Optical disc with different wobble patterns in different grooves
The S/N ratio is improved for recording data to grooves ( 2 - 1,2 - 2 ) of an optical disc so that as much information as possible can be recorded at the lowest possible frequency band. An optical disc using wobble patterns to record different information has a first groove ( 2 - 1 ) having a first wobble pattern ( 22 ) in which one wobble period has a sharp rising edge and a gradual falling edge; and a second groove ( 2 - 2 ) having a second wobble pattern ( 24 ) in which one wobble period has a gradual rising edge and a sharp falling edge. Each of the first and the second wobble pattern is represented by a first fundamental and a second harmonic of a Fourier series. The polarity of the second harmonic, which is an even harmonic, of the second wobble pattern is opposite that of the first wobble pattern. A method for manufacturing this optical disc is also provided.
1. An optical disc using wobble patterns to record different information, comprising:
a first groove having a first wobble pattern in which one wobble period has a sharp rising edge and a gradual falling edge;
a second groove having a second wobble pattern in which one wobble period has a gradual rising edge and a sharp falling edge;
wherein the first wobble pattern is represented by a first fundamental and a second harmonic of a Fourier series; and
wherein the second wobble pattern is represented by a first fundamental and a second harmonic of a Fourier series, the polarity of the second harmonic, which is an even harmonic, being opposite the polarity of the second harmonic of the first wobble pattern.
2. An optical disc according to claim 1 ,
wherein the first wobble pattern is further represented by a third harmonic and a fourth harmonic of a Fourier series; and
wherein the second wobble pattern is further represented by a third harmonic and a fourth harmonic of a Fourier series, where the polarity of the second harmonic and the polarity of the fourth harmonic, which are both even harmonics, are opposite the polarity of the second harmonic and the fourth harmonic of the first wobble pattern.
3. An optical disc according to claim 1 , wherein the first wobble pattern is further represented by using harmonics to an n-th harmonic, where n is a finite even number, of a Fourier series; and
wherein the second wobble pattern is further represented by using harmonics to an n-th harmonic, where n is a finite even number, of a Fourier series where the polarity of the even harmonics of the second wobble pattern are opposite those of the even harmonics of the first wobble pattern.
4. An optical disc according to claim 1 , wherein a ratio of a second coefficient of the second harmonic to a first coefficient of the first fundamental ranges from −13.5 dB to −10 dB.
5. An optical disc according to claim 4 , wherein said ratio further ranges from −13.5 dB to −12 dB.
6. An optical disc according to claim 1 , comprising:
data sub-blocks which include address data of physical addresses of the optical disc as the different information; and
a reference sub-block which includes one of the first wobble pattern and the second wobble pattern to be used as a reference for demodulating waveforms of the address data in the data sub-blocks.
7. A method for manufacturing an optical disc using wobble patterns to record different information, comprising steps of:
forming a first groove having a first wobble pattern represented by a first fundamental and second harmonic of a Fourier series, in which one wobble period has a sharp rising edge and a gradual falling edge; and
forming a second groove having a second wobble pattern represented by a first fundamental and second harmonic of a Fourier series, in which one wobble period has a gradual rising edge and a sharp falling edge such that the polarity of the second harmonic, which is an even harmonic, is opposite the polarity of the second harmonic of the first wobble pattern.
8. A method for manufacturing an optical disc according to claim 7 , wherein the step of forming the first groove further forms the first wobble pattern using a third harmonic and a fourth harmonic of a Fourier series; and
wherein the step of forming the second groove further forms the second wobble pattern using a third harmonic and a fourth harmonic of a Fourier series such that the polarity of the second harmonic and the polarity of the fourth harmonic, which are both even harmonics, are opposite the polarity of the second harmonic and the fourth harmonic of the first wobble pattern.
9. A method for manufacturing an optical disc according to claim 7 , wherein the step of forming the first groove further forms the first wobble pattern using harmonics to an n-th harmonic (where n is a finite even number) of a Fourier series; and
wherein the step of forming the second groove further forms the second wobble pattern using harmonics to the n-th harmonic (where n is a finite even number) of a Fourier series such that the polarity of the even harmonics of the second wobble pattern are opposite the polarity of the even harmonics of the first wobble pattern.
10. A method for manufacturing an optical disc according to claim 7 , wherein a ratio of a second coefficient of the second harmonic to a first coefficient of the first fundamental ranges from −13.5 dB to −10 dB.
11. A method for manufacturing an optical disc according to claim 10 , wherein said ratio further ranges from −13.5 dB to −12 dB.