JPH07110947A - Optical pickup and focus servo apparatus - Google Patents

Abstract

PURPOSE:To shorten the access time and easily reduce the size of apparatus and realize thinner apparatus. CONSTITUTION:A photo-interrupter 40 having the maximal value in the wider range than the RF signal is provided in the manner as movable like an objective lens 3a and a comparator 39 which can obtain a gate signal GATE indicating the wider positonal range of the objective lens including the positional range of the objective lens indicated by the FOK signal based on the light beam amount signal LS which is an output of the photointerrupter 40 is also provided. The optical pickup and focus servo apparatus is constituted so that the focus setup control is carried out in the section where the logical OR of the FOK signal and gate signal GATE can be obtained in the system controller 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention controls the focus of a light beam output from an optical pickup in a recording device and a reproducing device corresponding to a disc-shaped recording medium such as an optical disc and a magneto-optical disc, and an objective lens of the optical pickup. The present invention relates to a focus servo device.

[0002]

2. Description of the Related Art In a recording device and a reproducing device corresponding to a disc-shaped recording medium such as an optical disc and a magneto-optical disc, a light beam output from an optical head is controlled so as to have an appropriate focus state on a disc recording surface. Therefore, there is provided a focus servo device for driving the objective lens in the optical head in the direction of approaching and separating from the disk recording surface to perform focus control.

Since the range in which focus servo is possible (focus retractable range) is relatively narrow, recording / recording is possible.
At the start of the reproduction operation or after the track access, the focus search operation is first executed to control the objective lens position to the focus pull-in range, and then the focus servo loop is turned on to execute the focus servo. . As the start-up process for the recording or reproducing operation, focus search and focus servo are executed, and then spindle servo and tracking servo are executed. Then, when this start-up process is completed, scanning for recording or reproduction with a light beam for recording or reproduction becomes possible.

In the focus search operation, for example, the objective lens is forcibly moved between the position farthest from the disc surface and the position closest to the disc surface. At this time,
As the focus error signal E _F obtained by the calculation processing of the output of the 4-division detector that detects the reflected light in the optical head, an S-shaped curve is obtained at a certain point as shown in FIG. 7B. Further, the RF signal (sum signal of the four-division detector) is as shown in FIG. Where R
By comparing the F signal with a predetermined threshold value Th, the FOK signal is obtained as shown in FIG. 7C, and this FOK signal indicates the focus pullable range. Since the maximum value of the RF signal shown in FIG. 7A is obtained within a range of, for example, about 1 μm to 200 μm, the focus pullable range (FOK signal) shown based on this is also obtained. The range corresponding to this will be shown.

When the focus servo is turned on at the stage where the objective lens position is controlled to the focus pullable range which is the H period of the FOK signal by the focus search operation, proper focus control is executed. That is, the focus servo control for controlling the objective lens is executed with respect to the falling point of the focus zero-cross detection signal (FZC signal, that is, focus-on detection signal) in FIG. 7D in the focus pull-in range.

[0006]

FIG. 8 conceptually shows a cross section of an optical disk or a magneto-optical disk, wherein 1a is a signal surface on which audio data and the like are recorded, and 1b is formed of, for example, a transparent resin or the like. 2 shows the surface of a substrate to be processed. In such a disc-shaped recording medium, the signal surface 1a is a reflecting surface and reflects light as shown by the solid arrow in the figure, but the substrate surface 1b also reflects light to some extent as shown by the broken arrow. It is known to reflect, and the reflectance is about 8%. The reflectance of the signal surface 1a is different between the optical disc and the magneto-optical disc, and is about 70 to 80% for the optical disc and 15 to 25% for the magneto-optical disc.

Further, FIGS. 9A to 9E show the distance between the objective lens and the disc surface and the FOK signal, RF signal, and focus error signal (E) obtained corresponding to the distance.
_F ) and FZC signals. For example, assuming that the focus search operation is performed while moving the objective lens in the direction approaching from the position farther from the disc surface, first, as shown by the objective lens 3a ₁ , the substrate surface 1
When the distance is in focus with respect to b, the substrate surface 1b also has a reflectance as described above, and therefore, at this point, as shown in FIG.
The RF signal R _F and the focus error signal E _F as shown in (c) and (d) may be obtained in some cases. And wherein FOK signal is obtained as shown in FIG. 9 (b) when the time RF signal R _F has exceeded the threshold value Th, becomes the accompanying Here FZC signal also falls that this. When-focus for the signal surface 1a As further shown by the objective lens 3a ₂ approaching the disc surface, again the RF signal R _F and a focus error, as shown in FIG. (B) ~ (e) The FOK signal and the FZC signal are obtained based on the signal E _F.

