23 October 2001 Calibration techniques for fringe projectors
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Fringe Projection systems generate phase distributions of an object illuminated with a specific fringe pattern. These phase correspond to the object coordinates. It is mostly necessary to transform the dimension-less phases to a metric dimension. Until today this is realized by photogrammetric techniques, which are subdivided into three main processes. At first a reference plane is defined. Then a grid within this plane is fixed. In the third step, the height axis is calibrated by different methods, for example, by use of a single height step or another well defined base object. This article describes a new method to calibrate the measuring volume by a multi-value calibration algorithm. As a first step, the fringe projection systems detects the phase distribution of a plane, denoted as reference plane. The, the plane moves stepwise in z-direction. In each step the phase distribution is detected, while an interferometer measures the distance of the z-coordinate form the reference plane. Together with the discrete x-y-coordinates of a CCD- detection unit, a 3D measuring volume is defined. The volume calibration is performed by separate polynomials for each x- y-coordinate, which are derived from the corresponding values of the phase distributions and the interferometric height values. With this method some problems of the conventional 'single value calibration' can be solved. This contribution describes the theoretical solution of the problem and presents first experimental results.
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Joerg Peters, Joerg Peters, Stefan Patzelt, Stefan Patzelt, Frank Horn, Frank Horn, Gert Goch, Gert Goch, } "Calibration techniques for fringe projectors", Proc. SPIE 4398, Optical Measurement Systems for Industrial Inspection II: Application in Industrial Design, (23 October 2001); doi: 10.1117/12.445553; https://doi.org/10.1117/12.445553

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