JPH0476180B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for accessing information tracks of a recording medium in optical information recording and reproducing. The present invention relates to a method for accessing a track in a direction across the track.

[Conventional technology]

In an optical disk, which is an optical information recording medium, information recording units consisting of minute spots are arranged in a row to form an information track. The information tracks are arranged concentrically or spirally on the disk surface. When reading and reproducing recorded information from an optical disk, a light beam is irradiated onto the information track while the optical disk is rotated, and the reflected light is detected. At this time, since it is necessary to properly position the light beam spot with respect to the information track, the tracking state of the light beam is always detected from the reflected light, and control is performed to maintain a proper tracking state.

Conventionally, the following methods have been proposed as track access methods for such optical disks. That is, by using the tracking state detection signal and switching its control polarity as appropriate, the light beam spot can be moved onto a desired track by sequentially repeating the operation of first moving it between tracks and then moving it onto an adjacent track. The light beam spot is moved up to the point (S5-4 of the 1981 IEICE).

Here, the above-mentioned tracking state detection signal changes periodically as the light beam moves, and becomes zero when the light beam is irradiated onto the track and at an intermediate position between adjacent tracks, and when the light beam is irradiated on the track and at an intermediate position between adjacent tracks, the tracking state detection signal changes periodically as the light beam moves. The peak value and bottom value are taken alternately when the light is irradiated between the track and the track. The polarity is switched at a first timing while the tracking state detection signal changes from the peak value to the bottom value and at a second timing while the tracking state detection signal changes from the bottom value to the peak value.

[Problem that the invention seeks to solve]

However, in the above-described track access method, when access is made across a large number of tracks, a driving force in the same direction is continuously applied to the moving part of the optical head for irradiating the light beam, which causes the light beam to irradiate. There is a problem in that as the moving speed increases, it is difficult to stop the light beam spot on the target track. That is, in order to guide a light beam spot onto a target track, the light beam spot is stopped before it moves to the next track and normal tracking control is performed. This is because if the speed of the light beam spot on the target track is too high, the spot cannot follow the target track depending on the gain of the tracking control.

[Means for solving problems]

SUMMARY OF THE INVENTION An object of the present invention is to provide a track access method capable of solving the problems of the conventional techniques and accurately stopping a light beam on a target track.

The above-mentioned objects of the present invention include means for irradiating a light beam onto an optical information recording medium on which information tracks are arranged in parallel, a light beam deflecting means for deflecting the light beam in a direction across the tracks, and a light beam deflecting means for deflecting the light beam in a direction across the tracks. It changes periodically with the deviation of the information track, and becomes zero when the light beam is irradiated on the information track and at an intermediate position between adjacent information tracks, and when the light beam is irradiated between the intermediate position and the information track. A method for accessing a target information track using the light beam in an optical information recording/reproducing apparatus, comprising: means for detecting a tracking state detection signal that alternately takes a peak value and a bottom value when the track is being tracked; The tracking state detection signal and the tracking state at a first timing during which the tracking state detection signal changes from the peak value to the bottom value and a second timing during which the tracking state detection signal changes from the bottom value to the peak value. By applying a switching signal obtained by switching a polarity inversion signal obtained by inverting the polarity of the detection signal to the light beam deflecting means, the light beam is moved toward the target information track, and the light beam is A track access method characterized in that the light beam is stopped on the target information track by applying a braking pulse signal to the light beam deflecting means when the light beam reaches the vicinity of the target information track. will be achieved.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an embodiment of an optical information reproducing apparatus having a track access method according to the present invention.

In FIG. 1, 1 is an optical disk which is an optical information recording medium, and 2 is a motor for driving and rotating the optical disk 1 at, for example, 1800 rpm. 3 is a laser light source, 4 is a half mirror, 5 is a light beam deflection means provided with an objective lens 5A, and 6 is a photodetector. The light beam emitted from the light source 3 is converted into a parallel light beam and is reflected by the half mirror 4 to the optical disk 1.
A minute spot with a diameter of about 1 μm is formed on the optical disk 1 by the objective lens 5A. The reflected light from the disk 1 at the spot is reflected by the objective lens 5A and the half mirror 4.
and enters the photodetector 6. The photodetector 6 outputs a recording information signal and a tracking state detection signal (that is, the relative position between the beam spot irradiated onto the disk 1 and the information track). Tracking state detection can be done using push-pull method or 3
It is performed using the beam method.

