Optical integrator for an illumination system of a microlithographic projection exposure apparatus

An optical integrator, comprising:

• a) a first array of elongated first microlenses that are arranged side by side in a first plane and have first vertex lines;
• and
• b) a second array of elongated second microlenses that are arranged side by side in a second plane and have second vertex lines,
• wherein at least one second vertex line forms a zigzag or serpentine line, and the optical integrator is configured to produce a plurality of secondary light sources in an illumination system of a microlithographic projection exposure apparatus.

An optical integrator, comprising:

• a) a first array of elongated first microlenses that are arranged side by side in a first plane;
• and
• b) a second array of elongated second microlenses that are arranged side by side in a second plane,
• wherein at least one second microlens has a curved surface profile which varies along a longitudinal axis of the at least one second microlens, and the optical integrator is configured to produce a plurality of secondary light sources in an illumination system of a microlithographic projection exposure apparatus.