JPH07296394A - Midpoint searching method for track, track searching method and apparatus - Google Patents

Abstract

PURPOSE:To realize a jumping scanning method for shifting a light beam at a high speed to a target track on a high density disc, e.g. an L/G disc. CONSTITUTION:The midpoint detecting method 15 employed for a disc 3 provided with a track having alternating polarities for tracking control. The disc 3 is irradiated, at first, with a light beam from a disc/head block 33. A tracking control block 34 detects positional shift of the optical beam from a track based on a light reflected on the disc 3 and produces a tracking error signal S1 corresponding to the positional shift. Subsequently, a difference circuit 23 produces the difference signal S28 of the tracking error signal S1. Since the positional shift is nullified at the midpoint between tracks on such disc 3, arrival of the light beam at the midpoint between adjacent tracks can be detected based on the polarity change of the difference signal S28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track search in which a light beam for reproducing information from a disk having spiral or concentric tracks or for recording information on the disk is instantaneously skipped from one track to another. The present invention relates to a method, a method for detecting a midpoint of a track required for the search, and an apparatus using the method, and more particularly to an interlaced scanning method.

[0002]

2. Description of the Related Art Various types of conventional optical recording / reproducing devices have been proposed. In the optical recording / reproducing apparatus, for example, a recording medium is optically recorded / recorded on the surface of a base material having a track having a concentric concavo-convex structure.
A disc on which a reproducible material film is formed by a method such as vapor deposition is used. The optical recording / reproducing apparatus records / reproduces a signal by irradiating a disk having such a structure with a light beam generated by a light source such as a semiconductor laser. Specifically, for example, at the time of recording a signal, the light intensity of the light beam is strongly modulated according to the signal to be recorded, the reflectance of the material film of the disk is changed to perform recording, and when the signal is reproduced, The signal is read by changing the amount of light reflected from the disc with a relatively weak constant amount of light.

In such an optical recording / reproducing apparatus, focus control is performed so that the light beam is always in a substantially converged state on the material film, and the light beam always scans a predetermined track correctly. Tracking control to control is performed. Further, for example, Japanese Patent Application No. 62-13
As described in detail in No. 2467, a jumping scan for moving a light beam from one track to an adjacent track is performed.

The jumping scan is usually performed by using a tracking moving means for performing tracking control. The tracking moving means is means for moving the light beam relative to the track in a direction perpendicular to the track longitudinal direction and horizontal to the disk surface (disk radial direction).

The conventional jumping scan operation of a track when a jumping scan is performed from a certain track to, for example, a track adjacent to the inner circumference side of the disk will be described with reference to FIGS. 13 and 14.

FIG. 13 is a timing chart of jumping scanning. In FIG. 13, (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) shows a midpoint detection signal for detecting the midpoint between the track and its adjacent track. FIG. 14A is a diagram showing the positional relationship between the light beam 1 and the track 2 on the disk surface, and FIG. 14B is a tracking error corresponding to each position of the light beam 1 in FIG. 14A. It is a plot of the signal.

First, as shown in FIG. 13A, time T
At the timing of 1, the tracking control ON / OFF signal is set to the OFF level to disable the tracking control. At the same time, as shown in FIG. 13B, a rectangular acceleration pulse is applied to the tracking moving means to accelerate and move the light beam in the direction of the target track. 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. At the time when the light beam is located approximately at the midpoint between the tracks, that is, at the timing of time T2, a deceleration pulse having the same rectangular shape as the acceleration pulse but the opposite polarity is applied to decelerate the light beam. After the end of the deceleration pulse, the tracking control ON / OFF signal is turned to the ON level at the timing of time T3, and the tracking control is operated again. As a result, the light beam is drawn to the adjacent track, and the jumping scan ends.

An important point in the jumping scan is high-precision detection of the midpoint between the track and its adjacent track, that is, the track midpoint, in order to generate deceleration pulses at appropriate timings. This midpoint detection will be described below.

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. 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 an uneven structure with an optical depth λ / 8 (where λ is the wavelength of the light source). As shown in FIG. 14B, the tracking error signal has a sinusoidal shape according to the relative positional relationship between the light beam 1 and the track 2, the period of which is equal to the track pitch, and the light beam is at the track center. The amplitude reaches zero level when it is located. As shown in FIG. 13C, the polarity of the tracking error signal in the case of performing the jumping scan is inverted with respect to the track center, and the binarized signal thereof is shown in FIG.
As shown in (d), when jumping scanning is performed toward the outer circumference of the disk, the midpoint detection is executed by detecting the rising edge after the end of the acceleration pulse. That is,
The falling edge of the binarized signal of the tracking error signal after the end of the acceleration pulse is detected to generate the midpoint detection signal shown in FIG.

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. 15 shows an external view of such an L / G disc. The L / G disc will be described with reference to FIG.

In the conventional optical disk, information is recorded by using either the groove for tracking control or the land which is an intermediate area between the groove and the track. On the other hand, with L / G discs,
Information is recorded using both the land and the groove as tracks. This makes the track pitch equivalent to 1
Since it becomes / 2, the capacity of the optical disk can be doubled. In the L / G disc, a groove track using a groove (a hunting portion in FIG. 15),
A land track using a land (a portion sandwiched by a groove track) and the rest are alternately connected for each rotation to be formed. As a result, the track has a single spiral shape in which groove tracks and land tracks are alternately formed, so that continuous data recording or reproduction can be performed without interruption on the entire surface of the disk. The disc is provided with an address for track identification on each track. The address portion of each track is arranged so that its position is aligned in the circumferential direction, and the position is provided in front of the land / groove switching portion with respect to the disc rotation direction. The L / G disk having such a structure is referred to as one spiral L / G disk because one spiral exists on the disk.

FIG. 16 is an enlarged view of the address, land, and groove switching portions 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 is formed in a convex structure in which the optical depth d is approximately d = 8 / λ with respect to the wavelength λ of a light source such as a semiconductor laser, and the land track is a flat portion having no groove. Therefore, when the light beam moves along this spiral track, the light beam is 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. 17 shows an external view of an L / G disc of a type different from the L / G discs shown in FIGS. 15 and 16. The L / G disc shown in FIG. 17 has land tracks and groove tracks that are adjacent to each other. 1 land track and 1 groove track
It is a spiral of a book. Therefore, the L / G shown in FIG.
Unlike a disk, there is no one land track / groove track switching section for each track. The L / G disk having such a structure has two spirals, a land spiral and a groove spiral, and is called a two-spiral L / G disk.

Even in such a two-spiral L / G disc, land tracks and groove tracks are alternately present in the radial direction of the disc. Therefore, the polarity of tracking control is the same as in the one-spiral L / G disc. Is reversed.

In the two-spiral L / G disc, unlike the one-spiral L / G disc, when scanning along the spiral, it is not necessary to switch the polarity of tracking control for each track. However, it is impossible to record or reproduce continuous data over the entire circumference of the disc. That is, for example, after recording / reproducing data from the outer periphery to the inner periphery along the groove track spiral, it is necessary to move the light beam again to the outermost periphery to record / reproduce data on the land track spiral. . The structure of the other two spiral L / G disks is exactly the same as the above-mentioned (1) spiral L / G disk.

FIG. 18 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. In the L / G disk, the land area between the groove tracks corresponding to the conventional track becomes the land 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.

[0017]

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.

The same applies to the case of the sample servo format of the inversion wobble system, and the conventional method cannot detect the midpoint.

