Patent ID: 6757233
Filing Date: 2004-06-29
Classification: G11B

Abstract:
A pre-pit detecting apparatus for extracting a composite signal from an optical recording medium and binarizing the composite signal to generate a pre-pit signal, said optical recording medium having an information recording track wobbled at a predetermined frequency and pre-pits formed at a predetermined spacing on a guide track adjacent to the information recording track, said composite signal in which pre-pit signal components are superimposed on components of frequency of the wobbling, said apparatus comprising:a binarizing level setting device for setting a binarizing level for the composite signal; a pre-pit signal generating device for comparing the extracted composite signal with the set binarizing level to generate a pre-pit signal; and a first gate for periodically opening its gate only in a period during which the amplitude of the wobbling becomes a maximum one to make the generated pre-pit signal pass through the gate, wherein the binarizing level setting device counts the number of the pre-pit signals passing through the first gate and sets the binarizing level based on the relationship between the counted number per a reference time and a predetermined reference number.