JP3412244B2 - Track interlaced scanning method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track interlace scanning method for instantaneously interlacing a track with a light beam for reproducing information from a disc having spiral or concentric tracks or recording information on the disc. Regarding

[0002]

2. Description of the Related Art There is an optical recording / reproducing device as a conventional technique. Various types of optical recording / reproducing devices have been proposed. For example, a light beam generated by a light source such as a semiconductor laser is irradiated onto a disc on which a material film that is optically recordable / reproducible is formed on the surface of a base material having tracks with concentric concavo-convex structure by vapor deposition or the like. However, at the time of signal reproduction, a relatively weak constant light amount is read, the signal is read by the change of the reflected light amount from the disc, and at the time of signal recording, the light amount of the light beam is strongly modulated according to the signal to be recorded. In some cases, recording is performed by changing the reflectance of the material film. In such an optical recording / reproducing apparatus, focus control is performed so that the light beam is always in a substantially convergent state on the material film, and control is performed so that the light beam always scans a predetermined track correctly. Tracking control is being performed. Furthermore, for example, Japanese patent application Showa
As detailed in 62-132467, a jumping scan is performed that moves a light beam from one track to its adjacent track. The jumping scanning is usually performed by using a tracking moving unit that moves a light beam relative to a track in a direction perpendicular to the track longitudinal direction and horizontal to the disk surface (disk radial direction) for performing tracking control. FIG. 2 is a timing chart of jumping scanning to a track adjacent to the inner circumference side of the disk with respect to the track. Figure 2
a) is a tracking control ON / OFF signal, b) is a drive signal to the tracking moving means, c) is a tracking error signal, d) is a binarized signal of the tracking error signal, e)
Is a midpoint detection signal for detecting the midpoint between the track and its adjacent track. The tracking error signal is a signal indicating the relative positional relationship between the track and the light beam.
It is known that a tracking error signal is detected by a push-pull method for a track having a convex structure when viewed from the incident surface of a light beam having an optical depth λ / 8 (λ is the wavelength of a light source). 3a) is a diagram showing the positional relationship between the light beam 1 and the track 2 on the disk surface, and FIG. 3b) is a plot of the tracking error signal corresponding to each position of the light beam 1 in FIG. 3a). The tracking error signal has a sinusoidal shape in accordance with the relative positional relationship between the light beam 1 and the track 2, its period is equal to the track pitch, and the amplitude is zero level when the light beam is located at the track center. In the jumping scanning, at the same time as making tracking control inoperative, a rectangular acceleration pulse is applied to the tracking moving means to accelerate the light beam toward the target track (timing T1 in FIG. 2). After the acceleration pulse ends, the drive signal to the tracking moving means is set to zero level, and the light beam moves due to inertia. When the light beam is located approximately at the midpoint between the tracks, a deceleration pulse, which has a rectangular shape similar to the acceleration pulse but has the opposite polarity, is added to decelerate (timing T2 in the figure). After the deceleration pulse ends, the tracking control is activated again (T3 in the figure
Timing), the jumping scanning is completed by pulling the light beam into the adjacent track. The key point of jumping scanning is high-precision detection of the midpoint between the track and its adjacent track, that is, the midpoint of the track. The track midpoint is detected by detecting the edge of the binarized signal of the tracking error signal after the end of the acceleration pulse. In the jumping scan of FIG. 2 described above, the falling edge after the end of the acceleration pulse is detected to generate the midpoint detection signal (see FIGS. 2d and e)). As shown in FIG. 3, the tracking error signal has its polarity inverted with respect to the track center. Therefore, when jumping scanning is performed toward the outer circumference of the disk, the midpoint detection detects the rising edge after the end of the acceleration pulse. To be executed.

[0003]

On the other hand, in recent years, various high-density disc formats have been proposed for the purpose of increasing the capacity of the optical disc. One of them is a land / groove format optical disk (hereinafter referred to as L / G disk). FIG. 4 is an external view of an L / G disc. In a conventional optical disc, information is recorded by using either a groove for tracking control or a land which is an intermediate area between the groove and the track. On the other hand, in the L / G disc, information is recorded with both the land and the groove as tracks. As a result, the track pitch is equivalently halved, so that the capacity of the optical disk can be doubled. In the L / G disc, groove tracks using grooves ( hatched portions in FIG. 4) and land tracks using lands (portions sandwiched by groove tracks) are alternately connected for each rotation. It As a result, the track becomes a single spiral in which groove tracks and land tracks are alternately formed, so continuous data recording without interruption on the entire disk surface,
Alternatively, reproduction is possible. For example, as shown in FIG. 4, in a disc in which the disc rotation direction and the track spiral direction are set, the light beam moves from the outer circumference to the inner circumference by one track by the rotation of the disk. This type of disc is called a 1-spiral L / G disc.

Further, on the disc, an address for identifying a track is provided for each track. The address part of each track is arranged so that its position is aligned in the circumferential direction, and that position is a land, with respect to the disc rotation direction.
It is provided in front of the groove switching portion. FIG. 5 shows an enlarged view of the address, land, and groove switching section surrounded by circles in FIG. The switching portion is provided for each rotation of the disk, and the circumferential position thereof is provided so as to match regardless of the radial direction of the track. The groove has a convex structure when viewed from the incident surface of the light beam, and its height d is the wavelength λ of a light source such as a semiconductor laser,
It is formed so that the refractive index p of the disk base material satisfies approximately d = 8 / (λ * p). The land track is a flat portion between the grooves. Therefore, when the light beam moves along this spiral track due to the rotation of the disk, the light beam is alternately positioned on the groove track and the land track for each rotation. It is known that the address is formed by a pit row having a convex structure, and the address where the light beam is located can be read from the change in the amount of reflected light due to this pit row. The width of each pit of the address is smaller than the track width, and the length of the pit is about the radius to the diameter of the light beam.

FIG. 6 shows the positional relationship between the light beam 1 and the track 2 on the surface of such an L / G disk and the corresponding tracking error signal with the horizontal axis as the position. The L / G disk, there is <br/> land track in the land area between the groove track and the groove track corresponding to a conventional track. Focusing only on the groove track, the tracking error signal is exactly the same as that of the conventional disk. That is, when the light beam is located at the center of the groove track, it has a sinusoidal shape whose amplitude becomes zero level, and its period is equal to the pitch of the groove track. The land track exists at a position where the phase of the tracking error signal is shifted by 180 degrees with respect to the groove track. Therefore, the polarities of the tracking error signals are inverted between the groove track and the land track.

As described above, the midpoint detection essential for jumping scanning is performed by detecting the edge of the binarized signal of the tracking error signal. However, in the L / G disc, the edge of the binarized signal of the tracking error signal does not correspond to the midpoint position between the groove track and the land track, and the midpoint detection cannot be performed by the conventional method, so that the jumping scan can be performed. Can not.

[0007]

The object of the present invention is to provide L / G
It is an object of the present invention to provide a track search method for moving a light beam to a desired track at high speed in a high density disk such as a disk. In order to achieve the above object, the present invention provides alternating
Has a track whose polarity of tracking control is reversed
Irradiate a light beam onto the optical disc,
The position of the light beam and track from the reflected or transmitted light of
This is detected and based on the position shift signal, it is displayed on the track.
While tracking control so that the light beam is positioned,
Track jumping for use in devices that record or play information
The scanning method is for scanning tracks separated by N tracks.
Search one track to move the light beam to the adjacent track
A tiger jumped N1 times and jumped 2 tracks apart.
2-track jumping run to move the light beam to the rack
Perform N2 times to reach the target track
This is a cross-scan method. However, when N is an even number , N1 and N2 are : N1 = 0 N2 = N / 2 When N is an odd number, N1 = 1 N2 = (N-1) / 2

[0008]

According to the above method, when the light beam is moved by a plurality of tracks, the two-track jumping scan is repeated to move a large distance and the target track can be reached by the one-track jumping scan, so that the search operation is performed at high speed. It becomes possible.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a track search device which is a first embodiment embodying the jumping scanning method of the present invention. The track search device of FIG. 1 is roughly divided into four blocks. That is, a disk / head block 33 including a disk, an optical head, and an actuator, a tracking control block 34 including a circuit for realizing digital tracking control and a circuit for reading an address,
A 1-track jumping scanning block 35 for performing 1-track jumping scanning and a 2-track jumping scanning block 36 for performing 2-track jumping scanning. Referring to FIG. 1 below, 33, 3
The detailed configuration and operation of each of blocks 4, 35 and 36 will be described.

