CN115902920A - Coherent and incoherent laser cooperative detection method and system for aerial moving object - Google Patents
Coherent and incoherent laser cooperative detection method and system for aerial moving object Download PDFInfo
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Abstract
The invention provides a coherent and incoherent laser cooperative detection method and a system for an aerial moving target, which belong to the technical field of laser radar detection and comprise the following steps: acquiring an instantaneous laser distance image corresponding to each scanning direction; carrying out image splicing on the instantaneous laser distance image to obtain a single-photon three-dimensional distance image; extracting a distance extreme point in the single-photon three-dimensional distance image, and taking the distance extreme point as a suspected air moving target position; sequentially carrying out high-coherence laser pulse precision scanning and laser heterodyne detection on the position of a suspected air moving target so as to obtain an intermediate frequency signal of the suspected air moving target; acquiring motion characteristic information of a suspected aerial moving target; and correcting the single-photon three-dimensional distance image after confirming the suspected air moving target. The invention can realize accurate laser three-dimensional imaging with low false alarm rate under the consideration of large-field active detection, high-efficiency target search and small-field accurate measurement accuracy.
Description
Technical Field
The invention belongs to the technical field of laser radar detection, and particularly relates to a coherent and incoherent laser cooperative detection method and system for an aerial moving target.
Background
The laser detection technology has the capability of acquiring information of more than three dimensions of a target with high precision, and becomes a new means for key development of national defense safety and remote sensing detection. When the laser detection system and the target are in relative static states, the high-precision capability of the laser detection system and the target can be fully embodied, but when the laser detection system and the target move relatively, particularly for low-detectability aerial targets such as stealth airplanes and the like, due to the adoption of active and passive countermeasure technologies such as electronic countermeasure and stealth technologies, the capability of accurately acquiring multi-dimensional information of the target by traditional detection means such as infrared and radar is weakened, and particularly when remote detection is carried out, factors such as high background noise, complex transmission path and the like are faced, so that the measurement precision, the false alarm rate, the information acquisition dimension and the like are difficult to achieve ideal effects.
Disclosure of Invention
One of the objectives of the present invention is to provide a coherent and incoherent laser cooperative detection method for an aerial moving object, which can realize accurate laser three-dimensional imaging with low false alarm rate while considering large-field active detection, efficient object search and small-field accurate measurement accuracy.
The invention also aims to provide a coherent and incoherent laser cooperative detection system for the aerial moving object.
In order to achieve one of the purposes, the invention adopts the following technical scheme:
a coherent and incoherent laser cooperative detection method for an aerial moving object comprises the following steps:
the method comprises the following steps of S1, carrying out narrow-pulse multi-frequency laser rough scanning and single photon area array detection on possible areas of an air moving target in sequence to obtain an instantaneous laser distance image corresponding to each scanning direction;
s2, carrying out image splicing on the instantaneous laser distance images corresponding to all scanning directions to obtain single-photon three-dimensional distance images;
s3, extracting a distance extreme point in the single-photon three-dimensional distance image, and taking the distance extreme point as a suspected air moving target position;
s4, sequentially performing high-coherence laser pulse precision scanning and laser heterodyne detection on the position of the suspected air moving target to obtain an intermediate frequency signal of the suspected air moving target;
s5, acquiring motion characteristic information of the suspected aerial motion target according to the intermediate frequency signal;
and S6, correcting the single-photon three-dimensional distance image after confirming the suspected air moving target according to the movement characteristic information of the suspected air moving target.
Further, in the step S1, the specific process of acquiring the instantaneous laser distance image corresponding to each scanning direction includes:
s11, determining a relatively prime pulse period corresponding to each repetition frequency in the narrow-pulse multi-repetition-frequency laser to calculate the maximum non-fuzzy distance of the single-photon area array detection;
step S12, carrying out time-correlated single photon counting on a plurality of photon echo signals detected by the single photon area array in each scanning direction to determine a photon waveform detected by the single photon area array in each scanning direction;
s13, performing waveform noise reduction on the photon waveform detected by the single photon area array in each scanning direction;
step S14, constant ratio timing processing is carried out on the photon waveform subjected to waveform noise reduction to obtain echo time delay corresponding to each repetition frequency in the narrow-pulse multi-frequency laser;
s15, according to the maximum non-fuzzy distance and the echo time delay, distance fuzzy solving is conducted on the narrow-pulse multi-frequency laser scanning frame, and each point cloud in the narrow-pulse multi-frequency laser scanning frame and a first distance value of each point cloud in the single-photon area array detection direction are obtained;
and S16, carrying out self-adaptive noise reduction on each point cloud of the narrow-pulse multi-frequency laser scanning frame to obtain an instantaneous laser distance image corresponding to each scanning direction.
Further, in step S13, the specific implementation process of the waveform noise reduction includes:
s131, performing energy decomposition on the photon waveform detected by the single photon area array in each scanning direction to obtain a sub-waveform component corresponding to each energy of the photon waveform;
s132, removing the sub-waveform components corresponding to the high-frequency low-amplitude from all the sub-waveform components, and acquiring a local maximum value point and a local minimum value point of each removed sub-waveform component;
the wavelet components corresponding to the high frequency and the low amplitude are the first 2~3 wavelet components in all the wavelet components;
step S133, calculating a first average value of all local maximum value points and a second average value of all local minimum value points, and taking the average value of the first average value and the second average value as a first threshold value;
and S134, eliminating the sub-waveform component corresponding to the local maximum value point smaller than the first threshold value to obtain the waveform-denoised photon waveform.
