RU2653558C9 - Optical device for determining distance to object - Google Patents

Abstract

FIELD: measurement technology.SUBSTANCE: invention relates to the field of measuring distances to an object by means of electromagnetic waves. Optical device for determining distances to an object includes a radiation source to a modulated binary optical signal object, a probe sequence generator, a clock generator, an optical receiver operating in a non-linear mode, a first signal accumulation unit, a calculating unit of the correlation function of the reference and received signals, the second signal accumulation unit, the demultiplexer, the threshold detection module of the signal, the distance calculation module to the detected object by the time delay of the reflected signal, module for calculating the time delay of the reflected signal. Optical device also includes a signal conditioning module at each clock cycle n corresponding to a value of 0, 1 or -1, a conjunction unit, a sync pulse generating unit at the beginning of the sounding cycle, a sounding cycle counting unit, a probe sampling and processing unit.EFFECT: technical result consists in increasing the dynamic range of a lidar using signals modulated by pseudo-noise sequences as probing signals.5 cl, 10 dwg

Description

FIELD OF THE INVENTION

This invention relates to the field of measuring distances to an object using electromagnetic waves, and more particularly to optical devices for determining distances to an object, including a radiation source to the object of a modulated binary optical signal, a probe sequence generator, a clock signal generator, an optical receiving device operating in nonlinear mode, multiplexer, first signal accumulation unit, module for calculating the cross-correlation function of the reference and yatogo signals, a second signal storage unit, a demultiplexer, a threshold signal detection module, a distance calculating module to a detectable object according to the time delay of the reflected signal, and may be used, such as in navigation, including drones, as well as laser ranging.

The following terms are used in this description:

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

PWP, Pseudorandom (pseudo-noise) sequences are completely deterministic digital sequences that they seem random to an external observer.

Signal multiplexing - channel multiplexing, i.e. transmission of several streams of data signals on one channel.

Signal demultiplexing is the reverse operation.

VKF is a cross-correlation function. VKF Example:

, где [0, Т] интервал интегрирования, причем длительность опорного сигнала у(t), как правило, существенно меньше T.

, where [0, T] is the integration interval, and the duration of the reference signal y (t), as a rule, is significantly less than T.

This is a mathematical operation, a measure of the similarity of 2 signals (reference y (t) and received x (t)), the maximum point of the correlation function corresponds to the point of minimum quadratic deviation between the signals x and y.

Additional sequences. Additional sequences are known, (See L. Varakin, “Communication Systems with Noise-Like Signals.” - M.: Radio and Communications, 1985).

The sequences {a _n } and {ã _n } are called complementary if

при µ=0 или

при µ=+/-1, …, +/- (N-1), где

at µ = 0 or

for µ = + / - 1, ..., +/- (N-1), where

;

;

An example of such sequences are D codes.

Quantum efficiency is the probability of generation by a photon of a free carrier incident on the receiving device, which will reach a high-field region sufficient for impact ionization.

Optical radiation - in this patent, optical study refers to electromagnetic waves whose lengths are in the range with arbitrary boundaries from 3000 μm to 0.25 μm.

EPR (effective scattering surface) is a quantitative measure of the property of an object to scatter optical radiation towards a receiving sensor.

LFM - linear frequency modulation, a type of frequency modulation at which the frequency of the carrier signal changes linearly.

State of the art

RF patent RU 2605628 “Method and optical device for determining distances to an object” describes a method for generating D codes and their modifications, which consists in using a cascade computer, consisting of cascades connected in series, each of which contains a delay line and two adders. A diagram of such a cascade is shown in FIG. one.

Connecting such cascades in series as shown in FIG. 2, additional sequences can be generated, for which a single pulse is simultaneously supplied to input 2-1 and input 2-2 of the first stage, and additional sequences are read from outputs 2-1 ’and 2-2’ of the last stage.

The cascade calculator is used for coordinated filtering of signals modulated by additional sequences received from the outputs 2-1 ’and 2-2’ of the last cascade and read in the reverse order; we will call them, respectively, additional sequences “one” and “two”. These sequences are also optional. For consistent filtering, the filtered signal is simultaneously fed to input 2-1 and input 2-2 of the first stage. At the output 2-1 ’of the last stage, the cascade computer is a matched filter for the signal modulated by the sequence“ one ”, and at the output 2-2’, respectively, the sequence “two”. Cascade connections can be either output 2-1 ’to input 2-1, output 2-2’ to input 2-2, or cross-output 2-1 ’to input 2-2 and vice versa.

The delay cycles for the delay line in each stage are determined as

2 ^{(F ((i) -1)} , where i is the cascade number, F (i) is an arbitrary permutation function.

For example, if F (1) = 3, F (2) = 2, F (3) = 1, then in the first stage there will be a delay of 4 cycles, in the second by 2 and the third by 1 cycle.

The length of additional sequences is 2 ^N , where N is the number of cascades in the circuit.

For example, the circuit shown in FIG. 2 generates two additional codes of length 2 ³ = 8.

