Some recent advance on high-speed, high-resolution 3-D shape measurement using projector defocusing

High-speed, high-resolution 3-D shape measurement becomes increasingly important, with broad applications including medicine, homeland security, and entertainment. In recent years, we have made some progress, and developed an unprecedented 60 Hz rate 3-D shape measurement system with a digital fringe projection and phase-shifting method. However, a hardware bottleneck was met to further improve its speed. Since 2009, we have been studying a new method that could potentially eliminate this speed bottleneck. This technique is essentially to generate sinusoidal fringe patterns by properly defocusing binary ones. It coincides with the operation mechanism of the digital-light-processing (DLP) technology, and thus permits some speed breakthroughs. This paper summarizes some of our recent studies with this technology. In particular, we will include three major pieces: (1) double the speed of our real-time 3-D shape measurement system without significantly increase the hardware cost; (2) reach tens-of-kHz rate 3-D shape measurement by using a relatively inexpensive and off-the-shelf DLP projector; and (3) achieve kHz rate phase shifting for superior high-speed, high-quality 3-D shape measurement with the DLP Discovery platform. We will explain the principles of the technology, show some experimental results, and discuss the advantages and shortcomings of this technology.