

As can be seen from FIG. 5 - reflectograms B and E make it possible to determine the time position of the PIM sequence (the position of the trailing edge of the last pulse in the received PIM sequence) with an accuracy of ±100ps, and traces C and D allow positioning to within ±200 ps.

Thus, for use in distance measurements, the accuracy of determining the distance to the probed object will not exceed ±30 mm.

The practice of using PIM signals.

It is known that when probing objects, PIM pulse sequences are used, including those obtained by position-pulse modulation using a binary, PM sequence with the property "no more than one match" as a modulating sequence. ["High resolution waveforms suitable for a multiple target environment" / Resnick, Joel B / Thesis (M.S.) --MIT, Dept. of Electrical Engineering, 1962. URI: http://hdl. handle. net/1721.1/11436].

The use of modulated probing signals in this way makes it possible to improve the selectivity of the resolution of the probed objects after the matched filtering of the detected signal due to the low level of the side lobes of the normalized ACF (no more than 1/N), where N is the number of positions in the modulating binary sequence different from 0 and simultaneously with this, to minimize the losses in the signal-to-noise ratio for "ordinary" signals separated by matched filtering, if a signal receiver operating in the limiting receiver is used for their reception and a superposition of the received detected signals from various resolvable objects is fed to the input of this receiver . [Proc. IEEE vol. 54, p. 438-439 (1966) / DOk 10.1109/PROC.1966.4745].

The disadvantages of using probing signals with the property of the modulating sequence "no more than one match" is that the duration of the probing signal T _s depends squarely on N - the number of non-zero positions in the binary modulating sequence. According to the information given in the monograph [“Optimal discrete signals”/ M.B. Sverdik / “Sov. Radio” 1975]. The duration of the probed signal is T _s = (L - l)T _mocl = (0.71 - t- 0.83) T _mod N ² , where L is the number of members in the binary modulating sequence, T _{mod is} the duration of the PIM signal time position.

This drawback will lead to an increase in the probing time and the duration of the probing signal and does not solve the problem of reducing the time sounding, subject to the limitation on the maximum radiated power (pulse energy) of the pulsed emitter. Additionally, in the case of probing a high-speed target, there is also a limitation on the duration of the probing signal associated with its Doppler “stretching” or “compression”, depending on whether the probed object is moving away or approaching the sensor. The conditions limiting the application of the "Doppler" model are as follows: L <0.1(C/|/?|') where, C is the speed of light, L is the number of terms in the binary modulating sequence, |/?|' - velocity of the radius-vector modulus of the target. For example, if |/?|'= 6000 m/s, then L < 5000. This shortcoming can be overcome. So, for example, let a group target move towards the receiver (sensor), while the reflected signals from the target elements arriving at the sensor from the target elements are “compressed”. To compensate for this "squeezing" / "stretching", it is only necessary to increase / decrease the frequency of the strobe clock of the sensors. The new gate clock frequency will be determined as follows:

= f _d (1/(1 - 2|/?|'/C) where f _d is the gating frequency without radial velocity correction.

To compensate for the Doppler effect, in the block diagram of the lidar or other receiving device, a block for generating clock pulses with a frequency f _d (a block for generating clock reception pulses) must be provided.

It is possible to reduce the duration of the probed signal if we refuse to use PIM sequences with the property “no more than one match”, we will replace them with sequences with the property no more than “K matches”. This will reduce the duration of the probed signal by about K times, but at the same time, the level of side lobes of the ACF of the function of the probed signals will increase by K times, therefore, objects with low RCS, the responses from which on the reflectogram (response at the output of the matched filter) are smaller or commensurate with the level of side lobes. lobes, from responses from objects with "strong" EPR and will not be allowed.

Example #2.

In FIG. 6 shows a diagram of the formation and subsequent matched filtering of the PIM sequence. Block 3 for generating a PIM sequence of length l_=l_i+l_2- 1 =2017+74629-1 =76645 consists of two sequentially connected blocks for generating PIM sequences, 3.1 and 3.2, where block 3.1 generates a sequence of length _r , and block 3.2 generates a sequence of length L ₂ .

b ₂ \u003d M ₂ • (N - 1) + 1 \u003d 74629, M ₂ \u003d 2073,

2017, Mi = 56,

Block 4 matched filtering PIM sequence of length L consists of sequentially connected blocks 4.1 and 4.2 of matched filtering, block 4.1 for a sequence of length _r , block 4.2 for a sequence of length L ₂ .

When connected in series, a matched filter is obtained for the PIM sequence of length L=LI+I_2-1 =2017+74629-1 =76645.

Each of the blocks for the formation of PIM sequences 3.1 and 3.2 and blocks of matched filtering 4.1 and 4.2 consist of thirty-six stages, similar to those shown in figure 1.

The formulas for calculating the number of DL delay cycles for each stage are given in Table 3.

Table 3 Formulas for calculating the number of delay cycles in the DL of the first and second blocks for the formation of PIM sequences and the third and fourth blocks.

Additionally, a discrete notch filter 5 is introduced into the circuit in figure 6, consisting of

- signal limiter in amplitude 5.1,

- LPF (low-pass filter) 5.2 of the first order with a gain in the constant component of the signal equal to 1,

- amplifier 5.3 with a gain of 10-50,

- element 5.4, subtracting the signal from the output of the amplifier pos. 5.3 from the signal (sequence, response) input to the notch filter 5 and

- an additional element 5.5, which subtracts from the signal from the output of the element 5.4 the signal from the output of the LPF 5.2.

Further in the examples, a similar notch filter 5 is used.

Let us apply to the input of the circuit of Fig. 6 is a sequence of length 2L - 1, where L = 76645 in which the term with number 0 is equal to 1 and the remaining terms are equal to 0.

At point T1, a sequence of the same length will be fixed, the first L members of which are a PIM sequence matched with the PIM sequence filter 4 of Fig. 6.

At point T2, the response of the matched filter to the input to its input (input of block 3) of the matched PIM sequence will be recorded. At the 76644th cycle (the numbering of cycles starts from the zero cycle), at the point T2, a peak of the response with the amplitude K = N2 = 1369 will be recorded. The same cycle corresponds to the last member of the PIM sequence, equal to 1 applied to the input of the matched filter 4 of Fig. 6, consisting of blocks 4.1 and 4.2 connected in series. fig 6.

The amplitude of the other response terms (side lobes) at the output of the matched filter (output of block 4.1) will not exceed 60. To reduce the level of side lobes adjacent to the response peak, a notch filter 5 Fig 6 is used .. Due to which the amplitude of the side lobes is reduced from to 30 , which can be observed from a fragment of the reflectogram fixed at the point of TZ.

When using a similar (with the addition of notch filter 5 to blocks 4.1 and 4.2) matched filter when processing signals obtained by binary detection of an optical signal, it is important to note that the notch filter 5 also suppresses the DC component caused by the so-called. background illumination, “background light”, which is fed to the sensor along with the optical signal. Nonlinear element 5.1 amplitude limiter received on the band pass filter samples reduces the amplitude of transients when received at the input of the notch filter 5 peak response. Notch filter 5 with a non-linear element must be placed after the matched filter.

