Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/18—Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast
  • H04N7/183—Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast for receiving images from a single remote source
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
  • H04N7/00—Television systems
  • H04N7/18—Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast
  • H04N7/181—Closed-circuit television [CCTV] systems, i.e. systems in which the video signal is not broadcast for receiving images from a plurality of remote sources

Definitions

• the present invention relates to a video signal transmission apparatus that transmits a video signal.
• Patent Document 1 Japanese Patent Laid-Open No. 2000-20042
• each video output device when transmitting a plurality of video output devices in a daisy chain connection, each video output device has a path for transmitting its own video signal to a downstream video output device. Since there is a branch connected to the video output device on the upstream side, there is a situation in which signal reflection or the like caused by this branch occurs.
• the present invention has been made in view of the above circumstances, and is easily expandable.
• An object of the present invention is to provide a video signal transmission device capable of ensuring the quality of a video signal to be transmitted.
• the present invention firstly has an input terminal that can be connected to the output of the first video signal transmission device via a signal cable, and the digital signal is input to the video signal from the input terminal.
• a daisy chain connection output circuit having an output terminal that can be connected to the input of the second video signal transmission device via a signal cable and outputting a video signal to the output terminal, and a video signal And a video input circuit that outputs a video signal input from the video signal output device to the daisy chain connection output circuit, the daisy chain connection input circuit.
• the daisy chain connection output circuit is provided with a video signal transmission device having terminations that are matched with each other.
• the present invention is the video signal transmission device according to the first aspect, wherein the daisy chain connection input circuit and the daisy chain connection output circuit are configured by a DC coupling circuit.
• the present invention provides the video signal transmission device according to the first or second, wherein the video input circuit is a reference of a video signal input from the video signal output device.
• a clamp circuit for clamping the level to a predetermined level.
• the present invention provides the video signal transmission device according to the first or second aspect, wherein the video input circuit is provided between the video signal output device and the daisy chain connection output circuit. And a first output transistor connected to the output of the switching unit, the switching unit being connected between the video signal output device and the daisy chain connection output circuit.
• the first output traffic when the connection between the first output traffic Apply 0 noise to the transistor.
• the fifth aspect of the present invention is the video signal transmission device according to the fourth aspect, wherein the video input circuit is connectable to the plurality of video signal output devices, and the plurality of video signal output devices. And a plurality of clamp circuits for clamping the reference level of the video signal input from the power device to the same level, and the switching unit is input as the connection state via the clamp circuit. One of a plurality of video signals is selected.
• a single signal transmission device can switch video signals from a plurality of video output devices, and the reference levels of all video signals are clamped to a predetermined level. Even when the switching unit switches to a video signal from a different video output device, the quality of the video signal can be ensured.
• the present invention provides the video signal transmission apparatus according to the fourth or fifth aspect, wherein the daisy-chain connection input circuit is input to the first video signal transmission apparatus. It has a second output transistor that is turned off by a 0-bias signal.
• FIG. 1 is a block diagram showing a schematic configuration of a video signal transmission system according to an embodiment of the present invention.
• FIG. 2 is a diagram showing a schematic configuration of a video signal transmission apparatus according to an embodiment of the present invention.
• FIG. 3 shows an internal configuration of a clamp circuit in the video signal transmission device according to the embodiment of the present invention.
• FIG. 1 is a block diagram showing a schematic configuration of a video signal transmission system according to an embodiment of the present invention.
• a video transmission device that transmits a video signal from a video output device that outputs a video signal such as a camera
• a plurality of video signal inputs can be selected, and other relay device power can be selected.
• the relay apparatus 1 capable of transmitting signals will be described.
• signal cables are wired to the relay devices la, lb, and 1 c in the manner of one stroke.
• 256 video signals are input to the device input terminal 12 of the relay device la, lb, lc divided into three units, and based on an instruction input to the operation input device 5, the relay device la, One video signal is selected and transmitted by lb and lc. Then, the transmitted selected video signal is output to the display device 4 and displayed, for example.
• the case of the camera 2 will be described as an example of a video output device that outputs a video signal to the relay device 1.
• the relay devices la ⁇ : Lc each have, for example, 96 device input terminals 12, the relay device lc has the video signal power of the 1st to 96th cameras 2 and the relay device lb has the 97th to 192nd cameras 2 The video signal of the 193rd to 256th camera 2 is input to the relay device lc.
• Each relay device la, lb, lc has a daisy input terminal 13 that can be connected to the output of the upstream relay device via a signal cable, and an input circuit 30 to which video from the daisy input terminal 13 is input. And a digital output terminal 14 that can be connected to the input of the downstream relay device via a signal cable, an output circuit 40 that outputs a video signal to the daisy output terminal, and a video signal such as camera 2 is output.
