JPH0259528B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pickup that slides over a recording medium on which an information signal is recorded by substantially alternately forming magnetic parts and non-magnetic parts, and reproduces the information signal. It is.

In recent years, various methods have been proposed for recording information signals such as video signals at high density on disks or magnetic tapes and reproducing them.

For example, known video disc systems include mechanical compression, capacitance, and optical systems, each of which records and reproduces signals using different methods.

Now, in order to deepen the understanding of the present invention and to clarify the differences between the above three methods and the present invention, the above three methods will be briefly explained.

Mechanical compression method For example, a spiral V-shaped groove is formed on the surface of a disk with a thickness of 0.12 mm to 0.15 mm, and a signal (FM modulated video signal or audio signal) is carved into this groove surface in an uneven manner. The reproduction pick-up is called a piezoelectric type, and a piezoelectric ceramic is formed on the top of a diamond curvilinear needle, and these are fixed to the tip of a cantilever. When the disk rotates, the repulsive force of the unevenness in the grooves is transmitted to the piezoelectric ceramic through the diamond needle, where it is converted into an electrical signal and reproduced.

Capacitance method A diamond or sapphire needle has an electrode, and a thick disk made of conductive resin is used as the other electrode.These two electrodes form a capacitor, and the signal formed on the disk surface is used to generate a capacitor. This uses the change in capacitance of a capacitor to convert it into an electrical signal using a high frequency method and reproduce the signal.

The RCA method utilizes the fact that a spiral groove is formed on the surface of the disk, and a concave-convex signal is engraved on this groove surface, and the capacitance of the capacitor changes due to the concave-convex signal. The signal is recorded by a pit formed in a spiral shape, and the signal is read using the change in capacitance of the capacitor depending on the presence or absence of the pit.
There is a VHD format.

Optical method Spiral pits are formed on the surface of a thick disk, and signals are recorded depending on the presence or absence of these pits.
A playback pick-up does not make contact with the disk, but instead irradiates the disk with a laser beam, and the photoelectric conversion element receives the reflected (or transmitted) light from the disk, which varies in intensity depending on whether there is a pit, and reads it as a change in current. be.

The video disc system as described above cannot record data arbitrarily like a general audio record, but only has the function of reproducing a disc on which signals have already been recorded.

On the other hand, there is a so-called magnetic recording/reproducing method in which information signals are arbitrarily recorded and reproduced using the magnetization of a magnetic material, and those using magnetic disks or magnetic tapes are widely used. Two typical application examples in which information is recorded at high density using such a magnetic recording/reproducing method are as follows: Magnetic disk for recording and reproducing video signals A metal disk with a ferromagnetic layer on the surface is used, and concentric circles are formed on the surface. This device records and reproduces video signals by magnetizing them in a circular or spiral shape using a floating head, etc. Video signals can be recorded and reproduced arbitrarily, but the recording density is approximately 30 seconds.
There is only a certain degree.

Video tape recorder (VTR) Uses plastic tape with a ferromagnetic layer on its surface to magnetize and record information signals using a rotating head, and reproduces this information over a considerable length of time.

In addition to the above two application examples, these recordings are performed by magnetizing magnetic particles in a ferromagnetic layer provided on a disk or tape. The present invention provides a pickup for reproducing information signals that uses a completely new recording and reproducing method that is essentially different from the conventional recording and reproducing methods described above and that is capable of recording and reproducing information signals at high density.
That is, although the recording medium that is reproduced by the pickup according to the present invention has a magnetic layer on its surface, it does not record signals by electromagnetically magnetizing this magnetic layer as in the prior art. In this method, the magnetic layer is essentially made into a magnetic part and a non-magnetic part by physical or chemical treatment, and a signal is recorded by repeating the magnetic part and the non-magnetic part.

The pick-up according to the present invention is made of a magnetic material, a coil is wound around this magnetic material, and the pick-up itself has a magnetic field generating function such as a permanent magnet. The pickup is slid over the recorded recording medium to detect the difference in magnetic resistance between the magnetic and non-magnetic portions of the surface of the recording medium, and extracts a signal as a change in current.

The information signal reproducing pickup of the present invention is generally based on the basic configuration as described above, and the present invention will now be described in detail with reference to embodiments of the drawings.

First, the recording medium to be reproduced by the pickup according to the present invention and the recording of signals on this recording medium will be explained.

The recording medium according to the present invention has substantially magnetic portions and non-magnetic portions alternately formed on at least its surface in accordance with signals. The recording medium can take any shape such as a disk, tape, or card, but for the sake of simplicity, a disk will be explained here.

