The Difference Between Infrared vs Thermal Camera
Modern security systems have evolved with intelligent technologies, offering tailored solutions to meet diverse needs. Video security remains a cornerstone of effective protection. However, selecting the right technology is key to maximising efficiency and coverage.
What is Infrared and Thermal Camera
Infrared (IR) and thermal cameras both detect electromagnetic radiation. They do so in different spectral ranges and have different applications.
IR cameras are primarily used for day or night vision, requiring a light source, while thermal cameras are used for temperature measurement and detection of heat signatures, even in complete darkness
Infrared Cameras
Infrared cameras typically detect radiation in the near-infrared (NIR) range, with wavelengths from approximately 0.7 to 1.4 μm. This is just beyond the visible light spectrum.
These cameras are also sometimes called "day-and-night cameras". They use an IR-cut filter during the day to prevent distortion of colours as seen by the human eye.
In night mode, the IR-cut filter is removed, and the camera captures images using NIR light, displaying them in grayscale.
NIR imaging still requires some form of light source, either natural (like moonlight) or artificial (such as streetlights or dedicated IR lights).
An IR camera is basically an image converter, changing radiant thermal energy into a visible image.
Thermal Cameras
Thermal cameras function as heat sensors, detecting temperature differences between objects and their surroundings. It creates images based on the heat emitted by objects, rather than reflected light.
It does not require any external light source to generate an image, making them ideal for use in complete darkness. They can also be used in challenging conditions such as smoke or dust-filled environments.
Thermal cameras detect radiation in the infrared (IR) range, typically with longer wavelengths, up to around 14 μm.
This range is divided into sub-regions: short-wave infrared (1.4–3 μm), mid-wave infrared (MWIR, 3–8 μm), and long-wave infrared (LWIR, 8–15 μm).
Thermal cameras are often used to detect irregularities, suspicious activity, and for perimeter or area protection. They are also used in building security, emergency management, and in high-security locations.
The amount of radiation emitted by an object increases with temperature. Therefore, the hotter an object, the brighter it appears in a thermal image.
Thermal images are typically presented in grayscale, with brighter areas indicating warmer temperatures and darker areas indicating cooler temperatures. However, colour palettes can be added to enhance shades in the image.
Key Differences Summarised
Infrared cameras (NIR) operate in the near-infrared spectrum (0.7–1.4 µm) and rely on reflected NIR light to create images. They require an external light source—natural or artificial—for visibility, making them ideal for day/night vision and general surveillance. Their output resembles grayscale or colour images as perceived by the human eye.
In contrast, thermal cameras (IR) detect emitted heat (mid- to long-wave infrared, up to 14 µm) and do not depend on ambient light, enabling use in total darkness. They excel in temperature measurement, perimeter security, and detecting anomalies based on thermal signatures. Thermal images are typically grayscale or pseudocolour, with brightness or hues representing temperature variations.
Additional Considerations for Thermal Cameras
When selecting and utilising thermal cameras, several key factors influence their performance and effectiveness:
Emissivity
The ability of an object to emit thermal radiation is called emissivity, with a scale from 0 to 1. Duller, blacker materials have an emissivity closer to 1, while more reflective materials have a lower emissivity. The emissivity of an object affects the contrast of thermal images.
Sensor Types
Thermal cameras use two main types of sensors: cooled and uncooled.
- Uncooled sensors: Cost-effective and compact, uncooled sensors operate at or near ambient temperatures and are primarily designed for use in the LWIR band.
- Cooled sensors: Enclosed in a vacuum and cooled to extremely low temperatures, cooled sensors function in the MWIR band. They offer superior spatial resolution, detect smaller temperature differences, and excel in long-range detection.Lenses
Thermal cameras use lenses made of materials such as germanium or chalcogenide glass, as regular glass blocks thermal radiation.
Resolution
Thermal camera resolutions are generally lower than those of standard cameras because of the sensor technology involved in thermal imaging, which results in larger pixels and more costly materials.
Environmental factors
Environmental factors like weather conditions and the temperature difference between an object and its background can affect the quality and detection range of thermal images. Factors such as absorption by water vapour and scattering by particles reduce the thermal radiation that reaches the camera.
To Wrap Up
In summary, while both IR and thermal cameras detect electromagnetic radiation, they do so in different spectral ranges, and have different applications. IR cameras are primarily used for day/night vision requiring a light source, while thermal cameras are used for temperature measurement and detection of heat signatures, even in complete darkness.