Thermal cameras use a completely different type of image
sensor than our Near IR cameras. Our Near IR cameras have CCD or CMOS
image sensors. The CCD and CMOS image sensors are inherently IR
sensitive. All color digital cameras and camcorder require an internal IR
blocking filter (ICF) to block IR light otherwise the colors would be incorrect.
Thermal cameras have a microbolometer image sensor. A
microbolometer consists of thousands of tiny sensor elements. Each element
has a micro-resistor which changes its resistance as it heats up. The
thermal camera focuses heat onto the elements which in turn heat up. The
camera reads the changes in resistance to calculate the thermal image.
Because the technology is completely different than Near IR cameras, the two
cameras typically do not have any interchangeable parts other than perhaps a
memory card. You can't take a Near IR camera and convert it into a thermal
camera.
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There are big differences between types of thermal
cameras. Many of the thermal camera websites are operated by the same
company, so your choices may not be as great as they first appear. Some
important questions to consider are:
What is the size of the thermal sensor? Typically,
sensors are either 160 x 120 pixels or 320 x 240. The smaller has
19,200 pixels while the larger has 76,800 pixels. A larger sensor gives
you much more resolution but costs more.
Does camera display a false color thermal image or black
and white? Does the camera has user selectable palettes? Can the
user create their own palettes? Color palettes are convenient ways for you
to see a thermal image. For instance, you may chose to have cold be the
color blue, medium yellow and red hot. Or you might want everything black
and white with everything over 80 degF red. Or you might want cold to be
purple and hot to be yellow. Our cameras have a variety of pre-generated palettes
as well as allowing you to create your own and store them on the camera.
Can camera save an image to a data card? If you
can view a thermal image but not save it, the camera may be of limited
use. Can you include a voice annotation with image? Including a
voice memo can be very useful when analyzing the pictures later.
Does camera save a picture image or a temperature
measurement array? Some cameras save a simple picture which does not
actually contain any measurements. Other cameras store the actual
temperature measurements which can be brought into a PC later for analysis.
If camera stores a temperature array, does it comes with
analytical software? The more sophisticated cameras come with software
that allows you to do things like measure temperature points, gradients,
differences, bands, averages, assign color palettes and even generate complete
Microsoft Word reports with all relevant testing data.
How hard is camera to use? This is very
important. If camera takes special training to use, you will be spending
more time and money for every new user. Some cameras require complex
adjustments before operation. Some cameras require periodic software
adjustments to account for thermal drift as the camera electronics heat
up. Other camera automatically calibrate themselves.
Can camera automatically adjust to the thermal range of
interest? Some cameras require you to manually set the high and low
temperature points in order to set the false color display. It is
important to set as small a range as possible in order that you can see the
widest range of information. For example, if you need to measure small
temperature differences of 1 degree between 60 and 65 degrees, you will set your
camera up differently than if you are looking at something with a 50 to 500
degree temperature range. Some cameras will automatically set the range as
small as possible based on the highest and lowest temperatures it sees. If
you have to set the camera manually, you will likely be often readjusting the
camera parameters.
Does camera have a built in visual camera? Some
cameras include both a thermal image sensor and normal camera sensor allowing
you to switch between looking at a thermal image and a normal video image.
Does camera have a video output? If camera has a
NTSC video output, you can connect camera to a camcorder to record thermal
video.
How heavy and bulky is camera? We have thermal
cameras that are small enough to fit in your pocket to large ones that require
their own briefcase.
Does camera have a built in laser locater? Some
of our cameras have a built in laser pointer that allows you to easily see what
the camera is looking at.
Can camera be set to sound an audio alarm for a maximum
temperature? Our cameras can trigger an audio alarm if camera should
see any temperature above a user designated point. These alarms can be
useful to screen passengers or crowds for people with a fever that could be
carrying a hostile virus such as SARS.
If camera can store information, does camera have a built
in memory or data card? We have cameras which can store data on common
camera memory cards and have up to 8 GB of internal memory.
How long can camera operate on batteries? Our
smallest camera can operate for over two hours on a matchbox sized battery.