Real time spherical aberration correction with high resolution transmission election microscope based on active image processing method

本文提出了一种利用高分辨率透射电子显微镜校正球差的新技术。本研究的主要目的是对这种新技术进行详细的理论分析，并证实它在高分辨透射电子显微镜中的适用性。在理论研究方面，首先提出了一种基于主动离焦调制和正弦加权像积分的简单带通滤波方法，并在相干照明光学显微镜上进行了初步的实验研究。接着，将该方法推广到相干光学系统中的球差校正。在相干光学系统中存在球面像差的情况下，也可以解析地导出与散焦调制同步的用于该处理的加权函数。球面像差校正的模拟实验 关于我们 使用具有可变球差系数的物镜透镜成功地实现了光学显微镜中的光学成像。处理后的图像比未处理图像中最好的对应于Scherzer焦点的微离焦图像有更好的质量，在本理论研究的最后阶段，将这种离焦调制处理的概念推广到三维处理中。通过分析指出，利用离焦和样品位置调制的主动三维卷积器可以消除强散射物体引起的非线性成像效应。在透射电子显微镜实验中，首先构造了一个小型静态透镜，实现了快速离焦调制。然而，该透镜由于机械精度不足导致的散焦调制的图像平移非常大而被重新用于本处理中。然后，只有一个简单的带通滤波器的功能已被检查，以验证目前的处理在透射电子显微镜。从实验结果来看，该滤波器函数在考虑了具有散焦变化的残差图像平移的情况下得到了很好的证实。由此，在电子光学系统随像平移充分调整的情况下，本球差校正技术可望应用于高分辨透射电子显微镜。少

A concept of new spherical aberration correction technique with high resolution transmission electorn microscorp has been in the present study (1986-1987, Grant-in-Aid for Scientific Research (C) ). Main aims of this study are to achieve the detailed theoretical analysis and to confirm the applicability of this new technigue in the high resolution transmission electron microscopy.On the theoretical study, at first, a simple band pass filtering based on the active defocus modulation and sinusoidally weighted image intergration has been proposed with preliminary experimental results obtained by a coherently illuminated optical microscorp. Next, this approach has been extended to the spherical aberration correction in the coherent optical system. The weighting function for this processing, synchronized to the defocus modulation can be also analytically derived in the case of the spherical aberration in the coherent optical system. A simulative experiment of the spherical aberrayion correc … More tion in the optical microscope has beeb successfully achieved using an objective lens with variable spherical aberration coefficient. The processed image shows better quality compared with the original slightly defocused image correspondig to the 'Scherzer' focus, which is considered to be best one with non-processed images.In the final stage of the present theoretical study, the concept of this defocus modulation processing has been extended to the 3D processing. From the analysis, It is pointed out that the nonlinear imaging effect caused by strongly scattered object can be removed by the active 3D convolver using both the defocus and sample position modulation.As to the experiments in the transmission electron microscope, at first, a mini-static lens has been constructed to achieve the very fast defocus modulation. However, this lens has been resigned to use in the present processing because of that the image translation is very large with the defocus modulation, caused by insufficient mechanical accuracy. Then only a simple band pass filter function has been examined as to the verification of the present processing in the transmission electron microscope. From experimental results, this filter function has been well confirmed in consideration of the residual image translation with the defocus alteration. From this, the present spherical aberration correction technigue is expected to be applicable to the high resolution transmission electron microscope under sufficient adjustment of the electron optical system with the image translation. Less