JPH1139739A - Reproducing light quantity control device in optical storage device and optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make enhancement of utilizing efficiency of a magneto-optical disk and high precision reproducing power control compatible. SOLUTION: A regenerative signal obtained by reproducing a reproducing power control mark of the magneto-optical disk 1 of an ultra-high resolution system in a range of >=5 bytes and <=40 bytes is A/D-converted by an A/D converter 5, and levels of a short mark and a long mark of the reproducing power control mark are detected by a short mark level detecting circuit 6 and a long mark level detecting circuit 7, and their amplitude ratio is obtained by a divider 9 and is compared with a target value by a differential amplifier 10. Then, a reproducing power control circuit 11 is controlled in order to approach the target value so as to control reproducing power of a semiconductor laser 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source for irradiating an optical recording medium of a magnetic super-resolution type with a light beam and controlling the light amount of the light beam so that a reproduction signal from a recording mark approaches a predetermined value. The present invention relates to a reproduction light amount control device and an optical recording medium in a storage device.

[0002]

2. Description of the Related Art In a magneto-optical disk drive, a magneto-optical disk of a magnetic super-resolution type having a recording layer and a reproducing layer having in-plane magnetization is irradiated with a light beam from the reproducing layer side. The reproducing layer only in a portion (hereinafter, referred to as an aperture) whose temperature has risen to a predetermined temperature or higher in the irradiation area transfers the magnetization of the corresponding recording layer and shifts from in-plane magnetization to perpendicular magnetization, so that the light beam It is possible to reproduce a recording mark smaller than the spot diameter.

In this method, even if the driving current for generating the light beam is kept constant, the reproduction power of the light beam may fluctuate in accordance with the change in the environmental temperature during reproduction. If the reproduction power becomes too strong, the aperture becomes too large, the output of the reproduction signal from the adjacent track increases, and the ratio of the noise signal included in the reproduced data increases, causing a reading error. The probability increases. On the other hand, if the reproduction power becomes too weak, the aperture becomes smaller than that of the recording mark, and the output of the reproduction signal from the track to be read becomes smaller, which also increases the probability of occurrence of a read error.

Japanese Patent Laid-Open Publication No. Hei 8-63817 discloses reproducing power control marks of two different lengths on a magneto-optical disk and reproducing power control marks such that the ratio of the reproduced signals approaches a predetermined value. By controlling
The reproduction power is always kept at an optimum value, and the probability of occurrence of a reading error is reduced. FIG. 12 shows a schematic configuration of this device. When the light emitted from the semiconductor laser 2 is applied to the magneto-optical disk 12, the reflected light from the reproduction power control mark on the magneto-optical disk 12 is converted into a reproduction signal by the photodiode 3. The playback signal is A /
It is input to a D (Analog / Digital) converter 5 and a clock generation circuit 4. The clock generation circuit 4
A clock signal synchronized with the reproduction signal is generated by LL (Phase Locked Loop). And
In the A / D converter 5, the reproduced signal is converted into digital data based on the clock signal. The amplitude ratio detection circuit 13 detects only the digital data at the upper and lower peak points from the digital data input for each clock signal, and averages the digital data at a predetermined number of samples, thereby detecting the average value of the amplitude values. As described above, the average amplitude values of the long mark and the short mark are detected, the ratio between them is obtained, and the ratio is output as the average amplitude ratio. The differential amplifier 10 compares the average amplitude ratio with the target value, and the reproduction power control circuit 11 controls the drive current to the semiconductor laser 2 so that feedback is applied in a direction in which the difference becomes smaller. In this way, the drive current of the laser light is controlled so that the optimum reproduction power is always provided.

[0005]

However, if the number of samples used for obtaining the average value of the amplitude ratio is too large, the ratio of the recording area of the reproduction power control mark in the optical recording medium becomes too large, and The use efficiency of the recording medium is deteriorated. On the other hand, if the number of samples is too small, the variation in the detected amplitude ratio increases, and the control error of the reproduction power increases.

According to the present invention, reproduction power control is performed by setting the number of peak value samples used for averaging the amplitude ratio for reproduction power control in an optimum range, thereby reducing variations in the average amplitude ratio obtained. It is an object of the present invention to reduce the error and to reduce the recording area of the reproduction power control mark to improve the use efficiency of the optical recording medium.

[0007]

According to a first aspect of the present invention, there is provided a reproduction light amount control device for an optical storage device, wherein an aperture smaller than a light spot diameter of an irradiated light beam is generated in a reproduction layer to thereby generate a light from a recording layer. A reproduction light amount control device in an optical storage device using an optical recording medium for reproducing recorded information and having control means for controlling a reproduction power by detecting a reproduction signal from a reproduction power control mark recorded on the optical recording medium. The control means controls the reproduction power based on a reproduction signal obtained by reproducing the reproduction power control mark in a range of 5 bytes or more and 40 bytes or less.

According to a second aspect of the present invention, there is provided a reproducing light amount control device for an optical storage device, wherein an aperture smaller than a light spot diameter of an irradiated light beam is generated in a reproducing layer to reproduce recorded information from the recording layer. Using a recording medium, in a reproduction light amount control device in an optical storage device having a control unit that controls a reproduction power by detecting a reproduction signal from a reproduction power control mark recorded on the optical recording medium, the control unit includes: The reproduction power control mark is set to (40 /
3) The reproduction power is controlled based on a reproduction signal obtained by reproducing in a range of not less than samples and not more than 120 samples.

According to a third aspect of the present invention, there is provided a reproduction light amount control device for an optical storage device, wherein the reproduction signal is A / D converted. Averaging means for averaging a plurality of obtained amplitude values.

According to a fourth aspect of the present invention, there is provided an optical recording medium for reproducing recorded information from a recording layer by generating an aperture in the reproducing layer smaller than the light spot diameter of the irradiated light beam. It is characterized in that a reproduction power control mark of not less than bytes and not more than 40 bytes is recorded.

The optical recording medium according to the fifth aspect is the fourth aspect of the invention.
Wherein the read power control mark is composed of a short mark repetition pattern and a long mark repetition pattern, and each repetition pattern is 5 bytes or more and 40 bytes or less.

The optical recording medium according to the sixth aspect is the fourth aspect.
3. The optical recording medium according to claim 1, wherein the reproduction power control mark is provided for each sector.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a super-resolution magneto-optical disk reproducing apparatus. However, portions having the same functions as those of the conventional device shown in FIG.

FIG. 2 schematically shows the sector structure of the magneto-optical disk 1. FIG. 3 shows a reproduction power control mark composed of a short mark and a long mark. In FIG. 2, a sector 100 has a short mark recording area 101 in which a repetition pattern (shown in FIG. 3A) of 2Tc (Tc is a channel bit length) as a short mark is recorded in K bytes, and a repetition pattern of 8Tc as a long mark ( FIG. 3B) also shows a long mark recording area 102 in which K bytes are recorded.
7) It has a data recording area 103 for recording RLL-modulated digital data.

In FIG. 1, this reproducing apparatus is different from the conventional apparatus in that the magneto-optical disk 1 includes a plurality of sectors having the above-described structure, and a short mark level detecting means for detecting an average amplitude value of a repetitive pattern of short marks. A circuit 6, a long mark level detection circuit 7 for detecting an average amplitude value of a repeated pattern of a long mark, a data reproduction circuit 8 for reproducing digital data recorded in the data recording area 103, and an output and a length of the short mark level detection circuit 6. The configuration of a divider 9 that divides the output of the mark level detection circuit 7 and outputs the average amplitude ratio is different.

