JPH073693B2 - Optical beam access control device - Google Patents

Description

The present invention relates to a light beam access control device used in an optical disk device or the like.

[Conventional technology]

Conventionally, a method has been proposed in which a light beam is largely moved to near a desired position by rough access, and then the light beam is moved for each track.

[Problems to be solved by the invention]

However, in such a conventional method, it takes about 1 millisecond to move one head by one track, and therefore, for example, it takes 50 milliseconds to move five tracks, which is a problem of slow access. .

[Means for solving problems]

In order to solve such a problem, the present invention shortens the access time of the light beam to the track by using the relative velocity and the position shift signal after the rough access is completed.

[Work]

 Multiple tracks are accessed at once.

〔Example〕

FIG. 1 is a block diagram showing one embodiment of the present invention.
Reference numeral 1 is a spindle motor for holding and rotating an optical disk medium, 2 is an optical disk medium, 3 is an optical head, 4 is a photo detector for detecting the light reflected by the optical disk medium 2 out of the optical head 3, and 5 is an optical head 3. Of these, an actuator that drives a light beam emitted from the optical disk medium 2 in the radial direction (track direction), 6 is a position sensor that senses the movement of the actuator 5 with respect to the housing, and 7 is the output of the position sensor 6. A moving amount detecting circuit for detecting the moving amount of the actuator 5, 8 is an output of the moving amount detecting circuit 7, 9 is an output line group of the photodetector 4, and 10 is a position for detecting the displacement between the track and the beam from the output of the photodetector 4. A detection circuit, 11 is the output of the position detection circuit 10, and 14 is a track passage pattern that outputs one pulse each time the peak of the output of the position detection circuit 10 is sensed. Pulse generation circuit, 15 is the output of the track passing pulse generation circuit 14, 16 is the relative speed detection circuit that detects the relative speed between the track and the beam, 17 is the output of the relative speed detection circuit 16, and 18 is the reference speed. Reference speed generation circuit, 19 is the output of the reference speed generation circuit 18, 20 is the output 17 of the relative speed detection circuit 16 and the output 19 of the reference speed generation circuit 18.
And 21 are speed error detection circuits that take a difference after being multiplied by a constant, 21 is an output of the speed error detection circuit 20, 22 is a power amplifier, and 23 is an output of the power amplifier 22.

To operate this device, the optical disk medium 2 is mounted on the spindle motor 1 and rotated. The optical desk medium 2 is the second
Grooves as shown are formed when the optical desk medium 2 is manufactured. The laser light sent from the optical head 3 is focused by an optical system (not shown) of the optical head 3 and is incident perpendicularly on the surface of the optical disc medium 2. The laser light is diffracted and reflected on the surface of the optical desk medium 2 and detected by the photo detector 4. FIG. 3 shows the configuration of a two-divided detector as an example of the detection method for detecting the positional deviation. The laser light applied to the surface of the optical disk medium is diffracted and reflected by the groove on the surface of the optical disk medium. As a result, two photodiodes 4a, 4
There is an imbalance in the amount of light received at b. The outputs of the photo diodes 4a and 4b are terminated by the resistors 10a and 10b and differentially amplified by the differential amplifier 10c. As a result, when the actuator moves in the radius r direction of the medium as shown in FIG.
Each time it passes through the groove shown in FIG. 4 (a), the positional deviation signal shown in FIG. 4 (b) is sent to the output 11. (Hereinafter, this signal will be referred to as a position shift signal 11.) As shown in FIG. 5 (a), the position sensor 6 for detecting the movement amount of the actuator 5 is composed of one light emitting element, a reflecting mirror and a two-division photo detector. Then, the output of the position sensor 6 is input to the movement amount detection circuit 7. Similarly to FIG. 3, the movement amount detection circuit 7 obtains a signal proportional to the movement amount as shown in FIG. 5 (b) when the mirror interlocked with the actuator 5 moves in the direction of arrow x.

The position sensor that detects the amount of movement of the actuator 5 can also be configured by means that detects the drive current of the actuator.

