JP2002319201A - Optical disk heat treatment equipment - Google Patents

Abstract

(57) [Summary] [Problem] To smoothly perform a domain wall moving operation in a high-density disk of a domain wall moving method (DWDD), along a virtual line on a first wobble pit 16 and a second wobble pit 17,
An optical disk heat treatment apparatus capable of tracking a heat treatment beam is provided. A laser beam is divided into a plurality of optical paths (32, 33, 34), an optical disc 1 is subjected to a heat treatment with one of the divided beams (33), and tracking is performed with other divided beams (32, 34). As a result, heat treatment can be performed between the recording and reproducing tracks with a heat treatment width sufficiently narrower than the track pitch, and heat treatment can be performed while maintaining stable tracking characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for manufacturing an optical disk used for recording or reproducing information.

[0002]

2. Description of the Related Art In the field of optical disks, there is a demand for recording information at a higher density. As a method for realizing such high-density recording, DWDD (Domain Wall Dis
An optical disk of a placement detection type (domain wall movement detection type) has been proposed.

[0003] The optical disk of the DWDD system is a system capable of reproducing an information signal with high resolution by utilizing a domain wall moving phenomenon. By irradiating a reproducing light beam to a magneto-optical recording medium recorded as a set of micro mark portions formed by domain walls along a recording track and heating the recording track, a moving force is generated on the domain wall. The information signal is reproduced by moving the domain wall at high speed and detecting the movement.

In order to irradiate the reproducing light beam as described above and generate a moving force on the domain wall of the recording mark portion recorded along the track, it is necessary to weaken the magnetic coupling between adjacent recording tracks. is there. Therefore, when manufacturing an optical disk of the DWDD system, a heat treatment (also referred to as initialization or annealing) for weakening magnetic coupling between adjacent recording tracks is performed before recording an information signal. This heat treatment method irradiates a light beam focused to 1 μm or less between recording tracks, heats between the recording tracks,
This is achieved by weakening the magnetic coupling by reducing the magnetic anisotropy of the heated part. Such a heat treatment method has been conventionally proposed (JP-A-6-290496 and JP-A-10-340493).
Reference).

FIG. 9 shows an example of a conventional optical disk structure and a heat treatment method. As shown in FIG. 9, a conventional optical disc 1 includes a substrate 2, a first dielectric layer 3, a recording layer 4, a second dielectric layer 5, and a protective coat layer 6 sequentially laminated on the substrate 2. Is provided. A groove portion 7 is formed on the surface of the substrate 2 on the recording layer 4 side. A portion called a land portion 8 is between two groove portions 7 that are radially adjacent to each other. In such a grooved disk, there are two cases, that is, data is recorded in the groove portion 7 (referred to as groove recording) and data is recorded in the land portion 8 (referred to as land recording). Groove recording and land recording are also performed on a DWDD disk using a grooved substrate, but the case of groove recording will be described here.

In a conventional DWDD disc, a groove 7
Is 0.8 μm, for example, and the land 8 has a width of 0.1 μm.
4 μm. The recording layer 4 includes three or more magnetic layers for performing reproduction by the DWDD method.

Next, a heat treatment method for the optical disk 1 will be described. In the heat treatment of the optical disk 1, a laser beam 9 for heat treatment (for example, laser power: 10 mW, wavelength = 680 nm, N
A = 0.55) makes it possible to eliminate the magnetic coupling of the recording layer 4 on the land 8. In this heat treatment step, the moving speed of the light spot of the laser light 9 is, for example, 3 m / sec.

[0008]

In order to carry out the above heat treatment method, it is necessary to provide a disk provided with a groove portion 7 and a land portion 8 which is generally called a grooved disk. When recording / reproducing is performed in the groove section 7,
Laser light 9 focused by objective lens 10 of heat treatment apparatus
Is moved along the land portion 8 to heat-treat the land portion 8. Here, as a means for causing the laser beam 9 to travel along the land portion 8, a tracking method such as a push-pull method is generally employed.

