In the past, the approach to the coast for the Mariners was the most dangerous part of their journey.Due to adverse weather conditions or stranded coastal cliffs could cause a wreck.Rescued sailors beacons best navigational structure of that time.For a long time on their tops just stoked the fires and later served as sources of light kerosene lamps until electricity began to be used.In the XIX century, light, life-saving, became a Fresnel lens that makes the light beacon most bright and visible from afar.
Composite complex lens was created Augustin Fresnel, French physicist, founder of the wave theory of light.Fresnel lens composed of a small thickness of individual concentric rings adjacent to each other and forming a cylinder with a light source inside.The rings have a sectional shape of a prism.Each of the rings of light into a narrow beam of parallel rays, diverging from the center.When the cylinder rotates around the light source light rays extending to the horizon.Color rays, their number, the time interval between them is special unique handwriting lighthouse.A summary of the characteristics of the various lighthouses had on board ships, and it is for her sailors learned a lighthouse in front of them.
Fresnel lens installed on lighthouses, is an important step in equipping them with powerful light sources.These complex composite lens made it possible to increase the concentration of the light intensity of up to 80 000 cd.Before the invention of the Fresnel focus light or lamp burning wick could only putting the lantern into focus a converging lens of a sufficiently large diameter or a concave mirror.For this purpose a one-piece optical element requires a large size, which, under the influence of its own weight could burst.Therefore, used dozens of concave mirrors, the focus of each of them was a single lantern.This decision was uncomfortable.
Composite Fresnel lens has helped to achieve the increase of intensity, its concentration in a given direction.The assembly of individual optical elements do not reflect light, and worked up to the light, revolving around a radiating in all directions at a constant intensity of the light source.
Since the construction of Fresnel remain unsurpassed technical device used not only for river buoys and lighthouses.In a first Fresnel lens made of glass of different signaling lamps, traffic lights, car headlights, projector parts lecture.Then it was created the magnifying glass in the form of lines, made of transparent plastic, with inconspicuous circular grooves, each of which is a tiny ring prism, but in general they are a converging lens.The resulting lens is used as a magnifying glass to enlarge the subject as the camera lens, which creates an inverted image.
Over time, the scope of the Fresnel lens has expanded considerably.It includes the development of photographic equipment, different lighting, security systems, surveillance equipment, a hub for solar energy collectors, the mirrors used in telescopes.The optical properties of the lenses are also used in the field of multimedia.So, by DNP, the largest producer of high-tech projection screens, on the basis of the lens are screens Supernova.A rear projection screen is used not only Fresnel lens, but other optical technology to provide a unique means of display.
Depending on the application, the lens may have a different diameter, vary by type.There are two types of lenses: the ring and belt.First set up to direct the light beam in one direction.Circular lenses have been used in manual work with small details, displacing ordinary magnifying glass.Belt lens capable of transmitting light beams in any given direction, is used in the industrial sector.
Fresnel lens can be positive (collecting) and negative (diverging).Negative polyvinyl lens with a short focal point significantly increases the field of view.She is known as a Fresnel lens parking.Expansion of the viewing angle, which it provides, allows you to see obstacles that are at the bottom of the car, outside the field of view side mirror or rearview mirror.This lens is much easier to maneuver when parking, towing a trailer, and reversing, avoiding collision with playing children, animals or other objects.
Fresnel lens has become a multifunctional tool, its invention played an important role in the development of the technological sphere.
