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进行球差校正的新方法（1986-1987，科学研究资助项目(C)）。本研究的主要目的是进行详细的理论分析，并确认该新技术在高分辨率透射电镜中的适用性。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图像积分的简单带通滤波方法，并通过相干照明光学显微镜获得了初步的实验结果。其次，将该方法推广到相干光学系统的球像差校正。对于相干光学系统中存在球差的情况，也可以解析导出与离焦调制同步处理的加权函数。利用变球差系数物镜，成功地实现了光学显微镜球差系数的模拟实验。处理后的图像与原始的稍微散焦的图像相比，显示出更好的质量，对应于“Scherzer”焦点，这被认为是未处理图像的最佳图像。在本理论研究的最后阶段，将离焦调制处理的概念扩展到三维处理中。通过分析指出，采用离焦和采样位置调制的有源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，首先构造了微型静态透镜，实现了快速离焦调制。然而，由于机械精度不足导致的离焦调制导致图像平移非常大，因此在目前的处理中已经放弃使用该镜头。然后，在透射电子显微镜下，仅对一个简单的带通滤波函数进行了检验。从实验结果来看，该滤波函数在考虑残差图像平移和离焦变化的情况下得到了很好的验证。由此可见，在电子光学系统经过图像平移的充分调整下，本技术有望应用于高分辨率透射电镜。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