JP2003030831A - Optical disk unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To appropriately detect prepits arranged on an optical disk. SOLUTION: In this optical disk unit, data recording and data reproduction are performed by using an optical disk 4 where the prepits are formed at the side end parts of a track. The device is furnished with: a photo-irradiation element for irradiating the track of the optical disk 4 by a light beam; a photodetector 5 for detecting light reflected from the track irradiated by the light beam, i.e., for detecting 1st light reflected from the one side end part of the track and 2nd light reflected from the other side end part of the track; a subtracter for producing a differential signal between a 1st detection signal corresponding to the 1st reflection light and a 2nd detection signal corresponding to the 2nd reflection signal; and an amplifier for amplifying an output from the subtracter and capable of changing the amplification factor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc device for recording data on and / or reproducing data from an optical disc having prepits indicating address information and the like.

[0002]

2. Description of the Related Art In recent years, recordable optical disks such as CD-R and CD-RW have been generally used as a medium for storing computer data and recording music. Also,
Recently, DVD-RAM, DVD-R, DVD-RW
Optical discs having a higher recording density and capable of recording video data and the like have also been used. Of these, DVD
-R and DVD-RW are playback-only DV so that playback with a playback-only DVD drive can be realized relatively easily.
It has a disk format similar to a D-ROM disk.

More specifically, as shown in FIG. 1, an optical disc 4 such as a DVD-R is provided with a guide groove (groove) for guiding a light spot during data recording. Data is recorded along the groove.
The guide groove is wobbled at a constant frequency in order to generate a reference clock that controls the rotation speed of the disk.
Further, pre-pits are provided on adjacent lands (regions between the grooves) on one side or both sides of the guide groove. This pre-pit (so-called land pre-pit)
For example, it is used for phase correction of the recording clock during data recording. By using pre-pits formed in advance on the optical disc in this way, recording can be performed with higher accuracy.

The prepits formed on the adjacent lands are similar to the detection of wobbling of the groove, and the reflected light from the outside (adjacent land on the outer side in the radial direction of the disk) and the inside (adjacent land on the inner side in the radial direction of the disk) of the groove. ) Is detected as a differential signal from the reflected light. FIG. 2 shows the differential signal detected as described above and converted into an electrical signal. The differential signal includes a wobble signal component indicating wobbling information and a prepit signal component corresponding to a prepit. The method of detecting the pre-pit signal component is
For example, it is described in Japanese Patent Laid-Open No. 2000-195058.

[0005]

However, the shape of the prepits formed on the disk may deviate from the desired shape depending on the cutting conditions in the disk manufacturing process. Further, the reproduction signal spot shape (especially the beam spot shape in the radial direction) of the optical pickup when detecting the prepit, or the deflection (tilt) of the disk causes variations in the amplitude of the detection signal.
Furthermore, when data is recorded on the recording track,
Originally, in the differential signal, a signal component corresponding to the recording data that should be removed may be detected. For these reasons, it may happen that the pre-pit signal cannot be accurately detected depending on the combination of the disc and the device used.

Therefore, it is necessary to adjust the pre-pit signal detection system in the optical disk device for each individual device and the optical disk. In particular, as the density of recorded data becomes higher, it becomes more difficult to properly detect the pre-pit signal. Therefore, in an optical disk device corresponding to an optical disk with a larger recording capacity, the pre-pit signal is detected more accurately and the sync signal is detected. It is important to create.

The present invention has been made based on the above-mentioned conventional problems, and an object thereof is to provide a disk device capable of detecting a pre-pit signal more accurately.

[0008]

The optical disk device of the present invention records data on an optical disk having prepits formed on at least one side end of a track on which data is recorded, and / or records data from the optical disk. An optical disk device for reproducing, comprising a light irradiation element for irradiating the track of the optical disk with a light beam, and a photodetector for detecting reflected light from the track irradiated with the light beam, A photodetector for detecting the first reflected light from one side end and the second reflected light from the other side end of the track, and a first detection signal corresponding to the first reflected light. And a subtracter for generating a differential signal between the second detection signal corresponding to the second reflected light and an amplifier for amplifying the output from the subtractor,
An amplifier capable of changing the amplification factor is provided, and the pre-pit is detected from the differential signal.

[0009] In a preferred embodiment, a prepit detection determination device for determining whether a signal component indicating a prepit in the differential signal corresponds to the prepit provided on the optical disc is further provided, and the prepit detection determination is performed. The amplification factor of the amplifier is set based on the output of the container.

In a preferred embodiment, a binarization circuit for binarizing the differential signal amplified by the amplifier is further provided, and the prepit detection / determination unit outputs the binarization signal output from the binarization circuit. It is determined whether the signal corresponds to the prepit provided on the optical disc.

In a preferred embodiment, the amplification factor of the amplifier is determined based on the output of the pre-pit detection / determination device when the amplification factor of the amplifier is changed while the slice level of the binarization circuit is fixed. Is set.

[0012] In a preferred embodiment, the amplification factor of the amplifier is based on a differential signal generated from the first and second reflected lights detected in a track portion of the optical disc where no data is recorded. Is set.

In a preferred embodiment, the light irradiation element is used to record information indicating the set amplification factor on the optical disc.

[0014] In a preferred embodiment, a storage device for storing information indicating the set amplification factor is further provided.

In a preferred embodiment, the first
Further comprising a balance adjuster for adjusting the ratio of the magnitudes of the first detection signal corresponding to the reflected light and the second detection signal corresponding to the second reflected light, wherein the subtractor is equal to the magnitude. A differential signal between the first detection signal and the second detection signal whose ratio is adjusted is generated.

In a preferred embodiment, the differential signal further includes a prepit detection / determination device for determining whether or not a signal component indicating a prepit in the differential signal corresponds to the prepit provided on the optical disc.

In a preferred embodiment, a pre-pit detection rate measuring device for measuring a pre-pit detection rate based on the determination result of the pre-pit detection determining device is further provided, and the balance adjuster is configured to measure the pre-pit detection rate based on the pre-pit detection rate. Set the ratio of height.

