JPH02134730A - Focus servo pull-in system for optical pickup device - Google Patents

Abstract

PURPOSE:To reduce the automatic focus servo pull-in time by recording a signal level at a focal point of an objective lens for the execution again of a discrimination of the focal position of the objective lens based on the recorded signal level on such occasion. CONSTITUTION:A focus track servo control section 205 controls an actuator 203a to discriminate a focal position of an objective lens while moving the objective lens. Then a system control section 212 stores a signal level of a drive signal with respect to the actuator 203a at the focal position. Then in the case of executing the discrimination of the focal position again, the control section 212 moves the objective lens from a position in the vicinity of the preceding focal position based on a signal level to be stored by means of the actuator 203a. As a result, the time to find out the focal position is reduced. Thus, the focus servo pull-in time is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a focus servo pull-in method for an optical pickup device for recording and reproducing information on an optical disc.

[Prior Art] In an optical disk device, a laser beam is irradiated onto a recording track of an optical disk, which is a storage medium, while it is rotated, and the intensity of the laser beam is modulated in accordance with the recorded data, thereby storing data. It is recorded. Furthermore, recorded data is reproduced by detecting fluctuations in the level of reflected light of the laser beam from the recording track. An optical pickup device irradiates and detects a laser beam in this manner.

This optical pickup device is equipped with an actuator that moves an objective lens that condenses a laser beam in two directions for focusing that adjusts the focus of the laser beam and tracking that causes the laser beam to follow a recording track.

The actuator generally includes a yoke equipped with a magnet and a coil inserted into the yoke, or uses a near motor.

When performing the above-mentioned focusing, the objective lens is moved from a fixed position by the above-mentioned linear motor while irradiating the optical disc with a predetermined laser beam. During this time, the reflected light is detected by a predetermined method to determine the focal point position of the objective lens, and predetermined servo control is started at the focal point position.

That is, when performing such focus servo pull-in, as shown in FIG. 7, the focus drive signal E for driving the linear motor is changed from the initial voltage e0 to e. +Δe□ and move the objective lens a certain distance, for example, toward the optical disk side. Here, irradiation of the laser beam and detection of reflected light are started, the focus drive signal E is gradually lowered, and the objective lens is moved in the opposite direction. When the in-focus position is determined, the voltage value e at that time is fixed, and predetermined focus servo control is started.

In the above operation, Δe is a drive voltage corresponding to the distance by which the objective lens is once moved in one direction.

This size takes into consideration factors such as surface wobbling of the optical disc due to misalignment of chucking, distortion of the disc itself, variations in the mechanism of individual actuators, and variations in the distance between the objective lens and the optical disc in each optical disc device. , so that you can always find the focal point position.
A constant value is set in advance.

[Problems to be Solved by the Invention] However, when the above-mentioned factors are combined, the dispersion becomes large, so the value of Δe1 has to be set large accordingly. Therefore, there is a problem in that it takes a long time to pull in the focus servo until one in-focus position is found, as in the example shown in the figure, it takes time t1.

SUMMARY OF THE INVENTION An object of the present invention is to provide a focus servo pull-in method for an optical pickup device that can solve the above problems and shorten the focus servo pull-in time.

[Means for Solving the Problems] For this purpose, the present invention determines the focal point position of the objective lens, stores the signal level of the drive signal for the actuator at that position, and then re-determines the focal point position. The in-focus point position is determined by gradually changing the stop motion signal from a signal level set based on the stored signal level when executing the method. .

[Operation] When re-executing the determination of the focal point position, the deviation from the previously determined focal point position is small. Therefore.

When re-executing the in-focus position determination, the time it takes to find the in-focus position can be shortened by moving the objective lens from around the previous in-focus position based on the memorized signal level. , it becomes possible to shorten the focus servo pull-in time.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a block diagram of an optical disk storage device according to an embodiment of the present invention.

In the figure, an optical disc cartridge 1 containing an optical disc 101 is installed in an optical disc drive device 2.

In the optical disk drive device 2, a spindle motor 201 rotates a turntable 201a, and a spindle motor servo control section 202 controls the spindle motor 201 to rotate at a predetermined speed.

The optical pickup 203 irradiates the optical disc 101 with laser light and detects reflected light.

It records and reproduces information. This optical pickup 203 is provided with an actuator 203a that moves an objective lens (not shown) that directs the laser beam in a focusing direction and a tracking direction.

The linear motor 204 moves the optical pickup 203 in order to access a predetermined track on the optical disc 101. The focus/1-rack servo control section 205 controls the actuator 203a.

The signal reproducing/data recording/reproducing unit 206 reproduces the read signal from the optical pickup 203 and records/reproduces data on the optical disc 101 via the optical pickup 203 .

By the way, for focus servo control, in this embodiment, a focus error is detected by a known method such as the astigmatism method or the Knifezi method. In these methods, a focus sum signal S and a focus difference signal S, which are the sum and difference of detection signals from two optical sensors, are extracted, but these signals are extracted from the signal reproducing/data recording/reproducing section 206. It is output to the focus trunk servo control section 205.

