Thermal-Imaging & Digital Night Vision
Digital Night Vision
Digital night vision is a newer
consumer technology that gives results similar to Starlight technology
with some additions and advantages. The positive side is that this technology
can give results that are comparable to earlier Generation 1 devices at
less cost and without the distortions inherent in Generation 1 “Starlight
technology” night vision. The negative side is that this is about the
extent of its capabilities. It does not compare to Generation 2 or later
Starlight technology devices. Digital night vision also has a significantly
reduced range. Even some of today’s Generation 1 night vision devices
will often outperform these devices when viewing beyond reasonably close
The technology for this type
of night vision is quite different from standard night vision and generally
works like this. The light comes into the device through an objective
lens and is then processed through a highly sensitive charged coupling
device (CCD) and then sent to a Liquid Crystal Display (LCD) where you
can view the image. This can vary a bit and there might be an eyepiece
to look into to view the output rather than a LCD screen. If you are trying
to remain undetected by whom or what you are viewing, the eyepiece devices
are preferable, as they will not illuminate your face as an LCD will.
As with standard night vision devices, you are not looking directly at
an amplified image but rather a processed and recreated image. Some digital
video cameras have a "0 Lux" mode that works essentially the same way.
One great advantage of Digital
Night Vision is that you can also look through these devices in the daylight
without the concerns of damaging it. They are similar to Generation 1
night vision devices in that they only amplify available light and require
an IR illuminator to see in dark areas. Most digital night vision devices
are equipped with IR diodes (a bank of small IR lights). They also often
come with multiple filters so that the image can be viewed in shades of
green, red or gray. The green filters give you the greatest image contrast
and detail and appear similar to standard night vision devices. Red filters
are used to preserve your own night vision (like using a red light to
view star charts so your eyes don’t take such a long time to readjust
to the darkness). The gray or neutral filter minimizes the amount of light
to your eyes and appears somewhat like a black and white display.
“Thermal-Imaging Night Vision”
is much different than what we have looked at with light amplification
devices. We will only briefly define these types of devices since many
people confuse standard night vision devices with thermal-imaging abilities.
At this point, the technology starts at about $10,000 which is generally
cost-prohibitive for most consumers. Recent advances in technologies might
bring new thermal-imaging devices into the $1000 range very soon.
Thermal-imaging devices look
at heat, not visible light. Unlike image-intensifiers, they are unaffected
by smoke or fog and they can be used in absolute darkness since they are
not dependant on visible light. They have infrared-detectors that are
sensitive to the invisible infrared portion of the electromagnetic wave
(heat). All objects emit heat or infrared radiation. Thermal-imaging devices
have infrared-detector elements that see this portion of the spectrum
only. The image is usually seen as a gray-scale view contrasting with
image-enhancement technology that is viewed in green scale (that eerie
green view). Some of the more expensive models even display the resulting
views in color on small screens. Color representations or images are called
thermograms. By convention the cooler colors are represented by blacks,
blues and greens. Whites, reds, and yellows represent the warmer colors.
Detail in thermal-image viewing
is also very different since you are looking at heat differences and not
at light reflecting off surfaces that give you the shadows and details
we are accustomed to seeing with visible light. Other details that are
not seen in visible light are apparent when looking through a thermal-imaging
device. Since we are looking at heat, after leaning against a wall with
your hand, looking through a thermal-imaging device you would see a hand
print on the wall. Even the wall itself might show the internal studs
as a slightly different color since the part of the wall where the studs
are attached is slightly denser and subsequently heats and cools at a
different rate. Freshly painted areas would be a slightly different color
or freshly dug holes in the ground show up visually, whereas in daylight
these details are invisible to your eyes. These types of details make
thermal-imaging devices very applicable to law enforcement type of uses.
Thermal-Imaging devices come
in two basic designs: cooled and uncooled. The cooled versions are much
more expensive and more susceptible to damage. The elements in cryogenically-cooled
systems are also much more sensitive. By cooling the elements these systems
can have incredible resolution and sensitivity. They can “see” as
little as 0.2ºF differences in temperature at more than a 1000 feet away.
The elements in the cooled system are sealed and kept at a constant temperature
Uncooled devices are much more
common and durable… although these are all electronic devices that must
be handled with a reasonable level of care. In uncooled thermal-Imaging
devices the infrared-detector elements are contained in a unit that operates
at room temperature. The devices are completely quiet, have built in batteries,
and activate immediately.
How Thermal-Imaging Works
The basic operation of a thermal
imaging device is a five-step process:
- A special lens focuses the
incoming infrared radiation (heat given off from all objects) of the
objects in the view.
- The focused radiation is
scanned by a “phased array” of infrared detectors. Thousands of
points and heat readings for the field of view are collected in only
one thirtieth of a second. The detector elements create a very detailed
“temperature map” called a thermogram.
- The thermogram created by
the infrared detector elements is translated into electric impulses.
- The electric impulses are
sent to a circuit board, called a signal-processing unit, which has
a dedicated chip for translating the electric impulses into data for
- The signal-processing unit
sends the data to the display, where it appears as various colors or
shades depending on the temperature of the infrared emission. The image
is created from the combination of all the impulses from all of the
- Digital night vision devices,
like standard night vision devices, require available light to amplify.
They have a shorter range than standard night vision devices but lack
the distortions that are found in Generation 1 night vision.
- You can use digital night
vision devices in the daytime without concerns of damaging the elements
like with standard night vision devices.
- Thermal-imaging devices
look at the invisible heat being radiated from all objects and require
no light at all to operate.
- Since thermal-imaging devices
do not "look" at visible light they can be used in any condition of
lighting. The view is different than with light-amplification devices
and things like shadows, reflections, and shades that we are accustomed
to seeing in the light do not show up with thermal-imaging.
- New technologies may bring
thermal-imaging devices onto the market at much more reasonable and
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