US Patent 7149176 High-density optical disc

A compact high-density optical disc capable of securing recording/reproducing characteristics and high-density recording capacity. The high-density optical disc has a whole diameter of 80 mm or less to 28 mm, a whole thickness in a range of 0.3–0.7 mm, and a position where data starts being recorded in a range of 27–45 mm of the diameter. Thus, an existing disc drive can be used, the size of the high-density optical disc can be reduced, and high-density recording capacity can be secured.