JPH10154335A - Access controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a speed control just before the pull-in of a tracking servo to a target track by measuring a period in which a light beam traverses a track plural times whilst the light beams moves the inside of one track pitch. SOLUTION: A controller 11 obtains a track traversing speed value at which an optical head 3 is moving by reading out a track traversing speed value corresponding to a count value from a groove period detecting circuit 9 from a memory 12. When the track traversing speed becomes a value of not larger than a prescribed value, a traversing speed traversing one track is divided into prescribed four cases to be measured and measured traversing speeds are stored in the memory 12 and the ratio of variations of these data with respect to a time required to traverse a quarter track pitch is obtained and amounts equivalent to the variations are corrected when the times are converted into speeds. Thus, the wasteful time of a control system is reduced and the error of the track traversing speed from a target speed is made smaller by performing a track traversing period detection every quarter track pitch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an apparatus used for recording and reproducing information on and from a recording medium, and more particularly to an access control apparatus used when moving a recording or reproducing position.

[0002]

2. Description of the Related Art Conventional access control will be described by taking an optical disk device as an example. An optical disc has a plurality of concentric or spiral tracks on a recording surface.
Information is recorded along this track. During recording or reproduction, the optical disk device rotates the optical disk and irradiates the track with a light beam emitted from an optical head. From the reflected light of the irradiated light beam, a track error signal indicating a deviation amount between the light beam irradiation position and the track is generated. By moving the irradiation position of the light beam in the radial direction of the disk based on the track error signal, tracking control for causing the light beam to follow the track is performed.

When the light beam is moved to another track, the tracking control is stopped and the light beam is moved in the radial direction of the disk toward the target track. Each time the light beam traverses the track, a sinusoidal tracking signal is generated. At this time, by continuously detecting the track error signal, the number of tracks crossed by the light beam can be counted. When the number of tracks crosses a predetermined number, the movement of the light beam may be stopped.

While the light beam is moving, the moving speed is controlled. That is, by detecting the moving speed of the light beam, the moving speed of the light beam is controlled to be equal to the target moving speed as compared with the target moving speed. The groove period can be detected based on the track error signal. When the light beam is crossing the track, the track error signal is detected as a sine wave signal, and the period of the track error signal is obtained. Assuming that the track pitch is constant, the reciprocal of the cycle of the track error signal can be obtained, whereby the track crossing speed of the light beam (that is, the moving speed of the light beam) can be obtained.

In order to make the light beam follow the track again, the moving speed of the light beam is reduced, and tracking control is performed at the timing when the light beam comes on the track. In the tracking control, the position information is fed back so that the track error signal indicating the deviation of the light beam from the track center becomes zero.

[0006]

In the prior art as described above, when the light beam is moved to the target track, the tracking control is performed again at the timing when the light beam reaches the target track. When performing tracking control, it is necessary to perform tracking again under the condition that the moving speed of the light beam is equal to or higher than a certain value.

When the moving speed is increased, the overshoot at the time of pulling in the tracking servo becomes large, which causes a problem that the dynamic range of the tracking control is exceeded and the tracking servo cannot be performed. If the moving speed is reduced, there is a problem that the interval between track traverses becomes longer, the arrival at the target track is delayed, and the control system becomes unstable.

The present invention has been made in consideration of the above-mentioned conventional problems, and has as its object to provide an access control device capable of stably performing speed control immediately before pull-in of a tracking servo.

[0009]

Means for Solving the Problems To solve the above problems,
An access control device according to the present invention includes a beam irradiation unit that irradiates an optical disk having a plurality of concentric or spiral tracks on a recording surface with a light beam, and a moving unit that moves the beam irradiation unit in a desired track direction. A cycle detecting means for detecting a cycle in which the light beam crosses a track while the beam irradiation means is moving; a means for deriving a track crossing speed value from a cycle detected by the cycle detecting means; And a speed control means for controlling a moving speed of the beam irradiation means based on a result of comparing the target speed value and the target speed value, wherein the cycle detection means has a level of the track error signal at a predetermined value. And the time interval between the point at which the level of the total light amount signal reaches a predetermined value, and a plurality of points are measured while the light beam moves within one track pitch. And configured to perform a period measurement.

