JPH09297901A - Optical rotary transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit information with massive capacity of transmission band of several hundreds MHz-several GHz between a rotor and a stator. SOLUTION: In an optical rotary transformer performing signal transmission between a middle drum 3a and an upper fixed drum 6a by an optical signal, plural optical multiplex/demultiplex prisms formed using thin films 55a-55d, 55a1-55d1 transmitting light with a wavelength longer than a cut-off wavelength and reflecting the light with the wavelength shorter than the cut-off wavelength and with the cut-off wavelengths different from each other are provided. Then, multiplex/demultiplex bi-directional transmission devices 53, 53a each having plural multiplex/demultiplex prisms cascade-connected in multistage so that the cut-off wavelengths different from each other become longer successively according to a distance from a gap 56 are arranged on respective middle drum 3a and upper fixed drum 6a, and the optical axes of the multiplex/demultiplex bi-directional transmission devices 53, 53a are made to coincide with the rotary shaft of the middle drum 3a, and the multiplex/demultiplex bi-directional transmission devices 53, 53a are confronted with each other through the gap 56.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video tape recorder (hereinafter referred to as "VTR") which is provided between a magnetic head mounted on a rotating drum which is a rotating body and a VTR housing which is a non-rotating body. The present invention relates to an optical rotary transformer for transmitting a large capacity signal using a transmission method.

SUMMARY OF THE INVENTION The present invention relates to an optical rotary transformer, in which a half mirror formed by using a thin film having wavelength selectivity for light transmission and reflection is provided, and the cutoff wavelengths of the half mirrors are sequentially arranged. After controlling the thin film characteristics to make it longer, the half mirror group connected in cascade is built in the fixed drum and the rotating drum so that the optical axis of the half mirror group coincides with the rotating axis and one half mirror group is provided through the air gap. And the other half mirror group are arranged so as to face each other, and a large-capacity signal transmission between the fixed system and the rotating system of the VTR is enabled by an optical signal.

[0003]

2. Description of the Related Art A magnetic head of a VTR is mounted on a rotating drum, and a rotating drum rotates to obtain a relative speed with respect to a magnetic tape to write a signal on the magnetic tape or read a signal from the magnetic tape.

FIG. 4 shows a schematic sectional view of a rotary drum in a VTR. In FIG. 4, a magnetic head 4 is attached to the rotary drum 3, and rotary transformers 5 a and 5 b are provided below the rotary drum 3.

The rotary transformers 5a and 5b are composed of a core, and a winding 7b is wound around a concentric groove 7a of the core. The rotary transformer 5a is adapted to rotate together with the rotary drum 3, Transformer 5b
Are fixed to the fixed drum 6.

The rotary transformers 5a and 5b utilize electromagnetic coupling to transmit signals between the rotary drum 3 and a fixed drum 6 in the same fixed system as the VTR main body. The rotary drum 3 is rotated about a rotary shaft 8 by a motor 9 to move the magnetic head 4 relative to a magnetic tape (not shown) to record and reproduce signals.

At the time of recording, the signal from the fixed drum 6 in the fixed system is received by the rotary drum 3 side via the rotary transformers 5a and 5b and transmitted to the magnetic head 4. During reproduction, the signal from the magnetic head 4 is transferred to the rotary transformer 5
The fixed drum 6 receives the signal via a and 5b, and processes the signal by the electric circuit of the VTR main body.

As a method of transmitting a signal from a rotating body to a fixed body, there is an optical rotary joint utilizing optical transmission. FIG. 5 shows a schematic sectional view of the optical rotary joint. In FIG. 5, the optical fiber 71 is placed at the center of the rotary shaft 73.
a is provided, and a lens 75 is provided at the tip of the optical fiber 71a.
a is attached.

The rotary shaft 73 is supported by a bearing 77 through a plurality of bearings 76, an optical fiber 71b is attached to the bearing 77, and a lens 75b is attached to the tip of the optical fiber 71b so as to face the lens 75a. To be

The optical rotary joint having such a configuration converts a signal into light on the side of the rotary shaft 73, and transmits an optical signal from the optical fiber 71a on the side of rotation to the lens 75a and the lens 75b on the fixed side via the space. It is transmitted to the fiber 71b. A signal can be transmitted from the fixed side to the rotating side, and bidirectional signal transmission can also be performed.

