Event cameras are bio-inspired vision sensors with a high dynamic range (140 dB for event cameras vs. 60 dB for traditional cameras) and can be used to tackle the image degradation problem under extremely low-illumination scenarios, which is still not well-explored yet. In this paper, we propose a joint framework to compose the underexposed frames and event streams captured by the event camera to reconstruct clear images with detailed textures under almost dark conditions. A residual fusion module is proposed to reduce the domain gap between event streams and frames by using the residuals of both modalities. A multi-level reconstruction loss based on the variability of the contrast distribution is proposed to reduce the perceptual errors of the output image. In addition, we construct the first real-world low-illumination image enhancement dataset (mainly under 2 lux illumination scenes), named LIE, containing event streams and frames collected under indoor and outdoor low-light scenarios together with the ground truth clear images. Experimental results on our LIE dataset demonstrate that our proposed method could achieve significant improvements compared with existing methods.

Target search for moving and invisible objects has always been considered a challenge, as the floating objects drift with the flows. This study focuses on target search by multiple autonomous underwater vehicles (AUV) and investigates a multi-agent target search method (MATSMI) for moving and invisible objects. In the MATSMI algorithm, based on the multi-agent deep deterministic policy gradient (MADDPG) method, we add spatial and temporal information to the reinforcement learning state and set up specialized rewards in conjunction with a maritime target search scenario. Additionally, we construct a simulation environment to simulate a multi-AUV search for the floating object. The simulation results show that the MATSMI method has about 20% higher search success rate and about 70 steps shorter search time than the traditional search method. In addition, the MATSMI method converges faster than the MADDPG method. This paper provides a novel and effective method for solving the maritime target search problem.

The marine environment presents a unique set of challenges for human–robot interaction. Communicating with gestures is a common way for interacting between the diver and autonomous underwater vehicles (AUVs). However, underwater gesture recognition is a challenging visual task for AUVs due to light refraction and wavelength color attenuation issues. Current gesture recognition methods classify the whole image directly or locate the hand position first and then classify the hand features. Among these purely visual approaches, textual information is largely ignored. This paper proposes a visual–textual model for underwater hand gesture recognition (VT-UHGR). The VT-UHGR model encodes the underwater diver’s image as visual features, the category text as textual features, and generates visual–textual features through multimodal interactions. We guide AUVs to use image–text matching for learning and inference. The proposed method achieves better performance than most existing purely visual methods on the dataset CADDY, demonstrating the effectiveness of using textual patterns for underwater gesture recognition.

Underwater biological detection technology holds considerable promise for delving into the abundance of marine species and resources. It can seamlessly integrate into Autonomous Underwater Vehicles (AUVs), providing robust support for the application and enhancement of the Internet of Underwater Things (IoUT) systems. Recently, data-driven artificial intelligence technologies have exhibited considerable potential in underwater object detection. Nonetheless, the degraded underwater imaging environments present challenges for imaging devices on AUVs or other underwater devices. In this paper, we propose an advanced fish school detection framework designed to significantly contribute to the IoUT systems. This framework enhances performance in challenging conditions like inadequate illumination, blurriness, and high fish population density. The proposed framework demonstrates the capability to promptly identify changes in underwater species, such as migration or aggregation of large fish schools. The timely recognition of such changes offers vital information for IoUT applications, particularly in the management of marine biological resources. Furthermore, our framework can be flexibly deployed on AUVs and in-situ observation stations. Additionally, degraded underwater conditions and high acquisition costs hinder the scalability of data-driven methods. Therefore, we create a novel dense fish school detection dataset named DUFish, expertly annotated with high-quality bounding boxes. The proposed detection framework showcases exceptional performance on DUFish, outperforming state-of-the-art target detection algorithms. This has the potential to augment the capabilities of biological recognition and applications within the IoUT systems.

In typical alteration extraction methods, e.g., band math and principal component analysis (PCA), the bands or band combinations unitized to extract altered minerals are usually selected based on empirical models or previous rules. This results in significant differences in the alteration of mineral mapping even in the same area, thus greatly increasing the uncertainty of mineral resource prediction. In this paper, an intelligent alteration extraction approach was proposed in which an optimization algorithm, i.e., a genetic algorithm (GA), was introduced into the PCA; this approach is termed GA-PCA and is used for selecting the optimized band combinations of mineralized alterations. The proposed GA-PCA was employed to map iron oxides and hydroxyl minerals using the most commonly adopted multispectral data, i.e., Landsat-8 OLI data, at the Lalingzaohuo polymetallic deposits, China. The results showed that the spectral characteristics of GA-PCA-selected OLI band combinations in the research area were beneficial for enhancing alteration information and were more capable of suppressing the interference of vegetation information. The mapping alteration zones using the GA-PCA approach had a higher agreement with known ore spots, i.e., 25% and 33.3% in ferrous-bearing and hydroxyl-bearing deposits, compared to the classical PCA. Furthermore, two predicted targets (not shown in the classical PCA results) were precisely obtained via analyzing the GA-PCA alteration maps combined with the ore-forming geological conditions of the mine and its tectonic characteristics. This indicated that the intelligent selection of mineral alteration band combinations increased the reliability of remote sensing-based mineral exploration.

Underwater fine-grained classification technology is crucial for discerning subtle differences among marine life classes, playing a pivotal role in marine resource exploration and the discovery of new species. Autonomous underwater vehicles equipped with this technology can enhance their environmental interaction and perception, providing critical data for Internet of Underwater Things (IoUT) systems. However, popular vision transformer-based methods encounter challenges in complex marine environments, particularly due to limited computational resources. In this paper, we introduce an Efficient Vision Transformer with Token-selective and Merging Strategies (TSMVT), which significantly improves underwater fine-grained classification performance while reducing the number of processed tokens. TSMVT can be flexibly integrated into various IoUT systems, promoting the discovery of new species and the sustainable development of marine ecology. Firstly, we propose a dynamic token filtering mechanism that effectively retains important tokens, merges low-information tokens, and discards irrelevant background tokens, significantly reducing computational demands. Secondly, we propose the Multi-head Attention Weighting Token-Selective (MAWTS) module, which dynamically adjusts attention weights. MAWTS enables the network to focus on key features such as fin shape, head structure, and body proportions, thereby improving classification accuracy. With a 30% reduction in tokens, TSMVT achieves superior precision in classifying marine species, enhancing its applicability on various underwater mobile platforms. Extensive experiments conducted on four marine and three terrestrial datasets demonstrate the outstanding accuracy and efficiency of the proposed TSMVT.