Fourier transform optical profilometry using fiber optic Lloyd’s mirrors

Abstract

A fiber optic Lloyd's mirror assembly is used to obtain various optical interference patterns for the detection of 3D rigid body shapes. Two types of fiber optic Lloyd's systems are used in this work. The first consists of a single-mode optical fiber and a highly reflecting flat mirror to produce bright and dark strips. The second is constructed by locating a single-mode optical fiber in a v-groove, which is formed by two orthogonal flat mirrors to allow the generation of square-type interference patterns for the desired applications. The structured light patterns formed by these two fiber Lloyd's techniques are projected onto 3D objects. Fringe patterns are deformed due to the object's surface topography, which are captured by a digital CCD camera and processed with a Fourier transform technique to accomplish 3D surface topography of the object. It is demonstrated that the fiber-optic Lloyd's technique proposed in this work is more compact, more stable, and easier to configure than other existing surface profilometry systems, since it does not include any high-cost optical tools such as aligners, couplers, or 3D stages. The fringe patterns are observed to be more robust against environmental disturbances such as ambient temperature and vibrations.

3D phase stepping optical profilometry using a fiber optic Lloyd's mirror

“…A multicore fiber may not require any special polarization controllers or other equipment for precise alignment of the fiber cores; however, a fixed core-to-core separation limits the practicality of such a device. In this work, a fiber optic Lloyd's mirror method [7] is employed for the first time to obtain a structured light pattern in a phase stepping optical profilometry technique for threedimensional noninvasive shape measurements. This work is an extension of [7] where the Lloyd's mirror technique is used by Fourier transform optical profilometry (FTP).…”

“…In this work, a fiber optic Lloyd's mirror method [7] is employed for the first time to obtain a structured light pattern in a phase stepping optical profilometry technique for threedimensional noninvasive shape measurements. This work is an extension of [7] where the Lloyd's mirror technique is used by Fourier transform optical profilometry (FTP). One of the main advantages of the FTP algorithm is that it only needs one frame of the deformed interferogram to process the surface height of the target object.…”

Phase Error Caused by Speed Mismatch Analysis in the Line-Scan Defect Detection by Using Fourier Transform Technique

“…It is known that the Fourier transform profilometry was widely used in the machine vision, industry monitoring, production surface inspection, and so forth [1][2][3][4][5]. By using this type of phase extracting algorithm, the phase distribution of the deformed fringe patterns can be obtained with only one frame of image [6,7], so that the projection grating phase measurement method can be applied in the dynamic or moving object surface profile inspection [8]. Furthermore, the line-scan or the time delay and integration (TDI) CCD camera is used to capture the surface image in the moving object inspection [9,10].…”