However, when a grooved disk is used, if the land portion 8 is heat-treated and recording / reproducing is to be performed in the groove portion 7, the land portion 8 having good tracking characteristics can be obtained.
Must be formed. For this purpose, as shown in FIG. 10, the step 11 between the land portion 8 and the groove portion 7 needs to be about λ / 8 of the wavelength of the light beam for heat treatment, which is necessary for performing DWDD reproduction. There was a problem that it was not suitable. Here, 2 is a substrate, and 3, 4 to 5 are a first dielectric layer, a recording layer, and a second dielectric, respectively. The protective coat 6 is not shown.

That is, if a step of about λ / 8 is provided, it is difficult to form a smooth groove, and as shown in an enlarged view, a slight fluctuation 12 on the side surface of the groove is generated, which clearly impedes the DWDD operation. It became. In order to achieve high density, it is necessary to perform a smooth DWDD operation even when recording a short mark such as 0.3 μm or less, and for that purpose, it is necessary to eliminate or reduce the fluctuation on the side surface of the groove portion. .

One method of eliminating or reducing the fluctuation of the side surface of the groove is considered to be the adoption of a sample servo system having an extremely shallow groove (groove) of λ / 10 or less of the wavelength of the heat treatment light beam. Or a sample servo system without grooves. FIG. 11 shows an example of a sample servo type disk provided with an extremely shallow groove portion 7, as viewed from the pit formation surface. FIG.
In the figure, 13 is a servo area, 14 is a data area, and a segment area 15 is formed by the servo area and the data area.

A first wobble pit 16 and a second wobble pit 17 are provided in the servo area. The data area 14 along the recording / reproducing track 19 is used for recording / reproducing. The heat treatment is performed on the lands along the heat treatment tracks 20.

The reason for providing a very shallow groove is that there is little fluctuation on the side surface of the above-mentioned minute groove portion, and it has a slight effect of preventing heat diffusion of the heat treatment beam.
However, irradiating the land portion of the disk provided with the extremely shallow groove with the heat treatment beam causes unstable tracking of the heat treatment beam and has a problem in tracking control characteristics of the heat treatment beam.

On the other hand, FIG. 12 is a plan view of a normal sample servo type disk having no groove as seen from the side irradiated with the recording / reproducing beam in the same manner as described above. In FIG. 12, 13
Denotes a servo area, 14 denotes a data area, and a segment area 15 is formed by the servo area and the data area. A first wobble pit 16 and a second wobble pit 17 are provided in the servo area. The recording / reproducing track 21 used for recording / reproducing has a flat data area and no physical track, and the first wobble pit 16 and the second wobble pit 17
The recording / reproducing track 21 is on an imaginary line passing between the two. The number of heat treatment tracks for which heat treatment must be performed is 22. The heat treatment track 22 is on an imaginary line passing directly above the first wobble pit 16 or the second wobble pit 17.

The first wobble pit 16 and the second
Tracking a recording / reproducing beam on an imaginary line passing between the wobble pits 17 is performed by a normal sample servo technique. However, the light beam for heat treatment has the first wobble pit 16 and the second wobble pit 17.
There was a problem that the heat treatment track 22 had to be passed through.

According to the present invention, a first wobble pit 16 and a second wobble pit 17 are provided in order to solve the conventional problem.
It is an object of the present invention to provide an optical disk heat treatment apparatus capable of tracking a heat treatment beam along an upper virtual line.

[0017]

In order to achieve the above object, a first optical disk heat treatment apparatus of the present invention divides a laser beam into a plurality of optical paths, and applies one of the divided lights to an optical disk. It is characterized in that a heat treatment is performed and tracking is performed with another divided light.

A second optical disk heat treatment apparatus according to the present invention comprises a substrate and a recording layer disposed above the substrate, and reproduces an information signal using light incident from the substrate side. A heat treatment apparatus, wherein laser light incident from the recording layer side is divided into a plurality of optical paths, heat treatment of the recording layer is performed with one of the divided lights, and tracking is performed with another divided light. I do.

