JPH0262773A - Track retrieval device - Google Patents

Abstract

PURPOSE:To attain stable locking to an object track by applying a drive pulse in response to an output of a speed detection means to a moving means when an information conversion means reaches a prescribed position before the object track. CONSTITUTION:A tracking error signal being an output signal of a differential amplifier 12 is given to a voice coil motor 4 via a phase compensation circuit 14, a switch 15, an adder circuit 16 and a drive circuit 17 to constitute tracking control. An output signal of a command speed generator 27 is converted into an analog value by a D/A converter 28, given to a difference circuit and becomes a speed command signal for speed control. A larger speed command signal when a light beam is parted from an object track more and a smaller speed command signal is given to the speed control circuit as the light beam is closer to the object track. Even when an external large shock or vibration is exerted or the locking speed of tracking control is larger, the tracking control to the object track is implemented stably by applying a proper deceleration pulse.

Description

DETAILED DESCRIPTION OF THE INVENTION 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 Conventional devices include, for example, optical recording and reproducing devices.

An optical recording/reproducing device is an information carrier (hereinafter referred to as a disk) that has a material film that can be optically recorded and reproduced formed by vapor deposition or other methods on the surface of a base material that has tracks with a concentric uneven structure. , a light beam generated from a light source such as a semiconductor laser is converged using a converging lens, and when reproducing a signal, the light intensity is set at a relatively weak constant level, and the signal is read from the reflected light from the disk, and when recording a signal, it is adjusted according to the signal to be recorded. In this method, signals are written by modulating the intensity of the light beam.

In such an optical recording/reproducing device, focus control is performed so that the light beam is always in a substantially predetermined convergence state on the recording material film, and control is performed so that the light beam is always correctly scanned on a predetermined track. Tracking control is being performed. Furthermore, in order to move the beam to an arbitrary track on the disk, the tracking control is disabled, the light beam is directed toward the target track, is moved in the radial direction of the disk, and when the light beam reaches the target track, the tracking control is activated again. Track search control is performed to operate the .

One of the important things in track search control is that the light beam
There is a speed when crossing the target track, that is, a tracking pull-in speed. The control band for tracking control is limited, and is usually about several KHz. Therefore, if the dragging pull-in speed is too fast, tracking control pull-in to the target track will fail. On the other hand, if the tracking pull-in speed is too slow, the time required for trunk search becomes long.

Therefore, when moving the light beam in the radial direction of the disk during track search, the tracking pull-in speed is accurately controlled, and in order to stably pull the tracking control to the target track, speed control is used to control the speed of the light beam. is being carried out.

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

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

The tracking error signal is generated when the wavelength of the light beam is λ and the track has an uneven structure with an optical depth of approximately λ/8 as shown in Fig. 2(a).
, It is known that it can be extracted using the push-pull method as shown in (b), and its explanation will be omitted.

FIG. 2(C) shows the binarization of the tracking error signal, and FIG. 2(d) shows the edge detection signal whose rising edge is detected. This edge detection signal occurs when the light beam crosses the center of the truck, and is the trunk crossing signal.

Therefore, the value of this signal counted from the start of the track search represents the current position of the light beam. Further, since the tracks are provided on the disk at substantially the same intervals P in the radial direction, if the period of the track crossing signal is T, the speed V of the light beam can be determined as V=P/T.

Further, FIG. 2(e) is a signal obtained by detecting the rising and falling edges of FIG. 2(C).

If the period of this signal is t, the speed of the light beam is similarly V=P/2t It can also be found as

Problems to be Solved by the Invention As mentioned above, when detecting the speed of a light beam based on the period of the trunk crossing signal, the speed control band is limited by the phase delay caused by sampling because the speed detection becomes discrete. This is well known. Therefore, if the disk has a large eccentricity, or if vibrations or shocks are applied to the device from the outside, the control error in speed control will increase, and the tracking pull-in speed will become too large, making it difficult to control the tracking to the target track. There were times when the retraction failed.

