JPH0443338B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of the Invention) The present invention relates to a reproducing method and apparatus for reading magnetically recorded information from a recording medium such as a magnetic tape or a magnetic disk using a thin film magnetic head, and more particularly to an inductive thin film magnetic head. The present invention relates to a magnetic recording and reproducing method and apparatus for reproducing recorded information by projecting a light beam onto a surface, detecting changes in intensity of reflected light of the light beam due to the Kerr effect, and detecting the direction of internal magnetization.

(Prior Art) Various methods are known for recording and reproducing information on magnetic recording media such as magnetic tapes and magnetic disks, but various types of magnetic materials and magnetic heads are used to improve recording density. improvements have been made, and various new technologies have been developed. In order to significantly improve recording density, it is necessary to be able to reproduce with sufficient output even if the relative movement speed of the magnetic tape or disk to the head is considerably slowed down. ), the output of a magnetic induction type magnetic head inevitably decreases, making it impractical. In addition, with this magnetic induction type head, the level of the reproduced output signal is affected by the track width, so there is a limit to increasing the track density by reducing the track width. It is desired to do so.

Therefore, instead of the magnetic induction type that outputs the speed of change in internal magnetization within the magnetic head, a magnetic flux responsive type magnetic head was developed that directly responds to the direction and magnitude of magnetization within the magnetic recording medium. ing. This is called an MR (magnetoresist) head, and its output is not affected by tape feed speed or rack width, making it possible to play back high-density recordings. The reproduction output fluctuates greatly due to temperature changes, and the manufacturing cost is high because the head has a special structure.Furthermore, it is difficult to manufacture a head with consistent characteristics, which presents practical difficulties.

Additionally, a method called magneto-optical recording has been developed in which a light beam is projected onto a special magneto-optical recording medium, the reflected light is detected, and the internal magnetization of this medium is read using the Kerr effect, but this is also a special method. This method is difficult in practice because it requires the use of a magneto-optical recording medium.

(Objective of the Invention) The present invention allows conventional recording media such as magnetic tapes to be used as they are, and can also be used as a magnetic head by simply making some changes to the conventional induction type thin film magnetic head. The object of the present invention is to provide a method and apparatus for reproducing high-density recorded information that is suitable for practical use.

(Structure of the Invention) The present invention uses a transparent material for the substrate of a thin-film magnetic head, allows a light beam to enter the head obliquely from the substrate side, and changes the intensity of reflected light due to the transverse Kerr effect of the light beam. This is characterized by detecting and reading the direction of internal magnetization of the head.

In other words, it is characterized by photoelectrically reading the direction and magnitude of internal magnetization in the thin-film magnetic head using the longitudinal Kerr effect. Therefore, the recorded information can be read even when the tape is running at an extremely low speed.

(Effects of the Invention) According to the present invention, conventional magnetic recording media such as tapes and disks can be used as they are, and a conventional thin film magnetic head can also be used as a magnetic head by simply making the substrate transparent. As a result, magnetic flux response type reproduction can be performed, and high-density reproduction can be realized at low cost, and the practical effect is extremely large.

In particular, the level of the reproduced output signal is not affected by the track width, but by the power of the light such as the laser beam used for reproduction, so even if the track width is small, the laser light power can prevent the reproduction output from decreasing. It becomes possible to perform playback with a smaller track width and larger track density.

(Embodiments) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a front view showing the structure of a substrate of a thin film magnetic head 1, and FIG. 2 is a longitudinal section thereof. The thin film magnetic head 1 has a lower magnetic pole 11 on a transparent substrate 10,
The insulating layer 12, the conductive coil layer 13, the insulating layer 14, and the upper magnetic pole 15 are laminated in this order. Twelve edges are interposed to form a gap in the magnetic circuit. One end 13A of the conductive coil layer 13 extends outward so as to be connected to an external electric circuit, and the other end 13B is connected to the conductor 17. The basic structure of such a thin film magnetic head 1 is well known and is disclosed in, for example, Japanese Patent Application Laid-open No. 111115/1983, so its details will be omitted.

In the present invention, a material having a transparent, smooth surface (mirror surface) and high hardness is used for the substrate 10. An example of a material having such properties is a single crystal of sapphire.

As shown in FIG. 3, the thin film magnetic head 1 equipped with the transparent substrate 10 as described above is arranged on a magnetic recording medium 20 such as a magnetic tape so that the gap 16 is in contact with the magnetic recording medium 20, and the substrate 10 is passed through the thin film magnetic head 1. Lower magnetic pole 1
A light beam 30 such as a laser beam is obliquely incident on the surface of the substrate 1. The direction of this incidence is such that it is obliquely incident on the surface of the lower magnetic pole 11 in a plane perpendicular to the direction of internal magnetization (indicated by the arrow) of the thin-film magnetic head 1. Here, oblique refers to the angle at which the incident angle θ in the above plane is approximately 80° (θ80° if the magnetic pole is made of permalloy. There are optimum values for other magnetic materials). .

