JPH06274914A - Optical information recording and reproducing device - Google Patents

Abstract

PURPOSE:To speed-up the recording and reproducing speed of data. CONSTITUTION:A signal (FE) corresponding to a residual focus controlling error is fed to a light source driving element driving circuit 23 via a switch 30 and a phase compensating filter 22. A light source driving element 20 is driven, a semiconductor laser 8 is moved in the optical axis direction of the outgoing light of the laser and the focussing position of a laser beam due to a an objective lens 2 is changed by the output of the light source driving element driving circuit 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus which has a high data recording / reproducing speed.

[0002]

2. Description of the Related Art A conventional tracking / focusing servo device in an optical disk device will be described with reference to FIG. A drive current is supplied to the semiconductor laser 8 by the semiconductor laser (LD) drive circuit 9, and the semiconductor laser 8 emits light. Laser light emitted from the semiconductor laser 8 is coupled to the coupling lens 7, the beam splitter 6, the prism 5,
It is focused on the optical disc 1 through the objective lens 2.

Laser light reflected from the optical disk 1 is sent to a light receiving element 10 via a prism 5 and a beam splitter 6. The light receiving element 10 detects an intensity change of the reflected light from the optical disc 1 as an electric signal. The focus error signal detection circuit 11 detects a focus error signal representing the relative position between the objective lens 2 and the optical disc 1, that is, the focus shift, from the output signal of the light receiving element 10. The output of the focus error signal detection circuit 11 is the phase compensation filter 1
2. Feedback is provided to the focus actuator 3 via the current amplifier 13.

The focus actuator 3 moves the objective lens 2 in the optical axis direction according to the focus error signal,
Control is performed so that the laser light is focused on the optical disc 1 (this is called focusing). An example of the focus actuator is Japanese Patent Publication No. 53-26124.
There is a focusing mechanism described in the publication.

Further, the track error detection circuit 14 detects a track error signal representing a deviation of a laser beam spot with respect to a guide groove (track) provided in advance on the optical disc 1, that is, a track deviation from the output signal of the light receiving element 10. , Feedback to the tracking actuator 4 via the phase compensation filter 15 and the current amplifier 16.

The tracking actuator 4 moves the objective lens 2 in the direction orthogonal to the optical axis according to the track error signal, and controls the laser light spot to follow the guide groove (track) (this is called tracking).

[0007]

By the way, in recent years, there is an increasing demand for increasing the data recording / reproducing speed of an optical disk device, but for that purpose, the optical disk must be rotated at a high speed. As the number of rotations of the optical disk increases, the frequency of surface wobbling / track wobbling of the optical disk increases accordingly.

In other words, "the frequency of shake increases" means "acceleration increases", and in order to follow it, a mechanism capable of generating a larger acceleration is required.

In the conventional optical disk device shown in FIG. 2, the objective lens 2 is made to follow the surface wobbling / track wobbling of the optical disk 1, and the objective lens 2 including a holding mechanism thereof weighs several grams. There is. As is well known, since F = m × a (F is force, m is mass, and a is acceleration), in order to generate larger acceleration, the objective lens drive mechanism (focus actuator 3, tracking The actuator 4) has to generate a larger thrust.

In order to generate a large thrust, in the electromagnetic objective lens driving mechanism described in the above-mentioned publication, (1) the magnetic force of the permanent magnet is strengthened (2) the number of turns of the coil is increased (3) the coil There is a means to increase the current flowing through (the coil wire diameter increases), but in the case of (1) there is a limit,
In the cases of (2) and (3), since the driving portion is increased in size, there is a problem that the mass increases and thrust is further required.

Further, in order to achieve servo control at a high frequency, it is not possible to allow higher order resonance of the drive mechanism, so a mechanism with high rigidity is required, which leads to further size increase of the mechanism. become.

For the above reasons, in the conventional optical disk device, there is a mechanical limit to speeding up the data recording / reproducing speed, that is, the speed of the optical disk. Was about 3000 rpm. Although the present applicant has previously proposed an optical head in which the supporting structure for the light source and the light collecting means and the driving mechanism are simplified (see Japanese Patent Application Laid-Open No. 2-310830), there are the following drawbacks. . That is, (a) Focusing control is the same as the conventional one, and therefore no improvement has been made with respect to speeding up. (B) Since only the light source is displaced in the tracking control, the distance (50 ~
The light source must be displaced by about 100 μm).

It is very difficult to accurately move the light source in only one axis direction (tracking direction) in such a long distance range, and inevitably displacement occurs in another direction or the light source tilts. There is a problem that defocus and other aberrations occur in the light spot.