In a preferred embodiment, a binarization circuit for binarizing the differential signal is further provided, and the pre-pit detection / determination device outputs the binarized signal output from the binarization circuit to the optical disc. It is determined whether or not it corresponds to the provided pre-pit.

In a preferred embodiment, a slice level setting circuit capable of changing a slice level in the binarization circuit is further provided, and the slice level setting circuit sets the slice level based on the prepit detection rate. To do.

In a preferred embodiment, when the preset initial value of the size ratio is the initial balance value B0 and the preset initial value of the slice level is the initial slice value S0, It should be set by comparing the pre-pit detection rate D (B0) at the initial balance value B0 with the detection rate D (B1) at a balance value B1 different from the initial balance value B0 by a predetermined balance amount ΔB. The size ratio is estimated, and the pre-pit detection rate D (S
0) and the detection rate D (S1) at a slice value S1 different from the initial slice value S0 by a predetermined slice amount ΔS are compared to estimate the slice level to be set.

In a preferred embodiment, the size ratio and the slice level are differential generated from the first and second reflected lights detected in a track portion of the optical disc where data is recorded. It is set based on the signal.

In a preferred embodiment, the size ratio and the slice level are set during recording of data on the track of the optical disc.

In a preferred embodiment, the light irradiation element is used to record information indicating the set size ratio and slice level on the optical disc.

[0024] In a preferred embodiment, a storage device for storing the set size ratio and slice level is further provided.

In one preferred embodiment, the track of the optical disc is wobbled, and a wobble binarization circuit for generating a binarized signal corresponding to the wobble is further provided, and the pre-pit detection / determination unit is configured to perform the wobble. Using the pre-pit prediction signal generated based on the output of the binarization circuit, it is determined whether the signal component representing the pre-pit in the differential signal corresponds to the pre-pit.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

The optical disc apparatus of the present embodiment has a prepit at at least one side end portion (adjacent land in this embodiment) of an information track (a groove in this embodiment) on which data is recorded, as shown in FIG. Data is recorded on an optical disc (for example, a DVD-R) formed with
Alternatively, data can be reproduced from such an optical disc. The information track (hereinafter, simply referred to as a track) means a linear recording area divided on the optical disc, and typically indicates a groove and a land. In addition, the optical disc used in this embodiment,
Grooves are formed concentrically or spirally, and the grooves are wobbled at a predetermined frequency as shown in FIG.

FIG. 3 shows the overall structure of the optical disc apparatus 100 according to this embodiment. Optical disc device 100
Is an optical pickup 2 for writing and reading data to and from the optical disc 4, a semiconductor laser control block 1 and a servo processing block 21 for controlling the operation of the optical pickup 2, and a reproduction signal processing for processing a reproduction signal from the optical pickup 2. It includes a block 7, a central control block 10 for performing overall control of these, and the like.

The operation of the optical disc apparatus 100 for detecting the wobbles of the pre-pits formed on the optical disc 4 and the grooves formed on the optical disc 4 will be described below.

The semiconductor laser drive block 3 of the optical pickup 2 determines the drive current of the semiconductor laser device (not shown) provided in the optical pickup 2 based on the reproduction power set by the semiconductor laser control block 1. In this way, the optical pickup 2 irradiates the optical disc 4 with a light beam with a predetermined laser power, and forms a light spot on the track (here, groove) of the optical disc 4 as shown in FIG. 1 or FIG. .

The irradiated light beam is reflected by the optical disc 4, and the reflected light is detected by the photodetector 6 provided in the photodetector 5 of the pickup 2 (see FIG. 4B).
Detected by. The photo-detecting element 6 has at least two light-receiving portions arranged so as to be aligned in the direction orthogonal to the groove traveling direction (track direction) (that is, the disk radial direction) when detecting reflected light. . More specifically, the photodetector 6 has four light receiving portions A to D, the light receiving portions A and B are arranged on the outer peripheral side of the disc with respect to the track center L0, and the light receiving portions C and D are provided. Are arranged on the inner circumference side of the disc with respect to the track center L0.
Further, the photodetector 6 detects not only the reflected light from the groove but also the reflected light from the adjacent land and the prepits provided in the adjacent land in each of the light receiving portions A to D.

By using the photo-detecting element 6 constructed as described above, the reflected light from one side end R1 of the groove (outer peripheral side of the disc) and the other of the groove (as shown in FIG. 4A). The reflected light from the side end portion R2 (on the inner circumference side of the disk) can be detected. In the present specification, the side end portion of the groove corresponds to a region near the side end or side edge of the groove (boundary with a land adjacent to the groove), and may include the adjacent land.

Further, in the above description, for simplification of description, the photo-detecting element 6 detects the reflected light from one side end of the track and the reflected light from the other side end thereof, respectively. Although the expression is used, the light detecting element 6 does not actually have to detect each of the reflected lights distinguished as described above. The photodetection element 6 may be any one that can detect the asymmetry of the intensity distribution of the reflected light from the optical disc (asymmetry with respect to the line defining the center of the track when wobbles are ignored). Any signal can be used as long as it can obtain a signal indicating the asymmetry of the track shape. In the present specification, the photodetecting element having such a function is referred to as a photodetecting element for detecting the reflected light from one side end of the track and the reflected light from the other side end thereof, for convenience. I'm out.

As shown in FIG. 4B, the reflected light detected by the photo-detecting element 6 adds the outputs of the light receiving portions A and B and adds the outputs of the light receiving portions C and D. Thus, the tracking detection signals c and d are converted. The tracking detection signals c and d respectively correspond to the reflected light from the outer peripheral side end R1 and the reflected light from the inner peripheral side end R2. Further, the reflected light detected by the photodetector 6b as shown in FIG. 4C is converted into focus detection signals a and b. These detection signals a, b, c, d are input to the servo processing block 21 as shown in FIG. In the servo processing block 21, a focus control signal e is generated based on the focus detection signals a and b, and a tracking control signal f is generated based on the tracking detection signals c and d.
Is generated. The focus control signal e and the tracking control signal f are output to the optical pickup 2, which controls the optical pickup 2 so that the laser beam is accurately focused and tracked on the optical disc 4. Note that such focus control and tracking control are realized by a known method.

