An optical module includes an aperture device and a support structure supporting the aperture device. The aperture device defines an aperture edge and an aperture plane. The aperture edge is adapted to define a geometry of a light beam passing the aperture device along an optical axis. The support structure is adapted to hold the aperture device in a defined manner when the aperture plane is inclined with respect to a horizontal plane. A temperature distribution prevails within the aperture device and at least one of the aperture device and the support structure is adapted to maintain at least one of a relative position of the aperture edge with respect to the optical axis and a geometry of the aperture edge substantially unaltered upon an introduction of a thermal energy into the aperture device, where the thermal energy being adapted to cause an alteration in the temperature distribution.