The present invention has been made to solve the above-mentioned problems of the prior art, and is a jumping scanning method for moving a light beam to a target track at high speed on a high density disk such as an L / G disk. Another object of the present invention is to provide a method for detecting the midpoint of a track required for the search, and an apparatus using the method.

[0020]

A midpoint detecting method of the present invention is a method for detecting a midpoint between adjacent tracks of a recording medium having tracks whose polarity of tracking control is alternately inverted. , Irradiating the recording medium with a light beam, detecting the positional deviation between the light beam and the track from either the reflected light or the transmitted light from the recording medium, and detecting the positional deviation corresponding to the positional deviation. A step of generating a signal, a step of generating a midpoint signal corresponding to a differential signal obtained by calculating a differential of the position displacement signal, and a step of detecting a change in polarity of the midpoint signal, whereby the light beams are adjacent to each other. Detecting that the midpoint between the tracks has been reached, whereby the above objective is achieved.

The step of generating the midpoint signal includes the step of converting the position shift signal into a digital signal;
And a step of generating a difference signal obtained by calculating a difference between the position shift signals converted into the digital signal as the midpoint signal.

In the step of generating the midpoint signal, the differential signal may be generated as the midpoint signal.

The track search method of the present invention records and reproduces information on a recording medium having a track in which the polarities of the tracking control are alternately inverted while performing tracking control so that the light beam is positioned on the track. A device for performing at least one of: a track search method for locating the light beam on a target track, which comprises moving the light beam toward an adjacent track after disabling the tracking control; Detecting a positional deviation between the beam and the track, generating a positional deviation signal corresponding to the positional deviation, and generating a midpoint signal corresponding to a differential signal obtained by calculating a differential of the positional deviation signal, Generating a deceleration pulse for decelerating the movement of the light beam based on the polarity change of the midpoint signal; The step of reversing the polarity of the tracking control before the end of the scanning, and the step of moving the light beam to the target track by operating the tracking control again after the end of the deceleration pulse. By doing so, the above object is achieved.

The step of generating the midpoint signal includes the step of converting the position shift signal into a digital signal,
And a step of generating a difference signal obtained by calculating a difference between the position shift signals converted into the digital signal as the midpoint signal.

In the step of generating the midpoint signal, the differential signal may be generated as the midpoint signal.

The recording medium has a plurality of pairs of wobble marks for discretely detecting track deviations, each of which has a pair of wobble marks whose deviation directions are adjacent to each other. In the case of the sample servo type optical disc in which the direction of the deviation of the bull mark is opposite, in the step of generating the position deviation signal, the position deviation signal is a discrete signal reproduced from the plurality of pairs of wobble marks. Generated as a signal, the step of detecting the midpoint signal includes a step of calculating a derivative of the position deviation signal, and a step of calculating each peak value of the triangular wave signal corresponding to the discrete position deviation signal obtained by the differentiation. The device of the present invention may be configured so as to include a step of sampling and holding to obtain a midpoint signal. A device for recording and / or reproducing information on / from a recording medium having a rotating track, detecting a positional deviation between a light beam and the track, and generating a positional deviation signal corresponding to the positional deviation. Position shift signal generating means, tracking control means for performing tracking control so that the light beam is positioned on the track, switch means for switching operation / non-operation of the tracking control, and the tracking control by the switch means. After being deactivated, an accelerating means for moving the light beam toward an adjacent track, a midpoint detecting means for generating a midpoint signal corresponding to a differential signal obtained by calculating a differential of the positional deviation signal, Deceleration means for generating a deceleration pulse for decelerating the movement of the light beam based on a change in the polarity of the midpoint signal, and the deceleration pulse ending. Up to and including polarity reversing means for reversing the polarity of the tracking control, and means for giving a signal for reactivating the tracking control to the switch means after the deceleration pulse is completed. Thereby, the above object is achieved.

The middle point detecting means converts the positional deviation signal into a digital signal, and a difference signal for calculating a difference between the positional deviation signal converted into the digital signal as the middle point signal. Means may be provided.

The midpoint detecting means may be a differentiating means for generating the differential signal as the midpoint signal.

The recording medium has a plurality of pairs of wobble marks for discretely detecting track shifts, each of which has a pair of wobble marks whose deviation directions are adjacent to each other. In the case of an optical disk of a sample servo system in which the direction of the deviation of the bullmark is opposite, the position shift signal generating means generates the position shift signal as a discrete signal reproduced from the plurality of pairs of wobble marks. And the middle point detection means sample-holds each peak value of the triangular wave signal corresponding to the discrete position shift signal obtained by the differentiating means and the position shift signal. It may be provided with a sample and hold means for setting a midpoint signal.

[0030]

The midpoint detection method of the present invention is used for a recording medium having tracks in which the polarities of tracking control are alternately inverted. First, irradiate the recording medium with a light beam,
From either reflected light or transmitted light from the recording medium,
A positional deviation between the light beam and the track is detected, and a positional deviation signal corresponding to this positional deviation is generated. Next, a midpoint signal (this signal includes a difference signal) corresponding to the differential signal obtained by calculating the differential of the position shift signal is generated. In such a recording medium, the displacement between the tracks becomes zero at the midpoint between the tracks, and therefore the light beam reaches the midpoint between the adjacent tracks by detecting the change in the polarity of the midpoint signal. You can detect what you have done.

By applying this midpoint detection method,
One-track jumping scanning on such a recording medium becomes possible.

[0032]

Embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1) FIG. 1 shows a block diagram of a track search apparatus which is Embodiment 1 embodying the jumping scanning method of the present invention. The configuration of the track search device of this embodiment will be described below with reference to FIG.

The track search device of this embodiment is roughly divided into three blocks. That is, a tracking which is composed of a disk / head block 33 for irradiating the disk with a light beam and for receiving light from the disk, a circuit for realizing tracking control by digital control, and a circuit for address reading. A control block 34 and a jumping scanning block 35 for performing jumping scanning of one track. The detailed configuration and operation of each of the blocks 33, 34 and 35 will be described below.

First, the structure of the disk / head block 33 will be described. The disc / head block 33 moves the disc 3, which is an information recording medium, the disc motor 4 for rotating the disc 3, the optical head unit 9 for irradiating the optical disc 3 with a light beam, and the optical head unit 9. The transfer motor 13 of FIG.

The optical head unit 9 includes a light source 5 such as a semiconductor laser, a coupling lens 6 into which a light beam generated from the light source 5 is sequentially incident, a polarization beam splitter 7, and a quarter.
The wave plate 8, the converging lens 10, the tracking actuator 11, and the two-divided photodetector 12 on which the light beam from the disk 3 is incident are provided. The tracking actuator 11 includes a movable part having a tracking coil and a fixed part having a permanent magnet. The converging lens 10 is attached to the movable portion of the tracking actuator 11.
Is attached. The two-divided photodetector 12 has a light receiving region divided into two, and the direction of the dividing line corresponds to the track direction on the light receiving surface.

The operation of the disk / head block 33 having such a configuration will be described. The disk 3 is rotated at a predetermined speed by the disk motor 4. The light beam generated from the light source 5 is collimated by the coupling lens 6, passes through the polarization beam splitter 7 and the quarter-wave plate 8 in this order, and is converged on the disk 3 by the converging lens 10 to be irradiated. . The light beam reflected by the disk 3 passes through the converging lens 10 and the quarter-wave plate 8 in this order, is reflected by the polarization beam splitter 7, and then is irradiated onto the two-divided photodetector 12. The two light receiving regions of the two-divided photodetector 12 respectively convert the irradiation light into an electric signal and output it to the tracking control block 34.

