JPH04344329A - Inclination correcting device for optical head - Google Patents

Abstract

PURPOSE:To speedily control the incident angle of a light beam to an optical disk surface. CONSTITUTION:An optical head 3a is shifted in the radial direction of an optical disk 1 by radial driving voice coil motors 24 and 24a. An optical head 3a is supported in freely rotatably in the vertical direction of the surface of the optical disk 1 by an axis 7. A chilt driving voice coil meter 33 drives a pin 11b arranged to the optical head 3a up and down. The rotation of the optical head 3a is controlled by the chilt driving voice coil motor 33 in approximately vertical direction with the surface of the optical disk 1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head tilt correcting device, and more particularly to an optical head tilt correcting device for controlling the incident angle of a light beam onto an optical disk surface to a constant value.

0002

2. Description of the Related Art FIG. 2 is a side view showing the angle of incidence of a light beam from an optical head of an optical disc device onto an optical disc surface. FIG. 2(A) shows a state in which the optical head is tracking the inner circumferential portion of the optical disk, and FIG. 2(B) shows a state in which the optical head is tracking the outer circumferential portion of the optical disk.

In FIGS. 2A and 2B, an optical disc 1 is mounted on a spindle motor 2 and driven to rotate, and an optical head 3 is movable in the radial direction of the optical disc 1.
The desired track is accessed by As shown,
The optical disc 1 bends and warps downward in the figure at its outer periphery due to its own weight.

Therefore, as shown in FIG. 2A, even when the optical head 3 is tracking the inner circumference of the optical disk 1 and the light beam 4 is approximately perpendicularly incident on the surface of the optical disk, the optical head 3 When the optical disk 1 moves horizontally to the right in the figure in the radial direction of the optical disk 1 and tracks its outer circumference, the light beam 4 does not enter the optical disk surface perpendicularly, as shown in FIG. 2(B). If the light beam is not incident perpendicularly to the optical disk surface, optical performance may deteriorate.

On the other hand, some optical discs are prone to warping depending on the substrate material, but optical discs using glass substrates can reduce warping. However, optical discs using plastic substrates such as polycarbonate tend to warp. Further, the magnitude of warpage increases as the diameter of the optical disc increases. For example, 300mm in diameter
A plastic substrate of approximately 10 [mrad] warps, which is more than 10 times that of a glass substrate of the same diameter.

[0006] When using a plastic substrate that is more likely to warp than a glass substrate but is inexpensive, the inclination of the optical head is corrected so that the light beam from the optical head is incident perpendicularly to the surface of the optical disc even if the optical disc is warped. Devices for guaranteeing optical performance are conventionally known.

FIG. 3 is a partially cutaway side view of an example of a conventional optical head tilt correction device. In FIG. 3, a spindle motor 2 with an optical disk 1 mounted thereon is arranged on a base 6 together with a guide rail 5. As shown in FIG. On the other hand, the optical head 3 is rotatably supported via a shaft 7 with respect to a carriage 8 (stand). The carriage 8 is guided by a guide rail 5 and is configured to move in the radial direction of the optical disc 1, indicated by A and A' in the figure, substantially parallel to the optical disc surface.

The rotational driving force of the motor 9 is transmitted through a transmission mechanism 1 composed of the illustrated worm gear, reduction gear, cam, etc.
0, the pin 11 press-fitted into the optical head 3 is moved up and down. As a result, the optical head 3 rotates about the shaft 7 in the directions indicated by B and B' in the figure.

Warpage of the optical disk 1 is detected by a tilt error detector (not shown), and the control circuit controls the motor 9.
is driven to rotate the optical head 3, and the light beam from the optical head 3 is controlled to be incident perpendicularly to the optical disc surface.

FIG. 4 is a partially cutaway side view of an example of a conventional optical head tilt correction device. In FIG. 4, the spindle motor 2 to which the optical disc 1 is mounted is arranged on a base 6a together with a bearing 7a. On the other hand, a shaft 7b supported by a bearing 7a is disposed at an end of the guide rail 5a. The guide rail 5a guides the carriage 8a (stand) to move in the radial direction of the optical disc 1, indicated by A and A' in the figure, parallel to the optical disc surface.

