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MEMS based NIR spectrometer with extended spectral range

: Grüger, H.; Knobbe, J.; Pügner, T.


Piyawattanametha, Wibool (Hrsg.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
MOEMS and Miniaturized Systems XVIII : 2-4 February 2019, San Francisco, California, United States
Bellingham, WA: SPIE, 2019 (Proceedings of SPIE 10931)
ISBN: 978-1-5106-2504-4
ISBN: 978-1-5106-2505-1
Art. 1093107, 10 S.
Conference "MOEMS and Miniaturized Systems" <18, 2019, San Francisco/Calif.>
Conference "Optoelectronics, Photonic Materials and Devices" <2019, San Francisco/Calif.>
Fraunhofer IPMS ()

Miniaturized MEMS based spectrometers have attracted interest for mobile high volume applications. Performance parameters like resolution, stability and spectral range gain an increased attention for the comparison of different approaches in addition to the classical characteristics such as size and cost. The necessary resolution must be considered with the requirements of the spectral application in mind. For organic material analysis and similar tasks often resolutions around 10 nm have been regarded to be sufficient. Stability - here predominantly relevant is the wavelength scale - is important for the proper operation of the chemometric evaluation in the NIR range where overtone and combination bands have to be evaluated. Resonant scanner devices offer the opportunity to use simple position readout systems and gather accurate position information by tracking many cycles of the resonant movement. The deflection of the scanning grating device used in this kind of MEMS based spectrometers becomes a limiting factor for extending the spectral range. By using a plain scanner mirror which illuminates a fixed grating and gathers the reflected radiance simultaneously the spectral range can be doubled applying the same MEMS deflection. Furthermore, the wider spectral range can be supported by using two or more detectors with different spectral characteristics placed behind two or more separated exit slits. These slits could be integrated into the same MEMS chip like the scanner mirror device. Several optical designs for miniaturized setups have been compared to find an optimized option which requires affordable optical components only. Here especially the two mirrors in the setup are relevant for a suitable spectrometer performance with acceptable effort. Finally a folded Czerny-Turner type setup has been chosen which can be integrated by the "place and bend" assembly.