Study On Digital Storage Method For Optical Discs Made Of Inorganic Materials

With the advent of the era of big data,people pay more and more attention to the data acquisition and data storage.As a kind of stable performance and low-cost data storage medium,optical disc has shown advantages in the archive data storage field.However,due to the low thermal stability of the substrate and weak adhesive to its metal layer of polycarbonate material,common optical discs cannot meet the required reliability level and data storage time.Long-term data storage technology usually requires the material with good thermal stability,and can be effective against mechanical damage and chemical erosion.Therefore,inorganic materials were generally selected as the substrate of data storage discs.The main work of the thesis can be summarized as follows.First of all,through a large number of literature investigation,characteristics mainly about the crystal properties,Mohs hardness,melting point,heat transfer coefficient,chemical resistance,ultraviolet radiation resistance and other physical or chemical characteristics of inorganic materials,as well as the processing difficulty,manufacturing cost,and other industrial features which can be made for substrates of long-term data storage discs has been analyzed.Then sapphire single crystal has been discovered and demonstrated as an ideal kind of materials which can be used to make long-term data storage discs' substrates by introducing the Eyring model.The predicted results showed that under the storage condition of 20?,data survival time of a disc using sapphire as its substrate can be up to 4500 years.Secondly,the method of data recording process on the sapphire optical disk was introduced.Dry etching techniques as well as the ion beam etching system were emphasized.Experimental results showed that width of a pit was ~ 0.6?m,a pit depth was ~ 0.2?m and a track pitch was ~ 1.6?m.Parameters of the pits on the surface of sapphire optical disk were in compliance with ISO/IEC 10149:1995 defining CD-ROM.Therefore,it is feasible to adopt methods proposed in this paper to achieve digital data storage on sapphire optical discs.Finally,the birefringence in single sapphire crystal causes optical aberration which makes a failure for standard CD-ROM driver during process of reading information from the disc.Then,the propagation of the focused laser beam throughout a sapphire disc has been analyzed.The method of compensating aberrations when reading data from uniaxial birefringent medium was developed using quartz compensating plate,and the data reading experiment was conducted.Experimental results showed that 24% of the data can be directly read,76% of the data can be normally read after error correction through the error correction code,speed rate of the disc was about 1.71 X.Data results showed that the proposed aberration compensation method significantly improves the performance of information reading system from sapphire disc.