P3D light hazards

[John Toeppen <toeppen@xxxxxxxxxxx>]

Laser pointers can do damage.  Never stare into any bright light; arc
lamps, halogen lamps, or directly reflected sunlight.  You can gel up
your retina like the white of an egg.  I know one guy who lost central
vision in one eye by a prolonged stare into an arc lamp through the
reflector.  Another friend lost color vision in one eye by a long stare
into the finish of his white car at the reflection of the sun as he was
rubbing out a spot.  And another guy who watched the "interesting
effect" that he saw while he was aligning a powered laser while using
his safety glasses as a beam stop. He now has a blind spot.  These are
hard won lessons.  

Eyes are easily damaged by bright light, laser or not.   A projector
bulb is not safe to look at.  Fact is, the UV in sunlight will damage
your cornea and give you cataracts (fogged lenses) in time. Lasers can
do damage very quickly. Welding equipment, tanning rays, viewing of
molten materials, and flash equipment are often unrecognized eye
hazards. Avoid UV, IR,  and do not look directly into bright light.

A laser pointerís light can focus to a two micron size spot on the
retina.  The focused spot can raise to an intensity millions of times
greater than its intensity when it enters the eye.  Thus 5/1000ths of a
Watt per square cm. becomes thousands of Watts per square cm. in the
focal plane of the retina.  So, we treat laser pointers like very long
sharp sticks: not to be directed at the eye.

Higher power lasers are obviously used in display systems and medical
applications.  This is not always done with the greatest of wisdom. 
Standards exist which are not followed or enforced.  Other times
measurement and controls are carefully exercised.  A good rule of thumb
is that no more than a milliwatt should enter the eye from a point
source.  Standards require that we treat all lasers as point sources.

I have taken many stereo photos of large lasers.  Sometimes I would take
my photos "remotely" because nobody was allowed in the room with the
doors off.   Long ago our methods were different, and we relied on the
knowledge and care of the worker.  Now we use interlocked automatic
shutters, enclosures, safety eyewear (if required by power levels), and
worker training.

 View some LASER STEREO PHOTOS at:

http://home.pacbell.net/toeppen/CVLs.html

John Toeppen
http://home.pacbell.net/toeppen/


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