JPH0743900B2 - Tracking controller - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording / reproducing apparatus for irradiating a light beam on a record carrier to reproduce a signal recorded on the record carrier or record a signal on the record carrier. Irradiation on a record carrier having a recorded signal track or a tracking track previously provided for recording a signal (hereinafter, the signal track and the tracking track are simply referred to as a track). The present invention relates to a tracking control device for reproducing a signal or recording a signal by controlling a light beam being scanned so as to always scan a track.

Configuration of Conventional Example and Problems Thereof There are a magneto-optical recording / reproducing apparatus, an optical recording / reproducing apparatus, an optical reproducing apparatus, and the like as this type of apparatus, and the conventional example will be described by taking the optical recording / reproducing apparatus as an example.

For example, as an optical recording device, a light beam generated from a light source such as a semiconductor laser is converged by a converging lens into a minute beam diameter and irradiated on a rotating disc-shaped record carrier, and the light amount of the light beam is changed during recording. There is a method in which the signal is reproduced by changing the recording according to the signal to be recorded, and at the time of reproduction, the light amount of the light beam is set to a weak constant light amount and the reflected light or transmitted light from the record carrier is detected.

As a record carrier used in this kind of apparatus, for example, there is one in which a concave or convex track is previously provided on the surface of a base material, and a recording material layer is formed on the surface by means such as vapor deposition. Such tracks are spiral or concentric and have a very narrow track pitch and track width, for example, a pitch of about 1.6 μm and a width of about 0.6 μm.

Therefore, the above-mentioned optical recording / reproducing apparatus has a focus control for controlling the light beam irradiated on the rotating record carrier to have a constant small beam diameter in order to obtain a high quality reproduction signal. It is essential to have means and a tracking control means for controlling the light beam, which is focused on the record carrier, to always accurately scan the track.

Focus control detects the convergence state of the light beam on the record carrier from the light beam reflected from the record carrier, and moves the converging lens in the direction perpendicular to the surface of the record carrier according to the detected signal. However, the focus control is required to have extremely high accuracy.
It is 0.5 μm or less.

The tracking control detects the positional deviation between the light beam which is transmitted through the record carrier or the light beam which is reflected from the record carrier and the track which is converged on the record carrier and converges according to the detected signal. Although the lens is moved in the radial direction on the surface of the record carrier, the control accuracy of the tracking control is required to be extremely high as in the focus control, for example, ± 0.1 μm or less.

The range of movement of the converging lens in the radial direction on the surface of the record carrier is narrow, at most about 200 μm. Generally, tracking control is performed by the converging lens so that the light beam follows the eccentricity of the track. Move
Movement control is performed to move the entire optical system including the light source in the radial direction of the record carrier so that the movement of the converging lens becomes zero on average, that is, the movement is performed around the natural state.

Although the optical recording / reproducing apparatus has been described above, such an apparatus requires control with extremely high accuracy, and thus is extremely weak against external vibration or impact applied to the entire apparatus.

For example, if the acceleration of external vibration is 9.8 m / sec ² , 10 Hz
In case of the sine wave of, the whole device will move ± 2.5mm. Therefore, the loop gain of the focus control system must be 74 dB at 10 Hz and the loop gain of the tracking control system must be at least 88 dB at 10 Hz in order for the device to operate reliably against external vibration with an acceleration of 9.8 m / sec ² at 10 Hz. Is. In addition, high responsiveness of transfer control is required.

However, in the case of focus control, there is the surface wobbling acceleration of the record carrier, and in the case of tracking control, there is the center of gravity acceleration of the track. Therefore, the loop gains of the focus control system and the tracking control system are further required.

In order to construct a control system with such a high loop gain, it is extremely difficult to detect a high S / N control signal and a control element with high performance. It was extremely weak and unreliable.

OBJECT OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned conventional drawbacks and to provide a tracking control device having a simple structure, which is strong against external vibrations and shocks and has high reliability.

The present invention is directed to a light deflecting unit for directing a light beam to a record carrier, a converging unit for converging the light beam deflected by the light deflecting unit on a record carrier, and a light beam on the record carrier for tracking. First moving means for supporting the focusing means in a form capable of moving in a transverse direction, and second moving means for moving the first moving means and the light deflecting means so that the light beam on the record carrier crosses the track. A track deviation detecting means for detecting a positional deviation between the light beam on the record carrier and the track; and a first moving means in response to a signal from the track deviation detecting means to move the converging means to move the converging means. First control means for controlling the light beam to be positioned on the track;
When the second control means is operating, the second control means drives and controls the second moving means so that the movement of the converging means by the first control means becomes zero on average, and the second control means is added to the frame. And a disturbance detecting means for detecting acceleration of vibration or shock in the moving direction of the second moving means, adding a signal of the disturbance detecting means to the second moving means, and shifting the track against vibration or shock applied from the outside. Alternatively, it is designed so that track skipping does not occur.

Description of Embodiments One embodiment of the present invention will be described in detail below with reference to the drawings. In the numbers used in the description of the drawings, the same components are designated by the same numbers.

