JP2002222530A - Automatic adjustment method of digital servo of disk device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To contribute to the improvement of playability by allowing the fetch of the proper offset and realizing the stable automatic adjustment of a digital servo in a disk device for reading out data from the disk by using an optical pickup. SOLUTION: In the disk device provided with the optical pickup having a lens for image-forming the light from a light emitting element on the signal surface of the disk and a light receiving element for detecting the light reflected from this signal surface, a digital servo circuit for detecting various kinds of offsets from an output of the light receiving element in the ON state of the light emitting element to carry out the process for canceling these offsets, and a controller for controlling the optical pickup and the digital servo circuit, the lens of the optical pickup is arranged so as to approach (S5) to the disk up to the position where a focal point of the light from the light emitting element is dislocated from the signal surface of the disk and the surface of the disk, when the detection of the offset is carried out (S7).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact disc (CD) and a mini disc (M) using an optical pickup.
The present invention relates to a disk device for reading data from a disk such as D), and more particularly to a technique useful for properly taking in and canceling various offsets when adjusting a digital servo of an optical pickup.

[0002]

2. Description of the Related Art Data such as music is recorded on a CD or MD in a spiral or concentric manner by extremely small pits or grooves formed on the disk surface. 2. Description of the Related Art In a disk device such as a CD player and an MD player, the focus of light emitted from a light emitting element (typically, a semiconductor laser) of an optical pickup is focused on a signal surface of a disk (a “pit surface” for reproduction, and a recording surface) Tracks a pit row or a groove (hereinafter, referred to as a “track”) according to a “groove surface”, and reflects light reflected from a signal surface with a light receiving element (typically, a PIN photodiode) of an optical pickup. The data is read by detecting.

[0003] The signal surface of the disk is constantly displaced due to surface deflection when the disk is rotating, and the track is also constantly displaced due to core deflection when the disk is rotating.
For this reason, a disc device such as a CD player and an MD player has a focus servo and a disk drive so that the laser beam can track the track while keeping the focus of the laser beam from the optical pickup always on the signal surface. Equipped with pickup servo including tracking servo.

In order to read a signal recorded on a disk without error, it is necessary to adjust the servo characteristics of the pickup servo to an optimum state. There are an analog type and a digital type as a circuit constituting the pickup servo. In the case of an analog servo circuit, a semi-fixed resistor for servo characteristic adjustment is provided on the board, and the manufacturer adjusts the semi-fixed resistance while reproducing the reference disk before shipping the product, so that the servo characteristics can be adjusted. The best one.

However, the analog servo circuit often changes the optical characteristics, actuator characteristics, circuit coefficients, etc. of the pickup due to environmental changes due to aging or temperature changes due to long-term use. There is a disadvantage that characteristics are changed. In a state where the servo characteristics are poor, out-of-focus and out-of-tracking tend to occur due to vibration, scratches on the disk, and the like, resulting in sound interruption or sound skipping. In particular, in the case of an in-vehicle audio device, the vibration is severe, and if the servo characteristics are poor, sound interruptions and skips frequently occur.

In recent years, digitalization of electronic circuits in audio devices has been advanced, and pickup servo circuits in disk devices such as CD players have also been digitized. Also,
A disk device having a function of automatically digitally adjusting a pickup servo when a power is turned on or a disk is loaded has also been commercialized. In this type of disk device, it is easier to adjust the pickup servo to an optimal state than in the analog type, so
Good playability.

When performing automatic adjustment of the pickup servo in a disk device having such a digital servo circuit, a process for taking in various offsets (focus offset, tracking offset, etc.) and a process for canceling the offset (focus / focus). Tracking balance adjustment, gain adjustment, etc.) are performed. This offset capturing process is preferably performed under the same conditions as in the actual operation state. In addition, since the hologram unit-specific pickup easily generates stray light, the light-emitting element ( This is performed with the semiconductor laser) turned on. In this case, since the focus servo is in the “on” state, when the focus of the laser beam from the optical pickup is focused on the signal surface (pit surface or groove surface) of the disk, not only the offset to be originally detected but also the signal surface The recorded signal is also detected at the same time, and as a result, the proper servo automatic adjustment is not performed, and the playability is reduced. In order to avoid this, the position of the objective lens that forms the laser beam on the signal surface of the disk may be changed.