An object of the present invention is to provide an optical information recording / reproducing apparatus having a servo mechanism capable of high speed rotation.

Another object of the present invention is to provide an optical information recording / reproducing apparatus in which the displacement amount of the light source is reduced and the above-mentioned drawback (b) is solved.

[0016]

In order to achieve the above object, according to the invention of claim 1, in an apparatus for irradiating an optical recording medium with a light beam to record and reproduce information, a light source and a light source Means for condensing the emitted light beam as a minute light spot on the optical recording medium, and means for detecting the relative distance between the focal point of the condensing means and the optical recording medium by the reflected light from the optical recording medium. A first focus control means for driving the light focusing means according to the output of the detection means to control the focus of the light spot on the optical recording medium; and a light source for the light source according to the output of the detection means. Drive,
A second focus control means for controlling the focus of the light spot on the optical recording medium is provided.

According to a second aspect of the present invention, there is provided a first switch means provided in a first control loop including the first focus control means, and a second control means including the second focus control means. A second switch means provided in the loop, and when the focus control of the light spot is performed, the first switch means is closed and the first control loop is activated, and then the first switch loop is activated. It is characterized in that the second switch loop is activated by closing the second switch means.

According to the third aspect of the present invention, the optical recording medium having a guide groove provided in advance for recording / reproducing information is focused and irradiated with a light beam as a minute light spot, and along the guide groove. In a device for recording and reproducing information, a light source, a means for detecting a relative positional deviation between the light spot and the guide groove by reflected light from the optical recording medium, and driven according to the output of the detecting means, First spot position control means for moving the position of the light spot on the optical recording medium in a direction substantially orthogonal to the guide groove, and controlling the light spot to follow the guide groove. Driving the light source in accordance with the output of the detecting means to move the position of the light spot on the optical recording medium in a direction substantially orthogonal to the guide groove, so that the light spot is guided to the guide groove. Second controlled to follow by
And spot position control means.

According to a fourth aspect of the present invention, there is provided a first switch means provided in a first control loop including the first spot position control means, and a second switch means provided with the second spot position control means. And a second switch means provided in the control loop, and when the follow-up control of the light spot with respect to the guide groove is performed, the first switch means is closed and the first control loop is in an active state. After that, the second switch means is closed to activate the second control loop.

[0020]

In order to correct the residual focus control error, the light source driving element is driven to move the semiconductor laser in the optical axis direction of the emitted light, and in order to correct the residual tracking control error, the light source driving element is By driving, the semiconductor laser is moved in the direction orthogonal to the optical axis to perform precise servo.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to the drawings. FIG. 1 shows the configuration of an embodiment of the present invention.
In FIG. 1, the same components as those in the conventional example of FIG. In this embodiment, in addition to the configuration of FIG.
21 are provided, and light source drive element drive circuits 23 and 25 for controlling the light source drive elements 20 and 21, phase compensation filters 22 and 24, and switches 30 to 33 are provided.

At the time of focusing, first, the switch 31 is turned on and the switch 30 is turned off. Focus error signal (FE) detected by the focus error signal detection circuit 11
Is sent to the focus actuator 3 through the switch 31, the phase compensation filter (low-pass filter) 12 and the current amplifier 13, and performs focusing control in the same manner as described above.

Focusing control by the focus actuator 3 is limited at high speeds as described above,
In other words, since a control error remains, it can be called coarse servo. Therefore, the output of the focus error signal detection circuit 11 shows a signal corresponding to the residual focus control error that could not be controlled by the coarse servo.

Thereafter, the switch 30 is turned on while the switch 31 is on. The focus error signal (FE) passes through the switch 30 and the phase compensation filter (high-pass filter) 22, and passes through the light source drive element drive circuit 2
Sent to 3. The light source drive element 20 is driven by the output of the light source drive element drive circuit 23, and
Is moved in the optical axis direction of the emitted light, and the focus position of the laser light by the objective lens 2 is changed.

As described above, the focusing control by the light source driving element 20 has a small focal point movement distance (control dynamic range), but works to correct the remaining control error due to the rough servo and performs the fine servo. Since the residual focus control error is about 1 μm at most, the movable range of the light source driving element 20 may be within that range. The light source driving element 20 is, for example, an electrostrictive element (Japanese Patent Publication No. 62-62-
No. 38771) can be used.

At the time of tracking, first, the switch 33
Is turned on and the switch 32 is turned off. Track error signal (TE) detected by the track error signal detection circuit 14
Is sent to the tracking actuator 4 through the switch 33, the phase compensation filter (low-pass filter) 15 and the current amplifier 16, and the lens 2 is moved left and right (radial direction) in the same manner as described above to perform tracking (coarse servo). )I do.

