WO2004088646A1

WO2004088646A1 - Focus control device and method, and focus control program

Info

Publication number: WO2004088646A1
Application number: PCT/JP2004/004013
Authority: WO
Inventors: Hirofumi Yajima
Original assignee: Clarion Co. Ltd.
Priority date: 2003-03-31
Filing date: 2004-03-24
Publication date: 2004-10-14
Also published as: JP2004303329A

Abstract

A focus control device and method and focus control program for stable focusing even if the defocus of an optical pickup is large. The focus control device is provided with an actuator drive section (56) for controlling the drive of a two-axis actuator (43) so as to focus an objective lens (42) according to an electric signal from the optical pickup (4), a defocus setting section (53) for setting a defocus value used as a reference for the difference between the focal point of the objective lens (42) and the operating point, and a defocus changing section (54) for changing the defocus value to a preset one or zero.

Description

, Specification focus control device and control method and focus control program

The present invention relates to a focus control technique for optical pickup in a recording / reproducing apparatus for an optical recording medium, and more particularly to a focus control apparatus and control method with improved defocus adjustment, and a focus control program. Background art

2. Description of the Related Art In a disk device for recording and reproducing an optical disk such as a CD or DVD, a recording surface is irradiated with laser light via an optical pickup including an objective lens, and the reflected light is converted into an electric signal. As a result, the signal recorded on the disc is read. This optical pickup is provided so that it can move in the focus direction (up and down) and the tracking direction (left and right) according to the current flowing through the coil of the actuator, but focuses on the recording surface during playback. It is necessary to maintain the state that fits. -For this reason, in such a disk drive, the reflected light from the recording surface, which is received by the objective lens and separated by the beam splitter, is guided to a photo diode called a detector, and this detector responds to the amount of reflected light. It is configured to perform focus servo for finely adjusting the position of the objective lens according to the current flowing. For example, using the fact that the main spot does not draw a circle when it is out of focus, the amount of light in a section divided into four equal parts based on the center of the main spot is determined. This is used as a focus error signal based on the difference in the amount of light in the In order to move the optical pickup in the direction to cancel the error, control is performed so that current flows through the coil at a voltage corresponding to this.

Such an operation at the focus position is generally referred to as a focus pull-in operation. However, the focus pull-in operation is a detectable range of a focus error signal, that is, a focus position. Can only be performed within a small area before and after For this reason, such a disc apparatus is configured to perform an operation of moving an objective lens up and down, called a focus search, and turning on a focus servo when a focus error signal is obtained. (Japanese Unexamined Patent Application Publication No. 6-68477, Japanese Unexamined Patent Application Publication No. 8-39550).

At this point, as shown in Fig. 4, when the focus is retracted, the defocus point is set at the focus point, which is the point at which focus is initially set, and the focus operating point, which is the point at which the focus servo is actually operated. Is adjusted so that a shift called the This defocus adjustment is performed by moving the focus to the plus side and the minus side with respect to the focus point so that the RF signal (read information signal) becomes the best from the operating point after the focus servo is turned on. The point at which the amplitude of the RF signal is maximized is detected, and that point is used as the focus operating point. Such defocus adjustment is performed when the playback device is switched from the stopped state to the disk playback state. This is performed at the time of focus search, which is performed when defocus occurs due to scratches, vibration, etc., or at the time of layer jump, which is performed when switching the layer to be reproduced on a multi-layer disc such as a DVD. .

For example, a defocus adjustment procedure performed during a focus search will be described with reference to a flowchart of FIG. That is, from the focus servo off state (step 501), the four force Start search and perform focus pull-in operation (Step

5 0 2). After the focus pull-in operation, the focus servo is turned on (step 503) ^_ , and the other servos (spindle servo, tracking servo, and thread servo) are turned on (step 5). 0 4). During the above steps 501 to 504, the value A set at the time of the previous defocus and focus adjustment is used as the defocus value. '

Next, a new defocus adjustment is performed, and a defocus value A is set (step 505). Then, by inputting the set value of the adjustment result to the drive circuit of the actuator, the set value A of the defocus is replaced with a new defocus value A ′ (step 506). At the same time, the set value is stored in the memory (step 50.7). In this way, the disc is reproduced based on the newly set defocus value A, (Step 508).

On the other hand, a defocus setting procedure at the time of a layer jump will be described with reference to a flowchart of FIG. That is, based on the defocus value of the current layer, the state of playing the disc, etc. (Step 61), and when the layer jump is performed (Step 60) 2), when the previous defocus value の of the destination layer is input to the actuator driver circuit, the defocus setting value の is replaced with a new defocus value B ( Step 6 03).

After the focus pull-in operation is performed based on the defocus value B (step 604), the focus servo is turned on (step 605), and the other servos are turned on. (Step 606.), the disk of the destination layer is played back.

(Step 607).