The address detecting section 207 receives the reproduced data output from the signal reproducing/data recording/reproducing section 206 and detects the sector address recorded on the data track of the optical disc 10.

The linear motor servo control section 208 controls the linear motor 20
4 is servo controlled. Position detection times 1PI20
Reference numeral 9 detects the movement position of the optical pickup 203 using an encoder plate and a sensor (not shown) fixed to the linear motor 204. A home position detection circuit 210 detects the movement position of the optical pickup 203, which is the basic position of the linear motor 204. It detects the position.

The interface circuit 211 is for exchanging recording data, command information, etc. with a device on the host 1-computer side (not shown).

The system control section 212 receives detection signals from the above-mentioned detection sections and controls each control section.

FIG. 2 shows a detailed block diagram of the portion related to focus control among the above blocks.

The level determination circuit 205a in the focus/track servo control section 205 is connected to the signal reproduction/data recording/reproduction section 206.
The level determination circuit 205b receives the focus sum signal S from the input signal S, and the focus difference signal S is input to the level determination circuit 205b. These level determination circuits 205a and 205b each determine whether the signal level meets a predetermined condition.
Each determination result is sent to the CPU 212 of the system control unit 212.
It is input in a.

The CPU 212a controls the focus/track servo control section 205, and information necessary for the control is stored in the memory 212b.

The D/A (digital/analog conversion circuit) 205c converts the vibration signal of the actuator 203a, which is output as a digital signal from the system control unit 212, into an analog signal and outputs it as a focus movement signal E.

The focus movement signal E is input to a power amplifier 205f via a switch circuit 205d and an adder circuit 205e.

The phase compensation circuit 205g compensates the phase during servo control based on the focus difference signal, and the focus difference signal is inputted, and its output signal is sent via the switch circuit N205h and the addition circuit 205e. , are input to the power amplifier 205f. The power amplifier 205f drives the rotating near motor of the actuator 203a.

When using this optical disk storage device in the second configuration, the operator turns on the power and installs a desired cartridge 1 into the drive device 2.

FIG. 3 shows the operations that are activated when cartridge (2) is newly installed or when the power is turned on with cartridge (1) installed. in this case,
First, a process of positioning the optical pickup 203 to the reference track which is the home position of the optical pickup 203, which is called a recial operation, is performed. That is, first, the optical pickup 203 is moved with the reference track as a target, and focus servo pull-in is executed at that position. Then, a predetermined focus servo control is started, and a predetermined tracking control is started. Then, the address recorded on the track is read and the optical pickup 203 is caused to seek to the correct reference track position (process 1001).

Next, while the focus servo control continues as is,
Tracking servo control is stopped and optical pickup 2
03 is placed in a standby state where it is held at the reference position (process 1002).

After this, the R/W (
Read/write 1-) Wait for command (from N in process 1003 to process 1004. From N in process 1004 to process 1003)
.

Further, when this waiting time has passed a preset time limit (Y in process 1004), the focus servo control is stopped and set to an idle state (process 1005), and R
Wait for the /W command (proceed to process 1003).

Next, when an R/W command is received from the host computer side (Y in process 1003), it is determined whether it is in a standby state (process 1oo6). Here, in the case of the standby state (Y in process 1006), the focus servo control is continued, so the optical pickup 203 is made to seek to the target track position according to the R/W command (process 1
007), information is recorded or reproduced in a predetermined sector (process 1008).

After this, in the same way as above, wait for the next R/W command (processing 1
003).

FIG. 4 shows the focus servo pull-in operation executed in the above processing 1001 and processing 1009. That is, when this operation starts, the focus servo pull-in operation that has just started is executed in the above process 100.
1 or a re-execution operation corresponding to the above process 1009 (process 2001).

Here, in the case of the first operation (Y in process 2001), the switch circuit 205d is closed and the focus effect movement signal E is output from the D/A 205c as shown in FIG.

-d, initial voltage e. to a certain value Δe□ (
Processing 2002). As a result, the actuator 203a
As a result, an objective lens (not shown) moves a certain distance, for example, in the direction of the optical disk.

Next, while gradually lowering the focus drive signal E (process 2003), the focus sum signal S and a preset constant value X are compared (process 2004), and if S≦X1, this operation is continued. (Proceed to process 2003).

As a result, as the focus drive signal E decreases, the objective lens moves in the opposite direction.

This movement of the objective lens changes the focus state.

By the way, in the astigmatism method and the Knifezi method of this embodiment, the focus error is represented by the focus sum signal S and the focus difference signal R. For example, suppose that the objective lens is moved by changing the focus drive signal E, as shown in FIG. 5(a).

If it is assumed that the objective lens is at the focused position when the voltage is e, the level of the focus sum signal S is as shown in the figure (b
), the focus difference signal becomes a mountain-shaped curve with a maximum value at the in-focus position, while the focus difference signal becomes an S-shaped curve with a zero level at the in-focus position, as shown in (c) of the same figure. It has been known.

The constant value x1 is set in order to determine whether the magnitude of the focus error is within a range that can be detected by the focus difference signal.

