Positive Fresnel Lens:
The light enters from one side, passes through the lens and exits on the other side, and is focused into a point or emitted as parallel light. The focus is on the other side of the light and is finitely conjugated. This type of lens is usually designed as a collimator lens (such as a Fresnel lens for projection, a magnifying glass, etc.) and a condenser lens (such as a heat-collecting and concentrating Fresnel lens for solar energy).
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Negative Fresnel Lens
Contrary to the positive Fresnel lens, the focal point is on the same side as the light, and the surface is usually coated as the first reflecting surface. -
