Active Infrared: Invisible Security|
Growing in popularity due to increasing concerns with terrorism and criminal activities, active infrared technology has increased by leaps and bounds and led to an explosion in the low light security monitoring industry. No longer the sole realm of the military, night vision technology has been very successfully integrated into the civilian industrial sector as well and offers a distinct advantage over traditional forms of electronic security surveillance systems. Where traditional security cameras rely on a well lit area to monitor activities effectively, infrared technology allows monitoring in total darkness.
Although there are several types of technology available that allow electronic imaging in low or no light conditions, active infrared continues to be at the forefront of night vision technology. Using a system of infrared illuminators and receivers or cameras capable of capturing light in the infrared spectrum, active infrared technology produces high quality resolution and detail that other forms of night vision technology are currently unable to match. Thermal imaging, which relies on the infrared radiation emitted as heat by objects to form an image, although effective and powerful, is limited in the effectiveness with which it can be used in surveillance applications. Although preferred for many military applications because of its passive nature and long range, thermal imaging cannot produce detail at a definitive identification level. In security applications where positive identification of potential suspects is paramount, however, active infrared systems excel.
Active infrared systems rely on the invisible infrared end of the light spectrum to produce images. The cameras or receivers used in these systems are specially designed to capture light in the 760nm to 1000nm spectrum and resolve it into a clear image which is outputted to a screen or recording device. Since the infrared illumination used is invisible to the human eye, there is no tip off to those being monitored that their activities are being recorded. Although these systems are often quite capable of operating under very low light conditions as stand-alone equipment, the addition of an external infrared light source greatly improves the resolution of the images they are able to produce as well as extending their range. With these systems it is possible to not only “see” in the dark, but make out distinct facial features, and even read the lettering on clothing from considerable distances as well.
The real trick in active infrared monitoring is held in the unobtrusiveness of the systems. Cameras and receivers are often quite small, with some being mounted with little more than a pin hole sized opening in a wall or structure to indicate their presence. These cameras are highly sensitive and are able to gather an incredible amount of detail from a very small aperture. Despite their sensitivity, however, their full potential is not reached until an active source of infrared illumination is introduced. The key is to produce a large scale level of illumination from a small source that effectively bathes the area to be monitored in infrared light; the better the area is covered, the better the resolution and detail produced by the camera or receiver. Additionally, better infrared coverage will improve contrast and help to reduce the flatness sometimes associated with night vision imagery and dark spots that can sometimes interfere with views from some angles.
To produce the infrared illumination necessary to gain the full effectiveness of an active infrared system an independent IR emitter is needed. The problem here is that in order for the system to be effective, a large scale amount of infrared light must be produced. Typical IR emitters usually associated with security cameras are at best adequate and limited to short ranges. Although it is possible to produce large amounts of infrared light through the use of incandescent lamps and special filters, this type of IR light tends to be very inefficient, requires considerable allowances for heat generation, and still produces an oftentimes easily noticeable light source. These problems can be mitigated or eliminated entirely through the use of LED emitters which produce light only in the infrared spectrum and require no special filters or lenses. LED emitters like Larson Electronics’s LED IR Emitter Light use LEDs in their construction which only produce light in the infrared spectrum. LEDs are very efficient and because they can be tailored during design and construction to produce light of a specific wavelength, require no lenses or filters to produce light that is entirely in the infrared end of the light spectrum without any excess energy wasted producing visible light as well. The LED emitter’s efficiency also allows it to produce a great deal of infrared light from a small source, with little energy, which goes a long way towards maintaining the covert nature of the active infrared monitoring system as a whole.
Infrared LED emitters are ideal for illuminating large areas like military installation perimeters, industrial complexes, parking lots, warehouses, shopping centers and a malls just to name a few. For large areas, it is preferable to use LED emitters which produce their light in a wide flood pattern, and operate these emitters in strategically placed pairings which allow fuller coverage and maximum range. Applications that are spot specific can benefit from LED IR emitters which produce more of a localized spot pattern and concentrate the bulk of the infrared light onto a specific subject. Although the light produced by these emitters is invisible to the naked eye, it is important to remember that the cameras and receivers used with these systems are sensitive to IR and that they will behave the same as any camera that is too directly exposed to an intense light source.
Poorly placed infrared emitters can cause whiting out of images and possible automatic shutdowns of the camera or receiver’s internal circuitry intended to protect them from possible damage. This makes it necessary to insure that any supplemental high power infrared LED emitters are properly placed so as to not place the camera in the direct path of the light. Once properly installed and positioned, the images produced by these systems are highly detailed and very effective for use in identification and record keeping applications. Not only can people and objects be monitored in what for all intents is a pitch dark environment, but they can be readily identified as easily as if they were illuminated by regular daylight. For the unsuspecting criminal or offender, the dark is no longer a safe haven.