JPH05174404A - Optical head - Google Patents

Abstract

PURPOSE:To detect an accurate position of an objective lens despite the change of a contact position caused between a shaft and a hole part in regard to an optical heed which drives the objective lens that irradiates the light onto an optical disk in both focus and track directions. CONSTITUTION:A fixed part 4 has a shaft 41 and a movable part 5 has a hole pert 52 where the shaft 41 is fitted. The part 5 is provided with an objective lens 25 which irradiates the light of a light source 20 onto an optical disk 1. Then the part 5 is driven by the driving means 40 and 51 in the axial and revolving directions. In such a constitution, an optical head perform the focusing and tracking control operations. Then a light reflecting part 54 is added in the same side as the lens 25 against the center axis of the part 5 together with a position detector 6 which contains a light source 60 and plural photodetectors 61 and is set opposite to the part 54.

Description

Detailed Description of the Invention

(Table of Contents) Industrial Application Field of the Prior Art (FIGS. 5 to 6) Problem to be Solved by the Invention (FIG. 7) Means for Solving the Problem (FIG. 1) Action Embodiment (a) One Description of Embodiments (FIGS. 2 to 4) (b) Description of Other Embodiments Effects of the Invention

[0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical head for driving an objective lens for irradiating an optical disk with light in a focus and track direction.

The optical disk device (including the magneto-optical disk device) has an advantage that it has a larger storage capacity than the magnetic disk device, but it is more difficult to control the position of the light beam than the magnetic disk device.

The position control of the light beam includes a track servo for a track following operation with respect to the eccentricity of the optical disk and a focus servo for a focus positioning for the surface wobbling of the optical disk, and a two-dimensional actuator is provided in the optical head. used.

Among these two-dimensional actuators, the one that performs focusing and tracking by sliding and oscillating with respect to the axis has good mechanical vibration characteristics and the optical axis is easy to move. There are advantages.

In such an optical head, it is required that the detection of the swing amount and the direction of the two-dimensional actuator greatly contributes to the stability of the servo and can be accurately detected.

[0007]

2. Description of the Related Art FIG. 5 is an explanatory diagram of an optical disc, and FIG. 6 is an explanatory diagram of a conventional technique. As shown in FIG. 5, an optical head (carriage) 2 for irradiating a light beam onto the optical disc 1 is rotated by a motor (not shown) with respect to the optical disc 1 (magneto-optical disc) 1 rotated by a spindle motor (not shown). It is driven in the radial direction and seeks.

On the other hand, the minute amount such as eccentricity of the optical disc 1 is
By the two-dimensional actuator 3 provided on the carriage 2,
The objective lens 25 has a function of following the axis 41 by driving the shaft 41 in the sliding direction and the swinging direction.

[0009] The movements of the two are well linked to each other, and are important for realizing stable and quick access. To this end, detecting the swing amount and direction of the two-dimensional actuator 3 by some method contributes to the stability of the servo.

In the conventional optical head 2, as shown in FIG. 6, a fixed portion 4 having a magnetic circuit 40 and a central axis 41 is fixed to the carriage 2 and a movable portion 5 provided with an objective lens 25.
The center shaft 41 is fitted in the hole 52 of the center shaft 41 so as to be movable in the sliding direction and the swinging direction of the center shaft 41, and the focus / track coil 51 is provided in the core 50 of the movable part 5.

In such a structure, light from a light emitting source (not shown) enters the objective lens 25 through the prism 24, irradiates the optical disc 1 with convergent light, and a focus current is applied to the focus / track coil 51. The movable portion 5 is moved in the sliding direction of the central shaft 41 to perform focusing operation, and the focus / track coil 51 is moved.
A tracking current is passed to move the movable portion 5 in the swinging direction of the central shaft 41 to perform a tracking operation.

In such an optical head 2, the number of moving tracks is counted by the track error signal detected from the return light passing through the objective lens 25 during the seek operation, and when the objective lens 25 moves, the count goes wrong. Therefore, the focus / track coil 5 is detected by detecting the position of the objective lens.
A track current is applied to the lens 1, and a lens lock operation for fixing the position of the objective lens 25 in the track direction is performed.

