Fraunhofer-Institut für Photonische Mikrosysteme IPMS

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Repetitive nonlinear control for linear scanning micro mirrors

2018 , Schroedter, R. , Schwarzenberg, M. , Grahmann, J. , Sandner, T. , Janschek, K.

Various scanning applications like LIDAR sensors, OCT systems and laser projectors require a repeated periodic linear scanning trajectory performed by a quasi-static micro mirror. Since most MOEMS systems have inherent nonlinearities like a progressive spring stiffness and the quadratic voltage-deflection-relation of electrostatic drives, a nonlinear control scheme as presented in our previous paper significantly reduces parasitic oscillations of the resonance frequency and enables a high resolution raster scan combining a quasi-static axis with a cardanic mounted resonant axis. In this paper we address a novel control scheme using a flatness-based feedback control enhanced by a plug-in repetitive controller for the linear scanning axis. We demonstrate the applicability of this feedback control for a quasi-static moving micro mirror with electrostatic staggered vertical comb drives using a microcontroller-based driver. On-chip piezoresistive sensors serve as position feedback. We compare different scan trajectories and repetition rates with respect to the linearity and repeatability showing the robustness of the proposed control regime. Furthermore we discuss the advantage of this method to reduce the individual chip characterization for ramping up mass production.

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Compact optical position feedback scheme for MOEMS mirrors

2014 , Tortschanoff, A. , Baumgart, M. , Holzmann, D. , Lenzhofer, M. , Sandner, T. , Kenda, A.

Recently, we have realized a novel, very compact position sensing device for MOEMS mirrors, which is based on the measurement of a reflected light beam with a quadrant diode. This scheme is applicable to arbitrary trajectories and in this work we present the characteristics of this device, showing experimental results obtained with a test set-up, but also theoretical considerations and optical ray-tracing simulations.

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Quasistatisch-resonanter Mikroscanner zur adaptiven Auflösungssteuerung einer 3D ToF-Kamera

2014 , Sandner, T. , Grasshoff, T. , Schrödter, R. , Schwarzenberg, M.

Um zukünftig eine aktive, teilautonome Interaktion von Robotern mit ihrer Umgebung zu gewährleisten, werden neuartige 3D-Sensoren benötigt, die eine hinreichend genaue Erfassung ihrer Umgebung in Echtzeit ermöglichen und sich durch hohe Robustheit und Miniaturisierung auszeichnen. Laserscanner ermöglichen zwar eine präzise und robuste Entfernungsmessung über große Entfernungen sind aber bzgl. ihrer Messrate auf etwa 1 MVoxel/s begrenzt. In diesem Beitrag wird eine neuartige MEMS basierte 3D-Kamera vorgestellt, die durch den Einsatz von quasistatisch-resonanten Mikroscannern eine schnelle und situationsbezogene Steuerung der Scanbewegung und somit in Analogie zum menschlichen Auge eine adaptive Anpassung der räumlichen Auflösung im Scanbereich ermöglicht.

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Compact driver module for closed-loop control of resonant 2D-MOEMS scanners

2014 , Tortschanoff, A. , Kenda, A. , Sandner, T. , Kremer, M. , Frank, A.

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Hybrid assembled micro scanner array with large aperture and their system integration for a 3D ToF laser camera

2015 , Sandner, T. , Baulig, C. , Grasshoff, T. , Wildenhain, M. , Schwarzenberg, M. , Dahlmann, H.-G. , Schwarzer, S.

This paper presents a large aperture micro scanning mirror (MSM) array especially developed for the novel 3D-laser camera Fovea3D. This 3D-camera uses a pulsed ToF technique with 1MVoxel distance measuring rate and targets for a large measurement range of 30 ... 100m and FOV of 120 degrees x60 degrees at video like frame rates. To guarantee a large reception aperture of >= 20mm, large FOV and 3200 Hz bi-directional scanning frequency at the same time, a hybrid assembled MSM array was developed consisting of 22 reception mirrors and a separate sending mirror. A hybrid assembly of frequency selected scanner elements and a driving in parametric resonance were chosen to enable a fully synchronized operation of all scanner elements. For position feedback piezo-resistive position sensors are integrated on each MEMS chip. The paper discusses details of the MEMS system integration including the synchronized operation of multiple scanning elements.

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Optical design of MOEMS-based micro-mechatronic modules for applications in spectroscopy

2014 , Tortschanoff, A. , Kremer, M. , Sandner, T. , Kenda, A.

