JPH01184603A - Magnetic head device - Google Patents

Abstract

PURPOSE:To optically transmit the reproduced signal of a magnetic head to a fixed side by driving a light modulating element on a rotary drum by the output of the magnetic head, modulating the light of the light emitting element of the fixed side and transferring the modulated light to the light receiving element of the fixed side. CONSTITUTION:The light modulating element 16 is disposed on the rotary drum 11 and the light emitting element 17 and the light receiving element 18 are disposed on the fixed side. This light modulating element 16 is driven by an output from the magnetic head 14 to modulate the light from the light emitting element 17 projected on the light modulating element 16, detect the modulated light by the light receiving element 18 of the fixed side and demodulate 20 the detected output. Accordingly, since the light from the light emitting element 17 is modulated by the light modulating element 16 according to the reproducing output signal of the magnetic head 14, the reproducing signal of the magnetic head can be optical transmitted to the fixed side without requiring the conventional rotary transformer or a slip ring.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a magnetic head device, and more particularly to a device that transmits signals read by a magnetic head on a rotating body to a fixed side by optical transmission. Summary of the Invention The present invention provides a magnetic recording/reproducing device such as a VTR, in which a light emitting element and a light receiving element are installed outside the drum in order to transmit signals from a head provided on the rotating drum to an external fixed side. provided on the fixed side of the drum, the light from the light emitting element is optically modulated by a light modulating element on the drum using a signal read by a magnetic head, and the modulated optical signal is received by a light receiving element, In addition to making it possible to omit the rotary transformer and slip ring, the amount of power supplied to the rotating drum can be reduced by providing the light emitting element outside the rotating drum. [Prior Art] Generally, when a signal on a magnetic tape is reproduced by a VTR, the magnetic tape is helically wound around the outer circumferential surface of a head drum, and the magnetic tape is scanned while rotating the magnetic head together with the rotating drum. This allows the signal to be reproduced using the helical scan method. Conventionally, rotary transformers and slip rings have been used to transmit signals from the magnetic head installed on the rotating side to the stationary side. I was doing it. K Problems to be Solved by the Invention The signal transmission system using a rotary transformer has a drawback that the number of channels is limited by the size of the head drum. Further, rotary transformers have problems in that they have a complicated structure, are expensive, and are not easy to assemble. Furthermore, if the head amplifier is incorporated into the head drum in order to widen the band, there is a drawback that an additional slip ring for power transmission is required. In order to overcome these drawbacks, a possible method for transmitting the signals read by the head to the stationary side is to provide a light emitting element on the rotating drum and transmit the light from the light emitting element. In this method, a light emitting element on a rotating drum is directly modulated by an output signal from a head, and the modulated optical signal is detected by a fixed light receiving element. However, directly modulating the light emitting element has the disadvantage of increasing power consumption. Also, a light emitting element must be installed on the drum.
This would also be difficult in terms of space. The present invention was made in view of these problems, and does not require a rotary transformer or a slip ring.
Another object of the present invention is to provide a magnetic head device which does not require a light emitting element on the drum and which optically transmits the output signal of the head to a fixed side. Means for Solving Problem 1 of the Invention The present invention provides a light modulation element on a rotating body having a magnetic head, and also arranges a light emitting element and a light receiving element on a fixed side. The light emitted by the modulator is modulated and transmitted to the light receiving element. "Function" Therefore, according to the present invention, the light emitted from the light emitting element disposed on the fixed side is modulated by the light modulation element on the drum in accordance with the reproduction output signal of the magnetic head. It becomes possible to transmit the signal to the light receiving element.

