A system and method to improve astigmatism correction and collimation of a laser beam generated by a diode in a low-level laser therapy system, but without using a complex optical configuration. A first divergent lens is a cylindrical lens. The divergence of the first lens is applied in the direction in which the diode's beam has relatively small divergence. The first lens creates divergence in the beam in a first axis, which divergence approximates the divergence in the perpendicular second axis. This first axis divergence corrects the astigmatism in the optical system of the therapy apparatus. The therapy apparatus thus can emit a beam with an elliptical cross-section with an axes ratio of less than 2:1, despite a high axes ratio of the beam originated by the diode. A second lens of the system and method is a collimating lens with elliptical shape adapted to maximize emitted beam collimation.