JP4077290B2 - Optical disc cutting apparatus and optical disc manufacturing method - Google Patents

Description

BACKGROUND OF THE INVENTION
[0001]
The present invention relates to an optical disc cutting apparatus for producing a high-density optical disc substrate, and an optical disc manufacturing method.
[0002]
[Prior art]
In recent years, optical discs have been actively applied to AV (audio / visual). For example, in DVD (Digital Versatile Disc) mainly for movie content, write-once and rewritable formats such as DVD-R, DVD-RAM, and DVD-RW have been developed and are becoming popular as next-generation recorders for VTRs. .
[0003]
With the spread of BS digital broadcasting and broadband communication in the future, the appearance of large-capacity optical disc formats capable of recording compressed images with higher image quality, and smaller, portable, high-network compatibility optical disc formats with the same capacity are expected. .
[0004]
In order to realize a high-density optical disc as described above, it is essential to develop a high-definition, high-precision, high-density optical disc substrate along with the development of materials and formats capable of high-density recording. Some cutting methods hold the key to higher density. Specifically, it is important how to make narrow pitch tracks and fine prepits on the master with high accuracy.
[0005]
The point is miniaturization of the light spot and high-precision alignment of the light spot. The former is realized by shortening the wavelength of the laser light source and increasing the NA of the objective lens, and the latter is mainly the high precision of the objective lens feeding mechanism. For optical discs that require lowering the vibration of the cutting device and wobble, this can be realized by increasing the accuracy of deflection.
[0006]
In addition, a technique has been proposed in which laser light is deflected by an acousto-optic light deflector to improve the track pitch of the master disk (for example, see Patent Document 1 below). Furthermore, in a cutting device using an electron beam, a technique for cutting a high-precision and high-density pit pattern by deflecting the electron beam according to the difference between the reference value and the detected value from the master is proposed. (For example, refer to Patent Document 2 below.)
[0007]
In the following description, an optical disc cutting method will be described in the form of an optical disc cutting apparatus that specifically realizes the method. FIG. 9 shows an example of a conventional optical disc cutting apparatus, and shows only basic components. A laser light source 1 emits a parallel light beam Lc having a predetermined light amount. Usually, an Ar gas laser is used, and a light source in the visible light range of the order of 500 nm has been used. However, the wavelength has been shortened in response to the need for higher density, and recently, the wavelength has been in the range of 200 nm to 300 nm. A light source with an ultraviolet spectrum is used.
[0008]
Reference numeral 2 denotes an EO modulator (EOM: Electro-Optic Modulator), which can change the amount of light in an analog manner according to an applied voltage. Usually, the applied voltage is selected at the binary level of light on and off, and digitally modulated to create a pre-pit of the optical disc, or to keep on and create a groove. Reference numeral 3 denotes an EO deflector (EOD: Electro-Optic Deflector) which deflects a light beam traveling angle by an applied voltage and displaces a cutting light spot formed on the master 100 by an objective lens 5 described later.
[0009]
As a material for the EO modulator 2 and the EO deflector 3, a crystal material having a so-called Pockels effect in which the refractive index anisotropy changes when a high voltage is applied is used. In order to obtain an effective deflection amount and modulation amount for cutting, it is necessary to apply a high voltage of, for example, ± 200 V between the two electrodes provided in the EO element. Also, an acousto-optic element called AO (Acoustic-Optic) may be used instead of EO.
[0010]
The light beam Lc that has passed through the EO modulator 2 and the EO deflector 3 is reflected by the mirror 4, collected by the high NA objective lens 5, and the optical spot Sc on the optical disc master 100 controlled to rotate by the motor 6. Form. The mirror 4 and the objective lens 5 are constituted by an optical head for cutting held by a mechanism (not shown), and the optical head is continuously adapted to the track pitch according to the rotation of the motor 6 by a transfer system (not shown). Sent precisely. For cutting, a CAV method with a constant rotation speed or a CLV method with a constant linear velocity is generally used.
[0011]
A master on which spiral tracks are formed is created by precisely and continuously transferring one track pitch per master revolution. In the case of the CAV method, the light amount of the laser light source 1 is controlled to an appropriate value by the cutting radius. The optical disk produced in the transport direction shown in FIG. 9 is cut by the CAV method with the lead-in as the inner periphery.
[0012]
101 is an optical disc formatter, which controls the EO modulator 2 and the EO deflector 3 while controlling the light quantity of the laser light source 1 and the rotational speed of the motor 6 to create pre-pits and grooves on the master disk. Create a format. The output signal Vem of the formatter 101 is sent to the EOM driver 102. The EOM driver 102 directly amplifies Vem or switches a high voltage power supply and sends it to the EO modulator 2 as an EOM drive signal Vemd to modulate the light quantity of the light beam Lc. Here, Vem is controlled to “H” and “L” to turn on / off the light beam Lc.
[0013]
Further, the deflection signal Ved of the formatter 101 displaces the position of the light spot on the master in the radial direction. That is, control is performed as “inner circumference displacement, neutral, outer circumference displacement” according to the polarity “positive, zero, negative” of the deflection signal Ved, respectively. The EOD driver 103 receives the deflection signal Ved and directly amplifies it (hereinafter referred to as an analog deflection method) or switches a high voltage power source (hereinafter referred to as a digital deflection method) as an EOD drive signal Vedd. It is sent to the EO deflector 3 to control the deflection amount of the light beam Lc.
[0014]
In practice, when a groove is wobbled and a clock or address is superimposed on the groove, the wobble requires continuity with a small displacement of several tens of nanometers on the master disk of the optical disk. The applied voltage is about several tens of volts. Since it is small, an analog deflection method using an amplifier is adopted, and a digital deflection method is adopted in order to realize a large displacement amount of several hundreds of nanometers like a sample servo method. In the latter case, in order to simplify the circuit configuration, the deflection signal Ved is composed of two control signals indicating the inner circumference deflection or the outer circumference deflection. For example, switching is performed so that the positive electrode and the negative electrode of the power supply of about +200 V are removed. By applying it to the EO deflector 3, an EOD drive signal Vedd of ± 200V is equivalently obtained.
[0015]
The light beam Li indicated by a broken line in FIG. 9 is a state when the light signal Lc is deflected by the EO deflector 3 with the deflection signal Ved being positive. As a result, the light spot is displaced from the Sc position to the inner peripheral side and displaced to Si. FIG. 10 shows two specific examples of the optical disc that can be produced by the optical disc cutting apparatus as described above, and the operation of one example will be described with reference to FIG. 10A shows an example of a grooved sample servo type optical disk substrate, and FIG. 10B shows an example of a land / groove continuous groove type optical disk substrate. In both cases, the upper side of the figure is the inner circumference and the lower side is the outer circumference, and the recording / reproducing light spot is scanned from left to right.
[0016]
The optical disk substrate in FIG. 10A is a substrate suitable for a DWDD (Domain Wall Displacement Detection) method (domain wall displacement detection method), which is a kind of super-resolution method of a magneto-optical disk. In the DWDD type optical disc, it is necessary to weaken the magnetic coupling between adjacent recording tracks (reduction of magnetic anisotropy). For this reason, when a DWDD optical disc is manufactured, it is necessary to perform initialization (hereinafter referred to as annealing) to weaken magnetic coupling between adjacent recording tracks before recording an information signal. Groove is used when annealing.
[0017]
The structural unit of this optical disc is a segment as shown. A segment is composed of a servo area and a data area. One track is composed of a plurality of segments of 1000 or more. In the servo area, a first wobble pit 11, a second wobble pit 12, and an address pit 13 for sample servo are arranged. The tracking of the sample servo system is controlled so that the recording / reproducing light spot scans between the first wobble pit 11 and the second wobble pit 12.
[0018]
The address pits 13 are distributed in a plurality of segments, and the presence / absence of pits for each segment is collected and subjected to error correction or the like to be reproduced as a track address. The information tracks in the data area are composed of grooves 14, and lands 15 are formed between the information tracks. In this case, since the track pitch is as small as 0.6 μm or less, it is difficult to form a wobble pit independently for each track, and the wobble pit is shared by adjacent tracks. That is, there are basically two types of tracks, Ta and Tb as shown.
