US Patent 9476569 Apparatus light pen and its use

A light pen for writing on a polarized light sensitive surface is disclosed. Light emitting diodes emit non-polarized light and a polarization block comprising of a truncated cone shaped collimating optical element, a broad band polarization divider, a broadband semi-wave plate, shifting bi-prism and light beam coupler are built to convert the non-polarized light to be converted to polarized uniform intensity light that is focused using a set of projection lens to a writing surface. The said light pen can be used for creating non erasable writing on many types of articles, documents, and records that would provide verification of authenticity and security.