KR100917195B1 - Recording Method of Phase-change Optical Disc - Google Patents

Abstract

The present invention relates to a recording method of a phase change optical disk, wherein in the optical disk recording method, the start position of the last pulse of the 3T mark or the 4-8T mark is moved forward by a predetermined time t from the start position of each reference clock. Or to be shifted backwards.

Therefore, according to the present invention, the position of the small 2T, 3T mark and the large 4-8T mark derived when the multi-pulse (4-8MP) of the 4-8T mark is moved to improve the leading edge characteristics of the 4-8T mark. The imbalance is shifted by shifting the start position of the last pulses (3LP, 4-8LP) of the 3T mark or the 4-8T mark by a predetermined time t (0 <t≤3 / 16T) from the start position of each reference clock. The location imbalance can be reduced or eliminated.

Phase change optical disc recording, jitter characteristics

Description

Recording Method of Phase-change Optical Disc

1 is a view showing a conventional recording pulse waveform

Fig. 2A schematically shows a recording pulse waveform of a conventional 2-8T mark.

Figure 2b shows the waveform of the 2-8T mark when the multi-pulse (4-8MP) of the 4-8T mark is moved forward (right) than the reference clock in order to improve the leading edge characteristics of the conventional 4-8T mark. Schematic drawing

FIG. 2C is a diagram showing tab pictures of marks 2 to 8T when recording using the recording pulse waveform of FIG. 2A; FIG.

FIG. 2D is a diagram showing a tap photo of 2 to 8T marks when recording using the recording pulse waveform of FIG. 2B; FIG.

3A is a diagram showing recording pulse waveforms of marks 2-4T according to the present invention;

FIG. 3B is a diagram showing tab pictures of 2 to 4T marks when recording using the recording pulse waveform of FIG. 3A; FIG.

4A and 4B are graphs showing the jitter of the number of direct overwrites when evaluated after recording using the recording pulse waveform and the conventional recording pulse waveform of the present invention, respectively.

5 (a) and 5 (b) are graphs showing power margins when evaluated after recording using the recording pulse waveform and the conventional recording pulse waveform of the present invention, respectively.

6 (a) and 6 (b) are graphs showing the tentative tilt margins of jitter, respectively, measured after recording using the recording pulse waveform and the conventional recording pulse waveform of the present invention.

7 (a) and 7 (b) are graphs showing the radial tilt margins of the jitter when recording and evaluating using the recording pulse waveform and the conventional recording pulse waveform of the present invention, respectively.

8 is a schematic cross-sectional view of a phase conversion optical disk;

* Explanation of symbols for the main parts of the drawings

11: substrate 12: reflective layer

13: lower dielectric protective layer 14: lower interface layer

15: recording layer 16: upper interface layer

17: upper dielectric protective layer 18: polycarbonate cover sheet

The present invention relates to a recording method of a phase change optical disc, and more particularly, to a recording method of a phase change optical disc for improving the repetitive recording characteristics of an optical disc.

With the advent of the multimedia era, which comprehensively deals with video signals, audio signals and computer data signals including moving and still images, package media (e.g., various discs including CDs and DVDs) has become widespread. The same trend is expected to be more prominent.

Package media such as compact discs (CDs) and digital video (or multifunction) discs (DVDs) are largely composed of a substrate and a recording film and a protective film for recording information. Among these optical discs, read-only memory (ROM) optical discs have a circumferential direction formed with servo, position information or pit-shaped fine grooves, and have a reflective layer.

On the other hand, in the case of a recordable optical disc capable of recording information only once, and in the case of a rewritable optical disc capable of repeatedly writing, reading and erasing information, in addition to the pre-pits and the reflective layer, It is composed of a recordable die, a phase change or magneto-optical recording layer, and a protective layer for protecting the recording layer. Such repeatable disks have recently become higher in capacity and are expected to be used as storage media for personal computers (PCs) in addition to audio, video, music files, and playback. In order to be able to record enough repetitive recording media for PC, it is necessary to be able to record and play a much larger number of repetitive recordings than for audio / video.

