The backlighting phenomenon at the entrance and exit is a prominent issue in the installation and use of video surveillance. For this problem, a completely effective method has not been found yet. The three methods described below have a certain effect on improving the backlight phenomenon. We are using it. The process requires consideration of many conditions such as an integrated site environment to find the best solution.
Generally speaking, there are three methods to solve the camera's backlight. The first is to avoid direct sunlight when installing the camera; the other is to select a camera with a corresponding improvement function, such as a wide dynamic camera or a backlight compensation camera; three can improve the illumination of the indoor light source. Reduce contrast with outdoor light.
First, adjust the installation position of the entrance and exit cameras, try to avoid direct sunlight from the outside world, and to a great extent improve the back light of the entrance and exit. For example, if a camera needs to be installed at the entrance of a bank to monitor people entering and exiting the building, if we install the camera facing the entrance and exit, we may experience severe backlighting, which will result in blackening of the surveillance screen and the lack of clarity in shooting the actual object. At this time, experienced engineers will invert the cameras that monitor the entrances and exits, so that the camera's lens will face the personnel who exit the network. This is better than installing the camera at the entrance and exit, and it can better solve the problem of back light.
Second, improve backlighting by selecting cameras with corresponding functions. There are two types of cameras in the security camera that can better solve the problem of camera backlighting. One is a camera with backlight compensation, and the other is a wide dynamic camera.
Backlight compensation, also known as backlight compensation, divides the picture into several different areas, each of which is exposed separately. In some applications, the field of view may contain a very bright area, and the included subject is surrounded by a bright field. The picture is dark and has no hierarchy. Since the signal level detected by the AGC is not low at this time, the gain of the amplifier is very low, and the brightness of the screen body cannot be improved. When the backlight compensation is introduced, the camera only detects one subfield of the entire field of view. The average signal level of this area determines the operating point of the AGC circuit. Because the average level of the sub-area is very low, the AGC amplifier will have a higher gain, so that the amplitude of the output signal is increased, so that the subject on the monitor is clear, greatly reducing the subjective brightness difference between the background picture and the subject picture. The visibility of the field of view is improved. Although backlight compensation improves the brightness of the subject, the image quality deteriorates more or less.
Wide dynamics exposes twice at the same time, one at a time, and one at a time, and then combines to make it possible to see bright and dark objects on the screen at the same time. Both are to overcome the measures taken to see the target in a strong backlight environment, but the backlight compensation is at the expense of the contrast of the screen. In a sense, the wide dynamic technology is an upgrade of the backlight compensation.
Third, by improving the illumination of the indoor light source, the phenomenon of backlighting is improved. It can be imagined that the reason for the back light phenomenon is caused by the strong contrast of the light intensity in the field of view. The cameras installed at the entrance and exit have strong outdoor light in the monitored area and the indoor light is weak, and the black and white contrast of the image is formed. Too strong. In this way, if the indoor light is enhanced by increasing the illuminance of the indoor light source, and the contrast between the interior and the external light is reduced, the back light phenomenon can also be improved.
Generally speaking, there are three methods to solve the camera's backlight. The first is to avoid direct sunlight when installing the camera; the other is to select a camera with a corresponding improvement function, such as a wide dynamic camera or a backlight compensation camera; three can improve the illumination of the indoor light source. Reduce contrast with outdoor light.
First, adjust the installation position of the entrance and exit cameras, try to avoid direct sunlight from the outside world, and to a great extent improve the back light of the entrance and exit. For example, if a camera needs to be installed at the entrance of a bank to monitor people entering and exiting the building, if we install the camera facing the entrance and exit, we may experience severe backlighting, which will result in blackening of the surveillance screen and the lack of clarity in shooting the actual object. At this time, experienced engineers will invert the cameras that monitor the entrances and exits, so that the camera's lens will face the personnel who exit the network. This is better than installing the camera at the entrance and exit, and it can better solve the problem of back light.
Second, improve backlighting by selecting cameras with corresponding functions. There are two types of cameras in the security camera that can better solve the problem of camera backlighting. One is a camera with backlight compensation, and the other is a wide dynamic camera.
Backlight compensation, also known as backlight compensation, divides the picture into several different areas, each of which is exposed separately. In some applications, the field of view may contain a very bright area, and the included subject is surrounded by a bright field. The picture is dark and has no hierarchy. Since the signal level detected by the AGC is not low at this time, the gain of the amplifier is very low, and the brightness of the screen body cannot be improved. When the backlight compensation is introduced, the camera only detects one subfield of the entire field of view. The average signal level of this area determines the operating point of the AGC circuit. Because the average level of the sub-area is very low, the AGC amplifier will have a higher gain, so that the amplitude of the output signal is increased, so that the subject on the monitor is clear, greatly reducing the subjective brightness difference between the background picture and the subject picture. The visibility of the field of view is improved. Although backlight compensation improves the brightness of the subject, the image quality deteriorates more or less.
Wide dynamics exposes twice at the same time, one at a time, and one at a time, and then combines to make it possible to see bright and dark objects on the screen at the same time. Both are to overcome the measures taken to see the target in a strong backlight environment, but the backlight compensation is at the expense of the contrast of the screen. In a sense, the wide dynamic technology is an upgrade of the backlight compensation.
Third, by improving the illumination of the indoor light source, the phenomenon of backlighting is improved. It can be imagined that the reason for the back light phenomenon is caused by the strong contrast of the light intensity in the field of view. The cameras installed at the entrance and exit have strong outdoor light in the monitored area and the indoor light is weak, and the black and white contrast of the image is formed. Too strong. In this way, if the indoor light is enhanced by increasing the illuminance of the indoor light source, and the contrast between the interior and the external light is reduced, the back light phenomenon can also be improved.
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