THICKNESS EVALUATION OF TRANSPARENT PROTECTIVE COATINGS APPLIED TO OPHTHALMIC LENSES USING THE INTERFERENCE VISIBLE SPECTRUM

A high-precision, non-contact optical-interference procedure is proposed for estimating the thickness of transparent coatings on plastic, glass, or other transparent materials. The usefulness of the proposed method, whose theoretical fundaments are well known, is illustrated for the thickness measurement of polysiloxane coatings which are of the order of 3-5 mum, applied at the external side to plastic lenses for spectacles. The measurement inaccuracy varied between 0.06 and 0.12 mum.