JP2007052866A - Laser power controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser power controller capable of attaining stable laser power control when the recording mark of an optical disk is recorded. <P>SOLUTION: This laser power controller is configured in such a manner that laser power of a mark part is detected several times by a mark part power detecting signal processing means 9 in one multi-pulse emission section, and the laser power is controlled by a calculation means 11 so that the average value of the detected laser power becomes the target laser power, thereby attaining stable laser power control. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to laser power control used when forming a recording mark on an optical disc.

  Conventionally, in order to form a recording mark of quality that can maintain reproduction compatibility on an optical disc, a write strategy and recording power suitable for the optical disc to be recorded are important.

In recent years, as the speed of recording media has increased, optical discs have been developed in order to control the recording power in recording light emission including a pulse train to be recorded in a multi-pulse, as seen in write strategies such as DVD-R and RW. By detecting the space power and not being able to read the peak power emitted directly by the multi-pulse, one laser power is detected in the multi-pulse emission section, and the average value of each multi-pulse emission section is detected. In many cases, control is performed by estimating peak power.
JP 2004-319073 A

  However, the number of types of media has increased, and there are a wide variety of write strategies for forming optimum recording marks for discs that support high to low speeds. Even if the width of multipulses is the same speed, media manufacturers However, it is difficult to stably control the laser power. Therefore, it is necessary to increase the order of the LPF and the set number of band limiting frequencies, and the scale of the detection circuit increases. It becomes expensive.

  In order to solve the above problems, the present invention provides a laser power control apparatus for obtaining a detected value of laser power and controlling laser power more stably.

In order to solve the above-described conventional problems, a laser power control apparatus according to the present invention includes a recording data generation unit that generates a recording data string including multi-pulses, and a light emission pattern that generates a laser emission pulse string from the generated recording data. Generating means, computing means for computing drive current,
Laser drive means for outputting a recording pulse train corresponding to the generated laser emission pulse train and the calculated drive current, a pickup head for outputting a light emission pulse train corresponding to the recording pulse train, and light emission output from the pickup head Laser power detection means for detecting the laser power of the pulse train, mark portion discrimination means for extracting the mark portion of the generated recording data row, and a plurality of timing signals for sampling a plurality of times within one mark portion. A timing generation means, and a mark portion detection setting means for detecting a mark portion having a predetermined length from the extracted mark portions, and outputting a detection timing signal each time the timing generation device generates a timing signal; The laser power detected by the laser power detection means is detected by the mark portion detection. Sampling means based on a detection timing signal output from the setting means, and a mark power detection signal processing means for outputting to the calculation means as a mark power detection signal, the calculation means from the mark power detection signal processing means An average value of the plurality of mark part power detection signals output is set as an estimated value of the laser power of the mark part, and a drive current is calculated so that the estimated value becomes a target laser power.

  With this configuration, the laser power control apparatus of the present invention can estimate the laser power in a multipulse more accurately than in the past.

  According to the laser power device of the present invention, stable laser power control can be performed by accurately estimating the laser power.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block diagram of a laser power control apparatus according to Embodiment 1 of the present invention. 1, the laser power control apparatus according to the first embodiment of the present invention includes a laser power detection means 1, a recording data generation means 2, a space part discrimination means 3, a space part detection setting means 4, a space part power. Detection signal processing means 5, mark part discrimination means 6, timing generation means 7, mark part detection setting means 8, mark part power detection signal processing means 9, switching means 10, calculation means 11, and light emission pattern It is assumed that the generating unit 12, the laser driving unit 13, and the pickup head 14 are configured and controlled by a control unit (not shown).

  Hereafter, each structure and operation | movement of a laser power control apparatus are demonstrated. First, the laser power detection means 1 detects a part of a light emission pulse train corresponding to a recording pulse train generated to form a mark portion and a space portion on an optical disc (not shown), and a pin photodiode or OEIC A detection signal is generated and output by the (optoelectronic integrated circuit).