Further, in the step S5, the motion characteristic information includes a distance, a speed, a micro-vibration frequency, and a micro-vibration amplitude; the specific process for acquiring the motion characteristic information of the suspected air moving object comprises the following steps:
sequentially performing empirical mode decomposition noise reduction, hilbert transform and waveform decomposition on the intermediate frequency signal to determine a second distance value of the suspected aerial moving target in the laser heterodyne detection direction;
sequentially carrying out full-phase Fourier transform, data windowing processing and maximum discrete spectral peak estimation on the intermediate frequency signal to obtain a suspected air moving target speed corresponding to the frequency shift of the intermediate frequency signal;
and acquiring a time-frequency curve of the intermediate-frequency signal to determine the micro-vibration frequency and the micro-vibration amplitude of the suspected aerial moving target.
Further, the specific implementation process of step S6 includes:
s61, judging whether the speed, the micro-vibration frequency and the micro-vibration amplitude of the suspected aerial moving target are all larger than respective corresponding second threshold values, if so, entering S62; if not, ending;
s62, judging the high signal-to-noise ratio and the low signal-to-noise ratio of the intermediate frequency signal;
and S63, calculating a target distance correction amount according to the judgment result and the first distance value and the second distance value, and correcting the single photon three-dimensional distance image.
In order to achieve the second purpose, the invention adopts the following technical scheme:
a coherent and incoherent laser cooperative detection system for an airborne moving object, the coherent and incoherent laser cooperative detection system comprising:
the device comprises a first detection module, a second detection module and a third detection module, wherein the first detection module is used for carrying out narrow-pulse multi-frequency laser rough scanning and single photon area array detection on a possible existing area of an aerial moving target in sequence so as to obtain an instantaneous laser distance image corresponding to each scanning direction;
the image splicing module is used for carrying out image splicing on the instantaneous laser distance images corresponding to all the scanning directions to obtain single-photon three-dimensional distance images;
the extraction module is used for extracting a distance extreme point in the single-photon three-dimensional distance image and taking the distance extreme point as a suspected air moving target position;
the second detection module is used for sequentially performing high-coherence laser pulse precision scanning and laser heterodyne detection on the position of the suspected air moving target so as to obtain an intermediate frequency signal of the suspected air moving target;
the acquisition module is used for acquiring the motion characteristic information of the suspected air moving target according to the intermediate frequency signal;
and the image correction module is used for correcting the single-photon three-dimensional distance image after confirming the suspected air moving target according to the motion characteristic information of the suspected air moving target.
Further, the first detection module comprises:
the first calculation submodule is used for determining a relatively prime pulse period corresponding to each repetition frequency in the narrow-pulse multi-frequency laser so as to calculate the maximum non-fuzzy distance detected by the single photon area array;
the counting submodule is used for carrying out time-correlated single photon counting on a plurality of photon echo signals detected by the single photon area array in each scanning direction so as to determine a photon waveform detected by the single photon area array in each scanning direction;
the waveform noise reduction submodule is used for carrying out waveform noise reduction on the photon waveform detected by the single photon area array in each scanning direction;
the constant ratio timing processing submodule is used for carrying out constant ratio timing processing on the photon waveform subjected to waveform noise reduction to obtain echo time delay corresponding to each repetition frequency in the narrow-pulse multi-frequency laser;
the distance-resolving fuzzy processing submodule is used for carrying out distance-resolving fuzzy processing on the narrow-pulse multi-frequency laser scanning frame according to the maximum non-fuzzy distance and the echo time delay to obtain each point cloud in the narrow-pulse multi-frequency laser scanning frame and a first distance value of each point cloud in the single-photon area array detection direction;
and the self-adaptive noise reduction sub-module is used for carrying out self-adaptive noise reduction on each point cloud of the narrow-pulse multi-frequency laser scanning frame to obtain an instantaneous laser distance image corresponding to each scanning direction.
Further, the waveform noise reduction submodule includes:
the energy decomposition unit is used for carrying out energy decomposition on the photon waveform detected by the single photon area array in each scanning direction to obtain sub-waveform components corresponding to each energy of the photon waveform;
the first eliminating unit is used for eliminating the sub-waveform components corresponding to the high frequency and the low amplitude from all the sub-waveform components and acquiring the local maximum value point and the local minimum value point of each sub-waveform component after elimination;
the wavelet components corresponding to the high frequency and the low amplitude are the first 2~3 wavelet components in all the wavelet components;
the calculating unit is used for calculating a first average value of all local maximum value points and a second average value of all local minimum value points, and taking the average value of the first average value and the second average value as a first threshold value;
and the second eliminating unit is used for eliminating the sub-waveform components corresponding to the local maximum value points smaller than the first threshold value to obtain the photon waveform after waveform noise reduction.
Further, the motion characteristic information comprises distance, speed, micro-vibration frequency and micro-vibration amplitude; the acquisition module includes:
the waveform decomposition submodule is used for sequentially carrying out empirical mode decomposition noise reduction, hilbert transform and waveform decomposition on the intermediate frequency signal so as to determine a second distance value of the suspected aerial moving target in the laser heterodyne detection direction;
the maximum discrete spectrum peak estimation submodule is used for sequentially carrying out full-phase Fourier transform, data windowing processing and maximum discrete spectrum peak estimation on the intermediate frequency signal so as to obtain a suspected air moving target speed corresponding to the frequency shift of the intermediate frequency signal;
and the acquisition submodule is used for acquiring a time-frequency curve of the intermediate-frequency signal so as to determine the micro-vibration frequency and the micro-vibration amplitude of the suspected aerial moving target.
