KR20000040045A - Apparatus for generating clock signals for security camera with line lock capability - Google Patents

Abstract

PURPOSE: An apparatus for generating clock signals for security camera with line lock function is provided to decrease implementation cost and simplify design by synchronizing security cameras directly. CONSTITUTION: An apparatus for generating clock signals for security camera with line lock function includes a pulse generator(1), a phase comparator(2), a multiplexor(3), a first and second low pass filters(4,6), and a first and second voltage controlled oscillators(7,8). The pulse generator(1) generates rectangular pulses with a predetermined duty ratio. The phase comparator(2) outputs first and second frequency signals according to the difference of the output signal of the pulse generator(1) and a vertical frequency signal of the camera. The multiplexor(3) operates according to the status of an inner mode/line lock mode selection signal. The first and second low pass filters(4,6) are connected to output nodes of the multiplexor(3). The first and second voltage controlled oscillators(7,8) operates according to the first and second frequency signals, respectively.

Description

Clock Signal Generator of Surveillance Camera with Line Lock Function

The present invention relates to a surveillance camera, and more specifically, to synchronize each mounted surveillance camera using a power frequency applied from an AC power source of a camera used when mounting and controlling a plurality of surveillance cameras. It relates to a surveillance camera that allows.

Protect customers in banks and large shopping malls, prevent the risk of accidents, and illegally invade and possess expensive items or cash illegally. A surveillance camera using an imaging device such as a CD (Charge Coupled Device) is installed so that it can be determined quickly and appropriately.

In addition, if the interval to be monitored is wide, each surveillance zone is equipped with a surveillance camera, and then the central control system checks the video output from each equipped surveillance camera and monitors whether there is an abnormality in each corresponding interval.

At this time, in the central control system, the video output from each surveillance camera must be reproduced on a multi-segmented monitor through a screen splitter to monitor whether the output video is abnormal. The sync cable must be installed separately.

As a result, a problem arises in that a large additional cost for mounting a separate external synchronization cable is required.

In addition, since the crystal oscillator is used to generate the oscillation signal, a noise component included in the oscillation signal affects the operation control of the central control system, thereby reducing the accuracy of the operation and deteriorating reliability.

Therefore, the technical problem to be achieved by the present invention is to reduce the installation cost and simplify the design because each mounted monitoring camera is synchronized without using a separate external synchronization cable.

In addition, it is to reduce the occurrence of noise or malfunction due to signal interference and to improve the accuracy of the operation.

1 is a block diagram of a clock signal generator of a surveillance camera having a line lock function according to a first embodiment of the present invention;

2 is a block diagram of a clock signal generator of a surveillance camera having a line lock function according to a second embodiment of the present invention.

The clock signal generator of the surveillance camera having a line lock function according to the present invention for solving this problem is to compare the phase difference between the power frequency and the camera vertical frequency according to the state of the internal mode / line lock mode selection signal, A phase comparator for outputting a frequency signal having a magnitude;

A plurality of low pass filter units to which signals output from the phase comparison unit are input;

Connected with a plurality of low pass filter units, respectively, depending on the state of the internal mode / line lock mode selection signal, each operation state is changed and oscillation operation is performed according to the signal output from the phase comparison unit, And an oscillator for outputting an oscillation signal.

Preferably, the oscillator may use one oscillator.

Preferably, the oscillator uses a plurality of oscillators, uses a crystal oscillator that operates when the internal mode / line lock mode selection signal is in the internal mode, and the internal mode / line lock mode selection signal is in the line lock mode. It is preferable to use an oscillator composed of an operating resistor R, a coil L, and a capacitor C.

Then, with respect to the device for the line lock function of the surveillance camera according to an embodiment of the present invention with reference to the accompanying drawings that can be easily implemented by those of ordinary skill in the art The most preferred embodiment is described in detail.

1 is a block diagram of a clock signal generator of a surveillance camera having a line lock function according to a first embodiment of the present invention, and FIG. 2 is a surveillance camera having a line lock function according to a second embodiment of the present invention. Is a block diagram of a clock signal generator.

As shown in Fig. 1, the structure of the first embodiment of the present invention is as follows.

A pulse generator 1 to which a power frequency and synchronization timing adjustment signal is input, and a phase comparator to which an output of the pulse generator 1 and a camera vertical frequency (VD) signal are input, and an INT / LL selection signal is input (2). ), A multiplexer 3 to which the output of the phase comparator 2 and the INT / LL select signal are input, a first low pass filter 4 connected to the first output terminal of the multiplexer 3, and INT / LL selection. Inverter 5 to which a signal is input, a second low pass filter 6 connected to a second output terminal of the multiplexer 3, and output signals and INTs of the first low pass filter 4 and the inverter 5. The first voltage controlled oscillator 7 to which the / LL select signal is input, the second low pass filter 6 and the second voltage controlled oscillator 8 to which the INT / LL select signal is input, and the first and second low pass. It consists of a selector 9 into which the output signals of the pass filters 6, 7 are input.