[Embodiment 1] Fig. 1 shows a magnetic head device according to a first embodiment of the present invention.
1 and a fixed drum 12. A magnetic tape 13 is helically wound around these drums 11 and 12, and a magnetic head 14 is provided on the rotating drum 11. The magnetic head 14 is brought into contact with the magnetic tape 13 wound around the drum 11, 12, and by scanning the magnetic tape 13 obliquely, helical scanning is achieved. The magnetic head 14 is connected to an amplifier 15, and the output side of the amplifier 15 is connected to an AO element (acoustic optical device) 16 constituting a modulation element. On the other hand, a light emitting element 17 and a light receiving element 18 are disposed on the fixed side, and a prism 19 is provided in front of the light receiving element 18. In the above configuration, the reproduction output generated when the magnetic head 14 on the rotating drum 11 is brought into contact with the magnetic tape 13 is transmitted to the outside by optical transmission. The light from the light emitting element 17 is irradiated onto the light modulating element 16 on the drum 11, and the reflected light is detected by the light receiving element 18 through the prism 19. The output is demodulated by the demodulator 20. Moreover, since the optical modulation element 16 is designed to modulate with the output signal of the magnetic head 14, the output signal of the head 14 can be reproduced by the output of the demodulator 20. An LED or LD is used as the light emitting element 17, a photodiode or the like is used as the light receiving element 18, and an AO element is used as the light modulating element 16.
O element (acoustic optical device) 1
6 is supplied with acoustic waves and vibrates at several hundred M)h. The vibrations caused by such acoustic waves interfere with the incident light, and the angle of the emitted light changes. Therefore, by generating an acoustic wave in the light modulation element 16, light incident on the element 16 at a certain angle is diffracted at a predetermined angle. As shown in FIG. 1, the light from the light emitting element 17 is incident on the AO element 16 on the drum 11,
By changing the frequency of the acoustic waves applied to the rays, the angle of the diffracted light changes. Therefore, by using the prism 19, it is possible to turn on and off the light receiving element. Therefore, by driving the AO element 16 with the playback signal from the head 14, it becomes possible to obtain an optical signal modulated by the head signal, and by demodulating this it becomes possible to obtain a video playback signal. . According to a magnetic head device having such a structure, a wideband signal can be easily transmitted. Further, since the light emitting element 17 is not provided on the drum 11, the arrangement of the drum 11 becomes very easy, and the amount of power supplied to the rotating drum 11 can be reduced. Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, when transmitting a signal from the rotating drum 11, light from a light emitting section 17 provided on the fixed side is modulated by an MO element (magneto-optical device) 23 on the rotating drum 11. , the reflected light is received by the light receiving element 18 to transmit the signal. The reproduction signal from the magnetic head 14 is then used to modulate the MO element on the rotating drum 11. The MO element 23 is irradiated with light from a light emitting element 17 provided outside the rotating drum 11, and an element 18 that receives the reflected light detects the modulated light and reproduces the original signal. . If the light emitting element 17 is a reiga diode, for example, the light is sufficiently polarized, so it is configured in combination with a collimator lens. When an LED is used as the light emitting element 17, it is used in combination with a polarizer, and is emitted as sufficiently polarized light. Since the plane of polarization of the light receiving element 18 is rotated by the MO element 23, a combination of an analyzer 25 and a photodiode 18 is used to detect the rotation period. And this example is as described above.
Since the O element 23 modulates the light while reflecting it, the Keller effect in which the angle of the reflected light changes is applied. The MO element 23 has a Faraday effect in addition to the Keller effect, and the angle of the polarization plane of transmitted light within the MO element 23 changes. Therefore, as in the modification shown in FIG.
The light emitted by MO element 2 passes through the half mirror 28.
3, the light is reflected by a mirror 29 provided at the lower end of the MO element 23, and the light transmitted through the MO element 23 and returned is reflected by a half mirror 28. Two light receiving elements 18 for transmitting light and reflecting light
It may be detected by. In this case, the outputs of the two light receiving elements 18 are transferred to the differential amplifier 3.
It will be supplied to 1. In such a modified example, M
The O element 23 will be arranged on the axis of the drum 11, 12, and the light from the light emitting element 17 will be incident perpendicularly along the axis of the drum 11. And this MO element 2
3 is driven by the output of the magnetic head 14 via the amplifier 15, driver 24 and coil,
The Faraday effect is produced by the magnetic field provided by the coil connected to the driver 24, and the angle of the polarization plane of the transmitted light is polarized, resulting in optical modulation. Next, a third embodiment will be explained with reference to FIG. In this embodiment, when transmitting a signal from the rotating drum 11, the light from an external light emitting element 17 is modulated by a modulating element consisting of an EO element (electro-optical device) 34 on the rotating drum 11, and then the modulated light is transmitted. The signal is transmitted by receiving it with the light receiving element 18, and the signal from the magnetic head 14 is used to transmit the EO signal.
The element 34 is modulated. Therefore, the EO element 34 performs modulation according to the output signal of the magnetic head 14, and the light receiving element 18 receives the modulated reflected light and converts it into an electrical signal. Specifically, for example, an electric prism is used as the EO element 34. Also, circularly polarized light is used for light from outside. The light from the LD may be circularly polarized using a λ/4 plate. The EO element 34 may be arranged on the rotating drum 11, and an analyzer may be arranged in front of the EO element 34 so that polarized light is directly incident on the EO element 34. When the EO element 34 is modulated by the output signal of the head 14 via the amplifier 15 and driver 24, the polarization direction of the light changes. By returning only one of the light whose direction changes and the light whose direction does not change by the mirror 36, the light can be received by the light receiving element 18 on the fixed side via the half mirror 28. In this way, the device according to this embodiment uses the EO element (electro-optical device) 34 in which the direction of polarized light changes depending on the external voltage, so when no voltage is applied, the prism 35 The light returns along the same path as the incident path by the mirror 36, and is detected by the light receiving element 18. On the other hand, when a voltage is applied to the EO element 34, the incident light passes through the prism 35 as shown by the dotted line. Therefore, in this case, the light does not return and the light receiving element 18 does not detect the light. This allows the reproduction signal of the magnetic head 14 to be extracted by the light receiving element 18. [Effects of the Invention] As described above, the present invention modulates the light from the light emitting element provided on the fixed side by the light modulation element on the rotating side, and transmits the modulated light to the light receiving element. . Therefore, by driving the modulation element with the output of the magnetic head, it becomes possible to optically transmit the reproduction signal of the magnetic herad to the fixed side. According to this method, there is no need for a rotary transformer or a slip ring, there is no need to provide a light emitting element on the rotating side, and it is possible to reduce the amount of power supplied to the rotating side.

[Brief explanation of the drawing]

FIG. 1 is a front view of a magnetic head device according to a first embodiment of the present invention, FIG. 2 is a front view of a magnetic head device of a second embodiment, and FIG. 3 is a front view of a magnetic head device of a modified example. 4 are front views of the magnetic head device of the third embodiment. In addition, in the symbols used in the drawings, 11... Rotating drum 14... Magnetic head 16... AO element (modulating element) 17... Light emitting element 18... Light receiving element 23... MO element (modulating element) Element) 34...EO element (modulation element).

Claims (1)

[Claims] A light modulation element is provided on a rotating body having a magnetic head, and a light emitting element and a light receiving element are disposed on a fixed side, and the light emitted by the light emitting element is modulated by the light modulating element and sent to the light receiving element. A magnetic head device characterized in that it is configured to transmit data.