Analysis on the principle of multilevel optical data recording and the study on the processing of the front signals of a multilevel read-write system

This paper utilized the calculation methods in vector diffraction theory, such as the wave_coupled method and the finite difference time domain method, to a nalyze two multilevel optical recording methods in principle. Meanwhile the prin ciple to achieve multilevel optical recording by modulating the amplitude of pha se_change media is also discussed. According to these analysis, the multilevel d ata recording utilizes the mutual action between laser and recording media. Lase r beam has some special effects on the media; simultaneously the media will modu late some characteristics of the light. Generally, the diversities of these cha racteristics are more than two states, so the multilevel data recording can be a chieved by recording these different states. Besides, the design and development of the front signals processing system is also presented. It is an important pa rt of the experimental system for multilevel recording. It can output some servo and error signals such as TE, FE and RF etc, which will be fed back to the appr opriative chip for multilevel recording. Additionally the processing system not only can control the laser power and the writing time of the optical pickup, but it also can make the pickup realize focusing and tracking automatically.