JPH04153921A - Signal reproducing device for optical disk - Google Patents

Abstract

PURPOSE:To allow the detection of even the signals at the top and final end of a sector format region and sector data region by subjecting the waveform equalized signal to DC clamping with a synchronizing signal output as an input trigger and outputting this signal. CONSTITUTION:This device has an equalizing circuit 1 which makes waveform equalization of the reading out signal of the sector data region, a synchronizing signal circuit 2 which outputs the top and final end position signals of the sector data region, a clamping circuit 3 which subjects the waveform equalized signal to the DC clamping with the synchronizing signal output as the input trigger and outputs this signal, and a pulsing circuit 4. The generation of the erroneous data identification at the top and final end of the reading out signals of particularly the sector format region and sector data region is obviated in this way at the time of reading out the bit arrays in the sector format region and sector data region extremely increased in density.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal reproducing device related to a high recording density method such as an optical disk device.

[Conventional technology]

As an example of the prior art, an optical recording and reproducing apparatus in which sectors are divided will be described below, taking as an example a magneto-optical disk which is a particularly erasable type of optical recording disk. In general, magneto-optical disk drives use thermomagnetic recording, in which a recording medium made of a magnetic thin film is irradiated with focused laser light along guide grooves carved in a pre-warped substrate, and information is recorded as magnetized bumps on the recording medium. It will be done. This guide groove is carved in a spiral shape and serves as an information trunk.

At this time, a sector format area indicating sector information is previously engraved in the information trunk as a sector head area. A magneto-optical disk device recognizes the format and records and plays information.

Detection of synchronization signals is indispensable for format recognition and reproduction data identification.

A prohibition button determined by the modulation method is used as the synchronization signal button for the sector format area. In detecting this synchronization signal, the readout signal is subjected to a back-and-forth amplifier, thereby outputting a pulse of the synchronization signal.

Various methods have been used to record and reproduce information in this sector-divided data area. For example, in a 5-inch magneto-optical disk, a mark interval recording method is used for recording.

In this method, information is recorded at the center of the recording focus according to binary information. To identify the reproduction of the reproduced data, the readout signal is differentiated to detect the zero cross point, and at the same time, the reproduction clock determined by the modulation method is extracted, and the '0' and '1' bumps are determined from the timing relationship with the data detection window and the source is detected. Data information is being played back.

In an optical recording and reproducing apparatus that records and reproduces a large amount of information, there is a mark length recording method in which information is added to the edges of recording pits in order to further increase the recording capacity. It is well known that, ideally, this method can double the recording density compared to mark interval recording.

During playback, since the edge position cannot be detected by differentiation, it is usually pulsed at a fixed slice level, and at the same time extracts the playback clock determined by the modulation method, and determines "0°" and "1" bangs from the timing relationship with the data detection window. The information of the source data is being reproduced. In this case, for example, even if recording is performed using a modulation method that does not have a DC component, a DC component will be generated in the read signal due to heat conduction in the recording medium. Further, during mass production of optical disks, substrates having birefringence such as polycarbonate are often used. Therefore, DC fluctuations occur in the circumferential direction of the disk due to fluctuations in the envelope of the read signal.

[Problem to be solved by the invention]

Therefore, when reading data using a DC amplifier, there is a drawback that there is a high possibility of erroneous data identification in the entire data region where envelope fluctuations are directly observed.

On the other hand, when reading is performed using an AC coupled amplifier, envelope fluctuations due to birefringence are suppressed.

However, the read signal output by the AC coupled amplifier causes DC fluctuations at the beginning of the recording/reproduction data area of the sector. Therefore, the method of pulsing using a comparator at a fixed slice level has the disadvantage that the beginning of the data may be read incorrectly.

Also, in order to increase the recording density, it is possible to record by packing the recording pits together.However, if the recording pits are packed together, waveform interference will increase and the resolution will decrease.In addition, thermal recording using a light beam As a result, thermal interference between recording pits cannot be ignored, resulting in incomplete recording focus.Therefore, there is a drawback that data identification by pulsing becomes difficult.

On the other hand, from the viewpoint of format efficiency, it is desirable to increase the recording density when forming the sector format (61) area. However, as with recording pits, if the density becomes high, the resolution will decrease due to the influence of waveform interference, and the vFo
Recovered clock extraction in the gl region becomes unstable. Furthermore, format identification that does not depend on the reproduced clock becomes impossible. At the same time, in order to ensure format identification against DC fluctuations, the sector format area is extra large (
, and in order to improve the resolution, a 6M area is formed in a lower density format than the recording pit. In other words, these problems reduce formatting efficiency and impede capacity increase.

The purpose of the present invention is to improve the above-mentioned drawbacks, solve data identification errors at the beginning of sector-divided format areas and recording/reproducing data areas, and to provide an optical disc that enables high-density recording methods such as mark length recording methods. An object of the present invention is to provide a signal reproducing device.

