公开(公告)号：US06992289B2

公开(公告)日：2006-01-31

申请号：US10928573

申请日：2004-08-27

申请人： Willem Hendrik Maes ,  Robertus Johannes Michael Vucht ,  Hendrikus Petrus Maria Sterken

发明人： Willem Hendrik Maes ,  Robertus Johannes Michael Vucht ,  Hendrikus Petrus Maria Sterken

IPC分类号： H01J29/56 ,  H01J29/58

CPC分类号： H01J37/21 ,  H01J2237/216

摘要： Method for performing focusing in a particle-optical device with the aid of astigmatism in the particle beam.In a particle-optical device such as an electron microscope it is advantageous to perform the process of focusing automatically. In accordance with the invention, the electron beam which is to be focused is deliberately made astigmatic to a certain degree. With this astigmatic beam, two images of a specimen are made at two different settings of the objective, after which in each of the images the direction of the astigmatic smearing is determined—for example, with the aid of a two-dimensional Fourier transform (FFT). The directions of the astigmatic smearing are perpendicular to each other if, in the transition from a first setting of the objective to a second one, the point of optimum focus is passed. Through a process of interpolation (which process may be iterative) between these two settings, the point of optimum focus can now be determined. Possible anisotropy in the specimen itself can be eliminated by making two images at both of the settings of the objective and by subtracting the FFTs thereof from each other.

摘要翻译： 借助于散射光束中的散光在粒子光学器件中进行聚焦的方法。 在诸如电子显微镜的粒子光学器件中，有利的是自动执行聚焦过程。 根据本发明，要聚焦的电子束在一定程度上刻意散焦。 利用该散光束，在目标的两个不同设置处制作样本的两个图像，之后在每个图像中确定散光涂片的方向 - 例如，借助于二维傅立叶变换（ FFT）。 如果在从目标的第一设置到第二设置的过渡中，通过最佳焦点的点，则散光涂抹的方向彼此垂直。 通过这两个设置之间的内插过程（该过程可能是迭代的），现在可以确定最佳焦点。 可以通过在物镜的两个设置中通过在彼此中减去FFT来实现两个图像来消除样本本身中可能的各向异性。