JP2003077194A - Recording and reproducing device for information recording disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording and reproducing device for information recording disk, which prevents interference between magnetic fields of focus servo and tracking servo driving circuits and a recording magnetic field to a small- sized information recording disk. SOLUTION: The recording and reproducing device is suitable for miniaturization of a drive because an objective lens 50 and a coil 49 for the recording magnetic field are arranged on the same side of an optical disk 40. The interference between magnetic field of focusing and tracking magnetic circuits and a magnetic circuit for generating the magnetic field is not a problem because the focusing magnetic circuit comprising a focusing coil 44 and a magnet 45 and the tracking magnetic circuit comprising a tracking coil 46 and a magnet 47 are arranged apart from the magnetic circuit including a coil 49 for the recording magnet provided in an optical pickup 48 as the base side and the front end part of a cantilever.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording disk recording / reproducing apparatus, and more particularly to a disk-shaped magneto-optical recording medium (hereinafter referred to as M
The present invention relates to a recording / reproducing apparatus for an information recording disc that records and reproduces an information signal on / from an O disc.

[0002]

2. Description of the Related Art Conventionally, an MO disk is excellent in the characteristic that recording and reproduction are repeated many times.
The O board requires an external magnetic field. FIG. 10 is a sectional view showing an example of a conventional recording / reproducing apparatus for an information recording disk. This conventional device is the recording / reproducing device described in JP-A-2000-215447. In the figure, an MO disk 1 is an information recording disk capable of recording and reproducing on both sides, and high magnetic permeability layers 3a and 3b and photocurable resin layers 4a and 4b are respectively formed on both surfaces of a substrate 2.
And magneto-optical recording layers 5a and 5b and adhesive layers 6a and 6b
And the transparent protective plates 7a and 7b are laminated.

Two magneto-optical pickup devices are provided so as to face both sides of the MO board 1. These two magneto-optical pickup devices are respectively laser devices 8a and 8a.
8b, objective lenses 9a and 9b, focusing coils 10a and 10b, and tracking coils 11a and 11
b and these coils 10a and 11a, 10b and 1
1b is a cylindrical coil bobbin 12a around which 1b is wound.
2b, and a pickup including magnets 13a and 13b arranged outside the coil bobbins 12a and 12b, and conductors 15a and 15 for generating a magnetic field by passing a current of a high frequency signal on the surfaces of the optical glasses 14a and 14b.
b is composed of a magnetic field generator formed as a spiral coil pattern.

In this recording / reproducing apparatus, high-speed inversion control is performed according to a recording signal by supplying a high-frequency current obtained by amplifying a signal to be recorded, to a coil pattern formed by the conductors 15a and 15b of the magnetic field generator. Generated magnetic field is applied to the magneto-optical recording layers 5a and 5b, and the laser beams emitted from the laser devices 8a and 8b are applied to the magnetic field application regions of the objective lenses 9a and 9b and the optical glass 14a.
Focusing is performed via 14b, and the temperature at the focusing position is raised to above the Curie point for recording.

Such an MO board has a diameter of 64 mm, for example.
Although a small board of 50.8 mm has been put into practical use, in recent years,
Further studies have been made on miniaturization, and for example, a phase change type optical disc system having a diameter of 32 mm has been developed. In the case of such a small disk, there is a strong demand for downsizing and thinning of a recording / reproducing device (hereinafter, also referred to as a drive) to be used, and in that case, downsizing and thinning of the optical pickup are important factors. .

Generally, in order to shorten the distance between the coil for applying a magnetic field to the MO board and the MO board, a magnetic field generator is arranged on the side opposite to the laser beam incident surface of the transparent protective plate. Since it is necessary to have a pickup and a magnetic field generator on different sides of the MO board, it is difficult to miniaturize the drive. On the other hand, in the conventional device shown in FIG. 10, the pickup and the magnetic field generator are provided on the MO board 1.
Since they are arranged on the same side with respect to, the drive can be downsized.

On the other hand, in order to handle a small-sized optical disk, the structure in which a cantilever is used as a drive shares a radial feed mechanism of the optical disk and a tracking driver,
Further, the focus driver can be realized by having a common part with the tracking driver, which is useful for downsizing of the drive. A method of arranging the focus and tracking driver on the base side of the cantilever and arranging the optical pickup on the tip side of the cantilever is a write-once, that is, a phase change type optical disc that allows writing only once, a read-only optical disc (ROM disc) ), And three types of optical discs in which they coexist on a single disc.

In pursuit of a structure using a cantilever,
It is known that the focus and tracking driver is configured on the fulcrum side of the cantilever, and the optical system including the laser of the light source and the objective lens is arranged on the tip side of the cantilever as a small unit of several millimeters cubic. Since the force of the focus driver is transmitted to the objective lens via the cantilever, the objective lens makes a rotational movement, and the lens surface is not parallel to the optical disk surface correspondingly.