Further, the image modification module includes:
the first judgment submodule is used for judging whether the speed, the micro-vibration frequency and the micro-vibration amplitude of the suspected aerial moving target are all larger than respective corresponding second threshold values, if so, the intermediate frequency signal is transmitted to the second judgment submodule; if not, ending;
the second judgment submodule is used for judging the high signal-to-noise ratio and the low signal-to-noise ratio of the intermediate frequency signal;
and the second calculation submodule is used for calculating a target distance correction quantity according to the judgment result, the first distance value and the second distance value and correcting the single-photon three-dimensional distance image.
In summary, the scheme provided by the invention has the following technical effects:
according to the method, an instantaneous laser distance image corresponding to each scanning direction is obtained through narrow-pulse multi-frequency laser rough scanning and single-photon area array detection; carrying out image splicing on each instantaneous laser distance image to obtain a single-photon three-dimensional distance image; determining the position of a suspected aerial moving target by using a distance extreme point in the single-photon three-dimensional distance image; taking the position of the suspected aerial moving target as guide information, and sequentially performing high-coherence laser pulse precision scanning and laser heterodyne detection on the position of the suspected aerial moving target to obtain an intermediate frequency signal of the suspected aerial moving target; the method has the advantages that the motion characteristic information of the suspected air moving target is obtained through the intermediate frequency signal, the suspected air moving target is confirmed, the single-photon three-dimensional distance image is corrected, the detection efficiency, the detection reliability and the multi-dimensional information obtaining capability of the low-detectability air moving target are improved, the large-view-field active detection, the high-efficiency target search and the small-view-field precise measurement capability are considered, the false alarm rate is low, the distance measurement precision is high, and an effective method is provided for the precise and reliable detection of the air moving target.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic flow chart of a coherent and incoherent laser cooperative detection method for an airborne moving object according to the present invention;
FIG. 2 is a schematic diagram of target micro-motion characteristic detection according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The embodiment provides a coherent and incoherent laser cooperative detection method for an aerial moving object, and referring to fig. 1, the coherent and incoherent laser cooperative detection method includes the following steps:
s1, carrying out narrow-pulse multi-frequency laser coarse scanning and single-photon area array detection on areas where the moving targets possibly exist in the air in sequence to obtain instantaneous laser distance images corresponding to each scanning direction.
The embodiment realizes coarse scanning by emitting narrow-pulse multi-frequency laser to the area string where the aerial moving target may exist. The photon echo is received by the receiving and transmitting combined optical system, and the photon echo sequence detected by the single photon area array detection component is subjected to time-correlated single photon counting to obtain a photon waveform.
The specific process of acquiring the instantaneous laser distance image corresponding to each scanning direction in this embodiment includes:
s11, determining a relatively prime pulse period corresponding to each repetition frequency in the narrow-pulse multi-repetition-frequency laser to calculate the maximum non-fuzzy distance of the single-photon area array detection.
The maximum unambiguous distance of single-photon area array detection in this embodiment is:
R max =c[T 1 ,T 2 ,…,T n ]/2；
wherein the content of the first and second substances,R max the maximum non-fuzzy distance of single photon area array detection;cis the speed of light;T 1 ,T 2 ,…,T n respectively corresponding to each repetition frequency in the narrow-pulse multi-frequency laser,nis the number of repetition frequencies; [T 1 ,T 2 ,…,T n ]For the equivalent period of the narrow-pulse multi-frequency laser, takenThe least common multiple of the period of each pulse. Each pulse period in this embodiment is a relatively prime pulse period.
And S12, carrying out time-correlated single photon counting on a plurality of photon echo signals detected by the single photon area array in each scanning direction to determine the photon waveform detected by the single photon area array in each scanning direction.
The single photon area array detector can generate an avalanche effect due to both target photons and noise photons. But the time correlation of the noise photons is weak, the avalanche effect is triggered randomly and is distributed uniformly in the detection time interval. The target echo photon has strong time correlation and aggregation property in certain time windows, and a detected target echo signal can generate an envelope shape similar to a laser emergent waveform after being accumulated by multiple pulses. And accumulating a plurality of pulse echo photons within the set arrival time to obtain a photon echo histogram. Photons corresponding to the peak value of the photon echo histogram smaller than the photon threshold value are noise photons, photons corresponding to the peak value of the photon echo histogram larger than the photon threshold value are target photons, and the envelope of the photon echo histogram is a photon waveform.
And S13, performing waveform noise reduction on the photon waveform detected by the single photon area array in each scanning direction.
The photon waveform obtained by adopting the time correlation single photon counting method contains more random noise, and the laser echo has obvious non-stationarity due to the complex motion of the target, so that both high-frequency and low-frequency characteristics are required during filtering processing. The specific implementation process of waveform noise reduction comprises the following steps:
s131, performing energy decomposition on the photon waveform detected by the single photon area array in each scanning direction to obtain a sub-waveform component corresponding to each energy of the photon waveform;
and carrying out different energy decomposition on the photon waveform to obtain each sub-waveform component, wherein the sub-waveform components can be represented by multiple groups of eigenmode functions IMF and trend components.
S132, removing the sub-waveform components corresponding to the high-frequency low-amplitude from all the sub-waveform components, and acquiring a local maximum value point and a local minimum value point of each removed sub-waveform component;
the first 2~3 of all the wavelet components of the present embodiment almost concentrates the high-frequency low-amplitude portion of the entire noisy signal (i.e., is the main portion of the noise in the signal), so that these wavelet components can be removed from the decomposed signal.
