Infrared Sensor: The Working Principle and Key Applications

With technology having such an immense role in the society of today, it is impossible for us to imagine our lives without relying on certain machines and devices for performing both the very simple as well as the most complex tasks. Though the pace of technological development is moving at the speed of light, sort to speak, it is a painstaking process. And while it may seem as if the inventions of today are recent concepts, most of the ideas actually date long back in time. An example of this is the infrared light. The infrared waves, part of the EM (electromagnetic) spectrum, are not visible to humans since the infrared radiation has wavelengths longer than those of the light we can see, ranging from 0.75 to 1,000µm.

The infrared radiation, which is an electromagnetic radiation same as X-rays, ultraviolet rays, radio waves and microwaves, was discovered in 1800 by the British astronomer William Hersche. This occurred during his experiment measuring the variation of temperature in colours with a prism, retracting sunlight, and thermometer, which resulted in detecting infrared radiation through an increase from blue to red. This led to the beginnings of infrared astronomy – studying different astronomical objects through infrared radiation. Considering all objects emit heat, it can be detected by sensors, which is why the infrared sensor was created and it has an enormous role to sense and detect IR radiation. It made its way as being helpful in meteorology, night vision, climatology, petrol exploration, gas detector, including anesthesiology.

Infrared sensors can be classified in two types: thermal and quantum. Thermal ones are not dependent on the wavelength they detect so there is no need to wait for them to cool off, whereas quantum ones work faster and more efficiently, detecting at a higher level and they need to be cooled for a better performance. Depending on your requirements and preferences, you should be able to decide which infrared sensor will best suit you. The infrared sensors of today contain LEDs and lasers and in order for transmission to happen, the presence of a transmission medium is necessary which can simply be the atmosphere, an optical fiber or vacuum. These devices are able to detect radiation that is focused by the use of lenses, such as polyethylene Fresnel lenses and quartz optical lenses.

As previously mentioned in the article, infrared sensors find their way in night vision, which is possible because photons are converted to electrons through an electrical process, resulting in visible light. Missile systems also make great use of these sensors for tracking vehicles and people. Art historians immensely rely on sensors to uncover hidden layers in old paintings which is of importance to art collectors to discover the authenticity of a painting. The improvements in technology are yet to bring a wider use of infrared radiation.