The response recorded at point T2, in this example, provides information about the energy loss of the first signal (more precisely, the number of missed pulses of the first signal) when received jointly with the second signal, which is a replica of the first signal, delayed or ahead of the first signal by the number of cycles W, if the resulting the signal is obtained by disjunction of the first and second signals (disjunction is analogous to the joint reception of two singals by a threshold device). To estimate the number of missed pulses, it is necessary to plot the number of delay/advance cycles W along the X axis (clock/time axis) from the response peak, while the sidelobe amplitude corresponding to the distance W from the response peak determines the number of impulses in the first signal that will not be received since the sensor will be triggered by the pulses of the second signal. Thus, the NBL index calculated from the reflectogram recorded at point T2 gives an idea of the percentage of lost samples by signal 1 if it is received by binary detection with signal 2, which is a replica of signal 1 delayed by W cycles.

In FIG. 7 is a fragment of the filter response (from cycle 74000 to cycle 76750) at the output matched at point T2 (at the registration and display device T2) and at point TK (at the output of notch filter 5). Along the abscissa of Fig. 7 is the number of cycles multiplied by 10 ^-4 . The PIM sequence generated at the output of block 3 is not minimax in the sense of the minimum level of the side lobes of the ACF of the binary PIM sequence for given L and N, but the description of the method for obtaining it and matched filtering is the simplest and allows us to shorten the description of this patent.

In this example, we deviated from the “no more than one match” rule, which led to a reduction in the duration successively L = 76645 against the expected (0.71 0.83) / V ² = 1330654 - ^ 1555554, i.e. the duration of the sequence and, consequently, the time of emission of the probing signal decreased by 17–20 times, but at the same time, the level of side lobes of the ACF of the PIM signal increased by 60 times, used in sounding. In this example, the signal is not optimized for the level of ACF sidelobes and is used in the example to simplify and shorten the description, since the purpose of the present invention is not to reduce the sidelobe level of the PIM ACF signal.

Stand for imitation of lidar operation.

In FIG. Fig. 8 shows a functional diagram of the stand for imitation of the receiving and transmitting paths of the lidar, without the functional blocks for processing reflectograms implemented on a PC. Primary reflectograms, which are binary sequences, are recorded by the T4 block, see Fig.8 and then read out and transferred to a PC to form secondary reflectograms.

101 - The block for the formation of the clock pulse of the beginning of the probing cycle.

102 - Clock signal generation unit.

103 - Block for the formation of a modulating binary PIM sequence (poel. R).

103-1 - Entrance to block 103.

103-2 - Input for transmission to block 103 of the modulating sequence from the PC.

105 - Signal conditioning unit for adapting the gating signal.

105-1 - Entrance to block 105.

105-2 - Input for transmission from the PC to the block 105 of the sequence of adaptation of the gating

106 - Strobe signal adaptation block.

106-3 - entrance to block 106 and block 106-1

106-5 - entrance to block 106,

106-4 - input (inverted) to block 106-1

106-1 - An element that performs a conjunction operation on the operand from input 106-3 and the inverse value of the operand from input 106-4.

"0" - Logic zero setter block 106

106-2 - A two-position key that switches input 106-4 of element 106 - 1 either to the output of the logical zero generator "0" (the first position of the key is "no gating adaptation"), or to the output 105-3 of block 105 (second position key - "adaptation gating"). The key is controlled from a PC.

107 - Block of imitation of a complex probed object (BISO). 108 - Optical reception unit with adjustment unit.

108-4 - Optical input of block 108.

108-5 - Gate logic input.

108-1 - Sensor gating implementation unit. The block generates a signal that determines the current state of the sensor (operation mode) and its quantum efficiency. The block has two entrances. The first input is a gate logic signal from block 106.

108-1 -1 is the (second) input of block 108-1 through which a signal is supplied from block 108-2 that determines the quantum efficiency of the sensor of block 108-3.

108-2 - node for adjusting the quantum efficiency by the frequency of sensor activations.

108-3 - Optical sensor and binary detection signal generation circuit. The optical signal is supplied to block 108-3 through input 108-4 (first), the second input (108-3-1) of block 108-3 is supplied with a sensor control signal from block 108-1

108-3-1 - the second input of block 108-3, through which the sensor control signal is supplied.

SP1 - Setpoint of the a priori amplitude of the bias voltage of the sensor of block 108-3 or setter of the a priori quantum efficiency of the sensor of block 108-3, since the quantum efficiency of the sensor is determined by the bias voltage. The setpoint is transferred to the setter from the PC (the port for transferring the setpoint to the setter is not indicated in Fig. 8).

SP2 - Setpoint adjuster for the average normalized frequency of operation of the sensor block 108-3. The setpoint is transferred to the master from the PC (the port for transferring the setpoint to the master is not specified).

SP3 - Setpoint of a fixed bias voltage with amplitude V _bias , which determines the quantum efficiency of the sensor of block 108-3 or the quantum efficiency of the sensor of block 108-3. The setpoint is transferred to the setter from the PC (the port for transferring the setpoint to the setter is not specified in Fig. 8).

108-2-1 - Differential signal generator. (The element that performs the operation of subtracting the signal of binary detection from the block 108-3 from the regulation setting of the normalized frequency of the sensor operation of block 108-3)

108-2-2 - Difference signal integrator. 108-2-3 - An element that performs the operation of adding to the signal at the output of the integrator 108-2-2 the initial (a priori) bias voltage (or another signal that determines the a priori quantum efficiency of the sensor).

108-2-4 - A two-position switch that switches the input of block 108-2-5 either to the output of the master SP3 (the first position of the key is “given quantum efficiency of the sensor”), or to the output of the adder 108-2-3 (the second position of the key - "regulation (tuning) of the quantum efficiency of the sensor" block 108-3). Key position is controlled by PC.

108-2-5 - Bias voltage limiter limiting the range of the control signal from block 108-2 in the range [VbiasMiN^biasMAx] ( ^or another signal that regulates the quantum efficiency of the sensor).

T4 - Block of registration and reading of the primary reflectogram.

The stand consists of a block 101 for generating a clock pulse at the beginning of the probing cycle, connected to a block 102 for generating a clock signal, connected to the inputs of blocks 106 (Gating signal adaptation block), 105 (Gating signal adaptation signal generating block) and 103 (Binary modulating PIM sequence generation block)

The output of the block 105 is connected through the second input 106-5 of the block 106 with the input 108-5 of the block 108 (Optical signal receiving block in fast gating mode).

The output of block 103 is connected to the input of block 107 (BISO), the optical output of which is connected to the optical input 108-4 of block 108.

To the output of block 108 is connected to the block of registration and reading of the primary reflectogram pos. T4.

Block 103 Generates a PIM pulse train.

Gating adaptation signal generator 105 generates a gating adaptation signal that initiates sensor shutdown at time intervals where "strong" and "ordinary" or "strong" optical pulses arrive at the sensor. (Essentially, the bit adaptation sequence of the gating signal is computed by the PC and written to block 105 to further generate the gating adaptation signal. In this way, block 105 simulates the operation of a practical gating adaptation signal generator.

Block 107 simulates the reflected optical signal from a complex target. Unit 106 adapts the strobe logic signal, which is essentially the clock signal of unit 108, so that when "strong" and "ordinary" or "strong" optical pulses arrive at the optical sensor, the sensor of unit 108-3 is not in Geiger counter mode.

