OPTICAL DEVICE FOR READING INFORMATION AND METHOD OF DETERMINING MASS-UNBALANCE

摘要

An optical playback or recording device is equipped with mass-unbalance detection means (20) for detecting unbalance on the record carrier (2). Mass-unbalance causes vibration and sound in the optical device when the record carrier (2) is rotated at a relative high speed. When mass-unbalance is detected, the speed may be reduced so as to reduce the vibration and sound in the optical device. Mass-unbalance is detected by using a state (T) of the carriage (5). The position of the carriage (5) in radial direction (D) is such a state (T). The current position of the carriage (5) is measured by an absolute measuring device. The amplitude of the difference (Pe) between the setpoint (W) and the current position of the carriage (5) is used to determine the mass-unbalance. There is a relation between the amplitude of the difference (Pe) and the amount of vibration caused by mass-unbalance. If mass-unbalance is detected, the speed of the rotation of the record carrier (2) may be reduced.