A projector is able to accomplish a projection with the help of a combination of lenses along with the other technical things. A Fresnel lens projector is one which has different Fresnel lenses placed in the projector.
Fresnel Lens
Fresnel lens was invented by a French physicist, Augustin-Jean Fresnel. These lenses have a large aperture and a short focal length. They are very thin and are lighter in weight allowing more light to pass through. Thus, are used in the objects where bulky lenses are prohibited.
An Overhead projector (OHP) has a Fresnel lens. It has a box which acts as a stage area with a light lamp and a Fresnel lens on top of it which collimates the light. The box has a long arm which has a lens and a mirror used for focusing and redirecting the light. Transparencies are placed on top of the lens. The light travels from the lamp through the transparency and then into the mirror which is further displayed on the white screen. The projectors have the provision for the adjustment of the focal length of the Fresnel lens.
A low-profile overhead projector has a condensing lens system which has a combination of two lenses. It has a catadioptric Fresnel lens and a dioptric Fresnel lens. These lenses exhibit chromatic aberration. This means that if the catadioptric lens has negative dispersion then the dioprtic lens will be selected for positive dispersion and if the former has a positive dispersion then the latter is selected for negative dispersion. The dispersion of one lens cancels out the dispersion of the other lens. This results in collimation and dispersion of light. Overhead projectors are available in three optical designs: A) Direct Optics Configuration, B) Folded Optics or Chamber Optics and C) Reflected Optics.
The newer versions of the projectors like the LCD projectors have a little complex technology as compared to the simple lamp technology of the overhead projector. LCD projectors are the projectors which have Fresnel lenses placed in the active matrix LCD panel of the projector. Two lenses (one collimator and one collector) are used. The lenses are of different focal lengths. The collimator which has lower focal length is placed nearer to the light source and the collector is placed after the projection image.
LCD projector which is invented by Gene Dolgoff, are video projectors used to display video, images and computer data on a screen. They have the capability of producing higher lumen outputs resulting in better image quality. It gives an exceptional visual experience to its users.
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