JP2001184670A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-speed and highly reliable pull-in control by making a lens moving area to the absolute minimum at a sweep action and reducing arrival time at a pull-in position, in consideration of relative positional errors between a disk recording surface and an objective lens, or lens displacement and disk wobbling due to outside vibration. SOLUTION: The device is composed of an objective lens, focus actuator, disk rotation control means, focus error signal detecting means, feedback control means, pull-in control means, switching means, actuator driving means, memory means, posture detecting means, and lens displacement detecting means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus using a pickup, and more particularly, to an objective lens and an objective lens movable end by performing a preliminary operation before a sweep operation and minimizing a sweep operation range for each operation. TECHNICAL FIELD The present invention relates to an optical disk device capable of preventing a collision with an optical disk and shortening a pull-in operation time.

[0002]

2. Description of the Related Art In order to perform focus control in an optical disk apparatus, first, as shown in FIG. 2A, it is necessary that an objective lens is located at a position where a focus error signal appears (hereinafter referred to as a retracted position). It is. However, the range in which this focus error signal appears is several tens of μm.
On the other hand, the relative distance between the objective lens and the recording surface of the disk is several hundred μ when the mechanical error, the lens displacement due to gravitational acceleration and external vibration, and the surface deviation of the disk are combined.
m or more, they usually do not coincide with the focal length as shown in FIGS. 2B and 2C. Furthermore, since the magnitude and direction of these errors are unknown, it is difficult to directly move the objective lens to the retracted position by the retracting operation.

Therefore, in the sweep operation, as shown in FIG. 3, in consideration of mechanical errors and lens displacement due to gravity, a range that always includes the retracted position is set, and the objective lens is moved in this range. Here, in order to clarify the lens position with respect to the disk recording surface during the sweep, before the sweep operation indicated by arrows b and b ', the lens is once moved to the lens movable end as indicated by arrows a and a'. As shown in FIG. 4, when b and c near the just focus position are moving in the direction of the arrow, feedback control is started because it cannot be distinguished from the focus error signal when a and d are moving in the direction of the arrow. Since the polarity is reversed, positive feedback occurs and the pull-in operation is not performed normally, and a pull-in operation is required again.
Therefore, the above operation is performed so that the feedback control can be started after passing the extreme point of the error amplitude from the position a or d. For example, consider the case in FIG. 5 where the objective lens is once moved in a direction far from the disk before the sweep. If the mounting position of the objective lens is above the retracted position, that is, closer to the disk, the objective lens passes through the retracted position while moving the objective lens near the movable end of the lens. However, at this point, the control is not switched to the feedback control without reaching the movable end, and after passing through the retracted position after reaching the movable end.

[0004]

However, the lens displacement due to mechanical errors and gravitational acceleration is usually almost the same as the movable range, so that the sweep range is almost the same as the movable range of the objective lens. Often become. In this case, the objective lens collides with the movable end at the time of sweeping, and minute vibration occurs in the objective lens. This vibration adversely affects the pull-in operation. When external vibration occurs, the collision with the movable end further increases, and as a result, the performance of the pull-in deteriorates.

Further, at the time of pulling in, the relative speed between the recording surface of the disc and the objective lens needs to be suppressed, so that the objective lens is moved at a low speed in the sweep operation. Therefore, if the sweep range is wide, the start-up time of the device is prolonged, and as a result, the operability of the device is reduced. Furthermore, the operation of once moving the objective lens to the movable end before the sweep operation described above also causes a delay in the startup time. This operation causes a further delay in the startup time. Particularly, in portable equipment that requires power saving, a delay in the focus pull-in operation at the start of recording / reproduction greatly deteriorates the operability of the apparatus because the recording or reproduction operation is performed intermittently.

In order to eliminate the collision of the objective lens and the delay of the pull-in time during the sweep, the sweep range is narrowed to prevent the objective lens from moving near the movable end, and the time spent for the sweep is reduced. It is necessary to reduce it.

[0007]

SUMMARY OF THE INVENTION In order to achieve the object of the present invention, an optical disk apparatus according to the present invention comprises a mechanical error in the relative distance between a disk recording surface and an objective lens, and a lens displacement caused by gravitational acceleration or external vibration. By setting the lens movement range during the sweep operation to the minimum necessary in consideration of disk runout and shortening the time to reach the retracted position, it prevents collision with the movable end and shortens the startup time It works as follows.

