JPH05282681A - Tracking controlling device in optical disk device - Google Patents

Abstract

PURPOSE:To make an accurate tracking by pulling an optical head in the required track without fail for all cases of recording, reproduction, and deletion in the tracking controlling device in the optical disk device. CONSTITUTION:From the difference of detection signals Sa and Sb of a light receiving element 1, a tracking error detection circuit 2 outputs an error signal TE and a sum signal synthesizing circuit 3 outputs a sum signal TS from the addition of the signals Sa and Sb. A zero-cross detection circuit 8 detects the true zero cross of the error signal TE by referring to the sum signal TS and outputs a signal TZC. A level discrimination circuit 9 outputs a signal TWC during the period the level of the error signal TE is within a preset range + or -Vr. A CPU 10 turns on a switch 5 by outputting a pull-in signal when the lasting time of the signal TWC exceeds a preset reference value Min and the signal TZC comes within the period. After that, the accurate tracking is performed by operating the servo systems of a servo amplifier 4 and an actuator 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tracking control device used for tracking an optical head during recording or reproduction on an optical disk device.

[0002]

2. Description of the Related Art An optical disk is a reproduction-only CD (compact disk) or LD (laser) for reading information by changing the light quantity by utilizing interference of laser light due to irregularities (pits) on a recording surface depending on the presence or absence of a signal. Disk), and the signal is converted to light and shade on the recording surface by the thermal action of laser light.
Recording that records only once and reads information by the change of reflectance,
A rewritable write-once optical disc and a vertical magnetic field whose magnetic direction is different depending on the signal are repeatedly recorded, and the information is read by detecting the difference in the rotation angle of the polarization of the reflected light. There are rewritable magneto-optical disks.

In any of the optical discs, recording or reproducing must be performed in accordance with a desired track. However, since the pitch between tracks is as fine as μm, even if there is a slight eccentricity, one revolution of the disc is performed. Since each track reciprocates for several to several tens of tracks, it is necessary to track (track) an optical head such as an optical pickup or an optical storage head in accordance with a desired vibration of the track.
Therefore, a tracking control device is provided. Further, the tracking control device frequently repeats the pull-in operation of prompting a track including a desired sector at the time of recording or reproducing to enter into tracking in order to take advantage of the high-speed random access function of the optical disk.

FIG. 10 is a circuit diagram showing a conventional example of a tracking control device. The reflected light from the spots on the optical disk (not shown) are respectively reflected by the optical system of the optical head.
Two light receiving surfaces 31a, 31 of the light receiving element 31 divided into two
An image is formed on the boundary line of b, and when the spot is correctly on the center line of the track, an equal amount of light is incident on the light receiving surfaces 31a and 31b. Other light is reduced.

Therefore, the tracking error detection circuit 3
2 outputs a tracking error signal TE by taking the difference between the detection signals Sa and Sb output by the light receiving surfaces 31a and 31b of the light receiving element 31, respectively. Further, the sum signal synthesis circuit 33 calculates the sum of the detection signals Sa and Sb to obtain the sum signal T including the reflected light amount and the reproduced information signal component.
Output S.

The servo amplifier 34 receives the tracking error signal TE and zeros it out.
Is output to the driver 36 via the switch 35 that is on during tracking, and the actuator 37 is driven according to the control signal SS input by the driver 36, thereby performing servo control so that the spot always coincides with the track center. Is being carried out.

However, in order to perform tracking by servo control, it is necessary to pull in a desired track at the initial stage and start a tracking operation. Therefore, the zero-cross detection circuit 38 inputs the tracking error signal TE and the sum signal TS, detects the zero-cross when the spot coincides with the track center, and outputs the zero-cross signal TZC to the CPU 40 for each zero-cross.

CPU provided with ROM 41 and RAM 42
40 detects the zero-cross signal TZC and judges the point where the track eccentricity is the smallest, outputs a pull-in signal CC and turns on the switch 35 to start tracking. The level determination circuit 39 inputs the tracking error signal TE and outputs a signal TWC to a tracking determination circuit (not shown) if the level is within a certain level range. That is, the signal TWC indicates whether the spot is within a predetermined shift range from the center of the track or out of the track center during tracking.

