JPH11238233A - Optical disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably discriminate a track/between tracks regardless of before/ after recording information. SOLUTION: This optical disk device is provided with a top hold circuit 20 consisting of a diode 22, a resistor 23 and a capacitor having a time constant faster than a traverse frequency of a track and later than a frequency of a recording mark. An RF signal reproduced from an optical disk is supplied to the top hold circuit 20, and the track (groove)/between tracks (land) is discriminated according to a height of its output level.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk apparatus capable of stably discriminating between tracks when data is recorded / reproduced on / from an optical disk in which grooves are formed in advance.

[0002]

2. Description of the Related Art Recently, with the advance of digital signal processing technology and the development of recording materials, a disk-shaped optical information recording medium (hereinafter simply referred to as an optical disk) capable of high-density recording has been developed. A known recording / reproducing apparatus capable of writing and reading information on and from an optical disk has also been proposed. As a rewritable optical disk capable of writing and reading in this manner, an MO (magneto-optical disk), a PD (phase change disk) and the like are known. Further, there are a type in which erasable data can be repeatedly recorded and a type in which writing can be performed only once.

In addition, as an optical disk, it is known that a spiral or concentric groove having a predetermined depth and width is previously formed on the disk in order to detect a tracking error. The data is recorded on the bottom surface within the groove or on the land between the grooves.

When writing data to a desired position (defined by a track number, a sector number, etc.) on an optical disk, it is necessary to move an optical pickup as a writing means from a current position to a desired position. Such an operation is called a seek operation. Various methods have been proposed for controlling the movement of the optical pickup during the seek operation. A typical control method combines a coarse control in which the pickup is moved at a high speed in the radial direction of the disk and a deceleration is performed when the pickup approaches the target track, and a fine control in which the pickup is positioned on the target track.

In the coarse control, the pickup is fed at a high speed in the radial direction of the disk by a thread motor and a feed mechanism, and the number of tracks traversed is counted.
In the fine control, the tracking servo is turned on to displace the objective lens of the pickup in the disk radial direction. The number of tracks crossed is R
The detection is performed based on a change in the F signal.

[0006]

However, if data is recorded in a wide groove whose width exceeds 50% of the track pitch, and the reflectivity decreases after recording, the track (groove) may not be recorded. A problem arises in satisfactorily discriminating between tracks (referred to as lands). This problem will be described with reference to FIG.

FIG. 10A shows a radial cross section of the optical disk 61. The optical disk 61 is formed with a wide groove in advance. Data is recorded in the groove by a magneto-optical method, a phase change type method, or the like. The recording / reproducing laser beam is applied from above in FIG. 10A. Then, assuming that the optical pickup moves in the radial direction of the disk as shown by an arrow 62 in FIG. 10A, an RF signal detected by a photodetector when the laser beam spot from the optical pickup crosses the groove and the land. Before the data is recorded, the (track crossing signal) has a waveform in which the groove has a wider width than the land, and as shown in FIG. Become.

When data is recorded in a groove, the reflectivity decreases.
The signal has a waveform as shown in FIG. 10C. A mark as information recorded on a track is recorded at a frequency sufficiently higher than a modulation frequency of, for example, several tens of KHz due to crossing a track, usually, for example, MHz or more. The waveform becomes a waveform with a small period. Further, when the output shown in FIG. 10C is supplied to a low-pass filter to extract a low-frequency cross-track modulation waveform, as shown in FIG. 10D, a waveform in which the level of the read output of the groove is smaller than the read output of the land is obtained. Becomes

That is, a track crossing signal in the case of an unrecorded disc shown in FIG. 10B and a track crossing signal in the case of a recorded disc shown in FIG. 10D include a groove and a land, and the level of the RF signal. The correspondence is reversed. Therefore, when an unrecorded portion and a recorded portion are mixed on the same disk, the groove and the land are set to RF.
There is a problem that it is impossible to make a determination based on a signal (light intensity). In addition, even if the signal level of the groove is lower than that of the land before recording, and becomes higher after recording, there is a problem that the detection of the track crossing signal cannot be performed.

