JPS6232658B2 - - Google Patents

Description

Detailed Description of the Invention The present invention is a bidirectional optical transmitter between a rotating body and a fixed body, and more specifically, a non-contact transmission and reception of signals using light between a steering column and a vehicle body. The present invention relates to an optical transmitter.

Conventionally, the mainstream signal transmission method for the steering column of an automobile has been a method of transmitting signals via an energizing device such as a sliding wheel.

However, this method has problems such as an increase in electrical resistance due to the formation of an oxide film on the contact parts, and the generation of small sparks due to contact jumping, so it is limited to simple signal transmission that does not require high reliability, such as horn switch signals. In recent years, signals have been As information density increases and there is a trend toward bidirectionality, that is, transmission and reception of signals are performed in parallel, the above-mentioned methods are reaching their limits.

For this reason, contactless transmission methods using radio waves or light have been successively proposed, but methods using radio waves, for example, are inherently unreliable because cars have high noise sources such as spark plugs. Recently, transmission systems using light have been gaining importance due to the drawback of low transmission speed.

Now, a general signal transmission method between a rotating body and a fixed body using light will be explained in detail with reference to FIGS. 1 to 3. FIG. 1 shows a schematic diagram of a bidirectional optical transmitter between a rotating body that is integrally fixed to a rotating shaft and a fixed body that is a bearing part of the rotating body. A pair of light emitting elements 4, 5 and a pair of light receiving elements 3, 6 are arranged on opposing surfaces of the fixed body 7, respectively.

The operation switch signal on the control wheel, which is a rotating body, is transmitted to the vehicle body, and the electric signal transmitted from the vehicle body, which is a fixed body, to the display device on the control wheel is transmitted by the electric signals mounted on the rotating body and the fixed body, respectively. Light pulses are multiplexed and modulated by a circuit, and the light is transmitted and received between the light emitting element 4 and the light receiving element 3, and between the light emitting element 5 and the light receiving element 6.

FIG. 2 shows the path of light from the light emitting element to the light receiving element in this optical signal transmitter. The solid line 8 represents the original optical signal path, and the broken line 9
indicates leakage light that enters a light receiving element of another signal system while being reflected between opposing surfaces.

As leakage light increases, interference increases and SN
(signal-to-noise ratio) decreases. In this figure, since the elements of the same signal system are located facing each other, the solid line 8, which is the original optical signal path, is the shortest, and leakage light is considerably reduced. In the rotational position shown in Figure 3, the elements of the same optical signal system are
Because it is offset by 180 degrees and faces the elements of other systems,
The signal-to-noise ratio will drop significantly.

As described above, according to the present invention, leakage light increases and decreases due to relative rotational movement between a fixed body and a rotating body, and S/
This was done to prevent the N ratio from changing significantly, and its purpose is to create a barrier in the space between the rotating body and the fixed body concentrically with the rotating shaft, dividing the opposing surfaces into two. By arranging pairs of optical elements of the same system inside and outside the barrier, and by making the wavelength band of light and the carrier frequency of the optical modulation wave different, the leakage of light to other signal systems is reduced, thereby reducing interference. An object of the present invention is to provide a transmitter with improved S/N ratio.

Next, the present invention will be explained in detail based on the drawings.

FIG. 4 shows an embodiment of the present invention, and FIG. 5 shows a V-
A cross-sectional view along V′ is shown. Here, cylindrical light-shielding barriers 2' and 7' protruding from the rotating body 2 and the fixed body 7, respectively, are loosely fitted into the space A.
Pairs 3, 4 and 5, 6 of a light-receiving element and a light-emitting element are arranged on the inner space A separated by the barrier and the opposite surface to the outer space B, thereby preventing light from leaking from each other. It is configured to do this.

Further, the shape and configuration of this barrier are not limited to those described above, and the opposing surfaces are divided into two to reduce leakage light. The shape may be arbitrary, for example, the protrusion may be formed from only one side, or a cylindrical object may be detachably attached.

The number of optical elements is not limited to one pair each in order to improve light transmission efficiency. On the other hand, there is a slight gap between the light-shielding barriers 2' and 7', and it is inevitable that light will leak into other spaces through the gap. Therefore, in order to obtain an even better interference prevention effect, a method is used in which the characteristics of both optical elements are made different and a means using different optical wavelength bands is used.

FIG. 6 shows the characteristics of the most common and inexpensive light emitting element used in the implementation of this invention, where the horizontal axis represents wavelength and the vertical axis represents relative luminous intensity.

Here, 10 is the characteristic of a GAP S-based light emitting diode with a center wavelength of 500 to 600 (mm) and a spectral width of 30 (mm), and 11 is a characteristic of a _{GAP S} -based light emitting diode with a center wavelength of 900 (mm) and a spectral width of 40.
(mm) characteristics of G _{A S} type light emitting diodes are shown.

In contrast, the light-receiving element is one whose center sensitivity range matches the center wavelength range of the above-mentioned light-emitting element, or one whose sensitivity is adjusted by combining these with an optical filter to prevent overlapping wavelength bands in both directions and prevent interference. It eliminates the

Moreover, in order to obtain an even further interference prevention effect, means for modulating the optical pulse signal with different carrier frequencies is used.

FIG. 7 shows a block diagram of an electric circuit for completely amplitude modulating and transmitting an optical pulse signal.

The electrical signal from the rotating body is subjected to complete amplitude modulation at carrier frequency ₁ by the modulator 20, converted into a light pulse by the light emitting element 5, and received by the light receiving element 6. The received pulse passes from the filter circuit 21 to the detection circuit 22 and is demodulated into the original signal.

On the other hand, the electric signal from the fixed body is modulated and demodulated at carrier frequency ₂ in the same manner as described above, and demodulated into the original signal on the fixed body side.

As explained above, the present invention utilizes a rotating body and a fixed station that pivotally supports the rotating body when multiple modulating electrical signals, converting them into optical pulses, and transmitting and receiving them in bidirectional signal transmission between the control wheels and the vehicle body of an automobile. Optical signal transmission is achieved by providing a concentric barrier with respect to the rotation axis on at least one of the rotating body or the fixed body between opposing surfaces of the body, and further arranging a pair or plurality of light emitting elements on the barrier and on the outside respectively. Because the paths are separated and the optical wavelength bands and optical carrier frequencies are different, it is now possible to construct a bidirectional optical transmitter with less interference, which has been difficult to realize in the past.

[Brief explanation of the drawing]

Figure 1 is a block diagram of a general bidirectional optical signal transmitter, Figures 2 and 3 are schematic diagrams of the optical transmission path, and Figure 4 is a schematic diagram of the optical transmission path.
The figure shows one embodiment of the present invention, and FIG. 5 shows a cross-sectional view of the optical transmitter of FIG. 4 taken along the line VV.
FIG. 6 shows a light emission characteristic diagram of the optical element, and FIG. 7 shows an electric circuit block diagram. In the figure, 1... rotating shaft, 2... rotating body, 2', 7'... barrier, 3, 6... light receiving element, 4, 5... light emitting element.

Claims (1)

[Claims] 1. Between the opposing surfaces of the rotating body and the fixed body, at least one of the rotating body or the fixed body is provided with a light-shielding barrier that is concentric with the rotation axis, and the interior and exterior of the barrier In a bidirectional optical transmitter in which a pair or plurality of light-emitting elements and light-receiving elements are arranged, the wavelength band of light propagated in the space divided by the light-shielding barrier or the carrier frequency of the optically modulated wave are different. An optical transmitter featuring: 2. The optical transmitter according to claim 1, wherein the wavelength band of the light transmitted in the space divided by the light-shielding barrier and the carrier frequency of the optically modulated wave are different.