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High-resolution, High-speed, Three-dimensional Video Imaging with Digital Fringe Projection Techniques

Digital fringe projection (DFP) techniques provide dense 3D measurements of dynamically changing surfaces.&#160;Like the human eyes and brain, DFP uses ...

Iowa State University

This paper analyzes the phase error for a three-dimensional (3D) shape measurement system that utilizes our recently proposed projector defocusing technique. This technique generates seemingly sinusoidal structured patterns by defocusing binary structured patterns and then uses these patterns to perform 3D shape measurement by fringe analysis. However, significant errors may still exist if an object is within a certain depth range, where the defocused fringe patterns retain binary structure. In this research, we experimentally studied a large depth range of defocused fringe patterns, from near-binary to near-sinusoidal, and analyzed the associated phase errors. We established a mathematical phase error function in terms of the wrapped phase and the depth z. Finally, we calibrated and used the mathematical function to compensate for the phase error at arbitrary depth ranges within the calibration volume. Experimental results will be presented to demonstrate the success of this proposed technique.

Phase error compensation for three-dimensional shape measurement with projector defocusing.

This Letter investigates the effects of different phase-shifting algorithms on the quality of high-resolution three-dimensional (3-D) profilometry produced with nearly focused binary patterns. From theoretical analyses, simulations, and experiments, we found that the nine-step phase-shifting algorithm produces accurate 3-D measurements at high speed without the limited depth range and calibration difficulties that typically plague binary defocusing methods. We also found that the use of more fringe patterns does not necessarily enhance measurement quality.

Three-dimensional profilometry with nearly focused binary phase-shifting algorithms.

The purpose of this study was to determine if performing a morning total-body resistance exercise workout affects explosive power in an afternoon session. The secondary goal was to assess the usefulness of the backward overhead shot throw (BOST) as a measure of explosive power in experienced thrower in the sport of athletics. Throwers (N = 14) performed 1 control and 1 experimental trial on separate days. The control consisted of BOST and a vertical jump (VJ) testing performed in the afternoon. For the experimental trial, the participants reported for a short resistance training session in the morning then repeating the BOST and VJ testing 4-6 hours later. The BOST distance (meters) and VJ peak power (watts) were correlated in both trials (r ∼ 0.64, p < 0.05). The BOST distance improved in experimental trial over control (p < 0.05), but VJ power failed to improve. The results indicate that a morning resistance exercise bout can improve competitive throwing performance later on the same day. The results also suggest that BOST may be a useful performance testing tool for throwers in the sports of athletics.

Article	Year
Phase error compensation for three-dimensional shape measurement with projector defocusing. Applied optics\| PubMed ID: 21673758	2011
Three-dimensional profilometry with nearly focused binary phase-shifting algorithms. Optics letters\| PubMed ID: 22139228	2011
Assessing explosive power production using the backward overhead shot throw and the effects of morning resistance exercise on afternoon performance. Journal of strength and conditioning research / National Strength & Conditioning Association\| PubMed ID: 22395279	2013

Laura Ekstrand

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