CN102156286A - 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 photoelectronic imaging Detection Techniques under water, particularly a kind of Brillouin scattering underwater laser imaging detecting device based on photonic crystal filtering.
Background technology
In recent years, the photoelectronic imaging Detection Techniques just are being subjected to various countries researcher's pay attention to day by day because of it has extensive important use value in target detection, sea materials detection and the ocean geography engineering under water under water.But it is different with imaging technique in our the usual finding air, the characteristic of aqueous medium is strong scattering effect and fast Absorption power attenuation, therefore carrying out traditional photoelectronic imaging under water when surveying based on elastic scattering, the back scattering effect that light transmits in water is strong, cause picture noise big, image quality is poor, and defective such as the operating distance of system is limited, and detection sensitivity is low.
In order to address this problem, carried based on the notion that the photoelectronic imaging under water of Brillouin scattering is surveyed.Brillouin scattering causes by Doppler effect, and seawater has different Brillouin frequency shifts with different target under water, as long as record the corresponding variation that Brillouin scattering spectrum takes place, 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 40th the 3rd phase of 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.This method is gathered brillouin scattering signal with the F-P interferometer, with the Brillouin scattering spectrum that ICCD writes down search coverage, 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, this 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 detection of brillouin scattering signal at present is except adopting the F-P interferometer, and general employing in addition is 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 are formed, 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, guided laser is radiated at search coverage, connect on the other hand and comprise the Brillouin scattering wave filter, the signal receiving device that the gating signal receiver is formed 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 step operation chronologically 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 institute interested water body zone, and bluish-green laser pulse signal and water and submarine target effect produce the brillouin scattering signal of response; Contain reflected signal, back mixed signal, receive, transfer to the Brillouin scattering wave filter through the synchronous scanning device to elastic scattering signal, backward scattered brillouin scattering signal; Behind the mixed signal process Brillouin scattering wave filter, other signals of filtering, having only 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 and transfer 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 general at present 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 bromine, iodine steam to be carried out thermostatic control, use simple and easy because of the poor stability of bromine, the spectral absorption of iodine molecule wave filter.(2) owing to the scanning probe that strobe mechanism is applied to the 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 received signal front end of scanning imaging system, add Brillouin scattering wave filter based on photonic crystal filtering, utilize the 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 or the like 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 big, and the detection sensitivity height (is seen 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 have higher requirements to the incident light depth of parallelism, it is big to cause detecting error, 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 be subjected 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 big 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 constitutes.
Fig. 2 is the underwater laser Brillouin frequency shifts.
Fig. 3 is a Brillouin scattering wave filter spectrum transmitting rate curve.
Fig. 4 is Brillouin scattering photon number and the laser pulse detection range simulation curve that receives.
Fig. 5 is the Brillouin scattering underwater laser detected pixel gray level image of 150m distance based on the F-P interferometer.
Fig. 6 is the Brillouin scattering underwater laser detected pixel gray level image of 150m distance based on photonic crystal filtering.
Fig. 7 is the Brillouin scattering underwater laser detected pixel gray level image of 180m distance based on the F-P interferometer.
Fig. 8 is the Brillouin scattering underwater laser detected pixel gray level image of 180m distance based on 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 Brillouin scattering wave filter based on photonic crystal filtering, utilize the 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 are formed, 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, guided laser is radiated at search coverage, connect on the other hand and comprise Brillouin scattering wave filter 7, the signal receiving device that gating signal receiver 8 is formed 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 step operation chronologically 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 institute interested water body zone, and bluish-green laser pulse signal and water and submarine target effect produce the brillouin scattering signal of response; Contain reflected signal, back mixed signal, receive, transfer to Brillouin scattering wave filter 7 through synchronous scanning device 6 to elastic scattering signal, backward scattered brillouin scattering signal; Behind the mixed signal process Brillouin scattering wave filter 7, other signals of filtering, having only 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 and transfer 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 is formed 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 made up 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 the 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 imagery device, stepping circuit and step-by-step controller spare, the optical imagery device guides a bluish-green pulsed laser irradiation imaging detection interested water body zone on the one hand, produce brillouin scattering signal, converge the collection brillouin scattering signal on the other hand; Stepping circuit is subjected to the control of reference clock, and effect step-by-step controller spare drives the optical imagery device institute interested water body zone is scanned; When the fixed distance of brillouin scattering signal under water that signal gating receiver 8 receives, cooperate 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 of each step signal Processing, 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 medium brillouin scattering signal, and two-dimensional space zone interior pixel gray-scale value is set then, the seawater brillouin scattering signal, and promptly non-object pixel gray-scale value is 0 or 1; Non-seawater medium brillouin scattering signal, promptly the gray-scale value of object pixel is 1 or 0), so just formed binary image based on the imaging detection under water of Brillouin frequency shifts;
Select for use edge-protected smothing filtering that image is carried out denoising; and then adopt the processing mode of segmentation histogram equalization that it is carried out the figure image intensifying; be that edge-protected smothing filtering is based on recurrence rational number filtering (RRF); image after denoising at first uses a global threshold the image histogram separated into two parts; high gray area contains the target information of the overwhelming majority; again two parts are carried out equalization respectively; carry out in various degree compression at last to be combined into a complete image; processed images through the segmentation histogram equalization has improved picture contrast, the details sharp outline.
