Fresnel lenses are composed of a series of concentric grooves etched into one side of a sheet of plastic. Fresnel lenses are unlike typical spherical or aspherical optical lenses. The grooves of Fresnel Lenses act as individual refracting surfaces, making these lenses ideal for solar concentration, solar cell heat collection, overhead projection, and non-imaging light focusing applications. Monica Rainey, Optical Engineer, explains the advantages, disadvantages, and applications of these unique lenses. To learn more, read our Advantages of Fresnel Lenses application note.
Hi, I'm Monica one of the optical engineers here at Edmund Optics. Today I would like to talk with you about fresnel lenses and common applications in which they are used. A fresnel lens is a unique type of lens that operates differently than typical spherical or even aspheric lenses. They are composed of a series of concentric grooves etched into one side of a sheet of plastic like you see in this figure. The grooves in fresnel lenses act as individual refracting surfaces which bend parallel rays in a similar fashion to a conventional lens and thus have similarly specified focal lengths. However, fresnel lenses have a lighter and thinner design, far less absorption due to the smaller thickness and a larger variety of size options. Fresnel lenses have a variety of applications but are not appropriate in all optical systems. The drawbacks of these lenses include: chromatic aberration when used with broadband sources, distortion to any images formed, and poor image quality when used in imaging systems. Though still not recommended, higher groove densities do provide slightly better image formation. In our catalog you will find both spherical and aspheric fresnel lenses. One common application of fresnel lenses is solar collection. Due to the availability of fresnel lenses in large sizes they are the ideal choice for focusing sunlight to heat a sample placed at the focal point of the lens. They are also commonly used to collect light for solar cell heat collectors. Aspheric fresnel lenses will provide better light concentrating ability than a conventional spherical fresnel lens. Smaller fresnel lenses can accomplish the same focusing abilities as in a solar collection setup but on a smaller scale. They can collimate light emitted from LEDs or other light sources or can be used to focus light into sensors in a non-imaging setup. Fresnel lenses are also common in illumination systems since they are very useful for providing even illumination from non-uniform light sources. You have probably seen older projection TVs that have a large fresnel lens behind the screen or overhead projectors with a fresnel lens under the transparency to evenly illuminate the viewing screen. Although fresnel lenses are not recommended for imaging systems, they can be used as large magnifiers or to relay an image where image quality requirements are not stringent, and a glass lens may prove impractical. I hope this answers your questions about fresnel lenses and their unique applications. You can browse more of our technical application notes and videos to learn more key concepts and find answers to our common questions on our website.
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