JPH03250430A - Optical head - Google Patents

Abstract

PURPOSE:To provide the optical head with which a further higher acceleration is obtainable while preventing the rotation of the plane of polarization by freely turnably supporting a blade holding an objective lens at one end and freely rotatably supporting a substrate. CONSTITUTION:The blade 17 holding the objective lens 19 at one end is freely rotatably supported on the substrate 9 around a revolving shaft 18 and the substrate 9 is freely rotatably supported via bearing 5 in nearly the central part of a yoke 3. Two pieces of bar-shaped prisms 27, 29 are disposed on the lower side of the blade 17 and are irradiated with a laser beam LZ from a lower side, by which the recording and reproducing of information are executed via the objective lens 19. Since the parallel setting of the center line of the blade 17 and the tangent of the recording tracks of an optical disk in possible, the rotation of the plane of polarization of the laser beam returning from the optical disk is prevented. In addition, the execution of high-speed access by setting the acceleration of the rotation of the objective lens 19 at a high value is possible as well.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention (Field of Industrial Application) The present invention relates to an optical head used in disc devices for information equipment, video disc players, audio disc players, and the like.

(Prior Art) As a conventional optical head for recording information on an optical disk or reproducing recorded information by irradiating laser light, the one shown in FIG. 12 is known.

Optical head shown in FIG. 12] 01 is swing arm] 0
3 is rotatably provided around a rotating shaft 105 as a center of rotation. An optical actuator]] is held at one end of this swing arm 103. This optical actuator 11] includes an objective lens 107 and an objective lens 1
．． 07 in the focusing direction F1, that is, in a direction perpendicular to the disk surface of an optical disk (not shown). Further, the swing arm 103 is provided with a tracking coil 113, and by applying a current to the tracking coil 113 and rotating the swing arm 103, the objective lens 1.07 is moved in the tracking direction F2, that is, in the radial direction of the optical disc. move it.

As shown in FIG. 13, from the rotation axis 105 to the objective lens 10
When the distance to 7 is R and the angular acceleration is β, the acceleration α of the objective lens 107 is expressed by the following equation (1).

αa; RLxβ1 (1) (Problem to be Solved by the Invention) Incidentally, it is desired to further increase the value of the acceleration α in order to perform access even faster.

For this reason, it is conceivable to lengthen the distance RL mentioned above.

However, setting the distance RL to be long not only reduces the rigidity of the optical actuator 111 as a whole, but also causes the problem that the polarization plane of the laser beam that returns from the optical disc during reproduction rotates.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical head that can obtain even greater acceleration while preventing rotation of the plane of polarization.

[Structure of the Invention] (Means for Solving the Problems) The means provided by the present invention for achieving the above object include a first arm body and an objective lens held at one end of the first arm body. and a driving means for driving the objective lens in the focusing direction and the tracking direction, and a second arm body that holds the optical means and is rotatably supported. did.

(Function) The present invention holds the optical means on the second arm body, and
The arm body is rotatably supported.

Further, the optical means includes an objective lens held at one end of the first arm body, and a drive means for driving the objective lens in the focusing direction and the tracking direction.

Therefore, the acceleration of the objective lens can be increased in accordance with the lengths of the first arm body and the second arm body.

Further, since the center line of the first arm body can be set parallel to a straight line perpendicular to the tracking direction, that is, a tangent to the recording track of the optical disc, rotation of the plane of polarization can be prevented.

(Example) Hereinafter, an example according to the present invention will be described in detail with reference to the drawings.

First, the configuration of an optical head 1 according to the present invention will be explained with reference to FIGS. 1 to 3.

The optical head 1 is arranged below the optical disc 2.

Concentric recording tracks are formed on the optical disc 2.
Laser light LZ from the optical head 1 is irradiated from below to record or reproduce information.

A rotary shaft 7 is rotatably mounted approximately in the center of the yoke 3 via a bearing 5. This rotating shaft 7 is fixed to a substrate 9, which is a second arm body, and the substrate 9 is rotatably supported around the rotating shaft 7 as a rotation center.

A pair of access magnets 11 and a coil 13 are arranged inside the yoke 3. Yoke 3 as shown in Figure 8
and the magnetic field B1. generated between the magnet 11 and the magnet 11. and the current i flowing through the coil 13, the biasing force F1 is
occurs. This biasing force F causes the substrate 9 to move in the direction F3.
rotated to

A stepped mounting plate 9a is integrally formed on the substrate 9, and a lens actuator 15, which is an optical means, is mounted on this mounting plate 9a.
is retained. Therefore, by rotating the substrate 9 in the direction F3, the entire lens actuator 15 is moved in the tracking direction.