The pulse generator 1 changes the duty ratio of the input power source frequency and outputs the desired square wave, and the phase comparator 2 changes its operating state according to the input INT / LL selection signal.

That is, when the state of the input INT / LL selection signal is a signal corresponding to the internal mode INT, the phase comparator 2 outputs a signal having a horizontal frequency component. On the other hand, in the line lock mode (LL, Line Lock), after comparing the phase of the camera vertical frequency signal and the signal output from the pulse generator 1, the operation state changes according to the resultant signal so that the vertical frequency component Output the signal.

The multiplexer 3 outputs the output signal of the phase comparator 2 to the first output terminal or the second output terminal according to the INT / LL selection signal.

The first and second low pass filters 4 and 6 filter and integrate signals output through the first or second output terminals of the multiplexer 3 to remove unnecessary noise components and then apply a constant DC voltage to the first or second filter. 2 output to the voltage controlled oscillator (7,8).

The first and second voltage controlled oscillators 7 and 8 perform an oscillation operation by the DC voltages output from the first and second low pass filters 4 and 6 and, via the selector 9, the first or second voltage controlled oscillators 7 and 8. The oscillation signal output from the second voltage controlled oscillators 7 and 8 is output as the main clock signal.

At this time, the first voltage controlled oscillator 7 uses a crystal oscillator, and the second voltage controlled oscillator 8 uses an oscillator composed of a resistor R, a coil L, and a capacitor C.

Inverter 5 also inverts the state of the INT / LL select signal and outputs it to first voltage controlled oscillator 7.

The operation of the first embodiment of the present invention having such a structure will be described in detail.

First, the operation when the INT / LL selection signal for selecting the synchronization mode of the monitoring camera is selected as the line lock (LL) mode, that is, the power supply synchronization mode, will be described.

The power supply frequency is input to the pulse generator 1. At this time, the input power source frequency is a sine wave having a certain period, the pulse generator 1 converts the input sine wave into a square wave, and the power source frequency of a plurality of surveillance cameras mounted in accordance with the desired synchronization the same power source frequency. Have a frequency so that it can be synchronized.

At this time, the pulse generator 1 converts the input frequency to be a square wave having a frequency of about 60 Hz when the surveillance camera is driven by NTSC and a frequency of about 50 Hz by the PAL. Therefore, the surveillance camera according to the embodiment of the present invention can be applied to both NTSC and PAL methods.

Then, the pulse generator 1 changes the duty ratio of the square wave by changing the rising edge of the power source frequency in accordance with the input synchronization timing adjustment signal. Therefore, the duty ratio of the input power source frequency changes.

Thus, the plurality of surveillance cameras mounted by the synchronization adjustment signal are synchronized to the same power supply frequency.

Then, the phase comparator 2 into which the camera vertical frequency signal of the surveillance camera is input compares the duty-converted square wave input from the pulse generator 1 with the camera vertical frequency signal, and corresponds to the phase difference generated. The operating state changes according to the resultant signal, and outputs a frequency signal of 60 Hz (in the case of NTSC system) required to the multiplexer 3.

The multiplexer 3 changes the selection of the first or second output terminal according to the INT / LL selection signal applied to the other input terminal. However, since the state of the INT / LL select signal is the line lock mode, the multiplexer 3 outputs the corresponding signal to the second output terminal.

Therefore, the multiplexer 3 outputs the resultant signal of the phase comparator in the phase comparator 2 to the second low pass filter 6 as the second output terminal.

The second low pass filter 6 integrates a signal having an input power supply frequency component, removes unnecessary noise components, and outputs a DC voltage having a constant level to the second voltage controlled oscillator 8.

Therefore, the second voltage controlled oscillator 8 composed of the RLC oscillator executes the oscillation operation according to the input DC voltage of the corresponding level and is input to the selection unit 9.

At this time, the first voltage controlled oscillator 7 which is a crystal oscillator forcibly outputs a signal of a predetermined level to the selector 9 by the signal of the inverter 5 which inverts and outputs the INT / LL selection signal.

Therefore, the selector 9 outputs the oscillation signal output from the second voltage controlled oscillator 8 as the main clock signal of the corresponding monitoring camera.

