Tunable filters for multispectral imaging of aeronomical features

Goenka, Chhavi; Semeter, J. L.; Noto, J.; Dahlgren, Hanna; Marshall, R. A.; Baumgardner, Jeffrey; Riccobono, J.; Migliozzi, M. A.

doi:10.1016/j.asr.2013.06.014

Cited by 6 publications

(2 citation statements)

References 33 publications

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“…2). Three color values at each pixel location can be easily determined by interpolation from neighboring pixels (e.g., Gunturk et al, 2005) with Bayer demosaicing support built into many image processing software packages. The density of green pixels is twice that of red and blue; this configuration can be advantageous for observing aurora, which are often dominated in visible wavelengths by 557.7 nm atomic oxygen "green-line" emissions.…”

Section: Sony Icx285hqmentioning

confidence: 99%

Auroral spectral estimation with wide-band color mosaic CCDs

Jackel¹,

Unick²,

Syrjäsuo³

et al. 2013

Preprint

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Abstract. Color mosaic CCDs use a matrix of different wide-band micro-filters in order to produce images with several (often three) color channels. These devices are increasingly employed in auroral studies to provide time sequences of two dimensional luminosity maps, but the color information is typically only used for qualitative analysis. In this study we use Backus–Gilbert linear inversion techniques to obtain quantitative measures of effective spectral resolution for multi-channel color mosaic CCDs. These techniques also allow us to explore the possibility of further improvements by modifying or combining multiple detectors. We consider two spectrally calibrated commercial color CCDs (Sony ICX285AQ and ICX429AKL) in order to determine effective wavelength resolution of each device individually, together, and with additional filters. From these results we develop methods to enhance the utility of existing data sets, and propose ways to improve the next generation of low-cost color auroral imaging systems.

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Section: Sony Icx285hqmentioning

confidence: 99%

Auroral spectral estimation with wide-band color mosaic CCDs

Jackel¹,

Unick²,

Syrjäsuo³

et al. 2013

Preprint

View full text Add to dashboard Cite

show abstract

“…17c) requires the use of multiple filters or a single tunable filter (López-Alvarez et al, 2008;Sigernes et al, 2012;Goenka et al, 2013). In either case, the measurement process will involve a sequence of observations that are intrinsically nonsimultaneous.…”

Section: Combinations and Modificationsmentioning

confidence: 99%

Auroral spectral estimation with wide-band color mosaic CCDs

Jackel

Unick

Syrjäsuo

et al. 2014

Geosci. Instrum. Method. Data Syst.

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Abstract. Optical aurora can be structured over a wide range of spatial and temporal scales with spectral features that depend on the energy of precipitating particles. Scientific studies typically combine data from multiple instruments that are individually optimized for spatial, spectral, or temporal resolution. One recent addition combines all-sky optics with color mosaic CCD (charge-coupled device) detectors that use a matrix of different wide-band micro-filters to produce an image with several (often three) color channels. These devices provide sequences of two dimensional multispectral luminosity with simultaneous exposure of all color channels allowing interchannel comparison even during periods with rapidly varying aurora. At present color auroral image data are primarily used for qualitative analysis. In this study a quantitative approach based on Backus-Gilbert linear inversion was used to better understand the effective spectral resolution of existing and proposed instruments.Two spectrally calibrated commercial detectors (Sony ICX285AQ and ICX429AKL) with very different color mosaics (RGB (red, green, blue) vs. CYGM (cyan, yellow, green, magenta)) were found to have very similar spectral resolution: three channels with FWHM (full-width halfmaximum) ≈ 100 nm; a NIR (near infrared) blocking filter is important for stabilizing inversion of both three-channel configurations. Operating the ICX429AKL in a noninterlaced mode would improve spectral resolution and provide an additional near infrared channel. Transformations from arbitrary device channels to RGB are easily obtained through inversion. Simultaneous imaging of multiple auroral emissions may be achieved using a single-color camera with a triplepass filter. Combinations of multiple cameras with simple filters should provide ∼ 50 nm resolution across most of the visible spectrum. Performance of other instrument designs could be explored and compared using the same quantitative framework.

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