When a laser light source is irradiated to record or read information on these disks, the laser light is incident on a transparent polycarbonate substrate having a thickness of 0.6 mm or more in the above-described conventional optical disk, but recently, a short wavelength of blue band for high density recording ( 405 nm) When a laser is incident using a high numerical aperture (NA) objective lens, it passes through a cover layer of about 0.1 mm and enters a protective layer or an information recording layer on which information is recorded, and then a reflective layer. And a disk structure which is reflected by these multilayer films and returns to the photosensor (detector; generally photodiode).

In a phase change method of an iterative recording type optical disc, information is recorded as an amorphous mark on a crystalline matrix. In order to generate the amorphous mark, a laser must be irradiated. However, since the shape of the mark cannot be adjusted well due to heat accumulated when using a single pulse, a multi pulse as shown in FIG. 1 will be used. Doing.

FIG. 1 shows a conventional general recording pulse waveform, which defines three different laser power levels. The three power levels include a write power level (Pw: Write power level), which is a peak power of a pulse, and erase power (Pe) for erasing portions except for an overwrite mark to form a crystalline space. ), There is a bottom power (Pb: bottom power) level that defines the lowest power of the laser pulse.

In addition, FP is the first pulse, LE is the leading erase power time duration, MP is the Multi Pulse or Center Pulse, LP is the Last Pulse, TE Is a trailing cooling period deviation from a negative NRZI ending position. For example, 3FP is a first pulse of 3T mark, and 4-8MP is a 4-8T mark of multi-pulse. , 2TE represents the trailing cooling period deviation of the 2T mark, and 4-8LP represents the last pulse of the 4-8T mark.

Generally, the process based composition used for BD (Blue-ray Disc) recording using the blue band wavelength has growth dominant characteristics and the size of recording pulse width or cooling pulse width. The shape of the mark changes sensitively according to the position of each pulse.

Fig. 2A shows a conventional recording pulse waveform of 2T to 8T marks, in which all MP and LP positions are aligned with the rising edges of the corresponding reference clocks. The state of the 2-8T mark when recorded with the laser pulse in this case is shown in Fig. 2D. In this case, the trailing edge portion has a clear boundary between the crystalline and amorphous phases than the leading edge portion, and thus, when the laser is read back by the laser, the signal difference clearly appears at the boundary portion, and thus the jitter characteristic is good.

The recording principle of the phase change optical disk is to melt the crystalline and cool it at a high speed so that the melted part becomes amorphous. If the cooling speed is slow, the crystalline part grows from the adjacent part and reduces the part that can become amorphous.

In the conventional recording method, the cooling rate is lowered due to the heat applied by 4-8MP following 4-8FP of 4-8T, thereby reducing the amorphous area of the leading edge part. The jitter characteristic becomes bad.

In order to improve this, as shown in FIG. 2B, by moving the 4-8MP following the 4-8FP to the right with respect to the 4-8T mark, the heating time by 4-8MP is delayed, as shown in FIG. 2C. As a result, the amount of crystalline growth in amorphous phase is reduced, thereby improving the jitter characteristic at the leading edge of each 4-8T mark.

However, as described above, when the multi-pulse (4-8MP) of the 4T mark is moved to the right to improve the jitter characteristics of the leading edges of the 4-8T marks, the leading edges of the 4-8T marks become wider in the amorphous area. This produces the effect of shifting to the left, which results in jitter reduction due to an imbalance in the position of occurrence between the large marks of 4 to 8T and the small marks of 2T and 3T.

Accordingly, it is an object of the present invention to provide a method for recording a phase change type optical disc which reduces or eliminates the increase in jitter derived when the multi-pulse of the 4-8T mark is moved to improve the leading edge characteristics of the 4-8T mark. It is for.

The recording method of the phase change optical disk according to the present invention for achieving the above object shifts the start position of the last pulse of the 3T mark or the 4-8T mark forward or backward by a predetermined time (t) from the start position of each reference clock. to be shifted.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

In addition, the terms used in the present invention was selected as a general term widely used as possible now, but in certain cases, the term is arbitrarily selected by the applicant, in which case the meaning is described in detail in the corresponding description of the invention, It is to be clear that the present invention is to be understood as the meaning of terms rather than names.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3A shows a pulse waveform for implementing one embodiment of the present invention, and FIG. 3B shows a tap photo of a recording mark recorded using the pulse waveform.

