28 August 2016 Testing the performance of freeform LED optics by gradient based measurement
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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.
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David Hilbig, David Hilbig, Friedrich Fleischmann, Friedrich Fleischmann, Thomas Henning, Thomas Henning, } "Testing the performance of freeform LED optics by gradient based measurement", Proc. SPIE 9960, Interferometry XVIII, 99600M (28 August 2016); doi: 10.1117/12.2237766; https://doi.org/10.1117/12.2237766


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