提出了一个能增强图像边缘的异性扩散模型,结合P-M扩散模型和反热扩散模型各自的优点,能在去除图像噪声的同时增强图像的边缘,一定程度上克服了P-M扩散模型对图像边缘的模糊效应和反热扩散模型容易产生虚假边缘的缺点。实验结果表明:提...提出了一个能增强图像边缘的异性扩散模型,结合P-M扩散模型和反热扩散模型各自的优点,能在去除图像噪声的同时增强图像的边缘,一定程度上克服了P-M扩散模型对图像边缘的模糊效应和反热扩散模型容易产生虚假边缘的缺点。实验结果表明:提出的模型有很好的去噪和增强图像边缘的效果,其峰值信噪比(Peak Signal Noise Ratio,PSNR)在强噪声水平下,较P-M扩散模型大约提高1 dB。展开更多
For Hall plates, the ratio of signal over thermal noise is determined by material properties, thickness, layout geometry, magnetic field, and the electric power at which the plate is operated. For traditional Hall pla...For Hall plates, the ratio of signal over thermal noise is determined by material properties, thickness, layout geometry, magnetic field, and the electric power at which the plate is operated. For traditional Hall plates with four contacts, the optimum choice is a symmetrical device with medium-sized contacts. This paper shows that the signal-to-noise-ratio (<em>SNR</em>) can be further increased by up to 90% for Hall plates with more than four contacts. Supply currents flow through several pairs of contacts, while a signal conditioning circuit taps output voltages at all pairs of contacts and sums them up. We compute the total thermal noise of the sum of correlated noise voltages and relate it to the total magnetic sensitivity. We also prove that for electrically linear devices a spinning current scheme cancels out zero point errors (offset errors) in a strict sense. All our investigations use the definite resistance matrix of multi-port Hall plates. We develop an analytical theory based on recent advances in the theory of Hall plates, and then we compute the integrals and matrices numerically for symmetrical Hall plates with six to 40 contacts. We also present measurements in accordance with our theory.展开更多
目前,国内机构针对星敏感器的温控研究与设计较少,多集中于星图的图像处理和图像算法的优化。着重以星图中目标能量变化、信噪比、质心定位误差等参数为指标,分析温度对该星敏感器的热影响,从而实现高精度星敏感器在空间复杂热环境下的...目前,国内机构针对星敏感器的温控研究与设计较少,多集中于星图的图像处理和图像算法的优化。着重以星图中目标能量变化、信噪比、质心定位误差等参数为指标,分析温度对该星敏感器的热影响,从而实现高精度星敏感器在空间复杂热环境下的可靠应用。进一步基于星敏感器的结构及热分布,对星敏感器进行热设计及散热路径优化,提出星敏感器热电制冷器(Thermo electric cooler,TEC)的热控措施。以典型在轨高温工况与低温工况为例,利用有限元仿真软件进行该热设计的有效性与合理性仿真分析。在以上的设计与分析基础上,完成一套温度控制系统,通过模拟星敏感器在高温工况下的环境条件,使用热电制冷方式对星敏感器采取制冷措施,使星敏感器探测器温度维持在20℃±3℃,达到温控指标,保证星敏感器能够在恶劣温度环境下持续提供高精度姿态信息。重点阐明热环境因素与成像质量之间的关系,完成温度与星点识别精度的关联性分析,为后续星敏感器热控设计及定姿精度提升提供参考。展开更多
文摘提出了一个能增强图像边缘的异性扩散模型,结合P-M扩散模型和反热扩散模型各自的优点,能在去除图像噪声的同时增强图像的边缘,一定程度上克服了P-M扩散模型对图像边缘的模糊效应和反热扩散模型容易产生虚假边缘的缺点。实验结果表明:提出的模型有很好的去噪和增强图像边缘的效果,其峰值信噪比(Peak Signal Noise Ratio,PSNR)在强噪声水平下,较P-M扩散模型大约提高1 dB。
基金Research supported by natural science foundation of Xuzhou Normal University(08XLB06)the projects of the program for postgraduate researchinnovative in Xuzhou Normal University(09YLB026)
文摘For Hall plates, the ratio of signal over thermal noise is determined by material properties, thickness, layout geometry, magnetic field, and the electric power at which the plate is operated. For traditional Hall plates with four contacts, the optimum choice is a symmetrical device with medium-sized contacts. This paper shows that the signal-to-noise-ratio (<em>SNR</em>) can be further increased by up to 90% for Hall plates with more than four contacts. Supply currents flow through several pairs of contacts, while a signal conditioning circuit taps output voltages at all pairs of contacts and sums them up. We compute the total thermal noise of the sum of correlated noise voltages and relate it to the total magnetic sensitivity. We also prove that for electrically linear devices a spinning current scheme cancels out zero point errors (offset errors) in a strict sense. All our investigations use the definite resistance matrix of multi-port Hall plates. We develop an analytical theory based on recent advances in the theory of Hall plates, and then we compute the integrals and matrices numerically for symmetrical Hall plates with six to 40 contacts. We also present measurements in accordance with our theory.
文摘目前,国内机构针对星敏感器的温控研究与设计较少,多集中于星图的图像处理和图像算法的优化。着重以星图中目标能量变化、信噪比、质心定位误差等参数为指标,分析温度对该星敏感器的热影响,从而实现高精度星敏感器在空间复杂热环境下的可靠应用。进一步基于星敏感器的结构及热分布,对星敏感器进行热设计及散热路径优化,提出星敏感器热电制冷器(Thermo electric cooler,TEC)的热控措施。以典型在轨高温工况与低温工况为例,利用有限元仿真软件进行该热设计的有效性与合理性仿真分析。在以上的设计与分析基础上,完成一套温度控制系统,通过模拟星敏感器在高温工况下的环境条件,使用热电制冷方式对星敏感器采取制冷措施,使星敏感器探测器温度维持在20℃±3℃,达到温控指标,保证星敏感器能够在恶劣温度环境下持续提供高精度姿态信息。重点阐明热环境因素与成像质量之间的关系,完成温度与星点识别精度的关联性分析,为后续星敏感器热控设计及定姿精度提升提供参考。