As shown in FIG. 3A, in the pulse waveform according to the embodiment of the present invention, the start position of the multi-pulse (4-8MP) of the 4-8T mark is a predetermined time omnidirectional than the reference clock of the multi-pulse (4-8MP). In the recording method of a phase change optical disk for recording with a recording pulse waveform moved in the right direction in Fig. 3A, the last multi-pulse 3LP of 3T mark and the last pulse 4LP of 4-8T mark (represented by 4T mark). ) Is recorded on the phase change optical disk by using a recording pulse waveform shifted from the start edge of each of the Rx edges by a predetermined time t (0 <t <3 / 16T) from the reference clock (leftward in Fig. 3a). do. Step photographs of 2T, 3T, and 4T when recording using the above-described recording pulse waveform are as shown in Fig. 3B.

The recording pulse waveform according to the embodiment described above is an example in which the recording pulse waveforms of the 3T and 4T marks are modified, but the present invention is not limited thereto, and the start position of only the last pulse 3LP in the recording pulse waveform of the 3T mark is not limited thereto. May use a recording pulse waveform which is shifted backward by the time t (0 &lt; t &lt; 3 / 16T) with respect to the start position of the reference clock.

When data is recorded using such a recording pulse waveform, the multi-pulse (4-8MP) of the 4-8T mark is moved ahead of the predetermined time to improve the jitter characteristic of the leading edge of the 4-8T mark (in the drawing). When moving from the reference clock to the right), the positional imbalance between the small 2T, 3T mark and the 4-8T mark due to the effect that the leading edge of the 4-8T mark is moved rearward (left in the drawing) is changed to 3T mark or 4 By shifting the start positions of the last pulses 3LP and 4-8LP of the ~ 8T mark to the rear (left in Fig. 3A) by a predetermined time t (0 <t≤3 / 16T) from the start of each reference clock. By compensating for the position imbalance, the side effect of jitter increase due to the imbalance of the position occurring between the large marks 4 to 8T and the small marks 2T and 3T can be solved.

(Example)

Fig. 8 shows the Ag alloy reflecting layer 12 and the lower dielectric layer of ZnS-SiO ₂ on a dounut-shaped polycarbonate substrate 11 having an inner diameter of 15 mm, an outer diameter of 120 mm, a thickness of 1.1 mm, and a track pitch of 0.32 um (with land and groove). Protective layer 13, lower interface layer 14, recording layer 15 formed of an alloy of Ge-Sb-Te series, upper interface layer 16, and upper dielectric protective layer 17 of ZnS-SiO ₂ The multilayer thin film formed by laminating | stacking is formed. Then, a 80 μm polycarbonate cover sheet 18 is bonded to the multilayer thin film layer with a UV resin of 20 μm to manufacture a phase change optical disc, and the optical disc is initialized using an initialization device. Thereafter, the recording pulse waveform (FIG. 3A) for implementing the above-described present invention is recorded and reproduced using an optical disk driver and an evaluation equipment (for example, Pulstec's DDU-1000 equipment).

At this time, the recording and reproducing condition is as follows.

Channel Bit Clock = 132 MHz (1T = 7.5757 nano second)

Linear Velocity = 10.56 m / s

Disk Capacity = 23.3 GB / Single Side

Jitter Measuring Equipment: Yokogawa TA520

Sampling: 30,000

Reading Laser Power = 0.35㎽

Bottom Laser Power = 0.5㎽

Write Laser Power = 5.2㎽

Erase Laser Power = 1.9㎽

The position of the leading edge and trailing edge of the jitter is normalized to a channel bit length (CBL) in which the distribution of the deviation from the reference position in accordance with the PLL clock is normalized. In order to measure the N repetitive recording jitter, the waveform is recorded using a randomly mixed N-circuit random pulse waveform (2T, 3T, 4-8T) in one track.