[Means for Solving the Problems] A first invention is an optical disc signal reproducing device that outputs a reproduction signal from a read signal of a recording pit string in a sector-divided optical disc device, the waveform of a read signal of a sector data area an equalization circuit that performs equalization; a synchronization signal circuit that outputs the start and end position signals of the sector data area; and a clamp that clamps the waveform equalized signal to DC and outputs it using the synchronization signal output as an input trigger. It is characterized by being provided with a circuit.

A second invention is an optical disc signal reproducing device that outputs a sector format information signal from a read signal of a preformatted pit string in a sector-divided optical disc device, and performs waveform equalization of the read signal of a sector format area. an equalization circuit; a clock extraction circuit that receives the output signal of the equalization circuit as input and extracts a clock signal; A synchronization signal circuit that outputs the start and end position signals of the sector format area, and a clamp circuit that clamps DC and outputs the waveform-equalized signal using the synchronization signal output as an input trigger. shall be.

[Effect]

In the present invention, when reading pit strings in the high-density sector format area and sector data area on a sector-divided information track with an optical head, in particular, the beginning and end of the read signal of the sector format area and sector data area are This can solve the problem of data identification errors in the tail.

[Example] Next, the present invention will be described in detail with reference to FIGS. 1 to 5. In the embodiment, a magneto-optical disk divided into sectors using a mark length recording method will be explained as an example.

Among the information recorded on the information track of the magneto-optical disk, the sector format area is pre-engraved on the substrate, so data can be identified by the change in reflectance of the read signal. On the other hand, data can be read out from the sector data area where magneto-optical recording has been performed using the magneto-optic effect. It is assumed that each signal is operated by a signal processing circuit in a different system, for example.

FIG. 1 is a block diagram showing an embodiment of the optical disc signal reproducing apparatus of the first invention.

This optical disc signal reproducing apparatus relates to a sector-divided optical disc apparatus, and includes an equalizing circuit 1 that equalizes the waveform of a read signal of a sector data area in a circuit system that outputs a reproduced signal from a read signal of a recording pit string; It has a synchronization signal circuit 2 that outputs the start and end position signals of the sector data area, a clamp circuit 3 that clamps DC and outputs the waveform-equalized signal using the synchronization signal output as an input trigger, and a pulse generation circuit 4. are doing.

The waveform equalization circuit 1 is constructed using, for example, a transversal filter as shown in FIG.

Here, for example, semi-fixed tap coefficients (C,, C,...
A 7-tap transversal filter with C, ) is used. Here, Z-1 indicates a time delay element. By optimally setting each tap coefficient of this transversal filter, the resolution of a read signal whose resolution has been degraded due to code amount interference is improved.

The synchronization signal circuit 2 receives the waveform equalized output, detects a synchronization signal carved in a sector format area, for example, as described in the prior art, and outputs it as a pulse signal. At this time, the start or end position of the sector data area is outputted as a synchronization pulse signal by adjusting the timing from the synchronization signal of the sector format area or the synchronization signal of the sector data area.

In the clamp circuit 3, as shown in FIG. It basically consists of a circuit that outputs a waveform equalized output signal, and outputs the clamped waveform equalized output signal to the pulse generator 4.

Therefore, the pulsing circuit 4 can output reproduction signal pulses using the zero-cross comparator.

At this time, a clamp circuit may be configured to simply follow the waveform equalized signal, but as shown in Figure 2 (a), it is not possible to follow the steep C fluctuation, and as a result, the data make mistakes. Therefore, in order to quickly set the clamp level of the clamp circuit 3 at the change point from the sector format area to the sector data area and vice versa, the peak detection of the clamp circuit 3 is performed using the synchronization pulse signal output from the synchronization signal circuit 2 as a trigger. At the same time as the sample circuits 11 and 12 are turned on, a preset offset is superimposed and applied to the adder circuit 13 as an initial value. At this time, the initial value is set to, for example, half the amplitude of the equalized waveform, taking into account the polarity that causes the DC fluctuation. In this way, as shown in FIG. 2(1)), it is possible to suppress DC fluctuations at the head position of the sector data area, so that data identification can be performed without causing data errors. Although not shown in this figure, it is clear that the same holds true at the end of the sector data area.

Next, an embodiment according to the second invention is shown in FIG.

This optical disk signal reproducing device relates to a sector-divided optical disk device, and performs waveform equalization of a read signal of a sector format area in a circuit system that outputs a sector format information signal from a read signal of a preformatted pit string. an equalization circuit 5, a clock extraction circuit 8 which extracts a clock signal by inputting the output signal of this equalization circuit, and a clock extraction circuit 8 which extracts a clock signal based on the synchronization signal of the previous sector format area that has already been read out or the synchronization signal in the previous sector data area. The synchronization signal circuit 6 outputs the start and end position signals of the sector format area, the timing correction circuit 7 outputs the start position of the sector format as a pulse signal, and the clock extraction circuit 8 synchronize the waveform-equalized signals. It has a clamp circuit 9 that uses a signal output as an input trigger to clamp and output DC current.

