The interference effect in an optical beam deflection detection system of a dynamic mode AFM

Abstract

Optical beam deflection detection is one of the main techniques used to detect the vibrating amplitude of dynamic mode atomic force microscope cantilevers. Due to the limitations of optical beam deflection detection systems and cantilevers, light leakage of the incident laser beam around the cantilevers can occur. An interference effect between the reflected beam from the cantilever and some scattered light from the specimen surface occurs, and an interference error in the probe tip–specimen approaching curve arises from this effect. In this paper, the interference effect in a dynamic atomic force microscope is analysed and observed in different conditions, and the micro-profile measurement error caused by the optical interference is deduced and calculated mathematically. The influence of the interference effect on a grating pattern measurement is then simulated.