JP2002050051A - Optical disk and optical disk reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk capable of reducing crosstalk in a track adjacent to a header. SOLUTION: This optical disk includes a header area and a group area adjacent to each other. The header area is provided with an embossed prepit indicating a header data, and an embossed dummy pit for setting the optical reflectance of the header area to be lower than the optical reflectance of a mirror-shaped area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk having a header area and a groove area. Further, the present invention relates to an optical disk reproducing apparatus for reproducing an optical disk having a header area and a groove area.

[0002]

2. Description of the Related Art In recent years, research and development of optical disks such as DVDs (Digital Video Disks) have been actively pursued. For example, there is an optical disc having a single spiral structure in which a land track and a groove track are switched every turn. Further, such an optical disk is provided with a header portion, and the header portion is provided with embossed pre-pits. The pre-pit indicates header data.

[0003]

However, in the above-mentioned optical disk, since the header section and the groove track are adjacent to each other, there is a problem that the recording mark recorded on the groove track is not reproduced correctly due to the influence of crosstalk. Was. The cause of the crosstalk is an increase in the amount of reflected light serving as the base of the groove track due to the reflected light from the mirror-like region in the header portion.

An object of the present invention has been made in view of the above-mentioned circumstances, and has as its object to provide the following optical disk and optical disk reproducing apparatus.

(1) An optical disk capable of reducing crosstalk in a track adjacent to a header section.

(2) An optical disc device capable of reducing crosstalk in a track adjacent to a header section and reproducing header data correctly without being affected by the reduction in crosstalk.

[0007]

In order to solve the above-mentioned problems and achieve the object, an optical disk and an optical disk apparatus according to the present invention are configured as follows.

(1) The present invention is an optical disc in which a header area and a groove area are adjacent to each other, wherein the header area includes embossed prepits indicating header data;
Embossed dummy pits are provided to make the light reflectance of the header area lower than the light reflectance of the mirror-like area.

(2) The present invention is an optical disc in which a header area and a groove area are adjacent to each other, wherein the header area includes an embossed pre-pit indicating header data;
Embossed dummy pits are provided so as to make the light reflectance of the header area lower than the light reflectance of the mirror area within a range not to be lower than the light reflectance of the groove area.

(3) The present invention is an optical disc in which a header area and a groove area are adjacent to each other, wherein the header area includes embossed prepits indicating header data;
An optical disc reproducing apparatus for reproducing the optical disc, comprising: an embossed dummy pit for lowering the light reflectivity of the header area than the light reflectivity of the mirror-shaped area;
There is provided reproducing means for reproducing header data from pre-pits in the header area.

(4) The present invention is an optical disc in which a header area and a groove area are adjacent to each other, wherein the header area includes an embossed pre-pit indicating header data;
An optical disc reproducing device for reproducing the optical disc, comprising: embossed dummy pits for lowering the light reflectivity of the mirror area to a value not lower than the light reflectivity of the header area. However, there is provided reproducing means for reproducing header data from the pre-pits in the header area.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an information recording / reproducing section of an optical disc reproducing apparatus according to an embodiment of the present invention.

<<<< Function of Information Recording / Reproducing Unit >>>><< Basic Function of Information Recording / Reproducing Unit >> The following processing is performed in the information recording / reproducing unit.

1. Recording or rewriting of new information (including erasing of information) is performed at a predetermined position on the information storage medium (optical disk) 201 using a focused spot.

2. Reproduction of already recorded information is performed from a predetermined position on the information storage medium (optical disk) 201 by using a focused spot.

<< Means for Achieving Basic Functions of Information Recording / Reproducing Unit >>
> The information recording / reproducing unit performs the following processing as means for achieving the above basic functions.

1. Trace (follow) a focused spot along a track (not shown) on the information storage medium 201
Let it.

2. Switching of information recording / reproducing / erasing is performed by changing the amount of light of a converging spot irradiated on the information storage medium 201.

3. Convert the externally applied recording signal d into an optimal signal for recording at a high density and a low error rate.

<<<< Structure of Mechanism Section and Operation of Detection Section >>
>>>><Basic Structure of Optical Head 202 and Signal Detection Circuit >>><Signal Detection by Optical Head 202> Optical Head 202
Although basically not shown, it is composed of a semiconductor laser element as a light source, a photodetector and an objective lens.