The detection signal a output from the photodetector section 5,
b, c, d are also input to the data detection block 9 of the reproduction signal processing block 7, and the detection signals a, b, c, d
It is possible to reproduce the data recorded on the optical disc 4. Further, among the detection signals a, b, c, d output from the photodetection unit 5, the side end R1 on the outer peripheral side of the track.
The detection signal c corresponding to the intensity of the reflected light from and the detection signal d corresponding to the intensity of the reflected light from the side end portion R2 on the inner peripheral side of the track are transmitted to the pre-pit signal detection block 8 of the reproduction signal processing block 7. Is entered. The pre-pit signal detection block 8 detects the detection signal c as described in detail below.
The wobbles of the prepits and the grooves provided on the optical disc 4 are detected based on d and d.
The operations of the semiconductor laser control block 1, the servo processing block 21, and the reproduction signal processing block 7 described above are performed by the control signals g, h, i from the central control block 10.
can be controlled by j. In addition, the central control block 10
Can also be controlled by an external computer (not shown) by means of a control signal k via.

The pre-pit signal detection block 8 will be described in more detail below.

FIG. 5 shows the overall structure of the pre-pit signal detection block 8. As shown in the figure, the detection signal c and the detection signal d corresponding to the outer peripheral side and the inner peripheral side of the groove obtained as described above are input to the subtraction circuit 11. The subtraction circuit 11 subtracts these signals to generate the differential signal 1u as shown in FIG. However, the pre-pit signal detection block 8 includes a balance gain circuit 12 capable of adjusting the gain of the detection signal d before being input to the subtraction circuit 11.
The balance gain circuit 12 can adjust the ratio of the magnitudes of the detection signal c and the detection signal d. That is, the subtraction ratio in the subtraction circuit 11 can be adjusted. The gain adjustment in the balance gain circuit 12 is performed based on the balance gain control signal m, and the details of this operation will be described later.

The differential signal 1u output from the subtraction circuit 11
Is then input to the gain amplifier 13. The gain amplifier 13 is configured to be set to an arbitrary gain (that is, to be able to arbitrarily change the amplification factor) according to the gain amplifier control signal n. As a result, the differential signal 2u amplified by the predetermined amplification factor is obtained. As described above, in the present embodiment, the accuracy of pre-pit detection can be improved by appropriately amplifying the differential signal using the gain amplifier 13. The detailed operation of the gain amplifier 13 will be described later.

The differential signal 2u output from the gain amplifier 13 is then input to the prepit detection block 50 and the wobble detection block 60, and prepit detection and groove wobble detection are performed in each of them.

In the pre-pit detection block 50, the differential signal 2u input to the binarization circuit 14 is the slice signal o.
It is binarized by slicing at the slice level defined by The binarized signal is output to the central processing block 10 as a pre-pit binarized signal r. As the slice signal o, either the output of the constant voltage generation circuit 15 or the output of the DA converter 22 that can be set to an arbitrary level controlled by the slice level setting signal q is selected according to the slice signal selection signal p. Is selected.

On the other hand, in the wobble detection block 60, the differential signal 2u input to the wobble gain amplifier 16 is set to an arbitrary gain, and the signal output from the gain amplifier 16 is wobbled by the band pass filter 17. Only the fundamental wave component of the signal is extracted, and noise components other than the fundamental wave component are removed. The noise component of the wobble signal includes the reproduction signal and the prepit signal corresponding to the recording data. The wobble signal that has passed through the band pass filter 17 is binarized by the wobble binarization circuit 18, and is input to the central processing block 10 as the wobble binarization signal s, like the pre-pit binarization signal r.

In this way, the optical disc device 100 of the present embodiment detects the prepits and the wobbles from the differential signal 2u between the detection signals c and d, but the gain setting in the gain amplifier 13 and the balance gain circuit 1 are performed.
Setting of balance gain in 2 and binarization circuit 1
By setting the slice level in 4, the prepits are detected more accurately. More specifically, first, the gain signal is used to amplify the differential signal so that the pre-pit signal component in the differential signal is most easily detected, and then the balance gain circuit 12 outputs the differential signal. Prepits can be detected with high accuracy by adjusting the waveform and adjusting the slice level during binarization.

First, the operation relating to the gain setting in the gain amplifier 13 will be described. As shown in FIG. 1, the pre-pits on the optical disc 4 are detected by detecting the reflected light of the light beam that forms a light spot on the groove. In the case of adopting such a pre-pit detection method, when the pre-pit is formed smaller than the light spot, the differential signal 1u shown in FIG.
The amplitude (i.e., the amplitude of the pre-pit signal) tends to be small. On the contrary, when the pre-pits are formed larger than the light spot, the amplitude of the pre-pit signal tends to be large. Although the amplitude of the pre-pit signal may change depending on many other factors, it is not the same as described above. However, when the combination of the optical disc and the optical disc device changes, the size relationship between the pre-pit and the light spot also changes. As a result, the amplitude of the prepit signal changes. The amplitude of the pre-pit signal can change depending on, for example, the shape of the pre-pit formed on the optical disc 4, the reflectance of the recording medium applied as the recording film, the width of the groove track and the land track, and the like.

Therefore, depending on the combination of the optical disc and the optical disc device, the amplitude may not be appropriate unless the amplification factor of the differential signal is adjusted. In this case, the accuracy of pre-pit detection is lowered. 6 (a) to 6 (c)
Shows the pre-pit binarized signal generated when the amplitude of the differential signal 2u (that is, the signal including the pre-pit signal component and the wobble signal component) has large and small variations. As shown in FIG. 6A, when the amplitude is appropriate (normal amplitude), the desired prepit 2
While the binarized signal is obtained, as shown in FIG. 6B, when the amplitude of the differential signal 2u is smaller than that in the case of normal amplitude, the amplitude of the prepit signal is binarized. The pulse signal corresponding to the pre-pit signal may not be obtained because the slice level is not exceeded. Further, even if detection is possible, since the prepit signal is not sliced at an appropriate level, a binarized signal containing a lot of jitter in the pulse indicating the prepit is generated.

Further, as shown in FIG. 6C, when the amplitude of the differential signal 2u is larger than the normal amplitude, not only the prepit signal but also the wobble signal may be binarized. Occurs, and the desired pre-pit binarized signal cannot be obtained.