The position on the disk 3 to which the light beam is applied is adjusted by the transfer motor 13 and the tracking actuator 11. The transfer motor 13 moves the entire optical head unit 9 in the radial direction of the disk 3. The tracking actuator 11 changes the relative position of the fixed portion with respect to the permanent magnet by utilizing the electromagnetic force generated according to the current flowing through the coil of the movable portion, so that the tracking actuator 11 moves in the radial direction of the disk 3, that is, in the direction crossing the tracks. Move the light beam. The transfer motor 13 is used to transfer the entire optical head unit 9 in the disk radial direction, and the tracking actuator 11 is used to move the light beam for each track.

Next, the operation will be described together with the configuration of the tracking control block 34. The tracking control block 34 includes a circuit for tracking control and a circuit for reading addresses.

A circuit for tracking control includes a differential circuit 14, a sample / hold circuit 15, an A / D converter 16, an inverting circuit 17, a phase compensation circuit 18, a pulse width modulation (PWM) circuit 19, and a low frequency band. A pass filter 20 and a switch 21 are included.

The respective output signals corresponding to 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. It is widely known that the tracking error signal S1 is detected by the push-pull method using the differential circuit 14 configured in this way and the above-described L / G disk whose structure is shown in FIGS. 15 and 16. ing. The tracking error signal S1 output from the differential circuit 14 is passed through the sample / hold circuit 15 to A
The / D converter 16 converts the analog signal into a digital signal. The sample / hold circuit 15 is the differential circuit 1
4 is a circuit for discretely sampling the tracking error signal S1 output from the signal No. 4 and holding the signal sampled by the A / D converter 16 for a period required for A / D conversion. The tracking error signal S1 converted into a digital signal by the A / D converter 16 is supplied to the inverting circuit 17
This reverses the polarity of tracking control. The output signal from the A / D converter 16 is a jumping scan block 3
It is also output to 5.

The tracking error signal S1 whose polarity is inverted by the inversion circuit 17 is input to the phase compensation circuit 18. The phase compensation circuit 18 ensures the controllability of the tracking control system. The output signal of the phase compensation circuit 18 is input to the PWM circuit 19. The PWM circuit 19
A signal having a pulse width modulated according to the digital signal output of the phase compensation circuit 16 is output. The output cycle is A / D
It is equal to the A / D conversion period of the converter 16. PWM circuit 19
The output signal of is input to the low pass filter 20. The low pass filter 20 converts the pulse width modulation signal of the PWM circuit 19 into an analog signal, and its cutoff frequency flpf is the conversion cycle Tad of the A / D converter 16.
Is set to satisfy fflpf <1 / Tad.

The output terminal of the low pass filter 20 is connected to the switch 21. The switch 21 switches operation / non-operation of tracking control. When the switch 21 is short-circuited, the output signal of the low pass filter 20 is
Via the adder circuit 22, the tracking actuator 11
Added to. Therefore, when the switch 21 is short-circuited, the light beam is controlled so as to be always positioned substantially at the center of the track.

On the other hand, an address reading circuit includes an adder circuit 25 and an address reading circuit 26. The respective output signals corresponding to the two light receiving regions of the two-divided photodetector 12 are also input to the adding circuit 25.
The adder circuit 25 detects and outputs the sum of reflected light amounts from the disk 3. The address reading circuit 26 is an adding circuit 25.
The address provided in each track of the disk 3 is read from the output signal of (1) and the address signal is output to the search circuit 27.

When the address of the target track to be searched is input from an external means (not shown), the search circuit 27 controls the jumping scan repeatedly according to the input from the address read circuit 26 to move to the target track. From the search circuit 27, the jumping scan block 3
5, the jumping command signal S4 is output to the inverting circuit 3
2 to the jumping direction signal S3.

Finally, the configuration of the jumping scanning block 35 will be described. The jumping scan block 35 includes a difference circuit 23, a zero-crossing detection circuit 24, a jumping control circuit 28, an acceleration pulse generation circuit 29, a deceleration pulse generation circuit 30, and a differential circuit 31.

The zero-crossing detection circuit 24 includes the above-mentioned A / D.
The output signal of the converter 16 is input via the difference circuit 23. The zero-crossing detection circuit 24 detects a zero-cross of the input signal, generates a trigger signal S8, and outputs it to the deceleration pulse generation circuit 30.

On the other hand, the jumping control circuit 28 receives the jumping command signal S4 from the search circuit 27 described above. Upon receiving the jumping command signal S4, the jumping control circuit 28 receives various necessary command signals S4.
Is output to execute jumping scanning to a track adjacent to one track, and after completion, a jumping end signal S10 is output to the search circuit 27. The jumping control circuit 28 outputs an acceleration start signal S11 to the acceleration pulse generation circuit 29, a tracking control ON / OFF signal S5 to the switch 21, and a tracking polarity signal S6 to the inverting circuit 17 of the tracking control block 34. .

The acceleration pulse generation circuit 29 outputs the acceleration drive pulse S7 to the non-inverting terminal of the differential circuit 31, and the deceleration pulse generation circuit 30 outputs the deceleration drive pulse S9 to the differential circuit 31.
Output to the inverting terminal of. The output of the differential circuit 31 is input to the tracking actuator 11 via the inverting circuit 32 and the adding circuit 22. Further, the acceleration pulse generation circuit 29 outputs the acceleration end signal S12 to the deceleration pulse generation circuit 30.
The deceleration pulse generation circuit 30 outputs the deceleration end signal S
13 is output to the jumping control circuit 28.

Regarding the track search operation in the tracking search apparatus of the present embodiment having the above-mentioned structure,
Details will be described with reference to the timing chart of FIG.

FIG. 2A is an enlarged plan view of tracks on the disk 3. FIG. 2A shows two groove tracks 2G and a land track 2L sandwiched between the groove tracks 2G. The vertical direction in the figure is the disk radial direction, and the upward direction is the outer circumferential direction in the drawing. Here, during the track search operation in which the jumping scan is repeatedly performed, the light beam 1 indicated by a circle changes to the groove track 2
An example will be given of the case of moving to the land track 2L on the inner circumference side of one track from G by jumping scanning. The trajectory of the light beam 1 in this case is shown by a dotted line in FIG.

2B to 2I are timing charts of signals of respective parts corresponding to respective positions of the locus of the light beam 1 shown in FIG. 2A. 2B is a tracking error signal S1, FIG. 2C is a jumping direction signal S3,
(D) is a jumping command signal S4, (e) is a tracking control ON / OFF signal S5, (f) is a tracking polarity signal S6, (g) is an acceleration drive pulse S7 output from the acceleration pulse generation circuit 29, (h). Is a zero-crossing detection circuit 24
Is output from the deceleration pulse generation circuit 30 as the deceleration drive pulse S9.

Before the jumping scan is started, the tracking control ON / OFF signal S5 given from the jumping control circuit 28 to the switch 21 is as shown in FIG.
As shown in, the switch 21 is at the high level.
Is short-circuited. Therefore, the tracking control is operating. Further, the tracking polarity signal S6 for setting the polarity of the tracking control, which is input from the jumping control circuit 28 to the inverting circuit 17, is at a high level as shown in FIG. 2 (f). At this time, the inverting circuit 17
Performs a forward rotation operation in which the polarity of the light beam 1 is drawn into the groove track 2G by tracking control, for example, the input signal is output without being inverted. Further, the output signals of the acceleration pulse generation circuit 29 and the deceleration pulse generation circuit 30 are each at the zero level, and therefore the output of the differential circuit 31 to which these two signals are input is also at the zero level. At this time, the tracking error signal S1 output from the differential circuit 14 of the tracking control block 34 is at a substantially zero level, and the light beam 1 is always on a certain track 2G.
Alternatively, the address reading circuit 26 is located on 2L without causing a large control error, and each time the light beam 1 passes through the address part, the address reading circuit 26 sets the address of the track 2G or 2L where the light beam 1 is currently located. I am reading.

Prior to the jumping scan, the search circuit 2
The address of the target track is input to 7 by an external instruction means. When the target track address is entered,
The search circuit 27 fetches the address of the track 2G or 2L where the light beam 1 is currently located from the address reading circuit 26, and calculates the number and the direction of repeating the jumping scan. According to the calculated jumping scanning direction, the search circuit 27 sets the jumping direction signal S3 at time TS0, as shown in FIG. In the track search operation toward the inner circumference in this example, the jumping direction signal S3 is set to the low level.

Next, as shown in FIG. 2D, the search circuit 27 sets the jumping command signal S4 to a high level at time TS1 and then immediately sets it to a low level to output a positive pulse. . The jumping control circuit 28 is
When the rising edge of the jumping command signal S4 is detected, a positive pulse is output as the acceleration start signal S11, and at the same time, the tracking control ON / OFF signal S5 is set to a low level at time TS2 as shown in FIG. 2 (e). . As a result, the switch 21 is released and the tracking control is disabled. At the same time, the jumping control circuit 28 sets the tracking polarity signal S6 to low level, as shown in FIG. As a result, the inverting circuit 17 of the tracking control block 34 starts the inverting operation of inverting the polarity of the input and outputting it.

When a positive pulse is input to the acceleration start signal S11 from the jumping control circuit 28, the acceleration pulse generation circuit 29 has an acceleration drive pulse S7 having a predetermined peak value and a predetermined pulse width shown in FIG. 2 (g). Is output. The acceleration drive pulse S7 is applied to the differential circuit 31, the inverting circuit 32, and the adding circuit 2.
2 is input to the tracking actuator 11. The inverting circuit 32 is set to have the same polarity as the input signal when the jumping direction signal S3 is at the low level, and to invert and output when the jumping direction signal S3 is at the high level. As described above, since the jumping direction signal S3 is set to the low level now, the inverting circuit 32 outputs the input signal as a positive drive pulse having the same polarity. Tracking actuator 1
1 is connected so that the movable portion is moved in the inner circumferential direction of the disk at this time, and the light beam 1 is connected to the groove track 2G.
As a result, acceleration and movement are started toward the land track 2L adjacent to the inner peripheral side. When the acceleration pulse generation circuit 29 finishes outputting the predetermined acceleration drive pulse S7 at time TS2, it outputs the acceleration end signal S12 to accelerate the acceleration drive pulse S7.
The deceleration pulse generation circuit 30 is informed that 7 has ended.

As the light beam 1 moves, FIG.
As shown in (b), the tracking error signal S1 increases. At time TS3, the light beam 1 is in the groove track 2
When the midpoint between G and the land track 2L is reached, FIG.
As shown in (h), the zero-crossing detection circuit 24 outputs a positive pulse to the trigger signal S8. This midpoint detection will be described in more detail with reference to the timing chart of FIG.

FIG. 3A shows the tracking error signal S1 output from the differential circuit 14 (the curve indicated by the alternate long and short dash line in the figure) and A / when the jumping scan shown in FIG. 2 is executed.
The digital value of the tracking error signal S1 which is the output signal S2 of the D converter 16 (waveform shown by the solid line in the figure)
2 is a timing chart of. The output signal S2 of the A / D converter 16 has a step-like shape because the A / D converter 16 performs the conversion discretely with the change period Tad. Actually the A / D converter 16
The output signal S2 of the above is, for example, an 8-bit digital value, but the digital value is displayed on the vertical axis to facilitate the explanation.

FIG. 3B shows the output signal S2 of the difference circuit 23.
8 (c) is a trigger signal S8 output from the zero-crossing detection circuit 24. Also in FIG. 3B, the digital value of the output signal S28 of the difference circuit 23 is shown as the vertical axis. The difference circuit 23 calculates the amplitude difference of each sample (time interval Tad) of the tracking error signal S2 output from the A / D converter 16 and outputs it to the zero-crossing detection circuit 24. The zero-crossing detection circuit 24 detects that the light beam 1 has reached the midpoint between the groove track 2G and the land track 2L by detecting that the polarity of the differential signal has changed, and as a trigger signal S8 shown in FIG. The positive pulse shown in () is output to the deceleration pulse generation circuit 30.

On the other hand, the deceleration pulse generation circuit 30 detects the rising edge of the first trigger signal S8 after the end of the acceleration drive pulse S7, and a predetermined crest value and a predetermined pulse as shown in FIG. 2 (i). The width deceleration drive pulse S9 is configured to be output from time TS3. The deceleration drive pulse S9 is inverted by the differential circuit 31, and input to the tracking actuator 11 via the inversion circuit 32 and the addition circuit 22. As a result, the moving speed of the light beam 1 in the inner circumferential direction due to the acceleration drive pulse S7 is reduced.

When the deceleration drive pulse S9 ends at time TS4, the deceleration pulse generation circuit 30 decelerates the end signal S1.
3 is output to the jumping control circuit 28. When the deceleration end signal S13 is input, the jumping control circuit 28 immediately outputs the tracking control ON / OFF signal S5,
The high level is set as shown in FIG. As a result, the switch 21 is short-circuited to restart the tracking control. At this time, the light beam 1 is located on the land track 2L on the substantially inner side of one track, and the polarity of the tracking control is already switched so as to be opposite to that of the groove track 2G. Smoothly pulls in the tracking control to the land track 2L, and the jumping scan of one track is completed.

When the jumping scan of one track is completed, the jumping control circuit 28 outputs a jumping end signal S10 to the search circuit 27. In response to this, the search circuit 27 decrements the number of jumping scan iterations required to reach the target track calculated prior to the search operation by one. The search circuit 27 reaches the target track by repeating the jumping scan of one track described above until the number of repetitions of the jumping scan becomes zero, and ends the search operation.

In this embodiment, the midpoint of the track is detected by A
The tracking error signal S output from the / D converter 16
The difference of 1 is calculated by the difference circuit 23, and the polarity change is detected by the zero crossing detection circuit 24. Generally, the difference calculation can be replaced with a differential calculation to approximate the difference. Also in the 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 S2.

FIG. 4 shows a block diagram of a track search device which employs the midpoint detection by differentiation. 4 is the same in operation and configuration except that the differential circuit 23 of the track search device shown in FIG. The differentiating circuit 63 differentiates the tracking error signal S2 output from the A / D converter 16 and zero-crossing detecting circuit 2
Output to 4.

FIG. 5 shows a timing chart of midpoint detection using the differentiating circuit 63. FIG. 5A shows the tracking error signal S1 output from the differential circuit 14 during jumping scanning, and FIG. 5B shows the output signal S27 from the differential circuit 63.
(C) is a trigger signal S output from the zero-crossing detection circuit 24.
8 The differentiating circuit 63 becomes zero level when the light beam 1 reaches the track midpoint, and at that time, the zero-crossing detecting circuit 24 outputs a positive pulse as the trigger signal S8 to the deceleration pulse generating circuit 30 to detect the midpoint. .

