Analysis of Behavior of Focusing Error Signals in Astigmatic Method in the Scheme of Land–Groove Recording

We present the behavior of focusing error signals in a land-groove-type optical disk by theoretical analysis. A gain difference between focusing error signals from a land and a groove occurs because the focusing error signal from the land does not coincide with that from the groove. We also report the dependence of the gain difference on some factors, which are related to the intensity distribution of a laser beam. The physical format of digital versatile disk random access memory is used as a land-groove-type optical disk model. The simulation results show that coma aberration that distorts the intensity distribution unidirectionally causes a large gain difference.