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Design, Realization and Characterization of the Dichroic for Euclid
The objective of the activities comprehends the design and realization of the Dichroic filter for the Euclid Telescope. The optical filter has the scope to split spectrally the incoming radiation in its Visible (VIS) and Near Infrared (NIR) components. The separation between VIS and NIR will occur around 930nm, a minimum of 97% of the VIS component will be reflected on the space side surface of the window while a minimum of 95% of the NIR component will travel along the window and will find an Anti-Reflective coating on the instrument side surface. The operative angle of incidence is limited to the range 0°-18°. The WFE (Wave Front Error) requirements (Tilt excluded – Focus included) are of 20nm rms in transmission and 15nm rms in reflection at the operative temperature range of 160÷130K. It is considered very important to guarantee the same performances also at ambient temperature where the filter is mounted and aligned in the telescope. The challenge to satisfy the requirements was in the combination of obtaining on the same object high spectral performances and absolute flatness of the first reflecting surface and very low wave front error in transmission of the whole optic.
Belli Fabio, Cicciarelli Chiara, Laganà Paolo, Taglioni Giovanni, Venancio Luis Miguel Gaspar, Harnisch Bernd
Paper for Seminar/Symposium/Conference
ICSO 2014 - International Conference on Space Optics (07-10 October 2014, Tenerife - Canary Islands, Spain)
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