JPH082809Y2 - Phase change optical disk initialization device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to a phase-change type optical disk initialization device, and in particular, it is performed by irradiating a rotating optical disk with laser light that moves in the radial direction thereof. Regarding the initialization device.

[Conventional technology and its problems]

Conventionally, as this kind of initialization processing method, there is a method in which a disk is put in an oven and subjected to heat processing, but this causes a problem such as substrate deformation.

In addition, there is a method in which a plurality of laser irradiation points are arranged so as to partially overlap in the radial direction of a rotating optical disk, and are moved in the same direction for initialization. In this case, the initialization can be performed in a short time, but there is a drawback that the structure of the optical system becomes complicated and the cost becomes high.

[Purpose of device]

When the rotating optical disc is irradiated with laser convergent light having a predetermined spot diameter to initialize the phase-change optical disc, the irradiation points moving in the radial direction of the optical disc are moved independently of each other. This is performed by combining movement control and displacement control of the objective lens.
At this time, if the actuator is moved by comparing the detected position signal and the analog signal output from the D / A converter, the minimum movement pitch of the actuator is the bit of this D / A converter. Although it is determined by the number and the maximum movement distance, the displacement control of the objective lens is performed so as to compensate the movement of the irradiation point during the movement of the actuator by the displacement of the objective lens.

Further, by controlling the light quantity of the laser in conjunction with the movement of the irradiation point, the irradiation conditions of the laser light to the respective parts of the disk are made substantially the same.

[Means for solving problems]

A phase-change optical disk initialization device for mounting a phase-change optical disk and irradiating a converged laser beam having a predetermined spot diameter to perform initialization processing while the optical disk is rotated. In the radial direction, an actuator that is driven to move stepwise at every minimum movement pitch, an objective lens that is held by the actuator so as to be displaceable at least in the radial direction of the optical disk, and the objective lens in the positional relationship with the actuator. Is moved in one direction in the radial direction at a substantially constant speed in a first period that is proportional to the rotation period of the optical disc, by a predetermined movement width larger than the minimum movement pitch, and within a second predetermined period that follows. Drive this to repeat the reciprocating movement that quickly moves to the other direction in the radial direction and returns to the original position. Object lens driving means, actuator driving means for sequentially driving the actuator so as to complete the movement in the one direction by the minimum movement pitch in the second period, and the laser in the second period. The laser driving means controls the laser so that the second light amount level of the convergent light becomes smaller than the first light amount level of the laser convergent light in the first period.

(Operation) Even when the actuator moves only in steps, it becomes possible to irradiate the desired area of the optical disk with the laser convergent light of at least the first light amount level without interruption.

〔Example〕

FIG. 1 is a block diagram for explaining an embodiment of the device of the present invention. In the figure, 1 is a phase change type optical disc that rotates at a predetermined rotational speed about the rotary shaft 2, on the recording surface 1 ₁ having a pregroove formed in a spiral shape,
The convergent laser light is emitted by the actuator 3.
The actuator 3, the laser 3 _4, the light deflecting means 3 _1, the objective lens 3 _2, objective lens holder 3 _7, 4-split detector
3 _5, the displacement detector 3 _6, and consists of the driving coil 3 ₃ etc., the recording surface 1 ₁ by a laser beam emitted from the laser 3 ₄ into a convergent light
Irradiates a, and detecting the reflected light by the four-divided detector _35. The objective lens 3 ₂ held by the objective lens holder 3 ₇ is moved by the drive coil 3 ₃ acting on the objective lens 3 ₂ so that the arrow a,
It is configured to be movable within a predetermined range in the b direction, that is, the radial direction of the optical disc 1. Further, the displacement detector 3 _6, by detecting the displacement position of the objective lens holder 3 _7,
Detecting a displacement amount from a reference position of the objective lens 3 _2.