This incident light beam 30 is reflected by the surface of the lower magnetic pole 11 and reflected from the surface of the substrate 10 in the direction of incidence and reflection. At this time, the reflectance on the surface of the lower magnetic pole 11 changes according to the change in internal magnetization due to the effect of the transverse Kerr effect, so if this reflected light 31 is photoelectrically detected by the photo sensor 35, its output will change depending on the internal magnetization. The direction and size are indicated, and the information recorded on the magnetic recording medium 20 can be read out, that is, reproduced.

Although the embodiment described above shows the basic configuration of the present invention, multi-head type reproduction is possible by making the structure of the magnetic head 1 into a form in which a large number of lower magnetic poles are arranged in parallel, and by preparing optical systems corresponding to the number of channels. become. FIG. 4 is a horizontal sectional view showing one example (only the substrate 10A common to the lower electrode 11A is shown, other parts are omitted), FIG. 5 is a plan view thereof, and FIG. 6 corresponds to FIG. 4. This figure shows a cross section of it.
Portions common to the above-described embodiments shown in FIGS. 1 to 3 are designated by the same reference numerals, and a description thereof will be omitted. In FIG. 5, the symbols shown inside the tape 20 indicate the magnetization direction of the digital signals recorded on the tape 20.

This multi-head type allows multi-channel recording and reproduction, and multi-channel reproduction can be performed simultaneously with one magnetic head.

Furthermore, as shown in FIG. 7, if a head array chip (multi-head type structure) 40 in which a number of lower magnetic poles are arranged in one magnetic head is used, and a light beam is scanned over this chip, one laser beam can be scanned. The beam can be used to read out multiple heads. That is, a laser beam 41A from a laser light source 41 is deflected by a rotating prism 42, is incident on a head array chip 40 through an objective lens 43, and is scanned over this chip.
After this reflected light 41B is made into parallel light by a collimator lens 44, it is made incident on a photographic lens 46 by a condensing lens 45, and the output of the photographic material 46 is amplified by an amplifier 47.
By detecting changes in reflectance above 0, it is possible to read recorded information on a magnetic recording medium.

If the recording medium 20 such as a magnetic tape is run in the direction of arrow A in FIG. 4 and the laser beam for reading is switched to 30A, 30B...30N, the recording medium 20 will be slightly diagonal in the width direction. By repeating this process, the entire tape can be read in stripes. In addition, as shown in Figure 8, these striped tracks are arranged alternately as the first track (connecting the reading area of 1 bit unit, indicated by the circle mark) and the second track (the track indicated by the cross mark). By changing the shape, the recording density of the tape can be further increased. Arrows B and C in FIG. 8 indicate the return directions of the first track and the second track, respectively.

In each of the above embodiments, the case of a magnetic tape has been explained, but this is exactly the same in the case of a magnetic disk, and it is also possible to have a multi-head with many heads arranged in the radial direction of the disk, and in this case, a large number of lasers It is also possible to make the beams incident in parallel and perform simultaneous reproduction using a multi-channel method, or to scan with a single laser beam (the seventh method described above).
It is also possible to reproduce the data by scanning as shown in FIG. 8 (as in the example shown in the figure).

[Brief explanation of drawings]

FIG. 1 is a front view showing an example of a thin film magnetic head used in the method for reproducing magnetically recorded information according to the present invention, FIG. 2 is a longitudinal sectional view thereof, and FIG. FIG. 4 is a plan view showing another embodiment of the regeneration method of the present invention, and FIG.
The figure is a front view thereof, FIG. 6 is a longitudinal sectional view thereof, and FIG. 7 is a plan view showing still another embodiment of the present invention.
FIG. 8 is a plan view showing an example of a multi-track magnetic tape reproduced according to an embodiment of the present invention. 1... Thin film magnetic head, 10... Transparent substrate, 1
1... Lower magnetic pole, 12, 14... Insulating layer, 13...
... Conductive coil layer, 15 ... Upper magnetic pole, 16 ... Gap, 20 ... Magnetic tape, 30 ... Incident light,
31...Reflected light.

Claims (1)

[Scope of Claims] 1. An inductive thin film magnetic head that reads recorded information on a magnetic recording medium that moves in contact with a gap in a magnetic circuit as a change in internal magnetization. A light beam traveling obliquely to the surface in a plane substantially perpendicular to the direction of is incident, the reflected light from the part of the light beam is detected, and the direction of the internal magnetization is determined from the intensity of the reflected light. A method for reading and reproducing magnetic recording media. 2. A thin film magnetic head, which is made by laminating the layer structure of an inductive thin film magnetic head on a transparent substrate, which reads information recorded on a magnetic recording medium that moves in contact with the gap of a magnetic circuit as changes in internal magnetization. a light beam projecting means for projecting a light beam that travels obliquely to the surface in a plane substantially perpendicular to the direction of internal magnetization in the part through the substrate; A magnetic recording information reproducing device comprising photoelectric conversion means that receives reflected light from a portion and converts the intensity of the reflected light into an electrical signal.