The laser light emitted from the semiconductor laser element is transmitted to an information storage medium (optical disk) 2 by an objective lens.
The light is converged on 01. Information storage medium (optical disk) 20
The laser light reflected by the light reflecting film or the light reflective recording film is photoelectrically converted by a photodetector.

The detection current obtained by the photodetector is
3 is subjected to current-voltage conversion to become a detection signal. This detection signal is processed by the focus / track error detection circuit 217 or the binarization circuit 212. Generally, a photodetector is divided into a plurality of photodetection areas, and individually detects a change in the amount of light applied to each photodetection area. The focus / track error detection circuit 2
In step 17, the sum / difference is calculated to detect a focus shift and a track shift. Information storage medium (optical disk) 201
A signal on the information storage medium 201 is reproduced by detecting a change in the amount of light reflected from the light reflecting film or the light reflective recording film.

<Method of Detecting Defocus> One of the following methods is often used as a method of optically detecting the amount of defocus.

1. Astigmatism method: an optical element (not shown) for generating astigmatism in a detection optical path of a laser beam reflected by a light reflection film or a light reflection recording film of an information storage medium (optical disk) 201 A method for detecting a change in shape of a laser beam irradiated on a photodetector. The light detection area is divided into four diagonally. A focus / track error detection circuit 2 detects a detection signal obtained from each detection area.
The difference between the diagonal sums is obtained in 17 to obtain a focus error detection signal.

2. Knife edge method: information storage medium 201
A method of arranging a knife edge that asymmetrically shields a part of the laser light reflected by the light source. The light detection area is divided into two parts, and a difference between detection signals obtained from each detection area is obtained to obtain a focus error detection signal.

<Track Shift Detection Method> The information storage medium (optical disc) 201 has a spiral or concentric track, and information is recorded on the track. Information is reproduced or recorded / erased by tracing the focused spot along the track. In order to stably trace the focused spot along the track, it is necessary to optically detect the relative displacement between the track and the focused spot. The following method is generally used as a track shift detection method.

1. DPD (Differential Phase Detecti)
on) method: A change in the intensity distribution of the laser light reflected by the light reflecting film or the light reflecting recording film of the information storage medium (optical disk) 201 on the photodetector is detected. The light detection area is divided into four diagonally. A focus / track error detection circuit 21 detects a detection signal obtained from each detection area.
The track error detection signal is obtained by taking the difference between the diagonal sums in 7.

2. Push-Pull method: a change in the intensity distribution of the laser light reflected by the information storage medium 201 on the photodetector is detected. The light detection area is divided into two parts, and a track error detection signal is obtained by taking the difference between the detection signals obtained from each detection area.

3. Twin-Spot method: A diffraction element or the like is arranged in a light transmission system between the semiconductor laser element and the information storage medium 201 to split light into a plurality of wavefronts,
A change in the reflected light amount of the ± first-order diffracted light irradiated upward is detected.
A light detection area for individually detecting the reflected light amount of the + 1st-order diffracted light and the reflected light amount of the -1st-order diffracted light is arranged separately from the light detection area for detecting the reproduction signal, and a difference between the respective detection signals is calculated to obtain a track error detection signal. Get.

<<<< Object lens actuator structure >>
>>> An objective lens (not shown) for focusing laser light emitted from the semiconductor laser element on the information storage medium 201 is an objective lens actuator driving circuit 218.
Are movable in two axial directions in accordance with the output current of. The moving direction of the objective lens moves in a direction perpendicular to the information storage medium 201 for focus shift correction,
It moves in the radial direction of the information storage medium 201 for track deviation correction.

Although not shown, the mechanism for moving the objective lens is called an objective lens actuator. The following structures are often used as an objective lens actuator structure.

1. Shaft sliding method: A method in which a blade integrated with an objective lens moves along a central axis (shaft), and the blade moves in a direction along the central axis to shift the focus. A method of performing correction and correcting track deviation by rotating the blade with respect to the central axis.

