This PDF file contains the front matter associated with SPIE Proceedings Volume 10850, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

China is a country with vast ocean area, long coastline and abundant marine resources. In recent years, the State Council has put forward a series of strategic plans for building a powerful maritime country, which requires to strengthen the capacity of building the omni-directional stereoscopic ocean monitoring system. On September 12, 2017, the State Oceanic Administration issued the fax about "The notice on carrying out the research on aerospace science and technology serving in marine development". It is worth mentioning that the rapid development of UAV technology has brought new opportunities to the marine application. The UAV system can be used as an important supplement method compared with satellites, ships and helicopters, which could provide a good guarantee for reconnaissance, surveillance, intelligence collection, target positioning and emergency response missions with its high reliability, high efficiency and low cost and low risk. Construction and application of ocean big data platform based on UAV system is a hierarchical architecture including application layer, service layer, access layer and resource layer from top to bottom. Every layer has its responsibility and they cooperate with each other to provide the big data service and application throughout. The platform is obviously superior to others with its diversified, comprehensive, personalized and intelligent characteristics, which can efficiently provide real-time or quasi real-time marine environment data, continuously execute missions in all-weather condition day and night, flexibly approach the accident site and immediately take emergency measures. As what is shown in picture 1, the resource layer provides a wide range of hardware, software and data resources. The access layer provides a comprehensive access means with different kinds of UAV systems, which is the core component of the whole platform. The cruise altitude of CH-AUV, CH-804C, CH-3, CH-4, CH-5 and CH-T4 is respectively 1500m in the sea, 100m~3000m,80m~6400m,200m~7200m,500m~8000m,1000m~25000m, which could fully cover of the space base, air base ,land base and sea base. The max endurance of those above is10h,4h,12h,30h,40h,30days respectively, which makes it possible to execute the missions in all-weather condition. The max payload capacity ranges from 3kg to 1050kg, so the optical, microwave and laser payloads can be carried at the same time. The service layer is a data center providing big data modeling, retrieval, association, mining and integration service where users can get these diversified services and accurate data easily at any time anywhere. The service layer provides data security for the application layer and the application layer gives feedback to the service layer according to the application requirements. These two layers supplement each other to improve the quality and efficiency of the whole platform. The application layer consists of two parts: the basic application and the integrated application. The basic application meet the basic requirements of marine applications including ocean environmental protection, disaster prevention and mitigation, maritime law enforcement, ocean and islands monitoring and emergency response. The integrated application including environmental forecast, disaster warning and situation analysis shows the high intelligence of the platform, which just describes the real smart ocean system. Above all, construction and application of ocean big data platform based on UAV system can not only provide a variety of data accessing methods, but also provide intelligent services and applications. It will bring new chapters to intelligent monitoring, dynamic prediction, systematic analysis, emergency response and other marine applications with its capacity of all directions service, all time accessing and all business coverage.

The noise of tow ship seriously influences the detection of towed line array. Null steering beamforming(NSBF), inverse beamforming(IBF) and non-data based beam-space transformation(NDBBT) are applied to suppress interference of tow ship in this paper. These methods are evaluated according to the improvement of signal-noise ratio(SNR). Simulation and trial results show that all three methods can suppress interference of tow ship effectively to a certain degree, and NDBBT performs better in suppressing interference than NSBF and IBF.

In an underwater channel, sound rays often propagate along a bended curve for the existence of gradient in ocean sound speed, which would cause great error in acoustic navigation. The sound ray revision must be considered carefully to get high-precision acoustic autonomous navigation of UUV. In this paper, the concept of effective sound velocity is adopted to revise sound ray. An acoustic navigation method based on the correction of slope distance is proposed and the application of effective sound velocity under different sound speed gradients in acoustic navigation is investigated. Simulation shows that the correction can improve the precision of navigation effectively.

A 1553B bus test scheme is proposed for different types of airborne environments. The program is applicable to the SMS avionic bus and weapon bus (1553B) testing. The testing process includes analysis of the underlying hardware drivers and upper application software. The complete data flow testing process truly reflects the performance of the SMS products in the actual airborne communication environment. The test steps follow the five steps: forming a test environment, formulating test data protocols, configuring test data, writing test software, and analyzing and comparing test data. This article focuses on three key steps of how to develop a test data protocol, configure test data, and write test software. Finally, the feasibility of the test method was verified through a project example.