The disk 3 is rotated at a predetermined speed by a disk motor 4. A light beam generated from a light source 5 such as a semiconductor laser is collimated by a coupling lens 6, passes through a polarization beam splitter 7 and a quarter-wave plate 8, and is converged on a disk 3 by a converging lens 10 for irradiation. To be done. The light beam reflected by the disc 3 is
The light passes through the converging lens 10 and the quarter-wave plate 8, is reflected by the polarization beam splitter 7, and is irradiated onto the two-divided photodetector 12. The converging lens 10 is the tracking actuator 1.
1 is attached to the movable part. The tracking actuator 11 is composed of a tracking coil provided in the movable portion and a permanent magnet provided in the fixed portion. The converging lens 10 moves in the radial direction of the disk 3, that is, in the direction traversing the track due to the electromagnetic force according to the current flowing in the coil. To the optical head unit 9, a light source 5, a coupling lens 6, a polarization beam splitter 7, a quarter wavelength plate 8, a two-division photodetector 12, and a fixed portion of a tracking actuator 11 are attached.
The optical head unit 9 is configured to move in the radial direction of the disk 3 by the transfer motor 13. The disk / head block 33 is composed of the optical head unit 9, the transfer motor 13, the disk motor 4 and the disk 3 described above.

The two-divided photodetector 12 has two light receiving regions, and the direction of the dividing line is the track direction on the light receiving surface. The outputs of the two light receiving regions of the two-divided photodetector 12 are input to the inverting terminal and the non-inverting terminal of the differential circuit 14, which are part of the components of the tracking control block 34. The differential circuit 14 thus configured
It is widely known that the tracking error signal is detected by the push-pull method using the above-mentioned L / G disk whose structure is shown in FIGS. 4 and 5. The tracking error signal output from the differential circuit 14 is sample /
An analog signal is converted into a digital signal by the A / D converter 16 via the hold circuit 15. The sample / hold circuit 15 is a circuit for discretely sampling the output of the differential circuit 14 and holding it for a period required by the A / D converter 16 for A / D conversion. The tracking error signal converted into a digital signal by the A / D converter 16 includes an inverting circuit 17 for inverting the polarity of tracking control, a phase compensation circuit 18 for ensuring the controllability of the tracking control system, and a PWM. Circuit 19, low-pass filter 2
0, a switch 21 for switching the operation / non-operation of the tracking control, and a tracking control system configured by being added to the tracking actuator 11 via a 3-input adder circuit 38. As a result, when the switch 21 is short-circuited, the light beam is controlled to be always located at the center of the track. The PWM circuit 19 outputs a signal whose pulse width is modulated in accordance with the digital signal output of the phase compensation circuit 18 , and its output cycle is A / D of the A / D converter 16.
Equal to the D conversion period. Low-pass filter 20 is to convert the pulse width modulated signal PWM circuit 19 into an analog signal, the cut-off frequency fLPF, to the conversion period Tad of the A / D converter 16, flpf <1 / Tad Is set to meet. The output signal of the A / D converter 16 is input to the zero-crossing detection circuit 24 via a difference circuit 23 whose operation in the one-track jumping scanning block 35 will be described later. The zero crossing detection circuit 24 detects the zero crossing of the input signal and outputs a trigger signal to the deceleration pulse generation circuit 30. The output signal of the A / D converter 16 is the 2-track jumping scanning block 36.
It is input to the zero-crossing detection circuit 45 inside. The zero crossing detection circuit 45 detects the zero crossing of the input signal and outputs a trigger signal to the deceleration pulse generation circuit 42.

On the other hand, the output signal of the two-division photodetector 12 is
It is also input to the adder circuit 25, and the sum of the reflected light amounts from the disk 3 is detected. The address reading circuit 26 reads the address provided in each track of the disk 3 from the output signal of the adding circuit 25, and outputs it to the search circuit 37. The tracking control block 34 is composed of a circuit for the above-mentioned tracking control, that is, components from the differential circuit 14 to the switch 21, a circuit for address reading, that is, an adder circuit 25 and an address reading circuit 26.

When the address of the target track for the search is input from an external means (not shown), the search circuit 37 repeats the one-track jumping scan and the two-track jumping scan according to the input from the address reading circuit 26, and the target track. It controls to move to.
The 1-track jumping command signal from the search circuit 37 is sent to the 1-track jumping control circuit 28, which is one of the components of the 1-track jumping scanning block 35.
In addition, the jumping direction signal is inverted by the inverting circuit 32 and the inverting circuit 4.
4 is output to. Further, the search circuit 37 outputs a 2-track jumping command signal to a 2-track jumping control circuit 39 which is one of the constituent elements of the 2-track jumping scanning block 36. The 1-track jumping control circuit 28 outputs a 1-track jumping end signal, and the 2-track jumping control circuit 39 outputs
The 2-track jumping end signal is output to the search circuit 37 in reverse.

The 1-track jumping control circuit 28 is
When the 1-track jumping command signal is received, various necessary command signals are output to execute the jumping scan to the tracks adjacent to the 1-track, and after completion, the 1-track jumping end signal is output to the search circuit 37. From the 1-track jumping control circuit 28, an acceleration start signal is output to the acceleration pulse generation circuit 29, a tracking control ON / OFF signal is output to the switch 21 via the AND gate 40, and a tracking polarity signal is output to the inverting circuit 17. The acceleration drive pulse output from the acceleration pulse generation circuit 29 and the deceleration drive pulse output from the deceleration pulse generation circuit 30 are input to the non-inversion terminal and the inversion terminal of the differential circuit 31, respectively, and the difference between them is calculated, and the inversion circuit. The light beam is input to the tracking actuator via the 32-, 3-input adder circuit 38, and the light beam can be driven in the disk radial direction. An acceleration end signal is input to the deceleration pulse generation circuit 30 from the acceleration pulse generation circuit 29, and a deceleration end signal is input to the one-track jumping control circuit 28 from the deceleration pulse generation circuit 30. The 1-track jumping scanning block 35 includes the difference circuit 23, the zero-crossing detection circuit 24, and the 1-track jumping control circuit 2 described above.
8, acceleration pulse generation circuit 29, deceleration pulse generation circuit 3
0, a differential circuit 31.

The two-track jumping control circuit 39 is
When the 2-track jumping command signal is received, various necessary command signals are output to execute the jumping scan to the track separated by two tracks, and after completion, the 2-track jumping end signal is output to the search circuit 37. The 2-track jumping control circuit 39 outputs an acceleration start signal to the acceleration pulse generation circuit 41 and a tracking control ON / OFF signal to the AND gate 40. The acceleration drive pulse output from the acceleration pulse generation circuit 41 and the deceleration drive pulse output from the deceleration pulse generation circuit 42 are respectively generated by the differential circuit 4
3 is input to the non-inversion terminal and the inversion terminal, the difference between them is calculated, and the difference is input to the tracking actuator via the inversion circuit 44 and the 3-input addition circuit 38. The 3-input adder circuit 38 includes a 1-track jumping scanning block 3
The jumping drive pulse from 5 is input via the inverting circuit 32, and the tracking control drive signal from the tracking control block 34 is input via the switch 21, and the three inputs are added and output to the tracking actuator. . An acceleration end signal is input to the deceleration pulse generation circuit 42 from the acceleration pulse generation circuit 41, and a deceleration end signal is input to the two-track jumping control circuit 39 from the deceleration pulse generation circuit 42. The tracking control ON / OFF signal from the one-track jumping control circuit 28 is also input to the AND gate 40, and the tracking control ON from the two-track jumping control circuit 39 is turned on.
A logical product with the / OFF signal is calculated and input to the switch 21 in the tracking control block 34. Inversion circuit 4
Similarly to the inverting circuit 32, the jumping direction signal is input to the signal 4 from the search circuit 37 as its control signal. The output signal of the A / D converter 16 is input to the zero crossing detection circuit 45. The zero crossing detection circuit 45 detects the zero crossing of the input signal and outputs a trigger signal to the deceleration pulse generation circuit 42.

