JPS586204B2 - Rotary magnetic head device - Google Patents

Description

[Detailed Description of the Invention] In this light, a magnetic head installed inside a rotating body scans a medium according to the rotation of the rotating body and transmits the detected playback signal to a circuit in a fixed part outside the rotating body. The present invention also relates to a rotary magnetic head device having a configuration in which a recording signal given by a fixed part outside the rotary body is transmitted to the inside of the rotary body.

Conventionally, in a rotary magnetic head, as shown in FIG.
The rotating magnetic head 1 and the recording/reproducing circuit 2 of the fixed part were connected through a rotating transformer 3, but in order to maintain non-contact property and good electrical characteristics as a transformer, Through precise assembly processing, a gap of several to tens of micrometers is created in the magnetic circuit of the transformer. Due to the existence of this gap, the coupling must be lower than that of a normal transformer, and as a result, This causes a transmission loss of the reproduction signal output, an increase in noise due to an increase in the effective circuit input inductance, and a decrease in the resonant frequency, which has the disadvantage that the output of the reproduction head cannot be transmitted to the recording/reproduction circuit 2 without deteriorating the signal quality. .

In order to increase the coupling coefficient of this transformer, reducing the air gap in the transformer reduces the vibration of the drive motor and rotating shaft, improves the accuracy of the assembly process of the transformer core, and also increases the temperature control to avoid contact due to temperature expansion. It was extremely difficult to set up a compensation organization.

In FIG. 1, numeral 6 indicates a preamplifier, 7 a recording amplifier, 8 a switching circuit, A a rotating body, and B a fixed part.

The object of the present invention is to transmit signals inside and outside the rotating body using light-receiving elements such as light-emitting diodes and light-receiving diodes or light-receiving transistors, thereby eliminating the need for a rotating transformer, making installation easy, non-contact, and having a large specific bandwidth. The object of the present invention is to configure a rotary magnetic head having a signal transmission system.

FIG. 2 is an explanatory diagram showing a configuration example of a rotary magnetic head according to the present invention, in which 1 is a magnetic head, 2 is a recording/reproducing circuit,
4 and 4' are light emitting diodes, 5 and 5' are light receiving elements such as light receiving diodes or light receiving transistors, 6 is a preamplifier, 7 is a recording amplifier, 8 is a switching circuit, A is a rotating body, and B
is the fixed part.

In the present invention, the magnetic head 1 is directly connected to the recording/reproducing circuit 2, and the reproduced signal is amplified by the preamplifier 6 without passing through a rotary transformer.

Therefore, unlike the case where the reproduced signal is passed through a transformer, the reproduced signal is amplified to a necessary and sufficient signal level without degrading the signal quality.

The amplified reproduction signal is converted into a light intensity signal by the light emitting diode 4 and sent out to the outside of the rotating body.

This signal light is again converted into an electrical signal by a light receiving element 5 such as a light receiving diode or a light receiving transistor installed outside the rotating body.

The output of the light receiving element 5 is the light emitting diode 40, and the luminous efficiency is 10.
0% and the efficiency of the light receiving element 5 is not 100%, the output is lower than the output amplified in the rotating body by more than 10 dB, but this signal attenuation does not allow the gain of the preamplifier 6 to be sufficiently By setting it large, it does not affect the deterioration of signal quality.

Furthermore, since the output impedance can be kept constant and low, the signal fractional band does not deteriorate.

Similarly, the recording signal is externally converted into an optical signal by a light emitting diode 4' and transmitted to the rotating body, and then inversely converted into an electric signal by a light receiving element 5' installed inside the rotating body, and then sent to the recording circuit 7. can be transmitted.

Unlike the case of a rotary transformer, the signal transmitted at this time can pass through direct current, so it is possible to transmit and record recording signals containing a direct current component such as NRZ-■ modulation codes, which is impossible when using a rotary transformer. Can be done.

In the above embodiment, the upper limit of the usable band is determined exclusively by the frequency characteristics of the light emitting diode and the light receiving element, but as is well known, the light output of the light emitting diode has good linearity in current-brightness characteristics. with number n
For example, a GaAsP red light emitting diode (center emission wavelength λ=6600 Å) has a response speed of 5 ns.

In addition, the response speed of PIN type photodiodes and avalanche type photodiodes, which are known as high-speed light receiving elements, is 1n.
s or less, signal transmission over several tens of MHz is easy by using these in combination.

Therefore, in addition to AM modulation in which the signal is changed to the intensity of light, FM modulation using a high-frequency carrier can also be used, and there is a large degree of freedom in circuit configuration.

In addition, since light emitting diodes have good monochromaticity of light (for example, 350 Å in the case of the red light emitting diode mentioned above), by passing the light incident on the light receiving element through an interference filter or a colored glass filter, it is possible to Even when the spacing between the elements is widened, most of the stray light and extraneous light that cause signal-to-noise ratio deterioration can be removed.

From this, even if the same optical path is used, it is possible to multiplex the number of channels in the transmission path by using light emitting diodes that emit different colors.

Furthermore, since the sensitive wavelength range of the light-receiving element is wide, even if light of different colors is multiplexed on the same optical path, it is sufficient to place a filter that passes only the selected wavelength just before the light-receiving element. , such a filter can be integrated into the device and does not take up much space.

When realizing the present invention, a light emitting diode 4 installed inside the rotating body and a light receiving element 5 installed outside, or a light receiving element 5' installed inside the rotating body and a light emitting diode 4' installed outside are combined in one optical path. ? Because it is a good translation,
There are countless ways to configure it, but the easiest one is to provide one optical path on the rotation center axis, as shown in FIG.

