Datasheet
Thermal imaging, ONVIF / TECHNICAL CORNER 35
THERMAL IMAGING
Thermal cameras detect radiation in the infrared (IR)
spectrum, which is outside the range of visible light and
near-infrared light. Ordinary visible light has wave-
lengths of 0.4-0.7 µm. This is what the human eye can
see, and also what standard, non-day/night cameras
can detect and display. Light at this part of the spec-
trum requires a radiation source, e.g. the sun or a lamp.
Near-IR light, with wavelengths of 0.7-1.5 µm, is beyond
what the human eye can see, but most camera sensors
can detect it and make use of it. A day/night camera uses
an IR-cut lter during the day to lter out IR-light so
that it does not distort the colors of images as the human
eye sees them. When the camera is in night mode, the
IR-cut lter is removed and the camera delivers a black
and white image. Near-IR light also requires a light
source, which could be a natural part of the environment,
such as streetlights or moonlight, or a dedicated IR-lamp.
Thermal radiation is emitted at wavelengths of 3-1000 µm.
Thermal radiation does not require a separate light
source since the radiation comes from every object that
has a temperature above 0 degrees Kelvin. That means
that even very cold objects such as ice emit thermal ra-
diation. The hotter the object is the more thermal
radiation it emits. In other words, the greater the tem-
perature dierences in a scene, the clearer the thermal
image will be.
A thermal camera requires special sensors and special
optics. Regular glass cannot be used for the lenses since
this blocks the thermal radiation. This also means that
standard camera housings cannot be used. Most lenses
for thermal cameras are made using germanium, which
is transparent to IR-light and thermal radiation.
ONVIF
ONVIF is a non-prot organization founded by Axis,
Bosch and Sony in 2008.
The goal of ONVIF is to facilitate the development and
use of a global open standard for the interface of net-
work video products. The ONVIF specication will en-
sure interoperability between network video products
regardless of manufacturer. It will become even easier
for end users, integrators, consultants and manufactur-
ers to take advantage of the possibilities oered by net-
work video, resulting in more cost-eective and exible
solutions, expanded market opportunities and reduced
risk. Visit www.onvif.org for more information.
Axis was one of the rst companies on the market to
launch products with ONVIF support: AXIS P3301/-V
Fixed Dome Network Cameras. Most of the products in
the Axis portfolio now include ONVIF support.