埃利斑（Airy disk）

------可不是，雀斑！

埃利斑，称之为：Airy disk （or Airy disc），这都是源自于，Sir George Biddell Airy，他是一位天文学家。埃利斑以及周围的环组成的图案（图样），称之为：Airy pattern。

虽然，Airy disk、Airy pattern，不是Airy发现的（John Herschel最先描述），但是，却是他首先计算、阐述原理的。

1828年，John Herschel发现，1835年，Sir George Biddell Airy确认，埃利斑，算是诞生了。

请记住，艾里斑，是几乎所有光学系统中最基本的概念。

参考资料：

[1]  https://en.wikipedia.org/wiki/Airy_pattern  Airy pattern

Computer-generated image of an Airy disk. The gray scale intensities have been adjusted to enhance the brightness of the outer rings of the Airy pattern.

In optics, the Airy disk （or Airy disc） and Airy pattern are descriptions of the best focused spot of light that a perfect lens with a circular aperture can make, limited by the diffraction of light. The Airy disk is of importance in physics, optics, and astronomy.

The diffraction pattern resulting from a uniformly-illuminated circular aperture has a bright region in the center, known as the Airy disk, which together with the series of concentric bright rings around is called the Airy pattern. Both are named after George Biddell Airy. The disk and rings phenomenon had been known prior to Airy; John Herschel described the appearance of a bright star seen through a telescope under high magnification for an 1828 article on light for the Encyclopedia Metropolitana:

...the star is then seen （in favourable circumstances of tranquil atmosphere, uniform temperature, &c.） as a perfectly round, well-defined planetary disc, surrounded by two, three, or more alternately dark and bright rings, which, if examined attentively, are seen to be slightly coloured at their borders. They succeed each other nearly at equal intervals round the central disc....[1]

However, Airy wrote the first full theoretical treatment explaining the phenomenon （his 1835 "On the Diffraction of an Object-glass with Circular Aperture"）.[2]

Mathematically, the diffraction pattern is characterized by the wavelength of light illuminating the circular aperture, and the aperture's size. The appearance of the diffraction pattern is additionally characterized by the sensitivity of the eye or other detector used to observe the pattern.

The most important application of this concept is in cameras and telescopes. Due to diffraction, the smallest point to which a lens or mirror can focus a beam of light is the size of the Airy disk. Even if one were able to make a perfect lens, there is still a limit to the resolution of an image created by such a lens. An optical system in which the resolution is no longer limited by imperfections in the lenses but only by diffraction is said to be diffraction limited.

Real Airy disk created by passing a red laser beam through a 90 micrometer pinhole aperture with 27 orders of diffraction

Airy disk captured by 2000 mm camera lens at f/25 aperture. Image size: 1×1 mm.

[2]  http://www.guokr.com/article/49548/   艾里斑：我不是雀斑

2011-07-05 15:20   本文作者:cloudsforest

7月2日《非诚勿扰》上来了一位有趣的高能物理男，他的爱情宣言糅合了大量物理专业名词，给人耳目一新的感觉。不过，很多词大部分人都是第一次听到，很难体会他的良苦用心。比如，他提到“你透过我的瞳孔衍射在我的视网膜上留下一道艾里斑”，不解风情的乐嘉同学就把“艾里斑”给复述成“雀斑”了，物理男同学当时一定觉得很囧。那么到底艾里斑是什么？嘉宾的那句话对吗？艾里斑在物理和工程上有什么意义呢？

艾里斑是什么？

高中物理曾经介绍过狭缝衍射：一束光经过一道狭缝（本人注：应该与波长一个数量级宽度。），会在中间亮条纹的两侧呈现出一系列明暗交替的条纹。这是由于光是一种电磁波，它被狭缝限制时会发生衍射，偏离直线传播。

假如把狭缝换成一个圆孔，则它在各个方向上都限制了光的传播。这样就在一定的距离上（称为远场）形成了下图左边的圆孔衍射图样（艾里图样，airy pattern）。这个图案的中心有一个比较大的亮斑，集中了大部分的能量，我们叫它主极大，这个亮斑就是艾里斑（airy disc）。而它的外围有一些明暗交替的环。由于艾里斑比外围的衍射图样强度高很多，所以左图为了显示衍射图样，不得不把主极大过曝了。为了更直观地了解艾里图样各级之间强度的差别，右图把艾里斑的强度作为第三维，越高表示强度越大。它的形貌如下图所示。

艾里斑图示

……

……

艾里斑是几乎所有光学系统中最基本的概念，是我们只要睁着眼睛就会接触，但是却难以感受到的一样东西。了解了这一切，会不会你也开始将你的身边的一切，包括你爱的那个人幻化成脑海中的无数的艾里斑呢？

[3]  https://en.wikipedia.org/wiki/George_Biddell_Airy 

Sir George Biddell Airy KCB PRS（/ˈɛəri/; 27 July 1801 – 2 January 1892）was an English mathematician and astronomer, Astronomer Royal from 1835 to 1881. His many achievements include work on planetary orbits, measuring the mean density of the Earth, a method of solution of two-dimensional problems in solid mechanics and, in his role as Astronomer Royal, establishing Greenwich as the location of the prime meridian. His reputation has been tarnished by allegations that, through his inaction, Britain lost the opportunity of priority in the discovery of Neptune.