Pyrometry and Thermography

Abstract

Around the year 1800 Herschel ¹ discovered the infrared spectral region of optical rays. Although the first applications for thermography devices date back to 1900, the field of pyrometrics had however taken a different course of development. An exact definition of the two measurement methods shall not be made at this point; however, the following caracteristics may serve as a means of destinction. Pyrometry is a method which allows measurements of temperature to be recorded from surfaces emitting temperature radiation also known as heat radiation or thermal radiation. These temperature radiations are recorded by a pyrometer, a “radiation thermometer” (pointlike information). If the information obtained, for example, is optically recorded as an entire scene (buildings, operational equipment etc.) and displayed as a “temperature picture” — this is known as thermography. Important in the understanding this phenomena is the difference between infrared photography and similar methods which only record the reflected spectral portion of the optical spectrum (only in the near region of the infrared spectrum) and which generally do not permit any temperature intepretations of the recorded scene to be made.