5. Collimation

The divergence of a beam can be modified by appropriate optics. In this way, it can be made to diverge further or converge, in order, for example, to give it a diameter smaller than a given value when propagating over a certain distance.

• We then need to determine the characteristics of the optical element to be used and its position in the trajectory.

In all cases, this means defining, for a given trajectory length corresponding to a given working distance, the diameter of a fictitious tube in which the beam will occupy the largest volume without touching the edges. We can see that :

• the greater the length, the larger the tube diameter;

• for the same length, the larger the diameter, the greater the M ^2...