Hayashida Misa, Nomaguchi Tsunenori, Kimura Yoshihide, Takai Yoshizo
Department of Material and Life Science, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871, Japan.
Micron. 2007;38(5):505-12. doi: 10.1016/j.micron.2006.07.024. Epub 2006 Sep 8.
A computer-assisted minimal-dose system has been developed for the high-resolution observation of radiation-sensitive samples using a transmission electron microscope (TEM). This system consists of a CCD camera, a beam blanker and a control computer (PC) that also controls the TEM. A sample is illuminated by an electron beam only when the CCD camera takes images; otherwise, the beam blanker cuts off the electron beam. Emulated images, which are calculated from the images taken and the variable parameters of the TEM, such as magnification and sample stage position, are displayed on the control PC display. After a few times of repetition of exposures and emulations, the sample is positioned to final observation area. Subsequently to select the observation area, the system automatically adjusts the focus position from two different illuminating angle images and the TEM conditions are appropriate for taking a final image. The total electron dose before the final image is taken can be markedly decreased because the sample is irradiated by an electron beam only when images are taken. For the final image, a three-dimensional Fourier filtering method (3DFFM), which corrects the spherical aberration for the through-focus image series and enables the selection of the optimum focus condition later, is also included in our system.
已开发出一种计算机辅助的最小剂量系统，用于使用透射电子显微镜（TEM）对辐射敏感样品进行高分辨率观察。该系统由一个电荷耦合器件（CCD）相机、一个束流截止器和一台也控制TEM的控制计算机（PC）组成。仅当CCD相机拍摄图像时，样品才会被电子束照射；否则，束流截止器会切断电子束。根据拍摄的图像和TEM的可变参数（如放大倍数和样品台位置）计算出的模拟图像会显示在控制PC的显示屏上。经过几次曝光和模拟的重复后，将样品定位到最终观察区域。在选择观察区域之后，系统会根据两个不同照明角度的图像自动调整聚焦位置，并且TEM条件适合拍摄最终图像。由于仅在拍摄图像时样品才被电子束照射，因此在拍摄最终图像之前的总电子剂量可以显著降低。对于最终图像，我们的系统还包括一种三维傅里叶滤波方法（3DFFM），该方法可校正聚焦系列图像的球差，并能够在之后选择最佳聚焦条件。
