Why can 鈥檛 humans see the way some animals do at night? Night vision devices to
Some animals can see much better in the dark, because they have a larger eyeball, a
larger lens, larger optical aperture 鈥?which means the pupil looks as big as the eye
opening. A larger lens can gather and concentrate light, thus intensifying light to see
better in the dark than the human eye can alone. Many animals have a tissue layer in
the back of the eye that reflects light back making more light available. This called
eyeshine and is a visible effect on some animals when a light is shone into the eye and
the pupil appears to glow.
Human vision is confined to a small portion of the spectrum called visible light.
Since our pupils do not expand to the limits like nocturnal animals we gather a
smaller portion of light we see.
Night vision devices to the rescue! We have many ways to see in the night; these
include infared, thermal imaging and image intensification. Active infrared night
vision is just below the visible spectrum of the human eye. Active infrared is now
commonly used in commercial, residential for security purposes, where it enables
effective nighttime surveillance under low light conditions.
Thermal imaging perceives thermal radiation (heat) and does not need a source of
illumination. They produce an image in the darkest of nights and can see through light
fog, rain and smoke. Thermal imaging cameras make small temperature differences
visible. These are used in the home also to detect sources of heat loss. Thermal
imaging technologies work by detecting the temperature difference between the
background and the foreground objects.
Image intensification technology work on the principle of magnifying the amount of
received photons from various natural sources such as starlight or moonlight.
Examples of such technologies include night glasses and low light cameras.
Hunting gear such as night vision rifle scope, night vision binoculars, night vision
monocular are becoming common place. Some have a powerful infrared illuminator
into the scope. This allows you to see even in total darkness with outstanding clarity.
Used for Camping, Boating, Nature study, or Law Enforcement, lightweight, compact,
rugged, water and fog resistant and some are camera adaptable. They have come a
long way in a short time generation one to a generation four. So be careful what you
do and when it may not just be a security camera watching you, now everyone can see
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