JPH01122040A - Optical disk tracking device - Google Patents

Abstract

PURPOSE:To perform a correct tracking by catching by Meissner effect the superconductive body fitted to a pickup part in the magnetic field generated by passing a current to the spiral superconductive wire rod fitted to a disk. CONSTITUTION:Superconductive bodies 7, 9, 11, 13, 15 and magnetic bodies 8, 10, 12, 14 are provided by alternately connecting the superconductive body in plural pieces to the magnetic body. By using these plural superconductive bodies the superconductive body can strongly the caught at the intermediate upper part of a track. The device consisting of such a superconductive body 1,lens 2 and movable part arm 3 is fitted to a movable control part 4 and freely movable in the horizontal direction. According to the disk being rotated the movable part is moved to the inside or outside of the disk by tracing the specified track. A correct tracking can be done without any control mechanism by catching by Meissner effect the superconductive body 1 fitted to the pickup part in the magnetic field generated by passing a current.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical disc tracking device.

2. Description of the Related Art An example of a conventional optical disk tracking device is shown in FIG. In FIG. 6, 8 is a recording medium, 9 is a condensing lens, 1
0 is a tracking signal and a detection device, 11 is a movable arm, and 12 is an arm control device. In the conventional optical disk tracking device described above, the reflected light from the recording medium 8 is focused by the condenser lens 9 and sent to the tracking signal detection device 1o. The tracking signal detecting device 10 detects whether the pickup section consisting of the condensing lens 9 and the movable arm 11 is accurately tracing the track of the recording medium 8, and outputs the deviation from the track. A signal indicating this deviation is sent to the arm control device 12, which controls the pickup section to accurately trace. FIG. 6 is a diagram showing a detection method of the tracking signal detection device 10.

In Fig. 6, 13 is a disk, 14, 15°, 16 is a recording medium, 17, 18, 19 is incident light, 20, 21, 22
is the intensity distribution of the reflected light, 23°24.25 is the 4-division photodiode for detection, 28.27.28 is the differential amplifier, 2
9,30°31 is an output terminal. Figure 6 shows the incident light 17
is accurately incident on the track of the recording medium 14, and the intensity distribution 20 of the reflected light is symmetrical. This reflected light is received by the 4-split detection photodiode 23, but since the intensity distribution of the reflected light is symmetrical, it is The signal levels of C+D and C+D are the same. The differential amplifier 26 performs the following calculation.

(A0B) - (C+D) ・・・・・・・・・・・・
(1) Therefore, the output from the differential amplifier 26 becomes zero.

FIG. 6B shows a case where the tracking is shifted to the left, and the intensity distribution of the reflected light is also large on the left side. Therefore, the level of A+B in the four-division photodiode for detection is higher than C+D, and the output of the differential amplifier 27 becomes a positive signal. Further, FIG. 6C shows a case where the tracking is shifted to the right, and the intensity distribution 19 of one reflected light becomes stronger on the right side. Then, in the four-division photodiode for detection, A-1-B, pc-
(If the level of -D is large, the output from the differential amplifier 28 becomes a negative signal.

Problems to be Solved by the Invention However, with the above method, it is necessary to use a photodiode and a differential amplifier to detect tracking errors, and it is also necessary to have a high-precision servo drive mechanism to control the movable arm. However, there was a problem in that the mechanism was complicated.

In view of this point, the present invention provides a tracking mechanism with a simple configuration.

Means for Solving the Problems The present invention provides an optical disc pickup arm to which a superconducting material having a width substantially the same as the track width of the optical disc is attached, and an optical disc to which a spirally closed wire of the superconducting material is attached. This is an optical disc tracking device consisting of:

How it works: A magnetic field is created by passing a current through a closed superconducting spiral wire attached to an optical disk, and the superconducting material in the pickup arm is caught in this magnetic field by the Meissner effect, allowing accurate tracking. .

