JP2532633B2 - Truck search device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track search device for searching a desired track from a record carrier having a large number of tracks.

2. Description of the Related Art A conventional device is, for example, an optical recording / reproducing device.

An optical recording / reproducing apparatus is an information carrier (hereinafter referred to as a disc) in which a material film that can be optically recorded / reproduced is formed on a surface of a base material having a track having a concentric concavo-convex structure by a method such as vapor deposition, A light beam generated by a light source such as a semiconductor laser is convergently irradiated by a converging lens, a relatively weak constant light amount is read at the time of reproducing a signal, and a signal is read from light reflected from a disk. The light intensity of the light beam is modulated to write a signal.

In such an optical recording / reproducing apparatus, focus control is performed so that the light beam is always in a substantially convergent state on the recording material film, and control is performed so that the light beam always scans a predetermined track correctly. Tracking control is being performed. Furthermore, in order to move the beam to an arbitrary tarrack on the disc, the tracking control is disabled and the light beam is directed toward the target track and is transferred in the radial direction of the disc. When the light beam reaches the target track, the tracking control is performed again. The track search control for operating is performed.

One of the important things in the track search control is the speed at which the light beam crosses the target track, that is, the tracking pull-in speed. The control band of tracking control is finite, and is usually about several KHz. Therefore, if the tracking pull-in speed is too fast, pulling-in of the tracking control to the target track fails. On the contrary, if the tracking pull-in speed is too slow, the time required for track search becomes long.

Therefore, when transferring the light beam in the disk radial direction in the track search, the speed control to precisely control the tracking pull-in speed and to control the speed of the light beam to stably pull in the tracking control to the target track. I am doing.

The track search is performed by moving the light beam in the radial direction of the disk such that the speed of the light beam becomes a predetermined reference speed corresponding to the current position of the light beam during the search operation.

The current speed of the light beam required for speed control is detected from the period T of the track crossing signal generated when the light beam crosses the track. The current position of the light beam can be obtained by counting track crossing signals from the start track of the track search. FIG. 2 shows the tracking error signal and the track crossing signal generated when the light beam crosses the track in the disk radial direction.

It is known that the tracking error signal can be taken out by the push-pull method as shown in a and b of the figure for a track having a concavo-convex structure with a light beam wavelength λ and an optical depth of approximately λ / 8. .

FIG. 2c shows binarization of the tracking error signal,
FIG. 2d shows an edge detection signal obtained by detecting the rising edge. This edge detection signal is generated when the light beam crosses the center of the track and is a track crossing signal. Therefore, the value obtained by counting this signal from the start of track search represents the current position of the light beam. Since tracks are provided on the disk at substantially the same interval P in the radial direction, if the period of the track crossing signal is T, the speed V of the light beam can be obtained by V = P / T.

Further, FIG. 2e shows a signal obtained by detecting the rising and falling edges of FIG. 2c. When the period of this signal is t, the velocity V of the light beam can be similarly obtained by V = P / 2t.

As described above, when detecting the speed of a light beam based on the period of a track traversing signal, the speed control band is limited by the phase delay due to sampling because the speed detection is discrete. It is well known. Therefore, if the disc has a large eccentricity, or if vibration or shock is applied to the device from the outside, the control error of the speed control becomes large, and the tracking pull-in speed becomes too high, and the tracking control of the target track becomes too large. There were times when it failed to pull in.

On the contrary, if the tracking pull-in speed becomes too small, the time required for track search becomes long.

In order to solve the above problems, the present invention is to provide an apparatus that realizes stable pulling of tracking control to a target track without increasing the control band of speed control.

Means for Solving the Problems The present invention provides a conversion means for reproducing or recording a signal on an information carrier having information or a track on which the information is recorded, and the conversion means is abbreviated as the information carrier. A track search device having moving means for moving horizontally and in a direction vertical to the tracks, and moving the converting means to another desired target track from the track in which the converting means is located, A speed detecting means for detecting is provided, and when the converting means reaches a predetermined position set at least in front of the target track, a drive pulse corresponding to the output of the speed detecting means is applied to the moving means. It is configured to do.

The present invention is configured as described above, so that, for example, when a large vibration or shock is applied to the device from the outside or the eccentricity of the disk is large and the control error of the speed control is large, it is in front of the target track. Since the deceleration pulse or the acceleration pulse is applied a plurality of times, the fluctuation of the tracking pull-in speed is reduced and the track search can be stably performed.

Hereinafter, a track search device according to an embodiment of the present invention will be described.
This will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. The converging lens 1 and the reflecting mirror 2 are mounted on the transfer table 3, and the voice coil motor 4
The disk motor 5 is driven substantially in the radial direction of the disk 6 being rotated.

A light beam emitted from a light source 7 such as a semiconductor laser passes through a collimator lens 8 for collimating the light beam, a polarization beam splitter 9 and a 1 / 4λ plate 10 and a transfer table 3
It is irradiated to the reflection mirror 2 mounted on the. Reflection mirror 2
The light beam reflected by is converged by the converging lens 1 and applied to the disk 6. The reflected light from the disk 6 passes through the converging lens 1 and is reflected by the reflecting mirror 2 to be 1 / 4λ.
The light passes through the plate 10, is reflected by the polarization beam splitter 9, and enters the two-division photodetector 11. The dividing line of the two-divided photodetector 11 is arranged on the light receiving surface in the longitudinal direction of the track. The output signal of the 2-split photodetector 11 is a differential amplifier
Entered in 12. Differential amplifier configured in this way
It is known that the 12 output signals become the tracking error signal TE as shown in FIG. 2b.

The tracking error signal TE is input to the voice coil motor 4 via the phase compensation circuit 14, the switch 15, the addition circuit 16, and the drive circuit 17 to configure tracking control.

The phase compensating circuit 14 is provided to ensure controllability of tracking control, and the switch 15 is provided to switch between operation and non-operation of tracking control.

The tracking error signal TE is also input to the tracking crossing signal detection circuit 18. The track crossing signal detection circuit 18 is configured to detect and output the track crossing signal TC (the signal shown in FIG. 2d) from the tracking error signal TE as described with reference to FIG.

The track crossing signal TC is input to the timer 20. The timer 20 measures the period of the track crossing signal 19 and outputs the measured value as a digital value DT. The measurement value DT measured by the timer 20 is input to the speed calculation circuit 21. The speed calculation circuit 21 calculates the digital speed value DV of the light beam from the measured value DT according to the following equation DV = P / DT where P is the distance between tracks, that is, the track pitch.

Since the speed value DV is a value that is discretely sampled for each track traversal, the speed calculation circuit 21 determines the speed value after at least one sampling until at least the next sampling.
It is configured to hold DV.

The speed value DV is converted into an analog signal by the D / A converter 22, and is input to the addition circuit 16 via the differential circuit 23 and the switch 24, thereby configuring speed control. The switch 24 is for switching between operation and non-operation of the speed control.

The track crossing signal TE is also input to a counter 25 with a presettable count value. The counter 25 counts the number of tracks crossed.

The count value of the counter 25 is converted into a command speed by the command speed generator 27, further converted into an analog value by the D / A converter 28, and input to the other input terminal of the differential circuit 23.

The count value of the counter 25 is also input to the coincidence detection circuits 29, 30, 35. The coincidence detection circuits 29, 30 and 35 compare the count values of the counter 25 with predetermined values and output coincidence signals X1, X2 and X3 to a microcomputer (hereinafter referred to as a microcomputer) 26.

The output value of the speed detection circuit 21 is also input to the microcomputer 26, and the microcomputer 26 can capture the current speed of the light beam. Further, the microcomputer 26 is connected to the D / A converter 33 which is input to the adding circuit 16 via the output switch 34 thereof, and the microcomputer 26 can drive the transfer table 3.

The control signals of switches 15, 24 and 34 are
The operation is controlled by the microcomputer 26.

The detailed operation of each unit will be described below by sequentially explaining the operation of the track search.

Switch 15 must be on before switch search
4 and 34 are turned off, the tracking control is operated, and the light beam follows a predetermined track.