Tracking error detecting circuit (hereinafter, referred to as TE detection circuit) 4, 4 enter the light quantity signal outputted from the division detector _35, a TE signal s ₁ indicating a voltage value corresponding to the tracking error relative to the OV predetermined The voltage is applied to _one fixed terminal 51 of the switch 5 via the resistor. Displacement detection circuit 7 receives the detection signal output from the displacement detector 3 _6, the displacement signal s ₂ indicative of the voltage value corresponding to the amount of displacement from the reference position of the objective lens relative to the OV hysteresis circuit 8 It outputs and also the other fixed terminal 5 ₂ of the switch 5 through a predetermined resistor.
Output to. This displacement signal s ₂ is the arrow b of the objective lens 3 ₂ .
The polarity is set so that the level decreases as the direction moves, and conversely the level increases as the arrow a moves. The hysteresis circuit 8 operates according to the characteristic diagram shown in FIG. That is, when the input displacement signal s ₂ becomes equal to or higher than the voltage value V ₁ , the state of the determination signal s ₃ output is set to the “L” state, and the voltage value V ₂
It will be in the "H" state when the following occurs. Reference numeral 9 is a control circuit for processing input / output signals with digital signals in order to give various operation commands, and inputs the judgment signal s ₃ to its input terminal 9 ₄ . The control circuit 9 outputs a light intensity command signal s ₆ for commanding emission light intensity of the laser 3 ₄ from the output terminal 9 ₃ to the D / A converter 13. Laser drive circuit 14, so that the laser 3 ₄ outputs a laser beam of a quantity proportional to the voltage level of the light intensity command voltage signal s ₇ output from the D / A converter 13 supplies a drive current thereto.

Further, the control circuit 9, the objective lens from the output terminal 9 ₆
Displacement command signal s ₉ for displacing 3 ₂ is output. The displacement command signal s ₉ may, by the D / A converter 15 is converted into an analog signal, is applied to the other fixed terminal 5 _second switch 5 as a displacement command voltage signal s _10.

An objective lens driving circuit 6, as described later, and supplies a current to the tracking coil 3 ₃ in order to displace the objective lens 3 ₂ to a position where the voltage to be input becomes OV.

The actuator 3 is a movable arm 19 of the feeder 19.
_It is placed on ₁ and movable in the directions of arrows a and b. This moving range is set so as to cover at least the recording area x of the optical disc 1 in the radial direction, and the position thereof is detected by the potentiometer 17.

The potentiometer 17, for example in a state the objective lens 3 ₃ is in the reference position, OV becomes when the irradiation point was Kitasa has on the inner circumferential side starting point x ₁ of the recording area x of the optical disk 1, the outer peripheral side from this position the actuator position signal s ₁₃ indicating a voltage value proportional to the moving distance and outputs to the input terminal 9 ₉ of the control circuit 9 via an a / D converter 20 to be outputted to the feeder control circuit 18.

The feeder control circuit 18 uses this actuator position signal.
s ₁₃ and the position command signal s ₁₁ output from the output terminal 9 ₇ of the control circuit 9 for setting the position of this actuator are D / A
Position command voltage signal s converted to analog voltage by converter 16
_The feeder 19 is driven so that the voltage values of ₁₂ are equal.

Further, the control circuit 9 outputs a rotation speed command signal s ₄ from its output terminal 9 _{2 in} order to control the rotation speed of the spindle motor 12 axially coupled to the rotation shaft 2 of the optical disk, as described later. The motor control circuit 11 inputs this rotation speed command signal s ₄ via the D / A converter 10, and the spindle motor 12 is rotated so that the rotation speed ω ₀ of the spindle motor 12 is proportional to the level of the rotation speed command signal s _4. Control 12 On the other hand, the spindle motor 12 outputs a rotation information signal s ₅ of 1 pulse per rotation to the input terminal 9 ₁ of the control circuit 9, for example.

Although the structure of the focus control system is omitted, it is assumed that appropriate focus control is being performed during the operation of the above apparatus.

 The operation of the above configuration will be described.

First, when initializing the phase change type optical disc 1,
A case where the reflectance of the disk 1 is low and tracking control cannot be performed will be described.

At this time, the movable terminal 5 _third switch 5 is connected to the fixed terminal 5 ₂ side, the output signal of the control circuit 9 is formed on the basis of the following operations, and processing.

First, from the actuator position signal s ₁₃ , the objective lens 3
The distance of the irradiation point from the rotation axis 2 on the assumption that ₃ is at the reference position, that is, the radius R of the irradiation point is calculated. Then, the rotation speed ω of the spindle motor 12 for making the linear speed at this time the desired linear speed v is calculated by the following equation ω = v / R, and the actual rotation speed ω of the spindle motor 12 is calculated.
A rotation speed command signal s ₄ is output so that ₀ becomes the calculated ω.

