Infrared vs. Thermal Imaging
Key Differences Explained
In the field of imaging technology, infrared and thermal are terms often used interchangeably, but they refer to different technologies with unique capabilities. Understanding these differences is essential for selecting the right imaging solution for your needs.
What is Infrared Imaging?
Infrared imaging covers a broad range of wavelengths, from 0.75 µm to 14 µm, including the Near-Infrared (NIR), Short-Wave Infrared (SWIR), Mid-Wave Infrared (MWIR), and Long-Wave Infrared (LWIR) regions. Since these wavelengths are longer than those that the human eye can see, imaging in these spectral regions provide valuable information that would otherwise be undetectable. Infrared imaging devices operating within these regions capture images by detecting the electromagnetic radiation that is either emitted or reflected by objects; this is an important distinction.
All objects emit some amount of thermal energy, but objects that are at most typical temperatures (such as people, animals, vehicles, and background scenery) do not emit much energy at shorter wavelengths. In fact, objects with a temperature less than a few hundred degrees Celsius emit very low energy at wavelengths below 3 µm. This means that not all infrared imagers are thermal imagers.
Infrared imagers that operate at shorter wavelengths require an infrared illumination source to detect reflected light. This is commonly seen with some consumer-grade visual cameras with night mode. These devices are equipped with infrared illuminators which turn on in low-light conditions to allow imaging into the near infrared region. Imagers that operate in the NIR and SWIR regions, while still classified as infrared imagers, generally don’t capture thermal images. However, these imagers are valuable in applications such as remote sensing, and medical diagnostics, and some very short-range surveillance applications.
What is Thermal Imaging?
Thermal Imaging specifically detects and visualizes thermal energy or heat emitted by objects. Thermal imagers operate in the MWIR and LWIR regions, where objects emit enough thermal energy at typical temperatures to produce thermal imagery. These imagers excel at capturing temperature variations and creating images based on the heat emitted by objects in the scene. From a surveillance perspective, the items of interest (humans, animals, vehicles and most background scenes) produce enough thermal emissions to be usable in these spectral regions.
Infrared vs. Thermal Imaging: Choosing the Right Technology
Understanding the distinction between infrared and thermal imaging is essential when selecting the most suitable technology for a particular application. While common in surveillance applications, thermal imagers are also ideal for applications such as building diagnostics, industrial inspections, and search and rescue operations. They provide valuable information about thermal patterns, energy efficiency, and potential anomalies in various environments. In contrast, the NIR and SWIR regions offer unique advantages in scenarios where material identification, vegetation health assessment, or atmospheric analysis is critical. These imagers enable us to perceive information beyond what is visible to the human eye, opening doors to a wide range of applications in agriculture, environmental monitoring, and scientific research.
By appreciating the distinction between infrared and thermal imaging, we can make informed decisions when selecting imaging technologies for specific tasks. Each technology has its strengths and applications, and understanding their capabilities allows us to harness their potential effectively. Whether it is capturing temperature variations or revealing hidden material properties, infrared and thermal imaging continue to advance our understanding of the world and enhance our ability to make informed decisions across diverse industries.