To build lens Fresnel yourself need to have substantial understanding about the optics. Thus, in contrast to conventional lenses, the Fresnel is not solid glass, but of concentric rings, having in cross section a special form of prism. Perform calculations and define the boundaries of the zones of Fresnel. They are defined by the intersection of the wave front of an initial wave sequence offset relative to each other by l/2 wave fronts "of the projected wave".
Make a transparent ring, which will be odd zones of Fresnel. Their thickness should correspond to an additional phase of the RAID l/2 . For convenience, use the drawing.
To achieve the greatest effect, cover the ends of each prism are coated, for example, aluminum. Will solenice design, checking the position of the prism equation.
There are two types of lenses Fresnel – ring and waist. In contrast to the ring of the lens, guides the light flux in a specific direction, the belt spreads the light from the source in all directions. The lenses of Fresnel fields of application very diverse: from marine beacons and lenses to special film put on the rear window of the car to reduce the dead zone behind the car when using the rear view mirror.
Simultaneously with the creation of the lenses O. J. Fresnel had developed a complex technology of its manufacture. In a nutshell we are talking about the manufacture of lenses consisting of a set of several prisms in the form of thin rings. In the present context, such production is only possible using advanced high-precision processing, vacuum-deposition, control and measuring equipment.
In the manufacture of lenses of Fresnel technology is used HOTLENS holography, through which more precisely focuses the infrared radiation and reduces the penetration, for example, visible light. These lenses allow you to create more precise detection zone in space. In a set of technological equipment for the production of lenses of Fresnel includes precision lathes, which are used for trimming and pre-rounded blanks. Serotonergic machines for processing external and internal surfaces of the lens.
The most important stage – the grinding surface of the lens. It is held on the polishing machines. In the polishing process simultaneously removes roughness and improves the purity of the spherical surfaces of the lens. Special machine-polished edge of the lens, and for machining concave and convex surfaces of the lens are the special diamond tools. In addition, such companies made all the necessary technological equipment.
Advice 2 : How to make a lens
The lens is a transparent device, mainly from special glass designed to magnify the image. The lens is a major part of any optical system. Its principle of operation is based on refraction of light rays. To make a glass lens in the handicraft way is very difficult, especially without proper equipment in this case is not necessary. But based on the effect of light refraction, you can make a lens based on liquid.
You will need
- Plastic bottle, plasticine, glycerol, or water, syringe with needle, plastic bag.
Take a-liter plastic bottle. From the top of the bottle cut out two identical, convex circle (for convenience, cut out one circle and then it cut out the second diameter).
Then, take an ordinary clay or some other sticky material. This play-DOH glue both halves of the lens so that both sides of it was convex.
After that, in two places, between the halves of the lens make holes. In one of these holes with the syringe and pour the liquid (you can pour ordinary water, but it is better to use a liquid with a large refractive index, try to fill the lens with glycerin, the effect is better), fill it to the brim and it should not be air bubbles. The second hole is for air outlet, so as not to create pressure. After filling the lens with liquid paper over the holes.
In extreme conditions, for example, being in the forest in winter, not having matches, you can make a lens for a bonfire. For this, take an ordinary plastic bag and fill it with water. Give the package a spherical shape and let the water freeze. After freezing tear the package and get the lens. The lens can also be cut from the frozen ice.
Advice 3 : What is a Fresnel Lens
The Fresnel lens is almost the most first, according to the historical chronology, the device, which is based on the principle of light diffraction. Despite the remoteness of this invention, it today has not lost its relevance and has found application in many areas.
What is a Fresnel Lens
A Fresnel lens is called a compound lens. Unlike ordinary lenses, it does not consist of a solid polished piece of glass with a spherical surface and a concentric rings. They tightly abut each other and have small thickness. In cross section they present a prism of a special profile. The name of this type of lens was named who offered her a French physicist Augustin Fresnel, who worked in the field of physical optics.
Thanks to its unique design, this model of lens has a small weight and thickness. Section of her rings are constructed in such a way that its spherical aberration is very small, causing the rays, it refracted out of a single parallel beam. The diameter of Fresnel Lenses varies from a few centimetres up to several metres.
Fresnel lenses are subdivided into the ring and waist. First direct the beam of light in a single, predetermined direction. The second is to send the light from the source in all directions in one plane.
The Use Of Fresnel Lenses
To date, the Fresnel Lens has been widely used in many fields.
For example, they are used in large beacons, projection TV, navigation lights, railway traffic lights the lens and the lamps. And thanks to its low weight, the Fresnel Lens is also used in the lighting devices that you need in the process of operation to move.
And being placed on the rear window of the car in the form of a thin film, it greatly reduces the "dead" zone behind the car observed in the rear view mirror.
On the basis of Fresnel Lenses created extra flat light magnifier. It it is consulted by people with low vision when reading texts written in small font.
In addition, such lenses used in infra-red motion sensors and lens antennas.
There are a couple of promising directions in which possible to use of a Fresnel Lens. Its use is presumably possible when building the giant space telescopes of diameters.
Also probably its use as a solar concentrator for solar cells.
For all its virtues, the Fresnel Lens has one major drawback - the presence of a transitional boundary sites leads a high proportion of parasitic illumination and false images". This makes impossible its use in the construction of accurate optical images.