[0019]
When the track Ta is an even track 2m, the recording / reproducing light spot 16 is scanned so that the first wobble pit 11 is seen on the left and the second wobble pit 12 is seen on the right. The track Tb is an odd track 2m + 1, and the recording / reproducing light spot is scanned so that the first wobble pit 11 is seen on the right and the second wobble pit 12 is seen on the left, contrary to the track Ta. The track address is devised in the segment so that the track address can be reproduced independently by the track Ta and the track Tb (this is different from the gist of the present invention and will not be described in detail).
[0020]
In the annealing described above, the magnetic coupling is weakened by scanning the land 15 portion with a high power using an annealing light spot having a spot diameter smaller than that of the recording / reproducing light spot 16. The reason why the light spot for annealing is made small is that the annealing width is narrowed even at a narrow track pitch, and the track width remaining in the groove 14 where the DWDD operation is possible is widened to ensure the recording / reproducing performance. Therefore, for example, a laser with a wavelength of 405 nm and an objective lens with a NA of 0.75 to 0.85 are used as the light source for the annealing light spot, and the recording / reproducing light spot has a wavelength of about 650 nm and about half the diameter of NA. Focus on the spot.
[0021]
For tracking during annealing, a continuous servo system using a push-pull signal from the land 15 is used. Even if you use the wobble pit for recording and playback, you can only track on the groove, not on the land. If the dedicated wobble pits for annealing are arranged, the redundancy of the servo area is increased and the densification is hindered. Therefore, it is preferable to track with the lands 15 as described above. Since the land 15 is a continuous groove, the tracking accuracy is improved and it is also effective for geometrically and thermally separating the grooves, so that the groove 14 is effective for an optical disk even in the sample servo system.
[0022]
The optical disk substrate in FIG. 10B is an example of a land / groove continuous groove type optical disk substrate, and corresponds to a DVD-RAM format which is a rewritable phase change optical disk. The structural unit of this optical disc is a sector, and a track is composed of a plurality of sectors. A sector is composed of an address area and a data area.
[0023]
First, the data area is composed of tracks made up of grooves 23 or lands 24, and each time the optical disk is rotated, a groove track Tg made up of grooves 23 (2n: even tracks) and a land track Tl made up of lands 24 (2n + 1: The spiral configuration is such that the odd tracks are alternately scanned.
[0024]
The address area is arranged by offsetting an address called CAPA (Complementary Allocated Pit Address) by half of the track pitch. Reference numeral 21 denotes an LG common address portion that is used in common with the land track Tl on the inner peripheral side as viewed from the specific groove track Tg, and 22 is a GL common address portion that is used in common with the land track Tl on the outer peripheral side as viewed from the specific groove track Tg. Each of them is composed of a pre-pit group indicating address information.
[0025]
Although not shown in the figure, the groove 23 is superimposed with a clock based on wobble having an amplitude one digit or more smaller than the track pitch. In order to realize this, a deflector different from the EO deflector 3 is inserted into the light beam Lc of FIG. 9 and is deflected by the above-described analog deflection method using a clock superimposed signal separately output from the formatter 101. To do.
[0026]
FIG. 11 is a diagram showing an operation when cutting the optical disc of FIG. When this optical disk is cut, the above-described digital deflection method is adopted for the deflection of the EO deflector 3 (the EOD driver 103 is a switching type). FIG. 11A shows a timing chart of the control signal of the cutting device. The timing chart shows (a1) inner periphery deflection signal Vedi, (a2) outer periphery deflection signal Vedo, (a3) EOD drive signal Vedd, and (a4) EOM drive signal Vemd in order from the top.
[0027]
FIG. 11B shows the locus of the production target optical disc master and the cutting light spot. In order from the top, (b1) track Ta, (b2) track Tb, and (b3) Ta track have been created. Since the deflection is performed on the Ta track as shown in the locus in the figure, the first wobble pit 11 and the second wobble pit 12 are not created on the track Tb, and only the address pit 13 is created as necessary. (B3) shows the track Ta just created by the cutting light spot 31, and the prepits and grooves are hatched.
[0028]
In the creation of the track Ta shown in (b3), from the time t6 when the groove 14 is created until the next t1, the EO modulator 2 emits the cutting light spot 31 (increases the light amount), and the EO deflector. 3 cuts continuously without deflection. The servo area is formed between time t1 and time t6. The EOM drive signal Vemd emits light when the first wobble pit 11, the second wobble pit 12, and the address pit 13 are formed in the section.
[0029]
In addition, the EOD drive signal Vedd outputs a deflection voltage in a direction in which the first wobble pit 11 is displaced to the inner circumference side by setting the inner circumference deflection signal Vedi to “H” during the period t2 to t3, and t4 to t5. When the outer periphery deflection signal Vedo is set to “H” in the section of (2), the deflection voltage is output in the direction of displacing the second wobble pit 12 toward the outer periphery, and the deflection voltage is 0 so that the displacement becomes zero at other times. Is output as
[0030]
As a result, the cutting light spot 31 is scanned on the master 100 along a locus like an arrow, and prepits and grooves are formed that are hatched in combination with the light emission timing. Note that the actual ON / OFF timing of the EO drive signal Vemd is adjusted so that the master 100 is accurately placed at the position shown in FIG.
[0031]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-261245
[Patent Document 2]
Japanese Patent Laid-Open No. 11-288531
[0032]
[Problems to be solved by the invention]
However, the optical disc cutting apparatus as described above has the following problems. That is,
[0033]
(Problem 1) When the EO deflector is changed stepwise by a digital deflection method (hereinafter referred to as step deflection), unnecessary deflection (fluctuation) that appears as relaxation oscillation of the EO crystal material occurs. First, this phenomenon was found by measuring the tracking error signal of the optical disc as shown in FIGS. 10A and 10B and observing the groove with an electron microscope. Next, a deflection amount detecting means capable of observing the deflection amount in the optical path of the optical disc cutting apparatus was prepared and observed. As a result, it was found that this unnecessary deflection is, for example, noise of a fixed pattern from 500 kHz to 700 KHz, and is a signal that attenuates and disappears in about 10 μs after step deflection. Unnecessary deflection occurs at the beginning of the segment shown at time t7 in FIG.
[0034]
The deflection amount is relatively large as 10 to 20 nmpp on the master. Suppose that the track pitch is 0.50 μm (500 nm), a relatively wide groove having a width of 350 nm (bottom width) and a groove depth of 30 nm is formed. When the inclination angle of the side wall of the groove is 30 degrees, the occupying width of the inclined portion is 30 nm × √3 × 2 = 104 nm. As a result, the width of the upper side of the land formed between the grooves is at most 46 nm (= 500−350−104), and the deflection amount 20 nmpp is a value that cannot be ignored. If the width of the upper side is not maintained to some extent, the above-described annealing cannot be performed normally, which is a serious problem.
[0035]
Regarding cutting, in addition to this, irregularities in the transfer of the optical head for cutting, fluctuations in cutting power, irregularities in sensitivity of the photoresist, and irregularities in development are considered to be the fluctuation factors of the upper side, and the margin assigned to them is greatly reduced. Become. Naturally, since it is important to secure the land width in the subsequent molding process, it is necessary to suppress the fluctuation width of the upper side of the land as much as possible, and the unnecessary deflection observed here must be suppressed.
[0036]
In addition, if there is actually unnecessary deflection, the groove that should be formed straightly fluctuates, resulting in disturbance of the original signal detection (eg, envelope fluctuation) and disturbance of the tracking error signal (TE), and signal processing and servo. Reduce performance. Further, since the groove itself fluctuates, the stress applied to the recording film may be changed, or the heat distribution during recording / playback may be affected, thereby reducing the so-called off-track margin during recording / playback.
[0037]
In particular, since the segment or sector head is an important place to input a synchronization signal, it is necessary to maintain high recording / reproducing reliability of the portion. In this sense, suppression of unnecessary deflection is essential.
[0038]
(Problem 2) Further, when observed with the deflection amount detecting means, two types of unnecessary deflections other than those described in (Problem 1) were also observed. One is an unnecessary deflection component of a slow fluctuation of 1 Hz or less, which is considered to be caused by the fluctuation of air existing in the light beam path of the cutting device. The other is a deflection component of fluctuation of about 100 Hz to 1 kHz, which is considered to be caused by mechanical vibration of each optical component of the cutting apparatus.