(A) and (b) of FIG. 4, (a) and (b) of FIG. 5, (a) and (b) of FIG. 6, and (a) and (b) of FIG. The results of the recording evaluation using the recording and reproducing conditions of the above-described embodiment at the frequency and the disk rotation speed are shown in FIGS. 4A, 5A, 6A, and 7A. Is evaluated after recording using the recording pulse waveform (FIG. 3A) of this invention, and FIG. 4 (b), FIG. 5 (b), FIG. 6 (b), and FIG. 7 (b) are 1x speed. It is evaluated after recording at a double speed using a conventional recording pulse waveform conventionally used in Fig. 1. In each figure, the reference jitter for each recording pulse waveform is 10% for the upper limit of jitter evaluated using conventional EQ (Equalizer), and 6.5% for the upper limit of jitter evaluated using limit EQ (in bold lines in each figure). Display).

As shown in (a) and (b) of FIG. 4, when the conventional recording pulse waveform (FIG. 1) is used, jitter (%) for direct overwrite cycle when conventional EQ is used. Although a portion exceeding the upper limit of 10% has been generated, in the case of the present invention (FIG. 4 (a)), it can be seen that all are located below the upper limit of 10%, which is the reference jitter. can confirm.

5A and 5B show the margins of the recording power Pw of the present invention and the conventional recording pulse waveform, respectively, as shown in FIG. When the conventional EQ is recorded and the conventional EQ is evaluated, the range with the reference jitter of 10% or less is 4.9 Hz to 5.7 Hz, but in the conventional case, as shown in FIG. It can be seen that the%) is exceeded.

6A and 6B show tangential tilt margins when the present invention and the conventional recording pulse waveform are used, respectively, and FIGS. 7A and 7B show the present invention and The radial tilt margin when the conventional recording pulse waveform is used is shown.

As shown in (a) and (b) of FIG. 6, in the case of the present invention of FIG. 6 (a) of the present invention, the tangent tilt margin of jitter is within a range of −0.25 <θ <0.2. On the contrary, in the case of FIG. 6 (b), the jitter tangential tilt margin is significantly improved in the range of -0.1 &lt;

In addition, in the case of the present invention shown in FIG. 7A when evaluated with conventional EQ as shown in FIGS. 7A and 7B, the radial tilt margin of jitter is -0.8 <θ <0.75. In contrast, in the conventional case illustrated in FIG. 7B, the radial tilt margin of jitter is larger in the case of the present invention, -0.75 <θ <0.6.

As described above, according to the present invention, the position of the small 2T, 3T mark and the large 4-8T mark derived when the multi-pulse (4-8MP) of the 4-8T mark is moved to improve the leading edge characteristics of the 4-8T mark. The imbalance is shifted by shifting the start position of the last pulses (3LP, 4-8LP) of the 3T mark or the 4-8T mark by a predetermined time t (0 <t≤3 / 16T) from the start position of each reference clock. There is an effect that the position imbalance can be reduced or eliminated.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (9)

In the recording method of an optical disc, Write a mark to an optical disk with 3T to 8T marks using a pulse waveform including first pulse and last pulse, And the start position of the last pulse is shifted forward or backward by a predetermined time (t) than the start position of each reference clock. The method of claim 1, And said predetermined time (t) is larger than zero and smaller than 3T / 16. The method of claim 2, And T is a period of a reference clock. The optical disc recording method according to claim 1, wherein the pulse waveform may further include multi-pulses, and when the multi-pulse is included, the first pulse, the multi-pulse, and the last pulse are sequentially recorded. The method of claim 4, wherein And the multi-pulse of the pulse waveform is moved forward than the reference clock of the multi-pulse waveform. A 3T to 8T mark recorded using a pulse waveform comprising a first pulse and a last pulse, The start position of the last pulse is shifted forward or backward by a predetermined time (t) than the start position of the reference clock. The method of claim 6, And the predetermined time (t) is greater than 0 and less than 3T / 16. The method of claim 7, wherein And T is a period of a reference clock. The method of claim 6, The pulse waveform may further include multiple pulses, and when the multiple pulses are included, the first pulse, the multi pulse, and the last pulse are sequentially recorded.

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