Topic
A Fresnel lens possesses a large aperture and a short focal length, which allows it to capture and focus more from a light source than a conventional lens, and project it over vast distances while needing less mass and amount of material than a traditional lens would for the same characteristics. This allows them to be much thinner and comfortable in their application. These qualities are achieved by dividing the surface of the lens into a large number of ring-shaped concentric sections. The effectiveness of the lens increases number rings on the surface.
Nowadays Fresnel lenses have numerous applications in the modern society, and their value is hard to overestimate.
Discovery
Shipping played a pivotal role in the global commerce in the eighteenth and nineteenth centuries. It was essential for trade between coastal countries, as well as intercontinental trade. Traveling at sea was a dangerous endeavor, and many lives and thousands of tons of cargo were lost due to crashing into rocks or shallows. To combat this problem, a lot of research began into more efficient lighthouse construction. At that point, they were still very inefficient, and could not always serve as an adequate the beacon. This led to the invention of the Fresnel lens.
The concept of a more compact, thinner lens, with a surface covered in multiple concentric circular sections, has been circulating since the mid-nineteenth century and was discussed in the works of the French naturalist Georges-Louis Leclerc and mathematician Nicolas de Condorcet. However, it was not until 1823 that the first multipart lens was fully developed and utilizes. The credit for constructing this lens is attributed to the French engineer and physicist Augustin-Kean Fresnel, who built it for the Cordouan lighthouse on the Gironde estuary. Its light was focused and powerful enough that it could be seen from the distance of 20 miles (Beck par.1-4).
Development
The manufacturing process of the Fresnel lenses has evolved remarkably since their invention. In the eighteenth century, the process consisted of a continuous, procedural polishing of the glass by the workers themselves. The process was eventually simplified when the expertise became advanced enough that the lens could be developed by pouring molten glass into metal molds to give them the required shape.
However, at that point, it was still very expensive and did not become a practical and widespread technology until the twentieth century, with the advent of high-quality plastic, applicable for optical purposes, and the creation of the injection-molding technology. As a result of these advancements, a variety of materials became available for the manufacture of Fresnel lenses. These include acrylic, which is the most widely used material, rigid vinyl, and polycarbonate, and the choice depends on the desired wavelength (“Advantages of Fresnel Lenses” par.4-6).
Applications
Nowadays, Fresnel lenses are mostly used in devices designed to capture and collect light, to condense it or, as with lighthouses, to collimate it. Based on the presence or lack of a curve, they are differentiated into imaging lenses, which have curved cross-sections and produce sharp images, and non-imaging lenses, which are flat and don’t provide image sharpness.
Imaging lenses are used in a number of industries, including medicine, for correcting certain visual disorders, old televisions, applications in the automobile industry, which allow drivers better perception of the road around him. A particular particularly significant use is in photography since the use of Fresnel lenses reduces the size of the telephoto parts of the cameras.
Non-imaging lenses are used when quality if the image is not relevant. For example, they are utilized in traffic lights and automobile lamps, to make them more visible over distances and in general in illumination equipment (“Fresnel Lenses” p.7-9).
Works Cited
Advantages of Fresnel Lenses n.d. Web.
Beck, Adam n.d. The Million Dollar Lens: The Science and History behind the Fresnel Lighthouse Lens. Web.
Fresnel Lenses 2014. Web.