JPH11331814A - Mobile body signal transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely select and fix a specific light receiving device receiving an optical signal and to surely prevent mis-selection independently of a level of noise intruded from other light receiving device. SOLUTION: An A device group 10A (B device group 10B) is provided to a head (rear) cab of a vehicle 2. The A device group 10A consists of a light receiving device 11, a demodulator 12, a reception level discrimination circuit 13, a synchronization discrimination circuit 14, a changeover device 15, and a display device 18, and the light receiving device 11 on ground receives an infrared ray 4 from a light emitting device 3. The reception level discrimination circuit 13 discriminates an output signal level of the light receiving device 11 and the synchronization discrimination circuit 14 discriminates presence of a synchronizing signal in an output signal of the demodulator 12. The changeover device 15 selects a video signal demodulated by the demodulator 12 when both the reception level discrimination circuit 13 and the synchronization discrimination circuit 14 satisfy the discrimination result and provides an output to a display device 18, on which the video signal is displayed. On the other hand, a BA device group 10B is similarly configured of the A device group 10A and connects to the A device group 10A via on-vehicle transmission lines 5a, 5b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a specific light receiving device that receives an optical signal transmitted from the ground side by an optical space transmission system at optical receivers provided at the head and rear of a moving body, and receives the optical signal. And a mobile signal transmission system for connecting the mobile terminal to a transmission line in the mobile object.

[0002]

2. Description of the Related Art Conventionally, in a transportation system such as a railway running on a track, when a moving body, that is, a vehicle stops on a platform, the situation of passengers is photographed by a TV camera installed on the platform, and a video signal is transmitted. The signal is converted into a high-frequency band optical signal, transmitted to the vehicle side, and displayed on a display (monitor) provided in the driver's seat so that the driver can confirm safety. When the vehicle enters the platform, the status of the platform captured by the TV camera may be transmitted to the vehicle to confirm safety.

When an optical signal is transmitted from the ground to the vehicle as described above, generally, the light signal is transmitted forward or backward in the traveling direction of the vehicle.
Alternatively, light transmitters are installed in both to transmit optical signals. On the other hand, on the vehicle side, light receivers are installed at the head and tail of the vehicle, the presence or absence of a signal is determined based on the strength of the reception level, and the signal of the light receiver with the higher reception level is selected to transmit the signal on the vehicle , And transmits it to a display provided in the driver's seat.

[0004]

However, in the above-mentioned conventional system in which a photodetector is selected only by the intensity of the received signal and connected to a line, noise having a level stronger than the original signal level is generated by another noise. When mixed from the light receiving line, there is a problem that the light receiving unit containing the noise is selected, the light receiving line receiving the original signal is disconnected, and the communication is interrupted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is possible to reliably select and fix a specific light receiving device which has received an optical signal, regardless of the noise level mixed from another light receiving device. It is another object of the present invention to provide a mobile signal transmission system capable of reliably preventing a selection malfunction.

[0006]

According to the present invention, there is provided a light transmitter for converting a video signal photographed on the ground to an optical signal and transmitting the light signal to a moving body, and a light transmitter provided at the head and rear of the moving body. 1
And a second device group, wherein each of the first and second device groups receives a light signal transmitted from the light transmitter and converts the light signal into an electric signal. A reception level determination circuit that determines the reception level of each of the devices, a demodulator that demodulates a video signal from an output signal of the photodetector,
A synchronization determination circuit that determines the presence or absence of a synchronization signal with respect to a signal output from the demodulator, a display for displaying a video signal, and both the reception level determination circuit and the synchronization determination circuit satisfy the determination criteria. A switching device for selecting a video signal demodulated by the demodulator, outputting the video signal to the display device and displaying the video signal, and connecting the first and second device groups with a transmission line; A mobile signal transmission method characterized by mutually transmitting video signals demodulated by a demodulator.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a system configuration diagram of a mobile signal transmission system according to an embodiment of the present invention, and FIG. 2 is a functional block diagram in the embodiment.

In FIG. 1, reference numeral 1 denotes a track on which a moving body, that is, a vehicle 2 runs. The vehicle 2 is provided with, for example, a driver's cab at a head and a rear, so that the vehicle 2 can be driven in any direction. One of the cabs is provided with an A equipment group 10A, and the other cab is provided with a B equipment group 10B.

The A-device group 10A includes a light receiver 11, a demodulator 12, a reception level judgment circuit 13, a synchronization judgment circuit 14,
It comprises a switch 15 and a display 18. The above-mentioned light receiver 1
1 receives an infrared ray 4 from a light transmitter 3 installed on or near the track 1 and converts it into an electric signal in a high frequency band. The light transmitter 3 is provided, for example, when the vehicle 2 stops on the platform, is located in front of or behind the vehicle 2, or both.

The electric signal output from the light receiver 11 is input to a demodulator 12 and a reception level judgment circuit 13. The reception level determination circuit 13 determines whether or not the output signal level of the light receiver 11 is equal to or higher than a preset reference level, that is, whether or not the light receiver 11 is receiving a normal signal. The judgment result is input to the switch 15. In this case, for example, the reception level determination circuit 13 outputs “1” when it is determined that the light receiver 11 is receiving a normal signal, and outputs “0” in other cases.

The demodulator 12 demodulates the signal output from the photodetector 11, and outputs a synchronization judgment circuit 14 and a switch 15.
To enter. The synchronization determination circuit 14 determines whether or not a signal demodulated by the demodulator 12 includes a synchronization signal, and outputs a result of the determination to the switch 15.

The switch 15 comprises a changeover switch 16 and an AND circuit 17, as shown in FIG. 2. The results of the reception level judgment circuit 13 and the synchronization judgment circuit 14 are input to the AND circuit 17, and the AND circuit 17 The output signal of 17 serves as a switching control signal of the changeover switch 16. Also,
The changeover switch 16 includes fixed contacts a and b and a changeover contact c. An output signal of the demodulator 12 is input to the fixed contact a, and the changeover contact c is connected to an input terminal of the display 18. The fixed contacts a and b are connected to the B equipment group 10B via two on-board transmission lines 5a and 5b. When the output signal of the AND circuit 17 is "0", the switching contact c is connected to the fixed contact b, and when the output signal of the AND circuit 17 is "1", the switching contact c is fixed. a side.

The B equipment group 10B includes a light receiver 21, a demodulator 22, and a reception level determination circuit 2 similarly to the A equipment group 10A.
3, a synchronization determination circuit 24, a switch 25, and a display 28. The switch 25 comprises a changeover switch 26 and an AND circuit 27 as shown in FIG. 2, and the results of the determination by the reception level determination circuit 23 and the synchronization determination circuit 24 are input to the AND circuit 27. The output signal is a switching control signal for the changeover switch 26. The changeover switch 26 includes fixed contacts a and b and a changeover contact c. An output signal of the demodulator 22 is input to the fixed contact a,
The switching contact c is connected to the input terminal of the display 28. When the output signal of the AND circuit 27 is "0", the changeover switch c is connected to the fixed contact b, and the output signal of the AND circuit 27 is "1".
In this case, the switching contact c is connected to the fixed contact a. Then, the fixed contact a of the changeover switch 26,
b is connected to the two on-vehicle transmission lines 5a and 5b, but in a state opposite to the changeover switch 16, that is, the fixed contact a of the changeover switch 26 is connected to the on-vehicle transmission line 5b, b is connected to the onboard transmission line 5a.

Next, the operation of the above embodiment will be described for the case where the light transmitter 3 is provided in front of the A equipment group 10A side as shown in FIG. As shown in FIG. 1, when the vehicle 2 travels on the track 1 and stops on the platform, the TV camera installed on the platform captures the passengers of the vehicle 2 and modulates the image signal to apply a high frequency band signal. Signal, and the infrared ray 4 from the light transmitter 3
Send to. The light receiver 11 provided in the A device group 10A of the vehicle 2 receives the infrared ray 4 sent from the light transmitter 3 and converts it into an electric signal in a high frequency band. The electric signal output from the light receiver 11 is sent to a demodulator 12 and a reception level determination circuit 13. If the output signal level of the light receiver 11 is higher than the reference level, the reception level determination circuit 13 determines that the light receiver 11 is receiving the infrared ray 4 from the light transmitter 3 and outputs the “1” signal. The signal is input to the AND circuit 17 of the switch 15.

A demodulator 12 demodulates a video signal output from the photodetector 11, and outputs a demodulated signal to the synchronization determination circuit 14 and the switch 1
5 to the changeover switch 16. Synchronous determination circuit 1
4 outputs a “1” signal when the video signal output from the demodulator 12 includes a synchronization signal, and inputs the signal to the AND circuit 17 of the switch 15. As a result, the AND circuit 17
Since both input signals are "1", the logical condition is satisfied, a "1" signal is output, and the switching contact c of the changeover switch 16 is switched to the fixed contact a. As a result, the video signal output from the demodulator 12 is selected by the changeover switch 16, and
It is sent to the display 18 and displayed.

On the other hand, in the B equipment group 10B, since the infrared ray is not received by the light receiver 21, a "0" signal is output from the reception level judgment circuit 23 and the synchronization judgment circuit 24,
The gate of the AND circuit 27 of the switch 25 is kept closed. Therefore, the output signal of the AND circuit 27 is "0".
The changeover contact c of the changeover switch 26 is connected to the fixed contact b side. Therefore, the demodulator 1 of the A device group 10A
2 is input to the fixed contact "a" of the changeover switch 16 and the fixed contact "b" of the changeover switch 26 in the B equipment group 10B via the on-board transmission line 5a and to the display 28 via the changeover contact "c". Sent and displayed.

In the above state, even if noise enters the system of the photodetector 21 and a "1" signal is output from the reception level determination circuit 23, the output signal of the synchronization determination circuit 24 is "0". The output signal of the AND circuit 27 is kept at "0". Therefore, the changeover switch 2
6 is not switched, and the display 28 continuously displays the video signal sent from the A device group 10A.

When a light transmitter is installed in front of and behind the vehicle 2 and an infrared ray (video signal) is also input to the light receiver 21 of the B equipment group 10B, a reception level determination circuit is provided. The signal “1” is output from both the reference signal 23 and the synchronization determination circuit 24 and input to the AND circuit 27 of the switch 25.
Therefore, the output signal of the AND circuit 27 becomes "1", the switching contact c of the changeover switch 26 is switched to the fixed contact a side, the video signal demodulated by the demodulator 22 is selected by the changeover switch 26, and the display 28 Sent to and displayed.

As described above, when the A-device group 10A and the B-device group 10B respectively receive infrared rays, the video signals demodulated by the demodulators 12 and 22 are displayed on the display 18 and the display device 18 respectively.
It is displayed at 28.

When only the light receiver 21 on the B equipment group 10B side receives the infrared ray transmitted from the light transmitter, the video signal demodulated by the demodulator 22 is switched to the changeover switch 2
In addition to being displayed on the display 28 via the display 6, the data is sent to the A-device group 10 </ b> A via the on-board transmission line 5 b and displayed on the display 18.

As described above, according to the present invention, the photodetectors 11, 2
1 is used to determine the level of the received signal,
In addition to the determination at 23, the presence or absence of a synchronization signal in the received video signal is further determined by the synchronization determination circuits 14 and 24, and the photodetectors satisfying both determination criteria are selected by the switches 15 and 25. Regardless of the noise level mixed in from the other light receivers, the specific light receiver that has received the optical signal can be reliably selected and fixed, and the selection malfunction can be reliably prevented.

In the above-described embodiment, the case where the state of the passenger is photographed by the TV camera and transmitted to the vehicle 2 when the vehicle 2 stops at the platform has been described, but in addition, the vehicle 2 enters the platform. In this case, when the state of the platform is photographed by the TV camera and transmitted to the vehicle 2 to confirm safety, the same can be implemented.

In the above embodiment, the case where the A equipment group 10A and the B equipment group 10B are provided at the front end and the rear part of one vehicle 2 has been described. The same effect as in the above embodiment can be obtained by providing the A device group 10A in the vehicle and the B device group 10B in the last vehicle.

[0024]

As described above in detail, according to the present invention, in addition to the judgment based on the intensity of the signal received by the photodetector,
In addition to the presence / absence of a synchronization signal in the received video signal, in addition to the criterion, the receiver that satisfies both criteria is selected. Can be reliably selected and fixed, and a selection malfunction can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a mobile signal transmission system according to an embodiment of the present invention.

FIG. 2 is a functional block diagram according to the embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Track 2 Vehicle 3 Transmitter 4 Infrared ray 5a, 5b On-board transmission line 10A, 10B A equipment group 11, 21 Light receiver 12, 22, Demodulator 13, 23 Reception level judgment circuit 14, 24 Synchronization judgment circuit 15, 25 Switch 16, 26 Switch 17, 17, AND circuit 18, 28 Display

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[Procedure amendment]

[Submission date] June 24, 1999

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction contents]

[0004]

However, in the above-mentioned conventional system in which a photodetector is selected only by the intensity of the received signal and connected to a line, noise having a level stronger than the original signal level is generated by another noise. If mixed from the light receiver line, would select the contaminating light receiver of the noise, the light receiver circuit which receives the original signal is disconnected, the communication is interrupted by <br/> want earthenware pots, say problem There is.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

SUMMARY OF THE INVENTION A mobile signal according to the present invention
The transmission method includes a transmitter that converts a video signal photographed on the ground side into an optical signal and transmits the optical signal to the moving body, and first and second equipment groups provided at the head and rear of the moving body. The first and second equipment groups each include a light receiver that receives an optical signal transmitted from the light transmitter and converts the light signal into an electric signal, and a receiver that determines a reception level of each light receiver. A level determination circuit, a demodulator for demodulating a video signal from the output signal of the photodetector, a synchronization determination circuit for determining the presence or absence of a synchronization signal with respect to a signal output from the demodulator, and a video signal for displaying the video signal. A display unit, and a switching unit that selects a video signal demodulated by the demodulator when both the reception level determination circuit and the synchronization determination circuit satisfy the determination criterion, and outputs the video signal to the display unit for display. , The first
And a second device group are connected by a transmission path,
The video signal demodulated by the demodulator is mutually transmitted .

Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H04B 10/105 H04B 9/00 R 10/10 H 10/22 10/02 H04N 7/22

Claims (1)

[Claims] 1. A light transmitter for converting a video signal photographed on the ground side into an optical signal and transmitting the optical signal to a moving body, a first and a second equipment group provided at a head and a rear of the moving body. Wherein the first and second equipment groups each receive a light signal transmitted from the light transmitter and convert the light signal into an electric signal, and determine a reception level of each light receiver. A receiving level determining circuit, a demodulator for demodulating a video signal from the output signal of the photodetector, a synchronization determining circuit for determining the presence or absence of a synchronizing signal for the signal output from the demodulator, and displaying the video signal. A display for selecting a video signal demodulated by the demodulator when both the reception level determination circuit and the synchronization determination circuit satisfy the determination criterion, and a switch for outputting to the display for display. Wherein said first and second machines are Mobile signal transmission system between the groups are connected by a transmission line, and wherein the transmitting the video signal demodulated by the demodulator to each other.