In the above 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 also realized by repeating the jumping scan in the outer circumference direction. . At that time, the search circuit 27 performs the jumping direction signal S prior to the search operation.
Set 3 to high level. As a result, the reversing circuit 32 performs a reversing operation. Therefore, the acceleration driving pulse S7 output from the acceleration pulse generating circuit 29 operates so as to accelerate and move the tracking actuator 11, and thus the light beam 1 in the outer peripheral direction, and the deceleration pulse. The generation circuit 30 operates to slow down its movement. Further, the polarity of the tracking error signal S1 generated as the light beam 1 moves from the groove track 2G to the adjacent land track 2L on the outer peripheral side is opposite to that described with reference to FIGS. The operation of the detection circuit 24 is not influenced by the polarity of the tracking error signal S1 at all, so that the track midpoint is detected in the same manner.

Although the jumping scan from the groove track 2G to the land track 2L has been described here, the land track 2L to the groove track 2 is described.
Also in the jumping scan to G, the polarity of the tracking error signal S1 is opposite to that described in FIGS. 2 and 3, but similarly, the track midpoint is detected and the jumping scan is stably performed.

Further, the present invention is not limited to the above embodiments. For example, when the polarity of the output signal of the difference circuit 23 is inverted and the difference value exceeds a predetermined value, for example, in the case of FIG. 3, when the difference value exceeds a negative value slightly below 0, the togger signal is generated. The zero-crossing detection circuit 24 can be configured to generate S8. In this case, the reliability of track midpoint detection can be further improved. Further, the timing of inverting the polarity of the tracking control by the inverting circuit 17 is not limited to the timing of the above embodiment, but may be inverted during the period in which the tracking control is inoperative during jumping scanning. For example, it may be performed at the same time when the deceleration drive pulse S9 ends and the tracking control is operated. Further, since the coil of the tracking actuator 11 has a low pass filter characteristic, the low pass filter 20 can be omitted. Further, the inverting circuit 17 and the phase compensation circuit 1
8, the PWM circuit 19, the low-pass filter 20, the difference circuit 23, and the zero-crossing detection circuit 24 do not need to be configured by hardware. For example, a digital signal processor (DS)
If P) or the like is used, it can be realized by software-like processing.

(Embodiment 2) FIG. 6 is a block diagram of a track search apparatus which is Embodiment 2 embodying the jumping scanning method of the present invention. In the description of the second embodiment, the same components as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted. The disk used in this example is exactly the same as the disk used in Example 1.

The track search apparatus of this example is a combination of the track search apparatus shown in FIG. 1 and a conventional jumping scan for moving from groove track to groove track. By configuring in this way, L / G
The time required for the search operation on the disk can be significantly shortened as compared with the first embodiment.

As shown in FIG. 6, the track search device is roughly divided into four blocks. Among these four blocks, a disk / head block 33 composed of the disk 3, the optical head unit 9, the transfer motor 13 and the like, a tracking control block 34 composed of a circuit for tracking control and a circuit for address reading. , And the jumping scanning block 35 for performing the jumping scanning of one track are all the same in configuration and operation as in FIG. Example 2
Then, a 2-track jumping scanning block 36 for performing jumping scanning from groove tracks to groove tracks or from land tracks to land tracks.
Is newly established.

2-track jumping scan block 36
2 track jumping control circuit 39, acceleration pulse generation circuit 41, deceleration pulse generation circuit 42, differential circuit 4
3 and a zero-crossing detection circuit 45.

2-track jumping scan block 36
Accordingly, the search circuit 27 is replaced by the search circuit 37 of the first embodiment, and the search circuit 37 is replaced by the addition circuit 22 of the first embodiment.
An input adder circuit 38 is provided. The search circuit 37 has a structure and function for controlling the two-track jumping scan block 36 in addition to the structure and function of the search circuit 27 of the first embodiment. Specifically, in addition to the jumping command signal S4 to the jumping control circuit 28, which is a signal to the jumping scanning block 35, and the jumping direction signal S3 to the inverting circuit 32 from the search circuit 37, two-track jumping scanning is performed. A 2-track jumping start signal S14 to the 2-track jumping control circuit 36 and a jumping direction signal S3 to the inverting circuit 44, which are signals to the block 35, are output. Further, to the search circuit 37, in addition to the jumping end signal S10 from the jumping control circuit 28, the 2-track jumping end signal S19 is input from the 2-track jumping control circuit 39.

The two-track jumping control circuit 39 is
2 track jumping command signal S1 from search circuit 37
When 4 is received, various necessary command signals are output to perform jumping scan to the tracks separated by 2 tracks,
After completion, the 2-track jumping end signal S19 is output to the search circuit 37. 2 Track jumping control circuit 3
From 9, the acceleration start signal S20 is the acceleration pulse generation circuit 4
1, the tracking control ON / OFF signal S15 is output to the AND gate 40.

On the other hand, A of the tracking control block 34
The output signal S2 of the / D converter 16 is the zero crossing detection circuit 45.
Is also entered. The zero-crossing detection circuit 45 has its input signal S
The zero crossing of 2 is detected and the trigger signal S17 is output to the deceleration pulse generation circuit 42. Deceleration pulse generation circuit 42
Outputs the deceleration drive pulse S18 to the inversion terminal of the differential circuit 43, and the acceleration pulse generation circuit 41 outputs the acceleration drive pulse S16.
Is output to the non-inverting terminal of the differential circuit 43. Differential circuit 43
Then, the difference between the deceleration driving pulse S18 and the acceleration driving pulse S16 is calculated and input to the tracking actuator 11 via the inversion circuit 44 and the 3-input addition circuit 38. Thereby, the light beam 1 can be driven in the disk radial direction.

Further, the acceleration pulse generation circuit 41 outputs the acceleration end signal S21 to the deceleration pulse generation circuit 42, and the deceleration pulse generation circuit 42 outputs the deceleration end signal S22 to the two-track jumping control circuit 39. AND gate 40
The tracking control ON / OFF signal S5 from the jumping control circuit 28 is also input to the tracking control ON / OFF signal from the 2-track jumping control circuit 36.
The logical product with the OFF signal S15 is calculated and input to the switch 21 in the tracking control block 34. Three
The input addition circuit 38 further receives the jumping drive pulse from the jumping scanning block 35 and the inversion 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 11. Similar to the inverting circuit 32, the jumping direction signal S3 is input to the inverting circuit 44 from the search circuit 37 as its control signal.

The track search operation in the track search apparatus of this embodiment having the above configuration will be described.

Prior to the jumping scan, the search circuit 3
The address of the target track is input to 7 by an external instruction means. When the target track address is entered,
The search circuit 37 fetches the address of the track where the light beam 1 is currently located from the address reading circuit 26, and calculates the number N of tracks to be traversed and the direction. The search circuit 37 sets the jumping direction signal S3 according to the calculated jumping scanning direction. Assuming that the track search operation toward the inner circumference is now performed, the jumping direction signal S3 is set to the low level. Search circuit 37
Achieves N track movements by first performing N1 two-track jumping scans and then performing N2 jumping scans. Here, when N = even, N1 = N / 2 N2 = 0 N = when odd, N1 = (N −
1) / 2 N2 = 1.

