| Records |
Author  |
Bará, S.; Tilve, V.; Nievas, M.; Sanchez de Miguel, A.; Zamorano, J. |
| Title |
Zernike power spectra of clear and cloudy light-polluted urban night skies |
Type |
Journal Article |
| Year |
2015 |
Publication |
Applied Optics |
Abbreviated Journal |
Appl. Opt. |
| Volume |
54 |
Issue |
13 |
Pages |
4120-4129 |
| Keywords |
Skyglow; artificial ligh at night; light pollution; Zernike; power spectrum; atmospheric optics; imaging systems; image analysis |
| Abstract |
The Zernike power spectra of the all-sky night brightness distributions of clear and cloudy nights are computed using a modal projection approach. The results obtained in the B, V and R Johnson-Cousins' photometric bands during a one-year campaign of observations at a light-polluted urban site show that these spectra can be described by simple power laws with exponents close to -3 for clear nights and -2 for cloudy ones. The second-moment matrices of the Zernike coefficients show relevant correlations between modes. The multiplicative role of the cloud cover, that contributes to a significant increase of the brightness of the urban night sky in comparison with the values obtained in clear nights, is described in the Zernike space. |
| Address |
Area de Optica, Dept. Fisica Aplicada. Facultade de Fisica / Facultade de Optica e OptometrÃa Universidade de Santiago de Compostela Campus Sur, E-15782 Santiago de Compostela, Galicia, Spain; salva.bara@usc.es |
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Thesis |
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| Publisher |
Optical Society of America |
Place of Publication |
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Editor |
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| Language |
English |
Summary Language |
English |
Original Title |
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Approved |
no |
| Call Number |
IDA @ john @ |
Serial |
1156 |
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| Author |
Fiorentin, P.; Boscaro, F. |
| Title |
A method for measuring the light output of video advertising reproduced by LED billboards |
Type |
Journal Article |
| Year |
2019 |
Publication |
Measurement |
Abbreviated Journal |
Measurement |
| Volume |
138 |
Issue |
|
Pages |
25-33 |
| Keywords |
Lighting; Energy; Instrumentation; Planning; Light-emitting diode displays; Photometry; Video recording; Image analysis; CCD image sensors; Luminance; Glare |
| Abstract |
Improving knowledge of the light output of digital billboards is important to better assess their effect on driver distraction when they are installed along roads. In this work the emission of an LED based billboard is measured when playing advertising video-clips. In particular the average and the maximum values of the luminance are evaluated. The same video-clips are also analyzed when shown on an LCD monitor, aiming at separating the variability of the videos and of the playing device. The results allow to evaluate an utilization factor of the billboard: the videos have an average luminance around 11% and a peak luminance of 35% of the maximum luminance obtainable from the billboard. The power consumption of the billboard is measured, aside the photometric analysis. The luminance of the device are found linearly dependent on both the power and the effective current absorbed by the device from the grid, with a discrepancy within 6%. It could be a useful information for billboard manufacturers to qualify their product when they do not own photometric instruments. |
| Address |
Department of Industrial Engineering, University of Padova, Padova, Italy; pietro.fiorentin(at)unipd.it |
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Thesis |
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| Publisher |
Elsevier |
Place of Publication |
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Editor |
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| Language |
English |
Summary Language |
English |
Original Title |
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0263-2241 |
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no |
| Call Number |
GFZ @ kyba @ |
Serial |
2214 |
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