Prior to the track search, first, the track difference from the track search start track to the target track is preset from the microcomputer 26 to the counter 25.

The switch 15 is turned off and the switch 24 is turned on by a command from the microcomputer 26, the light beam starts moving toward the target track, and the search operation is started.

The counter 25 decrements the count value by 1 every time the track crossing signal TC is input during the track search operation. Therefore, the count value of the canter 25 during the track search represents the current position of the light beam with the target track as the reference. The command speed generator 27 is composed of a ROM (read only memory) in which the output line of the counter 25 is connected to the address line and the data line is connected to the D / A converter 28 as an output.

Each count value of the counter 25, that is, each address of the ROM corresponding to the current position of the light beam, stores the command speed of the light beam at that position as a digital value.

As shown in FIG. 3, data is set in the ROM such that the larger the count value of the counter 25 is, the higher the command speed is, as shown in FIG. The reason why the command speed is constant when the count value DX of the counter 25 is larger than a predetermined value is to prevent the adverse effect of controlling the dynamic range of speed control.

The output signal of command speed generator 27 is output from D / A converter 28
Is converted into an analog value, and is input to a differential circuit to be a speed command signal for speed control.

As a result, the speed control causes the light beam to move at a speed substantially equal to the command speed.

A larger speed command signal is given to the speed control as the light beam is farther from the target track, and a smaller speed command signal is given to the light track as the light beam is approached.

Accordingly, the track search is started, and as the light beam moves toward the target track, the count value of the counter 25 decreases, and further, the moving speed of the light beam decreases correspondingly. Go closer to the target track.

On the other hand, in the coincidence detection circuit 35, the count value of the counter 25 is 20
When it becomes, the coincidence signal X3 is output to "L", and otherwise "H" is output to the microcomputer 26.
When the coincidence signal X3 becomes "L", the light beam of the target track
You have reached the track 20 tracks before.

Immediately after the coincidence signal X3 becomes "L", the microcomputer 26 turns off the switch 24 to disable the speed control and reads the speed value DV calculated by the speed detection circuit 21. Microcomputer 26
Calculates and outputs a digital value H2 with polarity substantially satisfying the following expression to the D / A converter 33 based on the speed value DV, and outputs the switch 34 to "ON" for a period W2.

DVref (20) -DV = Gda * Gadd * Gdr * F * H2 * W2 / M However, DVref (20) -DV: Command speed before 20 tracks Gda: Conversion gain of D / A converter 33 Gadd: Adder circuit 16 Gain Gdr: Gain of the drive circuit 17 F: Thrust constant of the voice coil motor 4 M: Transfer mass Transfer mass M is the total mass of the components such as the converging lens 1 and the reflection mirror 2 on the transfer table, and the transfer table itself. It is the total mass of the masses.

For the polarity of the digital value H2 with polarity, DV is DVref (2
If it is larger than 0), the speed of the light beam is set to be reduced.

That is, if the speed of the light beam on the track 20 tracks before the target track is higher than the target command speed DVref (20), the speed is equivalent to decelerating to almost the light beam command speed DVref (20). It is configured to apply a pulse. When the speed of the light beam on the track 20 tracks before the target track is lower than the target command speed DVref (20), the light beam is moved to about the command speed DVref (20).
It is configured to apply an acceleration pulse equal to accelerating to.

After the lapse of the period W2, the switch 34 is turned “OFF” again, and the switch 24 is turned “ON” to operate the speed control again. At this time, the speed of the light beam is approximately the command speed DVref (20) for the track 20 tracks before the target track.

After that, the light beam moves toward the target track at a speed substantially equal to the command speed output by the command speed generator 27 by speed control.

On the other hand, the match detection circuit 29 determines that the count value of the counter 25 is 2
Is output to the microcomputer 26 when the coincidence signal X1 is "L", and "H" otherwise. When the coincidence signal X1 becomes "L", the light beam has reached a track two tracks before the target track. The microcomputer 26 immediately switches the switch 24 when the coincidence signal X1 becomes "L".
Turn OFF to disable speed control and speed detection circuit 2
Read the calculated speed value DV of 1. Microcomputer 26 has speed value D
Based on V, the digital value H1 with polarity that substantially satisfies the following equation is calculated and output to the D / A converter 33, and the switch
34 is turned “ON” over the period W1.

