困扰我好久的问题，关于光盘的存储原理。存在两种解释。

turf456

说到光盘的存储原理，网上大把资料。无外乎是在光盘的反光层上平面是0，坑是1。激光照射产生不同的反射，从而读取信息。很多书上也如此说。但我上次借了本很厚的关于数据恢复知识的书。里面在介绍光盘存储结构的时候说反光层上平面是0，坑也是0，因为坑底也是平的，也会反射激光。只有在坑的边缘，光才会被散射。代表1。因此光盘不能记录连续的1，如果遇见连续1，就根据两端数据特点插入识别码把1隔开。这么说也不无道理啊。网上的东西大家都知道是copy来copy去的。这本书里讲的很特别。那谁知道真正的原理。但如果按照书里的说法刻录机刻录光盘就不好解释了

huayuliang

。。。。
0和1是相对的，是否散射与焦距有关。

可刻录的光盘和压制的光盘不一样的。在足够激光照射下，涂层会发生变化。

ssaweee

可刻录的是靠大功率激光改变有机染色质的光学性能，这个没有坑，

如果靠边缘，压制的光盘中凹凸边缘太窄了吧，如何分辨？

fnems

CD data are stored as a series of tiny indentations known as "pits",
encoded in a spiral track molded into the top of the polycarbonate layer.
The areas between pits are known as "lands". Each pit is approximately
100 nm deep by 500 nm wide, and varies from 850 nm to 3.5 µm in length.

The distance between the tracks, the pitch, is 1.6 µm. A CD is read by
focusing a 780 nm wavelength (near infrared) semiconductor laser  through
the bottom of the polycarbonate layer. The change in height between pits
(actually ridges as seen by the laser) and lands results in a difference
in intensity in the light reflected. By measuring the intensity change
with a photodiode, the data can be read from the disc.

The pits and lands themselves do not directly represent the zeros and ones
of binary data. Instead, Non-return-to-zero, inverted  (NRZI) encoding is
used: a change from pit to land or land to pit indicates a one, while no
change indicates a series of zeros. There must be at least two and no more
than ten zeros between each one, which is defined by the length of the pit.
This in turn is decoded by reversing the eight-to-fourteen modulation used
in mastering the disc, and then reversing the Cross-Interleaved
Reed-Solomon Coding, finally revealing the raw data stored on the disc.

from Wikipedia

fnems

NRZ不归零码的介绍

In telecommunication, a non-return-to-zero (NRZ) line code is a binary code
in which 1's are represented by one significant condition  (usually a positive
voltage) and 0's are represented by some other significant condition (usually
a negative voltage), with no other neutral or rest condition. The pulses have
more energy than a RZ code. Unlike RZ, NRZ does not have a rest state. NRZ is
not inherently a self-synchronizing code, so some additional synchronization
technique (for example a run length limited constraint, or a parallel
synchronization signal) must be used to avoid bit slip.


also from Wikipedia

homemyc2

的确是这样.
光驱除了了读取数据还有很重要的事情要做就是循迹,就是激光头要非常准确的对着渐开的圆弧坑纹,所以必须要保持对焦良好.数据是经过编码的,不会存在过长的1,当然还有时钟信息和纠错信息.

对于可录光盘来说,染料可以分为2种,1种是被烧焦的,另一种仅仅是光学性能改变.不管那一种,都可以理解为一系列光学的坑,一样有坑的边缘,拿张刻过的光盘和没刻的用眼可以比对到变化.这是光盘刻录后可以和普通光驱兼容的原因.不过光学的坑和物理的坑还是不尽相同,早期的可录光盘生产者经常被兼容问题弄的焦头烂额,要在市场上买很多烂牌子的VCD去试放.

没刻的光盘实际不是你看到的这么平的,里面也已经预压了很浅的径向正弦的渐开的圆弧轨迹,是用来给刻录机循迹用的,这个很浅的轨迹,播放器也看不到.市场上的碟片有74MIN和80MIN,就是这个纹路长度不一样,当然80MIN的片子兼容性就比较差了.