That is, when the disk substrate surface has a certain degree of reflectance, the various signals indicating the focus pull-in range and focus on, which should be originally obtained only on the reflecting surface, are focused on the substrate surface. In some cases, it will be obtained in. Therefore, in the focus search operation, for example, if the objective lens is moved in a direction closer to the disk disk surface as described above, the substrate surface is focused before the reflection surface is obtained. There is a high possibility that a so-called false FOK signal, FZC signal, or the like indicating the focus pull-in range and focus-on will be obtained at that time. Then, in such a case, the servo loop is closed so as to focus on the substrate surface, and in the worst case, the signal reading becomes impossible, resulting in an inconvenient state. In particular, since the magneto-optical disk has a reflectance of 15 to 25% on the signal surface and is relatively close to the reflectance of 8% on the surface of the substrate, focus servo control is appropriately performed based on the reflection on the signal surface. By setting various gains so that it is possible to detect the reflections obtained on the substrate surface,
The possibility of the above-mentioned malfunction becomes remarkable.

To avoid this, when the focus search is performed by moving the objective lens in the direction away from the disc surface as described above, the FOK signal and the FZC signal obtained first are It is known that the control for turning on the focus servo is performed based on the FOK signal and the FZC signal obtained the second time, ignoring it. Thereby, for example, the objective lens 3a shown in FIG.
_The focus servo will be turned on at the appropriate position indicated by ₂ .

However, in the above-described method, when the reflection of the laser beam sufficient to generate the FOK signal and the FZC signal cannot be obtained on the substrate surface depending on the condition of the substrate surface of the disk and the like. Then, even if the FOK signal and the FZC signal are obtained on the signal surface, the focus servo is not turned on here, and there is a possibility that proper focus servo control cannot be obtained. In addition, if the disc height deviation or surface wobbling is significant, the FOK signal and FZC obtained at the second time
There is a problem of lack of reliability such that the signal is likely to be obtained on the substrate surface.

Therefore, as another focus search operation, first, the objective lens is forcibly brought close to the disc to a distance at which it does not come into contact with the disc surface, and in this state, the objective lens is moved away from the disc. A method is known in which the focus servo is turned on based on the FOK signal and the FZC signal that are initially obtained during this movement. In this case, since the FOK signal and FZC signal based on the signal surface of the disk having high reflectance are obtained first, it is possible to almost certainly shift to proper focus servo control.

However, in the above method, it is necessary to temporarily bring the objective lens close to the disc surface before the focus search operation is actually performed. The time required for the focus search is preferably as short as possible, but the time required for the above operation is included in the time until the focus pull-in, and as a result, it is difficult to shorten the time until the focus search is completed. have.

Further, in order to prevent collision between the objective lens and the disc surface when the objective lens is brought close to the disc surface, a mechanical stopper mechanism which normally regulates the movement of the objective lens is provided. However, since such a stopper mechanism has a mechanical structure, it requires a certain amount of space in the device, and in the configuration of the stopper mechanism, the working distance of the objective lens in the disc contacting / separating direction causes the disc surface deviation (for example, It is required to be larger than about ± 0.5 mm for a magneto-optical disk), and since the driving mechanism of the objective lens becomes large by the extent of securing this working distance, it is difficult to make the device thin and compact. I have a problem.

[0014]

In order to solve the above-mentioned problems, the present invention solves the above-mentioned problems by providing a first light amount signal detection unit capable of detecting the focus servo pull-in range based on the amount of light reflected from the disk, and the objective. A second light amount signal detection unit provided so as to be movable in the same manner as the lens and capable of detecting a predetermined range as a relative distance state with respect to the signal surface of the disc-shaped recording medium based on the amount of reflected light from the disc. It is decided to configure the optical pickup with.

Further, the first light amount signal detecting portion capable of detecting the focus servo pull-in range on the basis of the amount of light reflected from the disc and the objective lens are provided so as to be movable, and are reflected from the disc. A second light amount signal detection unit capable of detecting a predetermined range as a relative distance state with respect to the signal surface of the disc-shaped recording medium based on the light amount, a first light amount signal detection unit, and a second light amount signal detection unit. The focus servo device is configured by providing a control unit capable of performing the focus pull-in process based on the detection information of 1.

Further, the control means, when it is out of the predetermined range according to the detection information of the second light amount signal detecting section,
It is configured to perform control to move the objective lens away from the disc.

