![Fig. 9.4 — Microscope calibration](https://i0.wp.com/opticaltweezers.org/wp-content/uploads/2015/11/Fig9_4.png?fit=660%2C386)
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.
Fig. 9.4 — Microscope calibration