Block 108 performs binary reception of optical pulses arriving at the surface of the receiving sensor at the moments of its strobing (being in the Geiger counter mode) and generates a binary detection logic signal.

Description of the principles of operation and purpose of the stand blocks.

Block 101. Generates a pulse to start the probing cycle.

By the pulse of the beginning of the probing cycle, the counting of the clock pulses of the probing cycle begins, according to which:

1) recording of signals by the block of registration and reading (transmission) of the primary reflectogram (T4). The recording cycle is 400 ps

2) the formation of the PIM sequence block 103;

3) generation by block 105 of the gating adaptation signal.

Block 102. The block generates a binary sequence of periodically changing logical zeros and ones. The frequency of transition from one to zero is 2.5 GHz. The clock transition frequency is 5 GHz.

The logic unit signal at the output of block 102 on the rising edge -

1) at input 106-3 of block 106-1, provided that the signal at input 106-4 of block 106-1 is a logical zero, initiates the transfer of the sensor in block 108 to the Geiger counter mode;

2) at input 105-1 of block 105, initiates reading from block 105 of one bit of the gating adaptation signal to input 106-5 of block 106.

3) at the input 103-1 of block 103, it initiates the reading of two members of the PIM sequence from the serial memory of block 103 for the subsequent formation by the PIM block of a sequence of pulses supplied to the BISO block 107.

Block 103. Forms a PIM pulse sequence applied to block 107 (BISO). The block is a device for sequential reading of a two-bit code, which represents the modulating sequence. Reading is performed on the leading edge of the pulse logical unit from block 102. The even members of the PM sequence are represented by the first bit of the code, and the odd ones by the second bit of the code. After reading the two-bit code at the clock transition (the clock generator is not indicated on the functional diagram) to logic zero, an even pulse of the PIM sequence is generated if the first bit of the code is “1”, and with a delay of 200 ps at the next clock transition (from zero to unit) from the formation of an odd PIM pulse of a sequence of pulses, provided that the second bit of the code is equal to "1". If the code bits are equal to "0", the formation of pulses is not carried out. Thus, a PIM pulse sequence is formed with a modulation frequency of 5 GHz, equal to the frequency of the clock pulses. The clock pulse interval is 200ps and is denoted by the symbol T _o .

Figure 9 depicts the operation of block 103

9A - Schematic representation of ate, clock pulses and their numbering 9B - Schematic representation of the sequence log. ones and zeros generated by block 102 of Fig. 8 of the stand, and their numbering.

9C - Values of the binary modulating discrete sequence in binary code and its formal representation as an indexed sequence {u(0), te( 1 ), v(2) . . . . } of length (L + 1) /2

9D - Formed PIM pulse sequence its formal representation as a binary indexed sequence

{at(0), at(1), at(2), at(3) } of length L - 1. Time positions corresponding to counts equal to zero are marked with dots, time positions of counts equal to one are marked with vertical lines.

Block 105 generates a gate signal adaptation logic signal.

The signal is a binary logic signal generated based on the binary sequence read from the serial memory unit 105.

The reading is performed on a clock transition from a logical one to a logical zero in a binary signal from block 102. If a logical one is read, then at the next transition from logical zero to one, a logical one is formed at the output of block 105, which exists before the clock transition in the binary signal from block 102 from zero to one. And otherwise, if a logical zero is read, then a logical zero is formed that exists until the next formation of a logical unit when it is read. The logical unit in the signal, as a rule, is timed to the event of arrival on the surface of the sensor in block 108 at the time interval of gating duration T _d "strong" or "ordinary" optical pulse. If the two-position switch 106-2 is in the "gating adapt" position, then the logic-one signal from block 105 cancels the sensor gating at block 108.

Figure 10 depicts the operation of block 105 and block 106, and program module 307

15A - Schematic representation of ate, clock pulses and their numbering 15B - Schematic representation of the sequence log. units and zeros generated by the block 102 of the stand, and their numbering.

15C - Values of the binary sequence read from the memory of block 105 5 and its formal representation as an indexed sequence {b (0), b (1 ), b (2) } of length N

15D - Gating adaptation signal generated by block 105, 15E - gate signal adapted by block 106.

15G is the binary sequence generated by the program module 307 when simulating adaptive gating to calculate the auxiliary Y sequence.

Block 106 - adapts the gate logic signal supplied to the input 106-3 of block 106 from block 102 by excluding from the sequence of logical zeros and ones, logic ones, the time positions of which are timed with the time positions of logic ones in the sequence of the gate adaptation signal coming from block 105 to the input 106-5 of the block 106. Functionally, the block performs the operation of the conjunction of the gating signal and the inversion (in which logical units are replaced by zeros and vice versa) gating adaptation signal. The block is supplemented with a two-position key, position 106-2 in Fig. 8 (key positions “gating adaptation” and “no gating adaptation”), the position of which is controlled by the program installed on the PC. When the key is set to “no gating adaptation”, the gating signal is not adapted to the input 106-4 of block 106-1, a logical zero is supplied from the logical zero generator indicated in FIG. 8 icon "0".

Block 107. Block for simulating a signal from a probed object (BISO). Block diagram 107 is shown in FIG. eleven

Figure 11 shows:

201 - shaper of the optical probing signal and signal delay.

202 - optical signal splitter (splitter), dividing the signal into nine equal streams.

2031 -2039 - optical signal delay lines,

204 - optical adder,

2051-2053 - signal attenuators,

207 - signal generation lines simulating an interference signal.

Block 201 consists of a laser diode pulse power generation unit (2011), a laser diode (2012) that generates short pulses up to 100 ps, an optical attenuator (2013) and a delay line in the form of a fiber optic waveguide (2014) simulating the delay of the reflected signal from a complex object.

Nine optical signal delay lines (2031, 2032, ... 2039), which are fiber optic waveguides that delay the optical signal by the corresponding number of fractions ns and simulate the delay of reflected signals from reflective elements of a complex probed object.

Table 4. Specification for optical delay lines (DL)

Delay lines are connected to the first six inputs of adder 204, in the order listed in Table 4.

The signals from the delay lines 2037 and 2038, and 2039 are connected to the seventh, eighth and ninth inputs of the adder 204 through attenuators 2051, 2052, 2053.

The signal generation line simulating an interference signal 207 connected to the tenth input of the adder 204 consists of a laser diode supply voltage driver 2071, a laser diode 2072, a signal attenuator 2073, and a connecting optical waveguide 2074.

The laser diodes (2012 and 2072) and the sensor of block 108 are adapted to operate at a wavelength of 1550 pt. Laser diode 2012 generates short pulses with a duration of up to 100 ps based on a signal from block 103. A sequence of optical pulses from a laser diode 2012, simulating a probing signal, is fed through an attenuator 2013 and an optical waveguide 2014 to the input of the optical signal divider 202. It is summed through the delay lines and attenuators at the adder 204 and mixed at the adder 204 with the noise component from 207 and through an additional attenuator and an optical waveguide (not shown in Fig. 12) through the input 108-4 (Fig. 8) are fed to the optical signal sensor in block 108.