The "certain value" of the level of the track error signal is a center value of the amplitude of the track error signal, and the "certain value" of the level of the total light amount signal is May be set as the center value of the amplitude.
Also, the present invention provides a beam irradiation means for irradiating an optical disk having a plurality of concentric or spiral tracks on a recording surface with a light beam, and a moving means for moving the beam irradiation means in a desired track direction. A cycle detecting means for detecting a cycle in which the light beam crosses a track while the beam irradiation means is moving; a means for deriving a track crossing speed value from a cycle detected by the cycle detecting means; and A speed control unit for controlling a moving speed of the beam irradiation unit based on a result of comparison with a target speed value, wherein the period detection unit has a level of the total light amount signal having a predetermined value. A time interval between a point and a point at which the differentiated output level of the total light amount signal reaches a predetermined value is measured, and a period meter is used a plurality of times while the light beam moves within one track. It was configured to perform.

The "determined value" of the level of the total light quantity signal is a center value of the amplitude of the total light quantity signal, and the "determined value" of the differential output level of the total light quantity signal is:
The center value of the amplitude of the differential output of the total light amount signal may be used. Also, the present invention provides a beam irradiation means for irradiating an optical disk having a plurality of concentric or spiral tracks on a recording surface with a light beam, and a moving means for moving the beam irradiation means in a desired track direction. A cycle detecting means for detecting a cycle in which the light beam crosses a track while the beam irradiation means is moving; a means for deriving a track crossing speed value from a cycle detected by the cycle detecting means; and Speed control means for controlling a moving speed of the beam irradiation means based on a result of comparison with a target speed value, wherein the level of the focus error signal has reached a predetermined value. A time interval between a point and a point where the level of the total light amount signal reaches a predetermined value is measured, and a plurality of periodic measurements are performed while the light beam moves within one track. It was configured to perform.

The "certain predetermined value" of the level of the focus error signal is a center value of the amplitude of the focus error signal, and the "certain value" of the level of the total light amount signal is May be set as the center value of the amplitude. The plurality of times may be four times.

[0013]

FIG. 1 is a block diagram showing the configuration of an access control device according to an embodiment of the present invention. In FIG. 1, a plurality of concentric or spiral tracks are formed on an information recording surface of an optical disc 1. A convex portion on which information is recorded is a land portion, and a concave portion which is a groove is a groove portion. The spindle motor 2 rotates the optical disc 1. The optical head 3 irradiates a light beam 4 on the recording surface of the optical disc 1. The actuator 5 includes the optical head 3
Is moved in the radial direction of the optical disk 1 (the direction crossing the track).

The reflected light of the light beam 4 applied to the optical disk 1 returns to the optical head 3. The light is received by a photodetector (not shown) in the optical head 3 and converted into an electric signal. The electric signal is input to a track error (hereinafter, TE) signal generation circuit 6 and a total light quantity (hereinafter, IT) signal generation circuit 7. The TE signal generation circuit 6 generates and outputs a signal (TE signal) having a level corresponding to the amount of displacement of the light beam 4 on the optical disk 1 between the irradiation position on the optical disk 1 and the center of the land in the disk radial direction.

Similarly, the IT signal generation circuit 7 generates and outputs a signal (IT signal) having a level corresponding to the amount of the light beam 4 reflected on the optical disk 1. The IT signal is
When the light beam 4 irradiates the center of the land of the disk, it has the maximum level, and when it irradiates the center of the groove, it has the minimum level. The TE signal is fed back to the optical head 3 when performing control (tracking control) to keep the irradiation position of the light beam 4 to follow a certain track, and the irradiation position of the light beam 4 is changed according to the level of the TE signal. Used for control to fine-tune in the direction.

The operation for moving the irradiation position of the light beam 4 to another track from the state where the tracking control is performed (ie, the state where the irradiation position of the light beam 4 is following a track) is as follows. become that way. First,
The tracking control is stopped, and the actuator 5 starts moving the optical disk 1 in the radial direction with the optical head 3 directed to a desired track. When the optical head 3 moves in the radial direction, the irradiation position of the light beam 4 on the optical disk 1 crosses tracks one after another.

As a result, the TE signal output from the TE signal generation circuit 6 becomes a sine wave signal. At this time, I
The T signal is also a sine wave signal, but the waveform of the IT signal is
There is a case where the phase is advanced by 90 degrees from the TE signal or a case where the phase is delayed by 90 degrees depending on the crossing direction of the groove. The TE signal and the IT signal are input to the track crossing detection circuit 7. Track crossing detection circuit 7
Detects that the light beam 4 has crossed the 1/4 track pitch.