FIG. 1 shows an example of a disk, in which A is a perspective explanatory view and B is a cross-sectional explanatory view.
The disk base 1 is, for example, made of the same vinyl chloride resin as ordinary audio disks, and has a circumferential length of 0.5 to several μm and a depth of 0.1 to 0.2 μm, depending on the information signal to be recorded on the surface of the disk base 1. The uneven pits 2 are formed in a spiral shape (or concentric circle shape). Recording signals in such a form has already been applied to the optical system or VHD system of the video disc system described above.

The disk reproduced by the pick-up of the present invention has a disk base 1 on which uneven pits 2 are formed.
It is characterized by further having a thin magnetic layer 3 on the surface. What should be noted here is that even if the magnetic layer 3 is formed, the disk surface still maintains its uneven shape.

As a result, in relation to the pickup of the present invention which will be described later, the pit portion (recessed portion) essentially becomes the non-magnetic portion 5, and the other portions become the magnetic portion 4.

In addition, the above-mentioned disk can be a grooveless disk like the optical type and VHD type, and it can be a disk with a spiral or concentric V-shaped guide groove on the disk surface as seen in the mechanical compression type and RCA type. But it's okay. In this case, a concave-convex signal corresponding to the information signal is formed on the surface of the guide groove, and if a magnetic layer is provided on the surface while maintaining this concave-convex shape, the convex part becomes a magnetic part, and the concave part becomes The signal will be recorded as a non-magnetic part.

In manufacturing a disc in which signals are recorded in the uneven shape as described above, in the case of a non-grooved disc, a glass master on which a photosensitive resin or metal thin film is formed is used, and this photosensitive resin or metal thin film is coated with a glass master. A signal is recorded by exposure hardening or evaporation with a laser beam to form pits, and from this glass master, the father, mother, stamper and mold are returned, and in the stamper, the glass is made of vinyl chloride resin, etc. using a press or injection machine. disks can be manufactured. On the other hand, when manufacturing a disk having a V-shaped guide groove, a lacquer disc or a copper disc is used as a master, and this master is used to record the signals to be recorded using a V-shaped diamond cutting blade or the like integrated with piezoelectric ceramic. It cuts in an uneven shape by moving up and down in response to the movement. In this case, as in the case of grooveless disks, disks made of vinyl chloride resin or the like can be manufactured in large quantities from the stamper.

A desired disk can be obtained by forming a magnetic layer of nickel or the like on the surface of the disk, on which signals are recorded with or without pits or in an uneven shape, by plating, vapor deposition, sputtering, or the like.

A disk substrate with signals recorded in an uneven shape on its surface is prepared by using a stambar, and a magnetic layer is uniformly provided on the surface of this disk substrate.
Recording signals by forming substantially magnetic and non-magnetic parts alternately has the great advantage of being mass-producible, but as shown in Fig. The magnetic layer 13 may be formed only on the convex portion of the disk 11, forming a magnetic portion 14 and a non-magnetic portion 15. Alternatively, the magnetic layer 13 may be formed only on the convex portion of the disk 11, or the magnetic layer 13 may be formed on the convex portion of the disk 11, or the magnetic layer 13 may be formed on the convex portion of the magnetic layer 11 to form a magnetic portion 14 and a non-magnetic portion 15. Alternatively, the entire disk may be made of a magnetic material 21, and a magnetic portion 23 and a non-magnetic portion 24 may be formed.

It is also possible to coat the surface of the disk with a thin film of plastic or metal, thereby reducing the frictional resistance with the pick-up described later and reducing the wear of both the pick-up and the disk.

In the above explanation, signals are recorded using the magnetic and non-magnetic portions by utilizing the uneven shape of the disk surface, such as the presence or absence of pits.
Regardless of the shape of the unevenness, signals can be recorded by alternately forming magnetic portions and non-magnetic portions on the disk surface so that a significant difference in magnetic resistance appears in relation to the pickup described later. It goes without saying that such recording can be applied not only to disks but also to cards, tapes, etc.

Next, a pickup for reproducing a recording medium on which information signals are recorded as described above will be explained.

FIGS. 4 to 6 show diagrams of the principle of the pickup according to the present invention.

In Figure 4, permanent magnet 4 for obtaining a magnetic field.
Magnetic bodies 41 and 42 are provided at both ends of the magnetic body 5 .
One magnetic body 42 becomes a large-area flat contact part 44 that comes into contact with dozens or more pits, and the tip of the other magnetic body becomes a signal detection end 43 that comes into contact with the disk, and a coil 46 is placed at an appropriate position. is wrapped. The planar contact portion 44 not only reduces the stylus pressure per unit area by contacting the disk over a large area, but also has the effect of averaging out the presence or absence of pits, making them irrelevant.

