JP3380832B2 - Optical disk drive - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc device for writing or reading optical information on an optical disc, and more particularly to an optical disc device capable of preventing a collision between an optical disc and an objective lens.

[0002]

2. Description of the Related Art An optical disc apparatus irradiates a laser beam onto a optical disc from a pickup, detects the reflected light, and
Executes recording / playback of information. The pickup is composed of an objective lens that collects the laser light that illuminates the optical disc, an actuator that drives the objective lens in the optical axis direction, and an optical system that guides the laser light to the objective lens. The optical disc device detects the laser light reflected from the optical disc by a photodetector, and drives the objective lens by an actuator according to the detected defocus amount to execute focus servo control for adjusting the focal position of the laser light. There is.

However, when a large vibration or shock is applied to the optical disk device from the outside, the actuator may not be able to hold the objective lens, and the objective lens may shake greatly. Conventionally, the oscillation of such an objective lens, in order to prevent the objective lens collides into the optical disk, and the movable range of the actuator limit is provided a stopper.

[0004] Another way to prevent a collision between the objective lens and the optical disk is described in JP-A-7-129978. Here, in the optical disk apparatus existing light di <br/> disk within the movable range of the objective lens, by monitoring the drive signal of the actuator always when that drive signal indicates an abnormal value, immediately actuator how to flow the current to away from the optical disc is described. As another method, a dedicated detection means for detecting the position of the objective lens is provided, and the position signal of the objective lens is monitored, and when the signal shows an abnormal value, the optical signal is detected. A method is described in which a current is passed so as to avoid the collision between the disc and the objective lens.

Further, when the focus signal can not be detected, a method that is driven in a direction to release the objective lens from the optical disc is described in JP-A-2-218026.

[0006]

[0007] However, by providing a stopper on the movable range of the objective lens, to so as not to contact the objective lens and the optical <br/> disks configured in when the objective lens is closest to the optical disk Then, although possible to reliably prevent the collision between the optical disk and the objective lens is enabled, the distance between the objective lens and the optical disc (hereinafter, referred to as a working distance) inevitably take a large, thickness of the optical disc apparatus Is an obstacle to doing.

Further, when the method described in Japanese Patent Laid-Open No. 7-129978 is used, the working distance can be reduced, so that the device can be made thin, but the drive current of the actuator is monitored. To
A dedicated drive current detection circuit is required, and also in the case of monitoring the position signal of the objective lens, an objective lens position detector is additionally required, which complicates the device configuration.

Further, in the case of using the method as described in JP-A-2-218026, the collision of the optical disc and the objective lens can be prevented. However, in this method, when the focus signal can not be detected, the objective lens is in fact even without the situation where contact with the optical disc, resulting in executing the saving operation from the optical disc.
Accordingly, because, for example passing over the wound beam spot occurs on the optical disk, even when the focus signal can no longer be detected, would run the evacuation operation from the optical disc, each the time the focus Since it is necessary to perform the pull-in operation, stable signal reading may be hindered.

[0009] The present invention was made to solve the above problems, it is possible to avoid a collision between the optical disk and the objective lens, and an objective lens that can avoid a malfunction due to a scratch or the like on the optical disc An object is to provide an optical disk device having a retracting mechanism.

[0010]

An optical disk apparatus according to claim 1, wherein an objective lens for converging laser light to irradiate the optical disk, and an actuator for driving the objective lens in the optical axis direction of the laser light. A signal detecting means for detecting a focus error signal and a total signal from the reflected light of the laser light from the optical disc; and the actuator so that the laser light is focused on the optical disc based on the focus error signal. And a focus position control means for operating the optical disc device, the signal detection means having a value equal to or greater than a first determination value indicating an abnormal approach of the objective lens and the optical disk. When the focus error signal is detected, a first determination procedure that causes the signal detection means to detect the focus error signal again after a predetermined time. And a second determination unit that is operated by the first determination unit and causes the signal detection unit to detect a total signal when a focus error signal is not detected by the signal detection unit, and an operation performed by the second determination unit. The total signal detected by the signal detecting means is the second
If it is smaller than the judgment value of, the objective lens retracting control means for instructing to drive the actuator in the direction of separating the objective lens from the optical disc is provided.