  The recording data generating means 2 is a data string for recording data such as user data on an optical disc, for example, recording data such as NRZI or NRZ according to a modulation rule such as 1-7 modulation, 2-7 modulation, or 8-16 modulation. It consists of an encoder circuit that outputs a column.

  The space part discriminating means 3 extracts a space part from the mark portion and the output signal of the space part of the recording data string output from the recording data generating means 2, and the space part detection setting means 4 is supplied from the space part discriminating means 3. A detection timing signal indicating that a space portion having a specific length has been detected is output at a timing at which a space portion having a specific length is detected in the recording data length of the space portion which is the output recording data string. The space portion power detection signal processing means 5 is a sample that holds the data of the space portion of the detection signals output from the laser power detection means 1 according to the detection timing signal output from the space portion detection setting means 4. A hold circuit (S / H circuit) or the like is configured, and a signal detected by the detection timing signal is output to the switching means 10 as a space portion power detection signal.

  The mark part discriminating means 6 extracts a mark part from the output signals of the mark part and the space part of the recording data string output from the recording data generating means 2, and the timing generating means 7 performs mark part power detection signal processing described later. The means 9 detects the mark portion and generates a sample timing for performing sample hold, and the sample timing for performing this sample hold can be arbitrarily set. In addition, when generating the sample timing, the timing generation unit 7 generates a plurality of sample timings at a constant period, and in the present embodiment, generates four sample timings. These four sample timings are sample timings for sampling within one multi-pulse interval.

  The mark part detection setting unit 8 detects a mark part having a predetermined mark width from the recording data length (mark width) of the mark portion which is the recording data string output from the mark part discrimination unit 6, and generates the timing part 7. The mark timing power detection signal processing means 9 outputs a detection timing signal that is sampled and held in accordance with the sample timing generated in step (1). In the present embodiment, it is assumed that a mark portion having a mark width of 11T (where T represents one channel bit clock period) is detected.

  The mark part power detection signal processing means 9 extracts a feature of the detection signal from the detection signal output from the laser power detection means 1 by using a band limiting filter or the like, and holds the extracted signal. The detected signal is sampled and held in accordance with the detection timing signal output by the mark portion detection setting means 8 and output to the switching means 10 as a mark portion power detection signal. In the present embodiment, the mark portion power detection signal processing means 9 receives the detection timing signal four times from the mark portion detection setting means 8, and thus performs sample hold of the detected signal four times.

  The switching means 10 switches between the space part power detection signal output from the space part power detection signal processing means 5 and the mark part power detection signal output from the mark part power detection signal processing means 9 under the control of the control means. Output. Then, the calculation means 11 controls the recording power of the recording pulse output from the pickup head 14 based on the space power detection signal and the mark power detection signal output from the switching means 10 under the control of the control means. In order to control the target recording power and the target recording power of the mark portion, it is realized by an analog circuit such as a DSP or an operational amplifier that calculates or outputs the laser driving current by calculating the driving current output to the laser. . The target recording power is held by a storage means (not shown) such as a register or a memory in the laser power control apparatus.

  The light emission pattern generation means 12 converts the recording mark portion and the space portion into a laser light emission pulse train and outputs the recording data sequence output from the recording data generation means 2 on the optical disc. Then, the laser driving means 13 performs recording for outputting the recording mark output from the light emission pattern generating means 12 and the laser emission pulse train in the space portion to the laser diode in accordance with the laser driving current output from the calculation means 11. Convert to pulse train and output. The pickup head 14 outputs the recording pulse train output from the laser driving means 13 to the laser diode, irradiates the optical disc with a light emission pulse corresponding to the recording pulse train, and irradiates the optical disc with a reproduction signal from the detection signal returned. A recording clock signal is generated.

