Fresnel Lenses as an Economic Alternative to Aspheric Lenses

Lens in Fresnel technology.

© Hella

Fresnel lenses can be used for a variety of tasks in industrial applications. New design algorithms enable the creation of unusual shapes. Due to advances in engineering and manufacturing, these optical components are now manufactured in large-scale production. Thus, Fresnel lenses represent an economic alternative to aspheric lenses.

In machine vision systems, optimal illumination is essential. Illumination modules based on Fresnel lenses feature optical components that are tailored for industrial use. Advantages of these lenses are their low weight and their small dimensions. The low mass results in low costs.

The surface of Fresnel lenses might be considered as an alternating sequence of facets that direct the light into the desired direction and those that do not contribute. This implies that the efficiency is somewhat lower than the efficiency of a comparable aspheric lens. In many applications in inspection systems, the multiple advantages outweigh this disadvantage. 

Possibility of Different Refractive Structures

In industrial applications as inspection, an illumination with high homogeneity is important. It is the prerequisite that deviations or defective parts can be detected reliably. Using Fresnel lenses, a high homogeneity can be obtained. They are well suited to be employed in collimation optics, and allow to obtain a high degree of collimation.

Some tasks require structured illumination. It might be that the intensity should vary according to a prescribed function. Or a region of interest has to be emphasized against a peripheral background. To realize a scenario with structured illumination, Fresnel technology offers the advantage that a divided aperture is feasible. Partial areas can be provided with different refractive structures that feature different functionalities.