JPH0746580A - Video monitoring device - Google Patents

Abstract

PURPOSE:To display an image natural and clear to be observed at all times even when a video camera is installed in the state of making backlight incident to the partial area of a light receiving area at the video monitoring device applied to a monitoring system or the like. CONSTITUTION:An ND filter 4 is additionally provided in the back-light incidental area of a light receiving plane 1a at an imaging device of a video camera 1, and the horizontal scanning signal of a video area A corresponding to the additional area is compensated by a video signal correction unit 2 equally to the signal level of a video area B. Namely, at the time of making the backlight incident, the luminance of respective video areas A and B is equalized by attenuating the quantity of incidental light with the ND filter 4, in the state of no backlight, the average horizontal scanning signal in the video area A is kept equal with the average signal level of the video area B by controlling the gain of a variable amplifier circuit 7, considerable luminance difference is prevented from being generated at the time of making the backlight incident, and the image with equal luminance over the entire screen is always displayed on a monitor 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image monitoring device, and is applied to a surveillance system installed on a platform of a station, etc., even when a video camera is installed in a state where it is partially backlit. The present invention relates to a device for always monitoring a natural image with uniform brightness.

[0002]

2. Description of the Related Art Recently, a surveillance system using a video camera has been widely used for monitoring traffic congestion on roads and safety of stations, regular monitoring of dams and construction sites, and crime prevention monitoring at banks and shops. It's being used. In these usage modes, it is natural that the image received from the video camera is required to be always clear over the entire monitor screen. However, since the shooting range and the shooting angle are specified, It is not always possible to install a video camera in a place or angle where the conditions are good.

For example, looking at the installation conditions of the video camera in the road condition monitoring system, as shown in FIG. 4, no matter how the installation position or the installation angle is devised, the image pickup screen may be empty. In such a case, in that case, a large difference occurs in the amount of received light in the highlight region that receives the direct light on the imaging screen and the other regions. On the other hand, in a video camera, the iris diaphragm sets the diaphragm according to the average amount of received light, so that the image signal level outside the highlight region drops when the backlight is incident, and the highlight on the monitor screen as shown in FIG. In many cases, the brightness of the image other than the area is significantly reduced, making monitoring difficult.

Therefore, as a countermeasure against this, two video cameras having an ND (Neutral Density) filter on the entire front surface of the lens and two normal video cameras are installed side by side at the same location. Has adopted the method of switching to shoot with the latter camera. That is, in the daytime, the total incident light amount is reduced by the camera with the ND filter so that the entire image can be easily monitored even in the case of backlight, and at night, the normal camera can increase the incident light amount to obtain the brightest image as possible. I am trying.

[0005]

By the way, when two video cameras are installed as described above, the space for installing the cameras becomes large, the number of cables increases, and two video cameras are stored. In addition to the need for a housing, the burden of installation work increases.
And, of course, the cost of the overall surveillance system is expensive.

Further, for example, in a surveillance system or the like provided for safety confirmation at a subway station or the like, a video camera is installed so that the long boundary between the track and the platform fits on the screen. Backlighting frequently occurs due to the lights provided on the front of the train each time the vehicle enters. At present, two video cameras are not installed at the same location in the subway as described above, but even if the backlight is set by setting the aperture so that the amount of incident light is reduced in advance. It seems that it is devised so that extremely dark areas do not occur, and as a result, the brightness of the entire screen is constantly reduced, and from the viewpoint that it is necessary to always confirm safety with a clear image. There's a problem. Even in other monitoring systems, there are many cases in which a large brightness difference occurs on the screen in the highlight region and other regions in the image depending on the time of day or night or due to the relationship with the illumination device or the like.

Therefore, according to the present invention, in a surveillance system using a video camera, it is unavoidable that backlight is generated or an extreme brightness difference occurs in the photographing screen due to restrictions of the installation location and installation angle of the video camera. In this case, it was created for the purpose of providing a monitoring device capable of always displaying the entire image at an average brightness and eliminating the above-mentioned problems and problems.

[0008]

According to the present invention, in a video monitoring apparatus, a video camera in which a light amount attenuation filter is applied to a partial area of a light receiving surface, and a sync signal for detecting a sync signal from a composite video signal of the video camera. Detection means,
Variable amplifying means for amplifying the scanning signal of the composite video signal by changing the gain, and scanning time corresponding to the area provided with the light amount attenuation filter of the video camera based on the synchronizing signal detected by the synchronizing signal detecting means. Area setting means for outputting a control area signal to the band, detection position setting means for setting the detection timing of the scanning signal output by the variable amplification means, and the variable amplification means outputs at the timing set by the detection position setting means. The level setting means for detecting the signal level of the scanning signal, the level setting means for setting a desired scanning signal level at the scanning position on the image corresponding to the timing set by the detection position setting means, and the area setting means. The scanning signal level set by the level setting means and the level detecting means detect during the time period when the control area signal is being output. Comparison control means for outputting a gain control signal corresponding to a difference in scanning signal level to the variable amplification means is provided, and the variable amplification means changes its amplification gain in response to the gain control signal output by the comparison control means. However, the present invention relates to a video monitoring device characterized by outputting a composite video signal to the monitor side.

[0009]

According to the present invention, the amount of received light is always attenuated in the partial region of the video camera provided with the light amount attenuation filter, and even if backlight or the like enters the region, the video camera is highlighted. The aperture amount of does not become large, and the image on the monitor screen can secure a constant brightness as a whole. That is, it is possible to prevent the brightness of the area other than the partial area in the highlighted state from being extremely lowered,
Keep the entire image in a state that is easy to see.

On the other hand, when the backlight is not generated, the brightness of the image area corresponding to the partial area where the light amount attenuation filter is applied decreases, so that the scanning signal corresponding to the partial area is changed by the variable amplifying means. Is amplified and corrected to make the brightness of the entire image uniform. Therefore, first, it is necessary to set the amplification time zone of the variable amplifying means, but the synchronizing signal detecting means detects the synchronizing signal from the composite video signal, and the area setting means performs scanning corresponding to the partial area based on the synchronizing signal. The area control signal is output in the time zone. Regarding the setting of the amplification gain, the detection position setting means selectively sets at which position of the scanning area corresponding to the partial area the scanning signal level (level in the non-highlighted state) is to be compared. Then, the level detection means detects the scanning signal level of the variable amplification means at that position, and the desired scanning signal level (amplified level) at that position can be selectively set by the level setting means. ing.

Then, the comparison control means compares the scanning signal level set by the level setting means with the scanning signal level detected by the level detecting means during the time period during which the area setting means outputs the area control signal. By outputting the gain control signal corresponding to the difference to the variable amplification means, the variable amplification means amplifies the level of the scanning signal corresponding to the partial area to a desired scanning signal level. Therefore, if the desired scanning signal level by the level setting means is set to the scanning signal level of the area other than the partial area in the non-highlighted state, the image on the entire monitor screen is automatically controlled so as to always have uniform brightness. it can.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the video monitoring apparatus of the present invention will be described in detail below with reference to FIGS. First, Fig. 1
Shows a block circuit diagram of a surveillance system for safety confirmation at a subway station, and a surveillance video camera 1 installed so that the boundary between the track and the platform is within sight,
It is composed of a video signal correction unit 2 installed on the monitoring station side and a monitor (including a display control circuit) 3. In the system of the present embodiment, the ND filter 4 is provided in the lower area of the light receiving surface 1a of the solid-state image sensor in the video camera 1, and the composite video signal of the video camera 1 is converted into the video signal correction unit. It is characterized in that it is input to the monitor 3 side via 2.

