JPH05250707A - Controlling method for tracking of optical disk - Google Patents

Abstract

PURPOSE:To increase the expandability of an optical disk recording medium by applying a predetermined coefficient to one or both of reproduced signals of two wobbling pits to obtain a difference signal. CONSTITUTION:Predetermined two adjacent wobbling pits are selected, a difference signal of their reproduced signals is used as a tracking error signal, and tracking can be controlled at desired positions of tracks t1, t2, t3 within one basic track width. If the tracking is desired to be controlled corresponding to a pitch of the tracks of TP2 corresponding to a width between the tracks t1 and t2, a pair of wobbling pits for generating a tracking error signal at each one cycle of an optical disk may be sequentially selected. Thus, the expandability can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc tracking control method for a sampled servo type optical disc (magneto-optical disc), and more particularly to a recording / reproducing operation on an optical disc at an arbitrary track pitch. Is to be able to perform.

[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.

FIG. 8 shows an example of the format of an optical disk (magneto-optical disk) in which a recording track is formed by sample servo pits. S _{1 to} S
₄₂ indicates, for example, a sector divided into 42 in the circumferential direction.

A track for each sector is shown in FIG.
As shown in (a), a header segment H ₁ which is an area in which address data is recorded with pits formed in advance by embossing or the like is provided, and then a header segment H ₂ is provided. Further, following the header segment H ₂ , for example, a data segment S having a data recording area DB 30 in which 20-byte data is recorded is 30.
It is formed by being divided into G _{1 to} SG ₃₀ . In the recordable magneto-optical disk, this data segment SG ₁
The data recording area DB in SG ₃₀ is magneto-optical (MO).
The area is made available for data writing / reading.

Each of these data segments (SG _{1 to} S
G ₃₀ ) and header segments H ₁ and H ₂ are shown in FIG.
As shown in (b), the servo byte SB is arranged at the beginning, followed by the address, MO data, or ROM.
An area for recording data is formed.

The servo bite SB has a pair of wobbling pits P ₁ and P ₂ which are displaced from the center of the track T by at least 1/4 track pitch toward the outer peripheral side and the inner peripheral side.
And a clock pit P ₃ arranged on the center line of the track T is previously formed by embossing or the like, and an access code indicating track information (for example, lower 4 bits of the track address) forms a gray code Pit P. ₄ and P ₅ are similarly formed. A mirror surface M is formed at the rear of the wobbling pits P ₁ and P ₂ and the clock pit P ₃ , and the focus servo signal is detected by the laser light reflected from the mirror surface M and the laser power control is performed. You can also do

In such a magneto-optical disk, the reproduction signals S _P1 and S _P2 based on the reflected light when the wobbling pits P ₁ and P ₂ are usually detected at the sample points t ₁ and t ₂ are calculated (S
_P1− S _P2 )
E is formed, and the clock pit P ₃ is sampled at the sampling point t.
_The signal detected at ₃ forms the master clock signal.

[0008]

By obtaining the tracking error signal TE from the difference signal (S _P1 -S _P2 ) between the reproduction signals S _P1 and S _P2 due to the wobbling pits P ₁ and P ₂ , the tracking error signal TE = 0 In this state, the laser spot is accurately scanned on the track center T, but with such a tracking control method, tracking servo control cannot be performed so that the laser spot scans other than the track center T. ..

However, by using (S _P2 -S _P1 ) as the tracking error signal TE, tracking control can be performed at an intermediate point between adjacent tracks, but in any case, the tracking position can have a maximum of two stages. Can only be switched.

By the way, when the laser wavelength is shortened and the demand for high density recording is met, the track pitch is set to be narrow. However, when the above-mentioned optical disk tracking control method is used. Since the position where the tracking can be turned on (hereinafter, referred to as a trackable position) is limited by the wobbling pits P ₁ and P ₂ , servo areas (wobbling pits) are provided according to the set track pitches. An optical disk must be prepared, and it is not possible to perform recording / reproducing operation by performing tracking servo control for one kind of optical disk in accordance with various set track pitches. That is, in the conventional optical disc tracking control method,
There was a problem that it was not possible to provide expandability so that it could be adapted to various track pitches.