Next, the track search operation of this embodiment will be described. Search circuit 37 prior to jumping scan
The address of the target track is input to the external device. When the address of the target track is input, the search circuit 37 fetches the address of the track where the light beam is currently located from the address reading circuit 26, and calculates the number N of tracks to be traversed and the direction. According to the calculated jumping scanning direction, the search circuit 37
Sets the jumping direction signal. Assuming that the track search operation toward the inner circumference is performed, the jumping direction signal is set to the LOW level. The search circuit 37 achieves the movement of N tracks by first performing N2 two-track jumping scans and then performing N1 one-track jumping scans. That is, when N is an even number, two-track jumping scanning is performed N / 2 times to reach the target track. Further, when N is an odd number, first (N - 1) / 2 times 2 Run track jumping scan moves in the track adjacent to the search starting track side of the target track, then 1
Track jumping scanning is performed to reach the target track. This can be expressed as a mathematical expression as follows. N = even time N1 = 0 N2 = N / 2 N = odd time N1 = 1 N2 = (N-1) / 2 Next, the one-track jumping scan of the present embodiment will be described in detail with reference to the timing chart of FIG. Explained. FIG. 7a) is an enlarged plan view of the tracks on the disk 3. In FIG. 7a), the hatched portion is a groove track, and the portion sandwiched by the groove tracks is a land track. The vertical direction in the drawing is the disk radial direction, and the upward direction is the outer peripheral direction in the drawing. (Figure 7a)
The middle and dotted lines are the loci when the light beam indicated by the circle moves to the land track on the inner circumferential side of the groove track by one track jumping scan during the track search operation. 7b) to i) are timing charts of signals of respective parts corresponding to respective positions of the trajectory of the light beam shown in a). 7b) is a tracking error signal, c) is a jumping direction signal, d) is a jumping command signal, e) is a tracking control ON / OFF signal, f) is a tracking polarity signal, and g) is the output of the acceleration pulse generation circuit 29. Acceleration drive pulse, h)
Is a trigger signal output from the zero-crossing detection circuit 24, and i) is a deceleration drive pulse output from the deceleration pulse generation circuit 30. Before the 1-track jumping scan, the tracking control output from the 1-track jumping control circuit 28 is performed.
The ON / OFF signal and the tracking control ON / OFF signal output from the two-track jumping control circuit 39 are both at the high level. Therefore, the output of the AND gate 40 is at the high level, the switch 21 is short-circuited, and the tracking control operates. is doing. 1-track jumping control circuit 28
The tracking polarity signal input from the to the inversion circuit 17 is HIGH level. At this time, the inverting circuit 17 performs a normal rotation operation in which the tracking control pulls the groove into the groove track, for example, outputs the input signal without inverting. The outputs of the acceleration pulse generation circuits 29, 41 and the deceleration pulse generation circuits 30, 42 are zero level, and the outputs of the differential circuits 31, 43 are also zero level. At this time, the tracking error signal output from the differential circuit 14 is at a substantially zero level, and the light beam is always located on a certain track without causing a large control error. Each time it passes, it reads the address of the track where the light beam is currently located. Prior to the jumping scan, the search circuit 37 sets a jumping direction signal according to the jumping scan direction (time TS0). In the track search operation toward the inner circumference in this example, the jumping direction signal is LOW.
Set to level. Next, the search circuit 37 sets 1 at time TS1.
Set the track jumping command signal to HIGH level and then immediately set it to LOW level again to output a positive pulse. When the 1-track jumping control circuit 28 detects the rising edge of the 1-track jumping command signal, it immediately sets the acceleration start signal to the HIGH level and then immediately sets it to the LOW level to output a positive pulse, and at the same time, the tracking control is turned on. The / OFF signal is set to the LOW level, and the switch 21 is released to disable the tracking control (time TS2). At the same time, the tracking polarity signal is set to LOW level. As a result, the inverting circuit 17 starts the inverting operation of inverting the polarity of the input and outputting it. When a positive pulse is input to the acceleration signal from the one-track jumping control circuit 28, the acceleration pulse generation circuit 29 outputs an acceleration drive pulse having a predetermined peak value and a predetermined pulse width.
The acceleration drive pulse is transmitted to the tracking actuator 1 via the differential circuit 31, the inversion circuit 32, and the 3-input addition circuit 38.
Input to 1. The inverting circuit 32 is set to have the same polarity as the input signal when the jumping direction signal is at the LOW level, and to invert and output when the signal is at the HIGH level. As described above, since the jumping direction signal is set to the LOW level now, the inverting circuit 32 outputs the input signal with the same polarity as the drive pulse. At this time, the tracking actuator 11 is connected so that the movable portion moves in the inner circumferential direction of the disk, and the light beam starts acceleration and movement from the groove track toward the land track adjacent to the inner circumference side. Acceleration pulse generation circuit 29, the time
When the output of the predetermined acceleration drive pulse is completed at TS2, an acceleration end signal is output to inform the deceleration pulse generation circuit 30 that the acceleration drive pulse has been completed.

The tracking error signal increases as the light beam moves, and when the light beam reaches the midpoint of the groove track and the land track at time TS3, the zero-crossing detection circuit 24 outputs a positive pulse to the trigger signal. R.

The midpoint detection will be described in more detail with reference to the timing chart of FIG. 8A) shows the tracking error signal output by the differential circuit 14 (the curve indicated by the alternate long and short dash line in the figure) and the tracking error signal output by the A / D converter 16 during execution of the jumping scan shown in FIG. 6 is a timing chart of digital values (waveforms shown by solid lines in the figure). The A / D converter 16 discretely performs conversion at the conversion cycle Tad, so that its output has a step-like shape. Actually, the output of the A / D converter 16 is, for example, an 8-bit digital value , but the digital value is displayed on the vertical axis for ease of explanation. 8b) is the output of the difference circuit 23, and c) is the trigger signal output from the zero-crossing detection circuit 24. Also in FIG. 8b), the digital value of the output of the difference circuit 23 is displayed on the vertical axis. Difference circuit 2
Reference numeral 3 calculates the amplitude difference of each sample (time interval Tad) of the tracking error signal output from the A / D converter 16 and outputs it to the zero-crossing detection circuit 24. Zero-crossing detection circuit 2
4 detects that the polarity of the differential signal has changed to detect that the light beam has reached the midpoint of the groove track and the land track, and outputs the positive pulse shown in FIG. Output to 30. On the other hand, the deceleration pulse generation circuit 30 is configured to detect the rising edge of the first trigger signal after the end of the acceleration drive pulse and output the deceleration drive pulse having a predetermined peak value and a predetermined pulse width. That is, in the time chart shown in FIG. 7, the deceleration drive pulse is output from time TS3. The deceleration drive pulse is inverted by the differential circuit 31, and the inversion circuits 32, 3
It is input to the tracking actuator 11 via the input addition circuit 38. As a result, the moving speed of the light beam toward the inner circumference due to the acceleration drive pulse is reduced. The deceleration pulse generation circuit 30 outputs a deceleration end signal to the one-track jumping control circuit 28 when the deceleration drive pulse ends at time TS4. 1-track jumping control circuit 28
When the deceleration end signal is input, immediately set the tracking control ON / OFF signal to HIGH level and switch 21
Short circuit to activate tracking control. At this time, the light beam is located on the land track on the inner peripheral side of approximately one track, and the polarity of the tracking control has already been switched to the opposite polarity to the groove track. Therefore, the light beam smoothly moves to the land track. Then, the tracking control pull-in is performed, and the jumping scan of one track is completed. When the one-track jumping scan is completed, the one-track jumping control circuit 28 outputs a jumping end signal to the search circuit 37 to notify the search circuit 37 of the end of the one-track jumping scan.

Next, the operation of the 2-track jumping scan will be described in detail with reference to the timing chart of FIG. In FIG. 10, a) is an enlarged plan view of the tracks on the disk 3. In Figure 10, Hatchin
The grooved portion is a groove track, and the portion sandwiched by the groove tracks is a land track. The vertical direction in the drawing is the disk radial direction, and the upward direction is the outer peripheral direction in the drawing. Further, in FIG. 10a), the dotted line indicates that the light beam indicated by a circle moves to the groove track on the inner circumference side of the groove track by two tracks during the track search operation in which the jumping scan is repeated. Is the trajectory of. 10b) to 10h) are timing charts of signals of respective parts corresponding to respective positions of the trajectory of the light beam shown in a). 10 b) is a tracking error signal, c) a jumping direction signal, d) is a 2-track jumping command signal, e) is a tracking control ON / OFF signal output from the 2-track jumping control circuit 39, and f) is a jumping control circuit 606. The tracking polarity signal to be output, g) is the acceleration drive pulse output from the acceleration pulse generation circuit 41, h) is the trigger signal output from the zero crossing detection circuit 45, and i) is the deceleration drive pulse output from the deceleration pulse generation circuit 42. is there. Two
Before the track jumping scan, the 1- track jumping control circuit 28 outputs the tracking control ON / OFF.
The tracking control ON / OFF signals output from the signal and the two-track jumping control circuit 39 are both at the high level, therefore the output of the AND gate 40 is at the high level, and the switch 21 is short-circuited to perform the tracking control. The tracking polarity signal input from the 1-track jumping control circuit 28 to the inverting circuit 17 is HIGH.
It is a level. At this time, the inverting circuit 17 performs a normal rotation operation in which the tracking control pulls the groove into the groove track, for example, outputs the input signal without inverting. Further, the acceleration pulse generation circuits 29 and 41, the deceleration pulse generation circuit 3
The outputs of 0 and 42 are zero level, and the differential circuits 31 and 4 are
The output of 3 is also at zero level. At this time, the differential circuit 1
The tracking error signal output by 4 is at a substantially zero level, and the light beam is always positioned on a certain track without causing a large control error.

