CN112434589A - Space-based high-sensitivity differential detection method for quasi-molecular spectrum target - Google Patents
Space-based high-sensitivity differential detection method for quasi-molecular spectrum target Download PDFInfo
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Abstract
The invention discloses a space-based high-sensitivity differential detection method for a quasi-molecular spectrum target. Firstly, according to the radiation characteristics of background and target, extracting optimum detection spectrum delta lambda with different target radiation intensities but same background radiation intensity1And Δ λ2(ii) a Then the double-spectrum section is detected aiming at the scene, and a difference method is adopted for signal acquisition to obtain signals after background and interference are suppressed; and finally, target detection is realized by analyzing the obtained signals. The method can be applied to the detection of stealth airplanes, missiles and adjacent high-super-selectivity radiators, realizes the suppression of strong background and complex interference, and greatly improves the signal-to-noise ratio and the detection probability of the system.
Description
Technical Field
The invention relates to a space-based high-sensitivity differential detection method for a quasi-molecular spectrum target, which utilizes the difference of double spectral bands in the radiation characteristics of the quasi-molecular spectrum target to carry out differential on signals and inhibit background and interference.
Background
The space-based infrared photoelectric system is a core means for realizing early warning, guiding and detecting of missiles and stealth airplanes. With the increasing improvement of stealth performance of novel military weapons and the increasing complexity of military warfare backgrounds, how to inhibit strong background and complex interference and realize high-speed and high-accuracy detection becomes the primary requirement of infrared military application.
The conventional integral infrared detection method adopts a single spectrum section to carry out non-difference detection on a target pixel and a background pixel, and selects an optimal spectrum section through comparison. The method is limited by factors such as atmospheric path scattering, earth background clutter and the like, and has the problems that the integration time is difficult to further improve, the signal-to-background ratio influences the detection dynamic range, the signal-to-noise ratio of weak and small target detection reaches the background limit of a detection scene and the like.
Both the paper "band selection method for airplane target detection" and "target detection spectral band analysis based on system contrast" adopt a method of analyzing target radiation characteristics and background radiation characteristics and selecting an optimal spectral band. The method is greatly influenced by scenes, the integration time is difficult to improve, and the signal-to-noise ratio and the detection distance of the system are limited.
Disclosure of Invention
The invention aims to provide a space-based high-sensitivity differential detection method for a quasi-molecular spectrum target, aiming at the defects in the prior art, and the method can be used for inhibiting the background in the detection process, reducing the noise of a detection system, enhancing the signal-to-noise ratio of the system and improving the detection probability.
The purpose of the invention is realized by the following technical scheme:
1. a space-based high-sensitivity differential detection method for a quasi-molecular spectrum target is characterized by comprising the following steps of:
1) selecting spectrum, selecting optimum detection spectrum delta lambda according to the difference of target and background radiation characteristics under different spectrum1And Δ λ2The method comprises the following specific steps:
1-1) calculating the radiation intensity of targets and background signals of different spectral bands in the same scene;
1-2) performing spectrum selection according to the following steps: background signal in the spectral region Δ λ1And Δ λ2The difference of the detection spectral bands is less than 0.1%; target signal at Δ λ1And Δ λ2The difference of the two detection spectral bands is more than 95 percent.
2) Signal collection, collecting target and background signals of double spectrum band by difference mode, the concrete steps are as follows:
2-1) the detection system differentiates the signals obtained from the two detection spectra in real time during the acquisition process, i.e. before the response charges enter the integrating capacitor.
2-2) obtaining the signal after passing through the differential circuit, and the process restrains complex background signals and interference signals and keeps a target signal.
3) Analyzing the differential signal to realize target detection, and the specific steps are as follows:
3-1) calculating the signal-to-noise ratio of the target, judging the detectability of the target, wherein the signal-to-noise ratio calculation formula is as follows,
where SNR represents the signal-to-noise ratio; n is a radical oftarget、NbackRespectively representing the response electronic numbers of the target pixel and the background pixel; delta PtargetAnd Δ PbackRespectively representing the detected spectrum delta lambda1And Δ λ2Corresponding power difference of the lower target and the background pixel; t isintRepresenting the system integration time; noise is the system noise, nATTo read out noise, clutter is the background clutter.
