Thermograms

A thermogram is an image produced by thermography, a technique that visualizes the distribution of surface temperatures and thermal patterns on a scene or object. Infrared cameras detect the infrared radiation emitted by objects, convert it into electrical signals, and display a color- or grayscale map where colors correspond to temperature. Thermograms provide a rapid, non-contact view of heat flow and temperature differences.

There are two main approaches to thermography. Passive thermography relies on existing heat differences within a scene, capturing natural contrasts. Active thermography introduces a controlled thermal stimulus, such as rapid heating or cooling, and records how the object’s surface returns to equilibrium. In active methods, sequences of thermograms can reveal subsurface features based on variations in thermal diffusion and response time.

Applications span multiple fields. In industry, thermograms help detect overloaded electrical components, loose connections, bearing wear, or mechanical faults. In building science, they are used to locate insulation defects, air leaks, moisture intrusion, and thermal bridging. In nondestructive testing, thermography reveals defects in composites and metals. In medicine, thermal imaging has been studied as a noninvasive adjunct for assessing blood flow, inflammation, or fever screening; however, it is not generally used as a sole diagnostic tool and requires expert interpretation.

Limitations include dependence on surface temperature and emissivity, as well as environmental conditions such as humidity, wind, and reflections. Accurate quantitative measurements require calibration and correction for emissivity and geometry. Thermograms are most useful for qualitative visualization of heat patterns and for guiding further investigation.