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Sensors 2016, 16(11), 1794; doi:10.3390/s16111794

A 3D Optical Surface Profilometer Using a Dual-Frequency Liquid Crystal-Based Dynamic Fringe Pattern Generator

School of Electronics Engineering, Kyungpook National University, Daegu 41566, Korea
These authors contributed equally to this work.
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Author to whom correspondence should be addressed.
Academic Editor: Gonzalo Pajares Martinsanz
Received: 23 September 2016 / Revised: 22 October 2016 / Accepted: 24 October 2016 / Published: 27 October 2016
(This article belongs to the Special Issue Imaging: Sensors and Technologies)
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Abstract

We propose a liquid crystal (LC)-based 3D optical surface profilometer that can utilize multiple fringe patterns to extract an enhanced 3D surface depth profile. To avoid the optical phase ambiguity and enhance the 3D depth extraction, 16 interference patterns were generated by the LC-based dynamic fringe pattern generator (DFPG) using four-step phase shifting and four-step spatial frequency varying schemes. The DFPG had one common slit with an electrically controllable birefringence (ECB) LC mode and four switching slits with a twisted nematic LC mode. The spatial frequency of the projected fringe pattern could be controlled by selecting one of the switching slits. In addition, moving fringe patterns were obtainable by applying voltages to the ECB LC layer, which varied the phase difference between the common and the selected switching slits. Notably, the DFPG switching time required to project 16 fringe patterns was minimized by utilizing the dual-frequency modulation of the driving waveform to switch the LC layers. We calculated the phase modulation of the DFPG and reconstructed the depth profile of 3D objects using a discrete Fourier transform method and geometric optical parameters. View Full-Text
Keywords: optical surface profilometry; interference; phase modulation; liquid crystal; dynamic fringe pattern generator optical surface profilometry; interference; phase modulation; liquid crystal; dynamic fringe pattern generator
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MDPI and ACS Style

Joo, K.-I.; Kim, M.; Park, M.-K.; Park, H.; Kim, B.; Hahn, J.; Kim, H.-R. A 3D Optical Surface Profilometer Using a Dual-Frequency Liquid Crystal-Based Dynamic Fringe Pattern Generator. Sensors 2016, 16, 1794.

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