In a conventional disk drive equipped with a digital servo circuit, when performing an offset capturing process with a semiconductor laser turned on, an optical signal is not focused on the signal surface of the disk. This was performed with the objective lens of the pickup kept away from the disk (mechanically, the objective lens was slightly lowered from its original position).

As a form of an optical pickup used in such a disk device, for example, there is one as shown in FIG. In the figure, (a) is a pickup configuration using an optical system (bulk optical system) constituted by discrete type elements, and (b) is an optical system (unit) constituted by elements integrated in a one-chip form. (Optical system).

In a pickup using a bulk optical system, as shown by an arrow in FIG.
, Is reflected by the beam splitter 3 and directed to the objective lens 4, is imaged on the signal surface (pit surface or groove surface) of the disk 10 through the objective lens 4, and the light reflected on the signal surface is After passing through the objective lens 4 again and being refracted through the beam splitter 3, light detection is performed by a light receiving element (PIN photodiode) 5. The light receiving element 5 outputs an electric signal according to the detected light intensity.

On the other hand, in a pickup using a unit optical system, as shown by an arrow in FIG.
The laser light emitted from the semiconductor laser 6 in the unit S enters from the diffraction grating surface of the hologram element 7, passes through the element as it is, and passes through the objective lens 8 to the disk 10.
Is formed on the signal surface (pit surface or groove surface) of the hologram element, the light reflected on the signal surface passes through the objective lens 8 again, is refracted by the hologram surface of the hologram element 7 and passes through the inside of the element. Light detection is performed by a light receiving element (PIN photodiode) 9 arranged near the laser 6. Similarly, the light receiving element 9 outputs an electric signal according to the detected light intensity.

[0012]

As described above, in the conventional disk drive for performing the offset capturing process with the laser light source of the optical pickup turned on, the objective lens of the optical pickup is moved away from the disk when capturing the offset ( In the example of FIG. 1, the objective lenses 4 and 8 are lowered downward with respect to the disk 10) so that the laser light is not focused on the signal surface of the disk.

In this case, the focus position of the laser beam can be shifted from the signal surface (pit surface or groove surface) of the disk by lowering the objective lens from its original position.
Depending on a mechanism such as an actuator for moving the objective lens, when the objective lens is lowered, the focal point of the laser beam is focused on the disk surface (in the example of FIG.
(Lower surface). At this time,
The laser light is reflected on the surface of the disk, and so-called “return light” is generated.

When the offset capturing process is performed in a state where such return light is generated, similar to the case where the laser beam is focused on the signal surface of the disk as described above, in addition to the offset to be originally detected, The signal caused by the return light is also detected at the same time (detection of an incorrect offset value),
As a result, proper servo automatic adjustment is not performed, causing a decrease in playability.

To cope with this, it is conceivable to lower the objective lens further downward. However, there are cases where it is physically impossible to lower the objective lens to a specified value or more due to the mechanism of the optical pickup or restrictions on dimensions. Such a problem becomes more prominent especially in the case of a pickup using a unit optical system (see FIG. 1B). In the pickup using the unit optical system, the distance between the light emitting element (semiconductor laser 6) and the light receiving element 9 is extremely short, and there is little obstruction on the way, so that reflected light and leaked light from the surroundings become "stray light." The light is detected by the light receiving element 9 as it is. The intensity of this stray light is substantially constant if there is no "return light" as described above. Therefore, the light receiving element 9 can accurately detect the DC offset corresponding to the almost constant intensity of the stray light, and can reflect the result in the offset capturing process. However, in practice, the influence of the "return light" as described above cannot be ignored.