FIG. 1 shows an embodiment in which the present invention is applied to an optical recording / reproducing apparatus.

The record carrier 1 is attached to a disc motor 2 and is rotated at a predetermined rotation speed. The light beam 4 generated from the light source 3 is collimated by the coupling lens 5, passes through the deflecting beam splitter 6 and the 1/4 wavelength plate 7, is reflected by the reflecting mirror 8, is converged by the converging lens 9, and is recorded. Carrier 1
Is irradiated. Light beam 4 reflected by record carrier 1
Passes through the converging lens 9 again and is reflected by the reflecting mirror 8,
It passes through the quarter-wave plate 7, is reflected by the deflecting beam splitter 6, and is incident on the convex lens 10. The light beam 4 that has passed through the convex lens 10 is split by a split mirror 11, which will be described later in detail, so that a part of the light beam 4 is applied to a photodetector 12, and the remaining light beam 4 is reflected and the photodetector is detected. Irradiated to 13. The converging lens 9 is attached to a movable part of a control element 14 which moves in two axial directions, that is, a direction perpendicular to the surface of the record carrier 1 and a radial direction of the record carrier 1, and the control element 14 is provided.
Is configured so that it can be moved in two axial directions.
Light source 3, coupling lens 5, deflecting beam splitter 6,
The quarter-wave plate 7, the reflecting mirror 8, the control element 14, the convex lens 10, the split mirror 11, and the photodetectors 12 and 13 are attached to the moving table 15, and are integrated by the linear motor 16 so as to be integrated in the record carrier 1. It is configured to move in a radial direction.

The structures of the converging lens 10, the split mirror 11, and the photodetectors 12 and 13 will be described with reference to FIG. The split mirror 11 is composed of a total reflection mirror, and the reflecting surface of the split mirror 11 is a light beam 4
It is placed at 45 ° to the optical axis of. The split mirror 11 is arranged such that half of the light beam 4 that has passed through the converging lens 9 irradiates its reflection surface, and the half of the light beam 4 reflected by the split mirror 11 irradiates the photodetector 13. The other half of the light beam 4 is applied to the photodetector 12. To further explain, the split mirror 11 splits the light beam 4 into two in a direction perpendicular to the track direction in a plane perpendicular to the optical axis of the light beam 4, and halves the light beam 4 into a photodetector.
13 and the other half of the light beam 4 is applied to the photodetector 12.

The photodetectors 12 and 13 have a two-divided structure and have two light receiving regions. The photodetector 12 is arranged so that the direction of the dividing line is the track direction on the light receiving surface of the photodetector 12, and the photodetector 13 has the dividing line in the direction of the photodetector.
The 13 light receiving surfaces are arranged so as to be perpendicular to the track direction. The difference between the signals of the two light-receiving areas of the photodetector 12 becomes a signal indicating the positional deviation between the light beam 4 on the record carrier 1 and the track, and the difference of the signals of the two light-receiving areas of the photodetector 13 on the record carrier 1. It is known that the signal represents the converged state of the light beam 4 and is not described in detail.

In FIG. 1, the two outputs of the photodetector 12 are input to the differential amplifier 17, and the differential amplifier 17 outputs a signal corresponding to the difference between the two signals. As described above, the signal of the differential amplifier 17 becomes a signal indicating the positional deviation between the light beam 4 on the record carrier 1 and the track, that is, a tracking control signal. The signal of the differential amplifier 17 is applied to the tracking terminal of the control element 14 via the phase compensating circuit 18 for compensating the phase of the tracking control system, the synthesizing circuit 19 and the driving circuit 20 for power amplification. Therefore, the control element 14 moves the converging lens 9 in the radial direction of the record carrier 1 according to the signal of the differential amplifier 17 so that the light beam 4 on the record carrier 1 always scans the track. The signal from the differential amplifier 17 is applied to the linear motor 16 via a phase compensation circuit 21, a combination circuit 22, and a drive circuit 23 for power amplification, and the linear motor 16 has a radius of the record carrier 1 of the control element 14. The transfer table 15 is moved so that the movement in the direction becomes zero on average. (Hereinafter, this control is referred to as transfer control.) The transfer compensating circuit 21 is for compensating the phase of the transfer control system.

Reference numeral 24 denotes an acceleration detector such as a pressure sensor, which is attached to a frame 25 of the device supporting the disk motor 2 and the like. The acceleration detector 24 detects the acceleration applied from the outside in the radial direction of the record carrier 1, that is, the direction in which the control element 14 moves in response to the signal from the differential amplifier 17, and outputs the detected signal to the synthesis circuits 19 and 22. send. The synthesizing circuit 19 outputs a signal obtained by synthesizing the signal of the phase compensation circuit 18 and the signal of the acceleration detector 24, and the synthesizing circuit 22 outputs a signal obtained by synthesizing the signal of the phase compensation circuit 21 and the signal of the acceleration detector 24. Therefore, the control element 14 and the linear motor 16 are driven according to the signal of the acceleration detector 24.

