Patent ID: 7539097
Filing Date: 2009-05-26
Classification: G11B

Abstract:
1. An optical disk device comprising: a first photodetector for detecting a light from an optical recording medium on which address information exists intermittently in an embossed area, said first photodetector being divided into four parts by a track direction axis and a radial direction axis that is perpendicular to the track direction axis; an optical difference signal detection circuit for adding, among outputs from said first photodetector which have been current-to-voltage converted, the outputs corresponding to areas parallel to the track direction axis, and detecting a difference between the respective added values; an amplitude adjustment circuit for adjusting the amplitude of an output signal of said optical difference signal detection circuit; a clock generation circuit for generating, from the output signal of the optical difference signal detection circuit, a sampling clock having a frequency that is synchronized with digital data recorded on the optical recording medium; a first analog-to-digital converter for converting an output signal of said amplitude adjustment circuit into a digital sampling signal according to the sampling clock; an address polarity information detection circuit for detecting a peak envelope signal from the digital sampling signal, and comparing the peak envelope signal with a predetermined threshold value to detect address polarity information, wherein said address polarity information detection circuit comprises an address position information detection circuit for detecting a bottom envelope signal from the digital sampling signal, detecting signal amplitude information from a difference in amplitudes between the peak envelope signal and the bottom envelope signal, and comparing the signal amplitude information with a predetermined threshold value, thereby detecting address position information, wherein said address position information detection circuit comprises