JPH04291030A - Optical disk device - Google Patents

Abstract

PURPOSE:To enable the high speed rotation of a disk and to improve a transfer rate by correcting a light spot position on the disk while sharing frequency bands between first and second light spot position driving device. CONSTITUTION:First actuators 14 and 15 correcting and driving an objective lens 6 take care of a comparatively low frequency area; while first and second piezo-electric elements 40 and 42 correcting and driving a semiconductor laser 1 take care of a comparatively high frequency area. Thus, the high speed rotation of a disk 7 can be coped with without much improving the driving force at high frequency of the actuator 14 and without much raising the resonance frequency of a machine, and accordingly the transfer rate can be drastically improved. Furthermore, the improvement of performance can be realized while reducing the size, simplifying the construction and reducing power consumption.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an apparatus for optically recording and reproducing information, and more specifically, it is a device for optically recording and reproducing information, and more specifically, it is capable of highly accurate correction control of track deviation and defocus of a light spot focused on an information recording surface. The present invention relates to an optical disc device configured as described above.

0002

2. Description of the Related Art FIG. 4 is a schematic diagram showing an example of a conventional write-once optical disc device. In the figure, 1 is a semiconductor laser serving as a light source, which emits a light beam 16. 2 is a collimator lens, 3 is a shaping prism, 4 is a beam splitter (hereinafter referred to as PBS), 5 is a λ/4 wavelength plate, and 6 is an objective lens. A light spot 17 is formed. 8
9 is a condensing lens, and 9 is a half prism, which separates the light beam into transmitted light 16a and reflected light 16b. 10 is a knife edge, 11 and 12 are two-split photodetectors, 14 is a focus correction actuator, and 15 is a track correction actuator.

Next, the operation of the write-once optical disc device configured as described above will be explained. That is, the light beam 16 emitted from the semiconductor laser 1 passes through the shaping prism 3, the PBS 4, and the λ/4 wavelength plate 5, and forms a focused light spot 17 on the information recording surface of the disk 7 by the objective lens 6. The light beam reflected by the disk 7 travels backwards and is reflected by the PBS 4, passes through the condenser lens 8, and is separated by the half prism 9 into transmitted light 16a and reflected light 16b. The transmitted light 16a is received by the two-split photodetector 12, and from the differential output B thereof, the track deviation of the condensed light spot 17 with respect to the information recording track (not shown) is detected. Further, after half of the light beam of the reflected light 16b is blocked by the knife edge 10, it is received by the two-split photodetector 11, and the focal shift of the condensed light spot 17 with respect to the information recording surface is detected from the differential output A. Furthermore, all received optical power C is detected as an information signal.

On the other hand, since the disk 7 is rotated at high speed (for example, 1800 rpm) by the disk motor 13, the focused light spot 17 may be out of track with respect to the information recording track on the disk 7 due to image blur or eccentricity. This causes a focus shift with respect to the information recording surface. For this reason,
The above-mentioned defocus detection signal A and track deviation detection signal B are added to respective control circuits (not shown), and the objective lens 6
The actuators 14 and 15, which are driven two-dimensionally as shown by arrows E and D, are drive-controlled.

[0005] The two-dimensional drive actuator 14, 1
5 is configured as shown in FIGS. 5 and 6, and FIG.
6 is a plan view showing details of the two-dimensional drive actuators 14 and 15, and FIG. 6 is a sectional view thereof. In the same figure,
A fixed shaft 20 whose surface is coated with Teflon resin is erected on a fixed base 32. 21 is an aluminum bearing, and 22 is a movable holder, which holds the objective lens 6 at an eccentric position. 23 is a balancer, and 24 is a rubber damper, which defines the center of operation of the movable holder 22. 25
is a support shaft that supports the rubber damper 24 on the fixed base 32. 26 is a focus correction actuator magnet, 27 is magnet 2
6 constitutes a magnetic circuit; 28 is a focus control coil arranged in this magnetic circuit; 29a, 29b;
are track correction actuator magnets, 30a, 30b
is a track correction coil, and 31a and 31b are the magnets 29.
A and 29b constitute a yoke that constitutes a magnetic circuit.

