Optical memory accessing and tracking apparatus with pickup and lens servoing during tracking

A tracking system for setting an optical recording/reproducing apparatus at a command position radially along a disc-type information storage medium, comprising:

• pickup means including a laser source for recording/reproducing data on a storage medium, an objective lens having an optical axis and being operably associated with said laser source, and a lens driving means for adjusting the optical axis direction of said objective lens to vary a coincidence position at which said optical axis meets said storage information medium;
• pickup moving means for translating the pickup means radially relative to said information storage medium;
• detecting means coupled to said pickup moving means for measuring the position along said information storage medium of said pickup driving means and for generating a position signal when the pickup moving means is within a preset first range of said command position;
• sensing means coupled to said lens driving means for measuring the coincidence position along said information storage medium at which the optical axis of the objective lens meets said information storage medium and for generating a coincidence signal when the coincidence position is within a given second range of said command position;
• first control means responsive to said position signal of the detecting means for, when the pickup moving means is within said preset first range of said command position, closing a first circuit loop including the sensing means and the lens driving means, and second control means responsive to the sensing means for, while the coincidence position is outside said given second range of said command position, keeping open a second circuit loop including the sensing means and the moving means, said second range being smaller than said first range;
• and
• third control means responsive to said coincidence signal for closing the second circuit loop only after the first circuit loop is closed and for maintaining the first circuit loop closed.