CONTROL METHOD OF MULTIBEAM LASER POWER AND OPTICAL MULTIBEAM RECORDING AND REPRODUCING DEVICE

摘要

PURPOSE: To exactly control the powers of plural lasers and to reduce the influence affecting focusing servo and tracking servo at the time of controlling the power by performing the time division power control of a multibeam semiconductor laser for every specified time during data recording and reproduction by using plural light emitting elements and a photodetector. CONSTITUTION: This device is provided with four laser power control circuits composed of a laser power setting circuit 7, a hold circuit 8 and a current source 9 corresponding to light emitting elements a-d and performs the power control by taking out the output value of a photodetector 2 by time division. The following means are used for minimizing the influence on servo: (1) The putting-out period of a first light emitting element (a is shortened to the extent that it does not affect the servo. (2) During the putting-out of the first light emitting element (a), focusing and tracking servo loops are released and an interpolating signal is used. (3) During the putting-out of the first light emitting element (a), servo operation is performed by using the laser beam of another light emitting element. (4) The laser power of other light emitting element is controlled without putting out the first light emitting element (a).