〔task to solve〕 However, in the conventional defocus adjustment as described above, the operating point after the defocus adjustment is the best as the operating point after the focus servo on because the RF amplitude is the maximum. At the moment when the focus servo is turned on, the waveform fluctuates greatly. For this reason, if the defocus value becomes large, the control range of the focus signal shown in FIG. 7 may be deviated. Disclosure of the invention

An object of the present invention is to provide a focus control device, a control method, and a focus control program capable of performing a stable focus pull-in operation even when the defocus of the optical pickup becomes large. To provide. -The focus control device according to the present invention includes: an optical pickup for converting reflected light of laser light applied to an optical recording medium into an electric signal; and an optical pickup provided in the optical pickup, and configured to irradiate laser light and reflected light. An optical member for receiving light, an actuator for driving the optical member, and a drive for driving the actuator so that the optical member performs a focus pull-in operation based on an electric signal from the optical pickup. A focus control device comprising: an actuator driving unit for controlling; a defocus setting unit for setting a defocus value serving as a reference of a difference between a focus point of the optical member and an operating point of the optical member; A defocus switching unit that switches the scum value to a value set by the defocus setting unit or zero. It is characterized by doing. '

In the above mode, the defocus value can be temporarily set to zero before the focus servo starts, so that even if the set defocus value is large, the focus pull-in operation can be performed. The crop can be stabilized.

In a preferred embodiment, the apparatus further comprises a setting storage unit that stores the defocus value set by the defocus setting unit.

In the above aspect, by storing the defocus value, it is possible to return to the setting before the defocus value was set to zero. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a functional block diagram showing an embodiment of the focus control device of the present invention.

FIG. 2 is a flowchart showing a procedure for setting a default + − during a focus search according to the embodiment of FIG. -FIG. 3 is a flowchart showing a focus setting procedure at the time of a layer jump according to the embodiment of FIG.

Figure 4 is an explanatory diagram showing typical defocus set points. FIG. 5 is a flowchart showing a procedure for setting a default force at the time of focus search according to the related art.

FIG. 6 is a flowchart showing a procedure for setting a defocus at the time of a layer jump in the conventional technique. '

FIG. 7 is an explanatory diagram showing a control range of the focus signal. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments to which the present invention is applied will be specifically described with reference to the drawings. In this embodiment, the optical pickup is controlled by operating the computer and its peripheral circuits in accordance with a program for realizing the functions of each section described below. The mode of realizing the program can be variously changed. Therefore, in the following description, each of the present invention A virtual circuit block that realizes the function is used.

[Constitution]

In this embodiment, as shown in FIG. 1, the optical pickup 4 is driven by the control device 5 while the disk D chucked on the turntable 1 is rotated by the spin-drain motor 2. This is a disk device that records and reproduces information on the recording surface of the disk D. The optical pickup 4 includes a laser diode 41, an objective lens 42, a two-axis actuator 43, a detector 44, a cylindrical lens 47, a collimator lens 46, a beam splitter 45, etc. It has.

The laser diode 41 is a light source that emits a laser beam for irradiating the disk D. The objective lens 42 is a lens that focuses the laser light on the recording surface of the disk D. The two-axis actuator 43 is an actuator that drives the objective lens 42 in two directions, a tracking direction and a focusing direction, by a driving voltage. The detector 44 is a photodiode that converts the reflected light from the disk D into an electric signal. The beam splitter 45 guides the laser beam of the laser diode 41 to the objective lens 42 via the collimator lens 46 and reflects the reflected light from the disk D. Is a spectrometer that guides the light to a detector 44 via a cylindrical lens 47. It should be noted that any known technology can be applied to the amplifier for signal amplification, the optical pickup feed mechanism, and the like, and a description thereof will be omitted.

The control device 5 is a device for controlling the driving of the optical pickup 4, and includes a reflection signal processing unit 51, a focus error signal detection unit 52, a defocus setting unit 53, a defocus switching unit 54, and setting storage. A unit 55, an actuator driving unit 56, and the like are provided. The reflection signal processing section 51 is a means for processing a signal (RF signal, focus error signal, etc.) from the detector 44. Foca Suera —The signal detection section 52 is a means for detecting a focus error signal from the signal input to the reflection signal processing section 51. The default setting section 53 is a means for adjusting and setting the defocus value based on the RF signal and the focus error signal. The deformation force switching unit 54 is a means for appropriately selecting and switching the defocus value.

The setting storage unit 55 is a memory for storing various settings such as a defocus value and a focus servo control range. Does the actuator drive unit 56 appropriately apply a drive voltage to the two-axis actuator 43 based on the focus error signal, defocus value, and the like? ) Means. The configuration for controlling the scanning of the optical pickup 4 in the control device 5 and for other servos (spindle servo, tracking servo, thread support), and the like can be applied to any known technology. Is omitted.

[Action]

The operation of the present embodiment having the above configuration will be described.