Further, as shown in FIG. 6D, when data is recorded in the groove portion, a change in reflectance due to the presence or absence of a recording mark leaks into the differential signal 2u, and the root of the pre-pit signal and the wobble signal. Becomes a disturbance to. Therefore, when the amplitude of the differential signal 2u is relatively large with respect to the slice level, there arises a problem that a prepit signal is erroneously detected or jitter increases. Since the pre-pit binarized signal is used as a synchronization signal when the address of the optical disc 4 is detected, the fact that the pre-pit is not detected or the jitter increases means that accurate timing information cannot be obtained. means. As a result, address detection is not performed accurately. A similar leak phenomenon also occurs when data is recorded using the optical pickup 2. The pre-pit binarized signal is used to detect an accurate position on the optical disc during a data recording operation. Therefore, if an appropriate pre-pit binarized signal cannot be obtained, there may occur a problem that a recording mark is not formed at an accurate position with respect to a sector defined on the optical disc.

Therefore, particularly when the optical disc is loaded in the disc device, it is desirable to appropriately adjust the amplitude of the prepit signal, that is, the amplitude of the differential signal 1u so that the prepit detection is appropriately performed. Figure 7
FIG. 7A is a flowchart showing the amplitude adjustment operation of the differential signal 1u according to the present embodiment performed using the gain amplifier 13, and FIG. 7B shows the differential signal and the slice signal in each process. The relationship and the pre-pit binary signal and the wobble binary signal generated at that time are shown.

As shown in step S10, when the amplitude of the differential signal is adjusted, the signal level (slice level) of the slice signal o is a fixed level t1 set by the constant voltage generation circuit 15 by the slice signal selection signal p. Is set to. The fixed slice level t1 is preferably set near the upper limit of the dynamic range of the binarization circuit 14 that binarizes the prepit signal (that is, near the maximum value of the settable slice levels).

Next, as shown in step S12, the gain amplifier 13 is set to the minimum gain by the gain amplifier control signal n. When the gain amplifier 13 is set to the minimum gain, the pre-pit signal in the differential signal falls below the slice level, so that the pre-pit binarized signal generated in the binarization circuit 14 does not have a pulse corresponding to the pre-pit. .

After that, as shown in step 14, the gain of the gain amplifier 13 is gradually increased by the gain amplifier control signal n to amplify the differential signal. In this process, when the amplified differential signal reaches the slice level,
A pulse (hereinafter referred to as a prepit detection pulse) appears in the prepit binary signal. At this time, it is determined whether or not the appearing pulse actually corresponds to the prepit. This operation is performed by the prepit timing determination circuit 19 provided in the central control block 10 shown in FIG.

As shown in FIG. 8A, the prepit timing determination circuit 19 includes a prepit binarization signal r output from the binarization circuit 14 and a wobble binarization circuit 18.
The wobble binarized signal s output from is input.
Here, the format of the optical disc 4 is defined so that the pre-pit signal and the wobble signal are synchronized with each other, as shown in FIG. More specifically, the prepit signal exists at most once in one cycle of the wobble signal, and the phase relationship between the wobble signal and the prepit signal is always constant. In this way, the pre-pit signal is formed according to a certain rule with respect to the wobble signal, and therefore, based on the wobble binary signal s,
It is possible to generate the pre-pit prediction signal v for predicting the position of the pre-pit detection pulse as shown in FIG. 8 (b). Here, the pre-pit prediction signal v is generated as a signal having a pulse having a narrow width which rises at a timing substantially in the middle of the logical high period of the wobble binary signal s.

The pre-pit timing judgment circuit 19 judges whether or not the pre-pit detection pulse corresponds to the actual pre-pit by comparing the inputted pre-pit binary signal r and the pre-pit prediction signal v. . That is, if the pre-pit detection pulse in the pre-pit binarized signal r is detected at the active timing of the pre-pit prediction signal v, it is a regular pre-pit detection pulse. Is falsely detected. The pre-pit timing determination circuit 1 is performed in this procedure.
If a predetermined number or more of regular pre-pit detection pulses are detected in 9, it is determined that the pre-pits are properly detected, and the pre-pit timing determination circuit 19 outputs a pre-pit determination OK instruction.

The gain amplifier 13 sequentially increases the gain until the pre-pit determination OK is output, and sets the gain value when the detection OK is output as the optimum gain value of the gain amplifier 13. In this way, the gain of the gain amplifier 13 is set based on the output of the prepit timing determination circuit 19 which determines whether or not the signal component indicating the prepit in the differential signal corresponds to the prepit.

After the optimum gain of the gain amplifier 13 is set through such a procedure, the output of the DA converter 22 is selected as the slice signal o by the slice signal selection signal p as shown in step S16. The slice level of the binarization circuit 14 is set. The slice level by the DA converter 22 is, of course, constant voltage generation circuit 1
The voltage is set to a value lower than the voltage set in 5 (preferably, the value in the middle of the dynamic range of the binarization circuit 14). The slice level defined by the DA converter 22 can be further adjusted as necessary, as described later.

As described above, if the differential signal 1u is appropriately amplified by the gain amplifier 13, the binarization circuit 14 can perform binary conversion regardless of the amplitude of the differential signal generated by the subtractor. The amplitude of the differential signal to be converted is too small (FIG. 6B) or too large (FIG. 6B) with respect to the slice level.
It is possible to prevent a situation such as (c)) from occurring. In particular, if the peak level of the prepit signal and the maximum value of the slice level are amplified to such an extent that the differential signal is amplified, the prepit signal can be appropriately set by setting the slice level to, for example, an intermediate level during binarization. It is possible to slice at various levels. Therefore, the detection accuracy of the pre-pits can be improved.

When setting the gain of the gain amplifier 13, the reflected light is detected in a predetermined area of the optical disk 4 (that is, the predetermined area is reproduced).
As shown in (a), when reproducing an unrecorded area in which no data is recorded, since the reflectance does not change due to the recording mark, the amplitude of the prepit signal does not decrease and the amplitude is detected stably. To be done. When the gain of the gain amplifier 13 is set by reproducing the unrecorded area as described above, no serious problem occurs even when the area in which the data is recorded is reproduced.

