From: "Jerald F. Wright" 
To: Scott Ewart 
CC: atm{at}shore.net
Reply-To: "Jerald F. Wright" 




Scott Ewart wrote:

>     Just how much power do you think these things have, anyway?  It's a few
> milliwatts!  And I seriously doubt they're focused well enough to harm
> anything more than a mile away.
>     Astrophotographers are all worried about having an exposure ruined by a
> laser, but has anyone anywhere EVER seen or heard of a photo with even a
> hint of green laser?  Same with pilots.  Have any ever actually seen a green
> dot on the ground?
>
> Scott

    The laser pointers are "probably" not a big problem. The laser I was
injured
by (and that is the proper way to state it) was not a pointer. It was a
larger one about half the size of a shoe box. I don't know the power. My
statement was that I think at some power level lasers should be regulated. 
I probably over stated that and should have said may need regulation
depending on the frequency of injury by them.

    Actually I have heard of two incidents of pilots at least being temporarily
visually impaired by lasers. One was widely reported and involved a U. S.
Navy pilot being lasered by a Russian Ship.  This one was obviously a
military laser probably well beyond the power we are using in amateur
astronomy and probably with a wide beam.  So I discard this one as not
relevant to what we are talking about.  The other I can't put much stock in
either.  I only heard one news report (not an in depth report) of a airline
pilot that claimed his vision was impaired in flight by what he
"thought" was a laser.  I just don't know if I should believe it.
 I think it would be incredibly difficult to point a narrow laser beam in a
pilots eye more than a few micro seconds from a distance of a mile or more
because of the obvious problems of pointing at such a small target at all
let alone tracking.  But a high power laser could be made to have a
diverged beam to cover a significantly wider area at the target and still
deliver significant power into someone's eyes. It would be interesting to
search
the NTSB and FAA sites to see if there have been reported instances not
related to military situations.

    No. I do not believe the typical laser pointers are a big hazard that
should
be regulated.  Some do seem quite bright, particularly the green ones. So I
still wouldn't want people being foolish and pointing the beam at or near
anyone's eyes.  Just a little common sense goes a long way.  Keep in mind
that a
few milliwatts or even part of a milliwatt concentrated in a beam that will
entirely fit through the pupil of your eye is thousands of times the power
level
normally reaching your retina.  And it is focused by the lens of your eye
to an extremely small point on your retina. And if you happen to be looking
somewhat directly in the direction of the laser it is on the most sensitive
part of the retina.  When a light shines in your eye it is natural instinct
to look directly
at it to see where it is coming from.

    The problem I had after getting zapped in the eye for less than 1/10 second
was that the part of the retina used in seeing fine detail was injured. In
some ways I could see normal such as the panoramic view.  But when I
narrowed my attention to detail it was not there in my right eye.  I could
not read a printed word with that eye and even had difficulty recognizing a
face with my right eye alone.  My right eye is my dominate eye, the one I
use for shooting, telescope viewing, and other such things.  My left eye
was normal and that leads
to a sense that there is no trouble at times and much at other times. I
could see pretty much normal most of the time.  It is when you choose to
narrow your attention to some fine detail that requires that extra
resolution in your dominate eye that you know something is for sure wrong. 
It is a strange feeling. Try covering your dominate eye and read a page of
a book.  Then cover the non dominate eye and read another page. You will
"see" that it is easier with your dominate eye. If your dominate
eye's retina has has been blinded in that high resolution part of the
retina it greatly interferes with the non dominate eye in resolving the
print. It is even harder to read than just covering the dominate eye.  Your
dominate eye keeps trying to find what the other eye is seeing in order to
see it better. But it can't see a particular letter at all unless you move
your eye to the next letter which it won't be able
to see but you can see the ones adjacent but not as well enough to satisfy
the brain so your eyes wiggle. Interestingly if you use only the injured
eye you don't see a spot where you can't see.  Your brain merges what it
can see.  If you look at the printed word THE and try to look directly at
the H you see TE not T  E as I think most would expect. Think how difficult
it would be trying to
read like that!

    I am not terribly worried about pilots being blinded by an amateur
astronomers laser.  I am more worried about others nearby. And particularly
myself after what was fortunately a relatively short experience with the
debilitating effects of being zapped by one.  Even if you don't think they
are powerful enough to injure, put effort into not finding out if you are
right. Use them for the intended purposes and don't abuse them risking the
eyesight of others or yourself.  It would be terrible to find out that
those little suckers really can blind.

Jerry

--- BBBS/NT v4.00 MP