JP2005276398A - Device and method for initializing phase change optical disk - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phase change optical disk initializing device and initializing method capable of performing high-speed processing. <P>SOLUTION: In this phase change optical disk initializing device for emitting laser beams to a recording film of a phase change optical disk to form a linear laser spot 3 on the recording film and moving the linear laser spot 3 in a disk radial direction while applying rotation control to the disk to thereby change the recording film from an amorphous condition to a crystalline condition for initialization, when a linear scale 8 detects that the disk radial position of the laser spot 3 reaches a prescribed position, a line control method for the disk 4 is changed from a CAV (constant angular velocity) method to a CLV (constant linear velocity) method, or from the CLV method to the CAV method. In addition, at the time of execution of the CAV method, a laser output value is controlled in accordance with the linear velocity of the laser spot. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an initialization apparatus and initialization for a phase change optical disc that performs initialization by changing a recording film of a phase change optical disc from an amorphous state (As-deposition state) to a crystalline state (Crystal state) by laser spot irradiation. More particularly, the present invention relates to a phase change optical disc initialization apparatus and initialization method suitable for initialization of a phase change optical disc that requires a high rotational speed during initialization.

  In general, a recording medium called an optical disk is known as a medium capable of only reproducing information and a medium capable of both recording and reproduction. As the recording / reproducing medium, a recording film is a phase change material. The phase change optical disk is put into practical use.

  This phase change optical disc records and reproduces information by reversibly switching between a crystalline state and an amorphous state having different light reflectivities by thermal control using a laser or the like. The recording film of this phase change optical disk is formed through a sputtering method or the like in the manufacturing process. Immediately after the formation, the recording film has a very low reflectance called an amorphous state and is not suitable for normal use. A process called initialization for changing from an amorphous state to a crystalline state is required.

  A phase change optical disk initialization method according to the prior art is, for example, that a laser beam using a semiconductor laser element of several W class as a light source is perpendicular to the track direction of a disk recording film rotated by a spindle motor through an objective lens. There is a laser spot that is irradiated and focused to be initialized by this laser spot.

  The focused laser spot is a line extending in the radial direction of the disk with respect to the disk recording film, and is sent in the radial direction of the disk by a carriage driven in synchronism with the rotation of the disk. By scanning in a spiral manner with the direction as the scanning direction, the entire surface of the recording film is initialized.

  Here, in general, the rotation control method of the disk-shaped recording medium is a CAV (Constant Angular Velocity) method that keeps the rotation speed of the disk constant regardless of the laser spot position, and a CLV (Constant which has the same linear velocity of the laser spot to the disk). In order to obtain a good initial crystal on the entire surface of the disk recording film, the phase change optical disk initialization apparatus according to the prior art has a constant ratio of linear velocity and laser output and a constant high speed. A CLV system that can be initialized by laser output (high laser emission efficiency) is employed.

Incidentally, as a document describing a technique related to a phase change optical disk initialization apparatus that initializes a phase change optical disk using the laser spot, for example, the following patent publications can be cited.
Japanese Patent Laid-Open No. 10-11826

  In recent years, phase change optical discs have significantly improved data recording / erasing speeds. Therefore, even in the phase change optical disc initialization process, in order to obtain good initial crystallization, higher linear velocity (high rotation speed) and There is a need for high laser power. Further, from the viewpoint of the manufacturing process of the phase change optical disk, a high linear velocity (high rotation speed) of the phase change optical disk is demanded to reduce the tact time.

  However, when the disk is driven at a high rotational speed, the initialization apparatus according to the prior art also increases the surface deflection of the disk as the disk rotational speed increases, and this makes it possible for the laser spot to accurately follow the disk recording film. There was a problem that the initialization characteristics might be deteriorated.

  Further, the initialization apparatus according to the prior art has a problem that when the rotational speed of the disk exceeds about 10,000 [rpm], the rigidity of the disk itself cannot withstand vibration and may burst. Regarding the bursting of the disk, since the limit of the rotational speed is almost determined by the rigidity of the disk itself, it is difficult to increase the limit by strengthening the apparatus side.

  In order to solve the above problem, when the CLV method is adopted, it is conceivable to limit the peak rotational speed so as not to exceed the rotational speed limit of the disk. However, simply limiting the peak rotational speed has an initialization characteristic. There was also a problem that it could get worse.

  An object of the present invention is to solve the above-described disadvantages of the prior art, and an initialization apparatus capable of obtaining good initial crystallization characteristics for a phase change optical disk that requires a high number of revolutions in an initialization process, and It is to provide an initialization method.

In order to achieve the above object, the present invention comprises a laser head for outputting a laser beam and a spindle motor for rotating a phase change optical disk, and irradiates the phase change recording film with the laser beam to form a linear shape on the recording film surface. Phase change in which the recording film is changed from the amorphous state to the crystalline state by moving the linear laser spot in the radial direction of the disc while controlling the rotation of the disc. In the optical disk initialization apparatus, rotation control means for controlling rotation of the disk by a CAV system having the same number of rotations per unit time of the disk or a CLV system having the same linear velocity of the laser spot with respect to the disk, and the laser head Detecting means for detecting the position of the irradiated laser beam in the radial direction of the disk, wherein the detecting means When it is detected that the radial position of the laser spot on the disk has reached a predetermined position, the rotation control means switches the disk rotation control method from the CAV method to the CLV method, or from the CLV method to the CAV method. In the phase change optical disc initialization apparatus, the predetermined radial position is r _x [mm], and the linear velocity of the laser spot by the CLV method with respect to the phase change optical disc is V _CLV [m / s The second feature is that when the disk rotational speed limit value is N _max [rpm], the predetermined radius position r _x is (30000 · V _CLV ) / (π · N _max ) The phase change optical disk initialization apparatus further comprises output control means for controlling the laser beam output of the laser head, wherein the rotation control means is a disk. A third feature is that when the line control method is switched to the CAV method, the output control means controls the laser beam output to an optimum value for initialization according to the linear velocity of the laser spot to the disk by the CAV method. And

The present invention also irradiates a phase change recording film with a laser beam to form a linear laser spot on the surface of the recording film, and moves the linear laser spot in the radial direction of the disk while controlling the rotation of the disk. Thus, in the initialization method of the phase change optical disk that initializes the recording film by changing the recording film from the amorphous state to the crystalline state, when the laser spot reaches a predetermined radial position of the disk, the rotation control method of the disk is changed. Switching from the CAV method with the same rotation speed per unit time of the disc to the CLV method with the same linear velocity of the laser spot to the disc, or from the CLV method with the same linear velocity of the laser spot to the disc per unit time of the disc The fourth feature is that the rotation speed is switched to the CAV method with the same rotation speed. , The predetermined radial position _r x [mm], the linear speed _{V CLV} for phase change optical disk of the laser spot according to the CLV method [m / s], when the disk rotational speed limit value was _{N max} [rpm], the predetermined A fifth feature is that the radial position r _x is (30000 · V _CLV ) / (π · N _max ). In any one of the phase change optical disc initialization methods, the rotation control method of the disc is a CAV. When switching to the system, the sixth feature is that the laser beam output is controlled to an optimum value for initialization in accordance with the linear velocity of the laser spot of the CAV system with respect to the disk.

  The phase change optical disk initialization apparatus and initialization method according to the present invention has a peak rotational speed exceeding a predetermined rotational speed limit at a linear velocity at which a good initial crystal can be obtained when the conventional CLV initialization method is used. Discs are prevented from bursting and a good initial crystal can be obtained by switching to a CAV system in which the radius region where the rotational speed is exceeded is kept below the rotational speed limit and optimizing the laser output. Can do.

  Hereinafter, an embodiment of a phase change optical disk initialization apparatus and initialization method according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of an initialization apparatus according to the present embodiment, FIG. 2 is a schematic view during initialization as viewed from the direction perpendicular to the surface of the disk, and FIG. 3 is a disk rotation speed, linear velocity, and laser with respect to the radial position of the laser spot. It is an output correlation diagram.

  The phase change optical disc initialization apparatus shown in FIG. 1 records a laser spot using a semiconductor laser element having a maximum output of 4 [W] and a wavelength of about 810 [nm] as a light source through the objective lens 2. The film is irradiated and focused to form a linear laser spot 3 having a longitudinal width of about 150 [μm] and a short width of about 1 [μm] with the radial direction 5 of the disc as the longitudinal direction, and accompanying the rotation of the disc Corresponds to the laser head 1 that is autofocus controlled to follow the surface shake of the recording film, the function of moving the laser head 1 in the disk radial direction 5 via the carriage motor 7, and the position detection means of the laser spot 3. A linear scale 8 that detects the radial position 12 of the laser spot 3 and rotates the disk by adsorbing the disk 4 by vacuum pressure. The rotary encoder 10 corresponding to the detecting means includes a spindle motor 9 that detects the disk rotational speed by the rotary encoder 10, the laser output, the laser spot radius position 12, and the disk rotational speed are always controlled, and initialization according to this embodiment is performed. And a microprocessor 11 for executing the method.

