JPH02195528A - Optical head - Google Patents

Abstract

PURPOSE:To reduce the thickness of the optical head by utilizing the Meissner effect of a superconductor. CONSTITUTION:The optical head consists of a movable part 13 which supports an objective lens 14 directing its optical axis in the direction perpendicular to flat plates 10, 11 on these plates and is provided with >=2 sets of coils 15, 16 in the opposite positions on the plane where two sheets of the flat plates 10, 11 face each other and a stationary part 17 which is a flat plate made of the superconductor provided in parallel with the flat plates 10, 11 between the coils 15 and 16 facing each other. The movable part 13 is floated from the stationary part 17 of the flat plate made of the superconductor by the magnetic field generated when currents are passed to the coils 15, 16 and the Meissner effect generated in the stationary part 17. The movable part 13 is moved in the direction perpendicular to or parallel with the plane plate thereof by controlling the currents to be passed to the coils 15, 16, by which focusing and tracking are executed. The optical head thickness of which is reduced in this is obtd. in this way.

Description

[Detailed Description of the Invention] [Summary] Regarding an optical head for writing or reading in an optical disk device, for the purpose of making the optical head thinner, it has a structure in which two flat plates face each other in parallel, and the flat plates a movable part that supports an objective lens with its optical axis directed in a direction perpendicular to , and has two or more sets of coils provided at opposing positions on opposing planes of the two flat plates, and between the opposing coils. The movable part is made up of a fixed part of a superconductor flat plate installed parallel to the flat plate, and the magnetic field generated when current is passed through the coil and the Meissner effect generated in the fixed part of the superconductor flat plate cause the movable part to become a superconductor. The movable part is levitated relative to a fixed part of a flat plate and the movable part is moved in a direction perpendicular or parallel to the flat plate surface by controlling the current flowing through the coil to perform focusing and tracking.

[Industrial application field]

The present invention relates to an optical head that performs writing or reading in an optical disk device.

[Conventional technology]

FIGS. 6(a) and 6(b) show two examples of conventional optical heads. (a) In the figure, a shaft 3 is provided between a pair of fixed magnets 1.2, and the shaft 3 is equipped with a movable object having an objective lens 4, a focusing coil 5, a tracking coil (not shown), etc. A portion 6 is provided so as to be slidable and rotatable, and focusing and tracking can be controlled by adjusting the currents supplied to the focusing coil and the tracking coil.

In addition, the one shown in FIG. 1(b) has an objective lens 4 and a focusing coil 5 between a pair of fixed magnets 1 and 2.
, the movable part 6 having the tracking coil 7 etc. is a leaf spring 8
, 9 to be movable vertically and horizontally, and focusing and tracking can be controlled by adjusting the current supplied to the focusing coil 5 and the tracking coil 7.

[Problem to be solved by the invention]

In the conventional optical head shown in FIGS. 6(a) and 6(b), separate focusing and tracking coils are required, and a certain number of coil turns is required, so the thickness d of the movable part 6 is There are problems such as the size of the head and the fact that the thinning of the head has reached its limit.

SUMMARY OF THE INVENTION In view of the above conventional problems, it is an object of the present invention to provide an optical head that can be made into one type.

[Means to solve the problem]

In order to achieve the above object, the optical head of the present invention has a structure in which two flat plates 10 and 11 face each other in parallel, and an objective lens whose optical axis is oriented in a direction perpendicular to the flat plates 10 and 11. 14, and two or more sets of coils 15 at opposing positions on opposing planes of the two flat plates 10.11,
16 and the opposing coil 15
, 16, and a fixed part 17 made of a superconductor flat plate provided in parallel with the flat plates 10 and 11, and the coil 15
, 16 and the Meissner effect generated in the fixed part 17 of the superconductor flat plate, the movable part 13 is levitated relative to the fixed part 17 of the superconductor flat plate, and the coils 15 and 16 are It is characterized in that focusing and tracking are performed by moving the movable part 13 in a direction perpendicular or parallel to the flat surface of the movable part 13 by controlling the flowing current.

[For production]

By adjusting the magnetic field strength of the coil 15 arranged on one flat plate surface and the coil 16 arranged on the other flat plate surface among the coils 15 and 16 of 2Mi or more, the movable part 13 is made into a flat plate. The movable part 13 can be moved in a direction perpendicular to the plane, thereby enabling focusing of the objective lens 14, and the movable part 13 can be moved in the horizontal direction by changing the magnetic field strength of each of two or more sets of coils. This enables tracking of the objective lens 14.

〔Example〕

FIG. 1 is a diagram showing a first embodiment of the present invention, (a)
is a plan view, and (b) is a cross-sectional view taken along line bb in figure a.