2, 4 wires method: A method in which a blade integrated with an objective lens is connected to a fixed system by 4 wires, and the blade is moved in two axial directions by utilizing elastic deformation of the wires.

Each method has a permanent magnet and a coil,
The blade is moved by passing a current through a coil connected to the blade.

<<<< Rotation control system of information storage medium 201 >>
The information storage medium (optical disk) 20 is placed on a turntable 221 that is rotated by the driving force of the spindle motor 204.
1 is attached.

The number of rotations of the information storage medium 201 is detected based on a reproduction signal obtained from the information storage medium 201. That is, the detection signal (analog signal) of the output of the amplifier 213 is 2
The signal is converted into a digital signal by the value conversion circuit 212, and a fixed period signal (reference clock signal) is generated from the signal by the PLL circuit 211. Information storage medium rotation speed detection circuit 2
At 14, the number of rotations of the information storage medium 201 is detected using this signal, and the value is output.

A correspondence table of the number of revolutions of the information storage medium corresponding to the radial position to be reproduced or recorded / erased on the information storage medium 201 is recorded in the semiconductor memory 219 in advance. Once the playback position or recording / erasing position is determined,
The control unit 220 sets the target rotation speed of the information storage medium 201 with reference to the information of the semiconductor memory 219 and notifies the spindle motor drive circuit 215 of the value.

In the spindle motor drive circuit 215,
This target rotation speed and information storage medium rotation speed detection circuit 214
, And a drive current corresponding to the result is supplied to the spindle motor 204 so that the rotation speed of the spindle motor 204 is controlled to be constant. The output signal of the information storage medium rotation speed detection circuit 214 is a pulse signal having a frequency corresponding to the rotation speed of the information storage medium 201,
At 5, control is performed on both the frequency and pulse phase of this signal.

<< Optical Head Moving Mechanism >> An optical head moving mechanism (feed motor) 203 for moving the optical head 202 in the radial direction of the information storage medium 201 is provided.

In many cases, a rod-shaped guide shaft is used as a guide mechanism for moving the optical head 202, and the optical head 202 is moved using friction between the guide shaft and a bush attached to a part of the optical head 202. I do. In addition, there is a method of using a bearing in which a frictional force is reduced by using a rotary motion.

Although a driving force transmitting method for moving the optical head 202 is not shown, a rotating motor having a pinion (rotating gear) is arranged in a fixed system, and a rack, which is a linear gear meshing with the pinion, is attached to the optical head 202. And converts the rotational motion of the rotary motor into a linear motion of the optical head 202. As another driving force transmission method, a linear motor system in which a permanent magnet is arranged in a fixed system and current flows in a coil arranged in the optical head 202 to move the coil in a linear direction may be used.

In both the rotary motor and the linear motor, basically, a current is supplied to the feed motor to generate a driving force for moving the optical head 202. This drive current is supplied from the feed motor drive circuit 216.

<<<< Functions of Control Circuits >>>><< Condensed Spot Trace Control >>
Output signal (detection signal) of the track error detection circuit 217
A circuit for supplying a drive current to an objective lens actuator (not shown) in the optical head 202 according to the above is the objective lens actuator drive circuit 218. A phase compensating circuit for improving characteristics in accordance with the frequency characteristics of the objective lens actuator is provided internally in order to make the objective lens move quickly in a high frequency range.

Objective lens actuator drive circuit 21
In step 8, the following processing is performed according to the instruction from the control unit 220.

1. ON / OFF processing of focus / track deviation correction operation (focus / track loop).

2. Processing for moving the objective lens in the vertical direction (focus direction) of the information storage medium 201 at low speed (executed when the focus / track loop is OFF).

3. Information storage medium 2 using kick pulse
A process of moving the focused spot to the next track by slightly moving the spot in the radial direction of 01 (the direction crossing the track) is performed.

<< Laser Light Amount Control >><Switching Processing between Reproduction and Recording / Erasing> Switching between reproduction and recording / erasing is performed by changing the light quantity of a focused spot irradiated onto the information storage medium 201.

In general, the following relationship is established for an information storage medium using the phase change method.