Because the low-frequency wavelet components after being removed contain certain noise components, each IMF component (namely, the wavelet component) is processed by using a threshold value method. And determining local maximum value points and local minimum value points of the sub-waveform components through an energy decomposition process.
Step S133, calculating a first average value of all local maximum value points and a second average value of all local minimum value points, and taking the average value of the first average value and the second average value as a first threshold value;
and S134, eliminating the sub-waveform component corresponding to the local maximum value point smaller than the first threshold value to obtain the waveform-denoised photon waveform.
And S14, carrying out constant ratio timing processing on the waveform-denoised photon waveform to obtain echo time delay corresponding to each repetition frequency in the narrow-pulse multi-frequency laser.
And determining the echo time delay of the multi-frequency pulse detection by adopting a constant ratio timing method for the photon waveform after noise reduction.
And S15, performing distance ambiguity resolution on the narrow-pulse multi-frequency laser scanning frame according to the maximum unambiguous distance and the echo time delay to obtain each point cloud in the narrow-pulse multi-frequency laser scanning frame and a first distance value of each point cloud in the single photon area array detection direction.
In this embodiment, the distance value of the point cloud corresponding to each repetition frequency in the single photon area array detection direction can be obtained by the following equation:
R=c(q 1 T 1 +t 1 )/2=c(q 2 T 2 +t 2 )/2=…=c(q i T i +t i )/2=…=c(q n T n +t n )/2；
wherein the content of the first and second substances,Rthe distance value of the point cloud corresponding to each repetition frequency in the single photon area array detection direction is obtained;cis the speed of light;T 1 ,T 2 ,…,T n respectively corresponding to each repetition frequency in the narrow-pulse multi-frequency laser,nis the number of repetition frequencies;t 1 ,t 2 ,…,t n echo time delay, 0, corresponding to each repetition frequency in narrow-pulse multi-frequency laser<t n <T n ；q 1 ,q 2 ,…,q n The number of pulse periods corresponding to each echo time delay is a positive integer.
When in useRLess than the maximum unambiguous distance of single-photon area array detectionR max When the frequency is not equal to the frequency of the second group, the second group of the repetition frequencies can be obtainedRValue, and all ofRIs taken as a first distance value of each point cloud in the single photon area array detection directionR t 。
And S16, carrying out self-adaptive noise reduction on each point cloud of the narrow-pulse multi-frequency laser scanning frame to obtain an instantaneous laser distance image corresponding to each scanning direction.
The important characteristic of the three-dimensional point cloud is the characteristic of similar distance of echoes generated by the same target on a two-dimensional surface, or referred to as spatial neighborhood correlation. When the laser spot is smaller than the target, the adjacent detection points often correspond to local parts of the same target, and the local parts of the object do not have an extraordinary bulge, so that the local neighborhoods have similar distances. By means of the characteristic, the adaptive noise reduction is carried out on each point cloud of the narrow-pulse multi-frequency laser scanning frame.
And S2, carrying out image splicing on the instantaneous laser distance images corresponding to all scanning directions to obtain single-photon three-dimensional distance images.
And S3, extracting a distance extreme point in the single-photon three-dimensional distance image, and taking the distance extreme point as a suspected air moving target position.
When the laser active single-photon three-dimensional imaging is adopted for the air detection, the background is relatively simple, only a few extreme points exist, and the distance extreme points in the single-photon three-dimensional distance image can be the target position, namely the suspected air moving target position.
And S4, sequentially carrying out high-coherence laser pulse precision scanning and laser heterodyne detection on the position of the suspected air moving target so as to obtain an intermediate frequency signal of the suspected air moving target.
In the embodiment, the suspected air moving target position is used as the guide information, and the servo system is used for performing precise scanning, that is, high-coherence laser pulses are transmitted to the suspected air moving target position, and the echo is received in a heterodyne detection mode.
And S5, acquiring the motion characteristic information of the suspected air motion target according to the intermediate frequency signal.
In the embodiment, the intermediate frequency signal is utilized to obtain multi-dimensional information such as the distance, the speed, the micro-vibration frequency, the micro-vibration amplitude and the like of the suspected aerial moving target. And then judging the existence information of the target (namely whether the target is a real target) by utilizing the speed, the micro-vibration frequency and the micro-vibration amplitude of the suspected aerial moving target, and calculating the target distance correction amount to realize the correction of the single-photon three-dimensional distance image. In this embodiment, the motion characteristic information includes a distance, a speed, a micro-vibration frequency, and a micro-vibration amplitude. The specific process for acquiring the motion characteristic information of the suspected aerial motion target comprises the following steps:
1. performing empirical mode decomposition noise reduction, hilbert transform and waveform decomposition on the intermediate-frequency signal in sequence to determine a second distance value of the suspected aerial moving target in the laser heterodyne detection direction;
in order to reduce envelope distortion, the embodiment adopts an empirical mode EMD decomposition method to reduce noise of the intermediate frequency signal, and then obtains the envelope of the intermediate frequency signal by using a hilbert demodulation method.
The air moving target usually has a complex structure, and when a target in a laser spot has a plurality of distance distributions, a laser echo can be regarded as superposition of sub echoes of each microstructure of the target in the radial direction of laser heterodyne detection.
