Illumination system of a microlithographic exposure apparatus

An extreme-ultraviolet illumination system, having an optical axis and comprising a non-refractive zoom-collimator configured to transform a diverging extreme ultraviolet light bundle into a collimated light bundle of variable shape, wherein said zoom- collimator comprises:

• a) a first reflective optical element,
• b) a second reflective optical element, wherein
• c) the first reflective optical element receives the diverging light bundle and directs the received light bundle onto the second reflective optical element, and
• d) at least one of the reflective optical elements is mounted for being fixed at different axial positions along the optical axis.

A beam transforming device, comprising:

• a non-refractive zoom-collector configured to transform a diverging bundle of extreme- ultraviolet light into a collimated light bundle of variable shape,
• wherein said zoom-collector comprises a first reflective optical element and a second reflective optical element defining an optical axis,
• wherein the first reflective optical element is configured to receive the diverging light bundle and to direct the received light bundle onto the second reflective optical element, and
• wherein at least one of the reflective optical elements is configured to mount at plural positions along the optical axis.