The Brillouin scattering underwater laser imaging detecting device that the present invention is based on photonic crystal filtering is 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 institute interested water body zone, and bluish-green laser pulse signal and water and submarine target effect produce the brillouin scattering signal of response.
D. contain reflected signal, back mixed signal, behind synchronous scanning device 6, accept, transfer to Brillouin scattering wave filter 7 by optical system to elastic scattering signal, backward scattered brillouin scattering signal;
E. after mixed signal is passed through Brillouin scattering wave filter 7, other signals of filtering, having only 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 and transfers 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, the Doppler effect that moves owing to phonon changes the scattering light frequency, 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 with the Brillouin frequency shifts of different target under water, as long as record the corresponding variation that Brillouin scattering spectrum takes place, just shows the existence that immersed body is arranged somewhere.When laser transmits under water, Brillouin frequency shifts γ
BWith velocity of sound v
SSatisfy following relation:
Wherein, λ is an incident light wavelength in a vacuum, and n is the refractive index of medium, and θ is a scattering angle.γ in the clean seawater
BCan reach 7～8Ghz, line width is about 0.5～1.7GHz (see figure 2).
The receiver of pulse laser back scattering system is accepted the Brillouin scattering photoelectron number that individual pulse laser is produced, and can be represented by the formula:
Wherein, N
1Be the output photon number of each laser pulse, σ
BTo the Brillouin scattering coefficient, Δ Z is a range resolution for afterwards, 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 an attenuation coefficient to=exp.For the 532nm energy is the pulse laser of 500mJ/pulse, N
1=1.34 * 10
18The back is to the 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,, N is arranged for 100 meters return laser beams that produce apart from the place
Pe=34,000, promptly brillouin scattering signal is appreciable.Above-mentioned for Brillouin frequency shifts detect according to (see figure 4).
Wherein, place the Brillouin scattering wave filter 7 of signal gating receiver 8 front ends to form 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, and the material of selecting TiO2 and two kinds of different refractivities of SiO2 for use is 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 smaller 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 green glow wave filter 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 Lanzhou physics institute Wang Ji continent etc., and the film structure that the king of Tongji University accounts for the mountain is selected the TiO of high index of refraction for use
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 bigger 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 bigger influence 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, the energy gap to wave filter exerts an influence hardly simultaneously.
At the underwater laser Brillouin properties, the spectrum transmitting rate 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; Defective mould peak transmission T＞70%; Cut-off region transmissivity T＜1.0%.(see figure 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 bigger influence 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, the energy gap to wave filter exerts an influence hardly simultaneously.
(2) with photonic crystal Brillouin scattering filter applies in the imaging detection of submarine target, substitute the F-P interferometer and, improve the detection effect of brillouin scattering signal under water based on bromine, iodine molecule filter edge detection technique.
Underwater laser survey with atmosphere in the difference of laser acquisition maximum be the decay of light in seawater, the laser pulse signal that 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 subjected to the attenuation of seawater again in return course, consider that again the back is to the influence of the factors such as efficient of Brillouin scattering coefficient, the quantum efficiency that receives solid angle, sensitive detection parts, optical system in the water, the signal intensity that enters detector after brillouin scattering signal returns differs 10 especially
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 the seawater medium, 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 of being subjected 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 (promptly at this wave band, the decay minimum of light in seawater, transmission 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 the 20m (see figure 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 constituting detection part by these devices, because the influence of 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 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 repeatedly scattering situation, still very important for the detection of underwater laser brillouin scattering signal.
In the patent of the present invention, for avoiding or eliminate of the influence of above-mentioned factor to 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 brillouin scattering signal detector operation and dormant state, 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 on the distance of correspondence, the amplitude of so each detection signal close (or having only limited several numerical value), this reliability for Signal Processing and result of detection is a kind of guarantee.Its two, can avoid adjacent detection, laser pulse two-way process and the repeatedly influence of the brillouin scattering signal that produces of scattering process.Certainly, each time delay of measuring (gating opportunity) 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, have only brillouin scattering signal to be received, to handle, show then, obtain water body zone brillouin scattering signal two-dimensional space distributed image.
Submarine target imaging detection based on elastic scattering has 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 far as possible less.This method can effectively be subdued the backward scattered influence of imaging under water, 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, has only brillouin scattering signal to be accepted, to handle, and shows then.Cooperate scanning mechanism just can obtain the two-dimentional brillouin scattering signal distributed image of water body section again.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 medium brillouin scattering signal---object pixel is 1 (or 0), and promptly the imaging detection under water based on Brillouin frequency shifts can obtain binary image.The theory diagram of Brillouin scattering underwater laser imaging detection Proof-Of Principle device as shown in Figure 1.
(4) for avoiding adjacent detection, laser pulse to come and go and the repeatedly influence of the brillouin scattering signal of scattering generation, 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 are formed, 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, guided laser is radiated at search coverage, connect on the other hand and comprise Brillouin scattering wave filter (7), the signal receiving device that gating signal receiver (8) is formed 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 step operation chronologically 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 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 institute interested water body zone, and bluish-green laser pulse signal and water and submarine target effect produce the brillouin scattering signal of response; Contain reflected signal, back mixed signal, receive, transfer to Brillouin scattering wave filter (7) through synchronous scanning device (6) to elastic scattering signal, backward scattered brillouin scattering signal; Behind the mixed signal process Brillouin scattering wave filter (7), other signals of filtering, having only 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 and transfer 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.
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 signal selection pass receiver (8) work; This signal gating receiver (8) is made up 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 the 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 imagery device, stepping circuit and step-by-step controller spare, the optical imagery device guides a bluish-green pulsed laser irradiation imaging detection interested water body zone on the one hand, produce brillouin scattering signal, converge the collection brillouin scattering signal on the other hand; Stepping circuit is subjected to the control of reference clock, and effect step-by-step controller spare drives the optical imagery device institute interested water body zone is scanned; When the fixed distance of brillouin scattering signal under water that signal gating receiver (8) receives, cooperate 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 signal gating receiver (8) front end to form 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, and the material of selecting TiO2 and two kinds of different refractivities of SiO2 for use is as the high and low refractive index rete; 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, 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 smaller 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 the figure image intensifying, the control command of logical process parts (4) received pulse generators (1) wherein is according to reference clock, form the sequential order of each step signal Processing, control signal processing element (9) work; Signal Processing Element (9) passing threshold is selected, and screens out seawater brillouin scattering signal and non-seawater medium brillouin scattering signal, and two-dimensional space zone interior pixel gray-scale value is set then, the seawater brillouin scattering signal, and promptly non-object pixel gray-scale value is 0 or 1; Non-seawater medium brillouin scattering signal, promptly the gray-scale value of object pixel is 1 or 0), so just formed binary image based on the imaging detection under water of Brillouin frequency shifts;
Select for use edge-protected smothing filtering that image is carried out denoising; and then adopt the processing mode of segmentation histogram equalization that it is carried out the figure image intensifying; be that edge-protected smothing filtering is based on the filtering of recurrence rational number; image after denoising at first uses a global threshold the image histogram separated into two parts; high gray area contains the target information of the overwhelming majority; again two parts are carried out equalization respectively; carry out in various degree compression at last to be combined into a complete image; processed images through the segmentation histogram equalization has improved picture contrast, the details sharp outline.
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