10 March 2015 Characteristics of digital micromirror projection for 3D shape measurement at extreme speed
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3D shape measurement is one of the growing industrial applications of the Texas Instruments DLP® micro-mirror device. This paper presents investigations on precision and repeatability of that spatial light modulators output when it is driven up to its high-speed limit. The study concerns the basic switching behavior of the individual micro-mirror at different frame rates ranging over three orders of magnitude. The 3D shape measuring methodologies are focused on phase encoded triangulation, i.e. the projection of sinusoidal patterns. The DLP chip is a bi-stable device providing an on/off pattern at each certain moment in time, i.e. it has a native binary output. Sinusoidal patterns are the result of either a temporal integration of multiple on/off patterns or a spatial integration within one on/off pattern. Both approaches are studied experimentally with respect to precision and stability of the pattern output. The STAR-07 industrial projection unit, based upon the 0.7” DLP Discovery™4100 chipset, has been used for this work and the pattern frame rates cover the range from 225 frames per second (fps) to 50,000 fps. The STAR-07 output is detected by a photodiode, amplified, and analyzed in a Yokogawa digital storage oscilloscope. All results prove the very high precision and repeatability of the STAR-07 pattern projection, up to the extreme speed of 50,000 fps.
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Roland Höfling, Roland Höfling, Petra Aswendt, Petra Aswendt, Frank Leischnig, Frank Leischnig, Matthias Förster, Matthias Förster, "Characteristics of digital micromirror projection for 3D shape measurement at extreme speed", Proc. SPIE 9376, Emerging Digital Micromirror Device Based Systems and Applications VII, 937608 (10 March 2015); doi: 10.1117/12.2082525; https://doi.org/10.1117/12.2082525

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