[Light amount at the time of recording]> [Light amount at the time of erasing]>
[Light quantity at the time of reproduction] Generally, for an information storage medium using a magneto-optical method,
The following relationship holds:

[Light amount at the time of recording] ≒ [Light amount at the time of erasing]>
[Light Amount During Reproduction] In the case of the magneto-optical method, the information storage medium 2 is used at the time of recording / erasing.
The recording and erasing processes are controlled by changing the polarity of an external magnetic field (not shown) applied to 01.

At the time of reproducing information, a constant amount of light is continuously irradiated on the information storage medium 201.

When recording new information, a pulsed intermittent light amount is added to the light amount at the time of reproduction. When the semiconductor laser element emits a pulse with a large amount of light, the light reflective recording film of the information storage medium 201 locally causes an optical change or a shape change, and a recording mark is formed. Similarly, when overwriting an already recorded area, the semiconductor laser element emits a pulse.

When erasing already recorded information, a constant light amount larger than that at the time of reproduction is continuously irradiated. When information is continuously erased, the irradiation light amount is returned at the time of reproduction in a specific cycle such as a sector unit, and the information is intermittently reproduced in parallel with the erasing process. The track number and address of the track to be intermittently erased are reproduced, and the erasing process is performed while confirming that there is no error in the erased track.

<Laser Emission Control> Although not shown, the optical head 202 has a built-in photodetector for detecting the emission amount of the semiconductor laser element. The semiconductor laser drive circuit 205 calculates the difference between the photodetector output (detection signal of the light emission amount of the semiconductor laser element) and the light emission reference signal given from the recording / reproduction / erase control waveform generation circuit 206.
Based on the result, the driving current to the semiconductor laser is fed back.

<<<< Operations Related to Control System of Mechanism Part >>
>><< Start Control >> When the information storage medium (optical disk) 201 is mounted on the turntable 221 and start control is started, processing is performed according to the following procedure.

1. The target number of revolutions is transmitted from the control unit 220 to the spindle motor drive circuit 215, and a drive current is supplied from the spindle motor drive circuit 215 to the spindle motor 204 to start the rotation of the spindle motor 204.

2. At the same time, a command (execution command) is issued from the control unit 220 to the feed motor drive circuit 216, and a drive current is supplied from the feed motor drive circuit 216 to the optical head drive mechanism (feed motor) 203, and The head 202 moves to the innermost position of the information storage medium 201. It is confirmed that the optical head 202 is located further inward of the information storage medium 201 beyond the area where the information is recorded.

3. When the spindle motor 204 reaches the target number of revolutions, its status (status report) is sent to the control unit 220.

4. The semiconductor laser driving circuit 205 sends the optical head 202 according to the reproduced light amount signal sent from the control section 220 to the recording / reproducing / erasing control waveform generating circuit 206.
An electric current is supplied to the semiconductor laser element inside to start laser emission.

* The optimum irradiation light amount at the time of reproduction differs depending on the type of the information storage medium (optical disk) 201. At the time of startup, it is set to the value with the lowest irradiation light amount.

5. In accordance with a command from the control unit 220, the objective lens (not shown) in the optical head 202 is shifted to the position farthest from the information storage medium 201 so that the objective lens slowly approaches the information storage medium 201. The objective lens actuator drive circuit 218 controls.

6. At the same time, the focus / track error detection circuit 217 monitors the amount of defocus, and outputs a status to the control unit 220 when the objective lens comes near the focused position.

7. Upon receiving the notification, the control unit 220 issues a command to the objective lens actuator drive circuit 218 to turn on the focus loop.

8. The control unit 220 sets the focus loop to O
The optical head 202 is issued a command to the feed motor drive circuit 216 while keeping the information storage medium 201 slowly.
In the direction of the outer peripheral portion of.

9. At the same time, the reproduction signal from the optical head 202 is monitored, and the optical head 202
When the optical head 202 reaches the recording area on the optical disk 1, the movement of the optical head 202 is stopped, and a command to turn on the track loop is issued to the objective lens actuator drive circuit 218.

10. Information storage medium (optical disk) 201
The "optimum light quantity at the time of reproduction" and the "optimum light quantity at the time of recording / erasing" recorded on the inner peripheral portion of the disc are reproduced.
The data is recorded in the semiconductor memory 219 via the memory 20.