[0011]

In view of the above problems, the present invention provides a tracking control method for an optical disk which can turn on a tracking servo at a desired position for one type of optical disk. ..

That is, the servo areas are discretely arranged on the tracks formed in a concentric or spiral shape, and the servo areas are firstly arranged at predetermined positions deviated in the radial direction of the disk.
For the sampled servo type optical disc in which the second wobbling pits are formed, the reproduction output by the first and / or the second wobbling pits is set to the optical disc 1 from the coefficient group including a plurality of set coefficients. After giving a coefficient that is sequentially selected in a cycle unit, a tracking error signal is generated by the difference signal.

Further, servo areas are discretely arranged on concentric or spirally formed tracks, and within this servo area, three tracks are provided for each basic track width with one track number. In addition to providing a sampled servo type optical disc in which a plurality of wobbling pits described above are formed, when this optical disc is used, from among the plurality of wobbling pits, based on a predetermined rule given in advance. A tracking error signal is generated by the difference signal between the reproduction outputs of the two wobbling pits selected per one rotation of the optical disc.

[0014]

By applying a predetermined coefficient to one or both of the reproduced signals of the two wobbling pits and then obtaining the difference signal, or by selecting two from a plurality of wobbling pits of three or more, By obtaining the difference signal of the output signals, the trackable position is not restricted to a maximum of two types based on the wobbling pit formation position, and more types of trackable positions can be set.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the optical disk tracking control method of the present invention will be described below with reference to FIGS.
In this embodiment, a track having one track number, that is, a track on the disc format (hereinafter, referred to as a basic track, is used as a basic track, and a laser spot is scanned and recorded / recorded based on the tracking control method of this embodiment.
This is adopted when using a sampled servo type optical disc in which a pair of wobbling pits are formed for distinguishing from the actual track for reproduction).

FIG. 1 schematically shows a part of an optical disc (magneto-optical disc) in which a basic track having a track pitch T _P is set and pre-formatted,
Each basic track has track addresses At (... At _n , At _{n + 1} , At) in its predetermined area (for example, in the header segment H ₁ and gray code pits P ₄ and P ₅ in the servo byte SB in FIG. 9). _{n + 2} ...) is recorded. Further, a pair of wobbling pits WP ₁ and WP ₂ are formed in the servo areas discretely formed in each of the basic tracks, offset by a predetermined amount (for example, 1/4 track pitch) in mutually opposite directions.

According to the conventional optical disk tracking control method, the difference signal between the reproduction signals of the wobbling pits WP ₁ and WP ₂ is used as a tracking error signal for such an optical disk, and one basic track is indicated by a chain line. As shown, the tracking servo control is executed assuming that one track T is formed.

That is, each wobbling pit WP ₁ , W
_Assuming that the reproduced signals by P ₂ are S _WP1 and S _WP2 , the tracking error signal TE is

[Equation 1] (However, K = −1).

Here, (T _ON / T _P ) is the deviation amount when the track center at the track pitch T _P is 0,
That is, T _ON is set as the tracking possible position. Also, FIG.
, The reproduction signal S by the wobbling pit WP _1
WP1 is DC component S _{WP1 (DC)} and AC component (sine waveform)
It is a combination of _{SWP1 (AC)} and wobbling pit W
P ₁ and WP ₂ are each deviated from the track center by 1/4 track pitch (that is, shifted by 1/2 wavelength).
Therefore, the reproduction signal S _WP1 and S _{WP 2} phase is shifted 180 °.

Therefore, the above (Equation 1) is

[Equation 2] Can be

Then, the tracking error signal TE = 0
Since the case where the tracking servo is turned on is set to TE = 0 and the above (Equation 2) is transposed,

[Equation 3] Becomes That is, from this (Equation 3), it is understood that the trackable position T _ON can be arbitrarily set by changing the value of the coefficient K.

Therefore, in this embodiment, for example, four kinds of coefficients K (K ₁ , K ₂ , K ₃ , K ₄ ) are prepared, and _one coefficient of the optical disk is prepared.
The value of the coefficient K in the above (Equation 1) is calculated as K ₁ →
K ₂ → K ₃ → K ₄ → K ₁ ...

