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INTERNET CCTV GUIDE - Video surveillance with lighting
Additional lighting of some area is needed in many surveillance systems. It can be provided in the following ways:
  • traditional lighting - visible (lamps, floodlights)
  • infrared illuminators/lamps
Instead of using lighting equipment, there is also possibility of employing thermal cameras.
The use of devices for "night" surveillance.
Good traditional lighting has many advantages. However, it is visible, and it may be easy for an intruder to get round the light zones. It requires a lot of energy and is expensive.
IR illuminators - they can have quite long range - up to 200 m, and work in horizontal position - because their light doesn't dazzle. Therefore they are widely used for city monitoring, in parks, wide-area surveillance systems.
Saint Paul's Cathedral surroundings - camera installed in housing with wiper and IR illuminator.
Thermal cameras -they ensure long range - up to 1000m, the lowest power consumption, insensitiveness to smoke and fog. They don't emit radiation (it is hard to work out the surveillance system). Used to secure wide areas and dispersed locations (water pools, power plants, country borders), but also suitable for fire service.
Visible light is a fragment of electromagnetic radiation of wave length from 400 to about 700 nanometers (optical radiation). A little shorter waves are called ultraviolet whereas a little longer - infrared. Objects having temperature up to 400 deg C practically emit only infrared radiation. Infrared radiation is strongly attenuated by glass; therefore, when designing a system working in this band we should pay attention to all possible glass barriers.
Black and white cameras (with much lower sensitivity compared to visible light) allow quite good observation in fragment of infrared band.
Infrared illuminators/lamps.Two types of IR lamps are available:
  • based on ++LEDs+++ working in infrared, usually powered with 12V DC and having power up to a few tens of Watts [W]. The IR-150 M1650 illuminator (18W) is powered directly from 230V AC power network, and its range measured in main axis according to the manufacturer is around 150m. The measurement was made in good visibility conditions (good transparency of the air). Significant decrease of the range is caused by fog, smog, rain, snow etc.
  • Based on halogen lamps, equipped with filter stopping visible light and having power even up to a few hundreds of Watts.
Observation range depends on camera's infrared sensitivity and the power of the illuminator/lamp.
During the selection of a lamp, we should pay attention to emitted wave lengths. There can be found lamps wave lengths e.g. 715nm or 830nm. In the first case the light is a little visible for humans and in the second case it is completely invisible.
Mouse getting close to a trap - IR light is imperceptible for humans and animals.
Despite the fact that each camera is somewhat sensitive to all infrared band, we should rather match the length of wave emitted by the source to the sensitivity characteristic of camera's image sensor.
Almost all lamps have built-in dusk sensor, switching on the lamp only after outer illumination has fallen below certain level. Higher class lamps have, besides potentiometer (usually marked as lx) used to set lamp's switching threshold, also another potentiometer for adjusting output power.
Depending on the version, IR lamps can be powered with voltages 12V DC, 24V AC or 230V AC.
IR reflections
If we illuminate an object with IR lamp having high power and small angle of radiation beam, placed in close distance to a camera, we can cause situation in which the camera becomes dazzled by the light reflected from the object (especially dangerous in the case of flat surfaces). It is one of the main reasons (besides the price) why manufacturers of such integrated sets (camera-IR lamp) don't use "strong" illuminators. If illumination of a larger area is required, or when illumination has to be steady along some observed area, then additional infrared lamps are used with adequate power and selected beam angles.
Improper lighting - strong reflection, and proper IR illumination
Reflectors integrated with cameras.
Besides standard versions of IR lamps, there are also many combined solutions. They can be integral part of a camera, or lens. This solution is very practical, because it reduces the number of additional elements and additionally - lowers the cost of the installation. However, we should remember that this kind of lamps, built with a few LED pieces, usually can ensure point-type character of illumination with a range of up to a few meters.
Outdoor Color CCTV Camera with Lens: n-cam 115 IR
Vandal Proof CCTV Camera: V-CAM 412 IR
Compact Color Camera: V-CAM 315 IR
CCTV cameras with built-in IR illuminators
The world's specialist in the field of IR lamps is Derwent company - on their website you can can see the effects and examples of proper IR lighting.
"Typical" color cameras have no possibility of observation in infrared light, for the reason of built-in infrared filters eliminating influence of IR band on natural reproduction of colors.
When we want to use a color camera for observation during the night, then we have to use Day&Night type cameras. These cameras don't have infrared filter cutting off this kind of light, opposite to the standard ones. Thanks to it, the use of IR illuminators is possible. Such a camera construction (complete elimination of infrared filter) has its disadvantages. At normal illumination (visible light range) such camera has sometimes problems with white balance - it may show untrue colors. This "behavior" of a camera is often treated by installers as camera's damage. But it is a normal symptom caused by lack of IR filter and thereby the compromise between camera's price and quality of the image. Obviously, there are also cameras in which such filter is driven mechanically, e.g. M11205, but they are significantly more expensive, on account of the cost of additional servomechanism. In common video cameras, the choice of work mode - day or night - is limited to taking or placing IR filter, mostly using manual switch or lever, which enables the camera to operate properly in different lighting conditions.
Thermal cameras.
Capability of night observation can be achieved by use of lighting, or special type of cameras called thermal cameras. Because their prices have significantly dropped, they are increasingly being used in modern surveillance systems. Thermal cameras equipped with IRFPA sensors (Infra Red Focal Plane Array) observe objects within infrared wave lengths from 3 to 15 micrometers.
Each body with temperature above absolute zero is the source of radiation in infrared band
The way how a thermal camera (irreplaceable in each situation where temperature distribution is important) works, is based on the phenomenon that each body with temperature above absolute zero is the source of radiation in infrared band. Its intensity depends on temperature and features of the body's surface. This allows to distinguish e.g. brush from road sign, when they both have the same temperature. Thermal sensors are sensitive to a fragment of infrared radiation band. Creation of an image depends on properties of camera, transforming the radiation emitted by observed object, and processing into a false-color image. Thermal system is in fact a kind of special thermometer, which allows for remote measurement of temperature of many points at the same time.
Examples of using thermal cameras in surveillance systems can be seen on the website of Flir company