The search circuit 37 sets the two-track jumping command signal to the HIGH level at time TS6, and then immediately sets it to the LOW level again and outputs a positive pulse.

The two-track jumping control circuit 39 is
When the rising edge of the 2-track jumping command signal is detected , after setting the acceleration start signal to HIGH level,
Immediately set the LOW level again to output a positive pulse, and simultaneously set the tracking control ON / OFF signal to the LOW level. As a result, the output of the AND gate 40 becomes LOW level, the switch 21 is released, and the tracking control is disabled (time TS7). Acceleration pulse generation circuit 4
1 is acceleration from the 2-track jumping control circuit 39
When a positive pulse that is a start signal is input, an acceleration drive pulse having a predetermined peak value and a predetermined pulse width is output. The acceleration drive pulse is input to the tracking actuator 11 via the differential circuit 43, the inversion circuit 44, and the 3-input addition circuit 38. The inverting circuit 44 has a jumping direction signal of LO
It is set to have the same polarity as the input signal when it is at the W level, and to invert and output when it is at the HIGH level. As mentioned above, the jumping direction signal is now set to LOW level.
Because there, inverting circuit 44 outputs the input signal as a positive drive pulse remains the same polarity. At this time, the tracking actuator 11 is connected so as to move the movable portion in the inner circumferential direction of the disk, and the light beam is accelerated toward the inner circumference from the groove track and starts moving. When the acceleration pulse generation circuit 41 finishes outputting the predetermined acceleration drive pulse at time TS7, the acceleration pulse generation circuit 41 outputs an acceleration end signal to notify that the acceleration drive pulse is finished by the deceleration pulse generation circuit 42.
Let me know.

The tracking error signal increases as the light beam moves, and when the light beam reaches the land track at time TS8, the tracking error signal becomes zero level, and the polarity is eventually inverted. Zero-crossing detection circuit 45
Detects the zero crossing of the tracking error signal and outputs a positive pulse to the trigger signal. The deceleration pulse generation circuit 42 is configured to detect the rising edge of the first trigger signal after the end of the acceleration drive pulse and output a deceleration drive pulse having a predetermined peak value and a predetermined pulse width. That is, in the time chart shown in FIG. 10, time TS
Deceleration drive pulse is output from 8. The deceleration drive pulse is
The signal is inverted by the differential circuit 43 and input to the tracking actuator 11 via the inversion circuit 44 and the 3-input addition circuit 38. As a result, the moving speed of the light beam in the inner peripheral direction due to the acceleration drive pulse is reduced. The deceleration pulse generation circuit 42 outputs a deceleration end signal to the two-track jumping control circuit 39 when the deceleration drive pulse ends at time TS9. The 2-track jumping control circuit 39 immediately turns on the tracking control when the deceleration end signal is input.
The FF signal is set to HIGH level, and the switch 21 is short-circuited to operate the tracking control. At this time, the light beam is located on the groove track on the inner circumference side of the two tracks, and the polarity of the tracking control is the same as that before the start of the two-track jumping scan, so the light beam is smoothly drawn into the groove track. Then, the jumping scanning of the two tracks is completed. When the 2-track jumping scan is completed, the 2-track jumping control circuit 39 outputs a jumping end signal to the search circuit 37. In response to this, the search circuit 37 sets the number of repetitions N2 of the two-track jumping scan required to reach the target track calculated before the search operation to 1
Reduce. The search circuit 37 determines the number N of jumping scanning iterations.
The above two-track jumping scan is repeated until 2 becomes zero. After that, the target track is reached by executing the one-track jumping scan described above N1 times, and the search operation is ended. In this embodiment, 1
The track midpoint detection performed by the track jumping scan is performed by calculating the difference between the tracking error signals output from the A / D converter 16 by the difference circuit 23 and detecting the polarity change by the zero-crossing detection circuit 24. However, in general, the difference calculation can be replaced with a differential calculation to approximate the difference. Even in the one-track jumping scan of this embodiment, the midpoint detection can be substituted by the change in the polarity of the signal obtained by differentiating the tracking error signal. FIG. 16 shows a configuration diagram of a track search device that adopts the midpoint detection by differentiation. 16 is the same in operation and configuration except that the differential circuit 23 of the track search device shown in FIG. Differentiating circuit 63 is A
The tracking error signal output from the / D converter 16 is differentiated and output to the zero-crossing detection circuit 24. FIG. 17 shows a timing chart of midpoint detection using the differentiating circuit 63.
17a) is a tracking error signal output from the differential circuit 14 during jumping scanning , b) is an output from the differentiating circuit 63, and c) is a trigger signal output from the zero-crossing detecting circuit 24. The differentiating circuit 63 becomes zero level when the light beam reaches the track midpoint, and at that time, the zero crossing detecting circuit 24
Outputs a positive pulse to the trigger signal as the deceleration pulse generation circuit 30
Is output to and the midpoint is detected.

Further, in the above embodiment, the inner peripheral direction search operation in which the inner peripheral direction jumping scan is repeated has been described, but the outer peripheral direction search operation is similarly performed in the outer peripheral direction 1 track jumping scan and 2 track jumping. It is realized by repeating scanning. At that time, the search circuit 37
Sets the jumping direction signal to high level prior to the search operation. Thereby, the inverting circuit 32 and the inverting circuit 4
4 performs the inversion operation, the acceleration pulse generation circuits 29, 4
The acceleration drive pulse output by 1 operates so as to accelerate and move the tracking actuator, and thus the light beam in the outer peripheral direction, and the deceleration pulse generation circuits 30 and 42 operate so as to decelerate the movement. Further, the polarity of the tracking error signal generated as the light beam moves from the groove track to the outer peripheral side is opposite to that described in FIGS. 7, 8 and 10, but the difference circuit 23, the zero-crossing detection circuit 24,
It is clear that the operation of 36 is not affected by the polarity of the tracking error signal and the track midpoint is detected as well.

In the embodiment, the one-track jumping scan from the groove track to the land track has been described. However, even in the one-track jumping scan from the land track to the groove track, the polarities of the tracking error signals are as shown in FIGS. Contrary to the description, it is also clear that the track midpoint is detected and the jumping scanning is stably performed.

In the above embodiment, a 1-track jumping scan block 35 for performing a 1-track jumping scan and a 2-track jumping scan block 36 for performing a 2-track jumping scan are provided, and track search is performed by 1-track jumping scan and 2-track. Although the jumping scan is also used, the one-track jumping scan is not always necessary and only the two-track jumping scan may be performed. For example, in the disk shown in FIG. 4, the disk rotation direction and the track spiral direction are set so that the light beam moves from the outer circumference to the inner circumference track by the rotation of the disk. At this time, in order to perform the search operation of N tracks from the outer circumference toward the inner circumference, the search circuit 37 first executes N / 2 two-track jumping scans, and the light beam is rotated along the spiral by the disk rotation by the disk rotation. The track adjacent to the target track on the side opposite to the direction moving in the radial direction, that is,
In this case, the disk 3 is moved to a track adjacent to the outer circumference of the target track, and then the tracking control is operated to follow the spiral track.
The target track is reached by the rotation of. More generally, when doing a track search for inner
When N is an even number, two-track jumping scans are performed N / 2 times to reach the target track, and when N is an odd number, (N-1) / 2-track jumping scans are performed. When the track reaches an adjacent track on the outer circumference side of the target track, and then reaches the target track by the inner circumference movement along the spiral of the light beam due to the rotation of the disk, and N is an even number when performing a track search for the outer circumference. To reach the target track by performing N / 2 times of two-track jumping scanning, and when N is an odd number, (N + 1) / 2 times of two-track jumping scanning is performed and the outer peripheral side of the target track. It reaches the target track by arriving at a track adjacent to the target track and then moving inward along the spiral of the light beam due to the rotation of the disk.

