JPH08221766A - Focus control method for optical disk recording/ reproducing device - Google Patents

Abstract

PURPOSE: To detect the existence and its kind of a disk in a short time without providing a mechanical switch. CONSTITUTION: An optical pickup 2 is provided with a weighter 5, and operates integrally with a magnetic field modulation head 7. An optical head is constituted of the optical pickup 2 and the magnetic field modulation head 7. A focus control method is performed by following steps. A focus error signal value is measured while moving the optical head in the direction of focusing before servo control is turned on, and the presence and a reflectance of an optical disk 1 are judged using the focus error signal, etc., after the optical head is moved to a prescribed position. The predictive value of the focus error signal obtained when the optical head is moved again through the setting of power of a beam and the optimum control of the focus error signal according to the judgement result is operated. Then, the optical head is moved again, and the value of the focus error signal is measured, and the focus servo control is turned on using the predictive value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to appropriate control of an optical disk recording / reproducing apparatus for recording / reproducing a signal to / from a disk-shaped recording medium or a servo control mechanism of a recording / reproducing head of the optical disk reproducing apparatus. CD
(Compact disc), DVD high density (digital video disc) MD (mini disc) and PC (phase change type)
The present invention relates to a light beam focus control method in an information recording / reproducing apparatus for recording and reproducing data on a plurality of types of recording media having different reflectances such as a disc.

[0002]

2. Description of the Related Art In an information recording / reproducing apparatus of this type, for example, in the case of an MD apparatus, tracking control and focus control of an optical head are performed so that data can be accurately written and read during recording and reproduction. I have to. Such control is performed by controlling the optical head by a so-called servo control circuit. That is, the output power of the laser that gives a light beam spot to the disc at the time of recording (hereinafter referred to as laser power) is adjusted in multiple stages according to the wattage specified by the disc, and at the time of reproduction, several types with different reflectances (pre-mastered and The laser power is made variable in multiple steps with respect to the (MO) disc, and the gains of the tracking error signal and the focus error signal are switched in order to make the reproduction light proper, and the offset of these error signals is changed every time this switching is performed. Adjust. At this time, the offset and balance of the tracking error signal and the focus error signal must be adjusted accurately in consideration of compatibility with other devices.

In a servo control system including a servo control circuit,
Focus control and tracking control of a laser beam in an optical head or an optical pickup included in the optical head are performed. Focus control by astigmatism method 4
The output of each of the divided sensors is I / V converted and amplified, and is performed using the focus error FE of A + C-B-D generated from the output signals A, B, C, and D, and tracking control is performed by the 3-beam method sensor. Is performed using the tracking error TE of EF generated from the outputs E and F obtained by I / V converting and amplifying the respective outputs. These error signals are respectively supplied to the A / D converter of the servo circuit for digital servo processing, the output is output by the D / A converter, and the motor drive circuit forms a loop for driving the focus coil and the tracking coil. ing.

As described above, in order to surely control the laser power and the servo control in the tracking direction and the focus direction, it is first detected whether or not a disc is present. It is necessary to detect whether the disc has a high reflectance. Conventionally, a mechanical switch that turns on when the disc is inserted, a mechanical switch that engages with a recess provided on the disc to determine the type of the disc, or a level of focus error signal for a certain time is used. The above was judged by counting with a timer.

[0005]

A so-called micro switch or the like is used as such a mechanical switch, but it has an obstacle in miniaturization of the device because of its volume. Further, in the case of the method of making a judgment by observing the level of the focus error signal or the like for a certain time or longer, there is a problem that it takes a long time to judge the presence / absence of the disc and the usability is poor.

In view of the above conventional problems, the present invention can detect the presence of the disc and the type of the disc in a short time without providing a mechanical switch for detecting the presence of the disc and the type of the disc. An object is to provide a focus control method in a recording / reproducing apparatus.