When a small-diameter objective lens is used for recording / reproduction of a small optical disk, the distance between the objective lens and the optical disk, that is, the working distance becomes small, and the focus is pulled in when the focus servo is pulled in or the disk is damaged or disturbed. The servo is disturbed and the objective lens easily collides with the optical disc. Therefore, a recording / reproducing apparatus for an information recording disk has been conventionally known, which enables downsizing and thinning of an optical disk drive by performing focus servo for avoiding the above-mentioned collision (Japanese Patent Laid-Open No. 7-
6372 publication).

FIG. 11 is a block diagram showing an example of the above-mentioned conventional recording / reproducing apparatus for an information recording disk. In the figure, light emitted from a semiconductor laser (not shown) and reflected by the optical disc 21 is detected by a photodetector 25 through an optical pickup 24 having an objective lens 22, a mirror 23 and the like. The optical pickup 24 is rotated about the rotation shaft 24a by the focus actuator 26, so that the distance (working distance) between the objective lens 22 and the optical disk 21 in the focus axis direction changes.

The absolute displacement of the optical pickup 24 in the focus axis direction is detected by the optical displacement detector 27, and the detection signal is output by the comparator 28 at a position slightly before the focus point V1.
At the same time, it is compared by the comparator 29 with the output V2 at a position slightly in the focus point. When the objective lens 22 is near the in-focus point, that is, when the detection signal level is between V1 and V2, the comparator 28 at that time is detected.
And the output of 29, the controller 30 switches 3
2 is controlled to be connected to the terminal a side. As a result, the photodetector 2
The focus error signal from No. 5 is supplied as a drive signal to the focus actuator 26 through the phase compensation circuit 31, the switch 32, and the power amplifier 33 to perform focus servo.

On the other hand, when the objective lens 22 is not near the in-focus point, that is, whether the detection signal level is higher than V1 above,
When less than V2, the controller 30 sets the switch 32 to the terminal b based on the outputs of the comparators 28 and 29 at that time.
Switch control to the side. Thereby, the detection signal from the optical displacement detector 27 is set to 0 by the 0-point converter 34.
The signal obtained by converting as V is supplied as a drive signal to the focus actuator 26 through the phase compensation circuit 35, the switch 32, and the power amplifier 33 to perform focus servo.

The 0-point converter 34, the phase compensation circuit 35,
The second focus servo system including the power amplifier 33 has a wider focus detection range and lower detection sensitivity than the first focus servo system including the phase compensation circuit 31 and the power amplifier 33, and also scratches and disturbance of the optical disk 21. Or when the focus servo is pulled in, the focus servo operates by switching to this second focus servo system.
The objective lens 22 does not move largely, and collision with the optical disk 21 is avoided.

[0014]

However, in the conventional device shown in FIG. 10, the focusing coils 10a and 10b are provided.
And tracking coils 11a and 11b, cylindrical coil bobbins 12a and 12b around which the coils 10a and 11a, 10b and 11b are wound, and magnets 13a and 13b arranged outside the coil bobbins 12a and 12b. Since the focusing and tracking magnetic circuits composed of and the magnetic field generating device composed of the optical glasses 14a and 14b and the spiral coil pattern conductors 15a and 15b are arranged close to each other, the magnetic fields of the two interfere with each other. There is a problem that it interferes with the focus servo and tracking servo.

Further, in the conventional apparatus shown in FIG. 11, the focus servo is disturbed due to scratches on the optical disk during the focus servo operation, or the optical axis of the optical pickup is tilted because the optical disk is fast-forwarded in the radial direction of the disk. Even if disturbance of the focus servo occurs due to tracking groove information or reflected light from the header portion entering the focus servo detection as crosstalk due to the above, instead of immediately switching to the second focus servo system,
Since the objective lens 22 is switched to the second focus servo system only after the objective lens 22 is not in the vicinity of the in-focus point due to the disturbance of the focus servo, the collision avoiding operation of the objective lens 22 with respect to the optical disk 21 cannot be performed quickly. There is a problem.

Further, since the conventional device shown in FIG. 11 is not a device for recording / reproducing information signals to / from an MO board, a magnetic circuit for focusing and tracking and a magnetic field generating device for downsizing the device. Nothing is said about the structure of how to arrange.

The present invention has been made in view of the above points,
An object of the present invention is to provide a recording / reproducing apparatus for an information recording disc that can prevent interference between the magnetic fields of the focus servo and tracking servo drive magnetic circuits and the recording magnetic field on a small information recording disc.

Another object of the present invention is to record information in a recording / reproducing apparatus having a small working distance and a small working distance using a cantilever capable of promptly avoiding a collision between an optical disk and an objective lens caused by disturbance of focus servo. It is to provide a disk recording / reproducing device.

