JPH0612595B2 - Control device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device in a recording / reproducing apparatus for reproducing a signal recorded on a record carrier or recording a signal on the record carrier.

2. Description of the Related Art There are magnetic recording / reproducing devices, magneto-optical recording / reproducing devices, optical recording / reproducing devices, optical reproducing devices, capacitive reproducing devices, and the like as the above-mentioned types of devices. A conventional example will be described as an example.

For example, as an optical recording / reproducing apparatus, a light beam generated from a light source such as a semiconductor laser is converged into a minute beam diameter by a converging lens to irradiate a rotating disk-shaped record carrier, and the light amount of the light beam is used during recording. In some cases, the signal is reproduced by changing the recording amount 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 type of apparatus, for example, there is one in which a track having an irregular shape is provided in advance 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.

In tracking control, the record carrier detects the positional deviation between the light beam that is converged on the record carrier from the light beam that is transmitted or the light beam that is reflected from 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
The transfer control is performed so that the entire optical system including the light source is moved in the radial direction of the record carrier so that the movement of the converging lens becomes zero on average, that is, the movement occurs 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 , 10H
In the case of a sine wave of z, the entire device will move ± 2.5 mm. 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 an external vibration of acceleration of 9.8 m / sec ² at 10 Hz. Is. In addition, high responsiveness of transfer control is required.

However, in terms of focus control, there is surface wobbling acceleration of the record carrier, and in terms of tracking control, there is eccentric 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 having such a high loop gain, detection of a high S / N control signal and a high performance control element are indispensable. However, in the conventional device, since the above conditions were not achieved, the device was weak against vibration or shock applied from the outside, and there was a strong possibility that a track jump or defocus occurred. For example, if a track jump occurs while recording a signal, not only the signal itself will not be recorded correctly, but also the other tracks will be damaged or the signal already recorded on another track will be damaged. Bring results. Further, if a track jump occurs during reproduction of a signal that has already been recorded, naturally the expected signal cannot be reproduced.

In order to eliminate the above-mentioned drawbacks, the present inventors provide an acceleration detecting means for detecting an acceleration in the tracking direction due to an externally applied vibration or impact, and apply a signal of this acceleration detecting means to a tracking control element to perform tracking. It has already been proposed to improve the vibration resistance of control (Japanese Patent Application No. 58-228730). Further, by providing an acceleration detecting means for detecting an acceleration in a focus direction, that is, a direction perpendicular to the surface of the record carrier due to an externally applied vibration or shock, and applying a signal of the acceleration detecting means to the focus control element, vibration resistance of the focus control is obtained. We have already proposed to improve (Japanese Patent Application No. 58-
228733).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention In the above proposal, the focus deviation or the track deviation becomes very small in the state where the external vibration or the shock is applied, and the vibration resistance can be improved. Is added to the control element,
A high signal-to-noise ratio (hereinafter referred to as S / N) of the acceleration detecting means is required. When the quality of the signal of the acceleration detecting means is poor, the vibration resistance when a large external vibration or shock is applied is improved, but in the normal state, the noise contained in the signal of the acceleration detecting means acts as a disturbance. However, if the signal of the acceleration detecting means is not added, the focus shift or the track shift becomes smaller. When a signal with a bad S / N is applied, the current flowing through the control element increases, causing heat generation, which leads to deterioration of the control element or damage in extreme cases. Therefore, it is necessary to increase the signal S / N of the acceleration detecting means, which makes the acceleration detecting means complicated and expensive.

The object of the present invention was made in view of the above points, and it is an object of the present invention to provide a device capable of preventing heat generation of a control element without deteriorating control accuracy in a steady state even by using a simple and inexpensive acceleration detecting means. It is to be.

Means for Solving the Problems The present invention is provided with an acceleration level detecting means for detecting that the magnitude of vibration or shock applied to the device exceeds a predetermined value from the signal of the acceleration detecting means. Only when the signal of the means is generated, the signal of the acceleration detecting means is applied to the control element.

The present invention has the above-described configuration, and since the signal of the acceleration detecting means is applied to the control element only when an external vibration or impact exceeding a predetermined value is applied, it is included in the signal of the acceleration detecting means in the normal state. The generated noise does not lower the control accuracy or heat the control element.