[0007]

According to the present invention, in order to achieve the above object, the optical head is moved in a focus direction before turning on the servo control, and the focus error signal or The value of another signal generated from the output signal of the sensor divided into a plurality of parts is measured, and after the optical head has moved to a predetermined position, it is determined whether or not the disc is present by using the focus error signal or the other signal. At the same time, the disc reflectance is determined, and an instruction is given to the laser power control means to set the power of the corresponding laser beam according to the determined reflectance of the disc to optimize the focus error signal. It controls the automatic adjustment means and sets the predicted value of the focus error signal that will be obtained when the optical head moves again as a result of optimization. Move the optical head again in the focus direction, measure the value of the focus error signal while the optical head is moving, and detect that the value of the focus error signal obtained when moving the optical head again in the focus direction matches the predicted value. The focus servo control is turned on. Note that "to turn on the servo control in the focus control" means, in the focus servo control of the optical head (optical pickup), a servo control system for forcibly moving the optical head in the focus direction to perform a so-called focus search. The feedback loop of is changed from the open state to the closed state.

That is, according to the present invention, there is provided an optical disc recording / reproducing apparatus for recording information on a disc-shaped optical recording medium and / or reproducing the information recorded on the disc-shaped optical recording medium. Means for rotationally driving, an optical head for recording / reproducing data on / from the disk,
Laser power control means for controlling the power of the laser beam of the optical head, and a sensor that divides the reflected light of the laser beam from the disk into a plurality of parts to generate a tracking error signal and feed it back. Servo control including means for positioning the optical head in the track direction of the disk, and means for detecting the reflected light by a sensor divided into a plurality of parts to generate and return a focus error signal to position the optical head in the focus direction. Means, means for recording / reproducing information, and means for recording / reproducing information, modulation / demodulation means for modulating / demodulating a recording / reproducing signal, the tracking error signal and the focus error signal. Control method in an information recording / reproducing apparatus having automatic adjustment means for measuring and optimizing In the above, the optical head is moved in the focus direction before the positioning servo control of the optical head in the focus direction by the servo control means is turned on, and the focus error signal or the plurality of divisions are made during the movement of the optical head. Measuring the value of another signal generated from the output signal of the sensor, determining whether a disc is present using the focus error signal or the other signal, and determining the reflectance of the disc And a step of giving an instruction to the laser power control means to set the power of the corresponding laser beam according to the disc reflectivity determined, and controlling the automatic adjustment means to optimize the focus error signal. , The result of the optimization will be obtained when the optical head moves again Setting a predicted value of the focus error signal, moving the optical head again in the focus direction, measuring the value of the focus error signal again while the optical head is moving, and moving it again in the focus direction. And a step of turning on the focus servo control by detecting that the value of the focus error signal obtained at this time matches the predicted value, the focus control method in the information recording / reproducing device is provided. To be done.

[0009]

According to the focus control method of the present invention, the presence of the disc and the type of the disc can be detected in a short time without providing a mechanical switch for detecting the presence of the disc and the type of the disc.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a block diagram showing an MD recording / reproducing apparatus as an example of an optical disk recording / reproducing apparatus for realizing the focus control method of the present invention. FIG. 4 is a circuit diagram showing a main part of the preamplifier shown in FIG. 1 and 2
4 is a flowchart showing an example of a processing procedure until the servo control in the focus control during operation of the microcomputer 11 in FIG. 3 is turned on.

In FIG. 3, a magneto-optical disk (also referred to as a disk or an optical disk) 1 known as an MD (mini disk) has tracks formed in a spiral shape from the inner circumference to the outer circumference, and an optical pickup 2 By applying a laser beam spot to this track, bibliographic information, audio information, and video information in a predetermined format are optically recorded and reproduced. The disc 1 is servo-controlled by the servo circuit of the block 10 on the basis of the signal read and reproduced by the optical pickup 2.
It is rotated at CLV (constant linear velocity) by the spindle motor 3 and the motor driver / tracking focus control circuit 4. The optical pickup 2 has a superposing device 5 and operates integrally with the magnetic field modulation head 7. The optical pickup 2 and the magnetic field modulation head 7 constitute an optical head. The optical head can be moved in the radial direction of the disk 1 by a traverse motor 6.