The presence of breaking wave can significantly change the radiative properties of seawater and these changes will affect laser radar sensing and ocean target detection. In this work, impulse broadening effect of the breaking wave in the upper ocean are investigated using the Monte Carlo method. The breaking wave is divided into two structures according to the lifetime of evolution. The sea spray generation function and the bubble population model, which considers the effect of wind speed and depth on the spilling aerosols and foam bubble size distribution are used. The scattering coefficients and the scattering phase functions of bubbles in seawater are calculated using Mie theory, a Monte Carlo method is used to solve the radiative transfer equation.

This study is based on the principle of inter-mode interference for single-mode optical fiber. Two Mach-Zehnder interference sensors were manufactured by the fused tapered techniques of forward direction with butane torch and reverse direction with fiber fusion splicer, respectively. The temperature sensing characteristic of reverse fused tapered Mach-Zehnder interference sensor is 0.067 nm/°C. And the interference trough moves towards the long wave direction with increasing temperature. However, the temperature sensing characteristic of forward fused tapered Mach-Zehnder interference sensor is 1.059 nm/°C. And the interference trough moves towards the short wave direction with increasing temperature. The results show that, the Mach-Zehnder interference sensors could be flexibly manufactured by the fused tapered technique for different needs such as sensitivity and size. And this study has a high reference value for the practical study of optical fiber sensing.

High concentration of nitrate will cause many problems, such as water eutrophication and compromise of human beings’ health. A fast and stable approach was applied to predict nitrate concentration in solutions using the dual optical active correction continuous spectrum analyzer designed by our research group. Firstly, standard normal variate (SNV) was used to pretreat the spectral data. Then characteristic wavelengths of spectral curve were selected by using successive projections algorithm (SPA) and genetic algorithm (GA) respectively. Finally, partial least-squares regression (PLSR) was applied to build the spectral prediction model to predict nitrate concentration, and coefficient of determination (R²) and root mean square error of prediction (RMSEP) were introduced as the evaluation indicators of prediction models. For SNV-GA-PLS model, R²=0.9966 and RMSEP=0.1712, which outperformed than SNV-UVE-SPA-PLS model (R²=0.9896, RMSEP=0.3952). It demonstrated that he model which selects spectral characteristic wavelengths by GA can decrease the complexity of prediction model building and ensure the accuracy as well. Hence, SNV-GA-PLS model can be used to predict nitrate concentration in water with quick and steady performance.

The water- leaving radiance (L_w) and remote sensing reflectance (R_rs)are not only the main apparent optic properties (AOPs) of water but also the basic parameters of ocean water color remote sensing. In order to realize the measurement of water- leaving radiance and remote sensing reflectance in the spectrum with the range from 300 nm to 900 nm, the high precision of the sea-surface radiance, the sky radiance and the sea-surface incident irradiance should be first obtained. The radiometer is composed of the measurement unit, control unit and tracking unit. The measurement unit is the core of the radiometer. Comparing with the previous tunnel radiometer, the measurement unit of the automatic observation radiometer is designed. In order to collect the spectral images of the incident slit into a plane, the radiometer uses flat-field concave grating for diffraction spectroscopy. And the linear array detector can detect the intensity signals of each spectrum simultaneously on the same plane. At the same time, in order to guarantee 10° field of view, the radiometer is equipped with the lens. It is also required to ensure the spectral observation principal plane make 135° with the principal plane so that it can avoid the influence of solar flares. In addition, the instrument shell adopts multi-layer coating treatment to avoid the erosion of the instrument structure parts by sea water and foggy sea atmosphere. After the spectrometer is installed, spectral calibration is done in the laboratory. The full width at half maximum of the radiometer is less than 4nm and the spectrum completely covers from 300nm to 900nm. The development of radiometer fills the gap of the automatic measurement of water- leaving radiance in China. It can inspect and correct satellite data and remote sensing products, and provide continuous and reliable on-site observation data for satellite remote sensing radiation calibration and product authenticity inspection.