The rotational driving force of the motor 9a moves a pin 11a press-fitted into the tip of the guide rail 5a up and down via a transmission mechanism 10a constituted by a worm gear, a reduction gear, a cam, etc., as shown. As a result, the optical head 3 rotates together with the guide rail 5a and the carriage 8a about the shaft 7b in the directions indicated by B and B' in the figure.

Warpage of the optical disk 1 is detected by a tilt error detector (not shown), and the control circuit controls the motor 9.
a is driven to rotate the optical head 3, and the light beam 4 from the optical head 3 is controlled so as to be incident perpendicularly to the optical disc surface.

[0013]

[Problems to be Solved by the Invention] In the conventional optical head tilt correction device, as described above, the driving force of the motor is transferred to the gear,
The optical head was transmitted using a transmission mechanism such as a cam, and the optical head was rotated together with a guide rail, a carriage, etc., and the tilt of the optical head was controlled.

[0014] Therefore, the moving parts had considerable mass. Additionally, it was necessary to provide clearance for the transmission mechanism, and a preload spring was sometimes required to eliminate gear backlash. Therefore, it took time to transmit the driving force of the motor and properly control the tilt of the optical head, and the frequency characteristic was approximately 1 to 2 [Hz], making it impossible to access the optical disk at high speed.

[0015] Recent optical head tilt correction devices for optical disk devices compatible with high-speed read/write processing have a 20 to 50 [
Hz] is required, and conventional optical head tilt correction devices are not suitable for this.

In view of the above points, it is an object of the present invention to provide an optical head tilt correction device capable of high-speed access, which can be applied to recent optical disk devices compatible with high-speed read/write processing.

[0017]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention includes a platform that is reciprocated in the radial direction of the optical disk by a first voice coil motor, and a platform that is mounted in a direction substantially perpendicular to the surface of the optical disk. an optical head that is rotatably supported by a shaft and that irradiates a light beam onto the optical disc; a second voice coil motor that is disposed on the base and biases the optical head to rotate in a direction substantially perpendicular to the surface of the optical disc; and tilt detection means for detecting the reflected light of the light beam from the optical disk to detect that the light beam is incident approximately perpendicularly to the optical disk surface, and the light beam is The second voice coil motor is configured to control the rotation of the optical head so that the optical head is incident approximately perpendicularly onto the surface of the optical disc.

[0018]

[Operation] According to the present invention having the above structure, the optical head is rotated in a direction substantially perpendicular to the optical disc surface by the driving force of the second voice coil motor without using mechanical parts such as gears and cams, and the optical head is is controlled so that it is incident perpendicularly to the optical disc surface.

[0019]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a partially cutaway two-dimensional view of an embodiment of the present invention. FIG. 1(A) is a partially cutaway plan view, and FIGS. 1(B) and 1(C) are partially cutaway side views. In FIG. 1(B), the optical head 3a is tracking a track closer to the inner circumference of the optical disc 1, and in FIG. 1(C), the optical head 3a is tracking a track closer to the outer circumference of the optical disc 1. .

In the figure, a spindle motor 2a with an optical disk 1 mounted thereon is disposed on a base 6b. The optical head 3a is rotatably supported by a carriage 8b (stand) using a shaft 7c as a pivot shaft. Coils 20, 20a are arranged on the side surfaces of the rectangular box-shaped carriage 8b.

The base 6b is provided with side yokes 21, 21a whose ends are bent toward the optical disk. Permanent magnets 22,
22a is fixed. Center cores 23, 23a are fixed to both bent ends of the side yokes 21, 21a. Coils 20, 20a arranged on the side surfaces of the carriage 8b are wound so as to surround the center cores 23, 23a.

As mentioned above, the carriage 8b has the coil 2
0, 20a, side yoke 21, 21a, permanent magnet 22
, 22a, and center cores 23, 23a, respectively, for radial drive voice coil motors 24, 24a (
The base 6b is driven by the first voice coil motor in the radial direction of the optical disc 1, indicated by A and A' in the figure, substantially parallel to the optical disc surface.

A tracking actuator 25 and a tilt error detector 26 (tilt detecting means) are arranged in the optical head 3a so as to face the optical disc 1. An objective lens 27 is disposed on the top surface of the tracking actuator 25. The tracking actuator 25 drives an optical system (not shown) so that the light beam focused on the optical disc surface by the objective lens 27 tracks a desired track on the optical disc 1.

