JPH0734266B2 - Optical information processing device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk used for optically reading information recorded on an information recording medium such as an optical disk or tape or for optically writing information on the information recording medium. The present invention relates to an information processing device.

[0002]

2. Description of the Related Art In recent years, in the field of audio equipment and the like, a digital recording / reproducing system using a PCM (pulse code modulation) technique has appeared in order to achieve high fidelity as much as possible. Among those adopting such a recording / reproducing system, those intended for a disc are called a DAD (Digital Audio Disc) system, and those adopting an optical system for the reproduction are the mainstream.

Among the DAD systems, in an optical disc record reproducing apparatus using a CD (compact disc) system, unevenness called PCM pits are formed on the surface of a resin substrate, and a metal thin film is deposited thereon. A disc having a diameter of 12 cm and a thickness of 1.2 mm is driven at a constant linear velocity, and information recorded on the disc is optically read in this state. The pit train provided on the disk is called a track, and the track pitch is about 1.6 μm and the pit width is about 0.5 μm. Therefore, a so-called optical information processing device for reading information from a disc controls the position of the objective lens so that the light flux used for reading is always positioned on the focal plane of the objective lens and at the same time traces the center of the track. There is a need.

FIG. 2 shows a schematic configuration of a typical optical information processing device. In this optical information processing apparatus, a light beam emitted from a light source (semiconductor laser or the like) 1 is irradiated onto a recording surface of a disk 4 through an objective lens 3, and is reflected by the recording surface, and then an optical path of the light beam passing through the objective lens 3. Beam splitter 2
The light beam that has been bent is incident on an astigmatism system in combination with the cylindrical lens 5, and the light that has passed through this astigmatism system is incident on a photoelectric conversion element (SiPIN photodiode, etc.) 6 and converted into an electrical signal. is doing. Then, a part of the signal passed through the signal processing circuit 7 is given to the driving circuit 8, the output of the driving circuit 8 is applied to a driving means (not shown) such as a coil, and the objective lens 3 is moved to a desired position by its electromagnetic force. I'm trying to drive. The closed loop control system traces the pit train.

FIG. 3 shows a light receiving system that employs an astigmatism method as a method for adjusting the focal plane to the recording surface (referred to as focusing). In this light receiving system, diffracted light from the disk recording surface 10 is made incident on the objective lens 11 and then passed through the astigmatism lens system 12. A circle of least confusion 15 is formed at a substantially central portion between the front focal plane 13 and the rear focal plane 14 of the astigmatic lens system 12. A multi-divided photodiode is placed at this position, and the output of each element is processed by a logic circuit to obtain a focus error signal. The tracking signal can be obtained by logically processing the output of the photodiode.

Further, in order to stably obtain the tracking signal, a diffraction grating is inserted between the light source 1 and the beam splitter 2 shown in FIG. 2 to form three beams of 0th order and ± 1st order light, and the ± 1st order Instead of a beam splitter to create a tracking signal from the reflected and diffracted light of the light to position the spot in the center of the tracking line, and to reduce the fluctuation of the laser oscillation light due to the effective use of the light flux and the return light to the laser diode. There is also a proposal to combine a polarizing beam splitter and a quarter-wave plate.

On the other hand, as the driving means for focusing and tracking, the one having the structure shown in FIG. 4 is usually used. That is, the movable plate 2 supporting the fixed shaft 21 erected on the fixed side yoke 20 and the objective lens 28.
2, a slide bearing 23 fitted to the fixed shaft 21 so as to be slidable in the axial direction (B direction) and rotatable about the shaft (± A direction), and a neutral position of the movable plate 22. A rubber damper 24 for determining the position, a damper holder 25 also serving as a balancer for fixing one end side of the rubber damper 24 to one end of the movable plate 22, and another end side of the rubber damper 24 for fixing the fixed side yoke 20. A fixed holder 26,
It is composed of a static magnetic field for applying an electromagnetic force to the movable plate 22 and a focus and tracking coil 27 wound around a bobbin integrated with the movable plate 22.

