US Patent 7660045 Object lens and condenser

An object lens includes a first optical system that obtains a magnified image of an object, a second optical system that guides dark field illumination light to the object, a barrel that contains the first optical system and the second optical system and has an optical path around the first optical system for the dark field illumination light, and a shield mechanism that is disposed on the optical path and that varies the incident area of the dark field illumination light to shield the dark field illumination light.