Types, characteristics, and functions of an overhead projector

An overhead projector (OHP) is an output device that enlarges and projects images into a bigger surface. The images can be static, like data, graphical, or moving images (video). The projector does this by passing the image to be projected through a lens that enlarges the image. Read more on how projectors work.

Types of overhead projectors include LCD, DLP, LCoS, and LED projectors. if you are buying a new projector screen ensure you check resolution, brightness, contrast, lamp life, price, warranty, and brand type among other factors.

overhead projector

Functions and benefits of an overhead projector

  1. Content presentation

They are mainly used for the presentation of content. The presentation can be done by different people in different professions.
A lecturer can use a projector to present lectures to his student in a classroom. A manager can use it also to present the company’s growth over the past year and so on. So in general a projector is used by any person who wants to communicate with a large group of people. Today almost every company and business enterprise owns a projector.

The presentation can be created using a variety of presentation software in the market. They offer the user ways of creating slides that can be used to represent an ideal per slide. The common presentation software is MS PowerPoint from Microsoft Corporation.

  1. Clarity of data or information

A projector can also be used to enlarge images that are small and viewing them directly will strain the eyes and won`t give the required information. For example, an object from a crime scene can be projected to try and get the information inscribed on a surface.

  1. Watching movies

Projectors are used in movie theatres to enlarge the movie on a larger surface. This allows more people to watch the same movie.

4. Comfortable with the eyes

Since the projector enlarges the image to a bigger surface it reduces eye strain.

Type of overhead projectors (OHP)

3 types are used today depending on the technology that they use.

a) LCD projectors

They are also known as 3LCD because they use light that is passed through 3 LCD panels before it is projected on the surface. These are the most common type of projectors. They are advanced from the slide projector that was used to project small images to enlarge them. They are small and have better performance than the slide projectors.

b) DLP projectors

Digital Light Processing projectors. It is made up of a DLP chip which is composed of many micro-mirrors. The light is reflected off these mirrors through a lens and onto the projection surface. The mirrors are movable and can be used to display different colors.

c) LCoS projectors:

Liquid Crystal on Silicon. The liquid crystals are arranged in silicon. The light is then passed through the silicon to the projection screen. They are better than others but they are more expensive.

d) LED projectors:

These projectors can use any of the other technology but the source of light is Light Emitting Diode instead of the lamp that is used by the other. Also, some projectors that use laser beams are in use today.

Characteristics of an overhead projector to consider when buying

When you need to acquire an overhead projector you can check on the following feature and characteristics to ensure you get the best.

1. Projector weight

The weight of the projector may be considered if you intend to be carrying it around. If you intend to use it as a fixed projector then weight may not matter that much. LCD projectors are known to be a bit heavy than DLP. Most common overhead projectors are portable.

2. Resolution

It is the measure of the number of dots per inch that the projector can give (dots per square inch). The higher the number of dots the better the image clarity. A 1024 X 768 is good for a detailed clear presentation. Again the resolution may be affected by the source of data resolution. If the source of data has high then the overall resolution will be good.

3. Price

Depending on the budget that you have for the projector that you want, you can get varying prices. Follow your budget, but remember sometimes cheap may end up being expensive.

4. Brightness and contrast

Brightness is measured in lumens. Higher numbers of lumens are better, for a bigger room that needs more light. For a smaller room around 800 lumens is good brightness.

Contrast is the difference between the bright and dark parts of the image. The high the ratio the clearer the image. Select a projector with high contrast ratio.

5. Lamp life

For the projector that uses a lamp as a source of light, you may want to consider the life of the lamp. Choose a projector that has a high lamp life because replacing a new lamp will mean extra cost.

6. Connection Port

The different projector comes with different ways of connecting to the source of data, and power. They include USB, WIFI, VGA, HDMI, and DVI for data connectors. Choose one that offers more than one way of connecting to the source.

7. Type of projector

Depending on the preference one may want to consider a projector type and manufacturer.

8. Warranty

Check the period that the manufacturer offers a warranty and the type. Can it be returned or repaired in case it has a problem? A more warranty period means the company has confidence in its product.

Connecting the overhead projector to a laptop

Connect the projector to the power source, and then connect the VGA cable on one side to the laptop and the other side to the projector VGA port. Tighten the cables to the ports by screwing. Press the power button on the projector to switch it on. When the projector is fully on and ready the light on the “ON button” should turn to green.

When using a laptop the VGA cable should be connected to the port labeled INPUT and not MONITOR. After the connection, the projection is by now supposed to be that on the laptop.

If no display yet you can either use the FN key with one of the function keys with a symbol of a monitor, for laptop users, (the function key with the symbol may vary from one laptop to another).

You can also go to the laptop control panel then display and click on connect to the projector it will give you options (for those using Windows). It gives the option of viewing from a laptop screen alone, both projector and laptop screen and projector only. The below image shows the option offered in Windows 7.

window projector setting

After connection, the next thing that you can do to get the best image is use the function on the projector, like focusing the image, increasing brightness, and the like.

With that, you will be ready to go. Make sure your laptop is not set to go on sleep mode or have a screen saver because most of the time it may interrupt your presentation.

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