Accordingly, an object of the present invention is to provide an optical disk apparatus capable of stably discriminating tracks / tracks irrespective of unrecorded / recorded.

[0011]

In order to solve the above-mentioned problems, the invention of claim 1 is directed to a signal processing method for an optical disc in which the relationship of brightness between tracks is reversed before and after recording. An optical disk device for performing recording of an optical disk, comprising: a holding unit that receives a reproduction signal and top-holds the reproduction signal; and discriminates between tracks on the optical disk based on an output of the holding unit. Device. The invention of claim 2 is
In an optical disc apparatus for recording a signal on an optical disc in which the relationship of brightness between tracks is reversed before and after recording, a reproduction signal is input and hold means for bottom-holding the reproduction signal is provided. An optical disk apparatus characterized in that it discriminates between tracks on the optical disk based on the output of the holding means.

In the present invention, a top hold circuit having a predetermined time constant characteristic faster than the track crossing frequency and slower than the recording mark frequency is provided as the top hold means, and a reproduction signal is supplied to the top hold circuit. Then, discrimination between tracks is performed based on the obtained signals.

[0013]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an optical disk device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes, for example, a phase change optical disk. The optical disc 1 is driven to rotate at a CAV by a spindle motor 2.
An optical pickup 3 is provided for recording data on the optical disc 1 and reproducing data from the optical disc 1.

When data from an external host processor is E
The signal is supplied to the write channel unit 14 via the signal processing unit 10 including a CC (error correction) encoder, an ECC decoder, a buffer controller, and a host interface. A buffer memory 11 is connected to the signal processing unit 10. Write data from the host processor is stored in the buffer memory 11 via an interface connector (not shown) and the signal processing unit 10.
In the write channel unit 14, processes such as conversion of write data into a sector structure, addition of a frame synchronization signal, and digital modulation are performed.

The recording data from the write channel section 14 is supplied to a laser driver 15. Laser driver 1
In 5, a drive waveform having a predetermined level relationship for recording recording data on the optical disc 1 is generated. The output of the laser drive 15 is supplied to the optical pickup 3 and data is recorded.

The signal detected by the optical pickup 3 is RF.
It is supplied to the amplifier 4. The RF amplifier 4 calculates detection signals generated from the four regions of the photodetector divided into four parts of the optical pickup 3, and calculates an RF signal, a tracking error signal TE, and a focus error signal FE.
Is generated. These signals are supplied to the read channel and the servo unit 5. Read channel, servo unit 5
Generates a signal for controlling the biaxial device of the optical pickup 3 based on the tracking error signal TE and the focus error signal FE. These control signals are supplied to the biaxial device via the biaxial driver 6. Also,
The RF amplifier 4 receives a detection signal corresponding to the laser power generated by the semiconductor laser of the optical pickup 3,
Laser power control for controlling the laser power to an appropriate value is performed.

The read channel and servo unit 5 generates a control signal for a spindle driver 7 for driving the spindle motor 2. The optical disc 1 is driven to rotate at CLV by the spindle motor 2. Further, the read channel and the servo section 5 generate a control signal for a thread driver 9 for driving the thread motor 2. The optical pickup 3 is moved in the disk radial direction by the thread motor 8.

The reproduced data from the read channel and the servo unit 5 is supplied to the signal processing unit 10. A buffer memory 11 is connected to the signal processing unit 10. Reproduction data from the signal processing unit 10 is sent to the host processor via an interface connector (not shown).

In order to control the operation of the entire drive, M
A system controller 12 composed of a PU is provided. A ROM 13 for storing programs is connected to the system controller 12.

FIG. 2 shows an example of the optical pickup 3. The optical pickup 3 includes an objective lens 32, a cylindrical lens 37,
It comprises lenses 33 and 36, a beam splitter 34, a four-divided photodetector 38, a semiconductor laser 35 and the like. The optical disk 31 is irradiated with a laser beam from the semiconductor laser 35 as indicated by an arrow 39. The reflected beam from the optical disk 31 is applied to the photodetector 38 as shown by an arrow 40.

