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

本文提出了一种新的高分辨率透射式电子显微镜球差校正技术的概念(1986-1987，科学研究补助金(C))。在理论研究方面，首先提出了一种基于主动散焦调制和正弦加权图像积分的简单带通滤波方法，并利用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中的球差校正。在相干光学系统中球差的情况下，也可以解析地推导出与散焦调制同步的用于该处理的加权函数。球差COREC…的模拟实验采用球差系数可变的物镜，成功地实现了光学显微镜中的更多像差。在本理论研究的最后阶段，这种离焦调制处理的概念已经扩展到3D处理，处理后的图像比原始的与谢尔泽焦点对应的稍微散焦的图像具有更好的质量。通过分析指出，采用散焦调制和样品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。对于在透射电子显微镜上的实验，首先构造了一个微型静态透镜来实现非常快的离焦调制。然而，这种透镜已经准备好在目前的处理中使用，因为由于机械精度不足，在散焦调制下图像平移很大。然后，仅检查了简单的带通滤波函数，以验证在透射电子显微镜中的当前处理。实验结果表明，该滤波函数能够很好地考虑离焦变化引起的残差图像平移。由此，本球差校正技术可望在充分调整电子光学系统的基础上，通过像移的方法，应用于高分辨率的电子显微镜。较少

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