Patent ID: 6639882
Filing Date: 2003-10-28
Classification: G11B

Abstract:
A pre-pit detecting apparatus for an optical recording medium, which has information tracks with recording pits carrying record information formed thereon and guide tracks for guiding a light beam to the information tracks, and further has pre-pits carrying pre-information formed on the guide tracks, the pre-pit detecting apparatus including an amplitude correcting circuit, which when the optical beam is irradiated to one of the information tracks, corrects the amplitude of a first read signal and the amplitude of a second read signal generated on the basis of the outputs of electrical signals from a light receiving unit, divided into two parts by a division line at least optically parallel with the information track, such that the pre-pit detecting apparatus performs a computation on the difference between the corrected first and second read signals to generate a difference signal so as to detect a pre-pit signal on the basis of the difference signal, whereinsaid amplitude correcting circuit comprises: an addition signal generating device for adding the first read signal to the second read signal to generate an addition signal; a first amplitude correcting device for correcting the amplitude of the first read signal, on the basis of the generated addition signal, for an RF signal component corresponding to a recording pit, which is contained in the first read signal; and a second amplitude correcting device for correcting the amplitude of the second read signal, on the basis of the generated addition signal, for an RF signal component corresponding to a recording pit, which is contained in the second read signal.