JPH04247332A - Track counter device - Google Patents

Abstract

PURPOSE:To measure the number of track crossing with high accuracy at the time of high-speed access with an optical recording and reproducing device. CONSTITUTION:A gain changeover amplifier 28 corrects the the fall of the track error signal amplitude of a preformat part by changeover of a gain at the time when an optical head passes the preformat part. The signal added with a lens position error signal is subjected to waveform shaping by an adding amplifier 27B in order to correct the offset of a preformat part track error signal 201 by a deviation in the lens position delivered from a differential amplifier 26. The number of the track crossing is counted by counting the signals subjected to waveform shaping with the counter 30.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention counts the number of track crossings of a light beam when an optical recording/reproducing device accesses a track by concentrating and reflecting a laser beam on the surface of a medium and converting the reflected light into an electrical signal. The present invention relates to a track counting device for positioning an optical head.

0002

2. Description of the Related Art In an optical recording and reproducing apparatus, that is, an optical disk apparatus, a track access operation is generally performed when recording and reproducing information. In this method, the difference between the current track address and the target track address is determined, and the track is moved by the difference, thereby positioning to the target track. To count the amount of truck feed,
This is done by counting the number of tracks crossed when the optical head moves. Then, by stopping when the error with the target track becomes zero, the positioning operation to the target track is performed. In such a track counting method, the track counting signal is detected by zero slicing the tracking error signal.

As a track counting technique, there is a track counting method as shown in FIG. In addition, FIG.
FIG. 3 is an output waveform diagram of the track counting method. In such a track counting method, the laser diode 51
The emitted light enters the collimator lens 52A, becomes parallel light, and enters the objective lens 52B. The light passing through the objective lens 52B is reflected by the medium 61. The reflected light passes through the objective lens 52B again and enters the beam splitter 52.
C enters the aperture lens 52D.

[0004] The light focused by the diaphragm lens 52D is 2
The light enters the split photodetector 53, and is converted into an electrical signal by the two-split photodetector 53. The electrical signal converted by the two-split photodetector 53 is differentially amplified by the differential amplifier 54 and becomes a track error signal 501. Track error signal 50
1 is compared with Vref502 by a comparator 55,
Pulsed. Here, Vref becomes 0V. Track cross pulse 503 pulsed by comparator 55 is connected to counter 56 . Then, the counter 56 counts the number of tracks traversed by the light beam focused on the medium 61. The positioning mechanism is accelerated or decelerated by a reference speed signal set corresponding to the number of residual tracks up to the target track, and is moved to the target track position.

[0005]

The track counting method described above performs rough positioning using a head moving mechanism during high-speed track access operations. At this time, the moving speed of the head moving mechanism is set to a constant acceleration or a constant deceleration depending on the remaining distance of movement based on the speed reference signal. When this acceleration or deceleration operation is performed,
Since an external force is applied to the lens, a positional shift occurs in the lens according to acceleration or deceleration. This positional shift causes an offset as shown in FIG. 7 or 8 in the tracking error signal.

Here, as shown in FIG. 9, the offset amount of the tracking error signal is determined by the fact that the amplitude center of the tracking error signal cannot be detected by zero slicing when detecting the track counting pulse due to lens position deviation. False positives occur. Although the offset amount of the ID portion is smaller than the offset amount of the portion other than the ID, erroneous detection is likely to occur because the amplitude of the tracking error signal is small. In addition, when a faster track access operation is attempted, the passing time for one track becomes shorter, and the tracking error signal amplitude in the ID section decreases due to interference between the group in the ID section and the preformat, resulting in erroneous track detection. increases, and the positioning accuracy of coarse access decreases. Furthermore, when attempting to generate a speed signal by F/V converting the track counting pulse, there is a drawback that a highly accurate speed signal cannot be obtained due to erroneous track detection.

On the other hand, in the track counting method shown in FIG.
When the optical beam passes through the preformatted portion of the medium while the optical head is moving to the target track, the amplitude of the track error signal drops to about 50% compared to the unrecorded portion. This is because a preformat portion is formed on the medium 61, so that the amount of light reflected from the medium surface is reduced. Also,
When moving the optical head to the target track, the acceleration of the optical head causes the objective lens to shift from the optical axis.
An offset occurs in the track error signal. When performing a seek operation of an optical head, a method of counting the amount of movement of the head is to count track cross pulses generated by detecting zero crosses of a track error signal.

