JP2002152717A - Video image monitor system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a video image monitor system that can simply switch video images photographed by monitoring cameras through remote control from a monitor and simplify a video image transmission system so as to reduce the cost of the transmission system. SOLUTION: Camera changeover switch circuits 12a, 12b, etc., are connected in series to the monitor 10 through a metallic cable 11, and the monitoring cameras 13a, 13b, etc., are connected to the switch circuits 12a, 12b, etc. The switch circuits 12a, 12b, etc., are operated by detecting a specific DC voltage applied from the monitor 10 and normally thrown to the position of the metallic cable 11. The switch circuits 12a, 12b, etc., are thrown to the position of the cameras 13a, 13b, etc., when detecting the specific DC voltage. Thus, when the switch circuits 12a, 12b, etc., receive the DC voltage in response to a selection instruction from the monitor 10, the switch circuits 12a, 12b, etc., detect the DC voltage designating any of themselves and selectively switch any of the cameras 13a, 13b, etc., and the selected camera provides its video signal to the monitor 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video surveillance system for switching and monitoring images taken by a plurality of surveillance cameras according to instructions from a monitor.

[0002]

2. Description of the Related Art Conventionally, when monitoring a wide area, such as monitoring various facilities in a factory, monitoring a river, monitoring the state of an expressway, etc., a plurality of monitoring cameras are installed to monitor a captured video signal. The data is transmitted to the center and monitored at the monitoring center. Conventionally, in a system that performs wide-area monitoring as described above, video signals captured by each monitoring camera are multiplexed digitally or analogly and transmitted to a monitoring center. Incoming images are separated and sequentially switched, or a desired image is selectively extracted and displayed on a monitor screen.

[0003]

However, in the conventional method of multiplexing video signals photographed by the respective monitoring cameras by digital or analog and transmitting the multiplexed video signals to the monitoring center, the multiplexing process is complicated. The process of separating the multiplexed video is also complicated, resulting in a problem that the system becomes expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can easily switch an image shot by each monitoring camera by remote control from a monitor device.
It is an object of the present invention to provide a video monitoring system capable of simplifying a transmission system and reducing costs.

[0005]

A video surveillance system according to a first aspect of the present invention includes a plurality of surveillance cameras for photographing each surveillance object and outputting a video signal of the surveillance object, respectively. A monitoring device that outputs a DC voltage having a different value through a metal cable in accordance with a channel selection instruction and monitors a video signal of the monitoring camera, and the monitoring camera connected in series to the metal cable and Are connected to the monitor device, and detect the value of the DC voltage supplied from the monitor device to designate themselves, and selectively switch the surveillance camera. The video signal of the surveillance camera is transmitted to the monitor via the metal cable. And a switch circuit for sending the signal to the device. By supplying a DC voltage having a value according to the channel selection instruction from the monitor device to the plurality of switch circuits connected in series as described above, each switch circuit detects the value of the DC voltage designating itself. Since each monitoring camera is selectively switched, the video of each monitoring camera can be arbitrarily selected and monitored, eliminating the need for multiplexing the video output of each monitoring camera, simplifying the transmission system and reducing costs. It can be reduced.

