JPH09161337A - Optical disk initializing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical disk initializing device capable of initializing two layers of the phase transition type opticals disk of large capacity whose recording layer is constituted of two layers at a time or two sheets of the phase transition type optical disk constituted of an ordinary one recording layer simultaneously and also capable of initializing the recording layers without the unevenness. SOLUTION: This device is provided with a rotating mechanism 40 rotating an optical disk 5 while holding it, a high output semiconductor laser 1, a collimating lens 2 collimating laser luminous fluxes, a half mirror 4 splitting the laser luminous flux into two parts, first and second objective lenses 11, 12 converging the split parallel luminous fluxes on the optical disk 5 and first and second focusing mechanisms allowing the first and second objective lenses 11, 12 to focus the luminous fluxes from the high output semiconductor laser 1 on the optical disk 5 by making first and second low output semiconductor lasers 21, 31 light sources and a transfer mechanism 41 relatively displacing the optical disk 5 in the radial direction. Then, this device initializes two recording layers simultaneously by making a longitudinal direction of activating layer in the high output semiconductor laser 1 correspond to a direction orthogonal to track of the optical disk 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk initialization apparatus having a phase-change recording layer, and more particularly to initialization of a large-capacity optical disk having two phase-change recording layers and two disks. The present invention relates to an optical disk initialization device that enables simultaneous initialization of a phase change optical disk.

[0002]

2. Description of the Related Art In an optical disk having a phase change type recording layer, a crystal layer of a recording material is irradiated with light to change the light irradiation portion to an amorphous phase for recording. Therefore, the recording layer must be a "crystalline layer" in the initial state (a state in which optical recording is possible). Since this recording layer is generally formed by sputtering or the like, it is in an "amorphous phase" at the manufacturing stage. Therefore, an "initialization process" for crystallizing the entire recording layer is required.

In the technique disclosed in Japanese Examined Patent Publication No. 7-52526, the laser beam is divided into two and then focused on the optical disc as a superposition interference beam. Then, the direction of the interference fringes is parallel to the circumferential direction of the disc, and the pitch of the interference fringes is
It is set to 20 μm or less. The effect is to prevent the generation of microcracks in the heat insulating layer during initialization.

In addition, the light from the high power semiconductor laser is
Focus on the recording layer as a 2 μm x 95 μm light spot,
It has been reported that good initialization is possible by scanning the optical disk while rotating it in the radial direction (The 5th Phase Change Recording Workshop: Symposium Proceedings 3)
0, 1993).

[0005]

As an optical disk having a phase-change type recording layer, one having a recording layer formed on one side of an optical disk substrate has been conventionally used. However, as the demand for increasing the memory capacity has increased, a method of doubling the memory capacity by using two optical discs bonded together has come to be considered. That is,
In this method, the recording layers substantially exist on the front and back of the optical disc, and the capacity is doubled.

When an optical disc having two recording layers is initialized, a conventional initialization device is used to first initialize the first recording layer, then turn the disc over and set it again to the second recording layer. Will perform initialization of the recording layer of
It becomes a big problem at the time of manufacturing an optical disk such as turning over the disk and doubling the time required for initialization.

The present invention has been made in view of the above circumstances, and in the optical disk initializing apparatus according to the first aspect, it is possible to simultaneously perform the initial crystallization process on two recording layers or two optical disks. The purpose is to

Further, in the optical disk initializing device according to the second aspect of the present invention, it is another object of the present invention to further increase the condensing power on the optical disk surface to significantly reduce the initial crystallization processing time. .

Further, in the optical disk initializing device according to the third aspect of the present invention, the object is to perform efficient crystallization by reducing the size of the focused spot in the longitudinal direction to increase the optical power density. To do.

Further, in the optical disk initializing device according to the fourth aspect, uniform crystallization energy is applied to the entire surface of the optical disk to be crystallized, so that uniform crystallization is performed over the entire surface of the disk. It is intended.

