JPH0562218A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce power consumption and to shorten an access time in the case of a zone access making access to a target track within the movable range of a light beam by a precise actuator. CONSTITUTION:A switch 5 is turned to (a) side, the switch 6 to (d) side and the switch 9 to (e) side respectively, the precise actuator 1 is controlled sufficiently by a jump pulse JP and a light spot is moved to the target track at a high speed. Then, the switch 5 is changed over to (b) side, the precise actuator 1 is driven by a holding current Ih and the light spot is held to the target track position. The amplitude of the holding current Ih is reduced gradually, simultaneously, a tracking error signal TE is outputted from a tracking error detecting circuit 3 and supplied to a rough actuator 2 through an LPF 7, etc. Thus, an optical head is moved to the target track at a low speed and the light spot is held to the target track position as it is.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus suitable for a magneto-optical disk, a write-once optical disk, etc., and more particularly to track access by a two-stage servo of a coarse actuator and a precision actuator.

[0002]

2. Description of the Related Art In this kind of optical information recording / reproducing apparatus, highly accurate tracking is possible over a wide track area on a recordable / reproducible optical disk (hereinafter referred to as an optical disk) such as a magneto-optical disk or a write-once optical disk. For this purpose, a coarse actuator that moves the carriage carrying the optical head in the radial direction of the optical disk and a precision actuator that moves the objective lens for focusing the light beam on the optical head onto the optical disk are provided.

FIG. 5 is a perspective view showing the structure of an example of such an optical information recording / reproducing apparatus, for example, a magnetic disk 20.
A carriage 23 on which an optical head 24 is mounted is provided below the carriage 23. The carriage 23 can be moved along the guide rod 22 in the radial direction of the magneto-optical disk 20 by a linear motor 21 which is a coarse actuator. Further, the optical head 24 mounted on the carriage 23 has a precision actuator, which allows the objective lens to move. The electromagnet 25 gives a bias magnetic field to the magneto-optical disk 20 during recording.

FIG. 6 is a perspective view showing an example of the optical head 24 mounted on the carriage 23 of FIG. 5, in which a shaft 26 perpendicular to the surface of the magneto-optical disk 20 (FIG. 5) is provided with a spring 2.
7, focusing coil 28, tracking coil 2
9 is attached, and the objective lens 30 is provided on the spring 27. The spring 27 and the tracking coil 29 constitute the above-mentioned precision actuator, and when a drive current is passed through the tracking coil 29, the spring 27 is deformed and the optical axis of the objective lens 30 is tilted with respect to the shaft 26. As a result, the spot of the light beam that has passed through the objective lens 30 on the magneto-optical disk 20 is displaced in the track width direction, and tracking control is performed. When a drive current is passed through the focusing coil 28, the objective lens 30 is displaced along the shaft 26 due to the deformation of the spring 27, and focusing control is performed on the magneto-optical disk 20.

Conventionally, coarse actuators are used to access the target track and fine actuators are used to track on the desired track.

[0006]

Such an optical information recording / reproducing apparatus has a very large recording capacity as compared with a fixed magnetic head recording / reproducing apparatus, but on the other hand, it consumes a large amount of power even when a target access is made at a short distance. There is a problem that the access time (data search time) is long. The main reasons are: (1) The optical head weighs more than an order of magnitude compared to the magnetic head, and very large electric power is required to move the optical head (to operate the coarse actuator). ..

(2) The track pitch of the optical disk is about one digit narrower than that of the fixed magnetic head, and the track deviation due to the eccentricity of the optical disk is large in order to convert the optical disk in the optical information recording / reproducing apparatus. , It is very difficult to position accurately on the target track.

(3) In the coarse actuator, an acceleration pulse is supplied until it moves half the set moving distance, and then a deceleration pulse having a characteristic opposite to that of the acceleration pulse is supplied until a desired track is reached. Although control is performed, the deceleration pulse may be too strong to reach the target track.

An object of the present invention is to solve the above problems and to provide an optical information recording / reproducing apparatus capable of significantly reducing the power consumption and the access time when accessing a target track at a short distance. To provide.

[0010]

In an optical information recording / reproducing apparatus having a precision actuator and a coarse actuator, when the objective lens is moved by the precision actuator, the light spot moves over a considerable number of tracks. The present invention has been made in view of the fact that the target track can be accessed mainly by the precision actuator when the target track is within the movable range of the light spot by the precision actuator.

Therefore, in order to achieve the above object, the present invention provides high-speed access to a target track by a precision actuator when the target track for access is within a movable range of a light spot by the precision actuator. The coarse actuator moves the optical head at a low speed in the direction of the target track, and after the high speed access is completed, the optical head is set at a position facing the target track.

Further, in the present invention, the high speed access is performed by bang-bang control of the precision actuator, and the ratio of the pulse widths of the acceleration pulse and the deceleration pulse is changed according to the number of moving tracks by the high speed access.

Further, according to the present invention, after the high speed access is completed, a holding signal corresponding to the number of tracks moved by the high speed access is given to the precision actuator, and the holding signal is changed with the movement of the optical head.

[0014]

When the target track is accessed, the access operation is completed by moving the optical head to the position facing the target track by the coarse actuator regardless of the position of the current position of the light spot.

However, according to the present invention, when the target track within the possible movement range of the light spot by the precision actuator is accessed (hereinafter referred to as zone access), the precision actuator provides high-speed access to the target track. At the same time, the coarse actuator moves the optical head at a low speed in the direction of the target track. Since the weight of the moving part by the precision actuator is smaller than the weight of the moving part by the coarse actuator by one digit or more, the access by the precision actuator consumes less power than the access by the coarse actuator, and the rise is steep and can be performed at high speed. The optical head is finally set to a position facing the target track by the coarse actuator, and the optical head is moved at a low speed by the coarse actuator until the position is set. This is much smaller than when moving the optical head at high speed. Further, it takes a long time for the optical head to be positioned as described above, but during this period, the target track is accessed by the precision actuator.
Therefore, low power consumption and short access time are realized at the same time.

When the precision actuator is bang-bang controlled by an acceleration pulse and a deceleration pulse having a constant pulse width ratio, the light spot may not reach the target track or may exceed the target track depending on the number of moving tracks. Therefore, in the present invention, by setting the pulse width ratio of the acceleration pulse and the deceleration pulse according to the number of moving tracks, the light spot can be surely located on the target track regardless of the number of moving tracks. I have to.

When the light spot reaches the target track by the access by the precision actuator, a holding signal is applied to the precision actuator, which holds the light spot on the target track in a tracking controllable state. Therefore, even when the optical head is moving toward the target track by the coarse actuator, the light spot is kept in a good tracking state on the target track. It becomes possible to record / reproduce the data.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a block diagram showing an embodiment of an optical information recording / reproducing apparatus according to the present invention, in which 1 is a precision actuator, 2 is a coarse actuator, 3 is a tracking error detecting means, 4 is a phase compensation circuit, and 5 and 6 are. Switch, 7 is LP
F (low-pass filter), 8 is a phase compensation circuit, 9 is a switch, 10 and 11 are drive circuits, 12 is a binarization circuit, 13
Is a cross track counter, 14 is a speed control circuit, 15
Is a speed detection circuit, 19 is an LPF, and 17 is a phase compensation circuit.

In the figure, in the case of zone access for accessing the target track within the movable range of the light spot by the precision actuator 1, the switch 6 is closed on the d side and the switch 9 is closed on the e side. In this zone access, the precision actuator 1 is subjected to so-called bang-bang control by the acceleration pulse and the deceleration pulse. Therefore, the switch 5 is closed to the side a, and the jump pulse JP including the acceleration pulse and the deceleration pulse is input. To be done.

Next, the zone access will be described. When the target track to be accessed is set and it is determined that this target track is the target of zone access, first, the switch 5 is on the a side, the switch 6 is on the d side,
The switches 9 close to the e side, respectively. Then, a jump pulse JP is supplied from the control unit such as a microcomputer (not shown) to the drive circuit 10 via the switch 5, and the bang-bang control of the precision actuator 1 is performed. As a result, the objective lens of the optical head moves, and the light spot moves toward the target track at high speed in the radial direction of the optical disc. In this bang-bang control, the light spot is accelerated by the acceleration pulse of the jump pulse JP and then decelerated by the deceleration pulse to reach the target track.