After the intermediate frequency signal after Hilbert conversion is subjected to waveform decomposition, the echo time delay of each component waveform is obtainedt m ，m=1,2,…M，MThe number of the component waveforms is obtained, and then a second distance value of the suspected air moving target in the laser heterodyne detection direction is obtained as follows:
；
wherein the content of the first and second substances,R h a second distance value of the suspected air moving target in the laser heterodyne detection direction is obtained;cis the speed of light;t m is a firstmThe echo time delay of the waveform of each component,m=1,2,…M，Mis the number of component waveforms.
2. Carrying out full-phase Fourier transform, data windowing processing and maximum discrete spectral peak estimation on the intermediate frequency signal in sequence to obtain a suspected air moving target speed corresponding to the frequency shift of the intermediate frequency signal;
the full-phase FFT (apFFT) has excellent capability of suppressing spectrum leakage, thereby reducing the inter-spectrum interference of each frequency component, highlighting the intermediate frequency signal, being beneficial to extracting the frequency and the amplitude of the signal and needing no extra correction measures.
In the embodiment, a Hannning window is adopted for data windowing, so that the frequency spectrum leakage is further reduced. And then extracting the maximum discrete spectrum peak value from the frequency spectrum, wherein the speed of a suspected aerial moving target corresponding to the frequency shift of the intermediate frequency signal is as follows:
；
wherein the content of the first and second substances,vis composed ofThe suspected air moving object speed corresponding to the frequency shift of the frequency signal;kthe frequency point sequence number corresponding to the maximum discrete spectrum peak value in the intermediate frequency signal frequency spectrum; λ is the laser wavelength;f s is the echo sampling rate; delta off shift Is the initial frequency shift amount of the intermediate frequency signal;Nthe number of sampling points of the intermediate frequency signal is obtained.
3. And acquiring a time-frequency curve of the intermediate-frequency signal to determine the micro-vibration frequency and the micro-vibration amplitude of the suspected air moving target.
In this embodiment, the intermediate frequency signal is processed by a smooth pseudo wigner-wiry distribution (SPWVD) method to obtain a time-frequency curve. The time-frequency curve obtained by the method can still keep higher time-frequency aggregation performance under the condition of low signal-to-noise ratio. Then, the corresponding relation between each pixel point in the time-frequency curve and time and frequency is utilized, a first time-frequency curve of a single pixel is obtained through cosine law fitting, and the amplitude value of the first time-frequency curve is obtained through fast Fourier transform of the first time-frequency curveASum frequencyf v The amplitude is a function of the target micro-vibration amplitude, and the frequency is the micro-vibration frequency of the suspected aerial moving target.
As shown in fig. 2, the lidar is located at the origin of a fixed coordinate system (X, Y, Z),Pthe point represents a scattering center of a suspected airborne moving object in a reference coordinate system (A), (B), (C)x,y,z) Origin pointQIs a central edge
The direction is simple harmonic vibration.α p Andβ p respectively represent->
In a coordinate system ofx,y,z) The azimuth angle and the pitch angle in (1),αandβrespectively representQAzimuth and elevation angles of the points relative to the lidar.
The micro-vibration amplitude of the suspected aerial moving target of this embodiment is:
wherein the content of the first and second substances,D v the micro-vibration amplitude of the suspected aerial moving target is obtained;Athe amplitude of the first time-frequency curve;f v the micro-vibration frequency of the suspected aerial moving target is obtained; λ is the laser wavelength;βthe pitch angle of the origin of a fixed coordinate system where the laser radar is located relative to the laser radar is set;α p is the azimuth angle of the micro-vibration direction of the suspected airborne moving object in the reference coordinate system.
S6, according to the motion characteristic information of the suspected aerial motion target, correcting the single-photon three-dimensional distance image after confirming the suspected aerial motion target.
The target speed of cloud layer, flying bird and the like is relatively low relative to the supersonic cruising speed of the stealth aircraft, and a speed threshold value is setv th =40m/s whenv>v th Then the pulse echo originates from the low detectability target body.
When it is satisfied withf v >f th And isD v >D th Then the pulse echoes originate from low detectability target bodies.f th AndD th respectively a jiggle frequency threshold and a jiggle amplitude threshold.
To reduce the false alarm rate, whenv>v th 、f v >f th AndD v >D th when satisfied at the same time, the pulse echo is derived from a low detectability target body. Therefore, the specific implementation process of this step includes:
s61, judging whether the speed, the micro-vibration frequency and the micro-vibration amplitude of the suspected aerial moving target are all larger than respective corresponding second threshold values, if so, entering S62; if not, ending;
and S62, judging the high signal-to-noise ratio and the low signal-to-noise ratio of the intermediate frequency signal.
When the intermediate frequency signal isSignal to noise ratioSNRGreater than a signal-to-noise ratio thresholdSNR th When the signal to noise ratio of the intermediate frequency signal is high, the signal to noise ratio of the intermediate frequency signal is high; otherwise, the signal-to-noise ratio of the intermediate frequency signal is a low signal-to-noise ratio.
And S63, calculating a target distance correction quantity according to the judgment result and the first distance value and the second distance value, and correcting the single photon three-dimensional distance image.
When the judgment result is a high signal-to-noise ratio, the target distance correction quantity is:
ΔR 1 =R t -R h ；
wherein, deltaR 1 Is the target distance correction amount;R t andR h the first distance value of the suspected air moving target in the single photon area array detection direction and the second distance value of the suspected air moving target in the laser heterodyne detection direction are respectively.
When the judgment result is a low signal-to-noise ratio, the target distance correction quantity is:
wherein, deltaR 2 Is a target distance correction amount;R t andR h respectively obtaining a first distance value of the suspected aerial moving target in the single photon area array detection direction and a second distance value in the laser heterodyne detection direction;SNR t andSNR h the signal-to-noise ratios during single-photon area array detection and laser heterodyne detection are respectively.
