JPH01263951A - Optical pickup device - Google Patents

Abstract

PURPOSE:To correctly record and reproduce information by being equipped with a 2-divided photodetector to detect the relative angle dislocation between an objective lens and a disk, and eliminating the relative angle dislocation between the disk with the rotation-direction of the objective lens. CONSTITUTION:The two-dividing line of photodetectors 21a and 21b is arranged in a direction to correspond to a data train direction (y) recorded on a disk 5 or generated from the disk, reflected light from the disk 5 is positioned approximately at the center of the two-dividing line, and the differential output of outputs Ia and Ib from the 2-divided photodetectors 21a and 21b is detected as the tilt error of the disk 5 and the objective lens 4. When the light axis of the objective lens 4 tilts toward the disk 5, the tilt is detected as the output difference from the 2-divided photodetectors 21a, and 21b, and the objective lens 4 is rotation-driven so that the difference may be at 0. Thus, the light axis of the objective lens 4 can be held at right angles with respect to the disk 5, and the information is correctly recorded and reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in an optical pickup device used in an optical recording/reproducing device or the like.

[Prior Art] Fig. 5 is a configuration diagram of an optical pickup, where 1 is a light source, 2 is a light beam, 3 is a half mirror, 14 is an objective lens, 5 is an optical disk, 6 is a photodetector, 7 is an electric signal, 8 is a signal processing device.

In the figure, the light 2 output from the light source 1 is the half mirror 3.
The light is reflected by the objective lens 4 and focused on the information recording surface of the disk 5. The light that has obtained information on the disk 5 is reflected by the information recording surface of the disk, passes through the half mirror 3, and enters the photodetector 6. The light 2 incident on the photodetector 6 is converted into an electrical signal 7 by the photodetector 6, and then converted into audio and images in a signal processing device.

In order to correctly reproduce information in the above-mentioned apparatus, it is necessary to support the optical axis of the objective lens 4 perpendicularly to the surface of the disk 5 and to make the objective lens 4 follow the surface wobbling and eccentricity of the disk 5. That is, it is necessary to correct a focus error by moving the objective lens 4 up and down, and to correct a tracking error by moving it horizontally.

For this reason, for example, in Japanese Patent Application Laid-open No. 62-287441,
A movable part that holds an objective lens is engaged with a fixed member via four mutually parallel linear elastic support members, and the lens holder, that is, the objective lens is displaced in the focusing direction and the tracking direction by an electromagnetic drive means. An objective lens driving device is disclosed.

FIG. 6 is a perspective view of the objective lens driving device, in which 4 is the objective lens, 9 is the optical axis, 10 is the movable part, 11 is the elastic support member, 12 is the fixed member, 13 is the focus coil, 14
15 is a tracking coil, 15 is a permanent magnet for focusing and tracking, and 16 is a fixed base.

In the figure, a movable part 10 holding an objective lens 4 is supported by a fixed member 12 by four linear elastic support members 11 so as to be movable vertically and horizontally. Such a linear elastic support member 11 is made of, for example, a metal wire, but in order to reduce the influence of resonance of the metal wire, the metal wire 11a is passed through a rubber tube llb as shown in FIG. I am trying to make it work as. Furthermore, a damper member 11C made of rubber is integrally fixed around the metal wire 11a of the elastic support member 11, and furthermore, the damper member 1
Since 1c is fixed to the fixing member 12 via an adhesive, the vibration energy of the metal wire 11a is transmitted to and absorbed by the damper member.

FIG. 8 is a configuration diagram of a focusing error and tracking error correcting device of the objective lens driving device. Error detection is performed using a photodetector 6. In the figure, 20a to 20d are four-divided light-receiving surfaces for focus error detection, 20e and 2Of are light-receiving surfaces for tracking error detection, 21.22 is an arithmetic unit, and 23.24 is a power amplifier. 13 is the focus coil, and 14 is a tracking coil. The light receiving surfaces 20a to 20d are determined by the computing unit 21.
d - (I a + I c) - (I b + 1 d) - is calculated from the output currents Ia to Id of is controlled to displace the movable part 10 up and down. The tracking error is also corrected by controlling the current of the tracking coil 14 and horizontally displacing the movable part 10 so that the difference in the current IesIf becomes zero. In this way, the optical pickup operates while constantly correcting errors.