The optical pickup 2 also has a laser diode LD for emitting a laser beam to the disc 1, and outputs signals RF1 and RF2 for reproducing the optical information recorded on the disc 1 based on the reflected light. Or the astigmatism 4-division focus error signal detection signal A
.About.D and two tracking error signal detection signals E and F of the 3-beam method are output. These signals RF1, RF
2, A to F are amplified by the head amplifier 8 and output to the preamplifier 9 that operates as a detection / adjustment unit. Further, a signal for driving the laser diode LD in the optical pickup 2 is applied from the preamplifier 9 to the head amplifier 8.

The preamplifier 9 is a memory controller / EF
The reproduced EFM signal, ADIP signal, focus error signal FEO, tracking error signal TEO, etc. are output to the M modulation / demodulation / error correction / ADIP (address implementation groove) / servo circuit block 10.
The block 10 servo circuit is, for example, a DSP.
(Digital signal processor). Four
The MB DRAM 13 compresses data during recording and reproduction,
During decompression, the data is temporarily stored, and writing and reading are controlled by the memory controller of the block 10 which receives an instruction from the microcomputer 11.

A memory controller / EFM modulation / demodulation / error correction / ADIP / servo circuit block 10 encodes recording data at the time of recording, modulates it into an EFM signal, and outputs it to the head 7 via a driver 7a. The servo circuit of the block 10 also uses the EF from the preamplifier 9 during reproduction.
The M signal is demodulated for error correction decoding, and the focus error signal FEO and the tracking error signal TE are also included.
Based on O, the optical pickup 2 controls through the motor driver / tracking / focus control circuit 4 so as to track and focus on the track of the disk 1. The motor driver / tracking / focus control circuit 4 constitutes, together with the preamplifier 9 and the block 10, servo control means as two positioning means in tracking and focus control.

When the information recording / reproducing apparatus is turned on or when the disc is inserted, the optical pickup 2 is adjusted for offset and balance of the tracking error signal TEO as will be described later.
Near the innermost circumference (TOC: Table Of Contents and UTO
C: User Table Of Contents) and necessary ID
Read information. The D / A converter / A / D converter block 14 A / D converts the analog recording signal to block 10
The reproduced signal from the block 10 is D / A converted and output as an analog signal to the outside.

The microcomputer 11 is an A / D converter 1 which takes in various signals A to F, FEO, TEO, etc. from the preamplifier 9.
1a, a PWM section 11b for controlling the output power of the laser diode LD by driving the laser diode LD in the optical pickup 2 with a signal corresponding to, for example, a 12-bit PWM signal, and a PWM signal from the PWM section 11b. Is converted into a DC voltage by a low-pass filter (LPF) 12 and is converted into a laser power control circuit (LPC) 22 shown in FIG.
Then, the laser diode LD in the optical pickup 2 is driven via the head amplifier 8. RAM 11c for work area etc. and ROM for programs etc.
It has 11d and CPU11e etc. which perform control as mentioned below, and these circuits 11a-11e are connected via bus 11f. Further, the RAM 11c has an area for storing a balance of the focus error signal, an offset adjustment value, or the like for the CPU 11e to perform the adjustment described later. Further, the microcomputer 11 is connected with an input means 16 and a display means 18, respectively, and receives an instruction from a user and displays a recording / reproducing state, a control state and the like.

