Phase unwrapping method based on reliability and digital point array

Abstract

Phase unwrapping, which usually involves complicated and time-consuming procedures, is crucial for phase-measuring profilometry. Unwrapping isolated phase regions with global phase discontinuity is challenging for traditional reliability ordering based phase unwrapping methods. This paper presents a novel method that combines the advantages of digital point array based active triangulation profilometry with a reliability of modulation ordering algorithm. Table entries that store spatial coordinates of sampling points are established, and the true phases measured by geometrical relationships are used to direct phase unwrapping. Different from the proposed 2D spatial unwrapping algorithms until now, the fringe order can be easily identified by referencing the patterns of multiple points. Additionally, unwrapping from the interior part of isolated regions following an optimized path is guaranteed. The prevention of penetration through invalid pixels into isolated regions ensures this new method will alleviate errors due to phase ambiguity. Simulation and experimental results demonstrate that the proposed technique can feasibly measure objects with a wide range of height variation. C 2011 Society of Photo-Optical Instrumentation Engineers (SPIE).

Intelligent Tea-Picking System Based on Active Computer Vision and Internet of Things

“…Based on the classical principle of triangulation optics, fringe patterns that consist of a sinusoidal distribution of gray scale patterns are projected onto the object, and the distorted patterns are then captured by the imaging system. Further processing by phase unwrapping, exact 3D information can be obtained [13].…”

“…First, the sinusoidal fringe patterns which have π/2 phase shifts relatively are projected onto the object as shown in Figure 2, and the distorted pattern captured by the CCD camera can be used to calculate the wrapped phase by Equation (1). Second, the obtained wrapped phase can be demodulated into an absolute phase map by the phase-unwrapping algorithm [13]:…”

“…us, many methods based on reliability ordering have been presented in this field aiming to alleviate the error propagation, such as water flood algorithms and modulation-based algorithms. However, error accumulation and propagation are still an obstacle, if only passing through invalid areas with global discontinuities is needed [13].…”