Infrared comes from two words, namely “infra,” which means “under,” and “red,” which means red. In essence, the word “infrared” refers to the area beyond or below the red end of the visible color spectrum.
Infrared operates through the region outside the visible light spectrum. Everything that is in the infrared wavelength must emit energy. Thermal imaging devices will visually capture the energy.
Every wavelength in the infrared spectrum emits radiation. This radiation beam can be transmitted and captured via thermal imaging.
In infrared, there are three types of different wavelength ranges. The three types of wavelengths are Short Wavelength Infrared (SWIR), Medium Wavelength Infrared (MWIR), and Long Wavelength Infrared (LWIR).
All types of thermal imaging devices that operate at infrared wavelengths are named ‘imagers.’ In more general language, this imager is often referred to as a camera.
The device called the camera does not have a camera section in general. The device called the imager is a sensor that detects the heat of an object.
In its application, each type of wavelength has its camera to produce visual images. Likewise, when applied to drones.
Therefore, the understanding of drone pilots and technicians on wavelengths and cameras will result in visual mapping activities that are per the target.
The following explanation and difference between SWIR, MWIR, and LWIR can be an initial guide to further understanding infrared.
Short Wave Infrared (SWIR)
SWIR is usually defined as a wavelength range of 0.9 – 1.7 μm.
SWIR or short wave is usually used as additional data to complement the results of LWIR and MWIR imaging. The SWIR detector is a photodetector. SWIR cameras generally have limited benefits compared to their counterparts (MWIR/LWIR).
In contrast to LWIR or MWIR imaging, most SWIR imaging utilizes reflected light. The detection process is very similar to a camera or the human eye. Therefore, the visual image of SWIR is identical to the visual of a black and white photo.
SWIR imagers can capture vivid detail through smog, clouds, and fog. The SWIR camera is the only wavelength technology that can penetrate clouds and capture clear images.
One application of SWIR is starlight imaging during the day. SWIR on drones is commonly used in vegetation mapping activities.
Mid-Wave Infrared (MWIR)
MWIR is usually defined as a wavelength range of 3.0 – 5.0 μm.
The MWIR area is often referred to as “thermal infrared.” The reason is that the object itself generates the radiation and its visual image without an external light source.
Two critical factors that play a role in determining how bright an object’s visual radiance is for the imager are the temperature and emissivity of the object.
When the temperature of an object becomes hotter, it will produce more energy emissions. In effect, the visual thing will appear brighter in the thermal imaging system.
MWIR cameras are susceptible to smoke, dust, and fog. Therefore, the MWIR camera is used as a gas leak detection system.
MWIR cameras play a vital role when detecting gas leaks which, in general, are invisible to the human eye. The MWIR camera is also used to get accurate details. Generally, MWIR cameras are also used for airport security needs.
Long Wave Infrared (LWIR)
LWIR is usually defined as a wavelength range of 8.0 – 14.0 m.
LWIR (longwave infrared) and MWIR (mid-wave infrared) cameras are easy to find in various military activities. LWIR cameras are capable of detecting human thermals and different other objects in an environment.
The LWIR camera is the most common vital device used in object temperature checking practice. LWIR cameras can detect distinct temperature differences between objects.
LWIR is the most common type of Infrared technology encountered in daily human life. Generally, LWIR imaging detects the radiated temperature of an object which provides essential information to the operator.
LWIR cameras on drones can be applied in various forms of applications, such as agricultural analysis, office building inspections, and so on.
Another typical problem is the difference with night vision technology. A lot of thermal imaging confuses infrared technology with night vision technology.
Therefore, it is imperative to understand infrared to clarify it. A night vision device is a camera that can increase the small visible camera for an object/area.
When compared with SWIR, MWIR, and LWIR technology, the difference will be visible. The three infrared technologies lie in invisible light that is at a specific wavelength.
Understanding the differences between SWIR, MWIR, and LWIR is expected to adjust the technology application and targets so that they are aligned and effective.