[Focus search]

First, a defocus setting procedure at the time of a focus search will be described with reference to a flowchart of FIG. That is, in the focus servo off state, the value A set during the previous defocus adjustment is stored in the setting storage unit 55 as the defocus value (step 201). Then, before starting the focus search, the defocus switching unit 54 changes the defocus value for controlling the actuator drive unit 56 from A force to 0 (step 202). . Next, a focus search is started to perform a focus pull-in operation (step 203). After the focus is pulled in, the focus is turned on and the servo is turned on (step 204). In this way, the defocus value is set to 0 during the period from the focus pull-in operation to the focus service, and The focus servo is turned on at the center of the focus error waveform. Then, after the focus servo waveform becomes stable (for example,

3 2 ms. Later), the defocus switching section 54 returns the defocus value for controlling the actuator drive section 56 to the previous defocus value A (step 205). Further, as in the prior art, after turning on the other servos (step 206), a new defocus adjustment is performed by the defocus setting unit 53, and the defocus value A ′ is set. Is set (Step 2 07), and the defocus switching unit 54 replaces the defocus set value A with a new defocus value (Step 2 08), and the adjustment result is stored in the setting storage unit 55. It accumulates (step 209). In this way, the disk is reproduced based on the newly set defocus value A '(step 210). -[Layer jump]

Next, the defocus setting procedure at the time of a layer jump will be described. That is, based on the defocus value A in the current layer, from the state where the disc is being played (step 301), before the layer jump movement is performed, the defocus switching unit 54 is operated by the actuator driving unit. The defocus value for controlling 56 is changed from A to 0 (step '302). Next, when a layer jump is performed (step 303), a focus pull-in operation is performed based on the defocus value 0 (step 304). (Step 305) In this way, during the period from the focus pull-in operation to the focus servo on, the defocus value is set to 0, and the focus servo is turned on at the center of the focus error waveform.

After the focus servo waveform is stabilized, the defocus switching unit 54 controls the actuator drive unit 56. Is switched to the previous defocus value B of the layer (step 306). Further, as in the prior art, after turning on the other services (step 307), the layer at the movement destination is reproduced (step 308).

[Effect]. '

According to the present embodiment as described above, the defocus value is set to 0 before the focus servo is turned on, and the previous value of the defocus value is input after the focus servo is turned on. Therefore, even if the defocus value is large, it is possible to prevent the deviation from the control range and to stabilize the focusing operation. In particular, since the defocus value is input after the focus servo waveform is stabilized, deviation of the focus signal control range can be reliably prevented. Therefore, the situation where the optical pickup collides with the disc does not occur. On the other hand, after the waveform of the focus servo is stabilized, the focus servo can be operated at the position where the RF signal becomes the best.

[Other embodiments]

Note that the present invention is not limited to the above embodiment. For example, the structure of the optical pickup, the method of detecting the focus error signal, the control range by the focus error signal, the defocus value, the time setting for stabilizing the waveform of the focus servo, and the like are not limited to specific structures and numerical values. The optical recording medium to which the present invention is applied is not limited to CD and DVD, and can be applied to all types of optical recording media. Industrial applicability

As described above, according to the present invention, a focus control device capable of performing a stable focus pull-in operation even when the defocus of an optical pickup becomes large. It is possible to provide a positioning and control method and a focus control program.

Claims

The scope of the claims

.1. An optical pickup that converts reflected light of laser light applied to the optical recording medium into an electric signal, an optical member that is provided in the optical pickup, performs irradiation of laser light and receives reflected light, and performs IT. A focus control device comprising: an actuator that drives a member; and an actuator drive unit that controls driving of the actuator so that the optical member performs a focus pull-in operation based on an electric signal from the optical pickup. hand,

A de-force setting unit for setting a defocus value serving as a reference for a difference between a focus point of the optical member and an operating point of the optical member;

A defocus switching unit that switches the defocus value to a set value or zero by the defocus setting unit;

A focus control device, comprising: .

2. The focus control device according to claim 1, further comprising a setting storage unit configured to store the default value set by the default setting unit.

3. The optical pickup irradiates the optical recording medium with laser light via the optical member, converts reflected light into an electric signal, and focuses on the optical member based on the electric signal from the optical pickup. In a focus control method in which the optical member performs a focus pull-in operation so that a servo can be performed, a reference of a difference between a focus point of the optical member and an operating point of the optical member is determined. Set the defocus value

Before starting the focus service, the defocus value is set to zero, The focus control method is to switch the default value to a value set by the default setting unit after the start of the focus service.

4. The focus according to claim 3, wherein after the start of the focus servo, after the electric signal from the optical pickup is stabilized, the defocus value is switched to a value set by the defocus setting unit. Control method.

5. The focus control method according to claim 3, wherein the operating point of the optical member is a point at which the amplitude of the RF signal in the electric signal from the optical pickup is maximized.

6. A function of irradiating the optical pickup with a laser beam to the optical recording medium via the optical member and converting the reflected light into an electric signal, and the optical member based on the electric signal from the optical pickup. In a focus control program that allows a computer to implement the function of causing the optical member to perform a focus pull-in operation so that a focus service by a computer can be performed.

A function of setting a defocus value which is a reference of a brush between a focus point of focus by the optical member and an operating point of the optical member; and a function of setting the defocus value to zero before the start of a focus servo. ,

A focus control program, wherein the computer realizes a function of switching the defocus value to a value set by the defocus setting unit after the start of focus servo.