  The initialization apparatus configured as described above is perpendicular to the track direction (circumferential direction) of the phase change optical disk 4 as shown in FIG. The laser spot 3 formed by laser irradiation from the laser head 1 by driving the carriage 6 in a state where the disk is rotated in the rotation direction 20 while irradiating the disk with the laser spot 3 extending in the direction (radial direction of the disk). Is sent in the radial direction 5 of the disk while controlling the focus on the recording film, and the recording spot of the phase change optical disk 4 is initialized entirely by scanning the laser spot 3 in a spiral manner. In FIG. 2, the hatched part (reference numeral 21) indicates an uninitialized part, and the part without hatching (reference numeral 22) indicates an initialized (already) part.

  In the phase change optical disk initialization apparatus according to the present embodiment, when the linear scale 8 detects that the laser spot 3 has reached a predetermined radial position of the phase change optical disk 4, the microprocessor 11 rotates the disk 4 by the spindle motor 9. The control method is switched from the CAV method in which the rotational speed per unit time of the disc is the same to the CLV method in which the linear velocity of the laser spot to the disc is the same, or conversely from the CLV method in which the linear velocity of the laser spot to the disc is the same. Switching to the CAV method with the same rotation speed per unit time of the disk is performed. Further, when the rotation control method of the disk is switched to the CAV method, the laser beam output is controlled to an optimum value for initialization according to the linear velocity of the laser spot with respect to the disk by the CAV method. Will be described next.

Here, the conditions for obtaining a good initial crystal in the CLV system are the phase change in which the linear velocity V _CLV is 30 [m / s], the laser power P _CLV is 4000 [mW], and the rotation speed limit N _max is 10000 [rpm]. An optical disk will be described as an example.

  FIG. 3A shows the transition of the disk rotational speed N [rpm] with respect to the radial position r [mm] of the laser spot of the initialization apparatus according to this embodiment, and FIG. 3 shows the transition of the linear velocity V [m / s]. b) The transition of the laser output P [mW] is shown in FIG.

  As shown in FIG. 3A, the disk rotation speed N [rpm] of the initialization apparatus according to the present embodiment is the same as the rotation control method when the radial position is in the range of 0 to 28.65 [mm]. In the range in which the radial position exceeds 28.65 [mm], the rotation control method is the same as the linear velocity (30 [30] [10000 [rpm]). m / s]) and control to switch to the CLV system.

The disk radial position for switching the rotation method will be described. First, the relationship of the following numerical formula 1 is established among the radial position r, the disk rotational speed N, and the linear velocity V.
(Equation 1)

  V = (π · N · r) / 30000

In this embodiment, since the CAV method and the CLV method are continuously switched at a predetermined radius position r _x [mm] so that N ≦ N _max , the switching radius position r _x is given by Equation 2 below. .
(Equation 2)

r _x = (30000 · V _CLV ) / (π · N _max )

Further, the relationship between the linear velocity V _CAV [m / s] and the radial position r _CAV [mm] (≦ r _x ) in the CAV method is given by Equation 3 below.
(Equation 3)

V _CAV = (π · N _max · r _CAV ) / 30000

As described above, the initialization apparatus according to the present embodiment operates to switch between the CAV method and the CLV method at the disk radius position given by the above equation, and the laser output P _CAV [mW] in the CAV method is expressed as a linear velocity. By controlling the laser output as shown in FIG. 3C according to the following formula 4, the peak rotational speed of the disk is suppressed to the rotational speed limit N _max or less so that the ratio of the laser output to the entire recording film is constant. In addition, good initial crystals can be obtained.
(Equation 4)

P _CAV = P _CLV · (V _CAV / V _CLV )

In addition, when a good initial crystal cannot be obtained by Equation 4, it can be considered that the correction laser output P ′ _CAV is obtained by multiplying P _CAV by an arbitrary correction coefficient C as shown in Equation 5 below.
(Equation 5)

P ′ _CAV = C · P _CLV · (V _CAV / V _CLV )
In the present invention, the rotation switching radius position r _x of the rotation method is not limited to the above-mentioned definition of (Equation 2), and a plurality of arbitrary radial positions may be set. In this case, the disk rotation speed N and the laser power P can be set and optimized independently for each radial region so that a good initial crystal can be obtained.

  The phase change optical disc initialization apparatus and initialization method according to the present embodiment has a peak rotational speed limit at a predetermined rotational speed limit at a linear velocity at which a good initial crystal is obtained when the conventional CLV initialization method is used. By switching to a CAV system with a radius region exceeding the rotation speed limit below the rotation speed limit and optimizing the laser output for the disk that exceeds the rotation speed, the disk is prevented from bursting and a good initial crystal is obtained. I can do things.

  Further, in this embodiment, even if the peak rotational speed is below the rotational speed limit of the disk, if the proofing device side has insufficient proof strength against the vibration of the disk due to the rotation, the radius region where the rotational speed is exceeded is determined as the rotational speed of the apparatus. A good initial crystal can be obtained by switching to the CAV system which is suppressed to a number limit or less and optimizing the laser output. Furthermore, in this embodiment, switching to the CAV method and optimization of the laser output are performed for a radius region where conditions for obtaining a good initial crystal are partially different from each other due to restrictions on standards and disk manufacturing. Thus, a good initial crystal can be obtained on the entire surface of the disk.

  The phase change optical disc initialization apparatus and initialization method of the present invention can be applied to a disk-shaped recording medium that requires initialization.

1A and 1B are diagrams for explaining an initialization apparatus and initialization method for a phase change optical disc according to an embodiment of the present invention. The schematic diagram in execution of initialization seen from the surface perpendicular | vertical direction of the disk by this embodiment. FIG. 4 is a correlation diagram of the disk rotational speed, linear velocity, and laser output with respect to the radial position of the laser spot according to the present embodiment.

Explanation of symbols

1: laser head, 2: objective lens, 3: laser spot, 4: phase change optical disc, 5: radial direction of disc, 6: carriage, 7: carriage motor, 8: linear scale, 9: spindle motor, 10: rotary encoder 11: Microprocessor, 12: Laser spot radius position, 20: Direction of rotation.

Claims (6)

A laser head that outputs a laser beam; and a spindle motor that rotates a phase change optical disk. The phase change recording film is irradiated with the laser beam to form a linear laser spot on the recording film surface. An apparatus for initializing a phase change optical disk for performing initialization by changing the recording film from an amorphous state to a crystalline state by moving the linear laser spot in the disk radial direction while controlling rotation,
Rotation control means for controlling the rotation of the disk by a CAV system having the same rotational speed per unit time of the disk or a CLV system having the same linear velocity of the laser spot with respect to the disk, and a disk of the laser beam irradiated from the laser head Detection means for detecting a position in the radial direction, and when the detection means detects that the radial position of the laser spot on the disk has reached a predetermined position, the rotation control means is a disk rotation control system. Is switched from the CAV system to the CLV system, or is switched from the CLV system to the CAV system. 2. The initialization apparatus according to claim 1, wherein the predetermined radial position is r _x [mm], the linear velocity of the laser spot phase change optical disk by the CLV method is V _CLV [m / s], and the disk rotation speed limit value is N An initialization apparatus for a phase change optical disc, wherein the predetermined radial position r _x is (30000 · V _CLV ) / (π · N _max ) when _max [rpm] is set. The phase change optical disk initialization apparatus according to claim 1 or 2, further comprising output control means for controlling a laser beam output of the laser head, wherein the rotation control means switches the disk rotation control system to the CAV system. An apparatus for initializing a phase change optical disc, wherein the output control means controls the laser beam output to an optimum value for initialization according to the linear velocity of the laser spot to the disc by the CAV method. By irradiating the phase change recording film with a laser beam to form a linear laser spot on the surface of the recording film and moving the linear laser spot in the radial direction of the disk while controlling the rotation of the disk, Is a method for initializing a phase change optical disk, wherein the phase is changed from an amorphous state to a crystalline state and initialized.
When the laser spot reaches a predetermined radial position of the disk, the disk rotation control system is switched from the CAV system having the same rotation speed per unit time of the disk to the CLV system having the same linear velocity of the laser spot with respect to the disk. Or a method of initializing a phase change optical disk, wherein the CLV system having the same linear velocity of the laser spot with respect to the disk is switched from the CAV system having the same rotational speed per unit time of the disk. 5. The initialization method according to claim 4, wherein the predetermined radial position is r _x [mm], the linear velocity of the laser spot with respect to the phase change optical disk by the CLV method is V _CLV [m / s], and the disk rotation speed limit value is N _max. A method of initializing a phase change optical disc, wherein the predetermined radial position r _x is (30000 · V _CLV ) / (π · N _max ) when [rpm] is set. 6. The phase change optical disk initialization method according to claim 4 or 5, wherein when the disk rotation control method is switched to the CAV method, the laser beam output is initialized according to the linear velocity of the laser spot with respect to the disk by the CAV method. A method for initializing a phase-change optical disk, characterized in that the control is performed to a value that is optimal for manufacture.

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