However, the optical information processing apparatus configured as described above has the following problems. That is,
In the conventional optical information processing apparatus, the rubber damper 24 is attached only between the fixed yoke 20 and the end of the movable plate 22 that is located on the opposite side of the end on which the objective lens 28 is fixed. ing. With such a configuration, since only one end of the movable plate 22 is connected to the rubber damper 24, when the movable plate 22 is displaced in the focus direction, a moment about the orthogonal axis is generated in the movable plate 22. . The magnitude of this moment changes nonlinearly with respect to the displacement in the focus direction. A reaction force corresponding to the moment is generated on the inner surface of the slide bearing 23 that restricts rotation around the orthogonal axis. Since the sliding friction of the sliding bearing 23 is almost proportional to the normal force, it changes according to the displacement in the focus direction. If the magnitude of the sliding friction changes according to the amount of displacement in the focus direction, it becomes difficult to pull in the position servo, and stable focusing control and tracking control may not be possible.

[0009]

As described above, in the conventional optical information processing apparatus, stable focusing control is achieved by the influence of the damper member incorporated in the objective lens drive system and determining the neutral position of the objective lens. Also, there is a possibility that tracking control cannot be performed.

Therefore, an object of the present invention is to provide an optical information processing device which can realize stable focusing control and tracking control.

[0011]

In order to solve the above-mentioned problems, the present invention provides an objective lens, a movable body holding the objective lens, an axial slip of the movable body, and an axial rotation direction. A sliding bearing mechanism that supports rotation in a permitted state, an electromagnetic drive mechanism that drives the movable body in an axial direction and an axial direction by electromagnetic force, and a damper member provided between the movable body and a stationary portion. In the optical information processing apparatus comprising: the damper member, the damper member is formed in an annular shape that makes one round in the axial direction about the axis of the plain bearing mechanism in the axial direction, and the thickness in the axial direction is greater than that of the damper member. It is characterized in that the thickness in the direction orthogonal to the axial direction is thin.

[0012]

[Function] Since the damper member is formed into an annular shape that makes one revolution in the axial direction in an axially symmetrical manner about the axis of the plain bearing mechanism, for example, two locations 180 degrees apart in the circumferential direction are used as stationary portions. 2 fixed in the middle and located between the above two
By fixing each part to the movable plate, even if the displacement in the focus direction increases, it is possible to suppress an increase in the normal force applied to the slide bearing mechanism. That is, with respect to the displacement in the focus direction, the parts of the damper member that face each other with the axial center line therebetween counterbalance by generating a moment about the orthogonal axis in the opposite direction, thus suppressing an increase in vertical reaction force applied to the slide bearing mechanism. It Therefore, it is possible to prevent the pulling in from becoming difficult due to the vertical drag force during the servo control, and it becomes possible to perform stable focusing control and tracking control. Further, since the damper member whose thickness in the direction perpendicular to the axial direction is thinner than that in the axial direction is used, the damper member can be comfortably deformed when the movable plate rotates in the axial direction. You can Therefore, even if the movable plate largely rotates in the axial direction, the bent portion of the damper member is not likely to be deformed into an unreasonable shape such as buckling. Therefore, the permissible rotation angle in the axial direction is not limited, and a stable function can be exerted over a wide range.

[0013]

Embodiments will be described below with reference to the drawings.

FIG. 1 shows an optical information processing apparatus according to an embodiment of the present invention in a partially cutaway state.

In the figure, a light beam emitted from a light source, for example, a laser diode 30 is divided into three beams by a diffraction grating 31 and then transmitted through a polarization beam splitter 32,
Then, it is converted into parallel light by the collimator lens 33. The collimated light has its optical path bent by the prism mirror 34, and then passes through the quarter-wave plate 35 to be circularly polarized light and is incident on the objective lens 36. Then, the incident light is converged by the objective lens 36 and irradiated on a disc pit surface (recording surface) (not shown) as a minute spot.

The diffracted light reflected from the recording surface is the objective lens 3
After passing through the 6 and 1/4 wavelength plate 35, it becomes a linearly polarized light which is the reverse of the going, has its optical path bent by the prism mirror 34, and then passes through the collimator lens 33 to become convergent light. The convergent light has its optical path bent at a right angle by the polarization beam sputter 32, and then enters the photoelectric conversion element 38 through the astigmatism lens system 37 including a cylindrical lens.

On the other hand, the objective lens 36 is fixed to one end of a flat movable plate 39. This movable plate 3
A counterweight 40 is attached to the other end side of 9. A slide bearing 41 is provided at the center of the movable plate 39 so as to extend vertically in the drawing. This plain bearing 4
Reference numeral 1 is fitted to a shaft 42 that is erected on a stationary portion so as to be slidable in the axial direction and rotatable about the axis. In addition, the stationary portion and the movable plate 39 have a drive mechanism having the same structure as that shown in FIG. 4, that is, a magnetic circuit 43 for positioning the movable plate 39 by driving the movable plate 39 in the focusing direction and the tracking direction by electromagnetic force. An electromagnetic drive mechanism including a drive coil 44 mounted on the movable plate 39 is provided.

Below the movable plate 39, a damper member 45 formed in an annular shape, that is, in the shape of a square V, is arranged around the shaft 42 in the direction around the axis. This damper member 4
Reference numeral 5 is formed by punching out a silicon-based rubber, and has a thin thickness Y in the direction orthogonal to the axial direction with respect to the axial thickness X. The damper member 45 is fixed to the lower surfaces of both end portions of the movable plate 39 at two locations that are 180 degrees apart in the circumferential direction, and the middle position of the portions located on both sides of the line connecting the two locations is stationary. Each part is screwed.

With such a structure, the movable plate 3 is operated in the same manner as the conventional device by operating the electromagnetic drive mechanism.
9, that is, the objective lens 36 can be moved in the focus direction and the tracking direction. The amount of movement at this time is a position where the force given by the electromagnetic drive mechanism and the reaction force obtained by the damper member 45 are balanced.

In this case, the damper member 45
Is formed in an annular shape that makes one revolution in the axial direction in an axially symmetrical manner about the axis of the plain bearing 41.
As in the embodiment, the movable plate 3 is provided at two locations 180 degrees apart in the circumferential direction.
It is fixed to both ends of 9 and is 90 degrees out of phase with the above 2
By fixing the portions to the stationary portions, it is possible to suppress an increase in the normal force applied to the slide bearing 41 with respect to the displacement in the focus direction. That is, when a displacement in the focus direction is given, the parts of the damper member 45 that face each other with the axial center line therebetween counterbalance by generating opposite moments about orthogonal axes. Therefore, the vertical resistance applied to the slide bearing 41 does not increase. Therefore,
It is possible to prevent difficulty in pulling in due to vertical drag force during servo control, and to realize stable focusing control and tracking control. Further, as the damper member 45, the thickness Y in the direction orthogonal to the axial direction is greater than the thickness X in the axial direction.
Since the thin plate is used, the damper member 45 can be reasonably deformed when the movable plate 39 rotates in the axial direction. Therefore, even if the movable plate 39 largely rotates in the direction around the axis, the bent portion of the damper member 45 is not likely to be deformed into an unreasonable shape such as buckling. Therefore, the allowable rotation angle in the axial direction is not limited, and the control in the tracking direction can be stably exerted over a wide range.

[0021]

As described above, according to the present invention, even when the displacement in the focus direction is increased, it is possible to suppress an increase in the vertical shaft force applied to the slide bearing mechanism, which facilitates pulling in during servo control. And stable focusing control and tracking control can be realized. Further, it is possible to prevent the damper member from being deformed excessively during tracking control, which contributes to the realization of stable tracking control over a wide range in the axial direction.

[Brief description of drawings]

FIG. 1 is a perspective view showing an optical information processing apparatus according to an embodiment of the present invention with a part thereof cut away.

FIG. 2 is a diagram showing a schematic configuration of a conventional optical information processing device.

FIG. 3 is a diagram for explaining focusing control in the same device.

FIG. 4 is a perspective view showing a conventional optical information processing device with a part thereof cut away.

[Explanation of symbols]

Reference numeral 36 ... Objective lens, 39 ... Movable plate, 40 ... Counter weight, 41 ... Slide bearing, 42 ... Shaft, 43 ... Magnetic circuit forming part of electromagnetic driving mechanism, 44 ... Coil forming part of electromagnetic driving mechanism, 45 ... Damper member.

Claims (2)

[Claims] Claim: What is claimed is: 1. An objective lens, a movable body holding the objective lens, a slide bearing mechanism for supporting the movable body in a state in which it is allowed to slide in the axial direction and to rotate in the direction around the axis, and an electromagnetic force. In an optical information processing device comprising an electromagnetic drive mechanism for driving the movable body in an axial direction and an axial direction, and a damper member provided between the movable body and a stationary portion, the damper member is the The slide bearing mechanism is formed in an annular shape that makes one round in the axial direction symmetrically with respect to the axis of the slide bearing mechanism, and that the thickness in the direction orthogonal to the axial direction is thinner than the thickness in the axial direction. A characteristic optical information processing device. 2. The damper member is fixed to the stationary portion at two positions 180 degrees apart in the circumferential direction, and is fixed to the movable plate at two positions intermediate between the two positions. The optical information processing apparatus according to claim 1, wherein: