JP2699412B2 - Optical head tilt device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention controls an optical axis of an optical head of an optical disk reproducing apparatus such as an LV (laser vision disk) and a CD (compact disk) perpendicularly to a disk surface. In the tilt device, servo control of tilt means is performed so as to keep the distance between the optical disk and the optical pickup constant.

[Conventional technology]

An optical disk reproducing apparatus uses an optical head having an optical pickup for reading a signal recorded on the disk surface of the optical disk. Usually, the optical axis of the optical pickup is moved while moving the optical pickup in the radial direction of the optical disk. Regardless of the movement in the direction, the recorded signal is always read perpendicular to the disk surface.

However, in an actual optical disk, the optical disk may be bent from the beginning due to the action of heat or gravity, or the outer peripheral portion may be bent downward due to its own weight in a state where the optical disk is loaded in an optical disk reproducing device. When the diameter of the optical disk is large, the amount of deflection also increases, and the optical axis of the optical pickup often does not become perpendicular to the disk surface.

Conventionally, tilt control for controlling the angle of the optical pickup with respect to the inclination of the optical axis of the optical pickup so that the optical axis is always perpendicular to the disk surface has been performed.

As a specific mechanism for performing the tilt control, for example, as shown in FIG. 7, a rotating shaft parallel to the optical disc D and orthogonal to the optical disc radial direction is mounted on a base frame 2 on which a disc drive motor 1 for rotating the optical disc D is mounted. The sub-frame 4 is mounted on the rotating shaft 3 so as to be rotatable.

Then, both ends of a feed feed shaft 6 for sliding the optical pickup 5 in the radial direction of the optical disc are fixed to the sub-frame 4, and a tilt feed (not shown) screwed into the outer peripheral end of the optical disc D of the sub-frame 4. A mechanism is used in which the sub-frame 4 is rotated around the rotation shaft 3 by rotating with a screw and a tilt drive motor and changing the distance between the base frame 2 and the sub-frame 4.

Further, as a tilt servo means for controlling the tilt mechanism, a tilt angle sensor 7 is mounted adjacent to the optical pickup 5, and a tilt drive motor is controlled by a detection signal from the tilt angle sensor 7 to control the tilt of the optical pickup 5. Servo is performed so that the optical axis is at a constant angle.

As another mechanism for performing tilt control, there is a mechanism that employs a tilt mechanism as shown in FIG.

This tilt mechanism fixes both ends of a feed feed shaft 6 arranged in the radial direction of the optical disk in parallel with the optical disk D on a base frame 2 on which a disk drive motor 1 for rotating the optical disk D is mounted. A sub-frame (4) reciprocated against the shaft (6) is provided.

The subframe 4 is provided with a shaft 8 that rotates about a rotation shaft 3 that is parallel to the optical disc D and that is orthogonal to the radial direction of the optical disc. The optical pickup 5 is attached to the shaft 8.

Then, a tilt feed screw (not shown) screwed into the end of the shaft 8 on the outer peripheral side of the optical disk D is rotated by a tilt drive motor, and the distance between the sub-frame 4 and the shaft 8 is changed to change the rotation shaft 3 , The angle of the optical pickup 5 is changed for each axis 8.

Further, as the tilt servo means for controlling the tilt mechanism, for example, the same as that shown in FIG. 7 is employed, and a tilt drive motor is provided by a detection signal from a tilt angle sensor 7 mounted adjacent to the optical pickup 5. Is controlled so that the axis 8 is tilted so that the optical pickup 5
Servo is applied so that the optical axis of the lens has a constant angle.

[Problems to be solved by the invention]

However, in either case of the tilt mechanism for tilting the feed feed shaft 6 shown in FIG. 7 or the tilt mechanism for tilting the shaft 8 separately from the feed feed shaft 6 shown in FIG.
Since the servo control of the tilt mechanism is made to keep the angle of the optical axis of the optical pickup 5 constant based on the value detected by the tilt angle sensor 7, if a large warp occurs in the optical disc D, the optical pickup 5 is moved in the radial direction. Although the optical axis can be made perpendicular to the optical disk D regardless of the position of the optical disk D, the distance between the optical disk D and the optical pickup 5 at the center side and the outer peripheral side of the optical disk D greatly changes to L1 and L2.

Therefore, there is a problem that the light beam cannot be focused on the disk surface unless the focus stroke of the focus servo system is increased.

The present invention has been made in view of the problems of the prior art, and has a simple structure in which the optical axis of the optical pickup can be perpendicular to the curved optical disk surface even with a small focus stroke. It is intended to provide a device.

