What is a Projector Lamp?

A projector lamp is a device used to make an image appear on a screen. Projector lamps are used most commonly in movie theaters, classrooms and conference rooms. Earlier versions of projector lamps were used in slide projectors to make tiny pictures appear much larger. They have been used for decades in old-fashioned movie reel projectors. Even though projector lamps have been ubiquitous in our culture for some time, they have become more technologically advanced in recent years. Today, projectors are capable of handling high definition television or movies, which is a huge improvement over older versions.

Types of Projector Lamps

There are three kinds of projector lamps: slide projectors, overhead projectors and multimedia projectors. Each has its own particular purpose and contains its own components. They can project slides, moving film or images and text on a transparent sheet of paper.

Overhead Projectors

An overhead projector consists of a bulb surrounded by a concave bowl-shaped mirror. The mirror is designed to reflect the light into a head positioned over the mirror. The head contains a second mirror that further reflects the light horizontally upwards, filling a drop-down screen. The primary disadvantage of an overhead projector is the heat produced by the halogen lamp. The light produced has a dim yellowish cast. A fan must be turned on to prevent the lamp from melting due to the intense heat created. The halogen bulb also does not last very long and needs to be replaced every 100 hours of usage or so.

More recent overhead projectors use liquid crystal display (LCD) technology. LCD projectors use arc lamps, which have a higher luminous efficacy and last for thousands of hours longer. The downside is the time it takes for the arc lamp to warm up before it can be used. Overhead projectors can be used to display graphs, charts and writing assignments before a large audience. They are the cheapest to purchase, usually costing less than $200.

Slide Projectors

These use a powerful lamp to project the images from 35 millimeter slides onto a screen. The projector consists of a circular canister with multiple slots for the slides. A mechanical device rotates each slide into position as a button is pressed by a human controller. Slides are often made from physical camera images so people can show pictures of vacations, sightseeing trips or other adventures. Slides are easy to store and last for a very long time. A typical slide projector costs between $200 to $300.

Multimedia Projectors

These are used to project images from films, newsreels and DVDs onto a screen or a blank wall. They are the most expensive type of projector lamp. A good quality multimedia projector will cost well over $500. Multimedia projectors are most often used in home theater and home entertainment systems.

The Components of a Projector Lamp

Multiple high-tech components are used to make a projector lamp. Pressurized mercury vapor, an arc tube, a quartz globe or reflector, electrical wiring, a spoke, a bolt, a screw and a fastener are all used to make one of these lamps. The arc tube is the device that actually generates the light. Pressurized mercury vapor inside the arc tube is ignited by high voltage electricity modulated by electrical ballasts. The quartz globe focuses the light produced by the arc tube. The fastener, bolt and screw mount the electrical wiring that carries power to the arc tube. The entire assembly is encased in plastic housing.

Alternative designs use metal halide bulbs to generate light instead of arc tubes with pressurized mercury vapor. Which design is used depends on the manufacturer in question. Projector lamps are extremely useful and always carry a respectable price.