Further, as a device utilizing this kind of optical signal transmission, there is, for example, a rotary electronic device described in Japanese Patent Laid-Open No. 59-160344. As a device for transmitting signals between the VTR housing and the rotary drum, there is, for example, a rotary head cylinder described in Japanese Patent Laid-Open No. 60-239901.

In the rotary electronic device, a light emitting element is provided on a fixed base and a rotatable electronic device, and a light receiving element is provided on the fixed base and the electronic device on a locus drawn by light emitted from the light emitting device due to rotation of the electronic device. It is provided to transmit and receive optical signals between the light emitting element and the light receiving element.

Further, the rotary head cylinder is provided with a light emitting / receiving element in addition to the magnetic head on a rotatable upper cylinder,
The fixed side external circuit is also provided with a light emitting / receiving element facing the light receiving / emitting element of the upper cylinder, and an optical signal is transmitted / received between the upper cylinder and the external circuit.

That is, in any of these devices, in the signal transmission between the rotating body and the fixed body, the light of the laser diode (hereinafter referred to as LD) directly modulated is converted into the photodiode (hereinafter referred to as PD). It is called)).

Further, as one that realizes signal transmission between the VTR housing and the drum, for example, Japanese Patent Laid-Open No. 62-
There is a magnetic recording / reproducing apparatus described in Japanese Patent No. 117105. In this magnetic recording / reproducing apparatus, as shown in FIG. 6, light of wavelengths λ1, λ2 and λ3 output from the light emitting diodes 115a to 115c at the time of recording is reflected by the lenses 118a to 11a.
It is condensed by 8c.

The light of wavelength λ1 is reflected by the mirror 127 and then enters the beam splitter 119. Wavelength λ2
Light is also incident on the beam splitter 119 and has a wavelength of λ1.
Mixed with the light of. The light having the wavelength λ3 is reflected by the mirror 128, then enters the beam splitter 120, and is mixed with the light having the wavelengths λ1 and λ2.

The light emitted from the beam splitter 120 passes through the beam splitter 121, and enters the relay lens 123 on the rotating side via the relay lens 122. Lens 1
By aligning the optical axes of 22, 123 and the optical axis of the rotary magnetic head device, the light can be transmitted and received without being affected by the rotation.

The light emitted from the relay lens 123 is reflected by the beam splitter 124 and enters the spectral prism 125. The spectral prism 125 transmits the incident light to wavelengths λ1 and λ
The light is split into three wavelengths of 2, λ3. The respective light is condensed by the condensing lenses 126a to 126c into the photo detector 117.
It is projected on a to 117c and converted into photocurrent.

On the other hand, at the time of reproduction, the light emitting diode 11 provided on the rotation side and emitting light of wavelengths λ1, λ2 and λ3.
The optical outputs of 2a to 112c are lenses 129a to 129.
c, mirrors 130 and 131, beam splitter 132,
The light is mixed by 133, passes through the beam splitter 124, is incident on the relay lens 123, and is incident on the fixed-side relay lens 122 from the rotation side in the direction opposite to that at the time of recording.

The light that has passed through the relay lens 122 is reflected by the beam splitter 121, and then the spectral prism 134.
Is incident on. The spectral prism 134 transmits the incident light to the wavelength λ.
The light is split into three wavelengths of 1, 1, 2 and 3. The respective lights are projected onto the photodetectors 113a to 113c by the condenser lenses 135a to 1356c and converted into photocurrents.

That is, the magnetic recording / reproducing apparatus transmits the signals of the three channels to the three wavelengths and transmits them without being influenced by the rotation by the same optical axis matching the rotation axis of the drum. Note that it is also possible to transmit signals bidirectionally.

On the other hand, there is a multi-channel same transmission path system by wavelength demultiplexing, which is one of the optical communication technologies currently put to practical use in optical fibers and the like. This transmission line system transmits light of many wavelengths in the same fiber,
Light having a wavelength corresponding to each channel is multiplexed and sent to a fiber, light emitted from the fiber is demultiplexed, and each light is made incident on a light receiving element corresponding to each channel.

In this case, a prism or a half mirror coated with a metal or dielectric thin film that reflects only a specific wavelength and transmits other wavelengths is used to combine light of wavelengths corresponding to each channel.・ Demultiplex.

By the way, recording / recording a large capacity information medium
A device capable of high-capacity and high-density recording is required for reproduction. As one of the VTRs, in order to increase the recording capacity, narrow tracks, multi-channels, and high drum rotation speeds have been achieved. In this case, the amount of information transmitted between the magnetic head for exchanging information and the magnetic tape for storing information increases, and the signal system is required to have a wide band.

[0025]

However, the conventional rotary transformer shown in FIG. 4 has a narrow transmission band of several tens of MHz, and it is difficult to transmit a large amount of information of several hundred MHz to several GHz. there were.

Further, in the conventional optical rotary joint shown in FIG. 5, the drum rotating at a high speed has an eccentricity of about several μm, so it is necessary to allow a margin for the transmission line. Further, when the number of parts of the bearing 76 increases, eccentricity is likely to occur. For this reason, in order to realize optical transmission, it is necessary to design the eccentricity with considerably improved accuracy, and it is difficult to use the optical rotary joint.

Further, in the rotary electronic device disclosed in JP-A-59-160344 and the rotary head cylinder disclosed in JP-A-60-239901, only signals for one channel can be transmitted. Therefore, the rotary electronic device and the rotary head cylinder cannot be used in the VTR system that needs to simultaneously transmit signals from a plurality of magnetic heads.

Further, the magnetic recording / reproducing apparatus described in the above-mentioned Japanese Patent Laid-Open No. 62-117105 uses a spectral prism to separate the multiplexed lights of a plurality of wavelengths. However, the relative positioning of the spectral prism, the lens system, and the light receiving element is troublesome.

Further, in the channel separation system based on the polarization characteristic of light described in Japanese Patent Laid-Open No. 62-117105, the plane of polarization is rotated in the rotating body. For this reason, a mechanism that follows the rotation of the polarization plane is required, and the device is complicated.

An object of the present invention is to provide a transmission band of several hundred MHz between a rotating body and a fixed body used in a VTR or the like.
To provide an optical rotary transformer capable of transmitting a large amount of information of up to several GHz, miniaturizing and reducing the amount of parts mounted on a rotating body, and being less susceptible to the rotational speed, position, and eccentricity of the rotating body. It is in.

[0031]

The present invention employs the following means in order to solve the above-mentioned problems. According to the invention of claim 1, in an optical rotary transformer for transmitting a signal between two electronic devices rotatably connected by one rotation shaft by an optical signal, a light having a wavelength longer than a cutoff wavelength is transmitted, and the cutoff wavelength is longer than the cutoff wavelength. Providing a plurality of light transmitting / reflecting portions formed by using a thin film that reflects light of a short wavelength and having different cutoff wavelengths, the plurality of light transmitting / reflecting portions so that the different cutoff wavelengths are sequentially lengthened as the distance from the air gap increases. A group of light transmitting / reflecting parts, which are connected in cascade in multiple stages, is arranged in each of the two electronic devices, the optical axis of the light transmitting / reflecting part group is aligned with the rotation axis, and one of the two electronic devices is arranged. And a group of light transmitting / reflecting portions provided on the other of the two electronic devices are opposed to each other via the gap.

According to the present invention, in the light transmission / reflection section group provided in one of the two electronic devices, for example, an LD
The light of each cutoff wavelength emitted by is reflected by the light transmitting / reflecting portion corresponding to the light of each cutoff wavelength. Then, since each cutoff wavelength is sequentially lengthened with increasing distance from the air gap, the light of each cutoff wavelength is transmitted through the light transmission reflection part cascade-connected in the subsequent stage of the light transmission reflection part, through the air gap, It is sent to the light transmitting / reflecting unit group provided in the other electronic device.