A video surveillance system according to a second aspect of the present invention includes a plurality of surveillance cameras for photographing each monitored object and superimposing an identification signal indicating that the own station is on the video signal of the monitored object, and outputting the signals. And a monitoring device that outputs a DC voltage having a different value through a metal cable in accordance with a tuning instruction of the monitoring camera and monitors a video signal of the monitoring camera, and is connected in series to the metal cable. Connected to the surveillance camera, respectively, and detects the value of the direct-current voltage supplied from the monitor device to designate itself, selectively switches the surveillance camera, and outputs the video signal and identification of the surveillance camera. A switch circuit for sending a signal to the monitor device via the metal cable, wherein the monitor device is sent together with a video signal from the monitoring camera. Identification signal detection means for detecting an identification signal, a variable DC power supply, and controlling the variable DC power supply in accordance with a channel selection instruction for selecting a monitoring camera to output a DC voltage having a different value; Identifies whether the identification signal sent from the surveillance camera matches the one specified by the channel selection instruction, and in the case of non-coincidence, determines the identification signal of the surveillance camera that matches the channel selection instruction by the above variable. Control means for variably controlling the output voltage of the DC power supply. As described above, the video signal output from each monitoring camera is superimposed with the identification signal indicating that it is the own station, transmitted to the monitor device, and the monitor device detects the identification signal and belongs to the designated station. By judging whether or not it is different from the specified station, by changing the value of the DC voltage supplied to obtain a predetermined identification signal, a large number of monitoring cameras are installed and the monitoring device Even when the level difference between the DC voltage values supplied to the respective cameras decreases, the malfunction of the switch circuit can be corrected and the specified camera can be correctly selected.

[0007]

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

(First Embodiment) FIG. 1 is an overall configuration diagram of a video surveillance system according to a first embodiment of the present invention.
In FIG. 1, reference numeral 10 denotes a monitor device installed in a monitoring center. Camera monitor switch circuits 12a, 12b,... Are sequentially connected in series to the monitor device 10 via a metal cable 11 such as a coaxial cable. The monitoring cameras 13a, 13b,... Are connected to these camera switching switch circuits 12a, 12b,.

The switch circuits 12a, 12b,...
A switch that operates by detecting a specific DC voltage value supplied from the monitor device 10 via the metal cable 11, that is, a DC voltage value designating itself, and is normally switched to the metal cable 11 side. Are switched to the cameras 13a, 13b,... Side. In this case, the operating voltage values of the switch circuits 12a, 12b,... For example, three switch circuits 12a, 12b,
12b is provided, the operating voltage of the switch circuit 12a closest to the monitor device 10 is the highest H level,
The operating voltage of the next switch circuit 12b is an intermediate M level,
The operating voltage of the farthest switch circuit 12c is set to the lowest L level. As a specific example, the operating voltage of the switch circuit 12a is set to 3V, the operating voltage of the next switch circuit 12b is set to 2V, and the operating voltage of the farthest switch circuit 12c is set to 1V.

When the operating voltages of the switch circuits 12a to 12c are set to 3V, 2V, and 1V as described above, the monitor device 10 sets "3" to select the image of the camera 13a.
V "," 2V "when selecting the image of the camera 13b,
When selecting an image from the camera 13 c, a DC voltage of “1 V” is output to the metal cable 11.

When the monitor device 10 outputs a DC voltage of 3 V, the switch circuit 12a operates and switches the switching contact to the camera 13a, so that the video signal output from the camera 13a is transmitted to the switch circuit 12a and the metal cable. The data is sent to the monitor device 10 via the monitor 11.

When the monitor device 10 outputs a DC voltage of 2V, the switch circuit 12a does not operate, and
Is sent to the switch circuit 12b via the switch circuit 12a. Therefore, since the switch circuit 12b detects the DC voltage of 2V and switches the switching contact to the camera 13b, a video signal output from the camera 13b is transmitted from the switch circuit 12b to the monitor device via the switch circuit 12a and the metal cable 11. Sent to 10.

When the monitor device 10 outputs a DC voltage of 1V, the switch circuits 12a and 12b do not operate, and the DC voltage of 1V is applied to the switch circuits 12a and 12b.
The signal is sent to the switch circuit 12c via b. Therefore,
The switch circuit 12c detects this 1 V DC voltage and switches the switching contact to the camera 13c side.
Is output from the switch circuit 12c to the monitor device 10 via the switch circuits 12b and 12a and the metal cable 11.

Next, the switch circuits 12a, 12b,.
Will be described with reference to FIG. FIG. 2 shows the configuration of the switch circuit 12a, but the other switch circuits 12b,. The switch circuit 12a includes a switch element 21 and a voltage detector 22. The voltage detection unit 22 detects a DC voltage value supplied from the monitor device 10 via the metal cable 11 and determines whether or not the voltage value is a preset own voltage value. Then, the switch element 21 is switched to the camera 13a side, and if the voltage value is any other value, the switch element 21 is not switched. When the switch element 21 is switched by the voltage detection unit 22, the video signal of the camera 13 a is selected by the switch element 21 and the monitor device 10 is connected via the metal cable 11.
Sent to If the switch element 21 has not been switched, the DC voltage supplied from the monitor device 10 is sent to the next-stage switch circuit 12b.

FIG. 3 shows an example of the configuration of the voltage detector 22. The voltage detector 22 includes, for example, a low-pass filter (LPF) 23, a voltage comparator 24, and a reference power supply (Vref) 25. The switch element 21 is switched by the output voltage of the voltage comparator 24. As the low-pass filter 23, for example, an analog filter including an inductance L and a capacitor C or another filter is used. The low-pass filter 23 passes a DC voltage supplied from the monitor device 10 via the metal cable 11, and is photographed by the camera 13a or the like. Cut the video signal.
The DC voltage that has passed through the low-pass filter 23 is input to the + terminal of the voltage comparator 24. The reference power supply 25 is connected to the negative terminal of the voltage comparator 24.

The voltage value of the reference power supply 25 is set to a different value depending on the switch circuits 12a, 12b,..., For example, "3V" for the switch circuit 12a, "2V" for the switch circuit 12b, and "2V" for the switch circuit 12c. It is set to “1V”. When the voltage value of the reference power supply 25 is set to, for example, “3 V”, when the voltage supplied from the monitor device 10 becomes “3 V” or more, a “1” signal is output from the voltage comparator 24 and the switch element 21 13
It is switched to the a side. However, when the voltage supplied from the monitor device 10 is lower than “3 V”, the voltage comparator 2
4 is "0", and the switching element 21 is not switched.

By configuring the switch circuits 12a, 12b,... As shown in FIGS.
, 13b,... can be selected.

According to the first embodiment, the monitoring device 1
By supplying a DC voltage from 0 to a value corresponding to the channel selection instruction to a plurality of switch circuits 12a, 12b,... Connected in series, each of the switch circuits 12a, 12b,. The values are detected and the cameras 13a, 13
b,... are selectively switched, so that each of the cameras 13a, 13
b,... can be arbitrarily selected and monitored. Therefore, it is not necessary to multiplex the video outputs of the cameras 13a, 13b,..., And the transmission system can be simplified and the cost can be reduced.

In the example shown in FIG. 3, a case is described in which an analog filter is used as the low-pass filter 23 of the voltage detection unit 22, but other than that, for example, video signals output from the cameras 13a, 13b,. A horizontal synchronization signal or a vertical synchronization signal can be sampled and detected. That is, the video signals output from the cameras 13a, 13b,... Have the same level of the horizontal synchronization signal or vertical synchronization signal, but when superimposed on the DC voltage supplied from the monitor device 10, In this state, the horizontal synchronization signal or the vertical synchronization signal is supplied to the switch circuits 12a, 12b,
.. To detect the DC level, the switching element 21 can be switched according to the DC level.

Further, the voltage detecting section 22 shown in FIG.
Since the switching element 21 is switched by the output signal of the voltage comparator 24 when the voltage is equal to or higher than 5, the operating voltage value of the switch circuits 12a, 12b,. Is set to
However, if the voltage detector 22 is configured to detect the value of the DC voltage supplied from the monitor device 10 within a predetermined range, the operating voltage values of the switch circuits 12a, 12b,. It is not necessary to set it to be higher, but can be set arbitrarily.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. The first
In the embodiment, as the number of cameras 13a, 13b,... Increases, the level difference between the DC voltage values supplied from the monitor device 10 corresponding to the cameras 13a, 13b,. May malfunction.

In order to solve the above-mentioned problem, the second embodiment has a means for detecting a malfunction of the switch circuits 12a, 12b,... And a switch circuit 1 for detecting the malfunction.
Means for adjusting the value of the DC voltage to be supplied to the switch circuits 12a, 12b,.
If the cameras b,... malfunction, the designated cameras 13a, 13b,... can be correctly selected by adjusting the DC voltage value.

FIG. 4 shows a switch circuit 1 according to the second embodiment.
, And the cameras 13a, 13b,..., And FIG. 5 is a configuration diagram of the monitor device 10 side. The cameras 13a, 13b,... In the second embodiment include a camera section 131 for photographing an object and an identification signal generating section 132 for generating a camera identification signal, as shown in FIG. The video signal output from the camera unit 131 is usually 4
Since the frequency up to MHz is used, the identification signal generator 132 outputs a higher frequency than the video signal, for example, 4 to 6 MHz.
Is generated as an identification signal, and is synthesized with a camera video signal and output. In this case, the identification signal generator 132
The frequency of the identification signal is set to a different value within the range of 4 to 6 MHz depending on each of the cameras 13a, 13b,.

The video / identification signals output from the cameras 13a, 13b,...
.. Are sent to the monitor device 10 by the metal cable 11.

The monitor device 10 is provided with a variable DC power supply 31 as shown in FIG. 5, extracts a DC voltage output from the variable DC power supply 31 through a low-pass filter 32 (LPF) 32, and outputs the DC voltage through a metal cable 11. To the switch circuits 12a, 12b,... The low-pass filter 32 is for blocking a video signal. Further, the monitor device 10 includes an identification signal detection unit 33 that detects identification signals sent from the cameras 13a, 13b,..., And inputs the detected identification signals to the control unit 34. The control unit 34 is provided with a channel selection instruction for selecting the cameras 13a, 13b,. The channel selection instruction is updated by manual operation of the operator or automatically at fixed time intervals.

The control section 34 sets the output voltage of the variable DC power supply 31 in accordance with the channel selection instruction, and then sets the camera 13 based on the identification signal identified by the identification signal detection section 33.
It is determined whether or not a, 13b,... have been correctly selected, and if they have not been correctly selected, the output voltage of the variable DC power supply 31 is finely adjusted. That is, the control unit 34 determines from the identification signal whether the actually selected camera is positioned higher or lower than the specified camera, and accordingly increases the output voltage of the variable DC power supply 31 by a fixed value or Lower it. By adjusting the output voltage of variable DC power supply 31, switch circuits 12a, 12b,... Perform voltage detection again. When the cameras 13a, 13b,... Are correctly selected in response to the channel selection instruction, the control unit 34 maintains the output voltage of the variable DC power supply 31 as it is. The video / identification signals sent from the selected cameras 13a, 13b,... Are extracted only through the high-pass filter 35 and the low-pass filter 36, and are displayed on the display unit 37. The high-pass filter 35 removes the DC component and passes the video signal, and the low-pass filter 36 removes the identification signal having a higher frequency than the video signal. As described above, the cameras 13a, 13b,.
Is correctly selected according to the channel selection instruction, and the video signal can be displayed on the display unit 37.

According to the second embodiment, the camera 13
are provided, and even when the level difference between the DC voltage values supplied from the monitor device 10 corresponding to the cameras 13a, 13b,.
are corrected by correcting the malfunction of the cameras 13a, 13b,.
b,... can be correctly selected. Also, camera 1
Since the identification signal generator 132 provided in 3a, 13b,... Uses a sine wave having a frequency higher than that of the video signal as the identification signal, it does not affect the video signal.

In the second embodiment, a case has been described where a high frequency sine wave is generated by the identification signal generating section 132 and superimposed on the video signal. However, a signal having a higher frequency than the video signal is modulated by the sine wave. You may do it. As a modulation method, amplitude modulation, frequency modulation, phase modulation, or the like can be used. Also, specifically, for example, FSK (frequency shift keying)
A method or the like is used. In the FSK method, the FSK modulation / demodulation I
Since C has been put to practical use, it can be easily implemented.

In the above embodiment, the video signal is extracted by using the high-pass filter 35 and the low-pass filter 36 in the monitor device 10 shown in FIG. 5. However, for example, a band-pass filter (BPF) may be used.
May be used to extract the video signal.

[0030]

As described above, according to the present invention, a DC voltage having a value corresponding to a channel selection instruction is supplied from a monitor device to a plurality of switch circuits connected in series.
Since each switch circuit detects the value of the DC voltage designating itself and selectively switches each camera, the video of each camera can be arbitrarily selected and monitored. Therefore, it is not necessary to multiplex the video output of each camera, and the transmission system can be simplified and the cost can be reduced.

Also, according to the present invention, an identification signal indicating the own station is superimposed on a video signal output from each camera and transmitted to a monitor device, and the monitor device detects and specifies the identification signal. It is determined whether or not the station belongs to the station, and a predetermined identification signal is obtained by changing the value of the DC voltage supplied when the station is different from the designated station. Even when the level difference between the DC voltage values supplied to the respective cameras from the camera becomes smaller, the malfunction of the switch circuit can be corrected and the specified camera can be correctly selected.

[Brief description of the drawings]

FIG. 1 is a diagram showing an overall configuration of a video monitoring system according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of a switch circuit in the embodiment.

FIG. 3 is a diagram illustrating a configuration example of a voltage detection unit in the switch circuit of FIG. 2;

FIG. 4 is a configuration diagram of a camera and a switch circuit according to a second embodiment of the present invention.

FIG. 5 is an exemplary block diagram showing the configuration of the monitor device according to the embodiment;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Monitor apparatus 11 Metal cable 12a, 12b ... Switch circuit 13a, 13b ... Monitoring camera 131 Camera part 132 Identification signal generation part 21 Switch element 22 Voltage detection part 23 Low-pass filter 24 Voltage comparator 25 Reference power supply 31 Variable DC power supply 32 low-pass filter (LPF) 33 identification signal detection unit 34 control unit 35 high-pass filter (HPF) 36 low-pass filter (LPF) 37 display unit

Claims (3)

[Claims] 1. A plurality of surveillance cameras for photographing each surveillance object and outputting a video signal of the surveillance object, respectively, and a direct current voltage having a different value according to a channel selection instruction of the surveillance camera. And a monitor device for monitoring the video signal of the surveillance camera and outputting a signal via the monitor cable. The monitor device is connected to the metal cable in series and connected to the surveillance camera, respectively, and specifies the self supplied from the monitor device. And a switch circuit for selectively switching the surveillance camera by detecting a value of the DC voltage to be transmitted and transmitting a video signal of the surveillance camera to the monitor device via the metal cable. Video surveillance system. 2. A plurality of surveillance cameras that photograph each surveillance object and superimpose an identification signal indicating that the surveillance object is a self-station on a video signal of the surveillance object, and select the surveillance camera. A monitoring device that outputs a DC voltage having a different value through a metal cable according to an instruction and monitors a video signal of the monitoring camera, and is connected to the metal cable in series and connected to the monitoring camera, respectively. Connected, detects the value of the DC voltage supplied from the monitor device and specifies the self, selectively switches the surveillance camera, and transmits the video signal and the identification signal of the surveillance camera via the metal cable. A switch circuit for sending to the monitor device, wherein the monitor device detects an identification signal sent together with a video signal from the monitoring camera. And a variable DC power supply. The variable DC power supply is controlled in accordance with a channel selection instruction for selecting the monitoring camera to output a DC voltage having a different value, and an identification sent from the selected monitoring camera. Identify whether the signal matches the one instructed to select the channel, and if not, variably control the output voltage of the variable DC power supply so as to obtain an identification signal of the monitoring camera that matches the selected instruction. A video surveillance system comprising a control unit. 3. The video surveillance system according to claim 2, wherein the identification signal superimposed on the video signal of the surveillance camera is set using a sine wave having a higher frequency than the video signal.