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MEMS-based Spectrographs
Recent Advances on their Optical Design P. Spanò INAF Osservatorio Astronomico di Brera, ITALY STScI, Baltimore June 25, 2010
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MEMS-based Spectrographs: Advances on their Optical Design
INAF & O.A.Brera Since 2003 O.A.Brera is one of the 19 institutes currently part of the Instituto Nazionale di Astrofisica (INAF) 12 “Observatories” and 7 Institutes former belonging to the National Research Council (CNR) STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
Merate Observatory STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
From ground to SPACE We, GOLEM (Gruppo Ottiche e LEnti Merate) are a small team of astronomers and engineers located in Merate We works mainly for ground-based telescopes (e.g., the GRB shooter REM in La Silla, Chile) and focal plane instrumentation (e.g., X-shooter on ESO VLT in Paranal, Chile, again) for optical-to-NIR wavelengths More recently, we were involved in space-based projects, like SPACE (now EUCLID) STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
SPACE STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
ESA led a study to merge together the two Dark Energy missions, SPACE and DUNE into EUCLID Weak-lensing and BAOs as probes for DE 1.2m shared telescope VIS + NIR photometry NIR spectroscopy STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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Digital Micromirror Devices
STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
DMD principles - I ON: +12° OFF: -12° Incident ray DMD micromirror can tilt (along its diagonal) by +/- 12 deg (in the Cinema DLP) They correspond to two different states: On and Off A third state (power off) exists, with a 0° angle DMD micromirror DMD surface STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
DMD principles - II STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
DMD principles - III Tilt happens along the diagonal of the micromirror, so a 45 deg rotation of the device is required to keep chief rays within a plane perpendicular to the DMD surface STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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DMD illumination geometry - I
Rotation axis of the DMD mirror 45° Reflected ray DMD area DMD micromirror 0° 24° (angle w.r.t. DMD normal) DMD normal STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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DMD illumination geometry - II
28º 16.73º 24º 16.73º 4º 17.9º 20º 17.9º 23º 24º 4º 23º Minimum and maximum Equal amplitude One perpendicular to field STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
RITMOS (Meyer et al. 2004) F/8 beam 0.8” micromirrors 0.6m tel.) 11’x8’ FoV 0.6m tel.) um R=6000 STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
IRMOS (MacKenty et al. 2004) F/5.6 beam 17um micromirrors 4m) 3’x2’ FoV 4m) um (ZJHK) R= STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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SPACE DMD-baseline (Content et al., Durham Univ.)
F/2.2 beam 14um micromirrors 1.2m) 49’x34’ FoV um R=400 Very complex mirrors, large & heavy, complex mechanisms STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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SPACE DMD altenative I (by Grange et al., Lab. Astroph. Marseille)
F/2.7 beam 14um micromirrors 1.2m) 26’x14’ FoV um R=400 Simpler, smaller, reduced performances STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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SPACE DMD altenative II (by Spanò et al., INAF)
F/4 beam 14um micromirrors 1.2m) 20’x11’ FoV um R=400 Very compact, small field 50cm STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
TIR prisms STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
TIR on beamers STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
Beamer Requirements STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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Example of TIR image quality
(Bowron, et al. SPIE 5186,2003) STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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DMD @ Galileo Telescope
STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
A simplified approach Modular design, simple layout, cheap optics Low resolution “Large” field of view High efficiency “Off-the-shelf” optics STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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The starting idea (Zamkotsian et al., ASP Conf. 207, 2000)
F/7 beam Proposed for NIRMOS Two spherical mirrors and a convex spherical grating 1:1 Offner-like design STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
The design Two arms: Spectro & Imaging Wavelengths: nm Spectral resolution: 250 Focal ratio: F/4 FoV: 4.5’x7’ Detectors: 2kx2k (spect.), 1kx1k (imaging) STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
Optical details STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
Slits and spectra STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
Mechanical layout STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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MEMS-based Spectrographs: Advances on their Optical Design
Summary DMD spectrographs with enhanced FoV can be designed with faster beams TIR prisms can be very effective to keep size very small Simpler designs if Offner-type configurations are selected STScI Baltimore June 25, 2010 MEMS-based Spectrographs: Advances on their Optical Design
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