Heat from Invisible Rays

In 1800 William Herschel, a German astronomer and composer, while testing filters to observe sun spots passed sunlight through a prism, observed a heating effect in the visible red portion of the spectrum.  Testing further, he detected the presence of the greatest amount of heat in the area just beyond the red end of the visible spectrum now called Near-Infrared (NIR).   He wrote two papers detailing his findings and later that year, presented his discovery of invisible "Calorific rays" to the Royal Society of London.  Thirty-five years later Andre-Marie Ampere employed the newly invented thermocouple to demonstrate that near-IR (NIR) radiation was in fact invisible light. It wasn't until 1900 that the term infrared was applied to the part of invisible spectrum contiguous to the red end of the visible spectrum that comprises wavelengths from 0.74 microns to 300 microns.

Near IR

IR was first used in an industrial process in the 1930's in automotive paint curing applications.  It was discovered that NIR (Near Infrared) wavelengths, which are the shortest form of infrared radiation generate the greatest amount of heat. NIR can penetrate most materials quickly and bring them to a prescribed temperature extremely rapidly.

NIR for Analyzers

In the early 50's while working for the US Dept of Agriculture, K.H. Norris, considered by many to be the "father" of NIR, designed a system using NIR to make measurements of agricultural products.  Dickey-John produced the first commercial  analyzer using a tungsten-halogen IR source.

ISO 20473 specifies Near Infrared as the wavelength from 0.78 to 3 micrometers roughly equivalent to the International Commission on Illumination (CIE) combined IR-A and-B divisions.

Near IR Furnaces

Over 30 years ago, Radiant Technology Corporation pioneered the development of short wavelength infrared continuous belt ovens and furnaces.  In the '70's RTC introduced the first high-temperature infrared furnace capable of operating at 1000°C with extremely tight temperature control.  From 1972 to 2006, RTC became the undisputed leader in infrared heating technology and developed precise, efficient, cost-effective, and reliable thermal processing equipment for the photovoltaic, semiconductor processing, electronics packaging and assembly technology industries. Many of the original developments are still found in most near-IR furnaces today.