Portable Overhead Projectors

Overhead Projectors
The Overhead projectors are commonly used by teachers in schools, colleges and universities. Most of the people must have seen overhead projectors in their daily lives. It can be described as a huge box containing a long overhead lamp and a powerful fan to cool it off, there is a lens placed inside the box. The transparent paper containing an image, wordings, diagrams are placed on the top of the box, the shining light from the overhead lamp passes through the transparent paper and the lens and then it is shone forward onto a screen which allow the entire class to see it clearly.

Latest overhead projectors offer an adjustment wheel on the lamp of the projector so that the height of the overhead lamp can be adjusted to focus the image, This is also to make the projected image bigger or smaller depending upon the distance of the overhead projector and the screen or the size of the room where the projector is placed. Most overhead projectors use high wattage halogen lamp that may consume up to 750 watts, due to this high heat output a powerful blower is required to keep the bulb from melting itself. Sometimes the high heat causes the halogen lamp to fail quickly. For this reason an arc lamp is used in modern LCD or DLP which is more reliable, lasting for more than thousands of hours, produce much more light with less wattage and much more energy efficient as compared to halogen lamp.

There are three types of overhead projectors easily available in the market today and these are stage, portables and briefcase. The stage overhead projector is the biggest as compared to the other overhead projectors. It has its own base with the power cord fixed in the base. Some advantages of the stage overhead projector are improved imaging, correction of color and extra bulb. The disadvantages are that they need a fan to keep the bulb from melting itself. Handling is very difficult because of huge size and weight of the projector and if you want to change the place of the projector you will need a cart.

The portable overhead projector folds down and can easily be transported from one location to another. The light comes from the head of the unit down through the transparent paper and a mirror that bounces the image to the screen. Overhead projectors require no fan, give better imaging and are light weight and portable.

The briefcase overhead projector folds down into a case approximately to the size of a briefcase and works just like the portable overhead projector. The biggest advantage of this type of projector is the size that makes it easily transportable from one place to another without any problem. Some disadvantages are that it gets hot and has no spare bulb at all.
If you are planning to purchase an overhead projector for yourself then it is better to have some know how of it. You can also find used overhead projectors and its parts online through retailers and online shopping sites. You should know your liking and budget and so you should also keep in mind the comparison of a variety of overhead projectors.