In addition, the signal detection end 43 must detect the presence or absence of pits, and has a size c that has sufficient detection ability for the size of the pits, for example, if the length of the smallest of the pits 2 on the disk is 0.5 μm. Then, the dimension c has a length of 0.5 μm or less. Further, the planar contact portion 44 and the signal detection end portion 43 are sufficiently spaced apart from each other so that there is no influence of presence or absence of pits from sources other than the signal detection end portion 43.

Regarding another aspect of the pickup having such a configuration, the one shown in FIG. 5 is one in which the periphery of the signal detection end 43 of the pickup shown in FIG. It is filled and covered with a protective material 47 such as a non-magnetic metal, which increases the contact area with the disk to improve wear resistance, and eliminates protrusions to make the structure strong.

Furthermore, the one shown in FIG. 6 is provided with a permanent magnet, a coil, and two magnetic bodies serving as planar contact portions to protect the signal detection end 43 and to increase the detected signal voltage.

In the above description, a permanent magnet is used as a method of obtaining a pickup magnetic field, but it is of course possible to obtain a magnetic field by applying a direct current bias or a high frequency bias to the coil itself.

Next, a method for reproducing a disc on which signals have been recorded using a pit row as shown in FIG. 1 using such a pickup will be described. Theoretically, it is possible to detect signals without contact by providing a small gap between the pick-up and the disk, but here we will use the mechanical compression method and capacitance method explained in the conventional technology to detect the signal between the pick-up and the disk. shall be in contact with. The disks are shown in Figures 5 to 6.
It is assumed that it rotates in the direction of arrow d in the figure. When the signal detection end 43 of the pick-up is located on the convex part of the rotating disk (the part without the pit 2) (the state shown in Fig. 4), the magnetic flux from the permanent magnet etc. passes through the magnetic layer of the disk, and a magnetic circuit is formed. When the disk rotates further and the signal detection end of the pickup comes to a pit position as shown in Figure 6, the signal detection end and the magnetic layer of the disk do not come into contact and the magnetic resistance decreases. will increase.

In this way, the magnetic resistance changes depending on the presence or absence of pits, and the magnetic flux passing through the coil changes accordingly, a voltage is induced in the coil, and a signal is extracted.

When reproducing such a grooveless disc, tracking can be performed in the same way as in the optical system of a video disc system.

The above explanation has been made assuming that a disc on which signals are recorded by a pit row is played back, but based on the same principle, a disc, card, tape, etc. that has a guide groove, etc. Media can be played.

As described in detail above, the pickup of the present invention records information signals by alternately providing substantially magnetic portions and non-magnetic portions on the surface of the recording medium, and a certain level of information is recorded on the surface of the recorded recording medium. It applies a magnetic field, reads the difference in magnetic resistance between the magnetic part and the non-magnetic part, and reproduces the signal as a change in current, which is completely different from known means of reproducing information signals. This has the following effects.

In other words, when reproducing a recording medium in which signals are recorded by repeating magnetic and non-magnetic parts by physical or chemical state changes, instead of recording signals by magnetization as in the past, a magnetic field is applied to the recording medium. Since the change in magnetoresistance between the magnetic portion and the non-magnetic portion can be detected successfully, the signal recorded on the recording medium can be successfully reproduced.

[Brief explanation of drawings]

The drawings show embodiments of the present invention.
Figures 3 to 3 are explanatory diagrams of the recording medium of the present invention;
6 through 6 are explanatory diagrams showing the pickup of the present invention and the principle of reproduction using this pickup. 1, 11... disk base, 2, 12, 22...
...Pitt, 3,13,21...Magnetic material, 4,1
4, 23...Magnetic part, 5, 15, 24...Non-magnetic part, 41, 42...Magnetic body, 43...Signal detection end, 46...Coil.

Claims (1)

[Claims] 1. A pickup for reproducing information signals recorded by sliding on the surface of a recording medium and substantially providing magnetic portions and non-magnetic portions alternately on the surface of the recording medium. , is entirely formed of a magnetic material, one end of this magnetic material serves as a signal detection end and is in contact with the recording medium surface, and the other end is in contact with the recording medium surface over a large area, and the signal detection end is in contact with the recording medium surface. The length of the surface is set to be equal to or less than the length of the magnetic or non-magnetic portion of the surface of the recording medium, and a coil is wound around the magnetic material to induce a current according to changes in magnetism, and a constant magnetic field is applied. Information characterized in that the signal detecting end is provided with a magnetic field generating means that generates a magnetic part of the recording medium, and extracts the change in magnetic flux caused by repeatedly connecting and disconnecting the magnetic portion of the recording medium as a change in current and reproduces the signal. Pickup for signal playback. 2. The information signal according to claim 1, characterized in that the periphery of the signal detection end portion is covered with a protective material such as glass, shaft fat, or non-magnetic metal to widen the contact area with the recording carrier. Pickup for playback.