Then, as shown in FIG. 3, each coefficient (K
₄ in the basic track based on ₁ , K ₂ , K ₃ , K ₄ )
The tracking servo is turned on at the position of the type. In other words, the basic track At Within _n tracks _{T 1 (n) ~T 4 (} n), the track T ₁ is in the basic track _{At n + 1 (n + 1} ) ~T 4 (n + 1) ··· As described above, it is possible to set a track having a track pitch T _P1 and perform tracking control so that a recording / reproducing operation is actually performed on an optical disc in which basic tracks are pre-formatted at a track pitch T _P. it can. Of course, by setting various values and types of the coefficient K, it is possible to further set tracks of various desired track pitches and perform the recording / reproducing operation.

The coefficient groups (K _{1 to} K _n ) are previously stored in a ROM or RAM for storing coefficient groups in the optical disk recording / reproducing apparatus, and are stored in the disk 1 at the time of recording / reproducing.
It suffices to sequentially read and use each cycle. Further, by storing a plurality of coefficient groups and selecting an arbitrary coefficient group at the time of recording / reproducing, an optical disk recording / reproducing apparatus capable of dealing with various track pitches may be configured. Further, although the coefficient is given to the reproduced signal of one wobbling pit, it may be considered to be given to the reproduced signal of both wobbling pits.

Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, three tracks are provided in a track having one track number, that is, three basic tracks.
This is a tracking control method for an optical disc that is proposed when a sampled servo type optical disc in which at least Y wobbling pits are formed is used. For the sake of explanation, it is assumed that the optical disc has three wobbling pits formed in one basic track. Note that P _A indicates a pit expressing a track number.

FIG. 4 schematically shows a part of an optical disk (magneto-optical disk) in which a basic track having a track pitch T _P is set and pre-formatted,
Each basic track has track addresses At (... At _n , At _{n + 1} , At) in its predetermined area (for example, in the header segment H ₁ and gray code pits P ₄ and P ₅ in the servo byte SB in FIG. 9). _{n + 2} ...) is recorded. Further, in the servo area formed discretely in each basic track, three wobbling pits WP ₀ , WP ₁ and W corresponding to one basic track width range are provided.
P ₂ is formed so as to deviate by a predetermined amount.

For such an optical disc, two adjacent wobbling pits are selected and the difference signal between the reproduced signals is used as the tracking error signal TE, so that the dashed line in the figure shows Tracking control can be performed at a desired position among the tracks t ₁ , t ₂ , and t ₃ within one basic track width.

That is, the wobbling pits WP ₀ , WP
₁ , the reproduction signals by WP ₂ are S _WP0 , S _WP1 , and
Let S _WP2 , if TE = S _WP0 −S _WP1 , then track t ₁ TE = S _WP1 −S _WP2 , then track t _{2 If} TE = S _WP2 −S _{WP 0} , then set a light spot on track t ₀ respectively. Tracking control is performed so that scanning is performed.

Therefore, when it is desired to perform the tracking control corresponding to the track pitch of T _P2 corresponding to the width between the tracks t _{1 and} t _2, a pair of tracking error signals is generated for each revolution of the optical disc. You just have to select the wobbling pits sequentially. That, n tracks _{(t 1) ············ TE = S} WP0 -S WP1 n + 1 tracks _{(t 2) ········ TE = S} WP1 -S WP2 n + 2 tracks (T ₀ ) _... TE = S _WP2- S _WP0 n + 3 tracks (t ₁ ) _... TE = S _WP0- S _{WP1 :::} Select wobbling pits in sequence. Then, tracking control is performed. Then, for the optical disc of FIG. 4 in which the basic tracks are pre-formatted with the track pitch T _P , the recording / reproducing operation can be performed with the tracks (t ₁ , t ₂ , t ₃ ) of the track pitch T _P2 shown by the chain line become.

If the track pitch is set to 2T _P2 as indicated by the one-dot chain line in FIG. 5, then n tracks (t ₁ ) _... TE = S _WP0 -S _WP1 n + 1 tracks (T ₀ ) _... TE = S _WP2- S _WP0 n + 2 tracks (t ₂ ) ... TE = S _WP1- S _WP2 n + 3 tracks (t ₁ ) ... ··· TE = S _WP0 −S _WP1 : _:: It is only necessary to select two wobbling pits for each revolution and obtain a difference signal.

