JPH0845128A - Track-jumping detecting circuit of optical disk device - Google Patents

Abstract

PURPOSE:To conduct a normal recording by discriminating a track-jumping and a defect by a track-jumping detecting flag. CONSTITUTION:A defect signal f from a defect circuit 16 is inverted by an inverter 21. The circuit 16 compares the signals from a main spot detector 9M employing 77% of the average level of the signals from the detector 9M as a threshold value and outputs them. An offtrack circuit 17 performs the comparison of the signals using the average level of the signals from the detector 9M as a threshold value and outputs them. Signals from side spot detectors 9A and 9B are supplied to a tracking error signal generating circuit 12 and the signals from the detector 9M are supplied to the circuits 16 and 17. The output of a sample-and-hold circuit 15 is supplied to a control microcomputer. When the phase difference between the pulses from a masking means and the reproduced signal level pulses is within a prescribed range, a track-jumping flag is outputted, a track-jumping and a defect are discriminated and a normal recording is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track jump detection circuit for an optical disk device, and more particularly to a track jump detection circuit for an optical disk device which detects a track jump based on a tracking error signal.

[0002]

2. Description of the Related Art In a mini disk device (hereinafter abbreviated as MD) which is an optical disk device, if the device is vibrated during recording and reproduction, the optical pickup is likely to lose tracking or defocus.

When a sound skip occurs due to a tracking error or a focus error during reproduction, the optical pickup is returned to the position of the read data immediately before the vibration and a retry search is performed to read the data again.
Eventually, the skipping of sound is prevented.

On the other hand, if tracking error occurs during recording, for example, U-, which is the user's directory information.
TOC (USER TABLE OF CONTENT
S) If tracking deviation occurs during recording,
High-power laser light is emitted from the laser diode. Therefore, if the tracking error occurs and the laser beam is emitted to another recorded track, the recorded data on the track may be destroyed.

Therefore, in order to prevent the destruction of recorded data, by detecting a track jump and starting to jump from the original track to another track, the laser beam is powered down or the recording operation is stopped. There is. Track jump detection is performed using a tracking error signal, and the generation of the tracking error signal by the MD will be described here.

FIG. 5 is a diagram showing a three-beam optical system of MD.

In FIG. 5, laser light emitted from the laser diode 1 passes through a diffraction grating 2 and a main beam 2
It is divided into three sub-beams. After passing through the polarizing prism 3, each beam is collimated by the collimation lens 4 into parallel light. Each beam that is made parallel light is 1/4
After passing through the wave plate 5, it is condensed on the optical disk 7 by the biaxial device 6. The optical disc 7 is irradiated with a main spot M and side spots A and B.

Each reflected beam from the optical disc 7 is reflected by the polarizing prism 3 after following the optical path opposite to the above. Each reflected beam reflected by the polarizing prism 3 is
The cylindrical lens 8 irradiates the main spot detector 9 _M and the side spot detectors 9 _A and 9 _{B. A} tracking error signal is generated by subtracting the output signals from the side spot detectors 9 _A and 9 _B from each other.

FIG. 6 is a diagram for explaining generation of a tracking error signal using a 3-beam optical system.

FIG. 6A is a diagram showing the positional relationship between the track and each light spot. From time t ₁ to time t ₅ , the main spot M changes from track T ₁ to track T _2.
It shows how to fly to.

At time t ₁ , the main spot M is located at the center of the track T ₁ , the side spot A is displaced to the right from the center of the track T ₁ , and the side spot B is displaced from the center of the track T ₁ to the left by the same distance. There is. Therefore, the tracking error signal (FIG. 6 (B)) obtained from AB becomes zero level.

At time t ₂ , each light spot M,
A and B move to the track T ₂ side and the side spot A
The center of is the groove G between the tracks T ₁ and T _2.
Located in the center. On the other hand, the center of the side spot B is located at the center of the track T ₁ . Therefore, A <B
And the tracking error signal (FIG. 6 (B)) shows a negative peak.