Under the influence of the return light, the intensity of the stray light becomes
When the laser beam is focused on the signal surface of the disk or the surface of the disk, the level increases from the original stray light level. This increased amount is detected as a signal component other than the DC offset which should be originally detected. As a result, stable automatic servo adjustment is not performed, and the playability is reduced. The present invention has been made in view of the problems in the related art, and enables a disk device that reads data from a disk using an optical pickup to capture an appropriate offset, thereby achieving stable automatic adjustment of a digital servo. It is another object of the present invention to provide a digital servo automatic adjustment method that can contribute to improvement of playability.

[0017]

According to a basic aspect of the present invention, at least a light-emitting element and a lens for imaging light from the light-emitting element on a signal surface of a disk are provided. An optical pickup having a light receiving element for detecting reflected light from a signal surface of the disk and outputting an electric signal corresponding to the light intensity, and an output from the light receiving element when the light emitting element is turned on. In a disk device including a digital servo circuit that detects various offsets from the received electric signal and performs processing for canceling the offsets, and a controller that controls the optical pickup and the digital servo circuit, the offset detection is performed. When performing, the lens of the optical pickup, the focus of the light from the light emitting element is the signal surface of the disk and the disk To a position out of the plane, automatic adjustment method for digital servo of the disk device, characterized in that close to the disk is provided.

According to the automatic adjustment method of the digital servo of the disk device according to the present invention, when detecting various offsets (taking in offsets) with the light emitting element of the optical pickup turned on, the light from the light emitting element is detected. The optical pickup lens is brought close to the disc so that the focal point of the disc does not coincide with the signal surface of the disc and the surface of the disc.

As a result, only the offset to be originally detected can be taken into the digital servo circuit, and as a result, stable automatic adjustment of the digital servo can be realized. This contributes to improving playability. Also, since the light from the light emitting element is not reflected on the surface of the disk, "return light" as in the prior art does not occur, and as a result, stray light with almost constant intensity can be detected. Can be. This contributes to stable automatic adjustment of the digital servo and improvement of playability.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 schematically shows a part of the structure of a disk device for realizing a digital servo automatic adjusting method according to an embodiment of the present invention. In the figure, reference numeral 10 denotes a disk (CD or MD in this embodiment) on which data such as music to be reproduced is recorded, and reference numeral 11 denotes a turntable on which the disk 10 is placed. The disk 10 loaded by the loading unit described below is a turntable 1
1 and a holding plate (not shown) to be chucked. Reference numeral 12 denotes a turntable 11 on which the disk 10 is mounted.
, A spindle servo circuit 13 for driving and controlling the spindle motor 12, and 14 an optical pickup for irradiating the disk 10 with a laser beam and reading data recorded on the disk 10 by the reflected light. The optical pickup 14 outputs a signal (A / B signal) obtained from the main spot of the laser beam and a signal (C / D signal) obtained from the side spot.

As the optical pickup 14, for example, a pickup using a unit optical system as shown in FIG. 1B can be used. This optical pickup 14
Although not particularly shown, the objective lens is
It has an actuator for moving in the direction perpendicular to the zero plane, and has a mechanism for tilting the lens holder holding the objective lens near the bottom dead center. And
When detecting the offset, a bias voltage corresponding to the amount of movement of the objective lens is applied to the actuator.

Reference numeral 15 denotes a sled motor for moving a sled (not shown) on which the optical pickup 14 is mounted in the radial direction of the disk 10, 16 a thread servo circuit for driving and controlling the sled motor 15, and 17 an optical pickup 14 (R) that amplifies the signal output from
F) Shows an amplifier. From the RF amplifier 17, the current-
The voltage-converted A signal, B signal, C signal, D signal and R
An F signal (A + B) is output. 18 is a DSP
(Digital signal processor), RF
A digital signal processing circuit for digitally processing an RF signal output from the amplifier 17 to output a digital audio signal; 19, a DRAM for temporarily storing compressed data of data to be reproduced; and 20, a digital signal processing circuit 1 shows a D / A converter for converting a digital audio signal output from 18 into an analog audio signal.

