How to Calibrate the Astigmatism of Objective Lens?

How to Calibrate the Astigmatism of the Objective Lens?

1. At magnification = 100 kX.

2. Use the Trackball to select a large amorphous region for calibration.

3. On the software, click “Start View”. Select a suitable exposure time, like 0.5 seconds.

4. Turn on Live FFT.

5. Activate the "OBJ STIG" and optimize the ring of FFT with "DEF X" and "DEF Y" (turn one knob only at once)
   Focus --> DEF X or Y --> Focus --> DEF X or Y (iteratively).

6. After the FFT ring is circular, deactivate "OBJ STIG".

1. The calibrations of condenser astigmatism and objective astigmatism are performed at ≥ 100 kX for effectiveness. Do not attempt to do it below 100kX. The higher the magnification the better the alignment but the harder to perform, so we perform it at a middle magnification.

3. At a high magnification, we may need to use Objective aperture as Objective astigmatism is not fully corrected.