Output 11 of position detection circuit 10 and output 8 of movement amount detection circuit 7
Is input to the relative speed detection circuit 16. The relative speed detection circuit 16 can be realized by the configuration shown in FIG. Position shift signal 11
Is differentiated by the differentiating circuit 100 and input to the switch 102, and also input to the switch 102 through the inverting circuit 101. When the position shift signal 11 shown in FIG. 7 (a) is input, the signal shown in FIG. 7 (b) is output from the differentiating circuit 100, and the signal shown in FIG. 7 (c) is output from the inverting circuit 101. It The switch 102 outputs the output of the differentiating circuit 100 as it is while the count value of the track passing pulse, which will be described later, is even, and outputs the output of the inverting circuit 101 during the odd part.
The output of 02 outputs a waveform as shown in FIG. 7 (d). Further, the position shift signal 11 is input to the comparison circuit 106 and also to the comparison circuit 108 through the inversion circuit 107. The comparator circuits 106 and 108 use the position shift signal 11 and the signal obtained by inverting the position shift signal 11 as a comparison level between the center and the peak (L1 and L2 in FIG. 7A) and the position shift signal 11 and While the inverted signal is higher than the comparison level, a high level signal is output and is input to the OR circuit 109. The OR circuit 109 takes the OR of the two input signals and outputs a waveform as shown in FIG. 7 (e). A section in which the output of the OR circuit 109 is at a high level is a portion where the position shift signal 11 loses its linearity (waveform peak portion).

A movement amount detection circuit 7 for detecting the movement amount of the actuator 5.
The output of is differentiated by the differentiating circuit 104 and becomes a signal indicating the moving speed of the light beam with respect to the stationary system, and FIG.
The signal shown in is input to the switch 105. The switch 105 sends the output of the differentiating circuit 104 as it is while the output of the OR circuit 109 is at the high level, and sends the "0" level while it is at the low level. It outputs the indicated signal. The output of switch 102 is applied to the positive input terminal of differential amplifier 112, and the output of switch 105 is the output of differential amplifier 1
The signals are applied to the 12 negative input terminals, differentially amplified, and input to the switch 110 with a sample hold function as a signal shown in FIG. 7 (h). The switch 110 with a sample hold function sends out the output of the differential amplifier 112 as it is while the output of the OR circuit 109 shown in (e) is low level, and the output of the differential amplifier 112 at the moment when it becomes high during the high level. The value that holds the output is sent out. Therefore, the output of the switch 110 with the sample hold function has the waveform of FIG. 7 (i), and as is clear from the above description, while the output of the OR circuit 109 is at the low level, that is, the position shift signal 11 is linear. In the region where the property is maintained, it is the differential value of the positional deviation, that is, the relative velocity, and during the high level, it is the value obtained by subtracting the moving velocity of the light beam from the relative velocity at the moment when the high level is reached, that is, the track eccentric velocity. There is. The output of the switch 110 with a sample hold function is input to the summing amplifier 111 together with the output of the switch 105, summingly amplified, and the output 17 shown in FIG. 7 (j) is sent out.

As a result, the positional deviation signal 11 is a signal indicating the relative displacement between the beam and the track, and a signal obtained by differentiating this in the section where the proportional relationship is established between the displacement and the output signal, that is, the relative velocity is output to the output 17. Sent out. In the section where the proportional relationship is not established, the value obtained by adding the moving speed of the beam itself to the value that holds the track eccentric velocity at the moment when the section where the proportional relationship is established and the section where the proportional relationship is not established is held is output.

Although the relative speed itself cannot be accurately detected in such a section where the proportional relationship is not established, the movement speed of the track is mainly caused by eccentricity, and thus the disk rotation speed component (50 Hz at 3000 rpm) Therefore, if the relative speed is set to about 2 cm / s, the time to move in a section that changes periodically (thus, in the case of 1.6 micron pitch disks, 0.4 micron) is 40 microseconds. It is considered that the change in the track moving speed during this period is almost zero during this time. Therefore, as described above, by holding the track eccentric velocity at the moment when it enters the section where the proportional relationship of the positional deviation signal does not hold, and adding the beam moving velocity to this, the relative velocity can be approximately obtained. become.

The position shift signal 11 is input to the track passage pulse generation circuit 14 and the reference speed generation circuit 18. As shown in FIG. 8, the track passing pulse generation circuit 14 is composed of a voltage comparator 200, a pulse edge detection circuit 201, an integrator 202, a comparator 203, and a reference voltage 204. In this circuit, the signal (positional deviation signal 11) shown in FIG. 9 (a) is input to the voltage comparator 200 and the level is compared at 0 volt. Each time the positional deviation signal 11 becomes positive, the circuit shown in FIG. ), The first pulse is output. The output of the voltage comparator 200 is input to the pulse edge detection circuit 201 and has a sufficiently narrow width (the pulse width is 1/10 or less of the first pulse) corresponding to the rising edge and the falling edge of the first pulse. A second pulse is emitted as shown in c).

