Fresnel lens present in the overhead projector focuses the beam of light produced by the projection lamp. It projects itself to the optics in head assembly. Actually, a thin piece of plastic magnifying lens present in the overhead projection screen is known as th
e Fresnel lens, which is completely flat on one side and ridged on other. In most of the overhead projection screen, two pieces of thin acrylic lens are placed together, known as dual element Fresnel lens. But in fact, these lenses were used to focus the light beam on the lighthouse lamps.
The plastic lenses are used wherever a concentrated stream of light is required. Therefore, these lenses are used in the overhead projector where a concentrated light beam is used to project an image on the wall or screen. The function of Fresnel lens can be improved by the usage of spattering technology which is suited to the requirement of micro mini lens. It is indeed a delight to know that the performance of the lens can be calculated on the basis of coating degree and thus can be managed and controlled according to requirement.
Another advantage of the Fresnel lens is that it can easily reduce the amount of material used in building the lens in comparison to conventional spherical lens by dividing it into a set of concentric sections called Fresnel zones. Though a Fresnel lens appears to be a single glass piece, it actually is composed of numerous smaller pieces of glass. Fresnel lenses with a single piece are used in automobile headlamp, brake, parking and turn signal lenses, to name a few.