Therefore, the present invention provides an objective lens, a focus actuator, a disk rotation control means, a focus error signal detection means, a feedback control means, a pull-in control means, a switching means, an actuator drive means, a memory, Means, attitude detecting means,
Lens displacement detecting means.

Since the mechanically generated error is always constant after the apparatus is assembled, the error is detected and stored in the memory means after the assembly, and the mechanically generated error is canceled before the sweep operation in the pull-in operation. To move the objective lens. Similarly, since the lens displacement due to gravity is uniquely determined from the lens mass, the displacement amount is stored before using the apparatus at the time of shipping or the like, and the posture detection means and the stored displacement amount are used before the sweep operation is performed. The actual lens displacement is calculated, and the objective lens is moved in advance so as to cancel the lens displacement. When the attitude detecting means is not used, the sweep range is set based on the stored lens displacement.

[0010] By these preliminary operations before the sweep,
Since the lens position has almost moved to the retracted position, the focus error signal shown in FIG. 6A can be obtained without performing a normal sweep operation. This is because the surface deviation of the disk is usually on the order of several tens of μm, and the relative distance between the disk recording surface and the objective lens changes periodically by rotating the disk. As shown in FIG. 6A, after the preparatory operation is completed, if the objective lens is located at a position deviated substantially from the center of the surface deviation, the s-shaped waveform of the focus error signal does not appear at a constant cycle, so that the objective lens is very small. It is moved and adjusted so that an s-shaped waveform is generated at regular intervals as shown in FIG. The minute movement amount at this time is stored in the memory means and used for the preliminary operation before the next pull-in.

When a waveform in the range indicated by * in FIG. 6B is obtained, it is determined that the objective lens is at the position a or d in FIG. Therefore, after passing through the range indicated by *, the feedback control is started by passing through the extreme point of the error amplitude. In addition, the relative speed between the recording surface and the objective lens at the time of detecting the s-character can be calculated by detecting the period of the s-polarity. Immediately before the feedback control is started after passing through the pole in the above-described process, the operation is performed so as to reduce the relative speed by moving the objective lens according to the calculated speed.

On the other hand, when the error of the disk is small and the error signal shown in FIG. 6 does not appear after the above-described preliminary operation, a sweep operation is performed so as to gradually increase the amplitude width as shown in FIG. The retraction position at this time is stored in the memory means and used for the preliminary operation before the next retraction.

By operating with the above means, it is possible to suppress the sweep operation range to a necessary minimum at the time of pulling in, and to shift to the feedback control without moving the objective lens near the end of the lens movable range. Therefore, since the collision at the movable end is eliminated, the focus pull-in characteristic can be improved, and the time required for pull-in can be shortened, so that the operability of the apparatus can be improved.

Here, the data of the mechanical error, the lens position, and the fine movement amount stored in the memory means are not data on the distance, but a control signal for moving the objective lens by the same distance or a drive signal value of the focus actuator. The effect is the same.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the optical disk drive of the present invention will be described with reference to FIG.

First, the configuration of the optical disk device of the present invention will be described.

1 is a disk, 2 is an objective lens, 3 is a focus actuator, 4 is a tracking actuator, 5 is a feed mechanism, 6 is a detector, 7 is focus error signal detecting means, 8 is focus feedback control means, and 9 is memory means. Reference numeral 10, a posture detecting means, 11 a lens displacement detecting means, 12 a pull-in control means, 13 a switching means, 14 a focus actuator driving means, 15 a tracking error detecting means, 16 a tracking feedback control means, 17 a tracking actuator Drive means, 18 is a feed mechanism drive means, 1
9 is a spindle motor, 20 is a disk rotation frequency generating means, and 21 is a disk rotation control means.

Next, the relationship between the above blocks will be described. The disk rotation frequency generating means 20 outputs a signal synchronized with the rotation frequency of the spindle motor 19 (hereinafter FG: Fr).
Described as an equency generator signal. ) Is sent to the disk rotation frequency control means 21. The disk rotation control means 21 drives the spindle motor 19 to rotate at a predetermined angular speed based on the sent FG.

