Terahertz sensing ‘v’ thermal imaging

24th January 2022

Terahertz photons pass through insulation and cladding

Terahertz energy – also known as T-waves & THz – refers to electromagnetic energy in the frequency range between 0.1 to 3 THz. Wavelengths in the terahertz region range from 1 mm to 0.01 mm.

The electromagnetic THz region is located between the microwave and thermal regions, and subsequently demonstrates properties of both these regions.

THz energy penetrates dielectric materials (such as pipeline insulation and non-metallic cladding) and can be used for material characterisation, substrate inspection, and in certain applications can provide a low-energy alternative to X-rays for producing internal inspection images of solid objects.

SubTera’s corrosion and moisture detection technology operates in the lower frequency range of the THz region and is therefore referred to as the sub-terahertz region.

Thermal imaging measures surface temperature

The thermal region of the electromagnetic spectrum, sits between the THz region and red light, which is visible to the human eye.

Thermal imaging technology is well developed and is an excellent method of accurately measuring the surface temperature of a structure under test. However, thermal cameras cannot see through most materials, and even then, they can only see through extremely thin layers such as plastic bags.

As an example, when using a thermal camera to detect moisture within processing pipeline insulation, if the external cladding layer is in contact with water beneath the surface, the surface temperature will be affected by the temperature of the water. In this scenario, a thermal camera can detect the presence of the water located immediately beneath the surface.

Terahertz sensing detects CUI and moisture deep within insulation

If the water, in the previous example, was not in contact with the surface cladding material, the thermal camera would not detect it. In many real world scenarios, moisture can reside throughout a pipeline insulation system, reducing the benefit of relying solely on thermal imaging to detect concealed moisture.

Terahertz sensing detects CUI and moisture deep beneath the surface, where they are not in contact with the external non-metallic cladding layer.