The present invention relates to an apparatus for influencing a light beam arrangement comprising a plurality of light beams (4) arranged alongside one another, wherein provision is made of at least one optical element (5, 15, 25) which is movable transversely with respect to the light beams and by which the light beams can be influenced if the light beams pass through the optical element, and which has at least one light-absorbing region (9, 19, 29), wherein the apparatus comprises a drive device for the optical element, a measuring device for detecting the light of the light beam and a control unit, wherein the control unit is designed such that the drive device is controlled in a manner dependent on the position of the light-absorbing region. Furthermore, the present invention also relates to a projection exposure apparatus for microlithography comprising a multi-mirror array, in which the corresponding apparatus can be used, and to a method for operating the corresponding apparatus or the projection exposure apparatus.