暗視野像

dark-field image

対物レンズの後焦点面上に形成される回折図形中の1個の回折波を対物絞りで選んで結像した像。選んだ回折波が起こっている試料上の場所が像の上で明るく見える。明視野像とともに、格子欠陥の解析や試料の膜厚測定に利用される。

FeAl合金の結晶欠陥（転位線）の暗視野像⇒図
右下の回折図形の矢印で示した回折斑点(スポット)を用いた。転位線のところだけがブラッグの回折条件を満たすようにして撮られているので、転位線は明るく見えている。

An image that is produced by one diffracted wave in a diffraction pattern formed on the back focal plane of the objective lens, using the objective aperture. A location in the image, where the selected diffracted wave takes place, appears bright. The dark-field image, together with the bright-field image, is used for analysis of lattice defect and measurement of specimen thickness.

Fig. Dark-field image of lattice defects (dislocation lines) in an FeAl alloy.
The image was taken with a diffraction spot (indicated by an arrow) of the lower-right diffraction pattern at satisfying the Bragg diffraction condition only at the dislocation lines. Thus, the dislocation lines appear bright.