Signals from delay lines 2031-2036 imitate "strong" reflected signals from the elements of the probed object.

Signals from delay lines 2038-2039 imitate "weak" reflected signals from the elements of the probed object.

Signals from the delay line 2037 simulates the "ordinary" reflected signal from the elements of the probed object.

Block 108. Block for receiving an optical signal in the fast strobing mode, including the sensor. The diagram of the receiving unit 108 with the adjustment unit is shown in FIG. 8.

Block 108-1. Sensor strobing block.

The signal that controls the gating of the sensor block 108-3 is fed to the input 108-3-1 of the block 108-3 is formed by the block 108-1, based on the gate logic signal applied to the input 108-5 and the signal that specifies the quantum efficiency of the sensor block 108-3 and applied to the input 108-1 -1 and is a superposition of a DC bias voltage with an amplitude v _bias and a rectangular gating signal with a period T _d and the duration of the gating pulses T _d and the amplitudes of the positive and negative half-waves v _m+ and v _m _, respectively. The total amplitude v _g =v _bias + v _m+ determines the quantum efficiency of the sensor in the gating interval of duration T _d . In this case, for the implementation of gating, the condition V _off =V _bias ~ ^V m- < ^V br (CM. FIG. 3 and Table 2) must be met. GATE SIGNAL - A RECTANGULAR signal with given amplitudes V _m+ and V _m _ and the duration of the strobing pulses T _d is formed in the same block based on the signal input 108-5 of block 108. The time position of the leading edge of the strobing pulses coincides with the position of the leading edge of the logical units in the logical gate signal at the input 108-5 block 108.

Block 108-2. Node for adjusting the signal controlling the quantum efficiency of the sensor.

The regulation of the signal controlling the quantum efficiency of the sensor is carried out by the adjustment node 108-2, which

1 ) when the average, normalized to f _g (frequency of the non-adapted gating signal) sensor actuation frequency F _c (hereinafter, the normalized frequencies are denoted by the capital letter F) is lower than the average sensor actuation frequency setting F _SP or the normalized frequency control setting range [F _MiN F _MAX ] increases the amplitude of the gating voltage v _g at the gating intervals (gating signal generated by block 108-1 and supplied to the sensor of block 108-3 through input 108-3-1 ) so that the current average normalized sensor actuation frequency is within the specified range of control settings [F _MIN FMAX] OR is at least as close as possible to the specified setting range or control setpoint F _SP , but in such a way that v _g does not exceed the maximum allowed gate voltage operating range v _gMAX ,

2) with an increase in the average normalized sensor actuation frequency F _c , below the setting F _SP or the limit of the settings_regulation range [F _MIN F _MAX ], reduces the gating voltage amplitude v _g at the gating intervals, so that the current average normalized sensor actuation frequency is within the specified setting range [F _MIN F _MAX ] or is at least as close as possible to the specified setting range or control setpoint F _SP , but in such a way that v _g does not fall below v _br . Such an adjustment unit can be made, for example, in the form of a standard control loop, consisting of an integrating controller (1-controller), the output signal of which can vary in the range of acceptable values that determine the range of change in the gating voltage or bias voltage, or the quantum efficiency of the sensor, and the input is a signal representing the difference between the control setpoint F _SP and the binary signal from the output of block 8-3. The constant component of the signal at the output of block 8-3 is proportional to the normalized frequency of sensor responses. The setpoint for regulating the normalized average frequency of sensor operation (F _SP ) is formed by the SP2 setter, according to the value written to it (in the setter) from the PC.

The preferred value for the control setpoint F _SP lies in the range [0.2 0.6]. The difference between the regulation setpoint of the normalized average frequency of sensor operation F _SP and the signal from the output of block 108-3 (the signal can be represented as the sum of the constant component of the signal and the variable) from element 108-2-1 is fed to the integrator 108-2-2, which increases the signal at its output only if the difference between the setpoint and the constant component of the signal is positive and, conversely, reduces if the difference is negative and does not change anything if the difference is zero. The variable component of the signal is maximally suppressed by the integrator 108-2-2 and does not affect the regulation process. The weighting factor for the integration performed by the integrator 108-2-2 is inversely proportional to the constant t of the control loop. The weighting coefficient of integration is chosen so as to provide a sufficient relative error in the regulation of the average normalized frequency of sensor responses and relative fluctuations in the steady state control mode. To speed up the regulation, it is possible to dynamically change the weighting coefficient of integration, so if the amplitude of the difference signal at the output of block 8-2-1 is large enough, then the weighting factor can be increased by 2-3 times, but as the amplitude of the difference signal decreases, it must be reduced to the initial value .

To speed up the regulation process (tuning the quantum efficiency of the sensor), in addition to the signal at the output of the integrator (108-2-2 Fig. 8), block 108-2-3 adds the setpoint generated by the SP1 generator. This the setting specifies the value of the a priori (expected) quantum efficiency at the gating intervals of the block 108-3 sensor.

For the implementation of comparative example No. 7, block 108-2 can also operate in the mode of issuing a fixed signal to the input 108-1 -1 of block 108-1, the amplitude of which determines the fixed quantum efficiency at the gating intervals of the sensor of block 108-3. This mode is used to compare reception with regulation (adjustment) of quantum efficiency (examples No. 4,5,6) with the reception of a signal with a constant quantum efficiency of the sensor (example No. 7) . To switch to this mode, a two-position key 108-2-4 is used; in the mode of fixing the quantum efficiency, a setpoint signal is supplied from the signal generator SP3 to the input 108-1 -1 of block 108-1, the amplitude of which determines the specified quantum efficiency _SP of the sensor of block 108 -3. Block 108-2-5 is a control signal limiter that determines the range of bias voltage and/or gating voltage and/or quantum efficiency of the sensor block 108-3.

Block 108-3. Optical sensor and binary detection signal (sequence) generation circuit.

At the output of block 108-3, a binary detection signal is generated, which is a sequence of logical zeros and ones. The logical unit corresponds to the event of the sensor operation at the gating interval, logical zero, the absence of sensor operation at the gating interval. A logical signal with an information transfer rate of 2.5 Gbps from block 108-3 is fed to the block of registration and reading pos. T4.

By block T4, the first member of the binary detection diskette sequence is entered in the cell with the number i = 0, the second in the cell with the number i = 1, and so on. The last member of the binary detection sequence is entered in cell N - 1, where N is the number of members of the binary detection sequence. Thus, a binary detection sequence p(i) of length =40000 is formed, i is the number of a member of the binary detection sequence.

In FIG. 12 is a schematic representation of the relationship of samples in the binary detection sequence (plot E in FIG. 13) with gate time intervals (plot D) and clock timing (plot B). Fig 12:

13A - numbering of clock pulses,

13B is a schematic representation of the clock pulse sequence),

13C is a schematic representation of the optical pulses supplied to the sensor,

13D is a schematic representation of a gate signal,

13E - binary detection logic generated by block 108,

13F - numbering of samples of the logical signal.

13J - p binary detection sequence

The average normalized frequency of sensor responses F _c is the estimate of the probability of sensor response in the interval T _d .

