JPH08273235A - Magneto-optical recording and reproducing device - Google Patents

Abstract

PURPOSE: To obtain a stable reproduced RF signal by correcting an amplitude change and a phase change of a low band signal. CONSTITUTION: This is the magneto-optical recording and reproducing device for reproducing a recording data from an optical disk recorded with a preformat data in each sector. The data reproduced from the optical disk is supplied via a high pass filter to a waveform equalizer 18, and the output of the waveform equalizer is supplied to a comparator 30 and is binarized, so that its amplitude is fixed. Afterward, the binary output is supplied via a Nyquist matching low pass filter 32 for imparting the same characteristic as the waveform equalizer to this output to a quantization feedback equalizer 40 to obtain a reproducing output corrected in amplitude and phase. Thus, by performing quantization feedback processing after stabilizing the amplitude, the regenerative RF signal corrected in amplitude and phase can be outputted. By utilizing this signal, decoding processing is stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-optical recording / reproducing apparatus using a magneto-optical disk capable of recording / reproducing data, in which a reproduction output level is fixed and then a quantized feedback process is performed. The disk reproduction signal whose level has fluctuated by means of which is surely reproduced.

[0002]

2. Description of the Related Art In a magneto-optical disk, as shown in FIG. 3A, it is divided into an inner recording area (channel 1) and an outer recording area (channel 2), and one track formed in each recording area is It is composed of a plurality of sectors, for example, 42 sectors. As shown in FIG. 3B, one sector is composed of a precoded address portion (address area) ADD and a recording data write area (data recording portion MO).

In the address part ADD, as shown in FIG. 1B, the sector marker SM is followed by three pieces of address data of the same content.
It is formed repeatedly. The reason for repeating three times is to ensure that the address data can be read even when there is a read error. This address data is composed of VFO data, address marker AM, and identification data ID. A VFO (variable frequency osillator) is a single-frequency signal used for pulling in the operation of the PLL oscillator for clock generation because it generates a reference signal (reference clock). Postamble data PA is recorded following the address data.

All of these address data are pre-formatted data and are formed by pits. There is a data recording unit MO following the address unit ADD, and a test area is provided at the beginning of this data recording unit MO. In the test area, ALPC data (Auto
matic Laser Power Control data), followed by VFO data VFO4 (the same data as VFO1 to VFO3).

A buffer area (non-recording portion) is provided at the end of the data recording portion MO to clarify the boundary with the address portion ADD. The number of sectors and the number of bytes constituting one sector shown in the figure are merely examples.

To record data on the MO disc 1 and reproduce the recorded data or address data, the MO disc 1 is irradiated with laser light. As is well known, the address data recorded on the MO disk 1 and the laser power for reproducing the recorded data are relatively low,
Although it is about 1.2 mW, the laser power required for recording or erasing has a large value of about 8 to 9 mW.

When such a laser power is applied, the output current (reproduction RF signal) flowing through the photodiode PD which is a photodetector is supplied to the magneto-optical recording / reproducing apparatus shown in FIG. 4 to demodulate (reproduce) data. Be done.

In this magneto-optical recording / reproducing apparatus, reproduction R
The F signal is supplied to the waveform equalizer (equalizer EQ) 3 and is given a cosine descending characteristic. The reason for giving the cosine descending characteristic is to increase the aperture ratio of the eye pattern of the reproduction signal by reducing the intersymbol interference of the reproduction RF signal within the transmission band. This is because when the aperture ratio of the eye pattern increases, the waveform shaping error of the reproduction signal decreases and the reproduction signal can be correctly demodulated (decoded).

The high frequency signal of the reproduced RF signal whose waveform has been equalized is supplied to the waveform shaping circuit 10 and converted into a pulse signal corresponding to the data. The waveform-shaped reproduced RF signal is supplied to the discrimination circuit 5 and is also supplied to the PLL circuit 4 to generate a synchronization signal for discrimination. The PLL circuit 4 generates a synchronization signal (clock signal) CK synchronized with the basic cycle of the pulse signal described above, and this synchronization signal becomes a window pulse to discriminate the reproduction signal (pulse signal).

The discrimination circuit 5 forms a detection code string according to the presence or absence of data, and this is supplied to the decoder 6 at the subsequent stage and decoded into a data bit string, that is, a data bit string at the time of recording.

When the recording data is recorded / reproduced in the area other than the pre-format as described above, the recording / reproduction processing is performed in units of sectors. As described above, the laser power when recording data and the laser power when reproducing preformatted data or recorded data are significantly different. In addition to recording and reproducing by changing the laser power in this way, when the mode is changed from the address section to the data recording section due to factors such as uneven sensitivity of the disk, fluctuations in the reflectance of the disk, recording fluctuations, and even servo errors. During the transition from the reproduction mode to the erase mode or from the reproduction mode to the recording mode, a transient occurs in the reproduction RF signal.

