Suqare fresnel lens

** What is a Fresnel lens used for?
    Fresnel lens, succession of concentric rings, each consisting of an element of a simple lens, assembled in proper relationship on a flat surface to provide a short focal length. The Fresnel lens is used particularly in lighthouses and searchlights to concentrate the light into a relatively narrow beam.

**  What can I do with a Fresnel lens?
    Since plastic Fresnel lenses can be made larger than glass lenses, as well as being much cheaper and lighter, they are used in industrial applications to concentrate sunlight for heating in solar cookers, in solar forges, and in solar collectors used to heat water for domestic use.

**  How are Fresnel lenses made?
    The basic idea behind a Fresnel lens is simple. Imagine taking a plastic magnifying glass lens and slicing it into a hundred concentric rings (like the rings of a tree). Each ring is slightly thinner than the next and focuses the light toward the center. … Large Fresnel lenses are often used as solar concentrators.

**  Are glass lens better than plastic?
    Glass is much more scratch resistant than plastic, making the glasses last longer. … Plastic lenses are less reflective than glass lenses, making them clearer and less prone to glare. Glass lenses generally have a higher index than plastic lenses, making them slightly thinner and more attractive looking.