Abstract: The speed detecting system 12 detects the beam spot speed relative to the optical disk 1 on the basis of track count pulses and reference clock pulses. The period of each track count pulse is the time taken in order for the beam spot to traverse a track. The reference clock pulses include first pulses, which are shorter in period than the track count pulses, and second pulses, which are longer in period than the track count pulses. In an area where the beam spot speed is low, the reference clock count method for counting the number of first pulses per track count pulse is used. In an area where the beam spot speed is high, the traverse count method for counting the number of track count pulses per second pulse is used.

Abstract: To accurately count the tracks traversed on an optical disk, even in the presence of noise and eccentricity, a track-counting apparatus is provided, this apparatus having an edge-detection circuit that detects the edges of a track-crossing signal and generates an edge-crossing signal, a logical AND circuit that takes the logical AND of the edge-crossing signal and a mirror signal to generate an effective edge signal, a direction-discriminating circuit which switches the logic state of the track-crossing signal based on the direction of movement toward the target track, thereby generating a pulse-discriminating signal, a count pulse separating circuit which, based on this pulse-discriminating signal, separates the effective edge signal into a count-down signal and a count-up signal, and a track counter which counts the number of tracks traversed, based on both the count-down signal and the count-up signal which are generated by the count pulse separating circuit.

Abstract: An optical disk device is provided which enables the focus offset to be automatically adjusted with a high accuracy. In automatic control in a microcomputer, initial focus offset adjusting data (AO) are first output, and the data is stepwise changed from the initial value AO. In this case, a difference in phase between reproduced EFM signals and channel clocks is integrated in an integration circuit at given time intervals, and, thereafter, focus offset adjusting data, which provide the minimum phase difference integration data, are output as the optimal focus offset adjusting data.