chapter  3
22 Pages

Characterization of infrared detectors

ByAntoni Rogalski

Infrared (IR) radiation itself was unknown until 218 years ago, when Herschel’s experiment with the thermometer was first reported. The first detector consisted of a liquid in a glass thermometer with a specially blackened bulb to absorb radiation. Herschel built a crude monochromator that used a thermometer as a detector so that he could measure the distribution of energy in sunlight. In April 1800, he wrote [1]:

Thermometer No. 1 rose 7 degrees in 10 minutes by an exposure to the full red colored rays. I drew back the stand... thermometer No. 1 rose, in 16 minutes, 8⅜ degrees when its centre was ½ inch out of the visible rays.