In the optical disk recording / reproducing apparatus to which the present invention is applied, the tracking servo control and the focus servo control are performed by the servo control means composed of the blocks 4 and 10 and the preamplifier 9 during recording or reproduction.
As shown in the flow charts of FIGS. 1 and 2, after the power is turned on or after the disc is replaced, before the focus servo control is turned on (closed loop state), it is judged whether or not the disc is present and the disc reflectivity of the disc is checked. A type decision is made. Before the description, the contents of servo control will be described. First, the configuration of the preamplifier 9 will be described in detail with reference to FIG. The RF signals RF1 and RF2 input from the optical pickup 2 via the head amplifier 8 are output to the EFM modulation / demodulation / error correction / ADIP circuit 10 via the information reproduction signal output circuit 21 as EFM signals, ADIP signals and the like. Also, to adjust the focus balance, EF
The envelope signal EFMENV of the M signal is EFMENV
A / in the microcomputer 11 detected by the detection circuit 21a
It is output to the D converter 11a.

Further, the output signals A to D of the four-division sensor for detecting the focus error signal are applied to the focus balance differential amplifier 23F to calculate the signal FE = A + C-B-D. A focus balance voltage determined by the focus balance variable resistance means 24F1 and 24F2 is applied to the + terminal of the differential amplifier 23F. Therefore, the differential amplifier 23F has {α (A + C) -B-
D} (α is a coefficient corresponding to the focus balance adjustment amount)
The focus error signal FE is output. Further, by applying an offset voltage to the focus offset differential amplifier 27F, a focus error signal FE for changing the positioning position on the error signal of (A + D) − (B + D) + β is output. Further, the signals A to D are given to the adder 20, and the sum signal ASO is produced and sent to the servo circuit of the block 10.

Here, focus balance variable resistance means 24F1 and 24F2, focus gain variable resistance means 26F, focus offset variable resistance means 28F, and tracking balance variable resistance means 2 which will be described later.
4T1, 24T2, tracking gain variable resistance means 26T, and tracking offset variable resistance means 28
Each T is composed of a plurality of stages of resistance ladders and analog switches. Further, two variable resistance values for the focus balance variable resistance means 24F1 and 24F2, and two for the tracking balance variable resistance means 24T1 and 24T2.
The two variable resistance values are controlled in conjunction.

These variable resistance means 24F, 26F, 2
Each of the 8F, 24T, 26T, and 28T analog switch groups is a register (RAM 11) of the microcomputer 11 shown in FIG.
Focus balance signal FBAL, focus gain signal FG, focus offset signal FOFS, tracking balance signal TB according to the data set in c)
The AL, the tracking gain signal TG, and the tracking offset signal TOFS are given from the microcomputer data I / F 36 to selectively turn them on or off. Therefore, the resistance value changes in steps, and the balance (BAL) of the focus (F) signal, the gain (G) and the offset (OFS), and the balance (BA) of the tracking (T) signal.
L), gain (G) and offset (OFS) can be adjusted.

The output voltage FE of the differential amplifier 23F is amplified on the basis of the focus gain signal FG by the focus gain amplifier 25F and the variable resistance means 26F, and then by the focus offset differential amplifier 27F and the variable resistance means 28F. Focus offset signal FOF
The focus offset is adjusted based on S. This signal is used as the focus error signal FEO in the servo circuit 1
0 and is output to the A / D converter 11a in the microcomputer 11.

The polarities of the output signals E and F of the two-divided sensors E and F for detecting the tracking error signal from the optical pickup 2 are the polarity selection signal TE from the microcomputer 11.
The polarity can be switched by the polarity switching circuit 29 based on SEL. The output signals E and F of the polarity switching circuit 29 are applied to the tracking balance differential amplifier 23T and the differential amplifier 23T and the variable resistance means 24T1 and 24T2.
Therefore, when the signal TESEL is straight based on the tracking balance signal TBAL, the tracking error signal (βF-E) (β is the tracking balance adjustment amount) is obtained, and when the signal TESEL is cross, the tracking error signal (βE-F) is obtained. Is generated.

