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.