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Testing the performance of freeform LED optics by gradient based measurement
Author(s): David Hilbig; Friedrich Fleischmann; Thomas Henning
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Paper Abstract

Light-emitting diodes (LED) increasingly replace conventional filaments in various illumination applications due to higher performance and efficiency. However, their common luminous intensity profiles do not match all requirements and need to be adapted using secondary beam shaping optics. Aside from reflectors, such optics are commonly realized by freeform optical components. More sophisticated tasks such as safety and security applications are covered by strict regulations and demand a well defined spatial distribution of the emitted light. Up to now, correct functionality is only verified at system level by determining the resulting radiation pattern with a photogoniometer after packaging the optic with the light source and the fixture. However, the correct functionality of the individual optical component is usually not verified and in a fail case, the actual error source cannot be identified. A new measurement method based on experimental ray tracing (ERT) is introduced that enables performance testing of beam shaping secondary optics at component level. Rays emerging from a virtual point source are traced through the device under test. The angle of the refracted ray is recorded as a function of the incident angle. In an additional step, the resulting radiation distribution is determined based on the energy conservation law. Measurement result of a freeform lens for marine application are presented as an example and compared to results from a photogoniometer.

Paper Details

Date Published: 28 August 2016
PDF: 7 pages
Proc. SPIE 9960, Interferometry XVIII, 99600M (28 August 2016); doi: 10.1117/12.2237766
Show Author Affiliations
David Hilbig, Hochschule Bremen Univ. of Applied Sciences (Germany)
Friedrich Fleischmann, Hochschule Bremen Univ. of Applied Sciences (Germany)
Thomas Henning, Hochschule Bremen Univ. of Applied Sciences (Germany)

Published in SPIE Proceedings Vol. 9960:
Interferometry XVIII
Katherine Creath; Jan Burke; Armando Albertazzi Gonçalves, Editor(s)

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