When the light emitted from the semiconductor laser 2 accesses the sector 100 on the magneto-optical disk 1, the short mark recording area 101 is first irradiated. Light reflected from the short mark recording area 101 is converted into a reproduction signal by the photodiode 3. The reproduction signal is input to the clock generation circuit 4, and a clock signal synchronized with the channel bit frequency of the reproduction signal is generated and output. A / D converter 5
Converts the reproduction signal into a digital signal based on the timing of the clock signal output from the clock generation circuit 4 and outputs the digital signal to the short mark level detection circuit 6. The short mark level detection circuit 6 keeps holding all the input digital signals until the reproduction of the short mark recording area 101 is finished, and extracts and averages only the upper and lower peak sampling points of the held digital signal when the reproduction is finished. Process and output as a short mark amplitude value. Next, the light emitted from the semiconductor laser 2 is applied to the long mark recording area 102, the same processing as that for the short mark is performed, and the long mark level detection circuit 7 outputs the long mark amplitude value. The divider 9 calculates the ratio between the input short mark amplitude value and long mark amplitude value and outputs the result as an average amplitude ratio. The output average amplitude ratio is compared with a target value by the differential amplifier 10, and the reproduction power control circuit 11 controls the drive current to the semiconductor laser 2 so that feedback is applied in a direction in which the difference is reduced. After the driving current of the laser beam is controlled so that the optimum reproducing power is given in this way, the emitted light is irradiated to the data recording area 103, and the read reproduction signal is transmitted to the A / D converter 5. After that, the binary data is input to the data reproducing circuit 8 and output at a low error rate. Then, when the outgoing light reaches the next sector, the same processing is repeated,
The optimum reproduction power is newly set. As described above, the recording area of the reproduction power control mark is provided separately for each sector, and the reproduction signal control for the reproduction power control is detected for each sector, whereby the reproduction power control responds at a short time interval. Thus, it is possible to follow a short-term fluctuation of the optimum reproducing power.

Here, the detection processing of the short mark amplitude value in the short mark level detection circuit 6 will be described in detail with reference to FIGS. FIG. 4A is a schematic diagram showing A / D conversion sampling points in a reproduction signal of a repeated pattern of short marks. The upper peak point (ds _4i ), the middle point (ds _{4i + 1} ), and the lower peak point (d
s _{4i + 2} ) and the intermediate point (ds _{4i + 3} ).

FIG. 5 shows a detailed configuration of the short mark level detection circuit 6. The digital reproduction signal of the short mark input for each clock is sequentially stored in the 4N-stage shift register 61. Since the upper peak point of the short mark is input at every four sampling points, the digital values (ds ₀ , ds ₄ ,..., Ds _{4 (N−1)} ) at every four sampling points are added as shown in the figure. The value added at 62 and divided by N at the divider 64 becomes the average value Ts _mean of the upper peak points. Similarly, the digital value of the lower sampling point (d
s ₂ , ds ₆ ,..., ds _{4 (N−1) +2} ) are added by the adder 63, and a value obtained by dividing by N in the divider 65 is the average value Bs _{mean of the} lower peak point. Becomes The difference (Ts _mean -Bs _mean ) obtained by the subtractor 66 is output as the average amplitude value of the short mark.

Next, the detection processing of the long mark amplitude value in the long mark level detection circuit 7 will be described in detail with reference to FIGS. FIG. 4B is a schematic diagram showing A / D conversion sampling points in a reproduction signal of a long mark repeating pattern. According to the clock signal, four upper envelope points (dl _16i , dl _{16i + 1} , dl _{16i + 2} , dl
_{16i + 3} ), 4 intermediate points (dl _{16i + 4} , dl _{16i + 5} , dl
_{16i + 6} , dl _{16i + 7} ), 4 lower envelope points (dl
_{16i + 8} , dl _{16i + 9} , dl _{16i + 10} , dl _{16i + 11} ), 4 intermediate points (dl _{16i + 12} , dl _{16i + 13} , dl _{16i + 14} , dl
_{16i + 15} ).