In order to reduce this transient, it is sufficient to use only the high frequency component of the reproduction output, but this time the amplitude of the low frequency component of the reproduction RF signal is changed by the high pass filter used to extract this high frequency component. Fluctuations and phase fluctuations occur, and the aperture ratio of the eye pattern of the reproduced waveform decreases.

To solve this problem, means shown in FIG. 5 can be considered. The example shown in FIG. 5 is a case where the quantization feedback technique used in the digital processing technique is used. As is well known, the quantization feedback technique is a technique for reproducing the low frequency component lost in the transmission line.

A specific example will be described with reference to FIG. A reproduction RF signal reproduced from the MO disk 1 is supplied to the terminal 12. The reproduced RF signal is supplied to the high-pass filter 16 via the preamplifier 14 to reduce the transient of the reproduced RF signal. After that, the reproduced RF signal is supplied to the waveform equalizer 3 and is given a cosine descending characteristic.

This reproduced RF signal with improved characteristics is an AG
It is supplied to the C circuit 20 and controlled so that the reproduction output level becomes constant. After that, the phase fluctuation of the reproduction output supplied to and input to the quantization feedback equalizer 22 is corrected. AG
The waveform shaping circuit 1 including the C circuit 20 and the quantization feedback equalizer 22.
0 is configured.

[0016]

In order to obtain a binarized output in which the phase fluctuation is corrected by using the quantization feedback technique, the level of the signal input to the quantization feedback equalizer 22 should be kept constant. There must be. Therefore, in the example of FIG.
Circuit 20 is used.

However, the reproduction R using the AGC circuit 20 is performed.
Attempting to correct the amplitude of the F output level causes various problems as described below. (1) VF provided in the sector when AGC is applied
Although it is necessary to control the amplitude of the reference signal of the O area, this VFO signal exists only in units of sectors and exists only for a very short period. It is difficult to stably apply AGC based on such an intermittent signal. (2) When the AGC is applied, it is expected that the level fluctuation of the reproduction output will become large because the S / N is bad. This is because the sensitivity of the disk is large and the recording wavelength is short.
Because I can't get it. (3) Address data in the pre-formatted area needs to be reproduced even at the time of seek, but at the time of seek, it may be necessary to scan the off-track area without tracking. Since the reflectance of the laser light in the off-track area is high, the AGC operation becomes unstable at this time.

In the recording / reproducing system of the type in which the operation mode is switched in the sector unit as described above, even if the AGC circuit is used, the function cannot be sufficiently exerted.
It is not enough to stabilize the amplitude of the playback output.

Therefore, the present invention solves such a conventional problem and proposes a magneto-optical recording / reproducing apparatus utilizing a quantized feedback technique capable of effectively correcting the amplitude change and phase change of a reproduction signal. Is.

[0020]

In order to solve the above-mentioned problems, according to the present invention, a magneto-optical recording / reproducing apparatus for reproducing recorded data from an optical disk in which pre-formatted data is recorded for each sector is reproduced from the optical disk. Data is supplied to the waveform equalizer through the high-pass filter, and the waveform equalization output level is fixed and then supplied to the quantization feedback equalizer to obtain a reproduction output whose amplitude and phase are corrected. It is characterized in that it is obtained.

[0021]

The amplitude of the reproduced RF signal whose waveform has been equalized is fixed by binarizing it by a comparator. The reproduced output binarized by the high-pass filter provided for reducing transients (binarized output) also has its edges varied. That is, a binarized output that has undergone phase fluctuation is obtained.

The binarized output is R equivalent to a reproduced signal whose amplitude is fixed by a low-pass filter for Nyquist shaping.
The F signal is obtained, and then the edge of the reproduced RF signal input thereto is moved by the quantization feedback equalizer to correct the phase fluctuation. Therefore, the output of the quantization feedback equalizer becomes a reproduced RF signal (binarized signal) whose amplitude and phase are respectively corrected, and an RF signal close to that before the high-pass processing is obtained.

[0023]

Next, an example of a magneto-optical recording / reproducing apparatus according to the present invention using a magneto-optical disk will be described in detail with reference to the drawings.

Also in the magneto-optical recording / reproducing apparatus according to the present invention shown in FIG. 1, the RF signal reproduced from the MO disk 1 is supplied to the high-pass filter 16 of the CR structure via the preamplifier 14 to reduce the reproduction RF signal. After the band signal is cut, it is supplied to the waveform equalizer 18. This waveform equalizer 18
As described above, the cosine descending characteristic for improving the aperture ratio of the eye pattern is added.

After that, it is supplied to the waveform shaping circuit 10. The waveform shaping circuit 10 includes a first comparator 30, a Nyquist matching low-pass filter 32, and a quantization feedback equalizer 40. The waveform-equalized reproduction RF signal is transmitted to the first comparator 30.
And the reproduced RF signal is binarized. Although the amplitude of the reproduced RF signal fluctuates by the high-pass processing, the fluctuation of the amplitude is largely compensated by this binarization processing.
The edge of the binarized output is moved from the position of the edge before the high-pass processing by the low-frequency cutoff processing of the high-pass filter 16 described above. That is, the output has undergone phase fluctuation.