If it is necessary to carry out calculations from M channels in parallel, then the number of delay clocks in all digital delay lines used in the cascade computer in each of the cascades should be increased M times. The signals in the cascade calculator are supplied through the multiplexer. This simplifies processing and reduces the amount of memory used for computing.

US Pat. No. 5,499,134, published in March 1996, describes a laser device generating short laser pulses (femtosecond). The device includes a generator that generates and outputs a beam of short seed pulses, a tensile module that stretches the duration of the seed pulses by chirping them (stretching a broadband pulse in a dispersive optical medium / system), and an amplifier that receives stretched seed pulses amplifies the amplitude of the selected stretched seed pulses to create amplified chirped pulses and outputs a laser beam of amplified stretched pulses to the compression module which compresses their duration (when a pulse passes through a medium with backward dispersion), outputs a laser beam of amplified short pulses. This method is called - “Chirped pulse amplification method”.

At the moment, modulated laser devices that generate sequences of femtosecond pulses with a repetition rate of femtosecond pulses of up to 200 MHz with a duration of less than 20 fs (femtoseconds) are available devices on the market of fiber-optic communication systems.

Example 1. A MenloSystems YLMO laser with a pulse duration of less than 150 fs and a repetition rate of 100 MHz is used. Over a period of 300 μs using such a laser, it is possible to emit a PWB consisting of 15,000 optical pulses. The radiation power of each single pulse is at least 26 kW. Processing the adopted IFB allows us to obtain the effect (to achieve the same signal-to-noise ratio at the output of the receiver) that we would have obtained using a laser generating a power of 150 fs pulse of the order of 3.2 MW. This will make it possible to increase the range of resolved ranges (compared with the monopulse sensing option) by 3.3 times for non-directional optical radiation from the source, if all the radiated energy is focused on the probed object, the range will increase by 11 times.

For the purposes of sounding, reflectometry, fiber-optic communication, compression of chirped pulses can occur in the receiving path. The essentially similar method is widely used in radar and is called the harmonized LFM signal filtering. The difference is that the optical chirped signal is not coherent.

Known sensors for detecting optical radiation, used to register single photons operating in a nonlinear mode. An example of such a sensor is the sensor described in patent RU 2346357, published in 2009, based on thin-film superconducting structures.

Sensors of this kind are characterized by:

1) quantum efficiency up to 80-90%,

2) the operating wavelength ranges of the detected radiation from 0.25 to 3 μm,

3) a temporary resolution of up to 25 ps.

Based on such receivers, integrated registration systems are created that have dozens of channels (pixels).

US patent 5892575 "Method and apparatus for imaging a scene using a light detector operating in non-linear geiger-mode", published in April 1999, describes a device that includes a pulsed optical radiation source that directs radiation to the probed object , an optical system that collects optical radiation and directs it to a photodetector made in the form of an array of sensors, which use avalanche diodes operating in the Geiger counter mode (SPAD), a system for measuring the time of flight of an emitted optical pulse to the surface of the object and back to the photodetector, computing device (processor) and display for displaying information. The time-counting system fixes the time (counted in the pulses of the clock from the moment the emission starts) between the start of the emission of the optical pulse and the response time of the corresponding array sensor that responds to single photons. When the corresponding sensor is triggered, the corresponding memory cell is confined to the content of which (initially zero) is added to the content of the pulse, which is counted in the pulses of the clock generator.

Sensors can also be triggered by third-party radiation sources and spontaneously with a certain average frequency. The process of emitting optical pulses and probabilistic registration / reception of the photons generated by them is cyclical. The process ends when the values recorded in the memory cells are confined to specific sensors and time instants of a certain threshold value. The distance to the area on the surface of the sensed object or target from the corresponding sensor of the photodetector is determined by the pulse number of the clock generator, counted from the beginning of the sensing cycle, to which the memory cell corresponds / confined with a maximum value written in it that exceeds the specified detection threshold.

This patent provides an example of reliable measurement of the distance to the object’s surface when the probability of the sensor triggering from the reflected signal generated by a single probe pulse, which is only 3%.

However, the method described in this patent has the disadvantage associated with a long range determination time, due to the fact that the signal accumulation time is a multiple of the time of the recurrence period for sending probe pulses, the duration of which is longer than the maximum resolved range R _max times 2 / C.

So let's say if the probability of detecting a reflected signal generated by a single emitting pulse (reflected from a reflecting object) in the time interval T _o is 5%, then for measuring the relative reflectivity of an object (measured in sensor responses in seconds) with a standard deviation of 5% it is necessary to count the received photons on 8000 segments T _о σ = 0.05 = 1 / (0.05⋅8000) ^1/2 .

Thus, the measurement time increases to

8000⋅T _R, where T _R - recurrent period which can not be less than R _max ⋅2 / C, where R _max - maximum allowable range, and C - the velocity of light.

So for R _max = 10 km, when the signal is accumulated over 8000 recurrence periods, it will take at least 0.53 s.

