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Optimised projection lens for the use in digital fringe projection

: Bräuer-Burckhardt, C.; Palme, M.; Kühmstedt, P.; Notni, G.


Osten, W.:
Fringe 2005, The 5th International Workshop on Automatic Processing of Fringe Patterns
Berlin: Springer, 2006
ISBN: 3-540-26037-4
ISBN: 978-3-540-26037-0
International Workshop on Automatic Processing of Fringe Patterns (Fringe) <5, 2005, Stuttgart>
Conference Paper
Fraunhofer IOF ()
digital fringe projection; projection lens; correction of distortion

The quality of fringe projection is mainly influenced by the optical properties of the projection lens because the projected fringes directly influence the metric of the measurement.
In order to achieve best measuring results the properties of the lenses used should be optimised according to the measruring condtions. The aim is to achieve a minimum of distortion from lens design and/or the correction of the remaining distortion.
Usually, only lateral distortion effects in the image plane (2D grid distortion) are taken into account but the change of aberration along depth (z-axis) is neglected. Here, we will introduce approaches for a distortion compensation including z direction.
In typical applications the aperture should be large to give more light to the object. But this will reduce the usable range of depth in z-axis. the design of the optics will try to reduce this contrariety by a specific adapted modulation transfer function (MTF). Digitising effects due to the discrete structure of the microdisplays should be suppressed by this specific MTF design, too.