This paper presents a zooming and shaping system for a semiconductor laser beam based on aspheric lens group. Firstly, a theoretical model for transforming Gaussian beam into flat-top beam is established from Gaussian beam model and flattop beam model. Secondly, using the model and the derived mapping function formula, the shaping system is automatically optimized with optical design software to realize the conversion from Gaussian beam to flat-top beam. Finally, a zooming optical path with aspheric lens group is designed by optical design software to achieve laser beam zooming and shaping, and a surface type equation with machinability is obtained. Research results: The designed optical system forms a relatively uniform spot in far field, such as 500m, and the divergence angle can achieve continuous change of 8-32mrad. The research results have certain reference value and guiding significance for the shaping and homogenization design of semiconductor laser beam.
In order to enhance the robustness of IR fast small target tracking, a novel mean shift tracking algorithm using improved similarity measure of is proposed. Firstly, problems of local background interfering in original mean shift algorithm for tracking fast motion small target is analyzed, and the reasons is located in the Bhattacharyya coefficient similarity measure expression for all gray weights of components are same, which cannot reflect the advantage contribution of the small target’s gray component in the process of measuring similarity, causing serious interference of the background in the tracking process, leaving the algorithm converging easily. Therefore, to solve this problem, the improvements Bhattacharyya coefficient similarity measure with the local background information fused is proposed. Then, shift vector is deduced in the framework of mean shift by regarding Bhattacharyya coefficients as the similarity measure.In shifting process, the robustness of the small target tracking is improved effectively according to target gray level of large membership degree with high shift weight, and vice versa with low shift weight, which the background interference is suppressed to some extent. In sake of verifying the performance of the proposed algorithm, the classical mean shift algorithm and the algorithm of this paper is used in the target tracking simulation experiment, as well as the infrared image sequences containing the small fast targets of uncooled infrared camera is used. Finally the experimental result indicates that the performance of tracking the small fast target in IR images is robust.
The modeling and the validation methods of the spectral BRDF on the material surface of space target were presented. First, the microscopic characteristics of the space targets’ material surface were analyzed based on fiber-optic spectrometer using to measure the direction reflectivity of the typical materials surface. To determine the material surface of space target is isotropic, atomic force microscopy was used to measure the material surface structure of space target and obtain Gaussian distribution model of microscopic surface element height. Then, the spectral BRDF model based on that the characteristics of the material surface were isotropic and the surface micro-facet with the Gaussian distribution which we obtained was constructed. The model characterizes smooth and rough surface well for describing the material surface of the space target appropriately. Finally, a spectral BRDF measurement platform in a laboratory was set up, which contains tungsten halogen lamp lighting system, fiber optic spectrometer detection system and measuring mechanical systems with controlling the entire experimental measurement and collecting measurement data by computers automatically. Yellow thermal control material and solar cell were measured with the spectral BRDF, which showed the relationship between the reflection angle and BRDF values at three wavelengths in 380nm, 550nm, 780nm, and the difference between theoretical model values and the measured data was evaluated by relative RMS error. Data analysis shows that the relative RMS error is less than 6%, which verified the correctness of the spectral BRDF model.
In this paper, a new method to recognize bridge in the complicated background is presented. The algorithm takes full
advantages of the characteristics of the bridge image. Firstly, the image is preprocessed and the object edges are
extracted. Then according to the limitations of traditional Hough transform (HT), the extraction method of the image line
segment characteristic of HT is improved, which eliminates spurious peaks on the basis of global and local thresholds,
discriminates the position relation between two straight line segments, and merges segments with near endpoints, etc.
Experiments show that this algorithm is more precise and efficient than traditional HT, moreover it can provide a
complete description of the bridge in a complicated background.
In this paper, by analyzing the basic road features in remote sensing images, the model of road extraction is discussed.
The popular methods of road extraction and their advantages and disadvantages are generalized. The recent progress and
results of our research group at relative aspects are introduced. The development of the issue is also presented.
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