The tracking actuator 4 moves the objective lens 2 in the radial direction of the disk 1, and positions the focused focal point on a track on the disk 1. The light reflected from the disk 1 is sent to a tracking error detector 15. The tracking error detection means 15 detects the tracking error amount and sends the obtained tracking error signal to the tracking feedback control means 16. The tracking feedback control means 16 generates a tracking feedback control signal based on the tracking error signal, and outputs the generated control signal or the control signal at the time of the track jump to the tracking actuator driving means 17.
And a generated control signal or a control signal at the time of seek operation is sent to the feed mechanism driving means 18. The tracking actuator driving means 17 drives the tracking actuator 4 based on the sent control signal. The feed mechanism driving means 18 drives the feed mechanism 5 based on the sent control signal.

The focus actuator 3 moves the objective lens 2 in a direction perpendicular to the recording surface of the disk 1, and positions the focused focal point on the disk recording surface. Disc 1
Is reflected to the focus error signal detecting means 7. The focus error signal detection means 7 detects the focus error amount and sends the detected focus error signal to the focus feedback control means 8. The focus feedback control means 8 generates a focus feedback control signal based on the focus error signal, and sends the generated control signal to the switching means 13.

During the focus feedback control operation, the switching means 13 sends the sent focus feedback control signal to the focus actuator driving means 14. The focus actuator driving unit 14 drives the focus actuator 3 based on the sent focus feedback control signal. During the focus pull-in operation, the switching means 13 sends a focus pull-in control signal described later to the focus actuator driving means 14. The focus actuator driving unit 14 drives the focus actuator 3 based on the sent focus pull-in control signal.

Next, a method of generating the focus pull-in control signal will be described including the operations of the memory means 9, the attitude detecting means 10, the lens displacement detecting means 11, and the pull-in control means 12. The pull-in control means 12 detects mechanical error data of the relative distance between the disk recording surface and the objective lens 2, lens displacement data due to gravitational acceleration, and learning data 1 and learning data 2 to be described later. The data thus obtained are stored in the memory means 9. The attitude detecting means 10 detects the attitude direction of the apparatus, and sends the detected attitude direction data to the pull-in control means 12. The lens displacement detecting means 11 detects the moving speed of the objective lens 2 in the focus direction from the back electromotive force generated in the focus actuator 3, converts the speed into lens displacement, and sends the obtained lens displacement data to the pull-in control means 12.

Next, the operation of the pull-in control means 12 during the pull-in operation and in the preliminary operation before the pull-in operation will be described. The pull-in control means 12 reads mechanical error data and lens displacement data due to gravitational acceleration from the memory means 9. The amount of displacement of the objective lens 2 caused by the gravitational acceleration is calculated from the read lens displacement data and the posture direction data sent from the posture detecting means 10. Based on the calculated displacement and mechanical error data, lens driving a and b shown in FIG. 8 are performed. At this time, if the focus position is not substantially at the center of the disk surface shake, the focus error signal sent from the focus error signal detection means 7 is the same as that shown in FIG.
An s-shaped waveform is generated with a biased period as shown in FIG. The pull-in control means 12 detects the generation cycle of the s-shaped waveform,
The lens driving c shown in FIG. 8 is performed so that the V-shape waveform is generated at an equal period as shown in FIG. 6B.

Here, the driving voltage used for the lens driving c is stored in the memory means 9 as learning data 1, and in the next preliminary operation, the lens driving c is used for the lens driving a and b.
Then, the s-shaped signal is made equal in period. After the lens drive c is completed, the pull-in control means 12 measures the occurrence cycle of the positive peak and the negative peak of the s-shaped waveform as shown in FIG. Is calculated. Next, an s-shaped peak for performing the pull-in operation is detected, and a drive signal is output so that the objective lens 2 operates at a speed corresponding to the relative speed calculated immediately before. Thereafter, the switching means 13 switches the output signal and performs focus feedback control.

