Device for measuring a power density distribution of a radiation source

A device for measuring a power density distribution of a radiation source, the device comprising:

• a radiation source adapted to emit a light beam in a radiation direction;
• a transparent substrate disposed downstream of the radiation source in the radiation direction and having an extent in an x-direction and a y-direction, the substrate having a lesser first region and at least one further second region, the first region comprising a diffractive structure adapted to separate the light beam impinging on the diffractive structure into a zeroth order of diffraction and at least one first order of diffraction;
• and
• a detector unit disposed downstream of the substrate in the radiation direction and adapted to measure the intensity of the first order of diffraction transmitted through the diffractive structure and to derive a power density distribution therefrom,
• wherein the first region is configured such that only one specific portion of the light beam is separated into a zeroth order of diffraction and at least one first order of diffraction, and the substrate or the radiation source is movable and, during a movement of the substrate or of the radiation source, a multiplicity of portions of the light beam are separated into a zeroth order of diffraction and at least one first order of diffraction.