What is a Fresnel lens?

Fresnel lens is based on the French photophysicist “FRESNEL” invented the principle of design using different processing methods (ultra-precision computer numerical control machine tool technology, electroforming mold technology and PE (polyethylene) material suppression process). The first in 1800 used in the navigation lighthouse, after the extension with so far, now more use of polyethylene plastic injection molding process.
Fresnel lens (Fresnel lens), also known as thread lens, mostly made of polyolefin material injection of thin slices, but also made of glass, the surface of the lens side of the smooth side, the other side burned from small to large concentric circles , Which is a fine structure of the optical components, from the front to see it like a dart plate, by a ring of concentric circles. Its texture is the use of light interference and interference and according to the relative sensitivity and reception angle requirements to design, the lens requirements are high.

Its working principle is very simple: Suppose a lens of the refractive energy only occurs in the optical surface (such as: lens surface), remove as much as possible optical materials, while retaining the curvature of the surface.
Another understanding is that the lens continuous surface part “collapsed” to a plane. From the profile, the surface consists of a series of zigzag groove, the central part of the oval arc, each groove with the adjacent groove between the different angles, but will focus on one light, the formation of the central focus, That is the focus of the lens. Each groove can be seen as a separate small lens, the light is adjusted to parallel light or condenser. This lens also eliminates part of the spherical aberration.

Fresnel lens classification
1 from the optical design up division:
A) positive Fresnel lens:
The light enters from one side and passes through the Fresnel lens on the other side to focus on one or the parallel light. Focus on the other side of the light, and is a finite conjugate.
This type of lens is usually designed as a collimator (such as projection with Fresnel lens, magnifying glass) and condenser lens (such as solar concentrating heat with Fresnel lens.
B) negative Fresnel lens:
In contrast to the positive chenille lens, the focus and light are on the same side, usually on its surface, as a first reflective surface.

2 Structured:
A) round Fresnel lens
B) Fresnel lens array
C) Columnar Fresnel lens
D) Linear Fresnel lenses
E) diffraction of Fresnel lenses
F) Fresnel reflection lens
G) Fresnel beam splitter and Fresnel prism.

Fresnel lens application
Fresnel lenses are used in a number of fields, including:
Projection display: Fresnel projection TV, rear projection Fresnel screen, overhead projector, collimator
Spotlight: solar Fresnel lens, projection with Fresnel spotlight, Fresnel magnifier
Air Navigation: Lighthouse with Fresnel lens, Fresnel flight simulation
Scientific research: laser detection systems
Infrared detection: passive motion detectors
Lighting optics: car headlights, traffic signs, optical landing system

Fresnel lens compared with the traditional lens, with a large area, light weight, relatively low price, easy to carry, etc., is a very wide range of optical components, its design and manufacture of a number of technical areas, including Optical engineering, polymer materials engineering, CNC machining, diamond turning process, nickel plating process; molding, injection molding, casting and other manufacturing processes. Therefore, large-scale, high-precision Fresnel lens design, development and production of the current US-US technology production sector technology development of the main direction.

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