[0019]

In order to achieve the above object, the present invention irradiates a magneto-optical information recording disk with a laser beam through an objective lens to obtain a signal recording surface of the magneto-optical information recording disk. An optical pickup that detects the reflected light from the photodetector through an objective lens and also applies the recording magnetic field generated by the magnetic field generator to the magneto-optical information recording disk during recording on the magneto-optical information recording disk. And a focusing coil and a tracking coil are provided on the base side, and an optical pickup is provided at a position facing the magneto-optical information recording disk at the tip end in close proximity to and away from the magneto-optical information recording disk. It is configured to be rotatable in the focus axis direction on a plane perpendicular to the surface of the disk, and
A reproduction signal is generated based on a signal from a cantilever that is rotatable about the tracking axis in the tracking axis direction on a plane parallel to the surface of the magneto-optical information recording disk, and a signal from the photodetector of the optical pickup. Based on the signals from the reproduction signal processing system and the photodetector of the optical pickup, a drive current is supplied to the focusing coil and the tracking coil to generate a magnetic force together with the magnetic field of the focusing magnet and the tracking magnet. , A servo circuit for rotating the cantilever in the focus axis direction and the tracking axis direction, and a rotating means for rotating the magneto-optical information recording disk.

In the present invention, the magnetic field generator for applying the recording magnetic field to the magneto-optical information recording disk is provided in the same optical pickup having the objective lens, and the optical pickup, that is, the magnetic field generator is provided at the tip of the cantilever. The magnetic field for focusing, which includes the focusing coil and the focusing magnet, and the tracking magnetic circuit, which includes the tracking coil and the tracking magnet, are placed on the base side of the cantilever. It can be arranged on the same side as the magneto-optical information recording disk, and the magnetic field generating device can be separated from the focusing magnetic circuit and the tracking magnetic circuit by substantially the length of the cantilever.

In order to achieve the above object, the present invention is, in addition to the configuration of the above invention, a height sensor for optically detecting the height of the bottom surface of the cantilever with respect to a fixed reference surface, and an optical pickup. Based on the signal from the photodetector, the abnormality determination circuit that determines the abnormality due to dust and scratches on the magneto-optical information recording disk, and the abnormality determination signal from the abnormality determination circuit And a switching means for switching the drive current flowing through the switch from a signal based on the output signal of the photodetector of the optical pickup to a signal based on the output signal of the height sensor.

According to the present invention, when the abnormality determining circuit determines an abnormality due to dust or scratches on the magneto-optical information recording disk, the drive current supplied to the tracking coil is a signal based on the output signal of the photodetector of the optical pickup. Therefore, the height of the cantilever with respect to the fixed reference surface is switched to the signal based on the output signal of the height sensor that optically detects, so that the height of the magneto-optical information recording disk is not affected by scratches or dust at all. The cantilever whose focus servo loop is controlled based on the output signal of the sensor does not enter into a state where it can freely move, and the rigidity of the closed loop servo can be maintained. Also, when the optical pickup actually detects an abnormality due to dust or scratches on the magneto-optical information recording disk before approaching the magneto-optical information recording disk less than the predetermined distance, the focus servo loop is switched. it can.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the essential parts of a first embodiment of an information recording disk recording / reproducing apparatus according to the present invention. In the figure, an optical disk 40 is a magneto-optical information recording disk (MO disk) suitable for erasing / reproducing a plurality of times, and its center hole 40a is fitted and held by a spindle 41 which is a shaft of a spindle motor and is rotated at a high speed. It The optical disc 40 is a small disc having a diameter of, for example, about 25 mm to 50 mm. Here, it is assumed that the optical disc 40 has a diameter of 32 mm.

A cantilever 42 is arranged at a position close to the surface of the optical disc 40, and is configured to be rotatable about a focus shaft 43 in the vertical focus axis direction in the drawing. . The focusing coil 4 is provided on the bottom surface of the cantilever 42 near the focus axis 43.
4. A tracking coil 46 is arranged, a focusing magnet 45 is provided around the focusing coil 44, and a tracking magnet 47 is provided around the tracking coil 46. Further, an optical pickup 48 is arranged at the tip of the cantilever 42 so as to face the signal recording surface of the optical disc 40 closely and separately.

FIG. 2 is a schematic perspective view of the cantilever 42.
A movement amount corresponding to the magnitude of the focus error signal current flowing in the focusing coil 44 shown in FIG. 1 in the focus axis direction indicated by arrow F around the focus axis 43, and
It is rotated in a direction corresponding to the direction of the electric current (that is, in the drawing, in the upward or downward direction). Also, the cantilever 42 is
With the tracking axis shown in FIG. 2 as the center, in the tracking axis direction shown by the arrow T, there is a movement amount corresponding to the magnitude of the tracking error signal current flowing in the tracking coil 46 shown in FIG. 1, and the direction of the current. Is rotated in the direction (that is, leftward or rightward in the drawing).

As the cantilever 42 rotates in the focus axis direction F and the tracking axis direction T, the optical pickup 48 provided at the tip of the cantilever 42 also rotates integrally with the cantilever 42.

