Camera based fire detection

Since present systems do not allow any kind of visual inspection or in depth assessment of the conditions inside of the affected cargo compartment by the crew, any alert initiates the same activities (activation of the Halon fire suppression system and a subsequent emergency landing), as required by aviation authorities (FAA / JAA).

These activities are both costly and very detrimental to the image of the airlines. This unsatisfactory situation calls out for a more flexible and reliable system in addition to the primary smoke detectors. Additionally to the swift message (response time less than 1 second) confirming or not confirming the primary alarm, our system provides data to the system display in the cockpit:

• Processed video images, e.g. including color enhancement of the observed event, visualization of cargo compartments and camera positions, time stamp etc.
• Direct and live video images into the affected cargo compartment, thus allowing the crew to assess the real conditions as well as the efficiency of fire suppression activities.

Components

The main components are a camera including advanced image processing capabilities and an illumination module, including temperature and relative humidity sensors. The camera is based on advanced CCD-Technology which is complemented by proprietary elements like filter and illumination modules as well as image processing software. This software helps detecting fire and so called "hot spots" having surface temperatures of 300°C and above.
  
Prevention of false alarms based on humidity and temperature sensors

In cargo compartments fog often develops due to variations of pressure during flights. These phenomenon activates traditional smoke detectors and therefore cause false alarms. In order to prevent those false alarms m·u·t developed and patented a measuring method working with camera-based fire detectors as well as temperature and humidity sensors. The relative humidity and the dew point temperature can be calculated from these data. The system now determines if the atmosphere tends to create fog or not. The base for these calculations is an aging stable sensor which is patented as well.

NIR-Technology

Measurement principle

According to Planck’s law, objects or surfaces emit electromagnetic radiation, which intensity and spectral distribution depends on the body’s temperature. Detectors for the near-infrared spectral range of 0.8µm to 1.1µm can detect thermal radiation from temperatures of approx. 300°C on surfaces. This temperature is far below the limit at which the human eye can see thermal radiation. Open fire also emits in this range. Therefore low-cost alarm systems are easy to realize in this wavelength range. For special applications detectors that measure up to 2.5µm can be used to increase the detection sensitivity. Radiation from open flames can easily be detected even behind objects by its reflected radiation, as NIR radiation is reflected by most surfaces. Direct view on the flames is not necessary.

Visibility at smoke

NIR radiation is reflected or scattered by aerosols such as fog, smoke and dust, usually present in most application fields. Therefore NIR technology can be used for detection and as an alarm system for smoke. Scattering of light by aerosols in this wavelength range is weaker than in the visible range. Therefore in many situations open fires can be localized through smoke where it is not possible with the human eye.

NIR - video

Based on NIR video images and processing, the measurement principle can be applied on every pixel of an image and therefore be used for precise localization of alarm sources. Real images are available for identification of alarm sources: haze in the air, reflection or direct view on a flame. This information provides a clear image of the affected area that can be used for fast and safe situation analysis in case of an alert. Counteractive measures can be initialized faster and much more targeted.

LWIR-Technology

Measurement principle

According to Planck’s law, objects or surfaces emit electromagnetic radiation, which intensity and spectral distribution depends on the body’s temperature¹. Dedicated detectors can receive such radiation in the range of the long-wave-infrared (LWIR) from 8-12µm and therefore measure the surface temperature contactless. The measurement range can start below -40°C or extend to more than 1000°C. Temperature differences of just 0.08K can be detected.

Visibility at smoke, dust & fog

Aerosols such as fog, smoke or dust, which occur in many applications are almost transparent in the LWIR wavelength range of 8-12µm. Therefore a LWIR camera can "look through smoke" in contrast to usual surveillance cameras or the human eye. This is very important for fire fighting. In other applications the LWIR camera ensures clear sight through dust and fog.

LWIR - thermography

LWIR thermography allows temperature measurement of each single pixel within a video image. The shown object is displayed with precise temperature values for each point on the surface. These information help to detect origins of fire before the flashpoint temperature is reached and therefore to prevent fire. In case of fire LWIR thermography ensures clear sight through dense smoke and allows search and rescue of humans as well as safe temperature measurement of object close to the fire.

¹Strictly speaking, Planck’s law does apply to the "ideal black body" only, but with slight corrections it can be used in good approximation for surfaces of real objects.