JPH07250338A - External synchronizing method for video camera - Google Patents

Abstract

PURPOSE:To obtain a television camera in which the synchronization of a synchronizing signal of the television camera is matched by using a commercial power supply, the phase of a chrominance subcarrier and a phase of a horizontal synchronizing signal are matched and the commercial power supply whose frequency is 50Hz is available for the camera in addition to the commercial power supply whose frequency is 60Hz. CONSTITUTION:A sub phase reference signal generating circuit 20 generates a high frequency sub phase reference signal by the PLL system based on a commercial power supply and a reference frequency signal is generated by controlling an oscillation circuit 35 of a synchronizing signal generating circuit 30 by using the PLL system based on the sub phase reference signal. Then the reference frequency signal is frequency-divided to form the chrominance subcarrier, the horizontal synchronizing signal and a vertical synchronizing signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for synchronizing a plurality of color television cameras with each other.

[0002]

2. Description of the Related Art Today, an image taken by a plurality of television cameras is often monitored by a single monitor television. Thus, when switching the images of a plurality of cameras on a single monitor television, The synchronization signals of the TV cameras are synchronized with each other so that the image on the monitor is not disturbed when switching.

In large equipment, a single sync signal generator also sends the same sync signal to each television camera, but in surveillance camera devices, the frequency of a commercial power supply of 60 hertz is used. The power supply synchronization method of controlling the reference frequency signal so as to match the frequency and timing of the vertical synchronization signal with the commercial power supply as the reference frequency is often used because of its simplicity.

In the power supply synchronization system based on the commercial power supply, the oscillation control by the PLL system is often used, and as shown in FIG.
A reference frequency signal of 4 megahertz is formed, and this reference frequency signal is divided by a frequency dividing circuit 17 to generate a horizontal synchronizing signal or horizontal synchronizing timing signal of about 15.7 kilohertz.
The reference frequency signal is divided by the frequency divider circuit 18 to form a 60 Hz vertical synchronizing signal or vertical synchronizing timing signal, and the zero cross detection circuit 12 is used to form a 60 Hz phase reference signal from the commercial power source power line 11. , The phase difference is detected by comparing the phase reference signal and the vertical synchronizing signal in the phase comparison circuit 13, and the timing of the vertical synchronizing signal is adjusted to the commercial power supply by controlling the oscillation circuit 15 via the loop filter 14. , The synchronization signals of all TV cameras using the same commercial power supply are synchronized with each other.

[0005]

As described above, the PLL
When the oscillator circuit is controlled to set the vertical synchronizing signal to 60 hertz by the method and the reference frequency signal is output from the transmitting circuit, the horizontal synchronizing signal becomes 15.75 kHz, and the frequencies of the vertical synchronizing signal and the horizontal synchronizing signal are Although it is within the allowable range, the vertical synchronization frequency is 59.94 hertz and the horizontal synchronization frequency is 15.73 according to the TNSC standard.
The standard is 4 kilohertz, and the standard for the color subcarrier of the color video signal is 3.579545 MHz.
The permissible error range of this color subcarrier is 10 hertz.

As described above, the permissible range regarding the color subcarrier is extremely strict with respect to the permissible range of the vertical synchronization and the horizontal synchronization, and the reference frequency signal adjusted so that the vertical synchronization signal has 60 Hz is divided. 2. Forming color subcarriers
Since it becomes 583125 MHz and cannot be used because an error of 3580 Hz occurs, only the color subcarrier is formed asynchronously using another oscillation circuit in the color television camera of the power supply synchronization type. Since the period of the horizontal sync signal is different from that of the horizontal sync signal, a dot-shaped image failure may appear on the screen of the monitor TV, and when the TV camera is switched, the color displayed on the monitor TV changes and the color shift occurs. Sometimes it was caused.

This power cycle method can be used in an area where commercial power of 60 hertz is used, but
It cannot be used in the commercial power source area of Hertz, and a system for sending a synchronization reference signal to each TV camera is required, which has a drawback that the system is complicated and expensive.

[0008]

According to the present invention, a high-frequency sub-phase reference signal is formed by a PLL system with a commercial power source as a reference, and the oscillation circuit is controlled by the PLL system by the sub-phase reference signal. Form a frequency signal,
The reference frequency signal is divided to form a color subcarrier, a horizontal sync signal, and a vertical sync signal.

Further, as the frequency of the sub-phase reference signal,
It is assumed that 60 kHz is used, and the sub-movement reference signal may be divided by the counter 1001 times to form a phase reference signal.

