CN102156286B - Brillouin scattering underwater laser imaging detector based on photonic crystal filter - Google Patents
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Abstract
The invention discloses a Brillouin scattering underwater laser imaging detector based on photonic crystal filter, comprising an impulse generator, a laser controller, a strobe controller, a logic processing component, a blue-green laser, a scanner, a Brillouin scattering filter, a strobe signal receiver, a signal processing component and a monitor, wherein the impulse generator is respectively connected to the laser controller, the strobe controller and the logic processing component; and the laser controller is connected to the blue-green laser. In the invention, a method of photonic crystal filter is used for collecting Brillouin scattering signals, displacing the currently adopted F-P (Fabry-Perot) interferometer, or the edge detection technology based on a bromine and iodine molecular filter, so that high requirements to the parallelism of incidents lights are not needed due to quite small solid angles received by the F-P interferometer, and bromine and iodine steams do not need constant temperature control due to the poor stability of spectral absorption of the bromine and iodine molecular filter; the use is simple and convenient.
Description
Technical field
The invention belongs to the Underwater Imaging Detection Techniques, particularly a kind of Brillouin scattering underwater laser imaging detecting device based on photonic crystal filtering.
Background technology
In recent years, the Underwater Imaging Detection Techniques just are being subject to various countries researcher's pay attention to day by day because it has extensive and important using value in target detection, sea materials detection and the ocean geography engineering under water.But different from imaging technique in our the usual finding air, the characteristic of aqueous medium is strong scattering effect and fast absorbed power decay, therefore carrying out traditional Underwater Imaging based on elastic scattering when surveying, the back scattering effect that light transmits in water is strong, cause picture noise large, image quality is poor, and the defective such as the operating distance of system is limited, and detection sensitivity is low.
In order to address this problem, carried out based on the concept that the Underwater Imaging of Brillouin scattering is surveyed.Brillouin scattering causes by Doppler effect, and seawater has different Brillouin frequency shifts from different target under water, as long as record the corresponding variation that Brillouin scattering spectrum occurs, just shows the existence that immersed body is arranged somewhere.The Liu Dahe of Beijing Normal University proposes a kind of method (2008 " Northeast China Normal University's journal " (natural science editions), the 3rd phase of the 40th volume) that the detection brillouin scattering signal carries out Underwater Target Detection of passing through of practicality in " with the brillouin scattering signal in F-P etalon and the ICCD detection water " article of delivering.The method gathers brillouin scattering signal with the F-P interferometer, records the Brillouin scattering spectrum of search coverage with ICCD, judges having or not of submarine target by the quantity of interference ring.But because the solid angle that Fabry-Perot (F-P) interferometer receives is very little, the depth of parallelism of incident light is required very high, the method is actual use very difficult.And because this constraint, the actual detection image quality is not high, and detection sensitivity is also very influenced.
Detection to brillouin scattering signal is the basis of all kinds of Brillouin scattering researchs.The at present detection of brillouin scattering signal is except adopting the F-P interferometer, and general also have employing based on the edge detecting technology of bromine, iodine molecule wave filter.But this Technology Need carries out thermostatic control to bromine, iodine steam, and to guarantee the stability of its spectral absorption, practicality is relatively poor.
Summary of the invention
The object of the present invention is to provide a kind of Brillouin scattering underwater laser imaging detecting device based on photonic crystal filtering, when when submarine target being carried out the laser imaging detection, it can effectively survey brillouin scattering signal, improves image quality.
