Thermal scanning, or thermography, translates the invisible heat energy radiating from objects into a visual image. This process allows for the visualization of temperature distribution across a scene or surface. By detecting subtle differences in thermal energy, the technology presents them as a distinct pattern, allowing users to “see” temperature variations. This non-contact method provides a powerful way to monitor conditions and examine objects.
The Physics of Infrared Energy
The foundation of thermal scanning lies in the properties of infrared (IR) radiation, a form of electromagnetic energy. Infrared occupies a region of the electromagnetic spectrum with wavelengths longer than visible light, making it undetectable by the human eye. Every object with a temperature above absolute zero continuously emits this energy. The amount of infrared energy an object emits is directly related to its temperature; as an object gets warmer, it radiates energy at a greater intensity. A thermal camera measures the intensity of this outgoing radiation and correlates it back to the object’s surface temperature.
How Thermal Imaging Cameras Function
Thermal imaging cameras are instruments designed to capture and process invisible infrared energy to form a recognizable image. The process begins with a specialized lens, often crafted from materials like germanium because standard glass blocks infrared wavelengths. This lens collects and focuses the incoming thermal radiation onto the camera’s sensor array.
The sensor array is typically a grid of detectors called a microbolometer. Unlike older thermal detectors that required cooling, the microbolometer functions by absorbing the focused infrared radiation. This absorption causes a slight, measurable change in the electrical resistance of its sensor elements, which is directly proportional to the intensity of the IR energy received.
An internal processor reads the electrical signal from each microbolometer element, translating the measured infrared intensity into a calculated temperature value. To create a visual representation, the processor assigns a specific color from a palette—often a gradient from blue (cooler) to red or white (warmer)—to each temperature value. This color-coded image, or thermogram, allows the human eye to easily discern temperature differences and visualize the heat distribution.
Diverse Applications in the Modern World
Thermal scanning provides non-destructive insights into the condition of systems and structures across numerous sectors.
Industrial and Building Maintenance
In industrial maintenance, thermal cameras are used for predictive inspections of machinery and electrical components. Identifying an abnormally warm connection or an overheating motor bearing provides a warning sign of a potential fault before a costly failure occurs. For building science, thermography assesses energy efficiency and structural integrity. Scans locate areas of poor insulation, often called thermal bridges, where heat is escaping or entering a building. They are also effective at detecting concealed moisture within walls or beneath roofing materials, which appears cooler due to evaporation.
Security and Medical Screening
The technology extends into security and medical screening, leveraging its ability to detect heat signatures in any light condition. Security teams use thermal cameras for night vision and surveillance, as a person’s body heat is readily apparent against a cooler background. In medical contexts, thermal imaging is employed as a non-contact method to screen for elevated body temperatures.
Factors Affecting Thermal Scan Accuracy
Obtaining accurate temperature measurements requires accounting for several external factors that influence the reading. The most significant factor is emissivity, which describes a surface’s ability to radiate thermal energy. Materials like human skin, paint, or brick have a high emissivity, meaning they radiate heat efficiently and provide reliable readings.
Conversely, highly polished metals have a low emissivity and reflect thermal energy from surrounding objects, similar to a mirror reflecting visible light. When pointed at a low-emissivity surface, the camera may measure reflected heat from a warmer source nearby, not the object’s true temperature. Users must manually input an emissivity setting specific to the target material to compensate for this.
Environmental conditions also introduce error, especially when scanning objects at a distance. Atmospheric interference from humidity or dust can absorb or scatter the infrared radiation traveling to the camera. Additionally, solar loading or reflections from the sun can create artificially warm spots on surfaces. For these reasons, thermal scans often deliver relative temperature data, showing differences and patterns, rather than absolute temperature values.