Figure 9.4 — Microscope calibration Figure 9.4 — Microscope calibration. The calibration of the system can be achieved either by imaging a regular structure or by tracking a particle stuck to the bottom of the sample (dashed line) as it is controllably moved by the stage. In our case we used a homemade grating with a period of 2 μm and we moved the particle along a 5 μm circle (solid line). The resulting calibration factors are approximatively 90 nm/px in both directions with both techniques.