Reference numeral 21 denotes a focus servo circuit for generating a focus error signal from the A signal and the B signal output from the RF amplifier 17, and reference numeral 22 denotes an optical pickup 14 based on the focus error signal output from the focus servo circuit 21. A servo driver that drives a focus actuator (not shown) and focuses the laser beam on the signal surface of the disk 10. A tracking servo circuit 23 generates a tracking error signal from the C signal and the D signal output from the RF amplifier 17. Reference numerals 24 denote servo drivers that drive a tracking actuator (not shown) of the optical pickup 14 based on a tracking error signal output from the tracking servo circuit 23 so that the laser light tracks the tracks on the disk 10.

A detection circuit 25 performs lower envelope detection of the RF signal. An A / D converter 26 converts an output (analog signal) of the detection circuit 25 into a digital signal.
Reference numeral 7 denotes a servo controller that controls the spindle servo circuit 13, the thread servo circuit 16, the focus servo circuit 21, and the tracking servo circuit 23 based on control from a system controller 28 described later. The servo controller 27 also has a function of adjusting the gain of the RF amplifier 17 as described later.

Reference numeral 28 denotes a system controller constituted by a microcomputer, which controls the digital signal processing circuit 18 and the servo controller 27. Also,
29 is an EEPROM for storing circuit offset data and the like measured in advance at the time of product shipment, 30 is an operation unit provided with various operation keys, and 31 is a disk 10
A loading unit 32 for performing loading / unloading of the disk 10, and a chucking detection unit 32 for detecting a chucking state of the disk 10. EEPROM 29,
The operation unit 30, the loading unit 31, and the chucking detection unit 32 are connected to the system controller 28, respectively.

Hereinafter, the offset fetch / cancel processing related to the automatic adjustment of the digital servo performed by the controllers 27 and 28 in the disk device of the present embodiment will be described with reference to FIGS. 3 and 4 showing an example of the processing flow. . First, as a pre-process prior to the start of this process, the system controller 28 detects that the power of the disk device has been turned on via the operation unit 30, and further detects the power of the disk 1 via the loading unit 31.
After detecting that 0 has been loaded, it detects via the chucking detector 32 that the disk 10 has been normally chucked. After that, the processing shifts to this processing.

In the first step S1, the system controller 28 gives an initial value to the servo controller 27 in accordance with the set program, and the servo controller 27
Sets the servo circuits 13, 16, 21 and 23 to the initial state. In the next step S2, the laser light source (the semiconductor laser 6 in FIG. 1B) of the optical pickup 14 is turned on by the servo controller 27 under the control of the system controller 28.

In the next step S3, the loading unit 3
1, the type of the loaded disc is determined by the system controller 28. That is, it is determined whether the loaded disc is an MD or a CD,
In the case of "MD", the process proceeds to step S4, and in the case of "CD", the process proceeds to step S6. In step S4 (when the disc is an MD), the type of the loaded MD is determined by the system controller 28 via the loading unit 31. That is, it is determined whether the MD is a recording MD (a magneto-optical disk (MO) having a groove) or a reproduction-only MD software (an optical disk having a pit similar to a CD). In this case, the process proceeds to step S5, and in the case of “MD software”, the process proceeds to step S6.

In the processing of steps S3 and S4, it is determined whether the light reflectance of the disk is relatively low or relatively high. In the present embodiment, it is determined that the light reflectance is relatively low in the case of an MO (MD for recording), and that the light reflectance is relatively high in the case of a CD or MD software. . In step S5 (when the optical reflectance of the disk is relatively low), the focus servo circuit 21 controls the focus actuator (not shown) of the optical pickup 14 via the servo driver 22 under the control of the servo controller 27. Is driven to bring the lens of the optical pickup 14 (the objective lens 8 in FIG. 1B) closer to the disk 10. This movement of the lens is performed until the focal point of the laser beam emitted from the optical pickup 14 deviates from the signal surface (pit surface or groove surface) of the disk 10 and the surface of the disk 10. At this time, a bias voltage according to the amount of movement of the lens is applied to the focus actuator. Thereafter, the process proceeds to step S7.

