JPH01220271A - Method and device for track access - Google Patents

Abstract

PURPOSE:To shorten an access time to arrive at an objective track by switching control for an optical travel motor from velocity control to track follow-up control when an optical head approaches the number of first regulation tracks found in advance. CONSTITUTION:When a track access command is inputted from the outside to a control circuit 8 and a targeted track distance is set, the velocity control is applied on a voice coil motor 2 according to a speed table 9 in which relation between the objective track distance and speed is stored in advance. And when the position of the optical head 1 arrives at the range of the first number of tracks regulated in advance, a switch SW1 is switched, then a mode is set at the track follow-up mode. Next, a track number is recognized by reading the content of the track, and when it is not the targeted track, a track jump signal is inputted to a current driver 3 to the targeted track, and track jump is repeated until it arrives the targeted track. In such a way, it is not required to provide a head actuator dedicated for following up the track separately, then, the access time can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a track access method and apparatus for an optical head in an optical disk device.

[Conventional technology]

Optical disks have been attracting attention as media for recording and reproducing text and graphic information due to their excellent characteristics such as high recording density and short access time.

The optical disk drive device that drives this optical disk is
A rotation drive system that rotationally drives an optical disk, an optical head that reads pits recorded along the tracks of the optical disk, a head actuator that positions the optical head on the track of the optical disk, and a head that moves the optical head in the radial direction of the optical disk. It is equipped with a feeding system.

A track access control method conventionally used in such an optical disc drive device will be described. FIG. 6 is a block diagram showing an example thereof.

In a normal recording/reproduction state, a head actuator 12 built into the optical head 1 causes an objective lens (not shown) to focus the light beam on the disk surface and follow the track row. controlled.

To explain this operation in the track following mode, the voltage output of the photodetection diode 4 installed inside the optical radar 1 is converted into a track position error by the track error calculation circuit 5, and then sent to the actuator driver via the phase compensation circuit 6. 13, the head actuator 12 is controlled so that the track position error becomes zero, that is, so that the light beam always follows the track row.

Next, the trunk access mode will be explained. When a track access command is input to the control circuit 8 from the outside, the switch SW forming a closed loop in the track following mode is turned off. Next, in order to access the optical head 1 to a position near the target track, a current corresponding to the target distance is applied to the voice coil motor 2 as a head feeding system via the current driver 3. The voice coil motor 2 has a structure in which a moving coil is placed in a fixed magnetic field and applies a moving force in the radial direction in proportion to the magnitude of the current flowing through the moving coil. This voice coil motor 2
is mechanically connected to the optical heald 1, and the optical held 1 is driven to a target position.

In this case, in order to accurately access the target track, the position of the optical radar 1 is monitored by the external optical scale 14 and the distance calculation circuit 15, and a speed signal corresponding to the distance to the target track is generated from the speed table 9. The speed of the optical radar 1 is controlled by the control circuit 8.

Thereafter, the switch SW is turned on to return to the track following mode. In the track following mode, the track number recorded in advance on the track is read, and if the target track cannot be accessed, the control circuit 8 supplies the actuator driver 13 with a track jump signal to repeatedly perform track jumps to reach the target track. For example, if it is detected that there is an error of three tracks, a jump command of three tracks is issued to the actuator driver 13.

[Problem to be solved by the invention]

However, in such a conventional control method, the voice coil motor 2 roughly positions the optical head 1 in the track access mode, and the optical head 1 is precisely positioned by the head actuator 12 in the track following mode. It is necessary to do it. As described above, since the head actuator 12 is incorporated inside the optical head 1 separately from the voice coil motor 2, the weight of the optical head 1 increases and the access time becomes longer.

Further, in the conventional example, although the speed of the optical head 1 is controlled by referring to the speed table 9 and the external optical scale 14, the control accuracy is not sufficient and the target track can be reached only in the track access mode. This is generally not possible and requires multiple track jumps.