[0017]

According to the above construction, it is determined that the FOK signal is obtained when the relative distance state from the signal surface of the disk is within the predetermined range based on the detection information of the first and second light amount signal detecting means. In that case, by turning on the focus servo, the focus servo control is properly performed on the signal surface of the disk. Further, when it is out of the predetermined range indicated by the detection information of the second light amount signal detecting means, the objective lens is configured to be moved in the direction away from the disc, so that the mechanical stopper mechanism of the objective lens is used. Therefore, it is possible to avoid the collision between the objective lens and the disc.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 6 is a block diagram of a magneto-optical disk recording / reproducing apparatus (mini disk recording / reproducing apparatus) including the focus servo apparatus of the embodiment.

In FIG. 6, reference numeral 1 is a magneto-optical disk or optical disk, and the disk 1 is rotationally driven by a spindle motor 2. An optical head 3 irradiates the disk 1 with laser light during recording / reproduction, and provides a high level laser output for heating the recording track to the Curie temperature during recording on the magneto-optical disk, and during reproduction. The magnetic Kerr effect provides a relatively low level laser output for detecting data from reflected light.

When the disk 1 is an optical disk in which data is recorded in the form of pits like a CD, the optical head 3 does not use the magnetic Kerr effect but the reflected light level depending on the presence or absence of pits as in the case of a CD player. The reproduction RF signal is extracted according to the change. Of course, the magnetic field recording operation described later is not executed on the optical disc.

In order to perform the data reading operation from the disk 1 as described above, the optical head 3 detects the laser diode as the laser output means, the optical system including the deflecting beam splitter and the objective lens, and the reflected light. A detector is installed. The objective lens 3a is held by a biaxial mechanism 4 so as to be displaceable in the disc radial direction and the direction in which it comes in and out of contact with the disc, and the entire optical head 3 is movable in the disc radial direction by a sled mechanism 5.

Further, in the optical head 3 of this embodiment,
At least the focus direction (direction toward and away from the disc)
In, a photo interrupter 40 is provided so that it can be displaced in the same manner as the objective lens 3a. And
The light amount signal L _S obtained from the photo interrupter 40
Is supplied to the focus servo device (servo circuit 9) to generate a gate signal GATE indicating a wide range of focus pull-in, which will be described later.

Reference numeral 6 denotes a magnetic head for applying a magnetic field modulated by the supplied data to the magneto-optical disk, and is arranged at a position facing the optical head 3 with the disk 1 in between.

The information detected from the disk 1 by the optical head 3 by the reproducing operation is supplied to the RF amplifier 7. The RF amplifier 7 processes the supplied information,
Reproduction RF signal, tracking error signal, focus error signal, absolute position information (absolute position information recorded as pregroove (wobbling groove) on magneto-optical disk 1), address information, subcode information, focus information (FOK signal) Etc. are extracted. Then, the extracted reproduction RF signal is supplied to the encoder / decoder unit 8. Further, the tracking error signal and the focus error signal are supplied to the servo circuit 9. Further, the FOK signal is supplied to the system controller 11.

The servo circuit 9 generates various servo drive signals according to the supplied tracking error signal, focus error signal, track jump command, seek command, rotational speed detection information from the system controller 11, etc. The sled mechanism 5 is controlled to perform focus and tracking control, and the spindle motor 2 is controlled to a constant angular velocity (CAV) or a constant linear velocity (CLV).

The reproduced RF signal is sent to the encoder / decoder unit 8
Then, the EFM demodulation and the decoding process such as CIRC are performed, and the memory controller 12 once writes the data in the buffer RAM 13. The reading of data from the magneto-optical disk 1 by the optical head 3 and the reproduction data transfer from the optical head 3 to the buffer RAM 13 are performed at 1.41 Mbit / sec (intermittently).

The data written in the buffer RAM 13 is read out at the timing when the reproduction data is transferred at 0.3 Mbit / sec, and is supplied to the encoder / decoder section 14. Then, a reproduction signal process such as a decoding process for the audio compression process is performed, an analog signal is formed by the D / A converter 15, and the analog signal is supplied from a terminal 16 to a predetermined amplification circuit section and reproduced and output. For example, it is output as L and R audio signals.

As described above, the data read from the disk 1 is once written into the buffer RAM 13 intermittently at a high speed rate, and then read out at a low speed rate to output audio, so that, for example, the tracking servo is temporarily deviated and the disk 1 is read. A so-called shock proof function is realized in which the voice output is continued without interruption even if the data reading from the device becomes impossible.

Absolute position information obtained by decoding the pre-groove information output from the address decoder 10,
Alternatively, the address information recorded as data is supplied to the system controller 11 via the encoder / decoder unit 8 and used for various control operations.