[0039]
The former generates a large displacement exceeding 100 nm due to the displacement on the master, which does nothing, but it can be considerably reduced to about 1/10 by covering the entire cutting device with a cover and suppressing the flow of air, but within the cutting device The heat generated by the laser light source remains, and the air flow cannot be completely reduced to zero.
[0040]
Further, as a countermeasure, it is conceivable to reduce the size of the cutting device and shorten the optical path itself. However, this is not a measure for completely suppressing the entire fluctuation due to the physical dimension limitation of each optical element constituting the cutting device. This fluctuation of 1 Hz or less does not directly cause unevenness of the track pitch due to the relationship with the rotational speed of the master, but causes the absolute position of the track to be shaken. The latter fluctuation amount of 100 Hz to 1 kHz is the level described in (Problem 1), and this is a band in which fluctuation is generated within one rotation of the master, and this causes unevenness of the track pitch.
[0041]
These two types of fluctuations are also observed in the tangential direction as well as in the radial direction of the master. The fluctuation in the tangential direction causes jitter at the pre-pit and groove start / end. The above fluctuations must be sufficiently suppressed in order to obtain a high-precision optical disc master.
[0042]
(Problem 3) In the above (Problem 1) and (Problem 2), it has been explained that the light beam used for cutting is subjected to unnecessary deflection and is problematic. In addition, it was also found that an unnecessary light amount change (light amount fluctuation) of the light beam almost synchronized with the deflection of (Problem 1) and (Problem 2) was observed.
[0043]
Although the laser light source itself is appropriately subjected to optical power servo, it is considered that the fluctuation of the polarization component of the light beam due to the characteristics of the EO modulator, the EO deflector, the optical components, and the optical path thereafter. Since the change in the amount of light during cutting directly changes the size of the prepit and the groove width, it is necessary to suppress such a change in the amount of light.
[0044]
In order to solve the above-described problems, the present invention provides an optical disc cutting apparatus capable of creating a high-definition and high-precision optical disc master by suppressing unnecessary deflection components and unnecessary light quantity change components generated in an optical disc cutting apparatus. And it aims at providing the manufacturing method of an optical disk.
[0045]
[Means for Solving the Problems]
In order to achieve the above object, a first optical disc cutting apparatus according to the present invention includes a light modulation means for controlling the light amount of a light beam emitted from a laser light source, and a deflection amount of the light beam in a radial direction on the optical disc master. A light beam control means including at least one of the light deflection means to be controlled;
[0046]
Deflection error detection means for detecting a deflection error in the radial direction included in the light beam controlled by the light beam control means;
A second light deflector disposed between the light beam controller and the deflection error detector and deflecting the light beam in the radial direction;
Feedback means for feeding back a feedback signal using the deflection error in the radial direction to the second optical deflection means is provided.
[0047]
The optical disc cutting apparatus according to the second aspect of the present invention includes at least one of a light modulation unit that controls the light amount of a light beam emitted from a laser light source, and a light deflection unit that controls a deflection amount of the light beam in a radial direction on an optical disc master. A light beam control means including any one of the following:
Deflection error detection means for detecting a deflection error in the radial direction included in the light beam controlled by the light beam control means;
Feedback means using the radial deflection error is fed back to the optical deflection means, and feedback means for superimposing the feedback amount on the control amount of the optical deflection means is provided.
[0048]
The third optical disc cutting apparatus of the present invention comprises a light beam control means including a light deflection means for controlling the deflection amount of the light beam emitted from the laser light source in the radial direction on the optical disc master,
Storage means for storing a deflection error in the radial direction measured in advance when the light beam is deflected by the light deflection means;
Second light deflection means for controlling the deflection amount of the light beam from the light deflection means;
When cutting the optical disc master, a feed forward signal using the radial deflection error stored in the storage means is input to the second light deflection means in accordance with the deflection timing of the light beam control means. And feed forward means.
[0049]
The fourth optical disc cutting apparatus of the present invention comprises a light beam control means including a light deflection means for controlling the deflection amount of the light beam emitted from the laser light source in the radial direction on the master optical disc,
Storage means for storing a deflection error in the radial direction measured in advance when the light beam is deflected by the light deflection means;
When the optical disk master is cut, a feed forward signal that uses the radial deflection error stored in the storage means in accordance with the deflection timing of the light beam control means is input to the optical deflection means. And a word means.
[0050]
Next, according to the first optical disk manufacturing method of the present invention, in the cutting process of the optical disk master, light modulation means for controlling the amount of light beam emitted from the laser light source, and the deflection amount of the light beam on the optical disk master. A light beam control means including at least one of light deflection means for controlling in the radial direction, and a method of manufacturing an optical disc for controlling the light beam,
A step of detecting a deflection error in the radial direction included in the light beam controlled by the light beam control means by a deflection error detection means;
Deflecting the light beam in the radial direction with a second light deflecting means placed between the light beam controlling means and the deflection error detecting means;
And a step of feeding back a feedback signal using the deflection error in the radial direction to the second optical deflection unit.
[0051]
The second optical disk manufacturing method of the present invention comprises a light modulating means for controlling the light quantity of a light beam emitted from a laser light source in a cutting process of the optical disk master, and a deflection amount of the light beam in a radial direction on the optical disk master. An optical disk manufacturing method for controlling the light beam by a light beam control means including at least one of the light deflection means to be controlled,
A step of detecting a deflection error in the radial direction included in the light beam controlled by the light beam control means by a deflection error detection means;
The feedback means includes a step of feeding back a feedback signal using the deflection error in the radial direction to the optical deflection means, and superimposing the feedback amount on a control amount of the optical deflection means.
[0052]
The third optical disk manufacturing method of the present invention is an optical disk manufacturing method in which, in the cutting process of the optical disk master, the light beam emitted from the laser light source is controlled to be deflected in the radial direction on the optical disk master by the light deflecting means. And
Before the cutting step of the optical disc master, comprising a step of measuring in advance a deflection error due to the control of deflecting in the radial direction and storing this in a storage means,
In the cutting process of the optical disc master,
A feed forward signal using the deflection error stored in the storage means is input to the second light deflection means for controlling the deflection amount of the light beam from the light deflection means in accordance with the deflection timing of the light beam. Including the step of:
[0053]
The fourth optical disk manufacturing method of the present invention is an optical disk manufacturing method in which, in the cutting process of the optical disk master, the light beam emitted from the laser light source is controlled to be deflected in the radial direction on the optical disk master by the light deflecting means. The
Before the cutting step of the optical disc master, comprising a step of measuring in advance a deflection error due to the control of deflecting in the radial direction and storing this in a storage means,
In the cutting process of the optical disc master,
The method further includes a step of inputting a feed forward signal using the deflection error in accordance with the deflection timing of the light beam.
[0054]
DETAILED DESCRIPTION OF THE INVENTION
According to the first and second optical disc cutting apparatuses of the present invention, since an unnecessary deflection amount in the optical path of the optical disc cutting apparatus can be detected and suppressed, the light spot on the master disc of the optical disc is positioned at a desired position. Optical discs with prepits and grooves with little fluctuation, track, pitch, and unevenness can be created. According to the second optical disc cutting apparatus, an increase in the number of light deflecting means to be added for suppressing the amount of light deflection can be minimized.
[0055]
According to the third and fourth optical disc cutting apparatuses of the present invention, since the deflection error in the radial direction when the light beam is deflected by the light deflecting means is measured and stored in advance, it is difficult for the servo means to suppress it. It is possible to easily suppress disturbance of the amount of light deflection inherent in the light deflection means that occurs during light deflection. According to the fourth optical disc cutting apparatus, an increase in the number of light deflecting means to be added for suppressing the amount of light deflection can be minimized.
[0056]
According to the first and second optical disc manufacturing methods of the present invention, since an unnecessary deflection amount in the optical disc cutting process can be detected and suppressed, the light spot on the master disc of the optical disc is positioned at a desired position, and fluctuations and Optical discs with pre-pits and grooves with little track, pitch and unevenness can be created. According to the second method for manufacturing an optical disk, an increase in the number of light deflecting means to be added for suppressing the amount of light deflection can be minimized.