In the optical disk 1 (31 in FIG. 2), tracks are previously formed by wobbling grooves in groove areas other than the emboss area, and the wobbling grooves represent absolute addresses. Therefore, the recording / reproducing apparatus can obtain information such as an absolute address from the reproduced signal of the groove.

FIG. 3 shows an example of the groove structure of the optical disc 1. In the groove area of the optical disc 1, a pre-groove 1a is formed in a spiral shape in advance from the inner circumference to the outer circumference. Of course, this pre-groove 1a
Can be formed concentrically. The left and right side walls of the pre-groove 1a are wobbled in correspondence with the address information, as shown in a partially enlarged manner. That is, wobbling is performed at a period corresponding to the wobbling signal generated based on the address. A land 1b is formed between the groove 1a and the adjacent groove 1a, and data is recorded in the groove 1a. Therefore, the track pitch is the distance between the center of the groove 1a and the center of the adjacent groove 1a, and the track pitch is, for example, 0.8 μm. And the groove width (groove 1a
Is set to, for example, 0.48 μm, and the width of the groove 1a is made larger than the width of the land 1b. Also,
The width of the groove 1a is smaller than the diameter of the laser spot LS.

The read channel and the servo unit 5 have an RF
Circuitry for generating a cross-track signal from the signal is included. FIG. 4 shows an example of the top hold circuit 20 for forming a track crossing signal. Top hold circuit 2
Numeral 0 is connected to an input terminal 21 to which an RF signal is supplied, and comprises a diode 22, a resistor 23 and a capacitor 24. The anode of the diode 22 is connected to the input terminal 21, the output terminal 25 is led out of the cathode of the diode 22, and the resistor 23 and the capacitor 24 are inserted in parallel between the cathode of the diode 22 and the ground.

The resistance 2 constituting the top hold circuit 20
3 and the capacitor 24 are set to be faster than the traversing frequency in the radial direction of the track (for example, several tens KHz) and lower than the frequency determined by the interval between recording marks and the rotation speed of the disk. I have. Therefore, even if the detection signal level of the light intensity detected by the photodetector 38 due to the modulation by the recording mark drops sharply, the charge remains stored in the capacitor 24, so that the output signal level does not decrease and When the light intensity decreases at the transverse frequency, the charge of the capacitor 24 is discharged through the resistor 23, so that the output signal level follows and decreases. As described above, the detection signal of the light intensity detected by the photodetector 38, which is supplied through the input terminal 21, is passed through the top hold circuit, so that the signal is top-held.

When the RF signal shown in FIG. 5A is supplied to the top hold circuit 20, the output signal shown in FIG. 5B can be obtained from the top hold circuit 20. FIG. 5A
The RF signal is a waveform when the optical pickup 3 moves in the radial direction of the optical disc 1. The first half shows a case where the optical signal has crossed a recorded area, and the latter half has a case where it has crossed an unrecorded area. As described above, even when a recorded area and an unrecorded area are mixed, as shown in FIG. 5B, the output signal of the top hold circuit 20 corresponds to the groove and the land and the signal level. The relationship does not reverse. Therefore, the number of tracks crossed from the output signal of the top hold circuit 20 is counted, and switching from coarse servo to fine servo by tracking servo using the counting result can be stably performed.

FIG. 6 shows an example of a circuit for generating a track crossing signal using the above-described top hold circuit 20. In FIG. 6, what is indicated by reference numeral 20 is the above-described top hold circuit. Input terminal 21 of top hold circuit 20
, An RF signal is supplied from an input terminal 41. Assuming that the optical pickup 3 moves in the radial direction of the optical disc 1 as shown by an arrow 51 in FIG. 7A, the RF signal is top-held in the top hold circuit 20, and a signal S1 shown in FIG. 7B is formed.

