The
laser pointer was originally invented as a handy tool for lecturers or
speakers to focus attention on particular part of a screen or
chalkboard. Since the early 1990s, however, they have become extremely
cheap, and are now bought primarily for the sake of being a novelty
electronics item. Most use a 630 nm wavelength red laser diode, and
typically output about 5 mW (milliwatts) of power, making them Class
IIIa laser devices, which means that they are safe for consumer use.
Green
laser pointers have a 532 nm wavelength, and are about 50 times
stronger than red ones. They are viewable in mid-air, whereas red
lasers generally are not, with a very long range of as far as 1.5 miles
(about 2.5 km) in heavy darkness. Green lasers are more expensive than
red ones, however. Even shorter-wavelength blue lasers are also in
development.
Laser
pointers are typically about 0.04 inch (1 mm) wide at their source.
Some produce light at a wavelength higher than the visible spectrum,
which is then filtered through a frequency doubler to produce visible
light.
Laser
pointers are used as cat toys, sights for firearms, tools for optics
experiments, to play with, and for presentations. They have frequently
been used to pull pranks, some of them dangerous. When shined in the
eyes, they can temporarily impair vision, cause the person to see spots,
and in rare cases, even damage the retina. Some people have shined them
into the eyes of airplane pilots, truck drivers, musicians, and others
appearing onstage, causing problems with their vision. For this reason,
health agencies have issued strong warnings against the use of laser
pointers for mischievous purposes, and these devices are often forbidden
from concert halls and sporting events. It is illegal to shine a laser
pointer at a police officer, for example.
Inexpensive
pointers, in conjunction with a few other devices, have been
successfully used by hobbyists to produce high-quality holograms. They
have also been used to blind security cameras. Some nations have worked
on superpowered laser pointers as antipersonnel weapons, but a U.N.
resolution adopted in 1996 forbids their use in warfare. These lasers,
not always above the blinding threshold, are often referred to as
“dazzlers.”