In this embodiment, a first distance value of the suspected airborne moving object in the single photon area array detection direction is: and a first distance value of a point cloud corresponding to a suspected air moving target in the narrow-pulse multi-frequency laser scanning frame in the single photon area array detection direction. And performing distance correction on each point cloud in the single-photon three-dimensional distance image by adopting the target distance correction quantity.
In the embodiment, instantaneous laser distance images corresponding to each scanning direction are obtained through narrow-pulse multi-frequency laser rough scanning and single-photon area array detection; carrying out image splicing on each instantaneous laser distance image to obtain a single-photon three-dimensional distance image; determining the position of a suspected aerial moving target by using a distance extreme point in the single-photon three-dimensional distance image; taking the position of the suspected aerial moving target as guide information, and sequentially performing high-coherence laser pulse precision scanning and laser heterodyne detection on the position of the suspected aerial moving target to obtain an intermediate frequency signal of the suspected aerial moving target; the method has the advantages that the movement characteristic information of the suspected air moving target is obtained through the intermediate frequency signal, so that the suspected air moving target is confirmed, the correction of a single-photon three-dimensional distance image is realized, the detection efficiency, the detection reliability and the multi-dimensional information obtaining capability of the low-detectability air moving target are improved, the large-view-field active detection, the high-efficiency target search and the small-view-field precise measurement capability are considered, the false alarm rate is low, the distance measurement precision is high, and an effective method is provided for the precise and reliable detection of the air moving target.
The embodiment can be realized by adopting a coherent and incoherent laser cooperative detection system of an aerial moving object, which is given by the following embodiments:
another embodiment provides a coherent and incoherent laser cooperative detection system for an airborne moving object, including:
the device comprises a first detection module, a second detection module and a third detection module, wherein the first detection module is used for carrying out narrow-pulse multi-frequency laser rough scanning and single photon area array detection on a possible existing area of an aerial moving target in sequence so as to obtain an instantaneous laser distance image corresponding to each scanning direction;
the image splicing module is used for carrying out image splicing on the instantaneous laser distance images corresponding to all scanning directions to obtain single-photon three-dimensional distance images;
the extraction module is used for extracting a distance extreme point in the single-photon three-dimensional distance image and taking the distance extreme point as a suspected air moving target position;
the second detection module is used for sequentially performing high-coherence laser pulse precision scanning and laser heterodyne detection on the position of the suspected air moving target so as to obtain an intermediate frequency signal of the suspected air moving target;
the acquisition module is used for acquiring the motion characteristic information of the suspected aerial motion target according to the intermediate frequency signal;
and the image correction module is used for correcting the single-photon three-dimensional distance image after confirming the suspected aerial moving target according to the movement characteristic information of the suspected aerial moving target.
Further, the first detection module comprises:
the first calculation submodule is used for determining a relatively prime pulse period corresponding to each repetition frequency in the narrow-pulse multi-frequency laser so as to calculate the maximum non-fuzzy distance detected by the single photon area array;
the counting submodule is used for carrying out time-correlated single photon counting on a plurality of photon echo signals detected by the single photon area array in each scanning direction so as to determine a photon waveform detected by the single photon area array in each scanning direction;
the waveform noise reduction submodule is used for carrying out waveform noise reduction on the photon waveform detected by the single photon area array in each scanning direction;
the constant ratio timing processing submodule is used for carrying out constant ratio timing processing on the photon waveform subjected to waveform noise reduction to obtain echo time delay corresponding to each repetition frequency in the narrow-pulse multi-frequency laser;
the distance-resolving fuzzy processing submodule is used for carrying out distance-resolving fuzzy processing on the narrow-pulse multi-frequency laser scanning frame according to the maximum non-fuzzy distance and the echo time delay to obtain each point cloud in the narrow-pulse multi-frequency laser scanning frame and a first distance value of each point cloud in the single-photon area array detection direction;
and the self-adaptive noise reduction sub-module is used for carrying out self-adaptive noise reduction on each point cloud of the narrow-pulse multi-frequency laser scanning frame to obtain an instantaneous laser distance image corresponding to each scanning direction.
Further, the waveform noise reduction sub-module includes:
the energy decomposition unit is used for carrying out energy decomposition on the photon waveform detected by the single photon area array in each scanning direction to obtain sub-waveform components corresponding to each energy of the photon waveform;
the first eliminating unit is used for eliminating the sub-waveform components corresponding to the high frequency and the low amplitude from all the sub-waveform components and acquiring the local maximum value point and the local minimum value point of each sub-waveform component after elimination;
the wavelet components corresponding to the high frequency and the low amplitude are the first 2~3 wavelet components in all the wavelet components;
the calculating unit is used for calculating a first average value of all local maximum value points and a second average value of all local minimum value points, and taking the average value of the first average value and the second average value as a first threshold value;
and the second eliminating unit is used for eliminating the sub-waveform components corresponding to the local maximum value points smaller than the first threshold value to obtain the waveform of the photons subjected to waveform noise reduction.
Further, the motion characteristic information comprises a distance, a speed, a micro-vibration frequency and a micro-vibration amplitude; the acquisition module includes:
the waveform decomposition submodule is used for sequentially carrying out empirical mode decomposition noise reduction, hilbert transform and waveform decomposition on the intermediate frequency signal so as to determine a second distance value of the suspected aerial moving target in the direction of laser heterodyne detection;
the maximum discrete spectrum peak estimation submodule is used for sequentially carrying out full-phase Fourier transform, data windowing processing and maximum discrete spectrum peak estimation on the intermediate frequency signal so as to obtain a suspected air moving target speed corresponding to the frequency shift of the intermediate frequency signal;
and the acquisition submodule is used for acquiring a time-frequency curve of the intermediate-frequency signal so as to determine the micro-vibration frequency and the micro-vibration amplitude of the suspected aerial moving target.
Further, the image modification module includes:
the first judgment submodule is used for judging whether the speed, the micro-vibration frequency and the micro-vibration amplitude of the suspected aerial moving target are all larger than respective corresponding second threshold values, if so, the intermediate frequency signal is transmitted to the second judgment submodule; if not, ending;
the second judgment submodule is used for judging the high signal-to-noise ratio and the low signal-to-noise ratio of the intermediate frequency signal;
and the second calculation submodule is used for calculating a target distance correction amount according to the judgment result, the first distance value and the second distance value and correcting the single-photon three-dimensional distance image.
The principles, formulas and parameter definitions related to the above embodiments are all applicable, and are not described in detail here.
It should be noted that the technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, however, as long as there is no contradiction between the combinations of the technical features, the scope of the present description should be considered. The above examples only express several embodiments of the present application, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent application shall be subject to the appended claims.
Claims (10)
1. A coherent and incoherent laser cooperative detection method for an aerial moving object is characterized by comprising the following steps:
s1, carrying out narrow-pulse multi-frequency laser coarse scanning and single-photon area array detection on possible areas of an empty moving target in sequence to obtain an instantaneous laser distance image corresponding to each scanning direction;
s2, carrying out image splicing on the instantaneous laser distance images corresponding to all scanning directions to obtain single-photon three-dimensional distance images;
s3, extracting a distance extreme point in the single-photon three-dimensional distance image, and taking the distance extreme point as a suspected air moving target position;
s4, sequentially performing high-coherence laser pulse precision scanning and laser heterodyne detection on the position of the suspected air moving target to obtain an intermediate frequency signal of the suspected air moving target;
s5, acquiring motion characteristic information of the suspected aerial motion target according to the intermediate frequency signal;
and S6, correcting the single-photon three-dimensional distance image after confirming the suspected aerial moving target according to the movement characteristic information of the suspected aerial moving target.
2. The coherent and incoherent laser cooperative detection method according to claim 1, wherein in the step S1, the specific process of acquiring the instantaneous laser range image corresponding to each scanning direction includes:
s11, determining a relatively prime pulse cycle corresponding to each repetition frequency in the narrow-pulse multi-frequency laser to calculate the maximum unambiguous distance detected by the single-photon area array;
step S12, carrying out time-correlated single photon counting on a plurality of photon echo signals detected by the single photon area array in each scanning direction to determine a photon waveform detected by the single photon area array in each scanning direction;
s13, performing waveform noise reduction on the photon waveform detected by the single photon area array in each scanning direction;
s14, carrying out constant ratio timing processing on the waveform-denoised photon waveform to obtain echo time delay corresponding to each repetition frequency in the narrow-pulse multi-frequency laser;
s15, according to the maximum unambiguous distance and the echo time delay, carrying out distance ambiguity resolution on the narrow-pulse multi-frequency laser scanning frame to obtain each point cloud in the narrow-pulse multi-frequency laser scanning frame and a first distance value of each point cloud in the single photon area array detection direction;
and S16, carrying out self-adaptive noise reduction on each point cloud of the narrow-pulse multi-frequency laser scanning frame to obtain an instantaneous laser distance image corresponding to each scanning direction.
3. The coherent and incoherent laser cooperative detection method according to claim 2, wherein in the step S13, the waveform noise reduction is implemented by:
s131, performing energy decomposition on the photon waveform detected by the single photon area array in each scanning direction to obtain a sub-waveform component corresponding to each energy of the photon waveform;
s132, removing the sub-waveform components corresponding to the high-frequency low-amplitude from all the sub-waveform components, and acquiring a local maximum value point and a local minimum value point of each removed sub-waveform component;
the wavelet components corresponding to the high frequency and the low amplitude are the first 2~3 wavelet components in all the wavelet components;
step S133, calculating a first average value of all local maximum value points and a second average value of all local minimum value points, and taking the average value of the first average value and the second average value as a first threshold value;
and S134, eliminating the sub-waveform component corresponding to the local maximum value point smaller than the first threshold value to obtain the waveform-denoised photon waveform.
4. The coherent and incoherent laser cooperative detection method according to claim 3, wherein in the step S5, the motion characteristic information comprises a distance, a speed, a micro-vibration frequency and a micro-vibration amplitude; the specific process for acquiring the motion characteristic information of the suspected aerial moving object comprises the following steps:
performing empirical mode decomposition noise reduction, hilbert transform and waveform decomposition on the intermediate-frequency signal in sequence to determine a second distance value of the suspected aerial moving target in the laser heterodyne detection direction;
carrying out full-phase Fourier transform, data windowing processing and maximum discrete spectral peak estimation on the intermediate frequency signal in sequence to obtain a suspected air moving target speed corresponding to the frequency shift of the intermediate frequency signal;
and acquiring a time-frequency curve of the intermediate-frequency signal to determine the micro-vibration frequency and the micro-vibration amplitude of the suspected aerial moving target.