On the other hand, as shown in FIG.
By reproducing the data recording section, the gain amplifier 13
When the gain setting is performed, the reflectance change due to the recording mark leaks into the detection signal, the level of the prepit signal becomes unstable, and the amplitude decreases. If the gain is set in such a state, the amplitude of the pre-pit signal may become too large when the unrecorded area of the data is reproduced (that is, when the reflectance change due to the recording mark is not affected). is there. In this case, even if the slice level is made smaller than the fixed level, the prepit detection rate is not improved, and as a result, the gain may not be set optimally.

From the above, it is preferable to set the gain of the gain amplifier by using the differential signal obtained when the area (or track portion) in which data is not recorded on the optical disc 4 is reproduced. This makes it possible to accurately detect the prepits regardless of the data recording area and the data non-recording area.

The optimum gain value (that is, the optimum amplification factor of the differential signal) set as described above is stored in the storage device (memory unit) provided in the central control block 10. As described above, the amplitude of the differential signal 1u varies depending on the combination of the optical disc 4 and the drive system such as the optical pickup 2. However, for the optical disc once mounted in the disc device, the optical disc The optimum gain value once set is valid unless it is discharged. Therefore, when the disk device is powered off and used next, it is sufficient to read the optimum gain value from the memory unit without performing the above-described gain value setting process again. In addition to the set optimum gain value, individual information of the used optical disk (information that enables the optical disk to be discriminated from other optical disks) may be stored in the memory unit. By doing this, even when the optical disc once ejected from the disc device is mounted on the disc device again and used again, the gain value suitable for the optical disc is set based on the stored individual information. It will be possible.

Further, instead of storing it in the memory section as described above, the optical pickup 2 is used and the optical disc 4 is used.
If the optimum gain value is recorded in the management information area, the optical disk device reads the optimum gain value recorded in the management information area and sets it in the gain amplifier 13 even if the optical disk 4 is taken in and out. Just get better. As a result, the start-up time of the optical disc system can be shortened. Further, the individual information of the optical disc 4 may be recorded in the management information area of the optical disc 4.

Next, a balance gain setting operation and a level (slice level) setting operation of the slice signal o in the balance gain circuit 12 will be described.

FIG. 10 shows the central control block 1 used for setting the balance gain and the slice level.
The pre-pit detection amount measuring circuit 20 provided at 0 is shown.
The prepit binary signal r and the wobble binary signal s are input to the prepit detection amount measuring circuit 20. The pre-pit detection amount measurement circuit 20 determines whether the pre-pit signal in the differential signal corresponds to the pre-pit provided on the optical disc, as in the above-described pre-pit timing determination circuit 19. More specifically, similar to the above, the normal prepit detection pulse appearing in the prepit binary signal r is detected. Pre-pit detection amount measuring circuit 20
Always detects this regular pre-pit detection pulse, and the detection amount (or detection rate) of pre-pits is
It is possible to measure

FIG. 11A shows prepits when the gain value of the balance gain circuit 12 (that is, the amplification factor of the detection signal d) is changed during the reproduction of the data recorded area on the optical disc 4. The detection rate is shown. The recording marks and spaces formed in the groove portion of the optical disc 4 appear as in-phase data signals in the tracking detection signals c and d. Therefore, when the differential signals of the detection signals c and d are generated, these data signals are canceled out and there is little leakage into the prepit signal and the wobble signal. However, the detection signal c and the detection signal d
If the ratio (balance) of the magnitudes of and is not appropriate, the ratio of canceling the in-phase data signal changes, and the pre-pit signal,
It will start leaking into the wobble signal. As a result, the quality of the pre-pit binarized signal r generated by the binarization circuit 14 may be deteriorated and the pre-pit detection amount may be reduced. Figure 1
In 1 (b) and (d), the imbalance of the detection signal c and the detection signal d is not appropriate, so that the size of the leaked data signal becomes large, thereby obtaining the desired prepit binary signal. It shows the case where it is not possible.

Therefore, as shown in FIG. 11C, by adjusting the gain value of the balance gain circuit 12 and appropriately setting the ratio of the magnitudes of the detection signal c and the detection signal d, the data signal It is desirable to reduce leakage. The gain of the balance gain circuit 12 is set to, for example, the gain value when the pre-pit detection amount output from the pre-pit detection amount measuring circuit 20 is the highest. Alternatively, a threshold value of the pre-pit detection amount output from the pre-pit detection amount measuring circuit 20 is set in advance, and the gain value is set to an intermediate gain value between the gain values of the two points exceeding this threshold value.

Further, as shown in FIGS. 12 (a) to 12 (d), similarly, with respect to the slice level, while the area on the optical disc 4 where the data is recorded is reproduced, the slice signal o is increased from the low level to the high level. It is preferable to find the appropriate slice level by changing to levels. This operation is performed by selecting the output of the DA converter 22 as the slice signal o by the slice level setting signal q and measuring the prepit detection amount by the prepit detection amount measurement circuit 20 while changing the output of the DA converter 22. . 12
As shown in FIG. 12B, while the slice level is low, the prepit detection amount is low because the root level of the prepit signal is binarized, but as shown in FIG. The pre-pit detection amount increases as the signal approaches the intermediate level. However, when the slice level exceeds a predetermined level, the prepit detection amount gradually decreases, and as shown in FIG. 12D, when the slice level is too high, the prepit detection amount becomes very small. Through these steps, the slice level is set to, for example, a level at which the pre-pit detection amount has a maximum value or an intermediate level between two levels at which the pre-pit detection amount reaches a detection threshold value exceeding a predetermined amount.

