Patent Number: 
Section: claims

1. An optical device comprisingat least one optical component in a vacuum chamber,wherein the optical component emits at least one of EUV and soft X-ray radiation during a period of operation,wherein the optical component comprises a plurality of collectors,wherein each collector includes a first surface and an opposite second surface,wherein each first surface is reflective and comprises a top layer of at least one surface material,a material source comprising the at least one surface material,wherein the material source is situated on the second side of at least one of the plurality of collectors, andan activation source,wherein, when activated by the activation source, the material source deposits the at least one surface material in-situ upon the first surface of at least one of the plurality of collectors. 2. An optical device comprising:at least one optical component in a vacuum chamber,wherein the optical component emits at least one of EUV and soft X-ray radiation during a period of operation, andwherein the optical component comprises at least one reflective surface comprising a top layer of at least one surface material;an activation source;a material source comprising the at least one surface material,wherein, when activated by the activation source, the material source deposits the at least one surface material in-situ upon the at least one reflective surface of the optical component,wherein the material source is arranged to be movable away from the at least one reflecting surface during the period of operation and close to the at least one reflecting surface during pauses of operation of the optical component. 3. The optical device of claim 1, wherein the material source is situated on the second surface of multiple collectors of the plurality of collectors, and, wherein, when irradiated by the radiation source, the material source deposits the at least one surface material upon the first surfaces of the multiple collectors. 4. The optical device of claim 1, wherein the optical device activates the activation source during the period of operation of the optical component. 5. The optical device of claim 1, wherein the activation source activates the activation source during a period of non-operation of the optical component. 6. The optical device of claim 1, wherein the activation source comprises a chemical vapor source, and the material source deposits the at least one surface material by chemical vapor deposition. 7. The optical device of claim 1, wherein the activation source comprises a radiation source, and the material source is a sputter target that deposits the at least one surface material by sputter deposition when the material source is irradiated. 8. The optical device of claim 1, wherein the activation source comprises a radio frequency (RF) power supply coupled to the material source, and a gas that provides accelerated ions that discharge the at least one surface material from the material source. 9. The optical device of claim 1, wherein each collector comprises a multilayer mirror. 10. The optical device of claim 1, wherein the plurality of collectors forms a plurality of concentric shells. 11. The optical device of claim 1, further comprising a measurement device that provides a measure of reflectivity of the optical device, and wherein the optical device activates the activation source in dependence upon the measure of reflectivity. 12. The optical device of claim 2, wherein the activation source activates the activation source during the operation pauses of the optical component. 13. The optical device of claim 2, wherein the activation source comprises a chemical vapor source, and the material source deposits the at least one surface material by chemical vapor deposition. 14. The optical device of claim 2, wherein the activation source comprises a radiation source, and the material source is a sputter target that deposits the at least one surface material by sputter deposition when the material source is irradiated. 15. The optical device of claim 2, wherein the activation source comprises a radio frequency (RF) power supply coupled to the material source, and a gas that provides accelerated ions that discharge the at least one surface material from the material source. 16. The optical device of claim 2, further comprising a measurement device that provides a measure of reflectivity of the optical device, and wherein the optical device activates the activation source in dependence upon the measure of reflectivity.