Creation of synchronization marks in multilevel optical data storage
Creation and detection of synchronization marks for a multilevel data storage medium is disclosed. A sequence of symbols is generated and the sequence of symbols is written to the multilevel data storage medium. A corresponding sequence may be generated by a detector and correlated with read data to detect the synchronization mark.
1. A method of detecting a synchronization mark on a multilevel data storage medium comprising:
generating a pseudo-noise sequence having a plurality of bits;
converting the pseudo-noise sequence to an expected synchronization sequence that would result from reading a synchronization mark generated using the pseudo-noise sequence;
correlating the expected synchronization sequence with a read sequence from the data storage medium to produce a correlation sequence of correlation sums; and
detecting the peak value of the sequence of correlation sums.
2. A method of detecting a synchronization mark on a multilevel data storage medium as recited in claim 1 wherein converting the pseudo-noise sequence to an expected synchronization sequence further includes applying a chip mask that produces a distinct peak correlation sum to the bits of the pseudo-noise sequence.
3. A method of detecting a synchronization mark on a multilevel data storage medium as recited in claim 1 wherein converting the pseudo-noise sequence to an expected synchronization sequence further includes up sampling.
4. A method of detecting a synchronization mark on a multilevel data storage medium as recited in claim 1 wherein converting the pseudo-noise sequence to an expected synchronization sequence further includes slicing the expected synchronization sequence into a predetermined number of levels.
5. A method of detecting a synchronization mark on a multilevel data storage medium as recited in claim 1 wherein detecting the peak value of the sequence of correlation sums includes activating a peak detector when the absolute value of one of the correlation sums exceeds an activation threshold.
6. A method of detecting a synchronization mark on a multilevel data storage medium as recited in claim 1 wherein detecting the peak value of the sequence of correlation sums includes deactivating a peak detector when the absolute value of one of the correlation sums is less than a deactivation threshold.
7. A method of detecting a synchronization mark on a multilevel data storage medium as recited in claim 1 wherein correlating the expected synchronization sequence with a read sequence from the data storage medium to produce a correlation sequence of correlation sums includes slicing the read sequence into a predetermined number of levels.
8. A method of detecting a synchronization mark on a multilevel data storage medium as recited in claim 1 wherein detecting the peak value of the sequence of correlation sums includes detecting whether the peak is a negative peak or a positive peak.
9. A method of detecting a synchronization mark on a multilevel data storage medium as recited in claim 8 further including determining the orientation of the synchronization mark based on whether the peak is a negative peak or a positive peak.
10. A synchronization detector for detecting a synchronization mark written to a multilevel data storage medium comprising:
a pseudo-noise sequence generator for generating a pseudo-noise sequence having a plurality of bits;
a processor configured to convert the pseudo-noise sequence to an expected synchronization sequence that would result from reading a synchronization mark generated using the pseudo-noise sequence;
a correlator configured to correlate the expected synchronization sequence with a read sequence from the data storage medium to produce a correlation sequence of correlation sums; and
a peak detector configured to detect the peak value of the sequence of correlation sums.