Consideration of optical step frequency reflectometry using band pass sampling

Optical step frequency is studied using serrodyne modulation. The position resolution of this method is determined by the optical frequency modulation width, and the maximum measurement position is determined by optical step frequency. This paper describes the zooming in on defect positions by combining two light sources and performing band pass sampling of optical frequency with the aim of measuring localized defects in optical components. It shows that localized defects in a sample having an optical path length of about 20 mm can be detected at a resolution of about 10 /spl mu/m.