JPH0478073A - Inter-track position detecting system - Google Patents

Abstract

PURPOSE:To realize high-speed and highly precise seeking operation by obtaining highly precise position information in which a track pitch is divided on the basis of the level order data of the reproduced signals of a pair of a wobbling pit and a clock pit. CONSTITUTION:Sampling circuits 23A to 23C sample-hold the reproduced RF signal at the positions of the clock pit and the wobbling pit in a sample servo pit on the basis of sampling pulses PS(A) to PS(C) supplied from a controller. Then, an arithmetic means 24 to compare the obtained reproduced RF signal levels and rank them is provided, and a position signal corresponding to the position of one eighth, at least, of the track pitch is detected by the level order data of each reproduced signal of the wobbling pit and the clock pit obtained by the arithmetic means 24. Thus, the controlled variable of a traverse servo circuit can be more finely controlled, and the high-speed seeking operation can be executed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for detecting inter-track position signals useful when moving a tracking actuator in the radial direction of a disk to access a desired track. .

[Summary of the Invention] The inter-track position detection method of the present invention samples the reproduced RF signal level from wobbling pits and clock pits that are formed as sample servo pits at predetermined positions on spiral or concentric tracks, for example. Based on this level order data, it is possible to detect a small number of positions (each divided into eight track pitches).

[Prior Art] An optical disk device that can irradiate an optical disk with a laser beam to record information and read out the recorded information is equipped with an optical head that moves in the radial direction of the optical disk. A coarse actuator for moving the entire optical head is driven by, for example, a linear motor.

FIG. 4 shows an outline of such an optical head.
a coarse actuator (linear motor) 5 arranged to slide against a pair of guides 4 extending across the F-rack 3 and in the radial direction of the magneto-optical disk;
It is made up of a fine (fine) actuator (two-axis mechanism) 6 mounted on this coarse actuator 5.

Reference numeral 7 denotes an objective lens that irradiates the magneto-optical disk 2 with a laser beam emitted from the fine actuator 6, and the laser beam tracks the recording track 3 of the magneto-optical disk 2, thereby causing the laser beam to emit light from the rotating magneto-optical disk 2. It is possible to read or write information.

Also, the seek operation for accessing the optical head 1 to a desired track on the magneto-optical disk 2 is performed by moving the optical head 1 to -a.
By supplying a predetermined drive signal to the coarse actuator 5 or fine actuator 6, the beam spot is moved in the radial direction of the magneto-optical disk 2 to seek a target track.

Figure 5 shows an example of a seek servo circuit that can perform such a seek operation. When seeking a desired track, a track jump is performed from the current track position to the target track position. Control data corresponding to the number of tracks is output from the target track setting section 10 and supplied to the tracking actuator 13 via the subtracter 11 and drive circuit 12, and a signal for reproducing the RF multiplied signal that changes as the tracking actuator 13 moves. The address detection circuit 15 detects the current track number from the output of the reproduction circuit 14, and supplies the track number on which the light spot is irradiated to the subtracter 11 to control the movement of the tracking actuator 13.

According to such a track access method, for example, as shown in the figure from the target track setting unit IO, the current track position TP changes over time to the target track T.
When a control signal (track number) that changes to 7 is output, the moving speed V of the tracking actuator 13 changes as shown by the dotted line, making it possible to perform a high-speed seek operation.

[Problem to be Solved by the Invention J] In this case, in an optical disc in which the optical disc is divided in the circumferential direction and each of the divided sectors is further divided and a sample servo pit is formatted at the tip of each segment, the traverse speed is For example, 0.125m1sec
If the traverse speed is approximately zero on the target track, it is possible to read the gray code recorded in the sample servo pit of each segment and apply speed servo on a track-by-track basis. In order to converge, the traverse speed must be lowered, or the value of the position information of the traverse track fed back to the subtractor 11 must be less than 1 track, in order to achieve a smooth landing on the target track. Therefore, there was a problem in that high-speed seek operations could not be performed as a result.

[Means for Solving the Problems] The present invention has been made in view of these problems.
In order to perform speed servo on a track-by-track basis, which has been done in the past, with even more fine-grained speed servo, and to apply speed servo based on position information divided by track pitch, for example, into 8, the reproduced RF obtained from a pair of wobbling pits and clock pits is used.
Means for sampling each signal level value and calculation means for ranking each sampled signal in order of level are provided, and the level order data of three units of bits constituting a sample servo pit obtained by this calculation means is tracked. An inter-track position detection method is provided in which the pitch interval is divided into eight pieces of position information data.

[Effect 1: The level of the reproduced RF signal obtained from the wobbling pit and the clock pit changes depending on the scanning position (tracking state) of the laser spot, so if the levels are detected, the inter-track position can be detected. It will be possible.

Then, by adding position information that is divided into finely divided tracks to the lower bits of the gray code detected during traversal, the position of the light spot during traverse can be detected with a value of one track pitch or less. By feeding back this track position information during a seek operation, the control amount of the traverse servo circuit can be controlled more finely, and a high-speed seek operation becomes possible.

[Example] Fig. 1 shows a block diagram of track position detection during traverse applied to the inter-track position detection method of the present invention, and Fig. 2 is an explanatory diagram of an outline of sample servo pits formed on a disk. be.

In FIG. 1, 21 is an optical disc D that is being recorded or played back.
An optical head 22 reads out the RF multiplied signal, and A detects the control data in the RF multiplied signal and sample bits in the sample servo pit area and converts them into digital signals.
/D converters 23A, 23B, and 23C are sampling pulses P supplied from a controller (not shown).
Based on 51AlI P 31Bl+ P 91C1, reproduce the reproduced RF signal at the position of the clock pit and wobbling pit in the sample servit through sample hole 1.
This is a sampling circuit that performs ~.

