Conventional video surveillance cameras struggle to capture usable images in complete darkness or under other challenging conditions such as smoke or fog, or when subjects are hiding or obscured by a complex background. The first true thermal network camera, introduced by Axis Communications this month, provides clear, usable images in all these situations, representing an important step forward for the security industry. But how does the technology work, and how will it be used? Effective video surveillance depends on accurately detecting and identifying objects, people or incidents, so that appropriate action can be taken. But all network cameras have a basic physical limitation: they need light to work. Sure, some network cameras have night and day functionality that allows them to operate in very poor lighting conditions, down to fractions of a lux. And of course, if natural light is not available it can be substituted by electrical light, either visible to the human eye or infrared. But in some instances these solutions have serious drawbacks – they can be expensive, and energy consuming; and illumination creates shadows where an intruder can hide – to mention a few.
Introducing thermal technology
Visible light, which the human eye can see and standard cameras can detect and display, requires a light source such as the sun or a flood light. Even day/night cameras, which use the near-infrared spectrum, require some light to operate – either natural or a dedicated IR-lamp. A thermal camera requires no light source, as it works by detecting radiation in the thermal infrared range of the electromagnetic spectrum, producing images of that radiation. Infrared radiation is emitted by all objects - even very cold objects, like ice - based on their temperatures and emissivity. This makes it possible for the camera to detect temperature changes and visualize objects in the dark and in other difficult conditions without any external light source. The amount of radiation emitted by an object increases with temperature, therefore a thermal camera allows the user to see variations in temperature. When viewed by a thermal camera warm objects stand out well against cooler backgrounds or vice versa.
Thermal images are sometimes associated with bright, intense colors – which may seem a bit odd considering that the camera works outside the spectrum of visible light. The answer is that the colors are created digitally, so-called pseudo-colors. Each color or nuance represents a different temperature, usually white and red for higher temperatures, over green, blue and violet for colder ones. The reason is foremost practical since the human eye is better at distinguishing different shades of color than different shades of grey.
Thermal detection becomes accessible
Thermal imaging is nothing new. But until recently, costs have usually been prohibitive, making practical applications outside the military rare. This has started to change as new sensors, new materials and other improvements are driving the volumes and making prices more reasonable. Thermal cameras can now be found in various lines of business such as the aircraft industry, shipping industry, and security and surveillance. The technology is also used in public services like fire fighting and law enforcement. Lately it has even appeared in consumer products, albeit often expensive ones like luxury cars.
So far, however, incorporating thermal cameras into a conventional video surveillance system has not been a straightforward operation. With the development of thermal network cameras, compatibility will of course, be far less of an issue. New devices will more easily integrate with, for example, existing video management systems.
Huge benefits for surveillance
Thermal network cameras provide an ideal first line of strength that triggers further action, thus dramatically enhancing the effectiveness of a surveillance system.
Thermal cameras quickly and unmistakably detect any incidents occurring in their field of view, even in complete darkness and other challenging conditions such as rain, fog, smoke etc. They are robust and cannot be blinded by strong lights or put out of order using laser pointers, and they are immune to most problems with light conditions, like shadows, which makes them ideal for video analytics. They achieve higher accuracy than conventional cameras in most intelligent video applications.
Thermal cameras detect thermal radiation from people, even when they are obscured by complex backgrounds, or trying to hide in shadows. They can provide discreet detection, where cameras need to be less visible to passersby. They are also a “greener” choice, since they eliminate the need for energy consuming floodlights.
Thermal cameras are excellent for detecting people, objects and incidents in darkness and other challenging conditions. Thermal cameras do not, however, deliver images that allow reliable identification – that is why thermal cameras and conventional cameras complement and support each other in a surveillance installation.
Many applications for thermal technology
With thermal imaging becoming relatively cheaper and an integral part of IP surveillance systems, a whole range of uses becomes both possible and economically viable. Thermal cameras can be an excellent complement in many situations where conventional cameras are inadequate or insufficient. Thermal cameras are the perfect option in areas that are very difficult to illuminate effectively, for example a sea front, a harbor, or any other vast expanse of open water. Artificial light not only runs the risk of revealing where the cameras are placed, enabling parties to avoid or vandalize them, but can also create projected shadows in which an intruder can avoid detection. Furthermore, spotlights can blind as well as illuminate. So cameras that do not rely on light can be the preferred solution in many different traffic situations, whether it is in railway tunnels, on air strips or on regular streets.
• Perimeter protection: An invisible thermal fence provides discreet and cost-effective detection. Powerful and cost-effective alternative to radio frequency intruder detection, electrified fences, CCTV/flood lights, etc. Typically used in ports and marinas, power plants, utilities and prisons.
- Strengthens/augments physical fences
- No IR illumination needed
- Discreet - No light pollution
• Area protection: Effective area protection gives cost-effective security - Thermal detection at outdoor locations triggers front line response to intruders, thereby helping to minimize vandalism, burglary and false alarms. Typically used in parking lots, schools and campuses, high-security premises and loading docks.
• Intelligent video applications: Detection of thermal radiation gives higher accuracy than conventional cameras in most intelligent video applications. Typically used in entrances, checkpoints and for building security.
- Reliable front-end for video analytics not sensitive to shadows, light and complex views
- Reduction of false triggers
- More effective analysis of recorded material
• Building security & emergency management: Detecting human presence indoors, after business hours or during emergencies: Typically used in retail stores, office buildings, prisons and warehouses. Quickly detecting human presence and incidents at indoor locations reduces or prevents:
- People hiding in the building after closing time
- Fire
- Riots
- False alarms
• People detection for safety & security: Detecting human presence in dangerous or off-limits areas enables fast remedial action.
Detection enhances safety and security in potentially dangerous environments, reduces accident risk and potential loss of life, and prevents vandalism and crime. Typically used in tunnels, railway tracks/platforms, bridges and crossroads. [www.axis.com]