In the first and second optical disk heat treatment apparatuses, it is preferable that the tracking system for recording and reproducing the optical disk is a sample servo system.

It is preferable that the spot size of the split light used for the heat treatment is smaller than the spot size of the split light used for the tracking.

Preferably, the wavelength of the laser light is 500 nm or less.

In addition, the optical disk uses a domain wall movement detection method (D
It is preferably a magneto-optical disk (WDD).

As described above, the present invention divides a laser beam into a plurality of optical paths on a sample servo type optical disc for tracking by arranging a plurality of pairs of wobble pits A and B, To perform a heat treatment, and perform tracking with another divided light. An optical disk of a sample servo system for performing tracking by arranging a plurality of pairs of wobble pits A and B, comprising: a substrate; and a recording layer disposed above the substrate. In an optical disc that reproduces an information signal by using the laser beam, a laser beam incident from the recording layer side is divided into a plurality of optical paths, heat treatment is performed with one of the divided beams, and tracking is performed with another divided beam. Accordingly, since the spot size of the divided light used for the heat treatment is smaller than the spot size of the divided light used for the tracking, the heat treatment can be performed with a narrow width.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

(Embodiment 1) FIG. 1 is a principle view showing a configuration of a heat treatment apparatus of the present invention. The disk 1 and the optical head 30 are arranged, and the disk rotates in the direction of arrow 31 by a disk rotating mechanism (not shown). Although not shown, the optical head can be moved in the radial direction of the disk by the optical head transfer mechanism. The light emerging from the optical head is split into three beams, 32, 33 and 34. 33 is a beam for heat treatment, and 32 and 34 are beams for tracking. The positional relationship between the disk and each beam will be described with reference to FIG. 2 which is a plan view seen from the recording film forming surface.

In FIG. 2, reference numerals 16 and 17 denote a first wobble pit and a second wobble pit, respectively, and a virtual line 21 between the first wobble pit 16 and the second wobble pit 17 is a recording / reproducing track. A line passing over each of the first wobble pit 16 and the second wobble pit 17 is the heat treatment track 22.

Reference numeral 15 denotes segments. Each segment includes a servo area 13 and a data area 14. Heat treatment beam 33 and tracking beams 32 and 34
Is irradiated onto the disk 1 to form a light spot 35 for heat treatment and light spots 36 and 37 for tracking.

The light spot for heat treatment 35 is controlled to pass through the heat treatment track 22 on the first wobble pit 16 or the second wobble pit 17. For this purpose, the tracking light spot 36 and the tracking light spot 37 are controlled so as to pass between the first wobble pit 16 and the second wobble pit 17, that is, the recording / reproducing track 21 by a sample servo method.

The distance between the heat treatment light spot 35 and the tracking light spot 36 is designed to be equal to the distance between the heat treatment light spot 35 and the tracking light spot 37. When the spot 37 passes through the recording / reproducing track 21, the heat treatment light spot 35 passes just between them, and heat treatment is performed along a line passing over the first wobble pit 16 or the second wobble pit 17.

When the disk rotates once, each light spot is located at the position shown on the right side of FIG. That is, it moves to an adjacent track. The amount of movement is equivalent to one track pitch for recording and reproduction. Therefore, when the heat treatment is performed by rotating the disk, the disk is heat-treated along the line above the first wobble pit 16 and the second wobble pit 17.

FIG. 1 shows how the three light beams are formed.
Return to the explanation. The optical head 30 includes a laser 40, a collimating lens 41, a diffraction grating 42, a deflecting beam splitter 43, a quarter-wave plate 44, a mirror prism 45,
It comprises a concave lens 46, an objective lens 10 and a photodetector 47. However, an actuator for driving the objective lens in the focus direction or the tracking direction (radial direction of the disk) is omitted.