If the target signal-to-noise ratio SNR is greater than or equal to the threshold signal-to-noise ratio TNR, i.e., SNR ≧ TNR, the target is generally considered detectable.
3-2) detecting and identifying the target by combining target imaging.
The invention has the advantages and positive effects that:
1. the space-based high-sensitivity differential detection method for the quasi-molecular spectrum target subverts the original integral detection method, and inhibits the influence of background and interference on target detection through the difference of target and background signals.
2. The method provided by the invention can be applied to the detection of similar molecular spectrum targets under complex backgrounds and strong interference, and is beneficial to improving the detection probability.
Drawings
FIG. 1 is a flow chart of the space-based high-sensitivity differential detection method for molecular-like spectrum targets of the present invention.
FIG. 2 is an IR emissivity curve for a hydrocarbon fuel based molecular spectroscopy target.
FIG. 3 is a schematic diagram of the principle of the differential detection method for the molecular-like spectrum target according to the embodiment of the present invention.
Fig. 4 is a comparison graph of simulation results of the differential detection method employed in the present invention and the conventional detection method. Wherein, graph (a) is the simulation result of the conventional detection method, and graph (b) is the simulation result of the proposed differential detection method.
Detailed Description
The present invention will be further described with reference to the accompanying drawings by taking an aircraft object in flight as an example.
For targets such as stealth airplanes and missiles in flight states, the infrared radiation characteristics of the targets mainly come from two parts, namely target skin and target tail flame, which both obey the Planck radiation law, namely
Wherein M istarIs the spectral radiance exitance, ε of the targettarRepresenting the spectral emissivity of the target, λa、λbRepresents the start-stop wavelength of the spectrum, λ represents the wavelength, T represents the emitter temperature, εtarAs spectral emissivity, c1And c2First and second radiation constants, respectively.
The spectral emissivity of the target tail flame can change along with the change of the wavelength, so that the radiation characteristics of the target tail flame have large difference under different wavelengths, and the target is called a molecular spectrum-like target. An infrared emissivity of a tail flame produced by hydrocarbon fuel is shown in fig. 2.
1) Detection target and background simulation
Calculating the target radiation intensity under each spectral band according to the spectral radiation characteristics of the target skin and the tail flame,
spectral band Delta lambda1Lower target radiation intensity Itarget1：
Itarget1＝Iskin1+Iplume1
Spectral band Delta lambda2Lower target radiation intensity Itarget2：
Itarget2＝Iskin2+Iplume2
Wherein, Iskin1、Iskin2Spectral radiance of the skin representing the target in two spectral bands, Iplume1、Iplume2Representing the spectral radiance of the tail flame of the target in two spectral bands.
Selecting a detection background, simulating by using an atmosphere transmission model Modtran, and calculating background spectral radiation intensity I of two spectral bands after atmospheric attenuationback1、Iback2。
Simulated atmospheric transmission rate tauaAnd (lambda) and the like, and calculating the entrance pupil radiation intensity of the target pixel and the background pixel.
2) Difference of signal
Typically, when a space-based infrared system is used to detect a high-speed flying target, the target is a point target and is much smaller in size than the ground resolution of the detection system, from which the detector response is calculated
Wherein, PtargetResponse power, P, for pixels containing objectsbackIs the response power of the background picture element, ItarIs the intensity of the target radiation, IbackFor background radiation intensity, R is the detector-to-target distance, AoptIs the optical entrance pupil area, τoptIs optical efficiency, η isQuantum efficiency, EE, is the energy concentration.
Respectively calculating target pixel responses P of two detection spectral bandstarget1、Ptarget2Background Pixel response Pback1、Pback2And difference is performed.