The exploration and utilization of marine resources is one of the most important topics in human development. In this paper, a fiber-optic hydrophone was proposed and demonstrated experimentally for submarine ultrasonic detection. The device contained a refractive index modification window in the cladding of tapered fiber-optics tip, making it as a quasi-Michelson interferometer. Moreover, a plastic cone structure was formed and employed to focus the ultrasonic field on the fiber, which highly promote the coupling efficiency of ultrasonic-to-interferometer. Using the spectral-side band filtering technology, the hydrophone was working well for ultrasonic wave detection.

The backscattering properties of four marine phytoplankton from three size-classified taxa at different chlorophyll concentrations were directly measured in the laboratory using a Hydroscat-6 instrument. The ancillary parameters measured included the absorption and scattering coefficients, chlorophyll-a concentration, cell size, and cell concentration. We found that the value of the backscattering coefficients at each band increased with an increase in chlorophyll concentration for each alga, and the spectral shape at the blue bands were changed for the picophytoplankton and nanophytoplankton while it remained the same for microphytoplankton with changes in the chlorophyll-a concentration. We also found that the backscattering variation range changed with the increase in the chlorophyll concentration: the larger the cell size, the smaller its range of change. In addition, the smaller particles had relatively higher backscattering at shorter wavelengths, but no relationship between the cell size and contribution to the backscattering was found. Moreover, we also found a relationship between size and both the backscattering ratio and backscattering cross-section, in accordance with previous results. The results from this work provide a good foundation for improving the accuracy of identifying red tide algae using water color remote sensing.

To tackle the increasingly serious information security issue of submarine cables, this article summarizes various kinds optical fiber eavesdropping defense means, and analyzes their advantages and disadvantages one by one. Then it puts forward two feasible secrecy system design proposals, and offers some advices and suggestions for information security protection system construction of submarine optical cables in China.

Aiming at the problem of image distortion caused by light refraction and the limitations of existing solutions, we propose a three-dimensional information extraction algorithm based on spatial mapping. Main procedures of the algorithm are as follows. First, we obtain the pixel coordinate information of the underwater image. Then, we convert the target underwater image into the equivalent air image through the pixel-pixel spatial mapping relationship. At last, the three-dimensional information is extracted from the equivalent air image. The algorithm can be applied to extract three-dimensional information of multiple underwater targets. Experiment results show that compared with the actual three-dimensional information of the target, the average error rate of the distance extracted by the proposed algorithm is 1.475%, and the average error of the attitude angle extracted by the proposed algorithm is 2.559°, which means the three-dimensional information of the target can be accurately extracted by the proposed algorithm.

The polarization state of light is somewhat affected by propagation in a broad-spectrum, high numerical aperture (NA) and other optical systems with oblique incident angles. Changes in the polarization state, known as polarization aberrations, may result in severe deterioration of the imaging quality. This paper reviews the theory of polarization aberration, including the definition of polarization aberration, polarization ray tracing, analysis of the function of polarization aberration, and some new theories related to calculation and analysis procedures. Increasingly, the theory of polarization aberration has been analyzed and applied in optical systems such as interferometers, microscopes, telescopes, and lithography devices. In optical design, the combined calculation and simulation of a polarization aberration can contribute to the efficient optimization of optical system performance.

3D measurement of underwater targets could recover 3D morphology of objects/scenes in water, which has extensive application prospects in the fields of submarine map drawing, underwater resource exploration, and marine archaeology et al. 3D reconstruction based on stereoscopic vision is playing a more and more important role in the field of measurement due to its incomparable advantages, such as high automation, rapid accuracy and non-contact. However, its application in underwater target detection is limited by the complex underwater environment, the absorption and scattering of light in the water and so on, which will seriously affect the quality of the image collection. In this paper, a 3D reconstruction method of underwater target based on multi view stereo vision technology was studied. A 3D profilometry system which works underwater was set up. The collection of multi-view image data is completed by a single camera and a rotating device. Firstly, camera’s back projection model is used to calibrate the motion and parameters of the underwater vision system. Secondly, the underwater target is fixed on the rotating device, and a series of images under different viewpoints are collected. Then, feature detection and matching were carried out, and dense surface point clouds were generated by several steps of expansion and filtering operations. Finally, based on the generated dense point cloud, the 3D geometric mesh model of the target is obtained by using the Poisson reconstruction method. Color and texture are fused into the 3D mesh model to get the target with high fidelity.