Next, the displacement command signal s ₉ and the position command signal s ₁₁ output to control the movement of the irradiation point will be described.

Radius R control circuit 9 calculates are the radial position of the optical axis 3 ₈ of the actuator 3 detected by the potentiometer, the moving velocity only actuator ideally
It is desirable to control so that it becomes va. This moving speed va
Is calculated by the following equation when the actuator 3 is set to move by the pitch P while the optical disc 1 rotates y.

However, T is a rotation period of the optical disc 1, and is a rotation information signal.
It can be calculated by detecting s ₅ .

However, the minimum movement pitch Δx of the actuator 3
₄ is decided by the bit number k of the D / A converter 16. For example, as the optical axis 3 ₈ of the actuator 3 can move the distance l ₁ between the between the starting point x ₁ and the end point x ₂ recording region x, as set most efficiently, the minimum movement pitch [Delta] x ₄ thereof, [Delta] x ₄ = l _1/2 ^K, and the example l ₁ = 50 mm, when a k = 12, minimum movement pitch [Delta] x ₄ becomes 12.2Myuemu. Therefore, when the irradiation spot diameter is 12.2 μm or less, unirradiated portions are generated.

According to the present application, the control circuit 9 comprises, for example, 8 bits and 12 bits.
From each D / A converter 15 and 16 of the bit, FIG.
Each command signal s so that the displacement command voltage signal s ₁₀ and the position command voltage signal s ₁₂ having a voltage waveform as shown in (b) are output.
_It outputs ₉ and s ₁₁ .

The displacement command voltage signal s ₁₀ shown in FIG. 3A has a voltage value Δv ₃ of one step for each detected cycle T of the optical disk.
It increases only up to (2 ⁸ -1) steps. Then, during a predetermined reset time Tr, the sawtooth wave is reduced at the same number of steps by the same number of steps and returns to the original level. Since the objective lens drive circuit 6 displaces the objective lens 3 ₂ so that the sum of the displacement command voltage signal s ₁₀ and the displacement signal s ₂ becomes OV, the objective lens 3 ₂ has a sawtooth displacement command voltage signal.
It vibrates in synchronization with s ₁₀ . Incidentally, it is configured to move in a direction to the arrow b direction when the increase of the objective lens 3 ₂ is displaced command voltage signals s _10, also during reduced.

Therefore, the voltage value Delta] v ₃ is intended to determine the minimum moving pitch [Delta] x ₃ of the objective lens 3 _2, the step voltage setting signal s ₈ output from the output terminal 9 ₅ of the control circuit 9, this minimum movement pitch [Delta] x ₃ Is settable to, for example, 0.6 μm to 2 μm.

The minimum movement pitch [Delta] x ₃ of the objective lens 3 _2, by such linearity of the displacement detector 3 _6, it may be quite possible to vary depending on the displacement position, it is desirable that as much as possible constant.

On the other hand, the position command voltage signal s ₁₂ shown in FIG.
One formed in synchronism with the displacement command voltage signals s _10, at the timing of the level decrease start of the displacement command voltage signals s _10,
The voltage signal has a staircase waveform that increases by n steps. The voltage value Δv ₄ that increases in one step determines the minimum movement pitch Δx ₄ of the actuator 3, and as described above, for example,
It is configured to be 12.2 μm.

The increase step number n is determined so that the control circuit 9 satisfies the following condition n · Δx ₄ <(2 ⁸ -1) Δx ₃ <(n + 1) · Δx ₄ (1).

FIG. 3 (c) is a diagram for explaining the movement of the irradiation point on the optical disc when the displacement command voltage signal s ₁₀ and the position command voltage signal s ₁₂ are output, and the vertical axis indicates the radius. ing.

Assuming now that the actuator 3 follows the change of the position command voltage signal s ₁₂ without delay and follows the movement locus of the dotted line m ₁ ′ near time t ₀ , the irradiation point may show the locus of the dotted line m ₂ ′. To be understood. However, since the mass of the actuator 3 is large, the actual response shows a step response delayed with respect to the change of the position command voltage signal s ₁₂ as shown by the solid line m ₁ , so that the irradiation point follows the locus of the solid line m _2. .