11. Further, the control unit 220 sends a signal corresponding to the "optimum light amount at the time of reproduction" to the recording / reproduction / erase control waveform generation circuit 206 to reset the light emission amount of the semiconductor laser element at the time of reproduction.

12. The light emission amount of the semiconductor laser element at the time of recording / erasing is set in accordance with the “optimum light amount at the time of recording / erasing” recorded on the information storage medium 201.

<< Access Control >><Reproduction of Access Destination Information on Information Storage Medium 201> Information on what kind of information is recorded in which location on the information storage medium 201 is information storage. Medium 201
And is generally recorded in the information storage medium 201 as follows.

1. Directory management area: The directory management area is collectively recorded in the inner peripheral area or the outer peripheral area of the information storage medium 201.

2. Navigation Pack: VO based on the data structure of MPEG2 PS (Program Stream)
It is included in a BS (Video Object Set) and records information on where the next video is recorded.

When it is desired to reproduce or record / delete specific information, the information in the above-mentioned area is reproduced first, and the access destination is determined from the obtained information.

<<<< Coarse Access Control >>>> Control Unit 220
Then, the radius position of the access destination is obtained by calculation, and the distance from the current position of the optical head 202 is determined.

Speed curve information that can be reached in the shortest time with respect to the moving distance of the optical head 202 is recorded in the semiconductor memory 219 in advance. The control unit 220 reads the information and controls the movement of the optical head 202 in the following manner according to the speed curve.

After the control unit 220 issues a command to the objective lens actuator drive circuit 218 to turn off the track loop, the feed motor drive circuit 216 is controlled to start the movement of the optical head 202.

When the focused spot crosses a track on the information storage medium 201, a track error detection signal is generated in the focus / track error detection circuit 217. Using this track error detection signal, the relative speed of the focused spot with respect to the information storage medium 201 can be detected.

The feed motor drive circuit 216 calculates the difference between the relative speed of the condensed spot obtained from the focus / track error detection circuit 217 and the target speed information sent one by one from the control unit 220, and uses the result as the optical head. The optical head 202 is moved while applying feedback to the drive current to the drive mechanism (feed motor) 203.

As described in "<< Optical head moving mechanism >>", frictional force always acts between the guide shaft and the bush or bearing. When the optical head 202 is moving at high speed, kinetic friction is applied. However, at the start of movement and immediately before the stop, the moving speed of the optical head 202 is low, and static friction is applied. At this time, since the relative frictional force has increased (especially immediately before the stop), the amplification factor (gain) of the current supplied to the optical head driving mechanism (feed motor) 203 in response to a command from the control unit 220 is increased. .

<<<< Fine Access Control >>>> Optical Head 2
When 02 reaches the target position, the control unit 220 issues a command to the objective lens actuator drive circuit 218 to turn on the track loop.

The focused spot reproduces the address or track number of that portion while tracing along the track on the information storage medium 201.

The current focus spot position is determined from the address or track number, the number of error tracks from the target position is calculated in the control unit 220, and the number of tracks required for moving the focus spot is determined by the objective lens actuator. Notify the drive circuit 218.

Objective lens actuator drive circuit 21
When one set of kick pulses is generated in 8, the objective lens slightly moves in the radial direction of the information storage medium 201, and the focused spot moves to the next track.

Objective lens actuator drive circuit 21
In FIG. 8, the track loop is temporarily turned off, the kick pulse is generated a number of times in accordance with the information from the control unit 220, and then the track loop is turned on again.

After completion of the fine access, the control unit 220 reproduces information (address or track number) of the position where the focused spot is traced, and confirms that the target track is being accessed.

<< Continuous Recording / Reproduction / Erase Control >> A track error detection signal output from the focus / track error detection circuit 217 is input to the feed motor drive circuit 216. The control unit 220 controls the feed motor drive circuit 216 so as not to use the track error detection signal during the “start control” and the “access control” described above.

After confirming that the focused spot has reached the target track by accessing, a part of the track error detection signal is transmitted to the optical head drive mechanism (feed motor) via the motor drive circuit 216 by a command from the control unit 220. ) 203 is supplied as a drive current. This control is continued during the period in which the reproduction or the recording / erasing process is continuously performed.

