Profile measurement of the surface defects (with the depth of dozens of microns), based on the low-coherent interferometry, is discussed in this paper. The major challenge for production of such devices is selecting interference fields, which are used to determine the isolines of the defect depth. A direct way to find low-contrast interference fields in a large dynamic light range appears to be an extremely difficult procedure. We propose an effective interference fields localization technique based on the reference wave phase modulation that against others provides high measurement accuracy and reliability. The reconstructed 3D - image and depth isoline map of 50μm deep defect on the metallic surface of the fuel element are also presented. The system for surface profile measurement with the following characteristics was developed: surface reconstruction error, less than 0,8 μm, surface reconstruction range on depth, more 1,8 mm.
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