A novel single shot interferometry with a wide field of view by reference plates coated with various metals

A laser microscope with a wide field of view developed in our previous study allowed us to observe the whole surface of a cylinder in a very short time. In that study, resolution of the laser microscope in the depth direction was sacrificed to obtain a wide field of view. To overcome this shortcoming and achieve nano-level measurement of 3-dimensional profiles of various objects, we have introduced two-beam interferometry to the wide field of view laser microscope. To achieve a high contrast interference fringe pattern, a glass reference plate was coated with a thin Cr film or other pure metals. The interference fringe pattern was distorted from sinusoidal wave into a sawtooth-like waveform. The distortion of the interference fringe pattern appeared to correspond to the inclination of the specimen surface measured. This shows the possibility of realizing a novel single shot interferometry method capable of determining the surface profile from only one image of the interference fringe pattern without using the phase shift method. The type of distortion of intensity distribution was different for each metal. The mechanisms by which the intensity distribution of the interference fringes changed to sawtooth pattern are discussed from both a Fourier-transform analysis and an electromagnetic approach.