Here, since the incident image on the objective lens is vertically inverted, the attached area of the ND filter 4 in the video camera 1 becomes a light receiving area corresponding to the image area A of the monitor 3 in FIG. Specifically, when the subway train 30 enters the platform, it corresponds to the area where the light beam of the front light 31 is directly projected. Further, the video signal correction unit 2 includes a buffer circuit 5 for buffering and storing the composite video signal input from the video camera 1, a clamp circuit 6 for holding the DC potential of the sync chip of the sync signal, and a scanning of the composite video signal. Variable amplifier circuit 7 that amplifies the signal while changing the gain, clamp circuit 8, and output amplifier circuit that amplifies the output signal to the monitor 3 side
9, a sync signal separation circuit 10 for detecting the sync signal of the composite video signal from the buffer circuit 5, and a vertical sync signal (V) and a composite sync signal (C) obtained from the sync signal separation circuit 10 in this unit. Sync signal generation circuit 11 for generating various sync signals used in, a counter 12 for counting the horizontal sync signal (H) set by the vertical sync signal (V) of the sync signal generation circuit 11, and a reset for the counter 12. The area setting unit 13 for specifying and inputting the count value (SET1), the ramp wave generation circuit 14 for generating the ramp wave (LA) during the count pulse generation period of the counter 12, and the scanning signal from the output side of the clamp circuit 8. Level detection circuit 15 that detects the signal level of
And the detection timing information (SET2:
Detection position setting unit 16 for specifying and inputting (corresponding to the position of the horizontal scanning line on the screen), modulation sync signal (Va: changing the duty ratio of the vertical sync signal) of sync signal generation circuit 11, and sync signal separation circuit A detection timing generation circuit 17 that outputs a detection timing signal to the level detection circuit 15 based on the detection timing information (SET2) set by the detection position setting unit 16 using the horizontal synchronization signal (H) of 10 and the detection position setting unit A level setting unit 18 for designating and inputting a desired signal level (SET3) of the scanning signal at the detection position set in 16, and a detection position setting unit 16 while the ramp wave generation circuit 14 is generating a ramp wave (LA). Gain control signal (CONT) corresponding to the difference between the set signal level (SET3) and the average signal level detected by the level detection circuit 15.
Amplification control circuit 19 for outputting to the variable amplification circuit 7, the detection index generation circuit 20 for displaying the index (square mark) 20a at a predetermined position on the screen corresponding to the detection timing signal of the detection timing generation circuit 17, and the index thereof. It is composed of a switch 21 for selecting whether or not to display a signal. The clamp circuits 6 and 8 and the variable amplifier circuit 7 operate in synchronization with the clamp pulse (CP) and the blanking pulse (BLK) separately generated by the synchronization signal generation circuit 11.

Then, the monitoring system having the above configuration is initialized by the following procedure. First, the number of horizontal scanning lines of the image area A obtained through the ND filter 4 of the video camera 1 is input from the area setting unit 13, and the value is set as the reset count value (SET1) of the counter 12.
Next, while monitoring while the train is not in traffic, switch 21 is turned on and the detection index generation circuit
The index 20a generated by 17 is displayed on the screen of the monitor 3. At this stage, since the level setting unit 18 is not adjusted, the brightness of the video area A obtained through the ND filter 4 and the video area B other than that are significantly different, and the brightness difference on the screen of the monitor 3 depends on the brightness difference. The areas A and B divided into two can be visually confirmed, and in that state, the detection position setting unit 16 is adjusted and the index 20a is moved up and down to obtain almost average brightness in the image area A. The index 20a is positioned in the horizontal scanning area. That is, when the detection position setting unit 16 is operated, the detection timing information (SET2) of the detection timing generation circuit 17 changes, the output timing of the index signal by the index generation circuit 20 is controlled, and the index 20a moves up, down, left and right on the screen. However, the detection timing in the level detection circuit 15 can be set by setting the index 20a at the desired position.

Next, when the position adjustment of the index 20a is completed, the level setting unit 18 is operated to adjust the entire image on the monitor 3 to a substantially uniform brightness state. in this case,
The counter 12 is reset by the vertical synchronizing signal (V) of the synchronizing signal generating circuit 11 to start counting the horizontal synchronizing signal (H),
It is reset when the reset count value (SET1) set by the area setting unit 13 is counted, but the ramp wave generation circuit 14 is generating a ramp wave (LA) during that time, and the amplification control circuit 19 The difference between the signal level (SET3) set by the level setting section 18 and the average signal level of the horizontal scanning signal detected by the level detection circuit 15 from the clamp circuit 8 is obtained in the wave (LA) generation time zone, and the difference is calculated. The gain of the variable amplifier circuit 7 is controlled by the control signal corresponding to. The level detection circuit 15 detects the horizontal scanning signal at the previously set timing (horizontal scanning timing corresponding to the position of the index 20a). Therefore, while watching the monitor 3, the level setting unit 18
Adjusting causes the gain of the variable amplifier circuit 7 to change,
The average brightness of the image area A can be made equal to the average brightness of the image area B, and the initial setting procedure ends when the adjustment operation is completed. Also, when this adjustment is completed, switch 21 to the off state,
Turn off 20a.

After the initialization is completed by the above procedure, the subway monitoring system operates as follows. First, as shown in FIG. 2, the direct light from the front light 31 is incident on the image capturing section of the video camera 1 in the process of the train 30 entering the ND filter 4 in the area where the direct light is incident.
The incident light quantity in that area is attenuated. Therefore, when the ND filter 4 is not applied, the iris diaphragm is greatly narrowed down as the amount of received light in the incident area of the direct light is significantly increased, and the image area B of the monitor 3 is the same as in the case of FIG. However, since the ND filter 4 is interposed in the present embodiment, the amount of received light becomes substantially uniform over the entire light receiving surface. As a result, as shown in the graph on the right side of FIG. 2, the horizontal scanning signal level of the composite video signal output from the output amplifier circuit 9 to the monitor 3 is almost the same in each of the video areas A and B, and the iris diaphragm is not so much. Since it is not narrowed down significantly, the entire screen is configured as an easy-to-see image. In other words, it is possible to clearly monitor the state of the platform at the time of train entry, which requires the most safety confirmation.

On the other hand, as shown in FIG. 3, when the train is not in traffic, the amount of received light in that area is attenuated by the ND filter 4, and no correction is made to the composite video signal. When the output is performed without performing the above, the horizontal scanning signal level in the image area A is reduced by the amount of light attenuated by the ND filter 4, as shown by the dotted line in the graph on the right side of FIG. However, in the monitoring system of this embodiment, the video signal correcting unit 2 compensates and amplifies the horizontal scanning signal level in the video area A by the amount of the decrease,
It is made equal to the average horizontal scanning signal level of the image area B in the state where no train is arriving. That is, during the ramp wave (LA) generation period by the ramp wave generation circuit 14 corresponding to the horizontal scanning time zone of the image area A, the amplification control circuit 19 sets the horizontal scanning signal level during that period to the signal set by the level setting unit 18. Since the gain of the variable amplifier circuit 7 is controlled so as to be equal to the level (SET3) and the signal level (SET3) is set in advance as the average signal level in the image area B, the graph on the right side of FIG. As indicated by the solid line, the horizontal scanning signal level of the composite video signal is kept substantially uniform over the entire screen. As a result, the image area A is corrected to have the same brightness as that of the image area B, and the state of the platform and the track when the train is out of the premises can be clearly monitored.

By the way, although the above description is made separately for the time when the train 30 is entering and when the train is not entering, the received light amount continuously changes depending on the position of the train when the train 30 is entering. And the ND filter
It is necessary to select the light amount attenuation rate of 4 in accordance with the state in which the direct light of the front light 31 has the maximum light amount.
Although not so much as when the train 30 is not entering, a state occurs in which the amount of received light in the region where the ND filter 4 is applied becomes smaller than the amount of received light in the other regions during the passage of time when the train 30 enters. However, the video signal correction unit 2 of the present embodiment has the variable amplifier circuit 7
Since the horizontal scanning signal level of the image area A is corrected to be equal to the scanning signal level of the image area B by controlling the gain in real time, it is easy to see the monitor image where the brightness of the entire screen is always constant even when the train is entering the train. Is displayed on monitor 3.

In the present embodiment, the case where the video area is divided into the upper and lower parts is described. However, it is optional if the ND filter 4 is attached and the area setting method by the counter 12 and the area setting section 13 is devised. It is possible to control the brightness in a plurality of areas, and it is possible to give a great degree of freedom to the installation location and installation angle even if the back light incidence state on the video camera 1 is complicated.

[0020]

The video monitoring device of the present invention has the following effects due to the above configuration. In the case where the light receiving surface of the video camera receives a partial back light, a light amount attenuation filter is attached to the partial area, and a means for compensating and amplifying the scanning signal corresponding to the partial area is used, whereby It is possible to always display a natural image with uniform brightness on the monitor regardless of whether the light is incident or not. In particular, in surveillance systems, etc., it is often the case that the video camera must be installed at an installation location or installation angle where optical conditions are bad,
By applying the present invention, it is possible to always monitor with a clear image, and the degree of freedom regarding the installation conditions of the video camera is greatly expanded. Further, in the conventional surveillance system, a system in which a video camera having an ND filter on the entire surface and a normal video camera are installed in parallel and the cameras used are switched depending on the time zone is adopted. Since only one video camera can be used, the installation space of the camera and the structure of the housing can be reduced.
It is possible to realize a monitoring system that has the advantages that the number of cables is reduced, the labor required for installation work is reduced, and the cost of the entire system is reduced.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a safety confirmation monitoring system in a subway station to which the “video monitoring device” of the present invention is applied.

FIG. 2 is a graph showing an average signal level of horizontal scanning signals in a vertical direction with respect to a monitor screen when a train enters a train.

FIG. 3 is a graph showing an average signal level of a horizontal scanning signal in a vertical direction with respect to a monitor screen when a train is not entering a train.

FIG. 4 is a diagram showing a state of a monitor screen when direct light is incident on an image pickup screen of a video camera to generate a highlight area.

[Explanation of symbols]

1 ... Surveillance video camera, 1a ... Video camera light-receiving surface, 2
... video signal correction unit, 3 ... monitor, 4 ... ND filter, 5 ... buffer circuit, 6, 8 ... clamp circuit, 7 ... variable amplification circuit (variable amplification means), 9 ... output amplification circuit, 10 ... synchronization signal separation circuit (Synchronization signal detection means), 11 ... Synchronization signal generation circuit
(Synchronizing signal detecting means), 12 ... Counter (area setting means), 13
... Area setting unit (area setting means), 14 ... Ramp wave generation circuit
(Area setting means), 15 ... Level detection circuit (level detection means), 16 ... Detection position setting section (detection position setting means), 17 ... Detection timing generation circuit (detection position setting means), 18 ... Level setting section (level) Setting means), 19 ... Amplification control circuit (comparison control means), 20 ... Detection index generating circuit, 20a ... Index, 21 ... Switch, 30 ... Train, 31 ... Train front light, A, B ... Image area, BLK ... Blanking pulse, C ... Composite sync signal, CONT ... Gain control signal, CP ... Clamp pulse, H
… Horizontal sync signal, LA… Ramp wave (control area signal), SET1…
Reset count value, SET2 ... Detection timing information (position information of horizontal scanning line on screen), SET3 ... Desired signal level value, V ... Vertical sync signal, Va ... Modulation sync signal.

Claims (1)

[Claims] 1. A video monitoring apparatus, wherein a video camera having a light amount attenuation filter applied to a partial area of a light receiving surface, a sync signal detecting means for detecting a sync signal from a composite video signal of the video camera, and a composite video signal A variable amplification means for changing the gain of the scanning signal and amplifying the scanning signal, and a control area in the scanning time zone corresponding to the area where the light amount attenuation filter of the video camera is applied based on the synchronization signal detected by the synchronization signal detecting means. Area setting means for outputting a signal,
Detection position setting means for setting the detection timing of the scanning signal output by the variable amplification means; and level detection means for detecting the signal level of the scanning signal output by the variable amplification means at the timing set by the detection position setting means. A level setting means for setting a desired scanning signal level at a scanning position on the image corresponding to the timing set by the detection position setting means, and the level in a time zone in which the area setting means outputs a control area signal. Comparison control means for outputting a gain control signal corresponding to the difference between the scanning signal level set by the setting means and the scanning signal level detected by the level detection means to the variable amplification means is provided, and the gain control output by the comparison control means is provided. The variable amplification means outputs the composite video signal to the monitor side while changing its amplification gain in response to the signal. Features and the video monitoring device.