Further, in the disk shown in FIG. 4, the relationship between the direction of disk rotation and the direction of spiral is opposite. For example, when the direction of disk rotation is opposite, the light beam is rotated from the inner circumference to the outer circumference by the rotation of the disk. Move to the truck. In this case, the two-track jumping scan may be repeatedly moved to a track adjacent to the inner circumference side of the target track. Generally, when performing a track search for a stripped outer circumference, if N is an even number, N /
When the target track is reached by performing two 2-track jumping scans and N is an odd number, (N-1)
/ Two times of 2-track jumping scanning is performed to reach the adjacent track on the inner circumference side of the target track, and then the target track is reached by moving the disk toward the outer circumference along the spiral of the light beam due to the rotation of the disk, and then the inner circumference. If N is an even number when performing a stripped track search, N / 2 times 2
When the track jumping scan is performed to reach the target track, and N is an odd number, (N + 1) / 2 times of the two-track jumping scan is performed to reach the track adjacent to the inner circumference side of the target track, After that, the target track is reached by the movement of the light beam toward the outer circumference along the spiral due to the rotation of the disk.

Furthermore, the present invention is not limited to the above-described embodiments. For example, the zero-crossing detection circuit 24 is configured to generate a trigger signal when the polarity of the output signal of the difference circuit 23 is inverted and the difference value exceeds a predetermined value.
With the configuration, it is possible to further improve the reliability of the track midpoint detection. Further, the timing at which the polarity of the tracking control is inverted by the inversion circuit 17 is not limited to the timing in the embodiment, and may be performed at the same time as the deceleration drive pulse ends and the tracking control is operated.
That is, it may be reversed during the period in which the tracking control is disabled during the 1-track jumping scan. Further, the coil of the tracking actuator 11 has a low pass filter characteristic, and the low pass filter 20 can be omitted. Further, an inverting circuit 17, a phase compensation circuit 18, a PWM circuit 19, a low pass filter 20,
The difference circuit 23 and the zero-crossing detection circuits 24 and 45 do not have to be configured by hardware, and can be realized by software processing by using, for example, a digital signal processor (DSP).

The present invention is not limited to the single spiral L / G disc shown in FIG. Figure 20
The above-mentioned embodiment of the present invention is the same as the one spiral L / G.
FIG. 7 is a structural diagram of a two-spiral L / G disc applicable to the same as a disc. In the two-spiral disc, the land track and the groove track are adjacent to each other, and the polarity of tracking control is reversed, which is the same as in the one-spiral L / G disc. However, the land track and the groove track are each one spiral, and there is not one land track and groove track switching section for each track unlike the one-track L / G disk. Therefore, it is not necessary to switch the polarity of tracking control for each track as in the case of one spiral L / G disk, but continuous data recording or reproduction is impossible over the entire circumference of the disk. For example, a groove track spiral. Therefore, after recording / reproducing data from the outer circumference to the inner circumference, it is necessary to move the light beam to the outermost circumference again to record / reproduce data on the land track. The track search operation of the 2 spiral L / G disk is the same as the above 1
It is exactly the same as the spiral L / G disc. That is, the search circuit 37 calculates the address N of the target track and the number N of tracks to be traversed by the address of the track where the light beam is currently located and the direction. A jumping direction signal is set according to the calculated jumping scanning direction, N tracks are moved, N2 two-track jumping scans are executed first, and N1 one-track jumping scans are executed after that. To achieve by.
That is, when N is an even number, two-track jumping scanning is performed N / 2 times to reach the target track. When N is an even number, first, (N-1) / 2
Perform two 2-track jumping scans and move to the track adjacent to the search start track side of the target track,
After that, one-track jumping scanning is performed to reach the target track. This can be expressed as a mathematical expression as follows. N = even time N1 = 0 N2 = N / 2 N = odd time N1 = 1 N2 = (N-1) / 2 2 spiral 1 track jumping scan on L / G disk, 2 track jumping scan also 1 spiral mentioned above Since it is exactly the same as the case of the L / G disc, and its time chart has already been described with reference to FIGS. 7, 8 and 10, the description thereof will be omitted.

Next, a track search device according to a second embodiment of the present invention will be described. Since the configuration of the track search device of the second embodiment is the same as that of the first embodiment shown in FIG. 1, its explanation is omitted. The difference between the second embodiment and the first embodiment is that the order and combination of executing the 1-track jumping scan and the 2-track jumping scan during the search operation of N tracks starting from the groove track are different. That is, when the search start track is a groove track and the target track is also a groove track, the step of executing one-track jumping scan, the step of executing (N / 2−1) times of two-track jumping scan, and the one-track jumping scan are performed. When the target track is reached in three steps of execution steps and the search start track is a groove track and the target track is a land track, a step of executing one-track jumping scan, (N-1) / 2 times of two tracks When the target track is reached in two steps of executing the jumping scan, and the search start track is the land track and the target track is also the land track, the target track is reached in the step of executing the N / 2 times two-track jumping scan. Reach and start search tiger If the track is a land track and the target track is a groove track, the target track is reached in two steps of (N-1) / two-track jumping scan step 1 It is a thing.

That is, to put it more simply, the two-track jumping scans that are repeatedly executed are all performed by jumping scans from land tracks to land tracks.

FIG. 9 is a timing chart for explaining the operation of the track search device according to the second embodiment of the present invention. FIG. 9 shows a tracking error signal output from the A / D converter 16 and a) a jumping direction output from the search circuit 37 when the search operation is performed on the groove tracks on the inner circumference side of 6 tracks from the groove track. Signal, c) is 1 to 1 track jumping control circuit 28
A track jumping command signal, d) is a 2-track jumping command signal to the 2-track jumping control circuit 39, e) is a 1-track jumping end signal, and f) is a 2-track jumping end signal.

According to the procedure described above, the search circuit 37 first sets the jumping direction signal to the LOW level corresponding to the search operation toward the inner circumference at time TS20. Continued time T
At S21, a positive pulse is output to the 1-track jumping command signal to the 1-track jumping control circuit 28. In response to this, the 1-track jumping control circuit 28 becomes 1
Performs track jumping scan and, after completion, time TS22
Outputs a positive pulse to the 1-track jumping end signal. At this time, the light beam is located on the land track on the inner circumference side of one track. At time TS23 and TS24, the search circuit 37 sends the 2 track jumping control circuit 39
Output a positive pulse to the track jumping command signal,
The two-track jumping control circuit 39 executes the two-track jumping scan twice, and after the completion, the two-track jumping scan is performed at time TS25.
Outputs a positive pulse to the track jumping end signal. At this time, the light beam is located on the land track on the inner circumference side of the five tracks with respect to the groove track before the start of the search operation. After that, the search circuit 37 outputs a positive pulse to the 1-track jumping command signal again at time TS26, the 1-track jumping control circuit 28 executes the 1-track jumping scan, and the light beam is on the inner track side of the 6-track groove track. Located above, the search operation is complete. The merits of executing the track search as described above will be described.

FIG. 19a) is a plan view showing the positional relationship between the tracks on the disk 3 and the light beam. The vertical direction of the drawing is the track longitudinal direction, the horizontal direction is the disk radial direction, and the right hand is the outer peripheral direction. The hatched portion is the groove track, and the portion sandwiched between the groove track tracks is the land track. 19b) and 19c are plots of tracking error signals corresponding to the respective positions of the light beam of a). Also, the left side of the tracking error signal on the sine wave in FIGS. 19 b) and 19 c is a plot of the reflected light beam from the disk 3 on the two-division photodetector 12. 19b) and c), the vertical direction is the track longitudinal direction, the horizontal direction is the disk radial direction, and the right hand is the outer peripheral direction. This means that the mapping of the tracks on the disk by the optical system has the above relationship in the two-division photodetector 12 and the light beam portion. FIG. 19b) is a tracking error signal when the reflected light beam is shifted to the outer peripheral side on the two-divided detector 12, and FIG. 19c) is a tracking error signal when it is shifted to the inner peripheral side. When the reflected light beam shifts to the outer circumference side, the tracking error signal has a positive offset with respect to the zero level, and conversely, when it shifts to the inner circumference side, it has a negative offset. It is widely known that the tracking error signal by the push-pull method shows the above-described change with respect to the groove and land having a depth of about 8 / λ. It is also well known that the change of the reflected light beam on the two-divided detector 12 as shown in FIGS. 19b) and c) is caused by the movement of the tracking actuator 11 in the disk radial direction. For example, when the disk 3 has an eccentricity caused by the center of rotation of the spiral track and the center of rotation thereof being displaced, the tracking control is activated and the light beam is displaced in the disk radial direction in order to follow the eccentricity. Occurs in More specifically,
When the tracking actuator 11 is displaced to the outer circumference to follow the eccentricity on the outer circumference side, the light beam shifts to the outer circumference side on the two-divided photodetector 12, and the tracking error signal has a positive offset. On the contrary, when the tracking actuator 11 is displaced to the inner circumference in order to follow the eccentricity on the inner circumference side, the light beam shifts to the inner circumference side on the two-divided photodetector 12, and the tracking error signal has a negative offset. Have.

