Transducer positioning system

Claim 1

In a system for positioning a transducer means among a plurality of selectable transverse positions with respect to a predetermined direction of relative movement between said transducer means and a recording medium, the improvement comprising: position control information recorded on said medium in said direction of relative movement, said position control information comprising a first plurality of parallel transitions having an angle α 1 relative to said direction of relative movement and at least one second transition having an angle α 2 relative to a direction opposite to said direction of relative movement, the choice of α 1 and α 2 being limited in that neither α 1 nor α 2 can be 0°, and wherein only one of α 1 and α 2 can be 90°, said first plurality of transitions having a spacing S measured in said direction of relative movement which is chosen in conjunction with the spacing P between said selectable positions so as to satisfy the equation: S = P {(1/tan α.sub.1) + (1/tan α.sub.2)}; first and second position control transducers coupled to said transducer means for transverse movement in accordance therewith, said first and second position control transducers being constructed and arranged for sensing said first and second transitions respectively; digitizing means responsive to the sensing of said first and second transitions for producing respective first and second pulses corresponding thereto; and detecting means for indicating the transverse position of said transducer means relative to said medium based upon a detection of coincidence between predetermined ones of said first and second pulses produced by said digitizing means.