JPH1166580A - Information reproducer, information recording/ reproducing apparatus and on track/off track detection circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a correct ON track/OFF track detection signal without changing the frequency of a reproduction signal and without being affected by a fluctuations in the drive of a drive means of a reproduction means, fluctuations in and the offset of the reproduction signal, a change in the degree of modulation of the reproduction signal or the like in an information reproducing apparatus which has an ON track/OFF track detection circuit to be supplied with the reproduction signal as obtained when the reproduction means crosses tracks arranged side by side on a recording medium. SOLUTION: An ON track/OFF track detection circuit 18 has an envelope extractor 2 to which a reproduction signal is supplied to extract an envelope signal, a changing component extractor 3 to which the envelope signal is supplied to extract a changing component based on the warping of a storage medium and a comparator 4 to compare level between the envelope signal and the changing component signal. Thus, a ON track/OFF track detection signal is obtained from the comparator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an information reproducing apparatus having an on-track / off-track detecting circuit, such as an optical information reproducing apparatus and a recording / reproducing apparatus, an information recording / reproducing apparatus, and an on-track / off-track detecting circuit.

[0002]

2. Description of the Related Art Referring to FIGS. 4 and 5, an information recording / reproducing apparatus having a conventional on-track / off-track detecting circuit and its on-track / off-track detecting circuit (Japanese Patent Publication No. 6-9087) will be described. Will be described. First, an optical information recording / reproducing apparatus will be described with reference to FIG. 4B.

[0003] Reference numeral 6 denotes an optical disk (including a magneto-optical disk) as a recording medium, and reference numeral 7 denotes a spindle motor for driving the optical disk 7. Reference numeral 8 denotes an optical head, which is driven by a linear motor 9 in the positive and negative directions between the innermost circumference and the outermost circumference of the optical disk 8 so as to cross a concentric or spiral track along the radial direction.

[0004] The optical head 8 will be described. The optical head 8 irradiates the optical disk 6 with a reference laser beam from now on to reproduce an information signal from the reproduction laser beam,
When the optical disc 6 is a writable disc, the recording laser light modulated by the information signal from the optical head 8 is irradiated on the optical disc 6 to record the information signal.

[0005] In the optical head 8, a divergent laser beam from a laser light source 10 such as a semiconductor laser is converted into a parallel laser beam by a collimator lens 11, and the parallel laser beam is incident on an objective lens 13 through a polarizing beam splitter 12. Focused.

The focused laser light emitted from the objective lens 13 focuses on the recording surface of the optical disk 6. Reference numeral 14 denotes an actuator that drives the objective lens 13 in a direction to approach and separate from the optical disk 6 and in a direction perpendicular to the tracks of the optical disk 6.

The reflected laser light from the optical disk 6 returns to the objective lens 13 to become a parallel laser light, and the parallel laser light returns to the polarizing beam splitter 12 and is reflected by the reflection surface, and its optical path is deflected by 90 °. Is done. The parallel laser light is incident through the light detection lens 15 so as to be focused on the light detection surface of the multi-segment light detector 16.

A focus error signal and a tracking error signal are obtained by an arithmetic operation based on a known method such as an astigmatism method or a push-pull method, based on the detection output of each light detection unit from the multi-segment light detector 16. The signal is supplied to the focus and tracking control circuit 17. The focus and tracking control signals from the control circuit 17 are supplied to the actuator 14 and the objective lens 13
Focus and tracking control is performed.

When the reference laser beam from the optical head 8 accesses a desired track on the optical disk 6,
The optical head 8 itself is moved by the linear motor 9 on the radius of the optical disk 6, that is, across the aligned tracks, or a track jump signal is supplied to the actuator 14 to move the objective lens 13 in the direction across the tracks. Or let it.

At this time, an on-track / off-track signal is used to determine the position and the moving direction of the reference laser beam from the optical head 8 on the optical disk. This on-track / off-track signal is a total light detection signal which is the total of the detection outputs of the respective photodetectors of the multi-segment photodetector 16, that is, one peak value each time the reference laser beam crosses the track of the optical disk 6. And a bottom value are obtained alternately, and this total light detection signal is obtained by signal processing by an on-track / off-track detection circuit 18 '.

