Optical 3D Surface Reconstruction by a Multi-Period Phase Shift Method

Abstract

<p class="MsoNormal" style="text-align: left; margin: 0cm 0cm 0pt; layout-grid-mode: char;" align="left"><span class="text"><span style="font-family: ";Arial";,";sans-serif";; font-size: 9pt;">One problem of classical phase shifting for optical 3D surface reconstruction is the occurrence of ambiguities due to the use of fringe projection. We generally derive a number-theoretical approach to calculate absolute phase measurements which can be used as a base for a reliable surface reconstruction without any ambiguity. The essence of our method is the application of pattern sequences with different periods whereby we homogeneously use all pictures which were taken for the measurement. This leads to a higher average accuracy in the surface reconstruction. Furthermore we propose a technique to avoid typical calculation errors that are produced in classical phase shifting caused by discontinuities, occlusions and reflections on the surface.</span></span><span style="font-family: ";Arial";,";sans-serif";; font-size: 9pt;"></span></p&gt

Stable and fast techniques for unambiguous compound phase coding

“…Again, in its basic formulation, phase-shifted structured light renders only relative phase values and thus it is ambiguous. When both an extended measuring range and a high resolution are required, a combined approach proves to be very powerful: the integration of Gray code and phase shift [8,9] is an effective technique bringing together the advantages of both, providing disambiguation and high resolution, but the number of patterns to be projected increases considerably, and each strategy introduces a source of error [3].…”

“…The second contribution is the introduction of a novel encoding technique which adopts a fine-to-coarse strategy allowing for smaller quantization at the fine level to increase precision, and larger quantization at the coarse level to reduce the total number of phases to be encoded. With the addition of a coding strategy derived from [3], we analyze a total of four different encoding schemes. Fig.…”

“…1 shows examples of the patterns generated with the four schemes. The two rows show the pattern generation methods, while the columns show the coding strategies, with numbertheoretic referring to the scheme derived from [3], and algebraic the newly proposed scheme.…”

“…The number-theoretic scheme presented in [3] uses period co-primality to map the phase vector onto a larger linear range. In particular, it projects sinusoidal patterns whose wavelengths are mutually co-prime, thereby allowing to deduce the overall position from the detected remainders.…”

Rigid and Non-rigid Shape Matching for Mechanical Components Retrieval

“…The support has been designed to be able to hold an eyewear frame with minimal occlusion and to present it to the scanning head with an angle that allows for a complete and watertight acquisition while turning on a single axis. The scanning head comprises two cameras and a DLP projector used to create light fringes according to the Phase Shift coding variant presented in [30]. A single range image requires about 3 seconds to be captured, and a total of 24 ranges are needed for the complete surface reconstruction.…”