Digital Holographic Microscopes (DHM) have been around for many years, but its main application has been in imaging of transparent biological samples [1]. Recently, a DHM was developed around a conventional optical microscope for the observation of opaque samples, specifically the surface relief in low-carbon steel [2] and in Widmanstätten and bainitic ferrites [3]. A standalone DHM setup was designed and built using off-the-shelf components to accommodate the larger space required by the tensile tester, and also in the prospect of higher lateral and height resolutions. This work focuses on the improvement of the performance of the latter aforementioned DHM through hardware modification of the laser and optical path.

Calibration for lateral measurements was against a standard micrometer slide. Height measurements were calibrated against a standard AFM grating. Preliminary data show slip bands from a polished sample of Fe-1%Si after applying 200 MPa tension. The hologram has high image quality and defined fringe. After unwrapping and assigning of height calibration to gray values, the amplitude image is plotted in 3D and a line profile of the slip bands is shown. Not only are the fine slip bands clearly resolved, but also the bulk deformation of the grains can be visualized.