JPH0666733B2 - Optical space transmission device for mobiles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a communication system between a mobile station provided on an object that moves on a fixed trajectory such as a delivery facility and a fixed station provided along the trajectory. In particular, the present invention relates to an optical space transmission device for a mobile object using an information space transmission system using light rays.

[Prior art and its drawbacks]

Conventionally, as a communication system of this type, there is a system in which a trolley wire is provided along a moving locus of a moving object such as a delivery vehicle and a signal is transmitted and received by a slider provided on the moving object. However, this method is easily affected by noise and the amount of information that can be transmitted is limited, so that image transmission and the like is extremely difficult.

On the other hand, there is a so-called leaky coaxial communication system in which communication is performed by a leaky coaxial cable laid along the vicinity of a movement locus and a transmitting / receiving device provided on a moving object.
However, this method is not only required to lay a special cable for radiating radio waves uniformly in the space along the length direction along the trajectory of the moving body, but is also restricted by the Radio Law. Furthermore, since this communication method is communication by radio waves, it is disadvantageous to noise caused by electromagnetic induction.

In addition, there is also a method using wireless communication, but it is not limited to the radio law in the same manner as the above-mentioned leaky coaxial communication method, and has a drawback that it is weak against noise due to electromagnetic induction and noise due to multiple reflection.

Therefore, the communication with the moving object of infrared or visible light,
A method realized by spatial transmission using so-called light rays has been considered.

FIG. 2 is a general block diagram of the optical space transmission device. In the figure, 1 is a light transmitter for sending light rays into space,
A light receiver 2 receives the light beam from the light transmitter 1. In the light transmitter 1, 3 is a video input terminal for inputting a video signal from a television camera, 4 is a video amplifier for amplifying the video signal, and 5 is a video for frequency-modulating the video signal.
FM modulator, 6 is an audio input terminal for inputting an audio signal, 7 is an audio amplifier for amplifying the audio signal, 8 is an audio FM modulator for frequency modulating the audio signal, 9 is a frequency-modulated video signal and audio A mixer for mixing a signal, a light emitting diode drive circuit 10 for driving the light emitting diode 11, that is, a brightness modulation, and an optical lens system 12 for sending a light beam signal from the light emitting diode 11 into parallel light beams and sending them to space.

That is, the light transmitter 1 transmits a video signal and an audio signal,
It is amplified to a sufficient level by the video amplifier 4 and the audio amplifier 7, frequency-modulated by the video FM modulator 5 and the audio FM modulator 8, and mixed by the mixer 9. Then, the output of the mixer 9 is guided to the light emitting diode drive circuit 10, the light source of the light emitting diode 11 is brightness-modulated, and the light source signal is transmitted from the optical lens system 12 to the space.

On the other hand, in the light receiver 2, 13 is an optical lens system that collects the light beam signal from the light transmitter 1, 14 is a photodetector that converts the light beam signal into an electric signal, and 15 is a photodetector 14
The preamplifier for amplifying the electric signal from, that is, the mixed signal of the frequency-modulated video signal and the audio signal, 16 is a demultiplexer for separating the video signal and the audio signal, 17 is the frequency-modulated video signal Video FM demodulator to restore the original video signal, 18
Is a video amplifier that amplifies the video signal from this FM demodulator 17, 19 is an audio FM demodulator that returns the frequency-modulated audio signal to the original signal, and 20 is an audio that amplifies the audio signal from this FM demodulator 19. An amplifier, 21 is a monitor amplifier, 22 is a monitor output terminal, 23 is a video output terminal, and 24 is an audio output terminal.

That is, the light receiver 2 collects the light beam signal from the light transmitter 1 by the optical lens system 13 and converts the light reception signal into an electric signal by the photodetector 14. Then, this electric signal is high-frequency amplified by the preamplifier 15 and then guided to the demultiplexer 16 to be separated into a frequency-modulated video signal and an audio signal. After that, the video FM demodulator 17 and the audio FM demodulator 19 demodulate the original video signal and the audio signal, and further, the video amplifier 18 and the audio amplifier 20 amplify them to a predetermined level and output them. The light receiver 2 is also provided with a monitor terminal as required.

The typical ones of the spatial light transmission devices using light rays have been described above. When communicating with a moving body using the light transmitter 1 and the light receiver 2, the infrared light rays are roughly classified. There are cases where visible light is used.

In the case of using infrared rays, the light emitting diode 11 that emits infrared rays is used, but it is generally easy to obtain a large output. Further, the photodetector 14 used is one for infrared rays, but it is generally easy to obtain a photodetector with high sensitivity (quantum efficiency). Further, since infrared rays have a high transmittance, they are suitable when a large transmission distance (distance between the light transmitter 1 and the light receiver 2) is required.