The center position of the information storage medium 201 is mounted with an eccentricity slightly shifted from the center position of the turntable 221. When a part of the track error detection signal is supplied as a drive current, the optical head 202 is adjusted in accordance with the eccentricity.
The whole moves slightly.

When the reproduction or the recording / erasing process is continuously performed for a long time, the condensed spot position gradually moves in the outer circumferential direction or the inner circumferential direction. When a part of the track error detection signal is supplied as a drive current to the optical head moving mechanism (feed motor) 203, the optical head 202 gradually moves in the outer circumferential direction or the inner circumferential direction accordingly.

In this way, the burden of correcting the track deviation of the objective lens actuator can be reduced, and the track loop can be stabilized.

<< End Control >> When a series of processing is completed and the operation is ended, the processing is performed according to the following procedure.

1. A track loop is sent from the control unit 220 to the objective lens actuator drive circuit 218.
A command is issued to cause an F.

2. The focus loop is set to O from the control unit 220 to the objective lens actuator drive circuit 218.
A command to make FF is issued.

3. The control unit 220 issues a command to the recording / reproducing / erasing control waveform generating circuit 206 to stop the light emission of the semiconductor laser device.

4. Notify the spindle motor drive circuit 215 of 0 as the reference rotation speed.

<<< Flow of Recorded / Reproduced Signal to / from Information Storage Medium >>>><< Signal Format Recorded on Information Storage Medium 201 >> ~ 3
In order to satisfy the requirement, the information recording / reproducing unit (physical block) performs "addition of an error correction function" and "signal conversion (modulation / demodulation of a signal) for recorded information".

1. It is possible to correct a recording information error caused by a defect on the information storage medium 201.

2. The reproduction signal processing circuit is simplified by setting the DC component of the reproduction signal to 0.

3. Information is recorded on the information storage medium 201 as densely as possible.

<< Signal Flow During Recording >><Error Correction Code (ECC) Addition Processing> Information to be recorded in the information storage medium 201 is input to the data input / output interface unit 222 as a recording signal d in the form of a raw signal. You. This recording signal d is used as it is in the semiconductor memory 21.
9 and then ECC encoding circuit 20
In step 8, ECC addition processing is executed as follows.

An embodiment of an ECC adding method using a product code will be described below.

The recording signal d is 1 in the semiconductor memory 219.
One row is arranged sequentially every 72Bytes, and one set of E is composed of 192 rows.
Let it be a CC block. This "row: 172 x column: 192 bytes
s ", the inner code PI of 10 Bytes is calculated for each row of 172 Bytes for the raw signal (recording signal d) in a set of ECC blocks, and is additionally recorded in the semiconductor memory 219. The outer code PO of 16 Bytes is calculated for each column of and the additional code is recorded in the semiconductor memory 219.

As an embodiment of recording on the information storage medium 201, a total of 2366 bytes (2366 = (12 + 1) × (17) of 12 lines including the inner code PI and 1 line for the outer code PO
2 + 10)) is recorded in one sector of the information storage medium in units.

When the addition of the inner code PI and the outer code PO is completed, the ECC encoding circuit 208 reads a signal of 2366 bytes for one sector from the semiconductor memory 219 and transfers it to the modulation circuit 207.

<Signal Modulation> The DC component of the reproduced signal (DS
V: Digital Sum Value) is approached to 0, and in order to record information on the information storage medium 201 at high density, signal modulation which is a conversion of a signal format is performed in the modulation circuit 207.

A conversion table indicating the relationship between the original signal and the modulated signal is provided in the modulation circuit 207 and the demodulation circuit 210. The signal transferred from the ECC encoding circuit 208 is divided into a plurality of bits according to the modulation scheme, and converted into another signal (code) with reference to a conversion table.

For example, 8/16 modulation (R
When the LL (2,10) code is used, there are two types of conversion tables, and a DC component (DSV: Disita
l SumValue) is sequentially switched so that the reference conversion table approaches 0.

<Generation of Recording Waveform> When recording a recording mark on the information storage medium (optical disk) 201, there are generally the following two types of recording methods.

1. Mark length recording method: A method in which "1" comes to the front end position and the rear terminal position of a recording mark.

