Tracking servo system with a variable equalizing characteristic

Claim 1

A tracking servo system for use in a disc player having a pickup, for playing an information recording disc having a recording track, said tracking servo system comprising: means for generating a tracking error signal corresponding to an amount of deviation, in a radial direction of said disc, of an information reading spot of said pickup with respect to said recording track, an equalizing circuit means for compensating for a frequency characteristic of said tracking error signal, said equalizing circuit means performing a compensation operation in accordance with a predetermined compensation characteristic during a normal playback of said disc; a driving means for shifting said information reading spot in said radial direction of disc in response to said tracking error signal passed through said equalizing circuit means; and a servo loop switch adapted to open in response to a jump command signal generated in said disc player, and to close at a predetermined timing in a period of a jump operation, wherein coefficients determining predetermined compensation characteristic of said equalizing circuit means are made variable, and said tracking servo system is provided with a control means for varying said coefficients so that said compensation characteristic has a phase margin in a middle frequency range larger than a corresponding phase margin in said predetermined compensation characteristic at said predetermined timing, and a middle frequency gain of said equalizing circuit means is gradually increased with time until said compensation characteristic equals said predetermined compensation characteristic when a predetermined time period elapses.