DVref-DV = Gda * Gadd * Gdr * F * H1 * W1 / M However, DVref: Target pull-in speed Gda: Conversion gain of D / A converter 33 Gadd: Gain of adder circuit 16 Gdr: Gain of drive circuit 17 F: Voice Thrust constant of the coil motor 4 M: Transfer mass The polarity of the digital value H1 with polarity is set so as to reduce the speed of the light beam when DV is larger than DVref.

That is, if the speed of the light beam in the track two tracks before the target track is higher than the target pull-in speed DVref, a deceleration pulse equal to substantially reducing the light beam to the target pull-in speed is applied. Is configured. If the speed of the light beam on the track two tracks before the target track is lower than the target pull-in speed DVref, an acceleration pulse equivalent to accelerating the light beam to approximately the target pull-in speed is applied. It is configured.

After the period W1 has elapsed, the switch 34 is turned off again. At this time, the speed of the light beam is substantially the target pull-in speed. Thereafter, the light beam moves toward the target track by inertia. On the other hand, the match detection circuit 30
When the count value of the counter 25 becomes 0, the coincidence signal X2 is set to "L", otherwise, it is set to "H".
It is configured to output to.

Therefore, when the light beam subsequently reaches the target track and the coincidence signal becomes "L", the microcomputer 26 immediately turns on the switch 15 to operate the tracking control, and the track search is completed.

With such a configuration, for example, a vibration or shock larger than the outside is applied to the device, or the eccentricity of the disk is large, the control error of the speed control becomes large, and the pulling speed of the tracking control becomes large. Even in such a case, by applying an appropriate deceleration pulse a plurality of times, it is possible to eliminate an increase in the tracking pull-in speed and to stably perform the track search without failing to pull in the tracking control to the target track.

On the contrary, when the pull-in speed of the tracking control is small, it is possible to reduce the increase in the time required for track search by applying an appropriate acceleration pulse a plurality of times.

The feature of the embodiment according to the present invention is that the difference between the actual tracking pull-in speed and the target pull-in speed caused by the disturbance is not limited by the speed control band or gain.

Further, in the present embodiment, the coincidence detection circuits 29 and 35 are configured to detect that the count values of the counter 25 have become 2 and 20, respectively, but this is determined by N1 and N2 (N1 and N2 are positive). However, it is clear that the same effect can be obtained by expanding N2> N1). The coincidence signals X1 and X3 become "L" when the light beams are located on the tracks N1 and N2 before the target track, respectively.

Furthermore, the peak value H1 and the width W1 of the acceleration pulse or the deceleration pulse applied according to the speed of the light beam from the track N1 before the target track are configured by the microcomputer 26, but the peak value H1 and the width W1 are set. Even if one is fixed and the other is set by the microcomputer 26, the same effect is obtained.

Similarly, the microcomputer 26 is configured to set the peak value H2 and width W2 of the acceleration pulse or deceleration pulse applied according to the speed of the light beam from the track N2 ahead of the target track. Even if one of W2 is fixed and the other is set by the microcomputer 26, the same effect is obtained.

The acceleration pulse and the deceleration pulse are rectangular waves,
Obviously, the waveform does not matter, such as triangular wave or trapezoidal wave.

In this embodiment, the number of application of the deceleration pulse or the acceleration pulse is set to two times in one track search operation, but if this is set to N3 times (N3 is an integer of 2 or more), the same or similar effect is obtained. It is clear that it will be obtained.

In this embodiment, the track crossing signal detection circuit 18 is the second
Although it is assumed that the light beam crosses the center of the track as shown in FIG. 2D, it is detected that the light beam crosses the center of the track and the midpoint between the tracks as shown in FIG. 2E. It is obvious that the same effect can be obtained even with the configuration.

