The eye is well adapted to protect itself against overly intense broad-band optical radiation (ultraviolet, visible and infrared radiant energy) from the natural environment and mankind has learned to use protective measures, such as hats and eye-protectors, to shield against the harmful effects upon the eye from very intense ultraviolet radiation (UVR) and blue light present in sunlight over snow or sand. The eye is also protected against bright light by the natural aversion response to viewing brightly visible light sources. The aversion response normally protects the eye against injury from viewing bright light sources such as the sun, arc lamps and welding arcs, since this aversion limits the duration of exposure to afraction of a second (about 0.25 s). The infrared LEDs employed in most infrared LED eyetrackers do not, however, produce a strong
aversion response, as they are barely visible, and the spectral emission is limited to the near-infrared (IRA, 780-1400 nm) spectral band
The exposures typical of LED eyetrackers are typically below Maximum Permissible Exposure (MPE) limits, and therefore well below actual retinal injury thresholds (Ham & Mueller, 1989; Sliney et al, 2005). The best available data for retinal injury thresholds for large-image exposure at 810 nm comes from work published by Ham and Mueller (1989)
While reading I found this "kind of older" thread. I also wondered if IR LEDs could harm the eye, when I build a DIY tracker based on ITU Gaze Tracker. I did some research. In the end I asked my neighbor (medical), if he knows something about that topic. He gave me a link to the following study (german only):
http://www.baua.de/de/Publikationen/Fachbeitraege/F2115.html
Publisher is the German Federal Agency for Employment Protection.
They researched the impact of LEDs especially for the human eye.
Since I did not have access to measuring equipment I dropped my research at that point. Nevertheless this could be important for deploying pupil.
Kind regards,
Michael Barz
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