JPH09265636A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk device capable of stably setting a final target speed and shortening a time required for moving to a target track. SOLUTION: A target speed generating means 14 is controlled so as to output the target speed of an optical head 4 in order to set a target speed just before a target track becomes a lower value than a final target speed at the time of reaching the target track by using a signal generated by the fact that an optical spot crosses the track of an optical disk 1. The target speed outputted from the target speed generating means 14 and the actual moving speed of the optical head 4 detected by a speed detecting means 15 are introduced to a linear actuator driving control circuit 17 and the speed of the optical head 4 is controlled. Consequently, the deviation of speed is absorbed even in the vicinity of the target track position while keeping large decelerating force as it is and the final target speed is quickly set. Since the high target speed is kept up to the vicinity of the target track position, the moving time to the target track is shortened.

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 for recording / reproducing information on / from an optical disk having information recording tracks.

[0002]

2. Description of the Related Art An optical disk device is equipped with an optical head having an objective lens for forming an optical spot at the position of a target track on the optical disk. This optical head moves in the radial direction of the optical disk, that is, an information recording track. A seek operation is performed by being moved in the transverse direction.

This seek operation is realized by a linear actuator such as a linear motor. Then, the target value corresponding to the number of remaining tracks up to the target track is calculated by using the count value of the number of traversed tracks, and the speed control is performed by the configuration in which the detected moving speed of the linear actuator follows this target speed. There is.

Here, the detected moving speed is obtained based on the reciprocal of the track crossing time interval, and is 1
It is a value that changes every time a track, 1/2 track or 1/4 track is crossed. The operation amount input to the linear actuator is calculated based on the difference between the value of the detected moving speed and the target speed corresponding to the number of remaining tracks, and the linear actuator is driven by this. Therefore, the detected moving speed is controlled so as to follow the target speed.

On the other hand, the performance of the seek operation is evaluated by guiding the optical head to the target track at high speed and accurately pulling it into the target track. In order to realize the accurate pull-in operation to the target track, it is essential that the relative speed of the optical head when reaching the target track is stably within the pullable speed range, and this condition is not satisfied. And the seek operation fails. Therefore, the speed at which a stable pull-in operation can be achieved is
That is, a speed control system is required which can be prepared as the final target speed before the remaining number of tracks is 0, 1/2 track or 1/4 track and the optical head can surely follow the final target speed.

From the above requirements, it has been necessary to set the final target speed value to a value at which pull-in can be realized with a high probability. At the same time, the target speed near the target track, that is, when the number of remaining tracks is small,
It is necessary to set the value in the graph shape as shown in FIG. 5, for example, so that the amount of change becomes zero or negative as the number of remaining tracks decreases.

However, in the seek operation based on the target speed thus designed, there is always a speed deviation defined by the speed control band. Therefore, when decelerating to the final target speed, increasing the decelerating acceleration inevitably increases the deviation. For example, in order to realize high-speed movement to the target track, a large speed is used as the target value near the target track position, and the amount of change in the target speed thereafter is set to a large negative value to increase the deceleration to the final target speed. If this is attempted, the speed deviation near the target track position will increase due to the above action.

As a means for compensating for this and ensuring the trackability to the final target speed, the target speed value between the target track and the front several tracks is made equal to the value of the final target speed, and the trackability is secured. The deceleration to the track position, that is, the amount of change in the target speed with respect to the decrease in the number of remaining tracks is gradually reduced, or a second deceleration is provided as shown in FIG. 6 to determine the amount of speed deviation at the target track position. Measures such as reduction have been taken.

However, with the compensation method as described above, although the followability to the target speed can be secured as shown in FIG. 7, the target speed near the target track position does not become zero and has a small deviation. The actuator for moving the optical head continues to be driven at a low speed for a long time until the target track is reached. That is, in order to ensure the followability to the final target speed, the moving time to the target track becomes long, and this cannot be shortened.

[0010]

The above-mentioned deviation is
It was defined by the speed control band and was difficult to remove. On the other hand, in order to shorten the travel time to the target track, it is necessary to maintain a high speed as close as possible to the target track position and increase the deceleration thereafter, but if this acceleration increases, the deviation will also increase. It gets bigger. In the conventional target speed design method, the upper limit is set to the deceleration acceleration so that the deviation amount does not become too large, and at the same time, the change amount of the target speed value near the target track position is made small, especially the same value as the final target speed. The target speed is set to a relatively long time, and the deviation is controlled to be absorbed.
In other words, in order to ensure that the speed on the target track follows the final target speed, the target speed for several tracks up to the target track must be set to the same as the final target value on the target track. Since the actuator is continuously driven at a low speed for a long time near the target track position, there is a problem in that the movement time of the optical head is shortened.

Therefore, in order to solve the above-mentioned problems, it is an object of the present invention to provide an optical disk device capable of stably setting the final target speed and shortening the time required to move to the target track.

[0012]

In order to achieve the above object, the present invention provides a movable body, an objective lens mounted on the movable body, which forms an optical spot on an optical disk surface having an information recording track, and The moving means for moving the movable body in the direction crossing the information recording track, the moving speed detecting means for detecting the moving speed of the movable body, and the signal generated by the optical spot crossing the track are used to set the target. Target speed generating means for outputting the target speed of the movable body and a target output from the target speed generating means so that the target speed before the track becomes a value smaller than the final target speed when the target track is reached. The optical disk device has a speed and a control means for controlling the moving means by using the moving speed detected by the moving speed detecting means.

Here, the target speed generating means may be configured to output a target speed smaller than the final target speed in the course of reaching the target track, and then output a target speed higher than the final target speed. it can.

The target speed generating means may be configured to maintain an output of a positive target speed in the course of reaching the target track. According to the present invention configured as described above, when controlling the movement of the movable body equipped with the objective lens, for example, the target speed stored as a value corresponding to the number of tracks up to the target track is set in front of the target track. It is possible to control the speed to be a value smaller than the final target speed. Therefore, even in the vicinity of the target track position, the speed deviation can be absorbed with a large deceleration force, and the final target speed can be settled quickly. Further, since the target speed can be increased to the vicinity of the target track position, the moving time to the target track can be shortened.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a device configuration diagram of an optical disk device of the present invention. Information recording tracks are formed in a spiral or concentric pattern on the surface of the optical disc 1, and are mounted on the disc motor 2. The disk motor 2 is rotationally driven at a predetermined speed by the disk motor driving device 3.

At a position close to the optical disc 1, an optical head (movable body) 4 is arranged so as to be movable in the radial direction of the optical disc 1. By controlling the movement of the optical head 4, it is possible to accurately move / stop the optical disc 1 to a predetermined position in the radial direction.

Various optical elements are built in the optical head 4. The laser light emitted from the semiconductor laser oscillator 5 is converted into parallel light by the collimator lens 6, passes through the polarization beam splitter 7, passes through the λ / 4 plate 8 and is reflected upward by the rising mirror 9. Then, it is converged on the rotating optical disc 1 through the objective lens 10 to form an optical spot.

On the other hand, the laser light reflected from the optical disk 1 returns from the objective lens 10 to the polarization beam splitter 7, is reflected by the polarization beam splitter 7 in the direction of 45 degrees, and enters the split photodetector 11. The light incident on the split photodetector 11 is photoelectrically converted by the split photodetector 11, and the photoelectrically converted signal is output by the adder / subtractor amplifier circuit 12 as a sum signal and a tracking error signal.

The track counter circuit 13 uses the tracking error signal and the sum signal output from the add / subtract amplifier circuit 12 to generate a track detection pulse. The track detection pulse signal is output to the speed detecting means 15 and the target speed generating means 14, respectively.

The speed detecting means 15 receives the track detecting pulse from the track counter circuit 13 and calculates the reciprocal of the cycle of the track detecting pulse to generate the relative speed between the optical head 4 and the optical disk 1. This relative speed signal is output to the linear actuator drive control circuit 17.

In the target speed generating means 14, a track detection pulse is inputted from the track counter circuit 13 and the track detection pulse is used to down-count or up-count the passing tracks to thereby determine the number of remaining tracks up to the target track. To calculate.

A target speed corresponding to the number of remaining tracks is stored in the memory (storage means) 16 in advance in the form of a table. When the target speed generating means 14 calculates a target speed value corresponding to the number of remaining tracks, the target speed is referenced from the memory 16. This target speed is output to the linear actuator drive control circuit 17.

The target speed generating means 14 may be configured to calculate the target speed by an arithmetic expression prepared in advance instead of reading it from the memory 16. The track counter circuit 13 and the target speed generating means
14, for details of the speed detecting means 15, see JP-A-5-36095.
Japanese Patent Publication No. 5 (page 11, line 11 to page 7, line 7), JP-A-5-89485 (specially page 3, line 12 to page 6,
Since it is described in the 7th line), detailed description is omitted here. Further, the target speed generating means 14 and the speed detecting means 15 may be configured to perform calculation in consideration of the eccentricity component due to the eccentricity of the optical disc 1.

The linear actuator drive control circuit 17 takes in the target speed signal output from the target speed generating means 14 and the moving speed signal output from the speed detecting means 15, and outputs a drive signal based on the difference between these signals. Calculate,
Output to the linear actuator (moving means) 18.

The linear actuator 18 moves the optical head 4 in the track traverse direction (radial direction of the optical disk 1) based on the drive signal from the linear actuator drive control circuit 17.
Move to

In the present invention having the above-mentioned structure, the target velocity is generated as follows. As shown in FIG. 2, the target speed in this embodiment is set to be smaller than the final target speed in the vicinity (front) of the target track position. This is completely different from the conventional method (see FIG. 5) in which the target speed of the same value as the final target speed is set. The target speed of the present invention is stored in the memory 16 in a form corresponding to the number of remaining tracks up to the target track.

Here, as is apparent from FIG. 2, the final target speed is always set to a positive value. If the target speed is designed to have a value smaller than the final target speed in the vicinity of the target track position, it is theoretically possible to set the target speed to be negative in an extreme case. However, having a negative target speed means that the optical head may run backward in the direction in which seek should be originally performed, which is not preferable in practice. Therefore, the target speed should always maintain a positive value,
It is appropriate and practical to set negative or zero values as little as possible.

When the seek operation is performed using the target speed in the graph shape shown in FIG. 2, the relationship between the relative speed (with the optical disk 1) of the optical head 4 and the target speed is as shown in FIG. . As is clear from the figure, it can be seen that the final target speed is settled in a short time as compared with the conventional technique shown in FIG.

Further, looking at the relationship between the minimum value of the target speed and the final target speed, the speed deviation Ev at the end of deceleration when the deceleration acceleration is constant is as the control band Fv and the deceleration acceleration D.

[0030]

## EQU1 ## Ev = D / (2πFv) Equation (1) is given. Based on this relationship, in order to quickly remove the theoretically estimated speed deviation, it is possible to adopt a method of setting the minimum target speed value to be smaller than the final target speed value by Ev. it can.

Further, the speed detection by the speed detection means 15 is
Due to the appearance of unique characteristics depending on the detection method and the like, the detection is performed with a slight detection delay as shown in FIG.
Therefore, especially when the optical head 4 is decelerating, the speed detecting means 15 detects a speed higher than the actual speed. Detection speed is linear actuator drive control means 17
At the time of generating the drive signal in (1), since it is used for subtraction from the target speed, a deceleration force larger than the deceleration to be performed with respect to the actual speed is generated. Further, this effect becomes more remarkable as the actual speed of the optical head 4 becomes slower, and the speed is excessively reduced from the theoretically desired value.

On the other hand, if the target speed in the vicinity of the target track position is set too small with respect to the final target speed, the above effect is further promoted, which is not appropriate. Therefore, in practice, it is considered that there is a smaller amount of deviation than the speed deviation Ev calculated from equation (1), and to offset this, the difference Ve between the final target speed and the minimum target speed Ve However, it is preferable to set it so that it is smaller than Ev (Fig. 2).

Further, the graph shape of the target velocity near the target track position needs to be one that does not excite the vibration characteristics and electrical characteristics of the optical head 4. Therefore, it is appropriate to set the graph shape of the target speed until the minimum value of the target speed is reached and the graph shape of the increase from the minimum value to the final target speed to be as smooth as possible.

As described above, the target speed set in the present invention is considered so that it can have a relatively large deceleration even near the target track position. for that reason,
Seek operation, which requires rapid deceleration of the optical head,
In particular, it is extremely effective in seek operation when the distance between moving tracks is short.

Generally, at the initial stage of the seek operation, it is necessary to accelerate and control the optical head during the tracking operation so as to have a sufficiently large positive velocity with respect to the target track so as not to lose the eccentric velocity due to the eccentricity of the optical disk. is there. Since the initial acceleration force of the optical head is almost the same for long distance seeks and short distance seeks, such acceleration control is necessary regardless of seek distances.

However, in the case of a short-distance seek operation, there is no sufficient time margin for deceleration with respect to the initial acceleration. Therefore, in the conventional way of giving the target speed, the initial acceleration near the target track position There is a high possibility that the target track will be reached at a high speed due to the effect of. Therefore,
The shorter the seek operation distance, the more the target speed effect of the present invention will be exhibited.

In practice, it is preferable to apply the target speed of the present invention to seek operations of about 30 tracks or less. In this case, it is preferable to store them individually in the memory 16 so as to be distinguished from the target speed when performing long distance seek.

Then, when the seek operation is started, the track counter circuit 13 calculates the number of remaining tracks. If the number of remaining tracks obtained by the calculation is 30 tracks or less, the target speed table for seek of 30 tracks or less is selected from the target speed tables stored in the memory 16 so that the target speed table is selected. The speed generating means 14 is controlled. In this case, the target speed generating means 14 may calculate the target speed without referring to the memory 16. For example, the target speed may be calculated only in the seek operation of 30 tracks or less.

[0039]

As described above, according to the present invention, an optical disk device capable of shortening the time required to move to a target track is realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a device configuration of an optical disc device of the present invention.

FIG. 2 is a diagram in which an example of the target speed of the optical head proposed in the present invention is plotted on the horizontal axis and the number of remaining tracks is plotted on the vertical axis.

FIG. 3 is a diagram showing an actual moving speed of the optical head when a seek operation is performed using the target speed shown in FIG.

FIG. 4 is a diagram showing a relationship between a moving speed of an optical head and a detection speed during deceleration control.

FIG. 5 is a diagram showing a design example of a target speed in a conventional optical disk device.

FIG. 6 is a diagram showing another design example of the target speed in the conventional optical disc device.

FIG. 7 is a diagram showing an actual velocity of the optical head when a seek operation is performed using the design example of the target velocity shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Optical disk 2 ... Disk motor 3 ... Disk motor drive device 4 ... Optical head (movable body) 5 ... Semiconductor laser oscillator 6 ... Collimator lens 7 ... Polarization beam splitter 8 ... λ / 4 plate 9 ... Stand-up mirror 10 ... Objective lens 11 ... Divided photodetector 12 ... Addition / subtraction amplifier circuit 13 ... Track counter circuit 14 ... Target speed generation means 15 ... Speed detection means 16 ... Memory (storage means) 17 ... Actuator drive control circuit 18 ... Linear actuator (moving means)

Claims (3)

[Claims] 1. A movable body, an objective lens mounted on the movable body for forming an optical spot on an optical disk surface having an information recording track, and a moving means for moving the movable body in a direction crossing the information recording track. A moving speed detecting means for detecting the moving speed of the movable body, and a final target speed when the target speed before the target track reaches the target track, using a signal generated by the optical spot crossing the track. A target speed generating means for outputting a target speed of the movable body, a target speed output from the target speed generating means, and a moving speed detected by the moving speed detecting means are used so as to have a smaller value than And a control means for controlling the moving means. 2. The target speed generating means outputs a target speed smaller than a final target speed in the course of reaching the target track, and then outputs a target speed higher than the final target speed. 1. The optical disk device described in 1. 3. The optical disk apparatus according to claim 1, wherein the target speed generating means maintains an output of a positive target speed in the process of reaching the target track.