JPH05250703A - Controlling method for servo and disklike recording medium - Google Patents

Abstract

PURPOSE:To realize a stable servo control of a grooveless optical disk by a continuous composite servo (CCS) system. CONSTITUTION:A CCS type disk in which information to be recorded is modulated through a run length limited system such as a 1-7 modulation, 2-7 modulation, etc., or a block code system and a pit is formed corresponding to '0' of a modulated signal is provided. A method for controlling a servo comprises the steps of detecting a reflected light to obtain a tracking information signal and/or focus information signal and a total light amount signal of the reflected light and dividing the tracking information signal and/or the focus information signal by the total light amount signal to generate a tracking error signal and/or a focus error signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disc-shaped recording medium having a format suitable for a continuous composite servo system and a servo control method for the disc-shaped recording medium.

[0002]

2. Description of the Related Art An optical disk system capable of irradiating a spiral track with a laser beam to record various data on an optical disk and reading the recorded data is a track on which data on the optical disk is arranged. There are known a continuous system in which the tracks are formed by pregrooves and a sampled servo system in which tracks for arranging data are formed by sample servo pits that are discretely arranged.

Regarding the optical disk (magneto-optical disk) of the continuous composite servo system (hereinafter referred to as CCS system), the modulation (coding) system of the recording signal is so-called run length limited such as 1-7 modulation and 2-7 modulation. In the case of the code (Run Length Limited Code) method or the block code method such as 8-10 modulation, the pit position recording method on the optical disc,
That is, if a pit is formed at a position corresponding to "1", the focus and tracking servo information cannot be obtained directly from the recorded data, that is, the pit.

For example, in the case of the 2-7 modulation method of FIG. 4 (a), when pit cutting is performed by the recording operation control signal of FIG. 4 (b), pits P are formed as shown in FIG. 4 (c). However, in the case of such pit position recording,
As shown in the figure, the laser spot SP may not cover the pit P at the time of reproduction. Of course, when the pit P is not irradiated with the laser spot SP, it is impossible to detect the pit-shaped edge and extract the servo error information. For servo control, an information amount (for example, 40 KHz) that is about 20 times that of the servo signal band (for example, 2 KHz) is required, but this sampling theorem is based on the above pit position recording method and is not limited to pit detection information. Can not meet.

Therefore, in the case of the CCS system, a groove G having a depth of λ / 8 (λ: laser wavelength) is provided between the tracks as shown in FIG. 5A, and the pit P is formed on the land L. I am trying to record along. As a result, a push-pull signal can be obtained by detecting the edge of the groove G, and tracking servo information can be obtained. The depth of the pit P is λ / 4, and the land L
The phase difference between the light diffracted and reflected by the pit P and the light diffracted and diffracted by the pit P is π, that is, depending on the pit P, only the RF signal is extracted and push-pull information cannot be obtained.

[0006]

However, the groove G
However, the following problems have arisen in the case of providing. First, for example, the wall portion between the pit P and the groove G as shown by W in the cross-sectional views of FIGS. 5A and 5B is shown in FIG.
As shown by W _{X in} (b), it has collapsed. In particular, in accordance with the demand for high-density recording, the track pitch becomes narrower, and the wall portion W becomes remarkable as the wall portion W becomes thinner. In this case, the edge information of the land L and the groove G cannot be accurately extracted. Further, since it must be considered to prevent this, disk molding (stamping, laser cutting, etc.) becomes difficult.

Further, the provision of the groove G is contrary to the request for high density recording, that is, the groove G is set to 1
The fact that it must be provided for each track limits the narrowing of the track pitch.

[0008]

SUMMARY OF THE INVENTION In view of such problems, an object of the present invention is to realize stable servo control for a grooveless optical disk by the CCS method. Therefore, the recorded information is, for example, 1-7
Modulation method, or run length limited method of 2-7 modulation method or block code method, and "0" of this modulated (coding) signal is recorded corresponding to pits, The present invention provides a disc-shaped recording medium of a continuous composite servo system, detects reflected light of laser light scanning on such an optical disc, and obtains a tracking information signal and / or a focus information signal. A servo control method for generating a tracking error signal and / or a focus error signal by obtaining a light amount signal and dividing the tracking information signal and / or the focus information signal by the total light amount signal.

[0009]

In the above-mentioned coding method, in the optical disc of the pit position recording in which "0" corresponds to the pit,
The pits are formed to the extent that sufficient information is obtained to satisfy the sampling theorem for extracting servo information using only pit detection information.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. This embodiment is an optical disk (magneto-optical disk) in which pits are recorded by adopting the 2-7 modulation method and a servo control method therefor.

FIG. 1 is an explanatory view of the pit shape of the optical disk of this embodiment. For example, the data to be recorded is shown in FIG.
When coded with 2-7 modulation method like
As the pits correspond to "0" information,
Pits P (ROM pits) are formed by cutting as shown in FIG. The depth of this pit P is λ / 4 to λ /
8 is set, that is, both the push-pull signal and the RF signal are obtained from the pit P.

In this case, the laser spot SP is the pit P.
The pit detection information (push-pull signal) based on the reflected light of the laser spot SP can be obtained sufficiently to satisfy the sampling theorem for generating servo information. In other words, in the case of this optical disc,
Pit P even if there is no groove between tracks
A push-pull signal for generating servo information can be obtained only from the above.

