Method for optically recording information on an optically re-writable information medium

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein a relation between said length (ML) of said mark along said track and a diameter (BD) of said laser spot satisfies ML≦BD, and
• a product of said pulse width of said rectangular recording pulse signal and said relative linear velocity is less than 20% of said diameter (BD) of said laser spot.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein a size of said mark is modulated according to said information by means of modulating a pulse width of said off-pulse signal so that a time interval between a rising edge of said rectangular recording pulse signal and a rising edge of said rectangular erasing pulse signal corresponds to said size of said mark, and
• wherein a relation between said length (ML) of said mark along said track and a diameter (BD) of said laser spot satisfies ML≦BD, and
• a product of said pulse width of said rectangular recording pulse signal and said relative linear velocity is less than 20% of said diameter (BD) of said laser spot.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said track is divided into a plurality of cells and said mark is recorded in said cell so that a center of said mark is placed at a center of said cell by means of adjusting both a rising edge of said rectangular recording pulse signal and a rising edge of said rectangular erasing pulse signal, and
• wherein a relation between said length (ML) of said mark along said track and a diameter (BD) of said laser spot satisfies ML≦BD, and
• a product of said pulse width of said rectangular recording pulse signal and said relative linear velocity is less than 20% of said diameter (BD) of said laser spot.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said size of said mark is fine-adjusted by controlling timing of a falling edge of said rectangular recording pulse signals, and
• wherein a relation between said length (ML) of said mark along said track and a diameter (BD) of said laser spot satisfies ML≦BD, and
• a product of said pulse width of said rectangular recording pulse signal and said relative linear velocity is less than 20% of said diameter (BD) of said laser spot.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said size of said mark is fine-adjusted by controlling said strength of said laser light modulated by said rectangular recording pulse signal, and
• wherein a relation between said length (ML) of said mark along said track and a diameter (BD) of said laser spot satisfies ML≦BD, and
• a product of said pulse width of said rectangular recording pulse signal and said relative linear velocity is less than 20% of said diameter (BD) of said laser spot.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said size of said mark is fine-adjusted by controlling timing of a falling edge of said rectangular recording pulse signal, and
• wherein timing of a rising edge of said rectangular recording pulse signal is controlled so that a center of said mark is placed at a center of said cell, and
• wherein a relation between said length (ML) of said mark along said track and a diameter (BD) of said laser spot satisfies ML≦BD, and
• a product of said pulse width of said rectangular recording pulse signal and said relative linear velocity is less than 20% of said diameter (BD) of said laser spot.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein a relation between a length of a minimum mark (MLmin) along said track except when there is no mark and a diameter (BD) of said laser spot satisfies MLmin/BD≦0.10, and
• each level of said multi-level signal is assigned so that the level difference between adjacent levels becomes equidistant except when there is no mark.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein a size of said mark is modulated according to said information by means of modulating a pulse width of said off-pulse signal so that a time interval between a rising edge of said rectangular recording pulse signal and a rising edge of said rectangular erasing pulse signal corresponds to said size of said mark, and
• wherein a relation between a length of a minimum mark (MLmin) along said track except when there is no mark and a diameter (BD) of said laser spot satisfies MLmin/BD≦0.10,
• and each level of said multi-level signal is assigned so that the level difference between adjacent levels becomes equidistant except when there is no mark.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said track is divided into a plurality of cells and said mark is recorded in said cell so that a center of said mark is placed at a center of said cell by means of adjusting both a rising edge of said rectangular recording pulse signal and a rising edge of said rectangular erasing pulse signal, and
• wherein a relation between a length of a minimum mark (MLmin) along said track except when there is no mark and a diameter (BD) of said laser spot satisfies MLmin/BD≦0.10, and
• each level of said multi-level signal is assigned so that the level difference between adjacent levels becomes equidistant except when there is no mark.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said size of said mark is fine-adjusted by controlling timing of a falling edge of said rectangular recording pulse signal, and
• wherein a relation between a length of a minimum mark (MLmin) along said track except when there is no mark and a diameter (BD) of said laser spot satisfies MLmin/BD≦0.10, and
• each level of said multi-level signal is assigned so that the level difference between adjacent levels becomes equidistant except when there is no mark.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said size of said mark is fine-adjusted by controlling said strength of said laser light modulated by said rectangular recording pulse signal, and
• wherein a relation between a length of a minimum mark (MLmin) along said track except when there is no mark and a diameter (BD) of said laser spot satisfies MLmin/BD≦0.10, and
• each level of said multi-level signal is assigned so that the level difference between adjacent levels becomes equidistant except when there is no mark.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said size of said mark is fine-adjusted by controlling timing of a falling edge of said rectangular recording pulse signal, and
• wherein timing of a rising edge of said rectangular recording pulse signal is controlled so that a center of said mark is placed at a center of said cell, and
• wherein a relation between a length of a minimum mark (MLmin) along said track except when there is no mark and a diameter (BD) of said laser spot satisfies MLmin/BD≦0.10, and
• each level of said multi-level signal is assigned so that the level difference between adjacent levels becomes equidistant except when there is no mark.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein a relation between a length of a maximum mark (MLmax) along said track, except for a mark that has about the same length as a diameter of said laser spot, and a diameter (BD) of said laser spot satisfies MLmax/BD≦0.70, and
• each occupied mark ratio of said multi-level signal is assigned so that the difference between said occupied mark ratios corresponding to adjacent levels of said multi-level signal becomes equidistant except for said mark that has about the same length as said diameter of said laser spot.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein a size of said mark is modulated according to said information by means of modulating a pulse width of said off-pulse signal so that a time interval between a rising edge of said rectangular recording pulse signal and a rising edge of said rectangular erasing pulse signal corresponds to said size of said mark, and
• wherein a relation between a length of a maximum mark (MLmax) along said track, except for a mark that has about the same length as a diameter of said laser spot, and a diameter (BD) of said laser spot satisfies MLmax/BD≦0.70, and
• each occupied mark ratio of said multi-level signal is assigned so that the difference between said occupied mark ratios corresponding to adjacent levels of said multi-level signal becomes equidistant except for said mark that has about the same length as said diameter of said laser spot.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said track is divided into a plurality of cells and said mark is recorded in said cell so that a center of said mark is placed at a center of said cell by means of adjusting both a rising edge of said rectangular recording pulse signal and a rising edge of said rectangular erasing pulse signal, and
• wherein a relation between a length of a maximum mark (MLmax) along said track, except for a mark that has about the same length as a diameter of said laser spot, and a diameter (BD) of said laser spot satisfies MLmax/BD≦0.70, and
• each occupied mark ratio of said multi-level signal is assigned so that the difference between said occupied mark ratios corresponding to adjacent levels of said multi-level signal becomes equidistant except for said mark that has about the same length as said diameter of said laser spot.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium:
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said size of said mark is fine-adjusted by controlling timing of a falling edge of said rectangular recording pulse signal, and
• wherein a relation between a length of a maximum mark (MLmax) along said track, except for a mark that has about the same length as a diameter of said laser spot, and a diameter (BD) of said laser spot satisfies MLmax/BD≦0.70, and
• each occupied mark ratio of said multi-level signal is assigned so that the difference between said occupied mark ratios corresponding to adjacent levels of said multi-level signal becomes equidistant except for said mark that has about the same length as said diameter of said laser spot.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium:
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said size of said mark is fine-adjusted by controlling said strength of said laser light modulated by said rectangular recording pulse signal, and
• wherein a relation between a length of a maximum mark (MLmax) along said track, except for a mark that has about the same length as a diameter of said laser spot, and a diameter (BD) of said laser spot satisfies MLmax/BD≦0.70, and
• each occupied mark ratio of said multi-level signal is assigned so that the difference between said occupied mark ratios corresponding to adjacent levels of said multi-level signal becomes equidistant except for said mark that has about the same length as said diameter of said laser spot.

A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:

• focusing a laser light to a laser spot to form a mark on said optically re-writable information medium;
• and
• modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and
• wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal an off-pulse signal and a second rectangular erasing pulse signal,
• said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark,
• said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark,
• a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks,
• said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and
• a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and
• wherein said size of said mark is fine-adjusted by controlling timing of a falling edge of said rectangular recording pulse signal, and
• wherein timing of a rising edge of said rectangular recording pulse signal is controlled so that a center of said mark is placed at a center of said cell, and
• wherein a relation between a length of a maximum mark (MLmax) along said track, except for a mark that has about the same length as a diameter of said laser spot, and a diameter (BD) of said laser spot satisfies MLmax/BD≦0.70, and
• each occupied mark ratio of said multi-level signal is assigned so that the difference between said occupied mark ratios corresponding to adjacent levels of said multi-level signal becomes equidistant except for said mark that has about the same length as said diameter of said laser spot.