If the above-mentioned s-shaped waveform does not appear at the time when the lens drives a and b are performed, the sweep operation is performed while sequentially increasing the range as shown in FIG. At this time, based on the lens displacement data sent from the lens displacement detecting means 11, the pull-in control means 12 compares the case where there is a lens displacement due to external vibration with the case where there is no lens displacement.
The drive signal is output so that the sweep range is reduced as shown in FIG.

Finally, a method for detecting mechanical error data and lens displacement data due to gravitational acceleration will be described.
As shown in FIGS. 11 (a) and 11 (b), in a state where the apparatus is arranged so that the gravity applied to the objective lens 2 is in the ± focus direction, the actuator is driven by the pull-in control means 12, and the s-shaped waveform becomes equal. The objective lens 2 is moved so as to appear in a cycle. The output values Va and Vb of the pull-in control means 12 necessary for moving the lens are detected. here,
Retraction control means 12 required due to mechanical errors
Is Ve, and the output value of the pull-in control means 12 required by the lens displacement due to the gravitational acceleration is Vg. Va = Ve + Vg Vb = Ve-Vg, so that Ve = (Va + Vb) / 2 Vg = (Va-Vb) / 2. Based on this, mechanical error data and lens displacement data due to gravitational acceleration are created and stored.

As described above, the relative position error between the disk recording surface and the objective lens 2 is stored, the operation is performed to cancel the error before the sweep operation, and the sweep operation range is set in consideration of the lens displacement due to external vibration. By deciding, it is possible to shift to the feedback control without moving the objective lens 2 near the end of the lens movable range.
The focus pull-in characteristic can be improved without collision at the movable end. Further, the operability of the apparatus can be improved because the time required for the retraction can be reduced.

Here, in the present embodiment, when detecting the mechanical error data and the lens displacement data due to the gravitational acceleration, it is described that the detection is performed in two states of FIGS. 11A and 11B.
The present invention is not limited to this. The same data can be detected in the case where the force in the focus direction applied to the objective lens 2 becomes zero as shown in FIG. 11C and in the two states shown in FIG. 11A or 11B. That is, the same effect can be obtained by detecting in any one of the two states of FIGS. 11 (a), (b) and (c).

[0029]

As described above, according to the present invention, the initial object can be achieved. That is, the relative position error between the disk recording surface and the objective lens 2 is stored, the operation is performed to cancel the error before the sweep operation, and the sweep operation range is determined in consideration of the lens displacement due to external vibration. There is no collision of the objective lens 2 at the movable end, and the focus pull-in characteristic can be improved. Further, since the time required for the pull-in operation can be reduced, the operability of the apparatus can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a diagram illustrating an operation of a conventional example.

FIG. 3 is a diagram illustrating a sweep operation of a conventional example.

FIG. 4 is an explanatory diagram of a pull-in operation of a conventional example.

FIG. 5 is a diagram illustrating a sweep operation of a conventional example.

FIG. 6 is an explanatory diagram of a pull-in operation of the embodiment of the present invention.

FIG. 7 is an explanatory diagram of a pull-in operation of the embodiment of the present invention.

FIG. 8 is an explanatory diagram of a pull-in operation of the embodiment of the present invention.

FIG. 9 is an explanatory diagram of a pull-in operation of the embodiment of the present invention.

FIG. 10 is an explanatory diagram of a pull-in operation of the embodiment of the present invention.

FIG. 11 is a diagram illustrating a data detection operation according to the embodiment of the present invention.

[Explanation of Symbols] 1 ... disk, 2 ... objective lens, 3 ... focus actuator, 4 ... tracking actuator, 5 ... feed mechanism, 6 ... detector, 7 ... focus error signal detection means, 8 ... focus feedback control means, 9 ... Memory means, 10 posture detection means, 11 lens displacement detection means, 12 pull-in control means, 13 switching means, 14 focus actuator driving means, 15 tracking error detection means, 16 tracking feedback control means, 17 ... Tracking actuator driving means 18 feeding mechanism driving means 19 spindle motor 20 disk rotation frequency generation means 21 disk rotation control means

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Koji Iijima 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in the Digital Media Development Division, Hitachi, Ltd. 5D117 AA02 BB03 BB06 CC07 DD03 DD06 DD12 DD14 FF03 GG02

Claims (12)

