Pre-pit detecting device and binarizing level setting method

摘要

A composite signal (Srpp) in which pre-pit signal components are piggypacked onto frequency components of wobbling, is extracted from an optical recording medium (50). The composite signal is binarized, so that pre-pit signals (S LPP1 ,S LPP2 ) are generated. The pre-pit signals pass through a first gate (5a) when the gate is open. The gate is periodically opened only in a period during which the amplitude of the wobbling (Swb) becomes a maximum one (2). The number of the pre-pit signals passing through the gate is counted (count signal), so that a binarizing level for generating the pre-pit signal is set based on the relationship between the counted number per a reference time and a predetermined reference number.