This output voltage is amplified by the tracking gain amplifier 25T and the variable resistance means 26T based on the tracking gain signal TG, and then the tracking offset differential amplifier 27T and the variable resistance means 28 are used.
The offset is adjusted by T based on the tracking offset signal TOFS. This signal is output as a tracking error signal TEO to the servo circuit 10 and the A / D converter 11a in the microcomputer 11. Also, in order to adjust the balance and offset of the tracking error signal TEO, the voltage H above the tracking error signal TEO is adjusted.
And the lower voltage L is held by the peak hold circuit 30 which operates as peak measuring means. The peak hold circuit 30 can be reset by a reset signal from the microcomputer 11.

Next, a preferred embodiment of the focus control method in the optical disk recording / reproducing apparatus of the present invention will be described with reference to the flow charts of FIGS. When the power switch of the optical disk recording / reproducing apparatus shown in FIG. 3 is turned on or the disk is exchanged, the flow of FIGS. 1 and 2 is executed by the CPU 11e of the microcomputer 11.
First, in step S1, offset adjustment of the focus error signal and the tracking error signal is performed. That is, with the laser of the optical pickup 2 not turned on, the focus error signal FEO and the tracking error signal T
EO is taken in through the A / D converter 11a of the microcomputer 11, and adjustment signals FOFS, T are sent through the microcomputer data I / F 36 so that each becomes equal to the reference voltage.
The OFS is given to the preamplifier 9. The reference voltage of the focus error signal FEO is ref1 as shown in FIG. 5 described later.

Next, in step S2, primary initialization is performed.
In this primary initial setting, the laser power is set to a predetermined value between the optimum value for the ROM disk and the optimum value for the RAM disk. The optimum value for high reflectance ROM disks is 0.
The optimum value for a RAM disk with a low reflectance of 25 mW is 0.
When it is 5 mW, the primary initial setting is, for example, 0.375 mW which is a value between them. Further, a focus balance adjustment signal FBAL and a tracking balance adjustment signal TBAL, which are adjustment signals for the focus balance and the tracking balance, are output, and the focus gain signal FG, the tracking gain signal TG, and the reproduction signal gain signal RFG are set to predetermined initial values. To be done. Next, in step S3, the focus coil of an actuator (not shown) is energized to increase the current. As a result, the optical pickup 2 moves toward the disc 1 in the focus direction. By repeatedly executing step S3, the current supplied to the focus coil linearly increases from 0 to the predetermined maximum value Imax.

In step S4, the output signal A of the amplifier 23
SO, that is, the maximum value AS1 of the sum signal of the output signals ABCD of the four-division sensor, the maximum value FE2 and the minimum value FE1 of the focus error signal FEO are fetched and stored. In step S5, the focus coil current I is the maximum value IM.
It is determined whether or not it becomes AX, and steps S3 and S4 are repeatedly executed until the current I reaches the maximum value Imax. When the current I increases to the maximum value Imax, that is, when the current I moves to the position closest to the predetermined disc 1 in the movement of the optical pickup 2 in the focus direction, the next step S6 is performed without further approach. To execute.

In step S6, the maximum value A of the sum signal ASO is
It is determined whether S1 is smaller than the first predetermined value Asa. This first predetermined value ASa is preferably set to the lowest value as the level of the sum signal ASO obtained by reflection in any type of disc 1. Therefore, when it is determined that the maximum value AS1 is smaller than the first predetermined value ASa, it can be determined that any type of disc is not loaded in the optical disc recording / reproducing apparatus. In this case, a predetermined error process such as displaying a message such as "Please insert the disc" on the display means 18 is performed.

On the contrary, the maximum value AS1 of the sum signal ASO is the first
If the maximum value AS1 of the sum signal ASO is smaller than the second predetermined value ASb, it is determined in the next step S7. As shown in the waveform diagram of FIG. 5, the second predetermined value ASb is the sum signal A obtained when the disc has a low reflectance.
It is set to be larger than the maximum value AS1 of SO and smaller than the maximum value AS1 of the sum signal ASO obtained when the disc has a high reflectance. Therefore, the maximum value AS1 is the second
By determining whether the loaded disk 1 is a low reflectance disk (RAM disk) or a high reflectance disk (R).
OM disc) can be identified. Figure 5
The reference value of the sum signal ASO is indicated by ref2.

