Do not stare at high
s, because doing so may cause permanent damage to
The optics of our eyes focus visible light onto the retina, which is
the light sensitive part of our eyes, similar to the way a magnifying
glass can focus an image of the sun onto a piece of paper. Just as the
piece of paper might smolder and catch fire, a light that is brightly
focused on your retina can cook and thus permanently damage your eye.
Exposure to bright white and blue LEDs can also cause permanent damage
to your eyes through photochemical action.
Here is a link to an article about the particular hazards of blue
The key factors that determine whether or not a particular exposure to
light from an LED causes permanent damage are the wavelength and
intensity of the light, the length of the exposure occurs, and the
distance from the light source to the eye.
This danger is most pronounced with the use of the newer high output
blue and white LEDs. These are intended to illuminate large areas, and
for those designed for direct view applications, to be viewed at a
significant distance. These LEDs can be identified by packaging or
mountings that are designed to carry heat away from the junction. LEDs
without these special thermal management features can also pose a
danger when operated beyond their specified maximum current.
Infrared and ultraviolet LEDs can also be hazardous, and when using
those, please consult the manufacturer's data sheets or IEC
60825-1:2001 for guidance with respect to safety. You may find IEC
60825-1:2001 summarized on the web. The standard can be purchased from
IEC's web store http://webstore.iec.ch/
The IEC specification was written to apply to primarily to lasers ,
though it also applies to LEDs. A new standard, IEC TR 60825, is
in development that promises that includes a section that is intended
to address LEDs directly. You might want to check the web for drafts or
summaries of this standard in the future.
The standards mentioned above rely on measurements that can only be
made with very expensive specialized equipment, though some
manufacturers state the safety classification of their LEDs, under
specified operating conditions, in their data sheets. Take note
of these comments on the data sheets for LEDs you may use. In the mean
time, play it safe by not staring at any bright LEDs.
My thanks to Geoff Davies of Lucid Optical Services Ltd. (http://www.lucidos.co.uk
for raising the issue of permanent eye
damage, and providing the information contained in this section.