Analysis of a Fresnel lenses concentrator - IEEE Conference Publication

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The Fresnel lens consists of a series of concentric grooves etched in plastic. Thin and lightweight structures, small and large availability, and excellent focusing power make them useful in various applications. Fresnel lenses are most commonly used in light collection applications such as light collection systems or transmitter / detector settings. They can also be used as magnifying or projection lenses in lighting systems, as well as image recipes. The Fresnel lens replaces the surface of a conventional optical lens with a series of concentric grooves. These contours serve as individual refracting surfaces that bend parallel rays to a common focal length (Figure 1). Thus, while Fresnel lenses can physically focus light as well as conventional optical lenses under a narrow profile, they have several advantages over their thicker counterparts.

The largest Fresnel lens is called a superradiative Fresnel lens. When I decided to construct and equip Makapuu Point Light in Hawaii, there was one such shot. Instead of ordering a new lens it uses hundreds of prisms and a huge optical structure at a height of 7 meters (12 feet). There are two main types of Fresnel lenses, imaging and non-imaging. The imaging Fresnel lens produces a sharp image using a portion with a curved cross section while a non-imaging lens has a portion with a flat cross section and does not produce a sharp image. As the number of segments increases, the two lenses are similar to each other. In the abstract case of an infinite number of segments, the difference between curve segments and flat segments disappears.

The thin plastic you are using is called Fresnel lens. One side is flat and the other side is clear. The Fresnel lens we used for the first time in the 19th century functioned as a lens to focus the beam in the beacon light. A plastic Fresnel lens is used as a magnifying glass when a thin and light lens is required. Image quality is not as good as continuous glass lens quality, but in many applications (such as RV) perfect image quality is not required. The basic idea of ​​Fresnel lenses is simple. Imagine cutting a plastic magnifying lens into hundreds of concentric circles (such as annual rings). Each wheel is slightly thinner than the next wheel and focuses the light to the center. Now remove each ring and modify it so that one side is flat, making it the same thickness as the other rings. To maintain the ability of the ring to focus around the light, the angles of the ramps of each ring will be different.