JPS6242350B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for performing servo control in a magnetic disk device using an optical disk device.

As the capacity of magnetic disk devices increases, it is required to use a servo plane for controlling the magnetic head as a data plane and to perform more precise servo control.

However, in recent years, the environment in which magnetic disk drives have been installed has become closer to that of general offices, and magnetic disk drives have come to be of the sealed disk head enclosure type. Misalignment occurs because the disks in the configuration have different degrees of expansion.
Accordingly, with conventional magnetic head positioning control in which a servo plane is provided on a separate disk, it is becoming difficult to position the magnetic head with respect to a desired track with the desired accuracy.

The purpose of the present invention is to satisfy the above-mentioned needs and defect correction all at once.The purpose of the present invention is to record servo information and track information using optical signals on a substrate, and to record servo information and track information on a substrate using a thin magnetic layer formed on the surface of the substrate. Record a desired information signal, record or reproduce the desired information signal with a magnetic head, detect the servo information and track information with an optical pickup provided in the magnetic head, and control the positioning operation of the magnetic head. In a magnetic disk device for inputting signals to a servo circuit, a concentric track portion has a reflective film layer interposed in the middle of a substrate made of a transparent material, and has a surface parallel to the surface of the substrate; This is achieved by a self-servo magnetic disk device characterized in that concentric guard bands having surfaces inclined with respect to the track portions are alternately formed on the reflective film layer.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an explanatory diagram of one embodiment of the present invention, and FIGS. 2 and 3 are explanatory diagrams of the operation.

In FIG. 1, a magnetic disk disk 1 is composed of a substrate 2 made of a light-transmitting material and a magnetic thin film layer 4 formed on both surfaces of the substrate and capable of magnetic recording. The substrate 2 is made up of a pair of light-transmissive substrates 21 and 22 joined together, and includes a concentric track portion TR having a surface parallel to the surface of the substrate, and a track portion TR having a surface parallel to the surface of the substrate.
A reflective film layer 3 formed by alternately forming concentric guard bands GB having surfaces inclined with respect to the TR is formed on the joint surface of the light-transmitting substrates 21 and 22.

In addition, to explain in detail one example of the method for forming the reflective film layer 3, concentric irregularities are formed in advance on the light-transmissive substrate 21 made of acrylic or the like by a stamping process, and then a reflective film made of a thin metal film such as aluminum is formed on the concentric irregularities. A film layer 3 is formed. Thereafter, a light transmitting material such as acrylic is casted on the reflective film layer 3 to form a light transmitting substrate 22.

Now, in this device, a device corresponding to a conventional servo head is an optical pickup 5 embedded in a magnetic head (not shown), and the optical pickup 5 includes at least one illumination optical fiber 5.
1 and deviation detection optical fibers 52 and 53 disposed on both sides thereof. On the other hand, the deviation detection unit 6 includes a light source 61 made of a semiconductor laser and photodetectors 6 such as photodiodes arranged on both sides of the light source 61.
The other end of the illumination optical fiber 51 is connected to the light source 61, and the deviation detection optical fiber 52, 53 is connected to the light source 61.
The other ends are opposed to photodetectors 62 and 63, respectively.

Next, the operation of the self-servo magnetic disk device will be described in detail. In FIG. 1, the light source 61
The laser beam 7 emitted from the optical pickup 5
The light is propagated through the illumination optical fiber 51 and illuminates the magnetic disk disk 1. The laser beam 7 irradiated onto the magnetic disk disc 1 passes through the magnetic thin film layer 4 formed on the surface, is reflected by the track portion TR of the reflective film layer 3 inside the substrate, and the reflected light 8 is again The light passes through the magnetic thin film layer 4 and enters the illumination optical fiber 51 again.

FIG. 2 is a diagram showing a state during on-track. The diameter of the illumination optical fiber 51 is approximately equal to the width of the track portion TR, and during on-track, all of the reflected light 8 from the track portion TR is transferred to the illumination optical fiber 5.
1 and never enters the deviation detection optical fibers 52 and 53 disposed on both sides of the illumination optical fiber 51. Therefore, the photodetectors 62, 63
It is determined that the outputs are balanced and that the on-track state is present.

FIG. 3 is a diagram showing the state during off-track, where the irradiated laser beam 7 is reflected by the track portion TR and the slope of the guard band GB. All of the reflected light 8 from the track portion TR enters the illumination optical fiber 51 again, but the reflected light 9 from the slope of the guard band GB is further reflected by the opposite slope and passes through the optical fiber 52 or 53 for deviation detection. and is input to a photodetector 62 or 63.

As a result, the outputs of the photodetectors 62 and 63 are unbalanced, and it is determined that an off-track state is occurring. The photodetectors 62 and 63 are connected to a servo control circuit SCC, and when the outputs of the photodetectors 62 and 63 become unbalanced, the servo control circuit SCC
The optical pickup 5 is moved until the output voltages of 2 and 63 are balanced.

In conventional magnetic disks, there was a deviation of ±10 μm for a track width of about 50 μm, but with the servo control method using reflected light from the guard band GB as described above, the deviation for a track width of about 1 μm at most. Control of 0.1μm becomes possible. Incidentally, the magnetic thin film layer 4 formed on the surface of the magnetic disk disc 1 has a thickness of several tens to 100 mμ and easily transmits light in the near-infrared region.
By using a semiconductor laser that has an output of several mW to several tens of mW and emits light in the near-infrared region, the light reflected on the reflective film layer 3 inside the substrate is detected by the photodetectors 62 and 63. Servo control circuit that detects and controls the position of the magnetic head by
It is fully possible to output control signals to the SCC.

As described above, according to the present invention, precise servo information can be formed using an inexpensive method, the cost of detection and reproduction can also be reduced, and control accuracy can be sufficiently improved, so the effects are great.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, and FIGS. 2 and 3 are explanatory diagrams of the operation. Note that FIG. 2 shows an on-track state diagram, and FIG. 3 shows an off-track state diagram. In the figure, 1 is a magnetic disk disc, 2 is a transparent substrate, 3 is a reflective film layer, 4 is a magnetic thin film layer, 5 is an optical pickup, 6 is a deviation detection section, 7 is a laser beam, 8,
9 is reflected light, 21 and 22 are light-transmissive substrates, 51 is an illumination optical fiber, 52 and 53 are deviation detection optical fibers, 61 is a light source, 62 and 63 are photodetectors,
TR is the track section, GB is the guard band, and SCC is the servo control circuit.

Claims (1)

[Claims] 1. Servo information and track information by optical signals are recorded on a substrate, and a desired information signal is recorded on a thin film magnetic layer formed on the surface of the substrate, and a magnetic head is used to record the desired information signal. In a magnetic disk device that records or reproduces data, detects the servo information and track information with an optical pickup provided in the magnetic head, and inputs signals to a servo circuit that controls the positioning operation of the magnetic head. A reflective film layer is interposed in the middle of a substrate formed by a concentric track portion having a surface parallel to the substrate surface, and a concentric guard band having a surface inclined with respect to the track portion, A self-servo magnetic disk device characterized in that the reflective film layers are alternately formed.