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 focusing system.
