Information recording system and an information recording method

1. An information recording system for recording information on an optical disc using a reference clock signal generated based on a push-pull signal including a wobble frequency component, the system comprising:

an amplitude obtaining unit for obtaining an amplitude value of the push-pull signal;

a threshold calculation unit for calculating a displacement threshold of the push-pull signal based on the amplitude value obtained by the amplitude obtaining emit; and

a noise reduction unit for generating a corrected push-pull signal by correcting the push-pull signal such that a displacement exceeding the displacement threshold is reduced,

wherein the reference clock signal is generated based on the corrected push-pull signal generated by the noise reduction unit.

2. The information recording system according to claim 1 , wherein the amplitude obtaining unit detects a peak value and a bottom value of the push-pull signal in a predetermined wobble cycle and obtains the amplitude value based on the detected peak and bottom values.

3. The information recording system according to claim 1 , wherein

the threshold calculation unit calculates the displacement threshold by multiplying the amplitude value from the amplitude obtaining unit by a gain value such that the amplitude value is reduced, and

the threshold calculation unit outputs the displacement threshold at a constant level before the amplitude obtaining unit obtains the amplitude value.

4. The information recording system according to claim 1 , wherein when the system is in a predetermined state, the reference clock signal is generated based on the corrected push-pull signal generated by the noise reduction unit.

5. The information recording system according to claim 4 , wherein the predetermined state is a track following mode.

6. The information recording system according to claim 4 , further comprising a binary signal generating unit for generating a wobble binary signal based on the push-pull signal,

wherein the predetermined state is a mode in which a cycle of a reference clock generated with reference to the wobble binary signal generated by the binary signal generating unit follows a wobble on the optical disc.

7. The information recording system according to claim 4 , wherein the predetermined state is a mode of recording information on the optical disc.

8. The information recording system according to claim 4 , further comprising a binary signal generating unit for generating a wobble binary signal based on the push-pull signal,

wherein the predetermined state fulfills at least one of the following conditions determined by a displacement reduction gate control signal: a condition in which the system is in a track following mode; a condition in which a cycle of a reference clock generated with reference to the wobble binary signal generated by the binary signal generating unit is in a mode of following a wobble on the optical disc; and a condition in which the system is in a mode of recording information on the optical disc.

9. The information recording system according to claim 1 ,

wherein the noise reduction unit reduces a displacement exceeding the displacement threshold calculated by the threshold calculation unit to a displacement multiplied by a displacement reduction gain value, and

wherein the system further comprises a displacement reduction gain selection unit for switching the displacement reduction gain value according to a state of the system.

10. The information recording system according to claim 9 , further comprising a binary signal generating unit for generating a wobble binary signal based on the push-pull signal,

wherein the displacement reduction gain selection unit switches the displacement reduction gain value according to at least one of the following conditions: whether the system is in a track following mode; whether the wobble binary signal generated by the binary signal generating unit is in a mode of following a wobble on the optical disc; and whether the system is in a mode of recording information on the optical disc.

11. An information recording method for recording information on an optical disc using a reference clock signal generated based on a push-pull signal including a wobble frequency component, the method comprising:

an amplitude obtaining step of obtaining an amplitude value of the push-pull signal;

a threshold calculation step of calculating a displacement threshold of the push-pull signal based on an amplitude value obtained in the amplitude obtaining step; and

a noise reduction step of generating a corrected push-pull signal by correcting the push-pull signal such that a displacement exceeding the displacement threshold is reduced,

wherein the reference clock signal is generated based on the corrected push-pull signal generated in the noise reduction step.