JPH04315328A - Digital signal transmitter - Google Patents

Abstract

PURPOSE:To obtain the small sized digital signal transmitter easy to manufacture when the transmission of multi-channel digital signal is implemented between a rotor and a stator through optical space transmission in a rotary head type magnetic recording and reproducing device. CONSTITUTION:2N-sets of electrooptic conversion circuits 4-1-4-8 and N-sets of optoelectric conversion circuits 3-1-3-8 provided onto a circle around a rotary shaft at an equal interval for the transmission of N-channels of digital signals are arranged to faces of a stator 1 and a rotor 1 opposite to each other, and a switch circuit 8 and a control circuit 12 controlling switch ON/OFF of the switch circuit 8 are provided between N-sets of input signals and the 2N-sets of electrooptic conversion circuits 4-1-4-8 and the control circuit 12 controls the switch circuit 8 so that the N-sets of input signals and outputs of the N-sets of optoelectric conversion circuits 3-1-3-8 are always in 1:1 correspondence even when the N-sets of optoelectric conversion circuits 3-1-3-8 at the rotor side 1 are rotated. The circuit integration of the electrooptic conversion circuits, the optoelectric conversion circuits, the switch circuit and the control circuit is facilitated.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

[Field of Industrial Application] This invention relates to a digital signal transmission device for optically transmitting and receiving digital signals between a rotating side and a stationary side in a rotary head type magnetic recording/reproducing device without contact. It is.

0002

[Prior Art] Generally, in a rotary head type magnetic recording/reproducing device, a rotary transformer is used to transmit and receive signals in a non-contact manner between a rotating side equipped with a magnetic head, preamplifier, magnetic head driver, etc., and a stationary side. is used.

A rotary transformer is a type of transformer that consists of a rotating element and a stationary element that are magnetically coupled through a small air gap, but in order to perform signal transmission over a wide band with little signal loss, the air gap should be 30 μm. It is very small, ~50 μm, and must be installed with high precision. In order to solve such problems, an optical transmission means has been proposed in which a light emitting element and a light receiving element are provided on a rotating side and a stationary side, and an electric signal is converted into light for spatial transmission.

Japanese Patent Laid-Open No. 58-50838 discloses that a plurality of signals on the rotating side or on the fixed side are converted into light by a plurality of light emitting elements that generate light of different wavelengths, and a half mirror or the like is used to convert the signals on the rotating side to the rotating shaft. It is a multi-channel light beam that is focused, wavelength-multiplexed, and then spatially transmitted, separated into multiple lights by a half mirror or wavelength-selective optical element (optical filter) on the light-receiving side, and converted into an electrical signal by the light-receiving element. A signal transmission device is disclosed. This signal transmission device spatially transmits the light of each channel on a single rotation axis, so the transmission characteristics do not change depending on the rotation angle of the rotation side, but it has half mirrors and wavelength selectivity corresponding to the number of channels. There is a problem that an optical element is required, making the device complicated and large.

[0005] As a signal transmission device in which each channel has an independent optical transmission space, Japanese Patent Application Laid-open No. 58-50839 discloses a system in which concentric light guide members are provided and transmission is performed using their directional coupling effect. The device has been disclosed in Japanese Unexamined Patent Application Publication No. 1986-
Japanese Patent No. 50840 discloses a device that transmits light using concentric light scattering elements. However, light guide members with a directional coupling function and elements with a light scattering function have poor light transmission efficiency, and leakage to other channels is quite large. Furthermore, the size of the element itself becomes considerably large.

Furthermore, Japanese Patent Application Laid-Open No. 63-282903 discloses a device that uses a reflecting mirror to transmit light from a plurality of light emitting elements located not on the rotation axis to a plurality of light receiving elements placed on the rotation axis. However, since the reflecting mirror is large, there is a problem that the device becomes large. Also, JP-A-1-1846
No. 04 and Japanese Unexamined Patent Publication No. 1-317204 disclose a device that performs multi-channel optical transmission by placing an arc-shaped light receiving element on a surface facing a light emitting element placed not on the rotation axis. However, the light-receiving element disclosed in JP-A-1-184604 uses an optical fiber, so it is large. Therefore, there was a problem in that it was difficult to manufacture.

[0007]

[Problems to be Solved by the Invention] As described above, conventional signal transmission devices using spatial optical transmission have problems in that as the number of signal transmission channels increases, the device becomes complicated and large, and the fabrication of the light receiving element becomes difficult. was there.