[0057]
According to the third and fourth optical disc manufacturing methods of the present invention, the step of measuring in advance the deflection error due to the control of deflecting in the radial direction and storing it in the storage means before the optical disc master cutting step is provided. Therefore, it is possible to easily suppress the disturbance of the light deflection amount inherent to the light deflection means that occurs during the light deflection that is difficult to be suppressed by the servo means. According to the fourth method for manufacturing an optical disk, an increase in the number of light deflecting means to be added for suppressing the amount of light deflection can be minimized.
[0058]
In the first optical disk cutting apparatus of the present invention, a third optical disk is placed between the light beam control means and the deflection error detection means, and deflects the light beam in a tangential direction on the optical disk master. Further comprising light deflecting means,
The deflection error detection means further detects the deflection error in the tangential direction of the light beam controlled by the light beam control means independently of the deflection error in the radial direction,
It is preferable that the feedback unit further feeds back a feedback signal using a deflection error in the tangential direction to the third optical deflection unit. According to this configuration, fluctuation in the tangential direction in addition to the radial direction can be suppressed, and an unnecessary amount of light deflection can be suppressed two-dimensionally.
[0059]
The light beam control means includes the light modulation means,
The deflection error detection means can further detect an intensity error of the light amount of the light beam controlled by the light beam control means,
The feedback means preferably further feeds back a feedback signal using the intensity error to the optical modulation means. According to this configuration, the amount of unnecessary light deflection can be suppressed, and the intensity of the light spot at the time of cutting can be suppressed to a desired value, so that it is possible to provide a good optical disc with little variation in pit dimensions and track pitch. it can.
[0060]
Further, the light beam control means further includes a light modulation correction means for controlling the light amount of the light beam controlled by the light beam control means,
The deflection error detection means can further detect an intensity error of the light amount of the light beam controlled by the light beam control means,
The feedback means preferably further feeds back a feedback signal using the intensity error to the light modulation correction means. Even in this configuration, since the intensity of the light spot at the time of cutting can be suppressed to a desired value, it is possible to provide a good optical disk with little variation in pit dimensions and track pitch.
[0061]
In the third optical disc cutting apparatus, the second optical deflecting unit has the same deflection direction as that of the optical deflecting unit, and the feedforward signal reverses the polarity of the deflection error in the radial direction. It is preferable that the signal be a signal.
[0062]
A deflection error detecting means for detecting a second deflection error in the radial direction included in the light beam from the second light deflecting means;
It is preferable that the apparatus further includes a feedback unit that feeds back a feedback signal using the second deflection error in the radial direction to the second optical deflection unit. According to this configuration, an unnecessary deflection amount can be suppressed more reliably.
[0063]
And a third light deflecting unit disposed between the light beam control unit and the deflection error detecting unit and deflecting the light beam in a tangential direction on the optical disc master,
The deflection error detection means further detects the deflection error in the tangential direction of the light beam controlled by the light beam control means independently of the deflection error in the radial direction,
It is preferable that the feedback unit further feeds back a feedback signal using a deflection error in the tangential direction to the third optical deflection unit. According to this configuration, fluctuation in the tangential direction in addition to the radial direction can be suppressed, and an unnecessary amount of light deflection can be suppressed two-dimensionally.
[0064]
In addition, it further comprises a light modulation means for controlling the light amount of the light beam controlled by the light beam control means,
The deflection error detection means can further detect an intensity error of the light amount of the light beam controlled by the light beam control means,
The feedback means preferably further feeds back a feedback signal using the intensity error to the optical modulation means. According to this configuration, the amount of unnecessary light deflection can be suppressed, and the intensity of the light spot at the time of cutting can be suppressed to a desired value, so that it is possible to provide a good optical disc with little variation in pit dimensions and track pitch. it can.
[0065]
In the fourth optical disc cutting apparatus, deflection error detection means for detecting a second deflection error in the radial direction included in the light beam from the light deflection means,
It is preferable that the apparatus further includes a feedback unit that feeds back a feedback signal using the second deflection error in the radial direction to the optical deflection unit and superimposes the feedback amount on a control amount of the optical deflection unit. According to this configuration, an unnecessary deflection amount can be suppressed more reliably.
[0066]
In the first optical disk manufacturing method, a third optical disk is disposed between the light beam control means and the deflection error detection means, and deflects the light beam in a tangential direction on the optical disk master. Further comprising light deflecting means,
In the step of detecting the deflection error, the deflection error detection means further detects the deflection error in the tangential direction of the light beam controlled by the light beam control means independently of the deflection error in the radial direction. ,
In the feedback step, it is preferable that the feedback unit further feeds back a feedback signal using a deflection error in the tangential direction to the third optical deflection unit. According to this configuration, fluctuation in the tangential direction in addition to the radial direction can be suppressed, and an unnecessary amount of light deflection can be suppressed two-dimensionally.
[0067]
The light beam control means includes the light modulation means,
In the step of detecting the deflection error, the deflection error detection means further detects an intensity error of the light amount of the light beam controlled by the light beam control means,
In the feedback step, it is preferable that the feedback means further feeds back a feedback signal using the intensity error to the optical modulation means. According to this configuration, the amount of unnecessary light deflection can be suppressed, and the intensity of the light spot at the time of cutting can be suppressed to a desired value, so that it is possible to provide a good optical disc with little variation in pit dimensions and track pitch. it can.
[0068]
Further, the light beam control means further includes a light modulation correction means for controlling the light amount of the light beam controlled by the light beam control means,
In the step of detecting the deflection error, the deflection error detection means further detects an intensity error of the light amount of the light beam controlled by the light beam control means,
In the feedback step, it is preferable that the feedback unit further feeds back a feedback signal using the intensity error to the optical modulation correction unit. Even in this configuration, since the intensity of the light spot at the time of cutting can be suppressed to a desired value, it is possible to provide a good optical disk with little variation in pit dimensions and track pitch.
[0069]
In the third optical disc manufacturing method, a step of detecting a second deflection error in the radial direction included in a light beam from the second light deflection unit by a deflection error detection unit;
Preferably, the method further includes a step of feeding back a feedback signal using the second deflection error in the radial direction to the second optical deflecting unit by a feedback unit. According to this configuration, an unnecessary deflection amount can be suppressed more reliably.
[0070]
Further, in the step of detecting the second deflection error in the radial direction, the deflection error in the tangential direction of the light beam controlled by the light deflection means is further independent of the second deflection error in the radial direction. To detect
In the step of feeding back, it is preferable that a feedback signal using the deflection error in the tangential direction is further fed back to a third optical deflection unit that deflects the light beam in the tangential direction on the optical disk master. According to this configuration, fluctuation in the tangential direction in addition to the radial direction can be suppressed, and an unnecessary amount of light deflection can be suppressed two-dimensionally.
[0071]
In addition, the method further includes a step of controlling the light amount of the light beam controlled by the light deflecting unit with the light modulating unit,
In the step of detecting the second deflection error, the deflection error detection means further detects an intensity error of the light amount of the light beam controlled by the light deflection means,
In the feedback step, it is preferable that a feedback signal using the intensity error is fed back to the optical modulation means. According to this configuration, the amount of unnecessary light deflection can be suppressed, and the intensity of the light spot at the time of cutting can be suppressed to a desired value, so that it is possible to provide a good optical disc with little variation in pit dimensions and track pitch. it can.
[0072]
Further, in the fourth optical disc manufacturing method, a step of detecting a second deflection error in the radial direction included in a light beam from the light deflection unit by a deflection error detection unit;
It is preferable that the method further includes a step of feeding back a feedback signal using the second deflection error in the radial direction to the optical deflection unit and superimposing the feedback amount on a control amount of the optical deflection unit. . According to this configuration, an unnecessary deflection amount can be suppressed more reliably.
[0073]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, an optical disc cutting method will be described using an optical disc cutting apparatus that actually cuts an optical disc master.