Among them, the jumping scanning executed N2 times is the same as that in the first embodiment, and therefore its explanation is omitted. The operation of the 2-track jump that repeats N1 times will be described in detail with reference to the timing chart of FIG.

FIG. 7A is an enlarged plan view of tracks on the disk 3. FIG. 7A shows two groove tracks 2G and a land track 2L sandwiched between the groove tracks 2G. The vertical direction in the figure is the disk radial direction, and the upward direction is the outer circumferential direction in the drawing. Here, during the track search operation in which the jumping scan is repeatedly performed, the light beam 1 indicated by a circle changes to the groove track 2
2 in the groove track 2G on the inner circumference side of 2 tracks from G
An example will be given of the case of moving by track jumping scanning. The trajectory of the light beam 1 in this case is shown by a dotted line in FIG.

7B to 7I are timing charts of signals of respective parts corresponding to respective positions of the locus of the light beam 1 shown in FIG. 7A. 7B is a tracking error signal S1, FIG. 7C is a jumping direction signal S3,
(D) is a 2-track jumping command signal S14,
(E) is the tracking control ON / OFF signal S15 output from the two-track jumping control circuit 36, (f) is the tracking polarity signal S6 output from the jumping control circuit 36, and (g) is the acceleration output from the acceleration pulse generation circuit 41. The drive pulse S16, (h) is the trigger signal S17 output by the zero-crossing detection circuit 45, and (i) is the deceleration drive pulse S18 output by the deceleration pulse generation circuit 42.

Before the two-track jumping scan, the tracking control O output from the jumping control circuit 28 is output.
Both the N / OFF signal S5 and the tracking control ON / OFF signal S15 output from the 2-track jumping control circuit 39 are at high level. Therefore, both signals S5
The output of the AND gate 40 to which S15 and S15 are input is at a high level, the switch 21 is short-circuited, and the tracking control is operating. In the jumping scanning block 35, the tracking polarity signal S6 input from the jumping control circuit 28 to the inverting circuit 17 is at high level. At this time, the inverting circuit 17 performs the normal rotation operation of outputting the input signal without inverting the polarity of drawing the light beam 1 into the groove track 2G by tracking control. Further, the acceleration pulse generation circuits 29, 41,
The output signals of the deceleration pulse generation circuits 30 and 42 are zero level, and the output signals of the differential circuits 31 and 43 are also zero level. At this time, the tracking error signal S1 output from the differential circuit 14 is at a substantially zero level, and the light beam 1 is always positioned on a certain track without causing a large control error.

As shown in FIG. 7D, the search circuit 37 causes the two-track jumping command signal S1 at time TS6.
After setting 4 to the high level, the low level is immediately set again to output a positive pulse. The 2-track jumping control circuit 36 has a 2-track jumping command signal S.
When the rising edge of 14 is detected, the acceleration start signal S
At the same time as outputting a positive pulse to 20, the tracking control is turned on / off at time TS7 as shown in FIG. 7 (e).
The signal S15 is set to the low level. As a result, the output of the AND gate 40 becomes low level, and the switch 21
Is released and tracking control becomes inoperative.

When a positive pulse is input to the acceleration start signal S20 from the 2-track jumping control circuit 39, the acceleration pulse generation circuit 29 accelerates the predetermined peak value and predetermined pulse width shown in FIG. 7 (g). The pulse S16 is output. The acceleration drive pulse S7 is applied to the differential circuit 43 and the inverting circuit 4
It is input to the tracking actuator 11 via the 4- and 3-input addition circuit 38. The inverting circuit 44 is set to have the same polarity as the input signal when the jumping direction signal S3 is at the low level, and to invert and output when the signal is at the high level. As described above, the jumping direction signal S3
Is set to the low level now, the inverting circuit 44 outputs a positive drive pulse having the same polarity as the input signal. At this time, the tracking actuator 11 is connected so as to move the movable portion in the inner circumferential direction of the disc, and
Starts accelerating and moving inward from the groove track 2G. When the acceleration pulse generation circuit 41 finishes outputting the predetermined acceleration drive pulse S16 at time TS7, it outputs the acceleration end signal S21 to inform the deceleration pulse generation circuit 42 that the acceleration drive pulse S16 has finished. .

As the light beam 1 moves, FIG.
As shown in (b), the tracking error signal S1 increases. At time TS8, light beam 1 is land track 2L
When the tracking error signal S1 reaches, the tracking error signal S1 becomes zero level, and the polarity is eventually inverted. Zero-crossing detection circuit 45
Detects the zero crossing of the tracking error signal S1,
As shown in FIG. 7H, a positive pulse is output to the deceleration pulse generation circuit 30 as the trigger signal S17.

On the other hand, the deceleration pulse generation circuit 42 detects the rising edge of the first trigger signal S17 after the end of the acceleration drive pulse S16, and the predetermined peak value and the predetermined pulse width shown in FIG. It is configured to output the deceleration driving pulse S18. That is, in the time chart shown in FIG. 7, the deceleration drive pulse S18 is output from time TS8. The deceleration drive pulse S18 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 1 toward the inner circumference by the acceleration drive pulse S16 is reduced.

When the deceleration drive pulse S18 ends at time TS9, the deceleration pulse generation circuit 42 decelerates the end signal S.
22 is output to the 2-track jumping control circuit 39. The 2-track jumping control circuit 39 immediately receives the tracking control O when the deceleration end signal S22 is input.
The N / OFF signal S15 is set to a high level as shown in FIG. As a result, the switch 21 is short-circuited to operate the tracking control. Light beam 1 at this time
Is located on the groove track 2G on the inner circumference side of approximately two tracks, and the polarity of the tracking control is the same as before the start of the two-track jumping scanning, so the light beam 1 is smoothly drawn into the groove track 2G. Then, the jumping scanning of the two tracks is completed.

When the two-track jumping scan is completed, the two-track jumping control circuit 39 outputs a jumping end signal S19 to the search circuit 37. In response to this, the search circuit 37 decrements by one the number of repetitions N1 of the two-track jumping scan required to reach the target track calculated prior to the search operation. The search circuit 37 repeats the above-mentioned 2 until the number N1 of jumping scanning iterations becomes zero.
Repeat the jumping scan of the track. After that, as described in the first embodiment, the jumping scanning of one track is performed N2 times to reach the target track,
The search operation ends.

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 the track jumping scan and the one track jumping scan. At that time, the search circuit 37 performs the jumping direction signal S prior to the search operation.
Set 3 to high level. As a result, the inverting circuit 32,
44 performs a reversing operation, whereby a search operation toward the outer circumference can be realized.

(Embodiment 3) FIG. 8 shows a sample servo format disk (hereinafter referred to as S
FIG. 7 is a block diagram of a track search device that obtains the same effect as that of the above-described embodiment in an S disc). Before describing the configuration of the track search device in FIG. 8, 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. FIG. 9A is a plan view of the SS disc. Disk 46
For example, a track having alternating servo regions 47 and information regions 48 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 vapor-deposited on the track. And the like. 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 where information is recorded or where information is recorded. The servo area 47 and the information area 48 are the disk 46.
A plurality of, for example, about 1500, are provided at equal intervals in the circumferential direction and aligned in the radial direction per one round. Therefore, the servo area 47 and the information area 48 are formed so as to radially spread from the disk center of the disk 46 as shown in the drawing.