Here, since the cantilever 42 rotates around the focus shaft 43, the objective lens 5 in the optical pickup 48 provided at the tip of the cantilever 42.
Since 0 makes a rotational movement accordingly, the optical axis is not perpendicular to the surface of the optical disc 40 due to the focus operation, and the transparent protection between the incident surface of the laser on the optical disc 40 and the signal recording layer of the optical disc 40 is prevented. The layer causes coma (for convenience of illustration, the thickness of the transparent protective layer is zero in FIG. 1).

Since the thickness of the transparent protective layer is directly proportional to the coma aberration, the thickness of the transparent protective layer is preferably thin from the viewpoint of reducing the coma aberration. On the other hand, the transparent protective layer plays a role of separating the recording / reproducing laser from the focus with respect to dust on the surface of the disc, and therefore the thicker transparent protective layer is preferable from this viewpoint.

There are two thicknesses of the transparent protective layer satisfying these conditions. The first thickness is 0.05-0.15mm
It is thick. That is, a DVD (Dig with an optical plate thickness of 0.6 mm
If a coma aberration of 1/4 or less of italVersatile Disc) is assigned, the thickness becomes 0.15 mm or less. It is preferably 0.05 mm or more.

With the thickness of 0.05 to 0.15 mm, the out-focus effect is maintained for dust particles having a diameter on the order of several μm, which are often attached to the surface of the optical disk. An optical disk having a transparent protective layer having such a thickness can be manufactured by a means for sticking a transparent film sheet typically having this thickness as already known.

The second thickness is several μm or less. The transparent protective layer having this thickness can be obtained by a spin coating method of a photocurable resin or a means for producing a transparent dielectric in vacuum. With this thickness, dust on the surface of the optical disk directly interferes with the recording / reproducing light during recording / reproduction, and therefore it is necessary to improve the signal error correction capability more than that of the conventional optical disk device. In view of the above points, in the present embodiment, the transparent protective layer of the optical disc 40 is set to 0.15 mm or less.

As shown in FIGS. 1 and 2, an optical pickup 48 is attached to the tip of the cantilever 42 so as to face the signal recording surface of the optical disc 40 in close proximity and separation. As shown in FIG. 3, the optical pickup 48 includes a recording magnetic field coil 49, an objective lens 50, a semiconductor laser 51,
Half mirror 52, prism 53, and photodetectors 54 and 5
It is composed of 5 and. The half mirror 52 is provided on the inclined surface of the prism 53.

In this optical pickup 48, the laser light emitted from the semiconductor laser 51 is reflected by the half mirror 52 and enters the objective lens 50, and the light formed on the surface of the disc substrate 40b of the optical disc 40 by the objective lens 50. The magnetic film 40c is focused and irradiated. The reflected light reflected here passes through the objective lens 50 and the half mirror 52.
Incident on the prism 5 through the half mirror 52.
The reflected light refracted by 3 and refracted once is detected by the photodetector 5.
The reflected light that is incident on the beam No. 4 and is reflected twice more by the prism 53 enters the photodetector 55.

Here, the recording magnetic field coil 49 for giving a magnetic field to the optical disc 40 at the time of recording is the optical disc 40.
On the other hand, it is arranged on the same side as the objective lens 50.
From the viewpoint of making the recording magnetic field coil 49 small and reducing the power consumption, it is desirable that the distance between the recording magnetic field coil 49 and the optical disk 40 is short. That is, from the viewpoint of applying a recording magnetic field, it is desirable that the thickness of the above-mentioned transparent protective layer is thin.

On the other hand, the distance (working distance) between the tip of the objective lens 50 or the recording magnetic field coil 49 and the surface of the optical disk 40 is desired to be large from the viewpoint of avoiding collision between the two. Practically, the working distance is preferably 0.3 mm or more, and when the working distance is 0.1 mm or less, it is expected that collision, damage to the surface of the optical disc 40, and the like will occur. In this embodiment, as shown in FIG.
Since the recording magnetic field coil 49 is arranged at the tip of the objective lens 50, the working distance becomes smaller than the working distance of the objective lens 50 alone by the recording magnetic field coil 49.

Desired numerical aperture (NA) of the objective lens 50
Is 0.6 to 0.8, and in this case, the working distance of the objective lens 50 alone can be secured to be 0.5 mm to 1 mm. Here, since the recording magnetic field coil 49 is arranged at the tip of the objective lens 50, assuming that the working distance of the recording magnetic field coil 49 is 0.2 mm, the tip of the recording magnetic field coil 49 and the optical disk 40. The working distance from the surface of the can be set to 0.3 mm or more to secure a practically possible distance. In this embodiment, the NA of the objective lens 50 is set to 0.6, and the working distance between the objective lens 50 and the surface of the optical disc 40 is set to 0.5 mm.

As described above, in this embodiment, as can be seen from FIGS. 1 to 3, since the objective lens 50 and the recording magnetic field coil 49 are arranged on the same side with respect to the optical disc 40, the drive of the drive is reduced. Suitable for downsizing.