FIG. 6 shows a detailed configuration of the long mark level detection circuit 7. The digital signal of the long mark input for each clock is sequentially stored in the 16M-stage shift register 71. As the upper envelope point of the long mark is input at 4 sampling points every 16 sampling points, 16
The digital value of four sampling points (d
_{l 0, dl 1, dl 2} , dl 3, ···, dl 16 (M-1), d
l _{16 (M-1) +1} , dl _{16 (M -1) +2} , dl _{16 (M-1) +3} ) are added by an adder 72, and a value obtained by dividing by 4M by a divider 74 is It becomes the average value Tl _mean of the upper peak point. Similarly, every 16 sampling points, the digital value (dl ₈ , dl ₉ , dl ₁₀ , dl ₁₁ ,.
dl16 _{(M-1) +8} , dl16 _{(M-1) +9} , dl16 _{(M-1) +10} , dl
_{16 (M-1) +11} ) is added by an adder 73, and a value obtained by dividing by 4M by a divider 75 is an average value Bl _{mean of the} lower envelope point.
Becomes These differences (Tl _mean −
Bl _mean ) is output as the average amplitude value of the long mark.

The amplitude ratio (Ts) thus detected
The accuracy of _mean− Bs _mean ) / (Tl _mean −Bl _mean ) is
It changes depending on the averaged byte number K of the reproduction power control mark used for control. FIG. 7 shows the average number of bytes K and the accuracy of the detected amplitude ratio (represented by the standard deviation of the distribution of the detection results for 100 times. The smaller the standard deviation, the smaller the variation. 3) shows the results of the actual measurement of the relationship (1). According to FIG. 7, the averaged byte number K is 40
It can be seen that the standard deviation hardly changes when the size exceeds bytes. Therefore, it is sufficient that the number of averaged bytes is 40 bytes or less.

On the other hand, in view of the correction capability of the error correction processing circuit used in the reproducing apparatus, it is generally considered that the bit error rate should be 1E-4 (= 1 × 10 ^-4 ) or less. FIG. 8 shows the results of a measurement of the relationship between the reproducing power of the semiconductor laser, the bit error rate (BER) of the reproduced binary data, and the amplitude ratio of the long and short marks, using the same reproducing apparatus as in FIG. 8, the amplitude ratio is in the range of 0.14 to 0.28, that is, 0.21 ±.
At a reproduction power of 0.07, the bit error rate is 1E-4 or less. When performing the reproduction power control based on the amplitude ratio, first, the amplitude ratio (0.21) that becomes the optimum reproduction power is detected and set as a target value, and thereafter, control is performed such that the detected amplitude ratio approaches the target value as needed. Therefore, it is necessary to determine an allowable detection error so that the bit error rate satisfies 1E-4 or less even when the detection error of the target value and the detection error of the control amplitude ratio are combined. Therefore, it is sufficient to consider a condition that the allowable detection error of the amplitude ratio is ± 0.035 (± 0.07 / 2). According to statistics, when the standard deviation of the distribution of the average amplitude ratio (which can be regarded as almost a normal distribution) is σ, and if 3σ is 0.035 or less, the error of the average amplitude ratio is ± 99.7% or more with a probability of 99.7% or more. 0.035
σ needs to be 0.0117 (0.035 / 3) or less. Therefore, it can be seen from FIG. 7 that the number of averaged bytes K must be 5 bytes or more.

By the way, in the above-described actual measurement mode, the results in the case where (1,7) RLL is used as the modulation method, the 2Tc repetition pattern is used as the short mark, and the 8Tc repetition pattern is used as the long mark are shown. 9 and 10 show actual measurement results when the modulation method is NRZI, the short mark is an alternating repetition pattern of 1Tc and 2Tc, and the long mark is a repetition pattern of 8Tc. FIG.
Is the relationship between the number of averaged bytes K 'and the accuracy of the detected amplitude ratio (expressed as the standard deviation of the distribution of the detection results for 100 times) in a magnetic super-resolution magneto-optical disk reproducing apparatus using NRZI as the modulation method. Is the result of actual measurement. FIG.
In the same reproducing apparatus, the reproducing power of the semiconductor laser,
Bit error rate of reproduced binary data (BE
It is the result of actually measuring the relationship between R) and the amplitude ratio of the long and short marks.

FIG. 9 shows that when the averaged byte number K 'is 25 bytes or more, the standard deviation hardly changes. Since this is smaller than 40 bytes in the (1,7) RLL, it is sufficient to set the averaged byte number to 40 bytes or less.

On the other hand, considering the case of the (1, 7) RLL modulation in the same manner as in the case of the (1,7) RLL modulation, in FIG. Since it can be seen that the bit error rate is 1E-4 or less, the allowable detection error of the amplitude ratio is ± 0.03.
75 (± 0.075 / 2).
That is, the standard deviation σ of the distribution of the average amplitude ratio is 0.012.
5 (0.0375 / 3) or less.
Therefore, it can be seen from FIG. 9 that the averaged byte number K 'must be 5 bytes or more.

To summarize the above results, the number of averaged bytes must be at least 5 bytes, and at most 40 bytes or less is sufficient. That is, each of the short mark recording area and the long mark recording area may be set to 5 bytes or more and 40 bytes or less. Thus, more than 5 bytes and 40
Since the reproduction power control mark recorded beforehand in bytes or less is reproduced, and the reproduction power is controlled based on the signal averaged by A / D conversion, the recording area of the reproduction power control mark is made smaller to perform optical recording. It is possible to improve the use efficiency of the medium and to control the reproduction power with sufficiently high accuracy in a short time.

As shown in FIG. 11A, (1,
7) In the short mark of the RLL modulation, one upper and lower peak point is included for every 4 channel bits, so that an amplitude value of 3 samples is obtained for each byte (12 channel bits), and for the long mark, every 16 channel bits. Contains four upper and lower envelope points, so
Three sample amplitude values are obtained for each byte.
Further, as shown in FIG. 11B, in the short mark of the NRZI modulation, one upper and lower peak point is included for every three channel bits, so that one byte (8 channel bits)
Approximately 2.7 (= 8/3) samples are obtained for each channel, and the long mark contains six upper and lower envelope points for every 16 channel bits. can get.

Therefore, in the case of the (1,7) RLL modulation reproduction power control mark, three digital amplitude values can be obtained from a 1-byte recording mark, so that the digital amplitude values of 15 to 120 samples are averaged. It is also possible to adopt a configuration in which the amplitude ratio is obtained by converting to Also, in the case of a reproduction power control mark of NRZI modulation, a digital amplitude value of 8/3 samples can be obtained from a 1-byte recording mark, so that digital amplitude values of (40/3) samples or more and 120 samples or less are averaged. A configuration for obtaining the amplitude ratio may be adopted.

In the above-described embodiment, the configuration has been described in which the averaging calculation is performed after all the predetermined number of digital amplitude values are input using the shift register. However, the present invention is not limited to this. A configuration may be adopted in which the data is sequentially added without being held in the register, and finally divided by the number of samples and averaged. In the above embodiment,
The optical storage device has been described with reference to a reproducing device of a magneto-optical disk, but the present invention is not limited to this, and may be applied to a reproducing device of an optical card or an optical tape.

[0030]

According to the reproducing light quantity control device in the optical storage device of the present invention, the recording area of the reproducing power control mark can be reduced to improve the utilization efficiency of the optical recording medium and to achieve a sufficiently high precision. This makes it possible to control the reproduction power in an appropriate manner.

According to the optical recording medium of the present invention, since the data recording area can be enlarged, it is possible to improve the utilization efficiency of the optical recording medium and to control the reproducing power with high accuracy. By providing the recording area of the power control mark dispersedly for each sector, the reproduction power can be controlled for each sector. Therefore, the reproduction power control responds at short time intervals and follows short-term fluctuations of the optimum reproduction power. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a super-resolution magneto-optical disk reproducing apparatus according to an embodiment.

FIG. 2 is a diagram schematically showing a sector structure of the magneto-optical disk according to the embodiment.

