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What are Fresnel Lenses used for?

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Each Fresnel lens is built for a purpose. It depends on the application and reason for the lens that determines how the Fresnel lens is built and used. But for the most part Fresnel lenses were used where image quality was not an issue as much as the amount of light passing through the lens was. So what are some of the things that Fresnel lenses were made for? These include:

• Overhead projectors: Overhead projectors use Fresnel lenses quite often for the benefits they produce. If you look at a projector, you will notice a top piece of glass and a plastic lens below it. This plastic lens has a lot of circular lines on it. This is the Fresnel lens. The Fresnel lens in this case is used to project the light to a mirror which reflects the light to the board or screen.
• Projection televisions: Many high-definition or rear projection TVs use Fresnel lenses to transfer the light from the light source to the screen for viewing. Since Fresnel lenses are built to reflect light more than images, the Fresnel lens in a projection TV will provide more light for people to see. If you look at a screen of a high-definition TV or rear projection TV, you may notice the picture quality may not be as good as it should but the brightness may be exceptional. Newer Fresnel lenses are being developed so as to reflect images better as well as light. This will give your image more quality.
• Magnifying glasses: Magnifying glasses are used for magnifying an object so it appears larger than normal. The magnifying glass creates the magnified virtual image of the object behind the lens. But the length between the lens and the object must be shorter than the focal length of the lens in order to see the object in this manner. Focal length is the measure of how strongly the lens focuses light.
• Solar Forge: This is a device that uses the sun's energy to met materials including asphalt. The Fresnel lens purpose, in this kind of situation, is as a lid of a hollow standing cylinder. The lens takes the sun's radiation and focuses it on a point inside the cylinder. Inside the cylinder is material that is being melted. As a kid, did you ever take a magnifying glass in your backyard in the heat of summer, and aim the lens to a dry leaf on the ground? Did you notice the sun's rays going though the glass and shooting a beam of light at the leaf, eventually causing the leaf to burn? Well this is the same principal the Fresnel lenses do in solar forges.

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