Depending on the identification result of step S7, the initial settings for the low reflectance disc and the initial settings for the high reflectance disc are performed in steps S8 and S9, respectively. These initial settings are called secondary initial settings to distinguish them from the initial settings in step S2. In the first initial setting of step S2, the laser power is 0.375 in this embodiment.
In step S8 of the secondary initialization, the laser power is set to 0.
The laser power is set to 5 mW, and in step S9, the laser power is set to 0.25 mW for a disk having a high reflectance. Also, in these secondary initialization steps S8 and S9, as the optimization processing, the focus gain signal FG, the tracking gain signal TG, and the reproduction signal gain signal RFG are set to the predetermined low-reflectance disc and high-reflectance disc, respectively. Set to the value.

After step S8 or step S9 is completed,
As a further optimization process, in step S10, the focus balance signal FBAL is adjusted so that the ratio of the maximum value FE2 and the minimum value FE1 of the focus error signal FEO read in the previous step S4 becomes approximately 1: 1. Specifically, the difference and the sum of the maximum value FE2 and the minimum value FE1 are calculated, and K
= (FE2-FE1) / (FE2 + FE1) is calculated and the ROM 11 of the microcomputer 11 is set so that the value of K becomes 0.
The value of the focus balance signal FBAL is sequentially changed by referring to the table previously written in d. If the difference between FE2 and FE1 is too large to set K to 0 due to a defect of the optical pickup 2 or the like, set this to step S
The error processing can be performed by making a judgment in 11.

If K = 0 is determined in step S11,
In the next step S12, the predicted value FEa of the focus error signal FEO is calculated. This predicted value FEa is calculated in step S
8 or how much the value of the laser power of the secondary initial setting set in step S9 is changed from the value of the laser power of the primary initial setting in step S2, and similarly, the focus gain signal FG and the tracking gain signal TG are changed. Min., The maximum value FE2 and the minimum value FE1 of the focus error signal FEO read in step S4, and the focus balance signal FB adjusted and set in step S10.
Taking into account the amount of change in AL, calculation is performed to predict a value having a predetermined relationship with the maximum value at the positive or negative peak of the S curve of the focus error signal FEO obtained when the optical pickup 2 moves next time. To do. The predicted value FEa of the calculation result is held in the memory. The predicted value FE
Although a can be obtained by calculation in this way, it may be read from a table. Further, since it is known in advance that the predicted value FEa will be a predetermined value when the above optimization is sufficiently performed, such a predetermined fixed value may be used as the predicted value FEa. In this case, the predicted value FEa is S
The value can be about 70% of the maximum value at the positive or negative peak on the curve.

In the next step S13, the current applied to the focus coil is reduced to move the optical pickup 2 in the direction away from the disc 2. In step S14, it is determined whether or not the value of the focus error signal FEO once exceeds the predicted value FEa and then drops to the reference voltage ref1. In FIG. 5, the value of the focus error signal FEO at the moment when it exceeds the predicted value FEa is shown as FE3.
Step S14 is repeatedly executed together with S13 until it becomes YES. When step S14 is YES, the focus servo control is turned on in step S15, the normal focus servo control is started, the PLL circuit (not shown) in the block 10 is phase-locked, and a so-called pull-in state is set, resulting in the focus error signal FEO. Is the reference voltage ref1
It converges near. In FIG. 5, the portion where the waveform is shown by the dotted line shows the expected waveform change when the servo control is not turned on, and when the servo control is turned on, the waveform shown by the solid line is Become. Note that the timing of turning on the focus servo control is not when the value of the focus error signal FEO once exceeds the predicted value FEa and then drops to the reference voltage ref1 as in the above embodiment, and the value of the focus error signal FEO is It is also possible that the predicted value FEa is once exceeded and then a predetermined time elapses, or another predetermined voltage is reached.