7 is an inverter for inverting the polarity of the tracking state detection signal of the photodetector 6; 8 is a switch for switching between the tracking state detection signal and the output signal of the inverter 7; 11 is a bias generator;
It outputs a positive or negative bias voltage based on the movement direction signal input from the outside. A comparator 9 compares the tracking state detection signal with the bias voltage and outputs a binary signal. The polarity changeover switch 8 is controlled by the binary signal.
A counter 10 counts the binary signal output from the comparator 9, and a count start signal and a count set value signal are inputted to the counter 10 from the outside.
The counter 10 outputs a signal indicating that counting is in progress, and a switch 12 provided on the output line of the bias generator 11 is controlled by this signal. A pulse generator 13 receives a moving direction signal from the outside and generates appropriate pulses based on this signal and the output signal of the counter 10.

Reference numeral 14 denotes an adder, in which the outputs of the switches 8, 12 and the pulse generator 11 are added, and the combined output signal is input to the compensation controller 15. The compensation controller 15 deflects the optical beam deflecting means 5 in a direction substantially orthogonal to the information track of the optical disk 1 based on the composite signal, and includes a phase compensation circuit, a drive circuit, and the like.

The light beam deflection means 5 is, for example, a compensation controller 15.
The objective lens 5 has a coil whose energization amount is controlled by an output signal of the coil and a permanent magnet for generating a magnetic field at the position of the coil, and is fixed to the coil based on the electromagnetic force acting on the coil.
This is to deviate A. As the light beam deflecting means, other suitable means such as a galvanometer mirror objective lens driving type or an optical head whole driving type can be employed.

The apparatus of this embodiment is provided with a control loop for performing focusing control so that the light beam focused by the objective lens 5A forms a sufficiently small spot on the disk 1, but it is not shown here.

Next, the operation of the apparatus of this embodiment will be explained.

During normal recording information signal reproduction, the moving direction signal, counting start signal, and counting setting value signal are not input from the outside, so the spots 8 and 12 are in the state shown in the figure, and there is no output from the pulse generator 13, so
The tracking state detection signal output from the photodetector 6 is directly input to the compensation controller 15, and the light beam deflecting means 5 is controlled so that the light beam spot follows a predetermined track.

Track access, in which the light beam spot is moved in a direction across the track and positioned on a target track, will be explained with reference to FIG. FIG. 2a schematically shows how the light beam spot traverses the tracks, with O indicating the information track position and P indicating the intermediate position between the tracks. 2b shows the tracking state detection signal output from the photodetector 6, and FIG. 2c shows the bias switch 12 output from the counter 10.
2d represents the binary signal output from the comparator 9, and FIG. 2e represents the control signal of
represents the output signal of the pulse generator 13, and FIG.
represents the input signal to. In addition, in Fig. 2b,
Q ₁ and Q ₂ are positive and negative voltages corresponding to the bias voltage output from the bias generator 11, respectively, and are the threshold values of the comparator 9.

First, at time _t1 , a counting start signal is received from the outside,
When the count setting value signal and the moving direction signal are input, the bias switch 12 becomes conductive based on the counting start signal inputted to the counter 10, and also according to the moving direction signal inputted to the bias generator 11. A positive or negative bias voltage (ie, Q ₁ or Q ₂ in FIG. 2b) is output from the bias generator 11. The bias voltage is added to the tracking state detection signal at a summing point 14 and input to a compensation controller 15.

As a result, a signal for moving the light beam spot in a predetermined direction from the center of the track is input to the light beam deflecting means 5, and the beam spot starts moving.

When the tracking state detection signal reaches the threshold _Q2 at time _t2 , the binary output signal of the comparator 9 changes, which causes the changeover switch 8 to change, and the switch 8 outputs the polarity of the tracking state detection signal. The inverted signal (shown by the dotted line in FIG. 2b), ie the output of the inverter 7, is now supplied to the summing point 14.

