JP2005228440A - Optical disk unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk unit capable of forming a good recording mark in which the position of a rear edge is made clear by eliminating the tapering of the rear end part of the recording mark. <P>SOLUTION: The optical disk unit is provided with an optical pickup for irradiating the recording surface of an optical disk with a laser beam, and a drive circuit for driving the optical pickup, and records data by forming a recording mark on the recording surface of the optical disk by the laser beam, wherein the laser beams of a first write level and a bias level are alternately output during the period of forming the recording mark from its distal end to the near side of the the rear end when a continuous recording mark is formed, and the laser beam of a second write level higher than the first write level is output in the period of forming the rear end part of the recording mark. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an optical disc apparatus that records data by forming a recording mark on a recording surface of an optical disc, and relates to a technique for forming a recording mark having a good shape.

  For example, in recordable CDs (compact discs), DVDs (digital versatile discs), and optical discs for blue-violet lasers, the recording surface is phase-changed by the heat of the laser beam, thereby forming recording marks and data. There is something that realizes recording.

  For recordable CDs and DVDs, media that can be erased and rewritten (CD-RW, DVD-RW, DVD + RW, etc.) and media that can be written only once (CD-R) depending on the composition of the recording surface. , DVD-R, DVD + R, etc.), and there are a plurality of types of media (for example, DVD-R, RW and DVD + R, RW) having different characteristics relating to the generation of recording marks.

  When forming a recording mark, when a recording mark is generated by irradiating laser light with the same intensity for a predetermined section, as shown in FIG. 4A, a trace like a tapered tail is formed at the rear end portion of the recording mark. X1 may be formed.

  Further, as shown in FIG. 4B, as a general laser output waveform used for DVD-RW recording, a peak level for forming a recording mark, a bias level that does not affect the formation erasing of the recording mark, and Even when a multi-pulse output waveform that alternately repeats is used, a trace X2 like a tapered tail may be formed at the rear end portion of the recording mark.

  Such a tapering trace is not preferable because it appears as a decrease in the S / N ratio of the reproduction signal or jitter of the reproduction signal during data reproduction.

Conventionally, various laser output waveforms (also referred to as recording strategies) are used to generate a good recording mark with a clear front edge and rear edge by eliminating the taper of the leading and trailing edges of the recording mark. Has been proposed. For example, Patent Document 1 discloses a technique for accurately outputting a laser pulse having a short period, and Patent Document 2 discloses a technique for increasing the pulse level of the laser beam at the head portion in order to reduce the taper at the head portion of the recording mark. Proposed. Further, in Patent Documents 3 and 4, in order to reduce the taper of the rear end portion of the recording mark, as shown in FIG. 4C, the output W1 lower than the bias level is performed at the end of the recording pulse, so that the rear end portion. Techniques have been proposed that allow the to cool rapidly.
JP-A-11-213428 JP 2001-291261 A Japanese Patent Laid-Open No. 2001-351239 (page 17, FIGS. 8 (d) and 8 (e)) Japanese Patent Laying-Open No. 2003-085753 (page 13, FIG. 17)

  The inventor of the present application examined a laser output waveform capable of clarifying the rear edge by eliminating the taper of the rear end of the recording mark at the time of recording on the DVD-RW. Therefore, in the techniques disclosed in Patent Documents 3 and 4, the output level immediately after the recording pulse is made lower than the bias level, so that the trailing end portion of the recording mark is rapidly cooled and becomes a taper like a tail. Although X3 decreased, it was found that the trace X3 could not be completely erased and there was still room for improvement.

  Further, it has been found that the techniques disclosed in Patent Documents 3 and 4 have the following problems because the laser output level needs to be lower than the bias level. That is, when the bias level of the laser output is set to the minimum level necessary for reducing power consumption, for example, the laser output becomes lower than the minimum level when forming the rear edge of the recording mark. Immediately after that, the laser output becomes unstable.

  Further, when the bias level is set to zero or very low, it is difficult in the first place to make the laser output level lower than the bias level, and the techniques of Patent Documents 3 and 4 cannot be used. There was also.

  An object of the present invention is to provide an optical disc apparatus capable of forming a good recording mark capable of clearly reading the rear edge of the recording mark with almost no taper at the rear end portion of the recording mark. .

  Another object of the present invention is to provide an optical disc apparatus capable of forming a good recording mark with a clear rear edge by eliminating the taper of the rear end portion of the recording mark even when the bias level is set low. There is.

  In order to achieve the above object, the present invention comprises an optical pickup that irradiates a recording surface of an optical disc with a laser beam and a drive circuit that drives the optical pickup, and records on the recording surface of the optical disc by the irradiation of the laser beam. In an optical disk apparatus that records data by forming a mark, when forming a series of recording marks, the output level of the laser beam that is output for forming the trailing edge of the recording mark is It was set as the structure set so that it might become higher than the output level of the laser beam output for formation of the front part from the front end to the rear end.

  According to such means, the output waveform of the laser beam when forming the rear end portion of the recording mark is shifted from a high level to, for example, a bias level (or may be an erase level). Since the output level at the end is increased, the level difference before and after that can be increased. Since the difference in output level is large, the trailing edge of the recording mark can be eliminated and the rear edge can be made clear.

  Also, since the rear edge is made clear by increasing the laser output that forms the trailing edge of the recording mark, even if the bias level is set low and it is difficult to output at a level lower than the bias level, there is no problem. The method of the present invention can be applied.

  The reason why the rear edge of the recording mark becomes clear by increasing the output level of the laser beam at the rear end portion of the recording mark and increasing the level difference immediately after that is as follows. That is, when the output of the laser beam at the rear end portion is increased, the amount of heat generated by the irradiation of the laser beam is increased, and thermal interference in which this heat is diffused before and after the irradiation position is increased. Further, although the recording mark spreads backward due to this thermal interference, the way of spreading is not a taper shape, and the amount of heat spreads radially in the width direction. On the other hand, since the laser output immediately after that becomes a relatively low level, the influence is drowned out by the above-described thermal interference, and the influence on the recording mark is hardly visible. Therefore, although the rear end portion of the recording mark is slightly wider, a taper mark such as a tail is not formed, and the position of the rear edge becomes clear.

  Specifically, the output level of the laser light emitted from the optical pickup includes a first light level at which a recording mark can be formed on the recording surface, and a second light level higher than the first light level. And a erase level that can erase the recording mark and a bias level that is output to keep the operating characteristics of the laser output element constant and does not affect the erasure formation of the recording mark. When the recording mark is formed, the laser beam of the first write level and the bias level is alternately output during the period in which the front part from the front end to the rear end of the recording mark is formed, and the period in which the rear end part of the recording mark is formed. It is preferable that the second light level laser beam is set to be output.

  With such a configuration, it is possible to easily realize control for increasing the laser output when forming the rear end portion of the recording mark.

  Further, the output level of the laser light irradiated by the optical pickup further includes a first low level lower than the bias level, and when the continuous recording mark is formed, a rear end portion of the recording mark It may be set such that the level of the laser light output during the period of forming the first light level is changed to the first low level after the second light level.

  According to such a configuration, when an output lower than the bias level is possible, the level difference between the laser output forming the rear end portion and the level immediately thereafter can be increased, so that the rear edge of the recording mark becomes clearer. Can be made.

  The above-described configuration is particularly effective when a DVD-RW medium is used as an optical disk for recording data.

  As described above, according to the present invention, the trailing edge of the recording mark can be almost eliminated, and the rear edge of the recording mark can be made clear. Thereby, it is possible to improve the S / N ratio of the reproduction signal and reduce the jitter of the reproduction signal during data reproduction.

  For example, even when the bias level is set low and it is difficult to realize an output level lower than that, the method of the present invention does not require an output level lower than the bias level. The rear edge of the recording mark can be clarified.

Embodiments of the present invention will be described below with reference to FIGS.
[First Embodiment]
FIG. 1 is a block diagram showing a circuit configuration of an optical disc apparatus according to an embodiment of the present invention.