Embodiment An 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 eccentric 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. The carrier 1 is irradiated. The light beam 4 reflected by the record carrier 1 again passes through the converging lens 9, is reflected by the reflecting mirror 8, passes through the quarter-wave plate 7, and is polarized by the polarization beam splitter 6.
It is reflected by and enters the convex lens 10. Convex lens 10
The light beam 4 that has passed through the split mirror 1 will be described in detail later.
1, a part of the light beam 4 is divided by the photodetector 1
2 and the remaining light beam 4 is reflected and applied to the photodetector 13. The converging lens 9 is attached to a movable part of a control element 14 that 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 is moved by the control element 14 in two axial directions. It is configured to be able to. Light source 3, coupling lens 5, polarization beam splitter 6, quarter wave plate 7, reflecting mirror 8, control element 14, convex lens 10, split mirror 11, photodetector 1
2 and 13 are attached to a transfer table 15, and are configured to move integrally in the radial direction of the record carrier 1 by a linear motor 16.

Converging lens 10, split mirror 11, photodetectors 12 and 1
The configuration of No. 3 will be described with reference to FIG. Split mirror 1
Reference numeral 1 denotes a total reflection mirror, and the reflecting surface of the split mirror 11 is arranged so as to be 45 ° with respect to the optical axis of the light beam 4. The split mirror 11 is arranged so that its reflection surface irradiates half of the light beam 4 that has passed through the converging lens 9, 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 irradiated onto the photodetector 12. More specifically, 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,
The photodetector 13 is irradiated with half of the light beam 4, and the photodetector 12 is irradiated with the other half of the light beam 4.

The photodetectors 12 and 13 have a two-divided structure and have two light receiving regions. The photodetector 12 is arranged such 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 direction on the track of the light receiving surface of the photodetector 12. It is arranged so that it is perpendicular to the 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. Light beam 4
It is known that the signal represents the converged state of, and will not be described in detail.

In FIG. 1, the two outputs of the photodetector 12 are respectively input to the differential amplifier 17, and the differential amplifier 17 outputs a signal according to the difference between the two signals. As mentioned above,
The signal of the differential amplifier 17 becomes a signal representing 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 compensation circuit 18 for compensating the phase of the tracking control system, the combining circuit 19 and the drive 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 of the differential amplifier 17 is applied to the linear motor 16 via the phase compensation circuit 21, the combination circuit 22, and the 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 phase compensation circuit 21 is for compensating the phase of the transfer control system.

Focus control will be described below.
The two outputs are respectively input to the differential amplifier 24,
The differential amplifier 24 outputs a signal according to the difference between the two signals.
As described above, the signal of the differential amplifier 24 becomes a signal representing the convergence state of the light beam 4 on the record carrier 1, that is, a focus shift signal. The signal of the differential amplifier 24 is applied to the focus terminal of the control element 14 via the phase compensation circuit 25 for compensating the phase of the focus control system, the synthesizing circuit 26, and the drive circuit 27 for power amplification. 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 of the differential amplifier 24 so that the converged state of the light beam 4 on the record carrier 1 is always constant. To do.

Reference numerals 28, 29 and 30 denote acceleration detectors attached to the frame 31 of the device supporting the disk motor 2 and the like. The acceleration detector 28 detects the acceleration of vibration or impact 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 accordance with the signal from the differential amplifier 17. The acceleration detector 29 detects the acceleration of vibration or shock applied from the outside in the direction perpendicular to the surface of the record carrier 1, and the acceleration detector 30 detects the direction of the track on the record carrier 1, that is, the control element 14 performs the differential amplification 17. The acceleration of vibration or impact applied from the outside in the direction perpendicular to the moving direction is detected according to the signal of.

There are various types of acceleration sensors, and for example, there is one that detects an acceleration by detecting an electric charge (this effect is called a piezoelectric effect) generated when a force is applied to a piezoelectric element. This kind of acceleration sensor cannot detect a constant acceleration like gravitational acceleration, and is limited to a specific frequency range.