The signal S1 is supplied to one peak hold circuit 43 and also supplied to the other peak hold circuit 44 via the inverting amplifier 42. The output signal S1 of the top hold circuit 20 is supplied to the other input terminal of the comparison circuit 46.

In one peak hold circuit 43,
The peak hold of the signal S1 is performed, and an output corresponding to the peak of the signal S1 is formed in the peak hold circuit 43. This hold output is supplied to one input terminal of the averaging circuit 45. The other peak hold circuit 4
At 4, the inverted output of the signal S1 is peak-held. That is, an output corresponding to the bottom level of the signal S1 is formed in the peak hold circuit 44. This hold output is supplied to the other input terminal of the averaging circuit 45.

The averaging circuit 45 performs an operation of adding the peak value supplied to one input terminal and the bottom value supplied to the other input terminal and multiplying by ２ to form an average output S2. The average output S2 formed in the averaging circuit 45 is supplied to one input terminal of the comparison circuit 46.

The signal S1 from the top hold circuit 20 is supplied to the other input terminal of the comparison circuit 46.
A comparison process with the average output S2 supplied to one input terminal is performed. That is, the average output S2 is set to the slice level, and the signal S1 is binarized.
A land determination output (track crossing signal) S3 is formed. This judgment output S3 is taken out via the output terminal 47. The number of traversed tracks is detected from the determination output S3.

FIG. 7D shows a tracking error signal. The number of tracks is counted by the determination signal S3. In the vicinity of the target track, tracking servo is performed by a tracking error signal.
A position for recording or reproduction can be stably pulled in.

In one embodiment of the present invention,
Although the case where a detection circuit including a diode or the like is used as the means for top-holding has been described, another circuit capable of top-holding may be used.

Further, in the above-described embodiment of the present invention, the output of the groove is larger than the output of the land before recording, while the output of the groove is smaller (darker) after recording on the groove. It is an example. The present invention is not limited to this example, and the present invention is similarly applied to a case where the output of the land is large compared to the output of the groove before recording, and the output of the land is small after recording on the land side. be able to.

Further, the present invention can be applied not only to an optical disk having a characteristic of becoming dark after recording, but also to an optical disk having a characteristic of becoming bright after recording. That is, FIG. 8A shows a waveform of an RF signal obtained when the optical pickup moves in the radial direction of such an optical disc. In FIG. 8A, in the first half, the area after recording is crossed,
In the latter half, the case where it crosses the unrecorded area is shown. As can be seen from the waveform of the RF signal in the area after recording, the area becomes brighter after recording. More specifically, before recording, the output of the groove is larger than the output of the land, while after recording on the land, the output of the land is larger. Further, before recording, the output of the land may be larger than the output of the groove, and after recording on the groove, the output of the groove may be larger.

By applying the present invention to an optical disk in which the waveform shown in FIG. 8A is generated, as shown in FIG. 8B, the correspondence between the groove and the land and the level of the signal level is inverted. You can get output that you do not need. However, as can be seen from the relationship between the waveforms shown in FIGS. 8A and 8B, it is necessary to hold the bottom of the RF signal shown in FIG.

FIG. 9 shows another example of the track crossing signal generation circuit. Other examples include a case where recording becomes dark as in the above-described embodiment, a case where recording is performed in a bright place, and a case where recording becomes bright as shown in FIG.
In any case of recording in a dark place, it is possible to identify the track (land or groove) and the space between the tracks (groove or land).

In FIG. 9, portions corresponding to those in FIG. 6 are denoted by the same reference numerals. In another example shown in FIG. 9, the determination output S3 is output from the output terminal 25 of the top hold circuit 20.
The configuration up to the output terminal 47 from which the signal is extracted is the same as the configuration shown in FIG.
Is the same as The difference from FIG. 6 is that a switch circuit 49 is provided between the input terminal 41 to which the RF signal is supplied and the input terminal 21 of the top hold circuit 20. The switch circuit 49 includes an input terminal m for guiding the RF signal from the input terminal 41 to the input terminal 21 of the top hold circuit 20 as it is, and an input terminal for guiding the input RF signal to the input terminal 21 of the top hold circuit 20 via the inverting amplifier 48. A terminal n.