2. Recording method between marks: A method in which the center position of a recording mark coincides with the position of "1".

When mark length recording is performed, it is necessary to form a long recording mark. In this case, if the recording light amount is continuously irradiated for a certain period, a “raindrop” recording mark having a wide width only at the rear portion is formed due to the heat storage effect of the light reflective recording film of the information storage medium 201. To remove this evil,
When forming a long recording mark, the recording mark is divided into a plurality of recording pulses, or the recording waveform is changed stepwise.

Recording / reproducing / erasing control waveform generating circuit 206
Inside, the above-described recording waveform is created in accordance with the recording signal sent from the modulation circuit 207 and transmitted to the semiconductor laser driving circuit 205.

<< Flow of Signal During Reproduction >><Binarization / PLL Circuit> As described in "<Signal Detection by Optical Head 202>", the light reflection film or light reflection of the information storage medium (optical disk) 201 A signal on the information storage medium 201 is reproduced by detecting a change in the amount of reflected light from the recording layer. The signal obtained by the amplifier 213 has an analog waveform. The binarization circuit 212 converts the signal into a binary digital signal consisting of “1” and “0” using a comparator.

A reference signal for information reproduction is extracted from the reproduced signal obtained by the PLL circuit 211. PL
The L circuit 211 has a built-in variable frequency oscillator. The frequency and phase between the pulse signal (reference clock) output from the oscillator and the output signal of the binarization circuit 212 are compared, and the result is fed back to the oscillator output.

<Demodulation of Signal> A conversion table indicating the relationship between the modulated signal and the demodulated signal is stored in the demodulation circuit 210.
Have inside. The signal is returned to the original signal while referring to the conversion table in accordance with the reference clock obtained by the PLL circuit 211. The returned (demodulated) signal is recorded in the semiconductor memory 219.

<Error Correction Processing> Semiconductor Memory 219
The error correction circuit 209 detects an error portion of the signal stored in the error code using the inner code PI and the outer code PO, and sets a pointer flag of the error portion.

Thereafter, while reading the signal from the semiconductor memory 219, the signal at the error location is sequentially corrected in accordance with the error pointer flag, the inner code PI and the outer code PO are removed, and the signal is transferred to the data input / output interface unit 222.

The signal sent from the ECC encoding circuit 208 is transmitted to the data input / output
2 as a reproduction signal c.

The description of the information recording / reproducing section has been completed.

FIG. 2 is an enlarged view of a header portion of an optical disc according to an embodiment of the present invention and a groove track adjacent to the header portion.

As shown in FIG. 2, the optical disk has a transparent substrate 7. On the transparent substrate 7, an optical recording layer 8 is provided.
Is provided. Further, in this optical disc, a pre-groove (groove track) 1 is arranged adjacent to the header portion H. The header section H is provided with a pre-pit section 2 where the amount of reflected light decreases on the photodetector, and a dummy pit section 3 where the amount of reflected light increases on the photodetector. The header data is recorded by the pre-pit section 2. The dummy pit section 3 is for suppressing crosstalk, and does not particularly record data.

FIG. 3 is a diagram for explaining a difference in appearance by an optical microscope when the depth is the same and the groove width is changed.

When the width of the pre-groove is the narrowest, FIG.
As shown in FIG. 3A, the shadow of the pre-groove is thin, and if the width of the pre-groove is gradually increased, the line of the pre-groove gradually becomes dark as shown in FIG. 3B. When the pre-groove has a specific groove width, the pre-groove line looks darkest as shown in FIG. 3 (c), and as the width is further increased, the center becomes bright as shown in FIG. 3 (e), the slope (wall surface) looks dark, and the reflectivity at the center of the pre-groove increases.

As shown in FIG. 3, by changing the width of the pre-groove while keeping the same depth, the light reflectivity changes and a pre-pit can be formed. As shown in FIG. 2, the light reflectance increases when the width is large like the dummy pit portion 3, and decreases when the width is small like the pre-pit portion 2.