The present invention provides a compact and easy-to-manufacture digital signal transmission device when multi-channel digital signal transmission between the rotating side and the fixed side is performed by spatial optical transmission in a rotary head type magnetic recording/reproducing device. The purpose is to do something. [Structure of the invention]

[0009]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the digital signal transmission device of the present invention has a rotating shaft on the fixed side when transmitting N-channel digital signals from a fixed side to a rotating side. 2N electrical-to-optical conversion circuits are provided at equal intervals on the circumference centered on the rotation axis, and on the rotating side opposite to this fixed side, N electrical-to-electrical conversion circuits are provided on the circumference centered on the rotation axis. The circuits are arranged at equal intervals to perform spatial transmission of light, and a switch circuit is provided between the N input signals on the fixed side and the 2N electrical-to-optical conversion circuits to convert the optical-to-electrical conversion circuits on the rotating side. By controlling the switch circuit depending on the rotation angle so that the switch circuit transmits a signal to every other N electrical-to-optical conversion circuits closest to the optical-to-electrical conversion circuit even when the switch circuit rotates. , is characterized in that it is configured such that N input signals on the fixed side and output signals from the optical-to-electric conversion circuit are transmitted in a one-to-one correspondence.

0010

[Operation] In the digital signal transmission device for optical transmission according to the present invention, N-channel digital signal transmission controls N optical-electric conversion circuits, 2N electric-optical conversion circuits, switch circuits, and switch circuits. Can be configured with a control circuit. The optical-to-electrical conversion circuit consists of a light-receiving element such as a photodiode and a broadband amplifier, and the electric-to-optical conversion circuit consists of a light-emitting element such as a light-emitting diode or a laser diode and its driving amplifier, and can be integrated into an integrated circuit (for example, Shimada et al. , Sakura and Katagiri, “100 Mbps Optical Transmission Link” (Toshiba Review, Vol. 44, No. 12, 1989,
(pages 972 to 974), etc.). Further, the switch circuit and the control circuit can be integrated into one chip by using a gate array. Therefore, the digital signal transmission device according to the present invention can be easily integrated into a circuit, making it extremely compact. Furthermore, the light receiving element is a commonly used photodiode or the like and is easy to manufacture.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram of a digital signal transmission device according to an embodiment of the present invention, and FIG. 2 is a waveform diagram for explaining a method of controlling the switch circuit of FIG. 1, in which the number of signal transmission channels is four. It shows the case.

In FIG. 1, four light receiving elements 3-1 to 3-4, such as photodiodes, are arranged on the rotating side 1 at equal intervals along the circumference on the opposing surfaces of the rotating side 1 and the fixed side 2. However, on the fixed side, there are eight light emitting elements 4-1 to 4- such as light emitting diodes.
8 is placed. Four light receiving elements 3-1 on rotation side 1
The output of ~3-4 is the output of four broadband amplifiers 5-1~5-4.
and output terminals 6-1 to 6-4 respectively.
is output to. On the other hand, the eight input terminals 7-1 on the fixed side 2
The inputs from ~7-8 are applied to the switch circuit 8, and the eight outputs of the switch circuit 8 are applied to the eight light receiving elements 4-1 to 4 through eight drivers 9-1 to 9-8, respectively. -8
has been added to.

Further, inputs from input terminals 10 and 11 are applied to three outputs of a control circuit 12 to a switch circuit 8, so that the relationship between input and output of the switch circuit 8 is controlled. The input terminal 10 has a terminal 1 synchronized with the rotation of the rotating side 1.
A pulse PG shown in FIG. 2(a) whose period is rotation is applied to the input terminal 11, and 8
A clock signal CK synchronized with the pulse PG having pulses ×m (m is a positive integer: 5 in FIG. 2(b)) is applied. The control circuit 12 is a circuit that uses the pulse PG and the clock signal CK to create a signal that divides one cycle of the pulse PG synchronized with the pulse PG into eight equal parts, that is, into eight light emitting elements, as shown in FIG. 2(d), ( Three output signals S0 shown in e) and (f)
, S1 and S2 are output. That is, for one period of the pulse PG, S0 is a 4-cycle rectangular wave, S1 is a 2-cycle rectangular wave, S2 is a 1-cycle rectangular wave, and S0, S
1, S2, where the high level is expressed as "1" and the low level is expressed as "0", one period of pulse PG, that is, one rotation period of rotation side 1, as shown in Fig. 2 (g). T0 can be equally divided into eight intervals T1 to T8. On the other hand, the odd numbered terminals 7-1, 7 of the input terminals 7-1 to 7-8
-3, 7-5, 7-7 are respectively applied with four channels of digital signals I0, I1, I2, I3 to be transmitted, and the even numbered terminals 7-2, 7-4, 7-6, 7
All “0” signals are added to −8. Now, it is assumed that the rotating side 1 rotates clockwise at a constant speed, and time t=
It is assumed that the light receiving element 3-1 is located on the line O-Y shown in FIG. 1 at the reference time 0. At this time, the eight outputs Q0, Q1,
The truth table for Q2, Q3, Q4, Q5, Q6, Q7 is the 4-channel digital signal I0, I
1, I2, I3 and the outputs of the control circuit S0, S1
, S2 is expressed as shown in Table 1.

[0014]

[Table 1]

Due to such a logical operation of the switch circuit 8, for example, focusing on the digital signal I0, in the interval from time t to T1, the light receiving element 3-1 is switched to the light emitting element 4-1.
1, the digital signal I0 is sent to the output terminal 6-1 via the output Q0 of the switch circuit 8, the driver 9-1, the light emitting element 4-1, the light receiving element 3-1, and the broadband amplifier 5-1. In the section where time t is T2, the light receiving element 3-1 exists near the light emitting element 4-8, so I0 is transmitted to the output Q7 of the switch circuit 8 and the driver 9.
-8, is transmitted to the output terminal 6-1 via the light emitting element 4-8, the light receiving element 3-1, and the broadband amplifier 5-1. Similarly T
At T3, the digital signal I0 is applied to the light emitting element 4-7 near the light receiving element 3-1, and at T4, I0 is applied to the light emitting element 4-6 near the light receiving element 3-1 at T5.
In this case, I0 is the light emitting element 4- near the light receiving element 3-1.
5, at T6, I0 is connected to the light emitting element 4-4 near the light receiving element 3-1, and at T7, I0 is connected to the light receiving element 3-1.
At T8, I0 is added to the light emitting element 4-3 located near the light receiving element 3-1, and is transmitted to the output terminal 6-1. Therefore, input terminal 7-1
The input I0 from the switch circuit 8 is always applied to the light emitting element located near the light receiving element 3-1 by the logic operation of the switch circuit 8, and is transmitted to the output terminal 6-1 by spatial transmission of light. Similarly, the digital signals I1, I2, and I3 are always transmitted to the output terminals 6-2, 6-3, and 6-4, respectively. Regarding crosstalk between channels,
Among the light emitting elements 4-1 to 4-8, the digital signal I0
, I1, I2, and I3 are added to every other light emitting element, and "0" is always added to the light emitting elements in between, so even if a little light from an adjacent light emitting element is received, more light is added. Crosstalk does not occur unless light from an adjacent light emitting element is received. It is easy to arrange the light emitting element and the light receiving element in this way.

Here, the switch circuit 8 is a logic element called an 8-bit shift matrix or barrel shifter, and an example of an integrated circuit is F100158 manufactured by Fairchild Corporation. The control circuit 12 can be configured with a counter, as is clear from the waveform diagram of FIG. Therefore, the switch circuit 8 and the control circuit 12 can be formed into a one-chip integrated circuit using a gate array or the like. Furthermore, since the light emitting elements 4-1 to 4-8 and the light receiving elements 3-1 to 3-4 are not light emitting elements or light receiving elements with special specifications, the drivers 9-1 to 9-8 and the broadband amplifiers 5-1 to Like 5-4, it is easy to integrate into an integrated circuit and is suitable for miniaturization.

It should be noted that the present invention is not limited to the above-mentioned embodiment. For example, in the embodiment, the case where the number of signal transmission channels is 4 has been described, but the number of signal transmission channels is 2 or more. The present invention can also be applied to. In addition, in the above embodiment, the light emitting element and the light receiving element are arranged on opposing surfaces in the radial direction on the rotating side. Of course, N light-receiving elements on the rotating side and 2N light-emitting elements on the fixed side may be arranged facing each other on the circumference of the rotating side and the fixed side of the radius. Further, in the above embodiment, the rotation side is rotated clockwise, but by changing the truth table of Table 1, it is also possible to rotate the rotation side counterclockwise.

Furthermore, although a logic circuit such as a counter is used in the control circuit that controls the switch circuit, if the switch circuit is controlled using a detection circuit that detects the rotational position of the rotation side, the rotation side will not rotate at a constant speed. It is possible to transmit signals even if In addition, the present invention can be implemented with various modifications without departing from the scope of the invention.

[0019]

[Effects of the Invention] In the digital signal transmission device according to the present invention, the light emitting element and the light receiving element do not require special specifications, and the electrical-to-optical conversion circuit, the optical-to-electrical conversion circuit, the switch circuit, and the control circuit can be integrated into circuits. Since it is easy, it is possible to downsize the device.

[Brief explanation of the drawing]

FIG. 1 A schematic block diagram of a digital signal transmission device according to an embodiment of the present invention.

[Figure 2] Waveform diagram to explain the operation in Figure 1

[Explanation of symbols]

1...Rotation side
2... Fixed side 3-1 to 3-4... Light receiving element
4-1 to 4-8...Light emitting element

Claims (2)

[Claims] Claim 1: A digital signal transmission device for transmitting and receiving N-channel digital signals between a solid body side and a rotating side in a non-contact manner by spatial optical transmission, wherein the digital signal transmission device is arranged on a surface of the solid body side facing the rotating side. 2N (N>0: integer) electrical-to-optical conversion circuits, and N (N>0: integer) light-to-electrical conversion circuits disposed on the opposing surface of the solid side on the rotating side. , one of the 2N electrical-optical conversion circuits
A switch circuit that adds the N-channel digital signal every third time, and an ON/OFF switch of this switch circuit.
and a control circuit for controlling F, and the control circuit is configured to control the N-channel digital signals so that they are output in one-to-one correspondence with the N optical-to-electrical conversion circuits. A digital signal transmission device characterized by: 2. The digital signal transmission device according to claim 1, wherein the control circuit controls the switch circuit according to the rotation angle of the rotation side.