First-order layout of a two-lens varifocal objective focusing a CO2 laser beam in a post-objective three-axis scanner

In this paper we describe a procedure to work out the first-order layout of a two-lens varifocal objective for a post-objective three-axis scanner. In particular, the two lenses are considered thin, the laser beam is propagated paraxially (ABCD law) and the focal lengths of the two lenses and the maximum value of the distance between them are worked out in accordance with the specifications of the objective. Finally, the plots of the dimension and the position of the focused light spot versus the distance between the two lenses are evaluated.