According to a second aspect of the present invention, in the optical disc apparatus according to the first aspect, the predetermined time is equal to or longer than a time required for a laser beam to pass through a defect having a predetermined size on the optical disc. It is configured.

An optical disk device according to a third aspect is the optical disk device according to the first or second aspect, wherein:
During the period from the detection of the focus error signal of the first judgment value or more by the signal detection means to the elapse of the predetermined time, the drive current of the actuator is set to the signal detection means by the focus of the first judgment value or more. It has a current setting means for setting the current value immediately before the error signal is detected.

An optical disk device according to a fourth aspect is the optical disk device according to the first or second aspect,
A current setting means for setting the drive current of the actuator to 0 from the detection of the focus error signal equal to or more than the first judgment value to the signal detection means until the predetermined time elapses. Is.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a flow chart for explaining a retracting operation of an actuator which is a characteristic part of the present invention.
FIG. 2 is a diagram showing the configuration of the optical disk device. Less than,
The present embodiment will be described based on these drawings.

[0015] In this optical disk apparatus, when receiving the operation start instruction from the control circuit 8, rotates the optical disc 1 by driving the spindle motor 9. When the optical disc <br/> 1 starts to rotate operation, the laser diode (hereinafter, L
2) will start emitting laser light to the optical disc 1. The objective lens 4 makes an oscillating motion, and passes through a focus position where the focus of the emitted light is exactly on the surface of the optical disc 1. At this time, the photo detector (hereinafter, PD
5) receives the reflected light of the recording information reading light beam projected on the optical disc 1 through the objective lens 4,
It is converted into an electrical signal and output. The PD 5 is divided into a plurality of parts, and the differential signal (focus error signal) and the sum signal (total signal) of the plurality of elements are FES.
The signal is generated by the total signal generation circuit 6.

An example of the method of generating the focus error signal and the total signal will be described with reference to FIGS. Figure 5
FIG. 6 is a diagram showing an optical system for receiving the reflected light from the optical disc, and FIG. 6 is a diagram showing the configuration of the PD 5. The reflected light from the optical disk 1 passes through the objective lens 4 and the collimator lens 33 and enters the diffraction element 32. The diffractive element 32 splits the reflected light into two and makes them incident on the PD 5. PD
Reference numeral 5 is divided into three areas A, B, and C as shown in FIG. 6, and a focus error signal and a total signal can be obtained from the amount of light incident on each area as shown in the following equation.
6A shows the case where the optical disc 1 is closer than the focus position, FIG. 6B shows the case where the optical disc 1 is at the focus position, and FIG. It is a figure which shows the mode that the reflected light injects into each area | region, when it is distant from the focus position.

[0017] As shown in the focus error signal = B-C total signal = A + B + C Figure 6 (b), the focus error signal is zero and becomes such a configuration when the objective lens is in-focus position with respect to the optical disk Therefore, a focus error signal output is generated at a position deviated from the in-focus position. The objective lens drive circuit 7 receives a control command from the control circuit 8
In the case of −a, the objective lens 4 is moved so that the focus error signal becomes zero.

As shown in FIG. 3, this focus error signal is output as an S-shaped waveform that changes once positively and negatively when the objective lens 4 passes through the in-focus position. Further, since no voltage is normally output as this focus error signal at the time of focusing, the focus error signal cannot be detected when the focus servo is ON. When such an on-focus state, when the objective lens 4 is moved largely in the optical disc side by an impact from the outside,
The focus error signal is momentarily detected, and then the focus error signal is no longer detected.

In such a case, the predetermined value S _f shown in FIG.
When a focus error signal equal to or more than the (first determination value in claims) is detected (in FIG. 1), the control circuit 8 starts the operation of the objective lens retracting mechanism, and the FES signal and total signal generation circuit 6 After a predetermined time t ₁ , the focus error signal detection operation is performed again (in FIG. 1).

At this time, when the focus error signal indicates a position deviated from the on-focus position (see FIG. 1).
-A), the objective lens drive circuit 7 moves the objective lens so that the focus error signal becomes zero by using the focus servo (-a in FIG. 1).

On the contrary, when the focus error signal cannot be detected (-b in FIG. 1), the FES signal / total signal generation circuit 6 detects the total signal (-b in FIG. 1). Then, the value of this total signal is the predetermined value S _t shown in FIG. 3 (the second judgment value in the claims).
If it is (-a in FIG. 1), the control circuit 8 determines that the objective lens 4 is in the on-focus position (FIG. 1).
-A).

