Understanding radiation safety of high-intensity light-emitting diodes

Light emitting diodes (LEDs) continue to increase in optical output power. Conventional wisdom that considers them to be safe with respect to radiation hazards to the eye and skin may no longer hold. The governing standards for LED radiation hazard rating, including IEC 62471, may not account for these new high-power LEDs, especially for applications that allow use closer than the typical minimum tested distance of 200 mm, such as pulse oximetry and optical tomography. Because LEDs are small sources with divergent radiation cones, the irradiance increases as the observer approaches the LED and may exceed the levels of safety for both eye and skin. Additionally, the natural aversion response to bright lights may not be present for near-infrared LEDs.