A beam modifying device configured to receive an input radiation beam along a first optical axis, and configured to emit an output radiation beam along a second optical axis. The beam modifying device includes a divider disposed along the first optical axis and configured to divide the incoming radiation beam into a first part and a second part, the divider being configured to direct the first part along the second optical axis and to direct the second part via a delay path. The beam modifying device further includes optics forming the delay path, the optics being configured to receive the second part and to direct the second part via the delay path and then along the second optical axis. The optics are arranged to mirror the second part such that the second part is mirrored with respect to the first part.