Patent ID: 7799136
Filing Date: 2010-09-21
Classification: G02B,G03F

Abstract:
1. A method of cleaning a first portion of at least one surface of an optical device disposed in a vacuum chamber, which device is at least partially contaminated by contaminants introduced by a radiation source, the method comprising the acts of: adjusting at least one of a temperature prevailing on the at least one surface and a pressure in the vacuum chamber such that the contaminants hitting the at least one surface are removed from the first portion of said at least one surface; providing at least one obstacle located at a second portion of said at least one surface, the second portion being outside the first portion to be cleaned; and collecting the contaminants at said at least one obstacle, wherein said at least one obstacle includes at least one recess formed in said at least one surface and the at least one recess includes at least one of a slot and a groove.