The light beam of linearly polarized light (P-polarized light in the figure) emitted from the laser 40 becomes parallel light by the collimator lens 41 and is divided into three beams by the diffraction grating 42. The polarization beam splitter 43 is designed to pass P-polarized light and reflect S-polarized light. Therefore, the light split into three passes through the polarizing beam splitter and is divided into a quarter.
It enters the wave plate 44.

Each light beam is converted into a circularly polarized light by the quarter-wave plate 44, and an angle of 90 degrees is bent by the mirror prism 45. Next, the light is condensed on the surface of the disk 1 by the objective lens 10, and three spots 35, 36, and 37 are formed. The light reflected from the disk 1 is collected by the objective lens 1, reflected by the mirror prism 45, and enters the quarter-wave plate 44. Most of the reflected light is mainly a circularly polarized light component, and is returned to linearly polarized light again by the quarter-wave plate 44. At this time, since the light is s-polarized with respect to the polarization beam splitter 43, the light is reflected upward without being returned to the laser.

The reflected light is magnified by the concave lens 46,
Each of the three beams enters the light detecting element 47. The light detecting element 47 is divided into three regions 47a, 47b, and 47c. The light entering the area 47b corresponds to the light returned from the heat treatment light spot 35 on the disk surface. Region 47
a and the light entering the area 47c correspond to the light from the tracking light spots 36 and 37 on the surface of the disk 1, respectively.

The area 47b of the light detecting element 47 is further divided into four areas, and the focus is detected by calculating the light in the four areas. As one method of focus detection, the focus can be detected by an astigmatic method using an inverted concave lens 46.

The areas 47a and 47c of the light detecting element 47
In the case of this embodiment, each is composed of one region. As shown in FIG. 3, when the tracking light spots 36 and 37 relatively travel on the disk 1 from left to right in the figure, the light amounts entering the areas 47a and 47c of the photodetector 47 become 50 and 50, respectively. It looks like 51. Here, 52 is the level of zero light quantity.

Looking at the tracking light spot 36 in FIG. 3, Δ is slightly lower than the recording / reproducing track 21 in the figure.
s, the first wobble pit 1
When passing through the position where the second wobble pit 17 exists, the modulation degree becomes small at the first wobble pit 16 and becomes the modulation amplitude A1. When passing through the position where the second wobble pit 17 exists, the modulation degree becomes small. Large modulation amplitude B
It becomes 1. The time difference tw at which the modulation amplitude A1 and the modulation amplitude B1 appear is the time during which the tracking light spot 36 passes over the first wobble pit 16 and the second wobble pit 17.

On the other hand, when the tracking light spot 37 is viewed, since it travels slightly lower than the recording / reproducing track 21 by Δs, the modulation degree is large at the first wobble pit 16. The amplitude B2 and the second
When the signal passes through the position where the wobble pit 17 exists, the amplitude A2 has a small modulation factor. The time difference at which the amplitude B2 and the amplitude A2 appear is also tw. The temporal relationship of the modulation of the tracking light spots 36 and 37 by the first wobble pit 16 and the second wobble pit 17 is shifted by t. This is the tracking light spot 37
Is ahead of the tracking light spot 36 by the time t. Here, it is assumed that each light spot moves from left to right on the paper.

In order to cause the light spot 35 for heat treatment to travel along the middle position of the recording / reproducing track 21, it is controlled by one of the following 1), 2) and 3). 1) The modulation amplitudes A1 and B2 when the tracking light spots 36 and 37 pass over the first wobble pit 16 are made equal. 2) The modulation amplitudes B1 and A2 when the tracking light spots 36 and 37 pass over the second wobble pit 17 are made equal. 3) The relationship between the amplitudes when the tracking light spots 36 and 37 pass over the first wobble pit 16 and the second wobble pit 17 is set so that B2-A2 = A1-B1.

However, the distance between the tracking light spots 36 and 37 in the radial direction (the direction perpendicular to the running direction) is L1, and the pit pitch of the first wobble pit 16 or the second wobble pit 17 in the radial direction is LW1, When LW2, L1１n × LW1, L
It must be designed so that 1 ≠ n × LW2 (n is an arbitrary positive integer) is satisfied. If the above are equal, even if the tracking light spots 36 and 37 are shifted in the vertical direction in the drawing, the modulation amplitudes A1 and B2 are always equal, and both values only increase or decrease at the same time. Of course, the relationship between the modulation amplitudes B1 and A2 is the same, and control cannot be performed with this.

Next, a method for realizing the above control 3) will be described with reference to FIG. In FIG. 4, 47a, 4
Reference numerals 7c denote photodetectors in the optical head 30 shown in FIG. Light reflected from the tracking light spots 36 and 37 shown in FIG. 1 enters the light detection elements 47a and 47c, respectively. The signals detected by the light detecting elements are amplified by amplifiers 60 and 61.
The signals amplified by the amplifiers 60 and 61 are input to four sample and hold circuits 62, 63, 64 and 65. The outputs of the sample and hold circuits 62 and 63 are input to a differential amplifier 66, and the difference is calculated.

On the other hand, the outputs of the sample and hold circuits 64 and 65 are input to a differential amplifier 67 and the difference between them is calculated. The outputs of the differential amplifiers 66 and 67 are further input to the differential amplifier 68, and the difference is calculated. Differential amplifier 6
The output of 8 is input to the drive amplifier 69, and the output controls the actuator 70 for tracking the optical head. Reference numeral 71 denotes a timing signal generator which supplies sample and hold timing signals p1, p2, p3 and p4 to the sample and hold circuits 62, 63, 64 and 65. The sample hold circuit 64 has t1 + nT (n
Is a positive integer), and the timing signal p1 is supplied to the sample and hold circuits 62, 65, and 63, respectively.
1 + t + nT, t1 + tw + nT, and t1 + t + tw + nT (n is a positive integer) at timing signals p2, p3, p
4 are supplied.

The means for generating each of these timing signals is omitted here for the sake of simplicity, but clock pits (omitted from the pit arrangement diagram of the disk) arranged on the sample servo type disk are shown. Based on the timing signal generated and the signal light amounts 50 and 51 when passing through the first wobble pit 16 and the second wobble pit 17.
Can be generated based on the change in

Therefore, the timing signal p1 (= t1 + n)
T), sample and hold circuit 6 for sample and hold
4 outputs the modulation amplitude B2 shown in FIG. Similarly, modulation amplitudes A1, A2, and B1 are output from sample and hold circuits 62, 65, and 63 that sample and hold with timing signals p2, p3, and p4, respectively.

The differential amplifier 67 outputs the difference between the modulation amplitudes B2 and A2, and the differential amplifier 66 outputs the difference between the modulation amplitudes A1 and B1. The differential amplifier 68 further outputs a difference between these outputs, and the actuator 70 is driven according to the output. That is, the value of the modulation amplitude B2-A2 = A1-B1
The actuator is driven so that When the actuator is controlled in this way, the light spot for heat treatment 35 shown in FIG.
A heat treatment can be performed just above the wobble pit 17 and just between the recording / reproducing tracks 21.

The above is the modulation amplitude value B2-A2 = A1-B1
The means for controlling the actuator has been described so that A1 = B2 or B1 described in 1) and 2) above.
The control of 1 = A2 can be similarly performed.

In order to perform a heat treatment between recording tracks for a DWDD disc and to smoothly perform a DWDD operation,
It is necessary to perform a heat treatment between the recording tracks. The narrower the heat treatment width, the narrower the track pitch and the higher the density. In order to perform a heat treatment with a narrow width, in the optical disc heat treatment apparatus of the present invention, it is desirable to use a short wavelength laser having a wavelength of the laser 40 of 500 nm or less.

