well, using lasers that are outside of the human visual range for comms is quite doable. the less hazardous would be in the infrared range and would also require less energy. you can amplitude modulate a laser (or use digital in on/off sequences). there are some laser projects on line that make this relatively easy.

DE n7zzt Eric

On Oct 30, 2015, at 6:12 PM, Martin McCormick wrote:

> 	Lasers concentrate all their light in to a beam which can
> be very narrow. There are regulations on the power levels for
> lasers that are sold to the general public and they are
> surprisingly low power such as ten milliwatts or so but the light
> appears very bright due to the fact that all of it is
> concentrated in a little spot maybe the size of the point of a
> pin.
> 
> 	In addition, lasers are one frequency of light just like
> a crystal-controlled transmitter transmits a carrier on only one
> frequency which means that the light stays in a column over quite
> a distance and does not spread out as much as light from a light
> bulb or an LED  which is several frequencies. If you could hear
> the energy from a laser as sound, it would be a pure tone. An
> incandescent light bulb or a LED would produce something that
> sounded more like the hiss of noise. If you ran that through a
> prism, you would see several slightly different shades of the
> color of a LED and a fairly full spectrum from the incandescent
> bulb. The laser would produce one sharp line of color if sent
> through a prism or diffraction grating.
> 
> 	The green laser pointers that cause the biggest problem
> with airplanes or people at a distance deliver even more energy
> to the eye so they can temporarily blind someone easier than the
> red laser pointers.
> 
> 	There are a lot of valid uses for those red and green
> lasers but as long as we have idiots out there, some are going to
> abuse them and cause trouble.
> 
> 	By the way, did you know that if you aim two lasers of
> nearly the same frequency at a target, the two signals will
> heterodyne just like two RF carriers. The reason is that they
> really are two RF carriers that transmit at a frequency of radio
> we call light.
> 
> 	The laser beam toys you describe do their thing by using
> wiggling mirrors to reflect a beam left and right and up and down
> in some sort of calculated way to produce projections.
> 
> 	If you had eyes capable of seeing really fast things like
> bullets and the individual wing beats of flies and other bugs,
> you would see a tiny spot of light racing back and forth and up
> and down in a way that produces the picture you see. The human
> eye has visual persistence which runs that rapid movement
> together in to what looks for all the world like the shape of an
> animal or person. It's pretty cool and rock bands that do laser
> light shows have very expensive and complicated versions of those
> same devices that can be programmed to produce anything your
> imagination and the hardware will let you produce.
> 
> Martin
> 
> Phil Scovell <[log in to unmask]> writes:
>> Although I was the first patient in the state of Iowa in October of 1964 
>> to
>> have his retinas treated using a laser surgical machine, I never got to 
>> see
>> an actual laser beam of light itself.  By the way, the laser treatment did
>> not work on me because my retinas were shredded, by this point, into tiny
>> fragments and the lasers were not narrow beamed enough to tack anything
>> down.  I left totally blind on November 13 of 1964, and that was after 13
>> operations and procedures before the laser came to the University of Iowa
>> hospital.  Anyhow, as my kids grew, laser beam toys became quite popular.
>> As I recall, that last time my young son had one was when he was 14 or 15.
>> It would display a picture of a bird on a wall from 40 feet away.  Over 
>> the
>> years, I've heard many reports, and just recently for that matter, of 
>> people
>> lasering inbound commercial aircraft and blinding, to the point of
>> distraction, the pilots.  To accomplish this, there must be a long 
>> distance
>> way of amplifying a laser beam to reach that far out to an approaching
>> plane.  I'm assuming, the more power, the longer the laser beam can reach
>> but how much power would it take to reach hundreds of yards out to an
>> approaching aircraft?  I wouldn't think lasers of that type would be
>> available on the open market but I haven't done that much reading about 
>> such
>> a device in the first place.  Anybody on here have some knowledge on the
>> topic?
>> 
>> Phil.
>> K0NX
>> 
>>