Imaging properties of bright-field and annular-dark-field scanning confocal electron microscopy: II. point spread function analysis

The imaging properties of bright field and annular dark field scanning confocal electron microscopy (BF-SCEM and ADF-SCEM) are discussed based on their point spread functions (PSFs) in comparison with multislice simulations. Although the PSFs of BF-SCEM and ADF-SCEM show similar hourglass shapes, their numerical distributions are quite different: BF-SCEM PSF is always positive and shows a center of symmetry whereas the ADF-SCEM PSF is complex and has Hermitian symmetry. These PSF properties explain the large elongation effect in BF-SCEM for laterally extended object and almost no-elongation in ADF-SCEM, illustrating the importance of the numerical analysis of PSFs. The Hermitian symmetry of the ADF-SCEM PSF results in an interesting “edge enhancement effect” at the interface. Simulation using the PSF and the multislice method verified this effect at GaAs surfaces and InAs interfaces embedded in GaAs. This unique feature of ADF-SCEM can potentially be useful for depth sectioning. It is also pointed out that a PSF imaging model cannot be applicable for BF-SCEM of a phase object, when the system is symmetric and aberration free.     

TDI-CCD总剂量辐射效应及其测试研究

摘要：对应用于某空间相机中定制的TDI-CCD,为评估空间辐射效应对其成像性能的影响,从器件的电路结构入手,分析了总剂量辐射效应对器件主要性能指标的影响;研究了针对此器件的总剂量辐照实验测试方法并研制了测试装置;对器件进行了60Co γ射线源总剂量辐照实验,定量测试了受辐照前后器件的光电响应性能及对比度传递函数的变化情况。实验结果表明,总辐照剂量达到20kRad(Si)时,定制TDI-CCD的相对响应度、暗电流、动态范围、最大信噪比相对于该器件没受辐照的初始值变化量小于5%,对比度传递函数(CTF)没有明显变化,说明定制的TDI-CCD器件能够满足某空间相机的使用要求。