Further, a high NA objective lens (for example, NA =
It is also effective to use 0.8) to narrow the beam spot. In using the high NA objective lens, the optical disk heat treatment apparatus of the present invention irradiates a light beam from the recording layer forming side of the disk to avoid distortion of the beam spot due to aberration even if the disk is tilted. When light is injected through the substrate, especially when using an objective lens with a high NA, a change in the thickness of the substrate may cause a focus shift, or a coma aberration may occur due to the tilt of the disk, and a good heat treatment may be performed. Is difficult.

Further, in the optical disk heat treatment apparatus shown in FIG.
Of the three light spots 35, 36, 37, the heat treatment light spot 35 is designed to be smaller than the tracking light spots 36, 37. The heat treatment light spot 35 is desirably as small as possible, but the tracking light spots 36 and 37 need to have an appropriate size.

When the tracking light spots 36 and 37 pass near or immediately above the first wobble pit 16 and the second wobble pit 17, the light amount of 50 to 5
This is because the modulation amplitudes A1, A2, B1, and B2 of 1 need to be values suitable for tracking control. For example, when LW1 = LW2 = 1.2 μm, the diameters of the first wobble pit 16 and the second wobble pit are 0.4 to 0.5.
6 μm is desirable, and the tracking light spots 36, 3
The spot size of 7 has a half width of 0.35 μm to 0.4.
A spot size of 5 μm is desirable. It is desirable that the light spot 35 for heat treatment be narrowed to 0.3 μm or less.

A method of making the heat treatment light spot 35 smaller than the tracking light spots 36 and 37 as described above will be described with reference to FIG. FIG. 5 shows a part of FIG. 1, and the numbers of the respective parts correspond to those of FIG. Reference numeral 80 in FIG. 5 is a view of the diffraction grating 42 viewed from the light incident direction. The portion of the diffraction grating 42 where the grating is actually formed is the diffraction region 81 near the center. Parallel light is incident on the diffraction grating 42 in a region indicated by a broken line 82. Only the light that has passed through the central part is
Diffracted in three directions. The first-order diffracted light of the diffracted light becomes the tracking beams 32 and 34.

The tracking beams 32 and 34 become only a part of the light incident on the diffraction grating 42 and pass only a part of the objective lens. Therefore, the substantial aperture, that is, the NA value is small. On the other hand, portions other than the diffraction region 81 of the light beam incident on the region indicated by the broken line 82 of the diffraction grating 42 are not diffracted, and therefore enter the objective lens while maintaining the same light beam diameter. Since this light beam, that is, the heat treatment beam 33, enters almost the entire area of the objective lens, the aperture degree increases and the spot diameter decreases.

By using the diffraction grating 42 having a diffraction function only at the center as described above, the first-order diffracted light, that is, the tracking light spots 36 and 37 formed by the tracking beams 32 and 34 can be changed to the heat treatment light spots. It can be smaller than 35, and each light spot optimal for tracking and heat treatment can be formed. Further, since the tracking beams 32 and 34 are first-order diffracted lights of light incident only on the diffraction region 81 of the diffraction grating 42,
The light intensity is lower than that of the heat treatment beam 33.

The intensity of the tracking beams 32 and 34 and the heat treatment beam 33 can be changed by changing the area of the diffraction region 81 or changing the ratio of the primary light by designing the diffraction grating. Tracking beam 32, heat treatment beam 3
3, and the ratio of the light intensity of the tracking beam 34 is desirably about 1: 8: 1. This is because the intensity required for tracking may be lower than the light intensity used for the heat treatment. Numeral 84 indicates the state of the spot formed on the disk surface, and arrow 31 indicates the rotation direction of the disk. Tracking light spots 36 and 3
The direction of the diffraction grating of the diffraction region 81 is also inclined with respect to the disk surface so that 7 has a positional relationship inclined with respect to the running direction 85 of the disk, so that each spot is formed as shown in FIG. are doing.