This disadvantage is eliminated through the use of probing signals in the optical range modulated by the FBW. This makes it possible, at the same power of the optical radiation source, to reduce the accumulation time commensurate with the duration of the FSB, which contains the number of optical pulses commensurate with the number of recurrence periods during single-pulse sounding.

In the application for US patent 20150120241, published in April 2015, it is indicated that the so-called SPAD (single-photon avalanche avalanche diodes) can be used to receive optical IFBs reflected from the object.

However, the use of sensing methods using FWP has the disadvantage that, due to the limited dynamic range of the receiving device, when receiving a signal that is a superposition of two or more optical FWPs and the noise component of the signal, the total measured radiation intensity cannot always be measured correctly.

So, for example, if an avalanche diode operating in the nonlinear mode of a Geiger counter is used as a radiation detector, there is a time interval between the moment of formation of the avalanche initiated by the received photon, its quenching, and also between the quenching and restoration (this time interval is called dead time, denoted by, T _d ). During this period of time, registration of other additional photons is impossible.

Thus, no matter what the intensity of the received radiation at a time interval of at most T _d , no more than one photon can be recorded. It should be added that only a part (depending on the types of sensors and wavelength) from 1-2% to 90% of the photons that hit the surface of the avalanche photodiode causes an avalanche process. Therefore, it is obvious that radiation with the intensity of optical radiation incident on the receiving surface of a sensor operating in a nonlinear mode of a Geiger counter and measured in the number of sensor operations per unit time, greater than 1 / T _d , cannot be measured.

The parameter 1 / T _d is called the maximum photon counting / recording frequency and determines the upper boundary of the dynamic range of the receiving devices based on single photon receivers.

The parameter, defined as the average number of false photon detections per unit time, determines the lower boundary of the dynamic range of a single-photon receiving device, respectively (it can be false positives per second).

A disadvantage of lidars and reflectometers that use optical FWPs as probing signals, and non-linear devices that are characterized by limiting current growth with increasing intensity of received radiation, or an avalanche-like increase in current due to impact ionization (Geiger counter mode), is a receiving sensor that the reflected received signal will be a superposition of optical signals from the object / s the distance to which is measured, as well as signals from other (objects). Moreover, the intensity of signals from all or some objects may be higher than the upper threshold of linearity of the receiving device.

In FIG. Figure 3 shows the experimentally obtained dependence of the probability of detecting a photon during a time T _o = 490 ps on the radiation intensity, expressed as the average number of photons arriving at the surface of the sensor under study during a time T _o . Figure 3 is taken from Optics Express Vol. 18 (2010), Issue 6, pp. 5906-5911 // Method for characterizing single photon detectors in saturation mode by cw laser // J.Oh, C. Antonelli, M. Tur, M. Brodsky https://doi.org/10.1364/OE.18.005906

Indeed, if inside the time interval T _o , the probability of the receiving device (sensor) operating in the Geiger counter mode from the radiation generated by the first radiation source is 10%, and the probability of the same sensor from the radiation generated by the second radiation source is 98%, the probability of detection in the time T _{of the} radiation, which is a superposition of radiation from both sources will be close to 98%.

When adding radiation from two sources, the probability of detecting a photon from which during T _o is 5%, the probability of detection will be close to 10%, i.e. probability of triggering the sensor in the time T depends _{on the} additive on the intensities of radiation sources, if superposition of radiation does not exceed the range of linear dependence of the probability of intensity of the sensor response (see figure 3.). Due to this, it becomes possible to isolate (detect) pseudo-noise signals detected by a sensor operating in the Geiger counter mode, the intensities of optical pulses of which are in the range of the linear dependence of the probability of the sensor activating on the radiation intensity of each optical pulse in the FSB supplied to the sensor receiving surface. Signal extraction is carried out by calculating the correlation between the reference signal and the signal received by the sensor.

If, however, the intensities of optical radiation in the signal, which is a superposition of pseudo-noise signals from resolvable objects, exceed the linearity threshold, then this leads to the fact that during subsequent correlation processing there will be suppression of signals from resolvable objects (decrease in the amplitude of the correlation response from the resolvable object), the appearance of false correlation responses in the trace obtained as a result of correlation processing. Such distortions are called nonlinear distortions.

If in monopulse lidars, including with the accumulation of the received signal, it is possible to eliminate reflected signals from foreign objects (which may be a grid / fence, shrub, aerosol) that effectively reflect the optical signal and are located before / after the object, the distance to which measured by recording / accumulating the signal only in the desired (predefined) time interval, then when used as a probe optical FBI, this becomes impossible since Optical signals from various objects overlap each other in time.

Let us cite examples showing the existing reduction in the ability to detect / isolate an optical pseudo-noise signal reflected from a sensed object when mixed with other optical pseudo-noise signals, the intensities of optical pulses in which significantly exceed the linear range of a receiver operating in the photon counting mode, and examples showing overcoming this flaw.

Example 2. (Two “weak” signals)

Prior to detection by a sensor operating in the photon counting mode, the received signal is a superposition of two optical IFBs, one and two, with intensities of optical pulses in sequences within the limits of the linearity range of the sensor. The probability of a sensor triggering from each optical pulse in an optical IFB is ≈10%. The signal "two" is a signal "one", delayed by a time of 50T _o. Optical signals “one” and “two” simulate the reflected signals from two objects located in the alignment of the radiation directed at them, from a modulated PWB radiation source. Object “two” is located along the beam from the lidar (reflectometer) 25T _o / C further than object “one”. T _about is 500 ps, the frequency of false positives of the receiving sensor is 3 MHz. The time in the sensing cycle is counted from the beginning of the sensing cycle in sync pulses with a repetition period T _about. The point in time in the cycle sensing falling during the time interval, the beginning _of which ≈T ⋅ (n-1) and the end _of ≈T ⋅ (n), is confined to the clock number n, reckoned in each cycle from the start of sensing sensing loop.

Four sensing cycles are carried out. Each sounding cycle uses its own unique probing optical IFP, consisting of 512 positions occupying a time interval of 4⋅T _about each. At a temporary position, there is radiation or not radiation of an optical pulse of duration Ti less than or slightly more than T _o. The value of the term modulating FBP sequence member “0” corresponds to “not radiation”, but “1”, respectively, “radiation”. All FWPs used to modulate a pseudo-noise optical signal are obtained from two additional FWPs of length 512, whose members take the values “+1” and “–1”. In the first sensing cycle, the modulated waveguide is used for modulation, obtained from the first additional sequence by replacing "-1" with "0" in it. In the second cycle, obtained from the first additional sequence by replacing “1” with “0” in it and “-1” with “1”. In the second sensing cycle, for the modulation, PCB is used, obtained from the second additional sequence by replacing “-1” with “0” in it. In the third cycle, obtained from the second additional sequence by replacing “1” in it with “0” and “-1” with “1”.

The reception of the optical signal is as follows. In each sensing cycle, when registering optical radiation at a point in time dedicated to the clock number n, “1” is sent to the calculator / matched filter at the nth clock (counted from the beginning of the probe cycle) or “-1 »In probing cycles with odd numbers. The sequences read from the output of the calculator / matched filter are added to the contents of the memory cells of the accumulation block. Before the first sensing cycle, the contents of the memory cells of the accumulation block were zeroed. The memory cells in the accumulation block are confined to the numbers of the members of the sequence read from the calculator / matched filter in each sensing cycle.

In FIG. Figure 5 shows a fragment of a discrete sequence (trace) obtained by reading the contents of the memory cells of the accumulation unit, after accumulating in it four sequences obtained from the output of the calculator / matching filter in four sensing cycles. On the abscissa axis of the graph in FIG. 5, the numbers of memory cells of the accumulation block (with numbers corresponding to the numbers of clock pulses counted in each sensing cycle) are plotted, and on the ordinate axis are the amplitudes read from the memory cells of the accumulation block with the numbers corresponding to the abscissa axis.

Responses 5-1 and 5-2 are visible, making it possible to distinguish / detect the signal "one" and the signal "two" and determine the delay between them, equal to 50T _o .

Example 3. ("Weak" signal in the presence of "strong")

The difference from Example 1 is that in the alignment of the beam directed at the objects of optical radiation from the modulated IFB radiation source are three objects, schematically reflected in FIG. four.

As shown in FIG. 4, an extended reflective object 4-1 is located in front of the probed object 4-2, and a reflective partition 4-3 is located behind the probed object 4-2. The probing optical radiation 4-4 is directed at objects 4-1, 4-2, 4-3. The probability of triggering a lidar receiving sensor (reflectometer) from each single optical pulse (in the optical probing PCB) reflected from object 4-2 and received by a sensor operating in the Geiger counter mode is ≈10%. The probability of a sensor triggering from a single optical pulse reflected from an object 4-3 (reflective partition) is ≈98%. The object 4-1 extended in the direction of the probing radiation reflects a light pulse stretched in time to the lidar sensor, causing four to five sensor operations during 5T _about , characterizing the length of object 4-1.

The distance from the front edge of the object 4-1 to the radiation source to the probed object is 25T _o / C, and to the reflecting wall 50T _o / _C.

In FIG. Figure 6 shows a fragment of a discrete sequence (trace) obtained by reading the contents of the memory cells of the accumulation block after the fourth sensing cycle. Responses 6-1 and 6-2, 6-3 are visible, allowing to distinguish / detect signals from an extended object 4-1, a sensed object 4-2 and a reflective partition 4-3.

Example 4 differs from example 3 in that all FWBs used to modulate a pseudo-noise optical signal are obtained from two binary FWBs of length 512, which are not additional.

In FIG. Figure 7 shows a fragment of a discrete sequence (trace) obtained by reading the contents of the memory cells of the storage unit after the fourth sensing cycle. In FIG. 7, responses 7-1 and 7-3 are clearly visible, allowing one to distinguish / detect a signal from an extended object 4-1 and a reflective partition 4-3. The signal from the object 4-2 in amplitude does not stand out against the background of the noise component of the trace.

Example 5 differs from example 3 in that the probability of a sensor from each single optical pulse reflected from the object 4-2 in the optical IFW is ≈4%. The number of sounding cycles has been increased to 16. In each of the next four sounding cycles, two unique additional sequences of length 512 are used for modulation.

In FIG. Figure 8 shows a fragment of a discrete sequence (trace) obtained by reading the contents of the memory cells of the accumulation block after the 16th probe cycle. The responses 8-1, 8-2, 8-3 are visible, allowing to distinguish / detect a signal from an extended object 4-1, a point object 4-2 and a reflective partition 4-3. The response from the object 4-2 in amplitude stands out clearly against the background of the noise component of the trace.

In the course of the research, it was observed that the use of the method (modulation of the probing signals and their subsequent processing) described in the patent of the Russian Federation No. 2605628, published in 2016, allows one to effectively distinguish / isolate simultaneously received signals with the intensity of pulses in the FSB lying in within the range of the linear dependence of the signal from the sensor output on the intensity of the radiation fed to the sensor surface, and signals with an intensity exceeding the linear dependence range.

It was also found that the same effect persists when replacing a receiving device that generates a current that is integrated on the segments T _o with a binary receiving device operating in the Geiger counter mode. For example, the so-called SPAD or SSPD (Superconducting Single Photon Counter) sensors. As it turned out, such a replacement allows probing signals to be distinguished when using a binary sensor, even if the average sensor response frequency is up to 70% of the sync pulse repetition rate equal to 1 / T _o . Preferably, the average sensor response rate is less than 50% of the clock repetition rate.

An optical device for determining distances to an object according to the specified level of technology described in the patent of the Russian Federation No. 2605628, published in 2016, includes

• a radiation source to an object of a modulated binary optical signal, the input of which is connected to the output

• generator for generating a probe sequence, the first input of which is connected to the first output

• clock generator,

• optical receiving device, the output of which is connected to the input

• a multiplexer whose output is connected to the first input

• the first signal storage unit, the output of which is connected to the first input

• a module for calculating the cross-correlation function of the reference and received (detected) signals, the output of which is connected to the first input

• the second signal storage unit, the output of which is connected to the input

• demultiplexer, the output of which is connected to the input

• a threshold detection module for a signal whose output is connected to an input

• module for calculating the distance to the determined object by the time delay of the received signal, including

• module for calculating the time delay of the received signal.

This device is the closest in technical essence and the achieved technical result and is selected as a prototype of the invention.

The disadvantage of this prototype is the limited ability to simultaneously extract from the received signal correlation responses from signals reflected from the sensed objects, if the received signal contains signals with peak radiation intensities on the sensor surface lying in the range of the linear dependence of the probability of the receiving sensor from the radiation intensity of the signal at a time interval of a given duration, and signals with peak radiation intensities, the call which trigger the sensor on a time interval of the same duration with probabilities close to 100%.

Thus, the problem to which the present invention is directed is the narrow dynamic range of the lidar (OTDR), poor resolution of signals from objects with different EPR, using signals modulated by PWB as sounding signals, and the technical result is an increase in the dynamic range of the lidar using as probing signals, signals modulated by PWB.

It becomes possible to simultaneously receive and simultaneously determine the distances to the surfaces of objects reflecting signals, consisting of sequences of short optical pulses (flashes) and containing units of photons (the amount of radiated energy). The probability of a sensor triggering from each such pulse in the received sequence is proportional to the radiation intensity of the optical pulses. So are objects reflecting signals, consisting of sequences of short optical pulses and containing the number of photons (the amount of radiated energy), sufficient to trigger the sensor from each such optical pulse with a probability close to 100%.

Disclosure of invention

Based on this original observation, the present invention mainly aims to provide an optical device for determining distances to an object, which allows at least to smooth out at least one of the above disadvantages, namely, to increase the dynamic range of a lidar that uses probing signals signals modulated by pseudo-noise sequences due to the use of optical sequences modulated by PWB as probing signals radiated from binary additional codes, and as a receiving optical sensor of the lidar receiving path, a binary optical sensor operating in the nonlinear mode of the Geiger counter and allowing probabilistic (with a recording probability proportional to the number of photons contained in a short optical pulse) to register as short optical pulses incident on the sensor surface and containing units of photons, as well as optical pulses incident on the sensor surface and containing the number of photons, obviously Olsha than necessary which leads to sensor trig with probability close to 100%.

To achieve this goal:

• the device includes a signal generation module at each clock cycle n, corresponding to the value 0, if the radiation is not detected by the sensor in the time interval starting with the clock pulse n and ending with the clock pulse n + 1, and 1 or -1 if the radiation is fixed at the same time interval the first input of which is connected to the output of the receiving device (optical sensor), the second input of which is connected to the second output of the clock signal generator, and the output of which is connected to the input of the multiplexer,

• the device includes a conjunction block, the first input of which is connected to the third output of the clock signal generator, the second input of which is connected to the output of the module for calculating the distance to the detected object by the time delay of the reflected signal, the first output of which is connected to the third input of the signal conditioning module at each clock cycle , and the second output of which is connected to the second input of the first signal accumulation unit,

• the device includes a clock pulse generating unit at the beginning of the sensing cycle, the first input of which is connected to the fourth output of the clock signal generator, the first output of which is connected to the second input of the module for calculating the distance to the detected object from the time delay of the reflected signal, and the second output of which is connected to the input

• block for counting sounding cycles, the output of which is connected to the input

• a probe sampling and processing unit, the first output of which is connected to the third input of the first signal storage unit 7, the second output of which is connected to the second input of the module 8 for calculating the cross-correlation function of the emitted and reflected signals, the third output of which is connected to the second input of the second accumulation unit signal, the fourth output of which is connected to the third input of the module for calculating the distance to the detected object by the time delay of the reflected signal, the fifth output of which is connected from the second input generator creating probe sequence.

Thanks to these advantageous characteristics, it becomes possible that a binary sequence is formed in which the number of each member is confined to the number of the clock pulse, counted from the moment the probe cycle begins and takes the value “0”, if the sensor did not trigger until the next clock pulse (registration of the optical radiation quantum) , and “1” or “-1”, if the sensor triggered, this allows you to efficiently distinguish the probing signals (correlation responses) when using the binary sensor ora even if the average frequency of the sensor alarms 70% of the clock frequency of 1 / T _o.

There is an embodiment of the invention in which it includes a reference source of accurate time and frequency signals, the first output of which is connected to the input of the clock signal generator, and the second output of which is connected to the second input of the clock generating unit at the beginning of the sensing cycle.

Thanks to these advantageous characteristics, it is possible to synchronize the operation of optical devices in time, which allows several optical devices to simultaneously operate on the same probed objects in the same frequency (optical) range.

There is, in addition, an embodiment of the invention in which the reflected optical signal detection sensor, or the optical device itself, or the receiving path of the optical device is located on the optical stabilization device or is equipped with an optical stabilization device.

Due to this advantageous characteristic, it becomes possible to expand the use of the proposed solution for vehicles, in particular for unmanned aerial vehicles, which can use the proposed solution as the basis for technical vision.

There is a possible embodiment of the invention in which the optically sensitive element for detecting the reflected optical signal has a polarizing filter placed in front of the input of the optical signal to the optically sensitive element.

Due to this advantageous characteristic, it becomes possible to increase the signal-to-noise ratio and, therefore, increase the accuracy of measuring distances to reflecting objects.

There is a possible embodiment of the invention in which the sensor for detecting the reflected optical signal from the object is made in the form of elements of an optically sensitive matrix.

Thanks to this advantageous characteristic, it becomes possible to simultaneously obtain reflectograms / measure distances to a multitude of objects lying in the angle of the field of view of the optical path of the sensor.

The set of essential features of the invention is unknown from the prior art for methods of similar purpose, which allows us to conclude that the criterion of "novelty" for the invention in relation to the method. The non-obviousness of the solution indicates the non-obviousness of the solution for a person skilled in the art and thus the compliance of the invention with the criterion of "inventive step".

Brief Description of the Drawings

Other distinctive features and advantages of the present invention clearly follow from the description below for illustration and not being restrictive, with reference to the accompanying drawings, in which:

- figure 1 depicts a diagram of series-connected cascades, each of which contains a delay line and two adders, according to the prior art,

- figure 2 depicts the connection sequence of the cascades of figure 1 to generate additional sequences, according to the prior art,

- figure 3 depicts the experimentally obtained dependence of the probability of detecting a photon during a time T _o on the radiation intensity, expressed as the average number of photons arriving at the surface of the sensor under study during a time T _o , according to the prior art,

- figure 4 depicts the location of objects in the alignment of the directional radiation of the lidar,

- figures 5-8 depict fragments of a discrete sequence obtained by reading the contents of memory cells, according to the prior art,

- figure 9 depicts a functional diagram of an optical device for determining distances to an object according to the invention,

- figure 10 depicts the steps of the optical device for determining the distances to the object according to the invention.

