Optical filters are used for a variety of purposes at astronomical telescopes. In the near infrared region, from 0.8 to
2.5 μm, bandpass and edge filters are used to separate the different astronomical channels, such as the J, H, and K
bands. However, in the same wavelength range light emission generated in the earth's atmosphere is superimposed on
the stellar radiation. Therefore, ground based astronomical instruments measure, in addition to the stellar light, also
unwanted contributions from the earth's atmosphere. The characteristic lines of this OH emission are extremely narrow
and distributed over the complete NIR spectral range.
The sensitivity of future telescopes, like the European Extreme Large Telescope (E-ELT) which is currently being
designed by ESO, can be dramatically improved if the atmospheric emission lines are effectively suppressed while the
stellar radiation is efficiently transferred to the detector systems. For this task, new types of optical filters have to be
developed. In this framework new design concepts and algorithms must be used, combining the measurement needs
with practical restrictions. Certainly, the selected deposition process plays the key role in the manufacturing process.
Precise and highly stable deposition systems are necessary to realise such filter systems with an appropriate
homogeneity. Moreover, the production control techniques must be adapted to match the high level of precision
required in the NIR range. Finally, the characterisation set-ups for such filters systems have to be provided. The
manufacturing of such a filter system for a feasibility study of an E-ELT instrument is presented. The design
development, the deposition with adapted Ion Beam Sputtering deposition plants, and the characterisation of such filters
in the J-Band is described.