A bit of history
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In 1665, Sir Isaac Newton became the first to slit sunlight into colors with a prism, thus demonstrating the existence of light as radiated energy of differing wavelengths. About 135 years later, another English astronomer/scientist, William Herschel, measured the heat content of each the colors of Newton’s spectrum. Herschel was shocked to discover that his thermometer registered the greatest heat beyond the red – in an area of the spectrum he could not see: a serendipitous result, as lore has it, of his thermometer rolling off the red area of the spectrum. He coined the term INFRARED to describe this heat energy, which was beyond the red. All objects emit infrared energy at temperatures above absolute zero (-273°C, -460°F).

Herschel demonstrated that infrared heat radiation and light are simply two forms of electromagnetic energy. Our eyes see light energy because we are equipped to see the wavelengths of light. We cannot see infrared because the wavelengths are too long for our eyes. The very first non contact thermometer was the human eye. An example of a special infrared sensing adaptation from the animal world is the pit viper, which can actually locate warm-blooded animals in the dark with its infrared sensing pit organs below its eyes. An infrared sensor, like Herschel’s thermometer and the viper’s pit organs, is slightly heated when viewing the longer wavelengths of infrared energy, and provides quantitative information regarding the source of energy.

At the turn of the twentieth century, the German physicist Max Planck discovered the correct mathematical formulation of the relationship between temperature and infrared radiation, for which he won the Nobel Prize, thus paving the way for its use as a method of measuring temperature WITHOUT CONTACT. An unanticipated result of Planck’s discovery was quantum physics, arguably the most important scientific development of this century. Then of course we have the unforgettable AlbertEinstein who confirmed Planck’s Quanta by using the photoelectric effect although Einstein did not really like the result. Recent advances in the technology of infrared temperature measurement have stimulated development of devices that are without doubt, more sensitive than Herschel’s thermometer. Several applications of this technology have made it possible to designdevices capable of making fast, accurate, and safe non-invasive measurement