Patent ID: 6310847
Filing Date: 2001-10-30
Classification: G11B

Abstract:
A reading system for reading a writable optical disc having an information writing track, and a guiding track for introducing a laser beam to the information writing track, and prepit information including address information recorded on the guiding track, the system comprising:a photodetector having photodetecting elements divided at least by a dividing line optically parallel with a radial direction of the disc for detecting reflected light of a laser beam irradiated to the information writing track,difference signal producing means for producing a difference signal based on a difference between outputs of the divided photodetecting elements,addition signal producing means for producing an addition signal based on an addition between outputs of the divided photodetecting elements,noise cancel signal producing means for producing a noise cancel signal which cancels noise component of the difference signal occurring by information recorded on the information writing track based on the addition signal, andprepit signal producing means for producing a prepit signal based on subtracting the noise cancel signal from the difference.