JPH0421252B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention focuses a light beam generated from a light source and irradiates it onto a record carrier to record a signal on the record carrier or to record a signal on the record carrier. The present invention relates to an optical recording/reproducing device for reproducing signals, and in particular to a focus control device for controlling the convergence state of a light beam on a record carrier to be always constant.

Configuration of conventional examples and their problems For example, as an optical recording/reproducing device, a light beam generated from a light source such as a semiconductor laser is converged to a minute beam diameter by a converging lens, and a rotating disc-shaped record carrier is used. During recording, the light intensity of the light beam is changed according to the signal to be recorded, and during playback, the light intensity of the light beam is set to a weak constant light intensity, and reflected light or transmitted light from the record carrier is detected to record the signal. There is something to play.

In the recording carrier used in this type of device, for example, there is one in which uneven tracks are 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 the track pitch and track width are very narrow, for example, the pitch is very narrow.
The thickness is 1.6 μm and the width is approximately 0.6 μm.

Therefore, in order to obtain high-quality reproduction signals, the above-mentioned optical recording and reproducing apparatus uses a focus control system that controls the light beam irradiated onto the rotating record carrier so that it always has a constant, minute beam diameter. Control means and tracking control means are essential for controlling the light beam 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 convergence lens in a direction perpendicular to the record carrier surface according to the detected signal. However, the control precision of focus control is required to be extremely high, for example, ±0.5 μm or less.

In addition, tracking control detects the positional deviation between the light beam that is focused on the record carrier and the track from the light beam that has passed through the record carrier or the light beam that has been reflected from the record carrier, and converges the track based on the detected signal. This is carried out by moving the lens in the radial direction within the plane of the record carrier, but tracking control requires extremely high control accuracy, like focus control, for example, ±0.1 μm or less.

The range of movement in which the converging lens can be moved in the radial direction within the plane of the record carrier is narrow, and at most ±
Generally speaking, tracking control moves the converging lens so that the light beam follows the eccentricity of the track, and so that the movement of the converging lens becomes zero on average, that is, in the natural state. Transfer control is performed to move the entire optical system, including the light source, in the radial direction of the record carrier so as to move around the center.

Although the optical recording/reproducing apparatus has been described above, such an apparatus requires extremely high precision control and is therefore extremely vulnerable to external vibrations or shocks applied to the entire apparatus.

For example, if the acceleration of external vibration is 98 m/sec ² , the entire device will be ±2.5 mm in the case of a 10 Hz sine wave.
will also be moved. Therefore, at 10Hz 9.8m/
In order for the device to operate reliably against external vibrations with an acceleration of sec ² , the loop gain of the focus control system must be at least 74 dB at 10 Hz, and the loop gain of the tracking control system must be at least 88 dB at 10 Hz.
In addition, the responsiveness of transfer control is also required to be fast.

However, when talking about focus control, there is the surface runout acceleration of the record carrier, and when talking about tracking control, there is the eccentric acceleration of the track.

Therefore, loop gains for the focus control system and tracking control system are further required.

In order to configure a control system with such a high loop gain, it is necessary to detect a control signal with a high S/N,
It requires high performance control elements and is extremely difficult, and conventional devices are extremely susceptible to external vibrations and shocks and have low reliability.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a focus control device which eliminates the above-mentioned conventional drawbacks, has a simple structure, is resistant to vibrations or shocks applied from the outside, and is highly reliable.

Configuration of the Invention The present invention includes a converging means for converging a light beam generated from a light source and irradiating it onto a record carrier, a convergence state detection means for detecting a convergence state of the light beam on the record carrier, and a convergence state detection means for detecting a convergence state of the light beam on the record carrier. A moving means for moving the means in a direction substantially perpendicular to the surface of the record carrier, and a moving means for moving the moving means in accordance with a signal from the convergence state detection means, to determine the convergence state of the light beam on the record carrier. and disturbance detection means for detecting the acceleration of vibration or impact applied to the device in a direction substantially perpendicular to the surface of the record carrier, and the signal of the disturbance detection means is is added to the moving means, and is configured so that no focus shift occurs due to vibrations or shocks applied from the outside.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Note that the same numbers are used to describe the drawings.

