US 6,185,172 B2Granted

Rotation control apparatus, reproduction apparatus to which rotation control apparatus is applied, and rotation control method

AssigneeSony Corporation

InventorTetsuji Nakazawa

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Abstract

A rotation control apparatus which does not rely upon a drop of a signal is provided. A lower limit frequency and an upper limit frequency calculated based on generation patterns of run length limited codes which may possibly be generated stochastically are set as a frequency variation range. When rotation control is performed based on an error between a frequency of run length limited codes reproduced from a disk and a reference frequency while a PLL circuit is not in a locked condition, the reference frequency is varied between the upper limit frequency and the lower limit frequency. Then, the reference frequency which is currently used for comparison when the PLL circuit is put into a locked condition is stored as a fixed value and used as the reference frequency for later rotation control.

Claims7

Dependent claims

A rotation control apparatus for controlling rotation of a disk based on run length limited codes reproduced from the disk, comprising:

reception means for receiving the run length limited codes reproduced from the disk;
reference signal generation means for generating a reference frequency;
frequency counting means for counting a frequency of the run length limited codes received by said reception means with reference to the reference frequency from said reference signal generation means;
variable frequency setting means for setting an upper limit frequency and a lower limit frequency of the run length limited codes based on a probability of appearance of the run length limited codes reproduced from the disk;
lock discrimination means for discriminating whether or not a synchronizing signal included in the run length limited codes is locked to a predetermined frequency;
frequency variation means for varying, when it is discriminated by said lock discrimination means that the synchronizing signal is not locked to the predetermined frequency, the predetermined frequency so as to sweep within a range defined by the upper limit frequency and the lower limit frequency set by said variable frequency setting means;
comparison means for comparing the frequency of the run length limited codes counted by said frequency counting means and the frequency varied to sweep by said frequency variation means;
storage means for storing the frequency varied to sweep by said frequency variation means at a point of time when it is discriminated by said lock discrimination means that transition from a condition wherein the synchronizing signal is not locked to the predetermined frequency to another condition wherein the synchronizing signal is locked to the predetermined frequency occurs;
calculation means for calculating a difference between the frequency of the run length limited codes counted by said frequency counting means and the frequency stored in said storage means;
and
rotational driving control means for controlling rotational driving of the disk based on the difference information obtained by said calculation means.

8 more elements

A reproduction apparatus which controls rotation of a disk based on run length limited codes reproduced from the disk;

comprising:
reproduction means for reproducing the run length limited codes recorded in advance on the disk;
reference signal generation means for generating a reference frequency;
frequency counting means for counting a frequency of the run length limited codes reproduced by said reproduction means with reference to the reference frequency from said reference signal generation means;
variable frequency setting means for setting an upper limit frequency and a lower limit frequency of the run length limited codes based on a probability of appearance of the run length limited codes reproduced from the disk;
lock discrimination means for discriminating whether or not a synchronizing signal included in the run length limited codes is locked to a predetermined frequency;
frequency variation means for varying, when it is discriminated by said lock discrimination means that the synchronizing signal is not locked to the predetermined frequency, the predetermined frequency so as to sweep within a range defined by the upper limit frequency and the lower limit frequency set by said variable frequency setting means;
comparison means for comparing the frequency of the run length limited codes counted by said frequency counting means and the frequency varied to sweep by said frequency variation means;
storage means for storing the frequency varied to sweep by said frequency variation means at a point of time when it is discriminated by said lock discrimination means that transition from a condition wherein the synchronizing signal is not locked to the predetermined frequency to another condition wherein the synchronizing signal is locked to the predetermined frequency occurs;
calculation means for calculating a difference between the frequency of the run length limited codes counted by said frequency counting means and the frequency stored in said storage means;
and
rotational driving control means for controlling rotational driving of the disk based on the difference information obtained by said calculation means.

9 more elements

Dependencies are inferred from the claim text.