Nikon Corporation

Shunji Hoshino

Naoto Inaba

Hiroya Ohkuma

A laser power monitor circuit for monitoring the power of a laser used in a magneto-optical disk device and other related devices. In order to provide marks in the recording medium, a write power of the laser is required, and in between the marks, the laser is to have a pedestal power. During recording on the magneto-optical disk, recording corrections are performed at the start of the pedestal power and write power of the laser to provide marks in the recording medium which are properly shaped. The laser power monitor circuit accurately monitors the power of the laser light on a recording medium and includes a reverse correction circuit to provide reverse correction of the recording corrected values among the monitored values of laser power to bring the laser to the appropriate write power or pedestal power.

Laser power monitor circuit used in a magneto-optical disk device

Optical recording/reproducing apparatus of the 2-head or 3-head type uses a simplified controller but is nevertheless capable of high-speed read-after-write check. In a 2-head embodiment a switching circuit supplies either a reproducing output of a recording head or a reproducing output of a reproducing head to a signal processing circuit selectively. When the reproducing output of the reproducing head is supplied, a signal generator supplies a signal to the signal processing circuit corresponding to the reproducing output of the recording head. In a 3-head embodiment a circuit compares identification signals in reproducing outputs of an erasing head and a recording head, respectively, and supplies the recording head with data to be recorded from a FIFO memory. A 3-head embodiment may also use a switching circuit for supplying either a reproducing output of an erasing head or a reproducing output of a reproducing head to a signal processing circuit.

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Yokohama, Japan

Shunji Hoshino