Further, for example, the proposal disclosed in Japanese Patent Laid-Open No. 61-253677 is included in the sum signal TS when the information recorded on the optical disk is reproduced when the zero-cross detection circuit 38 detects the zero-cross. The present invention is common in that the presence or absence of a high-frequency signal that exists is used to perform the lead-in, and the lead-in is performed based on the zero-cross signal TZC.

[0010]

However, if the optical disk has a slight eccentricity, the reciprocal movement (vibration) of the relative position between the spot and the track is several tens to several tens of tracks when the tracking is not performed by the servo control. Some things have already been mentioned.

Therefore, the following conditions must be satisfied in order for the tracking pull-in to be performed smoothly. (1) The spot is at or near the center of the track. (2) The relative velocity of the spot and the track in the radial direction is as small as possible.

Not to mention the former condition (1), in the past, therefore, the pull-in was performed based on the zero cross of the tracking error signal TE. In the latter condition (2), on the contrary, when the relative speed is large, even if the pull-in signal CC is output at the zero-cross point, the spot is tracked by the time the actuator 37 operates and the servo control effectively operates. It may be off-center or moved to another track, which is effective in preventing such mistakes.

However, in the conventional technique based on only the zero-cross signal TZC, it is possible to detect the timing when the relative velocity between the spot and the track required for the condition (2) is small even if the condition (1) can be satisfied. I could not do it.
Further, the zero-cross of the tracking error signal TE is such that a true signal output when the spot coincides with the track center and a false signal output when the spot is in the center between the two tracks appear alternately. There was a serious problem.

According to the proposal disclosed in the above-mentioned Japanese Patent Laid-Open No. 61-253677, it is a true signal if there is a high frequency signal when a zero cross is detected, and a false signal if it does not. However, this is effective when reproducing the recorded information, and when recording the information on the virgin track,
It has no effect because there is no high frequency signal to be reproduced.

The present invention has been made in view of the above points, and the tracking control device of the optical disk device can surely pull the optical head into a desired track and perform correct tracking in any of recording, reproducing and erasing. The purpose is to do so.

[0016]

In order to achieve the above object, the present invention forms a tracking error signal based on a detection signal obtained by detecting light reflected from a spot on an optical disk by a light receiving element, and the tracking error signal is formed. In a tracking control device of an optical disk device that controls tracking according to

Zero-cross detection means for detecting the zero-cross of the tracking error signal when the spot coincides with the track center, and whether or not the tracking error signal is within a preset level range, are determined within the level range. When there is a level discriminating means for outputting a level discriminating signal, and when the duration of the level discriminating signal output by the level discriminating means is equal to or greater than a preset reference value and the zero cross detecting means detects a zero cross, a pull-in signal is output. And a tracking pull-in means for performing a tracking pull-in operation according to the pull-in signal output by the pull-in signal output means.

Further, the zero-cross detecting means for detecting the zero-cross of the tracking error signal and whether or not the tracking error signal is within a preset level range are determined to be within the level range and the spot is within the track. In this case, the level discriminating means outputs the level discriminating signal, and the pull-in signal is output when the duration of the level discriminating signal output by the level discriminating means is equal to or more than a preset reference value and the zero cross detecting means detects the zero cross. A pull-in signal output unit and a tracking pull-in unit that performs a tracking pull-in operation according to the pull-in signal output by the pull-in signal output unit are provided.

In the tracking control device of the above optical disk device, when the pull-in signal output means cannot output the pull-in signal when the tracking control device starts tracking, a pull-in error occurs, which is set in the level discriminating means. It is advisable to provide a level range correction means for gradually expanding the level range. Alternatively, a reference value correction means for stepwise shortening the preset reference value may be provided in the pull-in signal output means each time the occurrence occurs.

