Error analysis for 3D shape measurement with projector defocusing

This paper analyzes the phase error for a 3-D shape measurement system that utilizes our recently proposed projector defocusing technique. In this technique, by defocusing binary structured patterns, seemingly sinusoidal ones can be generated, and 3-D shape measurement can be performed by fringe analysis. However, there are still significant errors if the object is not within a certain depth range where the defocused fringe patterns still have binary structures. In this research, we experimentally studied a large depth range of defocused fringe patterns, from close to be binary to to be sinusoidal, and its associated phase errors are analyzed. We established a mathematical phase error function in terms of the wrapped phase and the depth z. Finally, the mathematical function is calibrated and is used to compensate for the phase error at arbitrary depth ranges within the calibration volume. Experiment will be presented to demonstrate the success of this proposed technique. © 2010 Copyright SPIE - The International Society for Optical Engineering.