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Proceedings Paper

Miniaturized multiwavelength digital holography sensor for extensive in-machine tool measurement
Author(s): Tobias Seyler; Markus Fratz; Tobias Beckmann; Alexander Bertz; Daniel Carl
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Paper Abstract

In this paper we present a miniaturized digital holographic sensor (HoloCut) for operation inside a machine tool.
With state-of-the-art 3D measurement systems, short-range structures such as tool marks cannot be resolved inside a machine tool chamber. Up to now, measurements had to be conducted outside the machine tool and thus processing data are generated offline.
The sensor presented here uses digital multiwavelength holography to get 3D-shape-information of the machined sample. By using three wavelengths, we get a large artificial wavelength with a large unambiguous measurement range of 0.5mm and achieve micron repeatability even in the presence of laser speckles on rough surfaces. In addition, a digital refocusing algorithm based on phase noise is implemented to extend the measurement range beyond the limits of the artificial wavelength and geometrical depth-of-focus. With complex wave field propagation, the focus plane can be shifted after the camera images have been taken and a sharp image with extended depth of focus is constructed consequently.
With 20mm x 20mm field of view the sensor enables measurement of both macro- and micro-structure (such as tool marks) with an axial resolution of 1 µm, lateral resolution of 7 µm and consequently allows processing data to be generated online which in turn qualifies it as a machine tool control.
To make HoloCut compact enough for operation inside a machining center, the beams are arranged in two planes: The beams are split into reference beam and object beam in the bottom plane and combined onto the camera in the top plane later on. Using a mechanical standard interface according to DIN 69893 and having a very compact size of 235mm x 140mm x 215mm (WxHxD) and a weight of 7.5 kg, HoloCut can be easily integrated into different machine tools and extends no more in height than a typical processing tool.

Paper Details

Date Published: 26 June 2017
PDF: 12 pages
Proc. SPIE 10329, Optical Measurement Systems for Industrial Inspection X, 103290F (26 June 2017); doi: 10.1117/12.2270087
Show Author Affiliations
Tobias Seyler, Fraunhofer-Institut für Physikalische Messtechnik (Germany)
Markus Fratz, Fraunhofer-Institut für Physikalische Messtechnik (Germany)
Tobias Beckmann, Fraunhofer-Institut für Physikalische Messtechnik (Germany)
Alexander Bertz, Fraunhofer-Institut für Physikalische Messtechnik (Germany)
Daniel Carl, Fraunhofer-Institut für Physikalische Messtechnik (Germany)

Published in SPIE Proceedings Vol. 10329:
Optical Measurement Systems for Industrial Inspection X
Peter Lehmann; Wolfgang Osten; Armando Albertazzi Gonçalves Jr., Editor(s)

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