Tian Jindong

A pitch-variation moiré fringes method of temporal phase unwrapping profilometry

A method of pitch-variation moiré fringes is proposed to realize the temporal phase unwrapping for three-dimensional profilometry. On the basis of the principle of moiré pattern, we achieve variable spatial frequencies of fringes in a moiré pattern by rotating two gratings. Furthermore a five-point fitting method is used to automatically compute the central position of side-lobe spectrum of the moiré fringes. Finally, a generalized temporal phase unwrapping algorithm is introduced to process the three-dimensional reconstruction. The theoretical analysis and experimental results show the validity of the proposed method.

Model-based optical metrology and visualization of 3-D complex objects

This letter addresses several key issues in the process of model-based optical metrology, including three dimensional (3D) sensing, calibration, registration and fusion of range images, geometric representation, and visualization of reconstructed 3D model by taking into account the shape measurement of 3D complex structures, and some experimental results are presented.

Impedance analysis of eddy current testing based on transmission line theory

Eddy current testing is an important and widely used method in non-destructive testing and evaluation. In this paper, an impedance analysis model of eddy current testing based on mutual inductance equivalent circuit is established using transmission line theory, and an analytical expression of impedance of the testing workpiece is obtained. Then the changes of impedance plane of ECT sensor affected by such as the thickness, the conductivity of the tested workpiece and the lift-off are studied. Experiment results are consistent with the theoretical analysis, which proves the validity of the model. All the conclusions derivated by the model can be helpful for eddy current testing optimization. This electronic document is a “live” template. The various components of your paper [title, text, heads, etc.] are already defined on the style sheet, as illustrated by the portions given in this document.

All-solid-state microscopic interferometer with frequency-variation and phase-shifting capability

A novel microscopic interferometry with ability of frequency-variation and phase-shifting is proposed for microstructures testing. By using acousto-optic technique, sequential carriers can be generated with different spatial frequencies so that the temporal phase unwrapping method can be applied for decoding the height information. Combined with phase-shifting technique realized by spatial light modulator, this method is especially suitable for interferometric measurement with high precision and large dynamic range.