FIG. 13 is a range (prepit detection margin) in which the prepit detection is preferably performed when the horizontal axis represents the balance gain and the vertical axis represents the slice level.
Indicates. When reproducing a disc area in which no data is recorded in the groove portion, as shown by the range M1, the detection margin is relatively large with respect to the change of the balance gain and the change of the slice level. On the other hand, when playing a disc area where data is recorded in the groove,
As described above, if the balance gain is an appropriate value, the reflectance change due to the recording mark is removed as a common-mode signal in the differential signal, but if the balance is lost, the mark leaks as shown in FIG. The amount increases. Therefore, the range M2 of the balance gain and the slice level at which the prepits can be stably detected in the track on which the data is recorded is narrower than the range M1 when the data is not recorded. Therefore, in order to stably detect the pre-pits, it is desirable to set the optimum balance gain and slice level by reproducing the groove portion in which data is recorded and which has a narrow pre-pit detection margin. . This makes it possible to detect the prepits with high accuracy regardless of whether the data recording area or the data unrecorded area is reproduced.

FIG. 13 also shows the relationship between the balance gain and slice level and the prepit detection margin during recording of predetermined data on the optical disc. As can be seen from the figure, the pre-pit detection margin M3 during the recording operation becomes narrower than the detection margins M1 and M2 during the reproduction. This is because the laser light modulated according to the mark to be recorded is emitted from the optical pickup 2 according to the laser emission waveform as shown in FIG. 14 during the recording operation. When the emission intensity of the laser light thus irradiated changes, the intensity of the reflected light detected by the photodetector also changes.
As a result, the obtained differential signal 2u includes
As shown in (b) to (d), the laser emission waveform will leak.

Originally, since the laser emission waveform also appears as the in-phase signal in the detection signals c and d, it is ideally canceled in the differential signal 2u, but the leakage of the laser emission waveform cannot be completely eliminated. Have difficulty. Further, the amount of leakage of the laser emission waveform during the recording operation is larger than the amount of leakage of the data signal during reproduction of the recorded track. Therefore, it is necessary to more appropriately set the balance gain and the slice level in order to appropriately detect the prepits, and therefore the margin of the balance gain and the slice level is further reduced.

The reason why the amount of leakage of the laser emission waveform is large is that the recording power P of the laser emission waveform shown in FIG.
The ratio of 1 to the bottom power P2 is large. For example, in the case of DVD-R, the recording power P1 is set to 10 times or more the bottom power P2. When the change in the laser emission intensity is extremely large as described above, the influence on the differential signal becomes large.

Further, according to the experiment of the present inventor, when the leak amount is large as described above, as shown in FIG. 15C, even if the balance gain is set evenly, the balance gain cannot be completely removed. As shown in FIG. 15 (d), it was found that the pre-pit detection rate may be improved by performing unbalanced detection. As shown in FIG. 15A, the relationship between the magnitude of the balance gain and the pre-pit detection rate during the recording operation is the relationship between the magnitude of the balance gain and the pre-pit detection rate during the reproducing operation shown in FIG. 11A. Will be different from.

From the above, when detecting the pre-pit signal during recording, it is preferable to set the optimum balance gain and slice level different from those at the time of reproduction. In the optical disc device 100 of the present embodiment, it is possible to set the balance gain and the slice level separately during the reproducing operation and the recording operation based on the prepit detection amount output from the prepit detection amount measuring circuit 20. Therefore, in any case, it is possible to accurately detect the prepits.

The balance gain adjustment and the slice signal adjustment can be executed in the data unrecorded area of the optical disk 4, but it is preferable to execute them in the data recorded area. As described above, the amount of pre-pit detection may be affected by the leakage caused by the change in reflectance due to the recorded mark, so it is more difficult for pre-pit detection to make adjustments in the recorded area of data. Adjustment will be made under the conditions. Therefore, if the adjustment is performed in the area where the data is recorded, the pre-pit detection in the unrecorded portion is also suitably performed.

The optimum balance gain and slice level set value set as described above are stored by the memory unit of the central control unit, like the gain value of the gain amplifier 13 described above. Alternatively, it is recorded in the management information area of the optical disc 4. Further, the individual information of the optical disc 4 may be recorded in the memory section of the optical disc device or the optical disc in the same manner. If you do this,
This is effective for shortening the start-up time of the optical disk device.

An embodiment of the balance gain and slice level adjustment method has been described above.
A more simplified balance gain and slice level adjustment method (optimum point estimation method) will be described.

FIG. 16 is a diagram for explaining another method of adjusting the balance gain and slice level. As shown in the figure, the prepit detection rate is distributed in a contour line when the balance gain and the slice level are two axes.
That is, a range M5 in which the prepit detection rate is lower exists around the range M4 centering on the range M4 of the balance gain and the slice level capable of realizing the desired prepit detection rate. In the following, the value of the balance gain (for example, B0) is expressed as the coordinate on the horizontal axis,
The slice level value (for example, S0) is expressed as the coordinate on the vertical axis, and the combination thereof is expressed as (B0, S0).

First, the prepit detection rate D (B0, S0) when the balance gain and the slice level are set to preset initial values (B0, S0) is measured. Here, it is assumed that D (B0, S0) = 100% is obtained. The prepit detection rate can be measured by the prepit detection amount measuring circuit 20 shown in FIG. That is, the prepit detection rate is measured by measuring the ratio of the actual prepit detection amount output from the prepit detection amount measurement circuit 20 to the prepit detection amount when it is assumed that all the prepits are detected.

Next, the pre-pit detection rate when the balance gain is changed by ± ΔB and the pre-pit detection rate when the slice level is changed by ± ΔS are measured from the initial value (B0, S0). Note that ΔB and Δ
S is a preset increase / decrease amount (referred to as a balance amount and a slice amount). In this method, the initial value (B
0, S0), the slice level and the balance gain are not changed continuously, but the slice level and the balance gain are changed discretely, and the pre-pit detection rate is measured at each measurement point. As a result of the measurement in this way, the pre-pit detection rate D (B0 + ΔB,
S0) = 20%, D (B0-ΔB, S0) = 10%, D
(B0, S0 + ΔS) = 20%, D (B0, S0−Δ)
S) = 10% is assumed to be obtained.

In this case, the pre-pit detection rate D (B0, S0) is highest when the initial value (B0, S0) is used.
Therefore, it is understood that the optimum balance gain and the optimum slice level should be set to the initial values (B0, S0).