On the other hand, since the signal 17 which is the relative speed is input to the integrator 202, the integrator 202 sets the output to 0 in the section where the second pulse is at the high level, and the second pulse shown in (c) becomes the low level. The signal from the moment when the relative velocity starts to be integrated until the second pulse becomes high level, that is, the second pulse is at low level, is a signal indicating the relative velocity as shown in FIG. 9 (d). Continue to integrate 17. The section where the second pulse is at the low level is a section (track pitch 1/2) from the center of the track to the center of the land or from the center of the land to the center of the groove, and is therefore a constant distance. The output of the integrator 202 is as shown in FIG. 9 (d). The final value is a voltage equivalent to 1/2 of the track pitch and is constant regardless of the magnitude of the relative speed. Therefore, the output of the integrator 202 is input to the comparator 203, and the level L of about 1/2 of the final value is input.
By making a comparison (corresponding to the distance to the boundary between the groove and the land), the third pulse is output as shown in FIG. 9 (e). The rising edge of the third pulse shown in FIG. 9 (e) can be brought to the peak position of the position shift signal by adjusting the level L. Therefore, the comparator 203
Is output as a track passing pulse 15. There is also a method of using a differentiating circuit to detect the peak, but since the address prepets are arranged at equal intervals on the track of the optical disk medium, the peak of the position deviation signal is due to this prepet. It may be crushed or a pseudo peak may occur. Therefore, the method of using the derivative is not desirable for ensuring the stability, and the method of using the integration as in the present application does not cause a problem in the stability.

In this way, by detecting the peak of the sinusoidal position shift signal obtained when the light beam crosses the track, it is possible to count the number of tracks that have moved, and to detect the stepwise signal of the reference speed generation circuit. The position shift signal enables smoothing. This is done as follows. The track passing pulse 15 is input to the reference speed generating circuit 18. The reference speed generation circuit 18 continues counting the track passing pulse 15 and the count value is lower than the value Na obtained by subtracting a predetermined number n (for example, 3) from twice the number of tracks given as the access distance. Delivers a reference speed of constant DC level to output 19. The reason why the number of tracks is doubled here is that the position shift signal has two peaks while the light beam moves one track. Then, after the count value exceeds Na, the DC level is changed to the constant DC level as shown in FIG. 9 (f) every half cycle of the position shift signal (each time the count increases by 1).
While decreasing in 1/4 steps in a stepwise manner, changing the polarity of the misalignment signal so that it always has a negative slope and the peak-to-peak position of the misalignment signal is equal to 1/4 of the constant DC level. In addition to the stepwise wave signal, a standard speed that becomes 0 at the access target position is sent to the output 19 as a signal for adjusting the level so as to become as shown in FIG.

The relative speed 17 and the reference speed 19 are input to the speed error detection circuit 20, multiplied by k1 and k2, and then subtracted. k1 and k2 are quantities that determine the relationship between the residual distance to the target position and the speed, and also determine the total gain of the closed loop. The speed error is output to the output 21, input to the power amplifier 22, converted into voltage and current, and supplied to the actuator 5 through the signal line 23.

As described above, the actuator that moves the beam in the track direction is driven by the relative speed error and is controlled so as to follow the reference speed that becomes 0 at the target track. With this structure, even if there is eccentricity of the track, the relative velocity of the beam with respect to the eccentricity is detected, and acceleration / deceleration is performed from 0 to positive (or negative) and 0. , As if the eccentricity was zero. Therefore, the effect is that the access can be completed by one access operation without being affected by the eccentricity when moving to a plurality of tracks.

FIG. 10 shows another method for detecting relative speed. In the figure,
A switch 102, which is a signal obtained by converting the differential value of the output signal 11 of the position detection circuit 10 into an absolute value, in a section in which the position shift signal has linearity (a section in which the output signal of the OR circuit 109 is low level).
A signal holding the output of is output from the switch 110 with a sample hold function. On the other hand, the output signal of the differentiating circuit 104, which is a signal obtained by differentiating the output 8 of the moving amount detecting circuit 7 that detects the moving amount of the head with respect to the stationary system, is the differential amplifier 1
It is supplied to the non-inverting input terminal of 12a and also to the inverting input terminal of the differential amplifier 112a through the switch 113 with a sample hold function. The switch 113 with a sample hold function sends the output of the differentiating circuit 104 as it is while the output signal of the OR circuit 109 is low level, and holds the value of the input signal at the moment when it becomes high level while it is high level. It is supposed to output. Therefore, the output of the differential amplifier 112a is low while the output of the OR circuit 109 is low level.
That is, the position shift signal is 0 in the section having line formation, and during the high level, that is, in the section in which the position shift signal loses linearity, the change in the head moving speed from the moment when the position shift signal loses linearity. It's a minute.