The signals of the acceleration detectors 28, 29, 30 are band filters 32, 33, 3 whose pass band is 1 Hz to 2 KHz, for example.
4 and switches 35, 36 and 37, respectively, and input to the acceleration level detection circuit 38.

The acceleration level detection circuit 38 will be described with reference to FIG.

Switches 35 and 3 are provided in the level detection circuits 51, 52 and 53.
The signals 6 and 37 are input respectively, and the signals of the level detection circuits 51, 52 and 53 are input respectively to the OR circuit 54. Level detection circuits 51, 52 and 53
Is configured to output a HIGH signal when the amplitude of the signals of the acceleration detectors 28, 29 and 30 exceeds a predetermined value. For example, the output signals of the acceleration detectors 28, 29 and 30 are a ₁ , a ₂ and a ₃ , respectively, and the level detection circuit 5
When the detection levels of ₁ , 52 and 53 are V ₁ , V ₂ and V ₃ , respectively (where V ₁ , V ₂ and V ₃ are positive real numbers), the level detection circuit 51 has a ₁ <-V ₁ or a. ₁ >
When V ₁ , it outputs a HIGH signal, and the level detection circuit 52 outputs a ₂ <
-V ₂ or _a 2> outputs a HIGH signal when _{V 2,} the level detection circuit 53 outputs a HIGH signal when _{a 3} <-V 3 or _{a 3> V} 3. The polarities of a ₁ , a ₂ , and a ₃ represent the direction of acceleration.

Detection levels V _{1 of} the level detection circuits 51, 52 and 53,
The values of V ₂ and V ₃ must be determined to be larger than the noise level of the acceleration detectors 28, 29, 30 and to consider the vibration resistance and shock resistance of the device.

That is, the vibration resistance and shock resistance of the device differ depending on the direction, and the tracking control system is generally lower than the focus control system. This is the tracking control accuracy (± 0.
(1 μm or less) and focus control accuracy (± 0.5 μm or less).

The OR circuit 54 outputs a signal according to the logical sum of the level detection circuits 51, 52 and 53, and the level detection circuits 51, 5
When even one of the signals 2, 53 outputs a HIGH signal, the OR circuit 54 outputs a HIGH signal, which is output to the switch 3 in FIG.
9 and 40 are sent to the input terminals for opening and closing, respectively.

The signal of the acceleration detector 28 is input to the combining circuits 19 and 22 via the bandpass filter 32 and the switches 35 and 39. The combining circuit 29 outputs a signal obtained by adding the signal of the phase compensation circuit 18 and the output signal of the switch 39, and the combining circuit 22 outputs a signal obtained by adding the signal of the phase compensation circuit 21 and the output signal of the switch 39. Therefore, when the device is vibrated or shocked in the tracking direction, that is, in the direction in which the control element 14 moves according to the signal of the differential amplifier 17,
The output of the acceleration level detection circuit 38 becomes HIGH, the switch 39 is short-circuited, and the control element 14 and the linear motor 16 are driven according to the signal of the acceleration detector 28.

When the entire device receives an external vibration or shock in the radial direction of the record carrier 1, that is, in the direction in which the control element 14 moves according to the signal of the differential amplifier 17, the record carrier 1 receives the external vibration or shock and the frame of the device responds to the external vibration or shock. Although it fluctuates together with 31, the movable portion of the linear motor 16 including the transfer table 15 receives an inertial force. Therefore, if the acceleration detector 28 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 31. When vibration or shock is applied from the outside and the frame 31 and the transfer table 15 move integrally, the movable part of the control element 14 including the converging lens 9 similarly receives an inertial force. Therefore, the acceleration detector 28
When the signal of is applied to the tracking terminal of the control element 14 to cancel the inertial force, the converging lens 9 moves together with the frame 31.

As described above, if the signal of the acceleration detector 28 is applied to the tracking terminal of the control element 14 and the linear motor 16 to cancel the inertial force, the converging lens 9 and the transfer table 15 move integrally with the frame 31, Even if external vibration or impact is applied, it is possible to prevent track deviation or track jump as much as possible.

