Diffraction and Imaging. Topics. Objective aperture selection BF/DF imaging Relationship of DP to image. BFP. stronger lens - shorter focal length. Image vs. Diffraction. Objective aperture selection. The BFP contains the DP (shows reciprocal space) and the objective aperture.
stronger lens - shorter focal lengthImage vs. Diffraction
Large aperture – lower contrast
Small aperture – higher contrastObjective Aperture Size
How do you center DF beam?
If you move diffracted spot into center, it will disappear.
If you move direct beam to +g spot, -g will light up.
Beam Tilts in DF modeDF controls
Beam Tilt DisplayDF page
1st intermediate imageDP under/over focus
Diffraction FocusDiffraction Focus
34° CCWRotation angle