Silent Sentinel - THE FOGS OF WAR (AND PEACE)


Thermal imaging was developed for war time, but its application is prolific in peace time.

The ability of thermal imaging to provide visibility in all manner of hostile terrains – through sand storms to burning buildings, has made it a weapon of choice – not only in the theatre of war, but in the battle to fight nocturnal crime and saving lives. Developed for military use, the technology now has a wide range of applications in the fire and rescue environment as well as the obvious security applications, where visibility is impaired by darkness or obscured by fog.

Firstly, developed first in the 1950s, it works by creating a photographic image or video sequence of light emitted by an object at terrestrial temperatures. It is superior to night vision because it does not depend upon the principle of light amplification, meaning that in a totally dark environment it would still provide a strong image.

Consequently, the use of Thermal Imaging cameras within a CCTV scheme has seen rapid growth over the past years an expansion that is forecast to accelerate as the cost of production reduces still further. To respond to this demand, Silent Sentinel has significantly expanded its CCTV Thermal Imaging product range and now offers the most complete product set of any manufacturer.

“We have been supplying specialist Thermal Imaging cameras for many years and have now used all our experience to develop a product range to satisfy most CCTV applications,” says Paul Elsey, Managing Director of Silent Sentinel.

In essence, they are the camera and lens technology that provide the ability to see in complete darkness, through fog, smoke and other similar obstructions that limit the use of conventional video. They are also thought of as long range detection devises when paired with video analytics and work equally as well day or night, although an understanding of the technology enables the numerous benefits of Thermal Imaging to be fully realised.

So how does it work?

Warm objects emit energy in the infrared region of the electromagnetic spectrum. It is this infrared energy within the field of view that is optically captured and focused, as with visible light, and presented as an image. Thermal cameras use a Germanium lens which allows the infrared energy to pass through as it cannot pass through glass.

There are two types of thermal imagers, Cooled and Uncooled. Cooled thermal imagers are very sensitive to temperature change which enables them to operate at very long ranges, although they are much more costly and are normally only used in specialist applications within the CCTV industry. Uncooled thermal imagers are more reliable with lower maintenance and purchase cost which means they are more likely to be seen in use within CCTV schemes.

Thermal imaging cameras are specified with a Field of View (FOV) or a Focal Length and most cameras have a fixed focus non-zoom lens. Although duel FOV and electronic focus lenses are available, they can add significantly to the cost.

The detection zones of a thermal imaging camera are specified using the Johnson Criteria Charts, which allow the detection, recognition and identification ranges to be compared between thermal cores. Silent Sentinel provides this detection range information across its product range to make it easier to select the camera that is fit for purpose.

Silent Sentinel has a number of combined video and thermal imaging units within its product range from fixed units, through the Oculus Ti range to the longer-range capabilities of the Osiris PTZ positioning system.

“Combining video with thermal imaging in the same device is becoming the most common style of unit we supply,” said James Longcroft of Silent Sentinel.

As thermal imaging cores need to be licenced for sale in certain countries, including the Middle East and South Africa, it is important that the right processes are followed.

Paul Elsey, explains: “Silent Sentinel has obtained a blanket licence for their standard thermal product range which means obtaining the right paperwork takes days and not months as it can with some products”.

Silent Sentinel also supply cooled thermal core cameras when the application demands the additional range and performance. “We would be happy to speak to anyone who wants to understand more about how to select the right thermal imaging camera for the task they have in mind. We are all engineers here and enjoy sharing our knowledge and experience with our industry colleagues.”

Elsey adds: “The logic for Thermal Imaging is clear as day: Although developed more than 60 years ago, the time of Thermal Imaging has finally arrived with a wider range of applications in civilian life and a broader technological offering in the CCTV market.”