[0010]

[Operation] In the present invention, since the high frequency sub-phase reference signal is formed by the PLL system with the commercial power supply as a reference, the cycle of the sub-phase reference signal can be set to the timing matched with the cycle of the commercial power supply. Further, since the oscillation circuit is controlled by using the PLL method with the sub-phase reference signal, the reference frequency signal output from the oscillation circuit can be synchronized with the timing based on the synchronization of the commercial power supply, and the sub-phase reference signal can be divided. The frequency of the reference frequency signal can be easily changed by the frequency ratio.

If the sub-phase reference signal is set to 60 kilohertz and the frequency of the reference frequency signal is controlled by dividing the sub-phase reference signal by a counter 1001 times and comparing it with the vertical synchronization signal, the frequency of the vertical synchronization signal is controlled. To 59.94
It is possible to obtain an NTSC standard vertical synchronizing frequency in Hertz.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a periodic signal forming circuit of a color television camera according to the present invention includes a zero-cross detecting circuit 12 connected to a power supply line 11 and a sub-phase reference signal generating circuit 20.
And a sync signal generating circuit 30, and the sub-phase reference signal generating circuit 20 is composed of one phase comparing circuit 23, a loop filter 24, a frequency dividing circuit 27, and an oscillating circuit 25. Reference numeral 30 is composed of four frequency dividing circuits 31, 41, 43 and 45, one phase comparison circuit 33, a loop filter 34 and an oscillation circuit 35.

The sub-phase reference signal generating circuit 20 outputs a 60-kHz sub-phase reference signal to the synchronizing signal generating circuit 30 by using a 60-kHz oscillation circuit for the first oscillation circuit 25 which is its oscillation circuit. The sub-phase reference signal is also input to the first frequency dividing circuit 27 of the sub-phase reference signal generating circuit 20. In this embodiment, the first frequency dividing circuit 27 is 1
A 000-time counter is used. The first frequency dividing circuit 27 divides the sub-phase reference signal to form a signal of 60 Hertz, and this signal is fed to the first phase comparison circuit 23 of the sub-phase reference signal generating circuit 20. The phase reference signal from the zero-cross detection circuit 12 is also input to the first phase comparison circuit 23.

In the first phase comparison circuit 23, the phase difference between the phase reference signal from the zero-cross detection circuit 12 and the sub-phase reference signal from the first oscillation circuit 25 is divided by the first frequency division circuit 27. A signal based on the output signal is returned to the first oscillating circuit 25 via the first loop filter 24, so that the sub-phase reference signal generating circuit 20 outputs a 60-Hz phase reference signal at a constant timing. It forms a sub-phase reference signal of kilohertz.

Therefore, the sub-phase reference signal generating circuit 20
Is a sub-phase reference signal of 60 kilohertz formed by a PLL system using a commercial power supply. Then, in the synchronizing signal generating circuit 30, the second oscillating circuit 35 has a 14.3
A reference frequency signal is output using an 1818 MHz oscillation circuit, and the reference frequency signal is output by the third frequency dividing circuit 41 to 4
The frequency division is divided by 1 to form a color subcarrier, and the fourth division circuit 43 divides by 1 to 910 to form a horizontal synchronization signal or a horizontal synchronization timing signal, which is divided by 525 and 455. One-third
The frequency is divided by 238875 to form a vertical synchronizing signal or a vertical synchronizing timing signal, and the color subcarrier, the horizontal synchronizing signal, and the vertical synchronizing signal are output to the camera circuit, and the vertical synchronizing signal is generated in the synchronizing signal generating circuit 30. The signal is input to the second phase comparison circuit 33, and a 1001 times counter is used as the second frequency dividing circuit 31, and a signal obtained by dividing the sub-phase reference signal by 1001 is also used as the second frequency dividing circuit 31.
It is input to the phase comparison circuit 33.

Therefore, in the second phase comparison circuit 33, the vertical synchronizing phase reference signal of 59.94005994 Hz obtained by dividing the sub phase reference signal is inputted from the second frequency dividing circuit 31,
The phase difference between the vertical synchronizing phase reference signal and the vertical synchronizing signal from the fifth frequency dividing circuit 45 is detected, and the output signal based on this detection is returned to the second oscillating circuit 35 via the second loop filter 34. The oscillating frequency of the 2 oscillating circuit 35 is controlled to 14.31818 MHz, and the synchronizing signal generating circuit 30 forms the reference frequency signal based on the sub-phase reference signal by the PLL method.

Therefore, the vertical synchronizing signal becomes 59.94 hertz and is output from the fifth frequency dividing circuit 45, the horizontal synchronizing signal becomes 15.73425 hertz and is output from the fourth frequency dividing circuit 43, and the color subcarrier is It is output from the third frequency dividing circuit 41 as 3.5795454 MHz, and all of the color subcarrier and the horizontal synchronizing signal and the vertical synchronizing signal are NT.
It can be formed in synchronization with the commercial power supply cycle while satisfying the SC standard.