[0074]
(Embodiment 1)
FIG. 1 is a block diagram of an optical disc cutting apparatus according to Embodiment 1 of the present invention. The block diagram shown in this figure shows the configuration and process of the optical disc cutting apparatus, and is also a block diagram of the optical disc master production process in the optical disc manufacturing process. This also applies to the following FIGS. The same parts as those in the conventional optical disc cutting apparatus described with reference to FIG. Here, it is assumed that the EO deflector 3 is driven by a digital deflection method.
[0075]
The format of the optical disk to be cut is assumed to be a sample servo system with a groove as shown in FIG. In this optical disc cutting apparatus, an unnecessary deflection suppression unit which is servo means surrounded by a broken line 200 is added in order to suppress an unnecessary deflection amount in the radial direction of the master disk. This object is mainly to suppress the unnecessary deflection after the step deflection by the EO deflector of (Problem 1) described in the problem to be solved by the invention and the fluctuation shown in (Problem 2) by servo means. It is in.
[0076]
In FIG. 1, 201 is a beam splitter, 202 is a condenser lens, and 203 is a two-divided detector. The two-divided detector 203 is arranged perpendicular to the paper surface of FIG. 1, and is divided in the direction corresponding to the left and right, that is, the radial direction of the master disc of the optical disc. The beam splitter 201 splits the light beam Lc into the objective lens 5 and the condenser lens 202 at a predetermined ratio. The division ratio is desirably 50% each if the power of the laser light source 1 is sufficient from the viewpoint of securing the SNR of the detection signal. The beam shape of the light beam directed to each needs to be stored in the same shape as when entering the beam splitter 201.
[0077]
The condenser lens tries to focus on Dc, but a two-divided detector 203 is disposed in front of it. The two-divided detector 203 is mounted on the XYZ stage for easy adjustment. The condensed light beam Lc is all guided to the effective area of the two-divided detector 203 so that no detection error due to vignetting occurs.
[0078]
The output of the two-divided detector 203 is connected to the differential amplifier 204 and detected as a deflection detection signal Vdet corresponding to the deflection amount. This differential amplifier 204 is also preferably mounted on the XYZ stage from the viewpoint of securing SNR. Basically, the two-divided detector 203 performs alignment so that the deflection detection signal Vdet becomes zero when the deflection amount is zero.
[0079]
Here, FIG. 2A shows the deflection detection signal Vdet at the time of actual cutting. In the waveform of FIG. 2A, (a1) is when the first wobble 11 is deflected to the inner periphery side, (a2) is when the second wobble 12 is deflected to the outer periphery, and (a3) is the groove cutting. Indicates when you started. In particular, a fluctuation due to unnecessary deflection as shown by (a4) is observed immediately after the deflection. Address pits 13 are not formed in this segment. It can be seen that the fluctuation due to the unnecessary deflection is considerably attenuated when 15 μs (about 10 μs from the groove start end) has passed since the inner circumferential deflection. The amount of deflection is about 10 to 20 nmpp as a displacement on the master 100.
[0080]
When converted on this scale, the wobble displacement seems to be displaced by a little less than 60 nm, but in reality it is a waveform when displaced by approximately 200 nm. This is based on the non-linearity of the deflection detection shown in FIG. That is, if the two-divided detector is arranged in the vicinity of the focus of the detection lens (condensing lens) 202 so as to increase the detection sensitivity by the deflection amount detection method as described above, the deflection detection voltage Vdet becomes saturated. For linear control, only the linear region shown in FIG. 2 (b1) is used, or in order to use it in a wider range, it is necessary to perform nonlinear partial correction shown in (b2).
[0081]
In order to increase the linear region, the two-divided detector 203 may be moved away from the focal position of the condensing lens to the extent that the light beam is not vignetted at the expense of detection sensitivity. However, the detection sensitivity falls. The confirmation of the linearity can be determined by changing the applied voltage proportional to the deflection amount to the EO deflector 3 and plotting the relationship with the deflection detection voltage Vdet.
[0082]
Returning to FIG. 1, the description will be continued. The deflection detection voltage Vdet is sent to a 205 sample hold (S / H) circuit. The S / H circuit 205 constitutes a 20 dB / dec primary low-pass filter by RC. The sample section is controlled by the S / H signal from the formatter 101a so as to be a section in which the groove 14 is cut. Actually, as shown in (a5) of FIG. 3, a section slightly narrower than the section of the groove 14 is set as the sample section. The other section, that is, the section during deflection and the light amount of 0 is set as the hold section.
[0083]
The difference between the formatter 101a and the formatter 101 in FIG. 9 is that the former outputs an S / H signal. Further, FIG. 3 is obtained by adding the S / H signal to FIG. 11, and the other parts are as described in the conventional example.
[0084]
The output of the S / H circuit 205 is connected to the error amplifier 206 in order to bring the error from the output of the target value setting unit 207 (here, set to 0) close to 0. The output of the error amplifier 206 is sent to the gain setting / phase compensation circuit 208 which is feedback means for compensating the gain of the servo means and the phase as necessary.
[0085]
The output FB is DC-amplified as a feedback signal by a second EOD driver 209 using an analog deflection method. The second EOD driver 209 is preferably a high-speed, high-voltage bipolar power supply, and faithfully amplifies the output of the previous gain setting / phase compensation circuit 208 with a constant amplification factor. The output of the second EOD driver 209 is connected to a second EO deflector 210 placed between the EO deflector 3 and the beam splitter 201.
[0086]
According to the present embodiment configured as described above, the unnecessary deflection amount in the radial direction of the master is set to 1 Hz or less as described in (Problem 2) by appropriately setting the gain in the gain setting / phase compensation circuit 208. The fluctuation component of 100 Hz to 1 kHz is sufficiently suppressed by the primary low-pass filter characteristic of the S / H circuit 205.
[0087]
However, the fluctuation after stepwise deflection described in (Problem 1) is 700 kHz, so the fluctuation amount is several due to the group delay of the second EOD driver 209 and other circuit elements. I was able to suppress it only to a fraction. Nevertheless, the actual fluctuation amount can be suppressed to several nanometers or less and the low-frequency fluctuation can be sufficiently suppressed, so that it can be said that the practical effect as a high-density optical disc cutting apparatus is great.
[0088]
In the present embodiment, the light beam after passing through the beam splitter 201 travels on an independent optical path and may be affected by the fluctuation of air in each optical path. It is desirable that the condensing lens 202 is also close to the beam splitter 201.
[0089]
In order to avoid such an influence, it is also effective to detect the deflection amount from the reflected light from the master 100. That is, the optical system around the beam splitter 201 and the objective lens 5 is changed, the light beam Lc is allowed to pass through once, and once focused on the master 100 as a light spot through the objective lens 5, the reflected light is divided into the two-divided detector 203. The deflection amount may be detected from the light beam. In this case, however, it is necessary to remove the influence of vignetting from the objective lens 5 and disturbance light from the light source for focusing the objective lens.
[0090]
In order to suppress the servo gain fluctuation due to the power setting change at the time of cutting, it is preferable to include an AGC circuit that adds both outputs of the two-divided detector 203 to the differential amplifier 204 and divides both differences. Alternatively, it is desirable to construct an AGC that keeps the gain constant by sending the power control signal of the laser light source 1 to the gain setting / phase compensation circuit 208.
[0091]
In addition, when the wavelength of the laser light source 1 is less than 300 nm, a normal resin-sealed Si-based detector absorbs light by the resin and cannot obtain detection sensitivity. It is necessary to choose. In this embodiment, when creating a format for wobbling the groove 14, a value corresponding to the wobble amount is output from the formatter 101 and input to the target value setting unit 207. It can be realized by doing.
[0092]
Further, in the present embodiment, an example of an apparatus provided with both the EO modulator 2 that is an optical modulation means and the EO deflector 3 that is an optical deflection means has been described, but an EO modulator according to the format of the optical disk. Even an apparatus including any one of 2 and EO deflector 3 can suppress the amount of unnecessary deflection in the radial direction of the master as described above.
[0093]
In the present embodiment, the second EO deflector 210 is provided separately from the EO deflector 3. However, the second EO deflector 210 is not provided, and the feedback signal is sent to the EO deflector 3. And the feedback amount may be superimposed on the control amount of the EO deflector 3.
