JP2556855B2 - 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 optically recording and reproducing information, and particularly to focusing control and tracking control of an optical head integrally driven by a movable part. Performance improvement and reliability improvement.

[Conventional technology]

Reference 1 "Optical integrated circuit of optical disk pickup"
(Ura, Suhara, Nishihara, Oyama, 85 Optical Memory Symposium pp
113-120), in the case of constructing an optical head device using an optical integrated circuit (optical IC) pickup, the light-collecting spot by the irradiation light from the optical IC pickup is used as the information recording medium. In order to follow the above recording pit accurately, it is necessary to drive the entire optical IC pickup. Therefore, FIG. 12 shows a configuration of an optical head device capable of focusing control and tracking control by using the conventional technique. In the figure, (1) is an optical IC-based pick-up body (hereinafter simply referred to as "optical pick-up") as an optical head body, and this optical pick-up (1)
Is composed of a semiconductor laser (2), a photodetector (3), a converging grating coupler (4), a beam splitter (5), and the like. The light emitted from the optical pickup (1) is condensed on the information recording medium (6) via the condensing grating cupper (4). (7) is a recording pit provided on the information recording medium (6). (8a) (8b)
Is a damper for holding the movable part (12) holding the optical pickup (1), (9a) and (9b) are coils for controlling a trading instrument, and (10a) and (10b) are magnets. Also (11a) (1
1b), (11c) and (11d) are leads from the movable part (12). The focusing control coil (not shown) is wound inside the movable portion (12).

Next, the operation of the conventional optical head device based on the above configuration will be described. First, the light emitted from the semiconductor laser (2) is injected into a conductor thin film waveguide layer (not shown) of the optical pickup (1), and the laser light guided in the waveguide layer is collected by the focusing grating. The plastic (4) focuses and irradiates the information recording medium (6). Next, after reading the signal pits (7) on the information recording medium (6), the reflected light from the information recording medium (6) is re-dielectric thin film by the condensing grating cupper (4). Guided into the waveguide. Thereafter, the guided laser light is symmetrically divided into two by the beam splitter (5) at an angle of 30 degrees or less with respect to the traveling direction of the laser light. This two-divided guided light is converted into an electric signal by the photodetector (3). The output from this photodetector is the lead wire (11a) (11
b) It is possible to obtain the focusing control signal, the tracking control signal, the information reproducing signal, etc. by taking out using (11c) and (11d) and performing an arithmetic operation by an external electric circuit (not shown). Note that details of the operation and the like are described in the above-mentioned Document 1 (Optical disc pickup is made into an optical integrated circuit).

Tracking control coils (9a) (9b) according to the tracking control signals obtained by these external electric circuits.
The movable part is driven by passing a current through the track, and the track follows.

The coil (9a) (9b) and the magnet (10
(a) and (10b) are for tracking control, and the focusing control coil and the magnet are arranged inside the movable part (12) in the invisible part of the figure. Then, focusing control is also performed by the focusing control signal. Since the focusing control coil and the tracking control coil are arranged in the movable part (12),
Lead lines are also required for these.

[Problems to be solved by the invention]

A conventional optical head device using an optical IC pickup has required a large number of lead wires with one end connected to a movable part and the other end connected to a fixed part. For this reason, there is a problem in that the large number of lead lines limit the movement of the movable portion that holds the optical IC pickup and deteriorate the so-called servo characteristics such as current sensitivity and frequency characteristics of the movable portion.

The present invention has been made in order to solve the above problems, and an object thereof is to obtain an optical head device having good servo characteristics by eliminating a lead wire from a movable part.

[Means for solving problems]

The optical head device according to the present invention eliminates the lead wire from the movable part and transmits the signal and the energy by the rotary transformer.
In the invention, the optical head main body is rotated and is movable in the direction of the rotational axis, and the focus of the optical head main body with respect to the information recording medium is controlled by moving the rotational body in the axial direction. Focusing control means, tracking control means for controlling tracking of the optical head main body with respect to the information recording medium by rotating the rotary body around the axis, fixed body provided opposite the rotary body, The rotating body and the fixed body are provided with at least one pair of coils respectively electromagnetically coupled to each other, and the coils are provided for supplying necessary energy to the optical head body or transmitting an output signal from the photodetector. According to a second aspect of the invention, in addition to the means of the first aspect of the invention, the rotating body is provided with an output signal of the photodetector. A reproduction signal corresponding to information recorded on said information recording medium by a Fuokashingu control signal, is provided with a detecting means for outputting respectively a tracking control signal.

