JPS61220145A - Optical pickup - Google Patents

Abstract

PURPOSE:To prevent the generation of wastes due to wear and make an optical pickup small in size by floating an objective lens of the optical pickup with the force of magnetism to support it without contacting and giving focusing and tracking functions. CONSTITUTION:Exciting coils 26 and 27 having plural magnetic cores are arranged above, under, in the right of, and in the left of a permanent magnet ring 28 required gaps apart from the outside of the ring 28, and the ring 28 is supported without contacting by the magnetic force of coils 26 and 27. Inclination information is superposed to a fixed position current, which is flowed to exciting coils 26 to float and stop the ring 28 in a middle fixed position in the vertical direction, to control the attitude, and a focusing error signal is superposed to said current to perform the focusing servo control. Exciting coils 27 are so set that the control direction of the ring 28 is the radial direction of a recording medium 6, and a tracking error signal is superposed to a fixed position current, which floats and stops the ring 28 in a middle fixed position in the horizontal direction, to perform the focusing servo control.

Description

DETAILED DESCRIPTION OF THE INVENTION [Summary] The essential objective lens of an optical pickup is levitated by magnetic force and supported in a non-contact manner, and also performs focusing and tracking functions.

[Industrial application field]

The present invention relates to an optical pickup, and particularly to a method for performing focusing and tracking operations at high speed without contact.

[Conventional technology]

FIG. 6 is a block diagram of a conventional optical recording/reproducing device, in which 1 is a semiconductor laser serving as a light source, 2 is a collimating lens for collimating the light beam emitted from the semiconductor laser 1, 3 and 4 are optical elements for separating light beams, and are first polarizing beam splitters 3 and 174.
It is composed of a wave plate 4.

5 is an objective lens for condensing the light beam onto the recording medium 6, 7 is a second polarizing beam splitter that splits the reflected light beam from the recording medium 6 into two, 8 is a polarization plane detection element, and 9 is a light receiving lens. , 10 is a photodetector for reproducing magneto-optical signals, and information recorded on the recording medium 6 is output here.

11 is a reflection mirror for further dividing the reflected light beam from the recording medium 6 into two; 12 and 13 are a light receiving lens and a two-split photodiode for detecting a focus error signal;
4 and 15 are a light receiving lens and a two-split photodiode for detecting a track error signal.

16 is a carriage that houses the optical system, and a bearing 16
a and 16b, and is driven on the guide rail 20 in the radial direction of the recording medium 6 by a voice coil motor (not shown).

17 is a small actuator fixed to the carriage 16, and is a tracking mechanism that minutely drives the objective lens 5 in the radial direction of the recording medium 6.

18 is a spring that supports the objective lens 5; 19 is a spring 18;
A focusing mechanism is constituted by a small actuator that minutely drives the objective lens 5 supported by the recording medium 6 in a direction perpendicular to the surface of the recording medium 6.

[Problem that the invention seeks to solve]

The objective lens 5 in conventional big amplifiers is supported by an elastic member in this way, so the size cannot be reduced and it is not possible to obtain a high band.Also, since there are contact points, the elastic member is not worn out due to friction. There are drawbacks such as generation of debris.

The present invention was created in view of the above-mentioned conventional drawbacks, and an object of the present invention is to provide an optical pickup that can secure a high frequency band, does not generate wear debris, and can be made small in size.

[Means to solve the problem]

In FIG. 1, in the optical pickup of the present invention, a ring 28 of a permanent magnet is fitted around the outer periphery of an objective lens 5 that collects a beam of light irradiated onto a reflective optical medium 6 on which information is recorded and receives a beam of light reflected therefrom. match. Also, the ring 2
Excitation coil 2 having a plurality of magnetic cores on the top, bottom, left and right of the outside of 8
6.27 are arranged with a required gap between them, and the excitation coil 2
A light emitting element 21 that supports the ring 28 in a non-contact manner using the magnetic force of 6.27, optically detects the inclination of the ring 28, and controls the inclination of each of the excitation coils 26 and 27; A photodiode 25 is provided, each of the excitation coils 26 and 27 is servo controlled, and the objective lens 5 has focusing and tracking functions.

[Effect]

The ring 28 is vertically irradiated with a minute light spot from the light emitting element 21, and the reflected light is received by the split photodiode 25.
The inclination information of the ring 28 is obtained from the divided output.

A fixed position current is applied to a plurality of excitation coils 26 arranged above and below a permanent magnet ring 28 with a required air gap between them, so that the ring 28 levitates and stops at an intermediate fixed position in the vertical direction.
Attitude control is performed by superimposing the tilt information on this fixed position current, and focusing servo control is performed by superimposing a focusing error signal.

A plurality of excitation coils 27 are arranged on the left and right sides of a permanent magnet ring 28 with required air gaps, and the control direction of the ring 28 is set to be in the radial direction of the recording medium 6, and the control direction of the ring 28 is set to be in the radial direction of the recording medium 6, and Focusing servo control is performed by applying a fixed position current that causes the object to levitate and stop at a fixed position, and by superimposing a tracking error signal on this fixed position current.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

In order to make the explanation of the configuration and operation easier to understand, the same parts are denoted by the same reference numerals throughout the drawings, and repeated explanation thereof will be omitted.

FIG. 1 shows a block diagram of an optical recording/reproducing apparatus to which the present invention is applied. In the figure, 21 is a light emitting element necessary to know the inclination of the objective lens 5, 22 is a slit for extracting the light emitted from the light emitting element 21 in a spot shape, and 23 is a reflecting mirror.

The emitted light from the light emitting element 21 is incident and reflected perpendicularly to the surface of the ring 28, and the returned reflected light is separated by the beam splitter 24, and then divided into 25 split photodiodes (here, corresponding to the number of horizontal divisions of the excitation coil). (Using a 4-split type).

When reading information on the recording medium 6, it is necessary to properly focus and track the light beam emitted from the semiconductor laser 1 onto the recording medium 6. The excitation coil 26 having a magnetic core provides the focusing function at this time.

Further, the excitation coil 27 having a magnetic core has a tracking function. Reference numeral 28 denotes a permanent magnet ring fitted around the outer periphery of the objective lens 5, and the ring 28 is floated and supported in the air in a non-contact state during control.

FIGS. 2, 3, and 4 show a perspective view, a top view, and a front view, respectively, of the objective lens floating mechanism of the present invention.

In FIGS. 2 to 4, there is a permanent magnet ring 28 in the center that integrally fits and supports the objective lens 5, and four excitation coils 2 are placed above the ring 28 with a required gap between them.
Similarly, four excitation coils 26a to 26d are arranged at the lower part of the ring 28 with a required gap between them.
゛ is placed.

Furthermore, two excitation coils 27a to 27b are arranged on the left and right sides of the ring 28 with a required gap in between.

The magnetic poles of the permanent magnet ring 28 and each excitation coil are oriented as shown in FIG. 1, for example.

Focusing error signal is 2-split photodiode 1
3, and based on this signal, it is determined whether the objective lens 5 is close or far from the recording medium 6, and the excitation coils 26a to 26d and 26a'' to 26d.

are controlled separately, and the force applied to the ring 28 is changed to displace the objective lens 5 up and down.

The tracking error signal is a two-split photodiode 15
This signal is used to detect the left and right deviation of the light beam with respect to the track, and controls the excitation coils 27a and 27b to change the force applied to the ring 28 and displace the objective lens 5 left and right.

FIG. 5 shows an explanatory diagram of the principle of detecting the inclination of the objective lens according to the present invention. Regarding the tilt of the objective lens 5, a tilt signal is obtained from the four-segment photodiode 25.

When the objective lens 5 is not tilted (when the support ring 28 of the objective lens is in contact with the lower excitation coils 26a'' to 26d'' without any control), as shown in FIG. The light reception distribution of the split photodiode 25 is set so that the reflected light beam from the ring 28 is centered, and the light amount of each of the four divisions is stored in advance.

Next, during control, if the support ring 28 of the objective lens is tilted, the light receiving distribution of the four-segment photodiode 25 changes to the fifth.
It shifts as shown in figure ('b). By comparing the light amount of each of the four divided photodiodes 25,
Since the inclination of the support ring 28 of the objective lens is known, the excitation coils 26a to 26d and 26a' to 26d' exert (control the force) on the ring 28 to eliminate this inclination.
Performs tilt posture control.

〔Effect of the invention〕

As explained in detail above, according to the optical pickup of the present invention, it is possible to focus and track the objective lens in a non-contact state and in a high frequency band, and there is no generation of wear debris (and the size can be reduced). effective.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an optical recording/reproducing device to which the present invention is applied; Figs. 2, 3, and 4 are perspective views, a plan view, and a front view of the objective lens floating mechanism of the present invention; Fig. 5; 6 is a diagram illustrating the principle of detecting the inclination of an objective lens according to the present invention, and FIG. 6 is a block diagram of a conventional optical recording/reproducing apparatus. In the figure, 5 is an objective lens, 6 is a recording medium, and 26a
~26d and 26a'~26d' and 27a~
27b is an excitation coil, and 28 is a ring. $ Item! Month 1; It depends on the word button 4 Yu 1 Pi Ward 1 L a
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Claims (1)

[Scope of Claims] An objective lens (5) is provided that collects a beam of light irradiated onto a reflective optical medium (6) on which information is recorded and receives a beam of light reflected from the reflective optical medium (6). In this optical pickup, a permanent magnet ring (28) is fitted into the objective lens (5), and excitation coils (26), (27) each having a plurality of magnetic cores are arranged on the top, bottom, left and right sides of the outside of the ring (28). ) are arranged with a required gap between them, and the magnetic force of the excitation coils (26) and (27) is used to support the ring (28) in a non-contact manner, and the inclination of the ring (28) is optically measured. A light-emitting element (21) and a split light-receiving element (25) are provided for detecting and controlling the inclination of each of the excitation coils (26) and (27), and each of the excitation coils (26) and (27) An optical pickup characterized in that servo control is performed and the objective lens (5) has focusing and tracking functions.