Ronald Willey. Willey Optical, Consultants, Melbourne, FL
Rugate optical thin films have been studied for several decades, particularly for the application to laser eye protection filters (LEPF). The principles of rugates and Herpin equivalent layers are briefly reviewed. The combination of these concepts to overcome the bandpass limitations of shortwave pass filters is shown. The use of Alfred Thelen’s minus filters to make LEPF is discussed. The use of higher harmonic bands of quarter wave optical thickness (QWOT) stacks for LEPF is explained. The application of thickness ratios in layer pairs other than QWOTs is shown to lead to better alternatives for LEPF than rugates.