JPH02123524A - Optical disk and method for accessing track for optical disk - Google Patents

Abstract

PURPOSE:To attain high speed access by forming a track so that a track detecting signal when an optical head crosses a track becomes at least two types. CONSTITUTION:For an optical disk 10, a groove 12g, which is a groove for guiding a track, and a land 12l, in which information is recorded, are alternately formed on the recording surface, and one track 12 is formed by a pair of grooves 12g and lands 12l. At the disk 10, the depth of the grooves 12g is changed for tracks 12. Namely, the grooves 12g of respective tracks 12 are formed by the depth of two types of the shallow groove in which a track crossing signal from an optical head strongly appears and the deep groove in which the track crossing signal does not strongly appear. The track to form a deep groove is corresponded to 0 and the track to form the shallow groove is corresponded to 1. Thus, without reading a track number with an optical head, the correct track number can be immediately known from a track detecting signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical disk in which a number of tracks are formed, and a track access method for the optical disk.

[Prior Art] Optical discs are currently attracting attention as a medium that can record an extremely large amount of information. Since a large amount of information is recorded, the number of tracks is also large, and it is required that the optical head access the target track as quickly as possible.

In a conventional optical head track access method, when a target track number is given, the number of the currently located current track is read and the difference between the current track number and the target track number is calculated. If the difference is large, perform targeted access while watching the potentiometer signal indicating the rough position of the optical head until it gets somewhat close to the target track. ¥11 After accessing, temporarily activate the tracking servo and read the current track number. By counting the track detection signals, the optical head gradually approaches the target track, and from several tracks before the target track, the tracking servo is applied again to read the trunk number for each track, and finally the optical head is moved to the target track.

[Problem to be Solved by the Invention u1] As described above, in the conventional optical head track access method, in order to know the track number where the optical head is currently located, the tracking servo is applied to read the track number recorded on the track. Had to read it. Track numbers are recorded in each sector in the trunk, so
In order to read the track number, it was necessary to wait until the optical disc rotated until the trunk number could be read. As described above, the conventional track access method has a problem in that the access time is long.

The present invention has been made in consideration of the above circumstances, and is an optical disc that allows the user to know the track number of the current position simply by moving the optical head across the track without reading the track number written on the track of the optical disc. and an optical disk track access method.

[Means for Solving Section U] The above object is to provide an optical disk in which a plurality of tracks are formed such that the tracks are formed such that at least two types of track detection signals are generated when an optical head crosses the tracks. This is achieved by an optical disc characterized by the following.

Further, the above object is to provide a track access method for an optical disc that accesses a target track of an optical disc, in which a track is formed so that there are at least two types of track detection signals when an optical head crosses the track, and where the optical head is currently positioned. detecting the track number of the current track based on a combination of types of track detection signals of a predetermined number of tracks up to the current track, and accessing the target track based on the detected current track number. This is achieved by an optical disc track access method characterized by:

[Function] According to the present invention, the track number can be known from the combination of the types of track and link detection signals when the optical head crosses the track, so the track number can be determined from the track detection signal without being read by the optical head. You can immediately know the exact track number.

[Example code] The present invention will be described below based on illustrated embodiments.

An optical disc 10 according to an embodiment of the present invention is shown in FIG. 1. The optical disc 10 of this embodiment has an appearance as shown in FIG. 1(a), and a recording surface as shown in FIG. 1(b). Group 12 is a track guide groove.
Lands 121 on which information is recorded are formed alternately, and a pair of groups 12g and lands 121 form one track 12.

The optical disc 10 of this embodiment is characterized in that the depth of the group 12g changes from track to track as shown in FIG. A case will be described in which recording tracks for a book are formed, but in reality, many more tracks are formed on the recording surface. In addition to 16 recording tracks, the optical disc has three access tracks on the inner circumferential side that are used only for access. The groups 12g of each track 12 are divided into a "shallow" group with a depth of λ/8n, where the cross-track signal from the optical head appears strongly, and a "shallow" group with a depth of λ/5n, where the cross-track signal from the optical head appears strongly.
Two types of depths are formed: a "deep" group in which a track-crossing signal such as λ/6n does not appear strongly. Here, λ is the wavelength of the laser beam used by the optical head, and n is the refractive index of 1° of the optical disk.

If a track in which a deep group is formed corresponds to "0" and a track in which a shallow group is formed to "1", the group depth of the access track and the recording track from the innermost circumference becomes roooololooollollloooo.
” is formed as a numerical value string for track access.

A method of forming this numerical value string will be explained using FIG. 2.

The 16 tracks can generally be represented by a 4-bit binary number. Figure 2 (a) shows the case where track numbers ``0'' to ``15'' are expressed in the usual 4-bit binary system. Track number ``0'' is expressed as ``000'' in the 4-bit binary system.
Track number "1" is represented as "roool" in 4-bit binary system, track number "2" is represented as "0010" in 4-bit binary system, and track number "1" is represented as "0010" in 4-bit binary system. 15'' is represented by ``1111'' in 4-bit binary notation.

In this example, a 4-digit binary number based on a 4-bit binary system is
The track number of each track is represented by a modified 4-bit binary system rearranged as shown in FIG. 3(b). This variable 4-bit binary system consists of all bits of track number ``0'' and the least significant bits of track numbers ``1'' to ``15'' (the numeric string surrounded by dotted lines in Figure 2(b)). ) as a numerical value string for track access as shown in FIG. 2(C).

By using this numerical value string for track access, it is possible to accurately know the number of the currently located track without reading the track number recorded on the track. In other words, if you know the numerical sequence depending on the depth of the group of four tracks up to a certain track, you can use the sequence shown in Figure 2 (b
) can be used to determine the track number from the 4-bit binary value.
0”, this numerical string “1010” is
Referring to FIG. 2(b), it can be seen that the track number "4" is represented by a variable 4-bit binary system.

Also, the group depth of four consecutive tracks is "
0,” “1,” “1,” and “1”, this numerical string “0111” represents the track number “11” in the variable 4-bit binary system, as shown in Figure 2(b). I understand that. In order to identify track number "0", three access tracks are provided inside the recording track with track number r□.

A track access method for an optical disc according to an embodiment of the present invention shown in FIG. 1 will be explained with reference to FIGS. 3 to 5.

FIG. 3 shows an optical disc device that implements the optical disc track access method of this embodiment. In this optical disk device, an optical disk 10 is driven by a motor 20, and is provided with an optical head 22 for writing/reading/erasing and a coil 24 for applying a writing/erasing magnetic field. The head drive section 26 drives the optical head 22, and the drive sub leg section 2
8 performs control as will be described later.

The optical head 22 reads a track detection signal when crossing the track 12 of the optical disc 10, and also
In this embodiment, only the track detection signal processing system related to the track access method of the optical disc 10 is shown in FIG.

The track detection signal from the optical head 22 is read by the reading section 30. This track detection signal is shown in Figures 4 and 5.
As shown in the figure. FIG. 4 shows a track detection signal when the optical head 22 is moved from the innermost circumference to the outermost circumference of the optical disk 10 by the head drive unit 26. The track detection signal in FIG. 4(a) is written corresponding to the cross section of the optical disc 10 shown in FIG. 4(b). The numerical value string based on the track detection signal matches the numerical value string for track access of the optical disc 10.

Details of the track detection signal are shown in FIG. As shown in the figure, the track detection signal reaches a peak when the optical head 22 is positioned at the edge of the group 12g of the tracks 12, and crosses to zero level in the middle of the group 12g and land 12''. The peak of the track detection signal is λ/5n for group 12g of track 12,
In the case of a depth DJ such as λ/6n, the track detection signal becomes a low level L layer signal in which a track crossing signal does not appear strongly. Also, the group 12g of the track 12 is λ/
In the case of a depth Dh of 8n, the track crossing signal becomes a signal of a high level Lh that appears strongly. When the track detection signal at the low level L1 is set to "0" and the track detection signal at the high level Lh is set to "1", the numerical value string based on the track detection signal matches the numerical value string for track access of the optical disc 10.