[0094]
(Embodiment 2)
Next, a second embodiment will be described. As described above, although the servo means in the first embodiment is sufficiently effective in practice, the fluctuation after step deflection described in (Problem 1) (hereinafter referred to as deflection fluctuation) cannot be suppressed to such an extent that it can be virtually ignored. The present embodiment shows an optical disc cutting apparatus provided with canceling means for canceling this deflection fluctuation by feed forward.
[0095]
Specifically, this is an example in which the canceling unit is added to the first embodiment. Of course, depending on the format of the optical disk, an optical disk cutting apparatus in which the servo unit of the first embodiment is omitted and only the cancel unit is mounted may be sufficient. The same applies to the following third embodiment.
[0096]
FIG. 4 is a block diagram of the optical disc cutting apparatus according to the present embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In this optical disc cutting apparatus, an unnecessary deflection cancel unit surrounded by a broken line 300 is added to cancel the above-described deflection fluctuation.
[0097]
In FIG. 4, reference numerals 301 to 304 denote waveform memories (1) to (4) in which deflection fluctuations generated after step deflection are stored. A timing control unit 305 determines the output timing of each waveform memory, and generates timing based on the deflection signal Ved output from the formatter 101a. Reference numeral 306 denotes an adder for adding the digital data output from the waveform memory (1) 301 to the waveform memory (4) 304, and outputs the waveform memory full addition output as digital data.
[0098]
Reference numeral 307 denotes a DA converter (DAC) which is a feed forward means for converting the digital data of the adder 306 into an analog signal and outputs it as a feed forward signal FF, and 308 is a gain setting of the servo means described in the first embodiment. A summing amplifier that adds the feedforward signal FF from the unnecessary deflection cancel unit of the present embodiment to the feedback signal FB of the phase compensation circuit 208. The output of the summing amplifier 308 drives the second EO deflector 210 via the second EOD driver 209.
[0099]
FIG. 5 is a timing chart showing output timings of the waveform memory (1) 301 to the waveform memory (4) 304. FIG. 5A shows the EOD drive signal Vedd of the EO deflector 3 driven by the deflection signal Ved. At times t1, t2, t3, and t4, it is driven so as to be deflected to the inner periphery, returned to neutral, deflected to the outer periphery, and returned to neutral.
[0100]
The timing control unit 305 outputs the waveforms stored in the waveform memory (1) 301 to the waveform memory (4) in the order of t1 to t4. In FIG. 5, the data in the waveform memory is digital data, but is displayed as analog waveforms (b), (c), (e), and (f) for easy understanding. In each waveform memory, the deflection fluctuation after the step response of the EO deflector 3 is stored. Such storage of the waveform memory is performed in advance before actually cutting the optical disk.
[0101]
In this description, the fluctuation waveform is modeled as a sine wave damped oscillation as shown in FIG. 5B, but since the actual deflection fluctuation is an irregular value including a harmonic component, it is not calculated by calculation. A step voltage is applied to the EO deflector 3 that is actually used, and is captured as a basic waveform by a digital oscilloscope or the like. If the deflection amount at each time is the same, the deflection direction and the deflection amount are adjusted, and the basic waveform is stored in each waveform memory. In this case, the waveform resulting from deflection at times t1 and t4 in which the deflection directions are the same is stored in the waveform memory (1) 301 and the waveform memory (4) 304.
[0102]
Further, the deflection direction at times t2 and t3 is opposite to the deflection direction at times t1 and t4. For this reason, waveforms having opposite polarities to the waveforms caused by deflection at times t1 and t4 are stored in the waveform memory (2) 302 and the waveform memory (3) 303. The feed forward signal FF for suppressing the deflection fluctuation is a waveform memory full addition output shown in (h) in which all the values of the above four waveform memories are added.
[0103]
The feed control signal FF adjusts the start by the timing control unit 305 so as to correct the delay of the circuit system and the drive system. The output of the waveform memory is set to 0 when the deflection fluctuation becomes practically negligible, and is prepared for the next deflection cycle.
[0104]
For reference, in FIGS. 5D and 5G, the deflection fluctuations when the pulse operation is performed when deflecting to the inner periphery and the outer periphery are shown as waveform memory (1) + (2), waveform memory (3). + (4) was shown. If this waveform is used, the waveform memory will increase to 8 when the deflection occurs four times as in the DVD-RAM shown in the conventional example, but each waveform is stored to save 4 waveform memories. it can.
[0105]
Further, although the values stored in each waveform memory have different polarities, they are substantially the same. Therefore, the waveform memory can be saved by controlling the timing of reading one waveform memory.
[0106]
Also, the data to be stored in the waveform memory is either integrated to eliminate the influence of disturbance so that there is no fluctuation effect as shown in (Problem 2), or only high-frequency disturbance while applying low-frequency servo. It is preferable to collect so that it may take out.
[0107]
According to the present embodiment described above, the deflection fluctuation that could not be completely suppressed by the servo means of the first embodiment can be sufficiently suppressed. In the first embodiment, only the deflection fluctuation of the groove 14 is suppressed, but in this embodiment, the deflection fluctuation of the first wobble pit 11 and the second wobble pit 12 and the address pit 13 being deflected is also canceled. Can do.
[0108]
Thereby, since both the deflection fluctuations of the first wobble pit 11 and the second wobble pit 12 can be canceled, the tracking accuracy of the sample servo is improved, and the center of the groove 14 can be accurately tracked.
[0109]
(Embodiment 3)
Next, a third embodiment will be described. The present embodiment is an improvement of the second embodiment. In the second embodiment, two EO deflectors are used. However, here, it is assumed that one is used, and an expensive EO deflector is not required. To do. FIG. 6 is a block diagram of the optical disc cutting apparatus according to the present embodiment. The same components as those in the second embodiment are denoted by the same reference numerals, and the description thereof is omitted. The difference is the formatter 101b, the addition amplifier 308a for sharing the EO deflector shown in the timing control units 305a and 400, and the EOD driver 103a. For sharing, the second EOD driver 209 and the second EO deflector 210 are deleted.
[0110]
The control signal Ved2 for controlling the EOD driver from the formatter 101b is an analog signal before amplification of the EOD drive signal Vedd shown in FIG. The timing control unit 305a extracts a timing signal from the control signal Ved2. Of course, instead of the control signal Ved2, the timing control unit may be the same as 305 as a configuration in which the deflection signal Ved, which is the same digital signal as in the second embodiment, is output from the formatter 101b.
[0111]
The addition amplifier 308a adds the feedback signal FB, the feed forward signal FF, and the EOD control signal to generate an EOD control signal Vedd3. Here, the EO deflection method is an analog deflection method. Therefore, although the cost is slightly increased and complicated, a high voltage and high slew rate DC type amplifier is used as the EOD driver 103a. Since the operation for suppressing unnecessary deflection is basically the same as that of the second embodiment, description thereof is omitted.
[0112]
With the above configuration, even when a new EO deflector cannot be inserted between the EO deflector 3 and the mirror 4, as long as the beam splitter 201 can be inserted, unnecessary deflection can be suppressed. Moreover, since a new EO deflector is inserted, the adverse effect of increasing the optical path length and increasing unnecessary deflection can be avoided.
[0113]
Note that an EO deflector in which two EO deflectors are included in one unit has been put to practical use. In an optical disc cutting apparatus using the EO deflector, the second embodiment has a higher voltage. This can be realized economically without adding a high slew rate DC type amplifier.
[0114]
In addition, this embodiment can perform the same operation with the following changes. That is, first, the order of the EO modulator 2 and the EO deflector 3 is reversed, and the beam splitter 201 is disposed immediately after the EO deflector 3 so that the deflection amount can always be detected. Next, the S / H circuit 205 inserts correction means capable of correcting the non-linearity shown in FIG. 2B between the S / H circuit 205 and the error amplifier 206 that are always in the sample state.
[0115]
The target value setting unit 207 receives the deflection signal Ved2 of the formatter 101b after being removed from the addition amplifier 308a. The phase compensation function in the gain setting / phase compensation circuit 208 is moved to the correction means so as not to cause a delay.
[0116]
When a closed loop is formed as described above, the EOD driver 103a has a signal obtained by superimposing an unnecessary deflection amount suppression component detected by the error amplifier on the drive signal obtained by amplifying the deflection signal Ved2, and canceling the signal by the waveform memory. Is entered. As a result, the EO deflector 3 can realize unnecessary deflection suppression substantially the same as in the third embodiment.
[0117]
(Embodiment 4)
Next, a fourth embodiment will be described. This embodiment is an example of suppressing unnecessary change in the tangential direction and unnecessary fluctuations in light quantity, whereas the first to third embodiments suppress unnecessary deflection only in the radial direction. FIG. 7 is a block diagram of the optical disc cutting apparatus of the present embodiment. The same components as those in the third embodiment are denoted by the same reference numerals, and the description thereof is omitted. FIG. 8 is a diagram showing a light amount and deflection amount detector in the present embodiment.
[0118]
Here, FIG. 8 will be described first. In FIG. 8, 203a is a four-divided detector comprising A, B, C, and D detectors, and is placed at the same position as the two-divided detector 203 in the first to third embodiments. Lm is a light beam formed on the quadrant detector 203a. When the light beam Lc is deflected, Lm is displaced on the quadrant detector 203a in the illustrated radial direction and tangential direction.
[0119]
The direction of the displacement direction is the same as the displacement of the light spot on the master. The displacement (deflection amount) in the tangential direction is detected by (A + B) − (C + D), and the displacement (deflection amount) in the radial direction is detected by (B + D) − (A + C). Each deflection amount is calculated by the composite amplifier 600. The photocurrent of each detection unit is converted into a voltage by the IV amplifiers 601 to 604. Thereafter, the values in parentheses of both the above formulas are calculated by the addition amplifiers 605 to 608.
[0120]
Further, the summing amplifier 609 calculates the total light amount Vsum = (A + B + C + D) of the light beam Lm, and is used for canceling the unnecessary light amount of the optical disc cutting apparatus in addition to the AGC described later. The differential amplifiers 610 and 611 calculate the difference between the two formulas to obtain the deflection amount in the tangential direction and the deflection amount in the radial direction, respectively.
[0121]
Further, these values are respectively divided by the total light amount Vsum of the addition amplifier 609 using the AGC circuits 612 and 613, and the standardized tangential deflection signal Vdett and radial deflection signal Vdetr are calculated and output. Vdetr is substantially the same as Vdet in the first to third embodiments.
[0122]
In FIG. 7, what is added to the third embodiment for the purpose of the present embodiment is a tangential direction unnecessary deflection suppression unit and a light amount fluctuation suppression unit enclosed by a broken line 500. Reference numerals 203a and 600 denote the above-described quadrant detector and composite amplifier, respectively. A radial deflection signal Vdetr is sent to the S / H circuit 205 constituting the conventional radial direction deflection suppressing unit, and a tangential deflection signal Vdett is used for tangential direction deflection suppression.
[0123]
The S / H circuit 501, error amplifier 502, target value setting unit 503, gain setting / phase compensation circuit 504, and third EO driver 505 are the S / H circuit 205, error amplifier 206, target value setting unit 207, gain, respectively. It performs the same function as the setting / phase compensation circuit 208 and the second EOD driver 209 in the first embodiment. Reference numeral 506 denotes a third EO deflector which is placed between the EO deflector 3 and the beam splitter 201 and can control the deflection of the light beam Lc in the tangential direction.
[0124]
Since the present optical disc cutting apparatus basically does not deflect in the tangential direction, the tangential deflection signal Vdett can be regarded as an unnecessary deflection amount as it is. An unnecessary deflection amount in the tangential direction can be suppressed by zero adjustment of the division position of the four-divided detector 203a and the offset voltage of the circuit system and setting the target value setting unit to zero.
[0125]
Next, unlike the above embodiment, the EOM driver 102a has a function of correcting a light amount variation. In other words, servo means for amplifying the difference between the target value Vem2 of the light amount output from the formatter 101c and the total light amount Vsum and feeding back to the drive signal Vemd2 of the EO modulator 2 is provided so that Vsum becomes substantially the same as Vem2. The amount of light on the master is controlled to Vem2 as intended.
[0126]
As described above, when CAV cutting is performed at the time of master disc cutting of the optical disc, the target value is also appropriately applied to the EOM driver 102a when the light amount control by the cutting radius is performed, for example, the emitted light amount of the laser light source 1 is increased toward the outer periphery. Set to an appropriate value.
[0127]
According to the fourth embodiment described above, in addition to an unnecessary deflection amount in the radial direction, an unnecessary deflection amount in the tangential direction and an unnecessary light amount fluctuation can be suppressed.
In the embodiment shown in FIG. 7, the example in which both the tangential direction unnecessary deflection suppression unit and the light amount variation suppression unit are provided has been described, but a configuration in which only one of them is provided may be employed.
[0128]
In addition, a function for suppressing an unnecessary deflection amount in the tangential direction as in the present embodiment and a function for correcting light quantity fluctuation may be added to the configuration of the first embodiment. In the case of adding a function for correcting the light amount variation to the configuration without the EO modulator 2 in FIG. 1, an EO modulator which is a light modulation correction means is added after the EO deflector 3 and a feedback signal regarding an intensity error is provided. What is necessary is just to feed back to this added EO modulator.
[0129]
(Create optical disc)
The glass master produced by the optical disc cutting apparatus of Embodiments 1 to 4 described above is finished into a stamper in the subsequent mastering process. That is, first, a developing process for removing the exposed photoresist as the groove and pit portion is performed. Next, nickel is vapor-deposited to prepare for plating, the thickness is increased by nickel plating, a stamper is formed, and the master and the stamper are peeled off.
[0130]
Further, the formed stamper is subjected to outer shape and hole processing for a molding machine, back surface polishing, and the like. Then, it is attached to an optical disk substrate molding machine and made into a transparent optical disk substrate by injection molding of polycarbonate. Thereafter, a recording film and a reflective film are formed by a sputtering apparatus, and a protective coat and bonding are performed as necessary, and the film is put into a cartridge case or the like to complete a desired optical disk.
[0131]
In this way, the optical disc produced using the optical disc cutting apparatus of the present invention is precisely created in the desired position for the prepit size and position, and the groove width and pitch. Since the tracking error signal accuracy and variation are small, the groove width and / or land width are stable, and the variation is small, the recording / reproducing performance and margin can be remarkably improved.
[0132]
Conversely, if an optical disc is made with the optical disc cutting device of the present invention, the same recording / playback performance and margin as the conventional cutting device can be ensured even if the track pitch and pit size are further reduced. This means that a high-density optical disc can be created.
[0133]
In the optical disk cutting method of each embodiment described above, the one-beam cutting method in which cutting is performed using one light beam is shown. In order to suppress the deflection fluctuation, if a two-beam cutting method is employed in which the pre-pit formation to be deflected and the groove formation not to be deflected are cut by different light beams, the groove is not influenced by the deflection in principle.
[0134]
However, in the two-beam cutting method, high-precision alignment of two light spots, that is, alignment in a two-dimensional direction of tangential and radial, is 0.01 μm or less. Even with two-beam cutting, a highly accurate optical disk can be cut by detecting and feeding back the unnecessary deflection and the change in the amount of unnecessary light in the present invention independently of the two beams.
[0135]
Further, the optical disk to which the first to fourth embodiments can be applied has been shown in FIG. 10A as an example of the conventional example, but the optical disk format is the same as the DVD-RAM shown in FIG. 10B. Various optical disc formats are possible, including various formats.
[0136]
For example, even in the case of an optical disc that cuts the presence or absence of pre-pits, such as CDs and DVD-ROMs, the deflection amount during pit formation is sampled to suppress unnecessary deflection amounts in the radial and tangential directions and change the light amount. Can be suppressed.
[0137]
This improves the size and position accuracy of the prepits, thereby suppressing fluctuations in the radial and tangential directions, improving the SNR and tracking accuracy, and realizing jitter reduction. Furthermore, the application is not limited to the optical disc, and the present invention can be applied to high accuracy of a system that forms a pattern with a laser light source.
[0138]
Moreover, since it has been known as a measurement result that the deflection fluctuation after changing the EO deflector step by step is reduced when the slew rate of the drive voltage is lowered, it is slow due to the relationship between the cutting speed and the format of the optical disc. If such deflection is acceptable, it is preferable to implement means for reducing the slew rate in combination with the embodiment of the present invention to suppress the deflection fluctuation that causes the slew rate.