Device description

According to FIG. 9, an optical device for determining distances to an object includes:

• radiation source 1 per object of a modulated binary optical signal, the input of which is connected to the output

• generator 3 create a probe sequence, the first input of which is connected to the first output

• generator 4 clock signal,

• non-linear optical receiving device 5, the output of which is connected to the input

• multiplexer 6, the output of which is connected to the first input

• the first block of signal accumulation 7, the output of which is connected to the first input

• module 8 for calculating the cross-correlation function of the reference and received signals, the output of which is connected to the first input

• the second block of signal accumulation 9, the output of which is connected to the input

• demultiplexer 10, the output of which is connected to the input

• module 11 threshold detection of the signal, the output of which is connected to the input

• module 12 calculating the distance to the determined object by the time delay of the reflected signal, including

• module 13 calculating the time delay of the reflected signal,

• the device includes a signal generating module 14 at each time interval starting with a clock pulse n and ending with a clock pulse n + 1, corresponding to a value of 0 if the radiation is not fixed on the time interval n confined to clock cycle n, and 1 or -1 if the radiation is fixed on the same time interval, the first input of which is connected to the output of the receiving device (optical sensor) 5, the second input of which is connected to the second output of the clock signal generator 4 and whose output is connected to the multipl exora 6,

• the device includes a conjunction block 15, the first input of which is connected to the third output of the clock signal generator 4, the second input of which is connected to the output of the module 12 for calculating the distance to the detected object by the time delay of the reflected signal, the first output of which is connected to the third input of the formation module 14 signal at each cycle, and the second output of which is connected to the second input of the first signal accumulation unit 7,

• the device includes a clock generating unit 16 at the beginning of the sensing cycle, the first input of which is connected to the fourth output of the clock signal generator 4, the first output of which is connected to the second input of the module 12 for calculating the distance to the detected object from the time delay of the reflected signal, and the second output of which connected to the input

• block 17 for counting sounding cycles, the output of which is connected to the input

• a block 18 of sampling and processing of sounding signals, the first output of which is connected to the third input of the first block of signal accumulation 7, the second output of which is connected to the second input of the module 8 for calculating the cross-correlation function of the emitted and reflected signals, the third output of which is connected to the second input of the second block the accumulation of signal 9, the fourth output of which is connected to the third input of the module 12 for calculating the distance to the detected object by the time delay of the reflected signal, the fifth output of which is connected to the second input of the probe generation generator 3.

The device optionally includes a reference source 19 of accurate time and frequency signals, the first output of which is connected to the input of the clock signal generator 4, and the second output of which is connected to the second input of the clock generating unit 16 at the beginning of the sensing cycle.

The radiation source 1 to the object / medium of the modulated binary optical signal may comprise a series-connected modulated short seed pulse generator, a seed pulse chirping module, a charm pulse amplifier and a chirped pulse compression module. The chirped pulse compression module may be located directly in front of the optical sensor (receiving device) 5. In FIG. 9 are not shown.

The sensor (receiving device) 5 (it is also an optically sensitive element for detecting the reflected optical signal, or the optical device itself, or the receiving path of the optical device) can be located on the gyroscopic stabilization device or contains an optical stabilization device. In FIG. 9 are not shown.

The sensor 5 may have a polarizing filter placed in front of the input of the optical signal to the photosensitive element. In FIG. 9 are not shown.

The sensor of the receiving device 5 can be made in the form of elements of an optically sensitive matrix.

The implementation of the invention

According to FIG. 10, an optical device for determining distances to an object operates as follows.

Here is the most comprehensive example of the invention, bearing in mind that this example does not limit the application of the invention.

Stage E1. The generator 3 creates the probe sequence modulation in the form of a binary pseudo-noise sequence, consistent with the computer VKF and radiate it into space.

Stage E2. The signal reflected from the objects is received by the optical receiving device 5.

Stage E3. A binary digital code is generated by module 14.

Stage E4. Using the module 6, multiplex the code generated in step 3 to the first accumulation block 7.

Stage E5. A binary digital code is supplied to the first accumulation unit 7, in which the discrete signal is accumulated by adding or subtracting the samples received from the output of the forming unit 14. Before starting the device, all memory cells of the first accumulation unit are reset.

Stage E6. Read the signal (sequence) accumulated in the memory cells of the accumulation unit 7, and feed it to the calculation module VKF 8.

Stage E7. Submit the sequence from the calculation module VKF 8 to the second accumulation unit 9 in the form of a discrete signal by adding or subtracting the samples received from the output of the calculation module VKF 8 with the contents of the memory cells. Before starting the device, all memory cells of the first storage unit 7 are reset.

Stage E8. The contents of the memory cells from the second storage unit 9 to the threshold detection module of the signal 11 corresponding to a specific pixel (photosensitive element for detecting the received signal from the receiving device 5) are demultiplexed using module 10 (read in a specific order).

Stage E9. If the threshold value is exceeded by one or two consecutive samples of the sample, the amplitudes and numbers of these samples are transmitted to the module 12 for calculating the distance to the determined object from the time delay of the reflected signal.

Stage E10. The distance to the reflecting object is calculated.

Stage E11. Repeat steps E1-E10.

Industrial applicability

The proposed optical device for determining distances to the object can be carried out by a specialist in practice and, when implemented, ensures the implementation of the declared purpose, which allows us to conclude that the criterion of "industrial applicability" for the invention is met.

In accordance with the proposed invention, calculations were made of the operation of the optical device to determine the distances to the object.

