Tokyo Institute of Technology, Ookayama, Tokyo, Japan.
Ultramicroscopy. 2013 Dec;135:71-9. doi: 10.1016/j.ultramic.2013.05.024. Epub 2013 Jun 19.
A generic method to determine the aberration center is established, which can be utilized for aberration calculation and axis alignment for aberration corrected electron microscopes. In this method, decentering induced secondary aberrations from inherent primary aberrations are minimized to find the appropriate axis center. The fitness function to find the optimal decentering vector for the axis was defined as a sum of decentering induced secondary aberrations with properly distributed weight values according to the aberration order. Since the appropriate decentering vector is determined from the aberration values calculated at an arbitrary center axis, only one aberration measurement is in principle required to find the center, resulting in /very fast center search. This approach was tested for the Ronchigram based aberration calculation method for aberration corrected scanning transmission electron microscopy. Both in simulation and in experiments, the center search was confirmed to work well although the convergence to find the best axis becomes slower with larger primary aberrations. Such aberration center determination is expected to fully automatize the aberration correction procedures, which used to require pre-alignment of experienced users. This approach is also applicable to automated aperture positioning.
建立了一种确定像差中心的通用方法，可用于像差校正电子显微镜的像差计算和轴对准。在该方法中，通过最小化固有初级像差引起的离轴次级像差来找到合适的轴中心。定义了用于找到最佳离轴矢量的适应度函数，该矢量是根据像差阶数适当分配权重值的离轴次级像差的总和。由于合适的离轴矢量是从任意中心轴计算的像差值确定的，因此原则上仅需要一次像差测量即可找到中心，从而实现非常快速的中心搜索。该方法针对基于 Ronchigram 的像差校正扫描透射电子显微镜的像差计算方法进行了测试。在模拟和实验中，尽管随着较大的初级像差，找到最佳轴的收敛速度变慢，但中心搜索被证实效果良好。这种像差中心的确定有望使像差校正过程完全自动化，而该过程过去需要经验丰富的用户进行预对准。该方法还适用于自动孔径定位。
