P3D Re: A Future 2D Photographer

[roberts@xxxxxxxxxxxxxxxxx (John W Roberts)]

>Date: Fri, 6 Nov 1998 12:27:41 -0700
>From: Bob_Maxey@xxxxxxxxxxxx
>Subject: P3D A Future 2D Photographer

>>>Well, actually, these tiny lasers are, at maximum, 5 mW. I used to own
>one
>back in the days I was making holograms, and have shined it in my eyes,
>though
>not for very long, with no ill effect. And I plan to shine the beam on an
>article of clothing, away from the face; that would cause no ill effects
>whatsoever.

>Want to go blind? Damage to the eye can easily occur if you do this,
>regardless of for how long. 5 mw is still a lot of power. Remember, the
>light is collimated and unfortunately, damage is cumulative.

I wouldn't stare into a 5mW laser, but also note that one of the common
safety classes of lasers is "< 5 mW", which could include devices which are
*much* less than 5 mW. I would think as a first approximation that a good
approach would be to follow the safety recommendations for the particular
device in question. Also, I believe the main mechanism for harm is heating
effects of the tissue of the retina - so while damage might be cumulative,
it would not be a linear function of lifetime (duration x intensity) exposure.
The peripheral vision appears to be much less prone to damage from bright
light than the foveal (central) vision, so avoiding looking directly at the
source could help.

Summary: follow the safety recommendations, work out the math, exercise
reasonable caution and common sense. (Also, have consideration for others,
and make sure those for whom you have some responsibility do not take
unwise risks.)

John R


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