Here, when the focus sum signal S becomes S>xL (Y in process 2004), the level of the focus difference signal is determined (process 2005), and if the focus difference signal is not at zero level (process 2005) N), the above operation is continued (proceed to process 2003).

Then, when the focus sum signal S reaches zero level (Y in process 2005), the focus hit vj signal E is fixed at the value at that time (process 2006). Then, the switch circuit 205h is closed. As a result, the focus difference signal is added to the focus drive signal E, the objective lens is driven, and focus servo control is started (processing 2
007).

Next, the fluctuation range of the focus difference signal is determined (processing 2
(008) Here, if the objective lens moves a certain distance away from the in-focus distance, focus servo control becomes impossible, and in this case, the level of the focus difference signal becomes high. Therefore, when the focus difference signal becomes equal to or greater than the preset constant value x2 (Y in process 2008), the above operation is re-executed from the beginning (proceed to process 2001).

On the other hand, if the focus difference signal is less than the above-mentioned constant value X2 (N in process 2008), the current value e of the focus drive signal E is stored (process 2009), and the above servo pull-in operation is ended.

This servo pull-in operation is re-executed in process 1009 in FIG. In the case of such re-execution (N in process 2001), the focus drive signal E is initially set to the sixth
As shown in the figure, the voltage is increased to the stored voltage value e+Δe2 (process 2010). Thereafter, the focus drive signal E is gradually lowered to find the in-focus position in the same manner as described above (proceed to process 2003).

By the way, when executing the servo pull-in operation in process 1001 in FIG. 3, the optical disk 101 may have been replaced. Therefore, the distance between the objective lens and the optical disk varies due to surface runout of the optical disk due to misalignment of chucking, distortion of the optical disk itself, and the like.

On the other hand, when the servo pull-in operation is executed in process 1009 in FIG. 3, the optical disc is the same as when executed in process 1001, and its chucking state has not changed. Therefore, the focal point position of the objective lens is considered to be near the position set in process 1001. Therefore, the constant value Δe2 in FIG. 6 may be smaller than the constant value Δe□ in FIG.

As a result, the time t2 required to gradually lower the focus drive signal E from the voltage e+Δe2 until it reaches the voltage e2 at the in-focus position is shorter than the time t in FIG. 6, and the focus servo pull-in time is shortened. Become so.

In the above embodiment, the value e of the focus drive signal E for the in-focus position for the actuator is newly stored each time the device is powered on or an optical disk is mounted, and the in-focus position is determined for the same disk. Occasionally,
Although the value e of the focus IWN motion signal is used, the value e of the previous focus drive signal may be used after replacing the optical disk or when the power is turned on again. In this case, when executing the in-focus position determination, the in-focus position is determined after the value e of the stored focus drive signal is shifted by more than a constant value Δe2. In this way, the value e of the focus drive signal at the time of starting the determination of the in-focus signal 1n may be set according to various conditions based on the stored value e of the focus drive signal.

[Effects of the Invention] As described above, according to the present invention, the signal level of the drive signal for the actuator at the focal point position of the objective lens is stored, and when re-executing the determination of the focal point position, the taste signal is stored. Since the in-focus point position is determined by gradually changing the signal level from around the previous in-focus point position based on the stored signal level 1, the time it takes to find the in-focus point position is shortened. Therefore, the focus servo pull-in time can be shortened.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an optical disk storage device according to an embodiment of the present invention, FIG. 2 is a detailed block diagram of a focus control section, FIG. 3 is a flowchart showing the overall operation, and FIG. 4 is a focus diagram. A flowchart showing the servo pull-in operation, Fig. 5 is a graph showing changes in each level of the focus drive signal, focus sum signal, and focus difference signal, and Fig. 6 shows the level changes in the focus active signal when re-executing focused point position determination. FIG. 7 is a graph showing changes in the level of the focus drive signal when executing the conventional in-focus position determination and when executing the in-focus position n determination for the first time in this embodiment. DESCRIPTION OF SYMBOLS 1... Optical disk cartridge, 2... Optical disk drive device, 101... Optical disk, 201... Spindle motor, 202... Spindle motor servo control unit, 203... Optical pickup, 203a...
Actuator, 204... Linear motor, 205...
... Focus 1 rack servo control unit, 205a
, 205b - level determination circuit, 205d. 205h...Switch circuit, 205e...Addition circuit, 20.5f...Power amplifier, 205g...
Phase compensation circuit, 206... Signal reproduction/data recording/reproducing section, 207. Address detection section, 208... Linear motor servo control section, 211... Interface circuit, 21
2...System control unit, 212a...CPU, 212
b...Memory. Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] The actuator moves the objective lens that condenses the laser beam to be irradiated onto the optical disk.The signal level of the drive signal is gradually changed from a constant level to move the objective lens, and the focal point position of the objective lens is determined. In a focus servo pull-in method of an optical pickup device that determines the focus position and then starts focus servo control, the signal level storage means stores the signal level at the focused position of the objective lens, and the determination of the focused position of the objective lens is provided. and a focused point position detection means for determining the focused point position by gradually changing the drive signal from a signal level set based on the stored signal level when re-executing. A focus servo pull-in method for an optical pickup device, which is characterized by: