Study Of Laser Underwater Three-dimensional Imaging Technology Based On SiPM Arrays

As we’ve seen, oceans cover more than70%of the earth, and therefore to researchand probe into the ocean has great significance. Tens of years’ research indicated thatthe laser radar for probing into the ocean is one of the most effectual techniques, andwhich would have vast application foreground if it is carried by the mobile aircraft. Atthe present time, laser radars for probing into the ocean are usually applied tobathymetry，hydrology observation, submersed target detection, orientation, recognition,classifying, ocean wave observation, and so on. During the past tens of years, theairborne oceanological laser radar techniques continually attracted people’s attention.Today they have been applied to many fields ripely, and many technical problems havebeen solved. However, with the appearance and development of many new techniques,such as the new photoelectric detectors’ appearance and the boosted performance of thedetectors, which make improving the equipment to boost the system performancecoming to be true. We starting with the new SiPM (Silicon Photomultiplier) arraysdetector, and some pivotal techniques research when the SiPM arrays are applied toairborne laser bathymetry systems (ALBS) are given in this paper.The SiPM (silicon photomultiplier) which has entered commercial phase for fewyears is a novel photon detector based on Geiger mode operating avalanche, and itssuperexcellent performance make a vast applied foreground. We apply this noveldetector into submersed target detection and survey, and look forward to advancedperformance brought by its superexcellent performance in submersed targetacquisition. The main work completed in this paper is as follows:(1) The history and development of Airborne Laser underwater three dimensionalimging techniques were summarized and analysed.(2) Starting with the fourfold concept of an oceanological lidar system, target,carrier, combinational sensors, and operator, and the principle of the airborne laserunderwater three dimensional imging system is introduced particularly, and factorsthat affect the system performance is explained and illuminated quantificationallybased on typical parameters as the lidar system is applied in bathymetry ofnear-shore ocean water. When the system is applied in hydrographic surveys ofnear-shore ocean water, the lidar system is an airborne laser bathymetry system, theprimary task of this kind of system is mensurating the depth of water, andperformance criterion of the system is expressed as the depth accuracy. (3) The principle of silicon photomultiplier arrays is introduced in detail, and theelectrical behaviour model of SiPM is given, and the advantage of SiPM for underwaterthree-dimensional depth sounder is discussed. Based the electrical behaviour model ofSiPM, a high speed, high bandwidth preamplifier is designed. Alternating currentanalysis and transient analysis showed that the preamplifier circuit has much high gainflatness in the bandwidth, and the phase to degrees is more than60degree. Analysis andthe testing results indicate that the SiPM arrays and the circuit design can satisfy therequirement of underwater three-dimensional depth sounder.(5) The factors that affect the instantaneously depth sounding performance isexplained and analysed quantificationally, and the fast signal acquisition system whichperformes digitization of the underwater returning signal at1.25giga samples/s areintroduced particularly.(5) New applications request much more accuracy in oceanological topographyand the ocean water quality reconnaissance, and need more accurate analytic modelof lidar return signals for bathymetry and reconstructing the water qualityparameters. In this work, the Fourier transform method is used to construct theanalytic model of bottom return signals and water backscattering signals formonostatic lidar based analytic beam spread function and ocean medium transferfunction given by Mclean et al, and in this analytic model the multiple scatteringand pulse stretching are considered and discussed, and the calculating methods ofthe downwelling irradiance attenuation coefficient and the lidar attenuationcoefficient are given, and the results indicated that the pulse stretching time canreach tens of nanoseconds in turbid harbor water. The analysis can offer somereferences for depth and water quality parameter reconstruction algorithms intheorizing.