High power mercury lamps are often used in for photolithography apparatus such as LSI and LCD steppers as light source, especially i-line (365nm) is the most famous line. The bandpass filters for photolithography are required to transmit the monochromatic mercury line efficiently to achieve optimal resolution for the photomask. Furthermore the reliability for environmental durability cannot be negligible to reduce running cost.
Asahi i-line bandpass filters are produced by ion assisted deposition (IAD) technology with monolithic substrate to assure the durability against high temperature and keep stable spectral performance over time.