注册 登录  
 加关注
   显示下一条  |  关闭
温馨提示!由于新浪微博认证机制调整,您的新浪微博帐号绑定已过期,请重新绑定!立即重新绑定新浪微博》  |  关闭

七郎 / Seven Liu

科学与艺术,恰如人生中的红颜知己。 本博内容保留所有权利.

 
 
 

日志

 
 

4.9 Beam waist of the laser spot 激光光斑的光腰  

2012-06-25 22:28:53|  分类: 读点英文 |  标签: |举报 |字号 订阅

  下载LOFTER 我的照片书  |

There is a physical limit to how small a focused spot can be. In the focal point, the light waves bend and form a narrow waist.

聚焦光点可以小到什么程度是有其物理极限的。在焦点处,光波发生弯曲现象并形成一个狭窄的光腰。

The size of the smallest object that could be resolved by the optical system is proportional to the beam waist. There is approximate relation between the NA and the smallest spot size or beam waist w for a given wavelength, λ.

光学系统可分辨的最小对象的尺寸与光腰大小成正比。对于给定的激光波长λ,数值孔径NA和最小光斑和大小或光腰w之间存在一个粗略的关系。

W ≈λ/2NA

The relation shows that to get a smaller spot size the NA has to be increased or the wavelength has to be decreased. The evolution of the optical disc technology has used both methods to get smaller spot sizes to increase the storage capacity. The table below shows the minimum beam waist for different formats. The values assume a perfect optical system combined with a light beam with a uniform intensity.

这个对应关系指出:要获得更小的聚焦光点,必须增大数值孔径NA或者降低激光波长λ。为获得更小的光斑以提高存储容量,光盘技术的更新换代同时应用了这两个方法。下表列出了不同格式光盘上的最小光腰尺寸。表中数值的前提,光学系统是拥有光强一致的激光束的完美光学系统。

Format

格式

Wavelength (λ)

波长

NA

数值孔径

Half Angle (θ)

光线锥角的一半

Minimum beam waist (w)

最小光腰

CD

780nm

0.45

27

0.87μm

CD-R/RW

780nm

0.50

30

0.78μm

DVD

650nm

0.60

37

0.54μm

DVD±R/RW

650nm

0.65

41

0.50μm

HD DVD

405nm

0.65

41

0.31μm

BD

405nm

0.85

58

0.24μm

 

The difficulties designing and producing lenses and optical systems increase with increasing NA, making such designs more expensive. As the industry has become more mature, the difficulties have been solved to make the cost realistic for the consumer market. The technology to manufacture laser diodes with shorter wavelengths has also evolved over the years.

随着数值孔径的提高,设计的难度、光学系统及镜头的制造难度,双双增加。做这样的设计,代价昂贵。好在产业成熟度越来越高,这些难度相继得到解决,使成本降低到消费市场可接受的程度。多年来,经过努力,更短波长激光二极管的制造技术也被攻克。

 

---------------------------------

Key Words:

·focal point 焦点

·focal plain 焦平面

·resolve 解决; [光学]分辨

·mature v成熟;adj成熟的,

·be proportional to 与…成正比

·beam waist 光腰

·realistic现实的;现实主义的;逼真的;实在论的

---------------------------------

扩展阅读:

Beam Waist

The beam waist of a Laser beam is the location along the propagation 传播 direction where the Beam Radius has a minimum. The waist radius is the beam radius at this location. A small beam waist can be obtained by focusing a Laser Beam with a Lens which has a high numerical aperture, and making sure that the lens aperture is largely filled by the input beam. For non-circular beams, the position of the beam waist can be different for different transverse横轴 directions. This phenomenon现象 is called astigmatism 象散, and it may be generated or removed by using cylindrical柱面的 optics.

  评论这张
 
阅读(438)| 评论(0)
推荐

历史上的今天

评论

<#--最新日志,群博日志--> <#--推荐日志--> <#--引用记录--> <#--博主推荐--> <#--随机阅读--> <#--首页推荐--> <#--历史上的今天--> <#--被推荐日志--> <#--上一篇,下一篇--> <#-- 热度 --> <#-- 网易新闻广告 --> <#--右边模块结构--> <#--评论模块结构--> <#--引用模块结构--> <#--博主发起的投票-->
 
 
 
 
 
 
 
 
 
 
 
 
 
 

页脚

网易公司版权所有 ©1997-2017