Two-dimensional modeling of an optical disk readout

Abstract

The design of high density digital optical storage systems requires a thorough understanding of the various interactions affecting the integrity of both data and servo signals under various readout conditions. Here, a 2-D Fourier optic model of the readout system is presented along with an efficient calculational procedure based on 2-D fast Fourier transforms (FFT). The model is utilized to examine the effects of data density, focus errors, tracking errors, lens fill conditions, phase pit depth, etc. on the quality of the readout signal. The derivation of servo signals is also studied through the modeling of a simple diffraction based scheme. It is shown that a reasonably constant servo signal (small variations with focus errors, track depth, or added amplitude data) can be generated by this technique provided that a λ/8 phase groove is present. The same technique can be shown to be unacceptable if an amplitude or λ/4 phase groove is utilized. © 1983 Optical Society of America.