Aiming at the problem of low accuracy of underwater target recognition due to the introduction of non-uniform illumination during underwater optical detection, this paper proposes an underwater target recognition algorithm under the influence of non-uniform illumination. The algorithm firstly uses the illumination invariant extraction algorithm based on Nonsubsampled Contourlet Transform (NSCT) to extract the essential features of underwater images. Then, the extracted underwater image is used as the input of the Convolutional Neural Network (CNN) to perform target recognition. The experimental results show that the recognition accuracy of the underwater target is 9% higher than the source image, reaching 96%.

An iterative algorithm is used to simultaneously determining the aerosol optical thickness(AOT) and the exponent of Junge power-law from AATSR L1B reflectance data of channel 0.87um and 1.61um over Taiwan Strait, in this paper. Considering the variation of aerosol complex refractive index(ACRI) with wavelength, the retrieval of aerosol is implemented under constant and variable ACRI. Suppose the MODIS aerosol product values are accurate. For constant ACRI, there are 47.87% and 96.96% pixels with acceptable retrieval AOT and the exponent of Junge power law value, respectively. Likewise, there are 61.02% and 67.01% pixels for variable ACRI. Compared with the retrieval error under constant ACRI, there are 91.79% and 8.3% pixels with smaller AOT and Junge power-law index retrieval error under variable ACRI, respectively. Besides, the precision of AOD retrieved under constant ACRI is equivalent with variable ACRI when AOT product is less than 0.3. However, both constant and variable ACRI can obtain consistent spatial and temporal distribution of AOT.

The deployment of sensors in Underwater Wireless Sensor Networks (UWSNs) is a fundamental issue in underwater wireless communications. Aiming at the problem of sensor nodes failure caused by the collection of information and too much data transformation in the deployment of sensor of UWSNs, the mobile sensor nodes scheduling algorithm based on grids competition in UWSNs is proposed. Firstly, a hexagonal grid partition model is designed to reduce the communication energy consumption combined with existing of grid computing. On the basis of the model, the energy consumption analysis and mathematical model of sensor node scheduling are given. Further, a length-search message exchange mechanism involved in the model is developed. Hence the scheduling plan among the grids can be computed therefore, the whole algorithm is proposed. Finally, simulation experiments illustrate the rationality and effectiveness of the proposed algorithm. The simulation results show that the proposed algorithm can significantly reduce the communication energy consumption and mobile consumption of sensor nodes. In a conclusion, the energy balance among sensor nodes can be guaranteed, and the network lifetime can be extended somewhat.

With the rapid development of marine satellites in China, several marine satellites are about to be launched in recent planning. It is important to evaluate the payload performance of marine satellites, but the research on satellite load assessment is almost carried out for terrestrial satellites. The imaging region of the Coastal Zone Imager includes marine water bodies, so some assessment methods for estimating the performance of terrestrial satellites may not be applicable. In this paper, by analyzing and comparing the advantages and disadvantages of the current calculation methods of load performance evaluation, combined with the characteristics of the Coastal Zone Imager, the load performance evaluation scheme for Ocean color satellite is selected, and the real remote sensing data is used to verify the results.

Solar blind ultraviolet communication has the advantages of non line of sight transmission and low eavesdropping rate. It is a kind of local secure optical communication technology which is especially suitable for the use of the marine communication. This paper briefly describes the principles and characteristics of the solar blind ultraviolet communication system and its potential applications in marine communications. The key technologies of UV communication system, including channel simulation, ultraviolet light source, single photon detector, transceiver optical system, modulation and coding mode, are summarized in this paper.

Optical fiber laser hydrophone which has more research potentiality and value owing to higher acoustic pressure sensitivity, smaller size and lower difficulty of multiplexing. However the detecting capacity to low frequency signal of optical fiber laser hydrophone will be limited because of the low frequency noise such as 1/f noise and thermal noise of optical fiber laser and pumped laser. In order to suppress these noises, the iterative discrete wavelet transformation algorithm was designed which used multi-scale trait of wavelet transform. The different spectral components of underwater acoustic signal were separated and the noises below 1kHz were eliminated on the basis of the target signal amplitude would not be weakened. The measured data acquisitive from anechoic tank showed that the algorithm reduced the noise below 1kHz nearly 50dB and the Signal to Noise Ratio(SNR) is improved from 55.23dB to 84.05dB.

