Track access control device for an optical disk drive

A track access control device for an optical disk drive which comprises a converging lens, an optical head for issuing a laser beam toward a medium via said converging lens to write or read data in or out of said medium, a lens driving circuit for generating a lens drive signal which moves said converging lens in a radial direction of said medium, a lens actuator responsive to said lens drive signal for moving said converging lens, lens position detecting means for generating a lens position signal representative of a position of said converging lens relative to said optical head, and head driving means responsive to said lens position signal for causing said optical head to follow a movement of said converging lens in such a manner as to reduce a positional deviation of said converging lens, said track access control device comprising:

• signal level comparing means for comparing a level of the lens position signal with a predetermined reference level to produce a comparison signal;
• a differentiating circuit for differentiating the lens position signal to produce a differentiation signal;
• and
• signal selecting means responsive to the comparison signal for feeding, when the positional deviation of the converging lens exceeds a predetermined range, the differentiation signal to the lens actuator in place of the lens drive signal.