Magnification: 4-5 times
Suitable for solar concentrator， concentrating plane amplification effect is very good.
When sunny confetti easily ignite flammable materials， but also ignite wood.
Early in the 18th century (1748)， it is discovered that conventional lens only occurs at the surface refractive power， a middle portion removed as much as possible， while retaining the curvature of the surface， forming a thin planar lens， still able to maintain a good energy transmittance.
The Fresnel lens is formed of a thin planar lens， which looks like a sawtooth cross-sectional shape， but in fact each adjacent zigzag angle is constantly changing with changes in the angle of the light to converge to the same focal point .
Fresnel lens Category:
According to its focal point is not the same shape， can be divided into point focus Fresnel lens and line focus Fresnel lens.
Point focusing Fresnel lens
Viewed from the front like a dart board， by a ring a ring of concentric circles;
With respect to the linear Fresnel lens is a Fresnel lens focus point is concerned， the front shape look like blinds， from a cross-sectional view， a zigzag shape also changing the angle of the disc-shaped Fresnel lens is different， it kind of lens to focus light to form a straight line:
and good feedbck