High-quality octa-level fringe pattern generation for improving the noise characteristics of measured depth maps

Since the introduction of the binary defocusing technique, various algorithms have been proposed to optimize binary fringe patterns for reducing the phase root mean square (rms) error. Our recent study showed that octa-level fringe patterns can further reduce the phase rms error at no extra cost and patch-based fringe patterns can cause harmonic distortion to the measured depth map. This paper presents a novel method to produce patch-based octa-level fringe patterns of ideal noise characteristics by (1) formulating the optimization problem in a better way, (2) starting the optimization process with a better initial estimate and (3) adopting a necessity-oriented strategy to refine the fringe patterns during the optimization process.