JPS6218871A - Phase synchronizing device - Google Patents

Abstract

PURPOSE:To switch plural monitor cameras smoothly at low cost by stopping sending a reference clock signal out to the monitor cameras for a constant period wherein an output signal based upon phase comparison is inputted to a gate circuit. CONSTITUTION:A phase comparator 12 compares the phase of a reference synchronizing signal A with the phase of a horizontal synchronizing signal which is obtained from a video output through a synchronizing separating circuit 13 and affected by the completion of vertical synchronism and generates an output signal H. This output signal H is passed through an integration circuit 15 and a differentiating circuit 17 to obtain a differential output I. The gate circuit 18 stops supplying the reference clock signal to the monitor cameras 1 for the constant period wherein the differential output I is inputted, so that the delay of a vertical synchronizing signal shown by * in G. Consequently, the monitor cameras 1 and a phase synchronizing device 20, and monitor cameras 1 are synchronized with each other vertically and horizontally, so the monitor cameras are switched smoothly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phase synchronization device that synchronizes a plurality of surveillance cameras that are used in conjunction.

[Prior art]

Conventionally, many surveillance cameras having a solid-state image element are used in pairs with a monitor television, and in this case, an internal synchronization method is used in which a reference clock signal generator is provided inside the surveillance camera.

Since this internal synchronization method does not particularly require synchronization with an external signal, there are few RCs for generating synchronization signals used in the above-mentioned surveillance cameras that have a function that can be operated by external synchronization signals. However, in recent years, banks and other institutions have improved their configuration by installing multiple surveillance cameras and switching between them to monitor the system using one monitor TV or a smaller number of monitor TVs than the number of above-mentioned surveillance cameras. It has come to be requested.

However, with the conventional configuration described above, when switching between images from multiple surveillance cameras for monitoring, there is a problem in that the monitor screens shift and synchronization occurs because the cameras are not synchronized. It had In addition, in order to achieve synchronization using a synchronization signal generator installed in the surveillance camera that does not have the function of synchronizing with an external synchronization signal, the only way is to modify the synchronization signal generation IC. . For this reason, it has had drawbacks such as requiring a significant increase in cost.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned conventional problems, and it is possible to smoothly switch images from each of the above-mentioned monitoring cameras by synchronizing the plurality of monitoring cameras used in conjunction. The purpose of this invention is to provide a phase synchronization device that can perform the following steps.

[Structure of the invention]

The phase synchronization device of the present invention is a phase synchronization device that synchronizes a plurality of surveillance cameras having a synchronization signal generation means therein, and includes a reference clock signal generation means and a reference clock signal that receives the reference clock signal and generates a reference synchronization signal. A reference vertical synchronization signal and a reference horizontal synchronization signal are extracted from the synchronization signal generating means and the reference synchronization signal, and a vertical synchronization signal and a horizontal synchronization signal are extracted from the video outputs of the plurality of surveillance cameras that have received the reference clock signal. phase separation means, phase comparison means for comparing the phases of the reference vertical synchronization signal and the vertical synchronization signal and the reference horizontal synchronization signal and the horizontal synchronization signal; The present invention is characterized in that it includes a gate circuit that stops sending the reference clock signal to each of the monitoring cameras, and is configured to be able to synchronize the monitoring cameras.

〔Example〕

An embodiment of the present invention will be described below based on the first section and FIG. 2.

FIG. 1 shows a block diagram of a surveillance camera 1 and a phase synchronization device 20 connected to the surveillance camera. still,
Although a plurality of monitoring cameras 1 are connected to the phase synchronization device 20, only a block diagram for one camera is shown here for the sake of simplicity. The surveillance camera 1 is provided with a synchronization signal generator 2, and a driver 3 for driving the solid-state image sensor 4 is connected to the synchronization signal generator 2. The solid-state image sensor 4 is for generating a video signal, and is connected to an amplifier 5 for amplifying the video signal. This amplifier 5 is connected to a synchronizing signal input circuit 6, which is connected to the synchronizing signal generator 2.
An output circuit 7 for receiving the video signal and transmitting a video output to the outside of the surveillance camera 1 is connected. On the other hand, the phase matching 1tl'l device 20 is provided with a crystal oscillator 8 for generating a reference clock signal.
A synchronization signal generator 9 for generating an nc signal (composite synchronization signal) is connected. This synchronization signal generator 9 includes a synchronization separation circuit 1 for obtaining a reference vertical synchronization signal and a reference horizontal synchronization signal from the output signal of the synchronization signal generator 9.
0 is connected. Connected to the synchronization separation circuit 10 are a phase comparator 11 that compares the phases of vertical synchronization signals and a phase comparator 12 that compares the phases of horizontal synchronization signals.

The phase comparison ill 12 is connected to the output circuit 7 of the surveillance camera 1, and is connected to a synchronization separation circuit 13 for obtaining a vertical synchronization signal and a horizontal synchronization signal from the input signal from the output circuit 7. . Above phase comparator 11.1
2 each include an integrating circuit 14 for removing an input signal having a pulse width less than a certain width that is considered to be a hazard.
・15 are connected to each other. This integrating circuit 14・
15 are connected to differentiating circuits 16 and 17 that convert input signals into differential waveforms, respectively, and these differentiating circuits 16 and 17
is connected to the crystal oscillator 8 and has the differential circuit 16.
A gate circuit 18 is connected which stops outputting the output signal for a certain period when there is an input signal from 17. This gate circuit 18 is an output circuit 19 provided at the final stage of this device.
This output circuit is connected to the synchronization signal generator 2 of the surveillance camera 1. Note that when a plurality of surveillance cameras 1 are connected to the phase synchronization device 2, the above-mentioned phase comparators 11 and 12, synchronization separation circuit 13, integration circuits 14 and 15, differentiating circuits 16 and 17, and gate circuit 18 are used.
And one output circuit is required for each of the plurality of surveillance cameras.

In the above configuration, each surveillance camera 1 is out of synchronization with the phase synchronization device 20 when each surveillance camera 1 and phase synchronization device 20 are activated. The reference clock signal generated from the crystal oscillator 8 of the phase synchronization device 20 is inputted to the synchronization signal generator 2 of the surveillance camera 1 from the output circuit 19 via the night circuit 18. In response to the reference clock signal, the synchronization signal generator 2 generates c, 5ync signals as shown in FIG. 2, and this c, 5ync signal B is applied to the synchronization signal input circuit 6. A video signal is generated in the solid-state image sensor 4, and this video signal is sent to the amplifier 5.
After being amplified, the signal is applied to the synchronizing signal input circuit 6. From this synchronization signal input circuit 6, a video output is sent to the synchronization separation circuit 13 of the phase synchronization device 20 via the output circuit 7 using the video signal and the c, 5sync signals B. In the synchronization separation circuit 13, from the video output, D
A vertical synchronization signal shown in is obtained, and this vertical synchronization signal D (
VD') is manually input to the phase comparator 11. On the other hand, the synchronization signal generator 9 receives the reference clock signal from the crystal oscillator 8 to obtain reference c, 5sync signals. This 51(,5sync signal is separated into a reference vertical synchronization signal shown in C and a reference horizontal synchronization signal shown in A in the synchronization separation circuit 10.The reference vertical synchronization signal A (VD)
and reference horizontal synchronization signal C(l(D)) are input to phase comparator 11 and phase comparator 12, respectively.
1, the reference vertical synchronizing signal C and the vertical synchronizing signal C are phase-compared, and the output signal shown in FIG. 1 corresponding to the phase difference between these two signals is obtained. The integrating circuit 14 passes only the signals of a certain pulse width or more out of the output signal E, and the waveform is shaped by the differentiating circuit 16, resulting in a differentiated output shown as F, which is input to the gate circuit 18.

This gate circuit 18 stops supplying the reference clock signal to the surveillance camera 1 for a certain period while the differential output F is being input. As a result, while including the variation in the operation of the miscellaneous circuits 10 and 13 and the delay due to the time constant of the integrating circuit 14 (indicated by * in the graph), the surveillance camera 1 and phase synchronization are achieved. Vertical synchronization between devices 20 is established. Further, in the phase comparator 12,
The reference horizontal synchronization signal A and the horizontal synchronization signal obtained from the video output via the synchronization separation circuit 13 are used to compare the phases of the horizontal synchronization signal G, which has been affected by the completion of the vertical synchronization. The output signal shown is obtained. With this output signal H, a differential output shown as I is obtained via an integrating circuit 15 and a differentiating circuit 17. The gate circuit 18 provides a reference clock to the surveillance camera 1 for a certain period of time when the differential output I is input.

By stopping the supply of the vertical synchronizing signal, the delay of the vertical synchronizing signal indicated by * in G is corrected. As a result, vertical and horizontal synchronization is achieved between the surveillance camera 1 and the phase synchronization device 20 and between each surveillance camera 1, and switching between the surveillance cameras 1 is performed smoothly. Note that even when another surveillance camera is newly connected to the phase synchronization device 20, each surveillance camera 1 is
synchronization between the two.

〔Effect of the invention〕

As described above, the phase synchronization device of the present invention sends a reference clock signal to a plurality of surveillance cameras that are used in conjunction,
Using this reference clock signal, the vertical synchronization signal and horizontal synchronization signal obtained from the video output of each surveillance camera are compared in phase with the reference vertical synchronization signal and reference horizontal synchronization signal of the reference synchronization signal, respectively, and the output signal from this phase comparison is The configuration is such that the monitoring cameras are synchronized by stopping the sending of the reference clock signal to the monitoring cameras for a certain period of time when the reference clock signal is being input to the gate circuit. This results in a relatively simple circuit configuration. moreover,
There is no need for improvement on the surveillance camera side, and smooth switching between the plurality of surveillance cameras can be realized at low cost.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a phase synchronization device and a surveillance camera showing an embodiment of the present invention, and FIG. 2 is a graph showing output signals from each circuit of the phase synchronization device and the surveillance camera shown in FIG. 1. . 1 is a surveillance camera, 20 is a phase synchronizer, 8 is a crystal oscillator, 9 is a synchronization signal generator, 10 and 13 are synchronization separation circuits, 1
1 and 12 are phase comparators, 14 and 15 are integrator circuits, and 16 and 15 are integrator circuits.
17 is a differential circuit, 18 is a gate circuit, and 19 is an output circuit. Patent applicant Sharp Corporation No.] Figure

Claims (1)

[Claims] 1. A phase synchronizer that synchronizes a plurality of surveillance cameras having a synchronization signal generation means therein, which includes a reference clock signal generation means and a synchronization signal generation means that receives the reference clock signal and generates a reference synchronization signal. Then, extract the reference vertical synchronization signal and reference horizontal synchronization signal from the reference synchronization signal,
phase separation means for extracting a vertical synchronization signal and a horizontal synchronization signal from the video outputs of the plurality of surveillance cameras receiving the reference clock signal; The device is characterized by comprising a phase comparison means for comparing phases, and a gate circuit that stops sending the reference clock signal to each of the surveillance cameras for a certain period of time when receiving an input from the phase comparison means. Phase synchronizer.