The technical solution that realizes the object of the invention is: a kind of Brillouin scattering underwater laser imaging detecting device based on photonic crystal filtering, by pulse producer, laser controller, Strobe Controller, the logical process parts, the bluish-green laser device, scanner, the Brillouin scattering wave filter, the gating signal receiver, Signal Processing Element and monitor form, pulse producer respectively with laser controller, Strobe Controller, the logical process parts connect, laser controller is connected with the bluish-green laser device, scanner connects the bluish-green laser device on the one hand, the guiding Ear Mucosa Treated by He Ne Laser Irradiation is in search coverage, connect on the other hand and comprise the Brillouin scattering wave filter, the signal receiving device that the gating signal receiver forms carries out synchronous collection to brillouin scattering signal; Brillouin scattering wave filter, gating signal receiver, Signal Processing Element link to each other successively with monitor, and Strobe Controller is connected with the gating signal receiver, and the logical process parts are connected with Signal Processing Element; The required reference clock of pulse producer generation work in the pulse producer, the chronologically step operation of control laser controller, Strobe Controller, logical process parts, scanner; Laser controller produces required driving power and the control signal of bluish-green laser device work under the effect of reference clock, the required bluish-green laser pulse signal of this bluish-green laser device output Brillouin scattering underwater laser imaging detection; The bluish-green laser pulse signal is under the effect of scanner, and in the mode of two-dimensional scan, scanning imagery is surveyed interested water body zone, and bluish-green laser pulse signal and water and submarine target effect produce the brillouin scattering signal of response; The mixed signal that contains reflected signal, backward elastic scattering signal, backward scattered brillouin scattering signal receives through the synchronous scanning device, transfers to the Brillouin scattering wave filter; Behind the mixed signal process Brillouin scattering wave filter, other signals of filtering, only having under water, brillouin scattering signal transfers to the gating signal receiver; The signal gating receiver receives the brillouin scattering signal on the different distance under the control of Strobe Controller, produce corresponding electric signal transmission to Signal Processing Element; Signal Processing Element carries out noise processed under the control of logical process parts, image reconstruction generates, and produces the brillouin scattering signal two-dimensional space distributed image in water body zone, sends to picture monitor and observes for the observer.
The present invention compared with prior art, its remarkable advantage: (1) uses the method for photonic crystal filtering to gather brillouin scattering signal, substituted the at present general F-P interferometer that adopts, or based on the edge detecting technology of bromine, iodine molecule wave filter, the very little depth of parallelism to incident light of solid angle that both need not to receive because of Fabry-Perot (F-P) interferometer proposes very high requirement, need not again because of the poor stability of bromine, the spectral absorption of iodine molecule wave filter bromine, iodine steam to be carried out thermostatic control, use simple and easy.(2) owing to strobe mechanism is applied to the scanning probe of underwater laser brillouin scattering signal, can improve reliability and signal to noise ratio (S/N ratio) that the underwater laser brillouin scattering signal is surveyed.(3) in the reception signal front end of scanning imaging system, add Brillouin scattering wave filter based on photonic crystal filtering, utilize photon frequency forbidden band characteristic and the photonic crystal defect of photonic crystal excellence to produce very narrow conduction band characteristic, extremely narrow spectral signal is carried out filtering, thereby overcome traditional F-P interferometer and based on bromine, when the edge detecting technology of iodine molecule wave filter is surveyed brillouin scattering signal to the requirement of the incident light depth of parallelism or to the requirement of environment temperature etc. all multiple constraints and adverse condition, improve the detection effect of underwater laser brillouin scattering signal, improve image quality.Judge by detecting the brillouin scattering signal frequency displacement whether the somewhere has object to exist, and the back scattering effect that light transmits weakens, and picture noise is little under water in water, good imaging quality, operating distance is large, and detection sensitivity is high (sees Fig. 5-Fig. 8).Contrast 150m distance is based on the Brillouin scattering underwater laser detected pixel gray level image of F-P interferometer with based on the Brillouin scattering underwater laser detected pixel gray level image of photonic crystal filtering, the former is owing to having higher requirements to the incident light depth of parallelism, cause detecting error large, and be subjected to the back scattering effects, picture noise is obvious, and latter's image quality is apparently higher than the former.Contrast 180m distance is based on the Brillouin scattering underwater laser detected pixel gray level image of F-P interferometer with based on the Brillouin scattering underwater laser detected pixel gray level image of photonic crystal filtering, owing to being subject to the detection range restriction, the former gained image is clear not as the latter, shows that Brillouin scattering underwater laser sniffer operating distance based on photonic crystal filtering is large and detection sensitivity is higher.
Below in conjunction with accompanying drawing the present invention is described in further detail.
Description of drawings
The Brillouin scattering underwater laser imaging detecting device that Fig. 1 is based on photonic crystal filtering consists of.
Fig. 2 is the underwater laser Brillouin frequency shifts.
Fig. 3 is Brillouin scattering wave filter spectral transmittance curve.
Fig. 4 is Brillouin scattering photon number and the laser pulse detection range simulation curve that receives.
Fig. 5 is that the 150m distance is based on the Brillouin scattering underwater laser detected pixel gray level image of F-P interferometer.
Fig. 6 is that the 150m distance is based on the Brillouin scattering underwater laser detected pixel gray level image of photonic crystal filtering.
Fig. 7 is that the 180m distance is based on the Brillouin scattering underwater laser detected pixel gray level image of F-P interferometer.
Fig. 8 is that the 180m distance is based on the Brillouin scattering underwater laser detected pixel gray level image of photonic crystal filtering.