[Means for solving the problem]

The optical head tilt device of the present invention that solves the above-mentioned problems is characterized in that an optical pickup that is reciprocated in a radial direction facing an optical disk is perpendicular and constant to the optical disk by servo control in accordance with the bending of the optical disk. A tilt device for an optical head that maintains a distance, wherein a feed feed shaft that guides reciprocation of the optical pickup is formed so as to be flexibly deformable, and one end of the feed feed shaft is fixed to a center end of the optical disc. On the other hand, at the other end of the feed feed shaft, a tilt means for bending the feed feed shaft in accordance with the bending of the optical disc is provided at an outer peripheral end of the optical disc, and the distance between the optical pickup and the optical disc is reduced. Detecting means for detecting a distance between the optical disk and the optical pickup based on a value detected by the detecting means; Is characterized in that said providing the servo means for controlling the tilting means as.

(Operation)

According to the tilt device of the optical head of the present invention, the feed feed shaft on which the optical pickup is reciprocated is fixedly supported at the end on the center side of the optical disk, and is bent by the tilt mechanism provided at the other end which is a free end. In the same way as the optical disk, the feed feed axis is curved, and the distance between the optical pickup and the optical disk is detected by a detector. Based on this, the tilt servo is applied to keep the distance between the optical pickup and the optical disk constant. Even if the optical disk is curved in an arc, the tilt servo takes part of the operation of the focus servo and the optical axis of the optical pickup is always perpendicular to the optical disk surface with a simple mechanism without increasing the focus stroke. Thus, a highly accurate reproduction signal can be obtained.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

As shown in a front view in FIG. 1 and a plan view in FIG. 2, the tilt device 20 of the optical head is mounted with a mechanical portion of an optical disk reproducing device such as a disk drive motor 21 for rotating the optical disk D. Base frame 22
On the upper side, two feed feed shafts 23 are arranged in parallel on both sides of a virtual line in the radial direction of the optical disk in parallel with the optical disk D.
One end of the base frame 22 is fixedly supported in a cantilever manner by two front and rear brackets 24 formed near the center of the optical disk D of the base frame 22.

An optical pickup 25 for detecting an optical signal is reciprocally mounted on the cantilevered feed feed shaft 23, and the optical axis moves in the radial direction of the optical disc D. .

As a tilt mechanism 26 that tilts the optical pickup 25 by bending the feed feed shaft 23, the feed shaft
23. A tilt arm 2 having an arm 27a whose outer end (free end) of the optical disc D is parallel to the base frame 22.
The tilt arm 27 is vertically guided along a guide plate 28 formed on the base frame 22.

A female screw is formed at the center of the arm portion 27a of the tilt arm 27, and a tilt feed screw 29 rotatably supported by the base frame 22 is screwed into the tilt drive motor 30.
When the tilt feed screw 29 is rotationally driven by the gear transmission mechanism 31, the two feed feed shafts 23 can be bent with the virtual point slightly outside the bracket 24 as an intersection.

A rack 32 is attached to the side of the optical pickup 25 as a feed mechanism for reciprocating the optical pickup 25 in the radial direction of the optical disk D along the feed feed shaft 23, and a pinion 33 meshing with the rack 32 is provided with a feed motor. It is designed to be driven by 34.

Servo system 40 for controlling such a tilt mechanism 26
Is for keeping the distance between the optical disc D and the optical pickup 25 constant. For example, as shown in FIG. 3, the focus drive DC voltage of the optical pickup 25 is changed to the distance between the optical disc D and the optical pickup 25. Is used as a signal for detecting

This focus drive DC voltage is input to the differential amplifier 43 via the differential amplifier 41 and the low-pass filter 42,
The control voltage is output to the tilt drive motor 30 via the power amplifier 44 so as to be equal to a preset reference voltage.

Then, the tilt feed screw 29 is rotated, and the tilt arm
27 is moved up and down to deflect the feed feed shaft 23 in the same manner as the optical disk D, and at the same time, servo is applied so that the distance between the optical pickup 25 and the optical disk D is always constant.

In the optical head tilt device 20 configured as described above,
If the optical disk D is warped during reproduction, the distance between the optical pickup 25 and the optical disk D changes, and the focus drive DC voltage of the optical pickup 25 also changes. Is output to the tilt drive motor 30 to perform servo control.

By this tilt servo control, the feed feed shaft 23 is bent to warp the optical disc D so as to bend from the vicinity of the bracket 24 on the center side of the optical disc D, and becomes a state approximated by a curve.

At the same time, this servo control allows the optical pickup
As shown in FIG. 4 (b), the distance L between the optical disk D and the optical disk D is equal to the distance L shown in FIG. Irrespective of this, the distance between the optical disc D and the optical pickup 25 is always kept constant.

Therefore, the optical pickup 25 is driven for reproduction along the shape of the optical disc D, and its optical axis is
, And converge on the optical disk D.

Further, since the feed feed shaft 23 is bent in a curved line approximate to the warp of the optical disk D, and the servo is applied so that the distance L between the optical disk D and the optical pickup 25 is constant, the servo for keeping the angle constant is required. The number of focus strokes can be reduced as compared with the case of performing.

Further, in the servo system 40, the distance between the optical disk D and the optical pickup 25 is used as a sensor using the optical pickup 25 itself.
Are not displaced, the accuracy of tilt control is improved, and the manufacturing can be simplified.

Next, a servo system 50 using an optical sensor separately from the optical pickup 25 will be described with reference to FIGS.

The optical sensor 51 used in the servo system 50 is an LE sensor.
It is a combination of D52 and two photosensors 53 and 54, and the light irradiated toward the optical disc D is received by the two photosensors 53 and 54, and the difference in the amount of light received by each photosensor 53 and 54 The distance between the optical pickup 25 and the optical disk D is detected.

That is, as shown in FIG. 6A, when the distance between the optical pickup 25 and the optical disk D is predetermined, the same amount of light is received by the two photosensors 53 and 54, and when the distance is large. In the case of approaching, it can be detected by increasing the amount of light received by one of the photosensors 53 or 54.

In the servo system 50, the detection signals from the two photosensors 53 and 54 are sent to the low-pass filter 56 via the differential amplifier 55, and the detection signals are sent to the tilt drive motor 30 so that the light reception amounts of the two photosensors 53 and 54 are equal. By outputting a voltage via a power amplifier as needed, servo control is performed so that the distance between the optical pickup 25 and the optical disc D is constant, and the angle and distance of the optical pickup 25 are corrected to predetermined values.

Even when such an optical sensor 51 is used, servo control of the tilt mechanism 26 can be performed in the same manner, and the distance of the optical pickup 25 is kept constant, so that the tilt mechanism 25 can be controlled without increasing the focus stroke. And the optical disk D can be reproduced.

In the case of such a tilt mechanism 26 that bends the feed feed shaft 23, the feed feed shaft 23 can be supported near the disk drive motor 21, and can be parallel to the radial direction of the optical disk D during assembly. It is easy to make them coincide with each other, and the alignment adjustment can be made unnecessary.

In addition, since the feed feed shaft 23 is bent, the feed feed shaft 23 is tilted near the fixed support point.
The vertical movement of the disk drive motor 21 is small.
The space nearby can be small, and the degree of freedom for mounting the optical pickup 25 increases.

Further, by adjusting the rigidity of the feed feed shaft 23 and the point of action of the force by the tilt mechanism 26, the bent shape of the feed feed shaft 23 can be changed, and the shape can be made very close to the optical disc D.

In the above embodiment, two feed feed shafts are used to bend. However, one feed feed shaft may be used.
It is also possible to use a plate-shaped feed feed shaft, as long as it can be bent when a force is applied by a tilt drive motor.

〔The invention's effect〕

As described above in detail with the embodiment, according to the tilting device for the optical head of the present invention, the feed feed shaft on which the optical pickup is reciprocated is fixedly supported at the end on the center side of the optical disk, and the free end The feed mechanism is curved in the same manner as the optical disk by bending it with the tilt mechanism provided at the other end, and the distance between the optical pickup and the optical disk is detected by a detector. The servo is applied to keep the distance to the optical disk constant, so that the optical axis of the optical pickup can be perpendicular to the optical disk surface without increasing the focus stroke, even if the optical disk is curved in an arc. The light beam can be focused on.

Therefore, a high-precision reproduction signal without an angle error can be obtained.

Further, in order to measure not the angle of the optical pickup but the distance to the optical disk, various distance detection methods can be employed, such as using not only an optical sensor but also a focus actuator as a sensor.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a tilt device for an optical head according to the present invention. FIG. 2 is a plan view showing an embodiment of a tilt device for an optical head according to the present invention. FIG. 3 and FIG. 4 are a schematic configuration diagram and an operation explanatory diagram showing one embodiment of a servo system of the tilt device of the optical head according to the present invention. 5 and 6 are a schematic configuration diagram and an operation explanatory diagram showing another embodiment of the servo system of the tilt device for the optical head according to the present invention. FIG. 7 and FIG. 8 are schematic explanatory diagrams of a conventional tilt device for an optical head. 20: Optical head tilt device, 22: Base frame,
23 ... Feed feed shaft, 24 ... Fixed support bracket, 25 ... Optical pickup, 26 ... Tilt mechanism, 30 ...
Tilt drive motor, 40, 50 ... Tilt servo system, 51 ...
Optical sensor, D ... optical disk.

Claims (1)

(57) [Claims] An optical head tilt device for holding an optical pickup reciprocally moved in a radial direction opposite to an optical disk at a constant distance perpendicular to the optical disk by servo control in accordance with bending of the optical disk. A feed feed shaft for guiding the reciprocation of the optical pickup is formed so as to be flexibly deformable, and one end of the feed feed shaft is fixedly supported at the center end of the optical disc, while the other end of the feed feed shaft is provided. A tilting means for bending the feed feed shaft in accordance with the bending of the optical disc, a detecting means for detecting a distance between the optical pickup and the optical disc, and a detecting means for detecting the distance between the optical pickup and the optical disc. Servo means for controlling the tilt means so as to keep the distance between the optical disc and the optical pickup constant based on the detected value Tilt apparatus for an optical head, characterized by comprising.