The magnitude F _c of the signal can be measured by measuring the amplitude of the DC component of the signal at the output of block 108-3. Let's give an explanatory example. Let the amplitude of the logical unit at the output of block 108-3 be equal to 1.0 V, and the amplitude of the logical zero 0.0 V, and the average frequency of sensor responses normalized to the gating frequency is 0.4, then the amplitude of the constant component of the signal at the output of block 108-3 will be 0.4 * 1 = 0.4 V To maintain the frequency of sensor operation at a constant level, it is necessary to apply a setting equal to 0.4 V from the setpoint adjuster SP2.

Functional diagrams for simulation of binary detection signal processing units, gating adaptation signal generation units, modulating PIM sequence generation units.

Some of the blocks implemented in a practical lidar were implemented on a bench installation by their software simulation. Software simulation is carried out:

1 ) On simulation cycle 1 : Formation of the modulating PIM sequence in a format convenient for writing to the memory array of block 103 of the stand.

2) On simulation cycle 2: processing of the primary reflectogram read from the T4 block of the stand or the accumulated primary reflectogram to obtain a secondary reflectogram in the form of an array of readings Z. 3) On simulation loop 3:

3.1) formation of a strobing adaptation sequence b in the form of an array of binary samples in a format convenient for writing to the gating adaptation signal generation unit 105 of the stand.

3.2) formation of an auxiliary sequence of readings Y. The member of the sequence K(i) is equal to the number of gating intervals at which the signal was received in the gating mode, contributing to the formation of the corresponding reading of the secondary reflectogram Z(i). That is, if Г(100) = 1500, then, consequently, the reading of the secondary reflectogram Z with the number 100 was obtained by processing 1500 informational (see the definition below) readings of the primary reflectogram.

Additionally, the program implements interface modules that read / write binary sequences from / to the simulation stand and visualization units of the data obtained during the work of the stand.

The functional scheme for processing the primary reflectogram with obtaining a secondary reflectogram and generating a gating adaptation signal) implemented in software imitates (with the exception of the interface blocks responsible for reading/writing the bench signals) a block diagram for processing the primary reflectogram in real time, i.e., it allows calculating the readings of the secondary reflectograms as they arrive at the input of the processing circuit for readings of the primary reflectogram.

In FIG. 13 shows a functional diagram of signal processing and generation. In the diagram, the software modules that imitate the functional blocks of the lidar and work during the simulation in a single cycle are circled with rectangles drawn by a dotted line.

Specification for the diagram of Fig. 13

IM1 (Interface module1) - designed to read the primary reflectogram from the stand on a PC into the memory area pos. P-1.

P-1 - an array of memory cells for recording, storing, accumulating and reading the primary reflectogram.

301 - Module for generating a primary reflectogram to a form adapted for processing by matched filtering.

302 - The matched filtering module is designed to calculate the secondary reflectogram. P-2 - an array of memory cells for recording, storing and reading the secondary reflectogram.

303 - Module for generating a secondary reflectogram in a form adapted for further processing.

304 - Threshold detection module.

305 - Strobe adaptation sequencing module.

306 - Module for making the gating adaptation sequence convenient for writing to the memory module of the gating adaptation signal generator 105.

P-3 - an array of memory cells for writing, storing and reading the strobing adaptation sequence.

IM2 - (Interface module 2) - is designed to transmit the strobing adaptation sequence for its subsequent recording in the memory module of the strobing adaptation signal generation unit 105.

307 - Module for generating a sequence that is analogous to an adapted gate logic signal.

308 - Module for generating an auxiliary sequence of readings Y.

P-4 - an array of memory cells for writing, storing and reading to visualize the auxiliary sequence Y.

309 - Input sequencing module for module 310.

310 - Module for the formation of the modulating PIM sequence.

311 - Module for bringing the modulating sequence to a form convenient for writing to the memory module of block 103.

P-5 - Memory area for recording, storing, reading the modulating PIM sequence.

IMZ - (Interface module 3) - is designed to transmit the modulating sequence, for subsequent recording in the memory module of block 103 of the stand.

Interface module IM1

The IM1 module is designed to read the primary reflectogram into the array of memory cells P-1 in a PC. On command from the control unit, the operating cycle of the stand (probing simulation cycle) is activated, in which the emission and reception of an optical signal is simulated in the form of a binary sequence (primary reflectogram) recorded in the memory block of the T4 block of the stand. Upon completion of the working cycle of the stand, the interface unit IM1 (on command from the control unit) reads from the unit of the stand T4 the primary reflectogram d. d(y) e [0; TV - 1]; TV = 40000.

Next, the interface block IM1 reads from the memory cells P-1 to the PC the reflectogram previously recorded in it (or zero values entered into the memory cells P-1 before the first probing cycle) and adds the read primary reflectogram d to it term by term and writes the result of addition term by term into memory cells P-1. The numbering of memory cells P-1 corresponds to the order of numbering of readings of the primary reflectogram. The sequence of operations indicated above (working cycle of the stand - reading - addition - writing) is carried out the required number of times from 1 to K.

As a result of the operations carried out in the array of memory cells P-1, a knee-length primary reflectogram d _k is formed, where the index K denotes the number of summed primary reflectograms. q _to (y) G [0; TV - 1]; TV = 40000.

The need to accumulate the primary reflectogram is due to the limited memory for recording the primary reflectogram in the stand. Therefore, one long cycle of sounding simulation is replaced by K cycles with the accumulation of the primary reflectogram. In the examples under consideration, K = 5. With a decrease in the power of the optical noise signal simulated on the bench by the 2072 laser diode, one cycle of the bench would be enough, but the essence of the examples is to show how the lidar works under conditions of strong interference, which requires PIM sequences of longer duration ( magnified by K times), which is simulated by the accumulation of reflectograms.

Interface module IM2.

The module is designed for reading from the array of memory cells P-3 and transferring to the stand for writing to the memory cells of the gating adaptation signal generation unit 105, the strobing adaptation sequence 6, 6(j E [0; N - 1]; W = 40000.

Interface module IMZ. The module is designed to read from the array of memory cells P-5 and transfer to the stand for writing to the memory cells of block 103 of the modulating sequence in a two-bit format and,

- 1 ] ; L = 76645.

Formation of the modulating PIM sequence (Operations in cycle 1)

The formation of the modulating PIM sequence is carried out in cycle 1. The variable t is the cycle counter, t e [0; L - 1] if L is even and otherwise t e [0; L] if L is odd. L is the number of members of the modulating PIM sequence.

As a modulating PIM sequence, a sequence of length L = 76645 is used.

Operation 309 - forming a member of the input sequence for module 310. The generated value is assigned to variable A. The number of the member of the input sequence for module 310 is determined by the value of the variable m. If the variable is the loop counter m = 0, then the variable A=1, in all other cases, the variable A = 0.

