Method for measuring an illumination angle distribution on an object field and illumination optics unit having an illumination channel allocation intended therefor

In order to measure an illumination angle distribution, which is established by means of a multiplicity of illumination channels (16i) of an illumination optics unit, on an object field by means of an obscured projection optics unit, a setpoint pupil lighting (27) of an illumination pupil (28) of the illumination optics unit is initially established. With the aid of the setpoint pupil lighting (27), whether splitting of a measurement pupil lighting into a reflection measurement pupil and a diffraction measurement pupil is necessary is checked. Depending on the result of the check, a reflection measurement pupil lighting (29) and/or a diffraction measurement pupil lighting (30) of the illumination optics unit is established by establishing corresponding illumination channels (16i). The reflection measurement pupil lighting (29) is measured by inserting a reflective object into the object field and/or the diffraction measurement pupil lighting (30) is measured by inserting a diffractive object into the object f