e2v technologies (uk) limited 2013 CR 114528 05 Apr 2013 DAS775571AA Version 1, page 14
3.11 Operating Notes
• Interpreting The Image – Relative Temperatures
The image displayed is simply a black and white picture of the infrared
energy entering the lens. The camera displays relative temperature
differences between individual objects and their surroundings
irrespective of overall ambient temperature.
The camera is set up to display objects at various shades between black
for cooler items and white for hotter bodies, e.g. in a room at 20 °C a cold
drink would appear black whilst a hot radiator would appear white.
However, in a room at 250 °C, it is possible that the same hot radiator
may appear darker than, for example, burning materials. Depending
upon the application mode selected, the image may be coloured
according to actual temperature (Fire mode) or relative temperature
(Search mode).
• Identification of Fire and Hotspots
The camera will represent zones of very high temperature as white or red
within the picture. When sufficient heat has been detected, e.g. a large
area of fire, the camera will automatically enter low sensitivity mode. This
will extend the dynamic range of the camera and allow the image of
surrounding objects to remain clearly visible.
• Hidden Fires
It is possible that fires may be burning or smouldering behind doors, in
ducting or in wall or floor cavities. In such circumstances, the operator
should look for areas that appear whiter when compared with the
surroundings. Search mode is particularly useful in this situation, as it
would colour the hottest areas red.
For example, a fire behind a door will cause the door to appear whiter
against the background. Similarly, a white area on an otherwise dark wall
could indicate an area of fire behind the masonry.
• Search for Persons and Objects
The camera is not restricted to locating fires. In many cases, the fire-
fighter will be using the camera to search for casualties, to seek out
dangerous items such as fuel tanks or gas cylinders and also as an aid
to navigation through unknown premises.
• Image Clarity
The sharpness and clarity of the image provided is related to the
temperature of the scene and objects in view. A cold room provides little
infrared energy and less detail is detected than in a warm environment
where objects give off significant energy. In general, the warmer the
scene, the more thermal contrast and hence the greater detail in the
picture.
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