How does a thermal camera work?
In the contemporary technological world, thermal cameras have become essential tools in a multitude of sectors, ranging from industrial maintenance to search and rescue operations. Their ability to detect and visualize temperature variations makes them valuable instruments for diagnosing problems, monitoring processes and even saving lives. Unlike traditional cameras which capture visible light, thermal cameras use infrared sensors to measure thermal radiation. This data is then processed and converted into a thermal image. This article aims to explore in depth the functioning of these cameras and their diverse and varied applications.
(How the thermal camera works)
Thermal cameras work by detecting infrared radiation emitted by objects based on their temperature.
(Electromagnetic spectrum – infrared.photo)
A) Capture of infrared radiation
Infrared thermal cameras rely on infrared-sensitive detectors to capture radiation emitted by objects in their field of view. These detectors, which can be based on various technologies such as bolometric detectors or cooled or uncooled solid-state detectors, convert thermal radiation into electrical signals. This results in the transformation of infrared radiation into an electrical signal proportional to its intensity, thus making it possible to quantify the heat emitted by the objects observed. Restoration of the thermal image
B) Restoration of the thermal image
Once the infrared radiation is captured, thermal cameras proceed to convert these electrical signals into a meaningful thermal image. Each pixel in this image represents an area of the observed scene, with its color or tone indicating the temperature of that area. This process is made possible by integrated processors that perform advanced digital processing on the captured data. This processing typically includes correcting distortions, calibrating the image for increased accuracy, and removing noise to improve image quality.
Initially, this image is in grayscale, representing the temperature variation of each pixel. However, during image processing, a color scale is applied to make temperature differences visible. In this color scale, warmer areas typically appear red or yellow, while lower temperatures are represented by cooler colors such as blue or purple. So although the thermal image may appear to be in color, it is actually a tonal image which, without processing, would be grayscale.
(Infrared radiation)
To choose an infrared camera that meets a specific need, several criteria must be taken into account. First of all, it is necessary to determine the purpose of using the thermal camera, whether it is building inspection, scientific research, security monitoring, etc. Next, you must choose the spectral range best suited to the application and budget. You must also ensure that the thermal sensitivity of the camera is sufficient to detect temperature variations relevant to your application.
Spatial resolution is also a crucial factor, as it determines the camera's ability to view the necessary details in your scene of interest. If the application involves motion, opt for a camera with a higher frame rate to capture smooth images. Finally, additional features such as temperature measurement, information overlay and network connectivity are considered, depending on specific needs.
The main technical characteristics of a thermal sensor include:
Thermal sensitivity: Measures the sensor's ability to detect small temperature variations.
Spatial resolution: Indicates the sensor's ability to distinguish spatial details in a thermal image.
Frame rate: The speed at which the sensor can capture and process thermal images, which is important for applications requiring motion monitoring.
Spectral Range: The range of infrared wavelengths in which the sensor can operate, thereby determining its capabilities and limitations.
Thermal cameras operating in different infrared wavelength ranges each offer their own advantages and disadvantages:
SWIR cameras, although more expensive, are known for their better resolution and their ability to penetrate through certain opaque materials, making them useful in applications requiring vision through obstacles.
In contrast, MWIR cameras feature high thermal sensitivity, ideal for precise thermal monitoring, but can be more expensive and have penetration limitations.
LWIR cameras, on the other hand, are often favored for their relatively low cost and their ability to detect heat emitted by objects at room temperature, despite sometimes lower resolution and increased sensitivity to atmospheric conditions.
Thus, the choice of spectral range depends on the specific needs of each application, taking into account the trade-offs between cost, performance and technical capabilities.
(Diagram of the principle of operation of a thermal camera)
The purchase price of a thermal camera varies depending on several factors, including the temperature range measured, infrared resolution, measurement accuracy, and additional features such as Wi-Fi connectivity or video recording capability . Prices can range from a few hundred to tens of thousands of euros, depending on the model and its specific features. For example, an entry-level thermal camera can cost around $500, while a high-end model with advanced features can reach several thousand dollars. It is essential to carefully assess the specific needs and requirements before choosing a thermal camera in order to invest wisely in suitable equipment.
In conclusion, thermal cameras, thanks to their ability to detect temperature variations, have become essential in many sectors. Their operation is based on the detection of infrared radiation to generate thermal images. With different camera types suited to different needs and budgets, these tools offer valuable possibilities for diagnostics, monitoring and security.
