there is one place most of us have seen an overhead projector, it's in
a classroom. These machines are valuable tools for teachers around the
world as a simple, cost-effective way to bring images to life for students.
In addition, overhead projectors are a standard tool in business allowing
professionals to create dynamic presentations with ease.
Types: There are two basic types of overhead projectors: transmissive and reflective. Transmissive projectors have the light source (bulb) in the base of the machine. The light is projected up through the glass stage of the projector, through a lens in the projector's head and then onto a projection screen. The light source for reflective projectors is in the head of the projector. The light shines down onto a reflective stage, and then reflects back up through the lens and onto a screen. Both types of projectors have their advantages. Transmissive projectors are usually brighter and the images are typically sharper, but they tend to be larger and heavier. If you want portability and will be only using transparency film, then a reflective projector is a good choice because they tend to be smaller and lighter in weight.
Before purchasing or using an overhead projector, it is a good idea to become familiar with the following components and options.
Lenses: Overhead projector lenses come in three different variations: singlet, doublet and triplet. The image projected will get sharper as your lens quality increases (singlet is the most basic lens; triplet is the most advanced). Not surprisingly, the price of an overhead projector increases with upgrades in lens quality. Also associated with the type of lens is the projector's focal length, which determines how close to or far from the screen the projector will focus.
Brightness: A projector's brightness is measured in lumens. Levels range from 1,700 to 11,000 lumens depending on the model you choose. Generally speaking, the type of image you are going to display (black/white or color), how far you intend to project your image, and the brightness of the room will dictate the desired brightness.
Lamps: Lamps are critical components of all overhead projectors and vary in type, life, wattage and cost. Some projectors offer high/low switches or are built to double the life of the lamp. These projectors can save you money in the future by reducing your lamp replacement costs. A lampchanger which allows the presenter to switch over to another lamp is also a very valuable feature. With a lampchanger, you can be assured that your meeting will continue if you do have a lamp fail.
Options: There are a variety of other options which are tailored to presenters who use LCD panels. These include built-in AC outlets on the projector and a "flip-in" magnifier. Two AC outlets are recommended on the projector: one for your LCD panel and the other for your computer. This makes setting up your equipment much easier. A flip-in magnifier is also a plus because it enlarges the projected image when using an LCD panel.
Stages on an overhead projector are the flat areas upon which transparency film is placed. Stages range from 10 inches to 11 1/4 inches, and it is important to ensure you have a stage that will work well with the size of your transparencies.
Lastly, an area which sometimes gets over looked is the warranty and ease of service for your overhead projector. A longer warranty is obviously the best choice, but also make sure that getting the equipment serviced is easy and convenient. Manufacturers who have servicing locations near you will make sure that you are not without your equipment for a long time.
projectors are versatile, cost-effective presentation tools that are easy
to use and transport. The key to making sure that you purchase the correct
model is to do a quick assessment of your needs and make sure that the
model you're considering fills them.
Copyright © 1998 3M
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