Optical radiation safety assessment of light emitting diodes (LEDs): Different approaches, standards and results

Abstract

Although they were developed from almost the same experimental basis, two different “historically grown” basic compilations of threshold limit values for optical radiation safety are provided, distinguishing monochromatic laser and broadband incoherent optical sources. Since they were developed for different uses and safety considerations, both limit-sets are accordingly different.However, due to different backgrounds and approaches, LEDs were generally included into the requirements and safety regulations for lasers as well as for conventional lamps. Whereas the inclusion of LEDs into optical safety regulations for incoherent broadband optical sources was caused by the similarity of (some) LEDs to lamps, the LED-inclusion into the IEC-laser safety regulations was initiated by the similarity of (some other) LED types and applications to lasers. Due to the obvious inappropriateness of the IEC laser safety standard for brought band sources in some aspects, other international or national standardisation bodies do not include LEDs in then laser safety regulations. A puzzling situation for safety considerations for the growing number of LED-applications and -users e.g. of illumination, signalling and automotive lighting is the result we see today.The present contribution summarises this uncomfortable situation, shows some implications and suggests first ideas of a possible strategy for a solution.Although they were developed from almost the same experimental basis, two different “historically grown” basic compilations of threshold limit values for optical radiation safety are provided, distinguishing monochromatic laser and broadband incoherent optical sources. Since they were developed for different uses and safety considerations, both limit-sets are accordingly different.However, due to different backgrounds and approaches, LEDs were generally included into the requirements and safety regulations for lasers as well as for conventional lamps. Whereas the inclusion of LEDs into optical safety regulations for incoherent broadband optical sources was caused by the similarity of (some) LEDs to lamps, the LED-inclusion into the IEC-laser safety regulations was initiated by the similarity of (some other) LED types and applications to lasers. Due to the obvious inappropriateness of the IEC laser safety standard for brought band sources in some aspects, other international or national standardisation bod...