Next, in the light transmitting / reflecting portion group provided in the other electronic device, the light having the respective cutoff wavelengths has a light transmitting / reflecting portion cascade-connected in front of the light transmitting / reflecting portion corresponding to the light having the respective cutoff wavelengths. And is reflected by the light transmitting / reflecting portion corresponding to the light of each cutoff wavelength.

Therefore, the light transmitting / reflecting portion group provided in one electronic device can combine and transmit lights having different cut-off wavelengths, and the light transmitting / reflecting portion group provided in the other electronic device can combine light. The emitted light can be demultiplexed. Also, an optical signal can be transmitted from the other electronic device to the one electronic device.

As a result, a large amount of information having a transmission band of several hundred MHz to several GHz is electrically transmitted between the two electronic devices.
It can be transmitted without receiving mechanical noise. Further, since the light transmitting / reflecting section is used in which the light transmitting / reflecting sections are connected in cascade in multiple stages, the components mounted on the rotating body can be miniaturized and reduced in quantity. Since it is not in contact with the equipment due to the air gap, the rotation speed, position, and
Less susceptible to eccentricity.

The invention of claim 2 is characterized in that each of the light transmitting / reflecting portions is a wavelength selective half mirror.

[0037]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an optical rotary transformer of the present invention will be described in detail below with reference to the drawings.

<First Embodiment> A first embodiment of the optical rotary transformer of the present invention will be described. FIG. 1 shows a block diagram of a configuration of an optical rotary transformer at the time of recording. In FIG. 1, an optical signal can be transmitted from a fixed VTR housing side 1 to a rotatable rotating drum side 3.

The VTR housing side 1 outputs a recording system signal processing circuit 11 for outputting a processed recording signal, LDs 15a to 15d corresponding to four channels, LD drivers 13a to 13d for driving the LDs 15a to 15d, and an LD 15a.
And a multiplexing / demultiplexing prism 17a that multiplexes the lights from 15d. The LDs 15a to 15d output lights having wavelengths different from each other, and the LDs 15a to 15d corresponding to the respective channels.
The wavelength of the light output from the
1, λ2, λ3, and λ4.

The combining / branching prism 17a includes LDs 15a ...
The respective lights output from 15d are combined and sent to the rotating drum side 3 through the air gap.

The rotating drum side 3 has a multiplexing / demultiplexing prism 17b for demultiplexing the demultiplexed light from the fixed-side demultiplexing / demultiplexing prism 17a, and PDs 19a to 1a corresponding to the demultiplexed lights.
9d and amplifiers 21a to 21d. A magnetic head is provided for each channel.

In the optical rotary transformer configured as described above, at the time of recording, a modulation current for converting the recording signal of each channel from the recording system signal processing circuit 11 of the VTR main body into an optical signal and causing the LDs 15a to 15d to emit light. The signal is transmitted to the LD drivers 13a to 13d for generating the.

Then, the light modulated by the signal equivalent to the recording signal is emitted from the LDs 15a to 15d. The lights of four wavelengths are combined by the combining / branching prism 17a so as to pass through one transmission path, and are transmitted from the VTR housing side 1 to the combining / branching prism 17b on the rotating drum side 3 through the air gap. To be done.

In the rotating body on the light receiving side, the combining / branching prism 17b demultiplexes the lights of four wavelengths in one transmission path into four separate transmission paths, respectively, and emits them. The light is incident on the PDs 19a to 19d on the side. The signal is demodulated and amplified by the amplifiers 21a to 21d on the rotating drum and transmitted to the magnetic head. Further, it is recorded on a magnetic tape as a magnetic signal.

FIG. 2 shows a block diagram of the configuration of the optical rotary transformer during reproduction. In FIG. 2, V from the rotating drum side 3
An optical signal can be transmitted to the TR housing side 1.