Due to the characteristics of the tracking error signal, the stability of tracking control changes between the land track and the groove track. First, consider the case where the tracking control is operating on the groove track.

Now, in order to follow the deviation of the disk eccentricity on the outer peripheral side, when the tracking actuator 11 is displaced to the outer peripheral side, the tracking error signal has a positive offset as shown in FIG. 19b). On the other hand, the tracking control is always controlled so that the tracking error signal becomes zero level. For this reason, in the tracking control in FIG. 19b), the operation is performed so as to pull in to the position X2 instead of the position X1 which is the amplitude center of the tracking error signal shown by the alternate long and short dash line. However, the band and gain of tracking control are finite, and it is impossible to follow a disturbance such as disk eccentricity with zero control error, and a control residual error occurs. Since the disk eccentricity that is now a disturbance is on the outer peripheral side, the control residual also occurs on the outer peripheral side,
As a result, the tracking control operates nearer the position X3 closer to the minimum point of the tracking error signal on the outer peripheral side of X2. In general, the tracking error signal has a sine wave shape as shown in FIG. 19, so that the detection sensitivity of the tracking error signal decreases near the minimum point and the maximum point, and the control loop gain decreases. Further, the differential coefficient is reversed on the side where the maximum point and the minimum point are passed, the amplitude of the tracking error signal decreases as the position error increases, and when the zero level is exceeded, the polarity of the tracking error signal is inverted and positive feedback is provided. As a result, the light beam deviates from the track on which the tracking control is operating and moves to another so-called track deviation.

For this reason, when the tracking control is operating at the position X3, track jumps are apt to occur and are unstable. This phenomenon follows the deviation of the disk eccentricity on the inner circumference side, and therefore is the same when the tracking actuator 11 is displaced on the inner circumference side. In this case, FIG.
In c), since the tracking control operates at the position X7 on the inner circumference side of the zero level of the tracking error signal, the track jump easily occurs due to the control error of the inner circumference and the disturbance.

Next, the case where the tracking control is operating on the land track will be considered. In order to follow the deviation of the disk eccentricity on the outer peripheral side, when the tracking actuator 11 is displaced to the outer peripheral side, the tracking control tries to pull in the position X5 where the tracking error signal is at the zero level. Since the control residual caused by the eccentricity is generated from the outer peripheral side as in the case of the groove track, tracking control is performed at the position X5 on the outer peripheral side from the position X5.
Works with 6. However, in this case, since the polarity of the tracking error signal is inverted, the tracking error signal operates at a signal level closer to the amplitude center of the tracking error signal than at the position X5. Therefore, the land track is less likely to jump and is more stable than the groove track.

Since this phenomenon follows the deviation of the disk eccentricity on the inner peripheral side, it is the same when the tracking actuator 11 is displaced to the inner peripheral side. In this case, FIG.
In c), the tracking control operates at the position X8 on the inner peripheral side of the zero level of the tracking error signal, so that track jump is less likely to occur as compared with the groove track.

Therefore, also in the jumping scan, when there is a disc eccentricity, the two-track jumping scan from the land track to the land track is more stable than the two-track jumping scan from the groove track to the groove track.

Therefore, by performing the search operation as in this embodiment, the search operation can be performed more stably even when there is a disturbance such as eccentricity. It should be added that the essence of the invention described in the second embodiment is not limited to the above embodiment. According to the present invention, the two-track jumping scan is performed as many as possible from the land track to the land track to ensure a stable search operation against eccentricity and the like. Therefore, in the above-described embodiment, the search to the groove track on the inner circumference side of 6 tracks from the groove track is repeated twice: 1) 1 track jumping scan to the inner circumference side, 2) 2 track jumping scan to the inner circumference side. , 3) Implemented by one-track jumping scan to the inner circumference side. However, for example,
Searching for groove tracks on the inner circumference side of 6 tracks from the same groove track, 1) 1 track jumping scan to the outer circumference side, 2) 2 track jumping scan to the inner circumference side, repeated 3 times, 3) to the inner circumference side Even if it is realized by the one-track jumping scanning, the same effect can be obtained. However, in this case, the number of jumping scans to be executed increases, resulting in a long search time.

Similarly, the same search is repeated twice: 1) one track jumping scan to the inner circumference side, 2) three track jumping scan to the inner circumference side, 3) one track jumping scan to the outer circumference side, or , 1) 1 track jumping scan to the outer circumference side, 2) 2 track jumping scan to the inner circumference side is repeated 4 times, and 3) 1 track jumping scan to the outer circumference side is obvious.

FIG. 11 is a block diagram of a track search device that obtains the same effect as that of the above-described embodiment by using a sample servo format disk (hereinafter referred to as SS disk) instead of the L / G disk. Before describing the configuration of the track search device in FIG. 11, the configuration of the SS disk will be described first. The physical format of the optical disc used in the conventional SS system will be described with reference to FIG. Figure 1
2a) is a plan view of the SS disk. In the disk 46, for example, a track in which servo areas 47 and information areas 48 are alternately arranged is spirally formed on one surface of a resin substrate such as a polycarbonate having a thickness of 1.2 mm, and a reflective layer such as aluminum is formed on the track. It is provided by a method such as vapor deposition. The servo area 47 is an area for obtaining a servo signal for performing focus control and tracking control necessary for the optical disk device. The information area 48 is an area in which information is recorded or information is recorded. A plurality of servo areas 47 and information areas 48, for example, about 1500 servo areas 47 and information areas 48, are provided at equal intervals in the circumferential direction and in the radial direction. Therefore, the servo area 47 and the information area 48 are formed on the disk 46 as shown.
It is formed so as to spread radially from the center of the disk.
FIG. 12 b) is an enlarged plan view of the disk 46. In the servo area 47, the clock mark 49 and the first wobble mark 5
0 and a second wobble mark 51 are provided. The clock mark 49 for synchronization is located on the track 62, and
The wobble mark 50 and the second wobble mark 51 are provided before and after the clock mark 49 in the track longitudinal direction. The first wobble mark 50 and the second wobble mark 51 are opposite to each other in the radial direction of the disk 46 with respect to the track 62 and are located in the middle of the tracks. For example, consecutively adjacent tracks 62a-
As for c, the first wobble mark 50 of the middle track 62b and the first wobble mark 50 of the track 62c.
Is shared, and the second wobble mark 5 on the track 62b is used.
1 and the second wobble mark 51 of the track 62a are shared. Therefore, for example, the first wobble mark 50
If the peak level of the reproduction signal of the second wobble mark 51 is detected and the tracking error signal is obtained from the difference between the two peak levels, the track 62a and the track 62 are
In b, the polarities of the tracking error signals are opposite. That is, the polarities of tracking control are alternately opposite for each track. The above-described format of the disk 46 is called an inverted wobble, and the method of detecting the tracking error signal and its characteristics are known, and therefore detailed description thereof will be omitted. FIG. 13 conceptually shows the format on the disk 46 of FIG. 12, and is a diagram for explaining how data is arranged. As shown in FIG. 13A, servo tracks 47 and information areas 48 are alternately formed on the tracks on the disk 46, and a pair of servo areas 47 and information areas 48 constitutes one block. As shown in FIG. 13B), one sector is composed of (n + 1) blocks, and an address (for example, track number and sector number) for identifying the sector is recorded in the information area 48 of the first block of the sector. It is the address area that has been set. Then, the data is recorded in the information area 48 of the n blocks following it. Further, as shown in FIG. 13c), one track is composed of m sectors, and when one track cannot be divided by one sector length, a surplus area is provided at the end of the track.

