Patent ID: 7212477

Claim:
An optical recording/reproducing apparatus for recording a sequence of data blocks onto an optical recording medium by using a laser driving current waveform to control emission of a laser beam by a semiconductor laser, and for reproducing the data blocks from the medium, the waveform including a sequence of mark and space data portions each having a data length that corresponds to a multiple of a period of a channel clock based on a recording data modulation method, the optical recording/reproducing apparatus comprising: a semiconductor laser driver supplying a selected one of a plurality of drive currents, including at least a first-level drive current and a second-level drive current, to the semiconductor laser to control the emission of a laser beam by the laser; a current driver selectively outputting one of a plurality of increment currents to the laser driver in response to control signals, the plurality of increment currents including a first increment current supplied to the laser driver during an automatic power control process and a second increment current supplied to the laser driver during a special power setting process; a detection unit detecting a first power sample signal, at a first sampling point of the waveform, from the laser beam emitted when the first increment current is supplied to the laser driver, and the detection unit detecting a second power sample signal, at a second sampling point of the waveform, from the laser beam emitted when the second increment current is supplied to the laser driver; and a calculation unit calculating a derivative efficiency of the laser based on the first and second power sample signals detected by the detection unit, so that the drive currents of the laser driver, supplied to the laser, are controlled based on the calculated derivative efficiency.