Embodiment
In conjunction with Fig. 1, the present invention is based on the Brillouin scattering underwater laser imaging detecting device of photonic crystal filtering, in scanning imaging system, add the Brillouin scattering wave filter based on photonic crystal filtering, utilize photon frequency forbidden band characteristic and the photonic crystal defect of photonic crystal excellence to produce very narrow conduction band characteristic, extremely narrow spectral signal is carried out filtering, thereby overcome traditional F-P interferometer and based on bromine, all multiple constraints and adverse condition when the edge detecting technology of iodine molecule wave filter is surveyed brillouin scattering signal, improve the detection effect of underwater laser brillouin scattering signal, improve image quality.By pulse producer 1, laser controller 2, Strobe Controller 3, logical process parts 4, bluish-green laser device 5, scanner 6, Brillouin scattering wave filter 7, gating signal receiver 8, Signal Processing Element 9 and monitor form, pulse producer 1 respectively with laser controller 2, Strobe Controller 3, logical process parts 4 connect, laser controller 2 is connected with bluish-green laser device 5, scanner 6 connects bluish-green laser device 5 on the one hand, the guiding Ear Mucosa Treated by He Ne Laser Irradiation is in search coverage, connect on the other hand and comprise Brillouin scattering wave filter 7, the signal receiving device that gating signal receiver 8 forms carries out synchronous collection to brillouin scattering signal; Brillouin scattering wave filter 7, gating signal receiver 8, Signal Processing Element 9 link to each other successively with monitor, and Strobe Controller 3 is connected with gating signal receiver 8, and logical process parts 4 are connected with Signal Processing Element 9; The required reference clock of pulse producer generation work in the pulse producer 1, the chronologically step operation of control laser controller 2, Strobe Controller 3, logical process parts 4, scanner 6; Laser controller 2 produces required driving power and the control signal of bluish-green laser device 5 work under the effect of reference clock, the required bluish-green laser pulse signal of these bluish-green laser device 5 output Brillouin scattering underwater laser imaging detections; The bluish-green laser pulse signal is under the effect of scanner 6, and in the mode of two-dimensional scan, scanning imagery is surveyed interested water body zone, and bluish-green laser pulse signal and water and submarine target effect produce the brillouin scattering signal of response; The mixed signal that contains reflected signal, backward elastic scattering signal, backward scattered brillouin scattering signal receives through synchronous scanning device 6, transfers to Brillouin scattering wave filter 7; Behind the mixed signal process Brillouin scattering wave filter 7, other signals of filtering, only having under water, brillouin scattering signal transfers to gating signal receiver 8; Signal gating receiver 8 receives the brillouin scattering signal on the different distance under the control of Strobe Controller 3, produce corresponding electric signal transmission to Signal Processing Element 9; Signal Processing Element 9 carries out noise processed under the control of logical process parts 4, image reconstruction generates, and produces the brillouin scattering signal two-dimensional space distributed image in water body zone, sends to picture monitor and observes for the observer.
The Strobe Controller 3 that the present invention is based on the Brillouin scattering underwater laser imaging detecting device of photonic crystal filtering forms by gate control circuit with apart from delay control switch, time delay according to underwater signal transmission different distance, be added to the work clock that obtains the different distance sensing point on the reference clock, pass through gate control circuit, obtain the gating gating pulse, 8 work of control signal selection pass receiver; This signal gating receiver 8 is comprised of avalanche photodide and gate control circuit, the gating gating pulse that Strobe Controller 3 is sent here changes the work threshold value of the avalanche photodide of surveying brillouin scattering signal through gate control circuit, determine that signal gating receiver 8 receives work and the dormant state of brillouin scattering signal, carries out gating control with this.
The scanner 6 that the present invention is based on the Brillouin scattering underwater laser imaging detecting device of photonic crystal filtering is made of optical imaging device, stepping circuit and step-by-step controller spare, optical imaging device guides the interested water body zone of bluish-green pulsed laser irradiation imaging detection on the one hand, produce brillouin scattering signal, converge on the other hand the collection brillouin scattering signal; Stepping circuit is subjected to the control of reference clock, and effect step-by-step controller spare drives optical imaging device interested water body zone is scanned; The distance of brillouin scattering signal under water that receives when signal gating receiver 8 is fixedly the time, and cooperation scanner 6 just can obtain the two-dimentional brillouin scattering signal distribution signal of this fixed range water body section.