Moreover, determining the value of the total signal when less than a certain value S _t shown in FIG. 3 may come into contact with (in -b Figure 1), the control circuit 8 optical disc 1 is an objective lens 4 Then, the control of the objective lens drive circuit 7 is switched from 7-a in FIG. 2 to 7-b. By control is switched to the 7-b, the objective lens driving circuit 8 is driven so away objective lens 4 from the optical disc (-b in Figure 1).

[0023] In this embodiment, since it has an objective lens retracting mechanism as described above, can be prevented from being damaged optical disc and the objective lens is in contact. Further, in such a case where the scratch on the optical de <br/> disc were present, even when the focus error signal exceeds the predetermined value S _f shown in FIG. 3, the top of the scratch on the optical <br/> disc beam The objective lens retracting mechanism does not operate until the spot passes. That is, when the objective lens and the optical disk is no possibility of contact,
Order not driven away the objective lens from the optical disc, it is possible to stable signal reading.

In the present embodiment, the signal detecting means in the claims is composed of the FES and the total signal generating circuit 6, and the focus position controlling means, the first judging means and the second judging means are provided .
The control unit 8 comprises a fixing unit , an objective lens retraction control unit, and a current setting unit.

Next, the predetermined time t in the above embodiment.
The setting of ₁ will be described. In addition, here, the parameters are described by the following symbols.

The maximum thrust acceleration alpha ₁ of the working distance WD (m) actuator (m / s ²⁾ objective lens retracting mechanism of the acceleration α ^₂ (m / s ₂₎ of the optical disc acceleration α ₃ (m / s ²⁾ optical disc the diameter D of the upper wound (m) (when passing through the wound) optical disk linear velocity V _d (m / s) first, the optical disc 1 is approaching the maximum acceleration towards the objective lens 4, the actuator also maximum thrust in an optical disk 1
Consider the time when the objective lens 4 and the optical disc 1 do not come into contact with each other.

(1) The actuator has the maximum thrust acceleration.
T ₁ seconds when approaching the optical disc 1: distance traveled by (t ₁ seconds until the objective lens retracting mechanism starts operating (the predetermined time described above)) is, (1/2) alpha ₁ t ₁ ² Is.

[0028] (2) t ₁ seconds after the Ri control switches, t ₂ -t ₁ second after the objective lens retracting mechanism is operated (t ₂ seconds:
Further in time) the objective lens 4 is closest to the optical disk 1
The distance traveled to is α ₁ t ₁ (t ₂ −t ₁ ) − (½) α ₂ (t ₂ −t ₁ ) ² (2) ′ Therefore, the actuator advances in t ₂ seconds.
The total distance ( actuator position after t ₂ seconds) is (1) +
From (2), it is (1/2) α ₁ t ₁ ² + α ₁ t ₁ (t ₂ −t ₁ ) − (1/2) α ₂ (t ₂ −t ₁ ) ² .

[0029] (3) the moving distance of t ₂ seconds after the light disk is a ^{_{(1/2) α 3 t 2 2}} .

[0030] Here, (2) '+ (3) <If WD, when the optical disk 1 and the objective lens 4 is calculated therefrom t ₁ does not _{collide, t 1 <√ [2WDα 2} 2 / {α 1 2 (Α ₁ + α ₂ ) + α ₁ (α ₂ ² + 2α ₂ α ₃ ) + α ₂ ² α ₃ }].

[0031] (4), the time the wound is present on the optical disc the beam spot passes are D / Vd (s), during which time it is desirable not to perform the evacuation operation.

From the above, the range of the predetermined time (t ₁ ) is D / V _d <t ₁ <√ [2WD α ₂ ² / {α ₁ ² (α ₁ + α ₂ ) + α ₁ (α ₂ ² + 2α ₂ α ₃ ). + Α ₂ ² α ₃ }]. By setting as large as possible the t _1, also allows the corresponding relative of larger optical disc scratches (large scratches value of the D), also by setting smaller the t _1, It is possible to more reliably prevent the contact between the objective lens and the optical disc.