FIG. 3 is a diagram illustrating a repetition pattern of long marks and a repetition pattern of short marks according to the embodiment.

FIG. 4 is a schematic diagram illustrating A / D sampling points of a reproduction signal of a long mark and a short mark according to the present embodiment.

FIG. 5 is a short mark level detection circuit 6 according to the embodiment;
FIG. 3 is a diagram showing a detailed configuration of the embodiment.

FIG. 6 is a long mark level detection circuit 7 according to the embodiment;
FIG. 3 is a diagram showing a detailed configuration of the embodiment.

FIG. 7 is a diagram of a measurement result showing a relationship between an averaged byte number and a found standard deviation of an amplitude ratio of a reproduction power control mark using (1,7) RLL modulation according to the present embodiment. is there.

FIG. 8 shows the reproduction power of the semiconductor laser, the bit error rate of the reproduced binary data, and the amplitude ratio of the long and short marks of the reproduction power control mark using (1,7) RLL modulation according to the present embodiment. FIG. 7 is a diagram of measurement results showing the relationship

FIG. 9 is a diagram of measurement results showing the relationship between the average number of bytes of the amplitude ratio and the obtained standard deviation of the amplitude ratio of the mark for reproducing power control using NRZI modulation according to the present embodiment.

FIG. 10 shows the relationship between the reproduction power of a semiconductor laser, the bit error rate of reproduced binary data, and the amplitude ratio of long and short marks of a reproduction power control mark using NRZI modulation according to the present embodiment. It is a figure of a measurement result.

FIG. 11 is a diagram for explaining sampling points of a repeated pattern of a long mark and a repeated pattern of a short mark in (1, 7) RLL modulation and NRZI modulation.

FIG. 12 is a diagram illustrating a configuration of a reproduction light amount control device in a conventional optical storage device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magneto-optical disk 2 Semiconductor laser 3 Photodiode 4 Clock generation circuit 5 A / D converter 6 Short mark level detection circuit 7 Long mark level detection circuit 8 Data reproduction circuit 9 Divider 10 Differential amplifier 11 Reproduction power control circuit

Claims (6)

[Claims] 1. An optical recording medium for reproducing recorded information from a recording layer by generating an aperture smaller than a light spot diameter of an irradiated light beam on the reproducing layer, and reproducing the information recorded on the optical recording medium. In a reproduction light amount control device for an optical storage device having a control means for controlling a reproduction power by detecting a reproduction signal from a power control mark, the control means sets the reproduction power control mark to a size of 5 bytes or more and 40 bytes or less. A reproduction light amount control device in an optical storage device, wherein reproduction power is controlled based on a reproduction signal obtained by reproducing in a range. 2. An optical recording medium for reproducing recorded information from a recording layer by generating an aperture in the reproducing layer smaller than the light spot diameter of the irradiated light beam, and reproducing the information recorded on the optical recording medium. In a reproduction light amount control device in an optical storage device having a control unit for controlling a reproduction power by detecting a reproduction signal from a power control mark, the control unit sets the reproduction power control mark to (40
/ 3) A reproduction light amount control device in an optical storage device, wherein reproduction power is controlled based on a reproduction signal obtained by reproducing in a range of not less than samples and not more than 120 samples. 3. The optical storage device according to claim 1, further comprising averaging means for averaging a plurality of amplitude values obtained by A / D converting the reproduced signal. Reproduction light amount control device. 4. An optical recording medium for reproducing recorded information from a recording layer by generating an aperture smaller than a light spot diameter of an irradiated light beam in a reproducing layer, wherein a reproduction power control of 5 bytes or more and 40 bytes or less. An optical recording medium having recorded thereon a use mark. 5. The reproduction power control mark according to claim 4, wherein the mark includes a repetition pattern of short marks and a repetition pattern of long marks, and each repetition pattern has a length of 5 bytes or more and 40 bytes or less. Optical recording medium. 6. The optical recording medium according to claim 4, wherein the read power control mark is provided for each sector.