At time t ₃ , each light spot M,
A, B is moved further in the track T ₂ close, the main spot M is located in the groove G center, side spot A is on the track T ₂ Towards groove G center, side spot B track T ₁ Towards groove G center They are offset by the same distance. Therefore, the tracking error signal (FIG. 6 (B)) obtained from AB becomes zero level again.

At time t ₄ , each light spot M,
A and B further move toward the track T _2, and the center of the side spot A is located at the center of the track T ₂ . on the other hand,
The center of the side spot B is the track T ₁ and the track T _2.
It is located at the center of the groove G between. Therefore, A
> B, and the tracking error signal (FIG. 6 (B)) shows a positive peak.

At time t ₅ , each light spot M,
A, B is moved further in the track T ₂ close, the main spot M is located in the track T ₂ center, side spots A is to the right from the track T ₂ center, side spots B, respectively to the left from the track T ₂ around the same It is off by the distance. Therefore, the tracking error signal (see FIG.
(B)) becomes zero level again.

As described above, the tracking error signal generated by the three-beam method has a zero-cross point which changes from positive to negative when the main spot M reaches the track center position,
When the main spot M reaches the center position of the groove G, it has a sinusoidal waveform having a zero-cross point that changes from negative to positive.

This tracking error signal is output from the comparator as shown in FIG.
Valued. The binarized signal is supplied to the control microcomputer, and the control microcomputer determines the track skip based on the binarized signal.

Also, using a window comparator,
When the tracking error signal level exceeds a certain positive and negative threshold value, the window comparator outputs a predetermined level, and the control microcomputer can detect it to predict a track jump.

[0019]

However, in the track jump detection circuit of the conventional three-beam method for the optical disc apparatus which obtains the track error signal from the side spot difference signal, various defects such as scratches on the reflection surface of the optical disc are detected. The waveform of the tracking error signal is similar to the waveform of the tracking error signal at the time of track jump, depending on the (defect) location and the result of dust adhesion.

FIG. 7 is a diagram for explaining generation of a tracking error signal due to a defect.

As shown in FIG. 7A, there is a defect 10 on a track T of an optical disc rotating in the direction of the arrow, and the track T has a main spot M and side spots A and B.
Is being irradiated.

When both side spots A and B are not in the defect 10, the difference signal B-A is at the zero level as shown in FIG. 7 (B). As the optical disc rotates, the side spot A preceding the main spot M has a defect 10
When it begins to intrude into, the difference signal B-A increases and becomes positive,
The difference signal B-A shows a positive peak when all the side spots A have entered the defect 10.

Subsequently, when the side spot B following the main spot M starts to enter into the defect 10, the difference signal B-A decreases, and the difference signal B with all the side spots B entered into the defect 10. -A becomes zero level.

Next, the side spot A is the defect 1
When starting from 0, the difference signal B-A further decreases and becomes negative, and when the side spot A completely comes out from within the defect 10, the difference signal B-A shows a negative peak. Then, when the side spot B starts to emerge from the defect 10, the difference signal B-A increases and the side spot B becomes the defect 10.
When the signal is completely output from the inside, the difference signal B-A returns to the zero level.

As described above, when the side spots A and B sequentially pass through the defect 10 with a time difference, the waveform of the difference signal B-A becomes a waveform similar to the waveform of the tracking error signal at the time of track jump. The polarity of the difference signal B-A differs depending on the rotation direction of the optical disc.
Further, if the difference signal is taken as AB, the polarities are opposite.

When the control microcomputer judges the track jump based on the binarized signal obtained by comparing the difference signal thus generated with the zero level as a threshold value, the tracking jump occurs from the tracking error signal due to the defect. However, there is a problem in that the laser beam is powered down and normal recording cannot be performed or the recording operation is terminated.

Therefore, the present invention has been made in view of the above points, and a track of an optical disk device which solves the above problems by discriminating a tracking error signal due to a defect and a tracking error signal at the time of track skipping. An object is to provide a jump detection circuit.

[0028]

In order to solve the above problems, the present invention has the following configuration.

That is, a tracking error signal generating means for generating a tracking error signal on the basis of the reflected light of the laser light irradiated on the optical disc is provided, and the track jump of the optical pickup which follows the track on the optical disc is tracked by the tracking error signal. In the track jump detection circuit of the optical disc device for detecting the defect based on the reflected light of the laser beam detected by the optical pickup, the defect detecting unit detects the defect on the optical disc, and the defect detecting unit detects the defect. Masking means for masking the second pulse output when the tracking error signal exceeds the threshold level by outputting the first pulse for the period;
Track jump detecting means for outputting a track jump detecting flag when the phase difference between the second pulse output from the masking means and the third pulse corresponding to the level of the reproduction signal from the optical disk is within a predetermined range. It was configured to do.

[0030]

According to the present invention having the above structure, when the phase difference between the second pulse output from the masking means and the third pulse according to the level of the reproduction signal from the optical disk is within a predetermined range, the track skipping occurs. It acts so that the detection flag is output.

[0031]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of the present invention.

The track skip detection circuit 11 shown in FIG.
Tracking error signal generation circuit 12 and comparison circuit 13
, The logical comparison circuit 14, and the sample hold circuit 15
And a defect circuit 16 corresponding to the defect detection means, and an off-track circuit 17.

The tracking error signal generation circuit 12 has
Side spot detector 9_AAnd 9 _BSignal from
The defect circuit 16 and the off-track circuit are
On the path 17 the main spot detector 9_MSignal from
Is paid. Also, the output of the sample hold circuit 15
The signal is supplied to a control microcomputer (not shown).

FIG. 2 is a block diagram specifically showing a part of the track skip detection circuit 11.

In FIG. 2, the comparison circuit 13 includes a resistor R ₁
˜R ₄ and comparator 18. The resistors R ₃ and R ₄ are connected in series between the negative voltage source V _EE and the ground, and the connection point between the resistors R ₃ and R ₄ is connected to the negative input terminal of the comparator 18. As a result, the comparator 18 compares the tracking error signal from the tracking error signal generation circuit 12 with a negative threshold value and binarizes it.

The logical comparison circuit 14 includes an edge detection circuit 19
And an AND circuit 20 corresponding to masking means and an inverter 21. The edge detection circuit 19 has a well-known configuration including a resistor R ₅ , a capacitor C, and an exclusive OR circuit 20. The edge detection circuit 19 detects a rising edge and a falling edge of the comparison signal from the comparison circuit 13.

The inverter 21 includes the defect circuit 16
The defect signal f from is inverted. AND circuit 20
Takes the logical product of this inverted defect signal and the edge detection signal from the edge detection circuit 19.

The defect circuit 16 compares the signal from the main spot detector 9 _M with a threshold of 77% of the average level of the signal from the main spot detector 9 _M , and outputs it. At this time, the falling time is provided with a delay time of ΔT and is output. Further, the off-track circuit 17 _compares the signal from the main spot detector 9 _M with the average level of the signal from the main spot detector 9 _M as a threshold value and outputs it.

The sample and hold circuit 15 is composed of a D latch 22 corresponding to a track jump detecting means, which has a SET terminal and a Q output terminal commonly connected. The CLK terminal of the sample hold circuit 15 receives the signal from the AND circuit 20, and the D terminal receives the signal from the off-track circuit 17.
A signal from the control microcomputer is input to each of the CLR terminals, and an output signal from the Q output terminal is supplied to the control microcomputer.

FIG. 3 is a diagram showing the waveform of each part of the track jump detection circuit 11 in the case of a track jump.

FIG. 3A shows the tracking error signal a from the tracking error signal generation circuit 12, which is compared with the negative threshold level V ₁ preset by the comparison circuit 13 as described above. Therefore, the output signal c from the comparison circuit 13 becomes a binarized signal as shown in FIG. Both edges of this binarized output signal are detected by the edge detection circuit 19, and the output signal d from the edge detection circuit 19 becomes a pulse as shown in FIG. The output signal d corresponds to the second pulse.

On the other hand, the signal b from the main spot detector 9 _M shown in FIG. 3B is a signal delayed by π / 2 phase from the tracking error signal a, and the off-track circuit 17 causes the signal b. Are compared using the average level V _{2 of the above} as a threshold value. Therefore, the output signal e from the off-track circuit 17 becomes a pulse having a duty ratio of 50% as shown in FIG. The output signal e corresponds to the third pulse.

The signal b from the main spot detector 9 _M is compared by the defect circuit 16 with a level V ₃ of 77% of the average level of the signal b as a threshold value. Since this signal b does not fall below V ₃ , the output signal f from the defect circuit 16 is shown in FIG.
As in (F), it is always at low level. This output signal f
Is inverted by the inverter 21 and is always at a high level (not shown). The output signal f corresponds to the first pulse.

The AND circuit 20 ANDs the high level signal from the inverter 21 and the output signal d from the edge detection circuit 19 to obtain the AND circuit 2.
As the output signal g of 0, the output signal d from the edge detection circuit 19 is output as it is as shown in FIG.

The D-latch 22 latches the high level of the output signal e from the off-track circuit 17 at the rising edge of the output signal g of the AND circuit 20 at time t ₆ , and as shown in FIG. 3 (H). The track skip detection flag h is supplied to the control microcomputer. When the track jump detection flag h is input, the control microcomputer determines that the track jump has occurred.

On the other hand, FIG. 4 is a diagram showing the waveform of each part of the track skip detection circuit 11 when there is a defect on the track.

FIG. 4A shows the tracking error signal a from the tracking error signal generation circuit 12, which is compared with the negative threshold level V ₁ preset by the comparison circuit 13 as described above. Therefore, the output signal c from the comparison circuit 13 becomes a binarized signal as shown in FIG. Both edges of this binarized output signal are detected by the edge detection circuit 19, and the output signal d from the edge detection circuit 19 becomes a pulse as shown in FIG.

On the other hand, the signal b from the main spot detector 9 _M shown in FIG. 4 (B) is a signal in which the amount of returning light is reduced according to the defect, and the off-track circuit 17
Are compared using the above-mentioned average level V ₂ as a threshold value. Therefore, the output signal e from the off-track circuit 17 becomes a rectangular wave that rises at time t ₇ and falls at time t ₁₀ as shown in FIG. 4 (E).

The signal b from the main spot detector 9 _M is supplied to the level V mentioned above by the defect circuit 16.
Comparing with ₃ as the threshold. The signal b according to the defect becomes V ₃ or less from time t ₈ to time t ₉ . Therefore, the output signal f from the defect circuit 16 is a rectangular wave which rises at time t ₈ and falls with a delay of ΔT from time t _{9 as} shown in FIG. 4 (F).
The output signal f is inverted by the inverter 21 (not shown).

Then, the AND circuit 20 inverts the output signal f from the inverter 21 and the edge detection circuit 1
The output signal d from 9 is ANDed, and the comparison circuit 1
The first pulse of the output signal d corresponding to the rising edge of the output signal c from 3 is masked by the AND circuit 20 because the inverted signal of the output signal f is at the low level. The next pulse of the output signal d corresponding to the falling edge of the output signal c from the comparison circuit 13 is not masked by the AND circuit 20 because the inverted signal of the output signal f is at the high level, as shown in FIG. Is output as is.

In the D latch 22, the output signal g of the AND circuit 20 which is the CLK input rises during a period (time t ₇ to time t ₁₀ ) in which the output signal e from the off-track circuit 17 which is the D input is at the high level. Therefore, the track jump detection flag h from the Q output is kept at the low level. Therefore, the control microcomputer determines that no track jump has occurred.

As described above, according to this embodiment, the peaks after the peaks of the tracking error signals having the opposite polarities which are successively generated and the portion where the signal from the main spot detector 9 _M decreases. The phase comparison is performed to detect whether or not a track jump has occurred, and a change in the tracking error signal due to a defect on the track is not recognized as a track jump.

Therefore, the tracking error signal due to the defect is mistakenly recognized as the tracking jump, and the laser beam is not powered down to perform normal recording, or the recording operation is not terminated and normal recording is not performed. Records can be made.

The threshold value is set to a negative value when the tracking error signal is compared, because the edge pulse of the rising portion is delayed by delaying the rising edge of the pulse rising when the tracking error signal decreases below the threshold value. Is always masked by the defect signal. Therefore, when the tracking error signal at the time of a defect is output in the opposite phase depending on the pickup used and the method of generating the error signal, it is necessary to set the polarity of the threshold to the opposite polarity.

By setting the threshold value, it is possible that the pickup slightly shakes the center of the track to the left or right while the servo is applied or the tracking error signal finely moves up and down near the zero level due to noise or the like. False detection of the comparator can be prevented.

In this embodiment, the track skip detection circuit 11
Although it is realized by hardware, it is of course possible to realize this by software. However, in this case, although the work load of the control microcomputer increases and the load increases, the control microcomputer is not excessively loaded by the hardware configuration as in the present embodiment.

Further, once the track skip detection flag is detected, it is held until it is cleared by the control microcomputer, so that the control microcomputer may check it intermittently. For example, D every 1 msec
The Q output of the latch may be checked so that the recording operation is ended immediately when the high-level track jump detection flag indicating the track jump is detected. Further, the Q output check may be performed by an interrupt routine that enters a routine that shifts to the next operation when the track skip detection flag is detected.

If a circuit for directly lowering the laser power by the generated control signal is added, the response will be further improved.

In this embodiment, the three-beam method using the returning light from the preceding spot and the following spot for detecting the tracking error signal has been described. However, the present invention is an optical disk device using an AGC circuit in the signal component portion. It is also applicable when recording.

That is, the reproduction RF signal and the tracking error signal are input to the AGC circuit and their levels are adjusted.
Here, if the amount of returned light decreases due to a defect,
The AGC circuit increases the gain in an attempt to keep the level constant. As a result, the tracking error signal has peaks in the positive direction. Next, when the amount of returning light increases, the gain has been set high until then, so this time, on the contrary, the gain is suddenly set low. As a result, the tracking error signal has peaks in the negative direction, and the same tracking error signal as the tracking error signal generated by the three-beam method is generated.

[0061]

As described above, according to the present invention, when the phase difference between the second pulse output from the masking means and the third pulse corresponding to the level of the reproduction signal from the optical disk is within a predetermined range. Since the track jump detection flag is output and the track jump and the defect can be discriminated, the tracking error signal due to the defect is mistakenly recognized as the tracking jump, and the laser beam is powered down to perform normal recording. There is a feature that normal recording can be performed without having to end the recording operation.

[Brief description of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram specifically showing a part of the track skip detection circuit 11.

FIG. 3 is a track jump detection circuit 1 in the case of a track jump.
It is a figure which shows the waveform of each part of 1.

FIG. 4 is a diagram showing waveforms at various parts of the track skip detection circuit 11 when there is a defect on a track.

FIG. 5 is a diagram showing a three-beam optical system of MD.

FIG. 6 is a diagram illustrating generation of a tracking error signal using a 3-beam optical system.

FIG. 7 is a diagram illustrating generation of a tracking error signal due to a defect.

[Explanation of symbols]

 12 tracking error signal generation circuit 13 comparison circuit 14 logical comparison circuit 15 sample hold circuit 16 defect circuit 17 off-track circuit 20 AND circuit 22 D latch

Claims (1)

[Claims] 1. A tracking error signal generating means for generating a tracking error signal based on a reflected light of a laser beam irradiated onto an optical disc, wherein the track jump of an optical pickup that follows a track on the optical disc is tracked. In a track jump detection circuit of an optical disk device for detecting based on an error signal, a defect detecting means for detecting a defect on the optical disk based on reflected light of a laser beam detected by the optical pickup, and a defect by the defect detecting means A masking means for masking the second pulse output when the tracking error signal exceeds the threshold level by outputting the first pulse during a period in which is detected, and the masking means outputs the first pulse. The second pulse and the optical disc Track jump detection means for outputting a track jump detection flag when the phase difference from the third pulse corresponding to the level of the reproduction signal is within a predetermined range. circuit.