[0020]

In the tracking control device of the optical disk device configured as described above, the zero-cross detection means detects the zero-cross of the tracking error signal when the spot coincides with the track center, and the level determination means presets the tracking error signal. When it is within the level range, the level discrimination signal is output. The pull-in signal output means compares the duration of the level discrimination signal output by the level discrimination means with a preset reference value, and if the duration is longer than that, the relative speed of the spot and the track is reduced to a certain value or less. If the zero-cross detection means detects a zero-cross while the determined level discrimination signal is being output, the pull-in signal is output.

The zero-cross detection means detects the zero-cross of the tracking error signal, and the level discrimination means outputs the level discrimination signal when the tracking error signal is within the preset level range and the spot is within the track. In this case as well, similarly to the above, the pull-in signal output means compares the duration of the level determination signal output by the level determination means with a preset reference value and if it is longer than that,
If the zero-cross detector detects a zero-cross signal while the level discrimination signal is being output, it outputs a pull-in signal.

In any case, when the two judgments are satisfied, the pull-in signal output means outputs the pull-in signal, and the tracking pull-in means performs the tracking pull-in operation in accordance with the pull-in signal, so that the target track is selected. You can reliably pull in and track correctly.

If the two judgments cannot be satisfied at the same time in the set level range or the reference value and the pull-in signal output means cannot output the pull-in signal and a pull-in error occurs, the level range correcting means makes the level change. The level range set in the determination means is expanded stepwise each time, and the pull-in signal output means makes the above determination in the expanded level range.

Alternatively, the reference value correction means shortens the reference value step by step each time a pull-in error occurs, and the pull-in signal output means makes the above determination based on the shortened reference value. Therefore, the two determinations are satisfied at the same time, and the pull-in signal output means outputs the pull-in signal, so that reliable pull-in is performed.

[0025]

1 is a circuit diagram showing a configuration of a tracking control device for an optical disk device according to a first embodiment of the present invention. A light receiving element 1 having light receiving surfaces 1a and 1b divided into two parts, and a tracking error. The tracking error detection circuit 2 that outputs the signal TE, the sum signal synthesis circuit 3 that synthesizes the sum signal TS, the servo amplifier 4, the switch 5, the driver 6, and the actuator 7 that form the tracking servo system, respectively, and the zero cross detection means. A certain zero-cross detection circuit 8, a level discrimination circuit 9 which is a level discrimination means, and a CP which is a pull-in signal output means for outputting a pull-in signal CC.
U10 and ROM11, R which are storage elements of CPU10
It is composed of AM12.

The tracking servo system switch 5
Is an analog switch that is a tracking pull-in unit that is always open and closes while the pull-in signal CC is input to input the control signal SS output from the servo amplifier 4 to the driver 6.

Reflected light from a spot on the optical disk (not shown) is divided into two by the optical system of an optical head such as an optical recording head or an optical pickup (not shown) or a head that combines the two. , 1
When the image is formed on the boundary line of b, and the center of the spot correctly tracks the center line of the track on the optical disk, the light amount is set to be incident on the light receiving surfaces 1a and 1b. When the center of the spot deviates to the left from the center line of the track, the amount of light incident on the light receiving surface 1a increases and the amount of light on the light receiving surface 1b decreases, and when it deviates to the right, the amount of light on the light receiving surface 1a decreases conversely. As a result, the amount of light on the light receiving surface 1b increases.

The tracking error detection circuit 2 detects the detection signal S output from the light receiving surfaces 1a and 1b of the light receiving element 1, respectively.
Since the difference signal (Sa-Sb) is taken as the tracking error signal TE by taking the difference between a and Sb, the center of the spot is left from the center line of the track if the tracking error signal TE is positive, and right if negative. If it is zero, you can see that you are tracking correctly. Further, since the irradiation light quantity of the spot, that is, the reflected light quantity is different by one digit or more between the recording mode and the reproduction mode, the tracking error detection circuit 2 outputs the tracking error signal TE of substantially the same level in any mode. To work.