For this purpose, it is necessary to detect the position of the objective lens 25, and a mounting portion 53 is provided on the side opposite to the objective lens 25 with respect to the central axis of the movable portion 5, and the mounting portion 53 has a light emitting portion ( LED) 60 is provided, and a two-divided photodetector 61 is provided at a position opposed to this, and the two-divided photodetector 6 is provided.
The position of the objective lens 25 was detected from the output difference between the two photodetectors No. 1 and No. 1.

By doing so, the light emitting source 60 can be provided in the movable portion 5 without disturbing the speed of light of the objective lens 25.

[0015]

FIG. 7 is a diagram for explaining the problems of the prior art. As shown in FIG. 7 (A), the shaft 41 of the fixed portion 4 and the hole 52 of the movable portion 5 need to be provided with a gap of about 10 μm because the movable portion 5 is movable with respect to the shaft 41. There is.

Therefore, as shown in FIG. 7B, when the carriage 2 moves at a high acceleration due to the seek operation, the fixing portion 4 is fixed to the carriage 2, and the shaft 41 has the hole 52. The movable part 5 is moved by contacting the wall in the moving direction.

At this time, depending on the positional relationship between the shaft 41 and the hole 52, the contact position may be as shown in FIG. 7C. In this case, for example, from the center of the shaft to the objective lens 25. And the distance L from the center of the axis to the light emitting section 60 are different, and the movement on the side of the objective lens 25 and the movement on the side of the light emitting section 60 across the axis are not equivalent.

Therefore, the conventional technique has the following problems. The position of the objective lens 25 cannot be detected accurately, and in the optical disc, since the track interval is several microns, the influence of such a difference in contact position is great.

Therefore, when servo control is performed depending on the position of the objective lens 25, an unstable state occurs. Therefore, it is an object of the present invention to provide an optical head that can accurately detect the position of an objective lens even if the contact position between the shaft and the hole changes.

[0020]

FIG. 1 shows the principle of the present invention. According to claim 1 of the present invention, the fixing portion 4 having the shaft 41 is provided.
And a movable portion 5 having a hole portion 52 fitted into the shaft 41, the movable portion 5 is provided with an objective lens 25 for irradiating the optical disc 1 with light from the light emitting source 20, and the driving means 40, 51 In an optical head that drives the movable portion 5 in the axial direction and the rotational direction to perform focusing and tracking,
A light reflecting portion 54 provided on the same side as the objective lens 25 with respect to the central axis of the movable portion 5, a light source 60 placed opposite to the light reflecting portion 54, and a plurality of photodetectors 61. And a position detector 6 having the same.

According to claim 2 of the present invention, in claim 1,
The light reflecting portion 54 is connected to the objective lens 2 of the movable portion 5.
It is characterized in that it is provided in the lower part of 5. Claim 3 of the present invention
According to claim 1 or 2, the light reflecting portion 54 is formed of a light reflecting tape provided on the movable portion 5.

A fourth aspect of the present invention is characterized in that, in the first, second or third aspect, the position detector 6 is constituted by providing the photodetectors 61 on both sides of the light source 60. Claim 5 of the present invention is claim 1 or 2 or 3 or 4
In the above, the driving means 40 and 51 are provided with the magnetic circuit 40 provided in the fixed portion 4 and the coil 5 provided in the movable portion 5.
It is characterized in that it is configured by 1.

[0023]

In the first aspect of the present invention, since the position is detected on the same side as the objective lens 25, the shaft 41 and the hole 52 are provided.
The position of the objective lens 25 can be accurately detected irrespective of the contact position relationship between the movable lens 5 and the movable portion 5, the light reflecting portion 54 is provided, and the position detector 6 having the light source 60 and the light detector 61 is provided. Since the position is detected, it does not interfere with the light flux of the objective lens 25, and it is not necessary to provide a light source or the like on the movable section 5, and since no mounting section is required, the movable section 5 can be made lighter and the mechanical vibration characteristics can be improved. Is improved.

