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Title: ACCURATE DETERMINATION OF THE NEAR-FIELD ILLUMINANCE FROM NARROW-BEAM LED ARRAYS USING RAY FILES
Authors: Jacobs, Valéry Ann
Ryckaert, Wouter
Rombauts, Patrick
Hanselaer, Peter
Issue Date: 4-Nov-2014
Host Document: PROCEEDINGS of CIE Expert Symposium on Measurement Uncertainties in Photometry and Radiometry for Industry
Conference: Expert Symposium on Measurement Uncertainties in Photometry and Radiometry for Industry location:Vienna date:8-12 September 2014
Article number: 10
Abstract: Most lighting manufacturers represent the angular distribution of the flux of their light sources
by a far-field representation, also known as luminous intensity distribution (LID.) For spatially
extended sources however, the inverse square law is only valid beyond the limiting
photometric distance. By consequence, this distribution does not allow for accurate
illuminances to be determined in the near-field region of the source. This problem is even
more pronounced for arrays of LEDs with focusing optics creating narrow beams. We
gathered a ray-file of several LED arrays using a near-field luminance goniophotometer. This
paper reports on measurements and simulations using ray-tracing. It shows that a far-field
representation cannot be used to calculate illuminance values in the near-field. In contrast, a
near-field representation allows the calculation of accurate illuminance values at any target
point, irrespective of the distance to the source and its luminous intensity distribution.
ISBN: 978-3-902842-22-0
Publication status: published
KU Leuven publication type: IC
Appears in Collections:Electrical Engineering (ESAT) TC, Technology Campuses Ghent and Aalst
Technologiecluster ESAT Elektrotechnische Engineering

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