This detection can be performed as follows. (1) Each of the TE signal and the IT signal is binarized at a predetermined comparator level (for example, the level of the amplitude center value). Each time the TE signal traverses one track, it becomes a one-cycle sine wave signal. When the light beam reaches the center of the land and the center of the groove, the TE signal is expected to be at the amplitude center value level. On the contrary,
The IT signal is expected to be 90 degrees out of phase with respect to the TE signal, and to have the amplitude center value level when the light beam reaches the center of the land and the groove. Therefore, 2
A detection signal (1/4 track crossing detection signal) may be output when each of the quantified signals rises and falls. (2) Create a differential signal of the TE signal. TE that is sinusoidal
By differentiating the signal, a sinusoidal signal having a phase shifted by 90 degrees is obtained. That is, it can be used instead of the IT signal in the case of (1). Therefore, it is sufficient to output a 1/4 track crossing detection signal in the same manner as (1).

As described above, the 1/4 track crossing detection signal output from the track crossing detection circuit 7 is output to the groove cycle detection circuit 9. The groove cycle detection circuit 9 measures the cycle at which the track crossing detection signal is input.
This measurement is performed by a clock generator that generates a reference clock having a constant frequency sufficiently higher than the frequency of the track crossing detection signal (in other words, a reference clock having a constant period sufficiently shorter than the cycle of the track crossing detection signal). make use of,
What is necessary is just to count how many reference clocks are output after the detection signal is input and before the next detection signal is input. Then, the count value is output to the controller 11.

The memory 12 stores a groove crossing speed deriving table. Assuming that the track pitch is L, the count value output from the groove cycle detection circuit 9 is N, and the frequency of the reference clock used for counting in the cycle detection circuit 8 is F, the track crossing speed Vs is Vs = 1/4 * L -It can be obtained by F / N. The groove crossing speed deriving table in the memory 12 stores a track crossing speed value corresponding to the count value from the groove cycle detection circuit 9 calculated based on the above equation.

The controller 11 reads out the track traversing speed value corresponding to the count value from the groove period detecting circuit 9 from the memory 12 to obtain the track traversing speed value while the optical head 3 is moving. Controller 1
1 sets the moving number (the number of tracks to be traversed) in the remaining track counter 10 when moving the light beam 4 to another track. 1/4 of track crossing detection circuit 8
The track crossing detection signal is also input to the remaining track counter 10, where the signal is frequency-divided and the remaining number of tracks is counted.
When the 1/4 track crossing detection signal is input four times, the number of movements may be reduced by one.

When the number of movements is 20 or less, and when the number of movements is 90 or less from the beginning, an acceleration / deceleration command is used as an acceleration / deceleration pulse based on the difference between the groove crossing speed value and a constant reference movement speed value. Feedback is provided to the actuator 5 via the D / A converter. The actuator 5 controls the moving speed of the optical head 3 according to the polarity and level of the difference signal. For example, when the track traversing speed value is smaller than the reference moving speed value, the moving speed of the optical head 3 is accelerated, and when it is opposite, the speed is reduced. The acceleration amount and the deceleration amount are determined according to the level of the difference signal.

When the track traversing speed value falls below a predetermined value (that is, when the optical head 3 approaches the target track and the speed decreases), the controller 11 sets the traversing speed during traversing one track as follows: Measurements are made separately for cases 1) to (4). (1) From the time when the level of the TE signal becomes the compare level to the time when the level of the IT signal becomes the compare level (during this time, the level of the IT signal is smaller than the compare level) (2) The IT signal From the time when the level of the TE signal becomes the compare level to the time when the level of the TE signal becomes the compare level (during this time, the level of the IT signal is larger than the compare level). From when the signal level reaches the comparator level to when the level of the IT signal reaches the comparator level (during this time, the level of the IT signal is higher than the comparator level). (4) When the level of the IT signal reaches the comparator level From when the level of the TE signal reaches the compare level (the level of the IT signal is For the case of Toreberu less than) the above (1) to (4), stores the measured transverse velocity values in the memory 12. And the above (1)-
The average of the data stored in the memory 12 is calculated for each case (4). 1/4 of each of (1) to (4)
The ratio of the variation to the time required for traversing the track pitch is obtained, and the variation is corrected when the speed is converted.

Traversing a 1/4 track pitch should take 1/4 the time required to traverse a track. However, when the 1/4 track traversing speed is to be obtained based on the levels of the TE signal and the IT signal as described above,
Since the phase of the signal and the IT signal are not always exactly shifted by 1/4 cycle (90 degrees), each of the speed values obtained in the above (1) to (4) may be different from the actual 1/4 track crossing. Variation occurs compared to the speed value. Therefore, as described above, the ratio of the variation is determined in advance, and the variation is corrected when the actual speed is detected.

With the above configuration, the track crossing period can be detected at every 1/4 track pitch. As a result, the waste time of the control system is reduced, the control band is increased, and the error of the track crossing speed from the target can be reduced. Further, it is possible to correct the groove cycle variation of the four divided areas within one track pitch when detecting the track crossing cycle.

[0026]

As described above, according to the present invention, the period in which the light beam crosses the track can be measured a plurality of times while the light beam moves within one track pitch. Therefore, even if the waste time of the control system is reduced and the moving speed of the light beam is reduced, the speed control immediately before the tracking servo is drawn into the target track can be stably performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an access control device according to an embodiment of the present invention.

[Explanation of symbols]

1: optical disk, 2: spindle motor, 3: optical head, 4: light beam, 5: actuator, 6: track error signal generation circuit, 7: total light amount signal signal generation circuit,
8: track crossing detection circuit, 9: groove cycle detection circuit, 1
0: remaining track counter, 11: controller, 12:
memory.

Claims (7)

[Claims] 1. A beam irradiation means for irradiating an optical disk having a plurality of concentric or spiral tracks on a recording surface with a light beam; a moving means for moving the beam irradiation means in a desired track direction; Cycle detecting means for detecting a cycle in which the light beam crosses a track while the beam irradiation means is moving; means for deriving a track crossing speed value from a cycle detected by the cycle detecting means; the speed value and a target Based on the result of comparing with the speed value,
Speed control means for controlling the moving speed of the beam irradiating means, wherein the period detecting means determines that the level of the track error signal has a predetermined value and the level of the total light amount signal has An access control device for measuring a time interval between the light beam and a point at which the light beam reaches a predetermined value, and performing a plurality of period measurements while the light beam moves within one track pitch. 2. A "certain value" of the level of the track error signal is a center value of the amplitude of the track error signal, and a "certain value" of the level of the total light quantity signal is 2. The access control device according to claim 1, wherein a central value of the amplitude of the light amount signal is used. 3. A beam irradiation means for irradiating an optical disk having a plurality of concentric or spiral tracks on a recording surface with a light beam; a moving means for moving the beam irradiation means in a desired track direction; Cycle detecting means for detecting a cycle in which the light beam crosses a track while the beam irradiation means is moving; means for deriving a track crossing speed value from a cycle detected by the cycle detecting means; the speed value and a target Based on the result of comparing with the speed value,
Speed control means for controlling a moving speed of the beam irradiation means, wherein the cycle detection means determines that a point at which the level of the total light quantity signal has reached a predetermined value and a differential output level of the total light quantity signal has Measure the time interval from the point where a certain value is reached,
An access control device, wherein a plurality of periods are measured while the light beam moves within one track. 4. A "determined value" of the level of the total light amount signal is a center value of the amplitude of the total light amount signal, and a "determined value" of the differential output level of the total light amount signal is:
4. The access control device according to claim 3, wherein a center value of an amplitude of a differential output of the total light amount signal is set. 5. A beam irradiating means for irradiating an optical disk having a plurality of concentric or spiral tracks on a recording surface with a light beam; a moving means for moving said beam irradiating means in a desired track direction; Cycle detecting means for detecting a cycle in which the light beam crosses a track while the beam irradiation means is moving; means for deriving a track crossing speed value from a cycle detected by the cycle detecting means; the speed value and a target Based on the result of comparing with the speed value,
Speed control means for controlling a moving speed of the beam irradiation means, wherein the cycle detection means determines that a point of a focus error signal has a predetermined value and a level of a total light amount signal has a predetermined value. An access control apparatus for measuring a time interval between the light beam and a point at which the light beam reaches a predetermined value, and performing a plurality of period measurements while the light beam moves within one track. 6. The "certain value" of the level of the focus error signal is a center value of the amplitude of the focus error signal, and the "certain value" of the level of the total light amount signal is 6. The access control device according to claim 5, wherein a central value of the amplitude of the light amount signal is used. 7. The access control device according to claim 1, wherein the plurality of times is four times.