Low temperature radiation receiver protection unit, e.g. for detector, comprises capillary lens cooled to low temperature and placed in radiation path

摘要

An arrangement for protecting a low temperature radiation receiver, e.g. a detector or a probe, against infra-red radiation, comprises a capillary lens (9) cooled to low temperature and placed in the radiation path. The capillaries allow the short wavelength radiation to penetrate, but absorb the infra red radiation, so the short wavelength radiation can be focussed on the detector (4).