Looking into the 7 important parts of an overhead projector

Projectors have become commonplace objects in all walks of life. Be it schools, colleges, or offices, having presentations is now an everyday thing. Humans have always responded better to visual representative tools better. It is a way of life. We learn by observing.

Overhead projectors dominated boardrooms until the data projector was invented. We have broken down the parts of an overhead projector to help you better understand. You may make substantial slides on transparency film and project them onto the space. You could even use wet-erase markers to write directly on the slide, fusing your presentation with a whiteboard. Even though they are now considerably less common, overhead projectors are still handy for sharing old transparencies or making fully interactive presentations.

the major parts of an overhead projector

There are a few key parts to the overhead projector. These parts cooperate to allow the overhead projector to carry out its intended function, just like with any machine or gadget (projecting an image onto a screen). Minor components like screws, nuts, and bolts hold together the major components of an object.

Therefore, it should only make sense that an everyday object like the overhead projector be understood by those handling it. In this article, we’ll be looking at the main parts of an overhead projector. 


Breaking Down The Parts of an overhead projector

Reflector and Lamp

A lamp that provides light is housed in the overhead projector’s base unit. A reflector is placed behind the lamp to direct the light in front of a mirror. A extremely weak projected picture would result from the light being scattered inside the base without this reflector. A condenser is located in the unit’s base between the bulb and the mirror. The light is directed or concentrated onto the mirror.

The box at the bottom of an overhead projector is its biggest component. Two essential parts of the box are a bulb and a cooling fan. To produce thousands of lumens of light, overhead projector lamps often use hundreds of watts of power.

They have two significant flaws. The lamp life of many projectors is around 100 hours due to the fact that many of them employ a filament similar to a typical incandescent light bulb that soon burns out. Second, they produce a lot of heat, which is dissipated outside the box by a cooling fan that occasionally spins too quickly and is too loud.


A cooling fan is required in the base unit since the bulb produces heat that must be dissipated. A blower that accomplishes this function is housed in the base unit. An electric motor drives the blower. A fan attached to the motor shaft distributes coolant throughout the device’s base.

Projection Media

A projector is nothing more than a large light box without projection material. Transparency film is commonly used with overhead projectors. Transparencies are typically constructed of acetate, are frequently letter-sized, and can be purchased with a variety of surfaces that enable writing, copying, laser printing, and inkjet printing. A projection panel can also be used if you need to use your overhead projector to display images from a computer or other video source. These resemble laptop screens but don’t have a back panel or back lighting. Similar to a data projector for a liquid crystal display, light from the projector goes through them and into the focusing lens.

Plate glass plus Fresnel lenses

Fresnel Lens
Fresnel Lens

On top of the projector’s main box is a sizable piece of glass known as the stage glass, which is where you set your slide or projection panel. The projector contains a unique kind of lens called a fresnel lens underneath that glass. These lenses, which are mainly composed of plastic, amplify the bulb, spreading its light over the entire plate glass. Credit-card sized magnifiers also use Fresnel lenses.

Transparencies are laid out for projection on the glass surface that serves as the overhead projector’s stage. The picture is magnified and focused upward on the projection stage using a Fresnel lens. A substance called a Fresnel lens has a surface made up of concentric rings that gives it a hazy or fuzzy appearance.

Upper Lens Assembly

The light that travels from the bulb through the fresnel lens and the projection media is collected and projected by the projector’s upper lens assembly, or head. While the head features a mirror that directs the light outward through its side-facing port or lens, the side facing down towards the stage glass has a lens. The head is typically height-adjustable so you can change the image’s focus.

Another set of parts is located above the stage and consists of a focusing knob, an objective lens that collects light coming through the Fresnel lens, and another mirror that projects the image onto a projection screen. To focus the image on the projection screen, turning the focusing knob causes the upper unit to move up or down.

Similar to a film or slide projector, an overhead projector (commonly abbreviated as OHP) uses light to display an enlarged image on a screen, allowing a large audience to view a small document or picture.

The picture to be projected is either printed or handwritten or drawn on a page-sized sheet of transparent plastic film, which is also referred to as a “foil” or “transparency” in an overhead projector. These are put on the projector’s glass platen, which is above and below by a projecting mirror and lens assembly (hence, “overhead”). Before video projectors became common, they were extensively employed in both business and education.

Parts of an overhead projector
Quip recap of the parts of the projector

To know more about overhead projectors, click here to read our article on guiding you to understand overhead projectors. Click right here to watch a video about the components of an overhead projector.

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