What is an Overhead Projector?

What is an Overhead Projector?

The overhead projector is probably one of the most versatile and useful visual aids that has been made available to the modern-day lecturer.
The overhead projector has long since replaced the traditional chalkboard as one of the main teaching aids and is used in lecture theaters and classrooms all over the world. Even though computer-based data projectors are increasing in popularity, they are indeed very expensive, and this means that they are in no way a match for the overhead projector. Therefore, it is very important for lecturers and teachers to know how to use the projectors effectively, so as to exploit its potential to the maximum level.

Beneficial Strengths

Teacher-Student Communication

This projector definitely has a number of advantages that would outdo most other visual teaching aids. For instance, a lecturer can use it in just the same way that he or she would use a chalkboard, but the biggest advantage would be that with the projector, lecturers all over the world now get to face the whole class and maintain eye contact all times with their students instead of having to turn around and write. As a teacher, you would know that this eye contact plays a very big role in both facilitative as well as expository teaching, and serves both as a means of receiving feedback from the class on how good or bad the session is and as an outward non-verbal communication medium for the teacher.

Multipurpose Tool

Another very important benefit that the projector has over the chalkboard is that it is multipurpose and can be used to present prior prepared material, which enables lecturers to build notes, tables, diagrams, and so on; and these can be used anytime, repeatedly. If designed well and planned well, these overhead transparencies will provide all the aides and cues that are needed during a lecture, so that you don't have to resort to the conventional note taking. These overhead transparencies are fairly compact when you compare them with some of the other types of visual aids, like charts and can easily be stored in boxes, folders, files, or large envelopes.


As compared to most other projected visual aids, the projector also has another big advantage, as it does not require a room to be darkened, so it allows students to take notes easily. It can also be used in any kind of room, except ones with extreme bright lights or in the direct sunlight. The projector is quiet, 'user-friendly', and clean and requires no technical knowledge or skill on the part of the person operating it, apart, of course, from the ability to change the lamps occasionally.

Possible Weaknesses
  • The drawbacks of this projector include the basic fact that it requires a constant power supply and also requires a white flat surface on which its image can be projected.
  • Another disadvantage is that if the surface is not suitable inclined at the correct angle, the image will suffer from a phenomenon called 'keystoning'.
  • Unlike marker boards and chalkboards, these projectors require a small amount of maintenance. They are more likely to crack or break, so you must be very careful and always keep a spare bulb close at hand.
  • Another disadvantage is that some teachers find the glare that is emitted from the projector quite bothersome, even though this can be overcome by attaching a shade to the device.
  • Besides these hardware 'glitches', the basic problems that are associated with the projectors arise from the fact that most users do not really provide enough thought or consideration to the production of their display material. The writing is generally too untidy or too small and can't be read easily, and apart from this, it could also extend beyond the area of transparency.
  • Lecturers and teachers always forget that this illuminated projection area in the projector is not the same exact size as the acetate sheets that produce the transparencies. However, most projectors are still of the older 'square' variety.
  • Lastly, lecturers and teachers tend to overuse these projectors only because they are so convenient. They employ it in situations where, on other occasions, other visual aids would have been more effective.
I hope this article has been able to answer your doubts regarding this useful device. Like most appliances, this one too requires proper care and maintenance, so use it carefully, and maintain it well.
Teaching with Overhead Projector
Overhead Projector on White