The sample servo pit type optical disk D has each recording track T, and as shown in FIG. It is recorded through processing, etc., and furthermore,
Gray codes QD, Q indicating track numbers are provided.

The two wobbling pits QA, Q, are shifted by 1/4 of the track pitch P from the center line of the track, and a tracking error signal is normally formed from a signal that detects the wobbling pits QA, Qc.

Also, the clock pit QIl is on the center line of the track, and by detecting this clock pit QIl,
A clock information signal is obtained and forms a reference clock signal when writing or reading data.

Additionally, bit Q detects the Gray code. .

The QE is coded to identify, for example, 16 track numbers, and can be used to count the number of traversed tracks even during high-speed track jumps.

This Gray code is then sampled by the sampling circuit 23D in FIG. 1 and supplied to the Gray code decoder 27.

Reference numeral 24 denotes an arithmetic circuit that compares the levels of each sample servo pin 1~ detected by the sampling circuits 23A, 23B, and 23C, sorts them into levels, and outputs data in the order of levels.

A decoder 25 encodes the level order data supplied from the arithmetic circuit 24 into, for example, 3 bits and outputs it as a positional information code signal obtained by dividing the track pitch into 8 parts. The inter-track position information code signal output from the decoder 25 is supplied to a first adding circuit 29A, where it is added to the 4-bit code signal output from the Cray code decoder 27 as the lower 3 bits.

Reference numeral 28 denotes an address decoder for detecting an address signal indicating sector information, and address data of a recording track is output as, for example, 15-bit data during normal recording and reproduction. This address data also includes the track position signal (
7 bits) are further added in the second adder circuit 29B.

Hereinafter, the operation of the inter-track position detection method of the present invention will be explained with reference to FIG.

FIG. 3(a) is an enlarged view of the servo bit portion of FIG. 2, and shows tracks Tn, Tn. One track pitch interval P is divided into eight unit areas, which are shown by ■ to ■.

When this servo bit part is irradiated with a light beam, the reproduced RF signal due to the reflected light is generated as shown in FIG. They will be shown as RF■ to RF■. For example, when scanning area (2) in an on-track state, the reproduction signal level due to the clock pit Q will be higher than the reproduction signal level due to the wobbling pits QA, Qc, and the light beam will scan the area (2) where the influence of the oblong pit Qc is large. The playback signal level in the detrack state being scanned decreases in the order of wobbling pit Qc, clock pit Q8, and wobbling pit QA. That is, for each region, a level order of the reproduced RF signal is generated as shown by (il to (iii) in the figure, and the state of the level order is different in each region.

Therefore, the reproduced RF signal of this servo pit is
) is the sampling pulse P! llAl~P 5l
A sampling circuit 23A based on cl.

By sampling by 23B and 23C and ranking the sampled level values in the arithmetic circuit 24, the position between the tracks can be detected.

The reproduced RF signal by each bit QA, Q, ,Qc is converted to VQA.
, VQ, , VQc, the areas correspond to the level orders fi) to 1iii) as shown in the table below.

Note that, for example, V in area ■, VQA, etc., fit ~ (i
A tie may occur in ii), but even if the level difference is not completely the same, it will be the same if the level difference is within the set range (for example, VQc4 VQ). By regarding it as a ranking, each region (1) to (2) between track pitches is determined as shown in the table above.

Once the arithmetic circuit 24 has ranked the levels (i) to (iii), the level ranking data is supplied to the decoder 25, and a code (3 bits) corresponding to each of the areas (1) to (3) is output.

With the above operation, in this embodiment, position detection is possible in units of eight areas divided between track pitches.
The control action by the traverse servo circuit can be made more precise, and in particular the braking servo just before the desired track position can be achieved more precisely.

Note that although the eight areas were discriminated only based on the ranking of level values, the level values were also used as discrimination data to determine each of the above areas
If the intermediate region (2) is also detected, it becomes possible to perform position detection in units of 16 divided regions.

[Effects of the Invention] As explained above, the inter-track position detection method of the present invention obtains highly accurate position information by dividing track pitches based on the level order data of the reproduction signal of a pair of wobbling pits and clock pits. By using this track position information, it is possible to perform seek operations faster and with higher precision than before, especially when seeking tracks recorded on optical discs. effective.

[Brief explanation of the drawing]

Figure 1 is a block diagram of track position detection during traverse applied to the inter-track position detection method of the present invention, Figure 2 is an explanatory diagram of sample servo pits and gray code bits that perform track control, and Figure 3 (a). ~(
C) An explanatory diagram of the inter-track position detection operation by detecting the position of the edge and bell. FIG. 4 is a device diagram for explaining the seek operation of an optical disc. FIG. 5 is a block diagram showing an example of a traverse servo circuit. 21 is an optical head, 22 is an A/D converter, 23A, 23
B, 23C are sampling circuits, 24 is an arithmetic circuit 24.
25 is a decoder, and 27 is a Gray code decoder.

Claims (1)

[Claims] A pair of wobbling pits that are deviated toward the inner and outer peripheries from the track center line of a spiral or concentric track, and a clock pit that is located on the track center line, are arranged at a predetermined interval. and a sampling means for sampling the reproduction signal level of each of the wobbling pits and clock pits on the optical disk as a sample servo pit, and comparing the reproduction signal levels obtained by the respective sampling means and ranking them. A calculation means is provided, and a position signal corresponding to a position obtained by dividing the track pitch by at least eight is detected based on the level order data of the reproduced signal of each of the wobbling pits and the clock pit obtained by the calculation means. Inter-track position detection method.