By the way, in 2-7 coding, the spectrum includes a DC component, that is, since it is not DC-free (the ratio of the pit portion and the non-pit portion is different), the DC component is superimposed on the reproduction information. To be done. This effect is due to CMRR (Common Mode Rejection Ra
If tio) is sufficient, then for push-pull signals it will appear as a gain variation.

Therefore, when the push-pull signal is obtained by the two-division or four-division detector, it is obtained by dividing the push-pull signal by the total amount of light detected by the two-division or four-division detector, that is, the sum signal and normalizing. The DC component can be eliminated from the servo information.

FIG. 2 shows the structure for obtaining the tracking error signal TE, and FIG. 3 shows the structure for obtaining the focus error signal FE. In each figure, 1 is a four-division detector having A, B, C, D light-receiving surfaces, and 2, 3, 4 are output signals S _{A of} voltage values according to the amount of light received from each light-receiving surface of the four-division detector 1. , S _B , S _C , S _D are supplied to perform a predetermined operation, and reference numerals 5 and 6 denote division circuits.

In order to obtain the tracking error signal TE, when the reflected light of the laser spot is detected by the 4-division detector 1, (S _A + S _B )-(S
_C + S _D ) is calculated, that is, the push-pull signal of the light receiving surface divided into two is output as the tracking information S _TP . On the other hand, in the arithmetic circuit 3, (S _A + S _B + S _C + S
The calculation of _D ) is performed, and information on the total amount of light received by the four-division detector 1 is output as a signal S _AL .

The tracking information S _TP and the total light amount information S _AL are supplied to the division circuit 5, and in this division circuit 5, (S _TP
/ S _AL ) is calculated and its output is used as the tracking error signal TE. This tracking error signal T
Since the DC component is eliminated from E as described above, even the tracking error signal TE extracted from the pit P recorded by the 2-7 modulation method of the present embodiment which is not DC-free, Stable servo operation is realized.

Further, in order to obtain the focus error signal FE, the reflected light of the laser spot is divided into four detectors 1.
Is detected by the arithmetic circuit 4, (S _A + S _C ) −
(S _B + S _D ) is calculated, that is, the focus information S _FP by the astigmatism method is output.

The focus information S _FP and the total light amount information S _{AL from the} arithmetic circuit 3 are supplied to the dividing circuit 6, and the arithmetic operation of (S _FP / S _AL ) is performed in the dividing circuit 6, and the output is focused. The error signal FE is used. Since the DC component of this focus error signal FE is similarly removed, stable servo operation is realized by the focus error signal FE extracted from the pit P recorded by the 2-7 modulation method which is not DC free. It

In the optical disc of the present embodiment and the servo control method corresponding thereto as described above, good servo control by the CCS method can be realized without providing a groove.
Therefore, it becomes easy to increase the recording density of the optical disc, that is, to set the track pitch narrower. Further, since the groove molding is unnecessary, the disk molding becomes easy.
Furthermore, Figure 1 of the pit position record corresponding to "0"
In such a pit, the laser scanning rarely crosses the non-pit portion during traverse, so that the traverse count operation does not have any adverse effect due to the absence of the groove.

In this embodiment, the recording signal is coded by the 2-7 modulation method.
The present invention can also be applied to the -10 modulation method and the like. That is, it may be a run length limited code or a block code. In the case of DC-free coding, it is not always necessary to divide the error information by the total light amount information as shown in FIGS.

[0022]

As described above, according to the present invention, the information to be recorded is modulated by the run length limited system or the block code system, and "0" of the modulated signal is recorded.
Provides a disc-shaped recording medium in which data is recorded corresponding to pits, and correspondingly, push-pull information and / or astigmatism information is detected from the pits to detect tracking information signals and / or focus information. Since a tracking error signal and / or a focus error signal is generated by dividing the tracking information signal and / or the focus information signal by the total light amount signal while obtaining the signal and the total light amount signal of the reflected light by the pit, Even if the track is not formed by providing the groove and the land, the information extracted from only the signal pit string is
Good servo control by the CS method is realized. Therefore, there is an effect that a grooveless CCS disk can be realized, and the track pitch can be narrowed to easily cope with high recording density. Further, there is an advantage that the optical disc molding becomes easy.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an optical disc according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a tracking error signal generation block according to the present embodiment.

FIG. 3 is an explanatory diagram of a focus error signal generation block according to the present embodiment.

FIG. 4 is an explanatory diagram of a 2-7 modulation method.

FIG. 5 is an explanatory diagram of a groove of an optical disc according to the CCS method.

[Explanation of symbols]

 1 4-division detector 2, 3, 4, arithmetic circuit 5, 6 division circuit

Claims (2)

[Claims] 1. A continuous composite servo system in which information to be recorded is modulated by a run length limited system or a block code system, and a phase pit is recorded corresponding to "0" of the modulated signal. With respect to the disk-shaped recording medium, the tracking light signal and / or the focus difference signal are obtained by detecting the reflected light of the laser light scanning and the tracking light signal and / or the focus difference signal are obtained. A servo control method characterized in that a tracking error signal and / or a focus error signal is generated by dividing by a total light amount signal. 2. A continuous composite servo system is adopted, and information to be recorded is modulated by a 1-7 modulation system or a 2-7 modulation system, and corresponds to "0" of the modulated signal. And a phase-shaped pit is recorded on the disk-shaped recording medium.