JPH04302827A - Optical disk device - Google Patents

Abstract

PURPOSE:To reduce the speed error generating amount at the time of changing over from the acceleration to deceleration in the speed control operation of a head movement mechanism at the track access time, by changing the setting of maximum speed value for a reference speed signal in accordance with the moving distance. CONSTITUTION:A track error signal is counted by a counter 2 after the waveform is rectified by a waveform rectifying circuit 1, and the counted value is sent to a microprocessor 4. By the microprocessor 4, the reference speed value corresponding to the moving distance up to an objective track from the counted value is sent to a D/A converter 5. At this time, the maximum speed value in accordance with the moving distance and the reference speed value corresponding to the remained moving distance are compared by the microprocessor 2, and when the reference speed value is higher than the maximum speed value, the maximum speed value is outputted. The output of a waveform rectifying circuit 1 is converted to the speed signal by an F/V conversion circuit 3 and subtracted with the reference speed by a differential amplifier 6 then sent to an optical head moving means 7 to drive the optical head movement mechanism.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc device, and more particularly to an optical disc device that records and reproduces information using a light beam.

0002

2. Description of the Related Art In optical disk drives, there is a reference speed setting device for controlling the speed of a head moving mechanism when positioning a beam spot on a target track.

[0003]This reference speed setting device, during recording and reproduction,
When positioning the beam spot on the target track, the difference between the current track and the target track is determined, and rough positioning is performed by the head moving mechanism. Then, track pull-in is performed, and then a precise positioning operation is performed by track jumping. During this rough positioning operation, the head is positioned by counting the number of tracks traversed, determining the error from the target track, and setting a reference speed according to the amount of error.

The speed of the head moving mechanism is determined by converting the frequency of the track error signal when crossing the track to F/V (frequency/voltage) to obtain the relative moving speed between the medium track and the optical head. There is. The reference speed VF for speed control when controlling the speed of the head moving mechanism is acceleration A,
If the distance is X,

[Math 1]

[0005]*IMG[001] has been done.

By the way, in an optical disk device, there is a reference speed generating device for controlling the speed of a head moving mechanism and moving it when positioning a beam spot on a target track.

This reference speed generating device determines the difference between the current track and the target track when positioning the beam spot on the target track during recording and reproduction. after that,
Rough positioning is performed using the head moving mechanism, and after this,
The beam spot is moved onto the target track by performing a precise positioning operation using a track jump operation.

[0009] Here, the rough positioning operation by the head moving mechanism is determined by determining the moving speed using a speed detector attached to the head moving mechanism, or by converting the frequency of the tracking error signal during movement from F/V. sought by,
This is done by moving near the target track by controlling the moving speed according to the reference speed. The reference speed VF at this time is as follows, where A is the acceleration and X is the distance between the current track and the target track.

[Math 2]

[0010]*IMG[001]

It is set as follows. This is a formula that gives the speed versus distance when decelerating with constant acceleration. Therefore, the reference speed is the difference between the target track and the current track.

0012

[Problems to be Solved by the Invention] In the reference speed setting of the reference speed setting device described above, when controlling the speed of the head moving mechanism, when switching from acceleration to deceleration in a track access operation with a long stroke, the change in acceleration at this time is Therefore, even if a tracking error occurs with respect to the reference speed, it is small compared to the actual traveling speed, and the response time for tracking can be secured, so the speed error near the target track hardly becomes a problem.

[0013] When accessing a truck over a short distance, the speed error when switching from acceleration to deceleration cannot be ignored with respect to the actual traveling speed, and the reference speed setting acts in the direction of increasing acceleration. , it becomes impossible to secure a sufficient response for tracking. For this reason, the speed error near the target track becomes large, and the speed cannot be sufficiently reduced to a level at which the track can be retracted stably. Therefore, it is necessary to stabilize track pull-in by reducing the acceleration during deceleration and reducing the speed error when switching from acceleration to deceleration, which is a factor that limits high-speed access.

On the other hand, in the reference signal generating device described above, in the case of coarse positioning (hereinafter referred to as coarse seek) operation, the reference speed and the actual movement speed do not match at the start of the operation, and the maximum acceleration that the movement mechanism can generate Increase speed at . When the reference speed and the moving speed match, a deceleration operation is performed in accordance with the change in the reference speed (deceleration at a constant acceleration). At this time, when switching from acceleration to deceleration, a delay time occurs in switching from acceleration current to deceleration current, so the traveling speed exceeds the reference speed, and a follow-up delay with respect to the reference speed occurs.

Therefore, the actual operating speed is as shown in FIG. Here, in a coarse seek operation over a long distance, it is possible to catch up to the reference speed before stopping. but,
In a short distance coarse seek operation, the reference speed becomes 0 before it can follow the reference speed during deceleration, so the speed accuracy at the end of the coarse positioning operation cannot be obtained, and the constant speed running time for speed stabilization is reduced. It is necessary to keep the speed offset small by either providing a For this reason, the time required for rough positioning increases, which is a factor that limits high-speed seek.

An object of the present invention is to eliminate such drawbacks and to improve the speed control operation of the head moving mechanism during seek.
An object of the present invention is to provide an optical disc device that can reduce the amount of speed offset that occurs when changing from an acceleration state to a deceleration state by changing the setting of the maximum speed value of a reference speed signal depending on the moving speed.

[0017]

[Means for Solving the Problems] The present invention provides an optical disk drive in which an optical head moving mechanism is moved based on a tracking error signal from an optical head, and when performing a track access operation to a target track based on the tracking error signal, the optical When setting the reference speed for moving the head movement mechanism, the maximum speed value of the reference speed is switched according to the distance between the current track address and the target track, and the error signal generated based on the switched reference speed is The optical head moving mechanism is characterized by having an error signal generation means for sending it to the optical head moving mechanism.

The present invention also provides a coarse seek operation in which the optical head moving mechanism is moved near a target track in an apparatus for moving an optical disk based on a tracking error signal from the optical head. When performing speed control of the optical head moving mechanism, a constant speed running section is provided between the acceleration operation and the deceleration operation of the reference speed signal for controlling the speed of the optical head moving mechanism, and the error signal generated based on the reference speed provided in this section is It is characterized by having an error signal generating means to be sent to the head moving mechanism.

[0019]

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

FIG. 1 is a block diagram showing one embodiment of the present invention. The optical disc device in FIG. 1 includes a waveform shaping circuit 1, a counter 2, an F/V conversion circuit 3, a microprocessor 4, a D/A (digital/analog) converter 5, a differential amplifier 6, and an optical head. A moving means 7 is provided.

In such an optical disk device, the waveform shaping circuit 1 shapes the waveform of the track error signal and outputs the waveform to the counter 2.
and the F/V conversion circuit 3.

Counter 2 counts the number of tracks crossed,
The value is transmitted to the microprocessor 4.

The F/V converter 3 performs frequency-voltage conversion on the waveform-shaped track pulse to generate a speed signal and transmits it to the differential amplifier 6.

The microprocessor 4 calculates the distance to the target track from the value of the counter 2, and sends a reference speed signal value corresponding to the distance to the D/A converter 5.

Differential amplifier 6 subtracts the output of D/A converter 5 from the output of F/V conversion circuit 3.

The optical head moving means 7 moves the optical head moving mechanism based on the output of the differential amplifier 6.

Next, the operation of this embodiment will be explained.

The reference speed when controlling the speed of the head moving mechanism is set to decelerate at a constant acceleration with respect to the distance X to the target track, and the reference speed is set to VF and the acceleration to *IMG[001].

[0030] Here, the actual track access operation will be explained with reference to FIG. The response speed relative to the reference speed is as shown by the dotted line, and when switching from acceleration to constant speed, from constant speed to deceleration, or from acceleration to deceleration, a response delay occurs due to a change in acceleration, and an error with the reference speed occurs. This amount of error changes depending on the amount of change in acceleration, and the larger the change in acceleration, the larger the error. In addition, this speed error is not so much of a problem as long as the actual traveling speed is high, but as the speed decreases, the ratio of the speed error to the actual traveling speed increases, so it is possible to travel faster than the original speed. As a result, the setting of the speed reference signal becomes faster than the original setting time, and therefore the value becomes larger than the originally set acceleration.

Here, in order to stabilize track access with a short stroke, the shorter the stroke, the smaller the change in acceleration at the time of switching between acceleration and deceleration. However, simply setting a speed reference signal that causes the acceleration to be small relative to the distance to the target track will result in a uniform reduction in acceleration even in track access operations with long strokes, which would not cause any problems even if the conventional method was used. This results in longer track access time and lower performance.

Next, reference speed setting in this embodiment will be explained with reference to FIG.

In order to suppress the change in acceleration when switching between acceleration and deceleration, it is sufficient to reduce the amount of change in acceleration, so it is sufficient to set a reference speed that does not directly switch from acceleration to deceleration. This can be done by changing the maximum speed according to the stroke during movement, as shown in FIG. In this case, the maximum speed is limited in advance so that the acceleration operation does not directly change to the deceleration operation, and the speed error when switching from acceleration to constant speed does not have a large influence on the speed error when switching to deceleration. It is necessary to set the maximum speed.

Here, to set the maximum speed, the maximum speed value for the moving distance is stored in the same manner as the reference speed value for the moving distance that the microprocessor has, and the reference speed value for the moving distance is set as the maximum speed value. This can be done by outputting the maximum speed value to the D/A converter until it becomes equal to . It is also possible to calculate and set the maximum speed from the acceleration during acceleration and the acceleration during deceleration.

As described above, the optical disk device of this embodiment uses the current track address and the target track when setting the reference speed for moving the optical head moving mechanism in the track access operation to the target track. The vehicle is provided with means for switching the maximum speed of the reference speed according to the distance.

[0036] This enables speed control operation with less speed error during track access, and improves deceleration characteristics.

That is, in this embodiment, by changing the maximum speed of the reference speed signal according to the moving distance during track access, the acceleration-constant speed-deceleration operation is achieved, as opposed to the conventional acceleration-deceleration operation. This makes it possible to suppress the amount of change in acceleration, reduce the occurrence of speed errors with the reference speed when changing from acceleration to deceleration, and ensure stable speed tracking performance. In order to stabilize the track access operation in the Track retracting operation becomes possible.

FIG. 4 is a block diagram showing another embodiment of the present invention. The optical disc device in FIG. 4 includes a waveform shaping circuit 4
1, a counter 42, an F/V conversion circuit 43, a microprocessor 44, a D/A converter 45, a differential amplifier 46, and an optical head moving means 47.

In such an optical disc device, the waveform shaping circuit 41 shapes the waveform of the track error signal and sends it to the counter 42 and the F/V conversion circuit 43.

Counter 42 counts the number of tracks crossed by counting track crossing pulses, and transmits the value to microprocessor 44 .

The F/V conversion circuit 43 performs F/V conversion on the track crossing signal to generate a track crossing speed and transmits it to the differential amplifier 46.

The microprocessor 44 has a counter 42
The distance to the target track is calculated from the value of , and a reference speed signal value corresponding to the distance is sent to the D/A converter 45.

The differential amplifier 46 is connected to the D/A converter 45
The output of the F/V conversion circuit 43 is subtracted from the output of .

The optical head moving means 47 includes a differential amplifier 46
The optical head moving mechanism is moved based on the output.

Next, the operation of this embodiment will be explained.

When controlling the speed of the head moving mechanism, the set speed VF is as shown in FIG. 5, where the acceleration is A and the distance to the target track is X.

[Math 4]

[0047] This is the value determined by *IMG[001]. The maximum set speed curve is
This is a curve of the calculated value of the maximum speed Vc for creating a constant speed section for a certain period of time between acceleration and deceleration operations during a rough seek operation. Also, here, the maximum value of VF is limited, which is 6000 for the maximum number of tracks 18000.
The maximum speed is set to reach the speed equivalent to a truck. Here, when starting up, acceleration A1, maximum speed value Vc in the constant speed section, acceleration A2 during deceleration, moving distance X,
Assuming constant speed running time tc,

[Math 5]

[0049]

From [0050]

[Math 6]

[0051]

[0052]

Here, in order to set Vc to the speed in the constant speed section, the D/A
It is sufficient to continue sending the value of Vc to the converter 45 instead of VF. Here, the value of tc is the response time to acceleration change of the speed control system, as shown in FIG.
In other words, it is set to a value such that the response delay when the state changes from acceleration to constant speed does not have an influence until the timing of the next change from constant speed to deceleration. Here, if the servo band of the speed control system is fm, then tc is approximately tc=3/ωn~5/ωn (ωn=
It is necessary to secure approximately 2πfc). By setting tc in this way, the acceleration change during speed control operation is
Even if the state changes from maximum acceleration state to constant speed state to deceleration state at the start of seek operation, there is a constant speed state in between, so the drive current in the constant speed section is almost 0A, and deceleration occurs. The delay in current rise when the state changes is small, and the speed offset can be kept small. Therefore, the acceleration during deceleration is different from the maximum generated acceleration of the optical head moving mechanism, due to variations in generated acceleration between devices.
It is sufficient to take into account the variation in acceleration caused by disturbances and a slight delay due to electrical constants when the current rises.

Next, in the case where there are variations in the generated acceleration at the start of a seek and fluctuations in the generated acceleration due to disturbances, in this case, the minimum acceleration A1min including the variation of the acceleration A1 at the start of the seek is determined in advance. , this value may be calculated as A1 to obtain tc, and the value of Vc may be determined. This ensures the stabilization time of the speed response when changing from an acceleration state to a constant speed state due to acceleration variation at the time of startup, thereby ensuring stability during deceleration.

Next, the actual method of generating the reference speed signal will be explained.

[0056] The set speed VF is

[Math 7]

[0057]*IMG[001]

The distance Xc at which VF=Vc from the speed Vc when traveling at a constant speed is:

Therefore, for the distance X from the current track to the target track, set the value VF=Vc from X to Xc, and from Xc to 0,

[Math. 9]

[0061]*IMG[001]

It can be seen that it is sufficient to set the value obtained by [0062] as the reference speed value. This is calculated in advance by the microprocessor 44 when setting the reference speed value in the D/A converter 45.

[0063]

[Math. 10]

*IMG[001]

It is sufficient to prepare a deceleration table of the values of [0065] and a table of the values of Xc with respect to X at the start of the seek operation, and to obtain the parameters at the time of setting from this table and the distance X.

Next, a processing flow is shown in FIG. Obtain the value from the table (step S62), D/A
A value of Vc is set in the converter 45. Next, a seek operation is started (step S63), and the distance X to the target track is calculated from the value of the counter 42, and X=X
It is determined whether it has become c (step S64). When it is detected that X≧Xc, the value of VF corresponding to X is acquired from the deceleration table (step S65) and sent to the D/A converter 45. In this operation, the distance to the target
It is executed repeatedly until (step S66), and X=
It ends when it becomes 0. Through the above-described processing, it is possible to generate a speed reference signal in which a constant speed section is provided between acceleration and deceleration operations.

FIG. 8 shows the difference in rough seek time between when the reference velocity signal correction according to the present invention is carried out and when it is not carried out. However, the seek time assumes that the accelerations during startup and deceleration are equal in both cases.

[0069] The conditions are that when starting up, the acceleration is 4.0G,
When decelerating, acceleration is 3.5G, speed control servo band 400
It is assumed that the frequency is around Hz. In this case, the difference between the two is 10
It appears below 00 tracks, but the shorter the travel distance, the more
The difference is large, and even with 10 tracks, it takes about 2 to 3 ms.
It only increases, and the difference becomes invisible with long strokes. Normally, when the number of tracks is 10 or less, the access operation is performed by track jumping, so there is no effect on the travel time for distances shorter than this. In reality, without correction, the seek performance up to this point cannot be obtained, and the acceleration during deceleration is kept low for stabilization, so the seek time after correction is shorter.

In addition, in this implementation, when setting the reference speed,

[Math. 11]

[0071]

The calculation formula was used, but

[Math. 12]

[0073]

By using [0074], it is possible to suppress the speed offset during deceleration to a low level, and it is possible to further stabilize track pull-in after rough seek. Note that in Equation 12, C is a correction time coefficient.

As described above, in this embodiment, when setting the reference speed for running the optical head moving mechanism, the maximum speed corresponding to the moving distance between the current track address and the target track is set. A first storage means for storing a speed value, and a second storage means for storing a reference speed value corresponding to the remaining travel distance.
a third storage means for storing the value of the remaining travel distance for switching from the maximum speed value to the reference speed value; and a third storage means for storing the value of the remaining travel distance for switching from the maximum speed value to the reference speed value; The value is acquired from the first storage means, and the switching point from the maximum speed to the reference speed is acquired from the third storage means.
The maximum speed value is set until the remaining travel distance reaches the value obtained from the third storage means, and after that, the reference speed value is obtained from the second storage means according to the remaining distance. It is equipped with a speed value setting means for setting the speed value.

That is, in this embodiment, when generating a reference speed signal during a coarse seek operation, the maximum value of the reference speed signal is limited according to the moving distance, and the By setting in advance so that a low speed section exists for a certain period of time, it is possible to ensure that the drive current always rises from 0 and generates acceleration during deceleration when transitioning from constant speed to deceleration. .

Therefore, in a rough seek operation over a short distance, in the prior art, when the state changes from acceleration to deceleration,
There was a delay in the rise of the deceleration current, and a sufficient deceleration current could not be obtained immediately after switching, resulting in a large delay time in the speed response.However, by providing a constant speed section, the response due to the acceleration rises within the constant speed section. is statically fixed, so when decelerating, it is only necessary to consider the speed offset of the acceleration during deceleration, and when setting the acceleration for deceleration, it is only necessary to consider the variation in the maximum generated acceleration between devices and the variation in the generated acceleration due to disturbance. Therefore, high acceleration becomes easy and high-speed seek operation becomes possible.

[0078]

As described above, the present invention has the effect of reducing the amount of speed error generated when switching from acceleration to deceleration by changing the reference signal.

[Brief explanation of drawings]

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

FIG. 2 is a diagram for explaining a track access operation.

FIG. 3 is a diagram for explaining the operation of the embodiment of FIG. 1;

FIG. 4 is a block diagram showing another embodiment of the present invention.

FIG. 5 is a diagram for explaining the operation of the embodiment of FIG. 4;

FIG. 6 is a diagram for explaining a rough seek operation in the embodiment of FIG. 4;

FIG. 7 is a flowchart of reference speed signal generation in the embodiment of FIG. 4;

FIG. 8 is an explanatory diagram of rough seek time.

FIG. 9 is a diagram for explaining a speed reference signal in the prior art.

FIG. 10 is a signal waveform diagram of a coarse seek operation in the prior art.

[Explanation of symbols]

1 Waveform shaping circuit 2 Counter 3 F/V conversion circuit 4. Microprocessor 5 D/A converter 6 Differential amplifier circuit 7 Optical head moving means

Claims (2)

[Claims] 1. In an optical disk device that moves an optical head moving mechanism based on a tracking error signal from the optical head, when a track access operation to a target track is performed based on the tracking error signal, a method for moving the optical head moving mechanism is provided. When setting the reference speed, the maximum speed value of the reference speed is switched according to the distance between the current track address and the target track, and an error signal generated based on the switched reference speed is sent to the optical head moving mechanism. An optical disc device characterized by having a generating means. 2. In an optical disk device that moves an optical head moving mechanism based on a tracking error signal from the optical head, when performing a coarse seek operation in which the optical head moving mechanism is moved near a target track based on the tracking error signal, the optical A constant speed running section is provided between the acceleration operation and the deceleration operation of the reference speed signal for controlling the speed of the head moving mechanism, and an error signal generated based on the reference speed provided in this section is sent to the optical head moving mechanism. An optical disc device comprising error signal generating means.