However, in the preformat section, the amplitude of the track error signal decreases to about 50%, and zero crossings may not be detected due to offset due to lens positional deviation, resulting in track count errors and seek errors. This has the disadvantage that the operation becomes unstable and the seek time increases as a result.

SUMMARY OF THE INVENTION An object of the present invention is to provide a track counting device that can eliminate these drawbacks and accurately count the number of track crossings during high-speed track access.

0010

[Means for Solving the Problems] The present invention provides a track counting device that uses an optical system to irradiate a light spot onto an optical disc medium, and obtains at least a reproduction signal and information regarding the irradiation position from the reflected light. A light receiving element divided into at least a first light receiving part and a second light receiving part, a signal obtained by the first light receiving part of the light receiving element, and a signal obtained from the first light receiving part of the light receiving element to obtain information regarding the irradiation position of the light receiving element. track error signal generation means for generating a track error signal by subtracting the signals obtained by the two light receiving elements; A preformat determination means for determining whether preformat information is recorded at the irradiation position of the spot; and an offset voltage corresponding to the lens position deviation signal from the lens position deviation signal generation means, and Voltage subtraction means for subtracting an offset voltage corresponding to a positional deviation signal from a tracking error signal by switching a subtraction gain between a preformat section and a section other than the preformat section according to the output of the preformat discriminating means; The present invention is characterized by comprising a waveform shaping means for generating a track crossing pulse from a tracking error signal obtained by subtracting a voltage corresponding to the lens positional deviation signal of the lens positional deviation signal generating means by the subtracting means.

The present invention also provides a track counting device that uses an optical system to irradiate a light spot onto an optical disk medium and obtains at least a reproduction signal and information regarding the irradiation position from the reflected light, in which the optical head is connected to a preformat section. It has a correction means for correcting a decrease in the amplitude of the track error signal of the preformat section by switching the gain when passing through the lens. It is characterized in that the number of track crossings is counted by shaping the waveform of the signal obtained by adding the position error signal.

0012

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit block diagram showing an embodiment of a track counting device according to the present invention. The track counting device in FIG. 1 includes a laser diode 1, a collimating lens 2A, an objective lens 2B, a beam splitter 2C, photodetectors 3 and 6, a light emitting diode 4, a reflector 5, and a differential amplifier 7A. , 7B, 7C, summing amplifier 8, amplifier 9, capacitor 10, waveform shaping circuits 11, 14
, timer circuit 12, and analog switch 13A, 1
3B and a track counter 15.

In such a track counting device, light from the laser diode 1 passes through the collimating lens 2A, the beam splitter 2C, and the objective lens 2B, and is incident on the medium 61. The light reflected by the medium 61 passes through the objective lens 2B and the collimating lens 2C, and is transmitted to the photodetector 3.
is incident on the

The output of the photodetector 3 is applied to a summing amplifier 8 and a differential amplifier 7B.

The output of the summing amplifier 8 passes through a capacitor 10 and is applied to a waveform shaping circuit 11. Waveform shaping circuit 1
The output of 1 is applied to the timer circuit 12. The output of the timer circuit 12 is applied to analog switches 13A and 13B.

The light from the light emitting diode 4 is reflected by the reflector 5 and enters the photodetector 6.

The output of photodetector 6 is applied to differential amplifier 7A. The output of differential amplifier 7A is applied to analog switch 13A and amplifier 9. The output of amplifier 9 is applied to analog switch 13B.

The output of the differential amplifier 7B is the output of the differential amplifier 7C.
is applied to the positive (+) terminal of the analog switch 1
The outputs of 3A and 13B are applied to the negative (-) terminal of differential amplifier 7C. The output of the differential amplifier 7C is applied to the waveform shaping circuit 14. The output of the waveform shaping circuit 14 is applied to a track counter 15.

Next, the operation of this embodiment will be explained with reference to FIG. FIG. 2 is an output waveform diagram of the track counting device of FIG. 1.