The radial direction of the record carrier 1, that is, the control element 14 is a differential amplifier.
When the entire apparatus is subjected to external vibration or shock in the direction of movement according to the signal of 17, the record carrier 1 fluctuates integrally with the frame 25 of the apparatus according to external vibration or shock, but the transfer table 15 The movable part of the linear motor 16 including the one receives an inertial force. Therefore, if the acceleration detector 24 detects the acceleration applied from the outside and applies this signal to the linear motor 16 to cancel the inertial force, the transfer table 15 moves together with the frame 25. When the frame 25 and the transfer table 15 move integrally as a result of external vibration or shock, the movable portion of the control element 14 including the converging lens 9 similarly receives an inertial force. Therefore, if the inertial force is canceled by applying the signal of the acceleration detector 24 to the tracking terminal of the control element 14, the converging lens 9 moves together with the frame 25.

As described above, the signal of the acceleration detector 24 is controlled by the control element.
If the inertial force is canceled in addition to the tracking terminals of 14 and the linear motor 16, the converging lens 9 and the transfer table 15 are set to the frame 25.
It will move as a unit and will not be displaced or jumped even if external vibration or shock is applied.

The focus control of FIG. 1 will be described below. The two outputs of the photodetector 13 are respectively input to the differential amplifier 26, and the differential amplifier 26 outputs a signal corresponding to the difference between the two signals. As described above, the signal of the differential amplifier 26 becomes a signal representing the converged state of the light beam 4 on the record carrier 1, that is, a defocus signal. The signal of the differential amplifier 26 is a phase compensation circuit 27 for compensating the phase of the focus control system, and a synthesis circuit 2
8 and the control element 14 via the drive circuit 29 for power amplification
Has been added to the focus terminal. Therefore, the control element 14
Moves the converging lens 9 in the direction perpendicular to the surface of the record carrier 1 according to the signal from the differential amplifier 26 so that the converged state of the light beam 4 on the record carrier 1 is always constant.

Reference numeral 30 is an acceleration detector such as a pressure sensor, and the frame 25
Is attached to. The acceleration detector 30 detects the acceleration applied from the outside in the direction perpendicular to the surface of the record carrier 1,
The detected signal is sent to the synthesis circuit 28. The synthesizing circuit 28 outputs a signal obtained by synthesizing the signal of the phase compensation circuit 27 and the signal of the acceleration detector 30. Therefore, the control element 14 is driven in the direction perpendicular to the surface of the record carrier 1 according to the signal of the acceleration detector 30.

When the entire apparatus is subjected to external vibration or impact in the direction perpendicular to the surface of the record carrier 1, the record carrier 1 fluctuates together with the frame 25, but the movable part of the control element 14 including the converging lens 9 has inertial force. Receive. Therefore, if the acceleration detector 30 detects the acceleration applied from the outside and applies this signal to the focus terminal of the control element 14 to cancel the inertial force, the converging lens 9 moves together with the frame 25, and the external vibration is generated. Alternatively, even if an impact is applied, the focus does not shift.

As described above, according to the present invention, it is possible to easily configure a control system that is strong against external vibration or impact without increasing the S / N of the control signal and the characteristics of the control element. It can be remarkably improved and the device can be made inexpensive, and the effect is extremely large.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment in which the present invention is applied to an optical recording / reproducing apparatus, and FIG. 2 is a diagram for explaining detection of a tracking control signal and a focus control signal. 1 ... record carrier, 2 ... disk motor, 3 ... light source,
4 ... Light beam, 9 ... Converging lens, 11 ... Split mirror, 12,13 ... Photodetector, 17,26 ... Differential amplifier, 18, 21,
27 …… Phase compensation circuit, 19,22,28 …… Composite circuit, 20,23,29
...... Driving circuit, 14 …… Control element, 15 …… Transfer stand, 16 ……
Linear motor, 24,30 ... Acceleration detector, 25 ... Frame.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroyuki Yamaguchi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-60-35377 (JP, A) (JP, U) Japanese Patent Publication 6-90799 (JP, B2) Japanese Patent Publication 4-21252 (JP, B2) Japanese Patent Publication 3-9557 (JP, B2)

Claims (1)

[Claims] 1. A light deflecting means for directing a light beam to a record carrier, a converging means for converging the light beam deflected by the light deflecting means onto a record carrier, and a light beam on the record carrier traverses a track. First moving means for supporting the converging means in a direction movable manner, and second moving means for moving the first moving means and the light deflecting means so that a light beam on a record carrier crosses a track. Moving means, track deviation detecting means for detecting a positional deviation between the light beam on the record carrier and the track, and driving the first moving means in response to a signal from the track deviation detecting means to move the converging means. First control means for controlling the light beam on the record carrier to be positioned on the track, and the movement of the converging means by the first control means when the first control means is operating. average Second control means for driving and controlling the second moving means so as to be zero, and disturbance detection means for detecting acceleration of vibration or impact applied to the frame in the moving direction of the second moving means. A tracking control device, comprising: a signal from the disturbance detecting means to be applied to the second moving means.