JPS6218870A - Phase synchronizing device - Google Patents

Abstract

PURPOSE:To switch plural monitor cameras smoothly at low cost by providing a synchronizing separating means which extracts a synchronizing signal from video outputs obtained from plural monitor cameras by receiving a reference clock signal and a phase comparing means which compares the phase of the synchronizing signal with the phase of the reference synchronizing signal. CONSTITUTION:The reference synchronizing signal A is inputted to the phase comparators 13a and 13b of a trailing stage. The phase comparator 13a compares with the phase of a reference synchronizing signal A with the phase of a synchronizing signal D from a synchronizing separating circuit 14a and the phase comparator 13a also compares the phase of the reference signal A with the phase of a synchronizing signal E from a synchronizing separating circuit 14b respectively. Consequently, output signals F and G corresponding to phase differences between the phase-compared synchronizing signals are led out of the phase comparators 13a and 13b. A reset signal H is supplied to a synchronizing signal generator 2 for said monitor cameras 1 and 11 through output circuits 18a and 18b, which are therefore synchronized with each other.

Description

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

[Prior art]

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

In this internal synchronization method, there is no particular synchronization with external signals, so the synchronization signal generation IC used in the above surveillance camera
However, there were few devices equipped with a function that could be operated using an external synchronization signal. However, in recent years, banks and other facilities have improved their configuration by installing multiple surveillance cameras and switching between the multiple surveillance cameras to monitor using one monitor TV or a smaller number of monitor TVs than the number of above-mentioned surveillance cameras. has come to be requested.

However, with the conventional configuration described above, when switching between images from multiple surveillance cameras for monitoring, each of the surveillance cameras is not synchronized, resulting in the problem of synchronization lag in which the monitor TV screen is played. 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 to achieve synchronization is to modify the synchronization signal generating RC. . For this reason, it has disadvantages such as requiring a large cost amplifier.

[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 synchronizing signal generating means to generate and the reference clock.

a synchronization separation means for extracting a synchronization signal included in video outputs obtained from the plurality of surveillance cameras that have received the signal; a phase comparison means for comparing the phases of the synchronization signal and the reference synchronization signal; A reset signal generating means is provided for outputting a reset signal to each of the surveillance cameras according to the output signal from the phase comparator when there is a phase shift between the respective synchronization signals, and synchronization between the surveillance cameras can be achieved. It is characterized by being configured as follows.

[Example 1] An example of the present invention will be described below based on FIGS. 1 and 2.

FIG. 1 shows a schematic diagram of a surveillance camera 1 and a phase synchronization device 8 connected to the surveillance camera. The surveillance camera 1 is provided with a synchronization signal generator 2, and a driver 3 is connected to the synchronization signal generator 2. The driver 3 is for driving the solid-state image sensor 4 provided at the next stage, and the solid-state image sensor 4 is connected to an amplifier 5 for amplifying the output from the solid-state image sensor 4. There is. A synchronizing signal input circuit 6 is connected to the amplifier 5, and an output circuit 7 and the synchronizing signal generator 2 are connected to the synchronizing signal input circuit 6. on the other hand,
The phase synchronizer 8 is provided with a crystal oscillator 9 for generating a reference clock signal, and this crystal oscillator 9 is connected to output circuits 10a and 10b. The output circuit 10a is connected to a synchronization signal generator 2 of the surveillance camera 1, and the output circuit 10b is connected to a synchronization signal generator (not shown) of another surveillance camera 11 having the same circuit configuration as the surveillance camera 1. It is connected.

Further, the crystal oscillator 9 is connected to a synchronization signal generator 12 for frequency-dividing the reference clock signal generated from the crystal oscillator 9 to obtain a reference synchronization signal. Phase comparators 13a and 13b are connected to the synchronization signal generator 12, and each of these phase comparators 13a and 13b has a synchronization separation circuit 14a and 14b for extracting a synchronization signal from the video output of the surveillance camera card 11. is connected.

Each output circuit 7 of the surveillance camera card 11 is connected to the synchronization separation circuits 14a and 14b, respectively.