In this embodiment, the sub-phase reference signal of 60 kHz is formed by the sub-phase reference signal generating circuit 20 by the PLL method based on the commercial power source, and the sub-phase reference signal is divided to perform vertical synchronization. Forming the phase reference signal,
An accurate vertical sync frequency of the NTSC standard can be obtained, and the reference frequency signal is formed by the PLL method based on the vertical sync phase reference signal. Therefore, the color subcarrier obtained by dividing the reference frequency signal is also the NTSC standard. The vertical synchronizing signal and horizontal synchronizing signal oscillating circuit can be shared as the color subcarrier oscillating circuit, and dot interference is not caused on the screen by adjusting the color subcarrier to the horizontal synchronizing signal cycle. Can be an image signal,
Since the vertical synchronization is synchronized with the commercial power source as a reference, the timings for resetting the second frequency dividing circuit 31 are adjusted for each television camera by using the phase reference signal, so that all the television cameras using the same power source It is also possible to easily match the vertical synchronization of.

Further, in this embodiment, the first frequency dividing circuit 27 has
Even though the 000-time counter is used, if the frequency of the sub-phase reference signal is divided by using the 1200-time counter, the frequency of the signal input to the first phase comparison circuit 23 becomes 50 kHz because the sub-phase reference signal is 60 kHz. It can be hertz, and can be used even in an area where the commercial power frequency is 50 hertz.

In the above embodiment, the subphase reference signal is 60
The second frequency dividing circuit 31 is a counter capable of dividing frequency by 1/100, and the first frequency dividing circuit 27 is 1/1000.
Or 60 using a counter that divides by 1/1200
Although it is supposed to be used in the Hertz region or the 50 Hertz region, the frequency of the sub-phase reference signal is made higher, and the frequency division ratios of the first frequency dividing circuit 27 and the second frequency dividing circuit 31 are appropriately selected to make it more accurate. Can form color subcarriers and sync signals,
Further, it is possible to form the frequency of the synchronization signal according to not only the NTSC standard but also other standards.

[0021]

According to the present invention, the PLL is based on the commercial power source.
A high-frequency sub-phase reference signal is generated by the method, the sub-phase reference signal is divided, and the oscillation method is controlled by using the PLL method again. Therefore, the reference frequency signal output from the oscillation circuit is synchronized with the commercial power supply. Can be matched.

Since the vertical synchronizing signal, the horizontal synchronizing signal, and the color subcarrier are formed based on this reference frequency signal,
By synchronizing the phase of the horizontal synchronizing signal and the color subcarrier, it is possible to prevent an image failure due to the color subcarrier. Further, since the synchronization signal is formed with the commercial power supply as a reference, it is possible to easily synchronize the television cameras using the same commercial power supply.

Further, since the method of dividing the sub-phase reference signal to detect the phase difference from the commercial power source is used, the frequency of the commercial power source can be easily applied not only in the region of 60 Hz but also in the region of 50 Hz. It is a method that can be implemented. If the frequency of the sub-phase reference signal is 60 kHz, phase comparison with a 50 Hz commercial power source and a 60 Hz commercial power source is easy, and an accurate vertical synchronization signal frequency is easily obtained. As a result, the frequency control of the reference frequency signal that allows the color subcarrier to fall within the allowable range can be easily performed.

[Brief description of drawings]

FIG. 1 is a circuit block diagram for implementing the method according to the invention.

FIG. 2 is a circuit block diagram showing a conventional PLL power supply synchronization system.

[Explanation of symbols]

11 Power Line 12 Zero Cross Detection Circuit 13 Phase Comparison Circuit 14 Loop Filter 15 Oscillation Circuit 17, 18 Frequency Division Circuit 20 Sub Phase Reference Signal Generation Circuit 23 First Phase Comparison Circuit 24 First Loop Filter 25 First Oscillation Circuit 27 First Minute Frequency divider circuit 30 Synchronous signal generation circuit 31 Second frequency divider circuit 33 Second phase comparison circuit 34 Second loop filter 35 Second oscillator circuit 41 Third frequency divider circuit 43 Fourth frequency divider circuit 45 Fifth frequency divider circuit

Claims (2)

[Claims] 1. A high frequency sub-phase reference signal is formed by a PLL system with a commercial power supply as a reference, and a reference frequency signal is formed by controlling an oscillation circuit by the PLL system by the sub-phase reference signal. An external synchronization method for a video camera, characterized by dividing a frequency signal to form a color subcarrier, a horizontal synchronization signal, and a vertical synchronization signal. 2. The video according to claim 1, wherein the oscillation frequency is controlled by setting the frequency of the sub-phase reference signal to 60 kilohertz, dividing the frequency by 1001 times by a counter and comparing the frequency with a vertical synchronizing signal. External synchronization method of the camera.