Optical radiation safety analysis of LEDs on the basis of guidelines for incoherent sources

Abstract

Since 1993, photobiological safety aspects of LEDs have been covered by the international IEC laser safety standard IEC 60825.As a consequence, compliance of products containing LED with this standard is mandatory and has to be declared on a legal basis on the EU market. In the past - as long as LEDs have only been usable as indicators, signal lamps etc. - there have been no real problems with the application of the laser safety-related limits and safety philosophy. However, due to increased efficiency and simultaneously enlarged application areas, the eye safety issue raises growing attention. As a result of a long term discussion, currently everything points to an exclusion of LEDs from the scope of the IEC laser standard. The optical radiation hazard of LEDs should more appropriately be assessed on the basis of safety requirements for incoherent sources, such as provided by the CIE “lamp safety standard”.This CIE-safety standard for incoherent sources requires a measurement of the source radiance under defined conditions. Since these measurement conditions are related to specific potentially hazardous viewing conditions and physiological features of the eye, they differ from usually applied radiance determination methods i.e. applied for optical characterization of a light source. For these measurements nearly no advice or guidance and also no purpose-built equipment is available at the moment. Therefore, in order to check the implications (not just) for LEDs, an assessment method based on geometrical-optical calculations is desirable. Both, a possible calculative method as well as the resulting impact of the CIE “lamp safety will be presented”.Since 1993, photobiological safety aspects of LEDs have been covered by the international IEC laser safety standard IEC 60825.As a consequence, compliance of products containing LED with this standard is mandatory and has to be declared on a legal basis on the EU market. In the past - as long as LEDs have only been usable as indicators, signal lamps etc. - there have been no real problems with the application of the laser safety-related limits and safety philosophy. However, due to increased efficiency and simultaneously enlarged application areas, the eye safety issue raises growing attention. As a result of a long term discussion, currently everything points to an exclusion of LEDs from the scope of the IEC laser standard. The optical radiation hazard of LEDs should more appropriately be assessed on the basis of safety requirements for incoherent sources, such as provided by the CIE “lamp safety standard”.This CIE-safety standard for incoherent sources requires a measurement of the source radiance under...