The concept of infrared light waves was described in the early 1800’s by William Herschel.
The application of the concepts of infrared light began during the Korean War with United States military’s need for night vision. Researchers from Honeywell and Texas Instruments applied the concept to develop night vision. Night vision technology became a “military secret”, it’s use and sale was under tight control for many years. (FLIR forward looking infrared)
Commercial imagers and documentation for the applications were developed in 1965.
As is typical with electronics the price drops as the capacity increases. To day a thermal temperature sensor can be purchase for less than $10.00 at all mass retailers for use by the homeowner to determine the temperature of items in the home.
The transistor developed by Texas Instruments and Bell Laboratories in the 1950’s made possible the development of sophisticated electronic apparatus necessary for the practical application of the electronics of today. At the time Texas Instruments was known as Geophysical Services Inc. involved in aerial mapping via aircraft among many other things. The mother of invention required smaller and less energy consuming devices. Planes of the day were not capable of carrying the bulky electronics used up to that time. A large truck to transport the Flir (Forward Looking Infra Red) electronics devices that are now a hand held apparatus.