The sum signal synthesizing circuit 3 synthesizes the detection signals Sa and Sb and outputs the sum signal TS. Similar to the tracking error detecting circuit 2, adjustment is performed according to the mode. Since the sum signal TS contains the information signal as a high frequency component when information is recorded on the optical disc or reproduced from the optical disc, the sum signal TS is output to a reproduction signal detection circuit (not shown) to separate the reproduction signal.

Further, the level of the sum signal TS does not change even if the detection signals Sa and Sb become unbalanced due to tracking bias, and shows the reflected light amount itself. As will be described later, the level of the optical disc on which tracks are recorded is shown. Since the amount of reflected light is large at the land portion and much smaller at the grave portion between tracks, it is also output to the zero-cross detection circuit 8 in order to determine the authenticity of the zero-cross according to the level.

The tracking error signal TE output from the tracking error detection circuit 2 is input to the servo amplifier 4, the zero-cross detection circuit 8 and the level discrimination circuit 9, respectively. The servo amplifier 4 inputs the tracking error signal TE and outputs a control signal SS, which has been subjected to phase correction of the entire servo system including the mechanism and the circuit so that it becomes zero, to the driver 6 via the switch 5. .. When the switch 5 is on, the driver 6 outputs a drive current according to the input control signal SS to drive the actuator 7, and servo-controls so that the spot always correctly tracks the track. When the switch 5 is off, it acts to lock the spot in the neutral position.

FIG. 2 is a circuit diagram showing an example of the configuration of the zero-cross detection circuit 8 of the first embodiment shown in FIG. This zero-cross detection circuit 8 has two comparators 15, 1
8, pulse shaping circuit 16 and LPF (low pass filter)
Of the zero crossings of the tracking error signal TE, the zero crossing signal T is formed when the spot coincides with the track center and is a true zero crossing.
ZC is output, and it is not output when the spot is a false zero cross near the center between tracks.

The comparator 15 has a negative input terminal connected to the ground to act as a zero-cross comparator,
A high signal is output to the pulse shaping circuit 16 when the tracking error signal TE input to the input terminal is positive, and a low signal is output when the tracking error signal TE is negative. The pulse shaping circuit 16 detects a rising edge and a falling edge of the input signal and outputs a single positive logic pulse signal to the AND circuit 1.
It outputs to the input terminal of 9.

Sum signal TS input from sum signal synthesis circuit 3
In addition to noise, a high frequency component such as a sector mark indicating the start of each sector, a sector number, or a signal from which information has been reproduced in the case of a track including a sector in which information has already been recorded is included. In order to determine whether the spot is on the land 26 (true state) or on the groove 27 (false state), since these high frequency components are an obstacle, the sum signal TS to be input is first LPF17. Then, the high frequency component is removed and the result is output to the comparator 18.

The comparator 18 has a + input terminal and a sum signal T
Since S is input and the threshold voltage Vs (> 0) is applied to the-input terminal, the AND circuit 19 outputs a high signal when the level of the sum signal TS is Vs or higher and a low signal when it is lower than Vs. Output to the other input terminal of. Therefore, the AND circuit 19 outputs the zero-cross signal TZC to the CPU 10 only when the level of the sum signal TS is equal to or higher than the threshold value Vs, that is, while the spot is on the land portion 26.

FIG. 3 is a circuit diagram showing an example of the configuration of the level discrimination circuit 9 shown in FIG. This level discrimination circuit 9
Is composed of a level range generation circuit 20, two comparators 21 and 22 and an AND circuit 23 forming a window comparator, and is high and level range when the tracking error signal TE is within a set positive and negative level range. When it is outside, it outputs a level determination signal TWC that goes low.

The level range generation circuit 20 stores r (digital value) indicating the range set by the CPU 10,
A positive / negative analog signal ± Vr corresponding to the stored digital value r is generated, and the upper limit value + Vr of the level range is set to the + input terminal of the comparator 21 that monitors the upper limit of the tracking error signal TE. It outputs to each-input terminal of the comparator 22 that monitors the lower limit.

