![]() Thus if you are temporarily not going to be watching video from your projector but you expect to be watching it again within thirty minutes, it is probably best to leave the projector turned on. While I have not seen any scientific study to confirm the specifics, there seems to be a general opinion among many experienced users that to achieve maximum lamp life, at least a 30 minutes cool-down period should be allowed before turning the projector back on again. Also lamp life can be shortened by not allowing adequate time for the lamp to fully cool down after being turned off before being started again. Lamp life is reduced each time the lamp is turned on. These are the number and frequency of on/off lamp cycles and having adequately cooling for the lamp. low lamp mode can impact lamp life there are other significant factors that should be considered. Many manufacturers will rate the lamp as having a longer operating life when the projector is operated in the low lamp mode. Most projectors will have a high lamp and a low lamp setting (labeled various names by the different projector manufacturers). This rating is for a 50% loss of the original light output. The lamp life for the UHP lamps used in consumer front projectors is typically rated by the projector manufacturer somewhere between 2,000 hours and 4,000 hours. Ideally a UHP lamp’s light loss will be gradual and well behaved in reaching one-half of the original light output after a few thousand hours of use. After that the rate of loss of the light output will typically slow down during the remaining nominal life of the lamp. The light output will be the greatest when the lamp is new and will typically lose on the order of 20% of the original light output over the initial several hundred hours of use. The light output of UHP lamps will decrease over time. Lamp Asssembly - Photo 2 How Lamps Age and Fail The two photos below show these part of the lamp assembly (photo is of a JVC lamp assembly). This reflector, placed toward the rear of the lamp assembly, is used to focus the light which exits the lamp assembly through a clear glass window in front of the bulb. The lamp assembly, or module, used within a projector includes a housing that contains a UHP bulb that is placed in front of a curved (e.g., parabolic) mirrored reflector. Virtually all projector manufactures purchase the UHP lamp itself (i.e., bulb) used in their lamp assemblies from one of very few UHP lamp manufacturers, including Philips, Osram, Ushio, Iwasaki, etc. The UHP lamp is a technology that was developed by Philips in 1995. Instead, UHP lamps require a high voltage electrical pulse to be applied to the lamp or order to create an electrical arc between internal electrodes which triggers the ignition of the lamp. These are arc lamps meaning they contain no filament, as used in common incandescent or halogen light bulbs. For the remainder of this blog I will refer to the overall class of such lamps as UHP. The gas is under high pressure within a gas envelope and such lamps using this technology are most frequently referred to as a UHP ( Ultra High Pressure) lamp, or for certain less common variations they are referred to as a SHP ( Super High Pressure) lamp. The vast majority of projectors available today that are suitable for use in a home theater use mercury vapor arc lamps (bulbs) with the mercury vapor gas contained within a glass envelope. ![]() ![]() However, there are other factors that can impact the lamp life and it can be useful for the projector owner to understand what these factors are where their projector’s lamp actually is in its life cycle. Therefore, when a projector manufacturer specifies that a specific model of projector has, for example, a lamp life of 2000 hours that means that they expect the lamp to lose one half of its original (i.e, when the lamp was new) light output after 2000 hours of use. The industry standard for lamp life is based on a 50% dimming of the lamp. Understanding the characteristics of the lamps used in video projectors and going as far as to track the light output of your projector can be a useful exercise for some home theater owners.
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