On the other hand, in step S6 (when the optical reflectivity of the disk is relatively high), the focus actuator of the optical pickup 14 is similarly driven, and the lens of the optical pickup 14 is moved in the opposite direction to the above. Keep away from Similarly, the lens is moved until the focal point of the laser beam from the optical pickup 14 deviates from the signal surface of the disk 10 and the surface of the disk 10. Is applied. Thereafter, the process proceeds to step S7.

In step S7, the servo controller 2
7, a process for capturing various offsets is performed. Specifically, the focus offset amount is determined based on the A / D conversion processing in the focus servo circuit 21, the tracking offset amount is determined based on the A / D conversion processing in the tracking servo circuit 23, and the RF is further determined. The offset amount of the RF signal output from the amplifier 17 is determined.

In the next step S8, the spindle motor 12 is driven via the spindle servo circuit 13 under the control of the servo controller 27 to rotate the disk 10. In the next step S9, the focus servo control (servo circuit 21) is turned on by the servo controller 27 under the control of the system controller 28, and the optical pickup 14 is moved up and down to perform a focus search.

In the next step S10, the system controller 28 determines whether or not the focus has been turned on. When the result of the determination is NO, that is, when the focus is not turned on, the process proceeds to step S11. When the result of the determination is YES, that is, when the focus is turned on, the process proceeds to step S12. In step S11, since the light reflectance of the CD-RW among the CDs is low, the processing that has been performed once after determining that the light reflectance of the disc is high is corrected. That is, the servo controller 2
7, the gain for CD-RW is set in the RF amplifier 17. Thereafter, the process returns to step S5 to repeat the above processing.

On the other hand, in step S12 (see FIG. 4),
The spindle motor 12 is driven via the spindle servo circuit 13 under the control of the servo controller 27,
The rotation of the disk 10 is controlled so that the linear velocity on the track is constant. That is, when the optical pickup 14 is on the inner peripheral side of the disk 10, the servo control is performed such that the rotational speed is relatively high, and when the optical pickup 14 is on the outer peripheral side of the disk 10, the servo control is performed such that the rotational speed is relatively low. Spindle rough servo).

In the next step S13, tracking balance adjustment is performed. That is, when the optical pickup 14 crosses a track due to eccentricity due to the disk and disk chucking, a tracking error signal is read by the servo controller 27 via the tracking servo circuit 23, and the upper and lower peak levels of this signal are read. The gain of the variable gain amplifier (not shown) in the tracking servo circuit 23 is adjusted so that the values of.

In the next step S14, the tracking servo control (servo circuit 23) and the thread servo control (servo circuit 16) are turned on by the servo controller 27 under the control of the system controller 28. In the next step S15, the servo controller 27
In the focus servo circuit 21 under the control of
Adjust the focus gain. This is a variable frequency oscillator (not shown) built in the focus servo circuit 21.
Is performed by adjusting the gain of a variable gain amplifier (not shown) based on the output of.

In the last step S16, the tracking servo circuit 2 is controlled under the control of the servo controller 27.
At 3, the tracking gain is adjusted. this is,
This is performed by adjusting the gain of a variable gain amplifier (not shown) based on the output of a variable frequency oscillator (not shown) incorporated in the tracking servo circuit 23. Then, this processing (automatic adjustment processing of the digital servo) is “end”. Thereafter, although not particularly shown, the flow shifts to data reproduction processing based on signal detection by the optical pickup 14.

As described above, according to the digital servo automatic adjustment method according to the present embodiment, when various offsets are captured while the semiconductor laser of the optical pickup 14 is turned on, the offset is loaded before the capture. It is determined whether the light reflectance of the disc 10 is relatively low or relatively high (steps S3 and S4). If the light reflectance is relatively low based on the determination result, the optical pickup is determined. The lens of the optical pickup 14 is brought close to the disk 10 so that the laser light from the disk 14 does not focus on the signal surface of the disk 10 and the surface of the disk 10 (step S5). Similarly, the lens of the optical pickup 14 is set on the disk 1 so that the laser beam does not focus on the signal surface of the disk 10 and the surface of the disk 10. They are kept away from (step S
6).