On the rotary drum side 3, amplifiers 23a to 23d for amplifying signals from the magnetic head, LDs 27a to 27d corresponding to the four channels, LD drivers 25a to 25d for driving the LDs 27a to 27d, and multiplexing / demultiplexing. And a prism 17b. The VTR housing side 1 has a combining / branching prism 17a, PDs 29a to 29d, and an amplifier 31a.
31 d and a reproduction system signal processing circuit 33 that processes the amplified reproduction signal of each channel.

According to this structure, the signal read by the magnetic head from the magnetic tape is reproduced by the amplifier 23 during reproduction.
The signals amplified by a to 23d are transmitted to the LD drivers 25a to 25d which generate the modulation current for causing the LDs 27a to 27d on the rotating drum to emit light.

Then, the light modulated by the signal equivalent to the reproduction signal is emitted from the LDs 27a to 27d. The light of four wavelengths is combined by the combining / splitting prism 17b so as to pass through one transmission path, and is transmitted from the rotating body to the fixed body via the air gap.

In the fixed body on the light receiving side, the multiplexing / branching prism 17a splits the lights of the four wavelengths in one transmission path into four separate transmission paths, respectively, and outputs them.
The light is incident on the PDs 29a to 29d on the R casing 1 side. The signal is demodulated and amplified by the amplifiers 31a to 31d on the VTR housing side 1, and the amplified signal is transmitted to the reproduction system signal processing circuit 33.

<Second Embodiment> Next, an optical rotary transformer according to a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing the configuration of a medium drum recording / reproducing apparatus including an optical rotary transformer. In FIG. 3, a rotatable middle drum 3a and an upper fixed drum 6a fixed to a VTR housing are provided.

The middle drum 3a is rotationally driven by a motor (not shown) installed on the lower fixed drum side, and the middle drum 3a and the upper fixed drum 6a are in contact with each other with a gap.

The upper fixed drum 6a has wavelengths λ different from each other.
LDs 41a to 41 that emit light of 1, λ2, λ3, and λ4
d, and collimator lenses 43a to 43d that convert the light from the LDs 41a to 41d into parallel light having a circular cross section.
Quarter-wave plates 45a to 45d that create circularly polarized light having no plane of polarization in a specific direction from the parallel light, isolators 47a to 47d that transmit light in only one direction, and PDs 49a to 49a.
49d, half mirrors 51a to 51d for demultiplexing the input light into two directions of PDs 49a to 49d and a demultiplexing / demultiplexing bidirectional transmission device 53, and a demultiplexing / demultiplexing bidirectional transmission device 53.
With.

The LD 41b is an LD that emits light having a wavelength λ2 shorter than the wavelength λ1 of the LD 41a.
Between the wavelength λ3 of the LD 41d and the wavelength λ4 of the LD 41d is λ1> λ2
>Λ3> λ4. LD 41a1 to be described later
Regarding the size relationship of the wavelength of the LD 41d1, the LD 41a
~ LD41d is exactly the same as those relationships. In the second embodiment, in order to divide four channels according to wavelengths, 1550 nm band, 1310 nm band, 850 nm band,
Four wavelengths in the 780 nm band are used.

The multiplexing / demultiplexing bidirectional transmission device 53 is composed of a multiplexing / demultiplexing prism coated or vapor-deposited with thin films 55a to 55d cascaded in multiple stages. The thin films 55a-5
Each of 5d reflects only light having a specific wavelength and transmits light having a wavelength other than the specific wavelength.

The thin film 55a reflects only the light of wavelength λ1. The thin film 55b reflects only the light having the wavelength λ2 and transmits the light having the wavelength λ1 or more. The thin film 55c reflects only the light having the wavelength λ3 and transmits the light having the wavelength λ2 or more. The thin film 55d reflects only the light having the wavelength λ4 and transmits the light having the wavelength λ3 or more.

The middle drum 3a also has the same structure as the upper fixed drum 6a, and includes LDs 41a1 to 41d1, collimator lenses 43a1 to 43d1, and quarter wavelength plates 45a1.
45d1, isolators 47a1 to 47d1, PD49
a1 to 49d1, half mirrors 51a1 to 51d1 and a multiplexing / demultiplexing bidirectional transmission device 53a.

