Re: laser safety

[P3D Greg Erker <erker@xxxxxxxxxxxxxx>]

Harold R. Baize wrote:

>I would like to know if anyone has definitive information on how
>harmful these low power laser pointers are. My belief is that they
>are fairly weak and would require a direct in-the-eye exposure of
>a substantial fraction of a second (or longer) to do any damage.
>Is this true, or am I endangering people when I play with the
>thing?

Here is something I found at:

http://www.oehs.upenn.edu/laser/laser_manual.html

----------------
8.0 Laser Classification

       8.1 Lasers are generally classified and controlled
according to the following criteria:

1. Class 1 : Low-power lasers and laser systems that cannot
   emit radiation levels greater than the Maximum Permissible
   Exposure (MPE). Class 1 lasers and laser systems are incapable
   of causing eye damage and are therefore exempt from any control
   measures.

2. Class 2: Visible, low power lasers or laser systems that are
   incapable of causing eye damage unless they are viewed directly
   for an extended period (greater than 1000 seconds).

3. Class 3 : Medium-power lasers and laser systems capable of causing
   eye damage with short-duration (<0.25 s) exposures to the direct or
   specularly reflected beam. Includes Class 3a and 3b lasers.

4. Class 3a : Lasers or lasers systems that normally would not produce
   a hazard if viewed for only momentary periods with the unaided eye.
   They may present a hazard if viewed using collecting optics.

5. Class 3b : Lasers or lasers systems that can produce a hazard if viewed
   directly. This includes intrabeam viewing of specular reflections.

6. Class 4: High power lasers and laser systems capable of causing severe
   eye damage with short-duration (<0.25 s) exposures to the direct,
   specularly reflected, or diffusely reflected beam. Class 4 lasers and
   laser systems are also capable of causing severe skin damage and igniting
   flammable and combustible materials.

-----------------

A commercial laser pointer should be labeled for what class it is. If class
1 or 2 you are probably safe playing with it.  A 3a is also probably safe for
"painting a scene" as long as there are no focusing optics in use (subject
looking thru binoculars for example). As I recall a 3a is not supposed to
cause eye damage in the short time (0.2 sec) that it takes a person to
close or avert their eyes due to the bright light. If you intentionally
stare into it they can cause damage.

A class 3b or 4 should never be pointed at anyone.

That's all I know. This information is worth what you paid for it (0),
so play with lasers at your own risk.

Greg E. (former home holographer with two working eyes)



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