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Updated: Aug 16, 2025

Determining 3D Flow Fields via Multi-camera Light Field Imaging
Published on: March 6, 2013
Extending vision ray calibration by determination of focus distances
Abstract:
The application of cameras as sensors in optical metrology techniques for three-dimensional topography measurement, such as fringe projection profilometry and deflectometry, presumes knowledge regarding the metric relationship between image space and object space. This relation is established by camera calibration and a variety of techniques are available. Vision ray calibration achieves highly precise camera calibration by employing a display as calibration target, enabling the use of active patterns in the form of series of phase-shifted sinusoidal fringes. Besides the required spatial coding of the display surface, this procedure yields additional full-field contrast information. Exploiting the relation between full-field contrast and defocus, we present an extension of vision ray calibration providing the additional information of the focus distances of the calibrated camera. In our experiments we achieve a reproducibility of the focus distances in the order of mm. Using a modified Laplacian based focus determination method, we confirm our focus distance results within a few mm.
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