Using the optical disk heat treatment apparatus having the above-described configuration, a heat treatment was attempted on a sample servo disk having a recording / reproducing track pitch of 0.6 μm using a blue semiconductor laser of 410 nm and an objective lens of NA 0.85. When the linear velocity of the disk was 5 m / s, and the total light power of the tracking beams 32 and 34 and the heat treatment beam 33 on the disk surface was 8 mW, the heat treatment was performed. On the imaginary line passing through with a width of 0.2 μm or less, and the reproduction characteristics in DWDD were also good.

In FIGS. 1, 2 and 3 described above, the sample servo disks having no grooves formed on the disks are used. However, the poles shown in FIG. Even in a sample servo disk having a shallow groove, the optical disk heat treatment apparatus can be used without any problem. This is because the groove provided on the disk is not used for tracking the light beam.

Although the diffraction region of the diffraction grating 42 used in the optical disk heat treatment apparatus of the present application is circular, the diffraction region shown in FIG. 6A is changed according to the beam profile of the light beam incident on the diffraction grating 42. Oval, or Figure 6B
And an optimal spot for heat treatment and tracking can be formed on the optical disc.

In this embodiment, the radial distance L1 between the tracking light spots 36 and 37 is 1/2 of the radial pit pitch LW1 or LW2 of the first wobble pit 16 or the second wobble pit 17. Although the case is shown, L1 ≠ n × LW1, L1 ≠ n × LW
As long as condition 2 is satisfied, control is possible without any problem. FIG. 7 shows an example of such a beam spot. In FIG. 7, L1 is approximately 3/4 of the distance between LW1 and LW2.

(Embodiment 2) FIG. 8 shows a case of the second embodiment. Corresponding numbers are the same as in the first embodiment, and a description of the numbers will be omitted. In the case of the second embodiment, the radial distance L1 between the tracking light spots 36 and 37 is equal to the distance LW1 between the first wobble pits 16.
Alternatively, this is the case where the distance is equal to the distance LW2 between the second wobble pits 17.

In the first embodiment, L1 ≠ n × LW1, L1
Although it has been described that control is not possible unless ≠ n × LW2, even when L1 = n × LW1 and L1 = n × LW2, 47a and 47c of the photodetector 47 are each set to 2
The tracking beams 32 and 34 can be made to travel along virtual lines on the first wobble pit 16 or the second wobble pit 17, respectively, by dividing them and using the differential signals. That is, when the tracking light spots 36 and 37 pass over the first wobble pit 16 or the second wobble pit 17, primary light is generated by the pit diffraction effect. This primary light component can be captured by the photodetectors 47a and 47c, which are divided into two, to generate a tracking error signal.

This will be described below with reference to FIG. In FIG. 8, the signals output from the respective divided areas of the area 47a of the photodetector 47 are d and e,
The signal of 7c is f and g. The signals d and f are added by the addition amplifier 90, and the signals e and g are added by the addition amplifier 91. These outputs are subtracted by a differential amplifier 92, and this output signal is input to a drive amplifier 93 to drive an actuator 94 to control the light beam spot in the radial direction. For example, when the tracking light spot 36 passes over the first wobble pit 16 and passes just above, the signals d and e become equal. The light entering the detection element 47a becomes asymmetric with respect to the two-divided area (shown in a half-moon shape in FIG. 8), and a difference appears between d and e. Similarly, there is a difference between the signals f and g. If d + f = e + g is controlled as described above, each tracking light spot passes over each wobble pit. Therefore, the heat treatment spot also passes over the wobble pits, and heat treatment can be performed between the recording and reproduction tracks.

Here, in the circuit configuration of FIG.
The differential amplifier denoted by reference numeral 1 has a sample-and-hold function, and the sample-and-hold timing is when passing through each wobble pit.

As described above, the optical disk heat treatment apparatus of the present configuration was also able to heat-treat a DWDD disk with good tracking characteristics.

