14 February 2009 Real-time 3D shape recording by DLP-based all-digital surface encoding
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The use of computer generated sinusoidal fringe patterns has found wide acceptance in optical metrology. There are corresponding software solutions that reconstruct the phase field encoded in the fringe pattern in order to get 3D-shape data via triangulation and deflection measuring setups, respectively. Short recording time is a common issue of high importance for all tasks on the factory shop floor as well as in medical applications and for security. Recent high-speed implementations take advantage of MEMS based spatial light modulators and the digital micro mirror chipset DLP DiscoveryTM* is the fastest proven component currently available for this aim. Being a bi-stable on-off-state system, the sinusoidal gray level pictures are generated by controlling the mirrors ON-time period during which an analogue detector is exposed. This digital generation of light intensity distributions provides outstanding precision and long-term stability. It is used in leading edge technology solutions that produce video type streams of 3D surface data with a sustained repetition rate of 40 Hz. A new proposal is discussed in this paper that goes beyond this state of the art by considering the optical encoding of the surface as an all-digital communication link. After a brief classification of state-of- the-art systems, the authors describe how future all-digital encoding leads to extremely high speed and precision in 3D shape acquisition.
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Roland Höfling, Petra Aswendt, "Real-time 3D shape recording by DLP-based all-digital surface encoding", Proc. SPIE 7210, Emerging Digital Micromirror Device Based Systems and Applications, 72100E (14 February 2009); doi: 10.1117/12.807573; https://doi.org/10.1117/12.807573

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