In the above embodiment, the actuator drive current is not shown until the predetermined time t ₁ elapses after the value of the focus error signal S _f shown in FIG. 3 is detected. However, as shown in FIG. 4A, the drive current of the actuator until the predetermined time t ₁ elapses may be kept at the current value immediately before the value S _f of the focus error signal is detected. . Thus, when the abnormality of the focus error signal is generated by a scratch or the like of the optical disc, the position of the optical de <br/> disc 1 and the position of the objective lens 4 is greatly shifted during the predetermined time t ₁ has elapsed Since it does not occur, it becomes easy to adjust to the on-focus position after that.

Further, as shown in FIG. 4B, the drive current of the actuator is zero until a predetermined time t ₁ elapses after the value of the focus error signal has detected a certain value S _f shown in FIG. if the, during acceleration of the actuator is 0, the time until the objective lens 4 and the optical disk 1 collides longer. Therefore, as shown in the following equation,
It is possible to lengthen the time t ₁ until retracting the objective lens 4 from the optical disc 1 can cope with more scratches larger optical disc <br/> click.

T ₁ <√ (2WD / α ₃ )

[0036]

According to the present invention, when the optical disc and the objective lens is abnormally close, because driven in a direction away objective lens from the optical disc, to prevent damaging the optical disk and the objective lens is in contact You can

Further, to distance the objective lens from the optical disc after a predetermined time has elapsed since the abnormality is detected in the focus error signal, if the focus error signal becomes abnormal by small scratches or the like existing on the optical disc a, it is possible to prevent the objective lens is moved away from the optical disc. Therefore, frequent occurrence of focus pull-in operation can be suppressed, and stable signal reading can be performed. Therefore, it is possible to reduce the thickness of the optical disc device and improve the reliability.

[Brief description of drawings]

FIG. 1 is a flowchart illustrating an avoiding operation of an objective lens retracting mechanism of an optical disc device according to the present invention.

FIG. 2 is a block diagram showing a configuration of an optical disc device of the present invention.

FIG. 3 is a diagram illustrating a total signal of a focus error signal (FES) and a focus error signal generated during an objective lens swing operation.

FIG. 4 is a diagram illustrating a current value supplied to an actuator that drives an objective lens.

FIG. 5 is a diagram showing an optical system for receiving reflected light from an optical disc.

FIG. 6 is a diagram showing a configuration of a PD.

[Explanation of symbols]

1 optical disc 4 the objective lens 5 PD 6 FES signal, total signal generation circuit 7 objective lens driving circuit 8 control circuit

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masaru Nomura 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Masaaki Hanano 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Sharp Corporation (56) References JP-A-59-28254 (JP, A) JP-A-62-252536 (JP, A) Fukuihei 1-162110 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 7/085 G11B 7/09 G11B 7/095

Claims (4)

(57) [Claims] 1. An objective lens for converging laser light to irradiate the optical disc, an actuator for driving the objective lens in the optical axis direction of the laser light, and a focus from reflected light of the laser light from the optical disc. Signal detection means for detecting an error signal and a total signal, and focus position control means for operating the actuator so that the laser light focuses on the optical disk based on the focus error signal. In the optical disc device, when the signal detection unit detects a focus error signal equal to or larger than a first determination value indicating an abnormal approach between the objective lens and the optical disc, the signal detection unit returns to the signal detection unit again after a predetermined time. First determination means for detecting a focus error signal, and the signal detection operated by the first determination means When the focus error signal is not detected in the stage, the second determination unit that causes the signal detection unit to detect the total signal, and the total signal detected by the signal detection unit that is operated by the second determination unit are the second Optical disc apparatus, the objective lens retraction control means for instructing to drive the actuator in a direction of separating the objective lens from the optical disc when the determination value is smaller than the determination value of. 2. The optical disk device according to claim 1, wherein the predetermined time is set to be equal to or longer than a time required for the laser light to pass through a defect having a predetermined size on the optical disk. Optical disk device. 3. The optical disc device according to claim 1, wherein the signal detecting unit detects the focus error signal equal to or more than a first determination value until the predetermined time elapses. An optical disk device comprising a current setting means for setting a drive current of an actuator to a current value immediately before a focus error signal having a first judgment value or more is detected by the signal detection means. 4. The optical disc device according to claim 1, wherein the signal detecting unit detects the focus error signal equal to or more than a first determination value until the predetermined time elapses. An optical disk device comprising a current setting means for setting a drive current of an actuator to 0.