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Special Feature

consider this!

choosing high-performance ir dome cameras IR cameras are the most common type of night-vision cameras found on the market, as they are discreet, reliable, and have long viewing distances. The following section discusses how to select IR dome cameras. n By Alf ChAng


n order to select which IR cameras are most suitable for the end users' requirements, one must be able to discern the strengths of one camera over others. The following considerations should be made when choosing a high-performance IR dome camera.

Operating cOnditiOnS OF ir illuminatOrS Generally speaking, the luminous efficacy of IR illuminators is proportional to the electric current. However, when the current rating is above the threshold, the luminous efficacy drops, as energy is lost through the heat that is generated. Hence, an electric current that is too high can reduce the lifespan of the IR illuminators or even destroy them, but at the same time a current that is too weak does not generate enough light. Current flows when the forward voltage goes above the threshold at around 0.8V, but IR illuminators such as LEDs have high voltage and current sensitivity. Since current is an exponential function of voltage, based on the Shockley Diode Equation, the voltage needs to be above the threshold and current below the


FEB 2014

rating for the IR illuminators to perform at an optimal level. In other words, current is required to be stable and within a specified range, as the luminous efficacy drops as the temperature of the operating environment rises, which may also be self-generated by the LEDs. Therefore, heat emission is an important consideration in the design and selection process, especially for long-range IR illuminators. As IR illuminators are dependent upon stable, reliable current and thermal management, the MCD, MDD, MED, and MBB series of cameras are all equipped with high-power IR illuminators (up to a maximum of 24 bulbs) and an internal

cooling design. Not only can these cameras achieve long-range night vision of up to 200 meters if supplied with high-current power supply, but they are also known for their long lifespans.

ir illuminatOrS and cOmplicatiOnS with OverexpOSed ir IR overexposure is the visible wavelengths emitted by IR illuminators. The IR lights are able to be adjusted to have absolutely no exposure by using infrared tubes with a wavelength of 940nm to 950nm or to have only slight exposure. The application of Aucister IR


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