In the second aspect of the present invention, the light reflecting portion 54 is
Since the movable portion 5 is provided below the objective lens 25, the light reflecting portion 54 can be provided without processing the objective lens 25.
Can be made flat and the detection accuracy can be easily improved.

In the third aspect of the present invention, the light reflecting portion 54 is
Since it is composed of the light reflecting tape provided on the movable part 5, it can be realized simply by attaching the reflecting tape, and can be easily realized. In the fourth aspect of the present invention, since the position detector 6 is configured by providing the photodetectors 61 on both sides of the light source 60, the position of the objective lens 25 can be easily detected from the light reflected by the light reflecting portion 54. it can.

In the fifth aspect of the present invention, the driving means 40, 5
Since 1 is composed of the magnetic circuit 40 provided in the fixed portion 4 and the coil 51 provided in the movable portion 5, high-speed (for example, 3 to 4 kHz) vibration operation can be realized.

[0027]

【Example】

(a) Description of an Embodiment FIG. 2 is a configuration diagram of an optical head of an embodiment of the present invention, FIG. 3 is a configuration diagram of an embodiment of the present invention, and FIG. 4 is an explanatory diagram of an embodiment of the present invention.

In the figure, the same components as those shown in FIGS. 1, 5 and 6 are designated by the same symbols. In FIG. 2, the optical head 2 is a semiconductor laser 20 which is a light emitting source.
The light from the parallel light is collimated by the collimator lens 21, and is transmitted through the composite element 22 such as the polarization beam splitter to the prism 2
3. The light enters the objective lens 25 from the prism 24, and is converged on the optical disc 1 by the objective lens 25.

The reflected light from the optical disc 1 passes through the prisms 24 and 23 through the objective lens 25, enters the composite element 26 at the composite element 22, passes through the cylindrical lens 27 from the composite element 26, and is divided into four photodetectors 28. Incident on.

As is well known, the focus error signal FES, track error signal TES, ID, and data signal are detected from the four photodetection currents of the four-division photodetector 28, and the focus servo control is performed by the focus error signal. Track servo control is performed by the track error signal.

As shown in FIG. 3, the movable portion 5 is provided with the objective lens 25 at one end, has a hole portion 52 at the center, and has a core 50.
A flat focus coil 51a and a flat track coil 51b are provided on the side surface of the, and the lower surface of the objective lens 25 is a flat surface, and a reflective tape 54 is attached.

On the other hand, the fixed portion 4 is provided with a shaft 41 at the center and a magnetic circuit 40. The position detector 6 is provided so as to oppose the reflection tape 54 of the movable portion 5. As shown in FIG. 4, a light source (LED) 60 is provided at the center and photodetectors 61 are provided on the left and right sides thereof.

With this arrangement, the movable portion 5 moves in the slid direction of the shaft 41 by passing the focus current to the focus coil 51a by the above-mentioned focus servo control, and the focus position of the objective lens 25 becomes the optical disc 1. It can be controlled according to the surface runout.

When a track current is applied to the track coil 51b by the track servo control described above, the movable portion 5 moves in the swinging direction of the shaft 41, and the track following control is performed according to the eccentricity of the optical disk 1. It will be possible.

On the other hand, when the lens lock operation is performed, such as during seek operation, the output of the position detector 6 is used, and the light from the light source 60 of the position detector 6 is moved to the movable portion 5 as shown in FIG.
The light reflected by the reflective tape 54 of the above is received by each photodetector 61, the difference between the detection outputs from each photodetector 61 is taken, a lens position signal is created, and the track coil 51
The servo control is performed so that the objective lens 25 does not move.

Similarly, at the time of seeking for a relatively short distance, the track coil 51b is driven to swing the movable part 5 to position the objective lens 25 on a desired track to enable high speed access. A double servo system is used in which the carriage 2 is moved by a motor (not shown) to return the objective lens 25 to the original position. The output of the position detector 6 is used as a control signal for the motor at that time.

Since the position of the movable portion 5 is detected on the side of the objective lens 25 in this manner, the position of the objective lens 25 can be accurately adjusted even if the contact position changes due to the mechanical gap between the shaft 41 and the hole 52. Can be detected.

The movable tape 5 is provided with the reflective tape 5.
Since only 4, the light weight and small size of the optical head 2 can be realized without disturbing the light flux of the objective lens 25.

Further, since the light reflecting portion is provided on the lower surface of the objective lens 25, a flat light reflecting portion can be easily formed, and since the reflection tape 54 is attached, mirror finishing for reflection is not necessary and the cost is low. realizable.

(B) Description of Other Embodiments In addition to the above-described embodiments, the present invention can be modified as follows. Although the magneto-optical disk device has been described as an example, it can be applied to an optical disk device.

The light reflecting portion 54 may be provided in the objective lens portion, or the surface of the objective lens may be mirror-finished. An optical system such as a light source 20 is provided outside the carriage 2,
Alternatively, only the carriage 2 may be moved.

Although the example in which two photodetectors 61 are provided has been described, three or more photodetectors 61 may be provided. Although the present invention has been described with reference to the embodiments, various modifications are possible within the scope of the gist of the present invention, and these modifications are not excluded from the scope of the present invention.

[0043]

As described above, according to the present invention,
It has the following effects. Since the position is detected on the same side as the objective lens 25, regardless of the contact position relationship between the shaft 41 and the hole 52,
The position of the objective lens 25 can be accurately detected.

The movable portion 5 is provided with the light reflecting portion 54, and the light source 6
Since the position detector 6 having 0 and the photodetector 61 is provided and position detection is performed by the reflection type, there is no obstruction to the light flux of the objective lens 25, and it is not necessary to provide a light source or the like on the movable portion 5, and it is mounted. Since it is not necessary to provide a part, the movable part 5 can be made lighter,
Mechanical vibration characteristics are further improved.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of an optical head according to an embodiment of the present invention.

FIG. 3 is a configuration diagram of an embodiment of the present invention.

FIG. 4 is an explanatory diagram of an embodiment of the present invention.

FIG. 5 is an explanatory diagram of an optical disc device.

FIG. 6 is an explanatory diagram of a conventional technique.

FIG. 7 is a diagram illustrating a problem of the conventional technique.

[Explanation of symbols]

 1 Optical Disc 2 Optical Head (Carriage) 3 Head Actuator 4 Fixed Part 5 Movable Part 6 Position Detector 20 Light Emitting Source 25 Objective Lens 40 Magnetic Circuit 41 Axis 51 Focus Track Coil 52 Hole 53 Light Reflecting Part (Reflecting Tape) 60 Light Source 61 Photodetector

Claims (5)

[Claims] 1. A movable part (5) having a fixed part (4) having a shaft (41) and a movable part (5) having a hole (52) fitted in the shaft (41), and emitting light to the movable part (5). An objective lens (25) for irradiating the optical disc (1) with light from a source (20) is provided, and the movable part (5) is driven in the axial direction and the rotational direction by a driving means (40, 51) to perform focusing. In an optical head for tracking, the objective lens (2
5) A position detector having a light reflection part (54) provided on the same side as the light reflection part (54), a light source (60) placed opposite to the light reflection part (54), and a plurality of photodetectors (61). 6) An optical head provided with and. 2. The optical head according to claim 1, wherein the light reflecting portion (54) is provided below the objective lens (25) of the movable portion (5). 3. The optical head according to claim 1, wherein the light reflecting portion (54) is composed of a light reflecting tape provided on the movable portion (5). 4. The position detector (6) is connected to the light source (6).
The optical head according to claim 1, 2 or 3, wherein the photodetectors (61) are provided on both sides of (0). 5. The drive means (40, 51) comprises a magnetic circuit (40) provided on the fixed part (4) and a coil (51) provided on the movable part (5). The optical head according to claim 1, 2 or 3 or 4.