With the development and progress of science and technology, some special industries also have special requirements for monitoring. Occupational environments such as chemical, petroleum, and coal have the presence of hazardous explosive gases or dust. Therefore, it is necessary to install explosion-proof cameras to ensure a safe industrial production environment, which is the primary meaning of the existence of explosion-proof monitoring cameras. Nowadays, the use of explosion-proof monitoring is becoming increasingly important in society. But what impact can the distance of explosion-proof surveillance cameras have?

      The explosion-proof monitoring camera system, as a security technology, is increasingly playing an important role in places such as chemical plants, oil depots, ports, and docks. Nowadays, petrochemical enterprises also use explosion-proof monitoring camera systems as an important means of security and safety production. In order to enable explosion-proof monitoring cameras to play a better role in industrial safety production, it is crucial to correctly select explosion-proof camera lenses for economic indicators and technical performance in each closed-circuit television monitoring project

      The classification of lenses can be roughly divided into:
      1. Wide angle lens: With a viewing angle of 90 degrees or above, it is generally used in small laboratories, halls, and other places with small line of sight and large viewing angles;
      2. Standard lens: With a viewing angle of around 30 degrees, it is generally used in places such as corridors and production site boundaries
      3. telephoto lens: with a viewing angle within 20 degrees and a focal length range from tens of millimeters to hundreds of millimeters, used for long-distance monitoring

      4. Zoom lens: The focal length range of the lens can be changed from wide-angle to telephoto, used in areas with large depth of field and wide viewing angle range;

      The determination of lens focal length is determined by the following factors when selecting a lens:
      (1) Monitor the size of the site;
      (2) The size of the object being photographed;
      (3) Object distance;

      (4) Focal length;:

      The selection of manual aperture and automatic aperture includes two types of lens aperture: manual aperture and automatic aperture. In the past, due to the use of explosion-proof infrared cameras outdoors or other special occasions, automatic aperture lenses were often used. In current monitoring projects, due to the extensive use of explosion-proof monitoring cameras in industrial production, indoor monitoring points account for a high proportion. Many engineering companies also prefer to use automatic aperture lenses when quoting engineering equipment. Although automatic aperture lenses have strong adaptability to changes in light at monitoring points, their price is significantly higher than manual fixed focus lenses with the same focal length. Nowadays, most explosion-proof cameras have electronic shutters and indoor light sources are also relatively stable. Therefore, it is not necessary to extensively use automatic aperture lenses in industrial monitoring projects; On the other hand, the automatic aperture lenses currently used in the market can be divided into two categories:

      a. Power driven automatic aperture lens;

      b. Video driven automatic aperture lens. The power driven automatic aperture lens is controlled by four wires, two of which are DC12V or AC24V power sources to drive the motor in the lens, and the other two control wires control the aperture size by sensing the illumination of external light sources through the light sensing points inside the lens; The video driven automatic aperture lens is controlled by three wires, one of which is a video trigger signal to start the aperture and control the aperture size, and the other two are DC12V or AC24V power lines to drive the motor.

      At present, most black and white or color explosion-proof cameras on the market have automatic aperture lens interfaces, but except for a few that can be compatible with both types of lenses, most explosion-proof cameras are not compatible and can only use power driven automatic aperture lenses or video driven automatic aperture lenses. If some explosion-proof cameras are damaged during use, the newly purchased explosion-proof camera may have compatibility issues with the original automatic aperture lens. But when the monitoring points in the project are outdoors, it is necessary to use a lens with an automatic aperture, because the dynamic range of outdoor light changes greatly, and the environmental illuminance under summer sunlight can reach 50000Lx-100000Lx; At night, the street light is only 10Lx, with a significant variation. In this case, whether or not the vehicle mounted explosion-proof camera has an automatic sensitivity adjustment function, the electronic shutter of the explosion-proof camera itself is no longer able to adapt to such a wide illumination range, and therefore cannot achieve the effect of controlling the image effect.

      It is very important to choose the correct explosion-proof monitoring camera lens based on the monitored environment on site in the monitoring system, as it directly affects whether the effect of the monitored surface seen on the end monitor of the system after system composition can meet the design requirements of the system (in terms of picture range or image details). Therefore, selecting the explosion-proof fixed focus camera lens correctly can optimize the system design and achieve good monitoring effects. Explosion proof zoom camera lenses can be divided into two types in terms of aperture: manual aperture lenses and automatic aperture lenses. In terms of focal length, they can also be divided into fixed focus lenses and zoom lenses.