When a recording operation is performed on the disk (magneto-optical disk) 1, the recording signal (analog audio signal) supplied to the terminal 17 is converted into an A / D converter 18
After being converted into digital data by, the data is supplied to the encoder / decoder unit 14 and subjected to audio compression encoding processing. The recording data compressed by the encoder / decoder unit 14 is once written in the buffer RAM 13 by the memory controller 12, is also read at a predetermined timing, and is sent to the encoder / decoder unit 8. Then, the encoder / decoder unit 8 performs CIRC encoding, E
The data is supplied to the magnetic head drive circuit 15 after being encoded by FM modulation or the like.

The magnetic head drive circuit 15 supplies a magnetic head drive signal to the magnetic head 6 according to the encoded recording data. That is, the N or S magnetic field is applied to the magneto-optical disk 1 by the magnetic head 6. Further, at this time, the system controller 11 supplies a control signal to the optical head 3 so as to output a laser beam of a recording level.

Reference numeral 19 denotes an operation input section provided with keys used for user operation, and 20 denotes a display section composed of, for example, a liquid crystal display.

In the magneto-optical disk 1, data for managing areas where data such as music is recorded and unrecorded areas are recorded as TOC information. The system controller 11 drives the spindle motor 2 and the optical head 3 at the time when the disk 1 is loaded or immediately before the recording or reproducing operation, and the TOC area set on the innermost circumference side of the disk 1, for example. To extract the data. And RF amplifier 7, encoder /
The TOC information supplied to the memory controller 12 via the decoder section 8 is stored in a predetermined area of the buffer RAM 13 and used for controlling the recording / reproducing operation for the disc 1 thereafter.

The focus servo apparatus of this embodiment mounted on such a recording / reproducing apparatus will be described with reference to FIGS. FIG. 3 shows the optical head 3 and RF in FIG.
Amplifier 7, servo circuit 9, and system controller 1
1 is shown in detail. It should be noted that FIG. 3 shows only a component part as a focus servo device, and illustration and description of the servo circuit configurations of the tracking, sled, and spindle are omitted.

First, as shown in FIG. 3, in the biaxial mechanism 4 of the optical head 3 of the present embodiment, a photo interrupter 40 is provided so as to be movable in the same manner as the objective lens 3a. In this photo interrupter 40, 4
Reference numeral 0a represents a light emitting element such as an LED, and 40b represents a light receiving element such as a photodiode.

The photo interrupter 40 will now be described with reference to FIGS. FIG. 4 is a diagram conceptually showing the focus actuator in the optical head 3 of this embodiment. The photo interrupter 40 is attached, for example, as shown in this figure. Reference numeral 4a denotes a focus actuator for driving the objective lens 3a in the direction in which the biaxial mechanism 4 comes into contact with and separates from the disc, and is shown by a cross section. This focus actuator 4a
In the figure, Y indicates a yoke, and M provided on the inner wall side of the yoke Y indicates a magnet. Further, B indicates a bobbin, to which the objective lens 3a and the photo interrupter 40 are fixedly attached. At this time, the objective lens 3a and the photo interrupter 40
The fixed positions of are preferably close to each other. L, which is wound around the outer wall of the bobbin B, is a coil. In this figure, 41 is a beam splitter, 42 and 45 are collimator lenses, 43 is an analysis grating, 44 is a Wollaston prism, 46 is a multi-lens, RD is a laser diode that outputs laser light, and PD is a disk 1 disc. Beam splitter 4 for reflected light
1, Wollaston prism 44, Collimator lens 4
5, a photodiode received via the multi-lens 46.

That is, in the focus actuator 4a having the above structure, the bobbin B is driven in the vertical direction shown in the figure according to the amount of current supplied to the coil L and the polarity. Thereby, the objective lens 3 fixed to the bobbin B
a moves toward and away from the disc surface in response to the movement of the bobbin B. At this time, since the photo interrupter 40 is also fixed with respect to the bobbin B, the photo interrupter 40 also moves toward the objective lens 3a. It will be the same movement as. At this time, the photo interrupter 4
The LED light output from the light emitting element 40a of No. 0 is reflected on the signal surface 1a of the disk 1 as shown by the arrow in the figure, and this reflected light is obtained by the light receiving element 40b. The level change of the light amount obtained at 40b is used as the output signal of the photo interrupter 40.

The output of the photo interrupter 40 has the characteristics shown by the curve in FIG. 5A, for example,
In this figure, the vertical axis shows the output, and the horizontal axis shows the distance between the photo interrupter 40 and the reflection target. It should be noted that the output here is relative, and the level of the light emission amount on the light emitting element side is not 100%, but the output when the light receiving level on the light receiving element side is maximum under given conditions is 100%. % The light receiving characteristic of the photo interrupter 40 is obtained as a curve showing a peak (100%) at a predetermined distance D _L as shown in this figure.

Therefore, in the present embodiment, the distance D _L is set so as to correspond to the just-focused distance between the objective lens 3a and the disc surface based on such a light receiving characteristic. Therefore, assuming that the reflection target of the photo interrupter 40 attached as shown in FIG. 4 is the signal surface of the magneto-optical disk, the distance between the photo interrupter 40 and the signal surface 1a is as shown by the curve in FIG. 5B. D
_{When it} reaches _L (the distance at which the objective lens 3a is just in focus with respect to the disc signal surface), the peak (100
%) Output will be obtained. The characteristic of the photo interrupter 40 in this embodiment has a maximum value within a range of, for example, about 200 μm to 5 mm, and therefore, the above-described about 1 μm to 20 μm.
It is possible to show a predetermined position range including the position where the objective lens 3a is just focused with respect to the signal surface of the disk, in a range wider than the RF signal that gives the maximum value in the range of 0 μm. It should be noted that the small undulations obtained at points closer than the distance D _L in the curve of FIG. 5B are caused by the light reflected on the substrate surface of the disk. Since the characteristic of 40 has a peak in a wide range, such a reaction becomes so small that it can be ignored.

Then, the output of the photo interrupter 40 obtained as described above is supplied to the comparator 39 as the light quantity level signal L _S, as shown in FIG. 3, and is compared _therewith with a predetermined reference voltage V _ref2. . As a result, the comparator 39
From the above, it becomes possible to generate a gate signal GATE, which has a wider range than the FOK signal and includes the position where the objective lens 3a is just focused on the signal surface of the disc, and outputs the gate signal GATE to the system controller 11.

Further, in the optical head 3 shown in FIG. 3, the four-division detector 3b (A, B,
C, D) and the side spot detector 3c (E,
F), a detector 3d (I, J) for detecting magneto-optical data and pit data, each of which has a detection signal of RF.
Supplied to the pump 7. In the RF amplifier 7, the detection signals (E, F) from the side spot detector 3c are used to generate a tracking error signal. The focus error signal E _F is the RF amplifier 7, four-output division detector 3b (A, B, C, D) calculation of (A + D) - (B + C) is generated is performed.

The RF signal is generated in the RF amplifier 7 by using the output (I, J) of the detector 3d. That is, I-J data is extracted for magneto-optical data, and I + J data is extracted for pit data. Furthermore, the calculation processing (A + B +) of the output of the four-division detector 3b
The sum signal is obtained by (C + D). The FOK signal described in FIG. 9 is generated by the comparison processing of the sum signal and a predetermined threshold value, and the system controller 1
1 is supplied.

The focus error signal E _F is sent to the servo circuit 9
At, the signal is supplied to the phase compensating circuit 30 via the resistors R ₁ and R ₂ , and the phase compensating process is performed. Then, the output of the phase compensation circuit 30 is supplied to the focus driver 32 via the resistor R ₃ and the differential amplifier circuit 31. Then, the output of the focus driver 32 is applied to the focus coil in the biaxial mechanism 4 as a focus drive signal. R ₄ is a feedback resistor of the differential amplifier circuit 31.

The above signal loop is a focus servo loop, and this loop functions when the switch SW ₁ is off, and the focus servo control is executed. When the switch SW ₁ is turned on, the feedback loop for this focus servo is opened and the focus servo operation is turned off.

Further, the focus error signal E _F is supplied to the comparator 33, and the FZC signal is generated by being compared with the reference voltage V _ref1 and supplied to the system controller 11.

Reference numerals 34 and 35 are current source circuits, and 34 is a current source circuit for outputting a drive current for driving (searching up) the objective lens 3a in the direction approaching the surface of the disk 1 in the focus search operation. Reference numeral 35 denotes a current source circuit that outputs a drive current for driving (searching down) the objective lens 3a in the direction away from the surface of the disk 1 in the focus search operation.

Each of these current source circuits has a switch S.
It is connected to a time constant circuit composed of a time constant capacitor C ₁ and a time constant resistor R ₇ via W ₃ and SW ₄ . The output differential amplifier circuit 38 of the time constant circuit, the resistor R _6, R
₅ through are adapted to be supplied to the differential amplifier circuit 31, the period switch SW ₂ is turned off, through a search drive current focus driver 32 from the current source circuit 34, 35 the two-axis mechanism No. 4 focus coil is applied.

The switch SW ₁ to SW ₄ is turned on / off by switch control signals S _SW1 to S _SW4 supplied from the system controller 11, respectively.

As the focus servo apparatus of this embodiment, the servo circuit (focus servo circuit) shown in FIG. 3 is used.
9 and system controller 11 has a control function for the focus servo circuit.

The focus search operation of the focus servo apparatus of the present embodiment having the above-mentioned structure will be described below with reference to FIG. FIG. 1A shows an objective lens 3a.
And the disc surface (ie, photo interrupter 40
And the distance from the disc surface). That is, in the focus search operation of this embodiment, the objective lens 3a is moved in the direction approaching from the position away from the disc surface, and the operation of pulling up the objective lens 3a so as to approach the disc once is not performed. And
The following waveform diagrams of FIGS. 1 (b) to 1 (h) are shown corresponding to the distance between the objective lens 3a of FIG. 1 (a) and the disc surface.

For example, if the focus search operation is started from a point P ₀ at which the objective lens 3a is separated from the disc surface by a certain distance, at this time, the laser light is emitted from the objective lens 3a and the light emitting element of the photo interrupter 40 is also used. For example, LED light is output from 40a. Then, in the process in which the objective lens 3a (and the photo interrupter 40) gradually approaches the disc surface, the laser light is reflected by the substrate surface 1b of the disc 1 as described above. If the point where the focus of the objective lens 3a coincides with the substrate surface 1b is the point P ₂ shown in the figure, the focus error signal E _F before and after this point P _{2 is} the point P ₂ as shown in FIG. You will get an S-shaped zero cross at ₂ . At this time, for example, when the RF signal is obtained as shown in FIG. 1B and exceeds the threshold level Th ₁ , as shown in sections P _{1 to} P ₃ of FIG. 1C,
A so-called false FOK signal is obtained. Further, based on this, as shown in FIG. 1 (e), a false FZC is obtained at the point P ₂ .
A signal will be obtained.

When the objective lens 3a (and the photo interrupter 40) is further driven so as to approach the disc surface of the disc 1, next, the focal point of the objective lens 3a with respect to the signal surface 1a of the disc 1. A matching point is obtained, and this point is, for example, the point P ₆ shown in the figure. At this time, the focus error signal E _F is shown in FIG.
Although S-be zero-cross at the point P _6, as shown in the resulting, this time the RF signal to the point P ₆ and peaks as shown in FIG. 1 (a) is obtained, P ₅ ~ of the RF signal in FIG. P
Assuming that the threshold level Th ₁ is exceeded in the section of _7, the section P _{5 to} P ₅ is set as shown in FIG.
_{At 7} , the FOK signal will be obtained. Further, based on the focus error signal E _F , an FZC signal is also obtained at the point P _{6 as} shown in FIG. 1 (e).

At this time, the output of the photo interrupter 40 (light amount signal L _S ) coincides with the distance at which the focus of the objective lens 3a is aligned with the signal surface 1a of the disc 1 as shown in FIG. 5 (b). In this case, the maximum output is obtained, so that a relatively broad curve having a peak at the point P ₆ is obtained as shown in FIG. 1 (f). Then, this light amount signal L _S is input to the comparator 39, and if it exceeds the threshold level Th ₂ (= reference voltage V _ref2 ) here, the H level gate signal GATE is obtained in that section. For example, in this figure, since the threshold level Th ₂ is exceeded in the sections P _{4 to} P ₈ before and after the point P ₆ , the gate signal GATE is at the H level in this section as shown in FIG. Becomes Then, based on the fact that the light amount signal L _S has a maximum value in a wider range than the RF signal as described above, the FO
The gate signal GAT of the H level is in the sections P _{4 to} P ₈ wider than the section P _{5 to} P ₇ in which the K signal is the H level.
E will be obtained.

Then, in the system controller 11, the input FOK signal and the gate signal GA are input.
Processing for obtaining the logical product of TE is performed. Therefore, in this case, the FOK signal and the gate signal GATE are at H level.
The level section, that is, F when the focus of the objective lens 3a is obtained with respect to the signal surface 1a of the disc 1
In the section P ₅ to P ₇ the OK signal is the H level, within the system controller 11 as shown in FIG. 1 (h), so that the H level is obtained as the operation result of the logical product.

In the system controller 11, for example, during the period when the logical product is H level, the FZC
When the signal is obtained, the switch control signal S _SW1 is output to turn off the switch SW ₁ , and the control for closing the focus servo loop is performed. Therefore, in this figure, the focus servo is turned on at the point P ₆ in FIG. 1E, and thereafter, proper focus servo control is executed.

