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Thermal imaging devices

This second article from the series of the Cluster Optronics in the specialist area Command and Control Systems aims to introduce readers to the world of thermal imaging devices.

Stefan Keller, Specialist area Command and Control systems, Competence sector Command and Control and Reconnaissance Systems

The graphic shows a thermal imaging device

Thermal imaging devices enable surroundings to be better perceived during the day, but in particular at night. They are used in a variety of ways – from being installed in a fixed position on planes, helicopters or vehicles, to use in drone defence or directly with soldiers and firefighters. The importance of the thermal imaging devices is enormous, as the all-weather and night combat capability of the fighting forces is significantly improved. It allows pilots and soldiers to see at night, quickly identify missing people and recognise and identify various objects over long distances. 

Example of medium-range thermal imaging device 19 (WBG MR 19)

Mid-range thermal imaging device 19
© Sam Bosshard

The WBG MR 19 is a compact, lightweight device and enables the section commander to monitor zones of action, as well as to reconnoitre and survey targets during the day, at night and in poor visibility conditions.

Example of long-range thermal imaging device 19 (WBG LR 19)

Long-range thermal imaging device 19
© Sam Bosshard

The WBG LR 19 creates a thermal image in the mid-wave infra-red (MWIR) range using its cooled sensor. The WBG MR 19, on the other hand, creates a thermal image in the long-wave infra-red (LWIR) range.

The WBG LR 19 with its cooled sensor and the creation of the thermal image in the mid-wave infra-red (MWIR) range enables observation over long distances, hence the name “long range”. This difference in performance from the WBG MR 19 (medium range) is also reflected in the slightly higher weight of the device.

They are primarily assigned to intelligence and surveillance formations. They are used as observation instruments with the tactical reconnaissance system TASYS and with the 8.1 cm mortar 19. They can be held in the hand or mounted on a tripod, to be able to make observations over greater distances in a stable manner.

Sight modes of the long-range thermal imaging device 19


Theory

The human eye reacts to visible light in the wavelength range from around 400 to 780 nanometres (nm).

Overview with visible spectrum in detail.
© wikimedia.org

Infra-red radiation (IR radiation) is often referred to as thermal radiation, as this kind of radiation is perceived as heat. Strictly speaking, the thermal radiation ranges from infra-red to visible light (VIS) and ultraviolet (UV), depending on the temperature. The IR radiation can no longer be perceived by the human eye and ranges in the electromagnetic spectrum from 780 nm to 1 mm (1 000 000 nm).

Further subdivision of the infra-red spectral range can be defined differently:

English description

English abbreviation

Abbreviation according to CIE and DIN Wavelength [µm] 

Near-infrared

NIR

IR-A

0.78 ... 1.4

Shortwave-infrared

SWIR

IR-B

1.4 ... 3.0

Midwave-infrared

MWIR

IR-C

3.0 ... 5.0

Long-infrared

LWIR

IR-C

8.0 ... 15.0

Far-infrared

FIR

IR-C

15.0 ... 1,000.0[ARRAX1] 

The further subdivision of the infra-red spectral range
© infratec.eu

Various different detectors and materials are required to detect the different wavelengths.

Diagram of the various materials for detecting the different wavelengths. Abbreviations: Indium gallium arsenide (InGaAs), Mercury cadmium telluride (MCT), Indium antimony (InSb)
© stemmer-imaging.com