In the figure, reference numerals 10 and 11 are flat plates made of non-magnetic material, and the flat plates 10 and 11 are connected to each other in parallel with a cylindrical body 12 to form a movable part 13. An objective lens 14 is provided so that its front axis is perpendicular to the flat plates 10 and 11. Also, the flat plate 10
．． On the opposing surface of 11, there are a plurality of opposing Mi (four groups in the figure).
Coils 15 and 16 are provided. Furthermore, a fixing part 17 made of a flat plate made of superconducting material is provided between the opposing coils 15 and 16. Note that this fixing part 17 is, for example, a superconductor flat plate 1 as shown in FIG.
The inside of the fixing portion 8 is hollow, and a coolant 19 such as liquid nitrogen is allowed to flow therein to bring the fixing portion 17 into a superconducting state.

In the embodiment configured in this way, assuming that the four coils formed on the flat plate 10 are 01 to C4, and the four coils formed on the flat plate 11 are C5 to C8, C8 and C
s, Cz and C,, C, and C? , C4 and C8 form opposing pairs.

The number of turns and diameter of C5 to C8 are all the same, C+-C.

If the currents flowing in are respectively 1 to I, then rI=
Iz = I3 = Ta = Ia Is = Ib =! ? When a current of = Is = 1++ is applied and the fixed part 17 is brought into a superconducting state, a demagnetizing field is generated in the fixed part 17 due to the Meissner effect, causing the movable part 13 to levitate.

At this time, Itt and 1. When the current value is changed, the movable part 13 moves in the direction perpendicular to the flat plates 10 and 11. This enables focusing of the objective lens 14.

Also, for example, It −rz <l, = I4, Is = I
h < 1? = Is, and when the current flowing through two adjacent sets of coils and the current flowing through the other two sets are changed, a difference occurs in the amount of leakage magnetic flux, and the movable part 13 becomes flat plate 10.
．． Move in a direction parallel to 11.

This allows tracking of the objective lens 14.

FIG. 3 is a diagram showing another optical system of this embodiment, in which two hologram lenses 20 are used instead of the objective lens 14 in FIG.
, 21 are used to irradiate the optical disk with light from a laser light source 22, and the reflected light is received by detectors 23 and 24.

According to the first embodiment described above, since the coils 15 and 16 can be flat ring-shaped coils, the device can be made thinner (about 5 times thicker) than the conventional example shown in FIG.

FIG. 4 is a diagram showing a second embodiment of the present invention, (a)
is a plan view, and (b) is a cross-sectional view taken along line bb in figure a. In this figure, the same parts as in FIG. 1 are designated by the same reference numerals.

This embodiment has almost the same structure as the first embodiment, and the difference is that six sets of coils 15 and 16 are arranged along the circumference. This embodiment configured as described above has the same effects as the first embodiment, and also allows movement in six directions within a plane. Note that the coil is generally nu (n22
) holds true for

FIG. 5 is a diagram showing another example of the coil portion.

This has a ferromagnetic material 30 placed in the center of the coil 15 or 16, and requires less power to generate the same magnetic field than a case without the ferromagnetic material 30.

Note that the coils 15 and 16 can also be formed by printing.

〔Effect of the invention〕

As described above, according to the present invention, by utilizing the Meissner effect of a superconductor, it is possible to realize an optical head that is thinner than the conventional one.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a first embodiment of the present invention, Fig. 2 is a diagram showing a cross section of a fixed part of the embodiment of the present invention, and Fig. 3 is a diagram showing another optical system of the embodiment of the present invention. 4 shows a second embodiment of the present invention, FIG. 5 shows another example of the coil portion of the embodiment of the present invention, and FIG. 6 shows two examples of a conventional optical head. FIG. In the figure, 10.11 is a flat plate made of a non-magnetic material, 12 is a cylindrical part, 13 is a movable part, 14 is an objective lens, 15 and 16 are coils, and 17 is a fixed part made of a superconductor flat plate. (b) Cross-sectional view taken along line b-b of Figure 0 Diagram showing the first embodiment of the present invention Figure (Q) Plan view Diagram showing the second embodiment of the present invention Figure Diagram showing a cross section of the fixed part Diagram showing another optical system according to the embodiment of the present invention Diagram showing another example of the coil portion according to the embodiment of the present invention

Claims (1)

[Claims] An objective lens (14) having a structure in which one or two flat plates (10, 11) face each other in parallel, and the optical axis is directed in a direction perpendicular to the flat plates (10, 11). and at opposing positions on opposing planes of the two flat plates (10, 11).
A movable part (1) provided with more than one set of coils (15, 16)
3), and a fixed part (17) of a superconductor flat plate provided parallel to the flat plate (10, 11) between the opposing coils (15, 16), and a current is applied to the coil (15, 16). The movable part (13
) is levitated relative to the fixed part 17 of the superconductor flat plate, and by controlling the current flowing through the coils (15, 16), the movable part (13) is moved in a direction perpendicular or parallel to the flat plate surface for focusing. and an optical head that performs tracking. 2. Two flat plates (10,
2. The optical head according to claim 1, wherein the part that integrates the optical head (11) is a cylindrical body (12), and a part or all of the head optical system is configured inside the cylindrical body (12). 3. The coils (15, 16) are printed on the movable part (17), and a ferromagnetic thin film (30
2. The optical head according to claim 1, further comprising: ).