In the above structure, the fixed shaft 20 provided on the fixed base 32 and the bearing 21 provided on the movable holder 22 are supported so as to be able to slide and rotate with low friction between Teflon resin and aluminum. The movable holder 22 holds the objective lens 6 at a position eccentric from the axis.
The focus control coil 28 provided in the magnet 26 and the yoke 2
7, and by supplying a desired current to this magnetic circuit, focus correction is performed in the direction of arrow D. Similarly, track correction coils 30a and 30b provided on the movable holder 22 are arranged in a magnetic circuit composed of magnets 29a and 29b and yokes 31a and 31b, and by applying a desired current to these, Arrow E
Perform track correction in the direction. Here, balancer 23
The rubber damper 24 serves to stabilize the movement as described above, and the rubber damper 24 functions to define the center of movement of the movable holder 22.

The focus control system block of such an optical disc device has a configuration as shown in FIG. In the same figure,
The components are a detection system G1, an amplifier circuit G2, a phase compensation circuit G3, and an actuator G4.
b is the control error, and c is the movement of the actuator. The track control system also has a similar configuration. That is, while moving the objective lens 6 in the optical axis direction to correct the focal shift,
This is to correct track deviation by moving in a direction perpendicular to the track.

[0008]

[Problems to be Solved by the Invention] Conventional optical disc devices are configured as described above, so correction operations are performed by moving only the objective lens, and the disc is rotated at high speed in order to improve the transfer rate. Therefore, the objective lens must be moved at high speed. For example, the acceleration increases approximately by the square of the number of rotations of the disk, so 1800
About 4 times the actuator driving force is required at 3600 rpm compared to the rotation at 3600 rpm. Furthermore, as the number of rotations increases, the control band is expanded, and the mechanical resonance frequency generated in the actuator also needs to be significantly increased as the number of rotations increases. This is contrary to the viewpoints of miniaturization, reduction of power consumption, and relaxation of design constraints, and has been a major problem in designing high-performance optical disk devices.

[0009] This invention was made in order to solve the above-mentioned problems, and it is possible to realize miniaturization, power consumption, and design freedom, and also to enable high-speed rotation of the disk and significantly increase the transfer rate. An object of the present invention is to provide an optical disc device that can be improved.

0010

[Means for Solving the Problems] An optical disc device according to the present invention provides an optical disk device that shares a relatively low frequency portion for correcting and driving a light beam from a light source in at least one direction of the optical axis or a direction perpendicular to the track. 1 optical spot position driving device, and a 2nd optical spot position driving device that handles relatively high frequency parts.
A light spot position driving device is provided, and the light spot position on the disk is corrected by the first and second light spot position driving devices.

[0011]

[Operation] According to the present invention, since the first and second light spot position driving devices share the frequency band and perform drive correction, each can be designed optimally, and the first light spot position driving device is freed from constraints such as improved driving force and improved mechanical resonance due to high-speed rotation, and it becomes easy to improve the control band with the second optical position driving device.

Furthermore, by sharing the frequency band between the two position driving devices, it is possible to achieve high performance while achieving miniaturization, simplification, and low power consumption.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an optical disk device according to an embodiment of the present invention. In the figure, the same or corresponding parts as in the conventional example shown in FIG. Omitted.

In FIG. 1, 40 is a first piezoelectric element for focus correction that drives the semiconductor laser 1 in the optical axis direction indicated by arrow F, 41 is a movable holding plate, and 42 is a track for semiconductor laser 1 indicated by arrow G. A second piezoelectric element for track correction is driven in a direction perpendicular to the first piezoelectric element 40, and together with the first piezoelectric element 40, constitutes a second light spot position driving device. Also,
The two-dimensional actuator (first optical spot position driving device) that drives the objective lens 6 is not shown here, but
This is the same as the conventional configuration shown in FIGS. 5 and 6.

FIG. 2 is a block diagram of the focus control system of the above embodiment, in which G5 is a defocus detection system and G6 is a defocus detection system.
is an amplification/compensation circuit, G7 is a piezoelectric element 40 that drives the semiconductor laser 1, G8 is a frequency coupling compensation circuit, and G9 is an actuator 14 that drives the objective lens 6 in the optical axis direction. Here, d is the surface vibration of the disk 7, e is the control error, and f
is the movement of the objective lens 6, and g is the movement of the condensed light spot.

[0016] Then, the first
The actuators 14, 15 and the first and second piezoelectric elements 40, 42 that correct and drive the semiconductor laser 1 are operated for several hundred hours.
z, and the first actuators 14 and 15 mainly share corrections below this combined frequency. That is, as the frequency becomes lower, the share ratio of the first actuators 14 and 15 increases. The first and second piezoelectric elements 40, 42 mainly share corrections for frequencies above that frequency, that is, as the frequency becomes higher, the second position driving device consisting of the first and second piezoelectric elements 40, 42 makes corrections. The ratio will increase. Although the focus control system has been described here, the tracking control system also has a similar configuration.

