Development of Digital Holographic Microscope for In-Situ Surface Relief Measurement of Low-Carbon Steel

Abstract

Digital holographic microscope (DHM) system was designed to extend an existing reflected light microscope. The developed DHM system was applied for the observations of plastic deformation of an upper bainite and martensitic transformation of a low-carbon steel to clarify its potential for analyzing surface reliefs observed during these processes. It was demonstrated that the height measurement accuracy is almost equivalent to that of AFM. The exceptional temporal and spatial resolutions provided by the developed DHM system was shown to have a potential to clarify the mechanism behind the formation of surface reliefs by plastic deformation and phase transformation.

Fig. 3 Reconstruction process of real image from holographic pattern. (a) Intensity obtained by CMOS camera, (b) Fourier transformed pattern, (c) filtered object beam, (d) object amplitude, (e) object phase shift, (f) unwrapped phase shift.