3D optical profilometry using fiber optics lloyd's mirror method

Abstract

A ber optic Lloyd's mirror assembly is investigated to obtain various optical interference patterns for the detection of three-dimensional shapes of rigid bodies. Two types of the ber optic Lloyds systems are used in this work. The rst one consists of a single mode optical ber and a highly re ecting at mirror to produce bright and dark strips. The second one is constructed by locating a single mode optical ber in a v-groove, which is formed by two orthogonal at mirrors to allow the generation of square type interference patterns for the desired applications. The structured light patterns formed by these two ber optic Lloyds techniques are projected onto three-dimensional objects. Fringe patterns are deformed due to the object0s surface topographies, which are captured by a digital CCD camera and are processed with the following signal processing techniques to accomplish their three-dimensional surface topographic maps: Fourier Transform Pro lometry, Phase Stepping Pro lometry, and Continuous Wavelet Transform Pro lometry. The method is developed for extracting 3D height distribution of various objects at the micron scale with a resolution of 5 m by elegantly interrogating the rst ber optic assembly to an optical microscope and a CCD camera. It is demonstrated that the proposed technique is quite suitable and practical to produce a structured light pattern with an adjustable frequency. By increasing the distance between the ber and the mirror with a micrometer stage in the Lloyd0s mirror assembly, the separation between the two bright fringes is lowered down to the micron scale without using any additional elements as part of the optical projection unit. The phase analysis of the acquired image is carried out by One Dimensional Continuous Wavelet Transform.