JPH09233460A - Camera system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a camera system with which a video signal is not degraded when synthesizing video and sound signals through a single cable, transmitting a synthetized signal from a transmission part to a reception part and separating it into both signals on the side of the reception. SOLUTION: The sound signal provided from a microphone 1 within the horizontal synchronizing pulse period of the video signal provided from a camera 3 is sampled, made into sound signal pulse and inserted into the horizontal synchronizing pulse period of the video signal, the synthetic signal is prepared by a synthesizer circuit 6, the sound signal pulse in the synthetic signal is sampled/held on the side of the reception part, the sound signal is restored and at the same time, the video signal is restored by removing the sound signal pulse from the synthetic signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surveillance camera system capable of synthesizing a video signal and an audio signal and transmitting the synthesized signal from a transmitting section to a receiving section with a single cable so that the receiving section can separate the two. It is about.

[0002]

2. Description of the Related Art In recent years, in a surveillance camera system for monitoring an image taken by a camera at a position distant from the camera, a structure capable of monitoring not only an image but also a sound has been strongly demanded in recent years. So, place a microphone near the camera,
If the microphone is used to create an audio signal, and this audio signal is combined with the video signal and sent from the transmitter to the receiver on the monitor side, and the receiver is configured to separate both signals, This can be done by connecting the receivers with a single cable.

As a surveillance camera system capable of synthesizing and separating a video signal and an audio signal in this way,
After the audio signal is FM-modulated on the transmitting side, it is synthesized with the baseband video signal and transmitted, and on the receiving side, the synthesized signal is FM
A method in which the audio signal is separated and the original audio signal is obtained after FM demodulation and the video signal is obtained after the FM audio signal is removed can be easily considered.

FIG. 6 is a block diagram of such a conventional technique. In FIG. 6, reference numeral 19 is a camera for creating a video signal, which outputs a baseband video signal. 2
0 is a microphone for audio signal input, 21 is a microphone 20
A microphone amplifier that amplifies the audio signal from the FM audio signal, 22 is an FM modulation circuit that FM-modulates the audio signal, and 23 is an FM audio signal that is output from the FM modulation circuit 22 that is superimposed on the baseband video signal. A combining circuit that outputs as a combined signal, and 24 is an output amplifier circuit that amplifies and outputs the combined signal.

The composite signal from the output amplifier circuit 24 is supplied to the monitoring monitor side, which is a receiving section, via the cable 25 for signal transmission, and is first input to the FM signal separation circuit 26, where FM is selected from the composite signals. Separates only the audio signal, F
The M audio signal is input to the FM demodulation circuit 27, and at the same time, the combined signal is input as it is to the FM signal removal circuit 30.

In the FM demodulation circuit 27, the input FM audio signal is FM demodulated, and the obtained audio signal is amplified by the output amplifier circuit 28 in the subsequent stage and then output from the speaker 29.

On the other hand, the combined signal is an FM signal removing circuit 30.
Then, the FM component is removed and the video signal is restored, and the output is amplified by the output amplifier circuit 31 and then displayed on the monitor television 32.

[0008]

In the above-mentioned prior art, since the FM signal of the sound is combined with the baseband video signal, the frequency of the FM signal is removed when the FM signal is removed by the FM signal removing circuit 30. When the frequencies of the high frequency components included in the video signal are close to each other, the high frequency components of the video signal are also damaged at the same time, and the resolution of the captured video is significantly deteriorated.

Further, if the frequency of the FM signal is increased so that the two frequencies do not come close to each other in order not to impair the high frequency component of the video signal, it becomes unnecessary radiation and is easily radiated from the cable.

[0010]

According to the present invention, an audio signal obtained from a microphone is sampled within a horizontal synchronizing pulse period of a video signal obtained from a camera on the side of a transmitting section, and a horizontal signal of the video signal is obtained as an audio signal pulse. Insert into the sync pulse period to create a synthesized signal, sample and hold the voice signal pulse in the synthesized signal on the receiving side, smooth this sample and hold output to restore the voice signal, and at the same time restore the voice signal pulse from the synthesized signal. Is removed to restore the video signal.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of the system of this embodiment. In the figure, 1 is a microphone for audio input, 2 is a microphone amplifier for amplifying the output of the microphone 1, 3 is a camera for inputting a video signal, 4 is a horizontal for separating a horizontal synchronizing pulse from a video signal output from the camera 3. A sync pulse separation circuit, 5 is a sampling pulse creation circuit that shapes the horizontal sync pulse to create an audio signal sampling pulse whose pulse width is narrower than the horizontal sync pulse within a period in which the horizontal sync pulse exists, and 6 is a video signal It is a synthesizing circuit that synthesizes an audio signal based on a sampling pulse and outputs it as a synthetic signal. Here, the synthesizing circuit 6 is composed of a sampling circuit 53 for sampling an audio signal in synchronization with a sampling pulse and an adding circuit 54 for adding the output of the sampling circuit 53 to a video signal as shown in FIG.

An output amplifier 7 amplifies and outputs the combined signal. A transmission unit is configured by a series of circuit groups from the microphone 1 and the camera 3 to the output amplifier 7.

Reference numeral 9 is a buffer circuit for an input synthetic signal, 10 is a horizontal sync pulse separating circuit for separating a horizontal sync pulse from the synthetic signal, and 11 is a sampling for sampling an audio signal pulse from the horizontal sync pulse. It is a sampling pulse creation circuit that creates a pulse.

Reference numeral 12 is a sample and hold circuit for sampling and holding the audio signal pulse in the composite signal based on the sampling pulse, and 16 is an audio signal removing circuit for removing the audio signal pulse from the composite signal and extracting only the video signal. Here, the audio signal removing circuit 16 is a sampling circuit 55 for sampling the output of the sample hold circuit 12 in synchronization with the sampling pulse as shown in FIG.
And a subtraction circuit 56 that subtracts the output of the sampling circuit 55 from the combined signal.

Reference numeral 17 is an output amplifier circuit for amplifying and outputting the taken-out video signal, 18 is a monitor television for displaying the video signal thus obtained, and 13 is audio sampled and held by the sample-hold circuit 12. A low-pass filter that smoothes the signal pulse to restore the original audio signal, 14 is an output amplifier circuit that amplifies and outputs the audio signal, and 15 is a speaker that outputs the audio signal. The series of circuit groups from the buffer circuit 9 to the speaker 15 and the monitor TV 18 constitute a receiver.

Further, the transmission section and the reception section are connected by a single transmission cable, and the composite signal from the output amplifier 7 is supplied to the buffer circuit 9 via this cable 8.

Next, the signal processing in the above block diagram is shown in FIG.
Will be described in more detail with reference to the waveform diagram of FIG. The audio signal (FIG. 2A) input from the microphone 1 and amplified by the amplifier 2 to a level suitable for synthesizing the video signal is synthesized with the video signal from the camera 3 (FIG. 2B). Here, the horizontal synchronizing pulse (FIG. 2C) of the video signal is separated by the horizontal synchronizing pulse separating circuit 4, and the sampling pulse creating circuit 5 is further separated.
A sampling pulse (FIG. 2 (d)) is created at, and this sampling pulse is input to the synthesis circuit 6.

Here, the sampling pulse creating circuit 5
Specifically, as shown in FIG. 4, the horizontal sync pulse is composed of a monomulti 51 to which a horizontal sync pulse is input and a delay circuit 52 which delays the output of the monomulti 51 by a predetermined time t. The pulse width of the output is set to, for example, 1/3 of the pulse width of the horizontal synchronizing pulse in synchronization with the edge 50 at the start point of, and the delay time t of the delay circuit 52 is also set to 1/3 of the pulse width of the horizontal synchronizing pulse. If set, the sampling pulse can be positioned at the center of the horizontal synchronizing pulse as shown in FIG. 2D and with a pulse width of 1/3 of the pulse width of the horizontal synchronizing pulse. still,
The metastable period of the monomulti 51 and the delay time of the delay circuit 52 need not be limited to the above values as long as the sampling pulse can be positioned within the pulse period of the horizontal synchronizing pulse.

In the synthesizing circuit 6, the audio signal is sampled by the sampling circuit 53 into an audio signal pulse in synchronism with the rising edge of the sampling pulse, and the audio signal pulse is mixed with the video signal by the adding circuit 54. The signal pulse is inserted within the period of the horizontal synchronizing pulse (FIG. 2 (e)).

The composite signal thus created passes through the cable 8 and the buffer circuit 9 and then the horizontal sync pulse separation circuit 1
0, sample hold circuit 12 and audio signal removal circuit 1
6 is input.

The horizontal sync pulse separation circuit 10 separates the horizontal sync pulse from the combined signal, and the sampling pulse creation circuit 11 delays the sampling pulse (FIG. 2) after a delay of a predetermined period t from the start edge of the horizontal sync pulse.
(F)) is output. Here, the sampling pulse creating circuit 11 has the same circuit configuration as the sampling pulse creating circuit 5 shown in FIG.

The sample-hold circuit 12 samples the composite signal with the sampling pulse from the sampling-pulse creating circuit 11, holds it until the next sampling pulse is input, and outputs a sample-hold output (FIG. 2 (g)). . Here, since the sampling pulse is synchronized with the voice signal pulse, sampling the composite signal is substantially equivalent to sampling the voice signal pulse.

This hold output is smoothed by the LPF 13 and restored to the original audio signal ((h) in FIG. 2), which is output from the speaker 15 via the output amplifier circuit 14.

On the other hand, in the audio signal removing circuit 16, the output of the sample hold circuit 12 sampled by the sampling circuit 55 in synchronization with the sampling pulse from the sampling pulse creating circuit 11 is output from the combined signal input from the buffer circuit 9. The subtraction circuit 56 subtracts the audio signal pulse inserted in the horizontal synchronizing pulse period of the combined signal to remove the original video signal (FIG. 2 (i)).
Will be created. Here, since the audio signal exists only during the horizontal synchronizing pulse period in which the video signal does not exist, even if the audio signal is removed, the audio signal pulse can be completely removed without affecting the video signal.

The video signal thus obtained is displayed on the monitor television 18 via the output amplifier circuit 17.

Due to the signal flow as described above, even if the signal transmission is performed by a single cable without providing a dedicated cable for each of the video signal and the audio signal, the monitor 3 can use the monitor TV 18 to allow the monitor 3 The captured image can be viewed without deterioration, and at the same time, the speaker 15 can hear the voice captured by the microphone 1.

[0027]

As described above, according to the present invention, since the audio signal is inserted as the audio signal pulse into the horizontal synchronizing portion of the video signal at the time of transmitting the signal, a single cable can be used for the signal transmission. Further, when separating or removing only the audio signal, the video signal is not deteriorated. Moreover, since the audio signal is not FM-modulated at a high frequency, unnecessary radiation does not increase.

[Brief description of drawings]

FIG. 1 is a block diagram of one embodiment of the present invention.

FIG. 2 is a waveform diagram of an example of the present invention.

3 is a block diagram of a synthesis circuit 6 in FIG.

FIG. 4 is a block diagram of a sampling pulse generation circuit 5 of FIG.

5 is a block diagram of an audio signal removing circuit 16 of FIG.

FIG. 6 is a block diagram of a conventional example of the present invention.

[Explanation of symbols]

 1 Microphone 3 Camera 4 Horizontal sync pulse separation circuit 5 Sampling pulse creation circuit 8 Cable 6 Compositing circuit 11 Sampling pulse creation circuit 12 Sample hold circuit 16 Audio signal removal circuit

Claims (2)

[Claims] 1. A sampling pulse creating means for outputting a sampling pulse within a horizontal synchronizing pulse period of a video signal obtained from a camera, and an audio signal obtained from a microphone by sampling the sampling pulse to produce a video signal as an audio signal pulse. Of the horizontal synchronizing pulse period, a transmitting section having a synthesized signal generating means for generating a synthesized signal, a sample hold means for sampling and holding a voice signal pulse in the synthesized signal, and a smoothing of the sample and hold output. A receiving unit having a filter unit for restoring an audio signal, and an audio signal removing unit for removing an audio signal pulse from the combined signal to restore a video signal, and a combined signal from the transmitting unit to the receiving unit. A camera system that includes a cable that enables transmission. 2. The sampling pulse creating means comprises a horizontal sync pulse separating means for separating a horizontal sync pulse from a video signal, and a pulse creating circuit for issuing a sampling pulse after a predetermined time has elapsed from the edge of the horizontal sync pulse. 2. The camera system according to claim 1, wherein the sample holding by the holding means is executed after the predetermined time from the edge of the horizontal synchronizing pulse of the combined signal.