It is common knowledge that thermal cameras allow users to detect heat in all types of scenarios, but understanding how thermal technology inside a camera works, and why it is perfect for security applications is less understood. Learning how thermal cameras work is the first step to revealing their true usefulness.
It is common knowledge that thermal cameras allow users to detect heat in all types of scenarios, but understanding how thermal technology inside a camera works, and why it is perfect for security applications is less understood. Learning how thermal cameras work is the first step to revealing their true usefulness.
Technology and applications for thermal security products have been in a constant state of development. With the growing demand for 24/7 video surveillance more and more verticals are beginning to see the major benefits of thermal technology in a security setting. Unfortunately, several factors have stunted the growth of the thermal industry in applications other than military, where it was born and continues to have a strong presence.
Higher starting costs, the mistaken belief that thermal imaging is only a military product, and the lack of education across all industry has created hurdles for the thermal industry, ones they have been working hard to climb over. Helping their cause is the declining price of thermal equipment. As the cost of thermal imaging components, such as bolometer arrays, decrease, the cost of thermal equipment has also decreased. Additionally, fierce competition and increasing demand have also helped to drive down prices, causing the thermal market to shift towards more commercial markets.
Regardless of price, understanding how and why thermal imaging equipment can benefit a situation is most important. Knowing where thermal cameras are needed, why they are more beneficial than traditional visible camera solutions, and how thermal technology works is the beginning to finding a permanent cure for thermal imaging woes.
Inner Workings of Thermal Cameras
Physics teaches that any object that radiates heat emits a certain amount of infrared radiation. Thermal imaging sensors receive this infrared radiation via the temperature difference in a scene, which is then formed into an image with different colors to make it easier to distinguish different shades. In other words, thermal sensors can turn temperature differences into real-time images; however, thermal imaging cameras only display different shades of heat for humans and objects, not details.
Thermal imaging technologies are built on the fact that all objects with a temperature above absolute 0 degrees (-273° C) emit infrared radiation. These objects emit different electromagnetic radiation with various wavelengths; the hotter a material is the more significant the thermal reactions among its molecules and atoms are. Radiation spectrum and wavelengths are dependent on the nature and temperature of an object. The ability to emit absorbed energy is termed emissivity. In general, the blacker a material is the higher its emissivity is and the stronger radiation it has. Conversely, a more reflective or brighter material has a lower emissivity value and weaker radiation.
The human eye can only see very limited wavelengths of electromagnetic radiation, which is called the visible spectrum. Radiation with wavelengths between 0.4-0.7μm can be seen by the human eye. Radiation in the 0.7μm-1mm spectrum is referred to as infrared (IR) and cannot be seen by the human eye. Modern thermal imaging devices work in radiation as mid-wave infrared (MWIR) of 3-5μm or long-wave infrared (LWIR) of 8-12μm; the human body, which has an emissivity of about 9.3μm, is right in the spectral response of a LWIR imager. Since, thermal imaging sensors can receive infrared radiation of objects and produce real-time thermal images that are easier and clearer for the human eye to distinguish, which makes thermal imagers an almost “perfect” human detector for security. Additionally, thermal imaging sensors are very sensitive and are able to detect temperature differences of less than 0.1° C.
In a scene, optics are used so that IR sensors in thermal imaging cameras can capture the infrared radiation being emitted by objects. That infrared data is then transformed into a standard video format to display on surveillance monitors or be recorded in storage media.
Since thermal imagers create images by detecting heat, they are not dependant on visible light; therefore, they work perfectly well both day and night situations. In addition, thermal imagers are passive devices that produce no light radiation or radio frequency energy. As a result, the locations of cameras and users can be hidden without being exposed.