The above is a specific example of selecting the wobbling pits in the case where the track pitch is T _P2 or 2T _P2 when three wobbling pits are formed for one basic track. become that way.

As shown in FIG. 6, Y (Y ≧ 3) wobbling pits (WP _{0 to} WP) per basic track.
_(Y-1) ) is formed, the minimum track pitch of the recording / reproducing tracks realized by selecting two adjacent wobbling pits is the track pitch T _P of the basic track. (T _P / Y).

Here, it is assumed that the tracking control is performed so that the track pitch becomes M × (T _P / Y). Then, it is assumed that the light spot is scanned from the first track to the Zth track at a track pitch of M × (T _P / Y).
When each reproduced signal by wobbling pits _{(WP 0 ~WP (Y-1} )) and _{(S WP (0) ~S WP} (Y-1)), the first track ······ TE = S _{WP { 0 (mod Y)}} -S _{WP {(0 + 1) (mod Y)}} 2nd track ... TE = S _{WP {(0 + M) (mod Y)}} -S _{WP {(0 + M + 1 (mod Y)}} 3rd track: TE = S _{WP {(0 + 2M) (mod Y)}} -S _{WP {(0 + 2M + 1) (mod Y)}} : Zth track ... TE = S _{WP {(0 + M (Z-1)) (mod Y)}} -S _{WP {(0 + M (Z-1) +1) (mod Y)}} (however, x (mod Y) indicates (remainder of x / Y), so that for the n-th track, the n-th track ... TE = S _{WP {(M (n-1)) (mod Y) The} tracking error signal TE is generated as −S _{WP {(M (n-1) +1) (mod Y)}} , that is, the wobbling pit selected for each turn of the optical disc is WP _{{(M ( n-1)) (mod Y)}} and WP _{{(M (n-
1) +1) (mod Y)}} .

By the way, when the tracking servo is continuously applied from the first track, it is sufficient to select two adjacent wobbling pits WP according to the rule which agrees with the above-mentioned general formula. When the track jump is performed on the basic track, it is first necessary to determine which wobbling pit WP is selected on the basic track to apply the tracking servo.

For example, in the case where recording / reproduction is performed with M = 2 (that is, track pitch = 2T _P2 ) as shown in FIG. 5, the basic track At _n ,
At At _{n + 2} , the servo is applied to the track t ₁ as the first track, and the basic tracks At _{n + 1} , At
_{At n + 3} , servo is applied to the track t ₂ .

For this reason, when this embodiment is adopted, the number Y of wobbling pits WP in the basic track and the set track pitch {M × (T _P /
Y)}, _where is the first track of the basic track At _n (t ₀ , t ₁ , t _{2 in} the example of three wobbling pits as shown in FIG. 5).
Which track), that is, which wobbling pit should be selected must be determined based on the track address.

Here, at the basic track of the track number At _n , there are At _n × Y wobbling pits WP counting from the basic track as the starting point (for example, the first basic track). Therefore, if the track pitch is {M × (T _P / Y)} and the track jumps to the basic track of the track number At _n , {(At _n · Y) / M} (mod Y) It is calculated, and this is made to correspond to the tracks marked with t ₀ to t _(Y-1) as shown in FIG. That is, the first track t _x in the basic track (At _n ) can be calculated as t _x = t _{{(Atn · Y) / M} (mod Y)} .

For example, in the case of FIG. 5, the track number At
_{When n} = 1, if a track jump is performed to the basic track At _{n + 2} , that is, the basic track of the track number = 3, {(3 · 3) / 2} (mod Y) = 1 The first track t _{x where the} tracking servo should be performed is determined as t _x = t _{{(3 · 3) / 2} (mod Y)} = t ₁ . Therefore, the tracking error signal is generated as TE = S _WP0 −S _WP1 .