The signal from the acceleration detector 29 is input to the synthesizing circuit 26 via the bandpass filter 33 and the switches 36 and 40. The synthesis circuit 26 outputs a signal obtained by adding the signal of the phase compensation circuit 25 and the output signal of the switch 40. Therefore, when the device is vibrated or shocked in the direction perpendicular to the surface of the record carrier 1, the output of the acceleration level detection circuit 38 becomes HIGH, the switch 40 is short-circuited, and the control element 14 responds to the signal of the acceleration detector 29. Driven.

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 changes together with the frame 31, but the control element 1 including the converging lens 9
The movable part of 4 receives inertial force. Therefore, the acceleration detector 29
By detecting the acceleration applied from the outside by applying this signal to the focus terminal of the control element 14 to cancel the inertial force,
The converging lens 9 moves integrally with the frame 31, and the focus shift can be made extremely small even if external vibration or shock is applied.

As described above, when the external vibration or shock is small, the output of the acceleration level detection circuit 38 does not go to the HIGH state, so the switches 39 and 40 are not short-circuited, and the focus control and tracking control by the acceleration detectors 28 and 29 are performed. Vibration resistance and shock resistance are not improved, but there is no problem because external vibration or shock is small.

In the embodiment shown in FIG. 1, when the output of the acceleration level detection circuit 38 is brought into a HIGH state due to a large vibration in the direction perpendicular to the surface of the record carrier 1, the switch 39 is short-circuited and the signal of the acceleration detector 28 is controlled. Although it is configured to be added to the tracking terminal of the element 14 and the linear motor 16, there is no problem even if the switch 39 is configured to be in the open state in this case. That is, the acceleration detector 2
Switch 39 only if the signal of 8 is larger than a predetermined value.
Is short-circuited, and the signal of the acceleration detector 28 is applied to the tracking terminal of the control element 14 and the linear motor 16. Similarly, the switch 40 is short-circuited only when the signal of the acceleration detector 29 is larger than a predetermined value. The signal from the acceleration detector 28 can be applied to the focus terminal of the control element 14.

The reason why the switches 35, 36 and 37 are provided will be described.

As described above, the device to which the present invention is applied is usually placed on a desk, and is rarely subjected to excessive vibration or impact at low frequency. Acceleration detector 28,2
Bandpass filters 32, 33 and 34 are provided for the purpose of eliminating the influence of fluctuations due to temperature changes of 9, 30 or improving the S / N of the signals of the acceleration detectors 28, 29, 30. However, when the device is turned on, a transient signal is output at the outputs of the bandpass filters 32, 33, 34.
This transient signal causes the acceleration level detection circuit 38 to HI.
In the GH state, an excessive current may flow through the control element 14 and the linear motor 16, which may damage the device. The switches 35, 36 and 37 are for preventing this. That is, the timer 41 sends signals for short-circuiting the switches 35, 36 and 37 to the input terminals for opening and closing after a predetermined time when the power of the device is turned on. Therefore, the signals of the band-pass filters 32, 33, 34 are transmitted to the acceleration level detection circuit 38 after a predetermined time has passed since the power of the device was turned on.
Therefore, a transient signal at the time of power-on does not damage the device.

Although the present invention has been described in detail above, the present invention is not limited to the embodiments.

For example, although the control element 14 has a biaxial structure in the embodiment shown in FIG. 1, an optical video reproducing apparatus for reproducing a video or the like has a triaxial structure. That is, the control element is configured to be movable in three axial directions, that is, a direction perpendicular to the surface of the record carrier, a track direction on the record carrier, and a direction perpendicular to the track direction on the record carrier. This is because it is necessary to correct the fluctuation of the time axis caused by the eccentricity of the record carrier.

Explaining general time axis correction control, the phases of the sync signal and the reference signal included in the reproduction signal are compared to obtain a signal corresponding to the phase difference between the two signals, and the signal corresponding to this phase difference is controlled. In addition to the terminal for controlling the time axis of the element, the light beam on the record carrier is moved and controlled in the track direction so that the phase of the synchronization signal included in the reproduction signal maintains a predetermined relationship with the phase of the reference signal. .

In the device having the time axis correction control as described above, the signal of the acceleration detector 30 is added to the terminal for time axis control of the control element via the switch, and when the signal of the acceleration detector 30 exceeds a predetermined value, the switch is activated. If it is configured to short-circuit, the time axis fluctuation can be minimized when external vibration or shock is applied.

Effect of the Invention Since the present invention is configured to apply the signal of the acceleration detecting means to the control element only when excessive vibration or impact is applied to the device, control is performed by noise included in the signal of the acceleration detecting means. It is possible to prevent the accuracy from decreasing and the control element from generating heat, and it is possible to make the acceleration detecting means simple and inexpensive.

[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, FIG. 2 is a diagram for explaining detection of a tracking control signal and a focus control signal, and FIG. 3 is an acceleration level detection circuit 38. It is a block diagram. 14 ... Control element, 19, 22, 26 ... Combining circuit, 2
0, 23, 27 ... Driving circuit, 28, 29, 30 ... Acceleration detector, 31 ... Frame, 32, 33, 34 ...
Band filter, 35, 36, 37, 39, 40 ... switch, 38 ... acceleration level detection circuit, 41 ... timer.

Claims (7)

[Claims] 1. A conversion means for recording a signal on a record carrier or for reproducing a signal recorded on a record carrier, and a scanning position of the conversion means so as to cross a track on the record carrier. A moving means, a track deviation detecting means for detecting a positional deviation between a track on the record carrier and a scanning position of the converting means, and a driving means for driving the moving means in response to a signal from the track deviation detecting means. Control means for controlling the scanning position to always be located on a track on the record carrier; and acceleration detecting means for detecting acceleration of vibration or impact applied to the device in the moving direction of the scanning position of the converting means by the moving means. And an acceleration level detecting means for detecting that the magnitude of the signal of the acceleration detecting means exceeds a predetermined value, and the signal of the acceleration level detecting means is generated. The signal of the acceleration detecting means that is configured to apply to the moving means to focus control apparatus according to claim. 2. The control device according to claim 1, wherein the acceleration level detecting means operates after a lapse of a predetermined time after the power of the device is turned on. 3. A conversion means for recording a signal on a record carrier or for reproducing a signal recorded on a record carrier and a scanning position of the conversion means so as to cross a track on the record carrier. Detecting a positional shift between a first moving means, a second moving means for moving the first moving means so as to cross a track on the record carrier, and a scanning position of the track on the record carrier and the converting means. The track shift detecting means and the first and second moving means are driven according to the signal of the track shift detecting means to control so that the scanning position of the converting means is located on the track on the record carrier. The control means, the acceleration detecting means for detecting the acceleration of vibration or impact applied to the device in the moving direction of the first moving means by the second moving means, and the magnitude of the signal of the acceleration detecting means are determined. Acceleration level detecting means for detecting that the value of the acceleration level detecting means is exceeded, and the signal of the acceleration detecting means is applied to the second moving means when the signal of the acceleration level detecting means is generated. A control device characterized by. 4. The control device according to claim 3, wherein the acceleration level detecting means operates after a lapse of a predetermined time after the power of the device is turned on. 5. The control device according to claim 3, wherein the signal of the acceleration detecting means is added to the first moving means when the signal of the acceleration level detecting means is generated. . 6. A converging means for converging a light beam generated from a light source and irradiating it on a record carrier, a converging state detecting means for detecting a converging state of the light beam on the record carrier, and the converging means. And a moving means for moving the recording medium in a direction substantially perpendicular to the surface of the record carrier, and the moving means is driven in response to a signal from the convergent state detecting means so that the convergent state of the light beam on the record carrier is always constant. Control means for controlling so that
Acceleration detecting means for detecting acceleration of vibration or impact applied to the device in a direction substantially perpendicular to the surface of the record carrier, and acceleration level for detecting that the magnitude of the signal of the acceleration detecting means exceeds a predetermined value. A control device having a detecting means, and configured to add the signal of the acceleration detecting means to the moving means when the signal of the acceleration level detecting means is generated. 7. The control device according to claim 6, wherein the acceleration level detecting means operates after a lapse of a predetermined time after the power of the device is turned on.