In FIG. 2A, the horizontal axis represents time and the vertical axis represents the amount of movement to the target track, and the curve A shows the amount of movement by the precision actuator. As is clear from the curve A, the target track represented by the numerical values 1 and 0 is
It will be reached in a short time until time t1.

In FIG. 1, this jump pulse JP
Is also supplied to the drive circuit 11 via the switch 9 as a signal which passes through the switch 6, is integrated twice by the LPF 7 and the phase compensation circuit 8, and then changes into a very gentle slope. As a result, the coarse actuator 2 moves the optical head at a low speed in the direction of the target track. The curve B in FIG. 2A shows the amount of movement by the coarse actuator.
This amount of movement is very small.

On the other hand, the tracking error detection circuit 3 detects a tracking error from the reflected beam from the optical disc and outputs a tracking error signal TE. In this case, since the light spot sequentially traverses the tracks on the optical disk at high speed by the access operation, as shown in FIG. 2B, the amplitude changes with the movement time of the track pitch as the period of the track pitch.

The tracking error signal TE is binarized by the binarization circuit 12 and supplied to the cross track counter 13. As described above, the tracking error signal TE is a signal whose period is the time required to move the light spot by the track pitch. Therefore, the output signal of the binarization circuit 12 is also the same, and the cross track counter 13 outputs 2 bits. By counting the rising or falling edges of the output signal of the binarization circuit 12, the number of tracks where the light spot has crossed is detected.

The count value of the cross-track counter 13 is supplied to a control unit (not shown), and the control unit switches from the count value to the acceleration pulse and the deceleration pulse with the jump pulse JP according to the number of tracks up to the target track. Set the timing. Here, if the pulse width ratio of the acceleration pulse and the deceleration pulse is constant, depending on the number of tracks (necessary number of moving tracks) that must be moved from the current track before access to the target track in the bang-bang control of the precision actuator. , The light spot does not reach the target track, or it exceeds the target track. In order to prevent this, the pulse ratio of the acceleration pulse and the deceleration pulse that ensures that the light spot can be reliably tracking-controlled on the target track for each required number of moving tracks is obtained by experiments, etc. Stored in. And the precision actuator 1
In bang-bang control, the control unit selects the pulse width ratio of the acceleration pulse and the deceleration pulse according to the number of necessary moving tracks up to the target track in advance, and counts the cross track counter 13 so that this pulse width ratio is achieved. Depending on the value, the switching timing of the jump pulse JP from the acceleration pulse to the deceleration pulse is set.

In this way, the precision actuator 1 reliably moves the light spot to the target track at high speed regardless of the number of required tracks to reach the target track. Therefore, when the bang-bang control of the precision actuator 1 is completed, the light spot is almost on this target track, and tracking control is possible on this target track.

Jump pulse J at time t1 in FIG.
When P is no longer supplied and the bang-bang control of the precision actuator 1 ends, the switch 5 switches to the b side,
The tracking error signal TE output from the tracking error detection circuit 3 passes through the phase compensation circuit 4 and the switch 5,
The drive circuit 10 on the one hand, and the switch 6, LPF on the other hand.
7, drive circuit 11 via phase compensation circuit 8 and switch 9
Are supplied to each. By the way, according to the bang-bang control of the above-mentioned precision actuator 1, the light spot is moved to the target track by displacing the objective lens against the elastic force of the spring (for example, the spring 26 of FIG. 6) by the jump pulse JP. Positioned. Then, at the time t1 when the bang-bang control is finished, as shown by the curve B in FIG. 2A, the optical head has hardly moved from the current track before access. It is in a state of being displaced against the elastic force.

When only the phase-compensated tracking error signal TE is supplied to the drive circuit 10 in such a state, the acting force of the precision actuator 1 is small. For this reason, the elastic force of the spring cannot be fully resisted, the light spot causes a tracking deviation from the target track, and as shown in FIG. 3B, a large tracking error occurs from time t1.

1 for eliminating such tracking error
As a method, it can be considered to improve the gain characteristic of the servo system of the precision actuator 1. FIG. 4 shows gain characteristics in the open loop of the servo system of the precision actuator. With such a gain characteristic, about 30 Hz
Has a main resonance, and the servo band is set to about 3 KHz in order to improve follow-up to disturbance and eccentricity of the optical disk, and the DC gain in this case is 6 kHz.
It becomes 6 dB. When the gain is further increased by such a gain characteristic, the response characteristic of the precision actuator 1 is improved and the tracking error signal after the time t1 in FIG. 3 is reduced, but on the other hand, the servo band of the gain characteristic shown in FIG. 4 is widened. The sub-resonance of the coarse actuator is included in this servo band, and the actuator resonates. Therefore, the gain of the precision actuator 1 cannot be increased.

On the other hand, in FIG. 1, when the bang-bang control of the precision actuator 1 is completed (time t1 in FIG. 2), the above-mentioned control unit (not shown) controls the target track as shown in FIG. 2 (c). Is proportional to the required number of moving tracks up to, and the holding current Ih having the polarity corresponding to the access direction is supplied to the drive circuit 10 by the amplitude of a value obtained by dividing this by the DC gain of the servo system, and feed-forward control is performed to the precision actuator 1. Call. As a result, the objective lens is maintained in the displaced state against the elastic force of the spring, and the light spot is subjected to target tracking control by the tracking error signal TE.

On the other hand, the tracking error signal TE output from the tracking error detection circuit 3 is phase-compensated by the phase compensation circuit 4, integrated by the LPF 7 and the phase compensation circuit 8, and supplied to the drive circuit 11. As a result, the coarse actuator 2 continuously moves the optical head in the direction of the target track.

As shown in FIG. 2C, the holding current Ih is gradually decreased. As a result, the elastic force of the spring causes the objective lens to return to its original stable position. At the same time, the light spot deviates from the target track, but this deviation appears in the tracking error signal TE, and the optical head moves in the direction of the target track so as to compensate for this deviation due to the action of the coarse actuator 2.

Therefore, as is clear from comparison between FIG. 2 (b) and FIG. 3 (b), the bang-bang of the precision actuator 1 is controlled by feedforward controlling the precision actuator 1 by the holding current Ih as described above. When the control ends (time t1), a good tracking state for the target track is immediately obtained.

When the objective lens is in a stable state where it is not subjected to the elastic force of the spring (time t2), the optical head is almost at the position facing the target track. After that, the precision actuator 1 and the coarse actuator 2 are controlled by the tracking error signal TE, and the actions of the precision actuator 1 and the coarse actuator 2 are complemented to each other so that the light spot is tracking-controlled on the target track. The curve C in FIG. 2A shows the total characteristics of the curves A and B.

As described above, in zone access, the precision actuator 1 first performs high-speed access to the target track. In this case, the moving part using a precision actuator such as an objective lens has a weight smaller than that of a moving part using a coarse actuator such as a carriage having an optical head by one digit or more. Therefore, this high-speed access is performed with very low power consumption. It can be done, and its rise becomes steep. Moreover, since the coarse actuator 1 moves the optical head smoothly at a low speed, no unnecessary power is consumed and even if it takes a long time to move the optical head to the target track, The power consumption is significantly reduced compared to the case of performing high-speed access with the coarse actuator.

After the high speed access by the precision actuator 1, the feedforward control by the holding current Ih of the precision actuator 1 as described above keeps the tracking state on the target track excellent.
Data recording / reproduction is possible from this time t1, and the high-speed access time by the precision actuator 1 becomes a substantial access time.

Therefore, according to this embodiment, it is possible to perform zone access with significantly reduced power consumption and access time, as compared with the prior art.

As a tracking error detection method, a push-pull method in which a main light beam for recording / reproducing data is also used for tracking error detection, and a main light beam is used only in recording / reproducing data, separately from this There is a three-spot method in which two sub light beams are provided for tracking error detection. In the push-pull method, when the objective lens moves, an offset occurs in the tracking error signal that is detected, so tracking is not good, and it is not preferable to record / reproduce data in such a state. Therefore, if the push-pull method is used as the tracking error detection method in FIG. 1, data recording / reproduction must be performed from time t2 in FIG. On the contrary,
In the 3-beam method, no offset occurs in the tracking error signal even when the objective lens is displaced. For this,
In FIG. 1, it is preferable to adopt the three-beam method, which allows recording / reproducing of data from time t1 in FIG.