  The optical disk apparatus of this embodiment is an apparatus for recording and reproducing data on, for example, a DVD-RW optical disk. The motor 11 rotates the optical disk D, a semiconductor laser as a laser output means, and various optical devices. And an optical pickup 12 for irradiating the recording surface of the optical disk D with laser light and detecting its reflected light, a laser drive circuit 21 for driving a semiconductor laser of the optical pickup 12, and an output pattern of the semiconductor laser. The recording pulse generation circuit for generating the recording pulse, the reproduction processing circuit 23 for performing signal processing at the time of data reproduction, the servo control circuit 24 for driving and controlling the objective lens of the motor 11 and the optical pickup 12, and these circuits are integrated. And a controller 25 for controlling the operation.

  According to such a configuration, at the time of data recording, recording data is sent from a separately installed microcomputer or the like to the controller 25, and a recording pulse is generated by the recording pulse generation circuit 22 based on this recording data. The semiconductor laser of the optical pickup 12 is driven according to the pulse. Then, the recording mark is formed by irradiating the recording surface of the optical disc with the laser beam output by this driving. On the other hand, at the time of data reproduction, a read level is output from the semiconductor laser and irradiated onto the recording surface of the optical disc, and the detection signal of the reflected light is binarized by the reproduction processing circuit 23 and reproduced via the controller 25. It is output as data.

  FIG. 2 is a time chart showing an example of a laser output waveform at the time of data recording in the optical disc apparatus.

  In this embodiment, the recording pulse generated by the recording pulse generation circuit 22 based on the recording data (write data) is as shown in FIG.

  First, the level of each signal included in the recording pulse will be described. The level of the recording pulse is higher than the erase level at which the recording surface of the optical disk is melted to be in a crystalline state, the first write level at which the recording surface is melted to be in an amorphous state by being higher than the erase level ( (For example, 120% to 150% of the first write level) includes a second write level and a bias level that is output to keep the operating characteristics of the semiconductor laser constant and does not affect the recording surface.

  Next, the waveform will be described. The level of the recording pulse is first set to the erase level during the period when the write data is at the low level. As a result, the previously recorded amorphous recording mark is returned to the crystalline state and erased.

  In the period in which the write data is set to the high level and the recording mark is formed, first, the multi-pulse output in which the output of the first write level and the bias level is alternately repeated is performed to form the recording mark. Specifically, the output of the first write level at the head of the multi-pulse is output with a delay of one cycle from the write clock after the write data becomes high level. This is because the heat of the leading pulse is conducted to the portion heated by the output of the previous erase level, and the recording mark protrudes forward. As a result, the rising edge of the write data corresponds to the front edge of the recording mark. Thereafter, recording marks having substantially the same width are formed by the multi-pulse.

  Before the falling edge at which the write data becomes low level, a second write pulse higher than the first write pulse is output as the final pulse of the multi-pulse. Thereafter, the bias level is output for a predetermined period. Since the second write pulse is output in this way, the level difference from the output of the bias level immediately after that increases, and this level difference eliminates the taper of the trailing end portion of the recording mark and the trailing edge of the recording mark is clear. It will be something. The reason for this is as explained in the section of means for solving the problem.

  Note that the amount of heat applied to the rear end portion of the recording mark is increased by the output of the second write level, and the amount of heat interference spreading to the surroundings increases, so that the rear edge of the recording mark is at the second write level. Shift backward from the position corresponding to the timing of the falling edge. Therefore, the correction processing is performed so that the output timing of the second light level is shifted forward accordingly. Also, during the last bias level output period, the previously formed recording mark is erased by the second write level thermal interference so that the previously formed recording mark will not remain unerased. It is set shorter than the interval.

  As described above, according to the optical disk apparatus of this embodiment, the trailing edge of the recording mark can be eliminated and the rear edge can be made clear. The ratio can be improved and the jitter of the reproduced signal can be reduced.

In this embodiment, since the rear edge is clarified by increasing the laser output for forming the rear end portion of the recording mark, the bias level is set low, so that it is difficult to output at a level lower than the bias level. Even in this case, the rear edge of the recording mark can be clarified by applying this method without any problem.
[Second Embodiment]
FIG. 3 is a time chart showing an example of a laser output waveform at the time of data recording according to the second embodiment of the present invention.

  This second embodiment is different from the first embodiment only in a part of the laser output waveform forming the recording mark. Therefore, only different points will be described.

