Fisheye camera method for spatial non-uniformity corrections in luminous flux measurements with integrating spheres
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© 2017 BIPM & IOP Publishing Ltd Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
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Date
2017-07-24
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Language
en
Pages
7
577-583
577-583
Series
Metrologia, Volume 54, issue 4
Abstract
This paper presents a fisheye camera method for determining spatial non-uniformity corrections in luminous flux measurements with integrating spheres. Using a fisheye camera installed into a port of an integrating sphere, the relative angular intensity distribution of the lamp under test is determined. This angular distribution is used for calculating the spatial non-uniformity correction for the lamp when combined with the spatial responsivity data of the sphere. The method was validated by comparing it to a traditional goniophotometric approach when determining spatial correction factors for 13 LED lamps with different angular spreads. The deviations between the spatial correction factors obtained using the two methods ranged from -0.15% to 0.15%. The mean magnitude of the deviations was 0.06%. For a typical LED lamp, the expanded uncertainty (k = 2) for the spatial non-uniformity correction factor was evaluated to be 0.28%. The fisheye camera method removes the need for goniophotometric measurements in determining spatial non-uniformity corrections, thus resulting in considerable system simplification. Generally, no permanent modifications to existing integrating spheres are required.Description
Keywords
angular intensity distribution, fisheye camera, integrating sphere, luminous flux, measurement uncertainty, photometry, spatial correction
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Citation
Kokka, A, Pulli, T, Poikonen, T, Askola, J & Ikonen, E 2017, ' Fisheye camera method for spatial non-uniformity corrections in luminous flux measurements with integrating spheres ', Metrologia, vol. 54, no. 4, pp. 577-583 . https://doi.org/10.1088/1681-7575/aa7cb7