| 摘要 |
PROBLEM TO BE SOLVED: To provide a tracking device of an optical disk capable of surely changing over a land and a groove without performing the complicated tracking control. SOLUTION: Signals of reflected lights of three light beams such as +1st order diffracted light, 0-order diffracted light and -1st order diffracted light on the surface of the optical disk at the time after the photoelectric conversion is made, are inputted to a matrix circuit 31. Based on them, four kinds of tracking error signals TE1 -TE4 are made out, and the displacements for each 1/8 of one track pitch are detected by the detection of these zero-cross points carried out in a zero-cross calculation device 32. The tracking error signal TE2 is made to be positive and negative signals through amplifiers 36, 37, and one of these signals is selected by a switch box 33, thereby excites a tracking coil 39. Consequently, the ON/OFF of the mute of the tracking servo or the setting of the polarity of excitation is accurately carried, then the changeover is ensured. |
