How does a night vision camera work?
Cameras with night vision are used to maximize a video surveillance system’s effectiveness in low light conditions. The fundamental feature that unites all such cameras is the presence of IR illumination, without which it is impossible even to imagine video surveillance at night. You need to know certain points not to be disappointed with the purchase when buying a camera with night vision, and we will now talk about them.
Features of night surveillance cameras
A good camera with night vision should have several relevant characteristics:
- Powerful IR illumination, preferably adaptive;
- Ability to switch from color mode to black and white;
- High light sensitivity of the sensor;
- ICR filter;
- Weatherproof housing.
Backlight. The first point is mandatory if you need quality night photography. You should pay attention to the backlight parameters declared by the manufacturer:
- Illumination angle;
- Range of action;
The backlight angle should ideally coincide with the angle of view of the camera lens. Otherwise, the image can get a bright spot in the middle of the frame and dark areas at the edges.
Its power determines the range of the IR illumination, and the greater this parameter, the more power will be required to power it. For example, to provide a distance exceeding 10 meters, the backlight diodes must have a total power of 5-10 W, while the current consumption can increase to 1 ampere. Due to the increased energy consumption, the LEDs of IR illumination rather heat up during operation. Therefore, when located in the cameras with night vision bodies, cooling radiators will be required.
A reasonable way out of the above situations is the utilization of home security cameras with night vision, which have similar spotlights outside the hull.
Cameras with night vision: selection categories
- Day/Night. The ability to automatically switch from color to black-and-white and vice versa is also a must when choosing cameras with night vision because the camera is the best shooting in monochrome in the dark. Now, most IP view cameras are equipped with a day/night mode, but if this function is absent in the cameras with night vision, don’t rush to buy it at night in the color mode, the image quality will not be satisfactory.
- Sensitivity. Now let’s talk about the light sensitivity of the sensor. For video surveillance in the dark, the camera matrix’s sensitivity should be as high as possible. For example, to obtain a normal image on a moonless night with a clear starry sky, the camera must have a sensitivity of 0.001 lux. With this sensitivity, the home security cameras with night vision can produce a decent black and white image at night.
- ICR filter. The ICR filter is a movable mechanical IR cut filter located in front of the cameras with a night vision sensor. The human eye cannot notice the IR illumination light, but the camera sensor sees it perfectly. If the picture quality remains good enough at night in monochrome mode, then the IR radiation has a significant effect on the image in the daytime. Deterioration of quality manifests itself in color distortion, contrast, and image blur. Also, the home security cameras with night vision are equipped with an IR cut filter to protect against rays. During the day, the filter closes the matrix, and with the onset of darkness, it shifts to the side.
- Housing. Suppose a video surveillance cameras with night vision is planned to be installed outside. In that case, it is worth purchasing devices with a special protective case that can withstand high and low temperatures and adverse environmental factors – dust and moisture. Usually, outdoor cameras with night vision are equipped with an anti-vandal hermetically sealed thermal casing capable of operating the device in the temperature range from -40 to 50 ° C, with a protection class IP66 – dust and moisture resistant. In some cases, the housing can be equipped with a heating system.
Three features of CCTV cameras for night vision
Сameras with night vision have their characteristics that are specific only for this type of device. These features can also be attributed to the disadvantages of night cameras:
- High sensitivity to the presence of small particles in the air – dust, rain, snow;
- Image ripple when working with unstable energy sources;
- Limited resources of IR LEDs:
- Snow, raindrops, or dust, falling into the field of view of the camera lens at night, tend to reflect the light of the IR illumination from itself. At the same time, it becomes almost impossible to distinguish something on the monitor screen. This happens only in a heavy snowstorm or pouring rain, but, unfortunately, other options for night video surveillance cameras without IR illumination have a high cost.
- Image ripple can occur primarily due to the difference between the camera’s recording rate (fps) and the backlight ripple rate.
- The service life of IR LEDs in CCTV cameras is limited, ranging from 20,000 to 50,000 hours. Thus, with an average operating time of the backlight of 12 hours per day, the service life is limited from 5 to 10 years, after which the LEDs will need to be replaced, or alternative sources of illumination – IR illuminators – must be used. Otherwise, the camera will no longer be suitable for night shooting. A blizzard with rain is not so often, therefore, night video surveillance cameras with IR illumination are a very good solution.
Today, the vast majority of CCTV cameras are equipped with IR illumination. Cameras with powerful IR illuminators are now quite difficult to find – most of the models have been discontinued. These cameras have remote IR illumination on the sides of the case and have the characteristics of cameras with IR illumination with increased power. The illumination of such devices is based on the continuous wave, electro-optical illumination. Such cameras can recognize license plates and faces of people at a distance of up to 200-400 meters. Longer range is achieved through the 120x zoom capability.