[0064]

As described above, the optical disk heat treatment apparatus of the present invention can perform a heat treatment between recording and reproduction tracks with a heat treatment width sufficiently narrower than the track pitch, and can perform a heat treatment while maintaining stable tracking characteristics.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical disk heat treatment apparatus of the present invention.

FIG. 2 is a diagram showing an irradiation position relationship of a light beam according to the present invention.

FIG. 3 is a diagram showing a change in reflected light when the light beam of the present invention travels.

FIG. 4 is a diagram showing a circuit configuration of an optical disk heat treatment apparatus of the present invention.

FIG. 5 is a diagram showing functions of a diffraction grating used in the optical disk heat treatment apparatus of the present invention.

FIG. 6 is a view showing another embodiment of the diffraction grating used in the optical disk heat treatment apparatus of the present invention, wherein A is an example of an ellipse and B is an example of a rectangle.

FIG. 7 is a diagram showing a positional relationship between a light beam of the present invention and each wobble pit.

FIG. 8 is a view for explaining a second embodiment of the optical disk heat treatment apparatus of the present invention.

FIG. 9 is a diagram showing a configuration of an optical disk.

FIG. 10 illustrates a conventional heat treatment.

FIG. 11 is a diagram of a sample servo type disk provided with an extremely shallow groove portion

[Figure 12] Diagram of sample servo disk without grooves

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical disk 2 Substrate 3 1st dielectric layer 4 Recording layer 5 2nd dielectric layer 6 Protective coating layer 7 Groove part 8 Land part 9 Laser beam 10 Objective lens of heat treatment apparatus 11 Step between land and groove 12 Side of groove part Fluctuation 13 servo area 14 data area 15 segment area 16 first wobble pit 17 second wobble pit 19, 21 recording / reproducing track 20, 22 heat treatment track 30 optical head 31 disk rotation direction 32, 34 tracking beam 33 heat treatment beam 36 , 37 Tracking light spot 35 Heat treatment spot 40 Laser 41 Collimating lens 42 Diffraction grating 43 Deflection beam splitter 44 Quarter wave plate 45 Mirror prism 46 Concave lens 47 Photodetector 50, 51 Light quantity 52 Light quantity 0 level 1, B1, A2, B2 Modulation amplitude 60, 61 Amplifier 62, 63, 64, 65 Sample hold circuit 66, 67, 68, 92 Differential amplifier 69, 93 Drive amplifier 70, 94 Actuator 71 Timing signal generator 80 Diffraction grating 81 Diffraction region 83 Diffraction direction 90, 91 Additive amplifier

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koichiro Nishikawa 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Hirotake Ando 3- 30-2 Shimomaruko, Ota-ku, Tokyo F-term (for reference) in non-corporation company 5D075 EE03 GG11 GG16 GG20

Claims (6)

[Claims] 1. An optical disk heat treatment apparatus, comprising: dividing a laser beam into a plurality of optical paths; performing heat treatment on the optical disk with one of the divided beams; and performing tracking with another divided beam. 2. A heat treatment apparatus for an optical disc, comprising: a substrate; and a recording layer disposed above the substrate, wherein the apparatus performs a reproduction of an information signal using light incident from the substrate side. An optical disk heat treatment apparatus, comprising: dividing an incident laser beam into a plurality of optical paths; performing heat treatment on the recording layer with one of the divided beams; and performing tracking with another divided beam. 3. The optical disk heat treatment apparatus according to claim 1, wherein the optical disk recording / reproducing tracking system is a sample servo system. 4. The optical disk heat treatment apparatus according to claim 1, wherein a spot size of the divided light used for the heat treatment is smaller than a spot size of the divided light used for the tracking. 5. The optical disk heat treatment apparatus according to claim 1, wherein the wavelength of the laser light is 500 nm or less. 6. An optical disk using a domain wall movement detection method (DWD).
The optical disk heat treatment apparatus according to any one of claims 1 to 5, which is a magneto-optical disk of D).