The multiplexing / demultiplexing bidirectional transmission device 53a is composed of a multiplexing / demultiplexing prism to which thin films 55a1 to 55d1 cascade-connected in multiple stages are applied or vapor-deposited. Thin film 55a
.About.55d and the thin film 55a1 to 55d1 have cutoff wavelengths that gradually increase with distance from the air gap 56.

The multiplexing / demultiplexing bidirectional transmission device 53 provided on the upper fixed drum 6a and the multiplexing / demultiplexing bidirectional transmission device 53a provided on the middle drum 3a are arranged to face each other with a gap 56 therebetween.
The optical axes 54 of the multiplexing / demultiplexing bidirectional transmission devices 53, 53a are aligned with the rotation axis (not shown) of the middle drum 3a.

A wavelength selective half mirror group formed by using the thin films 55a to 55d is arranged on each of the upper fixed drum 6a and the middle drum 3a instead of the multiplexing / demultiplexing prism having the thin film. Is also good.

The electric power of the element on the intermediate drum 3a (rotary drum) is the slip ring system, which is conventionally used,
Alternatively, it is supplied by a rotary transformer using electromagnetic coupling.

Next, the operation of the recording / reproducing apparatus thus constructed will be described. Here, one channel for recording will be described as an example. First, the modulated recording signal from the VTR main body directly modulates the LD 41a having the wavelength λ1 which is a light emission source to emit light, and the light from the LD 41a becomes parallel light having a circular cross section by the collimator lens 43a.

Here, if the light beam at the exit end of the collimator lens 43a has a polarized light due to the polarized light of the light source, it may be slightly reflected by the prism in the multiplexing / demultiplexing bidirectional transmission device 53 or the half mirror 51a. The amount of attenuation increases and the amount of light decreases. For this reason, the quarter-wave plate 45a provided on the exit side of the collimator lens 43a creates a circularly polarized wave having no plane of polarization in a specific direction to prevent a decrease in the amount of light.

However, when the reflecting element and the prism are designed so as not to be influenced by the polarized wave,
The wave plate 45a may not be used. That is, after measuring the polarization characteristics of the LD 41a to be used, the quarter wave plate 4
Determine whether to use 5a.

Further, the circularly polarized wave from the quarter-wave plate 45a passes through the isolator 47a and the half mirror 51a,
It is incident on the multiplexing / demultiplexing bidirectional transmission device 53.

The light of wavelength λ1 incident on the multiplexing / demultiplexing bidirectional transmission device 53 is reflected by the thin film 55a, changes its direction by 90 degrees, and travels to the thin film 55b.

Since all of the thin films 55b to 55d are processed so as to transmit the light having the wavelength λ1, the light having the wavelength λ1 goes straight as it is, and the multiplexing / demultiplexing bidirectional transmission device 53a in the middle drum 3a. Is incident on. The light having the wavelength λ1 incident on the multiplexing / demultiplexing bidirectional transmission device 53a receives the thin films 55b1 to 5b5.
5d1 is transmitted.

The transmitted light of wavelength λ1 is reflected by the thin film 55a1 and changes its direction by 90 degrees again. After that, the light of wavelength λ1 is reflected by the half mirror 51a1, reaches the PD 49a1, and the signal is transmitted to the magnetic head via a demodulator / head amplifier (not shown).

Here, after the prism blocks including the thin film 55a to 55d and 55a1 to 55d1 of the multiplexing and demultiplexing prism to be used, respectively, are manufactured, they are bonded together with an adhesive or the like that transmits light, and fixed. It is manufactured as two large blocks used in the system and the rotating system.

Next, when reproducing the signal recorded on the magnetic tape, the LD 41a1 is directly modulated to emit light,
The light is emitted from the collimator lens 43a1 and the quarter wave plate 4
5a1, isolator 47a1, half mirror 51a1
And is incident on the multiplexing / demultiplexing bidirectional transmission device 53a.

The light of wavelength λ1 incident on the multiplexing / demultiplexing bidirectional transmission device 53a is reflected by the thin film 55a1 and
The direction is changed to the thin film 55b1.

Thin films 55b1 to 55d1 and thin films 55b to 5
All of 5d transmit light of wavelength λ1, and the transmitted light of wavelength λ1 is reflected by the thin film 55a and changes its direction by 90 degrees again. After that, the light of wavelength λ1 is reflected by the half mirror 51a and is incident on the PD 49a, and the video signal is reproduced through the demodulation device.

Here, the transmission of the light of the cutoff wavelength λ1 emitted from the LD 41a has been described. Further, the LD4
1a and LD41b to LD41d transmit all the light emitted at the same time, the cutoff wavelength λ2 of LD41b
Light is reflected by the thin film 55b, and the thin films 55c to 55d, 5
5c1 to 55d1 are transmitted and reflected by the thin film 55b1.
The light of the cutoff wavelength λ3 of the LD 41c is reflected by the thin film 55c, transmitted through the thin films 55d and 55d1, and reflected by the thin film 55c1. The light of the cutoff wavelength λ4 of the LD 41d is the thin film 55d.
And the thin film 55d1.

Thus, the multiplexing / demultiplexing bidirectional transmission device 5
3,53a can be used to simultaneously transmit lights having different wavelengths.

That is, the multiplexing / demultiplexing bidirectional transmission device 53,
A large amount of information can be transmitted electrically or mechanically from the rotating drum of the VTR to the main body that is the fixed body of the VTR or from the main body that is the fixed body of the VTR to the rotary drum of the VTR by the optical transmission method using the 53a. It can be transmitted without being affected by various noises, and its band reaches several GHz.

Further, a system for dividing a channel by these different wavelengths and performing bidirectional transmission on one transmission line requires a device for efficiently multiplexing / demultiplexing a plurality of wavelengths. In the form 2, the system can be miniaturized by integrally manufacturing the prism that efficiently multiplexes and demultiplexes a plurality of wavelengths. In addition, the number of alignment parts can be reduced, and errors during mounting and operation can be reduced.

Further, an air gap 56 is provided between the fixed combining / splitting prism and the rotating combining / splitting prism.
The rotating system and the fixed system are not in contact with each other. For this reason, damage to the mechanism due to eccentricity does not occur, and there is no need to mechanically design for eccentricity. When eccentricity occurs, the center of the optical axis that coincides with the rotation axis also shifts, but in this case,
Collimator lenses 43a to 43d, 43a1 to 43d1
The design can be changed to make the diameter of the optical axis larger than the amount of eccentricity, and measures can be taken to prevent the influence of eccentricity.

In the second embodiment, in order to divide the four channels according to wavelengths, the 1510 nm band, 131
Although four wavelengths of 0 nm band, 850 nm band, and 780 nm band are used, another wavelength may be used, such as wavelength division within a narrow band of 1310 nm band. Further, the number of channels is not limited to four and can be increased.

Further, in FIG. 3, although the optical system is shown concentrated in one direction perpendicular to the rotation axis, the thin film 55a is shown.
Alternatively, the reflection angles of 55d and 55a1 to 55d1 may be changed to be radially arranged in a direction perpendicular to the rotation axis. Further, the present invention can be applied to information transmission between a rotating body having a general rotating shaft and a fixed body, or between rotating bodies.

[0079]

According to the present invention, a plurality of light transmitting / reflecting portions formed by using a thin film that transmits light having a wavelength longer than the cutoff wavelength and reflects light having a wavelength shorter than the cutoff wavelength are provided. , Each of the two electronic devices is provided with a light transmitting / reflecting portion group in which a plurality of light transmitting / reflecting portions are connected in cascade so that different cutoff wavelengths are sequentially lengthened as the distance from the air gap increases. Align the optical axis with the rotation axis,
In addition, since one light transmitting / reflecting portion group of the two electronic devices and the other light transmitting / reflecting portion group of the two electronic devices are opposed to each other through the gap, the light emitting source in one light transmitting / reflecting portion group. The light of each cutoff wavelength emitted by is reflected by the light transmitting / reflecting portion corresponding to the light of each cutoff wavelength, and since each cutoff wavelength gradually becomes longer as the distance from the air gap increases, the light transmitting / reflecting portion is provided in the subsequent stage. The light is transmitted through the light transmitting / reflecting portions connected in cascade, and is sent to the light transmitting / reflecting portion group provided in the other electronic device through the gap.

In the other group of light transmitting / reflecting portions, the light of each cutoff wavelength passes through the light transmitting / reflecting portion cascade-connected in front of the light transmitting / reflecting portion corresponding to the light of each cutoff wavelength, and the light of each cutoff wavelength is transmitted. Is reflected by the light transmitting / reflecting portion corresponding to.

Therefore, the light transmitting / reflecting portion group provided in one electronic device can combine and transmit lights having different cut-off wavelengths, and the light transmitting / reflecting portion group provided in the other electronic device combines them. Can split light. Moreover, an optical signal can be transmitted from the other electronic device to the one electronic device.

As a result, a large amount of information having a transmission band of several hundred MHz to several GHz can be electrically transferred between two electronic devices.
It can be transmitted without receiving mechanical noise. Further, since the light transmitting / reflecting section is used in which the light transmitting / reflecting sections are connected in cascade in multiple stages, the components mounted on the rotating body can be miniaturized and reduced in quantity. Since it is not in contact with the equipment due to the air gap, the rotation speed, position, and
Less susceptible to eccentricity.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of an optical rotary transformer at the time of recording of the present invention.

FIG. 2 is a configuration diagram of a first embodiment of an optical rotary transformer during reproduction according to the present invention.

FIG. 3 is a second embodiment of the optical rotary transformer of the present invention.
It is a block diagram of the recording / reproducing apparatus containing.

FIG. 4 is a schematic sectional view of a rotary drum in a conventional VTR.

FIG. 5 is a sectional view of a conventional optical rotary joint.

FIG. 6 is a configuration diagram showing an example of an optical system of a conventional magnetic recording / reproducing apparatus.

[Explanation of symbols]

1 VTR housing side 3 Rotating drum side 4 Magnetic head 5a, 5b Rotary transformer 6 Fixed drum 7a Groove 7b Winding 8 Rotating shaft 9 Motor 11 Recording system signal processing circuit 13a-13d, 25a-25d LD driver 15a-15d, 27a- 27d LD 17a, 17b Multiplexing / splitting prism 19a-19d, 29a-29d PD 21a-21d, 23a-23d, 31a-31d Amplifier 41a-41d1 LD 43a-43d1 Collimator lens 45a-45d1 1/4 wavelength plate 47a-47d1 Isolators 49a to 49d1 PDs 51a to 51d1 Half mirrors 53, 53a Combined demultiplexing bidirectional transmission device 54 Optical axes of combined demultiplexing bidirectional transmission device 55a to 55d1 Thin film applied to prism 56 Gap

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[Procedure amendment]

[Submission date] May 10, 1996

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

[Correction contents]

[Figure 3]

Claims (2)

[Claims] 1. An optical rotary transformer for transmitting a signal between two electronic devices rotatably connected by one rotating shaft by an optical signal, wherein a wavelength longer than a cutoff wavelength is transmitted and a wavelength shorter than the cutoff wavelength is transmitted. The plurality of light transmitting / reflecting portions having different cutoff wavelengths formed by using a thin film that reflects the light are provided, and the plurality of light transmitting / reflecting portions are sequentially lengthened as the different cutoff wavelengths are separated from the air gap. A group of light transmitting / reflecting sections cascade-connected in multiple stages is arranged in each of the two electronic devices, and an optical axis of the light transmitting / reflecting section groups is aligned with the rotation axis, and provided in one of the two electronic devices. An optical rotary transformer characterized in that the group of light transmitting / reflecting portions and the group of light transmitting / reflecting portions provided on the other of the two electronic devices are opposed to each other via the gap. 2. The optical rotary transformer according to claim 1, wherein each of the light transmitting / reflecting portions is a wavelength selective half mirror.