That is, the operation of reading the track number recorded in advance on the track to determine whether it is the target track or not, and performing another track jump if it is not the target track is repeated. Therefore, there is a problem in that it takes a long time to reach the final target track.

The present invention has been made in view of these conventional problems, and an object of the present invention is to shorten the time required to reach a target track, that is, the access time, with a simple configuration.

[Means to solve the problem]

In order to achieve this object, the track access method of the present invention moves an optical head in the direction of a target track by controlling the speed of a head moving motor, and moves the optical head in a predetermined first direction with respect to the target track. When the number of tracks approaches a predetermined number of tracks, the control of the optical head moving motor is switched from the speed control to track following control.

A voice coil motor is used as the optical head moving motor, and the driving current of the voice coil motor is controlled until the optical head enters the range of a second specified number of tracks that is greater than the first specified number of tracks with respect to the target track. The speed control is performed using the first reference signal obtained by integrating the number of trunks, and when the optical head enters the range of the second specified number of trunks, the pulsing that occurs when the optical head crosses the track is performed. The speed control can be performed using the second reference signal obtained by measuring the time interval of the track error signal.

Further, when the absolute speed of movement of the optical head and the relative speed in the radial direction with respect to the disk match, a reference signal for performing the speed control is changed from the first reference signal to the second reference signal. It is desirable to switch.

Further, the track access device of the present invention includes a first control means for positioning the optical head by speed control, a second control means for performing a track following operation, and a first control means for controlling the optical head during track access. The optical head is controlled by a control means, and includes a switching means for switching to control by the second control means when the optical head approaches a predetermined number of tracks with respect to the target track.

[Effect]

In the present invention, the optical head moving motor used for track access is also used for track following operation. That is, speed control for rough optical head position control and optical head track following control are selectively performed for the drive system of the same optical head moving motor. Initially, speed control is performed, and when the optical head roughly reaches the target track, speed control is switched to track following control, and a signal for track following, such as a track position error signal, is input to the optical head movement motor used for speed control. track following operation is performed.

This enables optical head access and track following operation.
It becomes possible to control using the same optical head moving motor.

In addition, the speed control is divided into two stages. First, the speed control is performed using the first reference signal obtained by integrating the drive current of the voice coil motor, so the optical head approaches the target track stably and at high speed. .

When the optical head approaches the target track to some extent, speed control is performed using a second reference signal obtained by measuring the time interval of a pulsed tracking error signal generated when the optical head crosses the track. Therefore, accurate positioning of the optical head is achieved.

Note that if the first reference signal is switched to the second reference signal when the absolute speed of movement of the optical head and the relative speed in the radial direction with respect to the disk match, the value of the reference signal becomes discontinuous. Stable speed control is performed without any problems.

〔Example〕

Hereinafter, features of the present invention will be specifically explained based on embodiments shown in the drawings.

FIG. 1 is a block diagram showing an example of a track access device based on the present invention.
Elements having the same functions as those of the conventional configuration shown in the figure are given the same reference numerals and redundant explanation will be omitted.

In this embodiment, a track counter 7 and a speed calculation circuit 1 are provided with the output from the track error calculation circuit 5.
1, the track position error signal obtained by the photodetection diode 4 and the track error calculation circuit 5 is converted into pulses by the track carantuff, and the pulse interval is measured by the speed calculation circuit 11 and converted into a relative speed signal 51K.

The output of the track counter 7 is also supplied to a control circuit 8, and is used to determine whether the eccentricity of the disk is at its maximum, as will be described later.

Also, the current value flowing through the voice coil motor 2 is determined by the integrating circuit 1.
The absolute speed signal SAs is obtained by integrating by 0.

These relative speed signal SIS and absolute speed signal SAS are
After being selected by the switch SW2 controlled by the control circuit 8, the control time! The difference from the reference signal from 88 is taken to obtain a speed error signal, and speed control is performed based on this speed error signal.