Since the tracking error signal TE input to the level discriminating circuit 9 is input to the negative input terminal of the comparator 21 and the positive input terminal of the comparator 22, respectively, the upper limit comparator 21 has a level of the error signal TE equal to or lower than the upper limit value + Vr. When it is, a high signal is output to the AND circuit 23, and when it is over, it outputs a low signal to the AND circuit 23. The lower limit comparator 22 outputs a high signal when the level of the error signal TE is the lower limit value -Vr or more, and a low signal when it is less than. It is output to the AND circuit 23.

Therefore, if the level of the tracking error signal TE is te, te> + V from the AND circuit 23.
Low when r or te <-Vr, + Vr ≧ te ≧ −
The level determination signal TWC that becomes high when Vr is output to the tracking determination circuit (not shown) as in the conventional example, but is also output to the CPU 10 at the same time in the first embodiment and the second embodiment described later. If the digital value r set by the CPU 10 changes, the upper and lower limit values ± Vr of the level range change accordingly, but the changed level range ± Vr
Accordingly, the tracking error signal TE is similarly discriminated and the level discrimination signal TWC is output.

Information reproduction, recording, or erasing is performed in units of sectors, and a plurality of, for example, 26 sectors are gathered to form one track. Therefore, when reproducing, recording, or erasing, the CPU 10 first makes the ROM 1
According to the program stored in 1, the pull-in signal CC is set low and the switch 5 is opened to put the servo system in the neutral state. Next, the optical head (not shown) is moved to stop at the desired position of the track including the desired sector, and the pull-in operation is performed. At this time, as described above, the track reciprocates (vibrates) in the radial direction with respect to the stationary spot due to the eccentricity of the optical disk or the like.

FIG. 4 is an explanatory diagram showing an example of the relationship between the relative motion in the radial direction and the signal waveform that accompanies it, where the horizontal axis is the time axis. 4A and 4B are a plan view showing a part of the relative movement (up and down in the radial direction) of the spot viewed from the track and an enlarged cross-sectional view of the optical disk portion, and FIG. Is a diagram showing the relative velocity (radial component) RV of the spot, (D), (E), (F) of FIG.
FIG. 4 is a waveform diagram showing a tracking error signal TE, a zero cross signal TZC, and a level determination signal TWC, respectively.

As shown in FIGS. 4A and 4B, the surface of the recordable / reproducible optical disk 25 is provided with grooves 27, which are shown by hatching in advance, and between the grooves. The remaining flat portion is the land 26 on which a track is to be formed. The center lines of the lands 26a to 26c (center lines of the tracks to be formed) are indicated by alternate long and short dash lines, and the grooves 27a to 2 are formed.
The center line of 7c is shown by a chain double-dashed line. Also, curve 2
Reference numeral 8 indicates the locus of the position of the spot with respect to the horizontal axis (time axis), and its apex is P.

When the spot makes the relative movement as shown by the curve 28, the relative velocity RV becomes zero at the apex P as shown in FIG. 4C, and becomes small near the point P. Therefore, the pull-in condition (2) described in the problem to be solved is satisfied. Further, in the vicinity of the point P, the tracking error signal TE changes as shown in FIG. 4D, and the spot takes an extreme value at the place where the center of the spot passes through the boundary between the land 26 and the groove 27, and the spot becomes It becomes zero where it passes through the center line of the land 26 indicated by the one-dot chain line and the center line of the groove 27 indicated by the two-dot chain line.

Therefore, the pulse shaping circuit 16 of the zero-cross detection circuit 8 (FIG. 2) outputs the pulse shown by the solid line and the chain double-dashed line in FIG. 4E, but in the former case, the curve 28 is the land 26. Is a true zero cross that coincides with the center of the groove, and the latter is a false zero cross that coincides with the center line of the groove 27.