The light emitted from the laser diode 1 passes through the collimating lens 2A, the beam splitter 2C, and the objective lens 2B, and is irradiated onto the medium 61. The light reflected from the medium 61 passes through the objective lens 2B, is reflected by the beam splitter 2C, and enters the photodetector 3. The outputs of the photodetectors 3 are summed by a summing amplifier 8 and then converted into reproduced signal pulses by a waveform shaping circuit 11. This reproduction pulse is input to the timer circuit 12, and an output pulse of a constant width is generated.

Here, by setting the output pulse width of the timer circuit 12 to be longer than the longest pulse period of the reproduction signal pulse, the output of the timer circuit 12 is set such that when the pulse train of the reproduction signal is input, during this period, It becomes a level signal. Here, in the magneto-optical recording medium 61, in the sum signal output of the photodetector 3, since there is a large amplitude difference between the preformat part signal and the data signal, only the preformat part is obtained as a pulse train of the reproduced signal. Therefore, the output signal of the timer circuit 12 represents the preformat portion. Further, the output of the photodetector 3 is subtracted by a differential amplifier 7B to become a tracking error signal.

On the other hand, the light emitted from the light emitting diode 4 is reflected by the reflective surface of the reflector 5 and is received by the photodetector 6. The output of the photodetector 6 is subtracted by a differential amplifier 7A,
This becomes a lens position deviation signal indicating the position of the lens. The lens position deviation signal is input to the analog switch 13A and the amplifier 9, where it is multiplied by a factor and sent to the analog switch 1.
It is input to 3B. Analog switch 13A and 13
B is ON/O by the output of the timer circuit 12.
However, as mentioned above, the output of the timer circuit 12 is turned FF (off) in the preformat section.
Become intense. The analog switch 13B is turned on in the preformat section, and the analog switch 13A is turned on in other than the preformat section. The outputs of the analog switches 13A and 13B are sent to the differential amplifier 7.
It is input to C.

The differential amplifier 7C subtracts the positional deviation signal output from the analog switches 13A and 13B from the tracking error signal, and outputs a corrected tracking error signal from which fluctuation components due to lens positional deviation have been removed. This corrected tracking error signal is input to the waveform shaping circuit 14, which outputs one track crossing pulse per track. The output of the waveform shaping circuit 14 is input to a track counter 15 to count the number of track crossings.

By the way, if a lens position shift occurs due to acceleration or deceleration during track access, an offset occurs in the tracking error signal in accordance with the lens position shift. As shown in Figure 8, the amount of offset at this time is different between the preformat part and the other parts due to the amount of lens position deviation, and the offset amount of the preformat part is about 1/2 of that of the other parts. Become.

Furthermore, since both offset amounts occur in proportion to the amount of lens positional deviation, a lens position signal is generated in accordance with the offset occurrence ratio in the preformat section and other sections, and this is used as the tracking error. By subtracting it from the signal, it is possible to remove the offset amount due to lens positional deviation when lens positional deviation occurs. It can be seen that the offset subtraction amount should be selected to a coefficient that makes the tracking error signal flat after the subtraction.

In this manner, the track counting device of this embodiment irradiates a light spot onto an optical disc medium,
In an optical disk device that obtains information regarding a reproduced signal and an irradiation position from reflected light, in order to obtain information regarding an irradiation position, a light receiving element divided into at least a first light receiving section and a second light receiving section, and a first light receiving section are provided. tracking error signal generation means for generating a tracking error signal by subtracting the signal obtained by the second light receiving section from the signal obtained by the second light receiving section; and a lens position deviation signal for generating a lens position deviation signal at the time of track access. a generating means, a preformat determining means for determining whether or not preformat information is recorded at the irradiation position of the light spot, and a preformat determining means for determining whether preformat information is recorded at the irradiation position of the optical spot, and a preformat determining means for subtracting an offset voltage according to the lens position deviation signal from the tracking error signal. Voltage subtraction means for subtracting by switching the subtraction gain between the preformat section and other sections according to the output of the means, and generating a track crossing pulse from the tracking error signal from which the voltage corresponding to the lens position deviation signal has been subtracted by the voltage subtraction means. and a waveform shaping means.

As a result, even if an offset corresponding to the amount of lens positional deviation occurs in the tracking error signal due to lens positional deviation during track access, the ratio of occurrence of offset to the amount of lens positional deviation between the preformat section and other parts can be adjusted. By switching and subtracting the coefficient for subtracting the lens position deviation signal from the tracking error signal according to the above, it is possible to obtain a tracking error signal in which no offset occurs even if a lens position deviation occurs. Therefore, since a track crossing pulse is obtained, a stable detection characteristic with fewer false detections can be obtained even when zero-cross sensing is performed, and a highly accurate positioning operation is possible. Further, even if a speed signal is generated by performing F/V conversion from a track crossing pulse, a highly accurate speed signal can be obtained, so a highly accurate and stable track access operation is possible.

FIG. 3 is a circuit block diagram showing another embodiment of the track counting device according to the present invention. The track counting device in FIG. 3 includes a laser diode 21, a collimating lens 22A, an objective lens 22B, a beam splitter 22C, a focusing lens 22D, an actuator 23, a lens position sensor 24, and a two-split photodetector 25.
, differential amplifier 26, addition amplifiers 27A, 27B,
Gain switching amplifier 28 and comparators 29A, 29B
and a counter 30.

In such a track counting device, the light from the laser diode 21 passes through the collimating lens 22A.
, passes through the beam splitter 22C and the objective lens 22B, and enters the medium 61. The light reflected by the medium 61 passes through the objective lens 22B, the collimating lens 22C, and the aperture lens 22D, and is applied to the two-split photodetector 25.

The output of the two-split photodetector 25 is applied to a differential amplifier 26 and a summing amplifier 27A. Differential amplifier 2
The output of 6 is applied to a gain switching amplifier 28. The output of summing amplifier 27A is applied to comparator 29A to which signal Vref is applied. Comparator 29A
The output of is applied to the gain switching amplifier 28.

The output from the lens position sensor 24 is applied to one positive (+) terminal of the summing amplifier 27B. The output from the gain switching amplifier 28 is added to the other plus (+) terminal of the summing amplifier 27B. The output of summing amplifier 27B is applied to comparator 29B to which signal Vref is applied. The output of comparator 29B is added to counter 30.

Next, the operation of this embodiment will be explained with reference to FIG. FIG. 4 shows waveforms of various parts when the optical head is moving.

The beam emitted from the laser diode 21 is turned into parallel light by the collimator lens 22A, and enters the objective lens 22B. The beam focused on the surface of the medium 61 by the objective lens 22B is reflected by the surface of the medium 61 and enters the beam splitter 22C. The beam extracted by the beam splitter 22C is incident on the focusing lens 22D. The beam focused by the focusing lens 22D is incident on the two-split photodetector 25. The signal divided by the two-split photodetector 25 is input to a differential amplifier 26 and an addition amplifier 27A.

The output of the differential amplifier 26 is input to the gain switching amplifier 28, and the output of the summing amplifier 27A is input to the comparator 29A. Comparator 29A has
Vref203 is input. The output of the comparator 29A is input to the gain switching amplifier 28. The output of the gain switching amplifier 28 and the output of the lens position sensor 24 are as follows.
The signal is input to an addition amplifier 27B, and the output of the addition amplifier 27B is input to a comparator 29B. Further, Vref22 is input to the comparator 29B, and the output of the comparator 28B is input to the counter 24.

By the way, while the optical head is moving to the target track on the medium 61, the light beam reflected from the surface of the medium 61 is
The light passes through the objective lens 22B, beam splitter 22C, and focusing lens 22D, and enters the two-split photodetector 25. The beam incident on the two-split photodetector 25 is split and converted into electrical signals. The divided output is sent to differential amplifier 2.
6 and an addition amplifier 27A, and output a track error signal 201 and a track sum signal 202, respectively. Track sum signal 202 is input to comparator 29A and compared with Vref 203. Further, the track error signal 201 is input to the gain switching amplifier 28.

As shown in FIG. 4, while the laser beam is passing through the preformat section, a track error signal 201 is generated.
The amplitude decreases to about 1/2. Further, since the signal level of the track sum signal 202 decreases to about 1/2 at the preformat portion, the preformat portion is detected by setting Vref 203 to an appropriate value. The output of the comparator 29A is input to the gain switching amplifier 28. The output 204 of the comparator 29A is a signal whose output becomes Low at the ID section, and the gain switching amplifier 28 increases the gain by 1 when the control input is High, and the gain is set to Low when the control input is High.
It has the function of doubling the gain with w. The output 205 of the gain switching amplifier 28 is input to the summing amplifier 27B and added to the output of the lens position sensor 24. This is because the offset in the preformat section of the output 205 of the gain switching amplifier 28 is due to the positional shift of the lens, so by adding the output of the lens position sensor 24, the preformat section offset is corrected. It is. Output 207 of summing amplifier 27B is input to comparator 29B and compared with Vref206. Here, Vref206 is set to 0V, and the addition amplifier 27
The zero cross of the output 207 of B is detected. The output of the comparator 29B becomes the track cross pulse 208,
It is input to the counter 30. And at counter 30,
The number of track crossings is counted. This counts the amount of movement of the optical head during the seek operation of the optical head.

As described above, this embodiment includes a gain switching circuit that compensates for the decrease in the amplitude of the track error signal when the light beam passes through the preformat section while moving the optical head to the target track on the medium surface. In order to correct the offset of the preformat section track error signal due to lens positional deviation, the signal obtained by adding the lens position error signal is waveform-shaped and counted.

That is, while the optical head is moving, the decrease in the amplitude of the track error signal at the preformat section is corrected by increasing the gain, and the lens position signal is added to the track error signal to improve the track error signal at the preformat section. By correcting the offset, a stable track error signal can be obtained even in the preformat section. As a result, the number of track crossings can be accurately counted, making it possible to position the optical head with high precision, and reducing the number of track jumps due to track counting errors, thereby shortening the seek time.

[0040]

[Effects of the Invention] As explained above, according to the present invention,
This has the effect of being able to count the number of track crossings with high precision during high-speed track access.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing an embodiment of a track counting device according to the present invention.

FIG. 2 is an output waveform diagram of the embodiment of FIG. 1;

FIG. 3 is a circuit block diagram showing another embodiment of the track counting device according to the present invention.

FIG. 4 is an output waveform diagram of the embodiment of FIG. 3;

FIG. 5 is a circuit block diagram showing an example of a conventional track counting method.

FIG. 6 is an output waveform diagram of the track counting method of FIG. 5;

FIG. 7 is a diagram for explaining a conventional technique.

FIG. 8 is a diagram showing the relationship between the amount of lens positional deviation and the offset of the tracking error signal.

FIG. 9 is an operation explanatory diagram illustrating the amount of lens positional deviation and the offset of the preformat section.

[Explanation of symbols]

1 Laser diode 2A Collimating lens 2B Objective lens 2C beam splitter 3,6 Photodetector 4 Light emitting diode 5 Reflector 7A, 7B Differential amplifier 8 Summing amplifier 9 Amplifier 10 Capacitor 11, 14 Waveform shaping circuit 12 Timer circuit 13A, 13B Analog switch 14 Track counter

Claims (2)

[Claims] [Claim 1] A track counting device that uses an optical system to irradiate a light spot onto an optical disc medium and obtains at least a reproduction signal and information about the irradiation position from the reflected light, for obtaining information about the irradiation position of the light spot on the optical disc medium. A light receiving element divided into at least a first light receiving part and a second light receiving part, a signal obtained by the first light receiving part of the light receiving element, and a signal obtained by the second light receiving element of the light receiving element. A track error signal generation means for generating a track error signal by subtracting the above, a lens position deviation signal generation means for generating a position deviation signal of a lens of an optical system at the time of track access, and preformat information at the irradiation position of the light spot. a preformat discriminating means for determining whether or not a track error signal has been recorded; When subtracting the signal from the tracking error signal, the voltage subtraction means switches the subtraction gain between the preformat part and the part excluding the preformat part according to the output of the preformat discriminating means, and the voltage subtraction means subtracts the lens position deviation signal. A track counting device comprising waveform shaping means for generating a track crossing pulse from a tracking error signal from which a voltage corresponding to a lens position deviation signal of the generating means has been subtracted. 2. A track counting device that uses an optical system to irradiate a light spot onto an optical disk medium and obtains at least a reproduction signal and information regarding the irradiation position from the reflected light, when the optical head passes through a preformat section. It has a correction means for correcting a decrease in the amplitude of the track error signal of the preformat section by switching the gain, and the lens position error signal is corrected for correcting the offset of the track error signal of the preformat section due to the lens position shift of the optical system. A track counting device that counts the number of track crossings by shaping the waveform of the added signals.