Abstract

From time to time, IR optical systems require blocking for all wavelengths from the middle ( 8μm ) to the far IR., beyond 40pm, ( even 50μm ). In many cases, particularly at cold temperatures, the use of the absorption of coating materials and substrates to block the radiation is not enough. Therefore interference filters are required to produce such wide wideband blocking. Furthermore, these interference filters sometimes require wideband reflectance at the long wavelengths complemented with wideband transmittance at the short wavelengths.Unfortunately, such special requirement cannot be met by the normal short wave pass filters with a basic period of ( H/2LH/2 ) or ( L/2HL/2 ). Epstein and Thelen have proposed approximate theories and designed a variety of filters with extended pass bands (1), (2), (3). Markov etc. (4). actually manufactured one type of such filters by using PbTe in the IR. region. In this paper, following the previously-proposed method, explained here is a simple and general design method, and several samples are also given.

© 1995 Optical Society of America