On the other hand, if the tracking pull-in speed becomes too low, the time required for trunk search becomes longer.

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an apparatus that realizes stable tracking control to a target track without increasing the control band of speed control.

Means for Solving the Problems The present invention provides a converting means for reproducing or recording a signal from an information carrier on which information is recorded or has a track on which information is recorded, and the converting means is abbreviated as the information carrier. A track search device having a moving means for moving horizontally and in a direction perpendicular to the track, and for moving the converting means to a desired target track other than the track where the converting means is located, and detecting the speed of the converting means. The moving means is provided with a speed detecting means, and is configured to apply a driving pulse to the moving means according to the output of the speed detecting means when the converting means reaches a predetermined position in front of the target track. .

By configuring the present invention as described above, for example, if large vibrations or shocks are applied to the device from the outside, or if the disk has a large eccentricity and the control error in speed control is large, the present invention can be configured as described above. Since a deceleration pulse or an acceleration pulse is applied, fluctuations in tracking pull-in speed are reduced, and track searches can be performed stably.

Embodiment Hereinafter, a trunk search device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention; a converging lens 1 and a reflecting mirror 2.
is mounted on the transfer table 3, and is driven by the voice coil motor 4.
Disc 6 being rotated by disc motor 5
is configured to be driven in a substantially radial direction. 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, passes through a polarizing beam splitter 9 and a 1/4λ plate 10, and passes through a reflecting mirror mounted on the transfer table 3. 2.

The light beam reflected by the reflecting mirror 2 passes through the converging lens 1
The light is converged and irradiated onto the disk 6. disk 6
The reflected light passes through a converging lens 1, is reflected by a reflecting mirror 2, passes through a 1/4λ plate 10, and is sent to a polarizing beam splitter 9.
, and enters the two-split photodetector 11 . The dividing line of the two-split photodetector 11 is arranged so as to be in the longitudinal direction of the track on the light receiving surface. Two-split photodetector 11
The output signal is input to the differential amplifier 12. It is known that the output signal of the differential amplifier 12 configured in this manner becomes a tracking error signal TE as shown in FIG.

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

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

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

The track crossing signal TC is input to a 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 measured 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 trunk pitch.

Since the speed value DV is a value that is sampled discretely every time a track is crossed, the speed calculation circuit 21 is configured to hold the speed value DV after one sampling until at least the next sampling. has been done.

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

The track crossing signal TE is also input to a counter 25 whose count value can be preset. The counter 25 counts the number of tracks crossed.

The count value of the counter 25 is converted into a command speed by a command speed generator 27, further converted into an analog value by a 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 minus number calculation circuit 29.30. The number calculation circuits 29 and 30 compare the counted values of the counter 25 with respective predetermined values and output matching signals X1 and x2 to the microcomputer (hereinafter referred to as microcomputer) 26, respectively.

The output value of the speed detection circuit 21 is also input to the microcomputer 26, and the microcomputer 26 can read the current speed of the light beam. Furthermore, a D/A converter 33 whose output is input to the adder circuit 16 via a switch 34 is connected to the microcomputer 26, so that the microcomputer 26 can drive the transfer table 3.

Control signals for the switches 15, 24, and 34 are output from the microcomputer 26, and their operations are controlled by the microcomputer 26.

Hereinafter, the detailed operation of each part will be explained by explaining the track search operation step by step.

Before performing a track search, the switch 15 is turned on, and the switches 24 and 34 are turned off, tracking control is activated, and the light beam follows a predetermined track.

Prior to the track search, the microcomputer 26 presets the track difference from the trunk search start track to the target track in the counter 25.

Switch 15 is turned off by command from microcomputer 26
, the switch 24 is turned on, the light beam begins to move toward the target track, and a search operation is started.