In FIG. 1, in the case of normal access, the switch 5 is closed to the side a, the switch 6 is closed to the side c, and the switch 9 is closed to the side f. The speed control circuit 14 outputs a speed control signal determined by the count value of the cross track counter 13, and the speed detection circuit 15 detects the moving speed of the light spot from the output signal of the binarizing circuit 12 and responds to this moving speed. Output a signal.

At the start of access, the count value of the cross track counter 13 is zero, so the speed control circuit 14 outputs a speed control signal according to the count value of zero. Further, since the moving speed of the light spot is zero, the speed detecting circuit 15 does not output a signal. Therefore, the speed control signal output from the speed control circuit 14 is supplied to the drive circuit 11 via the LPF 16, the phase compensation circuit 17, and the switch 9, whereby the coarse actuator 2 is activated and the optical head moves in the direction of the target track. Start moving.

When the optical head starts moving, the cross track counter 13 starts counting, and the speed detecting circuit 15 detects the moving speed of the light spot and outputs a signal of a magnitude corresponding to this. The speed control circuit 14 outputs a target speed signal according to the count value of the cross track counter 13. This count value represents the position of the light spot with the current track before access as the reference position, and the target speed signal is The target moving speed of the light spot at this light spot position is determined. At this time, since the light spot is moving at the speed detected by the speed detection circuit 15, the difference between the target speed signal and the output signal of the speed detection circuit 15 is the LPF 16 and the phase compensation circuit 17, and the drive circuit 11 Is supplied to. As a result, the coarse actuator 2 moves the optical head so that the light spot moves at a speed determined by the target speed signal from the speed control circuit 14.

The light spot is close to the target track,
When the moving speed of the light spot becomes equal to or lower than a predetermined value, the switch 5 is switched to the b side and the tracking servo is applied to the precision actuator 1.

Needless to say, the speed control circuit 14 is controlled by a controller (not shown) and outputs the target speed signal according to the number of moving tracks required for normal access.

[0044]

As described above, according to the present invention,
Power consumption in zone access can be significantly reduced, and access time can also be significantly reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical information recording / reproducing apparatus according to the present invention.

FIG. 2 is an operation explanatory diagram of the embodiment shown in FIG.

FIG. 3 is an operation explanatory diagram when the feedforward control is not applied to the precision actuator in FIG. 1.

FIG. 4 is a diagram showing gain characteristics in an open loop of a servo system of a precision actuator.

FIG. 5 is a perspective view showing an example of a mechanical section of the optical information recording / reproducing apparatus.

6 is a perspective view showing an internal structure of the optical head in FIG.

[Explanation of symbols]

 1 Precision Actuator 2 Coarse Actuator 3 Tracking Error Detection Circuit 4 Phase Compensation Circuit 7 LPF 8 Phase Compensation Circuit 10, 11 Drive Circuit 12 Binarization Circuit 13 Cross Track Counter JP Jump Pulse Ih Holding Current

Claims (4)

[Claims] 1. An optical information recording / reproducing apparatus comprising a coarse actuator for moving an optical head and a precision actuator for moving an objective lens of the optical head, when a target track is in a track area near a current scanning track, The high-speed access to the target track is performed by the precision actuator, and the coarse actuator moves the optical head at a low speed in the direction of the target track in response to the high-speed access by the precision actuator. An optical information recording / reproducing apparatus characterized in that the optical head is set at a position corresponding to the target track after the end. 2. The high-speed access by the precision actuator is performed by adding an acceleration pulse and a deceleration pulse to the precision actuator, and the acceleration pulse and the deceleration according to the number of moving tracks by the high-speed access. An optical information recording / reproducing device characterized in that a ratio of a pulse width to a pulse is made different. 3. The holding signal according to claim 1, wherein a holding signal is added to the precision actuator according to the number of moving tracks in the high speed access by the precision actuator when the high speed access is completed, and the holding signal is applied to the optical head. The optical information recording / reproducing apparatus is characterized in that the tracking state on the target track is maintained by changing in accordance with the movement of the. 4. The optical information recording / reproducing apparatus according to claim 1, wherein the tracking error is detected by the 3-spot method.