Next, a conventional on-track / off-track detecting circuit 18 'will be described with reference to FIG. 4A.
The total light detection signal from the input terminal 20 is supplied to a peak hold circuit 21 and a bottom hold circuit 22. The peak hold voltage from the peak hold circuit 21 and the bottom hold voltage from the bottom hold circuit 22 are applied to both ends of a series circuit of resistors 23 and 24 having the same resistance constituting a resistor voltage divider. Divided voltage,
That is, an intermediate voltage is obtained.

Next, the configurations of the peak hold circuit 21 and the bottom hold circuit 22 will be described with reference to FIGS. 5A and 5B. Diodes 32 are connected in series with each other on the output side of the differential amplifier 31, and the output side of the diode 32 is connected to the inverting input terminal side of the differential amplifier 31, and through a capacitor 33 constituting a time constant circuit. While being grounded, they are connected to a power supply + B and a ground, respectively, through a resistor 34 constituting a time constant circuit. The next stage of each time constant circuit has a differential amplifier 35 as a buffer.
Are connected respectively. Incidentally, 30 and 36 are a peak hold circuit 21 and a bottom hold circuit 22, respectively.
Input terminal and output terminal.

The total photodetection signal current from the photodetector 16 is converted into a total photodetection signal voltage by a current-voltage converter (not shown), and then supplied to a comparator 25 through an input terminal 20. The level is compared with the intermediate value voltage from the resistor voltage divider composed of the resistors 23 and 24.
The output side of the comparator 25 is connected to a power supply +
B.

Thus, the linear motor 9 of the optical head 8
When the focused laser light from the objective lens 13 of the optical head 8 moves in the positive or negative radial direction of the optical disk 6 by the driving of the optical head 8, a pulse signal that becomes logical 1 on track and logical 0 on off track, That is, an on-track / off-track detection signal is output to the output terminal 27.

[0015]

The on-track / off-track detecting circuit of such a conventional information recording / reproducing apparatus has four
An intermediate value between the peak hold value and the bottom hold value of the sum signal from the split photodetector is set as a reference value, and the comparator compares the level of the sum signal with the reference value to obtain an on-track / off-track detection signal. Therefore, there are the following disadvantages.

When the frequency of the total light detection signal from the photodetector changes, the time constant of each of the peak hold circuit and the bottom hold circuit changes, so that the peak hold value and the bottom hold value also change. Because of the fluctuation, a correct on-track / off-track detection signal cannot be obtained, and it is difficult to set the respective time constants.

In the case where the recording medium is warped, the driving of the recording medium is fluctuated, the detection output of the photodetector is offset, or the like, if the intermediate value does not correspond to these fluctuations, the correct on-track An off-track detection signal cannot be obtained.

Further, the power of the reference laser beam of the optical head, the offset of the detection output of the photodetector, and the like change the modulation degree and offset of the sum signal from the photodetector. , And an offset or the like, a correct on-track / off-track detection signal cannot be obtained.

In view of the foregoing, the present invention provides an information reproducing apparatus and an information reproducing apparatus, wherein a reproducing signal when a reproducing means crosses tracks arranged side by side on a recording medium is supplied to an on-track / off-track detecting circuit. In the recording / reproducing apparatus and its on-track / off-track detecting circuit, the frequency of the reproducing signal changes, the fluctuation of the driving of the driving means of the reproducing means, the fluctuation and offset of the reproducing signal, the change of the modulation degree of the reproducing signal, etc. Instead, it is intended to propose a device that can obtain a correct on-track / off-track detection signal.

[0020]

An information reproducing apparatus according to the present invention comprises: reproducing means for reproducing an information signal from a recording medium on which an information signal is recorded so as to form juxtaposed tracks;
Driving means for relatively driving the reproducing means and the recording medium such that the reproducing means crosses the juxtaposed tracks on the recording medium, and a reproduction signal when the reproducing means crosses the juxtaposed tracks on the recording medium are supplied. An on-track / off-track detection circuit, wherein the on-track / off-track detection circuit includes an envelope extractor for supplying a reproduction signal and extracting an envelope signal; A fluctuation extractor for extracting a fluctuation signal based on the warpage of the recording medium and the offset of the reproduction signal from the reproducing means, and supplying an envelope signal and the fluctuation signal, and converting the envelope signal into a fluctuation signal. And a comparator for level comparison, and an on-track / off-track detection signal is obtained from the comparator.

