High resolution mass spectrometry imaging of plant tissues ...
Ground-based imaging spectrometry for light pollution...
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Salva Bará, Raúl de la Fuente and Héctor González [email protected] Área de Óptica, Dept. Física Aplicada. Facultade de Óptica e Optometría Universidade de Santiago de Compostela http://www.facebook.com/Astronomia.na.beirarrua Ground-based imaging spectrometry for light pollution measurement
Transcript of Ground-based imaging spectrometry for light pollution...
Salva Bará, Raúl de la Fuente and Héctor Gonzá[email protected]
Área de Óptica, Dept. Física Aplicada. Facultade de Óptica e OptometríaUniversidade de Santiago de Compostela
http://www.facebook.com/Astronomia.na.beirarrua
Ground-based imaging spectrometry for light
pollution measurement
DISCLAIMER
This presentation is intended for educational, non-commercial use.
Trademarks, models and publications are quoted here merely for informative purposes, without any explicit or implicit endorsement by the Universidade de Santiago de Compostela (USC).
(c) The authors, except when indicated otherwise.
1. Imaging spectrometry
2. Why ground-based?
3. Some preliminary results
4. Additional remarks
Imaging spectrometry(Hyperspectral imaging)
Imaging spectrometry(Hyperspectral imaging)
A technique for obtaining spatially and spectrally resolved information of the
landscape
Imaging spectrometry(Hyperspectral imaging)
A technique for obtaining spatially and spectrally resolved information of the
landscape
A few arcmin per pixel (spatial)A few nm per pixel (spectral)
Imaging spectrometry(Hyperspectral imaging)
Imaging spectrometry(Hyperspectral imaging)
Imaging spectrometry(Hyperspectral imaging)
Imaging spectrometry(Hyperspectral imaging)
Imaging spectrometry(Hyperspectral imaging)
Imaging spectrometry(Hyperspectral imaging)
Airborne imaging spectrometers have been used in LP research for measuring the artificial light
emissions to the atmosphere and performing lamp type identification
Barducci et al (2003, 2006), Kruse and Elvidge (2009, 2010, 2011)
Why ground-based?
Why ground-based?
Several detrimental effects of light pollution at ground sites are determined not only (nor mainly) by the sky radiance but by the radiance directly received from the artificial sources through the line-of-sight and reflected
paths.
Why ground-based?
The circadian effects of light have been generally measured in terms of the spectral irradiance at a plane
tangent to the cornea and perpendicular to the visual axis
Creative Commons Attribution 3.0 UnportedArtwork by Holly Fischer
Some preliminary results
Why ground-based?
A spectral opponency model by MS Rea, MG Figueiro, A Bierman and R Hamner, "Modelling the spectral sensitivity of the human circadian system,"Lighting
Research and Technology 2012; 44:386-396.
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mpl: macular pigment transmittanceVl: Photopic luminous efficiency functionV'l: Scotopic luminous efficiency functionRodSat: Half-saturation constant for rods = 6.5W/m2
k=0.2616 (dimensionless)ab-y=0.6201 (dimensionless)arod=3.2347 W/m2
Why ground-based?
The spectral irradiance for arbitrary positions of the visual axis can be computed if the spectral radiance of the
environment is known
... and that's what an imaging spectrometer can do for us
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Some preliminary results
Some preliminary results
Imaging objective 1.4/17 mmSlit 15 µm x 8 (10) mm
Collim/Focuser 1.9/35 mmDiffraction grating 300 lines/mm
CCD mono 12 bits 2/3”pixels (6.45 µm)
Usually binned 4x4
260 channels spanning the range 390-1010 nm
Geom. Resol. (static): 5 arcmin/binpix
Vertical FOV 26.5º (32º)
Some preliminary results
Some preliminary results
Some preliminary
results
451 nm
480 nm
504 nm
516 nm
543 nm
552 nm
576 nm
596 nm
608 nm
649 nm
Some preliminary results
Some preliminary
results
Some preliminary
results
Some preliminary
results
Some preliminary
results
Additional remarks
Imaging spectrometry is a mature technology
Commercial setups are not particularly cheap: price tags in the tens of kiloEuros range
However, it is possible to implement them as a DIY approach in Optics labs, using off-the-shelf
components
Imaging spectrometers in University labs may have some free time slots and most researchers should
be eager to cooperate
Conclusions
Imaging spectrometry is a useful technology for obtaining a complete characterization of the radiance
of the urban nightscape
Albeit price may be an obstacle for widespread use, cooperation with university research labs may
grant us access to this technology
It allows to determine the spectral irradiance at the observer’s eye for any gaze direction and to compute
the relevant circadian illumination magnitudes.