The structure of the track search device using the above-mentioned SS disc will be described with reference to FIG. Figure 11
In the above, the structure and operation of the disk / head block 33 including the optical head unit 9 and the like are the same as those in the first embodiment whose structure is shown in FIG. However,
Disk 4 of sample servo format is used
It is 6. The output of the two-division photodetector 12 is the addition circuit 25.
Is added to calculate the sum of reflected light amount from the disk 46, and the sum is input to the PLL circuit 52, peak hold circuits (hereinafter referred to as PH circuits) 53 and 54, and the address reading circuit 26. The PLL circuit 52 compares the phase of the signal of the oscillator provided in the circuit with the reproduction signal of the clock mark 49 in the servo area 47 detected by the two-division photodetector 12, and determines the phase difference between the two signals. Are controlled to have a predetermined relationship. The timing circuit 55 generates a timing signal for operating the PH circuits 53 and 54 and the sample hold circuit (hereinafter, referred to as S & H circuit) 56 based on the output signal from the PLL circuit 52. The PH circuit 53 detects the peak level of the first wobble mark 50 in the servo area, and the PH circuit 54 detects the peak level of the second wobble mark 51 in the servo area. The differential circuit 57 outputs a signal corresponding to the level difference between the output signals of the PH circuits 53 and 54, that is, the positional shift between the track on the disk 46 and the light beam. Since this positional deviation signal is detected by the pair of wobble marks 50 and 51 in the servo area 47 on the disk 46, when the disk 46 is rotated at a constant rotation speed, it is discretely output at every predetermined cycle. S & H circuit 56
Each time the differential circuit 57 outputs a discrete position shift signal, the value is sampled and held, and a stepwise tracking error signal is output. This tracking error signal is used to invert the polarity of tracking control, a phase compensation circuit 18 for compensating the phase characteristic of the tracking control system to obtain control stability, and a tracking control loop for opening and closing. It is added to the tracking actuator 11 via the switch 21 and the 3-input adder circuit 38. As a result, the tracking control functions and the light beam is controlled so as to always be located at the center of the track.

Search circuit 37, 1-track jumping control circuit 28, acceleration pulse generation circuit 29, deceleration pulse generation circuit 30, differential circuit 31, inversion circuit 32, 2-track jumping scanning block 36, inversion circuit 44, and AND gate 40 Since the configuration and the operation are the same as those of the first embodiment shown in FIG. 1, the description thereof will be omitted.

In this example, the tracking error signal from the S & H circuit 56 is input to the zero-crossing detection circuit 60 via the differentiating circuit 58 and the sample hold circuit (hereinafter referred to as S & H circuit) 59. The S & H circuit 59 is a circuit that samples and holds the input signal in accordance with the timing signal from the timing circuit 55. S & H circuit 59
The output of is inputted to the zero-crossing detection circuit 60. The zero-crossing detection circuit 60 detects a zero-cross of the input signal and outputs a trigger signal to the deceleration pulse generation circuit 30. S &
The tracking error signal from the H circuit 56 is also input to the zero-crossing detection circuit 45, which is also used for midpoint detection during the 2-track jumping scanning.

Next, the track search operation of this embodiment will be described in detail with reference to the timing chart of FIG. Also in this embodiment, the address of the target track is inputted to the search circuit 37 from the external instruction means prior to the jumping scanning . When the address of the target track is input, the search circuit 37 fetches the address of the track where the light beam is currently located from the address reading circuit 26, and calculates the number N of tracks to be traversed and the direction.
According to the calculated jumping scanning direction, the search circuit 3
7 sets the jumping direction signal. Assuming that the track search operation toward the inner circumference is performed, the jumping direction signal is set to the LOW level. Search circuit 37 is N
Track movement is accomplished by first performing N2 two-track jumping scans and then performing N1 one-track jumping scans. That is, when N is an even number, two-track jumping scanning is performed N / 2 times to reach the target track. When N is an even number, first, (N-1) / 2 times of 2-track jumping scanning is performed to move to the track adjacent to the search start track side of the target track, and then 1-track jumping scanning is performed to perform the target track. To reach.

This can be expressed by a mathematical expression as follows. N = even time N1 = 0 N2 = N / 2 N = odd time N1 = 1 N2 = (N-1) / 2 Regarding one-track jumping scanning of the present embodiment FIG.
This will be described in detail with reference to the timing chart of. 14
8A is an enlarged plan view of two adjacent tracks 61a and 61b on the disk 46, which is moved from the track 61a to the track 61b by jumping scanning. The vertical direction in the figure is the disk radial direction, and in the figure,
The upward direction is toward the outer circumference. Further, in FIG. 14a), the dotted line is
It is a locus when the light beam indicated by a circle moves. Figure 1
4b) to i) are timing charts of signals of respective parts corresponding to respective positions of the trajectory of the light beam shown in a). 7b) is a tracking error signal, c) a jumping direction signal, d) is a jumping command signal, e) is a tracking control ON / OFF signal, f) is a tracking polarity signal, and g) is the acceleration output from the acceleration pulse generation circuit 29. The drive pulse, h) is a trigger signal output from the zero-crossing detection circuit 24 that performs midpoint detection, and i) is the deceleration drive pulse output from the deceleration pulse generation circuit 30.
The procedure of the 1-track jumping scan is the same as that of the first embodiment except for the detection of the midpoint, and therefore only the timing chart is shown in FIG. FIG. 15 is a timing chart for explaining midpoint detection during one-track jumping scanning. FIG. 15a) shows an S & H circuit 56,
b) is the output of the differentiation circuit 58, c) is the output of the S & H circuit 59, and d) is the output of the zero-crossing detection circuit 60. In the figure, the vertical dotted line is the timing at which the timing signal is output from the timing circuit 55. In the SS disk, the track deviation information is discretely detected from the servo area 47 which is provided about 1500 times per circumference of the disk 46.
The tracking error signal output by 6 has a stepwise waveform. Therefore, the output waveform of the differentiating circuit 58 obtained by differentiating the output of the S & H circuit 56 becomes a triangular wave-shaped signal as shown in FIG. 15b). The S & H circuit 59 peak-holds each peak level of the sawtooth signal of the differentiating circuit 58, that is, the maximum value when the triangular wave signal is a positive value, and the minimum value when the triangular wave signal is a negative value. The signal of is output. The zero-crossing detection circuit 60 detects that the polarity of the output signal of the S & H circuit 59 has changed, detects that the light beam has reached the middle point of the track, and decelerates the positive pulse shown in FIG. 15d) to the trigger signal. The pulse is output to the pulse generation circuit 30, and the midpoint detection ends. Thereafter, similarly to the first embodiment, the procedure after the output of the deceleration drive pulse is executed in response to the trigger signal, and the one-track jumping scan is completed. When the 1-track jumping scanning is completed, the 1-track jumping control circuit 28 searches for the 1-track jumping end signal 37.
To inform the search circuit 37 of the end.

Next, the 2-track jumping scanning will be described. The method and operation of the 2-track jumping scanning are the same as those of the first embodiment shown in FIG.
The description is omitted because they are the same except for the trigger signal output by. FIG. 18 is a timing chart for explaining the midpoint detection during 2-track jumping scanning. Figure 1
8a) is a tracking error signal output from the S / H circuit 56, and b) is a trigger signal output from the zero-crossing detection circuit 45. The zero-crossing detection circuit 45 detects a polarity change of the stepwise tracking error signal output from the S / H circuit 56 and outputs a positive pulse to the trigger signal. By this, it is detected that the light beam is located on substantially the adjacent track,
Since the deceleration driving pulse can be output by the deceleration pulse generation circuit 42, the two-track jumping scanning can be stably performed.

As described above, the search circuit 37 repeats the two-track jumping scan N2 times and then performs the one-track jumping scan N1 times to reach the target track and perform the search operation.

In the above-described embodiment, the search operation in the inner circumference direction in which the jumping scan in the inner circumference direction is repeated has been described, but the search operation in the outer circumference direction is similarly performed in the outer circumference direction.
It is realized by repeating track jumping scan and two track jumping scan. At that time, the search circuit 37 sets the jumping direction signal to the HIGH level prior to the search operation. As a result, the inversion circuit 32 and the inversion circuit 44 perform the inversion operation, so that the acceleration drive pulses output from the acceleration pulse generation circuits 29 and 41 are decelerated so as to accelerate and move the tracking actuator, and thus the light beam in the outer peripheral direction. The pulse generation circuits 30, 42 operate to slow down their movement. Also, the polarity of the tracking error signal generated as the light beam moves to the outer peripheral side is
Contrary to the description of FIGS. 14, 15, and 18, the operations of the differentiating circuit 58, the S & H circuit 59, and the zero-crossing detecting circuits 24 and 45 are not affected by the polarity of the tracking error signal at all, and likewise during tracking. It is clear that the points are detected.

[0051]

The present invention provides a track search method for moving a light beam to a desired track at a high speed on a high density disk such as an L / G disk, and therefore tracking control is performed on adjacent tracks. A light beam is emitted to a disc whose polarity is reversed, and a tracking error signal indicating the positional deviation between the light beam on the disc and the track is detected from the reflected light or the transmitted light from the disc, and the light beam is constantly detected based on the tracking error signal. It is a tracking device that controls so that it is located on the track.
This is a track search method in which a two-track jumping scan for moving a light beam to a track separated from a track and a one-track jumping scan for moving a light beam to an adjacent track are used together to reach a target track.

According to this track search method, when the light beam is moved by a plurality of tracks, it is possible to repeat the 2-track jumping scan to move a large distance and reach the target track by the 1-track jumping scan, so that the search is performed at high speed. It becomes possible to operate.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a track search device according to a first embodiment of the present invention.

FIG. 2 is a timing chart of conventional jumping scanning.

FIG. 3 is a relationship diagram of a positional relationship between a light beam and a track and a tracking error signal.

FIG. 4 is an external view of an L / G disc.

FIG. 5 is an enlarged external view of an L / G disc.

FIG. 6 is a diagram showing a tracking error signal of an L / G disc.

FIG. 7 is a timing chart of a track search operation.

FIG. 8 is a timing chart of midpoint detection.

FIG. 9 is a timing chart of a search operation according to the second embodiment of this invention.

FIG. 10 is a timing chart of a track search operation.

FIG. 11 is a configuration diagram of a track search device according to a third embodiment.

[FIG. 12] (a) Plan view of the SS disc (b) Partial enlarged view of the SS disc

FIG. 13 is a diagram showing the format of the SS disk.

FIG. 14 is a timing chart of jumping scanning.

FIG. 15 is a timing chart of midpoint detection.

FIG. 16 is a block diagram of a track search device that employs midpoint detection by differentiation.

FIG. 17 is a timing chart of midpoint detection using a differentiating circuit 63.

FIG. 18 is a timing chart of midpoint detection during 2-track jumping scanning.

FIG. 19 is a relationship diagram between a light beam on a two-division photodetector and a tracking error signal.

FIG. 20 is a structural diagram of a two-spiral L / G disc.

[Explanation of symbols]

Light beam 1 Track 2 Disk 3 Disk motor 4 Light source 5 Coupling lens 6 Polarization beam splitter 7 1/4 wavelength plate 8 Optical head section 9 Converging lens 10 Tracking actuator 11 2 Split photodetector 12 Transfer motor 13 Differential circuit 14 Sample / Hold circuit 15 A / D converter 16 Inversion circuit 17 Phase compensation circuit 18 PWM circuit 19 Low pass filter 20 Switch 21 Adder circuit 22 Difference circuit 23 Zero crossing detection circuit 24 Adder circuit 25 Address read circuit 26 Search circuit 27 1 track Jumping control circuit 28 Acceleration pulse generation circuit 29 Deceleration pulse generation circuit 30 Differential circuit 31 Inversion circuit 32 Disk / head block 33 Tracking control block 34 1 track jumping scan block 35 2 track jumping scan block C 36 Search circuit 37 3 Input addition circuit 38 2 Track jumping control circuit 39 AND gate 40 Acceleration pulse generation circuit 41 Deceleration pulse generation circuit 42 Differential circuit 43 Inversion circuit 44 Zero crossing detection circuit 45 Disk 46 Servo area 47 Information area 48 Clock Mark 49 First wobble mark 50 Second wobble mark 51 PLL circuit 52 Peak hold circuit 53, 54 Timing circuit 55 Sample hold circuit 56 Differential circuit 57 Differentiator circuit 58 Sample hold circuit 59 Zero crossing detection circuit 60 Track 61a, 61b Track 62a , 62b, 62c, 62d differentiating circuit 63

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G11B 7/085 G11B 21/08

Claims (9)

(57) [Claims] 1. A position shift signal is obtained by irradiating a light beam onto an optical disc having a track whose polarity of tracking control is alternately inverted and detecting a position shift between the light beam and the track from reflected light or transmitted light from the optical disc. A track interlaced scanning method used in a device for recording or reproducing information while performing tracking control so that a light beam is positioned on a track based on A track jump scanning method of arriving at a target track by performing 1-track jumping scan N1 times to move the target beam and N2 two-track jumping scans to move the light beam to tracks separated by 2 tracks. However, when N is an even number, N1 and N2 are: N1 = 0 N2 = N / 2 When N is an odd number, N1 = 1 N2 = (N-1) / 2 2. The method according to claim 1, wherein N2 two-track jumping scans are first performed to move to a target track or a track adjacent to the target track, and then one-track jumping scans are performed N1 times to reach the target track. Track jump scanning method. 3. A light beam is irradiated onto an optical disk having a spiral or concentric groove track having a convex structure as viewed from the incident surface of the light beam and a land track sandwiched by the groove tracks, and reflected from the optical disk. A track jump scanning method used in a device that detects the positional deviation between a light beam and a track from light or transmitted light, and records or reproduces information while performing tracking control so that the light beam is positioned on the track based on the positional deviation signal. And a step of performing a one-track jumping scan for moving the light beam to an adjacent track when N is an even number, to search for a track separated from the groove track by N tracks, (N / 2−1) times of land. Two tracks that move the light beam from the track to the land track, which is two tracks away. The step of performing the jumping scan and the step of performing the one-track jumping scan again. When N is an odd number, the step of performing the one-track jumping scan, (N-1) / 2 times of the two steps.
A track jump scanning method characterized in that it is performed in the step of performing track jumping scan. 4. An optical disc having two spiral tracks, a spiral track formed of groove tracks having a convex structure when viewed from the incident surface of a light beam, and a spiral track formed of land tracks sandwiched by the groove tracks. The optical disc is irradiated with a light beam, the positional deviation between the optical beam and the track is detected from the reflected light or the transmitted light from the optical disc, and the information is controlled by tracking control so that the optical beam is positioned on the track based on the positional deviation signal. A track interlaced scanning method used in a recording or reproducing apparatus, in which a track separated from a groove track by N tracks is searched, and when N is an even number, a 1-track jumping scan in which a light beam is moved to an adjacent track is performed. 2 steps from (N / 2-1) land tracks A two-track jumping scan for moving a light beam to a land track spaced apart from each other, a step for performing the one-track jumping scan again, and a step for performing the one-track jumping scan when N is an odd number. 1) A track jump scanning method, characterized in that it is carried out in the step of performing the two-track jumping scanning twice. 5. In the one-track jumping scanning, a step of generating an acceleration pulse for accelerating a light beam toward an adjacent track by making tracking control inoperative, and a step of generating a differential signal by calculating a differential of a position deviation signal When,
Detecting a change in the polarity of the differential signal and generating a deceleration pulse for decelerating the movement of the light beam; inverting the polarity of the tracking control until the deceleration pulse ends; ending the deceleration pulse 5. The track jump scanning method according to claim 1, further comprising the step of re-operating the tracking control. 6. The one-track jumping scan includes the steps of generating an acceleration pulse for accelerating a light beam toward an adjacent track by disabling tracking control, converting a position shift signal into a digital signal, and the digital signal. Generating a difference signal by calculating the difference between the positional displacement signals converted into signals, generating a deceleration pulse for decelerating the movement of the light beam by detecting the polarity change of the difference signal, and the deceleration pulse 5. The track jumping according to claim 1, further comprising the step of reversing the polarity of the tracking control until the end of the step, and the step of reactivating the tracking control after the end of the deceleration pulse. Scanning method. 7. In the two-track jumping scanning, a step of generating an accelerating pulse for accelerating a light beam toward an adjacent track by making tracking control inoperative, and a polarity change of the position deviation signal are detected to detect the light beam. 5. The track jump scanning method according to claim 1, further comprising: a step of generating a deceleration pulse for decelerating the movement, and a step of reactivating the tracking control after the end of the deceleration pulse. . 8. An optical disk is a sample servo type optical disk in which a pair of wobble marks for detecting a track deviation is formed so that the direction of deviation is opposite to that of an adjacent track. 2. The track jump scanning method according to claim 1, wherein the wobble mark is detected discretely from the reproduced signal. 9. The one-track jumping scan includes a step of generating an acceleration pulse for moving a light beam toward an adjacent track by disabling tracking control.
Differentiating the displacement signal, sampling and holding each peak value of the triangular wave signal corresponding to the discrete detection of the displacement signal obtained by this differentiation, and detecting the polarity change of the sampled and held signal. Generating a deceleration pulse for decelerating the movement of the light beam, inverting the polarity of the tracking control until the deceleration pulse ends, and reactivating the tracking control after the deceleration pulse ends 9. The interlaced track scanning method according to claim 8, comprising steps.