The binarized output is supplied to the low-pass filter 32 for Nyquist matching and is given the same frequency characteristic as given by the waveform equalizer 18. This filtering process is performed in order to smooth the edges of the output waveform and facilitate the phase adjustment of the edges.

The filtered binarized output is supplied to the quantization feedback equalizer 40. The quantization feedback equalizer 40 is an equalizer for DC reproduction used in the field of digital technology. The quantized feedback equalizer 40 is inputted with a comparator (second comparator) 42 to which a binarized output is supplied as shown in the figure, and a low-pass filter 44 which extracts only a low frequency component of the comparison output. The reproduction RF signal and the low frequency component are added in anti-phase with each other, and the addition output is supplied to the second comparator 42. In this example, the reference level of the second comparator 42 is set to zero level, but it is also possible to provide a timing circuit (not shown) for comparison processing.

The quantization feedback equalizer 40 is supplied with a binarized output (FIG. 2A) whose amplitude is fixed but whose phase is changed by the presence of the high-pass filter 16. Therefore, since the low-frequency component (FIG. 2B) of the binarized output output from the second comparator 42 includes the phase variation component of the edge, the low-frequency component is reverse-phased to the second comparator 42. If you feed it back and add it to the binarized output for comparison,
Finally, the reproduction R output from the second comparator 42
Since the edge of the F signal (binarized output) is centered around the average level, the opposite phase is corrected, so that the second comparator 42 removes the phase fluctuation component (in other words, the phase is corrected. A reproduced RF signal) is obtained (FIG. 2C).

When the amplitude of the binarized output input to the second comparator 42 is fluctuating, the amplitude of the phase fluctuating component included in the low frequency component also fluctuates. This is because the comparison process for performing the antiphase correction centering on the average level of the binarized output cannot be performed correctly.

By performing the above processing, the reproduction RF close to the signal before being input to the high pass filter 16 is obtained.
The signal is obtained. This reproduced RF signal is supplied to the discrimination circuit 5 shown in FIG. 4, and as is well known, discrimination processing is performed based on the clock CK formed from the reproduced RF signal.

[0031]

As described above, according to the present invention, the comparator is used to fix the amplitude of the reproduced RF signal, and then the same frequency characteristic as that of the reproduced waveform equalizer is applied to perform the quantized feedback process. It is a thing.

According to this, since the quantized feedback processing can be performed with the amplitude of the reproduction RF signal fixed, the reproduction RF signal can be correctly decoded, and the low frequency component of the reproduction RF signal can be removed, so that the sensitivity of the disk is uneven and Is not affected by fluctuations in reflectance, recording fluctuations, servo errors, etc. As a result, the data decoding process is improved. Since the amplitude of the reproduction RF signal can be stabilized even without using the AGC circuit, the phase of the reproduction RF signal is stable, which contributes to the stabilization of the data restoration process.

Therefore, the present invention is extremely suitable when applied to the recording / reproducing processing system using the above-mentioned magneto-optical disk.

[Brief description of drawings]

FIG. 1 is a system diagram of essential parts showing an example of a magneto-optical recording / reproducing apparatus according to the present invention.

FIG. 2 is an explanatory diagram of the operation.

FIG. 3 is an explanatory diagram showing an example of a recording format of a magneto-optical disk.

FIG. 4 is a system diagram showing an example of a reproducing system of the magneto-optical recording / reproducing apparatus.

FIG. 5 is a system diagram of a main part of a conventional magneto-optical recording / reproducing apparatus.

[Explanation of symbols]

 3 Waveform Equalizer 10 Waveform Shaping Circuit 16 High Pass Filter 22 Quantization Feedback Equalizer 30 Comparator 32 Nyquist Shaping Low Pass Filter

Claims (3)

[Claims] 1. A magneto-optical recording / reproducing apparatus for reproducing recorded data from an optical disc having preformatted data recorded for each sector, wherein the data reproduced from the optical disc is supplied to a waveform equalizer through a high-pass filter. A magneto-optical recording / reproducing apparatus characterized in that the waveform equalized output level is fixed and then supplied to a quantization feedback equalizer to obtain a reproduction output whose amplitude and phase are corrected. 2. The magneto-optical recording / reproducing apparatus according to claim 1, wherein a filter which obtains the same characteristic as that of the waveform equalizer is provided in the preceding stage of the quantization feedback equalizer. 3. The quantized feedback equalizer comprises a comparator and a filter for extracting the low frequency component output from the comparator, and the extracted low frequency component is supplied to the comparator. The magneto-optical recording / reproducing apparatus according to claim 1, wherein the magneto-optical recording / reproducing apparatus is configured as described above.