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Digital holography as a tool for high-speed high-precision 3D-measurements for industrial applications

: Fratz, Markus; Beckmann, Tobias; Seyler, Tobias; Bertz, Alexander; Carl, Daniel

Volltext urn:nbn:de:0011-n-6361374 (1.4 MByte PDF)
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Copyright Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Erstellt am: 29.6.2021

Lehmann, Peter (Hrsg.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Optical Measurement Systems for Industrial Inspection XII : 21-26 June 2021, Online Only, Germany
Bellingham, WA: SPIE, 2021 (Proceedings of SPIE 11782)
ISBN: 978-1-5106-4398-7
ISBN: 978-1-5106-4399-4
Paper 1178209, 6 S.
Conference "Optical Measurement Systems for Industrial Inspection" <12, 2021, Online>
Konferenzbeitrag, Elektronische Publikation
Fraunhofer IPM ()
digital holography; Multiwavelength Interferometry; height measurement; Sub-micron Resolution; industrial application

Digital multi-wavelength holography is an emerging technology for very precise and fast 3D measurement. Here, we present a novel digital holographic system that uses a 65-Megapixel camera to achieve high resolution measurements on an 18 × 14 mm² field of view resulting in a lateral sampling of ~2 μm in x- and y-direction. Using three single frequency lasers for illumination in a temporal phase shifting scheme, we achieve data acquisition times below 150 ms for full 65- Megapixel 3D-measurements. The choice of the three lasers enables an unambiguous axial measurement range of 400 μm. On a calibrated height standard with a 20 μm step repeatability of <0.01 μm (1 standard deviation) is demonstrated. More challenging and of high interest for industrial applications are measurement samples that consist of surfaces with varying surface roughness, reflectivity or material. These kinds of samples require a sensor with a high dynamic range and pose several geometrical optical challenges: Light from differently reflecting or scattering surfaces travels through the optical system on different paths. Without compensation, this results in small, yet non-neglectable errors in the measured height values. We have applied approaches well described for single-point interferometers to the full-field imaging system used in the presented optical setup. Without a-priori knowledge about surface quality of the sample, we can compensate for these errors. Thus, the presented digital holographic sensor is able to achieve repeatability of ~0.1 μm (1 standard deviation) for height features consisting of rough and specular surfaces.