[0011]

In order to achieve the above object, the present invention provides a rotating mechanism for holding and rotating a phase change type optical disk, a high power semiconductor laser, and a laser beam from the high power semiconductor laser. A collimating lens for collimating; a half mirror for splitting the light flux collimated by the collimating lens into two; a first objective lens for focusing each of the parallel light flux split by the half mirror on the optical disc; A second objective lens and a first
For focusing the light flux from the high-power semiconductor laser on the optical disk with respect to the first objective lens and the second objective lens respectively using the low-power semiconductor laser and the second low-power semiconductor laser as light sources. A first focusing mechanism and a second focusing mechanism, and a feed mechanism for relatively displacing the optical disc in the radial direction with respect to the focusing positions of the first objective lens and the second objective lens. The two recording layers are simultaneously initialized by making the longitudinal direction of the active layer in the high-power semiconductor laser correspond to the track orthogonal direction of the optical disk.

A rotating mechanism for holding and rotating the phase change type optical disk, a first high power semiconductor laser and a second high power semiconductor laser, a first high power semiconductor laser and a second high power semiconductor laser. A first collimator lens and a second collimator lens for collimating the respective laser light fluxes from the semiconductor laser, and respective light fluxes collimated by the first collimate lens and the second collimator lens on the optical disk. A first objective lens and a second objective lens for converging light, and a first low-power semiconductor laser and a second low-power semiconductor laser as a light source for the first objective lens and the second objective lens, respectively. On the other hand, a first focusing mechanism and a second focusing mechanism for respectively focusing the light flux from the high-power semiconductor laser on the optical disc, and the first focusing mechanism and the second focusing mechanism. A feed mechanism for relatively displacing the optical disc in the radial direction with respect to the focusing position by the object lens and the second objective lens, and the longitudinal direction of the active layer in the high-power semiconductor laser is orthogonal to the track of the optical disc. It is characterized in that two recording layers are simultaneously initialized in correspondence with the directions.

An anamorphic optical system for expanding a parallel light flux in the longitudinal direction of the active layer of the high-power semiconductor laser is arranged in the optical path between the collimator lens and the objective lens. It is a thing.

Further, the rotating mechanism is of a CLV rotating type.

With the above configuration, the light flux of the high-power semiconductor laser is divided into two, and each light flux is condensed by the objective lens and irradiated on the recording layer, so that two recording layers or two optical disks are provided. Can be initialized at the same time.

Further, if two high-power semiconductor lasers are used, the focusing power on the optical disk surface can be further increased, and the initial crystallization processing time can be greatly shortened.

Further, if the anamorphic optical system is used, the parallel light flux in the longitudinal direction of the active layer of the high-power semiconductor laser is enlarged, so that the focused spot shape becomes smaller in the longitudinal direction, and the optical power density is reduced. Is increased and crystallization can be performed more efficiently.

Further, the rotation mechanism is set to CLV (Consta
If the nt linear velocity (rotation) type is used, the output of the high-power semiconductor laser can be set constant and uniform crystallization energy can be applied to the entire surface of the optical disk to be crystallized. It will be possible to crystallize evenly throughout.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the present invention will be described below with reference to the drawings. As shown in FIG. 1, an optical disc initializing apparatus according to the present invention initializes each recording layer of a large capacity phase change type optical disc having two recording layers by simultaneously crystallizing and irradiating a high power semiconductor laser. A device for rotating an optical disk, a high-power semiconductor laser,
A collimator lens, an anamorphic optical system, a half mirror that splits the parallel light flux from the anamorphic optical system into two, two objective lenses that focus the split parallel light flux on each recording layer, and these objective lenses It has a focusing mechanism for adjusting the condensing position of the optical disc to the recording layer and a disc feeding mechanism.

More specifically, the rotating mechanism 40 holds and rotates the phase-change type optical disk to be initialized, and the high-power semiconductor laser (hereinafter, referred to as high-power LD) 1 has the thermal energy required for crystallization. The length of the active layer (the direction corresponding to the minor axis direction in the elliptical far-field pattern) is longer than that of a low-power semiconductor laser. The collimator lens 2 collimates the laser light flux from the high power LD 1, and the anamorphic optical system 3 is an optical system that expands the light flux only in the longitudinal direction of the active layer of the high power LD 1. The half mirror 4 splits the incident light flux into two, and the objective lenses 11 and 12 focus the respective split parallel light fluxes on the phase change recording portions 51 and 53 of the optical disk 5.