In order to correct the residual tracking control error, the switch 32 is turned on while the switch 33 is kept on. The signal (TF) passes through the switch 32 and the phase compensation filter (high pass filter) 24 and is input to the light source drive element drive circuit 25. Light source drive element drive circuit 25
The light source driving element 21 is driven by the output of the above, and the semiconductor laser (LD) 8 is moved in the direction orthogonal to the optical axis to perform precise servo. The tracking control described above may use a deflection mirror or the like in addition to the objective lens.

[0028]

As described above, according to the first aspect of the invention, the focus is controlled by moving the lightest semiconductor laser chip among the components constituting the optical pickup. The band can be increased and it is possible to follow a high speed disc. As a result, it is possible to realize an optical information recording / reproducing device in which the data recording / reproducing speed is increased. Further, the conventional focus control by the objective lens is the coarse servo, and the focus control performed by moving the semiconductor laser chip is the fine servo, and the fine servo is configured to work to correct the control error remaining by the coarse servo. Therefore, the movable range of the semiconductor laser chip can be made small, the accuracy is high, and the device can be downsized.

According to the second and fourth aspects of the invention, since the coarse servo is activated and then the fine servo is activated, both servos can be operated stably. As a result, it is possible to prevent the servo from being disengaged immediately due to the small movable range as in the fine servo.

According to the invention described in claim 3, since the lightest semiconductor laser chip among the components constituting the optical pickup is moved to perform the tracking control, the control band can be increased and the high speed can be achieved. It is possible to follow a rotating disk. As a result, it is possible to realize an optical information recording / reproducing device in which the data recording / reproducing speed is increased. Further, the conventional tracking control by the objective lens is a coarse servo, and the focus control performed by moving the semiconductor laser chip is a fine servo, and the fine servo is configured to work to correct the control error remaining by the coarse servo. Therefore, the movable range of the semiconductor laser chip can be made small, the accuracy is high, and the device can be downsized.

[Brief description of drawings]

FIG. 1 shows the configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a conventional example.

[Explanation of symbols]

 1 Optical Disc 2 Objective Lens 3 Focus Actuator 4 Tracking Actuator 5 Prism 6 Beam Splitter 7 Coupling Lens 8 Semiconductor Laser 9 Semiconductor Laser Drive Circuit 10 Photodetector 11 Focus Error Signal Detection Circuit 12, 15, 22, 24 Phase Compensation Filter 13, 16 Current amplifier 14 Track error detection circuit 20, 21 Light source drive element 23, 25 Light source drive element drive circuit 30, 31, 32, 33 Switch

Claims (4)

[Claims] 1. A light source in an apparatus for irradiating an optical recording medium with a light beam to record and reproduce information, and means for condensing the light beam emitted from the light source as a minute light spot on the optical recording medium. Means for detecting the relative distance between the focal point of the condensing means and the optical recording medium by the reflected light from the optical recording medium, and driving the condensing means according to the output of the detecting means to perform the optical recording. First focus control means for controlling the focus of the light spot on the medium, and second focus control means for driving the light source according to the output of the detecting means to control the focus of the light spot on the optical recording medium. An optical information recording / reproducing apparatus comprising: focus control means. 2. A first switch means provided in a first control loop including the first focus control means, and a second control loop provided in the second focus control means. A second switch means, and when performing the focus control of the light spot, the first switch means is closed to activate the first control loop, and then the second switch means is closed. 2. The optical information recording / reproducing apparatus according to claim 1, wherein the second control loop is activated. 3. An optical recording medium having a guide groove provided in advance for recording / reproducing information is focused and irradiated with a light beam as a minute light spot, and information recording / reproducing is performed along the guide groove. In the apparatus, a light source, a means for detecting relative positional deviation between the light spot and the guide groove by reflected light from the optical recording medium, and driven according to the output of the detecting means, on the optical recording medium. Moving the position of the light spot in a direction substantially orthogonal to the guide groove,
First spot position control means for controlling the light spot so as to follow the guide groove, and driving the light source according to the output of the detection means to position the light spot on the optical recording medium. And a second spot position control means for controlling the light spot to follow the guide groove so that the light spot moves in a direction substantially orthogonal to the guide groove. Playback device. 4. A first switch means provided in a first control loop including the first spot position control means and a second control loop provided in the second spot position control means. And a second switch means which is provided, and when the follow-up control of the light spot with respect to the guide groove is performed, the first switch means is closed to activate the first control loop, and then the first switch loop is activated. The optical information recording / reproducing apparatus according to claim 3, wherein the second switch means is closed to bring the second control loop into an active state.