In that case, the speed calculation circuit 21 calculates the measured value of the timer 20.
Calculate the digital velocity value DV of the light beam from DT according to the following equation DV = P / (2 * DT) where P is the distance between tracks.

Further, prior to the track search, a value of twice the track difference from the track search start track to the target track is first preset in the counter 25 by the microcomputer 26.
Therefore, in this case, the position to which the deceleration pulse or the acceleration pulse is applied can be specified in units of 0.5 tracks before the target track.

Further, in this embodiment, the switch 24 is "OFF" after the period W1 has elapsed.
The switch 24 is turned “ON” again, and then when the coincidence signal X2 becomes “L”, the switch 24 is turned “OF”.
The same effect can be obtained with F ".

EFFECTS OF THE INVENTION The present invention is configured as described above, and for example, the device is subjected to a larger vibration or shock than the outside, or the eccentricity of the disk is large, and the control error of the speed control becomes large. Even if the pull-in speed increases, it is possible to eliminate the increase in the tracking pull-in speed by applying an appropriate deceleration pulse multiple times, and to perform stable track search without failing to pull in the tracking control to the target track. it can.

Further, even when the pull-in speed of the tracking control is small, it is possible to reduce the increase in the time required for the track search by applying the appropriate acceleration pulse a plurality of times.

[Brief description of drawings]

1 is a block diagram of an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining a tracking error signal and a track crossing signal when a light beam crosses a track, and FIG. 3 is a count value of a counter. FIG. 4 is a characteristic diagram for explaining the relationship between the command speed and the command speed. 1 ... Convergence lens, 3 ... Transfer base, 4 ... Voice coil motor, 7 ... Light source, 11 ... Divided photodetector, 12 ... Differential amplifier, 15, 24, 34 ... Switch, 16 ...... Adding circuit,
18 …… Track crossing signal detection circuit, 20 …… Timer, 21
...... Speed calculation circuit, 22, 28, 33 …… D / A converter, 2
3 ... Differential circuit, 26 ... Microcomputer, 27 ...
Command speed generator, 29, 30, 35 ... Match detection circuit.

Claims (7)

(57) [Claims] 1. A converting means for recording or reproducing a signal on an information carrier having information or a track on which the information is recorded; the converting means being substantially horizontal to the information carrier and perpendicular to the tracks. Moving means for moving in any direction, speed detecting means for detecting the speed of the converting means, and speed for driving the moving means according to the output of the speed detecting means to move the converting means to a desired track. A track search device having control means, position detecting means for detecting that the converting means has reached at least a plurality of predetermined positions before the target track, and pulses for generating acceleration or deceleration pulses. Producing means and switching means for switching the output of the speed control means and the output of the pulse generating means to output to the moving means are provided. Switch the output of said pulse generating means and the output of said speed control means in accordance with the output of the detection means,
The pulse generation means accelerates or decelerates the drive pulse proportional to the difference between the output of the speed detection means and the non-zero target speed in accordance with the polarity of the difference between the output of the speed detection means and the non-zero target speed. A track search device, characterized in that it is applied to the moving means in a direction. 2. The track search device according to claim 1, wherein the drive pulse has a rectangular shape. 3. The track search device according to claim 2, wherein the width of the drive pulse is changed according to the output of the speed detecting means. 4. The track search device according to claim 2, wherein the peak value of the drive pulse is changed according to the output of the speed detecting means. 5. The converting means detects that the converting means has crossed on a track or near the midpoint between the tracks and counts the detected signal so that the converting means can detect a predetermined signal before the target track. That you have reached the position
2. The truck search device according to claim 1, wherein the truck search apparatus detects. 6. The speed detecting means detects that the converting means has crossed on a track or near the midpoint between the tracks and detects the speed of the converting means from the cycle of the detected signal. The truck search device according to claim 1. 7. The position detecting means detects that the converting means has crossed on the track or near the midpoint between the tracks, and the converting means counts the detected signals so that the converting means detects the position before the target track. 2. The truck search device according to claim 1, wherein arrival at a predetermined position is detected.