Next, with reference to FIG. 17, a case where the initial value (B0, S0) does not match the optimum value, which is different from the case shown in FIG. 16, will be described. As a result of measuring the pre-pit detection rate in the same manner as above, the initial values (B0, S
0), the pre-pit detection rate D (B0, S0) = 50% is obtained, D (B0-ΔB, S0) = 0%, D (B0 + Δ
B, S0) = 60%, D (B0, S0 + ΔS) = 60
%, And D (B0, S0-ΔS) = 0% is measured.

Here, D (B0, S0) and D (B0-Δ
B (S0), D (B0, S0) is larger, and D (B0, S0) and D (B0, S0-ΔS) are larger.
Comparing with, since D (B0, S0) is larger, it can be seen that the pre-pit detection result deteriorates when the balance gain or slice level is swung in the negative direction. Therefore, it is confirmed that the optimum point does not exist in that direction, but the optimum balance gain and the optimum slice level all exist in the positive direction.

Next, the measurement is performed when the balance gain and the slice level are further swung in the positive direction. That is, D (B0 + 2ΔB, S0) and D (B
0, S0 + 2ΔS) is measured. Here, the measurement result,
D (B0 + 2ΔB, S0) = 20%, D (B0, S0 +
It is assumed that 2ΔS) = 20% is obtained. In this case, since the pre-pit detection rate is reduced, it is estimated that the pre-pit detection rate is highest when the balance gain is B0 + ΔB, and the slice level is S0 +.
It is estimated that the pre-pit detection rate is highest when ΔS. Therefore, in this case, the optimum points of the balance gain and the slice level are (B0 + ΔB, S0 +
ΔS) can be inferred.

In this example, an inflection point at which the prepit detection rate starts to decrease when the balance gain and the slice level are changed to B0 + 2ΔB and S0 + 2ΔS can be found, but if not found, B0 + 3ΔB,
Alternatively, the inflection point may be found by shaking S0 + 3ΔS.

Even if the inflection point of the pre-pit detection rate is not found, if the pre-pit detection rate has reached the system allowable value, the balance gain and slice level at the time of reaching it are adopted as the optimum values. You may do so. Further, in the present embodiment, the measurement point is selected so that one of the balance gain and the slice level is fixed and the other one is changed, but the measurement is performed so that both the balance gain and the slice level are simultaneously changed. You may make it select a point.

It is desirable that the step width (balance amount) ΔB of the balance gain and the step width (slice amount) ΔS of the slice level be as small as possible in order to accurately estimate the optimum point. , If these are too small, the number of steps required to search for the optimum point increases,
It will increase the search time. Therefore, it is desirable that the balance amount and the slice amount are set to optimal sizes by experiments.

The optimum point estimation method described above has the advantage that the processing time can be shortened because the appropriate balance gain and slice level can be found by measuring the prepit detection rate at relatively few measurement points. For example, in a factory that manufactures optical disk devices,
The initial values (B0, S0) are set to appropriate values in advance by experiments, and when the optical disk device is actually operated after shipment from the factory, when the optical disk device is actually operated, changes with time from the state before shipment, temperature changes, and characteristics of the optical disk used. By correcting the variation of the optimum value due to variation or the like by the above method, the balance gain and the slice level can be determined in a short time.

Although the optical disk device according to the embodiment of the present invention has been described above, the order of executing the balance gain adjustment and the slice level adjustment is not particularly limited. Further, the balance gain adjustment and the slice level adjustment may be performed at the same time, or only one of the balance gain adjustment and the slice level adjustment may be performed.

[0087]

As described above, according to the present invention, the differential signal generated from the reflected light can be amplified to an arbitrary magnitude when the prepit is detected. It is possible to improve the pre-pit detection accuracy by amplifying the pre-pit. Also, by adjusting the ratio of the magnitudes of the two detection signals used to generate the differential signal, it is possible to reduce the noise component of the differential signal, and thus it is possible to improve the pre-pit detection accuracy. is there. Further, the precision of pre-pit detection can also be improved by adjusting the slice level of the binarization circuit that binarizes the differential signal.

[Brief description of drawings]

FIG. 1 is an enlarged perspective view showing a part of an optical disc.

FIG. 2 is a diagram showing differential signals (pre-pit signal and wobble signal) detected from an optical disc.

FIG. 3 is a diagram showing an overall system configuration of an optical disc device according to an embodiment of the present invention.

FIG. 4 is a diagram for explaining detection of reflected light in the optical disc device according to the embodiment of the present invention, (a) showing a light spot formed on the optical disc, and (b) and (c). The structure of a photodetector is shown.

FIG. 5 is a diagram showing a pre-pit signal detection block in the optical disc device according to the embodiment of the present invention.

FIG. 6 is a diagram for explaining that different pre-pit binarized signals are generated according to a differential signal;
(C) shows the case where the amplitudes of the differential signals are different, and (d) shows the case where the data signals leak into the differential signals.

7A and 7B are views for explaining a gain setting method in the optical disc device according to the embodiment of the present invention, FIG. 7A is a flowchart of the gain setting method, and FIG. 7B is a differential signal and pre-pit 2 in each step. The digitized signal is shown.

FIG. 8A shows a configuration of a prepit timing determination circuit of the optical disc device according to the embodiment of the present invention,
(B) shows a signal used in the pre-pit timing determination circuit.

9A and 9B are views for explaining a gain setting method in the optical disc device according to the embodiment of the present invention, FIG. 9A shows a case where a data unrecorded area is reproduced, and FIG. 9B shows a data recording area. The case is shown.

FIG. 10 is a diagram showing a configuration of a pre-pit detection amount measuring circuit of the optical disc device according to the embodiment of the present invention.

FIG. 11A is a graph showing the relationship between the balance gain and the pre-pit detection amount in the optical disc device according to the embodiment of the present invention, and FIGS. 11B to 11D are set to different balance gains. Indicate the case.

FIG. 12A is a graph showing the relationship between the slice level and the pre-pit detection amount in the optical disk device according to the embodiment of the present invention, and FIGS. 12B to 12D are set to different slice levels. Indicate the case.

FIG. 13 is a diagram showing a balance gain and a prepit detection rate with respect to a slice level in the optical disc device according to the embodiment of the present invention.

FIG. 14 is a diagram showing a laser emission waveform and a mark formed during recording in the optical disc device according to the embodiment of the present invention.

