An overhead projector is the most basic form of a projector. The projector consists of a cooling fan and a bright light that enlarges to form an image on the screen. The overhead projector was widely used in business meetings and classrooms. Still, with the advancement in technology and the availability of more fine projectors, the popularity of overhead projectors is declining. But this decline in popularity does not affect the usefulness of an overhead projector. In this article, let’s learn more about overhead projectors.

History of an overhead projector

The overhead projector was developed in the 1850s in France. The credit for its creation can be given to the French inventor, Jules Duboscq. The inventor also developed other optical devices such as the stereoscope, colorimeter, and polarimeter. Although overhead projectors could not make it to fame then, in 1945, they were used as an important tool by the U.S. army to train its service members during World War 2.

In 1954 before the overhead projectors became an inseparable tool in the classrooms, it was used to project scores in the bowling alleys. After that, there was no looking back for overhead projectors as they were popular in both classrooms and corporate meetings. The main reason for their popularity was because they were easy to handle and also cost-effective.

Types of overhead projectors

Inherently, only one type of projection material qualifies as overhead projection, and that is transmissive. But somehow, when discussing with inexpert presenters, the comparison lines get blurred. So you should at least know one of these two types of equipment used in the projections.

Transmissive 

A very bright light source is introduced in transmissive projection through a transparent material. The texts or graphics present on the surface of the material are projected into a series of different lenses and mirrors, which then display the resulting images on the screen. This projection method is widely used in classrooms, corporate meetings, seminars, and conferences as it does not require many services. The machine has only a few Motor parts and a bulb which needs to be changed periodically.

Reflective 

In reflective projection, as the name suggests, rather than traveling through the source material, the light reflects (bounces off) from its surface. The sequence of mirrors and lenses, which are used to project the image on the screen, can produce an enlarged image. Therefore this ability to magnify the source makes this method perfect for images that need to be presented on a larger scale.

How to use an overhead projector

Whether you are a professional overhead projectionist or projecting for the first time, you can do just fine in both scenarios if you follow the below-written tips on how to use an overhead projector.

• Place the projector on a low table. The table could be 2-3 feet off the ground.
• Ensure that the power source to the projector is reliable.
• Take the overhead transparency and place it over the flat glass surface.
• You can directly write on the transparency with the help of a wet erase overhead pen, or you can also put the transparency into a laser printer, and information can directly be printed on that.
• Switch on the projector. Usually, the overhead projectors have a big red power button to switch on and off.
• Tilt the mirror on the top and set its angle until the image is displayed on the projection wall or screen.
• Move the table on which the projector is set if you want to change the image size. Move it until the image fits on the screen.
• There is a circular knob on the projection arm of the projector. Turn this knob until you get a sharp and focused image on the screen.
• Turn off the projector after use. You can use it again after it has completely cooled down.

To know more about using overhead projectors, check out this piece.

Advantages of an overhead projector

Simple technology 

An overhead projector uses simple technology, which includes a bright lamp and a series of lenses and mirrors. With the help of this combination, the image is projected onto the screen. It does not require very vast technical knowledge or support. Nor does it require cables, software, or troubleshooting. Anyone provided with proper guidance and tips can use an overhead projector properly.

Transparency 

Although transparency films cost more than regular paper, they can be used however you want in a presentation. You can directly write on the transparency with the help of a wet erase overhead pen, or you can also put the transparency into a laser printer, and information can directly be printed on that. 

Cost of equipment 

Overhead projectors are cheap compared to their other LCD-based cousins. It uses simple technology, which includes a bright lamp and a series of lenses and mirrors. It does not require a lot of services. It only requires an occasional change of the light bulb.

Tips and tricks for an overhead projector presentation

• Using the project like a chalkboard with acetate or rolling the transparency sheet, you can use the project. You can also use wet soluble pens on the sheets.
• Do not face the screen while presenting, but face the audience.
• Cover the transparency sheet with an opaque cover once you are done using it 
• Bring a spare bulb and gloves to avoid bulb burnout during the presentation. Change the old bulb, but be very careful as the bulb will be hot.
• Place the screen diagonal to you to not block the screen from the viewers.