Since the operation at the time of focus search is performed as described above, even if the objective lens is driven in the direction of approaching from the position away from the disc 1, the focus of the objective lens 3a becomes the disc 1. Substrate surface 1b
The point obtained with respect to is passed, and the focus servo loop can be surely closed at the point where the focus of the objective lens 3a is obtained on the signal surface 1a of the disc 1, and the focus is focused on the substrate surface 1b of the disc 1. It is possible to prevent a malfunction such that the focus servo loop is closed in the state where there is. Although FIG. 1 shows the case where a false FOK signal is first obtained, the substrate surface 1b
Fake FOK signal is not obtained when there is a focus on
Even when the original FOK signal is first obtained, whether or not to turn on the focus servo loop depends on the logical product of the FOK signal and the gate signal GATE, so that an appropriate focus position is always searched. It is possible.
This makes it possible to omit the conventional operation of bringing the objective lens once closer to the disc surface. Further, since such an operation is omitted, it is possible to omit the stopper of the mechanical mechanism that is conventionally provided.

Further, in this embodiment, the photo interrupter 40 is used without using a mechanical stopper mechanism.
It is possible to prevent the disc surface and the objective lens from accidentally colliding with each other based on the gate signal GATE obtained based on the output of. As mentioned above, for example RF
The signal has a maximum value in a relatively narrow range of about 1 μm to 200 μm, whereas the output of the photo interrupter 40 is a signal having a maximum value in the range of 200 μm to 5 mm. Therefore, it is obtained based on the RF signal. The focus pull-in range indicated by the FOK signal and the gate signal GAT obtained based on the output of the photo interrupter 40.
If the ranges indicated by E are compared, the gate signal GA
TE indicates a wider range. That is, when the gate signal GATE is at L level, FOK
It can be regarded as completely deviating from the focus pullable range indicated by the signal.

[0058] Based on this, for example, the focus in the case where the servo loop focus servo is turned on are performed, outer than the interval P ₄ to P ₈ in FIG. 1 by moving the objective lens 3a is large by any Cause When the gate signal GATE is located in the range of, and the gate signal GATE is changed from the H level to the L level, the system controller 11 has a large possibility of colliding with the disc surface and the objective lens 3a. It is possible to forcibly separate the objective lens 3a from the surface of the disk 1, for example, move it to the point P _{0 in} FIG. Even when the gate signal GATE changes from the H level to the L level in a state where the objective lens 3a is farther from the disc 1 than the point P ₄ shown in FIG. 1, the objective lens 3a is forcibly moved in a direction away from the disc. However, the gate signal GATE is L
In the state in which the level is reached, since the focus pulling-in range is already largely deviated, for example, after the objective lens 3a is separated from the disc 1 as described above, FIG.
As described above, there is no particular problem because it is sufficient to perform the focus search and restore.

In the focus search, the objective lens 3a can be controlled so as not to collide with the disc 1 as follows. In this case, since the objective lens 3a moves in the direction approaching from the position away from the disc 1, the gate signal GATE first shows the L level as shown in FIG. 1 (g). Then, during this period, the system controller 11 continues the control for driving the objective lens 3a in the direction of approaching the disc 1. Then, when the distance between the objective lens 3a and the signal surface of the disc 1 becomes substantially proper, the gate signal GATE changes to the H level as shown in sections P _{4 to} P ₈ of FIG. 1 (g). If the focus servo loop is not turned on for some reason in the sections P _{4 to} P ₈ and the objective lens 3 a is driven so as to approach the disc 1 and exceeds the point P ₈ , the gate signal GA is again output.
TE changes to L level. Then, when the L level is obtained again, the system controller 11 performs control so as to forcibly move the objective lens 3a in a direction away from the disc 1. That is, in the focus search, when the gate signal GATE changes from L → H → L, the operation of moving the objective lens 3a away from the disc is executed. In this manner, it is possible to prevent the objective lens 3a from colliding with the disc surface during the focus servo and the focus search.

Therefore, the processing operation of the system controller 11 during the above operation will be described with reference to the flowchart of FIG. In this routine, the system controller 11 first determines whether the focus control mode is currently set to focus servo or focus search (F101). Therefore, if it is determined in step F101 that the focus servo is being performed, the process proceeds to step F102 to determine whether or not the gate signal GATE has changed to the L level. Here, when the gate signal GATE does not show a change to the L level, that is, when the H level is maintained, for example, the main routine is returned to and the required processing is performed. Is changed to the L level, the process proceeds to step F104 to perform a process of moving the objective lens 3a so as to forcibly separate it from the disc 1, and then the process returns to the main routine. As a specific process for separating the objective lens 3a from the disc 1 at this time, the system controller 11 uses, for example, FIG.
The switch SW ₁ shown in ( ₁₎ is turned on to open the focus servo loop, and the switch SW ₂ is turned off to bring about an operation state corresponding to the focus search. Then, the switch SW ₄ is turned on so that a drive current for search down is supplied from the current source circuit 35 to the focus actuator via the focus driver 3.

If it is determined in step F101 that the focus search is currently being performed, the process proceeds to step F103, in which the gate signal GATE up to the present at the time of the focus search is executed.
It is determined whether or not the signal change of L indicates L → H → L. Here, if the gate signal GATE does not indicate the change of L → H → L, for example, the process returns to the main routine, and in this case, necessary processing such as continuing the focus search control is performed. On the other hand, here, the gate signal GATE is changed from L → H.
If the change in L has occurred, the process proceeds to step F104, the objective lens 3a is moved away from the disc 1, and then the main routine is returned to. In the focus search of this embodiment, for example, the operation of each switch in FIG. 3 is such that the switch SW ₂ is in the off state and the switch ₃ is turned on to output the search-up drive current. In this case, by turning off the switch SW ₃ and turning on the switch SW ₄ , the operation of moving the objective lens 3 a in the direction away from the disc 1 is realized.

Although the optical pickup and the focus servo device mounted on the mini disk recording / reproducing apparatus are used in the above-mentioned embodiment, the optical pickup and the focus servo device of the present invention are not limited to this, and a CD or other disk-shaped recording medium. Can be applied to a recording device and a reproducing device corresponding to.

[0063]

As described above, the optical pickup and the focus servo apparatus of the present invention include the first light amount detecting means capable of indicating the normal focus pull-in range, and the predetermined amount from the signal surface of the disc by the photo interrupter or the like. Since the focus pull-in control can be performed on the basis of the detection information of the second light amount detecting means capable of indicating the distance state of, the false focus due to the light reflection that is obtained on the substrate surface of the disc. It becomes possible to apply focus servo at a point where the objective lens is surely focused on the signal surface of the disc, ignoring the pull-in information. For this reason, it becomes possible to immediately drive the objective lens in a direction approaching from a position away from the disc to perform a focus search.
The operation of bringing the objective lens closer to the disk once can be omitted, and as a result, the time required for the focus search can be shortened. Further, this eliminates the need for providing a mechanical stopper mechanism for the objective lens, which has the effect of facilitating downsizing and thinning of the device.

Further, when it is determined that the objective lens is located outside the focus pull-in range by using the detection information of the second light amount detecting means, the objective lens is pulled down so as not to collide with the disc. In this case as well, a mechanical objective lens stopper mechanism is not required, which is also effective for downsizing and thinning of the device, and this process can be realized by software, so the cost can be suppressed. It also has the effect.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing a focus search operation in an embodiment of a focus servo apparatus of the present invention.

FIG. 2 is a flowchart of a focus search operation of the embodiment.

FIG. 3 is a configuration diagram of an embodiment of a focus servo apparatus of the embodiment.

FIG. 4 is an explanatory diagram showing a fixed state of a photo interrupter in the optical pickup of the embodiment.

FIG. 5 is a curve showing the output characteristics of the photo interrupter of the example.

FIG. 6 is a block diagram of a recording / reproducing apparatus including the focus servo apparatus according to the embodiment.

FIG. 7 is an explanatory diagram of a focus search operation.

FIG. 8 is an explanatory diagram showing a light reflection state of a recording medium on a disc.

FIG. 9 is an explanatory diagram of a conventional focus search operation.

[Explanation of symbols]

1 disk 3 optical head 3a objective lens 4 two-axis mechanism 7 RF amplifier 9 servo circuit 11 system controller 31,38 differential amplifier circuit 32 focus driver 33,39 comparator 34,35 current source circuit 40 photo interrupter SW ₁ , SW ₂ , SW ₃ and SW ₄ switches

Claims (3)

[Claims] 1. A first light amount signal detecting means capable of detecting a focus servo pull-in range on the basis of the amount of light reflected from a disk-shaped recording medium, and the same movement of an objective lens in the optical axis direction. And a second light amount signal detecting means capable of detecting a predetermined range as a relative distance state with respect to the signal surface of the disc recording medium, based on the amount of light reflected from the disc recording medium. Characteristic optical pickup. 2. A first light amount signal detecting means capable of detecting a focus servo pull-in range based on a reflected light amount from a disc-shaped recording medium, and the same movement as an objective lens in an optical axis direction. A second light amount signal detecting means which is provided and can detect a predetermined range as a relative distance state with respect to the signal surface of the disc recording medium based on the amount of reflected light from the disc recording medium; A focus servo device comprising: a control unit capable of performing a focus pull-in process based on detection information of the signal detection unit and the second light amount signal detection unit. 3. The control means moves the objective lens in a direction away from the disc-shaped recording medium when the control information is out of the predetermined range according to the detection information of the second light amount signal detection means. The focus servo device according to claim 2, wherein the focus servo device is configured.