When the tracking state detection signal reaches the threshold _Q1 at time _t3 , the binarized output signal of the comparator 9 changes, which causes the changeover switch 8 to switch, and the tracking state detection signal is added from the switch 8. It is now supplied to point 14.

Thereafter, the changeover switch 8 is similarly switched based on the binary output signal of the comparator 9.
The counter 10 counts the number of times one of the two values appears from the binary output signal of the comparator 9 (corresponding to the number of times the light beam spot crosses the track), and calculates the number of times the light beam spot crosses the track. The bias switch 12 is opened when the count reaches the set value (time t _n ). At the same time, in the pulse generator 13,
At the falling edge of the control signal of the bias switch 12, a positive or negative pulse is generated depending on the moving direction signal. In the case of FIG. 2, the input to the compensation controller 15 is from time t ₁ to t _n
In contrast, the pulse generator 13 outputs a pulse of negative polarity. Therefore, from time t _n to time t _o when the pulse is generated, the input to the compensation controller 15 is the addition of the tracking state detection signal and the pulse from the pulse generator 11, as shown in FIG. As shown in , the signal becomes a sharply negative polarity signal.

As a result, a sudden braking signal is applied to the light beam deflecting means 5 between times t _n and t _o , and the speed of the light beam spot is reduced. Therefore, after the time _to when the pulse from the pulse generator 13 disappears, the light beam spot is caused to accurately follow the target track by normal tracking control.

In the above embodiments, the width and height of the pulses generated by the pulse generator 13 can be determined as appropriate depending on the movement characteristics of the light beam deflecting means 5.

Note that in order to adjust the control force of the light beam deflection means 5, instead of changing the width or height of the pulse, the compensation controller 15 is used during generation of the pulse.
And/or the gain of the light beam deflecting means 5 may be changed.

FIG. 3 is a block diagram showing a schematic configuration of another embodiment of an optical information reproducing apparatus having the track access method of the present invention. In this figure, the same components as in FIG. 1 are denoted by the same reference numerals, and their explanations will be omitted.

In this embodiment, the speed detector 17 detects the relative speed between the optical beam spot and the information track based on the tracking state detection signal, and its output is input to the pulse generator 13 to detect the relative speed near the target track. A suitable braking signal is obtained by changing the width or height of the pulse generated by the pulse generator according to the relative speed, increasing the width or height when the speed is high and decreasing the width or height when the speed is low. can be obtained.

Although an F-V converter may be used as the speed detector 17, other means may also be used.

FIG. 4 is a block diagram showing another embodiment of an optical information reproducing apparatus having the track access method of the present invention. In this figure, the same components as in FIG. 1 are denoted by the same reference numerals, and their explanations will be omitted.

In this embodiment, the output of the comparator 9 is connected to the one-shot multivibrator 1 with retriggerability.
8, while the output of counter 10 is inverted by inverter 19. The output of the one-shot multi 18 and the output of the inverter 19 are input to an AND gate 20, and the output thereof is amplified by an amplifier 21 and an inverting amplifier 22. Reference numeral 23 denotes a changeover switch, which connects one of the output of the amplifier 21 and the output of the inverting amplifier 22 to the summing point 14. The switch 23 is controlled by a moving direction signal input from the outside.

Next, the operation of the apparatus of this embodiment will be explained.

The operation during normal recording information signal reproduction is exactly the same as the embodiment shown in FIG.

FIGS. 5a, b, c and d are the same views as FIGS. 2a, b, c and d. 5g represents the output signal of the one-shot multiplier 18, FIG. 5h represents the output signal of the AND gate 20, and FIG. 5i represents the signal applied from the switch 23 to the summing point 14.

At time _t2 , the one-shot multiplier 18 is triggered at the rising edge of the output signal of the comparator 9, and is similarly triggered at the rising edge of the output signal from the comparator 9 to produce a series of pulses of a predetermined width.

At time t _n , the AND gate 20 outputs the time
A pulse with a width up to t _o is output. time _to
is the falling time of the last pulse of the one-shot multi 18.

In this embodiment, the changeover switch 23 is configured as shown in the figure based on the moving direction signal inputted from the outside, so that the output signal from the inverting amplifier 22 is supplied to the summing point 14.

Thus, in the device of this embodiment, FIG.
A signal similar to that shown in FIG.

In addition, according to the apparatus of this embodiment, a braking signal with a different pulse width (i.e., FIG.
signal) is obtained. The details will be explained based on FIGS. 6 and 7.

FIG. 6 is a time chart when the speed of the light beam spot is relatively fast, and FIG. 7 is a time chart when the speed of the light beam spot is relatively slow. In Figures 6 and 7, c, d,
g, h are c, d, g, h in Fig. 5, respectively.
FIG.

When the speed is high, the width of the final pulse of the output of the comparator 9 is relatively narrow as shown in FIG. 6d, so that the final _pulse is It is relatively long _until the fall time to of the final pulse of the one-shot multi 18 which is triggered by the rising edge of . Thus, if the speed is high,
As shown in FIG. 6h, the width of the output pulse of the AND gate 20 becomes relatively wide, and the pulse width of the braking signal generated based on this also becomes wide, so that relatively large braking can be achieved.

When the speed is low, the final pulse of the output of the comparator 9 has a relatively wide width as shown in _FIG . Falling time of the final pulse of 18
It will be relatively short until t _o . Thus, when the speed is low, the width of the output pulse of the AND gate 20 becomes relatively narrow as shown in FIG. Braking can be achieved.

In the embodiments described above, the output of the bias generator 11 is used to set the threshold value of the comparator 9, but the output of another voltage generation source may also be used.

Furthermore, in the embodiments described above, the braking signal is generated at the time of reaching the target track, but in the present invention, for example,
It can also be before a track or 10 tracks ago.

FIG. 8 is a time chart similar to FIG. 2 showing such an embodiment. That is, in this embodiment, control is performed in exactly the same way as shown in FIG. 2 until time t _n , and then After t _n , the pulse signal shown in FIG. 2 e is not added to the addition point 14. Then, the light beam spot passes through the target track at time t _x due to inertia. And the time
After _tx , a negative polarity signal is input to a certain time compensation controller 15 as shown in FIG. 8f. Therefore, the gain of the compensation controller 15 is increased to control the deflection means 5 with a larger driving force than during normal tracking. Note that the gain is increased during the period when the polarity of the signal shown in FIG. 8f is negative (that is, between times _tx and _ty ).

This allows the light beam spot to effectively access the target track.

Furthermore, although the above embodiments have been described with respect to the reproduction of optical disks, the present invention is also effective when using magneto-optical disks or other media as recording media, and when recording, reproducing, and erasing information. Of course.

Furthermore, the recording medium is not limited to a disk-shaped medium, and may of course be any medium in which information tracks are arranged in parallel.

〔Effect of the invention〕

According to the track access method of the present invention as described above, accurate and high-speed access can be performed.

[Brief explanation of the drawing]

1, 3, and 4 are block diagrams showing the structure of an optical information reproducing apparatus having the track access method of the present invention. Figures 2 and 5
6 and 7 are time charts of beam spot positions and various signals for explaining the track access method of the present invention. 1: Optical disk, 3: Light source, 5: Light beam deflection means, 5A: Objective lens, 6: Photodetector.

Claims (1)

[Claims] 1 means for irradiating a light beam onto an optical information recording medium on which information tracks are arranged in parallel; a light beam deflection means for deflecting the light beam in a direction across the tracks; It changes periodically, reaching zero when the light beam is irradiated on the information track and at an intermediate position between adjacent information tracks, and reaching a peak value when the light beam is irradiated between the intermediate position and the information track. A method for accessing a target information track with the light beam in an optical information recording/reproducing apparatus comprising means for detecting a tracking state detection signal that alternates with a bottom value, wherein the tracking state detection signal is at a peak value. The first while changing from the value to the bottom value
and a second timing between when the tracking state detection signal changes from the bottom value to the peak value, by switching between the tracking state detection signal and a polarity inversion signal obtained by inverting the polarity of the tracking state detection signal. Switching signal,
By applying to the light beam deflection means,
The light beam is moved toward the target information track, and when the light beam reaches the vicinity of the target information track, a braking pulse signal is applied to the light beam deflecting means to move the light beam toward the target information track. A track access method characterized by stopping on a track.