Abstract: In the context of a device for directing optical rays along a given path comprising a ray deflecting means there is a pivoting ray exit member, which simultaneously pivotally entrains the deflecting mirror and is arranged to pivot with the mirror about a third axis. The ray exit member is able to pivot about a first axis and the mirror pivots about a second axis and both are mounted on a rotary housing. The first and the second axes are parallel to each other and are located in the reflecting surface of the mirror. By means of a threaded rod and a return spring the ray exit member is turned and its pivoting motion is transmitted via an abutment to the mirror. The distance of the abutment from the first axis is half the size of the distance from the second axis in order thus to pivot the mirror through an angle which is half as large as the pivotal sweep of the ray exit member with the result that the central ray setting in the small exit opening is adhered to.