Laser interference can interfere with target detection systems to achieve the goal of protecting the target. For example, it can obscure the target and change information such as brightness and contrast in the surrounding region of the interference zone. Therefore, it is necessary to analyze the impact of laser interference on target detection algorithms and evaluate the anti-interference performance of the algorithm. This paper analyzes the impact of laser interference on two target detection algorithms, Faster-RCNN and YOLO-V3, from two perspectives: target occlusion rate and target similarity. Then, a target-oriented method for dividing the effective region of laser interference (TODERLI) is proposed. The effectiveness of the algorithm is verified through experiments.
The task of classifying small objects is still challenging for current deep learning classification models [such as convolutional neural networks (CNNs) and vision transformers (ViTs)]. We believe that these algorithms are not designed specifically for small targets, so their feature extraction abilities for small targets are insufficient. To improve the classification capabilities of CNN-based and ViT-based classification models for small objects, two multidomain feature fusion (MDFF) frameworks are proposed to increase the amount of feature information derived from images and they are called MDFF-ConvMixer and MDFF-ViT. Compared with the basic model, the uniquely added design includes frequency domain feature extraction and MDFF processes. In the frequency domain feature extraction part, the input image is first transformed into a frequency domain form through discrete cosine transform (DCT) transformation and then a three-dimensional matrix containing the frequency domain information is obtained via channel splicing and reshaping. In the MDFF part, MDFF-ConvMixer splices the spatial and frequency domain features by channel, whereas MDFF-ViT uses a cross-attention mechanism to fuse the spatial and frequency domain features. When targeting small target classification tasks, these two frameworks obviously improve the utilized classification algorithm. On the DOTA dataset and the CIFAR10 dataset with two downsampling operations, the accuracies of MDFF-ConvMixer relative to ConvMixer increase from 87.82% and 62.14% to 90.14% and 66.00%, respectively, and the accuracies of MDFF-ViT relative to the ViT increase from 79.22% and 36.2% to 88.15% and 59.23%, respectively.
At present, most of the full reference laser disturbing image quality assessment methods need to know the position information of the disturbing spot and the target in advance, so that the assessment process is restricted by the prior knowledge and the preprocessing method. Aiming at this problem, this paper proposes a laser disturbing image quality assessment method based on convolution feature similarity (CNNSIM), which analyzes the output features of the image before and after laser disturbing in the convolution network. The occlusion degree of key information in the disturbing image is assessed by using the hierarchy and the sensitivity to occlusion of features, thus avoiding the input requirement of target/spot location information. The simulation experiment verifies the effectiveness of the new assessment method in different scenarios.
Faster R-CNN is a general-purpose detection algorithm that performs well in most cases. However, Faster R-CNN performs poorly on detecting small-scale UAVs. In order to improve the detection performance for small-scale UAVs, a new anchor strategy (TLCS-Anchor) which could be adopted by Faster R-CNN is proposed in this paper. Firstly, the anchor templates are designed to be suitable for the UAV dataset by using the clustering method so that the aspect ratios and scales for anchors are more targeted to UAVs. Then, a new compensation strategy of anchors is proposed to help detect small-scale UAVs in this paper, which could not only improve the number of anchors matched with the UAVs, but also alleviate the problem that small-scale UAVs can’t match with enough anchors to some extent. Experimental results show that TLCS-Anchor can help improve the detection performance for UAVs, especially for small-scale UAVs. In theory, TLCS-Anchor can also be used to detect other small-scale targets.
With the application of image more and more widely, People put forward higher requirements on the image quality of small objects and details in the image. In recent years, with the development of deep learning, it achieved good results in the research of image super-resolution. In this paper, we proposed EDSRGAN, a single image super-resolution(SISR) algorithm, based on enhanced residual network and the adversarial network. Compared with SRGAN, which is also based on the adversarial network, EDSRGAN can greatly reduce the high-frequency noise contained in the super-resolution(SR) image, and it also leads SRGAN in terms of peak signal to noise ratio and structural similarity evaluation indicators. Although EDSRGAN lagged behind EDSR in terms of peak signal to noise ratio and structural similarity, the SR images generated by EDSRGAN were sharper than EDSR in the object edges and targets details. EDSRGAN could achieve good results in image super-resolution on small targets.
For the problem that VGG network cannot use the special information of feature maps, this paper proposes a new algorithm that constructs the sum pooling feature based on the feature map extracted by the convolutional neural network. And this algorithm retains the construction of original feature maps so that special information on the original feature map could be used more reasonably. And then, this paper uses DOTA datasets to verify the proposed method. The results show that compared with the VGG-16 network, the proposed SPFC algorithm improves the accuracy in rough aircraft classification and the fighter subdivision.
Scanning infrared imaging system often suffers from stripe non-uniformity. Considering the geometric characteristic of stripe non-uniformity in scanning images, the gradient of pixels cross scanning direction is much more than that in scanning direction, and the latter is more similar to the real scene. The reason for the above phenomenon is that pixels in scanning direction have uniformity parameters and those cross scanning direction have non-uniformity parameters. Therefore, a homogenization method based on a unidirectional variation model is proposed in this paper. The unidirectional variation model can minimize the gradient cross scanning direction. And the homogenization method is used to preserve the edge and detailed information in scanning direction. Experimental results demonstrate a good performance of our proposed method for stripe non-uniformity images.
An effective method for small and dim moving target detection in complicated background is proposed. The proposed approach takes advantage of the Non-local means filter, and applies a novel weight calculation model based on circular mask to the original background estimation pattern. By associating similarity of grayscale distribution of the images with temporal information, the extended method realize the complicated background estimation and point target extraction successfully. To compare existing target detection methods and the proposed method, signal-to-clutter ratio gain (SCRG) and background suppression factor (BSF) are employed for spatial performance comparison and receiver operating characteristics (ROC) is used for detection-performance comparison of the target trajectory. Experimental results demonstrate good performance of the proposed method in complicated scenes and low signal to noise ratio images.
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