In this article you will find some guidelines to keep in mind when using a surveillance system with night vision technology.
By: Mace
Night vision technology has evolved to become an important part of CCTV surveillance systems today and can be grouped into three basic forms: thermal cameras, infrared vision cameras and day and night cameras.Thermal cameras: Thermal cameras should not be confused with infrared cameras. Surely we have all seen images of police chases where silhouettes are shown that shine within a dark background, this is the product of a thermal camera by converting into images the heat that objects and people give off.
Many animals use this system to see without being observed, including several reptiles, and this technology copies nature something already existing. The prices of cameras like these are high and out of the budget of the general CCTV user, therefore they are not contemplated in this article.
What is infrared light?
The spectrum of light that the human eye perceives is made up of a scale of colors that goes from violet at the top to the red color at the lower end, each color responds to a specific frequency or vibration of light and its own wavelength, this when captured by the ocular system is transformed into information that the brain interprets as colors.
Outside this scale visible to the eye, there is a light that we do not see, so above the violet color are the well-known "ultraviolet rays" that are those that when we go to the beach, even in cloudy conditions, burn our skin. The "infrared light", which we deal with in this article, is located at the non-visible bottom of the spectrum and very close to heat.
Infrared vision: To produce images you first need a light source, since the images are formed by the reflections that the light makes when bouncing from the objects that it finds in its path. The same goes for infrared vision, but first illuminators are needed to work in this part of the light spectrum and second from cameras with the ability to see in this range and translate the images into the visible spectrum of the human eye.
Infrared light sources
The first generation infrared illuminators were based on incandescent lamps with optical filters that blocked light in other parts of the scale that was not only infrared, this technology was very inefficient due to its high electricity consumption, in addition most of this energy was wasted in heat.
Generally the large dimensions of the equipment were an inconvenience. Current infrared illuminators only use LEDs (light emiting diode), very similar to those found in front of the remote controls of our television. Manufacturers commonly have a number of these LEDs to achieve the necessary level of light according to the range, since the intensity produced by a single LED is relatively low.
With this technology you can achieve very compact and economical illuminators, which are usually incorporated into the cameras sharing the same housing and a common power supply.
Cameras with infrared vision
The images that come from cameras working with infrared are in black and white, since the full spectrum of colors is not generated in the illuminators, there are no other reflections than infrared and that the cameras with this capacity translate to the gray scale in which they can be seen by the human eye.
Generally all black and white cameras are capable of working in this IR range but those designed for this purpose will produce images with low noise content and more sharpness. In the beginning, systems in which night vision with IR technology was necessary had the disadvantage of sacrificing color images even when they had light during the day.
As a solution to this problem, cameras were designed with Day and Night (D/N) technology, which automatically switch to color images when light is sufficient. Thus we find compact and very economical systems where in a single housing the illuminators and the camera are integrated, in addition to a photo sensor that in low light levels activates the illuminators and goes from color to black and white and vice versa automatically.
Initial Purpose of IR Cameras
The main objective to decide the use of an infrared system would be to keep the condition of the monitoring system hidden when it was counterproductive to install common lamps for its operation at night. In this way it would be possible to document irruptions in properties without vandals noticing.
But is this procedure the most appropriate? We believe that no, it is more important to prevent a crime and that the monitoring system occupies a second deterrent function when exposed, either when positioning the cameras in visible places or when using motion-activated lamps. Then infrared light should be applied to places where the use of regular light is inconvenient.
Of course, when we find cameras with reasonable prices and that already include a light source or when the user is attracted by the IR technology at their fingertips, the deterrent aspect of the system goes to the background.
Its advantages
-It makes the system work undetectably as regular light sources are not necessary. This facilitates the documentation of internal criminal activities that would not occur before an "obvious" surveillance system.
-Saving time and investment by not needing the installation of additional lamps and the hiring of electricians for this purpose when cameras with built-in IR lighting are used.
-Infrared technology has a lot of value for the study of nocturnal animal life since being undetectable does not modify the natural behavior of these.
-Allows the monitoring of newborns during sleep without additional light disturbing them domestically or in nurseries.
In public places where very low lighting levels are necessary, such as cinemas, theatres, clubs and bars, IR light is the most viable option.
The disadvantages
-It is only possible to obtain black and white images.
-The limited amount of light from the illuminators built into the camera offer a reduced viewing area.
-Objects with dark colors will reflect a small percentage of the IR light generated, not enough to achieve identification.
-The user and many times the installers will assume that the lighting is sufficient because it is incorporated into the cameras, without considering the addition of illuminators or lamps in important areas within the visual field of the camera, but beyond the reach of the illuminators.
-It will reduce the deterrent that the CCTV system could provide during the night.
Even if a distant image can be viewed through a powerful lens, the effective range of IRs will never exceed 60 meters.
Cameras that don't need IR
There are cameras that can work with very low light levels without the need for IR light and generate color images, such as MACE's CBV series. Already on the market were products of this type with high prices close to US $ 10,000 per unit. The CBV model is capable of producing color images with only 0.002 LUX and at a reasonable cost.
It does this through a process in which the signal is amplified while reducing noise. The way this was achieved previously was by increasing the exposure time, in the same way that it is done in photography when we work with low light, but the drawback of this procedure when applied in CCTV is that the camera stops producing images in real time. This was solved with MACE's CBV series, which produce full-color, real-time images with lighting levels in which other products are inoperable.
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