- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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Underwater Wide-Area Layered Light Field for Underwater Detection
摘要： In underwater electro-optic detection, image quality can be degraded by the backscattering of light from the illuminated water volume. In practical systems, we tend to simultaneously require a high level of detection distance (DD), ?eld of view (FOV), and depth of ?eld (DOF), but these factors in?uence each other by the media scattering. To eliminate this restriction, we propose to explore the underwater wide-area layered light ?eld (UWLLF), which classi?es the underwater detection area by the DD and distribution characteristics of the light ?eld, to minimize the scattering in?uence on target detection. Based on the UWLLF, an underwater electro-optic detection system is designed that can achieve the speci?cations of a 70? FOV and 7.9-fold attenuation length (for the attenuation coef?cient 1.43 /m of 532 nm) DD. In addition, with the spatial separation of light energy, the non-detection zone at short ranges is eliminated, yielding an almost full DOF. With these three factors simultaneously improved, the ability of underwater exploration for object detection is enhanced.
关键词： object detection,Underwater technology,light ?eld,optical imaging,underwater detection
更新于2025-09-09 09:28:46
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Resolving Power of the Interferometric Method of Source Localization
摘要： Results of a computer simulation of the resolution of three noise sources with different intensities against the background of isotropic noise in an oceanic waveguide are presented. A comparative analysis of the error in determining their coordinates (bearing, radial velocity, distance, depth) is performed. A computational experiment is implemented based on the interferometric method of source localization using vector-scalar receivers.
关键词： source localization,vector-scalar receivers,interferometric method,underwater acoustics,oceanic waveguide
更新于2025-09-09 09:28:46
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Low-Cost Submersible Turbidity Sensors Using Low-Frequency Source Light Modulation
摘要： Submersible turbidimeter and fluorometer design generally involves tradeoffs between ambient light rejection, sensitivity, and cost. We introduce an optical backscatter transducer in which the light source is modulated with a low-frequency (tens of Hz) square wave, with a detection scheme that mitigates the effects of external interference from ambient light and from 50- and 60-Hz sources. With this design, high-pass filtering and subsequent amplification enable sensitive measurements using inexpensive circuitry. Additional accuracy-enhancing features include: a rail-splitting virtual ground, which eliminates the potential for clipping at low signal levels; a reference output, which provides correction for the intensity of the internal light source; and error-tracking provisions, which flag the output if circuit voltages reach saturation limits during measurement. We have designed, constructed, and evaluated submersible turbidimeters which incorporate this transducer. These sensors were inexpensive to fabricate (U.S. $70 of materials and 4 h of labor) and were proof tested to 7 atm of water pressure. They responded linearly and reproducibly to formazin turbidity standard, with negligible inherent offset. A calibrated sensor exhibited bias ≤0.11 NTU in suspensions ranging from 0 to 8 NTU. A similar sensor with reduced circuit gain exhibited a one-to-one response to increasing turbidity in suspensions ranging from 0 to 815 NTU.
关键词： water quality,underwater technology,nephelometer,turbidimeter,fluorometer,fluorescence,optical backscatter,Environmental monitoring,turbidity sensor
更新于2025-09-09 09:28:46
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Analyzing pre-processing filters sequences for underwater-image enhancement
摘要： Enhancement of the quality of a digital image is desirable in several scenarios such as underwater-image analysis, where improving visibility is necessary to reduce alterations caused by unbalanced lighting and the presence of sediments, among others. Many algorithms have been proposed oriented towards treatment of specific factors, such as contrast, color fidelity, noise, and lighting. This work explores the literature techniques and establishes a filter sequence for enhancing underwater images based on a pre-established quality metric. The resulting sequence begins by balancing the lighting using homomorphic filtering, improve the contrast by the Contrast Limited Adaptive Histogram Equalization (CLAHE) algorithm, and finally noise reduction and edge enhancement are done by using bilateral filtering. The results of the implementation suggest a qualitative improvement, in contrast, color, and sharpness of borders.
关键词： Underwater Image Enhancement,Image Processing,Contrast,Fish,Algorithms
更新于2025-09-09 09:28:46
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Design of Low-Complexity 3-D Underwater Imaging System With Sparse Planar Arrays
摘要： The development of a real-time 3-D underwater imaging system with a planar array is restricted by the huge hardware cost and computational burden associated with the large number of elements required. In this paper, a new design of low-complexity 3-D underwater imaging system is proposed, involving two key parts: a special sparse array with low hardware cost and an ef?cient beamforming with low computational burden. Especially, the simulated annealing algorithm is optimized based on distributed and parallel subarray (DPS) beamforming and results in fewer active elements than existing methods. To improve the computational ef?ciency especially for sparse arrays, an optimized DPS beamforming is presented with the pruning fast Fourier transform technology. To test the validity of the design, a real system based on the proposed methods was devised and employed in the lake and sea trials. The experiment results demonstrate that the low-complexity 3-D underwater imaging system can provide a satisfactory imaging quality.