FIG. 9B is an enlarged plan view of the disk 46. In the servo area 47, the clock mark 49, the first
A wobble mark 50 and a second wobble mark 51 are provided. The clock mark 49 for synchronization is the track 62a.
The first wobble mark 50 and the second wobble mark 51, which are located on the upper side of the disk 62, are located before and after the clock mark 49 in the longitudinal direction of the track. The first wobble mark 50 and the second wobble mark 51 are separated by the track 62.
They are opposite to each other in the radial direction of the disk 46 with respect to a to 62d and are located in the middle of the tracks. For example, as shown in the drawing, the tracks 62a that are continuously adjacent to each other are shown.
The first wobble mark 50 of the middle track 62b and the first wobble mark 50 of the track 62c are shared, and the second wobble mark 51 of the track 62b and the second wobble mark 51 of the track 62a are shared.
It is shared with. Therefore, for example, if the peak level of the reproduction signal of the first wobble mark 50 and the second wobble mark 51 is detected and the tracking error signal is obtained from the difference between the two peak levels, the tracking error between the track 62a and the track 62b. The polarities of the signals are opposite. That is, the polarities of tracking control are alternately opposite for each track. Such a format of the disk 46 is called an inversion wobble method, and a method of detecting a tracking error signal and its characteristics are known, and therefore a detailed description thereof will be omitted. For example, US patent U
It is described in SP5012460.

FIG. 10 conceptually shows the format on the disk 46 of FIG. 9, and is a drawing for explaining how data is arranged. Figure 10
As shown in (a), servo areas 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 form one block. As shown in FIG. 10B, one sector is composed of (n + 1) blocks, and the information area 48 of the first block of the sector has an address (for example, a track number and a sector number) for identifying the sector. Is recorded in the address area. Data is recorded in the information area 48 of the n blocks following it. Further, as shown in FIG. 10C, 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 configuration of the track search device using the above-mentioned SS disc will be described with reference to FIG. 8, the structure and operation of the disk / head block 33 including the optical head unit 9 and the like are shown in FIG.
Since it is the same as the above, its explanation is omitted. However, the disk 46 of the sample servo format is used.

The outputs of the two-division photodetector 12 of the disk / head block 33 are added by the adder circuit 25 to calculate the sum of the amount of reflected light from the disk 46, and the PLL circuit 52 and peak hold circuit (hereinafter referred to as PH circuit). ) 53, 5
4, input to the address reading circuit 26. The PLL circuit 52 compares the phase of the signal from the in-circuit oscillator with the reproduction signal of the clock mark 49 in the servo area 47 detected by the two-division photodetector 12, and the phase difference between the two signals has a predetermined relationship. Control to be. 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. This positional deviation signal is transmitted to the pair of wobble marks 5 in the servo area 47 on the disk 46.
Since it is detected from 0 and 51, when the disk 46 is rotated at a constant rotation speed, it is discretely output at every predetermined cycle.

The S & H circuit 56 samples and holds a discrete position deviation signal each time it is output from the differential circuit 57, and outputs a stepwise tracking error signal S23. The tracking error signal S23 includes an inverting circuit 17 for inverting the polarity of tracking control, a phase compensating circuit 18 for obtaining the control stability of the tracking control system, a switch 21 for opening and closing the tracking control loop, and an adding circuit. It is added to the tracking actuator 11 via 22. 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 27, jumping control circuit 2
8, acceleration pulse generation circuit 29, deceleration pulse generation circuit 3
0, the differential circuit 31, and the inverting circuit 32 have the same configurations and operations as those of the first embodiment shown in FIG.

In this example, the tracking error signal S23 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. S & H circuit 59
Is a circuit for sampling and holding the input signal according to the timing signal from the timing circuit 55. The output of the S & H circuit 59 is input to the zero crossing detection circuit 60. The zero crossing detection circuit 60 detects the zero crossing of the input signal and outputs the trigger signal S24 to the deceleration pulse generation circuit 30.

Next, the track search operation of this embodiment will be described in detail with reference to the timing chart of FIG. FIG. 11 is a timing chart of the jumping scan in the inner circumference direction of one track during the search operation in which the jumping scan is repeated.

FIG. 11A is an enlarged plan view of two adjacent tracks 61a and 61b on the disk 46.
The vertical direction in the figure is the disk radial direction, and the upward direction is the outer circumferential direction in the drawing. Here, the case of moving from the track 62a to the track 62b by jumping scanning is taken as an example. The trajectory of the light beam 1 in this case is shown in FIG.
It is indicated by a dotted line in (a).

11 (b) to 11 (i) are shown in FIG. 11 (a).
3 is a timing chart of signals of respective parts corresponding to respective positions of the trajectory of the light beam 1 shown in FIG. FIG. 11B shows the tracking error signal S23, and FIG. 11C shows the jumping direction signal S.
3, (d) is a jumping command signal S4, (e) is a tracking control ON / OFF signal S5, (f) is a tracking polarity signal S6, (g) is an acceleration drive pulse S7 output from the acceleration pulse generation circuit 29, ( h) is a trigger signal S24 output from the zero-crossing detection circuit 24 for detecting the midpoint,
(I) is the deceleration drive pulse S9 output from the deceleration pulse generation circuit 30.

Since the jumping scanning procedure is the same as that of the first embodiment except for the detection of the middle point, only the timing chart is shown in FIG. 11 and the description thereof is omitted.

FIG. 12 is a timing chart for explaining the midpoint detection during the jumping scan. 12
(A) is the output signal S23 of the S & H circuit 56, (b) is the output signal S25 of the differentiation circuit 58, and (c) is the S & H circuit 59.
Output signals S26 and (d) are output signals S24 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 disc, the track deviation information is discretely detected from the servo area 47 which is provided about 1500 times per revolution of the disc 46, and therefore the tracking error signal S23 output from the S & H circuit 56 is as shown in FIG.
As shown in FIG. 2 (a), it has a stepwise waveform. Therefore, S
Differentiating circuit 58 that differentiates the output signal S23 of the & H circuit 56.
The output waveform of is a triangular wave signal S25 as shown in FIG. The S & H circuit 59 peak-holds each peak level of the sawtooth signal S25 of the differentiating circuit 58, that is, the maximum value when the triangular wave signal S25 has a positive value, and the minimum value when the signal has a negative value. The stepwise signal S26 shown in c) is output. The zero-crossing detection circuit 60 is S & H.
The change in the polarity of the output signal S26 of the circuit 59 is detected to detect that the light beam 1 has reached the midpoint of the tracks 62a and 62b, and the trigger signal S24 is shown in FIG.
The positive pulse shown in (d) is output to the deceleration pulse generation circuit 30, and the midpoint detection ends. Thereafter, as in the first embodiment,
In response to the trigger signal S24 shown in FIG. 11 (h), the procedure after the output of the deceleration drive pulse S9 shown in FIG. 11 (i) is executed, and the jumping scan ends.

When the jumping scanning is completed, the jumping control circuit 28 outputs a jumping end signal S10 to the search circuit 27. In response to this, the search circuit 27 decrements the number of jumping scan iterations required to reach the target track calculated prior to the search operation by one. The search circuit 27 repeats the jumping scan described above until the number of repetitions of the jumping scan reaches zero, reaches the target track, and ends the search operation.

In the above-described embodiment, the search operation for the inner circumference is repeated by repeating the jumping scan for the inner circumference. However, the search operation for the outer circumference is also realized by repeating the jumping scan for the outer circumference. . At that time, the search circuit 27 performs the jumping direction signal S prior to the search operation.
Set 3 to high level. As a result, the inverting circuit 32 performs the inverting operation, and thus the search operation toward the outer circumference can be realized.