[0139]
【The invention's effect】
As is apparent from the above description, according to the present invention, unnecessary fluctuations in prepits and grooves caused by unnecessary deflection and / or unnecessary change in the amount of light from the master of the optical disk can be eliminated, and the high definition formed thereby Thus, an optical disk suitable for large capacity and high density can be provided using a highly accurate master.
[Brief description of the drawings]
FIG. 1 is a block diagram of an optical disc cutting apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram illustrating unnecessary deflection detected by the optical disc cutting apparatus according to Embodiment 1 of the present invention and sensitivity of a detection unit.
FIG. 3 is a timing chart for explaining the operation of the first embodiment of the present invention.
FIG. 4 is a block diagram of an optical disc cutting apparatus according to a second embodiment of the present invention.
FIG. 5 is a timing chart for explaining the operation of the second embodiment of the present invention.
FIG. 6 is a block diagram of an optical disc cutting apparatus according to a third embodiment of the present invention.
FIG. 7 is a block diagram of an optical disc cutting device according to a fourth embodiment of the present invention.
FIG. 8 is a diagram showing a light amount and deflection amount detection unit in Embodiment 4 of the present invention;
FIG. 9 is a block diagram of a conventional optical disc cutting apparatus.
FIG. 10 is a diagram showing a substrate configuration example of a sample servo system and a continuous servo system of an optical disk suitable for high density.
FIG. 11 is a timing chart for explaining the operation of the sample servo type optical disc cutting apparatus.
[Explanation of symbols]
1 Laser light source
2 EO modulator (EOM)
3 EO deflector (EOD)
4 Mirror
5 Objective lens
6 Motor
100 Optical disc master
101 formatter
102 EOM driver
103 EOD driver
Vdet deflection detection signal
200 Unnecessary deflection suppression unit
201 Beam splitter
202 condenser lens
203 Divided detector
204 Differential amplifier
205 Sample hold (S / H) circuit
206 Error amplifier
207 Target value setting section
208 Gain setting and phase compensation circuit
209 Second EOD driver
210 Second EO deflector
300 Unnecessary deflection cancel unit
301 Waveform memory (1)
302 Waveform memory (2)
303 Waveform memory (3)
304 Waveform memory (4)
305 Timing control unit
306 Adder
307 DAC
308 Summing amplifier
203a Quadrant detector
Shared section of 400 EO deflector
500 Tangential direction unnecessary deflection suppression unit and light intensity fluctuation suppression unit
501 Sample hold (S / H) circuit
502 Error amplifier
503 Target value setting section
504 Gain setting / phase compensation circuit
505 Third EOD driver
506 Third EO deflector
600 composite amplifier
601-604 IV amplifier
605 to 609 summing amplifier
610, 611 Differential amplifier
612, 613 AGC amplifier
Ta track 2m
Tb track 2m + 1
11 First wobble pit
12 Second wobble pit
13 Address pit
14 Groove
15 rand
16 Recording / playing light spot
Tg groove track
Tl Land Track
21 LG common address part
22 GL common address part
23 Groove
24 rand
25 Recording / playing light spot
31 Light spot for cutting

Claims (13)

A light beam control means including a light deflection means for controlling the deflection amount of the light beam emitted from the laser light source in the radial direction on the optical disc master;
Storage means for storing a deflection error in the radial direction measured in advance when the light beam is deflected by the light deflection means;
Second light deflection means for controlling the deflection amount of the light beam from the light deflection means;
When cutting the optical disc master, a feed forward signal using the radial deflection error stored in the storage means is input to the second light deflection means in accordance with the deflection timing of the light beam control means. An optical disc cutting apparatus comprising: a feed forward means for performing the operation. The second optical deflector is to match the polarization direction and the light deflecting means, the feedforward word word signals, according to claim 1 wherein a radial signal obtained by reversing the polarity of the deflection error of Optical disc cutting device. Deflection error detection means for detecting a second deflection error in the radial direction included in the light beam from the second light deflection means;
Optical disc cutting apparatus of claim 1, further comprising a feedback means for feeding back a feedback signal using a second deflection error of the radial direction to the second optical deflector. A third light deflecting unit disposed between the light beam control unit and the deflection error detecting unit, for deflecting the light beam in a tangential direction on the optical disc master;
The deflection error detection means further detects the deflection error in the tangential direction of the light beam controlled by the light beam control means independently of the deflection error in the radial direction,
4. The optical disc cutting apparatus according to claim 3 , wherein the feedback means further feeds back a feedback signal using the deflection error in the tangential direction to the third optical deflection means. A light modulation means for controlling the light amount of the light beam controlled by the light beam control means;
The deflection error detection means can further detect an intensity error of the light amount of the light beam controlled by the light beam control means,
4. The optical disc cutting apparatus according to claim 3 , wherein the feedback means further feeds back a feedback signal using the intensity error to the optical modulation means. A light beam control means including a light deflection means for controlling the deflection amount of the light beam emitted from the laser light source in the radial direction on the optical disc master;
Storage means for storing a deflection error in the radial direction measured in advance when the light beam is deflected by the light deflection means;
When the optical disk master is cut, a feed forward signal using the radial deflection error stored in the storage means in accordance with the deflection timing of the light beam control means is input to the optical deflection means. An optical disc cutting apparatus comprising a word means. Deflection error detection means for detecting a second deflection error in the radial direction included in the light beam from the light deflection means;
The feedback device according to claim 6 , further comprising: a feedback unit that feeds back a feedback signal using the second deflection error in the radial direction to the optical deflection unit and superimposes the feedback amount on a control amount of the optical deflection unit. Optical disc cutting device. In the optical disk master cutting process, an optical disk manufacturing method for controlling the light beam emitted from the laser light source in the radial direction on the optical disk master by means of light deflecting means,
Before the cutting step of the optical disc master, comprising a step of measuring in advance a deflection error due to the control of deflecting in the radial direction and storing this in a storage means,
In the cutting process of the optical disc master,
A feed forward signal using the deflection error stored in the storage means is input to the second light deflection means for controlling the deflection amount of the light beam from the light deflection means in accordance with the deflection timing of the light beam. The manufacturing method of the optical disk characterized by including the process to perform. A step of detecting a second deflection error in the radial direction included in the light beam from the second light deflection unit by a deflection error detection unit;
9. The method of manufacturing an optical disc according to claim 8 , further comprising a step of feeding back a feedback signal using the second deflection error in the radial direction to the second optical deflection unit by a feedback unit. In the step of detecting the second deflection error in the radial direction, the deflection error in the tangential direction of the light beam controlled by the light deflecting means is further detected independently of the second deflection error in the radial direction. And
In the step of the feedback, further wherein the feedback signal using the deflection error of the tangential direction, to claim 9 is fed back to the third light deflecting means for deflecting the light beam in the tangential direction on the optical disc master Optical disc manufacturing method. A light modulation means, further comprising a step of controlling the light quantity of the light beam controlled by the light deflection means;
In the step of detecting the second deflection error, the deflection error detection means further detects an intensity error of the light amount of the light beam controlled by the light deflection means,
The optical disk manufacturing method according to claim 9 , wherein in the feedback step, a feedback signal using the intensity error is fed back to the optical modulation unit. In the optical disk master cutting process, an optical disk manufacturing method for controlling the light beam emitted from the laser light source in the radial direction on the optical disk master by means of light deflecting means,
Before the cutting step of the optical disc master, comprising a step of measuring in advance a deflection error due to the control of deflecting in the radial direction and storing this in a storage means,
In the cutting process of the optical disc master,
A method of manufacturing an optical disc, comprising the step of inputting a feed forward signal using the deflection error in accordance with the deflection timing of the light beam into the light deflection means. A step of detecting a second deflection error in the radial direction included in the light beam from the light deflection means by a deflection error detection means;
13. The method according to claim 12 , further comprising the step of feeding back a feedback signal using the second deflection error in the radial direction to the optical deflection unit and superimposing the feedback amount on a control amount of the optical deflection unit. The manufacturing method of the optical disk as described in 1 ..

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