On the other hand, visible light is used when transmission is performed over a relatively short distance and it is difficult to align the directions of the light transmitter 1 and the light receiver 2. That is, in the case where the light transmitter 1 and the light receiver 2 are installed on a steel tower or the like, it is extremely easy to perform the alignment by using the visible light emitted from the light transmitter 1, and a special jig for aligning a direction or No equipment required. However, the light transmitter 1 using visible light may be mistaken for a traffic signal, and is not suitable for such a place. Further, the lifetime of the light emitting diode 11 is longer for infrared light than for visible light.

As described above, since the space transmission method using infrared rays and the space transmission method using visible rays have different characteristics, it is necessary to selectively use them depending on the installation conditions.

FIG. 3 shows a communication system with a moving body using the above-mentioned light transmitter and light receiver. In the figure, A is a locus along which the moving body 31 moves, and 32 is a light transmitter fixedly installed near the locus A. Reference numeral 33 denotes a light receiver installed on the moving body 31, and an arrow P indicates the traveling direction of the moving body 31. That is, by converting a video signal, an audio signal, a control signal, or the like from a television camera or the like into a light beam signal by the light transmitter 32 and transmitting the light beam to the space, the light receiver 33 provided in the moving body 31 receives the light signal. It communicates. For example, the mobile body 31 is controlled by a control signal, the video image transmitted by a television receiver installed in the mobile body 31 or the like or the sound is heard. in this case,
Since the light transmitter 32 cannot be placed on the locus A, the locus A is inevitable.
Therefore, the light receiver 33 is also installed on the moving body 31 at an angle θ so as to completely face the light transmitter 32 at a certain distance L1.

However, in the transmission device configured in this way,
Since the optical axes (directions of light rays) of the light transmitter 32 and the light receiver 33 are displaced as 31 approaches or moves away from the light transmitter 32 from the point of this distance L1, even when the light transmitter 32 is approached, for example. When it comes to the point of distance L2, the optical axis is completely deviated and communication becomes impossible. On the other hand, the same is true when the distance is longer than L1, and in this case, the communication is also disabled due to the fact that the light beam signal gradually weakens. Therefore, when the number of the light transmitters 32 is one as described above, there is a limit to the distance L that can be naturally communicated.

FIG. 4 shows a device configuration for solving the drawback of the transmission device in FIG. 3, that is, a plurality of light transmitters 32a,
32b, 32c, ... Are fixedly installed along the locus A of the moving body 31 at predetermined intervals. However, this fourth
If multiple transmitters are installed as shown in the figure, each transmitter 32
There are overlapping portions of the light beams from a, 32b, 32c, .... That is, in the portions where the light beams overlap as shown by the hatched portions B and C in the figure, both light transmitters 32a, 32
Since there is a difference in the transmission path of the b, 32b, and 32c light beams, interference occurs between the two, resulting in distortion of the video signal or audio signal, causing synchronization disorder or distortion on the TV screen. , The sound is distorted and it becomes difficult to hear.

Here, as a matter of course, in the case where the locus A of the moving body 31 is a straight line and a case where it is a curve, the number of light transmitters installed is different even if optical transmission is performed at the same distance. Needless to say, but much is needed. Therefore, when the movement locus is a curved line, there are inevitably more portions where the light beams interfere.

[Object of the Invention]

The present invention has been made in view of the above problems,
For example, even in the case where a plurality of light transmitters are arranged and fixed along the locus of a moving body, it is possible to perform reliable signal transmission without causing signal interference between the respective light transmitting units, and to the optical space for moving body. An object is to provide a transmission device.

[Main points of the invention]

That is, the paired mobile optical space transmission device according to the present invention is
An information signal transmission source that outputs a high-frequency signal modulated by an audio or video signal, and a transmission line that connects between a plurality of light transmitters that generate a light beam modulated by this high-frequency signal and send it to space, A variable delay device that variably adjusts the line equivalent length is provided, and by adjusting this variable delay device, the signal interference between the respective light transmitters that occurs at a specific position on the locus of the moving body is eliminated. It is a thing.

Example of Invention

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an optical space transmission apparatus for a moving body when the locus A of the moving body 31 is a curve.
Is a source of the information signal, and is a signal obtained by frequency (FM) modulating a carrier wave (high frequency) F1 with a baseband signal such as a video signal from a TV camera or an audio signal from a microphone, that is, the information signal source 40 is an FM. It is designed to output the modulated carrier wave F1. 42a to 42c are transmission lines, for example, coaxial cables. Next, 41a to 41c are variable delay devices for changing the equivalent transmission line length. And 35a-35c are
It is a light transmitter having a configuration in which the components indicated by reference numerals 3 to 9 are removed from the light transmitter 1 in FIG. Here, Q and R indicate specific position points on the moving body locus A where the light beams from the respective light transmitters 35a to 35c overlap. So this transmitter
The configurations of 35a to 35c mainly include a carrier wave input terminal (not shown) for inputting a signal from the information signal transmission source 40, a light emitting diode drive circuit 10, a light emitting diode 11 and an optical lens system 12. In the light transmitter 1 shown in FIG. 2, a video signal input terminal 3, a video amplifier 4, a video FM modulator 5, an audio signal input terminal 6, an audio amplifier 7, an audio FM modulator 8 and a mixer having a configuration other than the above are provided. It is assumed that all the information signal sources 9 are included in the information signal source 40.

That is, in the optical space transmission apparatus configured as described above, the lengths of the transmission lines 42a to 42c from the information signal transmission source 40 to the respective light transmitters 35a to 35c are different, and the R on the moving body locus A is changed. There is a difference in the distance from the light transmitters 35b, 35c to the point and the distance from the light transmitters 35a, 35b to the point Q. There is a time difference (that is, a difference in transmission) between the signals, which causes interference. Here, the variable delay devices 41a to 41c are adjusted to equivalently variably adjust the transmission line length. Then, it is possible to substantially eliminate the arrival time difference between the two signals at the R point or the Q point. That is, in order to eliminate the signal arrival time difference from the light transmitters 35b and 35c at the point R, the variable delay devices 41b and 41c are
Further, in order to eliminate the signal arrival time difference from the light transmitters 35a and 35b at the point Q, the variable delay devices 41a and 41b may be adjusted respectively.

Therefore, according to the optical free space transmission apparatus configured as described above, it is possible to completely eliminate the difference in the arrival time of the light beam signal between the respective light transmitters by adjusting the variable delay devices 41a to 41c, and the optical signal on the trajectory A Accurate signal transmission can be performed at any position.

In the above embodiment, the information signal source 40 and the light transmitters 35a-3a
Transmission lines 42a to 42c for connecting to 5c are separately laid, but for example, one signal transmission line is used to transmit signals from the information signal source 40, and a distributor is provided near the light transmitters 32a to 32c. May be provided, whereby the transmission signal is divided into three and transmitted to each of the light transmitters 35a to 35c through the transmission lines having the same length. As a result, the transmission line length from the information signal source 40 to each of the light transmitters 35a to 35c becomes the same, and the variable range of the variable delay devices 41a to 41c is also small, which is advantageous. In addition, along with this, the installation of the transmission line becomes easy and the construction cost can be reduced.

〔The invention's effect〕

As described above, according to the present invention, the variable delay device is installed between the light transmitter and the information signal source, and the transmission line lengths can be changed substantially. In optical space transmission between a moving mobile station and a ground fixed station, when receiving signals from a plurality of ground fixed stations (light transmitters) and each light transmitter by a light receiver provided in the mobile station, It is possible to transmit a video or audio signal or the like that is extremely reliable and has little distortion without causing signal interference between the light transmitters.

[Brief description of drawings]

FIG. 1 is a block diagram showing an optical space transmission apparatus for a mobile body according to an embodiment of the present invention, and FIG. 2 is a block diagram showing the configuration of an information space transmission apparatus using a light beam, FIGS. 3 and 4. FIG. 3 is a configuration diagram showing an example of an optical space transmission device for a mobile unit using the space transmission device in FIG. 2; 31 ... moving body, 33 ... photoreceiver, 35a, 35b, 35c, 35d ... transmitter, 40 ... information signal source, 41a to 41c ... variable delay device, 42a to 42c ... transmission line, A ... moving object trajectory, P ...
… The moving direction of the moving body.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoshi Arai 4-6 Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi, Ltd. (72) Inventor Kan Fukai 1406 Hasunuma, Omiya, Saitama Yagi Antenna Co., Ltd. Omiya Factory (72) Inventor Tsuneto Hirabayashi 1406 Hasunuma, Omiya-shi, Saitama Yagi Antenna Co., Ltd. Omiya Plant (56) References JP-A-57-170638 (JP, A) JP-A-58-92157 (JP, A)

Claims (1)

[Claims] 1. An information signal transmission source for outputting a high frequency signal modulated by an audio signal and / or a video signal, and a plurality of transmitting means for generating a light beam signal modulated by the high frequency signal and transmitting it to a space. An optical device, a plurality of variable delay devices interposed between each of the plurality of transmission lines laid between the plurality of light transmitters and the information signal transmission source to variably adjust the equivalent length of the line, and a fixed trajectory A light receiver for receiving a light beam signal from each of the light transmitters, which is installed on an object moving above and arranged along the locus thereof. Optical transmission system for moving objects, characterized in that the arrival times of the respective light signals at the positions where the light signals from the light transmitters are overlapped are made to eliminate the signal interference caused by the difference in the transmission paths of the light transmitters. .