Thus, by comparing the power supply frequency supplied to all surveillance cameras with the camera vertical frequency VD outputted from each surveillance camera in this manner, the camera vertical frequency VD is continuously fed back to be equal to the power supply frequency. By controlling, the synchronization of all surveillance cameras is adjusted to the same frequency.

However, the operation will be described when the state of the INT / LL selection signal is an internal mode INT, that is, a mode in which the operation of each surveillance camera is controlled separately without adjusting synchronization with all the mounted surveillance cameras.

The pulse generator 1 and the phase comparator 2 operate in the same manner as previously set, and output the signal to the multiplexer 3 as a result of the phase comparison.

At this time, however, since the state of the INT / LL selection signal is an internal mode, the phase comparator 2 outputs a signal having a horizontal frequency component to the multiplexer 3, and the multiplexer 3 is input to the first output terminal. Outputs signals with frequency components.

Therefore, it is integrated by the first low pass filter 4 and the noise is removed to output a DC voltage of a constant level to the first vertically controlled oscillator 7. Therefore, the oscillation signal having the corresponding period is output to the selector 9 by the oscillation operation of the first vertically controlled oscillator 7 composed of the crystal oscillator.

At this time, the second vertically controlled oscillator 8 outputs a voltage of a predetermined level without the operation being oscillated by the INT / LL selection signal.

Therefore, the selector 9 outputs the signal output from the first vertically controlled oscillator 7 as the main clock signal.

As described above, when the operation mode is the internal mode, the operation is controlled by a signal oscillated by the first vertically controlled oscillator 7 which is a crystal oscillator, so that synchronization adjustment with other surveillance cameras is not performed.

As described above, when the operation state of the plurality of surveillance cameras is synchronized with the operation of all the surveillance cameras in the line lock mode, the power supply is equally applied to all the surveillance cameras without applying a separate synchronization signal from the outside. Perform synchronous adjustment using frequency.

However, as in the first embodiment of the present invention, when the oscillation signal is output using the crystal oscillator for the internal mode of the surveillance camera, the oscillation operation is physically stopped using the output signal of the inverter 5. In addition, the oscillation signal generated by the self oscillation operation affects the oscillation frequency of the line lock mode oscillator due to the nature of the crystal oscillator.

Therefore, a noise component occurs at the oscillation frequency, which causes a problem of reducing the accuracy of the operation.

In order to solve this problem of the first embodiment, the second embodiment is shown in FIG. 2 is a block diagram of an apparatus for a line lock function of a surveillance camera according to a second embodiment of the present invention. Parts having the same structure as that of the first embodiment of the present invention and executing the same operations and functions are given the same reference numerals as the first embodiment.

As shown in FIG. 2, a pulse generator 1 to which a power frequency and a synchronization timing adjustment signal are input, a phase comparator 2 to which an output signal of the pulse generator 1 and a camera vertical frequency (VD) signal are input; A multiplexer 3 to which the output signal of the phase comparator 2 and the INT / LL select signal are input, and first and second low pass filters 4 and 5 connected to the first or second output terminals of the multiplexer 3. ) And a vertically controlled oscillator 60 connected to the output terminals of the first and second low pass filters 4 and 5.

Since the functions of the respective components are similar to those described in the first embodiment, detailed description thereof will be omitted.

In the second embodiment of the present invention, the voltage controlled oscillator 60 is an oscillator composed of a resistor R, a coil L, and a capacitor C.

The operation of the second embodiment of the present invention having such a structure is as follows.

First, the case where the state of the INT / LL select signal is in the line lock mode will be described.

When the power source frequency is input to the pulse generator 1, the pulse generator 1 converts the input power source frequency into a square wave, changes the duty ratio of the signal to the state in accordance with the synchronization timing adjustment signal, and the desired duty ratio. A square wave having? Is output to the phase comparator 2.

Since the phase comparator 2 inputs the INT / LL selection signal in the line lock mode, a result corresponding to the phase difference is compared by comparing the input camera vertical frequency signals using the signal output from the pulse generator 1 as a reference signal. The operation state changes in accordance with the signal, and outputs a signal having a power supply frequency component to the multiplexer 3.

At this time, since the state of the INT / LL select signal applied to the other input terminal of the multiplexer 3 is in the line lock mode state, the multiplexer 3 receives the phase-compared result signal inputted through the second output terminal in the second low pass. Output to the pass filter (5).

The second low pass filter 5 integrates a signal having an input power frequency component and filters out unnecessary noise components, and outputs them to the voltage controlled oscillator 60. At this time, since the output signal is not applied to the first low pass filter 4 from the multiplexer 3, no signal is output.

When the voltage of a predetermined level is input to the voltage controlled oscillator 60 by the operation of the second low pass filter 5, the voltage controlled oscillator 60 executes the oscillation operation to output a corresponding oscillation frequency to the main clock signal. Is used.

Therefore, the operation of each corresponding surveillance camera is controlled according to the main clock signal synchronized with the power supply frequency, and the camera vertical frequency signal is output and continuously feedback controlled, so that the operation of all surveillance cameras is synchronized in the same power supply frequency. This is done.

However, the operation when the INT / LL select signal is in the internal mode is as follows.

When the power source frequency is input, the pulse generator 1 performs the same operation as already described, and since the phase comparator 2 is in the internal mode, it outputs a signal having a horizontal frequency component to the multiplexer 3.

However, at this time, the multiplexer 3 selects the first output terminal by the state of the INT / LL select signal, and the signal having the horizontal frequency component input to the multiplexer 3 is output through the first output terminal. 1 is applied to the low pass filter (4).

Accordingly, the first low pass filter 4 integrates an input signal, removes unnecessary noise components, and outputs a signal having a corresponding level to the voltage controlled oscillator 60.

The voltage controlled oscillator 60 outputs an oscillation signal having a frequency of a corresponding state as a main clock signal for controlling the operation of the surveillance camera according to the signal output from the first low pass filter 4.

As described above, since the oscillation operation in the internal mode and the line lock mode is performed using one voltage controlled oscillator 60, the second embodiment of the present invention is unstable due to signal interference due to the crystal oscillator for the internal mode. Prevents oscillation behavior.

When mounting and using multiple surveillance cameras, it is not necessary to supply a synchronization signal for adjusting the synchronization of each surveillance camera using a separate external cable, thereby reducing additional costs for cable installation and simplifying complex designs. can do.

It also reduces signal interference, thus improving the accuracy of operation.

Claims (4)

A pulse generator for inputting a power source frequency and a synchronization timing adjustment signal to change a duty ratio according to the synchronization timing adjustment signal to output a square wave having a corresponding duty ratio; The operating state changes according to the internal mode / line lock mode selection signal, and compares a signal output from the pulse generator with a camera vertical frequency signal to a phase first to have a predetermined size according to a result signal corresponding to a phase difference. A phase comparator for outputting a second frequency signal; A multiplexer configured to output a first or second frequency signal output from the phase comparator through an output terminal selected according to a state of an internal mode / line lock mode selection signal inputted from the phase comparator; A first low pass filter connected to the output terminal of the multiplexer to pass only a first frequency signal; A second low pass filter connected to the other output terminal of the multiplexer to pass only a second frequency signal; A first voltage controlled oscillator configured to oscillate a signal having a set frequency and output a clock signal for an internal mode according to a first frequency signal output from the first low pass filter; And a second voltage controlled oscillator configured to oscillate a signal having a corresponding frequency according to a second frequency signal output from the second low pass filter, to oscillate a clock signal for a line lock mode. Clock signal generator of a surveillance camera having a function. The method of claim 1, The first oscillation portion is composed of a crystal oscillation portion, The second oscillation unit comprises a oscillation unit consisting of a resistor (R), a coil (L), and a capacitor (C) clock signal generator of a surveillance camera having a line lock function. The method according to claim 1 or 2, The internal mode / line lock mode selection signal is input, and when the state of the internal mode / line lock mode selection signal is the line lock mode, the inverter further outputs a signal for stopping the operation of the first oscillator to the first oscillator. Clock signal generator of a surveillance camera having a line lock function, characterized in that consisting of. A pulse generator for inputting a power source frequency and a synchronization timing adjustment signal to change a duty ratio according to the synchronization timing adjustment signal to output a square wave having a corresponding duty ratio; The operating state changes according to the internal mode / line lock mode selection signal, and compares a signal output from the pulse generator with a camera vertical frequency signal to a phase first to have a predetermined size according to a result signal corresponding to a phase difference. A phase comparator for outputting a second frequency signal; A multiplexer configured to output a first or second frequency signal output from the phase comparator through an output terminal selected according to a state of an internal mode / line lock mode selection signal inputted from the phase comparator; A first low pass filter connected to the output terminal of the multiplexer to pass only a first frequency signal; A second low pass filter connected to the other output terminal of the multiplexer to pass only a second frequency signal; And a voltage controlled oscillator for oscillating a signal having a corresponding frequency and outputting a clock signal according to a signal input from the first or second low pass filter. Clock signal generator of the camera.