  FIG. 2 is a detection waveform diagram of each part in the first embodiment of the present invention. FIG. 4A shows a recording data string output by NRZ output from the recording data generating means 2. (B) shows a light emission pulse train converted to a laser light emission pulse train by the light emission pattern generating means 12 based on the recording data train of (a) and outputted to the laser of the pickup head 14 by the laser driving means 13. (C) is obtained by detecting the recording pulse output from the pickup head 14 based on the light emission pulse train of (b) by the laser power detection means 1 and band-limiting the detected detection signal by the mark power detection means 9. The waveform of the signal is shown. (D) shows a detection timing signal output from the mark part detection setting means 8 and sampled and held by the mark part power detection signal processing means 9, and (d-1), (d-2), (D-3) and (d-4) are diagrams showing that detection timing signals are output at regular intervals. FIG. 3 is an enlarged view of the signal in FIG.

  Here, the configuration and operation of the laser power control apparatus according to the first embodiment of the present invention will be described in more detail. As shown in FIG. 2B, the recording pulse train outputs a recording pulse train called a multi-pulse due to the application of heat in order to form marks on the recording film. The width of the multi-pulse train of the recording pulse train differs depending on the recording medium and the recording double speed. In the case of the first embodiment, a waveform is output in which the double-speed multi-pulse train has a duty of 50%.

  Since the space portion of the recording pulse train is at the DC level, detection is relatively easy. However, it is difficult to detect the recording power of the mark portion because of the multi-pulse train. For example, in the case of Embodiment 1, the width of the multipulse is about 9 ns. Therefore, the mark portion power detection signal obtained at the detection timing of the mark portion detection setting means 8 based on the signal obtained by performing band limitation on the detection signal obtained from the laser power detection means 1 (see FIG. 2C). Then, from the space portion power detection signal obtained by the space portion power detection signal processing means 5, the multi-pulse recording power output from the pickup head 14 is estimated by the calculation means 11 so that the target recording power is obtained. Perform control calculations.

  In the first embodiment of the present invention, the timing generation unit 7 generates and transmits four sample timings to the mark part detection setting unit 8 at equal intervals to move the detection timing, and the result is shown in FIG. As shown, the mark portion detection setting means 8 outputs four detection timing signals at equal intervals (d-1), (d-2), (d-3), and (d-4) to mark portion power detection signal processing means. 9, the mark part power detection signal processing means 9 transmits four mark part power detection signals, which are band limit detection signals detected by the detection timing signal, to the calculation means 11. Then, the calculation means 11 takes the average value of the received four mark portion power detection signals, and uses the average value as the estimated value of the recording power at the mark portion of the recording pulse output from the pickup head. Thus, the laser drive current for operating the laser drive unit 13 is controlled so that the estimated value of the recording power approaches the target recording power. Here, the calculating means 11 calculates the average value of the recording power, but the mark portion power detection signal processing means 9 may determine the average value of the recording power and send the average value to the calculating means 11. .

  Further, as shown in FIG. 3, since the timing for starting the detection of the power of the mark portion is set so as to be a stable position behind the detected recording power, the recording estimated by the calculation means 11 is performed. Increased power reliability. This detection start timing is held by a storage means such as a register or a memory (not shown) and can be arbitrarily set.

  Further, the recording power band of the mark portion during recording is controlled below the frequency at which the mark portion detection setting means 8 outputs the detection timing signal, and the estimated recording power obtained from the mark portion power detection signal is used. In addition, the laser drive current is set from the calculation means 11 to the laser drive means 13 so as to achieve the target recording power.

  Specifically, in Embodiment 1 of the present invention, the mark length detected by the DVD-R recording control is 11T, and the timing at which the mark having the 11T mark length is detected is random. Since the information is weighted, the control band is determined from the appearance probability. The appearance probability of each mark length is about 8.9% for 3T, 22.3% for 4T, 25.3% for 5T, 20.4% for 6T, 9% for 7T. 7T, 8T is 5.3%, 9T is 4.1%, 10T is 2.6%, 11T is 1.1%, 14T is 0.4%, and 11T detected by the mark portion detection setting means 8 The appearance probability of a mark having a mark length of about 1.1% was found. This probability is that the probability that an 11T mark will appear among the marks from 3T to 14T is 1.1%. After 91 marks appear, an 11T mark appears once.

  And the mark of 11T length is 91 × (3T × 8.9% + 4T × 22.3% + 5T × 25.3% + 6T × 20.4% + 7T × 9.7% + 8T × 5.3% + 9T × 4.1% + 10T × 2.6% + 14T × 0.4%) = appears once at 493T. Also, since the time per 1T is about 19 ns at double speed, an 11T mark appears once in 493T × 19 [nS] = 9.4 [μS]. However, since 11T has a mark and a space, and the appearance probability is 50%, the timing at which the mark appears is 9.4 [μs] × 2 = 18.8 [μs]. Assuming that one detection value can be obtained at the detection timing 18.8 [μs] among the 11Ts that appear, four detection values are obtained, so 18.8 [μs] × 4 = 75.2 [μs] Therefore, the recording power can be controlled at 1 / (75.2 [μs] × 2) = 6.6 kHz or less from the Nyquist theorem.

  In this embodiment, recording power control is realized at about 600 Hz, which is about 1/10 of the band, and stable power control is realized. This is because the laser control is related to the temperature characteristics of the laser, and the main purpose is to suppress power fluctuation due to current fluctuation. Here, there is little power fluctuation due to temperature fluctuation, and it is about 0.1 mW per 1000 μs, so that it is not necessary to make the control band of 6.6 kHz, and it is possible to control in the vicinity of 1/10 600 Hz.

  As described above, in the laser power control apparatus according to the first embodiment of the present invention, a plurality of laser powers of the mark portion are detected in one multi-pulse light emission section, and the laser power is controlled based on the average value thereof. Therefore, the laser power can be accurately estimated, and the multi-pulse laser power can be stably controlled.

  However, it goes without saying that it is necessary to consider the control band in consideration of suppression of the temperature characteristics of the laser, disturbance noise, and the like. In addition, it is desirable that the sampling of detection has at least an interval of half or more of the multi-pulse period and the number of detections.

  In Embodiment 1 of the present invention, it goes without saying that a more stable detection value can be obtained by reducing the timing interval output from the timing generation means and increasing the detection value. It goes without saying that the detection value becomes more accurate if the number of mark portions to be detected is increased.

(Embodiment 2)
The second embodiment of the present invention aims to perform more accurate control of laser emission not only in the mark portion but also in the space portion. FIG. 4 is a block diagram of the laser power control apparatus according to the second embodiment of the present invention. The configuration and operation of the laser power control apparatus according to the second embodiment of the present invention will be described with reference to FIG. However, in FIG. 4, the description of the components having the same numbers as in FIG. 1 is omitted.

  Similarly to the mark portion detection setting means 8, 21 detects a space portion having a predetermined length from the recording data length of the space portion which is the recording data string output from the space portion discrimination means 3, and will be described later. Space portion detection setting means for outputting a detection timing signal sampled and held by the space portion power detection signal processing means 23 in accordance with the sample timing generated by the generation means 22.

  22, the mark portion power detection signal processing means 9 detects the mark portion and generates sample timing for performing sample hold, and the space portion power detection signal processing means 23 detects the space portion and performs sample hold. This is a timing generation means that also generates a sample timing. The timing generation unit 22 can arbitrarily set the sample timing for performing the sample hold, and generates a plurality of sample timings at a constant cycle when generating the sample timing.

  23 is realized and detected by a sample hold circuit or the like that extracts the characteristics of the detection signal from the detection signal output from the laser power detection means 1 using a band limiting filter or the like, and holds the extracted signal. In accordance with the detection timing signal output from the space portion detection setting means 21, a space portion power detection signal processing means that performs sample and hold a plurality of times in one space portion and outputs the signal to the switching means 10 as a space portion power detection signal. is there.