One of the important challenges for widespread application of MOEMS devices is to provide a modular interface for easy handling and accurate driving of the MOEMS elements, in order to enable seamless integration in larger spectroscopic system solutions. In this contribution we present in much detail the optical design of MOEMS driver modules comprising optical position sensing together with driver electronics, which can actively control different electrostatically driven MOEMS. Furthermore we will present concepts for compact spectroscopic devices, based on different MOEMS scanner modules with lD and 2D optical elements.

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Quasistatic microscanner with linearized scanning for an adaptive three-dimensional laser camera

2014 , Sandner, T. , Grasshoff, T. , Schwarzenberg, M. , Schroedter, R. , Schenk, H.

This paper reports on a gimbaled MEMS scanning mirror with quasistatic resonant actuation, specially developed for adaptive raster scanning in an innovative three-dimensional (3-D) time-of-flight (ToF) laser camera with real-time foveation. Large quasistatic deflections of 10 deg are provided by vertical comb drives in the vertical direction in contrast to resonant horizontal scanning. This mirror is 2.6 x 3.6 mm and operates at 1600 Hz with an 80-deg optical scan range. For position feedback, piezo-resistive position sensors are integrated on chip for both axes. To guarantee the full reception aperture of effectively 5 mm, a synchronized driven MEMS scanner array consisting of five hybrid assembled MEMS devices is used in an innovative 3-D ToF laser scanner. This enables a distance measuring rate of 1 MVoxel/s with an uncertainty in distance measurement of 3 to 5 mm for a 7.5-m measuring range for a gray target. Flatness-based open loop control is used for driving control of quasistatic axis in order to compensate for the dynamics of the low damped MEMS system.

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Publication

Quasistatisch-resonanter Mikroscanner zur adaptiven Auflösungssteuerung einer 3D ToF-Kamera

2014 , Sandner, T. , Grasshoff, T. , Schrödter, R. , Schwarzenberg, M.

Um zukünftig eine aktive, teilautonome Interaktion von Robotern mit ihrer Umgebung zu gewährleisten, werden neuartige 3D-Sensoren benötigt, die eine hinreichend genaue Erfassung ihrer Umgebung in Echtzeit ermöglichen und sich durch hohe Robustheit und Miniaturisierung auszeichnen. Laserscanner ermöglichen zwar eine präzise und robuste Entfernungsmessung über große Entfernungen sind aber bzgl. ihrer Messrate auf etwa 1 MVoxel/s begrenzt. In diesem Beitrag wird eine neuartige MEMS basierte 3D-Kamera vorgestellt, die durch den Einsatz von quasistatisch-resonanten Mikroscannern eine schnelle und situationsbezogene Steuerung der Scanbewegung und somit in Analogie zum menschlichen Auge eine adaptive Anpassung der räumlichen Auflösung im Scanbereich ermöglicht.

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Publication

Quasi-static microscanner with linearized scanning for an adaptive 3D laser camera

2014 , Sandner, T. , Grasshoff, T. , Schwarzenberg, M. , Schroedter, R. , Schenk, H.

This paper presents a gimbaled MEMS scanning mirror (MSM) especially developed for adaptive raster scanning in a novel 3D ToF laser camera. Large quasi-static deflections of ±10° are provided by vertical comb drives in vertical direction in contrast to resonant horizontal scanning of the 2.6x3.6mm elliptical mirror at 1600 Hz and 80° optical scan range. For position feedback piezo-resistive position sensors are integrated on chip for both axes. To guarantee the full reception aperture of effective 5 mm a synchronized driven MEMS scanner array-consisting of five hybrid assembled MEMS devices-are used in a novel 3D ToF laser scanner enabling a distance measuring rate of 1MVoxel/s and an uncertainty of ToF distance measurement of 3...5 mm at 7.5 m measuring range for a gray target.

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Translatory MOEMS actuator and system integration for miniaturized Fourier transform spectrometers

2014 , Sandner, T. , Grasshoff, T. , Gaumont, E. , Schenk, H. , Kenda, A.

A translatory MOEMS actuator with extraordinary large stroke especially developed for fast optical path length modulation in miniaturized Fourier transform infrared spectrometers (FTSs) is presented. A precise translational out-of-plane oscillation at 500 Hz with large stroke of up to 1.2 mm is realized by means of an optimized MEMS design using four pantograph suspensions of the comparative large mirror plate with 5-mm diameter. The MOEMS device is driven electrostatically resonant and is manufactured in a CMOS compatible silicon-on-insulator process. Up to +/- 600 mu m amplitude (typically 1 mm stroke) has been measured in vacuum of 30 Pa and 50 V driving voltage for an optimized pantograph design enabling reduced gas damping and higher driving efficiency. For FTS system integration, the MOEMS actuator has been encapsulated in a hybrid optical vacuum package. The thermal influences of packaging technology on MOEMS behavior are discussed in more detail.

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