"Asimov" writes:

"Sam Goldwasser" bravely wrote to "All" (16 Feb 05 19:11:03)
--- on the heady topic of " Laser Pointers on the Skin"

SG From: Sam Goldwasser
SG Xref: aeinews sci.electronics.repair:10721

SG "NSM" writes:

wrote in message
...
This is not about repair, but I thought someone on here might know.
...
So I took the thing away from them. As a test, I pointed the thing at
a spot on my hand, and they are correct, it does make the spot warm. ...

So does a 60 W light bulb.

SG As long as they keep it away from anyone's eyes, it is safe.
SG It's less tha 1/200th of a W.


One thing I've discovered about laser pointers is that the chip area
is purposely constructed so that it is impossible to collimate the
beam to make it into a dangerous device. What I think happens is that
there are multiple lasing areas which are slightly out of phase with
each other. When one tries to concentrate the beams onto a very tiny
spot they tend to subtract from each other and cancel out.

Actually, in principle, the types of laser diodes used in pointers
can be collimated or focused to the diffraction limit. But it takes
more than a simple lens.

High power laser diodes are what's called "multimode" which are in effect,
a bunch of smaller beams side-by-side, and they are limited in terms of
collimation and focusing.

--- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
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