One of the major challenges for effective speed dome function is nighttime imaging performance. Although speed domes generally deliver acceptable images during the day, darkness produces negative effects including noisy images, shadows and motion blur. Lighting is a key consideration that determines the effectiveness of surveillance systems under low and no light conditions.
Infrared (IR) illumination has been used for many years to solve the problems associated with surveillance in darkness and low light. When designed specifically for surveillance applications, infrared illumination is strategic, targeted lighting which security cameras use to produce effective images.
Mastering the application of infrared illumination is a relatively simple matter, with the key factors being wavelength, beam pattern and illumination range. Additionally, not all light is created equal and it is important to choose a quality of light appropriate for the application. For the security technician and installer, it’s important to look for infrared illuminators that produce high-uniformity light to eliminate hot spots and areas of underexposure within the light beam.
In the majority of applications, there are four different solutions to applying infrared illumination.
Solution No. 1: 360º wide area illumination
The most comprehensive approach is to install infrared illumination sufficient for 360º coverage. The 360º technique ensures light will be available in every direction around the
camera, thereby reducing risk of the camera missing important events hidden by darkness.
Conventional infrared illuminators presented challenges to security integrators because six or more units were required to achieve 360º coverage. However, new technology that incorporates micro-refraction to enable beam patterns of up to 120º from a single illuminator enables three infrared illuminator units to achieve 360º coverage.
Solution No. 2: Specific target illumination
An alternative solution to the above can be achieved by using “specific target” illumination. This is a method of providing illumination in and around the scene, to illuminate specific areas of risk rather than the whole area being viewed by the dome camera. The technique, involving the strategic positioning of infrared to illuminate targeted locations, matches the illumination to the vulnerable areas within the scene. Areas can include gates, doorways, pathways or anywhere the security manager perceives increased exposure to risk. During the full 360° rotation of the dome camera, there may be only two or three specific targets that need to be viewed under infrared illumination. The infrared units can be mounted on and around the camera pole to continuously illuminate these targets, allowing the camera to effectively monitor all key areas of the scene.
Solution No. 3: Local area illumination
Certain environmental factors may make it preferable or necessary to position infrared illumination away from the camera. For example, there may be power limitations at the camera site, requiring re-trenching of new cable lines. Or there may be a significant distance between the camera and target surveillance area, making it necessary to use more energy to illuminate an area far away. Under situations such as these, consider positioning the infrared illumination above or near the specific target. For best results, properly match the camera angle of view to the infrared illumination and position the illuminators in such a way to minimize shadows on target.