The output of the switch with sample-hold function 110 and the output of the differential amplifier 112a are supplied to the summing amplifier 111 and added together. Therefore, the output of the summing amplifier 111 is the differential value of the displacement signal in the section where the displacement signal has linearity,
That is, it takes the relative velocity of the light beam with respect to the track.
Further, in the section where the misalignment signal loses the linearity, the summing amplifier 111 holds a value obtained by adding the change in the moving speed of the light beam with respect to the stationary system to the value that holds the relative speed at the moment when the linearity is lost. Is output. As described in the explanation with reference to FIG. 6, the change in the moving speed of the track in the section where the positional deviation signal loses the linearity can be ignored, and thus the relative speed at the moment when the linearity is lost is held, By adding the change in the moving speed of the beam, the relative speed of the light beam with respect to the track can be approximately obtained even in the section in which the positional deviation signal loses the linearity.

According to the result confirmed by the experiment, by using the present invention, the relative velocity is accelerated to 2 cm / s and decelerated from the front of the target 2 tracks, so that 50 tracks (track bitch 1.6 micron) can be accessed in 5 milliseconds. We were able to. On the other hand, in the conventional method of repeating one track access multiple times, the time required to access 50 tracks is about 50 milliseconds.

〔The invention's effect〕

As described above, according to the present invention, the relative speed between the track and the beam is detected, the access target track becomes 0, and the relative speed is controlled to follow the reference signal proportional to the residual distance to the access target track. Therefore, a plurality of tracks can be accessed by one operation regardless of the size and speed of the track eccentricity, and the access time can be shortened as compared with the conventional method of repeating one track access operation a plurality of times. It has the effect of being able to.

[Brief description of drawings]

1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a perspective view showing an example of an optical disk medium, FIG. 3 is a circuit diagram showing an example of a photodetector, and FIG. 4 is a waveform of a displacement signal. 5 is a waveform diagram showing the configuration of the actuator movement amount detection circuit, FIG. 6 is a block diagram showing the configuration of the relative speed detection circuit, and FIG. 7 is a waveform diagram showing the operation waveforms of the relative speed detection circuit. , FIG. 8 is a block diagram showing the operation of the track passage pulse generation circuit, FIG. 9 is a waveform diagram for explaining the operation for detecting the peak of the position shift signal, and FIG. 10 is another circuit for detecting the relative signal. FIG. 3 is a block diagram showing the embodiment of FIG. 1 ... Spindle motor, 2 ... Optical disk medium, 3 ...
… Optical head, 4… Photo detector, 5… Actuator, 6… Position sensor, 7… Moving amount detection circuit, 10…
... Position detection circuit, 14 ... Track passing pulse generation circuit,
16 …… Relative speed detection circuit, 18 …… Reference speed generation circuit, 20
...... Speed error detection circuit, 22 …… Power amplifier.

Claims (2)

[Claims] 1. Reflecting from a medium when irradiating the medium with a light beam to stop moving the light beam positioned on a first track to a second track that is separated by any specified number of tracks. In a light beam access control device for positioning using a received light beam, a movement amount detection circuit that detects the movement amount of the light beam, a position detection circuit that detects the positional deviation between the track and the light beam, and a position detection Track passing pulse generation circuit that outputs a pulse each time the peak of the circuit output is sensed, and in the area where the position detection circuit output maintains linearity, the signal that differentiates the position detection circuit output signal is output as a relative speed signal,
In the region where the position detection circuit output cannot maintain linearity, the signal obtained by subtracting the differential value of the movement detection circuit output from the position detection circuit output signal at the moment when linearity cannot be maintained is output as a relative speed signal. The circuit and the number of pulses from the track passing pulse generation circuit are counted, and when the count value is less than or equal to the predetermined number determined as the access distance, a DC signal of a constant level is output as the reference speed, and the count value indicates the predetermined number. A reference speed generation circuit that outputs a signal that monotonically decreases so that the above-mentioned constant level DC signal becomes zero at the access target position when it exceeds, and a speed error that detects the speed error between the reference speed and the relative speed. An access control device for a light beam, comprising: a detection circuit. 2. A track passing pulse generating circuit integrates a relative speed of a light beam with respect to a track from a position where a position shift signal level becomes zero to a position where the position shift signal becomes next zero, and when the value exceeds a predetermined level. The light beam access control apparatus according to claim 1, wherein an output pulse is transmitted.