  When a plurality of space part power detection signals are output from the switching means 10 to the calculation means 11, the calculation means 11 receives the plurality of received space part power detection signals in the same manner as calculating the mark part power detection signal. The average value of the signals is taken, and the average value is used as the estimated value of the recording power in the space portion of the recording pulse output from the pickup head. The arithmetic means 11 causes the estimated value of the recording power to approach the target recording power. In addition, the laser driving current for operating the laser driving means 13 is controlled. Further, instead of obtaining the average value by the calculation means 11, the value averaged by the space power detection signal processing means 23 may be output to the calculation means 11 as a space power detection signal.

  As described above, in the laser power control apparatus according to the second embodiment of the present invention, the laser power of the mark portion is detected, and a plurality of samplings are performed at one multi-pulse mark portion to control the recording power of the mark portion. The laser power in the mark portion and the space portion is accurately estimated by detecting the laser power in the space portion and performing a plurality of samplings in one space portion to control the recording power in the space portion. The laser power can be controlled stably. That is, the laser power control apparatus according to the second embodiment of the present invention can further obtain the effect of suppressing disturbances and the like that are leaked into the detection signal generated in the space portion of the recording pulse train in addition to the effects of the first embodiment. As a result, the recording power can be controlled more stably.

  Further, as shown in FIG. 2B, the power of the recording pulse train has a large discrepancy between the recording power and the space power, and the detected value of the space power greatly affects the detected value of the recording power. The bottom power of the pulse train is detected as the power of the space portion. If the specific gravity of the multi-pulse train DUTY to the space power side increases, the influence of the space power increases, and the power of the space portion is at the DC level. Because the frequency characteristic of the laser power detection means 1 tends to shorten the detection signal width of the space portion after the mark portion and the influence of the space power increases, the configuration of the second embodiment can Since the disturbance of the part can be smoothed and a stable detection value of space power can be obtained, these influences can be reduced.

  Further, the power band of the space portion during recording is controlled below the frequency at which the space portion detection setting means 21 outputs the detection timing signal, and the recording power of the estimated value obtained from the space portion power detection signal is obtained. In addition, stable control can be realized by setting the laser drive current from the calculation means 11 to the laser drive means 13 so as to achieve the target space power. The laser power control apparatus according to the second embodiment of the present invention realizes control at about 600 Hz as in the first embodiment, thereby realizing stable power control.

  However, it goes without saying that the control band needs to be considered in consideration of suppression of the temperature characteristics of the laser, disturbance noise, and the like. In addition, it is desirable that the sampling of detection has at least an interval of half or more of the multipulse period and the number of detections.

  In Embodiment 1 of the present invention, it goes without saying that a more stable detection value can be obtained by reducing the timing interval output from the timing generation means and increasing the detection value. It goes without saying that the detection value becomes more accurate if the number of mark portions to be detected is increased.

(Embodiment 3)
The laser power control apparatus according to Embodiment 3 of the present invention is a laser power control apparatus having another configuration for performing stable laser power control. FIG. 5 is a block diagram of a laser power control apparatus according to Embodiment 3 of the present invention.

  In FIG. 5, the description of the same components as those of the second embodiment is omitted.

  Reference numeral 31 denotes a pickup head that outputs a synchronization signal as recording clock information extracted from a meandering groove (wobble) obtained at the time of recording / reproducing of the disk from the pickup head 14 of FIG. Reference numeral 32 denotes timing generation means for outputting a sample timing synchronized with the recording clock based on the synchronization signal output from the pickup head 31. Then, the timing generation means 32 outputs sample timings to the mark portion detection setting means 8 and the space portion detection setting means 4 respectively.