[Problem to be solved by the invention]

By the way, in the objective lens driving device described above, the linear elastic support member 11 has a damper member for absorbing the vibration energy of the metal wire, but basically the movable part is formed by a plurality of linear elastic support members 11. It has a cantilever flexible structure that supports it. In such a structure, in addition to the z-axis in the optical axis direction and the y-axis in the direction perpendicular to the optical axis, the respective resonance frequencies fy and fZ are - the bending spring stiffness of the metal wires, 1 the movable mass M, and the movable mass around the X-axis. When the moment of inertia of the movable part is IX, the dimension between the four metal wires is 11, and Ij, it is expressed by the following formula.

In addition, y I[[I The degree of freedom in the z-axis is functionally necessary to displace the objective lens in the tracking direction and the focusing direction, but the degree of freedom in the direction around the X-axis is the objective lens light. This means that the axis is no longer perpendicular to the disc, which is harmful to recording and reproducing information correctly.

Conventional objective lens drive devices attempt to absorb vibration energy in a damper member, but the damping effect is insufficient for such low-order fundamental vibration modes.
The damping effect is insufficient for a low-order fundamental vibration mode such as around the X-axis of the objective lens, and the displacement of the objective lens around the X-axis cannot be corrected. These points were problems with this device.

The present invention has been made to solve the above-mentioned problems of conventional devices, and is intended to provide a device that detects displacement around the X-axis in order to correct the displacement around the X-axis.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an objective lens support in which a movable part that holds an objective lens is engaged with a fixed member via a plurality of linear elastic indicating members. a mechanism, an electromagnetic drive means for driving the movable part in the focusing direction and a tracking direction, an electromagnetic drive means for rotating the movable part in a direction perpendicular to the two directions, and an objective lens or the like for transmitting light from a light source. In an optical pickup device, the optical pickup device includes an optical system that allows light to enter a disc through a light detector and to make light from the disc enter a two-split photodetector through an objective lens or the like. The dividing line is placed in a direction that matches the direction of the data string recorded on or reproduced from the disc, and the reflected light from the disc is positioned approximately at the center of the dividing line, so that the output from the two-split photodetector is The configuration is such that the differential output can be detected as a tilt error between the disk and the objective lens.

[Function] Since the present invention is configured as described above, if the optical axis of the objective lens is tilted with respect to the disk, the tilt is detected as the difference in the output from the two-split photodetector, and the difference is detected. If the objective lens is driven to rotate so as to make it zero, the optical axis of the objective lens can always be held perpendicular to the disk.゛As a result, information can always be recorded and played back correctly.

[Embodiment of the Invention] FIG. 1 is a block diagram of an optical pickup showing an embodiment of the present invention, and FIG. 2 is a diagram illustrating its principle.

In the figure, 1 to 12 are the same or equivalent parts as the conventional device, 21a
, 21b is a photodetector divided into two parts, 31 is an arithmetic unit that differentially calculates the output from the photodetector, 33 is a coil for rotationally driving the objective lens, and 34 is the light emitted from the light source that is connected to the objective lens. 35 is the intensity distribution of the light when it enters the objective lens again after being reflected by the tilted disk.

As shown in FIG. 2, the intensity distribution of the light emitted from the light source 1 has a two-dimensional normal distribution 34 when the light source is a semiconductor laser. Therefore, as shown in the figure, when the light is reflected by the half mirror 3 and enters the objective lens 4, the light intensity is strongest at the center of the lens, and becomes weaker at the periphery of the lens. The light that has passed through the objective lens 4 is focused on the disk 5, but if the objective lens 4 is tilted, for example, when it is reflected by the disk 5, it is tilted 2θy with respect to the optical axis and enters the objective lens again, and is further detected by light. Head to the vessel. At this time, the intensity distribution of the reflected light that enters the objective lens again is a distribution 35 that deviates from the normal distribution, as shown by the dotted line in the figure. The photodetector is composed of two light-receiving elements, and is located a little farther from the image point on the optical axis. Therefore, the high-intensity light beam directed toward the photodetector will be deviated from the optical axis and will be incident on the left-side detector 21a. Nearby light with high light intensity similarly gathers on the left detector, and as a result, the left detector output 1a becomes larger than the right detector output 1b. Note that when the objective lens 4 is not tilted, the left and right outputs are almost the same, and when it is tilted, Ib becomes larger than Ia.

