Recently, the frequency-shifting (FS) projection technique provides a promising alternative to the traditional phase-shifting (PS) fringe projection profilometry (FPP). It solves the absolute phase retrieval problem directly in a completely different fashion, without any phase unwrapping. However, due to the Nyquist sampling theorem (NST), a constant frequency-shift only supports for a limited effective field (EF). It only covers a limited region of the fringe pattern, and the phase retrieval quality degenerates dramatically for those out of the EF. This issue tends significant especially for a high-resolution fringe pattern, limiting the practical application in real life. To this end, we introduce the non-uniform sampling strategy into frequency-shifting technique. With a temporally varying frequency-shift, the EF can be improved significantly, achieving globally high quality across all regions in the pattern for the retrieved phase. Simulation and real experimental results have validated the efficacy of the proposed technique.
In fringe projection profilometry, highlight usually causes the saturation and blooming in captured fringes and reduces the measurement accuracy. To solve the problem, a regional-projection fringe projection (RP-FP) method is proposed. Regional projection patterns (RP patterns) are projected onto the tested object surface to avoid the saturation and blooming. Then, an image inpainting technique is employed to reconstruct the missing phases in the captured RP patterns and a complete surface of the tested object is obtained. Experiments verified the effectiveness of the proposed method. The method can be widely used in industrial inspections and quality controlling in mechanical and manufacturing industries.
Measuring objects with high dynamic range (HDR) reflectivity by coded structured-light, captured stripes are usually seriously distorted by reflectivity, causing inaccurate measurement results. A stripe enhancement method is proposed to deal with the problem. The method is based on the correspondence between phase and intensity of the stripe. First, the phase map of the captured stripe pattern is retrieved by phase-shift algorithm and multiexposure method, where saturation and low contrast of the stripe are eliminated; then, the modulation of stripes is normalized to eliminate the influence of reflectivity; finally, the enhanced stripe is obtained by assembling the modulation and the phase map. Experimental results demonstrate that the method is efficient for objects with HDR reflectivity and achieves high accuracy.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.