Near infrared

…In 1800, the British FW Herschel was the first to discover that there is a region of the solar spectrum with a large thermal effect on the longer wavelength side than the red part. Wavelengths of a few microns or less are called near infrared, wavelengths of 25 μm or more are called far infrared, and anything in between is called mid-infrared. Also, wavelengths above 25 μm, 30 μm, or 50 μm are sometimes referred to as far infrared, and anything below that is called near infrared. However, these boundaries are not clear, and electromagnetic waves with good coherence, especially those generated by electronic circuits, are called submillimeter waves, or other radio wave terms, even if they have short wavelengths. …

*Some of the terminology that refers to "near infrared" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…1800年にイギリスのF.W.ハーシェルが，太陽スペクトルの赤色部分より長波長側に熱効果の大きい部分があることを発見したのが最初である。波長数μm以下を近赤外，波長25μm以上を遠赤外，その間を中間赤外と呼び，また，波長25μm，30μmまたは50μmを境として，それ以上を遠赤外線，以下を近赤外線と総称することもある。ただし，これらの境界は明確ではなく，ことに電子回路で発生されるコヒーレンスのよい電磁波は波長が短くてもサブミリ波などと電波用語で呼ばれる。…

※「近赤外」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報