The present invention is based on the logical process parts 4 and Signal Processing Element 9 cooperatings of the Brillouin scattering underwater laser imaging detecting device of photonic crystal filtering, finish the binaryzation of brillouin scattering signal under water, reduce noise, and figure image intensifying, the control command of logical process parts 4 received pulse generators 1 wherein, according to reference clock, form the sequential order that each step signal is processed, 9 work of control signal processing element; Signal Processing Element 9 passing thresholds are selected, and screen out seawater brillouin scattering signal and non-Seawater brillouin scattering signal, and then grey scale pixel value in the two-dimensional space zone is set, the seawater brillouin scattering signal, and namely non-object pixel gray-scale value is 0 or 1; Non-Seawater brillouin scattering signal, namely the gray-scale value of object pixel is 1 or 0), so just formed the binary image of surveying based on the Underwater Imaging of Brillouin frequency shifts;
Select edge-preserving smoothing that image is carried out denoising; and then adopt the processing mode of subsection histogram equalization that it is carried out the figure image intensifying; be that edge-preserving smoothing is based on recurrence rational number filtering (RRF); image after denoising at first is divided into two parts to image histogram with a global threshold; high gray area contains the target information of the overwhelming majority; again two parts are carried out respectively equalization; carry out at last in various degree compression to be combined into a complete image; image through the processing of subsection histogram equalization has improved picture contrast, the details sharp outline.
The present invention is based on the Brillouin scattering underwater laser imaging detecting device of photonic crystal filtering when work:
A. the pulse producer in the pulse producer 1 produces the required reference clock of system works, the operation of control laser controller 2, Strobe Controller 3, logical process parts 4, scanner 6.
B. laser controller 2 produces required driving power and the control signal of bluish-green laser device 5 work under the effect of reference clock, the required bluish-green laser pulse signal of bluish-green laser device 5 output Brillouin scattering underwater laser imaging detections.
C. the bluish-green laser pulse signal is under the effect of scanner 6, and in the mode of two-dimensional scan, scanning imagery is surveyed interested water body zone, and bluish-green laser pulse signal and water and submarine target effect produce the brillouin scattering signal of response.
D. the mixed signal that contains reflected signal, backward elastic scattering signal, backward scattered brillouin scattering signal is accepted by optical system behind synchronous scanning device 6, transfers to Brillouin scattering wave filter 7;
E. after mixed signal is passed through Brillouin scattering wave filter 7, other signals of filtering, only having under water, brillouin scattering signal transfers to gating signal receiver 8.
F. the brillouin scattering signal on the signal gating receiver 8 reception certain distances produces corresponding electric signal transmission to Signal Processing Element 9.
G. Signal Processing Element 9 carries out noise processed, and image reconstruction generates, and produces the brillouin scattering signal two-dimensional space distributed image in water body zone, sends to picture monitor and observes for the observer.
The mentality of designing of Brillouin scattering underwater laser imaging detecting device that the present invention is based on photonic crystal filtering is as follows:
(1) in conjunction with underwater laser Brillouin scattering target and background characteristics, by photon crystal material, the research of photon crystal filter principle, the brillouin scattering signal wave filter of design photonic crystal filtering.
Wherein, underwater laser Brillouin scattering target and background characteristics are as follows.Brillouin scattering is caused by Doppler effect, when light and effect of phonon generation scattering, make the Frequency generated variation of scattered light owing to the Doppler effect of phonon motion, can the frequency of occurrences greater than with two scattered lights less than the incident light centre frequency, its frequency is distributed in the both sides of incident light centre frequency symmetrically.Seawater has different separately variations from the Brillouin frequency shifts of different target under water, as long as record the corresponding variation that Brillouin scattering spectrum occurs, just shows the existence that immersed body is arranged somewhere.During the Laser Underwater transmission, Brillouin frequency shifts γ
BWith velocity of sound v
SSatisfy following relation:
Wherein, λ is incident light wavelength in a vacuum, and n is the refractive index of medium, and θ is scattering angle.γ in the clean seawater
BCan reach 7～8Ghz, line width is about 0.5～1.7GHz (seeing Fig. 2).