The counter 25 decreases the count value by 1 each time the track crossing signal TC is input during the search operation. Therefore, the count value of the counter 25 during track search represents the current position of the light beam with respect to the target track. 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 an address line, and the data line is connected as an output to an A/D converter 28.

Each count value of the counter 25, ie, 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.

In order to smoothly perform a track search, data is set in the ROM such that the larger the count value of the counter 25, the larger the command speed, 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 adverse effects due to limitations on the dynamic range of speed control.

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

The farther the light beam is from the target track, the larger the speed command signal, and the closer the light beam is to the target track, the smaller the speed command signal is given for speed control.

Therefore, as the track search is started and the light beam moves toward the target track, the count value of the counter 25 decreases, and the moving speed of the light beam also decreases correspondingly. Approach the target truck.

On the other hand, the minus number output circuit 29 is configured to output the match signal X1 as "L" to the microcomputer 26 when the count value of the counter 25 reaches 2, and as "H" otherwise. There is. When the coincidence signal XI becomes "L", it means that the light beam has reached the track two tracks before the target track.

Immediately when the coincidence signal X1 becomes L', the microcomputer 26 turns off the switch 24 to disable speed control, and reads the speed value DV calculated by the speed detection circuit 21.

The microcomputer 26 calculates and outputs a polarized digital value H that substantially satisfies the following equation to the D/A converter 33 based on the speed value DV, and turns the switch 34 "ON" for a period W.

DVref-DV = Gda*Gadd*Gdr*F*H*W/M However, [)Vref: Target pull-in speed Gda: Conversion gain of D/A converter 33: Gain of addition circuit 16: Gain of drive circuit 17: Voice coil Thrust constant of motor 4 add dr M: Mass to be transferred The mass to be transferred M is the sum of the total mass of the parts on the transfer table, such as the converging lens 1 and the reflection mirror 2, and the mass of the transfer table itself.

The polarity of the digital value H with polarity is DV is DVref.
If it is larger than , the speed of the light beam is set to be reduced.

That is, when the speed of the light beam at the trunk two tracks before the target track is higher than the target pull-in speed DVref, a deceleration pulse equivalent to decelerating the light beam approximately to the target pull-in speed is applied. It is composed of In addition, if the speed of the light beam at 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 approximately to the target pull-in speed is applied. It is configured.

After the period W has elapsed, the switch 34 is turned "OFF" again. At this time, the speed of the light beam is approximately the target pull-in speed. Thereafter, the light beam moves toward the target track due to inertia. On the other hand, when the count value of the counter 25 becomes O, the - number calculation circuit 30
It is configured to output the match signal x2 to the microcomputer 26 as "L" and in other cases as "H". Therefore, when the light beam reaches the target track and the coincidence signal X2 becomes L'', the microcomputer 26 immediately turns on the switch 15, operates the tracking control, and completes the track search.

With this configuration, for example, there are cases where large vibrations or shocks are applied to the device from the outside, or the disk has a large eccentricity, which increases control errors in speed control and increases the pull-in speed of tracking control. Even in such a case, by applying an appropriate deceleration pulse, the increase in tracking pull-in speed can be eliminated, and trunk search can be performed stably without failing to pull the tracking control to the target track.

On the other hand, when the pull-in speed of tracking control becomes small, the increase in time required for track search can be reduced by applying an appropriate acceleration pulse.

A feature of the embodiment according to the present invention is that the difference between the tracking pull-in speed and the target pull-in speed caused by disturbance is not limited by the speed control band or gain. Further, in this embodiment, the coincidence detection circuit 29 is configured to detect when the count value of the counter 25 becomes 2, but the same result can be obtained even if this is extended to N (N is a positive integer). It is clear that this effect can be obtained. At this time, the light beam is located at a track N tracks before the target trunk.

Furthermore, although the microcomputer 26 is configured to set the peak value H1 width W of the acceleration pulse or deceleration pulse applied from the track N tracks before the target track according to the speed of the light beam, one of the peak value H2 width W Even if one is fixed and the other is set by the microcomputer 26, the same effect can be obtained.

