The lens received the name in honor of the creator – the outstanding French physicist Augustin Jean Fresnel. From the usual optical lens consisting of an integral polished piece of glass, Fresnel's lens differs in more difficult design. It is not simple to make it in house conditions at all.
Instruction
1. To construct Fresnel's lens it is independently necessary to have essential an idea of optics. So, unlike usual lenses, Fresnel consists not of whole glass, and of the concentric rings having the special form of a prism in section. Make calculations and define borders of zones of Fresnel. They decide by crossing of the wave front of an initial wave on the sequence displaced from each other on l/2 of wave fronts of "the projected wave".
2. Make transparent rings which will close odd zones of Fresnel. Their thickness has to correspond to additional phase attack of l/2. For convenience use the drawing.
3. For achievement of the greatest effect cover faces of each prism with dusting, for example, aluminum. Joint a design, having checked the provision of prisms the equation.
4. Distinguish two types of lenses of Fresnel – ring and zone. Unlike the ring lenses directing a light stream in strictly certain direction zone spread light from a source in all directions. At Fresnel's lens of scope of application are very different: from sea lighthouses and photolenses to a special film which is imposed on back glass of the car for reduction of a dead zone behind car when using of a rear-view mirror.
5. Along with creation of a lens O.Zh. Fresnel developed the most difficult technology of its production. Briefly it is about production of the lens consisting of a set of several prisms in the form of thin rings. In modern conditions such production is possible only with use modern high-precision processing, vacuum napylitelnogo and the control and measuring equipment.
6. By production of lenses of Fresnel on HOTLENS technology the holography thanks to which infrared radiation is more precisely focused is used and hit, for example, of visible light decreases. Such lenses give the chance to create more exact zone of detection in space. Precision lathes on which the tortsevaniye and a preliminary curve of preparations is carried out are included in the package of processing equipment on production of lenses of Fresnel. On sferotokarny machines the processing of external and internal surfaces of lenses is made.
7. The major stage – grinding of a surface of a lens. It is carried out on polishing machines. In the course of polishing, roughnesses at the same time are removed and purity of spherical surfaces of lenses improves. On special machines edges of lenses are polished, and for processing of concave and convex surfaces of lenses special diamond cutters are used. Besides, at the similar enterprises all necessary industrial equipment is produced.