Embodiment FIG. 1 shows an embodiment of an optical task tracking device according to the present invention. In FIG. 1, 1 is a superconductor, 2 is a condenser lens, 3 is a movable arm, 4 is a movable part control rod, and 6 is an optical disk. This optical disk has a closed spiral thin wire of superconducting substance attached along the track, some of which are indicated by a, b, c, and d in the figure. The current is in lines a and C
In FIG. 1, it flows approximately from right to left, and at lines d and 1, it flows approximately from left to right. Figure 2A shows the magnetic field generated by this superconducting wire and the current flowing through it. Second
In Figure A, lines a, b, c, d are lines a, b, c in Figure 1.
, d, and there is an optical disc track between b and c, but a and b.

There is no track between c and d. Also, in lines a and c, current flows from the back to the front of the paper, and in lines d and d, current flows from the front to the back. As shown in the figure, the magnetic field generated by this current is a downward magnetic field at the center of line C, a magnetic field from left to right on line C, and a magnetic field from right to left on line C. is occurring. When the superconductor 1 is placed between the wires 1 and 1, it floats in the air due to the Meissner effect due to the downward magnetic field. In addition, since there are opposite magnetic fields in the horizontal direction, the magnetic field is fixed at the midpoint of the track where the forces from the left and right are balanced due to the Meissner effect. Figure 2B
shows a case where the superconductor 1 is slightly shifted to the right. At this time, if it shifts to the right, the influence of the downward magnetic field weakens and the right side of the superconductor falls down a little, and the influence of the leftward magnetic field above line C increases, the force to the left increases, and the superconductor Return to the center of the track. As mentioned above, the superconductor 1 is fixed at the center of the track. Figure 3 shows a diagram in which a plurality of superconductors shown in Figure 2 are connected alternately with magnetic bodies.
11, 13, and 15 are superconductors, and 8 degrees and 10, 12, and 14 are magnetic materials. Further, the distance between adjacent superconductors is equal to the distance between tracks on an optical disk. By using a plurality of superconductors as shown in FIG. 3, the superconductors can be more strongly captured above the middle of the track. The superconductor shown in FIG. 3 corresponds to the superconductor 1 shown in FIG. Now, returning to FIG. 1, it is attached to a movable part control rod 4 consisting of a superconductor 1, a lens 2, and a movable part arm 3, but can move freely in the horizontal direction.

As the disk rotates, the movable part traces a predetermined track and moves to the inside or outside of the disk. FIG. 4 schematically shows the structure of a linear superconducting thin wire attached to a disk. As shown in the figure, when these wires are closed and current is applied, current flows in the opposite direction in the adjacent wires.

Effects of the Invention By attaching a closed superconducting wire to the disk and passing a current through it, the superconductor attached to the pick-up section is caught in the magnetic field by the Meissner effect, allowing accurate operation without a control mechanism. This allows for accurate tracking, and its practical effects are significant.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of the optical disk superconducting tracking device of the present invention, Fig. 2 is an explanatory diagram of the tracking method in the same embodiment, Fig. 3 is a structural diagram of the superconductor attached to the pickup section, and Fig. 4 is FIG. 5 is a structural diagram of a spiral superconductor attached to an optical disk, FIG. 5 is a configuration diagram of a conventional trunking method, and FIG. 6 is an explanatory diagram of a conventional tracking error detection method. 1...Superconductor, 2...Condensing lens,
3...Movable part arm, 4...Movable part control rod. Name of agent: Patent attorney Toshio Nakao and 1 other person5-
...Optical disc Figure 1 Figure 2 '7. C/, I/, 73.75-Electromotive groove material8.
/Q, 12.14-One microplate Fig. 3/1 mu No. 4 Country Fig. 5 Q Fig. 6

Claims (1)

[Claims] An optical disk pickup arm is provided with a superconductor having a width substantially the same as the width of the track of the optical disk, and a spiral formed of the superconductor is attached along the track of the optical disk. 1. An optical disc tracking device comprising an optical disc to which a shaped and closed wire is attached.