Further, the interference between the magnetic field of the magnetic circuit that gives a recording magnetic field and the magnetic field of the focusing and tracking magnetic circuits, which is a problem with such an arrangement, is caused by the focusing magnetic field formed by the focusing coil 44 and the magnet 45. Circuit, tracking coil 46 and magnet 4
The tracking magnetic circuit composed of 7 is disposed away from the magnetic circuit including the recording magnetic field coil 49 provided in the optical pickup 48 in terms of distance, so that there is no problem. Further, since the optical circuit for the focus servo and the tracking servo is not provided in the optical pickup 48, even if a magnetic field is applied to the optical disc 40 by using the recording magnetic field coil 49, the problem of magnetic interference occurs. Absent.

Next, the signal processing of the present invention will be described. FIG. 4 shows a block diagram of an example of a recording / reproducing system of the information recording disk recording / reproducing apparatus according to the present invention. In the figure, the same components as those in FIGS. 1 to 3 are designated by the same reference numerals, and the description thereof will be omitted. In FIG. 4, the shaft of the spindle motor 59 corresponds to the spindle 41 shown in FIG. Further, the magneto-optical head 60 includes a cantilever 42, a focusing coil 44, a focusing magnet 45,
It is composed of a tracking coil 46 and a tracking magnet 47.

First, the operation during recording will be described. The computer 61 is a computer that uses an optical disk drive as a storage, and the recording data output from the computer 61 is supplied to a signal modulator / demodulator and error correction circuit 63 through an interface circuit 62, where it is modulated and the post-optical pickup 48 and Magneto-optical head 6
It is input to the recording magnetic field coil of 0 (49 in FIG. 3).

On the other hand, the signal reproduced by the optical pickup 48 is supplied to the servo control circuit 65, where the focus error signal and the tracking error signal are generated from the reproduced signal based on the signal from the system controller 64, and the focus error is generated. The signal is passed through the focus drive section 66 to the focusing coil of the magneto-optical head 60 (4 in FIG. 1).
4), and the tracking error signal is supplied to the tracking coil (46 in FIG. 1) of the magneto-optical head 60 via the radial feed and tracking drive unit 67 to cause the optical pickup 48 to perform the focusing operation and the tracking operation, respectively. .

There are two methods for recording the recording data on the optical disc 40. In the first recording method, a modulation signal (recording data) is supplied to the recording magnetic field coil (49 in FIG. 3) of the magneto-optical head 60, the magnetic field applied to the optical disk 60 is modulated according to the information to be recorded, and recording is performed. This is a magnetic field modulation recording method. At this time, the laser light emitted from the semiconductor laser 51 in the optical pickup 48 and radiated to the optical disc 40 through the objective lens 50 is a direct current lighting which is always radiated with a constant light intensity, or a clock pulse which is intermittently radiated. Both of them may be turned on, but both are for heating the optical disc 40.

In the second recording method, the signal to be recorded is supplied to the semiconductor laser 51 in the optical pickup 48, and the optical intensity of the laser beam emitted from the semiconductor laser 51 is modulated by the signal to be recorded, and the magneto-optical head 60 is then recorded. The magnetic field generated by the recording magnetic field coil (49 in FIG. 3) is an optical modulation recording method in which only the magnetization direction for recording is applied to the optical disc 40. In the optical modulation recording method, since the recording magnetic field is applied in a direct current, the power consumption of the recording magnetic field coil (49 in FIG. 3) is small, but the direct current magnetic field is generated in the magnetic circuit of the focus servo or the tracking servo more than before. The interference given is a big problem. However, this interference is greatly improved in the present embodiment, as described above, because the magnetic circuit for the recording magnetic field is arranged at a distance from the magnetic circuit for the focus servo and the tracking servo.

During reproduction, the reflected light of the optical disk 40 is detected by the photodetector in the optical pickup 48, and the reproduced signal obtained by detecting it according to the polarization plane is supplied to the signal modulator / demodulator and error correction circuit 63. And is supplied to the servo control circuit 65. The reproduction data demodulated and error-corrected by the signal modulator / demodulator and error correction circuit 63 is supplied to the computer 61 through the interface circuit 62.
Further, the servo control circuit 65 calculates the focus error signal and the tracking error signal from the reproduction signal based on a predetermined arithmetic expression.

The above focus error signal is supplied to the focusing coil of the magneto-optical head 60 through the focus drive section 66 to control the rotation of the optical pickup 48 about the focus axis. It is supplied to the tracking coil of the magneto-optical head 60 through the tracking drive unit 67, and the optical pickup 48 is controlled so as to follow the recording track in the track width direction.

Here, the tracking driver also serves as a feed in the radial direction. For this reason, in the present embodiment, a feed mechanism is not required and the combination is good for downsizing and low power consumption.

Next, a second embodiment of the present invention will be described. FIG. 5 is a block diagram of the essential parts of a second embodiment of a recording / reproducing apparatus for an information recording disk according to the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. It should be noted that the recording / reproducing system of the present embodiment is similar to
The configuration is the same as that of. In FIG. 5, the cantilever 42
A height sensor 70 is provided at a position close to and away from the bottom surface of the.