Operation 310 is carried out by program module 310. Each time it is accessed, the module simulates one cycle of operation of block 3 of Fig. 6 of the formation of PIM sequences of length L = 76645. The number of the operation cycle of block simulator 3 (program module 310) corresponds to the value of the variable m. At each cycle, the input module 310, variable A and variable t are supplied. If (m)mod2 = 0, then the value of calculations simulating one cycle of block 3 is assigned to variable C, and if (m)mod2 = 1, then the reference value obtained as a result of calculations is assigned to variable B,

Operation 311 - bringing the modulating sequence to a format convenient for writing to the block of the stand 103 is carried out by the program module 311. The essence of the operation: if the condition (m)mod2 = 1 is satisfied for the variable m, then a two-bit code is entered into the cell array P-5 in the cell with the number (m - 1)/2, the first bit of which takes the value equal to the value of the variable C, and the second bit takes a value equal to the value of the variable B. Thus, in the array of memory cells P-5, a binary modulating discrete sequence is formed and in a format convenient for writing to block 103 of the stand.

Formation of a secondary reflectogram. (Operations in cycle 2) Before starting the formation of the secondary reflectogram, the primary accumulated reflectogram d _k (p , where i e [0; N-1].

Simulation of the operation of the matched filtering unit is carried out in a loop. The loop counter variable is denoted by i , i e [0; 2N - 1]; N = 40000.

Each simulation cycle is timed to a certain time interval of the stand operation in the probing simulation cycle, so the variable - cycle counter i , if i is even, corresponds to the time interval [ iT ₀ ; iT ₀ + Т _d ] i.e. this is the interval at which the sensor gating occurs, if it is not canceled by the gating adaptation signal (note: the time on the bench is counted from the leading edge of the zero clock pulse generated on the bench when simulating a probing cycle).

If i is odd, then the time interval [(i - 1)T ₀ +

+ 1)T ₀ ] is the time interval in which the sensor is always off.

Thus, the number of the cycle variable i is timed to the number of the clock pulse i (plot A in Fig. 10) synchronizing the operation of the sensor operating in the Geiger counter mode with fast gating.

For simplicity of presentation, since the intervals T _d and T _about are approximately equal. We assume that each simulation cycle corresponds to a real-time interval equal to 200 ps.

Operation 301 (formation of the primary reflectogram reading).

Operation 301 is performed by module 301 , which generates a binary detection sequence in a process-friendly (matched filtering) form |i ^m (i) of length 2N, i e [0; 2N - 1].

The formation of the sequence \im ^m , like all processing, occurs in the signal processing cycle, where the variable i - the counter of the processing cycle of the binary detection sequence (processing simulation cycle) is timed to the number of the sequence member p ^t .

The counts |i ^m (i) that correspond to the time intervals at which the sensor was turned on, we will call "informational" they can be equal to either zero or one, and the rest of the counts are always equal to zero. With matched filtering, only information samples form a response on the secondary reflectogram.

The formation of the sequence \ ^im is carried out as follows: if the variable i takes an even value, then the output of the module is formed by the sample \ ^im (i) = ji _K (i/2) by reading from the memory cell P-1 with the number i/2 of the sample

if the variable i takes an odd value, then a zero count is formed at the output of the module, i.e. \im ^m (i) = 0

At cycle number i ( i e [ 0.2N - 1] ), the module 301 generates a member of the sequence |i ^m (i) and submits to the operation 302 performed by the module 302 the simulation of the matched PIM filtering of the sequence of length L.

Operation 302 (formation of secondary reflectogram reading).

Operation 302 is performed by module 302 (consistent filtering module 302). Module 302 simulates the operation of a matched filter with a notch filter (blocks 4 and 5 connected in series in Fig. 6). At each processing cycle with a number (variable i - cycle counter changes from 0 to 2N-1 ), the H ^m (i) generated in module 301 is fed to the input of module 302 and in the same cycle, starting from cycle number i \u003d L - 1, the counts calculated in module 302 are entered into memory cells P-2, so that in the memory cell with the number k = 0 there will be a count calculated on i = L - 1 cycle, and in the memory cell k = 2 there will be a count calculated on i = L + 1 cycle and so on. Thus, in the memory cells P-2, an array Z of length 2N-L will be written, which we consider as a secondary reflectogram Z (k).

So, in the memory cell with number 0, the reflectogram count Z(0) will be placed, corresponding to the time interval [0; T _o ], in the cell with number 1, the count Z(l) corresponding to the time interval [T _o ; 2Т ₀ ] and so on.

Here we are talking about intervals along the delay axis of the optical signal reflected from the resolvable object.

Z(i) , i e [0, 2N - L - 1]

The Z-sequence thus obtained can be displayed on a PC screen as a trace using a visualization functional module (module not shown in the figures). Generating the Gating Adaptation Sequence (Operations in Cycle 3)

Formation of sequence b for gating adaptation (simulation modeling) and calculation of function Y, which makes it possible to estimate signal losses during reception in the adaptive gating mode for each sample on the secondary reflectogram.

The formation of a binary sequence 8 used as a gating adaptation signal from the gating adaptation signal generator 105 is carried out in the third processing cycle.

Sequence 8 is generated in a writeable format by its gating adaptation signal generator 105, 8(i) ; i G [0,/V - 1].

Additionally, the sequence Y is also calculated in the third processing cycle. Its essence is as follows: the sequence member with index k gives the sum of the number of gating intervals, the signal reception at which contributed to the formation of the Z(fc) reading of the secondary reflectogram.

The formation of both sequences 8 and Y is carried out in the third processing cycle after performing the operations of the second cycle based on the secondary reflectogram Z recorded in the array of memory cells P-2

When forming sequence 8, the following operations are performed. (On each calculation cycle, the k - variable cycle counter changes from 0 to 2N-1 ).

Operation 303 (module 303 for generating a secondary trace in a form adapted for subsequent processing):

If the loop counter variable k < 2N - L , then the count generated as a result of operation 303 is equal to the contents of the memory cell with the number k from the array of memory cells P-2.

Operation 304 (threshold detection module 304):

On cycle k, the result of operation 303 is compared with the detection threshold level - if the count obtained as a result of operation 3 exceeds or equals the threshold detection level, then a logical count of "1" and "0" is formed if otherwise.

Step 305 (Gating Adaptation Sequencing Unit 305) Module 305 on each cycle performs the same calculations as the block (item 3 in Fig. 6) for generating a PIM sequence of length L = 76645 on each cycle of its operation. That is, a cycle of work is equivalent to one calculation cycle.

Operation 306. (decimation module 306).

The report generated at operation 305 on the calculation cycle is written to the memory cell pos. P -3 with the number k / 2 if k is even, and vice versa, if k is odd, then no recording is made.

Thus, in memory cells with numbers from 0 to N- 1 (note: N is an even number), a sequence 8 of length N will be recorded transmitted (written) to the gating adaptation signal generator 105.

The rejection of every second sample in the generated sequence is performed because the numbers of the discarded samples are timed to the numbers of clock pulses (odd), according to which the gating signal of the sensor operating in the fast gating mode is not generated.

Operation 307 (module 307 generation of the sequence, which is analogous to the adapted signal of the gating signal formation)

Operation 307, like operation 306, is performed after operation 305

The essence of operation 307 is the formation of a sequence (plot 15G. See Fig. 10) that is analogous to the adapted gating signal (plot 15E. See Fig. 10).

The sequence is formed as follows: if the value of the variable k loop counter is even and the count calculated by module 305 (operation 305) is 0, then the result of the operation will be “1”, in all other cases the result of the operation is “0”.