As described above, the spot is the land 2
The amount of reflected light is large when it is on the groove 6, and is much smaller when it is on the groove 27. Since the comparator 18 (FIG. 2) compares the level of the sum signal TS corresponding to the amount of reflected light with the threshold voltage Vs, and makes the output high only when the spot is on the land 26, the AND circuit 19 prevents a false zero cross. Then, the zero-cross signal TZC becomes as shown by the solid line.

The level discrimination signal TW shown in FIG.
C is high when the tracking error signal TE is within the set ± Vr level range as shown in (D) of the figure, and is low when the tracking error signal TE is out of the level range.
As is clear from (E) and (F) of FIG.
In the vicinity of the point P where V is small, the interval of the zero-cross signal TZC and the duration of the level determination signal TWC (which is high) become long, and become shorter as the distance from the point P increases.

FIG. 5 shows the CPU 10 which is the pull-in signal output means and also the level range correction means or the reference value correction means.
FIG. 9 is a flowchart showing an example of a routine for performing a pull-in operation after moving the optical head to a track including a desired sector to start tracking.

A counter such as a timer and a TWC counter for recording elapsed time is provided in the RAM 12 in advance. Also, a digital value r that specifies the level range
Then, Min, which is a reference value for determining the elapsed time, is also set. The timer is cleared for each start command, and is constantly counting up during execution of this routine. TW
The C counter starts counting with a start command, and is cleared and stopped with a stop command.

When this pull-in operation routine starts,
First, the timer is started from 0 in S1 (step 1, the same applies hereinafter), and a loop from S2 onward is entered.

In S2, the rise of the level determination signal TWC is determined, and if not, the process proceeds to S4, and if it rises (the signal TE is within the level range), the process proceeds to S3, where it is 0. After starting the TWC counter, the process proceeds to S4. S
In 4, the trailing edge of the level determination signal TWC is determined, and if not, the operation proceeds to S6 (the signal TE goes out of the level range).
If so, the process proceeds to S5, the TWC counter is cleared and stopped, and then the process proceeds to S6. In step S6, it is determined whether or not the duration of the level determination signal TWC, which is the content of the TWC counter, that is, the time during which the tracking error signal TE is within the level range has exceeded the reference value Min. In S7, it is determined whether or not the zero-cross signal TZC is input.

If both S6 and S7 are yes,
By jumping to S10 and setting the pull-in signal CC to high, the switch 5 is turned on to perform the pull-in operation, and the process ends. After that, the servo system tracks the track including the target sector, and the information is reproduced, recorded, and erased.

If either S6 or S7 is NO, the process proceeds to S8 to determine whether or not the timer started at the beginning of the routine (S1) has overflowed. If NO, the process returns to S2 to loop. Repeat. If the pull-in signal CC is not output even if the timer overflows, that is, after a lapse of a predetermined time from the start of the routine, it is determined that there is a pull-in error, the process proceeds to S9, the pull-in error process is performed, and the process returns to S1 to restart this routine. Start over.

As can be seen from FIGS. 4D and 4F, it is desirable that the level range ± Vr is narrow and the reference value Min of the duration of the level discrimination signal TWC is long, so that the optical disk device is powered on. At the time of initializing the optical disc or at the time of exchanging the optical disc, they are respectively set to desirable values, but there is a reciprocal relation that the duration of the level discrimination signal TWC becomes short if the level range is narrow.

Therefore, when the relative velocity between the spot and the track becomes large due to the reason that the eccentricity of the optical disk is relatively large, or the vertex P is not at the convenient position as shown in FIG. If the center line of the land portion is not reached or if it is in the groove portion, zero-cross is not detected before or after the vertex P or the level determination signal TWC becomes low, and the pull-in signal CC is not output, and a pull-in error may occur. ..

Therefore, in the pull-in error processing in S9 of the flow chart shown in FIG. 5, the CPU 10 has the digital value r set in the level range generation circuit 20 (FIG. 3) of the level determination circuit 9 each time. It is corrected by adding a constant value (level range correction means) or C which is a pull-in signal output means.
The PU 10 itself reduces the reference value Min compared with the TWC counter (reference value correction means), or performs both of them simultaneously or alternately.