The above-mentioned phase comparators 13a and 13b each have an integrator 15a that removes a signal whose pulse width is considered to be a hazard from the output of these phase comparators 13a and 13b.
- Connected to 15b. These integrators 15a
・15b is an OR circuit 16 that takes the logical sum of these two dividers.
is connected to. This OR circuit 16 is
The differential circuit 17 is connected to a differential circuit 17 which generates a differential waveform from the output signal. The integrator 15a/15b10R circuit 16 and the differentiating circuit 17 constitute a reset signal generating means, and when there is a phase shift between the synchronization signals whose phases are compared by the phase comparators 13a and 13b, the reset signal is generated. is emitted. This differentiating circuit 17 includes an output circuit 1
8a and 18b are connected, and these output circuits 18a and 18b are connected to each synchronizing signal generator 2 of the surveillance camera card 11, respectively.

In the above configuration, when the monitoring camera card 11 and the phase synchronization device 8 are activated, the monitoring camera card 11 is asynchronous. The reference clock signal generated from the crystal oscillator 9 of the phase synchronizer 8 is input to each synchronizing signal generator 2 of the surveillance camera card 11 via output circuits 10a and 10b. The synchronization signal generator 2 outputs a synchronization signal obtained by dividing the frequency of the reference clock signal to the synchronization signal input circuit 6. A video signal is generated by the solid-state image sensor 4, and after being amplified by the amplifier 5, it is applied to the synchronization signal input circuit 6. This synchronization signal input circuit 6
From the video signal and the synchronization signal obtained from the synchronization signal generator 2, a video output as shown in FIG. 2B is obtained via the output circuit 7. A video output as shown by C is similarly obtained from another surveillance camera 11. The asynchronous video outputs B-C obtained from the surveillance camera 11 are sent to the synchronization separation circuit 14a of the phase synchronization device 8.
14b, the synchronization separation circuits 14a and 14b separate and extract only the synchronization signal components indicated by DE, respectively, and output them to the phase comparators 13a and 13b. On the other hand, a reference clock signal generated by the crystal oscillator 9 is frequency-divided by a synchronization signal generator 12 to obtain a reference synchronization signal as shown in A. This reference synchronization signal A is input to the next stage phase comparators 13a and 13b. The phase comparator 13a receives the reference synchronization signal A and the synchronization signal from the synchronization separation circuit 14a, and the phase comparator 13a receives the reference synchronization signal A and the synchronization signal E from the synchronization separation circuit 14b. be compared. As a result, output signals corresponding to the phase difference between the phase-compared synchronizing signals are taken out from the phase comparators 13a and 13b, respectively, as indicated by F and G. In the integrators 15a and 15b, only signals having a pulse width or more than a certain pulse width are extracted from the above output signal FG, and the OR circuit 16
The output signals from both of the integrators are logically summed at .

The output signal of this OR circuit 16 is input to a differentiating circuit 17, where it is differentiated and becomes a reset signal indicated by H. This reset signal H is output to the output circuit 18a/18
Each synchronization signal generator 2 of the surveillance camera card 11 via b
This synchronizes the surveillance cameras 11. Note that even when another surveillance camera is newly connected to the phase synchronization device 8, the synchronization between the surveillance cameras is performed by the same process as in the above-described embodiment.

〔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,
The phase of the synchronization signals from the plurality of surveillance cameras obtained using this reference clock signal is compared with the reference synchronization signal, and if there is a phase shift between the two, a reset signal is issued to synchronize the surveillance cameras. This is the configuration to take. Therefore, the phase relationship between the monitoring cameras is constantly monitored, and high reliability can be obtained. Further, there is no need to improve the surveillance camera, and smooth switching between the plurality of surveillance cameras can be achieved at low cost.

[Brief explanation of the drawing]

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 and 1 are surveillance cameras, 8 is a phase synchronizer, 9 is a crystal oscillator, 12 is a synchronization signal generator, 13a and 13b are phase comparators, 14a and 14b are synchronization separation circuits, 15a
15b is an integrator, 16 is an OR circuit, and 17 is a differential circuit. ,'〕Figure 1Figure 2

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. a synchronization separation means for receiving the reference clock signal and extracting a synchronization signal included in video outputs obtained from the plurality of surveillance cameras; a phase comparison means for comparing the phase of the synchronization signal and the reference synchronization signal; and reset signal generating means for outputting a reset signal to each of the surveillance cameras based on the output signal from the phase comparator when there is a phase shift between the synchronization signals to be phase-compared. Synchronizer.