The focusing mechanism is a low power semiconductor laser 2
1 and 31 are used as light sources, and focusing control for individually focusing the two split light beams from the high-power LD 1 on the recording units 51 and 53 is performed. The feeding mechanism moves the optical disc to be initialized in the radial direction with respect to the focusing position by the objective lens. In the above, the longitudinal direction of the active layer of the high power LD 1 is arranged so as to correspond to the direction orthogonal to the track of the optical disc.

The anamorphic optical system 3 may be a combination of a pair of cylinder lenses having a power only in the longitudinal direction of the active layer of the high power LD 1 so as to form an afocal system. The LD1 is composed of a pair of prisms having a refracting action only in the longitudinal direction of the active layer. Further, the anamorphic optical system 3 may be a single optical system fixedly incorporated into the apparatus, but the anamorphic optical system can be composed of a plurality of interchangeable optical elements, each optical element being approximately 2 to 4 times as large. It is possible to have different luminous flux expansion magnifications in the range of.

The focal length of the collimator lens 2 for collimating the laser light flux from the high power LD 1 is the objective lens 1
A range of 1 to 2 times the focal length of 1 and 12 is preferable. A CLV rotation system is suitable as a rotation mechanism for rotating the optical disk.

The initialization device of this embodiment is capable of initializing various phase change type optical disks. For example, recording portions 51 and 53 are formed on the polycarbonate substrates 50 and 54, and the recording portions 51 and 53 are bonded by the adhesive 52. It is possible to simultaneously initialize the phase change type optical disc 5 having two recording layers. In this case, as the layer structure of the recording portions 51 and 53, a lower protective layer which is a dielectric layer of ZnS-SiO ₂ with a thickness of 1800Å and a Ag-In-Sb-T layer with a thickness of 200Å are formed on a polycarbonate substrate.
Recording layer as e layer, thickness: 250 Å with ZnS-SiO ₂
Upper protective layer, which is the dielectric layer of Al, thickness: 1000Å Al
The initialization of the optical disk 5 having the reflection layer which is an alloy layer can be realized well (the initialization light is incident from the polycarbonate substrate side). In this case, the optical disk 5 may be two phase-change type optical disks instead of being bonded.

Next, the operation of this embodiment will be described. The beam waist diameter when the laser beam is focused is inversely proportional to the beam diameter incident on the optical system. The larger the beam system, the smaller the focused beam waist diameter. Become. In the semiconductor laser, the length of the active layer is large compared to the width, and the divergence angle of the emitted light beam is small in the longitudinal direction of the slipping layer. Therefore, when the laser light flux from the semiconductor laser is made parallel by the collimating lens, the diameter of the parallel light flux becomes large in the width direction of the active layer and becomes small in the longitudinal direction.

Therefore, the shape of the light spot obtained by condensing the parallel light beam as it is with the objective lens is generally an elliptical shape whose major axis is the longitudinal direction of the active layer. When the major axis of the light spot shape becomes extremely long, the energy density of the light spot becomes small. As a result, in order to increase the energy density, a high output power LD (semiconductor laser) is required for initialization. Therefore, in this embodiment, since the anamorphic optical system is arranged between the collimator lens and the objective lens and the luminous flux diameter in the longitudinal direction of the active layer is enlarged, the major axis length of the light spot is shortened and the energy density is high. Become. Further, since the optical disk initialization apparatus of this embodiment has a focusing mechanism for each objective lens, it is possible to always irradiate each recording layer with a spot of an appropriate size, so that the energy density of the light spot is increased. The fluctuation is extremely small.

Specific examples will be further described below. In FIG. 1, reference numeral 5 denotes a phase change type optical disk, which is held by a rotating mechanism 40 and rotates about a central axis. The rotation system of this rotation mechanism 40 is the CLV rotation system, and the optical disk 5 is rotated so that the linear velocity of the light spot irradiation position accompanying the rotation is always constant. The rotation mechanism 40 holding the optical disk 5 is fed at a constant speed in the radial direction of the optical disk 5 by the feeding mechanism 41 together with the optical disk 5.

The high-power LD1 shown in FIG. 1 has a width of 1 μm and a length of 20.
It has an active layer of 0 μm and an output of 2 W. The high-power LD 1 is arranged so that the longitudinal direction of the active layer is orthogonal to the track of the optical disc. The collimator lens 2 collimates the laser light flux from the high-power LD 1 and has a focal length of 4.3 mm and an NA (numerical aperture) of 0.5. The anamorphic optical system 3 is composed of a pair of prisms having a refracting action only in the parallel direction in the longitudinal direction of the active layer of the high-power LD1 (the horizontal direction in FIG. 1), and the longitudinal direction of the active layer of the high-power LD1 of incident parallel light flux The beam diameter is enlarged only in the direction.

An embodiment (not shown) in which the parallel light flux from the collimator lens 2 is directly condensed by the objective lenses 11 and 12 without using the anamorphic optical system 3 is also conceivable. The high-transmittance mirrors 9 and 10 are high-transmittance mirrors that transmit 99% of the laser beam from the high-power LD 1. The objective lenses 11 and 12 transmit the parallel light flux to the optical disk 5.
A lens for focusing light on each of the recording sections 51 and 53, having an effective diameter of 4 mmφ, a focal length of 4.3 mm and an NA of 0.5.

Next, the semiconductor lasers 21 and 31 are of low output, and the luminous fluxes emitted from these lasers are collimated by the collimating lenses 22 and 32, and the polarized beam splitters 23, 33, and 1/4 wavelength plate. 24, 3
4, focusing control is performed by the focus signal generating elements 25 and 35 and the actuators 26 and 36. The focus signal generating elements 25 and 35 are composed of an astigmatism generating optical element including a cylinder lens and a condenser lens and a four-division light receiving element when focusing is performed by, for example, an astigmatism aberration method. The optical disk 5 is initialized by the rotation mechanism 40.
While the optical disc 5 is being rotated, the high-power LD 1 is turned on while operating the focusing mechanism to focus the laser light on the recording portions 51 and 53, and at the same time, the optical disc 5 is fixed in the radial direction by the feeding mechanism 41. It is done by sending at high speed.

(1) A specific example of the anamorphic optical system 3 having a magnification of 4 will be described. The light spot shape of the high-power LD 1 focused on the optical disk 5 was 2 μm in the width direction of the active layer and 50 μm in the length direction of both the objective lenses 11 and 12 as measured by a CCD camera. The linear velocity of the optical disk 5 at the position of the optical spot for initialization is set to 4 m / S, the initialization power (power on each recording unit: mW) by the high output LD 1 and the optical disk 5 by the feeding mechanism 41.
Feed rate (amount of radial displacement per revolution: μm /
The initialization characteristics were investigated by changing r). After initialization, with a semiconductor laser with a wavelength of 780 mm, a linear velocity of 1.3 m / S,
Recording at the recording frequency f ₁ = 0.4 MHz, and then f ₂
= C / N when overwriting at 0.72MHz
(Carrier-to-noise ratio) (dB) and cancellation ratio (strength reduction rate of previous signal when new signal is overwritten) (d
B) was measured, and the state after initialization was observed with a microscope. At this time, the recording power is 12 mW and the bias power is 5 mW. The maximum output of the high-power LD1 corresponds to 700 mW in each recording section on the optical disk. The results are shown in [Table 1]. From this result, it has been found that up to a feed rate of 30 μm / r, good initialization can be performed on both layers simultaneously within the range of the output capability of the high-power LD1.

[0032]

[Table 1]

(2) A specific example of the anamorphic optical system 3 having a magnification of 3 will be described. The actual measurement value of the light spot by the CCD camera is 2 μm × 70 μm. The initialization characteristics were examined in the same manner as described above. The results are shown in [Table 2]. From this result, if the output of the high-power LD1 is maximized (700 mW in each recording unit of the optical disc), good initialization can be performed for both layers even at a feed speed of 50 μm / r, and at least 40 μ
Initialization at m / r can be reliably performed.

[0034]

[Table 2]

(3) A specific example of the anamorphic optical system 3 having a magnification of 2 will be described. The actual measurement value of the light spot by the CCD camera is 2 μm × 95 μm. Similarly, the initialization characteristics were examined. The results are shown in [Table 3]. From this result, the output of the high output LD1 is maximum (700 m in each recording unit).
With W), good initialization is possible for both layers even at a feed rate of 70 μm / r, and initialization at least at 60 μm / r can be reliably performed.

[0036]

[Table 3]

In the above three specific examples, the collimating lens 2 is used.
And the focal lengths of the objective lenses 11 and 12 are both 4.3 m
Since m is set, the collimator lens 2 and the objective lens 11
Alternatively, the imaging magnification of the imaging system configured with the objective lens 12 is equal, and the length of the light spot condensed on the optical disc 5 is the same as that of the active layer in the longitudinal direction of the active layer of the high power LD 1. It is determined by the length and the magnification of the anamorphic optical system 3. Therefore, if the focal length of the collimator lens 2 is made longer than the focal length of the objective lens, the magnification of the image forming system becomes large, so that the anamorphic optical system 3 has the same magnification as those of the three specific examples described above. Also, it is possible to further improve the light-collecting property of the light spot condensed on the optical disc and further increase the energy density of the light spot.

(4) A specific example in which the anamorphic optical system 3 has a magnification of 2 and the collimator lens 2 has a focal length of 8.6 mm and an NA of 0.5 will be described.
The actual measured value of the light spot by the CCD camera is 2 μm × 5
It is 1 μm, which is almost the same as the first specific example. The initialization characteristics were examined as before. The results are shown in [Table 4]. From this result, if the output of the high-power LD1 is increased (550 mW or more in each recording unit), the feeding speed is 40 μm / r.
Therefore, good initialization is possible for both layers.

[0039]

[Table 4]

By thus increasing the focal length of the collimator lens than the focal lengths of the objective lenses 11 and 12, the magnification of the image forming system is increased and the magnification of the anamorphic optical system 3 is combined so that it is transferred onto the optical disc. It is possible to increase the light collection efficiency. However, if the focal length of the collimator lens 2 becomes too large, a high power LD
Since the ratio of the component converted into a parallel light flux in the light flux radiated from No. 1 becomes small, the optical energy cannot be given to the optical disc with a sufficient density. Therefore, it is preferable that the focal length of the collimator lens 2 be in the range of 1 to 2 times the focal length of the objective lenses 11 and 12.

(5) When the anamorphic optical system 3 is not used, the collimating lens 2 has a focal length of 8.6 mm,
A specific example when NA is 0.5 will be described. The actual measurement value of the light spot by the CCD camera in this case is 2 μm × 98 μ
m, and the initialization characteristics were examined in the same manner as described above. The results are shown in [Table 5]. High output L from the results in [Table 5]
Increase the output of D1 (650 mW or more in each recording unit)
By doing so, good initialization is possible for both layers at a feed rate of 30 μm / r.

[0042]

[Table 5]

In the specific examples (1) to (5) described above, the rotation mechanism 40 is of the CLV rotation type, and the relative speed due to the rotation of the optical disk 5 with respect to the light spot is always constant, so that the initialization is performed over the entire area. Therefore, uniform light energy can be always given. Further, the rotation of the optical disc by the rotating mechanism 40 may be at a constant angular velocity, but in that case, the relative velocity associated with the rotation of the optical spot and the optical disc becomes slower toward the inner peripheral side of the disc, so that the initialization required at the outermost peripheral portion of the optical disc. High power LD so that the energy for use can be obtained
It is necessary to set the output settings for. In the embodiment described so far, the optical disc is moved to the objective lens 1 by the feeding mechanism 41.
Although the optical signals are sent in the radial direction of the disk with respect to Nos. 1 and 12, the optical system for initialization may be displaced in the radial direction of the disk with respect to the optical disk.

In order to shorten the time required for the initialization, it is preferable to use a semiconductor laser of higher output as the high output LD1. High power LD instead of high power semiconductor laser
It is possible to double the condensing power of each recording unit by arranging two sets of imaging optical systems for condensing on the recording units 51 and 53 by using two 1's, and it is possible to significantly increase the initialization time. Can be shortened to

[0045]

As described above, according to the initialization device of the first aspect of the present invention, the luminous flux of the high-power semiconductor laser is divided into two, and each luminous flux is condensed by the objective lens to form the recording layer. Since the irradiation is performed on two recording layers, two recording layers or two optical disks can be simultaneously subjected to the initial crystallization process.

Further, according to the initialization device of the second aspect of the present invention, it is possible to further increase the focusing power on the optical disk surface, and to significantly reduce the initial crystallization processing time.

Further, according to the initialization device of the third aspect of the present invention, since the focused spot shape becomes smaller in the longitudinal direction, the optical power density increases and the crystallization can be performed more efficiently.

Further, according to the initialization device of the fourth aspect of the present invention, the output of the high-power semiconductor laser is set to be constant, and uniform crystallization energy is given to the entire surface of the optical disk to be crystallized. It is possible to crystallize uniformly over the entire surface of the disc.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an embodiment according to the present invention.

[Explanation of symbols]

 1 High-power semiconductor laser 2 Collimating lens 3 Anamorphic optical system 4 Half mirror 5 Optical disk 6,7,8 Mirror 9,10 High transmittance mirror 11,12 Objective lens 21,31 Low-power semiconductor laser 22,32 Collimating lens 23,33 Polarizing beam splitter 24,34 1/4 wave plate 25,35 Focus signal generating element 26,36 Actuator 40 Rotating mechanism 41 Feeding mechanism 50,54 Polycarbonate substrate 51,53 Recording unit 52 Adhesive

Claims (4)

[Claims] 1. A rotating mechanism for holding and rotating a phase-change optical disk, a high-power semiconductor laser, a collimator lens for collimating a laser light flux from the high-power semiconductor laser, and a light flux collimated by the collimator lens. A half mirror for splitting the beam into two, a first objective lens and a second objective lens for respectively focusing each of the parallel light beams split by the half mirror on the optical disc,
For focusing the light flux from the high-power semiconductor laser on the optical disk with respect to the first objective lens and the second objective lens respectively using the low-power semiconductor laser and the second low-power semiconductor laser as light sources. A first focusing mechanism and a second focusing mechanism, and a feed mechanism for relatively displacing the optical disc in the radial direction with respect to the focusing positions of the first objective lens and the second objective lens. An optical disk initializing device comprising: a high power semiconductor laser, wherein the longitudinal direction of the active layer corresponds to the track orthogonal direction of the optical disk, and the two recording layers are simultaneously initialized. 2. A rotating mechanism for holding and rotating a phase change type optical disk, a first high power semiconductor laser and a second
High-power semiconductor laser, a first collimator lens and a second collimator lens for collimating the respective laser beams from the first high-power semiconductor laser and the second high-power semiconductor laser, and a first collimator A first objective lens and a second objective lens for respectively focusing the respective light fluxes collimated by the lens and the second collimator lens on the optical disc, a first low-power semiconductor laser and a second low-power semiconductor laser. A first focusing mechanism and a second focusing mechanism for respectively focusing the light flux from the high-power semiconductor laser on the optical disk with respect to the first objective lens and the second objective lens using the output semiconductor laser as a light source. Of the focusing mechanism and the feed for displacing the optical disc in the radial direction relative to the converging positions of the first objective lens and the second objective lens. And a structure, the high output semiconductor longitudinal active layer in the laser in correspondence with the track crossing direction of the optical disk initialization apparatus of an optical disk, characterized by simultaneously initialized two recording layers. 3. An anamorphic optical system for expanding a parallel light flux in the longitudinal direction of the active layer of the high-power semiconductor laser is disposed in the optical path between the collimator lens and the objective lens. The optical disk initialization device according to claim 1 or 2. 4. The optical disk initializing device according to claim 1, wherein the rotating mechanism is of a CLV rotating type.