The receiver of pulse laser back scattering system is accepted the Brillouin scattering photoelectron number that individual pulse laser produces, and can be represented by the formula:
Wherein, N
1Be the output photon number of each laser pulse, σ
BBe the backward Brillouin scattering coefficient, Δ Z is range resolution, and d Ω is for receiving solid angle, ε
PmBe the quantum efficiency of photomultiplier, ε
OsBe the efficient of whole optical system, T
λBe the transmitance of water to laser, T
λ(rz), r is attenuation coefficient to=exp.Be the pulse laser of 500mJ/pulse for the 532nm energy, N
1=1.34 * 10
18Backward Brillouin scattering factor sigma in the clean seawater
B=2.4 * 10
-4M-1sr
-1, suppose that seawater middle distance resolution ax/Z is about 1 meter, getting and receiving solid angle is d Ω=0.5/ (z+200)
2, the quantum efficiency ε of photomultiplier
Pm=0.13, the efficient ε of whole optical system
Os=0.4, the attenuation coefficient of clean seawater is about r=0.04m
-1, for 100 meters return laser beams that produce apart from the place, N is arranged
Pe=34,000, namely brillouin scattering signal is appreciable.The above-mentioned foundation (seeing Fig. 4) that detects for Brillouin frequency shifts.
Wherein, place the Brillouin scattering wave filter 7 of signal gating receiver 8 front ends to be formed by broad stopband binary channels narrow band pass filter, metal support, this broad stopband binary channels narrow band pass filter is made of 1-D photon crystal and defective, its film structure adopts heterostructure, selects the material of TiO2 and two kinds of different refractivities of SiO2 as the high and low refractive index rete.Broad stopband binary channels narrow band pass filter is fixed on the metal support of angle adjustable, adjusts the angle less than or equal to 3 degree.
About the detection of brillouin scattering signal, many employing F-P interferometers or employing are based on the edge detecting technology of bromine, iodine molecule wave filter in the document.The F-P interferometer is because the solid angle that receives is very little, and is high to the depth of parallelism requirement of incident light, the actual difficulty of using; And based on the edge detecting technology of bromine, iodine molecule wave filter, need carry out thermostatic control to bromine, iodine steam, to guarantee the stability of its spectral absorption.
Photonic crystal has the photon frequency forbidden band, and by manufacturing defect in photonic crystal or make grating constant produce perturbation, can produce very narrow conduction band in the forbidden band.Yuan of Electronic Engineering Institutes Of Guilin waits the research of having carried out Photonic Crystal Narrow Band Filter at Green Light Wave Band in length and breadth, and having designed wavelength with transfer matrix method is the photonic crystal narrow band filter of the green light band of 532nm.(440～670nm), the central peak transmissivity is almost 100% to the forbidden photon band width of the wave filter of its design, and line width is 0.0131nm.When 2 defect layers appear in 1-D photon crystal, 2 transmission peaks will obviously appear, and the king of Tongji University accounts for the mountain, and broad stopband binary channels narrow band pass filter has been studied in CAS Institute of Physics Wang Ji continent, Lanzhou etc., and the film structure that the king of Tongji University accounts for the mountain is selected the TiO of high index of refraction
2SiO with low-refraction
22 kinds of materials, adopt heterostructure.Wherein 1-D photon crystal is (1H 1L)
4, (1.2H 1.2L)
4, (1.4H 1.4L)
4, (1.6H 1.6L)
4, (1.8H 1.8L)
9Defective is (0.5H 0.5L), (4.6H 5.2L 5.8H 6L), (4.5H 6.15L 1.7H 1.7L).The H representative thickness is the high refractive index layer of 1/4 centre wavelength, and the L representative thickness is the low-index film of 1/4 centre wavelength.There is larger distance in above-mentioned result of study apart from the detection of underwater laser brillouin scattering signal, has proved still that however the imagination of surveying based on the underwater laser brillouin scattering signal of photonic crystal filtering is feasible.
And because Brillouin scattering filtering is a kind of binary channels utmost point narrow-band filtering, and the position of 2 passages is very near, and the error that produces in the optical filter coating process will be brought larger impact to its transmissivity.When skew appearred in transmission peaks, adjustable light incident angle (pitch angle of Brillouin scattering wave filter) was finely tuned the position of transmission peaks in actual the use.When the variation of incident angle is in 3 degree, not only can finely tune the position of the transmission peaks of wave filter, and the bandwidth that can dwindle passage, simultaneously the energy gap of wave filter exerted an influence hardly.
For the underwater laser Brillouin properties, the spectral transmittance curve of photonic crystal Brillouin scattering filtering as shown in Figure 3.Forbidden photon band width (440～670nm); The position γ of transmission peaks
1=γ
0± 7.5 (Ghz), γ
0Be the bluish-green laser frequency; Bandwidth 1.5～2.0Ghz; Defect Modes peak transmission T＞70%; Cut-off region transmissivity T＜1.0%.(seeing Fig. 3)
1-D photon crystal in the film structure and defective all can be copied the result of study of Wang Zhanshan, but parameter need redesign, to satisfy the filtering requirements bimodal to Brillouin scattering.Consider that Brillouin scattering filtering is a kind of binary channels utmost point narrow-band filtering, and the position of 2 passages is very near, the error that produces in the coating process will be brought larger impact to its transmissivity.When skew appearred in transmission peaks, adjustable light incident angle (pitch angle of Brillouin scattering wave filter) was finely tuned the position of transmission peaks in actual the use.When the variation of incident angle is in 3 degree, not only can finely tune the position of the transmission peaks of wave filter, and the bandwidth that can dwindle passage, simultaneously the energy gap of wave filter exerted an influence hardly.
(2) photonic crystal Brillouin scattering wave filter is applied to the imaging detection of submarine target, substitutes the F-P interferometer and based on bromine, iodine molecule filter edge detection technique, improve the detection effect of brillouin scattering signal under water.
Underwater laser survey with atmosphere in the difference of laser acquisition maximum be the decay of light in seawater, the laser pulse signal that the laser pulse signal that returns at the place for 5m under water and 50m place return, its signal intensity difference is very big.In addition, the intensity of underwater laser brillouin scattering signal itself just exists 10 with excitation laser pulse signal intensity
5The gap of the above order of magnitude, and brillouin scattering signal is subject to the attenuation of seawater again in return course, consider the impact of the factors such as efficient of backward Brillouin scattering coefficient in the water, the quantum efficiency that receives solid angle, sensitive detection parts, optical system, the signal intensity that enters detector after brillouin scattering signal returns differs 10 especially again
10The above order of magnitude.Therefore the detection of underwater laser brillouin scattering signal can not be indiscriminately imitated the scheme that adopts laser radar in the atmosphere, and Brillouin scattering underwater laser imaging detection is all the more so.
Monochromatic collimated light beam is by Seawater, and radiation energy is exponential damping to be changed
L(r)＝L(0)exp(-cr) (3)
Wherein c is seawater volume damper coefficient (m
-1).R is the transmission range of light.L (0) is 0 spoke brightness along the r direction of coordinate; L (r) is the spoke brightness of r place in path along the r direction.When by distance r=l and Cl=1, spoke brightness decay is to original e
-1, claim that then this distance l is the attenuation length (m) of water, at this moment L (r) is the e of L (0)
-1Light is because being subject to scattering and absorption decays in water, so
c＝a+b (4)
A is the volume absorption coefficient in the formula, and its characterizes the size that collimated light beam absorbs after by ocean water body unit's distance.B is the volume scattering coefficient.
The volume damper coefficient is the function of wavelength.The spectral transmission window (namely at this wave band, the decay of light in seawater is minimum, and transmission is maximum) that it has been generally acknowledged that littoral seawater is 0.520 μ m, and the volume damper coefficient is about 0.2～0.6m
-1, its attenuation length is about 1.2～5m.The spectral transmission window of ocean clean water is 0.480 μ m, and the volume damper coefficient is about 0.05m
-1, its attenuation length is about 20m (seeing Fig. 4).
For detector, in the scope of 1Mhz～1GMhz, the junction capacity under the 100KMhz reaches 1～10pF substantially for photomultiplier, PIN photodiode, APD avalanche diode equiband, and the response time is 1～10ns.After consisting of detection part by these devices, because the impact of the factors such as outside lead, printed circuit board, above-mentioned parameter also will descend.Although these devices do not exist as the necessary frame accumulation of the image devices such as ICCD, the cumulative effect in the detection process still exists.This is especially in adjacent detection, laser pulse two-way process and Multiple Scattering situation, still very important for the detection of underwater laser brillouin scattering signal.
In the patent of the present invention, for avoiding or eliminating above-mentioned factor to the impact of the detection of underwater laser brillouin scattering signal, in the scanning imagery detection process, introduced strobe mechanism, the method that the avalanche photodide passing threshold of surveying brillouin scattering signal is controlled is carried out gating control, determine work and the dormant state of brillouin scattering signal detector, to reach following two purposes.One, each laser pulse only carries out 1 (or limited several) brillouin scattering signal and detects, and for each laser pulse, corresponding detection is carried out in the distance of correspondence, the amplitude of so each detection signal close (or only having limited several numerical value), this is a kind of guarantee for the processing of signal and the reliability of result of detection.Its two, can avoid the impact of the brillouin scattering signal that adjacent detection, laser pulse two-way process and Multiple Scattering process produce.Certainly, each time delay (gating opportunity) of measuring can be regulated, to adapt to the needs of different distance imaging detection.
(3) method of employing scanning imagery, bluish-green pulse laser scans zone to be detected, return signal other signals of filtering behind the Brillouin scattering wave filter that comprise brillouin scattering signal, only have brillouin scattering signal to be received, to process, then show, obtain water body zone brillouin scattering signal two-dimensional space distributed image.
Submarine target imaging detection based on elastic scattering has the methods such as synchronous scanning, range gating.Laser instrument and receiver split certain distance in the synchronous scanning imaging, and illuminating bundle sweep trace and receiver sight line intersect at an angle in observed zone, thereby back scattering is entered in the receiver as little as possible.The method can effectively be subdued the backward scattered impact of Underwater Imaging, enlarges viewing distance and improves image quality.
Corresponding with the synchronous scanning method, Brillouin scattering underwater laser imaging detection also can adopt the method for laser scanning imaging, but laser instrument and receiver are close to placement, to accept brillouin scattering signal as much as possible.Bluish-green pulse laser scans water body to be detected zone, comprises return signal other signals of filtering behind the Brillouin scattering wave filter of brillouin scattering signal, only has brillouin scattering signal to be accepted, to process, and then shows.Cooperate again scanning mechanism just can obtain the two-dimentional brillouin scattering signal distributed image of water body section.The grey scale pixel value of Brillouin scattering underwater laser imaging detection is as follows: the seawater brillouin scattering signal---and non-object pixel gray-scale value is 0 (or 1); The gray-scale value of non-Seawater brillouin scattering signal---object pixel is 1 (or 0), namely surveys based on the Underwater Imaging of Brillouin frequency shifts and can obtain binary image.The theory diagram of Brillouin scattering underwater laser imaging detection verification facility as shown in Figure 1.
(4) for avoiding adjacent detection, laser pulse to come and go and the impact of the brillouin scattering signal that Multiple Scattering produces, accept link at signal and intend adopting the gating controlling mechanism, to improve the signal to noise ratio (S/N ratio) of detectable signal.
Claims (5)
1. Brillouin scattering underwater laser imaging detecting device based on photonic crystal filtering, it is characterized in that by pulse producer (1), laser controller (2), Strobe Controller (3), logical process parts (4), bluish-green laser device (5), scanner (6), Brillouin scattering wave filter (7), gating signal receiver (8), Signal Processing Element (9) and monitor form, pulse producer (1) respectively with laser controller (2), Strobe Controller (3), logical process parts (4) connect, laser controller (2) is connected with bluish-green laser device (5), scanner (6) connects bluish-green laser device (5) on the one hand, the guiding Ear Mucosa Treated by He Ne Laser Irradiation is in search coverage, connect on the other hand and comprise Brillouin scattering wave filter (7), the signal receiving device that gating signal receiver (8) forms carries out synchronous collection to brillouin scattering signal; Brillouin scattering wave filter (7), gating signal receiver (8), Signal Processing Element (9) link to each other successively with monitor, Strobe Controller (3) is connected with gating signal receiver (8), and logical process parts (4) are connected with Signal Processing Element (9); The required reference clock of pulse producer (1) generation work, the chronologically step operation of control laser controller (2), Strobe Controller (3), logical process parts (4), scanner (6); Laser controller (2) is under the effect of reference clock, produce required driving power and the control signal of bluish-green laser device (5) work, the required bluish-green laser pulse signal of this bluish-green laser device (5) output Brillouin scattering underwater laser imaging detection; The bluish-green laser pulse signal is under the effect of scanner (6), and in the mode of two-dimensional scan, scanning imagery is surveyed interested water body zone, and bluish-green laser pulse signal and water and submarine target effect produce the brillouin scattering signal of response; The mixed signal that contains reflected signal, backward elastic scattering signal, backward scattered brillouin scattering signal receives through scanner (6), transfers to Brillouin scattering wave filter (7); Behind the mixed signal process Brillouin scattering wave filter (7), other signals of filtering, only having under water, brillouin scattering signal transfers to gating signal receiver (8); Gating signal receiver (8) receives the brillouin scattering signal on the different distance under the control of Strobe Controller (3), produce corresponding electric signal transmission to Signal Processing Element (9); Signal Processing Element (9) carries out noise processed under the control of logical process parts (4), image reconstruction generates, and produces the brillouin scattering signal two-dimensional space distributed image in water body zone, sends to monitor and observes for the observer.