In addition, since the mounting plate 9a holding the lens actuator] 5 is integrally formed at the end of the substrate 9, it is possible to prevent the rotational deflection of the substrate 9 when the substrate 9 rotates in the direction F3. No balancer is provided.

Next, the lens actuator 15 will be explained with reference to FIGS. 4 and 5.

A blade 17, which is a first arm body, is rotatably supported around a rotating shaft 18, and the blade 17 is a first arm body.
An objective lens] 9 is held at one end of the lens 7. Therefore, the objective lens 19 is moved in the tracking direction F2, that is, in the radial direction of the optical disc 2, by the rotation of the blade 17.

A focus coil 21 and a track coil 23 are provided below the blade 17 and around the rotating shaft 18 . Further, magnets 25 are arranged inside a pair of yokes 24 vertically provided on the mounting plate 9a.

As shown in FIG. 6, a biasing force Ft is generated by the interaction between the magnetic field Byo generated between the yoke 24 and the magnet 25 and the current il flowing through the focus coil 21.

The objective lens 19 held at one end of the blade 17 is moved together with the blade 17 in the focusing direction F1 by this biasing force Fr.

Further, as shown in FIG. 7, a magnetic field B1. generated between the yoke 24 and the magnet 25. An urging force F is generated by the interaction with the current 1+ flowing through the track coil 23. This biasing force F moves the objective lens 19 held at one end of the blade 17 in the tracking direction F2.

Further, as shown in FIGS. 9 and 10, two rod-shaped brisms 27 and 29 are arranged below the blade 17 in parallel with the blade 17, and a laser beam LZ from an optical system (not shown) is disposed below the blade 17. or prism 29.27 and objective lens 1
The light is irradiated onto the recording track of the optical disc 2 via the light beam 9 .

As described above, the blade 1 holds the objective lens 19 at one end.
7 is freely rotatable with the rotating shaft 18 as the center of rotation. : It is supported, and the center line of this blade 17 and the optical disk 2
Since the tangent line of the recording track can be set parallel to the tangent line of the recording track, rotation of the polarization plane of the laser beam returning from the optical disk 2 can be prevented.

Next, the operation will be explained with reference to FIG.

As shown in FIG. 11, the distance from the objective lens 19 to the rotation axis 18 is RL□, the distance from the rotation axis 18 to the rotation axis 7 is RL2, and the angular acceleration of the blade 17 is β2,
When the angular acceleration of the substrate 9 is β1, the acceleration αゎ of the objective lens 19 is expressed by the following equation (2).The equation (2) is expressed as follows.

Q b ” (RLI R+, 2)×β1+RL2×
β2-Rl-β1+R1,2×(β2-β1)...(
3) As shown in ``2'' below, when the angular acceleration β2 is larger than β1, the acceleration α is Acceleration α
, set to a larger value.

[Effects of the Invention] As described above, according to the present invention, the optical means including the objective lens held on the first arm is held on the second arm, and the second arm is held on the second arm. Since it is configured to be rotatably supported, the acceleration of the objective lens can be set to a large value.

Furthermore, since the center line of the first arm body and the tangent to the recording track of the optical disk can be set parallel, rotation of the plane of polarization can be prevented.

[Brief explanation of drawings]

Fig. 1 is a perspective view of one embodiment of the present invention, Fig. 2 (A)
is a plan view of FIG. 1, FIG. 2(B) is a side view of FIG. 2(A), FIG. 3(A) is a sectional view of FIG. 2(B), and FIG.
) is a plan view of FIG. 3(A), FIG. 4 is a perspective view of the lens actuator, FIG. 5(A) is a perspective view of the blade holding the objective lens and its surroundings, and FIG. 5(B) ) is a perspective view showing a magnetic circuit for focusing and tracking, FIG. 6 is an explanatory diagram showing a focusing coil and the biasing force acting on this focusing coil, and FIG. 7 is a tracking coil and an explanatory view showing a biasing force acting on this tracking coil. An explanatory diagram showing the biasing force, FIG. 8 is an explanatory diagram showing the access magnetic circuit section and the biasing force acting on this magnetic circuit section, and FIGS. 9 and 10 are the arrangement relationship between the objective lens and the prism. FIG. 11 is an explanatory diagram showing the operation of the embodiment according to the present invention, FIG. 12 is a perspective view of the conventional example, and FIG. 13 is an explanatory diagram showing the operation of the conventional example. 9... Board 9a... Mounting plate 15... Lens actuator 17... Blade 19... Objective lens 1... Focus coil 23... Traction coil

Claims (1)

[Scope of Claims] Optical means comprising a first arm, an objective lens held at one end of the first arm, and a driving means for driving the objective lens in the focusing direction and the tracking direction. An optical head comprising: a second arm body that holds the optical means and is rotatably supported.