5. The coherent and incoherent laser cooperative detection method according to claim 4, wherein the specific implementation process of the step S6 includes:
s61, judging whether the speed, the micro-vibration frequency and the micro-vibration amplitude of the suspected air moving target are all larger than respective corresponding second threshold values, if so, entering S62; if not, ending;
s62, judging the high signal-to-noise ratio and the low signal-to-noise ratio of the intermediate frequency signal;
and S63, calculating a target distance correction amount according to the judgment result and the first distance value and the second distance value, and correcting the single photon three-dimensional distance image.
6. A coherent and incoherent laser cooperative detection system for an airborne moving object, comprising:
the system comprises a first detection module, a second detection module and a third detection module, wherein the first detection module is used for carrying out narrow-pulse multi-frequency laser rough scanning and single-photon area array detection on a possible existing area of an aerial moving target in sequence so as to obtain an instantaneous laser distance image corresponding to each scanning direction;
the image splicing module is used for carrying out image splicing on the instantaneous laser distance images corresponding to all the scanning directions to obtain single-photon three-dimensional distance images;
the extraction module is used for extracting a distance extreme point in the single-photon three-dimensional distance image and taking the distance extreme point as a suspected air moving target position;
the second detection module is used for sequentially performing high-coherence laser pulse precision scanning and laser heterodyne detection on the position of the suspected air moving target so as to obtain an intermediate frequency signal of the suspected air moving target;
the acquisition module is used for acquiring the motion characteristic information of the suspected aerial motion target according to the intermediate frequency signal;
and the image correction module is used for correcting the single-photon three-dimensional distance image after confirming the suspected aerial moving target according to the movement characteristic information of the suspected aerial moving target.
7. The coherent and incoherent laser cooperative detection system of claim 6, wherein the first detection module comprises:
the first calculation submodule is used for determining a relatively prime pulse period corresponding to each repetition frequency in the narrow-pulse multi-frequency laser so as to calculate the maximum non-fuzzy distance detected by the single photon area array;
the counting submodule is used for carrying out time-correlated single photon counting on a plurality of photon echo signals detected by the single photon area array in each scanning direction so as to determine a photon waveform detected by the single photon area array in each scanning direction;
the waveform noise reduction submodule is used for carrying out waveform noise reduction on the photon waveform detected by the single photon area array in each scanning direction;
the constant ratio timing processing submodule is used for carrying out constant ratio timing processing on the photon waveform subjected to waveform noise reduction to obtain echo time delay corresponding to each repetition frequency in the narrow-pulse multi-frequency laser;
the distance-resolving fuzzy processing submodule is used for carrying out distance-resolving fuzzy processing on the narrow-pulse multi-frequency laser scanning frame according to the maximum non-fuzzy distance and the echo time delay to obtain each point cloud in the narrow-pulse multi-frequency laser scanning frame and a first distance value of each point cloud in the single-photon area array detection direction;
and the self-adaptive noise reduction sub-module is used for carrying out self-adaptive noise reduction on each point cloud of the narrow-pulse multi-frequency laser scanning frame to obtain an instantaneous laser distance image corresponding to each scanning direction.
8. The coherent and incoherent laser cooperative detection system of claim 7, wherein the waveform noise reduction sub-module comprises:
the energy decomposition unit is used for carrying out energy decomposition on the photon waveform detected by the single photon area array in each scanning direction to obtain a sub-waveform component corresponding to each energy of the photon waveform;
the first eliminating unit is used for eliminating the wavelet components corresponding to the high frequency and the low amplitude from all the wavelet components and acquiring the local maximum value point and the local minimum value point of each eliminated wavelet component;
the wavelet components corresponding to the high frequency and the low amplitude are the first 2~3 wavelet components in all the wavelet components;
the calculating unit is used for calculating a first average value of all local maximum value points and a second average value of all local minimum value points, and taking the average value of the first average value and the second average value as a first threshold value;
and the second eliminating unit is used for eliminating the sub-waveform components corresponding to the local maximum value points smaller than the first threshold value to obtain the waveform of the photons subjected to waveform noise reduction.
9. The coherent and incoherent laser cooperative detection system of claim 8, wherein the motion characteristic information comprises distance, velocity, micro-vibration frequency and micro-vibration amplitude; the acquisition module includes:
the waveform decomposition submodule is used for sequentially carrying out empirical mode decomposition noise reduction, hilbert transform and waveform decomposition on the intermediate frequency signal so as to determine a second distance value of the suspected aerial moving target in the laser heterodyne detection direction;
the maximum discrete spectrum peak estimation submodule is used for sequentially carrying out full-phase Fourier transform, data windowing processing and maximum discrete spectrum peak estimation on the intermediate frequency signal so as to obtain a suspected air moving target speed corresponding to the frequency shift of the intermediate frequency signal;
and the acquisition submodule is used for acquiring a time-frequency curve of the intermediate-frequency signal so as to determine the micro-vibration frequency and the micro-vibration amplitude of the suspected aerial moving target.
10. The coherent and incoherent laser cooperative detection system of claim 9, wherein the image correction module comprises:
the first judgment submodule is used for judging whether the speed, the micro-vibration frequency and the micro-vibration amplitude of the suspected aerial moving target are all larger than respective corresponding second threshold values, if so, the intermediate frequency signal is transmitted to the second judgment submodule; if not, ending;
the second judgment submodule is used for judging the high signal-to-noise ratio and the low signal-to-noise ratio of the intermediate frequency signal;
and the second calculation submodule is used for calculating a target distance correction amount according to the judgment result, the first distance value and the second distance value and correcting the single-photon three-dimensional distance image.
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