Returning to the explanation of the optical disk device shown in FIG. 3, the comparison section 32 determines whether the track detection signal from the reading section 30 is a signal from the deep group 12g or the shallow group 12g. That is, the comparator 32 converts the track detection signal to an intermediate level Lm=Lm between the level Lj and the level Lh.
(LJ +Lh)/2, if the peak of the track detection signal is at an intermediate level and is greater than m, a digital signal of "1" is output, and if it is less than the intermediate level Lm, a digital signal of rQ is output.

The digital signal from the comparator 32 is sent to the 4-bit register 3.
4 are sequentially stored. Every time a digital signal is output from the comparator 32, the signal in the register 34 is shifted to the right by one bit, and the output digital signal is transferred to the register 34.
It is stored in the leftmost bit of 4. Therefore, the register 34 always stores the track detection signals of up to four previous tracks including the current track currently being traversed.

On the other hand, the table 36 stores the content of the variable 4-bit binary system of each track shown in FIG.
A variable 4-bit binary value of the track corresponding to the target track commanded by the track command signal from the 4-bit register 40 (not shown) is selected from the table 36.
Store in. Note that the relationship between the tracks actually stored in the register 40 and the target track will be described later.

The comparison unit 42 compares the register 34 and the register 40. When the values in the register 34 and the register 40 match, that is, when the optical head 22 is positioned on the track corresponding to the track number stored in the register 40, a deceleration command signal or a stop command signal is output to the drive control section 28. Drive control section 2
8 performs stop control, which will be described later, based on a deceleration command signal or a stop command signal.

Next, a method of accessing tracks on an optical disk in the optical disk device shown in FIG. 3 will be explained.

Similar to the conventional track access method, the track access method of this embodiment reads the number of the current track where the target track is currently located and calculates the difference between the current track number and the target track number. . If the difference is large, the drive control unit 28 causes the head drive unit 26 to drive the optical head 22 at high speed until it is somewhat close to the target track based on a signal from a potentiometer (not shown) indicating the approximate position of the optical head 22. Perform coarse access by moving. After rough access, main access is performed using the track access method of this embodiment.

This access uses the characteristic method of this embodiment of detecting the track number from the track detection signal, but this track number detection can be done by simply crossing each track without reading the track number recorded on each track. Because of this, it is possible to move at a fairly high speed. However, in order to stop the optical head 22 on the target track, it is necessary to decelerate the optical head 22. Therefore, in this access process, it is desirable to provide a high-speed access process in which the optical head 22 is moved at high speed, and a deceleration access process in which the optical head 22 is stopped at the target track. The variable 4-bit binary value of the track to be switched to the deceleration access process may be selected by the selector 38 and stored in the register 40. That is, the variable 4-bit binary value of the track located before the target track by the number of tracks corresponding to the distance at which the optical head 22 can be rapidly decelerated and stopped is stored in the register 40.

If the optical head 22 can be stopped immediately after detecting the track number even during high-speed access, the variable 4-bit binary value of the target track itself may be stored in the register 40.

In the high-speed access process of this access, the optical head 2
2 crosses the track 12 of the optical disc 10, the comparison unit 32 determines that the peak value of the track detection signal is set to level L.
It is compared with m to determine whether "o" is "1" or not, and the digital signal is input to the register 34. The comparison section 42
The values stored in register 34 and register 40 are compared. The drive control unit 28 controls the optical head 2 at high speed until the comparison unit 42 detects a match between the register 34 and the register 40.
Move 2. When a match is detected, the comparison unit 42 outputs a deceleration command signal to the drive control unit 28 and enters the deceleration access process.

In the deceleration access process, the optical head 22 is gradually decelerated so that it can stop at the target track. To stop at the target track, the number of peaks of the track detection signal may be counted while decelerating, or a variable 4-bit binary value of the track number of the target track may be newly stored in the register 40 and the comparison section The track number may be detected at 42.

In this way, according to this embodiment, the accurate track number can be immediately known from the track detection signal when the optical head crosses the track without having to read the track number with the optical head, so high-speed access is possible. .

An optical disc 10 according to another embodiment of the invention is shown in FIG. In the embodiment of FIG. 1, each group 12 of tracks 12
Although the track detection signal when the optical head 22 crosses the track is changed depending on the depth g, in this embodiment, the track detection signal is changed depending on the change in the pitch of the track. As shown in the cross-sectional view of the optical disk 10 in FIG. 6, the same method as shown in FIG. As in the example, to facilitate understanding, a case will be described in which 16 recording tracks are formed on the recording surface, but in reality, a large number of tracks are formed on the recording surface. Also, in the optical disc 1o of this embodiment, along with 16 recording tracks, three access tracks are formed on the inner circumferential side.

If a track with a wide pitch corresponds to "0" and a track with a narrow pitch corresponds to "1", the pitch of the access track and the recording track from the innermost circumference becomes the same numerical sequence for track access rOOOO10100110 as in the first embodiment.
1111000".

A track access method for accessing the tracks of the optical disc shown in FIG. 6 will be explained with reference to FIGS. 7 to 9. Components that are the same as those in the embodiment shown in FIGS. 3 to 5 are designated by the same reference numerals, and explanations thereof will be omitted.

FIG. 7 shows an optical disc device that implements the optical disc track access method of this embodiment. This optical disc HH
is characterized by the method of processing the track detection signal from the reading section 30.

The track detection signals of this embodiment are shown in FIGS. 8 and 9. FIG. The track detection signal shown in FIG. 8(a) is written corresponding to the cross section of the optical disc 10 shown in FIG. 8(b).

Details of the track detection signal are shown in FIG. As shown in FIG. 9, the peak interval periods of the track detection signal are periods ta and tb corresponding to the track pitches Pa and Pb. If the peak interval period of the track detection signal is ta, the track detection signal is set to "1", and if the peak interval period of the track detection signal is tb, the track detection signal is set to "0".

The peak interval period t of the track detection signal is
It depends on the track pitch P of , and also on the moving speed V of the optical head 22 . That is, if the moving speed V of the optical head 22 is fast, the peak interval period t of the track detection signal becomes short, and if the moving distance V of the optical head 22 is slow, the peak interval period t of the track detection signal becomes long. The optical disk device shown in FIG. 7 is configured to process track detection signals in consideration of this point.

The track detection signal from the reading section 30 is differentiated by a differentiating circuit 50. The differential signal from the differential circuit 50 is output to a sawtooth wave generator 52 and a threshold converter 54.

The sawtooth wave generator 52 is for detecting the peak interval period of the track detection signal. Every time the value of the differential signal of the track detection signal changes from a positive state to zero, the output from the sawtooth wave generator 52 is reset, and the voltage value of the sawtooth wave signal immediately before being reset is output to the comparison unit 32. Ru. This voltage value becomes the track interval period t of the track detection signal, and is compared with a threshold value in the comparator 32.

The threshold value conversion unit 54 calibrates the input threshold value tm according to a threshold value conversion graph 56 representing the relationship between the threshold value tm and the moving speed V of the optical head 22. As mentioned above, since the peak interval period t of the track detection signal also depends on the moving speed V of the optical head 22, this is to be corrected.

The input threshold tm is a predetermined reference movement distance V
It is determined as follows, where ta and tb are the peak interval periods. The moving speed {circle around (2)} is given to the threshold converting section 54 as a differential signal from the differentiating circuit 50 when the track detection signal from the reading section 30 crosses the zero level.

The comparator 32 converts the peak interval period t output from the sawtooth wave generator 52 into a threshold (i) converted by the threshold converter 54.
fftm, if the peak interval period t of the track detection signal is greater than the threshold tm, a digital signal of "0" is output, and if it is smaller than the threshold tm, a digital signal of "1" is output.