Depending on the characteristics of the optical disk to be used (whether dark or bright after recording) and the location to be recorded (bright before recording or dark before recording), it is determined by the user's setting. Alternatively, whether or not the switch circuit 49 is connected to one of the input terminals m and n is determined by automatic discrimination based on a discriminating shape or the like provided on the case of the optical disc.

According to the other example described above, when the characteristics of the optical disk become dark after recording and the recording location is a bright place before recording, a state is set in which the switch circuit 49 selects the input terminal m. On the other hand, if the characteristics of the optical disk become brighter after recording and the recording location is dark before recording, a state is set in which the switch circuit 49 selects the input terminal n. Thus, in any case, the level of the track crossing signal can be maintained in a predetermined relationship before and after recording.

In another example, a bottom hold circuit may be used instead of using the inverting amplifier 48.

[0041]

According to the present invention, discrimination between tracks is performed based on a signal obtained by holding an RF signal top or bottom. Therefore, according to the present invention, it is possible to stably discriminate between tracks irrespective of whether information is recorded or not, and it is possible to improve the stability of the tracking pull-in operation.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram illustrating an outline of an optical pickup according to an embodiment of the present invention.

FIG. 3 is a perspective view used for describing an optical disc in one embodiment of the present invention.

FIG. 4 is a connection diagram illustrating an example of a top hold circuit according to an embodiment of the present invention.

FIG. 5 is a waveform diagram used to explain the operation of the top hold circuit.

FIG. 6 is a block diagram of an example of a configuration for forming a track / inter-track discrimination signal.

FIG. 7 is a waveform diagram used for describing the operation of the configuration shown in FIG. 6;

FIG. 8 is a waveform chart for explaining another example of the track / inter-track discrimination signal generation circuit.

FIG. 9 is a block diagram of another example of a configuration for forming a track / inter-track discrimination signal.

FIG. 10 is a schematic diagram used to explain a problem of a conventional optical disk device.

[Explanation of symbols]

1 ... optical disk, 3 ... optical pickup, 5 ...
・ Read channel, servo unit, 20 ・ ・ ・ Top hold circuit, 31, 48 ・ ・ ・ Inverting amplifier, 32, 33 ・
..Peak hold circuits, 35 ... Comparison circuits

Claims (6)

[Claims] 1. An optical disc apparatus for recording a signal on an optical disc in which the relationship between the brightness between tracks before and after recording is reversed, wherein a reproduction signal is input, and a top hold of the reproduction signal is performed. An optical disc apparatus, comprising: a holding unit for performing the following: discriminating between tracks on the optical disc based on an output of the holding unit. 2. An optical disc apparatus for recording a signal on an optical disc in which the relationship of brightness between tracks is reversed before and after recording, wherein a reproduced signal is input and a bottom hold of the reproduced signal is performed. An optical disc apparatus, comprising: a holding unit for performing the following: discriminating between tracks on the optical disc based on an output of the holding unit. 3. The optical disk device according to claim 1, wherein the track is one of the groove and the land, and the space between the tracks is the other of the groove and the land. 4. The optical disk device according to claim 1, wherein the hold means has a time constant characteristic that is higher than a transverse frequency of the guide groove and lower than a frequency of the reproduction signal. 5. The track according to claim 1, further comprising: averaging means for averaging an output of the holding means; and comparing an output of the holding means with an output of the averaging means. Means for generating a binary signal corresponding to between the tracks. 6. The averaging device according to claim 5, wherein the averaging device includes a peak detecting device that detects a peak of an output of the holding device, a bottom detecting device that detects a bottom of an output of the holding device, and the peak detecting device. And an arithmetic unit for adding the output of the bottom detection unit and the output of the bottom detection unit to reduce the added output to １ ／.