Unmanned aerial vehicles (UAVs) have been widely applied in military and civilian fields, but they also pose great threats to restricted areas, such as densely populated areas and airports. Thermal infrared (IR) imaging technology is capable of monitoring UAVs at a long range in both day and night conditions. Therefore, the anti-UAV technology based on thermal IR imaging has attracted growing attention. However, the images acquired by IR sensors often suffer from small and dim targets, as well as heavy background clutter and noise. Conventional detection methods usually have a high false alarm rate and low detection accuracy. This article proposes a detection method that formulates the UAV detection as predicting the residual image (i.e., background, clutter, and noise) by learning the nonlinear mapping from the input image to the residual image. The UAV target image is obtained by subtracting the residual image from the input IR image. The constructed end-to-end U-shaped network exploits the depthwise separable residual dense blocks in the encoder stage to extract the abundant hierarchical features. Besides, the multiscale feature fusion and representation block is introduced to fully aggregate multiscale features from the encoder layers and intermediate connection layers at the same scale, as well as the decoder layers at different scales, to better reconstruct the residual image in the decoder stage. In addition, the global residual connection is adopted in the proposed network to provide long-distance information compensation and promote gradient backpropagation, which further improves the performance in reconstructing the image. The experimental results show that the proposed method achieves favorable detection performance in real-world IR images and outperforms other state-of-the-art methods in terms of quantitative and qualitative evaluation metrics.

Thermal infrared imaging possesses the ability to monitor unmanned aerial vehicles (UAVs) in both day and night conditions. However, long-range detection of the infrared UAVs often suffers from small/dim targets, heavy clutter, and noise in the complex background. The conventional local prior-based and the nonlocal prior-based methods commonly have a high false alarm rate and low detection accuracy. In this letter, we propose a model that converts small UAV detection into a problem of predicting the residual image (i.e., background, clutter, and noise). Such novel reformulation allows us to directly learn a mapping from the input infrared image to the residual image. The constructed image-to-image network integrates the global and the local dilated residual convolution blocks into the U-Net, which can capture local and contextual structure information well and fuse the features at different scales both for image reconstruction. Additionally, subpixel convolution is utilized to upscale the image and avoid image distortion during upsampling. Finally, the small UAV target image is obtained by subtracting the residual image from the input infrared image. The comparative experiments demonstrate that the proposed method outperforms state-of-the-art ones in detecting real-world infrared images with heavy clutter and dim targets.

Intelligent unmanned aerial vehicle (UAV) surveillance based on infrared imaging has wide applications in the antiUAV system for protecting urban security and aerial safety. However, weak target features and complex background distraction pose great challenges for the accurate detection of UAVs. To address this issue, we propose a novel differentiated attention guided network to adaptively strengthen the discriminative features between UAV targets and complex background. First, a novel spatial-aware channel attention (SCA) is introduced into deep layers via preserving critical spatial features and leveraging channel interdependencies to focus on the large-scale targets. The channel-modulated deformable spatial attention is introduced into shallow layers via refining channel context and dynamically perceiving the spatial features for focusing on the small-scale targets. A combination of the above two attention mechanisms is employed in intermediate layers of the network for concentrating on the medium-scale targets. Then, we embed a feature aggregator at the detection branches to guide the information exchange of high-level feature maps and low-level feature maps with a bottom-up context modulation, and integrate an SCA at the end to further boost the distinctive feature representation for task-awareness. The above design can adaptively enhance multiscale UAV target features and suppress complex background interferences, leading to better detection performance, especially for small targets. Extensive experiments on real infrared UAV datasets reveal that the proposed method outperforms the baseline object detectors by a large margin, validating its feasibility in real-world infrared UAV detection. The source code can be found at https://github.com/KALEIDOSCOPEIP/DAGNet .

Unmanned aerial vehicle (UAV) detection based on thermal infrared imaging has been one of the most important sensing technologies in the anti-UAV system. However, the technical limitations and long-range detection of thermal sensors often lead to acquiring low-resolution (LR) infrared images, thereby bringing great challenges for the subsequent target detection task. In this paper, we propose a novel spatial and contrast interactive super-resolution network (SCINet) for assisting infrared UAV target detection. The network consists of two main subnetworks: a spatial enhancement branch (SEB) and a contrast enhancement branch (CEB). The SEB embeds the lightweight convolution module and attention mechanism to highlight the spatial structure detail features of infrared UAV targets. The proposed CEB incorporates the center-oriented contrast-aware module and multi-branch collapsible module, which can provide local contrast priors to reconstruct the super-resolved UAV target image. The spatial features of the intermediate layers from the SEB are integrated into the CEB as a rich gradient prior. Besides, the output features of the CEB are aggregated into those of the SEB for further supplementing the contrast of spatial features in return. Dual-branch feature interaction of the SEB and CEB can further enhance the spatial details and target saliency of the targets. Additionally, we also introduce an infrared UAV detection network via a new dual-dimensional feature calibration module (DFCM) for boosting the detection performance. Extensive experiments demonstrate that the SCINet outperforms the state-of-the-art SR methods on real infrared UAV sequences and improves the detection performance of infrared small UAV targets. ¹

Unmanned aerial vehicles (UAVs) have been popular in many commercial and industrial applications, but they also pose great threats to urban safety and aerial security. Intelligent UAV surveillance based on thermal infrared imaging has attracted increasing attention for its long-range monitoring ability in both day and night scenarios. However, weak UAV target features, dynamically changing UAV states, and complex background interferences present serious challenges to the accurate tracking of UAVs. To tackle these problems, we propose a novel online multi-scale infrared UAV target tracking network (SiamCAP) incorporating the enhanced context feature awareness and pixel-wise attention modulation. We first introduce a novel contrast-enhanced multi-scale online re-parameterization block to effectively extract contrast difference intensity information between the target and background, and transform it into a single branch for both training and inference without introducing computational overhead. Then, we construct a feature fusion modulation module to guide cross-layer feature aggregation. It uses low-level attention to highlight the UAV target feature in the deep layer with the novel full spatial resolution channel attention, which calculates pixel-wisely importance without dimensionality compression. Finally, we propose a cross-attention based updatable feature interaction module to model the correlation between online updating multi-template and search frame, which improves the model’s robustness to changes in the state of UAVs and complex backgrounds. Extensive experiments on real infrared UAV datasets demonstrate that the proposed approach outperforms state-of-the-art target trackers under complex backgrounds while achieving a real-time tracking speed.