In the optical disk device shown in FIG. 7, the moving distance V of the optical head 22 is detected by the differential coefficient from the differentiating circuit 50 when the track detection signal crosses the zero level. The moving speed V may be determined from the coefficients, or may be determined from the average value of these differential coefficients.Furthermore, the optical head 22 may be provided with speed detecting means such as a linear scale or a semiconductor acceleration sensor.
The moving speed V may be determined by this speed detecting means.

The processing of the digital signal output from the comparator 32 is the same as that of the optical disk device shown in FIG. 3, so a description thereof will be omitted.

The present invention is not limited to the above-mentioned embodiments, and various modifications are possible.

For example, in the above embodiment, the number of tracks on the optical disk was assumed to be 16 for simplicity, and the track numbers were expressed using a variable 4-bit binary system. Create a variable 8-bit binary system or a variable 16-bit binary system in advance in the same way as the variable 4-bit binary system shown in Figure 1, and calculate the track number from the track detection signal that crosses the number of tracks corresponding to the number of bits. Just detect it.

Further, in the above embodiment, the depth of the track group and the track pitch are changed so that there are at least two types of track detection signals, but if the track detection signals can be made different, the tracks can be formed in any way. Good too.

Further, in the above embodiment, two types of track detection signals are discriminated, but three or more types of changes may be made to the track detection signal, and the number of tracks for determining the track number can be reduced.

[Effects of the Invention] As described above, according to the present invention, it is possible to know the currently located track number simply by moving the optical head across the track without reading the track number written on the track of the optical disk, and this enables high-speed Access is possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an optical disc according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a numerical sequence for track access on the same optical disc, and FIG. 3 is a diagram showing an optical disc track access method according to an embodiment of the present invention. FIG. 4 and FIG. 5 are diagrams showing track detection signals of the optical disc device, FIG. 6 is a diagram showing an optical disc according to another embodiment of the present invention, and FIG. 7 is a diagram showing the present invention. A block diagram of an optical disc device that implements the optical disc track access method according to the embodiment of the invention, FIGS. 8 and 9 are diagrams showing track detection signals of the optical disc device. 10... Optical disc, 12... Track, 12g.
... group (groove), 12 j- ... land (land), 20 ... motor, 22 ... optical head, 24 ... coil, 26 ... head drive section, 28 ...
... Drive control section, 30... Reading section, 32... Comparison section, 34... Register, 36... Table, 38...
- Selection section, 40... Register, 42... Comparison section, 5
0... Differential circuit, 52... Sawtooth wave generating section, 54...
...Darkness value conversion section, 56...Threshold value conversion graph. Applicant Toso Corporation Company Representative Patent Attorney Yoshihito Kitano (C) Figure 2

Claims (1)

[Claims] 1. In an optical disc on which a plurality of tracks are formed,
An optical disc characterized in that the track is formed so that there are at least two types of track detection signals when an optical head crosses the track. 2. The optical disc according to claim 1, wherein the depth of the track guide groove of the track is varied so that the track detection signal is of at least two types. 3. The optical disc according to claim 1, wherein the pitch of the tracks is varied so that the track detection signals are of at least two types. 4. In an optical disc track access method for accessing a target track of an optical disc, the track is formed so that there are at least two types of track detection signals when the optical head crosses the track, and the current track where the optical head is currently located. The track number of the current track is detected based on a combination of types of track detection signals of a predetermined number of tracks up to , and the target track is accessed based on the detected current track number. How to access tracks on an optical disc. 5. The optical disk track access method according to claim 4, wherein the track guide groove of the track is formed with varying depth so that the track detection signal is of at least two types, and the track guide groove of the track is detected by the track guide groove. A track access method for an optical disc, characterized in that the type of the track detection signal is determined by comparing the level of the track detection signal with a predetermined threshold. 6. The track access method for an optical disc according to claim 4, wherein the track pitch is varied so that the track detection signal is of at least two types;
A track access method for an optical disc, characterized in that the type of the track detection signal is determined by comparing an interval at which the track detection signal for detecting the track appears with a predetermined threshold.