Further, although the acceleration pulse and the deceleration pulse are rectangular waveforms, it is clear that the waveforms may be triangular waveforms, trapezoidal waveforms, or the like.

Further, in this embodiment, the track crossing signal detection circuit 18 is
As shown in Figure d, it is assumed that it is detected that the light beam crosses the center of the track, but as shown in Figure 2 e, it is assumed that it is detected that the light beam crosses the center of the track and the midpoint between the tracks. It is clear that the same effect can be obtained even if the configuration is configured.

In that case, the speed calculation circuit 21 calculates the digital speed value DV of the light beam from the measured value DT of the timer 20 according to the following equation.

DV=P/(2*DT) However, P is the distance between tracks.

Further, prior to the track search, the microcomputer 26 presets the counter 25 with a value twice the track difference between the track search start track and the target track. Therefore, in this case, the position at which the deceleration pulse or acceleration pulse is applied is set by 0.5 in the number of tracks before the target track.
You can specify the height of the plant.

Further, in this embodiment, after the period W has elapsed, the switch 24 is turned OFF.
Although the switch 24 remains "F", the switch 24 is turned ON again, and when the match signal X2 becomes "L", the switch 24 is turned ON again. A similar effect can be obtained even if the switch is set to OFF''.

Effects of the Invention By configuring the present invention as described above, for example, large vibrations or shocks may be applied to the device from the outside, or the eccentricity of the disk may be large, resulting in a large control error in speed control and tracking control. Even when the pull-in speed increases, the increase in the tracking pull-in speed can be eliminated by applying an appropriate deceleration pulse, and trunk search can be stably performed without failing to pull the tracking control to the target track.

Furthermore, even when the pull-in speed of tracking control becomes small, the increase in time required for track search can be reduced by applying an appropriate acceleration pulse.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 2 is an explanatory diagram of a tracking error signal and a track crossing signal when a light beam crosses a track, and Fig. 3 is an explanatory diagram of a counter count value and a command speed. It is an explanatory diagram for explaining the relationship. 1...Converging lens, 3...Transfer table, 4
...Voice coil motor, 7...Light source, 11...2-split photodetector, 12...
Differential amplifier, 18... Track crossing signal detection circuit, 20... Timer, 22.28.33...
... D/A converter, 21 ... Deceleration calculation circuit, 27 ... Command speed generator, 26 ...
...Microcomputer-29,30...
- Number circuit, 15, 24, 34... switch, 23... differential circuit, 16... adder circuit. Name of agent: Patent attorney Shigetaka Awano (1 person) Figure 1 Figure 1 Figure 1! ! Measurement cunning box

Claims (6)

[Claims] (1) A converting means for recording information or for reproducing or recording a signal from an information carrier having a track on which information is recorded, and converting the converting means in a direction approximately horizontal to the information carrier and perpendicular to the track. a moving means for moving the converting means to a desired target track other than the track where the converting means is located, the track searching device comprising a speed detecting means for detecting the speed of the converting means. . A track search device, characterized in that, when the converting means reaches a predetermined position in front of the target track, a drive pulse corresponding to the output of the speed detecting means is applied to the moving means. (2) The track search device according to claim (1), wherein the drive pulse has a rectangular shape. (3) Claim (2) characterized in that the width of the drive pulse is configured to change according to the output of the speed detection means.
Track search device as described. (4) Claim (4) characterized in that the peak value of the drive pulse is configured to change in accordance with the output of the speed detection means (
2) The track search device described above. (5) By detecting that the converting means crosses the track or near the midpoint between the tracks and counting the detected signals, the converting means is moved to a predetermined position in front of the target track. The track search device according to claim 1, wherein the track search device detects that the track has arrived. (6) The speed detecting means detects when the converting means crosses the track or near the midpoint between the tracks, and detects the speed of the converting means from the period of this detected signal. A track search device according to claim (1).