As shown in fig. 3, since the difference of the background signals of the target pixel in the two detection spectral bands is small, the background signals are suppressed during differential acquisition; and the difference of the target signals under the two detection spectral bands is large, so that the target signals are basically reserved when differential acquisition is carried out. Therefore, the image obtained after differential acquisition has good target-background contrast.
3) Detection system performance enhancement
And the signals acquired by the two detection spectral bands are differentiated, and the signals after the differential processing keep target signals as much as possible and remove background signals.
The number of the collected background electrons is greatly reduced, so that the time for the integrating capacitor to reach the full-well charge is prolonged, namely the integrating time of the detection system is prolonged.
In addition, the method also reduces the number of noise electrons generated by background clutter, further reduces the noise of a detection system, and according to a system signal-to-noise ratio (SNR) calculation formula,
wherein the target response power difference
ΔPtarget＝Ptarget1-Ptarget2
Background response power difference
ΔPback＝Pback1-Pback2
In the formula, NtargetAnd NbackNumber of response electrons, T, representing target and background, respectivelyintFor integration time, noise is a systemNoise of the system, nATTo read out noise, clutter is the background clutter. It can be seen that the method enhances the signal-to-noise ratio of the system, thereby improving the detection performance of the system.
Taking the detection of a stealth aircraft as an example, the system signal-to-noise ratio of the traditional detection method is about 1.5-2.5, and the detection probability is about 15%; the differential detection method can enable the signal-to-noise ratio of the system to reach more than 10 and improve the detection probability to be more than 90%.
The simulation result is shown in fig. 4, the target-background contrast is enhanced by the differential detection mode, and compared with the traditional detection method, the method has greater advantage in detecting the weak and small molecular spectrum target.
In conclusion, the scheme realizes a differential detection method for the molecular-like spectrum target.
While the invention has been described in connection with specific embodiments thereof, it will be understood that these should not be construed as limiting the scope of the invention, which is defined in the following claims, and any variations which fall within the scope of the claims are intended to be embraced thereby.
Claims (1)
1. A space-based high-sensitivity differential detection method for a quasi-molecular spectrum target is characterized by comprising the following steps of:
1) selecting spectrum, selecting optimum detection spectrum delta lambda according to the difference of target and background radiation characteristics under different spectrum1And Δ λ2The method comprises the following specific steps:
1-1) calculating the radiation intensity of targets and background signals of different spectral bands in the same scene;
1-2) performing spectrum selection according to the following steps: background signal in the spectral region Δ λ1And Δ λ2The difference of the detection spectral bands is less than 0.1%; target signal at Δ λ1And Δ λ2The difference of the two detection spectral bands is more than 95 percent;
2) signal collection, collecting target and background signals of double spectrum band by difference mode, the concrete steps are as follows:
2-1) the detection system differentiates signals obtained by the two detection spectral bands in real time in the acquisition process, namely before the response charges enter the integrating capacitor;
2-2) obtaining signals after passing through a differential circuit, wherein the process inhibits complex background signals and interference signals and retains target signals;
3) analyzing the differential signal to realize target detection, and the specific steps are as follows:
3-1) calculating the signal-to-noise ratio of the target, judging the detectability of the target, wherein the signal-to-noise ratio calculation formula is as follows,
where SNR represents the signal-to-noise ratio; n is a radical oftarget、NbackRespectively representing the response electronic numbers of the target pixel and the background pixel; delta PtargetAnd Δ PbackRespectively representing the detected spectrum delta lambda1And Δ λ2Corresponding power difference of the lower target and the background pixel; t isintRepresenting the system integration time; noise is the system noise, nATFor reading noise, clutter is background clutter;
if the SNR of the target signal-to-noise ratio is larger than or equal to the TNR of the threshold signal-to-noise ratio, namely the SNR is larger than or equal to the TNR, the target can be generally considered to be detected;
3-2) detecting and identifying the target by combining target imaging.
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