Diffraction image

Japanese: 回折像 - かいせつぞう

$Diffraction image$

...In contrast, the wavelength of light is extremely small compared to the size of the objects we encounter in our daily lives, so the discovery of the diffraction phenomenon was delayed, and as a result, the particle theory of light was believed for a long time. If a photographic plate is placed in an area where light diffracts into a shadow area, light and dark stripes appear on the plate according to the changes in the intensity of the diffracted light, and this is called a diffraction image. There are two types of light diffraction: Fresnel diffraction and Fraunhofer diffraction. ...

From [Light]

… When the light source and the observation point are at a finite distance from the aperture of the light shield, it is called Fresnel diffraction, and when they are at infinity, it is called Fraunhofer diffraction. When a plane wave is incident on a lens, the light does not converge to one point but spreads out. This is due to Fraunhofer diffraction, which uses the diameter of the lens as the aperture. At the focal plane, the center is the brightest, and the light intensity is distributed in a circular ring shape, resulting in a diffraction image with alternating light and dark. The radius of the first dark ring is given by 1.220 f λ ₀ / D , where D and f are the lens diameter and focal length. …

*Some of the terms mentioned in the "diffraction image" are listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…これに対して光の場合には，その波長が日常出会う物体の大きさに比較して著しく小さいため，回折現象の発見は遅れ，その結果，光の粒子説が長い間，信じられていたということができる。　回折によって光が影の部分にまわり込むところに写真乾板をおくと，写真乾板には回折光の強さの変化に応じた明暗の縞ができ，これを回折像と呼ぶ。光の回折には，フレネル回折とフラウンホーファー回折がある。…

【光】より

…　光源と観測点とが遮光板の開口部分から有限の距離にある場合をフレネル回折，無限遠にある場合をフラウンホーファー回折という。レンズに平面波を入射するとき，光は1点に集まらず広がってしまうが，これはレンズの直径を開口とするフラウンホーファー回折のためであり，焦点面においては中心がもっとも明るく，光の強度は円環状に分布し，明暗が交互の回折像が生ずる。第1の暗環の半径は，レンズの直径と焦点距離をDおよびfとして1.220fλ₀/Dで与えられる。…

※「回折像」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

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