According to the present invention, the reproducing means reproduces the information signal from the recording medium on which the information signal is recorded so as to form the juxtaposed tracks. Driving means relatively drives the reproducing means and the recording medium such that the reproducing means crosses the juxtaposed tracks on the recording medium. A reproduction signal when the reproducing means crosses the arranged tracks on the recording medium is supplied to an on-track / off-track detection circuit.
In the on-track / off-track detection circuit, the reproduced signal is supplied to an envelope extractor, and an envelope signal is extracted. The extracted envelope signal is supplied to a fluctuation extractor, and a fluctuation signal based on the warpage of the recording medium and the offset of the reproduction signal from the reproducing means is extracted. The envelope signal and the variation signal are supplied to a comparator, and the level of the envelope signal is compared with the variation signal to obtain an on-track / off-track detection signal from the comparator.

[0022]

DETAILED DESCRIPTION OF THE INVENTION An information reproducing apparatus according to the present invention comprises: reproducing means for reproducing an information signal from a recording medium on which an information signal is recorded so as to form juxtaposed tracks; As if crossing the track
Driving means for relatively driving the reproducing means and the recording medium;
An on-track / off-track detecting circuit to which a reproducing signal is supplied when the reproducing means crosses the arranged tracks on the recording medium.

An information recording / reproducing apparatus according to the present invention comprises a recording means for recording information signals so as to form tracks arranged side by side on a recording medium, and a recording medium on which information signals are recorded so as to form tracks arranged side by side. A reproducing means for reproducing the information signal; a driving means for relatively driving the reproducing means and the recording medium so that the reproducing means crosses the tracks arranged on the recording medium; and a reproducing means arranged on the recording medium. And an on-track / off-track detection circuit to which a reproduction signal when crossing a track is supplied.

The on-track / off-track detecting circuit according to the present invention, and the on-track / off-track detecting circuit in the information reproducing apparatus and the information recording apparatus according to the present invention,
An envelope extractor to which a playback signal is supplied to extract an envelope signal; and a fluctuation extraction to which a envelope signal is supplied to extract a fluctuation signal based on the warpage of the recording medium and the offset of the reproduction signal from the reproducing means. And a comparator for supplying an envelope signal and a variation signal, and comparing the envelope signal with the variation signal to obtain an on-track / off-track detection signal from the comparator. .

The above-mentioned envelope extractor can be constituted by a low-pass filter (first low-pass filter) having a predetermined cutoff frequency lower than the frequency of the information signal in the reproduced signal.

Further, the variation extractor may be constituted by a second low-pass filter having a predetermined cut-off frequency lower than the cut-off frequency of the first low-pass filter.

An on-track / off-track detecting circuit according to the present invention, and an on-track / off-track detecting circuit in the information reproducing apparatus and the information recording apparatus according to the present invention,
Offset adding means for adding an offset to the variation signal from the variation extractor is provided, and a signal obtained by adding an offset to the variation signal is supplied to a comparator, and an envelope signal is added to the variation signal by adding an offset. Compare levels with things.

Further, in the information reproducing apparatus and the information recording / reproducing apparatus according to the present invention, the recording medium is an optical disk,
The recording means is an optical head for irradiating the optical disc with recording light modulated by the information signal and recording the information signal on the optical disc, and the reproducing means irradiating the optical disc with reference light and irradiating the optical disc with the reference light. This is an optical head that detects the reproduction light.

Embodiment An information reproducing apparatus and an information recording / reproducing apparatus having an on-track / off-track detecting circuit according to an embodiment of the present invention will be described below with reference to FIG. First, an optical information recording / reproducing device (optical information reproducing device) will be described with reference to FIG. 1B.

Reference numeral 6 denotes an optical disk (including a magneto-optical disk) as a recording medium, and reference numeral 7 denotes a spindle motor for driving the optical disk 7. Reference numeral 8 denotes an optical head, which is driven by a linear motor 9 in the positive and negative directions between the innermost circumference and the outermost circumference of the optical disk 8 so as to cross a concentric or spiral track along the radial direction.

The optical head 8 will be described. The optical head 8 irradiates the optical disk 6 with a reference laser beam from now on to reproduce an information signal from the reproduction laser beam,
When the optical disc 6 is a writable disc, the recording laser light modulated by the information signal from the optical head 8 is irradiated on the optical disc 6 to record the information signal.

In the optical head 8, after divergent laser light from a laser light source 10 such as a semiconductor laser is converted into parallel laser light by a collimator lens 11, the parallel laser light is incident on an objective lens 13 through a polarization beam splitter 12. Focused.

The focused laser light emitted from the objective lens 13 focuses on the recording surface of the optical disk 6. Reference numeral 14 denotes an actuator that drives the objective lens 13 in a direction to approach and separate from the optical disk 6 and in a direction perpendicular to the tracks of the optical disk 6.

The reflected laser light from the optical disk 6 returns to the objective lens 13 and becomes a parallel laser light. The parallel laser light returns to the polarization beam splitter 12 and is reflected by the reflection surface, and its optical path is deflected by 90 °. Is done. The parallel laser light is incident through the light detection lens 15 so as to be focused on the light detection surface of the multi-segment light detector 16.

The optical disc 6 may be irradiated with reference laser light from the laser light source 10, and the transmitted laser light may be irradiated on the photodetector through the photodetection lens.

A focus error signal and a tracking error signal are obtained by a calculation based on a known method such as an astigmatism method or a push-pull method, based on the detection output of each light detection unit from the multi-segment light detector 16. The signal is supplied to the focus and tracking control circuit 17. The focus and tracking control signals from the control circuit 17 are supplied to the actuator 14 and the objective lens 13
Focus and tracking control is performed.

When the reference laser beam from the optical head 8 accesses a desired track on the optical disk 6,
The optical head 8 itself is moved by the linear motor 9 on the radius of the optical disk 6, that is, across the aligned tracks, or a track jump signal is supplied to the actuator 14 to move the objective lens 13 in the direction across the tracks. Or let it.

At this time, an on-track / off-track signal is used to determine the position and the moving direction of the reference laser beam from the optical head 8 on the optical disk. This on-track / off-track signal is a total light detection signal which is the total of the detection outputs of the respective photodetectors of the multi-segment photodetector 16, that is, one peak value each time the reference laser beam crosses the track of the optical disk 6. And the one bottom value are obtained alternately, and the signal is obtained by subjecting this total light detection signal to signal processing by the on-track / off-track detection circuit 18.

Next, an on-track / off-track detecting circuit according to an embodiment of the present invention will be described with reference to FIG. 1A. The total photodetection signal from the multi-segment photodetector 16 (photodetector 16
Is an undivided photodetector, it is simply a photodetection signal) is supplied to the first low-pass filter 2 through the input terminal 1.

The low-pass filter 2 is an envelope extractor, and a light detection signal (reproduction signal) from the light detector 16.
Low-pass filter having a predetermined cut-off frequency lower than the frequency of the information signal inside (first low-pass filter)
It can be composed of The low-pass filter 2 has a function corresponding to the speed at which the optical head 8 moves in the radial direction of the optical disk 6.
For example, the cutoff frequency is set so that a signal having a frequency such as 50 kHz or 250 kHz is passed.

The output of the low-pass filter 2 is supplied to a second low-pass filter 3. The second low-pass filter 3 is a variation extractor that extracts a variation signal based on the warpage of the recording medium and a laser beam from the laser light source 10, that is, a variation signal based on the variation of the reference light. It has a predetermined cutoff frequency lower than the cutoff frequency of the filter 2. The low-pass filter 3 includes a frequency signal corresponding to the rotation speed of the optical disc 6 and the laser light source 1.
The cut-off frequency is set so as to pass a fluctuating frequency signal of laser light from 0.

The first and second low-pass filters 2 and 3 may be constituted by passive circuits or may be constituted by active filters. If the speed at which the optical head 8 moves in the radial direction of the optical track 6 or the number of rotations of the optical disk 6 greatly changes, an active filter is suitable.

Next, the operation of the on-track / off-track detection circuit 18 of FIG. 1A will be described with reference to FIG.
The light detection signal (reproduction signal) a from the photodetector 16 (FIG. 2)
A) is supplied to the first low-pass filter 2. The light detection signal a is amplitude-modulated by the information signal b due to the fact that the reference laser light from the optical head 8 crosses tracks on the optical disk 6, the warpage of the optical disk 6 and the fluctuation of the laser light emitted from the laser light source 10. Signal.

The lower envelope d of the light detection signal a is based on the fluctuation caused by the reference laser beam from the optical head 8 crossing the track on the optical disk 6, and the upper envelope c is the upper envelope c of the optical disk 6. This is due to the warpage and the fluctuation of the laser light emitted from the laser light source 10. The envelope d has a higher frequency, and the envelope c has a lower frequency.

When the light detection signal a is supplied to the first low-pass filter 2, an envelope signal e (FIG. 2B) is extracted. This envelope signal e is a signal obtained by averaging the envelopes c and d.

Then, the envelope signal e is supplied to the second low-pass filter 3, and the fluctuation signal f due to the warpage of the optical disk 6 and the fluctuation of the laser light from the laser light source 10.
(FIG. 2C) is extracted.

Then, the envelope signal e from the first low-pass filter 2 and the fluctuation signal f from the second low-pass filter 3 are supplied to the comparator 4, and the envelope signal e is changed to the fluctuation signal f And an on-track / off-track detection signal g (FIG. 2D) is output. The detection signal g has a high level when the envelope signal e is larger than the fluctuation signal f, and has a low level when the envelope signal e is small.

In the above-described on-track / off-track detection circuit 18, when the information signal is not reproduced from the optical disk 6, or when the laser beam from the optical head 8 is completely on-track on the track of the optical disk 6, ,
No envelope signal is obtained from the first low-pass filter 2,
For this reason, the output of the first low-pass filter 2 matches the fluctuation signal of the second low-pass filter 3.

Therefore, as shown in FIG. 3A, an offset adding means for adding an offset to the variation signal from the second low-pass filter (variation extractor) 3 is provided, and the on-track / off-track detection is performed on the variation signal. A signal to which a small offset having a level that does not adversely affect the signal is added is supplied to the comparator 4, and the envelope signal is compared with the signal obtained by adding the offset to the fluctuation signal. This offset adding means includes an adder AD on the output side of the second low-pass filter 3 and, for example, -5.
Changes between 00mV and + 500mV (constant value is acceptable)
A DC voltage source E is provided, and the DC voltage is supplied to the adder AD, and the added output is compared with the envelope signal from the first low-pass filter 2. As a result, the initial value of the comparator 4 is determined to be high or low.

When the level of the envelope signal from the first low-pass filter 2 in the on-track / off-track detection circuit 18 of FIG. 1A is insufficient, the low-pass filter may be provided with an amplifying function. As shown, an amplifier 2A can be added to the next stage of the first low-pass filter 2.

The cutoff frequency of the first low-pass filter 2 is set to an optimum value according to the reading speed of the information signal and the frequency of the envelope.

The width of signal loss such as warpage or scratch of the optical disk 6 changes depending on the reading speed of the information signal.
Accordingly, the cutoff frequency of the second low-pass filter 3 is set to an optimal value.

When the information signal is not reproduced,
When the reference laser beam from the optical head 8 is on-track on the optical disk 6, the envelope signal cannot be obtained from the first low-pass filter 2, so that the initial value is not determined.
In the worst case, oscillation occurs. Therefore, in order to avoid this, an offset value is added to the output of the second low-pass filter 3.

[0054]

According to the first aspect of the present invention, reproducing means for reproducing information signals from a recording medium on which information signals are recorded so as to form juxtaposed tracks, and the reproducing means are juxtaposed on the recording medium. Driving means for relatively driving the reproducing means and the recording medium so as to cross the track, and an on-track / off-track detecting circuit to which a reproducing signal is supplied when the reproducing means crosses the juxtaposed tracks on the recording medium. In an information reproducing apparatus having an on-track / off-track detecting circuit, an on-track / off-track detecting circuit includes an envelope extractor to which a reproduction signal is supplied to extract an envelope signal, A variation extractor for extracting a signal, a comparator for supplying an envelope signal and a variation signal, and comparing the level of the envelope signal with the variation signal; Since the rack / off-track detection signal is obtained, an information reproducing apparatus in which the reproduction signal when the reproducing means crosses the juxtaposed tracks on the recording medium is supplied to the on-track / off-track detection circuit is provided. The correct on-track / off-track detection signal can be obtained without being affected by the change of the frequency of the reproduction signal, the fluctuation of the driving of the driving means of the reproduction means, the fluctuation and offset of the reproduction signal, the change of the modulation degree of the reproduction signal, etc. An information reproducing device that can be obtained can be obtained.

In the first aspect of the present invention, the same effect can be obtained when the recording medium is an optical disk and the reproducing means is an optical head for irradiating the optical disk with reference light and detecting the reproduction light from the optical disk. Is obtained.

According to the second aspect of the present invention, recording means for recording information signals so as to form tracks arranged side by side on a recording medium, and recording means for recording information signals so as to form tracks arranged side by side, A reproducing means for reproducing the information signal; a driving means for relatively driving the reproducing means and the recording medium so that the reproducing means crosses the tracks arranged on the recording medium; and a reproducing means arranged on the recording medium. On-track to which the playback signal is supplied when traversing the track
In an information reproducing apparatus having an off-track detection circuit, an on-track / off-track detection circuit includes an envelope extractor that is supplied with a reproduction signal and extracts an envelope signal.
A variation extractor that is supplied with an envelope signal and extracts a variation signal based on the warpage of the recording medium; and a comparison that supplies the envelope signal and the variation signal and compares the envelope signal with the variation signal. And an on-track / off-track detection signal is obtained from the comparator, so that the reproduction signal when the reproducing means crosses the juxtaposed tracks on the recording medium is supplied to an on-track / off-track detection circuit. In the information recording / reproducing apparatus which is supplied to the reproducing device, the frequency of the reproducing signal changes, the fluctuation of the driving of the driving means of the reproducing means, the fluctuation and offset of the reproducing signal, the change of the modulation degree of the reproducing signal, etc. Therefore, it is possible to obtain an information recording / reproducing apparatus capable of obtaining a correct on-track / off-track detection signal.

In the second aspect of the present invention, the recording medium is an optical disk, the recording means is an optical head for recording information signals so as to form tracks arranged side by side on the recording medium, and the reproducing means refers to the optical disk. Irradiate light,
The same effect can be obtained with an optical head that detects the reproduction light from the optical disk.

According to the third aspect of the present invention described above, an envelope extractor is provided for supplying a reproduction signal when the reproducing means crosses the juxtaposed tracks on the recording medium and extracting an envelope signal, A fluctuation extractor that is supplied with a signal and extracts a fluctuation signal based on the warpage of the recording medium and the offset of the reproduction signal from the reproduction means; and supplies an envelope signal and the fluctuation signal to change the envelope signal. A comparator for comparing the minute signal with the level, and an on-track / off-track detection signal is obtained from the comparator, so that the reproduction signal is supplied when the reproducing means crosses the juxtaposed tracks on the recording medium. In the on-track / off-track detection circuit, the frequency of the reproduction signal changes, the fluctuation of the driving of the driving means of the reproduction means, the fluctuation and offset of the reproduction signal, and the reproduction signal Without being influenced by change of furniture, it is possible to obtain what may be a correct on-track and off-track detection signal.

In the information reproducing apparatus, the information recording / reproducing apparatus and the on-track / off-track detecting circuit according to the first, second and third aspects of the present invention, the envelope extractor determines the frequency of the information signal in the reproduced signal. Since the filter is a low-pass filter having a low predetermined cutoff frequency, the cutoff frequency is changed in accordance with the read speed of the information signal and the frequency of the envelope signal in addition to the effects of the first, second, and third inventions. By doing so, it is possible to obtain an information reproducing apparatus, an information recording / reproducing apparatus, and an on-track / off-track detecting circuit that can easily obtain a correct on-track / off-track detecting signal.