  The detection signal of the laser power of the mark portion obtained from the laser power detection means 1 is multi-pulse light emission, and this multi-pulse light emission is output in synchronization with the recording clock obtained by the pickup head 14. As shown in FIG. 2C, a ripple appears, and this ripple is synchronized with the recording clock. Therefore, when sampling is performed by the mark portion power detection signal processing means, the estimated laser power estimated by the calculating means 11 can be reliable by sampling at timing synchronized with the multi-pulse recording clock. Needless to say.

  As described above, in the laser power control apparatus according to the third embodiment of the present invention, the timing generation unit 32 generates the sample timing by synchronizing with the recording clock read by the pickup head 31. As in the first embodiment, stable laser power control can be performed. Further, it is obvious that the same effect as that of the second embodiment can be expected from the control of the laser power in the space portion.

  In addition, since the recording clock is read from the disk and sampling is performed at the timing synchronized with the multi-pulse recording clock, the recording clock can be changed even if the recording multi-speed interval changes due to a change in the recording speed or the difference in the disk. Since the sampling timing can be followed according to the setting, the setting can be simplified.

  The laser power control apparatus according to the present invention is useful for optical disk recording because it can stably output recording power.

1 is a block diagram of a laser power control apparatus according to Embodiment 1 of the present invention. Operation waveform diagram of each part in the same laser power control device Enlarged view of the detected waveform in the laser power control device Block diagram of a laser power control apparatus according to Embodiment 2 of the present invention Block diagram of a laser power control apparatus according to Embodiment 3 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser power detection means 2 Recording data generation means 3 Space part discrimination means 4, 21 Space part detection setting means 5, 23 Space part power detection signal processing means 6 Mark part discrimination means 7, 22, 32 Timing generation means 8 Mark part detection Setting means 9 Mark part power detection signal processing means 10 Switch 11 Calculation means 12 Light emission pattern generating means 13 Laser driving means 14, 31 Pickup head

Claims (3)

Recording data generating means for generating a recording data string including a mark portion and a space portion;
A light emission pattern generating means for generating a laser light emission pulse train from the generated recording data;
Computing means for computing drive current;
Laser driving means for outputting a recording pulse train corresponding to the generated laser emission pulse train and the calculated drive current;
A pickup head for outputting a light emission pulse train corresponding to the recording pulse train;
Laser power detection means for detecting the laser power of the light emission pulse train output from the pickup head;
Mark part discriminating means for extracting the mark part of the generated record data sequence;
Timing generating means for generating a plurality of timing signals for sampling a plurality of times within one mark portion;
A mark part detection setting unit that detects a mark part of a predetermined length from the extracted mark part and outputs a detection timing signal each time the timing generation part receives a timing signal;
A mark power detection signal processing means that samples the laser power detected by the laser power detection means based on a detection timing signal output from the mark detection setting means and outputs the laser power to the calculation means as a mark power detection signal; With
The arithmetic means uses an average value of a plurality of mark portion power detection signals output from the mark portion power detection signal processing means as an estimated value of the laser power of the mark portion, and the estimated value becomes a target laser power. Laser power control device that calculates drive current. The timing generation means generates a plurality of timing signals for sampling a plurality of times in one space part,
Space part discriminating means for extracting a space part of the recording data string generated by the recording data generating means;
A space part detection setting unit that detects a space part of a predetermined length from the extracted space part and outputs a detection timing signal each time a timing signal generated by the timing generation unit is received;
A space part detection signal setting unit that samples the laser power detected by the laser power detection unit based on a detection timing signal output by the space part detection setting unit and outputs the laser power as a space unit power detection signal to a calculation unit; ,
The arithmetic means sets an average value of the plurality of space portion power detection signals output from the space portion power detection signal processing means as an estimated value of the laser power of the space portion, and uses the estimated value as a target laser power. The laser power control device according to claim 1, wherein the drive current is calculated. The laser power control apparatus according to claim 1, wherein the timing generation unit generates a timing signal synchronized with a recording clock read by the pickup head.

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