Calculations of the operation of the device showed that it provides the lidar if the reflected signal is a superposition of signals reflected from the detected / probed objects, and the superposition of the signals contains at least one reflected signal with light pulse intensities exceeding the dynamic range of the optical receiving device, This device provides reliable detection of signals from all objects.

Moreover, if in the method according to the patent of the Russian Federation No. 2605628, the received signal was generated in the form of a digital sequence supplied to the first accumulation unit, where the sequence member number is confined to the sync pulse number, according to which the integration of the photocurrent starts or ends on the time interval T _o , then in the present invention is formed a binary sequence in which the number of each member is confined to the number of the sync pulse, counted from the moment the probe cycle begins and takes on the value “0”, if before The sensor did not trigger the clock (registration of the optical edge), and “1” or “-1” if the sensor triggered.

Thus, in this invention, the goal is achieved - to increase the dynamic range of the lidar using signals modulated by pseudo-noise sequences as probing signals due to the use of optical sequences modulated by PWB as probing signals from PWBs obtained from binary additional sequences, and as a receiving optical sensor, a binary optical sensor operating in a nonlinear mode of a Geiger counter and allowing probabilistic but (with a probability of registration proportional to the number of photons contained in a short optical pulse), register both short optical pulses incident on the sensor surface and containing units of photons, and optical pulses incident on the sensor surface and containing a number of photons that are known to be larger than necessary I trigger the sensor with a probability close to 100%.

It is recommended to use this invention for:

 - vision systems, including for aircraft, robotic systems, incoherent reflectometers, terahertz radars.

Although the invention has been described in detail with examples of options that appear to be preferred, it must be remembered that these examples of the invention are provided only to illustrate the invention. This description should not be construed as limiting the scope of claims of the invention, since the circuit of the described invention by specialists in the field of signal processing and design of integrated circuits, etc. may be amended to adapt the invention to specific devices or situations, and not beyond the scope of the attached claims. Specialist in the art will understand that within the scope of the invention, which is determined by the claims, various variations and modifications are possible, including equivalent solutions.

Claims (23)

1. An optical device for determining distances to an object, including: • a radiation source to an object of a modulated binary optical signal, the input of which is connected to the output • generator for generating a probe sequence, the first input of which is connected to the first output • clock generator, • non-linear optical receiving device, the output of which is connected to the input • a multiplexer whose output is connected to the first input • the first signal storage unit, the output of which is connected to the first input • a module for calculating the cross-correlation function of the reference and received signals, the output of which is connected to the first input • the second signal storage unit, the output of which is connected to the input • demultiplexer, the output of which is connected to the input the threshold detection module of the signal, the output of which is connected to the input • module for calculating the distance to the determined object by the time delay of the reflected signal, including • module for calculating the time delay of the reflected signal, characterized in that • the device includes a signal generation module at each clock cycle n, corresponding to the value 0, if the radiation is not detected by the sensor in the time interval starting at the clock pulse n and ending at the clock pulse n + 1, and 1 or -1, if the radiation is fixed at the same a time interval, the first input of which is connected to the output of the receiving device (optical sensor), the second input of which is connected to the second output of the clock signal generator, and the output of which is connected to the input of the multiplexer, • the device includes a conjunction block, the first input of which is connected to the third output of the clock signal generator, the second input of which is connected to the output of the module for calculating the distance to the detected object by the time delay of the reflected signal, the first output of which is connected to the third input of the signal conditioning module at each clock cycle , and the second output of which is connected to the second input of the first signal accumulation unit, • the device includes a clock pulse generating unit at the beginning of the sensing cycle, the first input of which is connected to the fourth output of the clock signal generator, the first output of which is connected to the second input of the module for calculating the distance to the detected object from the time delay of the reflected signal, and the second output of which is connected to the input • block for counting sounding cycles, the output of which is connected to the input • a probe sampling and processing unit, the first output of which is connected to the third input of the first signal storage unit, the second output of which is connected to the second input of the module for calculating the cross-correlation function of the emitted and reflected signals, the third output of which is connected to the second input of the second signal storage unit, the fourth output of which is connected to the third input of the module for calculating the distance to the detected object by the time delay of the reflected signal, the fifth output of which is connected to the second Odom generator creating probe sequence. 2. The optical device according to claim 1, characterized in that it includes a reference source of accurate time and frequency signals, the first output of which is connected to the input of the clock signal generator, and the second output of which is connected to the second input of the clock generating unit at the beginning of the probe cycle . 3. The optical device according to claim 1, characterized in that the sensor for detecting the reflected optical signal, or the optical device itself, or the receiving path of the optical device is located on the optical stabilization device or is equipped with an optical stabilization device. 4. The optical device according to claim 1, characterized in that the optically sensitive element for detecting the reflected optical signal has a polarizing filter placed in front of the input of the optical signal to the optically sensitive element. 5. The optical device according to claim 1, characterized in that the sensor for detecting the reflected optical signal from the object is made in the form of elements of an optically sensitive matrix.

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