[Claims] 1. An optical disk device using a pickup, wherein at least one of a mechanical error relating to a relative distance between an objective lens and a disk recording surface and a displacement amount of the objective lens caused by gravity are stored. Before the sweep operation for moving the objective lens to the focus pull-in position, driving the objective lens so as to cancel at least one of the mechanical error and the lens displacement amount due to gravity. Characteristic optical disk device. 2. An optical disk apparatus using a pickup, wherein a focus error signal s generated during rotation of the disk is s.
An optical disk device, comprising: moving an objective lens to a focus pull-in position so as to make a generation cycle of a character signal constant; and storing a focus drive signal used for the movement. 3. An optical disk device using a pickup, wherein the operation of an objective lens caused by external vibration is detected, and the objective lens is moved to a focus pull-in position based on the detected lens operation by the detected external vibration. An optical disk device operable to change a range of a sweep operation. 4. An optical disk device using a pickup, comprising: a focus actuator for driving an objective lens mounted on the pickup; rotation control means for rotating a disk at a predetermined speed; Focus error signal detection means obtained; feedback control means for generating a feedback control signal for the pickup to focus on the disk recording surface based on the output of the focus error signal detection means; Control means for generating a control signal for controlling the focus actuator, a switching means for selectively outputting the output of the feedback control means and the output of the pull-in control means, and driving the focus actuator based on the output of the switching means. Actuator driving means, and memory means for storing at least one of a mechanical error relating to a relative distance between the objective lens and a disk recording surface, and a displacement amount of the objective lens due to gravity. Optical disk device. 5. The memory means, wherein at least two states in which the direction of gravity applied to the objective lens is different, a mechanical error relating to a relative distance between the objective lens and a disk recording surface, and a displacement of the objective lens due to gravity. 5. The optical disk device according to claim 4, wherein an output of said pull-in control means for canceling the amount is stored. 6. The pull-in control means, based on a mechanical error stored in the memory means,
Controlling the objective lens to move before a sweep operation for moving the objective lens to a focus pull-in position, and setting the sweep range based on the displacement amount due to gravity stored in the memory means. 6. The optical disk device according to claim 4, further comprising: a pull-in control unit that performs focus pull-in control. 7. An apparatus according to claim 7, further comprising: a posture detecting means for detecting a posture of the apparatus, wherein said pull-in control means comprises: an output of said posture detecting means; a mechanical error stored in said memory means; 6. The optical disk according to claim 4, wherein the optical disk is controlled so as to cancel the mechanical error and the amount of displacement of the objective lens due to gravity before the sweep operation. apparatus. 8. An s-shaped cycle detecting means for detecting an output cycle of an s-shaped waveform obtained from said focus error signal detecting means, wherein said pull-in control means performs s-based processing based on an output of said s-shaped cycle detecting means. Controlling the objective lens to move so that the period of the U-shape waveform is at equal intervals; and the memory means stores the movement amount in addition to the mechanical error and the objective lens displacement amount due to gravity. 8. The optical disk device according to claim 4, wherein: 9. An optical disk apparatus using a pickup, comprising: a focus actuator for driving an objective lens mounted on the pickup; rotation control means for rotating a disk at a predetermined speed; Focus error signal detection means obtained; feedback control means for generating a feedback control signal for the pickup to focus on the disk recording surface based on an output of the focus error detection means; displacement of the objective lens Lens displacement detection means for detecting, based on the output of the lens displacement detection means, a pull-in control means for setting a range of sweep operation for moving the objective lens to a focus pull-in position, and performing focus pull-in control; The feedback An optical disc device comprising: a switching unit for selectively outputting an output of a control unit and an output of the pull-in control unit. 10. The optical disk apparatus according to claim 9, wherein said lens displacement detecting means detects a displacement of said objective lens using an acceleration sensor. 11. The optical disk apparatus according to claim 9, wherein said lens displacement detecting means detects a displacement of said objective lens by detecting a back electromotive force generated in said actuator. 12. The pull-in control means controls the relative speed of the objective lens with respect to the recording surface of the disk based on the generation cycle of the positive peak value and the negative peak value of the s-shaped waveform. 11. The optical disk device according to claim 4, wherein: