Three-dimensional Multi-layer Optical Storage System And Computer Simulation

With the development of information technology, the requirements for high density data storage are increasing. As a method of improving storage capacity, three-dimensional optical data storage has been widely investigated.The paper mainly investigates the multilayer optical storage technology, such as the multi-wavelength multi-level optical storage and two-photon optical storage technology. In the multi-wavelength multi-level optical storage system, a multilayer optical media has been designed and a focus adjusting device with dip incidence has been adopted. Based on the laser diffraction theory, the light intensity distribution on detector is analyzed. In the two-photon optical storage system, the problems which are induced by the mismatch of refractive index are theoretically analyzed and simulated. The following are main contents of this thesis:Firstly, a multi-layer optical media is designed, the design requirements and analysis method are explained. In order to separate the signals among layers, to guarantee the signal intensity from the receiver and to avoid the crosstalk, a new focus adjusting technology of dip incidence has been applied.Secondly, aided by Zernike polynomial, the tolerance of optical system has been obtained based on wave aberration theory. This result is very important for designing and manufacturing of optical pickup head . Based on the diffraction theory analysis, the light intensity distribution on detector is achieved, and simulation is conducted and factors which affect light intensity distribution are analyzed. The simulation indicates that light intensity distribution of concave pit meets Strehl Standard. The system can perform 3-D reading and writing simultaneously, which proves that this theoretical analysis is practicable.Finally, the optical diffraction theory, without considering focus error, can not directly apply to the displacement of disk. The optical intensity distribution on detector under different defocusing amount is deduced on the basis of Fresnel formula and scalar diffraction theory. The simulation curves which indicate how the focus error intensity varies with defocusing signals. In the end, Since the data bits are stored within the media, laser light will pass through two kinds of media(such as air and storage media) with different refractive index. The mismatch of refractive index will influence the aberration and intensity in shithe focus. This problem has been analyzed based on theoretical analysis and computer simulation.In conclusion, some aspects of three-dimensional optical storage system have been investigated ,wich will be helpful to put three-dimensional optical data storage method into practice.