FIG. 15A is a graph showing the relationship between the balance gain and the pre-pit detection amount at the time of recording operation in the optical disk device according to the embodiment of the present invention, and FIGS.
Indicates the case where different balance gains are set.

FIG. 16 is a diagram for explaining a balance gain and slice level setting method in the optical disc apparatus according to the embodiment of the present invention.

FIG. 17 is a diagram for explaining a balance gain and slice level setting method in the optical disc device according to the embodiment of the present invention.

[Explanation of symbols]

1 Semiconductor laser control block 2 optical pickup 3 Semiconductor laser drive block 4 optical disks 5 Photodetector 6 Photodetector 7 Playback signal processing block 8 Pre-pit signal detection block 9 Data detection block 10 Central control block 11 Subtraction circuit 12 Balance gain circuit 13 gain amplifier 14 Binarization circuit 15 Constant voltage generator 16 wobble gain amplifier 17 bandpass filter 18 Wobble binarization circuit 19 Pre-pit timing judgment circuit 20 Pre-pit detection amount measurement circuit 21 Servo processing block 22 DA converter 50 pre-pit detection block 60 Wobble detection block a, b Focus detection signal c, d Tracking detection signal e Focus control signal f Tracking control signal g, h, i, j, k control signal 1u differential signal 2u differential signal m Balance gain control signal n gain amplifier control signal o Slice signal p slice signal selection signal q Slice level setting signal r Pre-pit binary signal s Wobble binary signal t1 fixed slice level

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takayuki Sakabayashi             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F-term (reference) 5D090 AA01 BB04 CC14 CC16 EE14                       EE18 JJ11 LL08

Claims (18)

[Claims] 1. An optical disc device for recording data on and / or reproducing data from an optical disc having prepits formed on at least one side end of a track on which data is recorded, said optical disc device comprising: A light irradiation element for irradiating the track with a light beam, and a photodetector for detecting reflected light from the track irradiated with the light beam, the first reflection from one side end of the track. A photodetector for detecting light and second reflected light from the other side end of the track, a first detection signal corresponding to the first reflected light, and the second
A subtractor for generating a differential signal with respect to the second detection signal corresponding to the reflected light of, and an amplifier for amplifying the differential signal output from the subtractor, the amplification factor being changeable. An optical disc device comprising an amplifier and detecting the prepits from a differential signal amplified by the amplifier. 2. A prepit detection determiner for determining whether a signal component indicating a prepit in the amplified differential signal corresponds to the prepit provided on the optical disc, the prepit detection determiner The optical disk device according to claim 1, wherein the amplification factor of the amplifier is set based on the output of the amplifier. 3. A binarizing device for binarizing the amplified differential signal.
The binarization circuit is further provided, The said pre-pit detection determination device determines whether the binarization signal output from the said binarization circuit respond | corresponds to the said pre-pit provided in the said optical disk. Optical disk device. 4. Based on a change in the output of the pre-pit detection / determination device when the amplification factor of the amplifier is changed while the slice level of the binarization circuit is fixed,
The optical disk device according to claim 3, wherein the amplification factor of the amplifier is set. 5. The amplification factor of the amplifier is set based on a differential signal generated from the first and second reflected lights detected in a track portion where data on the optical disc is not recorded. Item 5. The optical disk device according to any one of Items 2 to 4. 6. The optical disk device according to claim 2, wherein the light irradiation element is used to record information indicating the set amplification factor on the optical disk. 7. The optical disk device according to claim 2, further comprising a storage device that stores information indicating the set amplification factor. 8. A balance adjuster that adjusts a ratio of magnitudes of the first detection signal and the second detection signal, wherein the subtractor is the first adjuster of the magnitude ratios. The optical disk device according to claim 1, wherein a differential signal between the first detection signal and the second detection signal is generated. 9. The optical disc apparatus according to claim 8, further comprising a prepit detection determination unit that determines whether a signal component indicating a prepit in the differential signal corresponds to the prepit provided on the optical disc. 10. A pre-pit detection rate measuring device for measuring a pre-pit detection rate based on the determination result of the pre-pit detection determination apparatus, wherein the balance adjuster calculates the ratio of the sizes based on the pre-pit detection rate. The optical disk device according to claim 9, which is set. 11. A binarizing circuit for binarizing the differential signal, wherein the pre-pit detection / determining device has the binarized signal output from the binarizing circuit provided on the optical disc. The optical disc device according to claim 10, wherein it is determined whether or not the prepits are supported. 12. The slice level setting circuit capable of changing a slice level in the binarization circuit, wherein the slice level setting circuit sets the slice level based on the pre-pit detection rate. The optical disk device described in 1. 13. The initial balance value B0 when the preset initial value of the size ratio is an initial balance value B0 and the preset initial value of the slice level is an initial slice value S0. Pre-pit detection rate at D
By comparing (B0) with the pre-pit detection rate D (B1) at a balance value B1 different from the initial balance value B0 by a predetermined balance amount ΔB, the ratio of the sizes to be set is estimated, And the pre-pit detection rate D at the initial slice value S0
The slice level to be set is estimated by comparing (S0) with the pre-pit detection rate D (S1) at a slice value S1 different from the initial slice value S0 by a predetermined slice amount ΔS. 12. The optical disk device according to item 12. 14. The size ratio and the slice level are based on a differential signal generated from the first and second reflected lights detected in a track portion of the optical disc where data is recorded. Claim 1 set
2. The optical disk device described in 2. 15. The optical disk apparatus according to claim 12, wherein the size ratio and the slice level are set during recording of data on the track of the optical disk. 16. The optical disk device according to claim 12, wherein the light irradiation element is used to record information indicating the set size ratio and slice level on the optical disk. 17. A storage device for storing the set size ratio and slice level.
16. The optical disk device according to any one of 2 to 15. 18. The wobble binarization circuit for generating a binarization signal corresponding to the wobble, wherein the track of the optical disc is wobbled, and the pre-pit detection determination unit is the wobble binarization circuit. 10. The optical disk device according to claim 2, wherein it is determined whether or not a signal component representing a prepit in the differential signal corresponds to the prepit by using a prepit prediction signal generated based on the output of.