ABSTRACT
This chapter describes the principle of the method, shows the defects of the method and explains the restraints and conditions. These require the introduction of a cancelable optical circuit as a necessary condition. The chapter provides several desirable conditions for optical parts and mechanical parts used in the circuit, and lists some applications. The chapter also describes the basic view of the heterodyne method. The cancelable circuit is essential in the heterodyne method. The chapter also shows several significant factors that affect measuring accuracy, and discusses some countermeasures against these factors. Basically, the physical variable measured in the heterodyne method is a displacement. By considering why the displacement occurs, the displacement result can be applied to the detection of other physical variables. With superluminescent diode, 3D measurement is proposed in the full-field heterodyne white-light interferometry and the full-field step-and-scan white-light interferometry.
