JP2746696B2 - Optical head device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head device for recording / reproducing information on / from an optical disk, and in particular, controls the position of a light spot on the optical disk. The present invention relates to an optical head device.

[Conventional technology]

 FIG. 7 is a schematic view of a conventional optical head device.

In the figure, (1) is a base of the optical head device,
(2) is a fixed optical system fixedly provided with respect to the base, in which a light source, a photodetector and the like (not shown) are arranged. (3) is a light beam emitted from the fixed optical system (2), (4) is an optical disk, and (5) is an objective lens for condensing the light beam (3) on the optical disk (4). , (6a) and (6b) move the objective lens (5) in accordance with the arrow A in accordance with the surface shake of the optical disc (4).
Focus direction control device for driving control in the direction,
(7) is a prism for reflecting the light beam (3) emitted from the fixed optical system (2) so as to be incident on the objective lens (5), and (8) is a prism for reflecting the objective lens (5) and the prism ( 7) is a carriage on which the base (1) is supported by bearings (9a) and (9b) so as to be movable in a direction (arrow B direction) across the information track on the optical disk (4). Have been.

Next, the operation will be described. The light beam (3) emitted from the fixed optical system (2) is reflected by the prism (7) and condensed on the optical disk (4) by the objective lens (5). The light beam (3) reflected by the optical disk (4) follows an optical path opposite to that described above, is photoelectrically exchanged by the fixed optical system (2), and records or reproduces information on the optical disk (4).

The focus direction control devices (6a) and (6) control the movement of the optical disc (4) in the focus direction (surface blur, disturbance, etc.).
According to b), the correction is performed by controlling the drive of the objective lens (5) in the direction of arrow A.

In order to record (or reproduce) an arbitrary track on the optical disk (4), the carriage (8)
Is moved in the radial direction (the direction of arrow B) of the optical disk (4).

[Problems to be solved by the invention]

Since the conventional optical head device is configured as described above, a relative position change between the fixed optical system (2) and the carriage (8) occurs due to thermal change, aging, impact force, and the like. (Excluding translational movement in the direction of the arrow x-axis)
The central ray of the light beam (3) reflected by the optical disk (4) is the light beam (3) emitted from the fixed optical system (2).
However, there is a problem that the tracking sensor signal and the like obtained in the fixed optical system (2) are offset from each other because they do not coincide with the center light beam. The problem will be specifically described with reference to FIG.

FIG. 8 shows an example in which the relative position between the carriage (8) and the fixed optical system (2) changes by an angle θ due to aging or the like in the conventional optical head device. The light beam (3) indicated by the broken line is the optical path of the light beam in the initial state before the relative change occurs, and the light beam (3) indicated by the solid line is the optical path of the light beam after the relative change occurs. It is. As is clear from the figure, the central ray of the light beam reflected by the optical disk (4) does not coincide with the central ray of the light beam (3) emitted from the fixed optical system (2), and the central ray of the light beam is used as a tracking sensor. When a push-pull method or the like is used, a tracking sensor offset occurs. The mechanism by which the tracking sensor offset occurs is specified in “Micro-Optics News Vol.3 No.1 P78-82 Optical System for Magneto-Optical Disk”.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an optical head device capable of suppressing the tracking sensor offset amount to a small value.

[Means for solving the problem]

An optical head device according to the present invention is an optical head device for recording or reproducing information by guiding light from a light source to an information recording medium via an optical element and irradiating the information recording medium with a light spot. The optical element is held via a light distortion element, and the position of the light spot is controlled by driving and controlling the optical element according to the amount of light incident on the light distortion element.

[Action]

In the optical head device according to the present invention, the optical distortion element that detects the relative displacement between the light source and the optical element as a change in the amount of light automatically deforms in a direction to correct the relative displacement, and the optical element needs to be corrected. In the required direction.

(Example of the invention)

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

FIG. 1 is a schematic diagram of an optical head device according to one embodiment of the present invention, and the same or corresponding parts as in FIG. 7 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 1, (20
Reference numerals a) and (20b) denote optical distortion elements, which are provided on the carriage (8) and support the prism (7) as a reflection element via support members (21a) and (21b).

2 and 3 show an optical head device according to the present invention, in which, when the position of the light beam (3) incident on the carriage (8) changes, a correction operation is performed for the change. FIG.

In FIG. 2 and FIG. 3, (3) indicated by a solid line
Is a light beam emitted from the fixed optical system (2), in which the carriage (8) and the fixed optical system (2) are relatively displaced in the y-axis direction, that is, the light beam (3) shown by a broken line.
Shows a state when the light beam (3) has moved through a position different from the initial position (the light beam (3) has moved in the direction of arrow C in the figure).

Next, the operation will be described. First, in FIG.
The light beam (3) emitted from the fixed optical system (2) is reflected by the prism (7) and condensed on the optical disk (4) by the objective lens (5). The light beam (3) reflected by the optical disk (4) follows an optical path opposite to the above, and is photoelectrically exchanged by the fixed optical system (2).
Information is recorded or reproduced on the optical disk (4).

The focus direction control devices (6a) and (6) control the movement of the optical disc (4) in the focus direction (surface blur, disturbance, etc.).
According to b), the correction is performed by controlling the drive of the objective lens (5) in the direction of arrow A.

In order to record (or reproduce) an arbitrary track on the optical disk (4), the carriage (8)
Is moved in the radial direction (the direction of arrow B) of the optical disk (4).

Next, as shown in FIG. 2, when the carriage (8) and the fixed optical system (2) are relatively displaced in the y direction,
When viewed from the carriage (8), the light beam (3) enters from the position displaced in the direction of arrow C in the figure as shown by the solid line. In this case, when no correction operation is performed as in the conventional example, as shown by the solid line, the central ray of the reflected light path from the optical disk (4) does not coincide with the central ray of the incident light path, and the fixed optical path is not fixed. An offset will occur in the tracking sensor signal obtained in the system (2).

However, in the optical head device according to the present invention,
When the position of the light beam (3) incident on the carriage (8) changes, the amount of light incident on the optical distortion elements (20a) and (20b) changes. For example, as shown in FIG. 2, when the light beam (3) is displaced in the direction of arrow C, the light distortion element (20)
The amount of light incident on a) increases, and the amount of light incident on the optical distortion element (20b) decreases.

Since the optical distortion elements (20a) and (20b) have a property of expanding when the amount of light irradiated to the elements increases, the optical distortion elements (20a) and (20b)
a) will be extended and the supporting members (21a), (21b)
If the appropriate material is selected, the optical distortion element (20a), (20b)
Without damaging the prism, the prism (7) is moved to a desired position, and as shown in FIG. 3, the center ray of the incident light path and the center ray of the reflected light path of the light beam (3) shown by a solid line are almost equal. It coincides, and almost no offset occurs in the tracking error signal detected by the fixed optical system (2).

Regarding the characteristics of the optical distortion element, for example, see the magazine “O plus E 1
May 989, P68-70, New Technology "
It is possible to respond sufficiently at a time level at which aging occurs.

Further, as shown in FIG. 4, the light beam (3) incident on the carriage (8) is in an initial state (shown by a broken line).
When there is no correction angle (the angle θ in the figure), the central ray of the reflected optical path becomes the optical path indicated by P when there is no correction operation, and a large tracking offset occurs. In the head device, the prism (7)
Is driven in the direction of arrow E in the figure, and the central ray of the reflected light path is the optical path indicated by Q, and only a small offset occurs as compared with the central light ray of the reflected optical path indicated by P.

In the above embodiment, the example in which the optical distortion elements (20a) and (20b) are arranged in the optical path of the light beam (3) transmitted through the prism (7) is shown in FIG. 5 or FIG. As shown, it may be arranged on the entrance side of the carriage (8) in order to improve the reflectance of the prism (7). in this case,
When the light beam (3) is displaced in the direction of arrow C shown in FIG. 5, the amount of light incident on the optical distortion element (20a) increases and expands, and the amount of light incident on the optical distortion element (20b) decreases and contracts. ,
As shown in FIG. 6, the same result as in FIGS.

〔The invention's effect〕

As described above, according to the present invention, the reflecting element is supported by the plurality of optical distortion elements, and when the optical system is displaced with respect to the carriage, the amount of light incident on each optical distortion element changes. As a result, the position of the reflective element on the carriage is automatically corrected, and the light beam is incident on a fixed position of the reflective element. Therefore, the device can be reduced in size and weight, and complicated circuits and light receiving can be achieved. Optical axis correction can be performed without using an element, and there is an effect that an inexpensive and high-performance device can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an optical head device according to one embodiment of the present invention, FIGS. 2 to 4 are schematic diagrams showing how optical axis correction is performed by the optical head device according to one embodiment of the present invention, FIGS. 5 and 6 are schematic diagrams showing how optical axis correction is performed by an optical head device according to another embodiment of the present invention. FIG. 7 is a schematic diagram showing an optical head device according to a conventional example.
FIG. 8 is a schematic diagram showing a state in which an optical axis shift has occurred in an optical head device according to a conventional example. (3) ... light beam, (4) ... optical disk, (5) ...
... Objective lens, (7) ... Reflection element (prism), (20
a), (20b): Photostrictive element.

Claims (1)

(57) [Claims] An optical system fixedly provided on a base; a reflecting element having a reflecting surface for reflecting a light beam from the optical system at a right angle; and a light reflected by the reflecting surface being incident thereon. An optical head device comprising: an objective lens that forms a condensed spot on a recording medium; and a carriage mounted with the reflective element and the objective lens and movable in a tracking direction of the recording medium. While being supported by the optical distortion element, when the optical system is displaced with respect to the carriage, the position of the reflection element on the carriage is automatically adjusted by changing the amount of light incident on each of the optical distortion elements. An optical head device wherein a light beam is incident on a predetermined position of the reflection element.