Next, the operation of the above configuration will be explained. The actuator 14 that drives the objective lens 6 handles a relatively low frequency range (up to several hundred Hz), and the piezoelectric element 40 that drives the semiconductor laser 1 handles a relatively high frequency range (several hundred Hz or more). Therefore, without significantly improving the high-range driving force of the actuator 14,
And, even without increasing the mechanical resonance frequency too high,
It is possible to correspond to the high speed rotation of the disk 7, and the transfer rate can be significantly improved. Furthermore, in the focus control system, the movement of the semiconductor laser 1 in the high frequency range only needs to be corrected by a minute amount of about 1 μm, and in the tracking control system, it is only necessary to correct a minute amount of about 0.1 μm, which does not affect the optical system and causes mechanical resonance. can be easily achieved.

In the above embodiment, the entire semiconductor laser 1 is configured to be driven for correction, but in order to further reduce the size and improve efficiency, the semiconductor laser 1 is configured in the package as shown in FIG. You may.

In FIG. 3, 50 is a semiconductor laser package, 51 is a semiconductor laser element, 52 is a silicon mount, 53 is a heat sink, and 54 is a first drive unit that drives the semiconductor laser element 51 in the direction of arrow F through the heat sink 53. A piezoelectric element 55 is a support plate that holds one end of the piezoelectric element 54, and 56 is a second piezoelectric element that drives the semiconductor laser element 51 in the direction of arrow G via the support plate 55.

Although the detailed wiring of the semiconductor laser element 51 is omitted, according to the configuration shown in FIG. 3, the weight of the movable part to be driven can be significantly reduced, and further miniaturization and simplification can be achieved. .

[0021]

As described above, according to the present invention, the first driving device and the second driving device for correcting and driving the position of the light beam are combined, and a relatively low frequency region below the combined frequency is controlled. Since the first driving device is configured to share the responsibility and the second driving device is responsible for the relatively high frequency region higher than that frequency to correct the defocus and track deviation of the light spot, the first driving device It is possible to significantly expand the control band without increasing the frequency of the mechanical resonance of the beam position drive device, making it possible to support high-speed rotation of the disk, and easily realizing an improvement in the transfer rate of the entire device. can. Also, since the relatively high frequency drives the light source,
This has the effect of increasing the driving force in the high frequency region and enabling highly accurate correction control while realizing miniaturization of the device.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an optical disc device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a control system of an optical disc device according to the present invention.

FIG. 3 is a perspective view of a semiconductor laser driver according to another embodiment of the invention.

FIG. 4 is a schematic configuration diagram showing a conventional optical disc device.

FIG. 5 is a plan view of an objective lens driving device in a conventional apparatus.

FIG. 6 is a longitudinal cross-sectional view of FIG. 5;

FIG. 7 is a block diagram of a control system of a conventional optical disc device.

[Explanation of symbols]

1 Semiconductor laser (light source) 6 Objective lens 7 Disk 14 Focus correction actuator (first optical spot position driving device) 15 Track correction actuator (first optical spot position driving device) 16 Light beam 17 Focusing spot 40, 42 Piezoelectric element (second light spot position driving device)

Claims (2)

[Claims] Claim 1: A light beam emitted from a light source is irradiated onto the information recording surface of the disk, and a defocus of the light spot with respect to the information recording surface is detected, and a track deviation of the light spot with respect to the information track on the disk is detected. In an optical disk device configured to optically record and reproduce information while making a light spot follow an information track, the light beam from the light source is corrected in at least one direction, either the optical axis direction or a direction perpendicular to the track. The first light spot position drive device is provided with a first and second light spot position drive device for driving, the first light spot position drive device performs position correction at a relatively low frequency, and the second light spot position drive device performs position correction. 1. An optical disc device characterized in that the correction is performed so that a relatively high frequency portion is shared. 2. A first light spot for correcting and driving an objective lens for focusing the light beam from the light source onto the information recording surface of the disk in at least one direction of the optical axis or a direction perpendicular to the track. 2. The optical disc device according to claim 1, further comprising a position driving device and a second light spot position driving device for correcting and driving the light source in at least one direction of the optical axis or a direction perpendicular to the track.