Recording clock generating device and method thereof
View Patent ↗Crosstalk between tracks, land prepit leakage, and effects of recording power modulation can cause the wobble signal period to change irregularly, thereby producing jitter in the recording clock which is derived by frequency multiplying the wobble signal. This problem is resolved by a recording clock generating circuit having an arrangement to average the wobble signal period, a timer for generating a rectangular wave with substantially the same period as the average period, and a frequency multiplying PLL for multiplying the timer output. The period averaging arrangement in particular determines the approximate average period at every wobble period and reflects the phase difference between the wobble signal and the timer in the timer setting so as to improve recording clock stability.
1. A recording clock generating device for recording data to an optical disk having a recording groove wobbled at a specific frequency in the radial direction, and prepits formed at a unit interval including a specific number of wobble periods, said device comprising:
a wobble signal detector for detecting recording groove wobble and outputting a wobble signal;
a period averaging arrangement for obtaining an average period for periods of the wobble signal;
a timer for generating a rectangular wave with a period which is substantially equal to the average period obtained by the period averaging arrangement;
a frequency multiplying PLL for multiplying timer output and generating a recording clock; and
a phase difference measuring set for measuring a phase difference Z between the wobble signal and the rectangular wave;
wherein the period averaging arrangement has
a set for measuring a total time of N wobble signal periods, where N is a specific integer and holding the measured total time as a cumulative period V, and
a set for measuring a next wobble period X, subtracting (1/N) of the cumulative period V from the cumulative period V, adding X to the resultant difference, correcting the measured phase difference Z, and using the resultant sum as a new total time for the N periods.
2. A recording clock generating method for recording data to an optical disk having a recording groove wobbled at a specific frequency in the radial direction, and prepits formed at a unit interval including a specific number of wobble periods, said method comprising:
a wobble signal detection operation of detecting recording groove wobble and outputting a wobble signal;
a period averaging operation of obtaining an average period for periods of the wobble signal;
an operation of generating a rectangular wave with a period which is substantially equal to the obtained average period;
an operation of multiplying timer output and generating a recording clock; and
an operation of measuring a phase difference Z between the wobble signal and the rectangular wave;
wherein the operation of generating the rectangular wave includes
a set which measures a total time of N wobble signal periods, where N is a specific integer, and holding the measured total time as a cumulative period V, and
an operation of measuring a next wobble period X, subtracting (1/N) of the cumulative period V from the cumulative period V, adding X to the resultant difference, correcting the measured phase difference Z, and using the resultant sum as a new total time for the N periods.