鼠标DarkField技术

最近我的罗技鼠标刚过保就坏了，很是郁闷。而我的师傅不久前正好买了个很牛的罗技鼠标M905，那时他给我展示了这鼠标能在玻璃上使用，让我惊讶不已。功能虽强，但价格也吓死人。由于这些原因我对鼠标产生了兴趣，特别是罗技09的最新技术“无界”和“优联”。

拥有“优联”技术的独门密技的罗技，只需一个Nano接收器，就能轻松玩转家里、办公室和旅途中的6个无线设备，虽然很牛，但还是能想明白其中的原理。而“无界”让我感到很神奇，以前光学鼠标一碰到玻璃表面就傻眼了，现在竟然还可以在透明玻璃或碟片上。于是研究了下其原理。

先回顾下光学鼠标的原理。

现在市面上光电鼠标分两种，一种是普通光学，一种是激光的。激光引擎就是用激光二极管代替了光学引擎中的发光二极管，两者的设计和工作原理基本相同。我们通过图示和说明来了解鼠标的工作原理，图中右上方既是一颗二极发光管，其照亮移动表面，然后就像胶片电影那样，通过光学取景器以每秒几千帧的速度记录移动区域（黑框内区域），然后通过前后两幅记录的图像的差别来判断鼠标的移动方向和移动距离。而当用于比较的两帧图像因光源问题或者移动平面等问题无法提供足够的细节时，鼠标就会无法判断移动的方向和距离，从而导致了光学失效。

下面是对罗技“无界”技术的分析，其实他叫DarkField技术，由于是新技术，国内的文章都是介绍，都是说这技术怎么牛，而下面是一片国外网上对其的介绍，让我受益匪浅（以下有空我再翻译吧）

Fine structures can often not be seen in front of a bright background. This situation changes if the structures are illuminated from the side and viewed in front of as dark a background as possible. The structures then really seem to light up.

Fine structures become visible: The spider webs (left) are barely recognizeable in front of the bright background – a light green field in this case. The picture completely changes when a dark background – a dark forest – is chosen. The structure seems to light up (right). In both cases, the object is illuminated at an angle from above by the bright afternoon sun. However, the sunlight did not directly hit the camera; this direct illumination would have swamped everything else.

An artificial dark background is created in the microscope using a annular stop (1) in the condenser. Although the condenser optics (2) then illuminates the sample (3), it does so with a hollow cone of light. The light does not hit the objective (4), but passes it by on the outside. If there is no sample, the image seen in the eyepieces remains completely dark. However, if objects, e.g. small particles of bacteria, are in the object plane, light is laterally diffracted away from the straight path. Provided that this light hits the aperture cone of the objective, it is gathered by the objective and fused to form an image. The object becomes brightly visible in front of a dark background.

For this, it is necessary for the objective aperture to be smaller than the inner aperture of the illuminating light cone (case A). However, objectives with an integrated variable iris diaphragm (5) are also available to shutter out the indirect light even if it falls into the aperture cone of the objective (case B). This permits the use of very high apertures for darkfield.

The diatoms are barely visible in brightfield (left).	This is quite different in dark field (right) where they seem to light up.

呵呵，技术很牛吧，但其实华而不实啊，很少人会在玻璃上直接用鼠标，再说有个鼠标垫才舒服啊。于是最后决定买了M505，毕竟他是激光鼠标，而且拥有"优联"技术，而且价格正好好由于M905这些拥有"无界"技术的出现而跌了一半。呵呵，用下来很喜欢我的M505,希望不要再是过保就嗝屁了。