In this paper, we validate the feasibility of an onboard velocity sensor using the self-mixing effect. Roughness of the target surface, wet target surface, noncontrolled changes of incident angle, and speed vector vertical components have been considered during this development. A first prototype has been designed with an automotive application so to illustrate this feasibility. This low-cost and low-clutter prototype presents an interesting basic performance (/spl sigma//spl ap/0.22%). In order to improve the accuracy as well as the robustness of the system, a double-laser diode sensor has then been tested successfully (/spl sigma//spl ap/0.038%) by removing the influence of the pitching and the pumping effects.