Patent US 5,452,276

An optical disc record playback apparatus includes tracking circuitry for radially translating the scanning pickup device during normal playback of the disc. Coarse and fine drive circuits are responsive to tracking error signals to provide coarse and more precise radial translations respectively. The tracking error signals are monitored for the occurrence for abnormalities such as may be produced by dust on the disc surface, and responsive to the detection of such abnormalities the coarse drive system is disabled to preclude the pickup from leaving the track.