On the inner surface of the carriage 8b on the right side in the figure,
A side yoke 28 having both ends bent toward the optical head 3a is provided. A permanent magnet 29 is fixed to the side surface of the side yoke 28. A center core 30 is fixed to both bent ends of the side yoke 28.

There is a pin 1 on the right side of the optical head 3a in the figure.
1b is arranged substantially parallel to the optical disc 1. pin 11
b is inserted into the bearing portion of the tilt drive coil bobbin 31. A coil 32 wound around the center core 30 is disposed on the coil bobbin 31 . side yoke 28, permanent magnet 29, center core 30,
The coil bobbin 31 and the coil 32 constitute a tilt drive voice coil motor 33 (second voice coil motor).

The pin 11b is driven by a tilt drive voice coil motor 33 in directions B and B' in FIG. 1(B), and the optical head 3a is configured to rotate around an axis 7c. .

On the other hand, the tilt error detector 26 detects the reflected light from the optical disk 1 of the light beam from the light emitting diode 26a using photodetectors 26b and 26c. When the light beam from the optical head 3a is perpendicular to the optical disk surface, the detection outputs of the photodetectors 26b and 26c are made equal.

Therefore, a current is passed through the coil 32 in accordance with the detected value of the difference between the detection outputs of the photodetectors 26b and 26c.
By driving the tilt drive voice coil motor 33 to control the rotation of the optical head 3a about the axis 7c, it is possible to irradiate the optical disc surface with a light beam perpendicularly.

For example, when the optical head 3a is tracking a track near the outer circumference of the optical disc 1 as shown in FIG. 1(C), the tilt error detector 26 detects that the optical disc 1 is warped downward. Then, the tilt drive voice coil motor 33 operates to control the rotation of the optical head 3a in the B direction so that the light beam is perpendicularly incident on the optical disk surface.

According to the above embodiment, since the optical head is directly driven by the tilt driving voice coil motor 33, there is no intervening mechanism such as a gear or a cam as a driving force transmission mechanism. Therefore, there is no need to provide clearance for gear backlash, etc., and the optical head is quickly controlled to rotate to a desired position when driving force is applied to the voice coil motor.

According to the above embodiment, a frequency response of several tens of Hz can be obtained, and high-speed access applicable to recent optical disk devices capable of high-speed read/write processing is possible. Further, according to this embodiment, since a transmission mechanism is not required, there is an advantage that the vibration and noise of the device are small. Since there is little vibration in the device, the tracking actuator can operate stably.

[0033]

As described above, according to the present invention, the optical head can be controlled by the voice coil motor to rotate in a direction perpendicular to the optical disk surface so that the optical beam from the optical head is irradiated perpendicularly to the optical disk surface. Therefore, it has the advantage of enabling high-speed access that can be applied to recent optical disk devices that support high-speed read/write processing.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway two-dimensional view of an embodiment of the present invention.

FIG. 2 is a side view showing the incident angle of a light beam from an optical head of an optical disc device with respect to an optical disc surface.

FIG. 3 is a partially cutaway side view of an example of a conventional optical head tilt correction device.

FIG. 4 is a partially cutaway side view of an example of a conventional optical head tilt correction device.

[Explanation of symbols]

1 Optical disk 3, 3a Optical head 4 Light beam 8, 8a, 8b Carriage (stand) 20, 20a
32 Coil 21, 21a 28 Side yoke 22, 22a,
29 Permanent magnets 23, 23a 30 Center core 24 Radial drive voice coil motor (first voice coil motor) 24a Radial drive voice coil motor (first voice coil motor) 26 Tilt error detector (tilt detection means) 31
Coil bobbin 33 Tilt drive voice coil motor (second voice coil motor)

Claims (1)

[Claims] 1. A stand that is reciprocally driven in the radial direction of the optical disk by a first voice coil motor; a stand that is rotatably supported on the stand in a direction substantially perpendicular to the surface of the optical disk; an optical head that irradiates the optical disc; a second voice coil motor that is disposed on the platform and rotates and urges the optical head in a direction substantially perpendicular to the optical disc surface;
tilt detection means for detecting reflected light of the light beam from the optical disk to detect that the light beam is incident substantially perpendicularly to the surface of the optical disk; Accordingly, the optical head tilt correction device is characterized in that the optical head is rotationally controlled by the second voice coil motor so that the light beam is incident on the optical disk surface substantially perpendicularly.