关键词： sparse planar arrays,underwater acoustic imaging,sonar signal processing,simulated annealing (SA) algorithm,3-D sonar systems
更新于2025-09-09 09:28:46
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Guidelines for Underwater Image Enhancement Based on Benchmarking of Different Methods
摘要： Images obtained in an underwater environment are often affected by colour casting and suffer from poor visibility and lack of contrast. In the literature, there are many enhancement algorithms that improve different aspects of the underwater imagery. Each paper, when presenting a new algorithm or method, usually compares the proposed technique with some alternatives present in the current state of the art. There are no studies on the reliability of benchmarking methods, as the comparisons are based on various subjective and objective metrics. This paper would pave the way towards the definition of an effective methodology for the performance evaluation of the underwater image enhancement techniques. Moreover, this work could orientate the underwater community towards choosing which method can lead to the best results for a given task in different underwater conditions. In particular, we selected five well-known methods from the state of the art and used them to enhance a dataset of images produced in various underwater sites with different conditions of depth, turbidity, and lighting. These enhanced images were evaluated by means of three different approaches: objective metrics often adopted in the related literature, a panel of experts in the underwater field, and an evaluation based on the results of 3D reconstructions.
关键词： automatic colour equalization,3D reconstruction,non-local dehazing,benchmark,lab,colour correction,screened poisson equation,CLAHE,underwater image enhancement,dehazing
更新于2025-09-09 09:28:46
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Comparison of Modulation Techniques for Underwater Optical Wireless Communication Employing APD Receivers
摘要： In this study, we theoretically analyze the performance of an underwater optical wireless communications system using different modulation techniques and an avalanche photodiode APD receiver over underwater environment channels. Based on the LOS geometrical model and combined with signal to noise ratio model for Si and Ge APD and BER; then the impact of the distance of transmission and power of the transmitter and Jerlov water type are analyzed. The characteristics of bit error rate BER for different optical modulation techniques are studied. Simulation results indicate that the performance of H-QAM is more suited for an underwater optical wireless communication. On the other hand, the suitability of avalanche photodiodes under these modulation techniques is discussed, because the photodiode Si APD has more advantages compared with Ge APD when used in an underwater optical communication.
关键词： Avalanche photodiode APD,modulation,underwater optical communication,bit error rate BER
更新于2025-09-09 09:28:46
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Freshwater Fish Habitat Complexity Mapping Using Above and Underwater Structure-From-Motion Photogrammetry
摘要： Substrate complexity is strongly related to biodiversity in aquatic habitats. We illustrate a novel framework, based on Structure-from-Motion photogrammetry (SfM) and Multi-View Stereo (MVS) photogrammetry, to quantify habitat complexity in freshwater ecosystems from Unmanned Aerial Vehicle (UAV) and underwater photography. We analysed sites in the Xingu river basin, Brazil, to reconstruct the 3D structure of the substrate and identify and map habitat classes important for maintaining fish assemblage biodiversity. From the digital models we calculated habitat complexity metrics including rugosity, slope and 3D fractal dimension. The UAV based SfM-MVS products were generated at a ground sampling distance (GSD) of 1.20–2.38 cm while the underwater photography produced a GSD of 1 mm. Our results show how these products provide spatially explicit complexity metrics, which are more comprehensive than conventional arbitrary cross sections. Shallow neural network classification of SfM-MVS products of substrate exposed in the dry season resulted in high accuracies across classes. UAV and underwater SfM-MVS is robust for quantifying freshwater habitat classes and complexity and should be chosen whenever possible over conventional methods (e.g., chain-and-tape) because of the repeatability, scalability and multi-dimensional nature of the products. The SfM-MVS products can be used to identify high priority freshwater sectors for conservation, species occurrences and diversity studies to provide a broader indication for overall fish species diversity and provide repeatability for monitoring change over time.
关键词： Xingu river,Brazil,neural network,river,UAV,rugosity,fractal dimension,underwater
更新于2025-09-09 09:28:46
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An ultrasonic sensor composed of a fiber Bragg grating with an air bubble for underwater object detection
摘要： We present and experimentally demonstrate a novel optical fiber ultrasonic sensor composed of a fiber Bragg grating (FBG) with an air bubble for underwater object detection. The air bubble is formed by splicing etched FBG and single mode fiber (SMF) with taper-shaped holes. And because of the corrosive action, the diameters of FBG and SMF reduces from 125 μm to dozens of micrometers, which will be conducive to improving the sensor's performances. The experiment results indicate that the sensor has high voltage responses of 6.3 V and 7.1 V to the continuous and pulse ultrasonic wave (UW) at 1 MHz and could be used for underwater objects imaging with high signal-to-noise ratio (SNR). Subsequently, the environmental temperature will not influence ultrasonic measurements using the sensor on account of the low temperature sensitivity of 19.5 pm/°C.
关键词： Ultrasonic sensor,Fibre Bragg grating,Fibre-optic sensor,Underwater object detection
更新于2025-09-09 09:28:46
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[IEEE 2018 24th International Conference on Pattern Recognition (ICPR) - Beijing, China (2018.8.20-2018.8.24)] 2018 24th International Conference on Pattern Recognition (ICPR) - Single Shot Feature Aggregation Network for Underwater Object Detection
摘要： The rapidly developing ocean exploration and observation make the demand for underwater object detection become increasingly urgent. Recently, deep convolutional neural networks (CNN) have shown strong ability in feature representation and CNN-based detectors also achieve remarkable performance, but still facing the big challenge when detecting multi-scale objects in a complex underwater environment. To address this challenge, we propose a novel underwater object detector, introducing multi-scale features and complementary context information for better classification and location ability. In the auto-grabbing contest of 2017 Underwater Robot Picking Contest sponsored by National Natural Science Foundation of China (NSFC), we won the 1-st place by using proposed method for real coastal underwater object detection.
关键词： context information,multi-scale features,underwater object detection,deep convolutional neural networks
更新于2025-09-09 09:28:46