High quality three-dimensional (3D) shape measurement using intensity-optimized dithering technique

Abstract

In past decades, there has been an upsurge in the development of three-dimensional (3D) shape measurement and its applications. Over the years, there are a variety of technologies developed including laser scanning, stereo vision, and structured light. Among these technologies, the structured-light technique has the advantages of fast computation speeds and high measurement resolution. Therefore, it has been extensively studied in this field of research. Nowadays, with the rapid development of digital devices, different kinds of patterns can be easily generated by a video projector. As a result, digital fringe projection (DFP), a variation of the structured light method, has had many applications owing to its speed and accuracy. Typically, for a DFP system, ideal sinusoidal fringe pattern projection is required for high accuracy 3D information retrieval. Since traditional DFP projects 8-bit sinusoidal fringe patterns, it suffers from some major limitations such as the speed limit (e.g., 120 Hz), the requirement for nonlinear gamma calibration, and the rigid synchronization requirement between the projector and the camera. To overcome these limitations, the binary defocusing technology was developed which projects 1-bit square binary pattern and generates ideal sinusoidal pattern through projector defocusing. In the past few years, the binary defocusing technique has shown great potential for many applications owing to its speed breakthroughs, nonlinear gamma calibration free and no rigid synchronization requirement between the camera and the projector. However, a typical square binary pattern suffers from some major limitations: (1) highorder harmonics, introduced by a square wave, which affect the accuracy of measurement, cannot be completely eliminated by projector defocusing; (2) a reduced measurement