1 . Overhead projectors
Business owners often use overhead projectors to present ideas visually during presentations. Overhead projectors display images onto a screen via a bright lamp, a large fresnel lens, a smaller objective lens and a mirror. Although overhead projector designs vary by manufacturer, design elements shared across manufacturers can pose certain dangers to you and your audience.
2 . Function
An overhead projector is a metal box with mirrors, lenses and a bright light. The bright light from a bulb reflects on the Fresnel lens inside the overhead. The light then bounces to a reflecting mirror under a stage where you set the overhead transparency. This image is in reverse form. A convex mirror then reflects an enlarged image with the proper orientation from the overhead transparency to a screen behind the speaker and the overhead.
3 . Types
The three types of overhead projectors are the transmissive, reflective and opaque. The transmissive overhead projector is the most commonly used type. It relies on the Fresnel lens to reflect the image from the overhead transparency to the screen. Reflective overhead projectors work from an overhead light source rather than one underneath the presenters hand as in a transmissive overhead projector. This type of overhead projector gets the most use in large auditoriums. An opaque overhead projector allows you to show three dimensional objects as well as overhead transparencies.
4 . Precautions
Business owners can reduce these dangers by using overhead projectors per manufacturer safety rules. For example, if you have a child who spends time with you at your business, don t allow her to play or stand near the projector at any time whether it s in use or not. Position the projector close to an electrical socket, or use bright yellow or red reflective tape to alert others of the cord s position. Additionally, move seats away from the projector. If your mouth or throat gets dry when speaking, place a drink several feet from the projector, excuse yourself during the presentation and walk a couple of steps to your drink when you need it.
5 . Toxins
Given that an overhead projector can overheat enough to make parts melt or catch fire, another danger of using this equipment is potential exposure to toxic smoke. When certain parts, such as plastic, metal or fire retardant chemicals heat up or burn in equipment, toxic chemicals and heavy metals enter the air. Even with adequate indoor ventilation, you might experience short term or long term health issues including skin or eye irritation, upper respiratory problems, headache, nausea, fatigue or cancer, or exacerbation of pre existing issues like asthma.
6 . Electrical
Because an overhead projector is an electrical device, it might experience a short or fire when plugged into an electric socket. For example, you might cause the projector to short if, while drinking a beverage during your presentation, you accidentally spill some of it into the projectors air vents or another opening. Additionally, an electrical short or fire might occur if you use the equipment without getting it checked out after it falls, or neglect to repair it if it has a bad part, such as a frayed cord or damaged plug.
7 . Falls
During a presentation, you might move around a lot or gesticulate with your hands. Unless you ve clamped or bolted the projector by its housing to the tabletop, you might knock it over. The projector might injure you or someone nearby as it falls. Additionally, if you position the cord over the side of the table or on the floor, you or a member of your audience might trip and fall bodily, pull the projector off the table, or both, resulting in injury.
8 . Heat
An overhead projector contains several parts that heat up during use. You might burn yourself on these parts if you don t wait for the projector to cool completely before performing maintenance or repairs, such as lamp replacement. Certain actions might also cause these and other parts, including the fan or electrical cord, to overheat and burn. For example, you might cause the projector to overheat if you block the cooling air vents, use an extension cord rated for less amperage or run the projector for a long period.
9 . Basic Understanding
Spend time going over the equipment manual in detail and practicing in advance. Learn where the On/Off switch is located and where the lamp is if you need to replace it mid presentation keep a spare bulb on hand for this purpose. Before the presentation begins, tape the electrical cord to the floor for safety reasons and clean the projector glass. Adjust the projector so the image is easily readable and sitting high on the screen to provide all audience members a good view of the information on the screen. Stand at the projector and face the audience during the presentation. Talk to the audience, not to the screen. Stand on one side to minimize distractions caused by your movements.
10 . Overhead Transparencies
When preparing transparencies, use a variety of colors and no more than six bullet points per page. Use large type that is easy to see and read from a distance when it is projected on the screen. Place a piece of paper underneath the first transparency so the screen is blank and dark even when the projector is turned on. Slide the paper to reveal one bullet point at a time. Judge from the audience s reaction when to move to the next bullet point or topic. Use blank transparencies with multicolored felt tip pens for spontaneous writing and to encourage participation from the audience.