Patent ID: 6661522
Filing Date: 2003-12-09
Classification: G01B,G01J,G03F

Abstract:
A Fizeau interference system for causing interference between reflection lights from a reflection surface and a semi-transmission surface, respectively, along one and the same optical axis, comprising:a light source; an optical path difference applying optical system for dividing light from said light source into two lights and for re-combining them; and an interference optical system for causing reflection of the two lights passed through said optical path difference applying optical system, at corresponding one of the reflection surface and the semi-transmission surface, and to cause interference of them, wherein a difference &Dgr;F in optical path length of the light reflected by said reflection surface and with respect to the light reflected by the semi-transmission surface satisfies the following relation, where the optical path difference &Dgr;D between the two lights as applied by said optical path difference applying optical system is &Dgr;D, and the coherence length of the light from said light source is &Dgr;L: |&Dgr;Dâˆ’&Dgr;F|a spatial filter disposed between said optical path difference applying optical system and said interference optical system for reducing the difference in wavefront between the two lights.