Operation 308. (Module 308 generation of auxiliary sample sequence Y)

The module allows you to estimate the energy loss of the received signals (PIM of optical pulse sequences, due to the fact that the sensor receives an optical signal, it turns on only at the gating intervals, due to which a part of the optical pulses arriving at the sensor surface will not be accepted.

The module calculates a sequence of samples U(/s) that allows you to estimate the energy loss for each sample Z(fc) caused by the fact that the reception of the optical signal is conducted only at the sampling intervals of the sensor. So the G(/s) reading will be equal to the number of information readings of the primary reflectogram \im ^m , the summation of which with non-zero weighting coefficients in the process in the Z(fc) reading was used. Since the primary accumulated reflectogram is processed, the values of G(/s) increase by K times, where K is the number of cycles of formation of the accumulated reflectogram. In the examples K=5 and therefore Figs. 14 and 15, the values of SG(/s) are plotted along the ordinate.

Module 308 simulates the operation of the matched filter block 4 of FIG. 6. At each processing cycle with the number k (k the cycle counter changes from 0 to 2N - 1), the input of the module 308 is supplied with the count generated in the module 307 (graph 15G. Fig. 10) and in the same cycle, starting from the cycle with the number i = L - 1 counts calculated in module 308 are entered into the array of memory cells P-4, so that in the memory cell with the number k = 0 there will be a count calculated on i = L - 1 cycle, and in the memory cell k = 2 there will be a count calculated on i = L + 1 cycles and so on. Thus, in the array of memory cells P-4, a sequence Y of length 2N - L will be recorded, which we consider as an auxiliary sequence that allows us to estimate the energy loss for each sample Z(fc) caused by the features of the reception of the optical signal by the sensor, namely its strobing. For each sample Z(fc), the value K • K(/s), where K is the number of cycles of formation of the accumulated reflectogram determines the total number of gating intervals at which the optical signal was received, which contributed to the formation of the sample Z(fc)

Example 3

Practical options for generating a gating adaptation signal. Using an additional sensor.

The gating adaptation signal can also be obtained using an additional sensor located in an adjacent optical path, and the adjacent optical path is designed so that the moment of arrival of the front of the optical pulse wave on the surface of the additional optical sensor is ahead of the time of its arrival at the surface of the sensor, the gating of which is being adapted. In FIG. 16 shows a possible diagram of such an optical device. The device consists of two optical systems: an objective 404 that focuses optical radiation on the surface of the sensor (or sensors) 401 and a fragment of a parabolic mirror 403 that focuses optical radiation on the surface of the sensor (or sensors) 402. Both sensors are located at the focus of the parabolic sensor side by side, as shown in Fig.16.

The optical pulse reflected from the probed object is divided into two, the first of which reaches the surface of the sensor 401 before it reaches the surface of the sensor 402 with reflection from the parabolic mirror. The time delay is determined by the time of passage of the path segments of the beam A1 + B1 or A2 + B2. The transit time of these segments is the same and determines the time delay of the second optical pulse that hits the surface of the sensor 402 with respect to the first one that hits the surface of the sensor 401 .

So, if the sum of the lengths of segments A1 and B1 is 20 st, then the delay between the time the optical pulse reaches the sensor surface 402 and the optical pulse of the sensor surface 401 will be 0.66 ns, which is an acceptable time for processing the received first optical pulse and generating a signal on turning off the optical sensor 402.

A sensor 401 that receives only high-energy optical pulses (corresponding to "strong" or "strong" and "ordinary" optical pulses) striking the surface of the combined optical system of the type of FIG. 16), generates a signal to turn off the sensor 402. As a result, the frequency of the sensor 402 responses at a given quantum efficiency of the sensor 402 is reduced, which allows the sensor 402 to receive optical pulses at a higher quantum efficiency of the sensor 402, which is more preferable for receiving “weak” optical pulses. . Also, this allows you to simultaneously eliminate the influence on the detection of "weak" peaks of responses on the secondary reflectogram obtained by processing the signal from the sensor 402, side lobes (side peaks) of responses from the reception of "strong" or "strong" and "ordinary" optical pulses received only sensor 401 and increase the security of the path for receiving and processing the signal of the sensor 402 from impulse noise. Optical sensor 401 and optical sensor 402 may comprise multiple optical sensors to which appropriate gating signals are applied.

Use of a trial (pilot) probing signal.

Another variant of adaptive gating is based on the use of information about the time intervals of arrival of "strong" and "ordinary" optical pulses on the surface of the receiving sensor, obtained during the reception and processing of the test signal.

The essence of the solution is that in order to determine the signal transit time from the transmitter to an object with a “strong” and/or “ordinary” ESR and back to the receiving sensor, further than the transit time, it is sufficient to use probing sequences with a smaller number of optical pulses, the so-called . test signals.

The probe signal is emitted by the lidar before the main optical signal is sent. After receiving the secondary reflectogram and determining the time delays of the probing test signal, a gating adaptation signal is formed. The main probing signal is received already with the adaptation of the strobing signal. Emission and reception of test and main signals can be carried out in one probing cycle.

So, if the duration of the test signal is equal to T _p , and the delay in its processing in real time T _pg , the start time of the emission of the main signal must be delayed relative to the start of the emission of the test signal by at least 2 T _p + t _pg .

Table 5. Overview of examples 4-7.

Example 4

The main parameters of the stand in example 4

The number of probing cycles K = 5.

Information about the allowed delays arriving at the surface of the PIMPOI sensor is given in Table 4.

In total, 8 PIMPOIs arrive at the sensor surface, of which 5 are strong, in which the relative energy (normalized to the energy of one photon with a wavelength of 1550 pt) arriving at the sensor surface is 20 , one PIMPOI is an ordinary relative energy arriving at the sensor surface is 5 and two PIMPOIs are weak relative the energy delivered to the sensor surface is 1.2 .

PIMPOs are modulated with the sequence from example 2.

The number of optical pulses in each PIMPOI -1369

The equivalent power of the noise component of the signal detected by the sensor is 1.28 nW.

The setting for the adjustment unit of the normalized frequency of sensor operation F _SP - 0.3

In FIG. 14 (example 4)

Top Graph

The X-axis represents the time in the bench clock multiplied by 10 ^-4 .

The Y-axis shows the value of the auxiliary function Y multiplied by 5, where 5 is the number of accumulation cycles in the primary trace.

Bottom graph

The x-axis represents the time in bench clock multiplied by 10 ^-4 .

On the Y-axis, the values taken by the secondary Z trace obtained after processing the primary accumulated trace.

16A - peaks of responses on the secondary reflectogram from sequences of "strong" optical pulses,

16B - peak responses on the secondary reflectogram from a sequence of "ordinary" optical pulses.

16C - peaks of responses on the secondary reflectogram from sequences of "weak" optical pulses. As a result of accumulation of five primary reflectors and processing of the accumulated reflectogram, a secondary reflectogram was obtained, a fragment of which is shown in Fig. 14 (bottom graph).

The reflectogram clearly shows positive peaks of responses from weak and ordinary PIMPOIs with different delays and negative peaks of responses obtained as an effect of adaptive gating from strong PIMPOIs.

