JPS639719B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a signal transmission method for connecting an imaging device such as a television camera and a recording device such as a video tape recorder.

When connecting a television camera and a video tape recorder, the signals sent from the television camera to the video tape recorder generally include video signals, audio signals, video tape recorder operation command signals, and the like. Conventionally, these signals have been transmitted through individual signal lines using multi-core cables. For this reason, this connection cable is very heavy, has poor operability, requires a considerable amount of space when stored, and is very cumbersome. Furthermore, specific dedicated cables are required to send different types of signals such as video signals, audio signals, and operation command signals, and when making connections, multi-core connectors are required, which increases costs. , a number of problems arose.

In order to solve these problems, the video signal processing that is normally performed on the video tape recorder side during recording is first performed on the television camera side, thereby processing the video signal, audio signal, and operation command signal. A possible method is to add them together and transmit them through one signal line.

In this method, on the television camera side,
Among the video signals obtained from the camera head, the brightness signal is frequency modulated, and the two color signals are converted into modulated waves in a frequency band lower than the lower side wave band of the frequency-modulated brightness signal. Converts the frequency band of DC to approximately 100KHz to 50MHz, thereby converting the vacant frequency band of DC to 100KHz into the audio signal of the frequency band of 40Hz to 20KHz, and
Operation command signals based on high and low DC potentials are superimposed and transmitted to the video tape recorder through a single signal line, and on the video tape recorder side, the video signal is separated by a high-pass filter and recorded in its original frequency band. The audio signal is separated by a low-pass filter and recorded through an audio recording circuit, and the operation command signal is used to control the mode of the video tape recorder by detecting high or low DC potential.

Now, when optical fiber is used for the signal cable connecting the television camera and video tape recorder, it is necessary to apply a DC bias to the transmitted signal to reduce distortion due to the input/output nonlinear characteristics of the light emitting element. Usually, the DC bias of the light emitting element is set to a value that allows for minimum power consumption and distortion. Therefore, sending a new DC signal for controlling the recording device is not preferable from the viewpoint of power consumption and distortion. Furthermore, on the light receiving side, distinguishing from the signal bias DC level has the drawback of lacking stability in terms of temperature characteristics.

Furthermore, it is difficult to transmit a DC signal even when transmitting a transmission signal by modulating it with a radio frequency without using any signal cable.

In such cases, the operation command signal should be set to a high DC potential.
It must be transmitted by some other method.

One way to achieve this is to use frequency bands that are not used on this signal line (for example, 20KHz to 20KHz).
It is conceivable to modulate the operation command signal at a frequency of 100 KHz or 50 MHz or higher and transmit it.

However, in this case, on the television camera side,
A modulation circuit is required, and a detection circuit is also required on the video tape recorder side, which increases the cost and makes the circuit complicated.

In consideration of the above problems, the present invention transmits video signals and audio signals from a television camera through a single signal line, and also transmits operation command signals using a simple circuit configuration without using the DC band. This provides a method to do this.

FIG. 1 is a system diagram showing an example of a system for transmitting video signals and audio signals from a television camera through a single signal line. In the figure, camera head 1
A luminance signal Ey to which a synchronization signal has been added and a modulated color signal Ec subjected to quadrature two-phase modulation are output from the unit. Of the two signals, the luminance signal Ey has its signal level adjusted to a constant level by an automatic gain adjuster 2, and then enters a frequency modulation circuit 5 through an emphasis circuit 3 and a Cranip/Clip circuit 4. The luminance signal frequency-modulated by this frequency modulation circuit 5 passes through a high-pass filter 6 to attenuate low-frequency sideband components, and then enters a mixer 11 . On the other hand, the modulated color signal Ec has its color signal level adjusted to a constant level by the automatic color gain adjuster 7, and then
A frequency converter 8 receives the frequency of the oscillator 9 and converts the color carrier frequency to a low frequency. Then, in the mixer 11, it is mixed with the frequency-modulated luminance signal in different bands.

Next, the audio signal output from the microphone 12 is amplified by an amplifier 13, and then mixed with a modulated video signal by a mixer 14.

Both signals are then transmitted to the video tape recorder side through one signal line 15.

On the video tape recorder side, the modulated video signal of both signals is separated by a high-pass filter 16 and then sent to a video head 18 through a recording amplifier 17. On the other hand, the baseband audio signal is separated by a low-pass filter 19 and then sent to an audio head 21 through a recording amplifier 20.

With the above-described system, it is possible to transmit the video signal and the audio signal from the television camera side to the video tape recorder side through a single signal line.