As a result, the level range ± Vr is expanded and the duration of the level discrimination signal TWC is extended, or the pull-in signal CC can be output even if the duration is short. As a result, conditions suitable for the set optical disk are set, and thereafter, there is an effect that a frequent drawing operation can be smoothly performed every time after that.

FIG. 6 is a circuit diagram showing a configuration of a tracking control device for an optical disk device according to a second embodiment of the present invention. The difference from the first embodiment shown in FIG. The level discriminating circuit 9 becomes a zero cross detecting circuit 8a and a level discriminating circuit 9a, respectively, and the sum signal TS output from the sum signal synthesizing circuit 3 is the zero cross detecting circuit 8a.
It is input to the level discriminating circuit 9a instead of "a", and the other same parts are denoted by the same reference numerals and the description thereof will be omitted.

FIGS. 7 and 8 are circuit diagrams showing the configurations of the zero-cross detection circuit 8a and the level discrimination circuit 9a of the second embodiment shown in FIG. 6, respectively. The zero-cross detection circuit shown in FIGS. 8 and the level discriminating circuit 9 are different from the LP which constitutes the zero-cross detecting circuit 8.
The F17, the comparator 18, and the AND circuit 19 are moved to the level discrimination circuit 9a, and the 2-input AND circuit 19 and the 2-input AND circuit 23 of the level discrimination circuit 9 are integrated into 3
This is a point different from the input AND circuit 24, and other same parts are denoted by the same reference numerals.

FIG. 9 is an explanatory view showing an example of the relative movement of the spot and the track in the radial direction and the signal waveform according to the second embodiment. FIGS. 9A to 9D are respectively shown in FIG. This is the same as (A) to (D), and (E) and (F) of FIG. 9 correspond to (E) and (F) of FIG. 4, respectively.

By configuring as shown in FIGS. 6 to 8, the zero-cross detection circuit 8a is true (T) or false (T) at each zero-cross of the tracking error signal TE, as shown in FIG. 9 (E). The zero cross signal TZC is output regardless of F). On the other hand, the level discriminating circuit 9a outputs the level discriminating signal TWC only when the level of the tracking error signal TE is within the level range in a true state where the spot is on the land 26, as shown in FIG. Output.

In the second embodiment, even if the CPU 10 executes the routine shown in the flow chart of FIG. 5, the correct tracking pull-in operation is performed just as in the first embodiment. Because, in the first embodiment, (E) and (F) of FIG.
As shown in, the level discrimination signal TWC is output regardless of the true and false states, but the zero-cross signal TZC is output only in the true state. Therefore, in both the first and second embodiments, the elapsed time of the level determination signal TWC exceeds the reference value Min and the zero cross is detected and the pull-in signal CC is output while the signal TWC is being output. Is only possible in the true state.

The true and false states are problematic in the case where the tracking pull-in operation is performed, and the true and false states are true in the reproduction signal detection and the tracking determination of the information signal after the tracking state is entered. Since the state of is maintained, there is no problem. Therefore, after the tracking servo system enters the operating state, the digital value r stored in the level range generation circuit 20 of the level determination circuits 9 and 9a is stored in the RAM 12 until the start of the next pulling operation, and the level range generation circuit. A level range for tracking determination may be set in 20.

Further, the zero-cross detection circuit and the level discriminating circuit are constituted by a combination of the zero-cross detection circuit 8a (FIG. 7) and the level discriminating circuit 9 (FIG. 3), and the LPF 17 and the comparator 18 are independent circuits. By directly inputting the true / false signal output from the CPU 18 to the CPU 10,
The same effect can be obtained by providing a determination between S6 and S7 in the flow chart shown in FIG. 8 that the process proceeds to S7 if the true / false signal is true and jumps to S8 if it is false.

