We report here on the application of digital holographic microscopy as a metrological tool for the inspection and the micro-topography reconstruction of different microstructures fabricated in bulk lithium niobate by differential etching of reversed ferroelectric domain patterned crystals. These structures have a range of applications in optical ridge waveguides, alignment structures, V-grooves, micro-tips and micro-cantilever beams and precise control of the surface quality and topography is required. The technique allows us to obtain digitally a high-fidelity surface topography description of the specimen with only one image acquisition allowing us to have relatively simple and compact set-ups able to give quantitative information on object morphology. The advantages of this technique compared to traditional microscopy are discussed.