Furthermore, this reference signal and the signal from the phase compensation circuit 6 are selected by a switch SWI controlled by a control circuit 8 and supplied to the current driver 3. Then, the current flowing through the movable coil of the voice coil motor 2 is controlled by the current driver 3, and the optical head 1, which is integrally attached to the coil, moves in a direction across the track.

An example of the structure around the photoherad 1 and the heiscoil morph 2 is shown in FIG.

In the figure, reference numeral 21 indicates a pair of magnetic yokes arranged parallel to each other along the direction across the tracks of the optical disk, and each magnetic yoke 21 includes an engineered ferromagnetic material 21a and magnetically A pair of U-shaped ferromagnetic bodies 21b are fixed so as to be short-circuited to each other. A square bar-shaped permanent magnet 22 is fixed to the inner surface of each U-shaped ferromagnetic body 21b. Further, around each single-character-shaped ferromagnetic body 21H, a movable coil 23 having a square-shaped cross section is provided, floating from the ferromagnetic body 21a. This pair of moving coils 23
are connected by a figure 8-shaped support member 24 made of a non-magnetic material such as aluminum in order to increase the rigidity of the optical head 1 portion.

A triangular prism-shaped mirror 25 is attached to the upper surface of the horizontal portion 24H of this support member 24, and furthermore, this mirror 2
A lens 26 that moves integrally with the support member 24 is provided above the support member 24 .

Further, a linear bearing 27 is provided on the lower surface of the horizontal portion 24a of the support member 24. This linear bearing 27 is connected to the support member 2
4, and a fixed part 27b, which is attached to a base (not shown).
The movable part 27a is linearly movable in the direction of the arrow with respect to the fixed part 27b. Therefore, mirror 25.
The optical head 1 consisting of a lens 26 and the like has a movable coil 23 .
It becomes movable in the direction of the arrow together with the support member 24 and the like. Note that the optical head 1 is elastically held by a biasing means (not shown).

The mirror 25 is irradiated with a laser beam B from a laser (not shown), reflected by the mirror 25, bent at a right angle, and focused by a lens 26 to be focused on the track of the optical disc.

Here, when a current is applied to the moving coil 23, a magnetic force is generated between the permanent magnet 22 and the ferromagnetic body 21a by the moving coil 23, and a force is applied to the moving coil 23 in the direction of the arrow. Therefore, the optical head 1 integrated with the movable coil 23 also moves in the direction of the arrow. Therefore, by changing the magnitude of the current flowing through the movable coil 23, it is possible to move the optical head 1 in the direction of the arrow, that is, in the direction across the tracks, and access a predetermined track.

In this embodiment, the head actuator 12. shown in the conventional example shown in FIG. Actiniator driver 13.
External optical scale 14. A distance calculation circuit 15 and the like are not provided.

The operation of the track access device shown in FIG. 1 will be described below with reference to the flowcharts in FIGS. 3 and 4.

FIG. 3 is a flowchart of a seek operation to find a target track. When a track access command is input from the outside to the control circuit 8 and a target track distance is set (step 101), a speed table 9 consisting of a storage means such as a ROM and storing the relationship between the target track distance and speed in advance Accordingly, the speed of the voice coil motor (indicated by VCM in the figure) 2 is controlled (step 102). When the position of the optical head 1 approaches the target track until it reaches the range of the predetermined first specified number of tracks TRI, the switch SW is pressed.
I is switched to the opposite state from that shown to enter the track following mode (steps 103 and 104). Next, the contents of the track are read to recognize the track number pre-recorded on the track, and if it is not the target track, a track jump signal is manually sent to the current driver 3 to reach the target track, and the track jump is performed until the target track is reached. Repeat (steps 105 and 106). Note that the first specified number of tracks TRI is selected based on the condition that the number of track jumps is minimized. Ideally, this first specified number of tracks TRI is preferably zero, but in reality, due to the inertial force of the optical radar 1, etc., an error occurs between the target track and the actual track reached. Therefore, the specified number of tracks is set in consideration of this error. The first specified number of tracks TRI is desirably 10 or less.

After reaching the target track, the track position error signal obtained by the photodetection diode 4 and the track error calculation circuit 5 is transmitted to the phase compensation circuit 6 and the switch SWI.
A current is supplied to the driver 3 via the radiator to cause the optical radar 1 to follow the target track. Therefore, the optical disc 1 moves by a minute amount to follow the target track according to the eccentricity of the disc.

In this embodiment, as described above, the target track is first approached in the speed control mode, and then the track following mode is set. However, the speed control mode is further divided into two stages, and control based on absolute speed is performed first, and then relative speed control is performed. Control by speed.

Next, the above-mentioned speed control mode will be explained in detail with reference to the flowchart of FIG. 4. Note that this flowchart corresponds to step 102 in the flowchart of FIG.

In the initial state, the switches SWI and SW2 are assumed to be in the illustrated state.

First, when a track access command is input from the outside to the control circuit 8, the speed table 9 in which the relationship between distance and speed is recorded is referred to, and the control circuit 8 sends the current driver 3 to the current driver 3 according to the target distance. A speed signal or reference signal is provided. Therefore, a current corresponding to the speed signal flows through the movable coil 23 (see FIG. 2) of the voice coil motor 2, and the speed of the optical head 1 is controlled.
Start moving towards the target truck.

At the beginning of the movement of RAD 1 to this light, switch SW2
is in the state shown, and a reference signal is obtained by integrating the current value flowing through the voice coil motor 2 by an integrating circuit 10. This is because using the output of a speed calculation circuit 11 that measures the interval of pulses generated when an optical head crosses a track, which will be described later, as a reference signal would take too much calculation time, and the delay time would cause the speed control servo to This is because the loop becomes unstable. The signal obtained from this integrating circuit 10 is the absolute speed signal SAS.

The optical head 1 includes a voice coil motor 2. Integrating circuit 10.
Switch sw2. Switch sw1. Current driver 3. The speed is controlled by the loop of the voice coil motor 2 up to the vicinity of the target track. In this embodiment, the speed of the voice coil motor 2 is controlled in a closed loop using the integrated value of the current flowing through the voice coil motor 2 as a reference signal, so high-speed control is possible and the servo loop becomes unstable. It never becomes.

The optical head 1 moves the target track to the second prescribed number of tracks T.
If the disc approaches the range of R2 (>TR1) and is at a position on the track that shows the maximum disc eccentricity (step 203), the output of the control circuit 8 switches the switch SW2 to the opposite state as shown in the figure. , a reference signal is obtained from the speed calculation circuit 11 (step 204). This signal is the relative speed signal SR5. In addition, optical head 1
Since the number of tracks crossed by the optical head 1 is constantly counted by the track counter 7, the position of the optical head 1 can be detected at any time by checking the value of the track counter 7.

FIG. 5(a) is a time chart showing changes in the amount of eccentricity of the optical head 1 due to disk eccentricity, and FIG.
3 is a time chart showing the relationship between relative speed and absolute speed. Note that the absolute speed here refers to the speed relative to the stationary part.
That is, it means the speed of the optical head 1 as seen from the drive device, and the relative speed means the speed of the optical head 1 in the radial direction with respect to the optical disk, that is, the speed that includes fluctuations in eccentricity of the disk. As can be seen from the figure, at the position on the track where the disk eccentricity is maximum, the absolute speed of the head and the relative speed with respect to the disk match.

Therefore, the absolute speed signal SaS obtained based on the integral value
Relative speed signal RR8 obtained by speed calculation circuit 11 from
Even when switched to , the servo operates stably.

Whether the eccentricity is the maximum can be easily determined by supplying the pulse output of the track counter 7 to the control circuit 8 and detecting the maximum value of this pulse output interval.

When the optical head 1 approaches the target track, switch SW
2 is switched to the opposite state as shown, the track position error signal obtained by the photodetection diode 4 and the track error calculation circuit 5 is converted into pulses by the track counter 7, and the pulse interval is measured by the speed calculation circuit 11. and converts it into a relative speed signal SR5. Then, the speed of the optical head 1 is controlled using this relative speed signal SRS as a reference signal.

The reason why the speed signal is obtained from the pulse interval is as follows. The switch SW2 is switched when the moving speed of the optical head 1 is slow, but at this time, the current flowing through the voice coil motor 2 is small, so the absolute speed obtained by integrating this current is becomes inaccurate. On the other hand, the relative velocity obtained from the pulse interval is accurate because the pulse interval is long.

Through the control by the speed control loop described above, when the optical heald 1 approaches the target track until it is within the range of the first specified number of tracks TRI, the control circuit 8 causes the switch SW1 to change to the state opposite to that shown in FIG. The voice coil motor 2 and the optical head 1 enter the track following mode described above.

〔Effect of the invention〕

As described above, in the present invention, the same optical head moving motor is controlled by switching between speed control and track following control. Therefore, the access system can be realized using an optical head with a simple configuration, and there is no need to separately provide a head actiniator dedicated to track following as in the conventional system. Furthermore, since the structure of the optical head is simplified, the weight of the optical head can be reduced, and access time can be shortened.

Further, if the speed control for track access is performed separately into control based on absolute speed and control based on relative speed, the position of the optical head relative to the track can be determined quickly and accurately. Therefore, the number of track jumps required to reach the target track is reduced, and the time required for track following control is also shortened, making it possible to shorten the access time as a whole.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a perspective view showing the structure of a voice coil motor and an optical head, and Figs. 3 and 4 each show the operating procedure of the embodiment of the present invention. FIG. 5 is an explanatory diagram showing the control operation in this embodiment, and FIG. 6 is a block diagram showing an example of the configuration of a conventional optical disk drive device. 1: Optical head 2: Whiscoil morph 3:
Current driver 4: Photodetection diode 5; Track error calculation circuit 6-1: Phase compensation circuit 7: Track counter 8:
Control 119: Speed table 10: Integrating circuit
11: Velocity calculation circuit 12: Helad actiniator 13: Actiniator driver I4: External optical scale I5: Distance # calculation circuit 21: Magnetic yoke 22: Permanent magnet 23: Moving coil
24: Support member 25: Mirror 26: Lens Patent applicant Fuji Xerox Co., Ltd. Agent Masu Kobori (and 2 others) Figure 3 Figure 4

Claims (1)

[Claims] 1. The optical head is moved in the direction of the target track by controlling the speed of the optical head moving motor, and the optical head approaches the target track to a predetermined first specified number of tracks. A track access method characterized in that, at times, control of the optical head moving motor is switched from the speed control to track following control. 2. A voice coil motor is used as the optical head moving motor, and the optical head moves toward the target track in the first direction.
The speed control is performed using a first reference signal obtained by integrating the drive current of the voice coil motor until the speed is within a range of a second specified number of tracks that is greater than the specified number of tracks;
When the optical head enters the range of the second specified number of tracks, a second reference signal is obtained by measuring the time interval of a pulsed track error signal generated when the optical head crosses a track. 2. The track access method according to claim 1, wherein the speed control is performed by:. 3. When the absolute speed of movement of the optical head and the relative speed in the radial direction with respect to the disk match, a reference signal for performing the speed control is changed from the first reference signal to the second reference signal. 3. A track access method according to claim 1 or 2, characterized in that switching is performed. 4. a first control means for positioning the optical head by speed control; a second control means for performing a track following operation;
During track access, control of the optical head is controlled by the first control means, and when the optical head approaches a predetermined number of tracks with respect to the target track, control is switched to control by the second control means. A track access device comprising: switching means.