In the above embodiment, the sum signal ASO is used to judge the presence / absence of a disc and discriminate between a disc having a low reflectance and a disc having a high reflectance. However, the maximum value FE2 and the minimum value of the focus error signal FEO are determined. Sum of absolute values of FE1,
| FE1 | + | FE2 | may be obtained and used in place of the sum signal ASO. Further, in step S10 of the flowcharts of FIGS. 1 and 2, control is performed so that the ratio between the maximum value FE2 and the minimum value FE1 of the focus error signal FEO measured in step S4 is substantially 1, but this step Since the focus servo control may not be able to be turned on when the focus balance is out of order, such control is provided, and this control is not always necessary.

Further, in the above embodiment, the laser power is set to a predetermined value between the optimum value for the ROM disk and the optimum value for the RAM disk in the primary initialization at step S2, ie, 0.
Although it was set to 375 mW, in step S2 the laser power is 0.25 m for the high reflectance ROM disk.
Optimum value for RAM disk with W or low reflectivity is 0.5m
It is also possible to set it to either W and make the necessary changes in step S8 or step S9.
That is, the secondary initialization can be changed only when the laser power in the primary initialization is different from the detected disc type.

Further, in the above embodiment, the discrimination between the two types of discs having a low reflectance and a disc having a high reflectance is performed. However, step S7 is subdivided so that the maximum value AS1 of the sum signal ASO is set to a plurality of values. By comparing with the level, it is possible to discriminate a disk having three or more types of reflectance. In the above embodiment, the case where the signal recording layer in the disc is one layer has been described. However, in the case of a so-called multi-layer disc having two or more signal recording layers in the disc, the focus position is the number of layers. However, the same control as in the above embodiment can be performed for each layer.

Further, in the above embodiment, first, the current of the focus coil is increased to lower the optical pickup 2 to bring it closer to the disc 2, and then the current is decreased to raise the optical pickup 2 to raise the optical pickup 2 from the disc 2. Although the optical pickup 2 is moved away from the optical pickup 2, the moving direction of the optical pickup 2 may be reversed. That is, it is also possible to first decrease the current of the focus coil to raise the optical pickup 2 to move it away from the disc 2, and then increase the current to lower the optical pickup 2 to move it closer to the disc 2.

[0037]

As described above, according to the present invention, it is possible to detect the presence of the disc and the type of the disc in the sequence for turning on the focus servo control. In particular, it is superior to the conventional method in that the presence of the disc and the type of the disc can be detected in a short time without providing a mechanical switch for detecting the presence of the disc and the type of the disc. Further, in the mode in which the focus balance is adjusted together before the focus servo control is turned on, in a case where the servo control is turned on and the pull-in cannot be performed well because the focus balance is deviated. It is effective. That is, by adjusting the focus balance signal FBAL,
Rough balance adjustment of the focus servo control system enables stable focus pull-in.

Further, in the conventional focus servo control, after the focus servo control is turned on, time is required for measuring the sum signal ASO of the four-division sensor and the focus error signal FEO and then performing each automatic adjustment. However, in the present invention, such measurement and adjustment are performed before the focus servo control is turned on, so that unnecessary time is unnecessary.

[Brief description of drawings]

FIG. 1 is a first half of a flowchart showing an embodiment of a focus control method in an optical disc recording / reproducing apparatus of the present invention.

FIG. 2 is the latter half of the flowchart showing an embodiment of the focus control method in the optical disc recording / reproducing apparatus of the present invention.

FIG. 3 is a block diagram showing an MD recording / reproducing device as an example of an optical disc recording / reproducing device for realizing the focus control method of the present invention.

FIG. 4 is a block diagram showing a preamplifier in FIG.

