Patent Number: 
Section: claims

1. A mirror, having an optical effective surface and comprising:a mirror substrate;a reflection layer stack that reflects electromagnetic radiation incident on the optical effective surface;at least one piezoelectric layer arranged between the mirror substrate and the reflection layer stack;a first electrode arrangement situated on a side of the piezoelectric layer facing the reflection layer stack, and a second electrode arrangement situated on a side of the piezoelectric layer facing the mirror substrate, wherein the first electrode arrangement and the second electrode arrangement are arranged to apply an electric field to the piezoelectric layer that produces a locally variable deformation in the piezoelectric layer;wherein the first electrode arrangement and the second electrode arrangement each respectively has a plurality of electrodes, and wherein each of the electrodes has a respective lead configured to apply an electrical voltage relative to a respective other of the electrode arrangements; anda first mediator layer assigned to the first electrode arrangement and a second mediator layer assigned to the second electrode arrangement, wherein each of the mediator layers is arranged to set a respective continuous electrical potential profile along the respective electrode arrangement; andwherein the first and the second mediator layers differ from one another in average electrical resistance by a factor of at least 1.5. 2. The mirror as claimed in claim 1, wherein the mediator layers differ from one another in the average electrical resistance by a factor of at least 3. 3. The mirror as claimed in claim 1, wherein the mediator layers differ from one another in average thickness. 4. The mirror as claimed in claim 1, the mediator layers differ in stoichiometry from one another. 5. The mirror as claimed in claim 1, wherein at least one of the mediator layers comprises titanium dioxide (TiO2), LaCoO3, LaMnO3, LaCaMnO3 or LaNiO3. 6. A mirror, having an optical effective surface and comprisinga mirror substrate;a reflection layer stack that reflects electromagnetic radiation incident on the optical effective surface;at least one piezoelectric layer, arranged between the mirror substrate and the reflection layer stacka first electrode arrangement situated on a side of the piezoelectric layer facing the reflection layer stack, and a second electrode arrangement situated on a side of the piezoelectric layer facing the mirror substrate, wherein the first electrode arrangement and the second electrode arrangement are arranged to apply an electric field to the piezoelectric layer that produces a locally variable deformation in the piezoelectric layer; andat least one mediator layer assigned to at least one of the electrode arrangements and having a controllable electrical conductivity for setting a temporally variable continuous electrical potential profile along the at least one electrode arrangement. 7. The mirror as claimed in claim 6, further comprising at least one control electrode arranged to control the electrical conductivity of the mediator layer. 8. The mirror as claimed in claim 6, further comprising a plurality of mutually independently operable control electrodes arranged to control the electrical conductivity of the mediator layer. 9. The mirror as claimed in claim 1, configured for an operating wavelength of less than 30 nm. 10. The mirror as claimed in claim 1, configured for a microlithographic projection exposure apparatus. 11. An optical system configured as an illumination device or a projection lens of a microlithographic projection exposure apparatus, comprising a mirror as claimed in claim 1. 12. An optical system, comprising at least two mirrors,wherein each of the mirrors has a respective optical effective surface, a respective mirror substrate and a respective reflection layer stack that reflects electromagnetic radiation incident on the respective optical effective surface;wherein each of the mirrors has a respective piezoelectric layer arranged in each case between the respective mirror substrate and the respective reflection layer stackwherein each of the mirrors has a respective first electrode arrangement situated on a side of the respective piezoelectric layer facing the respective reflection layer stack, and a respective second electrode arrangement situated on a side of the respective piezoelectric layer facing the respective mirror substrate;wherein each of the mirrors has at least one respective mediator layer arranged to set a respective continuous electrical potential profile; andwherein each of the respective mediator layers has a respective average electrical resistance, such that the respective average electrical resistances differ from one another by a factor of at least 1.5. 13. The optical system as claimed in claim 12 and configured as an illumination device or as a projection lens of a microlithographic projection exposure apparatus. 14. The optical system as claimed in claim 12, wherein the mediator layers differ from one another such that the respective average electrical resistances differ by a factor of at least 5. 15. A microlithographic projection exposure apparatus comprising an illumination device and a projection lens, wherein at least one of the illumination device and the projection lens comprises an optical system as claimed in claim 12.