The step response of the actuator 3 is determined by the open-loop transfer function of this control system. In either case,
The movement trajectory until the actuator 3 reaches the target position has similar characteristics. Further, a delay relative to the displacement command voltage signal s ₁₀ of the objective lens 3 _2, and is sufficiently small relative to the delay of the actuator 3, the variation component of the stepwise be described as changes on the line is absorbed.

Therefore, as one method of setting the reset time Tr of the displacement command voltage signal s ₁₀ , the vibration width of the irradiation point during the step movement of the actuator 3 may be set as small as possible.

Further, another method of setting the reset time Tr (the period from time t ₀ to t ₁ ) may be as follows. Assuming that the irradiation point follows the locus of the dotted line m ₂ ′, the time t _{2 at} which the radial position Rn of the irradiation point immediately before the step movement of the actuator 3 is started again when the actuator 3 moves in the b direction is the actuator 3. This is set so that the vibration during the transition of is immediately after the vibration has subsided. By setting in this way, only during the period from the time t ₀ to the time t ₂ including the vibration period of the actuator 3 at the time of transition, for example, FIG.
If the level of the light quantity setting voltage signal s ₇ is lowered to lower the laser output to the light quantity level required for the minimum focusing as shown in (1), the irradiation conditions of the laser light to each part of the optical disc 1 become substantially the same.

However, it is difficult to set the reset time Tr that satisfies the above condition. Because the time t ₂ under the above conditions
Changes according to the change of ΔR shown in FIG. 3 (c), but due to the above inequality (1), this ΔR changes in the range of O <ΔR <Δx ₄ , so that the above condition is satisfied. Is
This is because it is necessary to appropriately set the reset time Tr according to ΔR.

Therefore, as another method of determining the effective reset time Tr, the following may be performed.

As shown in FIG. 3 (e), the reset time Tr is made to coincide with the period during which the vibration of the actuator 3 at the transient time is subsided, and the laser output is set low only during the reset time Tr. If this is done, the position fluctuation range of the irradiation point may become large during the transient state of the actuator 3, and the laser light will irradiate the portion ΔR twice, but the laser light to each part of the optical disc There is no leakage of irradiation, and the irradiation conditions are almost the same.

In the above embodiment, since the actuator 3 maintains the same position during the period Tm shown in FIG. 3, the rotation speed ω ₀ of the spindle motor 12 does not change during this period. Thus, the linear velocity v of the irradiation point is will have the error component of the cycle Tm, during which time a moving distance (Δx ₃ · 2 ^8), the radius R
However, since it is sufficiently small, there is no practical problem.

Further, in the above description, for simplicity, the center of the objective lens 3 _2, oscillates between the position of the optical axis 3 ₈ of the actuator and the arrow b direction a distance ([Delta] x ₃ · 2 ⁸⁾ by a position displaced It has been described as ones, if oscillates around the optical axis 3 _8, the movement locus m ₂ of irradiation points shown in FIG. 3 (c) is, relative movement locus m ₁ of the actuator, relative ([Delta] x ₃ · 2 ⁷⁾ only the only locus moves in the direction of arrow a, the other conditions are unchanged.

As described above, when initializing the phase change type optical disc 1,
The circuit operation in the case where the tracking control cannot be performed due to the low reflectance of the optical disk 1 has been described, but this operation will be temporarily referred to as a non-tracking initialization operation.

Next, the initialization operation when tracking control is possible will be described.

At this time, the movable terminal 5 _third switch 5 is connected to the fixed terminal 5 ₁ side. Therefore, the objective lens drive circuit 6 receives the TE signal s ₁ output from the TE detection circuit 4, and this voltage value is
As a result of controlling to OV, the irradiation point is always brought on the groove or land of the optical disc. Whether the groove or the land is selected depends on the polarity of the TE signal s ₁ , but the TE detection circuit 4 is assumed to have this polarity inversion function.

As a result, the objective lens 3 ₂ is, for displacing progressively in the direction of the arrow b, the level of the displacement signal s ₂ output from the displacement detecting circuit 7 gradually decreases accordingly. The hysteresis circuit 8 monitors the voltage level of this displacement signal s ₂ and
As shown in the figure, the determination signal s ₃ output when this voltage level reaches the voltage value v ₂ is set to the “H” state. Control circuit 9
Outputs a position command signal s ₁₁ that causes the actuator 3 to move in the direction of arrow b at a predetermined moving speed while the determination signal s ₃ is in the "H" state. Since even a tracking control during this period is continued, the objective lens 3 ₂ is moved relatively direction a, the voltage level of the displacement signal s ₂ is the voltage value v ₁ shown in FIG. 2 eventually increases rapidly To the level. At this point, the determination signal s ₃ becomes the “L” state again, and the control circuit 9
Stops the movement of the actuator 3 in the direction of arrow b and maintains its position. As a result of repeating the same operation thereafter, the irradiation point moves in the direction of arrow b in the recording area x of the optical disc 1 under the tracking control.

This series of operations is tentatively called a tracking initialization operation.

As described above, when initializing the phase change type optical disc 1,
The case where the tracking control is impossible and the case where the tracking control is possible have been described, but it is also possible to perform a combination of these operations.

For example, if in low phase change before initialization of the reflectance of the optical disk 1 of the tracking control is not possible, firstly the control circuit 9, the inner circumferential side of the recording area x of the optical axis 3 ₈ of the actuator 3 is the optical disc 1 The feeder 19 is controlled so as to come to the starting point x ₁ . Then perform non-tracking initialization operation described above by outputting a switching signal for connecting the movable terminal 5 ₃ to the fixed terminal 5 ₂ side from the output terminal 9 ₉ of the switch 5. And, thereby at the stage properties in reflectance optical disc 1 is made possible tracking control is changed, again moves the optical axes 3 ₈ of the actuator 3 to the inner circumferential side starting point x ₁ of the optical disc 1, this time of the switch 5 performing the tracking initialization operation to connect the movable terminal 5 ₃ to the fixed terminal 5 ₁ side.

The number of operations and the selection of these operations are appropriately performed according to the characteristics of the optical disc to be initialized.

[Effect of device]

According to the present invention, the movement of the irradiation point is controlled so that the movement of the objective lens compensates for the limited minimum movement distance of the actuator.
It is possible to control the movement of the actuator using the A converter.

Further, by limiting the irradiation energy of the laser convergent light while the objective lens returns to the original position, the irradiation conditions of each part on the optical disk can be made substantially the same.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the device of the present invention, FIG. 2 is an operation explanatory diagram of a hysteresis circuit, and FIG. 3 is a diagram for explaining the operation of the device of the present invention. 1 ... Phase change type optical disk, 2 ... Rotation axis, 3 ... Actuator, 3 ₂ ... Objective lens, 3 ₃ ... Drive coil, 3 ₄
…… Laser, 3 ₅ …… 4-division detector, 3 ₆ …… Displacement detector, 3 ₇ …… Objective lens holder, 4 …… Tracking error detection circuit, 5 …… Switch, 6 …… Objective lens drive circuit, 7 ...... Displacement detection circuit, 8 ...... Hysteresis circuit, 9 ...... Control circuit, 10, 13, 15, 16 ...... D / A converter, 11 ...
… Motor control circuit, 12 …… Spindle motor, 14 …… Laser drive circuit, 17 …… Potentiometer, 18 …… Feeder control circuit, 19 …… Feeder, 20 …… / D converter.

Claims (2)

[Scope of utility model registration request] 1. An initialization device for a phase-change type optical disk, which mounts a phase-change type optical disk and irradiates a converged laser beam having a predetermined spot diameter while rotating the optical disk to perform initialization processing. In the radial direction of the optical disc, an actuator that is driven to move stepwise at every minimum movement pitch, an objective lens that is displaceably held by the actuator at least in the radial direction of the optical disc, and a positional relationship between the actuator In the above, the objective lens moves in one direction in the radial direction at a substantially constant speed for a predetermined movement width slightly larger than the minimum movement pitch in a first period proportional to the rotation period of the optical disc, and then continues for a predetermined time. Within the second period, the reciprocating movement is rapidly repeated in the other radial direction to return to the original position. An objective lens driving means for driving the actuator, an actuator driving means for sequentially driving the actuator so as to complete the movement in the one direction by the minimum movement pitch in the second period, the second And a laser driving means for controlling the laser so that the second light quantity level of the laser convergent light in the period is smaller than the first light quantity level of the laser convergent light in the first period. Phase change optical disk initialization device. 2. The phase according to claim 1, wherein the first light amount level is set to a level required for initialization of the optical disc, and the second light amount level is set to a level required for focusing. Changeable optical disc initialization device.