5 is a waveform diagram of main signals in FIGS. 3 and 4 in the case of a low reflectance disc and a high reflectance disc in the control of FIGS. 1 and 2. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 optical disk 2 optical pickup (which constitutes an optical head together with a magnetic field modulation head) 3 spindle motor (means for rotationally driving a disk) 4 motor driver / tracking focus control circuit (servo having two positioning means together with preamplifier 9 and block 10) Control constituting control means) 7 magnetic field modulation head 9 preamplifier 10 memory controller / EFM modulation / demodulation / error correction / ADIP (address implement groove) / servo circuit block (modulation demodulation means) 11 microcomputer (constitutes automatic adjustment means together with preamplifier 9) ) 13 DRAM 14 D / A converter / A / D converter block 16 Input means 18 Display means 21 Information reproduction signal output circuit 21a EFMENV detection circuit 22 Laser power control circuit (laser power control means) 29 Polarity switching circuit 30 Peak hold circuit 36 Microcomputer data I / F

Claims (4)

[Claims] 1. An optical disc recording / reproducing apparatus for recording information on a disc-shaped optical recording medium and / or reproducing the information recorded on the disc-shaped optical recording medium, comprising means for rotationally driving the disc. An optical head for recording / reproducing data on / from the disk, a laser power control means for controlling the power of the laser beam of the optical head, and a sensor for dividing the reflected light of the laser beam from the disk into a plurality of parts. Detected and detected to generate a tracking error signal, which is returned to the optical head, and means for positioning the optical head in the track direction of the disk, and a sensor which divides the reflected light into a plurality of parts to generate and return a focus error signal. , Servo control means including means for positioning the optical head in the focus direction, means for recording / reproducing information, and recording of the information Information having a modulation / demodulation means for transmitting / receiving data to / from a reproducing means, for modulating / demodulating a recording / reproducing signal, and an automatic adjusting means for measuring the tracking error signal and the focus error signal and optimizing them. In a focus control method for a recording / reproducing apparatus, the optical head is moved in the focus direction before turning on the positioning servo control of the optical head in the focus direction by the servo control means, and the focus is moved during the movement of the optical head. Measuring the value of an error signal or another signal generated from the output signal of the sensor divided into a plurality of, and determining whether or not a disk is present using the focus error signal or the other signal and Depending on the step of determining the reflectance of the disc and the determined reflectance of the disc A step of giving an instruction to the laser power control means to set the power of the corresponding laser beam and controlling the automatic adjustment means to optimize the focus error signal, and the optical head moves again as a result of the optimization. And a step of setting the predicted value of the focus error signal that will be obtained when the optical head is moved in the focus direction again, and the value of the focus error signal is measured again during the movement of the optical head. A step of detecting that a value of the focus error signal obtained when the focus error signal is moved again in the focus direction matches the predicted value and turning on the focus servo control, Focus control method in reproducing apparatus. 2. The step of measuring the value of the focus error signal during the movement of the optical head includes moving the optical head in a direction closer to the disk, and changing the value of the focus error signal during the movement of the optical head. In the step of measuring again, the optical head is moved in the direction away from the disk, or in the step of measuring the value of the focus error signal while the optical head is moving, the optical head is moved in the direction away from the disk. 2. The focus control method for an optical disk recording / reproducing apparatus according to claim 1, wherein the step of measuring the value of the focus error signal again while the optical head is moving, moves the optical head in a direction approaching the disk. 3. The maximum value of the sum signal of the output signals of the plurality of divided sensors or the maximum value of the focus error signal in the step of judging whether or not the disk exists and the step of judging the reflectance of the disk. The focus control method in the optical disk recording / reproducing apparatus according to claim 1, wherein the sum of the absolute value of the minimum value and the absolute value of the minimum value is used. 4. The step of controlling the automatic adjusting means to optimize the focus error signal is to adjust a focus gain, or the step of controlling the automatic adjusting means to optimize the focus error signal includes: The focus in the optical disc recording / reproducing apparatus according to claim 1, wherein the focus balance signal is controlled so that the ratio between the maximum value and the minimum value of the focus error signal is substantially 1 in addition to adjusting the focus gain. Control method.