As shown in FIG. 6, the height sensor 70 includes a light emitting element 71 composed of a light emitting diode (LED), a focusing lens 72 for focusing the light from the light emitting element 71, and a focusing lens 72. Cantilever 4 through
It is composed of a two-divided light receiving element 73 that receives the light reflected by the bottom surface of the second light receiving element 2.

The height sensor 70 having such a structure receives the two-divided light when the distance between the drive base as the mounting surface of the height sensor 70, that is, the fixed drive reference surface and the bottom surface of the cantilever 42 is a predetermined value. The reflected light of the cantilever 42 is received by each of the two divided light receiving portions of the element 73 with the same area.
The reflection position of the light from the light emitting element 71 on the bottom surface of the cantilever 42 changes according to the vertical movement of the cantilever 42, and the light receiving area of each of the two divided light receiving portions described above correspondingly changes. The vertical movement of 42 can be detected.

Since an optical pickup 48 is provided at the tip of the cantilever 42 as shown in FIG. 5, the vertical movement of the cantilever 42 is
It corresponds to the vertical movement of the optical pickup 48,
This is proportional to the vertical movement of the objective lens 50 in the optical pickup 48.

Since the objective lens 50 moves up and down in the same phase following the surface wobbling of the optical disc 40 by the operation of the focus servo, the distance detected by the height sensor 70, that is, the height of the cantilever 42, is eventually determined. Optical disc 40
The amount is proportional to the surface runout of. However, since the height sensor 70 does not directly detect the optical disc 40, it is not affected by scratches or dust on the optical disc 40.

Returning to FIG. 5, the description will be continued. In this embodiment, the photodetector in the optical pickup 48 and the phase compensation circuit 7 are
4, the focus servo operation is performed in the first loop including the switch circuit 76, the power amplifier 78, and the focusing coil 44, or the height sensor 70, the phase compensation circuit 75, the switch circuit 76, the power amplifier 78, and the focusing coil 44. The focus servo operation is performed in the second loop consisting of Which loop is used for the focus servo operation depends on whether or not the abnormality determination circuit 77 determines an abnormality based on the signal from the optical pickup 48.
This is done by switching 6.

FIG. 7 is a circuit diagram showing an example of the abnormality judging circuit 77. In the figure, a photodetector 80 is a four-division photodetector in which the photodetectors 54 and 55 in the optical pickup 48 shown in FIG.
And D. The abnormality determination circuit 77 has a focusing differential amplifier 81 and a summing amplifier 82 which receive the output signal of the photodetector 80 as an input, and in addition to this, an automatic gain control (AGC) circuit 83 and a comparator 8 are provided.
4, 85, low-pass filter (LPF) 86, 1-volt addition circuit 87, 1-volt subtraction circuit 88, 2-input OR circuit 89
It is composed of

Next, the operation of this embodiment will be described with reference to FIG.
It will be described with reference to FIGS. 7 and 8 and the time charts of FIGS. The signal obtained by photoelectric conversion in each divided light receiving unit of the photodetector 80 shown in FIG. 7 in the optical pickup 48 is
The diagonal difference signal (A + C) − (B +) is supplied to the focus detection differential amplifier 81 shown in FIG.
D) and is taken out, while being supplied to the summing amplifier 82 and taken as a sum signal (A + B + C + D). Here, A, B, C and D are the photodetectors 80 of FIG.
The respective signals output from the divided light receiving parts A, B, C and D are shown.

The above-mentioned diagonal difference signal sensitively reacts to the shift of the focus of the objective lens 50 within ± 15 μm, which is the normal detection range, but the above sum signal changes the focus. Is insensitive to, and within a detection range of ± 15 μm, there is almost no change in focus shift, and the signal changes according to the amount of reflected light.

The AGC circuit 83 in the abnormality judging circuit 77 shown in FIG. 7 outputs the above-mentioned diagonal difference signal with its level controlled to be substantially constant regardless of the amount of reflected light. Here, when the level of the above sum signal is high, the gain of the AGC circuit 83 is
That is, it is controlled so as to decrease during recording / reproduction with respect to an optical disc having a high reflected light amount, and becomes high during recording / reproduction with a low level of the sum signal, that is, for an optical disc having a low reflected light amount. As a result, the AGC circuit 8
The diagonal difference signal indicated by e1 in FIG.

The above-mentioned diagonal difference signal e1 is the LP signal shown in FIG.
After the high frequency component is removed by F86, the high frequency component is supplied to the non-inverting input terminal of the comparator 84 and the inverting input terminal of the comparator 85, while 1 volt is added by the 1 volt adder circuit 87, and
In FIG. 8A, the first reference signal indicated by Ref1 is input to the inverting input terminal of the comparator 84, and 1 volt is subtracted by the 1 volt subtraction circuit 88, and the second reference signal indicated by Ref2 in FIG. Is input to the non-inverting input terminal of the comparator 85.

