Handling and Cleaning Fresnel Lenses

- Application Note 002 -

These instructions relate to the handling and cleaning of the standard Fresnel lenses which are incorporated into some of the StockerYale LED illuminators, which are manufacatured from optical grade acrylic (also called polymethylmethacrylate or PMMA).

Handling

For lenses which are incorporated into illuminator housings, do not handle the lens directly, but pick the component up using the housing.
For unmounted lenses, do not handle the active surface of the lens, but handle by the lens edges.
If you have to handle the lens directly, use protective finger-cots or latex gloves.
Do not use dry cloths or brushes to clean the lens surface, follow the procedure described below
Avoid exposing the lens to temperatures of more than 60 deg.C.

Cleaning

Make up a cleaning solution consisting of 10% IPA (Isopropyl Alcohol) in water.
If the lens is unmounted, immerse it in cleaning solution and then use a dust-filtered air or nitrogen line to dry each side.
If the lens is mounted in a linelight, use an air gun to blow loose dust from the inside of the linelight, and then use a fine-bristled nylon brush, moistened in the cleaning solution, to wash the grooved outside surface. Use a linear brushing motion which follows the line of the Fresnel grooves. Follow up with an air gun to dry the surface.
For most other StockerYale LED products only the outside lens surface is accessible. For example, if the lens is mounted in an arealight, use a fine-bristled nylon brush, moistened with the cleaning solution, to wash the grooved outside surface. Use a circular brushing motion which follows the direction of the Fresnel grooves. Follow up with an air gun to dry the surface.
Repeat if necessary
If the lens is heavily stained, especially with contaminant such as oil or grease, it may be necessary to start the cleaning with a dilute soap solution in lukewarm water, before using the procedure described above.
If the product is fitted with a diffuser there will be no grooves on the surface, and this procedure can be used to clean the diffuser only. In this case, since the Fresnel surface is internal, it will not need cleaning.