To summarize the above, when θy is negative, 1a>Ib θy-o, I a -1b - (3) θy
When is positive, I'a < Ib, and the direction and magnitude of the relative angle between the objective lens 4 and the disk 5 can be determined by observing Ia and Ib.

Utilizing this principle, as shown in Figure 1, in an objective lens drive mechanism supported by a linear elastic body, the direction of the linear elastic body is aligned with the y-axis direction of the data column direction, and the beam is divided into two parts. If the dividing line of the detector is arranged so that it coincides with the y-axis direction, the angle between the disk and the objective lens caused by the low-order torsional degree of freedom that the objective lens drive mechanism supported by the linear elastic body basically has. The deviation can be eliminated by amplifying the differential output of the outputs 1a and Ib of the two-split photodetector and rotating the objective lens in a direction that eliminates the angular deviation.

The specific electromagnetic driving means for rotationally driving the objective lens is as follows:
As shown in FIG. 3, for example, the coil 33 is placed at a position away from the center of gravity 40 of the movable part, and the magnet 41 is placed on the fixed base 16 so that a rotation couple 42 is generated for the center of gravity of the movable part. Bye. By passing a current as an amplified differential output through the coil 33, a Lorentz force 43 is generated, and as a result, it becomes possible to eliminate the relative angular deviation between the objective lens and the disk.

Further, as shown in FIG. 4, the shape of the photodetector is not limited to 2-division, but may be 4-division 508 to 50d, and by using the 4-division photodetector for focus error detection, differential output can be obtained. The calculation may be performed to obtain (Ia+I d)-(Ib+I c).

[Effects of the Invention] The present invention provides an optical pickup having a mechanism for supporting a movable part that holds an objective lens by a linear elastic support member.
Equipped with a split photodetector, the objective lens is rotationally driven to eliminate relative angular misalignment with the disk, so the optical axis of the objective lens can always be held at right angles to the disk, making it possible to transmit information. It is now possible to record and play back correctly at all times.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an optical pickup device showing an embodiment of the present invention, Fig. 2 is an explanatory diagram showing the principle of detecting the inclination of a disk, and Fig. 3 is a principle of an electromagnetic drive means for rotationally driving an objective lens. 4 is a configuration diagram of a photodetector showing another embodiment, FIG. 5 is a configuration diagram of a conventional tip pickup device, FIG. 6 is a perspective view of an objective lens drive device, and FIG. 7 is a configuration diagram of a photodetector showing another embodiment. FIG. 8, which is a sectional view of the elastic support member, is a configuration diagram of the focusing error and tracking error correcting mechanism. In the figure, 4 is an objective lens, 5 is an optical disk, 5a is its data string, 10 is a movable part, 11 is a linear elastic support member, 12 is a fixed member, 21a and 21b are two-split photodetectors, and 31 is a differential calculation 32 is a power amplifier, and 33 is a rotation drive coil. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Patent Attorney Souji Sasaki Figure 1 Figure 2 Figure 3 Figure 4 Figure 0c Figure 5 Figure 6 fJ7 Figure

Claims (1)

[Scope of Claims] An optical pickup device includes an objective lens support mechanism in which a movable part that holds an objective lens is engaged with a fixed member via a plurality of linear elastic support members, and the movable part is moved in a focusing direction. and a tracking direction; an electromagnetic drive means for rotationally moving around a direction perpendicular to the two directions; and an electromagnetic drive means for causing light from a light source to enter the disk through an objective lens or the like; It consists of an optical system that makes the reflected light from the disk enter a two-split photodetector through an objective lens, etc., and the two-split line of the photodetector is recorded on the disk or reproduced from the disk. The reflected light from the disk is positioned approximately in the center of the two-split line, and the differential output from the two-split photodetector is calculated from the tilt error between the disk and the objective lens. An optical pickup device characterized in that it is configured to be able to detect as follows.