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Fast and robust detection of a small target in an infrared image is one of the key techniques in infrared search and track systems. The Top-Hat transformation is an important technology in the field of infrared target detection. Many algorithms have been proposed to improve the Top-Hat transformation by modifying different structural elements. However, these methods can cause a high false alarm rate under conditions of small dim targets, low signal-to-noise, and complex background. To overcome this limitation, considering both detection performance and speed, an effective and robust detection model using multidirectional structural elements is proposed in this article. First, the non-concentric multidirectional ring structural elements are designed. Then, using the morphological transformation with designed structural elements, the background is suppressed, and a small target is enhanced in different directions. Finally, the results of the morphological transformations are fused to obtain the final result, further highlighting a small target. The experimental results demonstrate the robust performance of the proposed method for various backgrounds and targets. In addition, the proposed method can achieve a detection speed of up to 10.4 ms per frame under the image resolution of 240 × 320 pixels. Therefore, the proposed method is suitable for real-time applications.

To maintain the boundaries of salient objects in the detection results, some methods start to apply additional edge labels to train their networks to learn detailed information. These methods have made gratifying progress. However, since the quality of the saliency maps will be affected by boundary features, it is still worth exploring how to extract effective boundary features and fuse them with semantic features. In this

The determination and mathematical descriptions of the difference between the imaging radiation measurement and the non-imaging radiation measurement which is of maturity are necessary for extending the radiation measurement from non-imaging technology to imaging technology. In this paper, the mathematical descriptions of the imaging and non-imaging radiation measurement are deduced based on the basic equations of radiation measurement and the correspondence between the infinitesimal planes of the target and sensor array. Because the imaging plane does not change the radiation transfer between the target and sensor, the mathematical descriptions of the imaging effect can be obtained by comparing the two mathematical descriptions. A concrete analysis of the imaging effect based on pinhole imaging and lens imaging is carried out. The results show that the primary cause of the imaging effect is the imaging optical axis angle while the subsidiary cause is the imaging zenith angle, and the influence of the subsidiary cause is determined by the difference between the imaging optical axis angle and the imaging zenith angle.

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A series of Hf:Yb:Nd:LiNbO 3 crystals with different [Li]/[Nb] ratios (0.946, 1.05, 1.20, and 1.38) were grown using the Czochralski method. X-ray diffraction phase results of the samples show that the LiNbO 3 doped Hf 4+ , Yb 3+ , and Nd 3+ only have a slight change in the lattice constant. The birefringence gradient of the HfYbNd4 sample measured using the birefringence gradient method was 3.3 × 10 −5 ∆R/cm −1 , which was the best optical uniformity. The optical damage resistance ability was measured using the light-induced scattering exposure energy flus threshold method. When the [Li]/[Nb] ratios in the melt achieve 1.38, the exposure energy achieves 120.74 J/cm 2 , which is approximately 87 times higher than HfYbNd1.