2. the Brillouin scattering underwater laser imaging detecting device based on photonic crystal filtering according to claim 1, it is characterized in that Strobe Controller (3) forms by gate control circuit with apart from delay control switch, time delay according to underwater signal transmission different distance, be added to the work clock that obtains the different distance sensing point on the reference clock, pass through gate control circuit, obtain the gating gating pulse, control gating signal receiver (8) work; This gating signal receiver (8) is comprised of avalanche photodide and gate control circuit, the gating gating pulse that Strobe Controller (3) is sent here changes the work threshold value of the avalanche photodide of surveying brillouin scattering signal through gate control circuit, determine that gating signal receiver (8) receives work and the dormant state of brillouin scattering signal, carry out gating control with this.
3. the Brillouin scattering underwater laser imaging detecting device based on photonic crystal filtering according to claim 1, it is characterized in that scanner (6) is made of optical imaging device, stepping circuit and step-by-step controller spare, optical imaging device guides the interested water body zone of bluish-green pulsed laser irradiation imaging detection on the one hand, produce brillouin scattering signal, converge on the other hand the collection brillouin scattering signal; Stepping circuit is subjected to the control of reference clock, and effect step-by-step controller spare drives optical imaging device interested water body zone is scanned; The distance of brillouin scattering signal under water that receives when gating signal receiver (8) is fixedly the time, and cooperation scanner (6) just can obtain the two-dimentional brillouin scattering signal distribution signal of this fixed range water body section.
4. the Brillouin scattering underwater laser imaging detecting device based on photonic crystal filtering according to claim 1, it is characterized in that placing the Brillouin scattering wave filter (7) of gating signal receiver (8) front end to be formed by broad stopband binary channels narrow band pass filter, metal support, this broad stopband binary channels narrow band pass filter is made of 1-D photon crystal and defective, its film structure adopts heterostructure, selects the material of TiO2 and two kinds of different refractivities of SiO2 as the high and low refractive index rete; Wherein 1-D photon crystal is (1H 1L)
4, (1.2H1.2L)
4, (1.4H 1.4L)
4, (1.6H 1.6L)
4, (1.8H 1.8L)
9Defective is (0.5H 0.5L), (4.6H 5.2L5.8H 6L), (4.5H 6.15L 1.7H 1.7L), the H representative thickness is the high refractive index layer of 1/4 centre wavelength, the L representative thickness is the low-index film of 1/4 centre wavelength; Broad stopband binary channels narrow band pass filter is fixed on the metal support of angle adjustable, adjusts the angle less than or equal to 3 degree.
5. the Brillouin scattering underwater laser imaging detecting device based on photonic crystal filtering according to claim 1, it is characterized in that logical process parts (4) and Signal Processing Element (9) cooperating, finish the binaryzation of brillouin scattering signal under water, reduce noise, and figure image intensifying, the control command of logical process parts (4) received pulse generators (1) wherein, according to reference clock, form the sequential order that each step signal is processed, control signal processing element (9) work; Signal Processing Element (9) passing threshold is selected, screen out seawater brillouin scattering signal and non-Seawater brillouin scattering signal, then grey scale pixel value in the two-dimensional space zone is set, the seawater brillouin scattering signal, namely non-object pixel gray-scale value is 0 or 1; Non-Seawater brillouin scattering signal, namely the gray-scale value of object pixel is 1 or 0, has so just formed the binary image of surveying based on the Underwater Imaging of Brillouin frequency shifts;
Select edge-preserving smoothing that image is carried out denoising; and then adopt the processing mode of subsection histogram equalization that it is carried out the figure image intensifying; be that edge-preserving smoothing is based on the filtering of recurrence rational number; image after denoising at first is divided into two parts to image histogram with a global threshold; high gray area contains the target information of the overwhelming majority; again two parts are carried out respectively equalization; carry out at last in various degree compression to be combined into a complete image; image through the processing of subsection histogram equalization has improved picture contrast, the details sharp outline.
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| CN105783732A (en) * | 2016-03-15 | 2016-07-20 | 武汉华海创智科技有限公司 | Computer-vision-based underwater laser datum line measuring system |
| CN108226954A (en) * | 2017-12-28 | 2018-06-29 | 山东船舶技术研究院 | A kind of underwater scanning laser radar imaging method |
| CN109586807A (en) * | 2018-11-09 | 2019-04-05 | 北京华夏光谷光电科技有限公司 | Sky-water means of communication and device |
| CN110095784B (en) * | 2019-05-09 | 2020-11-24 | 北京航空航天大学 | Ocean-low atmosphere laser transmission modeling method under influence of complex environment |
| CN110672566A (en) * | 2019-10-18 | 2020-01-10 | 南昌航空大学 | Method for detecting stimulated Brillouin scattering acoustic photonic crystal structure in water |
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