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INTRODUCTION
Sony Corporation (Tokyo, Japan) and Philips N.V.(Eindhoven, The Netherlands) have completed the de-velopment of an optical digital disk system, the Compact Disc digital audio (CDDA or CD) system, in 1980 June [ 1]-[3]. The CDDA disk contains a spiral-shaped track of successive shallow depressions, also called pits, in a reflective layer. The encoded digital audio information reis
stored in the length of the pits and the gaps between them. The disk rotates at a constant linear velocity (CLV) of 1.2-1.4 m/s.
A laser beam emitted by a solid-state GaA1As laser (wavelength X -- 0.78 Ixm), focused on the disk, is reflected by the information layer. The reflected light, modulated by the information on the disk, is detected by a photodiode and will be processed further elec-tronically. The readout is contactless. Electromechanical servo systems focus the laser spot on the disk and follow the track to within the specified accuracy.
This CD system permits recording and reproduction of a 16-bit 2-channel stereo signal for more than 60 min on a 12-cm-diameter disk single sidedly. This re markable characteristic is obtained by the high-density recording eight-to-fourteen modulation (EFM)method and the highly efficient error-correction method CIRC (cross interleave Reed-Solomon code) [4], both of which have been developed in close cooperation between Sony and Philips.
Some of the requirements for the modulation method of the optical disk system are given in Section 1. Section 2 deals with the comparison of experimental results of modulation methods we have considered for the CD system. Section 3 gives details of the adopted modu-lation method, EFM. In Section 4, some of the frequency maxspectrum
characteristics of EFM are presented; and a brief summary is given in Section 5.
介绍
索尼公司（日本东京）和飞利浦NV（荷兰埃因霍温）已于1980年6月完成了激光数字光盘系统，光盘数字音频（CDDA或CD）系统的开发[1]-[3 ]。 CDDA盘在反射层中包含连续的浅凹陷（也称为凹坑）的螺旋形轨迹。编码的数字音频信息 存储在凹坑的长度和凹坑之间的间隙中。光盘以1.2-1.4 m / s的恒定线速度（CLV）旋转。
由固态GaA1As激光器发出的激光束（波长X-0.78um）聚焦在光盘上，被信息层反射。由光盘上的信息调制的反射光由光电二极管检测到，并将进一步进行电子处理。读数是非接触式的。机电伺服系统将激光点聚焦在光盘上，并寻迹在指定的精度内。
此CD系统可以在单面的直径为12cm的光盘上记录和再现16位2声道立体声信号60分钟以上。这一显著特性是通过高密度记录八到十四调制（EFM）方法和高效纠错方法CIRC（交叉交织里德-所罗门码）[4]获得的。两者都是在索尼和飞利浦之间紧密合作下开发的。
在第1节中给出了对光盘系统的调制方法的一些要求。第2节处理了我们为CD系统考虑的调制方法的实验结果的比较。第3节详细介绍了EFM调制采用的方法。在第4节中，介绍了EFM的一些最大频谱频率特征；并在第5节中进行了简要总结。 |
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发表于 2020-11-21 17:06
楼主