  In this second embodiment, as shown in FIG. 3, after the second write level is output, the first low level (lower than the bias level) is formed to form the rear end portion of the recording mark. The output efficiency of the rear end of the recording mark is increased by performing an output of zero output.

  According to such a configuration, since the level difference of the laser output at the rear end portion of the recording mark becomes larger, it is possible to eliminate the taper of the rear end portion of the recording mark and make the rear edge clearer. I can do it. Thereby, it is possible to improve the S / N ratio of the reproduction signal and reduce the jitter of the reproduction signal during data reproduction.

  The present invention is not limited to the above-described embodiment, and various modifications can be made. For example, although a multi-pulse waveform is employed as the recording pulse in the embodiment, the output of the write level is continuously performed instead of the multi-pulse, and finally the output of the second write level higher than the write level is performed. May be made.

  In the above embodiment, since the DVD-RW medium is targeted, an output period of a bias level is provided at the end of the recording pulse. However, for example, when DVD + RW media is targeted, FIG. As indicated by alternate long and short dash lines B1 and B2 in FIG. 3, after the second write level is output, the erase level is set (FIG. 2), or after the second write level is output, a second low level output lower than the erase level is performed. Alternatively, the output waveform may be returned to the erase level (FIG. 3).

  The present invention relates to an optical disk apparatus for recording data on a DVD-RW, an optical disk apparatus for media such as DVD-R, DVD + RW, DVD + R, CD-R, CD-RW, and an optical disk for blue-violet laser. It can be used for an optical disk device intended for the above.

It is a block diagram which shows the circuit structure of the optical disk apparatus of embodiment of this invention. It is a time chart which shows the laser output waveform which concerns on the 1st Embodiment of this invention. It is a time chart which shows the laser output waveform which concerns on the 2nd Embodiment of this invention. It is the figure which showed the laser output waveform in the conventional optical disk apparatus, and the recording mark formed by it.

Explanation of symbols

12 optical pickup 21 laser drive circuit 22 recording pulse generation circuit D optical disc P recording pulse

Claims (4)

An optical pickup for irradiating the recording surface of the optical disc with a laser beam and a drive circuit for driving the optical pickup are provided, and a recording mark is formed on the recording surface of the optical disc by the irradiation of the laser beam to record data. In an optical disk device,
The output level of the laser beam irradiated by the optical pickup includes a first write level capable of forming a recording mark on the recording surface, a second write level higher than the first write level, and an erasing of the recording mark. An erase level, a bias level that is output to keep the operating characteristics of the laser output element constant and does not affect the formation and erasure of the recording mark, and a first low level lower than the bias level are included,
When forming a series of recording marks, the laser light of the first write level and the bias level are alternately output during the period of forming the front portion from the leading end to the trailing end of the recording mark, An optical disc apparatus characterized in that the laser light of the second light level is output during a period for forming the rear end portion, and thereafter the output level of the laser light is lowered to the first low level. An optical disc comprising an optical pickup for irradiating a recording surface of an optical disc with a laser beam and a drive circuit for driving the optical pickup, and recording data by forming a recording mark on the recording surface of the optical disc by the irradiation of the laser beam In the device
When forming a series of recording marks, the output level of the laser beam output for forming the rear end portion of the recording mark is output for forming the front portion of the rear end from the leading end of the recording mark. An optical disc apparatus characterized by being set to be higher than an output level of laser light. The output level of the laser beam irradiated by the optical pickup includes a first write level capable of forming a recording mark on the recording surface, a second write level higher than the first write level, and an erasing of the recording mark. Includes an erase level and a bias level that is output to keep the operating characteristics of the laser output element constant and does not affect the erasure formation of the recording mark,
When forming a series of recording marks, the laser light of the first write level and the bias level are alternately output during the period of forming the front portion from the leading end to the trailing end of the recording mark, 3. The optical disc apparatus according to claim 2, wherein the second light level laser beam is set to be output during a period in which the rear end portion is formed. The output level of the laser light irradiated by the optical pickup further includes a first low level lower than the bias level,
When forming the continuous recording mark, the level of the laser beam output during the period of forming the rear end portion of the recording mark is changed to the first low level after the second write level. 4. The optical disk apparatus according to claim 3, wherein the optical disk apparatus is set.

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