A light based skin treatment device comprises a laser light source for providing a pulsed incident light beam for treating skin by laser induced optical breakdown of hair or skin tissue. In one arrangement, a focusing system has a pre-focusing lens for increasing the convergence of the an incident light beam and a skin contact lens having convex light input and light exit surfaces. The focal spot position is controlled by adjusting a spacing between the pre-focusing lens and the skin contact lens. In another arrangement, there is an adjustable lens system before an adjustable focusing system for providing compensation for aberration in the adjustable focusing system.