To assess the effect of gating on signal energy loss, an auxiliary sequence Z(i) is calculated, the essence of which is the value of the number of readings of the primary reflectogram that contribute to the formation of the reading of the secondary reflectogram Z(i). We defined such readings in the primary reflectogram, earlier in the description, as informational. Since the primary accumulated of 5 traces was used to obtain the secondary trace Z, the values of the Y function were multiplied by 5.

It can be seen from the upper graph that in the formation of each report of the secondary reflectogram, from 2900 to 3450 information samples from the primary reflectograms were used, which is associated with the gating of the sensor. In the absence of gating, the values of 5Y would be a constant equal to 1369 * 5 = 6845. Thus, due to gating, 42 to 50% of the optical pulses in the PIMPOI fall into the gating intervals.

The results for example 4 are shown in table 6

Example 5

Example 5 differs from Example 4 in that adaptive gating has been disabled.

In FIG. 15 (example 5)

Top Graph

The X-axis represents the time in the bench clock multiplied by 10 ^-4 .

The Y-axis shows the value of the auxiliary function Y multiplied by 5, where 5 is the number of accumulation cycles in the primary trace.

Bottom graph

The x-axis represents the time in bench clock multiplied by 10 ^-4 .

On the Y-axis, the values taken by the secondary Z trace obtained after processing the primary accumulated trace. 17A - peaks of responses on the secondary reflectogram from sequences of "strong" optical pulses

17B is the peak of responses on the secondary reflectogram from a sequence of ordinary optical pulses.

As can be seen from the example, when the gating adaptation function is turned off, it is not possible to determine the delays of weak PIMPOIs.

The results of example 5 are shown in table 6

Example 6

Example 6 differs from example 4 only in that the equivalent power of the noise component of the signal detected by the sensor is increased to 3.2p1 and the relative pulse energy (normalized to the energy of one photon with a wavelength of 1550 nm) in weak PIMPOI is increased to 2.

The results of example 6 are shown in table 6

Example 7

Example 7 differs from example 6 only in that the adaptive gating is disabled and the bias voltage is set to provide the maximum quantum efficiency of the sensor equal to “25%.

The results of example 7 are shown in table 6

Table 6 below summarizes the data for examples 4-7.

Cells with a negative result are highlighted in bold with underlining (no resolution on the secondary trace) - the response does not stand out above the background level of the trace.

Table 6. Summary of examples

* the number of simulated resolved objects - the number of objects delayed relative to the start time of emission of the probing optical sequence PIMPOI with the same energy in each optical pulse.

** the average number of photons in an optical pulse is the average energy of an optical pulse in PIMPOI, normalized to the energy of one optical radiation quantum with a frequency of 1550 pt.

***(s/N) _ln - is defined as the ratio of the energy of a single PIMPOI optical pulse that hits the sensor surface in the gating intervals to the sum of the energy of the noise radiation coming to the sensor surface in the gating intervals and the energy of the equivalent noise radiation, which characterizes the manifestation of the sensor's own noise at gating intervals, but without taking into account the equivalent noise emission caused by the APP effect. ****(s/N) _0Ut - according to the secondary reflectogram is defined as the minimum ratio of the amplitudes of the peaks of the corresponding responses ("ordinary" or "weak") to the maximum amplitude of the side lobes of the reflectogram based on a sample of 10 similar reflectograms, in Fig. Figures 14 and 15 show some of these reflectograms.

F _c - measured at the interval of reception of the optical signal, normalized to the gating frequency, the average frequency of the sensor operation, which was established by adjusting it according to the setting F _SP (examples 3,4,5) or with a fixed quantum efficiency of the sensor _SP (example 7). - the average quantum efficiency of the sensor at the gating intervals established as a result of the regulation of F _c (examples 3,4,5) according to the setting F _SP or set by the setting _SP (example 7).

Industrial applicability.

The proposed device for receiving an optical signal makes it possible to use relatively inexpensive, low power devices as sources of pulsed radiation.

Additional benefits:

1) noise immunity,

2) range resolution - from 3-5 st.

3) the possibility of resolving all objects in the beam alignment in one probing cycle.

4) the ability to control losses in the ratio (s/N) _0Ut . due to gating and the presence in the received signal of strong impulse noise or “strong” PIMPOI, which make it difficult to process the received signal, by calculating the auxiliary function Y.

An additional technical result is that the gating adaptation increases (s/N) _0Ut for the response peaks on the reflectogram of "weak" signals and the regulation of the average sensor actuation frequency allows you to set the optimal quantum efficiency of the sensor at which the maximum ratio (s/N) _0Ut is achieved.

In addition to the filed description, when filing an international application, an explanation is provided, which is written below. Additionally, figure 17 is shown, drawn up according to the claims.

In the figure 17 marked

17.1 - Clock signal generator;

17.2 - Optical receiver operating in a non-linear mode;

17.3 - Block of matched filtering;

17.4 - Threshold signal detection module;

17.5 - Strobe signal / clock signal;

17.6 - Gating adaptation signal;

17.7 - Photon that hits the device;

17.8 - Sensor.

The description indicates that a functional diagram of the stand is given.

“108-2-4 - A two-position switch that switches the input of block 108-2-5 either to the output of the master SP3 (the first position of the key is “given quantum efficiency of the sensor”), or to the output of the adder 108-2-3 (the second position key - "regulation (adjustment) of the quantum efficiency of the sensor" block 108-3). Key position is controlled by PC.

The same in more detail.

“106-2 - A two-position key that switches the input 106-4 of element 06-1 either to the output of the logical zero generator “0” (the first position of the key is “no Gating Adaptation"), or to the output 105-3 of the Gating Adaptation Signal Conditioner 105 (the second key position is "Gating Adaptation"). The key is controlled from a PC.

Key positions 106-2

A description of the operation of the device according to the patent is given in example 4.

"The input 106-4 of the element 106-1 is connected to the output 105-3 of the gating adaptation signal generator 105", and "the input of the block 108-2-5 is connected to the output of the adder 108-2-3". This commutation has been set forth in the following claims. In order not to draw four block connection diagrams in examples 4, 5, 6, 7, one functional diagram was used with two keys that functionally carry out the necessary block connections of the functional diagram to demonstrate examples 4, 5, 6, 7.

Claims

CLAIM

1 . A device for receiving an optical signal reflected from a probed object, including a clock signal generator 17.1 connected to an optical receiver 17.2 operating in a nonlinear mode, a matched filtering unit 17.3, a threshold signal detection module 17.4, characterized in that the device includes a node for adjusting the quantum efficiency by the frequency of the sensor operation 108-2 and a block for generating a gating adaptation signal 105.

2. A method for receiving an optical signal, in which a clock signal is generated, a signal reflected from a resolvable object is received by an optical receiver 17.2 operating in a nonlinear mode, having a matched filtering unit 17.3 and a threshold signal detection module 17.4, characterized in that the strobe signal is adapted, regulated quantum efficiency in terms of the frequency of sensor triggering.

3. The method according to claim 2, characterized in that the gating adaptation signal is generated in the probing process based on the results of matched filtering of a fragment of the probing PIM sequence or a separate probing pilot signal, which makes it possible to estimate the time delays of the optical pulses of the signals reflected from the elements of the probed object, which hit the surface of the sensor leads to its operation with a probability close to one.

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