FIG. 1 shows an embodiment of the focus control device of the present invention.

The record carrier 1 is attached to a disk motor 2 and rotated at a predetermined number of rotations. A light beam 4 generated from a light source 3 is made into parallel light by a coupling lens 5, passes through a polarizing beam splitter 6 and a quarter-wave plate 7, is reflected by a reflecting mirror 8, is converged by a converging lens 9, The record carrier 1 is irradiated. The light beam 4 reflected by the record carrier 1 is
It passes through the converging lens 9 again, is reflected by the reflecting mirror 8, passes through the 1/4 wavelength plate 7, is reflected by the polarizing beam splitter 6, and enters the convex lens 10.
The light beam 4 that has passed through the convex lens 10 is split by a splitting mirror 11, which will be described in detail later, and a part of the light beam 4 is irradiated onto the photodetector 12, and the remaining light beam 4 is reflected and becomes light. The detector 13 is irradiated with light. The converging lens 9 is arranged in two axes, i.e. in the direction of the record carrier 1.
It is attached to a movable part of a control element 14 that moves in a direction perpendicular to the plane of the record carrier 1 and in a radial direction of the record carrier 1, and is configured to be able to move in two axial directions by the control element 14. Light source 3, coupling lens 5, polarizing beam splitter 6, quarter wavelength plate 7, reflecting mirror 8, control element 14, convex lens 1
0, the split mirror 11, the photodetectors 12 and 13 are attached to the transfer table 15, and the linear motor 1
6 so as to move together in the radial direction of the record carrier 1.

Convergent lens 10, split mirror 11, photodetector 1
The configurations of 2 and 13 will be explained 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 arranged at an angle of 45° with respect to the optical axis of the light beam 4. The splitting mirror 11 is arranged so that half of the light beam 4 that has passed through the converging lens 9 is irradiated onto its reflecting surface, and the half of the light beam 4 reflected by the splitting mirror 11 is irradiated onto the photodetector 13. The remaining half of the light beam 4 is irradiated onto the photodetector 12 . To explain further, the splitting 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 irradiates the photodetector 13 with half of the light beam 4. The remaining half of the light beam 4 is irradiated onto the photodetector 12.

The photodetectors 12 and 13 have a two-part structure and have two light receiving areas. 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 is arranged so that the direction of the dividing line is the track direction on the light receiving surface of the photodetector 13. It is placed perpendicular to the direction. The difference between the signals of the two light-receiving areas of the photodetector 12 becomes a signal representing the positional deviation between the light beam 4 and the track on the record carrier 1, and the difference of the signals of the two light-receiving areas of the photodetector 13 becomes a signal representing the positional deviation between the light beam 4 and the track on the record carrier 1. Since it is known that the signal represents the convergence state of the light beam 4, detailed description thereof will be avoided.

In FIG. 1, two outputs of the photodetector 12 are input to a differential amplifier 17, respectively.
Differential amplifier 17 outputs a signal according to the difference between both signals.

As described above, the signal from the differential amplifier 17 becomes a signal representing the positional deviation between the light beam 4 and the track on the record carrier 1, that is, a tracking control signal.
The signal from the differential amplifier 17 is applied to the tracking terminal of the control element 14 via a phase compensation circuit 18 for compensating the phase of the tracking control system, a combining circuit 19, and a drive circuit 20 for power amplification. The control element 14 therefore moves the converging lens 9 in the radial direction of the record carrier 1 in response to the signal from the differential amplifier 17, so that the light beam 4 on the record carrier 1 always scans over the track. Also, the differential amplifier 1
7 is applied to the linear motor 16 via a phase compensation circuit 21, a synthesis circuit 22, and a drive circuit 23 for power amplification, and the linear motor 16 controls the movement of the control element 14 in the radial direction. The transfer table 15 is moved so that the average value becomes zero (hereinafter, this control will be referred to as transfer control). Phase compensation circuit 2
1 is for compensating the phase of the transfer control system.

24 is an acceleration detector such as a pressure sensor;
It is attached to the frame 25 of the device that supports the disk motor 2 and the like. The acceleration detector 24 is arranged in the radial direction of the record carrier 1, i.e. the control element 14
detects the acceleration applied from the outside in the direction of movement according to the signal from the differential amplifier 17, and sends the detected signal to the combining circuits 19 and 22. The synthesis circuit 19 combines the signal of the phase compensation circuit 18 and the acceleration detector 2.
A signal obtained by combining the signals of 4 and 4 is output, and the combining circuit 22
outputs a signal obtained by combining the signal from the phase compensation circuit 21 and the signal from the acceleration detector 24. Therefore, the control element 14 and the linear motor 16 are driven according to the signal from the acceleration detector 24.

in the radial direction of the record carrier 1, i.e. the control element 1
When the entire apparatus is subjected to external vibration or shock in the direction in which the record carrier 1 moves in response to the signal from the differential amplifier 17, the record carrier 1 moves together with the frame 25 of the apparatus in response to the external vibration or shock. ,
The movable portion of the linear motor 16 including the transfer table 15 is subjected to 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 integrally with the frame 25. When vibration or shock is applied from the outside and the frame 25 and transfer table 15 move together, the movable portion of the control element 14 including the converging lens 9 is similarly subjected to inertial force. Therefore, if the signal from the acceleration detector 24 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 25.

As explained above, if the signal from the acceleration detector 24 is applied to the tracking terminal of the control element 14 and the linear motor 16 to cancel out the inertial force, the converging lens 9 and the transfer table 15 move together with the frame 25, Even if external vibrations or shocks are applied, no track deviation or track jump will occur.

The focus control shown in FIG. 1 will be explained below. The two outputs of the photodetector 13 are connected to a differential amplifier 26.
The differential amplifier 26 outputs a signal corresponding to the difference between the two signals. As described above, the signal from the differential amplifier 26 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 from the differential amplifier 26 is applied to the focus terminal of the control element 14 via a phase compensation circuit 27 for compensating the phase of the focus control system, a combining circuit 28, and a drive circuit 29 for power amplification. Therefore, the control element 14 moves the converging lens 9 in a direction perpendicular to the surface of the record carrier 1 in accordance with the signal from the differential amplifier 26 so that the convergence state of the light beam 4 on the record carrier 1 is always constant. Make it.

30 is an acceleration detector such as a pressure sensor;
It is attached to the frame 25. The acceleration detector 30 detects acceleration applied from the outside in a direction perpendicular to the surface of the record carrier 1, and sends this detected signal to the synthesis circuit 28. The combining circuit 28 outputs a signal obtained by combining the signal from the phase compensation circuit 27 and the signal from the acceleration detector 30. Control element 14 is therefore driven in a direction perpendicular to the plane of record carrier 1 in accordance with the signal from acceleration detector 30 .

When the entire apparatus is subjected to external vibration or shock in a direction perpendicular to the plane of the record carrier 1, the record carrier 1 moves together with the frame 25, but the movable part of the control element 14 including the converging lens 9 is moved by inertia. Receive power. 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 Even if vibration or shock is applied, no focus deviation will occur.

Effects of the Invention As described above, according to the present invention, the control signal S/
Since a control system that is resistant to external vibrations or shocks can be easily configured without increasing the characteristics of the N and control elements, the reliability of the device can be significantly improved and the device can be made inexpensive; Extremely large.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of an optical recording/reproducing device using the focus control device of the present invention.
FIG. 2 is a block diagram of main parts 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, 1
1... Split mirror, 12, 13... Photodetector, 1
7, 26... Differential amplifier, 18, 21, 27...
Phase compensation circuit, 19, 22, 28... synthesis circuit,
20, 23, 29... Drive circuit, 14... Control element, 15... Transfer table, 16... Linear motor, 2
4, 30...acceleration detector, 25...frame.

Claims (1)

[Claims] 1 a converging means for converging a light beam generated from a light source and irradiating it onto a record carrier; a convergence state detection means for detecting a convergence state of the light beam on the record carrier; a moving means for moving the light beam in a direction substantially perpendicular to the surface of the carrier; and a moving means for moving the moving means in accordance with a signal from the convergence state detection means, so that the convergence state of the light beam on the record carrier is always constant. and disturbance detection means for detecting the acceleration of vibration or impact applied to the device in a direction substantially perpendicular to the surface of the record carrier, and the signal of the disturbance detection means is A focus control device configured to be added to the moving means.