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

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

We present a wafer-level vacuum-packaged (WLVP) translatory micro-electro-mechanical system (MEMS) actuator developed for a compact near-infrared-Fourier transform spectrometer (NIR-FTS) with 800–2500 nm spectral bandwidth and signal-nose-ratio (SNR) > 1000 in the smaller bandwidth range (1200–2500 nm) for 1 s measuring time. Although monolithic, highly miniaturized MEMS NIR-FTSs exist today, we follow a classical optical FT instrumentation using a resonant MEMS mirror of 5 mm diameter with precise out-of-plane translatory oscillation for optical path-length modulation. Compared to highly miniaturized MEMS NIR-FTS, the present concept features higher optical throughput and resolution, as well as mechanical robustness and insensitivity to vibration and mechanical shock, compared to conventional FTS mirror drives. The large-stroke MEMS design uses a fully symmetrical four-pantograph suspension, avoiding problems with tilting and parasitic modes. Due to significant gas damping, a permanent vacuum of ≤3.21 Pa is required. Therefore, an MEMS design with WLVP optimization for the NIR spectral range with minimized static and dynamic mirror deformation of ≤100 nm was developed. For hermetic sealing, glass-frit bonding at elevated process temperatures of 430–440 °C was used to ensure compatibility with a qualified MEMS processes. Finally, a WLVP MEMS with a vacuum pressure of ≤0.15 Pa and Q ≥ 38,600 was realized, resulting in a stroke of 700 µm at 267 Hz for driving at 4 V in parametric resonance. The long-term stability of the 0.2 Pa interior vacuum was successfully tested using a Ne fine-leakage test and resulted in an estimated lifetime of >10 years. This meets the requirements of a compact NIR-FTS.

No abstract

A translatory MOEMS actuator with extraordinary large stroke -especially developed for fast optical path length modulation in miniaturized FTIR-spectrometers -is presen¬ted. A precise translational out-of-plane oscillation at 500 Hz with large stroke of up to 1.2 mm is realized by means of a new suspension design of the comparative large mirror plate with 19.6 mm² aperture using four pantographs. The MOEMS device is driven electro -statically resonant and is manufactured in a CMOS compatible SOI process. Up to ± 600 µm amplitude (typically 1mm 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.Keywords: Optical SOI-MEMS, translatory micro mirror, optical path length modulation, Fouriertransform infrared spectrometers, optical vacuum packaging 1 Introduction Fourier Transform Infrared (FT-IR) spectroscopy is a widely used method to analyze different materialsorganic and inorganic. Current FT-IR spectrometers are large, usually static, and are operated by qualified personnel. By using translational MOEMS devices for optical path length modulation instead of conventional highly shock sensitive mirror drives a new class of miniaturized, robust, high speed and cost efficient FTIR-systems can be addressed. An early approach of a miniaturized MEMS based FTIR spectrometer has been developed in the past by IPMS and the CTR [1]. It was a combination of classical infrared optics with a translatory 5 kHz MEMS mirror using a folded bending spring mechanism. Due to the limited amplitude of ± 100 µm a spectral resolution of 30 cm -1 was realized allowing dynamic FTIR measurements in the ms-range [2]. To enhance the stroke IPMS introduced a first translational MEMS device with two pantograph mirror suspensions -originally designed for larger stroke of 500 µm. But due to superimposed parasitic torsional modes only ± 140 µm amplitude could be measured [2].In this paper, we now present an optimized MEMS device which overcomes the previous limitations enabling an extraordinary large stroke of 1 mm. The novel translatory MOEMS actuator was specially designed to enable a miniaturized MEMS based FTIR spectrometer with improved system performance of 5 cm -1 spectral resolution ( = 2.5…16 µm), SNR > 1000 and fast operation of 500 scans / sec. Hence, a large mirror aperture of 5 mm, enhanced amplitude of ± 500 µm and a small dynamic deformation of < /4 is required. Due to the significant viscous gas damping in normal ambient the translatory MEMS devices have to operate in vacuum -requiring a long term stable optical vacuum package with broadband IR window. The paper discusses the design, fabrication and experimental characteristics of the novel translatory MEMS actuator including first results of the optical vacuum packaging.To realize a large stroke of the mirror plate a pantograph like suspension was chosen. The new translatory MEMS actuator consists of four symmetric pantograph suspensions in contrast to two pantogr...