Data reading apparatus for identifying position of data tracks

Claim 1

A data reading apparatus for an optical card having a data area, comprising a reading means for reading a data area on the optical card, said data area of the optical card being formed of a plurality of generally parallel data tracks aligned along a predetermined direction, each of which consists of a plurality of data bits, and at least one reference line extending perpendicular to the direction of the data tracks; detecting means for reading a reference line and ouputting an average position signal of the reference line; and a data clock generating means for generating data clock pulses which serve as a reference when the data bits are read on the basis of the average position signal of the reference line, said detecting means including a reference line detecting circuit for detecting the reference line and ouputting a detection signal, said detecting means having a circuit ouput for outputting the average position signal of the reference line, a first timing comparing means for receiving said detection signal of said reference line detecting circuit and said average position signal of said detecting means and comparing the timings of said detection signal and said average position signal and generating a first comparison signal, and first integrating means for integrating said first comparison signal of said first timing comparing means and ouputting an integrated signal to said circuit output, said data clock generating means including an oscillating circuit for ouputting timing clock pulses having a predetermined frequency, a frequency dividing circuit receiving the average position signal output from said detecting means and outputting data clock pulses having a frequency one Nth of the predetermined frequency of the timing clock pulses from said oscillating circuit in synchronism with the average position signal, a pulse generating circuit receiving said data clock pulses and ouputting a reference pulse at a position corresponding to the interval between a pair of adjacent reference lines of the data clock pulses using the average position signal as a reference, a second timing comparing means for comparing the timing between a detection signal corresponding to a reference line and said reference pulse and generating a second comparison signal, and second integrating means for integrating said second comparison signal of said second timing comparing means and feeding back an integrated signal to said oscillating circuit to set said predetermined frequency.