RECORDING/REPRODUCING APPARATUS FOR DISC-SHAPED RECORDING MEDIUM, PHOTODETECTOR AND OPTICAL HEAD

摘要

A recording and/or reproducing apparatus for a disc-shaped optical recording medium includes a rotation drive mechanism, a head device, a discriminating device, a first processing device, a second processing device, a third processing device and a controller. A disc-shaped optical recording medium is loaded on the rotation drive mechanism and is run in rotation at a constant linear velocity. The head device includes a laser light source and a photodetector unit and is movable in the radial direction of the disc-shaped optical recording medium for recording/reproducing information signal on or from the disc-shaped optical recording medium. The discriminating device discriminates the type of the disc-shaped optical recording medium loaded on the rotation driving device. The photodetector unit includes first, second and third photodetectors. The first processing circuit takes a difference between output signals from the first photodetector and those from the second photodetector. The second processing circuit takes a sum of output signals from the first photodetector and those from the second photodetector. The third photodetector generates an error signal based on an output signal from the third photodetector. The controller selectively changes over an output from the first processing circuit to an output from the second processing circuit and vice versa based on a detection output from the discriminating device to produce reproducing signals.