Each track after the first track is discriminated in this way at the time of seek is the n-th track of the general formula described above ... TE = S _{WP {(M (n-1)) (mod It suffices} that the wobbling pit WP is selected and tracking servo is applied by _Y)} -S _{WP {(M (n-1) +1) (mod Y)}} . However, if the first track in the basic track of the seek destination is t _F , then t _F = t ₁ does not necessarily hold (t _F is from t ₀ to t).
_(Y-1) may be either).

For example, in the example of FIG. 5, the basic track (At
When seeking to ( _{n + 1} ), the first track t _F = t ₂ , and if M = 2, the second track is the track (At
_It must be t ₁ in ( _{n + 2} ). However, the above general formula is not fixed because it is expressed by fixing the first track = t ₁ . Therefore, after the track jump, the element of the first track t _F at that time is incorporated into the general formula to obtain the tracking error signal TE of the nth track.
TE = S _{WP {(M (n-1)) (mod Y) + (F-1)} (mod Y)} −S _{WP {(M (n-1) +1) (mod Y) + ( F-1)} (mod Y)}} .

In the above embodiments, two wobbling pits that are adjacent to each other are selected from among three or more wobbling pits, but of course, two wobbling pits that are not adjacent to each other are selected to perform tracking. A case may be provided in which an error signal is generated.

Then, for example, as shown in FIG. 7, there are more kinds of trackable positions. In this case, track t _A0 ... TE = S _WP2- S _WP1 track t _A1 ... TE = S _WP0- S _WP1 track t _A2 ... TE = S _WP0- S _WP2 track t _A3 ... ·· TE = S _WP1 -S _WP2 track _{t A4 ···· TE = S WP1 -S} WP0 track _{t A5 ···· TE = S WP2 -S} WP0 next, in other words, the track to be on some wobbling pit ( For t _A0 , t _A2 , t _A4 ), the difference signal between the reproduction signals of the wobbling pits on both sides of the difference may be taken.

Furthermore, the first and second embodiments described above are combined to select two out of three or more wobbling pits in the basic track, and the selected two are selected.
By providing a predetermined coefficient to both or one of the reproduction signals obtained by one wobbling pit and then obtaining the difference signal, it is possible to increase the types of trackable positions.

[0044]

As described above, the optical disk tracking control method of the present invention is such that the difference signal is obtained by giving a predetermined coefficient value to the reproduction signal from the pair of wobbling pits, or A tracking error signal for turning on the tracking servo at a desired position by selecting two of three or more wobbling pits provided in one basic track to obtain a difference signal of the reproduced signals. Can be generated. Therefore, by using the optical disc tracking control method of the present invention, one optical disc can be made compatible with various types of formats, and the expandability of the optical disc recording medium can be remarkably expanded. ..

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a reproduction signal of a wobbling pit.

FIG. 3 is an explanatory diagram of a trackable position according to the first embodiment.

FIG. 4 is an explanatory diagram of a second embodiment of the present invention.

FIG. 5 is an explanatory diagram of an example of a tracking state in the second embodiment.

FIG. 6 is a generalized explanatory diagram of the second embodiment.

FIG. 7 is an explanatory diagram of tracking control by another method in the second embodiment.

FIG. 8 is an explanatory diagram of an optical disc.

FIG. 9 is an explanatory diagram of a segment structure.

[Explanation of symbols]

T, t track T _P basic track pitch T _P1 track pitch WP wobbling pit

Claims (2)

[Claims] 1. Servo areas are discretely arranged on concentric or spirally formed tracks, and first and second wobbling are provided at predetermined positions deviated in the disk radial direction within the servo areas. For a sampled servo type optical disc in which pits are formed, the reproduction output by the first and / or the second wobbling pits is sequentially selected from a coefficient group including a plurality of set coefficients in units of one rotation of the optical disc. After giving the coefficient
A tracking control method for an optical disc, wherein a tracking error signal is generated by the difference signal. 2. Servo areas are discretely arranged on concentric or spirally formed tracks, and within the servo area, three or more servo tracks are provided for each basic track width with one track number. Using a sampled servo type optical disc in which a plurality of wobbling pits are formed, two wobbling pits are selected from the plurality of wobbling pits based on a predetermined rule in advance in a unit of one revolution of the optical disc. A tracking control method for an optical disc, wherein a tracking error signal is generated by a difference signal between reproduction outputs by wobbling pits.