JP2009010568A - Video signal multiplex transmission device and imaging apparatus using the video signal multiplex transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a transmission state at the start of a video signal multiplex digital transmission system. <P>SOLUTION: A digital video signal multiplex transmission device is disclosed which has a means for transmitting and receiving digital signals containing digitized video signal, audio signal and control signal in both directions via one transmission path and varying the bit rate of the digital signal; and a means for switching two power sources of a preparation power source and a main power source, wherein the digital video signal multiplex transmission device is equipped with a means for performing transmission at a low bit rate in a preparation power source mode, and varying the transmission rate to a high clock rate, after switching the power source to the main power source reestablishing the transmission state at a low clock rate again. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an improvement of a transmission method in a video signal multiplex transmission apparatus used for an imaging apparatus such as a television camera apparatus.

  Conventionally, in a television camera system, time division of transmission / reception of main line video signal, return video signal, audio signal, control serial data signal, and power supply between the imaging unit (camera head) and the control unit (Camera Control Unit: CCU) Bidirectional transmission is performed with a single triple coaxial (triax) cable. As a simple method, a normal coaxial cable may be used for the transmission line. Usually, these signals are frequency-modulated and frequency-multiplexed or digitally time-division multiplexed.

  Main video signals include NTSC with 485 effective scanning lines as SDTV and PAL with 575 effective scanning lines, 720 effective scanning lines and 1080 effective scanning lines as HDTV, 2160 effective scanning lines as SHDTV, and effective scanning as UHDTV. There are 4320 lines, and NTSC will be described as a representative.

  The NTSC 10-bit 4: 2: 2 broadcast video digital signal output from the camera unit has a data amount of 270 Mbps, and the video signal to be sent back has a data amount of about 50 Mbps even after data compression. In the case of time-division bidirectional transmission, the video signal is time-compressed to be a signal of about 360 Mbps, and is intermittently transmitted from the camera head to the camera control device in a short time. Then, during a period freed by time compression, a video signal for sending back time-compressed to 360 Mbps in the direction of the camera head from the camera control device is intermittently transmitted in a short time. The process is switched by an input / output switch at a rate of several times per second to realize time-division bidirectional transmission (Patent Document 1).

  Performing pulse waveform reproduction is called waveform equivalence. Normally, the attenuation of 360 MHz of a triax cable is as large as 170 dB at 1 km, and with the current waveform equivalent, only about 600 m can be extended between the camera head and the camera control unit. For the extension, it is necessary to correct in advance the deterioration of the cable frequency characteristic of the digital video signal based on the transmitted reference signal (Patent Document 2).

  The outline and operation of a conventional embodiment will be described with reference to FIG. FIG. 2 is a block diagram showing a triax camera system of a conventional example. In FIG. 2, the triax camera system includes an imaging unit 1, a triax cable 2, and a control unit 3.

  The imaging element 103 of the imaging unit 1 photoelectrically converts incident light imaged by the lens unit 101 and decomposed into RGB by the separation optical system 102 and outputs the incident light to the digital video signal processing unit 105. The image sensor 103 may be a CMOS image sensor or a peripheral circuit of a CCD image sensor, a drive circuit, CDS, AGC, and A / D. The digital video signal processing unit 105 performs processing such as level amplification and edge enhancement of the video signal and outputs the result. When the transmission path 2 is long, the video compression unit 106 performs video compression. When the transmission path 2 is short, the video signal is output to the time division bidirectional switching unit 104 as it is. In the time division bidirectional switching unit 104, the digital video signal and the digital audio signal are time division multiplexed and bidirectionally transmitted. The serial digital signal output from the imaging unit 4 is transmitted to the control unit 5 via the triax cable 2. The serial digital signal transmitted to the control unit 5 is decomposed by the time-division bidirectional switching unit 108, demodulated into the original digital video signal and digital audio signal, decompressed, and the digital signal processing unit 141 Output after processing.

  An external video signal that is input from the control unit 5 and output from the imaging unit 4 is also transmitted in the same manner as described above.

  In this system, there are two states: a ready power state and a main operation state. In the ready power supply state, only the intercom line can be used, and before starting broadcasting, etc., a talk is made between the cameraman and the person at the console as a preparation stage. At this time, in consideration of power consumption and the like, the power is sent at a low voltage of about DC36V. In the main operation state, the power supply is operated at a high voltage of about 230 VAC.

Here, in general, cables have different attenuation amounts depending on the frequency, and when transmission is performed at a low rate, the attenuation amount is small, so that it is not necessary to make a correction.
Japanese Patent Laid-Open No. 7-203399 JP-A-8-317251

  In the current digital triax transmission, bi-directional transmission is performed at a high rate in the main operation state, so when the cable length is extended, it can be operated only with a cable up to about 300 m due to the cable attenuation characteristic. It was.

Therefore, in order to extend the cable length, a system incorporating a correction circuit for correcting the attenuation amount of the cable length is desired.
Here, this system has two states, the ready power supply state and the main operation state. When the system is switched from the ready power supply state to the main operation state, the power supply is temporarily turned off. It will be reset.

  Further, in this system, in order to reduce power consumption, transmission is performed at a low voltage and a low clock rate in the preparation power supply state, and at a high voltage and a high clock rate in the main operation state. Since the attenuation amount in the cable becomes large at a high clock rate, it is necessary to switch the analog circuit cable length correction circuit in accordance with the cable length. However, the power supply sent to the camera control unit is different between the ready power supply state and the main operation state, and when switching from the preparation power supply state to the main operation state, the power supply is temporarily turned off and the power supply voltage is switched to a different power supply voltage. The circuit state of the part is also reset once.

  An object of the present invention is to improve a method for switching the bidirectional transmission rate between the above-described preparation power supply state and main operation state.

In order to achieve the above object, the present invention bi-directionally transmits a digital signal including a digitized video signal, audio signal, and control signal via a single transmission line, and changes the rate of the digital signal. In a digital video signal multiplex transmission apparatus having means for switching between two power sources, a preparation power source and a main power source,
Video signal multiplexing comprising means for performing bidirectional transmission at a low rate at the time of a preparation power source, establishing a bidirectional transmission state at a low rate by switching to the main power source, and then increasing the bidirectional transmission rate Device.

In the above, analog correction means (pre-boost and waveform equivalent) of the digital signal waveform, digital correction means (pre-D / A correction and post-A / D correction) of the digital signal waveform, and the transmission Having the function of varying the analog correction means and the digital correction means according to the length of the road;
An image characterized by measuring the length of the transmission line when establishing a transmission state at a low clock rate, and varying the analog correction unit and the digital correction unit according to the measured length of the transmission line This is a signal multiplex transmission apparatus.

  In other words, the present invention is characterized in that, when the power is switched, after setting data such as a cable correction circuit once reset at a low bidirectional transmission rate is established once again, switching to bidirectional transmission at a high bidirectional transmission rate is performed. This is a video signal multiplex transmission apparatus.

  Moreover, it is an imaging device provided with said video signal multiplex transmission apparatus.

  As described above, according to the present invention, the signal degradation between the frequency correction and the phase correction that occurs when the cable length is extended even at the start-up when the power supply voltage and the bit rate of bidirectional transmission are switched between the transmission side and the reception side. In this way, the bidirectional transmission state can be normally established and the cable length can be extended even in the digital video signal multiplex transmission apparatus.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. 1 which is a block diagram showing an entire triax camera system according to an embodiment of the present invention. First, the compressed video signal, CPU data, utility data (waveform correction circuit setting data, etc.) and audio signal are multiplexed by the control unit 3 and converted into a serial signal at P / S 144, and the overcorrection circuit 133, time-division bidirectional multiplexing unit 108 and the AC separation filter 129, superimposed on the AC power supply, passed through the triax cable 2, and transmitted to the imaging unit 4.

  In the imaging unit 4, the AC power supply and the transmission signal are separated by the AC separation filter 124. The separated transmission signal is subjected to waveform shaping due to cable deterioration by the analog waveform correction circuit 119 and the digital waveform correction circuit 118, is recovered by the clock recovery 117, and is returned to the parallel signal by the S / P 116. Video is output from the decompression unit 115. Similarly, the audio signal is expanded by the audio processing unit 114, converted to analog audio by the DAC 111, and output.

  The incident light from the imaging unit 4 passes through the lens 101 and is split into three colors of red (R), green (G), and blue (B) by the color separation optical system (Prism) 102, respectively. It is converted into a digital video signal by the image sensor 103. The image sensor 103 may be a CMOS image sensor, a CCD image sensor, a drive circuit, CDS, AGC, or A / D.

  The digital video signal from the image sensor 103 is subjected to signal processing such as black balance, white balance, and γ correction by the digital video signal processor 105. The output signal from the digital video signal processor 105 is compressed by the video compression unit 106, multiplexed with audio signals, CPU data, utility data (cable correction circuit setting data, etc.), converted into a serial signal at P / S 107, The signal is transmitted to the control unit 3 through the triax cable 2 through the correction circuit 109, the time division bidirectional multiplexing unit 104, and the AC separation filter 124.

  The signal transmitted from the imaging unit 4 passes through the AC separation filter 129, the signal waveform deterioration is corrected by the analog waveform correction circuit 132 and the digital waveform correction circuit 137, and the clock is recovered by the clock recovery unit 138. / P139 returns the signal to the parallel signal, and the video signal is expanded by the video expansion unit 140, processed by the digital video signal processing unit 141, and output. The audio signal is also returned to the pareler signal at S / P 146, processed by the audio processing unit 150, and output as analog audio through the DAC 151.

  In the present embodiment, there are two states: a preparation power supply mode (state) and a main operation mode (state).

  When the power is turned on, the operation starts in the ready power mode. In the preparation power supply mode, DC36V is sent from the POWER 131 of the control unit 3. Further, a signal obtained by synthesizing the audio signal of the audio processing unit 148 and the control signal from the CPU 156 is converted into a serial signal at P / S 144, passes through the overcorrection circuit 133, and the time division bidirectional multiplexing unit 108 and AC separation filter 129 are connected. After passing, it is superimposed on the DC 36 V and transmitted to the imaging unit 4 through the TRIAX cable 2. In this embodiment, the low bidirectional transmission rate at this time is equivalent to 3.75 MHz of 1/8 of 27 MHz, but may be an integer multiple of the horizontal synchronization frequency. The power source and data sent from the control unit 3 enter the imaging unit 4, and the power source passes through the LPF 125, is DC / DC converted by the POWER 126, and is used as an internal power source. The data passes through the AC separation filter 124, passes through the analog waveform correction circuit 119 and the waveform correction circuit (STBY) 122, is locked and reproduced by the clock reproduction unit 121, and is returned to the parallel signal by the S / P 120, and the audio processing unit Audio processing is performed at 114 and audio output is performed.

  Similarly, from the imaging unit 4 side, the signal is converted into a serial signal at P / S 107 and sent to the control unit 3 through the overcorrection circuit 109, the time division bidirectional multiplexing unit 104, and the AC separation filter 124.

  When the preparation power mode is shifted to the main operation mode, the POWER 131 of the control unit 3 is switched from DC 36V to AC 230V.

  The image capturing unit 4 and the control unit 3 transmit data in both directions. However, when the power of the image capturing unit 4 is temporarily turned off due to the action of switching the power source, the data that has been transmitted in both directions is transferred. It will be reset. The high bidirectional transmission rate in the main operation state is 360 Mbps, but it can be reduced by compressing the video signal, but it is 1500 Mbps when attempting to transmit HDTV uncompressed. At a high bidirectional transmission rate, it is necessary to set the analog correction circuits 119 and 132 and overcorrection circuits 109 and 133 according to the cable length. Even if transmission is to be performed, it cannot be determined which cable length should be set, and bidirectional transmission cannot be established.

  Therefore, the main switching power source is switched to AC 230 V, but transmission is performed at a low bidirectional transmission rate, the length of the cable length is measured again, and the setting conditions of the correction circuit are determined. When the cable length setting condition is determined, the cable correction circuit setting is switched and at the same time the process is switched to transmission at a high bidirectional transmission rate, even if the power is turned off and the setting is reset once, Bidirectional transmission can be performed stably.

  FIG. 3 shows the relationship between the operating state of one embodiment of the present invention, the power supply voltage supplied to the image pickup unit 4, and the bidirectional transmission bit rate. The horizontal axis is the elapsed time, the vertical axis is the power supply voltage supplied to the imaging unit 4, and the lower figure is the bidirectional transmission bit rate. First, in (a), the power supply of the control unit 3 is activated, the preparation power supply mode is started, and the low-speed transmission rate is started. At this time, the feed power supply voltage from the control unit 3 to the imaging unit 4 is low, and the bidirectional transmission rate is low. In this preparatory power mode, video signals are not transmitted, but intercom calls can be made. At this time, the length of the cable is measured. In the state of (b), the preparation power supply mode is terminated and the low-speed transmission rate is terminated. At this time, since the power is cut off during Δt1, the transmission is interrupted. Further, when the power of the imaging unit 4 is turned off, the setting of the imaging unit 4 is reset.

Therefore, in (c), the main power supply mode is started and the low-speed transmission rate is restarted, the set data is transmitted to the imaging unit 4 and reset. In the state of (d), when the resetting is completed, the high-speed transmission rate is started and the video signal and the like are transmitted. In (e), the main power supply mode ends and the high-speed transmission rate ends. In (f), the standby power supply mode is started and the low-speed transmission rate is started.

1 is a block diagram showing the overall configuration of an embodiment of the present invention. The block diagram which shows the whole structure of one conventional example. 4 is a schematic diagram showing the relationship between the operating state of one embodiment of the present invention, the power supply voltage to the camera device, and the transmission bit rate. (A) Control unit power activation, preparation power supply mode start, low-speed transmission rate start (b) preparation power supply mode End, low speed transmission rate end (c) Main power supply mode start, low speed transmission rate restart (d) High speed transmission rate start (e) Main power supply mode end, high speed transmission rate end (f) Preparation power supply mode start, low speed transmission rate start

Explanation of symbols

1, 4: Imaging unit, 2: Triax cable, 3, 5: Control unit 101: Lens unit, 102: Color separation optical system,
103: Image sensor (CMOS image sensor or CCD image sensor and drive circuit, CDS, AGC and A / D),
104, 108: Time-division bidirectional switching units 113, 152: ADC (A / D converter),
105, 141: video signal processing unit,
106, 147: video compression unit,
111,151,: DAC (D / A converter)
124,129: AC separation filter, 125,130: LPF, 126: POWER
119,132: Analog waveform correction circuit, 118,137: Digital waveform correction circuit
109,133: Overcorrection circuit, 112,134: Waveform correction circuit
115,140: Video expansion unit, 156,157: CPU
110,149: Correction circuit setting processor
158: Delay time processing section
107,144: P / S (parallel-serial converter)
116, 120, 139, 146: S / P (serial-parallel converter)
117,121,138,145: Clock recovery unit
114,150: Audio processor

Claims (3)

A digital signal including a digitized video signal, audio signal, and control signal is bidirectionally transmitted through one transmission line, and means for changing the bidirectional transmission rate of the digital signal, a preparation power source, and a main power source. In a digital video signal multiplex transmission apparatus having means for switching power,
Video signal multiplexing characterized by comprising means for performing bidirectional transmission at a low rate when preparing a power supply, establishing a bidirectional transmission state at a low rate by switching to the main power supply, and then increasing the bidirectional transmission rate apparatus. The video signal multiplexing device according to claim 1, wherein
Analog correction means (with pre-boost and waveform equivalent) of the digital signal waveform, digital correction means (with pre-D / A correction and post-A / D correction) of the digital signal waveform, and the length of the transmission path A function of varying the analog correction means and the digital correction means;
Measuring the length of the transmission path when establishing a transmission state at a low bidirectional transmission rate, and varying the analog correction means and the digital correction means according to the measured length of the transmission path Video signal multiplex transmission device. An imaging apparatus comprising the video signal multiplex transmission apparatus according to claim 1.

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