• a selection circuit 20 that can be connected to a video output device and outputs a video signal to which the video signal output device power is also input to the output circuit 40 is provided.
• the selection circuit 20 has a plurality of device input terminals 12 and can input a plurality of video signals, and selects a video signal according to an operation input signal from the operation input device 5.
• the daisy input terminals and the daisy output terminals of the relay devices la, lb, and lc have the daisy input terminals 13a, 13b, and 13c and the daisy output terminals 14a, 14b, and 14c, respectively.
• the device input terminal 12, the daisy input terminal 13, the daisy output terminal 14, the selection circuit 20, the input circuit 30, and the output circuit 40 have the same configuration.
• the relay apparatuses 1 are connected to each other by connecting a signal cable from the daisy output terminal 14 to the daisy input terminal 13.
• the relay device la and the relay device lb are connected by connecting the daisy one input terminal 13b of the relay device lb to the daisy one output terminal 14a of the relay device la in order from the upstream side.
• the relay device lb and the relay device lc are connected by connecting the daisy one input terminal 13c of the relay device lc to the daisy one output terminal 14b of the relay device lb.
• the selection output of the selection circuit 20 whose selection is not active in each relay device la, lb, lc is The selection circuit 20 which is not connected to the daisy input terminal 13 and the daisy output terminal 14 and whose selection is active is connected to the daisy input terminal. No signal is returned to 13.
• the video signal that is the final selection output is buffered between the daisy-input terminal 13c and the daisy-output terminal 14c of the relay device lc connected to the most downstream side, which is a common selection signal line for all input signals. Directly output via circuit 3.
• nota 3 is a selection of 256 video signal input power that is described as a circuit when it is necessary as a signal route to add or add some processing to the selected output signal, for example, to display characters If only processing is required, the video signal selected from the output terminal 14c of the output circuit 40 may be output, and therefore the relay devices la to Lc may all have the same configuration.
• FIG. 2 is a diagram showing a schematic configuration of the video signal transmission apparatus according to the embodiment of the present invention.
• the selection circuit 20 can be connected to the force camera 2 via a plurality of, for example, 96 device input terminals 12. Then, a clamp circuit 21 connected to each of the device input terminals 12 and one of the video signals input via the clamp circuit 12 based on an operation instruction from the operation input device 5 are output.
• a switching unit 22 that switches the circuit 40 between a connected state and a non-connected state, a PNP transistor 23 and an NPN transistor 24 provided on the output side of the switching unit 22, and a grounding resistor 25 are provided.
• the common power supply voltage 21v is applied to the clamp circuit 21, and the reference level such as the bottom level of the synchronization signal or the pedestal level is clamped to the same level in the video signal input from each camera 2. By doing so, it is possible to stably perform synchronous separation.
• FIG. 3 is a diagram showing an internal configuration of the clamp circuit in the video signal transmission apparatus according to the embodiment of the present invention.
• the clamp circuit 21 includes a DC coupling capacitor 211 connected to the device input terminal 12, a power supply voltage of 21 V connected to the base, and an emitter connected to the connection point A on the output side of the DC coupling capacitor 211.
• a transistor 212, a ground resistor 213 connected to the output of the DC coupling capacitor 211, and an NPN transistor 214, which is an output transistor having a base connected to the output of the DC coupling capacitor 211, are provided.
• the input signal becomes an AC component by the DC coupling capacitor 211 input from the device input terminal 12.
• the clamp voltage at node A drops below 1.0 [V]
• the NPN transistor The base-emitter voltage VBE of the transistor 212 becomes large (VBE> 0.7 [V]), and the NPN transistor 212 is turned on. Then, a current is supplied from the NPN transistor 212 and the DC coupling capacitor 211 is charged. This charging increases the potential at node A, and charging is performed until the minimum value of the input signal reaches 1.0 [V] or higher.
• the switching unit 22 has a configuration in which the open 22x can be selected in addition to the input from each clamp circuit 12.
• the output of the switching unit 22 is connected to the base of the PNP transistor 23, and the emitter of the PNP transistor 23 is connected to the base of the NPN transistor 24!
• the emitter of NPN transistor 24 becomes the output of the selection circuit.
• one end of the ground resistor 25 is connected to the connection point between the switching unit 22 and the PNP transistor 23, and the other end is grounded.
• the input circuit 30 has an OdB buffer 31 connected to the daisy input terminal 13, one end connected to a connection point between the daisy input terminal 13 and the OdB buffer 31, and the other end grounded.
• a resistor 32, a PNP transistor 33, and an NPN transistor 34 are provided.
• the base of the PNP transistor 33 is connected to the output of the OdB buffer 31, and the base of the NPN transistor 34 is connected to the emitter of the PNP transistor 33.
• the output circuit 40 includes a connection point between the output 20 of the selection circuit and the output of the input circuit 30, and a termination resistor. 6 dB driver 41 connected to the connection point between 50 and termination resistor 42 connected in series between 6 dB driver 41 and daisy output terminal 14.
• the selection circuit 20 of the relay apparatus la the video signal input to the device input terminal 12 is not selected, so that the switching unit 22 selects the open 22x. Therefore, the base of the transistor 23 is zero biased by the ground resistor 25, so that the transistor 24 is cut off. Therefore, the output circuit 40 of the relay device la transmits the 0 bias DC component to the daisy-one output terminal 14.
• the input circuit 30 of the relay device lb connected to the next stage of the relay device la is connected to the output circuit 40 of the relay device la, the input circuit 30 is in a 0 bias state, and the transistor 34 is turned off. Therefore, the circuit upstream of the input circuit 30 is connected to the transistor 24 of the selection circuit 20 of the relay device lb, and the state is reached.
• the switching unit 22 of the selection circuit 20 puts the selected device input terminal 12 into a connection state. Since a signal having a certain bias is obtained at the output of the switching unit 22 by the clamp circuit 21 connected to the selected device input terminal 12, the transistor 24 is turned on. As described above, since the transistor 34 in the input circuit 30 is off and connected as described above, the selected video output appears to the daisy output terminal 14b via the output circuit 40.
• the input circuit 30 of the relay device lc connected to the next stage of the relay device lb is connected to the output circuit 40 of the relay device lb.
• the output circuit 42 is provided with a termination resistor 42
• the input circuit 30 is provided with a termination resistor 32.
• the selection circuit 20 of the relay device lc since the video signal input to the device input terminal 12 is not selected, the switching unit 22 selects the open 22x. Therefore, the base of transistor 23 is zero biased by ground resistor 25, so transistor 24 is cut off. Obviously, since the selection circuit 20 is not connected to the transistor 34 of the input circuit, the signal input from the daisy input terminal 13c is output from the buffer circuit 3 via the input circuit 30.
• the relay device is exclusively provided with the input circuit 30 and the output circuit 40 for daisy connection, and each has a terminal portion that is matched with each other. Therefore, in the connected signal cable, etc. It becomes possible to suppress reflection. Also, no video signal is input.
• the bias of the output transistors of the selection circuit 20 and the input circuit 30 is set to zero. In this way, it is possible to exchange signals with directionality between relay devices connected in a daisy chain.
• the input circuit 30 and the output circuit 40 are configured by a DC coupling circuit so that DC transmission is possible between the upstream relay device and the downstream relay device. ing.
• the advantages of using a DC coupling circuit will be described below with reference to FIGS.
• FIG. 4 is a diagram showing a video signal switching circuit by AC coupling
• FIG. 5 is a diagram for explaining a video signal change at the time of video input switching by AC coupling.
• Fig. 5 (A) shows the signal waveform of the input video signal S1
• Fig. 5 (B) shows the signal waveform of the input video signal S2
• Fig. 5 (C) shows switching from the input video signal S1 to S2.
• Figure 5 (D) shows the separated sync signal when switching from the input video signal S1 to S2
• Figure 5 (E) shows the normally separated sync signal. It is.
• each of the input video signals SI and S2 is AC-transmitted using the capacitor C, and either one is selected by the switch SW.
• the output of switch SW is connected to the base of transistor TR. A fixed bias is applied to the base of the transistor TR.
• the input video signals SI and S2 have different DC levels, and the input video signal S1 has a low DC level as shown in Fig. 5 (A).
• the DC level of the video signal S2 is high, as shown in FIG. 5C, when the input video signal S1 is switched to the input video signal S2 by the switch SW at time tl, the selected signal is condensed.
• the data is output as is via C. Note that the DC level of the input video signal S2 after switching converges as time elapses due to discharge by a bias circuit or the like.
• the clamp circuit 21 is provided so that the reference level such as the sync chip voltage between the video signals to be selected is the same level.
• the DC level of the video input signal at the time of selection does not change even when switching in.
• the relay device 1 including the clamp circuit 21 that clamps to the reference level and capable of DC transmission is daisy chain connected with the DC potential of the synchronization signal fixed. Therefore, even when switching to a video signal input to a different relay device 1 is performed, the DC potential of the synchronization signal does not change, so that a stable image display with no detection loss in video signal force synchronization separation can be obtained. It is done.
• each video transmission device has a clamp circuit that makes the input video signal from the video output device equal and the clamp voltage equal to each other, and uses a circuit capable of DC transmission between the video transmission devices. By daisy chain connection, stable video input switching can be performed.
• a relay device that can select video signals from a plurality of video output devices has been described as a video transmission device.
• a device that can input only one video output device may be used. .
• the video signal transmission device of the present invention is easy to expand and has the effect of ensuring the quality of the video signal to be transmitted, and selects and transmits one video from a plurality of video signal inputs. This is useful for video signal transmission systems and the like.

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• Engineering & Computer Science (AREA)
• Multimedia (AREA)
• Signal Processing (AREA)
• Controls And Circuits For Display Device (AREA)
• Closed-Circuit Television Systems (AREA)
• Small-Scale Networks (AREA)
• Studio Circuits (AREA)

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Citations (6)

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• 2005
  • 2005-10-05 JP JP2005292503A patent/JP4312189B2/ja not_active Expired - Fee Related
• 2006
  • 2006-10-04 WO PCT/JP2006/319894 patent/WO2007040251A1/ja not_active Ceased
  • 2006-10-04 EP EP06811233A patent/EP1933560B1/en not_active Ceased
  • 2006-10-04 US US11/996,321 patent/US8144256B2/en not_active Expired - Fee Related
  • 2006-10-04 CN CN2006800313669A patent/CN101263715B/zh not_active Expired - Fee Related

Patent Citations (6)

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