Airy disk

…Resolution indicates the degree to which the fine details of a sample can actually be seen, and is expressed as the distance between the two closest points on the sample object that can be separated and identified. Even if the aberration of the objective lens is sufficiently corrected, a point on the object is not focused to a single geometric point due to the wave nature of light, but spreads out within a circle called the Airy disk. The radius of this Airy disk is proportional to the wavelength of light λ and inversely proportional to the numerical aperture (NA) of the lens (described below), and is expressed as 0.61λ/NA. …

*Some of the terminology that mentions "Airy disk" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…実際にどの程度まで試料の微細部が見えるかを表すのが分解能で，試料物体上分離して識別可能な最も近接した2点間の距離で表す。対物レンズの収差が十分補正されていたとしても，光の波動性のために物体の1点は幾何学的な1点に集光せず，エアリー円板Airy diskと呼ばれる円内にひろがる。このエアリー円板の半径は光の波長λに比例し，後述のレンズの開口数(NA)に反比例し，0.61λ/NAで表される。…

※「Airy disk」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