In view of the existing underwater sensors cannot obtain a relative positional relationship between the target and the underwater vehicle, as well as, target positioning based on binocular vision method which has systematic errors needs more accurate calibration result. An approach for vision of a recognized underwater target is proposed in this paper. The first step is to process the original image with image enhancement and filtering, identify the target image based on HSV threshold. In the next step for target positioning, a three dimensional (3D) re-construction method based on block matching after binocular vision calibration and a 3D re-construction method with learning neural network are studied. Aiming at the problems of slow convergence rate and local optimum of traditional BP networks, several improvements of traditional BP networks are proposed. Finally, the experiment proves that the method can obtain high precision result and good real-time performance under sufficient stylebook data.

NOTE: see pdf for symbols. The carbon in the ocean mainly remains in the system of the carbon dioxide and carbonate, the existence form of it including CO₂,H₂O₃, HCO₃−, CO_2/3− and so on. pCO₂ as the main parameter which need usually measured in the study of the system of the carbon dioxide and carbonate in the ocean, its mainly analysis methods is usually using infrared spectrum technology. In addition, about the HCO3 −dissolved in seawater, there is lacking of in-suit measurement equipment to study at present. Based on the above needs, in this paper, we using Raman spectroscopy technology to study the in-suit detection for the dissolved CO₂ and HCO₃- in seawater. We build a near-concentric cavity gas-liquid Raman spectroscopy combined detection system, the system mainly consists of the following three components: the detection optical of the gas, the detection optical of the liquid and the gas liquid separator. The field detection experimental took place in the Zhongyuan Wharf of Qingdao on December 1 ~ 2, 2016 (E 120.302° , S 36.053°). According to the analysis based on the results of the experiments, the Raman signal of N₂ ,O₂, CO₂ and SO_2/4−, HCO₃− dissolved in seawater were detected in the trial, at the same time the fluorescence signal of CDOM(Colored Dissolved Organic Matter) and chlorophyll had also been detected with the same system. The field experiment results demonstrated that near-concentric cavity gas-liquid Raman spectroscopy combined detection system has great potential to study the system of carbon dioxide and carbonate in seawater. However, considering the ingredients of seawater is very complex and the effect of seawater (especially the interference from fluorescence matter), after further research on the sensitivity improved and data processing, it is hope to apply the system to the quantitative detection in seawater.

The colored dissolved organic matter, abbreviated as CDOM, is an important ingredient that affects the light absorption characteristics of seawater, and one of the key elements for ocean color research. In the case of only few focus on temporal and spatial variation of CDOM in tropical East Indian Ocean, this paper analyzes the CDOM spectral characteristics of this area based on the optical data of the summer survey in Southeast Indian Ocean in 2016, the variation and the related factors affecting the CDOM absorption characteristics of this area by using MODIS/ VIIRS satellite remote sensing data. The results shows that 1) the CDOM absorption spectrum meets quasi-exponential decay characteristics, and the surface a_g(440) changes from 0.002 to 0.098 m^-1, which is smaller than that of inshore water is larger than that of Southeast Pacific Ocean; 2) a_g(440) in 8°S is significantly greater than 5°S, and the maximum appears in the southwest of the observation area (88°E, 8°S); 3) above the shallow depth of 100m, a_g(440) tends to increase with depth; 4) the distribution of surface CDOM absorption coefficient shows significant consistency with chlorophyll concentration (r=0.8495), while not related to sea surface temperature (r=0.0064). CDOM and chlorophyll have similar driving mechanisms in the research area. The spatial distribution of CDOM is influenced by the subaqueous equatorial currents, the low-temperature waters from the Southern Ocean, and short-term small-scale effects, while the profile distribution is related to light field and nutrients. This study provides a further reference for understanding the optical properties of tropical waters in the East Indian Ocean.

