Patent ID: 6972847
Filing Date: 2005-12-06
Classification: G03F

Abstract:
1. A method of detecting a mark formed on an object, the method comprising the steps of: dividing light from a light source into divided light beams, wherein one of the divided light beams is taken as light for illuminating the mark while the other is taken as a reference light; causing interference between light from the mark and the reference light, while setting a difference in an optical path length between the light from the mark and the reference light, at a first predetermined value, thereby to obtain a first image of the mark; causing interference between the light from the mark and the reference light, while setting a difference in an optical path length between the light from the mark and the reference light, at a second predetermined value, thereby to obtain a second image of the mark; and producing a third image of the mark on the basis of a difference between the first image and the second image.