As a result, the comparator 84 outputs a low level signal when the diagonal difference signal e1 is lower than the first reference signal Ref1, and a high level signal when the diagonal difference signal e1 is higher than the first reference signal Ref1.
Further, the comparator 85 outputs a low level signal when the diagonal difference signal e1 is higher than the second reference signal Ref2, and outputs a high level signal when the diagonal difference signal e1 is low. Comparators 84 and 85
Each output signal of is output as an abnormality determination signal through the 2-input OR circuit 89.

That is, in the abnormality determination signal extracted from the 2-input OR circuit 89, as shown by a1 in FIG. 8A, the level of the diagonal difference signal e1 is the reference signals Ref1 and Ref.
2 is normal at a low level as shown in FIG. 8 (B), a2 and a are shown in FIG. 8 (A).
As shown by 3, the level of the diagonal difference signal e1 is equal to the reference signal R
When it is larger than ef1 or smaller than Ref2, a high level abnormality is shown as shown in FIG. This corresponds to the fact that there is an abnormality on the surface of the optical disc that reduces the amount of reflected light when the diagonal difference signal e1 greatly changes and the sum signal also greatly drops.

The above-mentioned abnormality determination signal is supplied to the switch circuit 76 of FIG. 5, and is connected to the terminal a when the abnormality is determined, and is switched and connected to the terminal b side when the abnormality is determined. This allows
At the time of normality determination, the focus error signal extracted from the optical pickup 48, that is, the above-mentioned diagonal difference signal is subjected to phase compensation processing by the phase compensation circuit 74, and then passed through the switch circuit 76 and the power amplifier 78 to provide the focusing coil. 44, the cantilever 42 is rotated about the rotation shaft 43 so as to follow the surface wobbling of the optical disc 40.
Since the focus error signal (diagonal difference signal) supplied to the phase compensation circuit 74 indicates the residual component after the focus servo that follows the surface wobbling of the optical disc 40, it is as shown in FIG. 9 (A). The signal waveform has a poor S / N.

On the other hand, at the time of the above determination, the height detection signal extracted from the height sensor 70 is subjected to the phase compensation processing by the phase compensation circuit 75, and then is passed through the switch circuit 76 and the power amplifier 78 to the focusing coil 44. The cantilever 42 is supplied to rotate the cantilever 42 about the rotation shaft 43 in accordance with the detection result of the height sensor 70. The height detection signal supplied to the phase compensation circuit 75 is a level corresponding to the movement of the cantilever 42 and the objective lens 50 in the focus direction with respect to the fixed reference surface, and is a signal substantially equivalent to the surface wobbling of the optical disc 40. There is a signal waveform with good S / N as shown in FIG. 9 (B).

Here, the above-mentioned abnormality determining circuit 77 determines an abnormality when it deviates from the normal focus detection range due to scratches and dust on the optical disc 40, whereas the height sensor 70 has a fixed reference surface. The movements of the cantilever 42 and the objective lens 50 in the focus direction with respect to are detected and are not affected by scratches or dust on the optical disc 40 at all.

Since the focus servo loop at the time of abnormality determination is composed of the height sensor 70, the phase compensating circuit 75, the switch circuit 76, the power amplifier 78 and the focus coil 44, the cantilever 42 can freely move. However, the rigidity of the closed loop servo is maintained. Therefore, the operation of significantly reducing the risk of collision between the optical disc 40 and the objective lens 50, which has been a problem in the past, can be quickly started from the time when the scratch or dust on the optical disc 40 is detected.

When the abnormality determination circuit 77 makes a normal determination again after the abnormality determination, the switch circuit 76 is again switched and connected to the terminal a side, so that the focus servo operation by the focus servo loop using the original focus error signal is restarted. To be done. Since the height position of the objective lens 50 at this time is kept at substantially the same position as that at the time of abnormality determination by the focus servo loop at the time of abnormality determination, the focus servo operation is smoothly restarted.

[0065]

As described above, according to the present invention,
Since the magnetic field generator and the objective lens can be arranged on the same side as the information recording disk, the magnetic field generator and the magnetic circuit for focusing and the magnetic circuit for tracking can be provided while having a configuration suitable for downsizing of the drive. Since the cantilevers are separated from each other by almost the length of the cantilever, it is possible to prevent mutual interference of magnetic fields, and thus it is possible to construct a magneto-optical disk system using a smaller information recording disk and a smaller drive.

Further, according to the present invention, when an abnormality due to dust or scratches on the information recording disc is judged before the optical pickup actually approaches the information recording disc less than the predetermined distance, the information recording disc is detected. Based on the output signal of the height sensor that is not affected by scratches or dust at all, the cantilever does not move freely, and the focus servo loop that maintains the rigidity of the closed loop servo is switched. The operation that greatly reduces the risk of collision between the recording disk and the objective lens can be started quickly, and this allows the working distance to be made smaller than before, contributing to further miniaturization of the information recording disk. be able to.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part according to a first embodiment of the present invention.

