Fresnel Lens Characteristics

When a conventional convex lens is used, the edges and corners tend to appear dimmer and blurrier. This is because light refraction occurs only at the interface between different media; in a thick convex lens, the portion of the light that travels in a straight line through the glass leads to attenuation. If the straight-line propagation segment could be eliminated, retaining only the curved surface where refraction takes place, substantial material could be saved while achieving the same focusing performance.

When a conventional convex lens is used, the edges and corners tend to appear darker and blurrier. This is because light refraction occurs only at the interface between different media; in a thick convex lens, the portion of the light that travels in a straight line through the glass undergoes attenuation. If the straight-line propagation segment could be eliminated, leaving only the curved surface where refraction takes place, substantial material could be saved while achieving the same light-converging effect. Fresnel lenses operate on precisely this principle. Although they look like a piece of glass etched with countless concentric rings—known as Fresnel zones—they deliver the same optical performance as a conventional convex lens. When the incident light is collimated, the lens can focus it so that the brightness remains uniform across the entire image.

Key words:

Convex lens