Three-dimensional vector diffraction analysis for optical disc

Three-dimensional vector diffraction analysis for optical disc systems is described. The geometrical form of information pits and tracts is simplified to rectangular form. The disc surface and side wall of pits are perfect conductive. We considered two physical model of the pits: a) in the bottom of pits the partials waves of rectangular waveguide satisfy impedance condition; b) bottom of pits are connected to semi-infinite dielectric space. In the first case we obtained two-dimensional integral equation for electrical field in upper end of pit. In the second case we obtained two integral equation for upper and lower pit ends. The diffraction of laser beam by information pits was regarded in Fourier optics approach. We use the most exact theory of diffracted vector field to evaluate Fourier transform function for Gaussian beam. This approach gave us possibility to investigate the diffraction fields in the case of the lens with big aperture and small linear size. The obtained mathematical algorithm was applied then to the study of diffraction linear polarized Gaussian laser beam by disc information surface and to the diffraction laser beam by small rectangular aperture in infinite shield. The digital results showed that to obtain accuracy for integral characteristic of fields less then one percent it is necessary take eight Fourier members for every coordinate on the every pit end.