Eyes
have always been considered the gateway to one’s
soul. History shows us that sunglasses
were not always used to protect people’s eyes from the sun. There is
evidence
that early sunglasses
were used in ancient China
and Rome.
The
Roman Emperor Nero enjoyed watching gladiators
through polished gems.
In China,
sunglasses are believed to have been used before the 12th century.
Originally
sunglass lenses were made out of flat panes of smoky quartz. These
glasses were
used by
Chinese judges to hide their facial expressions while
interrogating
witnesses.
Until about the eighteenth
century sunglasses did
not
undergo any further changes until James
Ayscough, while apprenticed to
an
optician named James Mann, looked at ways to improve glasses.
He
experimented
with tinted glass and glass polarized. From there, sunglasses underwent
changes
leading to what we call sunglasses today. Sam Foster introduced them to
America
in 1929 designed
to protect people’s eyes from the sun. In 1936 Edwin
Land
discovered that lenses can be polarized.
He patented his process of making sunglasses
with polarized
optics and
called it a Polaroid filter.
From this original process polarized
sunglasses
have continued to evolve and become more refined.
When the sun shines on snow, water or any
other reflective
surfaces, the reflected light becomes
polarized. This means that most,
although
not all, of the reflected light waves move in one single plane.
Normal
light
moves in many planes but polarized lenses allow only light in one plane
to pass
through
the lens to your eye. This eliminates much of the glare.
Although light from the sun is
not polarized, when
it is
reflected by the surface of a standing body of
water it is separated
into two
polarized components that are reflected and transmitted in different
amounts. In most cases more of the horizontal component will be
reflected than
the
vertical
component. This reflected light
is said to be partially polarizing. A lens that is vertically polarized
can
then be used to help eliminate the glare. There are a number of
variables that
can affect the
degree of polarization and the effectiveness of
polarized
sunglasses such as the height of the sun.
However, polarized sunglasses will not
eliminate all reflected
light. They can only eliminate some
of the
reflected
light that helps reduce the glare. This becomes
critical in deciding how to choose
a pair of sunglasses
Fishermen that wear sunglasses that have
polarized filters
to help block the light reflected by the
waters surface can see under
the
water’s surface to where the fish are hiding.
Certain relatively flat
surfaces, such as water,
reflect a
lot of light resulting in bright spots and glare
that can be quite
distracting
and even hide underwater objects (such as fish). A good pair of
polarized
sunglasses can almost completely eliminate this kind of glare.
Polarization can
occur either naturally
or artificially. Natural polarization can be
seen any
time you look at a large body of water like a lake
or river. The glare
off of
the surface of the water is the light that doesn’t get absorbed by the
water
but is reflected. This is the reason you
often cannot see anything below the surface, even if the water
is
clear,
without polarized sunglasses.
Horizontally polarized light results when
light strikes
the
surface of the water. That is why you can’t
see anything but the glare
on the
water. Polarized lenses in sunglasses are designed in a way that only
allows
vertically polarized light to enter and eliminates the horizontal light
component. Polarized
sunglasses allow an
angler to see into the water spotting fish and structure where fish can
hide.
There is a difference between
polarized sunglasses
and
normal sunglasses. Basically, normal
sunglasses decrease the intensity
of all
light that passes through the lenses. While polarized sunglasses
decrease the
same light, they also do it selectively by eliminating the reflection
from the
light coming
from the water’s surface.
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