Thermal Imaging Cameras - Defying the Darkness
IP cameras, like the majority of cameras, need visible light in order to capture an
image. Thermal Imaging cameras do not. They are able to function not only
in total darkness, but under hostile conditions such as sand or dust storms as
well
Although we tend to think of light in terms of what you see
is what you get, visible light is but a fraction of the energy radiating in
waves of varying lengths from the sun. Since
all light is energy traveling at the same speed 186,000 miles per second, longer wavelengths occur at lower frequencies, and conversely, shorter wavelengths occur at higher frequencies.
Visible light is that part of the electro-magnetic spectrum with
wavelengths ranging from 400 to 700 nanometers.
Infra-red light travels on longer wavelengths and lies just beyond visible light’s parameters
Since Thermal Imaging cameras utilize infra-red light, let’s
examine it.
The Infra-red Portion of the Electro-Magnetic Spectrum
The prefix infra means below and is in the case of infra-red
light means it occurs at a lower frequency than red light in the visible
portion of the spectrum. Infra-red (IR) light can be divided into three
categories:
1.
Near-infra-red.
The near
in near-IR signifies that it is the portion of the I-R spectrum
closest to visible light with low
frequency wavelengths measuring from 700 –
1300 nanometers.
2.
Mid-infra-red
Mid-IR has lower frequency wavelengths of
1300 to 3,000 nanometers.
(Mid-IR and Near-IR near IR are used with a
variety of electronic devices including remote controls.)
3. Far infra-red (thermal)
Far -IR occupies the largest part of the
IR portion of the spectrum with wavelengths ranging from 3,000 Nano-meters to as
long as 30,000 nanometers.
The main difference between far IR and the other two is
that near- and mid-IR are reflected off of objects while far-IR is emitted by
them. Far-IR is also known as thermal-IR because this radiated energy gives off heat generated by
activity at the atomic level of the object. This heat is key to thermal imaging
technology.
How Thermal Imaging Works
All objects and beings give off some level of I-R radiation
in the form of heat, or to put it another way, anything above the temperature
of absolute zero (0 degrees Kelvin, or -469 degrees F) gives off measurable
I-R
energy. While the amount of radiation emitted by you, me, a cat, dog, or a
stone will differ, nothing radiates 100% of its temperature as I-R radiation.
Thermal imaging sensors work with emissivity, which is
defined as the specific percentage of thermal radiation, to calculate an object’s
true temperature in order to map out an image of the object within its environment.
At no time in the process is visible
light required for thermal imaging.
How a Thermal Imaging Camera Works
Thermal imaging cameras contain a special lens that focuses
the infra-red light emitted by everything in the field of view. Since there was
be several thousands of points in the camera’s field of view, thermal cameras need
special image sensors with a phased array of infra-red detector elements to
gather them all together. Once the elements have captured the information they
create a detailed temperature pattern known as a thermogram.
The thermogram is then translated into electric impulses
that are sent to a signal-processing unit, then on to a
display where it
appears as various colors depending on the intensity of the infra-red emission
of each object. Taken together, these impulses create an image of the subject
against its background.
Thermal Imaging to the Rescue
Thermal imaging technology is finding its way into the news
more and more. Unfortunately, the news was not cheerful news. Responders made
use of it during two very different tragedies.
In Boston, the police
used thermal imaging sensors to zero in on the surviving bomber in a residential
neighborhood who was hiding in a covered boat dry-docked in a dark back yard.
Then in May, a two mile wide tornado cleared a twenty two
mile swatch of Moore, Oklahoma, upending the majority of structures and leaving
in their place teetering piles of rubble. Responders included the Oklahoma
National Guard’s 146th Airborne Support who used thermal imaging
detectors to seek body heat under the five and six foot mounds of debris in an
effort to locate possible trapped survivors.
Our sales engineers are known as the experts in IP cameras
but Kintronics also has experience in designing thermal imaging cameras,
numbering the U.S. Armed Forces among our customers. If you’d like to know more
about thermal imaging or IP cameras www.kintronics.com or give us a call at
914-944-3425. You can also fill out an information request form and a sales
engineer will respond promptly.