In the information reproducing apparatus, the information recording / reproducing apparatus and the on-track / off-track detecting circuit according to the first, second and third aspects of the present invention, the envelope extractor is lower than the frequency of the information signal of the reproduced signal. A first low-pass filter having a predetermined cut-off frequency, and the variation extractor is a second low-pass filter having a predetermined cut-off frequency lower than the cut-off frequency of the first low-pass filter. 1, In addition to the effects of the second and third aspects of the present invention, changing the cutoff frequency in accordance with the reading speed of the information signal and the frequency of the envelope signal, and the signal such as warping or scratching of the recording medium Since the width of the missing portion changes depending on the reading speed of the information signal, the cutoff frequency of the second low-pass filter should be changed according to the reading speed of the information signal. Therefore, the information reproducing apparatus which can be easily obtained correct on-track and off-track detection signal, it is possible to obtain an information recording and reproducing apparatus and on-track and off-track detection circuit.

In the information reproducing apparatus, information recording / reproducing apparatus and on-track / off-track detecting circuit according to the first, second and third aspects of the present invention, the offset for adding an offset to the fluctuation signal from the fluctuation extractor. In addition to the provision of the adding means, the signal obtained by adding the offset to the fluctuation signal is supplied to the comparator, and the envelope signal is compared with the signal obtained by adding the offset to the fluctuation signal.
The same effects as those of the second and third inventions can be obtained,
An information reproducing apparatus, an information recording / reproducing apparatus, and an on-track / off-track detecting circuit capable of determining the initial value of the comparison output of the comparator can be obtained.

[Brief description of the drawings]

FIG. 1A is a block diagram showing an on-track / off-track detection circuit of the present invention. B is a block diagram showing an optical information recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of the on-track / off-track detection circuit according to the embodiment of the present invention;

FIG. 3A is a block diagram showing an on-track / off-track detection circuit according to another embodiment of the present invention; B is a block diagram showing an on-track / off-track detection circuit according to still another embodiment of the present invention.

FIG. 4A is a block diagram showing a conventional on-track / off-track detection circuit. B is a block diagram showing a conventional optical information recording / reproducing apparatus.

FIG. 5A is a circuit diagram showing a peak hold circuit of a conventional on-track / off-track detection circuit. B is a circuit diagram showing a bottom hold circuit of a conventional on-track / off-track detection circuit.

[Explanation of symbols]

1 input terminal, 2nd low-pass filter, 3rd
Low-pass filter, 4 comparators, 5 output terminals, 6
Optical disk, 7 spindle motor, 8 optical head,
9 linear motor, 10 laser light source, 11 collimator lens, 12 polarization beam splitter, 13 objective lens, 14 actuator, 15 light detection lens, 1
6 photodetector, 17 focus and tracking control circuit, 18 on-track / off-track detection circuit, A
D adder, E DC power supply.

Claims (14)

[Claims] 1. A reproducing means for reproducing an information signal from a recording medium on which an information signal is recorded so as to form a juxtaposed track, and said reproducing means crossing said juxtaposed track on said recording medium. A reproducing unit and a driving unit for relatively driving the recording medium; and an on-track to which a reproduction signal is supplied when the reproducing unit traverses the juxtaposed tracks on the recording medium.
An information reproducing apparatus having an off-track detection circuit, wherein the on-track / off-track detection circuit is provided with an envelope extractor that is supplied with the reproduction signal and extracts an envelope signal, and is supplied with the envelope signal. A fluctuation extractor for extracting a fluctuation signal based on the warpage of the recording medium and an offset of the reproduction signal from the reproducing means; and supplying the envelope signal and the fluctuation signal to change the envelope signal to the fluctuation. An information reproducing apparatus, comprising: a comparator for comparing a level of a minute signal with a level, wherein an on-track / off-track detection signal is obtained from the comparator. 2. Recording means for recording information signals so as to form tracks arranged side by side on a recording medium, and reproducing means for reproducing information signals from a recording medium on which information signals are recorded so as to form tracks arranged side by side. Driving means for relatively driving the reproducing means and the recording medium so that the reproducing means crosses the aligned tracks on the recording medium; and wherein the reproducing means is arranged side by side on the recording medium. On-track to which the playback signal is supplied when traversing the track
An information reproducing apparatus having an off-track detection circuit, wherein the on-track / off-track detection circuit is provided with an envelope extractor that is supplied with the reproduction signal and extracts an envelope signal, and is supplied with the envelope signal. A fluctuation extractor for extracting a fluctuation signal based on the warpage of the recording medium and an offset of the reproduction signal from the reproducing means; and supplying the envelope signal and the fluctuation signal to change the envelope signal to the fluctuation. An information recording / reproducing apparatus, comprising: a comparator for comparing a level with a minute signal, wherein an on-track / off-track detection signal is obtained from the comparator. 3. An envelope extractor, to which a reproduction signal is supplied when a reproducing means crosses a juxtaposed track on a recording medium and an envelope signal is extracted, and wherein said envelope signal is supplied to said recording medium. And a variation extractor that extracts a variation signal based on the warpage and the offset of the playback signal from the playback means, and supplies the envelope signal and the variation signal to convert the envelope signal into the variation signal. An on-track / off-track detection circuit, comprising: a comparator for comparing levels; and obtaining an on-track / off-track detection signal from the comparator. 4. The information reproducing apparatus according to claim 1, wherein the envelope extractor is a low-pass filter having a predetermined cutoff frequency lower than a frequency of an information signal in the reproduced signal. Information playback device. 5. The information recording / reproducing apparatus according to claim 2, wherein the envelope extractor is a low-pass filter having a predetermined cutoff frequency lower than a frequency of an information signal in the reproduced signal. Information recording and reproducing device. 6. The on-track / off-track detection circuit according to claim 3, wherein the envelope extractor is a low-pass filter having a predetermined cutoff frequency lower than a frequency of an information signal in the reproduction signal. An on-track / off-track detection circuit characterized by the following. 7. The information reproducing apparatus according to claim 1, wherein the envelope extractor is a first low-pass filter having a predetermined cutoff frequency lower than a frequency of an information signal of the reproduced signal. The information reproducing apparatus, wherein the variation extractor is a second low-pass filter having a predetermined cut-off frequency lower than the cut-off frequency of the first low-pass filter. 8. The information recording / reproducing apparatus according to claim 2, wherein the envelope extractor is a first low-pass filter having a predetermined cutoff frequency lower than a frequency of an information signal of the reproduced signal, The information recording / reproducing apparatus, wherein the variation extractor is a second low-pass filter having a predetermined cut-off frequency lower than a cut-off frequency of the first low-pass filter. 9. The on-track / off-track detection circuit according to claim 3, wherein the envelope extractor is a first low-pass filter having a predetermined cutoff frequency lower than a frequency of an information signal of the reproduction signal. An on-track / off-track detection circuit, wherein the variation extractor is a second low-pass filter having a predetermined cut-off frequency lower than a cut-off frequency of the first low-pass filter. 10. The information reproducing apparatus according to claim 1, further comprising: an offset adding means for adding an offset to the variation signal from the variation extractor, wherein the offset adding means adds the offset to the variation signal. An information reproducing apparatus, wherein the level is supplied to the comparator and the envelope signal is compared with a level obtained by adding the offset to the variation signal. 11. The information recording / reproducing apparatus according to claim 2, further comprising: offset adding means for adding an offset to the variation signal from the variation extractor, and adding the offset to the variation signal. An information recording / reproducing apparatus characterized in that the signal is supplied to the comparator, and the level of the envelope signal is compared with a level obtained by adding the offset to the fluctuation signal. 12. The on-track / off-track detection circuit according to claim 3, further comprising: offset adding means for adding the offset to the variation signal from the variation extractor; and providing the offset to the variation signal. An on-track / off-track detection circuit, which supplies a signal obtained by adding the offset to the comparator, and compares the level of the envelope signal with a signal obtained by adding the offset to the fluctuation signal. 13. The information reproducing apparatus according to claim 1, wherein the recording medium is an optical disk, and the reproducing means irradiates the optical disk with reference light and detects the reproduction light from the optical disk. An information reproducing apparatus, characterized in that: 14. The information recording / reproducing apparatus according to claim 3, wherein said recording medium is an optical disk, and said recording means irradiates said optical disk with recording light modulated by an information signal, and writes said information on said optical disk. An information recording / reproducing apparatus, which is an optical head for recording a signal, and wherein the reproducing means is an optical head for irradiating the optical disk with reference light and detecting the reproduction light from the optical disk.