In Figure 3, 9 is a half mirror, 10 is a lens,
Reference numeral 11 indicates a lead wire, 12 indicates a motor shaft, and 13 indicates a bearing, and other symbols indicate the same parts as those explained in connection with FIGS. 1 and 2.

Note that the half mirror 9 referred to here is a fine "blind" made of a part of the mirror and a transparent part on a transparent plate in the required ratio.
It also includes those formed in the shape of a shape or concentric circles.

According to this configuration, the light emitting diode 4 and the light receiving element 5, and the light emitting diode 4' and the light receiving element 5' are optically coupled via two half mirrors 9.

Generally, if a half mirror is placed at an angle of θ with respect to the rotation axis, one optical path will be at an angle of 0 (on the rotation axis) and a half mirror.
It is branched into two lines at an angle of 2θ from the mirror position.

As a result, the degree of freedom in arranging elements increases.

The angle θ is set to 45°, as can be seen from the arrangement of the mirrors shown in FIG.

Accordingly, the light emitting diodes 4, 4' and the light receiving element 5
, 5' can be designed as a point light source and a point receiving light source, respectively, so each element can be made small.

Furthermore, since the centrifugal force is zero on the rotation axis, there is no need to worry about the mechanical strength of the element.

FIG. 4 is a cross-sectional view of a main part showing an example of the configuration of an optical transmission system that performs multi-channel transmission using a selection filter, and the same parts as those explained in connection with FIG. 3 are indicated by the same symbols.

In the figure, 14 indicates a selective transmission filter.

In this embodiment, two channels can be transmitted from the fixed side to the rotating side, and one channel can be transmitted from the rotating side to the fixed side.

The example in Figure 3 uses a half mirror 9 to perform bidirectional optical transmission with one optical path, but it uses both sides of the rotation axis and transmits in each direction with two optical paths on each side. Of course, it is also possible to use it for

Although the condensing lens 10 is used to increase the light transmission efficiency, it goes without saying that the distance between the light emitting diode and the light receiving element can be set arbitrarily by designing this lens system.

Further, in the embodiment, the case where the magnetic head 1 is used for both recording and reproduction using the switching circuit 8 has been exemplified, but the present invention is of course also sufficiently effective when using dedicated heads for recording and reproduction respectively. It can be raised.

Furthermore, it is extremely easy to transmit the optical signal taken out to the outside to any desired location using optical fibers, prisms, mirrors, etc., and the effects of the present invention are not impaired in either case.

As explained above, in the present invention, a recording/reproducing circuit connected to a magnetic head is incorporated inside the rotating body, and a light emitting diode and a light receiving diode or a light receiving diode are used to connect signals between the circuit inside the rotating body and the external circuit. By using a combination of light-receiving elements such as transistors, wideband signal transmission is possible without deteriorating the signal quality of the reproduced signal, and a rotary magnetic head can be constructed without requiring high-precision assembly processing. be able to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of main parts of a conventional rotary magnetic head device, FIG. 2 is a block diagram of main parts of a rotary magnetic head device according to the present invention, and FIG. 3 is a configuration example of an optical transmission system to which the present invention is applied. FIG. 4 is a cross-sectional view of a main part showing a configuration example of an optical transmission system that performs multi-channel transmission using a selective transmission filter. 1 is a magnetic head, 2 is a recording/reproducing circuit, 3 is a rotating transformer, 4 and 4' are light emitting diodes, 5 and 5' are light receiving diodes, 6 is a preamplifier, 7 is a recording amplifier, 8 is a switching circuit, 9 is a 10 is a lens, 11 is a lead wire, 12 is a motor shaft, 13 is a bearing,
14 is a selective transmission filter, A is a rotating body, and B is a fixed part, respectively.

Claims (1)

[Scope of Claims] 1. A rotating body equipped with a magnetic head, a recording/reproducing circuit, a light emitting diode for transmitting optical signals, and a light receiving element, arranged to correspond to at least the light emitting diode and the light receiving element for transmitting optical signals. a fixed part on which a light-receiving element and a light-emitting diode are mounted, and a position between the light-emitting diode and light-receiving element mounted on the rotating body and the light-receiving element and light-emitting diode mounted on the fixed part, which coincide with the rotation axis of the rotating body. It has a half mirror inserted to couple the light in the optical path of the book, one of each of the elements placed on the rotating body and the fixed part is on the rotation axis, and one is placed with respect to the rotation axis. - A rotary magnetic head device characterized in that the half mirror is arranged at an angle of 2θ with respect to the rotation axis relative to the angle θ of the mirror. 2. A rotating body equipped with a magnetic head, a recording/reproducing circuit, and one or more light emitting diodes with different emission wavelengths and one or more light receiving elements for transmitting optical signals, and a rotating body that transmits optical signals corresponding to at least the light emitting diodes and the light receiving elements. a fixed part equipped with one or more light-receiving elements and one or more light-emitting diodes with different emission wavelengths arranged to transmit information; a light-emitting diode and a light-receiving element mounted on the rotating body; and a light-receiving element mounted on the fixed part. generation of one or more half mirrors 1 inserted to optically couple the element and the light emitting diode through one optical path coinciding with the rotation axis of the rotating body, and a corresponding light emitting diode immediately in front of each light receiving element; A rotary magnetic head device comprising a filter that selectively transmits light having a central wavelength.