FIG. 2 is a schematic perspective view of a cantilever in FIG.

3 is a configuration diagram of an example of the optical pickup in FIG.

FIG. 4 is a block diagram of an example of a recording / reproducing system of the present invention.

FIG. 5 is a configuration diagram of a main part according to a second embodiment of the present invention.

6 is a configuration diagram of an example of a height sensor in FIG.

7 is a circuit system diagram of an example of an abnormality determination circuit in FIG.

8 is a time chart for explaining the operation of FIG.

9 is a time chart for explaining the operation of FIG.

FIG. 10 is a cross-sectional view of an example of a conventional device.

FIG. 11 is a configuration diagram of another example of a conventional device.

[Explanation of symbols]

40 optical disc (information recording disk) 42 cantilever 43 rotation axis 44 Focusing coil 46 Tracking coil 48 optical pickup 49 Recording magnetic field coil 50 objective lens 51 Semiconductor laser 52 Half mirror 53 prism 54,55 Photodetector 60 magneto-optical head 66 Focus drive 67 Radius feed and tracking drive unit 70 Height sensor 71 light emitting element 72 Focusing lens 73 Two-segment photo detector 74,75 Phase compensation circuit 76 switch circuit 77 Abnormality judgment circuit 80 Photodetector (4 division photodetector) 81 Focus detection differential amplifier 82 Summing amplifier 83 Automatic gain control (AGC) circuit 84,85 Comparator 87 1-volt addition circuit 88 1-volt subtraction circuit

Claims (3)

[Claims] 1. A photodetector which irradiates a magneto-optical information recording disk with laser light through an objective lens, and reflects light reflected from a signal recording surface of the magneto-optical information recording disk through the objective lens. An optical pickup that applies a recording magnetic field generated by a magnetic field generator to the magneto-optical information recording disk during recording on the magneto-optical information recording disk, and a focusing coil and a tracking coil on the base side. A coil is provided, and the optical pickup is provided at a position at a tip end portion of the magneto-optical information recording disk that closely faces and separates from the magneto-optical information recording disk. The tracking axis is configured to be rotatable in the upper focus axis direction and is parallel to the surface of the magneto-optical information recording disk about the tracking axis. A cantilever configured to be rotatable in any direction, a reproduction signal processing system that generates a reproduction signal based on a signal from the photodetector of the optical pickup, and a signal from the photodetector of the optical pickup. Drive current is supplied to the focusing coil and the tracking coil to generate a magnetic force together with the magnetic field of the focusing magnet and the tracking magnet, and the cantilever is rotated in the focusing axis direction and the tracking axis direction. An information recording disk recording / reproducing apparatus comprising: a moving servo circuit; and rotating means for rotating the magneto-optical information recording disk. 2. A magneto-optical information recording disk is irradiated with laser light through an objective lens, and reflected light from a signal recording surface of the magneto-optical information recording disk is detected through the objective lens. An optical pickup that applies a recording magnetic field generated by a magnetic field generator to the magneto-optical information recording disk during recording on the magneto-optical information recording disk, and a focusing coil and a tracking coil on the base side. A coil is provided, and the optical pickup is provided at a position at a tip end portion of the magneto-optical information recording disk that closely faces and separates from the magneto-optical information recording disk. The tracking axis is configured to be rotatable in the upper focus axis direction and is parallel to the surface of the magneto-optical information recording disk about the tracking axis. A cantilever that is rotatable in any direction, a height sensor that optically detects the height of the cantilever with respect to a fixed reference surface, and a reproduction signal based on a signal from the photodetector of the optical pickup. Based on a reproduction signal processing system to generate and a signal from the photodetector of the optical pickup, a drive current is supplied to the focusing coil to generate a magnetic force together with a magnetic field by the focusing magnet, thereby causing the cantilever to move. A focus servo circuit that rotates in the focus axis direction, and a drive current is supplied to the tracking coil based on a signal from the photodetector of the optical pickup,
A magneto-optical information recording disk based on a tracking servo circuit that generates a magnetic force together with a magnetic field by a tracking magnet to rotate the cantilever in the tracking axis direction, and a signal from the photodetector of the optical pickup. An abnormality determination circuit for determining an abnormality due to dust and scratches on the above, and based on an abnormality determination signal from the abnormality determination circuit, a drive current flowing in the tracking coil at the time of abnormality determination is set to the photodetector of the optical pickup. An information recording / reproducing apparatus for an information recording disk, comprising: switching means for switching a signal based on an output signal to a signal based on an output signal of the height sensor; and rotating means for rotating the magneto-optical information recording disk. 3. The cantilever is provided with the focusing coil and the tracking coil on the base side of an opposite surface that does not face the magneto-optical information recording disk,
3. A recording / reproducing apparatus for an information recording disk according to claim 1, wherein the optical pickup is provided at the front end portion of a surface which faces the magneto-optical information recording disk in close proximity and separation.