Further, the track midpoint detecting method forming a part of the jumping scanning method of the present invention has various other uses in the L / G disk or the SS disk of the inverted wobble format. The following is one of its application examples.
I will explain one.

This midpoint detection method can be applied to a speed detector used in a track search device which searches for a long stroke track. The long-stroke track search refers to a search operation to a track far away, which is executed by, for example, transferring the entire optical head unit 9 shown in FIG. For more information on such long stroke track searches, see US Pat.
It is described in documents such as P4106058.

In the long stroke track search, speed control is performed to control the speed of the light beam being transferred. This ensures the pulling of the tracking control to the target track, which is generally performed at the final stage of the track search operation. The speed of the light beam required for speed control is generally detected by measuring the cycle of the light beam crossing the track or the cycle of the light beam crossing the midpoint between the tracks. Details are described in documents such as US Pat. No. 5,146,440. Therefore, a velocity detector for track search on an L / G disc or an SS disc of inverted wobble format can be constructed using the track midpoint detection method of the present invention.

[0110]

As is apparent from the above description, according to the midpoint detection method of the present invention, the light beam is moved to the target track at a high speed in a high density disc such as an L / G disc and an SS disc. A jumping scanning method can be realized.

[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] Timing chart of track search operation

FIG. 3 is a timing chart of midpoint detection

FIG. 4 is a block diagram of a track search device that employs midpoint detection by differentiation.

FIG. 5 is a timing chart of midpoint detection using a differentiating circuit.

FIG. 6 is a configuration diagram of a track search device according to a second embodiment of the present invention.

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

FIG. 8 is a configuration diagram of a track search device according to a third embodiment.

FIG. 9 is a plan view of an SS disc.

FIG. 10 is a diagram showing the format of an SS disc.

FIG. 11 is a timing chart of jumping scanning.

FIG. 12 is a timing chart of midpoint detection.

FIG. 13 is a timing chart of conventional jumping scanning.

FIG. 14 is a diagram showing a relationship between a positional relationship between a light beam and a track and a tracking error signal.

FIG. 15 is an external view of one spiral L / G disc.

FIG. 16 is an enlarged external view of an L / G disc.

FIG. 17 is an external view of a two-spiral L / G disc.

FIG. 18 is a diagram showing a tracking error signal of an L / G disc.

[Explanation of symbols]

 1 Optical Beam 3 Optical Disc 9 Optical Head 17 Inversion Circuit 23 Difference Circuit 24 Zero Crossing Detection Circuit 27 Search Circuit 28 Jumping Control Circuit 29 Acceleration Pulse Generation Circuit 30 Deceleration Pulse Generation Circuit 32 Inversion Circuit 33 Disk / Head Block 34 Tracking Control Block 35 Jumping scan block 36 2-track jumping scan block

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshiyuki Kino 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (11)

[Claims] 1. A method for detecting a midpoint between adjacent tracks of a recording medium having tracks in which the polarities of tracking control are alternately inverted, the method comprising irradiating a light beam onto the recording medium, A step of detecting a positional deviation between the light beam and the track from either the reflected light or the transmitted light from the recording medium, and generating a positional deviation signal corresponding to the positional deviation; and a step of differentiating the positional deviation signal. A step of generating a midpoint signal corresponding to the differential signal that has been calculated, and a step of detecting that the light beam has reached the midpoint between the adjacent tracks by detecting a change in polarity of the midpoint signal. A midpoint detection method including and. 2. The step of generating the midpoint signal includes the step of converting the displacement signal into a digital signal,
2. The midpoint detection method according to claim 1, further comprising the step of generating a difference signal obtained by calculating a difference between the position shift signals converted into the digital signal as the midpoint signal. 3. The midpoint detection method according to claim 1, wherein in the step of generating the midpoint signal, the differential signal is generated as the midpoint signal. 4. An apparatus for performing at least one of recording and reproduction of information on a recording medium having a track in which the polarity of tracking control is alternately inverted, while performing tracking control so that a light beam is positioned on the track. ,
A track search method for positioning the light beam on a target track, the method comprising: moving the light beam toward an adjacent track after disabling the tracking control; and the position of the light beam and the track. A step of detecting a shift and generating a position shift signal corresponding to the position shift; a step of generating a midpoint signal corresponding to a differential signal obtained by calculating a differential of the position shift signal; and a polarity change of the midpoint signal The step of 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 after the deceleration pulse ends, Re-operating the tracking control to move the light beam to the target track. 5. The step of generating the midpoint signal includes the step of converting the displacement signal into a digital signal.
5. The track search method according to claim 4, further comprising a step of generating a difference signal obtained by calculating a difference between the position shift signals converted to the digital signal as the midpoint signal. 6. The track search method according to claim 4, wherein in the step of generating the midpoint signal, the differential signal is generated as the midpoint signal. 7. The recording medium has a plurality of pairs of wobble marks, each of which is discretely arranged for detecting a track deviation, and the direction of deviation of the pair of wobble marks is one pair of adjacent tracks. In the step of generating the position shift signal, the position shift signal is a discrete servo reproduced from the plurality of pairs of wobble marks. Generated as a signal, the step of detecting the midpoint signal, the step of calculating the differential of the displacement signal, and the respective peak value of the triangular wave signal corresponding to the discrete displacement signal obtained by the differentiation 5. The track search method according to claim 4, further comprising the step of sample-holding to obtain a midpoint signal. 8. A device for performing at least one of recording and reproducing of information on a recording medium having a track in which the polarity of tracking control is alternately inverted, and detecting a positional deviation between a light beam and the track. A position deviation signal generating means for generating a position deviation signal corresponding to the position deviation, a tracking control means for performing tracking control so that the light beam is positioned on the track, and an operation / non-operation of the tracking control. A switch means for switching, an accelerating means for moving the light beam toward an adjacent track after the tracking control is disabled by the switch means, and a differential signal obtained by calculating a differential of the position displacement signal. A midpoint detecting means for generating a midpoint signal, and a deceleration pattern for decelerating the movement of the light beam based on a change in polarity of the midpoint signal. And a polarity reversing means for inverting the polarity of the tracking control until the deceleration pulse ends, and a signal for reactivating the tracking control after the deceleration pulse ends. A device including means for providing a switch means. 9. The midpoint detecting means generates a difference signal, which is a means for converting the positional deviation signal into a digital signal and a difference between the positional deviation signals converted into the digital signals, as the midpoint signal. 9. The apparatus according to claim 8, further comprising: 10. The apparatus according to claim 8, wherein the midpoint detecting means is a differentiating means for generating the differential signal as the midpoint signal. 11. The recording medium has a plurality of pairs of wobble marks for detecting track deviation, each of which is discretely arranged, and a pair of wobble marks has a deviation direction of one pair of adjacent tracks. Is a sample servo type optical disc that is opposite to the direction of the wobble mark deviation, and the position deviation signal generating means generates the position deviation signal,
Generating as a discrete signal reproduced from the plurality of pairs of wobble marks, the midpoint detecting means calculates a differential of the positional deviation signal, and the discrete positional deviation obtained by the differentiating means. 9. The apparatus according to claim 8, further comprising sample and hold means for sampling and holding each peak value of the triangular wave signal corresponding to the signal to obtain a midpoint signal.