The water has a strong absorption and scattering of light radiation, resulting in a certain depth of the underwater world in the dark. Therefore, underwater optical detection technology based on active lighting has become the main mode of deep-sea photo detection. Using a 532nm narrow-pulse laser and a self-built gain CCD system to form a underwater laser rang-gated imaging system, the forward and backward scattering are modeled and analyzed. Underwater laser rang-gated imaging system, was studied by laser pulse jitter, thus lead to the door of the control signal, the open time (earlier/later), the relationship between secondary scattering and image contrast curve, puts forward an optimal pulse with door control strategy. The correctness of the model is verified by the method of simulation and calculation of the relative ratio of the images acquired by the actual underwater laser distance gating imaging system. The results show that when the imaging system is not saturated, the image quality is best when the gate and the laser pulse are optimally matched. The effects of early opening and delayed opening on the image quality are different, and the duration of the gate opening is equal to the laser pulse width. At that time, the image quality is not optimal, and the effects of laser pulse jitter and secondary scattering are not all unfavorable. Based on the model, the opening time and the gate opening time are determined according to the contrast curve. It is generally advantageous to open the door lagging behind, and the duration of the gate opening should be 1- 3 times the laser pulse width.

Sun glint, the specular reflection of light from water surfaces, is a serious confounding factor for remote sensing of bathymetric measurements and benthic habitat mapping. In remote sensing of water color and water temperature, image saturation is one of the main noises of water color satellite images due to the influence of solar reflection. Therefore, sun glint correction is an important part of marine satellite image preprocessing. The existing high resolution satellite image flare elimination algorithm exploit the high absorption of water at NIR wavelengths and the consequence that the water-leaving radiance for these bands can be assumed negligible. Since the Fresnel reflectance of water is only weakly dependent on wavelength the strengths of the glint signal at visible and NIR wavelengths will vary in the same way, so the NIR signal can be used to indicate the amount of glint at visible wavelengths. In this paper, the WorldView-2 satellite 8 band remote sensing image is selected as the research area in the South China Sea region. The effects and differences of four kinds of solar flare elimination algorithms are compared. The main research contents and conclusions are as follows: firstly, four kinds of lighting elimination algorithms are introduced, including the method of: (1) Hedley et al.; (2) Lyzenga et al. (3) fixed coefficient; (4) coordinate axis rotation. Then, the radiometric calibration of the satellite images in the study area is carried out, and different algorithms are used to correct the solar flare. Finally, the results of the algorithms are compared and analyzed. The results show that the four lighting elimination algorithms have good visual effects. The bright spots in the original image decrease with the wave fluctuation, and the texture features that are originally covered under water can be revealed. In addition, the radiance value curve before and after the solar flare correction is analyzed. It is found that the values of each wave band after correction are basically reduced, the overall fluctuation of the curve is reduced, and the high frequency change decreases. Compared with other methods, the method of coordinate axis rotation has the best correction effect.

The purpose of this paper is to use digital holographic imaging to capture the hologram of the underwater particles. Digital holography includes two steps: wavefront recording and wavefront reconstruction. In the experiments of the underwater particles, some technique issues, such as the principle of digital holography, zero-order item suppressing and reconstruction algorithm are discussed. The complex amplitude of the underwater particles is reconstructed using numerical methods based on the Kirchhoff-Fresnel integral formula. In this case, it enables reconstruction of the object wavefield in a plane at a distance d from hologram. This novel method for imaging the underwater particles using digital holography is an extremely valuable technique for the study of underwater particles fields as it has many advantages such as large depth of field, no focusing, high resolution and has the ability to record the wavefront information of all particles in the entire volume. Finally, this paper demonstrates it is possible for digital holographic imaging setup with less complexity to image underwater particles according to our laboratory results.

Based on the Monte Carlo method, a model of ocean - atmosphere coupled polarized radiative transfer under the spherical condition is constructed. The model stratifies the spherical atmosphere in parallel with the sea surface as the underlying surface. An absolute reference coordinate system is established with the center of the earth as the origin, and the geometry of the solar incidence, detector observation, as well as the position，the motion direction and motion state of the simulated photon are projected onto this coordinate system. In order to improve the simulation efficiency, the backward Monte Carlo method is adopted, which greatly improves the contribution efficiency of photons in the multi-layer spherical atmosphere motion. The scattering and absorption of photons by atmospheric molecules and the reflection of sea surface on photons are introduced in detail. The Monte Carlo model constructed in this paper is used to simulate the upper radiation of the spherical and plane-parallel atmosphere, respectively. At the same time, we use the two models to verify each other. We find that the results obtained by the spherical model are quite different from those obtained by the aspheric model in the case of large solar zenith angle or large observing zenith angle. The model constructed in this paper lays a foundation for establishing the atmospheric correction algorithm under the great solar zenith angle.

Scattering is the fundamental issue in the field of underwater optics, meanwhile polarization state is also a key feature in underwater laser communications, laser imaging, and underwater quantum optical communication. Aiming at this problem, a software package Geant4 is applied in the simulation, furthermore, an algorithm based on the basic Henyey-Greenstein phase functions and typical polarization Monte Carlo model is proposed, the algorithm is used to simulate the polarization state when the laser is propagating underwater at different concentrations of water or transmission length. At the same time, the experiment is tested in a sink whose length is 10m and the polarization state detector is a laser power meter with accuracy up to 10nW. In this paper, the change of polarization state is expressed by the depolarization ratio. The result of numerical simulation and experimental show the variation of polarization state with concentration and distance respectively, the simulation result of Geant4 is more ideal, due to different kinds of external factors the experimental results are roughly, however, the overall change trend of the two is consistent.

The change of quantities and categories of plankton is essential for studying marine ecosystems. For decades development, there has been an accelerating advancement of plankton imaging system. To detect plankton accurately and effectively, the In situ Dark-field Microscope (OUC-IDM) was designed based on the principle of dark-field microscopy, with the purpose of detecting the plankton and macroscopic particles at the range of 100 μm to 10mm. The OUC-IDM is in a position to non-invasively imaging plankton in-situ at nearly micrometer resolution. It is worthwhile to mention that the design of OUC-IDM is more compact, smaller, and lighter than its predecessor, not only that, both cameras and embedded computers have been upgraded. Furthermore, Full-color information of plankton can be obtained by using a high-power white color LED as light source, which is favorable for identification of plankton in the advanced stage. To validate the usefulness of the OUC-IDM, the instrument was deployed along the coast in Qingdao several times, colorful and vividly in-situ images have been taken and directly used without or with sample image post-processing. Have regard to the functional differences, the OUC-IDM is best employed to complement rather than replace traditional studying.

Light Field camera is a kind of device which uses a microlens array to record the four-dimensional light field information in the scene and matches the light with the CCD to realize the function of image refocusing according to given relationship. In this paper, we apply the microlens array in the underwater microscopy system and use microscopic objective, microlens array and CCD to construct an underwater light field microscope. We improve microscopy system which has small depth and is difficult to focus and evaluate effect of microlens array on light field sampling and resolution of refocused images at different positions. In the experiments, we calibrate camera, confirm the magnification and field size and take some photos of marine plankton in the experimental environment.

Human activities and discharged river pollution affect the marine ecological environment. Therefore, it is very important to study how human activities affect the offshore ecological environment by monitoring the fluxes of terrestrial materials from rivers over long-times sequence. Landsat satellite data, which began in the 1970s, are of great value for monitoring changes in water quality in many small and medium-size rivers in China, which lacked field observation data in the early years. Because river water is usually turbid and the composition of water is complex, there is no uniform precise atmospheric correction. In addition, components of inland riverine water are different, so we need to build regional high-precision total suspended matter (TSM) inversion model. Based on Landsat-8/OLI (Operational Land Imager) data, we evaluate the applicability of different atmospheric correction methods (Fast Line-of-sight Atmospheric Analysis of Hypercubes-FLAASH, Dark Subtraction-DS and Quick Atmospheric Correction-QUAC) to Oujiang River. The results show that FLAASH gives good atmospheric correction, with the mean relative error of each band being around 15%. We collected three occurrences of measured data synchronized with the Landsat-8 satellite. Based on the measured TSM and remote sensing reflectance spectrum data, we analyze the correlation between different band combinations and TSM. The results show that the equivalent remote sensing reflectance ratio of OLI (482nm)/OLI (865nm) is highly correlated. Finally, we apply the established regional TSM inversion model to the OLI data in Oujiang River basin and comprehensively analyze the long-term changes of TSM concentration in the Oujiang River.

In recent years, blooms of Sargassum horneri have occurred frequently in the Yellow Sea and the East China Sea. Optical satellite remote sensing is an important means to monitor Sargassum horneri, the method being based mainly on exploiting the significant spectral differences between the water mixed with Sargassum horneri and the background seawater. Thus, it is necessary to study the spectral characteristics of Sargassum horneri in seawater with a view to improving measurement accuracy. To date, both laboratory-based experiments concerning the spectral characteristics of Sargassum horneri as well as satellite-based remote sensing monitoring have been performed, but these studies have focused mainly on large areas of Sargassum horneri, and there has been limited recognition of the differences in the spectral characteristics for situations where the Sargassum horneri outbreak is early, and where the Sargassum horneri and the background seawater have just mixed. In this study, experiments have been designed to carefully examine the spectral characteristics of Sargassum horneri in seawater.

The main findings are: (1) In general, the spectral distribution for the two forms of Sargassum (the strip form and the uniformly distributed form) are similar. (2) The peak wavelengths for the two forms of Sargassum horneri in seawater are different. The peak maximum for the strip form is at 825 nm while that for the uniformly distributed form is at 725 nm. Thus, spectral measurements may be used to distinguish between the two forms. (3) The concentration of suspended matter in the background seawater may influence the spectral characteristics of Sargassum horneri in seawater. These findings have great significance for remote sensing of the mixed state of Sargassum horneri in seawater, namely, the possibility for differentiation of the uniformly distributed form and strip distribution form. Also, the results have important implications for remote sensing of Sargassum horneri in seawater where the concentrations of suspended matter are variable.

Deep-sea optical imaging is an important method to explore mineral resource and detect biological or chemical activities in deep sea. As the premise of deep-sea imaging system, the deep-sea optical lighting system has a huge impact on the quality of optical images. And it has profound scientific significance and application prospect to improve the efficiency of deep-sea diving and save the cost of deep-sea expedition. In order to solve the problems of colour distortion and uneven brightness in deep-sea optical images, the investigation of non-uniform illumination design based on light attenuation is carried out in this paper. Firstly, the attenuation characteristics of light in deep-sea are established. Then the deep-sea lens and lens group are designed based on the light attenuation characteristic. The design shows that the light distribution area of the deep-sea lamp is rectangular, and the illumination uniformity of the design is more than 75% in sea-water. Finally, we can conclude that the attenuation characteristics of light can be used to design a better deep-sea lamp.

With the development of marine economy, the demand of underwater 3D imaging technology has become more insistent. Due to the absorption and scattering of water, the projection distance and the imaging range are shortened, which directly affects the applications and effectiveness of structured light techniques in underwater detection. In this paper, the imaging model of underwater camera is studied. An underwater structured light imaging system is established. A binary coding algorithm is investigated. The experimental results show that the proposed system can achieve a high accuracy measurement and has great potentials in underwater observing and engineering applications.

The edge method is one of the effective measurement methods based on image analysis for the Modulation Transfer Function of optical systems. By artificially changing the imaging environment, the corresponding changes of the MTF is obtained through the analysis of the object polarization images in the air and at different depth of water. The experimental results show that the MTF of the polarization optical system is stable when the water depth is within a certain range; when the water depth exceeds the threshold, the MTF of the system is drastically reduced. The change rule of MTF also varies with different materials.

The content of chlorophyll-a is one of the important indicators of eutrophication in marine ranching. Accurate measurement of chlorophyll-a content is of great significance for the sustainable development of marine ranching. In order to realize insite detection of chlorophyll-a content in marine ranching, a chlorophyll-a fluorometer based on lock-in amplifier was designed according to the fluorescence characteristics of chlorophyll-a. A high-brightness 460nm LED was used as the excitation source and the chlorophyll-a fluorescence was detected at 680nm by a photodiode through an interference filter. At the same time, a reference light path was used to compensate the change of light source. The response of the sensor was tested using chlorophyll-a solution, the results showed the sensor has good linearity in the dynamic range and the correlation coefficient is 0.996. The noise level was tested using pure water, the test results showed that the sensor has good noise performance and the resolution of the sensor is 0.2μg/L.