By arranging the dummy pit portion 3 in a portion which has conventionally been a mirror-like region, that is, in a header portion where no pre-pit is formed, the light reflectance is suppressed more than in the mirror-like region ( Reduction). As a result, the amount of crosstalk exerted on adjacent pregrooves can be reduced. More specifically, the dummy pit portion 3 according to the present invention is used to make the light reflectance of the header portion H lower than the light reflectance of the mirror-like region within a range not to be lower than the light reflectance of the pregroove. Things.

The information recording / reproducing section shown in FIG. 1 can reproduce the header data based only on the pre-pit section 2 of the header section H of the optical disk shown in FIG. That is, header data can be obtained by reproducing only the pre-pit portion 2 without being affected by the dummy pit portion 3. Since the size of the pre-pit 2 and the size of the dummy pit 3 are completely different (the size of the dummy pit 3 is much larger than the size of the pre-pit 2), only the signal obtained from the pre-pit 2 can be detected and reproduced.

Note that the present invention is not limited to the above-described embodiment, and can be variously modified in an implementation stage without departing from the scope of the invention. In addition, the embodiments may be implemented in appropriate combinations as much as possible, in which case the combined effects can be obtained. Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriate combinations of a plurality of disclosed constituent elements. For example, even if some components are deleted from all the components shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved and the effects described in the column of the effect of the invention can be solved. If you get
A configuration from which this configuration requirement is deleted can be extracted as an invention.

[0129]

According to the present invention, the following optical disk and optical disk reproducing apparatus can be provided.

(1) An optical disk capable of reducing crosstalk in a track adjacent to a header section.

(2) An optical disk device capable of reducing crosstalk in a track adjacent to the header section and capable of correctly reproducing header data without being affected by the reduction in crosstalk.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an information recording / reproducing unit of an optical disc reproducing apparatus according to an example of the present invention.

FIG. 2 is an enlarged view of a header portion of an optical disc according to an embodiment of the present invention and a groove track adjacent to the header portion.

FIG. 3 is a diagram for explaining a difference in appearance by an optical microscope when a groove width is changed at the same depth.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pre-groove 2 ... Pre-pit part 3 ... Dummy pit part H ... Header part

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Kazuo Watanabe, 1st Toshiba R & D Center, Komukai-ku, Kawasaki-shi, Kanagawa Prefecture (72) Inventor Yutaka Okamoto 70 Yanagicho, Yuki-ku, Kawasaki-shi, Kanagawa In the Toshiba Yanagicho Plant (72) Inventor Nobun Chosaku 70, Yanagicho, Saiwai-ku, Kawasaki City, Kanagawa Prefecture In the Toshiba Yanagicho Plant (72) Inventor Hiroshi Kashiwara 70, Yanagicho, Kochi-ku, Kawasaki City, Kanagawa Prefecture In-house F-term (reference) 5D029 WA31 WB11 5D090 AA01 BB04 CC12 DD01 EE13 FF04 FF14 FF45

Claims (4)

[Claims] 1. An optical disk having a header area and a groove area adjacent to each other, wherein the header area has embossed prepits indicating header data, and the light reflectance of the header area is the light reflectance of a mirror-shaped area. An optical disk comprising: embossed dummy pits for lowering the height; 2. An optical disk in which a header area and a groove area are adjacent to each other, wherein the header area has an embossed pre-pit indicating header data, and the light reflectance of the header area is calculated from the light reflectance of the groove area. An optical disc, comprising: embossed dummy pits for lowering the light reflectance of a mirror area within a range not to fall below. 3. An optical disk in which a header area and a groove area are adjacent to each other, wherein the header area has embossed prepits indicating header data, and the light reflectance of the header area is the light reflectance of a mirror-shaped area. An optical disk reproducing apparatus comprising: an embossed dummy pit for lowering the optical disk; and an optical disk reproducing apparatus for reproducing the optical disk, comprising: reproducing means for reproducing header data from prepits in the header area. 4. An optical disk in which a header area and a groove area are adjacent to each other, wherein the header area is formed by embossed prepits indicating header data, and the light reflectance of the header area is calculated from the light reflectance of the groove area. An emboss-shaped dummy pit for lowering the light reflectance of the mirror area within a range not to fall below, wherein an optical disc reproducing apparatus for reproducing the optical disc reproduces header data from pre-pits in the header area. An optical disk reproducing apparatus comprising: