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Third, increase the effective picture and depth of field 
Fourth, to avoid the appearance of images, side view phenomenon 
What do you need to consider before installing a monitoring project in Lanzhou?
What do you need to consider before installing the monitoring project? Always want to look at the situation, recently found a good summary in a forum, reprint it for everyone to see.
The importance of monitoring camera configuration and screen debugging is self-evident. If the camera image is not correctly and reasonably configured and debugged according to the specific structure, environmental conditions and target objects of the building, even if the resolution of the camera is higher, the technical level of the system will reach the highest standard. However, once the camera image appears overhead and sideways, When there are problems such as backlighting, effective pictures, and even blind spots and dead ends, the monitoring images still do not achieve the desired results and effects.
First, the camera configuration should be a reasonable specification
The configuration of the camera should be reasonable, standardized and uniform to meet the requirements of technical standards. If you make a thorough and careful analysis of the requirements for the use of surveillance images in the technical standards, you will find that the security surveillance image can be divided into three levels according to the level of detail displayed and the characteristics of the objects it reflects. One is to show people’s facial features or motor vehicle license plates, the other is to show the physical features of the person and the activities of the staff, and the third is to show the activities of people or vehicles in a specific area or venue and the behavior of people and vehicles. . It can also be seen from the above that not all monitoring images in the local area can clearly display the facial features of the person, and the monitoring range of the camera mainly depends on the characteristics of the object to be reflected.
The above table shows that the first level or the most demanding image is the image of entrances and exits and entrances and exits of the entrances and exits of the school district. It is required to be able to clearly display the facial features and motor vehicle numbers of the people entering and exiting. For this reason, each camera’s view The field angle is the smallest, the monitoring range is within a few meters (not more than 10 meters); the second level is the image of the interior corridors and passages of the building, and it is required to be able to display the physical characteristics and activities of the people. For this purpose, each camera The field of view is moderate, the monitoring range is generally more than 10 meters (not more than 20 meters); the third level or relatively low requirements are for the parking lot passage, road trunk road, parking lot, square, hall, perimeter, etc. The image only requires that it can display the activity and behavior characteristics of people and vehicles. For this reason, each camera has the largest field of view. The monitoring range is generally between 10 meters and more than 100 meters (not more than 200 meters). In the area, the monitoring range of each camera is from 10 square meters to more than 100 square meters.
Second, the entrance and exit surveillance images should not have blind spots or dead ends
In order to ensure that the entrance and exit surveillance images should not have blind spots or dead ends, the configuration of the entrance and exit cameras should adopt different schemes depending on different situations. The first thing to understand is related to the situation. The first is whether or not there is a back light problem at the entrance and exit of the installation camera, and the second is to The internal structure of the entrances and exits where the camera is installed is a straight passageway or a doorway (such as a hall or lobby) with a certain width on both sides. Then take different scenarios based on the above different situations. If there is no back light problem at the entrance and exit, the entrance and exit cameras should be installed facing the entrance and exit, so that the camera can monitor the personnel entering the entrance and exit, and in order to ensure that the surveillance image does not have the above problem of blind spots, the border of the entrance and exit should be displayed on the display, see Figure 1.
If there is a backlit problem at the entrance and exit, to prevent the image from appearing backlit, the camera should be mounted facing away from the entrance and exit, so that the camera can monitor the personnel leaving the entrance and exit. At this time, we should also pay attention to distinguishing the internal structure of the entrance, if the entrance is The internal structure is a straight passage with a width of 3m to 4m. If people leave the entrance and exit must go through this passage, then a camera can be installed to monitor the straight passage inside the entrance; if the entrance is an area with a certain width Like in the case of a lobby or hall, in order to avoid the installation of a camera, someone would close the entrance and exit on both sides of the entrance and exit, resulting in the presence of blind spots or dead spots in the surveillance image. At this time, two or more cameras should be installed. The two or more cameras complement each other's blind spots or dead corners, enabling people to completely exit the entrances and exits. See Figures II and III.
Each image should highlight the topic of the target to be monitored, ie the effective picture. What needs to be further clarified here is that the subject or effective image of the security monitoring image does not necessarily have to display the facial features of the person. As described above, some need to display the facial features of the person, and some must show the physical features of the person. Some of them only show the activity of people or vehicles, that is, behavioral characteristics. Once the theme is clear, the picture should highlight the picture related to the theme. The unrelated picture should appear as little as possible or even not appear.
We often encounter the problem that the effective image of the surveillance image is too small. For example, if the image of the entrance and exit is monitored, the display screens on both sides of the entrance and exit are often too large or too large. Not large, that is, the display image does not highlight the theme of the entrance, resulting in the entrance and exit of the entrance of the staff is too small, people's facial features can not be clear; another example is to monitor the corridor of the channel image, but also because of the channel on both sides of the wall and the ceiling of the screen Too much or too much, but really the screen of the promenade or aisle is not too much or too small, and the physical characteristics and activities of the people walking on the promenade or passage are not clear.
For this reason, there is a case where the effective picture of the quasi-image is not enough, and we can overcome it by adjusting the camera focal length so as to achieve the picture requirement sufficient to distinguish the target features. However, while solving one problem, it may cause another problem. Because of an ideal image, in addition to having an effective picture that can sufficiently distinguish the target features, there must be a certain range of depth of field. Those who participated in the screen debugging know that the effective image and depth range of the image are a pair of contradictory bodies. A large effective screen will directly affect the depth of field of the screen. In addition, if the effective screen is too large, the moving target will move too fast. The person or vehicle that appears in the image is short and flashes past. Eventually it will result in the screen of intercepting target features not clear when the evidence needs to be collected. Therefore, the effective picture is not as big as possible.
We must correctly handle the relationship between the effective image of the image and the range of depth of field. In the screen debugging of the security monitoring image, the effective image of the image only requires the ability to see the characteristics of the monitoring target, and it is enough to correctly identify the features of other people or vehicles. It does not need to be too large. When it is too large, it will directly affect the depth of field of the picture and affect the observation of the characteristics of the movement process of a person or a vehicle. The observation of the characteristics of the movement process of a person or vehicle is also part of the security monitoring content. The advantages and disadvantages of the effective image and depth of field of the image are shown in Figures 4 and 5.
The technical protection industry standards stipulate that the installation height of security cameras should not be less than 2.5m indoors, and should not be less than 3.5m outdoors. This is mainly to prevent the normal installation of the camera or the normal running of the vehicle after the installation of the camera is too low. . However, in actual installation, if only to avoid the above problems, the camera installation height control requirements within the range, pay attention to the perspective of the image, the image will appear overhead or side view problems, and the image once the top or side view problems The monitoring image will not be able to distinguish the target features.
The image does not appear to suffer from problems of overthrow and side view. The key is to look at the angle between the pointing and monitoring target of the camera (that is, the angle of view). The included angle is the vertical angle and the horizontal angle (the vertical angle is the camera's pointing and monitoring target. The formed high and low angles and horizontal angles are the horizontal angles formed by the camera's pointing direction and the front direction of the monitoring target). It is actually shown that when the vertical angle formed by the pointing and monitoring target of the camera is less than or equal to 30 degrees, the image does not appear to have a top view. When the horizontal angle formed between the camera's pointing direction and the monitoring target's front direction is ≤45°, the side view phenomenon does not appear in the image. After the camera installation angle reaches the above requirements, the image display can basically reflect the positive characteristics of the monitored target. Of course, the smaller these angles are, the more beneficial it is to improve the appearance of the image, as seen in Figure 6 and Figure 7.
In view of the above two issues and requirements, that is, to affect the normal walking of the person or the vehicle, the installation height of the camera should not be too low, but also to ensure that the image does not appear overhead, side phenomenon, the camera pointing and monitoring target clip The angle should not be too large. In this regard, the best or most appropriate solution is to install the camera a little further away from the surveillance target. Do not go too far. Practical experience shows that the distance between two indoor rooms should not be less than 3.5m, and the distance between the two rooms should not be less than 4m. However, the distance between the two should not be too large. When the distance is large, it is beneficial to the improvement of the image's pitch and side phenomenon. However, because the distance between the two is large, other objects may appear in the middle of the monitored target. The probability of occlusion increases.
Fifth, the entrance and exit cameras are installed in the same direction
Everyone should know that when there are multiple entrances and exits on the same site of a building, if the orientation of the cameras installed on their entrances and exits is inconsistent, there is a possibility that those who are attempting to mislead will be given a chance and the images monitored by the cameras will all be human. The back view does not show the person's frontal image (not to mention distinguishing the person's facial features). This problem is also a problem that occurs when the technicians of the technical protection project often pay no attention to the project construction. According to the location of the building's entrances and exits, it can be divided into three types of entrances and exits, one is the perimeter or entrance to the yard, the second is the entrance and exit of the building to the outside world, and the third is the entrance and exit of the interior floor, that is, the elevator hall and the stairway.
For cameras installed on perimeters or entrances and exits of hospitals, it is generally better to monitor the orientation of people or vehicles entering and exiting the entrance. This is because on the one hand, monitoring the entrance and exit images is better than leaving the entrance and exit images. On the other hand, cameras are more likely to be installed outside their jurisdiction than outside the jurisdiction (outside the jurisdiction, cameras are not allowed to be installed on their own). For cameras installed at entrances and exits of buildings that communicate with the outside world, generally, to avoid back light, it is better to face away from the entrance and exit to monitor the orientation of personnel leaving this port. For cameras installed on the entrances and exits of indoor floors, only the orientations of the cameras are required to be consistent. It is not necessary to emphasize the orientation. It is also necessary to point out that the installation orientations of the indoor floor entrance and exit cameras must be the same, which refers to the installation of all the entrance and exit cameras on each floor. Consistent orientation does not mean that the camera installation orientations of all the entrances and exits between the layers are also the same, and the installation orientation of the entrance and exit cameras between the layers may be inconsistent. With the same orientation of the cameras installed at the three entrances and exits, it will be ensured that anyone who enters or exits the perimeter or the campus will have at least three positive images. If they only enter and exit the building, they will be able to at least Take two positive images.
In summary, there are many factors that affect the effectiveness of image quality. Besides the well-known camera resolution and other technical parameters, the number, position, angle, light, and screen debugging of the camera installation and configuration are also relevant. The direct relationship, which one of the links has a problem, the monitoring image will affect the actual results.
Gansu Jinchuang Intelligent Technology Co., Ltd. released