Numerical Analysis of Tracking Error on High Density Optical Disks by Vector Diffraction Model

Abstract

High density optical disks are progressing rapidly recently. Shrinking the track pitch and the size of recorded pits are among the key technologies to attain higher density storage. However, the decrease in track pitch requires that the tracking servo control system be more precisely than conventional system. Scalar diffraction theory is usually used to calculate the optical readout of conventional optical disk storage system. However, scalar diffraction theory is valid only as long as the wavelength of the incident light is small compared with characteristic transverse dimensions of the scattering structure. As the transverse dimension of track pitch is no longer larger than the wavelength for higher density optical disks, vector diffraction theory1,2 becomes necessary to analyze the optical readout.