In this embodiment, the waveform equalization circuit 5. Clamp circuit 9
The operation is similar to that of the embodiment shown in FIG.

In a magneto-optical disk, a readout signal for a preformatted focus row is read out in a separate system from a readout signal for a recording pit row. The read signal of the sector format 6N area is waveform-equalized by the waveform equalization circuit 5 and simultaneously input to the synchronization signal circuit 6 which outputs the head position signal of the sector format area. It is impossible to recognize the beginning of the sector format area by yourself. Therefore, a timing correction circuit 7 is installed which adjusts the timing by inputting the synchronization signal of the previous sector format area or the synchronization signal of the sector data area that has already been read out.

This timing correction circuit outputs the leading position of the sector format as a pulse signal. At this time, in order to quickly set the clamp level of the clamp circuit 9 at the change point from the sector data area to the sector format area, the gate of the clamp circuit 9 is switched using the pulse signal output from the synchronization signal circuit 6 as a trigger. Similar to the embodiment shown in FIG. 1, the zero-cross comparator of the pulsing circuit 9 can output signal pulses. Further, at this time, since the clock extraction circuit 8 extracts the reproduced clock from the VFO signal of the waveform-equalized signal, a stable clock signal can be obtained even at high density.

In this way, it is possible to compensate for resolution degradation through waveform equalization, and at the same time suppress DC fluctuations at the beginning and end positions of the sector formant area, making it possible to identify format data without causing data errors. Become.

In the above embodiments, a transversal filter with semi-fixed tap coefficients is used as an example of the waveform equalizer, but a transversal filter with an automatic equalizer configuration that can adaptively change the tap coefficients may also be used.

In this case, it becomes possible to adaptively compensate for deterioration in reproduction characteristics due to variations in characteristics of the optical disk medium or head system, changes over time, etc., so stable and high-quality recording and reproduction is always possible.

Further, in the embodiment, an example of a clamp circuit is shown in which an intermediate value is output by detecting positive and negative peaks, but a smoothing circuit may be used to smooth the read signal and clamp the read signal.

(Effects of the Invention) As explained above, the optical disc signal reproducing device of the present invention can detect signals at the beginning and end of the sector format area and the sector data area without error. By using mark length recording, the information transfer rate can be increased to more than double that of the conventional method, and the information transfer rate can be improved, expanding the range of applications of optical discs.It is also advantageous from the viewpoint of format efficiency.

Although the present invention has been described using magneto-optical recording as an example, it can of course be similarly applied to optical disk systems using write-once type or other reflectance change type media or read-only disks.
It can contribute to increasing the capacity of various optical discs.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the signal reproducing device according to the first invention, FIG. 2 is a diagram for explaining the operation according to the present invention, and FIG. 3 is a signal reproducing apparatus according to the second invention. FIG. 4 is a system diagram showing an embodiment of the device, FIG. 4 is a system diagram showing a transversal filter, and FIG. 5 is a system diagram showing a clamp circuit. 1... Waveform equalization circuit 2... Synchronization signal circuit 3... Clamp circuit 4... Pulse conversion circuit! 5... Waveform equalization circuit 6... Synchronization signal circuit 7... Timing correction circuit 8... Clock extraction circuit 9... Clamp circuit 10... -Pulsing circuit 11・・Positive side peak detection circuit 12・・Negative side peak detection circuit I3・・Adder

Claims (2)

[Claims] (1) An optical disc signal reproducing device that outputs a reproduction signal from a read signal of a recording pit string in a sector-divided optical disc device, comprising: an equalization circuit that equalizes the waveform of a read signal of a sector data area; and the sector data. An optical disc signal comprising: a synchronization signal circuit that outputs a start and end position signal of a region; and a clamp circuit that clamps the waveform equalized signal using the synchronization signal output as an input trigger to DC-clamp and output the signal. playback device. (2) An optical disc signal reproducing device that outputs a sector format information signal from a read signal of a preformatted pit string in a sector-divided optical disc device, and an equalization circuit that equalizes the waveform of the read signal of the sector format area. a clock extraction circuit that receives the output signal of the equalization circuit as input and extracts a clock signal; and a clock extraction circuit that extracts a clock signal by inputting the output signal of the equalization circuit; an optical disc signal reproducing device comprising: a synchronizing signal circuit that outputs the head and end position signals of the waveform-equalized signal; and a clamp circuit that clamps the waveform-equalized signal using the synchronizing signal output as an input trigger and outputs the DC-clamped signal. Device.