[Work]

The optical head device according to the present invention comprises a rotary transformer composed of the rotary body and the fixed body, and a coil provided by electromagnetically coupling the rotary body and the fixed body to each other. A signal or energy is transmitted between the movable parts, and a lead line from the movable parts to the fixed parts is unnecessary.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a movable part of an optical head device according to an embodiment of the present invention, FIG. 2 is a perspective view of a movable part and a fixed part, FIG. 3 is a sectional view, and FIG. It is a block diagram which shows the flow of a signal etc.

In the figure, (1) is an optical IC type pickup (hereinafter simply referred to as an optical pickup) as the main body of the optical head,
This is the same as that shown in the conventional example. The optical pickup (1) is a semiconductor laser (2), a photodetector (3),
It is composed of a condensing grating cutter (4), a beam splitter (5), and the like. Further, (13) is an integrated electronic circuit composed of a head amplifier servo amplifier, and is placed at a place close to the optical pickup (1). (12) indicates the optical pickup (1) with arrow A
A rotating body (14a) capable of rotating in the direction of the axis (17a) and moving in the direction of the axis (17a) (arrow B).
(14b) is a winding provided on the rotating body (12), (16)
Is a fixed body provided opposite to the rotating body (12), (15
a) and (15b) are the above windings (14) on the inner circumference of this fixed body (16).
The windings are provided so as to face a) and (14b), respectively.
The winding (14a) is electromagnetically coupled to the winding (15a), the winding (14b) is electromagnetically coupled to the winding (15a), and the winding (14b) is electromagnetically coupled to the winding (15b). Is taking. In addition,
Such a rotary transformer is known, and for example, Sakata et al.
"Rotary Transformer", National Technical Report, Vol. 18, No. 4, pp. 357-369 (8th 1972). Further, (17) is a support shaft for supporting the rotating body (12), (16a) is a bearing portion, and (18) is the rotating body (12).
A ring-shaped focusing control coil provided on the internal protruding portion (12a) of the coil, (19) a ring-shaped magnet provided on the fixed body (16) so as to surround the focusing control coil (18). , (20) are tracking control coils provided on the rotating body (12), and (21) are magnets provided on the fixed portion (16) facing the tracking control coils (20).

The electronic circuit (13) processes the output signal of the photodetector (3) to generate a reproduction signal corresponding to the information recorded on the information recording medium (6), a focusing control signal and a tracking control signal. It is used as a detecting means for outputting. Further, the coil (18) and the magnet (19) constitute focusing control means, and the coil (20) and the magnet (21) constitute tracking control means.

Next, the operation will be described. Here, the operation of the optical pickup (1) is the same as that of the conventional example, and will be omitted. In this embodiment, a drive current is supplied from the electronic circuit (13) to the semiconductor laser (2), and the output line from the photodetector (3) on the optical pickup (1) is connected to the electronic circuit (13). ing. The output of the photodetector (3) is amplified and calculated by the electronic circuit (13), and as a result, a focusing control signal, a tracking control signal, and an information reproduction signal can be taken out as outputs. Among these, the information reproduction signal is transmitted from the winding (14b) provided on the rotating body (12) to the winding (15) provided on the fixed body (16).
transmitted to b).

The support shaft (17) is fixed to the rotating body (12) and serves as the center of rotation of the rotating body (12). Furthermore, the focusing coil (18) is a ring-shaped magnet (19).
Since it is arranged in the magnetic field constituted by, the rotating body (12) slides in the direction of the axis (17a) by applying a desired current to the focusing control coil (18), It becomes possible to perform focusing control.

Next, by passing a desired current through the tracking control coils (20a) (20b), the rotating body (12) is moved to the axis (17).
It can be rotated around a) and tracking control can be performed. The drive current for these focusing control operation and tracking control operation can be supplied from a servo amplifier (not shown) in the electronic circuit (13).

That is, as shown in FIG. 4, the coil (15a) provided on the fixed body (16) is energized by a preferably high-frequency current C supplied from a power source (not shown). The high frequency voltage C ′ induced in the coil (14a) provided opposite to the coil (15a) is rectified by a rectifier circuit (not shown) provided in the electronic circuit (13), and the optical pickup (1) is rectified.
Necessary drive current D of the semiconductor laser (2), a processing circuit (not shown) for the output signal E of the photodetector (3), a tracking control signal and a focusing control signal obtained by this processing circuit. It is supplied as electric energy required for a servo amplifier (not shown) to be processed, a driving current F supplied to the focusing control coil (18) and the tracking control coil (20) via the servo amplifier. The information reproduction signal G output from the electronic circuit (13) is passed through the pair of coils (14b) (15b) to the fixed portion (16).
On the side as signal G '.

Although the two coils (14a), (15a), (14b), and (15b) in the figure are used as the coils constituting the rotary transformer in the above embodiment, the coil set is not limited to this. It may be a pair. For example, in another embodiment shown in FIG. 5, the coil (22) is provided on the rotating body (12) and the coil (23) is provided on the fixed body (16). .

Further, the coils and magnets for focusing control and tracking control are provided inside the rotating body (12) or the fixed body (16), but these coils and magnets may be provided at any positions, for example, as shown in FIG. As shown in the figure, the focusing control coil (18) and the ring-shaped magnet (19) are provided in the upper part of the figure, and the track control coils (20a) (20b) and the magnets (21a) (21b) are provided in the lower part of the figure. Good. Furthermore, the sixth
As shown in the figure, the focusing control coil (24a) and the tracking control coil (24b), the focusing magnet (25a) and the tracking magnet (25b) are provided in the lower part of the figure, and the same effect as the above embodiment is obtained. Play.

7 to 9 show still another embodiment of the present invention. In this embodiment, a focusing control coil (18) and a tracking control coil (20) are provided in a fixed body (16), Magnets (19 (21a) (21
b) is provided on the rotating body (12).

In this embodiment, as shown in FIG. 9, the focusing control signal I is taken out to the fixed body (16) side as I'through the coils (14a) and (15a), and the information reproduction signal G and the tracking control signal H are These are superposed and taken out to the fixed body (16) side as G'and H'through the coils (14b) and (15b). Then, a drive current F corresponding to the control signals I'and H'is supplied to the focusing control coil (18) and the tracking control coil (20) by a servo circuit (not shown) provided on the fixed body side to perform focusing control and tracking. I'm trying to control. In the case of this embodiment, the energy required to energize the focusing control coil (18) and the tracking control coil (20) can be directly supplied from the fixed body (16) side.
There is an advantage that the coils (14a) (15a) as the rotary transformer can be made small.

In addition, regarding the embodiment shown in FIGS. 7 to 9,
Various modifications can be made. For example, as shown in FIG. 10, focusing magnets (25a) (25b) for focusing and tracking are provided at the lower part of the rotating body (12) in the figure (25a) (25b).
A focusing control coil (24a) and a tracking control coil (24b) facing each other may be provided below the fixed body (16).

Further, as shown in FIG. 11, in the case where the energy is supplied and the signal is transmitted by a pair of coils (22) and (23) forming a rotary transformer, the focusing control coil (18) is a fixed body (16). In the upper part of the figure, the tracking control coils (20a) (21b) may be provided in the lower part of the fixed body (16) in the figure.

By the way, the electronic circuit (13) as the detecting means in each of the above embodiments is provided with the optical pickup (1) and the rotating body (1).
It is desirable to provide it in 2), but it is not necessarily limited to this and it may be provided in the fixed body.

〔The invention's effect〕

As described above, according to the present invention, the optical head main body is provided on the rotary body that constitutes the rotary transformer, and focusing control is performed by moving the rotary body in the direction of the rotary shaft to rotate around the rotary shaft. Tracking control is performed by moving the rotating body and coils fixed to the rotating body and the fixed body opposed to the rotating body, which are electromagnetically coupled to each other. Since the output signal from the optical head is configured to be transmitted, there is no need for a lead wire of the connection conductor from the movable portion, and there is an effect that servo performance and reliability are improved.

Further, according to the second aspect of the invention, the detecting means for processing the output signal of the photodetector to obtain the reproduction signal, the focusing control signal and the tracking control signal is provided in the rotating body together with the optical head main body. There is an effect that reliability is further improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of an optical head device according to an embodiment of the present invention, FIG. 2 is a perspective view showing a rotating body and a fixed body in the above embodiment, and FIG. 4 is a block diagram for explaining signal transmission in the above embodiment, and FIGS. 5 and 6 are cross sectional views showing second and third embodiments of the present invention, respectively. Fig. 7,
FIGS. 8 and 9 show a fourth embodiment of the present invention. FIG. 7 is a perspective view of a main part assembly, FIG. 8 is a sectional view, and FIG. 9 is a block diagram showing signal transmission. Is. 10 and 11 are sectional views showing fifth and sixth embodiments of the present invention, respectively.
FIG. 12 is a perspective view showing a conventional device. In the figure, (1) is an optical head main body, (2) is a semiconductor laser as a light source, (3) is a photodetector, (6) is an information recording medium, (12) is a rotating body, and (13) is detection. Electronic circuits as circuits, (14a) (15a), (14b) (15b), (22)
(23) is a coil, (16) is a fixed body, (17a) is a rotating shaft,
(18) and (19) are focusing control coils and magnets as focusing control means. (20) and (21) are a tracking control coil and a magnet as tracking control means. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (5)

(57) [Claims] 1. A light source section and light projected from the light source section are condensed and irradiated onto an information recording medium, reflected light from the information recording medium is received, and a signal corresponding to information contained in the reflected light is received. An optical head main body having a photodetector for outputting, a rotary body capable of rotating the optical head main body and moving in the direction of a rotary axis, and of the optical head main body by moving the rotary body in the axial direction. Focusing control means for controlling the focus on the information recording medium, tracking control means for performing tracking control on the information recording medium of the optical head main body by rotating the rotating body around the axis, and facing the rotating body. Required for the optical head main body, which is provided with at least a pair of coils respectively provided by electromagnetically coupling the fixed body and the rotating body and the fixed body Energy supply and an optical head device in which transmission of the output signal from the optical detector and to perform through the coil. 2. The light source unit is a semiconductor laser, and the one for converging and irradiating the light projected from the light source unit onto the information recording medium is a conductor for guiding the laser light emitted from the semiconductor laser formed on the substrate surface. A thin film waveguide layer, and a condensing grating cut formed on the conductor thin film waveguide layer by a group of unequal-spaced curves to converge the laser light to a point on the information recording medium outside the conductor thin film waveguide layer. The optical head device according to claim 1, wherein the optical head device comprises a plastic. 3. The focusing control means comprises a magnet provided on the rotating body, and a focusing control coil provided on the fixed body facing the magnet. Alternatively, the optical head device according to the second aspect. 4. The tracking control means comprises a magnet provided on the rotating body and a tracking control coil provided on the fixed body so as to face the magnet. The optical head device according to any one of items 1 to 3. 5. A light source section and a light projected from the light source section are condensed and irradiated onto an information recording medium, reflected light from the information recording medium is received, and a signal according to information contained in the reflected light is received. An optical head main body having a photodetector for outputting, a reproduction signal corresponding to information recorded on the information recording medium by processing an output signal of the detector, and a focusing control signal,
Detecting means for outputting the tracking control signal and
A rotating body which supports the optical head main body and the detecting means and can rotate them and can move in the direction of the rotational axis, and the information recording of the optical head main body by moving the rotating body in the axial direction. Focusing control means for controlling the focus on the medium, tracking control means for performing tracking control on the information recording medium of the optical head main body by rotating the rotary body around the axis, and provided facing the rotary body. A fixed body, at least a pair of coils respectively electromagnetically coupled to the rotating body and the fixed body, respectively, for supplying energy required for the optical head body and transmitting an output signal from the detecting means. An optical head device which is configured to perform the above through the coil.