Abstract: The invention relates to an apparatus for effecting the sweep of a beam of light stricly plane and parallel to a given axis, comprising a sweeping mirror, mounted on an axis of rotation substantially perpendicular to the said given axis, and the plane of which substantially contains the said axis of rotation, and an optical device arranged substantially in the plane containing the said given axis of rotation. It comprises a first means of adjustment for adjusting the angle of incidence of the beam of light with respect to a predetermined plane passing through the said given axis and substantially perpendicular to the said axis of rotation of the mirror, and a second means of adjustment for adjusting the inclination of the axis of rotation of the mirror with respect to the said predetermined plane.