VIDEO: Alignment
Z Height Adjustment
Caption
17 sec
There is no audio.
This video demonstrates the technique for bringing the specimen into the focal plane.
First, the objective lens voltage must be set properly. In this example, the accelerating voltage is 200 kV, so the objective lens voltage is set to 4.52 V.
Note at the beginning of the video that there are dark rings around the particles indicating that the specimen is out of focus. In the subsequent frames, the Z height knob, located below the specimen rod on the goniometer, is slowly turned while observing the image. Initially, the specimen will come into focus at the point when image contrast is minimized. As we continue to turn the knob in the same direction the contrast will come to a maximum. At that point, we turn the knob in the opposite direction bringing the specimen back into focus.
Objective Stigmator Adjustment
Caption
20 sec
There is no audio.
The main video is the image. The synchronized inset video is the Fast Fourier Transform (FFT).
We start with an astigmatic image of amorphous carbon. Observing the FFT image, the presence of astigmatism is evidenced by an elliptical bright feature. The oval feature can be brought to a circle shape through adjustment of the DEF X, Y knobs on the main panel while the DEFLECTOR, OBJ STIG button is depressed. We recommend that you adjust one of the controls at a time. After producing a spherical FFT feature the astigmatism is corrected. Finally, the OBJ FOCUS knob is adjusted to bring the amorphous carbon image into focus. In the corrected image individual islands of carbon should be visible creating what has been called a "salt and pepper" image.