As a result, only the offset which should be detected can be taken in. As a result, stable automatic adjustment of the digital servo can be realized and playability can be improved. Also, since the laser light from the optical pickup 14 is not reflected on the surface of the disk 10, no so-called "return light" is generated, and as a result,
It is possible to detect stray light of almost constant intensity. This contributes to stable automatic adjustment of the digital servo and improvement of playability.

Further, the pickup using the unit optical system (see FIG. 1B) tends to have a relatively large stray light component more easily than the pickup using the bulk optical system (see FIG. 1A). , Especially a disk with low light reflectance (M
O, CD-RW, etc.).

[0041]

As described above, according to the present invention, an appropriate offset can be taken in a disk device for reading data from a disk by using an optical pickup, thereby enabling stable automatic adjustment of digital servo. And the playability can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of an optical pickup.

FIG. 2 is a block diagram schematically showing a part of a configuration of a disk device for realizing a digital servo automatic adjustment method according to an embodiment of the present invention.

FIG. 3 is a flowchart illustrating an example of an offset fetch / cancel process related to automatic adjustment of digital servo performed by a controller in FIG.

FIG. 4 is a flowchart showing a process following the process flow of FIG. 3;

[Explanation of symbols]

 Reference Signs List 10 disk 12 spindle motor 13 spindle servo circuit 14 optical pickup 15 thread motor 16 thread servo circuit 17 RF amplifier 18 digital signal processing circuit 21 focus servo circuit 22, 24 servo driver 23 tracking servo Circuit 27 ... Servo controller 28 ... System controller

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenji Uehara 1-1-8 Nishigotanda, Shinagawa-ku, Tokyo Alpine Inc. (72) Inventor Masatoshi Uchio 1-1-18 Nishigotanda, Shinagawa-ku, Tokyo Alpine, Inc. F-term (reference) 5D117 AA02 BB01 CC07 DD16 EE29 FF07 FF09 FF19 FF21 FX08 5D118 AA06 AA18 AA26 AA29 BA01 CA02 CA08 CA11 CA13 CB01 CD02 CD03 CD11

Claims (6)

[Claims] At least a light-emitting element, a lens for imaging light from the light-emitting element on a signal surface of a disk, and detecting reflected light from the signal surface of the disk to generate an electric signal corresponding to the light intensity An optical pickup having a light receiving element for outputting, and a digital servo circuit for detecting various offsets from an electric signal output from the light receiving element while the light emitting element is turned on, and performing processing for canceling the offset And a controller for controlling the optical pickup and the digital servo circuit, wherein when the offset is detected, the lens of the optical pickup is moved to the focal point of the light from the light emitting element of the disk. To the signal surface and the position off the surface of the disc,
A method of automatically adjusting a digital servo of a disk device, wherein the digital servo is brought closer to the disk. 2. The controller determines whether the loaded disk has a relatively low or relatively high light reflectance, and determines that the light reflectance of the loaded disk is relatively low. 2. The method according to claim 1, wherein the offset is detected by bringing a lens of a pickup close to the disk. 3. When it is determined that the optical reflectance of the disk is relatively high, when detecting the offset, the lens of the optical pickup is moved to focus the light from the light emitting element on the disk. 3. The method according to claim 2, wherein the disk is moved away from the disk until a signal surface of the disk and a position deviating from the surface of the disk. 4. The disk device according to claim 3, wherein when the disk is a CD-RW, the controller detects the offset by bringing a lens of the optical pickup close to the disk. Automatic adjustment method of digital servo. 5. The optical pickup further includes an actuator for moving the lens in a direction perpendicular to a surface of the disk, and the detection of the offset corresponds to the amount of movement of the lens when the offset is detected. 5. The method for automatically adjusting a digital servo of a disk drive according to claim 1, wherein a bias voltage is applied. 6. The optical pickup further includes a mechanism for tilting a lens holder holding the lens near a bottom dead center, and applying a bias voltage to the actuator to move the lens away from the disk. 6. The automatic digital servo of a disk device according to claim 5, wherein when detecting the offset, return light generated when light from the light emitting element forms an image on the surface of the disk is reduced. Adjustment method.