Incidentally, since the output signal wave of the frequency modulator 5 is generally a square wave, it contains odd-order harmonic components. Therefore, the frequency spectrum diagram of the signal sent to the signal line 15 is as shown in FIG. In the figure, 22 is a baseband audio signal;
3 is a modulated color signal subjected to carrier reduction conversion, and 24 is a frequency-modulated luminance signal. The frequency-modulated luminance signal 24 has its third harmonic 25.
and even higher-order odd-numbered harmonics.

These high-order harmonics are in a frequency band much higher than the recording/reproducing frequency band of a video tape recorder, so there is no problem in use, but it is desirable to reduce them using a filter.

Therefore, it is conceivable to use this high-order harmonic as a control signal. In other words, this high-order harmonic is used as a control signal depending on whether or not it is attenuated by a filter. The present invention attempts to utilize this as an operation command signal.

FIG. 3 is an example of a specific system diagram of the present invention. In FIG. 3, circuits that operate in the same way as in FIG. 1 are designated by the same numbers. 26 is a frequency modulator 5
The switch 27 is a low-pass filter or a band elimination filter for attenuating high-order harmonics of the output signal wave of the filter. use The operation command signal sent from the television camera to the video tape recorder generally switches the video tape recorder between two modes: a recording state and a recording standby state.

Therefore, in this case, the recording state mode of the video tape recorder is set to the position of the switch that attenuates the high-order harmonic components through the low-pass filter 26 (the side marked with . The video tape recorder is placed in the recording standby state at the position of the switch (the Γ side in the figure) where the switch remains open. Note that there is no problem in operation even if the case in which the high-order harmonic components are attenuated is used as the recording standby state mode, and the case in which the high-order harmonic components remain is used as the recording state mode.

On the video tape recorder side, on the other hand, it is necessary to detect the presence or absence of higher-order harmonics in this frequency-modulated luminance signal. Therefore, by extracting a signal of a specific high-order harmonic (for example, 3rd harmonic) component from the input signal wave by the band-pass filter 28 and passing it through the envelope detection circuit 29, it is possible to detect the presence or absence of high-order harmonics. is detected and output to the operation command signal output terminal 30.

The standby circuit of the video tape recorder may be controlled by the output signal from the operation command signal output terminal 30.

By adopting such a system, it becomes possible to control the recording standby circuit of a video tape recorder based on the presence or absence of high-order harmonics of the frequency-modulated luminance signal, and the operation can be performed without using any other special circuit. It is possible to transmit command signals, making it a very rational system.

The above explanation was based on the assumption that the video tape recorder was switched between two modes, recording mode and recording standby mode, by an operation command signal from the television camera side. Since the luminance signal generated by the output has multiple odd-numbered (3rd, 5th, 7th, etc.) harmonics, each of these high-order harmonics is removed as a residual by using a frequency band removal filter. Alternatively, it is attenuated and transmitted to the video tape recorder, and the video tape recorder side detects the presence or absence of each of these higher harmonics using its own bandpass filter. Additionally, it is also possible to transmit an operation command signal for switching between two modes other than the recording state and recording standby state (for example, playback state mode, rewind state mode, etc.). It is also possible to use the presence or absence of each of these high-order harmonics to command the operation of control circuits other than the mode control circuit of the video tape recorder.

As explained above, the present invention transmits an operation command signal by utilizing the presence or absence of each higher harmonic of a frequency-modulated luminance signal in a television camera and video tape recorder system.
Video signals, audio signals, and operation command signals can be transmitted from the television camera side to the video tape recorder side using a single signal line without using any other special circuits, and the DC band of the signal line is used. Because there is no such thing, use optical fiber etc. for the signal line,
This has the effect of creating a very rational and simple system that also enables wireless transmission.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing an example of a method for transmitting video and audio signals from a television camera using a single signal line, and Figure 2 is a system diagram showing an example of a method for transmitting video and audio signals from a television camera using one signal line. The frequency spectrum diagram in FIG. 3 is a system diagram showing one embodiment of the present invention. 1...Camera head, 5...Frequency modulator, 12...
Microphone, 15...Signal line, 18...Video head, 21...Audio head, 26...Low pass filter, 27...Operation command switch, 28...Band pass filter, 29...Envelope detection circuit, 30...Operation command signal output terminal.

Claims (1)

[Claims] 1 On the imaging device side, an angle-modulated luminance signal obtained by converting the luminance signal obtained from the imaging device into an angle-modulated wave and a color signal obtained from the imaging device are added to the lower side of the angle-modulated luminance signal. A composite signal obtained by adding at least two signals together with a modulated color signal obtained by converting into a modulated wave in a frequency band lower than the wave band is guided to the recording device as one signal, and the above-mentioned An operation command signal for controlling the mode of the recording device,
A connection method between an imaging device and a recording device, characterized in that the angle-modulated luminance signal is transmitted as the presence or absence of higher-order harmonics.