[0064]

As described above, the tracking control device for the optical disk device according to the present invention is capable of recording, reproducing,
In either case of erasing, the optical head can be surely drawn into a desired track for correct tracking.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the configuration of a first embodiment of a tracking control device for an optical disk device according to the present invention.

FIG. 2 is a circuit diagram showing an example of the configuration of the zero-cross detection circuit shown in FIG.

FIG. 3 is a circuit diagram showing an example of a configuration of a level determination circuit shown in FIG.

FIG. 4 is an explanatory diagram showing an example of relative movement of a spot and a track and a signal waveform of the first embodiment.

FIG. 5 is a flowchart showing an example of a tracking pull-in routine.

FIG. 6 is a second tracking control device of an optical disk device.
It is a circuit diagram which shows the structure of an Example.

7 is a circuit diagram showing an example of a configuration of the zero-cross detection circuit shown in FIG.

FIG. 8 is a circuit diagram showing an example of a configuration of a level determination circuit shown in FIG.

FIG. 9 is an explanatory diagram showing an example of relative movement of a spot and a track and a signal waveform of the second embodiment.

FIG. 10 is a circuit diagram showing a configuration of a conventional example of a tracking control device of an optical disc device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 light receiving element 1a, 1b light receiving surface 2 tracking error detection circuit 3 sum signal synthesis circuit 5 switch (tracking lead-in means) 8, 8a zero cross detection circuit (zero cross detection means) 9, 9a level determination circuit (level determination means) 10 CPU ( Pull-in signal output means, level range correcting means, reference value correcting means) TE tracking error signal TS sum signal CC pull-in signal TZC zero cross signal TWC level discriminating signal Min reference value r level range (digital value) ± Vr level range (analog value)

Claims (4)

[Claims] 1. A tracking control device for an optical disk device, wherein a tracking error signal is formed based on a detection signal obtained by detecting light reflected from a spot on the optical disk by a light receiving element, and tracking is controlled according to the tracking error signal. Zero-cross detection means for detecting a zero-cross of the tracking error signal when the spot coincides with the track center, and whether or not the tracking error signal is within a preset level range, and within the level range When it is, the level discriminating means for outputting the level discriminating signal, and the duration of the level discriminating signal output by the level discriminating means is equal to or more than a preset reference value, and the zero cross detecting means detects the zero cross. The pull-in signal output means for outputting the pull-in signal and the pull-in signal output means Depending on the pull signal for tracking control device of an optical disk apparatus characterized by comprising a tracking pull-in means for performing a tracking pull-in operation. 2. A tracking control device for an optical disk device, wherein a tracking error signal is formed based on a detection signal obtained by detecting light reflected from a spot on the optical disk by a light receiving element, and tracking is controlled according to the tracking error signal. Zero-cross detection means for detecting zero-cross of the tracking error signal, and determining whether or not the tracking error signal is within a preset level range, and within the level range, and the spot is within the track. In some cases, the level discriminating means for outputting the level discriminating signal, and when the duration of the level discriminating signal output by the level discriminating means is equal to or greater than a preset reference value and the zero cross detecting means detects the zero cross, the pull-in operation is performed. A pull-in signal output means for outputting a signal, and a pull-in signal output means for outputting Depending on the pull signal, a tracking control device of an optical disk apparatus characterized by comprising a tracking pull-in means for performing a tracking pull-in operation. 3. The tracking control device for an optical disk device according to claim 1, wherein when the tracking control device starts a tracking, a pull-in error in which the pull-in signal output means cannot output a pull-in signal occurs, A tracking control device for an optical disk device, comprising level range correction means for stepwise expanding the level range set in the level determination means each time it occurs. 4. The tracking control device for an optical disc device according to claim 1, wherein when the tracking control device starts tracking, a pull-in error in which the pull-in signal output means cannot output a pull-in signal occurs, A tracking control device for an optical disk device, wherein a reference value correction means for stepwise shortening a preset reference value is provided in the pull-in signal output means every time the occurrence occurs.